89,401 research outputs found
Method and apparatus for stable silicon dioxide layers on silicon grown in silicon nitride ambient
A method and apparatus for thermally growing stable silicon dioxide layers on silicon is disclosed. A previously etched and baked silicon nitride tube placed in a furnace is used to grow the silicon dioxide. First, pure oxygen is allowed to flow through the tube to initially coat the inside surface of the tube with a thin layer of silicon dioxide. After the tube is coated with the thin layer of silicon dioxide, the silicon is oxidized thermally in a normal fashion. If the tube becomes contaminated, the silicon dioxide is etched off thereby exposing clean silicon nitride and then the inside of the tube is recoated with silicon dioxide. As is disclosed, the silicon nitride tube can also be used as the ambient for the pyrolytic decomposition of silane and ammonia to form thin layers of clean silicon nitride
Empirical equations for electron backscattering coefficients
Empirical equations for electron backscattering coefficient
Backscattering and secondary-electron emission from metal targets of various thicknesses
Backscattering and secondary electron emission from metal targets of various thicknesse
Numerical Approach to CP-Violating Dirac Equation
We propose a new method to evaluate the chiral charge flux, which is
converted into baryon number in the framework of the charge transport scenario
of electroweak baryogenesis. By the new method, one can calculate the flux in
the background of any type of bubble wall with any desired accuracy.Comment: 14 pages, epsf.sty is needed, 3 figures appende
Cramer-Rao Lower Bound for Point Based Image Registration with Heteroscedastic Error Model for Application in Single Molecule Microscopy
The Cramer-Rao lower bound for the estimation of the affine transformation
parameters in a multivariate heteroscedastic errors-in-variables model is
derived. The model is suitable for feature-based image registration in which
both sets of control points are localized with errors whose covariance matrices
vary from point to point. With focus given to the registration of fluorescence
microscopy images, the Cramer-Rao lower bound for the estimation of a feature's
position (e.g. of a single molecule) in a registered image is also derived. In
the particular case where all covariance matrices for the localization errors
are scalar multiples of a common positive definite matrix (e.g. the identity
matrix), as can be assumed in fluorescence microscopy, then simplified
expressions for the Cramer-Rao lower bound are given. Under certain simplifying
assumptions these expressions are shown to match asymptotic distributions for a
previously presented set of estimators. Theoretical results are verified with
simulations and experimental data
The Masers Towards IRAS 20126+4104
We present MERLIN observations of OH, water and methanol masers towards the
young high mass stellar object IRAS 20126+4104. Emission from the 1665-MHz OH,
22-GHz H_2O and 6.7-GHz CH_3OH masers is detected and all originates very close
to the central source. The OH and methanol masers appear to trace part of the
circumstellar disk around the central source. The positions and velocities of
the OH and methanol masers are consistent with Keplerian rotation around a
central mass of ~ 5 Msun. The water masers are offset from the OH and methanol
masers and have significantly changed since they were last observed, but still
appear to be associated to the outflow from the source. All the OH masers
components are circularly polarised, in some cases reaching 100 percent while
some OH components also have linear polarisation. We identify one Zeeman pair
of OH masers and the splitting of this pair indicates a magnetic field of
strength ~ 11 mG within ~ 0.5" (850 AU) of the central source. The OH and
methanol maser emission suggest that the disk material is dense, n > 10^6
cm^-3, and warm, T > 125 K and the high abundance of methanol required by the
maser emission is consistent with the evaporation of the mantles on dust grains
in the disk as a result of heating or shocking of the disk materialComment: 9 pages, 7 figures and 6 table
CP Violating Bubble Wall and Electroweak Baryogenesis
The electroweak baryogenesis depends on the profile of the CP-violating
bubble wall created at the first order phase transition. We attempt to
determine it by solving the coupled equations of motion for the moduli and
phases of the two Higgs doublets at the transition temperature. A variety of
CP-violating bubble walls are classified by boundary conditions. We point out
that a sufficiently small explicit CP violation gives nonperturbative effects
to yield the baryon asymmetry of the universe.Comment: 19 pages, 6 EPS figures, uses epsf.st
Spontaneous CP Violation at Finite Temperature in the MSSM
By studying the effective potential of the MSSM at finite temperature, we
find that CP can be spontaneously broken in the intermediate region between the
symmetric and broken phases separated by the bubble wall created at the phase
transition. This type of CP violation is necessary to have a bubble wall
profile connecting CP conserving vacua, while violating CP halfway and
generating sufficient baryon number without contradiction to the experimantal
bounds on CP violations. Several conditions on the parameters in the MSSM are
found for CP to be broken in this manner.Comment: 26 pages, LaTeX, 16 eps figures (epsf.sty is needed
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