We report results on the searches of weakly interacting massive particles (WIMPs) with sub-GeV masses (mχ) via WIMP-nucleus spin-independent scattering with Migdal effect incorporated. Analysis on ...time-integrated (TI) and annual modulation (AM) effects on CDEX-1B data are performed, with 737.1 kg day exposure and 160 eVee threshold for TI analysis, and 1107.5 kg day exposure and 250 eVee threshold for AM analysis. The sensitive windows in mχ are expanded by an order of magnitude to lower DM masses with Migdal effect incorporated. New limits on σχNSI at 90% confidence level are derived as 2×10−32∼7×10−35 cm2 for TI analysis at mχ∼50–180 MeV/c2, and 3×10−32∼9×10−38 cm2 for AM analysis at mχ∼75 MeV/c2–3.0 GeV/c2.
We report the first results of a light weakly interacting massive particles (WIMPs) search from the CDEX-10 experiment with a 10 kg germanium detector array immersed in liquid nitrogen at the China ...Jinping Underground Laboratory with a physics data size of 102.8 kg day. At an analysis threshold of 160 eVee, improved limits of 8×10^{-42} and 3×10^{-36} cm^{2} at a 90% confidence level on spin-independent and spin-dependent WIMP-nucleon cross sections, respectively, at a WIMP mass (m_{χ}) of 5 GeV/c^{2} are achieved. The lower reach of m_{χ} is extended to 2 GeV/c^{2}.
Superconductivity arises from two distinct quantum phenomena: electron pairing and long-range phase coherence. In conventional superconductors, the two quantum phenomena generally take place ...simultaneously, while in the underdoped high- Tc cuprate superconductors, the electron pairing occurs at higher temperature than the long-range phase coherence. Recently, whether electron pairing is also prior to long-range phase coherence in single-layer FeSe film on SrTiO3 substrate is under debate. Here, by measuring Knight shift and nuclear spin-lattice relaxation rate, we unambiguously reveal a pseudogap behavior below Tp∼60 K in two kinds of layered FeSe-based superconductors with quasi2D nature. In the pseudogap regime, a weak diamagnetic signal and a remarkable Nernst effect are also observed, which indicates that the observed pseudogap behavior is related to superconducting fluctuations. These works confirm that strong phase fluctuation is an important character in the 2D iron-based superconductors as widely observed in high-Tc cuprate superconductors.
The epidemiology of candidaemia varies between hospitals and geographic regions. Although there are many studies from Asia, a large-scale cross-sectional study across Asia has not been performed. We ...conducted a 12-month, laboratory-based surveillance of candidaemia at 25 hospitals from China, Hong Kong, India, Singapore, Taiwan and Thailand. The incidence and species distribution of candidaemia were determined. There were 1601 episodes of candidaemia among 1.2 million discharges. The overall incidence was 1.22 episodes per 1000 discharges and varied among the hospitals (range 0.16–4.53 per 1000 discharges) and countries (range 0.25–2.93 per 1000 discharges). The number of Candida blood isolates and the total number of fungal isolates were highly correlated among the six countries (R² = 0.87) and 25 hospitals (R² = 0.77). There was a moderate correlation between incidence of candidaemia and the intensive care unit (ICU)/total bed ratio (R² = 0.47), although ICUs contributed to only 23% of candidaemia cases. Of 1910 blood isolates evaluated, Candida albicans was most frequently isolated (41.3%), followed by Candida tropicalis (25.4%), Candida glabrata (13.9%) and Candida parapsilosis (12.1%). The proportion of C. tropicalis among blood isolates was higher in haemato-oncology wards than others wards (33.7% versus 24.5%, p 0.0058) and was more likely to be isolated from tropical countries than other Asian countries (46.2% versus 18.9%, p 0.04). In conclusion, the ICU settings contribute, at least in part, to the incidence variation among hospitals. The species distribution is different from Western countries. Both geographic and healthcare factors contribute to the variation of species distribution.
We present results on light weakly interacting massive particle (WIMP) searches with annual modulation (AM) analysis on data from a 1-kg mass p-type point-contact germanium detector of the CDEX-1B ...experiment at the China Jinping Underground Laboratory. Datasets with a total live time of 3.2 yr within a 4.2-yr span are analyzed with analysis threshold of 250 eVee. Limits on WIMP-nucleus (χ-N) spin-independent cross sections as function of WIMP mass (m_{χ}) at 90% confidence level (C.L.) are derived using the dark matter halo model. Within the context of the standard halo model, the 90% C.L. allowed regions implied by the DAMA/LIBRA and CoGeNT AM-based analysis are excluded at >99.99% and 98% C.L., respectively. These results correspond to the best sensitivity at m_{χ}<6 GeV/c^{2} among WIMP AM measurements to date.
