Anwendungen der phasentransfer-katalyse—4: Halogenaustausch und reaktivitäten bei dibrom-, chlorbrom- und dichlorcarben

Exchange with external halogenide is possible in phase transfer catalytical generations of dihalocarbenes. CHBrCl₂ and CHBr₂Cl yield adducts of all three possible combinations, CBr₂, CBrCl and CCl₂. Consumption of haloform is accelerated by the presence of olefin, the amount of hydrolysis competing with carbene formation, however, is reduced thereby. Contrary to claims in the literature no optical induction is observed in CX₂ additions. These results support once more the intermediacy of free CX₂. CBr₂ is more reactive and electrophilic than CCl₂ under phase transfer catalysis conditions, again contrary to literature claims. An example of a differing mode of reaction of chloroform and bromoform is given.     

Spectra of delay-coupled heterogeneous noisy nonlinear oscillators

Complex systems are described by a large number of variables with strong and nonlinear interactions. Such systems frequently undergo regime shifts. Combining insights from bifurcation theory in nonlinear dynamics and the theory of critical transitions in statistical physics, we know that critical slowing down and critical fluctuations occur close to such regime shifts. In this paper, we show how universal precursors expected from such critical transitions can be used to forecast regime shifts in the US housing market. In the housing permit, volume of homes sold and percentage of homes sold for gain data, we detected strong early warning signals associated with a sequence of coupled regime shifts, starting from a Subprime Mortgage Loans transition in 2003–2004 and ending with the Subprime Crisis in 2007–2008. Weaker signals of critical slowing down were also detected in the US housing market data during the 1997–1998 Asian Financial Crisis and the 2000–2001 Technology Bubble Crisis. Backed by various macroeconomic data, we propose a scenario whereby hot money flowing back into the US during the Asian Financial Crisis fueled the Technology Bubble. When the Technology Bubble collapsed in 2000–2001, the hot money then flowed into the US housing market, triggering the Subprime Mortgage Loans transition in 2003–2004 and an ensuing sequence of transitions. We showed how this sequence of couple transitions unfolded in space and in time over the whole of US.     

Transient behavior in systems with time-delayed feedback

We investigate the transient times for the onset of control of steady states by time-delayed feedback. The optimization of control by minimizing the transient time before control becomes effective is discussed analytically and numerically, and the competing influences of local and global features are elaborated. We derive an algebraic scaling of the transient time and confirm our findings by numerical simulations in dependence on feedback gain and time delay.     

Analytical solution for quenching of hot rolled aluminium plates without passing through C-curve

Journal of Thermal Analysis and Calorimetry - At the end of the hot rolling process, quenching is deployed for obtaining the desired microstructure and mechanical properties. During the quenching...     

On pseudoparticle solutions in Yang's theory of gravity

Within the framework of differential geometry, Yang's parallel-displacement gauge theory is considered with respect to pure gravitational fields. In afour-dimensional Riemannian manifold it is shown that thedouble self-dual solutions obey Einstein's vacuum equations with the cosmological term, whereas the doubleanti-self-dual configurations satisfy the Rainich conditions of Wheeler'sgeometrodynamics. Conformal methods reveal that the gravitational analog of the instanton or pseudoparticle solution of Yang-Mills theory was already known to Riemann.