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P2P Lending recommender systems are embracing portraying schemes to obtain profiles of both loan and lender, and thus to overcome inherent limitations of general recommendation models. A successful recommendation method requires proper handling the interactions between loans and lenders. We argue that three fundamental problems need to be addressed: 1) how to fully utilize different properties of loan for establishing its profile, 2) how to adapt social and psychological factors for enhancing lender’s profile, and 3) how to exploit the interactions between loan and lender. To the best of our knowledge, there lacks a unified framework that addresses these problems. In this work, we contribute a new solution named RRWP (Recommendation via Random Walk with Profile of loan and lender), for learning recommender systems for P2P Lending. We develop a hybrid graph random walk-based model to capture the complicated interactions between loans and lenders. In particular, the algorithm consists of three stages for better P2P lending recommendation. (1) Loan profile is built by utilizing attributes of both loan and borrower; (2) Lender profile is established via his social and psychological factors together with interactions between loan and lender; (3) A hybrid graph is constructed based on which random walk is performed to recommend for both loan and lender. Extensive experiments on real-world dataset demonstrate the effectiveness of RRWP. Further analysis reveals that profile modelling is consistent with the basic investment theory in finance.

Poor safety and effectiveness is an outstanding challenge in the preparation of drug delivery systems (DDS) for cancer treatment. The pursuit of the high curative effect will inevitably increase the risk of adverse side effects. Herein, a bio-safe DDS was constructed by combining the advantages of functional zein and Au doped mesoporous silica nanoparticles (Au@SiO2) to achieve chemo-photothermal therapy. The cRGD functionalized zein (cRGD-Zein) was coated on the surface of Au@SiO2 which effectively avoided premature leakage of paclitaxel and realized sustained drug release. Meanwhile, the high hemolysis rate (107%) of Au@SiO2 had been significantly reduced to 4%. The anti-hemolysis mechanism of functionalized zein was explored to give a deeper understanding of the interaction between nanoparticles and RBCs. The results showed that the functional zein would change the protein conformation during the interaction with Au@SiO2 to protect the RBCs from the damage of Au@SiO2. And the release rate of hemoglobin was limited by the size of RBCs membrane cracks with approximately 40 nm in width and 470 nm in length. The cell cytotoxicity and uptake assays showed that the prepared DDS exhibited low tumour cell viability (35%) and enhanced uptake performance (99.3%). This work suggested that the prepared nanoparticles could serve as a promising carrier to achieve safe and efficacious tumour therapy.

The microphase behavior at different time scales was investigated to understand the mechanism of zein self-assembly during the built-in ultrasonic dialysis process (BUDP) in this study. The results indicated that the mutual mass transfer between zein solution and dialysate changed the solvent polarity, which caused the conformational transition of zein molecules, formation of stable droplets under the ultrasonic field, and further solidification of the compact microspheres. The effects of dialysate properties on zein self-assembly were investigated. The results showed that both pH and ionic strength had a great effect on the size, zeta potential, and morphology of the obtained zein particles, where zein microspheres with a size around 1–2 μm and zeta potential > 30 mV were obtained at pH 4–pH 8 and NaCl concentration ≤ 10 mM. And non-ionic Tween 60 could be used as a potential surfactant to improve the stability of zein samples through a physical combination.

Taking extruded Al–Zn–Mg–Cu alloy (7A04 alloy) bars as the research object, the effect and mechanism of pre-annealing treatments on the microstructure and mechanical properties of the aged alloy bars were investigated. The results show that a pre-annealing treatment at 350°C for 15 h before a T6 treatment substantially reduced the sensitivity of the microstructure and mechanical properties of the extruded 7A04 aluminum alloy specimens toward the extrusion temperature. The average grain sizes of the specimens extruded at 390 and 430°C after T6 treatment were 3.4 and 8.1 μm, respectively, and their elongations to failure were 7.0% and 9.2%, respectively. However, after pre-annealing + T6 treatment, the differences in both the grain sizes and the elongations of the specimens became small, i.e., their average grain sizes were 3.2 and 3.8 μm and their elongations were 12.0% and 13.3%, respectively. For the specimens extruded at the same temperature, pre-annealing treatment obviously improved the plasticity of the alloy, which is attributed to an increase in soft texture or to grain refinement in the specimens as a result of the pre-annealing + T6 treatment.

Effects of climate change on vegetation greenness have attracted considerable attention in the context of global change; however, the dependence of such climatic effects on elevation remains poorly understood. In this study, we examine the relationship between vegetation greenness change and climate change and, in particular, characterize how this relationship changes with elevation in the high mountains of southwest China by using the remotely sensed normalized difference vegetation index (NDVI), and observed temperature and precipitation data sets for the period of 1982–2013. The results show that vegetation exhibited a greening trend (slope: 0.0008 year−1, p 0.05). The vegetation greening and climate warming trends were stronger in the higher elevation plateaus than in the lower elevation mountains. Statistical analysis showed that temperature was the main driving factor on vegetation greening, and the driving effect was elevation-dependent. A substantially more significant correlation between climate warming and vegetation greening was found in the higher elevation plateaus, which reveals a higher temperature sensitivity of these plateaus. In addition, a significant correlation between inter-annual standard deviations of NDVI and precipitation during 1982–2013 was tracked over the entire study area.

To develop a safer, more stable and potent formulation of gefitinib (GFB), micro-spheres of GFB encapsulated into poly ( l -lactic acid) (PLLA) have been prepared by supercritical anti-solvent (SAS) technology in this study. Operating factors were optimized using a selected OA16 (45) orthogonal array design, and the properties of the raw material and SAS processed samples were characterized by different methods The results show that the GFB-loaded PLLA particles prepared were spherical, having a smaller and narrower particle size compared with raw GFB. The optimal GFB-loaded PLLA sample was prepared with less aggregation, highest GFB loading (15.82%) and smaller size (D50 = 2.48 μm, which meets the size of dry powder inhalers). The results of XRD and DSC indicate that GFB is encapsulated into PLLA matrix in a polymorphic form different from raw GFB. FT-IR results show that the chemical structure of GFB does not change after the SAS process. The results of in vitro release show that the optimal sample release was slower compared with raw GFB particles. Moreover, the results of in vitro anti-cancer trials show that the optimal sample had a higher cytotoxicity than raw GFB. After blending with sieved lactose, the flowability and aerosolization performance of the optimal sample for DPI were improved, with angle of repose, emitted dose and fine particles fractions from 38.4° to 23°, 63.21% to >90%, 23.37% to >30%, respectively.

