Density maxima in high-pressure supercooled water and liquid silicon dioxide

With glass capillary pressure vessels it has been possible to study the effect of pressure on the temperature of maximum density (TMD) and on the "sharpness" of the density maximum in liquid H(2)O and D(2)O in the important but little-studied supercooled regime. A pressure of 1200 bars produces a 33 degrees C depression of the TMD in these liquids and a considerable reduction in sharpness. Comparison with the rather flat density maximum for liquid SiO(2) supports the notion that the presence or absence of density anomalies in "tetrahèdral" liquids depends on the average bridge-bond angle, which is evidently unusually large in water at normal pressure.     

Highly supercooled cirrus cloud water: confirmation and climatic implications

Liquid cloud droplets supercooled to temperatures approaching -40 degrees C have been detected at the base of a cirrostratus cloud through a combination of ground-based, polarization laser radar (lidar) and in situ aircraft measurements, Solar and thermal infrared radiative budget calculations based on these observatoins indicate that significant changes in the atmospheric heating distribution and the surface radiative budget may be attributed to liquid layers in cirrus clouds.     

牛猪肉的持水性及其测定

以牛肉、猪肉为原料,用不同测定方法测定了两种肌肉的持水力值.结果发现:不同测定方法所测出的表示肌肉持水性的指标会出现相反的结论.失水率、压力法持水力值指标表明牛肉持水性高于猪肉,而加热离心法所测持水力和熟肉率、出品率三项指标所得出的结果是猪肉持水性优于牛肉.进一步相关分析发现,失水率、压力法持水力与肉出品率之间相关关系在统计上不显著.建议用加热离心法所测持水力值反映肌肉在加工过程中的持水性比较适宜.     

Anomalous water: characterization by physical methods

Anomalous water samples have been prepared in fused quartz capillaries from pure water in an unsaturated atmosphere. In agreement with observations of other investigators, water prepared in this manner, after concentration, exhibited an increased viscosity, a lowered vapor pressure, a phase separation at low temperatures, an index of refraction of 1.48 or greater, and a depression of the temperature of maximum density. However, electron microprobe examination indicated that a significant weight fraction of these concentrated anomalous water residues consists of sodium, boron, and oxygen. The presence of about 6 percent boron was also confirmed through neutron activation analyses and by mass spectrometric measurements. A parallel is drawn between the similar physical properties of anomalous water and highly concentrated sodium tetraborate solutions. The possibility of polymorphism in liquid water should be accepted only with serious reservations.     

Anomalous water: attempts at high-pressure synthesis

The high density, 1.4 grams per cubic centimeter, reported for anomalous water suggests that high pressures should be conducive to the formation of anomalous water. Six attempts at 60 kilobars in which water was cooled from about 600 degrees C in nickel or platinum tubes, with or without the presence of silica, did not produce any detectable amounts of anomalous water.     

堆肥余热辅热养殖水体的仿真与试验

为考察猪粪好氧堆肥余热辅热养殖水体的热量传递和温度变化规律,搭建了以发酵箱、储水箱和模拟鱼池为主体的小型试验装置,使用计算流体力学软件,建立试验装置几何模型,研究模型的热量传递和温度变化,并利用小型试验装置开展验证试验。试验结果显示：试验周期内,102.9 kg猪粪堆体模拟温度平均上升17.53 ℃,实测温度平均上升14.94 ℃;25 kg储水箱模拟温度平均上升16.86 ℃,实测温度平均上升11.85 ℃;24 kg模拟鱼池模拟温度平均上升13.55 ℃,实测温度平均上升9.42 ℃。试验结果表明：猪粪好氧堆肥辅热养殖水体具有可行性,且温度变化的实测结果与模拟结果表现出较好的一致性,一定程度上验证了模型的可靠性。     

Anomalous bottom water South of the grand banks suggests turbidity current activity

Highly turbid bottom water at the margin of the Sohm Abyssal Plain was identified by its temperature, salinity, and oxygen content as originating upslope on the continental rise. The fact that the particulate concentrations were one to two orders of magnitude higher than are normally found in deep ocean waters suggests a turbidity current as the agent bringing this water downslope.     

