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1

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

2

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...

3

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

4

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

5

Solidification phenomena of binary organic mixtures  

NASA Technical Reports Server (NTRS)

The coalescence rates and motion of liquid bubbles in binary organic mixtures were studied. Several factors such as temperature gradient, composition gradient, interfacial tension, and densities of the two phases play important roles in separation of phases of immiscible liquids. An attempt was made to study the effect of initial compositions on separation rates of well-dispersed organic mixtures at different temperatures and, ultimately, on the homogeneity of solidification of the immiscible binary organic liquids. These organic mixtures serve as models for metallic pseudo binary systems under study. Two specific systems were investigated: ethyl salicylate - diethyl glycol and succinonitrile - water.

Chang, K.

1982-01-01

6

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

7

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

8

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

Microsoft Academic Search

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

Weiyang Cheong; Paul I. Barton

1999-01-01

9

Azeotropic distillation in a middle vessel batch column. 2: Nonlinear separation boundaries  

SciTech Connect

On the basis of the analytical tools developed for the middle vessel column (MVC) operated under limiting conditions, analysis of the qualitative dynamics of the MVC in separating an azeotropic mixture is extended to the more realistic case in which the separation boundaries are nonlinear. The differences between batch stripper pot composition boundaries and batch rectifier pot composition being able to cross these pot composition boundaries. On the basis of these insights, operating procedures are developed in which ternary azeotropic mixtures of acetone, benzene, and chloroform can be separated into their constituent pure components, a separation not achievable with either the batch stripper or the batch rectifier. The operating procedures suggested for separating the ternary azeotropic mixture of acetone, benzene, and chloroform in the MVC are then shown to be the time analogues of sequences of continuous distillation columns that achieve the same separation. On the basis of this space-time analogy, further analogies are developed between the MVC and a continuous column, and it is postulated that many complex separations currently achieved with sequences of continuous columns can also be achieved with a single MVC. Thus, the MVC represents the ultimate multipurpose solvent recovery technology, as it can handle, in a batch multipurpose mode. separations that will otherwise require a dedicated continuous distillation sequence. Finally, the characteristics of perfect MVC batch entrainers, which allow the complete separation of any azeotrope into its constituent pure components in a single MVC, are discussed.

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

1999-04-01

10

Azeotropic line determination from the caloric data on binary stratifying systems  

NASA Astrophysics Data System (ADS)

The experimental isochoric heat capacity values of stratifying n-hexane-water mixtures of the compositions 0.120, 0.166, 0.200, and 0.256 H2O mole fractions were obtained using a high-temperature adiabatic calorimeter over the density ranges 244.74 498.25, 121.06 438.21, 252.02 500.00, and 208.11 398.88 kg/m3, respectively. The C V, x heat capacities were tabulated for the mixture with 0.120 H2O mole fractions. Liquid-liquid and liquid-gas phase equilibrium curves were plotted. The suggestion was made that the intersection point between these curves characterized the state of an azeotrope. The azeotropic line with the critical point at its end was constructed.

Bezgomonova, E. I.; Orakova, S. M.; Stepanov, G. V.; Shakhbanov, K. A.

2007-12-01

11

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

12

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...

13

The Viscosity of Organic Liquid Mixtures  

NASA Astrophysics Data System (ADS)

The paper reports measurements of the viscosity and density of two heavy hydrocarbon mixtures, Dutrex and Arab Light Flashed Distillate (ALFD), and of their mixtures with hydrogen. The measurements have been carried out with a vibrating-wire device over a range of temperatures from 399 to 547 K and at pressures up to 20 MPa. Measurements have also been carried out on systems in which hydrogen at different concentrations has been dissolved in the liquids. The measurements have an estimated uncertainty of ±5% for viscosity and ±2% for density and represent the first results on these prototypical heavy hydrocarbons. The results reveal that the addition of hydrogen reduces both the density and viscosity of the original hydrocarbon mixture at a particular temperature and pressure.

Len, C. W.; Trusler, J. P. M.; Vesovic, V.; Wakeham, W. A.

2006-01-01

14

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)] [Massachusetts Inst. of Tech., Cambridge, MA (United States)

1999-04-01

15

Lateral organization of complex lipid mixtures from multiscale modeling  

NASA Astrophysics Data System (ADS)

The organizational properties of complex lipid mixtures can give rise to functionally important structures in cell membranes. In model membranes, ternary lipid-cholesterol (CHOL) mixtures are often used as representative systems to investigate the formation and stabilization of localized structural domains (``rafts''). In this work, we describe a self-consistent mean-field model that builds on molecular dynamics simulations to incorporate multiple lipid components and to investigate the lateral organization of such mixtures. The model predictions reveal regions of bimodal order on ternary plots that are in good agreement with experiment. Specifically, we have applied the model to ternary mixtures composed of dioleoylphosphatidylcholine:18:0 sphingomyelin:CHOL. This work provides insight into the specific intermolecular interactions that drive the formation of localized domains in these mixtures. The model makes use of molecular dynamics simulations to extract interaction parameters and to provide chain configuration order parameter libraries.

Tumaneng, Paul W.; Pandit, Sagar A.; Zhao, Guijun; Scott, H. L.

2010-02-01

16

Cultivar mixtures of processing tomato in an organic agroecosystem  

Microsoft Academic Search

At an organic farm in California, managed biodiversity was manipulated by establishing a mustard cover crop (MCC) and fallow\\u000a during winter, and after incorporation, tomato mixtures of one, three, and five cultivars were planted in the spring (1-cv,\\u000a 3-cv, and 5-cv, respectively). It was hypothesized that cultivar mixtures may increase yields over a monoculture if disease\\u000a pressure or nitrogen (N)

Felipe H. Barrios-Masias; Marita I. Cantwell; Louise E. Jackson

2011-01-01

17

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

SciTech Connect

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 strongly bound than HF, thus it elutes much more slowly from the bed. The heat of adsorption for 134a in the vicinity of 200 C on Carbosieve G is {approximately}8.8 kcal/mol. In contrast, when the same azeotropic mixture is separated over PPFA-CMS prepared at 500 C, 134a is not adsorbed. As a result 134a elutes from the bed first, followed by HF. The reversal is brought about by the narrower pore size and pore size distribution of the PPFA-CMS versus that for Carbosieve G. Thus the separation over PPFA-CMS is an example of adsorbate shape selectivity and represents a limiting case of kinetic separation.

Hong, A.; Mariwala, R.K.; Kane, M.S.; Foley, H.C. [Univ. of Delaware, Nework, DE (United States)

1995-03-01

18

Respirator Cartridge Study Using Organic-Vapor Mixtures  

Microsoft Academic Search

The performance of respirator cartridges was measured during challenge by organic-vapor mixtures. All cartridges were tested in pairs under carefully controlled conditions of mass flow, temperature and relative humidity. Five chemical compounds were used during the testing: methyl ethyl ketone, isopropyl alcohol, hexane, n-butyl acetate and ethyl benzene. Cartridges were challenged by a single compound first at 1000 and then

P. M. SWEARENGEN; S. C. WEAVER

1988-01-01

19

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...

20

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...

21

The effect of azeotropism on combustion characteristics of blended fuel pool fire.  

PubMed

The effect of azeotropism on combustion characteristics of blended fuel pool fire was experimentally studied in an open fire test space of State Key Laboratory of Fire Science. A 30 cm × 30 cm square pool filled with n-heptane and ethanol blended fuel was employed. Flame images, burning rate and temperature distribution were collected and recorded in the whole combustion process. Results show that azeotropism obviously dominates the combustion behavior of n-heptane/ethanol blended fuel pool fire. The combustion process after ignition exhibits four typical stages: initial development, azeotropic burning, single-component burning and decay stage. Azeotropism appears when temperature of fuel surface reaches azeotropic point and blended fuel burns at azeotropic ratio. Compared with individual pure fuel, the effect of azeotropism on main fire parameters, such as flame height, burning rate, flame puffing frequency and centerline temperature were analyzed. Burning rate and centerline temperature of blended fuel are higher than that of individual pure fuel respectively at azeotropic burning stage, and flame puffing frequency follows the empirical formula between Strouhal and Froude number for pure fuel. PMID:24632362

Ding, Yanming; Wang, Changjian; Lu, Shouxiang

2014-04-30

22

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

23

Use of Statistical Mixture Designs to Evaluate Ternary Mixtures of Organics as Corrosion Inhibitors  

Microsoft Academic Search

Corrosion inhibitors are often mixtures of compounds which may or may not behave as a linear comination of the pure components in the mixture. Evaluation of the effect of the composition of the mixture on its inhibitory properties are often done on fragmentary data and there is an incomplete knowledge of the system being studied. Mixture Designs can be used

Frederick H. Walters

1990-01-01

24

Biofiltration of a mixture of volatile organic emissions.  

PubMed

Air biofiltration is now under active consideration for the removal of the volatile organic compounds (VOCs) from polluted airstreams. To optimize this emerging environmental technology and to understand compound removal mechanisms, a biofilter packed with peat was developed to treat a complex mixture of VOCs: oxygenated, aromatic, and chlorinated compounds. The removal efficiency of this process was high. The maximum elimination capacity (ECmax) obtained was approximately 120 g VOCs/m3 peat/hr. Referring to each of the mixture's components, the ECmax showed the limits in terms of biodegradability of VOCs, especially for the halogenated compounds and xylene. A stratification of biodegradation was observed in the reactor. The oxygenated compounds were metabolized before the aromatic and halogenated ones. Two assumptions are suggested. There was a competition between bacterial communities. Different communities colonized the peat-based biofilter, one specialized for the elimination of oxygenated compounds, the others more specialized for elimination of aromatic and halogenated compounds. There was also substrate competition. Bacterial communities were the same over the height of the column, but the more easily biodegradable compounds were used first for the microorganism metabolism when they were present in the gaseous effluent. PMID:15666471

Aizpuru, A; Malhautier, L; Roux, J C; Fanlo, J L

2001-12-01

25

Adsorption and desorption of binary mixtures of volatile organic contaminants on soil  

E-print Network

BET type 11 isotherms, which indicates multilayer adsorption on soil. The heats of adsorption indicate physical adsorption. Competitive adsorption of organic mixtures on soil was assessed by measuring the adsorption equilibria of binary mixtures...

Guo, Yang

2012-06-07

26

Application of the Firefly and Luus-Jaakola algorithms in the calculation of a double reactive azeotrope  

NASA Astrophysics Data System (ADS)

The calculation of reactive azeotropes is an important task in the preliminary design and simulation of reactive distillation columns. Classically, homogeneous nonreactive azeotropes are vapor-liquid coexistence conditions where phase compositions are equal. For homogeneous reactive azeotropes, simultaneous phase and chemical equilibria occur concomitantly with equality of compositions (in the Ung-Doherty transformed space). 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. In a previous paper (Platt et al 2013 J. Phys.: Conf. Ser. 410 012020), we investigated some numerical aspects of the calculation of reactive azeotropes in the isobutene + methanol + methyl-tert-butyl-ether (with two reactive azeotropes) system using two metaheuristics: the Luus-Jaakola adaptive random search and the Firefly algorithm. Here, we use a hybrid structure (stochastic + deterministic) in order to produce accurate results for both azeotropes. After identifying the neighborhood of the reactive azeotrope, the nonlinear algebraic system is solved using Newton's method. The results indicate that using metaheuristics and some techniques devoted to the calculation of multiple minima allows both azeotropic coordinates in this reactive system to be obtains. In this sense, we provide a comprehensive analysis of a useful framework devoted to solving nonlinear systems, particularly in phase equilibrium problems.

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

2014-01-01

27

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)] [Massachusetts Inst. of Tech., Cambridge, MA (United States)

1999-04-01

28

Rotary drum composting of different organic waste mixtures.  

PubMed

The effects of three different mixtures of organic waste on composting in a rotary drum were examined by measuring changes in physico-chemical and biological parameters. It was observed that the time courses of the three mixtures: run A (grass cuttings, vegetable waste and food waste), run B (cattle manure, vegetable waste and sawdust) and run C (cattle manure, food waste, vegetable waste, paper waste and sawdust) were quite diverse. Run B, with initial C/N ratio 22 and containing a large proportion of cattle manure produced high quality and mature compost within 20 days. It showed a final total nitrogen (2.1%), final total phosphorus 3.52 g kg(-1), final total organic carbon (TOC) (24.8%) and final moisture content (44%). At the end of 20 days, higher degradation led to final chemical oxygen demand (COD) (454 mg L(- 1)), biochemical oxygen demand (BOD) (107 mg L(- 1)), fecal coliform (1.2 x 10(2) bacteria g(- 1)), fecal streptococci (85 bacteria g(-1)) and low electrical conductivity (1.658 dS m(-1)), respectively. Furthermore, run C with initial C/N ratio of 30 and containing a larger amount of food and vegetable waste produced good quality compost and resulted in 4.34% total nitrogen and 2.42% total phosphorus after 20 days, but, it had higher final fecal coliform 2.5 x 10(4) bacteria g( -1), fecal streptococci 2.1 x 10(4) bacteria g(-1), high TOC and NH(4)-N and a BOD/COD ratio of 0.63, which rendered it hygienically unsafe and immature. Finally, run A with initial C/N ratio of 15 showed a higher amount of EC (4.84 dS m(-1)), NH(4)-N, BOD/COD ratio of 0.4 with 15% nitrogen loss, which indicated an unstable product even after 20 days of composting. Therefore, it was found that rotary drum composting of a combination of cattle manure, vegetable waste and sawdust resulted in a primary stabilized compost within 20 days of composting. PMID:19244412

Kalamdhad, Ajay S; Kazmi, Absar A

2009-03-01

29

Mixtures  

NSDL National Science Digital Library

Mixtures allows exploration of percents through two piles of colored and uncolored chips. The user must decide how many chips to color to create the desired percentage of colored chips compared to the total pile. Mixtures is one of the Interactivate assessment explorers.

30

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. PMID:3876109

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

1985-01-01

31

Retention capacity of an organic bio-mixture against different mixtures of fungicides used in vineyards  

Microsoft Academic Search

A laboratory experiment was carried out to test the efficiency of a bio-mixture made up of pruning residues at two (PR2) and five (PR5) years of composting and wheat straw (STW) in the biological cleaning of water contaminated by different mixtures of fungicides usually employed in vineyards. The experiment was conducted and reproduced at a scale of 1:100 of operating

Elga Monaci; Laura Coppola; Cristiano Casucci; Piero Perucci; Costantino Vischetti

2009-01-01

32

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)] [Massachusetts Inst. of Technology, Cambridge, MA (United States)

1996-11-27

33

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

34

ODOR AND IRRITATION EFFECTS OF A VOLATILE ORGANIC COMPOUND MIXTURE  

EPA Science Inventory

Human exposure to volatile organic compounds elicits a variety ofsymptoms, many of which are thought to be mediated by the olfactoryand trigeminal systems. his report describes evidence indicatingthat perceived odor intensity diminishes during prolonged exposure,whearas irritatin...

35

Determination of benzene and toluene in soils and plant material by azeotropic distillation  

SciTech Connect

The suspected dumping of gasoline near a garden resulted in the need for a method that would measure trace amounts of benzene and toluene in both soil and plant samples. In this report the authors show that a method involving methanolic extraction and azeotropic distillation is a highly sensitive technique that eliminated the contamination of the GC column by non-volatile material.

Kozloski, R.P.

1985-01-01

36

The solubility of hydrophobic aromatic chemicals in organic solvent/water mixtures  

SciTech Connect

The influence of dissolved organic solvents on the aqueous phase solubility of hydrophobic aromatic chemicals was investigated. To provide a basis for a comprehensive evaluation of the importance of cosolvent properties on solubility, the effects of several different organic cosolvents on the solubility of a model hydrophobic solute, naphthalene, were determined. Naphthalene solubility was measured in binary, ternary, and quaternary alcohol/water (methanol, ethanol, 1-propanol, 1-butanol, 1-pentanol) mixtures, binary ketone/water (acetone, methylethylketone, diethylketone), and aromatic organic solvent/water (benzene, toluene) mixtures. The solubility data were statistically evaluated and used to obtain an estimate of the overall accuracy of solubility measurements of hydrophobic chemicals in organic solvent/water mixtures. An accurate data base for mixed solvent solubility was established by combining the solubility data with additional solubility data obtained experimentally and from the literature. Thermodynamic models for predicting solubility in organic solvent/water mixtures were tested against the experimental data. The effects of organic cosolvent properties and solute hydrophobicity on solubility behavior and model predictive capability were evaluated. The results were used to evaluate the accuracy of existing models for predicting solubility and to explore possible molecular interactions in organic solvent/water mixtures.

Dickhut, R.M.

1989-01-01

37

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 GAC adsorber were designed, built, and operated in order to evaluate their performance for treating a groundwater contaminated with several volatile and synthetic organic chemicals. Several empty bed con...

38

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

39

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

40

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

41

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

42

Effect of organic fibers on open-graded friction course mixture properties  

Microsoft Academic Search

Open-graded friction course (OGFC) or porous asphalt mixtures are special mixes used for improving the surface friction, increasing surface permeability, and reducing pavement noise. The mix consists mostly of coarse size aggregate with little fines. This study was conducted to evaluate the effect of two types of organic fibers: date-palm fibers and textile fibers, in combination with styrene butadiene rubber

Hossam F. Hassan; Khalifa S. Al-Jabri

2005-01-01

43

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...

44

Fact or artifact: the representativeness of ESI-MS for complex natural organic mixtures.  

PubMed

Because mass spectrometers provide their own dispersion and resolution of analytes, electrospray ionization mass spectrometry (ESI-MS) has become a workhorse for the characterization of complex mixtures from aerosols to crude oil. Unfortunately, ESI mass spectra commonly contain multimers, adducts and fragments. For the characterization of complex mixtures of unknown initial composition, this presents a significant concern. Mixed-multimer formation could potentially lead to results that bare no resemblance to the original mixture. Conversely, ESI-MS has continually reflected subtle differences between natural organic matter mixtures that are in agreement with prediction or theory. Knowing the real limitations of the technique is therefore critical to avoiding both over-interpretation and unwarranted skepticism. Here, data were collected on four mass spectrometers under a battery of conditions. Results indicate that formation of unrepresentative ions cannot entirely be ruled out, but non-covalent multimers do not appear to make a major contribution to typical natural organic matter spectra based on collision-induced dissociation results. Multimers also appear notably reduced when a cooling gas is present in the accumulation region of the mass spectrometer. For less complex mixtures, the choice of spray solvent can make a difference, but generally spectrum cleanliness (i.e. representativeness) comes at the price of increased selectivity. PMID:24719347

Novotny, Nicole R; Capley, Erin N; Stenson, Alexandra C

2014-04-01

45

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

2012-08-01

46

Improved AIOMFAC model parameterisation of the temperature dependence of activity coefficients for aqueous organic mixtures  

NASA Astrophysics Data System (ADS)

This study presents a new, improved parameterisation of the temperature dependence of activity coefficients in the AIOMFAC (Aerosol Inorganic-Organic Mixtures Functional groups Activity Coefficients) model applicable for aqueous as well as water-free organic solutions. For electrolyte-free organic and organic-water mixtures the AIOMFAC model uses a group-contribution approach based on UNIFAC (UNIversal quasi-chemical Functional-group Activity Coefficients). This group-contribution approach explicitly accounts for interactions among organic functional groups and between organic functional groups and water. The previous AIOMFAC version uses a simple parameterisation of the temperature dependence of activity coefficients, aimed to be applicable in the temperature range from ~275 to ~400 K. With the goal to improve the description of a wide variety of organic compounds found in atmospheric aerosols, we extend the AIOMFAC parameterisation for the functional groups carboxyl, hydroxyl, ketone, aldehyde, ether, ester, alkyl, aromatic carbon-alcohol, and aromatic hydrocarbon to atmospherically relevant low temperatures with the introduction of a new temperature dependence parameterisation. The improved temperature dependence parameterisation is derived from classical thermodynamic theory by describing effects from changes in molar enthalpy and heat capacity of a multicomponent system. Thermodynamic equilibrium data of aqueous organic and water-free organic mixtures from the literature are carefully assessed and complemented with new measurements to establish a comprehensive database, covering a wide temperature range (~190 to ~440 K) for many of the functional group combinations considered. Different experimental data types and their processing for the estimation of AIOMFAC model parameters are discussed. The new AIOMFAC parameterisation for the temperature dependence of activity coefficients from low to high temperatures shows an overall improvement of 25% in comparison to the previous model version. The new parameterisation of AIOMFAC agrees well with a large number of experimental datasets and enables the calculation of activity coefficients of a wide variety of different aqueous/water-free organic solutions down to the low temperatures present in the upper troposphere.

Ganbavale, G.; Zuend, A.; Marcolli, C.; Peter, T.

2014-06-01

47

Comparison of activity coefficient models for atmospheric aerosols containing mixtures of electrolytes, organics, and water  

NASA Astrophysics Data System (ADS)

Atmospheric aerosols generally comprise a mixture of electrolytes, organic compounds, and water. Determining the gas-particle distribution of volatile compounds, including water, requires equilibrium or mass transfer calculations, at the heart of which are models for the activity coefficients of the particle-phase components. We evaluate here the performance of four recent activity coefficient models developed for electrolyte/organic/water mixtures typical of atmospheric aerosols. Two of the models, the CSB model [Clegg, S.L., Seinfeld, J.H., Brimblecombe, P., 2001. Thermodynamic modelling of aqueous aerosols containing electrolytes and dissolved organic compounds. Journal of Aerosol Science 32, 713-738] and the aerosol diameter dependent equilibrium model (ADDEM) [Topping, D.O., McFiggans, G.B., Coe, H., 2005. A curved multi-component aerosol hygroscopicity model framework: part 2—including organic compounds. Atmospheric Chemistry and Physics 5, 1223-1242] treat ion-water and organic-water interactions but do not include ion-organic interactions; these can be referred to as "decoupled" models. The other two models, reparameterized Ming and Russell model 2005 [Raatikainen, T., Laaksonen, A., 2005. Application of several activity coefficient models to water-organic-electrolyte aerosols of atmospheric interest. Atmospheric Chemistry and Physics 5, 2475-2495] and X-UNIFAC.3 [Erdakos, G.B., Change, E.I., Pandow, J.F., Seinfeld, J.H., 2006. Prediction of activity coefficients in liquid aerosol particles containing organic compounds, dissolved inorganic salts, and water—Part 3: Organic compounds, water, and ionic constituents by consideration of short-, mid-, and long-range effects using X-UNIFAC.3. Atmospheric Environment 40, 6437-6452], include ion-organic interactions; these are referred to as "coupled" models. We address the question—Does the inclusion of a treatment of ion-organic interactions substantially improve the performance of the coupled models over that of the decoupled models? Performance is judged by the extent to which each model is able to reproduce experimental water activity data for mixtures of organic acids (malonic, succinic, glutaric, citric, maleic, and malic acids) and inorganic electrolytes (NaCl and (NH 4) 2SO 4). It is found, based on the comparisons reported here, that the decoupled models perform as well as, and in some cases better than, the coupled models. Since such activity coefficient models are likely to continue to be developed in the future and because we consider here only a limited set of organic compounds, the current study should be viewed as an interim assessment. The scarcity of experimental data for mixtures of atmospheric relevance remains a limitation for testing activity coefficient models.

Tong, Chinghang; Clegg, Simon L.; Seinfeld, John H.

48

Mixture toxicity of nitrobenzene and trinitrobenzene using the marine bacterium Vibrio harveyi as the test organism.  

PubMed

Vibrio harveyi, a bioluminescent marine bacterium, was used to evaluate combined or mixture toxicity of two organic compounds, nitrobenzene and trinitrobenzene. An estimated median effective concentration (EC50) and confidence interval were determined for each chemical. These chemicals at their EC50 were evaluated in combination and an additive index method was used to determine a numerical toxicology value. Combinations at 20% intervals of the EC50 were performed using isopleths. The isopleths employed were the isobole plot and the isobologram. Bioluminescent change was also determined and graphed for evaluation of toxicity. Statistical evaluation of isopleths and the additive index method were employed by incorporating confidence intervals. Bioluminescent change and isopleths suggest that mixtures of nitrobenzene and trinitrobenzene are additive, while the additive index method is suggestive of synergism. Statistical evaluation between mixtures and single values, using the z test, was in some cases different at the 5% level. These data suggest that interaction of combinations should be evaluated and described by multiple methodologies. Evaluation of these data suggests, in part, that one mixture is statistically different for antagonism. This study supports the use of bioluminescent microbial toxicity tests with various evaluative methodologies for the determination of mixture interactions. PMID:9126438

Thomulka, K W; Lange, J H

1997-03-01

49

Modeling the surface tension of complex, reactive organic-inorganic mixtures  

NASA Astrophysics Data System (ADS)

Atmospheric aerosols can contain thousands of organic compounds which impact aerosol surface tension, affecting aerosol properties such as heterogeneous reactivity, ice nucleation, and cloud droplet formation. We present new experimental data for the surface tension of complex, reactive organic-inorganic aqueous mixtures mimicking tropospheric aerosols. Each solution contained 2-6 organic compounds, including methylglyoxal, glyoxal, formaldehyde, acetaldehyde, oxalic acid, succinic acid, leucine, alanine, glycine, and serine, with and without ammonium sulfate. We test two semi-empirical surface tension models and find that most reactive, complex, aqueous organic mixtures which do not contain salt are well described by a weighted Szyszkowski-Langmuir (S-L) model which was first presented by Henning et al. (2005). Two approaches for modeling the effects of salt were tested: (1) the Tuckermann approach (an extension of the Henning model with an additional explicit salt term), and (2) a new implicit method proposed here which employs experimental surface tension data obtained for each organic species in the presence of salt used with the Henning model. We recommend the use of method (2) for surface tension modeling of aerosol systems because the Henning model (using data obtained from organic-inorganic systems) and Tuckermann approach provide similar modeling results and goodness-of-fit (?2) values, yet the Henning model is a simpler and more physical approach to modeling the effects of salt, requiring less empirically determined parameters.

Schwier, A. N.; Viglione, G. A.; Li, Z.; McNeill, V. Faye

2013-11-01

50

Modeling the surface tension of complex, reactive organic-inorganic mixtures  

NASA Astrophysics Data System (ADS)

Atmospheric aerosols can contain thousands of organic compounds which impact aerosol surface tension, affecting aerosol properties such as cloud condensation nuclei (CCN) ability. We present new experimental data for the surface tension of complex, reactive organic-inorganic aqueous mixtures mimicking tropospheric aerosols. Each solution contained 2-6 organic compounds, including methylglyoxal, glyoxal, formaldehyde, acetaldehyde, oxalic acid, succinic acid, leucine, alanine, glycine, and serine, with and without ammonium sulfate. We test two surface tension models and find that most reactive, complex, aqueous organic mixtures which do not contain salt are well-described by a weighted Szyszkowski-Langmuir (S-L) model which was first presented by Henning et al. (2005). Two approaches for modeling the effects of salt were tested: (1) the Tuckermann approach (an extension of the Henning model with an additional explicit salt term), and (2) a new implicit method proposed here which employs experimental surface tension data obtained for each organic species in the presence of salt used with the Henning model. We recommend the use of method (2) for surface tension modeling because the Henning model (using data obtained from organic-inorganic systems) and Tuckermann approach provide similar modeling fits and goodness of fit (?2) values, yet the Henning model is a simpler and more physical approach to modeling the effects of salt, requiring less empirically determined parameters.

Schwier, A. N.; Viglione, G. A.; Li, Z.; McNeill, V. F.

2013-01-01

51

Mixture Toxicity of Nitrobenzene and Trinitrobenzene Using the Marine Bacterium Vibrio harveyias the Test Organism  

Microsoft Academic Search

Vibrio harveyi,a bioluminescent marine bacterium, was used to evaluate combined or mixture toxicity of two organic compounds, nitrobenzene and trinitrobenzene. An estimated median effective concentration (EC50) and confidence interval were determined for each chemical. These chemicals at their EC50were evaluated in combination and an additive index method was used to determine a numerical toxicology value. Combinations at 20% intervals of

K. W. Thomulka; J. H. Lange

1997-01-01

52

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

53

Human lung-cancer risks due to complex organic mixtures of combustion emissions  

SciTech Connect

The study of Xuan Wei fuel use and lung cancer mortality and also the interim case-control study suggested an association between domestic smoky coal use and Xuan Wei lung cancer. The collaborative studies of physical characterization, chemical analysis, and toxicology further substantiated this linkage. The Xuan Wei residents who used smoky coal inhaled extremely high concentrations of most submicron-sized particles, which were composed mostly of organic compounds (72%), including mutagenic and carcinogenic organic compounds (especially in the aromatic and polar fractions). In comparison to wood and smokeless coal combustion emissions, the organic extracts of smoky coal emission particles showed a much higher activity of genotoxicity and carcinogenicity. The results all point to a strong etiological link between the complex organic mixtures from smoky coal emissions and Xuan Wei lung cancer.

Mumford, J.L.; He, X.; Chapman, R.S.

1988-09-01

54

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

55

Annual and seasonal changes in production and composition of grazed clover-grass mixtures in organic farming  

Microsoft Academic Search

A grazed field experiment based on a randomised block design was conducted in Eastern Finland to evaluate the potential of alsike clover (Trifoliun hybridum L.), red clover (Trifolium pratense L.) and white clover (Trifolium repens L.) to support herbage production from clover-grass mixtures under organic farming practices. The effect of seed mixture (alsike clover, red clover, white clover, white and

Eeva Kuusela

2004-01-01

56

Organic tank safety project: Preliminary results of energetics and thermal behavior studies of model organic nitrate and/or nitrite mixtures and a simulated organic waste  

SciTech Connect

As a result of years of production and recovery of nuclear defense materials and subsequent waste management at the Hanford Site, organic-bearing radioactive high-level wastes (HLW) are currently stored in large (up to 3. ML) single-shell storage tanks (SSTs). Because these wastes contain both fuels (organics) and the oxidants nitrate and nitrite, rapid energetic reactions at certain conditions could occur. In support of Westinghouse Hanford Company`s (WHC) efforts to ensure continued safe storage of these organic- and oxidant-bearing wastes and to define the conditions necessary for reactions to occur, we measured the thermal sensitivities and thermochemical and thermokinetic properties of mixtures of selected organics and sodium nitrate and/or nitrite and a simulated Hanford organic-bearing waste using thermoanalytical technologies. These thermoanalytical technologies are used by chemical reactivity hazards evaluation organizations within the chemical industry to assess chemical reaction hazards.

Scheele, R.D.; Sell, R.L.; Sobolik, J.L.; Burger, L.L.

1995-08-01

57

Mineralization of organic contaminants under aerobic and anaerobic conditions in sludge-soil mixtures  

Microsoft Academic Search

Background and Main Features  The mineralization of eight organic chemicals (surfactants, substituted aromatic compounds, di(2-ethylhexyl)phthalate and\\u000a phenanthrene) was examined in sludge-soil mixtures under aerobic, denitrifying and methanogenic conditions.\\u000a \\u000a \\u000a \\u000a Results and Discussion  Most of the chemicals were extensively or partially mineralized under aerobic conditions with mineralization half-lives between\\u000a 1.5 and 12.5 days. Linear tridecyl tetra ethoxylate, di(2-ethylhexyl)phthalate and 2,4-dinitrophenol were also mineralized\\u000a partially

Bo Gejlsbjerg; Trine T. Andersen; Torben Madsen

2004-01-01

58

Capillary chromatography based on tube radial distribution of aqueous-organic mixture carrier solvents.  

PubMed

A capillary chromatography system was developed using open capillary tubes made of fused-silica, polyethylene, or poly(tetrafluoroethylene), and an aqueous-organic mixture (water-acetonitrile-ethyl acetate mixture) as a carrier solution. Model analyte mixture solutions, such as 2,6-naphthalenedisulfonic acid and 1-naphthol, Eosin Y and perylene, bis[N,N-bis(carboxymethyl)aminomethyl]fluorescein and 1,1'-bi-2-naphthol, and 2,7-naphthalenedisulfonic acid and p-nitroaniline, were injected into the capillary tube by a gravity method. The analyte solutions were subsequently delivered through the capillary tube with the carrier solution by a micro-syringe pump. The system worked under laminar flow conditions. The analytes were separated through the capillary tube and detected on-capillary by an absorption detector. For example, 2,6-naphthalenedisulfonic acid and 1-naphthol were detected in this order with a carrier solution of water-acetonitrile-ethyl acetate (volume ratio 15:3:2), while they were detected in the reverse order with a carrier solution of water-acetonitrile-ethyl acetate (volume ratio 2:9:4). The other analyte solutions were similarly separated by the system. The elution times of the analytes could be easily reversed by changing the component ratio of the solvents in the carrier solution. PMID:19635369

Jinno, Naoya; Itano, Minoru; Hashimoto, Masahiko; Tsukagoshi, Kazuhiko

2009-10-15

59

Ionic equilibria in aqueous organic solvent mixtures the dissociation constants of acids and salts in tetrahydrofuran\\/water mixtures  

Microsoft Academic Search

The dissociation constants of several acids (perchloric, hydrochloric, phosphoric, acetic and benzoic acids) and of some sodium salts (chloride, acetate and benzoate) have been conductometrically determined in tetrahydrofuran\\/water mixtures up to a 90% of tetrahydrofuran in volume. The results demonstrate that conductometry can be successfully applied to determine the dissociation constants of salts and moderately weak and strong acids in

Urmas Muinasmaa; Clara Ràfols; Elisabeth Bosch; Martí Rosés

1997-01-01

60

Complex Singular Points of the Tie-Line Vector Field Diagrams of Ternary Mixtures  

Microsoft Academic Search

Complex singular points of the tie-line vector field diagrams of liquid-vapor ternary systems are considered in terms of the theory of stationary vector fields and bifurcation theory. These complex singular points are found to be tangential azeotropic points of different orders, which play a decisive role in transformations of the diagrams of heterogeneous mixtures.

L. A. Serafimov; T. V. Chelyuskina

2005-01-01

61

Effect of Exposure to a Mixture of Organic Solvents on Hearing Thresholds in Petrochemical Industry Workers  

PubMed Central

Introduction: Hearing loss is one of the most common occupational diseases. In most workplaces, workers are exposed to noise and solvents simultaneously, so the potential risk of hearing loss due to solvents may be attributed to noise. In this study we aimed to assess the effect of exposure to mixed aromatic solvents on hearing in the absence of exposure to hazardous noise. Materials and Methods: In a cross-sectional study, 99 workers from the petrochemical industry with exposure to a mixture of organic solvents whose noise exposure was lower than 85 dBA were compared with 100 un-exposed controls. After measuring sound pressure level and mean concentration of each solvent in the workplace, pure-tone-audiometry was performed and the two groups were compared in terms of high-frequency and low-frequency hearing loss. T-tests and Chi-square tests were used to compare the two groups. Results: The mean hearing threshold at all frequencies among petrochemical workers was normal (below 25 dB). We did not observe any significant association between solvent exposure and high-frequency or low-frequency hearing loss. Conclusion: This study showed that temporary exposure (less than 4 years) to a mixture of organic solvents, without exposure to noise, does not affect workers’ hearing threshold in audiometry tests. PMID:25320701

Loukzadeh, Ziba; Shojaoddiny-Ardekani, Ahmad; Mehrparvar, Amir Houshang; Yazdi, Zohreh; Mollasadeghi, Abolfazl

2014-01-01

62

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

2007-03-01

63

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 (H 2Op) content. A new condensed aromatic kinetic mechanism employing uptake of organics in H 2Op 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

64

Importance of Aqueous-phase Secondary Organic Aerosol Formation from Aromatics in an Atmospheric Hydrocarbon Mixture  

NASA Astrophysics Data System (ADS)

Two new secondary organic aerosol (SOA) modeling frameworks are developed, one based on an aromatic gas and particle-phase kinetic mechanism and another based on a parameterized SOA model used in conjunction with an underlying gas-phase mechanism, both of which simulate SOA formation through partitioning to two stable liquid phases: one hydrophilic containing particle aqueous-phase and the other hydrophobic comprising mainly organic components. The models were evaluated against outdoor smog chamber experiments with different combinations of initial toluene, o-xylene, p-xylene, toluene and xylene mixtures, NOx, non-SOA-forming hydrocarbon mixture, initial seed type, and humidity. Aerosol data for experiments with either ammonium sulfate or initial background seed particles, in the presence of an atmospheric hydrocarbon mixture, NOx and in sunlight under a dry atmosphere (RH = 6 to 10%) show reduced SOA formation when compared to experiments with similar initial gas and particle concentrations at higher relative humidities (RH = 40 to 90%). Both frameworks simulated reasonable fits to the total observed SOA concentrations under all conditions. For both dry and wet experiments with low initial seed, semi-volatile product partitioning in particle organic-phase is mass-transfer limited and is modeled using a dynamic gas-particle partitioning algorithm with accommodation coefficient as the primary pseudo-transport parameter. Further, the modeled SOA product distributions for both frameworks clearly show the importance of the contribution of aqueous-phase SOA particularly under conditions of low initial seed concentrations and high-humidity. For both models, under these conditions, aqueous-phase SOA from uptake of glyoxal, methylglyoxal and related polar products to particle water phase dominates as compared to the partitioning of semi-volatiles to particle organic phase. Interestingly, both the kinetic and parameterized SOA frameworks simulate similar amounts of aqueous-phase SOA for each experiment. For wet experiments with initial ammonium sulfate seed, the modeled fraction of aqueous-phase SOA is up to 82% of the total ammonium sulfate mass and for wet experiment with initial background seed this fraction is as high as 60% of the total particle mass formed for the duration of the experiments. This suggests that aqueous-phase SOA from oxidation of toluene and xylene, under atmospherically relevant conditions, is significant and should be part of kinetic or parameterized SOA modeling frameworks in current air quality models.

Parikh, H. M.; Carlton, A. G.; Vizuete, W.; Zhang, H.; Zhou, Y.; Chen, E.; Kamens, R. M.

2010-12-01

65

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

66

SOA formation in a photoreactor from a mixture of organic gases and HONO for different experimental conditions  

NASA Astrophysics Data System (ADS)

Smog chambers have been extensively used to investigate the chemical routes of oxidation reactions for several organic gases. In this study we present the results of a set of experiments performed in the EUPHORE photoreactor to analyze SOA formation from a mixture of four organic gases related to anthropogenic emissions (1,3,5-trimethylbenzene, o-xylene, octane and toluene) with an oxidant under different experimental conditions. The effect of the organic mixture and oxidant initial concentration and the effect of SO 2 on SOA formation were analyzed. A mixture of three organic gases associated to biogenic emissions (isoprene, ?-pinene and limonene) was also examined. An on-line analysis of the aerosol concentration and particle size distribution was performed by TEOM and SMPS. Two off-line techniques were also used: ion chromatography to quantify the inorganic fraction (sulfates and nitrates) and derivatization followed by GC-MS to analyse the hydroxyl-containing compounds. The experiment with the mixture of biogenic parent organic gases led to the highest organic aerosol yields and larger particles. High initial SO 2 concentrations strongly increased aerosol yields for the anthropogenic mixture.

