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1.
Pollution characteristics of atmospheric fine particles and their secondary components in the atmosphere of Shenzhen in summer and in winter 总被引:4,自引:0,他引:4
NIU Yuwen HE Lingyan HU Min ZHANG Jing & ZHAO Yunliang . Shenzhen Graduate School of Peking University Shenzhen China . State Joint Key Laboratory of Environmental Simulation Pollution Control College of Environmental Sciences Peking University Beijing China 《中国科学B辑(英文版)》2006,49(5):466-474
Two field measurements for atmospheric fine particles were conducted in Baoan district of Shenzhen during the summer and winter in 2004. Totally 30 sets of 24 h samples were collected, and then the mass concentrations and chemical compositions were determined. The seasonal varia- tions and secondary pollution characteristics of fine particles during the sampling periods were dis-cussed with meteorological factors. The results show that seasonal variations of atmospheric particles are significant in Shenzhen. The average mass concentrations of PM2.5 and PM10 in summer were 35 μg·m-3 and 57 μg·m-3, respectively, and those in winter were 99 μg·m-3 and 135 μg·m-3, respec-tively. The concentrations of both PM2.5 and PM10 in winter increased 184% and 137%, respectively, compared to those in summer. PM2.5 accounted for 61% and 75% of PM10 in summer and in winter, respectively, indicating severe fine particle pollution in Shenzhen. During the summer and winter sampling periods, the mean OC/EC ratios were 3.4 and 1.6, respectively. The estimated secondary organic carbon (SOC) averagely accounted for 56% and 6% of the total OC in summer and in winter, respectively, which implies a major contribution of SOC to OC in summer. During the continuous high temperature period in summer, both the concentrations and fractions of secondary aerosol compo-nents in PM2.5 were highly elevated, suggesting severe secondary pollution again. The prevailing wind was from South China Sea in summer, and the air quality was good. The prevailing wind in winter was from Mainland China to the north, and the polluted air mass led to poor air quality. 相似文献
2.
Yi LIU Yu Lin DENG Rong ZHENG Pei Long ZHANG Hui ZHAI Kc Zhong LIU Chang Jin ZHU 《中国化学快报》2006,17(5):599-602
Small molecules with the ability to target predetermined sequences of DNA would be valuable tools in molecular biology and potentially in human medicine1-3. Synthetic polyamides consisting of N-methylpyrrole (Py), N-methylimidazole (Im) have received spec… 相似文献
3.
Apoptosis is described as a mechanism of cell death occurring after adequate cellular harm. Deregulation of apoptosis occurs in many human conditions such as autoimmune disorders, ischemic damage, neurodegenerative diseases and different cancer types. Information relating miRNAs to cancer is increasing. miRNAs can affect development of cancer via many different pathways, including apoptosis. Polymorphisms in miRNA genes or miRNA target sites (miRSNPs) can change miRNA activity. Although polymorphisms in miRNA genes are very uncommon, SNPs in miRNA-binding sites of target genes are quite common. Many researches have revealed that SNPs in miRNA target sites improve or decrease the efficacy of the interaction between miRNAs and their target genes. Our aim was to specify miRSNPs on CASP3 gene (caspase-3) and SNPs in miRNA genes targeting 5′UTR and coding exons of CASP3, and evaluate the effect of these miRSNPs and SNPs of miRNA genes with respect to apoptosis. We detected 141 different miRNA binding sites (126 different miRNAs) and 7 different SNPs in binding sites of miRNA in 5′UTR and CDS of CASP3 gene. Intriguingly, miR-339-3p’s binding site on CASP3 has a SNP (rs35372903, G/A) on CASP3 5′UTR and its genomic sequence has a SNP (rs565188493, G/A) at the same nucleotide with rs35372903. Also, miR-339-3p has two other SNPs (rs373011663, C/T rs72631820, A/G) of which the first is positioned at the binding site. Here, miRSNP (rs35372903) at CASP3 5′UTR and SNP (rs565188493) at miR-339-3p genomic sequence cross-matches at the same site of binding region. Besides, miR-339-3p targets many apoptosis related genes (ZNF346, TAOK2, PIM2, HIP1, BBC3, TNFRSF25, CLCF1, IHPK2, NOL3) although it had no apoptosis related interaction proven before. This means that miR-339-3p may also have a critical effect on apoptosis via different pathways other than caspase-3. Hence, we can deduce that this is the first study demonstrating a powerful association between miR-339-3p and apoptosis upon computational analysis. 相似文献
4.
