Randomized consistent statistical inference for random processes and fields

Statistical Inference for Stochastic Processes - We propose a randomized approach to the consistent statistical analysis of random processes and fields on $${\mathbb {R}}^m$$ and $${\mathbb {Z}}^m,...     

Femtosecond intermolecular electron transfer in condensed systems

We have investigated the ultrafast intermolecular electron transfer (ET) from an electron-donating solvent (aniline (AN) or N, N-dimethylaniline (DMA)) to an excited dye molecule (oxazines (Nile blue and oxazine 1) or coumarins). A non-exponential time dependence was observed in AN and can be explained by solvent reorientation and nuclear motion of the reactants. However, in DMA, a single exponential process was observed for Nile blue (160 fs) and oxazine 1 (280 fs), which can be explained by assuming that the rate of ET is limited mainly by ultrafast nuclear motion. A clear substituent effect on intermolecular ET was observed for the 7-aminocoumarins. When the alkyl chain on the 7-amino group is extended and a hexagonal ring with the benzene moiety is formed, the rate of ET is reduced by three orders of magnitude. This effect can be explained by a change in the free energy difference of the reaction and by the vibrational motion of the amino group.     

Direct quantitative analysis of peptides using matrix assisted laser desorption ionization

The protocol and various matrices were examined for quantification of biomolecules in both the low ca. 1200 amu and mid mass 6000-12000 amu ranges using an internal standard. Comparative studies of different matrices of MALDI quantitative analysis showed that the best accuracy and standard curve linearity were obtained for two matrices: (a) 2,5-dihydroxybenzoic acid (DHB) combined with a comatrix of fucose and 5-methoxysalicylic acid (MSA) and (b) ferulic acid/fucose. In the low mass range, the quantitative limit was in the 30 fmol range and in the mid mass range the quantitative limit was in the 250 fmol range. Linear response was observed over 2-3 decades of analyte concentration. The relative error of the standard curve slope was 1.3-1.8% with correlation coefficients of 0.996-0.998.The main problem for quantitative measurement was suppression of the signal of the less concentrated component (analyte or internal standard) by the more concentrated component. The effect was identified with saturation of the matrix by the analyte. The threshold of matrix saturation was found to be in the range of 1/(3000-5000) analyte/matrix molar ratio. To avoid matrix saturation the (analyte+internal standard) to matrix molar ratio should be below this threshold. Thus the internal standard concentration should be as low as possible.DHB/MSA/fucose and ferulic acid/fucose matrices demonstrated good accuracy and linearity for standard curves even when the internal standard had chemical properties different from the analyte. However, use of an internal standard with different chemical properties requires highly stable instrumental parameters as well as constant (analyte+internal standard)/matrix molar ratio for all samples.     

Synthesis and characterization of heavier dioxouranium(VI) dihalides

The synthesis and characterization of the dioxouranium(VI) dibromide and iodide hydrates, UO(2)Br(2)x3H(2)O (1), [UO(2)Br(2)(OH(2))(2)](2) (2), and UO(2)I(2)x2H(2)Ox4Et(2)O (3), are reported. Moreover, adducts of UO(2)I(2) and UO(2)Br(2) with large, bulky OP(NMe(2))(3) and OPPh(3) ligands such as UO(2)I(2)(OP(NMe(2))(3))(2) (4), UO(2)Br(2)(OP(NMe(2))(3))(2) (5), and UO(2)I(2)(OPPh(3))(2)(6) are discussed. The structures of the following compounds were determined using single-crystal X-ray diffraction techniques: (1) monoclinic, P2(1)/c, a = 9.7376(8) A, b = 6.5471(5) A, c = 12.817(1) A, beta = 94.104(1) degrees , V = 815.0(1) A(3), Z = 4; (2) monoclinic, P2(1)/c, a = 6.0568(7) A, b = 10.5117(9) A, c = 10.362(1) A, beta = 99.62(1) degrees , V = 650.5(1) A(3), Z = 2; (4) tetragonal, P4(1)2(1)2, a = 10.6519(3) A, b = 10.6519(3) A, c = 24.0758(6) A, V = 2731.7(1) A(3), Z = 4; (5) tetragonal, P4(1)2(1)2, a = 10.4645(1) A, b = 10.4645(1) A, c = 23.7805(3) A, V = 2604.10(5) A(3), Z = 4, and (6) monoclinic, P2(1)/c, a = 9.6543(1) A, b = 18.8968(3) A, c = 10.9042(2) A, beta =115.2134(5) degrees , V = 1783.01(5) A(3), Z = 2. Whereas 1 and 2 are the first UO(2)Br(2) hydrates and the last missing members of the UO(2)X(2) hydrate (X = Cl --> I) series to be structurally characterized, 4 and 6 contain room-temperature stable U(VI)-I bonds with 4 being the first structurally characterized room temperature stable U(VI)-I compound which can be conveniently prepared on a gram scale in quantitative yield. The synthesis and characterization of 5 using an analogous halogen exchange reaction to that used for the preparation of 4 is also reported.     

