Purpose
The aim of the present study was to evaluate the impact of the coronavirus (COVID-19) pandemic on joint arthroplasty service in Europe by conducting an online survey of arthroplasty surgeons.
...Methods
The survey was conducted in the European Hip Society (EHS) and the European Knee Associates (EKA). The survey consisted of 20 questions (single, multiple choice, ranked). Four topics were addressed: (1) origin and surgical experience of the participant (four questions); (2) potential disruption of arthroplasty surgeries (12 questions); (3) influence of the COVID-19 pandemic on the particular arthroplasty surgeon (four questions); (4) a matrix provided 14 different arthroplasty surgeries and the participant was asked to state whether dedicated surgery was stopped, delayed or cancelled.
Results
Two-hundred and seventy-two surgeons (217 EHS, 55 EKA) from 40 different countries participated. Of the respondents, 25.7% stated that all surgeries were cancelled in their departments, while 68.4% responded that elective inpatient procedures were no longer being performed. With regard to the specific surgical procedures, nearly all primary TJA were cancelled (92.6%) as well as aseptic revisions (94.7%). In most hospitals, periprosthetic fractures (87.2%), hip arthroplasty for femoral neck fractures and septic revisions for acute infections (75.8%) were still being performed.
Conclusion
During the current 2020 COVID-19 pandemic, we are experiencing a near-total shutdown of TJA. A massive cutback was observed for primary TJA and revision TJA, even in massively failed TJA with collapse, dislocation, component failure or imminent dislocation. Only life-threatening pathologies like periprosthetic fractures and acute septic TJA are currently undergoing surgical treatment.
Level of evidence
V.
The H/C mass ratio of the Earth's exosphere, which consists of the fluid envelopes plus the crust, is 1.95
±
0.15. In contrast, the H/C ratios of undegassed oceanic basalts are significantly lower, ...ranging from 1.2 down to 0.05. Reconstruction of source H/C ratios by accounting for H/C fractionation during partial melting and addition of carbon-enriched low-degree partial melts suggests that the source regions of MORB have H/C ratios in the range of 0.75
±
0.25 and those of OIB have ratios in the interval 0.5
±
0.3. Combining these estimates with plausible limits on the relative proportions of the OIB and MORB sources indicates that the total H inventory of the mantle is equivalent to between 0.2 and 1.6 times the H in the exosphere, assuming that there are no significant hidden reservoirs unsampled by oceanic basalts. Combining the H contents and H/C ratios of the mantle and the exosphere suggests that the H/C ratio of the bulk silicate Earth, (H/C)
BSE, is 0.99
±
0.42, significantly greater than the H/C ratio of chondrites, which have H/C ratios no greater than 0.55. The superchondritic (H/C)
BSE ratio likely results from preferential sequestration of C in the core, though it may also partly reflect a cometary origin for some portion of the BSE volatile inventory. The high (H/C)
BSE ratio, combined with a D/H ratio similar to chondrites, argues strongly that the BSE volatile inventory is not chiefly derived from a late veneer. The large difference in H/C ratio between the exosphere and the mantle could reflect early Earth processes such as preferential retention of C in a crystallizing magma ocean in reduced phases such as diamond, or selective loss of a massive CO
2-rich atmosphere. Alternatively, it may have arisen by enhanced subduction of carbon relative to hydrogen. If the latter is the case, carbon in the mantle is likely dominantly recycled.
The estimate of stellar metallicities (
Z
*
) of high-
z
galaxies are of paramount importance in order to understand the complexity of dust effects and the reciprocal interrelations among stellar ...mass, dust attenuation, stellar age, and metallicity. Benefiting from uniquely deep far-UV spectra of > 500 star-forming galaxies at redshifts 2 <
z
< 5 extracted from the VANDELS survey and stacked in bins of stellar mass (
M
*
) and UV continuum slope (
β
), we estimate their stellar metallicities
Z
*
from stellar photospheric absorption features at 1501 and 1719 Å, which are calibrated with Starburst99 models and are largely unaffected by stellar age, dust, IMF, nebular continuum, or interstellar absorption. Comparing them to photometric-based spectral slopes in the 1250–1750 Å range, we find that the stellar metallicity increases by ∼0.5 dex from
β
∼ −2 to
β
∼ −1 (1 ≲
A
1600
≲ 3.2), and a dependence with
β
holds at fixed UV absolute luminosity
M
UV
and stellar mass up to ∼10
9.65
M
⊙
. As a result, metallicity is a fundamental ingredient for properly rescaling dust corrections based on
M
UV
and
M
*
. Using the same absorption features, we analyzed the mass-metallicity relation (MZR), and find it to be consistent with the previous VANDELS estimation based on a global fit of the FUV spectra. Similarly, we do not find a significant evolution between
z
∼ 2 and
z
∼ 3.5. Finally, the slopes of our MZR and
Z
*
−
β
relation are in agreement with the predictions of well-studied semi-analytic models (SAM) of galaxy formation, while some tensions remain concerning the absolute metallicity normalization. The relation between the UV slope and stellar metallicity is fundamental to the exploitation of large volume surveys with next-generation telescopes and for the physical characterization of galaxies in the first billion years of our Universe.
