Hydrothermal synthesis of the complex fluorides LiBaF3 and KMgF3 with perovskite structures under mild conditions

The complex fluorides, LiBaF3 and KMgF3; which are isostructural with perovskite phases, are hydrothermally synthesized at 120-240 degrees C and characterized by powder X-ray diffraction, thermogravimetric analysis, IR spectroscopy and scanning electron microscopy.

SYNTHESIS AND STRUCTURAL CHARACTERIZATION OF THE DAWSON-TYPE TUNGSTOPHOSPHATE HETEROPOLY COMPLEXES SUBSTITUTED BY NIOBIUM

Eight new complexes alpha(2)-M(7-m)H(m)[P2W17NbO62]. H2O and alpha-1, 2, 3-M(g-m)H(m) [P2W15Nb3O62]. XH(2)O(M=K, TMA, TEA, TBA) were synthesized and characterized by IR and UV spectroscopy, polarography, XPS and XRD methods. P-31 and W-183 NMR studies show that the niobium atoms in the anions are on the polar sites. The crystal of alpha-1, 2, 3-K7H2 [P2W15Nb3O62]. 30H(2)O is hexagonal, its cell parameters: a=1.9836(4), b=1.9836(9), c=1.5498(6)nm, alpha=beta=90 degrees, gamma=120 degrees.

THE SYNTHESIS AND PHYSICAL-PROPERTIES OF THE NEW LAYERED LANTHANIDE ALKALINE-EARTH COBALT OXIDES [LN2MCO2O7 (LN=SM,GD M=SR,BA)]

Three new oxides Sm2SrCo2O7, Sm2BaCo2O7 and Gd2SrCo2O7 have been successfully synthesized by a solid state reaction method.The X - Ray diffraction spectra show that they are all isostructural with Sr8Ti 2O7, Ln2SrCo2O7(Ln=Sm, Gd) crystallized in the tetra

SYNTHESIS, STRUCTURE AND SPECTRA PROPERTIES OF THE NEODYMIUM MOLYBDOGERMANATE HETEROPOLY COMPLEX

K7H6[Nd(GeMo11O39)2].18H2O was first synthesized and the crystal structure was determined. Crystal structure data are as follows: monolinic, space group P2(1)/n, a = 1.7095(4), b = 2.6895(3), c = 2.1214(5) nm, beta = 103.11 (2)-degrees, V = 9.4994(3) nm3, Z = 4, D(m) = 3.14g/cm3, D(c) = 3.05g/cm3, mu(MoK-alpha) = 43.7 cm-1. Experimental evidence and theoretical foundation of the method inferring the molecule structure of heteropoly compounds using their IR spectra were gaved by studying IR spectra properties of the complex with results of structural analysis. Electronic spectra prove that 4f-obital of Nd3+ take part in bonding in the complex.

SYNTHESIS AND CRYSTAL-STRUCTURE OF THE TRIS(CYCLOPENTADIENYL)PHENYL COMPLEX OF NEODYMIUM, (LI-BULLET-3DME)[(ETA-5-C5H5)3NDC6H5]

(Li.3DME)[eta(5)-C5H5)3NdC6H5], 1 was synthesized by the reaction of NdCl3.2LiCl, 2 equivalents of cyclopentadienylsodium and one equivalent of phenyllithium in THF at -78-degrees-C, and crystallized from THF and DME. The crystal structure of 1 was determined by X-ray diffraction method at -80-degrees-C. The crystal of 1 is triclinic, space group P1BAR with a = 15.752(6), b = 16.232(3), c = 23.038(7) angstrom, alpha = 108.81(2), beta = 93.31(3), gamma = 108.38(2)-degrees, Z = 6 and D = 1.33 g/cm3. Least-squares refinement (5732 observed reflections) led to a final R of 0.053. The complex consists of disconnected ion pairs of (Li.3DME)+ and [(eta(5)-C5H5)3NdC6H5]-. The neodymium atom was connected to three eta(5)-bonded cyclopentadienyls and one sigma-bonded phenyl in a distorted tetrahedral arrangement with Nd-C(sigma-) 2.593(17), 2.613(13) and 2.601(13) angstrom.

