An extended mixture model for the simultaneous treatment of small‐scale and large‐scale interfaces

The aim of this work is to present a new model based on the volume of fluid method and the algebraic slip mixture model in order to solve multiphase gas–fluid flows with different interface scales and the transition among them. The interface scale is characterized by a measure of the grid, which acts as a geometrical filter and is related with the accuracy in the solution; in this sense, the presented coupled model allows to reduce the grid requirements for a given accuracy. With this objective in mind, a generalization of the algebraic slip mixture model is proposed to solve problems involving small‐scale and large‐scale interfaces in an unified framework taking special care in preserving the conservativeness of the fluxes. This model is implemented using the OpenFOAM^® libraries to generate a tool capable of solving large problems on high‐performance computing facilities. Several examples are solved as a validation for the presented model, including new quantitative measurements to assess the advantages of the method. Copyright © 2014 John Wiley & Sons, Ltd.     

LC-QqLIT MS analysis of nine sulfonamides and one of their acetylated metabolites in the Llobregat River basin. Quantitative determination and qualitative evaluation by IDA experiments

Robust instrumental analytical chemistry and the subsequent development of improved analytical methodologies and extraction procedures have enabled the detection at environmental levels of new emerging contaminants, for example pharmaceuticals. The objective of this study was to explore the potential of liquid chromatography–tandem quadrupole-linear ion trap (LC–QqLIT MS) for quantitative determination of nine sulfonamides (SAs) and one acetylated metabolite in surface water from the Llobregat River and one of its main tributaries, the Anoia River, in Catalonia (Spain). A total of 21 samples were taken in three sampling campaigns. Recoveries ranging from 26% to 123% were calculated for the SAs studied, and method limits of detection (MLODs) achieved were in the range 0.05–0.2 ng L⁻¹. Through the different campaigns, concentrations ranged from 0.74 ng L⁻¹ (sulfamethizole) to 2,482 ng L⁻¹ (sulfamethazine) in the Llobregat River, and from 0.27 ng L⁻¹ (sulfamethizole) to 168 ng L⁻¹ (sulfamethoxazole) in the Anoia River. Sulfamethoxazole and sulfapyridine were the two SAs most frequently detected (80% and 71% respectively). N ⁴-acetylsulfamethazine was detected in both rivers, but with different frequencies (4% of the samples from the Anoia River and 43% of those from the Llobregat River). Information-dependent acquisition (IDA) experiments were also developed in order to obtain enhanced product-ion spectra in surface water samples.     

Ecotoxicity and analysis of nanomaterials in the aquatic environment

Nanotechnology is a major innovative scientific and economic growth area. However nanomaterial residues may have a detrimental effect on human health and the environment. To date there is a lack of quantitative ecotoxicity data, and recently there has been great scientific concern about the possible adverse effects that may be associated with manufactured nanomaterials. Nanomaterials are in the 1- to 100-nm size range and can be composed of many different base materials (carbon, silicon and metals, such as gold, cadmium and selenium) and they have different shapes. Particles in the nanometer size range do occur both in nature and as a result of existing industrial processes. Nevertheless, new engineered nanomaterials and nanostructures are different because they are being fabricated from the “bottom up”. Nanomaterial properties differ compared with those of the parent compounds because about 40–50% of the atoms in nanoparticles (NPs) are on the surface, resulting in greater reactivity than bulk materials. Therefore, it is expected that NPs will have different biological effects than parent compounds. In addition, release of manufactured NPs into the aquatic environment is largely an unknown. The surface properties and the very small size of NPs and nanotubes provide surfaces that may bind and transport toxic chemical pollutants, as well as possibly being toxic in their own right by generating reactive radicals. This review addresses hazards associated and ecotoxicological data on nanomaterials in the aquatic environment. Main weaknesses in ecotoxicological approaches, controversies and future needs are discussed. A brief discussion on the scarce number of analytical methods available to determinate nanomaterials in environmental samples is included.     

Synthesis and antidepressant evaluation of three para-benzoquinone mono-oximes and their oxy derivatives

A series of three para-benzoquinone mono-oximes and four oxy-derivatives were prepared and tested for their antidepressant properties. The (4E) oxime of 2-isopropyl-5-methyl-para-benzoquinone (4) and the corresponding 2-diethylamino-ethyl derivative (10) present antidepressant activities and were slightly more potent than the reference standard.     

