13,280 research outputs found
Governance of Dual-Use Technologies: Theory and Practice
The term dual-use characterizes technologies that can have both military and civilian applications. What is the state of current efforts to control the spread of these powerful technologies—nuclear, biological, cyber—that can simultaneously advance social and economic well-being and also be harnessed for hostile purposes? What have previous efforts to govern, for example, nuclear and biological weapons taught us about the potential for the control of these dual-use technologies? What are the implications for governance when the range of actors who could cause harm with these technologies include not just national governments but also non-state actors like terrorists? These are some of the questions addressed by Governance of Dual-Use Technologies: Theory and Practice, the new publication released today by the Global Nuclear Future Initiative of the American Academy of Arts and Sciences. The publication's editor is Elisa D. Harris, Senior Research Scholar, Center for International Security Studies, University of Maryland School of Public Affairs. Governance of Dual-Use Technologies examines the similarities and differences between the strategies used for the control of nuclear technologies and those proposed for biotechnology and information technology. The publication makes clear the challenges concomitant with dual-use governance. For example, general agreement exists internationally on the need to restrict access to technologies enabling the development of nuclear weapons. However, no similar consensus exists in the bio and information technology domains. The publication also explores the limitations of military measures like deterrence, defense, and reprisal in preventing globally available biological and information technologies from being misused. Some of the other questions explored by the publication include: What types of governance measures for these dual-use technologies have already been adopted? What objectives have those measures sought to achieve? How have the technical characteristics of the technology affected governance prospects? What have been the primary obstacles to effective governance, and what gaps exist in the current governance regime? Are further governance measures feasible? In addition to a preface from Global Nuclear Future Initiative Co-Director Robert Rosner (University of Chicago) and an introduction and conclusion from Elisa Harris, Governance of Dual-Use Technologiesincludes:On the Regulation of Dual-Use Nuclear Technology by James M. Acton (Carnegie Endowment for International Peace)Dual-Use Threats: The Case of Biotechnology by Elisa D. Harris (University of Maryland)Governance of Information Technology and Cyber Weapons by Herbert Lin (Stanford University
How Tax Credits Have Affected the Rehabilitation of the Boston Office Market
This paper is concerned with the extent to which rehabilitation tax credits affect the conditional probability of commercial real estate rehabilitation. Very little has been written about the rehabilitation tax credit, despite the fact that it has been a feature of the U.S. tax code since 1978. Our analysis suggests that rehabilitation tax credits have been a significant determinant of the conditional probability of rehabilitation in the Boston office market. We also find that a significant portion of rehabilitation tax-credit investment is investment that would have been invested elsewhere, about 60 to 65 percent in certain periods, but rising to as high as 90 percent in other periods. We find that the rehabilitation tax credit has a significant and substantial influence on the conditional probability of rehabilitation. We also find that the greatest amount of slippage, not too surprisingly, generally occurs when the tax credit is low and when the gain from rehabilitation before the tax credit is high.
A logarithmic generalization of tensor product theory for modules for a vertex operator algebra
We describe a logarithmic tensor product theory for certain module categories
for a ``conformal vertex algebra.'' In this theory, which is a natural,
although intricate, generalization of earlier work of Huang and Lepowsky, we do
not require the module categories to be semisimple, and we accommodate modules
with generalized weight spaces. The corresponding intertwining operators
contain logarithms of the variables.Comment: 39 pages. Misprints corrected. Final versio
HST NICMOS imaging of z~2, 24 micron-selected Ultraluminous Infrared Galaxies
We present Hubble Space Telescope NICMOS H-band imaging of 33 Ultraluminous
Infrared Galaxies (ULIRGs) at z~2 that were selected from the 24 micron catalog
of the Spitzer Extragalactic First Look Survey. The images reveal that at least
17 of the 33 objects are associated with interactions. Up to one fifth of the
sources in our sample could be minor mergers whereas only 2 systems are merging
binaries with luminosity ratio <=3:1, which is characteristic of local ULIRGs.
