On the origin of magnetoresistance in Sr2_2FeMoO6_6

We report detailed magnetization ($M$) and magnetoresistance ($MR$) studies on a series of Sr$_2$FeMoO$_6$ samples with independent control on anti-site defect and grain boundary densities. These results, exhibiting a switching-like behavior of $MR$ with $M$, establish that the $MR$ is controlled by the magnetic polarization of grain boundary regions, rather than of the grains within a resonant tunnelling mechanism.Comment: 4 pages, 4 figure

Substellar Objects in Nearby Young Clusters (SONYC) VI: The planetary-mass domain of NGC1333

Within the SONYC - Substellar Objects in Nearby Young Clusters - survey, we investigate the frequency of free-floating planetary-mass objects (planemos) in the young cluster NGC1333. Building upon our extensive previous work, we present spectra for 12 of the faintest candidates from our deep multi-band imaging, plus seven random objects in the same fields, using MOIRCS on Subaru. We confirm seven new sources as young very low mass objects (VLMOs), with Teff of 2400-3100K and mid-M to early-L spectral types. These objects add to the growing census of VLMOs in NGC1333, now totaling 58. Three confirmed objects (one found in this study) have masses below 15 MJup, according to evolutionary models, thus are likely planemos. We estimate the total planemo population with 5-15 MJup in NGC1333 is <~8. The mass spectrum in this cluster is well approximated by dN/dM ~ M^-alpha, with a single value of alpha = 0.6+/-0.1 for M<0.6Msol, consistent with other nearby star forming regions, and requires alpha <~ 0.6 in the planemo domain. Our results in NGC1333, as well as findings in several other clusters by ourselves and others, confirm that the star formation process extends into the planetary-mass domain, at least down to 6 MJup. However, given that planemos are 20-50 times less numerous than stars, their contribution to the object number and mass budget in young clusters is negligible. Our findings disagree strongly with the recent claim from a microlensing study that free-floating planetary-mass objects are twice as common as stars - if the microlensing result is confirmed, those isolated Jupiter-mass objects must have a different origin from brown dwarfs and planemos observed in young clusters.Comment: 14 pages, 11 figures. Updated version after proof corrections, additional comment in Sect. 5.

Statistical mechanics approach to the phase unwrapping problem

The use of Mean-Field theory to unwrap principal phase patterns has been recently proposed. In this paper we generalize the Mean-Field approach to process phase patterns with arbitrary degree of undersampling. The phase unwrapping problem is formulated as that of finding the ground state of a locally constrained, finite size, spin-L Ising model under a non-uniform magnetic field. The optimization problem is solved by the Mean-Field Annealing technique. Synthetic experiments show the effectiveness of the proposed algorithm

Molecular dynamics study of the fragmentation of silicon doped fullerenes

Tight binding molecular dynamics simulations, with a non orthogonal basis set, are performed to study the fragmentation of carbon fullerenes doped with up to six silicon atoms. Both substitutional and adsorbed cases are considered. The fragmentation process is simulated starting from the equilibrium configuration in each case and imposing a high initial temperature to the atoms. Kinetic energy quickly converts into potential energy, so that the system oscillates for some picoseconds and eventually breaks up. The most probable first event for substituted fullerenes is the ejection of a C2 molecule, another very frequent event being that one Si atom goes to an adsorbed position. Adsorbed Si clusters tend to desorb as a whole when they have four or more atoms, while the smaller ones tend to dissociate and sometimes interchange positions with the C atoms. These results are compared with experimental information from mass abundance spectroscopy and the products of photofragmentation.Comment: Seven two-column pages, six postscript figures. To be published in Physical Review

Fuzzy control turns 50: 10 years later

In 2015, we celebrate the 50th anniversary of Fuzzy Sets, ten years after the main milestones regarding its applications in fuzzy control in their 40th birthday were reviewed in FSS, see [1]. Ten years is at the same time a long period and short time thinking to the inner dynamics of research. This paper, presented for these 50 years of Fuzzy Sets is taking into account both thoughts. A first part presents a quick recap of the history of fuzzy control: from model-free design, based on human reasoning to quasi-LPV (Linear Parameter Varying) model-based control design via some milestones, and key applications. The second part shows where we arrived and what the improvements are since the milestone of the first 40 years. A last part is devoted to discussion and possible future research topics.Guerra, T.; Sala, A.; Tanaka, K. (2015). Fuzzy control turns 50: 10 years later. Fuzzy Sets and Systems. 281:162-182. doi:10.1016/j.fss.2015.05.005S16218228

