Cut-elimination for the modal Grzegorczyk logic via non-well-founded proofs

We present a sequent calculus for the modal Grzegorczyk logic Grz allowing non-well-founded proofs and obtain the cut-elimination theorem for it by constructing a continuous cut-elimination mapping acting on these proofs.Comment: WOLLIC'17, 12 pages, 1 appendi

CD28 interaction with B7 costimulates primary allogeneic proliferative responses and cytotoxicity mediated by small, resting T lymphocytes.

Engagement of the CD3/T cell antigen receptor complex on small, resting T cells is insufficient to trigger cell-mediated cytotoxicity or to induce a proliferative response. In the present study, we have used genetic transfection to demonstrate that interaction of the B7-BB1 B cell activation antigen with the CD28 T cell differentiation antigen costimulates cell-mediated cytotoxicity and proliferation initiated by either anti-CD2 or anti-CD3 monoclonal antibody (mAb). Moreover, a B7-negative Burkitt's lymphoma cell line that fails to stimulate an allogeneic mixed lymphocyte response is rendered a potent stimulator after transfection with B7. The mixed leukocyte reaction proliferative response against the B7 transfectant is inhibited by either anti-CD28 or B7 mAb. We also demonstrate that freshly isolated small, resting human T cells can mediate anti-CD3 or anti-CD2 mAb-redirected cytotoxicity against a murine Fc receptor-bearing mastocytoma transfected with human B7. These preexisting cytotoxic T lymphocytes in peripheral blood are present in both the CD4 and CD8 subsets, but are preferentially within the CD45RO+ "memory" population. While small, resting T cells apparently require costimulation by CD28/B7 interactions, this requirement is lost after T cell activation. Anti-CD3 initiates a cytotoxic response mediated by in vitro cultured T cell clones in the absence of B7 ligand. The existence of functional cytolytic T cells in the small, resting T cell population may be advantageous in facilitating rapid responses to immune challenge

Spin and density longitudinal response of quantum dots in time-dependent local-spin-density approximation

The longitudinal dipole response of a quantum dot has been calculated in the far-infrared regime using local spin density functional theory. We have studied the coupling between the collective spin and density modes as a function of the magnetic field. We have found that the spin dipole mode and single particle excitations have a sizeable overlap, and that the magnetoplasmon modes can be excited by the dipole spin operator if the dot is spin polarized. The frequency of the dipole spin edge mode presents an oscillation which is clearly filling factor ($\nu$) related. We have found that the spin dipole mode is especially soft for even $\nu$ values, becoming unstable for magnetic fields in the region $1 < \nu \leq 2$. Results for selected number of electrons and confining potentials are discussed. An analytical model which reproduces the main features of the microscopic spectra has been developed.Comment: We have added some new references and minor changes on the mnuscript have been mad

Full security of quantum key distribution from no-signaling constraints

We analyze a cryptographic protocol for generating a distributed secret key from correlations that violate a Bell inequality by a sufficient amount, and prove its security against eavesdroppers, constrained only by the assumption that any information accessible to them must be compatible with the non-signaling principle. The claim holds with respect to the state-of-the-art security definition used in cryptography, known as universally-composable security. The non-signaling assumption only refers to the statistics of measurement outcomes depending on the choices of measurements; hence security is independent of the internal workings of the devices --- they do not even need to follow the laws of quantum theory. This is relevant for practice as a correct and complete modeling of realistic devices is generally impossible. The techniques developed are general and can be applied to other Bell inequality-based protocols. In particular, we provide a scheme for estimating Bell-inequality violations when the samples are not independent and identically distributed.Comment: 15 pages, 2 figur

Optical response of two-dimensional few-electron concentric double quantum rings: A local-spin-density-functional theory study

We have investigated the dipole charge- and spin-density response of few-electron two-dimensional concentric nanorings as a function of the intensity of a perpendicularly applied magnetic field. We show that the dipole response displays signatures associated with the localization of electron states in the inner and outer ring favored by the perpendicularly applied magnetic field. Electron localization produces a more fragmented spectrum due to the appearance of additional edge excitations in the inner and outer ring.Comment: To be published in Physical Review

Mn valence instability in La2/3Ca1/3MnO3 thin films

A Mn valence instability on La2/3Ca1/3MnO3 thin films, grown on LaAlO3 (001)substrates is observed by x-ray absorption spectroscopy at the Mn L-edge and O K-edge. As-grown samples, in situ annealed at 800 C in oxygen, exhibit a Curie temperature well below that of the bulk material. Upon air exposure a reduction of the saturation magnetization, MS, of the films is detected. Simultaneously a Mn2+ spectral signature develops, in addition to the expected Mn3+ and Mn4+ contributions, which increases with time. The similarity of the spectral results obtained by total electron yield and fluorescence yield spectroscopy indicates that the location of the Mn valence anomalies is not confined to a narrow surface region of the film, but can extend throughout the whole thickness of the sample. High temperature annealing at 1000 C in air, immediately after growth, improves the magnetic and transport properties of such films towards the bulk values and the Mn2+ signature in the spectra does not appear. The Mn valence is then stable even to prolonged air exposure. We propose a mechanism for the Mn2+ ions formation and discuss the importance of these observations with respect to previous findings and production of thin films devices.Comment: Double space, 21 pages, 6 figure

Cationic ordering control of magnetization in Sr2FeMoO6 double perovskite

The role of the synthesis conditions on the cationic Fe/Mo ordering in Sr2FeMoO6 double perovskite is addressed. It is shown that this ordering can be controlled and varied systematically. The Fe/Mo ordering has a profound impact on the saturation magnetization of the material. Using the appropriate synthesis protocol a record value of 3.7muB/f.u. has been obtained. Mossbauer analysis reveals the existence of two distinguishable Fe sites in agreement with the P4/mmm symmetry and a charge density at the Fe(m+) ions significantly larger than (+3) suggesting a Fe contribution to the spin-down conduction band. The implications of these findings for the synthesis of Sr2FeMoO6 having optimal magnetoresistance response are discussed.Comment: 9 pages, 4 figure