Three-dimensional Bi-chalcogenide topological insulators exhibit surface states populated by massless Dirac fermions that are topologically protected from disorder scattering. Here, we demonstrate ...that these states can be enhanced or destroyed by strain in the vicinity of grain boundaries on the surface of epitaxial Bi2 Se3 (0001) thin films. Using scanning tunnelling and transmission electron microscopy, we show that the low-angle tilt grain boundaries in Bi2 Se3 (0001) films consist of arrays of alternating edge dislocation pairs. Along the boundary, these dislocations introduce periodic in-plane compressive and tensile strains. From tunnelling spectroscopy experiments and first-principles calculations, we find that whereas the energy of the Dirac state shifts in regions under tensile strain, a gap opens in regions under compressive strain, indicative of the destruction of the Dirac states at the surface. These results demonstrate that Dirac states can be tuned by strain at the atomic scale.
Magnetic reconnection is a key mechanism involved in solar eruptions and is also a prime possibility to heat the low corona to millions of degrees. Here, we present ultra-high-resolution extreme ...ultraviolet observations of persistent null-point reconnection in the corona at a scale of about 390 km over one hour observations of the Extreme-Ultraviolet Imager on board Solar Orbiter spacecraft. The observations show formation of a null-point configuration above a minor positive polarity embedded within a region of dominant negative polarity near a sunspot. The gentle phase of the persistent null-point reconnection is evidenced by sustained point-like high-temperature plasma (about 10 MK) near the null-point and constant outflow blobs not only along the outer spine but also along the fan surface. The blobs appear at a higher frequency than previously observed with an average velocity of about 80 km s
and life-times of about 40 s. The null-point reconnection also occurs explosively but only for 4 minutes, its coupling with a mini-filament eruption generates a spiral jet. These results suggest that magnetic reconnection, at previously unresolved scales, proceeds continually in a gentle and/or explosive way to persistently transfer mass and energy to the overlying corona.
We present the improved constraints on couplings of solar axions and more generic bosonic dark matter particles using 737.1 kg days of data from the CDEX-1B experiment. The CDEX-1B experiment, ...located at the China Jinping Underground Laboratory, primarily aims at the direct detection of weakly interacting massive particles using a p-type point-contact germanium detector. We adopt the profile likelihood ratio method for analysis of data in the presence of backgrounds. An energy threshold of 160 eV was achieved, much better than the 475 eV of CDEX-1A with an exposure of 335.6 kg days. This significantly improves the sensitivity for the bosonic dark matter below 0.8 keV among germanium detectors. Limits are also placed on the coupling gAe < 2.48 × 10−11 from Compton, bremsstrahlung, atomic-recombination, and deexcitation channels and geffAN × gAe < 4.14 × 10−17 from a 57Fe M1 transition at 90% confidence level.
The c-Jun NH2-terminal kinase (JNK) pathway represents one subgroup of MAP kinases that are activated primarily by cytokines and exposure to environmental stress. Autophagy is a protein-degradation ...system characterized by the formation of double-membrane vacuoles termed autophagosomes. Autophagy-related gene beclin 1 plays a key role in autophagosome formation. However, the relationships between activation of JNK pathway, autophagy induction and Beclin 1 expression remain elusive. In this study, we used human cancer cell lines CNE2 and Hep3B to investigate the role of JNK-mediated Beclin 1 expression in ceramide-induced autophagic cell death. Ceramide-treated cells exhibited the characteristics of autophagy (that is, acidic vesicular organelle formation and the LC3-II generation). JNK was activated in these two cell lines exposed to ceramide and the phosphorylation of c-Jun also increased. In the meantime, we found that ceramide upregulated Beclin 1 expression in cancer cells. The upregulation of Beclin 1 expression could be blocked by SP600125 (a specific inhibitor of JNK) or a small interfering RNA (siRNA) directed against JNK1/2 or c-Jun. Chromatin immunoprecipitation and luciferase reporter analysis revealed that c-Jun was involved in the regulation of beclin 1 transcription in response to ceramide treatment. In addition, inhibition of JNK activity by SP600125 could inhibit autophagy induction by ceramide. Furthermore, Beclin 1 knockdown by siRNA also inhibited ceramide-mediated autophagic cell death. JNK-mediated Beclin 1 expression was also observed in topotecan-induced autophagy. These data suggest that activation of JNK pathway can mediate Beclin 1 expression, which plays a key role in autophagic cell death in cancer cells.
We report constraints on the dark photon effective kinetic mixing parameter (κ) with data taken from two p-type point-contact germanium detectors of the CDEX-10 experiment at the China Jinping ...Underground Laboratory. The 90% confidence level upper limits on κ of solar dark photon from 205.4 kg-day exposure are derived, probing new parameter space with masses (m_{V}) from 10 to 300 eV/c^{2} in direct detection experiments. Considering dark photon as the cosmological dark matter, limits at 90% confidence level with m_{V} from 0.1 to 4.0 keV/c^{2} are set from 449.6 kg-day data, with a minimum of κ=1.3×10^{-15} at m_{V}=200 eV/c^{2}.
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