Protodolomite Synthesis at 100{degrees}C and Atmospheric Pressure

Ordered protodolomite, CaMg(CO(3))(2), has been synthesized at 100 degrees C by reaction of metastable precipitated carbonates with aqueous magnesium-bearing solutions. Initial reaction products have expanded crystallographic cells, attributed to the presence of structural water. Longer reaction time produces a protodolomite approaching ideal composition and exhibiting order reflections in x-ray powder.     

A Spatially Resolved X-ray Image of a Star Like the Sun

Observations made with the x-ray satellite ROSAT (Roentgen Satellite) have produced the first spatially resolved x-ray image of a corona around a star like our sun. The star is the secondary in the eclipsing binary system alpha Coronae Borealis (CrB), which consists of one star of spectral type A0V and one of type G5V. The x-ray light curve of alpha CrB shows a total x-ray eclipse during secondary optical minimum, with the G star behind the A star. The totality of the eclipse demonstrates that the A-type component in alpha CrB is x-ray dark and that the x-ray flux arises exclusively from the later-type companion. The x-ray eclipse ingress and egress are highly asymmetric compared with the optical eclipse, indicating a highly asymmetric x-ray intensity distribution on the surface of the G star. From a detailed modeling of the ingress and egress of the x-ray light curve, an eclipse map of the G star was constructed by a method based on an optimization by simulated annealing.     

Stability of Perovskite (MgSiO3) in the Earth's Mantle

Available thermodynamic data and seismic models favor perovskite (MgSiO3) as the stable phase in the mantle. MgSiO3 was heated at temperatures from 1900 to 3200 kelvin with a Nd-YAG laser in diamond-anvil cells to study the phase relations at pressures from 45 to 100 gigapascals. The quenched products were studied with synchrotron x-ray radiation. The results show that MgSiO3 broke down to a mixture of MgO (periclase) and SiO2 (stishovite or an unquenchable polymorph) at pressures from 58 to 85 gigapascals. These results imply that perovskite may not be stable in the lower mantle and that it might be necessary to reconsider the compositional and density models of the mantle.     

肉制品中5种红曲色素的高效液相色谱测定

建立了肉制品中5种红曲色素含量的高效液相色谱分析方法。样品用甲醇+乙酸乙酯(2∶8,体积比)提取,采用Eclipse plus.C18[5μm,25 cm×4.6 mm(i.d.)]色谱柱分离,以磷酸溶液(pH=2.5±0.3)和乙腈为流动相梯度洗脱,流速1mL/min,检测波长为400 nm,分析时间为20 min,采用二极管阵列检测器进行检测。方法的相关系数r2≥0.99910,5种红曲色素检出限(信噪比为3)为0.52～1.05 mg/kg,相对标准偏差(n=8)为1.6%～7.6%,平均加标回收率为75%～108%。结果表明,该方法准确、灵敏、重现性好、分析时间短,适用于肉制品中红曲色素含量的测定。     

Efficient oxidative dechlorination and aromatic ring cleavage of chlorinated phenols catalyzed by iron sulfophthalocyanine

An efficient method has been developed for the catalytic oxidation of pollutants that are not easily degraded. The products of the hydrogen peroxide (H(2)O(2)) oxidation of 2,4,6,-trichlorophenol (TCP) catalyzed by the iron complex 2,9,16,23-tetrasulfophthalocyanine (FePcS) were observed to be chloromaleic, chlorofumaric, maleic, and fumaric acids from dechlorination and aromatic cycle cleavage, as well as additional products that resulted from oxidative coupling. Quantitative analysis of the TCP oxidation reaction revealed that up to two chloride ions were released per TCP molecule. This chemical system, consisting of an environmentally safe oxidant (H(2)O(2)) and an easily accessible catalyst (FePcS), can perform several key steps in the oxidative mineralization of TCP, a paradigm of recalcitrant pollutants.     

Internal Hydrogen Bond Formation in a syn-Hydroxyepoxide

The existence of an internal hydrogen bond in a compound representative of a syn diol epoxide (a possible intermediate in chemical carcinogenesis by certain polycyclic aromatic hydrocarbons) has been demonstrated by x-ray crystallographic and nuclear magnetic resonance studies. This internal hydrogen bond was found in 3,4-epoxy-2-methyl-1,2,3,4-tetrahydro-1-naphthol and was shown to persist in dioxane-water solutions containing up to 80 mole percent water. In this structure, the 1-hydroxy and 2-methyl groups are shown to occupy axial positions. In the anti diol epoxide, which has no internal hydrogen bond, analogous groups are equatorial. Crystals of the compound were unstable in the x-ray beam while the data were being collected (even at low temperatures), presumably as a result of decomposition.     

