Assessment of intracranial aneurysm rupture risk using a point cloud-based deep learning model.

Background and Purpose: Precisely assessing the likelihood of an intracranial aneurysm rupturing is critical for guiding clinical decision-making. The objective of this study is to construct and validate a deep learning framework utilizing point clouds to forecast the likelihood of aneurysm rupturing. Methods: The dataset included in this study consisted of a total of 623 aneurysms, with 211 of them classified as ruptured and 412 as unruptured, which were obtained from two separate projects within the AneuX morphology database. The HUG project, which included 124 ruptured aneurysms and 340 unruptured aneurysms, was used to train and internally validate the model. For external validation, another project named @neurIST was used, which included 87 ruptured and 72 unruptured aneurysms. A standardized method was employed to isolate aneurysms and a segment of their parent vessels from the original 3D vessel models. These models were then converted into a point cloud format using open3d package to facilitate training of the deep learning network. The PointNet++ architecture was utilized to process the models and generate risk scores through a softmax layer. Finally, two models, the dome and cut1 model, were established and then subjected to a comprehensive comparison of statistical indices with the LASSO regression model built by the dataset authors. Results: The cut1 model outperformed the dome model in the 5-fold cross-validation, with the mean AUC values of 0.85 and 0.81, respectively. Furthermore, the cut1 model beat the morphology-based LASSO regression model with an AUC of 0.82. However, as the original dataset authors stated, we observed potential generalizability concerns when applying trained models to datasets with different selection biases. Nevertheless, our method outperformed the LASSO regression model in terms of generalizability, with an AUC of 0.71 versus 0.67. Conclusion: The point cloud, as a 3D visualization technique for intracranial aneurysms, can effectively capture the spatial contour and morphological aspects of aneurysms. More structural features between the aneurysm and its parent vessels can be exposed by keeping a portion of the parent vessels, enhancing the model's performance. The point cloud-based deep learning model exhibited good performance in predicting rupture risk while also facing challenges in generalizability.

Left main coronary artery morphological phenotypes and its hemodynamic properties.

BACKGROUND: Atherosclerosis may be linked to morphological defects that lead to variances in coronary artery hemodynamics. Few objective strategies exit at present for generalizing morphological phenotypes of coronary arteries in terms of hemodynamics. We used unsupervised clustering (UC) to classify the morphology of the left main coronary artery (LM) and looked at how hemodynamic distribution differed between phenotypes. METHODS: In this study, 76 LMs were obtained from 76 patients. After LMs were reconstructed with coronary computed tomography angiography, centerlines were used to extract the geometric characteristics. Unsupervised clustering was carried out using these characteristics to identify distinct morphological phenotypes of LMs. The time-averaged wall shear stress (TAWSS) for each phenotype was investigated by means of computational fluid dynamics (CFD) analysis of the left coronary artery. RESULTS: We identified four clusters (i.e., four phenotypes): Cluster 1 had a shorter stem and thinner branches (n = 26); Cluster 2 had a larger bifurcation angle (n = 10); Cluster 3 had an ostium at an angulation to the coronary sinus and a more curved stem, and thick branches (n = 10); and Cluster 4 had an ostium at an angulation to the coronary sinus and a flatter stem (n = 14). TAWSS features varied widely across phenotypes. Nodes with low TAWSS (L-TAWSS) were typically found around the branching points of the left anterior descending artery (LAD), particularly in Cluster 2. CONCLUSION: Our findings demonstrated that UC is a powerful technique for morphologically classifying LMs. Different LM phenotypes exhibited distinct hemodynamic characteristics in certain regions. This morphological clustering method could aid in identifying people at high risk for developing coronary atherosclerosis, hence facilitating early intervention.

Meta-Lens Particle Image Velocimetry.

