330 research outputs found
10Gbit/s modulation of a fast switching slotted Fabry-Pérot tunable laser
The device used is a three-section, 3mum wide ridge waveguide laser based on commercially available material. During the fabrication a series of slots are introduced into the front and back sections, which act as sites of internal reflections. The slots are etched to a depth that just penetrates the top of the upper waveguide resulting in an internal reflectance of-1% at each slot. The front, middle, and back sections are 180, 690 and 170 microns long respectively. In this work the back and middle sections are tied together electrically allowing simpler control of the device. By varying the applied DC currents, eight discrete channels are observed over a range of approximately 19nm
Experimentation and self learning in continuous database marketing
We present a method for continuous database marketing that identifies target customers for a number of marketing offers using predictive models. The algorithm then selects the appropriate offer for the customer. Experimental design principles are encapsulated to capture more information that will be used to monitor and refine the predictive models. The updated predictive models are then used for the next round of marketing offers.<br /
Bryophytes of Uganda : 6., new and additional records, 3.
12 hepatics and 32 mosses are reported new to Uganda, 1 moss being also new to Africa, and 1 liverwort new to mainland Africa. Ectropothecium plumigerum (Broth.) Hedenäs is a new combination (basionym: Isopterygium plumigerum Broth.) with a new synonym Taxicaulis plumirameus Müll.Hal. nom. nud., and Taxiphyllum maniae (Renauld & Paris) M. Fleisch. is a new synonym of Taxiphyllum taxirameum (Mitt.) M.Fleisch. Three mosses are removed from the Uganda list
Parity and Time Reversal in the Spin-Rotation Interaction
A recently reported discrepancy between experimental and theoretical values
of the muon's g-2 factor is interpreted as due to small violations of the
conservation of P and T in the spin-rotation coupling. The experiments place an
upper limit on these violations and on the weight change of spinning
gyroscopes.Comment: 3 page
3 præsentationer fra Økologisk-Kongres 2017
3 præsentationer fra pEcoSystem projektet til Økologi-Kongress 2017
1)Bedre grisemiljø versus lavere klima- og miljøpåvirkning? Eller både og?
2)10 ugers fravænning
3)Træer i folde fordele og ulempe
Checkerboard local density of states in striped domains pinned by vortices
Within a Green's function formalism we calculate the electronic structure
around static extended magnetic and non-magnetic perturbations in a d-wave
superconductor. In partucular, we discuss recent elastic neutron scattering and
scanning tunneling experiments on High-T_c cuprates exposed to an applied
magnetic field. A physical picture consisting of antiferromagnetic vortex cores
operating as pinning centers for surrounding stripes is qualitatively
consistent with the neutron data provided the stripes have the usual antiphase
modulation. The low energy electronic structure in such a region reveals a
checkerboard interference pattern consistent with recent scanning tunneling
experiments.Comment: 5 pages, 4 figure
A generic estimate of trans-Planckian modifications to the primordial power spectrum in inflation
We derive a general expression for the power spectra of scalar and tensor
fluctuations generated during inflation given an arbitrary choice of boundary
condition for the mode function at a short distance. We assume that the
boundary condition is specified at a short-distance cutoff at a scale which
is independent of time. Using a particular prescription for the boundary
condition at momentum , we find that the modulation to the power spectra
of density and gravitational wave fluctuations is of order , where
is the Hubble parameter during inflation, and we argue that this behavior is
generic, although by no means inevitable. With fixed boundary condition, we
find that the shape of the modulation to the power spectra is determined
entirely by the deviation of the background spacetime from the de Sitter limit.Comment: 15 pages (RevTeX), 2 figure
Two nonmagnetic impurities in the DSC and DDW state of the cuprate superconductors as a probe for the pseudogap
The quantum interference between two nonmagnetic impurities is studied
