390 research outputs found
Immittance Matching for Multi-dimensional Open-system Photonic Crystals
An electromagnetic (EM) Bloch wave propagating in a photonic crystal (PC) is
characterized by the immittance (impedance and admittance) of the wave. The
immittance is used to investigate transmission and reflection at a surface or
an interface of the PC. In particular, the general properties of immittance are
useful for clarifying the wave propagation characteristics. We give a general
proof that the immittance of EM Bloch waves on a plane in infinite one- and
two-dimensional (2D) PCs is real when the plane is a reflection plane of the PC
and the Bloch wavevector is perpendicular to the plane. We also show that the
pure-real feature of immittance on a reflection plane for an infinite
three-dimensional PC is good approximation based on the numerical calculations.
The analytical proof indicates that the method used for immittance matching is
extremely simplified since only the real part of the immittance function is
needed for analysis without numerical verification. As an application of the
proof, we describe a method based on immittance matching for qualitatively
evaluating the reflection at the surface of a semi-infinite 2D PC, at the
interface between a semi-infinite slab waveguide (WG) and a semi-infinite 2D PC
line-defect WG, and at the interface between a semi-infinite channel WG and a
semi-infinite 2D PC slab line-defect WG.Comment: 8 pages, 6 figure
Magnetized Accretion-Ejection Structures: 2.5D MHD simulations of continuous Ideal Jet launching from resistive accretion disks
We present numerical magnetohydrodynamic (MHD) simulations of a magnetized
accretion disk launching trans-Alfvenic jets. These simulations, performed in a
2.5 dimensional time-dependent polytropic resistive MHD framework, model a
resistive accretion disk threaded by an initial vertical magnetic field. The
resistivity is only important inside the disk, and is prescribed as eta =
alpha_m V_AH exp(-2Z^2/H^2), where V_A stands for Alfven speed, H is the disk
scale height and the coefficient alpha_m is smaller than unity. By performing
the simulations over several tens of dynamical disk timescales, we show that
the launching of a collimated outflow occurs self-consistently and the ejection
of matter is continuous and quasi-stationary. These are the first ever
simulations of resistive accretion disks launching non-transient ideal MHD
jets. Roughly 15% of accreted mass is persistently ejected. This outflow is
safely characterized as a jet since the flow becomes super-fastmagnetosonic,
well-collimated and reaches a quasi-stationary state. We present a complete
illustration and explanation of the `accretion-ejection' mechanism that leads
to jet formation from a magnetized accretion disk. In particular, the magnetic
torque inside the disk brakes the matter azimuthally and allows for accretion,
while it is responsible for an effective magneto-centrifugal acceleration in
the jet. As such, the magnetic field channels the disk angular momentum and
powers the jet acceleration and collimation. The jet originates from the inner
disk region where equipartition between thermal and magnetic forces is
achieved. A hollow, super-fastmagnetosonic shell of dense material is the
natural outcome of the inwards advection of a primordial field.Comment: ApJ (in press), 32 pages, Higher quality version available at
http://www-laog.obs.ujf-grenoble.fr/~fcass
Heat-capacity anomalies at and in the ferromagnetic superconductor UGe
The heat-capacity and magnetization measurements under high pressure have
been carried out in a ferromagnetic superconductor UGe. Both measurements
were done using a same pressure cell in order to obtain both data for one
pressure. Contrary to the heat capacity at ambient pressure, an anomaly is
found in the heat capacity at the characteristic temperature where the
magnetization shows an anomalous enhancement under high pressure where the
superconductivity appears. This suggests that a thermodynamic phase transition
takes place at at least under high pressure slightly below
where becomes zero. The heat-capacity anomaly associated with the
superconducting transition is also investigated, where a clear peak of is
observed in a narrow pressure region ( GPa) around
contrary to the previous results of the resistivity measurement.
Present results suggest the importance of the thermodynamic critical point
for the appearance of the superconductivity.Comment: 4 pages, 4 figures, to appear in Phys. Rev. B, Rapid Communication
Measurement of solution parameters on sonication decellularization treatment
We have developed a sonication decellularization
system to decellularized biological scaffolds in short time by combining sonication and chemical method. The aim of this
study is to investigate decellularization efficiency on the
different treated solution parameters. As a result, decreasing of dissolved oxygen (DO) would increase the conductivity and pH of decellularization solution, and decreasing of pH would
increase conductivity. We found that the solution concentrationhas relation to its parameters and may influence the efficiency of sonication decellularization treatment
Is CP Violation Observable in Long Baseline Neutrino Oscillation Experiments ?
