1,547,087 research outputs found
Exobiology: The NASA program
The goal of NASA's Exobiology Program is to understand the origin, evolution, and distribution of life in the universe. To do this, the Exobiology Program seeks to provide a critical framework and some key research to allow NASA to bear the combined talents and capabilities of the agency and the scientific community, and the unique opportunities afforded by space exploration. To provide structure and direction to the quest for answers, the Exobiology Program has instituted a comprehensive research program divided into four elements which are being implemented at several of NASA's research centers and in the university community. These program elements correspond to the four major epochs in the evolution of living systems: (1) cosmic evolution of the biogenic compounds; (2) prebiotic evolution; (3) origin and early evolution of life; and (4) evolution of advanced life. The overall research program is designed to trace the pathways leading from the origin of the universe through the major epochs in the story of life
Markovian Monte Carlo program EvolFMC v.2 for solving QCD evolution equations
We present the program EvolFMC v.2 that solves the evolution equations in QCD
for the parton momentum distributions by means of the Monte Carlo technique
based on the Markovian process. The program solves the DGLAP-type evolution as
well as modified-DGLAP ones. In both cases the evolution can be performed in
the LO or NLO approximation. The quarks are treated as massless. The overall
technical precision of the code has been established at 0.05% precision level.
This way, for the first time ever, we demonstrate that with the Monte Carlo
method one can solve the evolution equations with precision comparable to the
other numerical methods.Comment: 38 pages, 9 Postscript figure
A Framework for Datatype Transformation
We study one dimension in program evolution, namely the evolution of the
datatype declarations in a program. To this end, a suite of basic
transformation operators is designed. We cover structure-preserving
refactorings, but also structure-extending and -reducing adaptations. Both the
object programs that are subject to datatype transformations, and the meta
programs that encode datatype transformations are functional programs.Comment: Minor revision; now accepted at LDTA 200
The CCFM Monte Carlo generator CASCADE
CASCADE is a full hadron level Monte Carlo event generator for e-p, gamma-p
and p-p_bar processes, which uses the CCFM evolution equation for the initial
state cascade in a backward evolution approach supplemented with off-shell
matrix elements for the hard scattering. A detailed program description is
given, with emphasis on parameters the user wants to change and common block
variables which completely specify the generated events.Comment: Program manual, 14 page
Numerical solution of Q^2 evolution equation for the transversity distribution Delta_T q
We investigate numerical solution of the Dokshitzer-Gribov-Lipatov-Altarelli-
Parisi (DGLAP) Q^2 evolution equation for the transversity distribution Delta_T
q or the structure function h_1. The leading-order (LO) and next-to-
leading-order (NLO) evolution equations are studied. The renormalization scheme
is MS or overline{MS} in the NLO case. Dividing the variables x and Q^2 into
small steps, we solve the integrodifferential equations by the Euler method in
the variable Q^2 and by the Simpson method in the variable x. Numerical results
indicate that accuracy is better than 1% in the region 10^{-5}<x<0.8 if more
than fifty Q^2 steps and more than five hundred x steps are taken. We provide a
FORTRAN program for the Q^2 evolution and devolution of the transversity
distribution Delta_T q or h_1. Using the program, we show the LO and NLO
evolution results of the valence-quark distribution Delta_T u_v + Delta_T d_v,
the singlet distribution sum_i (Delta_T q_i + Delta_T qbar_i), and the flavor
asymmetric distribution Delta_T ubar - Delta_T dbar.They are also compared with
the longitudinal evolution results.Comment: 1+29 pages, LaTeX2e, epsfig.sty, amsmath.sty, 6 eps figures.
Submitted for publication. Complete postscript file is available at
ftp://ftp.cc.saga-u.ac.jp/pub/paper/riko/quantum1 or at
http://www.cc.saga-u.ac.jp/saga-u/riko/physics/quantum1/structure.html Our
evolution program may be obtained upon email request. (See the WWW home page
for the details.) Email: [email protected], [email protected],
[email protected]
EvolveAGene 3: A DNA coding sequence evolution simulation program
EvolveAGene 3 is a realistic coding sequence simulation program that separates mutation from selection and allows the user to set selection conditions, including variable regions of selection intensity within the sequence and variation in intensity of selection over branches. Variation includes base substitutions, insertions and deletions. Output includes a log file, the true tree and both unaligned coding sequence and protein sequences and the true DNA and protein alignments
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