Total cross section for hadron production bye + e − annihilation between 9.4 and 9.5 GeV

The total cross section fore ⁺ e ^? annihilation into hadrons for center of mass energies from 9.4 to 9.5 GeV has been measured with the nonmagnetic DESY-Heidelberg detector at DORIS. A value ofR=σ_had/σ_µµ=3.8±0.7 for the continuum region around the Υ (9.46) resonance has been determined. The ratioΓ _ee Γ _had/Γ _tot of electronic, hadronic and total widths has been reevaluated to be (1.00±0.23) keV for the Υ resonance and (0.37±0.16) keV for the Υ′. In addition, a search for directly produced pohotons from Υ decays of the type Υ→γ+gluon+gluon has been performed. The Υ decay into muon pairs has also been searched for.     

Co2+/ Co(0) redox couple revealed by EPR spectroscopy triggers preferential coordination of reactants during SCR of NOx with propene over cobalt-exchanged zeolites

Catalytic reduction of NOx with propene over Co2+ -exchanged beta and ZSM-5 zeolites occurs with formation of zero-valent cobalt; NOx preferentially adsorbed on Co2+ plays the role of a metal reducing agent while ligation of propene is favored for Co(0) centers.     

Liebig–Denigès Method of Cyanide Determination: A Comparative Study of Two Approaches

The paper compares two approaches to the simulated argentometric titration of cyanide with the use of the modified Liebig?CDenigès (L-D) method, carried out according to GATES and applied with (1) classical and (2) pH-static titrations. Both approaches are discussed thoroughly and the results obtained from calculations are presented graphically. The calculations are performed with the use of an iterative computer program, based on charge and concentration balances and expressions for equilibrium constants, providing all physicochemical knowledge of the dynamic system in question. This way, physicochemical knowledge on complex electrolytic systems can be gained during the analytical procedure, i.e., the physicochemical and analytical knowledge are interrelated. The simulations follow the analytical procedures applied in experimental titrations and so provide an example of searching for the best a priori conditions for the quantitative analysis of cyanide. The computer program for pH-static titrations (described in this paper) enables one to carry out the simulation procedures with different preliminary data (concentrations, volumes).     

Analysis of NH3-TPD Profiles for CuSSZ-13 SCR Catalyst of Controlled Al Distribution – Complexity Resolved by First Principles Thermodynamics of NH3 Desorption,IR and EPR Insight into Cu Speciation**

NH₃ temperature-programmed desorption (NH₃-TPD) is frequently used for probing the nature of the active sites in CuSSZ-13 zeolite for selective catalytic reduction (SCR) of NO_x. Herein, we propose an interpretation of NH₃-TPD results, which takes into account the temperature-induced dynamics of NH₃ interaction with the active centers. It is based on a comprehensive DFT/GGA+D and first-principles thermodynamic (FPT) modeling of NH₃ adsorption on single Cu²⁺, Cu⁺, [CuOH]⁺ centers, dimeric [Cu-O-Cu]²⁺, [Cu-O₂²⁻-Cu]² species, segregated CuO nanocrystals and Brønsted acid sites (BAS). Theoretical TPD profiles are compared with the experimental data measured for samples of various Si/Al ratios and distribution of Al within the zeolite framework. Copper reduction, its relocation, followed by the intrazeolite olation/oxolation processes, which are concomitant with NH₃ desorption, were revealed by electron paramagnetic resonance (EPR) and IR. DFT/FPT results show that the peaks in the desorption profiles cannot be assigned univocally to the particular Cu and BAS centers, since the observed low-, medium- and high-temperature desorption bands have contributions coming from several species, which dynamically change their speciation and redox states during NH₃-TPD experiment. Thus, a rigorous interpretation of the NH₃-TPD profiles of CuSSZ-13 in terms of the strength and concentration of the active centers of a particular type is problematic. Nonetheless, useful connections for molecular interpretation of TPD profiles can be established between the individual component peaks and the corresponding ensembles of the adsorption centers.     

