11,973 research outputs found

    XAX: a multi-ton, multi-target detection system for dark matter, double beta decay and pp solar neutrinos

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    A multi-target detection system XAX, comprising concentric 10 ton targets of 136Xe and 129/131Xe, together with a geometrically similar or larger target of liquid Ar, is described. Each is configured as a two-phase scintillation/ionization TPC detector, enhanced by a full 4pi array of ultra-low radioactivity Quartz Photon Intensifying Detectors (QUPIDs) replacing the conventional photomultipliers for detection of scintillation light. It is shown that background levels in XAX can be reduced to the level required for dark matter particle (WIMP) mass measurement at a 10^-10 pb WIMP-nucleon cross section, with single-event sensitivity below 10^-11 pb. The use of multiple target elements allows for confirmation of the A^2 dependence of a coherent cross section, and the different Xe isotopes provide information on the spin-dependence of the dark matter interaction. The event rates observed by Xe and Ar would modulate annually with opposite phases from each other for WIMP mass >~100 GeV/c^2. The large target mass of 136Xe and high degree of background reduction allow neutrinoless double beta decay to be observed with lifetimes of 10^27-10^28 years, corresponding to the Majorana neutrino mass range 0.01-0.1 eV, the most likely range from observed neutrino mass differences. The use of a 136Xe-depleted 129/131Xe target will also allow measurement of the pp solar neutrino spectrum to a precision of 1-2%.Comment: 16 pages with 17 figure

    ArcGIS Digitization of Apollo Surface Traverses

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    The Apollo surface activities were documented in extraordinary detail, with every action performed by the astronauts while on the surface recorded either in photo, audio, film, or by written testimony [1]. The samples and in situ measurements the astronauts collected while on the lunar surface have shaped our understanding of the geologic history of the Moon, and the earliest history and evolution of the inner Solar System. As part of an ongoing LASERfunded effort, we are digitizing and georeferencing data from astronaut traverses and spatially associating them to available, co-registered remote sensing data. Here we introduce the products produced so far for Apollo 15, 16, and 17 missions

    Slavnov-Taylor Parameterization for the Quantum Restoration of BRST Symmetries in Anomaly-Free Gauge Theories

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    It is shown that the problem of the recursive restoration of the Slavnov-Taylor (ST) identities at the quantum level for anomaly-free gauge theories is equivalent to the problem of parameterizing the local approximation to the quantum effective action in terms of ST functionals, associated with the cohomology classes of the classical linearized ST operator. The ST functionals of dimension <=4 correspond to the invariant counterterms, those of dimension >4 generate the non-symmetric counterterms upon projection on the action-like sector. At orders higher than one in the loop expansion there are additional contributions to the non-invariant counterterms, arising from known lower order terms. They can also be parameterized by using the ST functionals. We apply the method to Yang-Mills theory in the Landau gauge with an explicit mass term introduced in a BRST-invariant way via a BRST doublet. Despite being non-unitary, this model provides a good example where the method devised in the paper can be applied to derive the most general solution for the action-like part of the quantum effective action, compatible with the fulfillment of the ST identities and the other relevant symmetries of the model, to all orders in the loop expansion. The full dependence of the solution on the normalization conditions is given.Comment: 23 pages. Final version published in the journa

    A Horizon Ratio Bound for Inflationary Fluctuations

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    We demonstrate that the gravity wave background amplitude implies a robust upper bound on the ratio: \lambda / H^{-1} < e^60, where \lambda is the proper wavelength of fluctuations of interest and H^{-1} is the horizon at the end of inflation. The bound holds as long as the energy density of the universe does not drop faster than radiation subsequent to inflation. This limit implies that the amount of expansion between the time the scales of interest leave the horizon and the end of inflation, denoted by e^N, is also bounded from above, by about e^60 times a factor that involves an integral over the first slow-roll parameter. In other words, the bound on N is model dependent -- we show that for vast classes of slow-roll models, N < 67. The quantities, \lambda / H^{-1} or N, play an important role in determining the nature of inflationary scalar and tensor fluctuations. We suggest ways to incorporate the above bounds when confronting inflation models with observations. As an example, this bound solidifies the tension between observations of cosmic microwave background (CMB) anisotropies and chaotic inflation with a \phi^4 potential by closing the escape hatch of large N (< 62).Comment: 4 pages, 1 figure; revised to close a loophole in the earlier version and clarify our assumption

