Martian surface paleotemperatures from thermochronology of meteorites

The temporal evolution of past martian surface temperatures is poorly known. We used thermochronology and published noble gas and petrographic data to constrain the temperature histories of the nakhlites and martian meteorite ALH84001. We found that the nakhlites have not been heated to more than 350 degrees C since they formed. Our calculations also suggest that for most of the past 4 billion years, ambient near-surface temperatures on Mars are unlikely to have been much higher than the present cold (<0 degrees C) state.     

Martian relief and the coming opposition

In the report "Martian relief and the coming opposition" (3 Mar., p. 1100), D. H. Harris stated that, "... the reduced contrast with decreasing (terminator distance) just balances the increase in visibility due to shadow length." This is obviously erroneous. A more careful examination of the problem shows that for favorable values of the Aerocentric EarthSun Sun angle, visibility of relief increases toward the terminator, clouds not withstanding.     

Martian relief and the coming opposition

Ground-based observations of Martian relief may be possible when the Earth-Mars geometry is optimum and the observing conditions are near perfect. There is some evidence that detectable relief is present. Groundbased observations of Martian relief during the coming opposition will be optimum between 1 February and 1 March and between 1 June and 15 August 1967.     

Seasonal flows on warm Martian slopes

Water probably flowed across ancient Mars, but whether it ever exists as a liquid on the surface today remains debatable. Recurring slope lineae (RSL) are narrow (0.5 to 5 meters), relatively dark markings on steep (25° to 40°) slopes; repeat images from the Mars Reconnaissance Orbiter High Resolution Imaging Science Experiment show them to appear and incrementally grow during warm seasons and fade in cold seasons. They extend downslope from bedrock outcrops, often associated with small channels, and hundreds of them form in some rare locations. RSL appear and lengthen in the late southern spring and summer from 48°S to 32°S latitudes favoring equator-facing slopes, which are times and places with peak surface temperatures from ~250 to 300 kelvin. Liquid brines near the surface might explain this activity, but the exact mechanism and source of water are not understood.     

响应曲面法优化铁盐除磷工艺

以响应曲面法研究铁盐除磷过程的主要操作条件[Fe/P、pH、快速搅拌速度(FMS)]对废水除磷效果的单独效应和联合效应。结果表明:各操作条件对除磷效率的贡献排序为:Fe/P>pH>FMS;操作条件间的复合效应Fe/P-pH和Fe/P-FMS为正效应,pH-FMS为负效应,其大小排序为:Fe/P-pH>pH-FMS>Fe/P-FMS;建立了"优先/联合"优化模式,确定了对于质量浓度为100mg/L含磷废水经优化的操作参数为:Fe/P 2.57,pH6.31,FMS 136r/min;以模拟废水和实际废水验证了"优先/联合"操作模式的实施效果,其铁盐除磷效率>97%,与模型预测结果误差<3%,模型具有可信性。     

Martian craters and a scarp as seen by radar

Radar observations of Mars with a surface resolution of 1.3 degrees in latitude and 0.8 degrees in longitude have been carried out during the opposition of 1971. With a precision in surface height measurement approaching 75 meters in regions of high reflectivity, it has been possible to measure the detailed characteristics of a number of craters. Many of these can be identified with craters shown in Mariner photographs of Mars. In addition, a scarp has been seen at 41 degrees west, 14 degrees south with an average slope of about 6 degrees extending over about 40 kilometers.     

