Efficient Synthesis of Narrowly Dispersed Brush Copolymers and Study of Their Assemblies: The Importance of Side Chain Arrangement

Efficient, one-pot preparation of synthetically challenging, high molecular weight (MW), narrowly dispersed brush block copolymers and random copolymers in high conversions was achieved by ring-opening metathesis (co)polymerization (ROMP) of various macromonomers (MMs) using the highly active, fast-initiating ruthenium olefin metathesis catalyst (H_2IMes)(pyr)_2(Cl)_2RuCHPh. A series of random and block copolymers were prepared from a pair of MMs containing polylactide (PLA) and poly(n-butyl acrylate) (PnBA) side chains at similar MWs. Their self-assembly in the melt state was studied by small-angle X-ray scattering (SAXS) and atomic force microscopy (AFM). In brush random copolymers containing approximately equal volume fractions of PLA and PnBA, the side chains segregate into lamellae with domain spacing of 14 nm as measured by SAXS, which was in good agreement with the lamellar thickness measured by AFM. The domain spacings and order−disorder transition temperatures of brush random copolymers were insensitive to the backbone length. In contrast, brush block copolymers containing approximately equal volume fractions of these MMs self-assembled into highly ordered lamellae with domain spacing over 100 nm. Their assemblies suggested that the brush block copolymer backbone adopted an extended conformation in the ordered state

ICTV Virus Taxonomy Profile: Chrysoviridae

The Chrysoviridae is a family of small, isometric, non-enveloped viruses (40 nm in diameter) with segmented dsRNA genomes (typically four segments). The genome segments are individually encapsidated and together comprise 11.5–12.8 kbp. The single genus Chrysovirus includes nine species. Chrysoviruses lack an extracellular phase to their life cycle; they are transmitted via intracellular routes within an individual during hyphal growth, in asexual or sexual spores, or between individuals via hyphal anastomosis. There are no known natural vectors for chrysoviruses. This is a summary of the International Committee on Taxonomy of Viruses (ICTV) Report on the taxonomy of the Chrysoviridae, which is available at www.ictv.global/report/chrysoviridae.Peer reviewe

Assessing what is needed to resolve a molecular phylogeny: simulations and empirical data from emydid turtles

<p>Abstract</p> <p>Background</p> <p>Phylogenies often contain both well-supported and poorly supported nodes. Determining how much additional data might be required to eventually recover most or all nodes with high support is an important pragmatic goal, and simulations have been used to examine this question. Most simulations have been based on few empirical loci, and suggest that well supported phylogenies can be determined with a very modest amount of data. Here we report the results of an empirical phylogenetic analysis of all 10 genera and 25 of 48 species of the new world pond turtles (family Emydidae) based on one mitochondrial (1070 base pairs) and seven nuclear loci (5961 base pairs), and a more biologically realistic simulation analysis incorporating variation among gene trees, aimed at determining how much more data might be necessary to recover weakly-supported nodes with strong support.</p> <p>Results</p> <p>Our mitochondrial-based phylogeny was well resolved, and congruent with some previous mitochondrial results. For example, all genera, and all species except <it>Pseudemys concinna</it>, <it>P. peninsularis</it>, and <it>Terrapene carolina </it>were monophyletic with strong support from at least one analytical method. The Emydinae was recovered as monophyletic, but the Deirochelyinae was not. Based on nuclear data, all genera were monophyletic with strong support except <it>Trachemys</it>, and all species except <it>Graptemys pseudogeographica</it>, <it>P. concinna</it>, <it>T. carolina</it>, and <it>T. coahuila </it>were monophyletic, generally with strong support. However, the branches subtending most genera were relatively short, and intergeneric relationships within subfamilies were mostly unsupported.</p> <p>Our simulations showed that relatively high bootstrap support values (i.e. ≥ 70) for all nodes were reached in all datasets, but an increase in data did not necessarily equate to an increase in support values. However, simulations based on a single empirical locus reached higher overall levels of support with less data than did the simulations that were based on all seven empirical nuclear loci, and symmetric tree distances were much lower for single versus multiple gene simulation analyses.</p> <p>Conclusion</p> <p>Our empirical results provide new insights into the phylogenetics of the Emydidae, but the short branches recovered deep in the tree also indicate the need for additional work on this clade to recover all intergeneric relationships with confidence and to delimit species for some problematic groups. Our simulation results suggest that moderate (in the few-to-tens of kb range) amounts of data are necessary to recover most emydid relationships with high support values. They also suggest that previous simulations that do not incorporate among-gene tree topological variance probably underestimate the amount of data needed to recover well supported phylogenies.</p