Site-specific drug delivery is an effective approach to decreasing drug toxicity and enhancing therapeutic effects. In this study, zein was decorated with folic acid (FA) for targeted delivery of 10-hydroxycamptothecin (HCPT). The reaction process was monitored using an online ATR-UV spectrophotometer, and the conjugation degree was quantified using a UV–vis spectrophotometer. Successful conjugation was evidenced using FT-IR and 1H NMR. The influence of FA conjugation on the self-assembly of zein molecules and cellular uptake was investigated in detail. FA conjugation facilitates the formation of small nanoparticles with good dispersity and stability and improves the cellular uptake in folate receptor positive cells. HCPT nanocrystals (NC) were prepared and incorporated into FA-zein. The drug release behavior of HCPT NC/FA-zein nanoparticles is more consistent with a diffusion mechanism than a matrix swelling/erosion mechanism of HCPT NC/zein particles; and HCPT NC/FA-zein nanoparticles induce higher anti...

A method to improve the homogeneities of microstructure and mechanical property in an Al-Zn-Mg-Cu extruded product, which changes cooling rate after homogenization treatment to obtain the different distribution characteristics of the precipitates, was proposed and the microstructure evolution and mechanical properties of the alloy were investigated. The results show that the precipitates in the water-quenched billet are of mainly coarse particles with the content of about 2.0%, while a large number of needle-shaped precipitates are dispersively distributed in the furnace-cooled billet with the content of about 9.8%. Numerous precipitates distributed dispersively can improve the homogeneities of microstructure and mechanical property of the alloy during extrusion. For example, when the water-quenched billets are extruded at 390 and 430 °C followed by solution-aging treatment, the average grain sizes of the two bars are 3.4 and 8.1 μm, and the elongations to failure are 7.0 and 9.2%, respectively. When the furnace-cooled billets are extruded at 390 and 430 °C followed by solution-aging treatment, the average grain sizes of the two bars are 3.1 and 3.5 μm, respectively, and the elongations are basically the same, indicating the better microstructure homogeneity and mechanical properties.

Supercritical CO2 anti-solvent (SAS) process is a green and effective method to produce particles with designated microstructures. In this study, the particle microstructures of gefitinib, a potent anticancer agent, are tailored by the SAS process to improve its aqueous solubility. The dichloromethane/ethanol (1:4, v/v) was selected as the suitable solvent from typical solvents used in the SAS process at first. Then, the effects of other SAS operating parameters, i.e., the flow rate of gefitinib solution (F), the concentration of gefitinib in the solution (C), the precipitation pressure (P) and the temperature (T), on the gefitinib particle size were investigated in detail. Lower F, lower C, higher P and suitable T were recommended for the formation of gefitinib particles with small particle size. The properties of the raw material and SAS processed samples of gefitinib were characterized by different methods. The results showed that a new polymorphic form (Form β) of gefitinib, which present different physicochemical properties, i.e., smaller particle size, narrower particle size distribution and higher solubility, with raw gefitinib (Form 1), was captured after the SAS process. The predicted structures of gefitinib crystals, which were consistent with the experiments, were performed from their experimental XRD data by the direct space approach using the Reflex module of Materials Studio. Meanwhile, the SAS processed gefitinib particles showed much higher solubility and faster dissolution rate than that of raw gefitinib, which had the potential to improve its bioavailability and decrease the dose-related adverse effects.

The effect of longitudinal alternating current (LAC) on the growth of the interfacial layers of the copper cladding aluminum (CCA) composite flat bar during isothermal annealing was investigated. The results showed that the application of LAC could remarkably inhibit the growth of interfacial compounds as well as improve the interfacial bonding property of the CCA composite. When the CCA flat bars were annealed at temperatures ranging from 723 to 773 K for 1 h with a LAC density higher than 0.625 A/mm2, the total thickness of the interfacial compound layers was reduced by more than 75% in comparison to CCA flat bars annealed without LAC. The reduction of the thickness of the interfacial layers resulted in an improvement of the bonding strength of the CCA composite. The mechanism of the inhibition effect was that the application of LAC could accelerate the vacancy annihilation in component metals.

In this study, methyl paraben (MP) was selected as the model component, and acetaminophen (APAP), p-methyl acetanilide (PMAA) and acetanilide (ACET), which share the similar molecular structure as MP, were selected as the three tailor-made additives to study the effect of tailor-made additives on the crystal growth of MP. HPLC results indicated that the MP crystals induced by the three additives contained MP only. Photographs of the single crystals prepared indicated that the morphology of the MP crystals was greatly changed by the additives, but PXRD and single crystal diffraction results illustrated that the MP crystals were the same polymorph only with different crystal habits, and no new crystal form was found compared with other references. To investigate the effect of the additives on the crystal growth, the interaction between additives and facets was discussed in detail using the DFT methods and MD simulations. The results showed that APAP, PMAA and ACET would be selectively adsorbed on the growth surfaces of the crystal facets, which induced the change in MP crystal habits.

By incorporating Cytochrome c (peroxidase, Cyt c) into a skeleton of its corresponding synthetic MOF analogue (peroxidase mimic, CuBDC), approximately 12-fold catalytic efficiency (kcat/KM) enhancement is observed compared to free Cyt c. Meanwhile, the shield endowed by CuBDC prevents encapsulated enzymes from deactivation by trypsin digestion, thermal treatment and long-term storage in vitro. This concept of combining enzymes and their MOF mimics with enhanced enzymatic activity and stability may provide new insights into the design of highly active, stable enzyme–MOF composite catalysts and holds promise for applications in biocatalysis, biosensing and drug delivery systems.

Questions (1) What are the primary factors determining the precipitation-use efficiency (PUE) in Northern Tibet? (2) How does PUE respond to the gradients of biotic and abiotic factors? (3) How do the composition and structure of plant functional groups (PFGs) affect PUE?. Location Northern Tibet, China. Methods A community survey of species composition, cover and aboveground net primary productivity (ANPP) was conducted within 1 × 1 m plots in 62 slightly disturbed sites. The effects of community features (total cover, cover of PFGs and species richness) and environmental factors (mean annual precipitation [MAP], mean annual temperature, surface soil bulk density, pH, and carbon and nitrogen content) on PUE were identified through Pearson's correlation analyses, hierarchical partitioning, and ordinary regressions. Results Along the precipitation gradient, ANPP and PUE increased exponentially. Among the community features, total cover and cover of PFGs, including forbs and sedges, were the primary factors that determined PUE. The three cover variables, together with species richness, positively affected PUE and accounted for 47.6% of the total variation in PUE. Among the environmental factors, MAP, surface soil pH, and nitrogen content were the most significantly related to PUE and accounted for 29.9% of the total contribution. Conclusion Communities with high cover, species richness, and nutrient content but low soil bulk density presented the highest PUE. At a regional scale, PUE depended mainly on plant cover, especially the cover of PFGs, namely, forbs and sedges. Environmental factors, including MAP and surface soil nitrogen and carbon contents, positively affected PUE, whereas soil pH and bulk density negatively affected PUE. Our results highlighted the importance of considering community structure to understand PUE variations in natural alpine grasslands. This article is protected by copyright. All rights reserved.