土壤冻结条件下水、热耦合运移数值模拟研究

根据冻结条件下非饱和土壤水分运动和热量迁移的基本方程,推求冻土水热耦合迁移的数学模型,采用Grank—Nicolson计算格式及迭代方法进行求解。通过计算与实验结果对比,表明采用的数学模型和数值计算方法可靠,为模拟各种不同条件下的土壤冻结过程创造了条件。     

Low-temperature relaxation and entropic barriers in supercooled liquids

The low-temperature relaxation dynamics of supercooled liquids are a long-standing theoretical problem of considerable interest. The vast amount of experimental data on such liquids indicates that viscosity and diffusion in supercooled liquids are non-Arrhenius over a wide range of temperatures. The non-Arrhenius temperature dependence of the relaxation time of the slow modes in glass-forming liquids is investigated in connection with the topology of the potential energy landscape in configuration space. An analogy is made between the derived dynamical equations and Cooper's formulation of the pair equation in superconductivity.     

稠油伴热管道结构参数对停输过程的影响

建立了伴热稠油管道的二维非稳态数学模型,研究了填充介质、保温层厚度及涂层发射率等结构参数对单管停输和双管停输时管内稠油温度分布的影响,进而确定不同参数条件下的安全停输时间.结果表明:单管停输时,温降幅度随填充介质传热系数增大而逐渐降低、随保温层厚度增加而先减小后增大、随涂层发射率降低而逐渐增大;双管停输时,稠油温度均随停输时间近似呈线性降低.对于伴热稠油管道,采用导热泥与涂层均能较大程度降低稠油的温降速率、温降幅度,保温层厚度宜取60 mm,其伴热效果较佳,而采用高发射率涂层可延长安全停输时间.     

A topographic view of supercooled liquids and glass formation

Various static and dynamic phenomena displayed by glass-forming liquids, particularly those near the so-called "fragile" limit, emerge as manifestations of the multidimensional complex topography of the collective potential energy function. These include non-Arrhenius viscosity and relaxation times, bifurcation between the alpha- and beta-relaxation processes, and a breakdown of the Stokes-Einstein relation for self-diffusion. This multidimensional viewpoint also produces an extension of the venerable Lindemann melting criterion and provides a critical evaluation of the popular "ideal glass state" concept.     

水体重金属污染的生物有效性评价研究进展

生物监测具有综合评价水体污染物的生物有效性及其毒性等优点。综述了水体重金属污染监测中指示生物的主要生态类群,概述了水体重金属污染的生物有效性评价的主要方法和研究进展,并对生物监测存在的一些问题进行了探讨。     

超稠油水膜输送减阻率与含水率的关系

利用水膜减阻输送技术可提高超稠油管道的输送效率.使用长200 m、管径108×6 mm的试验管道研究了具有流体特性的超稠油在70～85℃、含水率在4%～12%条件下,水膜输送减阻率与含水率的关系.为了减小误差,分别对管段1(0～100 m段)、管段2(100～200 m段)和管段3(整条管段)进行试验研究.结果表明:将...     

菱茎营养成分及重金属含量测定与评价

对汉川红菱和嘉鱼菱菱茎的13种营养成分和4种重金属元素含量进行了测定与评价。结果表明,汉川红菱菱茎营养成分含量总体高于嘉鱼菱菱茎;与104～140种新鲜蔬菜已知数据比较,菱茎均有高含量的钠、铁、锰及较高含量的干物质、粗纤维、钙、镁;菱茎的蛋白质、钾、锌和磷含量较低,未能检测出硒;菱茎的铅、砷、镉及汞元素含量符合食品安全国家标准的规定。     

