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Positive and Conservative Characteristic Block-Centered Finite Difference Methods for Convection Dominated Diffusion Equations

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Advances in Applied Mathematics and Mechanics 2022年第5期14卷 1087-1110页

作者： Xinshu Li Kai Fu School of Mathematical Sciences Ocean University of ChinaQingdaoShandong 266100China

In this work,spatial second order positivity preserving characteristic blockcentered finite difference methods are proposed for solving convection dominated diffusion problems.By using a Conservative piecewise parabolic interpolation with positive constraint,the temporal first order scheme is shown to conserve mass exactly and preserve the positivity property of solution.Taking advantage of characteristics,there is no strict restriction on time steps.The scheme is extended to temporal second order by using a particular extrapolation along the characteristics.To restore solution positivity,a mass Conservative local limiter is introduced and verified to keep second order accuracy.Numerical examples are carried out to demonstrate the performance of proposed methods.

关键词： Positivity preserving Conservative characteristic method

Invasive versus Conservative strategy in consecutive patients aged 80 years or older with non-ST-segment elevation myocardial infarction: a retrospective study in China

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Journal of Geriatric Cardiology 2019年第10期16卷 741-748页

作者： Yong-Gang SUI Si-Yong TENG Jie QIAN Yuan WU Ke-Fei DOU Yi-Da TANG Shu-Bin QIAO Yong-Jian WU Department of Cardiology Fuwai Hospital National Center for Cardiovascular Diseases Chinese Academy of Medical Sciences and Peking Union Medical College

Objective To investigate whether the very elderly patients with non-ST-segment elevation myocardial infarction (NSTEMI) will benefit from an invasive strategy versus a Conservative strategy. Methods 190 consecutive patients aged 80 years or older with NSTEMI were included in the retrospective study from September 2014 to August 2017, of which 69 patients received Conservative strategy and 121 patients received invasive strategy. The primary outcome was death. Multivariate Cox regression models were used to assess the statistical association between strategies and mortality. The survival probability was further analyzed. Results The primary outcome occurred in 17.4% patients in the invasive group and in 42.0% patients in the Conservative group (P = 0.0002). The readmission rate in the invasive group (14.9%) was higher than that in the Conservative group (7.2%). Creatinine level (OR = 1.01, 95% CI: 0.10–1.03, P = 0.05) and use of diuretic (OR = 3.65, 95% CI: 1.56–8.53, P = 0.003) were independent influential factors for invasive strategy. HRs for multivariate Cox regression models were 3.45 (95% CI: 1.77–6.75, P = 0.0003), 3.02 (95% CI: 1.52–6.01, P = 0.0017), 2.93 (95% CI: 1. 46–5.86, P = 0.0024) and 2.47 (95% CI: 1.20–5.07, P = 0.0137). Compared with the patients received invasive strategy, the Conservative group had remarkably reduced survival probability with time since treatment (P Conservative strategy in reducing mortality of patients aged 80 years or older with NSTEMI. Our results suggest that an invasive strategy is more suitable for the very elderly patients with NSTEMI in China.

关键词： Conservative strategy Death Invasive strategy Non-ST-segment elevation myocardial infarction

Un displaced subtle ligamentous Lisfranc injuries, con servative or surgical treatment with percutaneous position screws?

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Chinese Journal of Traumatology 2019年第4期22卷 196-201页

作者： Wei Ren Hai-Bo Li Ji-Ke Lu Yong-Cheng Hu Tianjin Medical University Tianjin 300070 China Department of Orthopedic Surgery United Family Hospital Beijing 100015 China Department of Orthopedic Tianjin Hospital Tianjin 300211 China

Purpose: Un displaced subtle ligamentous Lisfranc injuries are easy to miss or underestimate, and many cases are treated without surgical fixation. It has not yet widely known whether Conservative treatment for undisplaced subtle ligamentous Lisfranc injuries may lead to a poor outcome. The purpose of this study is to compare the outcomes of Conservative versus surgical management (percutaneous position screw) of undisplaced subtle ligamentous Lisfranc injury. Methods: We analysed 61 cases in this retrospective study, including 38 males and 23 females. Forty-one patients were managed Conservatively, while 20 patients received surgical treatment involving minimal invasive percutaneous pos让ion screw. American orthopaedic foot &ankle society (AOFAS), foot function index (FFI, including FFI disability, FFl pain score and activity limitation scale) scores, Maryland foot score and short form-36 (SF-36) were recorded and compared after a follow-up of 10-16 months (average 12.3). Results: Patients in the surgical management group had higher scores in all evaluation methods (p Conservative management group had higher incidenee, mainly including secondary diastasis (34.1% vs. 5.0%), joint stiffness after 3 months (82.9% vs. 0%), and secondary arthrodesis (12.2% vs. 0%). The highest rate of complication in surgical management group was temporary forefoot pain (55.0%). Conclusion: The results of this study suggest that the outcomes of the surgical management with percutaneous position screw fixation are better than the Conservative management to treat undisplaced subtle ligamentous Lisfranc injuries. This study can serve as a resource for orthopaedic surgeons in recog nizing and man aging such injuries.

