42 resultados para Lincoln-Nipissing Development Co. Ltd.
em Chinese Academy of Sciences Institutional Repositories Grid Portal
Resumo:
Located in the Central and West African, Chad, which is not well geological explored, is characterized by Mesozoic- Cenozoic intra-continental rift basins. The boreholes exposed that, during Mesozoic-Cenozoic times, volcanic activities were intense in these basins, but study on volcanic rocks is very weak, especially on those embedded in rift basins, and so far systematic and detailed work has still no carried out. Based on the project of China National Oil and Gas Exploration and Development Corporation, “The analysis of reservoir condition and the evaluation of exploration targets of seven basins in block H in Chad”, and the cooperative project between Institute of Geology and Geophysics, CAS and CNPC International (Chad) Co. Ltd., “Chronology and geochemistry studies on Mesozoic-Cenozoic volcanic rocks from southwestern Chad Basins”, systematic geochronology, geochemistry and Sr-Nd-Pb isotopic geochemistry studies on volcanic rocks from southwestern Chad basins have been done in the thesis for the first time. Detailed geochronological study using whole-rock K-Ar and Ar-Ar methods shows the mainly eruption ages of these volcanic rocks are Late Cretaceous- Paleogene. Volcanic rocks in the well Nere-1 and Figuier-1 from Doba basin are products of the Late Cretaceous which majority of the K-Ar (Ar-Ar) ages fall in the interval 95-75 Ma, whereas volcanic rocks in the well Ronier-1 from Bongor Basin and the Well Acacia-1 from Lake Chad Basin formed in the Paleogene which the ages concentrated in 66-52Ma. Two main periods of volcanic activity can be recognized in the study area, namely, the Late Cretaceous period and the Paleogene period. Volcanic activities have a general trend of south to north migration, but this may be only a local expression, and farther future studies should be carried on. Petrology study exhibits these volcanic rocks from southwestern Chad basins are mainly tholeiitic basalt. Major- and trace elements as well as Sr-Nd-Pb isotopic geochemistry studies show that the late Cretaceous and the Paleogene basalts have a definitely genetic relationship, and magmas which the basalts in southwestern Chad basins derived from were produced by fractional crystallization of olivine and clinopyroxene and had not do suffered from crustal contamination. These basalts are prominently enriched light rare earth elements (LREE), large-ion lithophile elements (LILE) and high field strength elements (HFSE) and depleted compatible elements. They have positive Ba, Pb, Sr, Nb, Ta, Zr, Hf anomalies and negative Th, U, P,Y anomalies. It is possible that the basalts from southwestern Chad basins mainly formed by mixing of depleted mantle (DM) and enriched mantle (EMⅡ) sources. The late Cretaceous basalts have higher (87Sr/86Sr)i ratios than the Paleogene basalts’, whereas have lower (143Nd/144Nd)i ratios than the latter, showing a significant temporal evolution. The mantle sources of the Late Cretaceous basalts may have more enriched mantle(EMⅡ) compositions, whereas those of the Paleogene basalts are relatively more asthenospheric mantle (DM) components. The mantle components with temporal change observed in basalts from Chad basins were probably correlated with the asthenospheric mantle upwelling and lithospheric thinning in Central and Western Africa since Mesozoic. Mesozoic- Cenozoic Volcanism in Chad basins probably is a product of intra- plate extensional stress regime, corresponded to the tectonic setting of the whole West and Central African during Cretaceous. Volcanism is closely correlated with rifting. As time passed from early period to late, the basaltic magma of Chad basins, characterized with shallower genetic depth, higher density and smaller viscosity, probably indicates the gradual strengthening evolution of the rifting. In the initial rife stage, volcanic activities are absent in the study area. Volcanic activities are basiccally corresponded with the strong extensional period of Chad basins, and the eruption of basalts was slightly lagged behind the extensional period. In the post-rift stage (30-0Ma), these basins shifted to the thermal sag phase, volcanic activities in the study area significantly decreased and then terminated.
