Transport behavior of selected nanoparticles with different surface coatings in granular porous media coated with Pseudomonas aeruginosa biofilm

Well-controlled laboratory column experiments were conducted to understand the influence of Pseudomonas aeruginosa (P. aeruginosa) biofilms on the transport of selected engineered nanoparticles (ENPs) in granular porous media representative of groundwater aquifers or riverbank filtration settings. To understand the importance of particle size on retention in the biofilm-coated granular (quartz sand) matrix, column experiments were carried out using nanosized (20 nm) and micrometer-sized (1 μm) sulfate-functionalized polystyrene latex particles (designated as 20 nSL and 1 mSL, respectively). Additional experiments conducted with nanosized (20 nm) carboxyl-modified latex particles (20nCL) and carboxyl-modified CdSe/ZnS quantum dots (QDs) provide information on the influence of particle surface chemistry on retention. Biofilm grown on the surface of the sand was characterized by total biomass quantification, confocal laser scanning microscopy (CLSM), and electrokinetic analysis. All four particles exhibit increased retention in the biofilm-coated packed bed: e.g., the attachment efficiency (α) of the 1 mSL particle increases from 0.40 to 1.7, whereas α for the 20 nSL particle increases from 0.04 to 0.10 in the biofilm-coated system. Particle surface chemistry can also influence the affinity of the ENPs for the biofilm coating as revealed by the greater attachment of the 20 nSL particle onto the biofilm-coated sand (α = 0.10) than its carboxylated counterpart (α = 0.04). Column experiments conducted using sand coated with growth medium (LB) or extracellular polymeric substances (EPS) extracted from P. aeruginosa biofilms further reveal that particle surface chemistry influences the interaction between the different ENPs and these coated sand surfaces. Namely, coating of sand surfaces with LB medium or bacterial EPS does not affect the transport of the sulfonated nanoparticle, but the LB coating leads to decreased retention of the carboxylated latex nanoparticle. Furthermore, our results show that EPS coatings are not necessarily good surrogates for biofilm-coated sand. Electrokinetic characterization of the clean and coated sand surfaces also reveals that the extent of particle retention is not controlled by electrical double layer interactions. Future studies should thus be aimed at improving our understanding of the fundamental mechanisms (both colloidal and noncolloidal) governing nanoparticle transport and fate in biofilm-laden granular aquatic environments.     

Fibers from fruit by-products enhance probiotic viability and fatty acid profile and increase CLA content in yoghurts

This study evaluated the effect of the supplementation of total dietary fiber from apple, banana or passion fruit processing by-products on the post-acidification, total titratable acidity, bacteria counts and fatty acid profiles in skim milk yoghurts co-fermented by four different probiotics strains: Lactobacillus acidophilus L10 and Bifidobacterium animalis subsp. lactis BL04, HN019 and B94. Apple and banana fibers increased the probiotic viability during shelf-life. All the fibers were able to increase the short chain and polyunsaturated fatty acid contents of yoghurts compared to their respective controls. A synergistic effect between the type of fiber and the probiotic strain on the conjugated linoleic acid content was observed, and the amount of α-linolenic acid was increased by banana fiber. The results of this study demonstrate, for the first time, that fruit fibers can improve the fatty acid profile of probiotic yoghurts and point out the suitability of using fibers from fruit processing the by-products to develop new high value-added fermented dairy products.     

Surface area and the seabed area, volume, depth, slope, and topographic variation for the world's seas, oceans, and countries

