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FIELD-SCALE EFFECTIVE MATRIX DIFFUSION COEFFICIENT FOR FRACTURED ROCK:RESULTS FROM LITERATURE SURVEY
Matrix diffusion is an important mechanism for solute transport in fractured rock. We recently conducted a literature survey on the effective matrix diffusion coefficient, D{sub m}{sup e}, a key parameter for describing matrix diffusion processes at the field scale. Forty field tracer tests at 15 fractured geologic sites were surveyed and selected for the study, based on data availability and quality. Field-scale D{sub m}{sup e} values were calculated, either directly using data reported in the literature or by reanalyzing the corresponding field tracer tests. Surveyed data indicate that the effective-matrix-diffusion-coefficient factor F{sub D} (defined as the ratio of D{sub m}{sup e} to the lab-scale matrix diffusion coefficient [D{sub m}] of the same tracer) is generally larger than one, indicating that the effective matrix diffusion coefficient in the field is comparatively larger than the matrix diffusion coefficient at the rock-core scale. This larger value can be attributed to the many mass-transfer processes at different scales in naturally heterogeneous, fractured rock systems. Furthermore, we observed a moderate trend toward systematic increase in the F{sub D} value with observation scale, indicating that the effective matrix diffusion coefficient is likely to be statistically scale dependent. The F{sub D} value ranges from 1 to 10,000 for observation scales from 5 to 2,000 m. At a given scale, the F{sub D} value varies by two orders of magnitude, reflecting the influence of differing degrees of fractured rock heterogeneity at different sites. In addition, the surveyed data indicate that field-scale longitudinal dispersivity generally increases with observation scale, which is consistent with previous studies. The scale-dependent field-scale matrix diffusion coefficient (and dispersivity) may have significant implications for assessing long-term, large-scale radionuclide and contaminant transport events in fractured rock, both for nuclear waste disposal and contaminant remediation
Pair production of neutralinos via gluon-gluon collisions
The production of a neutralino pair via gluon-gluon fusion is studied in the
minimal supersymmetric model(MSSM) at proton-proton colliders. The numerical
analysis of their production rates are carried out in the mSUGRA scenario. The
results show that this cross section may reach about 80 femto barn for
pair production and 23 femto barn
for pair production with suitable
input parameters at the future LHC collider. It shows that this loop mediated
process can be competitive with the quark-antiquark annihilation process at the
LHC.Comment: LaTex file, l4 pages, 5 EPS figure
Exact thermodynamics of an Extended Hubbard Model of single and paired carriers in competition
By exploiting the technique of Sutherland's species, introduced in
\cite{DOMO-RC}, we derive the exact spectrum and partition function of a 1D
extended Hubbard model. The model describes a competition between dynamics of
single carriers and short-radius pairs, as a function of on-site Coulomb
repulsion () and filling (). We provide the temperature dependence of
chemical potential, compressibility, local magnetic moment, and specific heat.
In particular the latter turns out to exhibit two peaks, both related to
`charge' degrees of freedom. Their origin and behavior are analyzed in terms of
kinetic and potential energy, both across the metal-insulator transition point
and in the strong coupling regime.Comment: 14 pages, 15 eps figure
Electroweak Corrections to the Charged Higgs Boson Decay into Chargino and Neutralino
The electroweak corrections to the partial widths of the decays including one-loop
diagrams of the third generation quarks and squarks, are investigated within
the Supersymmetric Standard Model. The relative corrections can reach the
values about 10%, therefore they should be taken into account for the precise
experimental measurement at future colliders.Comment: 21 pages, 6 eps figures, 1 Latex fil
Solar Intranetwork Magnetic Elements: bipolar flux appearance
The current study aims to quantify characteristic features of bipolar flux
appearance of solar intranetwork (IN) magnetic elements. To attack such a
problem, we use the Narrow-band Filter Imager (NFI) magnetograms from the Solar
Optical Telescope (SOT) on board \emph{Hinode}; these data are from quiet and
an enhanced network areas. Cluster emergence of mixed polarities and IN
ephemeral regions (ERs) are the most conspicuous forms of bipolar flux
appearance within the network. Each of the clusters is characterized by a few
well-developed ERs that are partially or fully co-aligned in magnetic axis
orientation. On average, the sampled IN ERs have total maximum unsigned flux of
several 10^{17} Mx, separation of 3-4 arcsec, and a lifetime of 10-15 minutes.
