220 research outputs found
Climate drives community-wide divergence within species over a limited spatial scale: evidence from an oceanic island
Geographic isolation substantially contributes to species endemism on oceanic islands when speciation involves the colonisation of a new island. However, less is understood about the drivers of speciation within islands. What is lacking is a general understanding of the geographic scale of gene flow limitation within islands, and thus the spatial scale and drivers of geographical speciation within insular contexts. Using a community of beetle species, we show that when dispersal ability and climate tolerance are restricted, microclimatic variation over distances of only a few kilometres can maintain strong geographic isolation extending back several millions of years. Further to this, we demonstrate congruent diversification with gene flow across species, mediated by Quaternary climate oscillations that have facilitated a dynamic of isolation and secondary contact. The unprecedented scale of parallel species responses to a common environmental driver for evolutionary change has profound consequences for understanding past and future species responses to climate variation
Inflammatory, procoagulant markers and HIV residual viremia in patients receiving protease inhibitor monotherapy or triple drug therapy: a cross-sectional study
The Near-Infrared Spectrograph (NIRSpec) on the James Webb Space Telescope II. Multi-object spectroscopy (MOS)
We provide an overview of the capabilities and performance of the
Near-Infrared Spectrograph (NIRSpec) on the James Webb Space Telescope (JWST)
when used in its multi-object spectroscopy (MOS) mode employing a novel Micro
Shutter Array (MSA) slit device. The MSA consists of four separate 98 arcsec
91 arcsec quadrants each containing individually
addressable shutters whose open areas on the sky measure 0.20 arcsec
0.46 arcsec on a 0.27 arcsec 0.53 arcsec pitch. This is the first time
that a configurable multi-object spectrograph has been available on a space
mission. The levels of multiplexing achievable with NIRSpec MOS mode are
quantified and we show that NIRSpec will be able to observe typically fifty to
two hundred objects simultaneously with the pattern of close to a quarter of a
million shutters provided by the MSA. This pattern is fixed and regular, and we
identify the specific constraints that it yields for NIRSpec observation
planning. We also present the data processing and calibration steps planned for
the NIRSpec MOS data. The significant variation in size of the mostly
diffraction-limited instrument point spread function over the large wavelength
range of 0.6-5.3 m covered by the instrument, combined with the fact that
most targets observed with the MSA cannot be expected to be perfectly centred
within their respective slits, makes the spectrophotometric and wavelength
calibration of the obtained spectra particularly complex. These challenges
notwithstanding, the sensitivity and multiplexing capabilities anticipated of
NIRSpec in MOS mode are unprecedented, and should enable significant progress
to be made in addressing a wide range of outstanding astrophysical problems
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The Near-Infrared Spectrograph (NIRSpec) on the James Webb Space Telescope II. Multi-object spectroscopy (MOS)
We provide an overview of the capabilities and performance of the
Near-Infrared Spectrograph (NIRSpec) on the James Webb Space Telescope (JWST)
when used in its multi-object spectroscopy (MOS) mode employing a novel Micro
Shutter Array (MSA) slit device. The MSA consists of four separate 98 arcsec
91 arcsec quadrants each containing individually
addressable shutters whose open areas on the sky measure 0.20 arcsec
0.46 arcsec on a 0.27 arcsec 0.53 arcsec pitch. This is the first time
that a configurable multi-object spectrograph has been available on a space
mission. The levels of multiplexing achievable with NIRSpec MOS mode are
quantified and we show that NIRSpec will be able to observe typically fifty to
two hundred objects simultaneously with the pattern of close to a quarter of a
million shutters provided by the MSA. This pattern is fixed and regular, and we
identify the specific constraints that it yields for NIRSpec observation
planning. We also present the data processing and calibration steps planned for
the NIRSpec MOS data. The significant variation in size of the mostly
diffraction-limited instrument point spread function over the large wavelength
range of 0.6-5.3 m covered by the instrument, combined with the fact that
most targets observed with the MSA cannot be expected to be perfectly centred
