Thermal multiferroics in all-inorganic quasi-two-dimensional halide perovskites.

Multiferroic materials, particularly those possessing simultaneous electric and magnetic orders, offer a platform for design technologies and to study modern physics. Despite the substantial progress and evolution of multiferroics, one priority in the field remains to be the discovery of unexplored materials, especially those offering different mechanisms for controlling electric and magnetic orders1. Here we demonstrate the simultaneous thermal control of electric and magnetic polarizations in quasi-two-dimensional halides (K,Rb)3Mn2Cl7, arising from a polar-antipolar transition, as evidenced using both X-ray and neutron powder diffraction data. Our density functional theory calculations indicate a possible polarization-switching path including a strong coupling between the electric and magnetic orders in our halide materials, suggesting a magnetoelectric coupling and a situation not realized in oxide analogues. We expect our findings to stimulate the exploration of non-oxide multiferroics and magnetoelectrics to open access to alternative mechanisms, beyond conventional electric and magnetic control, for coupling ferroic orders.

Epitaxial-strain-induced polar-to-nonpolar transitions in layered oxides.

Epitaxial strain can induce collective phenomena and new functionalities in complex oxide thin films. Strong coupling between strain and polar lattice modes can stabilize new ferroelectric phases from nonpolar dielectrics or enhance electric polarizations and Curie temperatures. Recently, strain has also been exploited to induce novel metal-insulator transitions and magnetic reconstructions through its coupling to nonpolar modes, including rotations of BO6 transition-metal octahedra. Although large strains are thought to induce ferroelectricity, here we demonstrate a polar-to-nonpolar transition in (001) films of layered A3B2O7 hybrid-improper ferroelectrics with experimentally accessible biaxial strains. We show the origin of the transition originates from the interplay of trilinear-related lattice mode interactions active in the layered oxides, and those interactions are directly strain tunable. Our results call for a careful re-examination of the role of strain-polarization coupling in ferroelectric films with nontrivial anharmonicities and offer a route to search for new functionalities in layered oxides.

Tunable Negative Thermal Expansion in Layered Perovskites from Quasi-Two-Dimensional Vibrations.

We identify a quasi-two-dimensional (quasi-2D) phonon mode in the layered-perovskite Ca_{3}Ti_{2}O_{7}, which exhibits an acoustic branch with quadratic dispersion. Using first-principles methods, we show this mode exhibits atomic displacements perpendicular to the layered [CaTiO_{3}]_{2} blocks comprising the structure and a negative Grüneisen parameter. Owing to these quasi-2D structural and dynamical features, we find that the mode can be utilized to realize unusual membrane effects, including a tunable negative thermal expansion (NTE) and a rare pressure-independent thermal softening of the bulk modulus. Detailed microscopic analysis shows that the NTE relies on strong intralayer Ti-O covalent bonding and weaker interlayer interactions, which is in contrast to conventional NTE mechanisms for perovskites, such as rigid-unit modes, structural transitions, and electronic or magnetic ordering. The general application of the quasi-2D lattice dynamics opens exciting avenues for the control of lattice dynamical and thermodynamic responses of other complex layered compounds through rational chemical substitution, as we show in A_{3}Zr_{2}O_{7} (A=Ca, Sr), and by heterostructuring.

Cardamonin Inhibits Angiogenesis by mTOR Downregulation in SKOV3 Cells.

The mammalian target of rapamycin is critical in hypoxia-triggered angiogenesis. Cardamonin inhibits proliferation of various cancer cells through suppressing the mammalian target of rapamycin. In this study, the antiangiogenic effect of cardamonin on CoCl2-mimicked hypoxic SKOV3 cells was investigated. Cardamonin exhibited an antiproliferative effect on normal and CoCl2-mimicked hypoxic SKOV3 cells. Messenger RNA expression of vascular endothelial growth factor was inhibited with cardamonin and rapamycin in SKOV3 cells under both conditions. However, cardamonin had little effect on the messenger RNA expression of hypoxia-inducible factor-α. Cardamonin inhibited the protein expression of hypoxia-inducible factor-1α, hypoxia inducible factor-2α, vascular endothelial growth factor, and the phosphorylation of mammalian target of rapamycin and ribosomal S6 kinase 1. Furthermore, angiogenesis induced by a medium of SKOV3 cells was reduced by cardamonin in a chicken embryo allantois membrane model. These findings suggest that cardamonin inhibits protein expression of hypoxia-inducible factor-α, and vascular endothelial growth factor, which was induced by CoCl2-mimicked hypoxia and this effect partially correlates with the mammalian target of rapamycin inhibition. Cardamonin might be a potential angiogenesis inhibitor for ovarian cancer therapy.