Many ocean island basalts (OIB) that have isotopic ratios indicative of recycled crustal components in their source are silica-undersaturated and unlike silicic liquids produced from partial melting ...of recycled mid-ocean ridge basalt (MORB). However, experiments on a silica-deficient garnet pyroxenite, MIX1G, at 2.0-2.5 GPa show that some pyroxenite partial melts are strongly silica- undersaturated M.M. Hirschmann et al. Geology 31 (2003) 481-484. These low- pressure liquids are plausible parents of alkalic OIB, except that they are too aluminous. We present new partial melting experiments on MIX1G between 3.0 and 7.5 GPa. Partial melts at 5.0 GPa have low SiO sub(2) (<48 wt%), low Al sub(2)O sub(3) (<12 wt%) and high CaO (>12 wt%) at moderate MgO (12-16 wt%), and are more similar to primitive OIB compositions than lower-pressure liquids of MIX1G or experimental partial melts of anhydrous or carbonated peridotite. Solidus temperatures at 5.0 and 7.5 GPa are 1625 and 1825 degree C, respectively, which are less than 50 degree C cooler than the anhydrous peridotite solidus. The liquidus temperature at 5.0 GPa is 1725 degree C, indicating a narrow melting interval (~100 degree C). These melting relations suggest that OIB magmas can be produced by partial melting of a silica-deficient pyroxenite similar to MIX1G if its melting residue contains significant garnet and lacks olivine. Such silica-deficient pyroxenites could be produced by interaction between recycled subducted oceanic crust and mantle peridotite or could be remnants of ancient oceanic lower crust or delaminated lower continental crust. If such compositions are present in plumes ascending with potential temperatures of 1550 degree C, they will begin to melt at about 5.0 GPa and produce appropriate partial melts. However, such hot plumes may also generate partial melts of peridotite, which could dilute the pyroxenite-derived partial melts.
•The origin of the high and non-chondritic C/N ratio of the BSE is not understood.•We determined N and C partitioning between metal and silicate melt at 1–3 GPa.•Core-formation decrease the C/N ...ratio, only a C-rich late veneer increase it.
One of the most remarkable observations regarding volatile elements in the solar system is the depletion of N in the bulk silicate Earth (BSE) relative to chondrites, leading to a particularly high and non-chondritic C:N ratio. The N depletion may reflect large-scale differentiation events such as sequestration in Earth's core or massive blow off of Earth's early atmosphere, or alternatively the characteristics of a late-added volatile-rich veneer. As the behavior of N during early planetary differentiation processes is poorly constrained, we determined together the partitioning of N and C between Fe–N–C metal alloy and two different silicate melts (a terrestrial and a martian basalt). Conditions spanned a range of fO2 from ΔIW−0.4 to ΔIW−3.5 at 1.2 to 3 GPa, and 1400 °C or 1600 °C, where ΔIW is the logarithmic difference between experimental fO2 and that imposed by the coexistence of crystalline Fe and wüstite.
N partitioning (DNmetal/silicate) depends chiefly on fO2, decreasing from 24±3 to 0.3±0.1 with decreasing fO2. DNmetal/silicate also decreases with increasing temperature and pressure at similar fO2, though the effect is subordinate. In contrast, C partition coefficients (DCmetal/silicate) show no evidence of a pressure dependence but diminish with temperature. At 1400 °C, DCmetal/silicate partition coefficients increase linearly with decreasing fO2 from 300±30 to 670±50. At 1600 °C, however, they increase from ΔIW−0.7 to ΔIW−2 (87±3 to 240±50) and decrease from ΔIW−2 to ΔIW−3.3 (99±6). Enhanced C in melts at high temperatures under reduced conditions may reflect stabilization of C–H species (most likely CH4). No significant compositional dependence for either N or C partitioning is evident, perhaps owing to the comparatively similar basalts investigated.
At modestly reduced conditions (ΔIW−0.4 to −2.2), N is more compatible in core-forming metal than in molten silicate (1≤DNmetal/silicate≤24), while at more reduced conditions (ΔIW−2.2 to ΔIW−3.5), N becomes more compatible in the magma ocean than in the metal phase. In contrast, C is highly siderophile at all conditions investigated (100≤DCmetal/silicate≤700). Therefore, sequestration of volatiles in the core affects C more than N, and lowers the C:N ratio of the BSE. Consequently, the N depletion and the high C:N ratio of the BSE cannot be explained by core formation. Mass balance modeling suggests that core formation combined with atmosphere blow-off also cannot produce a non-metallic Earth with a C:N ratio similar to the BSE, but that the accretion of a C-rich late veneer can account for the observed high BSE C:N ratio.
