Characteristics of the Permafrost Structure on the Fildes Peninsula, King George Island, Antarctica

Based on the data from the pitting, geoelectrical prospectings, temperature measuring, and the divided layers frost-heaving instruments, this paper, first, discusses the structure features of active layers in this region, and proves the presence of the bowlshaped frost table in the stone circles area. Second, it analyses the temperature distributive rule in the active layer, meantime, according to the vertical-profile parameters of granularity, clay mineral, salt content and resistivities, it also discusses the different features of permafrost structure and their control actions on the periglacial landform development between high and low places. It suggests that the four-layer structure should exist in the permafrost region (including under-bedrock), that is, active layer, frost sand and gravels layer, frost volcanic rock permeated by sea water, and frost volcanic rock unpermeated by sea water. Finally, the permafrost table and its vertical gradient are deduced.     

Fossil Sm-Nd Isotopic Dating of the Precambrian-Cambrian Boundary in the Meishucun Section, Jinning, Yunnan, China

It was for the first time that the fossil Sm-Nd isochron method was used to date the Precambrian-Cambrian boundary. The samples were collected from the Zhongyicun Member in the Meishucun section of Jinning County,Yunnan Province, southern China. The date of 562.8±7.9Ma B.P. was obtained from four hyolithid fossil samples; another date of 562.1±5.7Ma B.P. was provided by four hyolithid fossil samples and two collophanite samples. These figures suggest that the Precambrian-Cambrian boundary reference point A, which is slightly below the Zhongyicun Member, might be about 570Ma old, and the reference point B, which is near the top of the Zhongyicun Member, could be approximately 560Ma in age. This result contributed valuable reference to precise calibration of the base of the Cambrian System in the global geological time scale.     

Crystal structures of the complexes of rare earth picrates with N, N, N'''', N''''-tetraphenyl-3, 6-dioxaoctanediamide

The complexes of rare earth picrate with N,N,N',N'-tetraphenyl-3,6-dioxaoctanediamide(TDD),Eu(picc(TDD)] 2CH3CN and [ Y(pic)3(TDD)],have been synthesized.The crystal structures reveal that TDD at is as n tetradentate ligand,forming a ring-like coordination structure with its oxygen atoms together with one oxygen atom of the bidentate pterate In the Eu(Ⅲ) complex,the europium ion with a larger ionic radius lies out of the ring,while in the Y(Ⅲ) complex,the yttrium ion with a smaller ionic radius enters the cavity of the ligand.The structures of the complexes are greatly affected by the ionic radii due to participation of the picrates in coordination.     

Studies on the Cytology of Fertilization in the Chinese Mitten-handed Crab,Eriocheir sinensis (Crustacea, Decapoda)

The whole processes of fertilization in Eriocheir sinensis was investigated with artificial and natural insemination and artificial induction of acrosome reaction. Unlike most other arthropods, the E. sinensis egg has no micropyle. In the process of fertilization, a great number of sperms attach themselves to the egg, but only several of them penetrate the egg with one of them finally fertilizing it. Fertilization in E. sinensis is achieved not by fusion but by association.     

Construction of the Skeleton of Phthalascidin,Mechanism of the Formation o the Key Tricyclic Lactam Intermediate

The mechanism of the formation of a key tricyclic lactam intermediate 3 was studied. It was found that the E-form compound 3 was transformed from the Z-form compound 4. The formation of 4 was a kinetically controlled process while the formation of 3 was a thermodynamically favorable one. A possible mechanism was given in this paper.     

Quantum chemical studies on the structures, properties and decomposition of the azido derivatives of trinitrobenzenes

The geometries,heats of formation and electronic structures of 15 azido-derivatives of 1,2,3-TNB (Ⅰ),1,2,4-TNB (Ⅱ) and 1,3,5-TNB (Ⅲ) have been studied using quantum chemical AMI method at HF level.The effect of azido substitution on the structures and properties of TNBs has been discussed and the relative stability of the title compounds has been established.The processes of the decomposition of the title compounds by breaking C-NO2,C-N3 and CN-N2 bonds are investigated at UHF-AM1 level.It is shown that the decomposition of the title compounds may be initiated by the cleavage of both C-NO2 and N-N2 bonds.     