Vivanco, Marta G.; Santiago, Manuel; Martínez-Tarifa, Adela; Borrás, Esther; Ródenas, Milagros; García-Diego, Cristina; Sánchez, Miguel

2011-01-01

67

Molecular dynamics simulation studies on ethane and acetylene mixture in CuBTC metal organic framework  

NASA Astrophysics Data System (ADS)

Molecular Dynamics (MD) simulation studies have been carried out on the mixture containing ethane and acetylene molecules in 1:1 ratio at various concentrations of each species in CuBTC metal organic framework (MOF). MOFs are important class of materials which are tremendously useful for applications such as gas storage and separation. They have complex structure consisting of pore and pockets connected by windows. Results obtained from MD simulation showed that the self diffusivity of the ethane increases with the concentration while it decreases in case of acetylene. Correlation effects are responsible for this kind of phenomena. Pair distribution function showed the strong peaks at higher correlation length indicating the complex crystalline structure of the host matrix. We have also obtained the velocity auto correlation function (VACF) and velocity cross correlation functions (VCCF) at each studied concentration and found that the contribution from VCCF is almost negligible at lower concentration. Since the transport properties of mixture also depend on the mutual diffusivity and distinct diffusivity besides the self diffusivity, attempt has been made to quantify both the diffusivities. In the present system, at lower concentration, contribution to the mutual diffusivity comes from self diffusivities of species alone and distinct diffusivity contributes only at higher concentration.

Prabhudesai, S. A.; Sharma, V. K.; Mitra, S.; Mukhopadhyay, R.

2014-04-01

68

Improved electrolytes for Li-ion batteries: Mixtures of ionic liquid and organic electrolyte with enhanced safety and electrochemical performance  

Microsoft Academic Search

Physical and electrochemical characteristics of Li-ion battery systems based on LiFePO4 cathodes and graphite anodes with mixture electrolytes were investigated. The mixed electrolytes are based on an ionic liquid (IL), and organic solvents used in commercial batteries. We investigated a range of compositions to determine an optimum conductivity and non-flammability of the mixed electrolyte. This led us to examine mixtures

A. Guerfi; M. Dontigny; P. Charest; M. Petitclerc; M. Lagacé; A. Vijh; K. Zaghib

2010-01-01

69

Gas-particle partitioning of semivolatile organic compounds (SOCs) on mixtures of aerosols in a smog chamber.  

PubMed

The partitioning behavior of a set of diverse SOCs on two and three component mixtures of aerosols from different sources was studied using smog chamber experimental data. A set of SOCs of different compound types was introduced into a system containing a mixture of aerosols from two or more sources. Gas and particle samples were taken using a filter-filter-denuder sampling system, and a partitioning coefficient Kp was estimated using Kp = Cp/(CgTSP). Particle size distributions were measured using a differential mobility analyzer and a light scattering detector. Gas and particle samples were analyzed using GCMS. The aerosol composition in the chamber was tracked chemically using a combination of signature compounds and the organic matter mass fraction (f(om)) of the individual aerosol sources. The physical nature of the aerosol mixture in the chamber was determined using particle size distributions, and an aggregate Kp was estimated from theoretically calculated Kp on the individual sources. Model fits for Kp showed that when the mixture involved primary sources of aerosol, the aggregate Kp of the mixture could be successfully modeled as an external mixture of the Kp on the individual aerosols. There were significant differences observed for some SOCs between modeling the system as an external and as an internal mixture. However, when one of the aerosol sources was secondary, the aggregate model Kp required incorporation of the secondary aerosol products on the preexisting aerosol for adequate model fits. Modeling such a system as an external mixture grossly overpredicted the Kp of alkanes in the mixture. Indirect evidence of heterogeneous, acid-catalyzed reactions in the particle phase was also seen, leading to a significant increase in the polarity of the resulting aerosol mix and a resulting decrease in the observed Kp of alkanes in the chamber. The model was partly consistent with this decrease but could not completely explain the reduction in Kp because of insufficient knowledge of the secondary organic aerosol composition. PMID:14524443

Chandramouli, Bharadwaj; Jang, Myoseon; Kamens, Richard M

2003-09-15

70

Chronic impact of tetracycline on the biodegradation of an organic substrate mixture under anaerobic conditions.  

PubMed

The study evaluates the chronic impact of the antibiotic tetracycline on the biodegradation of organic substrate under anaerobic conditions. The experiments involved an anaerobic sequencing batch reactor fed with a synthetic substrate mixture including glucose, starch and volatile fatty acids, and operated in a sequence of different phases with gradually increasing tetracycline doses of 1.65-8.5 mg/L, for more than five months. Tetracycline exerted a terminal/lethal effect at 8.5 mg/L on the microbial community under anaerobic conditions, which caused the inhibition of substrate/COD utilization and biogas generation and leading to a total collapse of the reactor. The microbial activity could not be recovered and re-started within a period of more than 10 days, even after stopping tetracycline dosing. At lower doses, substrate utilization was not affected but a reduction of 10-20% was observed in the biogas/methane generation, suggesting that substrate utilization of tetracycline to the biomass was limiting their bioavailability. During the experiments, tetracycline was partially removed either through biodegradation or conversion into its by-products. The adverse long-term impact was quite variable for fermenting heterotrophic and methanogenic fractions of the microbial community based on changes inflicted on the composition of remaining/residual organic substrate. PMID:23561494

Cetecioglu, Z; Ince, B; Gros, M; Rodriguez-Mozaz, S; Barceló, D; Orhon, D; Ince, O

2013-06-01

71

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

Microsoft Academic Search

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

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

1997-01-01

72

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. PMID:3814530

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

1987-01-01

73

Biofiltration of a mixture of volatile organic compounds on granular activated carbon.  

PubMed

The performance of a biofilter packed with Active Carbon (AC) was evaluated. The effluent (alcohol, ketones, esters, aromatic and chlorinated compounds) treated was a representative mixture of most common industrial emissions. To achieve a better knowledge of multicomponent adsorption mechanisms, and to underline the interest of inoculating AC, a control abiotic humidified filter had been operated in the same conditions as the biofilter. For a load of 110 g VOC m(-3) AC h(-1), after 55 days of operation, the removal efficiency was higher in the biotic than in the abiotic filter (85% vs 55%, respectively). Moreover, in the biofilter, at steady state, the elimination of all compounds was almost complete except for chlorinated compounds and p-xylene (removal efficiency of 25% and 64%, respectively). The microbial colonization of AC involved a decrease of the adsorption sites accessibility and enhanced the treatment of VOCs (volatile organic compounds) having a lower affinity for activated carbon. Moreover, while aromatic compounds and MIBK were eliminated along the overall height of the biofilter, pollutants with reduced affinity for AC, such as methanol, acetone, and halogenated compounds were only treated on the second half of the reactor. Thus, the affinity for activated carbon was an important parameter controlling the biodegradation process. Nevertheless, the use of AC as packing material in biofilters treating complex mixtures of VOCs is limited. Actually, similar removal efficiency could be reached, in the same conditions, for a biofilter packed with granular peat. Furthermore, for the biofilter packed with AC, the column height necessary to remove biodegradable compounds, with reduced affinity for the support, was important. PMID:12800142

Aizpuru, A; Malhautier, L; Roux, J C; Fanlo, J L

2003-08-20

74

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...

75

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

76

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

77

Structure of Cholesterol/Ceramide Monolayer Mixtures: Implications to the Molecular Organization of Lipid Rafts  

PubMed Central

The structure of monolayers of cholesterol/ceramide mixtures was investigated using grazing incidence x-ray diffraction, immunofluorescence, and atomic force microscopy techniques. Grazing incidence x-ray diffraction measurements showed the existence of a crystalline mixed phase of the two components within a range of compositions of cholesterol/ceramide between 100:0 and 67:33. The mixed phase coexists with the ceramide crystalline phase in the range of compositions between 50:50 and 30:70; between 30:70 and 0:100 only the highly crystalline phase of ceramide was detected. The latter was determined and modeled. Immunolabeling was performed with an antibody specific to the cholesterol monohydrate crystalline arrangement. The antibody recognizes crystalline cholesterol monolayers, but does not interact with crystalline ceramide. Immunofluorescence and atomic force microscopy data show that in uncompressed ceramide monolayers, the highly crystalline phase coexists with a disordered loosely packed phase. In contrast, no disordered phase coexists with the new crystalline mixed phase. We conclude that the new mixed phase represents a stable homogeneous arrangement of cholesterol with ceramide. As ceramide incorporates the lipid backbone common to all sphingolipids, this arrangement may be relevant to the understanding of the molecular organization of lipid rafts. PMID:15722431

Scheffer, Luana; Solomonov, Inna; Weygand, Markus Jan; Kjaer, Kristian; Leiserowitz, Leslie; Addadi, Lia

2005-01-01

78

Modeling competitive adsorption of mixtures of volatile organic compounds in a fixed-bed of beaded activated carbon.  

PubMed

A two-dimensional mathematical model was developed to study competitive adsorption of n-component mixtures in a fixed-bed adsorber. The model consists of an isotherm equation to predict adsorption equilibria of n-component volatile organic compounds (VOCs) mixture from single component isotherm data, and a dynamic adsorption model, the macroscopic mass, energy and momentum conservation equations, to simulate the competitive adsorption of the n-components onto a fixed-bed of adsorbent. The model was validated with experimentally measured data of competitive adsorption of binary and eight-component VOCs mixtures onto beaded activated carbon (BAC). The mean relative absolute error (MRAE) was used to compare the modeled and measured breakthrough profiles as well as the amounts of adsorbates adsorbed. For the binary and eight-component mixtures, the MRAE of the breakthrough profiles was 13 and 12%, respectively, whereas, the MRAE of the adsorbed amounts was 1 and 2%, respectively. These data show that the model provides accurate prediction of competitive adsorption of multicomponent VOCs mixtures and the competitive adsorption isotherm equation is able to accurately predict equilibrium adsorption of VOCs mixtures. PMID:24670053

Tefera, Dereje Tamiru; Hashisho, Zaher; Philips, John H; Anderson, James E; Nichols, Mark

2014-05-01

79

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

80

Organized collapse structures in mixtures of chiral ethyl 2-azido-4-fluoro-3-hydroxystearates.  

PubMed

Monolayers of enantiomeric compounds as well as diastereomeric mixtures and racemic/diastereomeric mixtures of ethyl 2-azido-4-fluoro-3-hydroxystearates have been investigated using surface pressure-area isotherms and Brewster angle microscopy. All monolayers collapse out of the liquid-expanded phase, forming 3D collapse structures which were visualized with scanning force microscopy. The enantiomeric compound and the diastereomeric mixtures form unique fiber-like network structures with heights between 20 and 40 nm. Interestingly, the shape of the enantiomeric fiber structures is straight, whereas the diastereomeric mixtures exhibit curved fibers of different sizes. The racemic mixture however forms circular 10 nm high and 20-50 microm broad structures. The shape of unconventional collapse structures could be changed by using distinct ratios of diastereomeric or racemic/diastereomeric mixed compounds. PMID:16460057

Steffens, Silke; Oldendorf, Jens; Haufe, Günter; Galla, Hans-Joachim

2006-02-14

81

Transmission geometry laser desorption atmospheric pressure photochemical ionization mass spectrometry for analysis of complex organic mixtures.  

PubMed

We present laser desorption atmospheric pressure photochemical ionization mass spectrometry (LD/APPCI MS) for rapid throughput analysis of complex organic mixtures, without the need for matrix, electric discharge, secondary electrospray, or solvents/vaporizers. Analytes dried on a microscope slide are vaporized in transmission geometry by a laser beam aligned with the atmospheric pressure inlet of the mass spectrometer. The laser beam initiates a cascade of reactions in the region between the glass slide and MS inlet, leading to generation of reagent ions for chemical ionization of vaporized analyte. Positive analyte ions are generated predominantly by proton transfer, charge exchange, and hydride abstraction, whereas negative ions are generated by electron capture or proton transfer reactions, enabling simultaneous analysis of saturated, unsaturated, and heteroatom-containing hydrocarbons. The absence of matrix interference renders LD/APPCI MS particularly useful for analysis of small molecules (<2000 Da) such as those present in petroleum crude oil and petroleum deposits. [M + H](+) and M(+•) dominate the positive-ion mass spectra for olefins and polyaromatic hydrocarbons, whereas saturated hydrocarbons are observed mainly as [M - H](+) and/or M(+•). Heteroatom-containing hydrocarbons are observed predominantly as [M + H](+). [M - H](-) and M(-•) are the dominant negative ions observed for analytes of lower gas-phase basicity or higher electron affinity than O2. The source was coupled with a 9.4 T Fourier transform ion cyclotron resonance mass spectrometer (FTICR MS) to resolve and identify thousands of peaks from Athabasca bitumen heavy vacuum gas oil distillates (400-425 and 500-538 °C), enabling simultaneous characterization of their polar and nonpolar composition. We also applied LD/APPCI FTICR MS for rapid analysis of sodium and calcium naphthenate deposits with little to no sample pretreatment to provide mass spectral fingerprints that enable reliable compositional characterization. PMID:25347814

Nyadong, Leonard; Mapolelo, Mmilili M; Hendrickson, Christopher L; Rodgers, Ryan P; Marshall, Alan G

2014-11-18

82

Enzymatic synthesis of 6-O-glucosyl-poly(3-hydroxyalkanoate) in organic solvents and their binary mixture.  

PubMed

The effects of organic solvents and their binary mixture in the glucose functionalization of bacterial poly-3-hydroxyalkanoates catalyzed by Lecitase™ Ultra were studied. Equal volume binary mixture of DMSO and chloroform with moderate polarity was more effective for the enzyme catalyzed synthesis of the carbohydrate polymer at ?38.2 (±0.8)% reactant conversion as compared to the mono-phasic and other binary solvents studied. The apparent reaction rate constant as a function of medium water activity (aw) was observed to increase with increasing solvent polarity, with optimum aw of 0.2, 0.4 and 0.7 (±0.1) observed in hydrophilic DMSO, binary mixture DMSO:isooctane and hydrophobic isooctane, respectively. Molecular sieve loading between 13 to 15gL(-1) (±0.2) and reaction temperature between 40 to 50°C were found optimal. Functionalized PHA polymer showed potential characteristics and biodegradability. PMID:23305702

Gumel, A M; Annuar, M S M; Heidelberg, T

2013-04-01

83

Soil surface colonization by phototrophic indigenous organisms, in two contrasted soils treated by formulated maize herbicide mixtures.  

PubMed

Soil phototrophic microorganisms, contributors to soil health and food webs, share their particular metabolism with plants. Current agricultural practices employ mixtures of pesticides to ensure the crops yields and can potentially impair these non-target organisms. However despite this environmental reality, studies dealing the susceptibility of phototrophic microorganisms to pesticide mixtures are scarce. We designed a 3 months microcosm study to assess the ecotoxicity of realistic herbicide mixtures of formulated S-metolachlor (Dual Gold Safeneur(®)), mesotrione (Callisto(®)) and nicosulfuron (Milagro(®)) on phototrophic communities of two soils (Limagne vertisol and Versailles luvisol). The soils presented different colonizing communities, with diatoms and chlorophyceae dominating communities in Limagne soil and cyanobacteria and bryophyta communities in Versailles soil. The results highlighted the strong impairment of Dual Gold Safeneur(®) treated microcosms on the biomass and the composition of both soil phototrophic communities, with no resilience after a delay of 3 months. This study also excluded any significant mixture effect on these organisms for Callisto(®) and Milagro(®) herbicides. We strongly recommend carrying on extensive soil studies on S-metolachlor and its commercial formulations, in order to reconsider its use from an ecotoxicological point of view. PMID:25129149

Joly, Pierre; Misson, Benjamin; Perrière, Fanny; Bonnemoy, Frédérique; Joly, Muriel; Donnadieu-Bernard, Florence; Aguer, Jean-Pierre; Bohatier, Jacques; Mallet, Clarisse

2014-11-01

84

The effect of humidity on the collection efficiencies of two monitoring methods when exposed to a mixture of organic solvents  

E-print Network

THE EFFECT OF HUMIDITY ON THE COLLECTION EFFICIENCIES OF TWO MONITORING METHODS WHEN EXPOSED TO A MIXTURE OF ORGANIC SOLVENTS A Thesis by LORI ANN RUSHLOW Submitted to the Office of Graduate Studies of Texas A&M University in partial.../diffusionally controlled mass transport sampling mechanisms. ~ ~ Since the vapors enter the OVM by diffusional means rather than mechanical, there is no calibration or excess equipment required as with charcoal tubes. Many studies have been conducted to compare...

Rushlow, Lori Ann

2012-06-07

85

Identification and quantification of individual volatile organic compounds in a binary mixture by SAW multisensor array and pattern recognition analysis  

Microsoft Academic Search

We have developed a surface acoustic wave (SAW) multisensor array with five acoustic sensing elements configured as two-port resonator 433.92 MHz oscillators and a reference SAW element to recognize different individual components and determine their concentrations in a binary mixture of volatile organic compounds (VOCs) such as methanol and acetone, in the ranges 15-130 and 50-250 ppm, respectively. The SAW

M. Penza; G. Cassano; F. Tortorella

2002-01-01

86

Isocriterial manifolds during extractive distillation of a mixture of methanol- n -propyl acetate-toluene with aniline  

Microsoft Academic Search

The present study is devoted to the arrangement of isocriterial manifolds and regions of energetic optimality of extractive\\u000a distillation complexes within the simplex of the initial feed composition during the separation of methanol, n-propyl acetate,\\u000a and toluene mixture. The mixture being separated comprises one binary azeotrope with a boiling temperature being minimal (in\\u000a the binary pair of methanol-toluene), and one

B. B. Dolmatov; E. A. Anokhina; A. V. Timoshenko

2009-01-01

87

Flow boiling heat transfer coefficients at cryogenic temperatures for multi-component refrigerant mixtures of nitrogen-hydrocarbons  

NASA Astrophysics Data System (ADS)

The recuperative heat exchanger governs the overall performance of the mixed refrigerant Joule-Thomson cryocooler. In these heat exchangers, the non-azeotropic refrigerant mixture of nitrogen-hydrocarbons undergoes boiling and condensation simultaneously at cryogenic temperature. Hence, the design of such heat exchanger is crucial. However, due to lack of empirical correlations to predict two-phase heat transfer coefficients of multi-component mixtures at low temperature, the design of such heat exchanger is difficult.

Ardhapurkar, P. M.; Sridharan, Arunkumar; Atrey, M. D.

2014-01-01

88

Surface excess isotherms of organic solvent mixtures in a system made of liquid carbon dioxide and a silicagel surface.  

PubMed

The surface excess isotherms of methanol, ethanol, 2-propanol and acetonitrile from liquid carbon dioxide on a silica adsorbent were measured, using the minor disturbance method. The minor disturbance peaks - or system peaks - of each organic modifier were recorded using UV-detection in the whole composition range of the organic/liquid carbon dioxide mixtures, the whole composition range was completed by injecting the modifiers into pure liquid carbon dioxide as well. The excess isotherms were calculated based on the retention of the organic solvent signals. Our results show an enrichment of the organic modifier at the adsorbent surface. The alcohols show multilayer adsorption with an extremely high retention on the silica surface while acetonitrile shows weaker interactions and only a slight trend toward the formation of a multilayer above the surface. PMID:23953617

Vajda, Péter; Guiochon, Georges

2013-09-20

89

Separation of dilute organic\\/water mixtures with asymmetric poly(vinylidene fluoride) membranes  

Microsoft Academic Search

An in-depth investigation of integral asymmetric poly(vinylidene fluoride) (PVDF) membranes has been carried out for the extraction of polar and non-polar organic compounds from dilute organic-in-water feed solutions. Membrane performance for low and high-boiling non-polar organic feed components was excellent, with separation factors as high as 4900 and high organic transmembrane fluxes. Polar organic feed components such as ethanol and

K. Jian; P. N. Pintauro; R. Ponangi

1996-01-01

90

Binary Mixtures of Permanganate and Chlorinated Volatile Organic Compounds in Groundwater Samples: Sample Preservation and Analysis  

EPA Science Inventory

Ground water samples collected at sites where in-situ chemical oxidation (ISCO) has been deployed may contain binary mixtures of ground water contaminants and permanganate (MnO4-), an oxidant injected into the subsurface to destroy the contaminant. Commingling of the oxidant and ...

91

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...

92

Predicting Complex Organic Mixture Atmospheric Chemistry Using Computer-Generated Reaction Models  

Microsoft Academic Search

New measurement and chemical characterization technologies now offer unprecedented capabilities for detecting and describing atmospheric organic matter at the molecular level. As a result, very detailed and extensive chemical inventories are produced routinely in atmospheric field measurements of organic compounds found in the vapor and condensed phases (particles, cloud and fog droplets). Hundreds of organic compounds can constitute the complex

M. T. Klein; L. J. Broadbelt; M. A. Mazurek

2001-01-01

93

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

Microsoft Academic Search

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

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

2011-01-01

94

Solubility behaviors of ibuprofen and naproxen drugs in liquid “CO 2–organic solvent” mixtures  

Microsoft Academic Search

The “vanishing point” method was used for measuring the solubility of the two non-steroidal anti-inflammatory drugs ibuprofen and naproxen in CO2–expanded ethanol and CO2–expanded acetone at 10MPa and 298K. The solubility behavior of both drugs in ethanol\\/CO2 mixtures is quite similar, where the CO2 acts together with ethanol as co-solvents in a wide range of CO2 molar fractions. However, these

Maria Muntó; Nora Ventosa; Santiago Sala; Jaume Veciana

2008-01-01

95

Higher-Order Mass Defect Analysis for Mass Spectra of Complex Organic Mixtures  

Microsoft Academic Search

Higher-order mass defect analysis is introduced as a unique formula assignment and visualization method for the analysis of complex mass spectra. This approach is an extension of the concepts of Kendrick mass transformation widely used for identification of homologous compounds differing only by a number of base units (e.g., CH2, H2, O, CH2O, etc.) in complex mixtures. We present an

Patrick J. Roach; Julia Laskin; Alexander Laskin

2011-01-01

96

Effects of environmentally relevant mixtures of persistent organic pollutants on the developmental neurobiology in rats.  

PubMed

We report the developmental neuropathology for rat pups at postnatal day (PND) 37 and PND 77 and the molecular biomarkers for PND 35, 75, and 350 after perinatal exposure to a reconstituted mixture of persistent organochlorine pollutants (POPs) based on the blood profiles of people living in the Great Lake Basin. The developmental neuropathology included routine histopathology evaluation, quantification of cell proliferation and death in the subventricular zone, linear morphometric measurements, and transcriptional analysis. No histopathological, structural, or stereological changes were observed in animals treated with the POPs or Aroclor 1254, on PND 37 or PND 77. While no transcriptional changes were found in Arcolor-treated animals, significant transcriptional changes were observed on PND 350 in female offspring perinatally exposed to 0.13 mg/kg of the POP mixture. Markers of the cholinergic system including acetylcholinesterase and the muscarinic receptors (subtypes M1-M5) were downregulated 2- to 6-fold. In addition, structural genes including neurofilaments (NFLs) and microtubule-associated protein (MAP-2) were downregulated at least 2-fold or greater. Our results support that in utero and lactational exposure to the chemical mixture of POPs lead to developmental changes in adult rat brains. PMID:22872703

Gill, Santokh; Bowers, Wayne J; Nakai, Jamie S; Yagminas, Al; Mueller, Rudi; Pulido, Olga

2013-01-01

97

Phase equilibria and self-organizing behavior of side-chain liquid crystalline polymer mixtures  

NASA Astrophysics Data System (ADS)

Phenomenological models for elucidating phase diagrams of binary smectic-A mixtures, polymer/smectic-A mixtures, induced smectic in nematic mixtures, and nematic/smectic mixtures have been proposed on the basis of the combination of the Flory-Huggins (FH) free energy of isotropic mixing and Maier-Saupe-McMillan (MSM) free energy for nematic/smectic ordering. The nematic and smectic order parameters have been coupled through the normalized partition and the orientation distribution functions. Flory-Huggins interaction parameter (chi) for isotropic mixing and the coupling term involving the nematic interaction parameter (nu) and the McMillan smectic interaction parameter (alpha) for phase transitions of liquid crystals have been incorporated in the calculation. The predictive capability of the combined FH/MSM theory has been demonstrated by testing with reported phase diagrams. Dynamics of phase separation and morphology development in mixtures of a nematic liquid crystal and a polymer due to thermal quenching have been investigated theoretically in comparison with experimental results. In the proposed model, the combined free energy densities of Flory-Huggins theory for isotropic mixing and Maier-Saupe (MS) theory for nematic ordering have been incorporated into the time-dependent Ginzburg-Landau equation (TDGL, type C). The temporal evolution of the structure factor and the emergence of phase separated liquid crystal (LC) domains have been simulated on the basis of an explicit central difference method based on a square lattice with a periodic boundary condition. Of particular interest is the observed plateau (or inflection) region in the growth dynamic curve, which may be attributed to the breakdown of the interconnected domains caused by the nematic ordering. The emergence of LC domains during polymerization induced phase separation in a polymer dispersed liquid crystal (PDLC) has been solved numerically by incorporating the reaction kinetics into the TDGL equations in conjunction with the combined FH/MS theory. It was found that when polymerization is initiated at a single-phase temperature, an ordered lamella-like structure forms while the average domain size decreases with elapsed time. The variation of length scale follows a nucleation initiated spinodal decomposition (NISD) mechanism triggered by the polymerization.

Chiu, Hao-Wen

98

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

99

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...

100

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

2011-05-01

101

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

102

Levitated single-droplet drying: case study with itraconazole dried in binary organic solvent mixtures.  

PubMed

The objective of this case study of the single-droplet drying of two itraconazole/polymer formulations was to determine how the solvent system influences drying rate and dried particle morphology. A clear dual functionality of the two solutes could be identified. The polymeric component (PVP or HPMC) determined drying rate, whereas the drug determined end particle morphology. This could be related to solubilities of the two components in the binary solvent mixtures used. The formulation of a surface skin early on in drying only occurred with HPMC and strongly influenced drying rate but not dried particle morphology. PMID:19501641

Wulsten, Eva; Kiekens, Filip; van Dycke, Frederic; Voorspoels, Jody; Lee, Geoffrey

2009-08-13

103

A Comparison of delO18 Composition of Water Extracted from Suction Lysimeters, Centrifugation, and Azeotropic Distillation  

NASA Astrophysics Data System (ADS)

Concentration of delO18 in water samples extracted by suction lysimeters is compared to samples obtained by methods of centrifugation and azeotropic distillation. Intact soil cores (30 cm diameter by 40 cm height) were extracted from two different sites. Site 1 was rapid infiltration basin number 50, near Altamonte Springs in Seminole County, Florida on properties belonging to the Walt Disney World Resort Complex. Site 2 was the Missouri Management System Evaluation Area (MSEA) near Centralia in Boone County, Missouri. The delO18 water was analyzed on a mass spectrophotometer. Potassium Bromide (KBr) was also used as a tracer and analyzed by ion chromatography. A portion of the data obtained was modeled using CXTFIT. Water collected by centrifugation and azeotropic distillation data were about 2-5% more negative than that collected by suction lysimeter values from the Florida (sandy) soil and about 5-7 % more negative from the Missouri (well structured clay) soil. Results indicate that the majority of soil water in well structured soil is strongly bound to soil grain surfaces and is not easily sampled by suction lysimeters. Also, it is plausible that evaporation caused some delO18 enrichment in the suction lysimeters. Suction lysimeters preferentially sampled water held at lower matric potentials, which may not represent total soil water. In cases where a sufficient volume of water has passed through the soil profile and displaced all previous pore water, suction lysimeters will however collect a representative sample of all the water at that depth interval. It is suggested that for stable isotope studies monitoring precipitation and soil water, suction lysimeters be installed at shallow depths (10 cm). Samples should also be coordinated with precipitation events. The CXTFIT program worked well for Florida soils (a more homogeneous sand), but gave poor performance for Missouri soils (well structured clays) except for deeper depths where clay structure was less variable. The data also suggest that each extraction method samples a separate component of soil-pore water. Consequently, centrifugation can be used with good success, particularly for efficient sampling of large areas. Azeotropic distillation is more appropriate when strict qualitative and quantitative data for desorption, desorption, and various types of kinetic studies are needed.

Figueroa, A.; Tindall, J. A.; Friedel, M. J.

2005-12-01

104

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. PMID:23235441

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

2012-01-01

105

Pesticide Toxicity Index: a tool for assessing potential toxicity of pesticide mixtures to freshwater aquatic organisms  

USGS Publications Warehouse

Pesticide mixtures are common in streams with agricultural or urban influence in the watershed. The Pesticide Toxicity Index (PTI) is a screening tool to assess potential aquatic toxicity of complex pesticide mixtures by combining measures of pesticide exposure and acute toxicity in an additive toxic-unit model. The PTI is determined separately for fish, cladocerans, and benthic invertebrates. This study expands the number of pesticides and degradates included in previous editions of the PTI from 124 to 492 pesticides and degradates, and includes two types of PTI for use in different applications, depending on study objectives. The Median-PTI was calculated from median toxicity values for individual pesticides, so is robust to outliers and is appropriate for comparing relative potential toxicity among samples, sites, or pesticides. The Sensitive-PTI uses the 5th percentile of available toxicity values, so is a more sensitive screening-level indicator of potential toxicity. PTI predictions of toxicity in environmental samples were tested using data aggregated from published field studies that measured pesticide concentrations and toxicity to Ceriodaphnia dubia in ambient stream water. C. dubia survival was reduced to ? 50% of controls in 44% of samples with Median-PTI values of 0.1–1, and to 0% in 96% of samples with Median-PTI values > 1. The PTI is a relative, but quantitative, indicator of potential toxicity that can be used to evaluate relationships between pesticide exposure and biological condition.

Nowell, Lisa H.; Norman, Julia E.; Moran, Patrick W.; Martin, Jeffrey D.; Stone, Wesley W.

2014-01-01

106

Sewage sludge composting: influence of initial mixtures on organic matter evolution and N availability in the final composts.  

PubMed

The influence of bulking agents on organic matter (OM) stability and nitrogen (N) availability in sewage sludge composts was investigated. The same sludge was composted on an industrial plant with different mixtures of bulking agents. The composting process included an active phase and a curing phase, both lasting 6 weeks, separated by the screening of composts. The OM evolution was characterised by carbon (C) and N mass balances in biochemical fractions. The OM stability and N potential availability of final composts were measured during soil incubations. During composting, the C and N losses reached more than 62% of the initial C and more than 45% of the initial N, respectively, due to C mineralisation or N volatilization and screening. The bulking materials mostly influenced OM evolution during the active phase. They contributed to the mitigation of N losses during the active phase where N immobilisation through active microbial activity was favoured by bulking agents increasing the C:N ratio of the initial mixtures. However, the influence of bulking agents on OM evolution was removed by the screening; this induced the homogenisation of compost characteristics and led to the production of sludge composts with similar organic matter characteristics, C degradability and N availability. PMID:20627507

Doublet, Jérémy; Francou, Cédric; Poitrenaud, Maelenn; Houot, Sabine

2010-10-01

107

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-...

108

Thermodynamics of adsorption of binary aqueous organic liquid mixtures on a RPLC adsorbent  

Microsoft Academic Search

The surface excess adsorption isotherms of organic solvents commonly used in RPLC with water as co-eluent or organic modifiers (methanol, ethanol, 2-propanol, acetonitrile and tetrahydrofuran) were measured on a porous silica surface derivatized with chlorotrimethylsilane (C1-silica with 3.92??mol C1 groups per m2 of SiO2), using the dynamic minor disturbance method. The 5??m diameter particles were packed in a 150?mm ×4.6?mm

Fabrice Gritti; Georges Guiochon

2007-01-01

109

Higher-order mass defect analysis for mass spectra of complex organic mixtures.  

PubMed

Higher-order mass defect analysis is introduced as a unique formula assignment and visualization method for the analysis of complex mass spectra. This approach is an extension of the concepts of Kendrick mass transformation widely used for identification of homologous compounds differing only by a number of base units (e.g., CH(2), H(2), O, CH(2)O, etc.) in complex mixtures. We present an iterative renormalization routine for defining higher-order homologous series and multidimensional clustering of mass spectral features. This approach greatly simplifies visualization of complex mass spectra and increases the number of chemical formulas that can be confidently assigned for given mass accuracy. The potential for using higher-order mass defects for data reduction and visualization is shown. Higher-order mass defect analysis is described and demonstrated through third-order analysis of a deisotoped high-resolution mass spectrum of crude oil containing nearly 13,000 peaks. PMID:21526851

Roach, Patrick J; Laskin, Julia; Laskin, Alexander

2011-06-15

110

Higher-Order Mass Defect Analysis for Mass Spectra of Complex Organic Mixtures  

SciTech Connect

Higher-order mass defect analysis is introduced as a unique formula assignment and visualization method for the analysis of complex mass spectra. This approach is an extension of the concepts of Kendrick mass transformation widely used for identification of homologous compounds differing only by a number of base units (e.g., CH2, H2, O, CH2O, etc.) in complex mixtures. We present an iterative renormalization routine for defining higher order homologous series and multidimensional clustering of mass spectral features. This approach greatly simplifies visualization of complex mass spectra and increases the number of chemical formulae that can be confidently assigned for given mass accuracy. The potential for using higher-order mass defects for data reduction and visualization is shown. Higher-order mass defect analysis is described and demonstrated through third-order analysis of a de-isotoped high-resolution mass spectrum of crude oil containing nearly 13,000 peaks.

Roach, Patrick J.; Laskin, Julia; Laskin, Alexander

2011-06-15

111

Nitric acid-organic mixtures surveyed for use in separation by anion exchange methods  

NASA Technical Reports Server (NTRS)

Column elution-spectrographic analysis technique compares certain solvents directly to the methanol system, using inert rare earths instead of actinides. Distribution ratios for americium between 90 percent solvent, 10 percent 5 M nitric acid and Dowex 1 nitrate form resin for a large group of organics miscible in water was determined.

Bloomquist, C. A. A.; Faris, J. P.; Stewart, D. C.

1968-01-01

112

A NEW MASS SPECTROMETRIC TECHNIQUE FOR IDENTIFYING TRACE-LEVEL ORGANIC COMPOUNDS IN COMPLEX MIXTURES  

EPA Science Inventory

Most organic compounds are not found in mass spectral libraries and cannot be easily identified from low resolution mass spectra. Ion Composition Elucidation (ICE) utilizes selected ion recording with a double focusing mass spectrometer in a new way to determine exact mas...

113

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

114

Complex rhamnolipid mixture characterization and its influence on DPPC bilayer organization.  

PubMed

Rhamnolipids (RL) are one of the most important classes of biosurfactants produced by microorganisms using a wide range of carbon sources, from a simple carbon source like glucose to complex wastes such as the used cooking oils used in this work. The objective of this work was to learn about the rhamnolipid-phospholipid dipalmitoyl phosphatidyl choline (DPPC) molecular interactions through the behaviour observed in the neat products and four RL/DPPC mixtures. Size and z-potential were used to characterize the size and the charge of the vesicles, and small angle X-ray scattering (SAXS) was used to measure the vesicle bilayer characteristics, and the release of carboxyfluorescein to study the bilayer disrupting effect promoted by rhamnolipids. The results show that rhamnolipids are disposed in ordered bilayers with long repeating distances, which are stabilized by the charging of the bilayer and also by a strong fluidity of the bilayers. The ability of rhamnolipids to increase the fluidity of DPPC bilayers may be related with the strong haemolytic power of these molecules. PMID:24239913

Haba, E; Pinazo, A; Pons, R; Pérez, L; Manresa, A

2014-03-01

115

Testing secondary organic aerosol models using smog chamber data for complex precursor mixtures: influence of precursor volatility and molecular structure  

NASA Astrophysics Data System (ADS)

We use secondary organic aerosol (SOA) production data from an ensemble of unburned fuels measured in a smog chamber to test various SOA formation models. The evaluation considered data from 11 different fuels including gasoline, multiple diesels, and various jet fuels. The fuels are complex mixtures of species; they span a wide range of volatility and molecular structure to provide a challenging test for the SOA models. We evaluated three different versions of the SOA model used in the Community Multiscale Air Quality (CMAQ) model. The simplest and most widely used version of that model only accounts for the volatile species (species with less than or equal to 12 carbons) in the fuels. It had very little skill in predicting the observed SOA formation (R2 = 0.04, fractional error = 108%). Incorporating all of the lower-volatility fuel species (species with more than 12 carbons) into the standard CMAQ SOA model did not improve model performance significantly. Both versions of the CMAQ SOA model over-predicted SOA formation from a synthetic jet fuel and under-predicted SOA formation from diesels because of an overly simplistic representation of the SOA formation from alkanes that did not account for the effects of molecular size and structure. An extended version of the CMAQ SOA model that accounted for all organics and the influence of molecular size and structure of alkanes reproduced the experimental data. This underscores the importance of accounting for all low-volatility organics and information on alkane molecular size and structure in SOA models. We also investigated fitting an SOA model based solely on the volatility of the precursor mixture to the experimental data. This model could describe the observed SOA formation with relatively few free parameters, demonstrating the importance of precursor volatility for SOA formation. The exceptions were exotic fuels such as synthetic jet fuel that expose the central assumption of the volatility-dependent model that most emissions consist of complex mixtures with similar distribution of molecular classes. Despite its shortcomings, SOA formation as a function of volatility may be sufficient for modeling SOA formation in chemical transport models.

Jathar, S. H.; Donahue, N. M.; Adams, P. J.; Robinson, A. L.

2014-06-01

116

Adsorption of basic dyes in single and mixture systems on granular inorganic–organic pillared clays  

Microsoft Academic Search

The adsorption of two basic dyes, CI Basic Yellow 28 and CI Basic Green 4, was studied in single and binary solute systems using two classes of inorganic–organic pillared clay granules as sorbents (300–400 µm and 700–800 µm). These were prepared by high?shear wet granulation from an Al cetyltrimethylammonium bromide intercalated clay powder (particle diameter < 50 µm). Adsorption rate

Benamar Cheknane; Michel Baudu; Omar Bouras

2010-01-01

117

Nanostructural organization in carbon disulfide/ionic liquid mixtures: Molecular dynamics simulations and optical Kerr effect spectroscopy  

NASA Astrophysics Data System (ADS)

In this paper, the nanostructural organization and subpicosecond intermolecular dynamics in the mixtures of CS2 and the room temperature ionic liquid (IL) 1-pentyl-3-methylimidazolium bis{(trifluoromethane)sulfonyl}amide ([C5mim][NTf2]) were studied as a function of concentration using molecular dynamics (MD) simulations and optical heterodyne-detected Raman-induced Kerr effect spectroscopy. At low CS2 concentrations (<10 mol.% CS2/IL), the MD simulations indicate that the CS2 molecules are localized in the nonpolar domains. In contrast, at higher concentrations (>=10 mol.% CS2/IL), the MD simulations show aggregation of the CS2 molecules. The optical Kerr effect (OKE) spectra of the mixtures are interpreted in terms of an additivity model with the components arising from the subpicosecond dynamics of CS2 and the IL. Comparison of the CS2-component with the OKE spectra of CS2 in alkane solvents is consistent with CS2 mainly being localized in the nonpolar domains, even at high CS2 concentrations, and the local CS2 concentration being higher than the bulk CS2 concentration.

Yang, Peng; Voth, Gregory A.; Xiao, Dong; Hines, Larry G.; Bartsch, Richard A.; Quitevis, Edward L.

2011-07-01

118

Photocatalytic oxidation of toxic organohalides with TiO2/UV: the effects of humic substances and organic mixtures.  