Fluid flow behavior is visualized through particle image velocimetry (PIV) for understanding and studying experimental fluid dynamics. However, traditional PIV methods require multiple cameras and conventional lens systems for image acquisition to resolve multi-dimensional velocity fields. In turn, it introduces complexity to the entire system. Meta-lenses are advanced flat optical devices composed of artificial nanoantenna arrays. It can manipulate the wavefront of light with the advantages of ultrathin, compact, and no spherical aberration. Meta-lenses offer novel functionalities and promise to replace traditional optical imaging systems. Here, a binocular meta-lens PIV technique is proposed, where a pair of GaN meta-lenses are fabricated on one substrate and integrated with a imaging sensor to form a compact binocular PIV system. The meta-lens weigh only 116 mg, much lighter than commercial lenses. The 3D velocity field can be obtained by the binocular disparity and particle image displacement information of fluid flow. The measurement error of vortex-ring diameter is ≈1.25% experimentally validates via a Reynolds-number (Re) 2000 vortex-ring. This work demonstrates a new development trend for the PIV technique for rejuvenating traditional flow diagnostic tools toward a more compact, easy-to-deploy technique. It enables further miniaturization and low-power systems for portable, field-use, and space-constrained PIV applications.

The feasibility of early detecting coronary artery disease using deep learning-based algorithm based on electrocardiography.

BACKGROUND: Coronary Artery Disease (CAD) is a major cause of morbidity and mortality, yet it is frequently asymptomatic in the early stages and hence goes undetected. OBJECTIVE: We aimed to develop a novel artificial intelligence-based approach for early detection of CAD patients based solely on electrocardiogram (ECG). METHODS: This study included patients with suspected CAD who had standard 10-s resting 12-lead ECGs and coronary computed tomography angiography (cCTA) results within 4 weeks or less. The ECG and cCTA data from the same patient were matched based on their hospitalization or outpatient ID. All matched data pairs were then randomly divided into training, validation dataset for model development based on convolutional neural network (CNN) and test dataset for model evaluation. The accuracy (Acc), specificity (Spec), sensitivity (Sen), positive predictive value (PPV), negative predictive value (NPV) and area under the receiver operating characteristic curve (AUC) of the model were calculated by using the test dataset. RESULTS: In the test dataset, the model for detecting CAD achieved an AUC of 0.75 (95% CI, 0.73 to 0.78) with an accuracy of 70.0%. Using the optimal cut-off point, the CAD detection model had sensitivity of 68.7%, specificity of 70.9%, positive predictive value (PPV) of 61.2%, and negative predictive value (NPV) of 77.2%. Our study demonstrates that a well-trained CNN model based solely on ECG could be considered an efficient, low-cost, and noninvasive method of assisting in CAD detection.

Experimental comparative study of the effect of fractional CO2 laser combined with pulsed dye laser versus each laser alone on the treatment of hypertrophic scar of rabbit ears.

BACKGROUND AND OBJECTIVE: The use of fractional CO2  laser and pulsed dye laser (PDL) therapy to treat and/or prevent scarring following burn injury is becoming more widespread with a number of studies reporting reduction in scar erythema and pruritus following treatment with lasers. The objective of this study was to directly compare the efficacy of PDL, fractional CO2 , and PDL and fractional CO2  laser therapy in immature red hypertrophic scars in a standardized animal model. METHODS: Ten New Zealand big-eared rabbits were used to make rabbit ear hypertrophic scar models. A total of 80 hypertrophic scar models were obtained and randomly divided into groups: control (Group A), Fractional CO2  laser (Group B), pulse dye laser (Group C), combined (Group D), 20 in each group. Wound sites were treated with PDL, Fractional CO2  laser, or both at 28 days post-grafting. Grafts receiving no laser therapy served as controls. Hypertrophic scar appearance, morphology, size, and erythema were assessed, and punch biopsies were collected. At days 7 and 28, additional tissue was collected for biomechanical analyses and markers for HE staining, Masson staining, immunohistochemical method to determine the CD31 content in the scar; Western blot to detect the expression of VEGF protein in scars. After the day 7 and 28, the scars were collected. Histomorphological change in scars was observed by hematoxylin-eosin staining, Masson staining. The expression of CD31, VEGF protein, and the cell apoptosis rate was detected by immunohistochemical method. RESULTS: (i) In morphological observation, HE staining and Masson staining, both the number of fibroblasts and amount of collagen fibrils in the experimental group were significantly reduced compared with those in control group. (ii) Micro-vessel Density (MVD) value can be found much smaller in the experimental groups than the control (p < 0.05). Among the four experimental groups, there was a significant difference among 14d, 21d, and 28d groups (p < 0.05). (iii) On days 7 and 28 after treatment, expression of VEGF could be regulated in experimental group (p < 0.05). Among the three experimental groups, the decrease of VEGF in the combined group was significantly stronger than that of the other two. CONCLUSION: The effect of Fractional CO2  laser combined with pulsed dye laser treatment was shown to be better than that of Fractional CO2  laser or pulsed dye laser alone and inhibits the early hypertrophic scar in rabbit ears.

