Evidence suggests that the COVID-19 pandemic has generally increased levels of stress and depression among the public. However, the impact on college students in the United States has not been ...well-documented.
This paper surveys the mental health status and severity of depression and anxiety of college students in a large university system in the United States during the COVID-19 pandemic.
An online survey was conducted among undergraduate and graduate students recruited from Texas A&M University via email. The survey consisted of two standardized scales-the Patient Health Questionnaire-9 and the General Anxiety Disorder-7-for depression and anxiety, and additional multiple-choice and open-ended questions regarding stressors and coping mechanisms specific to COVID-19.
Among the 2031 participants, 48.14% (n=960) showed a moderate-to-severe level of depression, 38.48% (n=775) showed a moderate-to-severe level of anxiety, and 18.04% (n=366) had suicidal thoughts. A majority of participants (n=1443, 71.26%) indicated that their stress/anxiety levels had increased during the pandemic. Less than half of the participants (n=882, 43.25%) indicated that they were able to cope adequately with the stress related to the current situation.
The proportion of respondents showing depression, anxiety, and/or suicidal thoughts is alarming. Respondents reported academic-, health-, and lifestyle-related concerns caused by the pandemic. Given the unexpected length and severity of the outbreak, these concerns need to be further understood and addressed.
Family domain is crucial for language maintenance. It is also a critical avenue for children’s language acquisition. In Spolsky’s language management theory, family is one of the key domains for ...language management. In this study, we focus on family language management in Hakka families in Balik Pulau, Penang. Structured-interviews were conducted in November 2012. In total, 14 Hakka families were interviewed. In each family, one parent and one child were interviewed. This article examines family language policy from three perspectives: ideology, practice, and management. The results show that Hakkas in Penang give great importance to Mandarin and almost abandon Hakka in the family domain. However, they still have strong Hakka identity and some parents have restarted to speak Hakka with their children consciously. Multilingual capacity is a common expectation from parents. With multilingual input in the family domain, most of the children become passive bilinguals or multilinguals. The regional prestige dialect Hokkien is part of the repertoire of these Hakka families. However, there are no intentional efforts from the parents to teach Hokkien to their children. Conscious language management is only found for Mandarin and sometimes for English. This results from the parents’ language ideology that Mandarin is the most important language for Chinese Malaysians and English is an international language for their children’s future career. Findings from the current study contribute to the understanding of language maintenance and language shift in general.
The flexible tactile sensor has attracted widespread attention because of its great flexibility, high sensitivity, and large workable range. It can be integrated into clothing, electronic skin, or ...mounted on to human skin. Various nanostructured materials and nanocomposites with high flexibility and electrical performance have been widely utilized as functional materials in flexible tactile sensors. Polymer nanomaterials, representing the most promising materials, especially polyvinylidene fluoride (PVDF), PVDF co-polymer and their nanocomposites with ultra-sensitivity, high deformability, outstanding chemical resistance, high thermal stability and low permittivity, can meet the flexibility requirements for dynamic tactile sensing in wearable electronics. Electrospinning has been recognized as an excellent straightforward and versatile technique for preparing nanofiber materials. This review will present a brief overview of the recent advances in PVDF nanofibers by electrospinning for flexible tactile sensor applications. PVDF, PVDF co-polymers and their nanocomposites have been successfully formed as ultrafine nanofibers, even as randomly oriented PVDF nanofibers by electrospinning. These nanofibers used as the functional layers in flexible tactile sensors have been reviewed briefly in this paper. The β-phase content, which is the strongest polar moment contributing to piezoelectric properties among all the crystalline phases of PVDF, can be improved by adjusting the technical parameters in electrospun PVDF process. The piezoelectric properties and the sensibility for the pressure sensor are improved greatly when the PVDF fibers become more oriented. The tactile performance of PVDF composite nanofibers can be further promoted by doping with nanofillers and nanoclay. Electrospun P(VDF-TrFE) nanofiber mats used for the 3D pressure sensor achieved excellent sensitivity, even at 0.1 Pa. The most significant enhancement is that the aligned electrospun core-shell P(VDF-TrFE) nanofibers exhibited almost 40 times higher sensitivity than that of pressure sensor based on thin-film PVDF.
