8,308 research outputs found
Equivalence between Schwinger and Dirac schemes of quantization
This paper introduces the modified version of Schwinger's quantization
method, in which the information on constraints and the choice of gauge
conditions are included implicitly in the choice of variations used in
quantization scheme. A proof of equivalence between Schwinger- and
Dirac-methods for constraint systems is given.Comment: 12pages, No figures, Latex, The proof is improved and one reference
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Evolution of mixing state of black carbon in polluted air from Tokyo
The evolution of the mixing state of black carbon aerosol (BC) was investigated using a single-particle soot photometer (SP2) in polluted air transported from Tokyo. Ground-based measurements of aerosols and trace gases were conducted at a suburban site (Kisai) 50 km north of Tokyo during July-August 2004. The ratio of 2-pentyl nitrate (2-PeONO2) to n-pentane (n-C5H12) was used to derive the photochemical age. According to the SP2 measurement, the number fraction of thickly coated BC (Shell/Corel Ratio > ca. 2) with a core diameter of 180 nm increased at the rate of 1.9% h-1, as the photochemical clock proceeded under land-sea breeze circulation. Positive matrix factorization was applied to investigate the time-dependent contributions of different coating materials using the mass concentrations of sulfate, nitrate, and organics measured using an aerosol mass spectrometer. The main coating materials found in this study were sulfate and organics. Copyright 2007 by the American Geophysical Union
Halo-Galaxy Lensing: A Full Sky Approach
The halo-galaxy lensing correlation function or the average tangential shear
profile over sampled halos is a very powerful means of measuring the halo
masses, the mass profile, and the halo-mass correlation function of very large
separations in the linear regime. We reformulate the halo-galaxy lensing
correlation in harmonic space. We find that, counter-intuitively, errors in the
conventionally used flat-sky approximation remain at a % level even at very
small angles. The errors increase at larger angles and for lensing halos at
lower redshifts: the effect is at a few % level at the baryonic acoustic
oscillation scales for lensing halos of , and comparable with the
effect of primordial non-Gaussianity with at large
separations. Our results allow to readily estimate/correct for the full-sky
effect on a high-precision measurement of the average shear profile available
from upcoming wide-area lensing surveys.Comment: 12 pages, 4 figure
An exponential lower bound for Individualization-Refinement algorithms for Graph Isomorphism
The individualization-refinement paradigm provides a strong toolbox for
testing isomorphism of two graphs and indeed, the currently fastest
implementations of isomorphism solvers all follow this approach. While these
solvers are fast in practice, from a theoretical point of view, no general
lower bounds concerning the worst case complexity of these tools are known. In
fact, it is an open question whether individualization-refinement algorithms
can achieve upper bounds on the running time similar to the more theoretical
techniques based on a group theoretic approach.
In this work we give a negative answer to this question and construct a
family of graphs on which algorithms based on the individualization-refinement
paradigm require exponential time. Contrary to a previous construction of
Miyazaki, that only applies to a specific implementation within the
individualization-refinement framework, our construction is immune to changing
the cell selector, or adding various heuristic invariants to the algorithm.
Furthermore, our graphs also provide exponential lower bounds in the case when
the -dimensional Weisfeiler-Leman algorithm is used to replace the standard
color refinement operator and the arguments even work when the entire
automorphism group of the inputs is initially provided to the algorithm.Comment: 21 page
Ca2+ sparks and puffs are generated and interact in rat hippocampal CA1 pyramidal neuron dendrites
Author Posting. © The Authors, 2013. This article is posted here by permission of Society for Neuroscience for personal use, not for redistribution. The definitive version was published in Journal of Neuroscience 33 (2013): 17777-17788, doi: 10.1523/JNEUROSCI.2735-13.2013.1,4,5-Inositol trisphosphate receptors (IP3Rs) and ryanodine receptors (RyRs) mediate release of Ca2+ from internal stores in many neurons. The details of the spatial and temporal characteristics of these signals and their interactions in dendrites remain to be clarified. We found that localized Ca2+ release events, with no associated change in membrane potential, occurred spontaneously in the dendrites of rat hippocampal CA1 pyramidal neurons. Their rate, but not their amplitude or time course, could be modulated by changes in membrane potential. Together, these results suggest that the spontaneous events are similar to RyR-dependent Ca2+ âsparksâ found in cardiac myocytes. In addition, we found that we could generate another kind of localized Ca2+ release event by either a synaptic tetanus in the presence of 3-((R)-2-carboxypiperazine-4-yl)-propyl-1-phosphonic acid and CNQX or by uncaging IP3. These events had slower rise times and decay times than sparks and were more heterogeneous. These properties are similar to Ca2+ âpuffsâ found in oocytes. These two localized signals interact. Low-intensity tetanic synaptic stimulation or uncaging of IP3 increased the decay time of spontaneous Ca2+ events without changing their rise time or amplitude. Pharmacological experiments suggest that this event widening is attributable to a delayed IP3R-mediated release of Ca2+ triggered by the synergistic action of IP3 and Ca2+ released by RyRs. The actions of IP3 appear to be confined to the main apical dendrite because uncaging IP3 in the oblique dendrites has no effect on the time course of localized events or backpropagating action potential-evoked Ca2+ signals in this region.This work was supported in part by National Institutes of Health Grant NS016295.2014-05-0
