乍得西南部中新生代火山作用与盆地演化

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.

中国大陆地区远震体波接收函数与岩石圈厚度的研究

Movements of separation and convergence between the continental plates, as well as the interaction beween the lithosphere and asthenosphere is the dominant factor in plate evolution. Moreover, those phenomena, the formation, enrichment and storage of energy and mineral strorage, as well as intraplate earthquakes are all relate to plate movement and evolution. Therefore, the study of continental lithosphere, is not only helpful to analysing the dynamic model between lithosphere and asthenoshere as well as different plates, but also important to the nation's economy and the people's livelihood. And the lithospheric thickness or Lithosphere-Asthenosphere Boundary (LAB) is one of the most important parameters in study of continental lithospheric formation and evolution. Chinese continent composed by many small plates, possesses diverse type of lithospheric structure. But our knowledge ahout Chinese continental lithosphere, especially the regional research, is almost based on the low-resolution results of surface wave dispersion analysis and seismic wave tomography. Howere, recently a technique employing S-to-P converted body waves (the S receiver function technique) has been developed that can be used to identify the LAB with a higher resolution. This thesis has collected waveform data of 232 broadband seismic stations that are located in China and neighboring regions. Using teleseismic S-wave and P-wave receiver functions have studied the Chinese continental lithospheric structure. The results of this study indicate that, the thickness of Chinese continental lithosphere become thinner from west to east, and obvious difference exists between different blocks. Four types of lithosphere have been detected: (1) Convergence thicking lithosphere in Tibetan Plateau; (2) Stable lithosphere in Tarim basin and upper Yangtze craton; (4) Active lithosphere in Orogenic belts; (4) Break-up thinning lithosphere in east China craton

胶东蓬家夼式金矿床矿床成因模型与找矿模型研究

The dynamic environments of mineralization in Mesozoic Jiaodong gold mine concentrated area can be devided into two types, compressive environment which related to intracontinental collision and extensional environment which related to intracontinental volcanic rift. The altered rock type (Jiaojia type) and quartz vein type (Linglong type) which related to the former one, were discovered for several years, and became the main types of gold deposits in recent years. A new type gold deposit, syn-detachment altered tectonic breccia type gold deposit, such as Pengjiakuang gold deposit and Songjiagou gold deposit has been discovered on the northeastern margin of Jiaolai Basin. In this paper, the new type of gold deposit has been studied in detail. The study area is located at the northeastern boundaries of Jiaolai Basin, and between the Taocun-Jimo Fault and Wji-Haiyang Fault, in the eastern part of the Jiaodong Block. Pengjiakuang gold deposit and Songjiagou gold deposit occur in a arc-shape detachment fault zone between conglomerate of Lower Cretaceous Laiyang Formation and metamorphic complex of Lower Proterozoic Jingshan Group. Regional geological studies show that Kunyuanshan and Queshan granite intrusions and Qingshanian