Electric field x-ray scattering measurements on tobacco mosaic virus

The feasibility of electric field x-ray solution scattering with biological macromolecules was investigated. Electric field pulses (1.25 to 5.5 kilovolts per centimeter) were used to orient tobacco mosaic virus in solution (4.5 milligrams per milliliter). The x-ray scattering is characteristic of isolated oriented particles. The molecular orientation and its field-free decay were monitored with a time resolution of 2 milliseconds by means of synchrotron radiation and a multiwire proportional area detector. The method should also be applicable to synthetic polymers and inorganic colloids.     

Electron Population Parameters from Least-Squares Refinement of X-ray Diffraction Data

A least-squares refinement of x-ray diffraction data has been developed in which the parameters are the populations of atomic orbital products describing the molecular electron density distribution. The procedure is applied to alpha-oxalic acid dihydrate and cyanuric acid. Complementary structural information obtained by neutron diffraction has been used. In the absence of complementary information, the method allows simultaneous determination of structural and charge-density parameters. There is an indication of a migration of charge from the ppi to the psigma orbitals in both molecules.     

Energy spectra of a number of celestial x-ray sources in the energy range from 2 to 60 kiloelectron volts

The emission of 20 to 60 kev x-rays by an astronomical object in the constellation of Cygnus has been observed with a balloon-borne x-ray telescope flown from Hyderabad, India. The balloon data, used in conjunction with data pertaining to the flux in the wavelength range from 2 to 10 A can be fitted by a power law in photon energy varying as (h(v))-(1.7). The Cygnus object is the brightest object in the sky in the hard x-ray wavelength range and has the hardest spectrum of all observed objects that emit x-rays. The astronomical object should be capable of accelerating protons up to energies of the order of 10(18) electron volts. Upper limits to the hard x-ray fluxes from Sco XR-1, Cyg XR-2, Oph XR-1, and Ser XR-1 are established; it is shown that the Sco XR-1 spectrum is very soft.     

Baddeleyite-Type High-Pressure Phase of TiO2

A high-pressure phase of TiO(2), which had been observed by shock-wave experiments and remained unresolved, has been studied by in situ x-ray diffraction. The single phase was formed at 20 gigapascals and 770 degrees C with the use of sintered-diamond multianvils; it has the same structure as baddeleyite, the stable phase of ZrO(2) at ambient conditions. The coordination number of Ti increases from six to seven across the rutile to baddeleyite transition, and the volume is reduced by approximately 9 percent.     

羧甲基纤维素—甲基丙烯酸甲酯共聚物的合成

在水介质中用过硫酸钾作引发剂制备了羧甲基纤维素(CMC)和甲基丙烯酸甲酯(MMA)的接枝共聚物(CMC-g-MMA),合成水泥复合材料的偶联刑.实验得到最适合的反应条件.共聚物采用傅立时红外光谱.扫描电镜,热重分析,X射线衍射进行表征.并采用X射线散射能量分析测量共聚物中羧甲基纤维素和甲基丙烯酸甲酯结构单元的比例.结果表明,MMA被接枝到CMC结构单元上,产物的微观形貌发生变化.热分解温度与CMC相似,但热分解行为发生变化.接入MMA单元后,CMC的结晶度明显下降.由EDXA测得接枝聚合物分子中甲基丙烯酸甲酯与羧甲基纤维素结构单元之比为3.89.     

