Publications by authors named "Xu-Long Zhang"

4 Publications

  • Page 1 of 1

Impacts of climate change and human activities on grassland vegetation variation in the Chinese Loess Plateau.

Sci Total Environ 2019 Apr 4;660:236-244. Epub 2019 Jan 4.

State Key Laboratory of Grassland Agro-ecosystems, Institute of Arid Agroecology, School of Life Sciences, Lanzhou University, No. 222, South Tianshui Road, Lanzhou 730000, China. Electronic address:

China initiated the "Grain for Green Project" in 1999 to mitigate soil erosion. The vegetation cover of the Chinese Loess Plateau, one of the most erosive regions in the world, has been greatly increased. However, studies on quantitatively investigating the climate change and human activities on vegetation coverage change were rare. In this study, spatio-temporal changes in vegetation coverage were investigated using MODIS normalized difference vegetation index (NDVI) data over 2000-2016. And a new method was introduced using Net Primary Productivity (NPP) model and relationship between NPP and NDVI to quantitatively and spatially distinguish the NDVI affected by climate change and human activities. Results showed that mean NDVI value over 2009-2016 were 14.46% greater than that over 2000-2007. In order to quantify the contribution of climate change and human activities to vegetation change, an NPP model suitable for the grassland of the Chinese Loess Plateau was identified using biomass observations from field survey and literature. The NDVI affected by climate change (NDVI) was estimated by the NPP model and the relationship between NPP and NDVI. And the NDVI affected by human activities (NDVI) was calculated by actual NDVI minus NDVI. Comparison of the two stages showed that human activities and climate change contributed 42.35% and 57.65% respectively to the ΔNDVI on grassland in the Loess Plateau. After analysis of numerous NDVI related factors, the slopes restored by the "Grain for Green Project" was considered the main influence factor of human activities.
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http://dx.doi.org/10.1016/j.scitotenv.2019.01.022DOI Listing
April 2019

Valley-filtered edge states and quantum valley Hall effect in gated bilayer graphene.

J Phys Condens Matter 2017 May 6;29(18):185502. Epub 2017 Mar 6.

School of Physics Science and Technology, Xinjiang University, Urumqi 830046, People's Republic of China.

Electron edge states in gated bilayer graphene in the quantum valley Hall (QVH) effect regime can carry both charge and valley currents. We show that an interlayer potential splits the zero-energy level and opens a bulk gap, yielding counter-propagating edge modes with different valleys. A rich variety of valley current states can be obtained by tuning the applied boundary potential and lead to the QVH effect, as well as to the unbalanced QVH effect. A method to individually manipulate the edge states by the boundary potentials is proposed.
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http://dx.doi.org/10.1088/1361-648X/aa648aDOI Listing
May 2017

Transdermal permeation of drugs with differing lipophilicity: Effect of penetration enhancer camphor.

Int J Pharm 2016 Jun 3;507(1-2):90-101. Epub 2016 May 3.

Research Institute, the First Affiliated Hospital of Chinese PLA General Hospital, Beijing 100037, China.

The aim of the present study was to investigate the potential application of (+)-camphor as a penetration enhancer for the transdermal delivery of drugs with differing lipophilicity. The skin irritation of camphor was evaluated by in vitro cytotoxicity assays and in vivo transdermal water loss (TEWL) measurements. A series of model drugs with a wide span of lipophilicity (logP value ranging from 3.80 to -0.95), namely indometacin, lidocaine, aspirin, antipyrine, tegafur and 5-fluorouracil, were tested using in vitro transdermal permeation experiments to assess the penetration-enhancing profile of camphor. Meanwhile, the in vivo skin microdialysis was carried out to further investigate the enhancing effect of camphor on the lipophilic and hydrophilic model drugs (i.e. lidocaine and tegafur). SC (stratum corneum)/vehicle partition coefficient and Fourier transform infrared spectroscopy (FTIR) were performed to probe the regulation action of camphor in the skin permeability barrier. It was found that camphor produced a relatively low skin irritation, compared with the frequently-used and standard penetration enhancer laurocapram. In vitro skin permeation studies showed that camphor could significantly facilitate the transdermal absorption of model drugs with differing lipophilicity, and the penetration-enhancing activities were in a parabola curve going downwards with the drug logP values, which displayed the optimal penetration-enhancing efficiency for the weak lipophilic or hydrophilic drugs (an estimated logP value of 0). In vivo skin microdialysis showed that camphor had a similar penetration behavior on transdermal absorption of model drugs. Meanwhile, the partition of lipophilic drugs into SC was increased after treatment with camphor, and camphor also produced a shift of CH2 vibration of SC lipid to higher wavenumbers and decreased the peak area of the CH2 vibration, probably resulting in the alteration of the skin permeability barrier. This suggests that camphor might be a safe and effective penetration enhancer for transdermal drug delivery.
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http://dx.doi.org/10.1016/j.ijpharm.2016.05.004DOI Listing
June 2016

Cutting improves the productivity of lucerne-rich stands used in the revegetation of degraded arable land in a semi-arid environment.

Sci Rep 2015 Jul 13;5:12130. Epub 2015 Jul 13.

State Key Laboratory of Grassland Agro-Ecosystem, Institute of Arid AgroEcology, School of Life Sciences, Lanzhou University, Lanzhou, Gansu 730000, China.

Understanding the relationships between vegetative and environmental variables is important for revegetation and ecosystem management on the Loess Plateau, China. Lucerne (Medicago sativa L.) has been widely used in the region to improve revegetation, soil and water conservation, and to enhance livestock production. However, there is little information on how environmental factors influence long-term succession in lucerne-rich vegetation. Our objective was to identify the main environmental variables controlling the succession process in lucerne-rich vegetation such that native species are not suppressed after sowing on the Loess Plateau. Vegetation and soil surveys were performed in 31 lucerne fields (three lucerne fields without any management from 2003-2013 and 28 fields containing 11-year-old lucerne with one cutting each year). Time after planting was the most important factor affecting plant species succession. Cutting significantly affected revegetation characteristics, such as aboveground biomass, plant density and diversity. Soil moisture content, soil organic carbon, soil available phosphorus and slope aspect were key environmental factors affecting plant species composition and aboveground biomass, density and diversity. Long-term cutting can cause self-thinning in lucerne, maintain the stability of lucerne production and slow its degradation. For effective management of lucerne fields, phosphate fertilizer should be applied and cutting performed.
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http://dx.doi.org/10.1038/srep12130DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4499809PMC
July 2015
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