T-Muurolol Sesquiterpenes from the Marine Streptomyces sp M491 and Revision of the Configuration of Previously Reported Amorphanes

Two new sesquiterpenes, 15-hydroxy-T-muurolol (3d) and 11,15-dihydroxy-T-muurolol (3e), along with the plant cadinenes T-muurolol (3f) and 3 alpha-hydroxy-T-muurolol (3g), were isolated from the marine-derived Streptomyces sp. M491. Their absolute configuration was established via NMR spectroscopy and X-ray crystallography of 3-oxo-T-muurolol (3a), which was reisolated from this strain. In addition, the absolute configuration of further sesquiterpenes previously reported from this strain was revised. These products were tested for their cytotoxicity against 37 human tumor cell lines using the MTT method. Only 3d was cytotoxic against a range of human tumor cell lines with a mean IC50 of 6.7 mu g/mL.

江河源区高山嵩草（Kobresia pygmaea）草甸植物和土壤碳、氮储量对覆被变化的响应

以青海省果洛州藏族自治州甘德县青珍乡高山嵩草Kobresia pygmaea草甸轻度退化草地和重度退化草地为研究对象,通过植物地上部分主要功能群（禾草类、杂类草、莎草类）、植物根系和土壤碳、氮浓度及储量动态研究,结果表明：高寒小嵩草草甸轻度退化草地地上部分主要功能群碳、氮浓度和C∶N比值明显高于重度退化草地的浓度。同一草地类型主要功能群比较,碳、氮浓度依次为杂类草〉禾草类〉莎草类;植物地上部分的碳、氮浓度明显高于地下根系的碳、氮浓度。重度退化草地植物根系碳、氮浓度高于轻度退化草地植物根系碳、氮浓度。重度退化草地土壤总有机碳浓度显著低于轻度退化草地土壤总有机碳浓度,随着土层的加深碳、氮浓度有减少的趋势。江河源区高山嵩草草甸的土壤有机碳、氮储量最大,植物根系碳、氮储量居中,植物地上部分碳、氮储量最小。重度退化草地总有机碳储量（13554.3g/m~2）较轻度退化草地储量（14669.2g/m~2）下降7.60%。其中,0-40cm土壤层碳储量下降4.10%,植物根系碳储量下降59.97%,植物地上部分碳储量下降15.39%;重度退化草地总氮储量（3780.6g/m~2）较轻度退化草地储量（3352.7g/m~2）高12.76%,其中,0-40cm土壤中总氮储量高13.07%,植物根系全氮储量下降55.09%,植物地上部分全氮下降16.00%。由于草地退化损失有机碳11149kg/hm~2,而全氮增加4278kg/hm~2。

高寒金露梅灌丛生物量及年周转量

采用样方调查与挖掘相结合的方法，以金露梅（Potentilla fruticosa）灌丛多年累积枝干、地下生物量和当年新生枝叶量及6-9月冠面长度、宽度和高度为参数进行线性回归分析，结合金露梅灌丛与草本植物在样地所占比例，估算其年净初级生产量及年净固碳量。结果表明：2004年金露梅灌丛地下实际周转量为53．7g／m^2，周转率为26％；当年新生枝叶量为41．0g／m^2，年净初级生产量94．7g／m^2；以草本植物与金露梅灌丛在样地所占比例为60％和40％进行估算，2004年金露梅灌丛草甸总净初级生产量为858．3g／m^2，固碳量481．9g／m^2。

高寒草甸“黑土型”退化草地的成因及生态过程

研究分析退化草地的植被组成、地上生物量、优良牧草比例、高原鼠兔密度以及土壤理化性质等特征，探讨“黑土型”退化草地的成因及生态过程。结果表明，中度退化草地生物量最高（50.3g／0.25m2），重度退化草地最低（34.0g／m2）。原生植被优良牧草比例最高（78.40％）。重度退化草地最低（4.49％），轻度和中度退化草地居中（57.2％和16.42％）。中度退化草地高原鼠兔平均密度较高（148只／hm2），其危害程度较严重（494m2／hm2），二者之间呈显著的正相关（r＝O.9888，df＝3，P＜0.01）。土壤坚实度随草地退化程度加重而降低。“黑土型”退化草地的形成是一个长期的、连续的过程，草地退化则是诱发这一过程的主要因子，高原鼠兔挖掘洞道，破坏草皮及植被，又加剧了草地的进一步退化，最终导致了“黑土型”退化草地的形成和不断扩大。

