Spektroskopische Untersuchung der Prim?rprozesse bei der strahleninduzierten Polymerisation von 1,3-Butadien

Ohne Zusammenfassung     

Phenylselenenyl chloride in acetonitrile-water : A highly convenient reagent for hydroxyselenation of olefins and preparation of cyclic ethers from dienes

The reaction of phenylselenenyl chloride with olefins in aqueous acetonitrile affords β-hydroxyalkyl phenyl selenides in excellent yields, providing the most convenient method for hydroxyselenation of olefins so far reported. When the reaction was applied to conjugated dienes, monohydroxyselenated products were obtained in good to excellent yields. From non-conjugated dienes, on the other hand, cyclic ethers containing two phenylseleno groups were produced in good to excellent yields, the first step of this reaction being the hydroxyselenation of one double bond.     

Single-electron-capture cross sections for 0.4–5.0 keV He+ ions incident on alkali-vapor targets

Total cross sections for single-electron capture by He⁺ ions in vapor targets of Cs, Rb, K and Na have been determined in the energy range 0.4–5.0 keV. The energy dependence of the cross-section curves is very similar for all the targets. The cross sections for all the targets are maximum at about the same energy, 1.5 keV. Comparison is made with other reported experimental and theoretical results.     

Paths and edge-connectivity in graphs

Mader proved that for every k-edge-connected graph G (k ≥ 4), there exists a path joining two given vertices such that the subgraph obtained from G by deleting the edges of the path is (k - 2)-edge-connected. A generalization of this and a sufficient condition for existance of 3, 4, or 5 terminus k edge-disjoint paths in graphs are given.     

Selective 1,4-diacetoxylation of conjugated dienes with tellurium (IV) oxide

Oxidation of several linear conjugated dienes with tellurium (IV) oxide and lithium bromide in acetic acid affords an isomeric mixture of the corresponding diacetoxyalkenes (1,2- and 1,4-addition products), 1,4-isomer being highly selectively produced when the ratio of LiBr/TeO₂, is 5–10.     

Mechanics of a particle near the center of a rotating ring

The equations of motion of a test particle moving near the center of a massive rotating ring are derived up to the post-post-Newtonian order of approximation, by using the metric tensor for many body system which is Minkowskian at spatial infinity. Logarithmic divergences due to self-interaction of the ring appear in the equations of motion. These divergences can be removed by the procedure which is similar to the renormalization method in particle physics. In the equations of motion there appears a force directing to the rotation axis and depending on the angular velocity of the ring. This force vanishes when the magnitude of the gravitational constant times the mass of the ring divided by the radius of the ring is about one tenth of the square of the velocity of light. Under this condition it is shown that the relative magnitude of the Coriolis force to the centrifugal force in the equations of motion agrees with the expected one from the equations of motion in a rotating reference frame.     

A mild photoactivated hydrophilic/hydrophobic switch

Surface modification using light is one of the most powerful methods for controlling the physical and chemical properties offunctionalized surfaces. In this paper, we report on systems where soft UV irradiation (lambda = 365 nm) converts a "low" activity fluorocarbon to a "high" activity amine-functionalized surface. An amine-functionalized SAM (self-assembled monolayer) is first masked using a tertiary amine catalyzed reaction with an N-hydroxysuccinimidyl carbonyl reagent. This mild, room-temperature reaction introduces a hydrophobic photocleavable nitrobenzyl "protecting group" terminated with a fluorocarbon end-chain. UV irradiation (lambda = 365 nm) of this hydrophobic/fluorocarbon surface cleaves the nitrobenzyl residue, returning the surface to the original hydrophilic/amine-functionalized state. This provides a mild, generic method of producing surfaces with hydrophilic/hydrophobic patterns or patterned with amine functional residues. Two different protecting groups, one terminated with a single and the other with three fluorocarbon end chains, are compared. In the case of the more bulky protecting group, only a small proportion of the amine residues react, but the surface is equally hydrophobic and the amine residues equally well shielded from further reaction. Surfaces are characterized by X-ray photoelectron spectroscopy, ellipsometry, surface potential, and contact angle measurements. Images of the photopatterned SAMs were obtained using scanning electron microscopy.