282 research outputs found
Airborne next: rethinking airborne organization and applying new concepts
The airborne concept has had a lasting impact on military force structures since its employment on a large scale during World War II. It is puzzling to consider how little airborne organizational structures and employment concepts have changed in the intervening seven decades, considering the great amount of change occurring in warfare. This thesis examines the future potential of airborne concepts by rethinking traditional airborne organizational structures and employment concepts. Using a holistic approach in the areas of organization, doctrine, technology, and strategy as guiding frames of reference, this thesis recommends updating the organizational structures of airborne forces to model a small and many approach over a large and few approach, while incorporating a swarming concept. Utilizing historical and contemporary vignettes to demonstrate airborne utility, this research reveals how a parachute capability displays the unique attributes to complement a swarming concept. Under an updated organizational structure and new employment concept, airborne forces can offer renewed relevancy to the U.S. Department of Defense against modern adversaries in crises and conflict.http://archive.org/details/airbornenextreth1094545878Major, United States ArmyApproved for public release; distribution is unlimited
Nanocrystalline materials studied by powder diffraction line profile analysis
X-ray powder diffraction is a powerful tool for characterising the microstructure of crystalline materials in terms of size and strain. It is widely applied for nanocrystalline materials, especially since other methods, in particular electron microscopy is, on the one hand tedious and time consuming, on the other hand, due to the often metastable states of nanomaterials it might change their microstructures. It is attempted to overview the applications of microstructure characterization by powder diffraction on nanocrystalline metals, alloys, ceramics and carbon base materials. Whenever opportunity is given, the data provided by the X-ray method are compared and discussed together with results of electron microscopy. Since the topic is vast we do not try to cover the entire field
Quasi-free Compton Scattering and the Polarizabilities of the Neutron
Differential cross sections for quasi-free Compton scattering from the proton
and neutron bound in the deuteron have been measured using the Glasgow/Mainz
tagging spectrometer at the Mainz MAMI accelerator together with the Mainz 48
cm 64 cm NaI(Tl) photon detector and the G\"ottingen SENECA
recoil detector. The data cover photon energies ranging from 200 MeV to 400 MeV
at . Liquid deuterium and hydrogen targets
allowed direct comparison of free and quasi-free scattering from the proton.
The neutron detection efficiency of the SENECA detector was measured via the
reaction . The "free" proton Compton scattering cross
sections extracted from the bound proton data are in reasonable agreement with
those for the free proton which gives confidence in the method to extract the
differential cross section for free scattering from quasi-free data.
Differential cross sections on the free neutron have been extracted and the
difference of the electromagnetic polarizabilities of the neutron have been
obtained to be
in units . In combination with the polarizability sum deduced from photoabsorption data, the neutron electric and
magnetic polarizabilities, and
are obtained. The backward spin polarizability of the neutron was determined to
be
Upgrade of the Glasgow photon tagging spectrometer for Mainz MAMI-C
The Glasgow photon tagging spectrometer at Mainz has been upgraded so that it
can be used with the 1500 MeV electron beam now available from the Mainz
microtron MAMI-C. The changes made and the resulting properties of the
spectrometer are discussed.Comment: 20 pages, 12 figure
Quasi-free Photoproduction from the Bound Nucleon
Differential cross-sections for quasi-free photoproduction from the
proton and neutron bound in the deuteron have been measured for MeV at usind the Glasgow photon
tagger at MAMI, the Mainz 48 cm 64 cm NaI(Tl) photon
detector and the G\"ottingen SENECA recoil detector. For the proton
measurements made with both liquid deuterium and liquid hydrogen targets allow
direct comparison of "free" photoproduction cross-sections as extracted
from the bound proton data with experimental free cross sections which are
found to be in reasonable agreement below 320 MeV. At higher energies the
"free" cross sections extracted from quasifree data are significantly smaller
than the experimental free cross sections and theoretical predictions based on
multipole analysis. For the first time, "free" neutron cross sections have been
extracted in the -region. They are also in agreement with the
predictions from multipole analysis up to 320 MeV and significantly smaller at
higher photon energies
Neutron polarizabilities investigated by quasi-free Compton scattering from the deuteron
Measuring Compton scattered photons and recoil neutrons in coincidence,
quasi-free Compton scattering by the neutron has been investigated at MAMI
(Mainz) at in an energy range from 200 to 400 MeV.
