234 research outputs found
The Center for Medicare and Medicaid Innovation: Activity on Many Fronts
Provides an overview of the Innovation Center's organization, differences from CMS's traditional demonstration authority, payment and delivery reform initiatives, and first-year efforts to solicit and promote new ideas and collaborate with other payers
Double transverse-spin asymmetries in Drell--Yan and production from proton--antiproton collisions
We perform a NLO numerical study of the double transverse-spin asymmetries in
the resonance region for proton--antiproton collisions. We analyze the
large kinematic region, relevant for the proposed PAX experiment at GSI,
and discuss the implication of the results for the extraction of the
transversity densities.Comment: 8 pages, 6 figures, Talk given at "Transversity 2005" Como, Italy
7-10 Sep. 2005; eds. World Scientific in pres
QCD Supersymmetry and Low Energy Gravity
In this contributed paper we discuss some aspects of scenarios with Extra
Dimensions at the LHC and in cosmic rays.Comment: Contributed paper to the Conference "Quark confinement ant the Hadron
Spectrum VI 2004". Latex, 3 page
Radar Systems for Glaciology
This chapter deals with radar systems, measurements and instrumentation
employed to study the internal core and bedrock of ice sheets in glaciology. The Earth's ice sheets are in Greenland and Antarctica. They cover about 10% of the land surface of the planet. The total accumulated ice comprises 90% of the global fresh water reserve. These ice sheets, associated with the ocean environment, provide a major heat sink which significantly modulates climate.
Glaciology studies aim to understand the various process involved in the flow (dynamics), thermodynamics, and long-term behaviour of ice sheets.
Studies of large ice masses are conducted in adverse environmental conditions (extreme cold, long periods of darkness). The development of remote sensing techniques have played an important role in obtaining useful results. The most widely used techniques are radar systems, employed since
the 1950s in response to a need to provide a rapid and accurate method of measuring ice thickness. Year by year, polar research has become increasingly important because of global warming. Moreover, the discovery of
numerous subglacial lake areas (water entrapped beneath the ice sheets) has
attracted scientific interest in the possible existence of water circulation
between lakes or beneath the ice (Kapitsa et al., 2006; Wingham et al., 2006; Bell et al., 2007). Recent studies in radar signal shape and amplitude could provide evidence of water circulation below the ice (Carter 2007, Oswald and Gogineni 2008).
In this chapter the radar systems employed in glaciology, radio echo sounding (RES), are briefly described with some interesting results. RES are active remote sensing systems that utilize electromagnetic waves that penetrate the ice. They are used to obtain information about the electromagnetic properties of different interfaces (for example rock-ice, ice-water, seawater-ice) that reflect the incoming signal back to the radar.
RES systems are characterized by a high energy (peak power from 10 W to 10 KW) variable transmitted pulse width (about from 0.5 ns to several microseconds) in order to investigate bedrock characteristics even in the thickest zones of the ice sheets (4755 m is the deepest ice thickness measured in Antarctica using a RES system). Changing the pulse length or the transmitted signal frequencies it is possible to investigate particular ice sheet details with different resolution. Long pulses allows transmission of higher power than short pulses, penetrating the thickest parts of the ice
sheets but, as a consequence, resolution decreases. For example, the GPR system, commonly used in geophysics for rock, soil, ice, fresh water, pavement and structure characterization, employs a very short transmitted pulse (0.5 ns to 10 ns) that allow detailing of the shallow parts of an ice sheet (100-200 m in depth) (Reynolds 1997). Consequently, in recent years,
GPR systems are also employed by explorers to find hidden crevasses on glaciers for safety.
RES surveys have been widely employed in Antarctic ice sheet exploration and
they are still an indispensable tool for mapping bedrock morphologies and properties of the last unexplored continent on Earth. The advantage of using these remote sensing techniques is that they allow large areas to be covered, in good detail and in short times using platforms like aeroplanes
and surface vehicles
Twenty years of geomagnetic field observations at Mario Zucchelli Station (Antarctica)
During the 1986-87 austral summer a geomagnetic observatory was installed at Terra Nova Bay. During the first
years both geomagnetic field time variation monitoring and absolute measurements were carried out only during
summer. Since 1991 variometer measurements are automatically performed throughout the year, while absolute
measurements are still performed only during summer. In spite of this, interesting observations were obtained
during the life (quite long for Antarctica) of the geomagnetic observatory. In particular, this paper briefly
presents some of the most important results: studies on secular variation, daily variation (and its dependence
from solar cycle and seasons) and geomagnetic higher frequency variations, such as geomagnetic pulsations
The Kinetic Interpretation of the DGLAP Equation, its Kramers-Moyal Expansion and Positivity of Helicity Distributions
According to a rederivation - due to Collins and Qiu - the DGLAP equation can
be reinterpreted (in leading order) in a probabilistic way. This form of the
equation has been used indirectly to prove the bound
between polarized and unpolarized distributions, or positivity of the helicity
distributions, for any . We reanalize this issue by performing a detailed
numerical study of the positivity bounds of the helicity distributions. To
obtain the numerical solution we implement an x-space based algorithm for
polarized and unpolarized distributions to next-to-leading order in ,
which we illustrate. We also elaborate on some of the formal properties of the
Collins-Qiu form and comment on the underlying regularization, introduce a
Kramers-Moyal expansion of the equation and briefly analize its Fokker-Planck
approximation. These follow quite naturally once the master version is given.
We illustrate this expansion both for the valence quark distribution and
for the transverse spin distribution .Comment: 38 pages, 27 figures, Dedicated to Prof. Pierre Ramond for his 60th
birthda
EARTH'S MAGNETISM AT THE SOUTH POLE: A VIEW FROM INLAND AND COASTAL STATIONS AND FROM TEMPORARY INSTALLATIONS
Contributions to the knowledge of the Earth’s magnetism from polar regions is extremely important to understand the planetary phenomena which occur both below and above the Earth’s surface. At those areas the Earth’s magnetic field is stronger and the spatial and temporal changes are enhanced. At the same time polar regions are areas scarcely covered by observations for the adverse environmental conditions. We report the experience gained in years of management and maintenance of permanent stations (Mario Zucchelli, Dumont d’Urville (Victoria Land) and Concordia stations, Dome C) as well as temporary installations (Talos Dome) in Antarctica, showing how different acquisition systems, analysis and interpretation of data allow the scientific communities to contribute to originating important theories, models and results
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