Covalent functionalization of silicon nitride surfaces for anti-biofouling and bioselective capture

Microsieves – microengineered membranes – have been introduced in microfiltration technology as a new generation of inorganic membranes. The thin membranes are made of silicon nitride (SixN4), which gives the membranes outstanding features, such as chemical inertness and high mechanical strength. Microsieves have very well-defined pore size and pore shape, with an extremely homogeneous size distribution and high porosity. As a result, high-flux performance and excellent selectivity may be achieved. However, biofouling issues exert limitations on the application of microsieves in filtration and diagnostics. Surface functionalization was found to be a feasible way to minimize biofouling, but also to achieve biorecognition in microbiological applications. The aim of this thesis is to improve microsieve performance in biological applications by means of surface functionalization with organic coatings for protein repellence and selective capture of microorganisms. In this thesis, SixN4 surfaces were functionalized with organic monolayers via stable Si C and N-C linkages. Coatings to render SixN4 surfaces protein repellent were studied in depth by two approaches: grafting of ethylene oxide monolayers onto the surface (Chapter 2); and grafting of zwitterionic polymers from the surface (Chapter 3). UV induced surface modification with oligo(ethylene oxide) chains with three (EO3) and six (EO6) units and the detailed characterization of these modified surfaces are described in Chapter 2. Successful attachment of EO3 and EO6 on SixN4 surfaces was achieved. The modified surfaces exhibit excellent protein repellence in bovine serum albumin (BSA) solution (~ 94%), but only moderate (~ 80%) protein repulsion was observed in fibrinogen (FIB) solution. This observation motivated the study towards grafting zwitterionic polymer brushes from SixN4 surfaces for improved protein repellence. A new method to grow zwitterionic polymers from monolayers containing tertiary bromides, via atom transfer radical polymerization (ATRP) was developed. The zwitterionic polymer coated surfaces showed excellent protein repellence in FIB solution (> 99%), while exhibiting very stable performance in PBS during one week, i.e., unchanged thickness, no hydrolysis of the polymers occurred and protein repellence in FIB solution remained constant. The use of microsieves as detection platform for microorganisms was explored in Chapter 4. Microorganisms can be caught by microsieves whose pore sizes are smaller than the microorganisms while allowing an easy flow-through of other components. However, detection capacity of microsieves is severely hampered by fouling issues. To avoid this problem, the use of microsieves with pore sizes larger than the microorganisms, in combination with immobilized antibodies was investigated in Chapter 4. Anti Salmonella antibodies were immobilized onto epoxide monolayers on microsieve surfaces by reaction with the primary amines present in the antibody. The antibody-coated microsieves showed excellent detection of Salmonella with high sensitivity and selectivity, significantly improving detection efficiency in crude biological samples, and reducing analysis times. The capture efficiency of Salmonella in milk samples was, however, found to be lower than that achieved in buffered solution. Most likely, this is due to nonspecific adsorption of milk proteins on the antibody-coated microsieves. In addition, the use of a blocking solution before incubation with microorganism solution remained an essential step in order to avoid the occurrence of interfering background fluorescence. In order to minimize these problems, the incorporation of antibodies on top of protein-repellent zwitterionic polymers coated on SixN4 surfaces was studied in Chapter 5. Anti-Salmonella antibodies were immobilized on zwitterionic polymer brushes coated SixN4 surfaces through the bromide moieties retained at the end of the polymer chain after ATRP. Antibody-functionalized zwitterionic polymers adsorbed only minimal amounts of FIB, indicating excellent protein repellence of the modified surfaces. Moreover, anti-Salmonella antibodies immobilized onto zwitterionic surfaces exhibit highly selective capture and improved sensitivity, as compared to antibodies on epoxide coated surfaces. This achievement offers a new approach that enables highly sensitive and selective detection of microorganism, while minimizing nonspecific adsorption of proteins that are not of interest. In Chapter 6, an overview is given of the most important findings presented in the thesis. Recommendations, as well as additional ideas on how to bring this research into industrial application are discussed. </p

Towards a sensitive search for variation of the fine structure constant using radio-frequency E1 transitions in atomic dysprosium

