Studies of the Relationship between City Size and Urban Benefits in China Based on a Panel Data Model

Policy regarding the size of cities is an important component of China’s urban policy prescription. We used a curvilinear regression model in this study to identify the optimal function and conducted curve panel data regression analysis on the panel data of the benefits of the economy, ecosystem services, and city size in China. In doing so, we obtained the regression relationship between city size and the benefits of the economy, environment, and resources of a city. Our main findings are as follows: (1) city size is not the most important factor determining a city’s benefits. However, there is a significant difference in the average city benefit between cities of various sizes; (2) city per capita GDP increase exhibited an inverted-N-shaped relationship with increasing city size, initially decreasing but subsequently increasing. The city size corresponding to the maximum value was usually higher than or close to the actual city size. Thus, it can be concluded that when a city’s population is more than 1 million, its per capita output increases; (3) a city’s resource services benefits all exhibited the trend of improving with increasing city size. This trend was particularly pronounced among cities with a population of less than 1 million; and (4) a city’s environmental services benefits exhibited an inverted-U-shaped relationship with city size, initially increasing but subsequently decreasing

Spatial-Temporal Characteristics and LMDI-Based Impact Factor Decomposition of Agricultural Carbon Emissions in Hotan Prefecture, China

Greenhouse gas emissions from the agricultural ecosystem account for 7%–20% of the world’s total greenhouse gas emissions, while approximately 17% of China’s carbon emissions are from agriculture. In this study, based on the scientific calculation system of carbon emissions in agriculture, we calculated the carbon emissions of agriculture in the Hotan prefecture between 1999 and 2013 and analyzed their spatial-temporal characteristics; next, we used the LMDI model to study the driving factors of agricultural carbon emissions. The results demonstrated the following: (1) in time series, the agricultural carbon emissions showed three stages of change, i.e., “decline, continued to rise and decline”, during the period of 1999 to 2013 in the Hotan prefecture; (2) In space, the carbon emissions from agricultural land use, paddy fields, enteric fermentation, and manure management were different due to the different sizes of cities and counties. The intensity of agricultural carbon emissions was varied and high, but the agricultural production structure, agricultural carbon emissions structure and other aspects had a high degree of consistency and homogeneity in the cities and counties of the Hotan prefecture; (3) Regarding the driving mechanism, the labor factor, agricultural labor productivity, and planting-animal husbandry carbon intensity are the main factors that increase agricultural carbon emissions in the Hotan prefecture. Compared with 1999, three major factors cumulatively achieved a 199.68% carbon emission increment from 2000 to 2013, of which the labor factor cumulatively increased by 120.04%, the agricultural labor productivity factor cumulatively increased by 54.94% and the planting-animal husbandry carbon intensity factor cumulatively increased by 24.70%. The agricultural production structure factor largely inhibited agricultural carbon emissions of the Hotan prefecture, which cut 99.74% of the carbon emissions from 2000 to 2013. Finally, we proposed policy recommendations, including the acceleration of labor transfer, the innovation and promotion of science and technology, the scientific breeding and rational disposal of livestock waste, and the adjustment and optimization of the agricultural industry structure

New Andrastin-Type Meroterpenoids from the Marine-Derived Fungus Penicillium sp.

Three new andrastin-type meroterpenoids penimeroterpenoids A–C (1–3) together with two known analogs (4 and 5) were isolated from the cultures of the marine-derived Penicillium species (sp.). The structures of the new compounds were elucidated on the basis of 1- and 2-dimensional (1D/2D) Nuclear Magnetic Resonance (NMR) spectroscopic and mass spectrometric analysis. The absolute configurations of 1–3 were determined by comparison of experimental and calculated electronic circular dichroism (ECD) spectra. Compound 1 showed moderate cytotoxicity against A549, HCT116, and SW480 cell lines

The Impact of COVID-19 Policy Response on Food Prices: A Case Study in China

The COVID-19 pandemic has threatened human lives and caused an unprecedented impact on the global economy, notably on the global food system. COVID-19 itself and its policy response have severely affected food prices. This paper analyzes the short-term and long-term impacts of COVID-19 cases and policy responses (government response index (GRI), economic support index (ESI), stringency index (SI)) on food prices (Chinese cabbage price (CP), pork price (PP), flour price (FP), rice price (RP)) in China’s major food producing areas and major food selling areas through the autoregressive distribution lag error correction (ARDL-ECM) method and graphical analysis. as the purpose is to provide evidence for food security policy regulation to stabilize food prices and improve the food system’s ability to withstand similar emergencies in the future. This study finds that the short-term impact of COVID-19 policy responses on food prices is larger, while the long-term impact is smaller. The impacts of COVID-19 itself and COVID-19 policy responses on food prices vary by food type and food production and consumption region. For food type, the Chinese cabbage price was most affected by the COVID-19 policy response, followed by pork, and the staple food prices (flour price and rice price) were least affected. For regions, the Chinese cabbage price in food producing areas was more influenced by COVID-19 and the pork price in food selling areas was more influenced by COVID-19. For the single indexes, GRI and SI had uneven effects on different food prices. However, ESI had a significant positive impact on the Chinese cabbage price (CP) and pork price(PP), except in Guangdong and Hubei. Staple food prices were almost unaffected by COVID-19 confirmed cases and policy responses. Then, taking the Chinese cabbage price in Beijing, Shandong, and Hubei as an example, we find that “dynamic clearance” influenced the Chinese cabbage price in the short term, and Chinese cabbage price increased largely in the first stage. Finally, the reasons behind the research results of this paper are analyzed, and scientific suggestions are put forward for the implementation of food supply policies to ensure food price stability and food security in the face of similar pandemics in the future

