Zirconias, the strongest of the dental ceramics, are increasingly being fabricated in monolithic form for a range of clinical applications. Y-TZP (yttria-stabilized tetragonal zirconia polycrystal) ...is the most widely used variant. However, current Y-TZP ceramics on the market lack the aesthetics of competitive glass-ceramics and are therefore somewhat restricted in the anterior region. This article reviews the progressive development of currently available and next-generation zirconias, representing a concerted drive toward greater translucency while preserving adequate strength and toughness. Limitations of efforts directed toward this end are examined, such as reducing the content of light-scattering alumina sintering aid or incorporating a component of optically isotropic cubic phase into the tetragonal structure. The latest fabrication routes based on refined starting powders and dopants, with innovative sintering protocols and associated surface treatments, are described. The need to understand the several, often complex, mechanisms of long-term failure in relation to routine laboratory test data is presented as a vital step in bridging the gaps among material scientist, dental manufacturer, and clinical provider.
Abstract
We compute the spherically averaged power spectrum from four seasons of data obtained for the Epoch of Reionization (EoR) project observed with the Murchison Widefield Array (MWA). We ...measure the EoR power spectrum over k = 0.07–3.0 h Mpc−1 at redshifts $z$ = 6.5–8.7. The largest aggregation of 110 h on EoR0 high band (3340 observations), yields a lowest measurement of (43 mK)2 = 1.8 × 103 mK2 at k = 0.14 h Mpc−1 and $z$ = 6.5 (2σ thermal noise plus sample variance). Using the Real-Time System to calibrate and the CHIPS pipeline to estimate power spectra, we select the best observations from the central five pointings within the 2013–2016 observing seasons, observing three independent fields and in two frequency bands. This yields 13 591 2-min snapshots (453 h), based on a quality assurance metric that measures ionospheric activity. We perform another cut to remove poorly calibrated data, based on power in the foreground-dominated and EoR-dominated regions of the two-dimensional power spectrum, reducing the set to 12 569 observations (419 h). These data are processed in groups of 20 observations, to retain the capacity to identify poor data, and used to analyse the evolution and structure of the data over field, frequency, and data quality. We subsequently choose the cleanest 8935 observations (298 h of data) to form integrated power spectra over the different fields, pointings, and redshift ranges.
Highlights • Regional and network functional changes could be seen in the early stage of SCI. • Functional changes were associated with clinical symptom severity in SCI patients. • Functional ...reorganization may reflect a compensatory role in the recovery of SCI.
Magnetotail reconnection plays a crucial role in explosive energy conversion in geospace. Because of the lack of in-situ spacecraft observations, the onset mechanism of magnetotail reconnection, ...however, has been controversial for decades. The key question is whether magnetotail reconnection is externally driven to occur first on electron scales or spontaneously arising from an unstable configuration on ion scales. Here, we show, using spacecraft observations and particle-in-cell (PIC) simulations, that magnetotail reconnection starts from electron reconnection in the presence of a strong external driver. Our PIC simulations show that this electron reconnection then develops into ion reconnection. These results provide direct evidence for magnetotail reconnection onset caused by electron kinetics with a strong external driver.
ABSTRACT
Observations in the lowest Murchison Widefield Array (MWA) band between 75 and 100 MHz have the potential to constrain the distribution of neutral hydrogen in the intergalactic medium at ...redshift ∼13–17. Using 15 h of MWA data, we analyse systematics in this band such as radio-frequency interference (RFI), ionospheric and wide field effects. By updating the position of point sources, we mitigate the direction-independent calibration error due to ionospheric offsets. Our calibration strategy is optimized for the lowest frequency bands by reducing the number of direction-dependent calibrators and taking into account radio sources within a wider field of view. We remove data polluted by systematics based on the RFI occupancy and ionospheric conditions, finally selecting 5.5 h of the cleanest data. Using these data, we obtain 2σ upper limits on the 21 cm power spectrum in the range of $0.1~ h~{\mathrm{ Mpc}}^{-1}\lessapprox k \lessapprox 1 ~ ~h~{\mathrm{ Mpc}}^{-1}$ and at z = 14.2, 15.2, and 16.5, with the lowest limit being $6.3\times 10^6 ~\rm mK^2$ at $k=0.14 ~h~{\mathrm{ Mpc}}^{-1}$ and at z = 15.2 with a possibility of a few per cent of signal loss due to direction-independent calibration.
