Staying Home, Tweeting Hope: Mixed Methods Study of Twitter Sentiment Geographical Index During US Stay-At-Home Orders.

BACKGROUND: Stay-at-home orders were one of the controversial interventions to curb the spread of COVID-19 in the United States. The stay-at-home orders, implemented in 51 states and territories between March 7 and June 30, 2020, impacted the lives of individuals and communities and accelerated the heavy usage of web-based social networking sites. Twitter sentiment analysis can provide valuable insight into public health emergency response measures and allow for better formulation and timing of future public health measures to be released in response to future public health emergencies. OBJECTIVE: This study evaluated how stay-at-home orders affect Twitter sentiment in the United States. Furthermore, this study aimed to understand the feedback on stay-at-home orders from groups with different circumstances and backgrounds. In addition, we particularly focused on vulnerable groups, including older people groups with underlying medical conditions, small and medium enterprises, and low-income groups. METHODS: We constructed a multiperiod difference-in-differences regression model based on the Twitter sentiment geographical index quantified from 7.4 billion geo-tagged tweets data to analyze the dynamics of sentiment feedback on stay-at-home orders across the United States. In addition, we used moderated effects analysis to assess differential feedback from vulnerable groups. RESULTS: We combed through the implementation of stay-at-home orders, Twitter sentiment geographical index, and the number of confirmed cases and deaths in 51 US states and territories. We identified trend changes in public sentiment before and after the stay-at-home orders. Regression results showed that stay-at-home orders generated a positive response, contributing to a recovery in Twitter sentiment. However, vulnerable groups faced greater shocks and hardships during the COVID-19 pandemic. In addition, economic and demographic characteristics had a significant moderating effect. CONCLUSIONS: This study showed a clear positive shift in public opinion about COVID-19, with this positive impact occurring primarily after stay-at-home orders. However, this positive sentiment is time-limited, with 14 days later allowing people to be more influenced by the status quo and trends, so feedback on the stay-at-home orders is no longer positively significant. In particular, negative sentiment is more likely to be generated in states with a large proportion of vulnerable groups, and the policy plays a limited role. The pandemic hit older people, those with underlying diseases, and small and medium enterprises directly but hurt states with cross-cutting economic situations and more complex demographics over time. Based on large-scale Twitter data, this sociological perspective allows us to monitor the evolution of public opinion more directly, assess the impact of social events on public opinion, and understand the heterogeneity in the face of pandemic shocks.

China's Investments in Germany and the Impact of the COVID-19 Pandemic.

This paper analyses how China's investments in Germany have developed over time and the potential impact of the COVID-19 pandemic in this regard, based on four different datasets, including our own survey in mid-2020. Our analysis shows that Germany is currently one of the most attractive investment destinations for Chinese investors. Chinese state-owned enterprises have played an important role as investors in Germany - particularly in large-scale projects. The COVID-19 pandemic has had some negative but rather temporary effects on Chinese investments in Germany. Germany is expected to stay attractive to Chinese investors who seek to gain access to advanced technologies and know-how in the future.

High-Yield Synthesis of Sodium Chlorides of Unconventional Stoichiometries.

Abnormal salt crystals with unconventional stoichiometries, such as Na2 Cl, Na3 Cl, K2 Cl, and CaCl crystals that have been explored in reduced graphene oxide membranes (rGOMs) or diamond anvil cells, hold great promise in applications due to their unique electronic, magnetic, and optical properties predicted in theory. However, the low content of these crystals, only <1% in rGOM, limits their research interest and utility in applications. Here, a high-yield synthesis of 2D abnormal crystals with unconventional stoichiometries is reported, which is achieved by applying negative potential on rGOM. A more than tenfold increase in the abnormal Na2 Cl crystals is obtained using a potential of -0.6 V, resulting in an atomic content of 13.4 ± 4.7% for Na on rGOM. Direct observations by transmission electron microscopy and piezoresponse force microscopy demonstrates a unique piezoelectric behavior arising from 2D Na2 Cl crystals with square structure. The output voltage increases from 0 to ≈180 mV in the broad 0-150° bending angle regime, which meets the voltage requirement of most nanodevices in realistic applications. Density functional theory calculations reveal that the applied negative potential of the graphene surface can strengthen the effect of the Na+ -π interaction and reduce the electrostatic repulsion between cations, making more Na2 Cl crystals formed.