Laser therapy in the treatment of cicatricial ectropion.

INTRODUCTION: The objective of this study was to investigate the clinical effects of laser therapy in treating cicatricial ectropion. METHODS: Seven patients with cicatricial ectropion were entered into this clinical study. The ectropions were pretreated with the 595-nm pulsed dye laser if the scar color was red. If there was no red, the UltraPulse fractional CO2 laser was used and parameters were adapted according to the height of scar. MEBT/MEBO was used after laser treatment for wound healing. The degree of ectropion was measured for changes before and after treatment, and the scars were evaluated for changes in melanin, height, vascularity, and pliability using the Vancouver Scar Scale (VSS) before and after treatment. RESULTS: All seven patients with cicatricial ectropion entered into this protocol were completely corrected after 1-2 treatment sessions. The total VSS score, as well as the score for melanin and pliability in 7 patients, showed a decrease following the treatments, and this was statistically significant (P < 0.05). The scores for height and vascularity showed a decrease following the treatments, but there was no significant difference by statistical analysis (P ≥ 0.05). There were no adverse reactions reported. CONCLUSIONS: The treatment of cicatricial ectropion with laser therapy can not only correct the ectropion, but also improve the scars in the treatment area. Compared with the traditional repair of cicatricial ectropion, the use of fractional CO2 laser provides surgical precision and the advantage of a timely treatment without the need to wait for the scar to stabilize.

Wetting Kinetics and Microstructure Analysis of BNi2 Filler Metal over Selective Laser Melted Ti-6Al-4V Substrate.

The wetting kinetics of nickel-based filler metal (BNi2) over selective laser-melted Ti-6Al-4V (SLMed TC4) titanium alloy in a protective argon atmosphere is experimentally investigated using a real-time in situ hot stage equipped with an optical microscope. The spreading processes at different temperatures are similar, and the overall wetting/spreading process can be roughly divided into three stages: (i) an initial stage, (ii) a rapid spreading stage, and (iii) an asymptotic stage. Moreover, the wetting kinetics of the BNi2/SLMed TC4 system can be expressed by empirical power exponential function Rn~t with n = ~1. In the process of spreading, Ti-based solid solution (Ti(ss)) and intermetallic compound (Ti2Ni and TiB2) were formed at the interface within the reaction domain, and the phase transition of α' martensitic to α-Ti and ß-Ti also took place. The influence of elevated temperature on the spreading and wetting kinetics of the BNi2/SLMed TC4 system was studied, and the results show that the increase of temperature has a slightly promoting effect on the spreading, but a limited impact on the value of n. In addition, the spreading and wetting kinetics of BNi2/SLMed TC4 system are similar to those of BNi2 on conventional forged TC4 substrate.

Moist exposed burn therapy in recovery of patients with immature, red hypertrophic scars successfully treated with a pulsed dye laser in combination with a fractional CO2 laser.

