THE THERMAL-STABILITY OF POLYETHYLENE BLENDS DURING HEAT-PROCESSING AND SHORT-TERM PHOTOOXIDATION

The melt flow behaviour of LDPE/HDPE blends with various compositions have been determined by melt flow index (MFI) measurement. The effects of stabilizers, photo-sensitizers, multiple extrusions and short-term photooxidation have been studied. The results show that there is no marked thermal stability difference between homopolymers and blends without multiple extrusions, no matter whether stabilizers or photo-sensitizers are added. Multiple extrusions or photo-sensitizers reduce their thermal stability, shown by the decrease in MFI. The decrease in MFI of photooxidized samples does not imply serious structural change and shows that the active species formed during photooxidation induce a crosslinking reaction in the melt indexer. Multiple extrusions increase the number of active species formed in LDPE or blends and lead to an obvious decrease in MFI. It is suggested that LDPE and LDPE-rich blends after short-term photooxidation can be characterized by MFI measurement. In contrast, HDPE cannot be characterized by this method due to its linear structure.

A NEWLY PROPOSED MOLECULAR TOPOLOGICAL INDEX FOR THE DISCRIMINATION OF CIS/TRANS ISOMERS AND FOR THE STUDIES OF QSAR/QSPR

A new topological index, the general a(N)-index (GAI), on quantum chemistry, is described in this paper. The GAI can be applied to molecules that contain heteroatoms and multiple bonds, and performs well in distinguishing cis/trans isomers. The relationships between the GAIs and physicochemical properties of olefins and neutral phosphorus compounds were observed with satisfactory results.

Characterization, structure and function of linker polypeptides in phycobilisomes of cyanobacteria and red algae: An overview

Cyanobacteria and red algae have intricate light-harvesting systems comprised of phycobilisomes that are attached to the outer side of the thylakoid membrane. The phycobilisomes absorb light in the wavelength range of 500-650 nm and transfer energy to the chlorophyll for photosynthesis. Phycobilisomes, which biochemically consist of phycobiliproteins and linker polypeptides, are particularly wonderful subjects for the detailed analysis of structure and function due to their spectral properties and their various components affected by growth conditions. The linker potypeptides are believed to mediate both the assembly of phycobiliproteins into the highly ordered arrays in the phycobilisomes and the interactions between the phycobilisomes and the thylakoid membrane. Functionally, they have been reported to improve energy migration by regulating the spectral characteristics of colored phycobiliproteins. In this review, the progress regarding linker polypeptides research, including separation approaches, structures and interactions with phycobiliproteins, as well as their functions in the phycobilisomes, is presented. In addition, some problems with previous work on linkers are also discussed. (c) 2005 Elsevier B.V. All rights reserved.

Physiological and immune responses of zhikong scallop Chlamys farreri to the acute viral necrobiotic virus infection

The Zhikong Scallop, Chlamys farreri, is one of the most Important bivalve mollusks cultured in northern China However, mass mortality of the cultured C farreri has posed a serious threat to the maricultural Industry in recent years. Acute Viral Necrobiotic Virus (AVNV) is believed as an important etiological agent causing the scallop mass mortalities To understand the mechanism behind the AVNV associated scallop disease and mortality, we assessed the physiological and immune responses of C farreri to the virus infection using oxygen consumption rate, ammonium-nitrogen excretion rate, hemocyte copper, zinc superoxide dismutase gene expression, and plasma superoxide dismutase activity and alkaline phosphatase activity as indicators Scallops challenged by AVNV at 25 C developed typical disease signs 2 days after virus injection Before the disease manifested, scallop oxygen consumption and NH4+-N excretion rates rose and then fell back. Real-time PCR revealed that the hemocyte cytosol Cu, Zn SOD gene expression was upregulated followed by recovery The plasma SOD activity, however, augmented consistently following virus injection Moreover, plasma AKP activity first lowered and then elevated gradually to the highest level at 24 h post virus injection Scallops challenged by AVNV at 17 degrees C neither developed notable disease nor showed obvious responses that could be associated with the virus infection. While the results suggested a correlation between the elevated seawater temperature and the AVNV infection associated C farreri mortalities, they also indicated that the viral infection provoked multiple physiological and immune responses in the host scallops (C) 2010 Elsevier Ltd All rights reserved