关中盆地东部浅层地下水水化学与CFC年龄研究

Hydrochemistry, isotope and CFCs were used to determine groundwater transport in the eastern part of the Guanzhong Basin. In this paper, we systematically collected water samples and measured major ions, 2H-18O and CFCs in surface water and shallow groundwater. Groundwater in this region can be divided into three categories based on total dissolved solids (TDS): fresh water with TDS < 1g/L, brackish water with TDS between 1～3g/L, and saline water with TDS > 3g/L. Saline water is mainly located in the north of the Wei River, and saline groundwater is not in the south. Tributaries in the south of the Wei River and underlain groundwater had similar 2H-18O values, indicating a close hydraulic connection between them. Tributaries in the north of the Wei River characterized certain extent of evaporation, and 2H-18O values deviated to a differing extent between surface water and groundwater, indicating that surface water in the north bank of the Wei River has little hydraulic connection with underlain groundwater. The CFCs age of groundwater from the piedmont recharge area was young, and became older toward the Wei River valley. Vertically, the CFCs age of groundwater increased with well depth. The shallow groundwater is mainly composed of young water with ages < 60 years and old water with ages > 60 years. Young water is in a larger proportion. The NO3-N concentration positively correlates with the CFC-12 concentration in the groundwater, which indicates that young water is subjected to be contaminated. Keyword: Guanzhong Basin , shallow groundwater, isotope, CFC

南极格罗夫山陨石磁性分类研究

陨石分类是一项基础性的工作，是开展深入研究的前提。磁化率(χ)的测量提供了一种快速简单、无损的陨石分类方法，国外已有一些学者开始对陨石的磁性分类开展了研究，但国内尚无这方面研究的报导。本文主要对从南极格罗夫山回收的陨石开展了磁性分类的初步研究，论文主要工作包括以下几个方面： 1) 进行了磁化率测量模拟实验：由于陨石样品具有不规则和大小不等的形状，通过对模拟样品测量，了解上述几何因素对磁化率测量精度和准确性的影响，并作出MS2磁化率测量系统MS2D探头与MS2B传感器测量值之间的校正曲线。对模拟样品测量结果的分析表明，不同形状和大小的样品(所含磁性矿物分布均一)在进行MS2D测量时，测量相对偏差可控制在2%以内，表明上述测量系统可以用于陨石的磁化率测量。 2) 对所选600块南极格罗夫山陨石用MS2D探头进行了磁化率测量，得出这600块陨石的磁化率㏒χ(10-9m3/kg)数据，并用MS2B探头测量其中375块用来作岩石矿物学分类用的小块劈分样品的磁化率㏒χ(10-9m3/kg)。这600块格罗夫山陨石磁化率分布模式与南极其他区域收集的陨石较吻合，对应H、L、LL群呈3个明显的峰分布。相同的陨石用MS2D与MS2B两种探头测量，将它们的磁化率数据进行对比，显示它们的结果相当一致(相关系数R2=0.97)，也同时证明MS2D用于磁化率测量是行之有效的。 3)测量了44块沙漠陨石和9块降落型陨石的磁化率，在此基础上对南极格罗夫山陨石、沙漠陨石及降落型陨石数据做了对比讨论。格罗夫山陨石、沙漠陨石及降落型陨石磁化率值分布出现不同程度的偏移，总体来说磁化率㏒χ平均值为降落型陨石>南极陨石>沙漠陨石，这主要是由于陨石所受风化程度的差异造成的。风化作用使陨石部分金属发生氧化，因而降低了磁化率。 4)基于陨石的岩石矿物学分类，172块平衡型普通球粒陨石的磁化率分布，与文献上南极陨石磁化率分布基本一致，不过格罗夫山H、L、LL型普通球粒陨石磁化率分布范围更为狭窄，反映了南极不同地区陨石风化程度的差异。 5)讨论了陨石磁化率分类的有效性，分析了部分异常值出现的原因。磁化率分类结果与部分格罗夫山陨石的岩石矿物学分类(申请者作为陨石分类小组成员完成了其中的部分工作)结果相当吻合，仅在群之间约有5%的重叠，表明磁化率可作为化学群分类的重要参考数据。由于各陨石所受风化程度的差异，风化程度较强的少量陨石在磁性分类的基础上，还需其他工作加以证实。部分小质量(小于3g)且有部分或完整熔壳的陨石，磁化率受熔壳的影响达10%以上，偏离了其初始矿物的磁化率值，不能反映其真实的化学群类型，这部分磁化率数据仅供参考。

