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Soil organic carbon (SOC) affects the function of terrestrial ecosystem and plays a vital role in global carbon cycle. Yet, large uncertainty still existed regarding the changes in SOC stock and quality with forest succession. Here, the stock and quality of SOC at 1-m soil profile were investigated across a subalpine forest series, including shrub, deciduous broad-leaved forest, broadleaf-conifer mixed forest, middle-age coniferous forest and mature coniferous forest, which located at southeast of Tibetan Plateau. The results showed that SOC stock ranged from 9.8 to 29.9 ​kg⋅m−2, and exhibited a hump-shaped response pattern across the forest successional series. The highest and lowest SOC stock was observed in the mixed forest and shrub forest, respectively. The SOC stock had no significant relationships with soil temperature and litter stock, but was positively correlated with wood debris stock. Meanwhile, the average percentages of polysaccharides, lignins, aromatics and aliphatics based on FTIR spectroscopy were 79.89%, 0.94%, 18.87% and 0.29%, respectively. Furthermore, the percentage of polysaccharides exhibited an increasing pattern across the forest successional series except for the sudden decreasing in the mixed forest, while the proportions of lignins, aromatics and aliphatics exhibited a decreasing pattern across the forest successional series except for the sudden increasing in the mixed forest. Consequently, the humification indices (HIs) were highest in the mixed forest compared to the other four successional stages, which means that the SOC quality in mixed forest was worse than other successional stages. In addition, the SOC stock, recalcitrant fractions and HIs decreased with increasing soil depth, while the polysaccharides exhibited an increasing pattern. These findings demonstrate that the mixed forest had higher SOC stock and worse SOC quality than other successional stages. The high proportion of SOC stock (66% at depth of 20–100 ​cm) and better SOC quality (lower HIs) indicate that deep soil have tremendous potential to store SOC and needs more attention under global change.

Hypergraphs with infinitely many extremal constructions, Discrete Analysis 2023:18, 34 pp. A fundamental result in extremal graph theory, Turán's theorem, states that the maximal number of edges of a graph with $n$ vertices that does not contain a clique with $r$ vertices is attained by a complete $(r-1)$-partite graph with all its parts of equal size, or as close to equal size as divisibility constraints allow. The theorem can be proved with a short inductive argument, and finds its way into many undergraduate courses in graph theory. An obvious follow-up question is whether a similar result holds for hypergraphs. For example, is the maximal number of edges in a 3-uniform hypergraph with $n$ vertices that does not contain a clique with $k$ vertices (that is, a set $A$ of $k$ vertices such that all subsets of $A$ of size 3 belong to the hypergraph) attained by a complete $(k-1)$-partite 3-uniform hypergraph with vertex sets of (almost) equal size? As posed, this question is not too hard, because the answer turns out to be no, even when $k=4$. Indeed, in that case, not only is a complete tripartite hypergraph not of maximal size, it is not even maximal, since if the vertex sets are $A, B$ and $C$ and we already have all edges $abc$ with $a\in A$, $b\in B$ and $c\in C$, we can add all edges of the form $a_1a_2b$, $b_1b_2c$ and $c_1c_2a$. To see that this does not create a clique of size 4, note that such a clique would have to have two vertices in the same vertex set. If that vertex set is $A$, say, then the other two vertices have to belong to $B$, but then we have an edge $ab_1b_2$, which is not allowed. If $A$, $B$ and $C$ have equal size, then the probability that three random vertices are in different vertex sets is $2/9$, and the probability that two of them are in $A$ and the third in $B$ is approximately $1/9$, so the density of the hypergraph is approximately $2/9+3/9=5/9$. Of course, the next question is whether this slightly more complicated example is the extremal one, and more generally what the greatest possible density is of a 3-uniform hypergraph that contains no clique of size 4. This is one of the most famous open problems in extremal combinatorics. It is conjectured that the extremal density is 5/9, but a sign that the conjecture is hard is that if the conjecture is true, the example just presented is not _the_ extremal example, but merely _an_ extremal example, as it is now known that there is an infinite family of 3-uniform hypergraphs with no cliques of size 4 and with asymptotic density 5/9. Thus, the hypergraph problem appears to be markedly more complex than the graph one. The word "appears" is there because we don't actually _know_ that there is an infinite family of extremal examples, because we don't know that they are extremal! That raises another question. Is there _any_ example of a Turán-type problem for hypergraphs for which one can prove that there is an infinite family of extremal examples? That is the question addressed and answered by this paper, which gives an example (in fact, more than one example) of a finite set $\mathcal F$ of 3-uniform hypergraphs such that, writing $\text{ex}(\mathcal F)$ for the asymptotically extremal density of an $\mathcal F$-free 3-uniform hypergraph, there is not some bounded $s$ such that for each $n$, every $\mathcal F$-free hypergraph with $n$ vertices and of density close to $\text{ex}(\mathcal F)$ can be approximated by one of $s$ hypergraphs with $n$ vertices. (The answer was known for _exactly_ extremal examples: there is a 3-uniform hypergraph $F$ for which extremal $F$-free hypergraphs can be built with the help of Steiner triple systems, and any Steiner triple system can be used.) More precisely, let us define the _stability number_ of a family $\mathcal F$ as follows. It is the minimum $s$ such that for every $n$ we can find hypergraphs $G_1(n),\dots,G_s(n)$ such that for every $\epsilon>0$ there exists $\delta>0$ such that every $\mathcal F$-free hypergraph with $n$ vertices and of density at least $\text{ex}(\mathcal F)-\epsilon$ can be $\delta$-approximated by one of $G_1(n),\dots,G_s(n)$. (Note that everything here is up to isomorphism, so the approximation is by an isomorphic copy of one of the $G_i(n)$. A $\delta$-approximation is one for which the symmetric difference has size at most $\delta n^3$.) Previously it was known that finite families with arbitrarily large finite stability number existed. In this paper, the authors give an example, not conditional on any unproved hypotheses, of a finite family $\mathcal F$ with infinite stability number. To construct the families, the authors introduce and use an operation on hypergraphs that they call a _crossed blowup_. To analyse them, they use some observations about multilinear polynomials, which are connected to Turán densities via a concept known as a hypergraph Lagrangian, which was introduced by Frankl and Rödl. Their methods also allow them to answer a question about the _feasible region_ of a family $\mathcal F$ of $k$-uniform hypergraphs. This is the set of all $(x,y)\in[0,1]^2$ such that there is a sequence $F_1,F_2,\dots$ of $k$-uniform $\mathcal F$-free hypergraphs with size tending to infinity such that the density of $F_i$ tends to $x$ and the density of the lower shadow of $F_i$ (that is, the set of all sets of size $k-1$ that are contained in an edge of $F_i$) tends to $y$. The shape of this region is known to be the area below the graph of a reasonably nice function supported on an interval $[0,c]$. However, it was an open problem whether the function could have infinitely many global maxima. For the main family constructed by the authors, it turns out that the associated function attains its maximum everywhere on an interval, so they solve this problem in a strong way. Thus, the paper is a valuable contribution to the extremal theory of hypergraphs, and sheds interesting light on a notorious old conjecture.

