Study of the suppressed decays B- -->[K+pi-](D)K- and B- -->[K+pi-]Dpi-

We report a study of the suppressed decays B--->[K(+)pi(-)](D)K- and B--->[K(+)pi(-)](D)pi(-), where [K(+)pi(-)](D) indicates that the K+pi(-) pair originates from a neutral D meson. These decay modes are sensitive to the unitarity triangle angle varphi(3). We use a data sample containing 275 x 10(6) BB pairs recorded at the Upsilon(4S) resonance with the Belle detector at the KEKB asymmetric e(+)e(-) storage ring. The signal for B--->[K(+)pi(-)](D)K- is not statistically significant, and we set a limit r(B)<0.27 at 90% confidence level, where r(B) is the magnitude of the ratio of amplitudes |A(B--->D 0K-)/A(B--->D0K-)|. We observe a signal with 6.4sigma statistical significance in the related mode, B--->[K(+)pi(-)](D)pi(-).     

Coulomb- and antiferromagnetic-induced fission in doubly charged cubelike fe-s clusters

We report the observation of symmetric fission in doubly charged Fe-S cluster anions, [Fe(4)S(4)X(4)](2-)-->2[Fe(2)S(2)X(2)](-) (X=Cl,Br), owing to both Coulomb repulsion and antiferromagnetic coupling. Photoelectron spectroscopy shows that both the parent and the fission fragments have similar electronic structures and confirms the inverted energy schemes due to the strong spin polarization of the Fe 3d levels. The current observation provides direct confirmation for the unusual spin couplings in the [Fe(4)S(4)X(4)](2-) clusters, which contain two valent-delocalized and ferromagnetically coupled Fe2S2 subunits.     

Indications of suppression of excited Υ states in Pb-Pb collisions at √(s(NN))=2.76 TeV

A comparison of the relative yields of Υ resonances in the μ(+)μ(-) decay channel in Pb-Pb and pp collisions at a center-of-mass energy per nucleon pair of 2.76 TeV is performed with data collected with the CMS detector at the LHC. Using muons of transverse momentum above 4 GeV/c and pseudorapidity below 2.4, the double ratio of the Υ(2S) and Υ(3S) excited states to the Υ(1S) ground state in Pb-Pb and pp collisions, [Υ(2S+3S)/Υ(1S)](Pb-Pb)/[Υ(2S+3S)/Υ(1S)](pp), is found to be 0.31(-0.15)(+0.19)(stat)±0.03(syst). The probability to obtain the measured value, or lower, if the true double ratio is unity, is calculated to be less than 1%.     

Investigation on damage of BSA molecules under irradiation of low frequency ultrasound in the presence of FeIII-tartrate complexes

The interaction between bovine serum albumin (BSA) and Fe(III)-tartrate complexes ([Fe(III)(tar)(H(2)O)(3)](-) and [Fe(III)(tar)(2)](5-)) as well as the damage of BSA in the presence of Fe(III)-tartrate complexes under ultrasonic irradiation was studied by UV-vis and fluorescence spectra. In addition, the influences of ultrasonic irradiation time, Fe(III)-tartrate complex concentration, ionic strength and solution acidity (pH value) were also examined on the damage of BSA. The results showed that the fluorescence quenching of BSA caused by the Fe(III)-tartrate complexes belonged to the static quenching. The BSA and Fe(III)-tartrate complexes interacted with each other mainly through weak interaction and coordinate actions. The corresponding binding association constants (K) and the binding site numbers (n) were calculated. The results were as follows: K(1)=1.67x10(3)Lmol(-1) and n(1)=0.9699 for [Fe(III)(tar)(H(2)O)(3)](-), K(2)=1.54x10(3)Lmol(-1) and n(2)=0.8754 for [Fe(III)(tar)(2)](5-). Otherwise, under ultrasonic irradiation the BSA molecules were obviously damaged by the Fe(III)-tartrate complexes. The damage degree rose up with the increase of ultrasonic irradiation time, Fe(III)-tartrate complex concentration, pH value and ionic strength. And that, [Fe(III)(tar)(H(2)O)(3)](-) exhibited higher sonocatalytic activity in a way than [Fe(III)(tar)(2)](5-).     

