A STUDY ON POLYMER-POLYMER INTERACTIONS THROUGH MIXING CALORIMETRY

The aim of this work is to describe the most recent achievements in the field of the physical chemistry of mixing. The systems studied have been classified according to the amount of thermic effect due to the blending and its interpretation. When polystyrene (PS) and poly(alpha-methylstyrene) (P alpha MS) are blended, the interaction is weak and Delta(mix)H is close to zero. The presence of polar atoms and/or groups increases the stability of the blend and, therefore, Delta(mix)H becomes more negative. Poly(ethylene oxide) (PEO), poly(methyl acrylate) (PMA), poly(methyl methacrylate) (PMMA) and poly(vinylacetate) (PVAc), when mixed to form binary systems, show large differences from their properties when pure. If hydrogen bonding takes place, the interactions are readily detected and a large effect is calorimetrically determined. Cellulose diacetate (CDA) and poly(vinylpyrrolidone) (PVP) have been studied as an example of a strongly interacting system.

INTERACTIONS OF THIAMINE WITH ANIONS - STRUCTURE OF THIAMINE DITHIOCYANATE

The crystal structure analysis of {3-[(4-amino-2-methyl-5-pyrimidinyl)methyl]-5-(2-hydroxyethyl)-4-methylthiazol}ium dithiocyanate reveals that there are two types of anion bridges between the two aromatic rings of the same thiamine which adopts the usual F conformation, one of which involves a contact between H(C2) on the thiazolium ring and the hydroxy O atom from a neighbouring molecule. The crystal packing shows a novel triple helical structure formed by strongly hydrogen-bonded thiamine-SCN- molecular chains.

PROPERTIES OF BETA-CARBOXYETHYL-GERMANIUM SESQUIOXIDE AND INTERACTIONS OF IT WITH SOME SUBSTRATES

Three samples of β-carboxyethyl-germanium sesquioxide (Ge-132) have been prepared with different methods. Their IR, Raman, XPS, TG-DTA and FAB-MS spectra are quite different and indicate that they have different degree of polymerization and molecule structures. In the aqeous solution, all of them interaot strongly with fructose, but not with polypeptides such as GSH and GSSG. This faot may be important in understanding the bioactivity of Ge-132.

Allelopathic interactions between the macroalga Ulva pertusa and eight microalgal species

HETEROSIGMA-AKASHIWO RAPHIDOPHYCEAE; CENTRAL VENICE LAGOON; ALEXANDRIUM-TAMARENSE; RED-TIDE; COASTAL LAGOONS; PHYTOPLANKTON; GROWTH; BAY; DINOFLAGELLATE; COMPETITION

Size hierarchies affecting the social interactions and growth of juvenile Japanese flounder, Paralichthys olivaceus

Japanese flounder Paralichthys olivaceus (T. & S.)juveniles were size-graded and divided into three groups (small, large, and mixture of small and large flounder), and their social interactions (feeding, aggressive attacking and activity) and growth were investigated. The growth of the small flounder was markedly suppressed by the presence of the large flounder. Large flounder did not significantly suppress the overall food intake of the small flounder but exhibited high aggressive attacking on them and consequently inhibited their activity. Size dominance showed little influence on the aggressive behavior, feeding, activity and growth of the large flounder. The large flounder could not effectively defend the food in excess during the experiments ruling out disproportional food acquisition as the primary mechanism responsible for the size hierarchy effect. Aggressive interaction of the large flounder on the small flounder might be an important cause for the growth retardation of the small flounder. In culture, size grading could markedly improve the growth and survival of the early juvenile flounder. (C) 2004 Elsevier B.V. All rights reserved.