The ion-molecule reaction after multiphoton ionization in the binary cluster of ammonia and methanol

The binary cluster (CH3OH)(n)(NH3)(m) was studied by using a multiphoton ionization time-of-flight mass spectrometer (MPI-TOFMS). The measured two series of protonated cluster ions: (CH3OH)(n)H+ and (CH3OH)(n)NH4+ (1 less than or equal to n less than or equal to 14) were attributed to the ion-molecule reaction in the binary cluster ions. The mixed cluster of CH3OD with ammonia was also studied. The results implied that the proton transfer probability from the OD group was larger than that from CH3 group. The ab initio calculation of the binary cluster was carried out at the HF/STO-3G and MP2/6-31G** levels of theory, and indicated that the latter process of the proton transfer must overcome a barrier of similar to 29 kcal/mol. (C) 1999 Elsevier Science B.V. All rights reserved.

Controle da mancha de phomopsis em cupuaçuzeiro (Theobroma grandiflorum) com fungicida cúprico.

Visando obter controle da mancha de phomopsis em cupuaçuzeiro, foi aplicado experimentalmente o fungicida óxido cuproso na dosagem de 3g do produto comercial por litro de água em intervalos quinzenais, utilizando-se pulverizador costal.

TCP over CDMA2000 Networks: A Cross-Layer Measurement Study

Modern cellular channels in 3G networks incorporate sophisticated power control and dynamic rate adaptation which can have a significant impact on adaptive transport layer protocols, such as TCP. Though there exists studies that have evaluated the performance of TCP over such networks, they are based solely on observations at the transport layer and hence have no visibility into the impact of lower layer dynamics, which are a key characteristic of these networks. In this work, we present a detailed characterization of TCP behavior based on cross-layer measurement of transport, as well as RF and MAC layer parameters. In particular, through a series of active TCP/UDP experiments and measurement of the relevant variables at all three layers, we characterize both, the wireless scheduler in a commercial CDMA2000 network and its impact on TCP dynamics. Somewhat surprisingly, our findings indicate that the wireless scheduler is mostly insensitive to channel quality and sector load over short timescales and is mainly affected by the transport layer data rate. Furthermore, we empirically demonstrate the impact of the wireless scheduler on various TCP parameters such as the round trip time, throughput and packet loss rate.

TCP over CDMA2000 Networks: A Cross-Layer Measurement Study

Modern cellular channels in 3G networks incorporate sophisticated power control and dynamic rate adaptation which can have significant impact on adaptive transport layer protocols, such as TCP. Though there exists studies that have evaluated the performance of TCP over such networks, they are based solely on observations at the transport layer and hence have no visibility into the impact of lower layer dynamics, which are a key characteristic of these networks. In this work, we present a detailed characterization of TCP behavior based on cross-layer measurement of transport layer, as well as RF and MAC layer parameters. In particular, through a series of active TCP/UDP experiments and measurement of the relevant variables at all three layers, we characterize both, the wireless scheduler and the radio link protocol in a commercial CDMA2000 network and assess their impact on TCP dynamics. Somewhat surprisingly, our findings indicate that the wireless scheduler is mostly insensitive to channel quality and sector load over short timescales and is mainly affected by the transport layer data rate. Furthermore, with the help of a robust correlation measure, Normalized Mutual Information, we were able to quantify the impact of the wireless scheduler and the radio link protocol on various TCP parameters such as the round trip time, throughput and packet loss rate.

