Self-Consistent Field Theory of Multiply-Branched Block Copolymer Melts

We present a numerical algorithm to evaluate the self-consistent field theory for melts composed of block copolymers with multiply-branched architecture. We present results for the case of branched copolymers with doubly-functional groups for multiple branching generations. We discuss the stability of the cubic phase of spherical micelles, the A15 phase, as a consequence of tendency of the AB interfaces to conform to the polyhedral environment of the Voronoi cell of the micelle lattice.Comment: 12 pages, 10 includes figure

Lamellae Stability in Confined Systems with Gravity

The microphase separation of a diblock copolymer melt confined by hard walls and in the presence of a gravitational field is simulated by means of a cell dynamical system model. It is found that the presence of hard walls normal to the gravitational field are key ingredients to the formation of well ordered lamellae in BCP melts. To this effect the currents in the directions normal and parallel to the field are calculated along the interface of a lamellar domain, showing that the formation of lamellae parallel to the hard boundaries and normal to the field correspond to the stable configuration. Also, it is found thet the field increases the interface width.Comment: 4 pages, 2 figures, submitted to Physical Review

Looking for imprints of the first stellar generations in metal-poor bulge field stars

© 2016 ESO. Context. Efforts to look for signatures of the first stars have concentrated on metal-poor halo objects. However, the low end of the bulge metallicity distribution has been shown to host some of the oldest objects in the Milky Way and hence this Galactic component potentially offers interesting targets to look at imprints of the first stellar generations. As a pilot project, we selected bulge field stars already identified in the ARGOS survey as having [Fe/H] 1 and oversolar [α/Fe] ratios, and we used FLAMES-UVES to obtain detailed abundances of key elements that are believed to reveal imprints of the first stellar generations. Aims. The main purpose of this study is to analyse selected ARGOS stars using new high-resolution (R ∼ 45 000) and high-signal-tonoise (S=N > 100) spectra. We aim to derive their stellar parameters and elemental ratios, in particular the abundances of C, N, the α-elements O, Mg, Si, Ca, and Ti, the odd-Z elements Na and Al, the neutron-capture s-process dominated elements Y, Zr, La, and Ba, and the r-element Eu. Methods. High-resolution spectra of five field giant stars were obtained at the 8 m VLT UT2-Kueyen telescope with the UVES spectrograph in FLAMES-UVES configuration. Spectroscopic parameters were derived based on the excitation and ionization equilibrium of Fe i and Fe ii. The abundance analysis was performed with a MARCS LTE spherical model atmosphere grid and the Turbospectrum spectrum synthesis code. Results.We confirm that the analysed stars are moderately metal-poor (-1:04≤[Fe/H]≤-0:43), non-carbon-enhanced (non-CEMP) with [C/Fe] ≤+0:2, and α-enhanced.We find that our three most metal-poor stars are nitrogen enhanced. The α-enhancement suggests that these stars were formed from a gas enriched by core-collapse supernovae, and that the values are in agreement with results in the literature for bulge stars in the same metallicity range. No abundance anomalies (Na-O, Al-O, Al-Mg anti-correlations) were detected in our sample. The heavy elements Y, Zr, Ba, La, and Eu also exhibit oversolar abundances. Three out of the five stars analysed here show slightly enhanced [Y/Ba] ratios similar to those found in other metal-poor bulge globular clusters (NGC 6522 and M 62). Conclusions. This sample shows enhancement in the first-to-second peak abundance ratios of heavy elements, as well as dominantly s-process element excesses. This can be explained by different nucleosynthesis scenarios: (a) the main r-process plus extra mechanisms, such as the weak r-process; (b) mass transfer from asymptotic giant branch stars in binary systems; (c) an early generation of fast-rotating massive stars. Larger samples of moderately metal-poor bulge stars, with detailed chemical abundances, are needed to better constrain the source of dominantly s-process elements in the early Universe

Phase separation in a chaotic flow

The phase separation between two immiscible liquids advected by a bidimensional velocity field is investigated numerically by solving the corresponding Cahn-Hilliard equation. We study how the spinodal decomposition process depends on the presence -or absence- of Lagrangian chaos. A fully chaotic flow, in particular, limits the growth of domains and for unequal volume fractions of the liquids, a characteristic exponential distribution of droplet sizes is obtained. The limiting domain size results from a balance between chaotic mixing and spinodal decomposition, measured in terms of Lyapunov exponent and diffusivity constant, respectively.Comment: Minor changes - Version accepted for publication - Physical Review Letter

An in vitro DNA sensor-based assay to measure receptor-specific adhesion forces of eukaryotic cells and pathogens