Spatio-Temporal Patterns and Determinants of Inter-Provincial Migration in China 1995–2015

Inter-provincial migration causes dramatic changes in the population, as well as in the development of the social economy at both origin and destination, which is related to sustainable development in any country. Using inter-provincial migration data during the periods covering 1995⁻2000, 2000⁻2005, 2005⁻2010, and 2010⁻2015, we analyze the migration volume, intensity and flow, as well as its changes over time. We also examine the determinants associated with migration by applying Poisson pseudo-maximum-likelihood (PPML) estimation techniques. The results show that migrants move mainly from inland to coastal areas; however, since 2010, the number of migrants moving from coastal to inland areas has shown a continuous increase. This inter-provincial migration was driven largely by the influence of economic factors, such as high urban income per capita. A better model for the period of 2010⁻2015 is established by adopting an extended set of variables. New variables that represent regional disparities and industrial upgrades have a positive impact on inter-provincial migration, which shows that regional economic disparities and economic restructuring have played an important role in migration in recent years

A novel magnetoresistance induced by charge ordering in ferromagnetic/charge-ordered/ferromagnetic trilayers

Microstructure, magnetoresistance (MR) and magnetic properties of Pr0.7Sr0.3MnO3/La0.5Ca0.5MnO3/Pr0.7Sr0.3MnO3 trilayers, which are shown to be tunable with different La0.5Ca0.5MnO3 spacer thickness, are investigated. The trilayer with 6 nm thick La0.5Ca0.5MnO3 spacer show $\text{MR}\sim37{\%}$ at 195 K in 1 T and $\text{MR}\sim80{\%}$ at 220 K in 9 T, which is realized through the double-exchange mechanism. In contrast, trilayers with the thicker La0.5Ca0.5MnO3 spacer show enhanced MR at a wide low-temperature range. The obtained $\text{MR}\sim52{\%}$ at 50 K in 1 T in the trilayer with 18 nm thick La0.5Ca0.5MnO3 spacer is superior to that of other magnetic nanoscales. We surmise that this MR originates in the ferromagnetic/antiferromagnetic competition accompanied with the formation of a charge-ordered antiferromagnetic state and the collapse of the charge-ordered state at the applied magnetic field, rather than in the double-exchange mechanism. Large and tunable MR can be realized by controlling the strain state (the thickness of the La0.5Ca0.5MnO3 spacer), which can be applied in the used devices

Evaluation of Oasis Sustainability Based on Emergy and Decomposition Analysis

The human welfare and sustainability of oases have received wide attention because of the fragility of the ecological environment and the instability of these systems. In this study, the sustainability level and the driving forces of emergy utilization in the Hotan Prefecture (in the Xinjiang Uygur Autonomous Region, China) from 2005 to 2015 were evaluated using the emergy approach combined with the logarithmic mean Divisia index (LMDI) method. The emergy analysis showed that non-renewable resources (N) accounted for a large proportion of net emergy (U). The Emergy Sustainability Index (ESI) continued to decline in the study period, implying increasing environmental stress. From a long-term perspective, the system’s development is not sustainable. According to the emergy analysis and the LMDI results, it is imperative to pursue the following aims: (1) increase the per capita gross domestic product (GDP) and labor productivity, (2) improve the efficiency of state investment and aid fund utilization, (3) enhance the area’s sustainability level and economic independence, and (4) protect the area’s fragile ecological environment

Tuning photoluminescence of single-layer MoS2 using H2O2

Enhancing photoluminescence (PL) of single-layer (1L) MoS2 is critical to its application as the thinnest light-emitting material. In this report, we show that the PL intensity of 1L-MoS2 can be enhanced by 8 times using physisorption of H2O2 molecules as p-type dopants. By using toluene to form the sandwiched structure of H2O2/1L-MoS2/toluene, the PL intensity of 1L-MoS2 can be enhanced up to 27.4 times. Our research proposes a simple but effective method to enhance the light emitting properties of 1L-MoS2

Effects of Policy Intervention on Food System Resilience to Emergency Risk Shock: Experience from China during COVID-19 Pandemic

Achieving the goal of zero hunger within the goal of sustainable development requires improving the resilience of food systems to various types of risk shocks; food systems have shown significant vulnerability to COVID-19 outbreaks and transmission. By analyzing the impact of China’s lockdown policy and food security emergency policy in 2020 on food prices during the COVID-19 pandemic, we can clarify the role of policy intervention in enhancing the resilience of the food system, which can provide guidance, using China’s experience, for dealing with global food safety emergencies in the future. Firstly, we selected Beijing, Shanghai and Guangdong as food-consuming areas, and Shandong, Henan, and Hubei as food-producing areas. We also collected food security emergency policy data from the Chinese government website during the COVID-19 pandemic. Secondly, a difference-in-difference method was used to observe that Chinese cabbage and pork prices in the main food-producing areas and food-consuming areas rose more obviously after the adoption of lockdown policy, and Chinese cabbage and pork prices in the food-consuming areas increased more obviously than those in food-producing areas. However, staple food prices have not risen significantly. Thirdly, the response of four kinds of food prices to the food security emergency policy is analyzed quantitatively and graphically using the food price volatility index and food price increase rate; we observed that the response of food prices to the food security emergency policy is related to the food types and regions. For food types, the fluctuation degree and increase in Chinese cabbage and pork prices decreased significantly after the adoption of the food security emergency policy. For regions, when the food security emergency policy was adopted, the food prices in the main food-consuming areas fluctuated more obviously than those in food-producing areas. Finally, we found that the implementation of the transport policy and the joint supply emergency policy in the main producing and consuming areas has played a very significant and positive role in stabilizing food prices