2,000 research outputs found
Implications of new measurements of O-16 + p + C-12,13, N-14,15 for the abundances of C, N isotopes at the cosmic ray source
The fragmentation of a 225 MeV/n O-16 beam was investigated at the Bevalac. Preliminary cross sections for mass = 13, 14, 15 fragments are used to constrain the nuclear excitation functions employed in galactic propagation calculations. Comparison to cosmic ray isotonic data at low energies shows that in the cosmic ray source C-13/C approximately 2% and N-14/0=3-6%. No source abundance of N-15 is required with the current experimental results
Fundamental Strings in Open String Theory at the Tachyonic Vacuum
We show that the world-volume theory on a D-p-brane at the tachyonic vacuum
has solitonic string solutions whose dynamics is governed by the Nambu-Goto
action of a string moving in (25+1) dimensional space-time. This provides
strong evidence for the conjecture that at this vacuum the full (25+1)
dimensional Poincare invariance is restored. We also use this result to argue
that the open string field theory at the tachyonic vacuum must contain closed
string excitations.Comment: LaTeX file, 16 pages, references and clarification adde
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Isotopic composition of neon in the galactic cosmic rays: a high resolution measurement
A measurement of the isotopic composition of galactic cosmic ray neon in the energy range 70 to 260 MeV/amu has been made using the U.C. Berkeley HKH instrument aboard ISEE-3. A combination of high resolution and good statistical accuracy makes possible a precise determination of the local interplanetary neon composition. We find /sup 22/Ne//sup 20/Ne = 0.64 +- 0.07 and /sup 21/Ne//sup 20/Ne < 0.30 in local interplanetary space. These ratios, when interpreted in using standard galactic propagation and solar modulation models, yield cosmic ray source abundances which are inconsistent with a solar-like source composition
Dirac-Born-Infeld Action on the Tachyon Kink and Vortex
The tachyon effective field theory describing the dynamics of a non-BPS
D-brane in superstring theory has an infinitely thin but finite tension kink
solution describing a codimension one BPS D-brane. We study the world-volume
theory of massless modes on the kink, and show that the world volume action has
precisely the Dirac-Born-Infeld (DBI) form without any higher derivative
corrections. We generalize this to a vortex solution in the effective field
theory on a brane-antibrane pair. As in the case of the kink, the vortex is
infinitely thin, has finite energy density, and the world-volume action on the
vortex is again given exactly by the DBI action on a BPS D-brane. We also
discuss the coupling of fermions and restoration of supersymmetry and
-symmetry on the world-volume of the kink. Absence of higher derivative
corrections to the DBI action on the soliton implies that all such corrections
are related to higher derivative corrections to the original effective action
on the world-volume of a non-BPS D-brane or brane-antibrane pair.Comment: LaTeX file, 34 pages; references and other minor comments adde
Continuity Culture: A Key Factor for Building Resilience and Sound Recovery Capabilities
This article investigates the extent to which Jordanian service organizations seek to establish continuity culture through testing, training, and updating of their business continuity plans. A survey strategy was adopted in this research. Primary and secondary data were used. Semistructured interviews were conducted with five senior managers from five large Jordanian service organizations registered with the Amman Stock Exchange. The selection of organizations was made on the basis of simple random sampling. Interviews targeted the headquarters only in order to obtain a homogenous sample. Three out of five organizations could be regarded as crisis prepared and have better chances for recovery. The other two organizations exhibited characteristics of standard practice that only emphasizes the recovery aspect of business continuity management (BCM), while paying less attention to establishing resilient cultures and embedding BCM. The findings reveal that the ability to recover following major incidents can be improved by embedding BCM in the culture of the organization and by making BCM an enterprise-wide process. This is one of few meticulous studies that have been undertaken in the Middle East and the first in Jordan to investigate the extent to which service organizations focus on embedding BCM in the organizational culture
The Hitchin functionals and the topological B-model at one loop
The quantization in quadratic order of the Hitchin functional, which defines
by critical points a Calabi-Yau structure on a six-dimensional manifold, is
performed. The conjectured relation between the topological B-model and the
Hitchin functional is studied at one loop. It is found that the genus one free
energy of the topological B-model disagrees with the one-loop free energy of
the minimal Hitchin functional. However, the topological B-model does agree at
one-loop order with the extended Hitchin functional, which also defines by
critical points a generalized Calabi-Yau structure. The dependence of the
one-loop result on a background metric is studied, and a gravitational anomaly
is found for both the B-model and the extended Hitchin model. The anomaly
reduces to a volume-dependent factor if one computes for only Ricci-flat Kahler
metrics.Comment: 33 pages, LaTe
Covariant quantization of membrane dynamics
A Lorentz covariant quantization of membrane dynamics is defined, which also
leaves unbroken the full three dimensional diffeomorphism invariance of the
membrane. Among the applications studied are the reduction to string theory,
which may be understood in terms of the phase space and constraints, and the
interpretation of physical,zero-energy states. A matrix regularization is
defined as in the light cone gauged fixed theory but there are difficulties
implementing all the gauge symmetries. The problem involves the
non-area-preserving diffeomorphisms which are realized non-linearly in the
classical theory. In the quantum theory they do not seem to have a consistent
implementation for finite N. Finally, an approach to a genuinely background
independent formulation of matrix dynamics is briefly described.Comment: Latex, 21 pages, no figure
Three Keys to Success for Principals (and Their Teachers)
This is the author's accepted manuscript, post peer-review. The publisher's official version is available at: http://dx.doi.org/10.1080/00228958.2008.10516527.What is successful leadership and how can leadership concepts be applied to schools? Hundreds of books and articles and a plethora of executive seminars describe what leadership is and propose strategies for what effective leaders do. Most of these writings and presentations, however, focus on business, with much less information available about how to lead schools. In addition, there is a diversity of opinions about what makes leaders effective. This article suggests that it is possible to extract, reframe, and apply the best of what is known about leadership to help principals be more successful. Moreover, if principals are successful, teachers also are positioned to be successful, with the ultimate impact being successful student learning
Multi-Jet Event Rates in Deep Inelastic Scattering and Determination of the Strong Coupling Constant
Jet event rates in deep inelastic ep scattering at HERA are investigated
applying the modified JADE jet algorithm. The analysis uses data taken with the
H1 detector in 1994 and 1995. The data are corrected for detector and
hadronization effects and then compared with perturbative QCD predictions using
next-to-leading order calculations. The strong coupling constant alpha_S(M_Z^2)
is determined evaluating the jet event rates. Values of alpha_S(Q^2) are
extracted in four different bins of the negative squared momentum
transfer~\qq in the range from 40 GeV2 to 4000 GeV2. A combined fit of the
renormalization group equation to these several alpha_S(Q^2) values results in
alpha_S(M_Z^2) = 0.117+-0.003(stat)+0.009-0.013(syst)+0.006(jet algorithm).Comment: 17 pages, 4 figures, 3 tables, this version to appear in Eur. Phys.
J.; it replaces first posted hep-ex/9807019 which had incorrect figure 4
Use of satellite observations for operational oceanography: recent achievements and future prospects
The paper gives an overview of the development of satellite oceanography over the past five years focusing on the most relevant issues for operational oceanography. Satellites provide key essential variables to constrain ocean models and/or serve downstream applications. New and improved satellite data sets have been developed and have directly improved the quality of operational products. The status of the satellite constellation for the last five years was, however, not optimal. Review of future missions shows clear progress and new research and development missions with a potentially large impact for operational oceanography should be demonstrated. Improvement of data assimilation techniques and developing synergetic use of high resolution satellite observations are important future priorities
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