Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 17 de 17
Filtrar
Mais filtros










Base de dados
Tipo de estudo
Intervalo de ano de publicação
1.
Nature ; 600(7887): 59-63, 2021 12.
Artigo em Inglês | MEDLINE | ID: mdl-34666339

RESUMO

Mare volcanics on the Moon are the key record of thermo-chemical evolution throughout most of lunar history1-3. Young mare basalts-mainly distributed in a region rich in potassium, rare-earth elements and phosphorus (KREEP) in Oceanus Procellarum, called the Procellarum KREEP Terrane (PKT)4-were thought to be formed from KREEP-rich sources at depth5-7. However, this hypothesis has not been tested with young basalts from the PKT. Here we present a petrological and geochemical study of the basalt clasts from the PKT returned by the Chang'e-5 mission8. These two-billion-year-old basalts are the youngest lunar samples reported so far9. Bulk rock compositions have moderate titanium and high iron contents  with KREEP-like rare-earth-element and high thorium concentrations. However, strontium-neodymium isotopes indicate that these basalts were derived from a non-KREEP mantle source. To produce the high abundances of rare-earth elements and thorium, low-degree partial melting and extensive fractional crystallization are required. Our results indicate that the KREEP association may not be a prerequisite for young mare volcanism. Absolving the need to invoke heat-producing elements in their source implies a more sustained cooling history of the lunar interior to generate the Moon's youngest melts.

2.
Inorg Chem ; 57(7): 3761-3774, 2018 Apr 02.
Artigo em Inglês | MEDLINE | ID: mdl-29521502

RESUMO

A series of homoleptic mononuclear 8-coordinate FeII and CoII compounds, [FeII(L2)2](ClO4)2 (2), [FeII(L3)2](ClO4)2 (3), [FeII(L4)2](ClO4)2 (4), [CoII(L1)2](ClO4)2 (5), [CoII(L2)2](ClO4)2 (6), [CoII(L3)2](ClO4)2 (7), and [CoII(L4)2](ClO4)2 (8) (L1 and L2 are 2,9-dialkylcarboxylate-1,10-phenanthroline ligands; L3 and L4 are 6,6'-dialkylcarboxylate-2,2'-bipyridine ligands), have been obtained, and their crystal structures have been determined by X-ray crystallography. The metal center in all of these compounds has an oversaturated coordination number of 8, which is completed by two neutral homoleptic tetradentate ligands and is unconventional in 3d-metal compounds. These compounds are further characterized by electronic spectroscopy, cyclic voltammetry (CV), and magnetic measurements. CV measurements of these complexes in MeCN solution exhibit rich redox properties. Magnetic measurements on these compounds demonstrate that the observed single-ion magnetic (SIM) behavior in the previously reported [FeII(L1)2](ClO4)2 (1) is not a contingent case, since all of the 8-coordinate compounds 2-8 exhibit interesting slow magnetic relaxation under applied direct current fields.

3.
Chem Commun (Camb) ; 53(9): 1474-1477, 2017 Jan 26.
Artigo em Inglês | MEDLINE | ID: mdl-28083575

RESUMO

The synthesis and structure of an 8-coordinate Fe(ii) compound [FeII(L1)2](ClO4)2 (1) with a [FeN4O4] core are reported. 1 exhibits uni-axial anisotropy for which a slow magnetic relaxation is observed under 1.4 kOe dc field. It is the first example of an 8-coordinate Fe(ii) complex exhibiting field-induced single-molecule magnet (SMM) behaviour.

4.
Dalton Trans ; 45(21): 8790-4, 2016 Jun 07.
Artigo em Inglês | MEDLINE | ID: mdl-27143486

RESUMO

Two dinuclear dysprosium complexes with the Dy(iii) ions bridged by the neutral bipyrimidine (BPYM) ligand were synthesized and magnetically characterized. They crystallized in a monoclinic and triclinic crystal system, respectively, with almost the same structural core, only differing in the lattice solvent molecules. Alternating current (ac) susceptibility measurements revealed that they exhibit significant slow relaxation of magnetization until 25 K in the absence of a dc field. The single and double relaxation processes were assigned to one and two types of Dy(iii) environments in the two dimmers, respectively, with barriers of 266 and 345 K under zero field conditions. The magnetic hysteresis loops of 1 and 2 were both observed up to 2.5 K.

