Impact of electric-field dependent dielectric constants on two-dimensional electron gases in complex oxides

High-density two-dimensional electron gas (2DEG) can be formed at complex oxide interfaces such as SrTiO3/GdTiO3 and SrTiO3/LaAlO3. The electric field in the vicinity of the interface depends on the dielectric properties of the material as well as on the electron distribution. However, it is known that electric fields can strongly modify the dielectric constant of SrTiO3 as well as other complex oxides. Solving the electrostatic problem thus requires a self-consistent approach in which the dielectric constant varies according to the local magnitude of the field. We have implemented the field dependence of the dielectric constant in a Schrodinger-Poisson solver in order to study its effect on the electron distribution in a 2DEG. Using the SrTiO3/GdTiO3 interface as an example, we demonstrate that including the field dependence results in the 2DEG being confined closer to the interface compared to assuming a single field-independent value for the dielectric constant. Our conclusions also apply to SrTiO3/LaAlO3 as well as other similar interfaces

Polymer/Iron Oxide Nanoparticle Composites-A Straight Forward and Scalable Synthesis Approach

Magnetic nanoparticle systems can be divided into single-core nanoparticles (with only one magnetic core per particle) and magnetic multi-core nanoparticles (with several magnetic cores per particle). Here, we report multi-core nanoparticle synthesis based on a controlled precipitation process within a well-defined oil in water emulsion to trap the superparamagnetic iron oxide nanoparticles (SPION) in a range of polymer matrices of choice, such as poly(styrene), poly(lactid acid), poly(methyl methacrylate), and poly(caprolactone). Multi-core particles were obtained within the Z-average size range of 130 to 340 nm. With the aim to combine the fast room temperature magnetic relaxation of small individual cores with high magnetization of the ensemble of SPIONs, we used small (<10 nm) core nanoparticles. The performed synthesis is highly flexible with respect to the choice of polymer and SPION loading and gives rise to multi-core particles with interesting magnetic properties and magnetic resonance imaging (MRI) contrast efficacy

Учебная программа по учебной дисциплине "Теоретическая механика"

Учебная программа "Теоретическая механика" кафедры "Механика" для дневной формы получения образования: общее количество часов-350, трудоемкость учебной дисциплины — 10 з.е., форма контроля знаний — зачет, экзамен, РГР

Sensitive magnetic biodetection using magnetic multi-core nanoparticles and RCA coils

We use functionalized iron oxide magnetic multi-core particles of 100\ua0nm in size (hydrodynamic particle diameter) and AC susceptometry (ACS) methods to measure the binding reactions between the magnetic nanoparticles (MNPs) and bio-analyte products produced from DNA segments using the rolling circle amplification (RCA) method. We use sensitive induction detection techniques in order to measure the ACS response. The DNA is amplified via RCA to generate RCA coils with a specific size that is dependent on the amplification time. After about 75\ua0min of amplification we obtain an average RCA coil diameter of about 1\ua0\ub5m. We determine a theoretical limit of detection (LOD) in the range of 11 attomole (corresponding to an analyte concentration of 55 fM for a sample volume of 200\ua0\ub5L) from the ACS dynamic response after the MNPs have bound to the RCA coils and the measured ACS readout noise. We also discuss further possible improvements of the LOD