LOCAL DISTORTIONS AND VOLUME CHANGES IN SEMICONDUCTORS - DONORS IN SILICON

Experiments giving impurity-induced lattice distortion can measure quite distinct quantities. In particular EXAFS (extended X-ray fine structure) measures nearest-neighbour distances, whereas both volume changes and recent spectroscopic data measure long-range displacements. The relationship between the two depends strongly on the inter-atomic potential. The authors analyse this for impurities in silicon by adopting a variety of current potentials. There is a significant contradiction between the EXAFS results and the other experiments for all of the inter-atomic potentials. This problem may be associated with the high oxygen concentrations of Czochralski crystals used in the EXAFS study

Radioluminescence Based Biochemical Sensing and Imaging Strategies to Measure Local Drug Release and pH

In this dissertation we describe methods for measuring infection relevant biochemical analytes using radioluminescent and ultrasound luminescent materials. Films and nanoparticles fabricated with europium doped gadolinium oxysulfide (Gd2O2S:Eu3+) are used to quantitatively measure radiolabeled pharmaceutical concentration, specifically tritium labeled vancomycin (3H-vancomycin). Europium and dysprosium doped strontium aluminate is used to fabricate an ultrasound modulated, pH sensing film. These methods are indicated for theranostic evaluation of implant associated infection. Bacterial biofilms are inherently resistant to traditional antibiotic treatment and can coat biomedical implants. These biofilm related infections are difficult or impossible to eradicate non-invasively. As a result, implant coatings for early infection detection and prevention are a promising avenue of research. Non-invasive measurement of drug release is an important metric for development of effective treatment strategies because dosage must be sustained within a therapeutic window to be effective. In vitro methods of evaluating drug release are unable to replicate biological conditions and variability seen within patients. Furthermore, early detection of implant associated infection can aid early diagnosis and treatment to mitigate infection severity. For infection prevention, using a Gd2O2S:Eu3+ film we are able to quantitatively measure antibiotic concentration at the implant surface, through 5 mm of tissue. We also demonstrate proof of principle for application of this technique with synthesized Gd2O2S:Eu3+ nanoparticles. For early detection of infection, we have developed an ultrasound luminescent chemical imaging modality, and pH sensing film, to map local acidosis due to bacterial biofilm growth at the implant surface

Diffusion and jump-length distribution in liquid and amorphous Cu33_{33}Zr67_{67}

Using molecular dynamics simulation, we calculate the distribution of atomic jum ps in Cu$_{33}$Zr$_{67}$ in the liquid and glassy states. In both states the distribution of jump lengths can be described by a temperature independent exponential of the length and an effective activation energy plus a contribution of elastic displacements at short distances. Upon cooling the contribution of shorter jumps dominates. No indication of an enhanced probability to jump over a nearest neighbor distance was found. We find a smooth transition from flow in the liquid to jumps in the g lass. The correlation factor of the diffusion constant decreases with decreasing temperature, causing a drop of diffusion below the Arrhenius value, despite an apparent Arrhenius law for the jump probability

Numerical modeling of sediment transport in the Danube River: uniform vs. non-uniform formulation

River morphodynamics and sediment transportRiver morphology and morphodynamic

Chaos control in random Boolean networks by reducing mean damage percolation rate

Chaos control in Random Boolean networks is implemented by freezing part of the network to drive it from chaotic to ordered phase. However, controlled nodes are only viewed as passive blocks to prevent perturbation spread. This paper proposes a new control method in which controlled nodes can exert an active impact on the network. Controlled nodes and frozen values are deliberately selected according to the information of connection and Boolean functions. Simulation results show that the number of nodes needed to achieve control is largely reduced compared to previous method. Theoretical analysis is also given to estimate the least fraction of nodes needed to achieve control.Comment: 10 pages, 2 figure