3,546 research outputs found
Efficient computation of quasiperiodic oscillations in nonlinear systems with fast rotating parts
We present a numerical method for the investigation of quasiperiodic oscillations in applications modeled by systems of ordinary differential equations. We focus on systems with parts that have a significant rotational speed. An important element of our approach is to change coordinates into a co-rotating frame. We show that this leads to a dramatic reduction of computational effort in the case that gravitational forces can be neglected. As a practical example we study a turbocharger model for which we give a thorough comparison of results for a model with and without gravitational forces
Exploring deep microbial life in coal-bearing sediment down to ~2.5 km below the ocean floor
Microbial life inhabits deeply buried marine sediments, but the extent of this vast ecosystem remains poorly constrained. Here we provide evidence for the existence of microbial communities in ~40° to 60°C sediment associated with lignite coal beds at ~1.5 to 2.5 km below the seafloor in the Pacific Ocean off Japan. Microbial methanogenesis was indicated by the isotopic compositions of methane and carbon dioxide, biomarkers, cultivation data, and gas compositions. Concentrations of indigenous microbial cells below 1.5 km ranged from <10 to ~10^4 cells cm^(−3). Peak concentrations occurred in lignite layers, where communities differed markedly from shallower subseafloor communities and instead resembled organotrophic communities in forest soils. This suggests that terrigenous sediments retain indigenous community members tens of millions of years after burial in the seabed
Inhomogeneous Quasi-stationary States in a Mean-field Model with Repulsive Cosine Interactions
The system of N particles moving on a circle and interacting via a global
repulsive cosine interaction is well known to display spatially inhomogeneous
structures of extraordinary stability starting from certain low energy initial
conditions. The object of this paper is to show in a detailed manner how these
structures arise and to explain their stability. By a convenient canonical
transformation we rewrite the Hamiltonian in such a way that fast and slow
variables are singled out and the canonical coordinates of a collective mode
are naturally introduced. If, initially, enough energy is put in this mode, its
decay can be extremely slow. However, both analytical arguments and numerical
simulations suggest that these structures eventually decay to the spatially
uniform equilibrium state, although this can happen on impressively long time
scales. Finally, we heuristically introduce a one-particle time dependent
Hamiltonian that well reproduces most of the observed phenomenology.Comment: to be published in J. Phys.
Comparison of Conditional Average Using Threshold and Template Methods for Quasi-Periodic Phenomena in Plasmas
Schwinger-Dyson Analysis of Dynamical Symmetry Breaking on a Brane with Bulk Yang-Mills Theory
The dynamically generated fermion mass is investigated in the flat brane
world with (4+delta)-dimensional bulk space-time, and in the Randall-Sundrum
(RS) brane world. We consider the bulk Yang-Mills theory interacting with the
fermion confined on a four-dimensional brane. Based on the effective theory
below the reduced cutoff scale on the brane, we formulate the Schwinger-Dyson
equation of the brane fermion propagator. By using the improved ladder
approximation we numerically solve the Schwinger-Dyson equation and find that
the dynamical fermion mass is near the reduced cutoff scale on the brane for
the flat brane world with delta >= 3 and for the RS brane world. In RS brane
world KK excited modes of the bulk gauge field localized around the y = pi R
brane and it enhances the dynamical symmetry breaking on the brane. The decay
constant of the fermion and the anti-fermion composite operator can be taken to
be the order of the electroweak scale much smaller than the Planck scale.
Therefore electroweak mass scale can be realized from only the Planck scale in
the RS brane world due to the fermion and the anti-fermion pair condensation.
That is a dynamical realization of Randall-Sundrum model which solves the
weak-Planck hierarchy problem.Comment: 21 pages, 12 figures; typos corrected, references added and updated,
footnotes adde
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Attitudes toward depression among Japanese non-psychiatric medical doctors: A cross-sectional study
Abstract
Background: Under-recognition of depression is common in many countries. Education of medical staff, focusing on their attitudes towards depression, may be necessary to change their behavior and enhance recognition of depression. Several studies have previously reported on attitudes toward depression among general physicians. However, little is known about attitudes of non-psychiatric doctors in Japan. In the present study, we surveyed nonpsychiatric doctors’ attitude toward depression.
