5,811 research outputs found
The effect of phase inversion promoters on the structure and performance of polyetherimide hollow fiber membrane using in gas-liquid contacting process
Low molecular weight organic compounds were added to the spinning dope as phase inversion promoters and their effects on the structure of polyetherimide (PEI) hollow fibers as well as their performance as membrane contactor were investigated. Water, methanol, ethanol, glycerol and acetic acid were added individually to the solvent NMP to prepare a dope containing 15 wt% PEI, 4 wt% additive, 81 wt% NMP and hollow fiber membranes were fabricated via wet spinning method.The solution containing water as the additive had the lowest thermodynamic stability and highest viscosity, which yielded hollow fiber with a thin skin layer of high porosity and a sublayer with sponge-like structure. The four other polymer solutions were more stable thermodynamically and less viscous. Fast solvent/coagulant exchange yielded thick skin layers of lower porosity and sublayers of finger-like macrovoids.Among all fabricated follow fibers, adding methanol resulted in the highest absorption flux, which was ascribed to its high porosity and low tortuosity
Aharonov-Bohm Effect at liquid-nitrogen temperature: Frohlich superconducting quantum device
The Aharonov-Bohm (AB) effect has been accepted and has promoted
interdisciplinary scientific activities in modern physics. To observe the AB
effect in condensed matter physics, the whole system needs to maintain phase
coherence, in a tiny ring of the diameter 1 micrometer and at low temperatures
below 1 K. We report that AB oscillations have been measured at high
temperature 79 K by use of charge-density wave (CDW) loops in TaS3 ring
crystals. CDW condensate maintained macroscopic quantum coherence, which
extended over the ring circumference 85 micrometer. The periodicity of the
oscillations is h/2e in accuracy within a 10 percent range. The observation of
the CDW AB effect implies Frohlich superconductivity in terms of macroscopic
coherence and will provide a novel quantum interference device running at room
temperature.Comment: 11 pages, 4 figure
Leptonic Signals from off-shell Z Boson Pairs at Hadron Colliders
We study the gluon fusion into pairs of off-shell Z bosons and their
subsequent decay into charged lepton pairs at hadron colliders. We do not
restrict the intermediate state Z bosons to the narrow width approximation but
allow for arbitrary invariant masses. We compare the strength of this process
with the known leading order results for q q_bar -> Z Z -> 4 l and for g g -> H
-> Z Z -> 4 l .Comment: 18 p., DESY 94-06
A Microscopic Mechanism for Muscle's Motion
The SIRM (Stochastic Inclined Rods Model) proposed by H. Matsuura and M.
Nakano can explain the muscle's motion perfectly, but the intermolecular
potential between myosin head and G-actin is too simple and only repulsive
potential is considered. In this paper we study the SIRM with different complex
potential and discuss the effect of the spring on the system. The calculation
results show that the spring, the effective radius of the G-actin and the
intermolecular potential play key roles in the motion. The sliding speed is
about calculated from the model which well agrees with
the experimental data.Comment: 9 pages, 6 figure
Identifications and SEDs of the detected sources from the AKARI Deep Field South
In order to find counterparts of the detected objects in the AKARI Deep Field
South (ADFS) in all available wavelengths, we searched public databases (NED,
SIMBAD and others). Checking 500 sources brighter than 0.0482 Jy in the AKARI
Wide-S band, we found 114 sources with possible counterparts, among which 78
were known galaxies. We present these sources as well as our first attempt to
construct spectral energy distributions (SEDs) for the most secure and most
interesting sources among them, taking into account all the known data together
with the AKARI measurements in four bands.Comment: 4 pages, 10 figures, To appear in: the proceedings of the conference
"AKARI, a light to illuminate the misty Universe", February 16-19 2009, Toky
Electric Control of Spin Helicity in a Magnetic Ferroelectric
Magnetic ferroelectrics or multiferroics, which are currently extensively
explored, may provide a good arena to realize a novel magnetoelectric function.
Here we demonstrate the genuine electric control of the spiral magnetic
structure in one of such magnetic ferroelectrics, TbMnO3. A spin-polarized
neutron scattering experiment clearly shows that the spin helicity, clockwise
or counter-clockwise, is controlled by the direction of spontaneous
polarization and hence by the polarity of the small cooling electric field.Comment: 4 pages, 3 figure
Thermal Phase Transitions and Gapless Quark Spectra in Quark Matter at High Density
Thermal color superconducting phase transitions in three-flavor quark matter
at high baryon density are investigated in the Ginzburg-Landau (GL) approach.
We constructed the GL potential near the boundary with a normal phase by taking
into account nonzero quark masses, electric charge neutrality, and color charge
neutrality. We found that the density of states averaged over paired quarks
plays a crucial role in determining the phases near the boundary. By performing
a weak coupling calculation of the parameters characterizing the GL potential
terms of second order in the pairing gap, we show that three successive
second-order phase transitions take place as the temperature increases: a
modified color-flavor locked phase (ud, ds, and us pairings) -> a ``dSC'' phase
(ud and ds pairings) -> an isoscalar pairing phase (ud pairing) -> a normal
phase (no pairing). The Meissner masses of the gluons and the number of gapless
quark modes are also studied analytically in each of these phases.Comment: 15 pages, 6 figure
Melting Pattern of Diquark Condensates in Quark Matter
Thermal color superconducting phase transitions in high density three-flavor
quark matter are investigated in the Ginzburg-Landau approach. Effects of
nonzero strange quark mass, electric and color charge neutrality, and direct
instantons are considered. Weak coupling calculations show that an interplay
between the mass and electric neutrality effects near the critical temperature
gives rise to three successive second-order phase transitions as the
temperature increases: a modified color-flavor locked (mCFL) phase (ud, ds, and
us pairings) -> a ``dSC'' phase (ud and ds pairings) -> an isoscalar pairing
phase (ud pairing) -> a normal phase (no pairing). The dSC phase is novel in
the sense that while all eight gluons are massive as in the mCFL phase, three
out of nine quark quasiparticles are gapless.Comment: minor changes in the text, fig.2 modifie
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