HAMILTONIAN-BASED FREQUENCY-AMPLITUDE FORMULATION FOR NONLINEAR OSCILLATORS

Complex mechanical systems usually include nonlinear interactions between their components which can be modeled by nonlinear equations describing the sophisticated motion of the system. In order to interpret the nonlinear dynamics of these systems, it is necessary to compute more precisely their nonlinear frequencies. The nonlinear vibration process of a conservative oscillator always follows the law of energy conservation. A variational formulation is constructed and its Hamiltonian invariant is obtained. This paper suggests a Hamiltonian-based formulation to quickly determine the frequency property of the nonlinear oscillator. An example is given to explicate the solution process

Heteropolyacids supported on zirconia-doped γ, θ and α alumina: A physicochemical assessment and characterisation of supported solid acids

In this paper we carry out a surface study of promising supported solid acid catalysts commonly used for the production of high value chemicals derived from glycerol. In particular, γ, θ and α alumina (Al2O3) were modified by (i) grafting with 5 wt% zirconia, (ii) doping with 30 wt% silicotungstic acid (STA), and (iii) using both zirconia and STA. The aim is to rationalise the effect of these different parameters on structural properties and surface adsorption through a comprehensive multi-technique approach, including recently developed NMR relaxation techniques. XRD and laser Raman spectroscopy confirmed a strong interaction between STA and the γ-/θ-Al2O3 resulting in a distortion of the supported STA Keggin structure relative to that of bulk STA. Conversely, a much weaker interaction between the supported STA and α-Al2O3 was measured. NMR relaxation demonstrated that the STA doping increases the adsorption properties of the catalyst, particularly for γ-/θ-Al2O3. For catalysts based on α-Al2O3, such effect was negligible. Thermogravimetric/differential thermogravimetry (TGA/DTG) analysis suggested that zirconia-grafted and non-grafted θ-Al2O3 and γ-Al2O3 are suitable materials for increasing the thermal stability of STA whereas α-Al2O3 (both grafted and non-grafted) does not improve the thermal stability of STA

Hepcidin and iron metabolism in preterm infants

Background: Iron deficiency (ID) and ID anemia are widespread in low-income countries, particularly among preterm infants. Hepcidin is a key regulator of iron metabolism, which offers the possibility of new solutions to diagnose ID in premature infants. Objective: To explore the relationship between iron metabolism and hepcidin in premature infants. Materials and methods: The study involved 81 preterm infants between 28+1 and 36+6 who underwent iron status indicators and hepcidin testing at 6 months of corrected gestational age. The preterm infants were divided into two groups based on iron status indicators: ID and no ID. Results: Serum hepcidin was lower for premature infants with ID compared to those without ID (log10hepcidin, 1.18 ± 0.44 vs 1.49 ± 0.37, p = 0.002). A single-variate linear regression model was used to explore the correlation between hepcidin and other indicators of iron metabolism. A strongly positive relationship was observed between hepcidin levels and ferritin levels (p < 0.001) in the correlation analysis. Conclusions: Hepcidin can be used as an efficient indicator of iron storage and a promising indicator for the early diagnosis of ID in premature infants

Enabling the ability of Li storage at high rate as anodes by utilizing natural rice husks-based hierarchically porous SiO2/N-doped carbon composites

One of the greatest challenges in developing SiO 2/C composites as anode materials in lithium ion batteries (LIBs) is to improve the ability of Li storage at high rate over long-term cycles. Herein, biomass rice husks-based hierarchically porous SiO 2/N-doped carbon composites (BM-RH-SiO 2/NC) were prepared by ball mill and thermal treatment. BM-RH-SiO 2/NC can still retain a reversible capacity of 556 mAh g −1 over 1000 cycles at a high current of 1.0 A g −1. At 5.0 A g −1 the capacity is kept as high as 402 mAh g −1. This impressively long-term cyclic performance and high-rate capability of BM-RH-SiO 2/NC can be ascribed to the synergetic effect between the natural SiO 2 nanoparticles (< 50 nm) and the NC layer. The coating NC layer can not only effectively mitigate the volume strain during charge-discharge process to offer stably cyclic performance but also improve the electrical conductivity. Furthermore, the hierarchical porosity and better electrolyte wettability offer the rapid Li + diffusion and electron transfer, which enhance the pseudocapacitive behavior of whole electrode material and then guarantee fast electrochemical kinetics. Importantly, the unique Li-storage mechanism of active SiO 2 in BM-RH-SiO 2/NC composite was formed and found, which further validates the improved electrochemical capability

