Elliptic theta functions and the fractional quantum Hall effect

Algebro-geometric methods are applied to the theoretical understanding of the fractionary quantum Hall effect on a periodic lattice. The fermionic Fock space of the many-electron system is precisely identified, and as a consequence, the variational Haldane-Rezayi ground state is decomposed in terms of one-particle wave functions at the first Landau level; the filling factor is thus analytically computed. Quasi-hole and quasi-particle excitations are also analyzed. The center of mass dynamics is described in terms of a section in a very subtle stable vector bundle. The Hall conductance arises as a topological invariant; namely, the slope of the vector bundle previously mentioned.     

Application of thermal analysis for evaluating the digestion of microwave pre-treated sewage sludge

The effect of microwave pre-treatment (MwP) on anaerobic digestion of sewage sludge was studied by means of thermal analysis and evolved gas analysis. The effect of the pre-treatment at low energy input (<1000 kJ L^?1) on sludge solubilisation was studied with the aid of response surface methodology. The pre-treatment process was subsequently studied at energies of 488–2700 kJ L^?1 to evaluate the improvement in biogas production under mesophilic conditions. Organic matter modifications were studied using a Setaram TGA92 analyser at atmospheric pressure coupled to an MSC200 quadrupole mass spectrometer from Balzers. Particle size analysis was carried out using a Laser Diffraction Particle Size Analyser LS 13 320 Beckmann Coulter for evaluating the effect of MwP on sludge particles. Results showed an increase in organic matter solubilisation with the increase in the energy applied. Modifications in the specific surface area of the organic matter due to the MwP resulted in increments in methane yields. However, an accumulation of complex compounds was observed in thermal profiles at the maximum energy input (2700 kJ L^?1). Semi-continuous digestion experiments were evaluated using as substrate pre-treated sludge at the optimum energy value (975 kJ L^?1). Results showed a significant increase in methane yield (43 %) when evaluating the process at hydraulic retention times (HRTs) of 25–10 days.     

Selecting intervention strategies against eutrophication and the drastic decrease in bird abundance in Ringkøbing Fjord

Ringkøbing Fjord is a large and shallow brackish lagoon on the west coast of Denmark that has gone through two environmental regime shifts in recent decades. Different intervention strategies, including nutrient abatement and the construction of facilities to increase the water exchange between the lagoon and the outside sea, have been proposed to achieve good water quality in terms of trophic state and conditions for waterfowl. The selection of an intervention strategy is a complex decision-making problem in which several conflicting objectives, like costs of application and environmental or social impacts, must be taken into account simultaneously. We propose a PC-based decision support system, called the Generic Multi-Attribute Analysis system, to deal with such interdisciplinary analyses. It evaluates the intervention strategies by means of an additive multiattribute utility model accounting for imprecision of the various components of the analysis, such as intervention strategy performances and decision-makers’ preferences. Also, it implements what is known as decision making with partial information, through the application of Monte Carlo simulation techniques. This enables a straightforward analysis of the difference between an anthropocentrist and an ecocentrist view of the problem, from which a final recommendation can be reached.     

Sparse Dirichlet optimal control problems

Computational Optimization and Applications - In this paper, we analyze optimal control problems governed by an elliptic partial differential equation, in which the control acts as the Dirichlet...     

Passive mode-locking of acentric Yb-doped borate crystals

Passive mode locking of the self-frequency doubling Yb:YAB and Yb:YCOB crystals with a saturable absorber mirror is studied at the fundamental wavelength with diode pumping. All essential polarization orientations including the self-frequency doubling configuration are considered. For the first time sub-90 fs pulses at the fundamental are obtained with both materials and the improvement in terms of pulse length in comparison to previous work is about 2.3 times (Yb:YAB) and 2.8 times (Yb:YCOB). The Yb:YAB laser generates pulses as short as 87 fs at 1050 nm with a 0.4% output coupler. The shortest pulses (76 fs) are obtained with a Y-cut Yb:YCOB for E ∥ Z. With an output coupler of 0.4% the oscillation wavelength is 1056 nm. For E ∥ X the mode-locked Yb:YCOB laser operates on a different Stark transition (at longer wavelengths) than for E ∥ gg and E ∥ Z.     

Supersymmetric 3D anti-de Sitter space solutions of type IIB supergravity

For every positively curved K?hler-Einstein manifold in four dimensions, we construct an infinite family of supersymmetric solutions of type IIB supergravity. The solutions are warped products of AdS3 with a compact seven-dimensional manifold and have nonvanishing five-form flux. Via the anti-de Sitter/conformal field theory correspondence, the solutions are dual to two-dimensional conformal field theories with (0,2) supersymmetry. The corresponding central charges are rational numbers.     

Thin-disk Yb:KLu(WO(4))(2) laser with single-pass pumping

Single-pass pumping of a thin disk consisting of an only 50 microm thick epitaxial layer of 32 at.% Yb-doped KLu(WO(4))(2) grown on a 0.35 mm thick undoped KLu(WO(4))(2) substrate is demonstrated. The thin-disk laser delivered 9 W of continuous wave output power near 1030 nm with a slope efficiency of 77%.     

Molecular weight distributions of industrially-produced poly-(epsilon-caprolactams) by gel permeation chromatography

Gel permeation chromatography with differential refractometry is used to obtain molecular weight distributions (MWD) of poly-(epsilon-caprolactams). Elution is carried out using an m-cresolchlorobenzene mixture (50:50, v/v) at 50 degrees C. MW values are obtained by a Hamielec-based calibration method, using broad-MWD poly-(epsilon-caprolactam) standards with the same chemical nature and similar MWD to the samples. Relative errors for the number-average MW (Mn) using this calibration method range from 0.4% (in the low polyamide MW range) to 20% (in the high polyamide MW range). These values are much lower than those obtained from narrow-MWD polystyrene calibration, which range from 39% to 78%. Similar values have been obtained for the other usual average MW parameters. The ability to obtain repeatability parameters for a given confidence interval and the utilization of statistical criteria for chromatogram rejection allow this method to be used in quality control for MWD of poly-(epsilon-caprolactams). Thus, production variables are related to polyamide-6 behavior in its ulterior treatment. Typical relative standard deviation percentages (for n=6) of a polyamide sample range from 1.9% (for Mn) to 3.3% (for M(z+1)).