[Analysis of Vegetation Change and Influencing Factors in Southwest Alpine Canyon Area].

The southwest alpine canyon area is a typical ecologically fragile area. Understanding the characteristics of vegetation change here and its influencing factors can provide a theoretical basis for formulating countermeasures for ecological environment construction in the southwest alpine canyon area and has practical significance for realizing the harmonious and unified development of the regional economy, environment, and ecology. Based on the data set of NDVI, socio-economic factors, and natural factors from 2000 to 2019, the spatial and temporal variation and stability characteristics of NDVI in the southwest alpine canyon area were analyzed by using the methods of unary linear regression, Hurst index, geographic detector model, and coefficient of variation, and the influencing factors of the spatial differentiation of NDVI were also discussed. The results showed that:① in terms of spatial distribution, the vegetation was high in the southeast and low in the northwest. The area covered by medium and high vegetation accounted for 71.71%, and the vegetation cover was at a relatively high level. From the perspective of time, the area of vegetation showing an improvement trend accounted for 85.90%, and the recovery effect was obvious, and the future vegetation change trend will continue to be improved. ② Elevation, vegetation type, and soil type were the main factors affecting the spatial differentiation of NDVI, and the q value was no less than 0.40. Temperature and rainfall were secondary factors, with q values of 0.274 and 0.225, respectively. The dual-factor interaction enhanced the single factor influence, which was manifested as the dual-factor enhancement and nonlinear enhancement relationship. The highest q value was 0.714 for the combination of altitude ∩ vegetation, followed by 0.688 for the combination of altitude ∩ soil. ③ The overall stability of NDVI during the study period was good, and the proportion of the regional area with low fluctuating changes and slightly low fluctuating changes was 89.95%. The area with moderate fluctuation accounted for 10.05%, concentrated in the relatively fragile ecological environment with factors such as high altitude, low temperature, little rainfall, barren soil, and sparse vegetation. Vegetation change is the result of a combination of multiple factors, so it is necessary to adapt to local conditions and adopt different strategies to restore the ecological environment of the southwest alpine canyon area.

Tailoring the optical and mechanical properties of cellulose nanocrystal film by sugar alcohols and its pH/humidity-responsive behavior.

Cellulose nanocrystals (CNC) have gained widespread attention in intelligent food packaging because of their iridescent optical properties. Here, we report a CNC composite film employing CNC, sugar alcohols (e.g., maltol, erythritol, mannitol, sorbitol, and xylitol) and natural pigment anthocyanins, which has a special iridescent color that can be used as a pH and humidity sensor. The effects of five sugar alcohols with different addition ratios on the structural, optical, and mechanical properties of the CNC films were investigated. The results demonstrated that the addition of sugar alcohol made composite films exhibiting a red-shift of λmax, a more uniform color in visual observation, and a larger pitch. Among them, the CNC-mannitol composite film with a ratio of 10:1 exhibited the best mechanical properties, possessing a tensile stress strength of 57 MPa and toughness of 137 J/m3. Subsequently, anthocyanins were incorporated to this composite film, which showed a marked color change along with the pH from 2 to 12 and exhibited a reversible color change from red to transparent upon a relative humidity change from 35 % to 85 %. Overall, such multi-environment-responsive iridescent films with excellent mechanical properties have a great potential for use in intelligent food packaging applications.

Ni-Catalyzed Asymmetric C-P Cross-Coupling Reaction for the Synthesis of Chiral Heterocyclic Phosphine Oxides.

Nickel performs excellently in C-C and C-X cross-coupling reactions. Here, we disclose a Ni(II)-catalyzed asymmetric C-P cross-coupling reaction to afford valuable chiral heterocyclic tertiary phosphine oxides. The method is mild and efficient, which invokes a self-sustained nickel catalytic cycle without an external reductant, light irradiation, or electricity.

Nickel-catalysed enantioselective reaction of secondary phosphine oxides and activated vinylcyclopropanes.

Activated vinylcyclopropanes can form zwitterionic π-allylmetal species in the presence of transition metals and are widely used in organic synthesis. A nickel-catalyzed asymmetric allylation of secondary phosphine oxides with vinylcyclopropanes was described. Tertiary phosphine oxide products could be obtained with up to 91% yield and 92% ee.

Cellulose nanocrystals produced using recyclable sulfuric acid as hydrolysis media and their wetting molecular dynamics simulation.