volcanism were formed in different period of lithospheric thinning of East China in Mesozoic. Granite intrusions were formed in compressive environment, while Qingshanian volcanism were formed in extensional environment. They are all related to the detachment of Sulu Orogenic Belt and the sinistral motion of Tanlu Fault. The Pengjiakuang detachment systems which were formed in the the sinistral motion of Tanlu Fault are the important ore-controlling and ore-containing structure. The Pengjiakuang type gold deposit, controlled by detachment structure, was formed before Yanshanian volcanic period concerning with mixture of meteoric water and magmatic water found in fluid inclusions of gold ores. The minerogenetic epoch has been proposed in 90～120Ma. the host rocks have been extensively subjected to pyritization, silicification, sericitization and carbonatization. Individual ore-body has maximum length of 800m, oblique extension of 500～700m and gold grade of 1～43 * 10~(-6). Native gold is disseminated in silicified, phyllic or carbonatized tectonic breccia. Sulfur, carbon and lead isotope studies on gold ores and wall rocks show that the sulfur come from the metamorphic complex of Lower Proterozoic Jingshan Group, carbon comes from the marble in Jingshan Group, while a part of lead comes from the mantle. The mineralizing fluid is rich in Na~+ and Cl~-, but relatively impoverished in K~+ and F~-. According to the date from hydrogen and oxygen isotopic compositions (δ~(18)OH_2O = 0.59%～4.03%, δDH_2O = -89.5%～97.9%), the conclusion can be reached that the mineralizing fluid of Pengjiakuang gold deposit was a kind of mixed hydrothermal solution which was mainly composed of meteoric water and magmatic water. A genetical model has been formulated. Some apparent anomaly features which show low in the central part and high in the both sides corresponding to the gold-bearing structure, were sum up after analying a vast amount of date by prospecting the orebodies using gamma-ray spectrometer, electrogeochemical parameter technique, controlled source audio magnetic telluric (CSAMT) and shallow surface thermometry in Pengjiakuang gold deposit. The location forecasting problem of buried orebodies has been solved according to these features, and the successful rate is very high in well-drilling. The structural geological-geophysical-geochemical prospecting model has been formulated on the base of the study of geological, geophysical and geochemical characteristics of Pengjiakuang type gold deposit, and the optimum combinational process of geophysical and geochemical prospecting techniques has been summed up. A comparative study shows that the Pengjiakuang type gold deposit, the syn-detachment altered tectonic breccia type gold deposit, is different from Jiaojia type gold deposits and Linglong type gold deposits, in Jiaodong Block. In general, if formed under an extensional tectonic condition and located at detachment fault zone along the margin of Mesozoic Jiaolai basin, and the gold mineralization has also close genetic relationship with alkaline magamtism. Being a new type of gold deposit in Jiaodong gold mine concentrated area, it could be potential to explore in the same regions which processed the same ore-forming geological conditions and mineralization informations.

