Hypervelocity A & B Stars should be slow rotators

The most commonly accepted explanation for the origin of hypervelocity stars in the halo of the Milky Way is that they are the result of tidal disruption of binaries by the massive black hole at the center of the Galaxy. We show that, if this scenario is correct, and if the original binary properties are similar to those in the local stellar neighbourhood, then the hypervelocity stars should rotate with velocities measureably lower than those for field stars of similar spectral type. This may prove to be a more direct test of the model than trying to predict the position and velocity distributions.Comment: 11 pages, including 4 figures. To appear in Astrophysical Journal Letter

Surface effects in magnetic superconductors with a spiral magnetic structure

We consider a magnetic superconductor MS with a spiral magnetic structure. On the basis of generalized Eilenberger and Usadel equations we show that near the boundary of the MS with an insulator or vacuum the condensate (Gor'kov's) Green's functions are disturbed by boundary conditions and differ essentially from their values in the bulk. Corrections to the bulk quasiclassical Green's functions oscillate with the period of the magnetic spiral, $2\pi /Q$, and decay inside the superconductor over a length of the order $v/\pi T$ (ballistic limit) or $\sqrt{D/\pi T}$ (diffusive limit). We calculate the dc Josephson current in an MS/I/MS tunnel junction and show that the critical Josephson current differs substantially from that obtained with the help of the tunnel Hamiltonian method and bulk Green's functions.Comment: 10 pages 3 Figs; some misprints in fromulae corrected; submitted to Phys. Rev.

Silent Transitions in Automata with Storage

We consider the computational power of silent transitions in one-way automata with storage. Specifically, we ask which storage mechanisms admit a transformation of a given automaton into one that accepts the same language and reads at least one input symbol in each step. We study this question using the model of valence automata. Here, a finite automaton is equipped with a storage mechanism that is given by a monoid. This work presents generalizations of known results on silent transitions. For two classes of monoids, it provides characterizations of those monoids that allow the removal of \lambda-transitions. Both classes are defined by graph products of copies of the bicyclic monoid and the group of integers. The first class contains pushdown storages as well as the blind counters while the second class contains the blind and the partially blind counters.Comment: 32 pages, submitte

Hypervelocity Stars. I. The Spectroscopic Survey

We discuss our targeted search for hypervelocity stars (HVSs), stars traveling with velocities so extreme that dynamical ejection from a massive black hole is their only suggested origin. Our survey, now half complete, has successfully identified a total of four probable HVSs plus a number of other unusual objects. Here we report the most recently discovered two HVSs: SDSS J110557.45+093439.5 and possibly SDSS J113312.12+010824, traveling with Galactic rest-frame velocities at least +508+-12 and +418+-10 km/s, respectively. The other late B-type objects in our survey are consistent with a population of post main-sequence stars or blue stragglers in the Galactic halo, with mean metallicity [Fe/H]=-1.3 and velocity dispersion 108+-5 km/s. Interestingly, the velocity distribution shows a tail of objects with large positive velocities that may be a mix of low-velocity HVSs and high-velocity runaway stars. Our survey also includes a number of DA white dwarfs with unusually red colors, possibly extremely low mass objects. Two of our objects are B supergiants in the Leo A dwarf, providing the first spectroscopic evidence for star formation in this dwarf galaxy within the last ~30 Myr.Comment: 10 pages, uses emulateapj, accepted by Ap

Chemiluminescence in activated human neutrophils

Human neutrophils (PMNs) suspended in Hanks' balanced salt solution (HBSS), which are stimulated either by polycation-opsonized streptococci or by phorbol myristate acetate (PMA), generate nonamplified (CL), luminol-dependent (LDCL), and lucigenin-dependent chemiluminescence (LUCDCL). Treatment of activated PMNs with azide yielded a very intense CL response, but only a small LDCL or LUCDCL responses, when horse radish peroxidase (HRP) was added. Both CL and LDCL depend on the generation of Superoxide and on myeloperoxidase (MPO). Treatment of PMNs with azide followed either by dimethylthiourea (DMTU), deferoxamine, EDTA, or detapac generated very little CL upon addition of HRP, suggesting that CL is the: result of the interaction among H 2 O 2 , a peroxidase, and trace metals. In a cell-free system practically no CL was generated when H 2 O 2 was mixed with HRP in distilled water (DW). On the other hand significant CL was generated when either HBSS or RPMI media was employed. In both cases CL was markedly depressed either by deferoxamine or by EDTA, suggesting that these media might be contaminated by trace metals, which catalyzed a Fenton-driven reaction. Both HEPES and Tris buffers, when added to DW, failed to support significant HRP-induced CL. Nitrilotriacetate (NTA) chelates of Mn 2+ , Fe 2+ , Cu 2+ , and Co 2+ very markedly enhanced CL induced by mixtures of H 2 O 2 and HRP when distilled water was the supporting medium. Both HEPES and Tris buffer when added to DW strongly quenced NTA-metal-catalyzed CL. None of the NTA-metal chelates could boost CL generation by activated PMNs, because the salts in HBSS and RPMI interfered with the activity of the added metals. CL and LDCL of activated PMNs was enhanced by aminotriazole, but strongly inhibited by diphenylene iodonium (an inhibitor of NADPH oxidase) by azide, sodium cyanide (CN), cimetidine, histidine, benzoate, DMTU and moderately by Superoxide dismutase (SOD) and by deferoxamine. LUCDCL was markedly inhibited only by SOD but was boosted by CN. Taken together, it is suggested that CL generated by stimulated PMNs might be the result of the interactions among, NADPH oxidase, (inhibitable by diphenylene iodonium), MPO (inhibitable by sodium azide), H 2 O 2 probably of intracellular origin (inhibitable by DMTU but not by catalase), and trace metals that contaminate salt solutions. The nature of the salt solutions employed to measure CL in activated PMNs is critical.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/44510/1/10753_2004_Article_BF00918987.pd

