Search

Potassium (K) is an essential macronutrient for plant growth and development and influences yield and quality of agricultural crops. Maize (Zea mays) is one of the most widely distributed crops worldwide. In China, although maize consumes a large amount of K fertilizer, the K uptake/utilization efficiency (KUE) of maize cultivars is relatively low. Elucidation of KUE mechanisms and development of maize cultivars with higher KUE are needed. Maize KUE is determined by K+ uptake, transport, and remobilization, which depend on a variety of K+ channels and transporters. We review basic information about K+ channels and transporters in maize, their functions and regulation, and the roles of K+ in nitrogen transport, sugar transport, and salt tolerance. We discuss challenges and prospects for maize KUE improvement. [ABSTRACT FROM AUTHOR]

Facing the changes in China's agricultural products marketing channel, smallholder farmers with different characteristics choose various strategies to obtain more benefits. To analyze factors affecting smallholder farmers' marketing channel choice, we classify four types of channels—Broker Channel, Farmers' Retailing Channel, Wholesale Market Channel, and Cooperative Channel—and inspect 14 variables based on the survey data of 317 households from four provinces. We use a principal components analysis (PCA) to simplify these 14 variables into seven common factors and a multivariate logit model to study how the factors influence smallholder farmers' choices. We find that compared with the Broker Channel, the Farmers' Retailing Channel is mainly affected by the logistics factor, skill factor, risk factor, and size factor; the Wholesale Market Channel is influenced by the logistics factor and age factor; and the Cooperative Channel is mainly influenced by the age factor, logistics factor, and price factor. In conclusion, the logistics factor has a significant positive effect on each channel choice, and the improvement of the market and transportation conditions has a general promoting effect. [ABSTRACT FROM AUTHOR]

To determine the dynamic change characteristics of NO3–N in a rural–urban ecotone channel, five tracer tests were conducted in the Dongda Channel in the suburbs of Changchuan city, Jilin province, China, from October 2016 to April 2017. NaBr was used as conservative tracer and KNO3 served as an added nutritive salt. The kinetic features of NO3–N were simulated via the addition of tracers and by employing the spiralling curve characterization approach and the Michaelis–Menten (M–M) equation. The average absorption length of NO3−–N background concentration (Sw-amb) is 199 m, which is much less than the discharge channel length (2.5 km), thereby suggesting that the channel has a strong NO3–N retention potential. Moreover, the M–M equation fits well the kinetic features of NO3–N adsorption. The average maximum absorption rate and subsaturation constant are 631 μg (m2 s)−1 and 1.46 mg L−1, respectively. The correlation analysis reveals that Sw-amb and NO3−–N absorption rates (NO3–Namb) are significantly negatively correlated whereas the absorption rates of NO3−–N background concentration (Uamb) and NO3–Namb are significantly positively correlated. The other spiralling indices show faint correlations with the background concentration of NO3–N. Meanwhile, the hydrological factors slightly influence NO3–N retention, but the geomorphic features of the channel, including (width residual) Фw and (cross-sectional area residual) ФA, have significant correlations with most spiralling indices, thereby highlighting the relatively important roles of geomorphic features in NO3–N retention. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Remote Sensing is the property of Editorial Office of Journal of Remote Sensing & Science Publishing Co. and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Modern sedimentation plays a crucial role for understanding ancient sedimentation in the stratigraphic record. This study reveals 3D architecture and evolution of a modern braided fluvial system. The Weihe River is the largest tributary of the Yellow River in northern China. Recent archaeological excavations revealed sets of ancient bridges in the Xi'an segment over this waterway, which provided an opportunity to understand the inner architecture and evolution of this river. Excavated pits and adjacent natural gullies were analysed using the architectural elements methods, revealing nine lithofacies types, and seven distinct architectural elements. Architectural elements typical of braided fluvial deposits including downstream accretion, lateral accretion, and channel fill elements can be identified in the studied sections. The results suggest that the Xi'an segment of the Weihe River was deposited as a braided fluvial system during the Western Han Dynasty (ca. 2,000 years ago). The sandy sediments which filled in the abandoned riverbed were mainly transported by the main stream from the west, whereas the gravel lithofacies packages were supplied by near‐source tributaries that originated from the southern Qinling Mountains. Calculations based on empirical equations suggest that at the time of the Western Han Dynasty, the width of the river course was between 400 m and 500 m, and the river depth was between 2.7 and 3.4 m, similar to the dimensions recorded in historic documents. The Weihe River has migrated approximately 4.3 km to the north since the time of the Western Han Dynasty. Considering the regional geological setting, the data suggest that this northward migration was controlled by the continuous uplift of the Qinling Mountains as well as movement of syn‐sedimentary normal faults to the south of the Weihe Basin. These tectonic movements controlled the evolution of the basin and maintained the geomorphologic characteristics of such higher topography in the south and lower in the north over a long period of time. [ABSTRACT FROM AUTHOR]