转基因耐除草剂大豆及产品中外源成分检测方法的建立

分别从DNA和蛋白质2个水平上对转基因耐除草剂大豆及其产品的检测方法进行了研究．设计合成引物检测大豆内参照基因Lectin（大豆凝集素）及转基因抗除草剂Roundup Ready大豆外源基因,包括来自土壤细菌Agrobacterium tumefaciens株系CP4的5-烯醇丙酮酸莽草酸-3-磷酸合酶（5-enolpyruvylshikimate-3phosphate synthase,EPSPS）基因、花椰菜花叶病毒（Cauliflower mosaicvirus,CaMV）35S启动子、胭脂碱合酶3’端的转录终止子（nopaline synthase,NOS）．应用优化的常规PCR方法,对大豆及其加工产品进行了检测,检测灵敏度可达0．1％．通过PCR方法从转基因大豆中扩增出CP4-EPSPS基因,在大肠杆菌中表达,利用表达的外源蛋白质作为抗原免疫家免,得到该蛋白质的多克隆抗体,并建立了一套基于蛋白质印迹杂交（western hybridization）的检测转基因大豆及其粗加工品的方法,其检测极限达到1％以下．此两方法互相配合,互相印证,有助于规范化转基因检测方法的建立．     

Charge exchange-induced X-ray emission from comet C/1999 S4 (LINEAR)

Using soft x-ray observations of the bright new comet C/1999 S4 (LINEAR) with the Chandra x-ray observatory, we have detected x-ray line emission created by charge exchange between highly ionized solar wind minor ions and neutral gases in the comet's coma. The emission morphology was symmetrically crescent shaped and extended out to 300,000 kilometers from the nucleus. The emission spectrum contains 6 lines at 320, 400, 490, 560, 600, and 670 electron volts, attributable to electron capture and radiative deexcitation by the solar wind species C(+5), C(+6), N(+7), O(+7), and O(+8). A contemporaneous 7-day soft x-ray light curve obtained using the Extreme Ultraviolet Explorer demonstrates a large increase in the comet's emission coincident with a strong solar flare on 14 and 15 July 2000.     

Porous, crystalline, covalent organic frameworks

Covalent organic frameworks (COFs) have been designed and successfully synthesized by condensation reactions of phenyl diboronic acid {C6H4[B(OH)2]2} and hexahydroxytriphenylene [C18H6(OH)6]. Powder x-ray diffraction studies of the highly crystalline products (C3H2BO)6.(C9H12)1 (COF-1) and C9H4BO2 (COF-5) revealed expanded porous graphitic layers that are either staggered (COF-1, P6(3)/mmc) or eclipsed (COF-5, P6/mmm). Their crystal structures are entirely held by strong bonds between B, C, and O atoms to form rigid porous architectures with pore sizes ranging from 7 to 27 angstroms. COF-1 and COF-5 exhibit high thermal stability (to temperatures up to 500 degrees to 600 degrees C), permanent porosity, and high surface areas (711 and 1590 square meters per gram, respectively).     

拮抗棉花枯萎病菌的苦豆子内生细菌资源

对从塔里木盆地苦豆子中分离得到的内生细菌进行皿内涂布拮抗实验、对峙培养法拮抗实验和胞外分泌物的拮抗性测定等研究,结果表明塔里木盆地苦豆子中存在大量的拮抗性内生细菌资源.皿内涂布法筛选结果表明550株苦豆子内生细菌中有118株相对抑菌率超过50 ;.对峙培养法对118株拮抗性内生细菌进一步筛选结果表明对棉花枯萎病菌抑菌距离超过20 mm的菌株有56株.56株拮抗性内生细菌胞外分泌物对棉花枯萎病菌的抑菌距离超过5 mm的有35株,具有较好的生物防治潜力.56株拮抗性内生细菌经鉴定分别属于气芽孢杆菌属(Aerobacillus sp.,7株)、气单胞菌属(Aeromonas sp.,8株)、芽孢杆菌属(Bacillus sp.,25株)、黄单孢杆菌属(Xanthomonas sp.,5株)、假单胞杆菌属(Pseudomonas sp.,5株)、土壤杆菌属(Agrobacterium sp.,6株).     

