2,382 research outputs found
Self-compensating solenoid valve
A solenoid valve is described in which both an inlet and an outlet of the valve are sealed when the valve is closed. This double seal compensates for leakage at either the inlet or the outlet by making the other seal more effective in response to the leakage and allows the reversal of the flow direction by simply switching the inlet and outlet connections. The solenoid valve has a valve chamber within the valve body. Inlet and outlet tubes extend through a plate into the chamber. A movable core in the chamber extends into the solenoid coil. The distal end of the core has a silicone rubber plug. Other than when the solenoid is energized, the compressed spring biases the core downward so that the surface of the plug is in sealing engagement with the ends of the tubes. A leak at either end increases the pressure in the chamber, resulting in increased sealing force of the plug
Effects of Ram-Pressure from Intracluster Medium on the Star Formation Rate of Disk Galaxies in Clusters of Galaxies
Using a simple model of molecular cloud evolution, we have quantitatively
estimated the change of star formation rate (SFR) of a disk galaxy falling
radially into the potential well of a cluster of galaxies. The SFR is affected
by the ram-pressure from the intracluster medium (ICM). As the galaxy
approaches the cluster center, the SFR increases to twice the initial value, at
most, in a cluster with high gas density and deep potential well, or with a
central pressure of because the ram-pressure
compresses the molecular gas of the galaxy. However, this increase does not
affect the color of the galaxy significantly. Further into the central region
of the cluster ( Mpc from the center), the SFR of the disk
component drops rapidly due to the effect of ram-pressure stripping. This makes
the color of the galaxy redder and makes the disk dark. These effects may
explain the observed color, morphology distribution and evolution of galaxies
in high-redshift clusters. By contrast, in a cluster with low gas density and
shallow potential well, or the central pressure of ,
the SFR of a radially infalling galaxy changes less significantly, because
neither ram-pressure compression nor stripping is effective. Therefore, the
color of galaxies in poor clusters is as blue as that of field galaxies, if
other environmental effects such as galaxy-galaxy interaction are not
effective. The predictions of the model are compared with observations.Comment: 19 pages, 9 figures, to appear in Ap
Drift instability in the motion of a fluid droplet with a chemically reactive surface driven by Marangoni flow
We theoretically derive the amplitude equations for a self-propelled droplet
driven by Marangoni flow. As advective flow driven by surface tension gradient
is enhanced, the stationary state becomes unstable and the droplet starts to
move. The velocity of the droplet is determined from a cubic nonlinear term in
the amplitude equations. The obtained critical point and the characteristic
velocity are well supported by numerical simulations.Comment: 9 pages, 4 figure
Nonthermal Emission Associated with Strong AGN Outbursts at the Centers of Galaxy Clusters
Recently, strong AGN outbursts at the centers of galaxy clusters have been
found. Using a simple model, we study particle acceleration around a shock
excited by an outburst and estimate nonthermal emission from the accelerated
particles. We show that emission from secondary electrons is consistent with
the radio observations of the minihalo in the Perseus cluster, if there was a
strong AGN outburst >~10^8 yrs ago with an energy of ~1.8x10^62 erg. The
validity of our model depends on the frequency of the large outbursts. We also
estimate gamma-ray emission from the accelerated particles and show that it
could be detected with GLAST.Comment: Accepted for publication in ApJ
Open String on Symmetric Product
We develop some basic properties of the open string on the symmetric product
which is supposed to describe the open string field theory in discrete
lightcone quantization (DLCQ). After preparing the consistency conditions of
the twisted boundary conditions for Annulus/M\"obius/Klein Bottle amplitudes in
generic non-abelian orbifold, we classify the most general solutions of the
constraints when the discrete group is . We calculate the corresponding
orbifold amplitudes from two viewpoints -- from the boundary state formalism
and from the trace over the open string Hilbert space. It is shown that the
topology of the world sheet for the short string and that of the long string in
general do not coincide. For example the annulus sector for the short string
contains all the sectors (torus, annulus, Klein bottle, M\"obius strip) of the
long strings. The boundary/cross-cap states of the short strings are classified
into three categories in terms of the long string, the ordinary boundary and
the cross-cap states, and the ``joint'' state which describes the connection of
two short strings. We show that the sum of the all possible boundary conditions
is equal to the exponential of the sum of the irreducible amplitude -- one body
amplitude of long open (closed) strings. This is typical structure of DLCQ
partition function. We examined that the tadpole cancellation condition in our
language and derived the well-known gauge group .Comment: 56 pages, 11 figures, Late
High Metallicity of the X-Ray Gas up to the Virial Radius of a Binary Cluster of Galaxies: Evidence of Galactic Superwinds at High-Redshift
We present an analysis of a Suzaku observation of the link region between the
galaxy clusters A399 and A401. We obtained the metallicity of the intracluster
medium (ICM) up to the cluster virial radii for the first time. We determine
the metallicity where the virial radii of the two clusters cross each other (~2
Mpc away from their centers) and found that it is comparable to that in their
inner regions (~0.2 Zsun). It is unlikely that the uniformity of metallicity up
to the virial radii is due to mixing caused by a cluster collision. Since the
ram-pressure is too small to strip the interstellar medium of galaxies around
the virial radius of a cluster, the fairly high metallicity that we found there
indicates that the metals in the ICM are not transported from member galaxies
by ram-pressure stripping. Instead, the uniformity suggests that the
proto-cluster region was extensively polluted with metals by extremely powerful
outflows (superwinds) from galaxies before the clusters formed. We also
searched for the oxygen emission from the warm--hot intergalactic medium in
that region and obtained a strict upper limit of the hydrogen density
(nH<4.1x10^-5 cm^-3).Comment: Typo corrected. The published version is available on-line free of
charge by the end of 2008. http://pasj.asj.or.jp/v60/sp1/60s133/60s133.pd
Scherk-Schwarz SUSY breaking from the viewpoint of 5D conformal supergravity
We reinterpret the Scherk-Schwarz (SS) boundary condition for SU(2)_R in a
compactified five-dimensional (5D) Poincare supergravity in terms of the
twisted SU(2)_U gauge fixing in 5D conformal supergravity. In such translation,
only the compensator hypermultiplet is relevant to the SS twist, and various
properties of the SS mechanism can be easily understood. Especially, we show
the correspondence between the SS twist and constant superpotentials within our
framework.Comment: 16 pages, no figur
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