Resumo:
In the present study, EA-CATH1 and EA-CATH2 were identified from a constructed lung cDNA library of donkey (Equus asinus) as members of cathelicidin-derived antimicrobial peptides, using a nested PCR-based cloning strategy. Composed of 25 and 26 residues, respectively, EA-CATH1 and EA-CATH2 are smaller than most other cathelicidins and have no sequence homology to other cathelicidins identified to date. Chemically synthesized EA-CATH1 exerted potent antimicrobial activity against most of the 32 strains of bacteria and fungi tested, especially the clinically isolated drug-resistant strains, and minimal inhibitory concentration values against Gram-positive bacteria were mostly in the range of 0.3-2.4 mu g center dot mL-1. EA-CATH1 showed an extraordinary serum stability and no haemolytic activity against human erythrocytes in a dose up to 20 mu g center dot mL-1. CD spectra showed that EA-CATH1 mainly adopts an alpha-helical conformation in a 50% trifluoroethanol/water solution, but a random coil in aqueous solution. Scanning electron microscope observations of Staphylococcus aureus (ATCC2592) treated with EA-CATH1 demonstrated that EA-CATH could cause rapid disruption of the bacterial membrane, and in turn lead to cell lysis. This might explain the much faster killing kinetics of EA-CATH1 than conventional antibiotics revealed by killing kinetics data. In the presence of CaCl2, EA-CATH1 exerted haemagglutination activity, which might potentiate an inhibition against the bacterial polyprotein interaction with the host erythrocyte surface, thereby possibly restricting bacterial colonization and spread.
Resumo:
Fe-doped semi-insulating (SI) InP has become semi-conducting (SC) material completely after annealing at 900 V for 10 hours. Defects in the SC and SI InP materials have been studied by deep level transient spectroscopy (DLTS) and thermally stimulated current spectroscopy (TSC) respectively. The DLTS only detected Fe acceptor related deep level defect with significant concentration, suggesting the formation of a high concentration of shallow donor in the SC-InP TSC results confirmed the nonexistence of deep level defects in the annealed SI-InP. The results demonstrate a significant influence of the thermally induced defects on the electrical properties of SI-InP. The formation mechanism and the nature of the shallow donor defect have been discussed based on the results.
Resumo:
Hexagonal GaN films (similar to 3 mu m) were grown on 3c-SiC/Si(111) and carbonized Si(111) substrates using a thick AlN buffer Cracks are observed on the surface of the GaN film grown on the carbonized Si(111), while no cracks are visible on the 3c-SiC/Si(111). XRD exhibits polycrystalline nature of the GaN film grown on the carbonized Si(111) due to poorer crystalline quality of this substrate. Raman spectra reveal that all GaN layers are under tensile stress, and the GaN layer grown on 3c-SiC/Si(111) shows a very low stress value of sigma(xx) = 0.65 Gpa. In low-temperature Photoluminescence spectra the remarkable donor-acceptor-pair recombination and yellow band can be attributed to the incorporation of Si impurities from the decomposition of SiC.
Resumo:
4H-SiC layers have been homoepitaxially grown at 1500 degrees C with the use of a horizontal hot-wall chemical vapor deposition (CVD) system, which was built in the author's group. The typical growth rate was 2 mu m/h at a pressure of 40 Torr. The background donor concentration has been reduced to 2.3 x 10(15) cm(-3) during a prolonged growth run. It confirmed the idea that the high background concentration of thin films was caused by the impurities inside the susceptor and thermal insulator The FWHM of x-ray co-rocking curves show 9 similar to 15 aresecs in five different areas of a 32-mu m-thick 4H-SiC epilayer The free exciton peaks dominated in the near-band-edge low-temperature photoluminescence spectrum (LTPL), indicating high crystal quality.
Resumo:
Various techniques on the growth of self-assembled compound semiconductor nano-structures (quantum dots, QDs) have been tried to enhance the controlling on size, density, emitting wavelength, uniformity in size and ordering in location of the QDs. Optimized growth conditions have been used in the application of the QD materials in opto-electronic devices. High-power long-lifetime quantum-dot laser-diodes (QD-LDs) emitting near 1 mu m, QD-LDs emitting in red-light range, 1.3 mu m QD-LDs on GaAs substrate and quantum-dot super-luminescent diodes (QD-SLDs) have successfully been achieved.
Resumo:
A promising approach for positioning of InAs islands on (110)GaAs is demonstrated. By combining self-assembly of quantum dots with solid source molecular beam epitaxy (MBE) on cleaved edge of InGaAs/GaAs superlattice (SL), linear alignment of InAs islands on the InGaAs strain layers have been fabricated The cleaved edge of InGaAs/GaAs SL acts as strain nanopattern for InAs selective growth. Indium atoms incident on the surface will preferentially migrate to InGaAs regions where favorable bonding sites are available. The strain nanopattern's effect is studied by the different indium fraction and thickness of InxGa1-xAs/GaAs SL. The ordering of the InAs islands is found to depend on the properties of the underlying InGaAs strain layers.
