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With the rapid development of power-electronics-enabled power systems, the new converter-based generators are deteriorating the small-signal stability of the power system. Although the numerical differentiation method has been widely used for approximately calculating the eigenvalue sensitivities, its accuracy has not been carefully investigated. Besides, the ele-ment-based formulation for computing closed-form eigenvalue sensitivities has not been used in any commercial software due to the average efficiency, complicated formulation, and error-prone characteristics. Based on the matrix calculus, this paper proposes an easily manipulated formulation of the closed-form eigenvalue sensitivities with respect to the power generation. The distinguishing feature of the formulation is that all the formulas consist of vector and matrix operations, which can be performed by developed numerical algorithms to take full advantages of architectural features of the modern computer. The tests on WSCC 3-machine 9-bus system, New England to-ma-chine 39-bus system, and IEEE 54-machine 118-bus system show that the accuracy of the proposed formulation is superior to the numerical differentiation method and the efficiency is also greatly improved compared to the element-based closed-form formulation. The proposed formulation will be helpful to perform a more accurate and faster stability analysis of a power grid with converter-based devices.

Surgery is the most effective way to cure non-small cell lung cancer currently. Although sleeve lobectomy, with less reduction of respiratory function and a lower mortality rate, would not compromise oncological results in well-selected patients with central lung cancer, pneumonectomy is still necessary when complete resection could not be achieved by other surgical procedures. Cardiopulmonary complications are the most common complication after pneumonectomy. Fully understanding the related complications after pneumonectomy can help surgeons make a diagnosis timely, and further take relevant measures to reduce the adverse effects of postoperative complications on patients. What’s more, in order to avoid postoperative complications and improve the prognosis of patients as much as possible, it is necessary to fully understand the risk factors to minimize the risk and to make the patients benefit from pneumonectomy as much as possible.

BackgroundGastric cancer is one of the most common malignancies worldwide. Although the diagnosis and treatment of this disease have substantially improved in recent years, the five-year survival rate of gastric cancer is still low due to local recurrence and distant metastasis. An in-depth study of the molecular pathogenesis of gastric cancer and related prognostic markers will help improve the quality of life and prognosis of patients with this disease. The purpose of this study was to identify and verify key SNPs in genes with prognostic value for gastric cancer.MethodsSNP-related data from gastric cancer patients were obtained from The Cancer Genome Atlas (TCGA) database, and the functions and pathways of the mutated genes were analyzed using DAVID software. A protein-protein interaction (PPI) network was constructed using the STRING database and visualized by Cytoscape software, and molecular complex detection (MCODE) was used to screen the PPI network to extract important mutated genes. Ten hub genes were identified using cytoHubba, and the expression levels and the prognostic value of the central genes were determined by UALCAN and Kaplan-Meier Plotter. Finally, quantitative PCR and Western blotting were used to verify the expression of the hub genes in gastric cancer cells.ResultsFrom the database, 945 genes with mutations in more than 25 samples were identified. The PPI network had 360 nodes and 1616 edges. Finally, cytoHubba identified six key genes (TP53, HRAS, BRCA1, PIK3CA, AKT1, and SMARCA4), and their expression levels were closely related to the survival rate of gastric cancer patients.ConclusionOur results indicate that TP53, HRAS, BRCA1, PIK3CA, AKT1, and SMARCA4 may be key genes for the development and prognosis of gastric cancer. Our research provides an important bioinformatics foundation and related theoretical foundation for further exploring the molecular pathogenesis of gastric cancer and evaluating the prognosis of patients.

Background and objective To compare the predictive effect of the Masaoka-Koga staging system and the International Association for the Study of Lung Cancer (IASLC)/the International Thymic Malignancies Interest Group (ITMIG) proposal for the new TNM staging on prognosis of thymic malignancies using the Chinese Alliance for Research in Thymomas (ChART) retrospective database. Methods From 1992 to 2012, 2,370 patients in ChART database were retrospectively reviewed. Of these, 1,198 patients with complete information on TNM stage, Masaoka-Koga stage, and survival were used for analysis. Cumulative incidence of recurrence (CIR) was assessed in R0 patients. Overall survival (OS) was evaluated both in an R0 resected cohort, as well as in all patients (any R status). CIR and OS were first analyzed according to the Masaoka-Koga staging system. Then, they were compared using the new TNM staging proposal. Results Based on Masaoka-Koga staging system, significant difference was detected in CIR among all stages. However, No survival difference was revealed between stage I and II, or between stage II and III. Stage IV carried the highest risk of recurrence and worst survival. According to the new TNM staging proposal, CIR in T1a was significantly lower comparing to all other T categories (P