Ferroptosis is a newly discovered form of iron-dependent oxidative cell death and drives the loss of neurons in spinal cord injury (SCI). Mitochondrial damage is a critical contributor to neuronal death, while mitochondrial quality control (MQC) is an essential process for maintaining mitochondrial homeostasis to promote neuronal survival. However, the role of MQC in neuronal ferroptosis has not been clearly elucidated. Here, we further demonstrate that neurons primarily suffer from ferroptosis in SCI at the single-cell RNA sequencing level. Mechanistically, disordered MQC aggravates ferroptosis through excessive mitochondrial fission and mitophagy. Furthermore, mesenchymal stem cells (MSCs)-mediated mitochondrial transfer restores neuronal mitochondria pool and inhibits ferroptosis through mitochondrial fusion by intercellular tunneling nanotubes. Collectively, these results not only suggest that neuronal ferroptosis is regulated in an MQC-dependent manner, but also fulfill the molecular mechanism by which MSCs attenuate neuronal ferroptosis at the subcellular organelle level. More importantly, it provides a promising clinical translation strategy based on stem cell-mediated mitochondrial therapy for mitochondria-related central nervous system disorders.

AbstractGraph partitioning problem, which is one of the most important topics in graph theory, usually asks for a partition of the vertex set of a graph into pairwise disjoint subsets with various requirements. It comes from the well-known Max-Cut Problem: Given a graph G, find the maximum bipartite subgraph of G. In practice, one often needs to find a partition of a given graph to optimize several quantities simultaneously. Such problems are called judicious partition problems by Bollobás and Scott. In this survey, we present some new results and problems on graph partitioning.

IntroductionForest streams reserve more than 90% of the organic carbon (OC) in sediments, thus playing crucial roles in the global carbon cycle. Although forest streams are widely distributed across various forest regions, seasonal dynamics of OC in forest sediments have not been fully investigated.MethodsHere, we sampled soils (0–5 cm) in 15 representative forest stream sediments for 5 critical periods (snowmelt season, early growing season, growing season, late growing season, and seasonal snow cover season) during a one-year investigation in a geologically fragile subalpine coniferous forest catchment in the upper reaches of the Yangtze River in Sichuan province and the OC concentrations were measured by potassium dichromate external heating method.ResultsThe OC concentration of stream sediments ranged from 6.39 to 458.93 g kg−1, and the average was 84.56 g kg−1 for 15 streams in 5 critical periods during a 1-year investigation. Correspondingly, their stocks ranged from 2.05 to 310.56 kg m−2, and the average was 46.03 kg m−2. The maximum and minimum OC stocks were consistently observed during the late growing season and the snowmelt season, respectively. Otherwise, the OC stocks ranged from 1.31 to 218.05, 1.29 to 182.64, and 0.99 to 190.38 kg m−2 for the upstream, midstream, and downstream sediments, and the average was 39.36, 36.58, and 37.93 kg m−2, respectively. The average ratios of the OC stocks of the upstream and downstream ranged from 0.10–6.31, with an average of 1.43, during 5 critical periods, which indicated that the forest stream sediments may play crucial roles as carbon sources.DiscussionFurthermore, based on regression analysis, we found that the seasonal dynamics of OC concentrations and stocks were mainly regulated by precipitation, temperature, sediment depth, and litter carbon input to the streams together. These findings demonstrate that forest stream sediments may play crucial roles in the carbon biogeochemical cycle of subalpine forests and adjoining streams.