Destruction of indoleacetic acid : IV. Kinetics of enzymic oxidation

Kinetics of enzymic oxidation of indoleacetic acid (IAA) are interpreted as indicating that the reaction has an autocatalytic, cyclical mechanism involving unstable intermediates whose formation and disappearance are important in determining the over-all reaction rate. The kinetics do not support the idea that IAA oxidation occurs mainly by reaction with Mn+3, nor that the reaction is an electron transfer from IAA to O2 catalyzed by a pcroxidase-H2O2-Mn+2 complex, nor that Mn is essential to the reaction. H2O2 is probably not a major reaction intermediate. One-electron oxidation of IAA by peroxidase giving a free radical, followed by spontaneous reaction of the radical with oxygen to give a peroxy oxidant which can reoxidize the peroxidase to a peroxide complex, appears to be a likely mechanism.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/32324/1/0000394.pd

Radio continuum observations of Class I protostellar disks in Taurus: constraining the greybody tail at centimetre wavelengths

We present deep 1.8 cm (16 GHz) radio continuum imaging of seven young stellar objects in the Taurus molecular cloud. These objects have previously been extensively studied in the sub-mm to NIR range and their SEDs modelled to provide reliable physical and geometrical parametres.We use this new data to constrain the properties of the long-wavelength tail of the greybody spectrum, which is expected to be dominated by emission from large dust grains in the protostellar disk. We find spectra consistent with the opacity indices expected for such a population, with an average opacity index of beta = 0.26+/-0.22 indicating grain growth within the disks. We use spectra fitted jointly to radio and sub-mm data to separate the contributions from thermal dust and radio emission at 1.8 cm and derive disk masses directly from the cm-wave dust contribution. We find that disk masses derived from these flux densities under assumptions consistent with the literature are systematically higher than those calculated from sub-mm data, and meet the criteria for giant planet formation in a number of cases.Comment: submitted MNRA

Mass-Enhanced Fermi Liquid Ground State in Na1.5_{1.5}Co2_2O4_4

Magnetic, transport, and specific heat measurements have been performed on layered metallic oxide Na$_{1.5}$Co$_2$O$_4$ as a function of temperature $T$. Below a characteristic temperature $T^*$=30$-$40 K, electrical resistivity shows a metallic conductivity with a $T^2$ behavior and magnetic susceptibility deviates from the Curie-Weiss behavior showing a broad peak at $\sim$14 K. The electronic specific heat coefficient $\gamma$ is $\sim$60 mJ/molK$^2$ at 2 K. No evidence for magnetic ordering is found. These behaviors suggest the formation of mass-enhanced Fermi liquid ground state analogous to that in $d$-electron heavy fermion compound LiV$_2$O$_4$.Comment: 4 pages, 4 figures, to be published in Phys. Rev. B 69 (2004

Unprecedented inequivalent metal coordination environments in a mixed-ligand dicobalt complex

Bimetallic complexes of the transition metals containing mixed diimine and dithiolate ligands are of fundamental interest on account of their intriguing electronic properties. Almost always, such complexes are isolated as species in which both the metal centers are in identical coordination environments - this means that the two metals often have identical redox properties. In contrast, mixed-diimine/dithiolate bimetallic complexes of the first row transition metals where the two metals are in dissimilar coordination environments are exceedingly rare, and are only known for nickel. Herein, we report the first ever example of a mixed-diimine/dithiolate dicobalt complex where the two cobalt centers are in different coordination environments. The synthesis of this compound is straightforward, and produces a complex in which the two cobalt centers display very different redox properties

Physical properties of misfit-layered (Bi,Pb)-Sr-Co-O system: Effect of hole doping into triangular lattice formed by low-spin Co ions

Pb-doping effect on physical properties of misfit-layered (Bi,Pb)-Sr-Co-O system, in which Co ions form a two-dimensional triangular lattice, was investigated in detail by electronic transport, magnetization and specific-heat measurements. Pb doping enhances the metallic behavior, suggesting that carriers are doped. Pb doping also enhances the magnetic correlation in this system and increases the magnetic transition temperature. We found the existence of the short-range magnetic correlation far above the transition temperature, which seems to induce the spin-glass state coexisting with the ferromagnetic long-range order at low temperatures. Specific-heat measurement suggests that the effective mass of the carrier in (Bi,Pb)-Sr-Co-O is not enhanced so much as reported in NaCo${}_2$O${}_4$. Based on these experimental results, we propose a two-bands model which consists of narrow $a_{1g}$ and rather broad $e'{}_g$ bands. The observed magnetic property and magnetotransport phenomena are explained well by this model