Search

A temperature measurement subsystem (TMS) is a critical piece of infrastructure of the space gravitational wave detection platform, necessary for monitoring minuscule temperature changes at the level of 1 μ K / Hz 1 / 2 within the electrode house, in the frequency range of 0.1 mHz to 1 Hz . The voltage reference (VR), a key component of the TMS, must possess low noise characteristics in the detection band to minimize the impact on temperature measurements. However, the noise characteristics of the voltage reference in the sub-millihertz range have not been documented yet and require further study. This paper reports a dual-channel measurement method for measuring the low-frequency noise of VR chips down to 0.1 mHz . The measurement method makes use of a dual-channel chopper amplifier and an assembly thermal insulation box to achieve a normalized resolution of 3 × 10 − 7 / Hz 1 / 2 @ 0.1 mHz in the VR noise measurement. The seven best-performance VR chips documented at a common frequency range are tested. The results show that their noise at sub-millihertz frequencies can significantly differ from that around 1 Hz . [ABSTRACT FROM AUTHOR]

Flat-top Sun shield is a part of the disturbance reducing system on the space-based gravitational wave detector TianQin. The Sun shield is expected to guards temperature stability of the satellite's top deck from the low-frequency solar flux fluctuation. This paper introduces an analytic method to study the Sun shield's temperature response to sinusoidal variations of incoming heat flux. Oscillation mode of temperature field is described in the form of wave equation, which satisfies globally the thermal diffusion equation. The continuity equation is solved to reveal the wave behaviours when crossing different media. Three typical boundary conditions are studied in order to solve the wave equation. By applying the method to the TianQin's thermal model, the low-frequency temperature response of the Sun shield and the top deck are derived. The results suggest adopting insulation materials with low thermal diffusivity in the thermal design to shield the solar disturbances. [ABSTRACT FROM AUTHOR]

The statics and dynamics of supercooled water in the hydration layer of poly(ethylene glycol) (PEG) were studied by a combination of quasi-elastic neutron scattering (QENS) and molecular dynamics (MD) simulations. Two samples, that is, hydrogenated PEG/deuterated water (h-PEG/D2O) and fully deuterated PEG/hydrogenated water (d-PEG/H2O) with the same molar ratio of ethylene glycol (EG) monomer to water, 1:1, are compared. The QENS data of h-PEG/D2O show the dynamics of PEG, and that of d-PEG/H2O reveals the motion of water. The temperature-dependent elastic scattering intensity of both samples has shown transitions at supercooled temperature, and these transition temperatures depend on the energy resolution of the instruments. Therefore, neither one is a phase transition, but undergoes dynamic process. The dynamic of water can be described as an Arrhenius to super-Arrhenius transition, and it reveals the hydrogen bonding network relaxation of hydration water around PEG at supercooled temperature. Since the PEG-water hydrogen bond structural relaxation time from MD is in good agreement with the average relaxation time from QENS (d-PEG/H2O), MD may further reveal the atomic pictures of the supercooled hydration water. It shows that hydration water molecules form a series of pools around the hydrophilic oxygen atom of PEG. At supercooled temperature, they have a more bond ordered structure than bulk water, proceed a trapping sites diffusion on the PEG surface, and facilitate the structural relaxation of PEG backbone. [ABSTRACT FROM AUTHOR]

Titanium dioxide (TiO2) is a promising electrode material for reversible lithium storage. However, the poor electronic conductivity, sluggish diffusivity, and intrinsic kinetics limit hinder its fast lithium storage capability. Here we present that the oxygen‐deficient TiO2 hierarchical spheres can address the issues for high capacity, long‐term lithium‐ion battery anode. First‐principles calculations show that introducing oxygen vacancies to anatase TiO2 can reduce the bandgap, thus improving the electronic conductivity and further the lithium storage properties of TiO2. By annealing TiO2/H2Ti5O11⋅3H2O hierarchical spheres precursor in nitrogen, accompanying with the phase transfer process, the growth of TiO2 crystallites is restricted due to the generation of residual carbon species, resulting in a well maintained hierarchical spherical structure. Rich oxygen vacancies are generated in the oxygen‐deficient environment and evidenced by EPR, XPS, and UV‐Vis spectra, which enable the TiO2 hierarchical spheres reduced bandgap. The oxygen vacancies in the as‐obtained TiO2 hierarchical spheres together with the high structural integrity of the hierarchical spheres gives rise to superior lithium storage properties including a high specific capacity of 282 mAh g−1 at 200 mA g−1, and long‐term cycling stability with a capacity retention of 85.2 % at 4 A g−1 over 10000 cycles. [ABSTRACT FROM AUTHOR]