Subaru Deep Survey VI. A Census of Lyman Break Galaxies at z=4 and 5 in the Subaru Deep Fields: Clustering Properties
We investigate the clustering properties of 2,600 Lyman Break Galaxies (LBGs)
at z=3.5-5.2 in two large blank fields, the Subaru Deep Field and the
Subaru/XMM Deep Field (600arcmin^2 each). The angular correlation functions of
these LBGs show a clear clustering at both z~4 and 5. The correlation lengths
are r_0= 4.1^{+0.2}_{-0.2} and 5.9^{+1.3}_{-1.7} h_{100}^{-1} Mpc (r_0=
5.1^{+1.0}_{-1.1} and 5.9^{+1.3}_{-1.7} h_{100}^{-1} Mpc) for all the detected
LBGs (for L>L* LBGs) at z~4 and 5, respectively. These correlation lengths
correspond to galaxy-dark matter biases of b_g= 2.9^{+0.1}_{-0.1} and
4.6^{+0.9}_{-1.2} (b_g=3.5^{+0.6}_{-0.7} and 4.6^{+0.9}_{-1.2}), for all the
detected LBGs (for L>L^* LBGs) at z~4 and 5, respectively. These results,
combined with estimates for z~3 LBGs in the literature, show that the
correlation length of L>L^* LBGs is almost constant, ~5 h_{100}^{-1} Mpc, over
z~3-5, while the bias monotonically increases with redshift at z>3. We also
find that for LBGs at z~4 the clustering amplitude increases with UV-continuum
luminosity and with the amount of dust extinction. We estimate the mass of dark
halos hosting various kinds of high-z galaxies including LBGs with the analytic
model given by Sheth & Tormen (1999). We find that the typical mass of dark
halos hosting L>L^* LBGs is about 1x10^{12} h_{70}^{-1}Msol over z~3-5, which
is comparable to that of the Milky Way Galaxy. A single dark halo with ~10^{12}
h_{70}^{-1} Msol is found to host 0.1-0.3 LBG on average but host about four
K-band selected galaxies.Comment: 33 pages, 12 figures, ApJ in press. Paper with high resolution
figures is available at
http://hikari.astron.s.u-tokyo.ac.jp/~ouchi/work/astroph/SDS_V_VI/SDS_VI.pdf
(PDF) (The abstract was reduced by the revision.
Sodium dynamics in pyramidal neuron dendritic spines : synaptically evoked entry predominantly through AMPA receptors and removal by diffusion
© The Author(s), 2017. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Journal of Neuroscience 37 (2017): 9964-9976, doi:10.1523/JNEUROSCI.1758-17.2017.Dendritic spines are key elements underlying synaptic integration and cellular plasticity, but many features of these important structures are not known or are controversial. We examined these properties using newly developed simultaneous sodium and calcium imaging with single-spine resolution in pyramidal neurons in rat hippocampal slices from either sex. Indicators for both ions were loaded through the somatic patch pipette, which also recorded electrical responses. Fluorescence changes were detected with a high-speed, low-noise CCD camera. Following subthreshold electrical stimulation, postsynaptic sodium entry is almost entirely through AMPA receptors with little contribution from entry through NMDA receptors or voltage-gated sodium channels. Sodium removal from the spine head is through rapid diffusion out to the dendrite through the spine neck with a half-removal time of âŒ16 ms, which suggests the neck has low resistance. Peak [Na+]i changes during single EPSPs are âŒ5 mm. Stronger electrical stimulation evoked small plateau potentials that had significant longer-lasting localized [Na+]i increases mediated through NMDA receptors.This work was supported in part by National Institutes of Health Grants R21NS085729 and R01NS099122.2018-03-1
A Subaru Weak Lensing Survey I: Cluster Candidates and Spectroscopic Verification
We present the results of an ongoing weak lensing survey conducted with the
Subaru telescope whose initial goal is to locate and study the distribution of
shear-selected structures or halos. Using a Suprime-cam imaging survey spanning
21.82 square degree, we present a catalog of 100 candidate halos located from
lensing convergence maps. Our sample is reliably drawn from that subset of our
survey area, (totaling 16.72 square degree) uncontaminated by bright stars and
edge effects and limited at a convergence signal to noise ratio of 3.69. To
validate the sample detailed spectroscopic measures have been made for 26
candidates using the Subaru multi-object spectrograph, FOCAS. All are confirmed
as clusters of galaxies but two arise as the superposition of multiple clusters
viewed along the line of sight. Including data available in the literature and
an ongoing Keck spectroscopic campaign, a total of 41 halos now have reliable
redshifts. For one of our survey fields, the XMM LSS (Pierre et al. 2004)
field, we compare our lensing-selected halo catalog with its X-ray equivalent.
Of 15 halos detected in the XMM-LSS field, 10 match with published X-ray
selected clusters and a further 2 are newly-detected and spectroscopically
confirmed in this work. Although three halos have not yet been confirmed, the
high success rate within the XMM-LSS field (12/15) confirms that weak lensing
provides a reliable method for constructing cluster catalogs, irrespective of
the nature of the constituent galaxies or the intracluster medium.Comment: To appear in ApJ, High resolution preprint available at
http://anela.mtk.nao.ac.jp/suprime33/papers/p1.ps.g
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