PubMed

TiO2/UV photocatalytic oxidation of DDT (1,1,1-trichloro-2,2-bis(p-chlorophenyl)ethane), 1,2,3-trichlorobenzene and 4-chlorophenol were examined in aqueous solution in the presence of humic substances and organic mixtures to study if the degradation rates were affected. Both commercial and natural humic substances were observed to retard the photodegradation rates, with a greater effect from the natural humic substances. Acetonitrile and isopropanol also caused significant retardation of 4-chlorophenol photodegradation. The overall retardation can be attributed to the combination of light attenuation, inhibition and competition effects. Moreover, the TiO2/UV system favors the decomposition of compounds that have stronger adsorption onto the TiO2 surface. To engineer effective treatment facilities that use the TiO2/UV system for the treatment of toxic substances in wastewater, the methodology must allow for concerns about adventitious species which are present. PMID:17084883

Lin, Chitsan; Lin, Kuen-Song

2007-01-01

119

Nonthermal plasma alternative to the incineration of hazardous organic wastes. [Mixtures containing oil and trichloroethylene, carbon tetrachloride and trichloroethane  

SciTech Connect

We are developing silent discharge plasma (SDP) oxidation technology as an alternative to incineration and as a post-incinerator treatment process for hazardous organic wastes. As an alternative to incineration, SDP apparatus has been coupled to a high-temperature packed-bed reactor, the plasma apparatus serving as a second stage for treating gaseous effluent from the packed bed. As a post- incinerator treatment process, SDP apparatus has been evaluated using a prepared gaseous feed containing hazardous organic compounds which are expected to be found in the machining fluids (trichloroethylene (TCE), carbon tetrachloride (CCl{sub 4}), and trichloroethane (TCA)). In typical tests with the packed-bed reactor alone, we have treated mixtures containing oil and several per cent TCE, TCA, or CCl{sub 4} removing the chlorocarbons to levels of ppm-order for TCA and to order {approximately}100 ppb for TCE and CCl{sub 4}, as measured in the gaseous effluent. In representative stand-alone tests with the SDP reactor, we have removed TCE in the gaseous influent from 1,000 ppm concentrations to around 100 ppb in the gaseous effluent (CCl{sub 4} appears to be more treatment-resistant). The measured figures of merit for the SDP reactor (electrical energy per mass of removed chemical) are 10's of kW-hr/kg for >>99% removal of TCE and 100's of kW-hr/kg for 90% removal of CCl{sub 4}, both being non-optimized cases in terms of waste concentration, carrier gas composition, water content, flow rate, and electrical power. Using combined packed- bed/SDP reactors on chlorocarbon/oil mixtures, several per cent chlorocarbon concentrations have been removed to well below the 100-ppb level overall. We envision eventual reductions to levels of {approximately}10 ppb or less.

Rosocha, L.A.; McCulla, W.H.; Anderson, G.K.; Coogan, J.J.; Kang, M.; Tennant, R.A.; Wantuck, P.J.

1992-01-01

120

Adsorption of basic dyes in single and mixture systems on granular inorganic-organic pillared clays.  

PubMed

The adsorption of two basic dyes, CI Basic Yellow 28 and CI Basic Green 4, was studied in single and binary solute systems using two classes of inorganic-organic pillared clay granules as sorbents (300-400 microm and 700-800 microm). These were prepared by high-shear wet granulation from an Al cetyltrimethylammonium bromide intercalated clay powder (particle diameter < 50 microm). Adsorption rate data indicate that BY 28 adsorbs more rapidly than BG 4 and a pseudo-first-order model was found to fit the kinetic curves, with regression coefficients above 0.98. Adsorption isotherms in single solute systems at pH 3 and pH6 were respectively analysed according to the Langmuir and Freundlich models using non-linear regression. Best fits were obtained with the Langmuir model. In binary dye systems the adsorption at three molar ratios (1:9, 1:1 and 9:1) demonstrated that the adsorption of BG 4 was greater than that of BY 28 on all the sorbents studied; this was in agreement with the results obtained for single solute systems. Increasing the granule size decreased dye adsorption, an effect in accordance with the Sheindorf-Rebuhn-Sheintuch model. PMID:20586243

Cheknane, Benamar; Baudu, Michel; Basly, Jean-Philippe; Bouras, Omar

2010-06-01

121

Exergoeconomic analysis and optimization of an evaporator for a binary mixture of fluids in an organic Rankine cycle  

NASA Astrophysics Data System (ADS)

This paper focuses on the research of an evaporator with a binary mixture of organic working fluids in the organic Rankine cycle. Exergoeconomic analysis and performance optimization were performed based on the first and second laws of thermodynamics, and the exergoeconomic theory. The annual total cost per unit heat transfer rate was introduced as the objective function. In this model, the exergy loss cost caused by the heat transfer irreversibility and the capital cost were taken into account; however, the exergy loss due to the frictional pressure drops, heat dissipation to surroundings, and the flow imbalance were neglected. The variation laws of the annual total cost with respect to the number of transfer units and the temperature ratios were presented. Optimal design parameters that minimize the objective function had been obtained, and the effects of some important dimensionless parameters on the optimal performances had also been discussed for three types of evaporator flow arrangements. In addition, optimal design parameters of evaporators were compared with those of condensers.

Li, You-Rong; Du, Mei-Tang; Wang, Jian-Ning

2012-12-01

122

Kinetics of organic molecules in pulsed plasmas of nitrogen or N2/O2 mixtures at near atmospheric pressure  

NASA Astrophysics Data System (ADS)

In plasmas of atmospheric gases, the kinetics of some aliphatic organic molecules belonging to the hydrocarbons (propene, propane), aldehydes (acetaldehyde) and ketones (acetone) families were studied using a photo-triggered discharge (homogeneous plasma). It was shown that quenchings of N2 metastable states, A\\,^{3}\\Sigma_{u}^{+} and the group of singlets a'\\,^{1}\\Sigma_{u}^{-} , a 1?g and w 1?u, are important processes for the decomposition of such molecules. It plays a fundamental role in the nitrogen plasma, but it is also present in air. At low temperature, the oxidation reactions by the oxygen atom or by the hydroxyl radical are not always sufficiently effective to induce an increase of the molecule decomposition when oxygen is added to the nitrogen/organic mixture. For most cases, quenching processes appear purely dissociative. However, recent results obtained for propene lead to the conclusion that a non-dissociative exit route could exist. The quenching of the singlet states induces a break of the double bound C = O for the acetaldehyde and acetone molecules. Some kinetic analogies appear between filamentary and homogeneous plasmas, which could be very useful to get a comprehensive understanding of the physico-chemical processes in dielectric barriers or corona discharges used for various applications.

Pasquiers, S.; Blin-Simiand, N.; Magne, L.

2013-12-01

123

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

124

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

2013-03-15

125

Detailed chemical characterization of unresolved complex mixtures in atmospheric organics: Insights into emission sources, atmospheric processing, and secondary organic aerosol formation  

NASA Astrophysics Data System (ADS)

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 resolve a large number of constitutional isomers. Using a combination of gas chromatography and soft photoionization mass spectrometry, we characterize the unresolved complex mixture (UCM) of semivolatile aliphatic hydrocarbons observed in Pasadena, California (~16 km NE of downtown Los Angeles), and Bakersfield, California, during the California Research at the Nexus of Air Quality and Climate Change 2010. To the authors' knowledge, this work represents the most detailed characterization of the UCM in atmospheric samples to date. Knowledge of molecular structures, including carbon number, alkyl branching, and number of rings, provides important constraints on the rate of atmospheric processing, as the relative amounts of branched and linear alkanes are shown to be a function of integrated exposure to hydroxyl radicals. Emissions of semivolatile branched alkanes from fossil fuel-related sources are up to an order of magnitude higher than those of linear alkanes, and the gas-phase OH rate constants of branched alkanes are ~30% higher than their linear isomers. Based on a box model considering gas/particle partitioning, emissions, and reaction rates, semivolatile branched alkanes are expected to play a more important role than linear alkanes in the photooxidation of the UCM and subsequent transformations into SOA. Detailed speciation of semivolatile compounds therefore provides essential understanding of SOA sources and formation processes in urban areas.

Chan, Arthur W. H.; Isaacman, Gabriel; Wilson, Kevin R.; Worton, David R.; Ruehl, Christopher R.; Nah, Theodora; Gentner, Drew R.; Dallmann, Timothy R.; Kirchstetter, Thomas W.; Harley, Robert A.; Gilman, Jessica B.; Kuster, William C.; Gouw, Joost A.; Offenberg, John H.; Kleindienst, Tadeusz E.; Lin, Ying H.; Rubitschun, Caitlin L.; Surratt, Jason D.; Hayes, Patrick L.; Jimenez, Jose L.; Goldstein, Allen H.

2013-06-01

126

Organic tank safety project: Preliminary results of energetics and thermal behavior studies of model organic nitrate and\\/or nitrite mixtures and a simulated organic waste  

Microsoft Academic Search

As a result of years of production and recovery of nuclear defense materials and subsequent waste management at the Hanford Site, organic-bearing radioactive high-level wastes (HLW) are currently stored in large (up to 3. ML) single-shell storage tanks (SSTs). Because these wastes contain both fuels (organics) and the oxidants nitrate and nitrite, rapid energetic reactions at certain conditions could occur.

R. D. Scheele; R. L. Sell; J. L. Sobolik; L. L. Burger

1995-01-01

127

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. PMID:21047985

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

2011-01-01

128

Evaluation of the COSHH Essentials model with a mixture of organic chemicals at a medium-sized paint producer.  

PubMed

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. PMID:21047985

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

2011-01-01

129

Self-Organization in Active Cytoskeletal Mixtures: Cilia-like Beating of Microtubule Bundles and Spontaneous Bulk Mixing  

NASA Astrophysics Data System (ADS)

This thesis discusses circularization and supercoiling of actin biofilaments, as well as the various examples of self-organization observed in a simple non-equilibrium system of microtubules, motor clusters, and a depletion agent (PEG). When the ends of an actin filament approach each other, annealing can occur, resulting in the assumption of a circular conformation. In order to facilitate this experimentally, we dramatically reduce the space available for the ends to explore by confining the filaments to a quasi-2D region. This is accomplished through the use of a depletion attraction. In addition to the pronounced effects of this topological ring constraint on the statistical fluctuations of the filaments, we also observe a spontaneous supercoiling transition in fluorescently labeled actin rings that is directly driven by illumination. To better understand this transition in natural twist, we investigate real-time twist of a filament trapped between two beads, held by optical traps. The main focus of this graduate work was on the behavior of non-equilibrium in vitro mixtures of microtubules, kinesin motor clusters, and a depletion agent. We observed several striking and distinct examples of self-organization on near-macroscopic length scales, due to the interactions of very simple components. First we investigate the driving mechanism behind the beating of biological cilia and flagella, and find that this beating functionality can be reproduced in our vastly simpler system. This occurs only when minimalist components are reconstituted: motors, biofilaments, elastic links to hold the filaments together, and a basal attachment. Beyond the cooperativity of the motors to produce oscillatory beating in individual bundles, we also observe that active bundles in close proximity can synchronize their beating to produce stable, periodic metachronal waves that propagate along the bundle array. By changing only the length distribution of the microtubules in our system, we find that basal attachments at the chamber edge no longer form. Rather, bundles become unstable and interact in bulk by merging, extending, buckling, breaking, and recombining. These interactions lead to the emergence of a steady-state bulk mixing process that causes the super-diffusive transport of tracer particles and enhanced mixing of fluid. This mixing bears some resemblance to other mixing processes, including the biological example of cytoplasmic streaming. Finally, we show that a qualitatively new example of self-organization occurs when these active mixtures are put into water droplets in oil-water emulsions. The MT bundles migrate to the oil-water interface, forming a 2D active nematic. This active nematic exhibits a host of emergent properties, including the unbinding of +1/2 and -1/2 nematic defects from each other. The internal stresses of these active nematics also cause droplets to be self-propelled, leading to the possibility of studying a system of spherical swimmers, where new examples of self-organized behavior may occur.

Sanchez, Tim

130

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

PubMed Central

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

2013-01-01

131

Phase diagrams of (vapour + liquid) equilibrium for binary mixtures of ?,?,?-trifluorotoluene with ethanol, or benzene, or chloroform at pressure 101.4 kPa  

Microsoft Academic Search

(Vapour+liquid) equilibrium (VLE) of binary mixtures of (ethanol+?,?,?-trifluorotoluene), (benzene+?,?,?-trifluorotoluene), and (chloroform+?,?,?-trifluorotoluene) have been investigated at the pressure 101.4kPa using the dynamic-ebulliometry method over the whole composition range. The correlated VLE phase diagrams were adequately described by means of NRTL and UNIQUAC thermodynamic models. Fair attractive energies in the first two systems are capable to yield azeotropes, while moderate repulsive energies

Zadjia Atik

2008-01-01

132

The structural organization of N-methyl-2-pyrrolidone + water mixtures: A densitometry, x-ray diffraction, and molecular dynamics study  

NASA Astrophysics Data System (ADS)

A combined approach of molecular dynamics simulations, wide angle X-ray scattering experiments, and density measurements was employed to study the structural properties of N-methyl-2-pyrrolidone (NMP) + water mixtures over the whole concentration range. Remarkably, a very good agreement between computed and experimental densities and diffraction patterns was achieved, especially if the effect of the mixture composition on NMP charges is taken into account. Analysis of the intermolecular organization, as revealed by the radial and spatial distribution functions of relevant solvent atoms, nicely explained the density maximum observed experimentally.

Usula, M.; Mocci, F.; Marincola, F. Cesare; Porcedda, S.; Gontrani, L.; Caminiti, R.

2014-03-01

133

The structural organization of N-methyl-2-pyrrolidone + water mixtures: a densitometry, x-ray diffraction, and molecular dynamics study.  

PubMed

A combined approach of molecular dynamics simulations, wide angle X-ray scattering experiments, and density measurements was employed to study the structural properties of N-methyl-2-pyrrolidone (NMP) + water mixtures over the whole concentration range. Remarkably, a very good agreement between computed and experimental densities and diffraction patterns was achieved, especially if the effect of the mixture composition on NMP charges is taken into account. Analysis of the intermolecular organization, as revealed by the radial and spatial distribution functions of relevant solvent atoms, nicely explained the density maximum observed experimentally. PMID:24697455

Usula, M; Mocci, F; Marincola, F Cesare; Porcedda, S; Gontrani, L; Caminiti, R

2014-03-28

134

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

135

Natural mixtures of persistent organic pollutants (POPs) suppress ovarian follicle development, liver vitellogenin immunostaining and hepatocyte proliferation in female zebrafish (Danio rerio).  

PubMed

Persistent organic pollutants such as polychlorinated biphenyls (PCBs), polybrominated diphenyl ethers (PBDEs) and dichlorodiphenyltrichloroethane (DDT) are present in high concentrations in livers of burbot (Lota lota) in Lake Mjøsa, Norway. In order to assess effects of such pollutants on fish gonadal morphology, female zebrafish were exposed in two generations by food to mixtures of pollutants extracted from livers of burbot from Lake Mjøsa (high and low dose) and Lake Losna, which represents background pollution, and compared to a control group. Ovarian follicle counts detected a significant decrease in late vitellogenic follicle stages in fish exposed to the Losna and the high concentrations of Mjøsa mixtures in fish from the first generation. In addition, proliferation of granulosa cells, visualized by immunohistochemistry against proliferating cell nuclear antigen (PCNA), was decreased in all exposure groups in either early or late vitellogenic follicle stages compared to control. This was accompanied by increased apoptosis of granulosa cells. There was a decrease in proliferation of liver hepatocytes with exposure to both Mjøsa mixtures. In addition, immunopositivity for vitellogenin in the liver was significantly lower in the Mjøsa high group than in the control group. When analysing effects of parental exposure, fish with parents exposed to Mjøsa high mixture had significantly higher numbers of perinucleolar follicles than fish with control parents. We conclude that long-term exposure of a real-life mixture of pollutants containing high- and background levels of chemicals supress ovarian follicle development, liver vitellogenin immunostaining intensity and hepatocyte proliferation in the zebrafish model. PMID:22459409

Kraugerud, Marianne; Doughty, Richard William; Lyche, Jan L; Berg, Vidar; Tremoen, Nina H; Alestrøm, Peter; Aleksandersen, Mona; Ropstad, Erik

2012-07-15

136

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] [Escuela Superior de Ingenieros Industriales, Las Palmas (Spain). Laboratorio de Termodinamica y Fisicoquimica

1996-07-01

137

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

2011-08-01

138

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.  

PubMed

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 with background levels of polybrominated diphenyl ethers (PBDE), polychlorinated biphenyls (PCB), and dichlorodiphenyltrichloroethane metabolites (DDT). The concentration of POP measured in the zebrafish ranged from levels detected in wild fish from Lake Mjøsa to concentrations reported in human and wildlife populations, indicating that the experimental fish were exposed to concentrations comparable with wild fish. Phenotypic effects observed in both exposure groups included earlier onset of puberty, increased male/female sex ratio, and 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 include key regulator genes for steroid hormone functions (ncoa3), and growth (c/ebp, ncoa3). The effects observed in the experimental zebrafish model raise the question whether chemical pollution represents a risk to reproductive health of wild fish inhabitating the freshwater system. PMID:20526952

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

2010-01-01

139

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

140

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 ...

141

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

142

Integrating effects of stressors across levels of biological organization: examples using organophosphorus insecticide mixtures in field-level exposures  

Microsoft Academic Search

An important uncertainty often identified inecological risk assessment is the lack of ecologicalconnectivity between endpoints measured across themany levels of biological organization within anecosystem. In the present study, we address thisissue by quantitatively linking acetylcholinesterase(AChE) activity, a common biomarker of exposure toorganophosphorus (OP) insecticides, with endpoints athigher levels of biological organization in fish andinvertebrates, and to assess the utility of

P. K. Sibley; M. J. Chappel; T. K. George; K. R. Solomon; K. Liber

2000-01-01

143

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

144

Quantitative analyses of organic multicomponent mixtures of gases and vapors in industrial air emissions by IR-spectrometry  

Microsoft Academic Search

IR-spectrometry with full spectra evaluation by means of least squares fitting has been used for the simultaneous quantitative determination of up to 14 organic components at the ppm level in air. The method has been applied to air emissions from chemical production facilities. Tedlar bags have been used for sample collection and transport. Almost any compound with at least weak

T. Diiblin; H. J. Thöne

1989-01-01

145

Anion exchange of organic carboxylate by soils responsible for positive Km-fc relationship from methanol mixture.  

PubMed

The cosolvency model was not applicable for predicting the sorption of organic carboxylic acids. The reason of inapplicability was investigated by analyzing the solubility (Sm) and sorption (Km) of benzoic acid, 2,4-dichlorophenoxyacetic acid (2,4-D), and 2,4,6-trichlorophenol (2,4,6-TCP). The Sm and Km by two iron-rich soils was measured as a function of methanol volume fraction (fc), electrolyte compositions, and pH(app). For 2,4,6-TCP, the Km of both neutral and anion species was well-explainable by the cosolvency model, exemplifying the knowledge of cosolvency power (?) being sufficient to describe its sorption. However, for benzoic acid and 2,4-D, the Km of organic anions increased with fc, illustrating the organic carboxylate to be responsible for the deviation. The Sm of organic anions was not affected by the ionic valence (Ca(2+) vs. K(+)) of liquid phase. Among hydrophilic quantities of the 2,4-D sorption, the fraction of anion exchange increased with fc while the fraction of Ca-bridge decreased in the same range. Adding solvent in soil-water system is likely to render soil surface charge more positive, fortifying the anion exchange, but opposing the formation of Ca-bridging. Therefore, it can be concluded that the positive Km-fc relationship is due to the anion exchange of organic carboxylate with positively charged soil surface, whose contribution is >50% of overall sorption at solvent-free system and becomes greater with fc up to 82%. PMID:23732008

Kim, Minhee; Han, Junho; Hyun, Seunghun

2013-09-01

146

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

2012-01-30

147

Separating Mixtures  

NSDL National Science Digital Library

Students learn how to classify materials as mixtures, elements or compounds and identify the properties of each type. The concept of separation of mixtures is also introduced since nearly every element or compound is found naturally in an impure state such as a mixture of two or more substances, and it is common that chemical engineers use separation techniques to separate mixtures into their individual components. For example, the separation of crude oil into purified hydrocarbons such as natural gas, gasoline, diesel, jet fuel and/or lubricants.

National Science Foundation GK-12 and Research Experience for Teachers (RET) Programs,

148

Photosynthetic based algal-bacterial combined treatment of mixtures of organic pollutants and CO2 mitigation in a continuous photobioreactor.  

PubMed

An algal-bacterial microcosm was synthetically constructed of Chlorella vulgaris MMl and Pseudomonas MTl. This microcosm was able to treat simulated wastewater supplemented with mixtures of phenol and pyridine up to 4.6 and 4.4 mM, respectively, in a continuous stirred tank bioreactor (CSTR) using photosynthetic oxygenation. Complete pollutant removal and detoxification and 82 % removal of introduced chemical oxygen demand (COD) were achieved at a hydraulic retention time (HRT) of 2.7 days. Increasing the influent load to 5.3 and 6.3 mM reduced the removal of phenol, pyridine and COD to 78, 21 and 59 %, respectively. Fertilization of the photobioreactor with 24 mM NaHCO3 restored the treatment and detoxification efficiencies. The system was able to additionally mitigate up to 72 mM NaHCO3 at the same HRT. Although the fertilization increased the system treatment efficiency, the settleability of the algal-bacterial microcosm was significantly reduced. When the photobioreactor was operated at HRT of 2.7 days in a 12/12 h of dark/light cycle, complete removal of 4.7 mM phenol was recorded but only 11 % of 5.7 mM pyridine was removed. The COD removal efficiency and CO2 mitigation were also reduced to 65 and 86 %, respectively, and the effluent retained significant toxicity where 73 % inhibition was recorded. Elongation of the illumination time to 48 h (HRT of 4 days at 12/12 h dark/light cycle) restored the treatment and detoxification efficiencies. PMID:23296918

Essam, Tamer; ElRakaiby, Marwa; Hashem, Abdelgawad

2013-06-01

149

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

150

Determination of the H isotopic composition of individual components in fine-scale mixtures of organic matter and phyllosilicates with the nanoscale secondary ion mass spectrometry.  

PubMed

When organic matter is mixed on a nanometer scale with clay minerals, the individual D/H ratios of the two H-bearing phases cannot be directly measured even with the nominal spatial resolution of nanoscale secondary ion mass spectrometry (NanoSIMS, 50-100 nm). To overcome this limitation, a new analytical protocol is proposed based on the deconvolution of the D(-)/H(-) and (16)OD(-)/(16)OH(-) ionic ratios measured by NanoSIMS. Indeed, since the yields of H(-) and (16)OH(-) are different for organics and clays, it should be theoretically possible to determine the mixing ratio of these two components in the area analyzed by the ion probe. Using organics with different D/H ratios, the interdependence of the D(-)/H(-) and (16)OD(-)/(16)OH(-) ionic ratios was determined in pure samples. Then using the H(-) and (16)OH(-) yields and the isotopic ratios measured on pure organic matter and clays, the expected D(-)/H(-) and (16)OD(-)/(16)OH(-) variations as a function of the mixing proportions were determined. These numerical predictions are consistent with measurements on laboratory prepared mixtures of D-rich organic matter and D-poor phyllosilicates, validating both the proposed experimental protocol and its use for meteorites. With an improvement of the precision of the ionic ratios by a factor of 10, it should possible to expend this protocol to samples having natural terrestrial D/H variations. Such an improvement could be attainable with the development of synthetic deuterated reference samples. PMID:23121456

Piani, Laurette; Remusat, Laurent; Robert, François

2012-12-01

151

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. PMID:22082240

2011-01-01

152

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

153

Preparation of Highly Dispersed Antimony-doped Tin Oxide Nano-powder via Ion-exchange Hydrolysis of SnCl 4 and SbCl 3 and Azeotropic Drying  

Microsoft Academic Search

Antimony-doped tin hydroxide colloid precipitates have been synthesized by hydrolysis of SnCl4 and SbCl3 using: (1) an ion-exchange hydrolysis to remove chlorine ions, and (2) isoamyl acetate as an azeotropic solvent to obviate water. The obtained dried powder is of high dispersivity without any need for further grinding. The size and dispersivity of the final particles are investigated with the

Fen YANG; Xue-jun ZHANG; Fang TIAN; Xu WU; Fu-xing GAN

2007-01-01

154

Annual and seasonal changes in mineral contents (Ca, Mg, P, K and Na) of grazed clover-grass mixtures in organic farming  

Microsoft Academic Search

A grazed field experiment was established in 1995 to evaluate alsike clover ( Trifoliun hybridum L.), red clover (Trifolium pratense L.) and white clover (Trifolium repens L.) in clover-grass mixtures under or- ganic farming practices. In this study the effect of seed mixture (alsike clover, red clover, white clover, white and alsike clover or grass mixture), year (1997, 1998) and

Eeva Kuusela

2006-01-01

155

Perturbation theoretical study of the fluid phase of a binary mixture of hard-core molecules with square wells. Chemical potential surface and phase diagram  

NASA Astrophysics Data System (ADS)

Leonard-Henderson-Barker perturbation theory is applied to a binary mixture of hard-core molecules with square wells. Molecules are of equal core sizes, equal ranges of forces, and equal well depths, but of a relatively weak unlike-pair depth. The effect of change in the weakness parameter a of an unlike pair is examined in detail on the topological nature of the chemical potential surface of the fluid phase and hence on the phase diagram. How a positive or heterogeneous azeotrope appears and how the critical line changes with a are clearly demonstrated. Three liquid phases can coexist in equilibrium in the same range of a.

Ichimura, Takao; Ueda, Akira

1981-03-01

156

An acellular assay to assess the genotoxicity of complex mixtures of organic pollutants bound on size segregated aerosol. Part I: DNA adducts.  

PubMed

An acellular assay consisting of calf thymus DNA with/without rat liver microsomal S9 fraction was used to study the genotoxicity of complex mixtures of organic air pollutants bound to size segregated aerosols by means of DNA adduct analysis. We compared the genotoxicity of the organic extracts (EOMs) from three size fractions of aerosol ranging from 0.17?m to 10?m that were collected by high volume cascade impactors in four localities of the Czech Republic differing in the extent of the environmental pollution: (1) small village in proximity of a strip mine, (2) highway, (3) city center of Prague and (4) background station. The total DNA adduct levels induced by 100?g/ml of EOMs were analyzed by (32)P-postlabelling analysis with a nuclease P1 method for adduct enrichment. The main finding of the study was most of the observed genotoxicity was connected with a fine particulate matter fraction (<1?m). The concentrations of carcinogenic polycyclic aromatic hydrocarbons (c-PAHs) in EOMs indicate that fine fractions (0.5-1?m) bound the highest amount of c-PAHs in all aerosol sampling sites, which might be related to the higher specific surface of this fraction as compared with a course fraction (1-10?m) and higher mass as compared with a condensational fraction (0.17-0.5?m). As for aerosol mass, both fine and condensational fractions are effective carriers of c-PAHs. Similarly, the DNA adduct levels per m(3) of air were highest for the fine fraction, while the condensational fraction (strip mine site and city center) revealed the highest DNA adduct levels in cases where aerosol mass is taken into consideration. A strong correlation was found between the c-PAHs and DNA adduct levels induced by EOMs in all the localities and for various size fractions (R(2)=0.98, p<0.001). It may be concluded that the analysis of total DNA adducts induced in an acellular assay with/without metabolic activation represents a relatively simple method to assess the genotoxic potential of various complex mixtures. PMID:20600709

Topinka, Jan; Hovorka, Jan; Milcova, Alena; Schmuczerova, Jana; Krouzek, Jiri; Rossner, Pavel; Sram, Radim J

2010-10-20

157

Cooperative effect of temperature and linker functionality on CO2 capture from industrial gas mixtures in metal-organic frameworks: a combined experimental and molecular simulation study.  

PubMed

In this work, the cooperative effect of temperature and linker functionality on CO(2) capture in metal-organic frameworks (MOFs) was investigated using experimental measurements in combination with molecular simulations. To do this, four MOFs with identical topology but different functional groups on the linkers and three important CO(2)-containing industrial gas mixtures were adopted. The interplay between linker functionality and temperature was analyzed in terms of CO(2) storage capacity, adsorption selectivity, working capacity of CO(2) in temperature swing adsorption (TSA) processes, as well as sorbent selection parameter (S(ssp)). The results show that the effect of linker functionality on CO(2) capture performance in the MOFs is strongly interconnected with temperature: up to moderate pressures, the lower the temperature, the larger the effect of the functional groups. Furthermore, the modification of a MOF by introducing more complex functional groups can not only improve the affinity of framework for CO(2), but also reduce the free volume, and thus may contribute negatively to CO(2) capture capability when the packing effect is obvious. Therefore, when we design a new MOF for a certain CO(2) capture process operated at a certain temperature, the MOF should be designed to have maximized affinity for CO(2) but with a negligible or small effect caused by the reduction of free volume at that temperature and the corresponding operating pressure. PMID:22241397

Zhang, Wenjuan; Huang, Hongliang; Zhong, Chongli; Liu, Dahuan

2012-02-21

158

Measurement of Amount of Pattern Trim and Surface Chemistry for Organic Resist Etching in an Inductively Coupled Plasma in SO2-O2 Gas Mixtures  

NASA Astrophysics Data System (ADS)

We experimentally investigated the amount of pattern trim of the organic photoresist and its relation to the chemical compositions of the photoresist surface, as a function of gas mixture ratio between SO2 and O2 in an inductively coupled plasma (ICP) gaseous electronics conference (GEC) reference cell. Both the photoresist line pattern width loss and the photoresist thickness loss decreased along with the increase in the SO2 percentage from 10 to 68%. The ratio of the line pattern width loss to the thickness loss (= lateral-to-vertical etch rate ratio) decreased. The ratio corresponds to the amount of pattern trim in the bottom anti reflective coating (BARC) layer etching. We confirmed that photoresist pattern trim can be achieved in the ICP GEC reference cell as well as the gate etching process on a fabrication line. As the SO2 percentage increased, the density of atomic O in the bulk plasma decreased, while the atomic percentage of sulfur increased from 0.06 to 0.12 on the blanket photoresist surface. The reason why the lateral-to-vertical etch rate ratio decreased with the increase in the SO2 percentage is that the isotropic etching component by O atoms becomes smaller, and the anisotropic etching component, which is relevant to the sulfur on the photoresist surface, becomes larger with the increase in the SO2 percentage.

Goto, Takeshi K.; Makabe, Toshiaki

2007-08-01

159

Density functional theory of freezing for binary mixtures of 2D superparamagnetic colloids  

NASA Astrophysics Data System (ADS)

Density functional theory of freezing is used to study the phase diagram of a binary mixture of superparamagnetic colloidal particles in two dimensions. The particles interact via a purely repulsive potential that scales as the inverse cube of the inter-particle separation. This corresponds to a magnetic dipole interaction where the dipoles are induced by an external magnetic field applied normal to the plane. The pair correlation functions needed as input information in the density functional theory are calculated by the hypernetted chain integral equation closure. Considering the freezing into a disordered triangular solid phase, a spindle phase diagram is found for the susceptibility ratio 0.9 of the species, which changes to an azeotrope at a ratio 0.8. A eutectic-like phase diagram with an intervening solid phase emerges for the susceptibility ratio 0.7. The results are verifiable in real-space experiments on superparamagnetic colloids in external magnetic fields.

Mukherjee, Manjori; Mishra, Pankaj; Löwen, Hartmut

2014-11-01

160

Density functional theory of freezing for binary mixtures of 2D superparamagnetic colloids.  

PubMed

Density functional theory of freezing is used to study the phase diagram of a binary mixture of superparamagnetic colloidal particles in two dimensions. The particles interact via a purely repulsive potential that scales as the inverse cube of the inter-particle separation. This corresponds to a magnetic dipole interaction where the dipoles are induced by an external magnetic field applied normal to the plane. The pair correlation functions needed as input information in the density functional theory are calculated by the hypernetted chain integral equation closure. Considering the freezing into a disordered triangular solid phase, a spindle phase diagram is found for the susceptibility ratio 0.9 of the species, which changes to an azeotrope at a ratio 0.8. A eutectic-like phase diagram with an intervening solid phase emerges for the susceptibility ratio 0.7. The results are verifiable in real-space experiments on superparamagnetic colloids in external magnetic fields. PMID:25287741

Mukherjee, Manjori; Mishra, Pankaj; Löwen, Hartmut

2014-11-19

161

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

162

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

163

Variation of acidity constants and pH values of some organic acids in water—2-propanol mixtures with solvent composition. Effect of preferential solvation  

Microsoft Academic Search

A general equation which relates the dissociation constant of an acid with the solvent composition in binary solvent mixtures is derived. The equation considers that the two solvents interact to form mixed structures. The electrolyte interacts with the mixed solvent formed and with the two pure solvents mixed. The degree of these interactions determines the preferential solvation of the electrolyte

Elisabeth Bosch; Clara Ràfols; Martí Rosés

1995-01-01

164

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

165

Simulation of nonazeotropic refrigerant mixtures for use in a dual-circuit refrigerator/freezer with countercurrent heat exchangers  

SciTech Connect

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. In a standard cabinet, this RF appears to provide energy savings of 24%, compared to current U.S. RF designs. The NARMs modeled with the best performance included R-32/-152a, R-22/-142b, and R-32/-142b. An 18% improvement can be expected from the dual-circuit system using R-12 alone, and an additional 6% improvement can be gained by replacing R-12 with the selected NARMs in countercurrent heat exchangers. The advantages of the system include greatly reduced energy consumption, easy temperature and humidity control for each compartment, no humidity or odors transferred between compartments, and increased time between defrost cycles.

Bare, J.C.; Gage, C.L.; Radermacher, R.; Jung, D.

1991-01-01

166

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

167

Contributions of toluene and alpha-pinene to SOA formed in an irradiated toluene/alpha-pinene/NO(x)/ air mixture: comparison of results using 14C content and SOA organic tracer methods.  

PubMed

An organic tracer method, recently proposed for estimating individual contributions of toluene and alpha-pinene to secondary organic aerosol (SOA) formation, was evaluated by conducting a laboratory study where a binary hydrocarbon mixture, containing the anthropogenic aromatic hydrocarbon, toluene, and the biogenic monoterpene, alpha-pinene, was irradiated in air in the presence of NO(x) to form SOA. The contributions of toluene and alpha-pinene to the total SOA concentration, calculated using the organic tracer method, were compared with those obtained with a more direct 14C content method. In the study, SOA to SOC ratios of 2.07 +/- 0.08 and 1.41 +/- 0.04 were measured for toluene and (alpha-pinene SOA, respectively. The individual tracer-based SOA contributions of 156 microg m(-3) for toluene and 198 microg m(-)3 for alpha-pinene, which together accounted for 82% of the gravimetrically determined total SOA concentration, compared well with the 14C values of 182 and 230 microg m(-3) measured for the respective SOA precursors. While there are uncertainties associated with the organic tracer method, largely due to the chemical complexity of SOA forming chemical mechanisms, the results of this study suggest the organic tracer method may serve as a useful tool for determining whether a precursor hydrocarbon is a major SOA contributor. PMID:17612177

Offenberg, John H; Lewis, Charles W; Lewandowski, Michael; Jaoui, Mohammed; Kleindienst, Tadeusz E; Edney, Edward O

2007-06-01

168

IDENTIFICATION AND EXPERIMENTAL DATABASE FOR BINARY AND MULTICOMPONENT MIXTURES WITH POTENTIAL FOR INCREASING OVERALL CYCLE EFFICIENCY  

SciTech Connect

This report describes an experimental investigation designed to identify binary and multicomponent mixture systems that may be for increasing the overall efficiency of a coal fired unit by extracting heat from flue gases. While ammonia-water mixtures have shown promise for increasing cycle efficiencies in a Kalina cycle, the costs and associated range of thermal conditions involved in a heat recovery system may prohibit its use in a relatively low temperature heat recovery system. This investigation considered commercially available non-azeotropic binary mixtures with a boiling range applicable to a flue gas initially at 477.6 K (400 F) and developed an experimental database of boiling heat transfer coefficients for those mixtures. In addition to their potential as working fluids for increasing cycle efficiency, cost, ease of handling, toxicity, and environmental concerns were considered in selection of the mixture systems to be examined experimentally. Based on this review, water-glycol systems were identified as good candidates. However, previous investigations of mixture boiling have focused on aqueous hydrocarbon mixtures, where water is the heaviest component. There have been few studies of water-glycol systems, and those that do exist have investigated boiling on plain surfaces only. In water-glycol systems, water is the light component, which makes these systems unique compared to those that have been previously examined. This report examines several water-glycol systems, and documents a database of experimental heat transfer coefficients for these systems. In addition, this investigation also examines the effect of an enhanced surface on pool boiling in water-glycol mixtures, by comparing boiling on a smooth surface to boiling on a Turbo IIIB. The experimental apparatus, test sections, and the experimental procedures are described. The mixture systems tested included water-propylene glycol, water-ethylene glycol, and water-diethylene glycol. All experimental data were obtained at atmospheric pressure with the test section oriented horizontally. The effect of subcooling in pool boiling of mixtures is another area that has received limited attention. Therefore, experimental data were obtained for the water-propylene glycol and water-ethylene glycol systems for subcoolings ranging from 0 to 30 C. The experimental data showed that boiling heat transfer coefficients were found to have significant degradation due to the mixture effect for each of the water-glycol systems examined. This result is consistent with previous studies which examined water-hydrocarbon mixtures with large boiling ranges. The Turbo BIII surface was found to significantly increase heat transfer in each mixture and pure component in comparison to that for the smooth surface.

Stephen M Bajorek; J. Schnelle

2002-05-01

169

Hand-held gas chromatography-ion mobility spectrometry for on-site analysis of complex organic mixtures in air or vapors over waste sites  

SciTech Connect

The strengths of Ion mobility spectrometry (IMS) are low detection limits, a wide range of application, and simplicity of design and operation. The gentle ionization processes used in IMS impart a measure of selectivity to its response. However, atmospheric pressure chemical ionization with compounds of comparable proton affinities leads to mobility spectra for which interpretive and predictive models do not exist. An alternative approach for the analysis of complex mixtures with IMS is the use of a separation device such as a gas chromatograph (GC) as an inlet. Results suggest that an IMS cell temperature of ca. 150{degrees} to 175{degrees}C provided mobility spectra with suitable spectral detail without the complications of ion-molecule clusters or fragmentation. Significant fluctuation in peak heights were observed over a 30 day test period. Neural network pattern identification techniques were applied to data obtained at room temperature and at 150{degrees}. Results showed that spectral variables within compound classes as insufficient to distinguish related compounds when mobility data was obtained using the commercial room temperature IMS cell. Similar but less severe difficulty was encountered using the 150{degrees} data. 5 refs., 3 figs., 2 tabs.

Bell, S.C. (Los Alamos National Lab., NM (USA)); Eiceman, G.A. (New Mexico State Univ., Las Cruces, NM (USA). Dept. of Chemistry)

1991-01-01

170

Mixtures of quaternary ammonium compounds and anionic organic compounds in the aquatic environment: Elimination and biodegradability in the closed bottle test monitored by LC-MS/MS.  