TianQin is a proposed space-borne gravitational wave observatory in high geocentric orbits, exposed to radiating heat sources in space. Due to the stringent thermal stability requirements from the key payloads, the analysis of space thermal environment is of great importance. This paper studies the incident thermal radiation onto the TianQin satellites from the Sun–Earth–Moon system. The solar constant fluctuation (SCF) and the Earth's land-type features, based on the meteorological data, are considered, and an analytic function of lunar surface temperature is used. The analysis includes the solar radiation, the infrared radiation, and the albedo. The results are discussed in both time and frequency domains. The spectral analysis indicates that in the target frequency band of 0.1 mHz–1 Hz, the SCF plays a dominant role, and that the associated incident thermal disturbance is ∼5 W m−2 Hz−1/2 for TianQin, at the same level of the LISA in heliocentric orbits. In addition, the power spectra of the Earth's and Moon's heating fluctuation are given, both order-of-magnitude weaker than that of the solar radiation. The results may contribute to the thermal design and the noise analysis for TianQin. [ABSTRACT FROM AUTHOR]

Understanding the multiple phase transitions such as collapse transition, phase separation, and crystallization in solutions is of fundamental importance to control the solution structure of conjugated polymers in device processing. Combining in situ synchrotron radiation small and wide‐angle X‐ray scattering, ultrasensitive differential scanning calorimetry, ultraviolet–visible absorption spectroscopy, and polarized optical microscopy, we investigate the order–disorder transitions in poly(3‐hexylthiophene)/toluene solutions during cooling and heating processes. We demonstrate the occurrence of collapse transition of polymer chains from a random coil state to a lower dimensional network prior to the onset of crystallization during cooling in solution. This conformational preordering can lead to the formation of a lyotropic liquid crystalline phase, which is of great significance to the crystallization and ordering in polymer films, and further to promote its electric performance. It is examined that the mobility of films cast from chain‐collapsed solutions can be one order of magnitude higher than that from isotropic solutions with random‐coiled conformations. Thus, the conformational preordering in solutions is proposed to be a more efficient way than the postannealing of films to improve the electric performance of conjugated polymer films. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2019, 57, 1105–1114 [ABSTRACT FROM AUTHOR]

TianQin is a geocentric space-based gravitational-wave observatory mission consisting of three drag-free controlled satellites in an equilateral triangle with an orbital radius of 1 0 5 km. The constellation faces the white-dwarf binary RX J0806.3 + 1527 located slightly below the ecliptic plane, and is subject to gravitational perturbations that can distort the formation. In this study, we present combined methods to optimize the TianQin orbits so that a set of 5-year stability requirements can be met. Moreover, we discuss slow long-term drift of the detector pointing due to orbital precession, and put forward stable orbits with six other pointings along the lunar orbital plane. Some implications of the findings are pointed out. [ABSTRACT FROM AUTHOR]

