14,295 research outputs found
HAMEV and SQRED: Fortran 77 Subroutines for Computing the Eigenvalues of Hamiltonian Matrices Using Van Loanss Square Reduced Method
This paper describes LAPACK-based Fortran 77 subroutines for the reduction of a Hamiltonian matrix to square-reduced form and the approximation of all its eigenvalues using the implicit version of Van Loan's method. The transformation of the Hamilto- nian matrix to a square-reduced Hamiltonian uses only orthogonal symplectic similarity transformations. The eigenvalues can then be determined by applying the Hessenberg QR iteration to a matrix of half the order of the Hamiltonian matrix and taking the square roots of the computed values. Using scaling strategies similar to those suggested for algebraic Riccati equations can in some cases improve the accuracy of the computed eigenvalues. We demonstrate the performance of the subroutines for several examples and show how they can be used to solve some control-theoretic problems
Analysing the Security of Google's implementation of OpenID Connect
Many millions of users routinely use their Google accounts to log in to
relying party (RP) websites supporting the Google OpenID Connect service.
OpenID Connect, a newly standardised single-sign-on protocol, builds an
identity layer on top of the OAuth 2.0 protocol, which has itself been widely
adopted to support identity management services. It adds identity management
functionality to the OAuth 2.0 system and allows an RP to obtain assurances
regarding the authenticity of an end user. A number of authors have analysed
the security of the OAuth 2.0 protocol, but whether OpenID Connect is secure in
practice remains an open question. We report on a large-scale practical study
of Google's implementation of OpenID Connect, involving forensic examination of
103 RP websites which support its use for sign-in. Our study reveals serious
vulnerabilities of a number of types, all of which allow an attacker to log in
to an RP website as a victim user. Further examination suggests that these
vulnerabilities are caused by a combination of Google's design of its OpenID
Connect service and RP developers making design decisions which sacrifice
security for simplicity of implementation. We also give practical
recommendations for both RPs and OPs to help improve the security of real world
OpenID Connect systems
The Host Galaxy and Central Engine of the Dwarf AGN POX 52
We present new multi-wavelength observations of the dwarf Seyfert 1 galaxy
POX 52 in order to investigate the properties of the host galaxy and the active
nucleus, and to examine the mass of its black hole, previously estimated to be
~ 10^5 M_sun. Hubble Space Telescope ACS/HRC images show that the host galaxy
has a dwarf elliptical morphology (M_I = -18.4 mag, Sersic index n = 4.3) with
no detected disk component or spiral structure, confirming previous results
from ground-based imaging. X-ray observations from both Chandra and XMM show
strong (factor of 2) variability over timescales as short as 500 s, as well as
a dramatic decrease in the absorbing column density over a 9 month period. We
attribute this change to a partial covering absorber, with a 94% covering
fraction and N_H = 58^{+8.4}_{-9.2} * 10^21 cm^-2, that moved out of the line
of sight in between the XMM and Chandra observations. Combining these data with
observations from the VLA, Spitzer, and archival data from 2MASS and GALEX, we
examine the spectral energy distribution (SED) of the active nucleus. Its shape
is broadly similar to typical radio-quiet quasar SEDs, despite the very low
bolometric luminosity of L_bol = 1.3 * 10^43 ergs/s. Finally, we compare black
hole mass estimators including methods based on X-ray variability, and optical
scaling relations using the broad H-beta line width and AGN continuum
luminosity, finding a range of black hole mass from all methods to be M_bh =
(2.2-4.2) * 10^5 M_sun, with an Eddington ratio of L_bol/L_edd = 0.2-0.5.Comment: 19 pages, 16 figures, accepted for publication in Ap
Cleaving-temperature dependence of layered-oxide surfaces
The surfaces generated by cleaving non-polar, two-dimensional oxides are
often considered to be perfect or ideal. However, single particle
spectroscopies on Sr2RuO4, an archetypal non-polar two dimensional oxide, show
significant cleavage temperature dependence. We demonstrate that this is not a
consequence of the intrinsic characteristics of the surface: lattice parameters
and symmetries, step heights, atom positions, or density of states. Instead, we
find a marked increase in the density of defects at the mesoscopic scale with
