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1

Computing heterogeneous azeotropes in multicomponent mixtures  

Microsoft Academic Search

A fundamental approach to the calculation of homogeneous azeotropes of multicomponent mixtures was published by Fidkowski et al. (1993) [Fidkowski et al., Computers Chem Engng17, 1141 (1983)] recently. This paper is a generalization of that approach for cases where multiple liquid phases can coexist in equilibrium (heterogeneous azeotropes). An example for the mixture ethanol-water-cyclohexane-benzene is presented.

E. Eckert; M. Kubí?ek

1996-01-01

2

Extractive distillation of binary azeotropic mixtures  

Microsoft Academic Search

The conditions have been determined under which an azeotropic binary mixture can be separated by extractive distillation and\\u000a under which separation into almost pure components is impossible at any amount of the extracting agent. A general algorithm\\u000a is suggested for analysis of special manifolds in order to see whether extractive distillation is efficient.

L. A. Serafimov; A. K. Frolkova; D. I. Bushina

2008-01-01

3

Separation of azeotropic mixture by a biopolymer, chitin  

Microsoft Academic Search

The azeotropic mixture cannot be separated by the general distillation method. A biopolymer, chitin, packed into the straight glass column has been found to be able to separate various kinds of azeotropic mixtures at room temperature and under 1atm. The azeotropic mixtures such as cyclohexane–butanol, acetone–methanol, cyclohexane–acetone, ethyl acetate–methanol, benzene–ethanol, toluene–methanol etc., can be separated to obtain 100% pure main

Li-Yi Chen; Ji-Chao Zhang; Nan Wang; Mei-Yu Huang; Ying-Yan Jiang

2005-01-01

4

Separation of azeotropic mixtures by batch distillation using an entrainer  

Microsoft Academic Search

Batch Distillation is an efficient unit operation which allows the separation of a multicomponent mixture into its components in a single column. However, the separation of azeotropic mixtures via distillation is quite complex because at the azeotrope liquid and gas have the same composition and, therefore, the driving force for distillation disappears. A systematical presentation of batch distillation processes for

R. Düssel; J. Stichlmair

1995-01-01

5

Locating All Homogeneous Azeotropes in Multicomponent Mixtures  

Microsoft Academic Search

A novel approach for enclosing all homogeneous azeotropes in multicomponent mixturesis presented. The thermodynamic criteria for azeotropy are outlined, and mathematicalequations for each criterion are developed. The global optimization approach isbased on developing convex underestimators which are coupled with a branch and boundframework in which upper and lower bounds on the solution are refined by successivelypartitioning the target region into

S. T. Harding; C. D. Maranas; C. M. McDonald; C. A. Floudas

1997-01-01

6

Synthesis of separation systems for azeotropic mixtures: Preferred distillation region  

Microsoft Academic Search

An algorithm for automatic generation of sequences of distillation columns and decanters for separation of azeotropic mixtures has been developed where distillation boundaries can be crossed by moving them with pressure change, by exploring curvatures of distillation boundaries or by liquid-liquid splits in decanters. Based on a broad knowledge of distillation regions and distillation boundaries for the separated mixture, open-loop

Stanislaw K. Wasylkiewicz

2006-01-01

7

Pervaporation and vapor permeation at the azeotropic point or in the vicinity of the LLE boundary phases of organic\\/aqueous mixtures  

Microsoft Academic Search

Pervaporation and vapor permeation experiments have been performed in order to investigate separately the effect of feed density and concentration on the material transport from the bulk feed to the bulk permeate. Measurements have been carried out for the azeotropic mixtures ethanol\\/water, 1,4-dioxane\\/water and 2-propanol\\/water at 333 and 353 K using a hydrophilic PVA\\/PAN-composite-membrane. In particular the influence of the

M. S. Schehlmann; E. Wiedemann; R. N. Lichtenthaler

1995-01-01

8

Computing all the azeotropes in refrigerant mixtures through equations of state  

Microsoft Academic Search

Azeotropic mixtures of fluorocarbon (FC) and hydro fluorocarbon (HFC) with hydrocarbons are gaining popularity as drop-in substitutes for CFCs and HCFCs. A method to compute all the azeotropes in a refrigerant mixture through the equation of state approach is described. The method allows prediction of all the azeotropes in a refrigerant mixture and is in close agreement with the experimental

Naveed Aslam; Aydin K. Sunol

2004-01-01

9

Application of azeotropic mixtures as standards in testing gas chromatographic systems and components  

Microsoft Academic Search

Summary  The use of specially chosen azeotropes is proposed as standards when testing gas chromatographs, detectors, columns and sample introduction systems. These azeotropic mixtures permit us to minimize the errors due to composition changes during sampling and sample introduction systems (intended for gases or liquids). The potentialities and advantages of such applications are illustrated using the azeotropic mixture of benzene and

B. V. Ioffe; A. G. Vitenberg; A. N. Marinichev; L. M. Kuznetsova

1976-01-01

10

Effects of Ultrasonic Waves on Vapor-Liquid Equilibrium of an Azeotropic Mixture  

Microsoft Academic Search

Azeotropic and extractive distillation techniques used to separate azeotropic mixtures are among the most challenging separation processes in the chemical industry. In this work, an innovative distillation technique which employed ultrasonic waves was proposed to intensify the conventional multi-column azeotropic distillation method into a single-column alternative. The effects of ultrasonic intensity on the vapor-liquid equilibrium (VLE) of methyl-tert-butyl-ether (MTBE)-methanol was

Adnan Ripin; Siti Kholijah Abdul Mudalip; Zairina Sukaimi; Rosli Mohd Yunus; Zainuddin Abdul Manan

2009-01-01

11

Anthracene + Pyrene Solid Mixtures: Eutectic and Azeotropic Character  

PubMed Central

To better characterize the thermodynamic behavior of a binary polycyclic aromatic hydrocarbon mixture, thermochemical and vapor pressure experiments were used to examine the phase behavior of the anthracene (1) + pyrene (2) system. A solid-liquid phase diagram was mapped for the mixture. A eutectic point occurs at 404 K at x1 = 0.22. A model based on eutectic formation can be used to predict the enthalpy of fusion associated with the mixture. For mixtures that contain x1 < 0.90, the enthalpy of fusion is near that of pure pyrene. This and X-ray diffraction results indicate that mixtures of anthracene and pyrene have pyrene-like crystal structures and energetics until the composition nears that of pure anthracene. Solid-vapor equilibrium studies show that mixtures of anthracene and pyrene form solid azeotropes at x1 of 0.03 and 0.14. Additionally, mixtures at x1 = 0.99 sublime at the vapor pressure of pure anthracene, suggesting that anthracene behavior is not significantly influenced by x2 = 0.01 in the crystal structure.

Rice, James W.; Fu, Jinxia; Suuberg, Eric M.

2010-01-01

12

Anthracene + Pyrene Solid Mixtures: Eutectic and Azeotropic Character.  

PubMed

To better characterize the thermodynamic behavior of a binary polycyclic aromatic hydrocarbon mixture, thermochemical and vapor pressure experiments were used to examine the phase behavior of the anthracene (1) + pyrene (2) system. A solid-liquid phase diagram was mapped for the mixture. A eutectic point occurs at 404 K at x(1) = 0.22. A model based on eutectic formation can be used to predict the enthalpy of fusion associated with the mixture. For mixtures that contain x(1) < 0.90, the enthalpy of fusion is near that of pure pyrene. This and X-ray diffraction results indicate that mixtures of anthracene and pyrene have pyrene-like crystal structures and energetics until the composition nears that of pure anthracene. Solid-vapor equilibrium studies show that mixtures of anthracene and pyrene form solid azeotropes at x(1) of 0.03 and 0.14. Additionally, mixtures at x(1) = 0.99 sublime at the vapor pressure of pure anthracene, suggesting that anthracene behavior is not significantly influenced by x(2) = 0.01 in the crystal structure. PMID:21116474

Rice, James W; Fu, Jinxia; Suuberg, Eric M

2010-09-01

13

A new way of separating azeotropic mixtures in batch rectifier  

Microsoft Academic Search

Separation of a maximum boiling azeotrope (chloroform \\/ ethyl acetate) with intermediate boiling entrainer (2-chlorobutane) in batch rectifier is studied in this paper with a new configuration variant (IBED) of batch extractive distillation (BED). Feasibility study is performed, then the two configurations are compared on the basis of theoretical considerations, short-cut estimations, and rigorous simulations. More than 20 % of

C. Steger; Z. Lelkes; E. Rev; M. Meyer; Z. Fonyo

2004-01-01

14

A PROCESS FOR SEPARATING AZEOTROPIC MIXTURES BY EXTRACTIVE AND CONVECTIVE DISTILLATION  

DOEpatents

A method is described for separating an azeotrope of carbon tetrachloride and 1,1,2,2-tetrafluorodinitroethane boiling at 60 deg C. The ndethod comnprises, specifically, feeding azeotrope vapors admixed with a non- reactive gas into an extractive distillation column heated to a temperature preferably somewhat above the boiling point of the constant boiling mixture. A solvent, di-n-butylphthalate, is metered into the column above the gas inlet and permitted to flow downward, earrying with it the higher bomling fraction, while the constituent having the lower boiling point passes out of the top of the column with the non-reactive gas and is collected in a nitrogen cold trap. Other solvents which alter the vapor pressure relationship may be substituted. The method is generally applicable to azeotropic mixtures. A number of specific mixtures whicb may be separated are disclosed. (AEC)

Frazer, J.W.

1961-12-19

15

Expert system for the design of separation sequences for close-boiling and azeotropic mixtures  

SciTech Connect

Formation of azeotropes, or occurrence of close boiling components in a mixture, precludes straightforward rectification as a method of separation. Instead, recourse must be taken to special distillation processes which overcome distillation boundaries by the admixture of an entrainer or solvent, or by exploitation of inherent system properties. While the choice of a suitable entrainer is almost the only important factor in the design of extractive rectification processes, to sort out the numerous possible variants is difficult, due to the different distillation properties of the azeotropic mixture. A satisfactory approach is offered by the use of heuristic knowledge in the form of a knowledge-based expert system to provide alternatives which correspond to the requirements of the process. Starting with a small amount of readily available physical property data for pure components and mixtures, rectification processes which are suitable for the separation of a close boiling or an azeotropic mixture are selected, and appropriate process structures are generated. The expert proposes entrainers, meeting the demands of the process under consideration. The present paper presents a detailed description of the structure and the operation of the expert system for selecting entrainers and for process generation. The system consists of modules for pressure change, homoazeotropic, heteroazeotropic, extractive, and multiple azeotropic rectification, procedural strategy, and explanatory components.

Simmrock, K.H. [Univ. Dortmund (Germany). Lehrstuhl fuer Technische Chemie; Fried, A.; Welker, R. [BASF AG, Ludwigshafen (Germany)

1993-10-01

16

Design of separation process of azeotropic mixtures based on the green chemical principles  

Microsoft Academic Search

This paper presents an integrated methodology for synthesis of separation process of azeotropic mixture based on the green chemical principles, which inherently incorporates environmental factors into the separation process synthesis. Characterization of the environmental impact of a chemical process is carried out on the basis of our established environmental impact database (containing nine indices). The superstructure is optimized more effectively

Chunshan Li; Xiangping Zhang; Xuezhong He; Suojiang Zhang

2007-01-01

17

Dividing wall distillation columns for separation of azeotropic mixtures: feasibility procedure and rigorous optimization  

Microsoft Academic Search

In this work, we propose the use of dividing wall distillation columns, DWC, to separate azeotropic mixtures. First, we present a procedure to guarantee the feasibility of the desired split, based on material balances. Once the feasibility is verified, a preliminary design is calculated considering the DWC as an arrangement of three disengaged conventional distillation columns. Then, this design is

Abel Briones-Ramírez; Claudia Gutiérrez-Antonio

2009-01-01

18

THE SEPARATION OF HYDROGEN ISOTOPES BY DISTILLATION OF AZEOTROPIC MIXTURES OF STRONG ACIDS WITH WATER. III. THE TEMPERATURE DEPENDENCE OF THE ELEMENTARY SEPARATION FACTOR FOR THE AZEOTROPE NITRIC ACID-WATER  

Microsoft Academic Search

Because of the contribution of the isotopic exchange equilibria, a large ; separation parameter delta = alpha - 1 = (D\\/H)\\/sub steam\\/\\/(D\\/H)\\/sub liquid\\/ - ; 1 is to be expected for the distribution of hydrogen rsotopes between liquid ; azeotropic mixtures of strong acids with water and their vapor. In the case of ; azeotropic nitric acid, delta = 0.059,

K. Wetzel; H. Schuetze; G. Kretzschmann

1962-01-01

19

Wet compression versus dry compression in heat pumps working with pure refrigerants or non-azeotropic binary mixtures for different heating applications  

Microsoft Academic Search

Wet compression versus dry compression in heat pumps working with pure refrigerants or non-azeotropic binary mixtures is investigated in this paper. In total 34 pure refrigerants as well as 31 non-azeotropic binary mixtures at different concentrations are considered. This resulted in approximately 300 different mixtures being analysed. The pure refrigerants were analysed for three different heating applications found in practice:

P. P. J Vorster; J. P Meyer

2000-01-01

20

Experimental investigation of moderately high temperature water source heat pump with non-azeotropic refrigerant mixtures  

Microsoft Academic Search

Experimental investigations were carried out on non-azeotropic refrigerant mixtures, named M1A (mass fraction of 20%R152a and 80%R245fa), M1B (mass fraction of 37% R152a and 63%R245fa) and M1C (mass fraction of 50%R152a and 50%R245fa), based on a water-to-water heat pump system in the condensing temperature range of 70–90°C with a cycle temperature lift of 45°C. Performance of R245fa was tested for

Shengjun Zhang; Huaixin Wang; Tao Guo

2010-01-01

21

Heat transfer in pool boiling of binary and ternary non-azeotropic mixtures  

Microsoft Academic Search

Heat transfer coefficients in nucleate pool boiling of binary and ternary non-azeotropic hydrocarbon mixtures were obtained\\u000a experimentally using a vertical electrically heated cylindrical carbon steel surface at atmospheric pressure with several\\u000a surface roughness. The fluids used were Methanol\\/1-Pentanol and Methanol\\/1-Pentanol\\/1,2-Propandiol at constant 1,2-Propandiol\\u000a mole fraction of 30%. Heat fluxes were varied in the range 25–235 kW\\/m2. The cylindrical heater surface was

Ziad Nahra; Erling Næss

2009-01-01

22

Azeotropic distillation  

SciTech Connect

Recent and ongoing research in the distillation of nonideal mixtures is reviewed focusing on advances in the methodologies for the synthesis, design, analysis and control of separation sequences involving homogeneous and heterogeneous azeotropic towers. Maps of residue curves and distillation lines are examined, as well as geometric methods for the synthesis and design of separation sequences, trends in the steady-state and dynamic analysis of homogeneous and heterogeneous towers, the nonlinear behavior of these towers, and strategies for their control. Emphasis is placed on the methods of computing all of the azeotropes associated with a multicomponent mixture, on the features that distinguish azeotropic distillations from their zeotropic counterparts, on the potential for steady-state multiplicity, and on the existence of maximum and minimum reflux bounds. Important considerations in the selection of entrainers are examined. For the synthesis of separation trains, when determining the feasible production compositions, the graphical methods are clarified, especially the conditions under which distillation boundaries can be crossed and bounding strategies under finite reflux. The application of geometric theory to locate the fixed points, at minimum reflux, is reviewed in connection with homotopy-continuation algorithms for this purpose. The use of homotopy-continuation algorithms, especially for the steady-state simulation of heterogeneous azeotropic distillations, is justified. Methods for phase stability analysis are reviewed in connection with the location of real bifurcation points at phase transitions, an important feature of algorithms for the dynamic simulation of heterogeneous azeotropic distillations.

Widagdo, S. [Stevens Inst. of Tech., Hoboken, NJ (United States); Seider, W.D. [Univ. of Pennsylvania, Philadelphia, PA (United States). Dept. of Chemical Engineering

1996-01-01

23

Operation of a batch distillation column with a middle vessel: experimental results for the separation of zeotropic and azeotropic mixtures  

Microsoft Academic Search

Batch distillation in a column with a middle vessel can avoid many of the disadvantages associated with the regular batch distillation processes. In this paper, we present an experimental investigation of the separation of a zeotropic ternary mixture via total reflux operation and of the separation of an azeotropic binary mixture via batch-wise extractive distillation. Moreover, the results obtained for

M. Warter; D. Demicoli; J. Stichlmair

2004-01-01

24

Icke-azeotropa blandningar i vaermepumpar. Foerstudie foer fullskaleprojekt. (Non-azeotropic mixtures in heat pumps. Preliminary study for a full scale project).  

National Technical Information Service (NTIS)

An experimental heat pump with a non-azeotropic mixture as working fluid is being prepared. This will be the first full scale plant in Sweden. The influence of a non-azeotropic mixture, as compared with a pure fluid on the design of the components in the ...

L. Albert T. Berntsson M. Hoegberg L. Persson

1990-01-01

25

Azeotropic distillation  

Microsoft Academic Search

Recent and ongoing research in the distillation of nonideal mixtures is reviewed focusing on advances in the methodologies for the synthesis, design, analysis and control of separation sequences involving homogeneous and heterogeneous azeotropic towers. Maps of residue curves and distillation lines are examined, as well as geometric methods for the synthesis and design of separation sequences, trends in the steady-state

Soemantri Widagdo; Warren D. Seider

1996-01-01

26

Discovery of a reactive azeotrope  

Microsoft Academic Search

Mixtures are azeotropic if they can be distilled (or condensed) without a change of composition. The existence of azeotropes in multicomponent mixtures in the absence of chemical reactions is well understood phenomenologically, and theoretically,. Azeotropes place a fundamental limit on the compositions attainable in mixtures by fractional distillation, but they can in some cases be `broken' by carrying out chemical

W. Song; R. S. Huss; M. F. Doherty; M. F. Malone

1997-01-01

27

Heat transfer in pool boiling of binary and ternary non-azeotropic mixtures  

NASA Astrophysics Data System (ADS)

Heat transfer coefficients in nucleate pool boiling of binary and ternary non-azeotropic hydrocarbon mixtures were obtained experimentally using a vertical electrically heated cylindrical carbon steel surface at atmospheric pressure with several surface roughness. The fluids used were Methanol/1-Pentanol and Methanol/1-Pentanol/1,2-Propandiol at constant 1,2-Propandiol mole fraction of 30%. Heat fluxes were varied in the range 25-235 kW/m2. The cylindrical heater surface was polished to an average surface roughness of 0.2 ?m, and sandblasted yielding surface roughness of 2.98 and 4.35 ?m, respectively. The experimental results were compared to available prediction correlations, indicating that the correlations based on the boiling range are in better qualitative agreement than correlations based on the phase envelope. Increasing surface roughness resulted in an increase in the heat transfer coefficient, and the effect was observed to be dependent on the heat flux and fluid composition.

Nahra, Ziad; Næss, Erling

2009-05-01

28

Adsorption of binary gas mixtures in heterogeneous carbon predicted by density functional theory: on the formation of adsorption azeotropes.  

PubMed

Classical density functional theory (DFT) was used to predict the adsorption of nine different binary gas mixtures in a heterogeneous BPL activated carbon with a known pore size distribution (PSD) and in single, homogeneous, slit-shaped carbon pores of different sizes. By comparing the heterogeneous results with those obtained from the ideal adsorbed solution theory and with those obtained in the homogeneous carbon, it was determined that adsorption nonideality and adsorption azeotropes are caused by the coupled effects of differences in the molecular size of the components in a gas mixture and only slight differences in the pore sizes of a heterogeneous adsorbent. For many binary gas mixtures, selectivity was found to be a strong function of pore size. As the width of a homogeneous pore increases slightly, the selectivity for two different sized adsorbates may change from being greater than unity to less than unity. This change in selectivity can be accompanied by the formation of an adsorption azeotrope when this same binary mixture is adsorbed in a heterogeneous adsorbent with a PSD, like in BPL activated carbon. These results also showed that the selectivity exhibited by a heterogeneous adsorbent can be dominated by a small number of pores that are very selective toward one of the components in the gas mixture, leading to adsorption azeotrope formation in extreme cases. PMID:20712330

Ritter, James A; Pan, Huanhua; Balbuena, Perla B

2010-09-01

29

A general approach to generate distillation regions for azeotropic and heteroazeotropic multicomponent mixtures  

Microsoft Academic Search

The aim of this paper is to show how distillation boundaries can determined. The method developed in this paper can be applied to azeotropic, heteroazeotropic or reactive distillation. Our article is composed of three principal sections, each describing an essential step enabling us to built the distillation maps: determination of the azeotropes, as a function of the temperature and composition,

M. Meyer; J. M. Reneaume; J. M. Lelann

1999-01-01

30

Reliable computation of homogeneous azeotropes  

Microsoft Academic Search

It is important to determine the existence and composition of homogeneous azeotropes in the analysis of phase behavior and in the synthesis and design of separation systems, from both theoretical and practical standpoints. A new method for reliably locating any and all homogeneous azeotropes for multicomponent mixtures is presented. The method also verifies the nonexistence of homogeneous azeotropes if none

Robert W. Maier; Joan F. Brennecke; Mark A. Stadtherr

1998-01-01

31

Performance evaluation of two azeotropic refrigerant mixtures of HFC134a with R-290 (propane) and R-600a (isobutane)  

Microsoft Academic Search

The reduction in chlorofluorocarbon (CFC) and hydrochlorofluorocarbon (HCFC) production and the scheduled phase-out of these ozone-depleting refrigerants require the development and determination of environmentally safe refrigerants for use in heat pumps, water chillers, air conditioners, and refrigerators. This paper presents a performance evaluation of a generic heat pump with two azeotropic refrigerant mixtures of HFC-134a (1,1,1,2-tetrachloroethane) with R-290 (propane) and

M. S. Kim; W. J. Mulroy; D. A. Didion

1994-01-01

32

Performance Simulation and Experimental Testing of Moderately High Temperature Heat Pump Using Non-azeotropic Mixture for Geothermal District Heating  

Microsoft Academic Search

A water-to-water geothermal heat pump is a suitable technology to exploit heat from low-temperature geothermal sources for high-temperature district heating. A distributed parameter model simulation analysis was conducted for the system using non-azeotropic mixture of R245fa and R152a (0.63\\/0.37) under the condition that the input temperature and the flow rate of the heat transfer fluids were provided. The model was

Sheng-jun Zhang; Huai-xin Wang; Tao-guo; Chen Chen

2010-01-01

33

Azeotropic Distillation: A Review of Mathematical Models  

Microsoft Academic Search

Azeotropic distillation as an early and important special distillation process is commonly used in laboratory and industry. It can be used for separating the mixture with close boiling point or forming azeotrope. This paper tries to provide a review on azeotropic distillation for general readers, focusing on entrainer selection and mathematical models. Since the 1950s, along with extractive distillation, azeotropic

Jianwei Li; Zhigang Lei; Zhongwei Ding; Chengyue Li; Biaohua Chen

2005-01-01

34

Separation of organic–organic mixtures by pervaporation—a review  

Microsoft Academic Search

Separation of organic–organic mixtures using membrane separation techniques is being investigated extensively owing to its great importance in chemical and petrochemical industries. Pervaporation is today considered as a basic unit operation for separation of organic–organic liquid mixtures because of its efficiency in separating azeotropic and close-boiling mixtures, isomers and heat-sensitive compounds. Membranes used for separating the four major categories of

B Smitha; D Suhanya; S Sridhar; M Ramakrishna

2004-01-01

35

Performance evaluation of two azeotropic refrigerant mixtures of HFC-134a with R-290 (propane) and R-600a (isobutane)  

SciTech Connect

The reduction in chlorofluorocarbon (CFC) and hydrochlorofluorocarbon (HCFC) production and the scheduled phase-out of these ozone-depleting refrigerants require the development and determination of environmentally safe refrigerants for use in heat pumps, water chillers, air conditioners, and refrigerators. This paper presents a performance evaluation of a generic heat pump with two azeotropic refrigerant mixtures of HFC-134a (1,1,1,2-tetrachloroethane) with R-290 (propane) and R-600a (isobutane); R-290/134a (45/55 by mass percentage) and R-134a/600a (80/20 by mass percentage). The performance characteristics of the azeotropes were compared with pure CFC-12, HFC-134a, HCFC-22, and R-290 at the high temperature cooling and heating conditions including those using liquid-line/suction-line heat exchange. The coefficient of performance of R-290/134a is lower than that of HCFC-22 and R-290, and R-134a/600a shows higher coefficient of performance than CFC-12 and HFC-134a. The capacity for R-290/134a is higher than that for HCFC-22 and R-290, and R-134a/600a exhibits higher system capacity than CFC-12 and HFC-134a. Experimental results show that the discharge temperatures of the studied azeotropic mixtures are lower than those of the pure refrigerants, CFC-12 and HCFC-22.

Kim, M.S.; Mulroy, W.J.; Didion, D.A. (National Inst. of Standards and Technology, Gaithersburg, MD (United States). Building and Fire Research Lab.)

1994-06-01

36

Theoretical Consideration on the Characteristics and the Performance Evaluation for a Heat Pump Cycle of Non-azeotropic Refrigerant Mixtures  

NASA Astrophysics Data System (ADS)

The present paper treats a possibility of performance improvement and its evaluation method for a heat pump cycle of non-azeotropic refrigerant mixtures. Calculation is made for R22 + R114 and R22 + R11 mixtures under the conditions that the inlet temperature and flow rates of heat source fluids through a condenser and an evaporator of counter flow type, heat pump thermal output and FK-value (heat transfer area times average overall heat transfer coefficient) are given. It is graphically shown that the coefficient of performance (COP)h, pressures and volumetric flow rates at suction and discharge ports of a compressor depend on the FK-value and on the flow rate of heat source fluid as well as mixture composition. The characteristics of the heat pump cycle thus obtained are markedly different from those, in which the state points of the refrigerant mixture are fixed.

Fujii, Tetsu; Koyama, Shigeru; Miyara, Akio

37

Thermodynamic Properties of an Azeotropic Freon-22 and Freon-115 Mixture.  

National Technical Information Service (NTIS)

An azeotropic mixt. of Freon-22, 48.8%, and Freon-115, 51.2%, has a b.p. of -45.6C. Its vol. cooling power is considerably higher than that of Freon-12, Freon-22, and Freon-115. This mixt. is neither explosive nor toxic. Two equations for calculating the ...

I. S. Badylkes

1967-01-01

38

Locating all azeotropes in homogeneous azeotropic systems  

Microsoft Academic Search

A global optimization based approach for finding all homogeneous azeotropes in multicomponent mixtures is presented. The global optimization approach is based on a branch and bound framework in which upper and lower bounds on the solution are refined by successively partitioning the target region into small disjoint rectangles. The objective of such an approach is to locate all global minima

C. D. Maranas; C. M. McDonald; S. T. Harding; C. A. Floudas

1996-01-01

39

SIMULATION OF NON-AZEOTROPIC REFRIGERANT MIXTURES FOR USE IN A DUAL-CIRCUIT REFRIGERATOR/FREEZER WITH COUNTERCURRENT HEAT EXCHANGES  

EPA Science Inventory

The paper discusses a refrigerator/freezer (RF) system that has two complete and independent refrigeration cycles for the two compartments. It uses a non-azeotropic refrigerant mixture (NARM) in each cycle and countercurrent heat exchangers throughout. This RF is housed in a stan...

40

Reliable computation of reactive azeotropes  

Microsoft Academic Search

The determination of the existence and composition of reactive azeotropes is important from both theoretical and practical standpoints in the analysis of combined reaction and phase equilibrium and in the synthesis and design of reactive separation systems. We present here a new method for reliably locating, from given thermodynamic models, any and all reactive azeotropes for multicomponent mixtures. The method

Robert W. Maier; Joan F. Brennecke; Mark A. Stadtherr

2000-01-01

41

Electroosmotic Membrane Pump for the separation of water from azeotropic mixtures. Technical progress report, Phase 1  

SciTech Connect

The Electroosmotic Membrane (EOM) Pump is proposed as a process for saving energy during the separation of azeotropes of alcohol and water. The process is electrically driven and removes water from the process stream through ion-selective membranes by electroosmosis. A laboratory-scale Model Cell was constructed to test the EOM pump concept using commercially available ion exchange membranes. Tests were performed with the Model Cell at various (1) alcohol-water compositions, (2) feed molalities of lithium chloride and lithium bromide in water, (3) stack temperatures, and (4) other operating conditions, such as stack configuration and membrane thickness. As part of the integration of the EOM pump and distillation processes, the effect of salt injection into the reflux line of the distillation column was studied. A conclusion of the study is that the overhead composition can be substantially enriched in alcohol to essentially anhydrous alcohol with salt addition.

Lundstrom, J.E.

1986-03-01

42

On the temperature distribution in the counter flow heat exchanger with multicomponent non-azeotropic mixtures  

Microsoft Academic Search

The influence of mixture composition on the temperature distribution in the counter flow heat exchanger used in mixture Joule–Thomson refrigerators is investigated in this paper. A perfect heat capacity matching between the supply and the return streams can be achieved by optimizing the mixture composition. The deeper reason is that in two-phase state the latent heat makes a very important

M. Q Gong; E. C Luo; J. F Wu; Y Zhou

2002-01-01

43

Synthesis of separation flowsheets for multicomponent azeotropic mixtures on the basis of the distillation theory. Presynthesis: prediction of feasible product compositions  

Microsoft Academic Search

A general approach based on the theory of distillation-trajectory tearing off is adopted in the synthesis of optimal separation\\u000a flowsheets for multicomponent azeotropic mixtures. The first stage of the synthesis—presynthesis—is considered, at which feasible\\u000a product compositions are predicted for the separation in a simple column, a two-feed column, and a column with a decanter.

F. B. Petlyuk; R. Yu. Danilov

2000-01-01

44

Performance of a residential heat pump operating with a non-azeotropic binary refrigerant mixture - an interim report. [R22 vs non-azeotropic binary mixture of R13B1 and R152a  

SciTech Connect

This report presents results of laboratory measurement of the performance change of a substantially unmodified residential heat pump designed for R22 when charged with a non-azeotropic, binary mixture of R13B1 and R152a. Results are presented for various sizes of fixed expansion devices. The effect of gliding temperature in the saturation zone was found to be small. The effect of composition shift by flash distillation in the accumulator was found to measurably improve low temperature heating performance. There appears to be an inherent trade-off when operating an unmodified heat pump with mixtures so as to increase capacity at lower temperatures. This trade-off is that as the evaporator pressure decreases and refrigerant begins to flood through to the accumulator and thus allowing the composition shift to occur, the subcooling on the high pressure side also decreases causing a decrease in the available latent enthalpy difference. A possible solution to this problem might be to increase the amount of initial charge. This would cause on increase in head pressures which could be a problem in the cooling mode. A possible solution to this excessive head pressure problem would be to incorporate a receiver in the system in the branch line just ahead of the expansion device for the outdoor coil. Thus, when this coil is acting as an evaporator (i.e., heating mode) the stored refrigerant would be released into the circulating system allowing for more composition shift to occur. Such a solution will be pursued as one of the items of study during the next phase of this project. 9 refs., 11 figs., 1 tab.

Didion, D.; Mulroy, W.

1984-01-01

45

Moderately high temperature water source heat-pumps using a near-azeotropic refrigerant mixture  

Microsoft Academic Search

A ternary mixture of R124\\/R142b\\/R600a, named HTR01, for moderately high temperature heat pumps, was developed. Tests of material compatibility and oil miscibility showed that the mixture could be used with a R22 compressor in an HTR01 heat-pump system. A 2.92 kW moderately high temperature water source heat pump system was set up with HTR01 as the refrigerant to study the

Liu Nanxi; Lin Shi; Han Lizhong; Zhu Mingshan

2005-01-01

46

New extractive configuration separating azeotropic mixture in semi-batch way  

Microsoft Academic Search

A new variant of batch extractive distillation, the so-called inverse-fed batch extractive distillation is presented. The total amount of the entrainer is pre-loaded to the boiler, and the mixture charge to be separated is continuously fed to the column in this novel configuration.The feasibility study of conventional extractive distillation was extended and a thorough study was performed to separate a

Csaba Stéger; Endre Rév; László Horváth; Zsolt Fonyó; Michel Meyer; Zoltán Lelkes

2006-01-01

47

Reliable computation of homogeneous azeotropes  

SciTech Connect

It is important to determine the existence and composition of homogeneous azeotropes in the analysis of phase behavior and in the synthesis and design of separation systems, from both theoretical and practical standpoints. A new method for reliably locating any and all homogeneous azeotropes for multicomponent mixtures is presented. The method also verifies the nonexistence of homogeneous azeotropes if none are present. The method is based on interval analysis, in particular an interval-Newton/generalized-bisection-algorithm providing a mathematical and computational guarantee that all azeotropes are located. This general-purpose technique can be applied in connection with any thermodynamic models. The technique is illustrated in several example problems using the Wilson, NRTL, and UNIQUAC activity-coefficient models.

Maier, R.W.; Brennecke, J.F.; Stadtherr, M.A. [Univ. of Notre Dame, IN (United States). Dept. of Chemical Engineering

1998-08-01

48

Synthesis of azeotropic batch distillation separation systems  

Microsoft Academic Search

The sequencing of batch distillation systems, in particular batch distillation columns, can be complicated by the existence of azeotropes in the mixture. These azeotropes can form batch distillation regions where, depending on the initial feed to the batch column, the types of feasible products and separations are limited. It is very important that these distillation regions are known while attempting

Boyd T. Safrit; Arthur W. Westerberg

1997-01-01

49

Pervaporative separation of azeotropic methanol\\/toluene mixtures in polyurethane–poly(dimethylsiloxane) (PU–PDMS) blend membranes: Correlation with sorption and diffusion behaviors in a binary solution system  

Microsoft Academic Search

A separation of toluene\\/methanol binary mixtures was pervaporated using toluene-selective polyurethane (PU)–poly(dimethylsiloxane) (PDMS) blend membranes. The separation efficiency and toluene flux from the azeotropic mixtures reached a maximum in the blend containing 20% PU content. The toluene sorption behavior from the binary mixtures into the blend was predictable using the Flory–Huggins equation with the interaction parameters (?iM) determined from the

Shingjiang Jessie Lue; Jia Shyang Ou; Chun Hung Kuo; Hsin Yi Chen; Tzu-Huai Yang

2010-01-01

50

Evaluation of a locus of azeotropes by molecular simulation  

SciTech Connect

The technique proposed here for the evaluation of azeotrope lines by molecular simulation builds on ideas used to devise the Gibbs-Duhem integration (GDI) technique for evaluating phase equilibria by molecular simulation. Beginning with a known azeotropic state point, the method integrates a differential equation for the locus of azeotropes with a single semigrand-ensemble molecular simulation performed at each integration state point. Unlike the standard GDI method, fluctuation quantities are needed to conduct the integration. Although these quantities are measured less precisely than simple ensemble averages, the integration is not adversely affected by this difficulty. The method is demonstrated by applying to three model Lennard-Hones binaries. Among these mixtures in one in which the molecular diameter o one species is varied along the azeotrope line. This application shows how details of the intermolecular interactions affect azeotropic behavior. Such an understanding might be useful in formulating additives to break an azeotrope.

Pandit, S.P.; Kofke, D.A.

1999-10-01

51

Simulation, design, and analysis of azeotropic distillation operations  

Microsoft Academic Search

The computational tools needed for simulation, design, and analysis of azeotropic distillation operations are described. These tools include simple methods to identify the existence of binary and ternary azeotropes and to classify ternary mixtures as homogeneous or heterogeneous. The tools also include more complex methods to compute the phase diagram (or a heterogeneous liquid boiling surface), predict liquid-vapor phase equilibrium,

Bjarne S. Bossen; Sten Bay Joergensen; Rafiqul Gani

1993-01-01

52

Azeotropic data for binary and ternary systems at moderate pressures  

Microsoft Academic Search

For the synthesis and design of distillation columns the knowledge of azeotropic points is most important. Therefore, a computerized data bank for azeotropic data has been established at the University of Oldenburg to supplement the existing mixture information stored in the Dortmund Data Bank. To check questionable literature data and to extend the contents of the computerized data bank, more

Jürgen Gmehling; R. Boelts

1996-01-01

53

Azeotropic data for binary and ternary systems at moderate pressures  

SciTech Connect

For the synthesis and design of distillation columns the knowledge of azeotropic points is most important. Therefore, a computerized data bank for azeotropic data has been established at the University of Oldenburg to supplement the existing mixture information stored in the Dortmund Data Bank. To check questionable literature data and to extend the contents of the computerized data bank, more than 500 azeotropic and zeotropic data for binary and ternary systems have been measured up to pressures of 3.5 bar with the help of a wire band column. A total of 38 binary azeotropic and zeotropic data for various ethers (MTBE, TAME, TAEE, ETBE, IPTBE) with different alcohols have already been published (Gmehling et al., 1995). A total of 273 binary and 28 ternary azeotropic and zeotropic data are reported in this paper.

Gmehling, J.; Boelts, R. [Univ. Oldenburg (Germany)

1996-03-01

54

Application of the QSPR approach to the boiling points of azeotropes.  

PubMed

CODESSA Pro derivative descriptors were calculated for a data set of 426 azeotropic mixtures by the centroid approximation and the weighted-contribution-factor approximation. The two approximations produced almost identical four-descriptor QSPR models relating the structural characteristic of the individual components of azeotropes to the azeotropic boiling points. These models were supported by internal and external validations. The descriptors contributing to the QSPR models are directly related to the three components of the enthalpy (heat) of vaporization. PMID:21449551

Katritzky, Alan R; Stoyanova-Slavova, Iva B; Tämm, Kaido; Tamm, Tarmo; Karelson, Mati

2011-03-30

55

Azeotropic phase equilibrium diagrams: a survey  

Microsoft Academic Search

An analysis of the structural properties of vapor–liquid equilibrium (VLE) diagrams provides a fundamental understanding of the thermodynamic behavior of azeotropic mixtures upon distillation.In addition to a review of well-known fundamental work on the analysis of VLE diagrams, this survey comprises less-known published results, especially from the Russian literature. Some new results are also presented for the first time.

V. N. Kiva; E. K. Hilmen; S. Skogestad

2003-01-01

56

Review Azeotropic phase equilibrium diagrams: a survey  

Microsoft Academic Search

An analysis of the structural properties of vapor-liquid equilibrium (VLE) diagrams provides a fundamental understanding of the thermodynamic behavior of azeotropic mixtures upon distillation. In addition to a review of well-known fundamental work on the analysis of VLE diagrams, this survey comprises less-known published results, especially from the Russian literature. Some new results are also presented for the 6rst time.

V. N. Kiva; E. K. Hilmen; S. Skogestad

57

Enhanced bioethanol dehydration by extractive and azeotropic distillation in dividing-wall columns  

Microsoft Academic Search

The industrial production of anhydrous bioethanol requires energy demanding distillation steps to overcome the azeotropic behavior of ethanol–water mixture. In spite of the recent developments in pervaporation and adsorption with molecular sieves, the large scale production is dominated by extractive and azeotropic distillation as the separation of choice.This study proposes novel distillation technologies for enhanced bioethanol dehydration, by extending the

Anton A. Kiss; David J-. P. C. Suszwalak

58

Supercritical separation process for complex organic mixtures  

DOEpatents

A process is disclosed for separating low molecular weight components from complex aqueous organic mixtures. The process includes preparing a separation solution of supercritical carbon dioxide with an effective amount of an entrainer to modify the solvation power of the supercritical carbon dioxide and extract preselected low molecular weight components. The separation solution is maintained at a temperature of at least about 70.degree. C. and a pressure of at least about 1,500 psi. The separation solution is then contacted with the organic mixtures while maintaining the temperature and pressure as above until the mixtures and solution reach equilibrium to extract the preselected low molecular weight components from the organic mixtures. Finally, the entrainer/extracted components portion of the equilibrium mixture is isolated from the separation solution.

Chum, Helena L. (Arvada, CO); Filardo, Giuseppe (Palermo, IT)

1990-01-01

59

Supercritical separation process for complex organic mixtures  

DOEpatents

A process is disclosed for separating low molecular weight components from complex aqueous organic mixtures. The process includes preparing a separation solution of supercritical carbon dioxide with an effective amount of an entrainer to modify the solvation power of the supercritical carbon dioxide and extract preselected low molecular weight components. The separation solution is maintained at a temperature of at least about 70 C and a pressure of at least about 1,500 psi. The separation solution is then contacted with the organic mixtures while maintaining the temperature and pressure as above until the mixtures and solution reach equilibrium to extract the preselected low molecular weight components from the organic mixtures. Finally, the entrainer/extracted components portion of the equilibrium mixture is isolated from the separation solution. 1 fig.

Chum, H.L.; Filardo, G.

1990-10-23

60

Minimising environmental impact using CBR: an azeotropic distillation case study  

Microsoft Academic Search

This paper describes a Case Based Reasoning (CBR) system which aids the design of process sequences aimed at the separation of ternary mixtures containing azeotropes. The solution of such tasks is a non-trivial process particularly since many factors including environmental impact must be considered. CBR is an appropriate technique for design since it is rare that a completely new problem

Josh M. P. King; René Bañares-alcántara; Zainuddin A. Manan

1999-01-01

61

Study to determine the existence of an azeotropic R-22 `drop-in` substitute  

SciTech Connect

The reduction in chlorofluorocarbon (CFC) and hydrochlorofluorocarbon (HCFC) production and the scheduled phase-out of these ozone depleting refrigerants requires the development and determination of environmentally safe refrigerants for use in heat pumps, water chillers, air conditioners, and refrigerators. Azeotropic mixtures are attractive as alternative refrigerants because they behave very nearly as pure materials. A simple correlative scheme that allows one to judge whether or not an azeotrope is likely in a binary refrigerant mixture is discussed. This paper presents laboratory and computer simulation model evaluation of two of the azeotropic refrigerant mixtures which are identified, HFC-134a (1,1,1,2-tetrafluoroethane) with R-C290 (Propane) and HFC-134a with R-600a (Isobutane), in a generic heat pump apparatus. A third azeotropes mixture, HFC-134a with R-C290 (Cyclopropane) is examined by computer simulation only.

Kim, M.S.; Morrison, G.; Mulroy, W.J.; Didion, D.A.

1996-03-01

62

Synthesis of azeotropic batch distillation separation systems  

SciTech Connect

The sequencing of batch distillation systems, in particular batch distillation columns, can be complicated by the existence of azeotropes in the mixture. These azeotropes can form batch distillation regions where, depending on the initial feed to the batch column, the types of feasible products and separations are limited. It is very important that these distillation regions are known while attempting to synthesize sequences of batch columns so infeasible designs can be eliminated early on in the design phase. The distillation regions also give information regarding the feasible products that can be obtained when the mixture is separated by using a variety of batch column configurations. The authors will show how a tool for finding the batch distillation regions of a particular mixture can be used in the synthesis of batch distillation column sequences. These sequences are determined by the initial feed composition to the separation network. The network of all possible sequences will be generated by using state-task networks when batch rectifying, stripping, middle vessel, and extractive middle vessel columns are allowed. The authors do not determine which sequence is the best, as the best sequence will depend on the particular application to which one is applying the algorithms. They show an example problem for illustration of this technique.

Safrit, B.T. [Eastman Chemical Co., Kingsport, TN (United States); Westerberg, A.W. [Carnegie Mellon Univ., Pittsburgh, PA (United States)

1997-05-01

63

Nonlinear ultrasonic nature of organic liquid and organic liquid mixture.  

PubMed

Based on Jacobson's molecular free length theory in liquids and the relationship between ultrasonic velocity and the molecular free length in organic liquids, this paper deduces the equations for pressure coefficient and temperature coefficient of ultrasonic velocity and nonlinear acoustic parameter B/A in both of organic liquid and organic liquid binary mixtures. These nonlinear acoustic parameters are evaluated against the measured results and data from other sources. The equations reveal the connections between the nonlinear acoustic parameters and some internal structural of the medium or mixtures e.g. the sizes of molecule, several thermodynamic physical parameters and outside status e.g. condition of pressure and temperature of the liquid or liquid mixture. With the equations the nonlinear acoustic parameter B/A of organic liquid binary mixtures, which is impossible to know without the nonlinear acoustic parameter B/A of the tow components before, can be calculated based on the structural and physical parameters of organic liquid and organic liquid binary mixtures. PMID:16797046

Lu, Yi-gang; Zhang, Yang; Dong, Yan-wu

2006-06-06

64

Optimization study on the azeotropic distillation process for isopropyl alcohol dehydration  

Microsoft Academic Search

Modeling and optimization work was performed using benzene as an entrainer to obtain a nearly pure anhydrous isopropyl alcohol\\u000a product from dilute aqueous IPA mixture through an azeotropic distillation process. NRTL liquid activity coefficient model\\u000a and PRO\\/II with PROVISION 6.01, a commercial process simulator, were used to simulate the overall azeotropic distillation\\u000a process. We determined the total reboiler heat duties

Jungho Cho; Jong-Ki Jeon

2006-01-01

65

Secondary organic aerosol from biogenic volatile organic compound mixtures  

NASA Astrophysics Data System (ADS)

The secondary organic aerosol (SOA) yields from the ozonolysis of a Siberian fir needle oil (SFNO), a Canadian fir needle oil (CFNO), and several SOA precursor mixtures containing reactive and non-reactive volatile organic compounds (VOCs) were investigated. The use of precursor mixtures more completely describes the atmosphere where many VOCs exist. The addition of non-reactive VOCs such as bornyl acetate, camphene, and borneol had very little to no effect on SOA yields. The oxidation of VOC mixtures with VOC mass percentages similar to the SFNO produced SOA yields that became more similar to the SOA yield from SFNO as the complexity and concentration of VOCs within the mixture became more similar to overall SFNO composition. The SOA yield produced by the oxidation of CFNO was within the error of the SOA yield produced by the oxidation of SFNO at a similar VOC concentration. The SOA yields from SFNO were modeled using the volatility basis set (VBS), which predicts the SOA yields for a given mass concentration of mixtures containing similar VOCs.

Hatfield, Meagan L.; Huff Hartz, Kara E.

2011-04-01

66

Simulation, design, and analysis of azeotropic distillation operations  

SciTech Connect

The computational tools needed for simulation, design, and analysis of azeotropic distillation operations are described. These tools include simple methods to identify the existence of binary and ternary azeotropes and to classify ternary mixtures as homogeneous or heterogeneous. The tools also include more complex methods to compute the phase diagram (or a heterogeneous liquid boiling surface), predict liquid-vapor phase equilibrium, and/or predict liquid-liquid-vapor phase equilibrium for simulations of batch and continuous distillation column operations. Important new features of these tools are the incorporation of a fast and efficient method for test of phase stability in simulation of distillation operations, the ability to handle a large range of mixtures (including mixtures with supercritical compounds), and the ability for computations covering wide ranges of temperature and pressure. On the basis of these tools, simple and consistent design algorithms are developed. The applicability of the design algorithms is verified through process simulation and analysis of the predicted behavior and data from the open literature. Conditions are given for examples illustrating (when and how possible distillation boundaries can be crossed) how multiple steady states can be obtained. Finally, the effect of changes in operating on the dynamic behavior of the azeotropic distillation columns and the sensitivity of design to the prediction of phase equilibria are presented.

Bossen, B.S.; Joergensen, S.B.; Gani, R. (Technical Univ. of Denmark, Lyngby (Denmark))

1993-04-01

67

Fluothane-ether: an azeotropic mixture  

Microsoft Academic Search

\\u000a Résumé  Le mélange deux parties de Fluothane pour une partie ?éther fut étudié au point de vue de solution, toxicité, inflammabilité,\\u000a puissance et réaction.\\u000a \\u000a Les analyses de laboratoire nous ont démontré que le liquide de composition est azéotrope dans le voisinage de ces concentrations,\\u000a de même que dans la phase gazeuse et dans la partie récupérée de ?expiration.\\u000a \\u000a \\u000a \\u000a Au point de

Fernando Hudon; André Jacçues; Paul-A. Boivin

1958-01-01

68

Modeling and simulation of azeotropic distillation for chloroform (1) + methanol (2) + acetone (3)  

Microsoft Academic Search

Azeotropic distillation is a special case of multicomponent distillation used for separation of binary mixtures which are either difficult or impossible to separate by ordinary fractionation. It is commonly used to separate close boiling mixtures with far fewer trays than in conventional distillation and with less circulation, resulting in lower equipment and energy costs. It is widely used for the

D. Krishna; G Santhosh Kumar

2012-01-01

69

Optimal design of complex azeotropic distillation columns  

Microsoft Academic Search

Geometric methods are valuable tools for process synthesis and design since they provide designers with intuition and quantitative results. The calculation and graphical representation of azeotropes, residue curves and distillation boundaries provide a wealth of knowledge about the entire composition space. This paper shows how these tools can be used for optimal design of complex azeotropic distillation columns. Two examples

Stanislaw K Wasylkiewicz; Leo C Kobylka; Francisco J. L Castillo

2000-01-01

70

AZEOTROPE PREDICTION BY MONTE CARLO MOLECULAR SIMULATION  

Microsoft Academic Search

This article presents a methodology for checking the existence of the azeotrope and computing its composition, density, and pressure at a given temperature by integrating chemical engineering insights with molecular simulation principles. Liquid-vapor equilibrium points are computed by molecular simulations using the Gibbs ensemble Monte Carlo (GEMC) method at constant volume. The appearance of the azeotropic point is marked by

M. K. Hadj-Kali; V. Gerbaud; X. Joulia

2012-01-01

71

Multiperiod design of azeotropic separation systems II: approximate models  

Microsoft Academic Search

In this paper, the final in a two part series considering the multiperiod design of azeotropic separation systems, we focus on the development of simplified models for azeotropic distillation design. Several shortcut design techniques from the literature are reviewed and key aspects of a successful model for use in multiperiod azeotropic distillation design are identified. Simplified models for azeotropic design

K. H Tyner; A. W Westerberg

2001-01-01

72

Prediction of azeotropic behavior using equations of state  

Microsoft Academic Search

A shortcut method is developed to determine if an equation of state (EOS) is capable of predicting azeotropes in binary systems and if the azeotrope meets the critical gas–liquid equilibrium line. The method suggested allows an a priori prediction of subcritical azeotropes and an exact prediction of the azeotropic point (if any) at critical conditions. In addition, the approach developed

Hugo Segura; Jaime Wisniak; Pedro G. Toledo; Andrés Mej??a

1999-01-01

73

SECONDARY ORGANIC AEROSOL FORMATION FROM MIXTURES OF BIOGENIC HYDROCARBONS  

EPA Science Inventory

In this work the influence of hydrocarbon mixtures on the overall Secondary Organic Aerosol yield is investigated. Photochemical reaction experiments were conducted using mixtures of a-pinene, isoprene and propene in the presence of NOx. Results of the experiments show...

