236 research outputs found
Versatile multipass cell for laser spectroscopic trace gas analysis
The design, construction and characterization of a novel circular multipass cell for sensitive trace gas analysis are presented. This cell allows for easy modification of the optical path length without any changes of its physical parameters. Furthermore, it is suited for three different detection techniques: direct absorption, wavelength modulation and photoacoustics. To demonstrate its performance, mixing ratios of 13CO2 and N2O were measured from ambient air, using a quantum cascade laser. With the direct absorption method, noise equivalent 1-s precisions of 2.7ppb and 0.2ppb are achieved for 13CO2 and N2O, respectively. The wavelength modulation technique resulted in 4.3ppb precision with 1-s averaging for the 13CO2 measurements. AQ-factor of 190 and a normalized noise equivalent minimum absorption of 1.3×10−8cm−1 W Hz−1/2 are achieved using the photoacoustic techniqu
Evaluation of Adaptive Changes by Non-Invasive Imaging in Hepatic Vein Outflow Obstruction
Hepatic vein outflow obstruction induces remarkable changes of intra–hepatic blood circulation;
the significance of these changes remains uncertain. Six patients with obstruction of the
hepatic veins were evaluated by duplex Doppler ultrasound and computed tomography. The
adaptive changes secondary to obstruction were analyzed and their significance was correlated
with the clinical findings. Four patients presenting unilateral hepatic vein occlusion had
unilateral reversed portal flow. Two of them, with lobar liver atrophy and contralateral
compensatory hypertrophy required operation; the other two, with normal appearance of the
liver, benefitted from conservative treatment. Two patients with bilateral hepatic vein occlusion,
intra-hepatic bypasses, bilateral lobar atrophy and caudate lobe hypertrophy, received operations.
Intrahepatic unilateral portal flow reversal compensates for unilateral hepatic outflow
obstruction. The combination of complete or subtotal hepatic vein obstruction and atrophy–hypertrophy
complex predicates advanced disease despite flow reversal or spontaneous shunt
Reference hydrologic networks I: the status and potential future directions of national reference hydrologic networks for detecting trends
Identifying climate-driven trends in river flows on a global basis is hampered by a lack of long, quality
time series data for rivers with relatively undisturbed regimes. This is a global problem compounded by the lack
of support for essential long-term monitoring. Experience demonstrates that, with clear strategic objectives, and
the support of sponsoring organizations, reference hydrologic networks can constitute an exceptionally valuable
data source to effectively identify, quantify and interpret hydrological change—the speed and magnitude of which
is expected to a be a primary driver of water management and flood alleviation strategies through the future—and
for additional applications. Reference hydrologic networks have been developed in many countries in the past few
decades. These collections of streamflow gauging stations, that are maintained and operated with the intention of
observing how the hydrology of watersheds responds to variations in climate, are described. The status of networks
under development is summarized. We suggest a plan of actions to make more effective use of this collection of
networks
Radiocarbon Age Offsets Between Two Surface Dwelling Planktonic Foraminifera Species During Abrupt Climate Events in the SW Iberian Margin
[EN]This study identifies temporal biases in the radiocarbon ages of the planktonic foraminifera species Globigerina bulloides and Globigerinoides ruber (white) in a sediment core from the SW Iberian margin (so‐called Shackleton site). Leaching of the outer shell and measurement of the radiocarbon content of both the leachate and leached sample enabled us to identify surface contamination of the tests and its impact on their 14C ages. Incorporation of younger radiocarbon on the outer shell affected both species and had a larger impact downcore. Interspecies comparison of the 14C ages of the leached samples reveal systematic offsets with 14C ages for G. ruber being younger than G. bulloides ages during the last deglaciation and part of the Early and mid‐Holocene. The greatest offsets (up to 1,030 years) were found during Heinrich Stadial 1, the Younger Dryas, and part of the Holocene. The potential factors differentially affecting these two planktonic species were assessed by complementary 14C, oxygen and carbon isotopes, and species abundance determinations. The coupled effect of bioturbation with changes in the abundance of G. ruber is invoked to account for the large age offsets. Our results highlight that 14C ages of planktonic foraminifera might be largely compromised even in settings characterized by high sediment accumulation rates. Thus, a careful assessment of potential temporal biases must be performed prior to using 14C ages for paleoclimate investigations or radiocarbon calibrations (e.g., marine calibration curve Marine13, Reimer et al., 201
First insights into the ISM at z > 8 with JWST: Possible physical implications of a high [O iii] λ4363/[O iii] λ5007
We present a detailed analysis of the rest-frame optical emission line ratios for three spectroscopically confirmed galaxies at z > 7.5. The galaxies were identified in the James Webb Space Telescope (JWST) Early Release Observations field SMACS J0723.3 - 7327. By quantitatively comparing Balmer and oxygen line ratios of these galaxies with various low-redshift 'analogue' populations (e.g. Green Peas, Blueberries, etc.), we show that no single analogue population captures the diversity of line ratios of all three galaxies observed at z > 7.5. We find that S06355 at z = 7.67 and S10612 at z = 7.66 are similar to local Green Peas and Blueberries. In contrast, S04590 at z = 8.50 appears to be significantly different from the other two galaxies, most resembling extremely low-metallicity systems in the local Universe. Perhaps the most striking spectral feature in S04590 is the curiously high [O iii] λ4363/[O iii] λ5007 ratio (RO3) of 0.048 (or 0.055 when dust-corrected), implying either extremely high electron temperatures, >3 × 104 K, or gas densities >104 cm-3. Observed line ratios indicate that this galaxy is unlikely to host an AGN. Using photoionization modelling, we show that the inclusion of high-mass X-ray binaries or a high cosmic ray background in addition to a young, low-metallicity stellar population can provide the additional heating necessary to explain the observed high RO3 while remaining consistent with other observed line ratios. Our models represent a first step at accurately characterizing the dominant sources of photoionization and heating at very high redshifts, demonstrating that non-thermal processes may become important as we probe deeper into the Epoch of Reionization