We have studied CP violation originated by the phase of the neutrino mixing
matrix in the long baseline neutrino oscillation experiments. The direct
measurements of CP violation is the difference of the transition probabilities
between CP-conjugate channels. In those experiments, the CP violating effect is
not suppressed if the highest neutrino mass scale is taken to be 1\sim 5 \eV,
which is appropriate for the cosmological hot dark matter. Assuming the
hierarchy for the neutrino masses, the upper bounds of CP violation have been
caluculated for three cases, in which mixings are constrained by the recent
short baseline ones. The calculated upper bounds are larger than ,
which will be observable in the long baseline accelerator experiments. The
matter effect, which is not CP invariant, has been also estimated in those
experiments.Comment: 28 pages, LaTex file, 6 figures included using epsfig Matter effect
is estimated(Figs.3(a) (b)). Physical parameters are change
Radiatively inefficient MHD accretion-ejection structures
We present magnetohydrodynamic simulations of a resistive accretion disk
continuously launching transmagnetosonic, collimated jets. We time-evolve the
full set of magnetohydrodynamic equations, but neglect radiative losses in the
energetics (radiatively inefficient). Our calculations demonstrate that a jet
is self-consistently produced by the interaction of an accretion disk with an
open, initially bent large-scale magnetic field. A constant fraction of heated
disk material is launched in the inner equipartition disk regions, leading to
the formation of a hot corona and a bright collimated, super-fastmagnetosonic
jet. We illustrate the complete dynamics of the ``hot'' near steady-state
outflow (where thermal pressure magnetic pressure) by showing force
balance, energy budget and current circuits. The evolution to this near
stationary state is analyzed in terms of the temporal variation of energy
fluxes controlling the energetics of the accretion disk. We find that unlike
advection-dominated accretion flow, the energy released by accretion is mainly
sent into the jet rather than transformed into disk enthalpy. These magnetized,
radiatively inefficient accretion-ejection structures can account for
under-luminous thin disks supporting bright fast collimated jets as seen in
many systems displaying jets (for instance M87).Comment: Astrophysical Journal (in press). Figures are missing due to file
size restrictions. To have the complete paper just click on
http://www-laog.obs.ujf-grenoble.fr/~fcasse/MS56638.pd
Natural Neutrino Mass Matrix
Naturalness of the neutrino mass hierarchy and mixing is studied. First we
select among 12 neutrino mixing patterns a few patterns, which could form the
natural neutrino mass matrix. Further we show that if the Dirac neutrino mass
matrix is taken as the natural one in the quark sector, then only two mixing
patterns without the large mixing lead to the natural right-handed Majorana
mass matrix. The rest of the chosen patterns with three degenerate mass
solution lead to the unnatural right-handed Majorana mass matrix in the see-saw
mechanism. Notice however, that for the chosen two natural patterns there could
be a huge mass hierarchy such as in order to reproduce
the inverse mass hierarchy of the light neutrinos.Comment: 31 pages, LaTex file, no figures, arguments made more clear, main
conclusions unchanged, version accepted for publication in PRD Reort-no:
Lund-Mph-97/14 Revise
Muon-anti-neutrino <---> electron-anti-neutrino mixing: analysis of recent indications and implications for neutrino oscillation phenomenology
We reanalyze the recent data from the Liquid Scintillator Neutrino Detector
(LSND) experiment, that might indicate anti-nu_muanti-nu_e mixing. This
indication is not completely excluded by the negative results of established
accelerator and reactor neutrino oscillation searches. We quantify the region
of compatibility by means of a thorough statistical analysis of all the
available data, assuming both two-flavor and three-flavor neutrino
oscillations. The implications for various theoretical scenarios and for future
oscillation searches are studied. The relaxation of the LSND constraints under
different assumptions in the statistical analysis is also investigated.Comment: 17 pages (RevTeX) + 9 figures (Postscript) included with epsfig.st
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