74

The optimal design of refrigerant mixtures for a two-evaporator refrigeration system  

Microsoft Academic Search

The use of liquid-phase mixtures is common in a number of industrial applications. Mixtures have certain advantages over individual components, and these have been exploited advantageously. For the case of refrigerants, a number of azeotropic mixtures are used in practise. The use of non-azeotropic refrigerant mixtures, however, is not as common. This paper looks at the design of refrigerant mixtures

Nachiket Churi; Luke E. K. Achenie

1997-01-01

75

Estimation of Interfacial Tension between Organic Liquid Mixtures and Water  

SciTech Connect

Knowledge of IFT values for chemical mixtures helps guide the design and analysis of various processes, including NAPL remediation with surfactants or alcohol flushing, enhanced oil recovery, and chemical separation technologies, yet available literature values are sparse. A comprehensive comparison of thermodynamic and empirical models for estimating interfacial tension (IFT) of organic chemical mixtures with water is conducted, mainly focusing on chlorinated organic compounds for 14 ternary, three quaternary, and one quinary systems. Emphasis is placed on novel results for systems with three and four organic chemical compounds, and for systems with composite organic compounds like lard oil and mineral oil. Seven models are evaluated: the ideal and nonideal monolayer models (MLID and MLNID), the ideal and nonideal mutual solubility models (MSID and MSNID), an empirical model for ternary systems (EM), a linear mixing model based on mole fractions (LMMM), and a newly developed linear mixing model based on volume fractions of organic mixtures (LMMV) for higher order systems. The two ideal models (MLID and MSID) fit ternary systems of chlorinated organic compounds without surface active compounds relatively well. However, both ideal models did not perform well for the mixtures containing a surface active compound. However, for these systems, both the MLNID and MSNID models matched the IFT data well. It is shown that the MLNID model with a surface coverage value (0.00341 mmol/m2) obtained in this study can practically be used for chlorinated organic compounds. The LMMM results in poorer estimates of the IFT as the difference in IFT values of individual organic compounds in a mixture increases. The EM, with two fitting parameters, provided accurate results for all 14 ternary systems including composite organic compounds. The new LMMV method for quaternary and higher component systems was successfully tested. This study shows that the LMMV may be able to be used for higher component systems and it can be easily incorporated into compositional multiphase flow models using only parameters from ternary systems.

Yoon, Hongkyu; Oostrom, Martinus; Werth, Charles J.

2009-10-15

76

ACUTE TOXICITY OF ORGANIC CHEMICAL MIXTURES TO THE FATHEAD MINNOW  

EPA Science Inventory

The acute joint toxicity of industrial organic chemicals to the fathead minnow was determined for binary and equitoxic multiple chemical mixtures. Results from binary tests were used to define isobole diagrams. The degree of joint toxic action was determined among 27 chemicals fr...

77

Mass flow of a volatile organic liquid mixture in soils  

Microsoft Academic Search

The flow of kerosene, a volatile organic liquid mixture (VOLM), was studied in loam and clay soils and in a medium sand. The kerosene residual capacity and conductivity were determined for all three media at different initial moisture contents and with kerosene of different compositions. The kerosene conductivity of the soil was found to be strongly influenced by the soil

Z. Gerstl; Ts. Galin; B. Yaron

1994-01-01

78

Health and environmental research on complex organic mixtures: Proceedings  

Microsoft Academic Search

During the preceding decade, numerous studies involving chemists, biologists, environmental scientists, industrial hygienists and engineers were conducted to assess the potential harmful effects of various complex organic mixtures. As a result, a substantial health and environmental database had been developed on combustion products, coal conversion materials (liquefaction and gasification), shale oils, petroleum, solid wastes, dredging spoils, materials from biomass, and

R. H. Gray; E. K. Chess; P. J. Mellinger; R. G. Riley; D. L. Springer

1987-01-01

79

Multiple steady states in heterogeneous azeotropic distillation  

Microsoft Academic Search

In this article, the authors study multiple steady states in ternary heterogeneous azeotropic distillation. They show that in the case of infinite reflux and an infinite number of trays, one can construct bifurcation diagrams on physical grounds with the distillate flow as the bifurcation parameter. Multiple steady states exist when the distillate flow varies nonmonotonically along the continuation path of

Nikolaos Bekiaris; George A. Meski; Manfred Morari

1996-01-01

80

Multiple Steady States in Homogeneous Azeotropic Distillation  

Microsoft Academic Search

In this article we study multiple steady states in ternary homogeneous azeotropic distillation. We show that in the case of infinite reflux and an infinite number of trays, multiple steady states exist when the distillate flow varies non-monotonically along the continuation path of the bifurcation diagram with the distillate flow as the bifurcation parameter. We derive a necessary and sufficient

Nikolaos BekiarisGeorge; George A. Meski; Cristian M. Radu; Manfred Morari

1993-01-01

81

Toxicity of thiocyanate, phenol, and their mixtures to freshwater aquatic organisms: A mixture modeling approach  

SciTech Connect

Thiocyanate and phenol are two environmentally significant constituents of wastewater streams from coke production plants and coal conversion facilities. Acute and chronic toxicity experiments were conducted for thiocyanate and phenol with Daphnia magna at 20 C and Ceriodaphnia affinis/dubia at 25C in hard water to study their individual toxic effects on survival and reproduction. Statistical analysis of the dose response relationships for the individual chemicals indicated the type of combined effects that occur when thiocyanate and phenol are present simultaneously. Mixture models for toxicant interaction were used to predict joint toxic effects on survival and reproduction. The applicability of the mixture model was tested by performing joint toxicity experiments for specific thiocyanate and phenol mixtures to verify the model for toxic effects on specific whole organism performances. Neonate production and hatchability, two indices of reproduction, were selected to evaluate the chronic toxic effects of thiocyanate and phenol. The resulting dose response curves for mixtures were compared to curves predicted on the basis of the mathematical model for concentration addition. Low concentrations of thiocyanate, phenol and their mixtures generally caused a stimulation effect on D. magna and C. affinis/dubia reproduction.

Soboslay, E.G.

1987-01-01

82

Hetero-azeotropic distillation: combining fungal dehydration and lipid extraction.  

PubMed

A low-cost single-stage laboratory process combining fungal dehydration and lipid extraction was compared with a traditional two-stage method employing freeze-drying and subsequent mechanical disruption in the presence of solvent. The ability of a number of organic solvents to form hetero-azeotropes with water was exploited. Chloroform, cyclohexane and hexane were assessed in their abilities to both dry and extract lipid from the oleaginous phycomycete Mortierella alpina (ATCC 32222). Drying rate and lipid extraction were maximised under conditions that prevented fungal agglomeration. The total processing time was limited by the rate of dehydration rather than by the rate of lipid extraction. In all cases azeotropic distillation facilitated a greater rate of dehydration than was possible with freeze-drying. A consequent reduction in overall processing time was observed. Uniquely, both the solvent used and the mode of mixing employed controlled the morphology of the aggregates formed during distillation. In combination with mild mixing chloroform discouraged agglomeration whereas cyclohexane and hexane promoted aggregation. Successful lipid extraction was dependent on the use of dry biomass rather than on the application of heat to effect distillation. Neither the application of heat nor the solvent employed had any significant effect on the lipid composition of the extracted oil. PMID:16232815

Tough, A J; Isabella, B L; Beattie, J E; Herbert, R A

2000-01-01

83

Influence of organic solvent mixtures on biological membranes  

Microsoft Academic Search

A simple experimental model was used to study the influence of organic solvents and solvent mixtures on the integrity of biological membranes. Radiolabelled membranes were prepared biosynthetically by growing Escherichia coli in the presence of 14C-oleic acid; the bulk of the radioactivity was incorporated into 14C-phosphatidylethanolamine, the predominant phospholipid species in E coli membranes. The radiolabelled bacteria were incubated at

C Gustafson; C Tagesson

1985-01-01

84

Spectra and structure of binary azeotropes I. Acetone-chloroform.  

PubMed

Some characteristic vibrational modes of acetone and chloroform change due to the azeotrope formation. The extend of interaction of these molecules has significant effects on some vibrational modes involved, depending on unit structure in azeotrope cluster. Besides (1)H NMR signals undergo some chemical shifts, which show the effect of oncoming molecules on the target molecule. FT-IR and (1)H NMR spectra of pure substances and corresponding azeotrope were recorded, mutual influences due to azeotrope formation based on mole ratio, boiling point and spectral changes has been discussed. Unit structure of cluster deduced by investigating fundamental frequency shifts and (1)H NMR chemical shifts. PMID:16257732

Jalilian, M R; Alibabaei, L

2005-11-01

85

Adsorption of chromate/organic-acid mixtures in aquifer materials  

SciTech Connect

The overall objective of this project is to develop a fuller understanding of the interactions of mixtures of anionic co-contaminants with oxide-mineral surfaces. Our specific focus is on the competitive interactions of chromate and oxalic acid on ferric oxyhydroxide and on natural aquifer materials. Chromate and oxalate are of practical interest as widespread contaminants at many DOE facilities. However, these anions also are excellent model adsorbates for elucidating fundamental aspects of ionic adsorption processes, particularly with respect to organic acids.

Fish, W.; Palmer, C.D.

1991-07-15

86

Predicting flammability of gas mixtures containing volatile organic compounds  

SciTech Connect

One requirement regarding the transportation of transuranic (TRU) radioactive waste containers currently limits the total concentration of potentially flammable volatile organic compounds (VOCs) and flammable gases in the headspace of the waste container. Typical VOCs observed in the drums include aromatic hydrocarbons, ketones, alcohols, cyclohexane, as well as chlorinated hydrocarbons (alkanes and alkenes). Flammable gases, such as hydrogen and methane, may be generated in the containers by radiation-induced decomposition (radiolysis) of water and hydrocarbon waste forms. An experimental program was initiated to identify an accurate means for predicting flammability for gas mixtures containing one or more of the following species: hydrogen, carbon tetrachloride, 1,2-dichloroethane, toluene, or 2-butanone. The lower flammability limits (LFL) of gas mixtures containing equimolar quantity for each species were determined in a 19-liter laboratory flammability chamber using a strong spark ignition source. The group factor contribution method was determined to be more accurate than the LeChatelier method for estimating the LFL for these gas mixtures.

Liekhus, K. [Lockheed Martin Idaho Technologies Co., Idaho Falls, ID (United States). Idaho National Engineering and Environmental Lab.; Zlochower, I. [National Inst. for Occupational Safety and Health, Pittsburgh, PA (United States). Pittsburgh Research Lab.; Djordjevic, S.; Loehr, C. [Benchmark Environmental, Albuquerque, NM (United States)

1997-12-31

87

Simultaneous Design of Ionic Liquids and Azeotropic Separation Processes  

Microsoft Academic Search

A methodology for the design of azeotrope separation processes using ionic liquids as entrainers is outlined. A Hildebrand solubility parameter group contribution model has been developed to screen for or design an ionic liquid entrainer that is soluble with the azeotropic components. Using the best candidate, vapor-liquid equilibria data is predicted using a new ionic liquid UNIFAC model that has

Brock C. Roughton; John White; Kyle V. Camarda; Rafiqul Gani

2011-01-01

88

The Influence of Distillation Conditions on the Azeotropic Composition  

Microsoft Academic Search

The thermodynamic conditions that determine the presence of an azeotrope in a binary solution are developed and analyzed together with the criteria that define if the azeotrope has a maximum or minimum boiling point at constant pressure. It is shown that using simple models for describing vapor-liquid equilibria and vapor pressure data of the pure components it is possible to

Jaime Wisniak

1998-01-01

89

Calculation of a double reactive azeotrope using stochastic optimization approaches  

NASA Astrophysics Data System (ADS)

An homogeneous reactive azeotrope is a thermodynamic coexistence condition of two phases under chemical and phase equilibrium, where compositions of both phases (in the Ung-Doherty sense) are equal. This kind of nonlinear phenomenon arises from real world situations and has applications in chemical and petrochemical industries. The modeling of reactive azeotrope calculation is represented by a nonlinear algebraic system with phase equilibrium, chemical equilibrium and azeotropy equations. This nonlinear system can exhibit more than one solution, corresponding to a double reactive azeotrope. The robust calculation of reactive azeotropes can be conducted by several approaches, such as interval-Newton/generalized bisection algorithms and hybrid stochastic-deterministic frameworks. In this paper, we investigate the numerical aspects of the calculation of reactive azeotropes using two metaheuristics: the Luus-Jaakola adaptive random search and the Firefly algorithm. Moreover, we present results for a system (with industrial interest) with more than one azeotrope, the system isobutene/methanol/methyl-tert-butyl-ether (MTBE). We present convergence patterns for both algorithms, illustrating - in a bidimensional subdomain - the identification of reactive azeotropes. A strategy for calculation of multiple roots in nonlinear systems is also applied. The results indicate that both algorithms are suitable and robust when applied to reactive azeotrope calculations for this "challenging" nonlinear system.

Mendes Platt, Gustavo; Pinheiro Domingos, Roberto; Oliveira de Andrade, Matheus

2013-02-01

90

Azeotropic-like (congruent melting) phenomena of lamellar liquid crystals  

Microsoft Academic Search

The binary system of water and didecyldimethylammonium bromide (DDeAB), having a double hydrocarbon chain, was found to exhibit exhibit an azeotropic-like phase transition from lamellar liquid crystal to micellar solution. That is, the maximum limiting value of temperatures where the present system is allowed to exist in a lamellar liquid crystal corresponds to the socalled azeotropic point (AZP) or congruent

H. Kuniedal; H. Itol; S. Takebayashi; M. Kodama

1993-01-01

91

Hydrothermal oxidation of ammonia/organic waste mixtures  

SciTech Connect

Hydrothermal oxidation is a promising new technology for the treatment of radioactive contaminated hazardous organic wastes. Los Alamos National Laboratory is currently evaluating this technology for the U. S. Department of Energy. In this paper, we present experimental results from the study of the hydrothermal oxidation of an ammonia/alcohol/uranium waste mixture. The use of a co-oxidant system consisting of hydrogen peroxide combined with nitrate is discussed. Experiments demonstrate near complete destruction of ammonia and organic compounds at 500{degrees} C, 38 MPa, and 50 seconds reaction time. The ammonia and total organic carbon (TOC) concentrations in a waste simulant is reduced from 8,500 mg/L of ammonia and 12,500 mg/L TOC to 30 mg/L ammonia and less than 10 mg/L TOC. The major reaction products are CO{sub 2}, N{sub 2}, and a small amount of N{sub 2}O. Comparison experiments with nitrate and hydrogen peroxide used individually show the advantage of the co-oxidant system.

Luan, Li; Proesmans, P.I.; Buelow, S.J.

1997-05-01

92

SOIL SORPTION OF VOLATILE AND SEMIVOLATILE ORGANIC COMPOUNDS IN A MIXTURE  

EPA Science Inventory

Studies were conducted to evaluate lipophilicity as a predictor sorption for a mixture of organic compounds with high vapor pressures commonly present at hazardous waste sites. Sorption partition coefficients (Kp) for the mixture of 16 volatile and semivolatile ...

93

Kolbe electrolysis of mixtures of aliphatic organic acids  

SciTech Connect

Kolbe electrolysis of mixtures of n-butanoic with n-hexanoic acid and propranoic with n-hexanoic acid have been performed in aqueous solution at a smooth platinum anode. Typically, hexane production by the oxidation of butanoic acid, or butane production from propanoic acid, in aqueous solution is not observed to exceed a few percent In the current work, significant increases of these products were observed. In addition, a substantial fraction of the remaining C/sub 3/ or C/sub 4/ acids reacted were converted to mixed alkane dimers with hexanoic acid. These results are interpreted by a model in which n-hexanoic acid and its various oxidation products form a lipophilic layer at the anode surface which provides an environment where further oxidation to carbonium ions is disfavored. This model has been suggested previously to explain pressure effects on Kolbe electrolysis. This observation supports the feasibility of producing mixed linear alkanes for use as fuels and chemicals from mixed organic acids which may be produced by anaerobic fermentation of organic matter.

Levy, P.F.; Cheng, L.K.; Sanderson, J.E.

1984-04-01

94

PREDICTIONS OF AZEOTROPES FORMED FROM FLUORINATED ETHERS, ETHANES, AND PROPANES  

EPA Science Inventory

The paper discusses an evaluation of the potential for azeotrope formation and performance for fluorinated ethers, ethanes, and propanes. (NOTE: The synthesis of new non-chlorinated refrigerants expands the base of alternatives for replacing ozone-depleting chlorofluorocarbons (O...

95

Solubility, sorption, and transport of hydrophobic organic chemicals in complex mixtures. Environmental research brief  

Microsoft Academic Search

Environmental contamination problems commonly involve wastes consisting of complex mixtures of chemicals. The behavior of these mixtures has not been well understood because the primary chemodynamic properties of organic chemicals have usually been characterized in aqueous solutions which are simple in composition relative to many waste mixtures found at or near disposal\\/spill sites. The research summarized in the report focuses

P. S. C. Rao; L. S. Lee; A. L. Wood

1991-01-01

96

Behavioural evaluation of workers exposed to mixtures of organic solvents.  

PubMed Central

Reports from Scandinavia have suggested behavioural impairment among long term workers exposed to solvents below regulatory standards. A cross sectional study of behavioural performance was conducted among printers and spray painters exposed to mixtures of organic solvents to replicate the Scandinavian studies and to examine dose-response relationships. Eligible subjects consisted of 640 hourly workers from four midwestern United States companies. Of these, 269 responded to requests to participate and 240 were selected for study based on restrictions for age, sex, education, and other potentially confounding variables. The subjects tested had been employed on average for six years. Each subject completed an occupational history, underwent a medical examination, and completed a battery of behavioural tests. These included the Fitts law psychomotor task, the Stroop colour-word test, the Sternberg short term memory scanning test, the short term memory span test, and the continuous recognition memory test. Solvent exposure for each subject was defined as an exposed or non-exposed category based on a plant industrial hygiene walk-through and the concentration of solvents based on an analysis of full shift personal air samples by gas chromatography. The first definition was used to maintain consistency with Scandinavian studies, but the second was considered to be more accurate. The average full shift solvent concentration was 302 ppm for the printing plant workers and 6-13 ppm for the workers at other plants. Isopropanol and hexane were the major components, compared with toluene in Scandinavian studies. Performance on behavioural tests was analysed using multiple linear regression with solvent concentration as an independent variable. Other relevant demographic variables were also considered for inclusion. No significant (p greater than 0.05) relation between solvent concentration and impairment on any of the 10 behavioural variables was observed after controlling for confounding variables. Exposed/non-exposed comparisons showed a significantly poorer digit span among those exposed, but this has not been generally reported in the Scandinavian studies. The medical examination showed no abnormalities of clinical significance. The inability to replicate the findings of the Scandinavian studies could have been due to the shortness of the duration of workers' exposure, the type of solvents in the mixtures, use of different behavioural tests, or to selection factors.

Maizlish, N A; Langolf, G D; Whitehead, L W; Fine, L J; Albers, J W; Goldberg, J; Smith, P

1985-01-01

97

On protein denaturation in aqueous-organic mixtures but not in pure organic solvents  

SciTech Connect

FTIR spectroscopy was used to quantitatively assess the secondary structure of proteins in aqueous-organic mixtures ranging from pure water to a pure solvent. For every such solution/suspension, the {alpha}-helix content of the protein was independently calculated from the amide I and III spectral regions (which gave essentially identical results). In all cases studied (two unrelated enzymic proteins-lysozyme and subtilisin; three dissimilar water-miscible solvents-acetonitrile, tetrahydrofuran, and 1-propanol), the protein secondary structure was much more native-like in pure organic solvents than in most water-solvent mixtures, e.g., 60% (v/v) organic solvents. In fact, placing lyophilized (or crystalline) proteins in the anhydrous solvents tested had no appreciable effect on the {alpha}-helix content, whereas the latter declined markedly in the 60% (v/v) solvents. This behavior was found to be kinetically controlled, i.e., to be due to inherent restrictions on protein conformational mobility in anhydrous, in contrast to aqueous-organic, media. 34 refs., 3 figs., 2 tabs.

Griebenow, K.; Klibanov, A.M. [Massachusetts Inst. of Technology, Cambridge, MA (United States)

1996-11-27

98

ASPECTS OF MULTICOMPONENT MIXTURE SEPARATION IN THE PRESENCE OF SELECTIVE SOLVENTS  

Microsoft Academic Search

The extractive and autoextractive distillation of ternary and quaternary azeotropic solvent mixtures was adopted to demonstrate the relation between the structure of phase diagram of the azeotropic systems and the operating parameters of the extractive distillation column based on the relative volatility criterion. A set of separation schemes belonging to different structural classes have been investigated. The separation scheme that

H. Benyounes; A. K. Frolkova

2010-01-01

99

Azeotropic distillation in a middle vessel batch column. 3: Model validation  

SciTech Connect

A dimensional time model of the middle vessel batch distillation column (MVC) is developed in the ABACUSS process modeling environment, and simulations are conducted to validate the theoretical insights developed for the operation of the MVC based on a warped time model of the MVC. The qualitative dynamics of the MVC operated in the presence of linear separation boundaries are validated via simulations conducted on the ternary azeotropic mixture of acetone, chloroform, and methanol. It is also shown via simulation that the separation results obtained from a column with significant but reasonable amounts of holdup on the trays are not significantly different from a column in which holdup in the trays is assumed to be negligible. Theoretical operating policies for separating the azeotrope of acetone and chloroform using benzene as a batch entrainer are also validated using the ABACUSS model. Finally, the authors explore the advantages and disadvantages of different feasible operating policies for separating a mixture of acetone, benzene, and chloroform completely into its constituent pure components.

Cheong, W.; Barton, P.I. [Massachusetts Inst. of Tech., Cambridge, MA (United States)

1999-04-01

100

Survey of Binary Azeotropes as Physical Chemistry Lab Experiments with Attention to Cost, Safety, and the Environment  

NASA Astrophysics Data System (ADS)

A survey is presented of possible binary azeotropic systems suitable for study in an undergraduate physical chemistry laboratory. From a range of sources, a list has been compiled of the most acceptable systems on the basis of health, safety, waste disposal, and practicability concerns. More than 80 systems were reviewed. For comparison purposes, the list was reduced to a table showing 5 high-boiling and 19 low-boiling azeotropes with their exposure limits, approximate costs, and some physical properties of the mixtures. Comments are made about the strengths and weaknesses of the choice of each. The paper should supply the instructor with sufficient data to choose a binary system for study and with literature sources for further information.

Glinski, Robert J.; Smith, Christopher W.; Cooke, Jason B.

1999-02-01

101

Microbial Toxicity of Mixtures of Organic Chemicals: Modeling and Validation for Non-Uniform Mixtures.  

National Technical Information Service (NTIS)

Joint effects of binary and multi-component, uniform and non-uniform mixtures assayed in our microbial toxicity studies were found to be simply additive, or essentially simply additive. These results are in agreement with the conclusions reported in the l...

N. Khandan

1997-01-01

102

ANALYSIS OF NONSTATIONARY TIME SERIES BY MIXTURES OF SELF-ORGANIZING PREDICTORS  

Microsoft Academic Search

We present a method for the analysis of time series from drifting or switching dynamics. In extension to existing ap- proaches that identify switches or drifts between stationary dynam- ical modes, the method allows to analyze even continuously varying dynamics and can identify mixtures of more than two dynamical modes. The architecture is based on a mixture of self-organizing Nadaraya-Watson

Jens Kohlmorgen; Steven Lemm; Gunnar Ratsch; GMD FIRST

103

Analysis of nonstationary time series by mixtures of self-organizing predictors  

Microsoft Academic Search

Presents a method for the analysis of time series from drifting or switching dynamics. In an extension to existing approaches that identify switches or drifts between stationary dynamical modes, the method allows one to analyze even continuously varying dynamics and can identify mixtures of more than two dynamical modes. The architecture is based on a mixture of self-organizing Nadaraya-Watson kernel

Jens Kohlmorgen; Steven Lemm; Gunnar Rätsch; Klaus-robert Müller

2000-01-01

104

Inhibition of corrosion by a mixture of nonchromate pigments in organic coatings on galvanized steel  

Microsoft Academic Search

We consider several possible substitutes for toxic chromate pigments. Among the most promising compositions for the corrosion inhibition of galvanized steel with a protective organic coating, we should mention a mixture of phosphate- and calcium-containing pigments. As was shown earlier, such a mixture possesses a high efficiency under conditions of the corrosion of zinc and galvanized steel sheet; however, it

V. I. Pokhmurs’kyi; I. M. Zin’; S. B. Lyon

2004-01-01

105

Flash-point prediction for binary partially miscible aqueous–organic mixtures  

Microsoft Academic Search

Flash point is the most important variable used to characterize fire and explosion hazard of liquids. Herein, partially miscible mixtures are presented within the context of liquid–liquid extraction processes and heterogeneous distillation processes. This paper describes development of a model for predicting the flash point of binary partially miscible mixtures of aqueous–organic system. To confirm the predictive efficiency of the

Horng-Jang Liaw; Chien-Tsun Chen; Vincent Gerbaud

2008-01-01

106

Separation of organic mixtures by pervaporation using crosslinked rubber membranes  

Microsoft Academic Search

Natural rubber (NR) and poly(styrene-co-butadiene) rubber (SBR) has been crosslinked with sulfur and accelerator with three different doses of varied accelerator to sulfur ratios to obtain three crosslinked membranes from each of these two rubbers (NR-1, NR-2 and NR-3 and SBR-1, SBR-2 and SBR-3). These six rubber membranes were used for pervaporative separation of toluene–methanol mixture up to 10wt% of

S. Ray

2006-01-01

107

PROCEDURES FOR DERIVING EQUILIBRIUM PARTITIONING BENCHMARKS (ESBS) FOR THE PROTECTION OF BENTHIC ORGANISM: PAH MIXTURES  

EPA Science Inventory

This equilibrium partitioning sediment benchmark (ESB) document describes procedures to derive concentrations of PAH mixtures in sediment which are protective of the presence of benthic organisms. The equilibrium partitioning (EqP) approach was chosen because it accounts for t...

108

Imidazolium-organic solvent mixtures as electrolytes for lithium batteries  

Microsoft Academic Search

?-Butyrolactone (BL) has been mixed to the room temperature ionic liquid (RTIL) 1-butyl 3-methyl-imidazolium tetrafluoroborate (BMIBF4) (ratio: 3\\/2, v\\/v) in the presence of lithium tetrafluoroborate (LiBF4) for use as electrolyte in lithium-ion batteries. This mixture exhibits a larger thermal stability than the reference electrolyte EC\\/DEC\\/DMC (2\\/2\\/1)+LiPF6 (1M) and can be considered as a new RTIL as no free BL molecules

A. Chagnes; M. Diaw; B. Carré; P. Willmann; D. Lemordant

2005-01-01

109

Process for the heating and/or thermal conditioning of a building by means of a heat pump operated with a specific mixture of working fluids  

SciTech Connect

Buildings are advantageously heated or heat-conditioned with a heat pump operated with a non-azeotropic mixture consisting essentially of two working fluids, with the mixture comprising a major component of monochlorodifluoromethane and a minor component of trifluoromethane.

Ramet, C.; Rojey, A.

1985-02-12

110

Influence of multicomponent mass transfer on homogeneous azeotropic distillation  

Microsoft Academic Search

Residue-curve and distillation-line maps are useful tools for the design of azeotropic distillation sequences. The calculation of residue curves uses the assumption that the vapour and liquid are always in equilibrium. The computation of distillation lines assumes that the vapour and liquid leaving a tray are in equilibrium. In this work, the equations defining residue curves and distillation lines are

F. J. L. Castillo; G. P. Towler

1998-01-01

111

Experimental study of multiple steady states in homogeneous azeotropic distillation  

Microsoft Academic Search

Bekiaris et al. (1993) explained the existence of multiple steady states in homogeneous ternary azeotropic distillation, on the basis of the analysis of the case of infinite reflux and infinite column length (infinite number of trays). They showed that the predictions of multiple steady states for such infinite columns have relevant implications for columns of finite length operated at finite

T. E. Guettinger; Cornelius Dorn; Manfred Morari

1997-01-01

112

Optimal design and synthesis of homogeneous azeotropic distillation sequences  

Microsoft Academic Search

A systematic procedure for optimizing homogeneous azeotropic separation sequences has been developed. The procedure uses an explicit design technique which eliminates the need for recycle convergence schemes. The separation of ethanol from water using ethylene glycol as the entrainer is used to illustrate the optimization procedure. Comparisons are made with competing designs from the literature, illustrating the need to properly

Jennifer R. Knight; Michael F. Doherty

1989-01-01

113

SOLUBILITY, SORPTION AND TRANSPORT OF HYDROPHOBIC ORGANIC CHEMICALS IN COMPLEX MIXTURES  

EPA Science Inventory

The research summarized in this report focuses on the effects which organic cosolvents have on the sorption and mobility of organic contaminants. This work was initiated In an effort to improve our understanding of the environmental consequences associated with complex mixtur...

114

A simple hydrophobicity-based approach to predict the toxicity of unknown organic micropollutant mixtures in marine water  

Microsoft Academic Search

In this study, we propose a simple hydrophobicity-based approach to predict the toxicity of mixtures of marine organic micropollutants. Fifty mixtures were chosen, comprising individual chemicals randomly chosen from three halogenated benzenes, three phenols, two petroleum hydrocarbons, three polychlorinated biphenyls (PCBs), four organochlorine pesticides (OCPs) and two herbicides, with the intention of simulating the mixtures of organic micropollutants that may

Zhifen Lin; Ping Zhong; Xiaojun Niu; Kedong Yin; Hongxia Yu; Jianwei Du

2005-01-01

115

Energy efficient membrane processes for the separation of organic liquids: Part 1: Final report, September 28, 1982December 31, 1986  

Microsoft Academic Search

The potential usefulness of two membrane processes, namely, pervaporation and perstraction, for separating azeotropic mixtures of aromatic and aliphatic hydrocarbons was studied theoretically and experimentally. A third membrane process, osmotic phase-separation, was investigated experimentally. The separation of an azeotropic mixture of benzene and cyclohexane was used as an example. Part II of this report will discuss membrane processes for the

I. Cabasso; H. R. Acharya; E. Korngold; Z. Liu; S. A. Stern; W. Li; T. Makenzie; E. Poda

1987-01-01

116

Organic and conventional management of mixtures of wheat and spring cereals  

Microsoft Academic Search

Cereal mixtures may provide both organic and conventional producers with a more sustainable approach in reducing weed pressure,\\u000a crop rotation flexibility, improved yield stability, buffering against pests and diseases, minimizing soil variability and\\u000a increasing animal feed value. We examined the response of small grain mixtures containing wheat, oats, barley and triticale\\u000a to varying degrees of natural competition and environmental stress

A. H. E. E. Kaut; H. E. Mason; A. Navabi; J. T. O’Donovan; D. Spaner

2008-01-01

117

TiO 2-photocatalyzed oxidative degradation of binary mixtures of vaporized organic compounds  

Microsoft Academic Search

Rates of photocatalytic removal of the components for 14 binary mixtures of vaporized organic components over Degussa P-25 TiO2 at 360 nm in the presence of air were measured. In some cases, intermediate products were identified and their rates of removal measured. Seven binary mixtures were reacted in a static reactor: CH3OH strongly inhibited removal of CH2Cl2 while CH2Cl2 somewhat

N. N. Lichtin; M. Avudaithai; E. Berman; A. Grayfer

1996-01-01

118

Secondary organic aerosol formation from xylenes and mixtures of toluene and xylenes in an atmospheric urban hydrocarbon mixture: Water and particle seed effects (II)  

Microsoft Academic Search

Secondary organic aerosol (SOA) formation from the photooxidation of o-, p-xylene, and toluene with xylene mixtures was investigated in the UNC dual outdoor smog chambers. Experiments were performed with different initial background aerosol concentrations and levels of relative humidity (RH) in the environment of an eleven component mixture of non-SOA-forming dilute urban hydrocarbon mixture, oxides of nitrogen and sunlight. Post-nucleation

Yang Zhou; Haofei Zhang; Harshal M. Parikh; Eric H. Chen; Weruka Rattanavaraha; Elias P. Rosen; Wenxing Wang; Richard M. Kamens

2011-01-01

119

Flammability Limits of Fuel/Fluorocarbon Azeotropes.  

National Technical Information Service (NTIS)

Both Dehn and Thorne have intimated that flash point (FP) measurements could be used to define the gas-phase flammability limits of fire and retardant vapor mixtures above the surface of heated retardant containing flammable liquids. However, it was found...

N. J. Alvares P. R. Hammond K. Foote H. W. Ford

1981-01-01

120

ACTION CONCENTRATION FOR MIXTURES OF VOLATILE ORGANIC COMPOUNDS (VOC) & METHANE & HYDROGEN  

SciTech Connect

Waste containers may contain volatile organic compounds (VOCs), methane, hydrogen and possibly propane. These constituents may occur individually or in mixtures. Determining if a waste container contains a flammable concentration of flammable gases and vapors (from VOCs) is important to the safety of the handling, repackaging and shipping activities. This report provides the basis for determining the flammability of mixtures of flammable gases and vapors. The concentration of a mixture that is at the lowest flammability limit for that mixture is called the action concentration. The action concentration can be determined using total VOC concentrations or actual concentration of each individual VOC. The concentrations of hydrogen and methane are included with the total VOC or individual VOC concentration to determine the action concentration. Concentrations below this point are not flammable. Waste containers with gas/vapor concentrations at or above the action concentration are considered flammable.

MARUSICH, R.M.

2006-07-10

121

THERMODYNAMIC EVALUATION OF PREDICTED FLUORINATED ETHER, ETHANE, AND PROPANE AZEOTROPES  

EPA Science Inventory

The paper gives results of thermodynamic analyses, using basic thermophysical property data, to evaluate seven predicted fluorinated ether, ethane, and propane azeotropes: E125/RC270, E125/R134a, E143a/R134, R134a/E143a, E143a/ R152a, R134/R245cb, and R245cb/R227ea. he performanc...

122

Flammability limits of fuel/fluorocarbon azeotropes  

SciTech Connect

Both Dehn and Thorne have intimated that flash point (FP) measurements could be used to define the gas-phase flammability limits of fire and retardant vapor mixtures above the surface of heated retardant containing flammable liquids. However, it was found that ignitable mixtures exist above the liquid surface, where the concentration of the agent in the fluid is well beyond the limiting concentrating for inerting of alcohol fires. Clearly this anomaly results from diffusion competition of air and liquid vapor mixture at the position of the ignitor, as influenced by the design of the experimental apparatus. The authors are skeptical about the need or worth of attempting to define flammability limits using FP data, especially since unknown variables control the response. More important is to define the concentration of liquid phase retardant that will affect gas phase inerting. Thus, it is necessary to continue practical testing of retardant-containing liquids for their effectiveness in mitigating possible accidents, e.g., the next phase of this work will assess the effectiveness of halocarbons to inert high-pressure alcohol/agent leaks impinging on both electrical and flame ignition sources.

Alvares, N.J.; Hammond, P.R.; Foote, K.; Ford, H.W. Jr.

1981-02-10

123

Liquid-liquid phase separation in atmospheric aerosol particles: dependence on organic functionalities and mixture complexity  

NASA Astrophysics Data System (ADS)

In the troposphere, aerosol particles undergo phase transitions such as deliquescence and efflorescence during humidity cycles (Marcolli and Krieger, 2006). In addition, interactions between organic and inorganic compounds lead to liquid-liquid phase separation (LLPS) (Ciobanu et al., 2009). Recent studies on a limited number of model systems have shown that oxygen-to-carbon ratios (O:C) of the organic aerosol fraction might be a good predictor for LLPS in mixed organic/ammonium sulfate (AS) particles (Bertram et al., 2011; Song et al., 2011). However, in order to corroborate this hypothesis experiments with an organic fraction that consists of a higher number of components with different O:C ratios and functional groups are needed. In order to determine the influence of O:C ratio, the specific organic functionalities and the mixture complexity on LLPS, we subjected organic/AS particles deposited on a hydrophobically coated substrate to relative humidity (RH) cycles and observed phase changes using optical microscopy and micro-Raman spectroscopy. To determine the influence of mixture complexity, we mixed together up to 10 organic compounds. We also prepared mixtures that were rich in different types of functional groups like polyols, aromatics and dicarboxylic acids which were identified from field measurements. We screened for a miscibility gap by varying the organic-to-inorganic ratio from 2:1 to 1:6. AS in the investigated single particles effloresced at 27 - 50 %RH and deliquesced at 72 - 79 %RH during humidity cycles. The occurrence of LLPS is determined to a high degree by the O:C of the organics: there was no LLPS for mixtures with O:C > 0.8 and there was always LLPS for mixtures with O:C < 0.57. In the range in between, we observed a dependence on the specific functional groups: a high share of aromatic functionalities shifts the range of O:C for which LLPS occurs to lower values. A correlation was also found for the onset RH of LLPS as a function of O:C. We did not find any dependence of LLPS on the complexity of the mixture. Overall, the RH range of coexistence of two liquid phases depends in first place on the O:C ratio of the particles and in second place also on the specific organic functionalities.

Song, M.; Marcolli, C.; Krieger, U. K.; Zuend, A.; Peter, T.

2012-04-01

124

The Impact of Organic Aerosol Mixtures on Hygroscopicity: Comparison between Measurements and UNIFAC Model  

NASA Astrophysics Data System (ADS)

The presence of anthropogenic organic compounds in aerosols has the potential to contribute to global climate change by altering the hygroscopic behavior of cloud condensation nuclei. Dicarboxylic acids, including malonic, glutaric, and succinic acids, are among the more frequently measured water-soluble organic compounds in atmospheric aerosols. For solutions containing single or mixed inorganic species, aerosol water uptake has been most commonly modeled using the ZSR method. This approach has also been utilized for solutions containing mixtures of inorganics and organics. For solutions containing a single organic species, the UNIFAC or a modified UNIFAC model has been used, and the features it includes also allow it potentially to be utilized for mixtures. However, there is a dearth of experimental data involving the hygroscopic behavior of organic solution mixtures. In this study, water vapor pressure was measured at 12 C over aqueous bulk solutions containing dicarboxylic acids, using both a quadrupole mass spectrometer and a Baratron pressure transducer. The water uptake of malonic and glutaric acids showed good agreement with limited previous measurements reported in the literature that used an electrodynamic balance (EDB) or bulk solution method. Our experimental measurements of water uptake for malonic and glutaric acids also agreed to within 1% of the predictions using Peng's modified UNIFAC model (Environ. Sci. Technol, 35, 4495-4501, 2001). However, water vapor pressure measurements for solutions containing 50:50 molar mixtures of malonic and glutaric acids were not consistent with predictions using Peng's modified UNIFAC model for mixtures. In the modified UNIFAC model, this mixture of malonic/glutaric acids was predicted to fall roughly midway between the hygroscopicity of the two individual organics. In our measurements, malonic acid exerted the dominant influence in determining the overall water vapor pressure, so that the water uptake of the mixed solution closely followed that of malonic acid. This led to a greater water uptake than what was predicted by the modified UNIFAC model for mixtures. For mixtures of malonic and succinic acids, we added 0.3mol of succinic acid to 1, 3, and 5 mol/l of malonic acid solution. The modified UNIFAC model predicted an additional amount of water uptake due to addition of succinic acid that was essentially the same, regardless of the concentration of malonic acid. However, for our measurements, the influence of the succinic acid on water uptake was negligible for 1 and 3mol/l of malonic acid solutions. In contrast, the 5 mol/l malonic acid solution showed a significant increase in water uptake when 0.3mol of succinic acid was added.

Lee, J.; Hildemann, L.

2011-12-01

125

Molecular identification of organic compounds in atmospheric complex mixtures and relationship to atmospheric chemistry and sources.  

PubMed Central

This article describes a chemical characterization approach for complex organic compound mixtures associated with fine atmospheric particles of diameters less than 2.5 m (PM2.5). It relates molecular- and bulk-level chemical characteristics of the complex mixture to atmospheric chemistry and to emission sources. Overall, the analytical approach describes the organic complex mixtures in terms of a chemical mass balance (CMB). Here, the complex mixture is related to a bulk elemental measurement (total carbon) and is broken down systematically into functional groups and molecular compositions. The CMB and molecular-level information can be used to understand the sources of the atmospheric fine particles through conversion of chromatographic data and by incorporation into receptor-based CMB models. Once described and quantified within a mass balance framework, the chemical profiles for aerosol organic matter can be applied to existing air quality issues. Examples include understanding health effects of PM2.5 and defining and controlling key sources of anthropogenic fine particles. Overall, the organic aerosol compositional data provide chemical information needed for effective PM2.5 management.

Mazurek, Monica A

2002-01-01

126

PRENEOPLASTIC TRANSFORMATION OF RESPIRATORY EPITHELIAL CELLS BY COMPLEX ORGANIC MIXTURES IN A CLONAL ASSAY  

EPA Science Inventory

In the study complex organic mixtures that were extracts of particulate emissions from 3 heating sources were tested for the presence of agents that induce preneoplastic transformation of rat tracheal epithelial (RTE) cells in an in vitro clonal assay. The samples were derived fr...

127

Optical Properties of Fluorescent Mixtures: Comparing Quantum Dots to Organic Dyes  

ERIC Educational Resources Information Center

|The study describes and compares the size-dependent optical properties of organic dyes with those of semiconductor nanocrystals or quantum dots (QDs). The analysis shows that mixtures of QDs contain emission colors that are sum of the individual QD components.|

Hutchins, Benjamin M.; Morgan, Thomas T.; Ucak-Astarlioglu, Mine G.; Wlilliams, Mary Elizabeth

2007-01-01

128

MIXTURE EFFECTS IN THE CATALYTIC OXIDATION OF VOCS (VOLATILE ORGANIC COMPOUNDS) IN AIR  

EPA Science Inventory

The report gives results of a study of the deep oxidation of organic mixtures over a heterogeneous catalyst in an attempt to explain earlier observations concerning the apparent inhibition or enhancement of destruction of some components to establish a scientific basis for the de...

129

Sorption and Transport of Mixtures of Organic Molecules in Soils and Aquifers  

NASA Astrophysics Data System (ADS)

Van de Weerd et al (2002) uses a sorption and transport model to simulate sorption and transport of mixtures of natural organic molecules (NOM) in laboratory experiments and field experiments. The heterogeneity of the NOM mixture appeared to be very important and is included in the sorption model by varying the sorption affinity and capacity among the NOM fractions. Using this model a large amount of experimental observed phenomena like nonlinear kinetic adsorption/desorption, competitions between NOM fractions and apparent hysteresis of NOM sorption can be explained. Major results of the above research are presented together with the implication of these results for sorption and transport of organic compounds (e.g. organic micropollutants) in the presence of NOM. Besides mobilisation or immobilisation of organic compounds NOM may influence sorption and transport of organic compounds by blocking sorption sites or competition for the same sorption sites. (Reference: H. van de Weerd, A. Leijnse, and W.H. van Riemsdijk, 2002. Modelling transport of a mixture of natural organic molecules: effects of dynamic competitive sorption from particle to aquifer scale. Water Resour. Res. 38(8).)

van de Weerd, H.; Leijnse, A.; van Riemsdijk, W. H.

2003-04-01

130

Adsorption and desorption of mixtures of organic vapors on beaded activated carbon.  

PubMed

In this study, adsorption and desorption of mixtures of organic compounds commonly emitted from automotive painting operations were experimentally studied. A mixture of two alkanes and a mixture of eight organic compounds were adsorbed onto beaded activated carbon (BAC) and then thermally desorbed under nitrogen. Following both adsorption and regeneration, samples of the BAC were chemically extracted. Gas chromatography-mass spectrometry (GC-MS) was used to quantify the compounds in the adsorption and desorption gas streams and in the BAC extracts. In general, for both adsorbate mixtures, competitive adsorption resulted in displacing low boiling point compounds by high boiling point compounds during adsorption. In addition to boiling point, adsorbate structure and functionality affected adsorption dynamics. High boiling point compounds such as n-decane and 2,2-dimethylpropylbenzene were not completely desorbed after three hours regeneration at 288 °C indicating that these two compounds contributed to heel accumulation on the BAC. Additional compounds not present in the mixtures were detected in the extract of regenerated BAC possibly due to decomposition or other reactions during regeneration. Closure analysis based on breakthrough curves, solvent extraction of BAC and mass balance on the reactor provided consistent results of the amount of adsorbates on the BAC after adsorption and/or regeneration. PMID:22742925

Wang, Haiyan; Jahandar Lashaki, Masoud; Fayaz, Mohammadreza; Hashisho, Zaher; Philips, John H; Anderson, James E; Nichols, Mark

2012-07-16

131

Feasibility of separations for distillation of nonideal ternary mixtures  

Microsoft Academic Search

The product compositions in single-feed distillation columns can be specified only in certain regions of the composition space, which depend only on the pressure, feed, and vapor-liquid equilibrium for the mixture. In nonideal mixtures, even without azeotropes, the regions may allow unusual product distributions. For example, the distillate in a direct split is composed primarily of the lightest component. Intuition

Z. T. Fidkowski; M. F. Doherty; M. F. Malone

1993-01-01

132

Laboratory measurements of the oxidation kinetics of organic aerosol mixtures using a relative rate constants approach  

NASA Astrophysics Data System (ADS)

Organic aerosols in the atmosphere are exposed to oxidants, but the oxidation kinetics are largely unknown. We investigate the decay of organic species in laboratory-generated organic aerosols exposed to atmospherically relevant ozone concentrations in a smog chamber. The experiments were conducted using five different organic aerosols, varying in complexity from three to twelve components. These mixtures include alkenoic acids, alkanoic acids, alkanedioic acids, n-alkanes, and sterols and are designed to simulate meat cooking emissions. A relative rate constants approach was used to compare reaction rates of individual organic species and to compare the reaction rates of the aerosol species to gas phase tracers. Significant decay was observed for all species (except for the n-alkanes) in at least one of the experimental systems. By relating the decomposition of condensed phase alkenoic acids to gas phase alkenes, we show that the reaction rate constants of oleic acid and palmitoleic acid evolve as the aerosol is processed, decreasing by a factor of ˜10 over the course of a 4-hour experiment. The decay rate constants of cholesterol, oleic acid, and palmitic acid all depend strongly on aerosol composition, with more than an order of magnitude change in the effective rate constants depending on mixture composition. Effects of aerosol composition are likely to be even more significant in atmospheric aerosol, where particle compositions are highly variable. The data presented here indicate these mixture effects are complicated, making it difficult to extrapolate from simple laboratory systems to atmospherically relevant conditions.

Huff Hartz, Kara E.; Weitkamp, Emily A.; Sage, Amy M.; Donahue, Neil M.; Robinson, Allen L.

2007-02-01

133

Solubilities of polynuclear aromatic hydrocarbons in mixtures of common organic solvents  

SciTech Connect

The solubilities of naphthalene, acenaphthene, fluorene, and phenanthrene have been determined experimentally in five binary mixtures and one quaternary mixture of four common organic solvents (benzene, cyclohexane, thiophene, and pyridine) from 25/sup 0/C to the melting points of the solutes. The results have been correlated by using the classical equation for solid-liquid solubility and the experimental activity coefficients obtained have been compared to the values predicted by regular solution theory, extended regular solution theory, Wilson's equation, and UNIQUAC, after obtaining binary parameters from the solubility of each solute in the pure solvents.

Coon, J.E.; Troth, M.; Mc Laughlin, E.

1987-04-01

134

Acylceramide head group architecture affects lipid organization in synthetic ceramide mixtures.  

