Semi-parametric Estimation of the Second Order Parameter in Statistics of Extremes

We present a class of semi-parametric estimators for the second order parameter related to a probability distribution with a regularly varying tail. The second order parameter plays an important role whenever dealing with optimization problems in statistics of extreme values. Consistency and asymptotic normality are proven under appropriate conditions.     

Modulation of A 10 keV ion beam

Density modulation of a 10 keV - 1 mA - He⁺-ion beam at frequencies up to MHz has been achieved by deflecting the beam ions across an aperture. The modulation mechanism depends mainly on the periodical disturbance of the beam space charge neutrality.     

Design of a pistonphone

A harmonic pressure generator is developed based on the principle of plane sound waves. The pressure is generated in a cylindrical enclosure by a piston with a flat bottom; the piston is driven by a coil situated in a radial magnetic field. The coil is supplied with an alternating current; the corresponding amplitudes of the piston are measured by a precision accelerometer mounted inside the hollow piston. The apparatus was designed to calibrate the probe microphone described in [1] over a frequency range from 50 to 4000 Hz, with an accuracy of a few percent.     

Supersonic ejectors with mixing at constant cross-section

Summary Based upon the already classical concept of a mixing process divided into an expansion- and a mixing region, a simple integral theory was developed in part I.In this part is described an extensive experimental investigation in which the parameters are varied over a large range; e.g. it is found that a large primary after-expansion can be allowed provided the mixing tube is convergent in the region of expansion. Furthermore it is shown that the theory offers an explanation for the essential experimental phenomena; quantitatively corrections are necessary in points with a complex flow structure.Some general directions are given for the optimum design of an ejector.     

Influencing the selectivity of zeolite Y for triglycine adsorption

In prior work we studied the adsorption of triglycine on zeolite Y under reference conditions. This study aims to solve the question of which adsorbent properties and process conditions influence the adsorption triglycine from an aqueous solution by zeolite Y. Relevant zeolite parameters to study are: the amount of acidic sites (Si/Al(2) ratio), counter ion, micropore structure. Process conditions that may influence triglycine adsorption are pH, other components such as sugars, amino acids and salts, and temperature. Adsorption of triglycine on zeolite HY is dominated by ionic interaction. The capacity and selectivity of zeolite HY for triglycine can be changed by choosing different Si/Al(2) ratios or changing the counter ion. The presence of cations and basic anions in solutions reduces triglycine adsorption. Fructose and glycine have no significant influence on triglycine adsorption. Temperature only has a slight influence. The pore structure of zeolite Y is not a critical factor for triglycine adsorption, provided pores are accessible to triglycine and in the micropore range (<2 nm). While this allows other zeolites than zeolite Y to be applied, the presence of the supercage structure of zeolite Y is beneficial to obtain better adsorption of triglycine in its neutral form.     

A fast, rigorous technique for computing the regulator of a real quadratic field

We present a new algorithm for computing the regulator of a real quadratic field based on an algorithm for unconditionally verifying the correctness of the regulator produced by a subexponential algorithm, that runs in expected time under the Generalized Riemann Hypothesis. The correctness of our algorithm relies on no unproven hypotheses and is currently the fastest known unconditional algorithm for computing the regulator. A number of implementation issues and performance enhancements are discussed, and we present the results of computations demonstrating the efficiency of the new algorithm.

     

Electrophoretic ratcheting of spherical particles in well/channel microfluidic devices: Making particles move against the net field

We examine the electrophoresis of spherical particles in microfluidic devices made of alternating wells and narrow channels, including a system previously used to separate DNA molecules. Our computer simulations predict that such systems can be used to separate spherical particles of different sizes that share the same free-solution mobility. Interestingly, the electrophoretic velocity shows an inversion as the field intensity is increased: while small particles have higher velocities at low field, the situation is reversed at high fields with the larger particles then moving faster. The resulting nonlinearity suggests that asymmetric pulsed electric fields could be used to build separation ratchets: particles then have a net size-dependent velocity in the presence of a zero-mean external field. Exploiting the inversion mentioned above, we show how to design pulsed field sequences that make particles move against the mean field (an example of negative mobility). Finally, we demonstrate that it is possible to use pulsed fields to make particles of different sizes move in opposite directions, even though their charge have the same sign.     

Thermodynamics and kinetics of imidazole formation from glyoxal, methylamine, and formaldehyde: a computational study

Density functional theory calculations, including Poisson-Boltzmann implicit solvent and free energy corrections, are applied to study the mechanism of experimentally observed imidazole formation from the reaction of glyoxal and methylamine in solution. Our calculations suggest that a diimine species is an important intermediate in the reaction. Under acidic conditions, we find that the diimine acts as a nucleophile in attacking the carbonyl group of either formaldehyde or glyoxal to first generate an acyclic enol intermediate, which then goes on to close the ring and form imidazoles. Our results confirm that formaldehyde and, by extension, other small aldehydes are likely to be incorporated into imidazole ions in the presence of glyoxal and primary amines in clouds and aqueous aerosol. This is a new mechanism of aerosol formation by formaldehyde, the most abundant aldehyde in the atmosphere. The amount of aerosol formed will depend on the amounts of glyoxal and amines present.     

HPAI 9G DNAChip: discrimination of highly pathogenic influenza virus genes

The HPAI 9G DNAChip discriminates the single nucleotide polymorphism of H5N1, H5N1 (K), and H5N3 in a 60:1 ratio. It allows the simultaneous detection of highly pathogenic avian influenza viruses with a signal to background ratio of 200 and 100% target-specific hybridization in 30 min at 25 °C.     

Memory effects during the unbiased translocation of a polymer through a nanopore

Through a detailed Langevin dynamics simulation study, the role of memory effects during unbiased translocation is explored. Tests are devised to uncover the presence of memory effects by directly measuring forward/backward-correlated motion as well as the associated change in the dynamics. Conducting these tests at low and high viscosities, a range of behaviours across different time scales is revealed: short-time forward correlations at all viscosities, quasi-static behaviour at low viscosity, and long-time backward correlations at high viscosity. By applying these tests at different portions of the translocation process, these memory effects are also shown to vary as translocation proceeds. Combining this information with standard measurements, a physical picture of unbiased translocation as the diffusion of a local minimum is proposed.