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Despite high altitude was implicated in adverse birth outcomes, there remained a paucity of evidence on low-to-medium altitude effect. This study aimed to explore the association of low-to-medium altitude with birth outcomes. A population-based cross-sectional survey was performed using a stratified multistage random sampling method among women with their infants born during 2010–2013 in Northwestern China. Altitude was determined in meters based on the village or community of the mother’s living areas. Birth outcomes involved birth weight, gestational age, and small for gestational age (SGA). Generalized linear models were fitted to investigate the association of altitude with birth outcomes. Moreover, the dose–response relationship between altitude and birth outcomes was evaluated with a restricted cubic spline function. A total of 27 801 women with their infants were included. After adjusting for potential confounders, every 100-m increase in the altitude was associated with reduced birth weight by 6.4 (95% CI −8.1, −4.6) g, the slight increase of gestational age by 0.015 (95% CI 0.010, 0.020) week, and an increased risk of SGA birth (odds ratio 1.03, 95% CI 1.02, 1.04). Moreover, there was an inversely linear relationship between altitude and birth weight (P for overall < 0.001 and P for nonlinear = 0.312), and a positive linear relationship between altitude and SGA (P for overall < 0.001 and P for nonlinear = 0.194). However, a nonlinear relationship was observed between altitude and gestational age (P for overall < 0.001 and P for nonlinear = 0.010). The present results suggest that low-to-medium altitude is possibly associated with adverse birth outcomes.
The nitrogen-decorated CeO2/reduced graphene oxide nanocomposite (CeO2/N-rGO) was one-step synthesized by a facile hydrothermal technique and applied as counter electrode materials for dye-sensitized solar cells (DSSCs). For comparison, CeO2/rGO and rGO were also synthesized by adjusting corresponding reactants. It was found that the as-synthesized CeO2/N-rGO shows better electrocatalytic activity for triiodide/iodide reduction than that of pure rGO and CeO2/rGO, and a synergistic effect of nitrogen and CeO2 on the rGO sheets was observed. The photoelectric conversion efficiency of DSSCs based on CeO2/N-rGO counter electrode was 3.20%, which is higher than that of CeO2/rGO (2.45%) and rGO counter electrode (1.37%). Furthermore, the synergistic effect of nitrogen and CeO2 on the rGO sheets was also discussed in detail with different CeO2 amount levels. It is believed that this one-step synthetic method is a potential way to synthesize low-cost and efficient rGO-based multiple composited counter electrode materials to replace more expensive Pt.
Topological quantum materials are a class of compounds featuring electronic band structures, which are topologically distinct from common metals and insulators. These materials have emerged as exceptionally fertile ground for materials science research. The topologically nontrivial electronic structures of these materials support many interesting properties, ranging from the topologically protected states, manifesting as high mobility and spin-momentum locking, to various quantum Hall effects, axionic physics, and Majorana modes. In this article, we describe different topological matters, including topological insulators, Weyl semimetals, twisted graphene, and related two-dimensional Chern magnetic insulators, as well as their heterostructures. We focus on recent materials discoveries and experimental advancements of topological materials, and their heterostructures. Finally, we conclude with prospects for the discovery of additional topological materials for studying quantum processes, quasiparticles and their composites, as well as exploiting potential applications of these materials.
Fluid motion has two well-known fundamental processes: the vector transverse process characterized by vorticity, and the scalar longitudinal process consisting of a sound mode and an entropy mode, characterized by dilatation and thermodynamic variables. The existing theories for the sound mode involve the multi-variable issue and its associated difficulty of source identification. In this paper, we define the source of sound inside the fluid by the objective causality inherent in dynamic equations relevant to a longitudinal process, which naturally favours the material time-rate operator
rather than the local time-rate operator
, and describes the sound mode by inhomogeneous advective wave equations. The sources of sound physical production inside the fluid are then examined at two levels. For the conventional formulation in terms of thermodynamic variables at the first level, we show that the universal kinematic source can be condensed to a scalar invariant of the surface deformation tensor. Further, in the formulation in terms of dilatation at the second level, we find that the sound mode in viscous and heat-conducting flow has sources from rich nonlinear couplings of vorticity, entropy and surface deformation, which cannot be disclosed at the first level. Preliminary numerical demonstration of the theoretical findings is made for two typical compressible flows, i.e. the interaction of two corotating Gaussian vortices and the unsteady type IV shock/shock interaction. The results obtained in this study provide a new theoretical basis for, and physical insight into, understanding various nonlinear longitudinal processes and the interactions therein.
