Structural and optical performance of NiV/Ti multilayer mirrors for Z-pinch plasma diagnostic at the wavelength region of 350-450†eV.

This Letter reports on investigations of novel, to the best of our knowledge, NiV(Ni93V7)/Ti multilayer mirrors for the operation in the wavelength region of 350-450 eV. Such mirrors are promising optical components for the Z-pinch plasma diagnostic. The NiV/Ti multilayers show superior structural and optical performance compared to conventional Ni/Ti multilayers. Replacing Ni with NiV in multilayers decreases interface widths and enhances the contrast of the refractive index between the absorber and spacer layers. The improvement of interface quality contributes to the enhancement in reflectance. Under the grazing incidence of 13°, a peak reflectivity of 25.1% at 429 eV is achieved for NiV/Ti multilayers, while 17.7% at 427 eV for Ni/Ti.

Computational Screening of Promising Deep-Ultraviolet Light Emitters.

Deep-ultraviolet (DUV) light sources are technologically highly important, but DUV light-emitting materials are extremely rare; AlN and its alloys are the only materials known so far, significantly limiting the chemical and structural spaces for materials design. Here, we perform a high-throughput computational search for DUV light emitters based on a set of carefully designed screening criteria relating to the sophisticated electronic structure. In this way, we successfully identify 5 promising material candidates that exhibit comparable or higher radiative recombination coefficients than AlN, including BeGeN2, Mg3NF3, KCaBr3, KHS, and RbHS. Further, we unveil the unique features in the atomic and electronic structures of DUV light emitters and elucidate the fundamental genetic reasons why DUV light emitters are extremely rare. Our study not only guides the design and synthesis of efficient DUV light emitters but also establishes the genetic nature of ultrawide-band-gap semiconductors in general.

Interface-confined intermediate phase in TiO2 enables efficient photocatalysis.

As a prototypical photocatalyst, TiO[Formula: see text] has been extensively studied. An interesting yet puzzling experimental fact was that P25-a mixture of anatase and rutile TiO[Formula: see text]-outperforms the individual phases; the origin of this mysterious fact, however, remains elusive. Employing rigorous first-principles calculations, here we uncover a metastable intermediate structure (MIS), which is formed due to confinement at the anatase/rutile interface. The MIS has a high conduction-band minimum level and thus substantially enhances the overpotential of the hydrogen evolution reaction. Also, the corresponding band alignment at the interface leads to efficient separation of electrons and holes. The interfacial confinement additionally creates a wide distribution of the band gap in the vicinity of the interface, which in turn improves optical absorption. These factors all contribute to the enhanced photocatalytic efficiency in P25. Our insights provide a rationale to the puzzling superior photocatalytic performance of P25 and enable a strategy to achieve highly efficient photocatalysis via interface engineering.

Strain-induced electronic structures and band-gap of few-layer AgInP2S6.

The band gap and mechanical control ability of two-dimensional materials largely determine the application value of two-dimensional devices in optical and electronic properties, so the bandgap controllability of two-dimensional materials broadens the application range of multi-functional devices. In the layered van der Waals (vdW) material AgInP2S6, the band gap can be adjusted by the number of layers and flexible strain, and the few layers AgInP2S6have discrete band gap values, which are also relevant for optoelectronic applications. In the strain range of up to 2.7% applied, the band gap can be adjusted, and the film is relatively stable under strain. We further analyzed the physical mechanism of flexible strain band gap regulation and found that strain-regulation reduced the band gap and increased the chemical bond length. These studies open up new opportunities for the future development of vdW material photoelectric resonators represented by AgInP2S6, and have important reference value.

Bi nanoparticles confined in N,S co-doped carbon nanoribbons with excellent rate performance for sodium-ion batteries.