The smallest IN ERs have a maximum unsigned flux of several 10^{16} Mx,
separations less than 1 arcsec, and lifetimes as short as 5 minutes. Most IN
ERs exhibit a rotation of their magnetic axis of more than 10 degrees during
flux emergence. Peculiar flux appearance, e.g., bipole shrinkage followed by
growth or the reverse, is not unusual. A few examples show repeated
shrinkage-growth or growth-shrinkage, like magnetic floats in the dynamic
photosphere. The observed bipolar behavior seems to carry rich information on
magneto-convection in the sub-photospheric layer.Comment: 26 pages, 14 figure
BESII Detector Simulation
A Monte Carlo program based on Geant3 has been developed for BESII detector
simulation. The organization of the program is outlined, and the digitization
procedure for simulating the response of various sub-detectors is described.
Comparisons with data show that the performance of the program is generally
satisfactory.Comment: 17 pages, 14 figures, uses elsart.cls, to be submitted to NIM
Narrow width of a glueball decay into two mesons
The widths of a glueball decay to two pions or kaons are analyzed in the pQCD
framework. Our results show that the glueball ground state has small branching
ratio for two-meson decay mode, which is around . The predicted values
are consistent with the data of if particle is a
glueball. Applicability of pQCD to the glueball decay and comparison
with decay are also discussed.Comment: 12 pages, revtex, 2 ps figure
Formation of Nanopits in Si Capping Layers on SiGe Quantum Dots
In-situ annealing at a high temperature of 640°C was performed for a low temperature grown Si capping layer, which was grown at 300°C on SiGe self-assembled quantum dots with a thickness of 50 nm. Square nanopits, with a depth of about 8 nm and boundaries along 〈110〉, are formed in the Si capping layer after annealing. Cross-sectional transmission electron microscopy observation shows that each nanopit is located right over one dot with one to one correspondence. The detailed migration of Si atoms for the nanopit formation is revealed by in-situ annealing at a low temperature of 540°C. The final well-defined profiles of the nanopits indicate that both strain energy and surface energy play roles during the nanopit formation, and the nanopits are stable at 640°C. A subsequent growth of Ge on the nanopit-patterned surface results in the formation of SiGe quantum dot molecules around the nanopits
Internal representations of smell in the Drosophila brain
Recent advances in sensory neuroscience using Drosophila olfaction as a model system have revealed brain maps representing the external world. Once we understand how the brain's built-in capability generates the internal olfactory maps, we can then elaborate how the brain computes and makes decision to elicit complex behaviors. Here, we review current progress in mapping Drosophila olfactory circuits and discuss their relationships with innate olfactory behaviors
A lower bound on the mass of Dark Matter particles
We discuss the bounds on the mass of Dark Matter (DM) particles, coming from
the analysis of DM phase-space distribution in dwarf spheroidal galaxies
(dSphs). After reviewing the existing approaches, we choose two methods to
derive such a bound. The first one depends on the information about the current
phase space distribution of DM particles only, while the second one uses both
the initial and final distributions. We discuss the recent data on dSphs as
well as astronomical uncertainties in relevant parameters. As an application,
we present lower bounds on the mass of DM particles, coming from various dSphs,
using both methods. The model-independent bound holds for any type of fermionic
DM. Stronger, model-dependent bounds are quoted for several DM models (thermal
relics, non-resonantly and resonantly produced sterile neutrinos, etc.). The
latter bounds rely on the assumption that baryonic feedback cannot
significantly increase the maximum of a distribution function of DM particles.
For the scenario in which all the DM is made of sterile neutrinos produced via
non-resonant mixing with the active neutrinos (NRP) this gives m_nrp > 1.7 keV.
Combining these results in their most conservative form with the X-ray bounds
of DM decay lines, we conclude that the NRP scenario remains allowed in a very
narrow parameter window only. This conclusion is independent of the results of
the Lyman-alpha analysis. The DM model in which sterile neutrinos are
resonantly produced in the presence of lepton asymmetry remains viable. Within
the minimal neutrino extension of the Standard Model (the nuMSM), both mass and
the mixing angle of the DM sterile neutrino are bounded from above and below,
which suggests the possibility for its experimental search.Comment: 20 pages, published in JCA
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