Projected sensitivities of the LUX-ZEPLIN experiment to new physics via low-energy electron recoils

LUX-ZEPLIN is a dark matter detector expected to obtain world-leading sensitivity to weakly-interacting massive particles interacting via nuclear recoils with a ∼ 7 -tonne xenon target mass. This paper presents sensitivity projections to several low-energy signals of the complementary electron recoil signal type: 1) an effective neutrino magnetic moment, and 2) an effective neutrino millicharge, both for p p -chain solar neutrinos, 3) an axion flux generated by the Sun, 4) axionlike particles forming the Galactic dark matter, 5) hidden photons, 6) mirror dark matter, and 7) leptophilic dark matter. World-leading sensitivities are expected in each case, a result of the large 5.6 t 1000 d exposure and low expected rate of electron-recoil backgrounds in the < 100     keV energy regime. A consistent signal generation, background model and profile-likelihood analysis framework is used throughout

The 2021 battery technology roadmap

Sun, wind and tides have huge potential in providing us electricity in an environmental-friendly way. However, its intermittency and non-dispatchability are major reasons preventing full-scale adoption of renewable energy generation. Energy storage will enable this adoption by enabling a constant and high-quality electricity supply from these systems. But which storage technology should be considered is one of important issues. Nowadays, great effort has been focused on various kinds of batteries to store energy, lithium-related batteries, sodium-related batteries, zinc-related batteries, aluminum-related batteries and so on. Some cathodes can be used for these batteries, such as sulfur, oxygen, layered compounds. In addition, the construction of these batteries can be changed into flexible, flow or solid-state types. There are many challenges in electrode materials, electrolytes and construction of these batteries and research related to the battery systems for energy storage is extremely active. With the myriad of technologies and their associated technological challenges, we were motivated to assemble this 2020 battery technology roadmap

Background Determination for the LUX-ZEPLIN (LZ) Dark Matter Experiment

The LUX-ZEPLIN experiment recently reported limits on WIMP-nucleus interactions from its initial science run, down to $9.2\times10^{-48}$ cm$^2$ for the spin-independent interaction of a 36 GeV/c$^2$ WIMP at 90% confidence level. In this paper, we present a comprehensive analysis of the backgrounds important for this result and for other upcoming physics analyses, including neutrinoless double-beta decay searches and effective field theory interpretations of LUX-ZEPLIN data. We confirm that the in-situ determinations of bulk and fixed radioactive backgrounds are consistent with expectations from the ex-situ assays. The observed background rate after WIMP search criteria were applied was $(6.3\pm0.5)\times10^{-5}$ events/keV$_{ee}$/kg/day in the low-energy region, approximately 60 times lower than the equivalent rate reported by the LUX experiment.Comment: 25 pages, 15 figure

A search for new physics in low-energy electron recoils from the first LZ exposure

The LUX-ZEPLIN (LZ) experiment is a dark matter detector centered on a dual-phase xenon time projection chamber. We report searches for new physics appearing through few-keV-scale electron recoils, using the experiment's first exposure of 60 live days and a fiducial mass of 5.5t. The data are found to be consistent with a background-only hypothesis, and limits are set on models for new physics including solar axion electron coupling, solar neutrino magnetic moment and millicharge, and electron couplings to galactic axion-like particles and hidden photons. Similar limits are set on weakly interacting massive particle (WIMP) dark matter producing signals through ionized atomic states from the Migdal effect.Comment: 13 pages, 10 figures. See https://tinyurl.com/LZDataReleaseRun1ER for a data release related to this pape

The LUX-ZEPLIN (LZ) Experiment

We describe the design and assembly of the LUX-ZEPLIN experiment, a direct detection search for cosmic WIMP dark matter particles. The centerpiece of the experiment is a large liquid xenon time projection chamber sensitive to low energy nuclear recoils. Rejection of backgrounds is enhanced by a Xe skin veto detector and by a liquid scintillator Outer Detector loaded with gadolinium for efficient neutron capture and tagging. LZ is located in the Davis Cavern at the 4850' level of the Sanford Underground Research Facility in Lead, South Dakota, USA. We describe the major subsystems of the experiment and its key design features and requirements