► Animals tolerated a pCO2 up to 145Pa, their health status deteriorated at 284Pa. ► Exposure to elevated pCO2 reduced somatic and reproductive growth. ► N excretion increased, feeding rate decreased ...leading to a shift in energy budgets. ► First report of extracellular pH compensation by HCO3-accumulation in echinoderms. ► At high pCO2 71% of animals ceased feeding and revealed a strong metabolic acidosis.
Anthropogenic CO2 emission will lead to an increase in seawater pCO2 of up to 80–100Pa (800–1000μatm) within this century and to an acidification of the oceans. Green sea urchins (Strongylocentrotus droebachiensis) occurring in Kattegat experience seasonal hypercapnic and hypoxic conditions already today. Thus, anthropogenic CO2 emissions will add up to existing values and will lead to even higher pCO2 values >200Pa (>2000μatm). To estimate the green sea urchins’ potential to acclimate to acidified seawater, we calculated an energy budget and determined the extracellular acid base status of adult S. droebachiensis exposed to moderately (102–145Pa, 1007–1431μatm) and highly (284–385Pa, 2800–3800μatm) elevated seawater pCO2 for 10 and 45 days.
A 45-day exposure to elevated pCO2 resulted in a shift in energy budgets, leading to reduced somatic and reproductive growth. Metabolic rates were not significantly affected, but ammonium excretion increased in response to elevated pCO2. This led to decreased O:N ratios. These findings suggest that protein metabolism is possibly enhanced under elevated pCO2 in order to support ion homeostasis by increasing net acid extrusion. The perivisceral coelomic fluid acid–base status revealed that S. droebachiensis is able to fully (intermediate pCO2) or partially (high pCO2) compensate extracellular pH (pHe) changes by accumulation of bicarbonate (maximum increases 2.5mM), albeit at a slower rate than typically observed in other taxa (10-day duration for full pHe compensation). At intermediate pCO2, sea urchins were able to maintain fully compensated pHe for 45 days. Sea urchins from the higher pCO2 treatment could be divided into two groups following medium-term acclimation: one group of experimental animals (29%) contained remnants of food in their digestive system and maintained partially compensated pHe (+2.3mM HCO3−), while the other group (71%) exhibited an empty digestive system and a severe metabolic acidosis (−0.5 pH units, −2.4mM HCO3−). There was no difference in mortality between the three pCO2 treatments.
The results of this study suggest that S. droebachiensis occurring in the Kattegat might be pre-adapted to hypercapnia due to natural variability in pCO2 in its habitat. We show for the first time that some echinoderm species can actively compensate extracellular pH. Seawater pCO2 values of >200Pa, which will occur in the Kattegat within this century during seasonal hypoxic events, can possibly only be endured for a short time period of a few weeks. Increases in anthropogenic CO2 emissions and leakages from potential sub-seabed CO2 storage (CCS) sites thus impose a threat to the ecologically and economically important species S. droebachiensis.
•Ab initio calculation of the surface relaxation of metals.•Surface energy and surface stress of transition metals.•Surface energy and surface stress of simple metals and light actinides.
We ...investigated surface properties of metals by performing first-principles calculations. A systematic database was established for the surface relaxation, surface energy (γ), and surface stress (τ) for metallic elements in the periodic table. The surfaces were modeled by multi-layered slab structures along the direction of low-index surfaces. The surface energy γ of simple metals decreases as the atomic number increases in a given group, while the surface stress τ has its minimum in the middle. The transition metal series show parabolic trends for both γ and τ with a dip in the middle. The dip occurs at half-band filling due to a long-range Friedel oscillation of the surface charge density, which induces a strong stability to the Peierls-like transition. In addition, due to magnetic effects, the dips in the 3d metal series are shallower and deeper for γ and τ, respectively, than those of the 4d and 5d metals. The surface stress of the transition metals is typically positive, only Cr and Mn have a negative τ for the (100) surface facet, indicating that they are under compression. The light actinides have an increasing γ trend according to the atomic number. The present work provides a useful and consistent database for the theoretical modelling of surface phenomena.
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The extension of the cosmic-ray spectrum beyond 1 petaelectronvolt (PeV; 10
electronvolts) indicates the existence of the so-called PeVatrons-cosmic-ray factories that accelerate particles to PeV ...energies. We need to locate and identify such objects to find the origin of Galactic cosmic rays
. The principal signature of both electron and proton PeVatrons is ultrahigh-energy (exceeding 100 TeV) γ radiation. Evidence of the presence of a proton PeVatron has been found in the Galactic Centre, according to the detection of a hard-spectrum radiation extending to 0.04 PeV (ref.
