Modeling trophic positions of the alpine meadow ecosystem combining stable carbon and nitrogen isotope ratios

Stable carbon and nitrogen isotope ratios of single tissues or whole bodies were analyzed to establish trophic positions of main consumers living at the alpine meadow ecosystem in the Tibetan Plateau. The results demonstrated that delta C-13 and delta N-15 values of vertebrates showed great variations and ranged from -26.83 to -22.51 parts per thousand and from 2.33 to 8.44 parts per thousand, respectively. Plateau pika, root vole, plateau hare, infants of rodents and hatchlings of passerine bird species had the lowest delta C-13 and delta N-15 values. delta C-13 and delta N-15 values of omnivorous and insectivorous birds and amphibians showed intermediate. Carnivorous species, steppe polecat and Upland buzzard, and omnivorous Robin accentor and White wagtail possessed extremely higher VC and delta N-15 values. Omnivorous birds captured in earlier year had significantly less negative delta C-13 and greater delta N-15 values than those captured later. Based on steady angular enrichment between trophic levels, an "alpha and vector model" combing delta C-13 and delta N-15 values was introduced to reveal trophic positions, the results indicated that Tibetan sheep, Tibetan yak, plateau pika, root vole, plateau hare, infants of small rodents showed the lowest trophic positions (TP 1.81-2.38). While omnivorous and insectivorous birds, their hatchlings and amphibians showed intermediate trophic positions (TP 2.06-2.89), carnivorous species steppe polecat and Upland buzzard, migrant birds possessed extremely higher trophic positions (TP 2.89-3.05). The isotopic investigation of organisms and the introduced "alpha and vector model" successfully demonstrated the same trophic positions and diet prediction of consumers as nitrogen enrichment model at the alpine meadow ecosystem. Besides of this information, the "alpha and vector model" can also be incorporated into multiple isotope signatures to infer trophic relationships. This angular enrichment model has the potential to address basic ecological questions, such as trophic structure, trophic dynamics, and energy flow in other terrestrial ecosystems of properly handled. (C) 2005 Elsevier B.V. All rights reserved.

Characterization of photosynthetic pathway of plant species growing in the eastern Tibetan plateau using stable carbon isotope composition

The photosynthetic pathway of plant species collected at Menyuan, Henan, and Maduo sites, east of Tibetan Plateau, China, during the growing season were studied using stable carbon isotopes in leaves. The 232 samples leaves analyzed belonged to 161 species, 30 families, and 94 genera. The delta(13)C values (from -24.6 to -29.2 %o) indicated that all the considered species had a photosynthetic C-3 pathway. The absence of plant species with C-4 photosynthetic pathway might be due to the extremely low air temperature characterizing the Tibetan Plateau. The average delta(13)C value was significantly (p < 0.05) different between annuals and perennials at the three considered study sites. Hence the longer-lived species had greater water-use efficiency (WUE) than shorter-lived species, that is, longer-lived species are better adapted to the extreme environmental conditions of the Tibetan Plateau.

Analysis of diets of upland buzzards using stable carbon and nitrogen isotopes

We measured the stable carbon and nitrogen isotope ratios for muscles of the upland buzzards (Buteo hemilasius) and their potential food sources, plateau pikas (Ochotona curzoniae), Qinghai voles (Lasiopodomys fuscus), plateau zokors (Myospalax fontanierii), and several passerine bird species at the alpine meadow in Maduo county, Guoluo prefecture of Qinghai province, People's Republic of China, to provide diet information of upland buzzards, highlighting different diet composition of upland buzzards exposed to different locations. The results demonstrated that stable carbon isotope ratios of upland buzzards, passerine birds, plateau pikas, plateau zokors, and Qinghai voles were -24.42 +/- 0.25parts per thousand, -22.89 +/- 1.48parts per thousand, -25.30 +/- 1.47parts per thousand, -25.78 +/- 0.22parts per thousand, and -25.41 +/- 0.01parts per thousand, respectively, and stable nitrogen isotope ratios were 7.89 +/- 0.38parts per thousand, 8.37 +/- 2.05parts per thousand, 5.83 +/- 1.10parts per thousand, 5.23 +/- 0.34parts per thousand, and 8.86 +/- 0.06parts per thousand, respectively. Fractionation of stable carbon and nitrogen isotope ratios between upland buzzards and their food were 1.03parts per thousand and 2.11parts per thousand, respectively. Based on mass balance principle of stable isotopes and the Euclidean distance mixing model, upland buzzards depended mainly on plateau pikas as food (74.56%). Plateau zokors, Qinghai voles, and passerine birds only contributed a small proportion (25.44%) to diets of upland buzzards. The results were closely accordant with analyses of stomach contents and food pellets, which firmly supported the feasibility of using stable carbon and nitrogen isotope ratios to investigate diet information of upland buzzards. Another study based on stable carbon isotopes showed that upland buzzards living in the Haibei prefecture (another prefecture located in the southeast Qinghai province) mainly preyed on passerine birds (64.96% or more) as food supply. We were alarmed by the preliminary results that widespread poisoning activities of small mammals could reshape the food composition of upland buzzards, influencing the stability and sustainability of the alpine meadow. Bio-control on rodent pests should be carried out rather than the chemical measures.

