基于改进N-K模型的地铁盾构掘进安全风险耦合研究

为预防和控制地铁盾构掘进施工过程中的关键安全风险,并精准判断哪些风险耦合情境是导致事故发生的显著情境,提出改进N-K模型研究地铁盾构掘进安全风险耦合;综合运用文献研究、事故案例、专家访谈等方法,辨识地铁盾构掘进的关键安全风险因素;基于N-K模型提出新的地铁盾构掘进安全风险耦合评估模型,并选用安全事故案例验证该模型的适用性。结果表明:辨识得到地铁盾构掘进关键安全风险因素清单,包括4类一级风险因素,21个二级风险因素;地铁盾构掘进施工安全风险随着耦合因素种类的增加而变大,4因素风险耦合值最高,3因素风险耦合值次之,双因素风险耦合值最低,作业人员安全意识薄弱和机械故障参与作用的耦合情境更容易发生安全事故。

多发性骨髓瘤患者的血清PINP、DKK1和SFRP3水平及其临床意义

目的探讨多发性骨髓瘤(MM)患者的血清I型原胶原氨基端前肽(PINP)、dickkopf Wnt信号通路抑制因子1(DKK1)和分泌型卷曲相关蛋白3(SFRP3)水平及其临床意义。方法纳入150例MM患者(MM组)及150健康体检者(对照组)。比较两组研究对象之间、不同临床分期MM患者之间、不同临床疗效MM患者之间的血清DKK1、PINP、SFRP3水平。采用Logistic回归模型分析治疗前血清DKK1、PINP和SFRP3水平与MM患者临床疗效的关系。采用受试者工作特征(ROC)曲线分析治疗前血清DKK1、PINP和SFRP3水平对MM患者临床疗效的预测效能。结果MM组患者治疗前血清DKK1、PINP和SFRP3水平高于对照组(P<0.05);Ⅰ期、Ⅱ期、Ⅲ期MM患者治疗前血清DKK1、PINP、SFRP3水平依次升高(P<0.05);有效组患者治疗前血清DKK1、PINP、SFRP3水平低于无效组(P<0.05)。治疗前血清DKK1、SFRP3、PINP水平升高是影响MM患者临床疗效的独立危险因素(P<0.05)。治疗前血清DKK1和SFRP3水平对MM患者临床疗效无预测价值(曲线下面积<0.5,P>0.05),而治疗前血清PINP水平对MM患者的临床疗效有一定的预测价值(曲线下面积=0.663,P<0.05)。结论MM患者治疗前的血清DKK1、PINP和SFRP3水平高于健康人群,且与疾病严重程度有关,是MM患者临床疗效的影响因素。治疗前血清PINP水平对预测MM患者的临床疗效有一定的价值。

Recurrence in node-negative advanced gastric cancer:Novel findings from an in-depth pathological analysis of prognostic factors from a multicentric series

AIM To analyze the clinicopathological characteristics of patients with both node-negative gastric carcinoma and diagnosis of recurrence during follow-up. METHODS We enrolled 41 patients treated with curative gastrectomy for p T2-4 a N0 gastric carcinoma between 1992 and 2010,who developed recurrence(Group 1). We retrospectively selected this group from the prospectively collected database of 4 centers belonging to the Italian Research Group for Gastric Cancer,and compared them with 437 p T2-4 a N0 patients without recurrence(Group 2). We analyzed lymphatic embolization,microvascular infiltration,perineural infiltration,and immunohistochemical determination of p53,Ki67,and HER2 in Group 1 and in a subgroup of Group 2(Group 2 bis) of 41 cases matched with Group 1 according to demographic and pathological characteristics. RESULTS T4 a stage and diffuse histotype were associated with recurrence in the group of p N0 patients. In-depth pathological analysis of two homogenous groups of p N0 patients,with and without recurrence during longterm follow-up(groups 1 and 2 bis),revealed two striking patterns: lymphatic embolization and perineural infiltration(two parameters that pathologists can easily report),and p53 and Ki67,represent significant factors for recurrence.CONCLUSION The reported pathological features should be considered predictive factors for recurrence and could be useful to stratify node-negative gastric cancer patients for adjuvant treatment and tailored follow-up.