Two new oxovanadium(V) complexes, [VOL(mat)] (1) and [VOL(Et‐mat)] (2) (mat = maltolate, Et‐mat = ethyl maltolate), where L is the dianionic form of N′‐(3‐ethoxy‐2‐hydroxybenzylidene)‐3‐hydroxy‐4‐methoxybenzohydrazide (H2L), were prepared and characterized by elemental analysis, IR, UV/Vis, and 1H NMR spectra. The structures of the compounds were further confirmed by single‐crystal X‐ray diffraction. The hydrazone ligand coordinates to the V atoms through the phenolate oxygen, imino nitrogen, and enolate oxygen. The maltolate and ethyl maltolate ligands coordinated to the V atoms through the carbonyl oxygen and deprotonated hydroxyl oxygen. The V atom in each complex is in octahedral coordination. The complexes were administered intragastrically to both normal and alloxan‐diabetic mice for two weeks. The biological activity results show that the complexes at doses of 10.0 and 20.0 mg V·kg–1, can significantly decrease the blood glucose level in alloxan‐diabetic mice, but the blood glucose level in the treated normal mice was not altered. [ABSTRACT FROM AUTHOR]

This paper concerns the fundamental limitations of disturbance rejection for linear time-invariant discrete-time systems under the assumption that the sensor noise is ignorable. The environmental disturbance is modelled as a linear combination of a step signal, a stationary stochastic signal and several sinusoidal signals with different frequencies. Disturbance rejection is measured by the steady-state variance of the residual input of the plant. In studying this problem, it is shown that for minimum phase systems, perfect disturbance rejection can be achieved by minimising the closed-loop sensitivity function. Unlike the minimum phase systems, the performance limitations for non-minimum phase systems are lower bounded by its non-minimum phase zeros, unstable poles and characteristic quantities of the disturbance, where the typical and integral-type control are respectively addressed. Numerical examples are provided to illustrate the utility of the results by analysing the achievable performance. [ABSTRACT FROM AUTHOR]

ABSTRACT The effect of different functional groups of methylated urea on the phase transition of poly( N-isopropylacrylamide) (PNIPAM) aqueous solutions has been studied by a high-sensitivity differential scanning calorimetry. The results reveal that with the addition of osmolytes with NH groups, the enthalpy change increases with the number of DSC cycles, presumably due to the gradual formation of hydrogen bonds with dehydrated CO groups of PNIPAM at high temperature. Moreover, with the addition of tetramethylurea (TMU) without hydrogen bond donor groups, the enthalpy change of PNIPAM solution remains unchanged with the number of DSC cycles and decreases with the TMU concentration, suggesting that the van der Waals interactions between TMU and isopropyl groups of PNIPAM and the weakening of hydrophobic interactions between isopropyl groups play a dominant role in the effect of TMU on the phase transition of PNIPAM. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2016, 54, 1145-1151 [ABSTRACT FROM AUTHOR]

Background: Several occupational stress studies of healthcare workers have predicted a high prevalence of anxiety symptoms, which can affect their quality of life and the care that they provide. However, few studies have been conducted among community healthcare workers in China. We attempted to explore whether burnout mediates the association between occupational stress and anxiety symptoms. Methods: A cross-sectional survey was completed in Liaoning Province, China from November to December 2012. A total of 1,752 healthcare workers from 52 Community Health Centers participated in this study, and all participants were given self-administered questionnaires. These questionnaires addressed the following aspects: the Zung Self-Rating Anxiety Scale, the Chinese version of the effort-reward imbalance scale and the Maslach Burnout Inventory–General Survey. Finally, the study included 1,243 effective respondents (effective response rate, 70.95%). Hierarchical linear regression analysis, performed with SPSS 17.0, was used to estimate the effect of burnout. Results: The prevalence of anxiety symptoms among the community healthcare workers was 38.0%. After adjusting for demographic characteristics, the effort–reward ratio and overcommitment positively predicted anxiety symptoms. Meanwhile, the effort–reward ratio and overcommitment were positively related to the emotional exhaustion and cynicism subscales of burnout. In addition, the emotional exhaustion and cynicism subscales were positively related to anxiety symptoms. Thus, there is a link between burnout, occupational stress and anxiety symptoms. Conclusions: Burnout mediates the effect of occupational stress on anxiety symptoms. To effectively reduce the impact of occupational stress on anxiety symptoms, burnout management should be considered. [ABSTRACT FROM AUTHOR]

