Thermal and crystallization behaviors of polyethylene blends synthesized by binary late transition metal catalysts combinations

A series of reactor blends of linear and branched polyethylenes have been prepared, in the presence of modified methylaluminoxane, using a combination of 2,6-bis[1(2,6-dimethyphenylimino) pyridyl]-cobalt(II) dichloride (1), known as an active catalyst for producing linear polyethylene, and [1,4-bis(2,6-diidopropylphenyl)] acenaphthene diimine nickel(II) dibromide (2), which is active for the production of branched polyethylene. The polymerizations were performed at various levels of catalyst feed ratio at 10 bar. The linear correlation between catalyst activity and concentration of catalyst 2 suggested that the catalysts performed independently from each other. The weight-average molecular weights ((M) over bar (w)), crystalline structures, and phase structures of the blends were investigated, using a combination of gel permeation chromatography, differential scanning calorimetry, wide-angle X-ray diffraction, and small angle X-ray scattering techniques. It was found that the polymerization activities and MWs and crystallization rate of the polymers took decreasing tendency with the increase of the catalyst 2 ratios, while melting temperatures (T-m), crystalline temperatures (T,), and crystalline degrees took decreasing tendency. Long period was distinctly influenced by the amorphous component concentration.

Features of Late Cenozoic Deepwater Sedimentation in Southern Qiongdongnan Basin, Northwestern South China Sea

Based on high resolution 2D and 3D seismic data acquired in recent years, using sequence stratigraphy analysis and geophysical methods, we discuss the features of Late Cenozoic deepwater sedimentation in the southern Qiongdongnan (sic) basin. The study area entered a bathyal slope environment in the Miocene. The channel developed in the Sanya (sic) Formation was controlled by a fault break, and its shingled seismic characteristics represent multiple erosion and fill, which may indicate that turbidite current developed in the slope environment. The polygon faults found in mudstone of the Meishan (sic) Formation represent the deepwater hungry sedimentary environment. The large-scale channels developed on the top of Huangliu (sic) Formation could be the result of a big sea level drop and an increase of sediment supply. The fantastic turbidite channel developed in Late Quaternary in the slope environment has "fan-like" body and long frontal tiny avulsion channel. The analysis of these features suggests that the sediment supply of the study area in the post-rifting period was dominant from the Vietnam uplift in the southwest. These deepwater sedimentary features could be potential reservoirs or migration pathways for deepwater petroleum systems.

The complete mitochondrial genomes of the whistling duck (Dendrocygna javanica) and black swan (Cygnus atratus): dating evolutionary divergence in Galloanserae

Galloanserae is an ancient and diverse avian group, for which comprehensive molecular evidence relevant to phylogenetic analysis in the context of molecular chronology is lacking. In this study, we present two additional mitochondrial genome sequences of Galloanserae (the whistling duck, Dendrocygna javanica, and the black swan, Cygnus atratus) to broaden the scope of molecular phylogenetic reconstruction. The lengths of the whistling duck's and black swan's mitochondrial genomes are 16,753 and 16,748 bases, respectively. Phylogenetic analyses suggest that Dendrocygna is more likely to be in a basal position of the branch consisting of Anatinae and Anserinae, an affiliation that does not conform to its traditional classification. Bayesian approaches were employed to provide a rough timescale for Galloanserae evolution. In general, a narrow range of 95% confidence intervals gave younger estimates than those based on limited genes and estimated that at least two lineages originated before the Coniacian epoch around 90 MYA, well before the Cretaceous-Tertiary boundary. In addition, these results, which were compatible with estimates from fossil evidence, also imply that the origin of numerous genera in Anseriformes took place in the late Oligocene to early Miocene. Taken together, the results presented here provide a working framework for future research on Galloanserae evolution, and they underline the utility of whole mitochondrial genome sequences for the resolution of deep divergence.