5.
Chem Asian J ; 9(9): 2463-6, 2014 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-25045102

RESUMO

Two new trihydrazine bridged Co(II) chain compounds have been synthesized and magnetically characterized. The two compounds are both composed of [Co(N2H4)3](2+) chains. One exhibits antiferromagnetic ordering behavior while the other behaves as a single-chain magnet (SCM) at low temperature.

6.
Dalton Trans ; 42(11): 3876-87, 2013 Mar 21.
Artigo em Inglês | MEDLINE | ID: mdl-23325271

RESUMO

The synthesis, crystal structures and magnetic properties of six cyano-bridged heterobimetallic compounds prepared from a paramagnetic Ru(III) building block, trans-(PPh(4))[Ru(III)(Q)(2)(CN)(2)] (1) (Q = the anion of 8-hydroxyquinoline), are described. 1 reacts with hydrated MnCl(2) in MeOH or DMF to produce a trinuclear compound {[Ru(III)(Q)(2)(CN)(2)](2)[Mn(II)(MeOH)(4)]}·8MeOH (2), or a 1-D zigzag chain {[Mn(II)(DMF)(2)(Cl)](µ-CN)(2)[Ru(III)(Q)(2)]}(n)(3). The Mn(II) has a distorted octahedral environment in 2 and a trigonal-bipyramidal environment in 3. 1 reacts with [Mn(III)(L(1))(Cl)(H(2)O)] in MeOH to produce the 1-D {[Ru(III)(Q)(2)](µ-CN)(2)[Mn(III)(L(1))]}(n) (4) that consists of alternating Mn(III) and Ru(III) units. 1 also reacts with [Cu(II)(cyclam)Br(2)] and [Ni(II)(cyclam)Cl(2)] in MeOH to produce the trinuclear complexes [Ru(III)(Q)(2)(CN(2))](2)[M(II)(cyclam)] (M = Cu(II) (5) and Ni(II) (6)). On the other hand, the reaction of 1 with [Ni(II)(cyclen)Cl(2)] produces a 1-D zigzag chain {([Ru(III)(Q)(2)(CN(2))][Ni(II)(cyclen)])[Ru(III)(Q)(2)(CN(2))]}(n) (7). Compounds 2-4 exhibit antiferromagnetic coupling between Ru(III) and Mn(III/II) centres. Antiferromagnetic coupling also occurs between Ru(III) and Cu(II) centres in 5. On the other hand, compounds 6 and 7 exhibit ferromagnetic coupling between Ru(III) and Ni(II) through cyanide bridges.

7.
Dalton Trans ; 41(19): 5794-8, 2012 May 21.
Artigo em Inglês | MEDLINE | ID: mdl-22327897

RESUMO

Reaction of [Ru(VI)(N)(sap)Cl] with excess NaN(3) affords a novel paramagnetic triazidoruthenium(III) complex [Ru(III)(sap)(N(3))(3)](2-), which is isolated as a PPh(4)(+) salt (1). Reaction of 1 with Ni(2+) and Co(2+) ions produce two isostructural hexanuclear [Ru(4)M(2)] compounds, [Ru(IV)(4)M(II)(2)(µ(3)-OMe)(2)(µ-OMe)(2)(µ-N)(2)(µ-N(3))(2)(µ-O(phenoxy))(2)(sap)(4) (MeOH)(4)] (M = Ni 2 or Co 3). The molecular structures of 1-3 have been determined by X-ray crystallography. 1 is a mononuclear ruthenium(III) compound where three azide ligands are bonded to ruthenium in a meridional fashion, while compounds 2 and 3 are isostructural hexanuclear compounds containing a defective face-sharing dicubane-like core with two missing vertexes. Variable-temperature dc magnetic susceptibility studies have been carried out for 2 and 3. These data indicate that there are four diamagnetic Ru(IV) ions in 2 and 3 and there is ferromagnetic interaction between the two Ni(2+) in 2 and Co(2+) in 3 via the methoxy bridges.