CTRP3联合NT-proBNP对MVD患者发生HHcy的预测价值

目的探讨补体C1q/肿瘤坏死因子相关蛋白3(CTRP3)联合N末端B型利钠肽前体(NT-proBNP)对冠状动脉(冠脉)多支病变(MVD)患者发生高同型半胱氨酸血症(HHcy)的预测价值。方法回顾性分析200例MVD患者的临床资料,根据血浆同型半胱氨酸(Hcy)水平是否>15μmol/L分为高Hcy组(111例)和正常Hcy组(89例)。比较两组基线资料[年龄、性别、冠心病病程、吸烟史、糖尿病病史、高血压病史、体质量指数(BMI)],生化指标(NT-proBNP、尿酸(UA)、甘油三酯(TG)、总胆固醇(TC)、高密度脂蛋白胆固醇(HDL-C)、低密度脂蛋白胆固醇(LDL-C)、Hcy、CTRP3),采用二元Logistic回归分析法分析影响MVD患者发生HHcy危险因素,绘制受试者工作特征(ROC)曲线分析CTRP3联合NT-proBNP对MVD患者发生HHcy的预测效能。结果两组年龄、高血压病史、BMI、UA、TG、TC、HDL-C比较均无统计学差异(P>0.05);高Hcy组男性患者数量70例、冠心病病程(6.66±4.49)年、吸烟史55例、糖尿病病史60例,均大于正常Hcy组的36例、(3.67±2.31)年、28例、17例,NT-proBNP(5234.95±7476.76)pg/ml、LDL-C(3.55±0.95)mmol/L、Hcy(44.75±12.48)μmol/L均高于正常Hcy组的(1296.94±3864.78)pg/ml、(2.95±0.88)mmol/L、(10.58±2.80)μmol/L,CTRP3(65.20±13.61)μg/L低于正常Hcy组的(88.69±14.94)μg/L,两组间比较差异均具有统计学意义(P<0.05)。多因素Logistic回归分析显示:男性[OR=3.745,95%CI=(1.398,10.030)]、糖尿病病史[OR=3.262,95%CI=(1.264,8.417)]、冠心病病程[OR=1.194,95%CI=(1.022,1.394)]、LDL-C[OR=2.254,95%CI=(1.337,3.800)]为导致MVD患者发生HHcy的独立危险因素,而CTRP3[OR=0.902,95%CI=(0.873,0.933)]为其独立保护因素(P<0.05)。ROC曲线结果显示:CTRP3联合NT-proBNP预测MVD患者发生HHcy的AUC为0.901,敏感度为83.8%,特异度为86.5%,优于LDL-C、NT-proBNP或CTRP3单独预测(P<0.05)。结论性别、糖尿病病史、冠心病病程、LDL-C为导致MVD患者发生HHcy的独立危险因素,而CTRP3为其独立保护因素。血清CTRP3联合NT-proBNP可提高MVD患者发生HHcy的预测价值。

基于N-K模型的石化储罐事故风险耦合度分析

为预防石化储罐事故,通过收集212份石化储罐事故报告,将事故风险因素归纳为人为、设备、环境、管理4个类别,利用N-K模型分析事故风险因素之间的耦合作用,并运用N-K模型计算各种耦合模式下的风险耦合度,得出了石化储罐事故风险因素的耦合关系及耦合作用规律。结果表明,随着参与耦合的因素增多,风险耦合值总体呈现上升趋势;人为因素与其它因素耦合更容易导致事故;石化储罐区事故各风险因素之间的耦合作用程度相比其它行业更高。研究结果可为石化企业储罐事故管控提供依据和参考。

MAXIMAL NILPOTENT IDEALS AND ISOMORPHISMS OF LARGE SUBALGEBRAS OF NEST ALGEBRAS

Let N be a nest of projections on a Hilbert space H and T(N) be the corresponding nest algebra. Let A be a large subalgebra of T(N). It is proved that any maximal n-nilpotent ideal of A is in the form of A∩R F,where F is a finite subnest of N and R F is the Jacobson radical of T(F).Using this result can prove that two large subalgebras are isomorphic if and only if the corresponding nests are similar.

