The picophytoplankton in three Chinese lakes of different trophic status and its relationship to fish populations

A year-round comparison was made of the picophytoplankton populations in three lakes of different trophic status (oligotrophic, mesotrophic, and hypereutrophic), as well as in experimental enclosures stocked with various densities of fish. Picophytoplankton abundance was significantly different between the hypereutrophic lake and the oligotrophic lake (P<0.018) and between the hypereutrophic lake and the mesotrophic lake (P<0.021), whereas the difference between the mesotrophic and oligotrophic lakes was not significant (P<0.745). The effect of total nitrogen:total phosphorus ratio on the abundance of picophytoplankton was demonstrated in the oligotrophic lake, but such effect did not manifest itself in the other lakes or in the experimental enclosures. The average annual picophytoplankton population sizes in the three lakes in 1995-1998 were correlated with estimated fish abundance (r=0.824, n=9, P=0.006). The results of enclosure experiments demonstrated that the abundance of picophytoplankton increased with the stocking density of fish (r=0.619, n=8, P=0.100).

Adsorbed silica in stalagmite carbonate and its relationship to past rainfall

IEECAS SKLLQG

Structure/permeability and permselectivity relationship of polyetherimides from 1,4-bis(3,4-dicarboxyphenoxy) benzene dianhydride .2.

Gas permeability coefficients of a series of aromatic polyetherimides, which were prepared from 1,4-bis(3,4-dicarboxyphenoxy) benzene dianhydride (HQDPA) with various aromatic diamines, to H-2, O-2 and N-2 have been measured under 7 atm and at the temperature range 30-100 degrees C. A significant change in the permeability and permselectivity resulting from the systematic variation in chemical structure of the polyetherimides was found. Among the polyetherimides, that were prepared from phenylenediamine and methyl substituted phenylenediamines, the increase of permeability is accompanied by a decrease of permselectivity. The polyetherimides that were prepared from 3,5-diaminobenzoic esters have lower permselectivity than the others. However, the polyetherimide from 3,5-diaminobenzoic acid possesses much higher permselectivity than the others due to cross-linking. Copyright (C) 1996 Elsevier Science Ltd

Structure/permeability and permselectivity relationship of polyetherimides from 1,4-bis(3,4-dicarboxyphenoxy) benzene dianhydride .1.

Gas permeability coefficients of a series of aromatic polyetherimides, which were prepared from 1,4-bis(3,4-dicarboxyphenoxy) benzene dianhydride (HQDPA) and various aromatic diamines, to H-2, CO2, O-2, N-2 and CH4 have been measured under 7 atm pressure and over the temperature range 30-150 degrees C. A significant change in permeability and permselectivity, which resulted from a systematic variation in chemical structure of the polyetherimides, was found. Generally, increases in permeability of the polyetherimides are accompanied by decreases in permselectivity. The order of decrease of the permeability coefficients is as follows: HQDPA-IPDA > HQDPA-DDS > HQDPA-MDA > HQDPA-ODA > HQDPA-DABP > HQDPA-BZD. However, HQDPA-DMoBZD and HQDPA-DMoMDA, with bulky methoxy side-groups on the aromatic rings of the diamine residue, display both high permeability coefficients and high permselectivity. The favourable gas separation property, excellent thermal and chemical stability, and high mechanical strength make HQDPA-DMoBZD and HQDPA-DMoMDA promising candidates for membrane-based gas separation applications.

Structure/permeability and permselectivity relationship of polyetherimides from 1,4-bis(3,4-dicarboxyphenoxy) benzene dianhydride .3.

Gas permeability coefficients of a series of aromatic polyetherimides prepared from 1,4-bis(3,4-dicarboxyphenoxy) benzene dianhydride (HQDPA) and four (methylene dianiline)s with a methyl side group to H-2, CO2, O-2, N-2, and CH4 were measured under 7 atm and within a temperature range from 30 to 150 degrees C. The gas permeabilities and permselectivities of these polymers were compared with those of the HQDPA-based polyetherimides from methylene dianiline (MDA) and isopropylidene dianiline (IPDA). The number and position of the methyl side groups on the benzene rings of the diamine residues strongly affect the gas permeabilities and permselectivities of the HQDPA-based polyetherimides. The gas permeability of the polyetherimide progressively increases with an increase in the number of the methyl side groups. Both the gas permeability and permselectivity of the polyetherimides with methyl side groups are higher than those of HQDPA-MDA. The polyetherimide prepared from 3,3'-dimethyl 4,4'-methylene dianiline (DMMDA1) possesses both higher permeability and permselectivity than the polyetherimides prepared from 2,2'-dimethyl 4,4'-methylene dianiline (DMMDA2). However, two of the polyetherimides prepared 2,2',3,3'-tetramethyl 4,4'-methylene dianiline (TMMDA1) or 2,2', 5,5'-tetramethyl 4,4'-methylene dianiline (TMMDA2) possess almost the same gas permeability and permselectivity.