). Although γ-rays with energies slightly higher than 0.1 PeV have been reported from a few objects in the Galactic plane
, unbiased identification and in-depth exploration of PeVatrons requires detection of γ-rays with energies well above 0.1 PeV. Here we report the detection of more than 530 photons at energies above 100 teraelectronvolts and up to 1.4 PeV from 12 ultrahigh-energy γ-ray sources with a statistical significance greater than seven standard deviations. Despite having several potential counterparts in their proximity, including pulsar wind nebulae, supernova remnants and star-forming regions, the PeVatrons responsible for the ultrahigh-energy γ-rays have not yet been firmly localized and identified (except for the Crab Nebula), leaving open the origin of these extreme accelerators.
Fast radio bursts (FRBs) are millisecond-duration radio transients of unknown physical origin observed at extragalactic distances
. It has long been speculated that magnetars are the engine powering ...repeating bursts from FRB sources
, but no convincing evidence has been collected so far
. Recently, the Galactic magnetar SRG 1935+2154 entered an active phase by emitting intense soft γ-ray bursts
. One FRB-like event with two peaks (FRB 200428) and a luminosity slightly lower than the faintest extragalactic FRBs was detected from the source, in association with a soft γ-ray/hard-X-ray flare
. Here we report an eight-hour targeted radio observational campaign comprising four sessions and assisted by multi-wavelength (optical and hard-X-ray) data. During the third session, 29 soft-γ-ray repeater (SGR) bursts were detected in γ-ray energies. Throughout the observing period, we detected no single dispersed pulsed emission coincident with the arrivals of SGR bursts, but unfortunately we were not observing when the FRB was detected. The non-detection places a fluence upper limit that is eight orders of magnitude lower than the fluence of FRB 200428. Our results suggest that FRB-SGR burst associations are rare. FRBs may be highly relativistic and geometrically beamed, or FRB-like events associated with SGR bursts may have narrow spectra and characteristic frequencies outside the observed band. It is also possible that the physical conditions required to achieve coherent radiation in SGR bursts are difficult to satisfy, and that only under extreme conditions could an FRB be associated with an SGR burst.
Equilibrium condensation of solar gas is often invoked to explain the abundance of refractory elements in planets and meteorites. This is partly motivated, by the observation that the depletions in ...both the least and most refractory rare earth elements (REEs) in meteoritic group II calcium-aluminum-rich inclusions (CAIs) can be reproduced by thermodynamic models of solar nebula condensation. We measured the isotopic compositions of Ce, Nd, Sm, Eu, Gd, Dy, Er, and Yb in eight CAIs to test this scenario. Contrary to expectation for equilibrium condensation, we find light isotope enrichment for the most refractory REEs and more subdued isotopic variations for the least refractory REEs. This suggests that group II CAIs formed by a two-stage process involving fast evaporation of preexisting materials, followed by near-equilibrium recondensation. The calculated time scales are consistent with heating in events akin to FU Orionis- or EX Lupi-type outbursts of eruptive pre-main-sequence stars.
In this study, the effect of solution heat treatments on the microstructure and mechanical properties of Inconel 625 superalloy fabricated by laser solid forming was investigated. The microstructure ...of deposit was mainly composed of columnar grains, which didn't change until the solution temperature reached 1200 °C after solution heat treatment. Due to the large size Laves phase which can pin grain boundary and obstruct grain boundary migration, the recrystallization fully occurred when the solution temperature exceeded 1200 °C. With the increment of the solution temperature, the average diffusion coefficient of solute elements and the dissolution velocity increased obviously. Besides, the volume fraction and size of Laves phase decreased, and the dislocation density decreased apparently. As a result, the microhardness and yield strength decreased with the increment of the solution temperature, but the tensile strength didn't change much after solution heat treatment, and the elongation increased significantly with the solution temperature improving. The room-temperature tensile properties in different states of Inconel 625 fabricated by laser solid forming were higher than those of Inconel 625 fabricated by casting.
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•The microstructural evolution of solidification during the LSF process is explained.•The formation and dissolution of Laves phase are discussed in detail.•The effect of solution temperature on mechanical properties is investigated.•The contribution of different strengthening mechanisms is discussed in detail.
Data from clinical trials of human papillomavirus (HPV) vaccines showed that women naïve (negative for both type-specific antibodies and DNA) to vaccine types would derive benefit from vaccination; ...therefore, an understanding of the proportion of naïve women in different age groups is important for developing HPV vaccination strategies.
