Venus clouds: a dirty hydrochloric Acid model

The spectral and polarization data for Venus are consistent with micrometer-sized aerosol cloud particles of hydrochloric acid with soluble and insoluble iron compounds, whose source could be volcanic or crustal dust. The yellow color of the clouds could be due to absorption bands in the near ultraviolet involving ferric iron and chlorine complexes. The ultraviolet features could arise from variations in the concentrations of iron and hydrochloric acid in the cloud particles.     

Luminescence, electron paramagnetic resonance, and optical properties of lunar material

Dust samples have been found to luminesce weakly under proton excitation, but not under ultraviolet. Damage, recovery, and heating effects have been investigated. Chips of breccia show luminescence, from white inclusions only, under ultraviolet and protons. Some rock chips show general luminescence, mainly from plagioclase. No natural or excited thermoluminescence has been found for dust or chips. The electron paramagnetic resonance spectrum shows the same broad Fe(3+) dipole resonance for dust and for some chips; other chips show no response. The polarization characteristics of dust are found to be identical to those of the Sea of Tranquillity, independently of proton damage. Chips show characteristics unlike any part of the lunar surface.     

Orientational dielectric relaxation of collisionless molecules

The generation of the orientation component of the polarization of matter in an electric field has previously been thought to require interaction of molecules with their neighbors. It is demonstrated that, even in the absence of collisions between neighboring molecules, hot isolated polyatomic molecules can reorient in response to an external field, thereby giving rise to the orientation component of polarization. This reorientation occurs through the interaction of rotation with molecular vibrations, which provides a heat bath to establish thermal rotational equilibrium. This effect is demonstrated for o-difluorobenzene, o-dichlorobenzene, and p-chlorotoluene, with an inhomogeneous electric field used to deflect molecular beams of these molecules.     

Condensation of carbon in radioactive supernova gas

Chemistry resulting in the formation of large carbon-bearing molecules and dust in the interior of an expanding supernova was explored, and the equations governing their abundances were solved numerically. Carbon dust condenses from initially gaseous carbon and oxygen atoms because energetic electrons produced by radioactivity in the supernova cause dissociation of the carbon monoxide molecules, which would otherwise form and limit the supply of carbon atoms. The resulting free carbon atoms enable carbon dust to grow faster by carbon association than the rate at which the dust can be destroyed by oxidation. The origin of presolar micrometer-sized carbon solids that are found in meteorites is thereby altered.     

Massive-star supernovae as major dust factories

We present late-time optical and mid-infrared observations of the Type II supernova 2003gd in the galaxy NGC 628. Mid-infrared excesses consistent with cooling dust in the ejecta are observed 499 to 678 days after outburst and are accompanied by increasing optical extinction and growing asymmetries in the emission-line profiles. Radiative-transfer models show that up to 0.02 solar masses of dust has formed within the ejecta, beginning as early as 250 days after outburst. These observations show that dust formation in supernova ejecta can be efficient and that massive-star supernovae could have been major dust producers throughout the history of the universe.     

No evidence of a circumsolar dust ring from infrared observations of the 1991 solar eclipse

During the past 25 years there have been many attempts to detect a possible dust ring around the sun, with contradictory results. Before the 1991 eclipse, infrared eclipse experiments used single-element detectors to scan the corona along the ecliptic for excess surface brightness peaks. The availability of relatively large-format infrared array detectors now provides a considerable observational advantage: two-dimensional mapping of the brightness and polarization of the corona with high photometric precision. The 1991 eclipse path included the high-altitude Mauna Kea Observatory, a further advantage to measure the corona out to large angular distances from the sun. Results are reported from an experiment conducted on Mauna Kea with a HgCdTe-array detector sensitive to wavelengths between 1 and 2.5 micrometers, using broad-band J, H, and K filters. Although the sky conditions were not ideal, the H- and K-band surface brightnesses clearly show the inhomogeneous structure in the K-corona and the elliptical flattening of the F-corona, but no evidence of a circumsolar, local dust component out to 15 solar radii.     

High harmonic generation from multiple orbitals in N2

Molecular electronic states energetically below the highest occupied molecular orbital (HOMO) should contribute to laser-driven high harmonic generation (HHG), but this behavior has not been observed previously. Our measurements of the HHG spectrum of N2 molecules aligned perpendicular to the laser polarization showed a maximum at the rotational half-revival. This feature indicates the influence of electrons occupying the orbital just below the N2 HOMO, referred to as the HOMO-1. Such observations of lower-lying orbitals are essential to understanding subfemtosecond/subangstrom electronic motion in laser-excited molecules.     