Transformation of accommodation space of the Cretaceous Qingshankou Formation, the Songliao Basin, NE China

Analysis of accommodation space variation during deposition of the Cretaceous Qingshankou Formation in the Songliao Basin, NE China, indicates that accommodation space changed both through time and across the basin as a seesaw movement. The mid-upper Qingshankou Formation is divided into three units. In each unit, changes of accommodation space differ in the southern and northern part of the basin. Increasing accommodation in the southern part is accompanied by a decrease in the northern part, and vice versa. Between the northern and southern basin, there was a neutral belt that is like a fulcrum, called the transformation belt here, where the accommodation did not change to any significant degree. We call this response 'accommodation transformation', whose characteristics are defined by tectonic subsidence analysis, palaeontological and sedimentary analyses. The accommodation increasing belt, decreasing belt, transformation belt and accommodation transformation boundary together constitute the accommodation transformation system. The recognition of accommodation transformation in the Songliao Basin provides a new insight into sequence stratigraphy and might be widely applicable.

The sedimentation rates in the Okinawa trough during the Late Quaternary

On the basis of accelerator mass spectrometer radiocarbon (AMS C-14) dating, sedimentation rates of 11 cores collected from the northern to southern Okinawa Trough are discussed. The sedimentation rates in the Okinawa Trough roughly range from 11 to 39 cm/ka, and the average is 23.0 cm/ka. China's continental matter is the main sediment source of the middle Okinawa Trough and has important contribution to the northern and southern Okinawa Trough. The sedimentation rates during the marine oxygen isotope (MI5) 2 are uniformly higher than those during MIS 1 in the northern and middle Okinawa Trough while they are on the contrary in the southern Okinawa Trough. Sedimentation rates in the Okinawa Trough can be one of the proxies of sediment source and an indicator of cooling events.

Millennial-scale paleoceanography in Okinawa Trough during Late Quaternary period

Based on the analyses of foraminifer and accelerator mass spectrometer radiocarbon dating in DGKS9603 core from mid-Okinawa Trough close to bottom, oscillation curve, which expressed the relation between the surface water temperature and the depth, has been obtained by using foraminifer analysis and calculation of FP-12E transfer function. The whole core indicated seven cold phases and eight warm phases. Obvious expression of low temperature event during Middle and Late Holocene, YD,H1,H2,H3 and H4 events, as well as the short cold phase during the middle last glacial period, implied that short shifts since 50 kaBP would have been global significance. Sedimentation rate during cold phases is usually faster than that in warm stages, with the lowest rate in Holocene, which may be connected with rising sea level and principal axial of Kuroshio Current moving to west. Volcanic activities highly developed in Okinawa Trough during the Quaternary period, thus abundant volcanic glass and pumice were well preserved.

Origin, development and evolutionary model of shelf desertization environment in late stage of Upper Pleistocene

Based on the study of palaeo-environmental evolution in the shelves of the Eastern China Seas, the concept of ''shelf desertization'' in the late stage of Upper Pleistocene is defined; the environmental background and evolutionary process of shelf desertization are analysed. Study on the records of subbottom profiling and the data of core samples from shelf areas revealed that during low sea-level stages, the sedimentary environment in the exposed shelf plains was dominated by aeolian depositional process under cold and dry climatic conditions, i.e. under the action of strong winter-monsoon winds. Parts of the exposed marine strata were disintegrated, and aeolian sand dunes were formed on the disintegrated marine deposits, from which the finer sediment grains were blown away by wind and deposited in the downwind areas to form the derivative loess deposits. Thus a desertization environmental system was formed in the exposed shelf plains of the Eastern China Seas.

Evolution and variation of the Tsushima warm current during the late Quaternary: Evidence from planktonic foraminifera, oxygen and carbon isotopes