PubMed

Quaternary ammonium compounds (QACs) are widely used as disinfectants, detergents and fabric softeners. Anionic detergents are one of the most widely used chemical substances. QACs and anionic surfactants can form ionic pairs. In the present study we investigated the biodegradability of QACs in the presence of different anionic surfactants. The biodegradability of three QACs, namely benzalkonium chloride (BAC), didecyldimethylammonium chloride (DDMAC) and ethacridine lactate (EL), when applied as single substances and in combination with anionic surfactants such as benzene sulfonic acid (BSA), LAS, naphthalene sulfonic acid (NSA) and sodium dodecylsulfonate (SDS) was studied applying the closed bottle test (CBT) [OECD 301D, 1992. Guidelines for Testing of Chemicals. Closed bottle test. Organisation of Economic Cooperation and Development, Paris] at a ratio of 1:1 (mol:mol). Biodegradation was monitored by measuring oxygen concentration in the test vessels with an oxygen electrode in accordance with international standard methods [ISO 5414, 1990. Water quality - determination of dissolved oxygen. In: German Standard Methods for the Examination of Water, Wastewater and Sludge. VCH Verlagsgesellschaft, Weinheim, New York, Basel Cambridge]. Primary elimination of the QACs and of LAS was monitored by LC-MS/MS. There was little biodegradability of the QACs as either single compounds or in the presence of organic counter ions. The biodegradability of the organic counter ions was lower in the presence of QACs as compared to the single substances. Primary elimination of the QACs by sorption took place. PMID:18439651

Sütterlin, H; Alexy, R; Coker, A; Kümmerer, K

2008-06-01

171

An acellular assay to assess the genotoxicity of complex mixtures of organic pollutants bound on size segregated aerosol. Part II: oxidative damage to DNA.  

PubMed

Ambient air particulate matter (atmospheric aerosol; PM) is an important factor in the development of various diseases. Oxidative stress is believed to be one of the mechanisms of action of PM on the human organism. The aim of our study was to investigate the ability of organic extracts of size segregated aerosol particles (EOM; three fractions of aerodynamic diameter 1-10?m, 0.5-1?m and 0.17-0.5?m) to induce oxidative damage to DNA in an in vitro acellular system of calf thymus (CT) DNA with and without S9 metabolic activation. PM was collected in the Czech Republic at four places with different levels of air pollution. Levels of 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodG) tended to increase with decreasing sizes of PM. S9 metabolic activation increased the oxidative capacity of PM; mean levels of 8-oxodG/10(5) dG per 1000m(3) of air for samples with and without metabolic activation were 0.093 and 0.067, respectively (p<0.05). When results of oxidative damage to DNA were normalized per microgram of aerosol mass, mean levels of 8-oxodG/10(5) dG were 0.265 and 0.191, for incubation with and without S9 fraction, respectively (p<0.05). We observed a significant positive association between concentrations of polycyclic aromatic hydrocarbons (c-PAHs) bound to PM and levels of 8-oxodG/10(5) dG per 1000m(3) of air after metabolic activation of EOM samples (R=0.695, p<0.05). The correlation was weaker and non-significant for samples without metabolic activation (R=0.523, p=0.08). In conclusion, we showed that organic extracts of PM were able to induce oxidative damage to DNA in vitro; this ability was increased after S9 metabolic activation of EOM and with decreasing sizes of PM. PMID:20603203

Rossner, Pavel; Topinka, Jan; Hovorka, Jan; Milcova, Alena; Schmuczerova, Jana; Krouzek, Jiri; Sram, Radim J

2010-10-20

172

Element, Mixture, Compound  

NSDL National Science Digital Library

Students gain a better understanding of the different types of materials as pure substances and mixtures and learn to distinguish between homogeneous and heterogeneous mixtures by discussing an assortment of example materials they use and encounter in their daily lives.

National Science Foundation GK-12 and Research Experience for Teachers (RET) Programs,

173

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.

174

Mixtures Research at NIEHS: An Evolving Program  

PubMed Central

The National Institute of Environmental Health Sciences (NIEHS) has a rich history in evaluating the toxicity of mixtures. The types of mixtures assessed by the Division of the National Toxicology Program (DNTP) and the extramural community (through the Division of Extramural Research and Training (DERT)) have included a broad range of chemicals and toxicants, with each study having a unique set of questions and design considerations. Some examples of the types of mixtures studied include: groundwater contaminants, pesticides/fertilizers, dioxin-like chemicals (assessing the toxic equivalency approach), drug combinations, air pollution, metals, polycyclic aromatic hydrocarbons, technical mixtures (e.g. pentachlorophenol, flame retardants), and mixed entities (e.g. herbals, asbestos). These endeavors have provided excellent data on the toxicity of specific mixtures and have been informative to the human health risk assessment process in general (e.g. providing data on low dose exposures to environmental chemicals). However, the mixtures research effort at NIEHS, to date, has been driven by test article nominations to the DNTP or by investigator-initiated research through DERT. Recently, the NIEHS has embarked upon an effort to coordinate mixtures research across both intramural and extramural divisions in order to maximize mixtures research results. A path forward for NIEHS mixtures research will be based on feedback from a Request for Information (RFI) designed to gather up-to-date views on the knowledge gaps and roadblocks to evaluating mixtures and performing cumulative risk assessment, and a workshop organized to bring together mixtures experts from risk assessment, exposure science, biology, epidemiology, and statistics. The future of mixtures research at NIEHS will include projects from nominations to DNTP, studies by extramural investigators, and collaborations across government agencies that address high-priority questions in the field of mixtures research. PMID:23146757

Rider, Cynthia V; Carlin, Danielle J; DeVito, Micheal J; Thompson, Claudia L; Walker, Nigel J

2014-01-01

175

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

176

Remediation of the effect of adding cyanides on an algal/bacterial treatment of a mixture of organic pollutants in a continuous photobioreactor.  

PubMed

The effect of inorganic pollutants on the treatment of organic pollutants using algal/bacterial microcosm was investigated in a continuous photobioreactor. The microcosm was composed of Chlorella vulgaris MM1 and Pseudomonas MT1 and was able to efficiently treat artificial waste-water contaminated with 6.4 salicylate and 2.2 mM phenol at a hydraulic retention time of 4 days. No negative effect was recorded when the waste-water was supplemented with 1.6 mM thiocyanate; however, the treatment efficiency severely deteriorated when the system was challenged with 0.74 mM cyanide. Addition of 2 g NaHCO3 l(-1) did not improve the efficiency of the treatment. Toxicity of the pollutants to the alga was cyanide > thiocyanate > phenol > salicylate. The high toxicity of the waste-water was eliminated either by a 25-fold dilution or by photocatalytic pre-treatment which allowed the subsequent efficient biological treatment. PMID:24930096

Essam, Tamer; ElRakaiby, Marwa; Agha, Azza

2014-09-01

177

Optimal design and experimental validation of a simulated moving bed chromatography for continuous recovery of formic acid in a model mixture of three organic acids from Actinobacillus bacteria fermentation.  

PubMed

The economically-efficient separation of formic acid from acetic acid and succinic acid has been a key issue in the production of formic acid with the Actinobacillus bacteria fermentation. To address this issue, an optimal three-zone simulated moving bed (SMB) chromatography for continuous separation of formic acid from acetic acid and succinic acid was developed in this study. As a first step for this task, the adsorption isotherm and mass-transfer parameters of each organic acid on the qualified adsorbent (Amberchrom-CG300C) were determined through a series of multiple frontal experiments. The determined parameters were then used in optimizing the SMB process for the considered separation. During such optimization, the additional investigation for selecting a proper SMB port configuration, which could be more advantageous for attaining better process performances, was carried out between two possible configurations. It was found that if the properly selected port configuration was adopted in the SMB of interest, the throughout and the formic-acid product concentration could be increased by 82% and 181% respectively. Finally, the optimized SMB process based on the properly selected port configuration was tested experimentally using a self-assembled SMB unit with three zones. The SMB experimental results and the relevant computer simulation verified that the developed process in this study was successful in continuous recovery of formic acid from a ternary organic-acid mixture of interest with high throughput, high purity, high yield, and high product concentration. PMID:25240652

Park, Chanhun; Nam, Hee-Geun; Lee, Ki Bong; Mun, Sungyong

2014-10-24

178

First direct observation of secondary organic aerosol formation during cloud condensation-evaporation cycles in isoprene photo-oxidation reacting mixtures (CUMULUS project)  

NASA Astrophysics Data System (ADS)

Several field observations, laboratory and model studies suggest a potentially important role of cloud droplets in forming additional secondary organic aerosol (SOA) (Sorooshian et al., 2007; Altieri et al., 2008; Couvidat et al., 2013). While this SOAaq hypothesis seems to be robust and is considered quite established, so far, no direct observations of such a process have been provided. Recently a consortium of five laboratories has joined theirs efforts in a series of experimental simulation experiments to try to bring a direct confirmation of this hypothesis: the CUMULUS project (CloUd MULtiphase chemistry of organic compoUndS in the troposphere). The aim of the present work is to study SOA formation from isoprene photo-oxidation during cloud condensation-evaporation cycles. The chemistry occurring in the gaseous, particulate and aqueous phases, and the exchange between these phases were investigated through an original multiphase approach in a simulation chamber. Experiments were performed in the CESAM chamber (Wang et al., 2011) which was designed to investigate multiphase processes under realistic actinic flux, and accurate control of both temperature and relative humidity. A protocol was designed to generate cloud events in the simulation chamber, it has allowed us to generate clouds lasting for ca. 10 minutes in the presence of light and many clouds could be generated in a single experiment. Connected to the chamber, a large panel of instruments was used to monitor the gas-phase and the particulate phase during experiments. Gas-phase composition was analyzed in-situ via a Fourier Transform Infrared Spectrometer (FTIR) and a Proton Transfer Reaction Mass Spectrometer (PTR-TOF-MS) as well as NOx and O3 analyzers. A Scanning Mobility Particle Sizer (SMPS) measured dried SOA size distributions and total concentrations inside the chamber. An Aerodyne High Resolution Time-Of-Flight Aerosol Mass Spectrometer (HR-TOF-AMS) was also used to investigate aerosol composition. Cloud droplets size distributions were measured by a white light Optical Particle Counter (OPC). In each experiment, around 800 ppb of isoprene was injected in the chamber together with HONO under dry conditions before irradiation. In all experiments, the impact of the cloud generation on the gaseous and particulate phases has been highlighted, suggesting a significant production of SOA from isoprene photo-oxidation by interactions with cloud droplets. The overall results in additional SOA mass production, the dynamic of its mass concentration and some insight of its chemical composition will be presented. Altieri, K. et al. (2008). Atmospheric Environment 42(7): 1476-1490. Couvidat, F. et al. (2013). Environmental Science & Technology 47(2): 914-922. Sorooshian, A. et al. (2007). Environmental Science & Technology 41(13): 4647-4654. Wang, J. et al. (2011). Atmospheric Measurement Techniques 4(11): 2465-2494.

Brégonzio-Rozier, Lola; Siekmann, Frank; Giorio, Chiara; Temime-Roussel, Brice; Pangui, Edouard; Morales, Sébastien; Ravier, Sylvain; Monod, Anne; Doussin, Jean-François

2014-05-01

179

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

180

Potential Energy Savings by Using Alternative Technologies for the Separation of Fluid Mixtures  

E-print Network

Presents solids handling problems Distillation/ 16,000 Same Currently used azeotropic process distillation Energy integrated Note: MVR = mechanical vapor recompression Fi gure 2. consumption (more so if the waste heat use is considered... Presents solids handling problems Distillation/ 16,000 Same Currently used azeotropic process distillation Energy integrated Note: MVR = mechanical vapor recompression Fi gure 2. consumption (more so if the waste heat use is considered...

Bravo, J. L.

181

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

182

Symmetric normal mixtures  

NASA Technical Reports Server (NTRS)

We consider mixture density estimation under the symmetry constraint x = Az for an orthogonal matrix A. This distributional constraint implies a corresponding constraint on the mixture parameters. Focusing on the gaussian case, we derive an expectation-maximization (EM) algorithm to enforce the constraint and show results for modeling of image feature vectors.

Turmon, Michael

2004-01-01

183

Messin' with Mixtures  

NSDL National Science Digital Library

In this activity, students investigate the properties of a heterogeneous mixture, trail mix, as if it were a contaminated soil sample near a construction site. This activity shows students that heterogeneous mixtures can be separated by physical means, and that when separated, all the parts will equal the whole.

Integrated Teaching And Learning Program

184

Organs to go ...  

NSDL National Science Digital Library

In this activity the students design an experiment to investigate the storage of an organ before a transplant operation is performed. Essentially, the students create a "slush" type mixture to store the organ.

Sheryl Burris Deets (Belleville West High School REV)

1995-06-30

185

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

186

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

187

Short-Term Bioassays in the Analysis of Complex Environmental Mixtures V,  

National Technical Information Service (NTIS)

Topics presented in the book are: new chemical and biological methods in complex mixture research; molecular dosimetry as applied to complex mixtures; integrated in-situ monitoring; genotoxicology of aquatic organisms; atmospheric transportation processes...

S. S. Sandhu, D. M. DeMarini, M. J. Mass, M. M. Moore, J. S. Mumford

1987-01-01

188

Mixtures and Solutions  

NSDL National Science Digital Library

This activity was designed for blind learners, but all types of learners can use it to investigate heterogeneous and homogeneous mixtures and solutions, identify the differences, and explore the concepts of concentration and dilution. Learners with visual impairments as well as sighted learners will create both types of mixtures and solutions. Depending on the experience of the learners and the time available, this activity can be presented as three different activities or done sequentially. Materials can be edible, such as trail mix and powered drink mix, or nonedible, such as buttons.

Blind, Perkins S.

2012-06-26

189

Color appearance of mixture gratings.  

PubMed

We have examined how color appearance varies with spatial pattern. Subjects set color-matches between a uniform, 2 deg matching field and bars within squarewave patterns (1,2 and 4 c/deg) or the superposition of these squarewaves. The matches were set using squarewaves and squarewave mixtures with many different colors and contrasts. The color-matches satisfied the basic properties of a linear system to within a tolerance of twice the precision of repeated matches. Matches satisfied contrast-homogeneity: the contrast of the matching field was proportional to the contrast of the squarewave pattern or the mixture of squarewave patterns. Matches also satisfied pattern-superposition: if a bar in one squarewave matched one uniform field, and a bar in a second squarewave matched a second uniform field, the superposition of the two squarewave bars matched the superposition of the uniform matching fields. Matches are predicted by a model in which the color at a location is predicted by the responses of three linear, pattern-color separable mechanisms. As the individual mechanisms are pattern-color separable, meaningful pattern and color-responsivity functions can be estimated for each of the mechanisms. The estimated color-responsivity functions, based only on asymmetric color-matches, have an opponent-colors organization. PMID:8917788

Bäuml, K H; Wandell, B A

1996-09-01

190

Mass spectrometer mixture calibrations  

Microsoft Academic Search

Mass spectrometric analyses of hydrogen isotope mixtures can be difficult to make for a number of reasons. The most difficult problem is the possibility of confronting extremely great and extremely small relative mass differences in the same analysis. Commercial mass spectrometers are now available that can overcome these problems. The analytical capabilities and limitations of these instruments will be discussed.

Hicks

1986-01-01

191

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.

192

Simulation of nonazeotropic refrigerant mixtures for use in a dual-circuit refrigerator/freezer with countercurrent heat exchanges  

SciTech Connect

The paper discusses the simulation of Non-azeotropic Refrigerant Mixtures (NARMs) for use in a dual-circuit refrigerator/freezer (RF) with countercurrent heat exchangers. The simulated RF has two complete and independent refrigeration cycles for its two compartments. It uses a NARM in each cycle and countercurrent heat exchangers throughout. In a standard cabinet, the RF is simulated to provide energy savings of 24 percent compared to current U.S. RF designs. The NARMs modeled with the best performance are R-32/-152a, R-32/-142b, and R-22/-142b. An 18 percent improvement can be expected from the dual-circuit system using R-12 alone, and an additional 6 percent improvement can be gained by replacing R-12 with the selected NARMs in countercurrent heat exchangers. Advantages of the system include greatly reduced energy consumption, easy temperature and humidity control for each compartment, no humidity or odors transferred between compartments, and increased time between defrost cycles. Disadvantages include additional hardware requirements, compressor size, and the difficulties of using a NARM.

Bare, J.C.; Gage, C.L.; Radermacher, R.; Jung, D.S.

1992-01-01

193

Prediction with Mixture Autoregressive Models  

E-print Network

Prediction with Mixture Autoregressive Models Georgi N. Boshnakov First version: 31 January 2006 of Manchester #12;Prediction with mixture autoregressive models Georgi N. Boshnakov Mathematics Department.boshnakov@umist.ac.uk Tel: (+44) (0)161 200 3684 Fax: (+44) (0)161 200 3669 Abstract Mixture autoregressive (MAR) models

Sidorov, Nikita

194

Si l ti f Eth l D h d ti 2013 9 23()  

E-print Network

Pervaporation Method: Proposed by SKEC Vacuum Distillation Azeotrope between ethanol and water disappears as an Entrainer () Limit of Distillation by Azeotrope 1.0 Distillation range is restricted by the azeotropic mixtures, such as ethanol/water and IPA/water, can be separated into their pure components by distillation

Hong, Deog Ki

195

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

196

Transcriptional responses to complex mixtures: a review.  

PubMed

Exposure of people to hazardous compounds is primarily through complex environmental mixtures, those that occur through media such as air, soil, water, food, cigarette smoke, and combustion emissions. Microarray technology offers the ability to query the entire genome after exposure to such an array of compounds, permitting a characterization of the biological effects of such exposures. This review summarizes the published literature on the transcriptional profiles resulting from exposure of cells or organisms to complex environmental mixtures such as cigarette smoke, diesel emissions, urban air, motorcycle exhaust, carbon black, jet fuel, and metal ore and fumes. The majority of the mixtures generally up-regulate gene expression, with heme oxygenase 1 and CYP1A1 being up-regulated by all of the mixtures. Most of the mixtures altered the expression of genes involved in oxidative stress response (OH-1, metallothioneins), immune/inflammation response (IL-1b, protein kinase), xenobiotic metabolism (CYP1A1, CYP1B1), coagulation and fibrinolysis (plasminogen activator/inhibitor), proto-oncogenes (FUS1, JUN), heat-shock response (HSP60, HSP70), DNA repair (PCNA, GADD45), structural unit of condensed DNA (Crf15Orf16, DUSP 15), and extracellular matrix degradation (MMP1, 8, 9, 11, 12). Genes involved in aldehyde metabolism, such as ALDH3, appeared to be uniquely modulated by cigarette smoke. Cigarette smoke-exposed populations have been successfully distinguished from control nonexposed populations based on the expression pattern of a subset of genes, thereby demonstrating the utility of this approach in identifying biomarkers of exposure and susceptibility. The analysis of gene-expression data at the pathway and functional level, along with a systems biology approach, will provide a more comprehensive insight into the biological effects of complex mixtures and will improve risk assessment of the same. We suggest critical components of study design and reporting that will achieve this goal. PMID:17888717

Sen, Banalata; Mahadevan, Brinda; DeMarini, David M

2007-01-01

197

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. PMID:7515806

Mauderly, J L

1993-01-01

198

Laboratory evaluation of crumb rubber asphalt concrete mixtures using the concepts of SMA mixtures  

E-print Network

Eight CRM asphalt concrete mixtures were evaluated using AAMAS characterization procedures: Four wet-process mixtures and four dry-process mixtures. These mixtures were compared to a conventional dense graded mixture. It was determined that CRM has...

Rebala, Somasekhar Reddy

2012-06-07

199

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

200

Learning with Mixtures of Trees  

Microsoft Academic Search

This paper describes the mixtures-of-trees model, a probabilistic model for discrete multidimensional domains. Mixtures-of-trees generalize the probabilistic trees of Chow and Liu (6) in a different and complementary direction to that of Bayesian networks. We present efficient algorithms for learning mixtures-of-trees models in maximum likelihood and Bayesian frameworks. We also discuss additional efficiencies that can be obtained when data are

Marina Meila; Michael I. Jordan

2000-01-01

201

Learning Mixtures of DAG Models  

Microsoft Academic Search

Abstract We describe computationally efficient meth- ods for learning mixtures in which each com- ponent is a directed acyclic graphical model (mixtures of DAGs or MDAGs). We argue that simple search-and-score algorithms are infeasible for a variety of problems, and in- troduce a feasible approach in which param- eter and structure search is interleaved and expected data is treated as

Bo Thiesson; Christopher Meek; David Maxwell Chickering; David Heckerman

1998-01-01

202

Evaporating Drops of Alkane Mixtures  

E-print Network

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

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

2005-01-01

203

A review on the separation of benzene\\/cyclohexane mixtures by pervaporation processes  

Microsoft Academic Search

Separation of benzene (Bz) and cyclohexane (Chx) is one of the most challenging processes in the chemical industry. On account of the only 0.6°C difference in volatilities of the two components, conventional distillation processes are not practical. Azeotropic distillation and extractive distillation, on the other hand, although feasible and in use in many industries, are accompanied by high capital and

J. P. Garcia Villaluenga; A. Tabe-Mohammadi

2000-01-01

204

Preparation of ethanol-water mixtures for use in internal combustion engines and fuel cells  

Microsoft Academic Search

Apart from energy requirement estimations on the conventional normal-pressure process for ethanol concentration, economy comparisons on the azeotropic and extractive distillation for ethanol purification can be found in the literature. The processes introduced in this paper are compared with processes described in literature. The problem is, on one hand the studies were made on laboratory-scale units, on the other hand

Haertel

1983-01-01

205

Understanding Anthropogenic and Biogenic Primary and Secondary Aerosol Mixtures  

NASA Astrophysics Data System (ADS)

Atmospheric organic matter can constitute 20-70% of the total fine aerosol mass, yet much of its chemical composition is not well understood nor are the mechanisms via which these compounds form. Continental organic aerosol can be directly emitted as primary aerosol from combustion sources or formed in the atmosphere via secondary process with both biogenic and anthropogenic hydrocarbon precursors. In urban air masses, the mixture of anthropogenic primary emissions and secondary organic aerosol (SOA) is ubiquitous. Changes due to the mixing of the different organic chemical compositions can affect the oxidation state and ageing properties of particulates. Hence the change in state can consequently impact air quality, public health and regional climate. The mixing state and the affinity of primary emissions with SOA not well understood: very little is known about the properties of these mixtures. In this a study, SOA formed in the Carnegie Mellon University environmental smog chamber is mixed with diesel exhaust and motor oil aerosol. The objective is to combine two aerosol classes in an external mixture and to then watch the dynamics as well as total mass balance as the mixtures come to equilibrium, possibly forming a single, internal mixture. The SOA is formed from monoterpene and sesquiterpene precursors, specifically ?-pinene and ?- caryophyllene SOA formed via dark ozonlysis. Primary aerosol is injected into the chamber once the biogenic nucleation and growth has completed and the mixture is allowed to age for three to four hours. A suite of instruments characterize the changes in size, volatility, and chemical composition of the aerosol mixtures. Scanning Mobility Particle Sizers record changes in the size distribution before and after mixing. An Aerodyne High Resolution Time of Flight Aerosol Mass Spectrometer measures the change in mass spectra and the composition of separate size modes both before and after the mixing event, and a thermodenuder is used to characterize changes in mixed aerosol volatility.

Asa-Awuku, A.; Miracola, M.; Lee, B. D.; Kroll, J.; Pandis, S.; Robinson, A.; Donahue, N.

2008-12-01

206

MIXTURE DESIGN MANUAL AND PERFORMANCE-BASED SPECIFICATIONS FOR COLD PATCHING MIXTURES  

E-print Network

0-4872-P2 MIXTURE DESIGN MANUAL AND PERFORMANCE-BASED SPECIFICATIONS FOR COLD PATCHING MIXTURES................................................................................................................................... 1 Mixture Design Procedure

Texas at Austin, University of

207

Bridging environmental mixtures and toxic effects.  

PubMed

Biological Response Indicator Devices Gauging Environmental Stressors (BRIDGES) is a bioanalytical tool that combines passive sampling with the embryonic zebrafish developmental toxicity bioassay to provide a quantitative measure of the toxicity of bioavailable complex mixtures. Passive sampling devices (PSDs), which sequester and concentrate bioavailable organic contaminants from the environment, were deployed in the Willamette and Columbia Rivers within and outside of the Portland Harbor Superfund site in Portland, OR, USA. Six sampling events were conducted in the summer and fall of 2009 and 2010. Passive sampling device extracts were analyzed for polycyclic aromatic hydrocarbon (PAH) compounds and screened for 1,201 chemicals of concern using deconvolution-reporting software. The developmental toxicity of the extracts was analyzed using the embryonic zebrafish bioassay. The BRIDGES tool provided site-specific, temporally resolved information about environmental contaminant mixtures and their toxicity. Multivariate modeling approaches were applied to paired chemical and toxic effects data sets to help unravel chemistry-toxicity associations. Modeling elucidated spatial and temporal trends in PAH concentrations and the toxicity of the samples and identified a subset of PAH analytes that were the most highly correlated with observed toxicity. Although the present study highlights the complexity of discerning specific bioactive compounds in complex mixtures, it demonstrates methods for associating toxic effects with chemical characteristics of environmental samples. PMID:23001962

Allan, Sarah E; Smith, Brian W; Tanguay, Robert L; Anderson, Kim A

2012-12-01

208

Surface tensions of solutions containing dicarboxylic acid mixtures  

NASA Astrophysics Data System (ADS)

Organic solutes tend to lower the surface tension of cloud condensation nuclei, allowing them to more readily activate. The surface tension of various dicarboxylic acid aerosol mixtures was measured at 20 °C using the Wilhelmy plate method. At lower concentrations, the surface tension of a solution with equi-molar mixtures of dicarboxylic acids closely followed that of a solution with the most surface-active organic component alone. Measurements of surface tension for these mixtures were lower than predictions using Henning's model and the modified Szyszkowski equation, by ?1-2%. The calculated maximum surface excess (?max) and inverse Langmuir adsorption coefficient (?) from the modified Szyszkowski equation were both larger than measured values for 6 of the 7 mixtures tested. Accounting for the reduction in surface tension in the Köhler equation reduced the critical saturation ratio for these multi-component mixtures - changes were negligible for dry diameters of 0.1 and 0.5 ?m, but a reduction from 1.0068 to 1.0063 was seen for the 4-dicarboxylic acid mixture with a dry diameter of 0.05 ?m.

Lee, Jae Young; Hildemann, Lynn M.

2014-06-01

209

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

210

Some results on Gaussian mixtures  

NASA Astrophysics Data System (ADS)

We investigate Gaussian mixtures with independent components, whose parameters are numerically estimated. A decomposition of a Gaussian mixture is presented when the components have a common variance. We introduce a shifted and scaled t-Student distribution as an approximation for the distribution of Gaussian mixtures when their components have a common mean and develop a hypothesis test for testing the equality of the components means. Finally, we analyse the fitness of the approximate model to the logarithmic daily returns of the Portuguese stock index PSI-20.

Felgueiras, Miguel; Santos, Rui; Martins, João Paulo

2014-10-01

211

Learning mixtures of arbitrary gaussians  

Microsoft Academic Search

Mixtures of gaussian (or normal) distributions arise in a variety of application areas. Many techniques have been proposed for the task of finding the component gaussians given samples from the mixture, such as the EM algorithm, a local-search heuristic from Dempster, Laird and Rubin~(1977). However, such heuristics are known to require time exponential in the dimension (i.e., number of variables)

Arora Sanjeev; Ravi Kannan

2001-01-01

212

40 CFR 721.9540 - Polysulfide mixture.  

Code of Federal Regulations, 2012 CFR

... 2012-07-01 false Polysulfide mixture. 721.9540 Section 721.9540 ...Substances § 721.9540 Polysulfide mixture. (a) Chemical substance and significant...identified generically as a polysulfide mixture (PMN P-93-1043) is subject...

2012-07-01

213

14 CFR 29.1147 - Mixture controls.  

Code of Federal Regulations, 2010 CFR

... 2010-01-01 2010-01-01 false Mixture controls. 29.1147 Section 29.1147...Powerplant Controls and Accessories § 29.1147 Mixture controls. (a) If there are mixture controls, each engine must have a...

2010-01-01

214

14 CFR 27.1147 - Mixture controls.  

Code of Federal Regulations, 2011 CFR

...1 2011-01-01 2011-01-01 false Mixture controls. 27.1147 Section 27.1147 ...Powerplant Controls and Accessories § 27.1147 Mixture controls. If there are mixture controls, each engine must have a separate...

2011-01-01

215

14 CFR 29.1147 - Mixture controls.  

Code of Federal Regulations, 2012 CFR

... 2012-01-01 2012-01-01 false Mixture controls. 29.1147 Section 29.1147...Powerplant Controls and Accessories § 29.1147 Mixture controls. (a) If there are mixture controls, each engine must have a...

2012-01-01

216

16 CFR 1500.5 - Hazardous mixtures.  

...2014-01-01 2014-01-01 false Hazardous mixtures. 1500.5 Section 1500.5 Commercial Practices...ENFORCEMENT REGULATIONS § 1500.5 Hazardous mixtures. For a mixture of substances, the determination of whether...

2014-01-01

217

14 CFR 27.1147 - Mixture controls.  

...1 2014-01-01 2014-01-01 false Mixture controls. 27.1147 Section 27.1147 ...Powerplant Controls and Accessories § 27.1147 Mixture controls. If there are mixture controls, each engine must have a separate...

2014-01-01

218

40 CFR 721.9540 - Polysulfide mixture.  

Code of Federal Regulations, 2010 CFR

... 2010-07-01 false Polysulfide mixture. 721.9540 Section 721.9540 ...Substances § 721.9540 Polysulfide mixture. (a) Chemical substance and significant...identified generically as a polysulfide mixture (PMN P-93-1043) is subject...

2010-07-01

219

14 CFR 27.1147 - Mixture controls.  

Code of Federal Regulations, 2013 CFR

...1 2013-01-01 2013-01-01 false Mixture controls. 27.1147 Section 27.1147 ...Powerplant Controls and Accessories § 27.1147 Mixture controls. If there are mixture controls, each engine must have a separate...

2013-01-01

220

40 CFR 721.9540 - Polysulfide mixture.  

Code of Federal Regulations, 2013 CFR

... 2013-07-01 false Polysulfide mixture. 721.9540 Section 721.9540 ...Substances § 721.9540 Polysulfide mixture. (a) Chemical substance and significant...identified generically as a polysulfide mixture (PMN P-93-1043) is subject...

2013-07-01

221

16 CFR 1500.5 - Hazardous mixtures.  

Code of Federal Regulations, 2013 CFR

...2013-01-01 2013-01-01 false Hazardous mixtures. 1500.5 Section 1500.5 Commercial Practices...ENFORCEMENT REGULATIONS § 1500.5 Hazardous mixtures. For a mixture of substances, the determination of whether...

2013-01-01

222

14 CFR 29.1147 - Mixture controls.  

Code of Federal Regulations, 2013 CFR

... 2013-01-01 2013-01-01 false Mixture controls. 29.1147 Section 29.1147...Powerplant Controls and Accessories § 29.1147 Mixture controls. (a) If there are mixture controls, each engine must have a...

2013-01-01

223

14 CFR 27.1147 - Mixture controls.  

Code of Federal Regulations, 2012 CFR

...1 2012-01-01 2012-01-01 false Mixture controls. 27.1147 Section 27.1147 ...Powerplant Controls and Accessories § 27.1147 Mixture controls. If there are mixture controls, each engine must have a separate...

2012-01-01

224

16 CFR 1500.5 - Hazardous mixtures.  

Code of Federal Regulations, 2012 CFR

...2012-01-01 2012-01-01 false Hazardous mixtures. 1500.5 Section 1500.5 Commercial Practices...ENFORCEMENT REGULATIONS § 1500.5 Hazardous mixtures. For a mixture of substances, the determination of whether...

2012-01-01

225

16 CFR 1500.5 - Hazardous mixtures.  

Code of Federal Regulations, 2011 CFR

...2011-01-01 2011-01-01 false Hazardous mixtures. 1500.5 Section 1500.5 Commercial Practices...ENFORCEMENT REGULATIONS § 1500.5 Hazardous mixtures. For a mixture of substances, the determination of whether...

2011-01-01

226

40 CFR 721.9540 - Polysulfide mixture.  

Code of Federal Regulations, 2011 CFR

... 2011-07-01 false Polysulfide mixture. 721.9540 Section 721.9540 ...Substances § 721.9540 Polysulfide mixture. (a) Chemical substance and significant...identified generically as a polysulfide mixture (PMN P-93-1043) is subject...

2011-07-01

227

14 CFR 27.1147 - Mixture controls.  

Code of Federal Regulations, 2010 CFR

...1 2010-01-01 2010-01-01 false Mixture controls. 27.1147 Section 27.1147 ...Powerplant Controls and Accessories § 27.1147 Mixture controls. If there are mixture controls, each engine must have a separate...

2010-01-01

228

16 CFR 1500.5 - Hazardous mixtures.  

Code of Federal Regulations, 2010 CFR

...2010-01-01 2010-01-01 false Hazardous mixtures. 1500.5 Section 1500.5 Commercial Practices...ENFORCEMENT REGULATIONS § 1500.5 Hazardous mixtures. For a mixture of substances, the determination of whether...

2010-01-01

229

14 CFR 29.1147 - Mixture controls.  

Code of Federal Regulations, 2011 CFR

... 2011-01-01 2011-01-01 false Mixture controls. 29.1147 Section 29.1147...Powerplant Controls and Accessories § 29.1147 Mixture controls. (a) If there are mixture controls, each engine must have a...

2011-01-01

230

14 CFR 25.1147 - Mixture controls.  

Code of Federal Regulations, 2010 CFR

...2010-01-01 2010-01-01 false Mixture controls. 25.1147 Section 25.1147 Aeronautics...CATEGORY AIRPLANES Powerplant Powerplant Controls and Accessories § 25.1147 Mixture controls. (a) If there are mixture...

2010-01-01

231

14 CFR 23.1147 - Mixture controls.  

Code of Federal Regulations, 2010 CFR

...2010-01-01 2010-01-01 false Mixture controls. 23.1147 Section 23.1147 Aeronautics...CATEGORY AIRPLANES Powerplant Powerplant Controls and Accessories § 23.1147 Mixture controls. (a) If there are mixture...

2010-01-01

232

Modeling and analysis of personal exposures to VOC mixtures using copulas  

PubMed Central

Environmental exposures typically involve mixtures of pollutants, which must be understood to evaluate cumulative risks, that is, the likelihood of adverse health effects arising from two or more chemicals. This study uses several powerful techniques to characterize dependency structures of mixture components in personal exposure measurements of volatile organic compounds (VOCs) with aims of advancing the understanding of environmental mixtures, improving the ability to model mixture components in a statistically valid manner, and demonstrating broadly applicable techniques. We first describe characteristics of mixtures and introduce several terms, including the mixture fraction which represents a mixture component's share of the total concentration of the mixture. Next, using VOC exposure data collected in the Relationship of Indoor Outdoor and Personal Air (RIOPA) study, mixtures are identified using positive matrix factorization (PMF) and by toxicological mode of action. Dependency structures of mixture components are examined using mixture fractions and modeled using copulas, which address dependencies of multiple variables across the entire distribution. Five candidate copulas (Gaussian, t, Gumbel, Clayton, and Frank) are evaluated, and the performance of fitted models was evaluated using simulation and mixture fractions. Cumulative cancer risks are calculated for mixtures, and results from copulas and multivariate lognormal models are compared to risks calculated using the observed data. Results obtained using the RIOPA dataset showed four VOC mixtures, representing gasoline vapor, vehicle exhaust, chlorinated solvents and disinfection by-products, and cleaning products and odorants. Often, a single compound dominated the mixture, however, mixture fractions were generally heterogeneous in that the VOC composition of the mixture changed with concentration. Three mixtures were identified by mode of action, representing VOCs associated with hematopoietic, liver and renal tumors. Estimated lifetime cumulative cancer risks exceeded 10?3 for about 10% of RIOPA participants. Factors affecting the likelihood of high concentration mixtures included city, participant ethnicity, and house air exchange rates. The dependency structures of the VOC mixtures fitted Gumbel (two mixtures) and t (four mixtures) copulas, types that emphasize tail dependencies. Significantly, the copulas reproduced both risk predictions and exposure fractions with a high degree of accuracy, and performed better than multivariate lognormal distributions. Copulas may be the method of choice for VOC mixtures, particularly for the highest exposures or extreme events, cases that poorly fit lognormal distributions and that represent the greatest risks. PMID:24333991

Su, Feng-Chiao; Mukherjee, Bhramar; Batterman, Stuart

2014-01-01

233

VOCs, Pesticides, Nitrate, and Their Mixtures in Groundwater Used for  

E-print Network

VOCs, Pesticides, Nitrate, and Their Mixtures in Groundwater Used for Drinking Water in the United areas. For each sample, as many as 60 volatile organic compounds (VOCs), 83 pesticides, and nitrate were analyzed. On the basis of previous studies, nitrate concentrations as nitrogen g3 mg/L were considered

234

Method and compositions for the degradation of tributyl phosphate in chemical waste mixtures  

DOEpatents

A method and process for the degradation of tributyl phosphate in an organic waste mixture and a biologically pure, novel bacteria culture for accomplishing the same. A newly-discovered bacteria (a strain of Acinetobacter sp. ATCC 55587) is provided which is combined in a reactor vessel with a liquid waste mixture containing tributyl phosphate and one or more organic waste compounds capable of functioning as growth substrates for the bacteria. The bacteria is thereafter allowed to incubate within the waste mixture. As a result, the tributyl phosphate and organic compounds within the waste mixture are metabolized (degraded) by the bacteria, thereby eliminating such materials which are environmentally hazardous. In addition, the bacteria is capable of degrading waste mixtures containing high quantities of tributyl phosphate (e.g. up to about 1.0% by weight tributyl phosphate).

Stoner, Daphne L. (Idaho Falls, ID); Tien, Albert J. (Zurich, CH)

1995-01-01

235

Method and compositions for the degradation of tributyl phosphate in chemical waste mixtures  

DOEpatents

A method and process are disclosed for the degradation of tributyl phosphate in an organic waste mixture and a biologically pure, novel bacteria culture for accomplishing the same. A newly-discovered bacteria (a strain of Acinetobacter sp. ATCC 55587) is provided which is combined in a reactor vessel with a liquid waste mixture containing tributyl phosphate and one or more organic waste compounds capable of functioning as growth substrates for the bacteria. The bacteria is thereafter allowed to incubate within the waste mixture. As a result, the tributyl phosphate and organic compounds within the waste mixture are metabolized (degraded) by the bacteria, thereby eliminating such materials which are environmentally hazardous. In addition, the bacteria is capable of degrading waste mixtures containing high quantities of tributyl phosphate (e.g. up to about 1.0% by weight tributyl phosphate). 6 figs.

Stoner, D.L.; Tien, A.J.

1995-09-26

236

Investigations of Toxic and Genotoxic Effects of Heavy Metals and their Model Mixture on Plants  

Microsoft Academic Search

In the recent investigations of environment pollution, in order to determine toxic effects of industrial sewage, herbicides, and heavy metals, higher plants are more commonly investigated. Toxic and genotoxic effects of separate heavy metals and their mixtures on plants – test-organisms have been investigated. Concentrations of heavy metals that were found in the studied mixture were taken into account. Besides,

Danguol? Montvydien?; R?ta Laka?auskien?; Danut? Mar?iulionien?

1999-01-01

237

Application and validation of approaches for the predictive hazard assessment of realistic pesticide mixtures  

Microsoft Academic Search

In freshwater systems located in agricultural areas, organisms are exposed to a multitude of toxicologically and structurally different pesticides. For regulatory purposes it is of major importance whether the combined hazard of these substances can be predictively assessed from the single substance toxicity. For artificially designed multi-component mixtures, it has been shown that the mixture toxicity can be predicted by

Marion Junghans; Thomas Backhaus; Michael Faust; Martin Scholze; L. H. Grimme

2006-01-01

238

Unrestricted Mixture Models for Class Identification in Growth Mixture Modeling  

ERIC Educational Resources Information Center

Growth mixture modeling has gained much attention in applied and methodological social science research recently, but the selection of the number of latent classes for such models remains a challenging issue, especially when the assumption of proper model specification is violated. The current simulation study compared the performance of a linear…

Liu, Min; Hancock, Gregory R.

