2,015 research outputs found

    Finite bounded expanding white hole universe without dark matter

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    The solution of Einstein's field equations in Cosmological General Relativity (CGR), where the Galaxy is at the center of a finite yet bounded spherically symmetrical isotropic gravitational field, is identical with the unbounded solution. This leads to the conclusion that the Universe may be viewed as a finite expanding white hole. The fact that CGR has been successful in describing the distance modulus verses redshift data of the high-redshift type Ia supernovae means that the data cannot distinguish between unbounded models and those with finite bounded radii of at least cτc \tau. Also it is shown that the Universe is spatially flat at the current epoch and has been at all past epochs where it was matter dominated.Comment: 11 pages, revised versio

    Spheroidal and elliptical galaxy radial velocity dispersion determined from Cosmological General Relativity

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    Radial velocity dispersion in spheroidal and elliptical galaxies, as a function of radial distance from the center of the galaxy, has been derived from Cosmological Special Relativity. For velocity dispersions in the outer regions of spherical galaxies, the dynamical mass calculated for a galaxy using Carmelian theory may be 10 to 100 times less than that calculated from standard Newtonian physics. This means there is no need to include halo dark matter. The velocity dispersion is found to be approximately constant across the galaxy after falling from an initial high value at the center.Comment: 10 pages, 3 figure

    An approach to cork oak forest management planning: a case study in southwestern Portugal

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    This paper presents results of research aiming at the development of tools that may enhance cork oak (Quercus suber L.) forest management planning. Specifically, it proposes an hierarchical approach that encompasses the spatial classification of a cork oak forest and the temporal scheduling of cork harvests. The use of both geographical information systems and operations research techniques is addressed. Emphasis is on the achievement of cork even flow objectives. Results from an application to a case study in the Charneca Plioce´nica of Ribatejo in southern Portugal encompassing a cork oak forest extending over 4.8 thousand ha are discussed. They suggest that the proposed approach is capable of effective spatial classification of cork oak management units. They further suggest that it may be used to select optimal cork even flow scheduling strategies. Results also show that the proposed approach may lead to a substantial increase in net present value when compared to traditional approaches to cork oak forest management planning

    Optical Line Width Broadening Mechanisms at the 10 kHz Level in Eu3+:Y2O3 Nanoparticles

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    We identify the physical mechanisms responsible for the optical homogeneous broadening in Eu3+:Y2O3 nanoparticles to determine whether rare-earth crystals can be miniaturized to volumes less than λ3 whilst preserving their appeal for quantum technology hardware. By studying how the homogeneous line width depends on temperature, applied magnetic field, and measurement time scale the dominant broadening interactions for various temperature ranges above 3 K were characterized. Below 3 K the homogeneous line width is dominated by an interaction not observed in bulk crystal studies. These measurements demonstrate that broadening due to size-dependent phonon interactions is not a significant contributor to the homogeneous line width, which contrasts previous studies in rare-earth ion nanocrystals. Importantly, the results provide strong evidence that for the 400 nm diameter nanoparticles under study the minimum line width achieved (45±1 kHz at 1.3 K) is not fundamentally limited. In addition, we highlight that the expected broadening caused by electric field fluctuations arising from surface charges is comparable to the observed broadening. Under the assumption that such Stark broadening is a significant contribution to the homogeneous line width, several strategies for reducing this line width to below 10 kHz are discussed. Furthermore, it is demonstrated that the Eu3+ hyperfine state lifetime is sufficiently long to preserve spectral features for timescales up to 1 s. These results allow integrated rare-earth ion quantum optics to be pursued at a sub-micron scale and hence, open up directions for greater scaling of rare-earth quantum technology

    Particle Pair Production in Cosmological General Relativity

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    The Cosmological General Relativity (CGR) of Carmeli, a 5-dimensional (5-D) theory of time, space and velocity, predicts the existence of an acceleration a_0 = c / tau due to the expansion of the universe, where c is the speed of light in vacuum, tau = 1 / h is the Hubble-Carmeli time constant, where h is the Hubble constant at zero distance and no gravity. The Carmeli force on a particle of mass m is F_c = m a_0, a fifth force in nature. In CGR, the effective mass density rho_eff = rho - rho_c, where rho is the matter density and rho_c is the critical mass density which we identify with the vacuum mass density rho_vac = -rho_c. The fields resulting from the weak field solution of the Einstein field equations in 5-D CGR and the Carmeli force are used to hypothesize the production of a pair of particles. The mass of each particle is found to be m = tau c^3 / 4 G, where G is Newton's constant. The vacuum mass density derived from the physics is rho_vac = -rho_c = -3 / (8 pi G tau^2). The cosmic microwave background (CMB) black body radiation at the temperature T_o = 2.72548 K which fills that volume is found to have a relationship to the ionization energy of the Hydrogen atom. Define the radiation energy epsilon_gamma = (1 - g) m c^2 / N_gamma, where (1-g) is the fraction of the initial energy m c^2 which converts to photons, g is a function of the baryon density parameter Omega_b and N_gamma is the total number of photons in the CMB radiation field. We make the connection with the ionization energy of the first quantum level of the Hydrogen atom by the hypothesis epsilon_gamma = [(1 - g) m c^2] / N_gamma = alpha^2 mu c^2 / 2, where alpha is the fine-structure constant and mu = m_p f / (1 + f), where f= m_e / m_p with m_e the electron mass and m_p the proton mass.Comment: 14 pages, 0 figures. The final publication is available at springerlink.co

    Switch rates vary due to expected payoff but not due to individual risk tendency.