Although the role of coarse woody debris (CWD) in nurturing biodiversity has been well documented, there is little understanding of how CWD with varying diameters across the forest succession series affect the composition and diversity of the soil bacterial community. Therefore, this study investigated the soil bacterial community composition and biodiversity beneath debris with varying decay classes and diameters in six different successional forests, which constituted a subalpine forest series in the Wanglang National Nature Reserve in the eastern Qinghai–Tibet Plateau, China. The composition and functional groups of the soil bacterial communities in this study varied greatly with forest succession, decay classes and debris diameters. The alpha diversity of these communities decreased gradually along the succession gradients, whereas slight differences were observed among decay class and diameters. The soil bacterial communities beneath CWD were dominated by Proteobacteria and Acidobacteria under all soil conditions, and their relative abundance only varied greatly with the forest succession. The soil bacterial community structure varied significantly among different forest succession and diameters, but not decay classes. The functional groups were dominated by Chemoheterotrophy and aerobic chemoheterotrophy under all soil conditions. Nitrogen-fixing bacterial taxa and functional groups were enriched in the highly decayed classes. The soil nitrogen concentration and C:N ratio were negatively correlated with nitrogen-fixing bacterial communities. The soil temperature and CWD stock were significantly correlated with the diversity and composition of bacterial communities in soils beneath CWD. In conclusion, CWD with varying diameters and decay levels across different succession stages harbor some unique bacterial phyla and genera, and the association of nitrogen-fixing bacteria with highly decayed wood debris concluded that the existence of CWD in forest ecosystem could stimulate the ecosystem nitrogen fixation.

Abstract Aims To characterize surgical valvular heart diseases (VHDs) in China and disclose regional variations in VHD surgeries by analyzing the data derived from the Chinese Cardiac Surgery Registry (CCSR). Methods and results From January 2016 to December 2018, we consecutively collected the demographic information, clinical characteristics and outcomes of 38,131 adult patients undergoing valvular surgery in China. We sought to assess the quality of VHD surgery by examining in-hospital deaths of all patients from 7 geographic regions. Using a hierarchical generalized linear model, we calculated the risk-standardized mortality rate (RSMR) of each region. By comparing VHD characteristics and RSMRs, we pursued an investigation into regional variations. The mean age was 54.4 ± 12.4 years, and 47.2% of the patients were females. Among cases, the number of aortic valve surgeries was 9361 (24.5%), which was less than that of mitral valve surgeries (n = 14,506, 38.0%). The number of concurrent aortic and mitral valve surgeries was 6984 (18.3%). A total of 4529 surgical VHD patients (11.9%) also underwent coronary artery bypass grafting (CABG) surgery. The overall in-hospital mortality rate was 2.17%. The lowest RSMR, 0.91%, was found in the southwest region, and the highest RSMR, 3.99%, was found in the northeast. Conclusion Although the overall valvular surgical mortality rate in large Chinese cardiac centers was in line with high-income countries, there were marked regional variations in the characteristics and outcomes of surgical VHD patients across China.

Panax ginseng is a famous valuable folk herb, the price of which particularly depends on its cultivation age. Since the classical chemical analysis usually needs to destroy the plants which is not suitable for the old wild ginseng due to the huge cost, in the current study, we employed the headspace solid-phase microextraction (HS-SPME) GC-MS methodology which has the advantage of time-saving, nondestructive, and green to analyze the growth age of ginseng (roots) via determining the volatile components of ginseng stem and leaves (GSLs) combined with metabolic profiles way. 100 mg of finely ground GSL samples (3–7 years) were extracted by a 65 μm PDMS-DVB fiber in the headspace and then analyzed within 20 mins. The content assay of total saponins, crude polysaccharides, and total protein was also included. As a result of GC-MS-based profiling, the orthogonal partial least-squares discriminant analysis’ (OPLS-DA) score plots showed excellent classification of four comparison groups (the 3- and 4-, 3-and 5-, 3- and 6-, and 3- and 7-year-old GSL) with 100% discrimination rate, respectively. 263 common differential variables were gained referring to the VIP and P values. 32 volatile metabolites were identified and showed good age discrimination capacities with an area under the curve (AUC) value of more than 0.8 by the receiver operating characteristic (ROC) analysis. Remarkably, there was one volatile component of sesquiterpenes, 1-cyclohexene-1-carboxaldehyde, 2, 6, 6-trimethyl-, which showed an excellent prediction with the AUC value of 1.0 among all the four compared groups, which could be the potential biomarker to distinguish all the four compared groups. The total contents of different growth ages of components of ginseng stems and leaves were distinct. The contents of total protein (4.80 ± 0.27%) and crude polysaccharide (24.15 ± 0.89%) in the 4th year of GSLs were the highest among the five cultivation years. The content of total saponins (4.66 ± 0.38%) in the 5th year of GSLs was the highest. These results could provide a novel reference for the GSLs’ harvest and application periods. Moreover, the current study could also supply a promising way to set up a nondestructive, in situ, and green approach to discriminate the growth age of Panax ginseng rapidly without digging the roots out instead of detecting the VOCs of GSLs.

