Do ternary liquid mixtures exhibit negative main Fick diffusion coefficients?

Experimental data on Fick diffusion coefficients of ternary and higher mixtures depend on the reference frame; those which are in common use are associated with the average velocity either with respect to volume, mass or mole number. In this study, the dependence of diffusion coefficients on the reference frame is thoroughly analyzed for three ternary mixtures of different types. The first one, tetralin-isobutylbenzene-dodecane, can almost be considered as ideal, the second one, cyclohexane-toluene-methanol, exhibits liquid-liquid phase separation and the third one, water-ethanol-triethylene glycol, contains three associating species and is also strongly non-ideal. Experimental diffusion coefficient data sampled in the volume reference frame are transformed to the molar and mass reference frames. The required partial molar volumes are derived from present density measurements. Four additional mixtures are considered along a single or two composition paths. A highlight of this study is the existence of a strong similarity of the main diffusion coefficients in the volume and mass reference frames for all considered mixtures. When the excess volume is small, the coefficients in the molar reference frame are also similar. However, for the mixture with a large excess volume (containing water), the diffusion coefficients in the molar reference frame differ significantly, even indicating negative main diffusion coefficients. It is shown that negative main diffusion coefficients appear due to relatively large experimental uncertainties of cross diffusion coefficients, which are propagated and amplified by frame transformation.

Development of a novel multiplexed qPCR and Pyrosequencing method for the detection of human pathogenic yersiniae.

The purpose of this study was to develop a novel and robust molecular assay for the detection of human pathogenic yersiniae (i.e. Yersinia enterocolitica, Y. pseudotuberculosis and Y. pestis) in complex food samples. The assay combines multiplexed real-time PCR (qPCR) and Pyrosequencing for detecting and differentiating human pathogenic yersiniae with high confidence through sequence based confirmation. The assay demonstrated 100% specificity and inclusivity when tested against a panel of 14 Y. enterocolitica, 22 Y. pestis, 24 Y. pseudotuberculosis and a diverse selection of 17 other non-Yersinia bacteria. Pyrosequencing reads ranged from 28 to 40bp in length and had 94-100% sequence identity to the correct species in the GenBank nr database. Microbial enrichments of 48 ready-to-eat foods collected in the Greater Toronto Area from March 2014 to May 2014, including 46 fresh sprout and 2 salad products, were then tested using the assay. All samples were negative for Y. pestis and Y. pseudotuberculosis. Both salads (n=2) and 35% of sprout products (n=46) including 7.1% of alfalfa sprouts (n=14), 81% of bean sprouts (n=16), 12% of mixed sprouts (n=8) tested positive for Y. enterocolitica which was not detected in broccoli sprouts (n=5), onion sprouts (n=1), and pea sprouts (n=2). Cycle thresholds (Ct) of positive samples for Y. enterocolitica were between 23.0 and 37.9 suggesting post enrichment concentrations of approximately 1×102 to 1×106Y. enterocolitica per 1mL of enriched broth. An internal amplification control which was coamplified with targets revealed PCR inhibition in five samples which was resolved following a one in ten dilution. Pyrosequencing of qPCR amplicons suggests monoclonality and revealed a single nucleotide polymorphism that is present in Y. enterocolitica biotype 1A suggesting low pathogenicity of the detected strains. This study is the first to combine Pyrosequencing and qPCR for the detection of human pathogenic yersiniae and is applicable to a broad range of complex samples including ready-to-eat food samples.

Diffusion in Multicomponent Liquids: From Microscopic to Macroscopic Scales.

In spite of considerable research on the nature of aqueous alcohol mixtures that are characterized by microscopic inhomogeneity or incomplete mixing at the molecular level, transport properties have received little attention. We report the results of a study on diffusion in the ternary mixture of water with two alcohols, that is, water + methanol + ethanol, which is investigated on microscopic and macroscopic scales by means of molecular simulation and Taylor dispersion experiments. A novel protocol is developed for the comparison of mutual diffusion coefficients sampled by two fundamentally different approaches, which allows for their critical analysis. Because of complex intermolecular interactions, given by the presence of hydrogen bonding, the analysis of transport processes in this mixture is challenging for not only on the microscopic scale for simulation techniques but also on the macroscopic scale due to unfavorable optical properties. Binary limits of the Fick diffusion matrix are used for validation of the experimental ternary mixture results together with the verification of the validity of the phenomenological Onsager reciprocal relations. The Maxwell-Stefan diffusion coefficients and the thermodynamic factor are sampled by molecular simulation consistently on the basis of given force field models. The protocol for the comparison of the results from both approaches is also challenging because Fick diffusion coefficients of ternary mixtures depend on the frame of reference. Accordingly, the measured coefficients are transformed from the volume-averaged to the molar-averaged frame of reference, and it is demonstrated that both approaches provide not only similar qualitative behavior along two concentration paths but also strong quantitative agreement. This coordinated work using different approaches to study diffusion in multicomponent mixtures is expected to be a significant step forward for the accurate assessment of cross-diffusion.