Cellulose nanocrystals (CNCs) were successfully produced with good nanoscales and dispersibility, using a recycled sulfuric acid (H2SO4) hydrolysis process. This method, at the cost of an overall 25% increase in the hydrolysis time, could significantly reduce the dosage of H2SO4 by approximately 40% without affecting the per-batch yield and performance of CNCs. The obtained CNCs with an average diameter of 6.0-6.5 nm and an average length of 126-134 nm, were successfully applied in the preparation of oil-in-water (O/W) Pickering emulsions via high-pressure homogenization. The emulsions exhibited good storage stability when the concentration of CNC was 1.0 wt%. Further, understanding the wetting behaviors of surface modified CNCs with solvent is critical for the functional designing of Pickering emulsion. Hence, we gained insights into the wetting of hydrophobic and hydrophilic surfaces of sulfate modified CNCs with water and organic solvent (hexadecane) droplets, using molecular dynamic simulation. The results showed that both surfaces had hydrophilic as well as lipophilic properties. Although the sulfate-grafted surface was more hydrophilic than unmodified CNC, substantial local wetting heterogeneities appeared for both solvents. It provides a deeper understanding of the interfacial interactions between modified CNCs and solvent molecules at the molecular level.

Diverse Functionalization of Tetrahydro-ß-carbolines or Tetrahydro-γ-carbolines via Oxidative Coupling Rearrangement.

We report herein diverse functionalization of tetrahydro-ß-carbolines (THßCs) or tetrahydro-γ-carbolines (THγCs) via oxidative coupling rearrangement. The treatment of THßCs or THγCs with t-BuOOH (TBHP) afforded 3-peroxyindolenines, followed by HCl catalyzed indolation to form unexpected 2-indolyl-3-peroxyindolenines. Further rearrangement of these peroxides allows for rapid access to a skeletally diverse chemical library in good to excellent yields.

Polyaniline/reduced graphene oxide foams as metal-free cathodes for stable lithium-oxygen batteries.

Lithium-oxygen batteries (LOBs) are considered as next-generation energy storage devices owing to their high-energy densities, yet they generally suffer from low actual specific capacity and poor cycle performance. To solve these issues, a range of electrocatalysts have been introduced in the cathode to reduce the overpotential during charge/discharge cycles and minimize unwanted side reactions. Due to relative high costs and limited reserves of noble metals and their compounds, it is important to develop low-cost and efficient metal-free electrocatalysts. Here, we report a simple method to prepare three-dimensional porous polyaniline (PANI)/reduced graphene oxide foams (PPGFs) with different PANI contents via a two-step self-assembly process. When these foams are tested as the cathode in LOBs, the device using the PPGF with 50% PANI content exhibits a discharge capacity up to 36 010 mAh g-1 and an excellent cycling stability (260 cycles at 1000 mAh g-1 and 500 cycles at 500 mAh g-1), provid ing new insights into the design of next-generation metal-free cathodes for LOBs.

Construction of Bisindolines via Oxidative Coupling Cyclization.

Herein, we report a general approach for the efficient construction of three-dimensional bisindolines via oxidative coupling cyclization in an intermolecular manner. This reaction is featured by its operational simplicity, metal-free conditions, lack of protecting group, and high selectivity. Notably, a wide range of anilines are suitable in this intermolecular cyclization, furnishing corresponding bisindolines in up to 98% yield.

Stabilization of Transient 3-Chloroindolenines Enables Diverse Functionalization.

Transient intermediates as highly reactive species are difficult to manipulate due to their poor stability. Stabilization of unstable intermediates for functionalization is an attractive approach, but the practical applications are still rare. Herein, we explore a strategy that could effectively stabilize labile 3-chloroindolenines and significantly improve the lifetime from seconds to weeks. This chemistry was utilized to enable the synthesis of 55 diverse compounds which are unable to be achieved by traditional approach.

Development of pristane induced mice model for lupus with atherosclerosis and analysis of TLR expression.

OBJECTIVES: This study was designed to establish a murine model of lupus with atherosclerosis, and to investigate the expression of Toll-like receptors (TLRs) in the aorta and kidney. METHODS: The 9-week-old female ApoE-/- and C57BL/6 mice were randomly divided into a ApoE-/- pristane treated group (group A), ApoE-/- control group (group B), C57BL/6 pristane treated group (group C) and C57BL/6 control group (group D). Each mouse was given either a single intraperitoneal injection of 0.5 ml pristane or saline. RESULTS: We observed that group A mice specifically had poor spirit, less activity, obvious hair loss, splenomegalia and renomegaly. Levels of ANA, anti-ds-DNA and anti-Sm antibodies were significantly higher than those in other groups. The group A and B mice generally displayed intimal hyperplasia and atherosclerosis mottling in the lumen of the aorta. The kidney tissues from group A, B and C mice showed increased expression levels of TLR2, TLR4, TLR7 and TLR9 proteins in comparison to group D. However, Group A mice did not show any significant difference in TLR2 and TLR4 protein expression levels when compared to group B and C, but displayed higher TLR7 expression than group B and higher TLR9 expression than group B and C mice. In contrast, the group A and B mice apparently expressed TLR2 and TLR4. CONCLUSIONS: We concluded that pristane treated apoE-/- mice exhibited lupus-like phenotype and developed atherosclerosis. The pristane treatment also induced abnormally high expression of TLR2 and TLR4 in the aorta and TLR2, TLR4, TLR7 and TLR9 in the kidney of apoE-/- mice.