构树对菱镁矿区破损土地的生态适应性

[目的]研究菱镁矿粉尘对土壤理化性质的影响以及构树对镁粉尘污染土壤的耐受性.[方法]采用盆栽试验,室内模拟氧化镁粉尘沉降、人工掺和废矿堆.[结果]当镁粉尘施加量小于10％时,促进构树生长,当土壤镁含量为4.17 g/kg时,构树单株生物量达3.46g,明显大于洁净土壤的生物量（2.81 g）;构树对生长土质的要求低,土壤中矿石含量25％时,生物量最大为6.12g,明显比洁净土壤生物量高出3.31 g;施加镁粉尘明显改变了构树生长土壤的理化性质,pH由6.78升到9.48,电导率先增加到651.8 μS/cm后降至375.7 μS/cm,速效磷含量从52.1 mg/kg降至16.9 mg/kg,全镁含量从1.403 g/kg升至9.015 g/kg.[结论]构树对镁具有较强耐受能力,并对生长土质要求低,在不同程度破损土质中均能健康生长,在修复菱镁矿区镁污染土地方面具有相当大的潜力.     

辽宁中部城市群沙尘天气型分析

根据2001～2006年天气演变形势,分析了辽宁中部城市群受沙尘天气影响类型,发现共有4种沙尘天气类型,其中局地型最多见,主要原因是科尔沁沙地为其提供了充足的沙源。蒙古气旋携带上游沙尘过境,对中部城市群影响也很大,尤其配合其后部强冷空气影响时,沙尘对辽宁影响范围大、强度强、时间长。沙尘天气预报着眼点首先关注沙源地是否起沙;其次关注动力条件,包括气旋的生成和移动路径、冷暖平流、锋面的过境时间和产生大风的条件等;还要关注附近沙源地的气候条件;然后对照各影响天气型特点进行预测预报。     

沙尘对杏树座果率的影响及应对措施研究

[目的]沙尘对杏树座果率的影响及相应的防御措施.[方法]杏树安江胡安娜为试验材料,通过人工模拟南疆沙尘现象对盛花期的杏树进行沙尘及药剂干预试验.[结果]①沙尘可使盛花期杏树减产26.6;.②在杏树盛花期喷施硼酸(0.15;)、赤霉素(30 mg/L)、2,4-D(1.8 mg/L)、花粉(0.8 g/L)时,和自然授粉杏树的座果率(5.68;)相比,其提高效果分别为:花粉(4.11;)＞赤霉素(1.84;)＞2,4-D(1.64;)＞硼酸(1.01;).③在模拟沙尘条件下,喷施同样浓度的处理,座果率均高于自然授粉杏树的座果率(5.68;),且提高杏树座果率的高低顺序相同,提高最高的是喷花粉处理(2.23;).④模拟沙尘条件下,喷施药剂中分别加入0.8 g/L的花粉,和自然授粉杏树相比均可以提高杏树的座果率,其效果和前两个提高杏树座果率的高低顺序相同,且座果率均高于晴好天气杏树的座果率.[结论]沙尘对盛花期杏树的座果有很大危害,通过人工干预措施可以提高杏树的座果率,降低危害.     

基于叶面尘的银杏叶片光谱变化特征研究

沿北京市主道路网二、三、四、五环路均匀设置12个采样点,采集银杏叶片样本120片,研究其反射光谱与叶面尘土量的关系。利用光谱仪和电子分析天平获取除尘前后叶片反射光谱及叶面尘土量,分析数据并寻求银杏叶片光谱变化特征波段,筛选出与叶面尘土量相关性高的光谱反射率,利用传统回归和偏最小二乘（PLS）回归方法分别建立模型。结果表明：除尘前后叶片光谱曲线在300~710nm范围内,叶面尘土量与叶片反射光谱特征呈负相关关系;在710~850nm范围内,有尘叶片光谱率＞无尘叶片;在叶面尘土量与叶片光谱各波段组合关系研究中,红边面积和归一化指数与叶面尘土量具有相对较好的相关性,基于可见光波段与部分近红外波段的银杏叶片叶面尘土量预测结果较准;在叶片表面尘土量反演研究中,用偏最小二乘算法可在一定程度上提高叶面尘土量反演精度,在3种回归模型中偏最小二乘法反演效果相对较好。     

