Ventilation and oxygen consumption in the spotted stargazer Genyagnus monopterygius †     

M. E. Forster  L. Starling 《新西兰海洋与淡水研究杂志》2013,47(2):135-140

As with other benthic fish which bury themselves in sand, in Genyagnus monopterygius it is the branchiostegal apparatus which makes the major contribution to ventilation of the gills. The prolonged abduction of the branchiostegal membranes draws water in through the mouth, and exhaled water moves away from the fish through mucus‐lined channels in the sand. The steady and continuous flow of water during ventilation may avoid detection of the stargazer by prey or predators. Associated with its sluggish habits and the low gill surface area available for gas exchange, Genyagnus has a low rate of oxygen consumption (15.8 ml kg^‐1 h^‐1 for a 100 g fish at 17°C). At partial pressures of oxygen (PO2) below 6 kPa (45 mm Hg) oxygen consumption is reduced, but the fish does not emerge from the sand until the PO2 falls below 2 kPa. There is evidence that the fish can sustain an oxygen debt. Respiration in the stargazer is discussed in relation to the fish's ability to withstand temporary hypoxia when it is stranded above the water level in the intertidal zone.  相似文献   

中国城市科教职能等级划分及空间分布研究   总被引：6，自引：0，他引：6  

王言荣  刘洁 《地理科学》2001,21(2):183-187

运用层次分析法和多指标加权求和方法得出中国城市科教职能综合评价指数，并用纳尔逊统计方法分析的结果作为科教职能等级划分的依据，把中国科教职能城市分为四个大级、六个亚级，据此分析得出中国科教中心城市的空间分布特征，无论从数量上还是从职能强度上都呈现出由东向西递减的趋势，且明显地偏集于环渤海区和华东区，针对其中存在的问题，提出了今后的发展对策；加快中西部地带科技和教育的发展，地方政府对中小型科教中心城市应给予政策倾斜和投入支持，以逐步缩小东西部的差距。  相似文献   

Levels of Organochlorine Pesticide Residues in Some Organs of the Ganges Perch, Lates calcarifer, from the Ganges–Brahmaputra–Meghna Estuary, Bangladesh     

Sardar Md Abdul Jabber  Yusuf Sharif Ahmed Khan  M. Saifur Rahman 《Marine pollution bulletin》2001,42(12)

Levels of organochlorine pesticide residues (p,p′ DDT, DDD, DDE, Aldrin, Dieldrin, Lindane, Heptachlor and BHC) were analysed in the dry and wet seasons in four organs (muscle, liver, gut and egg samples) of Ganges Perch, Lates calcarifer, collected during October–November–December, 1996 and May–June–July, 1997 from the Ganges–Brahmaputtra–Meghna estuary. The residues were analysed by using gas-chromatography (GC) in electron capture detector (ECD) mode and were verified by thin layer chromatography (TLC). Among the four organs analysed, the residues were found in the order egg > gut > muscle > liver. The pesticide residues were found in the order ∑DDT > Heptachlor >Dieldrin > Aldrin. Higher levels of residues were found during the dry season due to high lipid content in fishes. A positive correlation was observed between the pesticide residues (∑DDT and ∑OCs) and lipid contents of fish, and the correlation was found to be linear. The concentrations of pesticide residues in muscle, liver and gut were below the FAO/WHO (1993) recommended permissible limit except in eggs.  相似文献   

论广州名城传统中轴线   总被引：1，自引：0，他引：1  

杨宏烈  陈思访 《热带地理》2002,22(1):28-33

广州名城固有传统中轴线集直轴、曲轴、实轴、虚轴、路轴、绿轴、山水轴、文脉轴、网络坐标轴于一身 ,在城市自然地理与人文地理发展过程中不可他移。深刻认识其空间环境艺术、历史渊源、文化内涵 ,探讨其复兴、整治、拓展的规划手法 ,营造一个山水生态型的城市主题文化旅游集锦带 ,对切实保护名城、积极建设新区都具有重要的现实意义  相似文献   

Accounting seasonal nonstationarity in time series models for short-term ozone level forecast     

Sung Eun Kim  Ashok Kumar 《Stochastic Environmental Research and Risk Assessment (SERRA)》2005,19(4):241-248