MECHANISM OF RADIATION CROSS-LINKING OF POLYMERS AND ITS RELATIONSHIP WITH STRUCTURAL MULTIPLICITY

In an attempt to explore the effect of structural multiplicity of polymers on the mechanism of radiation crosslinking, the adaptability of the Charlesby-Pinner's equation and its various modified versions are examined. It is recognized that both chemical and morphological multiplicity of polymer structure results in the multiplicity of crosslinking mechanism, and that any single equation can only be applicable to a certain step of the whole radiation process.

Phytoplankton distributions and their relationship with the environment in the Changjiang Estuary, China

This study was carried out in the Changjiang Estuary from 19 to 26 May 2003. Based on the data collected from 29 stations, including two anchor stations, phytoplankton taxonomic composition, abundance, diurnal variability and spatial distribution were examined. Eighty-seven species, including 54 species of diatoms and 16 red tide causative species, were identified. Average diversity index (H') and evenness (J) values were 1.04 and 0.40, respectively. A bloom in abundance of certain phytoplankton species, especially Prorocentrum dentatum and Skeletoneina costatum, was thought to be the cause of the low diversity index and evenness values. Total phytoplankton abundance averaged 6.75 x 10(5) cells 1(-1), and was much higher than previous investigation carried out in the same month in 1986. Abundance increased seaward showing a distinct spatial difference, and the dominant species varied with salinity. Correlation between phosphorus and abundance further supported the former conclusion that phosphorus is the controlling factor in phytoplankton growth in the Changjiang Estuary where light is not limiting. Based on the relationship between DO, pH and abundance, it is likely that the bloom was caused by rapid in situ growth of phytoplankton with high nutrients and sufficient light. The data also indicated that the duration of the bloom was not long and

Seasonal and spatial distribution of matrix-bound phosphine and its relationship with the environment in the Changjiang River Estuary, China

Sediment is commonly considered as a source of phosphine, which is a highly toxic and reactive atmospheric trace gas. This study aims to investigate the seasonal and spatial distribution of matrix-bound phosphine (MBP) and its relationship with the environment in the Changjiang River Estuary. A total of 43 surface sediments were collected in four seasons of 2006, and concentrations of MBP and relative environmental factors were analyzed. MBP ranged from 1.93 to 94.86 ng kg(-1) dry weight (dw) with an average concentration of 17.14 ng kg(-1) dw. The concentrations of MBP in the tipper estuary were, higher than those in the lower estuary, which could be attributed to greater pollutant inputs in the upper estuary. The concentrations of MBP also varied with season, with November > August > May > February. Significant correlations existed between MBP and total phosphorus (TP), organic phosphorus (OP), inorganic phosphorus (W), organic carbon (OC), total nitrogen (TN), the grain size, and redox potential (Eh), suggesting that these sedimentary environmental characteristics played an important role in controlling the MBP levels in the sediments. Notably, there were positive linear relationships between the concentrations of soluble reactive phosphorus (SRP), TP, and chlorophyll a (Chl a) in bottom water and MBP in sediments. These relationships might be very complicated and need further exploration. This work is the first comprehensive study of the seasonal and spatial distribution of MBP in sediments and its relationships with environmental factors in a typical estuary, and will lead to deeper understanding of the phosphorus (P) biogeochemical cycle. (C) 2008 Elsevier Ltd. All rights reserved.

Legislative policy, law and competitiveness: a mysterious and difficult relationship in the EU

The Lisbon Agenda places Europe in a uniquely difficult position globally, most particularly as an example of a social and regulatory experiment which many consider to be doomed to failure. The drive towards economic competitiveness has led to a focus on regulation and its effect on entrepreneurship, productivity and business growth but assessing this relationship is complex for a number of reasons. First, not all regulatory effects can be predicted precisely in relation to behavioural outcomes. Path-dependency scholars have also demonstrated that the regulation will have varying effects depending on context. Second, theoretically it is clear that many non-regulatory factors may contribute to economic and competitive success. Third, there is evidence of internal conflict within the Commission as to the relative importance of the Lisbon goals. Finally, the experience of distinct Member States presents challenges both for assessment and prescriptive remedies. The Commission has estimated that the cost of regulatory compliance obligations on businesses in the EU is between 4% and 6% of gross domestic product and that 15% of this figure is avoidable 'red tape' (the term used specifically to signify unnecessary compliance burdens). This article proposes to assess the likely outcomes of de-regulation as we rapidly approach 2010, the year for attainment of the Lisbon goals.