Interaction of mammalian cells with polymorphonuclear leukocytes: Relative sensitivity to monolayer disruption and killing

Monolayers of murine fibrosarcoma cells that had been treated either with histone-opsonized streptococci, histone-opsonized Candida globerata , or lipoteichoic acid-anti-lipoteichoic acid complexes underwent disruption when incubated with human polymorphonuclear leukocytes (PMNs). Although the architecture of the monolayers was destroyed, the target cells were not killed. The destruction of the monolayers was totally inhibited by proteinase inhibitors, suggesting that the detachment of the cells from the monolayers and aggregation in suspension were induced by proteinases released from the activated PMNs. Monolayers of normal endothelial cells and fibroblasts were much more resistant to the monolayer-disrupting effects of the PMNs than were the fibrosarcoma cells. Although the fibrosarcoma cells were resistant to killing by PMNs, killing was promoted by the addition of sodium azide (a catalase inhibitor). This suggests that the failure of the PMNs to kill the target cells was due to catalase inhibition of the hydrogen peroxide produced by the activated PMNs. Target cell killing that occurred in the presence of sodium azide was reduced by the addition of a “cocktail” containing methionine, histidine, and deferoxamine mesylate, suggesting that hydroxyl radicals but not myeloperoxidase-catalayzed products were responsible for cell killing. The relative ease with which the murine fibrosarcoma cells can be released from their substratum by the action of PMNs, coupled with their insensitivity to PMN-mediated killing, may explain why the presence of large numbers of PMNs at the site of tumors produced in experimental animals by the fibrosarcoma cells is associated with an unfavorable outcome.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/44503/1/10753_2004_Article_BF00916759.pd

Antichain cutsets of strongly connected posets

Rival and Zaguia showed that the antichain cutsets of a finite Boolean lattice are exactly the level sets. We show that a similar characterization of antichain cutsets holds for any strongly connected poset of locally finite height. As a corollary, we get such a characterization for semimodular lattices, supersolvable lattices, Bruhat orders, locally shellable lattices, and many more. We also consider a generalization to strongly connected hypergraphs having finite edges.Comment: 12 pages; v2 contains minor fixes for publicatio

Lysophosphatides enhance superoxide responses of stimulated human neutrophils

Human neutrophils which are pretreated with subtoxic concentrations of a variety of lysophosphatides (lysophosphatidytcholine, lysophosphatidylcholine oleoyl, lysophosphatidylcholine myrioyl, lysophosphatidylcholine stearoyl, lysophosphatidylcholine gamma- O -hexadecyl, lysophosphatidylinositol, and lysophosphatidylglycerol) act synergistically with neutrophil agonists phorbol myristate acetate, immune complexes, poly- L -histidine, phytohemagglutinin, and N -formyl methionyl-leucyl-phenyalanine to cause enhanced generation of superoxide (O 2 − ). None of the lyso compounds by themselves caused generation of O 2 − . The lyso compounds strongly bound to the neutrophils and could not be washed away. All of the lyso compounds that collaborated with agonists to stimulate O 2 − generation were hemolytic for human red blood cells. On the other hand, lyso compounds that were nonhemolytic for red blood cells (lysophosphatidylcholine caproate, lysophosphatidylcholine decanoyl, lysophosphatidylethanolamine, lysophosphatidylserine) failed to collaborate with agonists to generate synergistic amounts of O 2 − . However, in the presence of cytochalasin B, both lysophosphatidyiethanolamine and lysophosphatidylserine also markedly enhanced O 2 − generation induced by immune complexes. O 2 − generation was also very markedly enhanced when substimulatory amounts of arachidonic acid or eicosapentanoic acid were added to PMNs in the presence of a variety of agonists. On the other hand, neither phospholipase C, streptolysin S (highly hemolytic), phospholipase A 2 , phosphatidylcholine, nor phosphatidylcholine dipalmitoyl (all nonhemolytic) had the capacity to synergize with any of the agonists tested to generate enhanced amounts of O 2 − . The data suggest that in addition to long-chain fatty acids, only those lyso compounds that possess fatty acids with more than 10 carbons and that are also highly hemolytic can cause enhanced generation of O 2 − in stimulated PMNs.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/44499/1/10753_2004_Article_BF00924787.pd

Skin effect with arbitrary specularity in Maxwellian plasma

The problem of skin effect with arbitrary specularity in maxwellian plasma with specular--diffuse boundary conditions is solved. A new analytical method is developed that makes it possible to to obtain a solution up to an arbitrary degree of accuracy. The method is based on the idea of symmetric continuation not only the electric field, but also electron distribution function. The solution is obtained in a form of von Neumann series.Comment: 7 pages, 2 figure