488 research outputs found
Simulations of collision times in gravity driven granular flow
We use simulations to investigate collision time distributions as one
approaches the static limit of steady-state flow of dry granular matter. The
collision times fall in a power-law distribution with an exponent dictated by
whether the grains are ordered or disordered. Remarkably, the exponents have
almost no dependence on dimension. We are also able to resolve a disagreement
between simulation and experiments on the exponent of the collision time
power-law distribution.Comment: 7 pages, 5 figure
Isospin-violating dark-matter-nucleon scattering via two-Higgs-doublet-model portals
We show that in a multi-Higgs model in which one Higgs fits the LHC 125 GeV
state, one or more of the other Higgs bosons can mediate DM-nucleon
interactions with maximal DM isospin violation being possible for appropriate
Higgs-quark couplings, independent of the nature of DM. We then consider the
explicit example of a Type II two-Higgs-doublet model, identifying the h or H
as the 125 GeV state while the H or h, respectively, mediates DM-nucleon
interactions. Finally, we show that if a stable scalar, S, is added then it can
be a viable light DM candidate with correct relic density while obeying all
direct and indirect detection limits.Comment: Two subsections are added to address the collider bounds from direct
search for heavy Higgs bosons and from jet plus missing energy final states.
The LUX (2013) bound considered in the previous version is replaced by the
latest LUX (2016) bound and the SuperCDMS limit is taken into account. The
conclusions remain unchanged. A very minor change made in the title and new
references include
Two-Higgs-Doublet Models and Enhanced Rates for a 125 GeV Higgs
We examine the level of enhancement that can be achieved in the ZZ and
\gamma\gamma channels for a two-Higgs-doublet model Higgs boson (either the
light h or the heavy H) with mass near 125 GeV after imposing all constraints
from LEP data, B physics, precision electroweak data, vacuum stability,
unitarity and perturbativity. The latter constraints restrict substantially the
possibilities for enhancing the gg -> h -> \gamma\gamma or gg -> H ->
\gamma\gamma signal relative to that for the SM Higgs, hSM. Further, we find
that a significant enhancement of the gg -> h -> \gamma\gamma or gg -> H ->
\gamma\gamma signal in Type II models is possible only if the gg -> h -> ZZ or
gg -> H -> ZZ mode is even more enhanced, a situation disfavored by current
data. In contrast, in the Type I model one can achieve enhanced rates in the
\gamma\gamma final state for the h while having the ZZ mode at or below the SM
rate - the largest [gg -> h -> \gamma\gamma]/[gg -> hSM -> \gamma\gamma] ratio
found is of order ~1.3 when the two Higgs doublet vacuum expectation ratio is
tan\beta = 4 or 20 and the charged Higgs boson has its minimal LEP-allowed
value of m_{H^\pm} = 90 GeV.Comment: 15 pages, 9 figure
The Demographic Foundation of Education in the Great Plains
Presented at the School Conslidation in the Great Plains 2013 Symposium in Kearney, Nebraska
The 2005 Benson Residents Survey
The Center for Public Affairs Research and the Urban Studies Program at the University of Nebraska at Omaha organized a telephone survey of Benson-area residents. The survey identified various neighborhood perceptions and activity patterns of alliance residents. The interviews occurred between November 20 and December 4, 2005, with 387 interviews being completed
MN Draconis - peculiar, active dwarf nova in the period gap
Context: We present results of an extensive world-wide observing campaign of
MN Draconis.
Aims: MN Draconis is a poorly known active dwarf nova in the period gap and
is one of the only two known cases of period gap SU UMa objects showing the
negative superhumps. Photometric behaviour of MN Draconis poses a challenge for
existing models of the superhump and superoutburst mechanisms. Therefore,
thorough investigation of peculiar systems, such as MN Draconis, is crucial for
our understanding of evolution of the close binary stars.
Methods: To measure fundamental parameters of the system, we collected
photometric data in October 2009, June-September 2013 and June-December 2015.
Analysis of the light curves, diagrams and power spectra was carried out.
Results: During our three observational seasons we detected four
superoutburts and several normal outbursts. Based on the two consecutive
superoutbursts detected in 2015, the supercycle length was derived P_sc = 74
+/- 0.5 days and it has been increasing with a rate of P_dot = 3.3 x 10^(-3)
during last twelve years. Based on the positive and negative superhumps we
calculated the period excess epsilon = 5.6% +/- 0.1%, the period deficit
epsilon_ = 2.5% +/- 0.6%, and in result, the orbital period P_orb = 0.0994(1)
days (143.126 +/- 0.144 min). We updated the basic light curve parameters of MN
Draconis.
Conclusions: MN Draconis is the first discovered SU UMa system in the period
gap with increasing supercycle length.Comment: 14 pages, 20 figures, 8 tables, accepted for publication in Astronomy
and Astrophysic
Lunar surface engineering properties experiment definition. Volume 3 - Borehole probes Final report, 20 Jun. 1968 - 19 Jul. 1969
Failure mechanisms associated with use of borehole jack in rock
Nebraska’s Community Airports: A Study of Organizational, Financial, and Management Practices: Summary report
Rural and non-metropolitan public-use and general aviation airports play a critical role in the economic development of communities in agricultural states and states with dispersed populations. Not only do they serve as a vital link to markets and resources for both agricultural and non-agricultural businesses operating in the community, small airports provide needed transportation options for area residents. These airports also perform an important function in providing needed health and medical transport services in non-metropolitan locations. Airports can be described as critical “public assets” with needed services to the local community (Penney 2003)
Structural phase transitions and their influence on Cu+ mobility in superionic ferroelastic Cu6PS5I single crystals
The structural origin of Cu+ ions conductivity in Cu6PS5I single crystals is
described in terms of structural phase transitions studied by X-ray
diffraction, polarizing microscope and calorimetric measurements. Below the
phase transition at Tc=(144-169) K Cu6PS5I belongs to monoclinic, ferroelastic
phase, space group Cc. Above Tc crystal changes the symmetry to cubic
superstructure, space group F-43c (a=19.528); finally at 274K disordering of
the Cu+ ions increases the symmetry to F-43m, (a=9.794). The phase transition
at 274K coincides well with a strong anomaly in electrical conductivity
observed in the Arrhenius plot. Diffusion paths for Cu+ ions are evidenced by
means of the atomic displacement factors and split model. Influence of the
copper stechiometry on the Tc is also discussed.Comment: conference pape
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