PubMed

The lipid organization in the upper layer of the skin, the stratum corneum (SC), is important for the skin barrier function. This lipid organization, including the characteristic 13 nm lamellar phase, can be reproduced in vitro with mixtures based on cholesterol, free fatty acids and natural as well as synthetic ceramides (CER). In human SC, nine CER classes have been identified (CER1-CER9). Detailed studies on the effect of molecular structure of individual ceramides on the SC lipid organization are only possible with synthetic lipid mixtures, as their composition can be accurately chosen and systematically modified. In the present study, small-angle X-ray diffraction was used to examine the organization in synthetic lipid mixtures of which the synthetic ceramide fraction was prepared with sphingosine-based CER1 or phytosphingosine-based CER9. The latter acylceramide contains an additional hydroxyl group at the sphingoid backbone. The results show that a gradual increase in CER1 level consistently promotes the formation of the 13 nm lamellar phase and that partial replacement of CER1 by CER9 does not affect the phase behavior. Interestingly, complete substitution of CER1 with CER9 reduces the formation of the long periodicity phase and results in phase separation of CER9. PMID:15482479

de Jager, Miranda; Gooris, Gert; Ponec, Maria; Bouwstra, Joke

2004-11-01

135

Synthesizing alternative sequences via a P-graph-based approach in azeotropic distillation systems  

Microsoft Academic Search

The present work proposes a P-graph based approach capable of systematically generating all combinatorially feasible alternative sequences for both continuous and batch azeotropic distillation systems when the feeds, products, and operating units and their concomitant intermediate materials are known. To facilitate synthesis, a highly effective method has been established to identify processing or operating units necessary for constructing azeotropic-distillation systems

Gangyi Feng; L. T. Fan; F. Friedler

2000-01-01

136

APSA: A new cape tool for design and troubleshooting of azeotropic distillation columns  

Microsoft Academic Search

The azeotrope pressure sensitivity analysis (APSA) provides a dependence of compositions and temperatures of azeotropes with respect to changes in pressure. This information can be of critical importance in the design and troubleshooting of real distillation columns, especially when there is a substantial pressure drop in the column. In some cases, this can lead to a switch in topology of

Stanislaw K. Wasylkiewicz

2004-01-01

137

Ceramic-supported polymer membranes for pervaporation of binary organic\\/organic mixtures  

Microsoft Academic Search

Asymmetric tubular alumina-supported poly(vinyl acetate) (PVAc) and poly(vinyl pyrrolidone) (PVP) membranes were created and characterized by pervaporation separation of binary mixtures of methanol and methyl tert-butyl ether (MTBE). The active separation layer was created by free-radical graft polymerization of PVAc and PVP onto a vinylsilane-modified alumina substrate with an average native pore diameter of 50Å. The separation layer consisted of

Wayne Yoshida; Yoram Cohen

2003-01-01

138

Methods of analysis for complex organic aerosol mixtures from urban emission sources of particulate carbon  

SciTech Connect

Extractable organic compounds having between 6 to 40 carbon atoms comprise an important mass fraction of the fine particulate matter samples from major urban emission sources. Depending on the emission source type, this solvent-soluble fraction accounts for <20% to 100% of the total organic aerosol mass, as measured by quantitative high-resolution has chromatography (HRGC) with flame ionization detection. In addition to total extract quantitation, HRGC can be applied to further analyses of the mass distributions of elutable organics present in the complex aerosol extract mixtures, thus generating profiles that serve as fingerprints'' for the sources of interest. This HRGC analytical method is applied to emission source samples that contain between 7 to 12,000 {mu}g/filter organic carbon. It is shown to be a sensitive technique for analysis of carbonaceous aerosol extract mixtures having diverse mass loadings and species distributions. This study describes the analytical chemical methods that have been applied to: the construction of chemical mass balances based on the mass of fine organic aerosol emitted for major urban sources of particulate carbon; and the generation of discrete emission source chemical profiles derived from chromatographic characteristics of the organic aerosol components. 21 refs., 1 fig., 2 tabs.

Mazurek, M.A. (Brookhaven National Lab., Upton, NY (USA)); Hildemann, L.M. (Stanford Univ., CA (USA). Dept. of Civil Engineering); Cass, G.R.; Rogge, W.F. (California Inst. of Tech., Pasadena, CA (USA). Dept. of Environmental Engineering Science); Simoneit, B.R.T. (Oregon State Univ., Corvallis, OR (USA). Coll. of Oceanography)

1990-04-01

139

Abatement of mixture of volatile organic compounds (VOCs) in a catalytic non-thermal plasma reactor.  

PubMed

Total oxidation of mixture of dilute volatile organic compounds was carried out in a dielectric barrier discharge reactor with various transition metal oxide catalysts integrated in-plasma. The experimental results indicated the best removal efficiencies in the presence of metal oxide catalysts, especially MnO(x), whose activity was further improved with AgO(x) deposition. It was confirmed water vapor improves the efficiency of the plasma reactor, probably due to the formation of hydroxyl species, whereas, in situ decomposition of ozone on the catalyst surface may lead to nascent oxygen. It may be concluded that non-thermal plasma approach is beneficial for the removal of mixture of volatile organic compounds than individual VOCs, probably due to the formation of reactive intermediates like aldehydes, peroxides, etc. PMID:22975253

Karuppiah, J; Reddy, E Linga; Reddy, P Manoj Kumar; Ramaraju, B; Karvembu, R; Subrahmanyam, Ch

2012-08-24

140

[Effects of mixture of 22 kinds of volatile organic compounds on human body at different temperature].  

PubMed

Ten healthy volunteers were exposed to mixture of 22 kinds of volatile organic compounds with concentrations of zero to 10 mg/m3 at the temperature of 18, 22 and 26 C, respectively in an artificial climate room for 60 minutes a day and six days week for two consecutive weeks to study their effects on human bodies. Results showed that quality of indoor air decreased significantly, odor intensity increased, number of the subjects who need more ventilation increased, and irritation to eyes, nose and skin intensified under the mixture concentration of 10 mg/m3 and at temperature of 26 degrees C. No significant changes in psychological tests, tear film stability and cytological studies were found. Room temperature at 26 degrees C has a significant synergetic effects on human health. Therefore, quality of indoor air can not be evaluated only by organic compounds polluted in air, but by meteorological conditions. PMID:9812622

Liu, Z; Molhave, L

1997-03-01

141

Assessment of time to pregnancy and spontaneous abortion status following occupational exposure to organic solvents mixture  

Microsoft Academic Search

Purpose  Due to increasing usage of chemicals in various industries, occupational exposure of women with these materials is unavoidable.\\u000a Nowadays, some studies indicate adverse effects of exposure to these chemicals, especially organic solvents on the reproductive\\u000a system of females. This study aimed to assess the relationship between spontaneous abortion and occupational exposure to organic\\u000a solvents mixture in pharmaceutical industry.\\u000a \\u000a \\u000a \\u000a \\u000a Methods  This study

Mir Saeed Attarchi; Monir Ashouri; Yasser Labbafinejad; Saber Mohammadi

142

Laboratory appraisal of organic carbon changes in mixtures made with different inorganic wastes.  

PubMed

Mixtures of organic and inorganic wastes were incubated to examine the changes in organic C (OC) contents. An anaerobic sludge and a CaO-treated aerobic sludge, with OC concentrations of 235 and 129 gkg(-1), were used. The inorganic wastes used - referred to as "conditioners" - were shot blasting scrap, fettling, Linz-Donawitz slag, foundry sand (FS), and fly ash from wood bark combustion (FA). The total OC (TOC) and KMnO(4)(-) oxidized OC were determined. DTA-TGA profiles and FTIR spectra were also obtained. Mixtures made with the FS contained significantly lower (P<0.05) amounts of TOC (45 gkg(-1)) than the rest of mixtures, which was attributed to the non-existence of reactive surfaces in the conditioner and the increased aeration induced by this material. Those made with FA contained significantly higher (P<0.05) amounts of TOC (170 gkg(-1)), which was attributed to: (i) the addition of an extra source of C - black carbon (BC) - in the FA, and (ii) the inhibition of mineralization from the compounds present in this conditioner (e.g., amorphous aluminosilicates, BC). The results highlight the importance of the characteristics of the conditioners on the fate of the OM originating from the sludges. PMID:19632821

Arbestain, M Camps; Ibargoitia, M L; Madinabeitia, Z; Gil, M V; Virgel, S; Morán, A; Pereira, R Calvelo; Macías, F

2009-07-25

143

Technical Note: Dissolved organic matter fluorescence - a finite mixture approach to deconvolve excitation-emission matrices  

NASA Astrophysics Data System (ADS)

The analysis of the shape of excitation-emission matrices (EEMs) is a relevant tool for exploring the origin, transport and fate of dissolved organic matter (DOM) in aquatic ecosystems. Within this context, the decomposition of EEMs is acquiring a notable relevance. A simple mathematical algorithm that automatically deconvolves individual EEMs is described, creating new possibilities for the comparison of DOM fluorescence properties and EEMs that are very different from each other. A mixture model approach is adopted to decompose complex surfaces into sub-peaks. The laplacian operator and the Nelder-Mead optimisation algorithm are implemented to individuate and automatically locate potential peaks in the EEM landscape. The EEMs of a simple artificial mixture of fluorophores and DOM samples collected in a Mediterranean river are used to describe the model application and to illustrate a strategy that optimises the search for the optimal output.

Butturini, A.; Ejarque, E.

2013-09-01

144

Organic biowastes blend selection for composting industrial eggshell by-product: experimental and statistical mixture design.  

PubMed

Composting is one of the technologies recommended for pre-treating industrial eggshells (ES) before its application in soils, for calcium recycling. However, due to the high inorganic content of ES, a mixture of biodegradable materials is required to assure a successful procedure. In this study, an adequate organic blend composition containing potato peel (PP), grass clippings (GC) and wheat straw (WS) was determined by applying the simplex-centroid mixture design method to achieve a desired moisture content, carbon: nitrogen ratio and free air space for effective composting of ES. A blend of 56% PP, 37% GC and 7% WS was selected and tested in a self heating reactor, where 10% (w/w) of ES was incorporated. After 29 days of reactor operation, a dry matter reduction of 46% was achieved and thermophilic temperatures were maintained during 15 days, indicating that the blend selected by statistical approach was adequate for composting of ES. PMID:22592462

Soares, Micaela A R; Andrade, Sandra R; Martins, Rui C; Quina, Margarida J; Quinta-Ferreira, Rosa M

2012-01-01

145

Characterization of organic matter degradation during composting of manure-straw mixtures spiked with tetracyclines.  

PubMed

The objective of this study was to investigate humification and mineralization of manure-straw mixtures contaminated by tetracyclines during composting. Hen manure, pig manure and rice straw were used as the raw materials. The manure-straw mixtures were spiked with tetracycline, chlortetracycline, and oxytetracycline at the concentration of 60 mg/kg dry matter. The results show that tetracyclines had no obvious influence on the composting process and more than 93% of the tetracyclines was decreased during a 45-day composting. The Fourier transform infrared (FTIR) spectra indicated that easily biodegradable components such as aliphatic substrates, carbohydrates and polysaccharides were decomposed and the contents of aromatic components relatively rose during the composting. The X-ray diffraction (XRD) spectra confirmed the natural formation of struvite, the degradation of easily biodegradable components, and the mineralization of organic matter during the composting. Therefore, FTIR and XRD analysis can be useful tools for monitoring the composting process. PMID:21620695

Hu, Zhenhu; Liu, Yuanlu; Chen, Guowei; Gui, Xianyang; Chen, Tianhu; Zhan, Xinmin

2011-05-07

146

Estimation of rat blood:air partition coefficients of volatile organic chemicals using reconstituted mixtures of blood components  

Microsoft Academic Search

The objective of the present study was to estimate the rat blood:air partition coefficients (PC) of some volatile organic chemicals (VOCs) using reconstituted mixtures of blood components. Based on previous observations, three blood components (water, lipid, hemoglobin) should be necessary in the case of lipophilic VOCs (e.g. bromoform (BF), chlorobenzene (CB) chloroform (CF), and ethylbenzene (EB)) whereas a mixture of

Martin Béliveau; Kannan Krishnan

2000-01-01

147

Hybrid organic–inorganic phenyl stationary phases for the gas separation of organic binary mixtures  

Microsoft Academic Search

Organic–inorganic hybrid silica xerogels are versatile materials that can be used in the separation\\/purification of gases and vapours. In the present study, hybrid xerogels were synthesised at pH 10 using phenyltriethoxysilane (PhTEOS) and tetraethoxysilane (TEOS) as silica precursors with 20, 40 and 70% PhTEOS molar ratios. The xerogels were characterised by helium pycnometry, FTIR, TGA–DSC, N2 (77K) and CO2 (273K)

Paula Moriones; Xabier Ríos; Jesús C. Echeverría; Julián J. Garrido; João Pires; Moisés Pinto

2011-01-01

148

PROCEDURES FOR THE DERIVATION OF EQUILIBRIUM PARTITIONING SEDIMENT BENCHMARKS (ESBS) FOR THE PROTECTION OF BENTHIC ORGANISMS: PAH MIXTURES  

EPA Science Inventory

This equilibrium partitioning sediment benchmark (ESB) document describes procedures to derive concentrations of PAH mixtures in sediment which are protective of the presence of benthic organisms. The equilibrium partitioning (EqP) approach was chosen because it accounts for the ...

149

PROCEDURES FOR THE DERIVATION OF EQUILIBRIUM PARTITIONING SEDIMENT BENCHMARKS (ESBS) FOR THE PROTECTION OF BENTHIC ORGANISMS: METALS MIXTURES  

EPA Science Inventory

This equilibrium partitioning sediment benchmark (ESB) document describes procedures to derive concentrations of metal mixtures in sediment which are protective of the presence of benthic organisms. The equilibrium partitioning (EqP) approach was chosen because it accounts for th...

150

Prediction of excess molar volumes of binary mixtures of organic compounds from refractive indices  

Microsoft Academic Search

The excess molar volumes of 51 binary mixtures containing diverse groups of organic compounds: alcohols (methanol, ethanol,\\u000a propan-1-ol, butan-1-ol, pentan-1-ol, hexan-1-ol, and heptan-1-ol), (cyclo-) alkanes (hexane, heptane, octane, nonane, decane,\\u000a undecane, dodecane, and cyclohexane), esters (diethyl carbonate and ethyl chloroacetate), aromatics (o-xylene, m-xylene, p-xylene, and ethylbenzene), ketones (acetone), and ethers (anisole), were predicted from the refractive index data, using\\u000a three

Ivona R. Radovi?; Mirjana Lj. Kijev?anin; Marijan Z. Gabrijel; Slobodan P. Šerbanovi?; Bojan D. Djordjevi?

2008-01-01

151

Formation of secondary organic aerosol from irradiated ?-pinene\\/toluene\\/NOx mixtures and the effect of isoprene and sulfur dioxide  

Microsoft Academic Search

Secondary organic aerosol (SOA) was generated by irradiating a series of ?-pinene\\/toluene\\/NOx mixtures in the absence and presence of isoprene or sulfur dioxide. The purpose of the experiment was to evaluate the extent to which chemical perturbations to this base-case (?-pinene\\/toluene) mixture led to changes in the gas-phase chemistry which strongly influences mass and composition of SOA and secondary organic

Mohammed Jaoui; Edward O. Edney; Tadeusz E. Kleindienst; Michael Lewandowski; John H. Offenberg; Jason D. Surratt; John H. Seinfeld

2008-01-01

152

Effect of dissolved inorganic salts on the isothermal vapor–liquid equilibrium of the propionic acid–water mixture  

Microsoft Academic Search

Propionic acid–water is one of the minimum boiling point azeotropic binary mixtures. Alteration of the vapor–liquid equilibrium (VLE) by addition of inorganic salts is of interest, since it allows bypassing the azeotropic point due to salt-in and salt-out effects. The effect of NaCl, NH4Cl, CaCl2, and AlCl3 at salt concentrations of 1 m and the effect of NaCl molality (0.5–3

Fawzi Banat; Sameer Al-Asheh; Jana Simandl

2002-01-01

153

Azeotropic distillation in a middle vessel batch column. 1: Model formulation and linear separation boundaries  

SciTech Connect

A mathematical model for the middle vessel batch distillation column (MVC) is developed using the concept of warped time analysis and used to study the qualitative dynamics of the MVC when it is used to separate multicomponent azeotropic mixtures. A limiting analysis is then developed for a MVC with an infinite number of trays, operated under infinite reflux/reboil ratios, under the assumption of linear separation boundaries. It is determined that, under limiting conditions, the distillate product drawn from the MVC is given by the {alpha} limit set of the MVC still pot composition, while the bottoms product drawn from the MVC is given by the {omega} limit set of the MVC still pot composition. The net product composition is determined by taking a convex combination of the two products. The notions of steering the still pot composition, the vector cone of possible motion for the still pot composition, and the equivalency of the MVC to the combined operation of a batch rectifier and a stripper are also explored. The definition of batch distillation regions for the MVC operated at a given value of the middle vessel parameter {lambda}, and the bifurcation of these regions with the variation of {lambda}, are investigated. Lastly, a mathematical model incorporating the concept of warped time is developed for a multivessel column. The MVC can be viewed as a specific case of the multivessel column.

Cheong, W.; Barton, P.I. [Massachusetts Inst. of Tech., Cambridge, MA (United States)

1999-04-01

154

Characterization of secondary organic aerosol generated from ozonolysis of ?-pinene mixtures  

NASA Astrophysics Data System (ADS)

In the atmosphere, multiple volatile organic compounds (VOCs) co-exist, and they can be oxidized concurrently and generate secondary organic aerosol (SOA). In this work, SOA is formed by the oxidation (in presence of excess ozone) of mixtures containing ?-pinene and other VOCs. The VOC mixtures were made so their composition approached a commercially-available ?-pinene-based essential oil, Siberian fir needle oil. The SOA products were sampled using filters, solvent extracted and analyzed by gas chromatography/mass spectrometry with trimethylsilyl derivatization. The individual product yields for SOA generated from ?-pinene changed upon the addition of other VOCs. An increase in concentration of non-reactive VOCs (bornyl acetate, camphene, and borneol) lead to a decrease in individual product yields of characteristic ?-pinene SOA products. Although these experiments were carried out under higher VOC and ozone concentrations in comparison to the atmosphere, this work suggests that the role of non-reactive VOCs should be explored in SOA products formation.

Amin, Hardik S.; Hatfield, Meagan L.; Huff Hartz, Kara E.

2013-03-01

155

Natural Mixtures of Persistent Organic Pollutants (POP) Increase Weight Gain, Advance Puberty, and Induce Changes in Gene Expression Associated with Steroid Hormones and Obesity in Female Zebrafish  

Microsoft Academic Search

In the present study, developmental and reproductive effects of lifelong exposure to environmental relevant concentrations of two natural mixtures of persistent organic pollutants (POP) were investigated using classical and molecular methods in a controlled zebrafish model. The mixtures used were extracted from burbot (Lota lota) liver originating from freshwater systems in Norway: one mixture with high levels and one mixture

Jan L. Lyche; Rasoul Nourizadeh-Lillabadi; Camilla Almaas; Benedicte Stavik; Vidar Berg; Janneche Utne Skåre; Peter Alestrøm; Erik Ropstad

2010-01-01

156

Secondary organic aerosol formation from xylenes and mixtures of toluene and xylenes in an atmospheric urban hydrocarbon mixture: Water and particle seed effects (II)  

NASA Astrophysics Data System (ADS)

Secondary organic aerosol (SOA) formation from the photooxidation of o-, p-xylene, and toluene with xylene mixtures was investigated in the UNC dual outdoor smog chambers. Experiments were performed with different initial background aerosol concentrations and levels of relative humidity (RH) in the environment of an eleven component mixture of non-SOA-forming dilute urban hydrocarbon mixture, oxides of nitrogen and sunlight. Post-nucleation was observed in most of the experiments in the 14-20 nm range except under the conditions with high background aerosol (>5 ?g m-3) and with low o-xylene concentrations (<0.092 ppmv). The SOA yields of o-xylene varied from 0.8% to 6.5% depending on the RH and initial seed concentrations. p-Xylene had a lower SOA yield compared with o-xylene and the yields in experiments with toluene and xylene mixtures ranged from 1.1% to 10.3%. SOA yield was found to be positively correlated with the particle water (H2Op) content. A new condensed aromatic kinetic mechanism employing uptake of organics in H2Op as a key parameter was applied to all the experiments and the simulations showed reasonable fits to the observed data.

Zhou, Yang; Zhang, Haofei; Parikh, Harshal M.; Chen, Eric H.; Rattanavaraha, Weruka; Rosen, Elias P.; Wang, Wenxing; Kamens, Richard M.

2011-07-01

157

Concentration-Thermal Swing Adsorption Process for Separation of Bulk Liquid Mixtures  

Microsoft Academic Search

A novel concentration-thermal swing adsorption process is described for separation of bulk binary liquid mixtures. The process is designed to produce essentially two pure products with high recoveries of both components. It is particularly suited for separation of azeotropic or close-boiling liquid mixtures which are difficult to separate by distillation. An example of the performance of the new process for

M. B. Rao; S. Sircar

1993-01-01

158

IUPAC-NIST Solubility Data Series. 99. Solubility of Benzoic Acid and Substituted Benzoic Acids in Both Neat Organic Solvents and Organic Solvent Mixtures  

NASA Astrophysics Data System (ADS)

Solubility data are compiled and reviewed for benzoic acid and 63 substituted benzoic acids dissolved in neat organic solvents and well-defined binary and ternary organic solvent mixtures. The compiled solubility data were retrieved from the published chemical and pharmaceutical literature covering the period from 1900 to the beginning of 2013.

Acree, William E.

2013-09-01

159

Persistence and Potential Effects of Complex Organic Contaminant Mixtures in Wastewater-Impacted Streams.  

PubMed

Natural and synthetic organic contaminants in municipal wastewater treatment plant (WWTP) effluents can cause ecosystem impacts, raising concerns about their persistence in receiving streams. In this study, Lagrangian sampling, in which the same approximate parcel of water is tracked as it moves downstream, was conducted at Boulder Creek, Colorado and Fourmile Creek, Iowa to determine in-stream transport and attenuation of organic contaminants discharged from two secondary WWTPs. Similar stream reaches were evaluated, and samples were collected at multiple sites during summer and spring hydrologic conditions. Travel times to the most downstream (7.4 km) site in Boulder Creek were 6.2 h during the summer and 9.3 h during the spring, and to the Fourmile Creek 8.4 km downstream site times were 18 and 8.8 h, respectively. Discharge was measured at each site, and integrated composite samples were collected and analyzed for >200 organic contaminants including metal complexing agents, nonionic surfactant degradates, personal care products, pharmaceuticals, steroidal hormones, and pesticides. The highest concentration (>100 ?g L(-1)) compounds detected in both WWTP effluents were ethylenediaminetetraacetic acid and 4-nonylphenolethoxycarboxylate oligomers, both of which persisted for at least 7 km downstream from the WWTPs. Concentrations of pharmaceuticals were lower (<1 ?g L(-1)), and several compounds, including carbamazepine and sulfamethoxazole, were detected throughout the study reaches. After accounting for in-stream dilution, a complex mixture of contaminants showed little attenuation and was persistent in the receiving streams at concentrations with potential ecosystem implications. PMID:23398602

Barber, Larry B; Keefe, Steffanie H; Brown, Greg K; Furlong, Edward T; Gray, James L; Kolpin, Dana W; Meyer, Michael T; Sandstrom, Mark W; Zaugg, Steven D

2013-02-11

160

Technical Note: Dissolved organic matter fluorescence - a finite mixture approach to deconvolve excitation-emission matrices  

NASA Astrophysics Data System (ADS)

The analysis of the shape of excitation-emission matrices (EEMs) is a relevant tool for exploring the origin, transport and fate of dissolved organic matter (DOM) in aquatic ecosystems. Within this context, the decomposition of EEMs is acquiring a notable relevance. A simple mathematical algorithm that automatically deconvolves single EEM is described, creating new possibilities for the comparison of DOM fluorescence properties and EEMs that are very different from each other. A mixture model approach is adopted to decompose complex surfaces into sub-peaks. The laplacian operator and the Nelder-Mead optimization algorithm are implemented to individuate and automatically locate potential peaks in the EEM landscape. A small heterogeneous data set of 21 EEMs from a human-impacted Mediterranean river is used to describe the model application and to illustrate a strategy that optimises the search for the optimal output.

Butturini, A.; Ejarque, E.

2013-03-01

161

Molecular simulation of carbon dioxide/methane/hydrogen mixture adsorption in metal-organic frameworks.  

PubMed

This work performs a systematic computational study toward a molecular understanding of the separation characteristics of metal-organic frameworks (MOFs), for which the purification of synthetic gas by two representative MOFs, MOF-5 and Cu-BTC, is adopted as an example. The simulations show that both geometry and pore size affect largely the separation efficiency, complex selectivity behaviors with different steps can occur in MOFs, and the electrostatic interactions that exist can enhance greatly the separation efficiency of gas mixtures composed of components with different chemistries. Furthermore, the macroscopic separation behaviors of the MOF materials are elucidated at a molecular level to give insight into the underlying mechanisms. The findings as well as the molecular-level elucidations provide useful microscopic information toward a complete understanding of the separation characteristics of MOFs that may lead to general design strategies for synthesizing new MOFs with tailored properties, as well as guiding their practical applications. PMID:16956262

Yang, Qingyuan; Zhong, Chongli

2006-09-14

162

Extraction of betulin, trimyristin, eugenol and carnosic acid using water-organic solvent mixtures.  

PubMed

A solvent system consisting of ethyl acetate, ethyl alcohol and water, in the volume ratio of 4.5:4.5:1, was developed and used to extract, at room temperature, betulin from white birch bark and antioxidants from spices (rosemary, thyme, sage, and oregano) and white oak chips. In addition, under reflux conditions, trimyristin was extracted from nutmeg using the same solvent system, and eugenol from olives was extracted using a mixture of salt water and ethyl acetate. The protocol demonstrates the use of water in organic solvents to extract natural products from plants. Measurement of the free-radical scavenging activity using by 2,2-diphenyl-1-picrylhydrazyl (DPPH) indicated that the extraction of plant material using ethyl acetate, ethyl alcohol and water (4.5:4.5:1, v/v/v) was exhaustive when carried out at room temperature for 96 h. PMID:22864237

Lugemwa, Fulgentius N

2012-08-03

163

Atmospheric pressure photoionization proton transfer for complex organic mixtures investigated by fourier transform ion cyclotron resonance mass spectrometry  

Microsoft Academic Search

To further clarify the role of dopant solvent in proton transfer in atmospheric pressure photoionization (APPI), we employ\\u000a ultrahigh-resolution FT-ICR mass analysis to identify M+•, [M+H]+, [M-H]?, and [M+D]+ species in toluene or perdeuterotoluene for an equimolar mixture of five pyrrolic and pyridinic nitrogen heterocyclic model\\u000a compounds, as well as for a complex organic mixture (Canadian Athabasca bitumen middle distillate).

Jeremiah M. Purcell; Christopher L. Hendrickson; Ryan P. Rodgers; Alan G. Marshall

2007-01-01

164

Aqueous solubilities and octanol-water partition coefficients of binary liquid mixtures of organic compounds at 25°C  

Microsoft Academic Search

From thermodynamics and certain assumptions it is shown that, under the usual experimental conditions, the octanol-water partition coefficient (Ko\\/w) of a given organic liquid should be the same whether the substance is partitioned neat or as part of a mixture. Measurements of several mixtures of n-propylbenzene (log Ko\\/w=3.71±0.04)+ethylbenzene (log Ko\\/w=3.16±0.01) clearly confirm this. It is also shown that the aqueous

Y. B. Tewari; D. E. Martire; S. P. Wasik; M. M. Miller

1982-01-01

165

Determination of single photon ionization cross sections for quantitative analysis of complex organic mixtures.  

PubMed

Soft single photon ionization (SPI)-time-of-flight mass spectrometry (TOFMS) is well suited for fast and comprehensive analysis of complex organic gas mixtures, which has been demonstrated in various applications. This work describes a calibration scheme for SPI, which enables quantification of a large number of compounds by only calibrating one compound of choice, in this case benzene. Photoionization cross sections of 22 substances were determined and related to the yield of benzene. These substances included six alkanes (pentane, hexane, heptane, octane, nonane, decane), three alkenes (propene, butane, pentene), two alkynes (propyne, butyne), two dienes (butadiene, isoprene), five monoaromatic species (benzene, toluene, xylene, styrene, monochlorobenzene) and NO. The cross sections of organic compounds differ by about one order of magnitude but the photoionization properties of compounds belonging to one compound class are rather similar. Therefore, the scheme can also be used for an approximate quantification of compound classes. This is demonstrated by a fast characterization and pattern recognition of two gasoline samples with different origins (Germany and South Africa) and a diesel sample (Germany). The on-line capability of the technique and the scheme is demonstrated by quantitatively monitoring and comparing the cold engine start of four vehicles: a gasoline passenger car, a diesel van, a motorbike and a two-stroke scooter. PMID:17874081

Adam, Thomas; Zimmermann, Ralf

2007-09-14

166

A neurological evaluation of workers exposed to mixtures of organic solvents.  

PubMed Central

Workers with long term exposure to mixtures of organic solvents below regulatory limits have been reported to experience mild, but clinically detectable, sensory or sensorimotor polyneuropathies. In conjuction with a cross sectional study of behavioural performance a clinical neurological evaluation was conducted among printers and spray painters to examine dose response relations. All 240 subjects completed an occupational history and symptom questionnaire and underwent a clinical neurological examination. On average, subjects had been employed on their current job for six years. Classification of solvent exposure for each subject was based on exposed versus non-exposed job titles and observations during an industrial hygiene walk-through or on the measured concentration of solvents in full shift personal air samples. The average full shift solvent concentration was 302 ppm for printing plant workers and 6-13 ppm for workers at other plants. Isopropanol and hexane were the major constituents. Neurological abnormalities consistent with mild polyneuropathy were found in 16% of subjects; none was clinically significant. Exposed/non-exposed comparisons showed slightly higher frequency of symptoms in the exposed subjects which was not related to solvent level. Subjects categorised as exposed during the walk- through survey also had poorer vibratory sensation measured at the foot and diminished ankle reflexes. In multiple linear regression models, however, controlling for age, sex, alcohol intake, and examiner, no significant (p less than 0.05) relation was found between solvent concentration and poor neurological function except for two point discrimination measured at the foot. This investigation has not provided evidence for dose related adverse neurological effects from exposure to moderately low levels of solvent mixtures for a relatively short duration, although this may be due to the shortness of exposure duration, the type of solvent exposure, or to selection factors.

Maizlish, N A; Fine, L J; Albers, J W; Whitehead, L; Langolf, G D

1987-01-01

167

Health Effects of a Mixture of Indoor Air Volatile Organics, Their Ozone Oxidation Products, and Stress  

PubMed Central

In our present study we tested the health effects among women of controlled exposures to volatile organic compounds (VOCs), with and without ozone (O3), and psychological stress. Each subject was exposed to the following three conditions at 1-week intervals (within-subject factor): VOCs (26 mg/m3), VOCs + O3 (26 mg/m3 + 40 ppb), and ambient air with a 1-min spike of VOCs (2.5 mg/m3). As a between-subjects factor, half the subjects were randomly assigned to perform a stressor. Subjects were 130 healthy women (mean age, 27.2 years; mean education, 15.2 years). Health effects measured before, during, and after each 140-min exposure included symptoms, neurobehavioral performance, salivary cortisol, and lung function. Mixing VOCs with O3 was shown to produce irritating compounds including aldehydes, hydrogen peroxide, organic acids, secondary organic aerosols, and ultrafine particles (particulate matter with aerodynamic diameter < 0.1 ?m). Exposure to VOCs with and without O3 did not result in significant subjective or objective health effects. Psychological stress significantly increased salivary cortisol and symptoms of anxiety regardless of exposure condition. Neither lung function nor neurobehavioral performance was compromised by exposure to VOCs or VOCs + O3. Although numerous epidemiologic studies suggest that symptoms are significantly increased among workers in buildings with poor ventilation and mixtures of VOCs, our acute exposure study was not consistent with these epidemiologic findings. Stress appears to be a more significant factor than chemical exposures in affecting some of the health end points measured in our present study.

Fiedler, Nancy; Laumbach, Robert; Kelly-McNeil, Kathie; Lioy, Paul; Fan, Zhi-Hua; Zhang, Junfeng; Ottenweller, John; Ohman-Strickland, Pamela; Kipen, Howard

2005-01-01

168

Properties of organic-water mixtures. 11. Self-diffusion coefficients of Na\\/sup +\\/ in polyethylene glycol-water mixtures at 25°C  

Microsoft Academic Search

Self-diffusion coefficients, D, of Na\\/sup +\\/ (NaCl, m = 0.1) were measured by the radiometric porous frit method for water mixtures of polyethylene glycol (PEG, molecular weight ca. 20,000) at 25°C. As the organic fraction of the solution increases, D decreases from 1.28 x 10⁻⁵ cm²\\/s in water to 0.15 x 10⁻⁵ cm²\\/s in 48 vol percent PEG. The diffusion

H. O. Phillips; A. E. Marcinkowsky; S. B. Sachs; K. A. Kraus

1977-01-01

169

IUPAC-NIST Solubility Data Series. 98. Solubility of Polycyclic Aromatic Hydrocarbons in Pure and Organic Solvent Mixtures: Revised and Updated. Part 2. Ternary Solvent Mixtures  

NASA Astrophysics Data System (ADS)

This work updates Vols. 54, 58, and 59 in the IUPAC Solubility Data Series and presents solubility data for polycyclic aromatic hydrocarbon solutes dissolved in ternary organic solvent mixtures. Published solubility data for anthracene, phenanthrene, and pyrene that appeared in the primary literature between 1995 to the end of 2011 are compiled and critically evaluated. Experimental solubility data for 119 different solute-ternary solvent systems are included in the volume. Solubility data published prior to 1995 were contained in three earlier volumes (Vols. 54, 58, and 59) and are not repeated here.

Acree, William E.

2013-03-01

170

IUPAC-NIST Solubility Data Series. 98. Solubility of Polycyclic Aromatic Hydrocarbons in Pure and Organic Solvent Mixtures: Revised and Updated. Part 1. Binary Solvent Mixtures  

NASA Astrophysics Data System (ADS)

This work updates Vols. 54, 58, and 59 in the IUPAC Solubility Data Series and presents solubility data for polycyclic aromatic hydrocarbon solutes dissolved in binary organic solvent mixtures. Published solubility data for anthracene, naphthalene, phenanthrene, phenothiazine, and pyrene that appeared in the primary literature between 1995 to the end of 2011 are compiled and critically evaluated. Experimental solubility data for 360 different solute-binary solvent systems are included in the volume. Solubility data published prior to 1995 were contained in three earlier volumes (Vols. 54, 58, and 59) and are not repeated in this volume.

Acree, William E.

2013-03-01

171

A COMPARISON OF THE LETHAL AND SUBLETHAL TOXICITY OF ORGANIC CHEMICAL MIXTURES TO THE FATHEAD MINNOW (PIMEPHALES PROMELAS)  

EPA Science Inventory

The joint toxic effects of known binary and multiple organic chemical mixtures to the fathead minnow (Pimephales promelas) were defined at both the 96-h 50% lethal effect concentration (LC50) and sublethal (32-d growth) response levels for toxicants with a narcosis I, narcosis II...

172

Age-Dependent Partition Coefficients for a Mixture of Volatile Organic Solvents in Sprague-Dawley Rats and Humans  

Microsoft Academic Search

The absorption, distribution, metabolism, and excretion of volatile organic compounds (VOCs) are critically determined by a few chemical-specific factors, notably their blood and tissue partition coefficients (PC) and metabolism. Age-specific values for PCs in rats have rarely been reported or utilized in pharmacokinetic modeling for predicting dosimetry in toxicity studies with rats progressing through their lifestages. A mixture of six

Deirdre A. Mahle; Jeffery M. Gearhart; Claude C. Grigsby; David R. Mattie; Hugh A. Barton; John C. Lipscomb; Robert S. Cook

2007-01-01

173

Accumulation and Effects of Natural Mixtures of Persistent Organic Pollutants (POP) in Zebrafish after Two Generations of Exposure  

Microsoft Academic Search

Effects of exposure to environmentally realistic mixtures of persistent organic pollutants (POP) harvested from aquatic ecosystems in Norway were studied in an in vivo zebrafish model. POP were extracted from burbot (Lota lota) liver from two separate lakes, Lake Losna and Lake Mjøsa, and exposed to zebrafish through the diet in a two-generation study. Effects on survival, growth, sex ratio,

Vidar Berg; Jan L. Lyche; Camilla Karlsson; Benedicte Stavik; Rasoul Nourizadeh-Lillabadi; Nina Hårdnes; Janneche Utne Skaare; Peter Alestrøm; Elisabeth Lie; Erik Ropstad

2011-01-01

174

Synthesis of Organic Compounds from Mixtures of Methane with Carbon Dioxide in Dielectric-Barrier Discharges at Atmospheric Pressure  

Microsoft Academic Search

The entire range of gas phase reaction products, depending on the composition of initial binary mixtures of methane and carbon dioxide in dielectric barrier discharges, has been determined (saturated as well as unsaturated hydrocarbons and oxygenated organic compounds). The macro-kinetics of the basic chemical pathways of the system under consideration has been investigated. This system is found to display a

K. V. Kozlov; P. Michel; H.-E. Wagner

2000-01-01

175

Removal of four kinds of volatile organic compounds mixture in air using silent discharge reactor driven by bipolar pulsed power  

Microsoft Academic Search

A silent discharge reactor initiated by bipolar pulsed power substituting the traditional ac power was used to remove the volatile organic compounds (VOCs) mixture of acetone, benzene, tetrachloroethylene and m-xylene. The results indicated that the silent discharge driven by bipolar pulsed power could effectively input pulsed energy, produce strong instant discharge and energetic particles, and thus enhance the removal efficiency

Hongchang Wang; Duan Li; Yan Wu; Jie Li; Guofeng Li

2009-01-01

176

COMPARISON OF SORPTION ENERGTICS FOR HYDROPHOBIC ORGANIC CHEMICALS BY SYNTHETIC AND NATURAL SORBENTS FROM METHANOL/WATER SOLVENT MIXTURES  

EPA Science Inventory

Reversed-phase liquid chromatography (RPLC) was used to investigate the thermodynamics and mechanisms of hydrophobic organic chemical (HOC) retention from methanol/water solvent mixtures. The enthalpy-entropy compensation model was used to infer that the hydro- phobic sorptive me...

177

Transcriptional Regulation in Liver and Testis Associated with Developmental and Reproductive Effects in Male Zebrafish Exposed to Natural Mixtures of Persistent Organic Pollutants (POP)  

Microsoft Academic Search

Persistent organic pollutants (POP) occur as mixtures in nature and it is difficult to predict the toxicity of such mixtures based on knowledge about toxicity and mechanisms of action for single compounds. The present knowledge on the combined toxic effects and modes of actions of exposure to mixtures is limited. Thus, the scientifically based hazard and risk assessment of POP

Rasoul Nourizadeh-Lillabadi; Jan L. Lyche; Camilla Almaas; Benedicte Stavik; S. Jannicke Moe; Mona Aleksandersen; Vidar Berg; Kjetill S. Jakobsen; Nils Chr. Stenseth; Janneche Utne Skåre; Peter Alestrøm; Erik Ropstad

2009-01-01

178

Evidences of nonideal mixing in poly(ethylene glycol)/organic solvent mixtures by Brillouin scattering.  

PubMed

The concentration dependence of the hypersonic properties of solutions of poly(ethylene glycol) of mean molecular mass 600 g/mol (PEG600) in benzene and toluene has been investigated by Brillouin scattering. The two solvents are very similar in structure and chemical properties, but while benzene is nonpolar, toluene possess a modest dipole. In both solvents a high-frequency relaxation process has been observed at high concentrations which has been assigned to conformational rearrangements of the polymeric chains, triggered by reorientation of the side groups. In both cases, the concentration dependence of the adiabatic compressibility deviates significantly from linearity, indicating the existence of nonideal mixing phenomena driven by aggregation processes taking place in the systems. However, there is no temperature dependence for solutions of PEG600 in benzene; on the contrary, the results obtained for solutions of PEG600 in toluene are noticeably dependent on the temperature. The comparison of the experimental data with the results of previous experiments on similar systems allows a general picture for weakly interacting mixtures of hydrogen-bonded systems and organic solvents to be developed. In particular, in the presence of a nonpolar solvent molecule the local structure of the mixture is dominated by solute self-association processes and any resulting solute-solvent correlation is barely induced by excluded volume effects. At high enough dilution the self-aggregation of solute molecules produces a variety of new local topologies that cannot be observed in bulk solute, and as a consequence, the concentration evolution of the system is too rich to be described in terms of a linear combination of a few components over the whole concentration range. The situation seems to be simpler for the polar toluene solvent molecules, where a three-component model seems able to fit the experimental concentration dependence of the hypersonic velocity. This result is interpreted to imply that the interaction between the solvent dipoles and the active sites of the solute produces a relatively stable heterocoordination, while the relevance of self-association is partially reduced. PMID:16471559

Pochylski, M; Aliotta, F; B?aszczak, Z; Gapi?ski, J

2006-01-12

179

Feasibility of separations for distillation of nonideal ternary mixtures  

SciTech Connect

The product compositions in single-feed distillation columns can be specified only in certain regions of the composition space, which depend only on the pressure, feed, and vapor-liquid equilibrium for the mixture. In nonideal mixtures, even without azeotropes, the regions may allow unusual product distributions. For example, the distillate in a direct split is composed primarily of the lightest component. Intuition and experience with relatively ideal mixtures suggest that the next most plentiful component is the intermediate boiler. In nonideal mixtures, however, with or without azeotropes, the next most plentiful component may be the highest-boiling species with only trace amounts of the intermediate boiler. For azeotropic mixtures, distillation boundaries may give rise to additional restrictions on the product compositions. The authors describe how simple distillation boundaries deform into continuous distillation boundaries and, in a limited number of cases, how the simple distillation boundaries can be crossed in continuous columns for certain ranges of the design variables. Unfortunately, such designs may be quite sensitive to model uncertainties or to disturbances in the parameters.

Fidkowski, Z.T.; Doherty, M.F.; Malone, M.F. (Univ. of Massachusetts, Amherst, MA (United States). Dept. of Chemical Engineering)

1993-08-01

180

A non-ideal model for predicting the effect of dissolved salt on the flash point of solvent mixtures.  

PubMed

Flash point is one of the major quantities used to characterize the fire and explosion hazard of liquids. Herein, a liquid with dissolved salt is presented in a salt-distillation process for separating close-boiling or azeotropic systems. The addition of salts to a liquid may reduce fire and explosion hazard. In this study, we have modified a previously proposed model for predicting the flash point of miscible mixtures to extend its application to solvent/salt mixtures. This modified model was verified by comparison with the experimental data for organic solvent/salt and aqueous-organic solvent/salt mixtures to confirm its efficacy in terms of prediction of the flash points of these mixtures. The experimental results confirm marked increases in liquid flash point increment with addition of inorganic salts relative to supplementation with equivalent quantities of water. Based on this evidence, it appears reasonable to suggest potential application for the model in assessment of the fire and explosion hazard for solvent/salt mixtures and, further, that addition of inorganic salts may prove useful for hazard reduction in flammable liquids. PMID:16908098

Liaw, Horng-Jang; Wang, Tzu-Ai

2006-07-01

181

Toxicity to Eisenia andrei and Folsomia candida of a metal mixture applied to soil directly or via an organic matrix.  

PubMed

Regulatory limits for chemicals and ecological risk assessment are usually based on the effects of single compounds, not taking into account mixture effects. The ecotoxicity of metal-contaminated sludge may, however, not only be due to its metal content. Both the sludge matrix and the presence of other toxicants may mitigate or promote metal toxicity. To test this assumption, the toxicity of soils recently amended with an industrial sludge predominantly contaminated with chromium, copper, nickel, and zinc and soils freshly spiked with the same mixture of metals was evaluated through earthworm (Eisenia andrei) and collembolan (Folsomia candida) reproduction tests. The sludge was less toxic than the spiked metal mixture for E. andrei but more toxic for F. candida. Results obtained for the earthworms suggest a decrease in metal bioavailability promoted by the high organic matter content of the sludge. The higher toxicity of the sludge for F. candida was probably due to the additive toxic effect of other pollutants. PMID:21683441

Natal-da-Luz, T; Ojeda, G; Pratas, J; Van Gestel, C A M; Sousa, J P

2011-06-16

182

Design and control of acetic acid dehydration system via heterogeneous azeotropic distillation  

Microsoft Academic Search

Acetic acid dehydration is an important operation in the production of aromatic acid, such as terephthalic acid or in the manufacture of cellulose acetate. Although acetic acid and water does not form azeotrope, but using simple distillation to separate these two components is not practical. The reason is because the system has tangent pinch on the pure water end, thus

I. Lung Chien; Kai-Luen Zeng; Huan-Yi Chao; Jun Hong Liu

2004-01-01

183

Homoazeotropic distillation of maximum azeotropes in a batch rectifier with continuous entrainer feeding I. Feasibility studies  

Microsoft Academic Search

Our former method for the assessment of the feasibility of extractive distillation in a batch rectifier was extended for the investigation of the separation of maximum azeotropes. The method is based on the calculation of the still path and possible composition profiles of the column sections. The sequence of the separation steps was determined, then limiting values and the influence

P. Lang; G. Modla; B. Benadda; Z. Lelkes

2000-01-01

184

Novel azeotropic distillation process for synthesizing nanoscale powders of yttria doped ceria electrolyte  

Microsoft Academic Search

Nanoscale yttria doped ceria powder was successfully synthesized by azeotropic distillation process, which effectively dehydrated hydrous ceria and completely prevented the formation of hard agglomerates. After being calcined at 500°C for 2 h, the average powder size was less than 10 nm. Powder X-ray diffraction (XRD), transmission electron microscopy (TEM) and Raman spectroscopy were performed to characterize the powder properties.

Shaowu Zha; Qingxi Fu; Yin Lang; Changrong Xia; Guangyao Meng

2001-01-01

185

Systematic Generation of the Optimal and Alternative Flowsheets for Azeotropic-Distillation Systems  

Microsoft Academic Search

A systematic and rigorous method for synthesizing azeotropic-distillation systems, which is of utmost practical importance, is yet to be fully established. The available methods are based mainly on heuristics and graphical procedures. Our experience indicates that even in synthesizing a simple separation network, the structure of the optimal solution may be counterintuitive. For synthesizing a complex network structure necessary for

G. Fengb Friedler; L. T. Fan

186

Design and optimization of recycle policies for multicomponent azeotropic distillation processes with bifurcation analysis  

Microsoft Academic Search

A novel design method for finding cost-optimized recycle policies for multicomponent azeotropic distillation processes is presented. The design task is formulated in form of a nonlinear optimization problem with the aim of minimizing the energy consumption of the process. The minimum energy demand of each column is determined using the rectification body method (RBM). Closure of the mass balance around

Stefan Brüggemann; Wolfgang Marquardt

2004-01-01

187

Analysis of closed multivessel batch distillation of ternary azeotropic mixtures using elementary VLE cells  

Microsoft Academic Search

Introducing the concept of elementary topological cells, we illustrate how vapor-liquid equilibrium (VLE) diagrams like distillation lines and isotherms maps may be used in analysis of the closed (total reflux) multivessel batch distillation column. An indirect level control strategy is implemented that eliminates the need for pre-calculated vessel holdups and makes the closed operating policy flexible and simple to implement

E. K. Hilmen; V. N. Kiva; S. Skogestad

1999-01-01

188

Iodometric microdetermination of organic oxidants and ozone: resolution of mixtures by kinetic colorimetry  

Microsoft Academic Search

A basic technique of kinetic colorimetry was developed for determining oxidants in mixtures. An appropriate reagent to produce a slowly developed color was added. Components were resolved graphically using a plot of logarithm of undeveloped color (maximum absorbance minus that at given time) vs. reaction time. Iodometric microdeterminations were thus made of liquid dilutions of various oxidants. This technique was

B. E. Saltzman; Nathan Gilbert

1959-01-01

189

Newly developed ceramic membranes for dehydration and separation of organic mixtures by pervaporation  

Microsoft Academic Search

Polymeric pervaporation membranes sometimes show great variety in performance when they are alternately used for different solvent mixtures. In addition, membrane stability in time is a problem in case of some solvents. Therefore, newly developed ceramic silica membranes with a “dense” top layer were tested for pervaporation. In dehydration of the lower alcohols methanol, ethanol and 2-propanol selectivities of 400,

Robert W. van Gemert; F. Petrus Cuperus

1995-01-01

190

Pervaporation Separation of Water-Ethanol Mixtures Using Organic-Inorganic Nanocomposite Membranes  

EPA Science Inventory

Preyssler type heteropolyacid viz., H14[NaP5W30O110] incorporated chitosan nanocomposite membranes (NCMs) were prepared by solution casting, characterized using a variety of techniques and employed in the pervaporation separation of water-ethanol mixtures as a function of feed wa...

191

Neurological and neurophysiological examinations of workers occupationally exposed to organic solvent mixtures used in the paint and varnish production.  

PubMed

The aim of this work was to examine the nervous system of workers chronically exposed to mixtures of organic solvent at concentrations within or slightly exceeding the MAC values, used in the manufacture of paints and lacquers. The tests were performed on a group of 175 people, 107 men aged 22-59 (x = 41.25), and 68 women aged 20-55 (x = 38.62). The period of employment was x = 17.34 years and cumulative dose index 16.97 for males; for females, the corresponding values were x = 14.75 and x = 11.42, respectively. The control group included 175 people (107 men and 68 women) not exposed to chemicals matched according to sex, age, and work shift distribution. The neurological examinations included subjective and objective examinations of the nervous system, electroencephalographic (EEG) and visual evoked potential (VEP) evaluations. The assessment of organic solvent exposure was performed according to the method described in PN89/Z-04008/07, and the solvent mixtures were shown to contain xylenes, ethyltoluenes, trimethylbenzenes, propylbenzene, ethylbenzene, toluene, aliphatic hydrocarbons and the components of painter's naphtha. The most frequent complaints among the exposed males included headache, vertigo, concentration difficulties, sleep disorders, sleepiness during the day, increased emotional irritability, mood swings with a tendency to anxiety. The objective neurological examinations did not reveal organic lesions in the central or peripheral nervous systems. Generalised and paroxysmal changes were most common recordings in the abnormal EEG. VEP examinations revealed abnormalities, primarily in the latency of the response evoked. The results of this study suggest that exposures to concentrations within MAC values, or below 1.5 of the MAC values of organic solvents mixtures used in the manufacture of paints and lacquers produce subclinical health effect in the nervous system. PMID:8972166

Indulski, J A; Si?czuk-Walczak, H; Szymczak, M; Weso?owski, W

1996-01-01

192

Rapid removal of selected volatile organic compounds from gaseous mixtures using a new dispersive vapor extraction technique: a feasibility study.  