Motility of eukaryotic cells or pathogens within tissues is mediated by the turnover of specific interactions with other cells or with the extracellular matrix. Biophysical characterization of these ligand-receptor adhesions helps to unravel the molecular mechanisms driving migration. Traction force microscopy or optical tweezers are typically used to measure the cellular forces exerted by cells on a substrate. However, the spatial resolution of traction force microscopy is limited to ~2 μm and performing experiments with optical traps is very time-consuming. Here we present the production of biomimetic surfaces that enable specific cell adhesion via synthetic ligands and at the same time monitor the transmitted forces by using molecular tension sensors. The ligands were coupled to double-stranded DNA probes with defined force thresholds for DNA unzipping. Receptor-mediated forces in the pN range are thereby semi-quantitatively converted into fluorescence signals, which can be detected by standard fluorescence microscopy at the resolution limit (~0.2 μm). The modular design of the assay allows to vary the presented ligands and the mechanical strength of the DNA probes, which provides a number of possibilities to probe the adhesion of different eukaryotic cell types and pathogens and is exemplified here with osteosarcoma cells and Plasmodium berghei Sporozoites

Exploring teacher pedagogy, stages of concern and accessibility as determinants of technology adoption

© 2017 Association for Information Technology in Teacher Education. This research examines how the pedagogical orientations of teachers affect technology adoption in the classroom. At the same time, the authors account for the stage of concern that teachers are experiencing regarding the use of the technology, their access to the technology and the level of schooling at which they teach.The authors’ investigation of these factors occurs in the context of a contemporary technology, the interactive whiteboard (IWB), in Australian schools. A structural equation model was estimated using a reflective measure of technology usage with antecedents in the form of pedagogical-oriented beliefs and best–worst scaling derived scores for a teacher’s stage of concern regarding IWBs. Teachers with constructivist-oriented pedagogical beliefs were significantly more likely to use IWBs than transmission-oriented teachers. However, the strongest determinant of usage was whether the technology is immediately accessible or not

To weigh or not to weigh. Recommendations for communicating aggregated results of buildings LCA

Interpreting contradictory results of multiple midpoint environmental indicators is challenging task. Hence, partial or full aggregation into building single scores has gained ground for the clear message they convey. This paper helps to improve understanding of the possibilities and limitations of such practice. Partial aggregated scores of five buildings were explored, limited to the environmental indicators shared by the methods examined and inventoried for the case studies. In general, the buildings’ single score ranking was maintained regardless of the aggregation approach, but rank reversal is possible if e.g., ecotoxicity impact indicators are considered. Such indicators are directly influenced by the mass of metals used in a building. Furthermore, uncertainties on their results, in LCI data and in impact and damage assessment are high, and experience with them is still limited. No single best aggregation stands out per se. All of them can play their part if officially supported to ensure that coherent weights/factors are built upon solid, up-to-date data and fair intergenerational and income equity valuation procedures. In such cases, LCA practitioners are encouraged to use single scores in addition to environmental profiles or selected indicators. Overall aggregation procedures shall be transparently described, and zero pure time preference rate and equity weighting applied and explicitly declared. Sensitivity/uncertainty analysis shall be performed to assess results robustness, potential ranking reversal risks, and the effect of different discount rates. When partial aggregation is alternatively pursued, it shall be based on endpoint categories

Gliding motility protein LIMP promotes optimal mosquito midgut traversal and infection by Plasmodium berghei

© 2020 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).Substrate-dependent gliding motility is key to malaria transmission. It mediates host cell traversal, invasion and infection by Plasmodium and related apicomplexan parasites. The 110 amino acid-long cell surface protein LIMP is essential for P. berghei sporozoites where it is required for the invasion of the mosquito’s salivary glands and the liver cells of the rodent host. Here we define an additional role for LIMP during mosquito invasion by the ookinete. limp mRNA is provided as a translationally repressed mRNP (messenger ribonucleoprotein) by the female gametocyte and the protein translated in the ookinete. Parasites depleted of limp (Δlimp) develop ookinetes with apparent normal morphology and no defect during in vitro gliding motility, and yet display a pronounced reduction in oocyst numbers; compared to wildtype 82 % more Δlimp ookinetes remain within the mosquito blood meal explaining the decrease in oocysts. As in the sporozoite, LIMP exerts a profound role on ookinete infection of the mosquito.This study was supported by Fundação para a Ciência e a Tecnologia grants to GRM (PTDC/BIA-BCM/105610/2008 and PTDC/SAU-MIC/122082/2010) and JMS (SFRH/BD/63849/2009); the National Institutes of Allergy and Infectious Diseases to GRM (1R21AI139579-01A1); the Horizon 2020 Framework Programme Marie Sklodowska-Curie grant agreement No 660211 to SE; as well as a Human Frontier Science Program Grant (RGY/0071/2011) to FF. The funders had no role in study design, data collection and interpretation, or the decision to submit the work for publication. The authors have no competing interests to declare.info:eu-repo/semantics/publishedVersio