Background and objective To evaluate the role of preoperative induction therapy on prognosis of locally advanced thymic malignancies. Methods Between 1994 and 2012, patients received preoperative induction therapies (IT group) in the Chinese Alliance for Research in Thymomas (ChART) database, were compared with those having surgery directly after preoperative evaluation (DS group). All tumors receiving induction therapies were locally advanced (clinically stage III-IV) before treatment and those turned out to be in pathological stage I and II were considered downstaged by induction. Clinical pathological characteristics were retrospectively analyzed. To more accurately study the effect of induction therapies, stage IV patients were then excluded. Only stage I-III tumors in the IT group and stage III cases in the DS group were selected for further comparison in a subgroup analysis. Results Only 68 (4%) out of 1,713 patients had induction therapies, with a R0 resection of 67.6%, 5-year recurrence of 44.9%, and 5- and 10-year overall survivals (OS) of 49.7% and 19.9%. Seventeen patients (25%) were downstaged after induction. Significantly more thymomas were downstaged than thymic carcinomas (38.7% vs 13.9%, P=0.02). Tumors downstaged after induction had significantly higher 5-year OS than those not downstaged (93.8% vs 35.6%, P=0.013). For the subgroup analysis when stage IV patients were excluded, 5-year OS was 85.2% in the DS group and 68.1% in the IT group (P

Background and objective To evaluate the surgical outcomes of tumor resection with or without total thymectomy for thymic epithelial tumors (TETs) using the Chinese Alliance for Research in Thymomas (ChART) retrospective database. Methods Patients without preoperative therapy, who underwent surgery for early-stage (Masaoka-Koga stage I and II) tumors, were enrolled for the study. They were divided into thymectomy and thymomectomy groups according to the resection extent of the thymus. Demographic and surgical outcomes were compared between the two patients groups. Results A total of 1,047 patients were enrolled, with 796 cases in the thymectomy group and 251 cases in the thymomectomy group. Improvement rate of myasthenia gravis (MG) was higher after thymectomy than after thymomectomy (91.6% vs 50.0%, P

Background and objective Postoperative radiotherapy (PORT) for thymic tumor is still controversial. The object of the study is to evaluate the role of PORT for stage I/II/III thymic tumor. Methods The database of Chinese Alliance of Research for Thymomas (ChART) was retrieved for patients with stage I/II/III thymic tumor who underwent surgical therapy without neoajuvant therapy between 1994 and 2012. Univariate and multivariate survival analyses were performed. Cox proportional hazard model was used to determine the hazard ratio for death. Results 1,546 stage I/II/III patients were identified from ChART database. Among these patients, 649 (41.98%) underwent PORT. PORT was associated with gender, histologic type (World Health Organization, WHO), surgical extent, complete resection, Masaoka stage and adjuvant chemotherapy. The 5-yr and 10-yr overall survival (OS) rates and disease-free survival (DFS) rate for patients underwent surgery followed by PORT were 90% and 80%, 81% and 63%, comparing with 96% and 95%, 92% and 90% for patients underwent surgery alone (P=0.001, P

Background and objective Video-assisted thoracoscopic surgery (VATS) theoretically offers advantages over open thymectomy for clinically early-stage (Masaoka-Koga stage I and II) thymic malignancies. However, longterm outcomes have not been well studied. We compared the postoperative outcomes and survival from a cohort study based on the database of the Chinese Alliance for Research in Thymomas (ChART). Methods Between 1994 and 2012, data of 1,117 patients having surgery for clinically early-stage (Masaoka-Koga stage I and II) tumors were enrolled for the study. Among them, 241 cases underwent VATS thymectomy (VATS group), while 876 cases underwent open thymectomy (Open group). Univariate analyses were used to compare the clinical character and perioperative outcomes between the two groups. And multivariate analysis was performed to determine the independent predictive factors for long-term survival. Results Compared with the Open group, the VATS group had higher percentage of total thymectomy (80.5% vs 73.9%, P=0.028), resection rate (98.8% vs 88.7%, P

