Abstract
We present a rest-frame optical morphological analysis of galaxies observed with the NIRCam imager on the James Webb Space Telescope (JWST) as part of the GLASS-JWST Early Release Science ...program. We select 388 sources at redshifts 0.8 <
z
< 5.4 and use the seven 0.9–5
μ
m NIRCam filters to generate rest-frame
gri
composite color images, and conduct visual morphological classification. Compared to Hubble Space Telescope (HST)–based work we find a higher incidence of disks and bulges than expected at
z
> 1.5, revealed by rest-frame optical imaging. We detect 123 clear disks (58 at
z
> 1.5) of which 76 have bulges. No evolution of bulge fraction with redshift is evident: 61% at
z
< 2 (
N
= 110) versus 60% at
z
≥ 2 (
N
= 13). A stellar mass dependence is evident, with bulges visible in 80% of all disk galaxies with mass >10
9.5
M
⊙
(
N
= 41) but only 52% at
M
< 10
9.5
M
⊙
(
N
= 82). We supplement visual morphologies with nonparametric measurements of Gini and asymmetry coefficients in the rest-frame
i
band. Our sources are more asymmetric than local galaxies, with slightly higher Gini values. When compared to high-
z
rest-frame ultraviolet measurements with HST, JWST shows more regular morphological types such as disks, bulges, and spiral arms at
z
> 1.5, with smoother (i.e., lower Gini) and more symmetrical light distributions.
The NMDA receptor is a key player in excitatory transmission and synaptic plasticity in the central nervous system. Its activation requires the binding of both glutamate and a coagonist like
d-serine ...to its glycine site. As
d-serine is released exclusively by astrocytes, we studied the physiological impact of the glial environment on NMDA receptor-dependent activity and plasticity. To this end, we took advantage of the changing astrocytic ensheathing of neurons occurring in the supraoptic nucleus during lactation. We provide direct evidence that in this hypothalamic structure the endogenous coagonist of NMDA receptors is
d-serine and not glycine. Consequently, the degree of astrocytic coverage of neurons governs the level of glycine site occupancy on the NMDA receptor, thereby affecting their availability for activation and thus the activity dependence of long-term synaptic changes. Such a contribution of astrocytes to synaptic metaplasticity fuels the emerging concept that astrocytes are dynamic partners of brain signaling.
Analysis of excitatory synaptic transmission in the rat hypothalamic supraoptic nucleus revealed that glutamate clearance and, as a consequence, glutamate concentration and diffusion in the ...extracellular space, is associated with the degree of astrocytic coverage of its neurons. Reduction in glutamate clearance, whether induced pharmacologically or associated with a relative decrease of glial coverage in the vicinity of synapses, affected transmitter release through modulation of presynaptic metabotropic glutamate receptors. Astrocytic wrapping of neurons, therefore, contributes to the regulation of synaptic efficacy in the central nervous system.
Since the 2010 Deepwater Horizon (DWH) oil spill, the Gulf of Mexico Research Initiative (GOMRI) has studied the oil spill from the perspectives of ocean environment, ecosystems, socioeconomics and ...human health. As GOMRI sunsets in its tenth year after the DWH oil spill, synthesis efforts recently took place to assess the accomplishments of the program. In this paper, we report on DWH modeling as part of GOMRI's Synthesis and Legacy effort. We compile a list of 330 published applications by GOMRI, the Natural Resource Damage Assessment (NRDA), and others studying the DWH oil spill and look at a wide range of subjects, tools, achievements, and integration with field research. We offer highlights and synthesis based on discussions and public webinars held in 2019 and 2020. We synthesize the significant achievements and advancements that have been made in integrating the various disciplines and domains from a modeling perspective. There was a large diversity of tools used, including at least 74 unique modeling systems. Most studies employed circulation models. These hydrodynamic models were often coupled to wave, river, and atmosphere models, as well as representations of high pressure physics and oil chemistry. Several research groups used Lagrangian transport models and statistical inference to track subsurface oil. Some coupled biophysical models were also employed to study oil fate and weathering, larval transport, biological effects, and population dynamics. In a few cases, such biophysical models were linked to marine populations and to humans through socioeconomics effects and ecosystem services. We consider models made for response planning and remediation, damage assessment, and restoration planning. There are relatively few socioeconomic or human health models, although those few examples make good use of biophysical modeling products. Our conclusions offer some insights on how the development of new tools has better prepared us for studying environmental management challenges in the Gulf of Mexico.
Valence-Shell Photoionization of C4H5: The 2‑Butyn-1-yl Radical Hrodmarsson, H. R; Loison, J.-C; Jacovella, U ...