Long-term ecological interactions between nutrient and phytoplankton community in the Changjiang estuary

Both nitrate (NO (3) (-) ) and soluble reactive phosphate (PO (4) (3-) ) concentration in the freshwater end-member at the mouth of the Changjiang River have increased dramatically since the 1960s. Within the same period in the sea area, with surface salinity > 30, NO (3) (-) concentration has shown an obvious increase, PO (4) (3-) has not changed greatly and dissolved reactive silica (SiO (3) (2-) ) has deceased dramatically. An examination of the elemental ratio of NO (3) (-) to PO (4) (3-) at the mouth of the Changjiang River did not show a systematic trend from the 1960s to 2000s largely because both nutrients increased simultaneously. In comparison, the elemental ratio of dissolved inorganic nitrogen (DIN) to PO (4) (3-) in surface seawater, with salinity > 22, has shown a clearly increasing trend. Furthermore, an overall historical change of the SiO (3) (2-) :PO (4) (3-) ratio has undergone a reverse trend in this area. Based on the changes of SiO (3) (2-) :PO (4) (3-) and DIN:PO (4) (3-) ratios, we can conclude that an overall historical change of SiO (3) (2-) :DIN ratio has decreased in this area from the 1950-1960s to 2000s. The argument that phytoplankton productivity in the Changjiang estuary has been enhanced by increasing nutrient input from the riverine transport was supported by these results. A comparative study analyzing the shift of phytoplankton composition from the mid-1980s to 2000s was also made. The results indicated that the average yearly percentage of diatom species in the Changjiang estuary has decreased from 84.6% during 1985-1986 to 69.8% during 2004-2005. Furthermore, the average yearly percentage of diatom abundance in the Changjiang estuary decreased from 99.5% during to 75.5% over the same time period, while the abundance of dinoflagellates has increased dramatically, from 0.7% to 25.4%.

Interactions between the bloom-forming dinoflagellates Prorocentrum donghaiense and Alexandrium tamarense in laboratory cultures

Interactions between Prorocentrum donghaiense and Alexandrium tamarens, two bloom-forming dinoflagellates, were investigated using bi-algal cultures. All R donghaiense died, but A. tamarense was hardly affected by the end of the experiment when the initial cell density was set at 1.0 X 10(4) cells mL(-1) for P. donghaiense and 0.28 x 10(4) cells mL(-1) for A. tamarense. However, significant growth suppression occurred in either species when the initial cell density of P donghaiense increased to I. 0 X 105 Cells mL(-1) in the bi-algal culture, but no out-competement was observed. The simultaneous assay on the culture filtrates showed that P donghaiense filtrate prepared at a lower initial density (1.0 X 10(4) cells mL(-1)) stimulated growth of the co-cultured A. tanzarense (0.28 x 10(4) cells mL(-1)), but filtrate at a higher initial density (1.0 x 10(5) cells mL(-1)) depressed its growth. The filtrate of A. tamarense at a density of 0.28 x 10(4) cells mL(-1) killed all R donghaiense at a lower density (1.0 x 10(4) cells mL(-1)), but only exhibited an inhibitory effect on it at a higher density (1.0 x 10(5) cells mL(-1)). It is likely that these two species of microalgae interfere with each other mainly by releasing allelochemical substance(s) into the culture medium, and a direct cell-to-cell contact was not necessary for their mutual interaction. The allelopathic test further proved that A. tamarense could affect the growth of co-cultured P. donghaiense by producing allelochemical(s); moreover, A. tamarense culture filtrate at the stationary growth phase (SP) had a strongly inhibitory effect on P donghaiense compared to that at the exponential phase (EP). Results also demonstrated a dose-dependent relationship between the microalgal initial cell density and the degree of the allelopathic effect. The growth of R donghaiense and A. tamarense in the bi-algal cultures was simulated using a mathematical model to quantify the interaction. The estimated parameters from the model showed that the inhibition exerted by A. tamarense on P. donghaiense was about 17 and 8 times stronger than the inhibition P. donghaiense exerted on A. tamarense, when the initial cell density was set at 1.0 X 10(4) and 1.0 X 10(5) cells mL(-1) for P donghaiense, respectively. and 0.28 x 10(4) cells mL(-1) for A. tamarense in the bi-algal cultures. A. tamarense seems to have a survival strategy that is superior to that of P. donghaiense in bi-algal cultures under controlled laboratory conditions. (c) 2006 Elsevier B.V. All rights reserved.