Abstract Background The use of preoperative beta-blockers has been accepted as a quality standard for patients undergoing coronary artery bypass graft (CABG) surgery. However, conflicting results from recent studies have raised questions concerning the effectiveness of this quality metric. We sought to determine the influence of preoperative beta-blocker administration before CABG in patients with left ventricular dysfunction. Methods The authors analyzed all cases of isolated CABGs in patients with left ventricular ejection fraction less than 50%, performed between 2012 January and 2017 June, at 94 centres recorded in the China Heart Failure Surgery Registry database. In addition to the use of multivariate regression models, a 1–1 propensity scores matched analysis was performed. Results Of 6116 eligible patients, 61.7% received a preoperative beta-blocker. No difference in operative mortality was found between two cohorts (3.7% for the non-beta-blockers group vs. 3.0% for the beta-blocker group; adjusted odds ratio [OR] 0.82 [95% CI 0.58–1.15]). Few differences in the incidence of other postoperative clinical end points were observed as a function of preoperative beta-blockers except in stroke (0.7% for the non-beta-blocker group vs. 0.3 for the beta-blocker group; adjusted OR 0.39 [95% CI 0.16–0.96]). Results of propensity-matched analyses were broadly consistent. Conclusions In this study, the administration of beta-blockers before CABG was not associated with improved operative mortality and complications except the incidence of postoperative stroke in patients with left ventricular dysfunction. A more granular quality metric which would guide the use of beta-blockers should be developed.

Rotator cuff tear of shoulder is a common tendon injury. Current therapeutic strategies are unsatisfactory because of poor biomechanical properties of the repaired rotator cuff tendons. To solve this problem, a newly biofabricated tenogenic patch by uniaxial cold-drawing technology was applied for the treatment of acute rotator cuff tear and its therapeutic effects were evaluated in vitro and in vivo. The cytocompatibility results indicated that the engineered patch was capable of promoting the spreading, migration and proliferation of tendon fibroblasts in vitro. Stress–strain curves of the sutured patch indicated improved elasticity followed by the yield phenomena, nonlinear plasticity and obviously delaminated rupture. The tenogenic patch also showed significantly enhanced collagen I deposition and better tendon-to-bone healing in the rat rotator cuff tear models in vivo. Furthermore, implantation with the tenogenic patch also promoted the fibrocartilage formation in Safranin-O/Fast green-staining. The analysis of biomechanical properties showed that the tenogenic patch is capable of improving the ultimate load of the repaired tendon. Therefore, the tenogenic patch may constitute an efficient strategy to enhance tendon-to-bone healing for clinical repair applications of rotator cuff tear.

Abstract Background As a structurally and functionally important component in forest ecosystems, plant debris plays a crucial role in the global carbon cycle. Although it is well known that plant debris stocks vary greatly with tree species composition, forest type, forest origin, and stand age, simultaneous investigation on the changes in woody and non-woody debris biomass and their carbon stock with forest succession has not been reported. Therefore, woody and non-woody debris and carbon stocks were investigated across a subalpine forest successional gradient in Wanglang National Nature Reserve on the eastern Qinghai-Tibet Plateau. Results Plant debris ranged from 25.19 to 82.89 Mg∙ha− 1 and showed a global increasing tendency across the subalpine forest successional series except for decreasing at the S4 successional stage. Accordingly, the ratios of woody to non-woody debris stocks ranged from 26.58 to 208.89, and the highest and lowest ratios of woody to non-woody debris stocks were respectively observed in mid-successional coniferous forest and shrub forest, implying that woody debris dominates the plant debris. In particular, the ratios of coarse to fine woody debris stocks varied greatly with the successional stage, and the highest and lowest ratios were found in later and earlier successional subalpine forests, respectively. Furthermore, the woody debris stock varied greatly with diameter size, and larger diameter woody debris dominated the plant debris. Correspondingly, the carbon stock of plant debris ranged from 10.30 to 38.87 Mg∙ha− 1 across the successional series, and the highest and lowest values were observed in the mid-coniferous stage and shrub forest stage, respectively. Most importantly, the carbon stored in coarse woody debris in later successional forests was four times higher than in earlier successional forests. Conclusions The stock and role of woody debris, particularly coarse woody debris, varied greatly with the forest successional stage and dominated the carbon cycle in the subalpine forest ecosystem. Thus, preserving coarse woody debris is a critical strategy for sustainable forest management.

