Ag8Cl2[Se2P(OEt)2]6: A rare example containing a combination of discrete clusters and chains

The novel halide-centered Ag(I)8 cubic clusters containing diethyl diselenophosphato ligands are prepared and their solid state structures, a discrete unit or a one-dimensional chain, are dictated by the counter anions.     

Surface Aggregation of Candida albicans on Glass in the Absence and Presence of Adhering Streptococcus gordonii in a Parallel-Plate Flow Chamber: A Surface Thermodynamical Analysis Based on Acid-Base Interactions

Adhesive interactions between yeasts and bacteria are important in the maintenance of infectious mixed biofilms on natural and biomaterial surfaces in the human body. In this study, the extended DLVO (Derjaguin-Landau-Verwey-Overbeek) approach has been applied to explain adhesive interactions between C. albicans ATCC 10261 and S. gordonii NCTC 7869 adhering on glass. Contact angles with different liquids and the zeta potentials of both the yeasts and bacteria were determined and their adhesive interactions were measured in a parallel-plate flow chamber.Streptococci were first allowed to adhere to the bottom glass plate of the flow chamber to different seeding densities, and subsequently deposition of yeasts was monitored with an image analysis system, yielding the degree of initial surface aggregation of the adhering yeasts and their spatial arrangement in a stationary end point. Irrespective of growth temperature, the yeast cells appeared uncharged in TNMC buffer, but yeasts grown at 37 degrees C were intrinsically more hydrophilic and had an increased electron-donating character than cells grown at 30 degrees C. All yeasts showed surface aggregation due to attractive Lifshitz-van der Waals forces. In addition, acid-base interactions between yeasts, yeasts and the glass substratum, and yeasts and the streptococci were attractive for yeasts grown at 30 degrees C, but yeasts grown at 37 degrees C only had favorable acid-base interactions with the bacteria, explaining the positive relationship between the surface coverage of the glass by streptococci and the surface aggregation of the yeasts. Copyright 1999 Academic Press.     

High-spin structure of yrast-band in 78Kr

Lifetime of levels up to 22⁺, have been measured in ⁷⁸Kr and an oblate shape is assigned to the ground state using the CSM and the configuration dependent shell correction calculations. Calculations further show that ⁷⁸Kr is highly γ-soft nucleus. The experimental Q _t values coupled with theoretical calculations indicate an oblate shape for ⁷⁸Kr at low spins and triaxial shape at higher spins     

Structure of 72,74Se at high spin

Lifetimes of high spin states up to { }=22⁺ in the yrast positive parity bands have been measured to investigate the shape evolution with increasing spin in ^{72, 74}Se. The Q _t values derived from these measurements indicate that prolate shape stabilizes for ⁷²Se, while a triaxial shape develops for ⁷⁴Se at higher spins. Comparison of the observed trend in Q _t with spin for ^{72, 74}Se with that of the corresponding kryptones isotones emphasizes the stability provided by N=38 prolate shell gap even at high rotational frequency.     

Studies on the valence electronic structure of Fe and Ni in Fe x Ni1−x alloys

K _β-to-K _α X-ray intensity ratios of Fe and Ni in pure metals and in Fe _x Ni_1−x alloys (x=0.20, 0.50, 0.58) exhibiting similar crystalline structure have been measured following excitation by 59.54 keV γ-rays from a ²⁴¹Am point source, to understand as to why the properties of permalloy Fe_0.2Ni_0.8 is distinct from other alloy compositions. It is observed that the valence electronic structure of Fe_0.2Ni_0.8 alloy is totally different from other alloys which may be attributed to its special magnetic properties.     

New halide-centered discrete Ag(I)(8) cubic clusters containing diselenophosphate ligands, [Ag(8)(X)[Se(2)P(OR)(2)](6)](PF(6)) (X = Cl, Br; R = Et, Pr, (i)Pr): syntheses, structures, and DFT calculations

Six clusters Ag(8)(micro(8)-X)[Se(2)P(OR)(2)](6)(PF(6)) (R = Et, X = Cl, 1a, X = Br, 1b; R = Pr, X = Cl, 2a, X = Br, 2b; R = (i)Pr, X = Cl, 3a, X = Br, 3b) were isolated from the reaction of [Ag(CH(3)CN)(4)](PF(6)), NH(4)[Se(2)P(OR)(2)], and Bu(4)NX in a molar ratio of 4:3:1 in CH(2)X(2). Positive FAB mass spectra show m/z peaks at 2573.2 for 1a, 2617.3 for 1b, 2740.9 for 2a, 2786.9 for 2b, 2742.3 for 3a, and 2787.0 for 3b due to respective molecular cation, (M - PF(6))(+). (31)P NMR spectra of 1a-3b display a singlet at delta 82.3, 81.5, 82.9, 81.7, 76.3, and 75.8 ppm with a set of satellites (J(PSe) = 661, 664, 652, 652, 656, and 656 Hz, respectively). The X-ray structure (1a-2b) consists of a discrete cationic cluster in which eight silver ions are linked by six diselenophosphate ligands and a central micro(8)-Cl or micro(8)-Br ion with a noncoordinating PF(6)(-) anion. The shape of the molecule is a halide-centered distorted Ag(8) cubic cluster. The dsep ligand exhibits a tetrametallic tetraconnective (micro(2), micro(2)) coordination pattern, and each caps on a square face of the cube. Each silver atom of the cube is coordinated by three selenium atoms and the central chloride or bromide ion. Additionally, molecular orbital calculations at the B3LYP level of the density functional theory have been carried out to study the Ag-micro(8)-X (X = Cl, Br) interactions for cluster cations [Ag(8)(micro(8)-X)[Se(2)P(OR)(2)](6)](+). Calculations show very weak bonding interactions exist between micro(8)-X and Ag atoms of the cube.     

Synthesis of oleanolic disaccharide derivatives

Oleanolic acid 1 exists widely in food,medicinal herbs and other plants and possesses many attractive biological activities. Recently,some oleanolic derivatives were reported to have interesting anti-tumor activities.Herein,using association principle of drug design,OA disaccharide 17 was designed and synthesized by coupling a-L-rhamnopyranosyl-(1→2)-a-L-arabinopyranosyl disaccharide moiety,which has proved to be a unique sugar sequence with strongly antitumor activity,and modified OA with a nitrile at C-17.     

The interplay between the lattice and magnetism in La(Fe_11.4Al_1.6)C_0.02 studied by powder neutron diffraction

The crystallographic structure and magnetic properties of La(Fe 11.4 Al 1.6 )C 0.02 are studied by magnetic measure- ment and powder neutron diffraction with temperature and applied magnetic field. Rietveld refinement shows that La(Fe 11.4 Al 1.6 )C 0.02 crystallizes into the cubic NaZn 13 -type with two different Fe sites: Fe I (8b) and Fe II (96i), and that Al atoms preferentially occupy the Fe II site. A ferromagnetic state can be induced at a medial temperature of 39 K–139 K by an external magnetic field of 0.7 T, and a large lattice is correspondingly found at 100 K and 0.7 T. In all other conditions, La(Fe 11.4 Al 1.6 )C 0.02 has no net magnetization in the paramagnetic (T > T N = 182 K) or antifer- romagnetic states, and thus keeps its small lattice. Analysis of the Fe–Fe bond length indicates that the ferromagnetic state prefers longer Fe–Fe distances.