13,645 research outputs found
Motility of active fluid drops on surfaces
Drops of active liquid crystal have recently shown the ability to
self-propel, which was associated with topological defects in the orientation
of active filaments [Sanchez {\em et al.}, Nature {\bf 491}, 431 (2013)]. Here,
we study the onset and different aspects of motility of a three-dimensional
drop of active fluid on a planar surface. We analyse theoretically how motility
is affected by orientation profiles with defects of various types and
locations, by the shape of the drop, and by surface friction at the substrate.
In the scope of a thin drop approximation, we derive exact expressions for the
flow in the drop that is generated by a given orientation profile. The flow has
a natural decomposition into terms that depend entirely on the geometrical
properties of the orientation profile, i.e. its bend and splay, and a term
coupling the orientation to the shape of the drop. We find that asymmetric
splay or bend generates a directed bulk flow and enables the drop to move, with
maximal speeds achieved when the splay or bend is induced by a topological
defect in the interior of the drop. In motile drops the direction and speed of
self-propulsion is controlled by friction at the substrate.Comment: 11 pages, 8 figure
Light Curve Solutions of Eclipsing Binaries in SMC
We propose a procedure for light-curve solution of eclipsing binary stars in
the Small Magellanic Cloud for which photometric data have been obtained in the
framework of the OGLE project as well as way of determination of the global
stellar parameters on the basis of the obtained solutions, some empirical
relations as well as the distance to the SMC. Several examples illustrate this
procedure.Comment: 10 pages, 2 figures, accepte
Radiolysis of Amino Acids by Heavy and Energetic Cosmic Ray Analogs in Simulated Space Environments: -Glycine Zwitterion Form
In this work, we studied the stability of the glycine molecule in the
crystalline zwitterion form, known as {\alpha}-glycine
(NHCHCOO) under action of heavy cosmic ray analogs. The
experiments were conducted in a high vacuum chamber at heavy ions accelerator
GANIL, in Caen, France. The samples were bombarded at two temperatures (14 K
and 300 K) by Ni ions of 46 MeV until the final fluence of
ions cm. The chemical evolution of the sample was evaluated
in-situ using Fourrier Transformed Infrared (FTIR) spectrometer. The
bombardment at 14 K produced several daughter species such as OCN, CO,
CO, and CN. The results also suggest the appearing of peptide bonds
during irradiation but this must be confirmed by further experiments. The
halflives of glycine in Interstellar Medium were estimated to be 7.8 years (300 K) and 2.8 years (14 K). In the Solar System the
values were 8.4 years (300 K) and 3.6 years (14 K).
It is believed that glycine could be present in space environments that
suffered aqueous changes such as the interior of comets, meteorites and
planetesimals. This molecule is present in proteins of all alive beings. So,
studying its stability in these environments provides further understanding
about the role of this specie in the prebiotic chemistry on Earth.Comment: 28 pages, 12 figures, 9 tables. Accepted to be published at Monthly
Notices of the Royal Astronomical Society (MNRAS
Strategies for wheat stripe rust pathogenicity identified by transcriptome sequencing
Stripe rust caused by the fungus Puccinia striiformis f.sp. tritici (Pst) is a major constraint to wheat production worldwide. The molecular events that underlie Pst pathogenicity are largely unknown. Like all rusts, Pst creates a specialized cellular structure within host cells called the haustorium to obtain nutrients from wheat, and to secrete pathogenicity factors called effector proteins. We purified Pst haustoria and used next-generation sequencing platforms to assemble the haustorial transcriptome as well as the transcriptome of germinated spores. 12,282 transcripts were assembled from 454-pyrosequencing data and used as reference for digital gene expression analysis to compare the germinated uredinospores and haustoria transcriptomes based on Illumina RNAseq data. More than 400 genes encoding secreted proteins which constitute candidate effectors were identified from the haustorial transcriptome, with two thirds of these up-regulated in this tissue compared to germinated spores. RT-PCR analysis confirmed the expression patterns of 94 effector candidates. The analysis also revealed that spores rely mainly on stored energy reserves for growth and development, while haustoria take up host nutrients for massive energy production for biosynthetic pathways and the ultimate production of spores. Together, these studies substantially increase our knowledge of potential Pst effectors and provide new insights into the pathogenic strategies of this important organism.J.P.R. is an ARC Future Fellow (FT0992129). This project has been supported by Bioplatforms Australia through funding from the Commonwealth
Government NCRIS and Education Investment Fund Super Science programs
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