长白山北坡植物群落复杂性的海拔梯度变化(英文)

应用梯度格局法在长白山北坡海拔700m-2600m的坡面上每100 m海拔设置一样地,共计20块样地,通过对同一群落各样方间的相异性测定,对各海拔植物群落的复杂性进行了分析。结果表明,以主林层乔木种的二元数据计算的结果,除亚高山岳桦林外,其它各海拔群落的样方间均表现出较高的相异性,特别是低海拔的阔叶红松林平均相异系数达0.74,明显高于其它植被类型;暗针叶林各群落间差异不大,相对而言1400 m群落样方间的相异性略高于其它群落,表现出过渡性群落树种组成的复杂性;岳桦林树种组成简单,样[(\267\275\274\344\322\262\261\355\317\326\263\366\275\317\270\337\265\304\\317\340\313\306\320\324\241\243)-0.1(\322\324\271\340\304\276\326\326\265\304\266\376\324\252\312\375\276\335\\274\306\313\343\265\304\310\272)]落内的相异性,虽低海拔的阔叶红松林总体上高于其它群落,但差异趋势并不像乔木种那么明显。以各草本植物与所有植物种的二元数据计算的各海拔群落内样方间的相异性,表现出非常相近的趋势,群落内样方间草本植物及所有植物种均以阔叶红松林及高山冻原差异最大,暗针叶林基本稳定于比较相近的水平。图3表1参8。

Calorimetric study and thermal analysis of berberine sulphate

The heat capacities of berberine sulphate [(C20H18NO4)(2)SO4.3H(2)O] were measured from 80 to 390 K by means of an automated adiabatic calorimeter. Smoothed heat capacities,{H-T-H-298.15} and {S-T-S-298.15} were calculated. The loss of crystalline water started at about 339.3+/-0.2 K, and its peak temperature was 365.8+/-0.6 K. The peak temperature of decomposition for berberine sulphate was at about 391.4+/-0.4 K by DSC curve. TG-DTG analysis of this material was carried out in temperature range from 310 to 970 K. TG and DSC curves show that there is no melting in the whole heating process.

Proton transfer reactions within the pyridazine-methanol cluster ion

The multiphoton ionization of the hydrogen-bonding cluster pyridazine-methanol (C4H4N2-CH3OH) was studied using a time-of-flight mass spectrometer at the wavelengths of 355 and 532 nm. At both wavelengths, a series of protonated C4H4N2-(CH3OH)(n)-H+ cluster ions were obtained. Relevant ab initio calculations were performed with HF and B3LYP methods. Equilibrium geometries of both neutral and ionic C4H4N2-CH3OH clusters, and dissociation channels and dissociation energies of ionic clusters, are presented. The results show that when C4H4N2-CH3OH is vertically ionized, C4H4N2H+ and CH3O are the dominant products via proton transfer reaction. A high energy barrier makes another channel corresponding to the production of C4H4N2H+ and CH2OH disfavored. (C) 2002 Elsevier Science B.V. All rights reserved.

杉木火力楠混交林养分归还与生产力

通过对野外试验和室内测试数据的整理分析．比较研究了杉木火力楠混交林和 杉木纯林养分归还、吸收等生态过程的特征以及生产力结果表明混交促进了养分归还过 程．可提高土壤肥力和系统生产力．１５年生混交林技和叶凋落物分别是纯林的２倍和３ 倍，其中容易分解的火力楠凋落物占 ６４％．混交林通过凋落物分解所归还的养分是纯林 的 ２～ ３倍．相当年凋落量 ６５． ９％的混交林根系年死亡量是纯林的 ２倍，在整个系统养分 归还中占有很大的份额．混交林土壤全 Ｎ、 ＮＨ＋４－Ｎ和有效 Ｋ分别比纯林提高 ６４． ３％。 ８２． ３ ％和 ６３． １％．与此同时土壤孔隙组成和水分过程也大为改善．混交林生产力较纯林 提高５２．７％．混交林５种大量元素的归还／吸收比率是纯林的２倍，表明混交林养分循环 效率较高，较少的人为维持可以保持较高的生产力水平．

东北地区主导产业培育与产业体系重构研究

以东北地区主要工业行业区位商、生产竞争力、市场竞争力的计算结果为依据,对东北地区区域主导产业及产业体系特征进行分析,并通过聚类分析、判别分析统计分析模型将区域产业体系划分出四个组群,即有较大优势的行业、有一定优势的行业、无明显优势的行业以及衰退行业。在此基础上,总结出区域主导产业及产业体系特征的形成机理,提出主导产业培育框架、产业体系重构的构想方案及相应的政策建议。

Structural characterization, stability and electrical properties of strontium niobate ceramic

The double perovskite oxide Sr2CrNbO6 has a cubic structure according to powder X-ray diffraction. After reducing in CO, Sr2CrNbO6 still exhibited a cubic structure refined by Rietveld technique. The TG analysis indicated that Sr2CrNbO6 loses 0.127 oxygen per formula unit from 400 to 700 degrees C in H-2. The morphology and compositions of this ceramic did not significantly change on reduction