within their respective slits, makes the spectrophotometric and wavelength
calibration of the obtained spectra particularly complex. These challenges
notwithstanding, the sensitivity and multiplexing capabilities anticipated of
NIRSpec in MOS mode are unprecedented, and should enable significant progress
to be made in addressing a wide range of outstanding astrophysical problems
The Near-Infrared Spectrograph (NIRSpec) on the James Webb Space Telescope: IV. Capabilities and predicted performance for exoplanet characterization
The Near-Inrared Spectrograph (NIRSpec) on the James Webb Space Telescope
(JWST) is a very versatile instrument, offering multiobject and integral field
spectroscopy with varying spectral resolution (30 to 3000) over a
wide wavelength range from 0.6 to 5.3 micron, enabling scientists to study many
science themes ranging from the first galaxies to bodies in our own Solar
System. In addition to its integral field unit and support for multiobject
spectroscopy, NIRSpec features several fixed slits and a wide aperture
specifically designed to enable high precision time-series and transit as well
as eclipse observations of exoplanets. In this paper we present its
capabilities regarding time-series observations, in general, and transit and
eclipse spectroscopy of exoplanets in particular. Due to JWST's large
collecting area and NIRSpec's excellent throughput, spectral coverage, and
detector performance, this mode will allow scientists to characterize the
atmosphere of exoplanets with unprecedented sensitivity
Thermal niche evolution and geographical range expansion in a species complex of western Mediterranean diving beetles
[Background] Species thermal requirements are one of the principal determinants of their ecology and biogeography, although our understanding of the interplay between these factors is limited by the paucity of integrative empirical studies. Here we use empirically collected thermal tolerance data in combination with molecular phylogenetics/phylogeography and ecological niche modelling to study the evolution of a clade of three western Mediterranean diving beetles, the Agabus brunneus complex.[Results] The preferred mitochondrial DNA topology recovered A. ramblae (North Africa, east Iberia and Balearic islands) as paraphyletic, with A. brunneus (widespread in the southwestern Mediterranean) and A. rufulus (Corsica and Sardinia) nested within it, with an estimated origin between 0.60-0.25 Ma. All three species were, however, recovered as monophyletic using nuclear DNA markers. A Bayesian skyline plot suggested demographic expansion in the clade at the onset of the last glacial cycle. The species thermal tolerances differ significantly, with A. brunneus able to tolerate lower temperatures than the other taxa. The climatic niche of the three species also differs, with A. ramblae occupying more arid and seasonal areas, with a higher minimum temperature in the coldest month. The estimated potential distribution for both A. brunneus and A. ramblae was most restricted in the last interglacial, becoming increasingly wider through the last glacial and the Holocene.[Conclusions] The A. brunneus complex diversified in the late Pleistocene, most likely in south Iberia after colonization from Morocco. Insular forms did not differentiate substantially in morphology or ecology, but A. brunneus evolved a wider tolerance to cold, which appeared to have facilitated its geographic expansion. Both A. brunneus and A. ramblae expanded their ranges during the last glacial, although they have not occupied areas beyond their LGM potential distribution except for isolated populations of A. brunneus in France and England. On the islands and possibly Tunisia secondary contact between A. brunneus and A. ramblae or A. rufulus has resulted in introgression. Our work highlights the complex dynamics of speciation and range expansions within southern areas during the last glacial cycle, and points to the often neglected role of North Africa as a source of European biodiversity.This work was supported by an FPI grant to AH-G and projects CGL2007-61665 and CGL2010-15755 from the Spanish government to IR. We acknowledge support of the publication fee by the CSIC Open Access Publication Support Initiative through its Unit of Information Resources for Research (URICI).Peer reviewe
Prostate cancer risk and consumption of fish oils: a dietary biomarker-based caseâcontrol study
