Mass spectrometric fragmentation of saturated six membered heterocyclic systems containing two chalcogen family atoms

The mass spectra of six-membered saturated heterocycles containing oxygen, sulphur, selenium and tellurium in the 1,4-positions have been measured. The differing fragmentation modes have been characterized using high resolution, low voltage and metastable ion scan techniques. The important decomposition reactions of the molecular ions involve elimination of C₂H₄ and CH₂X (X is a chalcogen atom) and formation of [C₂H₄X]⁺ and C₂H₅⁺. The propensities of these reactions vary systematically as a function of the ability of the chalcogen to stabilize a positive charge.     

Atomic force microscopy measurement of the elastic properties of the kidney epithelial cells

Direct interaction force measurements using atomic force microscopy (AFM) were carried out between a silicon nitride tip and renal epithelial cells (Madin-Darby Canine Kidney-MDCK and proximal tubular epithelial cells derived from pig kidneys, LLC-PK1). The approaching (extending) portion of the force/distance curves is considered, and repulsive forces in the long range of 2-3 microm were seen in both MDCK as well as LLC-PK1 cells growing under normal conditions. The repulsive force in the shorter distance range of 50-200 nm was also observed, when cells were damaged exposing the underlying basal membrane. LLC-PK1 cells were more prone to damage than the MDCK cells, hence short-range forces were common in the former and long-range forces in the latter cells. The functional dependence of repulsive force on the indentation depth changes, at small indentation depth the force increases linearly, while at larger indentations the force is a quadratic function of the distance, which is attributed to the elasticity of the membrane and the solid-like response of cells, respectively. The oxalate treatment of cells for 2-4 h gives rise to an increase in the elastic modulus of the cells.     

Reactions of 2-aminooxazoles and 2-aminothiazoles with dienophiles. Isolation of stable diels-alder adducts

Room temperature reaction of 2-aminooxazole 1 and its 4- and 4,5-substituted derivatives, with dimethyl acetylenedicarboxylate gave good yields of Diels-Alder adducts 2 , isolated as stable crystalline compounds. A competing process produced oxazole[3,2-a]pyrimidines 3 , also in good yield. Minor products were also identified. 2-Amino-4-methylthiazole ( 6 ) reacted in a similar manner and gave the Diels-Alder adduct 7 and a thia-zolo[3,2-a]pyrimidine 8 as main products with a lesser amount of a thiazole [3,2-d][1:3]diazepine ( 9 ). The aminooxazoles reacted with olefinic dienophiles to give pyridine derivative, formed by breakdown of the original unstable adducts.     

Identification and characterization of active and inactive species for surface-enhanced resonance Raman scattering

The surface-enhanced resonance Raman scattering (SERRS) activity of a statistically significant number of silver nanoparticles has been studied using a correlated SERRS mapping and transmission electron microscopy (TEM) method. TEM allowed the nature of each entity to be directly identified, and the SERRS activity was obtained from the corresponding SERRS map. Particles in various states of aggregation were analyzed to establish relative activities. It was established that SERRS activity is dependent on the specific batch of colloid tested. By averaging different colloid batches, it was shown that increasing SERRS activity is observed with increasing numbers of particles in the aggregates. By reducing the surface coverage of the particles to the extent that single moieties could be examined optically, the ratio of the relative activities of single particles, dimers, trimers, and larger aggregates was estimated. High-resolution TEM images of a number of active and inactive particles are reported. However, no clear correlation between microstructure and SERRS activity was observed.     

Synthesis of cross linked platinum metal containing polyyne polymers

Reaction of Pt(PⁿBu₃)₂Cl₂ (1) or Pt(AsⁿBu₃₂Cl₂ (2) with stoichiometric amounts of 1,3,5-triethynylbenzene, [1,3,5-(H? C?C? )₃C₆H₃] (3)yields monomeric, [1,3,5-Cl(PⁿBu₃)₂(Pt? C? C? )₃C₆H₃] (4), [1,3,5-(C1)(AsⁿBu₃)₂Pt? C? C? ₃C₆H₃] (5) or polymeric, {1,3,5-[(PⁿBu₃)₂Pt? C?C? ]₃C₆H₃? )ⁿ (6), {1,3,5-[(AsⁿBu₃)₂Pt? C? C? ]₃C₆H₃? }ⁿ (7) complexes. Treatment of (1) with (3) and 2,5-diethynyl-p-xylene,H? C? C? C₆H₂(CH₃)₂? C? C? H (8) in varying molar ratios yields a series of high molecular weight cross linked platinum metal containing polyyne copolymers.     

