979 research outputs found
Control of polarization and mode mapping of small volume high Q micropillars
We show that the polarization of the emission of a single quantum dot embedded within a microcavity pillar of elliptical cross section can be completely controlled and even switched between two orthogonal linear polarizations by changing the coupling of the dot emission with the polarized photonic modes. We also measure the spatial profle of the emission of a series of pillars with
different ellipticities and show that the results can be well described by simple theoretical modeling
of the modes of an infinite length elliptical cylinder
Relative performance of four midge-resistant wheat varietal blends in western Canada
Non-Peer ReviewedOrange wheat blossom midge, Sitodiplosis mosellana (Géhin), causes significant yield losses to
spring wheat in western Canada in severe infestations. To mitigate losses, midge-resistant wheat
varietal blends, consisting of cultivars carrying the Sm1 midge resistance gene and 10%
interspersed midge susceptible refuge, have been made available to farmers. To test their
performance relative to conventional midge-susceptible cultivars, four varietal blends were
grown during four consecutive years, at eight locations in the provinces of Manitoba
Saskatchewan and Alberta, in comparison to four conventional, midge-susceptible cultivars.
Midge damage was higher in 2007 and 2010 than in 2008 and 2009. In general, the varietal
blends, as a group, yielded more grain than the susceptible cultivars, especially when grown in
environments with high midge pressure (5.5 - 35% seed damage). In environments with low
midge pressure (0 – 2.6% seed damage), the varietal blend average yield advantage was smaller
but still significant, indicating that some of the varietal blends had additional superior attributes,
in addition to midge resistance
The effect of incorporating the midge resistance (Sm1) gene in wheat
Non-Peer ReviewedOrange wheat blossom midge, Sitodiplosis mosellana (Géhin), was first detected in Manitoba in
1901, but now is present in all three prairie provinces of western Canada. In severe infestations,
this insect may cause significant yield losses to spring wheat. To mitigate losses, midge-resistant
wheat varietal blends, consisting of cultivars carrying the Sm1 midge resistance gene and 10%
interspersed midge susceptible refuge, are now available to farmers. The refuge prevents this
resistance to be overcome by the insect. To test the field performance of these varietal blends,
relative to conventional midge-susceptible cultivars, four varietal blends were grown during four
consecutive years, at eight locations in the provinces of Manitoba Saskatchewan and Alberta, in
comparison to four conventional, midge-susceptible cultivars. Midge damage was higher in 2007
and 2010, than in 2008 and 2009. In general, the varietal blends, as a group, yielded more grain
than the susceptible cultivars, especially when grown in environments with high midge pressure
(5.5 - 35% seed damage). In environments with low midge pressure (0 – 2.6% seed damage), the
varietal blend average yield advantage was smaller but still significant, indicating that some of
the varietal blends had additional superior attributes, in addition to midge resistance. Significant
differences in midge damage were observed within the resistant and the susceptible groups of the
cultivars tested. Midge resistance did not protect wheat against loss of market grade
Precise measurements of radio-frequency magnetic susceptibility in (anti)ferromagnetic materials
Dynamic magnetic susceptibility, , was studied in several intermetallic
materials exhibiting ferromagnetic, antiferromagnetic and metamagnetic
transitions. Precise measurements by using a 14 MHz tunnel diode oscillator
(TDO) allow detailed insight into the field and temperature dependence of
. In particular, local moment ferromagnets show a sharp peak in
near the Curie temperature, . The peak amplitude decreases and shifts to
higher temperatures with very small applied dc fields. Anisotropic measurements
of CeVSb show that this peak is present provided the magnetic easy axis is
aligned with the excitation field. In a striking contrast, small moment,
itinerant ferromagnets (i.e., ZrZn) show a broad maximum in that
responds differently to applied field. We believe that TDO measurements provide
a very sensitive way to distinguish between local and itinerant moment magnetic
orders. Local moment antiferromagnets do not show a peak at the N\'eel
temperature, , but only a sharp decrease of below due to the
loss of spin-disorder scattering changing the penetration depth of the ac
excitation field. Furthermore, we show that the TDO is capable of detecting
changes in spin order as well as metamagnetic transitions. Finally, critical
scaling of in the vicinity of is discussed in CeVSb and
CeAgSb
Thermal Unparticles: A New Form of Energy Density in the Universe
Unparticle \U with scaling dimension d_\U has peculiar thermal properties
due to its unique phase space structure. We find that the equation of state
parameter \omega_\U, the ratio of pressure to energy density, is given by
1/(2d_\U +1) providing a new form of energy in our universe. In an expanding
universe, the unparticle energy density \rho_\U(T) evolves dramatically
differently from that for photons. For d_\U >1, even if \rho_\U(T_D) at a
high decoupling temperature is very small, it is possible to have a large
relic density \rho_\U(T^0_\gamma) at present photon temperature ,
large enough to play the role of dark matter. We calculate and
\rho_\U(T^0_\gamma) using photon-unparticle interactions for illustration.Comment: 5 pages; v3, journal version
Using VR to investigate the relationship between visual acuity and severity of simulated oscillopsia
Purpose: Oscillopsia is a debilitating symptom resulting from involuntary eye movement most commonly associated with acquired nystagmus. Investigating and documenting the efects of oscillopsia severity on visual acuity (VA) is challenging. This paper aims to further understanding of the efects of oscillopsia using a virtual reality simulation.