SYNTHESIS AND MOLECULAR-STRUCTURE OF THE 5-COORDINATE ZIRCONIUM COMPLEX (CH3C5H4)2ZRCL(ALPHA-C10H7COO)

Bis(methylcyclopentadienyl)chloro(alpha-naphthoyloxy)zirconium, (CH3C5H4)2Zr Cl(alpha-C10H7COO), has been synthesized by the reaction between (MeCp)2ZrCl2 and equimolar sodium alpha-naphthoate in toluene at room temperature. The molecular structure of the title complex was determined by X-ray diffraction. The molecules have a five-coordinate bent metallocene structure in which the alpha-naphthoxyligand is bidentate [Zr-O, 2.317(2), 2.260(2) angstrom]. The remaining distances are [Zr-Cl, 2.521(1) angstrom; Zr-C, 480-2, 565 angstrom; Zr-cent-CH3C5H4 2.217 and 2.230 angstrom].

STUDY OF BIMETALLIC COMPLEXES OF RARE-EARTH LITHIUM - SYNTHESIS AND CRYSTAL-STRUCTURE OF THE (LACL)DME(MU-2-CL)5(MU-3-CL) (LA.DME)LI(THF)2

The reaction between LaCl_3 and LiCl in THF at room temperature, with hexane as precipitant and glycol dimethyl ether as complexing agent, has been studied. A complex with the composition of (LaCl)DME(μ_2-Cl)_5(μ_3-Cl)(La·DME)Li(THF)_2 has been synthesized, its structure was studied by single crystal X-ray diffraction technique. The diffraction intensities were collected at about —100℃. The complex belongs to the triclinic space group P1 with α=11.123(3), 6=16.564(5), c=8.653(3)A, α=95.16(3), β=...

SYNTHESIS AND CRYSTAL-STRUCTURES OF THE BIMETALLIC RARE-EARTH COMPLEXES AND STUDIES ON INSERTION MECHANISM OF DIENES POLYMERIZATION

The deepening of the studies on essentials of rare earth coordination catalyst brings about more and more reports on model compounds as active centre of the catalyst. Among them the most significant researches are those with identification of the crystal structures of compounds.

The synthesis and antioxidant activity of the Schiff bases of chitosan and carboxymethyl chitosan

Five kinds of Schiff bases of chitosan and carboxymethyl chitosan (CMCTS) have been prepared according to a previous method and the antioxidant activity was studied using an established system, such as superoxide and hydroxyl radical scavenging. Obvious differences between the Schiff bases of chitosan and CMCTS were observed, which might be related to contents of the active hydroxyl and amino groups in the molecular chains. (c) 2005 Elsevier Ltd. All rights reserved.

Size-Dependent Elastic Modulus And Fracture Toughness Of The Nanofilm With Surface Effects

The effective elastic modulus and fracture toughness of the nanofilm were derived with the surface relaxation and the surface energy taken into consideration by means of the interatomic potential of an ideal crystal. The size effects of the effective elastic modulus and fracture toughness were discussed when the thickness of the nanofilm was reduced. And the dependence of the size effects on the surface relaxation and surface energy was also analyzed.

Mitochondrial DNA variation, effective female population size and population history of the endangered Chinese sturgeon, Acipenser sinensis

The anadromous Chinese sturgeon (Acipenser sinensis), mainly endemic to the Yangtze River in China, is an endangered fish species. The natural population has declined since the Gezhouba Dam blocked its migratory route to the spawning grounds in 1981. In the near future, the completion of the Three Gorges Dam, the world's largest hydroelectric project, may further impact this species by altering the water flow of the Yangtze River. Little is currently known about the population genetic structure of the Chinese sturgeon. In this study, DNA sequence data were determined from the control region (D-loop) of the mitochondrial genome of adult sturgeons (n = 106) that were collected between 1995-2000. The molecular data were used to investigate genetic variation, effective female population size and population history of the Chinese sturgeon in the Yangtze River. Our results indicate that the reduction in abundance did not change genetic variation of the Chinese sturgeon, and that the population underwent an expansion in the past. AMOVA analysis indicated that 98.7% of the genetic variability occurred within each year's spawning populations, the year of collection had little influence on the diversity of annual temporary samples. The relative large effective female population size (N-ef) indicates that good potential exists for the recovery of this species in the future. Strikingly, the ratio of N-ef to the census female population size (N-f) is unusually high (0.77-0.93). This may be the result of a current bottleneck in the population of the Chinese sturgeon that is likely caused by human intervention.

