8,294 research outputs found
Far Field Monitoring of Rogue Nuclear Activity with an Array of Large anti-neutrino Detectors
The result of a study on the use of an array of large anti-neutrino detectors
for the purpose of monitoring rogue nuclear activity is presented. Targeted
regional monitoring of a nation bordering large bodies of water with no
pre-existing legal nuclear activity may be possible at a cost of about several
billion dollars, assuming several as-yet-untested schemes pan out in the next
two decades. These are: (1) the enabling of a water-based detector to detect
reactor anti-neutrinos by doping with GdCl; (2) the deployment of a
KamLAND-like detector in a deep-sea environment; and (3) the scaling of a
Super-Kamiokande-like detector to a size of one or more megatons. The first may
well prove feasible, and should be tested by phase-III Super-Kamiokande in the
next few years. The second is more of a challenge, but may well be tested by
the Hanohano collaboration in the coming decade. The third is perhaps the least
certain, with no schedule for construction of any such device in the
foreseeable future. In addition to the regional monitoring scheme, several
global, untargeted monitoring schemes were considered. All schemes were found
to fail benchmark sensitivity levels by a wide margin, and to cost at least
several trillion dollars.Comment: 17 pages, 8 figures, proceedings for Neutrino Sciences 2005,
submitted to Earth, Moon, and Planet
Solar System Processes Underlying Planetary Formation, Geodynamics, and the Georeactor
Only three processes, operant during the formation of the Solar System, are
responsible for the diversity of matter in the Solar System and are directly
responsible for planetary internal-structures, including planetocentric nuclear
fission reactors, and for dynamical processes, including and especially,
geodynamics. These processes are: (i) Low-pressure, low-temperature
condensation from solar matter in the remote reaches of the Solar System or in
the interstellar medium; (ii) High-pressure, high-temperature condensation from
solar matter associated with planetary-formation by raining out from the
interiors of giant-gaseous protoplanets, and; (iii) Stripping of the primordial
volatile components from the inner portion of the Solar System by super-intense
solar wind associated with T-Tauri phase mass-ejections, presumably during the
thermonuclear ignition of the Sun. As described herein, these processes lead
logically, in a causally related manner, to a coherent vision of planetary
formation with profound implications including, but not limited to, (a) Earth
formation as a giant gaseous Jupiter-like planet with vast amounts of stored
energy of protoplanetary compression in its rock-plus-alloy kernel; (b) Removal
of approximately 300 Earth-masses of primordial gases from the Earth, which
began Earth's decompression process, making available the stored energy of
protoplanetary compression for driving geodynamic processes, which I have
described by the new whole-Earth decompression dynamics and which is
responsible for emplacing heat at the mantle-crust-interface at the base of the
crust through the process I have described, called mantle decompression
thermal-tsunami; and, (c)Uranium accumulations at the planetary centers capable
of self-sustained nuclear fission chain reactions.Comment: Invited paper for the Special Issue of Earth, Moon and Planets
entitled Neutrino Geophysics Added final corrections for publicatio
Role of oxygen vacancy defect states in the n-type conduction of β-Ga[sub 2]O[sub 3]
Based on semiempirical quantum-chemical calculations, the electronic band structure of β-Ga2O3 is presented and the formation and properties of oxygen vacancies are analyzed. The equilibrium geometries and formation energies of neutral and doubly ionized vacancies were calculated. Using the calculated donor level positions of the vacancies, the high temperature n-type conduction is explained. The vacancy concentration is obtained by fitting to the experimental resistivity and electron mobility
The effect of medical therapy on IOP control in Ghana
Background: To investigate IOP control following twelve months of continuous medical therapy in Ghana.Methods: This retrospective case series included 163 glaucoma patients diagnosed at a referral eye center between 1996 and 2006. Information collected included age, gender, IOP at presentation, six months and oneyear post treatment and types of anti-glaucoma medications prescribed. Optimal IOP control was defined according to results from the Advanced Glaucoma Intervention Study (AGIS), which demonstrated arrest of visual field progression in patients with IOP < 18 mmHg at all visitations: Level 1 (post-treatment IOP . 21 mmHg); Level 2 (. 18 mmHg) and level 3 (. 16mmHg). The principal outcome measure was the achievement of IOP <18 mmHg at six months and twelve month visitations.Results: One hundred sixty three patients were analyzed. These included 68 males (41.7%) and 95 females (58.3%). The mean age was 57}16 (median 59 years; range 7 . 95 years). There was no significant difference in age (p=0.35) or mean IOP (p=0.08) between genders. The mean pre-treated IOP of 31.9}8.9 mmHg significantly decreased to 21.3}6.6 mmHg at 6 months (p=0.001), with 57.4% of eyes at Level 1 IOP control, 25.3% at Level 2 and 15.4% at Level 3 and decreased further at 12 months to 20.7}6.9 mmHg (p=0.48) with 69.7% of eyes at Level 1, 34.4% at Level 2, and 12.4% at Level 3.Conclusions: Current medical regimen is insufficient to reduce IOP to target levels as defined in the Advanced Glaucoma Intervention Study.Keywords: Glaucoma, POAG, IOP, Ghana, intraocular pressur
Low energy neutrino astronomy with the large liquid scintillation detector LENA
The detection of low energy neutrinos in a large scintillation detector may
provide further important information on astrophysical processes as supernova
physics, solar physics and elementary particle physics as well as geophysics.