单种属泥炭纤维素碳稳定同位素组成与全新世青藏高原东部西南季风变化

泥炭的形成和积累主要受控于气候，其次是地质、地貌和水文等因素。作为一种重要和理想的气候信息载体，泥炭己经与冰芯、海洋及湖泊沉积、黄土堆积、洞穴碳酸盐沉积、树轮和珊瑚礁等其它类型的自然地质档案一样，逐渐为国内外致力于古气候变化研究的学者所接受，并将其重点应用于全新世以来气候变化信息的提取。本研究在已有的泥炭混合植物残体纤维素碳稳定同位素记录青藏高原东部地区气候信息的基础上，首次提取泥炭中单一种属植物残体一木里苔草（Calexmulieensis）纤维素，测定其碳稳定同位素，并以其时间序列作为一种新的西南季风代用指标，揭示该区域全新世以来气候变化。研究表明：1．木里苔草的碳稳定同位素时间序列是西南季风强度变化的敏感代用指标。约11800～11加0 cal aBP期间，木里苔草纤维素的613C记录处于最大值，表明该时段西南季风活动鼻弱，气候干冷，对应于普遍发生并存在的新仙女木事件；它清晰地指示了该区全新世的下限年龄为约11200 cal aBP（14c年龄约9900aB玲从约11200 oal aBP起该区迅速进入湿暖的全新世阶段，季风活动迅速增强；在约10800～5500 cal aBP期间，季风总体保持在强盛状态，但其间有4次突然减弱，气候变干冷；约从5500 cala即起季风活动在波动中逐渐减弱，其中有4次减弱最为明显。2．木里苔草纤维素碳同位素所记录的犯000年以来的所有9次西南季风活动的突然减弱与同时期北大西洋发生的冰力｝漂移碎屑沉积物事件（IRD事件）一一对应。这种密切的相关关系表明，西南季风强度的波动可能是对全球气候变化特别是对海洋热盐环流引起的地球南北方气撇动变化的响应。3．木里苔草纤维素碳稳定同位素所指示的西南季风有952，乓57，475，312，211和77年等一系列周期。其中557年和77年两个周期分别与北大西洋深层海水环流的550年的周期和76年的气候周期非常吻合。这表明西南季风与北大西洋气候间有很好的相关关系。由于557年和77年的季风周期又都分别类似于53。年和80年的太阳活动周期，这表明太阳活动可能对西南季风和北大西洋气候间的联系有着影响。4．红原泥炭木里苔草纤维素和泥炭混合纤维素别3c时间序列在千年至万年时间尺度上的变化趋势很相近。两种代用记录都一致反映了冰后期的气候变化，即均指示西南季风强度变化可分为三个明显的大阶段。这说明它们对过去12000年的西南季风变化具有相同的响应。对于目前经过较详细研究的那些全球大范围发生的突然气候变化事件，木里苔草纤维素δ~(13)C代用记录与泥炭混合纤维素δ~(13)C代用记录一样，都有相同的响应，但是，相对于泥炭中单一的木里苔草敏感地记录到历次北大西洋I劝事件而言，泥炭混合纤维素δ~(13)C记录对其中的几次突然气候变化事件似乎没有表现出明显的响应。这个结果表明对数百年尺度的突然气候变化，木里苔草纤维素比混合纤维素的酬3c指标似乎要更敏感一点。因此，在能获得足够数量的单种植物·残体的情况下，单种植物残体纤维素的δ~(13)C指标有很好的使用价值。

高原湖泊沉积物碳酸盐稳定同位素及孔隙水碳酸盐体系地球化学研究

在沉积物早期成岩作用过程中，扩散、对流和化学反应等动力学因素共同影响着孔隙水的化学平衡性质，使孔隙水在水－沉积物界面附近出现方解石不饱和现象，而在深部却呈饱和状态。从云贵高原的洱海、泸沽湖和红枫湖等湖泊的研究可以发现：在方解石不饱和带中，孔隙水的HCO_3~-和Ca~(2+)的浓度梯度比值大于理论值（1.34），HCO_3~-和Ca~(2+)的垂直分布可以用非线性常微分方程组（3-10）来描述。对寄宿时间较长的非封闭湖泊，沉积物碳酸盐的C、O稳定同位素变化特征可以用δ~（13）C-δ~（13）O模式图表示出来；特别当输入寄宿时间与蒸发寄宿时间的比值较大时，随沉积深度的不同，碳酸盐的δ~（13）C和δ~（13）O值可能呈正相关波动变化，其δ~（13）O能够反映了湖区气温变化的特征。