A facile method to prepare a self-healing polymeric material with tunable mechanical properties is developed. The material has a remarkable self-healing efficiency via the formation of multiple dynamic hydrogen bonds. It can resist the corrosion of various organic solvents and can also be readily processed into a range of shapes. [ABSTRACT FROM AUTHOR]

Human upstream binding factor (hUBF) HMG Box-5 is a highly conserved protein domain, containing 84 amino acids and belonging to the family of the nonspecific DNA-binding HMG boxes. Its native structure adopts a twisted L shape, which consists of three α-helices and two hydrophobic cores: the major wing and the minor wing. In this article, we report a reversible three-state thermal unfolding equilibrium of hUBF HMG Box-5, which is investigated by differential scanning calorimetry (DSC), circular dichroism spectroscopy, fluorescence spectroscopy, and NMR spectroscopy. DSC data show that Box-5 unfolds reversibly in two separate stages. Spectroscopic analyses suggest that different structural elements exhibit noncooperative transitions during the unfolding process and that the major form of the Box-5 thermal intermediate ensemble at 55°C shows partially unfolded characteristics. Compared with previous thermal stability studies of other boxes, it appears that Box-5 possesses a more stable major wing and two well separated subdomains. NMR chemical shift index and sequential 1HN i-1HN i+1 NOE analyses indicate that helices 1 and 2 are native-like in the thermal intermediate ensemble, while helix 3 is partially unfolded. Detailed NMR relaxation dynamics are compared between the native state and the intermediate ensemble. Our results implicate a fluid helix-turn-helix folding model of Box-5, where helices 1 and 2 potentially form the helix 1-turn-helix 2 motif in the intermediate, while helix 3 is consolidated only as two hydrophobic cores form to stabilize the native structure. Proteins 2009. © 2009 Wiley-Liss, Inc. [ABSTRACT FROM AUTHOR]

Abstract: PbS microcrystals including multipods, truncated octahedrons and cubes were produced by the reaction of PbCl2 and thiosemicarbazide (CH5N3S) using diethylene glycol (DEG) as a solvent at 180°C. When the reaction time was prolonged, the final products grew into single-crystalline PbS cubes with diameters in the range of 0.3–2μm. A possible formation mechanism of the PbS cubes was proposed based on their shape evolutions. By changing the reactants or/and solvents, PbS dendrites and flowers could also be produced with high yield. It is found that the reaction temperature, reactants and solvents play important roles on the shape evolutions of the PbS microcrystals. [Copyright &y& Elsevier]

Single-mode-no-core-single-mode (SNS) optical fiber structures have valuable potential to encapsulate as high-precision temperature sensors, due to their great sensitivity. This paper is to improve the temperature sensitivity of SNS fibers by studying the parameters of fiber length, diameter, and refractive index of the seal liquid. Transmission spectra of the fibers are given in both aspects of experiment and numerical simulation. We find that using a slim no-core fiber section sealed with liquid of high refractive index can effectively improve the sensitivity, while the choice of fiber length mainly affects the width of transmission peak. The results may contribute to the development of high-sensitivity optic temperature sensor. [ABSTRACT FROM AUTHOR]

SnS 2 /reduced graphite oxide (rGO) composite materials show great potential as high-performance anode candidates in sodium-ion batteries (SIBs) owing to their high specific capacities and power densities. However, the repeated formation/decomposition of the solid electrolyte interface (SEI) layer around composite anodes usually consumes additional sodium cations, resulting in poor Coulombic efficiency and decreasing specific capacity upon cycling. Therefore, in order to compensate for the large irreversible sodium loss of the SnS 2 /rGO anode, this study has proposed a facile strategy by implementing organic solutions of sodium-biphenyl/tetrahydrofuran (Na-Bp/THF) and sodium-naphthylamine/dimethoxyethane (Na-Naph/DME) as chemical presodiation reagents. Particularly, the storage stability of Na-Bp/THF and Na-Naph/DME in ambient air accompanied by their presodiation behavior on the SnS 2 /rGO anode has been investigated, and both reagents exhibited desirable ambient air-tolerant storage stability with favorable sodium supplement effects even after 20 days of storage. More importantly, the initial Coulombic efficiency (ICE) of SnS 2 /rGO electrodes could be controllably increased by immersing in a presodiation reagent for different durations. Consequently, with a facile chemical presodiation strategy of immersion in Na-Bp/THF solution for only 3 min in ambient air, the presodiated SnS 2 /rGO anode has exhibited an outstanding electrochemical performance with a high ICE of 95.6% as well as an ultrahigh specific capacity of 879.2 mAh g -1 after 300 cycles (83.5% of its initial capacity), highly superior to the pristine SnS 2 /rGO anode. This efficient and scalable presodiation strategy provides a new avenue for the prevailing application of other anode candidates in high-energy SIBs.