Evaluation of DNA extraction methods for Bacillus anthracis spores isolated from spiked food samples.

AIMS: Nine commercial DNA extraction kits were evaluated for the isolation of DNA from 10-fold serial dilutions of Bacillus anthracis spores using quantitative real-time PCR (qPCR). The three kits determined by qPCR to yield the most sensitive and consistent detection (Epicenter MasterPure Gram Positive; MoBio PowerFood; ABI PrepSeq) were subsequently tested for their ability to isolate DNA from trace amounts of B. anthracis spores (approx. 6·5 × 10(1) and 1·3 × 10(2)  CFU in 25 ml or 50 g of food sample) spiked into complex food samples including apple juice, ham, whole milk and bagged salad and recovered with immunomagnetic separation (IMS). METHODS AND RESULTS: The MasterPure kit effectively and consistently isolated DNA from low amounts of B. anthracis spores captured from food samples. Detection was achieved from apple juice, ham, whole milk and bagged salad from as few as 65 ± 14, 68 ± 8, 66 ± 4 and 52 ± 16 CFU, respectively, and IMS samples were demonstrated to be free of PCR inhibitors. CONCLUSIONS: Detection of B. anthracis spores isolated from food by IMS differs substantially between commercial DNA extraction kits; however, sensitive results can be obtained with the MasterPure Gram Positive kit. SIGNIFICANCE AND IMPACT OF THE STUDY: The extraction protocol identified herein combined with IMS is novel for B. anthracis and allows detection of low levels of B. anthracis spores from contaminated food samples.

Investigation of biokinetics of radioiodine with a population kinetics approach.

The dosimetric studies required for planning individually tailored radioiodine therapy of benign thyroid pathologies may be too complex and time-demanding for many ordinary nuclear medicine departments. In this work, a preliminary population kinetics approach was applied to a model structure for iodine biokinetics in order to identify those model features that actually need to be individually investigated, in order to simplify the protocol for data collection in patients. Data from 29 patients undergoing radioiodine therapy for the treatment of the autonomous nodule syndrome were used in the analysis. The greatest inter-individual variations were observed in the parameters describing the transformation of iodide into organic iodine in the thyroid and in the kinetics of the organic form.

New calculations for internal dosimetry of beta-emitting radiopharmaceuticals.

The calculation of absorbed dose from internally incorporated radionuclides is based on the so-called specific absorbed fractions (SAFs) which represent the fraction of energy emitted in a given source region that is absorbed per unit mass in a specific target organ. Until recently, photon SAFs were calculated using MIRD-type mathematical phantoms. For electrons, the energy released was assumed to be absorbed locally ('ICRP 30 approach'). For this work, photon and electron SAFs were derived with Monte Carlo simulations in the new male voxel-based reference computational phantom adopted by the ICRP and ICRU. The present results show that the assumption of electrons being locally absorbed is not always true at energies above 300-500 keV. For source/target organ pairs in close vicinity, high-energy electrons escaping from the source organ may result in cross-fire electron SAFs in the same order of magnitude as those from photons. Examples of organ absorbed doses per unit activity are given for (18)F-choline and (123)I-iodide. The impact of the new electron SAFs used for absorbed dose calculations compared with the previously used assumptions was found to be small. The organ dose coefficients for the two approaches differ by not more than 6 % for most organs. Only for irradiation of the urinary bladder wall by activity in the contents, the ICRP 30 approach presents an overestimation of approximately 40-50%.

Characterization of Streptococcus thermophilus lytic bacteriophages from mozzarella cheese plants.

Phage infection still represents the main cause of fermentation failure during the mozzarella cheese manufacturing, where Streptococcus thermophilus is widely employed as starter culture. Thereby, the success of commercial lactic starter cultures is closely related to the use of strains with low susceptibility to phage attack. The characterization of lytic S. thermophilus bacteriophages is an important step for the selection and use of starter cultures. The aim of this study was to characterize 26 bacteriophages isolated from mozzarella cheese plants in terms of their host range, DNA restriction profile, DNA packaging mechanism, and the variable region VR2 of the antireceptor gene. The DNA restriction analysis was carried out by using the restriction enzymes EcoRV, PstI, and HindIII. The bacteriophages were distinguished into two main groups of S. thermophilus phages (cos- and pac-type) using a multiplex PCR method based on the amplification of conserved regions in the genes coding for the major structural proteins. All the phages belonged to the cos-type group except one, phage 1042, which gave a PCR fragment distinctive of pac-type group. Furthermore, DNA sequencing of the variable region VR2 of the antireceptor gene allowed to classify the phages and examine the correlation between typing profile and host range. Finally, bacterial strains used in this study were investigated for the presence of temperate phages by induction with mitomycin C and only S. thermophilus CHCC2070 was shown to be lysogenic.

Subterahertz superlattice parametric oscillator.

