The most energetic planetary collisions attain shock pressures that result in abundant melting and vaporization. Accurate predictions of the extent of melting and vaporization require knowledge of ...vast regions of the phase diagrams of the constituent materials. To reach the liquid‐vapor phase boundary of silica, we conducted uniaxial shock‐and‐release experiments, where quartz was shocked to a state sufficient to initiate vaporization upon isentropic decompression (hundreds of GPa). The apparent temperature of the decompressing fluid was measured with a streaked optical pyrometer, and the bulk density was inferred by stagnation onto a standard window. To interpret the observed post‐shock temperatures, we developed a model for the apparent temperature of a material isentropically decompressing through the liquid‐vapor coexistence region. Using published thermodynamic data, we revised the liquid‐vapor boundary for silica and calculated the entropy on the quartz Hugoniot. The silica post‐shock temperature measurements, up to entropies beyond the critical point, are in excellent qualitative agreement with the predictions from the decompressing two‐phase mixture model. Shock‐and‐release experiments provide an accurate measurement of the temperature on the phase boundary for entropies below the critical point, with increasing uncertainties near and above the critical point entropy. Our new criteria for shock‐induced vaporization of quartz are much lower than previous estimates, primarily because of the revised entropy on the Hugoniot. As the thermodynamics of other silicates are expected to be similar to quartz, vaporization is a significant process during high‐velocity planetary collisions.
Key Points
We measured the temperature on the liquid‐vapor curve of silica
We calculated the entropy on the quartz Hugoniot
We provide new criteria for shock‐induced vaporization of silica
Filamentary star formation in NGC 1275 Canning, R. E. A; Ryon, J. E; Gallagher, J. S ...
Monthly Notices of the Royal Astronomical Society,
10/2014, Letnik:
444, Številka:
1
Journal Article
Recenzirano
Odprti dostop
We examine the star formation in the outer halo of NGC 1275, the central galaxy in the Perseus cluster (Abell 426), using far-ultraviolet and optical images obtained with the Hubble Space Telescope. ...We have identified a population of very young, compact star clusters with typical ages of a few Myr. The star clusters are organized on multiple kiloparsec scales. Many of these star clusters are associated with ‘streaks’ of young stars, the combination of which has a cometary appearance. We perform photometry on the star clusters and diffuse stellar streaks, and fit their spectral energy distributions to obtain ages and masses. These young stellar populations appear to be normal in terms of their masses, luminosities and cluster formation efficiency; <10 per cent of the young stellar mass is located in star clusters. Our data suggest star formation is associated with the evolution of some of the giant gas filaments in NGC 1275 that become gravitationally unstable on reaching and possibly stalling in the outer galaxy. The stellar streaks then could represent stars moving on ballistic orbits in the potential well of the galaxy cluster. We propose a model where star-forming filaments, switched on ∼50 Myr ago and are currently feeding the growth of the NGC 1275 stellar halo at a rate of ≈−2 to 3 M⊙ yr−1. This type of process may also build stellar haloes and form isolated star clusters in the outskirts of youthful galaxies.
We report on a precision measurement of the parity-violating asymmetry in fixed target electron-electron (Møller) scattering: A(PV) = -131 +/- 14(stat) +/- 10(syst) x 10(-9), leading to the ...determination of the weak mixing angle sin2(thetaW(eff) = 0.2397 +/- 0.0010(stat) +/- 0.0008(syst), evaluated at Q2 = 0.026 GeV2. Combining this result with the measurements of sin2(thetaW(eff) at the Z0 pole, the running of the weak mixing angle is observed with over 6sigma significance. The measurement sets constraints on new physics effects at the TeV scale.
To report on the multidisciplinary approach, focusing specifically on the role of the interventional radiologist (IR), used to support the Biomarker-integrated Approaches of Targeted Therapy for Lung ...Cancer Elimination (BATTLE) and BATTLE-2 trials.
