13,051 research outputs found
Prediction of gas leakage of environmental control systems
Mathematical models of leakage configurations and various flow theories are presented with the substantive experimental test data to provide background material for future design and failure analysis. Normal-rate leakage and emergency, high-rate leakage are considered
The total nucleon-nucleon cross section at large N_c
It is shown that at sufficiently large for incident momenta which are
much larger than the QCD, the total nucleon-nucleon cross section is
independent of incident momentum and given by . This result is valid in the extreme large
regime of and has corrections of relative order . A possible connection of this result to the
Froissart-Martin bound is discussed.Comment: 4 page
The Indians and the Agriculture of Crow Creek Indian Reservation
The Crow Creek Indian Reservation is located in South Dakota, bordering the east side of the Missouri River, about forty miles below Pierre, the Capital. In fact, a part of Hughes county lies in the Big Bend District of the reservation, and the south end of Hyde County and the west end of Buffalo County make up the rest of it - in all 313,304,23 acres or 489.5 square miles - about 13.5 townships. Parallel 44° North Latitude cuts the southern part of the Reservation, while meridian 99° West Longitude is just east of it. The nearest rail road point is Chamberlain on the Chicago, Milwaukee and St. Paul R.R., which is about twenty five miles down the river, same being about one hundred and eighty miles north west of Sioux City
General Thomas J. Stonewall Jackson to William Cook Lewis
In this letter, General Jackson submits payment of $150 to William Cook Lewis for the lease of slave, Jim. Jim Lewis served as Stonewall Jackson\u27s cook and servant throughout the war, cared for Jackson while he was dying, and led Jackson\u27s horse during his funeral
Shock wave compression of single-crystal forsterite
Hugoniot equation of state measurements have been performed on pure synthetic single-crystal forsterite (Mg_2SiO_4) in the pressure range 70–160 GPa (0.7–1.6 Mbar). These and earlier data for polycrystalline forsterite are compared with theoretical Hugoniots for the assemblages 2MgO (rocksalt) + SiO_2 (stishovite) and MgO (rocksalt) + MgSiO_3 (perovskite). The densities attained by single-crystal forsterite at pressures in excess of 120 GPa are greater than those expected in the event of shock-induced transformation to the isochemical oxide mixture. A similar test of the hypothesis of shock-induced transformation to the perovskite-bearing assemblage is sensitive to the choice of MgSiO_3 (perovskite) bulk modulus. Recent static compression measurements of Yagi et al. (1978) yield a K_(0T) of 286 GPa (for K_(0T)′ = 5), which, along with other elastic and thermodynamic parameters, suggests that shocked forsterite may be more dense than the perovskite-bearing assemblage. Crystalline phases of up to 5% greater zeropressure density or equally dense short-range-order-only phases may well be involved. Alternatively, the use of an isentropic bulk modulus of 250 GPa (estimated by Liebermann et al., 1977) for MgSiO_3 (perovskite) allows consistency between the data and the calculated MgO + MgSiO_3 (perovskite) Hugoniot for a reasonable choice (∼3.8) of K_(0s)′ for the latter phase. The new forsterite data along with high-pressure Hugoniot data for other olivines and olivinitic rocks define a smooth isobaric variation of Hugoniot density with composition. It is shown that an estimated pyrolite (Ringwood, 1975) Hugoniot density of 5.31 g/cm^3 at 120 GPa is ∼2% less dense than inferred from typical lower mantle density profiles
Foldy-Wouthuysen transformation for a Dirac-Pauli dyon and the Thomas-Bargmann-Michel-Telegdi equation
The classical dynamics for a charged point particle with intrinsic spin is
governed by a relativistic Hamiltonian for the orbital motion and by the
Thomas-Bargmann-Michel-Telegdi equation for the precession of the spin. It is
natural to ask whether the classical Hamiltonian (with both the orbital and
spin parts) is consistent with that in the relativistic quantum theory for a
spin-1/2 charged particle, which is described by the Dirac equation. In the
low-energy limit, up to terms of the 7th order in ( and
is the particle mass), we investigate the Foldy-Wouthuysen (FW) transformation
of the Dirac Hamiltonian in the presence of homogeneous and static
electromagnetic fields and show that it is indeed in agreement with the
classical Hamiltonian with the gyromagnetic ratio being equal to 2. Through
electromagnetic duality, this result can be generalized for a spin-1/2 dyon,
which has both electric and magnetic charges and thus possesses both intrinsic
electric and magnetic dipole moments. Furthermore, the relativistic quantum
theory for a spin-1/2 dyon with arbitrary values of the gyromagnetic and
gyroelectric ratios can be described by the Dirac-Pauli equation, which is the
Dirac equation with augmentation for the anomalous electric and anomalous
magnetic dipole moments. The FW transformation of the Dirac-Pauli Hamiltonian
is shown, up to the 7th order again, to be also in accord with the classical
Hamiltonian.Comment: 18 page
Validity of effective material parameters for optical fishnet metamaterials
Although optical metamaterials that show artificial magnetism are mesoscopic
systems, they are frequently described in terms of effective material
parameters. But due to intrinsic nonlocal (or spatially dispersive) effects it
may be anticipated that this approach is usually only a crude approximation and
is physically meaningless. In order to study the limitations regarding the
assignment of effective material parameters, we present a technique to retrieve
the frequency-dependent elements of the effective permittivity and permeability
tensors for arbitrary angles of incidence and apply the method exemplarily to
the fishnet metamaterial. It turns out that for the fishnet metamaterial,
genuine effective material parameters can only be introduced if quite stringent
constraints are imposed on the wavelength/unit cell size ratio. Unfortunately
they are only met far away from the resonances that induce a magnetic response
required for many envisioned applications of such a fishnet metamaterial. Our
work clearly indicates that the mesoscopic nature and the related spatial
dispersion of contemporary optical metamaterials that show artificial magnetism
prohibits the meaningful introduction of conventional effective material
parameters
Representing Structural Information of Helical Charge Distributions in Cylindrical Coordinates
Structural information in the local electric field produced by helical charge
distributions, such as dissolved DNA, is revealed in a straightforward manner
employing cylindrical coordinates. Comparison of structure factors derived in
terms of cylindrical and helical coordinates is made. A simple coordinate
transformation serves to relate the Green function in cylindrical and helical
coordinates. We also compare the electric field on the central axis of a single
helix as calculated in both systems.Comment: 11 pages in plain LaTex, no figures. Accepted for publication in PRE
March, 199
Negative refractive index due to chirality
We demonstrate experimentally and numerically that metamaterials based on
bilayer cross wires give giant optical activity, circular dichroism, and
negative refractive index. The presented chiral design offers a much simpler
geometry and more efficient way to realize negative refractive index at any
frequency. We also developed a retrieval procedure for chiral materials which
works successfully for circularly polarized waves
Singular electrostatic energy of nanoparticle clusters
The binding of clusters of metal nanoparticles is partly electrostatic. We
address difficulties in calculating the electrostatic energy when high charging
energies limit the total charge to a single quantum, entailing unequal
potentials on the particles. We show that the energy at small separation
has a strong logarithmic dependence on . We give a general law for the
strength of this logarithmic correction in terms of a) the energy at contact
ignoring the charge quantization effects and b) an adjacency matrix specifying
which spheres of the cluster are in contact and which is charged. We verify the
theory by comparing the predicted energies for a tetrahedral cluster with an
explicit numerical calculation.Comment: 17 pages, 3 figures. Submitted to Phys Rev
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