165 research outputs found
Local trace formulae and scaling asymptotics in Toeplitz quantization, II
In the spectral theory of positive elliptic operators, an important role is
played by certain smoothing kernels, related to the Fourier transform of the
trace of a wave operator, which may be heuristically interpreted as smoothed
spectral projectors asymptotically drifting to the right of the spectrum. In
the setting of Toeplitz quantization, we consider analogues of these, where the
wave operator is replaced by the Hardy space compression of a linearized
Hamiltonian flow, possibly composed with a family of zeroth order Toeplitz
operators. We study the local asymptotics of these smoothing kernels, and
specifically how they concentrate on the fixed loci of the linearized dynamics.Comment: Typos corrected. Slight expository change
Isolation and characterization of extremely halophilic CO-oxidizing Euryarchaeota from hypersaline cinders, sediments and soils and description of a novel CO oxidizer, Haloferax namakaokahaiae Mke2.3\u3csup\u3eT\u3c/sup\u3e, sp. nov.
© FEMS 2016. All rights reserved. phylogenetic affiliations of organisms responsible for aerobic CO oxidation in hypersaline soils and sediments were assessed using media containing 3.8 M NaCl. CO-oxidizing strains of the euryarchaeotes, Haloarcula, Halorubrum, Haloterrigena and Natronorubrum, were isolated from the Bonneville Salt Flats (UT) and Atacama Desert salterns (Chile). A halophilic euryarchaeote, Haloferax strain Mke2.3T, was isolated from Hawai\u27i Island saline cinders. Haloferax strain Mke2.3T was most closely related to Haloferax larsenii JCM 13917T (97.0% 16S rRNA sequence identity). It grew with a limited range of substrates, and oxidized CO at a headspace concentration of 0.1%. However, it did not grow with CO as a sole carbon and energy source. Its ability to oxidize CO, its polar lipid composition, substrate utilization and numerous other traits distinguished it from H. larsenii JCM 13917T, and supported designation of the novel isolate as Haloferax namakaokahaiae Mke2.3T, sp. nov (= DSM 29988, = LMG 29162). CO oxidation was also documented for \u27Natronorubrum thiooxidans\u27 HG1 (Sorokin, Tourova and Muyzer 2005), N. bangense (Xu, Zhou and Tian 1999) and N. sulfidifaciens AD2T (Cui et al. 2007). Collectively, these results established a previously unsuspected capacity for extremely halophilic aerobic CO oxidation, and indicated that the trait might be widespread among the Halobacteriaceae, and occur in a wide range of hypersaline habitats
Relative Ruan and Gromov-Taubes Invariants of Symplectic 4-Manifolds
We define relative Ruan invariants that count embedded connected symplectic
submanifolds which contact a fixed stable symplectic hypersurface V in a
symplectic 4-manifold (X,w) at prescribed points with prescribed contact orders
(in addition to insertions on X\V) for stable V. We obtain invariants of the
deformation class of (X,V,w). Two large issues must be tackled to define such
invariants: (1) Curves lying in the hypersurface V and (2) genericity results
for almost complex structures constrained to make V pseudo-holomorphic (or
almost complex). Moreover, these invariants are refined to take into account
rim tori decompositions. In the latter part of the paper, we extend the
definition to disconnected submanifolds and construct relative Gromov-Taubes
invariants
Birational cobordism invariance of uniruled symplectic manifolds
A symplectic manifold is called {\em (symplectically) uniruled}
if there is a nonzero genus zero GW invariant involving a point constraint. We
prove that symplectic uniruledness is invariant under symplectic blow-up and
blow-down. This theorem follows from a general Relative/Absolute correspondence
for a symplectic manifold together with a symplectic submanifold. A direct
consequence is that symplectic uniruledness is a symplectic birational
invariant. Here we use Guillemin and Sternberg's notion of cobordism as the
symplectic analogue of the birational equivalence.Comment: To appear in Invent. Mat
Exotic smooth structures and symplectic forms on closed manifolds
We give a short proof of the (known) result that there are no Kaehler
structures on exotic tori. This yields a negative solution to a problem posed
by Benson and Gordon. W discuss the symplectic version of the problem and
analyze results which yield an evidence for the conjecture that there are no
symplectic structures on exotic tori.Comment: AMSLaTeX, 16 pages, a new version. A survey of the symplectic version
of the problem is adde
The lymphoma-associated NPM-ALK oncogene elicits a p16INKa/pRb-dependent tumour-suppressive pathway
Oncogene induced senescence (OIS) is a barrier for tumour development. Oncogene-dependent DNA damage and activation of the ARF/p53 pathway play a central role in OIS and, accordingly, ARF and p53 are frequently mutated in human cancer. A number of leukemia/lymphoma-initiating oncogenes, however, inhibit ARF/p53 and only infrequently select for ARF or p53 mutations, suggesting the involvement of other tumour-suppressive pathways. We report that NPM-ALK, the initiating oncogene of Anaplastic Large Cell Lymphomas (ALCLs), induces DNA-damage and irreversibly arrests the cell cycle of primary fibroblasts and hematopoietic progenitors. This effect is associated with inhibition of p53 and is due to activation of the p16INK4a/pRb tumour-suppressive pathway. Analysis of NPM-ALK lymphomagenesis in transgenic mice showed p16INK4a-dependent accumulation of senescent cells in pre-malignant lesions and decreased tumour latency in the absence of p16INK4a. Accordingly, human ALCLs showed no expression of either p16INK4a or pRb. Up-regulation of the histone-demethylase Jmjd3 and de-methylation at the p16INK4a promoter contributed to the effect of NPM-ALK on p16INK4a, which was transcriptionally regulated. These data demonstrate that p16INK4a/pRb may function as an alternative pathway of oncogene-induced senescence, and suggest that the reactivation of p16INK4a expression might be a novel strategy to restore the senescence program in some tumours
