Essential and Non-Essential Work of Fracture of PI/SiO2 Hybrid Thin Films

Essential work of fracture (EWF) analysis is used to study the effect of the silica doping level on fracture toughness of polyimide/silica (PI/SiO2) hybrid films. By using double-edge-notched-tension (DENT) specimens with different ligament lengths, it seems that the introduction of silica additive can improve the specific essential work of fracture (w (e) ) of PI thin films, but the specific non-essential work of fracture (beta w (p) ) will decease significantly as the silica doping level increasing from 1 to 5 wt.%, and even lower than that of neat PI. The failure process of the fracture is investigated with online scanning electron microscope (SEM) observation and the parameters of non-essential work of fracture, beta and w (p) , are calculated based on finite element (FE) method.

An investigation of electromagnetic wave propagation in plasma by shock tube

This paper presents the electromagnetic wave propagation characteristics in plasma and the attenuation coefficients of the microwave in terms of the parameters n(e), v, w, L, w(b). The phi800 mm high temperature shock tube has been used to produce a uniform plasma. In order to get the attenuation of the electromagnetic wave through the plasma behind a shock wave, the microwave transmission has been used to measure the relative change of the wave power. The working frequency is f = (2 similar to 35) GHz (w = 2pif, wave length lambda = 15 cm similar to 8 mm). The electron density in the plasma is n(e) = (3 x 10(10) similar to 1 x 10(14)) cm(-3). The collision frequency v = (1 x 10(8) similar to 6 x 10(10)) Hz. The thickness of the plasma layer L = (2 similar to 80) cm. The electron circular frequency w(b) = eB(0)/m(e), magnetic flux density B-0 = (0 similar to 0.84) T. The experimental results show that when the plasma layer is thick (such as L/lambda greater than or equal to 10), the correlation between the attenuation coefficients of the electromagnetic waves and the parameters n(e), v, w, L determined from the measurements are in good agreement with the theoretical predictions of electromagnetic wave propagations in the uniform infinite plasma. When the plasma layer is thin (such as when both L and lambda are of the same order), the theoretical results are only in a qualitative agreement with the experimental observations in the present parameter range, but the formula of the electromagnetic wave propagation theory in an uniform infinite plasma can not be used for quantitative computations of the correlation between the attenuation coefficients and the parameters n(e), v, w, L. In fact, if w < w(p), v(2) much less than w(2), the power attenuations K of the electromagnetic waves obtained from the measurements in the thin-layer plasma are much smaller than those of the theoretical predictions. On the other hand, if w > w(p), v(2) much less than w(2) (just v approximate to f), the measurements are much larger than the theoretical results. Also, we have measured the electromagnetic wave power attenuation value under the magnetic field and without a magnetic field. The result indicates that the value measured under the magnetic field shows a distinct improvement.

Filamentation control in the temperature gradient argon gas

A novel technique of controlling the evolution of the filamentation was experimentally demonstrated in an argon gas-filled tube. The entrance of the filament was heated by a furnace and the other end was cooled with air, which resulted in the temperature gradient distribution along the tube. The experimental results show that multiple filaments are merged into a single filament and then no filament by only increasing the temperature at the entrance of the filament. Also, the filament can appear and disappear after increasing the local temperature and input pulse energy in turn. This technique offers another degree of freedom to control the filamentation and opens a new way for multi-mJ level monocycle pulse generation through filamentation in the noble gas.