Lacidipine attenuates TNF-α-induced cardiomyocyte apoptosis.

This study was designed to investigate whether lacidipine elicited a protective role on cardiomyocyte against apoptosis induced by TNF-α. Neonatal rat cardiomyocytes were randomly assigned into different groups. TUNEL staining was utilized to detect apoptosis, and caspase-3 and caspse-12 were determined. To explore the underlying mechanism, Z-ATAD-FMK (a selective caspase-12 inhibitor) was used to identify the key molecule involved. TNF-α increased caspase-3 expression, which was mediated by increased caspase-12 expression. In the meantime, apoptosis was significantly induced by TNF-α. Lacidipine lowered caspase-12 and caspase-3 expression, and cardiomyocyte apoptosis induced by TNF-α. The results suggest that lacidipine attenuates TNF-α -induced apoptosis via inhibition of caspase-12 and caspase-3 successively.

Regulable high-contrast mechanofluorochromic enhancement behaviour based on substituent effects.

Herein, a facile strategy was established to build mechanoresponsive luminogens with high sensitivity to substituents and positional effects. Even in slightly different structures, distinct optical phenomena, including fluorescence efficiency and mechano-responsive properties, were clearly present. Outstanding mechanical-induced emission enhancement (5-100 times) properties and reversibility makes for promising applications in pressure sensors and OLEDs.

Study of Temperature Changes around Fibres in Super Pulse Thulium Fibre Laser in Vitro Lithotripsy.

PURPOSE: To investigate temperature changes around the fibres of the super pulse thulium fibre laser (SP-TFL) during in vitro lithotripsy. MATERIALS AND METHODS: Stones were placed in the in vitro model. The laser was continuously excited for 180 s; the probe was positioned 5 mm around the fibre; the laser power was set at 10, 15, 20, 25, and 30 W; and the irrigation rate was set at 0, 15, 25, 35 ml/min, using a domestic SP-TFL. The temperature variations around the fibre under different power settings and different irrigation rates were compared. RESULTS: Without irrigation, the temperature around the fibre rapidly reached the safety threshold of 43℃ at 24 s. At irrigation rate 15 ml/min and laser power <15 W, the temperature around the fibre was <43℃. Once the laser power increased to ≥20 W, the temperature around the fibre increased to >43℃ at its lowest plateau. At irrigation rate 25 ml/min and laser power ≤25 W, the temperature around the fibre was <43℃. At irrigation rate 35 ml/min and laser power <30 W, the fibre temperature was <43℃. When laser power was ≥30 W, the fibre temperature was >43℃. CONCLUSION: In extracorporeal ureteroscope SP-TFL lithotripsy, when the laser power is ≤15 W, ≤25 W, and ≤30 W, the irrigation rate should be maintained at ≥15 ml/min, ≥25 ml/min, and ≥35 ml/min, respectively.

Out-of-plane ferroelectricity and robust magnetoelectricity in quasi-two-dimensional materials.

Thin-film ferroelectrics have been pursued for capacitive and nonvolatile memory devices. They rely on polarizations that are oriented in an out-of-plane direction to facilitate integration and addressability with complementary metal-oxide semiconductor architectures. The internal depolarization field, however, formed by surface charges can suppress the out-of-plane polarization in ultrathin ferroelectric films that could otherwise exhibit lower coercive fields and operate with lower power. Here, we unveil stabilization of a polar longitudinal optical (LO) mode in the n = 2 Ruddlesden-Popper family that produces out-of-plane ferroelectricity, persists under open-circuit boundary conditions, and is distinct from hyperferroelectricity. Our first-principles calculations show the stabilization of the LO mode is ubiquitous in chalcogenides and halides and relies on anharmonic trilinear mode coupling. We further show that the out-of-plane ferroelectricity can be predicted with a crystallographic tolerance factor, and we use these insights to design a room-temperature multiferroic with strong magnetoelectric coupling suitable for magneto-electric spin-orbit transistors.

Targeting NR1D1 in organ injury: challenges and prospects.

