Soil water retention curves based on idealized models

Energy consideration of soil moisture as a medium bounded by the soil air and the soil solid phase allows us to obtain the water retention curve (WRC). A pedotransfer function (PTF) reflects approximations and simplifications made in the soil modeling. The main parameters of the PTF are the experimentally measured porosity and the volume of the specific surface area of the soil solid phase. This approach resulted in a PTF with the lowest disagreement with the experimental study.     

Critical behavior of a trapped interacting Bose gas

The phase transition of Bose-Einstein condensation was studied in the critical regime, where fluctuations extend far beyond the length scale of thermal de Broglie waves. We used matter-wave interference to measure the correlation length of these critical fluctuations as a function of temperature. Observations of the diverging behavior of the correlation length above the critical temperature enabled us to determine the critical exponent of the correlation length for a trapped, weakly interacting Bose gas to be nu = 0.67 +/- 0.13. This measurement has direct implications for the understanding of second-order phase transitions.     

Observation of superflow in solid helium

We report on the observation of nonclassical rotational inertia in solid helium-4 confined to an annular channel in a sample cell under torsional motion, demonstrating superfluid behavior. The effect shows up as a drop in the resonant oscillation period as the sample cell is cooled below 230 millikelvin. Measurement of 17 solid samples allows us to map out the boundary of this superfluid-like solid or supersolid phase from the melting line up to 66 bars. This experiment indicates that superfluid behavior is found in all three phases of matter.     

Mott transition in VO2 revealed by infrared spectroscopy and nano-imaging

Electrons in correlated insulators are prevented from conducting by Coulomb repulsion between them. When an insulator-to-metal transition is induced in a correlated insulator by doping or heating, the resulting conducting state can be radically different from that characterized by free electrons in conventional metals. We report on the electronic properties of a prototypical correlated insulator vanadium dioxide in which the metallic state can be induced by increasing temperature. Scanning near-field infrared microscopy allows us to directly image nanoscale metallic puddles that appear at the onset of the insulator-to-metal transition. In combination with far-field infrared spectroscopy, the data reveal the Mott transition with divergent quasi-particle mass in the metallic puddles. The experimental approach used sets the stage for investigations of charge dynamics on the nanoscale in other inhomogeneous correlated electron systems.     

新疆红山嘴油田红003稠油掺水的流动特性

针对新疆红山嘴油田红003井区稠油特性以及集输难题,结合该井区的地形特征,对比分析了常用稠油输送方法的优势与不足,提出了红003井区稠油掺水集输方法。以红003井区原油T1和TA为研究对象,采用原油含水率、流变学及密度测试方法,评价了两种原油的基本性质、流变与粘温特性;采用水平环道装置,对两种原油掺水的反相点及降粘减阻效果进行了试验。结果表明:红003井区原油T1和TA分别属于典型的普通稠油与特稠油,可以采用掺水等措施提高其流动性;其W/O型乳状液反相点分别约为40%和45%;当油水混合液含水率分别大于50%和55%时,在60～70℃的温度范围内管流表观粘度均在100mPas左右,降粘减阻效果显著,可实现顺利集输。     

温度对生物炭吸附重金属特性的影响研究

为探究温度条件对生物炭吸附重金属离子特性的影响,采用吸附试验研究25、45和65 ℃ 3种温度条件下生物炭对单一重金属离子溶液和多种重金属离子混合溶液的吸附能力变化。结果表明：生物炭对4种重金属的吸附均可采用Langmuir和Freundlich方程进行描述;温度是影响生物炭吸附重金属的重要因素,生物炭对Cu的吸附能力随温度的升高而减小,在25 ℃时吸附量最大,为5.27 mg·g^-1,去除率达到36.17%;生物炭对Zn的吸附能力随温度的升高而增加,在65 ℃时吸附量最大,为4.94 mg·g^-1,去除率达到45.36%;生物炭对Cd的吸附能力随温度的升高呈现先增加后降低的趋势,在45 ℃时吸附量最大,为5.82 mg·g^-1,去除率达到53.85%;生物炭对Pb的吸附能力随温度的升高而增加,在65 ℃时吸附量最大,为21.35 mg·g^-1,去除率达到98.61%。混合溶液中,生物炭对4种重金属的吸附强弱顺序为：Pb>Cu>Zn>Cd。温度升高能促进竞争吸附中生物炭对各重金属离子的吸附,对混合重金属离子的总吸附量也增大。     

