Tailoring nanoscale properties of ultrathin polymer brush films

The conformation of a polymer chain is very sensitive to changes in the surrounding environment. When polymer chains are chemically tethered at one end to a solid substrate or interface with a sufficiently high grafting density, the chains avoid overlapping and stretch along the surface normal to form a polymer brush layer. Thus, substrates and interfaces can be modified with thin (2-100 nm) highly dense polymer layers that have the ability to adapt, or exhibit switching of surface morphologies according to changes in their surrounding medium, such as solvent quality or pH. Dense, uniform glassy and rubbery brush layers were fabricated and thermal, mechanical, and thermo-elastic properties of the layers were directly measured with nanoscale resolution for the first time and compared with values found for polymer chains in the bulk state. For the binary polymer brush layers, atomic force microscopy force volume experiments indicate the bimodal response of the mechanically heterogeneous surface, with elastic modulus and adhesion distributions very different for the glassy state and the rubbery state . We demonstrate the complete reversible tailoring of one polymer brush layer possessing a very adhesive surface with elastic modulus around 50 MPa upon exposure to acetone, and switching to a glassy low energy surface with elastic modulus around 1-2 GPa after quick exposure to toluene. Such a surface is of great interest because versatile microsystems are now being designed that integrate mechanical, optical, fluidic, chemical gating, and biological devices to perform complex sensing functions

Hybrid structures for molecular level sensing

With substantial molecular mobility and segment dynamics relative to metals and ceramics, all polymeric materials, to some extent, are stimuli-responsive by exhibiting pronounced chemical and physical changes in the backbone, side chains, segments, or end groups induced by changes in the local environment. Thus, the push to incorporate polymeric materials as sensing/responsive nanoscale layers into next-generation miniaturized sensor applications is a natural progression. The significance and impact of this research is wide-ranging because it offers design considerations and presents results in perhaps two of the most critical broad areas of nanotechnology: ultrathin multifunctional polymer coatings and miniaturized sensors. In this work, direct evidence is given showing that polymer coatings comprised of deliberately selected molecular segments with very different chemistry can have switchable properties, and that the surface composition can be precisely controlled, and thus properties can be tuned: all in films on the order of 20 nm and less. Furthermore, active sensing layers in the form of plasma-polymerized polymers are successfully incorporated into actual silicon based microsensors resulting in a novel hybrid organic/inorganic materials platform for microfabricated MEMS sensors with record performance far beyond contemporary sensors in terms of detection sensitivity to various environments. The results produced in this research show thermal sensors with more than two orders of magnitude better sensitivity than what is attainable currently. In addition, a humidity response on the order of parts per trillion, which is four orders of magnitude more sensitive than current designs is achieved. Molecular interactions and forces for organic molecules are characterized at the picoscale to optimize polymeric nanoscale layer design that in turn optimize and lead to microscale hybrid sensors with unprecedented sensitivities

With Great Advantage Should Come Responsibility: How the Territorialist Approach in Private International Law Maybe Overcome to Ensure Justice is Done for those Left in the Wake of Canadian Business Abroad

Conflict of laws rules in Canada bias toward taking jurisdiction over matters involving human rights or environmental abuse inflicted abroad, particularly when inflicted by Canadian corporations. Contrary to enumerated tests for jurisdiction, many Canadian courts have instead preferred a regressive state-centric/hyper-comity anchor in applying such tests to putative foreign plaintiffs. This Thesis argues this preference can be effectively understood using the lens and language of Pierre Bourdieus field theory as representing a habitus of the Canadian judiciary. In light of the habitus of the Canadian judicial field, and in order to encourage an interpretation of conflict of laws rules in Canada that prefers an uptake of such claims, practitioners ought to introduce issues of jurisdiction to Canadian courts framed with respect to fairness, notably whether it is fair to provide Canadian corporations significant benefit when operating abroad and, through failure to take jurisdiction, allow such corporations to avoid civil prosecution