Nuclear receptor subfamily 1, group D, member 1 (NR1D1, also known as REV-ERBα) belongs to the nuclear receptor (NR) family, and is a heme-binding component of the circadian clock that consolidates circadian oscillators. In addition to repressing the transcription of multiple clock genes associated with circadian rhythms, NR1D1 has a wide range of downstream target genes that are intimately involved in many physiopathological processes, including autophagy, immunity, inflammation, metabolism and aging in multiple organs. This review focuses on the pivotal role of NR1D1 as a key transcription factor in the gene regulatory network, with particular emphasis on the milestones of the latest discoveries of NR1D1 ligands. NR1D1 is considered as a promising drug target for treating diverse diseases and may contribute to research on innovative biomarkers and therapeutic targets for organ injury-related diseases. Further research on NR1D1 ligands in prospective human trials may pave the way for their clinical application in many organ injury-related disorders.

[Effect of genistein on MAPK signal pathway in the collagen-induced arthritis fibroblast-like synoviocytes].

OBJECTIVE: To study the effect of genistein (Gen) on MAPK signal pathway in the CIA rat fibroblast-like synoviocytes (FLS). METHODS: The rat model of collagen-induced arthritis (CIA) was established. The cultured FLS of CIA rats were divided using randomized method. The effects of Gen (at the concentration of 50, 100, and 200 micromol/L, respectively) on the proliferation of FLS in CIA rats using methyl thiazolyl tetrazolium (MTT) assay. Effects of Gen (at the concentration of 50, 100, and 200 pmol/L, respectively) on the expressions of extracellular signal-regulated kinase (ERK) and phosphorylated extracellular signal-regulated kinase (p-ERK) in the FLS of CIA rats were detected. RESULTS: Gen could inhibit the proliferation of FLS in CIA rats. The FLS proliferation in the high dose Gen group at 72 h was only 1.10+/-0.04, significantly lower than that in the model group (2.12+/-0.03, P<0.01). Besides, after Gen's action on FLS, the expression of p-ERK was down-regulated. It was only 0.34+/-0.02 in the high dose Gen group, significantly lower than that in the model group (2.68+/-0.14, P<0.01). There was no change in the expression of ERK (P>0.05). CONCLUSIONS: Gen could inhibit the proliferation of FLS in CIA rats. Its mechanism of action was mainly correlated to down-regulating the tyrosine kinase of MAPK signal transduction pathway and inhibiting phosphorylation of ERK.

[Anti-angiogenic effects of genistein on synovium in a rat model of type II collagen-induced arthritis].

OBJECTIVE: To explore the anti-angiogenic effects of genistein on synovium in a rat model of type II collagen-induced arthritis (CIA). METHODS: Forty SD rats were randomly divided into normal group, model group, genistein group, methotrexate (MTX) group and Gen plus MTX group with 8 rats in each group. Arthritis in rats was induced by subcutaneous injection of type II collagen combined with complete Freund's adjuvant (CFA). On the second day after the injection, 1 mL of suspension liquid of genistein (30 mg/kg body weight, once daily) and MTX (0.2 mg/kg body weight, once a week) were administered by oral gavage respectively. The rats in normal group and model group were administered with normal saline in the same volume. Synovium of knee joints and peripheral serum were collected from the CIA rats. Microvessel density in synovium (MVD) was detected by immunohistochemical method and serum vascular endothelial growth factor (VEGF) and matrix metallopeptidase (MMP)-1, 2 and 9 levels were detected by using Western blotting. RESULTS: Arthritis index score, paw volume of rats in the model group were significantly higher than those in the normal group (P<0.05), which suggested that a model of CIA induced by injection of type II collagen and CFA was successfully constructed. The arthritis index scores of rats in the treatment groups were decreased compared with the model group. The results of Western blotting showed that genistein obviously attenuate the levels of VEGF and MMP-1, 2 and 9 in serum (P<0.05). Immunohistochemical method showed that MVDs in the treatment groups were reduced as compared with the model group. CONCLUSION: The expressions of VEGF and MMP-1, 2 and 9 are related to the synovial pannus formation in CIA rats. The anti-angiogenic activity of genistein may correlate to its inhibitory effect on the expressions of VEGF and MMP-1, 2 and 9 in serum of CIA rats; genistein plus MTX are superior to single agents in treating rheumatoid arthritis.