Thermochemistry and aqueous solubilities of hydrotalcite-like solids

Hydrotalcites are used in technology as catalysts and anion exchangers and are important sinks for environmental contaminants. Their compositional variability makes it important, but difficult, to estimate their aqueous solubility. We report calorimetric measurements of the heats of formation of cobalt-aluminum hydrotalcite phases. The heat and free energy of formation from the elements are equal to those of mechanical mixtures of binary compounds, namely hydroxides and carbonates. The interlayer anion is much more important than the cation in determining the solubility of the hydrotalcite phase and its ability to contain or release heavy metals to the environment. Because hydrotalcites do not have an unreactive polymer as a structural core, their aqueous stability will change dramatically with composition, particularly with anion content. This simple mechanical mixture model allows prediction of aqueous solubilities and trace metal retention in a variety of geochemical settings.     

Atmosphere and ionosphere of venus from the mariner v s-band radio occultation measurement

Measurements of the frequency, phase, and amplitude of the S-band radio signal of Mariner V as it passed behind Venus were used to obtain the effects of refraction in its atmosphere and ionosphere. Profiles of refractivity, temperature, pressure, and density in the neutral atmosphere, as well as electron density in the daytime ionosphere, are presented. A constant scale height was observed above the tropopause, and the temperature increased with an approximately linear lapse rate below the tropopause to the level at which signal was lost, presumably because heavy defocusing attenuation occurred as critical refraction was approached. An ionosphere having at least two maxima was observed at only 85 kilometers above the tropopause.     

黑河市张地营子乡土壤重金属污染综合评价

[目的]测定黑河市张地营子乡土壤重金属含量,并对重金属污染状况进行综合评价。[方法]研究了黑河市张地营子乡不同土地利用背景和相同土地利用背景下的3个功能区的6种重金属元素（Hg、As、Cd、Cr、Cu、Pb）的含量,对重金属含量与不同土地利用及采样深度的关系进行初步研究,并对重金属污染状况进行了总体评价。[结果]重金属在土壤中已有一定程度的累积,在地表的累积程度比较高,Hg的污染最为严重,已达到了警戒水平。但总体来说,黑河市张地营子乡所研究区域土壤处于清洁水平,满足绿色食品和蔬菜生产的要求。[结论]该研究可为对黑龙江省黑河市张地营子乡土壤重金属污染的认识积累科学依据,并为扩大无公害粮食、蔬菜的种植面积和促进当地农业发展奠定基础。     

1960～2010年宁夏降水和温度极端气候事件变化分析

利用1960～2010年宁夏9个观测站的日降水量、最高温度及最低温度资料,采用趋势分析方法分析了该地区的极端气候事件变化特征.结果表明,极端降水事件和暴雨日数的变化趋势表现为非均一性,主要以弱的减少趋势为主,具有明显的阶段性变化特征;20世纪80年代中期之后暴雨的主要爆发时间段较之前提前2侯;严重干燥（湿润）事件平均发生频次和持续日数均是由南向北逐渐递增（递减）,全区呈一致的增加（减少）趋势,90年代末之后降水趋向于极端性、不均衡性;全区高温（低温）日数呈一致的增加（减少）趋势,北部地区的变化速率相对较大,1998（1993）年发生突变,突变之后显著增加（减少）;全区极端高温（低温）事件呈一致的显著增加（减少）趋势,气温变暖在低温上的表现更加显著.     