Experimental studies suggest that the risk of prostate cancer is reduced with the intake of long-chain n-3 polyunsaturated fatty acids derived from marine foods, such as eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). However, few human studies have been conducted due to difficulties in assessing the dietary intake of these fatty acids. The authors examined the relationship between prostate cancer risk and EPA and DHA in erythrocyte biomarkers in a population-based caseâcontrol study in Auckland, New Zealand during 1996â1997 involving 317 prostate cancer cases and 480 age-matched community controls. Reduced prostate cancer risk was associated with high erythrocyte phosphatidylcholine levels of EPA (multivariate relative risk = 0.59; 95% confidence interval 0.37â0.95, upper vs lowest quartile) and DHA (multivariate relative risk = 0.62; 95% confidence interval 0.39â0.98, upper vs lowest quartile). These analyses support evidence from in vitro experiments for a reduced risk of prostate cancer associated with dietary fish oils, possibly acting via inhibition of arachidonic acid-derived eicosanoid biosynthesis. © 1999 Cancer Research Campaig
Decreased thermal tolerance under recurrent heat stress conditions explains summer mass mortality of the blue mussel Mytilus edulis
Extreme events such as heat waves have increased in frequency and duration over the last decades. Under future climate scenarios, these discrete climatic events are expected to become even more recurrent and severe. Heat waves are particularly important on rocky intertidal shores, one of the most thermally variable and stressful habitats on the planet. Intertidal mussels, such as the blue mussel Mytilus edulis, are ecosystem engineers of global ecological and economic importance, that occasionally suffer mass mortalities. This study investigates the potential causes and consequences of a mass mortality event of M. edulis that occurred along the French coast of the eastern English Channel in summer 2018. We used an integrative, climatological and ecophysiological methodology based on three complementary approaches. We first showed that the observed mass mortality (representing 49 to 59% of the annual commercial value of local recreational and professional fisheries combined) occurred under relatively moderate heat wave conditions. This result indicates that M. edulis body temperature is controlled by non-climatic heat sources instead of climatic heat sources, as previously reported for intertidal gastropods. Using biomimetic loggers (i.e. 'robomussels'), we identified four periods of 5 to 6 consecutive days when M. edulis body temperatures consistently reached more than 30â°C, and occasionally more than 35â°C and even more than 40â°C. We subsequently reproduced these body temperature patterns in the laboratory to infer M. edulis thermal tolerance under conditions of repeated heat stress. We found that thermal tolerance consistently decreased with the number of successive daily exposures. These results are discussed in the context of an era of global change where heat events are expected to increase in intensity and frequency, especially in the eastern English Channel where the low frequency of commercially exploitable mussels already questions both their ecological and commercial sustainability.Funding Agency
French Ministere de l'Enseignement Superieur et de la Recherche
Region Hauts-de-France
European Funds for Regional Economical Development
Pierre Hubert Curien PESSOA Felloswhip
Fundacao para a Ciencia e Tecnologia (FCT-MEC, Portugal)
IF/01413/2014/CP1217/CT0004
National Research Foundation - South Africa
64801
South African Research Chairs Initiative (SARChI) of the Department of Science and Technology
National Research Foundation - South Africainfo:eu-repo/semantics/publishedVersio
The Near-Infrared Spectrograph (NIRSpec) on the James Webb Space Telescope: I. Overview of the instrument and its capabilities
We provide an overview of the design and capabilities of the near-infrared
spectrograph (NIRSpec) onboard the James Webb Space Telescope. NIRSpec is
designed to be capable of carrying out low-resolution () prism
spectroscopy over the wavelength range m and higher resolution
( or ) grating spectroscopy over
m, both in single-object mode employing any one of five fixed
slits, or a 3.13.2 arcsec integral field unit, or in multiobject
mode employing a novel programmable micro-shutter device covering a
3.63.4~arcmin field of view. The all-reflective optical chain of
NIRSpec and the performance of its different components are described, and some
of the trade-offs made in designing the instrument are touched upon. The
faint-end spectrophotometric sensitivity expected of NIRSpec, as well as its
dependency on the energetic particle environment that its two detector arrays
are likely to be subjected to in orbit are also discussed
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