Patients who underwent percutaneous image-guided biopsy for the BATTLE and BATTLE-2 trials were reviewed. A radiology-based, three-point, lesion-scoring system was developed and used by two IRs. Lesions were given a score of 3 (most likely to yield sufficient material for biomarker analysis) if they met the following criteria: size >2 cm, solid mass, demonstrated imaging evidence of viability, and were technically easy to sample. Lesions not meeting all four criteria were scored 2 with the missing criteria noted as negative factors. Lesions considered to have risks that outweighed potential benefits receive a score of 1 and were not biopsied. Univariate and multivariate analyses were performed to evaluate the score's ability to predict successful yield for biomarker adequacy.
A total of 555 biopsies were performed. The overall yield for analysis of the required biomarkers was 86.1% (478/555), and 84% (268/319) and 88.9% (210/236) for BATTLE and BATTLE-2, respectively (p=0.09). Lesions receiving a score of 3 were adequate for biomarker analysis in 89% of cases. Lesions receiving a score of 2 with more than two negative factors were adequate for molecular analysis in 69.2% (IR1, p=0.03) and 74% (IR2, p=0.04) of cases. The two IRs scored 78.4% of the lesions the same indicating moderate agreement (kappa=0.55; 95% confidence interval CI: 0.48, 0.61).
IRs add value to clinical trial teams by optimising lesions selected for biopsy and biomarker analysis.
•Lesion selection for biopsy impacts adequacy for biomarker analysis.•IRs actively participate in medical decision making for clinical trials.•A team-science approach facilitates consistent yields for biomarker analysis.
Finding a sample of the most massive clusters with redshifts z > 0.6 can provide an interesting consistency check of the Λ cold dark matter (ΛCDM) model. Here, we present results from our search for ...clusters with 0.6 ≲ z ≲ 1.0 where the initial candidates were selected by cross-correlating the ROSAT All Sky Survey (RASS) faint and bright source catalogues with red galaxies from the Sloan Digital Sky Survey DR8. Our survey thus covers ≈ 10 000 deg2, much larger than previous studies of this kind. Deeper follow-up observations in three bands using the William Herschel Telescope and the Large Binocular Telescope were performed to confirm the candidates, resulting in a sample of 44 clusters for which we present richnesses and red sequence redshifts, as well as spectroscopic redshifts for a subset. At least two of the clusters in our sample are comparable in richness to RCS2-J232727.7−020437, one of the richest systems discovered to date. We also obtained new observations with the Combined Array for Research in Millimeter Astronomy for a subsample of 21 clusters. For 11 of those we detect the Sunyaev–Zel'dovich effect signature. The Sunyaev–Zel'dovich signal allows us to estimate M
200 and check for tension with the cosmological standard model. We find no tension between our cluster masses and the ΛCDM model.
Shelf sediments play a vital role in global biogeochemical cycling and are particularly important areas of oxygen consumption and carbon mineralisation. Total benthic oxygen uptake, the sum of ...diffusive and faunal mediated uptake, is a robust proxy to quantify carbon mineralisation. However, oxygen uptake rates are dynamic, due to the diagenetic processes within the sediment, and can be spatially and temporally variable. Four benthic sites in the Celtic Sea, encompassing gradients of cohesive to permeable sediments, were sampled over four cruises to capture seasonal and spatial changes in oxygen dynamics. Total oxygen uptake (TOU) rates were measured through a suite of incubation experiments and oxygen microelectrode profiles were taken across all four benthic sites to provide the oxygen penetration depth and diffusive oxygen uptake (DOU) rates. The difference between TOU and DOU allowed for quantification of the fauna mediated oxygen uptake and diffusive uptake. High resolution measurements showed clear seasonal and spatial trends, with higher oxygen uptake rates measured in cohesive sediments compared to the permeable sediment. The significant differences in oxygen dynamics between the sediment types were consistent between seasons, with increasing oxygen consumption during and after the phytoplankton bloom. Carbon mineralisation in shelf sediments is strongly influenced by sediment type and seasonality.