The evolution and variation history of the Tsushima warm current during the late Quaternary was reconstructed based on the quantitative census data of planktonic foraminiferal fauna, together with oxygen and carbon isotope records of mixed layer dweller a ruber and thermocline dweller N. dutertrei in piston core CSH1 and core DGKS9603 collected separately from the Tsushima warm current and the Kuroshio dominated area. The result showed that the Tsushima warm current vanished in the lowstand period during 40-24 cal ka BP, while the Kuroshio still flowed across the Okinawa Trough, arousing strong upwelling in the northern Trough. Meanwhile, the influence of freshwater greatly increased in the northern Okinawa Trough, as the broad East China Sea continental shelf emerged. The freshwater reached its maximum during the last glacial maximum (LGM), when the upwelling obviously weakened for the lowest sea-level and the depression of the Kuroshio. The modern Tsushima warm current began its development since 16 cal ka BP, and the impact of the Kuroshio increased in the middle and northern Okinawa Trough synchronously during the deglaciation and gradually evolved as the main water source of the Tsushima current. The modern Tsushima current finally formed at about 8.5 cal ka BP, since then the circulation structure has been relatively stable. The water of the modern Tsushima current primarily came from the Kuroshio axis. A short-term wiggle of the current occurred at about 3 cal ka BP, probably for the influences from the enhancement of the winter monsoon and the depression of the Kuroshio. The cold water masses greatly strengthened during the wiggle.

Petroleum geological framework and hydrocarbon potential in the Yellow Sea

Sedimentary basins in the Yellow Sea can be grouped tectonically into the North Yellow Sea Basin (NYSB), the northern basin of the South Yellow Sea (SYSNB) and the southern basin of the South Yellow Sea (SYSSB). The NYSB is connected to Anju Basin to the east. The SYSSB extends to Subei Basin to the west. The acoustic basement of basins in the North Yellow Sea and South Yellow Sea is disparate, having different stratigraphic evolution and oil accumulation features, even though they have been under the same stress regime since the Late Triassic. The acoustic basement of the NYSB features China-Korea Platform crystalline rocks, whereas those in the SYSNB and SYSSB are of the Paleozoic Yangtze Platform sedimentary layers or metamorphic rocks. Since the Late Mesozoic terrestrial strata in the eastern of the NYSB (West Korea Bay Basin) were discovered having industrial hydrocarbon accumulation, the oil potential in the Mesozoic strata in the west depression of the basin could be promising, although the petroleum exploration in the South Yellow Sea has made no break-through yet. New deep reflection data and several drilling wells have indicated the source rock of the Mesozoic in the basins of South Yellow Sea, and the Paleozoic platform marine facies in the SYSSB and Central Rise could be the other hosts of oil or natural gas. The Mesozoic hydrocarbon could be found in the Mesozoic of the foredeep basin in the SYSNB that bears potential hydrocarbon in thick Cretaceous strata, and so does the SYSSB where the same petroleum system exists to that of oil-bearing Subei Basin.

Paleoenvironment evolution of the East Philippine Sea recorded in the new-type ferromanganese crust since the terminal Late Miocene

From systemic research of microstructure, geochemistry, uranium-series and Be-10 isotope dating on a new-type deepwater ferromanganese crust from the East Philippine Sea, the paleoenvironment evolution of the target area since the terminal Late Miocene was recovered. The vertical section changes of microstructure and chemical composition are consistent in the studied crust, which indicate three major accretion periods and corresponding paleoenvironment evolution of the crust. The bottom crust zone was formed in the terminal Late Miocene (5.6 Ma) with loose microstructure, high detritus content and high growth rate. Reductions of mineral element content, accretion rate and positive Ce-anomaly degree at 4.6 Ma indicate temporal warming, which went against the crust accretion and finally formed an accretion gap in the terminal Middle Pliocene (2.8-2.7 Ma). The more active Antarctic bottom seawaters in the Late Pliocene (2.7 Ma) facilitated the fast transfer to the top pure crust zone. Hereafter, with the further apart of volcanic source and the keeping increase of eolian material (1.0 Ma), although surrounding conditions were still favorable, mineral element content still shows an obvious reducing trend. It thereby offers new carrier and data for the unclear paleoceanographic research of the target area since the terminal Late Miocene.