numerically in both the d-wave superconducting (DSC) and the d-density wave
(DDW) state. In all calculations we include the tunnelling through excited
states from the CuO planes to the BiO layer probed by the STM tip. Compared
to the single impurity case, a systematic study of the modulations in the
two-impurity local density of states can distinguish between the DSC or DDW
states. This is important if the origin of the pseudogap phase is caused by
preformed pairs or DDW order. Furthermore, in the DSC state the study of the
LDOS around two nonmagnetic impurities provide further tests for the potential
scattering model versus more strongly correlated models.Comment: 6 pages, 6 figure
Nucleosynthesis Constraints on a Massive Gravitino in Neutralino Dark Matter Scenarios
The decays of massive gravitinos into neutralino dark matter particles and
Standard Model secondaries during or after Big-Bang nucleosynthesis (BBN) may
alter the primordial light-element abundances. We present here details of a new
suite of codes for evaluating such effects, including a new treatment based on
PYTHIA of the evolution of showers induced by hadronic decays of massive,
unstable particles such as a gravitino. We also develop an analytical treatment
of non-thermal hadron propagation in the early universe, and use this to derive
analytical estimates for light-element production and in turn on decaying
particle lifetimes and abundances. We then consider specifically the case of an
unstable massive gravitino within the constrained minimal supersymmetric
extension of the Standard Model (CMSSM). We present upper limits on its
possible primordial abundance before decay for different possible gravitino
masses, with CMSSM parameters along strips where the lightest neutralino
provides all the astrophysical cold dark matter density. We do not find any
CMSSM solution to the cosmological Li7 problem for small m_{3/2}. Discounting
this, for m_{1/2} ~ 500 GeV and tan beta = 10 the other light-element
abundances impose an upper limit m_{3/2} n_{3/2}/n_\gamma < 3 \times 10^{-12}
GeV to < 2 \times 10^{-13} GeV for m_{3/2} = 250 GeV to 1 TeV, which is similar
in both the coannihilation and focus-point strips and somewhat weaker for tan
beta = 50, particularly for larger m_{1/2}. The constraints also weaken in
general for larger m_{3/2}, and for m_{3/2} > 3 TeV we find a narrow range of
m_{3/2} n_{3/2}/n_\gamma, at values which increase with m_{3/2}, where the Li7
abundance is marginally compatible with the other light-element abundances.Comment: 74 pages, 40 Figure
Cosmological parameters from SDSS and WMAP
We measure cosmological parameters using the three-dimensional power spectrum
P(k) from over 200,000 galaxies in the Sloan Digital Sky Survey (SDSS) in
combination with WMAP and other data. Our results are consistent with a
``vanilla'' flat adiabatic Lambda-CDM model without tilt (n=1), running tilt,
tensor modes or massive neutrinos. Adding SDSS information more than halves the
WMAP-only error bars on some parameters, tightening 1 sigma constraints on the
Hubble parameter from h~0.74+0.18-0.07 to h~0.70+0.04-0.03, on the matter
density from Omega_m~0.25+/-0.10 to Omega_m~0.30+/-0.04 (1 sigma) and on
neutrino masses from <11 eV to <0.6 eV (95%). SDSS helps even more when
dropping prior assumptions about curvature, neutrinos, tensor modes and the
equation of state. Our results are in substantial agreement with the joint
analysis of WMAP and the 2dF Galaxy Redshift Survey, which is an impressive
consistency check with independent redshift survey data and analysis
techniques. In this paper, we place particular emphasis on clarifying the
physical origin of the constraints, i.e., what we do and do not know when using
different data sets and prior assumptions. For instance, dropping the
assumption that space is perfectly flat, the WMAP-only constraint on the
measured age of the Universe tightens from t0~16.3+2.3-1.8 Gyr to
t0~14.1+1.0-0.9 Gyr by adding SDSS and SN Ia data. Including tensors, running
tilt, neutrino mass and equation of state in the list of free parameters, many
constraints are still quite weak, but future cosmological measurements from
SDSS and other sources should allow these to be substantially tightened.Comment: Minor revisions to match accepted PRD version. SDSS data and ppt
figures available at http://www.hep.upenn.edu/~max/sdsspars.htm
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