Magnetic topological semimetals, a novel state of quantum matter with a nontrivial band topology, have emerged as a new frontier in physics and materials science. An external stimulus such as ...temperature or magnetic field could be expected to alter their spin states and thus Fermi surface anisotropies and topological features. Here, we perform angular magnetoresistance measurements and electronic band structure calculations to reveal the evolution of HoSb's Fermi surface anisotropies and topological nature in different magnetic states. The angular magnetoresistance results show that its Fermi surface anisotropy is robust in the paramagnetic state but is significantly modulated in the antiferromagnetic and ferromagnetic states. More interestingly, a transition from the trivial (nontrivial) to nontrivial (trivial) topological electronic phase is observed when HoSb undergoes a magnetic transition from the paramagnetic (antiferromagnetic) to antiferromagnetic (ferromagnetic) state induced by temperature (applied magnetic field). Our study suggests that HoSb provides an archetype platform to study the correlations between magnetism and topological states of matter.
The topological nature of electronic states in HoSb significantly depends on spin orderings (NM, AFM or FM spin configuration). Only the electronic band structure in HoSb's antiferromagnetic state is confirmed to be topologically nontrivial.
Inconceivably large changes (up to 106%) of the resistivity induced by external magnetic field-a phenomenon known as the extreme magnetoresistance effect has been reported in a great number of exotic ...semimetals. The very recent and exciting discoveries mainly pay attention to the compounds without magnetic ground states, which appears to limit the potential growth of semimetal family. For fundamental scientific interests, introduction of spin degree of freedom would provide an almost ideal platform for investigating the correlation effect between magnetism, crystallographic structure and electric resistivity in materials. Here, we report the experimental observation of metamagnetic behaviors and transport properties of HoBi single crystals. Being a magnetic member of the rare earth monopnictide family, the magnetoresistance of HoBi is significantly modulated by the magnetic orders at low temperature, which shows a nonmonotonic increment across the successive magnetic phases and reaches 104% (9 T and 2 K) in the ferromagnetic state. Kohler's rule predicts that more than one type of carriers dominates the transport properties. Well fitted magnetoresistance and Hall resistivity curves by the semiclassical two-band model suggest that the densities of electron and hole carriers are nearly compensated and the carrier mobilities in this compound are ultrahigh. Besides, the inverted band structures and nonzero Z2 topological invariant indicate that possible nontrivial electronic states could generate in the ferromagnetic phase of HoBi. Combining the experimental and theoretical results, it is found that the cooperative action of carrier compensation effect and ultrahigh mobility might contribute to the extreme magnetoresistance observed in the titled compound. These findings suggest a paradigm for obtaining the extreme magnetoresistance in magnetic compounds and are relevant to understand the rare-earth-based correlated topological materials.
Human pituitary tumour-transforming gene 1 (hPTTG1) is an oncogenic transcription factor that is overexpressed in many tumour types, especially tumours with metastatic abilities. However, how hPTTG1 ...overexpression drives metastasis is not yet clear. As a transcription factor, hPTTG1 may promote metastasis by activating target genes that are involved in the metastatic process. Here, we showed that Rho guanine nucleotide exchange factor-H1 (GEF-H1) was transcriptionally activated by hPTTG1, thereby promoting breast cancer metastasis. Luciferase reporter analyses and chromatin immunoprecipitation (ChIP) assays showed that hPTTG1 directly bound and activated the GEF-H1 gene promoter. In this study, RNA interference-mediated knockdown of hPTTG1 in highly metastatic breast tumour cells decreased GEF-H1 expression and RhoA activation, thereby reducing cell motility and invasion, and interfering with cytoskeletal remodelling in vitro, and impairing the tumour metastasis in vivo. The restoration of GEF-H1 expression in hPTTG1-knockdown cells rescued the hPTTG1-knockdown effects on cytoskeletal changes in vitro and tumour metastasis in vivo. Conversely, ectopic expression of hPTTG1 in non-metastatic breast tumour cells induced cytoskeletal rearrangements, and allowed these cells to metastasise in a mouse model by orthotopic implantation. In human tumour samples, hPTTG1 expression was also correlated to GEF-H1 expression in aggressive breast carcinoma. Altogether, these findings definitively establish a role for hPTTG1 in activating the GEF-H1/RhoA pathway as a newly identified mechanism in breast cancer metastasis.
