2,462 research outputs found
Direct measurement of DNA-mediated adhesion between lipid bilayers
Multivalent interactions between deformable mesoscopic units are ubiquitous
in biology, where membrane macromolecules mediate the interactions between
neighbouring living cells and between cells and solid substrates. Lately,
analogous artificial materials have been synthesised by functionalising the
outer surface of compliant Brownian units, for example emulsion droplets and
lipid vesicles, with selective linkers, in particular short DNA sequences. This
development extended the range of applicability of DNA as a selective glue,
originally applied to solid nano and colloidal particles. On very deformable
lipid vesicles, the coupling between statistical effects of multivalent
interactions and mechanical deformation of the membranes gives rise to complex
emergent behaviours, as we recently contributed to demonstrate [Parolini et
al., Nature Communications, 2015, 6, 5948]. Several aspects of the complex
phenomenology observed in these systems still lack a quantitative experimental
characterisation and fundamental understanding. Here we focus on the
DNA-mediated multivalent interactions of a single liposome adhering to a flat
supported bilayer. This simplified geometry enables the estimate of the
membrane tension induced by the DNA-mediated adhesive forces acting on the
liposome. Our experimental investigation is completed by morphological
measurements and the characterisation of the DNA-melting transition, probed by
in-situ F\"{o}rster Resonant Energy Transfer spectroscopy. Experimental results
are compared with the predictions of an analytical theory that couples the
deformation of the vesicle to a full description of the statistical mechanics
of mobile linkers. With at most one fitting parameter, our theory is capable of
semi-quantitatively matching experimental data, confirming the quality of the
underlying assumptions.Comment: 16 pages, 7 figure
A bibliometric analysis of the scientific literature on Fairtrade labelling
Since its foundation, the Fairtrade movement has attracted the attention of consumers, practitioners, media and scholars. Discussing the role that Fairtrade can play on a global yet locally rooted scale is very complex, as research reports contrasting results about its usefulness and effectiveness. This study examines scientific research on Fairtrade over the last decades by conducting a bibliometric analysis of the literature published on the ISI Web of Knowledge Core Collection, which included 876 papers by 1,293 authors in 432 journals. Results show that despite this being a relatively recent field of study, Fairtrade has been approached from different disciplines with different methodologies and objectives. The structured quantitative study of the literature enabled us to inspect how research has evolved over the years in the light of the changes faced by Fairtrade, to explore its scope in the broader field of the global market, to detect current research schools and perspectives within the network and to identify hitherto unaddressed issues and unconnected subfields
Clinical significance of epithelial-to-mesenchymal transition in laryngeal carcinoma: Its role in the different subsites
Background: During epithelial-to-mesenchymal transition, cancer cells lose adhesion capacity gaining migratory properties. The role of the process on prognosis has been evaluated in 50 cases of laryngeal carcinoma. Methods: E-cadherin, N-cadherin, β-catenin, α-catenin, γ-catenin, caveolin-1, and vimentin immunohistochemical expression were evaluated using a double score based on staining intensity and cellular localization. Results: Cytoplasmic E-cadherin and α/γ catenin staining were associated with a decrease in survival, cytoplasmic β-catenin was associated with advanced stage, and N-cadherin and vimentin expression were associated with poor differentiation and tumor relapse. On the basis of cancer cells, epithelial or mesenchymal morphological and immunophenotypic similarity we identified 4 main subgroups correlated with a transition to a more undifferentiated phenotype, which have a different pattern of relapse and survival. Conclusion: The negative prognostic role of epithelial-to-mesenchymal transition has been confirmed and a predictive role in glottic tumors has been suggested, leading us to propose epithelial-to-mesenchymal transition as an additional adverse feature in laryngeal carcinoma
Introduction to the special issue on Antarctic oceanography in a changing world
Author Posting. © The Oceanography Society, 2012. This article is posted here by permission of The Oceanography Society for personal use, not for redistribution. The definitive version was published in Oceanography 25, no. 3 (2012): 14-17, doi:10.5670/oceanog.2012.68."Antarctic Oceanography in a Changing World" commemorates the twentieth anniversary of the commissioning of Research Vessel Icebreaker (RVIB) Nathaniel B. Palmer and the fifteenth anniversary of Antarctic Research and Supply Vessel (ARSV) Laurence M. Gould. The addition of these two Antarctic research vessels to the US fleet in the 1990s ushered in a new era of Antarctic oceanographic research for US scientists and their international collaborators. Although several US Coast Guard icebreakers in the Arctic and Antarctic waters conduct oceanographic research, their primary mission is icebreaking to facilitate access to land-based stations. The Palmer was, and remains to this day, the first and only purpose-built US research icebreaker in Antarctic service and has been serving sea-going scientists in all areas of Antarctica's seas for two decades. The Gould has afforded reliable year-round access to Palmer Station and has conducted oceanographic research in the Antarctic Peninsula area since 1997
Chemo-Archaeological Downsizing in a Hierarchical Universe: Impact of a Top Heavy IGIMF
We make use of a semi-analytical model of galaxy formation to investigate the
origin of the observed correlation between [a/Fe] abundance ratios and stellar
mass in elliptical galaxies. We implement a new galaxy-wide stellar initial
mass function (Top Heavy Integrated Galaxy Initial Mass Function, TH-IGIMF) in
the semi-analytic model SAG and evaluate its impact on the chemical evolution
of galaxies. The SFR-dependence of the slope of the TH-IGIMF is found to be key
to reproducing the correct [a/Fe]-stellar mass relation. Massive galaxies reach
higher [a/Fe] abundance ratios because they are characterized by more top-heavy
IMFs as a result of their higher SFR. As a consequence of our analysis, the
value of the minimum embedded star cluster mass and of the slope of the
embedded cluster mass function, which are free parameters involved in the
TH-IGIMF theory, are found to be as low as 5 solar masses and 2, respectively.
A mild downsizing trend is present for galaxies generated assuming either a
universal IMF or a variable TH-IGIMF. We find that, regardless of galaxy mass,
older galaxies (with formation redshifts > 2) are formed in shorter time-scales
(< 2 Gyr), thus achieving larger [a/Fe] values. Hence, the time-scale of galaxy
formation alone cannot explain the slope of the [a/Fe]-galaxy mass relation,
but is responsible for the big dispersion of [a/Fe] abundance ratios at fixed
stellar mass.We further test the hyphothesis of a TH-IGIMF in elliptical
galaxies by looking into mass-to-light ratios, and luminosity functions. Models
with a TH-IGIMF are also favoured by these constraints. In particular,
mass-to-light ratios agree with observed values for massive galaxies while
being overpredicted for less massive ones; this overprediction is present
regardless of the IMF considered.Comment: 24 pages, 15 figures, 2 tables. (Comments most welcome). Summited to
MNRA
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