Crystal growth and TG-DTA properties of K(2)Ln(NO3)(5).2H(2)O (Ln = La, Ce, Pr, Nd, Sm)

Single crystals of KLnN(Ln=La, Ce, Pr, Nd, Sm) can be grown in water solution with pH approximate to 1 similar to 2 at about 40 degrees C. Crystals of KLnN (Ln=La, Ce, Pr, Nd) are orthorhombic with space group Fdd2. KPrN crystal was grwon and its crystal structure was determined for the first time. The KPrN crystal parameters obtained by the direct method are as follows: a=21.411(3) Angstrom, b=11.2210(10)Angstrom, c=12.208(2) Angstrom, Z=6, R=0.0240. The TG-DTA curves of KLnN(Ln=La,Ce, Pr, Nd, Sm) demonstrate that the processes of dehydration, melt, irreversible phase transition and decomposition of NO3- take place in sequence with the temperature increasing(except KCN). There are three steps in the decomposition of NO3- in KLnN(Ln=La, Nd, Sm) while two steps in KLnN (Ln=Ce, Pr). K(2)Ln(NO3)(5). 2H(2)O are formed at about 225 degrees C by the reaction of the starting materials of KNO3 and Ln(NO3)(3). nH(2)O.

Synthesis and properties of optically active aromatic polyimides derived from optically pure 1,1'-bi-2-naphthol

A series of new optically active aromatic polyimides containing axially dissymmetric 1,1'-binaphthalene-2,2-diyl units were prepared from optically pure (R)-(+)-or (S)-(-)-2,2'-bis(3,4-dicarboxyphenoxy)-1,1'-binaphthalene dianhydrides and various aromatic diamines via a conventional two-step procedure that included ring-opening polycondensation and chemical cyclodehydration. The optically pure isomer of dianhydride was prepared by a nucleophilic substitution of optically pure (R)-(+)or (S)-(-)1,1'-bi-2-naphthol with 4-nitrophthalonitrile in aprotic polar solvent and subsequent hydrolysis of the resultant tetranitrile derivatives, followed by the dehydration of the corresponding tetracarboxylic acids to obtain the dianhydrides. These polymers were readily soluble in common organic solvents such as N,N-dimethylacetamide, N-methyl-2-pyrrolidone, and m-cresol, etc., and have glass transition temperatures of 251-296 degrees C, and 5% weight loss occurs not lower than 480 degrees C. The specific rotations of the optically active polyimides ranged from +196 degrees to +263 degrees, and the optical stability and chiroptical properties of them were also studied. (C) 1997 John Wiley & Sons, Inc.

The synthesis of a 1,1'-bi-2-naphthol-based bis(ether anhydride) and aromatic polyimides derived therefrom

2,2'-Bis(3,4-dicarboxyphenoxy)-1,1'-binaphthyl dianhydride was used as a new monomer with various aromatic diamines to obtain polyimides by the usual two-step method. The bis(ether anhydride) was prepared by a nucleophilic substitution of I,1'-bi-2-naphthol with N-phenyl-4-chlorophthalimide, N-methyl-4-nitrophthalimide or 4-nitrophthalonitrile in aprotic polar solvent, and subsequent hydrolysis of the resulting bis(ether imide)s or bis(ether dinitrile), and then dehydration of the corresponding tetracarboxylic acid to afford the dianhydride. Most of the obtained polyimides were soluble in chloroform, pyridine, DMF, etc. The polyimide prepared from p-phenylene diamine was partial crystalline, whereas the others showed amorphous patterns in a WAXD study. These polymers have glass transition temperatures between 255-294 degrees C and 5% weight loss temperatures in the range of 502-541 degrees C in nitrogen and 473-537 degrees C in air. (C) 1997 Elsevier Science Ltd.

