Crystal structure and magnetism of UFe3B2

The structure of the UFe₃B₂ compound has been refined down to R=0.022 and wR₂=0.052 from single crystal X-ray diffraction data. This uranium boride crystallizes in the CeCo₃B₂ type-structure (P6/mmm space group no. 191, Z=1, ρ=10.79 g/cm³), with lattice parameters at room temperature a=0.5052(1) nm, c=0.3002(1) nm and V=0.664(1) nm³. Magnetization measurements made between 2 K and 800 K suggested that UFe₃B₂ is an antiferromagnet with a rather high Néel temperature of T_N=268±5 K. No other magnetic transitions were observed down to the lowest studied temperature.     

Simple and facile approach to synthesize magnetite nanoparticles and assessment of their effects on blood cells

In this paper, a very simple and facile approach for the large scale synthesis of uniform and size-controllable single-domain magnetite nanoparticles is reported. These magnetite nanoparticles were synthesized via thermal decomposition of a ferric nitrate/ethylene glycol solution. The structural and morphological properties of the synthesized nanoparticles were carefully studied. Nearly spherical nanoparticles with inverted spinel structure and average particle and crystallite sizes smaller than 20 nm were obtained. The magnetic measurements revealed that magnetite nanoparticles have a magnetic saturation value near that of the bulk magnetite. The erythrocyte cytotoxicity assays showed no hemolytic potential of the samples containing magnetite nanoparticles, indicating no cytotoxic activity on human erythrocytes, which makes these interesting for biotechnological applications.     

A two-player competitive discrete location model with simultaneous decisions

In this paper we will describe and study a competitive discrete location problem in which two decision-makers (players) will have to decide where to locate their own facilities, and customers will be assigned to the closest open facilities. We will consider the situation in which the players must decide simultaneously, unsure about the decisions of one another, and we will present the problem in a franchising environment. Most problems described in the literature consider sequential rather than simultaneous decisions. In a competitive environment, most problems consider that there is a set of known and already located facilities, and new facilities will have to be located, competing with the existing ones. In the presence of more than one decision-maker, most problems found in the literature belong to the class of Stackelberg location problems, where one decision-maker, the leader, locates first and then the other decision-maker, the follower, locates second, knowing the decisions made by the first. These types of problems are sequential and differ significantly from the problem tackled in this paper, where we explicitly consider simultaneous, non-cooperative discrete location decisions. We describe the problem and its context, propose some mathematical formulations and present an algorithmic approach that was developed to find Nash equilibria. Some computational tests were performed that allowed us to better understand some of the features of the problem and the associated Nash equilibria. Among other results, we conclude that worsening the situation of a player tends to benefit the other player, and that the inefficiency of Nash equilibria tends to increase with the level of competition.     

Study of ferrofluids by Mössbauer spectroscopy

The parameters of the log‐normal size distribution of a MnFe₂O₄ ferrofluid powder sample have been determined by X‐ray diffraction. The mean blocking temperature was determined from the maximum of _Xi . Mössbauer spectra at 4.2–300 K are interpreted by a new simple theory of superparamagnetism and taking a reduction of the internal magnetic field for small particles, a size dependence of the anisotropy constant, the size distribution and collective excitations into account.     

Conditions for equality of decomposable symmetric tensors

Let x₁,…,x_m be linearly independent vectors. We give a necessary and sufficient condition for $\text{x}{}_1\text{1…1x}{}_{\mathrm{m}}\text{=y}{}_1\text{1…1y}{}_{\mathrm{m}}$ to hold. Some consequences of this result are also presented.     

Semi microscopic description of84Kr

The experimental information on the⁸⁴Kr nuclei is compared with the model calculation in which two neutron holes are coupled to the vibrational field. Based on the lower-order terms of a perturbative expansion of theE2 andM1 transition matrix elements, a simple rule is obtained for the sign and the magnitude of theδ (E2/M1) ratios for the transitions between the second and first 2⁺ states in some vibrational nuclei. [Nuclear structure⁸⁴Kr, calculated levelsJ, π and δ(E2/M1), Cluster-phonon model. Pairing interaction].     

Additives as ionizing elements in N2 TE UV lasers

This work reports the role some additives have in pre-ionizing a N₂ TE UV laser (337.1 nm). The modifications in both stimulated radiation characteristics and excitation-pulse period prove the different ionizing power of each element. The laser operating without a pre-ionizing wire device and with N₂ plus different additives was able to generate pulses with a temporal width of the same order than those obtained when it was operating with N₂ and a pre-ionizing wire device. Also, a relation between ionization efficiency and interelectrode distance has been established allowing the prediction of conditions for optimum laser-pulse width generation.