609 research outputs found
Possible Young Stellar Objects without Detectable CO Emission
We found that at least 18 Young Stellar Object candidates invisible at
optical and near-infrared wavelengths, as well as ^12CO emission. They are IRAS
point sources with FIR colors similar to those of usual YSOs, and the infrared
spectral indices between 2.2 um and 25 um correspond to those of class I YSOs.
These peculiar far-infrared objects are highly concentrated around the galactic
plane and the distances are estimated to be around 1 kpc. Although their
distribution is away from molecular clouds, some of them seem to be associated
with large dark clouds or weak radio sources.Comment: 10 pages with 4 figures, LaTeX, accepted for publication in PASJ.
Images(fig2) are included in source file as JPEG files. PDF files are
avilable at ftp.kusastro.kyoto-u.ac.jp/pub/iwata/preprint
Non-ergodic transitions in many-body Langevin systems: a method of dynamical system reduction
We study a non-ergodic transition in a many-body Langevin system. We first
derive an equation for the two-point time correlation function of density
fluctuations, ignoring the contributions of the third- and fourth-order
cumulants. For this equation, with the average density fixed, we find that
there is a critical temperature at which the qualitative nature of the
trajectories around the trivial solution changes. Using a method of dynamical
system reduction around the critical temperature, we simplify the equation for
the time correlation function into a two-dimensional ordinary differential
equation. Analyzing this differential equation, we demonstrate that a
non-ergodic transition occurs at some temperature slightly higher than the
critical temperature.Comment: 8 pages, 1 figure; ver.3: Calculation errors have been fixe
Alongādip variation in seismic radiation of the 2011 Ibarakiāoki, Japan, earthquake ( M w 7.9) inferred using a multipleāperiodāband source inversion approach
To elucidate the spatial variation in periodādependent seismic radiation for the 2011 Ibarakiāoki earthquake (Mw 7.9) in Japan, we applied a multipleāperiodāband source inversion approach to nearāsource strongāmotion waveforms of this earthquake. We estimated source models of this earthquake in three successive period bands (5ā10, 10ā25, and 25ā50 s) using strongāmotion data and Green's functions based on a 3āD velocity structure model. The source models in the period bands of 10ā25 and 25ā50 s had large slips in the area to the south and southeast of the hypocenter in the depth range of 23ā35 km, while the large slip area for the source model in the period band of 5ā10 s was located in the deeper region ~30 km west of the hypocenter in the depth range of 35ā45 km. These results indicate that longāperiod (10ā25 and 25ā50 s) and shortāperiod (5ā10 s) seismic waves were predominantly radiated from these different regions along the dip direction during the 2011 Ibarakiāoki earthquake. This alongādip variation in the dominant period of seismic radiation can be explained by the variation in scale in unstable sliding patches according to depth
Scale-free patterns at a saddle-node bifurcation in a stochastic system
We demonstrate that scale-free patterns are observed in a spatially extended
stochastic system whose deterministic part undergoes a saddle-node bifurcation.
Remarkably, the scale-free patterns appear only at a particular time in
relaxation processes from a spatially homogeneous initial condition. We
characterize the scale-free nature in terms of the spatial configuration of the
exiting time from a marginal saddle where the pair annihilation of a saddle and
a node occurs at the bifurcation point. Critical exponents associated with the
scale-free patterns are determined by numerical experiments.Comment: 4 pages, 6 figure
Theoretical analysis for critical fluctuations of relaxation trajectory near a saddle-node bifurcation
A Langevin equation whose deterministic part undergoes a saddle-node
bifurcation is investigated theoretically. It is found that statistical
properties of relaxation trajectories in this system exhibit divergent
behaviors near a saddle-node bifurcation point in the weak-noise limit, while
the final value of the deterministic solution changes discontinuously at the
point. A systematic formulation for analyzing a path probability measure is
constructed on the basis of a singular perturbation method. In this
formulation, the critical nature turns out to originate from the neutrality of
exiting time from a saddle-point. The theoretical calculation explains results
of numerical simulations.Comment: 18pages, 17figures.The version 2, in which minor errors have been
fixed, will be published in Phys. Rev.
Fibroblast growth factor receptor 3 activation plays a causative role in urothelial cancer pathogenesis in cooperation with Pten loss in mice
Although somatic mutations and overexpression of the tyrosine kinase fibroblast growth factor receptor 3 (FGFR3) are strongly associated with bladder cancer, evidence for their functional involvement in the pathogenesis remains elusive. Previously we showed that activation of Fgfr3 alone is not sufficient to initiate urothelial tumourigenesis in mice. Here we hypothesize that cooperating mutations are required for Fgfr3-dependent tumourigenesis in the urothelium and analyse a mouse model in which an inhibitor of Pi3kāAkt signalling, Pten, is deleted in concert with Fgfr3 activation (UroIICreFgfr3+/K644EPtenflox/flox). Two main phenotypical characteristics were observed in the urothelium: increased urothelial thickness and abnormal cellular histopathology, including vacuolization, condensed cellular appearance, enlargement of cells and nuclei, and loss of polarity. These changes were not observed when either mutation was present individually. Expression patterns of known urothelial proteins indicated the abnormal cellular differentiation. Furthermore, quantitative analysis showed that Fgfr3 and Pten mutations cooperatively caused cellular enlargement, while Pten contributed to increased cell proliferation. Finally, FGFR3 overexpression was analysed along the level of phosphorylated mTOR in 66 T1 urothelial tumours in tissue microarray, which supported the occurrence of functional association of these two signalling pathways in urothelial pathogenesis. Taken together, this study provides evidence supporting a functional role of FGFR3 in the process of pathogenesis in urothelial neoplasms. Given the wide availability of inhibitors specific to FGF signalling pathways, our model may open the avenue for FGFR3-targeted translation in urothelial disease. Copyright Ā© 2014 Pathological Society of Great Britain and Ireland
Dynamics of k-core percolation in a random graph
We study the edge deletion process of random graphs near a k-core percolation
point. We find that the time-dependent number of edges in the process exhibits
critically divergent fluctuations. We first show theoretically that the k-core
percolation point is exactly given as the saddle-node bifurcation point in a
dynamical system. We then determine all the exponents for the divergence based
on a universal description of fluctuations near the saddle-node bifurcation.Comment: 16 pages, 4 figure
Modelling of incident sound wave propagation around sound barriers using cellular automata
In the present study, acoustic wave propagation in the field including sound isolation panel is simulated using Cellular Automata (CA). CA is a discrete system which consists of finite state variables, arranged on a uniform grid. CA dynamics is described by a local interaction rule which is used for computation of new state of each cell from the present state at every time step. In this study a sound field is modeled using CA where the sound isolation panel exists and the numerical simulation results are evaluated quantitatively by the insertion loss. The results showed good correspondence with analytical solutions. Ā© 2012 Springer-Verlag Berlin Heidelberg
Singular perturbation near mode-coupling transition
We study the simplest mode-coupling equation which describes the time
correlation function of the spherical p-spin glass model. We formulate a
systematic perturbation theory near the mode-coupling transition point by
introducing multiple time scales. In this formulation, the invariance with
respect to the dilatation of time in a late stage yields an arbitrary constant
in a leading order expression of the solution. The value of this constant is
determined by a solvability condition associated with a linear singular
equation for perturbative corrections in the late stage. The solution thus
constructed provides exactly the alpha-relaxation time.Comment: 15 pages, 4 figure
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