A New High-Temperature Superconductor: Bi2Sr3-x Cax Cu2O8+y

A new superconductor that displays onset behavior near 120 K has been identified as Bi(2)Sr(3-x)Ca(x)Cu(2)O(8+y), with x ranging from about 0.4 to 0.9. Single crystal x-ray diffraction data were used to determine a pseudo-tetragonal structure based on an A-centered orthorhombic subcell with a = 5.399 A, b= 5.414A, and c = 30.904 A. The structure contains copper-oxygen sheets as in La(2)CuO(4) and YBa(2)Cu(3)O(7), but the copper-oxygen chains present in YBa(2)Cu(3)O(7) do not occur in Bi(2)Sr(3-x)Ca(x)Cu(2)O(8+y). The structure is made up of alternating double copper-oxygen sheets and double bismuth-oxygen sheets. There are Ca(2+) and Sr(2+) cations between the adjacent Cu-O sheets; Sr(2+) cations are also found between the Cu-O and Bi-O sheets. Electron microscopy studies show an incommensurate superstructure along the a axis that can be approximated by an increase of a factor of 5 over the subcell dimension. This superstructure is also observed by x-ray diffraction on single crystals, but twinning can make it appear that the superstructure is along both a and b axes. Flux exclusion begins in our samples at about 116 K and is very strong by 95 K. Electrical measurements on a single crystal of Bi(2)Sr(3-x)Ca(x)Cu(2)O(8+y) show a resistivity drop at about 116 K and apparent zero resistivity at 91 K.     

Shocked quartz in the cretaceous-tertiary boundary clays: evidence for a global distribution

Shocked quartz grains displaying planar features were isolated from Cretaceous- Tertiary boundary clays at five sites in Europe, a core from the north-central Pacific Ocean, and a site in New Zealand. At all of these sites, the planar features in the shocked quartz can be indexed to rational crystallographic planes of the quartz lattice. The grains display streaking indicative of shock in x-ray diffraction photographs and also show reduced refractive indices. These characteristic features of shocked quartz at several sites worldwide confirm that an impact event at the Cretaceous-Tertiary boundary distributed ejecta products in an earth-girdling dust cloud, as postulated by the Alvarez impact hypothesis.     

防风内生真菌DL02菌株次生代谢产物的结构与活性

为探究防风内生真菌DL02次生代谢产物的结构与活性,采用形态学特征和ITS序列鉴定菌株,利用硅胶柱层析、Sephadex LH-20柱层析和重结晶等方法对该菌株的发酵产物进行分离和纯化,并结合所得化合物的理化性质和波谱数据鉴定其结构,通过最小抑菌浓度（MIC）对其次生代谢产物进行活性测试。结果表明,菌株DL02为裂褶菌（Schizophyllum commune Franch.）,从其发酵产物中分离得到7个化合物,分别为烟酸（1）、丁二酸（2）、麦角甾醇（3）、22E-5α,8α-桥二氧麦角甾-6,22-二烯-3β-醇（4）、色胺酮（5）、lawsaritol A（6）、胡萝卜苷（7）,其中化合物6为首次从真菌发酵产物中分离得到,化合物5有很好的抑菌活性,其中对大肠杆菌的MIC值为3.9 μg·mL^-1。     

Solution of a protein crystal structure with a model obtained from NMR interproton distance restraints

Model calculations were performed to test the possibility of solving crystal structures of proteins by Patterson search techniques with three-dimensional structures obtained from nuclear magnetic resonance (NMR) interproton distance restraints. Structures for crambin obtained from simulated NMR data were used as the test system; the root-mean-square deviations of the NMR structures from the x-ray structure were 1.5 to 2.2 A for backbone atoms and 2.0 to 2.8 A for side-chain atoms. Patterson searches were made to determine the orientation and position of the NMR structures in the unit cell. The correct solution was obtained by comparing the rotation function results of several of the NMR structures and the average structure derived from them. Conventional refinement techniques reduced the R factor from 0.43 at 4 A resolution to 0.27 at 2 A resolution without inclusion of water molecules. The partially refined structure has root-mean-square backbone and side-chain atom deviations from the x-ray structure of 0.5 and 1.3 A, respectively.     

Diffuse-double layer at a membrane-aqueous interface measured with x-ray standing waves

The ion distribution in an electrolyte solution in contact with a charged polymerized phospholipid membrane was directly measured with long-period x-ray standing waves. The 27-angstrom-thick lipid monolayer was supported on a tungsten/silicon mirror. X-ray standing waves were generated above the mirror surface by total external reflection of a 9.8-kiloelectron volt x-ray beam from a synchrotron undulator. The membrane surface, which contained negatively charged phosphate headgroups, was bathed in a dilute ZnCl2 solution. The concentration of Zn2+ in the condensed layer at the membrane surface and the Zn2+ distribution in the diffuse layer were measured as a function of headgroup charge. The Debye length of the diffuse layer varied between 3 and 58 angstroms. The results qualitatively agree with the Gouy-Chapman-Stern model.