Methods for physical separation and characterization of soil organic matter fractions

Turnover of soil organic matter (SOM) is coupled to the cycling of nutrients in soil through the activity of soil microorganisms. Biological availability of organic substrate in soil is related to the chemical quality of the organic material and to its degree of physical protection. SOM fractions can provide information on the turnover of organic matter (OM), provided the fractions can be related to functional or structural components in soil. Ultrasonication is commonly used to disrupt the soil structure prior to physical fractionation according to particle size, but may cause redistribution of OM among size fractions. The presence of mineral particles in size fractions can complicate estimations of OM turnover time within the fractions. Densiometric separation allows one to physically separate OM found within a specific size class from the heavier-density mineral particles. Nutrient contents and mineralization potential were determined for discrete size/density OM fractions isolated from within the macroaggregate structure of cultivated grassland soils. Eighteen percent of the total soil C and 25% of the total soil N in no-till soil was associated with fine-silt size particles having a density of 2.07-2.21 g/cm3 isolated from inside macroaggregates (enriched labile fraction or ELF). The amount of C and N sequestered in the ELF fraction decreased as the intensity of tillage increased. The specific rate of mineralization (mug net mineral N/mug total N in the fraction) for macroaggregate-derived ELF was not different for the three tillage treatments but was greater than for intact macroaggregates. The methods described here have improved our ability to quantitatively estimate SOM fractions, which in turn has increased our understanding of SOM dynamics in cultivated grassland systems.

Synthesis, photophysical and electrophosphorescent properties of mononuclear Pt(II) complexes with arylamine functionalized cyclometalating ligands

Four cyclometalated Pt(II) complexes, i.e., [(L-2)PtCl] (1b), [(L-3)PtCl] (1c), [(L-2)PtC CC6H5] (2b) and [(L-3)PtC CC6H5] (2c) (HL2 = 4-[p-(N-butyl-N-phenyl)anilino]-6-phenyl-2,2'-bipyridine and HL3 = 4-[p(-N,N'-dibutyl-N'-phenyl)phenylene-diamino]-phenyl-6-phenyl-2,2'-bipyridine), have been synthesized and verified by H-1 NMR, C-13 NMR and X-ray crystallography. Unlike previously reported complexes [(L-1)PtCl] (1a) and [(L-1)PtC CC6H5] (2a) (HL1 = 4,6-diphenyl-2,2'-bipyridine), intense and continuous absorption bands in the region of 300-500 nm with strong metal-to-ligand charge transfer ((MLCT)-M-1) (d pi(Pt) -> pi*(L)) transitions (epsilon similar to 2 x 10(4) dm(3) mol (1) cm (1)) at 449-467 nm were observed in the UV-Vis absorption spectra of complexes 1b, 1c, 2b and 2c.

First-principles investigation on the elastic, magnetic and electronic properties of MFe3N (M = Fe, Ru, Os)

The elastic, magnetic and electronic properties of MFe3N (M = Fe, Ru, Os) are investigated via first-principles calculations. The calculated results are in agreement with the experimental and other theoretical data. The high ratios of bulk modulus to shear modulus 2.7, 2.0, and 1.8 for gamma'-Fe4N, RuFe3N, and OsFe3N, respectively, indicate that they have good ductility. gamma'-Fe4N possesses the largest B/C-44 (3.41) ratio, which suggests that it is much prone to shearing. The net magnetic moment per formula unit decreases from 9.90 for gamma'-Fe4N, 7.66 for RuFe3N, to 6.80 mu(B) for OsFe3N.

