Very recently, two-dimensional (2D) boron sheets (borophene) with rectangular structures were grown successfully on single crystal Ag(111) substrates (Mannix et al 2015 Science 350 1513). The ...fabricated boroprene is predicted to have unusual mechanical properties. We performed first-principle calculations to investigate the mechanical properties of the monolayer borophene, including ideal tensile strength and critical strain. It was found that monolayer borophene can withstand stress up to 20.26 N m−1 and 12.98 N m−1 in a and b directions, respectively. However, its critical strain was found to be small. In the a direction, the critical value is only 8%, which, to the best of our knowledge, is the lowest among all studied 2D materials. Our numerical results show that the tensile strain applied in the b direction enhances the bucking height of borophene resulting in an out-of-plane negative Poisson's ratio, which makes the boron sheet show superior mechanical flexibility along the b direction. The failure mechanism and phonon instability of monolayer borophene were also explored.
•Crack initiation stress (σci) and crack damage stress (σcd) of the Beishan granite under uniaxial and triaxial compressions are determined.•3D distributions of AE events in the rock samples at ...different loading stages in the compression tests are obtained.•Methods of indentifying σci and σcd at different confinements are discussed.•Confinement-dependent damage stress characteristics are analyzed.
This paper reports for the first time the identification of a magnetic structure around a magnetic null in a magnetic reconnection region in the magnetotail. Magnetic reconnection is one of the ...fundamental processes in astrophysical and solar‐terrestrial plasmas. Though the concept of reconnection has been studied for many years, the process that really occurs has not been fully revealed by direct measurements. In particular, the lack of a description of three‐dimensional (3‐D) reconnecting magnetic field from observations makes the task more difficult. The Cluster spacecraft array provide an opportunity to reconstruct the 3‐D magnetic reconnection structure based on magnetic field vectors simultaneously measured at four positions. The identification of this structure comes from a new method of analysis of in situ measurements proposed here. Applying a fitting model of 10 spherical harmonic functions and a Harris current sheet function, plus a constant field, we reconstruct a 3‐D magnetic field configuration around the magnetic null in an reconnection event observed by Cluster in the geo‐magnetotail.
MiR-646 has been reported to be aberrantly expressed in human cancers. However, the underlying molecular mechanisms of action of miR-646 in gastric cancer (GC) have not yet been investigated.
In ...vitro function of miR-646 in GC was evaluated using EdU assay, plate colony formation assay, and matrigel invasion assay. Real-time PCR or western blotting was performed to detect miR-646 and FOXK1 expressions. In vivo tumour growth and metastasis were conducted in nude mice.
MiR-646 expression was downregulated in GC tissues compared with adjacent normal tissues. Low miR-646 expression is associated with malignant progression. Transient transfection of GC cells with miR-646 inhibited their growth and migration. Moreover, miR-646 influenced the expression of epithelial-mesenchymal transition (EMT)-associated proteins. TGF-β1 treatment significantly suppressed the expression of miR-646 and overexpression of this microRNA counteracted the influence of the TGF-β1-induced EMT phenotype. In terms of the underlying mechanism, miR-646 directly targeted FOXK1. In vivo, it inhibited the FOXK1-mediated proliferation and EMT-induced metastasis. Consistently, inverse correlations were also observed between the expression of miR-646 and FOXK1 in human GC tissue samples. Furthermore, miR-646 regulated Akt/mTOR signalling after FOXK1.
miR-646 inhibited GC cell proliferation and the EMT progression in GC cells by targeting FOXK1.
Primary ovarian insufficiency (POI) is the depletion or loss of normal ovarian function, which cause infertility in women before the age of 40 years. Two homozygous germline truncation mutations in ...STAG3 gene had been reported to causes POI in consanguineous families. Here, we aimed to identify the genetic cause of POI in 2 affected sisters manifested with primary amenorrhea and partial development of secondary sexual characters with normal range of height of a consanguineous Han Chinese family. Whole‐exome and Sanger sequencing identified a homozygous donor splice‐site mutation (NM_012447.2: c.1573+5G>A) in the STAG3 gene. RT‐PCR revealed that the mutation causes loss of wild‐type donor splice‐site which leads to aberrant splicing of STAG3 mRNA and consecutive formation of STAG3 alternative transcript (p.Leu490Thrfs*10) . This is the first report of splice‐site mutation of STAG3 gene causes POI in 2 Han Chinese patients.
Aldosterone/renin ratio (ARR) is currently regarded as the most reliable and available screening test for primary aldosteronism (PA), however, the falling accuracy of ARR with increasing age has ...posed crucial challenge for PA screening among older-aged population. To clarify potential effects of age on screening for PA, 216 subjects with PA and 657 subjects with non-PA were recruited and subdivided into four age groups (⩽39, 40-49, 50-59 and ⩾60 years) and their biochemical parameters were compared. As expected, plasma renin activity (PRA) lowered more than plasma aldosterone concentration (PAC) and led to gradually elevated ARR with increasing age in the non-PA group (P<0.001), whereas this phenomenon was unconspicuous in the PA group. The best cut-off values of ARR for PA screening were elevated in subjects ⩾50 years, whereas the area under the receiver operating characteristic curves (AUCs), sensitivity, specificity and Youden's index (YI) of ARR were declined with increasing age, especially in patients ⩾60 years (AUC=0.863, sensitivity=95.2%, specificity=69.0%, YI=0.643). The AUCs of PAC increased with increasing age and even slightly surpassed that of ARR in patients ⩾60 years (AUCPAC=0.884). Our data suggest that the criteria of ARR for PA screening in patients ⩾50 years may need setting higher; the falling accuracy of ARR with increasing age, especially in patients ⩾60 years, could be improved by taking into account the absolute value of the PAC when applicable by the center.
We compute the helicity-dependent strange quark distribution in the proton in the framework of chiral effective theory. Starting from the most general chiral SU(3) Lagrangian that respects Lorentz ...and gauge invariance, we derive the complete set of hadronic splitting functions at the one meson loop level, including the octet and decuplet rainbow, tadpole, Kroll-Ruderman and octet-decuplet transition configurations. By matching hadronic and quark level operators, we obtain generalized convolution formulas for the quark distributions in the proton in terms of hadronic splitting functions and quark distributions in the hadronic configurations, and from these derive model-independent relations for the leading nonanalytic behavior of their moments. Within the limits of parameters of the Pauli-Villars regulators derived from inclusive hyperon production, we find that the polarized strange quark distribution is rather small and mostly negative.
Temperature and biodiversity changes occur in concert, but their joint effects on ecological stability of natural food webs are unknown. Here, we assess these relationships in 19 planktonic food ...webs. We estimate stability as structural stability (using the volume contraction rate) and temporal stability (using the temporal variation of species abundances). Warmer temperatures were associated with lower structural and temporal stability, while biodiversity had no consistent effects on either stability property. While species richness was associated with lower structural stability and higher temporal stability, Simpson diversity was associated with higher temporal stability. The responses of structural stability were linked to disproportionate contributions from two trophic groups (predators and consumers), while the responses of temporal stability were linked both to synchrony of all species within the food web and distinctive contributions from three trophic groups (predators, consumers, and producers). Our results suggest that, in natural ecosystems, warmer temperatures can erode ecosystem stability, while biodiversity changes may not have consistent effects.
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