1,164 research outputs found

    Volume 4. Article 4. A contribution to the study of the natural food-cycle in aquatic environments. With particular consideration of micro-organisms and dissolved organic matter.

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    https://elischolar.library.yale.edu/bulletin_yale_bingham_oceanographic_collection/1107/thumbnail.jp

    Roulette Inflation with K\"ahler Moduli and their Axions

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    We study 2-field inflation models based on the ``large-volume'' flux compactification of type IIB string theory. The role of the inflaton is played by a K\"ahler modulus \tau corresponding to a 4-cycle volume and its axionic partner \theta. The freedom associated with the choice of Calabi Yau manifold and the non-perturbative effects defining the potential V(\tau, \theta) and kinetic parameters of the moduli bring an unavoidable statistical element to theory prior probabilities within the low energy landscape. The further randomness of (\tau, \theta) initial conditions allows for a large ensemble of trajectories. Features in the ensemble of histories include ``roulette tractories'', with long-lasting inflations in the direction of the rolling axion, enhanced in number of e-foldings over those restricted to lie in the \tau-trough. Asymptotic flatness of the potential makes possible an eternal stochastic self-reproducing inflation. A wide variety of potentials and inflaton trajectories agree with the cosmic microwave background and large scale structure data. In particular, the observed scalar tilt with weak or no running can be achieved in spite of a nearly critical de Sitter deceleration parameter and consequently a low gravity wave power relative to the scalar curvature power.Comment: Version submitted to Phys.Rev.D. 29 pages, 12 Figures, minor change

    Laparoscopic cholecystectomy: the missed diagnosis

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    Background: All 534 laparoscopic cholecystectomies performed by five surgeons at a single institution over a 3-year period were reviewed as part of a quality assurance process. The aim of the review, which has previously been published in this journal, was to identify and quantify complications of the procedure. Five cases in this series were recognized where major intra-abdominal pathology not identified at the time of laparoscopic cholecystectomy required laparotomy shortly thereafter. These five cases are reported here because there has been little discussion in the literature of this problem associated with laparoscopic cholecystectomy. Methods: The records of all 534 patients having a laparoscopic cholecystectomy between October 1990 and September 1993 were reviewed and entered into a computer database (Microsoft Access). This data collection and recording have subsequently become an ongoing process of quality assurance. Results: Five of 534 patients treated by laparoscopic cholecystectomy failed to have resolution of their symptoms post-operatively. A laparotomy was subsequently required within 3ā€“12 months which demonstrated causative pathology present, but not detected at, the time of laparoscopic cholecystectomy. Where possible, treatment of these laparotomy findings resolved the initial presenting symptoms of colicky epigastric pain. Conclusions: The rate of ā€˜missed diagnosisā€™ is found to be < 1%. Laparoscopic cholecystectomy is a therapeutic, rather than diagnostic, procedure, and pre-operative discussion should include the possibility of further procedures being required subsequently, particularly when symptoms and signs are atypical

    Cosmic microwave background snapshots: pre-WMAP and post-WMAP

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    Abbreviated: We highlight the remarkable evolution in the CMB power spectrum over the past few years, and in the cosmological parameters for minimal inflation models derived from it. Grand unified spectra (GUS) show pre-WMAP optimal bandpowers are in good agreement with each other and with the one-year WMAP results, which now dominate the L < 600 bands. GUS are used to determine calibrations, peak/dip locations and heights, and damping parameters. These CMB experiments significantly increased the case for accelerated expansion in the early universe (the inflationary paradigm) and at the current epoch (dark energy dominance) when they were combined with `prior' probabilities on the parameters. A minimal inflation parameter set is applied in the same way to the evolving data. Grid-based and and Monte Carlo Markov Chain methods are shown to give similar values, highly stable over time and for different prior choices, with the increasing precision best characterized by decreasing errors on uncorrelated parameter eigenmodes. After marginalizing over the other cosmic and experimental variables for a weak+LSS prior, the pre-WMAP data of Jan03 cf. the post-WMAP data of Mar03 give Omega_{tot} =1.03^{+0.05}_{-0.04} cf. 1.02^{+0.04}_{-0.03}. Adding the flat prior, n_s =0.95^{+0.07}_{-0.04} cf. 0.97^{+0.02}_{-0.02}, with < 2\sigma evidence for a log variation of n_s. The densities have concordance values. The dark energy pressure-to-density ratio is not well constrained by our weak+LSS prior, but adding SN1 gives w_Q < -0.7. We find \sigma_8 = 0.89^{+0.06}_{-0.07} cf. 0.86^{+0.04}_{-0.04}, implying a sizable SZ effect; the high L power suggest \sigma_8 \sim 0.94^{+0.08}_{-0.16} is needed to be SZ-compatible.Comment: 36 pages, 5 figures, 5 tables, Jan 2003 Roy Soc Discussion Meeting on `The search for dark matter and dark energy in the Universe', published PDF (Oct 15 2003) is http://www.cita.utoronto.ca/~bond/roysoc03/03TA2435.pd

