In this paper, we report two homologous circular-ribbon flares associated with two filament eruptions. They were well observed by the New Vacuum Solar Telescope and the Solar Dynamics Observatory on ...2014 March 5. Prior to the flare, two small-scale filaments enclosed by a circular pre-flare brightening lie along the circular polarity inversion line around the parasitic polarity, which has shown a continuous rotation since its first appearance. Two filaments eventually erupt in sequence associated with two homologous circular-ribbon flares and display an apparent writhing signature. Supplemented by the nonlinear force-free field extrapolation and the magnetic field squashing factor investigation, the following are revealed. (1) This event involves the emergence of magnetic flux ropes into a pre-existing polarity area, which yields the formation of a 3D null-point topology in the corona. (2) Continuous input of the free energy in the form of a flux rope from beneath the photosphere may drive a breakout-type reconnection occurring high in the corona, supported by the pre-flare brightening. (3) This initiation reconnection could release the constraint on the flux rope and trigger the MHD instability to first make filament F1 lose equilibrium. The subsequent more violent magnetic reconnection with the overlying flux is driven during the filament rising. In return, the eruption of filament F2 is further facilitated by the reduction of the magnetic tension force above. These two processes form a positive feedback to each other to cause the energetic mass eruption and flare.
Genetic evidence for anatomically modern humans (AMH) out of Africa before 75 thousand years ago (ka) and in island southeast Asia (ISEA) before 60 ka (93-61 ka) predates accepted archaeological ...records of occupation in the region. Claims that AMH arrived in ISEA before 60 ka (ref. 4) have been supported only by equivocal or non-skeletal evidence. AMH evidence from this period is rare and lacks robust chronologies owing to a lack of direct dating applications, poor preservation and/or excavation strategies and questionable taxonomic identifications. Lida Ajer is a Sumatran Pleistocene cave with a rich rainforest fauna associated with fossil human teeth. The importance of the site is unclear owing to unsupported taxonomic identification of these fossils and uncertainties regarding the age of the deposit, therefore it is rarely considered in models of human dispersal. Here we reinvestigate Lida Ajer to identify the teeth confidently and establish a robust chronology using an integrated dating approach. Using enamel-dentine junction morphology, enamel thickness and comparative morphology, we show that the teeth are unequivocally AMH. Luminescence and uranium-series techniques applied to bone-bearing sediments and speleothems, and coupled uranium-series and electron spin resonance dating of mammalian teeth, place modern humans in Sumatra between 73 and 63 ka. This age is consistent with biostratigraphic estimations, palaeoclimate and sea-level reconstructions, and genetic evidence for a pre-60 ka arrival of AMH into ISEA. Lida Ajer represents, to our knowledge, the earliest evidence of rainforest occupation by AMH, and underscores the importance of reassessing the timing and environmental context of the dispersal of modern humans out of Africa.
Gas clouds in present-day galaxies are inefficient at forming stars. Low star-formation efficiency is a critical parameter in galaxy evolution: it is why stars are still forming nearly 14 billion ...years after the Big Bang and why star clusters generally do not survive their births, instead dispersing to form galactic disks or bulges. Yet the existence of ancient massive bound star clusters (globular clusters) in the Milky Way suggests that efficiencies were higher when they formed ten billion years ago. A local dwarf galaxy, NGC 5253, has a young star cluster that provides an example of highly efficient star formation. Here we report the detection of the J = 3→2 rotational transition of CO at the location of the massive cluster. The gas cloud is hot, dense, quiescent and extremely dusty. Its gas-to-dust ratio is lower than the Galactic value, which we attribute to dust enrichment by the embedded star cluster. Its star-formation efficiency exceeds 50 per cent, tenfold that of clouds in the Milky Way. We suggest that high efficiency results from the force-feeding of star formation by a streamer of gas falling into the galaxy.
Ten years after its discovery, the small ubiquitin-like protein modifier (SUMO) has emerged as a key regulator of proteins. While early studies indicated that sumoylation takes place mainly in the ...nucleus, an increasing number of non-nuclear substrates have recently been identified, suggesting a wider stage for sumoylation in the cell. Unlike ubiquitylation, which primarily targets a substrate for degradation, sumoylation regulates a substrate's functions mainly by altering the intracellular localization, protein-protein interactions or other types of post-translational modifications. These changes in turn affect gene expression, genomic and chromosomal stability and integrity, and signal transduction. Sumoylation is counter-balanced by desumoylation, and well-balanced sumoylation is essential for normal cellular behaviors. Loss of the balance has been associated with a number of diseases. This paper reviews recent progress in the study of SUMO pathways, substrates, and cellular functions and highlights important findings that have accelerated advances in this study field and link sumoylation to human diseases.