The complete chloroplast genome sequence of the chlorophycean green alga Scenedesmus obliquus reveals a compact gene organization and a biased distribution of genes on the two DNA strands

BACKGROUND: The phylum Chlorophyta contains the majority of the green algae and is divided into four classes. While the basal position of the Prasinophyceae is well established, the divergence order of the Ulvophyceae, Trebouxiophyceae and Chlorophyceae (UTC) remains uncertain. The five complete chloroplast DNA (cpDNA) sequences currently available for representatives of these classes display considerable variability in overall structure, gene content, gene density, intron content and gene order. Among these genomes, that of the chlorophycean green alga Chlamydomonas reinhardtii has retained the least ancestral features. The two single-copy regions, which are separated from one another by the large inverted repeat (IR), have similar sizes, rather than unequal sizes, and differ radically in both gene contents and gene organizations relative to the single-copy regions of prasinophyte and ulvophyte cpDNAs. To gain insights into the various changes that underwent the chloroplast genome during the evolution of chlorophycean green algae, we have sequenced the cpDNA of Scenedesmus obliquus, a member of a distinct chlorophycean lineage. RESULTS: The 161,452 bp IR-containing genome of Scenedesmus features single-copy regions of similar sizes, encodes 96 genes, i.e. only two additional genes (infA and rpl12) relative to its Chlamydomonas homologue and contains seven group I and two group II introns. It is clearly more compact than the four UTC algal cpDNAs that have been examined so far, displays the lowest proportion of short repeats among these algae and shows a stronger bias in clustering of genes on the same DNA strand compared to Chlamydomonas cpDNA. Like the latter genome, Scenedesmus cpDNA displays only a few ancestral gene clusters. The two chlorophycean genomes share 11 gene clusters that are not found in previously sequenced trebouxiophyte and ulvophyte cpDNAs as well as a few genes that have an unusual structure; however, their single-copy regions differ considerably in gene content. CONCLUSION: Our results underscore the remarkable plasticity of the chlorophycean chloroplast genome. Owing to this plasticity, only a sketchy portrait could be drawn for the chloroplast genome of the last common ancestor of Scenedesmus and Chlamydomonas

Distinctive architecture of the chloroplast genome in the chlorodendrophycean green algae Scherffelia dubia and Tetraselmis sp. CCMP 881

The Chlorodendrophyceae is a small class of green algae belonging to the core Chlorophyta, an assemblage that also comprises the Pedinophyceae, Trebouxiophyceae, Ulvophyceae and Chlorophyceae. Here we describe for the first time the chloroplast genomes of chlorodendrophycean algae (Scherffelia dubia, 137,161 bp; Tetraselmis sp. CCMP 881, 100,264 bp). Characterized by a very small single-copy (SSC) region devoid of any gene and an unusually large inverted repeat (IR), the quadripartite structures of the Scherffelia and Tetraselmis genomes are unique among all core chlorophytes examined thus far. The lack of genes in the SSC region is offset by the rich and atypical gene complement of the IR, which includes genes from the SSC and large single-copy regions of prasinophyte and streptophyte chloroplast genomes having retained an ancestral quadripartite structure. Remarkably, seven of the atypical IR-encoded genes have also been observed in the IRs of pedinophycean and trebouxiophycean chloroplast genomes, suggesting that they were already present in the IR of the common ancestor of all core chlorophytes. Considering that the relationships among the main lineages of the core Chlorophyta are still unresolved, we evaluated the impact of including the Chlorodendrophyceae in chloroplast phylogenomic analyses. The trees we inferred using data sets of 79 and 108 genes from 71 chlorophytes indicate that the Chlorodendrophyceae is a deep-diverging lineage of the core Chlorophyta, although the placement of this class relative to the Pedinophyceae remains ambiguous. Interestingly, some of our phylogenomic trees together with our comparative analysis of gene order data support the monophyly of the Trebouxiophyceae, thus offering further evidence that the previously observed affiliation between the Chlorellales and Pedinophyceae is the result of systematic errors in phylogenetic reconstruction