Lingding Bay has two main huh ports and connected deep water waterways in South China. Maintaining the stable pattern of "three heaches and two troughs" is the key hasis for the Western trough deepwater waterways development in Cuangzhou Port. Since 2008, due to artificial sand digging on the middle beach, three huge sand pits with total volume of 7 × 108 m3 has been formed, which directly affects the evolution of the beach and trough in Lingding Bay. By means of field investigation and numerical simulation, the influence of sand mining on surrounding water body and topography is analyzed. It is pointed out that the sediment concentration in the sediment digging area can increase greatly from 0.2 kg/m3 to 1.5-2.8 kg/m3 (up to 5 kg/m3). This will increase the deposition of the nearby seabed and also affect the waters of the Hong Kong-Zhuhai-Maeao Bridge. The influence of hydrological factors on the formation of sand pits are calculated. The results show that the main changes of tide level, tidal current and tidal volume are in the sand pit and its adjacent waters. The main changes are the tidal level decreases (less than 1cm), the tidal current decreases, and sediment deposition is mainly in the sand pit (33 cm/a). The seabed around the pit is scoured, and the scour in the south side is larger. At present, sand pits are mainly silted up, and the time of silting back is expected to take 20 years. When 2#, 3# sand pits or 2#, 4# sand pits are connected, it is possible to form a new tidal current channel, change the existing pattern of "three beaches and two troughs", and have a negative impact on the existing channel maintenance and port production. [ABSTRACT FROM AUTHOR]

The accurate prediction of debris flows occurrence that will allow the reduction or prevention of economic losses and human casualties is presently the most difficult aspect of debris flows studies but also the aspect that receives most attention. Most prediction methods are based on rainfall as the basic parameter, with the moment of occurrence as only result, and without a prediction of debris flow travel time and size. This paper takes Jiangjia Gully in Dongchuan of Yunnan Province as an example, and considers, on the basis of the fulfillment of the essential condition: the abundant availability of loose materials, the conditions for the formation of debris flows. Based on the mechanism of the initiation of debris flows in channels and the volume of rainfall in the basin, this paper also gives a systematic analysis on the travel time and size of the debris flow and suggests that the hydrological condition for forming debris flow is the unit discharge of the flood ≥0.35 m/s.m. It uses the 10-min rainfall intensity to calculate both the run-off of the rainfall and the unit discharge caused by the run-off, thus predicting the occurrence of debris flows. The velocity and the travel time of a debris flow can also be determined using the unit discharge of the run-off. The total volume of debris flows can be calculated using the 10-min intensity of rainfall and the total volume of the run-off, together with the volume concentration of the sediment in a debris flow. [ABSTRACT FROM AUTHOR]

The article presents a study which investigates the dynamic changes of sedimentation and erosion in the Jiangsu reach of the Yangtze River in China from 1959 to 2003 through geographic information system technology. It reveals that there was a switch from sedimentation to erosion status in 1985 due to decline of solid load from the upper part of the river. It also notes that the erosion rate of the lower part was larger than the middle and the upper segments due to channel flow and tide current.

The observed precipitation was suggestive of abundant precipitation in upstream Qilian mountains and low precipitation in the downstream oasis and desert in an endorheic basin. However, precipitation in mountains generated from the recycled moisture over oasis and desert areas has rarely been studied. The climatological patterns of water vapor from 1980 to 2017 in the Qilian Mountain Region (QMR) and Hexi Corridor Region (HCR) were investigated by the European Centre for Medium-Range Weather Forecasts Interim reanalysis dataset and the Modern-Era Retrospective Analysis for Research and Application, Version 2 reanalysis dataset. The results suggest that the precipitable water content decreases from the adjacent to the mountain areas. There are two channels that transport water vapor from the HCR to the QMR in the low troposphere (surface—600 hPa), suggesting that parts of recycled moisture generated from evapotranspiration over the oasis and desert of the HCR is transported to the QMR, contributing to the abundant precipitation in the QMR. This indicates that the transport mechanism is probably because of the "cold and wet island effect" of the cryosphere in QMR. This is likely one of the essential mechanisms of the water cycle in endorheic river basins, which has rarely been reported. [ABSTRACT FROM AUTHOR]

