Acoustic Emission (AE) waveforms contain information on microscopic structural features that can be related with damage of coal rock masses. In this paper, the Hilbert-Huang transform (HHT) method is ...used to obtain detailed structural characteristics of coal rock masses associated with damage, at different loading stages, from the analyses of the characteristics of AE waveforms. The results show that the HHT method can be used to decompose the target waveform into multiple intrinsic mode function (IMF) components, with the energy mainly concentrated in the
C
1
–
C
4
IMF components, where the
C
1
component has the highest frequency and the largest amount of energy. As the loading continues, the proportion of energy occupied by the low-frequency IMF component shows an increasing trend. In the initial compaction stage, the Hilbert marginal spectrum is mainly concentrated in the low frequency range of 0–40 kHz. The plastic deformation stage is associated to energy accumulation in the frequency range of 0–25 kHz and 200–350 kHz, while the instability damage stage is mainly concentrated in the frequency range of 0–25 kHz. At 20 kHz, the instability damage reaches its maximum value. There is a relatively clear instantaneous energy peak at each stage, albeit being more distinct at the beginning and at the end of the compaction phase. Since the effective duration of the waveform is short, its resulting energy is small, and so there is a relatively high value from the instantaneous energy peak. The waveform lasts a relatively long time after the peak that coincides with failure, which is the period where the waveform reaches its maximum energy level. The Hilbert three-dimensional energy spectrum is generally zero in the region where the real energy is zero. In addition, its energy spectrum is intermittent rather than continuous. It is therefore consistent with the characteristics of the several dynamic ranges mentioned above, and it indicates more clearly the low-frequency energy concentration in the critical stage of instability failure. This study well reflects the response law of geophysical signals in the process of coal rock instability and failure, providing a basis for monitoring coal rock dynamic disasters.
The 2+2 cycloaddition of allenes with alkenes is of much interest and importance as a straightforward route for the construction of four‐membered carbocycles but has remained much underexplored to ...date. Herein we report for the first time the intermolecular regio‐ and diastereoselective formal 2+2 cycloaddition of a wide range of allenes with amino‐functionalized alkenes by half‐sandwich rare‐earth catalysts. The reaction proceeded through an allene C(sp2)−H activation mechanism initiated by the site‐selective deprotonation of the allene unit by a rare‐earth metal alkyl species followed by alkene insertion into the resulting metal‐allenyl bond and the subsequent intramolecular cycloaddition to an allene C=C bond. This protocol offers a unique route for the synthesis of a new family of cyclobutane and cyclobutene derivatives which were difficult to access previously.
Half‐sandwich rare‐earth catalysts serve as a unique platform for the regio‐ and diastereoselective formal 2+2 cycloaddition of a wide range of allenes with amino‐functionalized alkenes via allene C(sp2)−H activation, affording a new family of cyclobutane and cyclobutene derivatives which were difficult to access previously.
Direct measuring of CO2 flux remains challenging for global lakes. The traditional sampling and gas transfer models used to estimate lake CO2 fluxes are variable and uncertain, and ice‐covered ...periods are often excluded from the annual carbon budget. Here, the first longtime (2013−2017) direct measurement of CO2 flux by eddy covariance system over the largest saline lake (Qinghai lake) in the Qinghai‐Tibet Plateau (QTP) revealed that ice‐covered period draws large amounts of CO2 from the atmosphere (−0.87 ± 0.38 g C m−2 d−1), a value more than twice the CO2 flux rate during the ice‐free period (−0.41 ± 0.35 g C m−2 d−1). The total CO2 uptake by all saline lakes on the QTP was estimated to −10.28 ± 1.65 Tg C yr−1, an equivalent to approximately one third of the net terrestrial ecosystems carbon sink in QTP. Our results indicate large sink for CO2 in winter is controlled by both seasonal hydrochemistry processes and lake ice absorption in saline lakes. This research also demonstrates decreasing CO2 uptake from the atmosphere by saline lakes on the QTP, which may turn carbon sinks to carbon sources with future warming.
The first direct measurement of CO2 flux over Qinghai lake revealed that significant winter CO2 uptake by saline lakes controlled by seasonal hydrochemistry processes and lake ice absorption on the Qinghai‐Tibet Plateau (QTP). The finding highlights the importance of ice‐covered period for saline lakes in global carbon budge. All saline lakes on the QTP draw 10.28 ± 1.65 Tg C yr−1 CO2 from the atmosphere, an equivalent to approximately one‐third of the net terrestrial ecosystems carbon sink in the QTP. Increasing future climate warming may change saline lakes from carbon sinks to carbon sources by end‐2000s.
