Approximate Solutions to the Discontinuous Riemann-Hilbert Problem of Elliptic Systems of First Order Complex Equations

Several approximate methods have been used to find approximate solutions of elliptic systems of first order equations. One common method is the Newton imbedding approach, i.e. the parameter extension method. In this article, we discuss approximate solutions to discontinuous Riemann-Hilbert boundary value problems, which have various applications in mechanics and physics. We first formulate the discontinuous Riemann-Hilbert problem for elliptic systems of first order complex equations in multiply connected domains and its modified well-posedness, then use the parameter extensional method to find approximate solutions to the modified boundary value problem for elliptic complex systems of first order equations, and then provide the error estimate of approximate solutions for the discontinuous boundary value problem.

Cooperative spectrum sharing of multiple primary users and multiple secondary users

This paper proposes a multiple-input multiple-output （MIMO） based cooperative dynamic spectrum access （DSA） framework that enables multiple primary users （PUs） and multiple secondary users （SUs） to cooperate in spectrum sharing. By exploiting MIMO in cooperative DSA, SUs can relay the primary traffic and send their own data at the same time, which greatly improves the performance of both PUs and SUs when compared to the non- MIMO time-division spectrum sharing schemes. Especially, we focus on the relay selection optimization problem among multiple PUs and multiple SUs. The network-wide cooperation and competition are formulated as a bargaining game, and an algorithm is developed to derive the optimal PU-SU relay assignment and resource allocation. Evaluation results show that both primary and secondary users achieve significant utility gains with the proposed framework, which gives all of them incentive for cooperation.

Boundary Value Problems for Nonlinear Elliptic Equations of Second Order in High Dimensional Domains

This paper mainly concerns oblique derivative problems for nonlinear nondivergent elliptic equations of second order with measurable coefficients in a multiply connected domain. Under certain condition, we derive a priori estimates of solutions. By using these estimates and the fixed-point theorem, we prove the existence of solutions.

General Boundary Value Problems for Nonlinear Uniformly Elliptic Equations in Multiply Connected Infinite Domains

This article discusses the general boundary value problem for the nonlinear uniformly elliptic equation of second order in D (0.1) and the boundary condition,(0.2) in a multiply connected infinite domain D with the boundary T. The above boundary value problem is called Problem G. Problem G extends the work [8] in which the equation (0.1) includes a nonlinear lower term and the boundary condition (0.2) is more general. If the complex equation (0.1) and the boundary condition (0.2) meet certain assumptions, some solvability results for Problem G can be obtained. By using reduction to absurdity, we first discuss a priori estimates of solutions and solvability for a modified problem. Then we present results on solvability of Problem G.

Clinical practice guidelines for nutritional assessment and monitoring of adult ICU patients in China

The Chinese Society of Critical Care Medicine(CSCCM)has developed clinical practice guidelines for nutrition assessment and monitoring for patients in adult intensive care units(ICUs)in China.This guideline focuses on nutrition evaluation and metabolic monitoring to achieve optimal and personalized nutrition therapy for critically ill patients.This guideline was developed by experts in critical care medicine and evidence-based medicine methodology and was developed after a thorough review of the system and a summary of relevant trials or studies published from 2000 to July 2023.A total of 18 recommendations were formed and consensus was reached through discussions and reviews by expert groups in critical care medicine,parenteral and enteral nutrition,and surgery.The recommendations are based on currently available evidence and cover several key fields,including screening and assessment,evaluation and assessment of enteral feeding intolerance,metabolic and nutritional measurement and monitoring during nutrition therapy,and organ function evaluation related to nutrition supply.Each question was analyzed according to the Population,Intervention,Comparison,and Outcome(PICO)principle.In addition,interpretations were provided for four questions that did not reach a consensus but may have potential clinical and research value.The plan is to update this nutrition assessment and monitoring guideline using the international guideline update method within 3–5 years.

The causal role of immune cells in susceptibility and severity of COVID-19:A bidirectional Mendelian randomization study

To the Editor,Previous studies have demonstrated close associations of specific immune cell profiles in the occurrence and development of COVID-19.[1,2]However,due to confounding factors and reverse causality in traditional observational studies,it remains unclear whether these associations reflect a causal link.Mendelian randomization(MR)is a reliable method of causal inferences that uses genetic variants(usually single-nucleotide polymorphisms[SNPs])as instrumental variables(IVs)to estimate the causal effect of exposure on outcome.