PubMed

A new dispersive vapor extraction (DVE) technique for rapid removal of selected volatile organic compounds (VOCs) from gaseous mixtures was investigated. In this technique, less than 1.0 mL of a volatile solvent was vaporized for 8 min in a 250-mL flask containing a gaseous mixture. The flask was then cooled under running tap water for 2-3 min to induce condensation of the vapor and co-extraction of the VOCs from the headspace. The technique was tested over a concentration range of 4-23 ppb, and resulted in extraction efficiencies ranging from 80 to 97% for the VOCs tested. Because of its simplicity and the relatively short sampling time, DVE could potentially lead to high sample throughput and rapid air analysis. PMID:20602963

Farrell, E S; Pacey, G E

2010-05-26

193

Complex mixture analysis of organic compounds in green coffee bean extract by two-dimensional NMR spectroscopy.  

PubMed

A complex mixture analysis by one- and two-dimensional nuclear magnetic resonance (NMR) spectroscopy was carried out for the first time for the identification and quantification of organic compounds in green coffee bean extract (GCBE). A combination of (1)H-(1)H DQF-COSY, (1)H-(13)C HSQC, and (1)H-(13)C CT-HMBC two-dimensional sequences was used, and 16 compounds were identified. In particular, three isomers of caffeoylquinic acid were identified in the complex mixture without any separation. In addition, GCBE components were quantified by the integration of carbon signals by use of a relaxation reagent and an inverse-gated decoupling method without a nuclear Overhauser effect. This NMR methodology provides detailed information about the kinds and amounts of GCBE components, and in our study, the chemical makeup of GCBE was clarified by the NMR results. PMID:20818806

Wei, Feifei; Furihata, Kazuo; Hu, Fangyu; Miyakawa, Takuya; Tanokura, Masaru

2010-11-01

194

[Assessment of hearing impairment in workers exposed to mixtures of organic solvents in the paint and lacquer industry].  

PubMed

Clinical and experimental studies indicate a possible harmful effect of chemicals, especially organic solvents, on the hearing system. In combined exposure to noise and solvents, very common in industry, it is most likely that a synergetic action of these factors enhances the traumatising effect of exposure to noise. The aim of this study was to assess the incidence and the risk of hearing impairment in 117 paint and lacquer factory workers exposed to a mixture of organic solvents. An analysis of organic solvent mixtures reveals that xylene and ethyl acetate are their major components whose concentrations depend on individual workposts. The control group consisted of 76 workers exposed to noise exceeding, Threshold Limit Value and 125 healthy subjects exposed neither to noise nor to solvents in their occupational setting. Pure tone audiometry revealed the highest hearing thresholds in workers exposed to solvents, lower thresholds in those exposed to noise, and the lowest ones in the non-exposed individuals. Hearing loss was found in 30% of workers exposed to organic solvents, in 20% of noise-exposed subjects, and in only 6% of non-exposed subjects. The comparison of relative risk values also indicated significantly enhanced probability of hearing impairment in workers of the paint and lacquer factory (9.6; 3.2-25.6), which is even more strongly pronounced than in the group of subjects exposed to noise (4.2; 1.2-13.2). An analysis of hearing impairment risk in particular frequencies suggests that organic solvents may damage the inner ear in much greater extent than noise. The results of the study show that exposure to organic solvents may create a significant risk of hearing impairment. Therefore, further steps should be taken to include the exposed population into effective preventive programmes. PMID:10857071

Sliwi?ska-Kowalska, M; Zamys?owska-Szmytke, E; Koty?o, P; Weso?owski, W; Dudarewicz, A; Fiszer, M; Pawlaczyk-Luszczy?ska, M; Polita?ski, P; Kucharska, M; Bilski, B

2000-01-01

195

Mechanisms of action of two different natural mixtures of persistent organic pollutants (POPs) in ovarian follicles.  

PubMed

The present work investigated the effects of two different natural mixtures on aryl hydrocarbon receptor (AhR) and oestrogen receptor (ER)beta protein levels, as well as on the activity of cytochrome P450 (CYP) 1A1 and CYP2B. Consequently, the authors observed the effects of these mixtures on gonadotropine-stimulated steroid secretion by ovarian follicles. The natural mixtures that were studied were 'Mjosa' extracted from burbot liver, which contains a high level of PBDEs, and 'Marine mix', extracted from Atlantic cod liver, which contains a high level of polychlorinated biphenyls (PCBs). Follicular cells were exposed in vitro to 'Marine mix' and 'Mjosa mix' at doses of 3.6 and 1.4 microg ml(-1), respectively. Media were collected and used for steroid analysis and cell viability assays. Cells were used to estimate aromatase activity (CYP19), AhR and ER protein levels, and CYP1A1 and CYP2B1 activity. Western blot analysis indicated down-regulation of AhR by 'Marine mix' and down-regulation of ERbeta by Mjosa mix. Up-regulation of CYP1A1 expression and activity were seen following treatment with Marine mix, but not Mjosa mix. Increased CYP2B1 activity was noted after treatment with both 'Marine mix' and Mjosa mix. Both mixtures increased luteinizing hormone (LH)-stimulated progesterone and testosterone secretion, follicle-stimulating hormone (FSH)-stimulated oestradiol secretion, and CYP19 activity. These results suggest that: (1) 'Marine mix' is a mixed-type CYP inducer; (2) 'Mjosa mix' is an inducer of ERbeta and CYP2B; and (3) both 'Marine mix' and 'Mjosa mix' stimulate aromatase activity as a consequence of oestradiol secretion through activation of CYP19. PMID:19219750

Gregoraszczuk, E L; Ptak, A; Skaare, J U; Mularz, K; Chmielowiec, A; Wojtowicz, A; Ropstad, E

2009-01-01

196

PROCEDURES FOR DERIVING EQUILIBRIUM PARTITIONING SEDIMENT BENCHMARKS (ESBS) FOR THE PROTECTION OF BENTHIC ORGANISMS: METALS MIXTURES (CADMIUM, COPPER, LEAD, NICKEL, SILVER, AND ZINC)  

EPA Science Inventory

This equilibrium partitioning sediment benchmark (ESB) document describes procedures to derive concentrations of metal mixtures in sediment which are protective of the presence of benthic organisms. The equilibrium partitioning (EqP) approach was chosen because it accounts for t...

197

Hazardous and Corrosive Gas Production in the Radiolysis of Water/Organic Mixtures in Model TRU Waste  

SciTech Connect

Experiments in combination with diffusion-kinetic modeling incorporating track structure simulations are used to examine the radiation chemistry of aqueous systems containing chlorinated hydrocarbons. Irradiations with both Co-60 gamma rays and alpha particles are employed in order to simulate typical mixed radiation environments encountered in waste management. The goal is to determine fundamental mechanisms, kinetics, and yields for the formation of potentially explosive gases and corrosive agents, such as H2 and HCl, respectively, in the radiolysis of water-organic mixtures. The radiation chemical systems studied are found throughout the DOE portfolio and are important in radioactive waste remediation and management.

LaVerne, Jay A.

2005-06-01

198

Adsorption of chromate/organic-acid mixtures in aquifer materials. Technical progress report, 1 July 1990--30 June 1991  

SciTech Connect

The overall objective of this project is to develop a fuller understanding of the interactions of mixtures of anionic co-contaminants with oxide-mineral surfaces. Our specific focus is on the competitive interactions of chromate and oxalic acid on ferric oxyhydroxide and on natural aquifer materials. Chromate and oxalate are of practical interest as widespread contaminants at many DOE facilities. However, these anions also are excellent model adsorbates for elucidating fundamental aspects of ionic adsorption processes, particularly with respect to organic acids.

Fish, W.; Palmer, C.D.

1991-07-15

199

Theory of Phase Diagrams and Azeotropic Conditions for Two-Phase Reactive Systems  

Microsoft Academic Search

Expressions for the partial derivatives of the intensive properties that characterize the equilibrium states in two-phase systems, in which the components undergo one equilibrium chemical reaction, are derived. The necessary and sufficient conditions for an azeotropic transformation to occur are found. It is shown that whereas stationary points in the isobaric temperature-composition or isothermal pressure-composition equilibrium surfaces correspond to the

D. Barbosa; M. F. Doherty

1987-01-01

200

Adsorbate shape selectivity: Separation of the HF\\/134a azeotrope over carbogenic molecular sieve  

Microsoft Academic Search

Experimental evidence is provided for adsorptive shape selectivity in the separation of the azeotrope between HF and 1,1,1,2-tetrafluoroethane (134a) over pyrolyzed poly(furfuryl alcohol)-derived carbogenic molecular sieve (PPFA-CMS). The separation can be accomplished over coconut charcoal or Carbosieve G on the basis of the differences in the extent of equilibrium adsorption of HF and 134a. On these adsorbents 134a is more

Allan Hong; Ravindra K. Mariwala; Michael S. Kane; Henry C. Foley

1995-01-01

201

Effect of solvent annealing on phase separation of donor/acceptor species in organic mixtures  

NASA Astrophysics Data System (ADS)

Studies on phase separation of mixtures of tetranitro zinc- phthalocyanine (tn-ZnPc) and [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) were performed in which we controlled the evaporation rate of the solvent (chloroform). Phase-contrast AFM analysis reveals that slowing down the evaporation rate of the solvent facilitates the nucleation of the donor component, and the two components phase-separate. The size of the molecular agglomerates and single small particles decreases for slow solvent evaporation and the density of small particles per unit area increases by an order of magnitude over the range studied.

Cezza, Miriam; Shao, Qian; Guo, Shy-Hauh; Phaneuf, Raymond J.

2013-03-01

202

Pervaporation separation of ethyl acetate–ethanol binary mixtures using polydimethylsiloxane membranes  

Microsoft Academic Search

Pervaporation separation of azeotrope forming ethyl acetate–ethanol mixtures was investigated by using a selfmade polydimethylsiloxane (PDMS) membrane. Sorption, desorption and pervaporation experiments for ethyl acetate–ethanol mixture with different concentrations were conducted at 30, 40 and 50°C. The effect of process parameters such as feed concentration and temperature on flux and selectivity is discussed. Equilibrium curves are determined by vapor–liquid equilibrium

A. Hasano?lu; Y. Salt; S. Kele?er; S. Özkan; S. Dinçer

2005-01-01

203

Isothermal vapor-liquid equilibria for mixtures of methyl tert-butyl ether, methyl acetate, and ethyl acetate  

Microsoft Academic Search

A static apparatus was applied to measure isothermal vapor-liquid equilibrium (VLE) data for binary and ternary mixtures composed of methyl tert-butyl ether (MTBE), methyl acetate, and ethyl acetate at temperatures from 353 K to 373 K. Maximum pressure azeotropes were exhibited in the MTBE + methyl acetate system. All the binary data passed thermodynamic consistency tests. Data reduction was made

Ming-Jer Lee; Chien-Chih Hsiao; Ho-mu Lin

1997-01-01

204

In vitro steroidogenic effects of mixtures of persistent organic pollutants (POPs) extracted from burbot (Lota lota) caught in two Norwegian lakes.  

PubMed

This study investigated the effects of two mixtures of persistent organic pollutants (POPs) on steroidogenesis in the H295R cell line. The two mixtures were obtained from the livers of burbot (Lota lota) caught in two Norwegian lakes (Mjøsa and Losna) with different contaminant profiles. Steroid hormone levels in the cell culture medium and mRNA levels of 16 genes involved in steroidogenesis were investigated. The crude Lake Mjøsa extract had to be diluted ten times more than the Lake Losna extract in order to prevent cytotoxicity. The ten times diluted Lake Mjøsa mixture had higher levels of DDT and derivates (?DDTs, 1.7 times) and brominated flame retardants (?BDEs and HBCD, 15-25 times) than the Lake Losna mixture, which, on the other hand, had higher concentrations of ?PCBs (1.5 times higher) and also of HCB, ?HCH isomers and ?chlordane isomers (5-20 times higher). In the cell culture media, only cortisol levels were increased at the highest exposure concentration to the Lake Mjøsa mixture, while both cortisol and estradiol levels were increased following exposure to the two highest Lake Losna mixture exposure concentrations. Testosterone levels decreased only at the highest exposure concentration of the Lake Losna mixture. Multivariate models suggested that ?PCBs, and to a lesser extent ?DDTs, were responsible for the cortisol responses, while estradiol and testosterone alterations were best explained by HCB and ?PCBs, respectively. Exposure to the mixtures generally increased mRNA levels, with smaller effects exerted by the Lake Mjøsa mixture than the Lake Losna mixture. It was concluded that both mixtures affected steroidogenesis in the H295R cells. Small differences in mixture composition, rather than the high content of brominated flame retardants in the Lake Mjøsa mixture, were suggested to be the most probable reason for the apparent differences in potencies of the two mixtures. PMID:21420147

Zimmer, Karin E; Montaño, Mauricio; Olsaker, Ingrid; Dahl, Ellen; Berg, Vidar; Karlsson, Camilla; Murk, Albertinka J; Skaare, Janneche U; Ropstad, Erik; Verhaegen, Steven

2011-03-21

205

EVALUATION OF THE NEPHROTOXICITY OF COMPLEX MIXTURES CONTAINING ORGANICS AND METALS: ADVANTAGES AND DISADVANTAGES OF THE USE OF REAL-WORLD COMPLEX MIXTURES  

EPA Science Inventory

The nephrotoxicity of complex industrial waste mixtures and a chemically-characterized synthetic chemical mixture are described and reviewed, respectively. dult, male F-344 rats were gavaged with samples of complex industrial waste and nephrotoxicity evaluated 24 hr later. of the...

206

Photonic Crystal Based Sensor for Organic Solvents and for Solvent-Water Mixtures  

PubMed Central

Monodisperse polystyrene nanoparticles with a diameter of 173 nm were incorporated into a polydimethylsiloxane matrix where they display an iridescent color that can be attributed to the photonic crystal effect. The film is of violet color if placed in plain water, but turns to red in the presence of the non-polar solvent n-hexane. Several solvents were studied in some detail. We show that such films are capable of monitoring the water content of ethanol/water mixtures, where only 1% (v/v) of water leads to a shift of the peak wavelength of reflected light by 5 nm. The method also can be applied to determine, both visually and instrumentally, the fraction of methanol in ethanol/methanol mixtures. Here, a fraction of 1% of methanol (v/v) results in a wavelength shift of 2 nm. The reflected wavelength is not influenced by temperature changes nor impeded by photobleaching. The signal changes are fully reversible and response times are <1 s.

Fenzl, Christoph; Hirsch, Thomas; Wolfbeis, Otto S.

2012-01-01

207

Photonic crystal based sensor for organic solvents and for solvent-water mixtures.  

PubMed

Monodisperse polystyrene nanoparticles with a diameter of 173 nm were incorporated into a polydimethylsiloxane matrix where they display an iridescent color that can be attributed to the photonic crystal effect. The film is of violet color if placed in plain water, but turns to red in the presence of the non-polar solvent n-hexane. Several solvents were studied in some detail. We show that such films are capable of monitoring the water content of ethanol/water mixtures, where only 1% (v/v) of water leads to a shift of the peak wavelength of reflected light by 5 nm. The method also can be applied to determine, both visually and instrumentally, the fraction of methanol in ethanol/methanol mixtures. Here, a fraction of 1% of methanol (v/v) results in a wavelength shift of 2 nm. The reflected wavelength is not influenced by temperature changes nor impeded by photobleaching. The signal changes are fully reversible and response times are <1 s. PMID:23235441

Fenzl, Christoph; Hirsch, Thomas; Wolfbeis, Otto S

2012-12-12

208

Neurotoxic Effects of Controlled Exposure to a Complex Mixture of Volatile Organic Compounds.  

National Technical Information Service (NTIS)

Subjective reactions of discomfort, impaired air quality, irritation of mucosal membranes, and impaired memory have been reported in chemically sensitive subjects during exposure to volatile organic compounds (VOCs) found in new buildings. 66 normal healt...

D. A. Otto L. Molhave H. K. Hudnell G. Goldstein J. O'Neil

1990-01-01

209

EXPOSURE OF HUMANS TO A VOLATILE ORGANIC MIXTURE: I. BEHAVIORAL ASSESSMENT  

EPA Science Inventory

Subjective reactions of discomfort, impaired air quality, irritation of mucosal membranes, and impaired memory have been reported to chemically sensitive subjects during exposure to volatile organic compounds (VOC's) found in new buildings. 6 normal healthy male subjects aged 18-...

210

NEUROTOXIC EFFECTS OF CONTROLLED EXPOSURE TO A COMPLEX MIXTURE OF VOLATILE ORGANIC COMPOUNDS  

EPA Science Inventory

Subjective reactions of discomfort, impaired air quality, irritation of mucosal membranes, and impaired memory have been reported in chemically sensitive subjects during exposure to volatile organic compounds (VOC's) found in new buildings. 6 normal healthy male subjects aged 18-...

211

Organic carbon aerogels from the sol-gel polymerization of phenolic-furfural mixtures  

DOEpatents

The sol-gel polymerization of a phenolic-furfural mixture in dilute solution leads to a highly cross-linked network that can be supercritically dried to form a high surface area foam. These porous materials have cell/pore sizes .ltoreq.1000 .ANG., and although they are dark brown in color, they can be classified as a new type of aerogel. The phenolic-furfural aerogel can be pyrolyzed in an inert atmosphere at 1050.degree. C. to produce carbon aerogels. This new aerogel may be used for thermal insulation, chromatographic packing, water filtration, ion-exchange, and carbon electrodes for energy storage devices, such as batteries and double-layer capacitors.

Pekala, Richard W. (Pleasant Hill, CA)

1998-04-28

212

Organic aerogels from the sol-gel polymerization of phenolic-furfural mixtures  

DOEpatents

The sol-gel polymerization of a phenolic-furfural mixture in dilute solution leads to a highly cross-linked network that can be supercritically dried to form a high surface area foam. These porous materials have cell/pore sizes.ltoreq.1000.ANG., and although they are dark brown in color, they can be classified as a new type of aerogel. The phenolic-furfural aerogel can be pyrolyzed in an inert atmosphere at 1050.degree. C. to produce carbon aerogels. This new aerogel may be used for thermal insulation, chromatographic packing, water filtration, ion-exchange, and carbon electrodes for energy storage devices, such as batteries and double-layer capacitors.

Pekala, Richard W. (Pleasant Hill, CA)

1995-01-01

213

Organic aerogels from the sol-gel polymerization of phenolic-furfural mixtures  

DOEpatents

The sol-gel polymerization of a phenolic-furfural mixture in dilute solution leads to a highly cross-linked network that can be supercritically dried to form a high surface area foam. These porous materials have cell/pore sizes .ltoreq.1000.ANG., and although they are dark brown in color, they can be classified as a new type of aerogel. The phenolic-furfural aerogel can be pyrolyzed in an inert atmosphere at 1050.degree. C. to produce carbon aerogels. This new aerogel may be used for thermal insulation, chromatographic packing, water filtration, ion-exchange, and carbon electrodes for energy storage devices, such as batteries and double-layer capacitors.

Pekala, Richard W. (Pleasant Hill, CA)

1996-01-01

214

Energy efficient membrane processes for the separation of organic liquids: Part 1: Final report, September 28, 1982--December 31, 1986  

SciTech Connect

The potential usefulness of two membrane processes, namely, pervaporation and perstraction, for separating azeotropic mixtures of aromatic and aliphatic hydrocarbons was studied theoretically and experimentally. A third membrane process, osmotic phase-separation, was investigated experimentally. The separation of an azeotropic mixture of benzene and cyclohexane was used as an example. Part II of this report will discuss membrane processes for the separation of alcohol/water mixtures. Mathematical models of pervaporation and perstraction were developed for computer simulations of the processes. The perstraction model presented herein is the first of its kind. Additionally, the energy requirements and capital investments costs for the separation of an azeotropic benzene/cyclohexane mixture were determined and compared with those for extractive distillation. 31 refs., 64 figs., 19 tabs.

Cabasso, I.; Acharya, H.R.; Korngold, E.; Liu, Z.; Stern, S.A.; Li, W.; Makenzie, T.; Poda, E.

1987-10-01

215

Complete degradation of anthracene by Manganese Peroxidase in organic solvent mixtures  

Microsoft Academic Search

The goal of this study is the development of a system based on the use of the ligninolytic enzyme Manganese Peroxidase (MnP) for the degradation of polycyclic aromatic hydrocarbons (PAHs), of which anthracene was selected as an example. A main problem of these compounds is their poor solubility in aqueous media. Therefore, the addition of different water miscible organic solvents

G. Eibes; T. Lú-Chau; G. Feijoo; M. T. Moreira; J. M. Lema

2005-01-01

216

SOLUBILITY OF ORGANIC BIOCIDES IN SUPERCRITICAL CO2 AND CO2+ COSOLVENT MIXTURES  

EPA Science Inventory

Solubilities of four organic biocides in supercritical carbon dioxide (Sc-CO2) were measured using a dynamic flowr apparatus over a pressure range of 10 to 30 MPa and temperature of 35-80 degrees C. The biocides studied were: Amical-48 (diiodomethyl p-tolyl sulfone), chlorothalo...

217

Lethal Body Residue of Chlorophenols and Mixtures of Chlorophenols in Benthic Organisms  

Microsoft Academic Search

The lethal body residue (LBR) of a few chlorophenol congeners were measured in the oligochaete worm Lumbriculus variegatus, and the LBR of pentachlorophenol was measured also in a midge, Chironomus riparius larvae. LBR is defined as the concentration of the compound in the organism, on molar basis, to cause death, and the LBR50 is defined as the calculated LBR value

J. V. K. Kukkonen

2002-01-01

218

Polymer coated quartz crystal microbalance sensors for detection of volatile organic compounds in gas mixtures  

Microsoft Academic Search

By coating different conducting polymers of thiophene and its derivatives on quartz crystal microbalance (QCM) sensor surfaces, new novel QCM gas sensors have been produced in two simple ways, which could classify testing gas samples of volatile organic compounds (VOCs) gases. Principle components analysis (PCA) has been performed based on the QCM measurement results, which shows that our QCM sensors

Pengchao Si; John Mortensen; Alexei Komolov; Jens Denborg; Preben Juul Møller

2007-01-01

219

Non-Porous Organic Solids Capable of Dynamically Resolving Mixtures of Diiodoperfluoroalkanes (Postprint).  

National Technical Information Service (NTIS)

A well-known class of organic non-porous compounds, polymethylene bismethonium iodides, undergoes selective capture and release of a,w- diiodoperfluoroalkanes in a dynamic and controlled manner, in solution and from the gas phase. Despite a lack of porosi...

G. Resnati K. Rissenen M. Lahtinen P. Metrangolo Y. Carcenac

2009-01-01

220

Assessing Interactions of Organic Compounds during Biodegradation of Complex Waste Mixtures by Naturally Occurring Bacterial Assemblages.  

National Technical Information Service (NTIS)

Selected organic chemicals were tested to determine the minimum concentrations at which complete inhibition of microbial degradative processes occurred. Complete inhibition did not occur at less than 2 g/L phenol, 10 g/L toluene or n-butanol, and 100 g/L ...

H. M. Hwang R. E. Hodson D. L. Lewis

1989-01-01

221

Measuring the dielectric properties of soil-organic mixtures using coaxial impedance dielectric reflectometry  

NASA Astrophysics Data System (ADS)

Contamination of soils with non-aqueous phase liquids (NAPLs) is frequently produced by accidental spills and storage tanks or pipes leakage. The main goals dealing with soil and groundwater contamination include determining the extension of the affected zone, monitoring the contaminant plume and quantifying the pollution degree. The objective of this work is to evaluate the potential of dielectric permittivity measurements to detect the presence of NAPLs in sands. Tested samples were fine, medium, coarse and silty sand with different volumetric contents of water and paraffin oil. The dielectric permittivity was measured by means of a Coaxial Impedance Dielectric Reflectometry method in specimens with either known fluid content or at different stages during immiscible displacement tests. A simplified method was developed to quantify the amount of oil from dielectric permittivity measurements and effective mixture media models. Obtained results showed that groundwater contamination with NAPL and the monitoring of immiscible fluid displacement in saturated porous media can be clearly identified from dielectric measurements. Finally, very accurate results can be obtained when computing the contamination degree with the proposed method in comparison with the real volumetric content of NAPL (r2 > 90%).

Francisca, Franco M.; Montoro, Marcos A.

2012-05-01

222

High performance liquid chromatography study of complex oxygenated alkane mixtures from organic aerosols  

NASA Astrophysics Data System (ADS)

The composition of secondary organic aerosol particles is of primary importance both in identifying particle sources and in determining physical parameters, such as cloud condensation nucleus propensity. Further, measurements of composition are valuable in determining the chemistry of formation and aging. In this work, we describe the application of a recently-developed derivatization technique to a complex synthetic organic aerosol derived from the photolysis of 1-iodooctane. The technique utilizes high-performance liquid chromatography (HPLC) coupled to both ultravioletvisible (UV/VIS) spectroscopy and tandem mass spectrometry (MS-MS) to determine the overall distribution of hydroxyl (OH), non-acid carbonyl (C=O), and carboxylic acid (COOH) moieties as well as the specific identities of chromatographically separated products. This composition data will then be used to constrain models of the particle formation mechanisms.

Kalafut-Pettibone, Alicia J.; Klems, Joseph P.; McGivern, W. Sean

2013-05-01

223

Enhancement of organ regeneration in animal models by a stem cell-stimulating plant mixture.  

PubMed

Adult stem cells play an important role in the regeneration of damaged organs. Attempts have already been made to enhance stem cell production by cytokines, in order to increase the improvement of cardiac functions after myocardial infarction. In our present study we investigated the possibility whether instead of cytokine injection dietary stimulation of stem cell production accelerates the organ regeneration in animals. A dietary supplement, Olimpiq StemXCell (Crystal Institute Ltd., Eger, Hungary), containing plant extracts (previously proved to increase the number of circulating CD34(+) cells) was consumed in human equivalent doses by the experimental animals. In the first experiment carbon tetrachloride was applied to CBA/Ca mice, to induce liver damage, and liver weights between StemXCell-fed and control animals were compared 10 days after the treatment. In the second model experimental diabetes was induced in F344 rats by alloxan. Blood sugar levels were measured for 5 weeks in the control and StemXCell-fed groups. The third part of the study investigated the effect of StemXCell on cardiac functions. Eight weeks after causing a myocardial infarction in Wistar rats by isoproterenol, left ventricular ejection fraction was determined as a functional parameter of myocardial regeneration. In all three animal models StemXCell consumption statistically significantly improved the organ regeneration (relative liver weights, 4.78 +/-0.06 g/100 g vs. 4.97 +/- 0.07 g/100 g; blood sugar levels at week 5, 16 +/- 1.30 mmol/L vs. 10.2 +/- 0.92 mmol/L; ejection fraction, 57.5 +/- 2.23 vs. 68.2 +/- 4.94; controls vs. treated animals, respectively). Our study confirms the hypothesis that dietary enhancement of stem cell production may protect against organ injuries and helps in the regeneration. PMID:20406138

Kiss, István; Tibold, Antal; Halmosi, Róbert; Bartha, Eva; Koltai, Katalin; Orsós, Zsuzsanna; Bujdosó, László; Ember, István

2010-06-01

224

Extraction of lignins from aqueous-ionic liquid mixtures by organic solvents.  

PubMed

The commercial development of ionic liquids (ILs) to pretreat lignocellulose by dissolution of whole biomass and cellulose precipitation by addition of water is hindered by the absence of an effective technique to recover the lignin content of the biomass from the IL. Three organic solvents [ethyl acetate, 1,4-dioxane, and tetrahydrofuran (THF)] were studied for their ability to form a two-liquid-phase system with water and 1-ethyl-3-methylimidazolium acetate ([C(2)mim][OAc]), and for partitioning model lignins and lignin monomers between the two liquid phases. Ternary diagrams were obtained for three [C(2)mim][OAc]/organic solvent/water systems at 22°C. Partition coefficients were measured for several types of lignin in these three systems. Partition coefficients increase with rising water content in the IL phase, and depend strongly on the type of lignin and on the organic solvent. Partition coefficients rise as the pH of the ionic-liquid-rich phase falls. Small molecule model lignin monomer compounds (guaiacol, syringaldehyde) are also readily extracted from the IL/water system by THF. PMID:22095406

Xin, Qin; Pfeiffer, Katie; Prausnitz, John M; Clark, Douglas S; Blanch, Harvey W

2011-11-21

225

Evaluation of the COSHH Essentials Model with a Mixture of Organic Chemicals at a Medium-Sized Paint Producer  

PubMed Central

The Control of Substances Hazardous to Health (COSHH) Essentials model was evaluated using full-shift exposure measurements of five chemical components in a mixture [acetone, ethylbenzene, methyl ethyl ketone, toluene, and xylenes] at a medium-sized plant producing paint materials. Two tasks, batch-making and bucket-washing, were examined. Varying levels of control were already established in both tasks and the average exposures of individual chemicals were considerably lower than the regulatory and advisory 8-h standards. The average exposure fractions using the additive mixture formula were also less than unity (batch-making: 0.25, bucket-washing: 0.56) indicating the mixture of chemicals did not exceed the combined occupational exposure limit (OEL). The paper version of the COSHH Essentials model was used to calculate a predicted exposure range (PER) for each chemical according to different levels of control. The estimated PERs of the tested chemicals for both tasks did not show consistent agreement with exposure measurements when the comparison was made for each control method and this is believed to be because of the considerably different volatilities of the chemicals. Given the combination of health hazard and exposure potential components, the COSHH Essentials model recommended a control approach ‘special advice’ for both tasks, based on the potential reproductive hazard ascribed to toluene. This would not have been the same conclusion if some other chemical had been substituted (for example styrene, which has the same threshold limit value as toluene). Nevertheless, it was special advice, which had led to the combination of hygienic procedures in place at this plant. The probability of the combined exposure fractions exceeding unity was 0.0002 for the batch-making task indicating that the employees performing this task were most likely well protected below the OELs. Although the employees involved in the bucket-washing task had greater potential to exceed the threshold limit value of the mixture (P > 1 = 0.2375), the expected personal exposure after adjusting for the assigned protection factor for the respirators in use would be considerably lower (P > 1 = 0.0161). Thus, our findings suggested that the COSHH essentials model worked reasonably well for the volatile organic chemicals at the plant. However, it was difficult to override the reproductive hazard even though it was meant to be possible in principle. Further, it became apparent that an input of existing controls, which is not possible in the web-based model, may have allowed the model be more widely applicable. The experience of using the web-based COSHH Essentials model generated some suggestions to provide a more user-friendly tool to the model users who do not have expertise in occupational hygiene.

Lee, Eun Gyung; Slaven, James; Bowen, Russell B.; Harper, Martin

2011-01-01

226

Mixture of [60] and [70]PCBM giving morphological stability in organic solar cells  

NASA Astrophysics Data System (ADS)

Mix-PCBM, comprising [6,6]-phenyl-C61-butyric acid methyl ester (PC60BM) and [6,6]-phenyl-C71-butyric acid methyl ester (PC70BM), is a promising acceptor material for use in organic solar cells with higher device stability and cost performance. The inverted photovoltaic device using poly(3-hexylthiophene) (P3HT) and mix-PCBM exhibited a power conversion efficiency (PCE) of 3.34% (open-circuit voltage = 0.63 V, short-circuit current density = 8.55 mA/cm2, and fill factor = 0.60), slightly higher than that using P3HT and PC60BM (PCE = 3.27%). More importantly, the mix-PCBM device was more stable to heating at 150 °C than the PC60BM device, due to little morphological change, which was characterized by atomic force microscope and light absorption measurements.

Santo, Yoshihide; Jeon, Il; Sheng Yeo, Kee; Nakagawa, Takafumi; Matsuo, Yutaka

2013-08-01

227

Accumulation and effects of natural mixtures of persistent organic pollutants (POP) in Zebrafish after two generations of exposure.  

PubMed

Effects of exposure to environmentally realistic mixtures of persistent organic pollutants (POP) harvested from aquatic ecosystems in Norway were studied in an in vivo zebrafish model. POP were extracted from burbot (Lota lota) liver from two separate lakes, Lake Losna and Lake Mjøsa, and exposed to zebrafish through the diet in a two-generation study. Effects on survival, growth, sex ratio, and timing of puberty were investigated. In addition, the biomarkers 7-ethoxyresorufin O-deethylase (EROD) and vitellogenin (Vtg) were measured. The ratios of contaminant levels in extracts collected from Lake Mjøsa:Lake Losna were 6, 10, and 270 for polychlorinated biphenyls (PCB), dichlorodiphenyltrichloroethanes (DDT), and polybrominated diphenyl ethers (PBDE), respectively. The concentration range of POP measured in zebrafish was lower than in burbot originating from Lake Mjøsa, but comparable to concentrations previously reported in humans and wildlife. The results showed that exposure to environmentally realistic mixtures of POP exerted a negative effect on survival of fish in both generations. The marked drop in survival during 9-20 days post fertilization (dpf) suggested that this period may be a critical window for development. In both generations an earlier onset of puberty was observed and a higher proportion of males than females was noted in exposed fish compared to controls. Suprising effects of exposure were found on body weight. In the first generation (F(0)), body weight was significantly higher in both exposure groups compared to controls, while in the next generation (F(1)) the same exposures were associated with a decrease in body weight. Zebrafish exposed to relatively low quantities of POP showed a significant induction of biomarkers (EROD and Vtg), while fish exposed to higher exposure doses did not demonstrate induction. PMID:21391088

Berg, Vidar; Lyche, Jan L; Karlsson, Camilla; Stavik, Benedicte; Nourizadeh-Lillabadi, Rasoul; Hårdnes, Nina; Skaare, Janneche Utne; Alestrøm, Peter; Lie, Elisabeth; Ropstad, Erik

2011-01-01

228

A chromatographic method to analyze products from photo-oxidation of anthropogenic and biogenic mixtures of volatile organic compounds in smog chambers.  

PubMed

A method for quantifying secondary organic aerosol compounds (SOA) and water soluble secondary organic aerosol compounds (WSOA) produced from photo-oxidation of complex mixtures of volatile organic compounds (VOCs) in smog chambers by gas chromatography/mass spectrometry (GC/MS) has been developed. This method employs a double extraction with water and methanol jointly to a double derivatization with N,O-bis (trimethylsilil) trifluoroacetamide (BSTFA) and O-(2,3,4,5,6)-pentafluorobenzyl-hydroxylamine hydrochloride (PFBHA) followed by an analysis performed by GC/MS. The analytical procedure complements other methodologies because it can analyze SOA and WSOA compounds simultaneously at trace levels. As application, the methodology was employed to quantify the organic composition of aerosols formed in a smog chamber as a result of photo-oxidation of two different mixtures of volatile organic compounds: an anthropogenic mixture and a biogenic mixture. The analytical method allowed us to quantify up to 17 SOA compounds at levels higher than 20 ng m(-3) with reasonable recovery and a precision below 11%. Values found for applicability, selectivity, linearity, precision, recovery, detection limit, quantification limit and sensitivity demonstrated that the methodology can be satisfactorily applied to quantify SOA and WSOA. PMID:23598091

Pindado Jiménez, Oscar; Pérez Pastor, Rosa M; Vivanco, Marta G; Santiago Aladro, Manuel

2012-12-12

229

From the organized nanoparticles of copper and vanadium containing LDHs to the small nanoparticles of mixtures of mixed oxides: A simple route  

Microsoft Academic Search

Well-dispersed nanoparticles of homogeneous mixtures of mixed oxides with an average size of 2.7 nm are obtained by using as precursors copper and vanadium containing layered double hydroxides (LDHs) possessing new self-organized morphology characteristics. The tailored organized pattern of the large nanoparticles of LDHs and the formation of the small nanoparticles of the mixed oxides are followed by the TEM

Gabriela Carja; Hiroo Niiyama

2005-01-01

230

Nitrogen transformation during organic waste composting by the Rutgers system and its effects on pH, EC and maturity of the composting mixtures  

Microsoft Academic Search

The evolution of the different forms of nitrogen during the composting of several wastes was studied, as well as its relation to the pH, electrical conductivity and parameters of maturity of the composts obtained. Four mixtures were prepared from different organic materials: sewage sludge, municipal solid waste, brewery sludge, sorghum bagasse, cotton waste and pine bark. The evolution of the

M. A. Sánchez-Monedero; A. Roig; C. Paredes; M. P. Bernal

2001-01-01

231

Formation of Secondary Organic Aerosol from Irradiated a -Pinene/Tolueme/NOx Mixtures and the Effect of Isoprene and Sulfur Dioxide  

EPA Science Inventory

Secondary organic aerosol (SOA) was generated by irradiating a series of a-pinene/toluene/NOx mixtures in the absence and presence of isoprene or sulfur dioxide. The purpose of the experiment was to evaluate the extent to which chemical perturbations to this base-case (a-pinene/...

232

Influence of the organic component on the geometry and stability of Dy(III) complexes with benzoic and aminobenzoic acids in water-80 vol % DMSO (DMFA) mixtures  

SciTech Connect

The stability and structure of dysprosium (III) benzoate and aminobenzoate complexes are estimated pH-metrically and magnetooptically in water and water-80 vol% DMSO (DMFA) mixtures. The factors responsible for the structural and stability changes that take place upon transition from water to water-organic solvents are discussed.

Kondrashina, Y.G.; Mustafina, A.R.; Devyatov, F.V. [Arbuzov Institute of Organic and Physical Chemistry, Tatarstan (Russian Federation)] [and others

1995-07-01

233

Organic chemistry of NH3 and HCN induced by an atmospheric abnormal glow discharge in N2-CH4 mixtures  

NASA Astrophysics Data System (ADS)

The formation of the chemical products produced in an atmospheric glow discharge fed by a N2-CH4 gas mixture has been studied using Fourier Transform InfraRed (FTIR) and Optical Emission Spectrometry (OES). The measurements were carried out in a flowing regime at ambient temperature and pressure with CH4 concentrations ranging from 0.5% to 2%. In the recorded emission spectra the lines of the second positive system CN system and the first negative system of N2 were found to be the most intensive but atomic H?, H?, and C (247 nm) lines were also observed. FTIR-measurements revealed HCN and NH3 to be the major products of the plasma with traces of C2H2. These same molecules have been detected in Titan's atmosphere and the present experiments may provide some novel insights into the chemical and physical mechanisms prevalent in Titan's atmosphere with these smaller species believed to be the precursors of heavier organic species in Titan's atmosphere and on its surface.

Horvath, G.; Krcma, F.; Polachova, L.; Klohnova, K.; Mason, N. J.; Zahoran, M.; Matejcik, S.

2011-01-01

234

Self-organization of mixtures of fluorocarbon and hydrocarbon amphiphilic thiolates on the surface of gold nanoparticles.  

PubMed

Self-assembled monolayers composed of a mixture of thiolate molecules, featuring hydrocarbon or perfluorocarbon chains (H- and F-chains) terminating with a short poly(oxoethylene) (PEG) moiety, are the most extreme example of surfactant immiscibility on gold nanoparticles reported so far. The phase segregation between H-chains and F-chains and the consequent, peculiar folding of PEG chains are responsible for the increased affinity of a selected radical probe for the fluorinated region, which increases as the size of the fluorinated domains decrease, independently of the shape of such domains. This feature has been revealed by ESR measurements and an in silico innovative multiscale molecular simulations approach in explicit water. Our results reveal an underlying mechanism of a transmission of the organization of the monolayer from the inner region close to the gold surface toward the external hydrophilic PEG region. Moreover, this study definitively proves that a mixed monolayer is a complex system with properties markedly different from those characterizing the parent homoligand monolayers. PMID:22804477

Posocco, Paola; Gentilini, Cristina; Bidoggia, Silvia; Pace, Alice; Franchi, Paola; Lucarini, Marco; Fermeglia, Maurizio; Pricl, Sabrina; Pasquato, Lucia

2012-07-27

235

Two phase flow heat transfer of binary mixtures inside enhanced surface tubing  

Microsoft Academic Search

The primary heat transfer parameters such as coefficient of heat transfer and pressure drop observed during condensation of binary azeotropic refrigerant mixtures R-410a (R125\\/R32: 50\\/50), and R-507 (R125\\/R143a: 50\\/50) are presented in this paper.Experiments showed that for Reynolds numbers higher than 4.2 E06, R-410a appears to have greater heat transfer rates more than the other blends under investigation. Furthermore, it

S. M. Sami; B. Poirier

1998-01-01

236

Modeling of Mass Transfer in Nonideal Multicomponent Mixture with Maxwell-Stefan Approach  

Microsoft Academic Search

The Intalox metal tower packing was used to simulate an industrial relevant extractive distillation column for purifying azeotropic multicomponent mixture. In order to explain the inconsistencies in the modeling of transfer process in nonideal multicomponent distillation column, a method was developed with equilibrium stage models (EQ) and non-equilibrium model (NEQ) incorporated with Maxwell-Stefan diffusion equations in the framework of AspenONE(r)

Yiming SONG; Jinrong SONG; Ming GONG; Bin CAO; Yanhong YANG; Xiaoxun MA

2010-01-01

237

Thermodynamic and kinetic control of charged, amphiphilic triblock copolymer assembly via interaction with organic counterions in solvent mixtures  

NASA Astrophysics Data System (ADS)

Amphiphilic block copolymers, consisting of at least two types of monomers with different affinity to the dissolving solvent(s), have been recognized as a molecular building unit for their chemical tunability and design flexibility. Amphiphilic block copolymers with a chargeable block have structural features of polyelectrolytes, block copolymers and surfactants. The combination of these different features offers great flexibility for developing novel assembled morphologies at the nanoscale and outstanding ability to control and manipulate those morphologies. The nanostructures, formed from the spontaneous association of amphiphilic block copolymer in selective solvents, show promise for applications in nanotechnology and pharmaceuticals, including drug delivery, tissue engineering and bio-imaging. A basic knowledge of their modes of self-assembly and their correspondence to application-related properties is just now being developed and poses a considerable scientific challenge. The goal of this dissertation is to investigate the associative behavior of charged, amphiphilic block copolymers in solvent mixtures while in the presence of organic counterions. Self-assembly of poly (acrylic acid)- block-poly (methyl acrylate)-block-polystyrene (PAA- b-PMA-b-PS) triblock copolymers produces nanodomains in THF/water solution specifically through the interaction with organic counterions (polyamines). These assembled structures can include classic micelles (spheres, cylinders and vesicles), but, more importantly, include non-classic micelles (disks, toroids, branched micelles and segmented micelles). Each micelle structure is stable and reproducible at different assembly conditions. The assembled micellar structures depend on not only solution components (thermodynamics) but also mixing procedure and consequent self-assembly pathway (kinetics). The key factors that determine the thermodynamic interactions that partially define the assembled structures and the kinetic assembly process include THF/water ratio, PS block length, the type and amount of organic counterions, and the mixing pathway. Their formation mechanism has been investigated from three aspects: (i) the chain structure of organic counterions, including spacer length, chain hydrophobicity between ionizable groups and the number of ionizable groups (amine group); (ii) molecular structure of the triblock copolymer, including block length of polystyrene and chain architecture; (iii) relative variation of the components, such as different ratios of THF to water and the different ratios of amine groups to acid groups. The first example of a novel micelle formed was the toroidal micelle. The toroidal micelle morphology, which is theoretically predicted but rarely observed, has been produced by the self assembly of PAA99- b-PMA73-b-PS66 in combination with 2,2-(ethylenedioxy)diethylamine (EDDA) and mixed THF/H2O solvent. It was found that toroids can be constructed by two mechanisms: elimination of energetically unfavored cylindrical micelle endcaps or perforation of disk-like micelles. Three-fold junctions were formed as intermediate structures to facilitate toroidal formation from cylindrical micelles. In order to construct toroids from cylindrical micelles, three requirements must be met: lower bending modulus (flexibility of cylinders), selfattraction between cylinders, and extra endcapping energy originating from chain packing frustration. Extremely high energy spheres can also fuse into toroids. Disk-like micelles can transform into a toroidal morphology when cylindrical packing geometry was initiated along the rims of disk-like micelles via solvent mixing that eventually perforated the disk center. The toroidal morphology can be kinetically trapped by either ridding the system of organic solvent or chemically crosslinking the PAA corona with EDDA via addition of 1-[3-(dimethylamino)propyl]-3-ethylcarbodiimide methiodide (DPEM). The interaction of positively-charged, multivalent organic amines with the negatively-charged PAA corona plays a decisive role in the formatio

Cui, Honggang

238

CONTRIBUTIONS OF TOLUENE AND Î? -PINENE TO SOA FORMED IN AN IRRADIATED TOLUENE/Î?-PINENE/NOX/AIR MIXTURE: COMPARISON OF RESULTS USING 14C CONTENT AND SOA ORGANIC TRACER METHODS  

EPA Science Inventory

An organic tracer method, recently proposed for estimating individual contributions of toluene and α-pinene to secondary organic aerosol (SOA) formation, was evaluated by conducting a laboratory study where a binary hydrocarbon mixture, containing the anthropogenic aromatic hydro...

239

Condensation of Non-Azeotropic Refrigerant Blends of R114 and R113 in a Horizontal Annulus with an Enhanced Inner Tube  

NASA Astrophysics Data System (ADS)

Experiments were performed to study the flow characteristics and heat transfer during condensation of non-azeotropic refrigerant blends (NARBs) of R114 and R113 in the annulus of a horizontal double tube. The inner tube was a 19.1mm o.d. corrugated tube with soldered wire fins on the outer surface. The outer tube was a 29.9mm i.d. smooth tube. Experiments were performed at two vapor mass fractions of R114 at the test section inlet of 0.23 and 0.36. The mass velocity of the test fluids ranged from 50 to 200kg/m2·s. The frictional pressure gradient data were correlated fairly well by an empirical equation for condensation of pure R11 and R113 reported in a previous paper. The double tube showed a significant heat transfer enhancement over a smooth tube value. The heat transfer coefficient for NARBs was considerably smaller than that for pure R113. The decrease was more significant for a low mass velocity. A dimensionless correlation for the vapor phase mass transfer coefficient was derived, where the dimensionless parameters for forced convection condensation from a vapor-gas mixture flowing normal to a cylinder was extended to the case of NARBs.

Nozu, Shigeru; Honda, Hiroshi; Aoyama, Tohru; Shibukuwa, Ken-Ichi

240

Factors associated with sources, transport, and fate of volatile organic compounds and their mixtures in aquifers of the United States  

USGS Publications Warehouse

Factors associated with sources, transport, and fate of volatile organic compounds (VOCs) in groundwater from aquifers throughout the United States were evaluated using statistical methods. Samples were collected from 1631 wells throughout the conterminous United States between 1996 and 2002 as part of the National Water-Quality Assessment (NAWQA) Program of the U.S. Geological Survey. Water samples from wells completed in aquifers used to supply drinking water were analyzed for more than 50 VOCs. Wells were primarily rural domestic water supplies (1184), followed by public water supplies (216); the remaining wells (231) supplied a variety of uses. The median well depth was 50 meters. Age-date information shows that about 60% of the samples had a fraction of water recharged after 1953. Chloroform, toluene, 1,2,4-trimethylbenzene, and perchloroethene were some of the frequently detected VOCs. Concentrations generally were less than 1 ??g/L. Source factors include, in order of importance, general land-use activity, septic/sewer density, and sites where large concentrations of VOCs are potentially released, such as leaking underground storage tanks. About 10% of all samples had VOC mixtures that were associated with concentrated sources; 20% were associated with dispersed sources. Important transport factors included well/screen depth, precipitation/groundwater recharge, air temperature, and various soil characteristics. Dissolved oxygen was strongly associated with VOCs and represents the fate of many VOCs in groundwater. Well type (domestic or public water supply) was also an important explanatory factor. Results of multiple analyses show the importance of (1) accounting for both dispersed and concentrated sources of VOCs, (2) measuring dissolved oxygen when sampling wells to help explain the fate of VOCs, and (3) limiting the type of wells sampled in monitoring networks to avoid unnecessary variance in the data, or controlling for this variance during data analysis.

Squillace, P. J.; Moran, M. J.

2007-01-01

241

Design and Synthesis Procedure for Homogeneous and Heterogeneous Azeotropic Distillations: Annual Report for Period March 1, 1986 to February 29, 1987.  

National Technical Information Service (NTIS)

The column sequencing problem for heterogeneous azeotropic distillation is investigated. It is shown that residue curve maps play an important role in interpreting the behavior of these systems. Classes of residue curve maps which give rise to feasible co...

M. F. Doherty

1986-01-01

242

Steroid secretion following exposure of ovarian follicular cells to three different natural mixtures of persistent organic pollutants (POPs).  

