8 research outputs found
Reprocessing of Soft X-ray Emission Lines in Black Hole Accretion Disks
By means of a Monte Carlo code that accounts for Compton scattering and
photoabsorption followed by recombination, we have investigated the radiation
transfer of Ly alpha, He alpha, and recombination continua photons of H- and
He-like C, N, O, and Ne produced in the photoionized atmosphere of a
relativistic black hole accretion disk. We find that photoelectric opacity
causes significant attenuation of photons with energies above the O VIII
K-edge; that the conversion efficiencies of these photons into lower-energy
lines and recombination continua are high; and that accounting for this
reprocessing significantly (by factors of 21% to 105%) increases the flux of
the Ly alpha and He alpha emission lines of H- and He-like C and O escaping the
disk atmosphere.Comment: 4 pages including 4 encapsulated postscript figures; LaTeX format,
uses aastex.cls and emulateapj5.sty; accepted on 2004 January 13 for
publication in The Astrophysical Journa
Analyzing Regional Impacts of Climate Change using Natural Language Processing Techniques
Understanding the multifaceted effects of climate change across diverse
geographic locations is crucial for timely adaptation and the development of
effective mitigation strategies. As the volume of scientific literature on this
topic continues to grow exponentially, manually reviewing these documents has
become an immensely challenging task. Utilizing Natural Language Processing
(NLP) techniques to analyze this wealth of information presents an efficient
and scalable solution. By gathering extensive amounts of peer-reviewed articles
and studies, we can extract and process critical information about the effects
of climate change in specific regions. We employ BERT (Bidirectional Encoder
Representations from Transformers) for Named Entity Recognition (NER), which
enables us to efficiently identify specific geographies within the climate
literature. This, in turn, facilitates location-specific analyses. We conduct
region-specific climate trend analyses to pinpoint the predominant themes or
concerns related to climate change within a particular area, trace the temporal
progression of these identified issues, and evaluate their frequency, severity,
and potential development over time. These in-depth examinations of
location-specific climate data enable the creation of more customized
policy-making, adaptation, and mitigation strategies, addressing each region's
unique challenges and providing more effective solutions rooted in data-driven
insights. This approach, founded on a thorough exploration of scientific texts,
offers actionable insights to a wide range of stakeholders, from policymakers
to engineers to environmentalists. By proactively understanding these impacts,
societies are better positioned to prepare, allocate resources wisely, and
design tailored strategies to cope with future climate conditions, ensuring a
more resilient future for all
Collisional Plasma Models with APEC/APED: Emission Line Diagnostics of Hydrogen-like and Helium-like Ions
New X-ray observatories (Chandra and XMM-Newton) are providing a wealth of
high-resolution X-ray spectra in which hydrogen- and helium-like ions are
usually strong features. We present results from a new collisional-radiative
plasma code, the Astrophysical Plasma Emission Code (APEC), which uses atomic
data in the companion Astrophysical Plasma Emission Database (APED) to
calculate spectral models for hot plasmas. APED contains the requisite atomic
data such as collisional and radiative rates, recombination cross sections,
dielectronic recombination rates, and satellite line wavelengths. We compare
the APEC results to other plasma codes for hydrogen- and helium-like
diagnostics, and test the sensitivity of our results to the number of levels
included in the models. We find that dielectronic recombination with
hydrogen-like ions into high (n=6-10) principal quantum numbers affects some
helium-like line ratios from low-lying (n=2) transitions.Comment: 5 pages, 6 figures, accepted by ApJ Letter
Enabling NATO’s Collective Defense: Critical Infrastructure Security and Resiliency (NATO COE-DAT Handbook 1)
In 2014 NATO’s Center of Excellence-Defence Against Terrorism (COE-DAT) launched the inaugural course on “Critical Infrastructure Protection Against Terrorist Attacks.” As this course garnered increased attendance and interest, the core lecturer team felt the need to update the course in critical infrastructure (CI) taking into account the shift from an emphasis on “protection” of CI assets to “security and resiliency.” What was lacking in the fields of academe, emergency management, and the industry practitioner community was a handbook that leveraged the collective subject matter expertise of the core lecturer team, a handbook that could serve to educate government leaders, state and private-sector owners and operators of critical infrastructure, academicians, and policymakers in NATO and partner countries. Enabling NATO’s Collective Defense: Critical Infrastructure Security and Resiliency is the culmination of such an effort, the first major collaborative research project under a Memorandum of Understanding between the US Army War College Strategic Studies Institute (SSI), and NATO COE-DAT.
The research project began in October 2020 with a series of four workshops hosted by SSI. The draft chapters for the book were completed in late January 2022. Little did the research team envision the Russian invasion of Ukraine in February this year. The Russian occupation of the Zaporizhzhya nuclear power plant, successive missile attacks against Ukraine’s electric generation and distribution facilities, rail transport, and cyberattacks against almost every sector of the country’s critical infrastructure have been on world display. Russian use of its gas supplies as a means of economic warfare against Europe—designed to undermine NATO unity and support for Ukraine—is another timely example of why adversaries, nation-states, and terrorists alike target critical infrastructure. Hence, the need for public-private sector partnerships to secure that infrastructure and build the resiliency to sustain it when attacked. Ukraine also highlights the need for NATO allies to understand where vulnerabilities exist in host nation infrastructure that will undermine collective defense and give more urgency to redressing and mitigating those fissures.https://press.armywarcollege.edu/monographs/1951/thumbnail.jp
U.S. Peanut Industry
The United States, with 25 percent of world peanut exports and 10 percent of world peanut production, is the leading peanut exporter and the third largest producer; only India and China produce more. U.S. production has nearly doubled since the early fifties, chiefly because of increases in yields. Most peanut consumption in the United States is for food, especially peanut butter, whereas most foreign countries use peanuts for oil. Canada is the leading importer of U.S. peanuts