Kondo effect and spin quenching in high-spin molecules on metal substrates

Using a state-of-the art combination of density functional theory and impurity solver techniques we present a complete and parameter-free picture of the Kondo effect in the high-spin ($S=3/2$) coordination complex known as Manganese Phthalocyanine adsorbed on the Pb(111) surface. We calculate the correlated electronic structure and corresponding tunnel spectrum and find an asymmetric Kondo resonance, as recently observed in experiments. Contrary to previous claims, the Kondo resonance stems from only one of three possible Kondo channels with origin in the Mn 3d-orbitals, its peculiar asymmetric shape arising from the modulation of the hybridization due to strong coupling to the organic ligand. The spectral signature of the second Kondo channel is strongly suppressed as the screening occurs via the formation of a many-body singlet with the organic part of the molecule. Finally, a spin-1/2 in the 3d-shell remains completely unscreened due to the lack of hybridization of the corresponding orbital with the substrate, hence leading to a spin-3/2 underscreened Kondo effect.Comment: 5 pages, 2 figure

Hydrogenated Graphene Nanoribbons for Spintronics

We show how hydrogenation of graphene nanoribbons at small concentrations can open new venues towards carbon-based spintronics applications regardless of any especific edge termination or passivation of the nanoribbons. Density functional theory calculations show that an adsorbed H atom induces a spin density on the surrounding $\pi$ orbitals whose symmetry and degree of localization depends on the distance to the edges of the nanoribbon. As expected for graphene-based systems, these induced magnetic moments interact ferromagnetically or antiferromagnetically depending on the relative adsorption graphene sublattice, but the magnitude of the interactions are found to strongly vary with the position of the H atoms relative to the edges. We also calculate, with the help of the Hubbard model, the transport properties of hydrogenated armchair semiconducting graphene nanoribbons in the diluted regime and show how the exchange coupling between H atoms can be exploited in the design of novel magnetoresistive devices

Van der Waals spin valves

We propose spin valves where a 2D non-magnetic conductor is intercalated between two ferromagnetic insulating layers. In this setup, the relative orientation of the magnetizations of the insulating layers can have a strong impact on the in-plane conductivity of the 2D conductor. We first show this for a graphene bilayer, described with a tight-binding model, placed between two ferromagnetic insulators. In the anti-parallel configuration, a band gap opens at the Dirac point, whereas in the parallel configuration, the graphene bilayer remains conducting. We then compute the electronic structure of graphene bilayer placed between two monolayers of the ferromagnetic insulator CrI$_3$, using density functional theory. Consistent with the model, we find that a gap opens at the Dirac point only in the antiparallel configuration.Comment: 5 pages, 4 figure

Localized basis sets for unbound electrons in nanoelectronics

It is shown how unbound electron wave functions can be expanded in a suitably chosen localized basis sets for any desired range of energies. In particular, we focus on the use of gaussian basis sets, commonly used in first-principles codes. The possible usefulness of these basis sets in a first-principles description of field emission or scanning tunneling microscopy at large bias is illustrated by studying a simpler related phenomenon: The lifetime of an electron in a H atom subjected to a strong electric field.Comment: 6 pages, 5 figures, accepted by J. Chem. Phys. (http://jcp.aip.org/

Coupling of Josephson flux-flow oscillators to an external RC load

We investigate by numerical simulations the behavior of the power dissipated in a resistive load capacitively coupled to a Josephson flux flow oscillator and compare the results to those obtained for a d.c. coupled purely resistive load. Assuming realistic values for the parameters R and C, both in the high- and in the low-Tc case the power is large enough to allow the operation of such a device in applications.Comment: uuencoded, gzipped tar archive containing 11 pages of REVTeX text + 4 PostScript figures. To appear in Supercond. Sci. Techno

Percolation in living neural networks

We study living neural networks by measuring the neurons' response to a global electrical stimulation. Neural connectivity is lowered by reducing the synaptic strength, chemically blocking neurotransmitter receptors. We use a graph-theoretic approach to show that the connectivity undergoes a percolation transition. This occurs as the giant component disintegrates, characterized by a power law with critical exponent $\beta \simeq 0.65$ is independent of the balance between excitatory and inhibitory neurons and indicates that the degree distribution is gaussian rather than scale freeComment: PACS numbers: 87.18.Sn, 87.19.La, 64.60.Ak http://www.weizmann.ac.il/complex/tlusty/papers/PhysRevLett2006.pd

Is Big Data for everyone? The challenges of Big Data adoption in SMEs

The aim of this paper is to present an investigative study on the concept of Big Data and its challenges towards implementation in manufacturing SMEs. Big Data aims to facilitate the collaborative approach in SMEs through the creation of real time data visualization to address key challenges to many of the market variations for every sector SMEs. Although, earlier research studies have highlighted the importance of Big Data from technological perspectives, this study focuses towards SMEs due to its feasibility and flexibility within the market space. This research aims to investigate the use of case study approach for the re-use, adoption and understanding of strategic future direction from the findings. The findings and early analysis from this paper could be referred by researchers when addressing the use of big data analytics within manufacturing SMEs. Finally, the paper provides a key strategic point towards the exploration of Big Data within SMEs

MAXIMS: a computer program for estimating the food consumption of fishes from diel stomach contents data and population parameters

MAXIMS (Computer file), Food consumption, Stomach content, Population characteristics, Computer programmes Pisces

Distribution of melanopsin positive neurons in pigmented and albino mice: evidence for melanopsin interneurons in the mouse retina.

Here we have studied the population of intrinsically photosensitive retinal ganglion cells (ipRGCs) in adult pigmented and albino mice. Our data show that although pigmented (C57Bl/6) and albino (Swiss) mice have a similar total number of ipRGCs, their distribution is slightly different: while in pigmented mice ipRGCs are more abundant in the temporal retina, in albinos the ipRGCs are more abundant in superior retina. In both strains, ipRGCs are located in the retinal periphery, in the areas of lower Brn3a(+)RGC density. Both strains also contain displaced ipRGCs (d-ipRGCs) in the inner nuclear layer (INL) that account for 14% of total ipRGCs in pigmented mice and 5% in albinos. Tracing from both superior colliculli shows that 98% (pigmented) and 97% (albino) of the total ipRGCs, become retrogradely labeled, while double immunodetection of melanopsin and Brn3a confirms that few ipRGCs express this transcription factor in mice. Rather surprisingly, application of a retrograde tracer to the optic nerve (ON) labels all ipRGCs, except for a sub-population of the d-ipRGCs (14% in pigmented and 28% in albino, respectively) and melanopsin positive cells residing in the ciliary marginal zone (CMZ) of the retina. In the CMZ, between 20% (pigmented) and 24% (albino) of the melanopsin positive cells are unlabeled by the tracer and we suggest that this may be because they fail to send an axon into the ON. As such, this study provides the first evidence for a population of melanopsin interneurons in the mammalian retina