The COVID-19 pandemic and its related public health restrictions are having an increasingly serious impact on mental health, and measures need to be taken to curb this trend. The positive ...relationship between physical exercise and mental health has been well-established, but during the COVID-19 pandemic, with various restrictions, the space and facilities for physical exercise are limited. This article explores the relationship between physical exercise and mental health during the COVID-19 pandemic based on the latest research findings published in 2019-2021. We offer a novel model that consists of three central arguments. First, physical exercises during COVID-19, especially supervised exercises, are conducive to enhancing happiness and improving mental health. Second, physical exercise reduces people's anxiety, sadness and depression during the COVID-19 pandemic. Third, the maintenance and improvement of mental health are related to the intensity and frequency of physical exercise. Intensive and frequent physical exercise are conducive to maintaining mental health. Finally, this article proposes important directions for future research.
The morphology and substructure of α′ martensite in Ti-6Al-4V cuboid samples produced by selective laser melting (SLM) have been investigated to explore the formation mechanism and control method of ...α′ martensite. Results showed that the microstructures of SLMed Ti-6Al-4V samples are composed of a typical hierarchical martensite structure with a high density of dislocations and twins, including primary, secondary, tertiary and quartic α′ martensites within columnar prior β grains. Also, the formation and evolution mechanisms of such hierarchical martensites are proposed based on heat history of SLM, material characteristics and substructure features. Besides, based on quantitative metallography, the lengths of major and minor axes as well as aspect ratio of primary and secondary α′ martensites are mainly in the range of 10–70μm, 1.0–2.0μm and 5–40, respectively. The martensitic sizes increase with hatch spacing, but firstly increase and then decrease with the increase of scanning velocity from 600 to 1100mm/s. So, martensitic size can be controlled by adjusting the SLM processing parameters.
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•A hierarchical α′ structure is observed in selective laser melted Ti-6Al-4V.•Martensitic size of selective laser melted Ti-6Al-4V is measured.•Formation mechanism of α′ during multiple thermal cycles is proposed.•Varying parameters of selective laser melting can control martensitic size.
Nickel, as one of the most abundant elements in the earth's crust, plays many roles in human reproduction and life. It is an essential trace element for the human body, but can be harmful in excess ...amounts. Nickel has a significant impact on endocrine hormones in humans and animals, potentially causing abnormal secretions and changing the structure and function of endocrine organs. This article systematically reviews the effects of nickel on hormone secretion and target organs in the endocrine system and identifies areas of insufficient research.
All data in this article were extracted from peer-reviewed articles. The PubMed, SciFinder, Google Scholar, Web of Science, and China National Knowledge Infrastructure databases were searched for relevant articles. Data on nickel’s effect on endocrine system hormones and target organs were retrieved, and manually sorted prior to inclusion in this review.
Nickel acts on the endocrine system and affects the release and regulation of endocrine hormones. Disorders of endocrine hormones may lead to retardation of human growth and mental development, disturbance of water and salt regulation, and even a decline in reproductive ability. Nickel affects the hypothalamus and pituitary gland by regulating organs upstream of the endocrine axis; it can cause abnormal secretion of pituitary hormones, which affects target organs of the endocrine axis, resulting in dysfunction therein and abnormal secretion of related hormones. Nickel also damages target organs, mainly by inducing apoptosis, which triggers oxidative stress, cell autophagy, free radical release, and DNA damage. However, there are few studies on the endocrine axis, and some of the data are contradictory. Nevertheless, it is clear that nickel affects the endocrine system.
Nickel can damage organs in the endocrine system, such as the hypothalamus and pituitary. It also affects the secretion of hormones and damages the target organs of these hormones; this can result in endocrine system dysfunction. However, the results have been equivocal and further research is needed.
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•Nickel affects the release of gonadal hormone in human body and the reproduction of human beings.•In nickel-contaminated areas, it may result in short stature of children in nickel-contaminated areas.•Nickel acts on the endocrine system and affects the release and regulation of endocrine hormones.
•The soil bulk density is correlated with soil types and the biochar applied rates.•The soil organic carbon and total nitrogen increased after eight-year field study.•The soil NO3−–N is correlated ...with soil types and biochar application rates.•The effect of biochar application on NH4+–N and total phosphorus are very limited.