increased cleave temperature. The potential generality of these defects to
oxide surfaces may have broad consequences to interfacial control and the
interpretation of surface sensitive measurements
C4 olefin conversion on reduced nickel y faujasite. Evidence for C5 olefin formation via C4 olefin disproportionation
The Voluntary Adjustment of Railroad Obligations
Automatic memory management techniques eliminate many programming errors that are both hard to find and to correct. However, these techniques are not yet used in embedded systems with hard realtime applications. The reason is that current methods for automatic memory management have a number of drawbacks. The two major ones are: (1) not being able to always guarantee short real-time deadlines and (2) using large amounts of extra memory. Memory is usually a scarce resource in embedded applications. In this paper we present a new technique, Real-Time Reference Counting (RTRC) that overcomes the current problems and makes automatic memory management attractive also for hard real-time applications. The main contribution of RTRC is that often all memory can be used to store live objects. This should be compared to a memory overhead of about 500% for garbage collectors based on copying techniques and about 50% for garbage collectors based on mark-and-sweep techniques
Local adsorption structure and bonding of porphine on Cu(111) before and after self-metalation
We have experimentally determined the lateral registry and geometric
structure of free-base porphine (2H-P) and copper-metalated porphine (Cu-P)
adsorbed on Cu(111), by means of energy-scanned photoelectron diffraction
(PhD), and compared the experimental results to density functional theory (DFT)
calculations that included van der Waals corrections within the
Tkatchenko-Scheffler approach. Both 2H-P and Cu-P adsorb with their center
above a surface bridge site. Consistency is obtained between the experimental
and DFT-predicted structural models, with a characteristic change in the
corrugation of the four N atoms of the molecule's macrocycle following
metalation. Interestingly, comparison with previously published data for cobalt
porphine adsorbed on the same surface evidences a distinct increase in the
average height of the N atoms above the surface through the series 2H-P, Cu-P,
cobalt porphine. Such an increase strikingly anti-correlates the DFT-predicted
adsorption strength, with 2H-P having the smallest adsorption height despite
the weakest calculated adsorption energy. In addition, our findings suggest
that for these macrocyclic compounds, substrate-to-molecule charge transfer and
adsorption strength may not be univocally correlated
Laboratory Diagnosis of Mycobacterial Infections: New Tools and Lessons Learned
Even in the 21st century, tuberculosis continues to be a problem. Although the number of cases continues gradually to decrease in the United States, cases get more difficult to treat, specifically those that are multiple-drug resistant. Infection of one-third of the world's population ensures that tuberculosis will not disappear in the near future. In light of this, it will be useful to know the goals for the health care system and how these goals may be accomplished. Laboratory testing in the mycobacteriology field is experiencing more changes today than ever before. Determining what assays will be most useful to the clinician is a challenge, and acceptance of the new technology by the medical community an even greater one. Clinicians must use the best available resources to determine the most appropriate care for their patients and work together with the laboratory to ensure that the communication channels are open. This review focuses on current state-of-the-art resources useful for accurate and rapid laboratory diagnosis of mycobacterial infection
Evidence for Different Freeze-Out Radii of High- and Low-Energy Pions Emitted in Au+Au Collisions at 1 GeV/nucleon
Double differential production cross sections of negative and positive pions
and the number of participating protons have been measured in central Au+Au
collisions at 1 GeV per nucleon incident energy. At low pion energies the pi^-
yield is strongly enhanced over the pi^+ yield. The energy dependence of the
pi^-/pi^+ ratio is assigned to the Coulomb interaction of the charged pions
with the protons in the reaction zone. The deduced Coulomb potential increases
with increasing pion c.m. energy. This behavior indicates different freeze-out
radii for different pion energies in the c.m.~frame.Comment: IKDA is the Institute for Nuclear Physics in Darmstadt/German
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