PubMed

This study investigated in vitro endocrine disrupting effects of three mixtures of POPs: 'Marine mix' extracted from Atlantic cod liver, and two mixtures extracted from burbot liver, 'Mjøsa mix' and 'Losna mix'. The POP mixtures were chemically characterized. Co-culture of theca and granulosa cells, were exposed for 48h with different doses of 'Marine mix', 'Mjøsa mix' or 'Losna mix'. As an end point cell viability was determinated by LDH test, steroid analysis by EIA and caspase-3 by colorimetric substrate. Chemical characterization of the mixtures demonstrated that the 'Marine mix' contained high levels of DDTs and PCBs. In the 'Mjøsa mix', the dominant pollutants were BDEs and HBCD. The concentrations of POPs measured in the 'Losna mix' were considerably lower. All mixtures used in the present study had a stimulatory effect on testosterone and estradiol secretion with 'Marine mix'>'Mjøsa mix'>'Losna mix'. These results show that even a mixture containing background concentrations of POPs significantly affected steroid secretion. A higher steroidogenic response in low dose ranges, compared with high dose ranges indicated xenobiotic-conditioning hormesis. This could complicate predictions of effects in risk assessments. PMID:18024081

Gregoraszczuk, Ewa L; Milczarek, Katarzyna; Wójtowicz, Anna K; Berg, Vidar; Skaare, Janneche U; Ropstad, Erik

2007-10-09

243

Evaluation of the inclusion of a mixture of organic acids or lactulose into the feed of pigs experimentally challenged with Salmonella Typhimurium  

Microsoft Academic Search

A mixture of organic acids and lactulose for preventing or reducing colonization of the gut by Salmonella Typhimurium was evaluated in pigs. A total of 63 4-week-old commercial piglets were randomly distributed into three different experimental dietary groups: a plain diet without additives (PD) and the same diet supplemented with either 0.4% (w\\/v) formic acid and 0.4% lactic acid (w\\/v)

Sandra Martín-Peláez; Adele Costabile; Lesley Hoyles; Robert A. Rastall; Glenn R. Gibson; Roberto M. La Ragione; Martin J. Woodward; Enric Mateu; Susana M. Martín-Orúe

2010-01-01

244

Effect of organic acid and salt mixture on shelf-life extension and growth inhibition of Staphylococcus aureus and Escherichia coli O157:H7 in moo yor  

Microsoft Academic Search

This research investigated the effects of organic acids and salts solution on shelf-life extension and growth inhibition of Staphylococcus aureus and Escherichia coli O157:H7 in moo yor (pork bologna). A mixture of lactic acid, acetic acid, citric acid and their sodium salts was added to moo yor at various concentrations of 0 (control), 0.5, 0.75 and 1% (w\\/v) then stored

Puntarika Ratanatriwong; Preyatudsaney Prachaiyo; Pisit Wongsa-Ngasri

245

Ignitability of Spray Clouds of Organic Solvents, Solvent\\/Water Mixtures, and Water-Based Paints by Electric Sparks, Arcs, and Open Flames  

Microsoft Academic Search

The ignitability of spray clouds of organic solvents, solvent\\/water mixtures, and water-based paints by electric discharges and open flames was investigated under worst-case conditions that typically apply to electrostatic paint spraying. More than 200 substances were sprayed with a high-rotation bell spraying device. Rotation speed, substance throughput, and shaping air were optimized in order to achieve an individual ignition optimum

Ulrich von Pidoll

2008-01-01

246

[Synthesis of phthalocyanine conjugates with monoclonal antibodies in AOT/n-octane reversed micelles and in water-organic solvent mixtures].  

PubMed

Conjugates of cobalt and aluminum phthalocyanines with monoclonal antibodies were synthesized using an AOT/n-octane reversed micellar system or water-organic mixtures with a low content of organic solvent as media. The effect of the degree of hydration of the micelles and the concentration of phthalocyanines on the composition of conjugates was studied. The immune activity of the resulting conjugates in comparison to that of native antibodies was evaluated. The catalytic activity of free cobalt phthalocyanines and their antibody conjugates was studied in the reaction of ascorbic acid oxidation. PMID:9551204

Matveeva, E G; Meerovich, I G; Savitski?, A P

1998-01-01

247

Study of binary and ternary azeotropes formed by 1,4-butylene glycol and diethylene glycol with alcohols and hydrocarbons  

SciTech Connect

The azeotropic parameters in the 1,4-BG-C/sub 9/C/sub 15/ alcohol series at 13.33 kPa and the DEG-C/sub 9/-C/sub 16/ alcohol series at 2.67 kPa were experimentally determined. Azeotropy was experimentally studied in 14 1,4-BG-alcohol-hydrocarbon ternary systems. It was found that C/sub 8/ and C/sub 15/ alcohols are the alcohols with the lowest and highest molecular weights which form ternary azeotropes with 1,4-BG, and they are C/sub 8/ and C/sub 16/ alcohols for DEG. 1,4-BG is recommended as a separating agent for purification of hydrocarbons from the C/sub 17/-C/sub 20/ fraction of alcohols by the method of heteroazeotropic rectification.

Shleinikova, M.V.; Smirnova, T.N.; Kushner, T.M.

1988-04-10

248

Removal of Volatile Organic Compounds (VOCs) Mixture by Multi-Pin-Mesh Corona Discharge Combined with Pulsed High-Voltage  

NASA Astrophysics Data System (ADS)

Removal of single component and binary mixtures of benzene and m-xylene using a multi-pin-mesh reactor was studied to find the decomposition characteristics, carbon balance and CO2 selectivity. The decomposition rate of benzene in mixture was approximately 16% lower than that of single component benzene. However, the decomposition rate of m-xylene in mixture was slightly higher than that of single component m-xylene. Carbon balance of the mixture decomposition process achieved a lower level than that of single component benzene/m-xylene. Increase in the specific input energy was helpful to improve CO2 selectivity in the single component decomposition process, while the specific input energy had a negligible effect on CO2 selectivity in the mixture decomposition process. By changing the oxygen content in background gas, we found that different types of radicals showed different reaction activities toward benzene and m-xylene. Benzene was more likely to react with nitrogen-containing radicals, while m-xylene was more likely to react with oxygen-containing radicals.

Zhang, Yue; Li, Duan; Wang, Hongchang

2010-12-01

249

The enthalpies of solution of L-?-alanyl-L-?-alanine in water-organic solvent mixtures at 298.15 K  

NASA Astrophysics Data System (ADS)

The integral enthalpies of solution ( T = 298.15 K) of L-?-alanyl-L-?-alanine in aqueous-organic solvents (acetonitrile, 1,4-dioxane, acetone, formamide, N-methylformamide, N,N-dimethylformamide, N,N-diethylformamide, and N,N-dimethylsulfoxide) were measured at organic component concentrations x 2 = 0 0.3 mole fractions. The standard enthalpies of solution (?sol H o) and transfer (?tr H o) of the peptide from water into mixed solvents were calculated. The influence of the structure and properties of solutes and mixture composition on solute thermochemical characteristics is considered. The enthalpy pair interaction coefficients h xy between L-?-alanyl-L-?-alanine and organic solvent molecules were calculated. The linear Kamlet-Taft four-parameter equation was used to reveal correlation between the h xy values and the properties of organic solvents.

Smirnov, V. I.; Badelin, V. G.

2008-09-01

250

High temperature hot water heat pump with non-azeotropic refrigerant mixture HCFC22\\/HCFC141b  

Microsoft Academic Search

A water-to-water high temperature heat pump was studied experimentally. The performance of the system was characterized by refrigerant compositions, compressor RPM and water temperature change. For the experimental conditions of the inlet water temperature of evaporator of 40 °C and the inlet and outlet water temperatures of the condenser of 70 and 80 °C, respectively, the experiment shows that the

T. X. Li; K. H. Guo; R. Z. Wang

2002-01-01

251

Evaluation of the risk of mixtures of paddy insecticides and their transformation products to aquatic organisms in the Sakura River, Japan.  

PubMed

To assess the risk of mixtures of six paddy insecticides and their transformation products (TPs) to aquatic organisms in the Sakura River, Japan, their concentrations in the river water were monitored during the rice cultivation season in 2008 and 2009, and acute toxicity tests for Cheumatopsyche brevilineata (caddisflies) and Daphnia magna (daphnids), surrogate test species for caddisflies and cladocerans, respectively, were conducted. The mixture of fipronil, applied in the rice nursery box, and its desulfinyl, sulfide, and sulfone TPs were detected in the river for several months after transplanting, and they were more toxic to C. brevilineata than the other tested compounds. The toxicities of the parent compound and its TPs, such as fipronil and its TPs, may be related to their hydrophobicities. Risk quotients for mixtures (RQ(mix)) of only parent compounds did not exceed 1, but, in mid-June 2009, the RQ(mix) of parent compounds and TPs for caddisflies exceeded 1. Diazinon, fenitrothion, and fenthion sprayed on the rice crop and their TPs posed a sporadic risk for cladocerans, depending on the application timing, whereas fipronil TPs contributed to the RQ(mix) for caddisflies for several months after transplanting. The risk of mixtures of insecticides and their TPs differed seasonally between caddisflies and cladocerans, depending on insecticide application timing and the persistence and toxicity of TPs. PMID:21560145

Iwafune, Takashi; Yokoyama, Atsushi; Nagai, Takashi; Horio, Takeshi

2011-05-23

252

Transcriptional regulation in liver and testis associated with developmental and reproductive effects in male zebrafish exposed to natural mixtures of persistent organic pollutants (POP).  

PubMed

Persistent organic pollutants (POP) occur as mixtures in nature and it is difficult to predict the toxicity of such mixtures based on knowledge about toxicity and mechanisms of action for single compounds. The present knowledge on the combined toxic effects and modes of actions of exposure to mixtures is limited. Thus, the scientifically based hazard and risk assessment of POP requires analytical and toxicological data from studies with environmental mixtures of POP. The application of genome wide transcription profiling in toxicology, in combination with classical endpoints, will improve the current understanding of the mechanisms of toxic processes. Furthermore, gene expression data may be useful in establishing new hypothesis and discovering new biomarkers for known toxicity as well as not yet recognized toxicity endpoints. In the present study, developmental and reproductive effects of lifelong exposure to environmental relevant concentrations of two natural mixtures of POP were investigated using classical and molecular methods in a controlled zebrafish model. The mixtures used were extracted from burbot (Lota lota) liver originating from freshwater systems in Norway: one mixture with high levels and one mixture with background levels of polybrominated diphenyl ethers (PBD), polychlorinated biphenyls (PCB), and DDT. The concentration of POP in the zebrafish ranged from levels detected in wild fish from Lake Mjøsa, to concentrations reported in human and wildlife populations. Phenotypic effects observed in both exposure groups included (1) reduced survival, (2) earlier onset of puberty, (3) increased male/female sex ratio, and (4) differences in body weight at 5 mo of age. Interestingly, genome-wide transcription profiling showed changes in regulation of genes involved in endocrine signaling and growth. The transcriptomics changes included (1) key regulator genes for steroid and thyroid hormone functions (cga, ncoa3), (2) insulin signaling and metabolic homeostasis (pik3r1, pfkfb3, ptb1), and (3) p53 activation (mdm4). The effects observed in the experimental zebrafish model raise the question of whether chemical pollution represents a risk to the reproductive health of wild fish inhabiting the freshwater system. PMID:19184727

Nourizadeh-Lillabadi, Rasoul; Lyche, Jan L; Almaas, Camilla; Stavik, Benedicte; Moe, S Jannicke; Aleksandersen, Mona; Berg, Vidar; Jakobsen, Kjetill S; Stenseth, Nils Chr; Skåre, Janneche Utne; Alestrøm, Peter; Ropstad, Erik

2009-01-01

253

A COMPARISON OF THE LETHAL AND SUBLETHAL TOXICITY OF ORGANIC CHEMICAL MIXTURES TO THE FATHEAD MINNOW (PIMEPHALES PROMELAS)  

EPA Science Inventory

This study was designed to define the degree of concentration addition found for mixtures of certain xenobiotics that are thought to act through a similar or different mode of toxic action for the acute mortality and sublethal growth toxicity endpoints, and for a freshwater fish ...

254

Morphology-dependent exciton emission and energy transfer in fluorene-polymer-related fluorescent and phosphorescent composite films spin cast from a mixture of two dissimilar organic solvents  

SciTech Connect

We report morphology-dependent exciton emission and energy transfer in fluorene-conjugated polymer poly(9,9-dioctylfluorenyl-2,7-diyl)-related fluorescent and phosphorescent materials by using a mixture of two dissimilar organic solvents for spin-cast film formation. The electron microscopic characterizations revealed that the mixture of a high-boiling-point orthodichlorobenzene and a low-boiling-point chloroform results in a formation of both crystalline and amorphous morphological structures in fluorene-conjugated polymers. The UV-visible absorption and photoluminescence studies indicated that the low-energy crystalline phase domains, randomly distributed in the continuous high-energy amorphous phase, function as potential quantum wells. As a consequence, the mixture of two dissimilar organic solvents significantly affects the exciton emission from fluorescent fluorene-conjugated polymer and the energy transfer in phosphorescent composite of fluorene polymer and iridium complex molecules, presenting a pathway to control fluorescent and phosphorescent processes in polymer light-emitting materials.

Wu, Yue [University of Tennessee, Knoxville (UTK); Hu, Bin [University of Tennessee, Knoxville (UTK); Howe, Jane Y [ORNL

2005-01-01

255

Synthesis of ammonium and organic compounds from N2,H2O vapor, and CO2 gas mixtures by synchrotron radiation induced photochemical reactions at atmospheric pressure and at room temperature  

NASA Astrophysics Data System (ADS)

Several compound materials were synthesized from N2,H2O vapor, and CO2 gas mixtures using synchrotron radiation induced photochemical reactions at atmospheric pressure and at room temperature. Ammonium and nitrogen oxides were successfully synthesized from N2,H2O vapor, and O2 gas mixtures. It was also found that organic compounds such as carboxyl acids and amino acids were formed from a N2,H2O vapor, and CO2 gas mixture.

Utsumi, Yuichi; Hattori, Tadashi

2002-03-01

256

Phase equilibria for hydrate formation from binary mixtures of ethane, propane and noble gases  

Microsoft Academic Search

Equilibrium conditions for hydrate formation from binary mixtures of C2H6, C3H8 and noble gases such as Ar, Kr and Xe were experimentally determined at the temperatures of 273.5, 276.5 and 278.5K. The binary systems of Xe+C3H8, Kr+C3H8 and Kr+C2H6 mixtures have hydrate azeotropes with pressure minimum points in the isothermal pressure-composition diagrams. Hydrate structural transitions were also observed in the

Tatsuo Maekawa

2006-01-01

257

A Combined Kinetic and Volatility Basis Set Approach to Model Secondary Organic Aerosol from Toluene and Diesel Exhaust/Meat Cooking Mixtures  

NASA Astrophysics Data System (ADS)

Secondary organic aerosol (SOA) is simulated for 6 outdoor smog chamber experiments using a SOA model based on a kinetic chemical mechanism in conjunction with a volatility basis set (VBS) approach. The experiments include toluene, a non-SOA-forming hydrocarbon mixture, diesel exhaust or meat cooking emissions and NOx, and are performed under varying conditions of relative humidity. SOA formation from toluene is modeled using a condensed kinetic aromatic mechanism that includes partitioning of lumped semi-volatile products in particle organic-phase and incorporates particle aqueous-phase chemistry to describe uptake of glyoxal and methylglyoxal. Modeling using the kinetic mechanism alone, along with primary organic aerosol (POA) from diesel exhaust (DE) /meat cooking (MC) fails to simulate the rapid SOA formation at the beginning hours of the experiments. Inclusion of a VBS approach with the kinetic mechanism to characterize the emissions and chemistry of complex mixture of intermediate volatility organic compounds (IVOCs) from DE/MC, substantially improves SOA predictions when compared with observed data. The VBS model includes photochemical aging of IVOCs and evaporation of POA after dilution. The relative contribution of SOA mass from DE/MC is as high as 95% in the morning, but substantially decreases after mid-afternoon. For high humidity experiments, aqueous-phase SOA fraction dominates the total SOA mass at the end of the day (approximately 50%). In summary, the combined kinetic and VBS approach provides a new and improved framework to semi-explicitly model SOA from VOC precursors in conjunction with a VBS approach that can be used on complex emission mixtures comprised with hundreds of individual chemical species.

Parikh, H. M.; Carlton, A. G.; Zhang, H.; Kamens, R.; Vizuete, W.

2011-12-01

258

High-precision D/H measurement from organic mixtures by gas chromatography continuous-flow isotope ratio mass spectrometry using a palladium filter.  

PubMed

Continuous-flow high-precision determination of D/H ratios from an organic mixture is described using gas chromatography coupled to a Pd filter system as an interface for isotope ratio mass spectrometry. A gas chromatograph and combustion and reduction furnaces are connected to a Pd filter via a postcolumn head pressure makeup gas to increase chromatographic sensitivity. This interface is evaluated using benzene as an internal standard in a mixture of ethylbenzene and cyclohexanone in hexane with analyte quantities of < 3 ng (< 300 pg of H). A calibration curve is constructed using four benzene samples over a range of -48 to 372/1000 (delta DSMOW), resulting in an average benzene D/H precision of SD < 5/1000 (delta DSMOW) and deviations of < 4/1000 from the calibration curve. Ethylbenzene and cyclohexanone of a single D enrichment are analyzed as unknowns in three sample mixtures with varying D-enriched benzene and result in precisions of SD < 5/1000. No apparent memory is observed between peaks of differently enriched analytes within the same chromatogram. All results are corrected for ion source nonlinearities characteristic of hydrogen analysis, using the internal peakwise correction algorithm, described previously. A small dependence of isotope ratio on palladium membrane temperature is demonstrated over a range of 4 degrees C; therefore, with tighter control of palladium temperature, precision can probably be improved. The data indicate that this system is useful for rapid continuous-flow IRMS analysis of D/H ratios from organics in complex mixtures characteristic of geological and biological samples. PMID:8794931

Tobias, H J; Brenna, J T

1996-09-01

259

Mixture effects of organic micropollutants present in water: towards the development of effect-based water quality trigger values for baseline toxicity.  

PubMed

In this study we propose for the first time an approach for the tentative derivation of effect-based water quality trigger values for an apical endpoint, the cytotoxicity measured by the bioluminescence inhibition in Vibrio fischeri. The trigger values were derived for the Australian Drinking Water Guideline and the Australian Guideline for Water Recycling as examples, but the algorithm can be adapted to any other set of guideline values. In the first step, a Quantitative Structure-Activity Relationship (QSAR) describing the 50% effect concentrations, EC50, was established using chemicals known to act according to the nonspecific mode of action of baseline toxicity. This QSAR described the effect of most of the chemicals in these guidelines satisfactorily, with the exception of antibiotics, which were more potent than predicted by the baseline toxicity QSAR. The mixture effect of 10-56 guideline chemicals mixed at various fixed concentration ratios (equipotent mixture ratios and ratios of the guideline values) was adequately described by concentration addition model of mixture toxicity. Ten water samples were then analysed and 5-64 regulated chemicals were detected (from a target list of over 200 chemicals). These detected chemicals were mixed in the ratios of concentrations detected and their mixture effect was predicted by concentration addition. Comparing the effect of these designed mixtures with the effect of the water samples, it became evident that less than 1% of effect could be explained by known chemicals, making it imperative to derive effect-based trigger values. The effect-based water quality trigger value, EBT-EC50, was calculated from the mixture effect concentration predicted for concentration-additive mixture effects of all chemicals in a given guideline divided by the sum of the guideline concentrations for individual components, and dividing by an extrapolation factor that accounts for the number of chemicals contained in the guidelines and for model uncertainties. While this concept was established using the example of Australian recycled water, it can be easily adapted to any other set of water quality guidelines for organic micropollutants. The cytotoxicity based trigger value cannot be used in isolation, it must be applied in conjunction with effect-based trigger values targeting critical specific modes of action such as estrogenicity or photosynthesis inhibition. PMID:23618317

Tang, Janet Y M; McCarty, Shane; Glenn, Eva; Neale, Peta A; Warne, Michel St J; Escher, Beate I

2013-03-19

260

Antimould activity of sourdough lactic acid bacteria: identification of a mixture of organic acids produced by Lactobacillus sanfrancisco CB1  

Microsoft Academic Search

Sourdough lactic acid bacteria, cultivated in wheat flour hydrolysate, produced antimould compounds. The antimould activity\\u000a varied greatly among the strains and was mainly detected within obligately heterofermentative Lactobacillus spp. Among these, Lb. sanfrancisco CB1 had the largest spectrum. It inhibited moulds related to bread spoilage such as Fusarium, Penicillium, Aspergillus and Monilia. A mixture of acetic, caproic, formic, propionic, butyric

A. Corsetti; M. Gobbetti; J. Rossi; P. Damiani

1998-01-01

261

Detailed Chemical Characterization of Unresolved Complex Mixtures (UCM) inAtmospheric Organics: Insights into Emission Sources, Atmospheric Processing andSecondary Organic Aerosol Formation  

EPA Science Inventory

Recent studies suggest that semivolatile organic compounds (SVOCs) are important precursors to secondary organic aerosol (SOA) in urban atmospheres. However, knowledge of the chemical composition of SVOCs is limited by current analytical techniques, which are typically unable to...

262

Molecular organization and aggregation in Langmuir and Langmuir-Blodgett films of azo dye/liquid crystal mixtures  

NASA Astrophysics Data System (ADS)

A study of azo dye/liquid crystal mixtures in monolayers formed at air-water (Langmuir films) and air-solid substrate (Langmuir-Blodgett films) interfaces was performed. Three azo dyes with various molecular structure and two liquid crystal materials: 4-octyl-4'-cyanobiphenyl (8CB) and trans-4-octyl(4'-cyanophenyl)-cyclohexane (8PCH) were used. The morphology of Langmuir films was monitored by means of a Brewster angle microscope (BAM). Moreover, a surface pressure and electronic absorption spectra of the monolayer spread on the water surface of dye/liquid crystal mixtures as a function of a mean molecular area were simultaneously recorded. In addition, the absorption for Langmuir-Blodgett films deposited on quartz plates was measured. Information about intermolecular interactions in the mixtures of the nonamphiphilic dye and the liquid crystal with polar terminal group was obtained. Conclusions about the formation of self-aggregates between dye molecules have been drawn. The influence of the dye molecular structure and its concentration on aggregates’ geometry was found.

Inglot, K.; Marty?ski, T.; Bauman, D.

2009-06-01

263

Hazardous and Corrosive Gas Production in the Radiolysis of Water/Organic Mixtures in Model TRU Waste  

SciTech Connect

Scope. The radiation chemistry of aqueous systems containing chlorinated hydrocarbons is investigated using a multi-pronged approach employing 60Co gamma ray and alpha particle irradiation experiments in conjunction with diffusion-kinetic modeling incorporating track structure simulations. The goal is to determine mechanisms, kinetics, and yields for the formation of potentially explosive gases and corrosive agents, such as H2 and HCl, respectively, in the radiolysis of water-organic mixtures. The information obtained is of a fundamental nature, but the radiation chemical systems studied are found throughout the DOE portfolio and are important in radioactive waste remediation and management. Program Highlights. Radiation-induced production of H2 and HCl from chlorinated hydrocarbons. 60Co gamma-radiolysis experiments and stochastic kinetic modeling have been used to investigated the radiation-induced yield of H2 and Cl- from aqueous solutions of 1,2-dichloroethane (1,2-DCE) and 1,1-dichloroethane (1,1-DCE) over the concentration range 1-80 mM. In deoxygenated solution, the yield of H2 from both 1,2-DCE and 1,1-DCE solutions decreases as the concentration of DCE is increased. The decrease in the H2 yield shows that the reaction of H atom with DCE does not lead to the production of H2. This observation is unexpected and reflects the reverse of the effect seen in the gas phase, where the reaction of H atom with 1,2-DCE and 1,1-DCE leads to the production of H2. The yield of Cl- from 1,2-DCE and 1,1-DCE solutions increases slightly from 2.8 ions/100eV to 3.6 over the concentration range 10-50 mM, demonstrating the increased competition of the DCE with intra-track processes. Comparison of the measured yields of Cl- with the predictions of stochastic kinetic modeling shows that the reactions of eaq- with 1,2-DCE and with 1,1-DCE are quantitative, and that the reaction of H atom with both DCEs leads to the production of Cl- (and Haq+). In aerated solution, the yield of Cl- from 1,2-DCE and from 1,1-DCE solutions is very significantly higher ({approx} x 3-4) than from deoxygenated solution. Furthermore, the observed yield is both dose and dose rate dependent. The mechanisms for Cl- production in aerated aqueous solutions of 1,2-DCE and of 1,1-DCE are currently under investigation. Rate coefficients for the reaction of eaq- and -OH with chlorinated hydrocarbons. There is considerable disagreement over the rate coefficients for the reaction of the primary radiation-produced reducing and oxidizing radicals from water, eaq- and -OH respectively, with 1,2-DCE and with 1,1-DCE. Electron pulse-radiolysis experiments monitoring the decay of eaq- have been used to measure the rate coefficients: 1,2 DCE eaq- + CH2Cl-CH2Cl ' CH2Cl-CH2- + Cl- k1 = 2.3 x 109 dm3 mole-1 s-1 1,1 DCE eaq- + CH3Cl-CHCl2 ' CH3-CHCl- + Cl- k2 = 3.5 x 109 dm3 mole-1 s-1 while competition kinetic experiments were employed to determine the rate coefficients: 1,2 DCE -OH + CH2Cl-CH2Cl ' CH2Cl-CHCl- + H2O k3 = 1.8 x 108 dm3 mole-1 s-1 1,1 DCE -OH + CH3Cl-CHCl2 ' CH3-CCl2- + H2O k4 = 1.1 x 108 dm3 mole-1 s-1 The values obtained are similar to those measured by Asmus and co-workers, but there is a significant discrepancy from the estimate of Getoff and co-workers for k1. Rate coefficient for the reaction of OH with thiocyanide ion. The rate coefficient for the reaction of the -OH radical with a chlorinated hydrocarbon is obtained by a competition experiment, in which the change in the radiation-induced yield of (SCN)2-- from an aqueous SCN- solution is monitored on the addition of the hydrocarbon. The mechanism for the radiation-induced formation of (SCN)2-- from a SCN- is complex and involves a number of equilibria. Careful electron pulse radiolysis experiments have been performed and analyzed, employing the full, complex reaction mechanism, to re-evaluated the rate coefficient for the fundamental reaction -OH + SCN- ' (HOSCN)-- k5 = 1.4 x 1010 dm3 mole-1 s-1 This reaction is central to the experimental determination of the rate coefficient of a solute with OH using the

LaVerne, Jay A.

2004-12-01

264

Modeling of non-additive mixture properties using the Online CHEmical database and Modeling environment (OCHEM).  

PubMed

The Online Chemical Modeling Environment (OCHEM, http://ochem.eu) is a web-based platform that provides tools for automation of typical steps necessary to create a predictive QSAR/QSPR model. The platform consists of two major subsystems: a database of experimental measurements and a modeling framework. So far, OCHEM has been limited to the processing of individual compounds. In this work, we extended OCHEM with a new ability to store and model properties of binary non-additive mixtures. The developed system is publicly accessible, meaning that any user on the Web can store new data for binary mixtures and develop models to predict their non-additive properties.The database already contains almost 10,000 data points for the density, bubble point, and azeotropic behavior of binary mixtures. For these data, we developed models for both qualitative (azeotrope/zeotrope) and quantitative endpoints (density and bubble points) using different learning methods and specially developed descriptors for mixtures. The prediction performance of the models was similar to or more accurate than results reported in previous studies. Thus, we have developed and made publicly available a powerful system for modeling mixtures of chemical compounds on the Web. PMID:23321019

Oprisiu, Ioana; Novotarskyi, Sergii; Tetko, Igor V

2013-01-15

265

Mixtures and Solutions  

NSDL National Science Digital Library

This unit covers introductory concepts of mixtures and solutions. Students think about how mixtures and solutions, and atoms and molecules can influence new technologies developed by engineers. The first lesson explores the fundamentals of atoms and their structure. The building blocks of matter (protons, electrons, neutrons) are covered in detail. The next lesson examines the properties of elements and the periodic table â one method of organization for the elements. The concepts of physical and chemical properties are also reviewed. Finally, the last lesson introduces the properties of mixtures and solutions. A comparison of different mixtures and solutions, their properties and their separation qualities are discussed.

Integrated Teaching And Learning Program

266

Determination of Partition coefficients for a Mixture of Volatile Organic Compounds in Rats and Humans at Different Life Stages.  

National Technical Information Service (NTIS)

Pharmacokinetic differences in child, adult and elderly populations remain ill defined. Partition coefficients (PCs) are an integral component of pharmacokinetic models and determining differences in tissue partitioning of volatile organic chemicals acros...

D. A. Mahle J. M. Gearhart R. J. Godfrey D. R. Mattie R. S. Cook

2004-01-01

267

Poly(lactic acid)\\/poly(vinyl pyrrolidone) blend membranes: Effect of membrane composition on pervaporation separation of ethanol\\/cyclohexane mixture  

Microsoft Academic Search

Poly(vinyl pyrrolidone) (PVP) was used as an additive to modify the structure and the physical–chemical properties of poly(lactic acid) (PLA) membranes. The membranes with different PVP contents up to 21.33wt% were employed for pervaporation separation of ethanol\\/cyclohexane (EtOH\\/CHx) azeotropic mixture. Several characterization tests were carried out on the membranes including contact angle measurements, mechanical properties before and after immersion in

S. Zereshki; A. Figoli; S. S. Madaeni; S. Simone; J. C. Jansen; M. Esmailinezhad; E. Drioli

2010-01-01

268

Mixture Experiments  

SciTech Connect

A mixture experiment involves combining two or more components in various proportions or amounts and then measuring one or more responses for the resulting end products. Other factors that affect the response(s), such as process variables and/or the total amount of the mixture, may also be studied in the experiment. A mixture experiment design specifies the combinations of mixture components and other experimental factors (if any) to be studied and the response variable(s) to be measured. Mixture experiment data analyses are then used to achieve the desired goals, which may include (i) understanding the effects of components and other factors on the response(s), (ii) identifying components and other factors with significant and nonsignificant effects on the response(s), (iii) developing models for predicting the response(s) as functions of the mixture components and any other factors, and (iv) developing end-products with desired values and uncertainties of the response(s). Given a mixture experiment problem, a practitioner must consider the possible approaches for designing the experiment and analyzing the data, and then select the approach best suited to the problem. Eight possible approaches include 1) component proportions, 2) mathematically independent variables, 3) slack variable, 4) mixture amount, 5) component amounts, 6) mixture process variable, 7) mixture of mixtures, and 8) multi-factor mixture. The article provides an overview of the mixture experiment designs, models, and data analyses for these approaches.

Piepel, Gregory F.

2007-12-01

269

Olive orchard amended with two experimental olive mill wastes mixtures: Effects on soil organic carbon, plant growth and yield  

Microsoft Academic Search

Amendments of olive orchard soil with two different preparations of olive mill solid waste (OMWMs) at the rate of 9tonha?1 per year for five years in two different plots were compared with an industry standard soil amendment using urea. Both the OMWMs amendments showed significant increases in total organic carbon and humic substances in soil of approximately 40% and 58%,

Roberto Altieri; Alessandro Esposito

2008-01-01

270

Densities and vapor-liquid equilibria in binary mixtures formed by propyl methanoate + ethanol, + propan-1-ol, and + butan-1-ol at 160.0 kPa  

SciTech Connect

Densities and excess volumes were determined at 298.15 K for propyl methanoate + ethanol, + propan-1-ol, and + butan-1-ol. The results of those quantities were then correlated to get the concentrations of vapor-liquid equilibrium obtained isobarically at 160 kPa for the same mixtures. Two mixtures show azeotropes: for propyl methanoate (1) + ethanol (2), x{sub 1} = 0.443 at T = 358.7 K; and for propyl methanoate (1) + propan-1-ol (2), x{sub 1} = 0.762 at T = 368.2 K. The mixtures are thermodynamically consistent, and the predictions made using several group-contribution models are satisfactory.

Falcon, J.; Ortega, J.; Gonzalez, E. [Escuela Superior de Ingenieros Industriales, Las Palmas (Spain). Laboratorio de Termodinamica y Fisicoquimica

1996-07-01

271

Phase diagrams of binary mixtures of patchy colloids with distinct numbers and types of patches: The empty fluid regime  

NASA Astrophysics Data System (ADS)

We investigate the effect of distinct bonding energies on the onset of criticality of low functionality fluid mixtures. We focus on mixtures of particles with two and three patches as this includes the mixture where ``empty'' fluids were originally reported. In addition to the number of patches, the species differ in the type of patches or bonding sites. For simplicity, we consider that the patches on each species are identical: one species has three patches of type A and the other has two patches of type B. We have found a rich phase behavior with closed miscibility gaps, liquid-liquid demixing, and negative azeotropes. Liquid-liquid demixing was found to pre-empt the ``empty'' fluid regime, of these mixtures, when the AB bonds are weaker than the AA or BB bonds. By contrast, mixtures in this class exhibit ``empty'' fluid behavior when the AB bonds are stronger than at least one of the other two. Mixtures with bonding energies ?BB = ?AB and ?AA < ?BB, were found to exhibit an unusual negative azeotrope.

Heras, Daniel de las; Tavares, José Maria; da Gama, Margarida M. Telo

2011-03-01

272

Phase diagrams of binary mixtures of patchy colloids with distinct numbers and types of patches: the empty fluid regime.  

PubMed

We investigate the effect of distinct bonding energies on the onset of criticality of low functionality fluid mixtures. We focus on mixtures of particles with two and three patches as this includes the mixture where "empty" fluids were originally reported. In addition to the number of patches, the species differ in the type of patches or bonding sites. For simplicity, we consider that the patches on each species are identical: one species has three patches of type A and the other has two patches of type B. We have found a rich phase behavior with closed miscibility gaps, liquid-liquid demixing, and negative azeotropes. Liquid-liquid demixing was found to pre-empt the "empty" fluid regime, of these mixtures, when the AB bonds are weaker than the AA or BB bonds. By contrast, mixtures in this class exhibit "empty" fluid behavior when the AB bonds are stronger than at least one of the other two. Mixtures with bonding energies ?(BB) = ?(AB) and ?(AA) < ?(BB), were found to exhibit an unusual negative azeotrope. PMID:21405190

de las Heras, Daniel; Tavares, José Maria; da Gama, Margarida M Telo

2011-03-14

273

Densities and isobaric vapor-liquid equilibria for the mixtures formed by four butyl esters and 1-butanol  

SciTech Connect

Densities of 298.15 K and the vapor-liquid equilibria for 1-butanol + butyl methanoate, + butyl ethanoate, + butyl propanoate, and + butyl butanoate have been measured at 101.32 kPa in small capacity ebulliometer. All results were found to be thermodynamically consistent with a point-to-point test. The mixtures containing butyl methanoate and butyl ethanoate show azeotropes at T = 379.14 K, x = 0.871 and T = 389.64 K, x = 0.222, respectively. Different group-contribution methods were applied to these mixtures.

Gonzalez, E.; Ortega, J. [Univ. of Las Palmas de Gran Canaria (Spain)

1996-01-01

274

Performance of innovative PU-foam and natural fiber-based composites for the biofiltration of a mixture of volatile organic compounds by a fungal biofilm.  

PubMed

The performance of perlite and two innovative carriers that consist of polyurethane (PU) chemically modified with starch; and polypropylene reinforced with agave fibers was evaluated in the biofiltration of a mixture of VOCs composed of hexane, toluene and methyl-ethyl-ketone. At a total organic loading rate of 145 gCm(-3)h(-1) the elimination capacities (ECs) obtained were 145, 24 and 96 gCm(-3)h(-1) for the biofilters packed with the PU, the reinforced polypropylene, and perlite, respectively. Specific maximum biodegradation rates of the mixture, in the biofilters, were 416 mgCg(protein)(-1)? h(-1) for the PU and 63 mgCg(protein)(-1)?h(-1) for perlite, which confirms the highest performance of the PU-composite. 18S rDNA analysis from the PU-biofilter revealed the presence of Fusarium solani in its sexual and asexual states, respectively. The modified PU carrier significantly reduced the start-up period of the biofilter and enhanced the EC of the VOCs. Thus, this study gives new alternatives in the field of packing materials synthesis, promoting the addition of easily biodegradable sources to enhance the performance of biofilters. PMID:22178276

Gutiérrez-Acosta, O B; Arriaga, S; Escobar-Barrios, V A; Casas-Flores, S; Almendarez-Camarillo, A

2011-11-28

275

Energy efficient membrane processes for the separation of organic liquids: Part 3 (Supplement report): Final report, September 28, 1982--December 31, 1986  

SciTech Connect

In this supplemental report, two pilot plants are described. The first is air purge pervaporation (or air sweep pervaporation hollow fiber system) for the separation of azeotropic aqueous liquids. The second describes pilot plant construction and operation for the perstraction process. Several configurations for the air purge pervaporation process were studied and were shown to yield high purity products e.g., isopropanol from the azeotropic mixture with water was enriched to 99.9%. Parallel and U-module configuration were used and durability experiments up to 120 days were carried out successfully. The report describes the first successful low scale pilot plant unit and elements for perstraction process. The conclusion and outcome of this study are two fold. First, membrane systems in a pilot plant unit proved to be very efficient in upgrading nonpermeable components in a membrane system and especially when dealing with azeotropic mixtures. For example, more than 99% isopropanol can be produced from a feed liquid which is 88% i-PrOH (azeotropic mixture with water). The membrane system proved to be durable within the time limit of the experiments (120 days). Second, all parameters including the various configurations of the pilot plants (which are still being studied) are available for chemical, petroleum, and other US industries. 3 refs., 22 figs., 2 tabs.

Cabasso, I.; Acharya, H.R.; Korngold, E.; Liu, Z.; Stern, S.A.; Li, W.; Makenzie, T.; Poda, E.

1987-10-01

276

Hydrophobic treatment of organics against glass employing nonequilibrium atmospheric pressure pulsed plasmas with a mixture of CF{sub 4} and N{sub 2} gases  

SciTech Connect

A hydrophobic organics surface selectively against glass was realized by employing nonequilibrium atmospheric-pressure pulsed plasmas with a mixture of CF{sub 4} and N{sub 2} gases. The organic surface was drastically altered to have a high hydrophobicity, while the glass surface itself remained hydrophilic after the plasma treatment with the addition of a small amount of CF{sub 4} to the N{sub 2} gas. After 100 CF{sub 4}/N{sub 2} plasma treatments, no thin film deposition was observed on the organic material. To investigate the characteristics of the CF{sub 4}/N{sub 2} plasma, the exhaust gas from the plasma was measured by using ion attachment mass spectroscopy (IAMS). The IAMS spectrum indicated that the amounts of CF{sub 3} and F radicals were increased drastically with increasing addition of CF{sub 4}. A mechanism of the selective surface modification was clarified on a result of surface chemical bonding with the gas phase.

Inui, Hirotoshi; Takeda, Keigo; Ishikawa, Kenji; Sekine, Makoto; Hori, Masaru [Department of Electrical Engineering and Computer Science, Nagoya University, Aichi 464-8603 (Japan); Yara, Takuya; Uehara, Tsuyoshi [Sekisui Chemical Co., Ltd., Kyoto 601-8105 (Japan)

2011-01-01

277

Compression Heat Pump Utilizing Water-Ethanol Mixture as a Working Fluid  

NASA Astrophysics Data System (ADS)

Theoretical cycle analysis was done on compression heat pump system, which uses water -ethanol mixture as a working fluid. Working temperature level was set below 100°C. At the low temperature region the pressure of the suction gas is low, and the influence of mechanical loss of the compressor on coefficient of performance (COP) will be large. Relations of COPs and mechanica1 loss of the compressor has been made clear on the ethanol mol fraction range (0 to 1). Water-ethanol mixture cycle can increase COP and lower the working temperature compared with a water cycle. Another effect of adding ethanol is to decrease the irreversible loss at the heat exchangers. As the water -ethanol mixture is a non-azeotropic mixture, temperature changes in two phase regions. This characteristic is valid when a second coolant is used.

Endo, Naoki; Yabe, Akira; Yamashita, Iwao

278

A case study on co-exposure to a mixture of organic solvents in a Tunisian adhesive-producing company  

PubMed Central

Objectives to assess environmental and biological monitoring of exposure to organic solvents in a glue-manufacturing company in Sfax, Tunisia. Methods Exposure of volunteer workers, in the solvented glue-work-stations, in the control laboratory and in the storage rooms of the finished products, was assessed through indoor-air and urine measurements. Informed consent of the workers was obtained. Results and discussion The exposure indexes were found with high values in the solvented workshop as well as in the control laboratory and were respectively, 8.40 and 3.12. These indexes were also correlated with hexane and toluene indoor air concentrations. As to urine, the obtained results for the 2,5-hexandione and hippuric acid, metabolites of hexane and toluene, respectively, were in accord with the indoor-air measurements, with an average of 0.46 mg/l and 1240 mg/g of creatinine. Conclusion This study assessed for the first time biological exposure to organic solvents used in Tunisian adhesive industries. Although values are likely to underestimate true exposure levels, some figures exceed European and American occupational exposure guidelines.

2011-01-01

279

The performance of a residential heat pump operating with a nonazeotropic binary refrigerant mixture  

NASA Astrophysics Data System (ADS)

Results of laboratory measurement of the performance change of a substantially unmodified residential heat pump designed for 222 when charged with a non azeotropic, binary mixture of R1381 and R152a is presented. Results are presented for various sizes of fixed expansion devices. The effect of gliding temperature in the saturation zone was found to be small. The effect of compositions shift by flash distillation in the accumulator was found to measurably improve low temperature heating performance. It was further observed that some system modification (such as the addition of a receiver) could have further enhanced this low temperature heating performance improvement.

Didion, D.; Mulroy, W.

280

Closed-loop phase diagrams, vaporization, and multicriticality in binary liquid mixtures  

SciTech Connect

The coupled Potts-Ising models of Walker and Vause, which successfully describe closed-loop phase diagrams in hydrogen-bonding mixtures, are generalized to encompass the vapor phase, and are studied using position-space renormalization-group techniques. Global phase diagrams are generated, exhibiting such features as miscibility-immiscibility criticality, liquid-vapor critical points, critical end points, and bicritical and tricritical points. In addition, new types of phase diagrams are found, involving upper and lower azeotropes, for example, which are expected to be physically realizable in experimental systems.

Caflisch, R.G.; Walker, J.S.

1983-09-01

281

Adsorption of a binary gas mixture which laterally interacts on a random heterogeneous surface  

SciTech Connect

Analytical expressions for the adsorption of a binary gas mixture which laterally interacts on a heterogeneous surface are developed. The lateral interactions are of the Bragg-Williams type and the surface heterogeneity is modeled via a random distribution of sites described by a uniform distribution of Henry's Law constants. The parametric study shows that complex phase behavior can be predicted, including azeotropes and sigmoidal shaped X-Y diagrams. Also, this model may be useful for modeling and designing adsorption processes as it requires few iterations to simultaneously solve the implicit and coupled algebraic expressions.

Ritter, J.A.

1992-01-01

282

Adsorption of a binary gas mixture which laterally interacts on a random heterogeneous surface  

SciTech Connect

Analytical expressions for the adsorption of a binary gas mixture which laterally interacts on a heterogeneous surface are developed. The lateral interactions are of the Bragg-Williams type and the surface heterogeneity is modeled via a random distribution of sites described by a uniform distribution of Henry`s Law constants. The parametric study shows that complex phase behavior can be predicted, including azeotropes and sigmoidal shaped X-Y diagrams. Also, this model may be useful for modeling and designing adsorption processes as it requires few iterations to simultaneously solve the implicit and coupled algebraic expressions.

Ritter, J.A.

1992-10-01

283

Two-phase flow heat transfer of binary mixtures inside enhanced surface tubing  

SciTech Connect

The primary heat transfer parameters such as coefficient of heat transfer and pressure drop observed during condensation of binary azeotropic refrigerant mixtures R-41Oa (R25/R32: 50/50), and R-507 (R125/R143a: 50/50) are presented in this paper. Experiments showed that for Reynolds numbers higher than 4.2 E06, R-410a appears to have greater heat transfer rates more than the other blends under investigation. Furthermore, it is quite evident from this data that R-507 has the highest pressure drop among the refrigerants under investigation.

Sami, S.M.; Poirier, B. [Univ. of Moncton, New Brunswick (Canada)

1998-08-01

284

Greening pharmaceutical applications of liquid chromatography through using propylene carbonate-ethanol mixtures instead of acetonitrile as organic modifier in the mobile phases.  

PubMed

Substitution of acetonitrile (ACN) as organic modifier in mobile phases for liquid chromatography by mixtures of propylene carbonate (PC) and ethanol (EtOH) may be considered a greener approach for pharmaceutical applications. Such a replacement is achievable without any major compromise in terms of elution order, chromatographic retention, efficiency and peak symmetry. This has been equally demonstrated for reverse phase (RP), ion pair formation (IP) and hydrophilic interaction liquid chromatography (HILIC) separation modes. The impact on the sensitivity induced by the replacement between these organic solvents is discussed for UV-vis and mass spectrometric detection. A comparison between Van Deemter plots obtained under elution conditions based on ACN and PC/EtOH is presented. The alternative elution modes were also compared in terms of thermodynamic parameters, such as standard enthalpy (?H?) and entropic contributions to the partition between the mobile and the stationary phases, for some model compounds. Van't Hoff plots demonstrated that differences between the thermodynamic parameters are minor when shifting from ACN/water to PC/EtOH/water elution on an octadecyl chemically modified silicagel stationary phase. As long as large volume injection (LVI) of diluents non-miscible with the mobile phase is a recently developed topic having a high potential of greening the sample preparation procedures through elimination of the solvent evaporation stage, this feature was also assessed in the case of ACN replacement by PC/EtOH. PMID:23277155

Tache, Florentin; Udrescu, Stefan; Albu, Florin; Mic?le, Florina; Medvedovici, Andrei

2012-12-07

285

Evaluation of the inclusion of a mixture of organic acids or lactulose into the feed of pigs experimentally challenged with Salmonella Typhimurium.  

PubMed

A mixture of organic acids and lactulose for preventing or reducing colonization of the gut by Salmonella Typhimurium was evaluated in pigs. A total of 63 4-week-old commercial piglets were randomly distributed into three different experimental dietary groups: a plain diet without additives (PD) and the same diet supplemented with either 0.4% (w/v) formic acid and 0.4% lactic acid (w/v) (AC) or 1% (w/v) lactulose (LC). After 7 days of adaptation, two-thirds of the pigs (14 from each diet) were challenged with a 2-mL oral dose of 10(8)CFU/mL of Salmonella Typhimurium, leaving the remaining animals unchallenged (UC). After 4 and 10 days post-challenge, pigs were euthanized and the ileum and caecum content were aseptically sampled to (a) quantify lactic, formic, and short-chain fatty acids (SCFA), (b) quantify bacterial populations and Salmonella by fluorescence in situ hybridization and (c) qualitatively analyse bacterial populations through denaturing gradient gel electrophoresis (DGGE). Modification of fermentation products and counts of some of the bacterial groups analysed in the challenged pigs receiving the treatments AC and LC were minimal. Treatments only influenced the bacterial diversity after 10 days post-challenge, with AC generating a lower number of DGGE bands than UC (P<0.05). Neither the inclusion of a mixture of 0.4% (w/v) formic and 0.4% (w/v) lactic acids nor of 1% (w/v) lactulose in the feed influenced numbers of Salmonella in the ileum and caecum of experimentally challenged pigs. PMID:19914785

Martín-Peláez, Sandra; Costabile, Adele; Hoyles, Lesley; Rastall, Robert A; Gibson, Glenn R; La Ragione, Roberto M; Woodward, Martin J; Mateu, Enric; Martín-Orúe, Susana M

2009-10-20

286

Role of organic additives on non-aqueous tape casting of SiAlON ceramics  

Microsoft Academic Search

Suspensions consisting of precursor ?\\/? SiAlON forming powders, azeotropic solvent mixture of 60MEK\\/40E, dispersant, binder, and plasticizer were optimized for tape casting by rheological measurements and tape properties. Sodium tripolyphosphate (STPP) was introduced as a dispersant for low temperature applications of ?\\/?-SiAlONs. Optimum STPP amount was determined as 0.012g\\/m2 (of the particle surface) for stable ?\\/?-SiAlON suspensions. Different amounts of

Ali Ceylan; Ender Suvaci; Hasan Mandal

2011-01-01

287

Heat transfer of ternary mixtures inside enhanced surface tubing  

Microsoft Academic Search

Two phase flow heat transfer parameters such as coefficient of heat transfer and pressure drop observed during condensation of ternary azeotropic refrigerant mixtures R-404A (R125\\/Rl34a\\/R143a:44\\/4\\/52), R-407B (R32\\/R125\\/R134a:10\\/70\\/20), R407C (R32\\/R125\\/R 134a:23\\/25\\/52) and R408A (R22\\/R125\\/R143a:46\\/7\\/47) are presented in this paper. Experiments showed that for Reynolds numbers higher than 3.00 E06, R-408A appears to have greater heat transfer rates than the other blends

S. M Sami; D. E Desjardins

2000-01-01

288

Activation of the aryl hydrocarbon receptor is the major toxic mode of action of an organic extract of a reference urban dust particulate matter mixture: The role of polycyclic aromatic hydrocarbons  

Microsoft Academic Search

Many of the toxic and carcinogenic effects of urban air pollution have been linked to polycyclic aromatic hydrocarbons (PAHs) adsorbed to airborne particulate matter (PM). The carcinogenic properties of PAHs in complex organic mixtures derived from PM have been chiefly attributed to their mutagenicity. Nevertheless, PAHs are also potent activators of the aryl hydrocarbon receptor (AhR), which may contribute to

Zden?k Andrysík; Jan Vondrá?ek; So?a Marvanová; Miroslav Ciganek; Ji?í Ne?a; Kate?ina P?n?íková; Brinda Mahadevan; Jan Topinka; William M. Baird; Alois Kozubík; Miroslav Machala

2011-01-01

289

Crystal nucleation in binary hard sphere mixtures: a Monte Carlo simulation study.  