2014-01-01

239

Blind Identification of Overcomplete MixturEs of sources (BIOME)  

Microsoft Academic Search

The problem of Blind Identification of linear mixtures of independent random processes is known to be related to the diagonalization of some tensors. This problem is posed here in terms of a non-conventional joint approximate diagonalization of several matrices. In fact, a congruent transform is applied to each of these matrices, the left transform being rectangular full rank, and the

Laurent Albera; Anne Ferréol; Pierre Comon; Pascal Chevalier

2004-01-01

240

5. Finite mixture models Proposer: Eleni Matechou  

E-print Network

5. Finite mixture models Proposer: Eleni Matechou Finite mixture models analyses, whether of an appropriate model. When a finite mixture model is fitted, one has to decide on the form of the model but also selection criteria. General R-code to fit mixture models using the EM algorithm will be provided. References

Goldschmidt, Christina

241

Dipole oscillations in fermionic mixtures  

SciTech Connect

We study dipole oscillations in a general fermionic mixture. Starting from the Boltzmann equation, we classify the different solutions in the parameter space through the number of real eigenvalues of the small oscillations matrix. We discuss how this number can be computed using the Sturm algorithm and its relation with the properties of the Laplace transform of the experimental quantities. After considering two components in harmonic potentials having different trapping frequencies, we study dipole oscillations in three-component mixtures. Explicit computations are done for realistic experimental setups using the classical Boltzmann equation without intraspecies interactions. A brief discussion of the application of this classification to general collective oscillations is also presented.

Chiacchiera, S.; Macri, T.; Trombettoni, A. [Centro de Fisica Computacional, Department of Physics, University of Coimbra, P-3004-516, Coimbra (Portugal); SISSA and INFN, Sezione di Trieste, via Beirut 2/4, I-34151, Trieste (Italy)

2010-03-15

242

Olfactory discrimination of complex mixtures of amino acids by the black bullhead Ameiurus melas.  

PubMed

On the basis of previous findings of behavioural discrimination of amino acids and on the knowledge of electrophysiology of the catfish (genera Ictalurus and Ameiurus) olfactory organs, behavioural experiments that investigated olfactory discrimination of amino acid mixtures were carried out on the black bullhead Ameiurus melas. Repeated presentations of food-rewarded mixtures released increased swimming activity measured by counting the number of turns >90° within 90 s of stimulus addition. Non-rewarded amino acids and their mixtures released little swimming activity, indicating that A. melas discriminated between the conditioned and the non-conditioned stimuli. Two questions of mixture discrimination were addressed: (1) Are A. melas able to detect components within simple and complex amino acid mixtures? (2) What are the smallest differences between two complex mixtures that A. melas can detect? Three and 13 component mixtures tested were composed primarily of equipotent amino acids [determined by equal electroolfactogram (EOG) amplitude] that contained L-Cys at ×100 the equipotent concentration. Ameiurus melas initially perceived the ternary amino acid mixture as its more stimulatory component alone [i.e. cysteine (Cys)], whereas the conditioned 13 component mixture containing the more stimulatory L-Cys was perceived immediately as different from L-Cys alone. The results indicate that components of ternary mixtures are detectable by A. melas but not those of more complex mixtures. To test for the smallest detectable differences in composition between similar multimixtures, all mixture components were equipotent. Initially, A. melas were unable to discriminate the mixtures of six amino acids from the conditioned mixtures of seven amino acids, whereas they discriminated immediately the mixtures of four and five amino acids from the conditioned mixture. Experience with dissimilar mixtures enabled the A. melas to start discriminating the seven-component conditioned mixture from its six-component counterparts. After fewer than five training trials, A. melas discriminated the mixtures of nine and 10 amino acids from a conditioned mixture of 12 equipotent amino acids; however, irrespective of the number of training trials, A. melas were unable to discriminate the 12 component mixture from its 11 component counterparts. PMID:21722109

Valentincic, T; Miklavc, P; Kralj, S; Zgonik, V

2011-07-01

243

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

244

PREDICTION OF THE SOLUBILITY OF HYDROPHOBIC COMPOUNDS IN NONIDEAL SOLVENT MIXTURES  

EPA Science Inventory

The solubility of hydrophobic organic chemicals (HOCs) in partially-miscible solvent mixtures was investigated. In agreement with previous findings, it was observed that there is a limited domain in which nonideality effects are important; appreciable concentrations of partially-...

245

PREDICTION OF THE SOLUBILITY OF HYDROPHOBIC COMPOUNDS IN NONIDEAL SOLVENT MIXTURES  

EPA Science Inventory

The solubility of hydrophobic organic chemicals (HOCs) in partially-miscible solvent mixtures was investigated. In agreement with previous findings, it was observed that there is a limited domain in which nonideality effects are important; appreciable concentrations of partially ...

246

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

247

Mixture Modeling by Affinity Propagation  

Microsoft Academic Search

Clustering is a fundamental problem in machine learning and has been approached in many ways. Two general and quite different approaches include iteratively fitting a mixture model ( e.g., using EM) and linking to- gether pairs of training cases that have high affinity ( e.g., using spectral methods). Pair-wise clustering algorithms need not compute sufficient statistics and avoid poor solutions

Brendan J. Frey; Delbert Dueck

2005-01-01

248

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

249

Easy Computatioll of Bayes Factors arid Normalizing Constants for Mixture Models via Mixture Importance  

E-print Network

Easy Computatioll of Bayes Factors arid Normalizing Constants for Mixture Models via Mixture Computation of Bayes Factors and Normalizing Constants for Mixture ~1odels via Mixture Importance Sampling a method for approximating integrated likelihoods, or posterior normalizing constants, in finite mixture

Washington at Seattle, University of

250

Morphological robustness in polythiophene/fullerene mixtures  

NASA Astrophysics Data System (ADS)

The morphology of the photoactive layer of organic solar cells evolves differently under different processing conditions such as annealing temperature, annealing time and casting solvent. Hence, characterizing it is crucial in understanding its effect on device performance. In our study, we used Grazing Incidence Small Angle X-ray Scattering (GISAXS) and Energy-Filtered Transmission Electron Microscopy (EFTEM) to characterize the in-plane morphology of poly(3-hexylthiophene-2,5-diyl) (P3HT)/[6,6]-phenyl-C61-butyric acid methyl ester (PCBM) mixtures. We found that the characteristic length scale determined through GISAXS did not vary significantly for different processing conditions thus making P3HT/PCBM a robust system. For example, different spin-casting solvents did not significantly affect lateral phase separation, and consequently, device performance was similar once thickness effects are accounted for.

Vajjala Kesava, Sameer; Kozub, Derek; Wang, Cheng; Hexemer, Alexander; Gomez, Enrique

2012-02-01

251

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

2009-10-30

252

International issues on human health effects of exposure to chemical mixtures.  

PubMed Central

In this article, we highlight new developments and recent studies concerning adverse human health effects related to chemical mixtures. One group of activities comprises the development of a new computer program for analyzing mixture studies and a mathematical model as a basis for combination rules that predict the toxicity of mixtures. Other new activities in the area of experimental studies are the application of gene expression technologies in mixture research, and pattern recognition as a tool in safety evaluation of complex mixtures. A "bottom-up" approach for chemosensory detection of mixtures has recently been presented. Other topics include a method for the safety evaluation of natural flavoring complexes, and an evaluation of the possible health effects of the simultaneous intake of food additives. Examples of issues related to mixtures of airborne chemicals are potential interaction of fine particles and gaseous pollutants in ambient air, nasal cancer associated with inhaled chemical mixtures, and the recommendation of a limit value for volatile organic compounds. Topics of a more strategic nature include studies concerning the public health effects of large airports, and the development of criteria for a harmonized classification of chemical mixtures. This overview illustrates that strategies to tackle the safety evaluation of combined exposures and complex mixtures as well as models facilitating the interpretation of findings in the context of risk assessment of mixtures have become increasingly important. It is true that exposure of humans to chemical mixtures is the rule rather than the exception, and therefore health risk assessments should focus on mixtures and not on single chemicals. It is also true, however, that humans have learned to cope with exposure to huge numbers of chemicals simultaneously (food, water, air, soil, and consumer products). Therefore, in view of limited resources for toxicological research, the focus in toxicology should be on priority mixtures--priority being determined by (estimated) health risk (= toxicity and exposure). PMID:12634116

Feron, Victor J; Cassee, Flemming R; Groten, John P; van Vliet, Petronella W; van Zorge, Job A

2002-01-01

253

General theory of mixture procedures for gatekeeping.  

PubMed

The paper introduces a general approach to constructing mixture-based gatekeeping procedures in multiplicity problems with two or more families of hypotheses. Mixture procedures serve as extensions of and overcome limitations of some previous gatekeeping approaches such as parallel gatekeeping and tree-structured gatekeeping. This paper offers a general theory of mixture procedures constructed from nonparametric (p-value based) to parametric (normal theory based) procedures and studies their properties. It is also shown that the mixture procedure for parallel gatekeeping is equivalent to the multistage gatekeeping procedure. A clinical trial example is used to illustrate the mixture approach and the implementation of mixture procedures. PMID:23423821

Dmitrienko, Alex; Tamhane, Ajit C

2013-05-01

254

Consensus sediment quality guidelines for polycyclic aromatic hydrocarbon mixtures  

SciTech Connect

Sediment quality guidelines (SQGs) for polycyclic aromatic hydrocarbons (PAHs) have been derived from a variety of laboratory, field, and theoretical foundations. They include the screening level concentration, effects ranges-low and -median, equilibrium partitioning concentrations, apparent effects threshold, {Sigma}PAH model, and threshold and probable effects levels. The resolution of controversial differences among the PAH SQGs lies in an understanding of the effects of mixtures. Polycyclic aromatic hydrocarbons virtually always occur in field-collected sediment as a complex mixture of covarying compounds. When expressed as a mixture concentration, that is, total PAH (TPAH), the guidelines form three clusters that were intended in their original derivations to represent threshold (TEC = 290 {micro}g/g organic carbon [OC]), median (MEC = 1,800 {micro}g/g OC), and extreme (EEC = 10,000 {micro}g/g OC) effects concentrations. The TEC/MEC/EEC consensus guidelines provide a unifying synthesis of other SQGs, reflect causal rather than correlative effects, account for mixtures, and predict sediment toxicity and benthic community perturbations at sites of PAH contamination. The TEC offers the most useful SQG because PAH mixtures are unlikely to cause adverse effects on benthic ecosystems below the TEC.

Swartz, R.C. [Environmental Protection Agency, Newport, OR (United States)

1999-04-01

255

Supercritical extraction of organic mixtures from soil-water slurries  

E-print Network

society to enact and conform to environmental remediation legislation. The United States Superfund, a result of the Comprehensive Environmental Response, Compensation, and Liability Act of 1980 (CERCLA), and the Superfund Amendments and Reauthorization... Act of 1986 (SARA), allows for the identification, evaluation, and restoration of abandoned or uncontrolled hazardous waste sites. Currently, there are more than 1, 200 Superfund sites on the National Priorities List (NPL). In response to SARA...

Green, Lynda Ann

2012-06-07

256

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...

257

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

258

Generalized Beta Mixtures of Gaussians  

PubMed Central

In recent years, a rich variety of shrinkage priors have been proposed that have great promise in addressing massive regression problems. In general, these new priors can be expressed as scale mixtures of normals, but have more complex forms and better properties than traditional Cauchy and double exponential priors. We first propose a new class of normal scale mixtures through a novel generalized beta distribution that encompasses many interesting priors as special cases. This encompassing framework should prove useful in comparing competing priors, considering properties and revealing close connections. We then develop a class of variational Bayes approximations through the new hierarchy presented that will scale more efficiently to the types of truly massive data sets that are now encountered routinely.

Armagan, Artin; Dunson, David B.; Clyde, Merlise

2012-01-01

259

MULTIVARIATE KERNEL PARTITION PROCESS MIXTURES  

PubMed Central

Mixtures provide a useful approach for relaxing parametric assumptions. Discrete mixture models induce clusters, typically with the same cluster allocation for each parameter in multivariate cases. As a more flexible approach that facilitates sparse nonparametric modeling of multivariate random effects distributions, this article proposes a kernel partition process (KPP) in which the cluster allocation varies for different parameters. The KPP is shown to be the driving measure for a multivariate ordered Chinese restaurant process that induces a highly-flexible dependence structure in local clustering. This structure allows the relative locations of the random effects to inform the clustering process, with spatially-proximal random effects likely to be assigned the same cluster index. An exact block Gibbs sampler is developed for posterior computation, avoiding truncation of the infinite measure. The methods are applied to hormone curve data, and a dependent KPP is proposed for classification from functional predictors. PMID:24478563

Dunson, David B.

2013-01-01

260

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

261

Effective permittivity of dielectric mixtures  

NASA Technical Reports Server (NTRS)

General mixing formulas are derived for discrete scatterers immersed in a host medium. The inclusion particles are assumed to be ellipsoidal. The electric field inside the scatterers is determined by quasi-static analysis, assuming the diameter of the inclusion particles to be much smaller than one wavelength. The results are applicable to general multiphase mixtures, and the scattering ellipsoids of the different phases can have different sizes and arbitrary ellipticity distribution and axis orientation, i.e., the mixture may be isotropic or anisotropic. The resulting mixing formula is nonlinear and is suitable for iterative solutions. The formula contains a quantity called the apparent permittivity, and with different choices of this quantity, the result leads to the generalized Lorentz-Lorenz formula, the generalized Polder-van Santen formula, and the generalized coherent potential-quasicrystalline approximation formula. The results are applied to calculating the complex effective permittivity of dry and wet snow, and sea ice.

Sihvola, Ari H.; Kong, Jin AU

1988-01-01

262

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...

263

Improved Stability of Solid Mixture Nanoparticles  

E-print Network

Engineering #12;Flash Nanoprecipitation Hydrophobic regions simultaneously precipitate to form nanoparticles nanoprecipitation to form a stabilized hydrophobic mixture by co-precipitating Hydrophobic Active Hydrophobic Inert Flash Nanoprecipitation Hydrophobic active Hydrophobic Inert Block copolymer Mixture Nanoparticles

Petta, Jason

264

Perfluoroolefin and perfluoroparaffin mixture and process for making same  

SciTech Connect

Straight chain perfluoroolefins compounds of medium length with terminal or double bonds and a minor proportion of trifluoromethyl side chains or mixtures of such perfluoroolefins with perfluoro paraffins of equal chain length and corresponding structure, the perfluoroolefins being present in the mixture in an amount of 40 to 70% are prepared. The compounds are valuable as highly reactive intermediate products in the production of surface active agents. The compounds are made by subjecting a highly fluorinated organic compound to degradation by means of a high energy radiation of a density of 0.3 to 3.0 w/cm2 effected in a radiation chamber which has been subjected to a preceding rinsing with an inert gas or with a monomeric highly fluorinated organic compound.

Dietrich, P.; Engler, G.; Ferse, A.; Grimm, H.; Gross, U.; Handte, D.; Lunkwitz, K.; Muller, U.; Prescher, D.; Schulze, J.

1980-09-30

265

Organic Vegetable Organic Vegetable  

E-print Network

- tem that promotes biodiversity, biological cycles, and soil biological activity. Organic production .......................................................3 Soil Fertility ......................................................3 Seeds and Transplants .....................................................19 Organic Web sites ...........................................19 Soil Fertility Publications

266

Optimal Mixture Models in IR Victor Lavrenko  

E-print Network

Optimal Mixture Models in IR Victor Lavrenko Center for Intelligent Information Retrieval. We explore the use of Optimal Mixture Models to represent topics. We analyze two broad classes of mixture models: set-based and weighted. We provide an original proof that estimation of set-based models

Edinburgh, University of

267

Tutorial on mixture models (2) Christian Hennig  

E-print Network

Tutorial on mixture models (2) Christian Hennig September 2, 2009 Christian Hennig Tutorial on mixture models (2) #12;1 Overview Cluster validation, robustness and stability Potential problems with mixture model-based clustering Outliers Non-normality Instability Interpretation vs. model

Hennig, Christian

268

Simplifying Mixture Models Using the Unscented Transform  

E-print Network

Simplifying Mixture Models Using the Unscented Transform Jacob Goldberger, Hayit Greenspan, and Jeremie Dreyfuss Abstract--Mixture of Gaussians (MoG) model is a useful tool in statistical learning. In many learning processes that are based on mixture models, computational requirements are very demanding

Goldberger, Jacob

269

Negative Binomial Process Count and Mixture Modeling  

E-print Network

1 Negative Binomial Process Count and Mixture Modeling Mingyuan Zhou and Lawrence Carin Abstract The seemingly disjoint problems of count and mixture modeling are united under the negative binomial (NB process, gamma process, hierarchical Dirichlet process, mixed membership modeling, mixture modeling

Carin, Lawrence

270

Multinomial Mixture Modelling for Bilingual Text Classification  

E-print Network

Multinomial Mixture Modelling for Bilingual Text Classification Jorge Civera and Alfons Juan`encia, Spain {jcivera,ajuan}@dsic.upv.es Abstract. Mixture modelling of class-conditional densities-conditional multinomial mixtures can be seen as a generalisation of the Naive Bayes text clas- sifier relaxing its (class

Juan, Alfons

271

Multisensor Multitarget Mixture Reduction Algorithms for Tracking  

E-print Network

Multisensor Multitarget Mixture Reduction Algorithms for Tracking Lucy Y. Pao Signal Processing Department The MITRE Corporation Bedford, Massachusetts 01730 Abstract A single�sensor single�target Mixture In the problem of tracking targets in random clutter, the optimal Bayesian solution leads to Gaussian mixture

Pao, Lucy Y.

272

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

273

MIXTURES IN CONCRETE Technical Report Documentation Page  

E-print Network

-- portland cement -- silica fume -- slag -- ternary mixtures 19. Security Classification (of this report) 20The Use of TERNARY MIXTURES IN CONCRETE May 2014 #12;#12;Technical Report Documentation Page 1. Title and Subtitle 5. Report Date The Use of Ternary Mixtures in Concrete May 2014 6. Performing

274

Toxicity of four antifouling biocides and their mixtures on the brine shrimp Artemia salina.  

PubMed

Zinc pyrithione (ZPT), Copper pyrihione (CPT), Chlorothalonil and Diuron are four of the most widely used as alternative to tributlytin (TBT) antifouling biocides in boat paints. As most previous laboratory bioassays for these biocides have been conducted solely based on acute tests with a single compound, information on the possible combined toxicity of these common biocides to marine organisms are limited. In this study, the toxicity of binary (in several proportions), ternary and quaternary mixtures were evaluated using the brine shrimp Artemia salina as test organism. Mixture toxicities were studied using the concentration addition model (isobolograms and toxic unit summation), and the mixture toxicity index (MTI). The ZPT-CPT combination had a strictly synergistic effect which requires attention because the coexistence of ZPT and CPT in the marine environment, due to transchelation of ZPT, may occur. The binary mixtures of Diuron with the metal pyrithiones exhibited various interactive effects (synergistic, antagonistic or additive) depending on concentration ratios, whereas all binary mixtures that contained Chlorothalonil exhibited antagonistic effects. The different types of combined effects subsequent to proportion variation of binary mixtures underline the importance of the combined toxicity characterization for various ratios of concentrations. The four ternary mixtures tested, also exhibited various interactive effects, and the quaternary mixture exhibited synergism. The models applied were in agreement in most cases. The observed synergistic interactions underline the requirement to review water quality guidelines, which are likely underestimating the adverse combined effects of these chemicals. PMID:17765949

Koutsaftis, A; Aoyama, I

2007-11-15

275

BBC Bitesize: Compounds and Mixtures  

NSDL National Science Digital Library

This animated tutorial for grades 6-9, published by the British Broadcasting Corporation, explores the molecular basis of compounds and mixtures. It is written in "bite-size" pieces so that adolescent learners can grasp the concepts more easily and connect information with prior knowledge. Each page is supplemented with audio narration and illustrations. Learners will try to fuse or separate elements, giving them insight into the bonding process without introducing advanced vocabulary. They will also view animations of filtration and evaporation. The tutorial ends with a brief quiz that allows students to self-test their understanding.

Bitesize, General C.

2011-06-27

276

BBR Asphalt mixture creep test BBR Asphalt mixture creep size effect  

E-print Network

#12;Outline Ã?BBR Asphalt mixture creep test Ã?BBR Asphalt mixture creep size effect Ã?BBR Asphalt mixture strength test Ã?BBR Asphalt binder strength test #12;Asphalt Pavements Ã?Recent efforts under NCHRP Idea funding to explore the possibility of testing small asphalt mixture specimens at low temperatures

Minnesota, University of

277

SAR IMAGES AS MIXTURES OF GAUSSIAN MIXTURES Peter Orbanz and Joachim M. Buhmann  

E-print Network

by a parametric mixture model. For a grayscale input image, we extract local histograms from the image histograms with parametric mixture-of-mixture models. These models represent each cluster by a single mixture model of simple parametric components, typically truncated Gaussians. Clustering requires unsupervised

Columbia University

278

Accelerated Hazards Mixture Cure Model  

PubMed Central

We propose a new cure model for survival data with a surviving or cure fraction. The new model is a mixture cure model where the covariate effects on the proportion of cure and the distribution of the failure time of uncured patients are separately modeled. Unlike the existing mixture cure models, the new model allows covariate effects on the failure time distribution of uncured patients to be negligible at time zero and to increase as time goes by. Such a model is particularly useful in some cancer treatments when the treat effect increases gradually from zero, and the existing models usually cannot handle this situation properly. We develop a rank based semiparametric estimation method to obtain the maximum likelihood estimates of the parameters in the model. We compare it with existing models and methods via a simulation study, and apply the model to a breast cancer data set. The numerical studies show that the new model provides a useful addition to the cure model literature. PMID:19697127

Zhang, Jiajia; Peng, Yingwei

2010-01-01

279

Boiling of multicomponent liquid mixtures  

SciTech Connect

This article reviews the significant advances in the understanding of the boiling process germane to mixtures. The scope of this review is limited to miscible systems. The effects of impurities (such as lubricating oils in refrigerants), surfactants, soluble salts, and dissolved gases are excluded from consideration. Both pool and convective boiling are addressed. The ultimate goals of the study of boiling of liquid mixtures are: to predict the superheat required for the inception of boiling, to predict their heat transfer coefficients with a reasonable degree of accuracy, and to predict the variation in the peak nucleate and dry out heat fluxes with composition. These goals are closer to being met for pool boiling than they are for convective boiling. The topics discussed in this survey are presented in much the same order as when an increasing heat flux is applied to a surface to cause boiling. Thus bubble nucleation or boiling incipience is considered first, since this defines the criteria required for boiling to commence. Then the growth of the vapor bubbles from vapor nuclei up to and including their departure from the surface is discussed. This is followed by a survey of the heat transfer mechanisms, resulting from the vaporization process, which affect the nucleate pool boiling curve, and this leads to a discussion of equations for predicting nucleate pool boiling heat transfer coefficients. The peak nucleate heat flux in pool boiling is examined prior to a description of film boiling. Several aspects of convective boiling are then presented.

Thome, J.R.; Shock, R.A.W.

1984-01-01

280

Oscillatory convection in binary mixtures  

NASA Astrophysics Data System (ADS)

Two-dimensional oscillatory convection in a binary fluid mixture in an infinite plane porous layer heated from below is studied. Small-amplitude nonlinear solutions in the form of standing and traveling waves are found and their relative stability is established. Stable traveling waves are preferred near onset. The interaction of the two types of wave with steady overturning convection is also studied. As the Rayleigh number is increased the period of each type of wave approaches infinity, standing waves as -ln(RSW-Rc) and traveling waves as 1/(RTW-Rc), where Rc is the critical Rayleigh number at which the transition to finite amplitude overturning convection occurs. This transition is hysteretic. The presence of modulated traveling waves (i.e., waves with two distinct frequencies) is also predicted. These predictions are made on the basis of analyses of multiple bifurcations in the presence of O(2) symmetry. This symmetry is present in two-dimensional problems with periodic boundary conditions and a reflection symmetry in a vertical plane. The relevance of the results to recent experiments on binary fluids, both in bulk mixtures and in a porous medium, is discussed.

Knobloch, E.

1986-08-01

281

Purification of metal-organic framework materials  

DOEpatents

A method of purification of a solid mixture of a metal-organic framework (MOF) material and an unwanted second material by disposing the solid mixture in a liquid separation medium having a density that lies between those of the wanted MOF material and the unwanted material, whereby the solid mixture separates by density differences into a fraction of wanted MOF material and another fraction of unwanted material.

Farha, Omar K.; Hupp, Joseph T.

2012-12-04

282

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

283

The Analysis of Ethnic Mixtures  

PubMed Central

Populations of ethnic mixtures can be useful in genetic studies. Admixture mapping, or mapping by admixture linkage disequilibrium (MALD), is specially developed for admixed populations and can supplement traditional genome-wide association analyses in the search for genetic variants underlying complex traits. Admixture mapping tests the association between a trait and locus-specific ancestries. The locus-specific ancestries are in linkage disequilibrium (LD) which is generated by the admixture process between genetically distinct ancestral populations. Because of highly correlated locus-specific ancestries, admixture mapping performs many fewer independent tests across the genome than current genome-wide association analysis. Therefore, admixture mapping can be more powerful because of the smaller penalty due to multiple tests. In this chapter, I introduce the theory behind admixture mapping and how we conduct the analysis in practice. PMID:22307714

Zhu, Xiaofeng

2013-01-01

284

[Development of methodical approaches to determination of nitrates and nitrites in multicomponent salting mixtures used in meat product industry].  

PubMed

A unified photometric method for determination of nitrates and nitrites in multicomponent salting mixtures containing sodium nitrate and nitrite, chlorides, phosphates, polyphosphates, ascorbic acid, or ascorbates, antioxidants, organic acids, vegetative and animal proteins, carbohydrates is proposed. With use of the developed method, content of nitrates and nitrites in a number of salting mixtures meat production was estimated. PMID:10509455

Zhukova, G F; Torskaia, M S; Liubchenko, V I; Rodin, V I; Khotimchenko, S A

1999-01-01

285

Separating Mixtures: How We Concentrate Natural Materials  

NSDL National Science Digital Library

This activity involves separating mixtures of minerals on the basis of their physical properties. Students are shown a piece of granite and see that it is clearly a mixture. Students will try to devise ways of separating some simple mixtures and then see how some of the same methods are used to separate real minerals from mixtures. Students will discover that many useful materials are found as part of mixtures. For example, salt is found in underground deposits mixed with sand and clay. The mixture is called rock salt. Minerals are chemicals found naturally in the Earth and many of them are very useful. To get at the useful minerals, we usually have to separate them from less-useful material which are often called gangue (pronounced gang) by miners.

286

Atomically detailed models of gas mixture diffusion through CuBTC membranes  

Microsoft Academic Search

Metal–organic frameworks are intriguing crystalline nanoporous materials that have potential applications in adsorption-based and membrane-based gas separations. We describe atomically detailed simulations of gas adsorption and diffusion in CuBTC that have been used to predict the performance of CuBTC membranes for separation of H2\\/CH4, CO2\\/CH4 and CO2\\/H2 mixtures. CuBTC membranes are predicted to have higher selectivities for all three mixtures

Seda Keskin; Jinchen Liu; J. Karl Johnson; David S. Sholl

2009-01-01

287

Nucleation kinetics of emulsified triglyceride mixtures  

Microsoft Academic Search

The purpose of this study is to determine character istic nucleation parameters such as the surface free energy for nucleus\\u000a formation in mixtures of fully hydrogenated palm oil (HP) in sunflower oil (SF). These parameters will be used to model the\\u000a bulk crystallization kinetics of the same mixtures. This was achieved by determining the crystallization kinetics in emulsified\\u000a triglyceride mixtures

William Kloek; Pieter Walstra; Ton van Vliet

2000-01-01

288

Thiopentone and propofol: a compatible mixture?  

PubMed

The physical compatibility of thiopentone and propofol mixtures was investigated. The investigations used were macroscopic and microscopic observations, zeta potential and oil droplet size measurements. There was no evidence of instability in the mixtures. The thiopentone-propofol mixture has the potential advantage of reducing the pain on injection, provides synergistic interaction, does not prolong recovery when used for induction of anaesthesia, may reduce the incidence of convulsions and is cost-effective. PMID:9699097

Paw, H G; Garrood, M; Fillery-Travis, A J; Rich, G T

1998-07-01

289

Gas-Mixture Cryocoolers Optimization: Theory & Experiment  

Microsoft Academic Search

The use gas mixture cryocoolers can be widely applied in spacecraft under 300-20K. The advantages of such mixtures are three-fold: (1) High reliability, (2) low noise level, and (3) application over the temperature range. Until recently the range we are addressing has been validated only theoretically. The results are based on calculations of gas-mixture properties and counter-flow heat exchangers. We

V. T. Arkhipov; V. F. Getmanets; Yu. I. Gorpinko; O. V. Yevdokimova; V. V. Yakuba; M. P. Lobko; H. Stears

1999-01-01

290

SOLVENT EXTRACTION OF ORGANIC WATER POLLUTANTS  

EPA Science Inventory

Based on experiments with model systems of known organic water pollutants and environmental samples, conclusions are reached concerning the best general solvent for extraction and the most appropriate methods for related manipulations. Chloroform, methylene chloride-ether mixture...

291

Automatic NMR-based identification of chemical reaction types in mixtures of co-occurring reactions.  

PubMed

The combination of chemoinformatics approaches with NMR techniques and the increasing availability of data allow the resolution of problems far beyond the original application of NMR in structure elucidation/verification. The diversity of applications can range from process monitoring, metabolic profiling, authentication of products, to quality control. An application related to the automatic analysis of complex mixtures concerns mixtures of chemical reactions. We encoded mixtures of chemical reactions with the difference between the (1)H NMR spectra of the products and the reactants. All the signals arising from all the reactants of the co-occurring reactions were taken together (a simulated spectrum of the mixture of reactants) and the same was done for products. The difference spectrum is taken as the representation of the mixture of chemical reactions. A data set of 181 chemical reactions was used, each reaction manually assigned to one of 6 types. From this dataset, we simulated mixtures where two reactions of different types would occur simultaneously. Automatic learning methods were trained to classify the reactions occurring in a mixture from the (1)H NMR-based descriptor of the mixture. Unsupervised learning methods (self-organizing maps) produced a reasonable clustering of the mixtures by reaction type, and allowed the correct classification of 80% and 63% of the mixtures in two independent test sets of different similarity to the training set. With random forests (RF), the percentage of correct classifications was increased to 99% and 80% for the same test sets. The RF probability associated to the predictions yielded a robust indication of their reliability. This study demonstrates the possibility of applying machine learning methods to automatically identify types of co-occurring chemical reactions from NMR data. Using no explicit structural information about the reactions participants, reaction elucidation is performed without structure elucidation of the molecules in the mixtures. PMID:24551112

Latino, Diogo A R S; Aires-de-Sousa, João

2014-01-01

292

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

293

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 assessment: (1) additive joint toxic action of mixture components; (2) toxicological interactions of mixture components; and (3) chemical composition of complex mixtures. It is proposed that scientific support for basic assumptions used in chemical mixtures risk assessment should be developed by expert panels, risk assessment methods experts, and laboratory toxicologists. This is imperative to further develop and refine quantitative methods and provide guidance on their appropriate applications. Risk assessors need scientific support for chemical mixtures risk assessment methods in the form of toxicological data on joint toxic action for high priority mixtures, statistical methods for analyzing dose-response for mixtures, and toxicological and statistical criteria for determining sufficient similarity of complex mixtures.

Teuschler, Linda K. [U.S. Environmental Protection Agency, Office of Research and Development, National Center for Environmental Assessment, 26 W. Martin Luther King Dr. (MS-A110), Cincinnati, OH 45268 (United States)], E-mail: teuschler.linda@epa.gov

2007-09-01

294

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

295

Surface and Interfacial Properties of Nonaqueous-Phase Liquid Mixtures Released to the Subsurface at the Hanford Site  

SciTech Connect

Surface and interfacial tensions that arise at the interface between different phases are key parameters affecting Nonaqueous Phase Liquid (NAPL) movement and redistribution in the vadose zone after spill events. In this study, the impact of major additive components on surface and interfacial tensions for organic mixtures and wastewater was investigated. Organic mixture and wastewater compositions are based upon carbon tetrachloride (CT) mixtures released at the Hanford site, where CT was discharged simultaneously with dibutyl butyl phosphonate (DBBP), tributyl phosphate (TBP), dibutyl phosphate (DBP), and a machining lard oil (LO). A considerable amount of wastewater consisting primarily of nitrates and metal salts was also discharged. The tension values measured in this study revealed that the addition of these additive components caused a significant lowering of the interfacial tension with water or wastewater and the surface tension of the wastewater phase in equilibrium with the organic mixtures, compared to pure CT, but had minimal effect on the surface tension of the NAPL itself. These results lead to large differences in spreading coefficients for several mixtures, where the additives caused both a higher (more spreading) initial spreading coefficient and a lower (less spreading) equilibrium spreading coefficient. This indicates that if these mixtures migrate into uncontaminated areas, they will tend to spread quickly, but form a higher residual NAPL saturation after equilibrium, as compared to pure CT. Over time, CT likely volatilizes more rapidly than other components in the originally disposed mixtures and the lard oil and phosphates would become more concentrated in the remaining NAPL, resulting in a lower interfacial tension for the mixture. Spreading coefficients are expected to increase and perhaps change the equilibrated organic mixtures from nonspreading to spreading in water-wetting porous media. These results show that the behavior of organic chemical mixtures should be accounted for in numerical flow and transport models.

Nellis, Scott; Yoon, Hongkyu; Werth, Charlie; Oostrom, Martinus; Valocchi, Albert J.

2009-05-01

296

The Potential of Growth Mixture Modelling  

ERIC Educational Resources Information Center

The authors of the paper on growth mixture modelling (GMM) give a description of GMM and related techniques as applied to antisocial behaviour. They bring up the important issue of choice of model within the general framework of mixture modelling, especially the choice between latent class growth analysis (LCGA) techniques developed by Nagin and…

Muthen, Bengt

2006-01-01

297

PATTERN CLUSTERING BY MULTIVARIATE MIXTURE ANALYSIS  

Microsoft Academic Search

Cluster analysis is reformulated as a problem of estimating the para- meters of a mixture of multivariate distributions. The maximum-likelihood theory and numerical solution techniques are developed for a fairly general class of distributions. The theory is applied to mixtures of multivariate nor- mals (\\

JOHN H. WOLFE

1970-01-01

298

Separation of gas mixtures by centrifugation  

NASA Technical Reports Server (NTRS)

Magnetohydrodynamic (MHD) centrifuge utilizing electric currents and magnetic fields produces a magnetic force which develops supersonic rotational velocities in gas mixtures. Device is superior to ordinary centrifuges because rotation of gas mixture is produced by MHD force rather than mechanical means.

Park, C.; Love, W. L.

1972-01-01

299

Effective thermal conductivity estimates of particulate mixtures  

Microsoft Academic Search

Several theories have been advanced to estimate effective thermal conductivities of particulate mixtures, but most theories have focused on the dilute case. A method is proposed to estimate the effective thermal conductivity coefficient of mixtures of arbitrary concentration. Earlier the authors developed a theory to determine the expected contact area between different species. This theory is employed to determine the

Christiaan Richter; Hendrik J. Viljoen; N. F. J. van Rensburg

2003-01-01

300

Energy deposition in a gaseous mixture  

Microsoft Academic Search

Existing models in planetary aeronomy involve a variety of possible gaseous mixtures subjected to charged particle bombardment. In the present paper, a phenomenological approach to electron degradation in such mixtures is proposed to facilitate analysis of such problems. Existing parameterized yield spectra for a variety of gases, computed by a discrete energy bin method, are used as a basis for

L. R. Peterson; R. H. Garvey; A. E. S. Green

1978-01-01

301

Energy Deposition in a Gaseous Mixture  

Microsoft Academic Search

Current models proposed in planetary aeronomy involve a large variety of possible gaseous mixtures which are subjected to charged particle bombardment. To facilitate the analysis of such problems, we propose a phenomenological approach to electron degradation in gaseous mixtures that is a natural outgrowth of recent studies of yield spectra in pure gases. Existing parameterized yield spectra for a variety

L. R. Peterson; R. H. Garvey; A. E. S. Green

1978-01-01

302

RENAL CANCER STUDIES OF DRINKING WATER MIXTURES  

EPA Science Inventory

Current default risk assessments for chemical mixtures assume additivity of carcinogenic effects but this may under or over represent the actual biological response. A rodent model of hereditary renal cancer (Eker rat) was used to evaluate the carcinogenicity of a mixture of DBPs...

303

Variational inference for Dirichlet process mixtures  

Microsoft Academic Search

Dirichlet process (DP) mixture models are the cornerstone of nonpara- metric Bayesian statistics, and the development of Monte-Carlo Markov chain (MCMC) sampling methods for DP mixtures has enabled their applications to a variety of practical data analysis problems. However, MCMC sampling can be prohibitively slow, and it is important to explore alternatives. One class of alternatives is provided by variational

David M. Blei; Michael I. Jordan

2005-01-01

304

Modified asphalt mixtures resistance to permanent deformations  

Microsoft Academic Search

Permanent deformations, primarily in the form of ruts, are one of the basic asphalt pavement damages impairing its service properties. Application of appropriate asphalt mixtures and binder modification are effective methods for improving asphalt courses resistance. While being manufactured, stored, fitted into a road pavement and during long term service, bitumen binders and asphalt mixtures are subject to continuous unfavourable

Piotr Radziszewski

2007-01-01

305

Gas mixtures for spark gap closing switches  

DOEpatents

Gas mixtures for use in spark gap closing switches comprised of fluorocarbons and low molecular weight, inert buffer gases. To this can be added a third gas having a low ionization potential relative to the buffer gas. The gas mixtures presented possess properties that optimized the efficiency spark gap closing switches. 6 figs.

Christophorou, L.G.; McCorkle, D.L.; Hunter, S.R.

1987-02-20

306

Probabilistic expert systems for DNA mixture profiling  

Microsoft Academic Search

We show how probabilistic expert systems can be used to structure and solve complex cases of forensic identification involving DNA traces that might be mixtures of several DNA profiles. In particular, this approach can readily handle cases where the number of contributors to the mixture cannot be regarded as known in advance. The flexible modularity of the networks used also

J. Mortera; A. P. Dawid; S. L. Lauritzen

2003-01-01

307

Can the joint effect of ternary mixtures be predicted from binary mixture toxicity results?  