Synthesis and thermo-decomposition mechanism of rare earth complexes with phenylacetic acid

Rare earth complexes with phenylacetic acid (LnL(3) . nH(2)O, Ln is Ce, Nd, Pr, Ho, Er, Yb and Y, L is phenylacetate, n = 1-2) were prepared and characterized by elemental analysis, IR spectroscopy, chemical analysis, and X-ray crystal structure. The mechanism of thermal decomposition of the complexes was studied by means of TG-DTG, DTA and DSC. The activation energy and enthalpy change for the dehydration and melting processes were determined.

THE EFFECTS OF LANTHANIDE IONS AND THEIR COMPLEXES ON THE PHASE-TRANSITION PROPERTY OF DIPALMITOYLPHOSPHATIDYLETHANOLAMINE LIPOSOMES

The effects of metal ions and lanthanide complexes on the gel-to-liquid crystal phase transition temperature T-m of dipalmitoylphosphatidylethanolamine liposomes have been studied by differential scanning calorimetry (DSC) method. The results show that the addition of metal ions to the dipalmitoylphosphatidylethanolamine (DPPE) liposomes dispersions increases the main phase transition temperature T-m in the order of monovalent< divalent< trivalent cations. The enhancement of T-m is not large as increasing the lanthanide ions concentration. The enhancement of Pr3+ is larger than that of La3+. Remarkable differences were observed between La-citrate and La-lactate complexes at different pH solutions. At pH 7.0, La-citrate complex has no effect on the T-m, La-lactate complex, however, increases the T-m value, and the increase is larger than that of free lanthanide ions at the same concentration. The decrease of pH of complexes solutions lowers the phase transition temperature. We have preliminarily discussed the mechanism of the enhancements of lanthanide ions and the synergism of lanthanide ion and lactate ligand follow the ion induced dehydration of lipid and the potential effects of ion-lipid interaction.

CURE AND IONIC-CONDUCTIVITY OF A 2-COMPONENT EPOXY NETWORK POLYMER ELECTROLYTE

In order to raise the room temperature ionic conductivity and improve the mechanical strength of a PEO-based polymer electrolyte, a non-crystalline two-component epoxy network was synthesized by curing diglycidyl ether of polyethylene glycol (DGEPEG) with triglycidyl ether of glycerol (TGEG) in the presence of LiClO4 salt, which acts in this system as both a ring opening catalyst and a source of ionic carrier. The structure of the precursors, the curing process and the cured films have been characterized by C-13 NMR, IR, DSC and ionic conductivity measurement techniques. The electrolyte system exhibits an ionic conductivity as high as similar to 10(-5) S/cm at 25 degrees C and is mechanically self-supportable. The dependence of ionic conductivity was investigated as a function of temperature, salt content, MW of PEG segment in DGEPEG and the proportion of DGEPEG in DGEPEG/TGEG ratio.

IONIC-CONDUCTIVITY AND DYNAMIC MECHANICAL RELAXATION OF A 2-COMPONENT EPOXY NETWORK-LICLO4 ELECTROLYTE SYSTEM

The correlation between mechanical relaxation and ionic conductivity was investigated in a two-component epoxy network-LiClO4 electrolyte system. The network was composed of diglycidyl ether of polyethylene glycol (DGEPEG) and triglycidyl ether of glycerol (TGEG). The effects of salt concentration, molecular weight of PEG in DGEPEG and the proportion of DGEPEG (1000) in DGEPEG/TGEG ratio on the ionic conductivity and the mechanical relaxation of the system were studied. It was found that, among the three influential factors, the former reinforces the network chains, reduces the free volume fraction and thus increases the relaxation time of the segmental motion, which in turn lowers the ionic conductivity of the specimen. Conversely, the latter two increase the free volume and thus the chain flexibility, showing an opposite effect. From the iso-free-volume plot of the shift factor log at and reduced ionic conductivity, it is noted that the plot can be used to examine the temperature dependence of segmental mobility and seems to be useful to judge whether the incorporated salt has been dissociated completely. Besides, the ionic conductivity and relaxation time at constant reference temperature are linearly correlated with each other in all the three cases. This result gives an additional experimental confirmation of the coordinated motion model of the ionic hopping with the moving polymer chain segment, which is generally used to explain the ionic conduction in non-glassy amorphous polymer electrolytes.