PubMed

We present calculations of the nucleation barrier during crystallization in binary hard sphere mixtures under moderate degrees of supercooling using Monte Carlo simulations in the isothermal-isobaric semigrand ensemble in conjunction with an umbrella sampling technique. We study both additive and negatively nonadditive binary hard sphere systems. The solid-fluid phase diagrams of such systems show a rich variety of behavior, ranging from simple spindle shapes to the appearance of azeotropes and eutectics to the appearance of substitutionally ordered solid phase compounds. We investigate the effect of these types of phase behavior upon the nucleation barrier and the structure of the critical nucleus. We find that the underlying phase diagram has a significant effect on the mechanism of crystal nucleation. Our calculations indicate that fractionation of the species upon crystallization increases the difficulty of crystallization of fluid mixtures and in the absence of fractionation (azeotropic conditions) the nucleation barrier is comparable to pure fluids. We also calculate the barrier to nucleation of a substitutionally ordered compound solid. In such systems, which also show solid-solid phase separation, we find that the phase that nucleates is the one whose equilibrium composition is closer to the composition of the fluid phase. PMID:16848593

Punnathanam, S; Monson, P A

2006-07-14

290

Crystal nucleation in binary hard sphere mixtures: A Monte Carlo simulation study  

NASA Astrophysics Data System (ADS)

We present calculations of the nucleation barrier during crystallization in binary hard sphere mixtures under moderate degrees of supercooling using Monte Carlo simulations in the isothermal-isobaric semigrand ensemble in conjunction with an umbrella sampling technique. We study both additive and negatively nonadditive binary hard sphere systems. The solid-fluid phase diagrams of such systems show a rich variety of behavior, ranging from simple spindle shapes to the appearance of azeotropes and eutectics to the appearance of substitutionally ordered solid phase compounds. We investigate the effect of these types of phase behavior upon the nucleation barrier and the structure of the critical nucleus. We find that the underlying phase diagram has a significant effect on the mechanism of crystal nucleation. Our calculations indicate that fractionation of the species upon crystallization increases the difficulty of crystallization of fluid mixtures and in the absence of fractionation (azeotropic conditions) the nucleation barrier is comparable to pure fluids. We also calculate the barrier to nucleation of a substitutionally ordered compound solid. In such systems, which also show solid-solid phase separation, we find that the phase that nucleates is the one whose equilibrium composition is closer to the composition of the fluid phase.

Punnathanam, S.; Monson, P. A.

2006-07-01

291

The dynamic behavior of a liquid ethanol-water mixture: a perspective from quantum chemical topology.  

PubMed

Quantum Chemical Topology (QCT) is used to reveal the dynamics of atom-atom interactions in a liquid. A molecular dynamics simulation was carried out on an ethanol-water liquid mixture at its azeotropic concentration (X(ethanol)=0.899), using high-rank multipolar electrostatics. A thousand (ethanol)(9)-water heterodecamers, respecting the water-ethanol ratio of the azeotropic mixture, were extracted from the simulation. Ab initio electron densities were computed at the B3LYP/6-31+G(d) level for these molecular clusters. A video shows the dynamical behavior of a pattern of bond critical points and atomic interaction lines, fluctuating over 1 ns. A bond critical point distribution revealed the fluctuating behavior of water and ethanol molecules in terms of O-H···O, C-H···O and H···H interactions. Interestingly, the water molecule formed one to six C-H···O and one to four O-H···O interactions as a proton acceptor. We found that the more localized a dynamical bond critical point distribution, the higher the average electron density at its bond critical points. The formation of multiple C-H···O interactions affected the shape of the oxygen basin of the water molecule, which is shown in three dimensions. The hydrogen atoms of water strongly preferred to form H···H interactions with ethanol's alkyl hydrogen atoms over its hydroxyl hydrogen. PMID:21437345

Mejía, Sol M; Mills, Matthew J L; Shaik, Majeed S; Mondragon, Fanor; Popelier, Paul L A

2011-03-25

292

Distillation of binary mixtures with capillary porous plates  

SciTech Connect

Distillation of liquid mixtures using capillary porous plates is a new process which depends upon the use of the intermolecular interactions between solids and liquids to alter the normal vapor-liquid equilibrium of a given mixture. Distillation of different binary mixtures, namely ethanol-water, ethanol-benzene, and acetone-ethanol systems, of different compositions was experimentally studied in a continuous distillation column equipped with four, five, or six porous sintered stainless steel fractionating plates of 13.5 {micro}m pore diameter as well as six normal sieve plates. The results showed that the main factors affecting the separation efficiency in a given porous plate are the polarization of the pure liquids and the polarization difference between the mixture components. For the ethanol-water system, the results showed that while no separation was achieved in a distillation column with conventional stages, the zeotropic point of this system was broken in the distillation column with porous plates. A distillate of about 94 mol% ethanol was obtained for a feed of the zeotropic composition, i.e., 89.7 mol% ethanol. For the ethanol-benzene system, the azeotropic point was shifted from 40 mol% ethanol to about 30 mol% ethanol. For the acetone-ethanol system, there was no significant difference between the results obtained with normal stages and those with the porous plates. These results are in agreement with the developed theory.

Abu Al-Rub, F.A. [Jordan Univ. of Science and Technology, Irbid (Jordan). Dept. of Chemical Engineering; Akili, J.; Datta, R. [Univ. of Iowa, Iowa City, IA (United States). Dept. of Chemical and Biochemical Engineering

1998-07-01

293

Occurrence of a Double Azeotrope in the Binary System Hexafluorobenzene+Benzene  

Microsoft Academic Search

RECENTLY there has been much interest in the thermo-dynamic properties of binary mixtures of aromatic fluorocarbons and aromatic hydrocarbons. Experimental studies of the phase diagrams1,2, excess volumes3 and excess enthalpies4 of mixing can be interpreted by assuming that intermolecular complexing exists between the two components. This complexing is believed to result from charge-transfer interaction, with the fluorocarbon acting as the

W. J. Gaw; F. L. Swinton

1966-01-01

294

Large outdoor chamber experiments and computer simulations: (I) Secondary organic aerosol formation from the oxidation of a mixture of d-limonene and ?-pinene  

NASA Astrophysics Data System (ADS)

This work merges kinetic models for ?-pinene and d-limonene which were individually developed to predict secondary organic aerosol (SOA) formation from these compounds. Three major changes in the d-limonene and ?-pinene combined mechanism were made. First, radical-radical reactions were integrated so that radicals formed from both individual mechanisms all reacted with each other. Second, all SOA model species from both compounds were used to calculate semi-volatile partitioning for new semi-volatiles formed in the gas phase. Third particle phase reactions for particle phase ?-pinene and d-limonene aldehydes, carboxylic acids, etc. were integrated. Experiments with mixtures of ?-pinene and d-limonene, nitric oxide (NO), nitrogen dioxide (NO 2), and diurnal natural sunlight were carried out in a dual 270 m 3 outdoor Teflon film chamber located in Pittsboro, NC. The model closely simulated the behavior and timing for ?-pinene, d-limonene, NO, NO 2, O 3 and SOA. Model sensitivities were tested with respect to effects of d-limonene/?-pinene ratios, initial hydrocarbon to NO x (HC 0/NO x) ratios, temperature, and light intensity. The results showed that SOA yield ( YSOA) was very sensitive to initial d-limonene/?-pinene ratio and temperature. The model was also used to simulate remote atmospheric SOA conditions that hypothetically could result from diurnal emissions of ?-pinene, d-limonene and NO x. We observed that the volatility of the simulated SOA material on the aging aerosol decreased with time, and this was consistent with chamber observations. Of additional importance was that our simulation did not show a loss of SOA during the daytime and this was consistent with observed measurements.

Li, Qianfeng; Hu, Di; Leungsakul, Sirakarn; Kamens, Richard M.

295

Modeling secondary organic aerosol formation from xylene and aromatic mixtures using a dynamic partitioning approach incorporating particle aqueous-phase chemistry (II)  

NASA Astrophysics Data System (ADS)

Formation of secondary organic aerosol (SOA) is simulated for 14 outdoor smog chamber experiments using condensed gas-phase regulatory mechanisms and a new SOA framework. This framework is based on empirical parameterizations of independent chamber experiments and includes role of glyoxal and methylglyoxal in formation of particle aqueous-phase. To evaluate for regulatory applications, the chamber experiments include an urban non-SOA VOC mixture and NOx, with either injections of o/p-xylenes or toluene. The experiments are performed under varying conditions of relative humidity (RH) and in the presence of low initial background seed. Gas-particle partitioning of semi-volatile products into particle organic-phase is modeled using a dynamic partitioning approach with reactive uptake coefficient as the principal transport and kinetic parameter. Aqueous-phase SOA is predicted using formulations that describe the irreversible loss of both glyoxal and methylglyoxal to particle aqueous-phase. The predicted SOA mass in the new framework is evaluated using two regulatory gas-phase mechanisms - CB05 or SAPRC07 and, two regulatory parameterization schemes to predict semi-volatile product formation - an Odum-type two-product model and volatility basis-set (VBS). Predictions from the new SOA framework reproduce SOA mass within the uncertainty range of observations, irrespective of the choice of gas-phase mechanism and SOA parameterization scheme (root mean square error [RMSE] range of 0.18-3.08 ?g m-3). Further, model results suggest strong possibility of dominance of bulk-process under low seed conditions and surface-uptake process under high seed for aqueous-phase SOA formation. Sensitivity analysis to the hygroscopic nature of aqueous-phase SOA indicates an uncertainty of a factor of 2 in bulk-process and surface-uptake rates. In summary, the results strongly point to considering mass-transfer and kinetic limitations in regulatory air quality models at low ambient seed concentrations and highlight the importance of aqueous-phase SOA for aromatics under high-RH conditions.

Parikh, Harshal M.; Carlton, Annmarie G.; Zhou, Yang; Zhang, Haofei; Kamens, Richard M.; Vizuete, William

2012-09-01

296

Organic  

NSDL National Science Digital Library

Quiz questions from the organic chemistry question bank provide students with an excellent opportunity to review key concepts.. The Organic topic focuses on the basics of organic chemistry that are taught in general chemistry.

2007-12-07

297

New and extended parameterization of the thermodynamic model AIOMFAC: calculation of activity coefficients for organic-inorganic mixtures containing carboxyl, hydroxyl, carbonyl, ether, ester, alkenyl, alkyl, and aromatic functional groups  

NASA Astrophysics Data System (ADS)

We present a new and considerably extended parameterization of the thermodynamic activity coefficient model AIOMFAC (Aerosol Inorganic-Organic Mixtures Functional groups Activity Coefficients) at room temperature. AIOMFAC combines a Pitzer-like electrolyte solution model with a UNIFAC-based group-contribution approach and explicitly accounts for interactions between organic functional groups and inorganic ions. Such interactions constitute the salt-effect, may cause liquid-liquid phase separation, and affect the gas-particle partitioning of aerosols. The previous AIOMFAC version was parameterized for alkyl and hydroxyl functional groups of alcohols and polyols. With the goal to describe a wide variety of organic compounds found in atmospheric aerosols, we extend here the parameterization of AIOMFAC to include the functional groups carboxyl, hydroxyl, ketone, aldehyde, ether, ester, alkenyl, alkyl, aromatic carbon-alcohol, and aromatic hydrocarbon. Thermodynamic equilibrium data of organic-inorganic systems from the literature are critically assessed and complemented with new measurements to establish a comprehensive database. The database is used to determine simultaneously the AIOMFAC parameters describing interactions of organic functional groups with the ions H+, Li+, Na+, K+, NH4+, Mg2+, Ca2+, Cl-, Br-, NO3-, HSO4-, and SO42-. Detailed descriptions of different types of thermodynamic data, such as vapor-liquid, solid-liquid, and liquid-liquid equilibria, and their use for the model parameterization are provided. Issues regarding deficiencies of the database, types and uncertainties of experimental data, and limitations of the model, are discussed. The challenging parameter optimization problem is solved with a novel combination of powerful global minimization algorithms. A number of exemplary calculations for systems containing atmospherically relevant aerosol components are shown. Amongst others, we discuss aqueous mixtures of ammonium sulfate with dicarboxylic acids and with levoglucosan. Overall, the new parameterization of AIOMFAC agrees well with a large number of experimental datasets. However, due to various reasons, for certain mixtures important deviations can occur. The new parameterization makes AIOMFAC a versatile thermodynamic tool. It enables the calculation of activity coefficients of thousands of different organic compounds in organic-inorganic mixtures of numerous components. Models based on AIOMFAC can be used to compute deliquescence relative humidities, liquid-liquid phase separations, and gas-particle partitioning of multicomponent mixtures of relevance for atmospheric chemistry or in other scientific fields.

Zuend, A.; Marcolli, C.; Booth, A. M.; Lienhard, D. M.; Soonsin, V.; Krieger, U. K.; Topping, D. O.; McFiggans, G.; Peter, T.; Seinfeld, J. H.

2011-09-01

298

New and extended parameterization of the thermodynamic model AIOMFAC: calculation of activity coefficients for organic-inorganic mixtures containing carboxyl, hydroxyl, carbonyl, ether, ester, alkenyl, alkyl, and aromatic functional groups  

NASA Astrophysics Data System (ADS)

We present a new and considerably extended parameterization of the thermodynamic activity coefficient model AIOMFAC (Aerosol Inorganic-Organic Mixtures Functional groups Activity Coefficients) at room temperature. AIOMFAC combines a Pitzer-like electrolyte solution model with a UNIFAC-based group-contribution approach and explicitly accounts for interactions between organic functional groups and inorganic ions. Such interactions constitute the salt-effect, may cause liquid-liquid phase separation, and affect the gas-particle partitioning of aerosols. The previous AIOMFAC version was parameterized for alkyl and hydroxyl functional groups of alcohols and polyols. With the goal to describe a wide variety of organic compounds found in atmospheric aerosols, we extend here the parameterization of AIOMFAC to include the functional groups carboxyl, hydroxyl, ketone, aldehyde, ether, ester, alkenyl, alkyl, aromatic carbon-alcohol, and aromatic hydrocarbon. Thermodynamic equilibrium data of organic-inorganic systems from the literature are critically assessed and complemented with new measurements to establish a comprehensive database. The database is used to determine simultaneously the AIOMFAC parameters describing interactions of organic functional groups with the ions H+, Li+, Na+, K+, NH4+, Mg2+, Ca2+, Cl-, Br-, NO3-, HSO4-, and SO42-. Detailed descriptions of different types of thermodynamic data, such as vapor-liquid, solid-liquid, and liquid-liquid equilibria, and their use for the model parameterization are provided. Issues regarding deficiencies of the database, types and uncertainties of experimental data, and limitations of the model, are discussed. The challenging parameter optimization problem is solved with a novel combination of powerful global minimization algorithms. A number of exemplary calculations for systems containing atmospherically relevant aerosol components are shown. Amongst others, we discuss aqueous mixtures of ammonium sulfate with dicarboxylic acids and with levoglucosan. Overall, the new parameterization of AIOMFAC agrees well with a large number of experimental datasets. However, due to various reasons, for certain mixtures important deviations can occur. The new parameterization makes AIOMFAC a versatile thermodynamic tool. It enables the calculation of activity coefficients of thousands of different organic compounds in organic-inorganic mixtures of numerous components. Models based on AIOMFAC can be used to compute deliquescence relative humidities, liquid-liquid phase separations, and gas-particle partitioning of multicomponent mixtures of relevance for atmospheric chemistry or in other scientific fields.

Zuend, A.; Marcolli, C.; Booth, A. M.; Lienhard, D. M.; Soonsin, V.; Krieger, U. K.; Topping, D. O.; McFiggans, G.; Peter, T.; Seinfeld, J. H.

2011-05-01

299

Organization.  

ERIC Educational Resources Information Center

This theme issue on organization provides an annotated listing of Web sites, CD-ROMs and software, videos, books, and other resources related to organization to be used with K-8 students. Sidebars discuss being organized to be a good student, organizational identities, and organizing an election. Suggests student activities relating to…

Online-Offline, 1999

1999-01-01

300

Organization.  

ERIC Educational Resources Information Center

|This theme issue on organization provides an annotated listing of Web sites, CD-ROMs and software, videos, books, and other resources related to organization to be used with K-8 students. Sidebars discuss being organized to be a good student, organizational identities, and organizing an election. Suggests student activities relating to…

Online-Offline, 1999

1999-01-01

301

The Effect of Circuiting Arrangement on the Thermal Performance of Refrigeration Mixtures in Tube-and-Fin Condensing Heat Exchangers  

SciTech Connect

For the pure or azeotropic refrigerants typically used in present air conditioning and refrigeration applications, the refrigerant changes phase at a constant temperature. Thus, the refrigerant circuiting arrangement such as crossfiow, counterfiow, or cross-counterflow, has no effect on the thermal performance. For zeotropic refrigerant mixtures, however, the phase-change occurs over a temperature range, or "glide", and the refrigerant circuiting arrangement, or flow path through the heat exchanger, can affect the thermal performance of both the heat exchangers as well as the overall efficiency of the vapor compression cooling cycle. The effects of tsvo diflerent circuiting arrangements on the thermal performance of a zeotropic retligerant mixture and an almost azeotropic refrigerant mixture in a four-row cross-countertlow heat exchanger arrangement are reported here. The two condensers differ only in the manner of circuiting the refrigerant tubes, where one has refrigerant always flowing downward in the active heat transfer region ("identical order") and the other has refrigerant alternating flow direction in the active heat transfer region ("inverted order"). All other geometric parameters, such as bce are% fin louver geometry, refrigerant tube size and enhancement etc., are the same for both heat exchangers. One refrigerant mixture (R-41OA) un&rgoes a small temperature change ("low glide") during phase change, and the other retligerant mixture (a multi- component proprietary mixture) has a substantial temperature change ("high glide") of approximately 10"C during the phase change process. The overall thermal conductance, two-phase conductance, and pressure drop are presented. For the flow conditions of these tests, which are representative of resi&ntial cooling conditions, inverted order circuiting is more desirable than identical order. The potential thermal advantages of the i&ntical order arrangement for high-glide zeotropic refrigerant mixtures are negated by the increased parasitic refrigerant-side pressure drop utiortunately resulting from tkbrication requirements of the identical order circuiting.

Chen, D.T.; Conklin, J.C.

1999-03-15

302

Characterization of the Thermotropic Behavior and Lateral Organization of Lipid-Peptide Mixtures by a Combined Experimental and Theoretical Approach: Effects of Hydrophobic Mismatch and Role of Flanking Residues  

Microsoft Academic Search

A combined experimental and theoretical study was performed on a series of mixtures of dipalmitoylphosphatidylcholine (DPPC) and synthetic peptides to investigate their thermotropic behavior and lateral organization. The experimental study was based on differential scanning calorimetry (DSC) and phosphorous nuclear magnetic resonance (31P-NMR) techniques; the theoretical study was based on calculations on a microscopic molecular interaction model, where the lipid-peptide

Sven Morein; J. Antoinette Killian; Maria Maddalena Sperotto

2002-01-01

303

Liquid thermal conductivity of binary mixtures of difluoromethane (R32) and pentafluoroethane (R125)  

SciTech Connect

The thermal conductivities of refrigerant mixtures of difluoromethane (R32) and pentafluoroethane (R125) in the liquid phase are presented. The thermal conductivities were measured with the transient hot-wire method with one bare platinum wire. The experiments were conducted in the temperature range of 233--323 K and in the pressure range of 2--20 MPa. An empirical equation to describe the thermal conductivity of a near-azeotropic mixture, R32 + R125, is provided based on the measured 168 thermal conductivity data as a function of temperature and pressure. The dependence of thermal conductivity on the composition at different temperatures and pressures is also presented. The uncertainty of the measurements is estimated to be {+-}2%.

Ro, S.T.; Kim, M.S.; Jeong, S.U. [Seoul National Univ. (Korea, Republic of). Dept. of Mechanical Engineering

1997-07-01

304

Thermodynamics of polymer-supercritical solvent mixtures  

NASA Astrophysics Data System (ADS)

The objectives of this research are to experimentally investigate the high pressure fluid phase behavior of polymer solutions and to characterize the resultant phase behavior using contemporary polymer solution theories. The polymer solutions of interest are of three types: (1) a binary mixture of polymer and organic solvent; (2) a binary mixture of polymer and supercritical fluid (SCF) solvent; and (3) a ternary mixture of polymer, organic solvent, and SCF solvent. There are three goals of the experimental phase of this project. The first goal is to determine the effect of high pressure on the lower critical solution temperature (LCST) of the polymer-organic solvent mixture at conditions close to the critical point of the organic solvent. The second goal is to study the phase behavior of polymer - SCF solvent mixtures. The final experimental goal is to study the high pressure phase behavior of tenary mixtures consisting of a polymer, an organic solvent, and an SCF solvent.

McHugh, M. A.

1985-07-01

305

The effect of perphenazine on epinephrine-induced cardiac arrhythmias in dogs: I, anaesthesia with fluothane, and fluothane-ether azeotrope  

Microsoft Academic Search

Summary  Thirty acute standard experiments were carried out on twenty dogs during anaesthesia with 0.5 per cent Fluothane and 1 per\\u000a cent Fluothane-ether azeotrope with N2O:O2 (5:2) to determine whether perphenazine would prevent serious or fatal ventricular arrhythmias, provoked by a lethal dose\\u000a of ?epinephrine, after approximately 25 mm. of anaesthesia Pulmonary ventilation was controlled mechanically in a non-rebreathing\\u000a svstem during

Allen B. Dobkin; Noel Purkin

1959-01-01

306

Effect of pressure and the capability of 2-methoxyethanol as a solvent in the behaviour of a diisopropyl ether–isopropyl alcohol azeotropic mixture  

Microsoft Academic Search

Consistent vapour–liquid equilibrium data for the binary and ternary systems of diisopropyl ether+isopropyl alcohol at 30 and 101.3kPa and diisopropyl ether+2-methoxyethanol, isopropyl alcohol+2-methoxyethanol and diisopropyl ether+isopropyl alcohol+2-methoxyethanol at 101.3kPa are reported. The activity coefficients of the solutions were correlated with its composition using the Wilson, NRTL and UNIQUAC models. It is shown that the models allow a very good prediction

Estela Lladosa; Juan B. Montón; Rosa Muñoz

2007-01-01

307

Organics.  

ERIC Educational Resources Information Center

|Presents water analysis literature for 1978. This review is concerned with organics, and it covers: (1) detergents and surfactants; (2) aliphatic and aromatic hydrocarbons; (3) pesticides and chlorinated hydrocarbons; and (4) naturally occurring organics. A list of 208 references is also presented. (HM)|

Chian, Edward S. K.; DeWalle, Foppe B.

1978-01-01

308

Organic \\  

Microsoft Academic Search

This paper presents for the first time a 4-bit microelectromechanical systems (MEMS) phase shifter fabricated on, integrated, and packaged into an organic flexible low-permittivity material. A microstrip switched-line phase shifter has been optimized at 14 GHz for small size and excellent performance. In addition, the MEMS phase shifter was packaged in an all-organic flexible low-permittivity liquid-crystal polymer (LCP) package. The

Nickolas Kingsley; John Papapolymerou

2006-01-01

309

Influence of catalyticity of a porous medium on the concentration limit of filtration combustion of a water-organic mixture in a reversible flow reactor  

NASA Astrophysics Data System (ADS)

The problem on oxidation purification of water in a reversible flow reactor with the use of a catalyst has been studied by numerical methods. We have made comparative studies of the concentration limits of mixture combustion attained in inert and catalytic porous media reactors at varied values of the liquid flow rate, the reactor length, the heat loss coefficient, and the size of the packed bed. It has been established that the use of a catalyst leads to an insignificant decrease in the concentration limit: 11.6% against 13.4% (adiabatic case) and 12.5% against 13.9% (standard insulation).

Dobrego, K. V.; Koznacheev, I. A.

2012-09-01

310

Enhanced crystal stability in a binary mixture of charged colloidal spheres.  

PubMed

We report on the phase behavior of a binary charged sphere mixture of size ratio Gamma=0.68 and charge ratio Lambda approximately 1 as a function of composition p and number density n . For p=0.1-0.3 we observe freezing at densities well below the freezing densities of the pure components. At all compositions our data indicate the formation of substitutional alloy crystals of body centered cubic structure. No indications for compound formation were observed. Rather, our findings point at the first observation of an upper azeotrope. Measurements of the crystallization kinetics reveal a combined density and composition dependence of growth velocities and nucleation rate densities, with small but significant anomalies at p*=0.2 . These correlated deviations can be rationalized within classical theories of solidification and suggest an increased similarity between melt and solid for this particular composition. PMID:19792124

Wette, Patrick; Schöpe, Hans Joachim; Palberg, Thomas

2009-08-27

311

Vapor-liquid equilibria of binary and ternary mixtures of cyclohexane, 3-methyl-2-butanone, and octane at 101.3 kPa  

SciTech Connect

Vapor-liquid equilibria were measured at 101.3 kPa for the three binary and one ternary mixtures of cyclohexane, 3-methyl-2-butanone, and octane. The isobaric T-x-y data were reported, including an azeotropic point for the binary mixture cyclohexane + 3-methyl-2-butanone. The virial equation of state truncated after the second coefficient was used to calculate the vapor-phase fugacity coefficients. The Tsonopoulos correlation equation was applied to determine the second virial coefficients. Various activity coefficient models of the Wilson, the NRTL, and the UNIQUAC equations were used to correlate the binary experimental vapor-liquid equilibrium results. Optimally-fitted binary parameters of the activity coefficient models were obtained and those parameters of the NRTL model were employed to predict the ternary vapor-liquid equilibria. Satisfactory results were presented for the correlation and prediction of the vapor-liquid equilibrium data on binary and ternary mixtures.

Chen, C.C.; Tang, M.; Chen, Y.P. [National Taiwan Univ., Taipei (Taiwan, Province of China). Dept. of Chemical Engineering

1996-05-01

312

Development of more efficacious Tc-99m organ imaging agents for use in nuclear medicine by analytical characterization of radiopharmaceutical mixtures  

SciTech Connect

Capillary electrophoresis is being evaluated as a separation technique for analyzing Tc and Re diphosphonate radiopharmaceuticals. Advantages compared with currently used HPLC techniques include greater resolving power, smaller sample size and more rapid separations. Feasibility has been demonstrated with electropherograms obtained on a Re-HEDP sample. The Tc-PAA complexes in a radiopharmaceutical mixture were found to be unaffected by injection into a Sprague Dawley rat. This was determined by HPLC analysis of the rat's urine, which contained the same complexes as were in the injected sample. Proton NMR spectra have been obtained for samples of Tc-MDP and Re-MDP in order to provide structural information about these complexes. An in vivo sensor is being developed for a brain perfusion agent. Polymer coatings are being explored to extract the brain perfusion agent in order to enhance sensitivity for a microelectrode-based sensor. 4 refs., 2 figs.

Heineman, W.R.

1991-04-01

313

organism  

Microsoft Academic Search

The fitness of any evolutionary unit can be understood in terms of its two basic com- ponents: fecundity (reproduction) and viability (survival). Trade-offs between these fitness com- ponents drive the evolution of life-history traits in extant multicellular organisms. We argue that these trade-offs gain special significance during the transition from unicellular to multicellular life. In particular, the evolution of germ-soma

RICHARD E. MICHOD

314

Order of Photocatalytic Degradation as Ranked by Critical Photonic Times (CPTs) Indicates the Composition of Organic Dye Mixtures: Selectivity of Hydroxyl Radicals  

Microsoft Academic Search

A simple critical photonic time (CPT) ranking method for the simultaneous determination of known organic dyes in the industrial wastewater of different concentrations was developed. A kinetic-measure, CPT theory, was developed to discriminate between the dyes in the textile effluent solution. The CPTs were calculated and ranked 1–4 from the smallest to the largest. The ranks indicate the order in

NDITANGE SHIGWEDHA; ZHAOZHE HUA; JIAN CHEN

2006-01-01

315

Crystallization using reverse micelles and water-in-oil microemulsion systems: the highly selective tool for the purification of organic compounds from complex mixtures.  

PubMed

The active pharmaceutical ingredient orlistat is usually manufactured using a semi-synthetic procedure, producing crude product and complex mixtures of highly related impurities with minimal side-chain structure variability. It is therefore crucial for the overall success of industrial/pharmaceutical application to develop an effective purification process. In this communication, we present the newly developed water-in-oil reversed micelles and microemulsion system-based crystallization process. Physiochemical properties of the presented crystallization media were varied through surfactants and water composition, and the impact on efficiency was measured through final variation of these two parameters. Using precisely defined properties of the dispersed water phase in crystallization media, a highly efficient separation process in terms of selectivity and yield was developed. Small-angle X-ray scattering, high-performance liquid chromatography, mass spectrometry, and scanning electron microscopy were used to monitor and analyze the separation processes and orlistat products obtained. Typical process characteristics, especially selectivity and yield in regard to reference examples, were compared and discussed. PMID:23161204

Kljajic, Alen; Bester-Rogac, Marija; Klobcar, Andrej; Zupet, Rok; Pejovnik, Stane

2012-11-18

316

Large outdoor chamber experiments and computer simulations: (I) Secondary organic aerosol formation from the oxidation of a mixture of d-limonene and ?-pinene  

Microsoft Academic Search

This work merges kinetic models for ?-pinene and d-limonene which were individually developed to predict secondary organic aerosol (SOA) formation from these compounds. Three major changes in the d-limonene and ?-pinene combined mechanism were made. First, radical–radical reactions were integrated so that radicals formed from both individual mechanisms all reacted with each other. Second, all SOA model species from both

Qianfeng Li; Di Hu; Sirakarn Leungsakul; Richard M. Kamens

2007-01-01

317

Biological degradation of a mixture of municipal wastewater and organic garbage leachate in expanded bed anaerobic reactors and a zeolite filter.  

PubMed

Municipal wastewater was amended with organic garbage leachates at a concentration around 700 mgCOD(soluble)/L and fed to three different anaerobic systems to compare their performance: a down flow fluidized bed (DFFB), an expanded granular sludge bed (EGSB) and a zeolite-packed anaerobic filter reactor (ZPF). The DFFB and EGSB reactors were operated at HRT of 6 and 4 h and the ZPF reactor at 12 and 36 h. Organic loads rate for the DFFB reactor were 2.3+/-0.9 and 4.8+/-1.8 gCOD/L.d, with removal efficiencies around 40% and a methane productivity of 0.2+/-0.03 L/L(reactor).d. For the EGSB reactor, organic loads tested were 2.1+/-0.9 and 4.3+/-1.3 gCOD/L.d, removal efficiencies attained were of 77.6+/-12.7% and 84.4+/-4.9%, respectively at both conditions and total suspended solids were removed in 54.6+/-19.3%, while methane productivity at 4 h HRT was of 1.29+/-0.4 L/L(reactor).d. The ZPF reactor was operated at lower organic loading rates, 1.4+/-0.27 and 0.42+/-0.13 gCOD/L.d and attained removal efficiencies of 48+/-18% and 83+/-8%, respectively, reaching a methane productivity of 0.21+/-0.09 and 0.12+/-0.04 L/L(reactor).d, 83+/-8.0% of total suspended solids were retained in the reactor and as HRT was increased ammonium concentrations increased in 39%. Specific methanogenic activity in all systems was around 0.2 gCOD-CH(4)/gVSS d. PMID:19237766

Castilla, P; Aguilar, L; Escamilla, M; Silva, B; Milán, Z; Monroy, O; Meraz, M

2009-01-01

318

CHEMICAL MIXTURES: CONSEQUENCES FOR WATER QUALITY  

EPA Science Inventory

Chemicals have the potential to occur as mixtures in sediment, as well as bioaccumulate in aquatic organisms, sometimes resulting in adverse toxicological effects. Presently, assessments of contaminated sediment are based upon single chemical toxicological studies with the assump...

319

The product composition regions of azeotropic distillation columns. 2. Separability in two-feed columns and entrainer selection  

Microsoft Academic Search

A method to assess the product composition regions for distillation of ternary mixtures in single-feed distillation columns, introduced in the first paper of this series, is generalized to account for the effect of introducing multiple feeds of different trays. The method relies on so-called fixed point curves which are trajectories in the compositions space. These trajectories describe the possible compositions

Oliver M. Wahnschafft; Arthur W. Westerberg

1993-01-01

320

Inhibition of Listeria monocytogenes in full- and low-sodium frankfurters at 4, 7, or 10°C using spray-dried mixtures of organic acid salts.  

PubMed

In meat processing, powdered ingredients are preferred to liquids because of ease of handling, mixing, and storing. This study was conducted to assess Listeria monocytogenes inhibition and the physicochemical and organoleptic characteristics of frankfurters that were prepared with organic acid salts as spray-dried powders (sodium lactate-sodium acetate, sodium lactate-sodium acetate-sodium diacetate, and potassium acetate-potassium diacetate) or liquids (sodium lactate, sodium lactate-sodium diacetate, potassium lactate, and potassium lactate-sodium diacetate). Full-sodium (1.8% salt) and low-sodium (1.0% salt) frankfurters were prepared according to 10 and 5 different formulations (n = 3), respectively, and were dip inoculated with a six-strain cocktail of L. monocytogenes (?4 log CFU/g). Populations of Listeria and mesophilic aerobic bacteria were quantified during storage at 4, 7, and 10°C for up to 90 days. Four powder and two liquid full-sodium formulations and one powder low-sodium formulation, all of which contained diacetate except for 1% sodium lactate-sodium acetate powder, completely inhibited Listeria growth at 4°C. However, Listeria grew in full-sodium formulations at 10°C and in low-sodium formulations at 7 and 10°C except for the formulation containing 0.8% potassium acetate-0.2% potassium diacetate powder. All formulations were similar in terms of water activity, cooking yield, moisture, and protein content. Sodium content and pH were affected by the concentrations of sodium and diacetate, respectively. Frankfurter appearance, texture, flavor, and overall acceptability were similar (P > 0.05) regardless of the formulation, except for flavor and overall acceptability of the low-sodium formulation containing potassium acetate-potassium diacetate. Based on these findings, cosprayed powders appear to be a viable alternative to current liquid inhibitors for control of Listeria in processed meats. PMID:23992500

Sansawat, Thanikarn; Zhang, Lei; Jeong, Jong Y; Xu, Yanyang; Hessell, Gerald W; Ryser, Elliot T; Harte, Janice B; Tempelman, Robert; Kang, Iksoon

2013-09-01

321

Pervaporation study for the dehydration of tetrahydrofuran-water mixtures by polymeric and ceramic membranes.  

PubMed

Pervaporation technology can effectively separate a tetrahydrofuran (THF) solvent-water waste stream at an azeotropic concentration. The performance of a Sulzer 2210 polyvinyl alcohol (PVA) membrane and a Pervatech BV silica membrane were studied, as the operating variables feed temperature and permeate pressure, were varied. The silica membrane was found to exhibit a flux of almost double that of the PVA membrane, but both membranes had comparable separation ability in purifying the solvent-water mixture. At benchmark feed conditions of 96 wt% THF and 4 wt% water, 50 degrees C and 10 torr permeate pressure, the silica membrane flux was 0.276 kg/m(2)hr and selectivity was 365. For both membranes, flux was found to increase at an exponential rate as the feed temperature increased from 20 to 60 degrees C. The flux through the silica membrane increases at a 6% faster rate than the PVA membrane. Flux decreased as permeate pressure was increased from 5 to 25 torr for both membranes. The amount of water in the permeate decreased exponentially as the permeate pressure was increased, but increased linearly with increasing temperature. Optimum conditions for flux and selectivity are at low permeate pressure and high feed temperature. When a small amount of salt is added to the feed solution, an increase in flux is observed. Overall models for flux and permeate concentration were created from the experimental data. The models were used to predict scale-up performance in separating an azeotropic feed waste to produce dehydrated THF solvent for reuse and a permeate stream with a dilute THF concentration. PMID:18988105

McGinness, Colleen A; Slater, C Stewart; Savelski, Mariano J

2008-12-01

322

The Mixtures Lab  

NSDL National Science Digital Library

The representation illustrates the separation of mixtures using physical properties. The interactive simulation allows "lab attendants" to separate mixtures using virtual tools. Separation mechanisms are chosen based upon substances' physical properties, and findings are recorded in a chart.

323

Learning Mixtures of Gaussians  

Microsoft Academic Search

Mixtures of Gaussians are among the most fundamental and widely used statistical models. Current techniques for learning such mixtures from data are local search heuris- tics withweak performance guarantees. We present the first provably correct algorithm for learning a mixture of Gaus- sians. This algorithm is very simple and returns the true centers of the Gaussians to withinthe precision specified

Sanjoy Dasgupta

1999-01-01

324

Odorant composition for liquefied petroleum gases  

Microsoft Academic Search

Pennwalt Corp.'s new odorant for LP-gas remains fairly constant in concentration as the LP-gas cylinder is emptied with use, unlike conventional odorants which vary over a 20 to 50-fold range as evaporation continues. The odorant consists of an azeotropic mixture of ethyl mercaptan and\\/or dimethyl sulfide and a chemically inert, relatively nonodorous organic material capable of forming a minimum-boiling-point azeotrope

Nevers

1974-01-01

325

Mixtures of ionic liquids.  

PubMed

Simple ionic liquids have long been held to be designer solvents, based upon the ability to independently vary their cations and anions. The formation of mixtures of ionic liquids increases this synthetic flexibility. We review the available literature of these ionic liquid mixtures to identify how their properties change and the possibility for their application. PMID:22890419

Niedermeyer, Heiko; Hallett, Jason P; Villar-Garcia, Ignacio J; Hunt, Patricia A; Welton, Tom

2012-12-01

326

Identifiability of Finite Mixtures  

Microsoft Academic Search

In general, the class of mixtures of the family of normal distributions or of Gamma (Type III) distributions or binomial distributions is not identifiable (see [3], [4] or Section 2 below for the meaning of this statement). In [4] it was shown that the class of all mixtures of a one-parameter additively-closed family of distributions is identifiable. Here, attention will

Henry Teicher

1963-01-01

327

Experimental analysis of a window air conditioner with R-22 and zeotropic mixture of R-32/125/134a  

SciTech Connect

This study is the result of the cooperative research and development agreement (CRADA) between Oak Ridge National Laboratory and E.I. Du Pont De Nemours and Company, Inc., (CRADA No. 92-0161) for testing the use of heat exchangers as the evaporator and condenser in an air-conditioning rig. Heat exchangers at typical realistic operating conditions were tested with R-22 and with its potential replacement, a ternary mixture of R-32(30%)/R-125(10%)/R-134a(60%). A test rig was built that provided for operation of the low-temperature exchanger (evaporator) with flooded coils. The test results indicated that the performance of the evaporator heat exchanger using ternary mixture, in terms of cooling capacity, would be around 7.4% less than the performance using R-22. The cooling capacity for both refrigerants improved with flooded evaporator operation by 8.6% for R-22 and by 15% for ternary mixture. Compared with R-22 operation, operation with ternary mixture results in slightly higher compressor discharge pressure, lower compressor discharge temperature, slightly lower compressor power consumption, and a higher compressor high-low pressure ratio. Temperature glide for ternary mixture, for both evaporator and condenser, was clearly evident, but not as pronounced as expected because of the pressure drop (and thus the temperature drop) along the coils. Further improvement of the performance of ternary mixture is possible if the evaporator is arranged in a counter-cross-flow configuration to take advantage of the temperature glide. Current evaporator designs are mostly concurrent-cross-flow, which is more appropriate for single-component refrigerants or azeotropic refrigerant mixtures.

Mei, V.C.; Chen, F.C.; Carlstedt, J.; Hallden, D.

1995-08-01

328

Characterization of the thermotropic behavior and lateral organization of lipid-peptide mixtures by a combined experimental and theoretical approach: effects of hydrophobic mismatch and role of flanking residues.  

PubMed Central

A combined experimental and theoretical study was performed on a series of mixtures of dipalmitoylphosphatidylcholine (DPPC) and synthetic peptides to investigate their thermotropic behavior and lateral organization. The experimental study was based on differential scanning calorimetry (DSC) and phosphorous nuclear magnetic resonance ((31)P-NMR) techniques; the theoretical study was based on calculations on a microscopic molecular interaction model, where the lipid-peptide interaction is built on the hydrophobic matching principle. The chosen peptides, WALP and KALP, consist of a hydrophobic stretch, of variable length, of alternating leucine and alanine residues, flanked on both ends with tryptophan and lysine residues, respectively. By systematically varying the peptide hydrophobic length it was thus possible to explore different matching conditions between the peptide's hydrophobic length and the lipid bilayer hydrophobic thickness, and to investigate the potential role of flanking residues. The results show that both the WALP and the KALP peptides tend to favor the liquid-crystalline (or fluid) phase of the system; i.e., they tend to depress the main-transition temperature, T(m), of pure DPPC. However, the detailed effects of both peptides on the lateral phase behavior of the lipid-peptide system are dependent on the peptide length and the type of flanking residues. The results suggest that below T(m), the shortest among the WALP and KALP peptides induce gel-fluid phase separation in the system within an extensive temperature-composition region. The longer the hydrophobic length of the peptides is, the more narrow this region appears to become.

Morein, Sven; Killian, J Antoinette; Sperotto, Maria Maddalena

2002-01-01

329

Characterization of the thermotropic behavior and lateral organization of lipid-peptide mixtures by a combined experimental and theoretical approach: effects of hydrophobic mismatch and role of flanking residues.  

PubMed

A combined experimental and theoretical study was performed on a series of mixtures of dipalmitoylphosphatidylcholine (DPPC) and synthetic peptides to investigate their thermotropic behavior and lateral organization. The experimental study was based on differential scanning calorimetry (DSC) and phosphorous nuclear magnetic resonance ((31)P-NMR) techniques; the theoretical study was based on calculations on a microscopic molecular interaction model, where the lipid-peptide interaction is built on the hydrophobic matching principle. The chosen peptides, WALP and KALP, consist of a hydrophobic stretch, of variable length, of alternating leucine and alanine residues, flanked on both ends with tryptophan and lysine residues, respectively. By systematically varying the peptide hydrophobic length it was thus possible to explore different matching conditions between the peptide's hydrophobic length and the lipid bilayer hydrophobic thickness, and to investigate the potential role of flanking residues. The results show that both the WALP and the KALP peptides tend to favor the liquid-crystalline (or fluid) phase of the system; i.e., they tend to depress the main-transition temperature, T(m), of pure DPPC. However, the detailed effects of both peptides on the lateral phase behavior of the lipid-peptide system are dependent on the peptide length and the type of flanking residues. The results suggest that below T(m), the shortest among the WALP and KALP peptides induce gel-fluid phase separation in the system within an extensive temperature-composition region. The longer the hydrophobic length of the peptides is, the more narrow this region appears to become. PMID:11867456

Morein, Sven; Killian, J Antoinette; Sperotto, Maria Maddalena

2002-03-01

330

Tissue residue approach for chemical mixtures.  

PubMed

At the SETAC Pellston Workshop "The Tissue Residues Approach for Toxicity Assessment," held in June 2007, we discussed mixture toxicology in terms of the tissue residue approach (TRA). This article reviews the literature related to the TRA for mixtures of chemicals and recommends a practical, tiered approach that can be implemented in regulatory or risk assessment applications. As with the toxicity of individual chemicals, addressing mixture toxicity by means of the TRA has a number of significant advantages. Early work provided a theoretical basis and experimental data to support the use of TRA for mixtures; later work provided a field-based validation of the integration. However, subsequent development has been hindered by the lack of mixture toxicity data expressed in tissue or preferably target-site concentrations. We recommend a framework for addressing the toxicology of mixtures that integrates the TRA and mixture toxicology in a 3-tier approach. Tier I uses concentration addition (CA) to estimate the toxicity of mixtures regardless of the mechanism of action of the components. However, the common approach that uses a bioaccumulation factor (BAF) to predict TR from the exposure-water concentration for organics must be modified slightly for metals because, unlike organics, the BAF for a metal changes as 1) the aqueous exposure concentration changes, and 2) the concentration of other metals changes. In addition, total tissue residues of a metal are not a good predictor of toxicity, because some organisms store high concentrations of metals internally in detoxified forms. In tier I, if the combination of measured concentrations in the mixture exceeds that predicted to produce adverse effects or above-reference levels, it is necessary to proceed to tier II. Tier II is a mixed model that employs CA and independent action to estimate mixture toxicity. Tiers I and II estimate the toxicity of mixtures to individual species. In tier III, the TRA is integrated with the multisubstance potentially affected fraction (ms-PAF) method to derive TR levels that are protective of a selected percentage of species in aquatic communities (e.g., hazardous concentration for 5% of the species [HC5]). PMID:21184571

Dyer, Scott; St J Warne, Michael; Meyer, Joseph S; Leslie, Heather A; Escher, Beate I

2011-01-01

331

New model that describes adsorption of laterally interacting gas mixtures on random heterogeneous surfaces. 2: Correlation of complex binary and prediction of multicomponent adsorption equilibria  

SciTech Connect

The model developed in part 1 of this series for correlating single component and rather ideal binary adsorption equilibria demonstrated a remarkable ability for correlating complex binary adsorption equilibria, including adsorption azeotropes and sigmoidal-shaped x-y diagrams, using a single binary fitting parameter. This model was also extended successfully for predicting multicomponent adsorption equilibria on a heterogeneous adsorbent surface with a uniform distribution of Henry's law constant using single component adsorption isotherm parameters, along with one binary fitting parameter from each of the binary pairs in the multicomponent mixture. Overall, the results from this new model generally showed a marked improvement in the correlation of binary and prediction of multicomponent adsorption equilibria compared to that obtained with the multicomponent Langmuir model, which used only single component isotherm parameters, and compared to that obtained with two-dimensional fluid and loading ratio correlation models that also utilized binary fitting parameters.

Al-Muhtaseb, S.A.; Ritter, J.A.

1999-10-26

332

Kinematic separation of mixtures  

SciTech Connect

A phenomenon of spontaneous separation of components in an initially uniform fluid mixture is found experimentally. A qualitative explanation of the effect is proposed in terms of nonparallel streamlines in the medium.

Goldshtik, M.; Husain, H.S.; Hussain, F. (Department of Mechanical Engineering, University of Houston, Houston, Texas 77204-4792 (United States))

1992-06-15

333

Separating a Mixture  

NSDL National Science Digital Library

This activity was designed for blind learners, but all types of learners can explore means of physically separating a mixture using dissolving, filtration, and evaporation. Separating a sand/salt mixture is a common experiment in physical science class that requires almost no adaptation for learners with visual impairments. This activity also provides experience in popular laboratory techniques of dissolving, filtration, and evaporation. In this activity, the learner will use filters and funnels to separate sand and salt.

Blind, Perkins S.

2012-07-12

334

Condensate Mixtures and Tunneling  

SciTech Connect

The experimental study of condensate mixtures is a particularly exciting application of the recently developed atomic-trap Bose-Einstein condensate (BEC) technology: such multiple condensates represent the first laboratory systems of distinguishable boson superfluid mixtures. In addition, as the authors point out in this paper, the possibility of inter-condensate tunneling greatly enhances the richness of the condensate mixture physics. Not only does tunneling give rise to the oscillating particle currents between condensates of different chemical potentials, such as those studied extensively in the condensed matter Josephson junction experiments, it also affects the near-equilibrium dynamics and stability of the condensate mixtures. In particular, the stabilizing influence of tunneling with respect to spatial separation (phase separation) could be of considerable practical importance to the atomic trap systems. Furthermore, the creation of mixtures of atomic and molecular condensates could introduce a novel type of tunneling process, involving the conversion of a pair of atomic condensate bosons into a single molecular condensate boson. The static description of condensate mixtures with such type of pair tunneling suggests the possibility of observing dilute condensates with the liquid-like property of a self-determined density.

Timmermans, E.

1998-09-14

335

Monitoring Water Quality in the Future. Volume 2. Mixture Toxicity Parameters.  

National Technical Information Service (NTIS)

The objective of this report is to review the use of chemically defined group parameters for the estimation of the (potential) mixture toxicity of complex mixtures of organic micropollutants in water systems. Currently available extraction techniques for ...

W. M. G. M. van Loon J. L. M. Hermens

1995-01-01

336

Separation of methanol from methylesters by vapour permeation: experiences of industrial applications  

Microsoft Academic Search

Separation of water from its mixtures with organic liquids, especially from those with which it forms azeotropes by means of pervaporation and vapour permeation. has matured during the past 10 years to a state-of-the-art technology. The processes are applied in industrial plants worldwide for the dehydration of binary mixtures of light alcohols such as ethanol or isopropanol, esters such as

Eva Maus; Hartmut E. A. Brüschke

2002-01-01

337

Results of the IPCS collaborative study on complex mixtures  

Microsoft Academic Search

The International Program on Chemical Safety (IPCS) sponsored a collaborative study to examine the intra- and interlaboratory variation associated with the preparation and bioassay of complex chemical mixtures. The mixtures selected were National Institute of Standards and Technology (NIST) Standard Reference Materials (SRM). Twenty laboratories worldwide participated in the study. The participating laboratories extracted the organic portion of two particulate

L. D. Claxton; J. Creason; B. Leroux; E. Agurell; S. Bagley

1992-01-01

338

Apparatus for manufacturing fluid coal-oil-water fuel mixture  

Microsoft Academic Search

An apparatus is disclosed for manufacturing a coal-oil-water fuel mixture comprising a grinder for grinding coal to a relatively fine particle size, a mixer for controllably mixing the coal particle with oil, water and a high molecular weight organic mixture. These devices may be used in combination with coal cleaning apparatus for removal of ash and impurities from the coal.