Tumor necrosis factor-α mediates JNK activation response to intestinal ischemia-reperfusion injury

AIM:To investigate whether tumor necrosis factor-α(TNF-α)mediates ischemia-reperfusion(I/R)-induced intestinal mucosal injury through c-Jun N-terminal kinase(JNK)activation.METHODS:In this study,intestinal I/R was induced by 60-min occlusion of the superior mesenteric artery in rats followed by 60-min reperfusion,and the rats were pretreated with a TNF-α inhibitor,pentoxifylline,or the TNF-α antibody infliximab.After surgery,part of the intestine was collected for histological analysis.The mucosal layer was harvested for RNA and protein extraction,which were used for further real-time polymerase chain reaction,enzyme-linked immunosorbent assay and Western blotting analyses.The TNF-α expression,intestinal mucosal injury,cell apoptosis,activation of apoptotic protein and JNK signaling pathway were analyzed.RESULTS:I/R significantly enhanced expression of mucosal TNF-α at both the mRNA and protein levels,induced severe mucosal injury and cell apoptosis,activated caspase-9/caspase-3,and activated the JNK signaling pathway.Pretreatment with pentoxifylline markedly downregulated TNF-α at both the mRNA and protein levels,whereas infliximab pretreatment did not affect the expression of TNF-α induced by I/R.However,pretreatment with pentoxifylline or infliximab dramatically suppressed I/R-induced mucosal injury and cell apoptosis and significantly inhibited the activation of caspase-9/3 and JNK signaling.CONCLUSION:The results indicate there was a TNFα-mediated JNK activation response to intestinal I/R injury.

Factors Associated with Death Due to 2009 Influenza A (H1N1) Virus Infection and Acute Respiratory Distress Syndrome in Beijing, 2009-2011

Objective Patients with H1N1 virus infection were hospitalized and quarantined, and some of them developed into acute respiratory failure, and were transfered to the medical intensive care unit of Beijing Ditan Hospital, Capital Medical University in Beijing, China. Methods The clinical features and preliminary epidemiologic findings among 30 patients with confirmed H1N1 virus infection who developed into acute respiratory failure for ventilatory support were investigated. Results A total of 30 patients(37.43 ± 18.80 years old) with 2009 influenza A(H1N1) related acute respiratory distress syndrome(ARDS) received treatment with mechanical ventilation, 15 cases of whom were male and 17 cases died of ARDS. Fatal cases were significantly associated with an APACHE Ⅱ score(P = 0.016), but not with PaO 2 /FIO 2(P = 0.912) and chest radiograph(P = 0.333). The most common complication was acute renal failure(n = 9). Five patients received extracorporeal membrane oxygenation(ECMO), 3 of whom died and the others survived. The major causes of death were multiple organ dysfunction syndrome(MODS)(39%), intractable respiratory failure(27%) and sepsis(20%). Conclusions Most patients with respiratory failure due to influenza A(H1N1) virus infection were young, with a high mortality, particularly associated with APACHE Ⅱ score, secondary infection of lung or type 2 diabetes mellitus.

Hypoxia inducible factor-1alpha mediates protection of DL-3-n-butylphthalide in brain microvascular endothelial cells against oxygen glucose deprivation-induced injury

Studies have demonstrated that DL-3-n-butylphthalide can significantly alleviate oxygen glucose deprivation-induced injury of human umbilical vein endothelial cells at least partly associated with its enhancement on oxygen glucose deprivation-induced hypoxia inducible factor-1α expression.In this study,we hypothesized that DL-3-n-butylphthalide can protect against oxygen glucose deprivation-induced injury of newborn rat brain microvascular endothelial cells by means of upregulating hypoxia inducible factor-1α expression.MTT assay and Hoechst staining results showed that DL-3-n-butylphthalide protected brain microvascular endothelial cells against oxygen glucose deprivation-induced injury in a dose-dependent manner.Western blot and immunofluorescent staining results further confirmed that the protective effect was related to upregulation of hypoxia inducible factor-1α.Real-time RT-PCR reaction results showed that DL-3-n-butylphthalide reduced apoptosis by inhibiting downregulation of pro-apoptotic gene caspase-3 mRNA expression and upregulation of apoptosis-executive protease bcl-2 mRNA expression;however,DL-3-n-butylphthalide had no protective effects on brain microvascular endothelial cells after knockdown of hypoxia inducible factor-1α by small interfering RNA.These findings suggest that DL-3-n-butylphthalide can protect brain microvascular endothelial cells against oxygen glucose deprivation-induced injury by upregulating bcl-2 expression and downregulating caspase-3 expression though hypoxia inducible factor-1α pathway.

