110 research outputs found
On the strength of the finite intersection principle
We study the logical content of several maximality principles related to the
finite intersection principle (F\IP) in set theory. Classically, these are
all equivalent to the axiom of choice, but in the context of reverse
mathematics their strengths vary: some are equivalent to \ACA over \RCA,
while others are strictly weaker, and incomparable with \WKL. We show that
there is a computable instance of F\IP all of whose solutions have
hyperimmune degree, and that every computable instance has a solution in every
nonzero c.e.\ degree. In terms of other weak principles previously studied in
the literature, the former result translates to F\IP implying the omitting
partial types principle (). We also show that, modulo
induction, F\IP lies strictly below the atomic model theorem
().Comment: This paper corresponds to section 3 of arXiv:1009.3242, "Reverse
mathematics and equivalents of the axiom of choice", which has been
abbreviated and divided into two pieces for publicatio
Hyaluronidase of Bloodsucking Insects and Its Enhancing Effect on Leishmania Infection in Mice
Hyaluronidases are enzymes degrading the extracellular matrix of vertebrates. Bloodsucking insects use them to cleave the skin of the host, enlarge the feeding lesion and acquire the blood meal. In addition, resulting fragments of extracellular matrix modulate local immune response of the host, which may positively affect transmission of vector-borne diseases, including leishmaniasis. Leishmaniases are diseases with a wide spectrum of clinical forms, from a relatively mild cutaneous affection to life-threatening visceral disease. Their causative agents, protozoans of the genus Leishmania, are transmitted by phlebotomine sand flies. Sand fly saliva was described to enhance Leishmania infection, but the information about molecules responsible for this exacerbating effect is still very limited. In the present work we demonstrated hyaluronidase activity in salivary glands of various Diptera and in fleas. In addition, we showed that hyaluronidase exacerbates Leishmania lesions in mice and propose that salivary hyaluronidase may facilitate the spread of other vector-borne microorganisms
Lyapunov spectrum of asymptotically sub-additive potentials
For general asymptotically sub-additive potentials (resp. asymptotically
additive potentials) on general topological dynamical systems, we establish
some variational relations between the topological entropy of the level sets of
Lyapunov exponents, measure-theoretic entropies and topological pressures in
this general situation. Most of our results are obtained without the assumption
of the existence of unique equilibrium measures or the differentiability of
pressure functions. Some examples are constructed to illustrate the
irregularity and the complexity of multifractal behaviors in the sub-additive
case and in the case that the entropy map that is not upper-semi continuous.Comment: 44 page
Mycobacteria Exploit Host Hyaluronan for Efficient Extracellular Replication
In spite of the importance of hyaluronan in host protection against infectious organisms in the alveolar spaces, its role in mycobacterial infection is unknown. In a previous study, we found that mycobacteria interact with hyaluronan on lung epithelial cells. Here, we have analyzed the role of hyaluronan after mycobacterial infection was established and found that pathogenic mycobacteria can grow by utilizing hyaluronan as a carbon source. Both mouse and human possess 3 kinds of hyaluronan synthases (HAS), designated HAS1, HAS2, and HAS3. Utilizing individual HAS-transfected cells, we show that HAS1 and HAS3 but not HAS2 support growth of mycobacteria. We found that the major hyaluronan synthase expressed in the lung is HAS1, and that its expression was increased after infection with Mycobacterium tuberculosis. Histochemical analysis demonstrated that hyaluronan profoundly accumulated in the granulomatous legion of the lungs in M. tuberculosis-infected mice and rhesus monkeys that died from tuberculosis. We detected hyaluronidase activity in the lysate of mycobacteria and showed that it was critical for hyaluronan-dependent extracellular growth. Finally, we showed that L-Ascorbic acid 6-hexadecanoate, a hyaluronidase inhibitor, suppressed growth of mycobacteria in vivo. Taken together, our data show that pathogenic mycobacteria exploit an intrinsic host-protective molecule, hyaluronan, to grow in the respiratory tract and demonstrate the potential usefulness of hyaluronidase inhibitors against mycobacterial diseases
Horseshoes, solenoids, and holomorphic motions for Hénonmaps
In this dissertation we show that the McMullen-Sullivan holomorphic motion for topologically conjugate, complex polynomials with connected Julia set follows level sets of the Böttcher coordinate. Analogously, we prove that the Buzzard-Verma motion for hyperbolic, unstably connected, polynomial diffeomorphisms of [special characters omitted] follows level sets of the Bedford-Smillie solenoid map. It follows that this solenoid map is a homeomorphism for those Hénon maps that are perturbations of one-dimensional hyperbolic maps with connected Julia set. Also, we show that there is a natural holomorphic motion of the Julia set in the horseshoe setting as well as more generally; this motion lends itself nicely to a computer algorithm
THE SOLENOID AND HOLOMORPHIC MOTIONS FOR HÉNON MAPS
Abstract. The McMullen-Sullivan holomorphic motion for topologically conjugate, complex polynomials with connected Julia set follows level sets of the Böttcher coordinate. The Buzzard-Verma holomorphic motion for hyperbolic, unstably connected, polynomial diffeomorphisms of C 2 follows level sets of the Bedford-Smillie solenoid map. It follows that this solenoid map is a conjugacy for those Hénon maps that are perturbations of (one-dimensional) hyperbolic maps with connected Julia set. 1
A COMPARISON OF BEHAVIOR FOR TWO COHORTS OF CAPTIVE-REARED GREATER SANDHILL CRANES RELEASED IN NORTHERN ARIZONA
To determine how the behavior of greater sandhill cranes (Grus canadensis tabida) changes according to time of year, time of day, and number of days after release, we observed the activities of 2 groups of captive-reared greater sandhill cranes at Mormon Lake, northern Arizona. The behaviors we compared were alert, loafing, sleeping, foraging, preening, locomotion, and other. We found costume-reared subadult greater sandhill cranes that were established at the study site for a year spent more time foraging and being alert towards predators than parent -reared juvenile greater sandhill cranes that were recently released from captivity. We also found that with time juvenile sandhill cranes were increasingly alert and spent less time loafing. It appeared that captive-reared juvenile sandhill cranes learn behavior important for survival from previously released captive-reared cranes
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