Optimal Multi-TDMA Scheduling in Ring Topology Networks

A scheduling algorithm will be proposed for wireless ring topology networks, utilizing time division multiple access (TDMA) with possible simultaneous operation of nodes. The proposed algorithm finds the optimal schedule to minimize the turnaround time for messages in the network. The properties of the algorithm are mathematically analyzed and proven, and practical test results are also provided

Quantum criticality in a double quantum-dot system

We discuss the realization of the quantum-critical non-Fermi liquid state, originally discovered within the two-impurity Kondo model, in double quantum-dot systems. Contrary to the common belief, the corresponding fixed point is robust against particle-hole and various other asymmetries, and is only unstable to charge transfer between the two dots. We propose an experimental set-up where such charge transfer processes are suppressed, allowing a controlled approach to the quantum critical state. We also discuss transport and scaling properties in the vicinity of the critical point.Comment: 4 pages, 3 figs; (v2) final version as publishe

Reliable microspotting methodology for peptide-nucleic acid layers with high hybridization efficiency on gold SPR imaging chips

One-step direct immobilization of peptide-nucleic acid (PNA) probes onto gold surfaces through Au–S chemistry is critical in terms of generating self-assembled monolayers with high hybridization efficiency. We found that this problem is more severe if the immobilization is performed by contact microspotting to generate PNA arrays. Therefore, here we propose a novel microspotting-based immobilization method to generate PNA arrays with high hybridization efficiency on bare gold surface plasmon resonance imaging (SPRi) chips. The essence of the approach is to spot thiol labelled PNA strands prehybridized with a short complementary DNA strand instead of conventionally used single stranded PNA (ssPNA) probes. After immobilization the complementary DNA strands could be easily removed to activate the surface confined PNA probes. The incubation time and the type of spotting needle also have a marked influence on the hybridization efficiency of the PNA layers. However, we show that if all other conditions remain the same, PNA layers from prehybridized PNA probes exhibit superior hybridization efficiency than those from ssPNA probes

Modulated ultrasound-enabled particle and cell separation in surface acoustic wave microfluidic devices

In recent years considerable amount of research focussed on development of the socalled lab-on-a-chip (LoC) devices that feature complex laboratory sample preparation functions (such as sample washing, sorting, detection or drug delivery) on the microscale. These devices offer lower manufacturing costs, reagent use and the required sample size can be as small as a few microlitres. In this thesis, particle and cell separation is investigated utilising the primary acoustic radiation force in a surface acoustic wave device. After providing review of similar techniques, various phase and frequency modulation methods are proposed for achieving target separation based on size, density or compressibility difference. A special form of primary acoustic radiation force is presented for surface wave devices and is used to obtain particle trajectories in modulated fields for fast analytical comparison of the proposed methods. Experiments for size-based particle separation reveal 95% efficiency and >85% purity for particle size ratio as small as 1.45. Physical property-based separation of iron-oxide and polystyrene microparticles shows even higher figures of merit: >95% efficiency and >90% purity illustrating the versatility of the method. Biological cell separation is performed on human red blood cells and white blood cells, displaying 94% efficiency and >84% purity. Bandpass sorting of particles and cells is also proposed and validated by experiments. Various numerical models are developed for flow and acoustic field simulation, including investigation of secondary acoustic radiation force, and finally a Monte-Carlo study is carried out to verify the superiority of modulated acoustic sorting methods compared to static acoustic field separation techniques

Determination of nucleus density in semicrystalline polymers from non-isothermal crystallization curves.

The present study introduces a new calculation method for obtaining nucleus density formed during non-isothermal crystallization of semicrystalline polymers. Isotactic polypropylene homopolymer (iPP) was used as a semicrystalline model polymer and its crystalline structure was modified using highly efficient nucleating agents or different cooling rates in order to manipulate nucleus density (N) within a wide range. The melting and crystallization characteristics were studied by calorimetry (DSC) and the nucleus density was calculated from the crystallization curves recorded under non-isothermal conditions at constant cooling rate. The nucleus density was correlated to the optical property, in fact to the haze index of injection molded plaques in order to qualify the calculated values of N. It was found that N increases more orders of magnitude in nucleated samples and correlates strongly to the optical properties. These observations are according to our expectations and indicate clearly the reliability of the proposed calculation approach