Deep RNA sequencing at single base-pair resolution reveals high complexity of the rice transcriptome

Understanding the dynamics of eukaryotic transcriptome is essential for studying the complexity of transcriptional regulation and its impact on phenotype. However, comprehensive studies of transcriptomes at single base resolution are rare, even for modern organisms, and lacking for rice. Here, we present the first transcriptome atlas for eight organs of cultivated rice. Using high-throughput paired-end RNA-seq, we unambiguously detected transcripts expressing at an extremely low level, as well as a substantial number of novel transcripts, exons, and untranslated regions. An analysis of alternative splicing in the rice transcriptome revealed that alternative cis-splicing occurred in similar to 33% of all rice genes. This is far more than previously reported. In addition, we also identified 234 putative chimeric transcripts that seem to be produced by trans-splicing, indicating that transcript fusion events are more common than expected. In-depth analysis revealed a multitude of fusion transcripts that might be by-products of alternative splicing. Validation and chimeric transcript structural analysis provided evidence that some of these transcripts are likely to be functional in the cell. Taken together, our data provide extensive evidence that transcriptional regulation in rice is vastly more complex than previously believed.

Influence of composition of heteropolyphosphatotungstate catalyst on epoxidation of propylene

A series of heteropolyphosphatotungstate catalysts with different W/P ratio were prepared by different means. P-31 MAS NMR spectra show every heteropolyphosphatotungstate contains several species with different W/P ratio. Combined with propylene epoxidation results, it is shown that the band at chemical shift ca. delta = 5 ppm maybe corresponds to a catalyst precursor which can be the most efficiently converted to the structure {PO4 [WO(O-2)(2)](4)}(3-). Characterization results of ICP show, the catalysts with low W/P ratio show a good reactivity for propylene epoxidation. (C) 2004 Elsevier B.V. All rights reserved.

Calibration of an audio-frequency ion trap mass spectrometer

A method for calibration of an audio-frequency (AF) ion trap mass spectrometer is described. The method is proposed to surmount the obstacle that there is a lack of a proper calibrant for mass spectrometers in the mass-to-charge ratio (m/z) range of 10(6) to 10(10). To calibrate such mass spectra, we determine the point of ejection, q(eject), on the stability diagram of the ion trap operated in a mass-selective axial instability mode. This is accomplished by measuring the radial secular frequencies (and therefore, the m/z value) of a single trapped particle using a light scattering method, followed by monitoring the action of particle ejection in real time to obtain the q(eject). A delayed ejection with q(eject) = 0.949 +/- 0.004 is found at a trap driving frequency of Ohm/2pi = 200-600Hz. Theoretical analysis for the origin of the delayed ejection indicates that the delay is predominantly resulted from the existence of multipole components in the fields due to trap imperfections. Inclusion of -3% of the octopole with respect to the basic quadrupole field can satisfactorily account for our observations. An m/z accuracy approaching 0.1% is attainable after proper calibration of the AF ion trap mass spectrometer. (Int J Mass Spectrom 214 (2002) 63-73) (C) 2002 Elsevier Science B.V. All rights reserved.

水肥耦合对丘陵半干旱区春小麦产量的影响

在旱棚控制供水条件下,对丘陵半干旱区氮(N)、磷(P)、水(W)及其耦合作用的产量效应进行了3年定位试验.结果表明,供水不足时,水分是影响春小麦产量的主导因素;而供水充足时,N肥对产量的影响作用更敏感.N、P���W3个单因素对春小麦均有明显的增产作用,而且符合报酬递减率.N、W���间存在正耦合效应,供水不足时,过多施用N肥易加剧作物的干旱胁迫作用;N、P���间表现为负交互效应,低P���N同样能取得较高产量;P���W���间表现为负交互作用,缺水时增施P���可提高春小麦的抗旱能力.通过计算机模拟寻优,得出了丘陵半干旱区春小麦水肥管理优化方案.

ELECTROCHEMICAL INVESTIGATION OF LIQUID/LIQUID SYSTEMS USING VARIOUS ORGANIC SOLVENTS

The potential windows of the system water/pure solvent (W/P) and water/solvent mixtures(W/S) have been investigated by cyclic voltammetry with solvents whose dielectric constants lie between 5.87 and 34.82. In the presence of LiCI in the aqueous phase and tetrabutytammoniumtetraphenylborate(TBATPB) in the organic phase, the systems water/allyl iso-thiocyanate (W/AIT) and water/nitrobensene (W/NB) show a same wide epotential window. thermodynamic parameters of ion transfer W/AIT interface were determined. In systems of W/P and V/S the influence solvent effect on the standard gibbs energies of transfer of was discussed.