8.
Genet Test Mol Biomarkers ; 16(2): 102-8, 2012 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-22224559

RESUMO

PURPOSE: This study was carried out to estimate the allele and genotype frequencies of common variants in the CYP3A4, CYP2C19, and CYP2D6 in the Han, Uighur, Hui, and Mongolian Chinese populations and compare genetic polymorphisms difference between the Han and minority Chinese ethnicities. METHODS: We evaluated 672 unrelated, healthy Chinese volunteers (Han: 136; Uighur: 214; Hui: 164; Mongolian: 158). Genomic DNA was extracted from peripheral leukocytes and genotyped for CYP3A4*18, CYP2C19*2, *3, and CYP2D6*10 by polymerase chain reaction-restriction fragment length polymorphism analysis. RESULTS: The allele frequencies of CYP3A4*18 in the Han, Uighur, Hui, and Mongolian Chinese population were 18.4%, 14.0%, 19.2%, and 20.3%, respectively; the allele frequencies of CYP2C19*2 were 38.6%, 32.5%, 49.4%, and 41.5%, respectively; the allele frequencies of CYP2C19*3 were 5.2%, 2.1%, 5.2%, and 4.4%, respectively; and the allele frequencies of CYP2D6*10 were 57.4%, 22.4%, 39.7%, and 46.5%, respectively. CONCLUSION: The results showed that there was no significant ethnic difference in the distribution of CYP3A4*18 and CYP2C19*3 genotypes in the Han, Uighur, Hui, and Mongolian Chinese populations. For CYP2C19*2, the Han were not significantly different from the Uighur, Hui, or Mongolian; however, the Uighur were significantly lower than the Hui and the Mongolian, and the Mongolian were significantly lower than the Hui. For CYP2D6*10, the Mongolian were not significantly different from the Han and the Hui. However, the Uighur were significantly lower than the other three. Our findings confirm the existence of interethnic differences in the CYP2C9, CYP2C19, and CYP2D6 alleles and genotype frequencies in the Han, Uighur, Hui, and Mongolian Chinese populations.


Assuntos
Hidrocarboneto de Aril Hidroxilases/genética , Citocromo P-450 CYP2D6/genética , Citocromo P-450 CYP3A/genética , Frequência do Gene , Polimorfismo Genético , Adulto , Citocromo P-450 CYP2C19 , Feminino , Genótipo , Humanos , Masculino , Reação em Cadeia da Polimerase , Polimorfismo de Fragmento de Restrição , Adulto Jovem
9.
Ying Yong Sheng Tai Xue Bao ; 22(8): 2075-83, 2011 Aug.
Artigo em Chinês | MEDLINE | ID: mdl-22097370

RESUMO

By using the CERES-Maize crop model and Century soil model in Decision Support System of Agrotechnology Transfer (DSSAT) model, this paper studied the effects of crop management parameters, fertilizer N application rate, soil initial N supply, and crop residue application on the maize growth, crop-soil N cycling, and soil organic C and N ecological balance in black soil (Mollisol) zone of Jilin Province, Northeast China. Taking 12,000-15,000 kg x hm(-2) as the target yield of maize, the optimum N application rate was 200-240 kg N x hm(-2). Under this fertilization, the aboveground part N uptake was 250-290 kg N x hm(-2), among which, 120-140 kg N x hm(-2) came from soil, and 130-150 kg N x hm(-2) came from fertilizer. Increasing the N application rate (250-420 kg N x hm(-2)) induced an obvious increase of soil residual N (63-183 kg x hm(-2)); delaying the N topdressing date also induced the increase of the residual N. When the crop residue application exceeded 6000 kg x hm(-2), the soil active organic C and N could maintain the supply/demand balance during maize growth season. To achieve the target maize yield and maintain the ecological balance of soil organic C and N in black soil zone of Jilin Province, the chemical N application rate would be controlled in the range of 200-240 kg N x hm(-2), topdressing N should be at proper date, and the application amount of crop residue would be up to 6000 kg x hm(-2).


Assuntos
Agricultura/métodos , Carbono/análise , Nitrogênio/análise , Solo/análise , Zea mays/crescimento & desenvolvimento , Biomassa , China , Ecossistema , Fertilizantes , Modelos Teóricos , Ciclo do Nitrogênio , Compostos Orgânicos/análise , Zea mays/metabolismo
10.
Chem Commun (Camb) ; 47(30): 8694-6, 2011 Aug 14.
Artigo em Inglês | MEDLINE | ID: mdl-21725550

RESUMO

Reaction of [Ru(II)(PPh(3))(3)Cl(2)] with HQ and KCN produces a new dicyanoruthenium(III) building block, [Ru(III)(Q)(2)(CN)(2)](-). It reacts with hydrated CoCl(2) in MeOH or DMF to produce a trinuclear compound 2 or a 1-D zigzag chain 3.

