2,011 research outputs found
Non-monotonic temperature evolution of dynamic correlations in glass-forming liquids
The viscosity of glass-forming liquids increases by many orders of magnitude
if their temperature is lowered by a mere factor of 2-3 [1,2]. Recent studies
suggest that this widespread phenomenon is accompanied by spatially
heterogeneous dynamics [3,4], and a growing dynamic correlation length
quantifying the extent of correlated particle motion [5-7]. Here we use a novel
numerical method to detect and quantify spatial correlations which reveal a
surprising non-monotonic temperature evolution of spatial dynamical
correlations, accompanied by a second length scale that grows monotonically and
has a very different nature. Our results directly unveil a dramatic qualitative
change in atomic motions near the mode-coupling crossover temperature [8] which
involves no fitting or indirect theoretical interpretation. Our results impose
severe new constraints on the theoretical description of the glass transition,
and open several research perspectives, in particular for experiments, to
confirm and quantify our observations in real materials.Comment: 7 page
Exploring the Free Energy Landscape: From Dynamics to Networks and Back
The knowledge of the Free Energy Landscape topology is the essential key to
understand many biochemical processes. The determination of the conformers of a
protein and their basins of attraction takes a central role for studying
molecular isomerization reactions. In this work, we present a novel framework
to unveil the features of a Free Energy Landscape answering questions such as
how many meta-stable conformers are, how the hierarchical relationship among
them is, or what the structure and kinetics of the transition paths are.
Exploring the landscape by molecular dynamics simulations, the microscopic data
of the trajectory are encoded into a Conformational Markov Network. The
structure of this graph reveals the regions of the conformational space
corresponding to the basins of attraction. In addition, handling the
Conformational Markov Network, relevant kinetic magnitudes as dwell times or
rate constants, and the hierarchical relationship among basins, complete the
global picture of the landscape. We show the power of the analysis studying a
toy model of a funnel-like potential and computing efficiently the conformers
of a short peptide, the dialanine, paving the way to a systematic study of the
Free Energy Landscape in large peptides.Comment: PLoS Computational Biology (in press
Benefits and risks of the hormetic effects of dietary isothiocyanates on cancer prevention
The isothiocyanate (ITC) sulforaphane (SFN) was shown at low levels (1-5 µM) to promote cell proliferation to 120-143% of the controls in a number of human cell lines, whilst at high levels (10-40 µM) it inhibited such cell proliferation. Similar dose responses were observed for cell migration, i.e. SFN at 2.5 µM increased cell migration in bladder cancer T24 cells to 128% whilst high levels inhibited cell migration. This hormetic action was also found in an angiogenesis assay where SFN at 2.5 µM promoted endothelial tube formation (118% of the control), whereas at 10-20 µM it caused significant inhibition. The precise mechanism by which SFN influences promotion of cell growth and migration is not known, but probably involves activation of autophagy since an autophagy inhibitor, 3-methyladenine, abolished the effect of SFN on cell migration. Moreover, low doses of SFN offered a protective effect against free-radical mediated cell death, an effect that was enhanced by co-treatment with selenium. These results suggest that SFN may either prevent or promote tumour cell growth depending on the dose and the nature of the target cells. In normal cells, the promotion of cell growth may be of benefit, but in transformed or cancer cells it may be an undesirable risk factor. In summary, ITCs have a biphasic effect on cell growth and migration. The benefits and risks of ITCs are not only determined by the doses, but are affected by interactions with Se and the measured endpoint
DNA barcoding of Brazilian sea turtles (Testudines)
Five out of the seven recognized species of sea turtles (Testudines) occur on the Brazilian coast. The Barcode Initiative is an effort to undertake a molecular inventory of Earth biodiversity. Cytochrome Oxidase c subunit I (COI) molecular tags for sea turtle species have not yet been described. In this study, COI sequences for the five species of sea turtles that occur in Brazil were generated. These presented widely divergent haplotypes. All observed values were on the same range as those already described for other animal groups: the overall mean distance was 8.2%, the mean distance between families (Dermochelyidae and Cheloniidae) 11.7%, the mean intraspecific divergence 0.34%, and the mean distance within Cheloniidae 6.4%, this being 19-fold higher than the mean divergence observed within species. We obtained species-specific COI barcode tags that can be used for identifying each of the marine turtle species studied
Assessment of Attractiveness of Plants as Roosting Sites for the Melon Fly, Bactrocera cucurbitae, and Oriental Fruit Fly, Bactrocera dorsalis
