Space Trajectory Error Analysis Program (STEAP) for halo orbit missions. Volume 2: Programmer's manual

The six month effort was responsible for the development, test, conversion, and documentation of computer software for the mission analysis of missions to halo orbits about libration points in the earth-sun system. The software consisting of two programs called NOMNAL and ERRAN is part of the Space Trajectories Error Analysis Programs. The program NOMNAL targets a transfer trajectory from earth on a given launch date to a specified halo orbit on a required arrival date. Either impulsive or finite thrust insertion maneuvers into halo orbit are permitted by the program. The transfer trajectory is consistent with a realistic launch profile input by the user. The second program ERRAN conducts error analyses of the targeted transfer trajectory. Measurements including range, doppler, star-planet angles, and apparent planet diameter are processed in a Kalman-Schmidt filter to determine the trajectory knowledge uncertainty

A model of superoutbursts in binaries of SU UMa type

A new mechanism explaining superoutbursts in binaries of SU UMa type is proposed. In the framework of this mechanism the accretion rate increase leading to the superoutburst is associated with formation of a spiral wave of a new "precessional" type in inner gasdynamically unperturbed parts of the accretion disc. The possibility of existence of this type of waves was suggested in our previous work (astro-ph/0403053). The features of the "precessional" spiral wave allow explaining both the energy release during the outburst and all its observational manifestations. The distinctive characteristic of a superoutburst in a SU UMa type star is the appearance of the superhump on the light curve. The proposed model reproduces well the formation of the superhump as well as its observational features, such as the period that is 3-7% longer than the orbital one and the detectability of superhumps regardless of the binary inclination.Comment: LaTeX, 20 pages, 4 figures, to be published in Astron. Z

Multiple self-splicing introns in the 16S rRNA genes of giant sulfur bacteria

The gene encoding the small subunit rRNA serves as a prominent tool for the phylogenetic analysis and classification of Bacteria and Archaea owing to its high degree of conservation and its fundamental function in living organisms. Here we show that the 16S rRNA genes of not-yet-cultivated large sulfur bacteria, among them the largest known bacterium Thiomargarita namibiensis, regularly contain numerous self-splicing introns of variable length. The 16S rRNA genes can thus be enlarged to up to 3.5 kb. Remarkably, introns have never been identified in bacterial 16S rRNA genes before, although they are the most frequently sequenced genes today. This may be caused in part by a bias during the PCR amplification step that discriminates against longer homologs, as we show experimentally. Such length heterogeneity of 16S rRNA genes has so far never been considered when constructing 16S rRNA-based clone libraries, even though an elongation of rRNA genes due to intervening sequences has been reported previously. The detection of elongated 16S rRNA genes has profound implications for common methods in molecular ecology and may cause systematic biases in several techniques. In this study, catalyzed reporter deposition–fluorescence in situ hybridization on both ribosomes and rRNA precursor molecules as well as in vitro splicing experiments were performed and confirmed self-splicing of the introns. Accordingly, the introns do not inhibit the formation of functional ribosomes

Components of the dilepton continuum in Pb+Pb collisions at sNN=2.76\sqrt{s_{_{NN}}} = 2.76 TeV

The dilepton invariant mass spectrum measured in heavy-ion collisions includes contributions from important QGP probes such as thermal radiation and the quarkonium ($J/\psi$, $\psi'$ and $\Upsilon$) states. Dileptons coming from hard $q \bar q$ scattering, the Drell-Yan process, contribute in all mass regions. In heavy-ion colliders, such as the LHC, semileptonic decays of heavy flavor hadrons provide a substantial contribution to the dilepton continuum. The dilepton continuum can give quantitative information about heavy quark yields and their modification in the medium and thus it is important to know all different sources which populate the continuum. In the present study, we calculate $c \bar c$ and $b \bar b$ production and determine their contributions to the dilepton continuum in Pb+Pb collisions at $\sqrt{s_{_{NN}}} = 2.76$ TeV with and without including heavy quark energy loss. We also calculate the rates for Drell-Yan and thermal dilepton production. The contributions to the continuum from these dilepton sources are studied in the kinematic ranges relevant for the LHC detectors. The relatively high $p_T$ cutoff for single leptons excludes most dileptons produced by the thermal medium. Heavy flavors are the dominant source of dilepton production in all the kinematic regimes except at forward rapidities where Drell-Yan start dominating in high mass range beyond 10 GeV/$c^2$.Comment: 18 pages, 9 figure

