Siliceous plankton dominate primary and new productivity during the onset of El Niño conditions in the Santa Barbara Basin, California

The potential for carbon export and the role of siliceous plankton in the cycling of C and N was assessed in natural plankton assemblages in the Santa Barbara Basin, California, by examining uptake rates of inorganic carbon, nitrate and silicic acid. In April–August 1997, the concentrations of chlorophyll a, particulate organic carbon, particulate organic nitrogen and biogenic silica were measured twice monthly, and results revealed the occurrence of at least three blooms, the largest in June. Particulate elemental ratios of C, N and Si were similar to ratios of nutrient-replete diatoms, suggesting that they dominated this bloom. Mean integrated rates of carbon, nitrate and silicon uptake during the 4-month study period are similar to other productive coastal and upwelling regions (103, 8.3 and 13 mmol m⁻² day⁻¹, respectively). New production rates were twice as high as previously reported in this region and indicate that high rates of new production along eastern boundary currents are not confined to the major coastal upwelling regions. C/NO₃⁻, Si/NO₃⁻ and Si/C uptake ratios varied widely, and mean integrated ratios were 14±5.4, 1.6±1.0 and 0.12±0.07 (S.D.), respectively. That mean C/NO₃⁻ uptake ratio corresponds to an f-ratio of about 0.5 indicating a large potential for particulate export. Based on the average Si/NO₃⁻ and Si/C uptake ratios, diatoms could perform all of the primary production and nitrate uptake that occurred during the study; these rates also suggest that export is controlled by diatoms in this system. The mean Si/C biomass ratio was lower than the mean Si/C uptake ratio, consistent with the preferential export of Si relative to C observed in sediment traps in the basin. The study took place during a period of surface-water warming, with nitrate and silicic acid concentrations decreasing throughout the onset of the 1997–1998 El Niño conditions. Although diatoms contributed less to particulate biomass during the low nutrient conditions, high f-ratios (0.33–0.66) were maintained.     

Patterns and controls of chlorophyll-a and primary productivity cycles in the Southern California Bight

Factors that influence the magnitude and the depth of the chlorophyll maximum layer in the ocean off Southern California are explored using observations from the long-term California Cooperative Oceanic Fisheries Investigations (CalCOFI) program. The data record is sufficiently long to reveal patterns not always evident from single stations or single cruises. Processes such as coastal wind-driven upwelling, geostrophic circulation, and annual physical and chemical cycles are illustrated to demonstrate their effect on euphotic zone nutrient availability, and subsequent phytoplankton biomass and primary productivity. In this area, where the influence of wind-driven upwelling is spatially restricted and advected waters are generally nutrient depleted, geostrophically induced upwelling and winter convection become important in determining spatial and temporal patterns of phytoplankton.     

Modeling the time to the next primary and secondary incident: A semi-Markov stochastic process approach

Incidents are notorious for their delays to road users. Secondary incidents – i.e., incidents that occur within a certain temporal and spatial distance from the first/primary incident – can further complicate clearance and add to delays. While there are numerous studies on the empirical analysis of incident data, to the best of our knowledge, an analytical model that can be used for primary and secondary incident management planning that explicitly considers both the stochastic as well as the dynamic nature of traffic does not exist. In this paper, we present such a complementary model using a semi-Markov stochastic process approach. The model allows for unprecedented generality in the modeling of stochastics during incidents on freeways. Particularly, we relax the oftentimes restrictive Poisson assumption (in the modeling of vehicle arrivals, vehicle travel times, and incidence occurrence and recovery times) and explicitly model secondary incidents. Numerical case studies are provided to illustrate the proposed model.     