The deformation behaviours of the equiaxed-grained and columnar-grained Fe-6.5 wt%Si alloy were comparatively studied and the mechanism of the enhanced deformation properties of columnar-grained alloys was discussed. A grain orientation dependence of the deformation twinning was identified in the Fe-6.5 wt%Si alloy. Twins tend to occur in grains with a tensile orientation near the corner and a compressive orientation near the – line, which is closely related to the Schmid factor value of each orientation. The significant enhancement of the deformation properties of the columnar-grained Fe-6.5 wt%Si alloy was mainly ascribed to the promotion of twinning deformation by the grain orientation control. These results provide a theoretical guide for the microstructure design of brittle metals, such as Fe-6.5 wt%Si alloy.

Copper-clad aluminum (CCA) flat bars produced by the continuous casting–rolling process were subjected to continuous induction heating annealing (CIHA), and the effects of induction heating temperature and holding time on the microstructure, interface, and mechanical properties of the flat bars were investigated. The results showed that complete recrystallization of the copper sheath occurred under CIHA at 460°C for 5 s, 480°C for 3 s, or 500°C for 1 s and that the average grain size in the copper sheath was approximately 10.0 μm. In the case of specimens subjected to CIHA at 460–500°C for longer than 1 s, complete recrystallization occurred in the aluminum core. In the case of CIHA at 460–500°C for 1–5 s, a continuous interfacial layer with a thickness of 2.5–5.5 μm formed and the thickness mainly increased with increasing annealing temperature. After CIHA, the interfacial layer consisted primarily of a Cu9Al4 layer and a CuAl2 layer; the average interface shear strength of the CCA flat bars treated by CIHA at 460–500°C for 1–5 s was 45–52 MPa. After full softening annealing, the hardness values of the copper sheath and the aluminum core were HV 65 and HV 24, respectively, and the hardness along the cross section of the CCA flat bar was uniform.

Loess is a typical collapsible soil, which is widely distributed in the upper and middle areas around the Yellow River of China. The stabilization of loess with lime provides a significant improvement in the physical and the mechanical characteristics of the loess and is therefore widely used in the pavement base and subgrade. Therefore, a systematic investigation of Mohr-Coulomb failure envelope of lime stabilized loess needs to be conducted. In this pursuit, the present research envisages the investigation of the effects of the lime content, porosity and curing time on the strength parameters (friction angle (&phi, ) and cohesion (c)), using a series of triaxial tests performed on lime stabilized loess specimens. The experimental results revealed that the friction angle (&phi, ) was independent of the lime content, the porosity and the curing time of the specimen for a given lime stabilized loess, while the factors mentioned above had a significant effect on the cohesion (c) of the lime stabilized loess. For a relatively short curing time (7 days), the change in the lime content did not present an obvious effect on the cohesion (c) of the stabilized loess. However, when the curing time (28, 90 and 180 days) was longer, the increase of the lime content significantly enhanced the cohesion of the stabilized loess. When the lime content was constant, the cohesion (c) of the stabilized loess increased linearly with the decrease in the void ratio. A power function equation was proposed to assess the comprehensive influences of the factors like the lime content, porosity and curing time on cohesion (c). Finally, the Mohr-Coulomb failure envelopes were drawn based on the triaxial test for 47 specimens with various curing time and confining pressure, and the shear strength parameters obtained by the proposed equation were also compared with the experimental results.

Heavy metals are believed to impact soil processes by influencing microbial communities, nutrient cycling or exchanging for essential plant nutrients. Soil pH adjustment highly influences the bio-availability of nutrients and microbial processes. We examined the effect of soil pH manipulation and copper (Cu as CuCl

Zein nanoparticles have good prospects as a pharmaceutical carrier but limited in further application by its poor stability and re-dispersibility. To obtain high stability and pH-responsive drug delivery, succinylated-zein (Suc-zein) was synthesized by nucleophilic substitution reaction, the material obtained was used to prepare Suc-zein nanoparticles (SZs). The SZs prepared not only had good dispersibility but showed better stability than zein particles on pH, storage and salinity. After loading indomethacin (Indo) into zeolitic imidazolate framework-8 (ZIF-8), the core-shelled Indo-Suc-zein-ZIF-8 (Indo-SZZs) were fabricated by coating Suc-zein onto the surface of ZIF-8 with better stability and high drug loading. Indo-SZZs were pH-responsive and sustained a drug release profile in a simulated environment. Also SZZs presented as being non-toxic, having good biocompatibility and good cellular up-take performance, and the cytotoxicity of Indo-SZZs was significantly higher than that of Indo. This provides a new insight into the preparation of a zein-based oral drug delivery system.

FeNiCoAlTaB alloy with good superelasticity was fabricated by using the directional solidification technology to control grain orientation and solution-aging treatment to change the morphology and distribution of precipitates, and the superelasticity improving mechanism of the alloy was investigated in this study. The results indicated that with the melt zone temperature of 1420 ± 5 °C and withdrawing velocity of 0.5 mm/min, the columnar-grained FeNiCoAlTaB alloy with strong 〈100〉 fiber texture was obtained. After solution treatment at 1315 °C for 20 min and aging at 700 °C for 6 h, the columnar-grained FeNiCoAlTaB alloy exhibited the superelasticity strain of 1.7%, residual strain of 0.5% and tensile strength of 860 MPa. Compared with the non-superelastic equiaxed-grained alloy fabricated by vacuum melting and forging, the desired grain orientation, the size and distribution of the precipitates resulted in the good superelasticity of the columnar-grained FeNiCoAlTaB alloy.

Incorporation of drug nanocrystal (DNC) into a particulate carrier to form the DNC delivery system was conducted in this study, where 10-hydroxycamptothecin (HCPT) was selected as the model drug and zein was the carrier. The supercritical anti-solvent (SAS) process or the built-in ultrasonic dialysis process (BUDP) was applied to prepare HCPT NC-loaded zein microspheres (HCPT NC-Zein MS) at first respectively, but the results showed that the products obtained were unsatisfactory in their particle microstructures. Fortunately, by combining the SAS process with BUDP, i.e. the co-precipitation of HCPT and zein prepared using the SAS process was dispersed into ethanol–water as the dialysis solution for BUDP, the results showed that desirable HCPT NC-Zein MS were obtained. The formulations were evaluated quantitatively by an overall desirability function (DF), and the optimized HCPT NC- Zein MS was prepared according to the range analysis results of DF. Under the optimized conditions, HCPT NC-Zein MS with a mean particle size=1.10±0.12 µm, drug loading=5.98% and encapsulation efficiency=95.68% were obtained. The further characterizations of SEM, FT-IR, XRD and DSC demonstrated that HCPT NC was successfully incorporated into the interior of zein microspheres. The effects of the process parameters and the formation mechanism of HCPT NC-Zein MS were discussed in detail. Furthermore, it is presented that HCPT NC-Zein MS sustained HCPT release rate successfully, where about 50% HCPT was fast released in the first 20 h, then the release trend followed zero order kinetics and reached 70% in 82 h.