Evidence of simple intramolecular rearrangement at polymer end groups in secondary ion mass spectrometry

Polystyrenes with various end groups were analyzed by time-of-flight secondary ion mass spectrometry (TOF-SIMS). These end groups were obtained by termination of the active anionic group by sulfonate or chlorosilane derivatives. Characteristic end group fragments for each sulfonate derivative were observed. On the one hand, for PS capped by methyl sulfonate, or -(CH(2))(4)-O-SO(2)-CH(3), almost complete end group fragment is observed at m/z 95 and a [O-SO(2)-CH(3)](-) molecular structure. On the other hand, when PS is terminated by silyl methyl sulfonate, or -Si(CH(3))(2)-(CH(2))(3)-O-SO(2)-CH(3), the most characteristic fragment in the fingerprint secondary ion mass spectrum is located at m/z 153 with [Si(CH(3))(2)-O-SO(2)-CH(3)](+) and the complete end group peak, [Si(CH(3))(2)-(CH(2))(3)-O-SO(2)-CH(3)](+), at m/z 201, is absent. According to the molecular structure, characteristic end group secondary ions can be emitted as complete or rearranged fragments. Various silylalkyl alcohol or sulfonate functionalities are analyzed and fragmentation pathways are discussed. To our knowledge, this is the first time that such rearrangement at silyl functions has been observed and demonstrated in fingerprint secondary ion mass spectra. Copyright 1999 John Wiley & Sons, Ltd.     

铈激活磷光体的发光特性

Ce3+的发光属于f-d跃迁,它的荧光寿命非常短,发射光谱呈现带状,并随着基质的不同,发射峰位置发生显著的变化,能从紫外一直到可见区.Ce3+发射峰位置的变化与基质中直接配位的阴离子、阳离子以及阴离予基团等的变化有关,也受晶场劈裂、Stokes位移的影响.Ce3+发射峰位置的变化与化台物的共价程度有关,并得到一些规律性的结果,这将为材料设讨提供依据.文中对一些典型的Ce3+的能量传递和敏化作用作了介绍.     

Electron spin-relaxation via vibronic level of nickel (I) and nickel (III) cyanide complexes in NaCl single crystals

Electron spin-lattice relaxation rates for the low spin [Ni(CN)(4)](1-) and [Ni(CN)(4)](3-) complexes in NaCl host lattice were measured by the inversion recovery technique in the temperature range 7-50K. The data for both paramagnetic species fit very well to a relaxation process involving localized anharmonic vibration modes, also responsible for the g-tensor temperature dependence.     

Sources and circulation of water and arsenic in the Giant Mine, Yellowknife, NWT, Canada

Recovery of gold from arsenopyrite-hosted ore in the Giant Mine camp, Yellowknife, NWT, Canada, has left a legacy of arsenic contamination that poses challenges for mine closure planning. Seepage from underground chambers storing some 237,000 tonnes of arsenic trioxide dust, has As concentrations exceeding 4000 ppm. Other potential sources and sinks of As also exist. Sources and movement of water and arsenic are traced using the isotopes of water and sulphate. Mine waters (16 ppm As; AsV/AsIII approximately 150) are a mixture of two principal water sources--locally recharged, low As groundwaters (0.5 ppm As) and Great Slave Lake (GSL; 0.004 ppm As) water, formerly used in ore processing and discharged to the northwest tailings impoundment (NWTP). Mass balance with delta18O shows that recirculation of NWTP water to the underground through faults and unsealed drillholes contributes about 60% of the mine water. Sulphate serves to trace direct infiltration to the As2O3 chambers. Sulphate in local, low As groundwaters (0.3-0.6 ppm As; delta34SSO4 approximately 4% and delta18OSO4 approximately -10%) originates from low-temperature aqueous oxidation of sulphide-rich waste rock. The high As waters gain a component of 18O-enriched sulphate derived from roaster gases (delta18OSO4) = + 3.5%), consistent with their arsenic source from the As2O3 chambers. High arsenic in NWTP water (approximately 8 ppm As; delta18OSO4 = -2%) derived from mine water, is attenuated to close to 1 ppm during infiltration back to the underground, probably by oxidation and sorption by ferrihydrite.     

Superstructure Ga4InAs5

An epitaxial layer of the Ga_0.82In_0.18As solid solution is investigated. The coordination of arsenic atoms in the structure of this compound is determined by x-ray diffractometry. The ratio of arsenic atoms in the coordination 4Ga, 3Ga + In, and 2Ga + 2In corresponds to the superstructure in which an In atomic chain along the [110] direction alternates with four Ga chains. An ideal composition for this superstructure is Ga₄InAs₅. New specific features of the domain structure formed as a result of temperature-induced changes in the configuration of tetrahedral bonds are revealed.     