Flexural-gravity wave interactions with multiple cracks in an ice sheet of infinite extent are considered, based on the linearized velocity potential theory for fluid flow and thin elastic plate model for an ice sheet. Both the shape and location of the cracks can be arbitrary, while an individual crack can be either open or closed. Free edge conditions are imposed at the crack. For open cracks, zero corner force conditions are further applied at the crack tips. The solution procedure starts from series expansion in the vertical direction based on separation of variables, which decomposes the three-dimensional problem into an infinite number of coupled two-dimensional problems in the horizontal plane. For each two-dimensional problem, an integral equation is derived along the cracks, with the jumps of displacement and slope of the ice sheet as unknowns in the integrand. By extending the crack in the vertical direction into the fluid domain, an artificial vertical surface is formed, on which an orthogonal inner product is adopted for the vertical modes. Through this, the edge conditions at the cracks are satisfied, together with continuous conditions of pressure and velocity on the vertical surface. The integral differential equations are solved numerically through the boundary element method together with the finite difference scheme for the derivatives along the crack. Extensive results are provided and analysed for cracks with various shapes and locations, including the jumps of displacement and slope, diffraction wave coefficient, and the scattered cross-section.
LiMnxCoyNi1−x−yO2 (LMCNO) has been broadly investigated and commercialized primarily as lithium ion battery (LIB) cathodes, owing to its high operating voltage, large energy density, and superior electronic conductivity. However, poor cycling stability induced by the rapid structure degradation limits their further development. Coating is regarded as a very effective strategy to address the problem of structure degradation. Regrettably, the coating layers obtained by traditional methods are usually thick, which is not appropriate for delivering of integrated performance. As an emerging coating technology, atomic layer deposition (ALD) demonstrates immeasurable advantages in deposition of ultrathin coating materials because of its atomic-level precision, and has been widely applied in construction of the coating layers on LMCNO substrate materials. Herein, we firstly outline the development and mechanism of ALD technology, and then systematically summarize intrinsic reasons for the enhanced electrochemical performance. Finally, we propose new insights toward designing and preparing the coating structure of LMCNO cathodes by controllable ALD for the next-generation LIBs.
The development of GaN-on-diamond devices offers bright prospects for the creation of high-power density electronics. This article presents a process of fabricating GaN-on-diamond structure by depositing diamond films on dual sides, including heat dissipation diamond film and sacrificial carrier diamond film. Prior to heat dissipation diamond film layer preparation, aluminum nitride (AlN) is chosen as a dielectric layer and pretreated by nanodiamond (ND) particles, to enhance the nucleation density. Zeta potential measurements and X-ray photoelectron spectroscopy are used to analyze the AlN surface after each treatment. The results show that oxygen-terminated ND particles tend to adhere to an AlN surface because the oxygen-terminated NDs have –COOH and –OH groups, and hold a negative potential. On the contrary, fluorine-terminated AlN prefers to attract the hydrogen-terminated ND seeds, which resulted in higher diamond nucleation density. Based on this preliminary study, a dense high-quality GaN-on-diamond wafer is successfully produced by using AlN as the dielectric layer and a diamond film as the sacrificial carrier.
The experimental study on thermocapillary convection in liquid bridges of large Prandtl number has been carried out on Tiangong-2 in space. The purpose of these experiments is to study the oscillation instability of thermocapillary convection, and to discover and recognize the mechanism of destabilization of thermocapillary convection in the microgravity environment in space. In this paper, the geometry of a half-floating-zone liquid bridge is featured by the aspect ratio Ar and volume ratio Vr, and its influence on critical conditions of oscillatory thermocapillary convection is studied. More than 700 sets of space experiments have been finished. The critical conditions and oscillation characteristics of thermocapillary convection instability in the Ar–Vr parameter space have been fully obtained under microgravity conditions for the first time. It is found that the Ar–Vr parameter space can be divided into two regions of different critical conditions and oscillation characteristics: the region of low frequency oscillation, and the region of high frequency oscillation. More importantly, we obtain the complete configuration of these two stability neutral curves, and find that the low frequency mode is a ‘’ type curve. Based on this, we discuss the influence of heating rate on the oscillation mode. It is found that the heating rate affects the selection of critical mode, which results in a jump change of critical temperature difference. The findings of this study are helpful to better understand the critical modes and transition processes of thermocapillary convection in liquid bridges with different configurations.