Polypropylene as a carbon source for the synthesis of multi-walled carbon nanotubes via catalytic combustion

Multi-walled carbon nanotubes (MWCNTs) were efficiently synthesized by catalytic combustion of polypropylene (PP) using nickel compounds (such as Ni2O3, NiO, Ni(OH)(2) and NiCO3 (.) 2Ni(OH)(2)) as catalysts in the presence of organic-modified montmorillonite (OMMT) at 630-830 degrees C. Morphologies of the sample undergoing different combustion times were observed to investigate actual process producing MWCNTs by this method. The obtained MWCNTs were characterized by X-ray diffraction (XRD), transmission electron microscope and Raman spectroscopy. The yield of MWCNTs was affected by the composition of PP mixtures with OMMT and nickel compounds and the combustion temperature. The proton acidic sites from the degraded OMMT layers due to the Hoffman reaction of the modifiers at high temperature played an important role in the catalytic degradation of PP to supply carbon sources that are easy to be catalyzed by nickel catalyst for the growth of MWCNTs. The XRD measurements demonstrated that the nickel compounds were in situ reduced into the Ni(0) state with the aid of hydrogen gas and/or hydrocarbons in the degradation products of PP, and the Ni(O) was really the active site for the growth of MWCNTs. The combination of nickel compounds with OMMT was a key factor to efficiently synthesize MWCNTs via catalytic combustion of PP.

Structure identification of a prenylflavonol glycoside from Epimedium koreanum by electrospray ionization tandem mass spectrometry

A novel prenylflavonol glycoside, named acetylicariin, has been isolated from the aerial parts of Epimedium koreanum Nakai. The structure has been identified by electrospray ionization multi-stage tandem mass spectrometry (ESI-MSn) and other chemical evidence, which has been elucidated as 8-prenylkaempferol-4'-methoxyl-3-O-alpha-L-rhamnopyranosyl-7-O-beta-D-(2''-O-acetyl)glucopyranoside.

Calculation of the thermal expansion coefficient for Bi2Sr2CaCu2O8

An estimation method of thermal expansion coefficient in term of lattice energy which was developed earlier for simple materials is extended to a complex material of Bi2Sr2CaCu2O8 (Bi-2212). The calculation of the chemical bond property and thermal expansion coefficient of Bi-2212 has been carried out and the theoretical values were in good agreement with the corresponding experimental results. The dependence of the thermal expansion coefficient on the different structures and on the flexible oxidation states of Bi and Cu are investigated. The results indicate that the thermal expansion coefficients of Bi-2212 are insensitive to the low lattice distortion of the average structure and the changes of formal valences of Bi and Cu ions.

Hydrothermal synthesis and characterization of bimetallic cluster complex [{Mn(phen)(2)}(2)V4O12]center dot 1/2 H2O

A new bimetallic cluster complex with the formula [(Mn(phen)(2))(2)V4O12].1/2 H2O has been synthesized through hydrothermal reaction of vanadate staring material with manganese cation in the presence of nitrogen donor chelating ligand and characterized by single-crystal X-ray diffraction, elemental analysis, IR UV-vis, ESR spectrum and thermal analysis. The compound crystallize in the monoclinic space group P2(1)/c with a = 18.475(4) Angstrom, b = 11.473(2) Angstrom, c = 23.667(5) Angstrom, beta = 97.76(3)degrees, V = 4971(2) Angstrom(3) and Z = 4. The structure of [{Mn(phen)(2)}(2)V4O12].1/2 H2O is composed of a discrete V4O124- cluster covalently attached to two [Mn(phen)(2)](2+) fragments.

Synthesis and characterization of aromatic dianhydrides and polyesterimides derived from 4-hydroxyphthalic anhydride

4-Hydroxyphthalic anhydride, prepared from 4-chlorophthalic anhydride, was reacted with trimellitic anhydride monoacid chloride or arylene diacid chloride to give aromatic ester-containing dianhydrides (EDAs). These dianhydrides were characterized by element analysis, melt point, FTIR and H-1-NMR. A series of aromatic poly (amic ester acid)s was synthesized by polycondensation of these EDAs and various diamines in polar organic solvent. The inherent viscosity of poly (amic ester acid)s ranged from 0.55 to 0.89 dL/g, indicating the intermediate to higher molecular weight. Polyesterimides having glass transition temperatures between 184-219degreesC were produced by thermal imidization of corresponding poly (amic ester acid)s. These polymers were fairly resistant to organic solvent, but some of them were soluble in phenol solvents. Thermogravimetric analyses revealed that these polyesterimides were stable up to 400degreesC, and the 5% weight loss temperatures were recorded in the range of 432-483degreesC in air atmosphers and 451-490degreesC in nitrogen.

