Analytic Relations between Localizable Entanglement and String Correlations in Spin Systems

We study the relation between the recently defined localizable entanglement and generalized correlations in quantum spin systems. Differently from the current belief, the localizable entanglement is always given by the average of a generalized string. Using symmetry arguments we show that in most spin 1/2 and spin 1 systems the localizable entanglement reduces to the spin-spin or string correlations, respectively. We prove that a general class of spin 1 systems, which includes the Heisenberg model, can be used as perfect quantum channel. These conclusions are obtained in analytic form and confirm some results found previously on numerical grounds.Comment: 5 pages, RevTeX

Interband polarized absorption in InP polytypic superlattices

Recent advances in growth techniques have allowed the fabrication of semiconductor nanostructures with mixed wurtzite/zinc-blende crystal phases. Although the optical characterization of these polytypic structures is well eported in the literature, a deeper theoretical understanding of how crystal phase mixing and quantum confinement change the output linear light polarization is still needed. In this paper, we theoretically investigate the mixing effects of wurtzite and zinc-blende phases on the interband absorption and in the degree of light polarization of an InP polytypic superlattice. We use a single 8$\times$8 k$\cdot$p Hamiltonian that describes both crystal phases. Quantum confinement is investigated by changing the size of the polytypic unit cell. We also include the optical confinement effect due to the dielectric mismatch between the superlattice and the vaccum and we show it to be necessary to match experimental results. Our calculations for large wurtzite concentrations and small quantum confinement explain the optical trends of recent photoluminescence excitation measurements. Furthermore, we find a high sensitivity to zinc-blende concentrations in the degree of linear polarization. This sensitivity can be reduced by increasing quantum confinement. In conclusion, our theoretical analysis provides an explanation for optical trends in InP polytypic superlattices, and shows that the interplay of crystal phase mixing and quantum confinement is an area worth exploring for light polarization engineering.Comment: 9 pages, 6 figures and 1 tabl

Cell death induced by the application of alternating magnetic fields to nanoparticle-loaded dendritic cells

In this work, the capability of primary, monocyte-derived dendritic cells (DCs) to uptake iron oxide magnetic nanoparticles (MNPs) is assessed and a strategy to induce selective cell death in these MNP-loaded DCs using external alternating magnetic fields (AMFs) is reported. No significant decrease in the cell viability of MNP-loaded DCs, compared to the control samples, was observed after five days of culture. The amount of MNPs incorporated into the cytoplasm was measured by magnetometry, which confirmed that 1 to 5 pg of the particles were uploaded per cell. The intracellular distribution of these MNPs, assessed by transmission electron microscopy, was found to be primarily inside the endosomic structures. These cells were then subjected to an AMF for 30 min, and the viability of the blank DCs (i.e., without MNPs), which were used as control samples, remained essentially unaffected. However, a remarkable decrease of viability from approximately 90% to 2-5% of DCs previously loaded with MNPs was observed after the same 30 min exposure to an AMF. The same results were obtained using MNPs having either positive (NH2+) or negative (COOH-) surface functional groups. In spite of the massive cell death induced by application of AMF to MNP-loaded DCs, the amount of incorporated magnetic particles did not raise the temperature of the cell culture. Clear morphological changes at the cell structure after magnetic field application were observed using scanning electron microscopy. Therefore, local damage produced by the MNPs could be the main mechanism for the selective cell death of MNP-loaded DCs under an AMF. Based on the ability of these cells to evade the reticuloendothelial system, these complexes combined with an AMF should be considered as a potentially powerful tool for tumour therapy.Comment: In Press. 33 pages, 11 figure

Coalescence and Anti-Coalescence Interference of Two-Photon Wavepacket in a Beam Splitter

We study a general theory on the interference of two-photon wavepacket in a beam splitter (BS). We find that the perfect coalescence interference requires a symmetric spectrum of two-photon wavepacket which can be entangled or un-entangled. Furthermore, we introduce a two-photon wavepacket with anti-symmetric spectrum, which is related with photon entanglement and shows a perfect anti-coalescence effect. The theory present uniform and complete explanation to two-photon interference.Comment: 5 pages, 2 figure

Galaxy Counts, Sizes, Colours and Redshifts in the Hubble Deep Field

We compare the galaxy evolution models of Bruzual & Charlot (1993) with the faint galaxy count, size and colour data from the Hubble and Herschel Deep Fields (Metcalfe et al 1996). For qo=0.05, we find that models where the SFR increases exponentially out to z>2 are consistent with all of the observational data. For qo=0.5, such models require an extra population of galaxies which are only seen at high redshift and then rapidly fade or disappear. We find that, whatever the cosmology, the redshift of the faint blue galaxies and hence the epoch of galaxy formation is likely to lie at z>2. We find no implied peak in the SFR at z=1 and we suggest that the reasons for this contradiction with the results of Madau et al (1996) include differences in faint galaxy photometry, in the treatment of spiral dust and in the local galaxy count normalisation.Comment: 8 pages, 5 eps figures, needs paspconf.st

Abate humanitário de crocodilianos.

Para a implantação da prática de abate humanitário para os jacarés foi desenvolvida pela Gil Equipamentos e a Embrapa Pantanal, a pistola ZILKA (Fig.1). A pistola foi desenvolvida para atender uma solicitação de pesquisa da Embrapa Pantanal a durante a execução do projeto de manejo experimental do jacaré-do-pantanal, Caiman crocodilus yacare, no Pantanal Sul. A pistola causa respostas de sensibilidade nos jacarés com um rápido estado de inconsciência e a incapacidade de respostas a estímulos externos. Essa etapa é fundamental para garantir o abate dentro dos princípios humanitários, uma vez que garantirá a inconsciência dos jacarés até a sangria. A pistola ZILKA também pode ser usada para abate de outros animais criados em cativeiro (ovinos e caprinos) ou animais oriundos de manejo na natureza.bitstream/item/37477/1/CT59.pd

Upper bounds on success probabilities in linear optics

We develop an abstract way of defining linear-optics networks designed to perform quantum information tasks such as quantum gates. We will be mainly concerned with the nonlinear sign shift gate, but it will become obvious that all other gates can be treated in a similar manner. The abstract scheme is extremely well suited for analytical as well as numerical investigations since it reduces the number of parameters for a general setting. With that we show numerically and partially analytically for a wide class of states that the success probability of generating a nonlinear sign shift gate does not exceed 1/4 which to our knowledge is the strongest bound to date.Comment: 8 pages, typeset using RevTex4, 5 EPS figure