Calculation of transverse and longitudinal space charge effects within the framework of the fully six-dimensional formalism

In the following report we describe a method for calculating the envelope of a particle bunch in linear coupled storage rings and transport systems in the presence of transverse and longitudinal space charge forces using the (canonical) variablesx, p _x ,z, p _z , σ=s?v ₀·t,p _σ=ΔE/E ₀ of the fully six-dimensional formalism. This work is an extension of earlier calculations on transverse space charge forces [1] to include the synchrotron oscillations. The extension is achieved by defining a 6-dimensional ellipsoid in thex?p _x ?z?p _z ?σ?p _σ space. The motion of this ellipsoid under the influence of the external fields and the instantaneous space charge forces can be described by six generating orbit vectors which can be combined into a 6-dimensional matrixB(s). This “bunch-shape matrix”,B(s), contains complete information about the configuration of the bunch. The solution of the equations of motion is carried through in the thin lens approximation. The formalism can also encompass acceleration by cavity fields.     

1,4-Addition of benzene to a dihydrocyclopent[a]indene diradical: synthesis and DFT study

Photochemical cyclization of compound 1, a homoenediyne (-CCC=CCH2CC-) bearing two ethynylanthracene chromophores, yields two isomeric dihydrocyclopent[a]indene ring systems, spiro-fused to the 9-position of a 9,10-dihydroanthracene moiety. Evidence of a photochemically initiated diradical cyclization pathway is proposed on the basis of (i) hydrogen abstraction from reaction with 1,4-cyclohexadiene (1,4-CHD) and (ii) the observation of 1,4-addition of benzene (solvent). The reaction was further analyzed by a complete density functional theory (DFT) study, using an unrestricted approach (UBLYP) with a 6-31G* basis set for the open-shell triplet states of the reactants, products, and diradical intermediates to model the photochemical nature of observed transformation. A mechanism detailing the observed cyclization/addition reaction is proposed.     

Synthesis and NMR studies of (13)C-labeled vitamin D metabolites

Isotope-labeled drug molecules may be useful for probing by NMR spectroscopy the conformation of ligand associated with biological hosts such as membranes and proteins. Triple-labeled [7,9,19-(13)C(3)]-vitamin D(3) (56), its 25-hydroxylated and 1 alpha,25-dihydroxylated metabolites (58 and 68, respectively), and other labeled materials have been synthesized via coupling of [9-(13)C]-Grundmann's ketone 39 or its protected 25-hydroxy derivative 43 with labeled A ring enyne fragments 25 or 26. The labeled CD-ring fragment 39 was prepared by a sequence involving Grignard addition of [(13)C]-methylmagnesium iodide to Grundmann's enone 28, oxidative cleavage, functional group modifications leading to seco-iodide 38, and finally a kinetic enolate S(N)2 cycloalkylation. The C-7,19 double labeling of the A-ring enyne was achieved by the Corey-Fuchs/Wittig processes on keto aldehyde 11. By employing these labeled fragments in the Wilson-Mazur route, the C-7,9,19 triple-(13)C-labeled metabolites 56, 58, and 68 as well as other (13)C-labeled metabolites have been prepared. In an initial NMR investigation of one of the labeled metabolites prepared in this study, namely [7,9,19-(13)C(3)]-25-hydroxyvitamin D(3) (58), the three (13)C-labeled carbons of the otherwise water insoluble steroid could be clearly detected by (13)C NMR analysis at 0.1 mM in a mixture of CD(3)OD/D(2)O (60/40) or in aqueous dimethylcyclodextrin solution and at 2 mM in 20 mM sodium dodecyl sulfate (SDS) aqueous micellar solution. In the SDS micellar solution, a double half-filter NOESY experiment revealed that the distance between the H(19Z) and H(7) protons is significantly shorter than that of the corresponding distance calculated from the solid state (X-ray) structure of the free ligand. The NMR data in micelles reveals that 58 exists essentially completely in the alpha-conformer with the 3 beta-hydroxyl equatorially oriented, just as in the solid state. The shortened distance (H(19Z))-H(7)) in micellar solutions as compared to that in the solid state is most easily rationalized on the basis that the 5(10)-torsion angle in 58 is decreased in micellar solutions as compared to that in the solid state.     