From the data a polarizability difference of in units of has been
determined. In combination with the polarizability sum deduced from photo absorption data, the neutron electric and
magnetic polarizabilities, and ,
are obtained
Fabrication and characterization of dual function nanoscale pH-scanning ion conductance microscopy (SICM) probes for high resolution pH mapping
The easy fabrication and use of nanoscale dual function pH-scanning ion conductance microscopy (SICM) probes is reported. These probes incorporate an iridium oxide coated carbon electrode for pH measurement and an SICM barrel for distance control, enabling simultaneous pH and topography mapping. These pH-SICM probes were fabricated rapidly from laser pulled theta quartz pipets, with the pH electrode prepared by in situ carbon filling of one of the barrels by the pyrolytic decomposition of butane, followed by electrodeposition of a thin layer of hydrous iridium oxide. The other barrel was filled with an electrolyte solution and Ag/AgCl electrode as part of a conductance cell for SICM. The fabricated probes, with pH and SICM sensing elements typically on the 100 nm scale, were characterized by scanning electron microscopy, energy-dispersive X-ray spectroscopy, and various electrochemical measurements. They showed a linear super-Nernstian pH response over a range of pH (pH 2–10). The capability of the pH-SICM probe was demonstrated by detecting both pH and topographical changes during the dissolution of a calcite microcrystal in aqueous solution. This system illustrates the quantitative nature of pH-SICM imaging, because the dissolution process changes the crystal height and interfacial pH (compared to bulk), and each is sensitive to the rate. Both measurements reveal similar dissolution rates, which are in agreement with previously reported literature values measured by classical bulk methods
Ongoing outbreak of hepatitis A in Italy: preliminary report as of 31 May 2013
Since January 2013, an unusual increase in hepatitis A cases has been detected in northern Italy. A total number of 352 cases were reported to the integrated surveillance system between January and the end of May 2013 and this represents a 70% increase compared to the same period of the previous year. The outbreak is ongoing and the public health authorities are continuing their investigations to establish the transmission vehicle and to control the outbreak
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An i2b2-based, generalizable, open source, self-scaling chronic disease registry
Objective: Registries are a well-established mechanism for obtaining high quality, disease-specific data, but are often highly project-specific in their design, implementation, and policies for data use. In contrast to the conventional model of centralized data contribution, warehousing, and control, we design a self-scaling registry technology for collaborative data sharing, based upon the widely adopted Integrating Biology & the Bedside (i2b2) data warehousing framework and the Shared Health Research Information Network (SHRINE) peer-to-peer networking software. Materials and methods Focusing our design around creation of a scalable solution for collaboration within multi-site disease registries, we leverage the i2b2 and SHRINE open source software to create a modular, ontology-based, federated infrastructure that provides research investigators full ownership and access to their contributed data while supporting permissioned yet robust data sharing. We accomplish these objectives via web services supporting peer-group overlays, group-aware data aggregation, and administrative functions. Results: The 56-site Childhood Arthritis & Rheumatology Research Alliance (CARRA) Registry and 3-site Harvard Inflammatory Bowel Diseases Longitudinal Data Repository now utilize i2b2 self-scaling registry technology (i2b2-SSR). This platform, extensible to federation of multiple projects within and between research networks, encompasses >6000 subjects at sites throughout the USA. Discussion We utilize the i2b2-SSR platform to minimize technical barriers to collaboration while enabling fine-grained control over data sharing. Conclusions: The implementation of i2b2-SSR for the multi-site, multi-stakeholder CARRA Registry has established a digital infrastructure for community-driven research data sharing in pediatric rheumatology in the USA. We envision i2b2-SSR as a scalable, reusable solution facilitating interdisciplinary research across diseases
Atomic-scale modeling of the deformation of nanocrystalline metals
Nanocrystalline metals, i.e. metals with grain sizes from 5 to 50 nm, display
technologically interesting properties, such as dramatically increased
hardness, increasing with decreasing grain size. Due to the small grain size,
direct atomic-scale simulations of plastic deformation of these materials are
possible, as such a polycrystalline system can be modeled with the
computational resources available today.
We present molecular dynamics simulations of nanocrystalline copper with
grain sizes up to 13 nm. Two different deformation mechanisms are active, one
is deformation through the motion of dislocations, the other is sliding in the
grain boundaries. At the grain sizes studied here the latter dominates, leading
to a softening as the grain size is reduced. This implies that there is an
``optimal'' grain size, where the hardness is maximal.
Since the grain boundaries participate actively in the deformation, it is
interesting to study the effects of introducing impurity atoms in the grain
boundaries. We study how silver atoms in the grain boundaries influence the
mechanical properties of nanocrystalline copper.Comment: 10 pages, LaTeX2e, PS figures and sty files included. To appear in
Mater. Res. Soc. Symp. Proc. vol 538 (invited paper). For related papers, see
http://www.fysik.dtu.dk/~schiotz/publist.htm
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