Bismuth (Bi) has emerged as a promising candidate for sodium-ion battery anodes because of its unique layered crystal structure, superior volumetric capacity, and high theoretical gravimetric capacity. However, the large volume expansion and severe aggregation of Bi during the alloying/dealloying reactions are extremely detrimental to cycling stability, which seriously hinders its practical application. To overcome these issues, we propose an effective synthesis of composite materials, encapsulating Bi nanoparticles in N,S co-doped carbon nanoribbons and composites with carbon nanotubes (N,S-C@Bi/CNT), using Bi2S3 nanobelts as templates. The uniform distribution of Bi nanoparticles and the structure of carbon nanoribbons can reduce the diffusion path of ions/electrons, efficiently buffer the large volume change and prevent Bi from aggregating during cycles. As expected, the N,S-C@Bi/CNT electrode shows superior sodium storage performance in half cells, including a high specific capacity (345.3 mA h g-1 at 1.0 A g-1), long cycling stability (1000 cycles), and superior rate capability (336.0 mA h g-1 at 10.0 A g-1).

Mixed stitching interferometry with correction from one-dimensional profile measurements for high-precision X-ray mirrors.

This work presents a mixed stitching interferometry method with correction from one-dimensional profile measurements. This method can correct the error of stitching angles among different subapertures using the relatively accurate one-dimensional profiles of the mirror, e.g., provided by the contact profilometer. The measurement accuracy is simulated and analyzed. The repeatability error is decreased by averaging multiple measurements of the one-dimensional profile and using multiple profiles at different measurement positions. Finally, the measurement result of an elliptical mirror is presented and compared with the global algorithm-based stitching, and the error of the original profiles is reduced to one-third. This result shows that this method can effectively suppress the accumulation of stitching angle errors in classic global algorithm-based stitching. The accuracy of this method can be further improved by using high-precision one-dimensional profile measurements such as the nanometer optical component measuring machine (NOM).

Comparison of thermal stability of Mo/Si multilayers with different crystallinities of Mo layers.

To investigate the thermal stability of Mo/Si multilayers with different initial crystallinities of Mo layers, two kinds of Mo/Si multilayers were deposited by DC magnetron sputtering and annealed at 300°C and 400°C. The period thickness compactions of multilayers with crystalized and quasi-amorphous Mo layers were 0.15 nm and 0.30 nm at 300°C, respectively, and the stronger the crystallinity, the lower the extreme ultraviolet reflectivity loss. At 400°C, the period thickness compactions of multilayers with crystalized and quasi-amorphous Mo layers were 1.25 nm and 1.04 nm, respectively. It was shown that multilayers with a crystalized Mo layer had better thermal stability at 300°C but were less stable at 400°C than multilayers with a quasi-amorphous Mo layer. These changes in stability at 300°C and 400°C were due to the significant transition of the crystalline structure. The transition of the crystal structure leads to increased surface roughness, more interdiffusion, and compound formation.

Influence of FeCo layer thickness on the interfacial asymmetry of FeCo/Si multilayers fabricated by direct current magnetron sputtering.

FeCo/Si is a promising material combination for polarized neutron supermirrors because of its appropriate optical constants. Five FeCo/Si multilayers with monotonically increasing FeCo layer thicknesses were fabricated. Grazing incidence x-ray reflectometry and high-resolution transmission electron microscopy were performed to characterize the interdiffusion and asymmetry of the interfaces. Selected area electron diffraction was used to determine the crystalline states of FeCo layers. It was found that the asymmetric interface diffusion layers existed in FeCo/Si multilayers. Furthermore, the FeCo layer started the transition from amorphous to crystalline when the thickness of the FeCo layer reached 4.0 nm.

Comparative Study on Microstructure of Mo/Si Multilayers Deposited on Large Curved Mirror with and without the Shadow Mask.