The decline and impending extinction of the South China tiger

The South China tiger Panthera tigris amoyensis is the rarest of the five living tiger subspecies, the most critically threatened and the closest to extinction. No wild South China tigers have been seen by officials for 25 years and one was last brought into captivity 27 years ago. The 19 reserves listed by the Chinese Ministry of Forestry within the presumed range of the tiger are spatially fragmented and most are too small to support viable tiger populations. Over the last 40 years wild populations have declined from thousands to a scattered few. Despite its plight and occasional anecdotal reports of sightings by local people, no intensive field study has been conducted on this tiger subspecies and its habitat. The captive population of about 50 tigers, derived from six wild-caught founders, is genetically impoverished with low reproductive output. Given the size and fragmentation of potential tiger habitat, saving what remains of the captive population may be the only option left to prevent extinction of this tiger subspecies, and even this option is becoming increasingly less probable. This precarious dilemma demands that conservation priorities be re-evaluated and action taken immediately to decide if recovery of the wild population will be possible.

Biomarker responses and reproductive toxicity of the effluent from a Chinese large sewage treatment plant in Japanese medaka (Oryzias latipes)

The present study was conducted to assess the potential toxicity of the effluent from a large sewage treatment plant (GBD-STP) in Beijing. Japanese medakas (Oryzias latipes) at reproduction active period were exposed to a serial of graded concentrations of the effluent or 100 ng l(-1) of 17-alpha-ethinylestradiol (EE2, positive control). Growth, gonadosomatic index (GSI), hepatosomatic index (HSI), reproductive success, induction potency of vitellogenin (VTG) in male fish and that of 7-ethoxyresorufin-o-deethylase activity (EROD) in male fish liver were used as test endpoints. The growth suppression of fish was observed in a dose-dependent manner, resulting in significant differences in both body length and body weight of medaka above 5% effluent. This effluent can inhibit the growth of gonad of medakas and are more sensitive to male than to female. At exposure concentration of 40% and higher, there was an unexpected decrease of HSI values, which may be resulted from sub-lethal toxicity of effluent to fish liver. VTG of plasma in males were induced in all exposure concentration levels, but not in a dose-dependent manner. The concentration of 5% effluent would be the lowest observed adverse effect level (LOAEL) affecting reproductive success when examining fertile individuals, fecundity and fertilization rate. The overt CYP1A response and higher reproductive toxicity may be indicative of low process efficiency of this STP. (c) 2004 Elsevier Ltd. All rights reserved.

Differential screening and characterization analysis of the egg envelope glycoprotein ZP3 cDNAs between gynogenetic and gonochoristic crucian carp

Gynogenetic silver crucian carp, Carassius auratus gibelio, is an intriguing model. system. In the present work, a systemic study has been initiated by introducing suppression subtractive hybridization technique into this model system to identify the differentially expressed genes in oocytes between gynogenetic silver crucian carp and its closely related gonochoristic color crucian carp. Five differential cDNA fragments were identified from the preliminary screening, and two of them are ZP3 homologues. Moreover, the full length ZP3 cDNAs were cloned from their oocyte cDNA libraries. The length of ZP3 cDNAs were 1378 bp for gyno-carp and 1367 bp for gono-carp, and they can be translated into proteins with 435 amino acids. Obvious differences are not only in the composition of amino acids, but also in the number of potential O-linked oligosaccharide sites. In addition, gyno-carp ZP3 amino acid sequence has an unexpected higher identity value with common carp (83.5%) than that with the closely related gono-carp (74.7%). The unique homology may be originated from the ancient hybridization. Northern blot analysis confirmed that expression of the ZP3 gene occurred exclusively in the oocytes. Because O-linked oligosaccharides on ZP3 have been demonstrated to play very important roles in fertilization, it is suggested that the extra O-linked glycosylation sites may be related to the unique sperm-egg recognition mechanism in gynogenesis.