This study aimed to identify the important capacities that were most urgently needed during emergency response and factors associated with the Centers for Disease Control and Prevention (CDC) professionals’ field coping-capacity for public health emergency.
Professional workers (N = 1854) from 40 CDC institutions were chosen using the stratified cluster random sampling method in all 13 municipalities of Heilongjiang Province, China. Descriptive analysis and multivariate logistic regression were used.
Of 10 key capacities, the 3 that were most urgently needed during emergency response fieldwork as identified by respondents were crisis communication capacity, personal protection capacity, and laboratory detection capacity. Overall, 38.1% of respondents self-rated as “poor” on their coping-capacity. The logistic regression found that proficiency in emergency preparedness planning, more practical experiences in emergency response, effectiveness in training and drills, a higher education level, and a higher professional position were significantly associated with the individual’s field coping-capacity.
This study identified CDC professionals’ most urgent capacity need and the obstructive factors and highlighted the importance of enhancing the capacity in crisis communication, personal protection, and laboratory detection. Intervention should be targeted at sufficient fund, formalized, and effective emergency training and drills, more operational technical guidance, and all-around supervision and evaluation.
Thermocapillary convection has always been one of the most important research topics in microgravity fluid physics. A space experimental study on the thermocapillary convection in an open annular liquid pool – a typical thermocapillary flow system – has been conducted on the SJ-10 satellite of China. This space experiment has observed the spatial temperature distribution of the liquid free surface using an infrared thermal imager, obtained the flow pattern transition process, analysed the oscillation characteristics and revealed the instability mechanism of themocapillary convection. The shape effects on the flow instability are researched by changing the volume ratio, Vr, which denotes the ratio of the liquid volume to the volume of the cylindrical gap between the walls. The volume ratio effect has been focused on for the first time. For a certain volume ratio, the flow pattern would transform from the steady state to the oscillation state accompanied by directional propagating hydrothermal waves with increasing temperature difference. In addition, the significant influences of the volume ratio on the critical conditions and wavenumber selection have been analysed in detail.
Harnessing the nonvolatility of magnetism and the power of electric control, magnetoelectric devices that control magnetism electrically promise to deliver next-generation electronics systems that can store and compute large amounts of information with minimal power consumption and ultrafast processing speed. We highlight progress in magnetoelectric memory and logic prototypes using the voltage-controlled magnetic anisotropy (VCMA) effect. First, important performance metrics of VCMA-based magnetoelectric random access memory (MeRAM) are benchmarked against embedded complementary metal oxide semiconductor and other emerging embedded nonvolatile memories. We then discuss scaling of MeRAM from the physics and materials perspectives of the VCMA effect, as well as the use of magnetoelectric logic devices and circuits to realize new computing paradigms with VCMA. Finally, challenges to realize the full potential of VCMA-based memory and logic are presented: VCMA coefficient of 1000 fJ/V-m for energy-efficient write with low errors and tunneling magnetoresistance of 1000% for high density and low noise margin readout. New approaches for deterministic switching based on VCMA are needed. We share perspectives to address these challenges using new materials and device operation schemes.
To examine the association between household food insecurity and dietary diversity in the past 24h (dietary diversity score (DDS, range: 0–9); minimum dietary diversity (MDD, consumption of three or more food groups); consumption of nine separate food groups) among pregnant and lactating women in rural Malawi.
Two rural districts in Central Malawi.
Pregnant (n 589) and lactating (n 641) women.