From November 2012 to April 2013, a total of 7372 healthy women aged 18–45 years were recruited in five provinces in China. Cervical specimens and serum samples were collected for each woman at entry. Cervical specimens were first tested by the HPV DNA enzyme immunoassay method; if positive, the specimens were then tested by reverse hybridization line probe assay and HPV-16 and HPV-18 specific polymerase chain reactions. Neutralizing antibodies against HPV-16 or HPV-18 were tested with a pseudovirion-based neutralization assay.
The overall prevalence of high-risk HPV DNA was 14.8% (1088/7367, 95% CI 14.0–15.6), and the seroprevalence of neutralizing antibodies against HPV-16 and HPV-18 was 12.6% (925/7367) and 4.9% (364/7367), respectively. In younger women (18–26 years) and middle-aged women (27–45 years), 83.8% (3116/3719) and 81.4% (2968/3648) were naïve to both HPV-16 and HPV-18 (both neutralizing antibodies and DNA were negative), respectively. In addition, 98.5% (3664/3719) and 98.0% (3575/3648) of the younger or middle-aged women were naïve to at least one HPV type (HPV-16 or HPV-18).
This study revealed that the majority of Chinese women aged 18–26 years and 27–45 years were naïve to both HPV-16 and HPV-18 and would thus derive full benefit from bivalent HPV vaccination.
Asian Citrus Psyllid (ACP), Diaphorina citri, is a key vector transmitting the causative agent of Huanglongbing (HLB) disease. Population growth of ACP is evident after feeding on plant flush shoots, ...as they only oviposit here. However, the underlying mechanism as to why flush shoots govern oviposition is unclear. This study compares the fecundity and ovarian morphology of ACP between young flush and mature leaves. Furthermore, the transcriptome of mated females infesting Murraya paniculata was analysed. Finally, the gene of the key Target of Rapamycin (TOR) signalling pathway was silenced by RNAi. Results indicated that flush shoot feeding activated the development of the psyllids ovary and therefore induced oviposition. A total of 126 and 2794 differentially expressed genes were detected at 1 and 5 days, respectively, after pest infestation of flush shoots compared to mature leaves. Many genes are involved in protein metabolism, Mitogen‐Activated Protein Kinase (MAPK) signalling pathway, hormone synthesis, and TOR signalling pathway: all thought to activate reproduction. Silencing of the positive regulator gene DcRheb in the TOR pathway resulted in lower levels of ecdysone and juvenile hormone and decreased vitellogenin synthesis, further disrupting reproductive ability. This study enhances understanding of the molecular mechanism underlying ACP's reproductive strategy.
Asian Citrus Psyllid (ACP) only oviposits on flush shoots.
Protein metabolism, Mitogen‐Activated Protein Kinase (MAPK) signalling, hormone synthesis and Target of Rapamycin (TOR) signalling in ACP are involved in activating reproduction following feeding on flush shoots.
TOR signalling plays important role via transferring and inducing hormone synthesis and vitellogenesis.
► A model for concrete in FRP-confined steel tubular columns is presented. ► The behavior of the steel tube under biaxial loading is rigorously represented. ► The proposed model provides accurate ...predictions of experimental results.
Concrete-filled steel tubes (CFTs) are widely used as columns in many structural systems. In CFTs, degradation in steel confinement, strength and ductility can result from inelastic outward local buckling. To overcome this deficiency of CFTs, external confinement of CFTs with an FRP jacket has been explored in recent studies. This paper presents a theoretical model in an incremental–iterative form for circular FRP-confined CFTs (CCFTs) under monotonic axial compression, with the focus being on the stress–strain behavior of the confined concrete. The proposed stress–strain model for concrete in CCFTs is based on the same approach as that commonly adopted by existing models for FRP-confined concrete and includes three components: (a) an active-confinement model; (b) a lateral strain equation; and (c) equations for determining the total confining pressure from the steel tube and the FRP jacket. It is shown that the lateral dilation behavior of concrete in CCFTs differs significantly from that of FRP-confined concrete in the initial stage because the former experiences more severe micro-cracking than the latter in the initial stage of loading; this difference is reflected in the proposed model. In general, the predictions of the proposed model are in close agreement with existing test results. The proposed model provides a useful tool for a parametric study on the stress–strain behavior of confined concrete in CCFTs to produce results for the formulation of simple stress–strain model in closed-form expressions for design use.
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