Efficacy and safety of awake prone positioning in the treatment of non-intubated spontaneously breathing patients with COVID-19-related acute respiratory failure:A systematic review and meta-analysis

Background Since the beginning of the coronavirus disease 2019(COVID-19)pandemic,prone positioning has been widely applied for non-intubated,spontaneously breathing patients.However,the efficacy and safety of prone positioning in non-intubated patients with COVID-19-related acute hypoxemic respiratory failure remain unclear.We aimed to systematically analyze the outcomes associated with awake prone positioning(APP).Methods We conducted a systematic literature search of PubMed/MEDLINE,Cochrane Library,Embase,and Web of Science from January 1,2020,to June 3,2022.This study included adult patients with acute respiratory failure caused by COVID-19.The Preferred Reporting Items for Systematic Reviews and Meta-Analyses(PRISMA)guidelines were followed,and the study quality was assessed using the Cochrane risk-of-bias tool.The primary outcome was the reported cumulative intubation risk across randomized controlled trials(RCTs),and the effect estimates were calculated as risk ratios(RRs;95%confidence interval[CI]).Results A total of 495 studies were identified,of which 10 fulfilled the selection criteria,and 2294 patients were included.In comparison to supine positioning,APP significantly reduced the need for intubation in the overall population(RR=0.84,95%CI:0.74–0.95).The two groups showed no significant differences in the incidence of adverse events(RR=1.16,95%CI:0.48–2.76).The meta-analysis revealed no difference in mortality between the groups(RR=0.93,95%CI:0.77–1.11).Conclusions APP was safe and reduced the need for intubation in patients with respiratory failure associated with COVID-19.However,it did not significantly reduce mortality in comparison to usual care without prone positioning.

Expert consensus on blood pressure management in critically ill patients

Introduction For critically ill patients with unstable hemodynamics,goal‑directed therapy for arterial blood pressure is needed with continuous daily bedside monitoring.The prevalence of hypertension in Chinese adults is 25.2%,of which 1–2%of patients may experience a hypertensive emergency,with a mortality rate of 6.9%in the acute phase.The mortality and readmission rates within 90 days of onset are as high as 11%.[1]Furthermore,the mortality rate for patients who experience hypertensive emergencies can reach 50%within 12 months of the incident.[2]The incidence of perioperative hypertension in patients undergoing cardiac surgery is approximately 50%,with this figure dropping to 25%for non-cardiac surgery.Surgery may increase the incidence of perioperative cardio-cerebrovascular adverse events by 3–5%.[3]

我和杜斌——非同寻常的师生

1994年,杜斌(图1)在ICU报到,博士学位。第一印象,聪明勤快,一个还没有长大的大孩子。优点和缺点,一望而知,没有遮掩。他声称潘家绮是他导师,由此推算,我是他导师的配偶。我和家绮能有这么一位学生,是件喜事。我当丈夫的被称为夫人的配偶,也心甘情愿。其实杜斌是按“老协和”的传统培养出来的,在校8年学制,毕业后进入北京协和医院,接受4年的住院医师培训。医学院毕业就获博士学位。他在校学习期间,潘家绮曾经是他博士论文的导师(图2)。

ICU的护士——“提灯女郎”之光

(一)1853年克里米亚战争爆发。1854年,弗洛伦斯·南丁格尔(Florence Nightingale,1820年至1910年)(图1)收到军务大臣的委托信,几天内她赶赴战地服务。她是统计学家,分析军事档案的过程中,她发现约16000名士兵因受伤后得不到必要的救护而死亡,远比死在战场上的更多。于是,她坚持白天在医院大厅内巡视,认真观察,夜间提.灯夜巡,挨个看管伤员。她的努力使得战地医院病死率降低了2/3。她的关爱和服务,令战士们深受感动,称她是“提灯女郎”。美国诗人朗费罗(Longfellow,1807年至1882年)曾写诗一首,赞美南丁格尔。

我选择了危重病医学

(一)人有内在兴趣。社会及教育环境可以影响兴趣的选择,从有志于学到而立之年,是选择兴趣并确立志向的关键性的15年。1947年我进入原震旦大学医学院。学医之初,我对生理学感兴趣。因此,我喜欢内科学。

Activating transcription factor 4 protects mice against sepsis-induced intestinal injury by regulating gut-resident macrophages differentiation