The chloroplast genome sequence of the green alga Leptosira terrestris: multiple losses of the inverted repeat and extensive genome rearrangements within the Trebouxiophyceae

<p>Abstract</p> <p>Background</p> <p>In the Chlorophyta – the green algal phylum comprising the classes Prasinophyceae, Ulvophyceae, Trebouxiophyceae and Chlorophyceae – the chloroplast genome displays a highly variable architecture. While chlorophycean chloroplast DNAs (cpDNAs) deviate considerably from the ancestral pattern described for the prasinophyte <it>Nephroselmis olivacea</it>, the degree of remodelling sustained by the two ulvophyte cpDNAs completely sequenced to date is intermediate relative to those observed for chlorophycean and trebouxiophyte cpDNAs. <it>Chlorella vulgaris </it>(Chlorellales) is currently the only photosynthetic trebouxiophyte whose complete cpDNA sequence has been reported. To gain insights into the evolutionary trends of the chloroplast genome in the Trebouxiophyceae, we sequenced cpDNA from the filamentous alga <it>Leptosira terrestris </it>(Ctenocladales).</p> <p>Results</p> <p>The 195,081-bp <it>Leptosira </it>chloroplast genome resembles the 150,613-bp <it>Chlorella </it>genome in lacking a large inverted repeat (IR) but differs greatly in gene order. Six of the conserved genes present in <it>Chlorella </it>cpDNA are missing from the <it>Leptosira </it>gene repertoire. The 106 conserved genes, four introns and 11 free standing open reading frames (ORFs) account for 48.3% of the genome sequence. This is the lowest gene density yet observed among chlorophyte cpDNAs. Contrary to the situation in <it>Chlorella </it>but similar to that in the chlorophycean <it>Scenedesmus obliquus</it>, the gene distribution is highly biased over the two DNA strands in <it>Leptosira</it>. Nine genes, compared to only three in <it>Chlorella</it>, have significantly expanded coding regions relative to their homologues in ancestral-type green algal cpDNAs. As observed in chlorophycean genomes, the <it>rpoB </it>gene is fragmented into two ORFs. Short repeats account for 5.1% of the <it>Leptosira </it>genome sequence and are present mainly in intergenic regions.</p> <p>Conclusion</p> <p>Our results highlight the great plasticity of the chloroplast genome in the Trebouxiophyceae and indicate that the IR was lost on at least two separate occasions. The intriguing similarities of the derived features exhibited by <it>Leptosira </it>cpDNA and its chlorophycean counterparts suggest that the same evolutionary forces shaped the IR-lacking chloroplast genomes in these two algal lineages.</p

Carotenoids as biomarkers of fruit and vegetable intake in men and women

High fruit and vegetable (FAV) intake is associated with a lower prevalence of chronic diseases. Identifying the ideal number of FAV servings needed to reduce chronic disease risk is, however, difficult because of biases inherent to common self-report dietary assessment tools. The aim of our study was to examine the associations between daily FAV intake and plasma carotenoid concentrations in men and women enrolled in a series of fully controlled dietary interventions. We compiled and analysed data from a group of 155 men and 109 women who participated in six fully controlled dietary interventions and compared post-intervention fasting plasma carotenoid (a-carotene, ß-carotene, ß-cryptoxanthin, lutein, lycopene, zeaxanthin) concentrations with regard to the daily FAV servings consumed by the participants. We found that plasma ß-cryptoxanthin, lutein and zeaxanthin concentrations were positively associated with daily FAV servings (P=0·005). However, daily FAV intake was negatively associated with plasma a-carotene (P<0·0005) and lycopene (P<0·0001) concentrations, whereas no association was noted with plasma ß-carotene. When men and women were analysed separately, we found that for any given number of FAV servings consumed women had higher circulating lutein concentrations compared with men (P<0·01). Significant sex×FAV (P<0·0001) and sex×dietary ß-cryptoxanthin (P<0·0005) interactions were also noted favouring higher plasma ß-cryptoxanthin concentrations in women than in men for a given FAV consumption. Results from these fully controlled dietary feeding studies indicate that plasma ß-cryptoxanthin and lutein concentrations can be used as robust biomarkers of FAV consumption. They also suggest the existence of sex differences influencing circulating ß-cryptoxanthin and lutein concentrations following FAV consumption