Severe Novel Influenza A(H1N1) in Shanghai:Clinical Features, Therapeutic Management and Risk Factors for Mortality

Objective To analyze the clinical features,therapeutic management and risk factors for mortality of patients with severe novel A(H1N1)influenza in Shanghai,China.Methods All patients were diagnosed by influenza A(H1N1)virus mRNA detection.Chest CT scan,routine blood,hepatic function,humoral and cellular immunity,sputum smears,and sputum cultures were performed.Logistic analysis was applied to identify risk factors for mortality.Results Total of 68 patients were enrolled in this study,the primary clinical symptoms including cough(66,97.1%),expectoration(41,60.3%),and polypnea(41,60.3%).Altogether,37(54.4%)and 11(16.2%)patients were infected with bacterial and fungal,respectively.CT scan demonstrated that 67(98.6%)patients had pneumonia.Oxygen therapy,oseltamivir,antibiotic and antifungal drugs were performed in 68(100%),66(97.1%),39(57.4%),and 11(16.2%)patients,respectively.Finally,4 of 68 patients died.Logistic analysis demonstrated that there was a significant correlation between the percentage of neutrophils and mortality before therapy and direct bilirubin content and mortality after therapy,respectively.Conclusions Patients with severe H1N1 influenza were susceptible to bacterial and/or fungal infection.The risk factors for mortality may be associated with pre-therapeutic neutrophil percentage and post-therapeutic direct bilirubin content.

Factors controlling N_2O and CH_4 fluxes in mixed broad-leaved/Korean pine forest of Changbai Mountain, China

Using the closed chamber technique, the in situ measurements of N2O and CH4 fluxes was conducted in a broad-leaved Korean pine mixed forest ecosystem in Changbai Mountain, China. from June 1994 to october 1995. The relationships between fluxes (N2O and CH4) and some major environmental factors (temperature, soil water content and soil availabIe nitrogen) were studied. A significant positive correlation between Nzo emission and air/soil temperature was observed, but no significant correIation was found between N2O emission and soil water content (SWC). This result showed that temperature was an important controlling factor of N2O flux. There was a significant correlation between CH4 uptake and SWC, but no significant correlation was found between CH4 uptake and temperature. This suggested SWC was an important factor controlling CH4 uptake. The very significant negative correlation between logarithmic N2O flux and soil nitrate concentration, significant negative correlation between CH4 flux and soil ammonium content were also found.

Electroacupuncture promotes peripheral nerve regeneration after facial nerve crush injury and upregulates the expression of glial cell-derived neurotrophic factor

The efficacy of electroacupuncture in the treatment of peripheral facial paralysis is known, but the specific mechanism has not been clarified. Glial cell-derived neurotrophic factor(GDNF) has been shown to protect neurons by binding to N-cadherin. Our previous results have shown that electroacupuncture could increase the expression of N-cadherin mRNA in facial neurons and promote facial nerve regeneration. In this study, the potential mechanisms by which electroacupuncture promotes nerve regeneration were elucidated through assessing the effects of electroacupuncture on GDNF and N-cadherin expression in facial motoneurons of rabbits with peripheral facial nerve crush injury. New Zealand rabbits were randomly divided into a normal group(normal control, n = 21), injury group(n = 45) and electroacupuncture group(n = 45). Model rabbits underwent facial nerve crush injury only. Rabbits in the electroacupuncture group received facial nerve injury, and then underwent electroacupuncture at Yifeng(TE17), Jiache(ST6), Sibai(ST2), Dicang(ST4), Yangbai(GB14), Quanliao(SI18), and Hegu(LI4; only acupuncture, no electrical stimulation). The results showed that in behavioral assessments, the total scores of blink reflex, vibrissae movement, and position of apex nasi, were markedly lower in the EA group than those in the injury group. Hematoxylin-eosin staining of the right buccinator muscle of each group showed that the cross-sectional area of buccinator was larger in the electroacupuncture group than in the injury group on days 1, 14 and 21 post-surgery. Toluidine blue staining of the right facial nerve tissue of each group revealed that on day 14 post-surgery, there was less axonal demyelination and fewer inflammatory cells in the electroacupuncture group compared with the injury group. Quantitative real time-polymerase chain reaction showed that compared with the injury group, N-cadherin mRNA levels on days 4, 7, 14 and 21 and GDNF mRNA levels on days 4, 7 and 14 were significantly higher in the electroacupuncture group. Western blot assay displayed that compared with the injury group, the expression of GDNF protein levels on days 7, 14 and 21 were significantly upregulated in the electroacupuncture group. The histology with hematoxylin-eosin staining and Nissl staining of brainstem tissues containing facial neurons in the middle and lower part of the pons exhibited that on day 7 post-surgery, there were significantly fewer apoptotic neurons in the electroacupuncture group than in the injury group. By day 21, there was no significantly difference in the number of neurons between the electroacupuncture and normal groups. Taken together, these results have confirmed that electroacupuncture promotes regeneration of peripheral facial nerve injury in rabbits, inhibits neuronal apoptosis, and reduces peripheral inflammatory response, resulting in the recovery of facial muscle function. This is achieved by up-regulating the expression of GDNF and N-cadherin in central facial neurons.