The Mo/Si multilayer mirror has been widely used in EUV astronomy, lithography, microscopy and other fields because of its high reflectivity at the wavelength around 13.5 nm. During the fabrication of Mo/Si multilayers on large, curved mirrors, shadow mask was a common method to precisely control the period thickness distribution. To investigate the effect of shadow mask on the microstructure of Mo/Si multilayers, we deposited a set of Mo/Si multilayers with and without the shadow mask on a curved substrate with aperture of 200 mm by direct current (DC) magnetron sputtering in this work. Grazing incidence X-ray reflectivity (GIXR), diffuse scattering, atomic force microscope (AFM) and X-ray diffraction (XRD) were used to characterize the multilayer structure and the EUV reflectivity were measured at the National Synchrotron Radiation Laboratory (NSRL) in China. By comparing the results, we found that the layer microstructure including interface width, surface roughness, layer crystallization and the reflectivity were barely affected by the mask and a high accuracy of the layer thickness gradient can be achieved.

Spectromicroscopy of Nanoscale Materials in the Tender X-Ray Regime Enabled by a High Efficient Multilayer-Based Grating Monochromator.

The combination of near edge X-ray absorption spectroscopy with nanoscale X-ray imaging is a powerful analytical tool for many applications in energy technologies, catalysis, which are critical to combat climate change, as well as microelectronics and life science. Materials from these scientific areas often contain key elements, such as Si, P, S, Y, Zr, Nb, and Mo as well as lanthanides, whose X-ray absorption edges lie in the so-called tender photon energy range 1.5-5.0 keV. Neither conventional grazing incidence grating nor crystal monochromators have high transmission in this energy range, thereby yielding the tender photon energy gap. To close this gap, a monochromator setup based on a multilayer coated blazed plane grating and plane mirror is devised. The measurements show that this novel concept improves the photon flux in the tender X-ray regime by two-orders-of-magnitude enabling previously unattainable laboratory and synchrotron-based studies. This setup is applied to perform nanoscale spectromicroscopy studies. The high photon flux provides sufficient sensitivity to obtain the electronic structure of Mo in platinum-free MoNi4 nanoparticles for electrochemical energy conversion. Additionally, it is shown that the chemical bonding of nano-structures in integrated circuits can be distinguished by the electronic configuration at the Si-K edge.

Effect of Ta Interlayers on Texture and Magnetic Properties of FeSi Films with Micrometer Thickness.

Magnetized soft ferromagnetic films with micrometer thickness were studied. A FeSi film, with a total thickness of 2000 nm, separated by 10 nm-thick Ta interlayers, was fabricated using the direct-current magnetron sputtering technique. The thickness of each FeSi layer between adjacent Ta layers was 100 nm. Hysteresis loop measurement was used to characterize the magnetic properties of the layer. X-ray diffraction patterns and high-resolution transmission electron microscopy were used to characterize its texture. The experimental results showed that the FeSi film separated by Ta interlayers exhibited a lower saturation magnetization and a higher coercivity than those of the 1140 nm-thick FeSi film. The insertion of Ta interlayers resulted in the disappearance of the crystal plane of FeSi (221), and better texture of the crystal plane of FeSi (210). The FeSi film exhibited a crystal plane of FeSi (210) with a bcc crystalline structure. The Ta interlayers were partially amorphous, exhibiting crystal plane of Ta (002) and TaSi2 (310). The matching of magnetic properties between interlayers and soft magnetic layers played an important role in maintaining its soft magnetic properties.

Cr/C multilayer growth on a heavy metal layer for upgrading of high efficiency tender x-ray gratings.