Strontium optical lattice clocks have the potential to simultaneously interrogate millions of atoms with a high spectroscopic quality factor of 4 × 1017. Previously, atomic interactions have forced a ...compromise between clock stability, which benefits from a large number of atoms, and accuracy, which suffers from density-dependent frequency shifts. Here we demonstrate a scalable solution that takes advantage of the high, correlated density of a degenerate Fermi gas in a three-dimensional (3D) optical lattice to guard against on-site interaction shifts. We show that contact interactions are resolved so that their contribution to clock shifts is orders of magnitude lower than in previous experiments. A synchronous clock comparison between two regions of the 3D lattice yields a measurement precision of 5 × 10−19 in 1 hour of averaging time.
We perform a statistical study of electromagnetic ion cyclotron (EMIC) waves detected by the Van Allen Probes mission to investigate the spatial distribution of their occurrence, wave power, ...ellipticity, and normal angle. The Van Allen Probes have been used which allow us to explore the inner magnetosphere (1.1 to 5.8 RE). Magnetic field measurements from the Electric and Magnetic Field Instrument Suite and Integrated Science on board the Van Allen Probes are used to identify EMIC wave events for the first 22 months of the mission operation (8 September 2012 to 30 June 2014). EMIC waves are examined in H+, He+, and O+ bands. Over 700 EMIC wave events have been identified over the three different wave bands (265 H+‐band events, 438 He+‐band events, and 68 O+‐band events). EMIC wave events are observed between L = 2–8, with over 140 EMIC wave events observed below L = 4. Results show that H+‐band EMIC waves have two peak magnetic local time (MLT) occurrence regions: prenoon (09:00 < MLT ≤ 12:00) and afternoon (15:00 < MLT ≤ 17:00) sectors. He+‐band EMIC waves feature an overall stronger dayside occurrence. O+‐band EMIC waves have one peak region located in the morning sector at lower L shells (L < 4). He+‐band EMIC waves average the highest wave power overall (>0.1 nT2/Hz), especially in the afternoon sector. Ellipticity observations reveal that linearly polarized EMIC waves dominate in lower L shells.
Key Points
A statistical study of EMIC waves observed by the Van Allen Probes is performed
The occurrence and wave properties of the EMIC waves are examined
Linearly polarized EMIC waves dominate lower L shells (L < 4)
lncRNAs play important roles in the epigenetic regulation of carcinogenesis and progression. Previous studies suggest that HOTAIR contributes to gastric cancer (GC) development, and the ...overexpression of HOTAIR predicts a poor prognosis. In this study, we found that HOTAIR was more highly expressed in diffuse-type GC than in intestinal type (P=0.048). In the diffuse type, there is significant relationship between HOTAIR expression and DFS (P<0.001). CDH1 was downregulated in diffuse-type GC tissues (P=0.0007) and showed a negative relationship with HOTAIR (r(2)=0.154, P=0.0354). In addition, HOTAIR knockdown significantly repressed migration, invasion and metastasis both in vitro and vivo and reversed the epithelial-to-mesenchymal transition in GC cells. We also showed that HOTAIR recruiting and binding to PRC2 epigenetically represses miR34a, which controls the targets C-Met (HGF/C-Met/Snail pathway) and Snail, thus contributing to GC cell-EMT process and accelerating tumor metastasis. Moreover, it is demonstrated that HOTAIR crosstalk with microRNAs during epigenetic regulation. Our results suggest that HOTAIR acts as an EMT regulator and may be a candidate prognostic biomarker and a target for new therapies in GC patients.
► The focus is simultaneous determination of seven neonicotinoid residues in grains. ► It is a rapid and reliable method that we have developed to analyse seven pesticides. ► It is the first time to ...analyse seven neonicotinoid residues in maize, millet and oat.
A method using dispersive solid-phase extraction and dispersive liquid–liquid micro-extraction cleanup followed by high performance liquid chromatography (HPLC) has been established for determination of seven neonicotinoid insecticides residues in grains including brown rice, maize, millet and oat. Based on an appraisal of the characteristics of HPLC, validation experiments were conducted for seven neonicotinoid insecticides. In the method, dispersive solid-phase extraction was carried out using PSA and bonded C18 coupled with graphitised carbon black with acetonitrile as the eluted solvent. In the linear range of each pesticide, the correlation coefficient was R2⩾0.99. At the low, medium and high three fortification levels of 0.05–0.8mgkg−1, recoveries fell within 76–123%. The relative standard deviation was between 0.9% and 12.6% for seven neonicotinoid pesticides. Low limits of detection (0.002–0.005mgkg−1) and quantification (0.007–0.018mgkg−1) were readily achieved with this method for all tested pesticides.
PDF
