Ion-beam mixing in Fe/Si bilayers by singly and highly charged ions: evolution of phases,spike mechanism and possible effects of the ion-charge state

Applied Physics A - Silicide formation and ion beam mixing of Fe/Si bilayers due to Ar-, Xe- and Au-ion irradiations at room and liquid-nitrogen temperatures were investigated. For the study of...     

Effects of slight variations in nutrient loadings on pore plugging in soil columns

The high nutrient concentrations that would exist near the nutrient injection well during the application of cometabolicin situ bioremediation may lead to the development of significant quantities of biomass at this point in the subsurface. This biomass can decrease the porosity of the soil to such an extent that nutrient injection is no longer possible. In this work, experiments were conducted using a porous media biofilm reactor, operated under constant substrate loading conditions, such that the pressure drop across the reactor was allowed to increase to maintain a constant volumetric flow rate through the reactor. Results suggest that biomass production, and hence biofilm thickness, near the injection feed port is highly sensitive to substrate loading. In addition, these variations in biofilm thickness produce dramatic differences in the pressure drop that is attained across the reactor. Use of the Kozeny-Carman equation can be used to predict that once a critical depth has been exceeded, the pressure drop across the bed will increase exponentially within biofilm depth. This result means that pressure is not a reliable indicator of the onset of pore plugging.     

Riccati type transformations for second-order linear difference equations

Oscillation and comparison theorems for a linear homogeneous second-order difference equation are proved by employing various equivalent non-linear equations obtained by means of transformations analogous to the Riccati transformation for ordinary differential equations.     

Some differences between difference equations and differential equations

In this expository paper we discuss some instances in which analogues which might be expected between the behavior of solutions of differential equations and difference equations fail to hold, focussing particularly on questions related to boundedness and oscillation.     

Das Verfahren zur Erkennung des Saccharins

Ohne Zusammenfassung     

Constraints on the symmetry energy from observational probes of the neutron star crust

A number of observed phenomena associated with individual neutron star systems or neutron star populations find explanations in models in which the neutron star crust plays an important role. We review recent work examining the sensitivity to the slope of the symmetry energy L of such models, and constraints extracted on L from confronting them with observations. We focus on six sets of observations and proposed explanations: i) The cooling rate of the neutron star in Cassiopeia A, confronting cooling models which include enhanced cooling in the nuclear pasta regions of the inner crust; ii) the upper limit of the observed periods of young X-ray pulsars, confronting models of magnetic field decay in the crust caused by the high resistivity of the nuclear pasta layer; iii) glitches from the Vela pulsar, confronting the paradigm that they arise due to a sudden recoupling of the crustal neutron superfluid to the crustal lattice after a period during which they were decoupled due to vortex pinning; iv) the frequencies of quasi-periodic oscillations in the X-ray tail of light curves from giant flares from soft gamma-ray repeaters, confronting models of torsional crust oscillations; v) the upper limit on the frequency to which millisecond pulsars can be spun-up due to accretion from a binary companion, confronting models of the r-mode instability arising above a threshold frequency determined in part by the viscous dissipation timescale at the crust-core boundary; and vi) the observations of precursor electromagnetic flares a few seconds before short gamma-ray bursts, confronting a model of crust shattering caused by resonant excitation of a crustal oscillation mode by the tidal gravitational field of a companion neutron star just before merger.     

Applications of TGA in quality control of SWCNTs

Carbon nanotubes exhibit a range of chemistries, including mixtures of different nanotube diameters, lengths, and chiralities coupled with various concentrations of metallic and non-nanotube-carbon impurities. The performance of a given material for a specific application depends on the chemistry, which is dictated in large part by the manufacturing process. Here, thermogravimetric analysis is utilized as a bulk characterization method for determining nanotube quality after manufacturing. The application of thermogravimetric analysis for quantifying basic nanotube chemistry is described (e.g., carbon-to-metal content, homogeneity). In addition, extension of the method to analyze specific nanotube properties (i.e., length and diameter) is reported. Results indicate that thermogravimetric analysis is sufficiently sensitive to enable quality control at both the macro-scale (carbon-to-metal ratio) and nano-scale (single-walled to multi-walled) and can detect subtle modifications in manufacturing processes.