Numerical study on space–time pulse compression

A numerical study of the properties of Gaussian pulses propagating in a planar waveguide under the combined effects of positive Kerr-type nonlinearity, diffraction in planar waveguides and anomalous or normal dispersion, is presented. It is demonstrated how the relative strength of dispersion and diffraction, the strength of nonlinearity and the initial spatial and temporal pulse chirps effect the parameters of pulse compression, such as the maximal compression factor and the distance to the point of maximal compression. This revised version was published online in November 2006 with corrections to the Cover Date.     

Inherently Chiral Spider‐Like Oligothiophenes

The racemate of an inherently chiral “spider‐like” octathiophene monomer T8₃ , in which chirality is generated by torsion in its backbone, was synthesized. The racemate was resolved into configurationally stable antipodes by HPLC on a chiral stationary phase. Electrooxidation of the enantiomers resulted in materials displaying high enantiorecognition ability towards the antipodes of some chiral probes. Moreover, the T8₃ racemate demonstrated great aptitude to stimulate formation of 3D rigid architectures if used as a cross‐linking monomer for molecular imprinting. This feature was exploited to devise a molecularly imprinted polymer‐based chemosensor selective for a thymine–adenine oligonucleotide.     

DFT calculations of magnetic parameters for molybdenum complexes and hydroxymethyl intermediates trapped on silica surface

Density functional theory (DFT) calculations of EPR parameters and their structure sensitivity for selected surface paramagnetic species involved in oxidative dehydrogenation of methanol over silica grafted molybdenum catalyst were investigated. Two surface complexes, Mo(4c)/SiO2 and {O(-)-Mo(4c)}/SiO2, as well as *CH2OH radical trapped on the SiO2 matrix were taken as the examples. The spin-restricted zeroth order regular approximation (ZORA) implemented in the Amsterdam Density Functional suite was used to calculate the electronic g tensor for those species. The predicted values were in satisfactory agreement with experimental EPR results. Five different coordination modes of the *CH2OH radical on the silica surface were considered and the isotropic 13C, 17O, and 1H hyperfine coupling constants (HFCC) of the resultant surface complexes were calculated. Structure sensitivity of the HFCC values was discussed in terms of the angular deformations caused by hydrogen bonding with the silica surface.     

Finite-element simulation of temperature-dependent three-point bending process of glass

Simulation of strains and stresses distributions in the glass subjected to a bending load during heat treatment is presented in the paper. The main objective of the work is to combine the temperature-dependent experimental test of three-point bending with simulation of this test and to apply inverse analysis to determine the properties of glass. The thermo-mechanical analysis (TMA) was used to test a temperature-dependent glass deformation. The Adina finite element software was used for simulations of the viscous flow. Two parameters in the Williams–Landell–Ferry (WLF) equation were identified by optimization of the square root error between measured and predicted deflection of the sample. Performed experiments and simulations yielded the values of these coefficients: C ₁ = 26.3 and C ₂ = 62.7. The proposed model with the optimized coefficients confirmed good agreement with the experimental data.     

Ion-exchange resins in non-aqueous solvents-III Solvent-uptake properties of ion-exchange resins and related adsorbents

Solvent-uptake properties for several synthetic resins and common adsorbents were determined by the centrifugation method. Data are reported for eighteen different solvents, which include water and the common polar and non-polar organic solvents. The cation-exchange resins are of two varieties: the microreticular or gel type and the macroreticular or porous type. The latter resin being rigid and porous takes up all types of solvents, whereas the former resin, which relies on swelling of the resin matrix, does not take up the nonpolar solvents. Data for the H(+) form and Na(+) form macroreticular resin are compared. Unsulphonated polystyrene-divinylbenzene polymers which possess similar micro- and macroreticular properties to the cation-exchange resins were also studied in the same solvents. The swelling properties of these non-polar resins are compared with each other and with the polar cation resins. Other adsorbents, which are frequently used as supports in chromatography were also examined in the same solvents. Several of these have large average pore diameters and surface areas like the macroreticular resin.