To increase efficiency of single layer gratings used in the tender x-ray range, a high reflectance multilayer can be directly grown on single layer gratings. Multilayer growth quality was studied by depositing the Cr/C multilayer on a Pt single layer using flat substrates. Their structure quality and adhesion were characterized by atomic force microscopy (AFM), grazing incidence x-ray reflectivity (GIXRR), x-ray scattering (XRS), x-ray diffraction (XRD), and layer adhesion measurement. AFM results showed that the surface roughness was 0.218 nm for the multilayer without the Pt layer and 0.272 nm for the multilayer with the Pt layer. As GIXRR results showed, the average interface widths were 0.39 nm for the multilayer without the Pt layer and 0.42 nm for the multilayer with the Pt layer. XRS results indicated that the existence of a Pt layer enlarged slightly the roughness of the multilayer. Simulation results exhibited that these slight changes caused by the Pt layer had an insignificant effect on reflectivity. As XRD results displayed, the crystallization of the Pt layer had negligible effects on the crystallization of Cr in films. The layer adhesion measurement revealed that the critical loads to peel off the layer from the substrate were 84.64 mN for the multilayer without the Pt layer and 33.99 mN for the multilayer with the Pt layer. After 6 months, the latter layer structure is undamaged, demonstrating that the coating is not easily peeled off. This study proves the feasibility to upgrade a low efficiency single Pt layer grating to a highly efficient multilayer grating.

Surface Morphology Evolution during Chemical Mechanical Polishing Based on Microscale Material Removal Modeling for Monocrystalline Silicon.

Chemical-mechanical polishing (CMP) is widely adopted as a key bridge between fine rotation grinding and ion beam figuring in super-smooth monocrystalline silicon mirror manufacturing. However, controlling mid- to short-spatial-period errors during CMP is a challenge owing to the complex chemical-mechanical material removal process during surface morphology formation. In this study, the nature of chemical and mechanical material removal during CMP is theoretically studied based on a three-system elastic-plastic model and wet chemical etching behavior. The effect of the applied load, material properties, abrasive size distribution, and chemical reaction rate on the polishing surface morphology is evaluated. A microscale material removal model is established to numerically predict the silicon surface morphology and to explain the surface roughness evolution and the source of nanoscale intrinsic polishing scratches. The simulated surface morphology is consistent with the experimental results obtained by using the same polishing parameters tested by employing profilometry and atomic force microscopy. The PSD curve for both simulated surface and experimental results by profilometry and atomic force microscopy follows linear relation with double-logarithmic coordinates. This model can be used to adjust the polishing parameters for surface quality optimization, which facilitates CMP manufacturing.

Tumor vessel normalization and immunotherapy in gastric cancer.

Gastric cancer (GC) is a common malignant tumor, and patients with GC have a low survival rate due to limited effective treatment methods. Angiogenesis and immune evasion are two key processes in GC progression, and they act synergistically to promote tumor progression. Tumor vascular normalization has been shown to improve the efficacy of cancer immunotherapy, which in turn may be improved through enhanced immune stimulation. Therefore, it may be interesting to identify synergies between immunomodulatory agents and anti-angiogenic therapies in GC. This strategy aims to normalize the tumor microenvironment through the action of the anti-vascular endothelial growth factor while stimulating the immune response through immunotherapy and prolonging the survival of GC patients.

Differences in the Sublethal Effects of Sulfoxaflor and Acetamiprid on the Aphis gossypii Glover (Homoptera: Aphididae) Are Related to Its Basic Sensitivity Level.