大别－苏鲁造山带与华北陆块东部岩石层三维速度结构

The 3-D velocity images of the crest and upper mantle beneath the region of 112° -124°E, 28°-39°N including the Dabie-Sulu orogenic belt are reconstructed by using 36405 P-wave arrivals of 3437 regional and 670 distant earthquakes during the period from 1981 to 1996, and gridding the area of 0.5° * 0.5°. The results of tomography demonstrate that: 1. The results of tomographic imaging show a broad heterogeneity in P wave velocity structure for the lithosphere beneath the Dabie-Sulu orogenic belt. 2. In the Dabie orogenic belt, the velocity patterns in the crust are different among various tectonic units. The Dabie and Qinling orogenic belts are remarkable in the tomographic images, and in mm the Hongan and Dabie blocks in the Dabie orogenic belt are also imaged very distinguishably. 3. A velocity (about 5.9～6.0 km/s) layer exists in the Dabie block at depth between 15～25 km, which is coincident with the low-resistance layer at the depth of 12-23 km, being inferred to be the tectonic detachment zone and suggesting that the extension detachment structure was formed in the middle crust. Beneath the southern and northerm Dabie tectonic units, the north-dipping high-velocity (at level of 6.5 ～ 6.6 km/s) block was developed in the crust, which might be correlated with the UHP rockswith low content of the meta-ultramafic rocks. This result is in agreement with the geological observation on the surface. 4. The velocity image at 40 km depth reveals the features at the top of mantle and the configuration of the Moho discontinuity. The depth of the Moho changes slightly along the trend of the orogenic belt. It in Hongan block is less than 40 km, but it is different in the western and eastern parts of the Dabie block, the former is more than 40 km, and the latter less than or equal to 40 km. The remnant of the mountain root exists between the Shangcheng-Macheng fault and the line of Huoshan-Yuexi-Yingshan in the Dabie orogenic belt, and beneath the southern and northern Dabie tectonic units. However, the thickness of the Moho is about 40 km and there is no obvious changes, which suggest that the Dabie orogenic belt has been experienced quite in the gravity equilibration. The Moho's depth in the Sulu is less than 40 km. 5. There is a dipping slab-like high-velocity body in the uppermost mantle. It is sandwiched by slow velocities and exists beneath the Dabie-Sulu orogenic belt in the range of depths between the Moho discontinuity and 110 km at least. This high-velocity body outlines a picture of the slab interpreted as the remnant of the Triassic subducted YZ. 6. The Sulu orogenic belt displays "crocodilian" velocity structure, the upper crust of the Yangtze thrusted over the Huabei crest, and the Huabei crust indented into the Yangtze crust, where the ancient subduction zone of the Yangtze lithosphere located. Based on the previous geological data, this structure is not related with the collision between the Yangtze and Sino-Korean Blocks, but caused by the sinistral offset of the Tan-Lu Fault. Studied on the velocity structure of the eastern Huabei lithosphere indicates: 1. The 'present-day' lithosphere of the eastern Huabei is between 40-100 km thick with greatly thinned lithosphere around the Bohai Sea. Generally, thickness of the lithosphere in this region decreased eastwards. 2. The attenuation of the lithosphere is attributed to the strongly uplift of the asthenosphere. In the area between the Taihang Mountains and the Tan-Lu Fault, there is a 'lever' with red low velocity belt, it is clearly defined, transverse continuity, depth between 100-150 km, local variations visible, and an upwards trend towards the Bohai Sea. Generally, the velocity structure in the mantle beneath the lithosphere displays irregular column-shape consisting of alternating high and low velocities, and when cold high velocity ancient lithosphere connects with the hot low velocity mantle materials forming precipitous compact structure. More heat pathways from the mantle occur towards the Tan-Lu Fault. 3. The strongly irregular characteristics of the contact between the asthenosphere and the lithosphere is induced by the long-term hot, chemical erosion and alteration on the contact. 4. There are still preserved high velocity lithosphedc root beneath Huabei with 'block-shape' distribution and surrounded by hot materials. Results of our studies indicate that the evolution models of the eastern China mantle are characterized by the direct contact between the uplifted lithosphere and the Huabei Craton accompanying the upwelling of the deep mantle materials. At the contact betwen the lithosphere and the asthenosphere, the upwelled mantle materials replaced and altered the lower lithosphere forming the metasome through the hot and chemical modifications impacted on the Craton lithosphere, and changed it into the lithosphere gradually, resulting in the lithospheric thinning. Thus, the lithospheric thinning is the result of the upwelling of the asthenosphere.

