Collective states of interacting ferromagnetic nanoparticles

Discontinuous magnetic multilayers [CoFe/Al₂O₃] are studied by use of magnetometry, susceptometry and numeric simulations. Soft ferromagnetic Co₈₀Fe₂₀ nanoparticles are embedded in a diamagnetic insulating a-Al₂O₃ matrix and can be considered as homogeneously magnetized superspins exhibiting randomness of size (viz. moment), position and anisotropy. Lacking intra-particle core-surface ordering, generic freezing processes into collective states rather than individual particle blocking are encountered. With increasing particle density one observes first superspin glass and then superferromagnetic domain state behavior. The phase diagram resembles that of a dilute disordered ferromagnet. Criteria for the identification of the individual phases are given.     

A stochastic programming model for asset liability management of a Finnish pension company

This paper describes a stochastic programming model that was developed for asset liability management of a Finnish pension insurance company. In many respects the model resembles those presented in the literature, but it has some unique features stemming from the statutory restrictions for Finnish pension insurance companies. Particular attention is paid to modeling the stochastic factors, numerical solution of the resulting optimization problem and evaluation of the solution. Out-of-sample tests clearly favor the strategies suggested by our model over static fixed-mix and dynamic portfolio insurance strategies. Financial support from the Foundation for the Helsinki School of Economics under grants number 9981114 and 9981117 for P. Hilli and M. Koivu is gratefully acknowledged. The work of T. Pennanen was supported by Finnish Academy under contract no. 3385     

INDISTINGUISHABLE PARTICLES AND HIDDEN VARIABLES: PART II

In a previous work it was shown that it is possible to deal with collections of indistinguishable elementary particles in a set-theoretical framework, by using hidden variables. We propose in the present paper a set-theoretical axiomatics for collections of indiscernibles with no explicit mention to hidden variables. We also show, in this context, the fundamental role of the (micro) state in the process of individuation of classical and quantum particles. Finally, we discuss the importance of the axiom of choice in Zermelo-Fraenkel set theory in the context of quantum distributions of bosons and fermions.     

Synthesis,characterization and thermal behaviour of solid-state compounds of yttrium and lanthanide benzoates

Solid-state Ln(Bz)₃·H₂O compounds where Ln stands for trivalent yttrium or lanthanides and Bz is benzoate have been synthesized. Simultaneous thermogravimetry-differential thermal analysis (TG-DTA), X-ray powder diffractometry, infrared spectroscopy and chemical analysis were used to characterize and to study the thermal behaviour of these compounds. The results led to information about the composition, dehydration, thermal stability and thermal decomposition of the isolated compounds.     

Synthesis of Long‐Chain 3‐Alkylpyrroles Bearing Terminal Carboxy or Amino Groups

Two new ω‐(1H‐pyrrol‐3‐yl)alkanoic acids 8a , b and the corresponding amines 9a , b were prepared on large scale in 41–51 and 27–39% overall yield, respectively, starting from N‐phenylsulfonyl‐protected pyrrole. The target compounds contain the desired functional groups for attachment of biomolecules such as proteins. During synthesis, an unprecedented partial reduction of the pyrrole ring with NaBH₃CN in glacial AcOH was observed, for which a plausible mechanism is proposed (Scheme 3).     

Determination of the REE in environmental samples near a coal power station based on k0-standardized NAA with counting in a LEPD

The Ree contents in lichens and plants determined by k₀-standardized NAA with LEPD and HPGe are compared. We obtain similar values for Sm, Eu, Tb and Yb and better values for Ce and Nd by using LEPD Besides, LEPD allows the determination of Gd, Tm and Lu. The study of REE concentrations in the neighbourhood of two coal power stations show that: i) in the station under construction (C. T. Pego), the index of accumulation of each REE by the lichens and olive tree leaves is identical in two sampling loci where the soils have different REE concentration; and ii) in the station in operation (C. T. Sines), the REE contents in the soils is identical and the differences observed in the lichens and wild terrestrial plants are most probably due to the fly-ashes emmission from the station.     

Corrosion resistance study of Fe–Mn–Al–C alloys using immersion and potentiostatic tests

The interaction of the Fe–32.7Mn–6.59Al–1.26Si–0.25C (wt.%) and Fe–32.3Mn–8.54Al–1.31Si–0.54C (wt.%) alloys with the environment was evaluated. Potentiostatic and total immersion tests, planned and analyzed by the statistic model of fixed effects were used for the evaluation of corrosion in gasoline, alcohol fuel, lactic acid solution (40 wt.%), sodium chloride solution (3 wt.%), and boiler water. Potentiostatic tests in 1N H₂SO₄ medium presented that the alloys showed a tendency towards passivation. The role that aluminum and silicon play in alloy corrosion mechanism was discussed.     

Preparation of aqueous sols containing well-shaped boehmite crystals

The paper describes the preparation of aqueous sols of crystalline boehmite, containing about 70 grams of AlOOH per liter from three different starting materials; gels of Al(OH)₂Ac are obtained and are hydrolyzed by thermal aging into sols of fibrillar pseudoboehmite. The pseudoboehmite fibrils are hydrothermally recrystallized at 200°C producing well-shaped hexagonal laths of boehmite, also as stable sols.