Background: User engagement is a key performance variable for eHealth websites. However, most existing studies on user engagement either focus on a single website or depend on survey data. To date, we still lack an overview of user engagement on multiple eHealth websites derived from objective data. Therefore, it is relevant to provide a holistic view of user engagement on multiple eHealth websites based on cross-site clickstream data.Objective: This study aims to describe the patterns of user engagement on eHealth websites and investigate how platforms, channels, sex, and income influence user engagement on eHealth websites.Methods: The data used in this study were the clickstream data of 1095 mobile users, which were obtained from a large telecom company in Shanghai, China. The observation period covered 8 months (January 2017 to August 2017). Descriptive statistics, two-tailed t tests, and an analysis of variance were used for data analysis.Results: The medical category accounted for most of the market share of eHealth website visits (134,009/184,826, 72.51%), followed by the lifestyle category (46,870/184,826, 25.36%). The e-pharmacy category had the smallest market share, accounting for only 2.14% (3947/184,826) of the total visits. eHealth websites were characterized by very low visit penetration and relatively high user penetration. The distribution of engagement intensity followed a power law distribution. Visits to eHealth websites were highly concentrated. User engagement was generally high on weekdays but low on weekends. Furthermore, user engagement gradually increased from morning to noon. After noon, user engagement declined until it reached its lowest level at midnight. Lifestyle websites, followed by medical websites, had the highest customer loyalty. e-Pharmacy websites had the lowest customer loyalty. Popular eHealth websites, such as medical websites, can effectively provide referral traffic for lifestyle and e-pharmacy websites. However, the opposite is also true. Android users were more engaged in eHealth websites than iOS users. The engagement volume of app users was 4.85 times that of browser users, and the engagement intensity of app users was 4.22 times that of browser users. Male users had a higher engagement intensity than female users. Income negatively moderated the influence that platforms (Android vs iOS) had on user engagement. Low-income Android users were the most engaged in eHealth websites. Conversely, low-income iOS users were the least engaged in eHealth websites.Conclusions: Clickstream data provide a new way to derive an overview of user engagement patterns on eHealth websites and investigate the influence that various factors (eg, platform, channel, sex, and income) have on engagement behavior. Compared with self-reported data from a questionnaire, cross-site clickstream data are more objective, accurate, and appropriate for pattern discovery. Many user engagement patterns and findings regarding the influential factors revealed by cross-site clickstream data have not been previously reported. [ABSTRACT FROM AUTHOR]

• Impact of retirement on health is an important research topic related to public finance as well as individual welfare. • We focus on Body Mass Index and weight outcome effects due to mandatory retirement-age policy for employees in urban China. • After reaching mandatory retirement age, retirement rates increase markedly and discontinuously for Chinese men and women. • Retirement increases weight and BMI among men but not women. This male effect is much larger for men with low education. • Drinking and eating more, fewer physical activities are channels which may induce related male weight and BMI increases. This paper analyzes the causal impact of retirement in China on Body Mass Index (BMI) and weight, which are a good gauge of the risk for some diseases. Many middle income developing countries are aging very rapidly and may have to adjust the retirement age to have financially feasible government budgets. It is important to know and understand any plausible health consequences of raising the retirement age in developing countries, and which sub-populations within these countries may be most affected. By using 2011, 2013 and 2015 waves of the China Health and Retirement Longitudinal Study (CHARLS), our identification strategy uses variation in China's mandatory retirement age with a fuzzy discontinuity design to examine an exogenous shock to retirement behavior. Our study finds that retirement will increase weight and BMI among men. This effect is much larger for men with low education. The channel may be that men with low education drink more and take less vigorous exercises after they get retired. Retirement does not affect weight and BMI for women. These effects are robust with different definitions of retirement, narrow retirement bandwidth for samples as well as dropping samples with rural Hukou. [ABSTRACT FROM AUTHOR]