The interaction of relativistically intense lasers with opaque targets represents a highly non-linear, multi-dimensional parameter space. This limits the utility of sequential 1D scanning of ...experimental parameters for the optimization of secondary radiation, although to-date this has been the accepted methodology due to low data acquisition rates. High repetition-rate (HRR) lasers augmented by machine learning present a valuable opportunity for efficient source optimization. Here, an automated, HRR-compatible system produced high-fidelity parameter scans, revealing the influence of laser intensity on target pre-heating and proton generation. A closed-loop Bayesian optimization of maximum proton energy, through control of the laser wavefront and target position, produced proton beams with equivalent maximum energy to manually optimized laser pulses but using only 60% of the laser energy. This demonstration of automated optimization of laser-driven proton beams is a crucial step towards deeper physical insight and the construction of future radiation sources.
•Haemoplasma infection was identified in 17.9% of Nigerian dogs.•The species-specific qPCR assay found Mycoplasma haemocanis infection in 7.3% dogs.•‘Candidatus Mycoplasma haematoparvum’ infection ...was found in only one dog (0.4%).•No association between haemoplasma positive status and risk factors was found.•No evidence of genetic variability with other M. haemocanis sequences was found.
Mycoplasma haemocanis (Mhc) and ‘Candidatus Mycoplasma haematoparvum’ (CMhp) are canine haemoplasma species that can induce anaemia in immunocompromised and/or splenectomised dogs. This study aimed to determine the prevalence and phylogeny of canine haemoplasma species in dogs from Nigeria and describe any risk factors for infection. Canine haemoplasma species-specific and generic haemoplasma qPCR assays were used. The species-specific qPCR assays found Mhc infection in 18 of 245 dogs (7.3%), and CMhp infection in only one dog (0.4%). The generic haemoplasma qPCR assays were positive in 44 of 245 (17.9%) dogs. Twenty-five dogs had discordant qPCR results in that they were generic haemoplasma qPCR positive but species-specific qPCR negative. Further evaluation of these dogs by 16S rDNA sequencing gave limited results but 5 were confirmed to be infected with non-haemoplasma species: 2 Anaplasma phagocytophilum, 1 Anaplasma ovis, 1 Serratia marcescens and 1 Aerococcus spp. The 16S rRNA gene sequences from Mhc species showed>99.8% identity with each other and>99.6% identity with GenBank sequences, and resided in a single clade with other global Mhc and Mycoplasma haemofelis sequences, indicating low 16S rRNA genetic variability amongst this canine haemoplasma species.
Vacuoles perform multiple functions in plants, and VCL1 (VACUOLESS1) is essential for biogenesis with loss of expression in the vcl1 mutant leading to lethality. Vacuole biogenesis plays a prominent ...role in gametophytes, yet is poorly understood. Given the importance of VCL1, we asked if it contributes to vacuole biogenesis during pollen germination. To address this question, it was essential to first understand the dynamics of vacuoles. A tonoplast marker, δ-TIP::GFP, under a pollen-specific promoter permitted the examination of vacuole morphology in germinating pollen of Arabidopsis. Our results demonstrate that germination involves a complex, yet definable, progression of vacuole biogenesis. Pollen vacuoles are extremely dynamic with remarkable features such as elongated (tubular) vacuoles and highly mobile cytoplasmic invaginations. Surprisingly, vcl1 did not adversely impact vacuole morphology in pollen germinated in vitro. To focus further on VCL1 in pollen, reciprocal backcrosses demonstrated reduced transmission of vcl1 through male gametophytes, indicating that vcl1 was expressive after germination. Interestingly, vcl1 affected the fertility of female gametophytes that undergo similarly complex vacuole biogenesis. Our results indicate that vcl1 is lethal in the sporophyte but is not fully expressive in the gametophytes. They also point to the complexity of pollen vacuoles and suggest that the mechanism of vacuole biogenesis in pollen may differ from that in other plant tissues.
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