HAl77-2 aluminum brass (UNS C68700) tubes with equiaxed grain (EG) structure and with an axial-oriented columnar grain (CG) structure were prepared by the traditional horizontal continuous casting (cooling mold casting) and heating-cooling combined mold horizontal continuous casting, respectively. The tubes were cold rolled, and the influences of microstructure on the deformation behavior, mechanical properties and residual stress of the cold-rolled tubes were investigated. It was found that visible cracks formed on the surface of the cold-rolled EG tube when the accumulative rolling reduction reached 80%, while the good surface quality cold-rolled CG tube without any cracks can be obtained when the accumulative reduction exceeded 95%. During cold rolling, intersecting planar dislocations, deformation twins and shear bands were successively developed in the EG tube. On the other hand, the planar dislocations, deformation twins and shear bands were almost parallelly distributed in the CG tube. The formation mechanisms of the different deformation microstructures were discussed. At 70% reduction, the circumferential and axial residual stresses of the CG tube were 201 MPa and 175 MPa, respectively, which were significantly lower than those (281 MPa and 238 MPa) of the EG tube. The uniform deformation and low residual stress in the CG tube contributed to the better cold-rolled performance and higher elongation than the EG tube.

Columnar-grained HAl77-2 aluminum brass ingot was fabricated by directional solidification method, and the tensile samples were then cut from the ingot along the different angles (0°, 15°, 30°, 45°, 60°, 75° and 90°) between the loading direction and the grain growing direction. The effects of the loading direction on the mechanical properties, strain hardening behavior and deformation mechanism of the alloy were investigated. The samples with the angles of 0–30° deformed mainly by dislocation planar slip mechanism during tensile deformation, showing low flow stress, uniform intragranular deformation and excellent plasticity, e.g., their elongations to failure were more than 80.0%. A number of deformation bands or intercrossed low-angle subgrain boundaries formed in the 45–90° samples during deformation, with high strain concentration inside the grains, which caused low plasticity, e.g. the elongations to failure were 62.9–65.2%. High density of dislocations, dense Lomer-Cottrell locks and geometrical hardening mainly contributed to the higher strain hardening rate and tensile strength of the 45° and 60° samples than those of the other samples. In order to obtain columnar-grained HAl77-2 alloy with excellent cold workability, it is supposed to control the angle between columnar grain growing direction and main extension deformation direction in a range of 0–30° by the directional solidification technology.

Nanotechnology associated with a crystal engineering approach was proposed for improving the solubility and efficacy of hydrophobic drugs in this study. 10-hydroxycamptothecin polymorphic nanoparticle dispersions (HCPT-PNDs) were prepared using the supercritical anti-solvent technique coupled with the high-pressure homogenization method. Shape- and polymorph-dependent tumor suppression was observed in both in vitro and in vivo models, where needle-shaped HCPT-PND exhibited dramatic improvement of antitumor efficacy. A benefit of controllable size and a large surface-to-volume ratio of needle-shaped nanoparticles is the improvement of dissolution properties, which facilitates enhancing pharmacokinetic and pharmaco-dynamic properties. The needle-shaped HCPT-PND, which with longer blood retention time and more effective cellular uptake, makes it possible to accumulate drug in tumor tissues and exhibit higher cytotoxicity. No severe systemic toxicity was observed due to sustained-dissolution and the low dose of drug in normal tissues. The results suggest that the needle-shaped HCPT-PND is an interesting nano-formulation of HCPT. From the Clinical Editor Nanotechnology has enabled the production of novel therapeutics drugs against cancer. Here, the authors investigated the use of a crystal engineering approach for the modification of camptothecin in order to improve its water solubility. Physicochemical and biological properties were studied. The results would suggest the applicability of this approach for nano-formulation.

Heating-cooling combined mold (HCCM) horizontal continuous casting technology developed by our research group was used to produce high axial columnar-grained CuNi10FeMn1 alloy tubes with different Fe contents. The effects of Fe content (1.08wt%–2.01wt%) on the microstructure, segregation, and flushing corrosion resistance in simulated flowing seawater as well as the mechanical properties of the alloy tubes were investigated. The results show that when the Fe content is increased from 1.08wt% to 2.01wt%, the segregation degree of Ni and Fe elements increases, and the segregation coefficient of Ni and Fe elements falls from 0.92 to 0.70 and from 0.92 to 0.63, respectively. With increasing Fe content, the corrosion rate of the alloy decreases initially and then increases. When the Fe content is 1.83wt%, the corrosion rate approaches the minimum and dense, less-defect corrosion films, which contain rich Ni and Fe elements, form on the surface of the alloy; these films effectively protect the α-matrix and reduce the corrosion rate. When the Fe content is increased from 1.08wt% to 2.01wt%, the tensile strength of the alloy tube increases from 204 MPa to 236 MPa, while the elongation to failure changes slightly about 46%, indicating the excellent workability of the CuNi10FeMn1 alloy tubes.

The cold-rolled NiTi alloy was treated by electropulsing and muffle furnace at the same temperature for minutes, respectively. In order to find the difference between two methods for the recrystallization of the NiTi alloy, the hardness, electrical resistivity and microstructure of the NiTi alloy were investigated. The hardness and microstructure evolution of NiTi alloy indicates that electropulsing can reduce the recrystallization temperature of NiTi alloy by 200 °C owing to the enhancement of atom diffusion. Compared with the traditional heat treatment, electropulsing can easily refines grain of the NiTi alloy with an average size of about 41 nm, due to increases of the nucleation rate and limited grain growth. In addition, electropulsing can decrease resistivity of NiTi alloy to the minimum value at the low frequency of electropulsing for 2.5 min. For NiTi alloy treated by furnace annealing at 300 and 350 °C, the phase transition from martensite to austenite induces the hardness increase with increasing temperature and prolonging time.

Three kinds of surface hardening states of the steel sheet were obtained by different mechanical surface preparation methods with flap disc and steel circumferential brushes before cold roll bonding of embedded 1060 aluminum-08Al steel composite sheets, and the influence of steel sheet surface hardening state on the interfacial bonding strength of the composite sheet and the related mechanism were studied. The results showed that numerous cracks formed between the broken work-hardened surface layer and its steel matrix during cold roll bonding, resulting in a large number of fragments at the interface, which was the main reason for the reduction of the bonding strength. It is an effective method for reducing the work-hardened surface layer hardness to improve the bonding strength of the composite sheet. The nano-hardness of the steel surface treated by flap disc was 4.5 GPa which was close to that (4.4 GPa) of the steel matrix, while the nano-hardnesses of the steel surfaces treated by the steel brushes made of Ф 0.3 mm wires and Ф 0.1 mm wires were 8.6 GPa and 5.7 GPa, respectively. For the thickness reduction of 25%, the peel strengths of the composite sheets whose original steel sheet surface were treated by the steel brush made of Ф 0.3 mm wires and Ф 0.1 mm wires were 0.9 N/mm and 2.9 N/mm, respectively, while the peel strength of the composite sheet whose steel sheet surface was treated by flap disc significantly rose to 14.9 N/mm.