BACKGROUND: The efficacy of pulsed dye laser combined (PDL) and UltraPulse fractional CO2 in treatment of hypertrophic scars is well documented. The present study investigates the efficacy of moist exposed burn ointment (MEBO)/moist exposed burn therapy (MEBT) in postlaser wound management. METHODS: Sixty-one patients with immature, red hypertrophic scars were enrolled in this clinical trial. Patients were randomly divided into two groups: (a) the MEBO treatment group (n = 30) and (b) the control group (n = 31) treated with chlortetracycline hydrochloride ointment. Demographic data such as age, gender, and cause of scars were recorded. A visual analogue score (VAS) was collected to measure pain at 1, 6, 24, 72 hours, and 7 days post-treatment. The Vancouver Scar Scale (VSS) was used to determine the response of the scars before and 3 months after the treatment. The wound healing time and pigmentation scores were also recorded. RESULTS: No significant differences were found in age, gender, and etiology of the scars in the two groups. The VAS scores in MEBO group were significantly lower than the control group within the first 3 days after treatment. The wound healing time of the MEBO group was significantly shorter than the control group. For both groups, VSS scores were significantly decreased and the scar markedly improved. However, the VSS scores were significantly lower in the MEBO group compared with the control group 3 months after treatment and pigmentation formation was dramatically lower in MEBO group compared with the control. CONCLUSION: MEBT/MEBO treatment reduced the post-treatment pain, shortened the wound healing duration, promoted the overall scar condition, and reduced the incidence of pigmentation.

Treatment of skin soft tissue embolism after hyaluronic acid injection for injection rhinoplasty in Asian patients.

INTRODUCTION: The purpose of this manuscript is to investigate the treatment of skin soft tissue embolization or vascular occlusion after the injection of hyaluronic acid (HA) for Injection Rhinoplasty (IR) in Asians with a special interest in the time occurrence of the occlusion. METHODS: A total of 35 cases were evaluated after receiving HA injections for IR who presented with a vascular occlusive event. They were divided into three stages based on the time to embolization. Immediate, ≤5 hours; early, ≤3 days; and late, >3 days. There were two cases of immediate, 28 deemed early, and five late. Methods to prevent tissue necrosis are reviewed in the manuscript based on these stages. RESULTS: Skin color gradually recovered to normal after 11 treatments in 11 patients with mild embolization. No ischemic aggravation or skin necrosis was observed in 19 patients with moderate embolization; red scarring was seen in two and hypertrophic scar with uneven skin color in one patient. The five patients in the severe category had longer healing, more red scars, and more hypertrophic scarring. CONCLUSION: The treatment of skin soft tissue embolization or vascular occlusion after HA IR in Asians can be effected by identifying the stage and degree of embolization and treating appropriately with the outlines presented in this manuscript.

Comparison of the effectiveness of pulsed dye laser vs pulsed dye laser combined with ultrapulse fractional CO2 laser in the treatment of immature red hypertrophic scars.

INTRODUCTION: The objective was to investigate the clinical effect of an adjustable pulse width Pulsed Dye Laser (PDL) vs an adjustable pulse width PDL combined with fractional CO2 laser in treating immature red hypertrophic scars. METHODS: Fifty-six patients (56 sites)were randomly divided into a treatment group and control group. The control group was treated with the 595 nm PDL at a fluence of 7-15J/cm2 and pulse widths of 1.5-3 ms, 7 mm spot size. The treatment group was treated with a fractional CO2 laser (UltraPulse CO2 : Deep FX, Energy: 30~50 mJ, Frequency: 300 Hz, Density 5%, Scan Shape, and Spot Size were decided by shape and area of scar) after utilizing the 595 nm adjustable pulse width PDL (Fluence: 7-15J/cm2 , Pulse widths: 1.5-3 ms, Spot size: 7 mm). MEBT/MEBO, previously described as a post-treatment wound ointment, was used after laser treatment. The scars of the treatment group and the control group were evaluated for changes in pigment, height, vascularity, and pliability using the Vancouver Scar Scale (VSS) after two laser treatments. RESULTS: The total VSS score, as well as the score for melanin, height, vascularity, pliability in both groups, showed an obvious decrease following the treatments. There were statistically significant differences between before treatment and after treatment (P < .05); however, the total score of the VSS, and score of the melanin, height, vascularity, and pliability in the control group decreased more than that of treatment group, and there was a statistically significant difference (P < .05). CONCLUSIONS: The 595 nm adjustable pulse width PDL combined with the fractional CO2 fractional laser appears to have a beneficial clinical effect on fresh red hypertrophic scars, with no severe adverse reactions seen.