The rest-frame optical luminosities of the sources are of the order 10^10-10^11
L_sun and their effective radii range from 1.4 to 4.9 kpc. The most compact
sources are either those with a strong active nucleus continuum or those with a
heavy obscuration in the mid-infrared regime, as determined from Spitzer
Infra-Red Spectrograph data. The luminosity of the 7.7 micron feature produced
by polycyclic aromatic hydrocarbon molecules varies significantly among compact
systems whereas it is typically large for extended systems. A bulge-to-disk
decomposition performed for the 6 brightest (m_H<20) sources in our sample
indicates that they are best fit by disk-like profiles with small or negligible
bulges, unlike the bulge-dominated remnants of local ULIRGs. Our results
provide evidence that the interactions associated with ultraluminous infrared
activity at z~2 can differ from those at z~0.Comment: ApJ, in press. Document revised to match the journal versio
The FLASHES Survey I: Integral Field Spectroscopy of the CGM around 48 QSOs
We present the pilot study component of the Fluorescent Lyman-Alpha
Structures in High-z Environments (FLASHES) Survey; the largest integral-field
spectroscopy survey to date of the circumgalactic medium at . We
observed 48 quasar fields between 2015 and 2018 with the Palomar Cosmic Web
Imager (Matuszewski et al. 2010). Extended HI Lyman- emission
is discovered around 42/48 of the observed quasars, ranging in projected,
flux-weighted radius from 21-71 proper kiloparsecs (pkpc), with 26 nebulae
exceeding in effective diameter. The circularly averaged
surface brightness radial profile peaks at a maximum of
( adjusted for
cosmological dimming) and luminosities range from
to
. The emission appears to have a highly
eccentric morphology and a maximum covering factor of ( for giant
nebulae). On average, the nebular spectra are red-shifted with respect to both
the systemic redshift and Ly peak of the quasar spectrum. The
integrated spectra of the nebulae mostly have single or double-peaked line
shapes with global dispersions ranging from to
, though the individual (Gaussian) components of lines
with complex shapes mostly appear to have dispersions
, and the flux-weighted velocity centroids of the lines
vary by thousands of with respect to the systemic QSO
redshifts. Finally, the root-mean-square velocities of the nebulae are found to
be consistent with gravitational motions expected in dark matter halos of mass
. We compare these results to existing
surveys at both higher and lower redshift
Observations Supporting the Role of Magnetoconvection in Energy Supply to the Quiescent Solar Atmosphere
Identifying the two physical mechanisms behind the production and sustenance
of the quiescent solar corona and solar wind poses two of the outstanding
problems in solar physics today. We present analysis of spectroscopic
observations from the Solar and Heliospheric Observatory that are consistent
with a single physical mechanism being responsible for a significant portion of
the heat supplied to the lower solar corona and the initial acceleration of the
solar wind; the ubiquitous action of magnetoconvection-driven reprocessing and
exchange reconnection of the Sun's magnetic field on the supergranular scale.
We deduce that while the net magnetic flux on the scale of a supergranule
controls the injection rate of mass and energy into the transition region
plasma it is the global magnetic topology of the plasma that dictates whether
the released ejecta provides thermal input to the quiet solar corona or becomes
a tributary that feeds the solar wind.Comment: 34 pages, 13 figures - In press Astrophysical Journal (Jan 1 2007
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Validation and clinical implementation of an accurate Monte Carlo code for pencil beam scanning proton therapy.
Monte Carlo (MC)-based dose calculations are generally superior to analytical dose calculations (ADC) in modeling the dose distribution for proton pencil beam scanning (PBS) treatments. The purpose of this paper is to present a methodology for commissioning and validating an accurate MC code for PBS utilizing a parameterized source model, including an implementation of a range shifter, that can independently check the ADC in commercial treatment planning system (TPS) and fast Monte Carlo dose calculation in opensource platform (MCsquare). The source model parameters (including beam size, angular divergence and energy spread) and protons per MU were extracted and tuned at the nozzle exit by comparing Tool for Particle Simulation (TOPAS) simulations with a series of commissioning measurements using scintillation screen/CCD camera detector and ionization chambers. The range shifter was simulated as an independent object with geometric and material information. The MC calculation platform was validated through comprehensive measurements of single spots, field size factors (FSF) and three-dimensional dose distributions of spread-out Bragg peaks (SOBPs), both without and with the range shifter. Differences in field size factors and absolute output at various depths of SOBPs between measurement and simulation were within 2.2%, with and without a range shifter, indicating an accurate source model. TOPAS was also validated against anthropomorphic lung phantom measurements. Comparison of dose distributions and DVHs for representative liver and lung cases between independent MC and analytical dose calculations from a commercial TPS further highlights the limitations of the ADC in situations of highly heterogeneous geometries. The fast MC platform has been implemented within our clinical practice to provide additional independent dose validation/QA of the commercial ADC for patient plans. Using the independent MC, we can more efficiently commission ADC by reducing the amount of measured data required for low dose "halo" modeling, especially when a range shifter is employed
Do Differences in Pleadings Standards Cause Forum Shopping in Securities Class Actions?: Doctrinal and Empirical Analyses
Federal appellate courts have promulgated divergent legal standards for pleading fraud in securities fraud class actions after the Private Securities Litigation Reform Act (PSLRA). Recently, the Supreme Court of the United States issued a decision in Tellabs, Inc. v. Makor Issues & Rights, Ltd. that could have resolved these differences, but did not do so. This Paper provides two significant contributions. We first show that Tellabs avoids deciding the hard issues that confront courts and litigants daily in the wake of the PSLRA\u27s heightened pleading standard. As a consequence, the opinion keeps very much alive the circuits\u27 disparate interpretations of the PSLRA\u27s fraud pleading standard. To be sure, Tellabs might ultimately be applied by lower courts to narrow the range of permissible approaches to satisfying the strong inference standard, but leaves a good deal of room within which wide variations in approach will continue. Our second contribution is empirical in that we seek to answer the question: do plaintiffs\u27 attorneys take advantage of the differences among the circuits\u27 interpretation of the pleading standard to select more favorable venues to file their cases, as some scholars have claimed? We find that 85 percent of the securities fraud class actions in our sample are filed in the home circuit of the defendant corporation. While we find that the differences in the circuits\u27 pleading standards do not have a statistically significant impact on the plaintiffs\u27 choice of venue, we find that plaintiffs are more likely to file low-value cases in jurisdictions other than the one in which the defendant\u27s headquarters is located
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