We investigate how environment affects satellite galaxies using their location within the projected phase space of their host haloes from the Wang et al.'s group catalogue. Using the Yonsei Zoom-in ...Cluster Simulations, we derive zones of constant mean infall time \overline{T}_inf in projected phase space, and catalogue in which zone each observed galaxy falls. Within each zone, we compute the mean observed galaxy properties including specific star formation rate, luminosity-weighted age, stellar metallicity, and α/Fe abundance ratio. By comparing galaxies in different zones, we inspect how shifting the mean infall time from recent infallers (\overline{T}_inf < 3 Gyr) to ancient infallers (\overline{T}_{inf}> 5 Gyr) impacts galaxy properties at fixed stellar and halo mass. Ancient infallers are more quenched, and the impact of environmental quenching is visible down to low host masses (≤group masses). Meanwhile, the quenching of recent infallers is weakly dependent on host mass, indicating they have yet to respond strongly to their current environment. α/Fe and especially metallicity are less dependent on host mass, but show a dependence on \overline{T}_{inf}. We discuss these results in the context of longer exposure times for ancient infallers to environmental effects, which grow more efficient in hosts with a deeper potential well and a denser intracluster medium. We also compare our satellites with a control field sample, and find that even the most recent infallers (\overline{T}_{inf} < 2 Gyr) are more quenched than field galaxies, in particular for cluster mass hosts. This supports the role of pre-processing and/or faster quenching in satellites.
We present a census of the active black hole population at 1 < z < 2, by constructing the bivariate distribution function of black hole mass and Eddington ratio, employing a maximum likelihood ...fitting technique. The study of the active black hole mass function (BHMF) and the Eddington ratio distribution function (ERDF) allows us to clearly disentangle the active galactic nuclei (AGN) downsizing phenomenon, present in the AGN luminosity function, into its physical processes of black hole mass downsizing and accretion rate evolution. We are utilizing type-1 AGN samples from three optical surveys (VVDS, zCOSMOS and SDSS), that cover a wide range of 3 dex in luminosity over our redshift interval of interest. We investigate the cosmic evolution of the AGN population as a function of AGN luminosity, black hole mass and accretion rate. Compared to z = 0, we find a distinct change in the shape of the BHMF and the ERDF, consistent with downsizing in black hole mass. The active fraction or duty cycle of type-1 AGN at z ~ 1.5 is almost flat as a function of black hole mass, while it shows a strong decrease with increasing mass at z = 0. We are witnessing a phase of intense black hole growth, which is largely driven by the onset of AGN activity in massive SMBHs (supermassive black holes) towards z = 2. We finally compare our results to numerical simulations and semi-empirical models and while we find reasonable agreement over certain parameter ranges, we highlight the need to refine these models in order to match our observations.
We present experiments from 0.7 to 3GPa that quantify solubility of H2 in silicate melts under controlled hydrogen fugacities (fH2). Two experimental series, one on synthetic basalt+COH and other ...with a synthetic andesite+OH, were conducted using a double capsule technique to impose a range of fH2, on the samples. Quenched glasses were analyzed by FTIR and SIMS. Both series follow simple solubility laws in which molecular H2 concentrations are proportional to fH2 and with a partial molar volume of molecular H2 of 11cm3/mole. Solubilities in andesitic melt are systematically greater than in basaltic liquid in a relationship consistent with control by the ionic porosity (IP) of the melts. Extrapolation based on IP allows estimation of the solubility of H2 in peridotitic melts applicable to magma oceans. The H2/(H2+H2O) ratio in silicate melts (where H2O includes molecular H2O and OH−) increases as conditions become more reduced, with increasing pressure, and with increasing total H. Under some conditions prevailing in the early Earth and terrestrial planets as well as in the deep Earth today, H2 can be a significant fraction of the dissolved H and at high pressure it may exceed “water” (H2O and OH−). Therefore, magmatic H2 may influence the initial distribution of volatiles and the redox evolution of terrestrial planets, as well as the ongoing formation and fate of hydrous melts in the deep Earth today. Hydrous species in melts in equilibrium with Fe-rich alloy at high pressure, for example during core formation from a magma ocean, could be chiefly H2, rather than H2O. Hence, delivery of H2 to the core by removal of Fe hydride need not be coupled to oxidation of the residual mantle. Although lunar basalts are much reduced, the fraction of H dissolved as molecular H2 is small owing to low total H concentrations. Extrapolation to conditions of potential hydrous partial melting in the deep Earth suggests that the chief magmatic volatile may be H2 rather than H2O. The very small partial specific density of magmatic H2 (0.18g/cm3 at low pressure) may provide significant positive buoyancy to deep partial melts.
► Molecular H2 solubility in magmas quantified and is proportional to H2 fugacity. ► H2 solubility increases with pressure and concentration, decreases with O2 fugacity. ► Magmatic H2 possibly important in early Earth, facilitating transport of H to core. ► Magmatic H2 limited in lunar basalts owing to low H concentrations.
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