The recrystallized microstructure and texture of AZ31 Mg alloy after rapid thermal annealing (RTA) was investigated. A mathematical model of RTA temperature of AZ31 Mg alloy was established based on the thermal equilibrium theory. The two double-peak textures with basal poles tilted 5–10° away from the normal direction towards the rolling direction or towards the transverse direction were formed in the AZ31 alloy during RTA. The tilted basal texture was originated from recrystallized grains formed along grain boundaries for the low rolling reduction or recrystallized grains formed within the shear bands and twins for the high rolling reduction. During RTA, the recrystallization mechanism was sensitive to the previous rolling reduction and the annealing temperature, and the mechanisms of the microstructure and texture evolution of the AZ31 alloy during RTA were discussed.

Zein microspheres with controllable particle size and narrow size distribution were self-assembled using a novel built-in ultrasonic dialysis process (BUDP). The effects of different variables on the microstructures of obtained zein particles were investigated using an OA 16 (4 5 ) orthogonal experimental design. The results showed that zein particles prepared by the BUDP possessed a spherical morphology with mean particle size ( Dp 50 ) from 431.2 ± 69.6 nm to 2335 ± 406.1 nm under different process parameters. Zein microspheres prepared at optimized conditions presented much smaller particle size and narrower size distribution ( Dp 50 = 398.2 ± 41.3 nm) than those obtained without ultrasound ( Dp 50 = 1776 ± 1181.1 nm). FT-IR, 1 H NMR, XRD, TG and DSC characterization results showed that the chemical structure, crystal structure and thermal behavior of the zein microspheres obtained by BUDP were similar with raw zein and that prepared without ultrasound. The ultrasound power and zein concentration were the most important process parameters affecting particle formation. The formation mechanisms of zein microspheres and the influence mechanisms of the operating parameters were discussed in detail. Also, a semi-empirical model was developed for predicting particle size. Furthermore, curcumin was encapsulated into zein microspheres using BUDP, and curcumin-loaded zein microspheres sustained curcumin release rate successfully in vitro.

Recrystallization and micronization of 9-nitro-camptothecin (9-NC) has been investigated using the supercritical anti-solvent (SAS) technology in this study. Five operating factors, i.e., the type of organic solvent, the concentration of 9-NC in the solution, the flow rate of 9-NC solution, the precipitation pressure and the temperature, were optimized using a selected OA16 (4(5)) orthogonal array design and a series of characterizations were performed for all samples. The results showed that the processed 9-NC particles exhibited smaller particle size and narrower particle size distribution as compared with 9-NC raw material (Form I), and the optimum micronization conditions for preparing 9-NC with minimum particle size were determined by variance analysis, where the solvent plays the most important role in the formation and transformation of polymorphs. Three new polymorphic forms (Form II, III and IV) of 9-NC, which present different physicochemical properties, were generated after the SAS process. The predicted structures of the 9-NC crystals, which were consistent with the experiments, were performed from their experimental XRD data by the direct space approach using the Reflex module of Materials Studio. Meanwhile, the optimal sample (Form III) was proved to have higher cytotoxicity against the cancer cells, which suggested the therapeutic efficacy of 9-NC is polymorph-dependent.

Winter-flooded rice paddy field (FR), characterized by water conserved in the field during the fallow period, is a typical cropping system in southwest China, leading to considerable methane (CH4) emissions. The effect of nitrogen (N) fertilization on CH4 emissions during rice-growing seasons is well studied in FR, further studies covering N fertilizer applied in the rice-growing seasons affects CH4 emissions during the subsequent fallow period is needed. Therefore, a field experiment was conducted in an FR of Sichuan province, China, with conventional N fertilized (CN) and N unfertilized (NN) treatments. The cumulative CH4 emission from CN treatment during the rice-growing season and the subsequent fallow period was 389 ± 29.4 and 158 ± 31.2 kg C ha−1, which were increased by 29.5% and 395% in comparison with the NN treatment, indicting N applied during the rice growing-season significantly facilitated CH4 emission during the subsequent fallow period. During the rice-growing season, higher CH4 emission from CN treatment could be attributed to elevated soil dissolved organic carbon (DOC) content that might have provided sufficient substrates for CH4 production. During the fallow period, as compared to NN treatment, higher CH4 emissions from CN treatment could be explained by greater linear regression slopes between CH4 fluxes, soil temperature and DOC to dissolved inorganic N (DIN) (DOC/DIN) ratio. Moreover, the structural equation model (SEM) described that the soil temperature exhibited the most significant effects on CH4 emissions for both treatments during the rice-growing season and subsequent fallow period. These findings are a major step forward to showing that N fertilizer applied in the rice-growing season could also affect CH4 emission during the subsequent fallow period, accompanying other soil parameters controlling CH4 emission.

Nitrous oxide (N2O) is an overwhelming greenhouse gas and agricultural soils, particularly acidic soils, are the main source of its release to the atmosphere. To ameliorate acidic soil condition, liming materials are added as an amendment. However, the impact of liming materials has not been well addressed in terms of exploring the effect of soil pH change on N2O emissions. In the present study, a soil with pH 5.35 was amended with liming materials (CaMg(CO3)2, CaCO3, Ca(OH)2 and CaO) to investigate their effects on N2O emissions. The results indicate that application of liming materials reduced the magnitudes of N2O emissions. The maximum reduction of soil N2O emissions took place for Ca(OH)2 treatment when compared to the other liming materials, and was related to increasing soil pH. Mineral N, dissolved organic C, and microbial biomass C were also influenced by liming materials, but the trend was inconsistent to the soil pH change. The results suggest that N2O emission mitigation is more dependent on soil pH than C and N dynamics when comparing the different liming materials. Moreover, ameliorating soil acidity is a promising option to mitigate N2O emissions from acidic soils The authors would like to thank the funding bodies of the National Science Foundation of China (417501 10485), China Post-Doctoral Science Foundation (2017 M 622478), and National Key R&D Program (2017 YFD 0800102) for financially assisting the present research SI

To our knowledge, the conversion of winter flooded rice paddy (RF) to rice-wheat rotation (RW) has markedly decreased methane (CH₄) emissions during the wheat-growing seasons. However, the effects of this conversion on CH₄ emissions during the rice-growing seasons are unclear. To determine CH₄ emissions during the rice-growing season and associated environmental factors under RF and RW systems, a split-plot design experiment was conducted in three RF fields in hilly areas of Sichuan province, China. One-half of each field was converted to RW, and the other half remained RF. Each plot of RW and RF was further divided into four subplots: three subplots for conventional nitrogen fertilization treatment (RW-CN and RF-CN) and one for unfertilized treatment (RW-NN and RF-NN). The study showed that the cumulative CH₄ emissions from RW-CN during the rice-growing seasons were 192.77 ± 11.36 and 302.07 ± 28.34 kg C ha⁻¹ in 2013 and 2014, respectively, which were decreased by 26.8% and 24.3% as compared to that from RF-CN. While for RW-NN, the cumulative CH₄ emissions decreased by 54.1% and 24.0% as compared to that from RF-NN (372.49 ± 67.05 and 300.53 ± 13.49 kg C ha⁻¹ in 2013 and 2014, respectively, P