The use of toxic protein bait sprays to suppress melon fly, Bactrocera cucurbitae (Coquillett) (Diptera: Tephritidae), populations typically involves application to vegetation bordering agricultural host areas where the adults seek shelter (“roost”). Although bait spray applications for suppression of oriental fruit fly, Bactrocera dorsalis (Hendel), populations have traditionally been applied to the host crop, rather than to crop borders, roosting by oriental fruit flies in borders of some crop species, such as papaya, Carica papaya L. (Brassicales: Caricaceae), suggests that bait spray applications to crop borders could also help in suppression of B. dorsalis populations. In order to develop improved recommendations for application of bait sprays to border plants for suppression of melon fly and oriental fruit fly populations, the relative attractiveness of a range of plant species, in a vegetative (non-flowering) stage, was tested to wild melon fly and oriental fruit fly populations established in a papaya orchard in Hawaii. A total of 20 plant species were evaluated, divided into four categories: 1) border plants, including corn, Zea mays L. (Poales: Poaceae), windbreaks and broad-leaved ornamentals, 7 species; 2) weed plants commonly found in agricultural fields in Hawaii, 6 species; 3) host crop plants, 1 species- zucchini, Cucurbita pepo L. (Violales: Curcurbitaceae), and 4) locally grown fruit trees, 6 species. Plants were established in pots and placed in an open field, in clusters encircling protein bait traps, 20 m away from the papaya orchard. Castor bean, Ricinus communis L. (Euphorbiales: Euphorbiaceae), panax, Polyscias guilfoylei (Bull) Bailey (Apiales: Araliaceae), tiger's claw, Erythnna variegata L. (Fabales: Fabaceae), and guava, Psidium guajava L. (Myrtales: Myrtaceae) were identified as preferred roosting hosts for the melon fly, and tiger's claw, panax, castor bean, Canada cocklebur, Xanthium strumarium L. (Asterales: Asteraceae), Brazilian pepper tree, Schinus terebinthifolius Raddi (Sapindales: Anacardiaceae), ti plant, Cordyline terminate (L.) Chev.(Liliales: Liliaceae), guava and several Citrus spp. were identified as preferred roosting hosts for oriental fruit fly. Guava had not previously been identified as a preferred roosting host for melon fly. Other than for the use of panax as a roosting host, there has previously been little attention to roosting hosts for oriental fruit fly. Establishment of preferred roosting hosts as crop borders may help to improve suppression of both fruit fly species by providing sites for bait spray applications. Further research is needed to assess the use of vegetation bordering other host crops as roosting hosts, especially for oriental fruit fly
Multiplicity of Galactic Cepheids from long-baseline interferometry. I. CHARA/MIRC detection of the companion of V1334 Cygni
This is the final version of the article. Available from the publisher via the DOI in this record.Context. More than 60% of Cepheids are in binary or multiple systems. Studying such systems could lead to a better understanding
of the age and evolution of Cepheids. These are also useful tools to estimate the mass of Cepheids, and constrain theoretical models
of their pulsation and evolution.
Aims. We aim at determining the masses of Cepheids in binary systems, as well as their geometric distances and the flux contribution
of the companions. The combination of interferometry with spectroscopy will offer a unique and independent estimate of the Cepheid
masses.
Methods. Using long-baseline interferometry at visible and infrared wavelengths, it is possible to spatially resolve binary systems
containing a Cepheid down to milliarcsecond separations. Based on the resulting visual orbit and radial velocities, we can then derive
the fundamental parameters of these systems, particularly the masses of the components and the geometric distance. We therefore
performed interferometric observations of the first-overtone mode Cepheid V1334 Cyg with the CHARA/MIRC combiner.
Results. We report the first detection of a Cepheid companion using long-baseline interferometry. We detect the signature of a
companion orbiting V1334 Cyg at two epochs. We measure a flux ratio between the companion and the Cepheid f = 3.10 ± 0.08%,
giving an apparent magnitude mH = 8.47 ± 0.15 mag. The combination of interferometric and spectroscopic data have enabled
the unique determination of the orbital elements. P = 1938.6 ± 1.2 days, Tp = 2 443 616.1 ± 7.3, a = 8.54 ± 0.51 mas, i =
124.7 ± 1.8
◦
, e = 0.190 ± 0.013, ω = 228.7 ± 1.6
◦
, and Ω = 206.3 ± 9.4
◦
. We derive a minimal distance d ∼ 691 pc, a minimum
mass for both stars of 3.6 M , with a spectral type earlier than B5.5V for the companion star. Our measured flux ratio suggests that
radial velocity detection of the companion using spectroscopy is within reach, and would provide an orbital parallax and model-free
massesThe authors would like to thank the CHARA Array and
Mount Wilson Observatory staff for their support. Research conducted at the
CHARA Array is funded by the National Science Foundation through NSF
grant AST-0908253, by Georgia State University, the W. M. Keck Foundation,
the Packard Foundation, and the NASA Exoplanet Science Institute. J.D.M.
acknowledges funding from the NSF grants AST-0707927 and AST-0807577.