The cotton aphid, Aphis gossypii, is an important insect pest of many crops around the world, and it has developed resistance to a large number of frequently used insecticides. The sublethal effects of insecticides not only have an environmental risk to arthropods but also have the potential to promote resistance evolution. The sublethal effects (inhibitory or stimulatory) are influenced by many factors, such as the type of insecticide, sublethal concentrations, pest species, and others. In this study, the sublethal effects of sulfoxaflor and acetamiprid on A. gossypii were compared using two field-collected populations. The results show that sulfoxaflor was more toxic than acetamiprid against A. gossypii in both populations, the LC50 concentrations of acetamiprid and sulfoxaflor were 6.35 and 3.26 times higher, respectively, for the Jinghe population than for Yarkant. The LC25 concentration of acetamiprid significantly reduced adult longevity and fecundity in exposed adults (F0) of the Jinghe population, but it had no significant effects on these factors in Yarkant. Similar inhibitory effects were found in the F1 and F2 generations, but the biological traits in the Yarkant population were significantly reduced when the parents (F0) were exposed to LC25 of acetamiprid, whereas the changes in the Jinghe population were not significant. However, sublethal sulfoxaflor showed a stimulatory effect on A. gossypii in the F0 and F1 generation; the adult fecundity and longevity of the F0 generation were significantly higher in Jinghe, while the biological traits of the F1 generation were obviously higher in Yarkant. In the F2 generation, the r and λ were significantly higher in Jinghe; meanwhile, these biological traits were reduced in Yarkant. These results indicate that sulfoxaflor and acetamiprid had different sublethal effects on A. gossypii that varied by generation. In addition, we speculate that the genetic background and the resistance levels of A. gossypii may also influence the sublethal effects. Our findings are useful for assessing the overall effects of sulfoxaflor and acetamiprid on A. gossypii.

Pressure-Quenched Superconductivity in Weyl Semimetal NbP Induced by Electronic Phase Transitions under Pressure.

The TaAs family (NbAs, TaAs, NbP, TaP) are kinds of Weyl semimetals with lots of novel properties, thus attracting considerable attention in recent years. Here, we systematically studied the Weyl semimetal NbP up to 72 GPa through the resistivity, Raman spectra, X-ray diffraction measurements, and first-principles density functional theory (DFT) calculations. A pressure-induced semimetal-metal transition was observed at ∼36 GPa, which was further confirmed by the DFT calculations. With further compression up to 52 GPa, a superconducting state was observed. Interestingly, the Tc increases significantly upon decompression and shows a dome-shaped trend as a function of pressure. Surprisingly, the pressure-induced superconductivity can be quenched to ambient pressure, and all transitions under pressure do not involve any structural change. Our work not only depicts a phase diagram of the NbP system under high pressure but also provides a new experimental insight for superconductivity in Weyl semimetals.

Ultrafast Time-Resolved Pump-Probe Investigation of Nanosecond Extreme Ultraviolet-Light-Induced Damage Dynamics on B4C/Ru Nano-Bilayer Film.

An ultrafast time-resolved pump-probe setup with both high temporal and spatial resolution is developed to investigate the transient interaction between a nanosecond extreme ultraviolet (EUV) pulse and matter. By using a delayed femtosecond probe pulse, the pattern evolution of surface modification induced by an EUV pump at a wavelength of 13.5 nm can be imaged at different delay times, which provides deep insight into the EUV-induced damage dynamics and damage mechanisms. As a demonstration, single-shot EUV damage on a B4C(6.0 nm)/Ru(30.4 nm)/D263 nano-bilayer optical film is studied using this pump-probe method. A recoverable phenomenon is found during the evolution process of the dome-shaped damage region. This is explained by the elastic and plastic deformations resulting from the huge compressive stress difference at the Ru-substrate interface with the help of simulations on the thermal effects and mechanical responses. This damage mechanism is further proven by the complementary experiments at a higher EUV fluence at 13.5 nm.

Cr/C lamellar multilayer grating in conical diffraction mounting for beam splitter used in X-ray free-electron lasers.

A lamellar multilayer grating in a conical diffraction mounting was proposed as a beam splitter for X-ray free-electron lasers. Theoretical calculations demonstrated that the distribution of diffraction efficiency can be adjusted by optimizing the groove depth or d-spacing. A Cr/C multilayer lamellar grating with a line density of approximately 2500 L/mm was fabricated. The performance of the element was measured in the Optics Beamline PM-1 (BESSY-II) at an energy of 1500 eV. A five-order diffraction pattern was recognized, and the diffraction efficiencies of the -/+first-order were approximately 12.6 and 4.4%, respectively. The asymmetric distribution of diffraction efficiency can be caused by the different sidewall angles of the grating groove.