    A SUSY SU(5) Grand Unified Model of Tri-Bimaximal Mixing from A4

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    We discuss a grand unified model based on SUSY SU(5) in extra dimensions and on the flavour group A4xU(1) which, besides reproducing tri-bimaximal mixing for neutrinos with the accuracy required by the data, also leads to a natural description of the observed pattern of quark masses and mixings.Comment: 19 page

    Implementing Unitarity in Perturbation Theory

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    Unitarity cannot be perserved order by order in ordinary perturbation theory because the constraint UU^\dagger=\1 is nonlinear. However, the corresponding constraint for K=ln⁡UK=\ln U, being K=−K†K=-K^\dagger, is linear so it can be maintained in every order in a perturbative expansion of KK. The perturbative expansion of KK may be considered as a non-abelian generalization of the linked-cluster expansion in probability theory and in statistical mechanics, and possesses similar advantages resulting from separating the short-range correlations from long-range effects. This point is illustrated in two QCD examples, in which delicate cancellations encountered in summing Feynman diagrams of are avoided when they are calculated via the perturbative expansion of KK. Applications to other problems are briefly discussed.Comment: to appear in Phys. Rev.

    The transcription factor FOXO3a is a crucial cellular target of gefitinib (Iressa) in breast cancer cells

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    Gefitinib is a specific inhibitor of the epidermal growth factor receptor (EGFR) that causes growth delay in cancer cell lines and human tumor xenografts expressing high levels of EGFR. An understanding of the downstream cellular targets of gefitinib will allow the discovery of biomarkers for predicting outcomes and monitoring anti-EGFR therapies and provide information for key targets for therapeutic intervention. In this study, we investigated the role of FOXO3a in gefitinib action and resistance. Using two gefitinib-sensitive (i.e., BT474 and SKBR3) as well as three other resistant breast carcinoma cell lines (i.e., MCF-7, MDA-MB-231, and MDA-MB-453), we showed that gefitinib targets the transcription factor FOXO3a to mediate cell cycle arrest and cell death in sensitive breast cancer cells. In the sensitive cells, gefitinib treatment causes cell cycle arrest predominantly at the G(0)-G(1) phase and apoptosis, which is associated with FOXO3a dephosphorylation at Akt sites and nuclear translocation, whereas in the resistant cells, FOXO3a stays phosphorylated and remains in the cytoplasm. The nuclear accumulation of FOXO3a in response to gefitinib was confirmed in tumor tissue sections from breast cancer patients presurgically treated with gefitinib as monotherapy. We also showed that knockdown of FOXO3a expression using small interfering RNA (siRNA) can rescue sensitive BT474 cells from gefitinib-induced cell-proliferative arrest, whereas reintroduction of active FOXO3a in resistant MDA-MB-231 cells can at least partially restore cell-proliferative arrest and sensitivity to gefitinib. These results suggest that the FOXO3a dephosphorylation and nuclear localization have a direct role in mediating the gefitinib-induced proliferative arrest and in determining sensitivity to gefitinib.Supported by the German Cancer Aide Foundation (J. Krol)and the Association of International Cancer Research (R. Francis).Andrew Sunters and Andreas Polychronic were fellows funded by CancerResearch UK. Andre Albergaria is a recipient of a grant from Fundação para a CiĂȘncia e a Tecnologia, Portugal. This work was sponsored by theBreast Cancer Research Trust and Cancer Research U

    An integrated microfluidic chip with 40 MHz lead-free transducer for fluid analysis

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    The design, fabrication, and evaluation of a high-frequency transducer made from lead-free piezoceramic for the application of microfluidic analysis is described. Barium strontium zirconate titanate [(Ba₀. ₉ ₅Sr₀. ₀ ₅)(Zr₀. ₀ ₅Ti₀.₉₅)O₃, abbreviated as BSZT] ceramic has been chosen to be the active element of the transducer. The center frequency and bandwidth of this high-frequency ultrasound transducer have been measured to be 43 MHz and 56.1%, respectively. The transducer was integrated into a microfluidic channel and used to measure the sound velocity and attenuation of the liquid flowing in the channel. Results suggest that lead-free high-frequency transducers could be used for in situ analysis of property of the fluid flowing through the microfluidic system.Department of Applied PhysicsAuthor name used in this publication: S. T. F. LeeAuthor name used in this publication: K. H. LamAuthor name used in this publication: L. LeiAuthor name used in this publication: X. M. ZhangAuthor name used in this publication: H. L. W. Cha
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