Distribution of calcifying and silicifying phytoplankton in relation to environmental and biogeochemical parameters during the late stages of the 2005 North East Atlantic Spring Bloom

The late stage of the North East Atlantic (NEA) spring bloom was investigated during June 2005 along a transect section from 45 to 66 degrees N between 15 and 20 degrees W in order to characterize the contribution of siliceous and calcareous phytoplankton groups and describe their distribution in relation to environmental factors. We measured several biogeochemical parameters such as nutrients, surface trace metals, algal pigments, biogenic silica (BSi), particulate inorganic carbon (PIC) or calcium carbonate, particulate organic carbon, nitrogen and phosphorus (POC, PON and POP, respectively), as well as transparent exopolymer particles (TEP). Results were compared with other studies undertaken in this area since the JGOFS NABE program. Characteristics of the spring bloom generally agreed well with the accepted scenario for the development of the autotrophic community. The NEA seasonal diatom bloom was in the late stages when we sampled the area and diatoms were constrained to the northern part of our transect, over the Icelandic Basin (IB) and Icelandic Shelf (IS). Coccolithophores dominated the phytoplankton community, with a large distribution over the Rockall-Hatton Plateau (RHP) and IB. The Porcupine Abyssal Plain (PAP) region at the southern end of our transect was the region with the lowest biomass, as demonstrated by very low Chla concentrations and a community dominated by picophytoplankton. Early depletion of dissolved silicic acid (DSi) and increased stratification of the surface layer most likely triggered the end of the diatom bloom, leading to coccolithophore dominance. The chronic Si deficiency observed in the NEA could be linked to moderate Fe limitation, which increases the efficiency of the Si pump. TEP closely mirrored the distribution of both biogenic silica at depth and prymnesiophytes in the surface layer suggesting the sedimentation of the diatom bloom in the form of aggregates, but the relative contribution of diatoms and coccolithophores to carbon export in this area still needs to be resolved.

渤海湾地区前第三系构造特征及其演化研究

Based on fine structural interpretation on seismic profiles of buried-hills in Huanghua depression, structural interpretation and balanced cross-section restoration of regional seismic profiles, drawing structural maps of main seismic interfaces, residual strata distribution of different ages in the Bohai Bay region and structural survey in the western Shandong uplifted area and the intracontinental orogeny of Yanshan mountain, the paper has studied pre-tertiary structural styles and tectonic evolution of the Bohai Bay region. There mainly develop 5 types of pre-tertiary structural style that are extension structure, compression structure, strike-slip structure, negative inversion structure and sliding structure in the Bohai Bay region. Among these 5 types of structural style, extension structure develops detachment fault and its controlling fault terrain structure and fault break slop; compression structure develops reverted fold, fault propagation fold, fault bent fold, imbricate thrust structure and triangle zone; strike-slip structure develops positive flower structure, negative flower structure, en-echelon structure and brush structure; negative reversion structure develops Indosinian compression and Yanshanian extension negative reversion structure, late Yanshanian compression and Cenozoic extension negative reversion structure; sliding structure develops interlayer sliding structure and detachment structure. According to Cangdong fault of SN direction, Zhangjiakou – Penglai fault and Qihe – Guangrao fault of NWW direction, the Bohai Bay region can be divided into 6 sub-regions in which structural direction and style is different from each other. Structural maps of bottom boundary of Cenozoic and upper Paleozoic manifest that main NNE structural direction is formed from late Yanshanian to Himalayan movement and minor NWW structural direction and a string of area more than 8000m are mainly suggest that Indosinian tectonic pattern strongly influence on Yanshanian and Himalayan movement. Residual strata distribution characteristics of middle to upper Neoproterozoic in the Bohai Bay region manifest that middle- to neo- aulacogen position may be corresponding to late Mesozoic uplifted zone. Residual Paleozoic distribution characteristics of main ENN suggest that structural alteration should be resulted from late Yanshanian to Himalayan movement while which of minor NWW structures suggest that deeper structure should restrict shallower structure. Structural patterns of main EW fold direction in the Bohai Bay region and thrust structure in eastern part are formed late Triassic in studied area. Granite magma intrusion of early to middle Jurassic mainly develops Yanshan mountain zone. Late Mesozoic rifting basins of NEE direction are widely distributed in the Bohai Bay region and granite magma intrusions are mainly distributed in Tancheng – Rongcheng zone. Mesozoic structural evolution in the Bohai Bay region is related to scissor convergent from east to west between North China plate and Yangtze plate and gradually reinforcing of the west circum-pacific tectonic tract while basin and range province of late Jurassic and early Cretaceous may be mainly related to lithospheric thinning of North China craton in late Mesozoic.