关键词： Undisplaced subtle ligamentous Lisfranc injuries Conservative management Surgical management Percutaneous position screw Complications

Quantifying the non-Conservative production of potential temperature over the past 22000 years

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Journal of Oceanology and Limnology 2019年第2期37卷 410-422页

作者： ZHANG Cunjie HAN Xueshuang LIN Xiaopei Physical Oceanography Laboratory/CIMST Ocean University of China and Qingdao National Laboratory for Marine Science and Technology Qingdao 266100 China Research Vessel Center Ocean University of China Qingdao 266100 China

The energy budgets of the ocean play a crucial role in the analysis of climate change. Potential temperature is traditionally used as a Conservative quantity to express variations associated with “heat” in oceanography, such as the heat content and heat transport. However, potential temperature is usually not conserved during turbulent mixing, so the use of Conservative temperature is more accurate. Based on climatological simulations under the modern and Last Glacial Maximum (LGM;~21 ka;ka=thousand years ago), as well as a transient climate simulation of the past 22 000 years, we quantify the errors induced by the neglect of the non-conservation of potential temperature in paleo-climate research for the first time. The temperature error reaches 0.9℃ near the coasts aff ected by river discharges but is much smaller in the open oceans, typically 0.03°C above the main thermocline and less than 0.01℃ elsewhere. The error of the ocean heat content (OHC) is roughly 3×10^22 J and is relatively steady over the past 22 000 years. However, the OHC increases to six times the original value during the last glacial termination from 20 ka to 7 ka. As a result, the relative OHC error decreases from 1.2% in the LGM climate to 0.14% in the modern climate. The error of the ocean meridional heat transport (OMHT) is generally smaller than 0.005 PW (1 PW=10 15 W), with very small temporal variations (typically 0.000 4 PW), and induces a relative OMHT error of typically 0.3% over the past 22 000 years. Therefore, the neglect of the non-conservation of potential temperature induces a relative error of generally less than 1% in the analyses of basin-scale climate variations.

关键词： Conservative temperature potential temperature ocean heat content ocean heat transport paleoclimate

Conservative reconstruction using stents as salvage therapy for disruption of esophago-gastric anastomosis

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World Journal of Gastroenterology 2015年第28期21卷 8723-8729页

作者： Taro Oshikiri Yoshinobu Yamamoto Ikuya Miki Masahiro Tsuda Tetsu Nakamura Yasuhiro Fujino Masahiro Tominaga Yoshihiro Kakeji Department of Gastroenterological Surgery Hyogo Cancer Center Department of Gastroenterological Oncology Hyogo Cancer Center Division of Gastrointestinal Surgery Department of Surgery Graduate School of MedicineKobe University

Esophagectomy with extended lymphadenectomy and gastric conduit reconstruction is a radical procedure for the treatment of esophageal cancer that is associated with a high morbidity rate.Gastric conduit necrosis is a fatal complication that occurs in 2%of patients.Conventionally,two-stage salvage surgery consisting of removal of the necrotic gastric conduit followed by reconstruction has been performed;however,this procedure has a high morbidity rate.We describe a61-year-old man who underwent minimally invasive esophagectomy complicated by slowly progressive gastric conduit necrosis associated with complete neck drainage and a stable overall condition.There was a 2 cm gap in the anastomosis.Because there was no evidence of residual gastric conduit necrosis,a removable,covered self-expanding metal stent(SEMS)was inserted to bridge the anastomosis.The stent was fixed to the patient's ear with silk thread through the lasso on its proximal end to prevent migration.Eight weeks after insertion,the stent was removed easily without any associated complications.The anastomotic defect was completely bridged with granulation tissue,showing progressive epithelialization without leakage or stenosis.The patient was discharged home in good general health.This is the first report of the successful Conservative management of esophago-gastric conduit anastomosis disruption with SEMS placement.

关键词： Esophagectomy Gastric conduit necrosis Disruption of anastomosis Self-expanding metal stent Hanarostent Conservative management

The transition from Conservative to dissipative flows in class-B laser model with fold-Hopf bifurcation and coexisting attractors

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Chinese Physics B 2022年第6期31卷 39-45页

作者：李月陈增强袁明峰仓诗建 College of Artificial Intelligence Nankai UniversityTianjin 300350China Department of Earth and Space Science and Engineering York University4700 Keele StToronto M3J 1P3Canada Department of Product Design Tianjin University of Science and TechnologyTianjin 300222China

Dynamical behaviors of a class-B laser system with dissipative strength are analyzed for a model in which the polarization is adiabatically eliminated. The results show that the injected signal has an important effect on the dynamical behaviors of the system. When the injected signal is zero, the dissipative term of the class-B laser system is balanced with external interference, and the quasi-periodic flows with Conservative phase volume appear. And when the injected signal is not zero, the stable state in the system is broken, and the attractors(period, quasi-period, and chaos) with contractive phase volume are generated. The numerical simulation finds that the system has not only one attractor, but also coexisting phenomena(period and period, period and quasi-period) in special cases. When the injected signal passes the critical value,the class-B laser system has a fold-Hopf bifurcation and exists torus “blow-up” phenomenon, which will be proved by theoretical analysis and numerical simulation.