Francesco Barbato Maria Immacolata La Rotonda Agnese Miro Patrizia Morrica Fabiana Quaglia 《Journal of inclusion phenomena and macrocyclic chemistry》2000,38(1-4):423-433
This study was carried out with the aim ofinvestigating the interactions between-cyclodextrin and carbaryl, a carbamatepesticide, and their effect on some physico-chemicalproperties of carbaryl, such as aqueous solubility andlipophilicity. The interactions between carbaryl and-cyclodextrin were thoroughly investigated bothin solution and in the solid state. The effect of-cyclodextrin on the aqueous solubility ofcarbaryl was evaluated by the phase solubility method.The amount of carbaryl dissolved increased linearlywith the addition of -cyclodextrin according toan AL type plot and without precipitation of thecomplex. The apparent stability constant of thecomplex was 289 ± 21 M-1, assuming a 1 : 1stoichiometry; this value was confirmed by a methodbased on circular dichroism measurements.Equimolar carbaryl/-cyclodextrin solid systemswere prepared by physical-mixing and freeze-drying,and fully characterised by Differential ScanningCalorimetry, X-ray powder diffractometry and FourierTransform Infra-Red analysis. The results of the solidstate study demonstrated that the freeze-drying methodyields a system with a high degree of amorphisationand yields an inclusion complex.The dissolution profile of the pesticide was affectedby the physico-chemical properties of each solidsystem, the freeze-dried form dissolving more rapidly. However, the physical association of-cyclodextrin and carbaryl enhanced the aqueoussolubility of the insecticide as well. 相似文献
5.
By UV-vis spectroscopy and use of the polarization of the emission, we show that the 9,9′-bianthryl (9,9′BA) symmetrical molecule exhibits an induced fluorescence in polyvinylalcohol (PVA) by hydrogen bonding of the type OH⋯π which depends on considered temperature. This anomalous behaviour does not occur when this molecule is included in a polyvinylchloride, aprotic polymer. 相似文献
6.
Xue Mei GAO* Shi Xi LIU Xiao Guang XIE Huai CAO Shu Shan DAI Department of Chemistry Yunnan University Kunming Modern Biological Center Yunnan University Kunming 《中国化学快报》2001,(7)
The theoretical study of small molecules containing transition metal atoms is one of the most active areas in quantum chemistry1. Very extensive studies have been done on first and second row transition metal hydrides2,3, oxides4-6 and the transition metal dimers7-9. But theoretical studies on the third row transition metal compounds are comparatively scarce.Tungsten is an important element for catalytic reactions, and the knowledge of the interaction between W and C/N atom has basis importan… 相似文献
7.
Giuseppe Buemi Felice Zuccarello Ponnambalam Venuvanalingam Marimuthu Ramalingam 《Theoretical chemistry accounts》2000,104(3-4):226-234
All the possible conformations of the three tautomeric isomers of simple β-carbonylamine were fully optimized at ab initio
MP2/6-31G** and B3LYP/6-31G** levels in order to determine the conformational equilibrium and the energies of the O—H···N
and O···H—N hydrogen bridges. For the most interesting conformations, further calculations in water solution were also carried
out. It was found that carbonylamine is the most stable tautomer, followed by enolimine and carbonylimine. This order of stability
does not change in solution. O—H···N is the strongest hydrogen bridge, but in solution its energy as well as that of the O···H—N
one are dramatically lowered. The deprotonation energy was also calculated and discussed.
Received: 16 September 1999 / Accepted: 3 February 2000 / Published online: 5 June 2000 相似文献
8.
Ligand modifications have played a crucial role in developing new catalyst precursors. A novel class of “constrained-geometry”ligands bearing a carboanion functionality has been developed by linking o-carboranyl and n-ligand together. They offer group 4 metal complexes higher activity in olefin polymerization compared to those with appeoded heteroatom systems. The results show that the [{η^5:σ-Me2A(C5H4)(C2B10H10)}M] moiety remains intact in olefin polymerization and insertion reactions of various unsaturated molecules, and the electron-deficient yet sterically hindered icosahedral carborane does play an important role in the reactions. This article provides an overview of our recent work on this subject. 相似文献
9.
The γ-radiation-initiated polymerization of acrylonitrile (AN) at 25[ddot] C has been studied, both in aqueous solution and in emulsion, at dose rates between 70 and 175 krad/hr. The effect of added emulsifier, sodium lauryl sulfate (SLS), on reaction rates, Rp, and on polymer molecular weight, Mn, has been investigated. G (monomer polymerized) values ranged from 7,500 in aqueous solution to 20,000 in bulk to 45,000 in emulsion, all based on the total energy absorbed. In the aqueous solution polymerization, where Rp is approximately first order in initial monomer concentration over the range 0.15 ± [AN]o ± 1.06 moles/liter, addition of SLS increases Rp but does not influence the order of the reaction with respect to [AN]o. In the emulsion system at 70 krad/hr and at a phase volume ratio AN/H2O of 1/2, (PR = 1/2), Rp varies as [SLS]0.1 over the concentration range 0.01 ± [SLS] ± 2.5± wt/vol of aqueous phase. At the same PR value, and at 80 krad/hr, Mn of the polymer (measured by viscometry in dimethylformamide solution) is effectively independent of [SLS] in the range of 0.01 ± [SLS] ± 10± wt/vol of aqueous phase. Initial Rp values are either independent of PR in the range 1/3 ± PR ± 1/1 or exhibit an insensitive and unsystematic dependence thereon. Based on measurements at 70 and at 175 krad/hr, the intensity exponent of Rp at PR = 1/2 is approximately 0.4. 相似文献
10.