Immobilization of g-C3N4 nanosheets on diatomite via electrostatic adsorption and their photocatalytic activity.

Graphitic carbon nitride (g-C3N4) nanosheets have been successfully immobilized on diatomite to form a g-C3N4/diatomite hybrid through a facile electrostatic adsorption method and subsequent calcination process. Electron microscopy studies confirm that the surface of the diatomite is tightly covered with g-C3N4 nanosheets. In addition, the characterization results of Fourier transform infrared spectra (FTIR) and X-ray photoelectron spectra (XPS) verify that there is a strong interaction between the g-C3N4 and diatomite components inside the hybrids. The visible light absorption edge of the hybrids exhibits a significant redshift compared with the bare g-C3N4 nanosheets and diatomite, which leads to the improvement of visible light absorption and utilization. The photocatalytic results demonstrated that the photocatalytic performance for methyl orange and phenol degradation using the hybrids as photocatalysts has been obviously improved compared to that of g-C3N4 nanosheets, which may be ascribed to its adsorption/photocatalysis synergistic effect.

Effectiveness of cognitive-coping therapy and alteration of resting-state brain function in obsessive-compulsive disorder.

BACKGROUND: Cognitive-coping therapy (CCT), integrating cognitive theory with stress-coping theory, is an efficacious therapy for obsessive-compulsive disorder (OCD). However, the potential brain mediation for the effectiveness remains unclear. We sought to investigate differences of resting-state brain function between OCD and healthy controls and if such differences would be changed by a four-week CCT. PATIENTS AND METHODS: Thirty-one OCD patients were recruited and randomized into CCT (n=15) and pharmacotherapy plus CCT (pCCT, n=16) groups, together with 25 age-, gender- and education-matched healthy controls. The Yale-Brown Obsessive Compulsive Scale (Y-BOCS) was scored to evaluate the severity in symptoms. Resting-state functional magnetic resonance imaging was scanned pre- and post-treatment. RESULTS: For patients, Y-BOCS scores were reduced during four-week treatment for CCT and pCCT (P<0.001), but no group difference was observed. No differences in amplitude of low-frequency fluctuation (ALFF) values were found between CCT and pCCT either pre- or post-treatment. Compared to controls, ALFF in OCD patients was higher in the left hippocampus, parahippocampus, and temporal lobes, but lower in the right orbitofrontal cortex, rectus, bilateral calcarine, cuneus, lingual, occipital, left parietal, postcentral, precentral, and parietal (corrected P<0.05). The ALFF in those regions was not significantly correlated to the severity of OCD symptoms. After a 4-week treatment, the ALFF differences between OCD patients and controls disappeared. LIMITATIONS: The pharmacotherapy group was not included since OCD patients generally do not respond to pharmacotherapy in four weeks. CONCLUSIONS: Our data indicated that resting-state brain function was different between OCD and controls; such differences disappeared after OCD symptoms were relieved.

Nitrogen acquisition by plants and microorganisms in a temperate grassland.

Nitrogen (N) limitation is common in most terrestrial ecosystems, often leading to strong competition between microorganisms and plants. The mechanisms of niche differentiation to reduce this competition remain unclear. Short-term (15)N experiments with NH4(+), NO3(-), and glycine were conducted in July, August and September in a temperate grassland to evaluate the chemical, spatial and temporal niche differentiation by competition between plants and microorganisms for N. Microorganisms preferred NH4(+) and NO3(-), while plants preferred NO3(-). Both plants and microorganisms acquired more N in August and September than in July. The soil depth had no significant effects on microbial uptake, but significantly affected plant N uptake. Plants acquired 67% of their N from the 0-5 cm soil layer and 33% from the 5-15 cm layer. The amount of N taken up by microorganisms was at least seven times than plants. Although microorganisms efficiently compete for N with plants, the competition is alleviated through chemical partitioning mainly in deeper soil layer. In the upper soil layer, neither chemical nor temporal niche separation is realized leading to strong competition between plants and microorganisms that modifies N dynamics in grasslands.

Highly efficacious cognitive-coping therapy for overt or covert compulsions.