The combination of chemo- and enzyme catalysis for multi-step tandem reactions has presented great challenges for decades. Herein, glucose oxidase (GOx) and a metal-organic framework MOF-545(Fe), which possessed peroxidase-like activity, were combined to construct a mimic multi-enzyme system for tandem catalysis. MOF-545(Fe) not only served as a support for the enzyme immobilization, but also contributed its catalytic activity to co-operate with natural enzymes for the cascade reactions. Based on the prepared mimic multi-enzyme system GOx@MOF-545(Fe), a colorimetric biosensor for glucose rapid detection was achieved with a low limit of detection (0.28 μM) and high specificity. Meanwhile, due to the protection of MOF-545(Fe), the immobilized enzyme exhibited excellent reusability and stability, e.g. long-term stability, thermal stability and anti-organic solvent stability. After being stored at room temperature for 7 days, the immobilized enzyme retained 92% of activity, while only 40% of activity of free enzyme was retained. And the immobilized enzyme maintained 71% of its initial activity after 5 cycles. This strategy of combining MOF mimics and natural enzymes for tandem catalysis may provide a novel and facile approach to design a highly efficient, stable, functional chemo-enzyme composites catalyst, which holds great promise for applications in biosensing, biopharmaceutical and industrial catalysis.

Crystallization is a complex process of heat and mass transfer, its product quality is affected by many factors, thus it is a challenge to control this process. Modelling and optimization of the manipulated variables is a feasible way to improve the product quality of crystallization. In this paper, a modified numerical scheme is developed to solve the process model of anti-solvent batch crystallization. The proposed numerical scheme can handle growth, nucleation, agglomeration and breakage kinetics by means of the Method of Characteristics (MOC), which provides an accurate and efficient result of the crystal size distribution (CSD). Then Non-linear Model Predictive Control (NMPC) and non-linear Moving Horizon Estimation (MHE) are presented to provide a temperature profile for optimizing the CSD. The result of case studies indicates that the calculated results of the MOC modified process model were in agreement with the experimental results, which indicated that the MOC method could deal with the specific crystallization process efficiently and accurately. The NMPC-MHE optimized temperature control strategy was tested using the verification experiment of anti-solvent crystallization of β-Artemether, the validated result indicated that the method developed had high feasibility and accuracy. The computational time for the MHE and NMPC formulations with 90 control and sampling steps is well within the sampling interval, which allows for real time process control.

Nitrous oxide (N2O) is a devastating greenhouse gas mainly released from soils to the atmosphere. Pasture soils, particularly acidic in nature, are large contributors of atmospheric N2O through deposition of urine-N. Devising strategies for reducing N2O emissions in acidic soils are the utmost need of the time. Therefore, the present study was carried out to investigate the possible efficacy of dolomite application to reduce N2O emissions from urine treated acidic soil. Application of urine to soil enlarged the production of NH4+-N, NO3−-N, microbial biomass C (MBC) and dissolved organic C (DOC), resulting in higher N2O emissions as compared to the control (soil only). The highest N2O emission rate (1.35 μg N2O-N kg−1 h−1) and cumulative flux (408 μg N2O-N kg−1) occurred in urine only treated soil. Dolomite addition, especially higher application dose, greatly reduced N2O emissions through improved soil pH. The results suggest that increasing pH of acidic soils is a good applicable approach for reducing N2O emissions from urine-treated soils.

A method based on ultra performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) was developed for the determination of 15 water-holding functional drugs in animal tissues.The analytes were extracted with acetonitrile containing 1.0%(v/v) methanol, purified by Oasis PRiME HLB SPE column, and analyzed by Acquity UPLC BEH C18 column (50 mm×2.1 mm, 1.7 μm) using methanol and 0.1%(v/v) formic acid aqueous solution as the mobile phases.The analytes were detected using an electrospray ionization (ESI) source under the MRM mode.The calibration curves of the analytes were linear in the range of 1.0-50.0 μg/kg (

In the next generation of VLSI circuits, concurrent optimizations will be essential to achieve the performance challenges. In this dissertation, we present techniques for combining traditional timing optimization techniques to achieve a superior performance. The method of buffer insertion is used in timing optimization to either increase the driving power of a path in a circuit, or to isolate large capacitive loads that lie on noncritical or less critical paths. The procedure of transistor sizing selects the sizes of transistors within a circuit to achieve a given timing specification. Traditional design techniques perform these two optimizations as independent steps during synthesis, even though they are intimately linked and performing them in alternating steps is liable to lead to suboptimal solutions. The first part of this thesis presents a new approach for unifying transistor sizing with buffer insertion. Our algorithm achieve from 5% to 49% area reduction compared with the results of a standard transistor sizing algorithm. The next part of the thesis deals with the problem of collapsing gates for technology mapping. Two new techniques are proposed. The first method, the odd-level transistor replacement (OTR) method, performs technology mapping without the restriction of a fixed library size, and maps a circuit to a virtual library of complex static CMOS gates. The second technique, the Static CMOS/PTL method, uses a mix of static CMOS and pass transistor logic (PTL) to realize the circuit, using the relation between PTL and binary decision diagrams. The methods are very efficient and can handle all ISCAS'85 benchmark circuits in minutes. On average, it was found that the OTR method gave 40%, and the Static/PTL gave 50% delay reductions over SIS, with substantial area savings. Finally, we extend the technology mapping work to interleave it with placement in a single optimization. Conventional methods that perform these steps separately will not be adequate for next-generation circuits. Our approach presents an integrated solution to this problem, and shows an average of 28.19%, and a maximum of 78.42% improvement in the delay over a method that performs the two optimizations in separate steps.

High activity and stability of immobilized enzymes have been constant pursuits and critical challenges for decades. Herein, Cytochrome c (peroxidase, Cyt c) and its corresponding enzyme mimic (Pd nanoparticles) were combined and successfully embedded into a zeolitic imidazolate framework-8 (ZIF-8) to enhance the enzymatic catalytic performance using a biomimetic mineralization approach. Owing to allosteric effects of Cyt c-Pd complexes, the as-synthesized Cyt c-Pd@ZIF-8 composites exhibit an increased turnover number (approximately 2.4-fold for kcat) and an enhanced catalytic efficiency (approximately 2.3-fold for kcat/KM) compared to free Cyt c; also the shielding effect of ZIF-8 endows enzyme with improved resistance against harsh conditions (e.g. high temperatures and organic solvents). The strategy, which integrates enzyme with its enzyme mimic derived from transition metal nanoparticles to enhance enzymatic catalytic performances, may provide a versatile and facile technique for designing highly efficient and multi-functional bio-catalysts.