W.G. and G.P. gratefully acknowledge financial support for this work from
the BASAL Centro de Astrofísica y Tecnologías Afines (CATA) PFB-06/2007.
Support from the Polish National Science Centre grant MAESTRO and the
Polish Ministry of Science grant Ideas Plus (awarded to G. P.) is also acknowledge.
This research received the support of PHASE, the high angular
resolution partnership between ONERA, Observatoire de Paris, CNRS,
and University Denis Diderot Paris 7. A.G. acknowledges support from
FONDECYT grant 3130361. LSz has been supported by the ESTEC Contract
No.4000106398/12/NL/KML. This work made use of the SIMBAD and VIZIER
astrophysical database from CDS, Strasbourg, France and the bibliographic informations
from the NASA Astrophysics Data System. This research has made
use of the Jean-Marie Mariotti Center LITpro service, co-developed by CRAL,
LAOG and FIZEAU, and SearchCal service, co-developed by FIZEAU and
LAOG/IPAG, and of CDS Astronomical Databases SIMBAD and VIZIER
Swab-yourself trial with economic monitoring and testing for infections collectively (SYSTEMATIC): Part 2. A diagnostic accuracy, and cost-effectiveness, study comparing rectal, pharyngeal and urogenital samples analysed individually, versus as a pooled specimen, for the diagnosis of gonorrhoea and chlamydia
This is the author accepted manuscript. The final version is available from Oxford University Press via the DOI in this recordBACKGROUND: Sexual history does not accurately identify those with extragenital Neisseria gonorrhoeae (NG) and Chlamydia trachomatis (CT) so universal extragenital sampling is recommended. Nucleic acid amplification tests (NAATs) are expensive. If urogenital, plus rectal and pharyngeal, samples are analysed the diagnostic cost is trebled. Pooling samples into one NAAT container would cost the same as urogenital samples alone. We compared clinician triple samples analysed individually with self-taken pooled samples for diagnostic accuracy, and cost, in MSM and females. METHODS: Prospective, convenience, sample in UK sexual health clinic. Randomised order of clinician and self-samples from pharynx, rectum, plus first catch urine (FCU) in MSM and vulvovaginal swabs (VVS) in females, for NG and CT detection. RESULTS: Of 1793 participants (1284 females, 509 MSM), 116 had NG detected (75 urogenital, 83 rectum, 72 pharynx). 276 had CT detected (217 urogenital, 249 rectum, 63 pharynx).There was no difference in sensitivities between clinician triple samples and self-pooled specimens for NG (99.1%, 98.3%) but clinician samples analysed individually identified 3% more chlamydia infections than pooled (99.3%, 96.0%; p=0.027). However, pooled specimens identified more infections than VVS/FCU alone. Pooled specimens missed 2 NG and 11 CT infections, whereas VVS/FCU missed 41 NG and 58 CT infections. Self-taken pooled specimens were the most cost-effective. CONCLUSIONS: Just FCU/VVS testing missed many infections. Self-taken pooled samples were as sensitive as clinician triple samples for identifying NG, but clinician samples analysed individually identified 3% more CT infections than pooled. The extragenital sampling was achievable at no additional diagnostic cost to the FCU/VVS. TRIAL REGISTRATION: ClinicalTrials.gov NCT02371109.National Institute for Health Research (NIHR
SIT for African malaria vectors: Epilogue
As a result of increased support and the diligent application of new and conventional anti-malaria tools, significant reductions in malaria transmission are being accomplished. Historical and current evolutionary responses of vectors and parasites to malaria interventions demonstrate that it is unwise to assume that a limited suite of tools will remain effective indefinitely, thus efforts to develop new interventions should continue. This collection of manuscripts surveys the prospects and technical challenges for applying a novel tool, the sterile insect technique (SIT), against mosquitoes that transmit malaria. The method has been very successful against many agricultural pest insects in area-wide programs, but demonstrations against malaria vectors have not been sufficient to determine its potential relative to current alternatives, much of which will hinge ultimately upon cost. These manuscripts provide an overview of current efforts to develop SIT and identify key research issues that remain
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