血清金属蛋白酶组织抑制因子-1和抑制因子-2在不同肝病中的意义

目的　建立一种改良固相致敏红细胞吸附技术 (SPASE) ,用于快速检测各种肝病患者血清中金属蛋白酶组织抑制因子 1 , 2 (TIMP 1 ,TIMP 2 ) ,了解血清TIMP 1和TIMP 2在各种肝病患者中的意义。方法　用TIMP 1和TIMP 2单克隆抗体分别包被微量血凝板 ,加热冲洗后加入待检血清标本 ,最后加入单克隆抗体致敏红细胞。用致敏红细胞作为指示系统 ,观察红细胞吸附状况来判定结果。结果　SPASE法全过程仅需要 2 5～ 3h ,共检测 6 5 4例肝病患者血清标本 ,TIMP 1和TIMP 2阳性率分别为急性肝炎组 1 7 3 9%、1 4 1 3 % ;慢性肝炎组 3 3 1 9%、2 7 88% ;肝硬化组 82 84%、6 7 1 6 % (P <0 0 0 1 )。结论　TIMP 1和TIMP 2表达的变化可作为肝纤维化较为有用的诊断指标 ,TIMP 1的诊断意义更大。SPASE法具有较高的敏感性、特异性和快速性 ,不需复杂的仪器设备 ,操作简单 ,尤适于医院及基层医疗单位。     

某公路隧道初期支护变形开裂分析

针对某公路隧道初期支护出现变形开裂并侵界的情况,通过对灾害原因的具体分析,提出了相关的工程处理措施和注意事项,为类似工程灾害的预防提供借鉴.     

关于国外公路项目前期设计特点分析

在海外总承包项目中,大部分前期设计存在基础资料不全,缺少地勘和测量等必要技术手段等不利条件,项目的标准、规范等边界条件也不确定.而为了满足企业投标报价、签订商务合同的需要,前期设计要求技术方案合理可行、工程数量基本准确、工程风险可控.因此,为了降低公路项目工程风险,应深入研究项目所在区域的具体情况及特点,积极推出、采用中国标准及规范,把握住设计深度,为企业提供满足其需要的设计成果.     

TIPS对肝血流动力学影响及并发症的观察

研究了经颈静脉肝内门体分流术（TIPS）对肝血流的影响和并发症的观察。对21例肝硬化门脉高压症患者实施TIPS治疗，采用超声多普勒检测门静脉主干血流速度、支架内血流速度，及核多功能仪检测肝总血流。结果表明，TIPS技术成功率85．7％，肝内分流道建立后，门静脉压力下降，门静脉流速增加，肝总血流减少不明显；一过性肝性脑病、支架狭窄，除与建立的分流道部位不同有关外，与血流动力学紊乱也有关系。     

肝硬化组织微卫星改变的临床研究

目的　研究微卫星改变 (microsatellitealteration ,MA)在肝硬化组织的发生情况及其与病毒性肝炎的关系。方法　运用聚合酶链式反应 -简单重复序列多态性方法 (PCR SSLP)对 30例肝硬化组织石蜡标本的微卫星不稳定性 (microsatelliteinstability ,MSI)和等位基因杂合性丢失 (lossofheterozygosity ,LOH)进行研究。 结果　 30例肝硬化组织中有 17例出现了MA(5 6 .7% ) ,其中至少有一个位点发生的MSI有 4例 (13.3% ) ,而有 15例至少有一个位点出现了LOH(5 0 % ) ,MA的发生与HBV感染及是否合并HCV感染无显著相关。结论　肝硬化作为肝癌的早期表现就已经存在有微卫星改变     

关于铁路通信同步网发展的探讨

铁路通信同步网分为时钟同步网和时间同步网。针对铁路同步网现状和存在的网络结构、覆盖、设备老化等问题进行分析,提出近期铁路同步网发展规划。出于未来通信对同步网的更高要求,从技术更新角度提出对远期同步网发展的考虑。     

Traditional Chinese medicine diagnosis and evaluation of the clinical effect in post-hepatitic cirrhosis based on fuzzy analysis

In view of the problem of traditional Chinese medicine (TCM) diagnosis, fuzzy comprehensive evaluation is introduced to the diagnosis and evaluation of the clinical effect of hepatitis. A new diagnosis and evaluation model of the TCM clinical effect standard was presented. The old disputed evaluation model by subjective analysis can be displaced by this objective method in its evaluation system. The foundation of this method is the fuzzy diagnosis model. This method has been realized to diagnose hepatitis and its values in practice has been validated through examples of clinical syndromes of post-hepatitic cirrhosis.