Pressure,O2, and CO2, in aquatic Closed Ecological Systems

Pressure increased during net photosynthetic O₂ production in the light and decreased during respiratory O₂ uptake during the dark in aquatic Closed Ecological Systems (CESs) with small head gas volumes. Because most CO₂ will be in the liquid phase as bicarbonate and carbonate anions, and CO₂ is more soluble than O₂, volumes of gaseous CO₂ and gaseous O₂ will not change in a compensatory manner, leading to the development of pressure. Pressure increases were greatest with nutrient rich medium with NaHCO₃ as the carbon source. With more dilute media, pressure was greatest with NaHCO₃, and less with cellulose or no-added carbon. Without adequate turbulence, pressure measurements lagged dissolved O₂ concentrations by several hours and dark respiration would have been especially underestimated in our systems (250–1000 ml). With adequate turbulence (rotary shaker), pressure measurements and dissolved O₂ concentrations generally agreed during lights on/off cycles, but O₂ measurements provided more detail. At 20 °C, 29.9 times as much O₂ will distribute into the gas phase as in the liquid, per unit volume, as a result of the limited solubility of O₂ in water and according to Henry’s Law. Thus even a small head gas volume can contain more O₂ than a larger volume of water. When both dissolved and gaseous O₂ and CO₂ are summed, the changes in Total O₂ and CO₂ are in relatively close agreement when NaHCO₃ is the carbon source. These findings disprove an assumption made in some of Taub’s earlier research that aquatic CESs would remain at approximately atmospheric pressure because approximately equal molar quantities of O₂ and CO₂ would exchange during photosynthesis and respiration; this assumption neglected the distribution of O₂ between water and gas phases. High pressures can occur when NaHCO₃ is the carbon source in nutrient rich media and if head-gas volumes are small relative to the liquid volume; e.g., one “worse case” condition developed 800 mm Hg above atmospheric pressure and broke the glass container. Plastic screw cap closures are likely to leak at high pressures and should not be assumed to seal unless tested at appropriate pressures. Pressure can be reduced by having larger head-gas volumes and using less concentrated nutrient solutions. It is important that pressure changes be considered for both safety and closure, and if total O₂ is used as the measure of net photosynthesis and respiration, the O₂ in the gas phase must be added to the dissolved O₂.     

飞机结构完整性及损伤类型的探究

特定区域的结构完整性监管不仅贯穿于飞机的整个服役阶段,同时也为适航性安全提供了保障.文中主要讨论了非裂纹损伤形式与传统裂纹损伤的关键性区别,说明了非裂纹损伤形式对现有的结构完整性设计方法提出的挑战.此种损伤类型不同于目前广泛研究的传统裂纹损伤,易造成预料之外及早期的机组结构破坏,给飞机维护及结构的完整性带来了威胁.最后对现有的结构完整性设计和管理方法提出了参考意见,并对未来可能面临的挑战提出建议,对实施和完善现有的飞机结构完整性管理方法有一定的参考价值.     

传统,即落后?——一种值得继承的传统教学方法:听写

首先探讨了目前大学英语课堂忽视听写教学的原因,然后从理论上阐述了听写是一种有效的听力教学手段,进而分析了从实践教学经验中得出的四种听写教学方法:1)语言语调,反复训练;2)先简后难,先短后长;3)控制步骤,因"材"施教;4)听写示范,积累经验。希望该文能让更多的教师认识到听写教学的重要性和可行性。     

对会计信息公开制度的探讨

会计的首要目标是为企业的经营决策提供有用的信息,会计信息公开是适应市场经济发展要求,顺应会计的国际化要求,符合内外部使用者的利益要求,同时也满足企业自身发展的要求的必然,会计信息公开制度的建立和完善是会计发展的趋势,尽管存在着多方面的不足,更多的是需要我们去发现和解决问题,完善和规范我国的会计体系。本文主要从两方面入手：一是确保企业公开的会计信息真实、可靠,前几个途径正是从这点入手的;二是投资者必须能识别和使用会计信息。     

中华传统美德与高校保卫人员的内涵养成

中华民族古老的传统美德是我们的瑰宝，通过分析中华传统美德与保卫人员内涵养成的关系，提出了加强保卫人员内涵养成的对策。     

转变法律教育观念培养合格法律人才

法律是科学的观念长期以来给法律教学模式带来深刻影响。当今社会发展，这种理念使法律教育弊端重重并与现实生活格格不入。法律非科学，法律是技术与艺术的结合，应当成为我们转变法律教育观念和法律教育模式改革的方向。     

我国人力资源法制化建设的政策分析——基于《劳动合同法》和《就业促进法》视角

我国新制定的《劳动合同法》和《就业促进法》是事关人民群众切身利益、企业规范管理和经济又好又快发展的法律保障。现实生活中经常存在的企业不签劳动合同、滥设试用期、无故拖欠工资、经常加班加点的侵权行为就会得以制止，我国经济与社会法制化、规范化的发展从此进入了新阶段。为此，文章在认真学习和深入研究的基础上，从我国人力资源新法规实施的背景以及新法规的主要内容和实施重点等方面进行了分析和阐述，供有关部门和劳资双方进行参考。     

对会计信息公开制度的探讨

会计的首要目标是为企业的经营决策提供有用的信息,会计信息公开是适应市场经济发展要求,顺应会计的国际化要求,符合内外部使用者的利益要求,同时也满足企业自身发展的要求的必然,会计信息公开制度的建立和完善是会计发展的趋势,尽管存在着多方面的不足,更多的是需要我们去发现和解决问题,完善和规范我国的会计体系。本文主要从两方面入手...     

LHD部件的失效机理与数值计算

通过检测数据的分析,探讨了LID部件潮解失效机制的物理、化学过程。根据质量作用定律,分子运动论和碰撞理论,给出了扩散系数的假定,从而建立了数学模型。利用建立的模型,对半径为P_o的实球体进行了数值计算。计算结果表明:描绘的曲线和拟合公式与试测曲线和回归公式相对比,形式上基本一致。由于部件实际形状并非实球,假设的参数很难与贮存条件一致,因此数值上有差别,这是很自然的。     

从分子生物学思路理解中医治疗癌症思想

癌症是组织细胞受到外界物理的、化学的、生物的、心理性的、长时间多重刺激而引起细胞多种基因突变 ,使得细胞信息调节和控制系统紊乱 ,机体免疫功能失调 ,而导致细胞自主性增殖的病变。中医通过调整脏腑阴阳平衡及气血津液失调状态 ,对细胞组织产生长期的、多重的良性刺激 ,让突变基因逆转 ,使癌细胞逆转为正常细胞 ,并进行正常分化、凋亡 ,最终使癌组织退行 ,消失