1,366 research outputs found
Quantum key distribution using polarized coherent states
We discuss a continuous variables method of quantum key distribution
employing strongly polarized coherent states of light. The key encoding is
performed using the variables known as Stokes parameters, rather than the field
quadratures. Their quantum counterpart, the Stokes operators
(i=1,2,3), constitute a set of non-commuting operators, being the precision of
simultaneous measurements of a pair of them limited by an uncertainty-like
relation. Alice transmits a conveniently modulated two-mode coherent state, and
Bob randomly measures one of the Stokes parameters of the incoming beam. After
performing reconciliation and privacy amplification procedures, it is possible
to distill a secret common key. We also consider a non-ideal situation, in
which coherent states with thermal noise, instead of pure coherent states, are
used for encoding.Comment: Inclusion of a discussion about noise not controlled by Eve;
inclusion of a figure. A simplified version of this paper was submitted to a
Conference in Brazil (XXVII ENFMC) in 16/02/200
Promoting nutrition sensitive and climate smart agriculture through increased use of traditional underutilised species in the Pacific
Poster presented at Tropentag 2014. International Conference on Research on Food Security, Natural Resource Management and Rural Development. "Bridging the Gap between Increasing Knowledge and Decreasing Resources" Prague (Czech Republic) Sep 17-19 2014
Vertical Melting of a Stack of Membranes
A stack of tensionless membranes with nonlinear curvature energy and vertical
harmonic interaction is studied. At low temperatures, the system forms a
lamellar phase. At a critical temperature, the stack disorders vertically in a
melting-like transition.Comment: 8 pages, 2 figure
Adaptive tracking notch filter system Patent
Adaptive notch filter, using modulation techniques for reversed phase noise signa
Quantum Key Distribution using Continuous-variable non-Gaussian States
In this work we present a quantum key distribution protocol using
continuous-variable non-Gaussian states, homodyne detection and post-selection.
The employed signal states are the Photon Added then Subtracted Coherent States
(PASCS) in which one photon is added and subsequently one photon is subtracted.
We analyze the performance of our protocol, compared to a coherent state based
protocol, for two different attacks that could be carried out by the
eavesdropper (Eve). We calculate the secret key rate transmission in a lossy
line for a superior channel (beam-splitter) attack, and we show that we may
increase the secret key generation rate by using the non-Gaussian PASCS rather
than coherent states. We also consider the simultaneous quadrature measurement
(intercept-resend) attack and we show that the efficiency of Eve's attack is
substantially reduced if PASCS are used as signal states.Comment: We have included an analysis of the simultaneous quadrature
measurement attack plus 2 figures; we have also clarified some point
DENDRITIC CELLS IN A MURINE MODEL OF BREAST CANCER: FUNCTIONAL AND PHENOTYPIC EVALUATION USING NANOPARTICLES
Dendritic cells play a pivotal role in antigen presentation and adaptive immune response activation. Studies on mice models reported that tumoral antigens-loaded DCs can induce therapeutic and protective anti-tumour immune responses, both in vitro and in vivo. These results provide an evidence of the possible use of DCs as vaccines. However, the efficacy of such therapeutic vaccination was recently questioned due to the limited degree of actual tumour regression in some clinical trials. Thus, it is necessary to better characterize immunological and clinical parameters of DCs immunization to increase the therapeutic efficay of the vaccines. In vivo imaging tecniques, as magnetic resonance imaging (MRI) and single photon emission tomography (SPET), are used to study cell trafficking mechanisms in vivo and state anti-tumoral treatments efficacy, allowing an accurate assessment.
In this work we initially set the optimal culture conditions to obtain functional immature DCs. Evaluations based on DCs number, cell viability and immature DCs percentage led to establish day 6 as the one in which the highest number of functionally active immature DCs can be achieved. We then set a DCs labelling protocol with commercial SPIO (Endorem\uae) evaluating Iron content using Perl\u2019s staining and relassometry. Time and dose-response kinetic evaluations allowed to define as optimal labelling conditions the use of 200 \u3bcg Iron of Endorem\uae/ ml of culture for 16 hours. Cell viability and phenotypic markers analysis proved that SPIO labelling had no influence on immature DCs viability or activation status. Images acquired by transmission electron microscopy showed that Endorem\uae were inside cells, in particular inside lysosomes, and were taken up by endocytosis mechanisms. We then focused on DCs antigens loading. Tumoral antigens were obtained lysing neoplastic masses extracted from a mammary tumour mouse model (MMTV-Ha-Ras). DCs pulsed with different antigen concentrations resulted mature by means of high levels of activation and maturation markers. Moreover, such cells were able to stimulate T lymphocytes extracted from MMTV-Ha-Ras spleens. 3H-thymidine and CFSE proliferation assays, together with IFN-\u3b3 production measured by ELISA, showed an increase in T lymphocytes activation when co-cultured with antigen-pulsed DCs. Cytokines production assessed by flow cytometry and ELISA allowed us to verify that tumoral antigen-pulsed DCs were able to elicit a specific T-lymphocyte response toward a Th1 type. Indeed, high amounts of IFN-\u3b3 were produced by T lymphocytes, high levels of IL-12 were produced by DCs and low levels of IL-10 were detectable. In vitro migration showed that tumoral antigen-pulsed DCs displayed migratory abilities toward MIP3\u3b2 and 6Ckine chemockines, responsible in vivo of mature DCs attraction. Flow cytometric analysis confirmed that migrated cells displayed a mature phenotype and expressed high levels of CCR7.
We then performed in vivo experiments in MMTV-Ha-Ras mice bearing neoplastic lesions and in control mice without tumours. MRI showed that Endorem\uae-labelled DCs pulsed with tumour antigens are able to migrate to the draining lymph site in vivo. Histological analysis on ex vivo lymph nodes showed the presence of Iron-labelled cells in the cortical area. Immunohistochemistry reveals co-localization of Iron-containing cells with CD208-labelled DCs, but not with macrophages. In vivo SPET migration of antigen-pulsed DCs labelled with 111In-oxine showed specific radiotracer presence in the lymph nodes omolateral to injection site; \u3b3-counter analysis of ex-vivo organs confirmed such results.
Taken together, these results suggest that this protocol could candidate for experimental use on animal models for in vivo tumour immunotherapy efficacy imaging
A Lattice Study of Spectator Effects in Inclusive Decays of B-Mesons
We compute the matrix elements of the operators which contribute to spectator
effects in inclusive decays of -mesons. The results agree well with
estimates based on the vacuum saturation (factorization) hypothesis. For the
ratio of lifetimes of charged and neutral mesons we find
, where the first error represents
the uncertainty in our evaluation of the matrix elements, and the second is an
estimate of the uncertainty due to the fact that the Wilson coefficient
functions have only been evaluated at tree-level in perturbation theory. This
result is in agreement with the experimental measurement. We also discuss the
implications of our results for the semileptonic branching ratio and the charm
yield.Comment: 25 pages (figures are included). Revised version (some numerical
integrals have been recomputed
- …