11.
Inorg Chem ; 50(1): 144-54, 2011 Jan 03.
Artigo em Inglês | MEDLINE | ID: mdl-21126016

RESUMO

By employing hydrothermal method, six transition metal sulfates containing hydrazine (N(2)H(4)) have been obtained: [M(SO(4))(2)(N(2)H(5))(2)](n) (M = Mn(1), Co(2), Ni(3)) and [M(N(2)H(4))SO(4)](n) (M = Mn(4), Co(5), Ni(6)). Their crystal structures and magnetic properties have been investigated experimentally and theoretically. Compounds 1-3 consist of one-dimensional sulfate bridged homometallic chains with protonated hydrazine molecule as terminal ligand, and compounds 4-6 are hydrazing-sulfate mixed bridged homometallic three-dimensional frameworks. Compounds 1-6 exhibit antiferromagnetic coupling between M(2+) ions, but their magnetic properties differ at low temperatures because of the different single-ion anisotropy and crystal structures. The magnetostructural correlations and the magnetic coupling mechanism are analyzed by density functional theory calculations (DFT).

12.
J Microencapsul ; 27(2): 171-7, 2010.
Artigo em Inglês | MEDLINE | ID: mdl-19538029

RESUMO

Microparticle protein delivery systems based on calcium alginate were fabricated using a very convenient method, i.e. directly shredding the protein-loaded calcium alginate beads into microparticles in a commercial food processor for 3 min. Bovine serum albumin (BSA) as a model protein was encapsulated in the calcium alginate microparticles. The obtained protein-loaded microparticles were then coated with chitosan. This fabrication method offered high encapsulation efficiency and a high particle yield. Compared with beads, the microparticles exhibited a faster release rate in the initial release stage. By comparing the release profiles of uncoated beads/microparticles and chitosan-coated beads/microparticles, it was found that the releases from chitosan-coated beads/microparticles were slower. To examine whether the loaded protein denatured during the microparticle fabrication, trypsin was encapsulated in the calcium alginate microparticles and the bioactivity of trypsin released from the microparticles was measured.


Assuntos
Alginatos/química , Preparações de Ação Retardada/química , Composição de Medicamentos/métodos , Soroalbumina Bovina/administração & dosagem , Animais , Bovinos , Quitosana/química , Composição de Medicamentos/economia , Ácido Glucurônico/química , Ácidos Hexurônicos/química , Tamanho da Partícula
13.
Acta Crystallogr Sect E Struct Rep Online ; 65(Pt 2): o365, 2009 Jan 23.
Artigo em Inglês | MEDLINE | ID: mdl-21581963

RESUMO

In the title compound, C(14)H(16)N(4) (2+)·2C(7)H(5)O(6)S(-)·2H(2)O, the 3,3'-(p-phenyl-enedimethyl-ene)diimidazol-1-ium dication lies on a crystallographic inversion center. In the crystal structure, dications, anions and solvent water mol-ecules are linked via O-H⋯O, N-H⋯O and C-H⋯O hydrogen bonds, and C-H⋯π inter-actions, forming a three-dimensional network containing R(2) (2)(4), R(2) (4)(12), R(4) (4)(22), R(8) (10)(32) and R(12) (14)(66) ring motifs.

