2,433 research outputs found
Masses, Oxygen and Carbon abundances in CHEPS dwarf stars
Reproduced with permission from Astronomy & Astrophysics. © 2019 ESOContext. We report the results from the determination of stellar masses, carbon, and oxygen abundances in the atmospheres of 107 stars from the Calan-Hertfordshire Extrasolar Planet Search (CHEPS) programme. Our stars are drawn from a population with a significantly super-solar metallicity. At least 10 of these stars are known to host orbiting planets. Aims. In this work, we set out to understand the behaviour of carbon and oxygen abundance in stars with different spectral classes, metallicities, and V sin i within the metal-rich stellar population. Methods. Masses of these stars were determined using data from Gaia DR2. Oxygen and carbon abundances were determined by fitting the absorption lines. We determined oxygen abundances with fits to the 6300.304 Å O I line, and we used 3 lines of the C I atom and 12 lines of the C 2 molecule for the determination of carbon abundances. Results. We determine masses and abundances of 107 CHEPS stars. There is no evidence that the [C/O] ratio depends on V sin i or the mass of the star within our constrained range of masses, i.e. 0.82 5 km s -1) are massive stars.Peer reviewedFinal Published versio
Automatisierte Generierung von 3-D Finite Elemente Codes des menschlichen Femurs - Automatic Preprocessing of 3-D Finite Element Codes of the Human Femur
Reference Standards for Body Fat Measure Using GE Dual Energy X-Ray Absorptiometry in Caucasian Adults
Background Dual energy x-ray absorptiometry (DXA) is an established technique for the measurement of body composition. Reference values for these variables, particularly those related to fat mass, are necessary for interpretation and accurate classification of those at risk for obesityrelated health complications and in need of lifestyle modifications (diet, physical activity, etc.). Currently, there are no reference values available for GE-Healthcare DXA systems and it is known that whole-body and regional fat mass measures differ by DXA manufacturer.
Objective To develop reference values by age and sex for DXA-derived fat mass measurements with GE-Healthcare systems.
Methods A de-identified sample of 3,327 participants (2,076 women, 1,251 men) was obtained from Ball State University\u27s Clinical Exercise Physiology Laboratory and University of Wisconsin- Milwaukee\u27s Physical Activity & Health Research Laboratory. All scans were completed using a GE Lunar Prodigy or iDXA and data reported included percent body fat (%BF), fat mass index (FMI), and ratios of android-to-gynoid (A/G), trunk/limb, and trunk/leg fat measurements. Percentiles were calculated and a factorial ANOVA was used to determine differences in the mean values for each variable between age and sex.
Results Normative reference values for fat mass variables from DXA measurements obtained from GE-Healthcare DXA systems are presented as percentiles for both women and men in 10- year age groups. Women had higher (p\u3c0.01) mean %BF and FMI than men, whereas men had higher (p\u3c0.01) mean ratios of A/G, trunk/limb, and trunk/leg fat measurements than women
Extended Kalman Filter for Photographic Data from Impact Acceleration Tests
This paper presents the development of an Extended Kalman Filter (EKF) that optimally processes photographic data collected during short-duration impact acceleration tests. The system is modeled by a non-linear state-space representation using quaternions for rotational kinematics. Three cameras are used to photograph up to 14 fiducials mounted on a plate attached to the subject\u27s mouth. The filter yields the history of the rotational and translational kinematics of the origin of the mouth plate. Results from the EKF and analysis of the estimation error are presented
The determinants of vulnerability to currency crises: country-specific factors versus regional factors
We investigate the determinants of exchange market pressures (EMP) for some new EU member states at both the national and regional levels, where macroeconomic and financial variables are considered as potential sources. The regional common factors are extracted from these variables by using dynamic factor analysis. The linear empirical analysis, in general, highlights the importance of country-specific factors to defend themselves against vulnerability in their external sectors. Yet, given a significant impact of the common component in credit on EMP, a contagion effect is apparent through the conduit of credit market integration across these countries under investigation
Abelian and non-Abelian geometric phases in adiabatic open quantum systems
We introduce a self-consistent framework for the analysis of both Abelian and
non-Abelian geometric phases associated with open quantum systems, undergoing