Background: Gut-resident macrophages (gMacs) supplemented by monocytes-to-gMacs differentiation play a critical role in maintaining intestinal homeostasis. Activating transcription factor 4 (ATF4) is involved in immune cell differentiation. We therefore set out to investigate the role of ATF4-regulated monocytes-to-gMacs differentiation in sepsis-induced intestinal injury.Methods: Sepsis was induced in C57BL/6 wild type (WT) mice andAtf4-knockdown (Atf4+/-) mice by cecal ligation and puncture or administration of lipopolysaccharide (LPS). Colon, peripheral blood mononuclear cells, sera, lung, liver, and mesenteric lymph nodes were collected for flow cytometry, hematoxylin and eosin staining, immunohistochemistry, quantitative reverse transcription polymerase chain reaction, and enzyme-linked immunosorbent assay, respectively.Results: CD64, CD11b, Ly6C, major histocompatibility complex-II (MHC-II), CX3CR1, Ly6G, and SSC were identified as optimal primary markers for detecting the process of monocytes-to-gMacs differentiation in the colon of WT mice. Monocytes-to-gMacs differentiation was impaired in the colon during sepsis and was associated with decreased expression of ATF4 in P1 (Ly6Chi monocytes), the precursor cells of gMacs.Atf4 knockdown exacerbated the impairment of monocytes-to-gMacs differentiation in response to LPS, resulting in a significant reduction of gMacs in the colon. Furthermore, compared with WT mice,Atf4+/- mice exhibited higher pathology scores, increased expression of inflammatory factor genes (TNF-α, IL-1β), suppressed expression of CD31 and vascular endothelial-cadherin in the colon, and increased translocation of intestinal bacteria to lymph nodes and lungs following exposure to LPS. However, the aggravation of sepsis-induced intestinal injury resulting fromAtf4 knockdown was not caused by the enhanced inflammatory effect of Ly6Chi monocytes and gMacs.Conclusion: ATF4, as a novel regulator of monocytes-to-gMacs differentiation, plays a critical role in protecting mice against sepsis-induced intestinal injury, suggesting that ATF4 might be a potential therapeutic target for sepsis treatment.

Lipopolysaccharide induced intestinal epithelial injury:a novel organoids-based model for sepsis in vitro

Background: Advances in organoid culture technology have provided a greater understanding of disease pathogenesis, which has been rarely studied in sepsis before. We aim to establish a suitable organoids-based intestinal injury model for sepsis.Methods: Stable passaged organoids were constructed and pre-treated with lipopolysaccharide (LPS) to mimic sepsis-induced intestinal injury. The LPS-induced sepsis model was used as a reference. We used quantitative real-time polymerase chain reaction to evaluate the RNA levels of inflammatory factors and antimicrobial peptides. Enzyme-linked immunosorbent assay was used to evaluate the protein levels, hematoxylin and eosin staining was used to evaluate the pathology of the small intestine of mice, and immunohistochemistry and immunofluorescence were used to evaluate the intestinal epithelial barrier function. Perkin Elmer OperettaTM was used to obtain high-resolution images of three-dimensional organoids.Results: An LPS concentration >150 μg/mL after 24 h was identified to cause organoid growth restriction. The fluorescence intensity of zonula occludens-1 and occludins at LPS concentrations >100 μg/mL decreased significantly after 24 h. After LPS stimulation for 8 h, the RNA expression levels of interleukin (IL)-1α, tumor necrosis factor alpha, granulocyte-macrophage colony-stimulating factor, IL-6, and regenerating islet-derived protein 3 alpha, beta, and gamma increased. These results resembled those of intestinal epithelial layer alterations in a mouse sepsis model. For IL-10, the RNA expression level increased only when the LPS level >200 μg/mL for 24 h.Conclusions: This study provides the primary intestinalin vitro model to study the effects of LPS-induced intestinal injury resembling sepsis. This model provides a platform for immune associated mechanism exploration and effective drug screening.

Expert consensus on the glycemic management of critically ill patients

Introduction The incidence of hyperglycemia is 40-60%in critically ill patients and is up to 60-80%in those who have undergone car-diac surgery.[1]The results of an epidemiological study in the United States showed that 28.6%of diabetic patients and 9.3%of non-diabetic patients had elevated mean daily glucose on the day of ICU admission.[2]In critically ill patients,elevated blood glucose is primarily the result of stress,and stress-induced hy-perglycemia is an independent risk factor associated with prog-nosis,regardless of a previous diagnosis of diabetes.Nutritional therapy has become an integral treatment option for patients in the ICU,[3,4]though nearly 30%of patients with enteral nu-trition and 44-50%with parenteral nutrition(PN)experience elevated glucose.[5,6]Intensive insulin therapy(IIT)is an impor-tant treatment for controlling hyperglycemia in critically ill pa-tients,but it also carries a corresponding risk of hypoglycemia.

