Decoding Active Sites for Highly Efficient Semihydrogenation of Acetylene in Palladium-Copper Nanoalloys.

Accurately decoding the three-dimensional atomic structure of surface active sites is essential yet challenging for a rational catalyst design. Here, we used comprehensive techniques combining the pair distribution function and reverse Monte Carlo simulation to reveal the surficial distribution of Pd active sites and adjacent coordination environment in palladium-copper nanoalloys. After the fine-tuning of the atomic arrangement, excellent catalytic performance with 98% ethylene selectivity at complete acetylene conversion was obtained in the Pd34Cu66 nanocatalysts, outperforming most of the reported advanced catalysts. The quantitative deciphering shows a large number of active sites with a Pd-Pd coordination number of 3 distributed on the surface of Pd34Cu66 nanoalloys, which play a decisive role in highly efficient semihydrogenation. This finding not only opens the way for guiding the precise design of bimetal nanocatalysts from atomic-level insight but also provides a method to resolve the spatial structure of active sites.

High-Entropy Metal Nitride Embedded in Concave Porous Carbon Enabling Polysulfide Conversion in Lithium-Sulfur Batteries.

The practical implementation of lithium-sulfur batteries is severely hindered by the rapid capacity fading due to the solubility of the intermediate lithium polysulfides (LiPSs) and the sluggish redox kinetics. Herein, high-entropy metal nitride nanocrystals (HEMN) embedded within nitrogen-doped concave porous carbon (N-CPC) polyhedra are rationally designed as a sulfur host via a facile zeolitic imidazolate framework (ZIF)-driven adsorption-nitridation process toward this challenge. The configuration of high-entropy with incorporated metal manganese (Mn) and chromium (Cr) will optimize the d-band center of active sites with more electrons occupied in antibonding orbitals, thus promoting the adsorption and catalytic conversion of LiPSs. While the concave porous carbon not only accommodates the volume change upon the cycling processes but also physically confines and exposes active sites for accelerated sulfur redox reactions. As a result, the resultant HEMN/N-CPC composites-based sulfur cathode can deliver a high specific capacity of 1274 mAh g-1 at 0.2 C and a low capacity decay rate of 0.044% after 1000 cycles at 1 C. Moreover, upon sulfur loading of 5.0 mg cm-2, the areal capacity of 5.0 mAh cm-2 can still be achieved. The present work may provide a new avenue for the design of high-performance cathodes in Li-S batteries.

A Cross-View Geo-Localization Algorithm Using UAV Image and Satellite Image.

Within research on the cross-view geolocation of UAVs, differences in image sources and interference from similar scenes pose huge challenges. Inspired by multimodal machine learning, in this paper, we design a single-stream pyramid transformer network (SSPT). The backbone of the model uses the self-attention mechanism to enrich its own internal features in the early stage and uses the cross-attention mechanism in the later stage to refine and interact with different features to eliminate irrelevant interference. In addition, in the post-processing part of the model, a header module is designed for upsampling to generate heat maps, and a Gaussian weight window is designed to assign label weights to make the model converge better. Together, these methods improve the positioning accuracy of UAV images in satellite images. Finally, we also use style transfer technology to simulate various environmental changes in order to expand the experimental data, further proving the environmental adaptability and robustness of the method. The final experimental results show that our method yields significant performance improvement: The relative distance score (RDS) of the SSPT-384 model on the benchmark UL14 dataset is significantly improved from 76.25% to 84.40%, while the meter-level accuracy (MA) of 3 m, 5 m, and 20 m is increased by 12%, 12%, and 10%, respectively. For the SSPT-256 model, the RDS has been increased to 82.21%, and the meter-level accuracy (MA) of 3 m, 5 m, and 20 m has increased by 5%, 5%, and 7%, respectively. It still shows strong robustness on the extended thermal infrared (TIR), nighttime, and rainy day datasets.

Type IV Collagen Promotes Adipogenic Differentiation of Adipose Stem Cells.