Methods: Fifteen right-beat horizontal nystagmus waveforms, with diferent amplitude (1°, 3°, 5°, 8° and 11°) and frequency (1.25 Hz, 2.5 Hz and 5 Hz) combinations, were produced and imported into virtual reality to simulate diferent severities of oscillopsia. Fifty participants without ocular pathology were recruited to read logMAR charts in virtual reality under stationary conditions (no oscillopsia) and subsequently while experiencing simulated oscillopsia. The change in VA (logMAR) was calculated for each oscillopsia simulation (logMAR VA with oscillopsia – logMAR VA with no oscillopsia), removing the inluence of diferent baseline VAs between participants. A one-tailed paired t-test was used to assess statistical signiicance in the worsening in VA caused by the oscillopsia simulations.
Results: VA worsened with each incremental increase in simulated oscillopsia intensity (frequency x amplitude), either by increasing frequency or amplitude, with the exception of statistically insigniicant changes at lower intensity simulations. Theoretical understanding predicted a linear relationship between increasing oscillopsia intensity and worsening VA. This was supported by observations at lower intensity simulations but not at higher intensities, with incremental changes in VA gradually levelling of. A potential reason for the diference at higher intensities is the inluence of frame rate when using digital simulations in virtual reality.
Conclusions: The frequency and amplitude were found to equally afect VA, as predicted. These results not only consolidate the assumption that VA degrades with oscillopsia but also provide quantitative information that relates these changes to amplitude and frequency of oscillopsia
ATIC and PAMELA Results on Cosmic e^\pm Excesses and Neutrino Masses
Recently the ATIC and PAMELA collaborations released their results which show
the abundant e^\pm excess in cosmic rays well above the background, but not for
the \bar{p}. Their data if interpreted as the dark matter particles'
annihilation imply that the new physics with the dark matter is closely related
to the lepton sector. In this paper we study the possible connection of the new
physics responsible for the cosmic e^\pm excesses to the neutrino mass
generation. We consider a class of models and do the detailed numerical
calculations. We find that these models can natually account for the ATIC and
PAMELA e^\pm and \bar{p} data and at the same time generate the small neutrino
masses.Comment: 7 pages, 5 figures. Published version with minor corrections and more
reference
Primary decomposition and the fractal nature of knot concordance
For each sequence of polynomials, P=(p_1(t),p_2(t),...), we define a
characteristic series of groups, called the derived series localized at P.
Given a knot K in S^3, such a sequence of polynomials arises naturally as the
orders of certain submodules of the sequence of higher-order Alexander modules
of K. These group series yield new filtrations of the knot concordance group
that refine the (n)-solvable filtration of Cochran-Orr-Teichner. We show that
the quotients of successive terms of these refined filtrations have infinite
rank. These results also suggest higher-order analogues of the p(t)-primary
decomposition of the algebraic concordance group. We use these techniques to
give evidence that the set of smooth concordance classes of knots is a fractal
set. We also show that no Cochran-Orr-Teichner knot is concordant to any
Cochran-Harvey-Leidy knot.Comment: 60 pages, added 4 pages to introduction, minor corrections otherwise;
Math. Annalen 201
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