基于改进物元可拓模型的鄱阳湖区耕地土壤重金属污染评价

为了解鄱阳湖区耕地土壤重金属污染状况,采集252个耕地表层土壤样品,分析测定了Hg、As、Pb、Cd、Cu、Cr、Zn7种重金属元素的含量。鉴于土壤重金属污染的模糊性和不确定性,尝试运用物元可拓模型并对其进行改进,同时引入Hakanson毒性响应系数修正传统超标倍数赋权法权重,建立了基于改进物元可拓模型的耕地土壤重金属污染评价模型,并将其评价结果与传统评价方法结果进行对比。结果表明:样品中7种重金属的平均含量均超过当地背景值,并有不同程度累积,超标率CrCuCdHgZnPbAs;运用改进后的物元可拓模型得到的鄱阳湖区耕地土壤重金属总体污染情况为尚清洁状态,都昌县、湖口县、共青城市的污染等级均为清洁级,其余地区均为尚清洁状态;改进物元可拓法与传统评价方法得到的评价结果基本一致,表明改进物元可拓模型在土壤重金属污染评价中同样适用,且更为合理。     

湘中典型矿区土壤对锑的吸附特征

[目的]研究矿区土壤对重金属锑的吸附行为。[方法]采取动态吸附的方法,通过改变污染物浓度、p H、吸附时间、温度等条件,研究矿区土壤对重金属锑的吸附特征。[结果]矿区土壤对重金属锑的吸附可以用Langmuir方程、Freundlich方程、Temkin方程进行较好地拟合,其中Langmuir方程的描述效果最优。不同温度试验中,矿区土壤对锑的吸附量的影响从大到小依次为35、25、15℃。随p H的升高,矿区土壤对重金属锑的吸附量逐渐递减。与双常数速率方程相比,Elovich方程更适合描述矿区土壤的动力学吸附过程。[结论]该研究可为预防和治理污染土壤提供科学依据。     

Seeing phenomena in flatland: studies of monolayers by fluorescence microscopy

Monolayers formed at the interface between air and water can be seen with fluorescence microscopy. This allows the phase behavior of these monolayers to be determined by direct observation and opens up the possibility of following the kinetics of phase transformations in two-dimensional systems. Some unexpected morphologies have been discovered that provide information about the nature of monolayer phases and have connections to pattern formation in other systems.     

Antibody active sites and immunoglobulin molecules

In order to obtain detailed information about the relationship between structure and function in antibody molecules, a method called affinity labeling has been devised to attach chemical labels specifically to amino acid residues in the active sites of antibody molecules. With antibodies to three different haptens, highly specific labeling of the active sites has been achieved. Tyrosine residues on both heavy and light polypeptide chains have been labeled in a molar ratio close to 2:1, and labels on the two chains are equally specific to the active sites. Peptide fragmentation studies of the labeled chains of one antibody system have shown that: (i) within 25 amino acid residues of the labeled tyrosine on either chain, substantial chemical heterogeneity exists among different antibody molecules of the same specificity; and (ii) the labeled peptide fragments from both chains are very similar in physicochemical characteristics, including average size, heterogeneity, and unusual hydrophobicity. These experimental results have led us to the view that a particular region of the heavy chain and a particular region of the light chain are utilized to construct the active sites of the three different antibodies, differences in specificity arising from chemical perturbations in these two regions. Correlated structural studies of affinity-labeled antibodies and of the homogeneous light chains (Bence Jones proteins) and heavy chains produced in multiple myeloma may permit the identification of these special active-site regions. The view that active sites of different specificity are chemical perturbations of a particular region of the antibody molecule has a possible close analogue in enzyme systems, particularly among the esterases. The marked chemical similarities we have observed between the active site regions of heavy and light chains indicate to us that chemical homologies, but not identities, exist between the chains. This is reinforced by recently obtained amino acid sequence data which reveal homologies between the two chains near their carboxyl-terminals. These results indicate that the structural genes which code for the synthesis of heavy and light chains are related, presumably having arisen from some common ancestral gene during evolution. This conclusion strongly suggests that both heavy and light chains determine antibody specificity, and has important implications for the still-unknow mechanisms of antibody biosynthesis.     