痕量甲烷碳同位素真空制样系统的研制与贵州省一些水稻田甲烷碳同位素组成的初步测定

甲烷碳同位素（δ~(13)C）在辩识甲源汇和提示甲烷的产出机理、传输途径方面有重要作用国内因痕量甲烷的同位素制样问题未能开展有关的研究工作。我们研制了一套痕量甲烷碳同位素的真空制样系统，并对贵州省内一些水稻田的甲烷δ~(13)C值作了初步测定。痕量甲烷碳同位素真空制样系统充分考虑到气样中CO_2、H_2O、CO和非甲烷烃等杂质气体对甲烷同位素制样的干扰，在吸收和借鉴前人工作基础上研制出来，在设计上具有以下特点：（1）制样过程中杂质气体的清除采用多环“冷阱串”，保证冷冻过程的可靠性和稳定性。（2）甲烷的高温转化使用了新型HA-02贵金属催化剂，实验检测表明：在较低的温度下（400 ℃ - 500 ℃）HA-02催化剂能确保甲烷的充分氧化分解。（3）CO_2气样设计有样品管和熔封管两种接收方式，便于收集和贮存。（4）真空制样系统可以制备气样中CO_2、CO的同位素样本，与质谱仪配合可以同步监测CO_2、CO的碳氧同位素组成。同位素条件检测实验证明了痕量甲烷碳同位素真空制样的可行性。用自行研制的真空系统对贵州省内一些水稻田甲烷的δ~(13)C值初步测定表明：稻田甲烷以富集轻同位素为特征，δ~(13)C变化在-54.05 ～ -64.47‰，平均为-60.67 ± 3.56‰，比较接近肯尼亚水稻田的研究结果，同时甲烷δ~(13)C值在一天中从上竿到晚上有逐步富集~(13)C的趋势。

A novel silica-based column packing for reversed-phase HPLC of basic compounds

A novel bonded phase for reversed-phase HPLC was synthesized in two steps. Octylamine was first reacted with beta-(3,4-epoxycyclohexyl)ethyltrimethoxysilane (beta -ECTS) and then the intermediate product was coupled onto porous silica. The prepared packing was characterized by elemental analysis, solid-state C-13 NMR and Fourier transform infrared (FT-IR). Chromatographic evaluations were carried out by using a mixture of organic compounds including acidic, basic and neutral analytes and methanol-water as binary mobile phase. The results showed that the stationary phase has excellent chromatographic properties and is resistant to hydrolysis between pH = 2 similar to 8. It can be used efficiently for the separation of basic compounds.

Peak identification for PCDD/Fs in environmental samples at different temperature programs

A method has been developed for peak recognition of 136 polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) at different temperature programs. Their retention behaviours are predicted on the basis of an identification database of retention values (A, B) of gas chromatography. By the retention times of C-13 labelled 2,3,7,8-substituted PCDD/F internal standards, the retentions of all PCDDs and PCDFs can be calculated. After comparison with the retentions of practical environmental samples, the predicted values have been proved to be very accurate. (C) 2000 Elsevier Science Ltd. All rights reserved.

NMR studies on synthesized diosgenyl saponin analogs

The identification of six synthesized diosgenyl saponin analogs with up to five sugars was accomplished by NMR studies. A combination of homo- and heteronuclear two-dimensional NMR techniques was utilized to achieve the complete H-1 and C-13 NMR assignments. Copyright (C) 2000 John Wiley & Sons, Ltd.

Comonomer sequence distribution in metallocene-based ethylene/1-butene (S-34) and ethylene/1-hexene (S-43) copolymers

Metallocene based polyethylenes were prepared by SMOPEC's "metallocene adduct" technology in a gas phase fluidized bed model reactor. The C-13-NMR spectra of ethylene/1-butene (S-34) and ethylene/1-hexene(S-43) copolymers were studied in a manner analogous to that established by Hsieh and Cheng. The comonomer sequence distributions of copolymer samples were obtained. The results show that these metallocene based copolymers contain a small amount of butene and hexene, and the EE and EEE sequences are dominant.