Mechanism of photoinduced changes in the structure and optical properties of amorphous As2S3

We propose a mechanism of photostructural changes in amorphous As2S3 ( a-As2S3) on the basis of ab initio molecular orbital calculations on clusters of atoms modeling the local structure of the amorphous system. We have found that trigonal AsS3 pyramidal units can be transformed into a fivefold coordinated As site having four As-S bonds and one As-As bond via a photoionization process. This photoinduced coordination defect center exhibits a lower photoabsorption energy as compared with the usual pyramidal structure, explaining the observed photodarkening effect of a-As2S3.     

Atomic structures of GaAs(100)-(2 × 4) reconstructions

Atomic structures of the As-rich GaAs(100)-(2 × 4) reconstructions based on converged first-principles total-energy calculations are reported. All geometries are characterized by similar structural elements such as As dimers with a length of about 2.5 Å, dimer vacancies, and a nearly planar configuration of the three-fold coordinated second-layer Ga atoms leading to a steepening of the dimer block. For an As coverage of θ = 3/4 we find the two-dimer β2 phase to be energetically preferred over the three-dimer β phase. A structure with partial replacement of As by Ga in the uppermost layer corresponding to an As coverage of is found to be slightly less favourable than the phase of GaAs(100). Geometry parameters are given for all structures and compared with the available experimental results.     

Studies on the adsorption of arsenic on calix[6]arene

p‐tert‐butyl calix[6]arene (PTC6) was synthesized and characterized by solid‐ and liquid‐state NMR and LC‐MS techniques. The adsorption of arsenite and arsenate on calix[6]arene under different pH conditions and adsorbate doses was studied. The maximum adsorption of arsenic species on calix[6]arene was observed around neutral pH and the adsorption density of As (III) was higher than that of As (V). The adsorption of neutral H₃AsO₃ and negatively charged H₂AsO molecules on calix[6]arene was attributed to the condensation reaction between hydroxyl groups of PTC6 and arsenic species. The complexation of arsenite with phenolic oxygen was confirmed by solid‐state ¹³C NMR CP‐MAS. Exo attack mechanism was proposed to describe the interaction of arsenous and arsenic acid molecules with PTC6. The specific interaction between calix[6]arene and arsenic species was further substantiated by zeta‐potential (ζ‐potential) measurements and free energy of adsorption. The free energy of adsorption ( ) estimated from Stern–Grahame equation was found to be 25 kJ/mole for As (III) and 19 kJ/mole for As (V). Copyright © 2010 John Wiley & Sons, Ltd.     

Mass spectral study of substituted allyl aryl and allyl alkyl selenides and some analogous sulfides

The electron impact (EI) mass spectra of allyl aryl selenides showed abundant molecular ions and many fragment ions containing the selenium atom. alpha-Cleavage is the dominant process in the fragmentation of selenides, and cleavage product ions are characteristic of the substituents. In the case of 3-methyl allyl and related aryl selenides, characteristic delta-hydrogen migration to the selenium atom is observed. A McLafferty-type rearrangement is found in benzyl allyl selenides and substituted alkyl allyl selenides. The charge on the rearrangement products preferably remains on the fragments containing the phenyl group. The [M - SeH](+), [M - CH(3)](+) and [M - C(2)H(4)](+) ions are found only in the EI mass spectrum of allyl phenyl selenide, and are attributed to a Claisen rearrangement in the source of the mass spectrometer. All structurally informative fragmentation processes are supported by collision induced dissociation spectra of molecular ions. The fragmentation patterns found in methane chemical ionization (CI) spectra of the selenides were significantly different from those observed in EI. The EI and CI mass spectra of analogous sulfides showed similar behaviour to that observed in the corresponding selenides. Copyright 1999 John Wiley & Sons, Ltd.     