Mosses and leaves of vascular plants have been used as bioindicators of environmental contamination by heavy metals originating from various sources. This study aims to compare the metal accumulation capabilities of mosses and vascular species in urban areas and quantify the suitability of different taxa for monitoring airborne heavy metals. One pleurocarpous feather moss species, Haplocladium angustifolium, and two evergreen tree species, Cinnamomum bodinieri Osmanthus fragrans, and substrate soil were sampled in the urban area of different land use types in Wuhan City in China. The concentrations of Ag, As, Cd, Co, Cr, Cu, Mn, Mo, Ni, V, Pb, and Zn in these samples were analyzed by inductively coupled plasma mass spectrometry. The differences of heavy metals concentration in the three species showed that the moss species was considerably more capable of accumulating heavy metals than tree leaves (3 times to 51 times). The accumulated concentration of heavy metals in the moss species depended on the metal species and land use type. The enrichment factors of metals for plants and the correlations of metals in plants with corresponding metals in soil reflected that the accumulated metals in plants stemmed mostly from atmospheric deposition, rather than the substrate soil. Anthropogenic factors, such as traffic emissions from automobile transportation and manufacturing industries, were primarily responsible for the variations in metal pollutants in the atmosphere and subsequently influenced the metal accumulation in the mosses. This study elucidated that the moss species H. angustifolium is relatively more suitable than tree leaves of C. bodinieri and O. fragrans in monitoring heavy metal pollution in urban areas, and currently Wuhan is at a lower contamination level of atmospheric heavy metals than some other cities in China.

Epiphyllous liverworts form a special group of bryophytes that primarily grow on the leaves of understory vascular plants in tropical and subtropical evergreen broadleaf forests. Being sensitive to moisture and temperature changes, epiphyllous liverworts are often considered to be good indicators of climate change and forest degradation. However, they are a poorly collected and taxonomically complicated group, with an only partly identified distribution pattern. In this study, we built four models based on 24 environmental variables at four different spatial resolutions (i.e., 1 km, 5 km, 10 km, and 15 km) to predict the past distribution of epiphyllous liverworts in China, using Maxent model and 63 historical location records (i.e., presence‐only data). Both area under the curve of the receiver operating characteristic (AUC) and true skill statistic (TSS) methods are used to assess the model performance. Results showed that the model with the predictors at a 15‐km resolution achieved the highest predictive accuracy (AUC=0.946; TSS=0.880), although there was no statistically significant difference between the four models (p > 0.05). The most significant environmental variables included aridity, annual precipitation, precipitation of wettest month, precipitation of wettest quarter, and precipitation of warmest quarter, annual mean NDVI, and minimum NDVI. The predicted suitable areas for epiphyllous liverworts were mainly located in the south of Yangtze River and seldom exceed 35°N, which were consistent with the museum and herbarium records, as well as the historical records in scientific literatures. Our study further demonstrated the value of historical data to ecological and evolutionary studies.

Strategies for a particular drug delivery are always of great interest to the pharmaceutical industry, and efficient methods of preparing products with controlled particle microstructures are fundamental for the development and application of drug delivery. Supercritical fluid particle design (SCF PD) processes, as a green and effective alternative to traditional methods, have been effectively employed to produce particles with designated microstructures. Combining with research experiences in our research group, this review aims to provide a roadmap of SCF PD for particular drug delivery. For any drug delivery formulations, macroscopic properties (administration methods, drug release behaviour and targeting) are directly influenced by the particle microstructures (morphology, particle size, particle size distribution, crystal form, drug loading, encapsulation efficiency, etc). “Inverse” strategies are introduced at first to obtain the necessary particle microstructures for a particular drug delivery in this paper. Then, how to produce particles with designated microstructures via SCF PD processes is discussed, mainly focusing on the screening and selection of operating parameters according to thermodynamic and fluid dynamic studies. Recent examples of SCF micronization and co-precipitation/encapsulation processes are also summarized with an emphasis on how to tailor the particle microstructures by controlling the operating parameters. Finally, challenges and issues needing further study are briefly suggested for SCD PD.

Large-strain deformation by single electroplastic rolling (EPR) was imposed on AZ31 magnesium alloy strips. During EPR at low temperature (150–250°C), numerous twins formed in the alloy. After EPR at a high temperature (350°C), the number of twins reduced and some dynamic recrystallization (DRX) grains formed at grain boundaries and twinned regions. The synergic thermal and athermal effects generated by electropulsing, which promoted dislocation motion, induced a few small DRX grains, and ductile bandings were mainly responsible for large-strain deformation during EPR. The inclination angle of the basal pole stemmed from the counterbalance of the inclination direction of the basal pole between the DRX grains and deformed coarse grains.

Bryophytes, represented by mosses, liverworts, and hornworts, contribute substantially to forest ecosystems in terms of nutrient cycling, water retention, water availability, plant biomass, and plant community maintenance. Forests provide numerous types of habitat for bryophytes, especially the ground floor. To clarify the ground bryophyte diversity and distribution in broadleaved forests, we used microcoenose sampling to investigate ground bryophytes in 34 sample plots (10 × 10 m) in the Mabian Dafengding National Nature Reserve (MDNR), Sichuan Province. Species diversity and environmental factor relationships were analyzed by using α and β diversity indexes, as well as Pearson's correlation analysis. Detrended canonical correspondence analysis (DCCA) was applied to analyze the relationships between species distribution and environmental factors. A total of 230 bryophyte species were identified in MDNR. These species include 67 liverwort species belonging to 26 genera of 20 families and 163 moss species belonging to 65 genera of 28 families. Diversity of ground bryophytes was negatively correlated to shrub cover, canopy cover, and tree number, but without significant correlations to altitude, slope, aspect, vegetation type, and herb cover. The DCCA ordination of relationships between ground bryophytes and environmental factors showed that altitude, aspect, vegetation type, and shrub cover were important to the distribution of dominant ground bryophyte species. This study quantitatively related bryophytes diversity and distribution to environmental factors, which is helpful in understanding the ecological niche of various bryophytes.

The combination of carefully designed aging, cold-rolling and electropulsing treatment (EPT) was proposed to improve the strength and ductility of AZ91 alloy strip. Prior to cold-rolling, the extruded strip was aged in order to precipitate dispersed β-Mg17Al12 particles in the α-Mg matrix for improving the strength of the alloy. When EPT was applied to the cold-rolled strips, EPT rapidly completed the recrystallization of α-Mg matrix within several seconds at relatively low temperature of 508–553 K, and the pre-existed β-Mg17Al12 particles effectively impeded the α-Mg grain growth. The microstructure consisting of fine recrystallized grains and dispersed β-Mg17Al12 particles was obtained. The ultimate tensile strength, yield strength and elongation to failure of the EPT-samples were 362–370 MPa, 270 MPa and 27.6–28.4%, which were improved by 11–12%, 10% and 70–75%, respectively compared with those of the original extruded-strip. The mechanism of EPT improved the mechanical properties of the AZ91 alloy is discussed.