Pharmacotherapy and cognitive-behavioral therapy (CBT) present limitations when they are used to treat obsessive-compulsive disorder (OCD), a severe and debilitating psychiatric disorder. To search for more efficacious treatment, we investigated the effects of pharmacotherapy plus cognitive-coping therapy (pCCT) on adult OCD patients with overt or covert compulsions. Two hundred and fifteen OCD patients were randomized into pharmacotherapy plus psychological support (PPS, n=107) and pCCT (n=108). The Yale-Brown Obsessive Compulsive Scale (Y-BOCS) was used to measure severity of symptoms in the OCD patients. The Y-BOCS scores were significantly lower in pCCT than in PPS in both acute term (<3 months) and long-term follow-up. In pCCT, severity of symptoms was not different between those with covert compulsions and those with overt compulsions, but was significantly reduced at any post-treatment time-point. Y-BOCS scores in the two subtype compulsions were significantly lower in pCCT than in PPS at any post-treatpost-treatment time-point. Compared with PPS, effect size, response rate and remission rate were significantly higher in pCCT. Our findings corroborated with the hypothesis that pCCT could efficaciously treat OCD with overt compulsions or covert compulsion, suggesting that pCCT might be a potential option for adult OCD.

[A Retrospective Study of Chinese Herbal Medicine Combined with Systemic Chemotherapy and/or Regional Arterial Perfusion for Pancreatic Cancer with Liver Metastases].

OBJECTIVE: To evaluate the efficacy and safety of Chinese herbal medicine combined with systemic chemotherapy and/or regional arterial perfusion for pancreatic cancer with liver metastases (PCLM). METHODS: We retrospectively selected 292 patients with PCLM who were treated by Chinese herbal medicine combined with systemic chemotherapy and/or regional arterial perfusion at Tianjin Medical University Cancer Hospital from January 2001 to December 2010. All patients were assigned to the Western medicine treatment group (157 cases) and the integrative medicine treatment group (135 cases). Patients in the Western medicine treatment group were treated with gemcitabine (GEM)-based chemotherapy, and partial of them received regional arterial perfusion. Those in the integrative medicine treatment group additionally took Chinese herbs of clearing heat and eliminating mass for at least 4 weeks. The median survival time (MST) , adverse reactions and the incidence of complications were observed. RESULTS: There was no statistical significance in general data between the two groups (P > 0.05). There was statistical difference in MST between the two groups (4.8 months vs 5.5 months, P < 0.05). No death occurred during chemotherapy or regional arterial perfusion. All toxic or adverse reactions were tolerable. CONCLUSION: Chinese herbal medicine combined with systemic chemotherapy and/or regional arterial perfusion was effective and safe, and it could be optimally selected as palliative therapy for PCLM.

The use of the fractional CO2 laser resurfacing in the treatment of photoaging in Asians: five years long-term results.

BACKGROUND AND OBJECTIVE: The purpose of this clinical paper is to explore the therapeutic effects, healing times, adverse effects, and maintenance periods of using a CO2 fractional laser in the treatment of photoaging in Asian skin. STUDY DESIGN/MATERIALS AND METHODS: One fractional CO2 laser procedure was performed on the full face in 56 patients with photoaging. Based on the Dover scoring system, we evaluated the degree of skin aging before treatment and at one-month post laser and at five years post laser therapy in 30 of the patients. Statistical analysis was performed by the Wilcoxon's method. RESULTS: Thirty of the treated patients have had follow-up for 5 years at this time. The photoaging scores in these thirty patients were significantly changed (P < 0.01) at one month, one year, and five years after the fractional laser treatment, as compared with their baseline. Adverse events seen during this analysis were found to be minimal and not of clinical significance. CONCLUSIONS: Fractional CO2 laser resurfacing in the treatment of photoaging in Asians is a useful modality with results, for the first time, being shown to have continued efficacy for up to 5 years.

Ethyl 6-methyl-2-oxo-4-[4-(1H-tetra-zol-5-yl)phen-yl]-1,2,3,4-tetra-hydro-pyrimidine-5-carboxyl-ate-di-methyl-formamide-water (2/1/1).