喀斯特小流域不同背景区植物叶片δ13值及其影响因素的研究

喀斯特石漠化地区由于其特殊的地表、地下二元结构，使得该区生态系统结构和机能非常脆弱，一旦生态系统，尤其是植被系统遭到破坏，其恢复难度将很大。虽然在90年代末期对喀斯特石漠化的研究才受到普遍的重视，并且被提升到国家层面进行恢复治理，但由于经济的飞速发展和喀斯特区人民群众发展生产力以及脱贫致富愿望的诉求，使得该区人－地矛盾突出，出现生态建设超前、基础理论研究以及政策指向落后的现象，并且在不同的人为干扰方式下，导致本已脆弱的喀斯特石漠化生态环境进一步恶化。针对上述特点，本文从基础理论研究方向着手，以同处一喀斯特小流域内的喀斯特背景区和非喀斯特背景区为研究背景，排除了一些环境上垫面的影响因素，以土壤、植物作为主要研究对象，并且结合利用国际上流行的稳定性碳同位素（δ13C）技术指示植物水分利用效率（WUE）的方法，分别详细论述了不同背景区从非退化到退化过程中的土壤-植被系统的协变关系，以及不同影响因素对植物叶片δ13C值判别的影响效应，并且通过与非喀斯特背景区进行比较研究的方法，以期为喀斯特背景区，尤其是石漠化地区土壤-植被系统的生态恢复和更加科学营造该区植物局地水分利用模式以及植被恢复物种的选择配置提供一定参考价值。对此，本论文得出以下认识： 一、不同背景区植物叶片δ13C值 本论文所研究的植物叶片 δ13C值变化范围在-25.60‰～-32.68‰之间，属于典型的C3植物。其中，石漠化样地的小果蔷薇有着最高的WUE （δ13C =-25.60‰），而次生林土山样地的莎草则有最低的WUE（δ13C= -32.65‰）。喀斯特背景区从非退化到退化的过程中，其植物叶片δ13C值的分布范围在-28.52‰～-30.74‰、-25.60‰～-29.77‰之间，而非喀斯特背景区从非退化到退化的过程中，其植物叶片δ13C值的分布范围在-27.68‰～-32.68‰、-26.17‰～-30.11‰之间。在退化的石漠化和土山样地，植物叶片δ13C值显著比未退化的无石漠化和次生林土山样地要高，这也就表示植物的WUE具有随着从非退化到退化不断加强的趋势，并且石漠化与土山样地之间和无石漠化与次生林样地之间的植物WUE无显著性差异，喀斯特背景区植物的WUE总体上也要高于非喀斯特背景区的植物。 二、不同背景区土壤理化性质特征 本论文研究表明，不管是在喀斯特背景区还是在非喀斯特背景区，从非退化到退化的过程中，土壤的物理结构均发生了明显的压缩状况，而从土壤粒级含量和分形维数变化的趋势上看，在两背景区均呈现随着向退化过程的发展，土壤中大粒径颗粒增加，小粒径颗粒减少的的现象，特别是细粉粒最为显著。而从喀斯特背景区内土壤各级团聚体的变化中可以看出，当土壤退化至石漠化时，土壤大团聚体已遭到严重破坏，其抗蚀性能决定着地表植被一旦遭到破坏就会引起强烈退化。而在非喀斯特背景区，其大团聚体的百分比值远高于喀斯特背景区，土壤抵抗环境退化的承受力较强。 在不同背景区土壤化学性质方面，土壤均呈现随着退化程度的发展，土壤有机质、全N含量呈现降低的趋势。喀斯特背景区土壤中易于移动的营养元素表现出递减的趋势，而难于移动的元素呈现增加的趋势。而在非喀斯特背景区，由于非退化样地在其黄壤发育阶段经过了长期的、明显的脱硅富铝化过程，造成难移动的营养元素大量聚集的现象。因此土壤中移动性较高的营养元素随着退化程度的加深呈现逐渐递减的趋势，而移动性相对较弱的营养元素含量也呈现逐渐递减的现象。而不同背景区土壤有效态营养元素除P���K普遍低于临界值水平外，其余营养元素的变化趋势大致与全量变化趋势相似，并且喀斯特背景区的上述营养元素含量普遍要高于非喀斯特背景区。 在对土壤中营养元素含量与植物叶片δ13C值关系的研究中，尽管从非退化到退化过程中样方水平上来分析不同背景区土壤营养元素含量与植物叶片δ13C值的相关关系时与已有的研究结果存在一定的差异，但从宏观上比较喀斯特背景区与非喀斯特背景区，土壤中营养元素含量与植物叶片δ13C值呈现的是明显的正相关关系，即营养元素含量高的样地其植物WUE也随之增高。 