A domino reaction from 2-acetylfuran/2-acetylthiophene, benzaldehydes and sulfur powder has been developed to synthesize a series of tetrahydrothiophene derivatives. The reaction proceeds well to construct five new bonds and a tetrahydrothiophene ring by one-pot. A possible mechanism was proposed, involving a stepwise of Aldol/double Michael addition/internal SN2 cascaded reaction with sulfur powder acts as a source of sulfur. This method is characterized by mild reaction conditions, commercially available starting materials and transition-metal-free.

Abstract Background Data on the effect of smoking on In-hospital outcome in patients with left ventricular dysfunction undergoing coronary artery bypass graft (CABG) surgery are limited. We sought to determine the influence of smoking on CABG patients with left ventricular dysfunction. Methods A retrospective study was conducted using data from the China Heart Failure Surgery Registry database. Eligible patients with left ventricular ejection fraction less than 50% underwent isolated CABGS were included. In addition to the use of multivariate regression models, a 1–1 propensity scores matched analysis was performed. Our study (n = 6531) consisted of 3635 smokers and 2896 non-smokers. Smokers were further divided into ex-smokers (n = 2373) and current smokers (n = 1262). Results The overall in-hospital morality was 3.9%. Interestingly, current smokers have lower in-hospital mortality than non-smokers [2.3% vs 4.9%; adjusted odds ratio (OR) 0.612 (95% CI 0.395–0.947) ]. No difference was detected in mortality between ex-smokers and non-smokers [3.6% vs 4.9%; adjusted OR 0.974 (0.715–1.327)]. No significant differences in other clinical end points were observed. Results of propensity-matched analyses were broadly consistent. Conclusions It is paradoxically that current smokers had lower in-hospital mortality than non-smokers. Future studies should be performed to further understand the biological mechanisms that may explain this ‘smoker’s paradox’ phenomenon.

Abstract Background and objective Heart failure (HF) is a global health issue, and coronary artery bypass graft (CABG) is one of the most effective surgical treatments for HF with coronary artery disease. Unfortunately, the incidence of postoperative acute kidney injury (AKI) is high in HF patients following CABG, and there are few tools to predict AKI after CABG surgery for such patients. The aim of this study is to establish a nomogram to predict the incidence of AKI after CABG in patients with impaired left ventricular ejection fraction (LVEF). Methods From 2012 to 2017, Clinical information of 1208 consecutive patients who had LVEF 2 mg/dL), LVEF

Objective. To describe the natural history of the ascending aorta in elderly patients after aortic valve replacement (AVR) for aortic valve stenosis and to clarify the risk factors associated with the progression of the ascending aorta. Methods. This retrospective review included a total of 87 elderly patients who had undergone aortic valve replacement for severe aortic valve stenosis in Fuwai Hospital. The patients were categorized into two groups based on the height-based aortic height index (AHI) before AVR, as determined by echocardiography and computed tomography: Group A (n = 28) was defined as an AHI > 2.44 cm/m, and Group B (n = 59) was defined as an AHI ≤ 2.44 cm/m. The perioperative and follow-up data were collected, and a linear mixed-effect model was used to analyze and compare the change rate of the ascending aorta after AVR. Results. The mean follow-up period was 4.0 ± 1.3 years. The diameter of ascending aorta in group A increased from 37.2 ± 5.0 mm at discharge to 40.7 ± 4.7 mm at the last follow-up (P=0.001), while that of group B increased only from 33.3 ± 4.4 mm to 33.7 ± 4.1 mm (P>0.05).The ascending aorta diameter expansive rate was 0.81 mm/year in group A and 0.14 mm/year in group B. The expansive rate was significantly greater in patients with an AHI>2.44 cm/m than in those with anything else (P = 0.009). A univariable linear mixed model analysis revealed that the AHI>2.44 cm/m was the only significant risk factor for ascending aortic dilatation rate after AVR. There were 4 patients who died in hospital and 11 late follow-up deaths. Particularly, there was no aortic event that occurred during follow-up. Conclusion. For elderly patients with aortic stenosis, the possibility of progressive ascending aortic dilatation after AVR demands regular follow-up, and AHI may be an important risk factor for the change rate of the diameter of the ascending aorta.