Soil erosion on the Loess Plateau has been partly controlled, but soil nutrients remain limited throughout the region. Biochar amendments are an efficient method of improving availability of soil nutrients due to their strong adsorptive capacity; however, the effects of biochar amendments on different soil types on the Loess Plateau are not well understood. In this paper, we compared the effects of biochar on soil bulk density, soil organic carbon, and soil nitrogen and phosphorus contents among four soil types on the Loess Plateau. An eight-year field study was conducted in Loessal soil, Dark Loessial soil, Lou soil, and Aeolian sandy soil to investigate changes in soil bulk density and nutrient retention caused by biochar amendment at rates of 0 g/kg (control), 4 g/kg, 8 g/kg and 16 g/kg. Soil organic carbon, total nitrogen, total phosphorus, ammonium nitrogen, and nitrate nitrogen concentrations were measured eight years after biochar application. The biochar amendments significantly increased the soil organic carbon and nitrate nitrogen concentrations in the 0–40 cm layer of all soils. The nitrate nitrogen concentration in the Lou soil and Dark Loessial soil decreased with 4 g/kg biochar application and increased significantly with 8 g/kg and 16 g/kg biochar application, but it did not significantly change in the Loessal soil. In contrast, the nitrate nitrogen concentration in the Aeolian sandy soil decreased with increasing biochar application. Biochar amendments did not significantly influence soil ammonium nitrogen in the 0–20 cm soil layer. However, the soil phosphorus content in the 0–20 cm layer decreased with increasing biochar application, except in the Lou soil and Aeolian sandy soil. These data suggest that biochar-soil interactions on the Loess Plateau have the potential to enhance soil organic carbon and soil nitrogen storage. Moreover, using an appropriate biochar amendment rate according to soil type might help optimise the use of fertilizer on the Loess Plateau.
Near-fully dense Ti-6Al-4V and 304 stainless steel samples have been produced applying selective laser melting (SLM) in the present work. The microstructures, textures and microhardnesses on ...horizontal and vertical cross sections, as well as the tensile properties of horizontally and vertically SLMed samples are investigated. It is found that the microstructures of the two SLMed alloys are mainly composed of hexagonal close-packed (HCP) martensitic phase or face-centered cubic (FCC) austenitic phase within columnar structures in Ti-6Al-4V alloy and 304 stainless steel, respectively. For both SLMed alloys, the tensile properties and microhardnesses show anisotropic though the textures are weak. Especially, the Ti-6Al-4V samples show even stronger anisotropic mechanical properties compared with 304 stainless steel. The higher length-width ratios of the columnar structures, rather than the weaker textures or the less symmetry of HCP crystal structure in SLMed Ti-6Al-4V are believed to be responsible for the stronger mechanical anisotropies. As expected, heat treatment is an effective method to eliminate columnar structures and leads to nearly isotropic mechanical properties.
The crystallographic texture of Ti-6Al-4V produced by selective laser melting (SLM) under various laser energy densities was characterized by electron backscatter diffraction technique to explore its ...effect on the anisotropy in tensile properties. Results show that crystallographic orientation depending on laser energy density acts a significant role in determining the mechanical anisotropy of SLMed Ti-6Al-4V samples. The microstructure of the SLMed Ti-6Al-4V samples consists of fully martensites. As for the martensites, the fraction of basal orientations decreases, while the content of prismatic orientations increases with laser energy density increasing from 101 to 269J/mm3. And the order of the dominated crystallographic orientation of martensites with the laser energy density is (123−0)21−1−3→(112¯4)1−3−41→(112−0)11−01→(112−0)22−03. There is anisotropy in tensile properties between horizontally and vertically built samples, which is more obvious with laser energy density. The formation of such anisotropy is ascribed to the higher Schmid factor values of the grains in the vertically built tensile samples than those in horizontally built ones.
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•Crystallographic orientation affects the anisotropy of SLMed Ti-6Al-4V alloy.•The content of prismatic orientations increases with laser energy density.•The anisotropy of tensile properties is enhanced with laser energy density.•The various Schmid factor values result in the anisotropy of tensile properties.
The microstructures, potentiodynamic curves, and electrochemical impedance spectroscopy are characterized for Ti-6Al-4V samples produced by selective laser melting (SLM), SLM followed by heat ...treatment (HT), wire and arc additive manufacturing (WAAM), and traditional rolling to investigate their corrosion behaviors. Results show that the processing technology acts a significant role in controlling the microstructures, which in turn directly determine their corrosion resistance. The order of corrosion resistance of these samples is SLM < WAAM < rolling < SLM+HT. Among these microstructural factors for influencing corrosion resistance, type of constituent phase is the main one, followed by grain size, and the last is morphology. Finally, the application potentials of additive manufactured Ti-6Al-4V alloy are verified in the aspect of corrosion resistance.