山东莱芜中生代高镁侵入岩及其超镁铁质岩捕掳体的成因研究

In order to know better about the Phanerozoic lithosphere thinning process of Sino-Korea Plate, four Cretaceous intrusion complexes and their ultramafic xenoliths are investigated by this thesis, which are located in Laiwu, Shandong Province, Eastern China, a region far away from plate margin. The four complexes, Kuanshan, Jiaoyu, Jingniushan and Tietonggou, intruded into Archaeozoic granite gneiss and Paleozoic carbonate rocks with scam iron ore at their contact zone. The four complexes can be divided into two magma series, abyssal rocks for the early and hypabyssal rocks for the later. K-Ar dating show that the abyssal rocks intrusion began with 120 ±2 Ma and the hypabyssal rocks intruded about 113 Ma. Abyssal rocks, mainly made up of augite diorites, amphibole diorites and gabbros for the lesser, are chemically characterized with high-Mg (Mg#>0.5) high-K calcalklic rock, which are depleted with Nb, Ta and Ti related to LILE and extremely enriched with Sr and Pb. Comparatively, augite diorites are the most LREE enriched in abyssal rocks, and they show no Eu abnorrnity or weak positive Eu abnormity. Gabbros show the least LREE enrichment with a strong Eu abnormity relatively. In (~(87)Sr/~(86)Sr)_1 -ε Nd(T) diagram, the abyssal rocks show a mixing trend , a rapid change in ε Nd(T) with a relatively small change in (~(87)Sr/~(86)Sr)_1. Low radiogenic Sr and Pb composition with high radiogeic Nd composition indicate that the mixing processes happened in lower crust Melt-rock interactions in lower crust might be the most possible processes to produce these high-Mg and high-K calcalklic magmas. Hypabyssal rocks, mainly made up of granite porphyry and dioritic porphrite, show much higher ε Nd(T) than abyssal rocks. Granite porphyry are distinct with an adakite geochemical characteristics, high (La/Yb)_N, Sr/Y and low Rb/Sr ratio. The adakitic granite porphyry indicates a new lower crust produced by underplating within plate. Ultramafic xenoliths had been found only in augite diorites and amphibole diorites. Field investigations show that ultramafic xenoliths in augite diorites had been inherited from amphibole diorites, so ultramafic xenoliths had been only entrained by hydrous dioritic magma. Ultramafic xenoliths are mainly made up of dunite and harzburgite, orthopyroxenite and bistangite are the lessor. Coarse olivines in dunite often show many chromite exsolution lamellae. Opx in orthopyroxenite often show dense chromite exsolution lamellae. The presence of exsolution minerals indicates that ultramafic xenoliths had cooled before entraining. Metasomatism phenomenons are popular in dunite and harzburgite xenoliths, including two kinds of assemblage, cpx+phlogapite and opx+pl. The first metasomatism assemblage indicates an ancient enrichment. Rb-Sr dating of xenoliths shows that the ancient enrichment happened in 223 ± 7Ma. The second metasomatism assemblage indicates a recent, relatively not deep melt-rock interaction, which might be related with the genesis of the high-Mg high-K calcalklic rocks. Mineralogy and geochemistry indicate that these ultramafic xenoliths might sample the crust-mante transition zone (or the base of lower crust, moho). Investigation of high-Mg intrusions and their ultramafic xenoliths in Laiwu indicate that the thinning processes of Sino-Korea Plate can be divided into two stages. The first stage is lithosphere mantle thinning with crust thickening by underplating in lower crust. The second stage is that the thickened lower crust delaminated into the underlying mantle.

Multiple Dynamic Processes Contribute to the Complex Steady Shear Behavior of Cross-Linked Supramolecular Networks of Semidilute Entangled Polymer Solutions.

Molecular theories of shear thickening and shear thinning in associative polymer networks are typically united in that they involve a single kinetic parameter that describes the network -- a relaxation time that is related to the lifetime of the associative bonds. Here we report the steady-shear behavior of two structurally identical metallo-supramolecular polymer networks, for which single-relaxation parameter models break down in dramatic fashion. The networks are formed by the addition of reversible cross-linkers to semidilute entangled solutions of PVP in DMSO, and they differ only in the lifetime of the reversible cross-links. Shear thickening is observed for cross-linkers that have a slower dissociation rate (17 s(-1)), while shear thinning is observed for samples that have a faster dissociation rate (ca. 1400 s(-1)). The difference in the steady shear behavior of the unentangled vs. entangled regime reveals an unexpected, additional competing relaxation, ascribed to topological disentanglement in the semidilute entangled regime that contributes to the rheological properties.

Experimental investigation of thermal structures in regular three-dimensional falling films

Interfacial waves on the surface of a falling liquid film are known to modify heat and mass transfer. Under non-isothermal conditions, the wave topology is strongly influenced by the presence of thermocapillary (Marangoni) forces at the interface which leads to a destabilization of the film flow and potentially to critical film thinning. In this context, the present study investigates the evolution of the surface topology and the evolution of the surface temperature for the case of regularly excited solitary-type waves on a falling liquid film under the influence of a wall-side heat flux. Combining film thickness (chromatic confocal imaging) and surface temperature information (infrared thermography), interactions between hydrodynamics and thermocapillary forces are revealed. These include the formation of rivulets, film thinning and wave number doubling in spanwise direction. Distinct thermal structures on the films’ surface can be associated to characteristics of the surface topology.