PubMed

The joint effect of the majority of chemical mixtures can be predicted using the reference model of Concentration Addition (CA). It becomes a challenge, however, when the mixtures include chemicals that synergise or antagonise the effect of each other. In this study we examine if the deviation from CA of seven ternary mixtures of interacting chemicals can be predicted from knowledge of the binary mixture responses involved. We hypothesise that the strongest interactions will take place in the binary mixtures and that the size of the ternary mixture response can be predicted from knowledge of the binary interactions. The hypotheses were tested using a stepwise modelling approach of incorporating the information held in binary mixtures into a ternary mixture model, and comparing the model predictions with observed ternary mixture toxicity data derived from studies of interacting chemical mixtures on the floating plant Lemna minor and the bacteria Vibrio fischeri. The results showed that for both the antagonistic and the synergistic ternary mixtures the ternary model predictions were superior to the conventional CA reference model and provided robust estimations of the size of the experimentally derived ternary mixture toxicity effects. PMID:22542295

Cedergreen, Nina; Sørensen, Helle; Svendsen, Claus

2012-06-15

308

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

309

DETERMINATION AND QUANTIFICATION OF NON-AQUEOUS PHASE LIQUID MIXTURES IN ENVIRONMENTAL MEDIA  

SciTech Connect

It is important to recognize the presence of Non-Aqueous Phase Liquids (NAPLs) in soils at a waste site in order to design and construct a successful remediation system. NAPLs often manifest as a complex, multi-component mixture of organic compounds that can occur in environmental media, such as vadose zone soil, where the mixture will partition and equilibrate with soil particles, pore vapor, and pore water. Complex organic mixtures can greatly complicate the determination and quantification of NAPL in soil due to inter-media transfer. NAPL thresholds can also change because of mixture physical properties and can disguise the presence of NAPL. A unique analytical method and copyrighted software have been developed at the Department of Energy's Savannah River Site that facilitates solution of this problem. The analytical method uses a classic chemistry approach and applies the principals of solubility limit theory, Raoult's Law, and equilibrium chemistry to derive an accurate estimation of NAPL presence and quantity. The method is unique because it calculates an exact result that is mass balanced for each physical state, chemical mixture component, and mixture characteristics. The method is also unique because the solution can be calculated on both a wet weight and dry weight basis--a factor which is often overlooked. The software includes physical parameters for 300 chemicals in a database that self-loads into the model to save time. The method accommodates up to 20 different chemicals in a multi-component mixture analysis. A robust data display is generated including important parameters of the components and mixture including: NAPL thresholds for individual chemical components within the mixture, mass distribution in soil for each physical state, molar fractions, density, vapor pressure, solubility, mass balance, media concentrations, residual saturation, and modest graphing capabilities. This method and software are power tools to simplify otherwise tedious calculations and eliminate guesswork for site characterizations.

Rucker, G

2006-09-22

310

Mixing - Simulating Mixture Problems with Beads  

NSDL National Science Digital Library

This activity, created by Arthur N. DiVito, Ph.D, simulates mixture problems by using red and white colored beads. Mixture A is 70% red, and mixture B is 40% red (as determined by weight). The students are asked to created a "solution" with a given weight whose concentration of red is between 40% and 70% using the above solutions. Students empirically verify the final "solution" has the proper percent of red beads by separating colors and weighing them separately. As the author mentions, many students have difficult with mixture problems because they don't understand percents well. This hands on activity gives a tangible representation of percents in addition to the overarching concepts needed to solve mixture problems.

2011-01-01

311

Environmental quality standards for mixtures: a case study with a herbicide mixture tested in outdoor mesocosms.  

PubMed

Traces of pesticides are frequently detected in surface waters. As a consequence, specific environmental quality criteria (EQS) for a set of single pesticides in surface waters were defined by the environmental authorities in several countries. In this context, the aim of this study was to investigate if the sum of the five percentile hazard concentration (?HC(5-95 percent), meaning that 5 percent of the aquatic assemblage remains affected considering a 95 percent confidence interval) of three herbicides with the same mode of action derived from a species sensitivity distribution based on acute toxicity data (EC(50) values) of the most sensitive taxonomic group is a suitable EQS for surface water addressing the occurrence of herbicide mixtures as common exposure scenario. Therefore, an outdoor mesocosm study was performed with three replicates per treatment for a period of 173 days. Results demonstrated that a constant long-term exposure over 35 days to the HC(5-95 percent) of a mixture of three PSII inhibitors did not lead to adverse effects on the aquatic community in this field mesocosm study. Neither adverse effects on very sensitive functional endpoints such as photosynthesis measurements of algae and macrophytes nor adverse effects on structural endpoints such as abundance data and species composition were determined. In contrast and as a positive control, the HC(30) treatment affected statistically significant all investigated endpoints and it was demonstrated that the PSII inhibitors acted additive on various level of organization (Knauert et al., 2008). This study is filling the gap that no empirical evidence is published indicating that the chronic exposure at the HC(5-95 percent) estimate is leading to no adverse effects for the aquatic community and is therefore a suitable EQS for surface waters in the agriculture landscape. PMID:23273621

Knauer, Katja; Hommen, Udo

2013-03-01

312

Organic synthesis in experimental impact shocks.  

PubMed

Laboratory simulations of shocks created with a high-energy laser demonstrate that the efficacy of organic production depends on the molecular, not just the elemental composition of the shocked gas. In a methane-rich mixture that simulates a low-temperature equilibrium mixture of cometary material, hydrogen cyanide and acetylene were produced with yields of 5 x 10(17) molecules per joule. Repeated shocking of the methane-rich mixture produced amine groups, suggesting the possible synthesis of amino acids. No organic molecules were produced in a carbon dioxide-rich mixture, which is at odds with thermodynamic equilibrium approaches to shock chemistry and has implications for the modeling of shock-produced organic molecules on early Earth. PMID:9103191

McKay, C P; Borucki, W J

1997-04-18

313

Solubility modeling of refrigerant/lubricant mixtures  

SciTech Connect

A general model for predicting the solubility properties of refrigerant/lubricant mixtures has been developed based on applicable theory for the excess Gibbs energy of non-ideal solutions. In our approach, flexible thermodynamic forms are chosen to describe the properties of both the gas and liquid phases of refrigerant/lubricant mixtures. After an extensive study of models for describing non-ideal liquid effects, the Wohl-suffix equations, which have been extensively utilized in the analysis of hydrocarbon mixtures, have been developed into a general form applicable to mixtures where one component is a POE lubricant. In the present study we have analyzed several POEs where structural and thermophysical property data were available. Data were also collected from several sources on the solubility of refrigerant/lubricant binary pairs. We have developed a computer code (NISC), based on the Wohl model, that predicts dew point or bubble point conditions over a wide range of composition and temperature. Our present analysis covers mixtures containing up to three refrigerant molecules and one lubricant. The present code can be used to analyze the properties of R-410a and R-407c in mixtures with a POE lubricant. Comparisons with other models, such as the Wilson or modified Wilson equations, indicate that the Wohl-suffix equations yield more reliable predictions for HFC/POE mixtures.

Michels, H.H.; Sienel, T.H.

1996-12-31

314

Reproducibility of binary-mixture toxicity studies.  

PubMed

Binary-mixture studies often are conducted with the aim of elucidating the effect of one specific chemical on the biological action of another. The results can be interpreted in relation to reference models by the use of response-surface analyses and isobolograms. The amount of data needed for these analyses is, however, extensive, and the experiments therefore rarely are repeated. In the present study, we investigate the reproducibility of isobole shapes of binary-mixture toxicity experiments in terms of deviation from the reference model of concentration addition (CA), dose-level dependence, and isobole asymmetry. We use data from four herbicide mixtures tested in three to five independent experiments on the aquatic test plant Lemna minor and the terrestrial plant Tripleurospermum inodorum. The results showed that the variation both within and among experiments was approximately half the size for the aquatic test system compared to the terrestrial system. As a consequence, a consistent deviation from CA could be obtained in three of four herbicide mixtures for L. minor, whereas this was only the case for one or two of the herbicide mixtures tested on T. inodorum. For one mixture on T. inodorum, both CA synergism and antagonism were detected. Dose-dependent effects could not be repeated consistently, just as the asymmetry found in some isoboles could not. The study emphasizes the importance of repeating mixture toxicity experiments, especially for test systems with large variability, and using caution when drawing biological conclusions from the test results. PMID:17269472

Cedergreen, Nina; Kudsk, Per; Mathiassen, Solvejg Kopp; Sørensen, Helle; Streibig, Jens Carl

2007-01-01

315

Genotoxicity of complex mixtures: CHO cell mutagenicity assay  

SciTech Connect

A Chinese hamster ovary (CHO) mammalian cell assay was used to evaluate the genotoxicity of complex mixtures (synthetic fuels). The genotoxicity (mutagenic potency) of the mixtures increased as the temperature of their boiling range increased. Most of the genotoxicity in the 750/sup 0/F+ boiling-range materials was associated with the neutral polycyclic aromatic hydrocarbon (PAH) fractions. Chemical analysis data indicate that the PAH fractions of high-boiling coal liquids contain a number of known chemical carcinogens, including five- and six-ring polyaromatics (e.g., benzo(a)pyrene) as well as four- and five-ring alkyl-substituted PAH (e.g., methylchrysene and dimethylbenzanthracenes); concentrations are a function of boiling point (bp). In vitro genotoxicity was also detected in fractions of nitrogen-containing polyaromatic compounds, as well as in those with aliphatics of hydroxy-containing PAH. Mutagenic activity of some fractions was detectable in the CHO assay in the absence of an exogenous metabolic activation system; in some instances, addition of exogenous enzymes and cofactors inhibited expression of the direct-acting mutagenic potential of the fraction. These data indicate that the organic matrix of the chemical fraction determines whether, and to what degree, various mutagens are expressed in the CHO assay. Therefore, the results of biological assays of these mixtures must be correlated with chemical analyses for proper interpretation of these data. 29 references, 16 figures, 4 tables.

Frazier, M.E.; Samuel, J.E.

1985-02-01

316

ICA MIXTURE MODELS FOR UNSUPERVISED CLASSIFICATION AND AUTOMATIC CONTEXT SWITCHING  

E-print Network

ICA MIXTURE MODELS FOR UNSUPERVISED CLASSIFICATION AND AUTOMATIC CONTEXT SWITCHING Te­Won Lee,lewicki,terryg@salk.edu ABSTRACT We present an unsupervised classification algorithm based on an ICA mixture model. A mixture model. In an ICA mixture model, it is assumed that the data in each class are generated by a linear mixture

Lee, Te-Won

317

Dynamic structure factors of a dense mixture  

E-print Network

We compute the dynamic structure factors of a dense binary liquid mixture. These describe dynamics on molecular length scales, where structural relaxation is important. We find that the presence of a few large particles in a dense fluid of small particles slows down the dynamics considerably. We also observe a deep narrowing of the spectrum for a disordered mixture composed of a nearly equal packing of the two species. In contrast, a few small particles diffuse easily in the background of a dense fluid of large particles. We expect our results to describe neutron scattering from a dense mixture.

Supurna Sinha

2005-05-22

318

Hormesis in mixtures -- can it be predicted?  

PubMed

Binary mixture studies are well established for mixtures of pollutants, pesticides, or allelochemicals and sound statistical methods are available to evaluate the results in relation to reference models. The majority of mixture studies are conducted to investigate the effect of one compound on the inhibitory action of another. However, since stimulatory responses to low concentrations of chemicals are gaining increased attention and improved statistical models are available to describe this phenomenon of hormesis, scientists are challenged by the question of what will happen in the low concentration range when all or some of the chemicals in a mixture induce hormesis? Can the mixture effects still be predicted and can the size and concentration range of hormesis be predicted? The present study focused on binary mixtures with one or both compounds inducing hormesis and evaluated six data sets of root length of Lactuca sativa L. and areal growth of Lemna minor L., where substantial and reproducible hormetic responses to allelochemicals and herbicides have been found. Results showed that the concentration giving maximal growth stimulatory effects (M) and the concentration where the hormetic effect had vanished (LDS) could be predicted by the most-used reference model of concentration addition (CA), if the growth inhibitory concentrations (EC50) followed CA. In cases of deviations from CA at EC50, the maximum concentration M and the LDS concentration followed the same deviation patterns, which were described by curved isobole models. Thus, low concentration mixture effects as well as the concentration range of hormesis can be predicted applying available statistical models, if both mixture partners induce hormesis. Using monotonic concentration-response models instead of biphasic concentration-response models for the prediction of joint effects, thus ignoring hormesis, slightly overestimated the deviation from CA at EC20 and EC50, but did not alter the general conclusion of the mixture study in terms of deviation from the reference model. Mixture effects on the maximum stimulatory response were tested against the hypothesis of a linear change with mixture ratio by constructing 95% prediction intervals based on the single concentration-response curves. Four out of the six data sets evaluated followed the model of linear interpolation reasonably well, which suggested that the size of the hormetic growth stimulation can be roughly predicted in mixtures from knowledge of the concentration-response relationships of the individual chemicals. PMID:18640701

Belz, Regina G; Cedergreen, Nina; Sørensen, Helle

2008-10-01

319

Sound-propagation gap in fluid mixtures  

E-print Network

We discuss the behavior of the extended sound modes of a dense binary hard-sphere mixture. In a dense simple hard-sphere fluid the Enskog theory predicts a gap in the sound propagation at large wave vectors. In a binary mixture the gap is only present for low concentrations of one of the two species. At intermediate concentrations sound modes are always propagating. This behavior is not affected by the mass difference of the two species, but it only depends on the packing fractions. The gap is absent when the packing fractions are comparable and the mixture structurally resembles a metallic glass.

Supurna Sinha; M. Cristina Marchetti

2005-06-15

320

Assessing Cumulative Health Risks from Exposure to Environmental Mixtures--Three Fundamental Questions  

PubMed Central

Differential exposure to mixtures of environmental agents, including biological, chemical, physical, and psychosocial stressors, can contribute to increased vulnerability of human populations and ecologic systems. Cumulative risk assessment is a tool for organizing and analyzing information to evaluate the probability and seriousness of harmful effects caused by either simultaneous and/or sequential exposure to multiple environmental stressors. In this article we focus on elucidating key challenges that must be addressed to determine whether and to what degree differential exposure to environmental mixtures contributes to increased vulnerability of exposed populations. In particular, the emphasis is on examining three fundamental and interrelated questions that must be addressed as part of the process to assess cumulative risk: a) Which mixtures are most important from a public health perspective? and b) What is the nature (i.e., duration, frequency, timing) and magnitude (i.e., exposure concentration and dose) of relevant cumulative exposures for the population of interest? c) What is the mechanism (e.g., toxicokinetic or toxicodynamic) and consequence (e.g., additive, less than additive, more than additive) of the mixture’s interactive effects on exposed populations? The focus is primarily on human health effects from chemical mixtures, and the goal is to reinforce the need for improved assessment of cumulative exposure and better understanding of the biological mechanisms that determine toxicologic interactions among mixture constituents. PMID:17520074

Sexton, Ken; Hattis, Dale

2007-01-01

321

Chemical mixtures in untreated water from public-supply wells in the U.S.--occurrence, composition, and potential toxicity.  

PubMed

Chemical mixtures are prevalent in groundwater used for public water supply, but little is known about their potential health effects. As part of a large-scale ambient groundwater study, we evaluated chemical mixtures across multiple chemical classes, and included more chemical contaminants than in previous studies of mixtures in public-supply wells. We (1) assessed the occurrence of chemical mixtures in untreated source-water samples from public-supply wells, (2) determined the composition of the most frequently occurring mixtures, and (3) characterized the potential toxicity of mixtures using a new screening approach. The U.S. Geological Survey collected one untreated water sample from each of 383 public wells distributed across 35 states, and analyzed the samples for as many as 91 chemical contaminants. Concentrations of mixture components were compared to individual human-health benchmarks; the potential toxicity of mixtures was characterized by addition of benchmark-normalized component concentrations. Most samples (84%) contained mixtures of two or more contaminants, each at concentrations greater than one-tenth of individual benchmarks. The chemical mixtures that most frequently occurred and had the greatest potential toxicity primarily were composed of trace elements (including arsenic, strontium, or uranium), radon, or nitrate. Herbicides, disinfection by-products, and solvents were the most common organic contaminants in mixtures. The sum of benchmark-normalized concentrations was greater than 1 for 58% of samples, suggesting that there could be potential for mixtures toxicity in more than half of the public-well samples. Our findings can be used to help set priorities for groundwater monitoring and suggest future research directions for drinking-water treatment studies and for toxicity assessments of chemical mixtures in water resources. PMID:22687436

Toccalino, Patricia L; Norman, Julia E; Scott, Jonathon C

2012-08-01

322

C01\\lPUTING NORJ.\\tIALIZING CONSTANTS FOR FINITE MIXTURE MODELS VIA INCRElVlENTAL MIXTURE  

E-print Network

C01\\lPUTING NORJ.\\tIALIZING CONSTANTS FOR FINITE MIXTURE MODELS VIA INCRElVlENTAL MIXTURE, 98195 USA #12;#12;Computing Normalizing Constants for Finite Mixture rvlodels via Incremental Mixture propose a method for approximating integrated likelihoods in finite mixture models. We for- mulate

Washington at Seattle, University of

323

Uncertainty in Mixtures and Cumulative Risk Assessment  

EPA Science Inventory

Uncertainty in Mixtures and Cumulative Risk Assessment JC Lipscomb and GE Rice U.S. Environmental Protection Agency, Office of Research and Development, National Center for Environmental Assessment, Cincinnati, Ohio, USA Humans and environmental species are rarely exposed to sing...

324

Quantiles for Finite Mixtures of Normal Distributions  

ERIC Educational Resources Information Center

Quantiles for finite mixtures of normal distributions are computed. The difference between a linear combination of independent normal random variables and a linear combination of independent normal densities is emphasized. (Contains 3 tables and 1 figure.)

Rahman, Mezbahur; Rahman, Rumanur; Pearson, Larry M.

2006-01-01

325

Terahertz spectroscopy for quantifying refined oil mixtures.  

PubMed

In this paper, the absorption coefficient spectra of samples prepared as mixtures of gasoline and diesel in different proportions are obtained by terahertz time-domain spectroscopy. To quantify the components of refined oil mixtures, a method is proposed to evaluate the best frequency band for regression analysis. With the data in this frequency band, dualistic linear regression fitting is used to determine the volume fraction of gasoline and diesel in the mixture based on the Beer-Lambert law. The minimum of regression fitting R-Square is 0.99967, and the mean error of fitted volume fraction of 97# gasoline is 4.3%. Results show that refined oil mixtures can be quantitatively analyzed through absorption coefficient spectra in terahertz frequency, which it has bright application prospects in the storage and transportation field for refined oil. PMID:22907017

Li, Yi-nan; Li, Jian; Zeng, Zhou-mo; Li, Jie; Tian, Zhen; Wang, Wei-kui

2012-08-20

326

Environmental toxicity of complex chemical mixtures  

E-print Network

and wildlife tissues were collected from four National Priority List Superfund sites within the United States. In general, chemical analysis was not always predictive of mixture toxicity. Although biodegradation reduced the concentration of total...

Gillespie, Annika Margaret

2009-05-15

327

Membrane selective separation of binary gas mixtures  

Microsoft Academic Search

A general approach to solving a conjugate problem of mass transfer in the separation of binary gas mixtures in selectively\\u000a permeable membrane elements with allowance for the external convective and intramembrane diffusion resistances is suggested.

V. I. Baikov; N. V. Primak

2007-01-01

328

Separation of gas mixtures including hydrogen  

SciTech Connect

A process is described of separating a gas mixture comprising at least three components into three different fractions by pressure swing adsorption, comprising repeatedly performing a cycle including: passing said gas mixture sequentially through first and second adsorptive regions on each of which a second component of the mixture is more strongly adsorbed than a first component, but less strongly adsorbed than a third component; withdrawing a first fraction enriched in said first component from the downstream end of the second adsorptive region; stopping admission of the said gas mixture to the first adsorptive region; withdrawing a second fraction enriched in the second component from the downstream end of the first adsorptive region and from the upstream end of the second adsorptive region into a common pipeline; and withdrawing a third fraction enriched in the third component from the upstream end of the first adsorptive region.

Krishnamurthy, R.; Lerner, S.L.; Shukla, Y.; Stokley, A.G.

1993-08-10

329

Absorption of Gas Phase Contaminant Mixtures.  

National Technical Information Service (NTIS)

This project seeks to study the effect of multiple gas-vapor mixtures on the activated carbon adsorption breakthrough time and pattern. Activated carbon cartridges used for respiratory protection are tested in most cases for a single component at relative...

C. Lungu

2004-01-01

330

Predicting skin permeability from complex chemical mixtures  

SciTech Connect

Occupational and environmental exposure to topical chemicals is usually in the form of complex chemical mixtures, yet risk assessment is based on experimentally derived data from individual chemical exposures from a single, usually aqueous vehicle, or from computed physiochemical properties. We present an approach using hybrid quantitative structure permeation relationships (QSPeR) models where absorption through porcine skin flow-through diffusion cells is well predicted using a QSPeR model describing the individual penetrants, coupled with a mixture factor (MF) that accounts for physicochemical properties of the vehicle/mixture components. The baseline equation is log k {sub p} = c + mMF + a{sigma}{alpha} {sub 2} {sup H} + b{sigma}{beta} {sub 2} {sup H} + s{pi} {sub 2} {sup H} + rR {sub 2} + vV {sub x} where {sigma}{alpha} {sub 2} {sup H} is the hydrogen-bond donor acidity, {sigma}{beta} {sub 2} {sup H} is the hydrogen-bond acceptor basicity, {pi} {sub 2} {sup H} is the dipolarity/polarizability, R {sub 2} represents the excess molar refractivity, and V {sub x} is the McGowan volume of the penetrants of interest; c, m, a, b, s, r, and v are strength coefficients coupling these descriptors to skin permeability (k {sub p}) of 12 penetrants (atrazine, chlorpyrifos, ethylparathion, fenthion, methylparathion, nonylphenol, {rho}-nitrophenol, pentachlorophenol, phenol, propazine, simazine, and triazine) in 24 mixtures. Mixtures consisted of full factorial combinations of vehicles (water, ethanol, propylene glycol) and additives (sodium lauryl sulfate, methyl nicotinate). An additional set of 4 penetrants (DEET, SDS, permethrin, ricinoleic acid) in different mixtures were included to assess applicability of this approach. This resulted in a dataset of 16 compounds administered in 344 treatment combinations. Across all exposures with no MF, R{sup 2} for absorption was 0.62. With the MF, correlations increased up to 0.78. Parameters correlated to the MF include refractive index, polarizability and log (1/Henry's Law Constant) of the mixture components. These factors should not be considered final as the focus of these studies was solely to determine if knowledge of the physical properties of a mixture would improve predicting skin permeability. Inclusion of multiple mixture factors should further improve predictability. The importance of these findings is that there is an approach whereby the effects of a mixture on dermal absorption of a penetrant of interest can be quantitated in a standard QSPeR model if physicochemical properties of the mixture are also incorporated.

Riviere, Jim E. [Center for Chemical Toxicology Research and Pharmacokinetics, 4700 Hillsborough Street, North Carolina State University, Raleigh, NC 27606 (United States)]. E-mail: Jim_Riviere@ncsu.edu; Brooks, James D. [Center for Chemical Toxicology Research and Pharmacokinetics, 4700 Hillsborough Street, North Carolina State University, Raleigh, NC 27606 (United States)

2005-10-15

331

Separation of gas mixtures by supported complexes  

Microsoft Academic Search

The goal of this program is to determine the feasibility of solvent-dissolved coordination complexes for the separation of gas mixtures under bench-scale conditions. In particular, mixtures such as low-Btu gas are examined for CO and Hâ separation. Two complexes, Pdâ(dpm)âBrâ and Ru(CO)â(PPhâ)â, were examined in a bench-scale apparatus for the separation of binary (CO-Nâ or Hâ-Nâ) and quinary (Hâ, CO,

D. A. Nelson; M. A. Lilga; R. T. Hallen; S. E. Lyke

1986-01-01

332

Speaker Verification Using Adapted Gaussian Mixture Models  

Microsoft Academic Search

Reynolds, Douglas A., Quatieri, Thomas F., and Dunn, Robert B., Speaker Verification Using Adapted Gaussian Mixture Models, Digital Signal Processing10(2000), 19–41.In this paper we describe the major elements of MIT Lincoln Laboratory's Gaussian mixture model (GMM)-based speaker verification system used successfully in several NIST Speaker Recognition Evaluations (SREs). The system is built around the likelihood ratio test for verification, using

Douglas A. Reynolds; Thomas F. Quatieri; Robert B. Dunn

2000-01-01

333

Tracking colour objects using adaptive mixture models  

Microsoft Academic Search

Abstract The use of adaptive Gaussian mixtures to model the colour distributions of objects is described. These models are used to perform robust, real-time tracking under varying illumination, viewing geometry and camera parameters. Observed log-likelihood measurements were used to perform selective adaptation. q,1999 Elsevier Science B.V. All rights reserved. Keywords: Real-time tracking; Colour model; Gaussian mixture model; Adaptive learning

Stephen J. Mckenna; Yogesh Raja; Shaogang Gong

1999-01-01

334

A simplified, truncated virial equation for mixtures  

E-print Network

EOS yields a modified virial EOS which is exact for ideal solutions and is accurate for Lennard-Jones mixtures and Stockmayer mixtures. The modified virial EOS yields accurate estimates of the interaction third virial coefficients from a single... EOS 16 16 32 43 Lennard-Jones Model 49 Stockmayer Model Experimental Isotherms Correlations Optimized BACK EOS Tsonopoulos Correlation Vera Correlation 56 62 65 65 67 69 CONCLUSIONS AND RECOMMENDATIONS 74 Table of Contents (Continued...

McGregor, Duane Robert

2012-06-07

335

Iron (III)/multiacrylate-based holographic mixtures  

NASA Astrophysics Data System (ADS)

We propose an holographic mixture, based on a nonconventional photoinitiator mixed with an acrylate monomer, in which high resolution thick holographic gratings are written. The used mixture that preferably works at UV and Blue-visible wavelengths shows many interesting features, such as high post-polymerization transparency, high writing resolution, and high angular selectivity. The information is permanently storable. Standard experimental techniques have been used to characterize the physical properties of the written gratings.

Lucchetta, D. E.; Nucara, L.; Criante, L.; Simoni, F.; Boni, A.; Xu, Ji-Hua; Bizzarri, R.; Castagna, R.

2013-11-01

336

Non-electrolyte viscous liquid mixtures  

E-print Network

of non-electrolytes. Despite the numerous advances in rigorous statistical mechanics of flu1ds and fluid mixtures the past two decades (excluding Eyring's rate theory), two important aspects of the problem defy understanding: (I) The explicit... of non-electrolytes. Despite the numerous advances in rigorous statistical mechanics of flu1ds and fluid mixtures the past two decades (excluding Eyring's rate theory), two important aspects of the problem defy understanding: (I) The explicit...

Wakefield, Dawn Lee

2012-06-07

337

Flash evaporation of liquid monomer particle mixture  

DOEpatents

The present invention is a method of making a first solid composite polymer layer. The method has the steps of (a) mixing a liquid monomer with particles substantially insoluble in the liquid monomer forming a monomer particle mixture; (b) flash evaporating the particle mixture and forming a composite vapor; and (c) continuously cryocondensing said composite vapor on a cool substrate and cross-linking the cryocondensed film thereby forming the polymer layer.

Affinito, John D. (Kennewick, WA); Darab, John G. (Richland, WA); Gross, Mark E. (Pasco, WA)

1999-01-01

338

Flash evaporation of liquid monomer particle mixture  

DOEpatents

The present invention is a method of making a first solid composite polymer layer. The method has the steps of (a) mixing a liquid monomer with particles substantially insoluble in the liquid monomer forming a monomer particle mixture; (b) flash evaporating the particle mixture and forming a composite vapor; and (c) continuously cryocondensing said composite vapor on a cool substrate and cross-linking the cryocondensed film thereby forming the polymer layer. 3 figs.

Affinito, J.D.; Darab, J.G.; Gross, M.E.

1999-05-11

339

Thermal conductivity of nanoparticle-fluid mixture  

Microsoft Academic Search

Effective thermal conductivity of mixtures of fluids and nanometer-size particles is measured by a steady-state parallel-plate method. The tested fluids contain two types of nanoparticles, AlâOâ and CuO, dispersed in water, vacuum pump fluid, engine oil, and ethylene glycol. Experimental results show that the thermal conductivities of nanoparticle-fluid mixtures are higher than those of the base fluids. Using theoretical models

X. Wang; Xianfan Xu

1999-01-01

340

Thermodynamic modelling of aqueous aerosols containing electrolytes and dissolved organic compounds  

Microsoft Academic Search

A method for calculating the thermodynamic properties of soluble mixed inorganic\\/organic aerosols is proposed. It is based upon the use of existing models of inorganic (electrolyte) multicomponent solutions and water\\/organic mixtures in combination, together with simple thermodynamically consistent terms that express the effects of interactions between ions and organic molecules on the activities of all mixture components. The method is

Simon L. Clegg; John H. Seinfeld; Peter Brimblecombe

2001-01-01

341

Computationally Efficient Methods for Selecting Among Mixtures of Graphical Models  

E-print Network

Computationally Efficient Methods for Selecting Among Mixtures of Graphical Models B. THIESSON, C efficient methods for Bayesian model selection. The methods select among mixtures in which each component. Keywords : Model selection, asymptotic methods, mixture models, directed acyclic graphs, hidden variables

Heckerman, David

342

Introduction Training Regularisation Invariance Mixtures Summary Neural Networks  

E-print Network

stopping 4 Input invariance Tangent propagation Convolutional Neural Networks 5 Mixture of density networks stopping 4 Input invariance Tangent propagation Convolutional Neural Networks 5 Mixture of density networksIntroduction Training Regularisation Invariance Mixtures Summary Lecture 8 Neural Networks

Englebienne, Gwenn

343

FLOW OF A DENSE PARTICULATE MIXTURE USING A MODIFIED FORM OF THE MIXTURE THEORY  

Microsoft Academic Search

The objective of this work is to study the effect of the relative densities of the components in fluid-solid mixture using the formulation presented in Johnson et al., (1991 a,b). The mixture theory is modified to include the effect of buoyancy forces; for this purpose we introduce a term, A6 v grad?, in the mechanical interaction between mixture components. When

A. BRIGGS; C. C. HWANG; M. MASSOUDI

1999-01-01

344

A note on the meaning of mixture viscosity using the classical continuum theories of mixtures  

Microsoft Academic Search

In this paper we provide a brief review of the basic equations for the flow of two linearly viscous fluids using the mixture theory equations given in Atkin and Craine [R.J. Atkin, R.E. Craine, Continuum theories of mixtures: applications, J. Inst. Math. Appl. 17 (1976) 153; R.J. Atkin, R.E. Craine, Continuum theories of mixtures: basic theory and historical development, Quart.

Mehrdad Massoudi; Mehrdad

2008-01-01

345

Assessment of toxic interactions of heavy metals in a multicomponent mixture using Lepidium sativum and Spirodela polyrrhiza.  

PubMed

The toxicities of copper, chromium, cadmium, nickel, manganese, zinc, and lead ions and various concentrations of mixtures of them were studied using the aquatic plant Spirodela polyrrhiza and the terrestrial plant Lepidium sativum. The composition of the model mixture was based on average analytical data of the annual amounts of representative heavy metals (HM) in wastewater discharged from the Ignalina Nuclear Power Plant (Lithuania) during 1996. The observed and predicted effects of the HM mixture on tested plants were evaluated and compared with the prediction models used in describing the toxic interactions of heavy metals in the mixture. The type of toxic interaction at each tested concentration of the mixture was assessed by a statistical approach that tested the null hypothesis of additive toxicity (Ince et al., 1999) and the mixture toxicity index (MTI; Könemann, 1981). For both plant organisms the effect of the HM mixture calculated using the MTI was synergistic. However, assessment of the HM interaction type at 50% effect concentrations using the hypothesis of additive toxicity showed a synergistic effect for Spirodela polyrrhiza and an additive effect for Lepidium sativum. Though the results obtained using both prediction models for assessing the HM mixture's toxicity were similar, in our opinion, the additive toxicity model is more suitable than the MTI model because the former allows evaluation of the impact of various mixture concentrations, not only those with a 50% effect. PMID:15269907

Montvydiene, Danguole; Marciulioniene, Danute

2004-08-01

346

Polydisperse powder mixtures: effect of particle size and shape on mixture stability.  

PubMed

The effect of the shape and size of the components on the stability of mixtures was evaluated in binary mixtures of drug and carrier. Aspirin was used as model drug; spray-dried lactose and microcrystalline cellulose were used as carriers. The coefficient of variation (CV) of the drug in the mixture at various time intervals during mixing was used as a measure of homogeneity. The stability of mixtures was assessed under conditions that were conducive to segregation-in this case, prolonged mixing. The pattern of change in CV with time was analyzed in terms of convective, shear, and diffusive mixing stages. The variation resulting from a change in the shape of the carriers was smaller than that resulting from size differences. The segregation rate constant, calculated on the assumption of a first-order mixing process, was found to be larger in mixtures having components of different shape than in mixtures having components of similar shape. In mixtures of micronized drug and carrier, the pattern of change in the CV of drug with mixing time was attributed to the distribution of agglomerates of micronized drug during convective mixing, followed by shearing of agglomerates and, finally, the distribution of the primary particles during diffusive mixing. Mixtures of non-cohesive powders of similar size and shape behaved like random mixtures of non-interacting components. PMID:11858523

Swaminathan, Vidya; Kildsig, Dane O

2002-01-01

347

Note on inventory model with a mixture of back orders and lost sales  

Microsoft Academic Search

Competitiveness is an important means of determining whether a company will prosper. Business organizations compete with one another in a variety of ways. Among these competitive methods are time and cost factors. The purpose of this paper is to examine the inventory models presented by Padmanabhan and Vrat [International Journal of Systems Sciences 21 (1990) 1721] with a mixture of

Peter Chu; Kuo-lung Yang; Shing-ko Liang; Thomas Niu

2004-01-01

348

Qualitative and quantitative analysis of mixtures of compounds containing both hydrogen and deuterium  

NASA Technical Reports Server (NTRS)

Method allows qualitative and quantitative analysis of mixtures of partially deuterated compounds. Nuclear magnetic resonance spectroscopy determines location and amount of deuterium in organic compounds but not fully deuterated compounds. Mass spectroscopy can detect fully deuterated species but not the location.

Crespi, H. L.; Harkness, L.; Katz, J. J.; Norman, G.; Saur, W.

1969-01-01

349

Dissolution of PCB congeners from an Aroclor and an Aroclor\\/hydraulic oil mixture  

Microsoft Academic Search

Few measurements of the dissolution of individual polychlorinated biphenyl (PCB) congeners dissolved from Aroclor mixtures in water have been reported, and there is no available information on how the aqueous solubilities of these compounds are affected by their presence in organic liquids such as hydraulic oils. A series of experiments were performed to study the dissolution of specific PCB congeners

Richard G. Luthy; David A. Dzombark; Michael J. R. Shannon; Ronald Unterman; John R. Smith

1997-01-01

350

Chronic mixture toxicity study of Clophen A60 and diethyl phthalate in male rats  

Microsoft Academic Search

Chemical mixtures are an important area of research as individuals are exposed to low doses of persistent chemical agents known as environmental pollutants throughout their life time. Polychlorinated biphenyls (PCBs) and diethyl phthalate (DEP) are ubiquitous environmental pollutants that could be present in the same environmental compartment; hence organisms may get simultaneously exposed to both. Therefore, a study was undertaken

Contzen Pereira; Kranti Mapuskar; C. Vaman Rao

2008-01-01

351

Use of straight vegetable oil mixtures of rape and camelina as on farm fuels in agriculture  

Microsoft Academic Search

Possibilities for using straight vegetable oil (SVO) from Camelina sativa (L.) Crantz (camelina or false flax) and its mixtures with Brassica napus (rape) SVO as fuel in adapted diesel engines are described with chemical parameters, measurements in a test engine and a field test in a tractor. Camelina as a crop is attracting attention in organic farming and is often

Hans Marten Paulsen; V. Wichmann; U. Schuemann; B. Richter

2011-01-01

352

Effects of mixtures of oleic acid with chlorinated herbicides on Vibrio fischeri bacteria  

Microsoft Academic Search

Abbreviations: D, diuron; EC50, effective concentration,causing the inhibition of function fifty per cent; EDTA, ethylenediamine tetraacetic acid; FAs, fatty acids; M, monuron; OA, oleic acid; OP, organochlorine pollutants; POM, par- ticular organic matter The toxicity of chlorinated phenylurea herbicides and their mixtures with monoun- saturated oleic (fatty) acid, OA, to bioluminescence of Vibrio fischeri was investiga- ted. The EC50 of

A. Èetkauskaitë; J. Braþënaitë

353

Assessing Cumulative Health Risks from Exposure to Environmental Mixtures—Three Fundamental Questions  

Microsoft Academic Search

Differential exposure to mixtures of environmental agents, including biological, chemical, physical, and psychosocial stressors, can contribute to increased vulnerability of human populations and eco- logic systems. Cumulative risk assessment is a tool for organizing and analyzing information to eval- uate the probability and seriousness of harmful effects caused by either simultaneous and\\/or sequential exposure to multiple environmental stressors. In this

Ken Sexton; Dale Hattis

2007-01-01

354

Biodegradation of chlorinated aliphatic hydrocarbon mixtures in a single-pass packed-bed reactor  

Microsoft Academic Search

Aliphatic chlorinated compounds, such as trichloroethylene (TCE) and tetrachloroethylene (PCE), are major contaminants of\\u000a ground water. A single-pass packed-bed bioreactor was utilized to study the biodegradation of organic waste mixtures consisting\\u000a of PCE, TCE, and other short-chain chlorinated organics. The bioreactor consisted of two 1960-mL glass columns joined in a\\u000a series. One column was packed with sand containing a microbial

L. W. Lackey; T. J. Phelps; P. R. Bienkowski; D. C. White

1993-01-01

355

Unified Maxwell–Stefan description of binary mixture diffusion in micro- and meso-porous materials  

Microsoft Academic Search

The Maxwell–Stefan (M–S) formulation for binary mixture diffusion in micro-porous materials such as zeolites, metal organic frameworks (MOFs), and covalent organic frameworks (COFs), that have pore sizes typically smaller than 2nm, is formulated in a manner that is consistent with corresponding description for meso-porous systems. The M–S equations are set up in terms of species concentrations, ci, defined in terms

R. Krishna; J. M. van Baten

2009-01-01

356

Psychometric Functions for Ternary Odor Mixtures and Their Unmixed Components  

PubMed Central

People are often able to reliably detect a mixture of 2 or more odorants, even if they cannot reliably detect the individual mixture components when presented individually. This phenomenon has been called mixture agonism. However, for some mixtures, agonism among mixture components is greater in barely detectable mixtures than in more easily detectable mixtures (level dependence). Most studies that have used rigorous methods have focused on simple, 2-component (binary) mixtures. The current work takes the next logical step to study detection of 3-component (ternary) mixtures. Psychometric functions were measured for 5 unmixed compounds and for 3 ternary mixtures of these compounds (2 of 5, forced-choice method). Experimenters used air dilution olfactometry to precisely control the duration and concentration of stimuli and used gas chromatography/mass spectrometry to verify vapor-phase concentrations. For 2 of the 3 mixtures, agonism was approximately additive in general agreement with similar work on binary mixtures. A third mixture was no more detectable than the most detectable component, demonstrating a lack of agonism. None of the 3 mixtures showed evidence of level dependence. Agonism may be common in ternary mixtures, but general rules of mixture interaction have yet to emerge. For now, detection of any mixture must be measured empirically. PMID:19773409

Miyazawa, Toshio; Gallagher, Michelle; Preti, George

2009-01-01

357

Mixtures of Receiver Operating Characteristic Curves  

PubMed Central

Rationale and Objectives ROC curves are ubiquitous in the analysis of imaging metrics as markers of both diagnosis and prognosis. While empirical estimation of ROC curves remains the most popular method, there are several reasons to consider smooth estimates based on a parametric model. Materials and Methods A mixture model is considered for modeling the distribution of the marker in the diseased population motivated by the biological observation that there is more heterogeneity in the diseased population than there is in the normal one. It is shown that this model results in an analytically tractable ROC curve which is itself a mixture of ROC curves. Results The use of CK-BB isoenzyme in diagnosis of severe head trauma is used as an example. ROC curves are fit using the direct binormal method, ROCKIT and the Box-Cox transformation as well as the proposed mixture model. The mixture model generates an ROC curve that is much closer to the empirical one than the other methods considered. Conclusions Mixtures of ROC curves can be helpful in fitting smooth ROC curves in datasets where the diseased population has higher variability than can be explained by a single distribution. PMID:23643788

Gonen, Mithat

2014-01-01

358

Synergy and other ineffective mixture risk definitions.  