The asymmetric unit of the title compound, 2C15H16N6O3·C3H7NO·H2O, contains two independent ethyl 6-methyl-2-oxo-4-[4-(1H-tetra-zol-5-yl)phen-yl]-1,2,3,4-tetra-hydro-pyrim-id-ine-5-carboxyl-ate mol-ecules, in which the dihedral angles between the tetra-zole and benzene rings are 20.54 (12) and 12.13 (12)°. An intra-molecular C-H⋯O hydrogen bond occurs in each mol-ecule. In the crystal, N-H⋯O, N-H⋯N, O-H⋯O and O-H⋯N hydrogen bonds, as well as weak C-H⋯O and C-H⋯N hydrogen bonds, link the mol-ecules into a three-dimensional supra-molecular architecture. π-π stacking is also observed between parallel tetra-zole rings of adjacent mol-ecules, the centroid-centroid distance being 3.482 (6) Å.

The impacts of climate change and human activities on biogeochemical cycles on the Qinghai-Tibetan Plateau.

With a pace of about twice the observed rate of global warming, the temperature on the Qinghai-Tibetan Plateau (Earth's 'third pole') has increased by 0.2 °C per decade over the past 50 years, which results in significant permafrost thawing and glacier retreat. Our review suggested that warming enhanced net primary production and soil respiration, decreased methane (CH(4)) emissions from wetlands and increased CH(4) consumption of meadows, but might increase CH(4) emissions from lakes. Warming-induced permafrost thawing and glaciers melting would also result in substantial emission of old carbon dioxide (CO(2)) and CH(4). Nitrous oxide (N(2)O) emission was not stimulated by warming itself, but might be slightly enhanced by wetting. However, there are many uncertainties in such biogeochemical cycles under climate change. Human activities (e.g. grazing, land cover changes) further modified the biogeochemical cycles and amplified such uncertainties on the plateau. If the projected warming and wetting continues, the future biogeochemical cycles will be more complicated. So facing research in this field is an ongoing challenge of integrating field observations with process-based ecosystem models to predict the impacts of future climate change and human activities at various temporal and spatial scales. To reduce the uncertainties and to improve the precision of the predictions of the impacts of climate change and human activities on biogeochemical cycles, efforts should focus on conducting more field observation studies, integrating data within improved models, and developing new knowledge about coupling among carbon, nitrogen, and phosphorus biogeochemical cycles as well as about the role of microbes in these cycles.

Different inter-annual responses to availability and form of nitrogen explain species coexistence in an alpine meadow community after release from grazing.

Plant species and functional groups in nitrogen (N) limited communities may coexist through strong eco-physiological niche differentiation, leading to idiosyncratic responses to multiple nutrition and disturbance regimes. Very little is known about how such responses depend on the availability of N in different chemical forms. Here we hypothesize that idiosyncratic year-to-year responses of plant functional groups to availability and form of nitrogen explain species coexistence in an alpine meadow community after release from grazing. We conducted a 6 year N addition experiment in an alpine meadow on the Tibetan Plateau released from grazing by livestock. The experimental design featured three N forms (ammonium, nitrate, and ammonium nitrate), crossed with three levels of N supply rates (0.375, 1.500 and 7.500 g N m-2  yr-1 ), with unfertilized treatments without and with light grazing as controls. All treatments showed increasing productivity and decreasing species richness after cessation of grazing and these responses were stronger at higher N rates. Although N forms did not affect aboveground biomass at community level, different functional groups did show different responses to N chemical form and supply rate and these responses varied from year to year. In support of our hypothesis, these idiosyncratic responses seemed to enable a substantial diversity and biomass of sedges, forbs, and legumes to still coexist with the increasingly productive grasses in the absence of grazing, at least at low and intermediate N availability regimes. This study provides direct field-based evidence in support of the hypothesis that idiosyncratic and annually varying responses to both N quantity and quality may be a key driver of community structure and species coexistence. This finding has important implications for the diversity and functioning of other ecosystems with spatial and temporal variation in available N quantity and quality as related to changing atmospheric N deposition, land-use, and climate-induced soil warming.