Prediction of bisolute dye adsorption isotherms on activated carbon

The removal of acid dyes, Tectilon Blue 4R, Tectilon Red 2B and Tectilon Orange 3G, from single solute, bisolute and trisolute solutions by adsorption on activated carbon (GAC F400) has been investigated in isotherm experiments. Results from these experiments were modelled using the Langmuir and Freundlich adsorption isotherm theories with the Langmuir model proving to be the more suitable. The Ideal Adsorbed Solution (IAS) model was coupled with the Langmuir isotherm to predict binary adsorption on the dyes. The application of the IAS theory accurately simulated the experimental data with an average deviation of approximately 3% between modelled and experimental data.

Estimation of in situ stresses using anisotropic elasticity and suction measurements

Sampling and specimen preparation produce changes in mean effective stresses and pore water pressures, even with ‘perfect sampling’. The paper takes an existing simplified three-parameter cross-anisotropic elastic model and uses it to model these changes. The required ratio of cross-anisotropic parameters J/3G* can be obtained from standard CIU triaxial tests. If measurements are also made of suctions in unloaded specimens in the laboratory, then a combination of J/3G*, the measured suction, and the effective overburden pressure permits an estimation of the horizontal effective pressure and the K 0 ‘at rest’ coefficient. This can be helpful in numerical modelling that needs to start from in situ conditions, and in planning pressure levels for reconsolidation of clay specimens in the laboratory. Tests were done on Belfast Upper Boulder Clay from a depth of 28 m. Values of horizontal in situ effective stress estimated from these measurements compare favorably with conventional estimates of the ‘at rest’ coefficient K 0 and the overconsolidation ratio. Estimates of horizontal stress in London Clay were made using published data and the results compared with actual measurements. Again reasonable agreement was obtained.

Two-colour pulsed Raman studies of the lowest excited singlet state of tetraphenylporphyrin: band assignments and electronic structure

The resonance Raman spectra of the lowest lying singlet (S-1) state of free-base tetraphenylporphyrin and seven of its isotopomers were recorded under pump-and-probe conditions with a time delay of -2 ns between pump and probe laser pulses, In the S-1 spectra of the isotopomers, as in the ground state, there are dramatic splittings of what appear to be single bands in the natural isotopic abundance spectrum. The most structurally significant bands of the S-1 state were assigned on the basis of the isotope data, In some cases it was necessary to curve fit unresolved bands in the excited-state spectra in order to account for observed intensity ratios and to rationalize isotope shifts, The changes in band positions on excitation to the S-1 state were compared with those from earlier studies on the T-1 state. The changes in band positions were found to be similar For both excited states. Most notable was the similar shift in nu(2), the most widely used marker band for orbital character. The data are interpreted as implying that the lowest lying singlet state is a configuration interaction admixture of b(1u)b(2g) + a(u)b(3g) configurations with the coefficients weighted heavily in favour of b(1n)b(2g), which Is the configuration of the T-1 state. Copyright (C) 2000 John Wiley & Sons, Ltd.

Investigation of the solid-liquid phase transition of carbon at 150 GPa with spectrally resolved X-ray scattering

We have resolved the solid-liquid phase transition of carbon at pressures around 150GPa. High-pressure samples of different temperatures were created by laser-driven shock compression of graphite and varying the initial density from 1.30g/cm³ to 2.25g/cm³. In this way, temperatures from 5700K to 14,500K could be achieved for relatively constant pressure according to hydrodynamic simulations. From measuring the elastic X-ray scattering intensity of vanadium K-alpha radiation at 4.95keVat a scattering angle of 126°, which is very sensitive to the solid-liquid transition, we can determine whether the sample had transitioned to the fluid phase. We find that samples of initial density 1.3g/cm³ and 1.85g/cm³ are liquid in the compressed states, whereas samples close to the ideal graphite crystal density of 2.25g/cm³ remain solid, probably in a diamond-like state.