Effects of L-3-n-butylphthalide on caspase-3 and nuclear factor kappa-B expression in primary basal forebrain and hippocampal cultures after beta-amyloid peptide 1-42 treatment

BACKGROUND： L-3-n-butylphthalide （L-NBP） can inhibit phosphorylation of tau protein and reduce the neurotoxicity of beta-amyloid peptide 1-42 （Aβ1-42）. OBJECTIVE： To observe the neuroprotective effects of L-NBP on caspase-3 and nuclear factor kappa-B （NF- K B） expression in a rat model of Alzheimer＇s disease. DESIGN, TIME AND SETTING： A cell experiment was performed at the Central Laboratory of Provincial Hospital affiliated to Shandong University between January 2008 and August 2008. MATERIALS： L-NBP （purity 〉 98%） was provided by Shijiazhuang Pharma Group NBP Pharmaceutical Company Limited. Aβ1-42, 3-[4,5-dimethylthiazolo-2]-2,5 iphenyltetrazolium bromide （MTT）, and rabbit anti-Caspase-3 polyclonal antibody were provided by Cell Signaling, USA; goat anti-choactase and rabbit anti-NF- kB antibodies were provided by Santa Cruz, USA. METHODS： Primary cultures were generated from rat basal forebrain and hippocampal neurons at 17 or 19 days of gestation. The cells were assigned into five groups： the control group, the Aβ1-42 group （2 μmol/L）, the Aβ1-42 ＋ 0.1 μmol/L L-NBP group, the Aβ1-42 ＋ 1 μ mol/L L-NBP group, and the Aβ1-42 ＋ 10μmol/L L-NBP group. The neurons were treated with Aβ1-42 （2 μmol/L） alone or in combination with L-NBP （0.1, 1, 10 μmol/L） for 48 hours. Cells in the control group were incubated in PBS. MAIN OUTCOME MEASURES： Morphologic changes were evaluated using inverted microscopy, viability using the M-I-I- method, and the changes in caspase-3 and NF- k B expression using Western blot. RESULTS： Induction with Aβ1-42 for 48 hours caused cell death and soma atrophy, and increased caspase-3 and NF- K B expression （P 〈 0.05）. L-NBP blocked these changes in cell morphology, decreased caspase-3 and NF- k B expression （P 〈 0.05）, and improved cell viability, especially at the high dose （P 〈 0.05）. CONCLUSION： AI3^-42 is toxic to basal forebrain and hippocampal primary neurons; L-NBP protects against this toxicity and inhibits the induction of caspase-3 and NF- K B expression.