Background: Heart failure (HF) is one of the most important indications of the severity of valvular heart disease (VHD). VHD with HF is frequently associated with a higher surgical risk. Our study sought to develop a risk score model to predict the postoperative mortality of suspected HF patients after valvular surgery. Methods: Between January 2016 and December 2018, all consecutive adult patients suspected of HF and undergoing valvular surgery in the Chinese Cardiac Surgery Registry (CCSR) database were included. Finally, 14,645 patients (55.39 ± 11.6 years, 43.5% female) were identified for analysis. As a training group for model derivation, we used patients who had surgery between January 2016 and May 2018 (11,292 in total). To validate the model, patients who underwent surgery between June 2018 and December 2018 (a total of 3353 patients) were included as a testing group. In training group, we constructed and validated a scoring system to predict postoperative mortality using multivariable logistic regression and bootstrapping method (1000 re-samples). We validated the scoring model in the testing group. Brier score and calibration curves using bootstrapping with 1000 re-samples were used to evaluate the calibration. The area under the receiver operating characteristic curve (AUROC) was used to evaluate the discrimination. The results were also compared to EuroSCORE II. Results: The final score ranged from 0 to 19 points and involved 9 predictors: age ≥60 years; New York Heart Association Class (NYHA) IV; left ventricular ejection fraction (LVEF) 200 minutes and perioperative transfusion. In training group, observed and predicted postoperative mortality rates increased from 0% to 45.5% and from 0.8% to 50.3%, respectively, as the score increased from 0 up to ≥10 points. The scoring model’s Brier scores in the training and testing groups were 0.0279 and 0.0318, respectively. The area under the curve (AUC) values of the scoring model in both the training and testing groups were 0.776, which was significantly higher than EuroSCORE II in both the training (AUC = 0.721, Delong test, p < 0.001) and testing (AUC = 0.669, Delong test, p < 0.001) groups. Conclusions: The new risk score is an effective and concise tool that could accurately predict postoperative mortality rates in suspected HF patients after valve surgery.

Background: To preferably evaluate and predict the risk for in-hospital mortality in elderly patients receiving cardiac valvular surgery, we developed a new prediction model using least absolute shrinkage and selection operator (LASSO)-logistic regression and machine learning (ML) algorithms. Methods: Clinical data including baseline characteristics and peri-operative data of 7163 elderly patients undergoing cardiac valvular surgery from January 2016 to December 2018 were collected at 87 hospitals in the Chinese Cardiac Surgery Registry (CCSR). Patients were divided into training (N = 5774 [80%]) and testing samples (N = 1389 [20%]) according to their date of operation. LASSO-logistic regression models and ML models were used to analyze risk factors and develop the prediction model. We compared the discrimination and calibration of each model and EuroSCORE II. Results: A total of 7163 patients were included in this study, with a mean age of 69.8 (SD 4.5) years, and 45.0% were women. Overall, in-hospital mortality was 4.05%. The final model included seven risk factors: age, prior cardiac surgery, cardiopulmonary bypass duration time (CPB time), left ventricular ejection fraction (LVEF), creatinine clearance rate (CCr), combined coronary artery bypass grafting (CABG) and New York Heart Association (NYHA) class. LASSO-logistic regression, linear discriminant analysis (LDA), support vector classification (SVC) and logistic regression (LR) models had the best discrimination and calibration in both training and testing cohorts, which were superior to the EuroSCORE II. Conclusions: The mortality rate for elderly patients undergoing cardiac valvular surgery was relatively high. LASSO-logistic regression, LDA, SVC and LR can predict the risk for in-hospital mortality in elderly patients receiving cardiac valvular surgery well.

Abstract Objective To investigate the lung cancer-promoting mechanism of mesenchymal stem cell-secreted extracellular vesicles (MSC-EV). Methods EV were isolated from culture media of human bone marrow-derived MSCs that were pre-challenged with or without hypoxia (referred to as H-EV and N-EV, respectively). After treatment with N-EV or H-EV, A549 and H23 cell proliferation, apoptosis, trans-well invasion and epithelial-to-mesenchymal transition (EMT) were examined. Polarization of human primary monocytes-derived macrophages with or without N-EV or H-EV induction were analyzed by flow cytometry and ELISA. PTEN, PDCD4 or RECK gene was overexpressed in A549 cells, while miR-21-5p was knocked down in MSCs, A549 or H23 lung cancer cells or primary monocytes by miR-21-5p inhibitor transfection. Protein level of PTEN, PDCD4, RECK, AKT or STAT3 as well as phosphorylation level of AKT or STAT3 protein were assayed by western blot. Tumorigenicity of A549 and H23 cells with or without MSC-EV co-injection was assayed on immunocompromised mice. The xenograft tumor were examined for cell proliferation, angiogenesis, apoptosis and intra-tumoral M1/M2 macrophage polarization. Results Comparing to N-EV, H-EV treatment significantly increased A549 and H23 cell proliferation, survival, invasiveness and EMT as well as macrophage M2 polarization. MiR-21-5p knocked down significantly abrogated the cancer-promoting and macrophage M2 polarizing effects of H-EV treatment. H-EV treatment downregulated PTEN, PDCD4 and RECK gene expression largely through miR-21-5p. Overexpressing PTEN, PDCD4 and RECK in A549 cells significantly reduced the miR-21-5p-mediated anti-apoptotic and pro-metastatic effect of H-EV, while overexpressing PTEN in monocytes significantly reduced macrophage M2 polarization after induction with the presence of H-EV. H-EV co-injection significantly increased tumor growth, cancer cell proliferation, intra-tumoral angiogenesis and M2 polarization of macrophages in vivo partially through miR-21-5p. Conclusions Increased miR-21-5p delivery by MSC-EV after hypoxia pre-challenge can promote lung cancer development by reducing apoptosis and promoting macrophage M2 polarization.