Four New Isovalertatins M33, D13, D33, and D43, from the Culture Filtrate of Streptomyces luteogriseus

In a program of investigating the chemical constituents of the potentially α-amylase- inhibiting complex, WC670, extracted from the culture filtrate of Streptomyces luteogriseus, we found it contains the known aminooligosaccharides, isovalertatins M03, M…     

A Convenient Method for the Synthesis of Chiral N-Protected 1, 2-Amino Alcohols via the Reduction of the Aminoketones

A series of optically active N-protected 1,2-amino alcohols were synthesized via the reduction of the corresponding α-aminoketones starting from the readily available L-amino acids.     

美国《化学教育》“Ask the Historian”栏目内容评析与启示

简要介绍了美国《化学教育》杂志的Ask the Historian栏目中历年的化学史文章内容及其特点,从中得出对我国化学史教育的几点启示。     

Two New 9, 10-seco-Cycloartanes from the Seeds of Sphaerophysa salsula

Two novel compounds, named sphaerophyside SC and SD were isolated from the ethanolic extract of the seeds of Sphaerophysa salsula. The structures of the compounds were elucidated on the basis of the NMR data, especially the 2D NMR technique.     

Study on the Phase Equilibrium of the Ternary System Ethanol-Cesium Carbonate-Water at 10, 30 and 50℃

Introduction The salting out effect in the systems of aliphatic al-cohol-water is of industrial interest. The addition of or-ganic solvents to the aqueous solution of a salt normally decreases the solubility of the salt. So the method can be used for salting-out of inorganic salts to improve yield and purity.1-3 However, the phase diagrams of the inves-tigated systems are required as basic data. There are lots of aliphatic alcohol-water systems having been deter-mined. The 1-butanol-water-Na…     

Study on Chemisorption, Catalytic Behavior, and Stability of Supported Au Catalyst for the Propylene Epoxidation Reaction

The supported Au/TiO2 and Au/TiO2-SiO2 catalysts were prepared by deposition precipitation method. The TPD study reveals that propylene oxide competes with propylene to be adsorbed on the same adsorptive center-Tin site on the surface of the catalyst and that the adsorbing capacity of the catalyst for propylene oxide is larger than that for propylene. Catalytic behavior for propylene epoxidation with H2 and O2 was tested in a micro-reactor. Under typical conditions, the selectivity for propylene oxide is over 87%. The TG curves show that PO successive oxidation cause carbon deposition on the active center and deactivation of the Au catalysts. Because the amounts of Tin site decrease significantly, and consequently the separation between Tin sites increases, the Au/TiO2-SiO2 catalyst is more stable than Au/TiO2.     

Radioactive contamination of the environment as a result of uranium production: a case study at the abandoned Lincang uranium mine, Yunnan Province, China

The distribution of radioactive pollutants, such as ~(222)Rn, U, Th and ~(226)Ra in the air, sur-face waters, soils and crops around the Lincang uranium mine, Yunnan Province, China, is studiedThe mechanical, geochemical and biogeochemical processes responsible for the transport andfate of the radioactive elements are discussed based on the monitoring data. The pollutants con-centrations of effluents from the mine tunnels were dependent on pH and SO_4~(2-) which were con-trolled by biochemical oxidation of sulfide in the ore/host rocks. Radon anomalies in air reached 4km from the tailings pile depending on radon release from the site, topography and climate. ~(238)Uand ~(226)Ra abnormities in stream sediments and soil were 40-90 cm deep and 790-800 m awaydownstream. Anomalies of radioactive contaminants of surface watercourses extended 7.5-13km from the discharge of effluents of the site mainly depending on mechanical and chemical proc-esses. There were about 2.86 ha rice fields and 1.59 km stream sediments contaminated. Erosionof tailings and mining debris with little or no containment or control accelerated the contaminationprocesses.     