Assessment of the crucial factors influencing the responses of ammonia and nitrous oxide emissions to controlled release nitrogen fertilizer: A meta-analysis

Reducing ammonia(NH3) and nitrous oxide(N2O) emissions have great effects on mitigating nitrogen(N) nutrient loss and greenhouse gas emissions. Controlled release urea(CRU) can control the N release rate, which reduces reactive N loss and increases nitrogen use efficiency relative to conventional urea(CU). However, the crucial factors influencing the responses of NH3and N2O emissions to CRU relative to CU are still unclear. In this study, we evaluated the responses of NH3and N2O emissions to CRU based on collected field data with a meta-analysis. CRU reduced the NH3and N2O emissions by 32.7 and 25.0% compared with CU, respectively. According to subgroup analysis, CRU presented better mitigation of NH3and N2O emissions in soils with pH 6.5–7.5(–47.9 and –23.7%) relative to either pH<6.5(–28.5and –21.4%) or pH>7.5(–29.3 and –17.3%), and in the rice season(–34.8 and –29.1%) relative to the wheat season(–19.8 and –22.8%). The responses of NH3and N2O emissions to CRU increased from rainfed(–30.5 and –17.0%) to irrigated(–32.5 and –22.9%), and then to paddy(–34.8 and –29.1%) systems. In addition, the response of N2O emission mitigation increased with increases in soil total nitrogen(TN);however, soil TN did not significantly affect the response of NH3volatilization. The reduction in NH3emission was greater in sandy-textured soil(–57.7%) relative to loam-textured(–32.9%) and clay-textured(–32.3%) soils, whereas soil texture did not affect N2O emission. Overall, CRU was a good option for reducing the NH3and N2O emissions relative to CU in agricultural production. This analysis improves our understanding of the crucial environmental and management factors influencing the mitigation of NH3and N2O emissions under CRU application, and these site-specific factors should be considered when applying CRU to reduce reactive N loss and increase NUE.

Identification of Differentially Expressed Proteins and Validation of the Changes of N-Ethylmaleimide-sensitive Factor in Rats with Focal Cerebral Ischemia after Transection of the Cervical Sympathetic Trunk

Stellate ganglion blockade （SGB） protects patients from focal cerebral ischemic injury, and transection of the cervical sympathetic trunk （TCST） in a rat model can mimic SGB in humans. The purpose of this study was to investigate the mechanisms underlying the neuroprotective effects of TCST on neuronal damage in the hippocampus in a rat model of middle cerebral artery occlusion （MCAO） in an attempt to elucidate the neuroprotective effects of SGB. The modified method of Zea Longa was used to establish the permanent MCAO model. Male Wistar rats were randomly divided into three groups： sham-operated group, MCAO group, and TCST group. The animals in TCST group were sacri- ficed 48 h after TCST which was performed after the establishment of the MCAO model. Proteins were extracted from the ipsilateral hippocampus and analyzed by two-dimensional difference gel electropho- resis （2D-DIGE） and peptide mass fingerprinting （PMF）. The levels of N-ethylmaleimide-sensitive fac- tor （NSF） were measured as well. The results showed that 11 types of proteins were identified by 2D- DIGE. The expressions of eight proteins were changed both in the sham-operated and TCST groups, and the expressions of the other three proteins were changed in all three groups. Moreover, the expres- sion of NSF was higher in the TCST group than in the MCAO group but lower in the MCAO group than in sham-operated group. The ratio of NSF expression between the MCAO group and sham- operated group was -1.37 （P〈0.05）, whereas that between the TCST group and MCAO group was 1.35 （P〈0.05）. Our results imply that TCST increases the expression of NSF in the hippocampus of adult rats with focal cerebral ischemia, which may contribute to the protection of the injured brain. Our study pro- vides a theoretical basis for the therapeutic application of SGB to patients with permanent cerebral ischemia.

EFFECT OF GEAR WIDTH AND HELIX ANGLE ON FACTOR OF DYNAMIC LOAD OF DOUBLE CIRCULAR ARC HELICAL GEARING

Based on theory of mechanical dynamics, meshing characteristic as well as thedynamic model of double circular arc helical gearing, an analysis approach and a computer programhave been developed for studying the state of dynamic load and factor of dynamic load of thegearing, the changing situation of dynamic load and dynamic load factor vs some affecting factorssuch as gear width, helix angle and accuracy grade etc are investigated. A series of conclusions areobtained: ①With the increasing in the values of gear width, the dynamic load factor appears slowdecreasing tendency in most region of gear width. ②When the accuracy grades of the gearing areimproved, the values of dynamic load factor decrease. ③The value of dynamic load factor appears adecreasing tendency with the increasing of value of helix angle at the same ratio of criticalrotational speed.