SciTech Connect

A substantial effort has been spent over the past few decades to label toxicologic interaction outcomes as synergistic, antagonistic, or additive. Although useful in influencing the emotions of the public and the press, these labels have contributed fairly little to our understanding of joint toxic action. Part of the difficulty is that their underlying toxicological concepts are only defined for two chemical mixtures, while most environmental and occupational exposures are to mixtures of many more chemicals. Furthermore, the mathematical characterizations of synergism and antagonism are inextricably linked to the prevailing definition of 'no interaction,' instead of some intrinsic toxicological property. For example, the US EPA has selected dose addition as the no-interaction definition for mixture risk assessment, so that synergism would represent toxic effects that exceed those predicted from dose addition. For now, labels such as synergism are useful to regulatory agencies, both for qualitative indications of public health risk as well as numerical decision tools for mixture risk characterization. Efforts to quantify interaction designations for use in risk assessment formulas, however, are highly simplified and carry large uncertainties. Several research directions, such as pharmacokinetic measurements and models, and toxicogenomics, should promote significant improvements by providing multi-component data that will allow biologically based mathematical models of joint toxicity to replace these pairwise interaction labels in mixture risk assessment procedures.

Hertzberg, R.; MacDonell, M.; Environmental Assessment

2002-04-08

359

Coal-water mixture fuel burner  

DOEpatents

The present invention represents an improvement over the prior art by providing a rotating cup burner arrangement for use with a coal-water mixture fuel which applies a thin, uniform sheet of fuel onto the inner surface of the rotating cup, inhibits the collection of unburned fuel on the inner surface of the cup, reduces the slurry to a collection of fine particles upon discharge from the rotating cup, and further atomizes the fuel as it enters the combustion chamber by subjecting it to the high shear force of a high velocity air flow. Accordingly, it is an object of the present invention to provide for improved combustion of a coal-water mixture fuel. It is another object of the present invention to provide an arrangement for introducing a coal-water mixture fuel into a combustion chamber in a manner which provides improved flame control and stability, more efficient combustion of the hydrocarbon fuel, and continuous, reliable burner operation. Yet another object of the present invention is to provide for the continuous, sustained combustion of a coal-water mixture fuel without the need for a secondary combustion source such as natural gas or a liquid hydrocarbon fuel. Still another object of the present invention is to provide a burner arrangement capable of accommodating a coal-water mixture fuel having a wide range of rheological and combustion characteristics in providing for its efficient combustion. 7 figs.

Brown, T.D.; Reehl, D.P.; Walbert, G.F.

1985-04-29

360

Are individual NOEC levels safe for mixtures? A study on mixture toxicity of brominated flame-retardants in the copepod Nitocra spinipes.  

PubMed

In aquatic ecosystems organisms are exposed to mixtures of pollutants. Still, risk assessment focuses almost exclusively on effect characterization of individual substances. The main objective of the current study was therefore to study mixture toxicity of a common group of industrial substances, i.e., brominated flame-retardants (BFRs), in the harpacticoid copepod Nitocra spinipes. Initially, 10 BFRs with high hydrophobicity but otherwise varying chemical characteristics were selected based on multivariate chemical characterization and tested individually for effects on mortality and development using a partial life cycle test (six days) where silica gel is used as a carrier of the hydrophobic substances. Based on these findings, six of the 10 BFRs were mixed in a series of NOEC proportions (which were set to 0.008, 0.04, 0.2, 1, and five times the NOEC concentrations for each individual BFR), loaded on silica gel and tested in a full life cycle test (26 days). Significantly increased mortality was observed in N. spinipes after six and 26 days exposure at a NOEC proportion that equals the NOEC LDR value (x1) for each BFR in the mixture (p=0.0015 and p=0.0105, respectively). At the NOECx5 proportion all animals were dead. None of the other NOEC proportions caused significant negative responses related to development and reproduction. This shows that low concentrations of individual substances can cause toxicity if exposed in mixtures, which highlights the need to consider mixture toxicity to a greater extent in regulatory work. PMID:18561976

Breitholtz, Magnus; Nyholm, Jenny Rattfelt; Karlsson, Jenny; Andersson, Patrik L

2008-07-01

361

Thermophobicity of liquids: Heats of transport in mixtures as pure component properties—The case of arbitrary concentration  

NASA Astrophysics Data System (ADS)

We have measured Soret coefficients of a large number of binary mixtures of 23 different organic solvents. The present analysis is based on 77 equimolar mixtures and strongly supports the thermophobicity concept previously developed for the heats of transport of originally 10 different substances [S. Hartmann, G. Wittko, W. Köhler, K. I. Morozov, K. Albers, and G. Sadowski, Phys. Rev. Lett. 109, 065901 (2012)]. Among the investigated compounds, cis-decalin is the most thermophobic, hexane the most thermophilic one. In addition to the equimolar mixtures, we have also analyzed the composition dependence of the Soret coefficients and the heats of transport for 22 selected binary mixtures. Both the interpretation of the heats of transport in equimolar mixtures as pure component thermophobicities and the composition dependence of the Soret coefficient can be understood on the basis of the thermodiffusion theory developed by Morozov [Phys. Rev. E 79, 031204 (2009)], according to which the composition dependence is determined by the excess volume of mixing.

Hartmann, S.; Wittko, G.; Schock, F.; Groß, W.; Lindner, F.; Köhler, W.; Morozov, K. I.

2014-10-01

362

Toxicity of a hazardous chemical mixture in the planarian, Dugesia dorotocephala  

SciTech Connect

The responses of the planarian, Dugesia dorotocephala to toxic chemical mixtures representative of water contaminants associated with hazardous waste sites have been studied in laboratory experiments. These free-living flatworms are readily maintained under laboratory conditions and are a useful invertebrate model for toxicology studies. Their widespread occurrence also makes them potentially useful for environmental studies. Mature asexual Dugesia dorotocephala were exposed for 14 days to mixtures of seven contaminants frequently detected in water at hazardous waste sites. The complete 1X mixture contained both metals (As, 3.1 ppm; Cr, 0.7 ppm; Pb, 3.7 ppm) and organics (chloroform, 1.5 ppm; benzene, 5.0 ppm; phenol, 3.4 ppm; trichloroethylene, 3.8 ppm). Groups of planaria were treated with the complete mixture at 0.1X, 1X and 10X concentrations. Additional groups were exposed to the metals-only or organics-only submixtures, also at 0.1X, 1X and 10X concentrations. Treatment solutions were renewed daily. Suppression of fissioning was observed in all of the 1X and 10X treatment groups. Significant mortality occurred only in the 10X complete and 1 0X metals-only treatments. It appears that the toxic effects of the complete mixture are primarily associated with the metal components.

Ramsdell, H.S.; Matthews, C.M. [Colorado State Univ., Ft. Collins, CO (United States)

1995-12-31

363

Dielectric constant for mixtures Most media are mixture of different materials  

E-print Network

= "2 #"1 "2 + 2"1 ! f = NV Practical application of MG Eq. at T=0oC Dry snow: air and ice Melting on fractional volume · Air as background: solid line · Ice as background: dash line Dielectric constant factorDielectric constant for mixtures · Most media are mixture of different materials -snowflakes: air

Zhang, Guifu

364

Quantification of segregation dynamics in ice mixtures  

NASA Astrophysics Data System (ADS)

Context: The observed presence of pure CO2 ice in protostellar envelopes, revealed by a double peaked 15 ?m band, is often attributed to thermally induced ice segregation. The temperature required for segregation is however unknown because of lack of quantitative experimental data and this has prevented the use of ice segregation as a temperature probe. In addition, quantitative segregation studies are needed to characterize diffusion in ices, which underpins all ice dynamics and ice chemistry. Aims: This study aims to quantify the segregation mechanism and barriers in different H2O:CO2 and H2O:CO ice mixtures. Methods: The investigated ice mixtures cover a range of astrophysically relevant ice thicknesses and mixture ratios. The ices are deposited at 16-50 K under (ultra-)high vacuum conditions. Segregation is then monitored, at 40-70 K in the CO2 mixtures and at 23-27 K in the CO mixtures, through infrared spectroscopy. The CO2 and CO band shapes are distinctly different in pure and mixed ices and can thus be used to measure the fraction of segregated ice as a function of time. The segregation barrier is determined using rate equations and the segregation mechanism is investigated through Monte Carlo simulations. Results: Thin (8-37 ML) H2O ice mixtures, containing either CO2 or CO, segregate sequentially through surface processes, followed by an order of magnitude slower bulk diffusion. Thicker ices (>100 ML) segregate through a bulk process, which is faster than even surface segregation in thin ices. The thick ices must therefore be either more porous or segregate through a different mechanism, e.g. a phase transition, compared to the thin ices. The segregation dynamics of thin ices are reproduced qualitatively in Monte Carlo simulations of surface hopping and pair swapping. The experimentally determined surface-segregation rates follow the Ahrrenius law with a barrier of 1080±190 K for H2O:CO2 ice mixtures and 300±100 K for H2O:CO mixtures. Though the barrier is constant with ice mixing ratio, the segregation rate increases with CO2 concentration. Conclusions: Dynamical ice processes can be quantified through a combination of experiments and different model techniques and they are not scale independent as previously assumed. The derived segregation barrier for thin H2O:CO2 ice mixtures is used to estimate the surface segregation temperature during low-mass star formation to be 30±5 K. Both surface and bulk segregation is proposed to be a general feature of ice mixtures when the average bond strengths of the mixture constituents in pure ice exceeds the average bond strength in the ice mixture.

Öberg, K. I.; Fayolle, E. C.; Cuppen, H. M.; van Dishoeck, E. F.; Linnartz, H.

2009-10-01

365

Power to detect normal mixtures: Simulation results  

SciTech Connect

Twenty tests for normality were compared for the purpose of detecting mixtures of two normal components with unequal means but equal variance. The purpose of this study was to determine the power of tests specifically designed to detect mixtures, i.e., the likelihood ratio and Engelman-Hartigan tests, relative to other tests for normality. We considered the entire range of mixing proportions {pi}, 0 < {pi} < 1. For mixtures that are nearly symmetric (0.35 < {pi} < 0.65) the Engelman-Hartigan test was the most powerful. When {pi} > 0.85 or {pi} < 0.15, {radical}b{sub 1} was among the best tests. For intermediate mixing proportions, the likelihood ratio test was best. For situations in which the preferred test had power 50% or more, the power of the likelihood ratio test was also above 50% and within 15 percentage points of the preferred test.

Thode, H.C. Jr.

1992-07-22

366

Power to detect normal mixtures: Simulation results  

SciTech Connect

Twenty tests for normality were compared for the purpose of detecting mixtures of two normal components with unequal means but equal variance. The purpose of this study was to determine the power of tests specifically designed to detect mixtures, i.e., the likelihood ratio and Engelman-Hartigan tests, relative to other tests for normality. We considered the entire range of mixing proportions [pi], 0 < [pi] < 1. For mixtures that are nearly symmetric (0.35 < [pi] < 0.65) the Engelman-Hartigan test was the most powerful. When [pi] > 0.85 or [pi] < 0.15, [radical]b[sub 1] was among the best tests. For intermediate mixing proportions, the likelihood ratio test was best. For situations in which the preferred test had power 50% or more, the power of the likelihood ratio test was also above 50% and within 15 percentage points of the preferred test.

Thode, H.C. Jr.

1992-07-22

367

The NACA mixture analyzer and its application to mixture-distribution measurement in flight  

NASA Technical Reports Server (NTRS)

The NACA mixture analyzer was developed as a research instrument for the continuous indication of fuel-air ratios of aircraft engine installations throughout the range of engine operation. It has been evaluated by using it to measure the mixture distribution of a nine-cylinder radial aircraft engine in flight. The mixture distribution among the cylinders in flight was obtained at normal operating conditions for the engine at an altitude of 5000 feet. Some limited data was also obtained at an altitude of 20,000 feet. Results of these flight tests showed that the NACA mixture analyzer is a satisfactory and dependable instrument for continuous indication of the mixture in flight at all engine conditions regardless of altitude and temperature.

Gerrish, Harold C; Meem, J Lawrence, Jr; Scadron, Marvin D; Colnar, Anthony

1947-01-01

368

Joint Bayesian analysis of forensic mixtures.  

PubMed

Evaluation of series of PCR experiments referring to the same evidence is not infrequent in a forensic casework. This situation is met when 'series of results in mixture' (EPGs produced by reiterating PCR experiments over the same DNA mixture extract) have to be interpreted or when 'potentially related traces' (mixtures that can have contributors in common) require a combined interpretation. In these cases, there can be uncertainty on the genotype assignment, since: (a) more than one genotype combination fall under the same peak profile; (b) PCR preferential amplification alters pre-PCR allelic proportions; (c) other, more unpredictable technical problems (dropouts/dropins, etc.) take place. The uncertainty in the genotype assignment is in most cases addressed by empirical methods (selection of just one particular profile; extraction of consensual or composite profiles) that disregard part of the evidence. Genotype assignment should conversely take advantage from a joint Bayesian analysis (JBA) of all STRs peak areas generated at each experiment. This is the typical case of Bayesian analysis in which adoption of object-oriented Bayesian networks (OOBNs) could be highly helpful. Starting from experimentally designed mixtures, we created typical examples of 'series of results in mixture' of 'potentially related traces'. JBA was some administered to the whole peak area evidence, by specifically tailored OOBNs models, which enabled genotype assignment reflecting all the available evidence. Examples of a residual ambiguity in the genotype assignment came to light at assumed genotypes with partially overlapping alleles (for example: AB+AC?ABC). In the 'series of results in mixture', this uncertainty was in part refractory to the joint evaluation. Ambiguity was conversely dissipated at the 'potentially related' trace example, where the ABC allelic scheme at the first trace was interpreted together with other unambiguous combinations (ABCD; AB) at the related trace. We emphasize the need to carry out extensive, blind sensitivity tests specifically addressing the residual ambiguity that arises from overlapping results mixed at various quantitative ratios. PMID:22948016

Pascali, Vince L; Merigioli, Sara

2012-12-01

369

Organization Development  

ERIC Educational Resources Information Center

Organization Development (OD) is the application of behavioral-science knowledge to enhance an organization's effectiveness and efficiency. This article discusses the evolution of organization development, the basic components of an OD program, typologies of OD interventions, problems with organization development, and organization development in…

Huse, Edgar F.

1978-01-01

370

Extreme Value Mixture Modelling: evmix Package and Simulation Study  

E-print Network

Extreme Value Mixture Modelling: evmix Package and Simulation Study 2013 Joint NZSA to Extremes Outline Extreme Value Mixture Models New evmix package on CRAN Simulation Study Some Closing Value Mixture Models?2.2. KERNEL DENSITY ESTIMATION GPD Transition Function - Cauchy CDF Mixture al

Scarrott, Carl

371

mixtools: An R Package for Analyzing Finite Mixture Models  

E-print Network

mixtools: An R Package for Analyzing Finite Mixture Models Tatiana Benaglia1 Didier Chauveau2 David (R Development Core Team, 2008) provides a set of functions for analyzing a variety of finite mixture and multivariate normal mixtures, and newer methods that reflect some recent research in finite mixture models

Paris-Sud XI, Université de

372

Extreme Value Mixture Modelling with Simulation Study and Applications in  

E-print Network

Extreme Value Mixture Modelling with Simulation Study and Applications in Finance and Insurance mixture model. This thesis will review most of the existing extreme value mixture models in the literature value mixture models in the literature (e.g. parametric, semi-parametric and non-parametric), which

Scarrott, Carl

373

SMEM Algorithm for Mixture Models Naonori Ueda Ryohei Nakano  

E-print Network

SMEM Algorithm for Mixture Models Naonori Ueda Ryohei Nakano NTT Communication Science Laboratories for Mixture Models 1 #12; SMEM Algorithm for Mixture Models Abstract We present a split and merge EM (SMEM) algorithm to overcome the local max­ ima problem in parameter estimation of finite mixture models

Hinton, Geoffrey E.

374

Robotic Color Image Segmentation by Means of Finite Mixture Models  

E-print Network

Robotic Color Image Segmentation by Means of Finite Mixture Models Nicola Greggio , - IEEE Member of the number of components and the parameters of a mixture model for image segmentation. These serve applied to finite mixture models. Fitting a mixture model to the distribution of the data is equivalent

Instituto de Sistemas e Robotica

375

Dirichlet Process Mixture Models for Jonathan L Long  

E-print Network

Dirichlet Process Mixture Models for Vision Jonathan L Long #12;Motivation Scenes are hierarchical mixtures Sudderth et. al. 2005 "Learning Hierarchical Models of Scenes, Objects, and Parts" #12;Mixture a value from p(xn | *zn ) How should we choose the number of components? #12;Dirichlet Processes Mixture

O'Brien, James F.

376

Mixture autoregressive hidden Markov models for speech signals  

Microsoft Academic Search

In this paper a signal modeling technique based upon finite mixture autoregressive probabilistic functions of Markov chains is developed and applied to the problem of speech recognition, particularly speaker-independent recognition of isolated digits. Two types of mixture probability densities are investigated: finite mixtures of Gaussian autoregressive densities (GAM) and nearest-neighbor partitioned finite mixtures of Gaussian autoregressive densities (PGAM). In the

Biing-Hwang Juang; LAWRENCE R. RABINER

1985-01-01

377

SMEM Algorithm for Mixture Models Naonori Ueda Ryohei Nakano  

E-print Network

SMEM Algorithm for Mixture Models Naonori Ueda Ryohei Nakano {ueda, nakano mixture models. In the case of mixture models, non-global maxima often involve having too many components of a mixture model in one part of the space and too few in an- other, widely separated part of the space

Ghahramani, Zoubin

378

LETTER Communicated by Christopher Bishop SMEM Algorithm for Mixture Models  

E-print Network

LETTER Communicated by Christopher Bishop SMEM Algorithm for Mixture Models Naonori Ueda Ryohei to overcome the local maxima problem in parameter estimation of finite mixture models. In the case of mixture models, local maxima often involve having too many components of a mixture model in one part of the space

Ghahramani, Zoubin

379

ADDITIVITY ASSESSMENT OF TRIHALOMETHANE MIXTURES BY PROPORTIONAL RESPONSE ADDITION  

EPA Science Inventory

If additivity is known or assumed, the toxicity of a chemical mixture may be predicted from the dose response curves of the individual chemicals comprising the mixture. As single chemical data are abundant and mixture data sparse, mixture risk methods that utilize single chemical...

380

Taste mixture interactions: Suppression, additivity, and the predominance of sweetness  

Microsoft Academic Search

Most of what is known about taste interactions has come from studies of binary mixtures. The primary goal of this study was to determine whether asymmetries in suppression between stimuli in binary mixtures predict the perception of tastes in more complex mixtures (e.g., ternary and quaternary mixtures). Also of interest was the longstanding question of whether overall taste intensity derives

Barry G. Green; Juyun Lim; Floor Osterhoff; Karen Blacher; Danielle Nachtigal

2010-01-01

381

Mixture design—design generation, PLS analysis, and model usage  

Microsoft Academic Search

In this tutorial article, an introduction to the basics of mixture design is provided. The discussion on mixture design is made from the experimenter's point of view, rather than from an elaborate theoretical perspective. Much emphasis is placed on `how to think' when defining a mixture problem, and analyzing the resulting data. Also, a working strategy for mixture experimentation is

Lennart Eriksson; Erik Johansson; Conny Wikström

1998-01-01

382

Acute toxicity of commonly used forestry herbicide mixtures to Ceriodaphnia dubia and Pimephales promelas.  

PubMed

Because many herbicides selectively control specific species or types of vegetation, they are often applied as mixtures to achieve better control over undesirable vegetation. When herbicides are applied in forest ecosystems, streams, ponds, and other bodies of water are typically protected by buffer zones in which no herbicide is applied. However, in some landscapes, small wetlands and streams are difficult to see and avoid, thus the potential acute toxicity of herbicide mixtures to aquatic organisms is of interest, yet it has not been well-studied. We examined the acute toxicity of 23 different herbicide mixtures to Ceriodaphnia dubia and fathead minnows (Pimephales promelas) at environmentally relevant concentrations, and, where possible, characterized mixture interactions using Marking's Additive Index. Maximum exposure concentrations were equivalent to applying the maximum allowable rate for each component directly to the surface of a 6-in. deep pond with no dissipation following application. Under the conditions of this study, herbicide formulations containing Accord Concentrate (glyphosate), Arsenal AC (imazapyr), Chopper (imazapyr), Escort (metsulfuron methyl), Oust XP (sulfometuron methyl), and Velpar L (hexazinone) were not associated with appreciable acute toxicity to fathead minnows or C. dubia when used alone or in mixtures with each other and various surfactants and adjuvants. Herbicide mixtures for which Additive Indexes could be calculated exhibited primarily antagonistic or simple additive toxicity. In the few cases where synergistic toxicity was observed, the degree of synergism was slight, never exceeding approximately twice the effect estimated based on additive toxicity. Based on the results of this study, neither acute toxicity nor enhanced acute aquatic toxicity due to synergistic mixture effects appears to be a significant concern for applications of the herbicide mixtures most commonly used in forestry. PMID:21384491

Tatum, Vickie L; Borton, Dennis L; Streblow, William R; Louch, Jeffrey; Shepard, James P

2012-12-01

383

Cadmium, lead and their mixtures with copper: Paracentrotus lividus embryotoxicity assessment, prediction, and offspring quality evaluation.  

PubMed

The aim of this research was to assess the combined effects of three heavy metals (copper, lead, cadmium) on the fertilization and offspring quality of the sea urchin Paracentrotus lividus at EC50, NOEL, and EC1 concentrations. The observed data were compared with the predictions derived from approaches of Concentration Addition (CA) and Independent Action (IA) in order to evaluate the proper prediction of the observed mixture toxic effect. The P. lividus embryotoxicity of trace metals decreases as follows: Cu > Pb > Cd at all toxicity concentration tested. EC50 mixture revealed less toxic only than Cu; EC50 was 0.80 (± 0.07) mg/l, the offspring malformations were mainly P1 type (skeletal alterations) up to 20% mixture concentration, and P2 type from 70% concentration. The NOEL and EC1 mixtures evidenced that all compounds contribute to the overall toxicity, even if present at low concentrations: the former EC50 was 0.532 (± 0.058) mg/l and the latter was 1.081 (± 0.240) mg/l. The developmental defects observed were mainly P1 type in both mixtures. Both CA and IA models did not accurately predict mixture toxicity for EC50 and NOEL mixtures. Instead, EC1 mixture effects seemed well represented by the IA model. The protective action of the CA model, although quite accurate when applied to simple biological systems like algae and bacteria, but failed to represent the worst-case in this study with more complex organisms. It would be useful to introduce in the models one or more factors that take into account the complexity of these biological systems. PMID:20552397

Manzo, Sonia; Buono, Silvia; Cremisini, Carlo

2010-10-01

384

Organic constituents of carbonaceous chondrites.  

PubMed

From a brief discussion of forms of meteorite carbon it is concluded that almost all the carbon in the carbonaceous chondrites is present as organic matter. Attempts to extract and identify this organic matter are then reviewed. It is shown that only 25 per cent has been extracted and only about 5 per cent chemically characterized. Of this 5 per cent, most is a complex mixture of hydroxylated aromatic acids together with various hydrocarbons of the paraffin, naphthene and aromatic series. Small amounts of amino acids, sugars and fatty acids also are present. The possible chemical nature of the major fraction is discussed. It is suggested to be a mixture of high-molecular weight aromatic and hydrocarbon polymers. Possible sources of contamination of the meteorites are described and evidence indicating a general lack of organic contaminants is presented. It is concluded, that most of the organic constituents are indigenous to the meteorites and are extra terrestrial in origin. Synthetic processes for the compounds are mentioned and it is concluded that the organic material is probably of abiogenic origin. A brief review on studies of "organized elements" contained within the meteorites is presented. Difficulties of identification are discussed and photographs of some microstructures of several carbonaceous chondrites are presented. No final conclusion about the nature of these objects is possible, but some appear to be various indigenous organic and mineral structures, while others are terrestrial contaminants. PMID:11881656

Briggs, M H; Mamikunian, G

1964-01-01

385

Brief report on primary mixture preparation for precise CO observation  

NASA Astrophysics Data System (ADS)

Greenhouse gases (GHG) have been known as causing materials of the greenhouse effect. Because it is very important to reduce their emission, they has been paid attention since Kyoto protocol to the United Nations Framework Convention on Climate Change. Accurate observation data of ambient GHG are vital for the study of the relationship between GHGs and global warming, but it is not easy to quantify their mixing ratios owing to their globally and temporally tiny variation. For example, mixing ratio of carbon dioxide in the atmosphere, is reported to be growing by +1.7 ppm (parts per million)/year for recen 10 years according to GAW report. CO has contributed as an indicator in that an air mass is from source or background, although it lacks its traceability. CO is known to be emitted from industry, vehicle, and biomass burning. The atmospheric lifetime of CO varies from weeks to months depending on OH radical amount however ambient CO ranges from 50 nmol/mol to 300 nmol/mol at marine boundary, from 100 nmol/mol to 500 nmol/mol at city area. In order to monitor precisely CO at ambient, the World Meteorological Organization (WMO) requires its measurement capability of 2 nmol/mol uncertainty. For these reasons, it's necessary for the measurement results to be accurate and consistent among the assigned standards. . In order to prepare CO/air standard mixtures with an absolute scale we have studied several factors on gravimetry; purity analysis of CO and an artificial air and stability including unexpected contamination during preparation and adsorption on inner wall of cylinders. Currently we are going to present the preliminary results on the development of standard mixtures with ~ 300 nmol/mol. The mixtures were verified by comparing their amount with a Gas Chromatography / Electron Capture Detector (GC/FID) and cavity ring down spectrometer (CRDS). Analytical capability during comparison is within ± 2 ppb, which satisfies WMO DQO.

Lee, J.; Lee, J. B.; Moon, D. M.; Kim, J. S.

2012-04-01

386

Lubricating and additive mixtures for alcohol fuels and their method of preparation  

SciTech Connect

This patent describes a lubricating additive for alcohol fuels. The additive consists essentially of about 94-96%, by volume, organic solvent selected from the class consisting of mineral spirits, toluene, xylene, benzene, naphtha, cyclohexane, hexane, heptane, pentane, isopentane, and mixtures thereof; about 0.2-1.5%, by volume, emulsifier; at least about 3-4%, by volume, lubricant; and about 0.3-0.5, by volume, ethylene-vinyl acetate copolymer, wherein the additive is mixed with an alcohol fuel at about 4-6%, by volume, of the fuel-additive mixture.

Smith, E.J.

1986-06-17

387

Behavior of complex mixtures in aquatic environments: a synthesis of PNL ecological research  

SciTech Connect

The term complex mixture has been recently applied to energy-related process streams, products and wastes that typically contain hundreds or thousands of individual organic compounds, like petroleum or synthetic fuel oils; but it is more generally applicable. A six-year program of ecological research has focused on four areas important to understanding the environmental behavior of complex mixtures: physicochemical variables, individual organism responses, ecosystems-level determinations, and metabolism. Of these areas, physicochemical variables and organism responses were intensively studied; system-level determinations and metabolism represent more recent directions. Chemical characterization was integrated throughout all areas of the program, and state-of-the-art methods were applied. 155 references, 35 figures, 4 tables.

Fickeisen, D.H.; Vaughan, B.E. (eds.)

1984-06-01

388

ISOLATION OF ORGANIC WATER POLLUTANTS BY XAD RESINS AND CARBON  

EPA Science Inventory

The recovery efficiencies of XAD resins -2, -4, -7, and -8 and of resin mixtures were measured using distilled water samples containing 13 organic pollutants. An equal-weight mixture of XAD-4 and XAD-8 was most efficient. XAD-2 and XAD-4/8 were further tested and found effective ...

389

A note on optimal mixture and mixture amount designs 1 Berthold Heiligers and Ralf-Dieter Hilgers 2  

E-print Network

A note on optimal mixture and mixture amount designs 1 Berthold Heiligers and Ralf-Dieter Hilgers 2 University of Magdeburg and RWTH-Aachen In many applications of mixture experiments in medicine or biology, for example, not only the proportions of the involved mixture ingredients, but also their total amount

Gaffke, Norbert

390

Phase Behaviour of Ternary Mixtures: A Theoretical Investigation of the Critical Properties of Mixtures with Equal Size Components  

E-print Network

binary mixtures. The fluid phase equilibria of many binary mixtures have been observed experimentally been developed based on the critical equilibria behaviour of binary mixtures and increasingly accurate1 Phase Behaviour of Ternary Mixtures: A Theoretical Investigation of the Critical Properties

391

Solvatochromic Probe Response within Ionic Liquids and Their Equimolar Mixtures with Tetraethylene Glycol.  

PubMed

Synergism in a probe response within a mixture hints at the presence of strong interactions involving the solvent constituents of the mixture and possibly the probe. Unusual and rare "hyperpolarity" resulting from the synergism in probe response exhibited by ionic liquid (IL) mixtures with glycol family solvents is investigated in detail for equimolar mixtures of tetraethylene glycol (TEG) with many structurally different ILs using several UV-vis absorbance and fluorescence solvatochromic probes. Thirteen different ILs, of the same cation 1-butyl-3-methylimidazolium and different anions, of the same anion bis(trifluoromethylsulfonyl)imide and different cations, and of C2 methyl-substituted imidazolium cations, are used to assess the structural dependence of the IL on synergism exhibited by (IL + TEG) mixture. Responses from UV-vis absorbance probes are used to obtain ET [dipolarity/polarizability and/or H-bond donating (HBD) acidity] and Kamlet-Taft parameters [?* (dipolarity/polarizability), ? (HBD acidity), and ? (HB accepting basicity)] within (IL + TEG) mixtures. The band I-to-band III fluorescence intensity ratio of dipolarity probe pyrene along with the lowest energy fluorescence band maxima of pyrene-1-carboxaldehyde (PyCHO, a probe for the permittivity of the medium), coumarin-153 and N,N-dimethyl-6-propionyl-2-naphthylamine PRODAN (neutral photoinduced charge-transfer fluorescence probes), and 6-p-toluidine-2-naphthalenesulfonic acid (TNS) and l-anilinonaphthalene-8-sulfonate (ANS) (ionic photoinduced charge-transfer fluorescence probes) are used to assess whether synergism is exhibited by (IL + TEG) equimolar mixtures. Probe responses within TEG equimolar mixtures with ILs are compared to those with common organic solvents. An attempt is made to establish a correlation between the synergism observed in the probe response within an (IL + TEG) mixture and the structural features of the cation and anion of the IL, such as acidity of the protons of the cation, aromaticity of the cation, and size, shape, and coordinating ability of the anion. It is established that the solvatochromism exhibited by the probes within (IL + TEG) mixtures is due to complex coupling of several different interactions and dynamical processes involving the probe as well as IL and TEG within the mixture. PMID:25162184

Rai, Rewa; Pandey, Siddharth

2014-09-25

392

Prebiotic chemistry within a simple impacting icy mixture.  

PubMed

We present results of prebiotic organic synthesis in shock compressed mixtures of simple ices from quantum molecular dynamics (MD) simulations extended to close to equilibrium time scales. Given the likelihood of an inhospitable prebiotic atmosphere on early Earth, it is possible that impact processes of comets or other icy bodies were a source of prebiotic chemical compounds on the primitive planet. We observe that moderate shock pressures and temperatures within a CO2-rich icy mixture (36 GPa and 2800 K) produce a number of nitrogen containing heterocycles, which dissociate to form functionalized aromatic hydrocarbons upon expansion and cooling to ambient conditions. In contrast, higher shock conditions (48-60 GPa, 3700-4800 K) resulted in the synthesis of long carbon-chain molecules, CH4, and formaldehyde. All shock compression simulations at these conditions have produced significant quantities of simple C-N bonded compounds such as HCN, HNC, and HNCO upon expansion and cooling to ambient conditions. Our results elucidate a mechanism for impact synthesis of prebiotic molecules at realistic impact conditions that is independent of external constraints such as the presence of a catalyst, illuminating UV radiation, or pre-existing conditions on a planet. PMID:23639050

Goldman, Nir; Tamblyn, Isaac

2013-06-20

393

Dynamic responses of Bacteroides thetaiotaomicron during growth on glycan mixtures  

PubMed Central

Summary Bacteroides thetaiotaomicron (Bt) is a human colonic symbiont that degrades many different complex carbohydrates (glycans), the identities and amounts of which are likely to change frequently and abruptly from meal-to-meal. To understand how this organism reacts to dynamic growth conditions, we challenged it with a series of different glycan mixtures and measured responses involved in glycan catabolism. Our results demonstrate that individual Bt cells can simultaneously respond to multiple glycans and that responses to new glycans are extremely rapid. The presence of alternative carbohydrates does not alter response kinetics, but reduces expression of some glycan utilization genes as well as the cell’s sensitivity to glycans that are present in lower concentration. Growth in a mixture containing twelve different glycans revealed that Bt preferentially uses some before others. This metabolic hierarchy is not changed by prior exposure to lower priority glycans because re-introducing high priority substrates late in culture re-initiates repression of genes involved in degrading those with lower priority. At least some carbohydrate prioritization effects occur at the level of monosaccharide recognition. Our results provide insight into how a bacterial glycan generalist modifies its responses in dynamic glycan environments and provide essential knowledge to interpret related metabolic behavior in vivo. PMID:23646867

Rogers, Theresa E.; Pudlo, Nicholas A.; Koropatkin, Nicole M.; Bell, Joshua S. K.; Balasch, Monica Moya; Jasker, Kevin; Martens, Eric C.

2013-01-01

394

Microtubule Assembly of Isotypically Purified Tubulin and Its Mixtures  

PubMed Central

Numerous isotypes of the structural protein tubulin have now been characterized in various organisms and their expression offers a plausible explanation for observed differences affecting microtubule function in vivo. While this is an attractive hypothesis, there are only a handful of studies demonstrating a direct influence of tubulin isotype composition on the dynamic properties of microtubules. Here, we present the results of experimental assays on the assembly of microtubules from bovine brain tubulin using purified isotypes at various controlled relative concentrations. A novel data analysis is developed using recursive maps which are shown to be related to the master equation formalism. We have found striking similarities between the three isotypes of bovine tubulin studied in regard to their dynamic instability properties, except for subtle differences in their catastrophe frequencies. When mixtures of tubulin isotypes are analyzed, their nonlinear concentration dependence is modeled and interpreted in terms of lower affinities of tubulin dimers belonging to the same isotype than those that represent different isotypes indicating hitherto unsuspected influences of tubulin dimers on each other within a microtubule. Finally, we investigate the fluctuations in microtubule assembly and disassembly rates and conclude that the inherent rate variability may signify differences in the guanosine-5?-triphosphate composition of the growing and shortening microtubule tips. It is the main objective of this article to develop a quantitative model of tubulin polymerization for individual isotypes and their mixtures. The possible biological significance of the observed differences is addressed. PMID:18502790

Rezania, Vahid; Azarenko, Olga; Jordan, Mary Ann; Bolterauer, Hannes; Luduena, Richard F.; Huzil, J. Torin; Tuszynski, Jack A.

2008-01-01

395

Biogas Potential of Manure and Straw Mixtures  

Microsoft Academic Search

Wheat straw or manure or both were converted to a methane-rich gas mixture. Anaerobic biomethane production is an effective process for conversion of a broad variety of lignocellulosic materials to methane to substitute natural gas and medium calorific value gases. Methane generating bacteria (methanogens) and other microbes help digest dying plants in anaerobic (without oxygen) conditions. Wheat straw wastes represent

Ayhan Demirbas

2006-01-01

396

Regularized Finite Mixture Models for Probability Trajectories  

ERIC Educational Resources Information Center

Finite mixture models are widely used in the analysis of growth trajectory data to discover subgroups of individuals exhibiting similar patterns of behavior over time. In practice, trajectories are usually modeled as polynomials, which may fail to capture important features of the longitudinal pattern. Focusing on dichotomous response measures, we…

Shedden, Kerby; Zucker, Robert A.

2008-01-01

397

Estimating Mixture of Dirichlet Process Models  

Microsoft Academic Search

Current Gibbs sampling schemes in mixture of Dirichlet process (MDP) models are restricted to using “conjugate” base measures that allow analytic evaluation of the transition probabilities when resampling configurations, or alternatively need to rely on approximate numeric evaluations of some transition probabilities. Implementation of Gibbs sampling in more general MDP models is an open and important problem because most applications

Steven N. Maceachern; Peter Müller

1998-01-01

398

Dealing with label switching in mixture models  

Microsoft Academic Search

In a Bayesian analysis of finite mixture models, parameter estimation and clustering are sometimes less straightforward that might be expected. In particular, the common practice of estimating parameters by their posterior mean, and summarising joint posterior distributions by marginal distributions, often leads to nonsensical answers. This is due to the so-called \\

Matthew Stephens

2000-01-01

399

Estimation in Mixtures of Two Normal Distributions  

Microsoft Academic Search

This paper is concerned primarily with the method of moments in dissecting a mixture of two normal distributions. In the general case, with two means, two standard deviations, and a proportionality factor to be estimated, the first five sample moments are required, and it becomes necessary to find a particular solution of a ninth degree polynomial equation that was originally

A. Clifford Cohen

1967-01-01

400

Bayesian Density Estimation and Inference Using Mixtures  

Microsoft Academic Search

We describe and illustrate Bayesian inference in models for density estimation using mixturesof Dirichlet processes. These models provide natural settings for density estimation,and are exemplified by special cases where data are modelled as a sample from mixtures ofnormal distributions. Efficient simulation methods are used to approximate various prior,posterior and predictive distributions. This allows for direct inference on a variety of

Michael D. Escobar; Mike West

1994-01-01

401

TOXICOLOGY OF COMPLEX MIXTURES OF INDOOR AIR  

EPA Science Inventory

This review focuses on strategies for assessing the toxicology of indoor air pollutant mixtures. hese strategies are illustrated by reviewing the current problems and approaches to the toxicology of indoor air pollutants from three indoor source categories which make a major cont...