Background and objective It is so far not clear that how myasthenia gravis (MG) affected the prognosis of thymoma patients. The aim of this assay is to compare the postoperative survival between patients with thymoma only and those with both thymoma and MG. Methods The Chinese Alliance for Research in Thymomas (ChART) registry recruited patients with thymoma from 18 centers over the country on an intention to treat basis from 1992 to 2012. Two groups were formed according to whether the patient complicated MG. Demographic and clinical data were reviewed, Patients were followed and their survival status were analyzed. Results There were 1,850 patients included in this study, including 421 with and 1,429 without MG. Complete thymectomy were done in 91.2% patients in MG group and 71.0% in non-MG group (P

Background and objective To study the role of postoperative chemotherapy and its prognostic effect in Masaoka-Koga stage III and IV thymic tumors. Methods Between 1994 and 2012, 1,700 patients with thymic tumors who underwent surgery without neoajuvant therapy were enrolled for the study. Among them, 665 patients in Masaoka-Koga stage III and IV were further analyzed to evaluate the clinical value of postoperative chemotherapy. The Kaplan-Meier method was used to obtain the survival curve of the patients divided into different subgroups, and the Cox regression analysis was used to make multivariate analysis on the factors affecting prognosis. A Propensity-Matched Study was used to evaluate the clinical value of chemotherapy. Results Two-hundred-twenty-one patients were treated with postoperative chemotherapy, while the rest 444 cases were not. The two groups showed significant differences (P

Background and objective Traditional lobectomy techniques often lead to persistent air leak (PAL) for lung cancer patients companied with fused fissure. The aim of this study is to evaluate the outcomes of those patients undergoing fissureless lobectomy. Methods The clinical data were retro-respectively analyzed from 274 lung cancer patients with fused fissure who received surgical procedures from August 2011 to December 2012. Patients were divided into fissureless group (group A, n=121) and traditional group (group B, n=153) according to the type of lobectomy techniques. The data were analyzed using SPSS 17.0. The air leak cessation was determined using the Kaplan-Meier method. Multiple risk analysis was developed by Logistic regression. Results The incidences of PAL in 2 groups were 1.7% and 9.2%, respectively (P=0.009). The air leak cessation in group A was significantly lower than that in group B (P

In this article we consider elliptic equations whose nonlinear term depends on the gradient of the unknown. We assume that the nonlinearity has a asymptotically linear growth at zero and at infinity with respect to the second variable. By applying Morse theory and an iterative method, we prove the existence of nontrivial solutions.

BackgroundThe response to cytotoxic chemotherapy varies greatly in patients with advanced non-small cell lung cancer (NSCLC), and molecular markers may be useful in determining a preferable therapeutic approach for individual patients. This retrospective study was performed to evaluate the predictive value of ribonucleotide reductase regulatory subunit M1 (RRM1) on the therapeutic efficacy of platinum-based chemotherapy in patients with NSCLC.MethodsPatients with advanced NSCLC who received platinum doublet chemotherapy (n = 229) were included in this retrospective study, and their clinical outcomes were analyzed according to RRM1 expression.ResultsIn patients receiving gemcitabine-based therapy, the disease control rate (DCR) and progression-free survival (PFS) of patients with RRM1-negative tumors were significantly higher than in patients with RRMI-positive tumors (P = 0.041 and P = 0.01, respectively), and multivariate analysis showed that RRM1 expression was an independent prognostic factor (P = 0.013). No similar differences were found in patients receiving docetaxel- or vinorelbine-based therapy. In RRM1-positive patients, the DCRs for docetaxel and vinorelbine were higher than for gemcitabine (P = 0.047 and P = 0.047, respectively), and docetaxel and vinorelbine showed a longer PFS than gemcitabine-based chemotherapy (P = 0.012 and P = 0.007). No similar differences were found among patients with RRM1-negative tumors.ConclusionsNegative RRM1 expression in advanced NSCLC is associated with a higher response rate to gemcitabine-based chemotherapy. In patients with RRM1-positive tumors, docetaxel and vinorelbine showed a higher therapeutic efficacy than gemcitabine-based therapy. Additional prospective studies are needed to investigate the predictive meaning of RRM1 in the response to chemotherapy.