Dominant chloramphenicol-resistant bacteria and resistance genes in coastal marine waters of Jiaozhou Bay, China

Studies of abundance, diversity and distribution of antibiotic-resistant bacteria and their resistance determinants are necessary for effective prevention and control of antibiotic resistance and its dissemination, critically important for public health and environment management. In order to gain an understanding of the persistence of resistance in the absence of a specific antibiotic selective pressure, microbiological surveys were carried out to investigate chloramphenicol-resistant bacteria and the chloramphenicol acetyltransferase resistance genes in Jiaozhou Bay after chloramphenicol was banned since 1999 in China. About 0.15-6.70% cultivable bacteria were chloramphenicol resistant, and the highest abundances occurred mainly in the areas near river mouths or sewage processing plants. For the dominant resistant isolates, 14 genera and 25 species were identified, mostly being indigenous estuarine or marine bacteria. Antibiotic-resistant potential human or marine animal pathogens, such as Escherichia coli, Klebsiella pneumoniae, Proteus mirabilis and Shewanella algae, were also identified. For the molecular resistance determinants, the cat I and cat III genes could be detected in some of the resistant strains, and they might have the same origins as those from clinical strains as determined via gene sequence analysis. Further investigation about the biological, environmental and anthropogenic mechanisms and their interactions that may contribute to the persistence of antibiotic-resistance in coastal marine waters in the absence of specific antibiotic selective pressure is necessary for tackling this complicated environmental issue.

Development of the East Asian monsoon: Mineralogical and sedimentologic records in the northern South China Sea since 20 Ma

We here reconstruct the past change of the East Asian monsoon since 20 Ma using samples from Ocean Drilling Program (ODP) Site 1146 in the northern South China Sea based On a multi-proxy approach including a monomineralic quartz isolation procedure, identification of clay minerals by X-ray Diffraction (XRD) and grain-size analysis of isolated terrigenous materials. Terrigenous supply to ODP Site 1146 was dominated by changes in the strength of multiple sources and transport processes. Grain-size data modeled by an end-member modeling algorithm indicate that eolian dust from the and Asian inland and fluvial input have contributed on average 20% and 80% of total terrigenous material to ODP Site 1146, respectively. Specifically, about 40-53% of the total (quartz+feldspar) and only 6-11% of the total clay is related to eolian supply at the study site. Detailed analysis of the sedimentary environment, and clay minerals combined with previous studies shows that smectite originates mainly from Luzon, kaolinite from the Pearl River and illite and chlorite from the Pearl River, Taiwan and/or the Yangtze River. The proportion and mass accumulation rate (MAR) of the coarsest end-member EM1 (interpreted as eolian dust), ratios of (illite+chlorite)/smectite, (quartz+feldspar)% and mean grain-size of terrigenous materials at ODP Site 1146 were adopted as proxies for East Asian monsoon evolution. The consistent variation of these independent proxies since 20 Ma shows three profound shifts in the intensity of East Asian winter monsoon relative to summer monsoon, as well as aridity of the Asian continent, occurred at similar to 15 Ma, similar to 8 Ma and the youngest at about 3 Ma. In comparison, the summer monsoon intensified contemporaneously with the winter monsoon at 3 Ma. The phased uplift of the Himalaya-Tibetan plateau may have played a significant role in strengthening the Asian monsoon at similar to 15 Ma, 8 Ma and 3 Ma. (C) 2007 Elsevier B.V. All rights reserved.

Defoliation, nitrogen, and competition: effects on plant growth and resource allocation of Cleistogenes squarrosa and Artemisia frigida