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    When switching between different tasks, the initiation of task switches may depend on task characteristics (difficulty, salient cues, etc.) or reasons within the person performing the task (decisions, behavioral variability, etc.). The reasons for variance in switching strategies, especially in paradigms where participants are free to choose the order of tasks and the amount of switching between tasks, are not well researched. In this study, we follow up the recent discussion that variance in switching strategies might be partly explained by the characteristics of the person fulfilling the task. We examined whether risk tendency and impulsiveness differentiate individuals in their response (i.e., switch rates and time spent on tasks) to different task characteristics on a tracking-while-typing paradigm. In detail, we manipulated two aspects of loss prospect (i.e., "payoff" as the amount of points that could be lost when tracking was unattended for too long, and "cursor speed" determining the likelihood of such a loss occurring). To account for between-subject variance and within-subject variability in the data, we employed linear mixed effect analyses following the model selection procedure (Bates, Kliegl, et al., 2015). Besides, we tested whether risk tendency can be transformed into a decision parameter which could predict switching strategies when being computationally modelled. We transferred decision parameters from the Decision Field Theory to model "switching thresholds" for each individual. Results show that neither risk tendency nor impulsiveness explain between-subject variance in the paradigm, nonetheless linear mixed-effects models confirmed that within-subject variability plays a significant role for interpreting dual-task data. Our computational model yielded a good model fit, suggesting that the use of a decision threshold parameter for switching may serve as an alternative means to classify different strategies in task switching. [Abstract copyright: Copyright © 2022. Published by Elsevier B.V.

    Time evolution of the classical and quantum mechanical versions of diffusive anharmonic oscillator: an example of Lie algebraic techniques

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    We present the general solutions for the classical and quantum dynamics of the anharmonic oscillator coupled to a purely diffusive environment. In both cases, these solutions are obtained by the application of the Baker-Campbell-Hausdorff (BCH) formulas to expand the evolution operator in an ordered product of exponentials. Moreover, we obtain an expression for the Wigner function in the quantum version of the problem. We observe that the role played by diffusion is to reduce or to attenuate the the characteristic quantum effects yielded by the nonlinearity, as the appearance of coherent superpositions of quantum states (Schr\"{o}dinger cat states) and revivals.Comment: 21 pages, 6 figures, 2 table

    Compared to mycophenolate mofetil, rapamycin induces significant changes on growth factors and growth factor receptors in the early days post‐kidney transplantation

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    We found 1 article: Transplantation. 2002 Mar 27;73(6):915-20. Compared to mycophenolate mofetil, rapamycin induces significant changes on growth factors and growth factor receptors in the early days post-kidney transplantation. Oliveira JG, Xavier P, Sampaio SM, Henriques C, Tavares I, Mendes AA, Pestana M. Renal Department, Hospital S. João, Porto, Portugal. Abstract BACKGROUND: The new immunosuppressive drug Rapamycin (Rapa) is endowed with a mechanism of action that is distinct from that of calcineurin inhibitors. It has been claimed that Rapa does not significantly modulate either the cytokine expression or the transcription of several growth factors in mitogen-activated T cells. Previously, we reported that fine-needle aspiration biopsy (FNAB) sample cultures synthesize a large array of cytokines, and some of them may be powerful predictors of acute rejection in renal transplants. We hypothesized that Rapa may induce significant changes on cytokine production by FNAB sample cultures and on serum cytokine receptors when compared to other immunosuppressive drugs. METHODS: Kidney transplants treated with CsA-Rapa-Pred (Rapa group) were compared with transplants treated with CsA-mycophenolate mofetil-Pred (MMF group). They were studied on day 7 posttransplantation, and they remained rejection free for at least the first 6 months. FNAB samples were cultured and the supernatants were collected at 48 hr of incubation and analyzed by ELISA for interleukin 1 receptor antagonist (IL-1ra), IL-2, IL-6, IL-10, IL-18, monocyte chemotactic protein 1 (MCP-1), soluble tumor necrosis factor I, and transforming growth factor (TGF)-beta(1). The soluble receptors for IL-1, IL-2, IL-6, and tumor necrosis factor alpha, together with IL-2 and IL-18 were also measured in serum. RESULTS: Significant differences were observed when comparing Rapa with the MMF group. IL-18 and TGF-beta(1) synthesis were up-regulated, whereas IL-6 and MCP-1 were down-regulated in FNAB sample cultures. The Rapa group showed a significant down-regulation of each cytokine receptor and of IL-2 in serum. CONCLUSIONS: Rapa was associated with a decreased synthesis of primarily monocyte-derived cytokines and enhanced production of TGF-beta(1), which in an appropriate cytokine milieu may promote allograft tolerance. The down-regulation of cytokine receptors and IL-2 may be associated with a depressed immune response towards the kidney allograft. PMID: 11923692 [PubMed - indexed for MEDLINE
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