With three inexpensive and available zinc compounds as zinc source and sodium sulfide as sulfur source, a simple and efficient one-step impinging stream method was used to prepare fine, uniform, and ...well dispersed ZnS nanoparticles based on self-designed impinging stream equipment. The effects of zinc source, reactant concentration and reaction temperature on photocatalytic properties of ZnS nanoparticles under UV irradiation were investigated. The results showed that the ZnS with best photocatalytic activity and stability was obtained under the reaction condition where Zn（NO3）2·6 H2O was used as zinc source, the reactant concentration was 0.2 mol·L-1, and the reaction temperature is 80 ℃. The corresponding optimal degradation of methyl orange（MO） in 12 min reached 99.22%, and the degradation after three cycling test retained 85.24% of the original run.
Pollutant washoff from road-deposited sediment (RDS) is an increasing problem associated with the rapid urbanization of China that results in urban non-point source pollution. Here, we analyzed the ...RDS grain size distribution and its potential impact on heavy metal pollution in urban runoff from impervious surfaces of urban villages, colleges and residences, and main traffic roads in the Haidian District, Beijing, China. RDS with smaller grain size had a higher metal concentration. Specifically, particles with the smallest grain size (<44
μm) had the highest metal concentration in most areas (unit: mg/kg): Cd 0.28–1.31, Cr 57.9–154, Cu 68.1–142, Ni 25.8–78.0, Pb 73.1–222 and Zn 264–664. Particles with smaller grain size (<250
μm) contributed more than 80% of the total metal loads in RDS washoff, while suspended solids with a grain size <44
μm in runoff water accounted for greater than 70% of the metal mass in the total suspended solids (TSS). The heavy metal content in the TSS was 2.21–6.52% of that in the RDS. These findings will facilitate our understanding of the importance of RDS grain size distribution in heavy metal pollution caused by urban storm runoff.
•Polysaccharide extracted from Tremella fuciformis was degraded with the oxidation method.•The antioxidant activities of all the samples were investigated in three systems.•The degraded sample with ...lower molecular weight possessed higher antioxidant activity.
The free-radical degradation and antioxidant activity of polysaccharide from Tremella fuciformis was investigated. In present study, the combination of Fe2+, ascorbic acid and H2O2 was used as degradation regents in order to obtain the lower molecular weight product. The result ascertained oxidative-reduce degradation did not change the main structure of polysaccharides in the test conditions. Five degraded polysaccharides were selected to evaluate their antioxidant activities in vitro. It was found that the degraded sample with lower molecular weight possessed the higher antioxidant activities. It was possible that free-radical degradation is an effective way for enhancing antioxidant activity to decrease molecular weight of polysaccharides.
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Three amino-modified hyper-cross-linked resins (HCP-M, HCP-E, and HCP-D) were synthesized, and they were evaluated for adsorption of p-chlorophenol from aqueous solution. The results ...indicated that the uploading amounts of the amino groups on the three resins followed an order of HCP-M<HCP-E<HCP-D, while their Brunauer-Emmett-Teller surface area had an opposite order. The three resins were efficient for adsorption of p-chlorophenol from aqueous solution and hydrogen bonding was the main driving force for the adsorption. The isosteric adsorption enthalpy at zero fractional loading had an order of HCP-M (−44.92kJ/mol)<HCP-E (−57.12kJ/mol)<HCP-D (−61.53kJ/mol). At the initial concentration of 502.1mg/L and the flow rate of 68mL/h, the saturated dynamic capacities of HCP-M, HCP-E, and HCP-D were 388.1, 394.3, and 318.1mg/g dry resin, respectively, and these resins could be completely regenerated and repeatedly used.
Orbital forcing of climate 1.4 billion years ago Zhang, Shuichang; Wang, Xiaomei; Hammarlund, Emma U. ...
Proceedings of the National Academy of Sciences - PNAS,
03/2015, Letnik:
112, Številka:
12
Journal Article
Recenzirano
Odprti dostop
Fluctuating climate is a hallmark of Earth. As one transcends deep into Earth time, however, both the evidence for and the causes of climate change become difficult to establish. We report ...geochemical and sedimentological evidence for repeated, short-term climate fluctuations from the exceptionally well-preserved ∼1.4-billion-year-old Xiamaling Formation of the North China Craton. We observe two patterns of climate fluctuations: On long time scales, over what amounts to tens of millions of years, sediments of the Xiamaling Formation record changes in geochemistry consistent with long-term changes in the location of the Xiamaling relative to the position of the Intertropical Convergence Zone. On shorter time scales, and within a precisely calibrated stratigraphic framework, cyclicity in sediment geochemical dynamics is consistent with orbital control. In particular, sediment geochemical fluctuations reflect what appear to be orbitally forced changes in wind patterns and ocean circulation as they influenced rates of organic carbon flux, trace metal accumulation, and the source of detrital particles to the sediment.
