über den Temperaturkoeffizienten der Viskosität von Flüssigkeiten im Zusammenhang mit der Struktur von Kautschuk in Lösung

Colloid and Polymer Science -     

Auf ein Knallgasgebl?se

Ohne Zusammenfassung     

Side-chain oxidation of some phenyl-substituted alcohols in aqueous solution: Formation and fragmentation of radical-cations

The reactions of the hydroxyl radical (at low pH) and SO₄^−. have been employed to oxidize a number of phenyl-substituted alcohols in aqueous solution; ESR spectroscopy has been employed to study directly the radicals formed by fragmentation of first-formed radical-cations. Examples of deprotonation (to give benzyl radicals), C_α−C_β bond scission (e.g. PhCH₂CH₂OH to PhCH₂ ^.) and longer-range fragmentation (e.g. PhCH₂CH₂CMe₂OH to PhCH₂CH₂ ^.) are described and discussed: evidence is obtained for intramolecular nucleophilic attack as a route for overall electron-transfer from side-chain to aromatic ring. Solvation of the proton and of oxygen-conjugated carbonium ions is thought, at least in part, to account for differences between fragmentations induced in the gaseous and aqueous phases.     

Eine neue Form von Verbrennungsr?hren

Ohne Zusammenfassung     

Zur Herstellung chemisch reiner Phosphors?ure

Ohne Zusammenfassung     

The S.M.A.R.T. (small mass,affordable, rapid,transfer-less) digestion method for heavy metal determinations

The S.M.A.R.T. (small mass, affordable, rapid, transfer-less) digestion method was developed to determine heavy metal concentrations in small sample masses. The S.M.A.R.T. digestion method is a hot water bath digestion where sample digestion and dilution are performed in the original sample tube. This method is faster than the typical methods used and reduces potential sources of error. Masses as small as 0.01 g have been digested and analysed using this method. The preparation and digestion time is reduced from 10 h to less than 4 h. Acid volumes are reduced from millilitres to microlitres and the only disposable supplies needed are sample tubes and pipette tips. Method accuracy was determined by digesting seven replicates of two standard reference materials using the S.M.A.R.T. method and analysing samples by inductively coupled plasma mass spectrometry. The S.M.A.R.T. digestion method was found to provide excellent recoveries for Al (76 ± 2.7%), Mn (99 ± 11%), Co (92 ± 17%), Ni (93 ± 28%), Cu (109 ± 33%), Zn (97 ± 7.1%), As (108 ± 20%), Sr (90 ± 12%), Mo (84 ± 23%), Ag (91 ± 1.8%), Cd (95 ± 6.2%), Sn (139 ± 52%) and Pb (95 ± 22%). This study has successfully developed an efficient and reproducible digestion method for heavy metal determination in limited biomass samples.     

Deformation-induced accelerated dynamics in polymer glasses

Molecular dynamics simulations are used to investigate the effects of deformation on the segmental dynamics in an aging polymer glass. Individual particle trajectories are decomposed into a series of discontinuous hops, from which we obtain the full distribution of relaxation times and displacements under three deformation protocols: step stress (creep), step strain, and constant strain rate deformation. As in experiments, the dynamics can be accelerated by several orders of magnitude during deformation, and the history dependence is entirely erased during yield (mechanical rejuvenation). Aging can be explained as a result of the long tails in the relaxation time distribution of the glass, and similarly, mechanical rejuvenation is understood through the observed narrowing of this distribution during yield. Although the relaxation time distributions under deformation are highly protocol specific, in each case they may be described by a universal acceleration factor that depends only on the strain.     

Optimal Control of Non-convex Measure-driven Differential Inclusions

Necessary conditions for optimality in control problems with differential-inclusion dynamics have recently been developed in the non-convex case by Clarke, Vinter, and others. Using appropriate reparametrizations of the time variable, we extend these results to systems whose dynamics involve a differential inclusion where a vector-valued measure appears. An auxiliary result central to our proof is an extension of existing free end-time necessary conditions to Clarke’s stratified framework.