Synthesis and characterization of novel neutral nickel complexes bearing fluorinated salicylaidiminato ligands and their catalytic behavior for vinylic polymerization of norbornene

A series of salicylaldimine-based neutral Ni(II) complexes (3a-j) [ArN = CH(C6H40)]Ni(PPh3)Ph [3a,Ar = C6H5; 3b,Ar = C6H4F(o); 3c, Ar = C6H4F(m); 3d, Ar = C6H4F(p); 3e, Ar = C6H3F2(2,4); 3f, Ar = C6H3F2(2,5); 3g, Ar = C6H3F2(2,6); 3h, Ar = C6H3F2(3,5); 3i, Ar = C6H2F3(3,4,5); 3j, Ar = C6H5] have been synthesized in good yield, and the structures of complexes 3a and 3i have been confirmed by X-ray crystallographic analysis. Using modified methylaluminoxane as a cocatalyst, these neutral Ni(II) complexes exhibited high catalytic activities for the vinylic polymerization of norbornene.

Effects of ultrahigh pressure extraction conditions on yields and antioxidant activity of ginsenoside from ginseng

Ultrahigh pressure technique was employed to extract ginsenosides from roots of ginseng (Panax ginseng C.A. Meyer). The optimal conditions for ultrahigh pressure extraction (UPE) of total ginsenosides were quantified by UV-vis spectrophotometry with the ginsenoside Re as standard, the signal ginsenosides were quantified by HPLC and ELSD with ginsenosides Re, Rg(1), Rb-1, Rc and Rb-2 as standards. Orthogonal design was applied to evaluate the effects of four independent factors (extraction pressure, extraction temperature, extraction time and ethanol concentration) on the yield and 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity of ginsenoside, which are based on microwave extraction (ME), ultrasound extraction (UE), soxhlet extraction (SE) and heat reflux extraction (HRE) method. The results showed that UPE method can produce ginsenoside with the highest yield and the best radical scavenging activity compared to other used ones. Scanning electron microscopic (SEM) images of the plant cells after ultrahigh pressure treatment was obtained to provide visual evidence of the disruption effect.

A new class of high T-g and organosoluble polynaphthalimides

A new class of soluble six-membered ring polynaphthalimides (PNIs) was synthesized from asymmetrical fluorinated naphthalenesubstituted monomers. All the resulting PNIs were easily soluble in many organic solvents, such as N-methyl-2-pyrrolidinone (NMP), N,N-dimethylacetamide (DMAc), dimethyl sulfoxide (DMSO). and chloroform. They also showed good thermal stability with glass transition temperature of 340-386 degrees C, 10% weight loss temperature in excess of 529 degrees C. Polyimide 3c could be solution-cast into tough and flexible film. The film had a tensile strength, elongation at break, and Young's modulus of about 117.6 Wa, 23.6%, and 1.77 GPa, respectively. The gas permeation property of the film of 3c was investigated with oxygen permeability coefficient (PO2 = 3.99) and permeability selectivity coefficient of oxygen to nitrogen (P-O2/P-N2 = 5.27). Therefore, these materials are expected to be a good alternative to PIs based on five-membered rings with applications in gas separation membranes.

Efficient red organic light-emitting diodes based on a dinuclear europium complex

Pure red organic light-emitting diodes based on a dinuclear europium complex with a structure of (TTA)(3)Eu(PYO)(2)Eu(TTA)3 (TTA = thenoyltrifluoroacetonate, PYO = pyridine N-oxide) were presented. The devices showed pure red emission at a peak wavelength of 612 nm with a full width at half maximum of 3 nm, which is a characteristic emission from Eu3+ ion based on D-5(0) -> F-7(2) transition. The maximum brightness and electroluminescent (EL) efficiency reached 340 cd/m(2) at a driving voltage of 19 V and 2.4 cd/A (0.78 lm/W) at a current density of 0.14 mA/cm(2), respectively.

Effect of Y for enhanced age hardening response and mechanical properties of Mg-Gd-Y-Zr alloys

In this study, compositional dependence of age hardening response and tensile properties were investigated for Mg-10G(d-x)Y-0.4Zr (x = 1, 3, 5 wt.%) alloys. With increasing Y content, the age hardening response of the alloys enhanced and tensile properties increased. The Mg-10Gd-5Y-0.4Zr alloy exhibited maximum tensile strength and yield strength at aged-peak hardness, and the values were 302 MPa and 289 MPa at room temperature, and 340 MPa and 267 MPa at 250 degrees C, respectively. The strong peak age hardening was attributed to the precipitation of prismatic beta' plates in a triangular arrangement. The cubic shaped beta phase was also observed at grain boundaries. The remarkable improvement in strength is associated with a uniform and high dense distribution of beta' and cubic shaped beta precipitate phases in Mg matrix. Elongation of Mg-10Gd-0.4Zr alloys decreased with increasing Y content, and the elongation of Mg-10Gd-5Y-0.4Zr alloy was less than 3% below 250 degrees C, whereas the alloys containing I wt.% and 3 wt.% Y exhibited higher elongation than 5% at room temperature.