Unexpectedly efficient ion desorption of graphene-based materials.

Ion desorption is extremely challenging for adsorbents with superior performance, and widely used conventional desorption methods involve high acid or base concentrations and large consumption of reagents. Here, we experimentally demonstrate the rapid and efficient desorption of ions on magnetite-graphene oxide (M-GO) by adding low amounts of Al3+. The corresponding concentration of Al3+ used is reduced by at least a factor 250 compared to conventional desorption method. The desorption rate reaches ~97.0% for the typical radioactive and bivalent ions Co2+, Mn2+, and Sr2+ within ~1 min. We achieve effective enrichment of radioactive 60Co and reduce the volume of concentrated 60Co solution by approximately 10 times compared to the initial solution. The M-GO can be recycled and reused easily without compromising its adsorption efficiency and magnetic performance, based on the unique hydration anionic species of Al3+ under alkaline conditions. Density functional theory calculations show that the interaction of graphene with Al3+ is stronger than with divalent ions, and that the adsorption probability of Al3+ is superior than that of Co2+, Mn2+, and Sr2+ ions. This suggests that the proposed method could be used to enrich a wider range of ions in the fields of energy, biology, environmental technology, and materials science.

Ultrahigh Water Permeance of Reduced Graphene Oxide Membrane for Radioactive Liquid Waste Treatment.

Membrane methods exhibit great potential for application in radioactive liquid waste treatment. In this work, we prepared a reduced graphene oxide using the amino-hydrothermal method (AH-rGO) that exhibited effective rejection rates of 99.9% for CoCl2, ZnCl2, NiCl2, and radionuclide 60Co solutions with an ultrahigh water permeance of >71.9 L m-2 h-1 bar-1. The thickness of the AH-rGO membranes affects the water permeance, as the membrane with a thickness of ≈250 nm has the highest water permeance of up to 125.1 L m-2 h-1 bar-1 with the corresponding rejection rate of 86.8%. Importantly, this is the most permeable membrane with a satisfactory level of the rejection rate for typical radioactive ions of Co2+, Zn2+, and Ni2+. Moreover, the AH-rGO membranes presented excellent stability. These findings demonstrate the potential of reduced graphene oxide (rGO) membranes for radioactive liquid waste treatment.

[Magnetic Responses of Heavy Metals in Street Dust of Typical Mine-Based City, Northwest China].

Magnetic characteristics and heavy metal properties of 43 street dust samples collected from Baiyin City, northwest of China were systematically analyzed. The results revealed that the main magnetic minerals were low-coercivity magnetite and maghemite with coarse pseudo single domain (PSD) and multi-domain (MD) in magnetic grain size. Compared with the domestic comprehensive cities, low frequency magnetic susceptibility(χlf) value of street dust samples in Binyin varied from 43. 75 x 10(-8) m3.kg-1 to 1 340. 08 x 10(-8) m3.kg-1 with the average value of 245. 98 x 10(-8) m3.kg-1, the magnetic mineral content in street dust samples of Binyin was low relatively, hut it varied among distinct districts with industrial district was the highest and the stripe traffic area was more higher than those of other regions(commercial district, new district). Different functional zones of Baiyin had a single pollution source relatively. Additionally, the contribution to strong magnetic minerals was predominated by industrial pollution and the distribution of pollution degrees in Bainyin showed a significant spatial difference. Concentrations of heavy metals(Cu, Pb, Zn) were generally high in Baiyin street dust. The significantly positive correlation between magnetic parameters(χlf, χARM, SIRM, SOFT) and pollution load index(PLI) and their consistent spatial characteristics confirm that magnetic concentration parameters can effectively monitor urban heavy metals pollution and determine the bounds and areas of pollution, providing a valuable tool for further urban pollution control.