Thixotropic studies of lead-based solder, lead-free solder and conductive adhesive pastes

The stencil printing process is an important process in the assembly of Surface Mount Technology (SMT)devices. There is a wide agreement in the industry that the paste printing process accounts for the majority of assembly defects. Experience with this process has shown that typically over 60% of all soldering defects are due to problems associated with the flow properties of solder pastes. Therefore, the rheological measurements can be used as a tool to study the deformation or flow experienced by the pastes during the stencil printing process. This paper presents results on the thixotropic behaviour of three pastes; lead-based solder paste, lead-free solder paste and isotropic conductive adhesive (ICA). These materials are widely used as interconnect medium in the electronics industry. Solder paste are metal alloys suspended in a flux medium while the ICAs consist of silver flakes dispersed in an epoxy resin. The thixotropy behaviour was investigated through two rheological test; (i) hysteresis loop test and (ii) steady shear rate test. In the hysteresis loop test, the shear rate were increased from 0.001 to 100s-1 and then decreased from 100 to 0.001s-1. Meanwhile, in the steady shear rate test, the materials were subjected to a constant shear rate of 0.100, 100 and 0.001s-1 for a period of 240 seconds. All the pastes showed a high degree of shear thinning behaviour with time. This might be due to the agglomeration of particles in the flux or epoxy resin that prohibits pastes flow under low shear rate. The action of high shear rate would break the agglomerates into smaller pieces which facilitates the flow of pastes, thus viscosity is reduced at high shear rate. The solder pastes exhibited a higher degree of structural breakdown compared to the ICAs. The area between the up curve and down curve in the hysteresis curve is an indication of the thixotropic behavior of the pastes. Among the three pastes, lead-free solder paste showed the largest area between the down curve and up curve, which indicating a larger structural breakdown in the pastes, followed by lead-based solder paste and ICA. In a steady shear rate test, viscosity of ICA showed the best recovery with the steeper curve to its original viscosity after the removal of shear, which indicating that the dispersion quality in ICA is good because the high shear has little effect on the microstructure of ICA. In contrast, lead-based paste showed the poorest recovery which means this paste undergo larger structural breakdown and dispersion quality in this paste is poor because the microstructure of the paste is easily disrupted by high shear. The structural breakdown during the application of shear and the recovery after removal of shear is an important characteristic in the paste printing process. If the paste’s viscosity can drop low enough, it may contribute to the aperture filling and quick recovery may prevent slumping.

Study of the rheological behaviour of Sn-Ag-Cu solder pastes and their correlation with printing performance

Solder paste plays an important role in the electronic assembly process by providing electrical, mechanical and thermal bonding between the components and the substrate. The rheological characterisation of pastes is an important step in the design and development of new paste formulations. With the ever increasing trend of miniaturisation of electronic products, the study of the rheological properties of solder pastes is becoming an integral part in the R&D of new paste formulations and in the quality monitoring and control during paste manufacture and electronic assembly process. This research work outlines some of the novel techniques which can be successfully used to investigate the rheology of leadfree solder pastes. The report also presents the results of the correlation of rheological properties with solder paste printing performance. Four different solder paste samples (namely paste P1, P2, P3 and P4) with different flux vehicle systems and particle size distributions were investigated in the study. As expected, all the paste samples showed shear thinning behaviour. Although the samples displayed similar flow behaviour at high shear rates, differences were observed at low shear rates. In the stencil printing trials, round deposits showed better results than rectangular deposits in terms of paste heights and aperture filling. Our results demonstrate a good correlation between higher paste viscosity and good printing performance. The results of the oscillatory and thixotropy tests were also successfully correlated to the printing behaviour of solder paste.