三、不同背景区土壤-植被系统的退化协变关系 本论文重点对不同背景区退化过程中土壤-植被系统间土壤各项理化性质和植物叶片营养元素含量的相关性进行了分析。在喀斯特背景区退化的过程中，土壤物理性质与植物中P���素相关的要素是最多的，喀斯特背景区的P���素是一个重要的影响因子。而在非喀斯特背景区退化的过程中，土壤的物理性质与植物叶片营养元素之间均无显著性相关关系。并且在不同背景区退化的过程中，土壤化学性质与植物叶片营养元素含量大都呈现的是不显著相关关系。 对不同背景区从非退化到退化的过程中植物叶片的生物吸收系数与植物叶片营养元素含量和土壤营养元素含量的分析中表明，在喀斯特背景区退化的过程中，植物叶片营养元素的吸收系数受到植物和土壤中营养元素含量的双重影响。而在非喀斯特背景区退化的过程中，植物叶片营养元素的吸收系数受到的影响与植物自身营养元素的含量密切相关，而土壤营养元素含量的背景则对其吸收系数影响不大。 四、不同背景区植物叶片营养元素含量与植物叶片δ13C值的关系 在对不同背景区植物叶片营养元素含量的相关分析中表明，不管是喀斯特背景区还是非喀斯特背景区，植物叶片营养元素N、K、Ca、Mg 、Fe的含量都较高，但P���素的含量却低于临界值，营养元素的含量特点属于Ca＞K＞Mg型，Ca含量都高于10000μg/g。在喀斯特背景区退化过程中，植物叶片的营养元素N、Na、Ca、Mg、Mn、Cu、Zn含量与植物叶片δ13C值呈现正相关关系，而P���K、Fe营养元素的含量与δ13C值则呈现负相关关系。而非喀斯特背景区退化过程中，营养元素N、K、Ca、Mg、Cu的含量与δ13C值呈现负相关关系，Mn、Na与δ13C值呈现正相关关系，且营养元素P���Fe、Zn与δ13C值相关关系不显著。另外，喀斯特背景区植物w(N)／w(P)比值与δ13C值存在正相关关系，而非喀斯特背景区植物w(N)／w(P)比值与δ13C值则存在负相关关系。这些差异可能与不同背景区各样地之间小生境的条件和植物的种类差别有着一定的联系。 五、不同背景区土壤含水量的变化趋势与植物叶片δ13C值的关系 本论文选取了一场30mm降雨过后的7天，不同背景区土壤含水量与植物叶片 δ13C值的相关关系表明，石漠化样地土壤在7天内的失水幅度是最快的，尤其是在与该样地植物生长密切相关的0-20cm厚度范围内。这说明由于受其样地生境条件限制，土壤的水分蒸发量较大，含水量也较低；无石漠化样地由于受土壤厚度条件限制，其土壤含水量低于次生林土山；土山样地的土壤含水量也存在较大变化，而且其上、中、下坡的水分含量呈现逐渐递增的趋势，但无明显的显著性差异；次生林土山的土壤含水量变化幅度最小，说明其优越的生境条件对土壤水分保持是具有优势的。并且随着土壤含水量的逐渐增大，植物叶片δ13C值与之呈现显著的负相关关系，即土壤含水量越大，植物的WUE就越小。 六、不同背景区植物叶片解剖形态结构与植物叶片δ13C值的关系 本论文对不同背景区植物叶片解剖形态结构的分析表明，不同背景区退化样地上的植物叶片解剖形态结构中的栅栏组织厚度、海绵组织厚度、栅栏组织厚度/海绵组织厚度、上角质层厚度、下角质层厚度、最大导管直径和气孔密度均较未退化的样地呈现显著性差异。其中，随着从未退化到退化过程的发展，解剖形态结构中除海绵组织厚度逐渐变薄外，其余指标则逐渐增厚，并且石漠化样地上的植物叶片解剖形态结构上述指标均显著高于其它样地。而生长在喀斯特背景区和非喀斯特背景区的同种植物叶片解剖形态结构差异性不显著。不同背景区退化过程中的上述主要植物叶片解剖形态结构指标均与植物叶片δ13C值呈现正相关关系。这说明了在本研究小流域内，由于光、热、水、气等外部影响因素的一致性，植物为了适应环境的改变其自身产生的形态结构响应具有一致的趋势。