Individual participant data (IPD)-level meta-analysis of randomised controlled trials to estimate the vitamin D dietary requirements in dark-skinned individuals resident at high latitude.

CONTEXT AND PURPOSE: There is an urgent need to develop vitamin D dietary recommendations for dark-skinned populations resident at high latitude. Using data from randomised controlled trials (RCTs) with vitamin D3-supplements/fortified foods, we undertook an individual participant data-level meta-regression (IPD) analysis of the response of wintertime serum 25-hydroxyvitamin (25(OH)D) to total vitamin D intake among dark-skinned children and adults residing at ≥ 40° N and derived dietary requirement values for vitamin D. METHODS: IPD analysis using data from 677 dark-skinned participants (of Black or South Asian descent; ages 5-86 years) in 10 RCTs with vitamin D supplements/fortified foods identified via a systematic review and predefined eligibility criteria. Outcome measures were vitamin D intake estimates across a range of 25(OH)D thresholds. RESULTS: To maintain serum 25(OH)D concentrations ≥ 25 and 30 nmol/L in 97.5% of individuals, 23.9 and 27.3 µg/day of vitamin D, respectively, were required among South Asian and 24.1 and 33.2 µg/day, respectively, among Black participants. Overall, our age-stratified intake estimates did not exceed age-specific Tolerable Upper Intake Levels for vitamin D. The vitamin D intake required by dark-skinned individuals to maintain 97.5% of winter 25(OH)D concentrations ≥ 50 nmol/L was 66.8 µg/day. This intake predicted that the upper 2.5% of individuals could potentially achieve serum 25(OH)D concentrations ≥ 158 nmol/L, which has been linked to potential adverse effects in older adults in supplementation studies. CONCLUSIONS: Our IPD-derived vitamin D intakes required to maintain 97.5% of winter 25(OH)D concentrations ≥ 25, 30 and 50 nmol/L are substantially higher than the equivalent estimates for White individuals. These requirement estimates are also higher than those currently recommended internationally by several agencies, which are based predominantly on data from Whites and derived from standard meta-regression based on aggregate data. Much more work is needed in dark-skinned populations both in the dose-response relationship and risk characterisation for health outcomes. TRAIL REGISTRATION: PROSPERO International Prospective Register of Systematic Reviews (Registration Number: CRD42018097260).

Understanding Physical Activity Patterns Across the School Day in Urban Pre-Kindergarten and Elementary Schoolchildren.

PURPOSE: Despite recommendations that children accrue ≥60 min/day of moderate-to-vigorous physical activity (MVPA), numerous barriers may exist. We examined school-day MVPA patterns in lower-income children (pre-K to 5th grade) to determine whether they were meeting the minimum school-day guidelines of at least 30-min/day of MVPA and to identify opportunities for intervention. METHODS: Students (N = 629, pre-K-5th grade) from 4 urban schools wore Actigraph GT3X+ accelerometers over 2 school days. Mixed effects models evaluated sex- and grade-specific differences in MVPA and sedentary time. RESULTS: Only 34.6% of elementary and 25.3% of pre-K students met the school-time MVPA recommendation. Among elementary-aged children, boys accrued more MVPA than girls (30.8 ± 13.3 vs. 23.5 ± 10.7 min/day; p < 0.0001) with similar sex differences observed among pre-K children (51.3 ± 17.1 vs 41.9 ± 17.5 min/day; p < 0.001). Sedentary time also increased significantly with grade among elementary-aged children (207.9 ± 34.7 vs. 252.0 ± 36.1 min/day for those in 1st and 5th grade, respectively; p < 0.001), with girls accruing more sedentary time than boys (242.5 ± 48.2 vs. 233.8 ± 46.8 min/day; p < 0.0001). CONCLUSION: MVPA declines across elementary school years, with sex disparities observed as early as pre-K. Extended sedentary bouts and clustering of activity highlight opportunities for more movement throughout the school day.