A methodology for characterising new lead-free solder paste formulations used for flip-chip assembly applications

The paper reports on the investigation of the rheological behaviour new lead-free solder pastes formulations for use in flip-chip assembly applications. The study is made up of three parts; namely the evaluation of the effect of plate geometry, the effect of temperature and processing environment and the effect of torsional frequencies on the rheological measurements. Different plate geometries and rheological tests were used to evaluate new formulations in terms of wall slip characteristics, linear viscoelastic region and shear thinning behaviour. A technique which combines the use of the creep-recovery and dynamic frequency sweep tests was used to further characterise the paste structure, rheological behaviour and the processing performance of the new paste formulations. The technique demonstrated in this study has wide utility for R & D personnel involved in new paste formulation, for implementing quality control procedures used in paste manufacture and packaging and for qualifying new flip-chip assembly lines

An investigation into the rheological properties of different lead-free solder pastes for surface mount applications

Purpose – The purpose of this paper is to investigate the rheological behaviour of three different lead-free solder pastes used for surface mount applications in the electronic industry.Design/methodology/approach – This study concerns the rheological measurements of solder paste samples and is made up of three parts. The first part deals with the measurement of rhelogical properties with three different measuring geometries, the second part looks into the effect of frequencies on oscillatory stress sweep measurements and the final part reports on the characterisation and comparison of three different types of Pb-free solder pastes. Findings – Among the three geometries, the serrated parallel plate was found effective in minimising the wall-slip effect. From the oscillatory stresssweep data with different frequencies; it was observed that the linear visco-elastic region is independent of frequency for all the solder paste samples. To understand the shear thinning behaviour of solder paste, the well known Cross and Carreau models were fitted to the viscosity data. Moreover,creep-recovery and dynamic frequency-sweep tests were also carried out without destroying the sample’s structure and have yielded useful information on the pastes behaviour.Research limitations/implications – More extensive research is needed to fully characterise the wall-slip behaviour during the rheological measurements of solder pastes. Practical implications – The rheological test results presented in this paper will be of important value for research and development, quality control and facilitation of the manufacturing of solder pastes and flux mediums. Originality/value – This paper shows how wall-slip effects can be effectively avoided during rheological measurements of solder pastes. The paper also outlines how different rheological test methods can be used to characterise solder paste behaviours

Influence of solder paste components on rheological behaviour

Rheological properties of solder pastes are very important for a high quality surface mount technology process. The stencil/screen printing process of solder pastes is one of the most critical steps in the SMT assembly process, as most of the assembly defects can often be shown to originate from paste rheology and associated poor printing performance. This paper concerns an investigation of the effect of solder paste composition on the rheological properties and behaviour of four different solder pastes. We report on the evaluation of three different paste formulations based on the no-clean flux composition, with different alloy composition, metal content and particle size using a range of rheological characterisation techniques - including viscosity measurements, yield stress, oscillatory and creep-recovery tests. Our results show that in the viscosity test, all solder pastes exhibited a shear thinning behaviour in nature with different highest maximum viscosity. In the region of shear thinning behaviour the paste 3 delivered the best results. Viscosity test helps to understand the solid and cohesive behaviour of solder pastes. Good solid and cohesive behaviour indicates a good paste roll and helps to avoid paste bleeding. The yield stress test has been used to study the effect of temperature on the flow behaviour of solder pastes. Yield stress was measured for a range of temperature from 15deg C to 35deg C with an increment of 5degC. The result indicated a decreasing of the yield stress point if the temperature was increased. Paste 4 has shown the minimum dependence on temperature. The oscillatory test has been used to find out the linear visco-elastic range and to study the solid and liquid like behaviours of solder pastes. Paste 1 indicated the biggest linear visco-elastic region (LVR) and the highest value of G' and G" which means solder paste 1 will be needed a higher squeegee pressure in the printing process. In the creep recovery test paste 4 showed the best- - recovery and the lowest values of creep and recovery compliance which indicated a good printing behaviour. The test also has showed the solder paste with smaller particle size exhibit less recovery