Type IV collagen is a major component of the extracellular matrix in adipose tissue. It is secreted during the lipogenic differentiation of mesenchymal stem cells, but its direct impact and mechanism on the differentiation of adipose-derived stem cells (ASCs) into lipids are unclear. In this study, ASCs were obtained from human liposuction samples and cultured. Lipogenic induction of ASCs was achieved using lipogenic induction medium. Immunofluorescence analysis revealed differential expression of type IV collagen during the early and late stages of adipogenic induction, displaying a distinct morphological encapsulation of ASCs. Silencing of type IV collagen using siRNA resulted in a significant decrease in adipogenic capacity, as indicated by reduced lipid droplet formation and downregulation of adipogenic-related gene transcription. Conversely, supplementation of the culture medium with synthetic type IV collagen demonstrated enhanced adipogenic induction efficiency, accompanied by upregulation of YAP/TAZ protein expression and its downstream target gene transcription. Furthermore, inhibition of the YAP/TAZ pathway using the inhibitor Blebbistatin attenuated the functionality of type IV collagen, leading to decreased lipid droplet formation and downregulation of adipocyte maturation-related gene expression. These findings highlight the crucial role of type IV collagen in promoting adipogenic differentiation of ASCs and suggest its involvement in the YAP/TAZ-mediated Hippo pathway.No Level Assigned This journal requires that authors assign a level of evidence to each submission to which Evidence-Based Medicine rankings are applicable. This excludes Review Articles, Book Reviews, and manuscripts that concern Basic Science, Animal Studies, Cadaver Studies, and Experimental Studies. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266 .

Controlling desertification brings positive socioeconomic benefits beyond regional environmental improvement: Evidence from China's Gonghe Basin.

Large-scale desertification combatting programs (DCPs) are crucial tools for addressing climate change and improving the ecological environment. Despite existing research having predominantly focused on assessing the ecological benefits of DCPs, the understanding of their impacts on surrounding socioeconomic aspects remains limited, particularly at the household level. To comprehensively evaluate the returns of DCPs, this study chose the representative desertification control area of the Gonghe Basin on the Qinghai-Tibet Plateau as the research region and identified the dual benefits in terms of ecological environment and socioeconomic gains. Firstly, two essential ecosystem services, carbon sequestration (CS) and wind erosion prevention (WEP), were assessed using the MODIS NPP dataset and the RWEQ model from 2001 to 2021. Household surveys were conducted in 36 villages across 14 townships within the Gonghe Basin to gain a deeper understanding of the residents' socioeconomic conditions. Through regression analysis, the study assessed the impact of DCPs on the regional ecological environment and household socioeconomic status. The research findings revealed significant improvements in CS and WEP across a significant portion of the study area from 2001 to 2021. Upon analyzing data from 401 household questionnaires, it was generally perceived by residents in the Gonghe Basin that the implementation of DCPs led to environmental improvements and increased their income levels. Further regression analysis revealed a significant impact of both natural factors and the extent of resident participation in the projects on the ecological environment surrounding the villages and on household socioeconomic aspects. With increased resident engagement in the projects, the likelihood of increased household income and life satisfaction was higher. The diverse array of DCPs implemented in the Gonghe Basin not only improved the regional ecological environment but also stimulated socioeconomic development. In future projects, it is imperative to consider regional characteristics, align ecological effects, ensure the sustainability of livelihoods, and maximize the role of social capital.

The involvement of transient receptor potential channels in mast cell activation by microbubbles.