Search for B+/--->[K(-/+)pi(+/-)](D)K+/- and upper limit on the b-->u amplitude in B+/--->DK+/-

We search for B+/--->[K(-/+)pi(+/-)](D)K+/- decays, where [K(-/+)pi(+/-)](D) indicates that the K-/+pi(+/-) pair originates from the decay of a D0 or D (0). Results are based on 120x10(6) Upsilon(4S)-->BB decays collected with the BABAR detector at SLAC. We set an upper limit on the ratio R(Kpi) identical with[Gamma(B+-->[K(-)pi(+)](D)K+)+Gamma(B--->[K(+)pi(-)](D)K-)][Gamma(B+-->[K(+)pi(-)](D) / K+)+Gamma(B--->[K(-)pi(+)](D)K-)]<0.026 (90% C.L.). This constrains the amplitude ratio r(B) identical with|A(B--->D 0K-)/A(B--->D0K-)|<0.22 (90% C.L.), consistent with expectations. The small value of r(B) favored by our analysis suggests that the determination of the Cabibbo-Kobayashi-Maskawa phase gamma from B-->DK will be difficult.     

Unusual role of the substrate in droplet‐induced GaAs/AlGaAs quantum‐dot pairs

The structural complexity of GaAs quantum‐dot pairs has been revealed by cross‐sectional transmission electron microscopy. As a result of high‐temperature droplet epitaxy, the AlGaAs substrate beneath the quantum‐dot pairs is no longer immobile and its reconstruction is observed to define the crystallization of gallium droplets under an arsenic flux. The GaAs quantum‐dot pairs are immersed into the substrate and further confined by the re‐distributed AlGaAs materials above the substrate plane. There are two underlying mechanisms responsible for the final nanostructure configuration, melt‐back etching by the gallium droplets and preferential crystallization of gallium around reconstructed sidewalls. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

NMR paramagnetic relaxation enhancement: test of the controlling influence of zfs rhombicity for S = 1

Prior theoretical work has predicted that the NMR paramagnetic relaxation enhancement (NMR-PRE) produced by electron spin S = 1 ions is highly sensitive to orthorhombic terms in the static zero field splitting (zfs) tensor. Zfs orthorhombicity (which implies chemical inequivalence of the three principal directions of the zfs-principal axis system and is described by the zfs E-parameter) is predicted to suppress the NMR-PRE profoundly relative to the reference cylindrical zfs-limit situation. This expectation was tested experimentally by a comparison of the zfs-limit NMR-PRE produced by [Ni(II)(en)(3)](2+) (en = ethylenediamine), a trigonal complex which lacks zfs-rhombicity, with the zfs-limit NMR-PRE produced by two orthorhombic complexes, [Ni(II)(en)(2)(H(2)O)(2)](2+) and [Ni(II)(en)(H(2)O)(4)](2+). As predicted, the zfs-limit NMR-PRE produced by the orthorhombic complexes in the proton resonance of a dioxane probe species in the solvent was strongly suppressed (by factors of approximately 5 and 7, respectively) relative to the comparable measurement on the trigonal complex. The suppression of the NMR-PRE due to the orthorhombic zfs terms is counteracted by an applied Zeeman field, leading to a predicted rise in the NMR-PRE with increasing Zeeman field strength; this rise occurs when the Zeeman energy is comparable to the orthorhombic zfs splitting, 2E. This second prediction of theory was likewise confirmed: the expected rhombicity-induced magnetic field dependence in the NMR-PRE was observed for the orthorhombic complexes but not for the trigonal complex.     