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DOBA, EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, IZUM, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UILJ, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
Extreme magnetoresistance in nonmagnetic compounds has received considerable attention because this phenomenon challenges the classical understanding of electron transport under a magnetic field. In ...this study, YBi, which crystallizes in a NaCl-type structure, was synthesized via self-flux method to study its magnetotransport properties and electronic structure. Under zero magnetic field, metallic behavior was observed in the whole temperature interval ranging from 2 to 300 K. Interestingly, extreme magnetoresistance and a resistivity plateau developed when the applied magnetic field was increased; the magnetoresistance reaches 0.8 × 10 5 % at 9 T and 2 K. Multiple bands including one electron pocket and two hole pockets revealed by Kohler's rule and first-principle calculations were responsible for the transport processes. Moreover, the hidden band inversion was also uncovered, which suggests the existence of a topological nature in this compound. The contribution of a single Fermi pocket and the combination thereof for magnetotransport indicate that electron–hole compensation plays an important role in determining the electric properties. All these results point towards YBi being a semimetal member of the RPn family (R = rare earth; Pn = Sb and Bi).
Synergic effect of electronic correlation and spin-orbit coupling is an emerging topic in topological materials. Central to this rapidly developing area are the prototypes of strongly correlated ...heavy-fermion systems. Recently, some Ce-based compounds are proposed to host intriguing topological nature, among which the electronic properties of CeSb are still under debate. In this paper, we report a comprehensive study combining magnetic and electronic transport measurements, and electronic band-structure calculations of this compound to identify its topological nature. Quantum oscillations are clearly observed in both magnetization and magnetoresistance at high fields, from which one pocket with a nontrivial Berry phase is recognized. Angular-dependent magnetoresistance shows that this pocket is elongated in nature and corresponds to the electron pocket as observed in LaBi. Nontrivial electronic structure of CeSb is further confirmed by first-principle calculations, which arises from spin splitting in the fully polarized ferromagnetic state. These features indicate that magnetic field can induce nontrivial topological electronic states in this prototypical Kondo semimetal.
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CMK, CTK, FMFMET, IJS, NUK, PNG, UM
From a new viewpoint to improve plate plan view pattern during hot rolling, a plate edging process was proposed to roll back only the plate width spread of conventional rolling in this paper. Using ...commercial finite element (FE) analysis software DEFORM-3D, a three-dimensional rigid plastic FE model for vertical-horizontal (V-H) hot rolling was developed on the basis of a 5 m wide and heavy plate mill. Three hundred and twenty kinds of different V-H rolling processes were simulated by the FE model. Basing on the simulation results, the formation laws of dog bone shape during the vertical rolling and the width spread behaviours during the horizontal rolling were clarified. A plate edging model predicting the plate edging efficiency was established with the aid of an artificial neural network. The plate edging efficiency predicted by this plate edging model agreed well with those predicted by the existing strip edging models when the slab width/thickness ratio was small, which confirmed the validity of the plate edging model. The plate edging model expanded its application scope into the wide and heavy plate hot rolling.
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DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
The mechanisms of sensory transduction of pulmonary reactive oxygen species (ROS) by capsaicin-sensitive vagal lung afferent
fibres are unclear. To investigate the role of transient receptor ...potential vanilloid 1 (TRPV1) receptors and P2X purinoceptors
in this sensory transduction, we recorded fibre activity (FA) from 132 fibres of this type in 132 anaesthetized and ventilated
rats. Airway challenge of aerosolized H 2 O 2 (0, 0.2 and 0.4%) produced a concentration-dependant fibre stimulation. The fibre responses to 0.4% H 2 O 2 were attenuated by dimethylthiourea (a hydroxyl radical (·OH) scavenger; change in fibre activity (ÎFA), â55 ± 9%) or deferoxamine
(an iron-chelator that prevents formation of ·OH; ÎFA, â59 ± 9%), were prevented by catalase (an enzyme catalysing H 2 O 2 ; ÎFA, â96 ± 3%) and were unaffected by the vehicle for dimethylthiourea, iron-saturated deferoxamine or heat-inactivated
catalase. The fibre responses to 0.4% H 2 O 2 were attenuated by capsazepine (a TRPV1 receptor antagonist; ÎFA, â39 ± 9%) or iso -pyridoxalphosphate-6-azophenyl-2â²,5â²-disulphonate ( iso -PPADS, a P2X receptor antagonist; ÎFA, â51 ± 9%), were further reduced by capsazepine and iso -PPADS in combination (ÎFA, â70 ± 13%), and were unaltered by their vehicles. The fibre responses to cigarette smoke (20 ml),
an irritant that generates ROS, were attenuated by dimethylthiourea (ÎFA, â61 ± 9%) or capsazepine and iso -PPADS in combination (ÎFA, â67 ± 9%). These results suggest that both the TRPV1 and P2X receptors mediate the sensory transduction
of ROS, especially H 2 O 2 and ·OH, by capsaicin-sensitive vagal lung afferent fibres.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
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