乌兰布和沙漠东北部近地层沙尘水平通量和降尘量变化特征分析

研究沙尘随高度的变化特征对揭示沙尘物质在近地层分布特征具有重要意义。通过收集乌兰布和沙漠东北部近地层50 m沙尘水平通量和降尘量数据,研究了该区域防护林对沙尘水平和垂直通量变化特征的影响。结果表明:(1)沙尘水平通量及降尘量均随高度的增加而减小,防护林内二者与高度的关系符合幂函数,防护林外二者与高度的关系符合指数函数;(2)沙尘水平通量与降尘量之间为正相关关系,二者可用线性函数表示;(3)沙尘水平通量和降尘量均与风速呈现线性关系。     

Nuclear coupling and polarization in molecular transport junctions: beyond tunneling to function

Much current experimental research on transport in molecular junctions focuses on finite voltages, where substantial polarization-induced nonlinearities may result in technologically relevant device-type responses. Because molecules have strong polarization responses to changing charge state or external field, molecules isolated between electrodes can show strongly nonlinear current-voltage responses. For small applied voltages (up to approximately 0.3 volt), weak interaction between transporting electrons and molecular vibrations provides the basis for inelastic electron tunneling spectroscopy. At higher voltages and for certain time scale regimes, strong coupling effects occur, including Coulomb blockade, negative differential resistance, dynamical switching and switching noise, current hysteresis, heating, and chemical reactions. We discuss a general picture for such phenomena that arise from charging, strong correlation, and polarization (electronic and vibrational) effects in the molecule and at the interface.     

水分子对无机离子位移极化作用研究

本文讨论了水分子对离子的位移极化作用，计算了极化率大而极化能力小的离子（Ｋ＋，Ｒｂ＋，Ｃｓ＋，Ｆ－，Ｃｌ－，Ｂｒ－，Ｉ－Ｃａ２＋，Ｓｒ２＋，Ｂａ２＋）极化能及其水化热。结果表明，理论计算值与文献值非常相符，最大误差８．７％，表明所得模型与实际情况一致，处理方法可靠     

African droughts and dust transport to the Caribbean: climate change implications

Great quantities of African dust are carried over large areas of the Atlantic and to the Caribbean during much of the year. Measurements made from 1965 to 1998 in Barbados trade winds show large interannual changes that are highly anticorrelated with rainfall in the Soudano-Sahel, a region that has suffered varying degrees of drought since 1970. Regression estimates based on long-term rainfall data suggest that dust concentrations were sharply lower during much of the 20th century before 1970, when rainfall was more normal. Because of the great sensitivity of dust emissions to climate, future changes in climate could result in large changes in emissions from African and other arid regions that, in turn, could lead to impacts on climate over large areas.     

新疆农业大学校园主要绿化植物滞尘能力初探

对新疆农业大学校园内19种主要绿化植物进行了滞尘能力测定。结果表明,不同类型植物滞尘能力差异显著,灌木植物表现出极强的滞尘能力,其滞尘能力与藤本、落叶乔木在0．05水平有差异,滞尘能力的顺序为：灌木〉藤本〉阔叶乔木。同一类型的不同植物的滞尘能力也存在差异,有的可相差2～15倍以上。针叶树种中,油松平均滞尘量达到5．27g/kg;灌木植物中,树锦鸡儿和榆叶梅是优良的滞尘植物,平均滞尘量分别达到36．82和23．52g／m2;乔木植物中,以圆冠榆的滞尘量最大。     

新乡4种主要绿化树种叶片硫含量与大气污染物硫浓度的关系研究

用多重比较法(LSD法)分析豫北地区不同功能区毛白杨、三球悬铃木、国槐和小叶白蜡叶片与叶面尘中硫含量、大气硫浓度的差异,分别拟合叶片硫含量与叶面尘中硫含量、叶片硫含量与大气硫浓度之间的回归模型,并利用多元回归分析法建立三者之间的关系。结果表明：4种绿化树种叶片硫含量和叶面降尘中的硫含量均随大气硫浓度的增加而增加,增加幅度由大至小依次是毛白杨、国槐、三球悬铃木和小叶白蜡;毛白杨、三球悬铃木、国槐和小叶白蜡叶片硫含量与叶面降尘中硫含量拟合一元回归模型的决定系数(R²)依次为0.917、0.951、0.956和0.890;4种绿化树种叶片硫含量与大气硫浓度拟合一元回归模型的R²分别为0.950、0.932、0.909和0.887;4种绿化树种叶片硫含量、叶面降尘中的硫含量与大气硫浓度三者拟合二元回归模型R²分别达0.978、0.960、0.967和0.899。所有模型的F检验均达到极显著水平,因此,绿化树种叶片及其叶面降尘均可作为大气硫化物污染的有效生物指示剂,可为区域环境监测提供理论参考。     