Depth and topography directly and indirectly influence most ocean environmental conditions, including light penetration and photosynthesis, sedimentation, current movements and stratification, and thus temperature and oxygen gradients. These parameters are thus likely to influence species distribution patterns and productivity in the oceans. They may be considered the foundation for any standardized classification of ocean ecosystems and important correlates of metrics of biodiversity (e.g., species richness and composition, fisheries). While statistics on ocean depth and topography are often quoted, how they were derived is rarely cited, and unless calculated using the same spatial resolution the resulting statistics will not be strictly comparable. We provide such statistics using the best available resolution (1-min) global bathymetry, and open source digital maps of the world's seas and oceans and countries' Exclusive Economic Zones, using a standardized methodology. We created a terrain map and calculated sea surface and seabed area, volume, and mean, standard deviation, maximum, and minimum, of both depth and slope. All the source data and our database are freely available online. We found that although the ocean is flat, and up to 71% of the area has a < 1 degree slope. It had over 1 million approximately circular features that may be seamounts or sea-hills as well as prominent mountain ranges or ridges. However, currently available global data significantly underestimate seabed slopes. The 1-min data set used here predicts there are 68,669 seamounts compared to the 30,314 previously predicted using the same method but lower spatial resolution data. The ocean volume exceeds 1.3 billion km(3) (or 1.3 sextillion liters), and sea surface and seabed areas over 354 million km(2). We propose the coefficient of variation of slope as an index of topographic heterogeneity. Future studies may improve on this database, for example by using a more detailed bathymetry, and in situ measured data. The database could be used to classify ocean features, such as abyssal plains, ridges, and slopes, and thus provide the basis for a standards based classification of ocean topography.     

Characterisation of volatiles and polyphenols for quality assessment of alcoholic beverages prepared from Corsican Myrtus communis berries

In the present work, the essential oil compositions of Myrtus communis berries from ten Corsican localities were studied and no chemical variability was observed. HS–SPME, GC and GC/MS analysis were carried out for the characterisation of volatile fractions of M. communis berries and two derived commercial alcoholic beverages (liqueur and eau-de-vie). Quantitative variations due to the distillation process were observed between the two beverages. The volatile compositions of Corsican myrtle alcoholic products were characterised by high amounts of monoterpene hydrocarbons and oxygenated monoterpenes with α-pinene and 1,8-cineole as major components. The polyphenolic compositions of the berry extract and the liqueur were also established using HPLC–DAD and LC–MS–MS; high concentrations of flavonol glycosides, flavonols and flavanols were reported.     

Enhanced cellular uptake of a glutathione selective fluorogenic probe encapsulated in nanoparticles

Selective fluorogenic probes for the labelling of intracellular reduced glutathione (GSH), i.e.?ortho-phthaldialdehyde (OPA) and naphthalene-2,3-dicarboxaldehyde (NDA), have been encapsulated in polymeric nanoparticles (NPs) and the ability of the NPs to enhance uptake of the probe by microbial cells has been evaluated. Preparation of the probe-loaded NPs composed of Eudragit(?) E was based on an oil-in-water emulsification solvent evaporation method using an ultrasonic probe and polyvinyl alcohol as the surfactant. The encapsulation efficiency of the probes in lyophilized NPs was determined using high performance liquid chromatography (HPLC). A higher encapsulation rate of NDA than OPA was found: 47.6 ± 9.9?(n = 6) and 2.1 ± 0.2%?(n = 3), respectively. The NDA-loaded particle diameter and zeta potential were 224.6 ± 14.7?nm and +40.9 ± 6.5?mV, respectively. After 20?min incubation of cultured Candida albicans yeast cells with either free NDA or NDA-loaded NPs (final NDA concentration 100?μM), cells were harvested and corresponding lysates were analysed using HPLC coupled with spectrofluorimetric detection. Incubation of cells with NDA-loaded NPs increased intracellular levels of NDA-GSH adduct by about nine-fold in comparison with the free probe. Adhesion on the cells and the penetration behaviour of NPs loaded with either NDA or fluorescent label (Nile Red) were characterized qualitatively by confocal laser scanning microscopy.     

Including mixtures in the determination of water quality criteria for herbicides in surface water

Monitoring programs throughout America and Europe have demonstrated the common occurrence of herbicides in surface water. Nevertheless, mixtures are rarely taken into account in water quality regulation. Taking mixtures into account is only feasible if the water quality criteria (WQC) of the single compounds are derived by a common and consistent methodology, which overcomes differences in data quality without settling on the lowest common denominator but making best use of all available data. In this paper, we present a method of defining a risk quotient for mixtures of herbicides with a similar mode of action (RQm). Consistent and comparable WQC are defined for single herbicides as a basis for the calculation of the RQm. Derived from the concentration addition model, the RQm can be expressed as the sum of the ratios of the measured environmental concentration and the WQC for each herbicide. The RQm should be less than one to ensure an acceptable risk to aquatic life. This approach has the advantage of being easy to calculate and communicate, and is proposed as a replacement for the current limit of 0.1 microg/L for herbicides in Switzerland. We illustrate the proposed approach on the example of five commonly applied herbicides (atrazine, simazine, terbuthylazine, isoproturon, and diuron). Their risk profile, i.e., the RQm as a function of time for one exemplary river, clearly shows that the single compounds rarely exceeded their individual WQC. However, the contribution of peaks of different seasonally applied herbicides, whose application periods partially overlap, together with the continuously emitted herbicides from nonagricultural use, results in the exceedance of the RQm threshold value of one upon several occasions.     