Summary
Both sarcopenia and low bone mineral density (BMD) have become public health concerns. We found that presarcopenic and/or sarcopenic individuals were more likely to have lower BMD. And this ...relationship has race and sex-specific discrepancy.
Purpose
The purpose of the study was to investigate the racial and gender differences in the relationship between sarcopenia and BMD among older adults.
Methods
Totally, 5476 subjects (mean age = 65.7 ± 6.4) of non-Hispanic White (
n
= 3297), non-Hispanic Black (
n
= 1265), and non-Hispanic Asian (
n
= 914) were analyzed. Sarcopenia was defined according to the revised European consensus on definition and diagnosis of sarcopenia (EWGSOP2). General linear model and multivariable linear regression model were used to examine the relationship between sarcopenia and regional/whole body BMD stratified by race and sex. Adjustments were conducted for physiological, behavioral, and disease factors.
Results
Comparing with normal older participants, presarcopenic and sarcopenic elderly were more likely to have lower BMD. Although the difference was not statistically significant in a few sub-groups, among the three racial groups, the strongest association between sarcopenia and BMD was found in non-Hispanic Black people, followed by non-Hispanic White people and non-Hispanic Asian people. In addition, significant differences of BMD across sarcopenia stages were found in more sub-groups in women than in men after adjusting for covariates.
Conclusions
In this older cohort, sarcopenia is significantly related to low regional/whole-body BMD, and these associations vary by race and sex. Consideration in race and sex is warranted when developing strategies to maintain or minimize BMD loss.
The ferromagnetic Weyl semimetals with inversion symmetry usually possess odd pairs of Weyl fermions. Here, we present an inversion eigenvalue argument to dictate the existence of even pairs of ...ferromagnetic Weyl fermions. We show, by a combination of first-principles calculations and symmetry analyses, that this exotic topological feature can be verified in ferromagnetic oxides in different space groups. In particular, a realistic candidate, i.e., hollandite RbCr_{4}O_{8} with a high Curie temperature (∼295 K), hosts intriguing twin pairs of Weyl fermions, which are robustly stable against perturbations. Moreover, our effective model and symmetry analysis show that the twin pairs of Weyl fermions originate from a mirrored nodal ring pair. The nontrivial surface states and Fermi arcs of RbCr_{4}O_{8} are clearly visible, further revealing the topological features. This work strengthens the understanding of the parity analysis in exploring ferromagnetic topological materials with unconventional fermionic excitations.
The concept of the critical state in granular soils needs to make proper reference to the fabric structure that develops at critical state. This study identifies a unique property associated with the ...fabric structure relative to the stresses at critical state. A unique relationship between the mean effective stress and a fabric anisotropy parameter, K, defined by the first joint invariant of the deviatoric stress tensor and the deviatoric fabric tensor, is found at critical state, and is path-independent. Numerical simulations using the discrete-element method under different loading conditions and intermediate principal stress ratios identify a unique power law for this relationship. Based on the findings, a new definition of critical state for granular media is proposed. In addition to the conditions of constant stress and unique void ratio required by the conventional critical state concept, the new definition imposes the additional constraint that K reaches a unique value at critical state. A unique spatial critical state curve in the three-dimensional space K–e–p′ is found for a granular medium, the projection of which onto the e–p′ plane turns out to be the conventional critical state line. The new critical state concept provides an important reference state for a soil to reach, based on which the key concepts in the constitutive modelling of granular media, including the choice of state parameters, dilatancy relation and non-coaxiality, are reassessed, and future exploratory topics are discussed.
Phase diagrams are "maps" materials scientists often use to design new materials. They define what compounds and solutions are formed and their respective compositions and amounts when several ...elements are mixed together under a certain temperature and pressure. This monograph is the most comprehensive reference book on experimental methods for phase diagram determination. It covers a wide range of methods that have been used to determine phase diagrams of metals, ceramics, slags, and hydrides.* Extensive discussion on methodologies of experimental measurements and data assessments * Written by experts around the world, covering both traditional and combinatorial methodologies * A must-read for experimental measurements of phase diagrams
Phosphatidylinositol 3-kinases (PI3Ks) are crucial coordinators of intracellular signalling in response to extracellular stimuli. Hyperactivation of PI3K signalling cascades is one of the most common ...events in human cancers. In this Review, we discuss recent advances in our knowledge of the roles of specific PI3K isoforms in normal and oncogenic signalling, the different ways in which PI3K can be upregulated, and the current state and future potential of targeting this pathway in the clinic.
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