Adaptive intelligence applied to numerical optimisation

The article presents modification strategies theoretical comparison and experimental results achieved by adaptive heuristics applied to numerical optimisation of several non-constraint test functions. The aims of the study are to identify and compare how adaptive search heuristics behave within heterogeneous search space without retuning of the search parameters. The achieved results are summarised and analysed, which could be used for comparison to other methods and further investigation

Synthesis and characterization of polypyrrole-coated anthracene microparticles: a new synthetic mimic for polyaromatic hydrocarbon-based cosmic dust

Polyaromatic hydrocarbons (PAHs) are found throughout the universe. The ubiquity of these organic molecules means that they are of considerable interest in the context of cosmic dust, which typically travels at hypervelocities (>1 km s–1) within our solar system. However, studying such fast-moving micrometer-sized particles in laboratory-based experiments requires suitable synthetic mimics. Herein, we use ball-milling to produce microparticles of anthracene, which is the simplest member of the PAH family. Size control can be achieved by varying the milling time in the presence of a suitable anionic commercial polymeric dispersant (Morwet D-425). These anthracene microparticles are then coated with a thin overlayer of polypyrrole (PPy), which is an air-stable organic conducting polymer. The uncoated and PPy-coated anthracene microparticles are characterized in terms of their particle size, surface morphology, and chemical structure using optical microscopy, scanning electron microscopy, laser diffraction, aqueous electrophoresis, FT-IR spectroscopy, Raman microscopy, and X-ray photoelectron spectroscopy (XPS). Moreover, such microparticles can be accelerated up to hypervelocities using a light gas gun. Finally, studies of impact craters indicate carbon debris, so they are expected to serve as the first synthetic mimic for PAH-based cosmic dust

An absolute measurement of the efficiency of a BF3 proportional counter

We report an absolute measurement of the efficiency of a BF3 counter in narrow beam geometry in the energy range frame 0.024 eV to 0.111 eV. Agreement with calculated efficiency values is excellent. No significant end effects are noted. The basic feature of this experiment is the measurement of the incident neutron flux by gold foil activation and counting in an NaI well counter which was calibrated with gold foils irradiated in the National Bureau of Standards Standard Thermal Neutron Flux.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/33574/1/0000077.pd

Uric acid: an old actor for a new role

The role of uric acid as an independent risk factor for cardiovascular events is still debated. In fact, other confounding factors such as glucose intolerance, obesity, dyslipidaemia, hypertension, use of diuretics and insulin resistance may play a role in determining the increased vascular risk associated to elevated uric acid concentrations. These factors (including high uric acid) have been mentioned in one or more definitions of the metabolic syndrome. Recently, much attention has been paid to the metabolic syndrome due to its possible role as a risk factor for the development of type 2 diabetes and cardiovascular disease. The worldwide increase in the prevalence of obesity and diabetes is a reason not only for the increasing prevalence of the metabolic syndrome but also of hyperuricaemia. A better understanding of the role of uric acid in health and in disease states may help physicians to improve their performance in preventing and treating cardiovascular disease

Optimal low-thrust trajectories to asteroids through an algorithm based on differential dynamic programming

In this paper an optimisation algorithm based on Differential Dynamic Programming is applied to the design of rendezvous and fly-by trajectories to near Earth objects. Differential dynamic programming is a successive approximation technique that computes a feedback control law in correspondence of a fixed number of decision times. In this way the high dimensional problem characteristic of low-thrust optimisation is reduced into a series of small dimensional problems. The proposed method exploits the stage-wise approach to incorporate an adaptive refinement of the discretisation mesh within the optimisation process. A particular interpolation technique was used to preserve the feedback nature of the control law, thus improving robustness against some approximation errors introduced during the adaptation process. The algorithm implements global variations of the control law, which ensure a further increase in robustness. The results presented show how the proposed approach is capable of fully exploiting the multi-body dynamics of the problem; in fact, in one of the study cases, a fly-by of the Earth is scheduled, which was not included in the first guess solution

A Prolific Solvate Former, Galunisertib, under the Pressure of Crystal Structure Prediction, Produces Ten Diverse Polymorphs

The solid form screening of galunisertib produced many solvates, prompting an extensive investigation into possible risks to the development of the favored monohydrate form. Inspired by crystal structure prediction, the search for neat polymorphs was expanded to an unusual range of experiments, including melt crystallization under pressure, to work around solvate formation and the thermal instability of the molecule. Ten polymorphs of galunisertib were found; however, the structure predicted to be the most stable has yet to be obtained. We present the crystal structures of all ten unsolvated polymorphs of galunisertib, showing how state-of-the-art characterization methods can be combined with emerging computational modeling techniques to produce a complete structure landscape and assess the risk of late-appearing, more stable polymorphs. The exceptional conformational polymorphism of this prolific solvate former invites further development of methods, computational and experimental, that are applicable to larger, flexible molecules with complex solid form landscapes

Nucleon Charge and Magnetization Densities from Sachs Form Factors

Relativistic prescriptions relating Sachs form factors to nucleon charge and magnetization densities are used to fit recent data for both the proton and the neutron. The analysis uses expansions in complete radial bases to minimize model dependence and to estimate the uncertainties in radial densities due to limitation of the range of momentum transfer. We find that the charge distribution for the proton is significantly broad than its magnetization density and that the magnetization density is slightly broader for the neutron than the proton. The neutron charge form factor is consistent with the Galster parametrization over the available range of Q^2, but relativistic inversion produces a softer radial density. Discrete ambiguities in the inversion method are analyzed in detail. The method of Mitra and Kumari ensures compatibility with pQCD and is most useful for extrapolating form factors to large Q^2.Comment: To appear in Phys. Rev. C. Two new figures and accompanying text have been added and several discussions have been clarified with no significant changes to the conclusions. Now contains 47 pages including 21 figures and 2 table

Spontaneous Coherence and Collective Modes in Double-Layer Quantum Dot Systems

We study the ground state and the collective excitations of parabolically-confined double-layer quantum dot systems in a strong magnetic field. We identify parameter regimes where electrons form maximum density droplet states, quantum-dot analogs of the incompressible states of the bulk integer quantum Hall effect. In these regimes the Hartree-Fock approximation and the time-dependent Hartree-Fock approximations can be used to describe the ground state and collective excitations respectively. We comment on the relationship between edge excitations of dots and edge magneto-plasmon excitations of bulk double-layer systems.Comment: 20 pages (figures included) and also available at http://fangio.magnet.fsu.edu/~jhu/Paper/qdot_cond.ps, replaced to fix figure

Hamiltonian Theory of the FQHE: Conserving Approximation for Incompressible Fractions

A microscopic Hamiltonian theory of the FQHE developed by Shankar and the present author based on the fermionic Chern-Simons approach has recently been quite successful in calculating gaps and finite tempertature properties in Fractional Quantum Hall states. Initially proposed as a small-$q$ theory, it was subsequently extended by Shankar to form an algebraically consistent theory for all $q$ in the lowest Landau level. Such a theory is amenable to a conserving approximation in which the constraints have vanishing correlators and decouple from physical response functions. Properties of the incompressible fractions are explored in this conserving approximation, including the magnetoexciton dispersions and the evolution of the small-$q$ structure factor as \nu\to\half. Finally, a formalism capable of dealing with a nonuniform ground state charge density is developed and used to show how the correct fractional value of the quasiparticle charge emerges from the theory.Comment: 15 pages, 2 eps figure