Episodic outgassing as the origin of atmospheric methane on Titan

Saturn's largest satellite, Titan, has a massive nitrogen atmosphere containing up to 5 per cent methane near its surface. Photochemistry in the stratosphere would remove the present-day atmospheric methane in a few tens of millions of years. Before the Cassini-Huygens mission arrived at Saturn, widespread liquid methane or mixed hydrocarbon seas hundreds of metres in thickness were proposed as reservoirs from which methane could be resupplied to the atmosphere over geologic time. Titan fly-by observations and ground-based observations rule out the presence of extensive bodies of liquid hydrocarbons at present, which means that methane must be derived from another source over Titan's history. Here we show that episodic outgassing of methane stored as clathrate hydrates within an icy shell above an ammonia-enriched water ocean is the most likely explanation for Titan's atmospheric methane. The other possible explanations all fail because they cannot explain the absence of surface liquid reservoirs and/or the low dissipative state of the interior. On the basis of our models, we predict that future fly-bys should reveal the existence of both a subsurface water ocean and a rocky core, and should detect more cryovolcanic edifices.     

The Southern Ocean biogeochemical divide

Modelling studies have demonstrated that the nutrient and carbon cycles in the Southern Ocean play a central role in setting the air-sea balance of CO(2) and global biological production. Box model studies first pointed out that an increase in nutrient utilization in the high latitudes results in a strong decrease in the atmospheric carbon dioxide partial pressure (pCO2). This early research led to two important ideas: high latitude regions are more important in determining atmospheric pCO2 than low latitudes, despite their much smaller area, and nutrient utilization and atmospheric pCO2 are tightly linked. Subsequent general circulation model simulations show that the Southern Ocean is the most important high latitude region in controlling pre-industrial atmospheric CO(2) because it serves as a lid to a larger volume of the deep ocean. Other studies point out the crucial role of the Southern Ocean in the uptake and storage of anthropogenic carbon dioxide and in controlling global biological production. Here we probe the system to determine whether certain regions of the Southern Ocean are more critical than others for air-sea CO(2) balance and the biological export production, by increasing surface nutrient drawdown in an ocean general circulation model. We demonstrate that atmospheric CO(2) and global biological export production are controlled by different regions of the Southern Ocean. The air-sea balance of carbon dioxide is controlled mainly by the biological pump and circulation in the Antarctic deep-water formation region, whereas global export production is controlled mainly by the biological pump and circulation in the Subantarctic intermediate and mode water formation region. The existence of this biogeochemical divide separating the Antarctic from the Subantarctic suggests that it may be possible for climate change or human intervention to modify one of these without greatly altering the other.     

两种蛋白酶在生皮脱毛上应用试验

无公害工业化生产要求制革企业放弃制革工艺中沿用的传统有害物质,采用新方法生产高质量皮革制品。介绍了中俄科研人员用两种不同的方法(涂布法、浸酶法)和两种不同的脱毛酶制剂进行的生皮脱毛试验。试验证明,用酶制剂脱毛效果良好,完全可以替代传统的硫化碱,同时能够改善制革工艺,削弱碱性物质对皮革表面的侵害,减少制革业对水源污染。     

Connexins and pannexins in the skeleton: gap junctions,hemichannels and more

Regulation of bone homeostasis depends on the concerted actions of bone-forming osteoblasts and bone-resorbing osteoclasts, controlled by osteocytes, cells derived from osteoblasts surrounded by bone matrix. The control of differentiation, viability and function of bone cells relies on the presence of connexins. Connexin43 regulates the expression of genes required for osteoblast and osteoclast differentiation directly or by changing the levels of osteocytic genes, and connexin45 may oppose connexin43 actions in osteoblastic cells. Connexin37 is required for osteoclast differentiation and its deletion results in increased bone mass. Less is known on the role of connexins in cartilage, ligaments and tendons. Connexin43, connexin45, connexin32, connexin46 and connexin29 are expressed in chondrocytes, while connexin43 and connexin32 are expressed in ligaments and tendons. Similarly, although the expression of pannexin1, pannexin2 and pannexin3 has been demonstrated in bone and cartilage cells, their function in these tissues is not fully understood.     

顶岗实习管理机制提高就业率的研究与实践——以辽阳职业技术学院为例

通过对辽阳职业技术学院生物制药专业2010级、2011级学生顶岗实习情况的调查分析,构建"五化三落实"顶岗实习管理机制,提出顶岗实习是培养高技能人才的重要环节,是充分就业的有效途径.     

黑杨派新无性系研究——Ⅰ、苗期测定

<正>从I-69杨 ×小叶杨派间杂交 F_1中和从I-69杨×欧洲黑杨种间杂交 F_1中分别 初选出 19个和11个无性系。前者h~2_h= 86.0211％,h~2_d= 85. 1068％,h~2_v= 76.4196％; GCV_h= 15.8371％, GCV_d=17.5931％,GCV_v= 41.7448％。后者h~2_h= 86.6561％, h~2_d=96.6488％, h~2_v=88.0213％; GCV_h=17.0832％,GCV_d=18.8078％, GCV_v=42.9045％。说明从中选择优良无性系是可能的。 苗高、地径和材积三个性状之间的遗传、表型和环境相关系数都是极显著的,表明三个性状中任何一个性状均可作为优良无性系的选择性状。在前述初选的19个和11个无性系中又分别选择了5个和6个无性系,并估算了它们的遗传增益。