不同条件下乳铁蛋白对铁溶解度的影响

文章通过不同条件下乳铁蛋白对铁溶解度影响的测定,结果表明,随着加热温度升高和时间延长,乳铁蛋白对铁吸收逐渐降低,加热温度在75℃以下时,对铁溶解度影响不明显,加热温度75℃以上时,铁溶解度明显下降;当溶液pH11或pH3时都会影响乳铁蛋白对铁结合能力,随时间延长,铁溶解度逐渐降低,中性条件下有利于铁结合。试验表明,在中性条件下,巴氏杀菌对乳铁蛋白吸收铁影响最小。     

Martian valleys: morphology, distribution, age, and origin

Branching valley networks throughout the heavily cratered terrain of Mars exhibit no compelling evidence for formation by rainfall-fed erosion. The networks are diffuse and inefficient, with irregular tributary junction angles and large, undissected intervalley areas. Rather, the deeply entrenched canyons, with blunt amphitheater terminations, cliff-bench wall topography, lack of evidence of interior erosion by flow, and clear structural control, suggest headward extension by basal sapping. The size-frequency distributions of impact craters in these valleys and in the heavily cratered terrain that surrounds them are statistically indistinguishable, suggesting that valley formation has not occurred on Mars for billions of years.     

Sulfates in Martian layered terrains: the OMEGA/Mars Express view

The OMEGA/Mars Express hyperspectral imager identified hydrated sulfates on light-toned layered terrains on Mars. Outcrops in Valles Marineris, Margaritifer Sinus, and Terra Meridiani show evidence for kieserite, gypsum, and polyhydrated sulfates. This identification has its basis in vibrational absorptions between 1.3 and 2.5 micrometers. These minerals constitute direct records of the past aqueous activity on Mars.     

翅片管式风冷冷凝器耦合传热的数值研究

利用耦合传热理论对平直翅片的换热特性进行了数值研究,在此基础上建立了V型风冷冷凝器的传热模型,并对不同夹角、不同管排的V型冷凝器管外换热特性进行了初步的模拟分析,模拟采用商用软件PHOENICS3.6进行。其结论对于目前空调使用的风冷冷凝器的优化设计具有一定的指导作用。     

地表水地下水联合耦合模拟进展

地表水与地下水相互作用的耦合模拟在一个地区水资源的开发利用与管理中是十分重要的。本文梳理并分析了地表水与地下水耦合模拟中的主要问题、主要方法以及地表水地下水联合调度的主要策略,认为分布式水文模型对较长时空跨度的地表水与地下水水文循环进行耦合是未来水文模拟的重要方向,以流域为尺度的地表水地下水联合模拟调度将成为提高水资管理水平、保障水资源安全的重要手段,随着人类活动的不断加大,流域整体水循环模拟必须综合考虑人类活动的影响。     

耦合Burgers系统新的显示精确解

针对耦合Burgers系统,采用扩展F-展开法和Ricctia方程辅助,通过Maple辅助计算得到了双曲函数扭状孤波解、三角函数周期解和有理函数解.     

An iron-regulated ferric reductase associated with the absorption of dietary iron

The ability of intestinal mucosa to absorb dietary ferric iron is attributed to the presence of a brush-border membrane reductase activity that displays adaptive responses to iron status. We have isolated a complementary DNA, Dcytb (for duodenal cytochrome b), which encoded a putative plasma membrane di-heme protein in mouse duodenal mucosa. Dcytb shared between 45 and 50% similarity to the cytochrome b561 family of plasma membrane reductases, was highly expressed in the brush-border membrane of duodenal enterocytes, and induced ferric reductase activity when expressed in Xenopus oocytes and cultured cells. Duodenal expression levels of Dcytb messenger RNA and protein were regulated by changes in physiological modulators of iron absorption. Thus, Dcytb provides an important element in the iron absorption pathway.     

Size-driven structural and thermodynamic complexity in iron oxides

Iron oxides occur ubiquitously in environmental, geological, planetary, and technological settings. They exist in a rich variety of structures and hydration states. They are commonly fine-grained (nanophase) and poorly crystalline. This review summarizes recently measured thermodynamic data on their formation and surface energies. These data are essential for calculating the thermodynamic stability fields of the various iron oxide and oxyhydroxide phases and understanding their occurrence in natural and anthropogenic environments. The competition between surface enthalpy and the energetics of phase transformation leads to the general conclusion that polymorphs metastable as micrometer-sized or larger crystals can often be thermodynamically stabilized at the nanoscale. Such size-driven crossovers in stability help to explain patterns of occurrence of different iron oxides in nature.