This study was to explore the activation of mast cells by microbubbles, with the focus on transient receptor potential (TRP) channels mediated degranulation and calcium influx. Bone marrow-derived mast cells (BMMCs) were primarily obtained from femurs in mice and induced differentiation for 4 weeks. After the purity identification, BMMCs were contacted by homogeneous microbubbles with the diameter of 1 mm for 1 h. ß-hexosaminidase and histamine levels in supernatants were assessed by enzyme-linked immunosorbent assay (ELISA) and the CD63 expression was tested by flow cytometry. The intracellular calcium binding with Fluo-4 AM dyes in BMMCs was observed under the fluorescence microscope and the mean fluorescence intensity was quantitatively measured by flow cytometry. ß-hexosaminidase release, histamine concentration, CD63 expression and calcium influx were significantly increased in BMMCs group upon microbubble stimulation compared to the control groups. After preconditioning with the available inhibitors and microbubble contact, only transient receptor potential vanilloid 1 (TRPV1) and TRPV4 inhibitors robustly suppressed the microbubble-induced degranulation. Likewise, the elevated fluorescence intensity of cytosolic calcium level was also significantly weaken. The results demonstrated microbubble stimulus effectively promoted BMMCs degranulation, which could be substantially restrained by inhibitors targeted for blocking TRPV1 or TRPV4 channel. The alternation of intracellular calcium level in BMMCs was consistent with the changes of degranulation capacity. It's suggested that the activation of BMMCs by microbubbles may involve specific TRP calcium dependent channels.

Atomic Three-Dimensional Investigations of Pd Nanocatalysts for Acetylene Semi-hydrogenation.

Deciphering the three-dimensional (3D) insight into nanocatalyst surfaces at the atomic level is crucial to understanding catalytic reaction mechanisms and developing high-performance catalysts. Nevertheless, better understanding the inherent insufficiency of a long-range ordered lattice in nanocatalysts is a big challenge. In this work, we report the local structure of Pd nanocatalysts, which is beneficial for demonstrating the shape-structure-adsorption relationship in acetylene hydrogenation. The 5.27 nm spherical Pd catalyst (Pdsph) shows an ethylene selectivity of 88% at complete acetylene conversion, which is much higher than those of the Pd octahedron and Pd cube and superior to other reported monometallic Pd nanocatalysts so far. By virtue of the local structure revelation combined with the atomic pair distribution function (PDF) and reverse Monte Carlo (RMC) simulation, the atomic surface distribution of the unique compressed strain of Pd-Pd pairs in Pdsph was revealed. Density functional theory calculations verified the obvious weakening of the ethylene adsorption energy on account of the surface strain of Pdsph. It is the main factor to avoid the over-hydrogenation of acetylene. The present work, entailing shape-induced surface strain manipulation and atomic 3D insight, opens a new path to understand and optimize chemical activity and selectivity in the heterogeneous catalysis process.

An MRI radiomics approach to predict survival and tumour-infiltrating macrophages in gliomas.

Preoperative MRI is one of the most important clinical results for the diagnosis and treatment of glioma patients. The objective of this study was to construct a stable and validatable preoperative T2-weighted MRI-based radiomics model for predicting the survival of gliomas. A total of 652 glioma patients across three independent cohorts were covered in this study including their preoperative T2-weighted MRI images, RNA-seq and clinical data. Radiomic features (1731) were extracted from preoperative T2-weighted MRI images of 167 gliomas (discovery cohort) collected from Beijing Tiantan Hospital and then used to develop a radiomics prediction model through a machine learning-based method. The performance of the radiomics prediction model was validated in two independent cohorts including 261 gliomas from the The Cancer Genomae Atlas database (external validation cohort) and 224 gliomas collected in the prospective study from Beijing Tiantan Hospital (prospective validation cohort). RNA-seq data of gliomas from discovery and external validation cohorts were applied to establish the relationship between biological function and the key radiomics features, which were further validated by single-cell sequencing and immunohistochemical staining. The 14 radiomic features-based prediction model was constructed from preoperative T2-weighted MRI images in the discovery cohort, and showed highly robust predictive power for overall survival of gliomas in external and prospective validation cohorts. The radiomic features in the prediction model were associated with immune response, especially tumour macrophage infiltration. The preoperative T2-weighted MRI radiomics prediction model can stably predict the survival of glioma patients and assist in preoperatively assessing the extent of macrophage infiltration in glioma tumours.

Study on Purification, Identification and Antioxidant of Flavonoids Extracted from Perilla leaves.

