948 research outputs found
Density of States Scaling at the Semimetal to Metal Transition in Three Dimensional Topological Insulators
The quantum phase transition between the three dimensional Dirac semimetal
and the diffusive metal can be induced by increasing disorder. Taking the
system of disordered topological insulator as an important
example, we compute the single particle density of states by the kernel
polynomial method. We focus on three regions: the Dirac semimetal at the phase
boundary between two topologically distinct phases, the tricritical point of
the two topological insulator phases and the diffusive metal, and the diffusive
metal lying at strong disorder. The density of states obeys a novel single
parameter scaling, collapsing onto two branches of a universal scaling
function, which correspond to the Dirac semimetal and the diffusive metal. The
diverging length scale critical exponent and the dynamical critical
exponent are estimated, and found to differ significantly from those for
the conventional Anderson transition. Critical behavior of experimentally
observable quantities near and at the tricritical point is also discussed.Comment: 5 pages, 5 figures, to appear in PR
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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
The Anderson transition: time reversal symmetry and universality
We report a finite size scaling study of the Anderson transition. Different
scaling functions and different values for the critical exponent have been
found, consistent with the existence of the orthogonal and unitary universality
classes which occur in the field theory description of the transition. The
critical conductance distribution at the Anderson transition has also been
investigated and different distributions for the orthogonal and unitary classes
obtained.Comment: To appear in Physical Review Letters. Latex 4 pages with 4 figure
Magnetotransport in inhomogeneous magnetic fields
Quantum transport in inhomogeneous magnetic fields is investigated
numerically in two-dimensional systems using the equation of motion method. In
particular, the diffusion of electrons in random magnetic fields in the
presence of additional weak uniform magnetic fields is examined. It is found
that the conductivity is strongly suppressed by the additional uniform magnetic
field and saturates when the uniform magnetic field becomes on the order of the
fluctuation of the random magnetic field. The value of the conductivity at this
saturation is found to be insensitive to the magnitude of the fluctuation of
the random field. The effect of random potential on the magnetoconductance is
also discussed.Comment: 5 pages, 5 figure
Anderson transition in three-dimensional disordered systems with symplectic symmetry
The Anderson transition in a 3D system with symplectic symmetry is
investigated numerically. From a one-parameter scaling analysis the critical
exponent of the localization length is extracted and estimated to be . The level statistics at the critical point are also analyzed
and shown to be scale independent. The form of the energy level spacing
distribution at the critical point is found to be different from that
for the orthogonal ensemble suggesting that the breaking of spin rotation
symmetry is relevant at the critical point.Comment: 4 pages, revtex, to appear in Physical Review Letters. 3 figures
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Mesoscopic Stern-Gerlach spin filter by nonuniform spin-orbit interaction
A novel spin filtering in two-dimensional electron system with nonuniform
spin-orbit interactions (SOI) is theoretically studied. The strength of SOI is
modulated perpendicular to the charge current. A spatial gradient of effective
magnetic field due to the nonuniform SOI causes the Stern-Gerlach type spin
separation. The direction of the polarization is perpendicular to the current
and parallel to the spatial gradient. Almost 100 % spin polarization can be
realized even without applying any external magnetic fields and without
attaching ferromagnetic contacts. The spin polarization persists even in the
presence of randomness.Comment: 6 pages, 5 figures (2 color figures), to appear in Phys. Rev. B,
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Macromolecular organization of hemocyanins and apohemocyanins as revealed by electron microscopy
Comparative high resolution electron microscopic studies of structural organization of hemocyanins and apohemocyanins from mollusca and arthropod
Evolutionary Prisoner's Dilemma on heterogeneous Newman-Watts small-world network
We focus on the heterogeneity of social networks and its role to the
emergence of prevailing cooperation and sustaining cooperators. The social
networks are representative of the interaction relationships between players
and their encounters in each round of games. We study an evolutionary
Prisoner's Dilemma game on a variant of Watts-Strogatz small-world network,
whose heterogeneity can be tuned by a parameter. It is found that optimal
cooperation level exists at some intermediate topological heterogeneity for
different temptations to defect. Moreover, neither the most heterogeneous case
nor the most homogeneous one would favor the cooperators. At intermediate
heterogeneity in degree sequences, cooperators could resist the invasion of
defectors for large temptation to defect.Comment: Updated versio
One-parameter Superscaling at the Metal-Insulator Transition in Three Dimensions
Based on the spectral statistics obtained in numerical simulations on three
dimensional disordered systems within the tight--binding approximation, a new
superuniversal scaling relation is presented that allows us to collapse data
for the orthogonal, unitary and symplectic symmetry () onto a
single scaling curve. This relation provides a strong evidence for
one-parameter scaling existing in these systems which exhibit a second order
phase transition. As a result a possible one-parameter family of spacing
distribution functions, , is given for each symmetry class ,
where is the dimensionless conductance.Comment: 4 pages in PS including 3 figure
Cooper problem in the vicinity of Anderson transition
We study numerically the ground state properties of the Cooper problem in the
three-dimensional Anderson model. It is shown that attractive interaction
creates localized pairs in the metallic noninteracting phase. This localization
is destroyed at sufficiently weak disorder. The phase diagram for the
delocalization transition in the presence of disorder and interaction is
determined.Comment: revtex, 4 pages, 4 figure
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