Theoretical Studies on the Interaction between Metal Cations and Cytosine, Guanine

1 INTRODUCTION The study on the interaction between metal cations and biomacromolecules is one of the important subjects of bioinorganic chemistry. As is well known, the metal ions play an important role in keeping the basic structures and realizing the normal functions of biomacromolecules like proteins, nucleic acid, and peptide hormone[1]. However, at present the interac- tion mechanism has not been understood yet. In recent years remarkable achievements have been obtained in this fie…     

Studies on the Dihedral Angle and Torsional Barriers for 4,-Bipyridine

Using the Hartree-Fock, MP2, and the B3LYP, BLYP, mPW1PW91 density functional methods, each combined with the 6-31G(d), 6-311G(d), 6-311+(d), 6-311++G(d, p) cc-pvdz and cc-pvtz basis sets, the equilibrium geometry of 4,4∏-bipyridine was optimized and the internal rotational potential barriers heights at 0∑ (E0), 90∑ (E90) were obtained. For the best basis set (cc-pvtz) , the predicted dihedral angle ヨ ranges from 37.0 to 37.8∑ for all methods except the Hartree-Fock method (43.7).…     

Studies on the Electronic Structures of the C_60, C_60H_60 and C_60F_60

The present paper represents the electronic structures of the cluster C60 and its derivatives C60H60 and C60F60 with FOOT-type of structure. On the basis of the total energies and molecular orbital energies from CNDO/2 calculations the clusters' stabilities, electronic configurations and charge distributions are discussed. The calculation results and discussion are very beneficial to understanding physical and chemical properties of the cluster C60 and its derivatives.     

Tectonic Implications of Paleomagnetic Results From Upper Silurian Series Along the Hexi Corridor, Gansu, China

Characteristic directions of remanent magnetization of 38 samples from Upper Silurian Series (Hanxia Formation) along the Hexi Corridor passed fold test at a 99% confidence level. The corresponding paleopole is located at 45.1°N, 5.5°E (A_(95)= 4.7°, κ=25.1), close to the Late Permian pole for this area (41.4°N, 358.6°E; A_(95)= 4.3°, κ=26.6). However, there appears an obvious difference between paleolatitudes for these two stages (6°±). Based on paleomagnetic data, it can be deduced that the Hexi Corridor had probably been the western extension of the North China Block by the time of Late Silurian and kept being tectonically mobile compared with the principal parts of the North China Block. In addition, paleomagnetic data reveal that the Hexi Corridor experienced a southward displacement of about 600 km during the Late Paleozoic Era.     

A New Method to Synthesize the P,N-Heteromultifunctional Ligands

The nature of the highly polar P-N bond in phosphinimine makes a ligand of this kind become versatile in both coordination and organometallic chemistry.[1,2] Usually this kind of phosphinimine phosphine P,N-heterodifunctional ligands is prepared by the Staudinger reaction of azides with organophophine. Now a more mild and efficient method is provided. The product of Mannich reaction of 2-aminopyridine reacted with Ph2PCl in the presence of Et3N, giving the phosphinimine compound 1 in more than 90% yield.     

The Influence of Heteroatom M(M = B, Al, Ge, Ga, Fe)on the Adsorption Properties of M-ZSM-12 Zeolites

Heteroatom M-ZSM-12 zeolites(M=B, Al, Ge, Ga, Fe) are hydrothermally synthesized and it is proved that the heteroatom M is involved in the framework of synthesized molecular sieves by means of XRD, IR spectra. The results of adsorption and diffusion experiments indicate that the heteroatom M modifies the pore volume, specific surface area, and the channel of ZSM-12 molecular sieves.     

Correlation Analysis of the Runoff of the Rivers and the Seisms in China

In recent hundred years the annual discharge variations of the Changjiang River (represented by the Yichang station) and the Huanghe River (represented by Shanxian and Tangnaihe, respectively) have closely related to the geographical distribution of the earthquakes coming about in China in the same year, Both the occurrence of the destructive seism or seismic swarm in the river basins and the disappearance of the shocks in the east and south of the basins are the conditions that the Changjiang and Huanghe Rivers are the high flow while that the strong earthquake of magnitude 7 or more occurred in North China is the condition for the Changjiang low flow year and that of 6 or more in the Qilian Mountains area is for the Huanghe River. In the latter part of this paper, a 2-year sample is given to explain that the conditions of the 2 rivers being high flow years are that the north-south seismic belt is active and in the meanwhile no seism occurred in South China, and those of the low flow year are that the