A Comparison of Computerized Chemical Models for Equilibrium Calculations in Aqueous Systems
A survey of computer programs which are currently being used to calculate the distribution of species in aqueous solutions, especially natural waters, has been made in order to 1) provide an inventory of available programs with a short description of their uses, 2) compare the consistency of their output for two given test solutions and 3) identify major weaknesses or problems encountered from their use. More than a dozen active programs which can be used for distribution of species and activity calculations for homogeneos equilibria among the major anions and cations of natural waters have been inventoried. Half of these programs can also accept several trace elements including Fe, Al, Mn, Cu, Ni, Zn, Cd, Pb, Ag, Hg, As, Ba, Sr, and B. Consistency between programs was evaluated by comparing the log of the molal concentrations of free ions and complexes for two test solutions: a hypothetical seawater analysis and a hypothetical river water analysis. Comparison of the free major ion concentrations in the river water test case shows excellent agreement for the major species. In the seawater test case there is less agreement and for both test cases the minor species commonly show orders of magnitude differences in concentrations. These differences primarily reflect differences in the thermodynamic data base of each chemical model although other factors such as activity coefficient calculations, redox assumptions, temperature corrections, alkalinity corrections and the number of complexes used all have an affect on the output
Metastable chaos in the ammonia ring laser
We report experimental studies of metastable chaos in the far-infrared ammonia ring: laser. When the laser pump power is switched from above chaos threshold to slightly below, chaotic intensity pulsations continue for a varying time afterward before decaying to either periodic or cw emission. The behavior is in good qualitative agreement with that predicted by the Lorenz equations, previously used to describe this laser. The statistical distribution of the duration of the chaotic transient is measured and shown to be in excellent agreement with the Lorenz equations in showing a modified exponential distribution. We also give a brief numerical analysis and graphical visualization of the Lorenz equations in phase space illustrating the boundary between the metastable chaotic and the stable fixed point basins of attraction. This provides an intuitive understanding of the metastable dynamics of the Lorenz equations and the experimental system
Supersymmetric Wilson loops on S^3
This paper studies in great detail a family of supersymmetric Wilson loop
operators in N=4 supersymmetric Yang-Mills theory we have recently found. For a
generic curve on an S^3 in space-time the loops preserve two supercharges but
we will also study special cases which preserve 4, 8 and 16 supercharges. For
certain loops we find the string theory dual explicitly and for the general
case we show that string solutions satisfy a first order differential equation.
This equation expresses the fact that the strings are pseudo-holomorphic with
respect to a novel almost complex structure we construct on AdS_4 x S^2. We
then discuss loops restricted to S^2 and provide evidence that they can be
calculated in terms of similar observables in purely bosonic YM in two
dimensions on the sphere.Comment: Latex, 84 pages, 4 figures. v2: minor changes, references added; to
appear in JHE
Mirror Manifolds in Higher Dimension
We describe mirror manifolds in dimensions different from the familiar case
of complex threefolds. We emphasize the simplifying features of dimension three
and supply more robust methods that do not rely on such special characteristics
and hence naturally generalize to other dimensions. The moduli spaces for
Calabi--Yau -folds are somewhat different from the ``special K\"ahler
manifolds'' which had occurred for , and we indicate the new geometrical
structures which arise. We formulate and apply procedures which allow for the
construction of mirror maps and the calculation of order-by-order instanton
corrections to Yukawa couplings. Mathematically, these corrections are expected
to correspond to calculating Chern classes of various parameter spaces (Hilbert
schemes) for rational curves on Calabi--Yau manifolds. Our results agree with
those obtained by more traditional mathematical methods in the limited number
of cases for which the latter analysis can be carried out. Finally, we make
explicit some striking relations between instanton corrections for various
Yukawa couplings, derived from the associativity of the operator product
algebra.Comment: 44 pages plus 3 tables using harvma
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