关键词： Conservative flows dissipative attractors coexisting phenomena fold-Hopf bifurcation class-Blaser chaotic system

Conservative approach to the acute management of a large mesenteric cyst

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World Journal of Clinical Cases 2017年第9期5卷 360-363页

作者： Billy C Leung Ruth Sankey Matteo Fronza Mohamed Maatouk Department of General and Colorectal Surgery Milton Keynes HospitalEaglestone

Mesenteric cysts are rare, benign gastrointestinal cystic lesions, which are often non-troublesome and present as an incidental radiological finding. However, surgery is often performed in the acute setting to remove lesions that are symptomatic. This report highlights the case of a large, symptomatic mesenteric cyst managed successfully with initial Conservative measures followed by planned elective surgery. A 44-year-old female presented with a four-day history of generalised abdominal pain associated with distension, fever, diarrhoea and vomiting. Computer tomography revealed a large(21.7 cm × 11.8 cm × 14 cm) mesenteric cyst within the left abdomen cavity. She was admitted and treated Conservatively with intravenous fluids and antibiotics for four days, which lead to complete symptom resolution. Follow-up at intervals of one and three months revealed no return of symptoms. An elective laparotomy and excision of the mesenteric cyst was then scheduled and performed safely at nine months after the initial presentation. Compared to acute surgery, acute Conservative management followed by planned elective resection of a symptomatic mesenteric cyst may prove safer. The withholding of an immediate operation may potentially avoid unnecessary operative risk and should be considered in patients without obstructive and peritonitic symptoms. Our case demonstrated the safe use of initial Conservative management followed by planned elective surgery of a mesenteric cyst found in the acute setting, which was symptomatic but was not obstructive or causing peritonitic symptoms.

关键词： Conservative management Acute setting Mesenteric cysts Elective operation

Conservative treatment of knee osteoarthritis:A review of the literature

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World Journal of Orthopedics 2022年第3期13卷 212-229页

作者： Wei Boon Lim Oday Al-Dadah The Medical School Newcastle UniversityNewcastle-upon-Tyne NE24HHUnited Kingdom Department of Trauma and Orthopaedic Surgery South Tyneside District HospitalSouth Tyneside NE340PLUnited Kingdom Translational and Clinical Research Institute Faculty of Medical SciencesNewcastle UniversityNewcastle-upon-Tyne NE24HHUnited Kingdom

Knee osteoarthritis(KOA)is a common chronic debilitating disease with an estimated prevalence of 23.9%in the general adult population.The condition is characterised by joint pain,functional impairment and significant reduction in quality of life.Management for KOA can generally be divided into Conservative(non-operative)and surgical(operative)measures.Conservative management broadly compromises pharmacological and non-pharmacological options and is conventionally the first line treatment to avoid or delay the need for surgical management.The aim of this study is to provide an overview of the current recommendations,efficacy and safety profile of different Conservative treatments through a review of the literature.

关键词： Osteoarthritis Knee Conservative Non-surgical Treatment Management

A Conservative Lagrangian Scheme for Solving Compressible Fluid Flows with Multiple Internal Energy Equations

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Communications in Computational Physics 2012年第10期12卷 1307-1328页

作者： Juan Cheng Chi-Wang Shu Qinghong Zeng National Key Laboratory of Science and Technology on Computational Physics Institute of Applied Physics and Computational MathematicsBeijing 100088China Division of Applied Mathematics Brown UniversityProvidenceRI 02912USA Institute of Applied Physics and Computational Mathematics Beijing 100088China

Lagrangianmethods arewidely used inmany fields formulti-material compressible flow simulations such as in astrophysics and inertial confinement fusion(ICF),due to their distinguished advantage in capturing material interfaces automatically.In some of these applications,multiple internal energy equations such as those for electron,ion and radiation are involved.In the past decades,several staggeredgrid based Lagrangian schemes have been developed which are designed to solve the internal energy equation directly.These schemes can be easily extended to solve problems with multiple internal energy equations.However such schemes are typically not Conservative for the total energy.Recently,significant progress has been made in developing cell-centered Lagrangian schemes which have several good properties such as conservation for all the conserved variables and easiness for remapping.However,these schemes are commonly designed to solve the Euler equations in the form of the total energy,therefore they cannot be directly applied to the solution of either the single internal energy equation or the multiple internal energy equations without significant modifications.Such modifications,if not designed carefully,may lead to the loss of some of the nice properties of the original schemes such as conservation of the total energy.In this paper,we establish an equivalency relationship between the cell-centered discretizations of the Euler equations in the forms of the total energy and of the internal energy.By a carefully designed modification in the implementation,the cell-centered Lagrangian scheme can be used to solve the compressible fluid flow with one or multiple internal energy equations and meanwhile it does not lose its total energy conservation property.An advantage of this approach is that it can be easily applied to many existing large application codes which are based on the framework of solving multiple internal energy equations.Several two dimensional numerical examples for both Euler equations and three-temperatu

关键词： Lagrangian scheme Conservative cell-centered internal energy equation compressible fluid flow three-temperaturemodel