Long-term declining trend of zooplankton biomass in the Tropical Atlantic

We report evidences that the zooplankton biomass in the tropical Atlantic has declined with an almost 10-fold drop from the 1950s to 2000. The results of the multiple regression analysis showed that the decline in zooplankton biomass was positively related to the NAO-index and to phosphate concentration. We also found that the depth of the thermocline has decreased over the period of our investigation. Thus, the decline we report in zooplankton biomass may be related to the combined effect of two phenomena driven by global temperature increase: (1) the widening of the distributional range of tropical species due to the expansion of the ‘tropical belt’ and (2) a decrease in primary production resulting from the thinning of the thermocline. The decline of zooplankton biomass we report suggests that global warming of the ocean may be altering tropical food webs, and through them, it may also indirectly impact tropical oceans biogeochemical cycles.

Fundamentals of steady state, non-Newtonian rimming flow

Rimming flow on the inner surface of a horizontal rotating cylinder is investigated. Using a scale analysis, a theoretical description is obtained for steady-state non-Newtonian flow. Simple lubrication theory is applied since the Reynolds number is small and the liquid film is thin. Since the Deborah number is very small the flow is viscometric. The shear-thinning number, which characterizes the shear-thinning effect, may be small or large. A general constitutive law for this kind of flow requires only a single function relating shear stress and shear rate that corresponds to a generalized Newtonian liquid. For this case the run-off condition for rimming flow is derived. Provided the run-off condition is satisfied, the existence of a continuous steady-state solution is proved. The rheological models, which show Newtonian behavior at low shear rates with transition to power-law shear thinning at moderate shear rates, are considered. Numerical results are carried out for the Carreau and Ellis models, which exhibit Newtonian behavior near the free surface and power-law behavior near the wall of the rotating cylinder.

Pre-treatment with Depo-Provera modifies the pharmacokinetics of CMPD167 in rhesus macaques following vaginal ring administration

BACKGROUND: Vaginal ring devices are being developed to provide sustained release of HIV microbicides. To date, only limited pharmacokinetic data is available from animal or human studies. Here we report the effect of Depo-Provera (DP) pre- treatment, commonly used to thin the vaginal epithelium in challenge experiments, on the pharmacokinetic profile of CMPD167 (a small molecule CCR5 co-receptor antagonist) in rhesus macaques following vaginal ring administration.

METHODS: A single 400mg CMPD167 silicone elastomer vaginal ring was inserted into each of twelve female rhesus macaques. Six macaques were treated with (DP) 30 days before ring placement; the other six macaques were untreated. Blood, vaginal fluid and vaginal biopsies were collected prior to and at various times during 28 days of ring placement and assayed for CMPD167 levels by HPLC. Rings were assayed for residual CMPD167 at the end of the study and the calculated amount of CMPD167 released in vivo compared with in vitro release data.

RESULTS: Vaginal fluid, plasma and tissue levels of CMPD167 were detectable throughout ring placement. Significant differences were observed in mean daily vaginal fluid levels between the DP-treated (16–56 mcg/mL) and untreated groups (48–181 mcg/mL). Plasma CMPD167 levels were significantly higher peaking at 4 ng/mL and maintaining levels of 1–2 nM throughout the 14 days of testing in animals pre-treated with DP compared to non DP-treated macaques (<1 ng/mL maintained). Tissue levels were varied between 2–10 g/mL CMPD167 with no significant difference between the DP-treated and untreated macaques.

CONCLUSIONS: The study demonstrates that clinically relevant, and possibly protective doses of CMPD167 are released in the vaginal vault of rhesus macaques from vaginal rings through 28 days duration. DP is known to induce vaginal epithelial thinning and lower vaginal fluid levels, which accounts for the increased plasma levels of CMPD167. In contrast, macaques not treated with DP had minimal absorption into plasma compartments and significantly higher levels of CMPD167 in the vagina, similar to those previously shown to be protective against vaginal challenge.