5,360 research outputs found
Revealing Fibril Angle in Wood Sections By Ultrasonic Treatment
An effective method for inducing cell-wall checks in a microtomed wood radial section by ultrasonic treatment is described. Congo Red enhances cell-wall fibrillation in ultrasonic-treated sections. The amount of fibrillation and checking increases as ultrasonic treatment continues. However, too much fibrillation generated either by prolonged ultrasonic treatment or by Congo Red enhancement may visually obscure the checks. Less than three hours of ultrasonic treatment at 47 kHz frequency was found to be satisfactory to induce checks in 15-μm-thick southern pine sections. The ultrasound check-inducing technique is most effective on southern pine fibers with large diameters and high fibril angles
Multimode optical feedback dynamics in InAs/GaAs quantum dot lasers emitting exclusively on ground or excited states: transition from short- to long-delay regimes
© 2018 Optical Society of America. Users may use, reuse, and build upon the article, or use the article for text or data mining, so long as such uses are for non-commercial purposes and appropriate attribution is maintained. All other rights are reserved.The optical feedback dynamics of two multimode InAs/GaAs quantum dot lasers emitting exclusively on sole ground or excited lasing states is investigated. The transition from long- to short-delay regimes is analyzed, while the boundaries associated to the birth of periodic and chaotic oscillations are unveiled to be a function of the external cavity length. The results show that depending on the initial lasing state, different routes to chaos are observed. These results are of importance for the development of isolator-free transmitters in short-reach networks
Systematic {\em ab initio} study of the phase diagram of epitaxially strained SrTiO
We use density-functional theory with the local-density approximation to
study the structural and ferroelectric properties of SrTiO under misfit
strains. Both the antiferrodistortive (AFD) and ferroelectric (FE)
instabilities are considered. The rotation of the oxygen octahedra and the
movement of the atoms are fully relaxed within the constraint of a fixed
in-plane lattice constant. We find a rich misfit strain-induced phase
transition sequence and is obtained only when the AFD distortion is taken into
account. We also find that compressive misfit strains induce ferroelectricity
in the tetragonal low temperature phase only whilst tensile strains induce
ferroelectricity in the orthorhombic phases only. The calculated FE
polarization for both the tetragonal and orthorhombic phases increases
monotonically with the magnitude of the strains. The AFD rotation angle of the
oxygen octahedra in the tetragonal phase increases dramatically as the misfit
strain goes from the tensile to compressive strain region whilst it decreases
slightly in the orthorhombic (FO4) phase. This reveals why the polarization in
the epitaxially strained SrTiO would be larger when the tensile strain is
applied, since the AFD distortion is found to reduce the FE instability and
even to completely suppress it in the small strain region. Finally, our
analysis of the average polar distortion and the charge density distribution
suggests that both the Ti-O and Sr-O layers contribute significantly to the FE
polarization
Signals of New Gauge Bosons in Gauged Two Higgs Doublet Model
Recently a gauged two Higgs doublet model, in which the two Higgs doublets
are embedded into the fundamental representation of an extra local
group, is constructed. Both the new gauge bosons and are electrically neutral. While can be singly produced at
colliders, , which is heavier, must be pair produced. We
explore the constraints of using the current Drell-Yan type data
from the Large Hadron Collider. Anticipating optimistically that can
be discovered via the clean Drell-Yan type signals at high luminosity upgrade
of the collider, we explore the detectability of extra heavy fermions in the
model via the two leptons/jets plus missing transverse energy signals from the
exotic decay modes of . For the pair production in
a future 100 TeV proton-proton collider, we demonstrate certain kinematical
distributions for the two/four leptons plus missing energy signals have
distinguishable features from the Standard Model background. In addition,
comparisons of these kinematical distributions between the gauged two Higgs
doublet model and the littlest Higgs model with T-parity, the latter of which
can give rise to the same signals with competitive if not larger cross
sections, are also presented.Comment: 39 pages, 23 figures, 7 tables and two new appendixes, to appear in
EPJ
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