Abstract Background Veno-arterial extracorporeal membrane oxygenation (VA-ECMO) is widely used in postcardiotomy cardiac shock (PCS). The factors that affect mortality in patients who receive ECMO for PCS remain unclear. In this study, we analyzed the outcomes, predictive factors and complications of ECMO use for PCS. Methods A total of 152 adult subjects who received VA-ECMO for PCS in Fuwai Hospital were consecutively included. We retrospectively collected the baseline characteristics, outcomes and complications. Baseline characteristics were compared between survivors with non-survivors, and logistic regression was performed to identify predictive factors for in-hospital mortality. Results The mean age of the subjects was 49.5 ± 14.1 years, with a male dominancy of 73.7%. The main surgical procedures were heart transplantation (32.2%), coronary artery bypass graft (17%) and valvular surgery (11.8%). Intra-aortic balloon pumping (IABP) was initiated concurrently with ECMO in 32.2% subjects and sequentially in 18.4% subjects. The ECMO weaning rate was 56.6%, and the in-hospital mortality was 52.0%. When compared with non-survivors, survivors had less hypertension (15.1% vs. 35.4%, p = 0.004), secondary thoracotomy before ECMO initiation (19.2% vs. 39.2%, p = 0.007), pre-ECMO cardiac arrest/ventricular fibrillation (11.0% vs. 34.2%, p = 0.001), bedside implantation of ECMO (11.0% vs. 41.8%, p

The goal of this study is to summarize valvular surgery data from the Chinese Cardiac Surgery Registry (CCSR) and compare it to the most recent data from the Society of Thoracic Surgeons (STS). From 2016 to 2018, a total of 34,386 cases of the seven most common valvular surgical procedures was obtained from the CCSR. We calculated the proportions of different procedures in the CCSR cohort (n = 34,386) as well as the change in operation volume for each procedure. We also compiled rates of postoperative in-hospital mortality and five major complications across all procedures. All of the results were compared to the STS data. The CCSR and STS data showed divergent trends in valvular heart disease features and operation volume. Although the proportion of MV repair in the CCSR (13.7%) data was lower than in the STS data (23.2%), it demonstrated a substantial upward trend. In terms of operation volume, the CCSR data showed an upward trend, but the STS data showed a downward trend. CCSR procedures showed lower mortality (2% vs. 2.6%), reoperation (2.8% vs. 4.3%), and permanent stroke (0.5% vs. 1.6%) rates than STS procedures but higher rates of prolonged ventilation (22.4% vs. 10.4%) and renal failure (5.6% vs. 3.2%). Valvular surgery quality in China’s leading cardiac hospitals is roughly comparable to that in the United States. China, on the other hand, has some shortcomings that need improvement.

To explore the methodology for improving ultralow permeability reservoir recovery, cores of ultralow permeability reservoirs in China’s Ordos Basin were selected to study the dynamic imbibition micromechanism of crude oil in nanopore throat through core-flooding laboratory experiment and nuclear magnetic resonance (NMR) observation. In the meantime, the microimbibition characteristics and dynamic discharge of oil between matrix and fracture in partially closed boundary reservoirs were simulated to utmostly reflect the actual reservoir conditions. Our findings suggest that dynamic imbibition between fracture and matrix serves the core technology for improving the recovery of ultralow permeability reservoirs, while the main factors affecting dynamic imbibition efficiency include wettability, permeability, injection rate, fracture, water huff and puff cycles, and soaking time. Wettability, in particular, weighs the most, and imbibition can take place either on water-wet rocks or transformed oil-wet rocks with an imbibition agent added in during the waterflooding process. Meanwhile, the higher the permeability is in place, the greater the dynamic imbibition recovery might achieve. The experiments indicate that the dynamic imbibition recovery of a fractured core is 16.26% higher than that of a nonfractured core. Additionally, fractures can not only enhance imbibition recovery but also accelerate the occurrence of dynamic imbibition. The optimal water injection rate of dynamic imbibition is 0.1 mL/min; the reasonable huff and puff cycle of the ultralow permeability reservoirs tends to be two to three cycles; the optimal soaking time of ultralow permeability reservoir is speculated to be 30 days. Finally, the field practice shows that after Stimulated Reservoir Volume (SRV) and dynamic imbibition in 5 horizontal wells in An83 oilfield, there is a remarkable drop in water cut and a noticeable rise in oil production. This research underpins the significance of a dynamic imbibition effect in the development of ultralow permeability oilfield.