Disposable sodium electrodes

In this paper we describe a disposable sodium sensor in double matrix membrane technology. This sensor is prepared from filter paper with an evaporated silver conducting line on one side. For insulation the sensor is laminated with a pre-perforated heat-sealing film. A defined volume of an ion-sensitive polymer matrix membrane cocktail is filled into one hole. So an ion-sensitive coated film sensor in double matrix membrane technology is produced. The double matrix membrane is formed by the polymer matrix membrane and by the additional filter paper matrix. The response behaviour of the sodium electrode is comparable with conventional macro ion-selective electrodes. By this technology a mass production of low cost sensors is possible.     

A NMR method for the analysis of mixtures of alkanes with different deuterium substitutions

¹³C NMR at 125.76 MHz with ¹H and ²H decoupling, ²H NMR at 76.77 MHz with ¹H decoupling, and ¹H NMR at 500.14 MHz with ²H decoupling were employed as analytical tools to study the complex mixtures of deuterated ethanes resulting from the catalytic H–D exchange of normal ethane with gas-phase deuterium in the presence of a platinum foil. Reference samples consisting of 1:1 binary mixtures of pure normal ethane and ethane-d_n (n=1–6) were used to identify the peak positions in the ¹³C, ²H, and ¹H NMR spectra due to each individual isotopomer, and the effect of isotopic substitution on the chemical shifts was determined in each case. While the NMR of all three nuclei worked well for the identification of the individual components of the 1:1 standard mixtures, both ¹H and ²H NMR suffered from inadequate resolution when studying complex reaction mixtures because of the broadening of the lines due to ¹H–¹H (¹H NMR) and ²H–²H (²H NMR) couplings. ¹³C NMR was therefore determined to be the method of choice for the quantitative analysis of the reaction mixtures. Using the ¹³C NMR results, a correlation that takes into account the primary and secondary isotope substitution effects on chemical shifts was deduced. This equation was used for the identification of the individual components of the mixtures, and integration of the individual observed resonances was then employed for quantification of their composition. This study shows that ¹³C NMR with ¹H and ²H decoupling is a viable procedure for studying mixtures of deuterated ethanes. Furthermore, the additivity of the isotopic effects on chemical shifts and the transferability of the values obtained with ethane to other molecules makes this approach general for the analysis of other isotopomer mixtures.     

Charge effects during surface analysis of poorly conducting inorganic materials

Summary The properties of surfaces and interfaces often determine the behaviour of materials in a given application: typical examples are all kinds of corrosion, segregation, sensor activity, wear and friction, adhesion of coatings, joining processes, sintering, etc. It is the aim of this paper to provide materials scientists with a better understanding of the limits of applying modern surface analysis methods (SIMS, AES, etc.) to materials with low room temperature electrical conductivity like most ceramics and glasses. One feature common to all methods deserves special attention: this is the influence of surface and near surface charges on the distribution of mobile ionic species in the near surface region of the sample to be analyzed. The origin of these charges and their order of magnitude as a function of the experimental parameters can be deduced from charge balance considerations: the main result is that self-compensating methods should be most favorable.     

Calculation of Reactivity Ratios and Sequence Distributions in Copolymers from Monomers 13C-NMR Data

A screening procedure has been developed to predict the average sequence distribution in vinyl copolymers from monomer ¹³C-NMR data. The ¹³C-NMR absorption frequencies of the carbon atoms of the polymerizable double bond are used to calculate the Alfrey-Price Q and e values as previously described by Borchardt and Dalrymple. These, in turn, are used to calculate the monomer reactivity ratios. Reactivity ratios for 54 copolymerizations were calculated by this procedure and compared to literature values. The copolymer sequence distribution may then be determined by means of a computer program written by Harwood. The sequence distribution in copolymers of methacrylic acid and dimethyl-aminoethyl methacrylate, acrylonitrile and methyl methacrylate, 1,1-dichloroethylene and methacrylonitrile, ethyl acrylate and n-butyl methacrylate, and acrylamide and sodium 2-acrylamido-2-methylpropane sulfonate were calculated from reactivity ratios derived from ¹³C-NMR data and compared to literature values. This procedure may be used to calculate the reactivity ratios from ¹³C-NMR spectra of monomers for which no Q and e values are known. By this method the average sequence distribution of such monomers in copolymers may be predicted, significantly reducing the number of copolymers to be synthesized and tested for use in various applications.