In this contribution, a new project for Low Energy Neutrino Astronomy (LENA)
consisting of a 50kt scintillation detector is presented.Comment: Proccedings of the International School of Nuclear Physics, Neutrinos
in Cosmology, in Astro, Particle and Nuclear Physics, Erice (SICILY) 16 - 24
Sept. 200
Protostar Formation in Magnetic Molecular Clouds beyond Ion Detachment: III. A Parameter Study
In two previous papers we formulated and solved, for a fiducial set of free
parameters, the problem of the formation and evolution of a magnetically
supercritical core inside a magnetically subcritical parent cloud. In this
paper we present a parameter study to assess the sensitivity of the results (1)
to the density at which the equation of state becomes adiabatic; (2) to the
initial mass-to-flux ratio of the parent cloud; and (3) to ionization by
radioactive decay of different nuclei (40K and 26Al) at high densities (number
density > 10^12 particles per cubic cm). We find that (1) the results depend
only slightly on the density at which the onset of adiabaticity occurs; (2)
memory of the initial mass-to-flux ratio is completely lost at late times,
which emphasizes the relevance of this work, idependently of the adopted theory
of core formation; and (3) the precise source of radioactive ionization alters
the degree of attachment of the electrons to the field lines (at high
densities), and the relative importance of ambipolar diffusion and Ohmic
dissipation in reducing the magnetic flux of the protostar. The value of the
magnetic field at the end of the runs is insensitive to the values of the free
parameters and in excellent agreement with meteoritic measurements of the
protosolar nebula magnetic field. The magnetic flux problem of star formation
is resolved for at least strongly magnetic newborn stars. A complete detachment
of the magnetic field from the matter is unlikely. The formation of a "magnetic
wall" (with an associated magnetic shock) is independent of the assumed
equation of state, although the process is enhanced and accelerated by the
formation of a central hydrostatic core.Comment: 17 pages, 14 figures, emulateapj; accepted for publication in the
Astrophysical Journa
Recommended from our members
Revisiting global fossil fuel and biofuel emissions of ethane
Recent measurements over the Northern Hemisphere indicate that the long-term decline in the atmospheric burden of ethane (C2H6) has ended and the abundance increased dramatically between 2010 and 2014. The rise in C2H6 atmospheric abundances has been attributed to oil and natural gas extraction in North America. Existing global C2H6 emission inventories are based on outdated activity maps that do not account for current oil and natural gas exploitation regions. We present an updated global C2H6 emission inventory based on 2010 satellite-derived CH4 fluxes with adjusted C2H6 emissions over the U.S. from the National Emission Inventory (NEI 2011). We contrast our global 2010 C2H6 emission inventory with one developed for 2001. The C2H6 difference between global anthropogenic emissions is subtle (7.9 versus 7.2 Tg yr−1), but the spatial distribution of the emissions is distinct. In the 2010 C2H6 inventory, fossil fuel sources in the Northern Hemisphere represent half of global C2H6 emissions and 95% of global fossil fuel emissions. Over the U.S., unadjusted NEI 2011 C2H6 emissions produce mixing ratios that are 14–50% of those observed by aircraft observations (2008–2014). When the NEI 2011 C2H6 emission totals are scaled by a factor of 1.4, the Goddard Earth Observing System Chem model largely reproduces a regional suite of observations, with the exception of the central U.S., where it continues to underpredict observed mixing ratios in the lower troposphere. We estimate monthly mean contributions of fossil fuel C2H6 emissions to ozone and peroxyacetyl nitrate surface mixing ratios over North America of ~1% and ~8%, respectively
Heat flow of the Earth and resonant capture of solar 57-Fe axions
In a very conservative approach, supposing that total heat flow of the Earth
is exclusively due to resonant capture inside the Earth of axions, emitted by
57-Fe nuclei on Sun, we obtain limit on mass of hadronic axion: m_a<1.8 keV.
Taking into account release of heat from decays of 40-K, 232-Th, 238-U inside
the Earth, this estimation could be improved to the value: m_a<1.6 keV. Both
the values are less restrictive than limits set in devoted experiments to
search for 57-Fe axions (m_a<216-745 eV), but are much better than limits
obtained in experiments with 83-Kr (m_a<5.5 keV) and 7-Li (m_a<13.9-32 keV).Comment: 8 page
- …