11,119 research outputs found
Probing high-redshift galaxies with Ly intensity mapping
We present a study of the cosmological Ly emission signal at .
Our goal is to predict the power spectrum of the spatial fluctuations that
could be observed by an intensity mapping survey. The model uses the latest
data from the HST legacy fields and the abundance matching technique to
associate UV emission and dust properties with the halos, computing the
emission from the interstellar medium (ISM) of galaxies and the intergalactic
medium (IGM), including the effects of reionization, self-consistently. The
Ly intensity from the diffuse IGM emission is 1.3 (2.0) times more
intense than the ISM emission at ; both components are fair tracers
of the star-forming galaxy distribution. However the power spectrum is
dominated by ISM emission on small scales () with
shot noise being significant only above . At very lange
scales () diffuse IGM emission becomes important. The
comoving Ly luminosity density from IGM and galaxies, and at , is consistent with
recent SDSS determinations. We predict a power at for .Comment: 14 Pages, 13 figure
Patologie rare dell'orecchio
After fifty years of experience, mostly spent in ENT surgery
at the University of Palermo, I have pleasure in presenting
this Atlas of rare diseases of the ear, including clinical cases
observed and documented during this long period from 1958
to 2006.
We would prefer to divide all the case studies into three chapters:
the outer ear, middle ear and inner ear
Policy analysis for self-administrated role-based access control
Current techniques for security analysis of administrative role-based access control (ARBAC) policies restrict themselves to the separate administration assumption that essentially separates administrative roles from regular ones. The naive algorithm of tracking all users is all that is known for the security analysis of ARBAC policies without separate administration, and the state space explosion that this results in precludes building effective tools. In contrast, the separate administration assumption greatly simplifies the analysis since it makes it sufficient to track only one user at a time. However, separation limits the expressiveness of the models and restricts modeling distributed administrative control. In this paper, we undertake a fundamental study of analysis of ARBAC policies without the separate administration restriction, and show that analysis algorithms can be built that track only a bounded number of users, where the bound depends only on the number of administrative roles in the system. Using this fundamental insight paves the way for us to design an involved heuristic to further tame the state space explosion in practical systems. Our results are also very effective when applied on policies designed under the separate administration restriction. We implement our techniques and report on experiments conducted on several realistic case studies
Weight Control System
Weight Control System, a set of linked computer programs which provides weight and balance reports from magnetic tape files, provides weight control and reporting on launch vehicle programs. With minor format modifications the program is applicable to aerospace, marine, automotive and other land transportation industries
Security Analysis of Role-based Access Control through Program Verification
We propose a novel scheme for proving administrative role-based access control (ARBAC) policies correct with respect to security properties using the powerful abstraction based tools available for program verification. Our scheme uses a combination of abstraction and reduction to program verification to perform security analysis. We convert ARBAC policies to imperative programs that simulate the policy abstractly, and then utilize further abstract-interpretation techniques from program analysis to analyze the programs in order to prove the policies secure. We argue that the aggressive set-abstractions and numerical-abstractions we use are natural and appropriate in the access control setting. We implement our scheme using a tool called VAC that translates ARBAC policies to imperative programs followed by an interval-based static analysis of the program, and show that we can effectively prove access control policies correct. The salient feature of our approach are the abstraction schemes we develop and the reduction of role-based access control security (which has nothing to do with programs) to program verification problems
The Positive Feedback of Pop III Objects on Galaxy Formation
We study the formation of molecular hydrogen in cooling gas behind shocks
produced during the blow-away process thought to occur in the first collapsed,
luminous (Pop III) objects in the early universe. We find that for a wide range
of physical parameters the fraction is . The
mass produced in such explosions can exceed the amount of relic
destroyed inside the photodissociation region surrounding a given Pop III. We
conclude that these first objects, differently from the suggestion of Haiman et
al 1997, might have a net positive feedback on subsequent galactic formation.
We discuss the effects of radiation and the implications of our results for the
soft-UV background.Comment: 16 pages, aasms4.sty, LaTeX, 2 figures. submitted to ApJ Letter
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