2-COMPONENT EPOXY NETWORK-LICLO4 POLYMER ELECTROLYTE

An epoxy network-LiClO4 electrolyte system was prepared from diglycidyl ether of polyethylene glycol and triglycidyl ether of glycerol, cured in the presence of LiClO4 only. Various techniques were used to characterize the chemical structure of the precursors and the correlation between the viscoelasticity and conductivity of the cured films was examined.

STUDY ON COMPLEXES OF RARE-EARTH WITH L-PHENYLALANINE BY POTENTIOMETRY WITH CALORIMETRY

The stability constants and thermodynamic functions for complexes of rare earth with L-phenylalanine have been determined by potentiometry and calorimetry at 25-degrees-C and ionic strength of 0.15mol.dm-3(NaCl). Stability of the complexes shows the "Tetrad effect". The entropy change makes a predominant contribution to the stability of these complexes. The ligand is coordinated to rare earth ions through its -CO2- and -NH2 group, and dehydration of ions plays an important role in coordination reaction.

THERMAL DECOMPOSITIONS OF SOME BIOINORGANIC COMPLEXES OF EUROPIUM

Thermogravimetric and derivative thermogravimetric investigations for three kinds of bioinorganic complexes of europium with N-acetyl-DL-alanine, N-acetyl-DL-valine and DL-alanyl-DL-alanine have been performed. It was found that the water molecules in these solid state complexes are not directly coordinated to the europium ion and that there may be three or four steps in the thermal decomposition process of these complexes after dehydration. The possible thermal decomposition reactions of these bioinorganic complexes have been suggested and discussed.

CRYSTAL STRUCTURE AND THERMAL ANALYSIS OF ERBIUM COMPLEX WITH BENZENE ACETIC ACID

The crystal structure of erbium (III) complex of benzene acetic acid is reported. The complex crystallizes in the monoclinic space group P2(1)/a with a = 0,9008(3)nm, b=1.4242(5) nm, c=1.8437(7) nm, beta=98.80(3)degrees, V = 2.337(1) nm(3), Z = 4. The mechanism of thermal decomposition of complex has been studied by TG-DTG-DTA. The activation energy for dehydration reaction has been calculated by Freeman Carroll method. The enthalpy change for dehydration and phase change process has been determined.

TWO SPECIFIC CAUSES OF CELL MORTALITY IN FREEZE-THAW CYCLE OF YOUNG THALLI OF PORPHYRA YEZOENSIS (BANGIALES, RHODOPHYTA)1

Porphyra yezoensis Ueda is an important marine aquaculture crop with single-layered gametophytic thalli. In this work, the influences of thallus dehydration level, cold-preservation (freezing) time, and thawing temperature on the photosynthetic recovery of young P. yezoensis thalli were investigated employing an imaging pulse-amplitude-modulation (PAM) fluorometer. The results showed that after 40 d of frozen storage when performing thallus thawing under 10 degrees C, the water content of the thalli showed obvious effects on the photosynthetic recovery of the frozen thalli. The thalli with absolute water content (AWC) of 10%-40% manifested obvious superiority compared to the thalli with other AWCs, while the thalli thawed at 20 degrees C showed very high survival rate (93.10%) and no obvious correlation between thallus AWCs and thallus viabilities. These results indicated that inappropriate thallus water content contributed to the cell damage during the freeze-thaw cycle and that proper thawing temperature is very crucial. Therefore, AWC between 10% and 40% is the suitable thallus water content range for frozen storage, and the thawing process should be as short as possible. However, it is also shown that for short-term cold storage the Porphyra thallus water content also showed no obvious effect on the photosynthetic recovery of the thalli, and the survival rate was extremely high (100%). These results indicated that freezing time is also a paramount contributor of the cell damage during the freeze-thaw cycle. Therefore, the frozen nets should be used as soon as time permits.