Screening and Anti-Screening Effects in J/psi Production on Nuclei

The nuclear effects in J/psi hadro- and electroproduction on nuclei are considered in framework of reggeon approach. It is shown that screening regime which holds for electroproduction at x_F > 0.7 and for hadroproduction at x_F > -(0.3-0.4) is changed with anti-screening regime for smaller x_F values.Comment: 6 pages, 6 figures. Small changes in wordin

Enhanced charm hadroproduction due to nonlinear corrections to the DGLAP equations

We have studied the effects of nonlinear scale evolution of the parton distribution functions to charm production in $pp$ collisions at center-of-mass energies of 5.5, 8.8 and 14 TeV. We find that the differential charm cross section can be enhanced up to a factor of 4-5 at low $p_T$. The enhancement is quite sensitive to the charm quark mass and the renormalization/factorization scales.Comment: 4 pages, 3 eps-figures. To appear in the proceedings of the seventeenth international conference on Ultra-Relativistic Nucleus-Nucleus Collisions (Quark Matter 2004

Experimental evaluation of an advanced Space Shuttle main engine hot-gas manifold design concept

This study, using an extensively modified, full-scale space shuttle main engine (SSME) hot-gas manifold (HGM), established a detailed aerodynamic data base to support development of an advanced, three-dimensional, fluid-dynamic analysis computer model. In addition, the advanced SSME hot-gas manifold design used in this study demonstrated improved flow environment (uniformity) in the fuel side turbine exit and transfer duct exit regions. Major modifications were incorporated in the full-scale HGM flow test article model using two large transfer ducts on the fuel turbine side of the HGM in place of the three small transfer ducts in the present design. Other model features included an increases in the flow areas downstream of the 180-degree turn and in the fishbowl regions

Rigidly rotating dust solutions depending upon harmonic functions

We write down the relevant field equations for a stationary axially symmetric rigidly rotating dust source in such a way that the general solution depends upon the solution of an elliptic equation and upon harmonic functions. Starting with the dipole Bonnor solution, we built an asymptotically flat solution with two curvature singularities on the rotational axis with diverging mass. Apart from the two point singularities on the axis, the metric is regular everywhere. Finally, we study a non-asymptotically flat solution with NUT charge and a massless ring singularity, but with a well-defined mass-energy expression.Comment: typos corrected, final version published in Class. Quantum Gra

Nuclear suppression of heavy quark production at forward rapidities in relativistic heavy ion collisions

We calculate nuclear suppression $R_{AA}$ of heavy quarks produced from the initial fusion of partons in nucleus-nucleus collisions at RHIC and LHC energies. We take the shadowing as well as the energy loss suffered by them while passing through Quark Gluon Plasma into account. We obtain results for charm and bottom quarks at several rapidities using different mechanisms for energy loss, to see if we can distinguish between them.Comment: 21 pages including 13 figures. To appear in J. Phys.

Skewed parton distributions and the scale dependence of the transverse size parameter

We discuss the scale dependence of a skewed parton distribution of the pion obtained from a generalized light-cone wave function overlap formula. Using a simple ansatz for the transverse momentum dependence of the light-cone wave function and restricting ourselves to the case of a zero skewedness parameter, the skewed parton distribution can be expressed through an ordinary parton distribution multiplied by an exponential function. Matching the generalized and ordinary DGLAP evolution equations of the skewed and ordinary parton distributions, respectively, we derive a constraint for the scale dependence of the transverse size parameter, which describes the width of the pion wave function in transverse momentum space. This constraint has implications for the Fock state probability and valence distribution. We apply our results to the pion form factor.Comment: 10 pages, 4 figures; version to appear in Phys. Rev. D; Refs. added, new discussion of results for pion form factor in view of new dat