The flavonoids from Perilla leaves were extracted using flash extraction assisted by ultrasonic extraction with ethanol. Subsequently, macroporous resin was employed for the isolation and purification of these flavonoids, followed by an investigation into their antioxidant activity. The process conditions for the extraction of flavonoids from Perilla leaves were designed and optimized using a one-way experiment combined with a response surface methodology. The optimal extraction conditions were determined as follows: the liquid-solid ratio was 20:1, ethanol volume fraction of 60%, ultrasound temperature of 60 °C, ultrasound time of 10 min and flash evaporation time of 60 s. The optimal extraction rate of flavonoids is 9.8 mg/g. In terms of separation and purification, a high-performance macroporous resin (HPD450 resin) with high purification efficiency was selected through static analysis and adsorption experiments. The optimal enrichment conditions were as follows: loading concentration of 0.06 mg/mL, optimal loading concentration of 20 mL, elution concentration of 70% and 76 mL, providing a reference for the further development and utilization of Perilla leaf flavonoids.

Measuring pressure distribution under the seat cushion and dividing the pressure map in six regions might be beneficial for comfort studies of aircraft seats.

Seat pressure maps are often used to evaluate comfort of the users. In this study, we explored the relationships between pressure maps and comfort/discomfort of users in aircraft seats with a focus on a new 6-division method on the pressure maps collected at the bottom of the cushions. An experiment was designed where three cushions with identical shapes but different stiffnesses were prepared. 33 subjects joined the experiment and after sitting on each cushion in 4 postures, they completed comfort questionnaires. Pressure maps on the top as well as the bottom of cushions were collected and analysed. Results indicated that measures on the proposed 6 divisions, especially on the distal posterior thigh regions and regions close to ischial tuberosity of the bottom pressure maps, had larger correlation values to comfort scores compared to other division methods. Practitioner summary: The relations between comfort/discomfort and seat pressure maps collected from the top/bottom of three cushions were studied with 33 subjects in four postures. The distal posterior thigh and ischial tuberosity regions in the proposed 6-division of the bottom pressure maps had larger correlation values to comfort/discomfort compared to other methods.

Pelagibacterium xiamenense sp. nov., isolated from intertidal sediment.

A Gram-stain-negative, obligately aerobic bacterium, designated as HS1C4-1T, was isolated from a sediment sample from the tidal zone of the Haicang Coast, Xiamen, Fujian Province, PR China. The strain was yellowish-coloured, non-gliding, rod-shaped and motile, with a single polar flagellum. Cells of HS1C4-1T were oxidase- and catalase-positive. The strain could grow at 15-55 °C (optimum 37 °C), pH 6.0-10.0 (optimum, pH 7.0-9.0), in the presence of 0-12 % (optimum, 1 %) NaCl (w/v). Phylogenetic analysis based on the 16S rRNA gene sequences indicated that HS1C4-1T represented a member of the genus Pelagibacterium, and shared the highest similarity to Pelagibacterium luteolum CGMCC 1.10267T (97.6 %). Digital DNA-DNA hybridization values and average nucleotide identity between HS1C4-1T and all the species of genus Pelagibacterium were 18.7-20.2 % and 77.3-78.4 %, respectively. The principal fatty acids (>10 %) were C19 : 0 cyclo ω8c (50.5 %) and summed feature 8 (C18 : 1ω7c and/or C18 : 1ω6c; 29.1%). Q-10 was the sole respiratory quinone. The polar lipids included diphosphatidylglycerol, phosphatidylglycerol, two unidentified glycolipids and six unidentified lipids. The G+C content of the chromosomal DNA was 62.9 %. On the basis of phylogenetic, phenotypic, chemotaxonomic and genomic characteristics, HS1C4-1T represents a novel species within the genus Pelagibacterium, for which the name Pelagibacterium xiamenense sp. nov. is proposed. The type strain is HS1C4-1T (=MCCC 1A18759T=KCTC 92097T).

