791 research outputs found
Time-resolved torsional relaxation of spider draglines by an optical technique.
International audienceThe sensitivity of the torsional pendulum demonstrates the self-shape-memory effect in different types of spider draglines. Here we report the time-resolved noncovalent bonds recovery in the protein structure. The torsional dynamics of such multilevel structure governed by reversible interactions are described in the frame of a nested model. Measurement of three different relaxation times confirms the existence of three energy storage levels in such two protein spidroin systems. Torsion opens the way to further investigations towards unraveling the tiny torque effects in biological molecules
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Shovel logging and soil compaction : a case study
Shovel logging is a relatively new ground-based method of yarding tinther. It involves moving logs from stump to landing by successive swinging with a hydraulic excavator modified into a log loader by replacing the shovel bucket with a grapple. Loaders used in shovel yarding can weigh in excess of 100,000 pounds so that the opportunity for soil compaction is great. This study measured the amount of soil compaction that occurs with shovel yarding. The study was done on the Quinault District of the Olympic N.F. in Washington state. The results show that 20.5% of the total area logged consisted of shovel paths. Soil bulk densities in the shovel tracks when compared to undisturbed areas within the unit showed a statistically significant increase of about 7.5%. Soil compaction did not seem to increase after the initial pass up to seven passes. Production rate for the shovel was 7.8 net
inbf/hour. Logging with the shovel cost $18.57/inbf less than yarding the same unit with a Washington 208 slackline yarder. Three methods of economically analyzing the effects of soil compaction were reviewed and the idea that the value of soil compaction involves more than just the dollar value lost due to future decreased timber production was proposed. Values such as existence value, option value and quasi-option value need to also be considered in any decision allowing soil compaction to occur
The evolution of galaxy star formation activity in massive halos
There is now a large consensus that the current epoch of the Cosmic Star
Formation History (CSFH) is dominated by low mass galaxies while the most
active phase at 1<z<2 is dominated by more massive galaxies, which undergo a
faster evolution. Massive galaxies tend to inhabit very massive halos such as
galaxy groups and clusters. We aim to understand whether the observed "galaxy
downsizing" could be interpreted as a "halo downsizing", whereas the most
massive halos, and their galaxy populations, evolve more rapidly than the halos
of lower mass. Thus, we study the contribution to the CSFH of galaxies
inhabiting group-sized halos. This is done through the study of the evolution
of the Infra-Red (IR) luminosity function of group galaxies from redshift 0 to
~1.6. We use a sample of 39 X-ray selected groups in the Extended Chandra Deep
Field South (ECDFS), the Chandra Deep Field North (CDFN), and the COSMOS field,
where the deepest available mid- and far-IR surveys have been conducted with
Spitzer MIPS and Hersche PACS. Groups at low redshift lack the brightest,
rarest, and most star forming IR-emitting galaxies observed in the field. Their
IR-emitting galaxies contribute <10% of the comoving volume density of the
whole IR galaxy population in the local Universe. At redshift >~1, the most
IR-luminous galaxies (LIRGs and ULIRGs) are preferentially located in groups,
and this is consistent with a reversal of the star-formation rate vs .density
anti-correlation observed in the nearby Universe. At these redshifts, group
galaxies contribute 60-80% of the CSFH, i.e. much more than at lower redshifts.
Below z~1, the comoving number and SFR densities of IR-emitting galaxies in
groups decline significantly faster than those of all IR-emitting galaxies. Our
results are consistent with a "halo downsizing" scenario and highlight the
significant role of "environment" quenching in shaping the CSFH.Comment: 14 pages, 10 figures, accepted for publication by A&
A framework for the standardisation of tropical tuna purse seine CPUE: application to the yellowfin tuna in the Indian Ocean
We revised the existing framework for tuna CPUE standardisation in light of the increasing literature that
advocates the use of mixed effects models to account for the characteristics of logbook data. We apply the
framework on yellowfin tuna (YFT) from the Indian Ocean, caught by the purse seine EU fleet (Spain and
France) from 1984 to 2015. We used a comprehensive list of candidate covariates, including non- conventional covariates, and run exploratory models to assess the contribution of each covariate. Due to the
large number of covariates, the lasso – least absolute shrinkage and selection operator- method was applied
for data mining and model selection purposes. The results are two standardised YFT CPUE time series for the
period 1984-2015, one for large fish caught in free-school related sets, and one for mainly juveniles caught in
floating object related sets. Issues on the usefulness of highly aggregated data (low resolution: annual and
fleet wide) is discussed along with the need for more detailed information on the use of dFADs, preferably at
the level of a fishing trip.Preprin
The role of massive halos in the Star Formation History of the Universe
The most striking feature of the Cosmic Star Formation History (CSFH) of the
Universe is a dramatic drop of the star formation (SF) activity, since z~1. In
this work we investigate if the very same process of assembly and growth of
structures is one of the major drivers of the observed decline. We study the
contribution to the CSFH of galaxies in halos of different masses. This is done
by studying the total SFR-halo mass-redshift plane from redshift 0 to redshift
z~1.6 in a sample of 57 groups and clusters by using the deepest available mid-
and far-infrared surveys conducted with Spitzer MIPS and Herschel PACS and
SPIRE. Our results show that low mass groups provide a 60-80% contribution to
the CSFH at z~1. Such contribution declines faster than the CSFH in the last 8
billion years to less than 10% at z<0.3, where the overall SF activity is
sustained by lower mass halos. More massive systems provide only a marginal
contribution (<10%) at any epoch. A simplified abundance matching method shows
that the large contribution of low mass groups at z~1 is due to a large
fraction (>50%) of very massive, highly star forming Main Sequence galaxies.