It has been proposed that the radio-frequency electric-dipole (E1) transition between two nearly degenerate opposite-parity states in atomic dysprosium should be highly sensitive to possible temporal variation of the fine structure constant ($\alpha$) [V. A. Dzuba, V. V. Flambaum, and J. K. Webb, Phys. Rev. A {\bf 59}, 230 (1999)]. We analyze here an experimental realization of the proposed search in progress in our laboratory, which involves monitoring the E1 transition frequency over a period of time using direct frequency counting techniques. We estimate that a statistical sensitivity of |\adota| \sim 10^{-18}/yr may be achieved and discuss possible systematic effects that may limit such a measurement.Comment: 8 pages, 7 figure

Xmrk, Kras and Myc transgenic zebrafish liver cancer models share molecular signatures with subsets of human hepatocellular carcinoma

10.1371/journal.pone.0091179PLoS ONE93-POLN

Tight bounds for classical and quantum coin flipping

Coin flipping is a cryptographic primitive for which strictly better protocols exist if the players are not only allowed to exchange classical, but also quantum messages. During the past few years, several results have appeared which give a tight bound on the range of implementable unconditionally secure coin flips, both in the classical as well as in the quantum setting and for both weak as well as strong coin flipping. But the picture is still incomplete: in the quantum setting, all results consider only protocols with perfect correctness, and in the classical setting tight bounds for strong coin flipping are still missing. We give a general definition of coin flipping which unifies the notion of strong and weak coin flipping (it contains both of them as special cases) and allows the honest players to abort with a certain probability. We give tight bounds on the achievable range of parameters both in the classical and in the quantum setting.Comment: 18 pages, 2 figures; v2: published versio

Impact of foreign investment on household welfare: Evidence from Vietnam

Available online 27 July 2019We examine the impact of foreign direct investment in Vietnam on household and individual welfare and on migration using survey data for the period 2002 to 2016. We find that higher revenue from foreign invested firms measured at province level and normalized on population is associated with a variety of positive outcomes. At household level, income and expenditures per capita are higher and poverty incidence is lower. At individual level, non-farm employment and wages are higher. And at commune level, in-migration is higher. However, although these improvements register as statistically signficant, the magnitudes in economic terms are modest.Anh Tuan Bui, Cuong Viet Nguyen, Thu Phuong Pha

A generalized empirical interpolation method : application of reduced basis techniques to data assimilation

In an effort to extend the classical lagrangian interpolation tools, new interpolating methods that use general interpolating functions are explored. The method analyzed in this paper, called Generalized Empirical Interpolation Method (GEIM), belongs to this class of new techniques. It generalizes the plain Empirical Interpolation Method by replacing the evaluation at interpolating points by application of a class of interpolating linear functions. The paper is divided into two parts: first, the most basic properties of GEIM (such as the well-posedness of the generalized interpolation problem that is derived) will be analyzed. On a second part, a numerical example will illustrate how GEIM, if considered from a reduced basis point of view, can be used for the real-time reconstruction of experiments by coupling data assimilation with numerical simulations in a domain decomposition framework

Pharmacogenetic variants influence tamoxifen's estrogenic effect on bone density

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/109849/1/cptclpt200586.pd

Study on N-NH4+ removal from underground water by MBBR case study in Bach Khoa Ward, Hanoi, Vietnam

Moving bed biofilm reactor (MBBR) using porous carrier plastic material, Polyurethane (DHY-1) which has high porosity 92% -96%, has been researched and applied in many water treatment systems. The advantage of the material is that it has high surface area of about 6,000-12,000m2/m3 thereby increasing the density of biomass. In this research, they were tried to treat ammonium nitrogen (N-NH4+) in the ground water. It was found that the treatment efficiency was more than 90% with N-NH4+ concentration of 10-12mg/l. Different densities of carrier materials as well as different influent flow rates have significant impacts on the removal efficiency. The study showed that treatment capacity decreased with high influent flow rate while increased with high density of carrier materials

Singularities of bi-Hamiltonian systems

We study the relationship between singularities of bi-Hamiltonian systems and algebraic properties of compatible Poisson brackets. As the main tool, we introduce the notion of linearization of a Poisson pencil. From the algebraic viewpoint, a linearized Poisson pencil can be understood as a Lie algebra with a fixed 2-cocycle. In terms of such linearizations, we give a criterion for non-degeneracy of singular points of bi-Hamiltonian systems and describe their types