Two species, Artemisia frigida Willd. (C-3, semishrub, and dominant on overgrazed sites) and Cleistogenes squarrosa (Trin.) Keng (C-4, perennial bunchgrass, and dominant or codominant on moderately grazed sites) were studied to determine the effects of defoliation, nitrogen (N) availability, competition, and their interactions on growth, biomass, and N allocation in a greenhouse experiment. The main treatments were: two nitrogen levels (NO = 0 mg N pot(-1), N1 = 60 mg N pot(-1)), two defoliation intensities (removing 60% of total aboveground biomass and no defoliation), and three competitive replacement series (monocultures of each species and mixtures at 0.5:0.5). Our results were inconsistent with our hypothesis on the adaptive mechanisms of A. frigida regarding the interactive effects of herbivory, N, and competition in determining its dominant position on overgrazed sites. Cleistogenes squarrosa will be replaced by A. frigida on over-grazed sites, although C. squarrosa had higher tolerance to defoliation than did A. frigida. Total biomass and N yield and N-15 recovery of C. squarrosa in mixed culture were consistently lower than in monocultures, whereas those of A. frigida grown in mixtures were consistently higher than in monocultures, suggesting higher competitive ability of A. frigida. Our results suggest that interspecific competitive ability may be of equal or greater importance than herbivory tolerance in determining herbivore-induced species replacement in semi-arid Inner Mongolian steppe. In addition, the dominance of A. frigida on overgrazed sites has been attributed to its ability to shift plant-plant interactions through (lap colonization, root niche differentiation, and higher resistance to water stress.

