2,368 research outputs found
Pakistan-China Relations: CPEC and Beyond
Get PDFThis contribution is based on the proceedings of a session on the same title organized by the Institute of Policy Studies (IPS), Islamabad on August 10, 2017. The highlight of the event, as is recorded in this article, was the exclusive talk of H.E. Sun Weidong, Chinese ambassador to Pakistan while the opening and concluding remarks by Khalid Rahman, Executive President of IPS and Senator Raja Zafar-ul-Haq, Leader of the House in the Senate of Pakistan, respectively, are also part of the article. Pleasantries have been edited for the purpose of brevity and consistency
Pakistan-China Relations: CPEC and Beyond
No full textThis contribution is based on the proceedings of a session on the same title organized by the Institute of Policy Studies (IPS), Islamabad on August 10, 2017. The highlight of the event, as is recorded in this article, was the exclusive talk of H.E. Sun Weidong, Chinese ambassador to Pakistan while the opening and concluding remarks by Khalid Rahman, Executive President of IPS and Senator Raja Zafar-ul-Haq, Leader of the House in the Senate of Pakistan, respectively, are also part of the article. Pleasantries have been edited for the purpose of brevity and consistency.</jats:p
Geochemical perspectives on mantle dynamics and plate interactions in Asia - A special issue in honor/memory of Dr. Shen-su Sun Preface
No full texthttp://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=WOS:000310124900001&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=8e1609b174ce4e31116a60747a720701Geochemistry & GeophysicsSCI(E)EI0EDITORIAL MATERIAL,SI1-432
Total synthesis of 7-Epi-FR 66979 and 7-Epi-FR 900482
No full textThe completion of the total synthesis of 7-Epi-FR 66979 and 7-Epi-FR 900482 is presented in this thesis. The natural product FR 66979 and FR 900482 were isolated by the Fujisawa Pharmaceutical Corporation from Streptomyces sandaensis. They are antibiotics with potent antitumor activity. The first stage of the total synthesis is to make indole ester. For the preparation of the precursor of the indole ester, the commercial available starting material 3-hydroxymethylphenol was converted to benzyl aldehyde by using the reagents paraformaldehyde and lewis catalyst SnCl4 after the selective protection of hydroxymethyl group. After the phenol had been protected, this benzyl aldehyde precursor was transformed to indole ester by the Hemetsberger-Knittel reaction in 61% yield. The second stage of the total synthesis is to make fully functionalized pyrroloindole. The indole ester was reduced by DIBAL and then was oxidized to indole aldehyde. The vinylsulfonium salt reacted with this indole aldehyde to form the tetracyclic oxirane, then subsequently treated by sodium azide in acetone-water to afford pyrroloindole in 74% yield. The third stage of the total synthesis is to synthesize the core ring system. The fully functionalized pyrroloindole was successfully oxidized by two equivalents of dimethydioxirane (DMDO) in acetone/water to give ring expanded hydroxylamine hemiketal ring system in 57% yield. The final stage of the total synthesis is to complete the total synthesis. One of the challenging steps is to prepare the hydroxylmethyl group on this core structure. With many studies, the hydrosilylation-oxidation was found to be a good method to make the hydroxymethyl group on this complex molecule. After converting the hydroxymethyl group to urethane and deprotection, 7-Epi-FR 66979 was successfully obtained. With a one step oxidation of 7-Epi-FR 66979, 7-Epi-FR 900482 was prepared. This total synthesis is the shortest and most efficient so far. Epi-FR 66979 is synthesized in 20 steps while epi-FR 900482 required 21 steps. The attempt of making the beta configuration of the hydroxymethyl group on the 7-position for FR 66979 and FR 900482 is also described in this thesis. The efforts included intramolecular hydrosilylation-oxidation, less hindered intermolecular hydrosilylation-oxidation, catalytic hydroboration-oxidation and Danishefsky's methods of the epoxidation and opening. Both less hindered intermolecular hydrosilylation-oxidation and Danishefsky's methods provided intermediate with beta configuration of hydroxymethyl, but the final product was not obtained. A less hindered intermolecular hydrosilylation-oxidation method will provide the best chance to get the natural product when additional more intermediates are prepared in the future.Ph.D.Includes abstractVitaIncludes bibliographical referencesby Weidong Pa
Ocean sensors - for marine environmental monitoring
No full textVarious sensors and instruments were developed to measure the chemical and physical properties of sea water, but many are expensive and too large to be used on mass deployed vehicles such as the Argo float and submersed gliders. Marine mammal and fish tags require further sensor miniaturisation. This thesis describes the development of new in-situ micro sensor technology for marine environmental monitoring.Nitrite and nitrate are two forms of dissolved inorganic nitrogen in sea water and their availability is a key factor in the regulation of primary productivity in the sea. The in-situ determination of nitrite and nitrate in sea water presents a significant analytical challenge. In this thesis, a simple, low cost double beam spectrophotometer for use in a nitrite sensor for sea water analysis is presented. The sensor uses a colorimetric method to determinate nitrite concentration in sea water, based on Greiss reaction that forms as Azo dye whose absorbance is measured at a wave length of 540nm. The design incorporates a green LED and integrated photo-detectors to make the nitrite sensor compact, with low-cost and low-power consumption.A Conductivity, Temperature, Depth (CTD) sensor is the primary tool for determining the physical properties of sea water. A new CT (Conductivity and Temperature) micro sensor is presented in this thesis. The temperature sensor uses a thermistor, and the conductivity sensor uses a novel design of four planar electrodes built in an insulated channel. Conductivity sensors built of planar electrodes can be easily mass-produced on PCB boards, thus significantly reducing cost.This thesis includes the background of the measurement of conductivity, temperature and nitrite concentration in sea water. It also presents a comprehensive analysis of conductivity cells with two, four and five electrodes, together with the detailed multi-sensor interface design. The design and construction of the prototype sensors are described in detail, the key issues and test results are also presented
Eocene north-south trending dikes in central Tibet: New constraints on the timing of east-west extension with implications for early plateau uplift?
No full textEast-west extension has been a prominent feature of Cenozoic tectonics in central-southern Tibet, and the onset of this extension has been interpreted as indicating the surface uplift of the Tibetan Plateau to a critical level. Previous studies suggested that extension started in the Neogene between 18-13. Ma and 8. Ma, based on dating results from north-south trending normal faults, grabens or rifts, and dikes. We report here the discovery of widespread north-south trending diabase and andesitic porphyry dikes in and around the Shuang Hu graben, central Tibet, where crustal extension has previously been argued to start from 13.5. Ma based on mineral ages from graben-bounding faults. Our results show that dikes in this area were mainly formed in the Eocene (47-38. Ma). Geochemical and Nd-Sr isotopic data suggest that the diabase dikes originated from partial melting of an enriched lithospheric mantle source metasomatized by melts from subducted continental crust, and the andesitic porphyry dikes were probably derived from interactions between the subducted continental crust-derived melts and the mantle. Given that north-south trending Eocene dikes are found widely dispersed in central Tibet, we argue that the onset of east-west extension, and likely regional uplift of the Tibetan Plateau, began much earlier than previously thought. Our study implies that a large part of the Tibetan Plateau had already attained near-maximum elevation in the Eocene and is consistent with recent investigations regarding the Middle-Late Eocene (47-34. Ma) initiation of aridification in Asia, evidence from contemporary global oceanic O-Sr isotope curves and temperatures, and the carbon cycle. © 2010 Elsevier B.V
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