Synthesis of titanium silicalites in different template systems and their catalytic performance

Titanium silicalites have been synthesized in the TPABr+ammonia, TPABr+hexanediamine, TPABr+ethylenediamine, TPABr+diethylamine, TPABr+TEAOH, TPABr+n-butylamine, TPABr+TBAOH and TBAOH+n-butylamine systems. As-synthesized titanium silicalites were characterized by XRD, IR and C-13 CP MAS NMR. Catalytic performance in epoxidation of propylene and template effect was investigated. It has been shown that both TPABr and TBAOH serve as templating agent in TPABr+TBAOH system. But in other systems, when there is enough TPABr, organic amines or ammoniums only act as the bases. TEAOH or n-butylamine can take the role of template when less TPABr is added. It indicates that the ability of organic amines or ammoniums to direct the Pentasil structure decreases as follows: TPA(+)>TBA(+)>TEA(+)>n-butylamine. Catalysts exhibiting good performance in epoxidation of propylene can be attained using TPABr as the template and ammonia, n-butylamine, diethylamine, hexanediamine or TBAOH as bases. (C) 1999 Elsevier Science B.V. All rights reserved.

Synthetic studies on optically active Schiff-base ligands derived from condensation of 2-hydroxyacetophenone and chiral diamines

Three optically active Schiff-base ligands have been prepared by condensation of 2-hydroxyacetophenone with (IR,2R)-(-)-1,2-diaminocyclohexane, (1S,2S)-(-)1,2-diphenylethylenediamine or R-(+)-2,2'-diamino-1,1'-binaphthalene, respectively. The products have been characterized by their IR, H-1- and C-13-NMR spectra.

Highly ordered periodic mesoporous ethanesilica synthesized under neutral conditions

Highly ordered mesoporous ethanesilica (MES) with 2D hexagonal structure was synthesized from 1,2-bis(trimethoxysilyl) ethane under neutral conditions for the first time. Divalent salts, such as NiCl2, MgCl2, ZnCl2, ZnSO4 and Zn(NO3)(2), were used to help the formation of the ordered mesostructure. The MES samples were characterized by powder X-ray diffraction, nitrogen sorption, transmission electron microscopy, FT-IR, C-13 and Si-29 solid-state NMR and thermal gravimetric analysis. A phase transition from a disordered wormhole-like structure to an ordered P6mm structure was observed upon the addition of inorganic salts. The pore size of the MES decreases from 4.7 to 3.9 nm with increasing content of the inorganic salts. Fluoride was also found to be important for the formation of ordered MES under neutral conditions.

Structural relation properties of hydrothermally stable functionalized mesoporous organosilicas and catalysis

The surfactant assistant syntheses of sulfonic acid functionalized periodic mesoporous organosilicas with large pores are reported. A one-step condensation of tetramethoxysilane (TMOS) with 1,2-bis(trimethoxysilyi)ethane (BTME) and 3-mercaptopropyltrimethoxysilane (MPTMS) in highly acidic medium was performed in the presence of triblock copolymer Pluronic P123 and inorganic salt as additive. During the condensation process, thiol (-SH) group was in situ oxidized to sulfonic acid (-SO3H) by hydrogen peroxide (30 wt % H2O2). X-ray diffraction studies along with nitrogen and water sorption analyses reveal the formation of stable, highly hydrophobic, and well-ordered hexagonal mesoscopic structures in a wide range of -CH2CH2-concentrations in the mesoporous framework. The resultant materials were also investigated by Si-29 MAS and C-13 CP MAS NMR, thermogravimetric analyses, UV-Raman spectroscopy, and FT-IR spectroscopy. The role of the bridged organic group on the hydrothermal stability of the mesoporous materials was established, which revealed an enhancement in hydrothermal stability of the materials with incorporation of the bridged organic groups in the network. The catalytic performance of -SO3H functionalized mesoporous materials was investigated in the esterification of ethanol with acetic acid, and the results demonstrate that the ethane groups incorporated in the mesoporous framework have a positive influence on the catalytic behavior of the materials.

Synthesis and structural characterization of (pyrazolyl)alkenyl Fischer carbene complexes of chromium and tungsten

Michael addition of substituted pyrazoles 2 to 1-alkynyl Fischer carbene complexes (CO)(5)M=C(OEt)(CdropCPh) (1) (a, M = Cr and b M = W) afforded (pyrazolyl)alkenyl Fischer carbene complexes (CO)(5)M=C(OEt)(CH=C(R(1)R(2)R(3)pz)Ph) (R(1)R(2)R(3)pz = pyrazolyl) 3 (M = Cr) and 4 (M = W), respectively, with an exclusive (E)-configuration in mild to excellent yields. The reaction of la and 3,5-dimethylpyrazole (2b) was monitored to demonstrate the formation and decomposition of complex 3b by H-1 NMR measurements in CDCl3 at 23degreesC. Complexes 3 and 4 were characterized with H-1, C-13{H-1} NMR, IR spectroscopies and elemental analysis. When the substituted pyrazoles were 3-methylpyrazole (2a) and 3,5-di-tert-butylpyrazole (2d), molecular structures of the corresponding (pyrazolyl)alkenyl Fischer carbene complexes 3a and 4d were characterized by X-ray crystallographic study. (C) 2004 Elsevier Ltd. All rights reserved.