基于光谱分析的砷黄铁矿生物浸出过程中铁/砷/硫形态转化研究

基于同步辐射装置的As/S的K边及Fe的L边X射线吸收近边结构光谱(XANES)和X射线衍射(SR-XRD),结合扫描电镜(SEM)、傅里叶红外光谱(FTIR)、电感耦合等离子体发射光谱(ICP-AES)及各项浸出参数的测定,系统研究了(中度嗜热菌、嗜热硫化杆菌)浸出砷黄铁矿过程中铁、砷、硫的形态转化。结果表明,在生物作用下,砷黄铁矿的溶解速率明显高于化学浸出体系,伴随矿物溶解释放到溶液中的砷和铁在生物浸出体系中主要为As(Ⅴ)和Fe3+,而在无菌化学浸出体系则主要为As(Ⅲ)和Fe2+;细菌胞外多聚物(EPS)在细菌与硫化矿物的相互作用过程中起着至关重要的作用, FTIR的结果表明,生物浸出体系中吸附在矿物表面的吸附菌的EPS中蛋白质和多糖的含量均高于游离菌EPS;SEM的结果表明,砷黄铁矿表面在生物浸出过程中逐渐被腐蚀,且有浸出产物覆盖,而化学浸出10 d后,矿物表面依旧比较光滑;SR-XRD的结果表明,元素硫(S0)、黄钾铁矾和砷酸铁在生物浸出第4 d生成,并随时间延长逐渐累积,最终成为浸出渣中的主要成分。Fe的L边XANES结果表明,在细菌作用下矿物表面逐渐被Fe(Ⅲ)浸出产物覆盖;As的K边XANES结果表明,浸出渣中砷的价态包括As(-Ⅰ), As(Ⅲ)和As(Ⅴ),拟合结果表明,经过10 d的生物浸出,砷黄铁矿、雌黄(As2S3)和砷酸铁在矿渣中所占的比例分别为18.6%, 23.5%和57.9%,化学浸出10 d后,矿渣中除未溶解的砷黄铁矿外,仅有少量砷酸铁(6.2%)形成;S的K边XANES拟合结果表明,经过10 d的生物浸出,砷黄铁矿、 S0、硫代硫酸盐、施氏矿物和黄钾铁矾在矿渣中所占的比例分别为15.3%, 23.7%, 3.5%, 11.3%和46.2%,而在化学浸出10 d后的矿渣中,仅拟合到少量S0(7.8%)。基于上述结果可以得出,铁、砷、硫在砷黄铁矿生物作用下的形态转化过程分别为:Fe(Ⅱ)-Fe(Ⅲ), As(-Ⅰ)-As(Ⅲ)-As(Ⅴ), S-→S0→S2O■→SO■。结合溶液中的浸出参数发现,随着S0、黄钾铁矾、砷酸铁和雌黄的大量累积,砷黄铁矿的生物浸出严重受阻。硫代硫酸盐的生成表明砷黄铁矿的溶解途径与黄铁矿相似。     

Site percolation thresholds for Archimedean lattices

Precise thresholds for site percolation on eight Archimedean lattices are determined by the hull-walk gradient-percolation simulation method, with the results p(c)=0.697 043, honeycomb or (6(3)), 0.807 904 (3,12(2)), 0.747 806 (4,6,12), 0.729 724 (4,8(2)), 0.579 498 (3(4),6), 0.621 819 (3,4,6,4), 0.550 213 (3(3),4(2)), and 0.550 806 (3(2),4,3,4), with errors of about +/- 3 x 10(-6). [The remaining Archimedean lattices are the square (4(4)), triangular (3(6)), and Kagomé (3,6,3,6), for which p(c) is already known exactly or to a high degree of accuracy.] The numerical result for the (3,12(2)) lattice is consistent with the exact value [1-2 sin(pi/18)](1/2). The values of p(c) for all 11 Archimedean lattices, as well as a number of nonuniform lattices, are found to be well correlated by a nearly linear function of a generalized Scher-Zallen filling factor. This correlation is much more accurate than recently proposed correlations based solely upon coordination number.     

合成吲哚生物碱的1H NMR及立体化学

报道了5个咔啉和2个吲哚嗪的¹H NMK数据.根据它们的COSY谱指定了各质子信号的归属.根据NOESY谱讨论了一些化合物的立体化学.Ⅰ_b的1-H与3-H存在NOE相关峰,说明1-H与3-CO₂Me互为反式.Ⅲ的5'-H与4'-H无NOE相关峰,偶合常数为9.0Hz,它们应为反式.V的1-CHO与2-H有NOE相关峰,说明1-H与2-OH为顺式.由于Ⅱ_a与Ⅱ_b有几乎完全相同的NOESY谱.它们的1-H取向只好由经验规律暂定.     

Structure and magnetism of iron-sulfur clusters in proteins

Iron-sulfur clusters are mixed-valence systems exhibiting both localized and delocalized valence states. We discuss here spin-coupling models for two types of oxidized [3Fe-4S] clusters with localized Fe³⁺ valence states; a Heisenberg Hamiltonian with isotropic antiferromagnetic exchange fits the data well. Reduced [3Fe-4S] clusters, on the other hand, contain a trapped Fe³⁺ site and a delocalized Fe³⁺-Fe²⁺ pair. The pair has spin S₁₂=9/2 (formally ferromagnetic coupling) and is antiferromagnetically coupled to the Fe³⁺ S₃=5/2 spin to yield a system spin S=2. We discuss also recent results for [4Fe-4S] clusters such as [3Fe-4S]→[4Fe-4S] conversions, incorporation of other metals into the iron-sulfur core, and the observation of novel spin states.