Syntheses and reactions of heterometallic complexes of nickel and copper with tetrathiotungstates. The molecular structures of [Ph(4)P](2)[S2W(mu-S)(2)Ni(S-2)] and W(mu-S)(4)Cu-2(PPh(3))(4)center dot py

Reaction of [Ph(4)P]2WS4 With NiCl2 in methanol solution in the presence of NaOCH3 leads to the formation of [Ph(4)P](2) [S2W(mu-S)(2)Ni(S-2)] (I) A Similar reaction between (NH4)(2)WS4 and NiCl2 under O-2 atmosphere in the presence of Ph(4)PCl or (n)Bu(4)NCl affords [Ph(4)P](2)([(S-2)W(O)(mu-S)(2)]Ni-2] (IIa) and [(n)Bu(4)N](2)([(S-2)W(O)(mu-S)(2)]Ni-2} (IIb) Under argon the same reaction gives [Ph(4)P](2)[Ni(WS4)(2)] (IIIa) and [(n)Bu(4)N](2)[Ni(WS4)(2)] (IIIb). [Ph(4)P](2)[Ni(WOS3)(2)] (IV) and [Ph(4)P](2)[Ni(WO2S2)(2)] (V) can be prepared from the reaction of [Ph(4)P]2WOS3 and [Ph(4)P]2WO2S2 with NiCl2. Treatment of (NH4)(2)WS4 with CuCl in the presence of PPh(3) in boiling pyridine produces W(mu-S)(4)Cu-2(PPh(3))(3) (VI), which can further react with excess PPh(3) to give W(mu-S)(4)Cu-2(PPh(3))(4) . py (VII). Complex I crystallizes in the space group P2(1)/n with the cell parameters: a = 20.049(4), b = 17.010(4), c = 14.311(7) Angstrom; beta = 110.24(3)degrees and Z = 4; R = 0.058 for 4267 independent reflections. The structural study confirms that complex I contains two terminal sulfide ligands, two bridging sulfide ligands, a side-on disulfide ligand, and a planar central W(mu-S)(2)Ni four membered ring. Complex VII crystallizes in the space group C2/c with the cell parameters: a = 26.436(8), b = 20.542(6), c = 19.095(8) Angstrom; beta = 125.00(3)degrees and Z = 4; R = 0.080 for 3802 independent reflections. The structural study reveals a perfect linear arrangement of the three metal atoms Cu-W-Cu.