Abstract
We describe the selection of galaxies targeted in eight low-redshift clusters (APMCC0917, A168, A4038, EDCC442, A3880, A2399, A119 and A85; 0.029 < z < 0.058) as part of the Sydney-AAO ...Multi-Object Integral field spectrograph Galaxy Survey (SAMI-GS). We have conducted a redshift survey of these clusters using the AAOmega multi-object spectrograph on the 3.9-m Anglo-Australian Telescope. The redshift survey is used to determine cluster membership and to characterize the dynamical properties of the clusters. In combination with existing data, the survey resulted in 21 257 reliable redshift measurements and 2899 confirmed cluster member galaxies. Our redshift catalogue has a high spectroscopic completeness (∼94 per cent) for rpetro ≤ 19.4 and cluster-centric distances R < 2R200. We use the confirmed cluster member positions and redshifts to determine cluster velocity dispersion, R200, virial and caustic masses, as well as cluster structure. The clusters have virial masses 14.25 ≤ log(M200/M⊙) ≤ 15.19. The cluster sample exhibits a range of dynamical states, from relatively relaxed-appearing systems, to clusters with strong indications of merger-related substructure. Aperture- and point spread function matched photometry are derived from Sloan Digital Sky Survey and VLT Survey Telescope/ATLAS imaging and used to estimate stellar masses. These estimates, in combination with the redshifts, are used to define the input target catalogue for the cluster portion of the SAMI-GS. The primary SAMI-GS cluster targets have R <R200, velocities |vpec| < 3.5σ200 and stellar masses $9.5 \le {\rm log({\it M}}^*_{{\rm approx}}/$M⊙)≤12. Finally, we give an update on the SAMI-GS progress for the cluster regions.
G4-Quartet·M+ Borate Hydrogels Peters, Gretchen Marie; Skala, Luke P; Plank, Taylor N ...
Journal of the American Chemical Society,
05/2015, Letnik:
137, Številka:
17
Journal Article
Recenzirano
Odprti dostop
The ability to modulate the physical properties of a supramolecular hydrogel may be beneficial for biomaterial and biomedical applications. We find that guanosine (G 1), when combined with 0.5 equiv ...of potassium borate, forms a strong, self-supporting hydrogel with elastic moduli >10 kPa. The countercation in the borate salt (MB(OH)4) significantly alters the physical properties of the hydrogel. The gelator combination of G 1 and KB(OH)4 formed the strongest hydrogel, while the weakest system was obtained with LiB(OH)4, as judged by 1H NMR and rheology. Data from powder XRD, 1H double-quantum solid-state magic-angle spinning (MAS) NMR and small-angle neutron scattering (SANS) were consistent with a structural model that involves formation of borate dimers and G4·K+ quartets by G 1 and KB(OH)4. Stacking of these G4·M+ quartets into G4-nanowires gives a hydrogel. We found that the M+ cation helps stabilize the anionic guanosine-borate (GB) diesters, as well as the G4-quartets. Supplementing the standard gelator mixture of G 1 and 0.5 equiv of KB(OH)4 with additional KCl or KNO3 increased the strength of the hydrogel. We found that thioflavin T fluoresces in the presence of G4·M+ precursor structures. This fluorescence response for thioflavin T was the greatest for the K+ GB system, presumably due to the enhanced interaction of the dye with the more stable G4·K+ quartets. The fluorescence of thioflavin T increased as a function of gelator concentration with an increase that correlated with the system’s gel point, as measured by solution viscosity
A G4·K+ Hydrogel Stabilized by an Anion Peters, Gretchen Marie; Skala, Luke P; Plank, Taylor N ...