•Transition from reject water to mainstream led to decrease of aerobic capacity.•Mainstream deammonification operated during 16months at 25°C.•Intermittent aeration with phases duration of 15min gave ...the best performance.•AOB/NOB activity ratio is twice higher for suspended than for attached biomass.•Anammox activity, comparable to reject water systems was maintained.
In this study the combination of an upflow anaerobic sludge blanket (UASB) reactor and a deammonification moving bed biofilm reactor (MBBR) for mainstream wastewater treatment was tested. The competition between aerobic ammonium oxidizing bacteria (AOB) and nitrite oxidizing bacteria (NOB) was studied during a 5months period of transition from reject water to mainstream wastewater followed by a 16months period of mainstream wastewater treatment. The decrease of influent ammonium concentration led to a wash-out of suspended biomass which had a major contribution to nitrite production. Influence of a dissolved oxygen concentration and a transient anoxia mechanism of NOB suppression were studied. It was shown that anoxic phase duration has no effect on NOB metabolism recovery and oxygen diffusion rather than affinities of AOB and NOB to oxygen determine the rate of nitrogen conversion in a biofilm system. Anammox activity remained on the level comparable to reject water treatment systems.
An equiatomic AlCrCuFeNi high entropy alloy (HEA) is fabricated successfully from the alloy powders using selective laser melting (SLM). Microstructural characteristics and mechanical behavior of ...SLMed AlCrCuFeNi samples under optimal SLM processing parameters are studied in detail. It is revealed that the SLMed AlCrCuFeNi HEA shows high crack sensitivity, and the optimum processing window is narrow. The formation of FCC phase is inhibited, resulting in a simple BCC solid solution to accommodate high lattice distortion and elastic strain induced by rapid cooling rate for the SLMed AlCrCuFeNi HEA. Moreover, unique fine columnar grains containing multiple ultrafine sub-grains structures appear within the molten pool and present a preferred orientation. Nano-scale Cu-rich phases precipitate and exhibit chain-like at HAGBs while granular shape at LAGBs. Also, anomalous alternating bright and dark structures containing B2 and A2 phases with the width about 22 nm appear at the sub-grain boundaries due to rapid solidification. The SLMed AlCrCuFeNi HEA possesses superior properties with a compression strength of 2052.8 MPa and a fracture strain of 6.8% compared to the corresponding casting material. Fracture analysis indicates that the SLM (0°) specimen exhibits quasi-cleavage fracture while the SLM (90°) specimen shows intergranular fracture. The grain boundary strengthening effect, preferential growth orientation of BCC grain and the existing microcracks are proposed to explain the anisotropy of compression properties.
•A dual-phase high entropy alloy is fabricated using selective laser melting.•Unique columnar grains containing multiple ultrafine sub-grains are discovered.•Nano-scale Cu-rich phases exhibit chain-like at HAGBs while granular at LAGBs.•Anomalous spinodal structures containing B2 and A2 phases are discovered.•Anisotropy of compression properties exists in the SLMed AlCrCuFeNi alloy.
This paper is based upon 12 months of ethnographic study while living among the Tuva and Kazakh people in Xinjiang Uyghur Autonomous Region, China. Based on observation, interviews, participation and ...secondary documents the paper uses Coser's theory of Social Conflict to suggest a four part model of how tourism engenders different forms of social conflict and fluctuating alliances between stakeholders in an environment where tourism has been introduced by agents external to the indigenous community. The actors are ethnic groupings and members of those groups, governmental officials at local, regional and national level, intermediaries of the tourism industry and private sector entrepreneurs drawn from the majority and minority ethnic groups. Tensions are identified as being based on beliefs, resources and power, and a sequential pattern of primacy is identified consistent with stages of the tourist area life cycle.
► It is based upon 12 months fieldwork in an ethnic community of Xinjiang in China. ► It applies Coser's theories of social conflict to the impacts of tourism. ► Examples of social tension are provided. ► A tension-directed tourism destination development model is suggested. ► Emic approach is needed in both tourism research and destination management policies.
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