Below z~1 a quenching process must take place in massive halos to cause the
observed faster suppression of their SF activity. Such process must be a slow
one though, as most of the models implementing a rapid quenching of the SF
activity in accreting satellites significantly underpredicts the observed SF
level in massive halos at any redshift. Starvation or the transition from cold
to hot accretion would provide a quenching timescale of 1 Gyrs more consistent
with the observations. Our results suggest a scenario in which, due to the
structure formation process, more and more galaxies experience the group
environment and, thus, the associated quenching process. This leads to the
progressive suppression of their SF activity shaping the CSFH below z~1.Comment: 18 pages, 21 figures, accepted for publication by A&
A Multiwavelength Consensus on the Main Sequence of Star-Forming Galaxies at z~2
We compare various star formation rate (SFR) indicators for star-forming
galaxies at in the COSMOS field. The main focus is on the SFRs from
the far-IR (PACS-Herschel data) with those from the ultraviolet, for galaxies
selected according to the BzK criterion. FIR-selected samples lead to a vastly
different slope of the SFR-stellar mass () relation, compared to that of
the dominant main sequence population as measured from the UV, since the FIR
selection picks predominantly only a minority of outliers. However, there is
overall agreement between the main sequences derived with the two SFR
indicators, when stacking on the PACS maps the BzK-selected galaxies. The
resulting logarithmic slope of the SFR-{} relation is , in
agreement with that derived from the dust-corrected UV-luminosity. Exploiting
deeper 24m-Spitzer data we have characterized a sub-sample of galaxies
with reddening and SFRs poorly constrained, as they are very faint in the
band. The combination of Herschel with Spitzer data have allowed us to largely
break the age/reddening degeneracy for these intriguing sources, by
distinguishing whether a galaxy is very red in B-z because of being heavily
dust reddened, or whether because star formation has been (or is being)
quenched. Finally, we have compared our SFR(UV) to the SFRs derived by stacking
the radio data and to those derived from the H luminosity of a sample
of star-forming galaxies at . The two sets of SFRs are broadly
consistent as they are with the SFRs derived from the UV and by stacking the
corresponding PACS data in various mass bins.Comment: Accepted for publication in MNRA
Deciphering the infectious process of Colletotrichum lupini in lupin through transcriptomic and proteomic analysis
The fungal phytopathogen Colletotrichum lupini is responsible for lupin anthracnose, resulting in significant yield losses worldwide. The molecular mechanisms underlying this infectious process are yet to be elucidated. This study proposes to evaluate C. lupini gene expression and protein synthesis during lupin infection, using, respectively, an RNAseq-based transcriptomic approach and a mass spectrometry-based proteomic approach. Patterns of differentially-expressed genes in planta were evaluated from 24 to 84 hours post-inoculation, and compared to in vitro cultures. A total of 897 differentially-expressed genes were identified from C. lupini during interaction with white lupin, of which 520 genes were predicted to have a putative function, including carbohydrate active enzyme, effector, protease or transporter-encoding genes, commonly described as pathogenicity factors for other Colletotrichum species during plant infection, and 377 hypothetical proteins. Simultaneously, a total of 304 proteins produced during the interaction were identified and quantified by mass spectrometry. Taken together, the results highlight that the dynamics of symptoms, gene expression and protein synthesis shared similarities to those of hemibiotrophic pathogens. In addition, a few genes with unknown or poorly-described functions were found to be specifically associated with the early or late stages of infection, suggesting that they may be of importance for pathogenicity. This study, conducted for the first time on a species belonging to the Colletotrichum acutatum species complex, presents an opportunity to deepen functional analyses of the genes involved in the pathogenicity of Colletotrichum spp. during the onset of plant infection
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