Studying high-sensitivity fiber-optic temperature sensors is vital in pursuing high-precision temperature measurement. We propose a liquid-sealed multimode interference fiber temperature sensor with a double-taper structure. The influence of structure and sealed-liquid material on the temperature sensitivity of the sensor is analyzed experimentally. The results show that the tapered structure can effectively improve the temperature sensitivity of the sensor, and the effect becomes more evident with the increased refractive index of the sealed liquid. As the refractive index of the sealed liquid increases, the temperature sensitivity of the sensor can be effectively improved. However, the sealed liquid with a high refractive index will increase the failure temperature of the sensor. Near the failure temperature, the sensor achieves an ultra-high-temperature sensitivity of -8.28 n m / K . The results also prove that further increasing the refractive index of the sealed liquid no longer has a significant gain in temperature sensitivity. It is expected that the relevant research will contribute to the development of high-precision temperature-sensing systems.

The development of high-efficiency, robust, and available electrode materials for oxygen evolution reaction (OER) and lithium-ion batteries (LIBs) is critical for clean and sustainable energy system but remains challenging. Herein, a unique yolk-shell structure of Fe 2 O 3 nanotube@hollow Co 9 S 8 nanocage@C is rationally prepared. In a prearranged sequence, the fabrication of Fe 2 O 3 nanotubes is followed by coating of zeolitic imidazolate framework (ZIF-67) layer, chemical etching of ZIF-67 by thioacetamide, and eventual annealing treatment. Benefiting from the hollow structures of Fe 2 O 3 nanotubes and Co 9 S 8 nanocages, the conductivity of carbon coating and the synergy effects between different components, the titled sample possesses abundant accessible active sites, favorable electron transfer rate, and exceptional reaction kinetics in the electrocatalysis. As a result, excellent electrocatalytic activity for alkaline OER is achieved, which delivers a low overpotential of 205 mV at the current density of 10 mA cm -2 along with the Tafel slope of 55 mV dec -1 . Moreover, this material exhibits excellent high-rate capability and excellent cycle life when employed as anode material of LIBs. This work provides a novel approach for the design and the construction of multifunctional electrode materials for energy conversion and storage., (© 2021 The Authors. Small published by Wiley-VCH GmbH.)

In this work, we demonstrate an interesting structural phase transition from SnS2/reduced graphene oxide to SnS/sulfur-doped graphene at a moderate calcination temperature of 500 °C under an inert atmosphere. It is discovered that SnS2 chemically bound to rGO with a weakened C-S bond is easier to break and decompose into SnS, whereas it is difficult for pure-phase crystalline SnS2 to experience phase transformation at this temperature. Moreover, the thin-layered structure of SnS2 and rGO is an important factor for the effective doping of the dissociated Sx into graphene. Density functional theory calculations also reveal the feasibility of the structural phase transition process. Morphology characterization shows that partial SnS maintains the original nanosheet structure (∼100 nm) and the others are decomposed into tiny nanoparticles (10-20 nm). A high S-doping amount reduces the irreversible lithium storage sites on graphene, and the first coulombic efficiency is as high as 81.7%. In addition, thin-layered and small-sized SnS can alleviate the structural damage caused by volume expansion and shrinkage; therefore, a high specific capacity of 893.9 mA h g-1 is retained after 100 cycles.