Xiao Guang XIE* Xue Mei GAO Shi Xi LUI Huai CAO Shu Shan DAI Department of Chemistry Yunnan University Kunming Modern Biological Center Yunnan University Kunming 《中国化学快报》2001,(6)
The theoretical study of small molecules containing transition metal atoms is one of the most active areas in quantum chemistry1. Very extensive studies have been done on first and second row transition metal hydrides2,3, oxides4-6 and the transition metal dimers7-9. But theoretical studies on the third row transition metal compounds are more scarce.Platinum is an important element for catalytic reactions, and the knowledge of the interaction between Pt and C/N atom is basic, but important fo… 相似文献
11.
Cationic polyaspartamides including poly-α,β-[N'-(2-aminoethyl)-L-aspartamide] (PAEA), poly-α,β-[N'-(4- aminobutyl)-L-aspartamide] (PABA), poly-α,β-[N'-(6-aminohexyl)-L-aspartamide] (PAHA), poly-α,β-[N'-(5-amino- 3-azapentyl)-L-aspartamide] (PAAPA) and poly-α,β-[N'-(8-amino-3,6-diazaoctyl)-L-aspartamide] (PADAOA) were synthesized from polysuccinimide. Their properties were evaluated by ^1H NMR, IR, GPC, fluorescence measurement and in vitro cytotoxicity assays. The molecular weights per primary amine charge group of PAEA(1) (Mn= 2229), PAAPA and PADAOA are 212, 279, and 226. Polyaspartamides including PAEA(1), PAAPA, PADAOA and low molecular weight PAHA are markedly less toxic than poly(ethyleneimine) and poly(L-lysine), however, PABA and higher molecular weight PAHA are slightly less toxic than poly(L-lysine). Cell cytotoxicity of PAHA was seen to decrease with increasing molecular weight of PAHA, due to water solubility reduction. The negatively charged plasmid DNA has been found to be completely neutralized and complexed by the cationic polyaspartamides at an N/P ratio of 5 : 1 to 10 : 1, forming self-assembled polyplexes via ionic interactions. These polyaspartamide/DNA complexes possess stable zeta potentials and mean particle diameters of about 180 nm for PAEA (1)/DNA and PAAPA/DNA complexes and 280 nm for PADAOA/DNA complexes. 相似文献
12.
OLAJIRE A A AMEEN A B ABDUL-HAMMED M ADEKOLA F A 《燃料化学学报》2007,35(6):641-647
The metal contents of Nigerian coal minerals were analyzed using an atomic absorption spectrophotometer. Calcium, Na, and Fe occurred as the major elements with concentrations ranging from 9 782 μg/g for Ca to 432 μg/g for Na whereas K, Mg, Mn, Ni, Cr, Zn, Pb, and Cu, which occurred at trace levels ranged from 673.73 μg/g for Mg to 2.97 μg/g for Mn. The results of the quantitative analysis of porphyrins extracted from the coal minerals showed that Onyeama coal has the highest amount of porphyrins (ca~0.96 μg/g) while Okpara has the lowest (ca~0.30 μg/g). The porphyrins were qualitatively characterized by a combination of thin layer chromatography (TLC), infrared, and ultraviolet-visible spectrophotometers. The results of the mid infrared analysis (MIR) showed the presence of absorption bands at 3 440 cm~1~3 450 cm-1 and 1 640 cm-1~1 680 cm-1 , which are owing to the stretching vibrations of N - H and C = C of aromatics, with C- H out of plane (oop) bending vibrations at wavenumbers less than 900 cm-1, all of which are characteristic absorptions of porphyrin free base. The ultraviolet-visible data showed prominent peaks at ~400 nm(Soret band) and at wavelength ranges of 535 nm~550 nm(β-band) and 565 nm~ 600 nm (α-band) for the coal porphyrins analyzed. The geochemical significance of the metals and porphyrins in coal minerals are discussed. 相似文献
13.
