1,265 research outputs found

    De Grootloge van Adoptie, ‘La Loge de Juste’ Den Haag, 1751

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    Modernity (Religion and Modernity

    Aneuploidy in oocytes is prevented by sustained CDK1 activity through degron masking in cyclin B1

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    Successful mitosis requires that cyclin B1:CDK1 kinase activity remains high until chromosomes are correctly aligned on the mitotic spindle. It has therefore been unclear why, in mammalian oocyte meiosis, cyclin B1 destruction begins before chromosome alignment is complete. Here, we resolve this paradox and show that mouse oocytes exploit an imbalance in the ratio of cyclin B1 to CDK1 to control CDK1 activity; early cyclin B1 destruction reflects the loss of an excess of non-CDK1-bound cyclin B1 in late prometaphase, while CDK1-bound cyclin B1 is destroyed only during metaphase. The ordered destruction of the two forms of cyclin B1 is brought about by a previously unidentified motif that is accessible in free cyclin B1 but masked when cyclin B1 is in complex with CDK1. This protects the CDK1-bound fraction from destruction in prometaphase, ensuring a period of prolonged CDK1 activity sufficient to achieve optimal chromosome alignment and prevent aneuploidy

    CP Violating Bubble Wall Profiles

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    We solve the equations of motion for a CP violating phase between the two Higgs doublets at the bubble wall of the MSSM electroweak phase transition. Contrary to earlier suggestions, we do not find indications of spontaneous ``transitional'' CP violation in the MSSM. On the other hand, in case there is explicit CP violation in the stop and chargino/neutralino sectors, the relative phase between the Higgses does become space dependent, but only mildly even in the maximal case. We also demonstrate that spontaneous CP violation within the bubble wall could occur, e.g., if the Higgs sector of the MSSM were supplemented by a singlet. Finally we point out some implications for baryogenesis computations

    Advances in the proposed electromagnetic zero-point field theory of inertia

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    A NASA-funded research effort has been underway at the Lockheed Martin Advanced Technology Center in Palo Alto and at California State University in Long Beach to develop and test a recently published theory that Newton's equation of motion can be derived from Maxwell's equations of electrodynamics as applied to the zero-point field (ZPF) of the quantum vacuum. In this ZPF-inertia theory, mass is postulated to be not an intrinsic property of matter but rather a kind of electromagnetic drag force that proves to be acceleration dependent by virtue of the spectral characteristics of the ZPF. The theory proposes that interactions between the ZPF and matter take place at the level of quarks and electrons, hence would account for the mass of a composite neutral particle such as the neutron. An effort to generalize the exploratory study of Haisch, Rueda and Puthoff (1994) into a proper relativistic formulation has been successful. Moreover the principle of equivalence implies that in this view gravitation would also be electromagnetic in origin along the lines proposed by Sakharov (1968). With regard to exotic propulsion we can definitively rule out one speculatively hypothesized mechanism: matter possessing negative inertial mass, a concept originated by Bondi (1957) is shown to be logically impossible. On the other hand, the linked ZPF-inertia and ZPF-gravity concepts open the conceptual possibility of manipulation of inertia and gravitation, since both are postulated to be electromagnetic phenomena. It is hoped that this will someday translate into actual technological potential. A key question is whether the proposed ZPF-matter interactions generating the phenomenon of mass might involve one or more resonances. This is presently under investigation.Comment: Revised version of invited presentation at 34th AIAA/ASME/SAE/ASEE Joint Propulsion Conference, July 13-15, 1998, Cleveland, OH, 10 pages, no figure

    Heavy-light mesons with staggered light quarks

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    We demonstrate the viability of improved staggered light quarks in studies of heavy-light systems. Our method for constructing heavy-light operators exploits the close relation between naive and staggered fermions. The new approach is tested on quenched configurations using several staggered actionsn combined with nonrelativistic heavy quarks. The B_s meson kinetic mass, the hyperfine and 1P-1S splittings in B_s, and the decay constant f_{B_s} are calculated and compared to previous quenched lattice studies. An important technical detail, Bayesian curve-fitting, is discussed at length.Comment: 38 pages, figures included. v2: Entry in Table IX corrected and other minor changes, version appearing in Phys. Rev.

    Hybrid configuration content of heavy S-wave mesons

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    We use the non-relativistic expansion of QCD (NRQCD) on the lattice to study the lowest hybrid configuration contribution to the ground state of heavy S-wave mesons. Using lowest-order lattice NRQCD to create the heavy-quark propagators, we form a basis of ``unperturbed'' S-wave and hybrid states. We then apply the lowest-order coupling of the quark spin and chromomagnetic field at an intermediate time slice to create ``mixed'' correlators between the S-wave and hybrid states. From the resulting amplitudes, we extract the off-diagonal element of our two-state Hamiltonian. Diagonalizing this Hamiltonian gives us the admixture of hybrid configuration within the meson ground state. The present effort represents a continuation of previous work: the analysis has been extended to include lattices of varying spacings, source operators having better overlap with the ground states, and the pseudoscalar (along with the vector) channel. Results are presented for bottomonium (΄\Upsilon, ηb\eta_b^{}) using three different sets of quenched lattices. We also show results for charmonium (J/ψJ/\psi, ηc\eta_c^{}) from one lattice set, although we note that the non-relativistic approximation is not expected to be very good in this case.Comment: 9 pages, 7 figures, version to appear in Phys Rev
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