Supramolecular copper hydroxide tennis balls: self-assembly, structures, and magnetic properties of octanuclear [Cu(8)L(8)(OH)(4)](4+) clusters (HL = N-(2-pyridylmethyl)acetamide)

The self-assembly of supramolecular copper "tennis balls" that possess unusual magnetic properties using a small pyridyl amide ligand is described. Copper(II) complexes of N-(2-pyridylmethyl)acetamide (HL) were synthesized in methanol. In the absence of base, the mononuclear complex [Cu(HL)(2)](ClO(4))(2) (1) was prepared. The structure of 1, determined by X-ray crystallography, contains a copper(II) ion surrounded by bidentate HL ligands coordinated via the pyridyl N atom and the carbonyl O atom in a trans, square planar arrangement. Reactions carried out in the presence of triethylamine resulted in cluster complexes [Cu(8)L(8)(OH)(4)](ClO(4))(4) and [Cu(8)L(8)(OH)(4)](CF(3)SO(3))(4) [2(ClO(4))(4) and 2(OTf)(4), respectively]. The cationic portions of 2(ClO(4))(4) and 2(OTf)(4) are isostructural, containing eight copper(II) ions, eight deprotonated ligands (L(-)), and four mu(3)-hydroxide ligands. The top and bottom halves of the cluster are related by a pseudo-S(4) symmetry operation and are held together by bridging L(-) ligands. Solutions of 2(ClO(4))(4) and 2(OTf)(4), which were shown to contain the full [Cu(8)L(8)(OH)(4)](4+) fragment by electrospray mass spectrometry and conductance experiments, are EPR silent. Magnetic susceptibility measurements for 2(ClO(4))(4) as a function of temperature and magnetic field showed the Cu ions all to exhibit magnetic moments in the range expected for the d(9) configuration. At low temperatures, the magnetization was reduced due to predominantly antiferromagnetic interactions between ions. Analysis showed that partially frustrated interactions among the four Cu ions making up each half of the cluster gave good agreement with the data once a large molecular anisotropy was taken into account, with J(c) = 106 cm(-1), D = 27 cm(-1), and g = 2.17.     

Adsorption of strontium ions from aqueous solution on Pakistani coal

Summary The adsorption of strontium ions from aqueous solution on a Pakistani coal powder has been studied as a function of shaking time, amount of adsorbent, pH, and strontium ion concentration. Conditions for the maximum adsorption of strontium ions have been established. Results reveal that the diffusion of strontium ions into the pores of coal powder occurs during the adsorption process and intra-particle diffusion controls the kinetics of the process. The Langmuir and D-R adsorption equations are valid over the entire range of studied concentration. The influence of different anions on the adsorption of strontium ions was also studied.     

Synthesis, physico-chemical and thermal characteristics of seven and ten coordinated complexes of trivalent lanthanides derived from 4[N-(cinnamalidene)amino]antipyrine semicarbazone and diphenyl sulfoxide

In present studies a new series of twenty four complexes of seven and ten coordinated compounds derived from 4[Ncinnamalidene) amino]antipyrine semicarbazone (CAAPS) as primary ligand and diphenyl sulfoxide (DPSO) as secondary ligand has been reported. All the complexes have the general composition LnX_3.n(CAAPS).DPSO (Ln = La, Pr, Nd, Sm, Gd, Tb, Dy or Ho, X = NCS or ClO₄, n = 2, X = NO₃, n = 1). The compounds have been characterized by elemental analysis, molar conductance, magnetic susceptibility, infrared and electronic spectra. Thermal characteristics were also reported. Based on the data appropriate structures are assigned for these complexes.     

Study of the excited 0+ states through conversion electron spectroscopy of neutron rich Zr and Mo fission products

A windowless Si(Li) electron detector has been used in conjunction with the gas filled fission product separator JOSEF to study totally converted transitions in Zr and Mo isotopes. The existence of twoβ-decay modes in⁹⁶Y,⁹⁸Y and¹⁰⁰Nb is confirmed. The half-lives of theβ-decaying levels feeding O ₂ ⁺ states in⁹⁶Zr and⁹⁸Zr are 6.0 ± 0.4 sec and 0.60±0.05 sec respectively. A search for other first excited O ₂ ⁺ states shows that no such states are apparent in¹⁰⁰Zr and¹⁰⁴Mo.