Current hydraulic fracture models are mainly based on elastic theories, which fail to give accurate prediction of fracture parameters in plasticity formation. This paper proposes a fluid–solid coupling model for fracture propagation in elastoplastic formations. The rock plastic deformation in the model satisfies the Mohr-Coulomb yield criterion and plastic strain increment theory. The extended finite-element method (XFEM) combined with the cohesive zone method (CZM) is used to solve the coupled model. The accuracy of the model is validated against existing models. The effects of stress difference, friction angle, and dilation angle on fracture shape (length, width), injection pressure, plastic deformation, induced stress, and pore pressure are investigated through the model. The results indicate that compared with elastic formation, fracture propagation in elastoplastic formation is more difficult, the breakdown pressure and extending pressure are greater, and fracture shape is wider and shorter. The plastic deformation causes the fracture tip to become blunt. Under the condition of high stress difference or low friction angle formation, it is prone to occur large plastic deformation zones and form wide and short fracture. Compared with friction angle, dilation angle is less sensitive to plastic deformation, fracture parameters, and fracture geometry. For the formation with high stress difference and friction angle, the effect of plasticity deformation on fracture propagation should not be ignored.

Soil microbial processes are crucial for understanding the ecological functions of arid and semi-arid lands which occupy approximately 40% of the global terrestrial ecosystems. However, how soil microbial metabolic activities may change across a wide aridity gradient in drylands remains unclear. Here, we investigated three soil microbial metabolic indices (soil organic carbon (SOC)-based microbial respiration, metabolic quotient, and microbial biomass as a proportion of total SOC) and the degree of carbon limitation for microbial respiration along a 3,200 km transect with a wide aridity gradient. The aridity gradient was customarily expressed using the aridity index (AI) which was calculated as the ratio of mean annual precipitation to mean annual evaporation, therefore, a lower AI value indicated a higher degree of aridity. Our results showed non-linear relationships between AI values and the metabolic indices with a clear aridity threshold for each of the three metabolic indices along the aridity gradient, respectively (AI = 0.13 for basal respiration, AI = 0.17 for metabolic quotient, and AI = 0.17 for MBC:SOC ratio). These metabolic indices linearly declined when AI was above the thresholds, but did not show any clear patterns when AI was below the thresholds. We also found that soil microbial respiration was highly limited by available carbon substrates at locations with higher primary production and relatively lower level of water limitation when AI was above the threshold, a counter-intuitive pattern that microbes were more starved in ecosystems with more substrate input. However, the increasing level of carbon limitation did correspond to the declining trend of the three metabolic indices along the AI gradient, which indicates that the carbon limitation influences microbial metabolism. We also found that the ratio of microbial biomass carbon to SOC in arid regions (AI < 0.2) with extremely low precipitation and primary production were not quantitatively related to SOC content. Overall, our results imply that microbial metabolism is distinctively different in arid lands than in non-arid lands.

Based on the dynamic characteristics of water-flooding in ultra-low permeability oilfields, the concept of dynamic fracture is proposed and its formation mechanism and impacts on oilfield development are discussed. Dynamic fractures refer to the new-generated fracture channels when bottom hole pressure exceeds rock breakdown pressure and propagation pressure, or the effective fracture channels generated when the originally closed or filled natural fractures are reactivated, due to high pressure in near wellbore area of injection well in a long term water injection of the ultra-low permeability reservoir. Dynamic fractures, controlled by the current stress field, constantly extend toward the direction of the oil well with the rise of the injected water volume and bottom hole pressure, until connecting with the oil well hydraulic fractures. The analysis of the sealed coring well groups L76-60 and L88-40 located in the same block in the JA Oilfield, Changqing Oilfield, NW China shows that the dynamic fractures changed the seepage characteristics of water displacing oil in the ultra-low permeability reservoir, greatly aggravated the reservoir heterogeneity, which led to the reduction of profile producing degree and the distribution of remaining oil on both sides of the fractures in continuous or discontinuous belts. The generation and propagation of dynamic fractures are closely related to water injection pressure, injection-production ratio, oil and water well stimulation measures. When the porosity-permeability condition of the matrix allows effective oil displacement, high pressure water injection or oil and water well stimulation measures should be avoided as far as possible. Key words: dynamic fracture, ultra-low permeability reservoir, development geological attribute, formation mechanism, water-flooding swept volume

The temperature field of the anode rodding process is the root of most of problems related to the anode. A 3D transient thermal finite element model was developed, based on ANSYS in this paper. The temperature field of the rodding process was investigated using this model. The results were presented and analyzed in detail, including the transient temperature fields of different components in the anode, the characteristics of the cast iron solidification, and the cooling rate distribution. The conclusions were as follows. When the stub hole was filled up at 10 s, 30% by volume of cast iron was below the liquidus temperature. At 70 s, the cast iron solidified completely. The cast iron close to the stub solidified prior to that close to the carbon. The solidification mode was intermediate-freezing. The solidifying sequence was vertically from bottom to top, indicating that shrinkage cavities were less likely to occur. The temperature of the stub was higher than the carbon, and portion at high temperature was concentrated around the stub hole. The cooling rate during solidification was 4.3 °C s−1 to 43.7 °C s−1, and the gradient on the radial direction was relatively obvious.