23,211 research outputs found
Minimally Allowed Neutrinoless Double Beta Decay Rates From Approximate Flavor Symmetries
Neutrinoless double beta decay () is among the only realistic
probes of Majorana neutrinos. In the standard scenario, dominated by light
neutrino exchange, the process amplitude is proportional to , the
element of the Majorana mass matrix. Naively, current data allows for vanishing
, but this should be protected by an appropriate flavor symmetry. All
such symmetries lead to mass matrices inconsistent with oscillation
phenomenology. I perform a spurion analysis to break all possible Abelian
symmetries that guarantee vanishing rates and search for
minimally allowed values. I survey 230 broken structures to yield
values and current phenomenological constraints under a variety of scenarios.
This analysis also extracts predictions for both neutrino oscillation
parameters and kinematic quantities. Assuming reasonable tuning levels, I find
that eV at 99% confidence. Bounds below this value
might indicate the Dirac neutrino nature or the existence of new light (eV-MeV
scale) degrees of freedom that can potentially be probed elsewhere.Comment: 19 Pages, 4 .eps Figures, 3 Table
Thermally conducting electron transfer polymers
New polymeric material exhibits excellent physical shock protection, high electrical resistance, and thermal conductivity. It is especially useful for electronic circuitry, such as subminiaturization of components and modular construction of circuits
Improved thermally conducting electron transfer polymers
Development of polymers with improved heat transfer coefficients for use in encapsulating electronic modules is discussed. Chemical reactions for synthesizing the polymers are described and thermodynamic and physical properties are analyzed
Minimally Allowed Neutrinoless Double Beta Decay Rates Within an Anarchical Framework
Neutrinoless double beta decay is the only realistic probe of the Majorana
nature of the neutrino. In the standard picture, its rate is proportional to
, the e-e element of the Majorana neutrino mass matrix in the flavor
basis. I explore minimally allowed values within the framework of mass
matrix anarchy where neutrino parameters are defined statistically at low
energies. Distributions of mixing angles are well defined by the Haar
integration measure, but masses are dependent on arbitrary weighting functions
and boundary conditions. I survey the integration measure parameter space and
find that for sufficiently convergent weightings, is constrained
between (0.01-0.4) eV at 90% confidence. Constraints from neutrino mixing data
lower these bounds. Singular integration measures allow for arbitrarily small
values with the remaining elements ill-defined, but this condition
constrains the flavor structure of the model's ultraviolet completion. Bounds
below eV should indicate symmetry in the lepton
sector, new light degrees of freedom or the Dirac nature of the neutrino.Comment: BibTeX, 7 pages, 1 .eps Figure, Modified to match content of
published paper: References added, table added, clarified discussion. Results
are unchange
Laser ablated high T(sub c) superconducting thin YBa2Cu3O(7-x) films on substrates suitable for microwave applications
The development of high temperature superconducting YBa2Cu3O(7-x) thin films on substrates suitable for microwave applications is of great interest for evaluating their applications for space radar, communication, and sensor systems. Thin films of YBa2Cu3O(7-x) were formed on SrTiO3, ZrO2, MgO, and LaAlO3 substrates by laser ablation. The wavelength used was 248 nm from a KrF excimer laser. During deposition the films were heated to 600 C in a flowing oxygen environment, and required no post annealing. The low substrate temperature during deposition with no post annealing gave films which were smooth, which had their c-axis aligned to the substrates, and which had grains ranging from 0.2 to 0.5 microns in size. The films being c-axis aligned gave excellent surface resistance at 35 GHz which was lower than that of copper at 77 K. At present, LaAlO3 substrates with a dielectric constant of 22, appears suitable as a substrate for microwave and electronic applications. The films were characterized by resistance-temperature measurements, scanning electron microscopy, and x ray diffraction. The highest critical transition temperatures (T sub c) are above 89 K for films on SrTiO3 and LaAlO3, above 88 K for ZrO2, and above 86 K for MgO. The critical current density (J sub c) of the films on SrTiO3 is above 2 x 10(exp 6) amperes/sq cm at 77 K. The T(sub c) and J(sub c) are reported as a function of laser power, composition of the substrate, and temperature of the substrate during deposition
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Augmented paper applications: Initial user tests of a wireless pattern reader
A handheld pattern reader has been developed to read low visibility conductive patterns on paper. The patterns are formed by masking conductive paper with a non-conductive, printed lacquer. The reader was developed as part of an EU-funded project investigating methods of augmenting paper. Data read from the patterns was used to trigger events in the digital domain. Usability tests were undertaken to investigate the performance of the prototype. Results showed that at this stage of development there was significant variation in performance of the prototype from user to user. Further work is being undertaken to determine the causes of this variability
The 2p yields 1s pionic transition
Pion-atomic transitions, perturbation theory, S waves, and P wave
Simulating Impacts of Extreme Weather Events on Urban Transport Infrastructure in the UK
Urban areas face many risks from future climate change and their infrastructure will be placed under more pressure
due to changes in climate extremes. Using the Tyndall Centre Urban Integrated Assessment Framework, this paper
describes a methodology used to assess the impacts of future climate extremes on transport infrastructure in
London. Utilising high-resolution projections for future climate in the UK, alongside stochastic weather generators
for downscaling, urban temperature and flooding models are used to provide information on the likelihood of future
extremes. These are then coupled with spatial network models of urban transport infrastructure and, using thresholds
to define the point at which systems cease to function normally, disruption to the networks can be simulated.
Results are shown for both extreme heat and urban surface water flooding events and the impacts on the travelling
population, in terms of both disruption time and monetary cost
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