Social capital has been linked to health behaviours, but the underlying mechanism is unclear. Previous studies have found that health literacy played the role of a mediator in the relationships among ...social capital, individual physical activity and nutrition. But it is not clear whether eHealth literacy mediates the impact of social capital on health behaviours. Therefore, our research aimed to explore the relationships among social capital (structural and cognitive social capital), eHealth literacy, and the health behaviours of elderly people, and to analyse the mediating effect of eHealth literacy, while providing a theoretical basis for a health behaviour intervention for elderly people.
From January to February 2019, we conducted a cross-sectional survey of 1201 Chinese people aged over 60 years using the Chinese Shortened Social Capital Scale (contains two subscales of structural social capital and cognitive social capital), eHealth Literacy Scale, and Health-Promoting Lifestyle Profile. We used structural equation modelling to test a hypothetical mediation model.
The mean scores of social capital was 72.07 (SD = 13.03), 17.24 (SD = 9.34) for eHealth literacy, and 112.23 (SD = 23.25) for health behaviours. Social capital and eHealth literacy were significantly correlated with health behaviours, and social capital and structural social capital were significantly correlated with eHealth literacy. Lastly, eHealth literacy mediated the relationship between structural social capital and health behaviours.
eHealth literacy was an important mediating factor for elderly people's structural social capital and health behaviours. Therefore, social capital and eHealth literacy must be considered when designing and implementing health behaviour intervention programmes for elderly people.
Background and Purpose
Osteoarthritis (OA) pain remains a major clinical problem. It is urgent to identify novel therapeutic approaches for OA pain states. Bromodomain and extra‐terminal (BET) ...protein inhibitors have robust anti‐inflammatory effects in several pain models. However, the underlying mechanisms of these inhibitors in OA pain have not been determined. We, therefore, investigated the effects and the underlying mechanism(s) of BET inhibition on pain‐related behaviours in a rat model of OA.
Experimental Approach
The OA model was established by intra‐articular injection of monosodium iodoacetate (MIA) in rat knees. Pain behaviours were assessed in rats by hindlimb weight‐bearing asymmetry, mechanical allodynia and thermal hyperalgesia. Possible mechanisms underlying BET inhibition were explored in the MIA‐induced OA pain model in the spinal cord and dorsal root ganglia (DRG).
Key Results
Inhibiting bromodomain‐containing protein 4 (Brd4) with either JQ1 or MS417, or using AAV2/9‐shRNA‐Brd4‐EGFP‐mediated knockdown of Brd4 genes, significantly attenuated MIA‐induced pain behaviours. Brd4 inhibition suppressed NF‐κB and NF‐κB‐mediated inflammatory cytokines in both the spinal cord and DRG in rats with MIA‐induced OA pain. Brd4 inhibition also attenuated the oxidative stress and promoted nuclear factor erythroid‐2‐related factor 2 (Nrf2)‐dependent antioxidant genes in both the spinal cord and DRG in our odel of MIA‐induced OA pain.
Conclusions and Implications
In conclusion, Brd4 inhibition alleviated MIA‐induced OA pain in rats, via suppression of neuroinflammation and activation of Nrf2‐mediated antioxidant signalling. Although our model does not perfectly represent how OA develops in humans, inhibition of Brd4 may provide novel insights into possible treatments for OA pain.
Aluminum alloys and their welding structures have been widely used in aviation, aerospace, automobiles, ships, and other industrial fields. The non-uniform nature of welding structures of aluminum ...alloys causes intractable corrosion problems. Anodizing and subsequent sealing processes are common and effective methods to improve the corrosion resistance of welding structures. However, traditional sealing processes like hot water sealing and potassium dichromate sealing are criticized due to energy consumption or toxicity. In this work, a layered double hydroxide (LDH) sealing process with subsequent fluorinated siloxane modification is proposed to improve the corrosion resistance of the anodic oxide film of friction stir welding joints of typical aluminum alloys. The obtained sealing film with typical lamelliform structures of LDH grows well at the defects of oxidation film and also smoothens the sample surface. The hydrophobicity of the film can separate the corrosive medium from the sample surface and further enhance corrosion resistance. As a result, the corrosion current of the welded sample in 3.5 wt.% NaCl solution plummets about 3~4 orders of magnitude compared to the initial state without anodizing, indicating superior corrosion resistance brought by this method.
