1,886 research outputs found
Cyclostationary measurement of low-frequency odd moments of current fluctuations
Measurement of odd moments of current fluctuations is difficult due to strict
requirements for band-pass filtering. We propose how these requirements can be
overcome using cyclostationary driving of the measured signal and indicate how
the measurement accuracy can be tested through the phase dependence of the
moments of the fluctuations. We consider two schemes, the mixing scheme and the
statistics scheme, where the current statistics can be accessed. We also
address the limitations of the schemes, due to excess noise and due to the
effects of the environment, and, finally, discuss the required measurement
times for typical setups.Comment: 13 pages, 3 figure
Behavior of a Braced Sheet Pile Wall in Soft Clay
The earth pressure distribution against, and the displacement of, a braced sheet pile wall in soft clay have been examined. In connection with the construction of a fly-over, on the west cost of Sweden, two sections of a braced sheet pile wall were instrumented. The instrumentation consisted of earth pressure cells and inclinometer pipes mounted on three sheet piles. The sheet pile wall was also analyzed by means of the FLAC code in which the interaction between the sheet pile wall, the struts and the soil was studied. The movements and the calculations are compared with a conventional design method according to Peck. The results indicate that the earth pressure distribution and the deflection of the wall is strongly dependent on the construction procedure. The FLAC code was found to be a useful tool for parameter studies, but can hardly be used for design
Cyclostationary shot noise in mesoscopic measurements
We discuss theoretically a setup where a time-dependent current consisting of
a DC bias and two sinusoidal harmonics is driven through a sample. If the
sample exhibits current-dependent shot noise, the down-converted noise power
spectrum varies depending on the local-oscillator phase of the mixer. The
theory of this phase-dependent noise is applied to discuss the measurement of
the radio-frequency single-electron transistor. We also show that this effect
can be used to measure the shot noise accurately even in nonlinear
high-impedance samples.Comment: 3 pages, 2 figure
Hyperfine, rotational and Zeeman structure of the lowest vibrational levels of the Rb \tripletex state
We present the results of an experimental and theoretical study of the
electronically excited \tripletex state of Rb molecules. The
vibrational energies are measured for deeply bound states from the bottom up to
using laser spectroscopy of ultracold Rb Feshbach molecules. The
spectrum of each vibrational state is dominated by a 47\,GHz splitting into a
\cog and \clg component caused mainly by a strong second order spin-orbit
interaction. Our spectroscopy fully resolves the rotational, hyperfine, and
Zeeman structure of the spectrum. We are able to describe to first order this
structure using a simplified effective Hamiltonian.Comment: 10 pages, 7 figures, 2 table
The Role of NMDA Currents in State Transitions of the Nucleus Accumbens Medium Spiny Neuron
The nucleus accumbens (NAcb) integrates information from a wide range of glutamatergic afferent inputs, including the prefrontal cortex, hippocampus and amygdala. One of the glutamatergic receptors, the NMDA channel, has been implicated in the non-linearity of the current–voltage relationship in these cells under certain input conditions. In order to examine the relationship of the different glutamatergic receptors to the membrane response, we modeled the AMPA, GABAA and NMDA receptors in the medium spiny (MSP) cells and their afferent input. The model demonstrates that the NMDA current is capable of sustaining certain membrane states and contributes to the non-linearity of the membrane response to input
QCD-supression by Black Hole Production at the LHC
Possible consequences of the production of small black holes at the LHC for
different scenarios with large extra dimensions are investigated. The effects
from black hole production on some standard jet observables are examined,
concentrating on the reduction of the QCD cross section. It is found that black
hole production of partons interacting on a short enough distance indeed seem
to generate a drastic drop in the QCD cross section. However from an
experimental point of view this will in most cases be camouflaged by energetic
radiation from the black holes
Perspectives of wild medicine harvesters from Cape Town, South Africa
Cape Town is a fast-growing cityscape in the Cape Floristic Region in South Africa with 24 formally
protected conservation areas including the World Heritage Table Mountain National Park. These sites
have been protected and managed as critical sites for local biodiversity, representing potentially one-third
of all Cape Floristic Region flora species and 18% of South Africa’s plant diversity. Cape Town is also
inhabited by a rapidly growing culturally and economically diverse citizenry with distinct and potentially
conflicting perspectives on access to, and management of, local natural resources. In a qualitative study
of 58 locally resident traditional healers of distinct cultural groups, we examined motivations underlying
the generally illicit activity of harvesting of wild resources from Cape Town protected areas. Resource
harvester motivations primarily link to local economic survival, health care and cultural links to particular
resources and practices, ‘access for all’ outlooks, and wholesale profit-seeking perspectives. We
describe these motivations, contrast them with the current formal, legal and institutional perspectives for
biodiversity protection in the city, and propose managerial interventions that may improve sustainability
of ongoing harvest activities
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