The production of β-artemether, (3,12-epoxy-12 h-pyrano (4,3-j)-1,2-benzodioxepin, C16H26O5), an important active pharmaceutical ingredient for the treatment of malaria, uses crystallization as the purification step. This paper investigates the Metastable Zone Width (MSZW), nucleation and crystal growth kinetics of anti-solvent crystallization for β-artemether in ethanol + water system where water is the anti-solvent. Using a turbidity probe, the effect of process variables on MSZW was investigated, including initial the mass ratio of the solute to solvent, temperature, introduction rate as well as introduction location of the anti-solvent. The prediction model for MSZW was calibrated and proved reliable for this system. For anti-solvent crystallization of β-artemether in ethanol + water system, the chord length distribution data was collected using Focused Beam Reflectance Measurement, based on which the nucleation and crystal growth parameters were estimated using the method of moment. The crystal growth mechanism of β-artemether was also studied using a hot stage and imaging system and was found to follow a layer-by-layer growth mechanism.

With the feed-in of electricity proportion rising, Shanghai grid become a typical large city Receiving-end grid. Voltage stability make great influence to power grid operating safely and stably. Firstly, brief introduction of Shanghai power grid current situation. Secondly, analyze summer and winter voltage stability of Shanghai power grid in different operation modes, including normal operation and contingencies (N-1, N-2). Finally, specific study kinds of voltage stability control measures respectively, to ensure a stable and safe running of Shanghai grid, provide an effective and feasible solution for the power grid operation and management.

In order to confirm the correlation between interfacial properties of modified surface plasmon resonance (SPR) chips and their SPR responses to immobilized anti-IgG, SPR chips were modified by mercaptoundecanoic acid, poly(ethylene glycol) diacrylate (PEG), PEG-based copolymer and cyclodextrin coupled PEG using self-assembled or radical polymerization methods. The resulting interfacial properties such as film thickness and hydrophilicity were characterized by AFM, elliptic polarization scanners and contact angle meter. Immobilization of human IgG on the modified chips was achieved by EDC/NHS activation through an amide bond. The association between fixed IgG and free anti-IgG was reflected by the variation of SPR responses and the binding ability was evaluated by Langmuir isotherms. As observed, the adsorption between IgG and anti-IgG was affected by the interfacial properties of different modifiers, such that a chip with a thinner and more hydrophilic layer may result in a higher SPR response, producing a larger adsorption equilibrium constant for protein interaction.

The relationships between cover and AGB for the dominant and widely distributed alpine grasslands on the northern Tibetan Plateau is still not fully examined. The objectives of this study are to answer the following question: (1) How does aboveground biomass (AGB) of alpine grassland relate to plant cover at different spatial scales? (2) What are the major biotic and abiotic factors influencing on AGB–cover relationship? A community survey (species, cover, height, and abundance) was conducted within 1 m × 1 m plots in 70 sites along a precipitation gradient of 50–600 m. Ordinary linear regression was employed to examine AGB–cover relationships of both community and species levels at regional scale of entire grassland and landscape scale of alpine meadow, alpine steppe, and desert steppe. Hierarchical partitioning was employed to estimate independent contributions of biotic and abiotic factors to AGB and cover at both scales. Partial correlation analyses were used to discriminate the effects of biotic and abiotic factors on AGB–cover relationships at two spatial scales. AGB and community cover both exponentially increased along the precipitation gradient. At community level, AGB was positively and linearly correlated with cover for all grasslands except for alpine meadow. AGB was also linearly correlated with cover of species level at both regional and landscape scales. Contributions of biotic and abiotic factors to the relationship between AGB and cover significantly depended on spatial scales. Cover of cushions, forbs, legumes and sedges, species richness, MAP, and soil bulk density were important factors that influenced the AGB–cover relationship at either regional or landscape scale. This study indicated generally positive and linear relationships between AGB and cover are at both regional and landscape scales. Spatial scale may affect ranges of cover and modify the contribution of cover to AGB. AGB–cover relationships were influenced mainly by species composition of different functional groups. Therefore, in deriving AGB patterns at different spatial scales, community composition should be considered to obtain acceptable accuracy.

Questions Above-ground, below-ground and individual mass–density relationships for perennial herbs were examined along a natural precipitation gradient in northern Tibet. We asked: (1) how do the self-thinning exponents respond to variation in precipitation; and (2) what mechanisms drive the observed population self-thinning? Location The alpine grassland of northern Tibet. Methods Forty-seven fenced sites along a precipitation gradient were established and surveyed in 2011 and 2012. Data (geographic coordinates, elevation, and vegetation information) were collected for Stipa purpurea populations at each site. Population self-thinning exponents were estimated using reduced major axis regression. Results The self-thinning exponents for below-ground (−1.27, −0.47) and individual biomass (−1.26, −0.46) increased with increasing mean annual precipitation, but those for above-ground biomass decreased with precipitation (0.18, −0.25). Soil resources (moisture and nutrients) are a more important constraining factor for below-ground components than light is for above-ground components. Root competition for below-ground resources dominated in S. purpurea population self-thinning. The driving force of density regulation changed from above-ground competition to below-ground competition with increased drought stress. Our results indicate that an increased root/shoot ratio was linked to enhanced below-ground competition and weakened above-ground competition. Our study further confirmed the hypothesis that plant populations in different environments exhibit different biomass allocation patterns, which, in turn, leads to different biomass–density relationships. Conclusions Our study revealed the mechanisms of population self-thinning for perennial herbs in the extreme environment of northern Tibet, where below-ground processes play a critical role in regulating population self-thinning. Our study also advances understanding of the interactions between above- and below-ground processes, providing baseline knowledge useful for local grassland management.

As one of the most sensitive regions to climate change, the Qinghai-Xizang Plateau has been widely investigated as one unity for impacts of climate change on alpine grassland. However, previous findings might be confounded by distinct climate sensitivities at different elevations and different regional climates between Qinghai Province and Xizang Province, which lie at the two sides of Tanggula Mountains. In this study, we explored change trends of grassland vegetation, temperature and precipitation in growing season from 1982 to 2011, and elevation-dependent effects of climate change on grassland vegetation in the two provinces separately. The plateau grassland greenness gained improvement under climate warming and wetting during the past 30 years, especially in Qinghai Province. Temperature increased significantly with a warming magnitude of more than 1.5 degrees C over the plateau grassland. The interannual change of precipitation showed contrary trends between the two provinces. The main climate factor driving the grassland vegetation variation varied between the two provinces, with temperature being the main factor in Qinghai Province and precipitation being the main factor in Xizang Province. In particular, a more significant correlation between climate change and grassland vegetation variation was found at higher elevations, which reveals higher climate sensitivity in higher elevation areas of the plateau.