Correlates of the difference in plasma carotenoid concentrations between men and women

Health professionals consider the evaluation of eating habits to be challenging, given the potential biases of dietary questionnaires based on self-reported data. Circulating carotenoid concentrations are reliable biomarkers of dietary carotenoid intake and could be useful in the validation of dietary assessment tools. However, there is a sex difference in circulating carotenoids, with women displaying higher concentrations compared with men independent of intake. The aim of the present study was to identify the correlates of plasma carotenoid concentrations among men (n 155) and women (n 110) enrolled in six fully controlled dietary interventions with varying dietary carotenoid intakes. We looked at the associations of post-intervention fasting plasma carotenoid concentrations (α-carotene, β-carotene, β-cryptoxanthin, lutein, lycopene and zeaxanthin) with physical and metabolic characteristics. We found that increased body weight (r –0·47, P<0·0001) and waist circumference (r –0·46, P <0·0001) were associated with lower plasma total carotenoid concentrations, while elevated plasma LDLcholesterol (r 0·49, P<0·0001) and HDL-cholesterol (r 0·50, P<0·0001) concentrations were correlated with higher total carotenoids in plasma. Women had significantly higher plasma total carotenoid concentrations compared with men, despite significantly lower dietary carotenoid intake. Adjustment of circulating carotenoid concentrations for plasma HDL-cholesterol eliminated sex difference in plasma carotenoid concentrations. Our results suggest that physical characteristics as well as plasma lipids are associated with circulating carotenoid concentrations and that these variables should be taken into account when using plasma carotenoids as biomarkers for food intake in men and women

Validity and reliability of a brief selfreported questionnaire assessing fruit and vegetable consumption among pregnant women

Background: Short instruments measuring frequency of specific foods, such as fruit and vegetable (FV), are increasingly used in interventions. The objective of the study was to verify the validity and test-retest reliability of such an instrument among pregnant women. Methods: Pregnant women from the region of Quebec City, Quebec, Canada, were recruited through e-mails sent to female students and employees of the local university from October 2014 to April 2015. To assess the validity of the fruit and vegetable questionnaire (FVQ) developed by Godin et al. (Can J Public Health 99: 494-498, 2008), pregnant women were asked in a first mailing to complete the FVQ assessing FV intake over the past 7 days and a 3-day estimated food record. A subsample (n¿=¿33) also gave a fasting blood sample and completed a validated semi-quantitative FFQ administered by a trained registered dietitian during a visit at the research center. FV intakes for all instruments were calculated in terms of servings of FV based on Canada’s Food Guide definition of a serving of fruit or vegetable. In order to assess its test-retest reliability, respondents were asked to complete the FVQ 14 days later in a second mailing. Results: Forty-eight pregnant women from all three trimesters completed the questionnaires in the first mailing. FV intake assessed using the FVQ was correlated to FV consumption measured using the food record (r¿=¿0.34, p¿=¿0.0180) and the FFQ (r¿=¿0.61, p¿=¿0.0002). Results were similar when controlling for energy intake and the experience of nausea in the past month. Only ß-cryptoxanthin was significantly correlated to FV intake assessed by the FFQ when adjusted for the presence of nausea (r¿=¿0.35, p¿=¿0.0471). Data on the test-retest reliability was available for 44 women and the intra-class coefficient for the FVQ was 0.72 at a mean 28-day interval. Conclusions: The FVQ has acceptable validity and test-retest reliability values, but seems to underestimate FV servings in pregnant women. It represents an interesting alternative for researchers or clinicians interested in estimating quickly FV intake among pregnant women, such as in large trials or during prenatal visits. The FVQ should however be coupled with other self-reported measures, such as a food record, for assessing precise individual FV intake