重金属污染土壤的植物修复技术研究进展

土壤重金属污染在世界范围内广泛存在且日趋严重,全世界平均每年排放汞约1.5万t、铜约340万t、铅约500万t、锰约1500万t、镍约100万t。中国受汞、铬、镉、铅、镍等重金属污染的耕地面积已达2000多万hm^2,约占总耕地面积的1/5,每年受重金属污染的粮食约1200万t。中国城市土壤也存在重金属污染问题。重金属污染土壤的修复已迫在眉睫。     

高粱植株表面温度日变化规律研究

以4种高粱类型中的12个材料为试材,用多探头温度自动测定记录仪研究了高粱植株表面温度的变化规律.结果表明:高粱植株表面温度变化分低温稳定阶段、稳定上升阶段、高温波动定阶段、波动下降阶段和稳定下降阶段5个阶段.午间的高温波动定阶段是研究冠气温差的最佳时段,但存在温度浮动大而且频繁的特点,温度波动易导致试验误差.在温度稳定上升阶段,品种间以及品种与气温的差异表现相当稳定,重复率较高,此阶段也可以作为研究植株体表面温度和气温差异的合适阶段.不同高粱类型间、品种间表面温度存在差异,且在一日当中品种间温度差异表现不尽相同;午间温度低的品种,在温度上升阶段升温较快,品种间差异比午间还要高.这一研究结果为认识高粱的体表温度特征和利用体表温度作为筛选高粱抗旱、高产基因型的指标奠定了基础.     

Bright infrared emission from electrically induced excitons in carbon nanotubes

We used the high local electric fields at the junction between the suspended and supported parts of a single carbon nanotube molecule to produce unusually bright infrared emission under unipolar operation. Carriers were accelerated by band-bending at the suspension interface, and they created excitons that radiatively recombined. This excitation mechanism is approximately 1000 times more efficient than recombination of independently injected electrons and holes, and it results from weak electron-phonon scattering and strong electron-hole binding caused by one-dimensional confinement. The ensuing high excitation density allows us to observe emission from higher excited states not seen by photoexcitation. The excitation mechanism of these states was analyzed.     

High relatedness is necessary and sufficient to maintain multicellularity in Dictyostelium

Most complex multicellular organisms develop clonally from a single cell. This should limit conflicts between cell lineages that could threaten the extensive cooperation of cells within multicellular bodies. Cellular composition can be manipulated in the social amoeba Dictyostelium discoideum, which allows us to test and confirm the two key predictions of this theory. Experimental evolution at low relatedness favored cheating mutants that could destroy multicellular development. However, under high relatedness, the forces of mutation and within-individual selection are too small for these destructive cheaters to spread, as shown by a mutation accumulation experiment. Thus, we conclude that the single-cell bottleneck is a powerful stabilizer of cellular cooperation in multicellular organisms.     

Superconductivity of americium

The metal americium becomes superconducting at temperatures as high as 0.79 K for the room temperature, double-hexagonal-close-packed phase. We also have evidence of a slightly higher transition temperature for the face-centered-cubic phase. This discovery of superconductivity in the midst of nonsuperconducting manmade elements is somewhat surprising.     

稠油集输中催化裂化降粘技术的研究

分析了稠油粘度高、胶质沥青质含量高的根本原因,针对常规输油工艺的特点及存在的问题,提出了矿场催化裂化降粘的新思路,催化裂化主要是将稠油含碳数多的稠油大分子降解为含碳数少的轻质油小分子。阐述了稠油催化裂化及降粘原理,指出低温高效的稠油裂化催化剂的筛选、热驱方式的选择及矿场稠油裂化装置的布置与规划是该种新技术的关键。