Some Results on (1,2<i>n</i>– 1)-Odd Factors

Let G be a graph. If there exists a spanning subgraph F such that dF(x) ∈ {1,3,…2n – 1}, then is called to be (1,2n – 1)-odd factor of G. Some sufficient and necessary conditions are given for G – U to have (1,2n – 1)-odd factor where U is any subset of V(G) such that |U| = k.

Simulation of Modes of Ionosphere Alfven Resonator with High Quality Factors in the Case of Oblique Geomagnetic Field

The properties of the ionosphere Alfvén resonator (IAR) in the general case of an oblique geomagnetic field are investigated. The modes at the frequencies f = 0.2 - 10 Hz well localized within the ionosphere are considered, which are important for the lithosphere—ionosphere coupling. An attention is paid to the modes with quite high quality factors , where . A proper selection of calculated eigenfrequencies has been realized. Two independent simulation algorithms have been proposed. The resonant frequencies and the profiles of magnetic field components of the modes have been calculated. The modulation of electron and ion concentrations at the heights 170 - 230 km leads to essential shifting the resonant frequencies.

Patterns and driving factors of leaf C,N,and P stoichiometry in two forest types with different stand ages in a mid-subtropical zone

Background:Carbon(C),nitrogen(N),and phosphorus(P)stoichiometry is a key indicator of nutrient utilization in plants,and C/N/P ratios are related to the life histories and adaptation strategies of tree species.However,no consensus has been reached on how leaf stoichiometric characteristics are affected by forest type and stand ages.The relationships between leaf stoichiometry and geographical,meteorological,and soil factors also remain poorly understood.Methods:Leaf and soil were sampled from forest stands of different age groups(young,middle-aged,near-mature,and mature)in two forest types(Chinese fir(Cunninghamia lanceolata)forests and evergreen broadleaved forests).The relationships between leaf C,N,and P stoichiometric parameters and geographical,meteorological,and soil factors were analysed by using redundancy analysis(RDA)and stepwise linear regression analysis.Results:Leaf C concentrations peaked in the near-mature stands with increasing age irrespective of forest type.Leaf N and P concentrations fluctuated with a rising trend in Chinese fir forests,while decreased first and increased later from young to mature phases in natural evergreen broadleaved forests.Chinese fir forests were primarily limited by N and P,while natural evergreen broadleaved forests were more susceptible to P limitation.Leaf C,N,and P stoichiometric characteristics in Chinese fir forests were mainly affected by the soil total P concentration(SP),longitude(LNG),growing season precipitation(GSP)and mean temperature in July(JUT).The leaf C concentration was mainly affected by GSP and JUT;leaf N and P concentrations were both positively correlated with LNG;and leaf P was positively correlated with SP.In evergreen broadleaved forests,however,leaf stoichiometric parameters displayed significant correlations with latitude(LAT)and mean annual precipitation(MAP).Conclusions:Leaf stoichiometry differed among forest stands of different age groups and forest types.Leaf C,N,and P stoichiometry was primarily explained by the combinations of SP,LNG,GSP and JUT in Chinese fir forests.LAT and MAP were the main controlling factors affecting the variations in the leaf C,N,and P status in natural evergreen broadleaved forests,which supports the temperature-plant physiological hypothesis.These findings improve the understanding of the distribution patterns and driving mechanisms of leaf stoichiometry linked with stand age and forest type.

Parametric Equation of Stress Concentration Factor for Circular X-Joints Under Axial Loads

In engineering practice, tubular X-joints have been widely used in offshore structures. The fatigue failure of tubular X-joints in offshore engineering is mainly caused by axial tensile stress. In this study, the stress concentration factor distribution along the weld toe in the hot spot stress region for tubular X-joints subject to axial loads have been analyzed by use of finite element method. Through numerical analysis, it has been found that the peak stress concentration factor is located at the saddle position. Thereafter, 80 models have been analyzed, and the effect of the geometric parameters of a tubular X-joint on the stress concentration factor has been investigated. Based on the experimental values of the numerical stress concentration factor, a parametric equation to calculate the stress concentration factor of tubular X-joints has been proposed. The accuracy of this equation has been verified against the requirement of the Fatigue Guidance Review Panel, and the proposed equation is found capable of producing reasonably accurate stress concentration factor values for tubular X-joints subject to axial loads.