Valence change and luminescence of divalent samarium in strontium berates

The valence change of samarium from trivalent to divalent state in strontium berates (SrB6O10) prepared in air was observed. The high resolution spectra of Sm2+ in matrix were studied between 10 K and 300 K. The results showed that three crystallographic sites for Sm2+ were available in the host. Energy transfer among these sites was possible. The vibronic transition of D-5(0) --> F-7(0) of Sm2+ was studied at room temperature and the Huang-Rhys factor S was calculated. Due to the thermal population, D-5(1) --> F-7(0) transition at room temperature was observed.

Effect of hydrogen bonds on optical nonlinearities of inorganic crystals

This work probes the role of hydrogen bonds (such as O-H ... O and N-H ... O) in some inorganic nonlinear optical (NLO) crystals, such as HIO3, NH4H2PO4 (ADP), K[B5O6(OH)(4)] . 2H(2)O (KB5) and K2La(NO3)(5) . 2H(2)O (KLN), from the chemical bond standpoint. Second order NLO behaviors of these four typical inorganic crystals have been quantitatively studied, results show hydrogen bonds play a very important role in NLO contributions to the total nonlinearity. Conclusions derived here concerning the effect of hydrogen bonds on optical nonlinearities of inorganic crystals have important implications with regard to the utilization of hydrogen bonds in the structural design of inorganic NLO crystals. (C) 1999 Elsevier Science B.V. All rights reserved.

In vitro antioxidant activities of acetylated, phosphorylated and benzoylated derivatives of porphyran extracted from Porphyra haitanensis

Porphyran extracted from red algae Porphyra haitanensis is a sulfated polysaccharide, which possesses excellent antioxidant activities. In this study, we prepared the acetylated, phosphorylated and benzoylated derivatives of porphyran. And then the antioxidant activities of all the samples were investigated including scavenging effects of superoxide and hydroxyl radicals and reducing power. The results of chemical analysis and FT-IR spectrum showed the modifications of porphyran were successful. And in addition, we found that certain derivative exhibited stronger antioxidant activity than raw material. And the mechanism of the structure-function relationship of these derivatives needs to be attended to. (C) 2009 Elsevier Ltd. All rights reserved.

Host sex and ectoparasite infections of plateau pika (Ochotona curzoniae, Hodgson) on the Qinghai-Tibetan Plateau

A total of 449 plateau pika (Ochotona curzoniae Hudgson) individuals were sampled with rattraps from 21 plots (size 1 ha) randomly scattered over the area of the species distribution at the altitude 3275-4807 in a.s.l. in the Qinghai-Tibetan Plateau (West China). Two main ectoparasite species Hypoderma satyrus Brauer and Ixodes crenulatus Neumann of plateau pika were surveyed, and the relations between host sex and parasitism were analyzed. The results were: (i) although not significantly, the infection rate of female young was close to zero and lower than that of male young (6%), while the infection rate of female sub-adults (19%) was contrarily - higher than that of male sub-adults (11%); adult females had significantly higher (41%) infection rate than that of males (18%) (P<0.001); (ii) the parasite infection rates for both males and females increased with increasing age, but female age-groups had obviously steeper slope. We suggested that the differences of body mass, growth rate and home range between males and females had mainly caused the sex-biased parasitism (SBP) of plateau pika at each age stage. Also, due to the higher increases of body mass and maybe as well as of the home range differences between consecutive age-groups, the parasite infections of females became more sensitive to the influences of age than that of males.