Journal of the American Chemical Society,
09/2014, Letnik:
136, Številka:
36
Journal Article
Recenzirano
Odprti dostop
Supramolecular hydrogels derived from natural products have promising applications in diagnostics, drug delivery, and tissue engineering. We studied the formation of a long-lived hydrogel made by ...mixing guanosine (G, 1) with 0.5 equiv of KB(OH)4. This ratio of borate anion to ligand is crucial for gelation as it links two molecules of 1, which facilitates cation-templated assembly of G4·K+ quartets. The guanosine–borate (GB) hydrogel, which was characterized by cryogenic transmission electron microscopy and circular dichroism and 11B magic-angle-spinning NMR spectroscopy, is stable in water that contains physiologically relevant concentrations of K+. Furthermore, non-covalent interactions, such as electrostatics, π-stacking, and hydrogen bonding, enable the incorporation of a cationic dye and nucleosides into the GB hydrogel.
Context. Over the past few years, on several occasions, large, continuous rotations of the electric vector position angle (EVPA) of linearly polarized optical emission from blazars have been ...reported. These events are often coincident with high energy γ-ray flares and they have attracted considerable attention, since they could allow us to probe the magnetic field structure in the γ-ray emitting region of the jet. The flat-spectrum radio quasar 3C 279 is one of the most prominent examples showing this behaviour. Aims. Our goal is to study the observed EVPA rotations and to distinguish between a stochastic and a deterministic origin of the polarization variability. Methods. We have combined multiple data sets of R-band photometry and optical polarimetry measurements of 3C 279, yielding exceptionally well-sampled flux density and polarization curves that cover a period of 2008–2012. Several large EVPA rotations are identified in the data. We introduce a quantitative measure for the EVPA curve smoothness, which is then used to test a set of simple random walk polarization variability models against the data. Results. 3C 279 shows different polarization variation characteristics during an optical low-flux state and a flaring state. The polarization variation during the flaring state, especially the smooth ~360° rotation of the EVPA in mid-2011, is not consistent with the tested stochastic processes. Conclusions. We conclude that, during the two different optical flux states, two different processes govern polarization variation, which is possibly a stochastic process during the low-brightness state and a deterministic process during the flaring activity.
Individuals infected with hepatitis C virus (HCV) are at high risk of developing progressive liver disease, including cirrhosis and hepatocellular carcinoma (HCC). How HCV infection causes liver ...destruction has been of significant interest for many years, and apoptosis has been proposed as one operative mechanism. In this study, we employed a tissue culture-adapted strain of HCV (JFH1
) to test effects of HCV infection on induction of programmed cell death (PCD) in Huh-7.5 cells. We found that HCV infection reduced the proliferation rate and induced caspase-3-mediated apoptosis in the infected cell population. However, in addition to apoptosis, we also observed infected cells undergoing caspase-1-mediated pyroptosis, which was induced by NLRP3 inflammasome activation. By co-culturing HCV-infected Huh-7.5 cells with an HCV-non-permissive cell line, we also demonstrated induction of both apoptosis and pyroptosis in uninfected cells. Bystander apoptosis, but not bystander pyroptosis, required cell-cell contact between infected and bystander cells. In summary, these findings provide new information on mechanisms of cell death in response to HCV infection. The observation that both apoptosis and pyroptosis can be induced in bystander cells extends our understanding of HCV-induced pathogenesis in the liver.
Invasive predators can have dramatic impacts on invaded communities. Extreme declines in macroinvertebrate populations often follow killer shrimp (
Dikerogammarus villosus
) invasions. There are ...concerns over similar impacts on fish through predation of eggs and larvae, but these remain poorly quantified. We compare the predatory impact of invasive and native amphipods (
D. villosus
and
Gammarus pulex
) on fish eggs and larvae (ghost carp
Cyprinus carpio
and brown trout
Salmo trutta
) in the laboratory. We use size-matched amphipods, as well as larger
D. villosus
reflecting natural sizes. We quantify functional responses, and electivity amongst eggs or larvae and alternative food items (invertebrate, plant and decaying leaf).