We report a superlattice parametric oscillator (SPO), with a GaAs/AlAs superlattice as the active element. The SPO was pumped by a microwave field (power 4 mW) and produced third harmonic radiation at subterahertz frequencies (near 300 GHz; 0.1 mW). We attribute the parametric gain to the nonlinearity of the miniband transport.

Microstructure and rheology of yogurt made with cultures differing only in their ability to produce exopolysaccharides.

Yogurt was made using an exopolysaccharide-producing strain of Streptococcus thermophilus and its genetic variant that only differed from the mother strain in its inability to produce exopolysaccharides. The microstructure was investigated using confocal scanning laser microscopy, allowing observation of fully hydrated yogurt and the distribution of exopolysaccharide within the protein network. Yogurt made with the exopolysaccharide-producing culture exhibited increased consistency coefficients, but lower flow behavior index, yield stress, viscoelastic moduli and phase angle values than did yogurt made with the culture unable to produce exopolysaccharide. The exopolysaccharides, when present, were found in pores in the gel network separate from the aggregated protein. These effects could be explained by the incompatibility of the exopolysaccharides with the protein aggregates in the milk. Stirring affected the yogurt made with exopolysaccharide differently from yogurt without exopolysaccharide, as it did not exhibit immediate syneresis, although the structural breakdown was increased. The shear-induced microstructure in a yogurt made with exopolysaccharide-producing culture was shown to consist of compartmentalized protein aggregates between channels containing exopolysaccharide, hindering syneresis as well as the buildup of structure after stirring.

Honeydew sugars in wild-caught female deer flies (Diptera: Tabanidae).

Female deer flies (Chrysops spp.) were collected from 2 habitats in Algonquin Provincial Park, ON. Using thin-layer chromatography, 11 sugars were detected in the digestive tracts of these flies; these occurred in 41 different combinations. We argue that combinations including melezitose, stachyose, or both can be used to indicate when flies recently have fed on homopteran honeydew. Accordingly, 85.7% of Chrysops excitans (n = 49) and 61.1% of Chrysops mitis (n = 18) collected from an abandoned airfield and 69.8% of C. excitans (n = 53) and 60.0% of C. mitis (n = 15) from a bog habitat tested positive for these honeydew indicator sugars. The difference between species was significant at the airfield only. Possible reasons for this habitat-dependent difference are discussed.

Differences in baseline EEG measures for ADD and normally achieving preadolescent males.

This study was designed as a replication of previous studies describing dynamic EEG differences between behaviorally dissimilar groups. This study is intended as a reference point from which other researchers can continue to establish the EEG correlates of "on-task" behavior. Eight Attention Deficit Disordered (ADD) children and eight Normally Achieving Controls (NAC) were assessed using dynamic EEG measures. Results are reported for the tasks of baseline (eyes open), reading, and drawing as recorded from FZ, CZ, PZ, C3, and C4. Significant amplitude differences between the groups were demonstrated in the theta band (4-8 hertz) during all tasks and for all sites. Amplitude differences in the beta band (12-20 hertz) were negligible. Differences between groups expressed as a ratio of theta/beta revealed significant differences mainly in the parietal region for on-task conditions. These results are discussed in relation to EEG neuro-feedback training paradigms and the importance of establishing normative "on-task" EEG values.

Sequencing and characterization of pST1, a cryptic plasmid from Streptococcus thermophilus.

Eighty-six strains of S. thermophilus were examined for their plasmid content. Thirteen strains were found to contain one or two plasmids ranging in size from 2.1 to 7.4 kb. DNA-DNA hybridization analysis revealed the presence of five distinct groups of DNA homology. The complete nucleotide sequence of plasmid pST1 (Accession number X65856), which belongs to the major homology group, was determined. It has a molecular size of 2093 bp, a GC content of 35% and contains one major open reading frame of 945 bp (ORF A). The predicted protein, designated Rep A, showed sequence homology with replication proteins from a group of plasmids which are known to replicate via single-stranded DNA intermediates (ssDNA plasmids).

Comparative mapping of IGHG1, IGHM, FES, and FOS in domestic cattle.

The immunoglobulin genes have not been genetically characterized as thoroughly in cattle as in other mammals, particularly humans and mice. Comparative gene mapping in mammals suggests that the bovine immunoglobulin heavy chain genes, IGHG4 and IGHM might be syntenic with the FOS oncogene. Interestingly, however, when these genes were assigned to bovine syntenic groups utilizing a panel of bovine: hamster hybrid somatic cells, IGH genes were shown to be syntenic with the FES oncogene rather than FOS. In this study IGH and FES were assigned to Bos taurus chromosome 21 while FOS was assigned to chromosome 10. In addition, bovine-specific immunoglobulin-like sequences were observed in the hybrid somatic cells, and one, IGHML1, was mapped to bovine syntenic group U16. The probes used for somatic-cell mapping were also used to screen a small number of cattle of several different breeds for restriction fragment length polymorphisms. IGHG4 and IGHM were shown to be highly polymorphic, while FOS and FES were not.