Multilayer optimization in radio resource allocation for the packet transmission in wireless networks

Na última década tem-se assistido a um crescimento exponencial das redes de comunicações sem fios, nomeadamente no que se refere a taxa de penetração do serviço prestado e na implementação de novas infra-estruturas em todo o globo. É ponto assente neste momento que esta tendência irá não só continuar como se fortalecer devido à convergência que é esperada entre as redes móveis sem fio e a disponibilização de serviços de banda larga para a rede Internet fixa, numa evolução para um paradigma de uma arquitectura integrada e baseada em serviços e aplicações IP. Por este motivo, as comunicações móveis sem fios irão ter um papel fundamental no desenvolvimento da sociedade de informação a médio e longo prazos. A estratégia seguida no projecto e implementação das redes móveis celulares da actual geração (2G e 3G) foi a da estratificação da sua arquitectura protocolar numa estrutura modular em camadas estanques, onde cada camada do modelo é responsável pela implementação de um conjunto de funcionalidades. Neste modelo a comunicação dá-se apenas entre camadas adjacentes através de primitivas de comunicação pré-estabelecidas. Este modelo de arquitectura resulta numa mais fácil implementação e introdução de novas funcionalidades na rede. Entretanto, o facto das camadas inferiores do modelo protocolar não utilizarem informação disponibilizada pelas camadas superiores, e vice-versa acarreta uma degradação no desempenho do sistema. Este paradigma é particularmente importante quando sistemas de antenas múltiplas são implementados (sistemas MIMO). Sistemas de antenas múltiplas introduzem um grau adicional de liberdade no que respeita a atribuição de recursos rádio: o domínio espacial. Contrariamente a atribuição de recursos no domínio do tempo e da frequência, no domínio espacial os recursos rádio mapeados no domínio espacial não podem ser assumidos como sendo completamente ortogonais, devido a interferência resultante do facto de vários terminais transmitirem no mesmo canal e/ou slots temporais mas em feixes espaciais diferentes. Sendo assim, a disponibilidade de informação relativa ao estado dos recursos rádio às camadas superiores do modelo protocolar é de fundamental importância na satisfação dos critérios de qualidade de serviço exigidos. Uma forma eficiente de gestão dos recursos rádio exige a implementação de algoritmos de agendamento de pacotes de baixo grau de complexidade, que definem os níveis de prioridade no acesso a esses recursos por base dos utilizadores com base na informação disponibilizada quer pelas camadas inferiores quer pelas camadas superiores do modelo. Este novo paradigma de comunicação, designado por cross-layer resulta na maximização da capacidade de transporte de dados por parte do canal rádio móvel, bem como a satisfação dos requisitos de qualidade de serviço derivados a partir da camada de aplicação do modelo. Na sua elaboração, procurou-se que o standard IEEE 802.16e, conhecido por Mobile WiMAX respeitasse as especificações associadas aos sistemas móveis celulares de quarta geração. A arquitectura escalonável, o baixo custo de implementação e as elevadas taxas de transmissão de dados resultam num processo de multiplexagem de dados e valores baixos no atraso decorrente da transmissão de pacotes, os quais são atributos fundamentais para a disponibilização de serviços de banda larga. Da mesma forma a comunicação orientada à comutação de pacotes, inenente na camada de acesso ao meio, é totalmente compatível com as exigências em termos da qualidade de serviço dessas aplicações. Sendo assim, o Mobile WiMAX parece satisfazer os requisitos exigentes das redes móveis de quarta geração. Nesta tese procede-se à investigação, projecto e implementação de algoritmos de encaminhamento de pacotes tendo em vista a eficiente gestão do conjunto de recursos rádio nos domínios do tempo, frequência e espacial das redes móveis celulares, tendo como caso prático as redes móveis celulares suportadas no standard IEEE802.16e. Os algoritmos propostos combinam métricas provenientes da camada física bem como os requisitos de qualidade de serviço das camadas superiores, de acordo com a arquitectura de redes baseadas no paradigma do cross-layer. O desempenho desses algoritmos é analisado a partir de simulações efectuadas por um simulador de sistema, numa plataforma que implementa as camadas física e de acesso ao meio do standard IEEE802.16e.