Gordonia tangerina sp. nov., isolated from seawater.

A Gram-stain-positive, aerobic bacterium, designated GW1C4-4T, was isolated from the seawater sample from the tidal zone of Guanyinshan Coast, Xiamen, Fujian Province, PR China. The strain was reddish-orange, rod-shaped and non-motile. Cells of strain GW1C4-4T were oxidase-negative and catalase-positive. The strain could grow at 10-42 °C (optimum, 32-35 °C), pH 5-9 (optimum, pH 6) and with 0-10 % NaCl (w/v; optimum, 1 %). Phylogenetic analysis based on the 16S rRNA sequences indicated that strain GW1C4-4T belonged to the genus Gordonia, having the highest similarity to Gordonia mangrovi HNM0687T (98.5 %), followed by Gordonia bronchialis DSM 43247T (98.4 %). The G+C DNA content was 66.5 mol %. Average nucleotide identity and digital DNA-DNA hybridization values between strain GW1C4-4T and G. mangrovi HNM0687T were 85.8 and 30.0 %, respectively. The principal fatty acids of strain GW1C4-4T were C16 : 0, C18 : 0 10-methyl (TBSA) and summed feature 3 (C16 : 1 ω7c/C16 : 1 ω6c). MK-9 (H2) was the sole respiratory quinone. The polar lipids included diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylcholine and an unidentified lipid. Based on its phylogenetic, phenotypic, chemotaxonomic and genomic characteristics, it is proposed that strain GW1C4-4T represents a novel species within the genus Gordonia, for which the name Gordonia tangerina sp. nov. is proposed. The type strain is GW1C4-4T (=MCCC 1A18727T=KCTC 49729T).

Effects of oestrogen on vulvovaginal candidosis.

As a frequently occurring infectious disease mainly caused by Candida albicans, vulvovaginal candidosis (VVC) affects more than 100 million women worldwide every year. Multiple factors that influence C. albicans colonisation have been linked to the incidence of VVC, including high levels of circulating oestrogen due to pregnancy, the use of oral contraceptives, and hormone replacement therapy. This review provides an overview of the current understanding of the mechanism(s) by which oestrogen contributes to VVC, which might provide meaningful guidance to the prevention and treatment of this disease.

neoDL: a novel neoantigen intrinsic feature-based deep learning model identifies IDH wild-type glioblastomas with the longest survival.

BACKGROUND: Neoantigen based personalized immune therapies achieve promising results in melanoma and lung cancer, but few neoantigen based models perform well in IDH wild-type GBM, and the association between neoantigen intrinsic features and prognosis remain unclear in IDH wild-type GBM. We presented a novel neoantigen intrinsic feature-based deep learning model (neoDL) to stratify IDH wild-type GBMs into subgroups with different survivals. RESULTS: We first derived intrinsic features for each neoantigen associated with survival, followed by applying neoDL in TCGA data cohort(AUC = 0.988, p value < 0.0001). Leave one out cross validation (LOOCV) in TCGA demonstrated that neoDL successfully classified IDH wild-type GBMs into different prognostic subgroups, which was further validated in an independent data cohort from Asian population. Long-term survival IDH wild-type GBMs identified by neoDL were found characterized by 12 protective neoantigen intrinsic features and enriched in development and cell cycle. CONCLUSIONS: The model can be therapeutically exploited to identify IDH wild-type GBM with good prognosis who will most likely benefit from neoantigen based personalized immunetherapy. Furthermore, the prognostic intrinsic features of the neoantigens inferred from this study can be used for identifying neoantigens with high potentials of immunogenicity.

Global DNA 5-Hydroxymethylcytosine and 5-Formylcytosine Contents Are Decreased in the Early Stage of Hepatocellular Carcinoma.