    Cosmic neutrino decoupling and its observable imprints: insights from entropic-dual transport

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    Very different processes characterize the decoupling of neutrinos to form the cosmic neutrino background (CĪ½B) and the much later decoupling of photons from thermal equilibrium to form the cosmic microwave background (CMB). The CĪ½B emerges from the fuzzy, energy-dependent neutrinosphere and encodes the physics operating in the early universe in the temperature rangeT āˆ¼ 10 MeV to T āˆ¼ 10 keV. This is the epoch where beyond Standard Model (BSM) physics, especially in the neutrino sector, may be influential in setting the light element abundances, the necessarily distorted fossil neutrino energy spectra, and other light particle energy density contributions. Here we use techniques honed in extensive CMB studies to analyze the CĪ½B as calculated in detailed neutrino energy transport and nuclear reaction simulations of the protracted weak decoupling and primordial nucleosynthesis epochs. Our moment method, relative entropy, and differential visibility approach can leverage future high precision CMB and light element primordial abundance measurements to provide new insights into the CĪ½B and any BSM physics it encodes. We demonstrate that the evolution of the energy spectrum of the CĪ½B throughout the weak decoupling epoch is accurately captured in the Standard Model by only three parameters per species, a non-trivial conclusion given the deviation from thermal equilibrium and the impact of the decrease of electron-positron pairs. Furthermore, we can interpret each of the three parameters as physical characteristics of a non-equilibrium system. Though the treatment presented here makes some simplifying assumptions including ignoring neutrino flavor oscillations, the success of our compact description within the Standard Model motivates its use also in BSM scenarios. We further demonstrate how observations of primordial light element abundances can be used to place constraints on the CĪ½B energy spectrum, deriving response functions that can be applied for general deviations from a thermal spectrum. Combined with the description of those deviations that we develop here, our methods provide a convenient and powerful framework to constrain the impact of BSM physics on the CĪ½B

    Computing CMB Anisotropy in Compact Hyperbolic Spaces

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    The measurements of CMB anisotropy have opened up a window for probing the global topology of the universe on length scales comparable to and beyond the Hubble radius. For compact topologies, the two main effects on the CMB are: (1) the breaking of statistical isotropy in characteristic patterns determined by the photon geodesic structure of the manifold and (2) an infrared cutoff in the power spectrum of perturbations imposed by the finite spatial extent. We present a completely general scheme using the regularized method of images for calculating CMB anisotropy in models with nontrivial topology, and apply it to the computationally challenging compact hyperbolic topologies. This new technique eliminates the need for the difficult task of spatial eigenmode decomposition on these spaces. We estimate a Bayesian probability for a selection of models by confronting the theoretical pixel-pixel temperature correlation function with the COBE-DMR data. Our results demonstrate that strong constraints on compactness arise: if the universe is small compared to the `horizon' size, correlations appear in the maps that are irreconcilable with the observations. If the universe is of comparable size, the likelihood function is very dependent upon orientation of the manifold wrt the sky. While most orientations may be strongly ruled out, it sometimes happens that for a specific orientation the predicted correlation patterns are preferred over the conventional infinite models.Comment: 15 pages, LaTeX (IOP style included), 3 color figures (GIF) in separate files. Minor revision to match the version accepted in Class. Quantum Grav.: Proc. of Topology and Cosmology, Cleveland, 1997. The paper can be also downloaded from http://www.cita.utoronto.ca/~pogosyan/cwru_proc.ps.g
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