Poetschke

1983-01-01

339

Toxicology of complex mixtures of indoor air pollutants  

Microsoft Academic Search

This review focuses on strategies for assessing the toxicology of indoor air pollutant mixtures. These strategies are illustrated by reviewing the current problems and approaches to the toxicology of indoor air pollutants from three indoor source categories that make a major contribution to human exposure: environmental tobacco smoke, combustion emissions, and volatile organic compound (VOC) mixtures from materials and products.

J Lewtas

1989-01-01

340

Development of more efficacious Tc99, organ imaging agents for use in nuclear medicine by analytical characterization of radiopharmaceutical mixtures: Progress report for period September 1, 1987August 31, 1988  

Microsoft Academic Search

The long-range objective of this research is the development of more efficacious technetium-99m radiopharmaceuticals for use as imaging agents in diagnostic nuclear medicine. These objectives are being met by the development of analytical techniques which are capable of separating radiopharmaceutical mixtures into their component technetium complexes for subsequent evaluation. Three areas have been investigated during the second year of this

Heineman

1988-01-01

341

Fuel mixture control system  

SciTech Connect

A fuel mixture control apparatus for an electronic fuel injection system for internal combustion engines is disclosed. In a warm-up controller, the fuel injection control pulses are lengthened for enrichment of the fuel-air mixture during engine warm-up on the basis of signals supplied by a temperature transducer. In order to make the warm-up enrichment dependent on prevailing engine states, for example on the conditions of idling and partial or full load, circuitry is provided to sense these conditions and to suitably alter the enrichment factor. A further circuit suppresses the dependence or enrichment on engine status during engine starting. Various embodiments are presented.

Drews, U.; Gloss, E.; Kirn, D.; Moder, H.; Schnurle, H.; Steinbrenner, U.; Streit, K.; Werner, P.

1980-06-03

342

21 CFR 1310.12 - Exempt chemical mixtures.  

Code of Federal Regulations, 2010 CFR

...4) Iodine products that consist of organically bound iodine (a non-ionic complex) (e.g., iopamidol, iohexol, and amiodarone.) (e) The Administrator may, at any time, terminate or modify the exemption for any chemical mixture which...

2009-04-01

343

21 CFR 1310.12 - Exempt chemical mixtures.  

Code of Federal Regulations, 2010 CFR

...4) Iodine products that consist of organically bound iodine (a non-ionic complex) (e.g., iopamidol, iohexol, and amiodarone.) (e) The Administrator may, at any time, terminate or modify the exemption for any chemical mixture which...

2010-04-01

344

Method of extracting iodine from liquid mixtures of iodine, water and hydrogen iodide  

DOEpatents

The components of a liquid mixture consisting essentially of HI, water and at least about 50 w/o iodine are separated in a countercurrent extraction zone by treating with phosphoric acid containing at least about 90 w/o H.sub.3 PO.sub.4. The bottom stream from the extraction zone is substantially completely molten iodine, and the overhead stream contains water, HI, H.sub.3 PO.sub.4 and a small fraction of the amount of original iodine. When the water and HI are present in near-azeotropic proportions, there is particular advantage in feeding the overhead stream to an extractive distillation zone wherein it is treated with additional concentrated phosphoric acid to create an anhydrous HI vapor stream and bottoms which contain at least about 85 w/o H.sub.3 PO.sub.4. Concentration of these bottoms provides phosphoric acid infeed for both the countercurrent extraction zone and for the extractive distillation zone.

Mysels, Karol J. (La Jolla, CA)

1979-01-01

345

Combining Gaussian Mixture Models  

Microsoft Academic Search

A Gaussian mixture model (GMM) estimates a probability density function using the expectation-maximization algorithm. However, it may lead to a poor performance or inconsistency. This paper analytically shows that per- formance of a GMM can be improved in terms of Kullback-Leibler divergence with a committee of GMMs with different initial parameters. Simulations on synthetic datasets demonstrate that a committee of

Hyoung-joo Lee; Sungzoon Cho

2004-01-01

346

Lab Investigation Mixture Separation  

NSDL National Science Digital Library

This is a lab that is designed to have students write a lab procedure and separate out mixture of substances with different properties. It is also a good introduction to the different lab equipment that they will be using through out the year.

347

Alkylation of aromatic mixtures  

SciTech Connect

A process is described for preparing alkyl-substituted toluene and alkyl-substituted benzene alkylation products. The process comprises contacting a vapor mixture consisting of toluene and benzene with an alkylating agent at an elevated temperature and at least atmospheric pressure in the presence of a catalytic amount of a porous crystalline magnesium silicate.

Dianis, W.P.; Williams, A.J.

1987-05-12

348

Hydrodynamic gas mixture separation  

Microsoft Academic Search

The separation of gas mixtures is the basis of many chemical, petrochemical, and gas processes. Classical separation methods (absorption, adsorption, condensation, and freezing) require cumbersome and complex equipment. No adequate solution is provided by the cheapening and simplification of gas-processing apparatus and separation methods by hydration and diffusion. For example, an apparatus for extracting helium from natural gas by diffusion

Stolyarov

1982-01-01

349

Formation of 2-methyl tetrols and 2-methylglyceric acid in secondary organic aerosol from laboratory irradiated isoprene\\/NO X \\/SO 2\\/air mixtures and their detection in ambient PM 2.5 samples collected in the eastern United States  

Microsoft Academic Search

Recent observations in ambient PM2.5 of 2-methylthreitol, 2-methylerythritol and 2-methylglyceric acid, proposed isoprene oxidation products, suggest the contribution of isoprene to SOA formation, long thought to be relatively unimportant, should be reexamined. To address this issue, an isoprene\\/NOX\\/air mixture was irradiated in a flow reactor smog chamber in both the absence and presence of SO2 to measure the SOA yield

E. O. Edney; T. E. Kleindienst; M. Jaoui; M. Lewandowski; J. H. Offenberg; W. Wang; M. Claeys

2005-01-01

350

Theory of phase equilibria for model mixtures of n-alkanes, perfluoroalkanes and perfluoroalkylalkane diblock surfactants  

NASA Astrophysics Data System (ADS)

An extension of the SAFT-VR equation of state, the so-called hetero-SAFT approach [Y. Peng, H. Zhao, and C. McCabe, Molec. Phys. 104, 571 (2006)], is used to examine the phase equilibria exhibited by a number of model binary mixtures of n-alkanes, perfluoroalkanes and perfluoroalkylalkane diblock surfactants. Despite the increasing recent interest in semifluorinated alkanes (or perfluoroalkylalkane diblock molecules), the phase behaviour of mixtures involving these molecules with n-alkanes or perfluoroalkanes is practically unknown from the experimental point of view. In this work, we use simple molecular models for n-alkanes, perfluoroalkanes and perfluoroalkylalkane diblock molecules to predict, from a molecular perspective, the phase behaviour of selected model mixtures of perfluoroalkylalkanes with n-alkanes and perfluoroalkanes. In particular, we focus our interest on the understanding of the microscopic conditions that control the liquid-liquid separation and the stabilization of these mixtures. n-Alkanes and perfluoroalkanes are modelled as tangentially bonded monomer segments with molecular parameters taken from the literature. The perfluoroalkylalkane diblock molecules are modelled as heterosegmented diblock chains, with parameters for the alkyl and perfluoroalkyl segments developed in earlier work. This simple approach, which was proposed in previous work [P. Morgado, H. Zhao, F. J. Blas, C. McCabe, L. P. N. Rebelo, and E. J. M. Filipe, J. Phys. Chem. B, 111, 2856], is now extended to describe model n-alkane (or perfluoroalkane) + perfluroalkylalkane binary mixtures. We have obtained the phase behaviour of different mixtures and studied the effect of the molecular weight of n-alkanes and perfluoroalkanes on the type of phase behaviour observed in these mixtures. We have also analysed the effect of the number of alkyl and perfluoroalkyl chemical groups in the surfactant molecule on the phase behaviour. In addition to the usual vapour-liquid phase separation, liquid-liquid, positive azeotropes, and Bancroft points are found for different mixtures. This rich phase behaviour is a consequence of a delicate balance between the alkyl-alkyl, perfluoroalkyl-perfluoroalkyl, and alkyl-perfluoroalkyl interactions in different molecules. We used the SAFT-VR microscopic description of chain-like systems to analyse the conditions that n-alkane (or perfluoroalkane) + perfluoroalkyalkane mixtures should posses in order to exhibit complete liquid miscibility. Although the model proposed here is chosen to reproduce most of the quantitative features of the phase equilibria of some pure perfluoroalkylalkane diblock surfactants and their mixtures with n-alkanes, this is the first time the SAFT approach has been used to predict the phase behaviour of the mixtures considered here. The lack of experimental data for these systems does not allow us to test the accuracy of our theoretical predictions directly. However, since SAFT has proven to be an excellent approach for the prediction of the phase behaviour of complex mixtures, we expect that the theory will reproduce the most important qualitative trends exhibited by real mixtures.

Dos Ramos, María Carolina; Blas, Felipe J.

2007-05-01

351

Mixture toxicity and tissue interactions of Cd, Cu, Pb and Zn in earthworms ( Oligochaeta) in laboratory and field soils: A critical evaluation of data  

Microsoft Academic Search

Soil organisms inhabiting contaminated field sites are usually exposed to mixtures of toxicants. In such mixtures, toxicants can interact to express enhanced or weakened toxicity. Therefore, mixture effects should be considered in risk assessment methods for polluted soils. Data on mixture toxicity to soil organisms are scarce, however. In this paper, data on sublethal toxicity and tissue concentrations of Cd,

L. Weltje

1998-01-01

352

POTENTIAL EMISSIONS OF HAZARDOUS ORGANIC COMPOUNDS FROM SEWAGE SLUDGE INCINERATION  

EPA Science Inventory

Laboratory thermal decomposition studies were undertaken to evaluate potential organic emissions from sewage sludge incinerators. Precisely controlled thermal decomposition experiments were conducted on sludge spiked with mixtures of hazardous organic compounds, on the mixtures o...

353

New phase diagrams for dense carbon-oxygen mixtures and white dwarf evolution  

NASA Astrophysics Data System (ADS)

Context. Cool white dwarfs are reliable and independent stellar chronometers. The most common white dwarfs have carbon-oxygen dense cores. Consequently, the cooling ages of very cool white dwarfs sensitively depend on the adopted phase diagram of the carbon-oxygen binary mixture. Aims: A new phase diagram of dense carbon-oxygen mixtures appropriate for white dwarf interiors has been recently obtained using direct molecular dynamics simulations. In this paper, we explore the consequences of this phase diagram in the evolution of cool white dwarfs. Methods: To do this we employ a detailed stellar evolutionary code and accurate initial white dwarf configurations, derived from the full evolution of progenitor stars. We use two different phase diagrams, that of Horowitz et al. (2010, Phys. Rev. Lett., 104, 231101), which presents an azeotrope, and the phase diagram of Segretain & Chabrier (1993, A&A, 271, L13), which is of the spindle form. Results: We computed the evolution of 0.593 and 0.878 M? white dwarf models during the crystallization phase, and we found that the energy released by carbon-oxygen phase separation is smaller when the new phase diagram of Horowitz et al. is used. This translates into time delays that are on average a factor ~2 smaller than those obtained when the phase diagram of Segretain & Chabrier is employed. Conclusions: Our results have important implications for white dwarf cosmochronology, because the cooling ages of very old white dwarfs are different for the two phase diagrams. This may have a noticeable impact on the age determinations of very old globular clusters, for which the white dwarf color-magnitude diagram provides an independent way of estimating their age.

Althaus, L. G.; García-Berro, E.; Isern, J.; Córsico, A. H.; Miller Bertolami, M. M.

2012-01-01

354

Effect of stirring on the safety of flammable liquid mixtures.  

PubMed

Flash point is the most important variable employed to characterize fire and explosion hazard of liquids. The models developed for predicting the flash point of partially miscible mixtures in the literature to date are all based on the assumption of liquid-liquid equilibrium. In real-world environments, however, the liquid-liquid equilibrium assumption does not always hold, such as the collection or accumulation of waste solvents without stirring, where complete stirring for a period of time is usually used to ensure the liquid phases being in equilibrium. This study investigated the effect of stirring on the flash-point behavior of binary partially miscible mixtures. Two series of partially miscible binary mixtures were employed to elucidate the effect of stirring. The first series was aqueous-organic mixtures, including water+1-butanol, water+2-butanol, water+isobutanol, water+1-pentanol, and water+octane; the second series was the mixtures of two flammable solvents, which included methanol+decane, methanol+2,2,4-trimethylpentane, and methanol+octane. Results reveal that for binary aqueous-organic solutions the flash-point values of unstirred mixtures were located between those of the completely stirred mixtures and those of the flammable component. Therefore, risk assessment could be done based on the flammable component flash-point value. However, for the assurance of safety, it is suggested to completely stir those mixtures before handling to reduce the risk. PMID:20116168

Liaw, Horng-Jang; Gerbaud, Vincent; Chen, Chan-Cheng; Shu, Chi-Min

2010-01-13

355

Photoisomerization- and photopolymerization-induced phase transitions in mixtures of photoresponsive chromophores and reactive mesogens  

NASA Astrophysics Data System (ADS)

Phase diagram of various blend systems containing photochromophores and reactive mesogenic diacrylate monomers has been constructed both experimentally and theoretically. Differential scanning calorimetry was commonly utilized to determine phase transition temperature, and theoretical curve was obtained by solving self-consistently the combined free energy of Flory-Huggins, Maier-Saupe, and phase field theory. Depending on the system, it exhibited various single and coexistence phases including crystal, nematic, crystal + isotropic, nematic + isotropic, crystal + nematic, and crystal + crystal. Guided by the phase diagram, we further investigated (i) self-motion of azobenzene chromophore (AC) in triacrylate (TA) solution, (ii) photoisomerization-induced phase transition of liquid crystalline azobenzene (LCAC) and spiropyran (SP) chromophore in its mixtures with reactive mesogenic diacrylate (RMDA), and (iii) photopolymerization-induced phase separation of RMDA/low molecular weight liquid crystal (LMWLC) blends. Self-motion of AC single crystal in TA solution was investigated in relation to the solid-liquid phase diagram. Upon thermal quenching from the isotropic melt to the crystal + liquid gap, the concentration gradient that formed as the result of TA expulsion induced convective flows and generated spatial variability of surface tension usually responsible for Marangoni effect. A stationary rhomboidal crystal was also shown to swim upon irradiation with UV light due to mechanical torque generated by trans-cis isomerization. The trans-cis photoisomerization of LCAC not only exerted a dramatic effect on the mesophase transitions, but also on the stratification on the crystal morphology. The phase diagram of photoisomerized mixtures displayed a significant depression of nematic ordering. Meanwhile, spiropyran-merocyanine molecular shape change induced the I-N phase transition, which was infusible. Upon photopolymerization of RMDA/LMWLC blends, the homogeneous mixtures underwent phase separation. As the crystalline and nematic ordering of monomeric unit was frozen, LMWLC was dispersed in the continuum of isotropic or anisotropic networks. Phase diagram exhibited the broad immiscible regions. The phase diagram of annealed hyperbranched polymer/LMWLC mixtures was an upper azeotrope, exhibiting the coexistence of nematic + isotropic phase above the clearing temperature of neat LMWLC. With decreasing temperature a focal-conic fan shaped texture developed in the composition range of 63~93 wt %, suggestive of induced smectic phase in the mixture.

Kim, Namil

356

Mutation spectra of complex environmental mixtures  

SciTech Connect

Bioassay-directed chemical analysis of complex environmental mixtures has indicated that much of the genotoxic activity of mixtures is due to the presence of one or a few classes or chemicals within the mixture. We have extended this observation to the molecular level by using colony probe hybridization and PCR/DNA sequence analysis to determine the mutation spectra of {approximately}8,000 revertants induced by a variety of complex mixtures and their chemical fractions in TA100 and TA98 of Salmonella. For urban air, >80% of mutagenic activity was due to a base/neutral fraction that contained primarily PAHs. The mutation spectrum induced by unfractionated urban air was not significantly different from that produced by a model PAH, B(a)P. The mutation spectrum induced by organic extracts of chlorinated drinking water were similar to those produced by the chlorinated furanone MX, which accounted for {approximately}20% of the mutagenic activity of the samples. The base/neutral fraction of municipal waste incinerator emissions accounted for the primary class of mutations induced by the emissions, and a polar neutral fraction accounted for the secondary class of mutations induced by the emissions. The primary class of mutations induced by cigarette smoke condensate in TA100 (GC {yields} TA) is also the primary class of mutations in the p53 gene of lung tumors of cigarette smokers. These results confirm at the molecular level that the mutations induced by a complex mixture reflect the dominance of one or a few classes of chemicals within the mixture.

DeMarini, D.M. [EPA, Research Triangle Park, NC (United States)

1997-10-01

357

Hydrolysis of cellulose using ternary mixtures of purified cellulases.  

PubMed

The saccharification of microcrystalline cellulose by reconstituted ternary mixtures of purified cellulases (one endoglucanase and two cellobiohydrolases) has been studied over the entire range of mixture compositions. Ternary plots are used to compare the performance of five synthetic mixtures drawn from the cellulase systems of Acidothermus cellulolyticus, Trichoderma reesei, Thermomonospora fusca, and Thermotoga neapolitana. Results reveal that at least one synthetic mixture utilizing enzymes from three different organisms delivers performance competitive with that of a "native" (i.e., co-evolved) ternary system drawn exclusively from T. reesei. This heterologous system, consisting of the endoglucanase E1 from A. cellulolyticus and the exoglucanases CBHI from T. reesei and E3 from T. fusca, is forgiving from the system-design point of view, in that it delivers high saccharification rates over a wide range of mixture compositions. PMID:9627391

Baker, J O; Ehrman, C I; Adney, W S; Thomas, S R; Himmel, M E

1998-01-01

358

Hydrolysis of cellulose using ternary mixtures of purified celluloses.  

PubMed

The saccharification of microcrystalline cellulose by reconstituted ternary mixtures of purified cellulases (one endoglucanase and two cellobiohydrolases) has been studied over the entire range of mixture compositions. Ternary plots are used to compare the performance of five synthetic mixtures drawn from the cellulase systems of Acidothermus cellulolyticus, Trichoderma reesei, Thermomonospora fusca, and Thermotoga neapolitana. Results reveal that at least one synthetic mixture utilizing enzymes from three different organisms delivers performance competitive with that of a "native" (i.e., co-evolved) ternary system drawn exclusively from T. reesei. This heterologous system, consisting of the endoglucanase El from A. cellulolyticus and the exoglucanases CBHI from T. ressei and E3 from T. fusca, is forgiving from the system-design point of view, in that it delivers high saccharification rates over a wide range of mixture compositions. PMID:18576007

Baker, J O; Ehrman, C I; Adney, W S; Thomas, S R; Himmel, M E

1998-01-01

359

Thermodynamic study of (anthracene + benzo[a]pyrene) solid mixtures.  

PubMed

To characterize better the thermodynamic behavior of a binary polycyclic aromatic hydrocarbon mixture, thermochemical and vapor pressure experiments were used to examine the phase behavior of the {anthracene (1) + benzo[a]pyrene (2)} system. A solid-liquid phase diagram was mapped for the mixture. A eutectic point occurs at x(1) = 0.26. The eutectic mixture is an amorphous solid that lacks organized crystal structure and melts between T = (414 and 420) K. For mixtures that contain 0.10 < x(1) < 0.90, the enthalpy of fusion is dominated by that of the eutectic. Solid-vapor equilibrium studies show that mixtures of anthracene and benzo[a]pyrene at x(1) < 0.10 sublime at the vapor pressure of pure benzo[a]pyrene. These results suggest that the solid-vapor equilibrium of benzo[a]pyrene is not significantly influenced by moderate levels of anthracene in the crystal structure. PMID:20814451

Rice, James W; Suuberg, Eric M

2010-11-01

360

Thermodynamic study of (anthracene + benzo[a]pyrene) solid mixtures  

PubMed Central

To characterize better the thermodynamic behavior of a binary polycyclic aromatic hydrocarbon mixture, thermochemical and vapor pressure experiments were used to examine the phase behavior of the {anthracene (1) + benzo[a]pyrene (2)} system. A solid-liquid phase diagram was mapped for the mixture. A eutectic point occurs at x1 = 0.26. The eutectic mixture is an amorphous solid that lacks organized crystal structure and melts between T = (414 and 420) K. For mixtures that contain 0.10 < x1 < 0.90, the enthalpy of fusion is dominated by that of the eutectic. Solid-vapor equilibrium studies show that mixtures of anthracene and benzo[a]pyrene at x1 < 0.10 sublime at the vapor pressure of pure benzo[a]pyrene. These results suggest that the solid-vapor equilibrium of benzo[a]pyrene is not significantly influenced by moderate levels of anthracene in the crystal structure.

Rice, James W.; Suuberg, Eric M.

2010-01-01

361

Toxicological approaches to complex mixtures.  

PubMed Central

This paper reviews the role of toxicological studies in understanding the health effects of environmental exposures to mixtures. The approach taken is to review mixtures that have received the greatest emphasis from toxicology; major mixtures research programs; the toxicologist's view of mixtures and approaches to their study; and the complementary roles of toxicological, clinical, and epidemiological studies. Studies of tobacco smoke, engine exhaust, combustion products, and air pollutants comprise most of the past research on mixtures. Because of their great experimental control over subjects, exposures, and endpoints, toxicologists tend to consider a wider range of toxic interactions among mixture components and sequential exposures than is practical for human studies. The three fundamental experimental approaches used by toxicologists are integrative (studying the mixture as a whole), dissective (dissecting a mixture to determine causative constituents), and synthetic (studying interactions between agents in simple combinations). Toxicology provides information on potential hazards, mechanisms by which mixture constituents interact to cause effects, and exposure dose-effect relationships; but extrapolation from laboratory data to quantitative human health risks is problematic. Toxicological, clinical, and epidemiological approaches are complementary but are seldom coordinated. Fostering synergistic interactions among the disciplines in studying the risks from mixtures could be advantageous.

Mauderly, J L

1993-01-01

362

Organic waste converter  

Microsoft Academic Search

An airtight chamber insulated with an anti-corrosive coating allows the control of the heat and moisture content of organic wastes for rapid aerobic decomposition by naturally occurring thermal bacteria. Air is drawn into the chamber, over and through the organic waste and carbonaceous filler materials and is exhausted through an air scrubber. Agitation of the waste mixture is by means

Schlichting

1981-01-01

363

Pervaporation of dilute alcoholic mixtures using PDMS membrane  

Microsoft Academic Search

Pervaporation (PV) of methanol\\/water and ethanol\\/water mixtures through PDMS membrane was investigated using a PV cell (in laboratory scale). PDMS membrane is a well-known hydrophobic membrane for removing organics from aqueous mixtures. Experimental results were obtained at different initial alcohol (methanol and ethanol) concentrations (0.3–3wt%) and temperatures (30–50?C). Recirculation flow rate was kept constant at a value of 15.6l\\/h. Average

Toraj Mohammadi; Abdolreza Aroujalian; Ali Bakhshi

2005-01-01

364

Cough mixture abuse and rhabdomyolysis.  

PubMed

Cough mixture abuse is an emerging problem among young men in Oriental countries. Its metabolic consequences have been recognised only recently. Such abusers can develop severe folate deficiency, which may be related to peripheral and central nervous system defects. We report three cough mixture abusers with rhabdomyolysis. All suffered from folate deficiencies and also had a history of anti-psychotic drug use. This represents one more life-threatening side-effect from cough mixture abuse. PMID:22302917

Tsang, Jenny S K; Au, W Y

2012-02-01

365

The Infinite Gaussian Mixture Model  

Microsoft Academic Search

Abstract In a Bayesian mixture model it is not necessary a priori to lim it the number of components,to be finite. In this paper an infinite Gaussi an mixture model is presented which neatly sidesteps the difficult prob lem of finding the “right” number,of mixture components. Inference in the model is done using an efficient parameter-free Markov Chain that rel

Carl Edward Rasmussen

1999-01-01

366

Mixtures of functionalized colloids on substrates  

NASA Astrophysics Data System (ADS)

Patchy particles are a class of colloids with functionalized surfaces. Through surface functionalization, the strength and directionality of the colloidal interactions are tunable allowing control over coordination of the particle. Exquisite equilibrium phase diagrams of mixtures of coordination two and three have been reported. However, the kinetics of self-organization and the feasibility of the predicted structures are still largely unexplored. Here, we study the irreversible aggregation of these mixtures on a substrate, for different fractions of two-patch particles. Two mechanisms of mass transport are compared: diffusion and advection. In the diffusive case, an optimal fraction is found that maximizes the density of the aggregate. By contrast, for advective transport, the density decreases monotonically with the fraction of two-patch colloids, in line with the behavior of the liquid density on the spinodal of the equilibrium phase diagram.

Dias, C. S.; Araújo, N. A. M.; Telo da Gama, M. M.

2013-10-01

367

Development of more efficacious Tc-99, organ imaging agents for use in nuclear medicine by analytical characterization of radiopharmaceutical mixtures: Progress report for period September 1, 1987-August 31, 1988  

SciTech Connect

The long-range objective of this research is the development of more efficacious technetium-99m radiopharmaceuticals for use as imaging agents in diagnostic nuclear medicine. These objectives are being met by the development of analytical techniques which are capable of separating radiopharmaceutical mixtures into their component technetium complexes for subsequent evaluation. Three areas have been investigated during the second year of this project. (1) A chromatographic procedure has been developed for the separation of technetium dicarboxypropane diphosphonate (DPD) complexes. Tc-DPD complexes have been isolated from radiopharmaceutical preparations. The concentration of each complex in the preparation varies significantly depending on the pH of the preparation, the concentration of technetium, the presence or absence of oxygen, and the time interval after preparation. A single Tc-DPD complex has been isolated which shows good skeletal uptake and rapid soft tissue clearance. (2) An HPLC procedure for analyzing urine for Tc-Diphosphonate complexes has been developed. A Tc-HEDP complexd injected into a dog was found to concentrate rapidly in the bladder in the same chemical form. (3) An HPLC technique for the determination of /sup 99m/TcO/sub 4//sup -/ in disphosphonate radiopharmaceuticals and biological samples has been developed. 15 refs., 2 figs.

Heineman, W.R.

1988-04-01

368

Solvents for bulk removal of organics from coal-conversion condensate waters. [Methyl isobutyl ketone, diisopropyl ether and mixture of 25% w/w trioctyl phosphine oxide in diisobutyl ketone  

SciTech Connect

In this work chemical analyses and experimental tests of extraction solvents are discussed for condensate waters from a coal gasification plant. The results of the study showed that methyl isobutyl ketone (MIBK) provides much higher distribution coefficients than diisopropyl ether DIPE for phenol and dihydroxybenzenes. About 90% of the chemical oxygen demand (COD) from one condensate water sample had a sufficiently high K/sub D/ into MIBK that it could be removed by this solvent in a counter-current extraction process at an economically reasonable solvent-to-water ratio. TOPO (mixture of 25% w/w trioctyl phosphine oxide in diisobutyl ketone) in a suitable diluent has high equilibrium distribution coefficients for phenols and dihydroxybenzenes, and therefore has the potential to remove these compounds at lower solvent-to-water ratios. However, this solvent may be difficult to regenerate in a continuous condensate-water extraction process. Analytical techniques are discussed that provide higher recoveries for phenols and dihydroxybenzenes as compared to the standard MC/GC-MS technique. Hydantoins have been identified in four condensate water samples. About 20 to 30% of the COD remains unidentified in these four condensate water samples. Some of these unidentified compounds have very low values of K/sub D/ for extraction into MIBK. More information is required about these unidentified solutes before reliable solvent extraction processes can be designed. 6 tables.

Mohr, D.H.; King, C.J.

1983-03-01

369

Volume reduction and encapsulation process for water containing low-level radioactive waste  

SciTech Connect

Solutions or slurries of waste material in water are dewatered and encapsulated within a polymer for disposal, comprising the operations of removing water therefrom with azeotropic mixture evaporation and encasing the dewatered waste residue in an organic polymer. The method and system disclosed are especially useful for the safe disposal of radioactive waste.

Fox, D.W.; Miller, G.P.; Weech, M.E.

1984-02-28

370

Spinodal decomposition in binary mixtures  

Microsoft Academic Search

We study the early stage of the phase separation of a binary mixture far from its critical point of demixing. Whenever the mixture of two mutually repulsive species is quenched to a temperature below its critical point of miscibility, the effect of the enthalpic repulsive force prevails upon the entropic tendency to mix, so that the system eventually separates itno

Roberto Mauri; Reuel Shinnar; George Triantafyllou

1996-01-01

371

RISK ASSESSMENT OF COMPLEX MIXTURES  

EPA Science Inventory

Quantitative carcinogenic assessment of complex mixtures is complicated by the variability of the mixtures. Different samples of effluents from the same source may vary in their carcinogenic potency. A multiplicative effect could be produced by the action of different fractions o...

372

Global fluid phase behavior in binary mixtures of rodlike and platelike molecules  

NASA Astrophysics Data System (ADS)

The phase behavior of a liquid-crystal forming model colloidal system containing hard rodlike and platelike particles is studied using the Parsons-Lee scaling [J. D. Parsons, Phys. Rev. A 19, 1225 (1979); S. D. Lee, J. Chem. Phys. 87, 4972 (1987)] of the Onsager theory. The rod and plate molecules are both modeled as hard cylinders. All of the mixtures considered correspond to cases in which the volume of the plate is orders of magnitude larger that the volume of the rod, so that an equivalence can be made where the plates are colloidal particles while the rods play the role of a depleting agent. A combined analysis of the isotropic-nematic bifurcation transition and spinodal demixing is carried out to determine the geometrical requirements for the stabilization of a demixing transition involving two isotropic phases. Global phase diagrams are presented in which the boundaries of isotropic phase demixing are indicated as functions of the molecular parameters. Using a parameter z which corresponds to the product of the rod and plate aspect ratios, it is shown that the isotropic phase is unstable relative to a demixed state for a wide range of molecular parameters of the constituting particles due to the large excluded volume associated with the mixing of the unlike particles. However, the stability analysis indicates that for certain aspect ratios, the isotropic-nematic phase equilibria always preempts the demixing of the isotropic phase, irrespective of the diameters of the particles. When isotropic-isotropic demixing is found, there is an upper bound at large size ratios (Asakura and Oosawa limit), and a lower bound at small size ratios (Onsager limit) beyond which the system exhibits a miscible isotropic phase. It is very gratifying to find both of these limits within a single theoretical framework. We test the validity of the stability analysis proposed by calculating a number of phase diagrams of the mixture for selected molecular parameters. As the hard rod particles promote an effective attractive interaction between the hard-plate colloidal particles, the isotropic-isotropic demixing usually takes place between two rod-rich fluids. As far as the isotropic-nematic transition is concerned, a stabilization as well as a destabilization of the nematic phase relative to the isotropic phase is seen for varying rod-plate size ratios. Moreover, isotropic-nematic azeotropes and re-entrant phenomena are also observed in most of the mixtures studied. We draw comparisons between the predicted regions of stability for isotropic demixing and recent experimental observations.

Varga, Szabolcs; Galindo, Amparo; Jackson, George

2002-10-01

373

Zwanzig model of multi-component mixtures of biaxial particles: y3 theory re-visited  

NASA Astrophysics Data System (ADS)

The paper considers the thermodynamic and phase ordering properties of a multi-component Zwanzig mixture of hard rectangular biaxial parallelepipeds. An equation of state (EOS) is derived based on an estimate of the number of arrangements of the particles on a three- dimensional cubic lattice. The methodology is a generalization of the Flory-DiMarzio counting scheme, but, unlike previous work, this treatment is thermodynamically consistent. The results are independent of the order in which particles are placed on the lattice. By taking the limit of zero lattice spacing, a translationally continuous variant of the model (the off-lattice variant) is obtained. The EOS is identical to that obtained previously by a wide variety of different approaches. In the off-lattice limit, it corresponds to a third-level y-expansion and, in the case of a binary mixture of square platelets, it also corresponds to the EOS obtained from fundamental measure theory. On the lattice it is identical to the EOS obtained by retaining only complete stars in the virial expansion. The off-lattice theory is used to study binary mixtures of rods (R1 - R2) and binary mixtures of platelets (P1 - P2). The particles were uniaxial, of length (thickness) L and width D. The aspect ratios ?i = Li/Di of the components were kept constant (?1R = 15, ?1P = 1/15 and ?2R = 150, ?2P = 1/150), so the second virial coefficient of R1 was identical to P1 and similarly for R2 and P2. The volume ratio of particles 1 and 2, v1/v2, was then varied, with the constraints that viR = viP and ILM0001. Results on nematic-isotropic (N - I) phase coexistence at an infinite dilution of component 2, are qualitatively similar for rods and platelets. At small values of the ratio v1/v2, the addition of component 2 (i.e. a thin rod (e.g. a polymer) or a thin plate) results in the stabilization of the nematic phase. For larger values of v1/v2, however, this effect is reversed and the addition of component 2 destabilizes the nematic. For similar molecular volumes of the two components strong fractionation is observed: shorter rods and thicker platelets congregate in the isotropic phase. In general, the stabilization of the ordered phase and the fractionation between the phases are both weaker in the platelet mixtures. The calculated spinodal curves for isotropic-isotropic demixing are noticeably different between the R1 - R2 and the P1 - P2 systems. The platelet mixtures turn out to be stable with respect to de-mixing up to extremely high densities. The values of the consolute points for the R1 - R2 blends are remarkably similar to those obtained using the Parsons-Lee approximation for bi-disperse mixtures of freely rotating cylinders with similar aspect ratios [S. Varga. A. Galindo, G. Jackson, Mol. Phys., 101, 817 (2003)]. In a number of R1 - R2 mixtures, phase diagrams exhibiting both N - I equilibrium and I - I de-mixing were calculated. The latter is pre-empted by nematic ordering in all the cases studied. Calculations show the possible appearance of azeotropes in the N - I coexistence domain.

Sokolova, E. P.; Tumanyan, N. P.; Vlasov, A. Yu.; Masters, A. J.

374

Source separation in post-nonlinear mixtures  

Microsoft Academic Search

We address the problem of separation of mutually independent sources in nonlinear mixtures. First, we propose theoretical results and prove that in the general case, it is not possible to separate the sources without nonlinear distortion. Therefore, we focus our work on specific nonlinear mixtures known as post-nonlinear mixtures. These mixtures constituted by a linear instantaneous mixture (linear memoryless channel)

Anisse Taleb; Christian Jutten

1999-01-01

375

The genotoxic effect of carcinogenic PAHs, their artificial and environmental mixtures (EOM) on human diploid lung fibroblasts  

Microsoft Academic Search

The aim of this study was to investigate the genotoxic effect of single carcinogenic polycyclic aromatic hydrocarbons (c-PAHs), as well as their binary and artificial mixtures containing c-PAHs in the same relative proportions as real complex mixtures, and to investigate the genotoxic effect of environmental mixtures such as EOM (extractable organic matter adsorbed to respirable air particles). We used normal

Blanka Binková; Radim J. Šrám

2004-01-01

376

Asphalt Mixtures and Asphalt Chemistry.  

National Technical Information Service (NTIS)

The 23 papers in the report deal with the following areas: Field control test for debonding of asphaltic concrete; Moisture susceptibility behavior of asphalt concrete and emulsified asphalt mixtures using the freeze-thaw pedestal test; Assessment of stri...

R. A. Jimenez

1989-01-01

377

TEA laser gas mixture optimization  

SciTech Connect

The topographical plot of an optimized parameter, such as pulse energy or peak power, on the gas mixture plane is presented as a useful aid in realizing optimum mixtures of helium, carbon dioxide, and nitrogen, for operation of CO/sub 2/ TEA lasers. A method for generating such a plot is discussed and an example is shown. The potential benefits of this graphical technique are also discussed.

Lipchak, W.M.; Luck, C.F.

1982-11-01

378

Ionization coefficients in gas mixtures  

NASA Astrophysics Data System (ADS)

We have tested the application of the common E/N (E—electric field, N—gas number density) or Wieland approximation [Van Brunt, R.J., 1987. Common parametrizations of electron transport, collision cross section, and dielectric strength data for binary gas mixtures. J. Appl. Phys. 61 (5), 1773 1787.] and the common mean energy (CME) combination of the data for pure gases to obtain ionization coefficients for mixtures. Test calculations were made for Ar CH4, Ar N2, He Xe and CH4 N2 mixtures. Standard combination procedure gives poor results in general, due to the fact that the electron energy distribution is considerably different in mixtures and in individual gases at the same values of E/N. The CME method may be used for mixtures of gases with ionization coefficients that do not differ by more than two orders of magnitude which is better than any other technique that was proposed [Mari?, D., Radmilovi?-Ra?enovi?, M., Petrovi?, Z.Lj., 2005. On parametrization and mixture laws for electron ionization coefficients. Eur. Phys. J. D 35, 313 321.].

Mari?, D.; Šaši?, O.; Jovanovi?, J.; Radmilovi?-Ra?enovi?, M.; Petrovi?, Z. Lj.

2007-03-01

379

Choice of basis mixtures for the prediction of vapor-liquid equilibria using the UNIFAC model  

SciTech Connect

A link was established between the accurate prediction of vapor-liquid equilibria and azeotropes using the UNIFAC group model and the choice of the basis information. The component activity coefficients are plotted as functions of composition for all the sets of data in each binary system. The activity coefficients at infinite dilution are determined as graphical extrapolations of these plots. The plot for the butanol-hydrocarbon system is shown. It is shown that azeotrope parameters can be used as the basis information to predict vapor-liquid equilibria for several sets of systems.

Kushner, T.M.; Fainburg, G.D.; Vitman, T.A.; Serafimov, L.A.

1988-07-01

380

Water-enhanced solvation of organic solutes in ketone and ester solvents  

SciTech Connect

Previous research has shown that the solubilities of dicarboxylic acids in certain electron-donor solvents are substantially increased in the presence of water. Information on solubilities, liquid-liquid equilibria and maximum-boiling ternary azeotropes was screened so as to identify other systems where codissolved water appears to enhance solvation of organic solutes in solvents. Several carboxylic acids, an alcohol, diols, and phenols were selected for examination as solutes in ketone and ester solvents. Effects of water upon solute solubilities and volatilities were measured. Results showed that water-enhanced solvation is greatest for carboxylic acids. Solute activity coefficients decreased by factors of 2--3, 6--8, and 7--10 due to the presence of water for mono-, di and tricarboxylic acids, respectively. Activity coefficients decreased by a factor of about 1.5 for ethanol and 1,2-propanediol as solutes. Water-enhanced solvation of phenols is small, when existent.

Lee, J.H.; Brunt, V. van; King, C.J. (Univ. of California, Berkeley, CA (United States). Dept. of Chemical Engineering Lawrence Berkeley Lab., CA (United States))

1994-05-01

381

Nanostructured fluids from pluronic® mixtures.  

PubMed

Micellization and gelation of binary mixtures of EO99PO69EO99 (pluronic(®) F127) and EO80PO27EO80 (pluronic(®) F68) in aqueous solutions were investigated by means of micro-differential scanning calorimetry and rheology and for a total copolymer concentration fixed at 20 wt%. The aim of this investigation is to determine the interplay between micellization and macroscopic gelation of the mixed solutions. Micro-DSC reveals the formation of two distinct populations in F127/F68 mixtures during heating and subsequent cooling of the solutions. The enthalpies of micellization of each copolymer and the respective onset temperatures remained constant after mixing indicating the predominance of two independent processes of micellization in the mixtures. The F127 exhibits a crystallization transition, at a distinct temperature which persists, but increases in the mixtures with concentrations higher than 10 wt%. Rheological measurements were performed during heating ramps or after maturation periods versus frequency. They showed two types of gelation transitions: either a steep increase of the storage and the loss moduli, which corresponds to the crystallization temperature of the F127 micelles or a progressive jamming transition when no crystal can form. Maturation process has a major effect on the rheological properties of the mixed gels, possibly related to local rearrangements of the two micellar phases. This investigation highlights the unique features of the binary pluronic(®) mixtures, compared to dilution effects of single component aqueous solutions. PMID:23370436

Zhang, Min; Djabourov, Madeleine; Bourgaux, Claudie; Bouchemal, Kawthar

2013-01-28

382

An analytical evaluation of flammability limits of gaseous mixtures of combustible–oxidizer–diluent  

Microsoft Academic Search

This paper is aimed at the creation of new methods for the analytical evaluation of flammability limits of ternary gaseous mixtures of combustible–oxidizer–diluent. The physical nature of flammability limits is considered using some peculiarities of the chemical kinetics of combustion of gaseous organic substances in air. New features of lower flammability limits and compositions of mixtures near peak points of

Yu. N. Shebeko; W. Fan; I. A. Bolodian; V. Yu. Navzenya

2002-01-01

383

Calorimetric study of the reaction of cellulose with mixtures of nitric acid and methane derivatives  

Microsoft Academic Search

1.A study was carried out on the effect of chloro and nitro derivatives of methane on the nature and quantitative indices of the nitration of cellulose by nitric acid.2.The use of mixtures of HNO3 and an organic solvent gives rapid nitration of cellulose as a consequence both of the high rate of diffusion of these mixtures into the interior of

N. V. Novikova; Yu. N. Matyushin; V. F. Sopin; G. L. Ryzhova; Yu. A. Lebedev

1987-01-01

384

Bayesian Kernel Mixtures for Counts  

PubMed Central

Although Bayesian nonparametric mixture models for continuous data are well developed, there is a limited literature on related approaches for count data. A common strategy is to use a mixture of Poissons, which unfortunately is quite restrictive in not accounting for distributions having variance less than the mean. Other approaches include mixing multinomials, which requires finite support, and using a Dirichlet process prior with a Poisson base measure, which does not allow smooth deviations from the Poisson. As a broad class of alternative models, we propose to use nonparametric mixtures of rounded continuous kernels. An efficient Gibbs sampler is developed for posterior computation, and a simulation study is performed to assess performance. Focusing on the rounded Gaussian case, we generalize the modeling framework to account for multivariate count data, joint modeling with continuous and categorical variables, and other complications. The methods are illustrated through applications to a developmental toxicity study and marketing data. This article has supplementary material online.

Canale, Antonio; Dunson, David B.

2011-01-01

385

Bayesian Kernel Mixtures for Counts.  

PubMed

Although Bayesian nonparametric mixture models for continuous data are well developed, there is a limited literature on related approaches for count data. A common strategy is to use a mixture of Poissons, which unfortunately is quite restrictive in not accounting for distributions having variance less than the mean. Other approaches include mixing multinomials, which requires finite support, and using a Dirichlet process prior with a Poisson base measure, which does not allow smooth deviations from the Poisson. As a broad class of alternative models, we propose to use nonparametric mixtures of rounded continuous kernels. An efficient Gibbs sampler is developed for posterior computation, and a simulation study is performed to assess performance. Focusing on the rounded Gaussian case, we generalize the modeling framework to account for multivariate count data, joint modeling with continuous and categorical variables, and other complications. The methods are illustrated through applications to a developmental toxicity study and marketing data. This article has supplementary material online. PMID:22523437

Canale, Antonio; Dunson, David B

2012-01-24

386

Phylogenetic mixture models for proteins.  

PubMed

Standard protein substitution models use a single amino acid replacement rate matrix that summarizes the biological, chemical and physical properties of amino acids. However, site evolution is highly heterogeneous and depends on many factors: genetic code; solvent exposure; secondary and tertiary structure; protein function; etc. These impact the substitution pattern and, in most cases, a single replacement matrix is not enough to represent all the complexity of the evolutionary processes. This paper explores in maximum-likelihood framework phylogenetic mixture models that combine several amino acid replacement matrices to better fit protein evolution.We learn these mixture models from a large alignment database extracted from HSSP, and test the performance using independent alignments from TREEBASE.We compare unsupervised learning approaches, where the site categories are unknown, to supervised ones, where in estimations we use the known category of each site, based on its exposure or its secondary structure. All our models are combined with gamma-distributed rates across sites. Results show that highly significant likelihood gains are obtained when using mixture models compared with the best available single replacement matrices. Mixtures of matrices also improve over mixtures of profiles in the manner of the CAT model. The unsupervised approach tends to be better than the supervised one, but it appears difficult to implement and highly sensitive to the starting values of the parameters, meaning that the supervised approach is still of interest for initialization and model comparison. Using an unsupervised model involving three matrices, the average AIC gain per site with TREEBASE test alignments is 0.31, 0.49 and 0.61 compared with LG (named after Le & Gascuel 2008 Mol. Biol. Evol. 25, 1307-1320), WAG and JTT, respectively. This three-matrix model is significantly better than LG for 34 alignments (among 57), and significantly worse for 1 alignment only. Moreover, tree topologies inferred with our mixture models frequently differ from those obtained with single matrices, indicating that using these mixtures impacts not only the likelihood value but also the output tree. All our models and a PhyML implementation are available from http://atgc.lirmm.fr/mixtures. PMID:18852096

Le, Si Quang; Lartillot, Nicolas; Gascuel, Olivier

2008-12-27

387

Potential therapeutic roles for antibody mixtures.  

PubMed

With the enormous success of recombinant monoclonal antibodies (rMAbs) as human therapeutics, there are increasing efforts underway to explore new molecular entities that mimic rMAbs to replicate this huge success. In addition to naked intact rMAbs, antibody drug conjugates (ADCs), FAb and F(ab')2 fragments and also Fc fusion proteins have been developed and/or marketed as human therapeutics to treat different human diseases, including life-threatening diseases such as cancer. Several hundreds more intact rMAbs, ADCs, FAb, F(ab')2 fragments and Fc fusion proteins are currently undergoing human clinical trials. In addition to these molecules, new type of antibody fragments such as single-chain Fvs (scFvs), VH, scFv-Fc, scFv-CH, scFAb, scFv-zipper, diabodies, bispecific antibodies and similar types of constructs are also being investigated to be developed as human monotherapeutics. Further, there are quite a few current examples of combinations of biologics being developed. For example, currently, several biopharmaceutical companies are developing combinations of antibody mixtures as human therapeutics. Accordingly, the question posed here is whether it is time to consider the possibility of developing a broader range of combinations of therapeutic biologics. Combinations of small organic molecules have been successfully used as therapeutics for many years to treat many diseases, so the context of using polypharmacology to treat human diseases is not novel. For the past several decades, intravenous immunoglobulins have successfully been used in treating various autoimmune diseases. In this context, several biotechnology companies are exploring the use of combinations of antibody mixtures as human therapeutics. This editorial discusses these current efforts and the potential future role of antibody mixtures as human therapeutics. PMID:23886377

Raju, T Shantha; Strohl, William R

2013-07-26

388

Mixtures of environmental pollutants: effects on microorganisms and their activities in soils.  

PubMed

Soil is the ultimate sink for most contaminants and rarely has only a single contaminant. More than is generally acknowledge, environmental pollutants exist as mixtures (organic-organic, inorganic-inorganic, and organic-inorganic). It is much more difficult to study chemical mixtures than individual chemicals, especially in the complex soil environment. Similarly, understanding the toxicity of a chemical mixture on different microbial species is much more complex, time consuming and expensive, because multiple testing designs are needed for an increased array of variables. Therefore, until now, scientific enquiries worldwide have extensively addressed the effects of only individual pollutants toward nontarget microorganisms. In this review, we emphasize the present status of research on (i) the environmental occurrence of pollutant mixtures; (ii) the interactions between pollutant mixtures and ecologically beneficial microorganisms; and (iii) the impact of such interactions on environmental quality. We also address the limitations of traditional cultivation based methods for monitoring the effects of pollutant mixtures on microorganisms. Long-term monitoring of the effects of pollutant mixtures on microorganisms, particularly in soil and aquatic ecosystems, has received little attention. Microbial communities that can degrade or can degrade or can develop tolerance to, or are inhibited by chemical mixtures greatly contribute to resilience and resistance in soil environments. We also stress in this review the important emerging trend associated with the employment of molecular methods for establishing the effects of pollutant mixtures on microbial communities. There is currently a lack of sufficient cogent toxicological data on chemical mixtures for making informed decision making in risk assessment by regulators. Therefore, not only more toxicology information on mixtures is needed but also there is an urgent need to generate sufficient, suitable, and long-term modeling data that have higher predictability when assessing pollutant mixture effects on microorganisms. Such data would improve risk assessment at contaminated sites and would help devise more effective bioremediation strategies. PMID:21287391

Ramakrishnan, Balasubramanian; Megharaj, Mallavarapu; Venkateswarlu, Kadiyala; Sethunathan, Nambrattil; Naidu, Ravi

2011-01-01

389

PREDICTION OF MULTICOMPONENT ADSORPTION EQUILIBRIA IN BACKGROUND MIXTURES OF UNKNOWN COMPOSITION  

EPA Science Inventory

A technique has been developed to predict the adsorption equilibria of known organic solutes onto granular activated carbon (GAC) in mixtures of unknown composition. Ideal adsorbed solution theory (IAST) was used to describe the competitive interactions between adsorbates. Theore...

390

Pervaporation Separation of Ethanol-Water Mixtures Using Polyethylenimine Composite Membranes.  