Significance There is a wealth of evidence pointing to dramatic short-term climate change on Earth over the last few million years. Much of this climate change is driven by variations of Earth’s orbit around the Sun with characteristic frequencies known as Milankovitch cycles. Robust evidence for orbitally driven climate change, however, becomes rare as one descends deep into Earth time. We studied an exceptional record of climate change as recorded in 1.4-billion-year-old marine sediments from North China. This record documents regular changes in subtropical/tropical Hadley Cell dynamics. These changes in dynamics controlled wind strength, rainfall, and ocean circulation, translated into cyclic variations in sediment geochemistry, much like the orbital control on climate today and in the recent past.
The cycles of phosphorus, carbon and oxygen are intimately linked. Indeed, in many models, phosphorus is considered the driver of the carbon and oxygen cycles, and low concentrations of atmospheric ...oxygen during the Mesoproterozoic Era have been linked to extreme phosphorus limitation in the Mesoproterozoic oceans. To evaluate the Mesoproterozoic Era phosphorus cycle, we analyze the concentrations of phosphorus, organic carbon, and selected trace metals in several geological formations of Mesoproterozoic age. We combine these analyses with literature data to explore the relationship between phosphorus and organic carbon removal into Mesoproterozoic Era sediments through a variety of water depths and water-column chemistries. We find that the ratio of organic carbon to reactive phosphorus (Corg/Preact) is largely invariant between different paleo-settings with average Corg/Preact that is either equal to or less than the Redfield ratio of 106/1 through all environments we explored. We put these results in the context of the modern phosphorus cycle which is reviewed here. Compared to modern phosphorus dynamics, we see no evidence for an anoxic-euxinic feedback between phosphorus burial, carbon burial and oxygen production during Mesoproterozoic times. However, we do identify an additional potential phosphorus feedback related to the relationship between anoxia and deep-sea phosphorus dynamics that could have importance in oxygen regulation through time. We find that the average value of Corg/Preact during the Mesoproterozoic Era was greater than the average for modern sediments. This result suggests that equal or more organic carbon was buried per unit of phosphorus during Mesoproterozoic times compared to today, a conclusion broadly consistent with the carbon isotope record. These results offer the possibility of a strong oxygen source to the atmosphere during the Mesoproterozoic Era, raising the conundrum as to why atmospheric oxygen levels were lower then when compared to now. We suggest that a variety of factors may explain these differences in oxygen concentration including elevated rates of mantle degassing, reduced rates of phosphorus weathering and the lack of a terrestrial biosphere.
Low pressure N2 and CO2 adsorption experiments were performed on two low volatile bituminous coals to gain insights into mesopore and micropore characteristics and the effects of particle size, ...composition (mineral matter and maceral) and tectonic deformation on them. Original coal and tectonized coal were sieved into five particle size fractions, i.e., 18–35 mesh (0.50–1.00mm), 35–60 mesh (0.25–0.50mm), 60–120 mesh (0.125–0.250mm), 120–230 mesh (0.063–0.125mm) and 230–450 mesh (0.032–0.063mm). Low pressure gas adsorption analysis, proximate analysis and maceral analysis were conducted on each particle size fraction. Specific surface area of mesopore varies from 0.22m2/g to 3.06m2/g and from 1.00m2/g to 2.07m2/g in original coal and tectonized coal, and that of micropore is from 123.7m2/g to 164.6m2/g and from 100.7m2/g to 106.7m2/g, respectively. The vast majority of total specific surface area is within micropores. Mesopore specific surface area and volume are dependent on particle size. Decreasing particle size makes some inaccessible mesopores become accessible to N2 molecules, increasing mesopore specific surface area and volume. In contrast to mesopore characteristics, micropore characteristics are independent of particle size. Mineral matter contributes minimally to micropore specific surface area and volume. There is no consistent relationship between mineral matter and mesopore characteristics. Maceral composition, which is represented by the ratio of vitrinite to inertinite, has a uniformly negative correlation with mesopore characteristics, but plays a different role in micropore characteristics. The heterogeneity in composition resulting from sieving is reduced, so the effect of particle size on pore characteristics is weakened in the tectonized coal. Tectonic deformation enhances mesopore specific surface area and volume by removing constricted pore openings and increasing accessible mesopores. Moreover, tectonic deformation is likely to cause micropores collapse, which results in a significant decrease in micropore specific surface area and volume.
•Particle size affects mesopore characteristics, but not micropore characteristics.•Mineral matter contributes minimally to micropore characteristics.•Maceral influences mesopore characteristics uniformly.•Tectonic deformation increases accessible mesopores and causes micropores collapse.
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