Comparison of the Efficacy of Two Elastic Bandages for Forearm Hematoma After Transradial Coronary Intervention.

Background: This study compares the efficacy of two elastic bandages in treating forearm hematoma after transradial coronary intervention. Methods: A total of 60 patients with moderate or severe forearm hematoma following transradial coronary intervention were enrolled in this study. They were randomly divided into two groups, as follows: an Idealast-haft elastic bandage group (the observation group) and a control group. The patients in the Idealast-haft elastic bandage group received compression bandaging with Idealast-haft elastic bandages and the patients in the control group received compression bandaging with Nylexorgrip elastic bandages. Observation indexes related to, for example, forearm pain, arterial pulsation, blistering, skin color, and hemostasis time were compared between the two groups. Results: The results revealed that the times taken for pain disappearance, arterial pulse recovery, blister disappearance, skin color recovery, and compression hemostasis were significantly shorter in the Idealast-haft elastic bandage group than in the control group, and the differences were statistically significant (P < 0.05). The hematoma range and the arm circumference at the severest part of the hematoma decreased faster in the observation group than in the control group, and the differences were statistically significant (P < 0.05). Conclusion: The Idealast-haft elastic bandage is more effective than the Nylexorgrip elastic bandage in patients with forearm hematoma following transradial coronary intervention and should therefore be used in such cases.

An operating method with lateral scan for reducing the error in topography caused by the tip-sample angle in atomic force microscopy.

The atomic force microscopes (AFM) images are obtained by keeping the bending of the cantilever unchanged in contact mode. However, it is found that changes in the tip-sample angle during parallel scan result in error in the topographic image. It is also discovered that measurement results obtained in the blind scan region contained large errors. In contrast, regions opposite the blind scan region gave more reliable result. To eliminate this topographic error caused by change in the tip-sample angle, a new operating method with lateral scan is utilized in AFM. Comparative experiments have been performed, and the results show that the error could be eliminated or decreased by using the operating method.

[Effects of genistein on interleukin-1beta and tumor necrosis factor-alpha secreted by fibroblast-like synoviocytes isolated from type II collagen-induced arthritis rats].

OBJECTIVE: To investigate the effects of genistein (Gen) on interleukin-1beta (IL-1beta) and tumor necrosis factor-alpha (TNF-alpha) secreted by fibroblast-like synoviocytes (FLSs) of rats with type II collagen-induced arthritis (CIA). METHODS: Type II collagen was injected to induce arthritis in rats, and arthritis index was applied to evaluate whether the arthritis was induced successfully. The primary FLSs were separated from synovial membranes by using type II collagenase digestion. Then the expression of vascular cell adhesion molecule-1 (VCAM-1) was estimated by flow cytometry (FCM). After addition of different concentrations of Gen into the FLSs, IL-1beta and TNF-alpha contents in the supernatants were measured by enzyme-linked immunosorbent assay. RESULTS: Three days after collagen injection, the rats started to develop arthrocele and the arthritis index increased gradually. The arthritis index of CIA group was significantly higher than that of the control group. The expression of VCAM-1 was up to 85.5% in the 4th generation FLSs, indicating that most part of the cultured cells were type-B synoviocytes. After administration of different concentrations of Gen (100, 200, 400 micromol/L), the contents of IL-1beta and TNF-alpha in supernatants of FLSs were decreased dose-dependently. CONCLUSION: Genistein can suppress the secretion of TNF-alpha and IL-1beta in FLSs dose-dependently, which may be one of the mechanisms for genistein in inhibiting the arthromeningitis of CIA rats.

Pathogenesis of liver injury caused by antiviral drugs for coronavirus disease 2019 / 临床肝胆病杂志

Drug-induced liver injury is caused by the drug itself and/or its metabolites during drug use or occurs due to hypersensitivity or reduced tolerance to the drug in a particular body type. In the last three years of the diagnosis and treatment of coronavirus disease 2019 （COVID-19）， antiviral drugs have played a very important role， but there are many reports on liver injury caused by anti-COVID-19 drugs in China and globally， with unknown pathogenesis of liver injury caused by such drugs. This article reviews the research advances in the types of antiviral drugs for COVID-19 and their mechanism in inducing liver injury， in order to promote the rational use of antiviral drugs.