cyclic adiabatic evolution. We derive a general expression for geometric
phases, based on an adiabatic approximation developed within an inherently
open-systems approach. This expression provides a natural generalization of the
analogous one for closed quantum systems, and we prove that it satisfies all
the properties one might expect of a good definition of a geometric phase,
including gauge invariance. A striking consequence is the emergence of a finite
time interval for the observation of geometric phases. The formalism is
illustrated via the canonical example of a spin-1/2 particle in a
time-dependent magnetic field. Remarkably, the geometric phase in this case is
immune to dephasing and spontaneous emission in the renormalized Hamiltonian
eigenstate basis. This result positively impacts holonomic quantum computing.Comment: v3: 10 pages, 2 figures. Substantially expanded version. Includes a
proof of gauge invariance of the non-Abelian geometric phase, and an appendix
on the left and right eigenvectors of the superoperator in the Jordan for
Spin-1/2 particles moving on a 2D lattice with nearest-neighbor interactions can realize an autonomous quantum computer
What is the simplest Hamiltonian which can implement quantum computation
without requiring any control operations during the computation process? In a
previous paper we have constructed a 10-local finite-range interaction among
qubits on a 2D lattice having this property. Here we show that
pair-interactions among qutrits on a 2D lattice are sufficient, too, and can
also implement an ergodic computer where the result can be read out from the
time average state after some post-selection with high success probability.
Two of the 3 qutrit states are given by the two levels of a spin-1/2 particle
located at a specific lattice site, the third state is its absence. Usual
hopping terms together with an attractive force among adjacent particles induce
a coupled quantum walk where the particle spins are subjected to spatially
inhomogeneous interactions implementing holonomic quantum computing. The
holonomic method ensures that the implemented circuit does not depend on the
time needed for the walk.
Even though the implementation of the required type of spin-spin interactions
is currently unclear, the model shows that quite simple Hamiltonians are
powerful enough to allow for universal quantum computing in a closed physical
system.Comment: More detailed explanations including description of a programmable
version. 44 pages, 12 figures, latex. To appear in PR
A scalable readout system for a superconducting adiabatic quantum optimization system
We have designed, fabricated and tested an XY-addressable readout system that
is specifically tailored for the reading of superconducting flux qubits in an
integrated circuit that could enable adiabatic quantum optimization. In such a
system, the flux qubits only need to be read at the end of an adiabatic
evolution when quantum mechanical tunneling has been suppressed, thus
simplifying many aspects of the readout process. The readout architecture for
an -qubit adiabatic quantum optimization system comprises hysteretic dc
SQUIDs and rf SQUID latches controlled by bias lines. The
latching elements are coupled to the qubits and the dc SQUIDs are then coupled
to the latching elements. This readout scheme provides two key advantages:
First, the latching elements provide exceptional flux sensitivity that
significantly exceeds what may be achieved by directly coupling the flux qubits
to the dc SQUIDs using a practical mutual inductance. Second, the states of the
latching elements are robust against the influence of ac currents generated by
the switching of the hysteretic dc SQUIDs, thus allowing one to interrogate the
latching elements repeatedly so as to mitigate the effects of stochastic
switching of the dc SQUIDs. We demonstrate that it is possible to achieve
single qubit read error rates of with this readout scheme. We have
characterized the system-level performance of a 128-qubit readout system and
have measured a readout error probability of in the presence
of optimal latching element bias conditions.Comment: Updated for clarity, final versio
Effective Lorentz Force due to Small-angle Impurity Scattering: Magnetotransport in High-Tc Superconductors
We show that a scattering rate which varies with angle around the Fermi
surface has the same effect as a periodic Lorentz force on magnetotransport
coefficients. This effect, together with the marginal Fermi liquid inelastic
scattering rate gives a quantitative explanation of the temperature dependence
and the magnitude of the observed Hall effect and magnetoresistance with just
the measured zero-field resistivity as input.Comment: 4 pages, latex, one epsf figure included in text. Several revisions
and corrections are included. Major conclusions are the sam
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