Due to the nonlinear feature of a ozone process, regression based models such as the autoregressive models with an exogenous vector process (ARX) suffer from persistent diurnal behaviors in residuals that cause systematic over-predictions and under-predictions and fail to make accurate multi-step forecasts. In this article we present a simple class of the functional coefficient ARX (FARX) model which allows the regression coefficients to vary as a function of another variable. As a special case of the FARX model, we investigate the threshold ARX (TARX) model of Tong [Lecture notes in Statistics, Springer-Verlag, Berlin, 1983; Nonlinear time series: a dynamics system approach, Oxford University Press, Oxford, 1990] which separates the ARX model in terms of a variable called the threshold variable. In this study we use time of day as the threshold variable. The TARX model can be used directly for ozone forecasts; however, investigation of the estimated coefficients over the threshold regimes suggests polynomial coefficient functions in the FARX model. This provides a parsimonious model without deteriorating the forecast performance and successfully captures the diurnal nonstationarity in ozone data. A general linear F-test is used to test varying coefficients and the portmanteau tests, based on the autocorrelation and partial autocorrelation of fitted residuals, are used to test error autocorrelations. The proposed models were applied to a 2 year dataset of hourly ozone concentrations obtained in downtown Cincinnati, OH, USA. For the exogenous processes, outdoor temperature, wind speed, and wind direction were used. The results showed that both TARX and FARX models substantially improve one-day-ahead forecasts and remove the diurnal pattern in residuals for the cases considered.  相似文献   

工业磷矿石主要化学组分含量近似数学模型     

陶永和 《云南地质》2005,24(2):151-166

深入研究云南、中国及世界各地磷矿石物质成分基础上,揭示中外工业磷矿石化学组分与矿物化学组成的对应关系,建立工业磷矿石中主要化学组分含量之间函数定量数学模型。文中列举大量典型实例,可广泛应用于不同成因、产地的工业磷矿石化学组分分析、测试与预测,为磷矿石物质成分与质量研究构架一条快捷通道。  相似文献   

用实测风场资料提取基本气流   总被引：1，自引：1，他引：1       下载免费PDF全文

黄思训  张铭安洁 《应用气象学报》2004,15(5):572-578

该文从f平面线性无粘的二维Boussinesq方程组出发, 通过求取函数的极小值, 提出了从实测风场资料中提取基本气流的方案。用该方案提取的基本气流既满足控制方程, 同时又与实测风场之差其模的平方在垂直方向取平均后达到最小; 将实测风场与该基本气流相减, 可提取出扰动风场, 从而能研究基流的失稳问题和扰动场随时间的演变。该文还给出了该方案实际操作的数值计算方法, 并对实际个例进行了计算和分析, 实践表明用该方案提取基本气流是切实可行的。  相似文献   

前庭系统功能与震前动物行为异常     

施志远 《地震研究》1988,(5)

震前重力异常与震前声发射所需的地球物理条件相同,大体是伴生现象。所有的生物(从植物到人类)都能测知重力,但都离不开钙。重力改变相当于动物居处发生了高程变更。震前重力异常与动物异常在时空上有相关性。前庭系统受重力作用后可引起行为模式的改变。这启示我们;①地声监测与重力监测台网应并设;②研制整合的重力—地声监测地震仪;③研究、开发钙在重力仪中的功用和部件;④加强动物失重研究;⑤震前动物骚动的原因可能主要是重力异常和声发射,响应者是位听系统。  相似文献   

中国首台PET机的研制与正电子CT成像的新进展   总被引：1，自引：0，他引：1  

陈惟昌  朱国泓 《CT理论与应用研究》1994,3(2):42-47

正电子断面图像是最新的医学影象技术，它是通过研究正电子示踪核素标记的化合物在体内的动态分布，显示人体各部位的功能和代谢变化的图象。本文介绍正电子断层图的原理和应用以及我国科学工作者在推进中国ＰＥＴ研究工作的历程，重点介绍１９９２年以来我国第一台ＰＥＴ仪的研制过程、性能特点、应用概况及发展前景．  相似文献   

非线性混合边值问题及其抗差解     

杨元喜 《测绘学院学报》1994,(4)

本文从函数模型和随机模型两方面入手综合讨论大地测量混合边值问题及其解。函数模型方面，首先对混合边值问题进行了一般描述；继而分别建立了垂直边值和水平边值问题的二阶近似模型；随机模型方面，考虑到重力场的随机模型与随机观测量及其重力场本身的随机性有关，任何假设的理想模型都可能偏离实际模型。故文章中介绍了能抵制随机模型偏差影响的抗差估计原理。如果将重力场看成随机场，则建议采用抗差拟合推估解。  相似文献