14.
Biomed Environ Sci ; 22(6): 472-9, 2009 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-20337220

RESUMO

OBJECTIVE: To evaluate the effectiveness of universal salt iodization (USI) for the control of IDD in Hebei province since it was implemented in 1995, identify the problems currently encountered in the implementation of USI and provide practical proposals for addressing these problems. METHODS: Probability proportionate to size sampling (PPS) was employed in the surveillance of IDD, for which a total of 1200 school children aged 8-10 years were randomly selected from 30 counties around the whole province during each IDD survey. The iodine content of salt was determined quantitatively with the titration method. The iodine content of urinary samples was measured by the method of ammonium persulfate oxidation. RESULTS: The coverage of iodized salt increased from 65.0% in 1995 to 98.0% in 1999, then decreased to 88.1% in 2005 which was below the national standard of 90%. The median urinary iodine of children aged 8-10 years varied between 160.1 microg/L and 307.4 microg/L, which was above the national standard. The proportion of urinary samples with iodine content above 300 microg/L was over 30% in 2005, implying exorbitant iodine nutrition among the children. The goiter rate (TGR) among children aged 8-10 years dropped from 11.8% in 1995 to 2.7% in 2005, indicating that the spread of endemic goiter was under control. CONCLUSION: Preliminary elimination of IDD was achieved by USI in Hebei province. Nevertheless, some problems still existed in USI such as non-iodized salt competition, over iodization and un-standardized iodization. In order to address these problems, the management and supervision of salt market needs to be strengthened to prevent non-iodized salt from reaching households; updating equipment and modifying techniques are also necessary to ensure the quality of iodized salt; to clarify the causes of excessive urinary iodine content, the various sources of iodine from the diet need to be investigated in the future.


Assuntos
Bócio/prevenção & controle , Hipotireoidismo/prevenção & controle , Iodo/deficiência , Cloreto de Sódio na Dieta/farmacologia , Criança , China/epidemiologia , Feminino , Bócio/epidemiologia , Humanos , Hipotireoidismo/epidemiologia , Iodo/farmacologia , Iodo/urina , Masculino , Política Nutricional , Estado Nutricional , Fatores de Tempo
15.
Acta Crystallogr Sect E Struct Rep Online ; 64(Pt 4): o665-6, 2008 Mar 05.
Artigo em Inglês | MEDLINE | ID: mdl-21202060

RESUMO

In the title compound, C(4)H(12)N(2) (2+)·2C(6)H(2)N(3)O(7) (-)·C(4)H(10)N(2), the piperazine-1,4-diium cations and piperazine mol-ecules lie on crystallographic inversion centres. In the crystal structure, inter-molecular N-H⋯O and N-H⋯N hydrogen bonds link the components to form two-dimensional layers parallel to the (001) plane. These layers are, in turn, connected by weak inter-molecular C-H⋯O hydrogen bonds and π-π stacking inter-actions [centroid-centroid distance between parallel aryl rings = 3.764 (2) Å, interplanar spacing = 3.500 (2) Šand ring offset = 1.387 (2) Å], forming a three-dimensional framework.

16.
Acta Crystallogr Sect E Struct Rep Online ; 64(Pt 1): o32, 2007 Dec 06.
Artigo em Inglês | MEDLINE | ID: mdl-21200881

RESUMO

The asymmetric unit of the title structure, 2C(4)H(7)N(2) (+)·C(6)Cl(2)O(4) (2-), consists of one 2-methyl-imidazolium cation and one-half of a chloranilate anion, the formula unit being generated by crystallographic inversion symmetry. N-H⋯O hydrogen bonds link the ions into a two-dimensional framework parallel to the (102) plane. No π-π stacking or C-H⋯π inter-actions are observed in the crystal structure.

17.
Guang Pu Xue Yu Guang Pu Fen Xi ; 25(5): 792-5, 2005 May.
Artigo em Chinês | MEDLINE | ID: mdl-16128092

RESUMO

A rapid and sensitive methed for the determination of trace cadmium in environment water samples based on flowinjection on-line preconcentration on two-microcolumn system-flame atomic absorption spectrometry has been developed. The cadmium in samples was sequentially retained on two microcolumns with cation exchange resin and was eluted directly in the nebulizer by 1.5 mol x L(-1) HCl solution. The characteristic concentration (preconcentration time 1 min) for cadmium was 0.931 microg x L(-1). The relative standard deviation at the 5 microg x L(-1) level was 2.69% and the corresponding detection limit (3sigma) was 0.808 microg x L(-1). The method has been successfully applied to the determination of cadmium in water reference material GBW08608 and other water samples.


Assuntos
Cádmio/análise , Espectrofotometria Atômica/métodos , Poluentes Químicos da Água/análise , Abastecimento de Água/análise , Análise de Injeção de Fluxo , Concentração de Íons de Hidrogênio , Reprodutibilidade dos Testes , Espectrofotometria Atômica/instrumentação , Fatores de Tempo
SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA
...