Mind Perception: Real but Not Artificial Faces Sustain Neural Activity beyond the N170/VPP
Faces are visual objects that hold special significance as the icons of other minds. Previous researchers using event-related potentials (ERPs) have found that faces are uniquely associated with an increased N170/vertex positive potential (VPP) and a more sustained frontal positivity. Here, we examined the processing of faces as objects vs. faces as cues to minds by contrasting images of faces possessing minds (human faces), faces lacking minds (doll faces), and non-face objects (i.e., clocks). Although both doll and human faces were associated with an increased N170/VPP from 175–200 ms following stimulus onset, only human faces were associated with a sustained positivity beyond 400 ms. Our data suggest that the N170/VPP reflects the object-based processing of faces, whether of dolls or humans; on the other hand, the later positivity appears to uniquely index the processing of human faces—which are more salient and convey information about identity and the presence of other minds
The JWST Advanced Deep Extragalactic Survey: Discovery of an Extreme Galaxy Overdensity at z = 5.4 with JWST/NIRCam in GOODS-S
© 2024 The Author(s). Published by the American Astronomical Society. This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY), https://creativecommons.org/licenses/by/4.0/We report the discovery of an extreme galaxy overdensity at in the GOODS-S field using JWST/NIRCam imaging from JADES and JEMS alongside JWST/NIRCam wide field slitless spectroscopy from FRESCO. We identified potential members of the overdensity using HST+JWST photometry spanning . These data provide accurate and well-constrained photometric redshifts down to . We subsequently confirmed galaxies at using JWST slitless spectroscopy over through a targeted line search for around the best-fit photometric redshift. We verified that of these galaxies reside in the field while galaxies reside in a density around times that of a random volume. Stellar populations for these galaxies were inferred from the photometry and used to construct the star-forming main sequence, where protocluster members appeared more massive and exhibited earlier star formation (and thus older stellar populations) when compared to their field galaxy counterparts. We estimate the total halo mass of this large-scale structure to be using an empirical stellar mass to halo mass relation, which is likely an underestimate as a result of incompleteness. Our discovery demonstrates the power of JWST at constraining dark matter halo assembly and galaxy formation at very early cosmic times.Peer reviewe
The JWST Advanced Deep Extragalactic Survey: Discovery of an Extreme Galaxy Overdensity at with JWST/NIRCam in GOODS-S
We report the discovery of an extreme galaxy overdensity at in the
GOODS-S field using JWST/NIRCam imaging from JADES and JEMS alongside
JWST/NIRCam wide field slitless spectroscopy from FRESCO. We identified
potential members of the overdensity using HST+JWST photometry spanning
. These data provide accurate and
well-constrained photometric redshifts down to .
We subsequently confirmed galaxies at using JWST
slitless spectroscopy over through a
targeted line search for around the best-fit photometric
redshift. We verified that of these galaxies reside in the field while
galaxies reside in a density around times that of a random
volume. Stellar populations for these galaxies were inferred from the
photometry and used to construct the star-forming main sequence, where
protocluster members appeared more massive and exhibited earlier star formation
(and thus older stellar populations) when compared to their field galaxy
counterparts. We estimate the total halo mass of this large-scale structure to
be using an empirical stellar mass to halo mass relation, which is
likely an underestimate as a result of incompleteness. Our discovery
demonstrates the power of JWST at constraining dark matter halo assembly and
galaxy formation at very early cosmic times.Comment: Resubmitted to ApJ based on reviewer report; main text has 15 pages,
6 figures and 1 table; appendix has 1 page, 2 figure sets, and 2 table
MOONRISE: The Main MOONS GTO Extragalactic Survey
The MOONS instrument possesses an exceptional combination of large
multiplexing, high sensitivity, broad simultaneous spectral coverage (from
optical to near-infrared bands), large patrol area and high fibre density.
These properties provide the unprecedented potential of enabling, for the very first time, SDSS-like surveys around Cosmic Noon (z~1-2.5), when the star formation rate in the Universe peaked. The high-quality spectra delivered by MOONS will sample the same nebular and stellar diagnostics observed in
extensive surveys of local galaxies, providing an accurate and consistent
description of the evolution of various physical properties of galaxies, and
hence a solid test of different scenarios of galaxy formation and
transformation. Most importantly, by spectroscopically identifying hundreds of thousands of galaxies at high redshift, the MOONS surveys will be capable of determining the environments in which primeval galaxies lived and will reveal how such environments affected galaxy evolution. In this article, we
specifically focus on the main Guaranteed Time Observation (GTO) MOONS
extragalactic survey, MOONRISE, by providing an overview of its scientific
goals and observing strategy
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