Methods: The inclusion criteria of participants in the present study were as follows: 1) Japanese non-psychiatric doctors and 2) attendees in educational opportunities regarding depression care. We conveniently approached two populations: 1) a workshop to depression care for non-psychiatric doctors and 2) a general physician-psychiatrist (GP)network group. We contacted 367 subjects. Attitudes toward depression were measured using the Depression Attitude Questionnaire (DAQ), a 20-item self-report questionnaire developed for general physicians. We report scores of each DAQ item and factors derived from exploratory factor analysis.
Results: We received responses from 230 subjects, and we used DAQ data from 187 non-psychiatric doctors who met the inclusion criteria. All non-psychiatric doctors (n = 187) disagreed with "I feel comfortable in dealing with depressed patients' needs," while 60 % (n = 112) agreed with "Working with depressed patients is heavy going." Factor analysis indicated these items comprised a factor termed "Depression should be treated by psychiatrists" - to which 54 % of doctors (n = 101) agreed. Meanwhile, 67 % of doctors (n = 126) thought that nurses could be useful in depressed patient support. The three factors derived from the Japanese DAQ differed from models previously derived from British GP samples. The attitude of Japanese non-psychiatric doctors concerning whether depression should be treated by psychiatrists was markedly different to that of British GPs.
Conclusions: Japanese non-psychiatric doctors believe that depression care is beyond the scope of their duties. It is suggested that educational programs or guidelines for depression care developed in other countries such as the UK are not directly adaptable for Japanese non-psychiatric doctors. Developing a focused educational program that motivates non-psychiatric doctors to play a role in depression care is necessary to enhance recognition and treatment of depression in Japan
Algebraic Correlation Function and Anomalous Diffusion in the HMF model
In the quasi-stationary states of the Hamiltonian Mean-Field model, we
numerically compute correlation functions of momenta and diffusion of angles
with homogeneous initial conditions. This is an example, in a N-body
Hamiltonian system, of anomalous transport properties characterized by non
exponential relaxations and long-range temporal correlations. Kinetic theory
predicts a striking transition between weak anomalous diffusion and strong
anomalous diffusion. The numerical results are in excellent agreement with the
quantitative predictions of the anomalous transport exponents. Noteworthy, also
at statistical equilibrium, the system exhibits long-range temporal
correlations: the correlation function is inversely proportional to time with a
logarithmic correction instead of the usually expected exponential decay,
leading to weak anomalous transport properties
Towards Hybrid Classical-Quantum Computation Structures in Wirelessly-Networked Systems
With unprecedented increases in traffic load in today's wireless networks,
design challenges shift from the wireless network itself to the computational
support behind the wireless network. In this vein, there is new interest in
quantum-compute approaches because of their potential to substantially speed up
processing, and so improve network throughput. However, quantum hardware that
actually exists today is much more susceptible to computational errors than
silicon-based hardware, due to the physical phenomena of decoherence and noise.
This paper explores the boundary between the two types of
computation---classical-quantum hybrid processing for optimization problems in
wireless systems---envisioning how wireless can simultaneously leverage the
benefit of both approaches. We explore the feasibility of a hybrid system with
a real hardware prototype using one of the most advanced experimentally
available techniques today, reverse quantum annealing. Preliminary results on a
low-latency, large MIMO system envisioned in the 5G New Radio roadmap are
encouraging, showing approximately 2--10X better performance in terms of
processing time than prior published results.Comment: HotNets 2020: Nineteenth ACM Workshop on Hot Topics in Networks
(https://doi.org/10.1145/3422604.3425924
Singular Riemannian Foliations, variational problems and Principles of Symmetric Criticalities
A singular foliation on a complete Riemannian manifold is
called Singular Riemannian foliation (SRF for short) if its leaves are locally
equidistant, e.g., the partition of into orbits of an isometric action. In
this paper, we investigate variational problems in compact Riemannian manifolds
equipped with SRF with special properties, e.g. isoparametric foliations, SRF
on fibers bundles with Sasaki metric, and orbit-like foliations. More
precisely, we prove two results analogous to Palais' Principle of Symmetric
Criticality, one is a general principle for symmetric operators
on the Hilbert space , the other one is for symmetric
integral operators on the Banach spaces . These results together
with a version of Rellich Kondrachov Hebey Vaugon Embedding
Theorem allow us to circumvent difficulties with Sobolev's critical exponents
when considering applications of Calculus of Variations to find solutions to
PDEs. To exemplify this we prove the existence of weak solutions to a class of
variational problems which includes -Kirschoff problems.Comment: 54 page
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