Local Lyapunov exponents for spatiotemporal chaos

Local Lyapunov exponents are proposed for characterization of perturbations in distributed dynamical systems with chaotic behavior. Their relation to usual and velocity-dependent exponents is discussed. Local Lyapunov exponents are analytically calculated for coupled map lattices using random field approximation. Boundary Lyapunov exponents describing reflection of perturbations at boundaries are also introduced and calculated.     

Oxidation of bridging groups by carboxylate coordinated ligands in palladium clusters

Thermolysis of tetranuclear palladium clusters Pd₄(-Q)₄ Pd₄(-Q)₄(-O₂CR)₄ (Q=CPh₂ or CO;R=Me, CMe₃, Ph, CH₂Cl or CF₃) has been found to involve innersphere oxidation of carbene or carbonyl ligands during which an oxygen atom transfer occurs from the carboxylate group to the carbene or carbonyl ligand. The thermolysis of the carbonyl clusters gives rise to the products of CO₂ insertion into the C–H bond of benzene or toluene used as solvents forming benzoic acid from benzene and a mixture of phenylacetic and toluic acids from toluene. The reaction of [Pd(OAc)₂(PPh₃)]₂ with HCO₂H includes the transfer of an O atom from formate ligand to the P atom and cleavage of the P-Ph bond accompanied by transfer of the Ph group from PPh₃ ligand to the palladium atom. The structure of the complex formed, [Pd(-O₂PPh₂)(C₆H₅)(PPh₃)]₂, has been resolved by X-ray analysis.     

Interaction between indigo and adsorbed protein as a major factor causing backstaining during cellulase treatment of cotton fabrics

A model microassay system was developed to measure indigo backstaining on cotton fabrics in the presence of enzymes on a small laboratory scale. Backstaining indexes for 11 cellulase samples were measured, and the enzymes were ranked from lower to higher backstaining. Two multienzyme cellulase preparations were separated into fractions using chromatofocusing on a Mono P column. Adsorption ability and backstaining properties of purified enzyme fractions were studied. Evidence was obtained that protein adsorption on cotton fabrics is a crucial parameter causing backstaining (both for crude cellulase samples and purified enzyme components).     

Evaluation of cellulase preparations for hydrolysis of hardwood substrates

Seven cellulase preparations from Penicillium and Trichoderma spp. were evaluated for their ability to hydrolyze the cellulose fraction of hardwoods (yellow poplar and red maple) pretreated by organosolv extraction, as well as model cellulosic substrates such as filter paper. There was no significant correlation among hydrolytic performance on pretreated hardwood, based on glucose release, and filter paper activity. However, performance on pretreated hardwood showed significant correlations to the levels of endogenous β-glucosidase and xylanase activities in the cellulase preparation. Accordingly, differences in performance were reduced or eliminated following supplementation with a crude β-glucosidase preparation containing both activities. These results complement a previous investigation using softwoods pretreated by either organosolv extraction or steam explosion. Cellulase preparations that performed best on hardwood also showed superior performance on the softwood substrates.