The journal of physical chemistry. A, Molecules, spectroscopy, kinetics, environment, & general theory,
02/2019, Letnik:
123, Številka:
8
Journal Article
Recenzirano
Odprti dostop
We present new high-resolution data on the photoionization of the 2-butyn-1-yl radical (CH3CC–•CH2) formed by H atom abstraction from 2-butyne by F atoms. The spectra were recorded from 7.7 to 11 eV ...by using double-imaging, photoelectron–photoion coincidence spectroscopy, which allows the unambiguous correlation of photoelectron data and the mass of the species. The photoionization spectrum shows significant resonant autoionizing structure converging to excited states of the C4H5 + cation, similar to what is observed in the closely related propargyl radical (HCC–•CH2). The threshold photoelectron spectrum, obtained with a resolution of 17 meV, is also reported. This spectrum is consistent with previous measurements of the first photoionization band but has been extended to higher energy to allow the observation of bands corresponding to excited electronic states of the ion. A refined value of the adiabatic ionization energy is extracted: IE(C4H5) = 7.93 ± 0.01 eV. A determination of the absolute photoionization cross section of the 2-butyn-1-yl radical at 9.7 eV is also reported: σion(C4H5) = 6.1 ± 1.8 Mb.
Interactions between separate synaptic inputs converging on the same target appear to contribute to the fine-tuning of information processing in the central nervous system. Intersynaptic crosstalk is ...made possible by transmitter spillover from the synaptic cleft and its diffusion over a distance to neighboring synapses. This is the case for glutamate, which inhibits γ-aminobutyric acid (GABA)ergic transmission in several brain regions through the activation of presynaptic receptors. Such heterosynaptic modulation depends on factors that influence diffusion in the extracellular space (ECS). Because glial cells represent a physical barrier to diffusion and, in addition, are essential for glutamate uptake, we investigated the physiological contribution of the astrocytic environment of neurons to glutamate-mediated intersynaptic communication in the brain. Here we show that the reduced astrocytic coverage of magnocellular neurons occurring in the supraoptic nucleus of lactating rats facilitates diffusion in the ECS, as revealed by tortuosity and volume fraction measurements. Under these conditions, glutamate spillover, monitored through metabotropic glutamate receptor-mediated depression of GABAergic transmission, is greatly enhanced. Conversely, impeding diffusion with dextran largely prevents crosstalk between glutamatergic and GABAergic afferent inputs. Astrocytes, therefore, by hindering diffusion in the ECS, regulate intersynaptic communication between neighboring synapses and, probably, overall volume transmission in the brain.
Although stem cells succumbing to reproductive death are assumed to be the single relevant targets in radiation tissue damage, recent studies showed intestinal stem cell damage is conditionally ...linked to crypt endothelial apoptosis, defining a two-target model. Here we report that when mouse intestines were protected against microvascular apoptosis, radiation switched as the dose escalated to a previously unrecognized crypt stem cell target, activating ceramide synthase-mediated apoptosis to initiate intestinal damage. Whereas ataxia telangiectasia-mutated (ATM) kinase normally represses ceramide synthase, its derepression in Atm(-/-) mice increased crypt stem cell radiosensitivity 3.7-fold without sensitizing the microvascular response. Discovery of this intestinal radiosensitivity mechanism allowed design of an antisense Atm oligonucleotide treatment which phenocopied the Atm(-/-) mouse, reordering ceramide synthase-mediated stem cell death to become the first-line gastrointestinal response of wild-type littermates. These experiments indicate that tissues operate multiple potential targets activated consecutively according to their inherent radiosensitivities that may be reordered therapeutically to control radiation tissue responses.
Celotno besedilo
Dostopno za:
DOBA, IJS, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
Using historical (1994–2017) satellite‐tracked surface drifter trajectory data, we conduct a probabilistic Lagrangian circulation study which sheds light on the connectivity of Pulley Ridge with ...other locations in the Gulf of Mexico and adjacent areas. The analysis reveals that Pulley Ridge is connected with the North Atlantic, the Caribbean Sea, and most of the Gulf of Mexico. Preferred connecting pathways are identified and arrival times to potential reef sites computed. The study demonstrates the importance of Pulley Ridge as a source for neighboring regions like the Dry Tortugasa, the Florida Keys, Campeche Bank, and the east Florida coast as well as a self‐recruitment area for species with short competence time. The study further suggests that the reefs in the Caribbean Sea, the Dry Tortugas, the western Florida Keys, and the West Florida Shelf can act as sources for Pulley Ridge, indicating the importance of Pulley Ridge as a central refugium for species in the Gulf of Mexico.
Key Points
Historical drifter data reveal oceanographic connectivity pathways within the Gulf of Mexico
The uncovered pathways constitute a first-order constraint for any surface tracer (e.g., spilled oil, toxic algae bloom, buoyant egg masses)
Drifter data suggest the importance of Pulley Ridge mesophotic reef as a refugium for the Gulf of Mexico
On 14 September 2015, a gravitational wave signal from a coalescing black hole binary system was observed by the Advanced LIGO detectors. This paper describes the transient noise backgrounds used to ...determine the significance of the event (designated GW150914) and presents the results of investigations into potential correlated or uncorrelated sources of transient noise in the detectors around the time of the event. The detectors were operating nominally at the time of GW150914. We have ruled out environmental influences and non-Gaussian instrument noise at either LIGO detector as the cause of the observed gravitational wave signal.
PDF