Resumo:
The effect of thermal annealing of InAs/GaAs quantum dots (QDs) with emission wavelength at 1.3 mu m have been investigated by photoluminescence (PL) and transmission electron microscopy (TEM measurements. There is a dramatic change in the A spectra when the annealing temperature is raised up to 800 degrees C: an accelerated blushifit of the main emission peak of QDs together with an inhomogeneous broadening of the linewidth. The TEM images shows that the lateral size of normal QDs decreases as the annealing temperature is increased, while the noncoherent islands increase their size and densit. A small fraction of the relative large QDs contain dislocations when the annealing temperature increases up to 800 degrees C. The latter leads to the strong decrease of the PL intensity.
Resumo:
A novel technique of manufacturing Al0.3Ga0.7As pyramids by liquid phase epitaxy (LPE) for scanning probe microscopy (SPM) sensors is reported Four meticulously designed conditions-partial oxidation, deficient solute, air quenching and germanium doping result in defect-free homogeneous nucleation and subsequent pyramid formation. Micrometer-sized frustums and pyramids are detected by scanning electron microscopy (SEM). The sharp end of the microtip has a radius of curvature smaller than 50 nm. It is believed that such accomplishments would contribute not only to crystal growth theory, but also to miniature fabrication technology.
Resumo:
Raman scattering measurements have been performed in diluted magnetic semiconductor Ga1-xMnxAs prepared by Mn-ion implantation, deposition, and post-annealing technique. It is found that the Raman spectrum measured from the implanted surface of the sample shows some new weak modes in addition to the GaAs-like modes which are observed from the unimplanted surface. The new vibrational modes observed are assigned to MnAs-like modes. The coupled LO-phonon plasmon mode, and Mn and As related vibrational modes caused by Mn-ion implantation, deposition, and post-annealing are also observed. Furthermore, the GaAs-like modes are found to be shifted by approximately 4 cm(-1) in the lower frequency side, compared with those observed from the unimplanted surface.
Resumo:
The self-organized InAs/In0.52Al0.48As nanostructure were grown on InP (001) using molecular beam epitaxy (MBE). The nanostructure has been studied using transmission electron microscopy (TEM) and high resolution transmission electron microscopy (HRTEM). The edge dislocations with the Burgers vector b = ([001]/2) and extending along the [$(110) over bar $] direction are observed. The results show that in the region near an edge dislocation, no InAs wires were formed, while in the regions free of dislocation, wire-like nanostructures were formed. The mechanisms for the formation of the [001]/2 edge dislocations were discussed.
Resumo:
A novel approach to achieving a polarization-insensitive semiconductor optical amplifier is presented. The active layer consists of graded tensile strained bulk-like structure. which can not only enhance TM mode material gain and further realize polarization-insensitivity, but also get a large 3dB bandwidth due to different strain introduced into the active layer. 3dB bandwidth more than 40nm. 65nm has been obtained in die experiment and theory, respectively. The characteristics of such polarization insensitive structure have been analyzed, The influence of the amount of strain and of the thickness of strain layer on the polarization insensitivity has been discussed.
Resumo:
We show that the observed temperature dependence of the photoluminescence (PL) features can be consistently explained in terms of thermally activated carrier transfer processes in a multilayer structure of the self-organized Ge/Si(001) islands. The type II (electron confinement in Si) behavior of the Ge/Si islands is verified. With elevated temperature, the thermally activated electrons and holes enter the Ge islands from the Si and from the wetting layer (WL), respectively. An involvement of the type I (spatially direct) into type II (spatially indirect) recombination transition takes place at a high temperature.
Resumo:
Integrated multimode interference coupler based on silicon-on-insulator has been become a kind of more and more attractive device in optical systems. Thin cladding layers (<1.0mum) can be used in SOI waveguide due to the large index step between Si and SiO2, making them compatible with the VLSI technology. Here we demonstrate the design and fabrication of multimode interference (MMI) optical couplers and optical switches in SOI technology.
Resumo:
High speed reliable 1.55 mum AlGaInAs multi-quantum well ridge waveguide (RW) DFB laser is developed with a 9GHz -3dB bandwidth. A high speed self aligned constricted mesa 1.55 mum DFB laser is achieved with a 9.1GHz -3dB bandwidth and a more than 20mW output power. A cost effective single RW electroabsorption modulated DFB laser (EMLs) is proposed and successfully fabricated by adopting selective area growth techniques:. a penalty free transmission at 2.5Gbps over 280Km normal G.652 single mode fiber is realized by using this EML as light source. For achieving a better performance EMLs. a gain-coupled DFB laser with etched quantum wells is successfully integrated with a electroabsorption modulator (EAM) for a high single mode yield. the wavelength of a EML is tuned in a 3.2nm range by a integrated thin-film heater for the wavelength routing. a buried heterostructure DFB laser is also successfully integrated with a RW EAM for a lower threshold current. lower EAM parasitic capacitance and higher output power.