National Technical Information Service (NTIS)

Synthetic, organic, polymeric membranes were prepared from polyethylenimine for use with pervaporation apparatus in the separation of ethanol-water mixtures. The polymeric material was prepared in dilute aqueous solution and coated onto a polysulfone supp...

H. H. Neidlinger P. O. Schissel R. A. Orth

1985-01-01

391

Gas adsorption and gas mixture separations using mixed-ligand MOF material  

DOEpatents

A method of separating a mixture of carbon dioxiode and hydrocarbon gas using a mixed-ligand, metal-organic framework (MOF) material having metal ions coordinated to carboxylate ligands and pyridyl ligands.

Hupp, Joseph T. (Northfield, IL); Mulfort, Karen L. (Chicago, IL); Snurr, Randall Q. (Evanston, IL); Bae, Youn-Sang (Evanston, IL)

2011-01-04

392

Probing molecular structure at interfaces for comparison with bulk solution behavior: water/2-propanol mixtures monitored by vibrational sum frequency spectroscopy.  

PubMed

The orientation of the isopropyl group at the liquid/vapor interface in 2-propanol/water binary mixtures was studied by vibrational sum frequency spectroscopy. The CH(3) stretch modes of the two methyl groups were used to determine the molecule's orientation by employing a novel united atom approach to model the (CH(3))(2)X moiety. For this purpose, the changes in the molecular susceptibility of the isopropyl group stretches were derived in the laboratory frame as a function of the tilt and twist angles. The results indicated that the methyl groups lay down on the surface at low alcohol mole fraction and gradually twisted with increasing mole fraction. At the azeotrope, x(iso) = 0.68, one of the methyl groups aligned approximately parallel to the surface normal, whereas the other was nearly parallel with the liquid/vapor interface. When the mole fraction of 2-propanol was higher than 0.68, the orientation of 2-propanol remained almost constant. The change in the alcohol's orientation with 2-propanol mole fraction closely tracked changes in its bulk activity coefficient. Such results lead to a picture in which the surface structure and bulk properties of the system are closely linked. PMID:16620125

Kataoka, Sho; Cremer, Paul S

2006-04-26

393

A general model for predicting the flash point of miscible mixtures  

Microsoft Academic Search

A mathematical model is presented for predicting the flash point of miscible mixtures. This model is reducible and adequate for some specified systems as proposed previously. Except for multiple aqueous-organic solutions, the predictive capability of the reduced form for other miscible mixtures, including binary aqueous-organic solutions and flammables-only analogues, has been verified previously. The model was validated using the ternary

Horng-Jang Liaw; Yi-Yu Chiu

2006-01-01

394

Mixtures of (Constrained) Ultrametric Trees.  

ERIC Educational Resources Information Center

Presents a method for the estimation of ultrametric trees calibrated on subjects' pairwise proximity judgments of stimuli, capturing subject heterogeneity using a finite mixture formulation. An empirical example from published data shows the ability to deal with external constraints on the tree topology. (Author/SLD)

Wedel, Michel; DeSarbo, Wayne S.

1998-01-01

395

Chronic Toxicity of Polyphenyl Mixtures  

Microsoft Academic Search

In rats the ingestion of Santowax OM, a mixture of terphenyls used as a coolant, and Omre High Boilers over prolonged periods inhibits weight gain and leads to anemia and kidney and liver damage. At a daily dietary intake of 350 mg\\/kg or more, Santowax OM produces degenerative changes in the nephron; the Omre High Boilers at a daily dietary

A. Petkau; J. Hoogstraaten

1965-01-01

396

Entanglement teleportation via Bell Mixture  

Microsoft Academic Search

We investigate the teleportation of the bipartite entangled states through two equally noisy quantum channels, namely mixture of Bell states. There is a particular mixed state channel for which all pure entanglement in a known Schmidt basis remain entangled after teleportation and it happens till the channel state remains entangled. Werner state channel lacks both these features. The relation of

Sibasish Ghosh; Guruprasad Kar; Anirban Roy

397

Entanglement teleportation via Bell mixtures  

Microsoft Academic Search

We investigate teleportation of bipartite pure entanglement through two equally noisy quantum channel states, namely, a mixture of Bell states. There is a particular mixed-state channel for which all pure entangled states in a known biorthogonal product basis remain entangled after this inexact teleportation, which occurs for the duration of the entanglement. The Werner state channel lacks both these features.

Sibasish Ghosh; Guruprasad Kar; Anirban Roy; Debasis Sarkar; Ujjwal Sen

2002-01-01

398

Moderate strength lightweight concrete from organic aquagel mixtures  

Microsoft Academic Search

The present study describes a new approach for making lightweight concrete that uses aquagels in the concrete formulation. Aquagels are semi-rigid gels that contain mostly water and a small amount of solids that act as the gelling agent. Aquagels were made using wheat starch, algin, agar and high amylose corn starch (HACS). Concrete samples were made using each of the

G. M Glenn; R. M Miller; W. J Orts

1998-01-01

399

DESIGNING FIXED-BED ADSORBERS TO REMOVE MIXTURES OF ORGANICS  

EPA Science Inventory

A liquid-phase granular activated carbon (GAC) pilot plant and a full-scale GAG adsorber were designed, built, and operated in order to evaluate their performance for treating a groundwater contaminated with several volatile and synthetic organicchemicals. everal empty bed contac...

400

Separation and IR Analysis of a Mixture of Organic Compounds.  

ERIC Educational Resources Information Center

Presents an experiment which includes fractional distillation with gas-liquid chromatography (GLC) and infrared analysis. Objectives are to introduce students to fractional distillation and analysis of each fraction by GLC, to induce them to decide if each fraction is sufficient for infrared analysis, and to identify unknowns. (Author/JN)

Thompson, Evan M.; Almy, John

1982-01-01

401

Separation and IR Analysis of a Mixture of Organic Compounds.  

ERIC Educational Resources Information Center

|Presents an experiment which includes fractional distillation with gas-liquid chromatography (GLC) and infrared analysis. Objectives are to introduce students to fractional distillation and analysis of each fraction by GLC, to induce them to decide if each fraction is sufficient for infrared analysis, and to identify unknowns. (Author/JN)|

Thompson, Evan M.; Almy, John

1982-01-01

402

Adjusting Mixture Weights of Gaussian Mixture Model via Regularized Probabilistic Latent Semantic Analysis  

Microsoft Academic Search

Mixture models, such as Gaussian Mixture Model, have been widely used in many applications for modeling data. Gaussi an mixture model (GMM) assumes that data points are generated from a set o f Gaussian models with the same set of mixture weights. A natural extension of GMM is the probabilistic latent semantic analysis (PLSA) model, which assigns different mixture weights

Luo Si; Rong Jin

2005-01-01

403

Assessment of solid reactive mixtures for the development of biological permeable reactive barriers.  

PubMed

Solid reactive mixtures were tested as filling material for the development of biological permeable reactive barriers for the treatment of heavy metals contaminated waters. Mixture selection was performed by taking into account the different mechanisms operating in sulphate and cadmium removal with particular attention to bioprecipitation and sorption onto the organic matrices in the mixtures. Suspensions of eight reactive mixtures were tested for sulphate removal (initial concentration 3 g L(-1)). Each mixture was made up of four main functional components: a mix of organic sources for bacterial growth, a neutralizing agent, a porous medium and zero-valent iron. The best mixture among the tested ones (M8: 6% leaves, 9% compost, 3% zero-valent iron, 30% silica sand, 30% perlite, 22% limestone) presented optimal conditions for SRB growth (pH 7.8 +/- 0.1; E(h)= -410 +/- 5 mV) and 83% sulphate removal in 22 days (25% due to bioreduction, 32% due to sorption onto compost and 20% onto leaves). M8 mixture allowed the complete abatement of cadmium with a significant contribution of sorption over bioprecipitation (6% Cd removal due to SRB activity). Sorption properties, characterised by potentiometric titrations and related modelling, were mainly due to carboxylic sites of organic components used in reactive mixtures. PMID:19505754

Pagnanelli, Francesca; Viggi, Carolina Cruz; Mainelli, Sara; Toro, Luigi

2009-05-22

404

Process for separating relatively pure fractions of methane and carbon dioxide from gas mixtures  

SciTech Connect

Standard Oil's cryogenic liquids-removal and purification process uses lean oil as the absorbent, thus preventing the formation of solid CO/sub 2/ in the apparatus and CO/sub 2/-ethane azeotropes. Suitable for gas streams containing 20-95 mol % CO/sub 2/, the process provides a convenient way of obtaining foolproof operation in the methane separation step.

Goddin, C.S. Jr.; McGalliard, R.L.

1983-01-25

405

Phase equilibria of alkanol\\/alkane mixtures in new oil and gas process development  

Microsoft Academic Search

With the reduction of lead in gasolines, a growing number of processes in which alkanols and alkanes co-exist to produce oxygenated additives for gasolines are under development or have already reached the industrial production stage. In the processes selected the knowledge of the alkane\\/alkanol equilibria is essential for the separation techniques to be applied : azeotropic distillation of ethanol or

A. Pucci

1989-01-01

406

Pervaporation study for the dehydration of tetrahydrofuran-water mixtures by polymeric and ceramic membranes  

Microsoft Academic Search

Pervaporation technology can effectively separate a tetrahydrofuran (THF) solvent-water waste stream at an azeotropic concentration. The performance of a Sulzer® 2210 polyvinyl alcohol (PVA) membrane and a Pervatech BV® silica membrane were studied, as the operating variables feed temperature and permeate pressure, were varied. The silica membrane was found to exhibit a flux of almost double that of the PVA

Colleen A. McGinness; C. Stewart Slater; Mariano J. Savelski

2008-01-01

407

Theoretical and experimental study of integrated membrane \\/ distillation processes for industrial applications  

Microsoft Academic Search

In industrial practice the separation of an azeotropic mixture usually involves adding a third component to the distillation process to break the azeotrope. The major disadvantages of this so called azeotropic and extractive distillation are the relatively high capital and high energy costs and the possibility of product contamination.\\u000aA rather new alternative for breaking azeotropes and a fine example

P. Perez

2007-01-01

408

Electrostatics of colloids in mixtures  

NASA Astrophysics Data System (ADS)

We examine the force between two charged colloids immersed in salty aqueous mixtures close to the coexistence curve. In an initially water-poor phase, the short-range solvation-related forces promote the condensation of a water-rich phase at a distance in the range 1-100nm. This leads to a strong long-range attraction between the colloids and hence to a deep metastable or globally stable energetic state. Our calculations are in good agreement with recent experiments on the reversible aggregation of colloids in critical mixtures. The specific nature of the solvation energy of ions can lead to some surprising effects, whereby positively charged surfaces attract while negatively charged surfaces repel. For hydrophilic anions and hydrophobic cations, a repulsive interaction is predicted between oppositely charged and hydrophilic colloids even though both the electrostatic and adsorption forces alone are attractive.

Samin, Sela; Tsori, Yoav

2013-03-01

409

Local fluctuations in solution mixtures  

NASA Astrophysics Data System (ADS)

An extension of the traditional Kirkwood-Buff (KB) theory of solutions is outlined which provides additional fluctuating quantities that can be used to characterize and probe the behavior of solution mixtures. Particle-energy and energy-energy fluctuations for local regions of any multicomponent solution are expressed in terms of experimentally obtainable quantities, thereby supplementing the usual particle-particle fluctuations provided by the established KB inversion approach. The expressions are then used to analyze experimental data for pure water over a range of temperatures and pressures, a variety of pure liquids, and three binary solution mixtures - methanol and water, benzene and methanol, and aqueous sodium chloride. In addition to providing information on local properties of solutions it is argued that the particle-energy and energy-energy fluctuations can also be used to test and refine solute and solvent force fields for use in computer simulation studies.

Ploetz, Elizabeth A.; Smith, Paul E.

2011-07-01

410

High Pressure Thermodynamics of Mixtures  

Microsoft Academic Search

Abstract—In the present survey some important trends in the high pressure thermodynamics,of fluid mixtures of non-electrolytesare reviewed. First the pressure dependence,of excess functions such as the excess Gibbs energy GE, the excess enthalpy HE, the excess entropy SE and the excess heat capacity CE is discussed. It can be obtained from the knowledge,of the excess volume a function of pressure

G. M. Schneider

1976-01-01

411

Entanglement teleportation via Bell mixtures  

NASA Astrophysics Data System (ADS)

We investigate teleportation of bipartite pure entanglement through two equally noisy quantum channel states, namely, a mixture of Bell states. There is a particular mixed-state channel for which all pure entangled states in a known biorthogonal product basis remain entangled after this inexact teleportation, which occurs for the duration of the entanglement. The Werner state channel lacks both these features. The relation of these noisy channels to the violation of Bell's inequality and quantum two-entropy inequality is studied.

Ghosh, Sibasish; Kar, Guruprasad; Roy, Anirban; Sarkar, Debasis; Sen, Ujjwal

2002-08-01

412

Characterization of gas condensate mixtures  

SciTech Connect

Simulation of the phase behavior of gas condensate mixtures is a severe test of the employed equation of state and of the C/sub 7+/ - characterization procedure. This paper presents experimental and calculated results for the phase behavior of different gas condensate mixtures, one of which is near critical reservoir conditions. The calculations are based on the Soave-Redlich-Kwong equation of state. For the plus-fraction a continuous logarithmic dependence is assumed for the mole fraction against carbon number. The critical properties of the C/sub 7+/-fractions are calculated directly from measured physical properties of the fractions (molecular weight and density). The procedure is fully predictive. Accurate results are obtained for the phase properties and for the phase compositions. The model may be used successfully also for heavy oil mixtures. It is shown that deviations between the measured and calculated results often can be related to inaccuracies of the data related to the composition in particular of the results for the molecular weight of the plus fraction.

Pedersen, K.S. (CALSEP A/S, Lyngby Hovedgade 29, Dk-2800 Lyngby (DK)); Thomassen, P. (STATOIL, Forus, Postboks 300, N-4001 Stavanger (NO)); Fredenslund, A. (The Technical Univ. of Demark, Dk-2800 Lyngby (DK))

1988-01-01

413

Carbon mineralization from organic wastes at different composting stages during their incubation with soil  

Microsoft Academic Search

The decomposition of seven different organic waste mixtures prepared with sewage sludges, animal manures, city refuse and industrial and plant residues, was studied during their aerobic incubation with soil. The waste mixtures were composted by the Rutgers static pile system, and four samples of each mixture were collected at various composting stages: the initial mixture, and samples taken during the

M. P. Bernal; M. A. Sánchez-Monedero; C. Paredes; A. Roig

1998-01-01

414

CLUSTERING CRITERIA AND MULTIVARIATE NORMAL MIXTURES  

EPA Science Inventory

New clustering criteria for use when a mixture of multivariate normal distributions is an appropriate model are presented. They are derived from maximum likelihood and Bayesian approaches corresponding to different assumptions about the covariance matrices of the mixture componen...

415

Model Misspecification: Finite Mixture or Homogeneous?  

PubMed Central

A common problem in statistical modelling is to distinguish between finite mixture distribution and a homogeneous non-mixture distribution. Finite mixture models are widely used in practice and often mixtures of normal densities are indistinguishable from homogenous non-normal densities. This paper illustrates what happens when the EM algorithm for normal mixtures is applied to a distribution that is a homogeneous non-mixture distribution. In particular, a population-based EM algorithm for finite mixtures is introduced and applied directly to density functions instead of sample data. The population-based EM algorithm is used to find finite mixture approximations to common homogeneous distributions. An example regarding the nature of a placebo response in drug treated depressed subjects is used to illustrate ideas.

Tarpey, Thaddeus; Yun, Dong; Petkova, Eva

2007-01-01

416

Model Misspecification: Finite Mixture or Homogeneous?  

PubMed

A common problem in statistical modelling is to distinguish between finite mixture distribution and a homogeneous non-mixture distribution. Finite mixture models are widely used in practice and often mixtures of normal densities are indistinguishable from homogenous non-normal densities. This paper illustrates what happens when the EM algorithm for normal mixtures is applied to a distribution that is a homogeneous non-mixture distribution. In particular, a population-based EM algorithm for finite mixtures is introduced and applied directly to density functions instead of sample data. The population-based EM algorithm is used to find finite mixture approximations to common homogeneous distributions. An example regarding the nature of a placebo response in drug treated depressed subjects is used to illustrate ideas. PMID:18974843

Tarpey, Thaddeus; Yun, Dong; Petkova, Eva

2008-01-01

417

Endocrine-Disrupting Compounds and Mixtures: Unexpected Dose–Response  

Microsoft Academic Search

The current study examined the effects on the red-eared slider turtle of extremely low doses of three endocrine-disrupting compounds (EDCs)— trans-Nonachlor, chlordane, and p, p?-DDE—singly and in mixtures. Previous studies using the red-eared slider turtle have proven its value as an organism for obtaining information about the effects of endocrine-disrupting compounds. The sex of the turtle, easily manipulated by exposure

Emily Willingham

2004-01-01

418

The Kinetic Separation of Protein Mixtures Using Reverse Micelles  

Microsoft Academic Search

Commercial interest in cost-effective methods that can separate, concentrate, and purify proteins continuously, and be easily scaled-up, has increased markedly in recent years. Liquid–liquid extraction using reverse micellar organic solvents has been found to have this potential. The overall objective of this work was to investigate the kinetic separation of protein mixtures using reverse micelles. The kinetics of simultaneous forward

LUDGER H. POPPENBORG; ARISTIDIS A. BRILLIS; DAVID C. STUCKEY

2000-01-01

419

Assessing exposures to inhaled complex mixtures  

Microsoft Academic Search

In the course of daily activities, individuals spend varying amounts of time in different spaces where they are exposed to a complex mixture of gas, vapor, and particulate contaminants. The term complex is used in this paper to refer to binary mixtures as well as truly complex mixtures of three or more constituents. The diversity of the environments where pollution

B. P. Leaderer; P. J. Lioy; J. D. Spengler

1993-01-01

420

Plasticization of corn starch by polyol mixtures  

Microsoft Academic Search

Polyol mixtures including mixture of conventional plasticizer glycerol and higher molecular weight polyol (HP) such as xylitol, sorbitol and maltitol were used to plasticize corn starch by melt-blending method, and effect of the polyol mixture on the pocessibility, microstructures, thermal stability and mechanical properties of these starch composites (SC) were investigated. The introduction of HP providing greater processing torque can

Xiuying Qiao; Zhongzhu Tang; Kang Sun

2011-01-01

421

Modification of endocrine active potential by mixtures  

Microsoft Academic Search

Wildlife and humans are exposed to a complex mixture of endocrine active chem- icals. The activity of a specific chemical in any mixture can be modified through interactions with other components of the mixture. The toxic equivalency factor (TEF) approach for risk assessment was developed for chemicals such as halogenated aromatics that induce their ef- fects through ligand-activated receptors. For

Kevin Gaido; L. You; S. Safe

2003-01-01

422

Implications of chemical mixtures in public health practice.  

PubMed

The Agency for Toxic Substances and Disease Registry (ATSDR) is a federal public health agency that investigates and strives to prevent human health problems produced by exposure to toxic chemicals and their mixtures in the environment. Most human exposures involving toxic chemicals or mixtures are thought to originate from environmental and occupational sources; however, concurrent exposures are also likely from other sources, such as prescription and nonprescription drugs, indoor air pollutants, alcohol, and tobacco smoke. Thus, in evaluating the potential hazard following exposure to environmental mixtures, ATSDR not only considers the inherent joint toxicity of the mixture but also the influence of environmental, demographic, occupational, and lifestyle factors. To foster these goals, ATSDR has pursued a Mixtures Research and Assessment Program that consists of three component efforts: trend analysis, joint toxicity assessment, and experimental testing. Through trend analysis, ATSDR sets priorities for environmental mixtures of concern for which joint toxicity assessments are conducted as needed. If data are not available to conduct appropriate assessments, a research agenda is pursued through established extramural mechanisms. Ultimately, the data generated are used to support ATSDR's work at sites involving exposure to chemical mixtures. This pragmatic approach allows testable hypotheses or research needs to be identified and resolved and enhances our understanding of the mechanisms of joint toxicity. Several collaborative and cooperative efforts with national and international organizations such as the Toxicology and Nutrition Office, the Netherlands, and the Department of Energy are being pursued as part of these activities. ATSDR also develops guidance manuals to consistently and accurately apply current methodologies for the joint toxicity assessment of chemicals. Further, expert panels often are assembled to resolve outstanding scientific issues or obtain expert advice on pertinent issues. Recently, the need for studies on chemical mixtures has been proposed as one of the six priority areas the agency identified in its agenda for public health environmental research. This has been reinforced through the agency's close work with communities whose leaders have spoken passionately about their concern for information on exposures to chemical mixtures. The five other priority research areas the agency identified are exposure, susceptible populations, communities and tribal involvement, evaluation/surveillance of health effects, and health promotion/prevention. PMID:15371239

de Rosa, C T; El-Masri, H A; Pohl, H; Cibulas, W; Mumtaz, M M

423

Deliquescence properties of mixed organic aerosols  

NASA Astrophysics Data System (ADS)

The water soluble organic component of the tropospheric aerosol consists of a complex mixture comprising mono- and di-acids, polyols, dialkyl ketones, polyphenols and polycarboxylic acids. Its impact on the light scattering, hygroscopicity, and phase transitions is of prime interest to determine the aerosol’s cloud forming and climatic properties. By now, only a minor part of the organic mass can be resolved into specific molecular compounds. A number of laboratory studies have investigated the influence of the organic fraction on aerosol properties often using one dicarboxylic acid as a representative model compound. Up to know, little attention was paid to the fact that the organics constitute a mixture. In contrast, in this study the organic fraction is represented by a mixture of dicarboxylic acids. Saturated aqueous solutions have been prepared in an iterative procedure: small portions of material were added until the solution was saturated with respect to each component. The water activity of these eutonic compositions has been determined revealing the following trend: the deliquescence relative humidity decreases continuously with increasing number of components. This result is viewed as a general trend that holds for the whole water soluble organic fraction. Therefore, one can conclude that a liquid solution as the stable physical state becomes increasingly favored the more components the mixture contains. In a second step, inorganic salts were added to the organic mixture. The aqueous solubility and deliquescence properties of these mixtures were investigated.

Marcolli, C.

2003-04-01

424

Organic sludge-energy recycling method  

Microsoft Academic Search

A method is described for converting substantially untreated organic sludge into useful substances. The sludge may include primary sludge, a mixture of primary and secondary sludges from municipal wastewater treatment facilities, slurries of agricultural manure, and other organic wastes. The sludge is mechanically comminuted to reduce the size of organic solids, the sludge is then further mechanically disintegrated and thereafter

L. G. Erickson; H. E. Worne

1982-01-01

425

A thermodynamic model of mixed organic-inorganic aerosols to predict activity coefficients  

Microsoft Academic Search

Abstract. Tropospheric aerosols contain mixtures of inorganic salts, acids, water, and a large variety of organic compounds. Interactions between these substances in liquid mixtures lead to discrepancies from ideal thermodynamic behaviour. By means of activity coefficients, non-ideal behaviour can be taken into account. We present here a thermodynamic model named AIOMFAC (Aerosol Inorganic-Organic Mixtures Functional groups Activity Coefficients) that is

A. Zuend; C. Marcolli; B. P. Luo; T. Peter

2008-01-01

426

Organic waste disposal system  

SciTech Connect

Organic waste material is pneumatically transported within air and mixed therewith by swirling flow through an annular ejector passage of varying radial width into a reaction flow passage of an eductor nozzle section receiving the output plume of a plasma torch for initiating therein thermal gasification of the waste mixture. The plasma torch plume projects from the eductor section into a diffuser section within which thermal gasification is continued before discharge of gasified waste.

Nolting, E.E.; Colfield, J.; Richard, R.; Peterson, S.

1997-12-31

427

Demixing in symmetric supersolid mixtures  

NASA Astrophysics Data System (ADS)

The droplet crystal phase of a symmetric binary mixture of soft-core bosons is studied by computer simulation. At high temperature each droplet comprises on average equal numbers of particles of either component, but the two components demix below the supersolid transition temperature, i.e., droplets mostly consist of particles of one component. Clustering of droplets of the same component is also observed. Demixing is driven by quantum tunneling of particles across droplets over the system and does not take place in an insulating crystal. This effect provides an unambiguous experimental signature of supersolidity.

Jain, Piyush; Moroni, Saverio; Boninsegni, Massimo; Pollet, Lode

2013-09-01

428

Mixture theory-based poroelasticity as a model of interstitial tissue growth  

PubMed Central

This contribution presents an alternative approach to mixture theory-based poroelasticity by transferring some poroelastic concepts developed by Maurice Biot to mixture theory. These concepts are a larger RVE and the subRVE-RVE velocity average tensor, which Biot called the micro-macro velocity average tensor. This velocity average tensor is assumed here to depend upon the pore structure fabric. The formulation of mixture theory presented is directed toward the modeling of interstitial growth, that is to say changing mass and changing density of an organism. Traditional mixture theory considers constituents to be open systems, but the entire mixture is a closed system. In this development the mixture is also considered to be an open system as an alternative method of modeling growth. Growth is slow and accelerations are neglected in the applications. The velocity of a solid constituent is employed as the main reference velocity in preference to the mean velocity concept from the original formulation of mixture theory. The standard development of statements of the conservation principles and entropy inequality employed in mixture theory are modified to account for these kinematic changes and to allow for supplies of mass, momentum and energy to each constituent and to the mixture as a whole. The objective is to establish a basis for the development of constitutive equations for growth of tissues.

Cowin, Stephen C.; Cardoso, Luis

2011-01-01

429

High Efficiency Organic Photovoltaic Cells Employing Hybridized Mixed Planar Heterojunctions.  

National Technical Information Service (NTIS)

A device is provided, having a first electrode, a second electrode, and a photoactive region disposed between the first electrode and the second electrode. The photoactive region includes a first organic layer comprising a mixture of an organic acceptor m...

B. P. Rand J. Xue S. Forrest S. Uchida

2004-01-01

430

An Evaluation of Organic Vapor Respirator Cartridges Against Vinyl Chloride.  

National Technical Information Service (NTIS)

The service lives of four types of approved organic vapor respiratory cartridges and four types of approved front or back mounted organic vapor gas mask canisters were determined relative to several concentrations of vinyl chloride. Various mixtures of vi...

D. L. Smith W. S. Giesler

1974-01-01

431

Literaturstudie und experimentelle Untersuchungen zur Bildung von organischen Iodverbindungen in Alken-, Alkanol- sowie Benzol-Dampf/Luft-Gemischen mit Radioiod im Strahlenfeld. (Literature study and experimental investigations into the production of organic iodine compounds in alkene, alkanol as well as benzene-vapour/air mixtures with radioiodine in the radiation field).  

National Technical Information Service (NTIS)

It was assumed in these investigations that these compounds originated in the gas phase by irradiation - induced reactions with radioiodine. Benzene, alcohol (methanol, ethanol) and alkene (ethylene, propylene) vapour/air mixtures were radiolysed with iod...

W. Leskopf S. Holl K. Bleier

1992-01-01

432

Effect of Cement on Emulsified Asphalt Mixtures  

NASA Astrophysics Data System (ADS)

Emulsified asphalt mixtures have environmental, economical, and logistical advantages over hot mixtures. However, they have attracted little attention as structural layers due to their inadequate performance and susceptibility to early life damage by rainfall. The objective of this article is to provide an improved insight into how the mechanical properties of emulsion mixtures may be improved and to determine the influence of cement on emulsified asphalt mixtures. Laboratory tests on strength, temperature susceptibility, water damage, creep and permanent deformation were implemented to evaluate the mechanical properties of emulsified asphalt mixtures. The test results showed that mechanical properties of emulsified asphalt mixtures have significantly improved with Portland cement addition. This experimental study suggested that cement modified asphalt emulsion mixtures might be an alternate way of a structural layer material in pavement.

Oruc, Seref; Celik, Fazil; Akpinar, M. Vefa

2007-10-01

433

Thermodynamics of molten sulfate mixtures  

SciTech Connect

Quantitative studies of the formation of low melting point sulfates were made by equilibrating NiO-Na/sub 2/SO/sub 4/ mixtures with argon-SO/sub 2/-SO/sub 3/-air mixtures of different compositions in the temperature range 1000-1173 K. Using these data and the Na/sub 2/SO/sub 4/-NiSO/sub 4/ phase diagram, the enthalpy of fusion and melting temperature of NiSO/sub 4/ were estimated. An equation is given for the free energy change for the reaction NiO(s)+SO/sub 3/(g).NiSO/sub 4/(l) (dissolved in Na/sub 2/SO/sub 4/). This has then been used to calculate the minimum P/sub SO(3)/ required for liquid sulfate formation. Similar calculations were carried out from existing data for the CoSO/sub 4/-Na/sub 2/SO/sub 4/ system, and verified by a limited number of experiments. The calculated minimum P/sub SO(3)/ required for liquid sulfate formation is approximately an order of magnitude lower for Co-base alloys compared with Ni-base alloys, and the implications of this with regard to hot corrosion are briefly discussed. 16 refs.

Misra, A.K.; Whittle, D.P.; Worrell, W.L.

1982-08-01

434

Sludge organics bioavailability  

SciTech Connect

Concern over the bioavailability of toxic organics that can occur in municipal sludges threatens routine land application of sludge. Available data, however, show that concentrations of priority organics in normal sludges are low. Sludges applied at agronomic rates yield chemical concentrations in soil-sludge mixtures 50 to 100 fold lower. Plant uptake at these pollutant concentrations (and at much higher concentrations) is minimal. Chemicals are either (1) accumulated at extremely low levels (PCBs), (2) possibly accumulated, but then rapidly metabolized within plants to extremely low levels (DEHP), or (3) likely degraded so rapidly in soil that only minor contamination occurs (PCP and 2,4-DNP).

Eiceman, G.E.; Bellin, C.A.; Ryan, J.A.; O'Connor, G.A.

1991-01-01

435

Method of photocatalytic conversion of C-H organics  

DOEpatents

The present invention is the addition of a semiconductor material and energy to the reaction mixture of organic, acid (for example, trifluoroacetate), and oxygen. A transition metal ion may be added to the reaction mixture. The semiconductor material converts energy to oxidants thereby promoting oxidation of the organic. Alternatively, using metal in combination with exposure to light may be used.

Camaioni, Donald M. (Richland, WA); Lilga, Michael A. (Richland, WA)

1998-01-01

436

Method of photocatalytic conversion of C-H organics  

DOEpatents

The present invention is the addition of a semiconductor material and energy to the reaction mixture of organic, acid (for example, trifluoroacetate), and oxygen. A transition metal ion may be added to the reaction mixture. The semiconductor material converts energy to oxidants thereby promoting oxidation of the organic. Alternatively, using metal in combination with exposure to light may be used.

Camaioni, D.M.; Lilga, M.A.

1998-01-13

437

Modeling biofiltration of VOC mixtures under steady-state conditions  

SciTech Connect

Treatment of air streams contaminated with binary volatile organic compound (VOC) mixtures in classical biofilters under steady-state conditions of operation was described with a general mathematical model. The model accounts for potential kinetic interactions among the pollutants, effects of oxygen availability on biodegradation, and biomass diversification in the filter bed. While the effects of oxygen were always taken into account, two distinct cases were considered for the experimental model validation. The first involves kinetic interactions, but no biomass differentiation, used for describing data from biofiltration of benzene/toluene mixtures. The second case assumes that each pollutant is treated by a different type of biomass. Each biomass type is assumed to form separate patches of biofilm on the solid packing material, thus kinetic interference does not occur. This model was used for describing biofiltration of ethanol/butanol mixtures. Experiments were performed with classical biofilters packed with mixtures of peat moss and perlite (2:3, volume:volume). The model equations were solved through the use of computer codes based on the fourth-order Runge-Kutta technique for the gas-phase mass balances and the method of orthogonal collocation for the concentration profiles in the biofilms. Good agreement between model predictions and experimental data was found in almost all cases. Oxygen was found to be extremely important in the case of polar VOCs (ethanol/butanol).

Baltzis, B.C. [New Jersey Inst. of Tech., Newark, NJ (United States); Wojdyla, S.M. [Merck and Co., Inc., Rahway, NJ (United States); Zarook, S.M. [King Fahd Univ. of Petroleum and Minerals, Dhahran (Saudi Arabia). Dept. of Chemical Engineering

1997-06-01

438

Diamagnetic bulk susceptibility of mixtures  

NASA Astrophysics Data System (ADS)

This document is part of Subvolume C `Diamagnetic Susceptibility and Magnetic Anisotropy of Organic Compounds' of Volume 27 `Diamagnetic Susceptibility and Anisotropy' of Landolt-Börnstein - Group II Molecules and Radicals.

Kumar, M.; Gupta, R.

439

The Acid Catalyzed Dehydration of an Isomeric 2-Methylcyclohexanol Mixture: A Kinetic and Regiochemical Study of the Evelyn Effect  

Microsoft Academic Search

This paper details an experiment which serves as an introduction to organic laboratory research. The reaction is the dehydration of a cis, trans mixture of 2-methylcyclohexanols. At intervals of times the reactant mixture is sampled for the cis and trans reactants. At those same intervals of times the receiver flasks of product cyclohexanes being collected are changed, such that sequential

John J. Cawley; Patrick E. Linder

1997-01-01

440

Dielectric properties for the binary mixture of dimethylsuphoxide and dimethylacetamide with 2-nitrotoluene at microwave frequencies  

Microsoft Academic Search

The dielectric properties of various organic solvents and binary solvent mixtures at different temperatures over the frequency range of 10MHz–20GHz, are investigated using the time domain reflectometry technique, at various temperatures from 15 to 45°C. These solvent mixtures—dimethylacetamide–2-nitrotoluene and dimethylsulphoxide–2-nitrotoluene as well as pure solvents display a Debye type dispersion. Their frequency-dependent dielectric properties can be summarized by the three

Ajay Chaudhari; Harish Chaudhari; Suresh Mehrotra

2002-01-01

441

An Efficient Binary Solvent Mixture for Monoacylglycerol Synthesis by Enzymatic Glycerolysis  

Microsoft Academic Search

The present study was aimed at selecting an efficient binary solvent mixture for monoacylglycerol (MAG) synthesis by enzymatic\\u000a glycerolysis of soybean oil. Solvent combinations of tert-butanol\\/isopropanol (v\\/v) at different ratios were studied. Of the investigated cases, tert-butanol:isopropanol at ratio 80:20 was the most suitable organic medium. The optimum conditions for MAG synthesis under the\\u000a selected mixture were: water 10 wt% based

Nanjing Zhong; Lin Li; Xuebing Xu; Lingzhi Cheong; Bing Li; Songqing Hu; Xihong Zhao

2009-01-01

442

Maximum supercoolign in liquid /sup 3/He-/sup 4/He mixtures near the tricritical point  

SciTech Connect

Measurements of supercooling in liquid /sup 3/He-/sup 4/He mixtures near the tricritical point are presented. The reduced temperature range 0.001 < epsilon identical to (1 - T/T/sub t/) < 0.01 was investigated for three different rates of cooling using a pressure-quench technique. For epsilon < 0.012, the maximum supercooling was found to be a function of the cooling rate. Comparisons with data in organic binary mixtures are given.

Sinha, D.N.; Hoffer, J.K.

1984-01-01

443

Symmetrical mixtures in external fields.  

PubMed

We have studied the behavior of symmetrical binary mixtures of Lennard-Jones particles in contact with strongly adsorbing walls using Monte Carlo simulation methods in the grand canonical and semi-grand canonical ensembles. Two types of the surface potential have been applied. The first depends on the distance from the surface only, while the second involves periodic modulations in the directions parallel to the wall. In the latter case, it has been assumed that the solid substrate is a fcc crystal with the surface being the (100) face. We have considered the systems in which the surface potential is strong enough to induce the layer-by-layer adsorption at low temperatures and discussed the interplay between the demixing transition and the structure of thin films for several systems characterized by different parameters describing the interactions in the system. PMID:23822318

Materniak, S; Patrykiejew, A

2013-07-01

444

RELIABLE COMPUTATION OF REACTIVE AZEOTROPES. (R826734)  

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...

445

Limit Cycles in Homogeneous Azeotropic Distillation  

Microsoft Academic Search

In spite of significant nonlinearities even in the simplest model, the distillation literature generally takes for granted that distillation columns display relatively simple dynamic behavior. For example, although widely observed in chemical reactors, any instances of periodic oscillations have not yet been associated with models of distillation columns. In this paper we study the steady-state and dynamic behavior of the

Moonyong Lee; Cornelius Dorn; George A. Meski; Manfred Morari

1999-01-01

446

ANALYSIS OF AZEOTROPIC DISTILLATION SEQUENCES START UP  

Microsoft Academic Search

The optimal start-up of a two-distillation tower process involving multiple steady states is a very complex task, since a rigorous dynamic optimization is necessary. Searching for optimal start-up strategies for tower sequences is far from trivial. Besides of the multiplicity of solutions, one of the complicating factors is the activation of the recycle stream, which severely constrains the possible start-up

Nicolás J. Scenna; Sonia J. Benz; Nestor H. Rodríguez; Juan Ignacio Klaric

447

Chemical contaminants on DOE lands and selection of contaminant mixtures for subsurface science research  

SciTech Connect

This report identifies individual contaminants and contaminant mixtures that have been measured in the ground at 91 waste sites at 18 US Department of Energy (DOE) facilities within the weapons complex. The inventory of chemicals and mixtures was used to identify generic chemical mixtures to be used by DOE's Subsurface Science Program in basic research on the subsurface geochemical and microbiological behavior of mixed contaminants (DOE 1990a and b). The generic mixtures contain specific radionuclides, metals, organic ligands, organic solvents, fuel hydrocarbons, and polychlorinated biphenyls (PCBs) in various binary and ternary combinations. The mixtures are representative of in-ground contaminant associations at DOE facilities that are likely to exhibit complex geochemical behavior as a result of intercontaminant reactions and/or microbiologic activity stimulated by organic substances. Use of the generic mixtures will focus research on important mixed contaminants that are likely to be long-term problems at DOE sites and that will require cleanup or remediation. The report provides information on the frequency of associations among different chemicals and compound classes at DOE waste sites that require remediation.

Riley, R.G.; Zachara, J.M. (Pacific Northwest Lab., Richland, WA (United States))

1992-04-01

448

TOXICOKINETIC INTERACTIONS AND SURVIVAL OF HYALELLA AZTECA EXPOSED TO BINARY MIXTURES OF CHLORPYRIFOS, DIELDRIN, AND METHYL MERCURY  

EPA Science Inventory

Chemical mixture interactions of chlorpyrifos, dieldrin, and methyl mercury were evaluated in Hyalella azteca. Survival of adult and juvenile organisms was evaluated following exposure to individual chemicals and in binary combinations. Binary interactions of the model chemicals...

449

Performance-based asphalt mixture design methodology  

NASA Astrophysics Data System (ADS)

Today, several State D.O.T.s are being investigating the use of tire rubber with local conventional materials. Several of the ongoing investigations identified potential benefits from the use of these materials, including improvements in material properties and performance. One of the major problems is being associated with the transferability of asphalt rubber technology without appropriately considering the effects of the variety of conventional materials on mixture behavior and performance. Typically, the design of these mixtures is being adapted to the physical properties of the conventional materials by using the empirical Marshall mixture design and without considering fundamental mixture behavior and performance. Use of design criteria related to the most common modes of failure for asphalt mixtures, such as rutting, fatigue cracking, and low temperature thermal cracking have to be developed and used for identifying the "best mixture," in term of performance, for the specific local materials and loading conditions. The main objective of this study was the development of a mixture design methodology that considers mixture behavior and performance. In order to achieve this objective a laboratory investigation able to evaluate mixture properties that can be related to mixture performance, (in terms of rutting, low temperature cracking, moisture damage and fatigue), and simulating the actual field loading conditions that the material is being exposed to, was conducted. The results proved that the inclusion of rubber into asphalt mixtures improved physical characteristics such as elasticity, flexibility, rebound, aging properties, increased fatigue resistance, and reduced rutting potential. The possibility of coupling the traditional Marshall mix design method with parameters related to mixture behavior and performance was investigated. Also, the SHRP SUPERPAVE mix design methodology was reviewed and considered in this study for the development of an integrated performance based design procedure. Finally, the developed guidelines with easy-to-use flow charts for the integrated mix design methodology are presented.

Ali, Al-Hosain Mansour

450

PCA Fuzzy Mixture Model for Speaker Identification  

Microsoft Academic Search

\\u000a In this paper, we proposed the principal component analysis (PCA) fuzzy mixture model for speaker identification. A PCA fuzzy\\u000a mixture model is derived from the combination of the PCA and the fuzzy version of mixture model with diagonal covariance matrices.\\u000a In this method, the feature vectors are first transformed by each speaker’s PCA transformation matrix to reduce the correlation\\u000a among

Younjeong Lee; Joohun Lee; Ki Yong Lee

2003-01-01

451

Hydromechanical behaviour of bentonite pellet mixtures  

Microsoft Academic Search

Granular mixtures made of high-density pellets of bentonite are being evaluated as an alternative buffer material for waste isolation. Ease of handling is an often-mentioned advantage. The paper described the experimental program performed to characterize the hydro-mechanical behaviour of compacted pellet’s mixtures used in the engineered barrier (EB) experiment.The material tested in the laboratory was based in the pellet’s mixtures

C. Hoffmann; E. E. Alonso; E. Romero

2007-01-01

452

Effect of Cement on Emulsified Asphalt Mixtures  

Microsoft Academic Search

Emulsified asphalt mixtures have environmental, economical, and logistical advantages over hot mixtures. However, they have\\u000a attracted little attention as structural layers due to their inadequate performance and susceptibility to early life damage\\u000a by rainfall. The objective of this article is to provide an improved insight into how the mechanical properties of emulsion\\u000a mixtures may be improved and to determine the

Seref Oruc; Fazil Celik; M. Vefa Akpinar

2007-01-01

453

Polymorphic changes in mixtures of confectionery fats  

Microsoft Academic Search

The polymorphic behavior of mixtures of cocoa butter and high melting cocoa butter fraction with three types of confectionery\\u000a fats and mixtures of the confectionery fats with each other were investigated with a differential scanning calorimeter. The\\u000a confectionery fats were an interesterified-fractionated fat, a hydrogenated-fractionated fat, and a lauric acid fat. The lowered\\u000a melting point observed in mixtures of confectionery

N. V. Lovegren; M. S. Gray; R. O. Feuge

1976-01-01

454

Mutation spectra of complex environmental mixtures  

Microsoft Academic Search

Bioassay-directed chemical analysis of complex environmental mixtures has indicated that much of the genotoxic activity of mixtures is due to the presence of one or a few classes or chemicals within the mixture. We have extended this observation to the molecular level by using colony probe hybridization and PCR\\/DNA sequence analysis to determine the mutation spectra of â¼8,000 revertants induced

DeMarini

1997-01-01

455

Bayesian Methods for Mixtures of Normal Distributions  

Microsoft Academic Search

Bayesian Methods for Mixtures ofNormal DistributionsMatthew Stephens D. Phil. ThesisMagdalen College, Oxford Michaelmas Term, 1997Mixture distributions are typically used to model data in which each observationis assumed to have arisen from one of a number of different groups. Theyalso provide a convenient and flexible class of models for density estimation.While a Bayesian analysis of mixture models has certain advantages over

Matthew Stephens

1997-01-01

456

Results of the IPCS collaborative study on complex mixtures  

SciTech Connect

The International Program on Chemical Safety (IPCS) sponsored a collaborative study to examine the intra- and interlaboratory variation associated with the preparation and bioassay of complex chemical mixtures. The mixtures selected were National Institute of Standards and Technology (NIST) Standard Reference Materials (SRM). Twenty laboratories worldwide participated in the study. The participating laboratories extracted the organic portion of two particulate samples--an air particulate sample and a diesel particulate sample--and bioassayed the extracts. The laboratories simultaneously bioassayed a NIST-prepared extract of coal tar and two control compounds (benzo(a)pyrene, and 1-nitropyrene). The bioassay method used was the Salmonella/mammalian microsome plate-incorporation test using strains TA98 and TA100. Study design also allowed for a comparison of sonication and Soxhlet extraction techniques. The particulates samples were mutagenic in both strains with and without activation in all twenty laboratories. The paper provides a complete summary of the data collected during the collaborative study.

Claxton, L.D.; Creason, J.; Leroux, B.; Agurell, E.; Bagley, S.

1992-01-01

457

Cluster kinetics model for mixtures of glassformers  

NASA Astrophysics Data System (ADS)

For glassformers we propose a binary mixture relation for parameters in a cluster kinetics model previously shown to represent pure compound data for viscosity and dielectric relaxation as functions of either temperature or pressure. The model parameters are based on activation energies and activation volumes for cluster association-dissociation processes. With the mixture parameters, we calculated dielectric relaxation times and compared the results to experimental values for binary mixtures. Mixtures of sorbitol and glycerol (seven compositions), sorbitol and xylitol (three compositions), and polychloroepihydrin and polyvinylmethylether (three compositions) were studied.

Brenskelle, Lisa A.; McCoy, Benjamin J.

2007-10-01

458

Dielectric gas mixtures containing sulfur hexafluoride  

DOEpatents

Electrically insulating gaseous media of unexpectedly high dielectric strength comprised of mixtures of two or more dielectric gases are disclosed wherein the dielectric strength of at least one gas in each mixture increases at less than a linear rate with increasing pressure and the mixture gases are present in such proportions that the sum of their electrical discharge voltages at their respective partial pressures exceeds the electrical discharge voltage of each individual gas at the same temperature and pressure as that of the mixture.

Cooke, Chathan M. (Cambridge, MA)

1979-01-01

459

Engineering preliminaries to obtain reproducible mixtures of atelocollagen and polysaccharides.  

PubMed

The critical stage in producing blends of biomacromolecules consists in the mixing of component solutions to generate homogenous diluted colloidal systems. Simple experimental investigations allow the establishment of the design rules of recipes and the procedures for preparing homogenous and compositionally reproducible mixtures. Starting from purified solutions of atelocollagen, hyaluronan and native gellan, having as low as possible inorganic salts content, initial binary and ternary mixtures can be prepared up to a total dry matter content of 0.150 g/dL, in no co-precipitating conditions. Two pH manipulation ways are feasible for homogenous mixing: (i) unbuffered prior correction at pH 5.5, and (ii) "rigid" buffering at pH 9.0, using organic species. Atelocollagen including co-precipitates can be obtained in the presence of one or both polysaccharides, preferably in pH domains far from the isoelectric point of scleroprotein. A critical behavior has been observed in mixtures containing gellan, due to its macromolecular dissimilarities compared with atelocollagen. In optimal binary mixtures, the coordinates of threshold points on the phase diagrams are 0.028% w/w atelocollagen/0.025% w/w hyaluronan, and 0.022% w/w atelocollagen/0.020% w/w gellan. Uni- or bi-phasic ternary systems having equilibrated ratios of co-precipitated components can be prepared starting from initial mixtures containing up to 0.032 g/dL atelocollagen, associated with, for example, 0.040 g/dL hyaluronan and 0.008 g/dL gellan, following the first pH manipulation way. PMID:23498265

Lefter, Cristina-Mihaela; Maier, Stelian Sergiu; Maier, Vasilica; Popa, Marcel; Desbrieres, Jacques

2013-01-31

460

Sample preparation for semivolatile organics analysis of Hanford single-shell tank waste with high nitrate/nitrite and water content  

SciTech Connect

This report describes research work carried out to solve sample preparation problems associated with applying gas chromatography with mass spectrometric detection (GC/MS) to the analysis of single shell tank (SST) samples from Hanford for semivolatile organic compounds. Poor performance was found when applying the procedures based on the U.S. Environmental Protection Agency (EPA), Contract Laboratory Program, Statement of Work (CLP SOW). Analysis work was carried out on simulated drainable liquid modeled after the SST core samples which had evidenced analysis problems. Some work was also conducted on true SST samples. It was found that the pH range was too broad in the original procedure. It was also found that by decreasing the amount of methanol used in the extraction process, problems associated with the formation of an azeotrope phase could be avoided. The authors suggest a new procedure, whose eventual application to a wide array of SST samples will lend itself to better quality control limits.

Stromatt, R.W.; Hoppe, E.W.; Steele, M.J.

1993-11-01

461

Improved Medium for Organic Transplants  

Microsoft Academic Search

Organic vegetable transplants are produced in Israel in ‘Speedling’ trays. The commercial growth medium consists of a mixture of peat moss and vermiculite (PV). Commercially grown transplants frequently exhibit non-uniform quality. Growers experience unacceptable mortality rates during the first weeks after transplanting. Substituting part of the peat moss with compost, based on the coarse fraction of cattle manure (CPV), caused

Michael Raviv; Reuven Reuveni; Ben Zion Zaidman

1998-01-01

462

Deciding which chemical mixtures risk assessment methods work best for what mixtures  

SciTech Connect

The most commonly used chemical mixtures risk assessment methods involve simple notions of additivity and toxicological similarity. Newer methods are emerging in response to the complexities of chemical mixture exposures and effects. Factors based on both science and policy drive decisions regarding whether to conduct a chemical mixtures risk assessment and, if so, which methods to employ. Scientific considerations are based on positive evidence of joint toxic action, elevated human exposure conditions or the potential for significant impacts on human health. Policy issues include legislative drivers that may mandate action even though adequate toxicity data on a specific mixture may not be available and risk assessment goals that impact the choice of risk assessment method to obtain the amount of health protection desired. This paper discusses three important concepts used to choose among available approaches for conducting a chemical mixtures risk a