D. villosus
, especially large individuals, were more likely than
G. pulex
to kill trout larvae. However, the magnitude of predation was low (seldom more than one larva killed over 48 h). Trout eggs were very rarely killed. In contrast, carp eggs and larvae were readily killed and consumed by all amphipod groups. Large
D. villosus
had maximum feeding rates 1.6–2.0 times higher than the smaller amphipods, whose functional responses did not differ. In electivity experiments with carp eggs, large
D. villosus
consumed the most eggs and the most food in total. However, in experiments with larvae, consumption did not differ between amphipod groups. Overall, our data suggest
D. villosus
will have a greater predatory impact on fish populations than
G. pulex
, primarily due to its larger size. Higher invader abundance could amplify this difference. The additional predatory pressure could reduce recruitment into fish populations.
This book was produced by the Zoological Society of London and the University of Cambridge with two aims: to assess seabirds’ vulnerability to climate change in the North-East Atlantic, and to ...identify potential conservation actions that could reduce this vulnerability. 'Seabirds in the North-East Atlantic' collates information from the scientific literature, non-governmental organisations’ reports, conservation practitioner input and online databases into a single volume, and provides a reference manual to assist conservation planning. It is intended to be used by anyone who wishes to identify climate change threats to seabirds; to compare threats between different areas of the North-East Atlantic; to start a quantitative climate change vulnerability assessment for a local population; or to review options for conservation action in response to climate change. This book stems from research published in December 2022, but assessments may be updated based on feedback and newly available information. To check for updates to our assessments, please visit our website at: www.ZSL.org/seabird-guidelines.
•We review the potential ecological impact of the fungal disease ash dieback.•953 ash-associated species were identified including 44 obligate species.•Compared to other tree species the ecological ...functioning of ash is very different.•The potential of alternative tree species to replace ash is assessed.•Management that does not remove infected ash is better for biodiversity.
The death of native trees caused by non-native pathogens is a global problem. An assessment of the potential ecological and conservation impacts of any tree disease should identify: (1) ecosystem functions associated with the tree species; (2) which species use the tree and how; (3) the suitability of alternative tree species to replace the threatened tree species; and (4) potential management options to mitigate or reduce the impact of the disease.
We assess the potential ecological impact of Hymenoscyphus pseudoalbidus (ash dieback) on Fraxinus excelsior in the UK. 953 species were identified as associated with F. excelsior trees: 12 birds, 28 mammals, 58 bryophytes, 68 fungi, 239 invertebrates, 548 lichens. Forty-four ‘obligate’ species were identified: 11 fungi, 29 invertebrates and 4 lichens; and 62 ‘highly associated’ species.
Off-setting the loss of ash with ‘alternative tree species’ may be one ‘solution’ to the biodiversity threat. No single alternative tree species can act as host for all ash-associated species but Quercus robur/petraea can host 69%. In an assessment of ecosystem function, when compared to other European deciduous tree species, F. excelsior interacts with the environment in a unique way, particularly in relation to nutrient cycling.
Exploration of different management scenarios in response to ash dieback indicated that management which did not remove infected F. excelsior trees was the best for ‘obligate’ and ‘highly associated’ species.
The results highlight wide-ranging ecological implications of ash dieback of relevance to other invasive pests and pathogens that are threatening the integrity of other tree species and woodland ecosystems.
SABRE (Sodium iodide with Active Background REjection) is a direct detection dark matter experiment based on arrays of radio-pure NaI(Tl) crystals. The experiment aims at achieving an ultra-low ...background rate and its primary goal is to confirm or refute the results from the DAMA/LIBRA experiment. The SABRE Proof-of-Principle phase was carried out in 2020–2021 at the Gran Sasso National Laboratory (LNGS), in Italy. The next phase consists of two full-scale experiments: SABRE South at the Stawell Underground Physics Laboratory, in Australia, and SABRE North at LNGS. This paper focuses on SABRE South and presents a detailed simulation of the detector, which is used to characterise the background for dark matter searches including DAMA/LIBRA-like modulation. We estimate an overall background of 0.72 cpd/kg/keVee in the energy range 1–6 keVee primarily due to radioactive contamination in the crystals. Given this level of background and considering that the SABRE South has a target mass of 50 kg, we expect to exclude (confirm) DAMA/LIBRA modulation at 4(5)σ within 2.5 years of data taking.
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