Of surveyed pregnant and lactating women, 66·7 and 68·6 %, respectively, experienced moderate or severe food insecurity and only 32·4 and 28·1 %, respectively, met MDD. Compared with food-secure pregnant women, those who reported severe food insecurity had a 0·36 lower DDS (P<0·05) and more than threefold higher risk (OR; 95 % CI) of not consuming meat/fish (3·19; CI 1·68, 6·03). The risk of not consuming eggs (3·77; 1·04, 13·7) was higher among moderately food-insecure pregnant women. Compared with food-secure lactating women, those who reported mild, moderate and severe food insecurity showed a 0·36, 0·44 and 0·62 lower DDS, respectively (all P<0·05). The risk of not achieving MDD was higher among moderately (1·95; 1·06, 3·59) and severely (2·82; 1·53, 5·22) food-insecure lactating women. The risk of not consuming meat/fish and eggs increased in a dose–response manner among lactating women experiencing mild (1·75; 1·01, 3·03 and 2·81; 1·09, 7·25), moderate (2·66; 1·47, 4·82 and 3·75; 1·40, 10·0) and severe (5·33; 2·63, 10·8 and 3·47; 1·19, 10·1) food insecurity.
Addressing food insecurity during and after pregnancy needs to be considered when designing nutrition programmes aiming to increase dietary diversity in rural Malawi.
Despite their importance in the formation and evolution of stellar clusters and galaxies, the formation of high-mass stars remains poorly understood. We recently started a systematic observational study of the 22 GHz water and 44 GHz class I methanol masers in high-mass star-forming regions as a four-year KaVA large program. Our sample consists of 87 high-mass young stellar objects (HM-YSOs) in various evolutionary phases, many of which are associated with two or more different maser species. The primary scientific goals are to measure the spatial distributions and 3-dimensional velocity fields of multiple maser species, and understand the dynamical evolution of HM-YSOs and their circumstellar structures, in conjunction with follow-up observations with JVN/EAVN (6.7 GHz class II methanol masers), VERA, and ALMA. In this paper we present details of our KaVA large program, including the first-year results and observing/data analysis plans for the second year and beyond.
In light of government investment over the past decade, we explored the capacity for disaster response in Heilongjiang Province, identifying the factors that affect response capacity.
We surveyed 1257 medical staff in 65 secondary and tertiary hospitals in Heilongjiang province to explore their perceptions of disaster management capacity using a cross-sectional multistage, stratified cluster sampling method.
All tertiary hospitals (100%) and most secondary hospitals (93%) have documented disaster management plans that are regularly reviewed. In secondary hospitals, drills were less prevalent (76.7%) but the occurrence of simulated training exercises was closer to tertiary hospitals (86.0%). We noted that 95.4% of all hospitals have leadership groups responsible for disaster preparedness capacity building, but only 10.8% have a stockpiled network of reserve supplies.
Although response capacity has improved in Heilongjiang Province, vulnerabilities remain. We recommend that priorities should be targeted at preparedness capacity building, in terms of reliable and relevant operational response plans, the expansion of existing response mechanisms to oversee local education and scenario training, and to ensure there is sufficient access to protective equipment and materials, either held in reserve, or alternatively by activating resilient supply chain mechanisms. (Disaster Med Public Health Preparedness. 2018;12:176–183)
Novel hybrid diblock copolymers consisting of bidentate ligand-functionalized chains have been synthesized via click reaction and RAFT radical polymerization. The chemical structure and molecular weight of the synthesized poly(methacrylate-POSS)-block-poly(4-vinylbenzyl-2-pyridine-1H-1,2,3-triazole) (PMAPOSS-b-PVBPT) were characterized by NMR and GPC. The copolymers had been utilized to construct metal-containing polymer micelle by the metal–ligand coordination and electrostatic interaction in this study. The self-assembly behaviors of PMAPOSS-b-PVBPT in chloroform, a common solvent, under the effect of Zn(OTf)2 and HAuCl4 were investigated by TEM, DLS, and variable temperature NMR. Besides, micellization of this diblock copolymer was achieved in ethylene glycol, a selective solvent for PMAPOSS-b-PVBPT. The experimental results revealed that the incorporation of heterocyclic rings bearing nitrogen atoms in polymer side chains played an important role in the construction of metal-containing copolymer micelles. The prepared metal-containing PMAPOSS-b-PVBPT micelles had good dynamic and thermal stability due to the strong metal–ligand coordination interaction and electrostatic interaction.