Methylation of the fifth position of cytosine (5mC) is an important epigenetic modification of DNA. It has been shown that the oxidized derivatives of 5mC, namely 5-hydroxymethylcytosine (5hmC), 5-formylcytosine (5fC), and 5-carboxylcytosine (5caC), are in dynamic existence and have distinct regulatory functions. In the current study, we investigated whether there are changes in the contents of all three 5mC-oxidized derivatives in the hepatocellular carcinoma (HCC) genome and further explored the underlying mechanisms. We showed that both global genomic 5hmC and 5fC contents were decreased significantly in the very early stage (stage 0, Barcelona Clinic Liver Cancer [BCLC] staging) of HCC compared with those of paratumor tissues. Noteworthily, 5fC content continued to decrease in the late stage (BCLC staging from 0 to A) of HCC. The 5caC content in HCC tissues was below the detection threshold. Hepatitis B virus (HBV) infection was associated with 5mC, 5hmC, or 5fC decrease in HCC; and measurements in cell lines integrated with or without HBV DNA showed consistent results. On the other hand, both the expression level of ten-eleven translocation enzyme 2 (TET2) and α-ketoglutarate content were decreased significantly in HCC. The significantly positive correlations among the expression levels of DNA methylation-related enzymes in paratumor tissues were generally attenuated or even disappeared in HCC tumor tissues. The decreases of both 5hmC and 5fC contents in genomic DNA were associated with poor prognosis of HCC patients. Conclusion: Global 5hmC and 5fC contents were decreased significantly in the very early stage of HCC; the decrease of 5hmC and 5fC was mainly due to the decrease of 5mC and associated with HBV infection, decreased TET enzyme activity, and uncoordinated expression of DNA methylation-related enzymes.

The immunomodulatory role of PDEs inhibitors in immune cells: therapeutic implication in rheumatoid arthritis.

Rheumatoid arthritis (RA) is a chronic autoimmune disorder characterized by inflammatory synovitis and progressive joint. Although the etiology is extremely complex, overwhelming evidence suggests that dysregulation or imbalance of the immune system plays a central role in disease pathogenesis. The bone loss and joint destruction are immunological insults mediated by infiltration and abnormal activation of various immune cells. Since pharmacological inhibition of cyclic nucleotide phosphodiesterases (PDEs), which degrade cyclic AMP and cyclic GMP, can regulate the activity of multiple immune cells, which are considered as a potential strategy for treating RA. Therefore, this review attempted to summarize the modulating effects of PDEs on immune cells and described the molecular underpinnings and potential clinical application of PDEs inhibitors for RA.

Effects of liquorice on pharmacokinetics of aconitine in rats.

Aconite alkaloids are the main bioactive ingredients existing in Aconitum, for instance aconitine (AC), which exhibit potent analgesic, antirheumatic and other pharmacological effects. In this study, effects of long-term treatment with liquorice on pharmacokinetics of AC in rats were investigated. Pharmacokinetics of AC after oral administration of AC at 1.5 mg/kg either with pre-treatment of liquorice water extracts at 0.433 or 1.299 g/kg (crude drug), respectively, for one week or not were studied. Additionally, LS-180 cells and human primary hepatocytes were utilized to explore the potential effects of bioactive ingredients of liquorice on P-glycoprotein (P-gp) and Cytochromes P450 (CYPs), respectively. The results revealed that exposure of AC after pre-treatment with liquorice was altered remarkably. Area under the concentration-time curve (AUC) decreased from 161 ± 37.8 to 58.8 ± 8.97 and 44.7 ± 8.20 ng/mL*h, respectively. Similarly, Cmax decreased from 26.2 ± 5.19 to 11.8 ± 1.15 and 6.86 ± 0.600 ng/mL, respectively. In addition, expressions of CYPs of human primary hepatocytes were enhanced to various contents after induction. Moreover, accumulation of AC and hypaconitine (HA), not mesaconitine (MA) inside of LS-180 cells were reduced after pre-treatment by comparison with control. In conclusion, the exposure of AC in vivo declined after pre-treatment with liquorice extract, which may be highly associated with upregulated expression and/or function of CYPs and P-gp.

Supported catalysts based on layered double hydroxides for catalytic oxidation and hydrogenation: general functionality and promising application prospects.