Application of outcome-based education combined with team-based learning in practice teaching of pediatric emergency and critical care nursing / 中华医学教育探索杂志

Objective:To investigate the application value of outcome-based education (OBE) combined with team-based learning (TBL) in the practice teaching of pediatric emergency and critical care nursing.Methods:A total of 84 nursing students who studied in the pediatric intensive care unit (PICU) of The First Affiliated Hospital of Air Force Medical University were selected and divided into control group and observation group. The 41 nursing students in the control group received traditional teaching, and the 43 nursing students in the observation group received OBE+TBL teaching. The two groups were assessed in terms of theoretical knowledge, practical operation ability, clinical thinking ability, and self-learning ability after teaching, and the degrees of satisfaction with teaching and participation in teaching were compared between the two groups. SPSS 22.0 was used for the t-test and the chi-square test. Results:After teaching, the observation group had significantly better theoretical knowledge, practical operation ability, and self-learning ability than the control group ( P<0.05). Compared with the control group, the observation group had significantly higher scores of learning engagement (recognition, behavior, emotion) ( P<0.05) and satisfaction with classroom effect, knowledge mastery, and learning interest ( P<0.05). Conclusion:The application of OBE+TBL teaching in PICU nursing students can effectively improve their self-learning ability and participation and help them to understand PICU nursing priorities and improve their practical operation ability.

Comparison of temperature rise curve and steady state temperature during thulium and holmium laser lithotripsy / 中华泌尿外科杂志

Objective:To compare the temperature rise curve and steady-state temperature of thulium and holmium laser in lithotripsy.Methods:This study was conducted from November to December 2021. Firstly, we designed an experimental water tank(10 cm×10 cm×10 cm) that can carry out constant temperature water bath, with a 8ml simulated renal pelvis, and can carry out constant velocity perfusion in the simulated renal pelvis. A 1 cm×1 cm×1 cm cubic artificial stone was placed in the simulated renal pelvis to perform 36.5℃-37.5 ℃ water bath. The simulated renal pelvis was closed with an oak plug, the temperature measuring probe and flexible ureteroscope were placed through the hole on the oak plug and entered into the simulated renal pelvis. Flexible ureteroscope was carried out by urologists. The lithotripsy lasted a total of 180 seconds for thulium and holmium laser respectively under different parameter settings (10 Hz×1.0 J, 10 Hz×2.0 J, 10 Hz×3.0 J, 20 Hz×0.5 J, 20 Hz×1.0 J, 20 Hz×1.5 J, the corresponding gravel power is 10 W, 20 W and 30 W respectively), the constant speed water pump flow rate was separate as the high flow rate group (35 ml/min) and low flow rate group (15ml/min), and leave a temperature probe 5mm around the optical fiber. Water temperature change during the lithotripsy was recorded by probes, the average of 10 temperature values of two probes measured every 5 seconds was taken as the water temperature value of this period, with a total of 216 time points in 6 parameter settings. Under the same parameter settings, the temperature of two lasers at each time point was plotted and compared to form the corresponding temperature rise curve. The average temperature in the last 30 seconds during lithotripsy in the record was used as the steady-state temperature, which of thulium and holmium laser lithotripsy was compared under the same parameter setting and the same water flow velocity. Finally, 43℃ was taken as the safety threshold temperature to evaluate whether the temperature of the two lasers during lithotripsy exceeds the safety threshold.Results:According to the temperature rise curve, the water temperature of thulium laser during lithotripsy was higher than that of holmium laser at 77.7% (168/216)of time points. At the flow rate of 15 ml/min, thulium laser was significantly higher than that of holmium laser at 10 Hz×1.0 J[(32.43±2.19℃)vs. (30.99±0.90)℃, P<0.01], 10 Hz×2.0 J[(41.21±3.30℃) vs. (38.13±1.26)℃, P<0.01], 10 Hz×3.0 J[(49.54±2.44)℃vs. (44.91±0.65)℃, P<0.01], 20 Hz×0.5 J[(32.75±1.41)℃vs. (30.84±1.16)℃, P<0.01], 20 Hz×1.0 J[(41.67±1.76)℃vs. (37.51±1.25)℃, P<0.01], 20 Hz×1.5 J [(47.54 ± 3.48)℃vs. (46.12±1.04)℃, P<0.01]. At the flow rate of 35 ml/min, the thulium laser was significantly higher than that of holmium laser at 10 Hz×1.0 J[(28.01±0.57)℃ vs. (26.84±0.97)℃, P<0.01], 10 Hz×2.0 J[(31.31±1.07)℃vs.(30.41±1.39)℃, P<0.01], 10 Hz×3.0 J[(33.29±0.70)℃vs.(32.25±2.55)℃, P<0.01], 20 Hz×0.5 J[(28.36±0.99)℃vs.(26.22±0.66)℃, P<0.01], 20 Hz×1.0 J [(30.80±2.06)℃vs.(30.08±0.78)℃, P=0.012], and the steady-state temperature was not significant different between two laser at 20 Hz×1.5 J [(34.54±3.08)℃ and(33.93±1.49)℃, P=0.163]. In the low flow rate group, thulium laser at 10 Hz×1.0 J, 10 Hz×2.0 J, 20 Hz×0.5 J and 20 Hz×1.0 J does not exceed the safety threshold temperature, while in the high flow rate group, any combination of laser parameters of the two lasers does not exceed the safety threshold temperature. Conclusion:Under the same laser parameter setting and flow rate, the thermal eff of thulium laser is more obvious. When using thulium laser for lithotripsy, the flow rate in the process of lithotripsy being faster than that of holmium laser with the same laser setting should be ensured to avoid tissue damage.