中国大中型气田天然气成藏物理化学模拟研究

Natural gas pays more important role in the society as clean fuel. Natural gas exploration has been enhanced in recent years in many countries. It also has prospective future in our country through "85" and "95" national research. Many big size gas fields have been discovered in different formations in different basins such as lower and upper Paleozoic in Erdos basin, Tertiary system in Kuche depression in Tarim basin, Triassic system in east of Sichuan basin. Because gas bearing basins had been experienced multiple tectogenesis. The characteristics of natural gases usually in one gas field are that they have multiple source rocks and are multiple maturities and formed in different ages. There has most difficult to research on the gas-rock correlation and mechanism of gas formation. Develop advanced techniques and methods and apply them to solve above problems is necessary. The research is focused on the critical techniques of geochemistry and physical simulation of gas-rock correlation and gas formation. The lists in the following are conclusions through research and lots of experiments. I 8 advanced techniques have been developed or improved about gas-rock correlation and gas migration, accumulation and formation. A series of geochemistry techniques has been developed about analyzing inclusion enclave. They are analyzing gas and liquid composition and biomarker and on-line individual carbon isotope composition in inclusion enclave. These techniques combing the inclusion homogeneous temperature can be applied to study on gas-rock correlation directly and gas migration, filling and formation ages. Technique of on-line determination individual gas carbon isotope composition in kerogen and bitumen thermal pyrolysis is developed. It is applied to determine the source of natural is kerogen thermal degradation or oil pyrolysis. Method of on-line determination individual gas carbon isotope composition in rock thermal simulation has being improved. Based on the "95"former research, on-line determination individual gas carbon isotope composition in different type of maceral and rocks thermal pyrolys is has been determined. The conclusion is that carbon isotope composition of benzene and toluene in homogenous texture kerogen thermal degradation is almost same at different maturity. By comparison, that in mixture type kerogen thermal pyrolysis jumps from step to step with the changes of maturity. This conclusion is a good proof of gas-rock dynamic correlation. 3. Biomarker of rock can be determined directly through research. It solves the problems such as long period preparing sample, light composition losing and sample contamination etc. It can be applied to research the character of source rock and mechanism of source rock expulsion and the path of hydrocarbon migration etc. 4. The process of hydrocarbon dynamic generation in source rock can be seen at every stage applying locating observation and thermal simulation of ESEM. The mechanism of hydrocarbon generation and expulsion in source rock is discussed according to the experiments. This technique is advanced in the world. 5. A sample injection system whose character is higher vacuum, lower leaks and lower blank has been built up to analyze inert gas. He,Ar,Kr and Xe can be determined continuously on one instrument and one injection. This is advanced in domestic. 7. Quality and quantity analysis of benzene ring compounds and phenolic compounds and determination of organic acid and aqueous gas analysis are applied to research the relationship between compounds in formation water and gas formation. This is another new idea to study the gas-rock correlation and gas formation. 8. Inclusion analysis data can be used to calculate the Paleo-fluid density, Paleo-geothermal gradient and Paleo-geopressure gradient and then to calculate the Paleo-fluid potential. It's also a new method to research the direction of hydrocarbon migration and accumulation. 9. Equipment of natural gas formation simulation is produced during the research to probe how the physical properties of rock affect the gas migration and accumulation and what efficiency of gas migrate and factors of gas formation and the models of different type of migration are. II study is focused on that if the source rocks of lower Paleozoic generated hydrocarbon and what the source rocks of weathered formation gas pool and the mechanism of gas formation are though many advanced techniques application. There are four conclusions. 1.The maturity of Majiagou formation source rocks is higher in south than that in north. There also have parts of the higher maturity in middle and east. Anomalous thermal pays important role in big size field formation in middle of basin. 2. The amount of gas generation in high-over maturity source rocks in lower Paleozoic is lager than that of most absorption of source rocks. Lower Paleozoic source rocks are effective source rocks. Universal bitumen exists in Ordovician source rocks to prove that Ordovician source rocks had generated hydrocarbon. Bitumen has some attribution to the middle gas pool formation. 3. Comprehensive gas-rock correlation says that natural gases of north, west, south of middle gas field of basin mainly come from lower Paleozoic source rocks. The attribution ratio of lower Paleozoic source rocks is 60%-70%. Natural gases of other areas mainly come from upper Paleozoic. The attribution ratio of upper Paleozoic source rocks is 70%. 4. Paleozoic gases migration phase of Erdos basin are also interesting. The relative abundance of gasoline aromatic is quite low especially toluene that of which is divided by that of methyl-cyclohexane is less than 0.2 in upper Paleozoic gas pool. The migration phase of upper Paleozoic gas may be aqueous phase. By comparison, the relative abundance of gasoline aromatic is higher in lower Paleozoic gas. The distribution character of gasoline gas is similar with that in source rock thermal simulation. The migration phase of it may be free phase. IH Comprehensive gas-rock correlation is also processed in Kuche depression Tarim basin. The mechanism of gas formation is probed and the gas formation model has been built up. Four conclusions list below. 1. Gases in Kuche depression come from Triassic-Jurassic coal-measure source rocks. They are high-over maturity. Comparatively, the highest maturity area is Kelasu, next is Dabei area, Yinan area. 2. Kerogen thermal degradation is main reason of the dry gas in Kuche depression. Small part of dry gas comes from oil pyrolysis. VI 3.The K12 natural gas lays out some of hydro-gas character. Oil dissolved in the gas. Hydro-gas is also a factor making the gas drier and carbon isotope composition heavier. 4. The mechanism and genesis of KL2 gas pool list as below. Overpressure has being existed in Triassic-Jurassic source rocks since Keche period. Natural gases were expulsed by episode style from overpressure source rocks. Hetero-face was main migration style of gas, oil and water at that time. The fluids transferred the pressure of source rocks when they migrated and then separated when they got in reservoir. After that, natural gas migrated up and accumulated and formed with the techno-genesis. Tectonic extrusion made the natural gas overpressure continuously. When the pressure was up to the critical pressure, the C6-C7 composition in natural gas changed. The results were that relative abundance of alkane and aromatic decreased while cycloalkane and isoparaffin increased. There was lots of natural gas filling during every tectonic. The main factors of overpressure of natural gas were tectonic extrusion and fluid transferring pressure of source rocks. Well preservation was also important in the KL2 gas pool formation. The reserves of gas can satisfy the need of pipeline where is from west to east. IV A good idea of natural gas migration and accumulation modeling whose apparent character is real core and formation condition is suggested to model the physical process of gas formation. Following is the modeling results. 1. Modeling results prove that the gas accumulation rule under cap layer and gas fraction on migration path. 2. Natural gas migration as free phase is difficult in dense rock. 3. Natural gases accumulated easily in good physical properties reservoirs where are under the plugging layer. Under the condition of that permeability of rock is more than 1 * 10~(-3)μm~(-1), the more better the physical properties and the more bigger pore of rock, the more easier the gas accumulation in there. On the contrary, natural gas canonly migrate further to accumulate in good physical properties of rock. 4. Natural gas migrate up is different from that down. Under the same situation, the amount of gas migration up is lager than that of gas migration down and the distance of migration up is 3 times as that of migration down. 5. After gas leaks from dense confining layer, the ability of its dynamic plug-back decreased apparently. Gas lost from these arils easily. These confining layer can confine again only after geology condition changes. 6. Water-wetted and capillary-blocking rocks can't block water but gases generally. The result is that water can migrate continuously through blocking rocks but the gases stay under the blocking rocks then form in there. The experiments have proved the formation model of deep basin gas.