No abstract

No abstract

Slow recovery processes of the electronic environment following the electron-capture decay of 111 In can reduce the amplitude of the perturbed ␥␥-angular correlation of a nuclear decay. This effect was used to quantitatively extract recovery rates of an electrically stable environment at the probe ion 111 Cd in La 2 O 3 . The recovery rates depend on the availability of electrons at the probe site, which in turn is governed by the concentration of electron sources and the transport mechanisms. Both properties are experimentally analyzed by variations of the temperature and oxygen partial pressure and by doping with two ͑Ba, Mg͒ and four-valent ions ͑Ce, Zr͒. Tunneling processes between defect levels in the band gap are proposed to account for the temperature dependence of the recovery rates. Unexpectedly, an enhanced electron availability is observed at temperatures below 200 K. The electric field gradients of substitutional 111 Cd and those generated by intrinsic defects and dopants are analyzed. A comparison to the probe ion 111m Cd, not affected by electron capture, is presented.

Modern applications are designed in multiple tiers to separate concerns. Since each tier may run at a separate location, middleware is required to mediate access between tiers. However, introducing this middleware is tiresome and error-prone.We propose a multi-tier calculus and a splitting transformation to address this problem. The multi-tier calculus serves as a sequential core programming language for constructing a multi-tier application. The application can be developed in the sequential setting. Splitting extracts one process per tier from the sequential program such that their concurrent execution behaves like the original program.The splitting transformation starts from an assignment of primitive operations to tiers. A program analysis determines communication requirements and inserts remote procedure calls. The next transformation step performs resource pooling: it optimizes the communication behavior by transforming sequences of remote procedure calls to a stream-based protocol. The final transformation step splits the resulting program into separate communicating processes.The multi-tier calculus is also applicable to the construction of interactive Web applications. It facilitates their development by providing a uniform programming framework for client-side and server-side programming.