Anatomy of the photodissociation region in the orion bar

Much of the interstellar gas resides in photodissociation regions whose chemistry and energy balance is controlled by the flux of far-ultraviolet radiation upon them. These photons can ionize and dissociate molecules and heat the gas through the photoelectric effect working on dust grains. These regions have been extensively modeled theoretically, but detailed observational studies are few. Mapping of the prominent Orion Bar photodissociation region at wavelengths corresponding to the carbon-hydrogen stretching mode of polycyclic aromatic hydrocarbons, the 1-0 S(1) line of molecular hydrogen, and the J = 1-0 rotational line of carbon monoxide allows the penetration of the far-ultraviolet radiation into the cloud to be traced. The results strongly support the theoretical models and show conclusively that the incident far-ultraviolet radiation field, not shocks as has sometimes been proposed, is responsible for the emission in the Orion Bar.     

Mechanism of polarized light perception

As background for a report on our current selective adaptation experiments in decapod crustaceans, the various facts and hypotheses generally relevant to intraretinal sensitivity to polarized light in arthropods as well as cephalopods have been marshaled. On the basis of this review, the following working hypotheses have been made. 1) One ommatidium in the compound eye is the functional unit in image perception but contains in its component retinular cells subunits which can work independently in detecting other visual parameters, such as polarization. 2) Single retinular cells do respond differentially to light polarized in various planes. 3) Light sensitivity, including e-vector detection, is localized in the rhab domeres, which comprise closely packed arrays of microvilli protruding axially from retinular cells; the dichroism of the photopigment molecules, which are contained within the microvilli, provides the molecular basis of e-vector detection. 4) The visual pigment molecules have their major dichroic axis aligned predominantly parallel to the long axis of the microvillus containing them; typically all microvilli in a single rhab domere are closely parallel to one another, thus comprising at the cellular level a unit dichroic analyzer with maximum optical density to photons vibrating in the direction parallel to these microvillous protrusions. 5) In most decapod crustaceans, in cephalopods, and in some insects the microvilli in all rhabdomeres of a retinula are oriented in only two directions, perpendicular. to each other. Therefore, e-vector perception must depend at the retinular level on a two channel system consisting of a pair of dichroic analyzers with their major transmitting axes fixed at a 90 degrees angle determined by the two directions of microvillus orientation. Our new results on selective adaptation in the eye of Cardisoma provide direct experimental evidence for such a two-channel analyzer in which the pair of functional units have their maximum sensitivity to polarization in the same retinal directions as the rhab dom microvilli observed in electron micrographs. In turn, these directions correspond with the vertical and horizontal axes of the animal's normal spatial orientation. In e-vector detection the seven retinular cells of a single decapod ommatidium thus form two operational subgroups of four and three cells, respectively (39). The correspondence of the electrophysiological evidence for a dual polarization analyzer with the perpendicular directions shown by the microvilli in a single rhabdom strengthens the idea that one ommatidium is enough for detecting e-vector orientation. On this evidence we may conclude that the model developed above for a two-channel polarization analyzer effectively accounts for the relevant spectrophotometric, fine-structural, electrophysiological, and behavioral data currently available for a considerable number of arthropods and cephalopods.     

应用地质累积指数分析城市颗粒物源解析土壤风沙尘的污染

TSP和PM10来源解析表明,土壤风沙尘是颗粒物的重要尘源,为此收集了源解析土壤风沙尘17种元素的质量浓度谱(成分谱),应用地质累积指数(以土壤元素背景值为背景浓度)来分析人类活动对城市颗粒物源解析土壤风沙尘的污染,为选择标识元素和治理风沙尘提供参考。结果表明:⑴粗颗粒土壤风沙尘中Al、K、Ti基本未受到人类活动的影响,Ca、Ni、Cu、Zn、Pb已为中到强污染水平;⑵细颗粒土壤风沙尘中Na、Mg、Al、K、Ti、V、Fe、Ba、Mn未达到一般污染水平,Cr、Ni、Cu、Zn、Br元素达到较重的污染水平;⑶粗细颗粒元素地质累积指数城市间差别较大,细颗粒的地质累积指数相对高于粗颗粒元素的地质累积指数。