Hydrodynamic dispersion in shallow microchannels: the effect of cross-sectional shape

We highlight the fact that hydrodynamic dispersion in shallow microchannels is in most cases controlled by the width of the cross section rather than by the much thinner height of the channel. We identify the relevant time scales that separate the various regimes involved. Using the lubrication approximation, we provide simple formulas that permit a quantitative evaluation of dispersion for most shallow cross-sectional shapes in the "long-time" Taylor regime, which is effectively diffusive. Because of its relevance for microfluidic systems, we also provide results for the short-time "ballistic regime" (for specific initial conditions). The special cases of parabolic and quasi-rectangular shapes are considered due to their frequent use in microsystems.     

Two-photon excitation fluorescence microscopy with a high depth of field using an axicon

In conventional two-photon excitation fluorescence microscopy, the numerical aperture of the objective determines the lateral resolution and the depth of field. In some situations, as with functional imaging of dynamic events distributed in live biological tissue, an improved temporal resolution is needed; as a consequence, it is imperative to use optics with a high depth of field to simultaneously image objects at different axial positions. With a conventional microscope objective, increasing the depth of field is achieved at the expense of lateral resolution. To overcome this limitation, we have incorporated an axicon in a two-photon excitation fluorescence microscopy system; measurements have shown that an axicon provides a depth of field in excess of a millimeter, while the lateral resolution is maintained at the micrometer scale. Thus axicon-based two-photon microscopy has been shown to yield a high-resolution projection image of a sample with a single 2D scan of the laser beam while maintaining the improved tissue penetration typical of two-photon microscopy.     

Prediction of source rock origin by chemometric analysis of fourier transform infrared-attenuated total reflectance spectra of oil petroleum: evaluation of aliphatic and aromatic fractions by self-modeling mixture analysis

This study describes a new methodology for the interpretation of Fourier transform infrared (FT-IR) attenuated total reflectance (ATR) spectra of Algerian, Brazilian, and Venezuelan crude oils. It is based on a comparative study between a chemometric treatment and the classical one, which refers to indices calculation. In fact, the combined use of FT-IR indices and principal component analysis (PCA) has led to the classification of the studied samples in terms of geographic distribution. Quantitative analysis has been successfully realized by the supervised method partial least squares (PLS), which has permitted the prediction of the locations of oils. We have also applied another mathematical processing method, simple-to-use interactive self-modeling mixture analysis (SIMPLISMA), to evaluate the aromatic and aliphatic composition of the oils by extracting pure spectra representative of the different fractions.     

Validation of a stochastic modelling approach for Listeria monocytogenes growth in refrigerated foods

A stochastic modelling approach was developed to describe the distribution of Listeria monocytogenes contamination in foods throughout their shelf life. This model was designed to include the main sources of variability leading to a scattering of natural contaminations observed in food portions: the variability of the initial contamination, the variability of the biological parameters such as cardinal values and growth parameters, the variability of individual cell behaviours, the variability of pH and water activity of food as well as portion size, and the variability of storage temperatures. Simulated distributions of contamination were compared to observed distributions obtained on 5 day-old and 11 day-old cheese curd surfaces artificially contaminated with between 10 and 80 stressed cells and stored at 14 °C, to a distribution observed in cold smoked salmon artificially contaminated with approximately 13 stressed cells and stored at 8 °C, and to contaminations observed in naturally contaminated batches of smoked salmon processed by 10 manufacturers and stored for 10 days a 4 °C and then for 20 days at 8 °C. The variability of simulated contaminations was close to that observed for artificially and naturally contaminated foods leading to simulated statistical distributions properly describing the observed distributions. This model seems relevant to take into consideration the natural variability of processes governing the microbial behaviour in foods and is an effective approach to assess, for instance, the probability to exceed a critical threshold during the storage of foods like the limit of 100 CFU/g in the case of L. monocytogenes.