An in vitro study of temperature variation of super-pulsed thulium fiber laser in ureter / 现代泌尿外科杂志

【Objective】 The thermal effects of super-pulsed thulium fiber laser (TFL) at different powers,lithotripsy modes and irrigation rates were studied using a 3D kidney model to simulate ureteral lithotripsy in vivo. 【Methods】 A thermal effect model was established in vitro. Under the same conditions of laboratory temperature and equipment,the temperature around the optical fiber was measured and compared when different optical fiber diameters,powers,lithotripsy modes and irrigation rates were used to simulate lithotripsy by TFL. 【Results】 There was significant difference in the temperature around the optical fiber caused by two fibers with different diameters under the same conditions (P<0.05). Under the same conditions,different lithotripsic modes produced different temperatures,and the temperature of "high energy and low frequency" was lower than that of "low energy and high frequency" (P<0.05). When the power was 10 W and the minimum irrigation rate was 10 mL/min,the plateau temperature did not reach the safety threshold (43 ℃). When the power was 20 W and the minimum irrigation rate was 10 mL/min,the platform temperature exceeded the safety threshold. When the irrigation rate was 20 mL/min,the platform temperature did not reach the safety threshold. 【Conclusion】 In the study of ureteral lithotripsy in vitro,the power,mode,irrigation rate and optical fiber diameter are factors affecting the thermal effects of TFL. No matter what kind of lithotripsy mode and fiber diameter,the temperature around the fiber is safe when the lithotripsy power is ≤10 W and the irrigation rate is ≥10 mL/min;when the lithotripsy power is ≤20 W and the irrigation rate is ≥20 mL/min,the temperature around the fiber is safe.

[Relationship between vegetation C, N, P stoichiometry and species diversity in sand land.] / æ²™åœ°æ¤è¢«ç¢³æ°®ç£·åŒ–å­¦è®¡é‡ç‰¹å¾ä¸Žç‰©ç§å¤šæ ·æ€§çš„å ³ç³».

Vegetation stoichiometry represents plant nutrition limitation status. Whether it can affect the species diversity of plant community remains to be explored. In this study, we examined plant carbon (C), nitrogen (N), phosphorus (P) concentrations and stoichiometry, and further analyzed the relationship between stoichiometry and species diversity in Artemisia ordosica community and Salix psammophila community in sand land of the Ningxia Habahu National Nature Reserve. The results showed that, for the S. psammophila community growing in mobile and semi-fixed sand dunes, there was a significant negative correlation between Simpson index and vegetation C/N ratio, but no significant correlation between Simpson index and vegetation N/P ratio. For A. ordosica community distributed in semi-fixed and fixed dunes, the Shannon index had a significant positive correlation with vegetation N/P ratio and a significant negative correlation with vegetation C/N ratio. Combined the vegetation stoichiometry with the results of regression analysis (RDA), P concentration and thus N/P ratio had different influences on the species diversity for A. ordosica community and S. psammophila community. Our results showed that vegetation stoichiometry has an important influence on species diversity of plant community in sand land.