Eskişehir-Beylikahir ore contains rare earth elements (REE) and thorium as bastnaesite mixed with barite, calcite and fluorite
and small amounts of uranium. The mineralogical composition and Th, U, REE contents of the ore samples taken from different
sectors of the same region show important variations. For the spectrophotometric determination of Th and U in the ore, successive
anion-exchange and solvent extraction procedures are carried out to separate U and Th from each other and from accompanying
interfering elements. The accuracy and precision of the method is demonstrated by intercomparison of the thorium standard
reference samples S-14, S-15 and S-16 of IAEA. In all cases very good agreement was obtained. 相似文献
14.
《Tetrahedron letters》1987,28(32):3705-3706
Alkylations of dianions of β-hydroxysulfoxides and β-hydroxysulfones have been found to be affected by chelation of a Li cation with a sulfinyl group and by coordination of the cation with tetrahydrofuran rather than a sulfonyl group, respectively. 相似文献
15.
Single crystal X-ray diffraction studies show that the β-turn structure of tetrapeptide I, Boc-Gly-Phe-Aib-Leu-OMe (Aib: α-amino isobutyric acid) self-assembles to a supramolecular helix through intermolecular hydrogen bonding along the crystallographic a axis. By contrast the β-turn structure of an isomeric tetrapeptide II, Boc-Gly-Leu-Aib-Phe-OMe self-assembles to a supramolecular β-sheet-like structure via a two-dimensional (a, b axis) intermolecular hydrogen bonding network and π-π interactions. FT-IR studies of the peptides revealed that both of them form intermolecularly hydrogen bonded supramolecular structures in the solid state. Field emission scanning electron micrographs (FE-SEM) of the dried fibrous materials of the peptides show different morphologies, non-twisted filaments in case of peptide I and non-twisted filaments and ribbon-like structures in case of peptide II. 相似文献
16.
Recent studies on electrochemical meso- and β-functionalization of porphyrins and electrografting of diazonium porphyrin are presented. First, the electrochemical oxidative C–C coupling between porphyrins will be presented, followed by the intermolecular and intramolecular meso- and β-substitutions of porphyrins. Then, the latest results on diazonium porphyrin electrografting will be reviewed. 相似文献
17.
The distribution and forms of phosphorus (P) were investigated in the tidal flat sediments of the Yangtze Estuary and coast. The total P contents in surface sediments range from 18.0 to 31.4 μmol · g-1 along the southern coast. The spatial and temporal distribution of P in tidal flats is closely related to the location and pollution resources, especially in association with the variation of hydrodynamic conditions. Significant variations in the forms of P in different sites were observed. P bonded with Ca(Ca-P) is the dominant mineral form in all surface sediments, organic P(Org-P) is lower. Most P is of unstable form, suggesting that P has larger potential activity. P accumulation is the main behavior process between water and sediment in the coastal environment of the Yangtze Estuary. 相似文献
18.
S. Azhagiri S. Jayakumar R. Padmanaban S. Gunasekaran S. Srinivasan 《Journal of solution chemistry》2009,38(4):441-448
Densities and ultrasonic speeds of binary mixtures of benzaldehyde with n-hexane and cyclohexane at 30 °C were measured over the entire composition range. From these experimental data, the adiabatic
compressibility (K
S
), intermolecular free length (L
f), acoustic impedance (Z), relative association (R
a) and relaxation strength (r) were calculated. Also, the excess adiabatic compressibility (K
S
E), intermolecular free length (L
fE), acoustic impedance (Z
E), and ultrasonic velocity (U
E) were calculated. The observed variation of these parameters helps in understanding the nature of interactions in these mixtures.
Further, theoretical values of the ultrasonic speed were evaluated using theories and empirical relations. The relative merits
of these theories and relations were discussed. 相似文献
19.
Lorraine A. Malaspina Allan H. White Dieter Wege Michael B. Tolmie Brian W. Skelton Simon Grabowsky 《Structural chemistry》2017,28(5):1343-1357
Acyl-pyrazolones exist in four different tautomeric forms (two keto and two enol) in crystal structures. Routine crystal structure refinements using an independent atom model and routine isolated-molecule calculations fail in locating the mobile hydrogen atoms accurately in 22 investigated acyl-pyrazolone examples. However, a combination of both within the framework of quantum crystallography represented by the method of Hirshfeld atom refinement accurately locates the mobile hydrogen atom in a resonance-assisted hydrogen bond of title compound 3, a novel photolysis product. The impact of the hydrogen atom position on the resonance system of the non-hydrogen framework of the various tautomers is discussed, and the importance of intermolecular interactions for the positioning of the hydrogen atom is highlighted. 相似文献
20.
A. F. Fucaloro K. Dewey G. Fan K. Imuta D. Jensen M. Muranaka 《Journal of solution chemistry》2008,37(9):1289-1304
The partial molar volumes of uracil, thymine and adenine in water and adenine in aqueous solutions of uracil and thymine,
at fixed composition, were determined over a range of temperatures. The partial molar volumes of adenine in aqueous uracil
and thymine are less than in pure water. 相似文献