Protonierte fluorenon-ionen aus N.N-diarylsubstituierten 1.4-diazaspiro[4.4]nonanen: Eine neue elektronenstossinduzierte arylwanderung

Using collisional activation mass spectrometry (CA) and suitable reference ions it can be shown that the title compounds rearrange to protonated fluorene ions. The mechanism of this novel aryl migration as well as possible alternative ion structures are discussed.     

Electron-phonon interaction and coulomb pseudopotential in AuGa alloys from resistivity and superconductivity measurements

Measurements of the electrical resistivity as a function of temperature from 250 to 270 K for Au and f.c.c. phase AuGa alloys are presented. The linear dependence of the resistivity with temperature and previous results of the superconducting transition temperature of the alloys are used to obtain a value for T_c of pure Au. From these results a new method is introduced to estimate the Coulomb pseudopotential μ¹ for gold.     

The fragmentation of 5-phenyl-1,4-benzodiazepin-2-ones. Mechanism for the formation of [M ? H]+

The fragmentations under electron impact of 5-phenyl-1,4-benzodiazepin-2-ones are investigated with the aid of high resolution, metastable decompositions and deuterium labeling. Based on our data a mechanism for the formation of the [M – H]⁺ ion is proposed. It is shown that the [M – CHO]⁺ ion is probably formed by two different pathways. Data on two minor fragment ions give support to the structure proposed for the [M – CHO]⁺ ion.     

Resistivity of dilute AlMg and AlMn between 0° and 100°C a generalized approach

We have measured the resistivity of $\text{Al}$Mg and $\text{Al}$Mn up to 0.5 at. % impurity concentration between 0° and 100°C. The results for the resistivity for both systems can be analysed within one generalized model in which spinfluctuations as well as changes in the electron-phonon interaction are considered. For $\text{Al}$Mn a calculation of the impurity contribution to d?/dT is attempted. For $\text{Al}$Mg there are indications that the superconducting T_c will increase with Mg concentration.     

Empirical correlation between the superconducting Tc and the Hall constant

It is found that the superconducting transition temperature and the galvano-magnetic Hall constant at room temperature are correlated in a large number of non-transition elements and alloys.     

High-performance liquid chromatographic enantioseparation of flavanones on 2-hydroxy- 3-methacryloyloxypropyl beta-cyclodextrin copolymer coated silica phase

Chromatographic resolution of four flavanones is achieved by reversed-phase high-performance liquid chromatography (HPLC) on a chiral stationary phase based on silica coated with a (2-hydroxy-3-methacryloyloxypropyl beta-cyclodextrin-co-N-vinylpyrrolidone) copolymer. The influence of the mobile phase water content and the nature of the organic modifier on the retention and resolution is evaluated. Monosubstituted flavanones are better resolved than the unsubstituted one. Nevertheless, the 6- and 7-methoxy substituents enhance retention and chiral recognition to polymeric beta-cyclodextrin stationary phase less than the 6-hydroxy group.     

Balancing capacity and lot sizes

In many companies there is an on-going discussion about capacity, capacity utilization and capital tied up in inventories. However, traditional models such as the EOQ model only include capacity considerations in the set-up cost, or in the cost of a replenishment order. This implies e.g. that they do not consider the set-up time as a capacity constraint. Furthermore, in these models the set-up cost is usually treated as a constant, even though the opportunity cost for capacity in general is dependent upon the capacity utilization.The purpose of this paper is to derive an analytical model for the balancing of capacity and lot sizes. The model includes costs for capacity, work-in-process (queueing, set-up, and processing time), and finished goods inventory. The total costs are minimized with respect to capacity. Then, the corresponding, recommended lot sizes are determined. The model was tested with data from a Swedish manufacturing company. The results turned out to coincide with experiences of the company in many important respects. The model offers production management an opportunity to discuss the relationship between capacity, work-in-process, and lot sizes.     

Polystyrene-graft-polyglycerol resins: a new type of high-loading hybrid support for organic synthesis

The preparation of a dendritic graft polymer by a very efficient synthesis of polyglycerol directly on a polystyrene resin is presented. This one-step process can be performed on a multigram scale to provide a chemically stable polymeric support. The resulting hybrid polymers were fully characterized by diverse analytical methods (NMR, IR, ESEM, UV detection of cleaved protecting groups, and mass-spectrometric methods). They combine a high loading capacity (up to 4.3 mmol g(-1)) with good swelling properties in a wide range of solvents (including water), which is the major drawback for many existing solid phase supports. In comparison to the widely employed PEGylated resins, these hybrid materials offer a 10-fold higher loading capacity. Their suitability as supports for organic synthesis and for the immobilization of reagents has been demonstrated. These materials also swell in water, and consequently, it should be possible to use these new hybrid materials for synthesis in protic solvents.     

Magnetic properties of ferromagnetic quasi-1D copper-peptide compounds: exchange interactions and very low temperature phase transitions

The magnetic properties of the Cu(II)-peptide compounds (L-tyrosyl-L-leucinato)Cu(II) and (L-tryptophyl-glycinato)Cu(II), to be identified as Cu(II)Tyr-Leu and Cu(II)Trp-Gly, respectively, have been investigated by specific heat (0.08 < T < 28 K), dc magnetization (2 < T < 80 K, with B(0) = mu(o)H < or = 9 T), and ac magnetic susceptibility (with B(0) = 0 for 0.03 < T < 3 K and B(0) up to 9 T for 2 < T < 80 K) measurements. Above approximately 1 K, the specific heat and magnetization of both compounds display a ferromagnetic (FM) spin chain behavior sustained by syn-anti carboxylate bridges connecting equatorially Cu(II) ions at about 5 A. To model this behavior, we calculated the eigenvalues of Heisenberg chains with up to 20 spins 1/2 and used the method of Bonner and Fisher. A global fit of the model to the specific heat and magnetization data gives 2J(0)/k(B) = 3.60(5) K and 2.59(5) K for the intrachain exchange interactions in Cu(II)Tyr-Leu and Cu(II)Trp-Gly, respectively (H(ex)(i,j) = -2J(0) S(i).S(j)). These values of 2J(0) are discussed in terms of structural properties of the carboxylate bridges in the two compounds. Using the parameters obtained from the global fit, we calculated isothermal susceptibilities in agreement with the ac susceptibilities measured with small applied dc magnetic fields. However, the ac susceptibility measured with applied dc fields larger than 1 T lie between the values calculated for the isothermal and adiabatic susceptibilities. At 0.16 K for Cu(II)Tyr-Leu and 0.53 K for Cu(II)Trp-Gly, the observed specific heat and magnetic susceptibility display peaks associated to three-dimensional magnetic phase transitions. The interchain exchange couplings 2J(1) producing the 3D magnetic order are ferromagnetic and have magnitudes 2J(1)/k(B) approximately 0.015 and 0.073 K for Cu(II)Tyr-Leu and Cu(II)Trp-Gly, respectively.