402

A Skew-Normal Mixture Regression Model  

ERIC Educational Resources Information Center

A challenge associated with traditional mixture regression models (MRMs), which rest on the assumption of normally distributed errors, is determining the number of unobserved groups. Specifically, even slight deviations from normality can lead to the detection of spurious classes. The current work aims to (a) examine how sensitive the commonly…

Liu, Min; Lin, Tsung-I

2014-01-01

403

An Alternative Model for Mixtures of Experts  

Microsoft Academic Search

Abstract An alternative model is proposed for mixtures of experts by utiliz ing a di erent parametric form for the gating network The mod i ed model is trained by an EM algorithm In comparison with earlier models trained by either EM or gradient ascent there is no need to select a learning stepsize to guarantee the convergence of the

Lei Xu; Michael I. Jordan; Geoffrey E. Hinton

1994-01-01

404

Estrogenic activity of UV filter mixtures  

Microsoft Academic Search

UV-absorbing chemicals (UV filters) are widely used for protection against UV radiation in sunscreens and in a variety of cosmetic products and materials. Depending on the breadth and factor of UV protection, they are added as single compounds or as a combination thereof. Some UV filters have estrogenic activity, but their activity and interactions in mixtures are largely unknown. In

Petra Y.. Kunz; Karl. Fent

2006-01-01

405

Vegetation-soil spectral mixture analysis  

Microsoft Academic Search

This paper describes the measurement and analysis of laboratory reflectance of green leaf and soil mixtures. Various combinations of leaf area index and percent cover were generated by stacking leaf discs over a dry soil background. Reflectance spectra (400-2500 nm) of these miniature pixels were measured with a spectroradiometer (Fieldspec FR) under laboratory conditions. The measured spectra were then compared

Bisun Datt; Michelle Paterson

2000-01-01

406

Fatigue behavior of SMA and HMA mixtures  

Microsoft Academic Search

Fatigue crack is a main form of structural damage in flexible pavements. Under the action of repeated vehicular loading, deterioration of the asphalt concrete materials in pavements caused by the accumulation and growth of the micro and macro cracks gradually takes place. The indirect tensile tests was carried out on hot mix asphalt HMA and stone matrix asphalt SMA mixtures

F. Moghadas Nejad; E. Aflaki; M. A. Mohammadi

2010-01-01

407

Characterisation of stone matrix asphalt mixtures  

Microsoft Academic Search

This study applied conventional laboratory tests and advanced imaging techniques to experimentally verify the voids in coarse aggregate (VCA) method. Five stone matrix asphalt (SMA) mixtures designed to have different coarse aggregate skeletons were investigated to establish relationships between the VCA ratio, microstructure parameters and the mechanical response of SMA. X-ray CT and image analysis techniques were utilised to non-destructively

Laith Tashman; Brian Pearson

2012-01-01

408

Characterisation of stone matrix asphalt mixtures  

Microsoft Academic Search

This study applied conventional laboratory tests and advanced imaging techniques to experimentally verify the voids in coarse aggregate (VCA) method. Five stone matrix asphalt (SMA) mixtures designed to have different coarse aggregate skeletons were investigated to establish relationships between the VCA ratio, microstructure parameters and the mechanical response of SMA. X-ray CT and image analysis techniques were utilised to non-destructively

Laith Tashman; Brian Pearson

2011-01-01

409

Superconductor precursor mixtures made by precipitation method  

DOEpatents

Method and apparatus for preparing highly pure homogeneous precursor powder mixtures for metal oxide superconductive ceramics. The mixes are prepared by instantaneous precipitation from stoichiometric solutions of metal salts such as nitrates at controlled pH's within the 9 to 12 range, by addition of solutions of non-complexing pyrolyzable cations, such as alkyammonium and carbonate ions.

Bunker, Bruce C. (Albuquerque, NM); Lamppa, Diana L. (Albuquerque, NM); Voigt, James A. (Albuquerque, NM)

1989-01-01

410

Biosurfactant-enhanced solubilization of NAPL mixtures  

NASA Astrophysics Data System (ADS)

Remediation of nonaqueous phase liquids (NAPLs) by conventional pump-and-treat methods (i.e., water flushing) is generally considered to be ineffective due to low water solubilities of NAPLs and to mass-transfer constraints. Chemical flushing techniques, such as surfactant flushing, can greatly improve NAPL remediation primarily by increasing the apparent solubility of NAPL contaminants. NAPLs at hazardous waste sites are often complex mixtures. However, the equilibrium and nonequilibrium mass-transfer characteristics between NAPL mixtures and aqueous surfactant solutions are not well understood. This research investigates the equilibrium solubilization behavior of two- and three-component NAPL mixtures (containing akylbenzenes) in biosurfactant solutions. NAPL solubilization is found to be ideal in water (i.e., obeys Raoult's Law), while solubilization in biosurfactant solutions was observed to be nonideal. Specifically, the relatively hydrophobic compounds in the mixture experienced solubility enhancements that were greater than those predicted by ideal enhanced solubilization theory, while the solubility enhancements for the relatively hydrophilic compounds were less than predicted. The degree of nonideality is shown to be a nonlinear function of the NAPL-phase mole fraction. Empirical relationships based on the NAPL-phase mole fraction and/or micelle-aqueous partition coefficients measured in single-component NAPL systems are developed to estimate values for the multicomponent partition coefficients. Empirical relationships that incorporate both the NAPL-phase mole fraction and single-component partition coefficients yield much improved estimates for the multicomponent partition coefficient.

McCray, John E.; Bai, Guiyun; Maier, Raina M.; Brusseau, Mark L.

2001-03-01

411

The macromolecular organic composition of plant and microbial residues as inputs to soil organic matter  

Microsoft Academic Search

Plant litter and the microbial biomass are the major parent materials for soil organic matter (SOM) formation. Plant litter is composed of complex mixtures of organic components, mainly polysaccharides and lignin, but also aliphatic biopolymers and tannins. The composition and relative abundance of these components vary widely among plant species and tissue type. Whereas some components, such as lignin, are

Ingrid Kögel-Knabner

2002-01-01

412

Laminar flame speeds of moist syngas mixtures  

SciTech Connect

This work experimentally investigates the effect of the presence of water vapor on the laminar flame speeds of moist syngas/air mixtures using the counterflow twin-flame configuration. The experimental results presented here are for fuel lean syngas mixtures with molar percentage of hydrogen in the hydrogen and carbon monoxide mixture varying from 5% to 100%, for an unburned mixture temperature of 323 K, and under atmospheric pressure. At a given equivalence ratio, the effect of varying amount of water vapor addition on the measured laminar flame speed is demonstrated. The experimental laminar flame speeds are also compared with computed values using chemical kinetic mechanisms reported in the literature. It is found that laminar flame speed varies non-monotonically with addition of water for the carbon monoxide rich mixtures. It first increases with increasing amount of water addition, reaches a maximum value, and then decreases. An integrated reaction path analysis is further conducted to understand the controlling mechanism responsible for the non-monotonic variation in laminar flame speed due to water addition. On the other hand, for higher values of H{sub 2}/CO ratio the laminar flame speed monotonically decreases with increasing water addition. It is shown that the competition between the chemical and thermal effects of water addition leads to the observed response. Furthermore, reaction rate sensitivity analysis as well as binary diffusion coefficient sensitivity analysis are conducted to identify the possible sources of discrepancy between the experimental and predicted values. The sensitivity results indicate that the reaction rate constant of H{sub 2}+OH = H{sub 2}O+H is worth revisiting and refinement of binary diffusion coefficient data of N{sub 2}-H{sub 2}O, N{sub 2}-H{sub 2}, and H{sub 2}-H{sub 2}O pairs can be considered. (author)

Das, Apurba K. [Department of Mechanical and Aerospace Engineering, Case Western Reserve University, Cleveland, OH 44106 (United States); Kumar, Kamal; Sung, Chih-Jen [Department of Mechanical Engineering, University of Connecticut, Storrs, CT 06269 (United States)

2011-02-15

413

Solubility of anthracene in binary alcohol + dibutyl ether solvent mixtures  

SciTech Connect

Solid-liquid equilibrium data of organic nonelectrolyte systems are becoming increasingly important in the petroleum industry, particularly in light of present trends toward heavier feedstocks and known carcinogenicity/mutagenicity of many of the larger polycyclic aromatic compounds. Experimental solubilities are reported for anthracene dissolved in seven binary mixtures containing dibutyl ether with 1-propanol, 2-propanol, 1-butanol, 2-butanol, 1-octanol, 2-methyl-1-propanol, and 3-methyl-1-butanol at 25 C. Results of these measurements are used to test two mathematical representations based upon the combined nearly ideal binary solvent (NIBS)/Redlich-Kister equation and modified Wilson model. For the systems studied, the combined NIBS/Redlich-Kister provided the better mathematical representations, with deviations between experimental and back-calculated values being on the order of {+-} 1.5% or less in the case of the three-parameter form. Slightly larger deviations were noted for the modified Wilson mathematical representation.

Powell, J.R.; Acree, W.E. Jr. [Univ. of North Texas, Denton, TX (United States). Dept. of Chemistry

1995-07-01

414

Solubility of anthracene in binary alcohol + 2-propoxyethanol solvent mixtures  

SciTech Connect

Solid-liquid equilibrium data of organic nonelectrolyte systems are becoming increasingly important in the petroleum industry, particularly in light of present trends toward heavier feedstocks and known carcinogenicity/mutagenicity of many of the larger polycyclic aromatic compounds. Experimental solubilities are reported for anthracene dissolved in seven binary mixtures containing 2-propoxyethanol with 1-propanol, 2-propanol, 1-butanol, 2-butanol, 1-pentanol, 1-octanol, and 3-methyl-1-butanol at 25 C. Results of these measurements are used to test two mathematical representations based upon the combined nearly ideal binary solvent (NIBS)/Redlich-Kister equation and modified Wilson model. For the seven systems studied, both equations were found to provide an accurate mathematical representation of the experimental data, with an overall average absolute deviation between measured and calculated values being on the order of 0.5%.

McHale, M.E.R.; Powell, J.R.; Kauppila, A.S.M.; Acree, W.E. Jr. [Univ. of North Texas, Denton, TX (United States). Dept. of Chemistry] [Univ. of North Texas, Denton, TX (United States). Dept. of Chemistry

1996-03-01

415

Monitoring oil-water mixture separation by time domain reflectometry  

NASA Astrophysics Data System (ADS)

Effective separation of water and oil is an essential part of petroleum production. Time domain reflectometry (TDR) can be used to profile the separation of hydrocarbon oil-water mixtures. In such two-component systems, metal electrodes will become oil-coated due to their affinity to oil. This coating layer will impact water content measurements. By combining the TDR signals from two probes in a novel configuration, the thickness of the oil layer on the electrodes can be estimated and its effect on the TDR measurements corrected for. The probes consist of two rods of different diameter and spacing to a common ground/guard electrode. The measurement principle is demonstrated using a light fuel oil and a thicker organic oil. The results indicate that oil and water levels can be monitored during separation if the metal electrode oil-coating effect is accounted for.

Bruvik, E. M.; Hjertaker, B. T.; Folgerø, K.; Meyer, S. K.

2012-12-01

416

A new kind of Molotov? Gasoline-pool chlorinator mixtures.  

PubMed

This paper investigates the reaction between pool chlorinators and gasoline. In particular, the propensity for self-ignition and the resulting chemical products were studied. An organic pool chlorinator was combined with gasoline in varying proportions in an attempt to form a hypergolic mixture. None of the combinations resulted in self-ignition, but larger quantities of chlorinator produced vigorous light-colored smoke and a solid mass containing isocyanuric acid and copper chloride. Additionally, the chlorinating abilities of different commercially available pool chlorinators were explored. When Ca(ClO)(2) and sodium dichloro-s-triazinetrione-based chlorinators were used, the presence of gasoline was still visible after 10 days, despite limited chlorination. The trichloro-s-triazinetrione-based chlorinator, however, caused efficient chlorination of the C(2)- and C(3)-alkylbenzenes, making gasoline no longer identifiable. PMID:22335833

Hutches, Katherine; Lord, James

2012-07-01

417

Leaching of Mixtures of Biochar and Fly Ash  

SciTech Connect

Increasing atmospheric levels of greenhouse gases, especially CO2, and their effects on global temperature have led to interest in the possibility of carbon storage in terrestrial environments.2, 5, 6 Both the residual char from biomass pyrolysis7-9, 12 (biochar) and fly ash from coal combustion1, 13, 14 have the potential to significantly expand terrestrial sequestration options. Both biochar and fly ash also have potentially beneficial effects on soil properties. Fly ash has been shown to increase porosity, water-holding capacity, pH, conductivity, and dissolved SO42-, CO32-, Cl- and basic cations.10, 11, 16 Adding biochar to soil generally raises pH, increases total nitrogen and total phosphorous, encourages greater root development, improves cation exchange capacity and reduces available aluminum.3, 17 Combinations of these benefits likely lead to the observed increased yields for crops including corn and sugarcane.17 with biochar addition to soil. In addition, it has been found that soils with added biochar emit lower amounts of other greenhouse gases (methane and nitrous oxide) 8, 17 than do unammended soils. Biochar and fly ash amendments may be useful in promoting terrestrial carbon sequestration on currently underutilized and degraded lands. For example, about 1% of the US surface lands consist of previously mined lands or highway rights-of-way.18 Poorly managed lands could count for another 15% of US area. Biochar and fly ash amendments could increase productivity of these lands and increase carbon storage in the soil Previous results showed minimal leaching of organic carbon and metals from a variety of fly ashes.15 Here, we are examining the properties of mixtures of biochar, fly ash, and soil and evaluating leaching of organic carbon and metals from the mixtures.

Palumbo, Anthony Vito [ORNL] [ORNL; Porat, Iris [ORNL] [ORNL; Phillips, Jana Randolph [ORNL] [ORNL; Amonette, J. E. [Pacific Northwest National Laboratory (PNNL)] [Pacific Northwest National Laboratory (PNNL); Drake, Meghan M [ORNL] [ORNL; Brown, Steven D [ORNL] [ORNL; Schadt, Christopher Warren [ORNL] [ORNL

2009-01-01

418

Dynamics of binary phase separation in liquid He-3-He-4 mixtures  

NASA Technical Reports Server (NTRS)

Binary phase-separation dynamics in liquid mixtures of He-3 and He-4 has been investigated near the tricritical point with laser-light scattering techniques. Rapid decompression of the mixtures results in quenches into the miscibility gap so that both the metastable and unstable (spinodal) regions can be probed. Quenches into the unstable region allowed measurements of the normalized dynamic structure factor S(k,t) that confirm the dynamical scaling hypotheses for spinodal decomposition. Measurements made for concentrations well away from the tricritical value show different behavior and suggest the presence of a spinodal boundary. Forward scattering intensities for shallow quenches probe nucleation phenomena and permit quantitative measurements of anomalous super-cooling as a function of quench rate. Comparisons with data in organic binary mixtures are given.

Hoffer, J. K.; Sinha, D. N.

1986-01-01

419

A note on the meaning of mixture viscosity using the classical continuum theories of mixtures  

SciTech Connect

In this paper we provide a brief review of the basic equations for the flow of two linearly viscous fluids using the mixture theory equations given in Atkin and Craine [R.J. Atkin, R.E. Craine, Continuum theories of mixtures: applications, J. Inst. Math. Appl. 17 (1976) 153; R.J. Atkin, R.E. Craine, Continuum theories of mixtures: basic theory and historical development, Quart. J. Mech. Appl. Math. 29 (1976) 290]. We then look at certain principles (or more accurately assumptions) due to Truesdell [C. Truesdell, Sulle basi della thermomeccanica, Rand Lincei, Series 8 22 (1957) 33–38, and 158–166] and Adkins [J.E. Adkins, Non-linear diffusion, 1. Diffusion and flow of mixtures of fluids, Philos. Trans. Roy. Soc. London A 255 (1963) 607–633; J.E. Adkins, Non-linear diffusion, 2. Constitutive equations for mixtures of isotropic fluids, Philos. Trans. Roy. Soc. London A 255 (1963) 635–648] and show that if the ‘assumption of the limiting cases’ of Adkins is to hold, then a very specific structure on the material properties of the two fluids has to be imposed. This new hypothesis provides one such condition for this requirement. An attempt is made to derive a relationship for the mixture viscosity using these ideas.

Massoudi, Mehrdad

2008-07-01

420

Method development for aquatic ecotoxicological characterization factor calculation for hydrocarbon mixtures in life cycle assessment.  

PubMed

Most pollutants are released into the environment in the presence of other contaminants, creating complex mixtures. In life-cycle impact assessment (LCIA) methods, characterization factors (CFs) are used to obtain the potential impacts associated with each contaminant emission. Current LCIA methods do not include CFs to evaluate the potential impacts of complex organic mixtures on ecosystems. This study explores the possibility of developing new CFs for petroleum mixtures. Petroleum products are an example of mixtures whose constituents have a common toxic mode of action: the narcosis effect. Characterization factors were calculated for a series of representative constituents of a specific petroleum mixture and also for different fractions of the same mixture developed using the hydrocarbon block (HBM) and Total Petroleum Hydrocarbon Criteria Working Group (TPHWG) methods. Finally, CFs were developed for the mixture itself as a whole by using experimental property measurements and estimations. The soil-water partitioning coefficient, water solubility, degradation kinetic constant in soil, octanol-water partitioning coefficient, and vapor pressure were measured while the molar weight and the degradation kinetic constants in air, water, and sediments were estimated. The highest aquatic ecotoxicological CFs, no matter the approach chosen, were obtained for an emission to freshwater up to 2.2 × 10(+07) PAF·m(3) ·d/kg for the highest CF. CF distributions obtained using the different blocking method and experimental CFs obtained for oil as a whole are, on average, not significantly different, given the known uncertainty of ecotoxicological models in LCIA. Consequently, all the CFs obtained using the different blocking methods from the literature are considered relevant for characterizing the potential impact for aquatic ecotoxicity of petroleum substances. PMID:21805496

Bamard, Emilie; Bulle, Cécile; Deschênes, Louise

2011-10-01

421

Acute toxicity of mixture of acetaminophen and ibuprofen to Green Neon Shrimp, Neocaridina denticulate.  

PubMed

In recent years, numerous studies have indicated that various long-term use drugs, such as antibiotics or analgesics, not only cannot be completely decomposed via sewage treatment but also exhibit biological toxicity if they enter the environment; thus, the release of these drugs into the environment can damage ecological systems. This study sought to investigate the acute toxicity of two commonly utilized analgesics, ibuprofen (IBU) and acetaminophen (APAP), to aquatic organisms after these drugs have entered the water. To address this objective, the acute toxicity (median lethal concentration, LC??, for a 96-h exposure) of IBU alone, APAP alone, and mixtures containing different ratios of IBU and APAP in green neon shrimp (Neocaridina denticulata) were measured. The results of four tests revealed that the 96-h LC?? values for IBU and APAP alone were 6.07 mg/L and 6.60 mg/L, respectively. The 96-h LC?? for a 1:1 mixture of IBU and APAP was 6.23 mg/L, and the toxicity of this mixture did not significantly differ from the toxicity of either drug alone (p<0.05). The experimental results for mixtures containing unequal ratios of IBU and APAP indicated that mixtures with high APAP concentrations and low IBU concentrations exhibited markedly greater toxicity in N. denticulata (LC??=4.78 mg/L) than APAP or IBU alone. However, mixtures with high IBU concentrations and low APAP concentrations exhibited lower toxicity in N. denticulata (LC??=6.78 mg/L) than IBU or APAP alone. This study demonstrated that different mixtures of IBU and APAP were associated with different toxic effects in green neon shrimp. PMID:24860956

Sung, Hung-Hung; Chiu, Yuh-Wen; Wang, Shu-Yin; Chen, Chien-Min; Huang, Da-Ji

2014-07-01

422

Roles of biomarkers in evaluating interactions among mixtures of lead, cadmium and arsenic  

SciTech Connect

Human exposure to environmental chemicals is most correctly characterized as exposure to mixtures of these agents. The metals/metalloids, lead (Pb), cadmium (Cd), and arsenic (As), are among the leading toxic agents detected in the environment. Exposure to these elements, particularly at chronic low dose levels, is still a major public health concern. Concurrent exposure to Pb, Cd, or As may produce additive or synergistic interactions or even new effects that are not seen in single component exposures. Evaluating these interactions on a mechanistic basis is essential for risk assessment and management of metal/metalloid mixtures. This paper will review a number of individual studies that addressed interactions of these metals/metalloids in both experimental and human exposure studies with particular emphasis on biomarkers. In general, co-exposure to metal/metalloid mixtures produced more severe effects at both relatively high dose and low dose levels in a biomarker-specific manner. These effects were found to be mediated by dose, duration of exposure and genetic factors. While traditional endpoints, such as morphological changes and biochemical parameters for target organ toxicity, were effective measures for evaluating the toxicity of high dose metal/metalloid mixtures, biomarkers for oxidative stress, altered heme biosynthesis parameters, and stress proteins showed clear responses in evaluating toxicity of low dose metal/metalloid mixtures. Metallothionein, heat shock proteins, and glutathione are involved in regulating interactive effects of metal/metalloid mixtures at low dose levels. These findings suggest that further studies on interactions of these metal/metalloid mixtures utilizing biomarker endpoints are highly warranted.

Wang Gensheng [Department of Experimental Radiation Oncology, U.T.M.D. Anderson Cancer Center, Houston, TX 77030 (United States)], E-mail: genwang@mdanderson.org; Fowler, Bruce A. [Division of Toxicology and Environmental Medicine, ATSDR, Atlanta, GA 30333 (United States)

2008-11-15

423

Toxic effect of metal cation binary mixtures to the seaweed Gracilaria domingensis (Gracilariales, Rhodophyta).  

PubMed

The macroalga Gracilaria domingensis is an important resource for the food, pharmaceutical, cosmetic, and biotechnology industries. G. domingensis is at a part of the food web foundation, providing nutrients and microelements to upper levels. As seaweed storage metals in the vacuoles, they are considered the main vectors to magnify these toxic elements. This work describes the evaluation of the toxicity of binary mixtures of available metal cations based on the growth rates of G. domingensis over a 48-h exposure. The interactive effects of each binary mixture were determined using a toxic unit (TU) concept that was the sum of the relative contribution of each toxicant and calculated using the ratio between the toxicant concentration and its endpoint. Mixtures of Cd(II)/Cu(II) and Zn(II)/Ca(II) demonstrated to be additive; Cu(II)/Zn(II), Cu(II)/Mg(II), Cu(II)/Ca(II), Zn(II)/Mg(II), and Ca(II)/Mg(II) mixtures were synergistic, and all interactions studied with Cd(II) were antagonistic. Hypotheses that explain the toxicity of binary mixtures at the molecular level are also suggested. These results represent the first effort to characterize the combined effect of available metal cations, based on the TU concept on seaweed in a total controlled medium. The results presented here are invaluable to the understanding of seaweed metal cation toxicity in the marine environment, the mechanism of toxicity action and how the tolerance of the organism. PMID:24920431

Mendes, Luiz Fernando; Stevani, Cassius Vinicius; Zambotti-Villela, Leonardo; Yokoya, Nair Sumie; Colepicolo, Pio

2014-07-01

424

Mixtures of Chemical Pollutants at European Legislation Safety Concentrations: How Safe Are They?  

PubMed Central

The risk posed by complex chemical mixtures in the environment to wildlife and humans is increasingly debated, but has been rarely tested under environmentally relevant scenarios. To address this issue, two mixtures of 14 or 19 substances of concern (pesticides, pharmaceuticals, heavy metals, polyaromatic hydrocarbons, a surfactant, and a plasticizer), each present at its safety limit concentration imposed by the European legislation, were prepared and tested for their toxic effects. The effects of the mixtures were assessed in 35 bioassays, based on 11 organisms representing different trophic levels. A consortium of 16 laboratories was involved in performing the bioassays. The mixtures elicited quantifiable toxic effects on some of the test systems employed, including i) changes in marine microbial composition, ii) microalgae toxicity, iii) immobilization in the crustacean Daphnia magna, iv) fish embryo toxicity, v) impaired frog embryo development, and vi) increased expression on oxidative stress-linked reporter genes. Estrogenic activity close to regulatory safety limit concentrations was uncovered by receptor-binding assays. The results highlight the need of precautionary actions on the assessment of chemical mixtures even in cases where individual toxicants are present at seemingly harmless concentrations. PMID:24958932

Carvalho, Raquel N.; Arukwe, Augustine; Ait-Aissa, Selim; Bado-Nilles, Anne; Balzamo, Stefania; Baun, Anders; Belkin, Shimshon; Blaha, Ludek; Brion, François; Conti, Daniela; Creusot, Nicolas; Essig, Yona; Ferrero, Valentina E. V.; Flander-Putrle, Vesna; Fürhacker, Maria; Grillari-Voglauer, Regina; Hogstrand, Christer; Jonáš, Adam; Kharlyngdoh, Joubert B.; Loos, Robert; Lundebye, Anne-Katrine; Modig, Carina; Olsson, Per-Erik; Pillai, Smitha; Polak, Natasa; Potalivo, Monica; Sanchez, Wilfried; Schifferli, Andrea; Schirmer, Kristin; Sforzini, Susanna; Stürzenbaum, Stephen R.; Søfteland, Liv; Turk, Valentina; Viarengo, Aldo; Werner, Inge; Yagur-Kroll, Sharon; Zounková, Radka; Lettieri, Teresa

2014-01-01

425

Excess compressibility in binary liquid mixtures.  

PubMed

Brillouin scattering experiments have been carried out on some mixtures of molecular liquids. From the measurement of the hypersonic velocities we have evaluated the adiabatic compressibility as a function of the volume fraction. We show how the quadratic form of the excess compressibility dependence on the solute volume fraction can be derived by simple statistical effects and does not imply any interaction among the components of the system other than excluded volume effects. This idea is supported by the comparison of the experimental results with a well-established prototype model, consisting of a binary mixture of hard spheres with a nonadditive interaction potential. This naive model turns out to be able to produce a very wide spectrum of structural and thermodynamic features depending on values of its parameters. An attempt has made to understand what kind of structural information can be gained through the analysis of the volume fraction dependence of the compressibility. PMID:17581064

Aliotta, F; Gapi?ski, J; Pochylski, M; Ponterio, R C; Saija, F; Salvato, G

2007-06-14

426

UV sensors based on liquid crystals mixtures  

NASA Astrophysics Data System (ADS)

The Erythemal Response Spectrum is a scientific expression that describes the sensitivity of the skin to the ultraviolet radiation. The skin sensitivity strongly depends on the UV wavelength: a long exposition to UV radiation causes erythema once a threshold dose has been exceeded. In the past years several devices have been developed in order to monitor the UV exposure, most of them are based on inorganic materials that are able to mimic the human skin behaviour under UV radiation. We present a new device based on liquid crystals technology. The sensor is based on a liquid crystalline mixture that absorbs photons at UV wavelength and emits them at a longer one. This system presents several innovative features: the absorption range of the mixture can be varied to be sensitive to different wavelengths, the luminescence intensity can be tuned, the system can be implemented on flexible devices.

Chanishvili, Andro; Petriashvili, Gia; Chilaya, Guram; Barberi, Riccardo; De Santo, Maria P.; Matranga, Mario A.; Ciuchi, F.

2006-04-01

427

Excess compressibility in binary liquid mixtures  

NASA Astrophysics Data System (ADS)

Brillouin scattering experiments have been carried out on some mixtures of molecular liquids. From the measurement of the hypersonic velocities we have evaluated the adiabatic compressibility as a function of the volume fraction. We show how the quadratic form of the excess compressibility dependence on the solute volume fraction can be derived by simple statistical effects and does not imply any interaction among the components of the system other than excluded volume effects. This idea is supported by the comparison of the experimental results with a well-established prototype model, consisting of a binary mixture of hard spheres with a nonadditive interaction potential. This naive model turns out to be able to produce a very wide spectrum of structural and thermodynamic features depending on values of its parameters. An attempt has made to understand what kind of structural information can be gained through the analysis of the volume fraction dependence of the compressibility.

Aliotta, F.; Gapi?ski, J.; Pochylski, M.; Ponterio, R. C.; Saija, F.; Salvato, G.

2007-06-01

428

A mixture of Bose and Fermi superfluids.  

PubMed

Superconductivity and superfluidity of fermionic and bosonic systems are remarkable many-body quantum phenomena. In liquid helium and dilute gases, Bose and Fermi superfluidity has been observed separately, but producing a mixture in which both the fermionic and the bosonic components are superfluid is challenging. Here we report on the observation of such a mixture with dilute gases of two lithium isotopes, lithium-6 and lithium-7. We probe the collective dynamics of this system by exciting center-of-mass oscillations that exhibit extremely low damping below a certain critical velocity. Using high-precision spectroscopy of these modes, we observe coherent energy exchange and measure the coupling between the two superfluids. Our observations can be captured theoretically using a sum-rule approach that we interpret in terms of two coupled oscillators. PMID:25035409

Ferrier-Barbut, I; Delehaye, M; Laurent, S; Grier, A T; Pierce, M; Rem, B S; Chevy, F; Salomon, C

2014-08-29

429

Hydraulic Transport of Ice-Water Mixtures  

NASA Astrophysics Data System (ADS)

When an ice thermal storage system is introduced into a district cooling system,the hydraulic ice transport system must have an advantage over a conventional water transport system in saving pipe sizes and pumping powers. Referring to the literature providing direct information on the hydraulic transport of ice-water mixtures,the author comments on the following subjects : •Definitions of an ice packing factor. • The capacity of heat transported with ice-water mixtures. • District distribution system. • Flow patterns in ice-water two-phase flow in straight pipes. • General expressions for pressure losses in solid-liquid two-phase flow. • The characteristics of pressure losses in ice-water two-phase flow. •Choking phenomena in channels.

Fujita, Toshihiko

430

Coexistence in a binary isotopic polymer mixture  

Microsoft Academic Search

We have measured directly the phase coexistence characteristics in a high-molecular- weight binary isotopic polymer mixture over a range of temperatures around the critical point, using nuclear-reaction analysis. Our results reveal an equilibrium phase diagram with an upper critical solution temperature, in fair quantitative accord with the simplest form of the Flory-Huggins mean-field model. Deviations may be due to a

A. Budkowski; U. Steiner; J. Klein; G. Schatz

1992-01-01

431

Structure of films prepared from compounded mixtures  

Microsoft Academic Search

Summary 1.The structure of a polymer containing a macromolecular plasticizer differs substantially from the structure of the polymer with a plasticizer of low molecular weight.2.In the case of mixtures of amorphous and crystalline polymersthe crystalline fraction is responsible for the structure and the amorphous fraction acts as a coarse-structure plasticizer and is distributed between the structural elements of the spherolites,

I. N. Musaelyan; G. L. Berestneva

1964-01-01

432

Population mixture model for nonlinear telomere dynamics  

NASA Astrophysics Data System (ADS)

Telomeres are DNA repeats protecting chromosomal ends which shorten with each cell division, eventually leading to cessation of cell growth. We present a population mixture model that predicts an exponential decrease in telomere length with time. We analytically solve the dynamics of the telomere length distribution. The model provides an excellent fit to available telomere data and accounts for the previously unexplained observation of telomere elongation following stress and bone marrow transplantation, thereby providing insight into the nature of the telomere clock.

Itzkovitz, Shalev; Shlush, Liran I.; Gluck, Dan; Skorecki, Karl

2008-12-01

433

Asymmetric caging in soft colloidal mixtures  

NASA Astrophysics Data System (ADS)

The long-standing observations that different amorphous materials exhibit a pronounced enhancement of viscosity and eventually vitrify on compression or cooling continue to fascinate and challenge scientists, on the ground of their physical origin and practical implications. Glass formation is a generic phenomenon, observed in physically quite distinct systems that encompass hard and soft particles. It is believed that a common underlying scenario, namely cage formation, drives dynamical arrest, especially at high concentrations. Here, we identify a novel, asymmetric glassy state in soft colloidal mixtures, which is characterized by strongly anisotropically distorted cages, bearing similarities to those of hard-sphere glasses under shear. The anisotropy is induced by the presence of soft additives. This phenomenon seems to be generic to soft colloids and its origins lie in the penetrability of the constituent particles. The resulting phase diagram for mixtures of soft particles is clearly distinct from that of hard-sphere mixtures and brings forward a rich variety of vitrified states that delineate an ergodic lake in the parameter space spanned by the size ratio between the two components and by the concentration of the additives. Thus, a new route opens for the rational design of soft particles with desired tunable rheological properties.

Mayer, C.; Zaccarelli, E.; Stiakakis, E.; Likos, C. N.; Sciortino, F.; Munam, A.; Gauthier, M.; Hadjichristidis, N.; Iatrou, H.; Tartaglia, P.; Löwen, H.; Vlassopoulos, D.

2008-10-01

434

Efficient radiative transfer in dust grain mixtures  

E-print Network

The influence of a dust grain mixture consisting of spherical dust grains with different radii and/or chemical composition on the resulting temperature structure and spectral energy distribution of a circumstellar shell is investigated. The comparison with the results based on an approximation of dust grain parameters representing the mean optical properties of the corresponding dust grain mixture reveal that (1) the temperature dispersion of a real dust grain mixture decreases substantially with increasing optical depth, converging towards the temperature distribution resulting from the approximation of mean dust grain parameters, and (2) the resulting spectral energy distributions do not differ by more than 10% if >= 2^5 grain sizes are considered which justifies the mean parameter approximation and the many results obtained under its assumption so far. Nevertheless, the dust grain temperature dispersion at the inner boundary of a dust shell may amount to >>100K and has therefore to be considered in the correct simulation of, e.g., chemical networks. In order to study the additional influence of geometrical effects, a two-dimensional configuration -- the HH30 circumstellar disk -- was considered, using model parameters from Cotera et al. (2001) and Wood et al. (2002). A drastic inversion of the large to small grain temperature distribution was found within the inner approx. 1AU of the disk.

S. Wolf

2002-09-13

435

Dual-water mixture fuel burner  

DOEpatents

A coal-water mixture (CWM) burner includes a conically shaped rotating cup into which fuel comprised of coal particles suspended in a slurry is introduced via a first, elongated inner tube coupled to a narrow first end portion of the cup. A second, elongated outer tube is coaxially positioned about the first tube and delivers steam to the narrow first end of the cup. The fuel delivery end of the inner first tube is provided with a helical slot on its lateral surface for directing the CWM onto the inner surface of the rotating cup in the form of a uniform, thin sheet which, under the influence of the cup's centrifugal force, flows toward a second, open, expanded end portion of the rotating cup positioned immediately adjacent to a combustion chamber. The steam delivered to the rotating cup wets its inner surface and inhibits the coal within the CWM from adhering to the rotating cup. A primary air source directs a high velocity air flow coaxially about the expanded discharge end of the rotating cup for applying a shear force to the CWM in atomizing the fuel mixture for improved combustion. A secondary air source directs secondary air into the combustion chamber adjacent to the outlet of the rotating cup at a desired pitch angle relative to the fuel mixture/steam flow to promote recirculation of hot combustion gases within the ignition zone for increased flame stability.

Brown, Thomas D. (Finleyville, PA); Reehl, Douglas P. (Pittsburgh, PA); Walbert, Gary F. (Library, PA)

1986-08-05

436

Generalized Mixture Models for Molecular Phylogenetic Estimation  

PubMed Central

The rapidly growing availability of multigene sequence data during the past decade has enabled phylogeny estimation at phylogenomic scales. However, dealing with evolutionary process heterogeneity across the genome becomes increasingly challenging. Here we develop a mixture model approach that uses reversible jump Markov chain Monte Carlo (MCMC) estimation to permit as many distinct models as the data require. Each additional model considered may be a fully parametrized general time-reversible model or any of its special cases. Furthermore, we expand the usual proposal mechanisms for topology changes to permit hard polytomies (i.e., zero-length internal branches). This new approach is implemented in the Crux software toolkit. We demonstrate the feasibility of using reversible jump MCMC on mixture models by reexamining a well-known 44-taxon mammalian data set comprising 22 concatenated genes. We are able to reproduce the results of the original analysis (with respect to bipartition support) when we make identical assumptions, but when we allow for polytomies and/or use data-driven mixture model estimation, we infer much lower bipartition support values for several key bipartitions. PMID:21873377

Evans, Jason; Sullivan, Jack

2012-01-01

437

Separation of gas mixtures by thermoacoustic waves.  

SciTech Connect

Imposing sound on a binary gas mixture in a duct separates the two gases along the acoustic-propagation axis. Mole-fraction differences as large as 10% and separation fluxes as high as 0.001 M-squared c, where M is Mach number and c is sound speed, are easily observed. We describe the accidental discovery of this phenomenon in a helium-xenon mixture, subsequent experiments with a helium-argon mixture, and theoretical developments. The phenomenon occurs because a thin layer of the gas adjacent to the wall is immobilized by viscosity while the rest of the gas moves back and forth with the wave, and the heat capacity of the wall holds this thin layer of the gas at constant temperature while the rest of the gas experiences temperature oscillations due to the wave's oscillating pressure. The oscillating temperature gradient causes the light and heavy atoms in the gas to take turns diffusing into and out of the immobilized layer, so that the oscillating motion of the wave outside the immobilized layer tends to carry light-enriched gas in one direction and heavy-enriched gas in the opposite direction. Experiment and theory are in very good agreement for the initial separation fluxes and the saturation mole-fraction differences.

Swift, G. W. (Gregory W.); Geller, D. A. (Drew A.)

2001-01-01

438

Mixtures with relatives: a pedigree perspective.  

PubMed

DNA mixture evidence pertains to cases where several individuals may have contributed to a biological stain. Statistical methods and software for such problems are available and a large number of cases can be handled adequately. However, one class of mixture problems remains untreated in full generality in the literature, namely when the contributors may be related. Disregarding a plausible close relative of the perpetrator as an alternative contributor (identical twin is the most extreme case) may lead to overestimating the evidence against a suspect. Existing methods only accommodate pairwise relationships such as the case where the suspect and the victim are siblings, for example. In this paper we consider relationships in full generality, conveniently represented by pedigrees. In particular, these pedigrees may involve inbreeding, for instance when the parents of an individual of interest are first cousins. Furthermore our framework handles situations where the opposing parties in a court case (prosecution and defence) propose different family relationships. Consequently, our approach combines classical mixture and kinship problems. The basic idea of this paper is to formulate the problem in a way that allows for the exploitation of currently available methods and software designed originally for linkage applications. We have developed a freely available R package, euroMix based on another package, paramlink, and we illustrate the ideas and methods on real and simulated data. PMID:24572837

Egeland, Thore; Dørum, Guro; Vigeland, Magnus Dehli; Sheehan, Nuala A

2014-05-01

439

Tambar, Kano, and Stoltz, Supporting Information 1 Supplemental materials for  

E-print Network

ammonium molybdate, and potassium permanganate staining. ICN silica gel (particle size 0.032 - 0.063 mm.9 g, 131 mol). The mixture was refluxed with azeotropic removal of H2O. After stirring for 40 hours

Stoltz, Brian M.

440

Synergetic Antimicrobial Effects of Mixtures of Ethiopian Honeys and Ginger Powder Extracts on Standard and Resistant Clinical Bacteria Isolates  

PubMed Central

Purpose. To evaluate antimicrobial effects of mixtures of Ethiopian honeys and ginger rhizome powder extracts on Staphylococcus aureus (ATCC 25923), Escherichia coli (ATCC 25922), Staphylococcus aureus (MRSA), Escherichia coli (R), and Klebsiella pneumoniae (R). Methods. Agar diffusion and broth assays were performed to determine susceptibility of these standard and resistant clinical bacteria isolates using honey-ginger powder extract mixtures. Results. Honey-ginger powder extract mixtures produced the highest mean inhibition (25.62?mm ± 2.55) compared to the use of honeys (21.63?mm ± 3.30) or ginger extracts (19.23?mm ± 3.42) individually. The ranges of inhibitions produced by honey-ginger extract mixtures on susceptible test organisms (26–30?mm) and resistant strains (range: 19–27?mm) were higher compared to 7–22?mm and 0–14?mm by standard antibiotic discs. Minimum inhibitory concentrations (MIC) of mixture of honeys-ginger extracts were 6.25% (0.625?v/mL) on the susceptible bacteria compared to 75% for resistant clinical isolates. Minimum bactericidal concentration (MBC) of honey-ginger extracts was 12.5% (0.125?g/mL) for all the test organisms. Conclusion. The result of this study showed that honey-ginger powder extract mixtures have the potential to serve as cheap source of antibacterial agents especially for the drug resistant bacteria strains. PMID:24772182

Ewnetu, Yalemwork; Lemma, Wossenseged; Birhane, Nega

2014-01-01