43,937 research outputs found
Advanced silicon on insulator technology
Undoped, thin-layer silicon-on-insulator was fabricated using wafer bonding and selective etching techniques employing a molecular beam epitaxy (MBE) grown Si0.7Ge0.3 layer as an etch stop. Defect free, undoped 200-350 nm silicon layers over silicon dioxide are routinely fabricated using this procedure. A new selective silicon-germanium etch was developed that significantly improves the ease of fabrication of the bond and etch back silicon insulator (BESOI) material
Continuous-Time Random Walks at All Times
Continuous-time random walks (CTRW) play important role in understanding of a
wide range of phenomena. However, most theoretical studies of these models
concentrate only on stationary-state dynamics. We present a new theoretical
approach, based on generalized master equations picture, that allowed us to
obtain explicit expressions for Laplace transforms for all dynamic quantities
for different CTRW models. This theoretical method leads to the effective
description of CTRW at all times. Specific calculations are performed for
homogeneous, periodic models and for CTRW with irreversible detachments. The
approach to stationary states for CTRW is analyzed. Our results are also used
to analyze generalized fluctuations theorem
Log-periodic modulation in one-dimensional random walks
We have studied the diffusion of a single particle on a one-dimensional
lattice. It is shown that, for a self-similar distribution of hopping rates,
the time dependence of the mean-square displacement follows an anomalous power
law modulated by logarithmic periodic oscillations. The origin of this
modulation is traced to the dependence on the length of the diffusion
coefficient. Both the random walk exponent and the period of the modulation are
analytically calculated and confirmed by Monte Carlo simulations.Comment: 6 pages, 7 figure
Nonlinear photon transport in a semiconductor waveguide-cavity system containing a single quantum dot: Anharmonic cavity-QED regime
We present a semiconductor master equation technique to study the
input/output characteristics of coherent photon transport in a semiconductor
waveguide-cavity system containing a single quantum dot. We use this approach
to investigate the effects of photon propagation and anharmonic cavity-QED for
various dot-cavity interaction strengths, including weakly-coupled,
intermediately-coupled, and strongly-coupled regimes. We demonstrate that for
mean photon numbers much less than 0.1, the commonly adopted weak excitation
(single quantum) approximation breaks down, even in the weak coupling regime.
As a measure of the anharmonic multiphoton-correlations, we compute the Fano
factor and the correlation error associated with making a semiclassical
approximation. We also explore the role of electron--acoustic-phonon scattering
and find that phonon-mediated scattering plays a qualitatively important role
on the light propagation characteristics. As an application of the theory, we
simulate a conditional phase gate at a phonon bath temperature of K in the
strong coupling regime.Comment: To appear in PR
Use Best Crop Varieties
The largest return on the investment in our cropping program can be secured by obtaining and planting the best varieties. We are all looking for varieties which give top yields and have other desirable characters
Good Seed Corn for 1913
Whether Iowa farmers will have good seed corn for next spring\u27s planting will depend upon whether they select their seed In the Held early, before a sharp freeze, and whether they dry It properly this fall and store It In the right kind of a place this winter. If any one or these factors Is neglected, the man who neglects them Is more than likely to be without good seed corn In 1913.
Although a general alarm.about seed corn has been sounded regularly every fall for some years, the vitality of the seed In the spring has become worse rather than better. This Is true, not because or the greater attention given to the selection and care of seed In the tall, but rather In spite of it
Is Ladino For Iowa?
Ladino clover is a giant cousin of the white clover so common in most permanent pastures and in many lawns. Farmers have been asking about it. Is it reccomended for Iowa? Where does it grow well- where doesn\u27t it
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