Oxidation and hydrogenation catalysis plays a crucial role in the current chemical industry for the production of key chemicals and intermediates. Because of their easy separation and recyclability, supported catalysts are widely used in these two processes. Layered double hydroxides (LDHs) with the advantages of unique structure, composition diversity, high stability, ease of preparation and low cost have shown great potential in the design and synthesis of novel supported catalysts. This review summarizes the recent progress in supported catalysts by using LDHs as supports/precursors for catalytic oxidation and hydrogenation. Particularly, partial hydrogenation of acetylene, hydrogenation of dimethyl terephthalate, methanation, epoxidation of olefins, elimination of NOx and SOx emissions, and selective oxidation of biomass have been chosen as representative reactions in the petrochemical, fine chemicals, environmental protection and clean energy fields to highlight the potential application and the general functionality of LDH-based catalysts in catalytic oxidation and hydrogenation. Finally, we concisely discuss some of the scientific challenges and opportunities of supported catalysts based on LDH materials.

The role of vegetation-microclimate feedback in promoting shrub encroachment in the northern Chihuahuan desert.

Many arid and semi-arid landscapes around the world are affected by a shift from grassland to shrubland vegetation, presumably induced by climate warming, increasing atmospheric CO2 concentrations, and/or changing land use. This major change in vegetation cover is likely sustained by positive feedbacks with the physical environment. Recent research has focused on a feedback with microclimate, whereby cold intolerant shrubs increase the minimum nocturnal temperatures in their surroundings. Despite the rich literature on the impact of land cover change on local climate conditions, changes in microclimate resulting from shrub expansion into desert grasslands have remained poorly investigated. It is unclear to what extent such a feedback can affect the maximum extent of shrub expansion and the configuration of a stable encroachment front. Here, we focus on the case of the northern Chihuahuan desert, where creosotebush (Larrea tridentata) has been replacing grasslands over the past 100-150 years. We use a process-based coupled atmosphere-vegetation model to investigate the role of this feedback in sustaining shrub encroachment in the region. Simulations indicate that the feedback allows juvenile shrubs to establish in the grassland during average years and, once established, reduce their vulnerability to freeze-induced mortality by creating a warmer microclimate. Such a feedback is crucial in extreme cold winters as it may reduce shrub mortality. We identify the existence of a critical zone in the surroundings of the encroachment front, in which vegetation dynamics are bistable: in this zone, vegetation can be stable both as grassland and as shrubland. The existence of these alternative stable states explains why in most cases the shift from grass to shrub cover is found to be abrupt and often difficult to revert.

Simultaneous determination of six active components by a single standard to determine multicomponents combined with fingerprint analysis for the quality control of Rhizoma Chuanxiong.

To control the quality of Rhizoma Chuanxiong, a method based on high-performance liquid chromatography method coupled with diode array detection was developed for the quantitative analysis of six active ingredients using a single standard to determine multi-components and chemical fingerprint analysis for the first time. The separation was performed on an Agilent Zorbax SB-C18 column by gradient elution with methanol and aqueous phase (containing 0.5% glacial acetic acid) at a flow rate of 1.0 mL/min. The UV wavelength was set at 274 nm. This assay was fully validated with respect to precision, repeatability, and accuracy. All calibration curves showed good linearity (R(2) > 0.9994) within test ranges. The limit of detection and limit of quantification were lower than 0.01 and 0.03 µg/mL, respectively. The relative standard deviation for repeatability and the intermediate precision of six analytes were less than 1.6 and 2.5%, respectively, the overall recovery was 96.1-103.1%. In addition, fingerprint chromatography using hierarchical clustering analysis and similarity analysis was performed to differentiate and classify the samples. The method described here could provide a more comprehensive and reasonable scientific assessment of the quality of Rhizoma Chuanxiong. Therefore, the strategy is feasible, credible, and is easily and effectively adapted for evaluating the quality control of Rhizoma Chuanxiong.