8,190 research outputs found
Ground reaction force estimates from ActiGraph GT3X+ hip accelerations.
Simple methods to quantify ground reaction forces (GRFs) outside a laboratory setting are needed to understand daily loading sustained by the body. Here, we present methods to estimate peak vertical GRF (pGRFvert) and peak braking GRF (pGRFbrake) in adults using raw hip activity monitor (AM) acceleration data. The purpose of this study was to develop a statistically based model to estimate pGRFvert and pGRFbrake during walking and running from ActiGraph GT3X+ AM acceleration data. 19 males and 20 females (age 21.2 ± 1.3 years, height 1.73 ± 0.12 m, mass 67.6 ± 11.5 kg) wore an ActiGraph GT3X+ AM over their right hip. Six walking and six running trials (0.95-2.19 and 2.20-4.10 m/s, respectively) were completed. Average of the peak vertical and anterior/posterior AM acceleration (ACCvert and ACCbrake, respectively) and pGRFvert and pGRFbrake during the stance phase of gait were determined. Thirty randomly selected subjects served as the training dataset to develop generalized equations to predict pGRFvert and pGRFbrake. Using a holdout approach, the remaining 9 subjects were used to test the accuracy of the models. Generalized equations to predict pGRFvert and pGRFbrake included ACCvert and ACCbrake, respectively, mass, type of locomotion (walk or run), and type of locomotion acceleration interaction. The average absolute percent differences between actual and predicted pGRFvert and pGRFbrake were 8.3% and 17.8%, respectively, when the models were applied to the test dataset. Repeated measures generalized regression equations were developed to predict pGRFvert and pGRFbrake from ActiGraph GT3X+ AM acceleration for young adults walking and running. These equations provide a means to estimate GRFs without a force plate
Comparisons of Mesospheric Temperatures Between 70 and 110 km: USU Lidar, NASA\u27s TIMED Satellite, and the MSIS2 Empirical Model
Earth’s atmosphere can be characterized by its temperature structure, dividing the atmosphere into natural discrete regions. The mesosphere (50 to ~100 km) has been the least studied. Rayleigh-scatter lidars (RSL) and rockets can obtain local, high-resolution measurements above one spot, while satellites looking almost horizontally obtain global measurements. These two methods of measuring atmospheric conditions are compared using the USU RSL and the SABER instrument on NASA’s TIMED satellite. These measurements were graphed to show four sets of temperatures from several sources in the atmospheric region 70 km to 110 km above USU. The results show similar temperatures for many of the measured nights and some different temperatures, especially in the winter months
THE TAXONOMIC STATUS OF THE WYOMING TOAD, BUFO BAXTERI PORTER
The population of toads in southeastern Wyoming named Bufo hemiophrys baxteri by Porter in 1968 is presumed to be extinct in nature, except perhaps for released, captive-bred specimens. It is sufficiently distinct in several respects, and sufficiently isolated geographically from its nearest rela- tive, B. h. hemiophrys, that it should be regarded as a distinct species, forming a superspecies group with B. hemiophrys
Statistical comparison of ensemble implementations of Grover's search algorithm to classical sequential searches
We compare pseudopure state ensemble implementations, quantified by their
initial polarization and ensemble size, of Grover's search algorithm to
probabilistic classical sequential search algorithms in terms of their success
and failure probabilities. We propose a criterion for quantifying the resources
used by the ensemble implementation via the aggregate number of oracle
invocations across the entire ensemble and use this as a basis for comparison
with classical search algorithms. We determine bounds for a critical
polarization such that the ensemble algorithm succeeds with a greater
probability than the probabilistic classical sequential search. Our results
indicate that the critical polarization scales as N^(-1/4) where N is the
database size and that for typical room temperature solution state NMR, the
polarization is such that the ensemble implementation of Grover's algorithm
would be advantageous for N > 10^2
Mixed state Pauli channel parameter estimation
The accuracy of any physical scheme used to estimate the parameter describing
the strength of a single qubit Pauli channel can be quantified using standard
techniques from quantum estimation theory. It is known that the optimal
estimation scheme, with m channel invocations, uses initial states for the
systems which are pure and unentangled and provides an uncertainty of
O[1/m^(1/2)]. This protocol is analogous to a classical repetition and
averaging scheme. We consider estimation schemes where the initial states
available are not pure and compare a protocol involving quantum correlated
states to independent state protocols analogous to classical repetition
schemes. We show, that unlike the pure state case, the quantum correlated state
protocol can yield greater estimation accuracy than any independent state
protocol. We show that these gains persist even when the system states are
separable and, in some cases, when quantum discord is absent after channel
invocation. We describe the relevance of these protocols to nuclear magnetic
resonance measurements
Discrimination of unitary transformations in the Deutsch-Jozsa algorithm
We describe a general framework for regarding oracle-assisted quantum
algorithms as tools for discriminating between unitary transformations. We
apply this to the Deutsch-Jozsa problem and derive all possible quantum
algorithms which solve the problem with certainty using oracle unitaries in a
particular form. We also use this to show that any quantum algorithm that
solves the Deutsch-Jozsa problem starting with a quantum system in a particular
class of initial, thermal equilibrium-based states of the type encountered in
solution state NMR can only succeed with greater probability than a classical
algorithm when the problem size exceeds Comment: 7 pages, 1 figur
Probing the qudit depolarizing channel
For the quantum depolarizing channel with any finite dimension, we compare
three schemes for channel identification: unentangled probes, probes maximally
entangled with an external ancilla, and maximally entangled probe pairs. This
comparison includes cases where the ancilla is itself depolarizing and where
the probe is circulated back through the channel before measurement. Compared
on the basis of (quantum Fisher) information gained per channel use, we find
broadly that entanglement with an ancilla dominates the other two schemes, but
only if entanglement is cheap relative to the cost per channel use and only if
the external ancilla is well shielded from depolarization. We arrive at these
results by a relatively simple analytical means. A separate, more complicated
analysis for partially entangled probes shows for the qudit depolarizing
channel that any amount of probe entanglement is advantageous and that the
greatest advantage comes with maximal entanglement
Molecular electrostatic potentials by systematic molecular fragmentation
A simple method is presented for estimating the molecular electrostatic potential in and around molecules using systematic molecular fragmentation. This approach estimates the potential directly from the electron density. The accuracy of the method is established for a set of organic molecules and ions. The utility of the approach is demonstrated by estimating the binding energy of a water molecule in an internal cavity in the protein ubiquitin
Superconducting resonators as beam splitters for linear-optics quantum computation
A functioning quantum computer will be a machine that builds up, in a
programmable way, nonclassical correlations in a multipartite quantum system.
Linear optics quantum computation (LOQC) is an approach for achieving this
function that requires only simple, reliable linear optical elements, namely
beam splitters and phase shifters. Nonlinear optics is only required in the
form of single-photon sources for state initialization, and detectors. However,
the latter remain difficult to achieve with high fidelity. A new setting for
quantum optics has arisen in circuit quantum electrodynamics (cQED) using
superconducting (SC) quantum devices, and opening up the way to LOQC using
microwave, rather than visible photons. Much progress is being made in SC
qubits and cQED: high-fidelity Fock state generation and qubit measurements
provide single photon sources and detection. Here we show that the LOQC toolkit
in cQED can be completed with high-fidelity (>99.92%) linear optical elements.Comment: 4 pages, 3 figure
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