3种重金属离子对海水中亚硝化、硝化作用的影响

研究了Cu2 、Cd2 、Zn2 3种重金属离子对海水中亚硝化、硝化作用的影响。重金属离子对亚硝化作用影响的试验结果表明:当水体中Cu2 、Cd2 的浓度为0.1、0.5、1.0 mg/L以及Zn2 的浓度为0.5、1.0、5.0 mg/L时,NO2--N浓度的增加量与对照组相比明显缓慢,随着3种重金属离子浓度的增加,此现象不断加强;重金属离子对亚硝化作用抑制程度的顺序为Cu2 >Cd2 >Zn2 ,这与3种金属硫化物的稳定性是一致的。重金属离子对硝化作用影响的试验结果表明:低浓度试验组中NO2--N浓度的减少量与对照组比没有显著性差异,当Cu2 、Cd2 浓度增为5.0 mg/L时,对硝化作用产生明显的抑制;而同浓度的Zn2 对硝化作用却没有抑制;3种重金属离子对硝化作用抑制程度的顺序为Cu2 >Cd2 >Zn2 。试验还发现,Cu2 对硝化作用产生抑制后,其硝化功能很难得到恢复。     

荒漠生态系统水热平衡规律研究进展

荒漠生态系统水热平衡问题是研究气候和小气候形成及其变化机制的重要问题 ,也是维持现有生态系统平衡稳定以及退化生态系统恢复的关键 ,而且对防治荒漠化起着重要作用 .该文系统地综述了国内外荒漠生态系统水热平衡规律及系统小气候的最新研究进展 ;并从水量平衡与水文动态、水热交换与传输以及热量平衡等 3个方面 ,评述了荒漠生态系统水热平衡研究的若干方法 .最后 ,该文对水热平衡理论和研究方法、水热平衡耦合模型以及荒漠生态系统的水热结构优化模式等未来的研究方向和重点问题作了分析 .     

沱江流域地表水中重金属含量分布及风险评价

为了解四川盆地沱江流域重金属分布情况和污染水平下的健康风险,2018年对沱江流域24个站点地表水中7种重金属Hg、Pb、Cu、Zn、As、Cd、Cr（Ⅵ）含量进行监测,并对其时空分布特征进行分析,然后利用重金属污染指数法（HPI）和健康风险评价模型对沱江流域水体重金属进行风险评价。结果表明,沱江流域水体重金属浓度整体维持在较低的水平,低于《地表水环境质量标准》Ⅰ类标准,无明显污染情况,在一些人口密集地区部分河段的重金属浓度略有增加,但都低于《地表水环境质量标准》Ⅰ类标准;在沱江干流段除Cu和Zn浓度存在一定的季节变化外,其他重金属浓度季节变化不明显。从空间分布上看,Cu的浓度峰值出现在球溪河,Zn的浓度在毗河和球溪河较高,Cd的浓度峰值出现九曲河和阳化河,As和Pb的浓度在沱江中下游段都较高,Hg和Cr（Ⅵ）浓度的空间分布差异不明显;HPI和健康风险评价结果表明沱江流域地表水重金属污染对人体的健康风险较低。     

青豆种子等温线及等量吸附热的研究

为研究青豆种子在吸附和解吸过程中热量的变化规律,应用非线性回归方法确定了青豆种子等温线最优模型,采用水分活度等量吸附热模型方法,计算了青豆种子平衡含水率在5%～32%(干基)范围内的热动力参数———净等量吸附热与解吸热。结果表明:Halsey模型为青豆种子等温线最优模型,净等量吸附与解吸热分别为105.2～1 865.4 kJ.kg-1和111.6～1 939.0 kJ.kg-1,且随平衡含水率的增加而减少,等量解吸热高于等量吸附热。通过水分活度等量吸附热模型求解的数值在合理的范围之内。     

水生植物对氮磷及重金属污染水体的净化作用

为了治理氮、磷浓度过高造成的水体富营养化和工业过程中产生的重金属污染问题,水生植物有去除效果较显著、易于获得、有良好景观改善作用等优势而被广泛地应用于水体净化中。通过文献查阅和野外调查,综述了不同生活型水生植物的常见种类,阐释了其对氮、磷及重金属等消减作用的机制和差异性表现。在此基础上,分析了水生植物在水体净化研究中存在的问题,并提出了研究展望。文章对于农业面源污染防治中水生植物的应用具有一定的指导意义和理论价值。