A unified electrostatic and cavitation model for first-principles molecular dynamics in solution

The electrostatic continuum solvent model developed by [Fattebert and Gygi J. Comput. Chem. 23, 662 (2002); Int. J. Quantum Chem. 93, 139 (2003)] is combined with a first-principles formulation of the cavitation energy based on a natural quantum-mechanical definition for the surface of a solute. Despite its simplicity, the cavitation contribution calculated by this approach is found to be in remarkable agreement with that obtained by more complex algorithms relying on a large set of parameters. Our model allows for very efficient Car-Parrinello simulations of finite or extended systems in solution and demonstrates a level of accuracy as good as that of established quantum-chemistry continuum solvent methods. We apply this approach to the study of tetracyanoethylene dimers in dichloromethane, providing valuable structural and dynamical insights on the dimerization phenomenon.     

Sexually transmitted infections and the marriage problem

We study an SIS epidemiological model for a sexually transmitted infection in a monogamous population where the formation and breaking of couples is governed by individual preferences. The mechanism of couple recombination is based on the so-called bar dynamics for the marriage problem. We compare the results with those of random recombination – where no individual preferences exist – for which we calculate analytically the infection incidence and the endemic threshold. We find that individual preferences give rise to a large dispersion in the average duration of different couples, causing substantial changes in the incidence of the infection and in the endemic threshold. Our analysis yields also new results on the bar dynamics, that may be of interest beyond the field of epidemiological models.     

Quantitative trace analysis of fullerenes in river sediment from Spain and soils from Saudi Arabia

A quantitative method based on ultrasound-assisted toluene extraction followed by liquid chromatography–electrospray ionization–tandem mass spectrometry for the analysis of C₆₀ and C₇₀ fullerenes, N-methylfulleropyrrolidine, [6, 6]-phenyl C₆₁ butyric acid methyl ester and [6, 6]-thienyl C₆₁ butyric acid methyl ester has been developed. The method was validated using fortified blank river sediments according to the criteria of Commission Decision 2002/657/EC. The method limits of detection ranged from 14 to 290 pg/g, making it suitable for its application in environmental analysis. The method has been applied to investigate fullerene content in 58 soil samples collected from different urban and industrial areas in Saudi Arabia and in river sediment from six different sites in the Llobregat River Basin. In addition, in the case of the Llobregat River, superficial water samples from the same sites of the sediments were collected and analysed using a previous method. In soils from Saudi Arabia, C₆₀-fullerene was the only compound that was detected and quantified in 19 % of samples. In the sediments of the Llobregat River, C₆₀-fullerene was also the only one detected (33 % of the samples), while in river water, C₇₀-fullerene was the most frequent compound, and it was quantified in 67 % of the samples. However, C₆₀-fullerene was present in two of the six samples, but at higher concentrations than C₇₀-fullerene, ranging from 0.9 to 7.8 ng/L.     

Analysis of alcohol ethoxylates and alkylamine ethoxylates in agricultural soils using pressurised liquid extraction and liquid chromatography–mass spectrometry

Nonionic surfactants e.g. alcohol ethoxylates (AEOs) and alkylamine ethoxylates (ANEOs) are commonly utilised as adjuvants in pesticide formulations to enhance their effectiveness. In this study, analytical methods for AEO and ANEO determination in soil samples using pressurised liquid extraction (PLE) were developed and used in connection with LC–MS. The recovery of the method, which was highly dependent on the soil properties, varied in the range 47–106% for AEO and 27–109% for ANEO. Detection limits (LOD) were 7–13 µg kg^–1 for AEO and 24–43 µg kg^–1 for ANEO. The developed method has been applied to determine AEOs and ANEOs in surface soil samples from fields sprayed with glyphosate herbicides. Tallowalkylamine ethoxylates (an ANEO) were detected in the soil before and after pesticide application, with increasing concentrations after treatment. The highest concentration in the soil samples was observed for the ANEO homologues with the longest ethoxy chains; in the clay soil the concentration decreased with the length of the ethoxy chain. ANEOs added to pesticide formulations as a technical mixture will, as demonstrated in this study, behave as individual homologues, which is reflected in their behaviour in the environment.Abbreviations AEO Alcohol ethoxylates - ANEO Alkylamine ethoxylates - APEO Alkylphenol ethoxylates - APCI Atmospheric pressure chemical ionisation - ASE Accelerated solvent extraction - CEC Cationic exchange capacity - LC–MS Liquid chromatography–mass spectrometry - LOD Limit of detection - MAE Microwave-assisted extraction - PLE Pressurised liquid extraction - SD Standard deviation - SIM Selected-ion monitoring - SPE Solid-phase extraction - TEA Triethylamine