Target serum concentration of vancomycin may be reached earlier with a loading dose

Background:Vancomycin treatment failure against vancomycin-susceptible gram-positive cocci is not rare in the intensive care unit(ICU).One of the reasons for this is the substandard drug trough concentration.We aimed to examine the hypothesis that the target serum concentration could be reached earlier with a loading dose of vancomycin.Methods:This retrospective cohort study was conducted at our ICU between June 2018 and June 2020 and involved patients who were suspected of having,or confirmed to have,gram-positive cocci infection and treated with vancomycin.One group of the patients was administered a loading dose of vancomycin(loading group)and compared with the group that did not receive a loading dose(control group).The baseline characteristics,vancomycin serum concentrations,and clinical outcomes were collected and analyzed.Results:Fifty-five patients were finally included,of which 29 received a loading dose of vancomycin.The serum concentration of vancomycin before the second dose was significantly higher for the loading group than for the control group(10.3±6.1 mg/Lvs.5.7±4.4 mg/L,P=0.002).The results for both groups were similar before the fifth dose(12.4±7.3 mg/Lvs.10.3±6.3 mg/L in the loading and the control groups,respectively;P=0.251).The 28-day mortality was lower for the loading group than for the control group(6.7%vs.34.6%in the loading and control groups,respectively;P=0.026).No significant differences were observed in serum creatinine(Cr)concentrations of the two groups.Conclusion:With the loading dose of vancomycin,the target serum concentration of vancomycin may be reached earlier without increasing the risk of acute kidney injury.

Expert consensus on the diagnosis and treatment of severe and critical coronavirus disease 2019

This consensus focuses on severe and critical coronavi-rus disease 2019(COVID-19)mainly based on the consideration that mortality of severe and critical cases is higher than mild and mo derate cases of COVID-19.Severe patients usually developed dyspnea and/or hypoxemia in a short period of time,and in some cases progressively developed respiratory failure,septic shock,coagulation disorders,and multi-organ dysfunction.

Expert consensus on the diagnosis and treatment of severe and critical coronavirus disease 2019(COVID-19)

Introduction Coronavirus disease 2019(COVID-19),a disease caused by severe acute respiratory syndrome-coronavirus-2(SARS-CoV-2),is highly contagious[1]and has developed into a global pan-demic.Up to July 1,2022,COVID-19 has affected>200 coun-tries and regions across the globe and caused 545,226,550 con-firmed cases and 6334,728 deaths,[2]seriously compromising human life,public properties.

Identification and validation of prognostic factors in patients with COVID-19: A retrospective study based on artificial intelligence algorithms

Background:Novel coronavirus disease 2019(COVID-19)is an ongoing global pandemic with high mortality.Although several studies have reported different risk factors for mortality in patients based on traditional analytics,few studies have used artificial intelligence(AI)algorithms.This study investigated prognostic factors for COVID-19 patients using AI methods.Methods:COVID-19 patients who were admitted in Wuhan Infectious Diseases Hospital from December 29,2019 to March 2,2020 were included.The whole cohort was randomly divided into training and testing sets at a 6:4 ratio.Demographic and clinical data were analyzed to identify predictors of mortality using least absolute shrinkage and selection operator(LASSO)regression and LASSO-based artificial neural network(ANN)models.The predictive performance of the models was evaluated using receiver operating characteristic(ROC)curve analysis.Results:A total of 1145 patients(610 male,53.3%)were included in the study.Of the 1145 patients,704 were assigned to the training set and 441 were assigned to the testing set.The median age of the patients was 57 years(range:47-66 years).Severity of illness,age,platelet count,leukocyte count,prealbumin,C-reactive protein(CRP),total bilirubin,Acute Physiology and Chronic Health Evaluation(APACHE)II score,and Sequential Organ Failure Assessment(SOFA)score were identified as independent prognostic factors for mortality.Incorporating these nine factors into the LASSO regression model yielded a correct classification rate of 0.98,with area under the ROC curve(AUC)values of 0.980 and 0.990 in the training and testing cohorts,respectively.Incorporating the same factors into the LASSO-based ANN model yielded a correct classification rate of 0.990,with an AUC of 0.980 in both the training and testing cohorts.Conclusions:Both the LASSO regression and LASSO-based ANN model accurately predicted the clinical outcome of patients with COVID-19.Severity of illness,age,platelet count,leukocyte count,prealbumin,CRP,total bilirubin,APACHE II score,and SOFA score were identified as prognostic factors for mortality in patients with COVID-19.

Journal of Intensive Medicine:A leading forum for breakthroughs and progress in critical care medicine

Dear Readers,Critical care medicine is a discipline that was established in the early 1980s in China.Nearly 40 years later,its importance is widely recognized and it has been developed as a second-tier discipline with its own systems of clinical practice,teaching,and research.Critical care medicine has seen rapid progress in the last decade and has played an important role in emerging public health events,and is expected to further evolve in the post-pandemic era.