3,916 research outputs found
Impurity-doping induced ferroelectricity in frustrated antiferromagnet CuFeO2
Dielectric responses have been investigated on the triangular-lattice
antiferromagnet CuFeO2 and its site-diluted analogs CuFe1-xAlxO2 (x=0.01 and
0.02) with and without application of magnetic field. We have found a
ferroelectric behavior at zero magnetic field for x=0.02. At any doping level,
the onset field of the ferroelectricity always coincides with that of the
noncollinear magnetic structure while the transition field dramatically
decreases to zero field with Al doping. The results imply the further
possibility of producing the ferroelectricity by modifying the frustrated spin
structure in terms of site-doping and external magnetic field.Comment: 4 pages, 4 figure
Local virial relation and velocity anisotropy for collisionless self-gravitating systems
The collisionless quasi-equilibrium state realized after the cold collapse of
self-gravitating systems has two remarkable characters. One of them is the
linear temperature-mass (TM) relation, which yields a characteristic
non-Gaussian velocity distribution. Another is the local virial (LV) relation,
the virial relation which holds even locally in collisionless systems through
phase mixing such as cold-collapse. A family of polytropes are examined from a
view point of these two characters. The LV relation imposes a strong constraint
on these models: only polytropes with index with a flat boundary
condition at the center are compatible with the numerical results, except for
the outer region. Using the analytic solutions based on the static and
spherical Jeans equation, we show that this incompatibility in the outer region
implies the important effect of anisotropy of velocity dispersion. Furthermore,
the velocity anisotropy is essential in explaining various numerical results
under the condition of the local virial relation.Comment: 8 pages, 5 figures, Proceedings of CN-Kyoto International Workshop on
Complexity and Nonextensivity; added a reference for section
Comment on ``Quantum Statistical Mechanics of an Ideal Gas with Fractional Exclusion Statistics in Arbitrary Dimension"
It is mentioned that anyon thermodynamic potential could not
be factorized in terms characteristic of the ideal boson and
fermion gases by the relation in which , that claimed in Phys. Rev. Lett. 78,
3233 (1997). Our analyses indicate that the thermodynamic quantities of anyon
gas may be factorized as only in
the two-dimension system
"Risk homeostasis"or "teachable moment"? the interaction between smoking behavior and lung cancer screening in the Mayo Lung Project
The chest X-ray lung cancer screening program of Mayo Lung Project (MLP) yielded mixed results of improved lung case survival but no improvement in lung cancer mortality. This paper analyzes the smoking patterns of study participants in order to examine possible behavioral ramifications of periodic lung cancer screening. Using a longitudinal difference-of-difference model, we compared the smoking behavior, in terms of current smoker status among all subjects and the intensity of smoking among those continuing smokers, between those who received periodic lung cancer screening and those who received usual-care. In both arms of this lung cancer screening trial, there was a sizable decline in cigarette smoking one year after participants received baseline prevalence screening. There was no significant difference in current smoker status between the intervention group receiving periodic X-ray screening and the control group receiving usual care. While we detect that the continuing smokers in the intervention group smoked more than their counterparts in the control group, the magnitude of the difference is not sufficient to explain a substantial difference in lung cancer incidence between the two groups. Our study shows that periodic lung screening in MLP did not decrease smoking behavior beyond the observed decline following the initial prevalence screening conducted at baseline for both the intervention and control groups. Our results also indicate, paradoxically, that participants assigned to the intervention group smoked more cigarettes per day on average than those in the control group. Lung cancer screening programs need additional cessation components to sustain the abstinence effect typically observed following initial lung screening
Orbital Motion in the Radio Galaxy 3C 66B: Evidence for a Supermassive Black Hole Binary
Supermassive black hole binaries may exist in the centers of active galactic
nuclei like quasars and radio galaxies and mergers between galaxies may result
in the formation of supermassive binaries during the course of galactic
evolution. Using the very-long-baseline interferometer, we imaged the radio
galaxy 3C 66B at radio frequencies and found that the unresolved radio core of
3C 66B shows well-defined elliptical motions with a period of 1.05 +/- 0.03
years, which provides a direct detection of a supermassive black hole binary.Comment: 8 pages, 3 figures, to appear in the Scienc
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