Chemical Constituents of a Marine-Derived Endophytic Fungus Penicillium commune G2M

Cultivation of the endophytic fungus Penicillium commune, which was isolated from the semi-mangrove plant Hibiscus tiliaceus, afforded one new compound 1-O-(2,4-dihydroxy-6-methylbenzoyl)-glycerol (1) along with thirteen known products, including 1-O-acetylglycerol (2), N-acetyltryptophan (3), 3-indolylacetic acid methyl ester (4), 1-(2,4-dihydroxy-3,5-dimethylphenyl)ethanone (5), 2-(2,5-dihydroxyphenyl)acetic acid (6), (4R,5S)-5-hydroxyhexan-4-olide (7), thymidine (8), uracil (9), thymine (10), ergosterol (11), beta-sitosterol (12), beta-daucosterol (13), and ergosta-7,22-dien-3 beta,5 alpha,6 beta-triol (14). The structures of these compounds were established by detailed NMR spectroscopic analysis, as well as by comparison with literature data or with authentic samples.

Cloning and characterization of beta-carotene ketolase gene promoter in Haematococcus pluvialis

The unicellular green alga Haematococcus pluvialis accumulates a highly valuable ketocarotenoid, astaxanthin, under various environmental stresses. beta-carotene ketolase (BKT) plays a key role in astaxanthin biosynthesis in H. pluvialis. In this paper, an approximate 700 bp 5'-flanking region of the bkt gene containing a putative promoter was cloned through walking upstream. The results of the sequence analysis showed that this bkt 5'-flanking region might have cis-acting elements such as sterol regulatory element (SRE-1)-like motifs, the C-repeat/dehydration responsive element (DRE) and al-3 proximal element (APE)-like motifs, except for typical TATA and CCAAT boxes. The results of the P-galactosidase assay and the transient expression of lacZ driven by a series of sequential deletions revealed that a minimal promoter-like region might exist from -630 to -408 bp, and the highest promoter activity was observed to span the positions from -630 to -308 bp. The results of the site-directed mutagenesis of a C-repeat/DRE and two APE-like motifs in a promoter-like region (-630 to -308 bp) suggested that two APE-like motifs might be essential for transcriptional control of the bkt gene.

Toxicity and protective efficiency of cryoprotectants to flounder (Paralichthys olivaceus) embryos

With the purpose of finding an ideal cryoprotectant or combination of cryoprotectants in a suitable concentration for flounder (Paralichthys olivaceus) embryo cryopreservation, we tested the toxicities, at culture temperature (16 degrees C), of five most commonly used cryoprotectants-dimethyl sulfoxide (Me2SO), glycerol, methanol (MeOH), 1,2-propylene glycol (PG) and ethylene glycol (EG). In addition, cryoprotective efficiency to flounder embryos of individual and combined cryoprotectants were tested at -15 degrees C for 60 min. Five different concentrations of each of the five cryoprotectants and 20 different combinations of these cryoprotectants were tested for their protective efficiency. The results showed that the toxicity to flounder embryos of the five cryoprotectants are in the following sequence: PG < MeOH < Me2SO < glycerol < EG (P < 0.05); whereas the protective efficiency of each cryoprotectant, at -15 degrees C for a period of 60 min, are in the following sequence: PG > Me2SO approximate to MeOH approximate to glycerol > EG (greater symbols mean P < 0.05, and approximate symbols mean P > 0.05). Methanol combined with any one of the other cryoprotectants gave the best protection, while ethylene glycol combined with any one of the other cryoprotectants gave the poorest protection at -15 degrees C. Toxicity effect was concentration dependent with the lowest concentration being the least toxic for all five cryoprotectants at 16 degrees C. For PG, MeOH and glycerol, 20% solutions gave the best protection at -15 degrees C; whereas a 15% solution of Me2SO, and a 10% solution of EG, gave the best protection at -15 degrees C. (c) 2004 Elsevier Inc. All rights reserved.