The terahertz region is a special region of the electromagnetic spectrum that incorporates the advantages of both microwaves and infrared light waves. In the past decade, metamaterials with effective ...medium parameters or gradient phases have been studied to control terahertz waves and realize functional devices. Here, we present a new approach to manipulate terahertz waves by using coding metasurfaces that are composed of digital coding elements. We propose a general coding unit based on a Minkowski closed-loop particle that is capable of generating 1-bit coding (with two phase states of 0 and 180°), 2-bit coding (with four phase states of 0, 90°, 180°, and 270°), and multi-bit coding elements in the terahertz frequencies by using different geometric scales. We show that multi-bit coding metasurfaces have strong abilities to control terahertz waves by designing-specific coding sequences. As an application, we demonstrate a new scattering strategy of terahertz waves--broadband and wide-angle diffusion--using a 2-bit coding metasurface with a special coding design and verify it by both numerical simulations and experiments. The presented method opens a new route to reducing the scattering of terahertz waves.Light: Science & Applications (2015) 4, e324; doi:10.1038/lsa.2015.97; published online 11 September 2015
•Low-reversed cyclic loading tests were carried out on eight corroded reinforced concrete columns to study their mechanical characteristics and failure mechanisms. The test results are analyzed in ...detail, and the research on the decline in the seismic performance of concrete columns confined by corroded stirrups has been carried out for the first time.•A method for predicting the lateral strength of reinforced concrete columns confined by corroded stirrups is presented based on the axial-shear-flexure interaction approach for conventional concrete columns, with modifications to consider the effect of stirrup corrosion. There was good agreement is achieved between the test results and theoretical values. For the first time, the established model introduces the corrosion parameters of the stirrup.
To understand the seismic behaviors of concrete columns confined by corroded stirrups, low-reversed cyclic loading tests were carried out on eight corroded reinforced concrete columns to study their mechanical characteristics and failure mechanisms. The influence on seismic performance indicators such as bearing capacity, hysteresis characteristics, ductility, strength degradation, stiffness degradation, and energy dissipation was analyzed comparatively based on parameters such as stirrup diameter and stirrup-spacing changes. The experimental results showed that the restraint of concrete provided by corroded stirrups is reduced, which leads to a decline in seismic performance, and with increasing stirrup corrosion, the failure limit displacement of columns decreases. The pinch phenomenon of the hysteresis curve gradually increases, the attenuation degree of strength and stiffness increases, and the ductility and energy-dissipation capacity is reduced, while the accumulated energy increases under the same control displacement. A method for predicting the lateral strength of reinforced concrete columns confined by corroded stirrups is presented based on the axial-shear-flexure interaction approach for conventional concrete columns, with modifications to consider the effect of stirrup corrosion. There was good agreement is achieved between the test results and theoretical values.
The incidence of infertility has recently risen. Semen quality is an important male fertility indicator, and dietary factors can affect semen quality. We conducted this systematic review and ...meta-analysis to determine the effects of healthy dietary patterns on semen quality. A literature search was conducted in 3 databases (Embase, Web of Science and PubMed) on August 21, 2021. The included cross-sectional studies examined the influence of the Mediterranean, Dietary Approaches to Stop Hypertension (DASH), and prudent diet patterns on semen quality parameters; six studies (1244 subjects) were included. By comparing high consumption with low consumption of healthy dietary patterns, the results of the meta-analysis showed significantly higher sperm concentrations (mean difference MD = 6.88 × 106 ml−1, 95% confidence interval CI: 1.26 × 106 ml−1-12.49 × 106 ml−1; P < 0.05), a significant increase in total sperm count (MD = 16.70 × 106, 95% CI: 2.37 × 106-31.03 × 106; P < 0.05), and a significant increase in progressive sperm motility (MD = 5.85%, 95% CI: 2.59%-9.12%; P < 0.01). The sperm concentration, progressive sperm motility, and total sperm count were significantly higher in men with higher versus lower consumption of healthy dietary patterns. However, the results must be interpreted with caution.
Focusing on digital transformation of manufacturing enterprises, this paper investigates the relationship between digital transformation and financial performance of manufacturing enterprises through ...descriptive statistical analysis, correlation analysis, multilayer linear regression analysis, and group testing of the impact of digital transformation stages on the financial performance of enterprises, taking listed manufacturing companies that implement digital transformation as a sample. The research results show that there is a significant positive impact of digital transformation on financial performance of manufacturing enterprises; the more digitalized the information technology (IT) architecture is when enterprises undergo digital transformation, the closer to hybrid cloud platform + agile manufacturing, the higher the inventory turnover rate and total asset turnover rate of enterprises will be; in the early stage of digital transformation of enterprises, the profitability performance of enterprises will be reduced. However, as the digitalization process of enterprises deepens, the net sales margin and total asset return of enterprises will gradually increase, which may be due to the reason that the impact of enterprise digital transformation on profitability performance has a certain lag.
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