Development and application of a novel cake strength tester

Caking can cause many problems in industries during processing or storage of particulate materials. Caking magnitude depends on several factors, for instance temperature, consolidation stress and storage time. In this research paper, a novel force displacement and easy-to-use caking tester for measuring quantitatively cake strength as a result of elevated temperature, consolidation stress and storage time is introduced. The developed tester outweighed the conventional uniaxial unconfined failure caking tester due to the defined location of the failure plane to maximise repeatability, the necessity for a lower quantity of powder, maximised exposed surface and lower wall friction as well as production costs. The experimental design has been conducted by changing the temperature, consolidation stress and storage duration. The results showed that the tester could distinguish cake strength between different experimental conditions. A statistical model has been successfully developed to study the effect of each variable on the cake strength

Clues to the formation of spiral structure in M51 from the ages and locations of star clusters

We determine the spatial distributions of star clusters at different ages in the grand-design spiral galaxy M51 using a new catalog based on multi-band images taken with the Hubble Space Telescope (HST). These distributions, when compared with the spiral structure defined by molecular gas, dust, young and old stars, show the following sequence in the inner arms: dense molecular gas (and dust) defines the inner edge of the spiral structure, followed by an overdensity of old stars and then young stellar clusters. The offset between gas and young clusters in the inner arms is consistent with the expectations for a density wave. Clusters as old as a few hundred Myr remain concentrated close to the spiral arms, although the distributions are broader than those for the youngest clusters, which is also consistent with predictions from density wave simulations. The outermost portion of the west arm is different from the rest of the spiral structure in that it contains primarily intermediate-age (approximate to 100-400 Myr) clusters; we believe that this is a "material" arm. We have identified four "feathers," stellar structures beyond the inner arms that have a larger pitch angle than the arms. We do not find age gradients along any of the feathers, but the least coherent feathers appear to have the largest range of cluster ages

Adolescent obesity and maternal and paternal sensitivity and monitoring

Objective . To determine if adolescent obesity is associated with parenting characterized by lower sensitivity and lower monitoring of adolescent activities. Methods . We used data from 744 adolescents in the National Institute of Child Health and Human Development Study of Early Child Care and Youth Development. Height and weight were measured at age 15½ years and obesity defined as body mass index ≥ 95th percentile for age and sex. Maternal and paternal sensitivity were assessed by direct observation of a parent‐adolescent interaction task. Maternal and paternal monitoring were assessed by parent report. Lower sensitivity and lower monitoring were each defined as the lowest quartiles. Two separate multivariate logistic regression models were created to evaluate, individually for mothers and fathers, associations of sensitivity and monitoring with adolescent obesity, controlling for adolescent sex and race, family income‐to‐needs ratio, and parental obesity. Results . Fourteen percent of the adolescents were obese. Lower sensitivity was associated with adolescent obesity in the maternal parenting model (adjusted odds ratio [AOR] 2.36, 95% confidence interval [CI] 1.44–3.86, n = 709), but not paternal parenting model (AOR = 0.79, 95% CI 0.38–1.63, n = 460). Neither maternal nor paternal monitoring was associated with adolescent obesity (AOR = 1.03, 95% CI 0.63–1.68; AOR = 1.07, 95% CI 0.52–2.22, respectively). Conclusion . Lower maternal sensitivity, measured by direct observation of parent‐adolescent interactions, was associated with adolescent obesity. Efforts to prevent and treat childhood obesity, both at the practitioner level and the community level, may be enhanced by educating parents that their reactions to their children's behaviors may have consequences related to obesity.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/93554/1/ijpo_345_sm_Appendix.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/93554/2/17477166.2010.549490.pd

Cosmic String Formation from Correlated Fields

We simulate the formation of cosmic strings at the zeros of a complex Gaussian field with a power spectrum $P(k) \propto k^n$, specifically addressing the issue of the fraction of length in infinite strings. We make two improvements over previous simulations: we include a non-zero random background field in our box to simulate the effect of long-wavelength modes, and we examine the effects of smoothing the field on small scales. The inclusion of the background field significantly reduces the fraction of length in infinite strings for $n < -2$. Our results are consistent with the possibility that infinite strings disappear at some $n = n_c$ in the range $-3 \le n_c < -2.2$, although we cannot rule out $n_c = -3$, in which case infinite strings would disappear only at the point where the mean string density goes to zero. We present an analytic argument which suggests the latter case. Smoothing on small scales eliminates closed loops on the order of the lattice cell size and leads to a ``lattice-free" estimate of the infinite string fraction. As expected, this fraction depends on the type of window function used for smoothing.Comment: 24 pages, latex, 10 figures, submitted to Phys Rev