368 research outputs found
Comparative Study on Pantothenic Acid Separation by Reactive Extraction with Tri-n-octylamine and Di-(2-ethylhexyl) Phosphoric Acid
The mechanism of reactive extraction of pantothenic acid with tri-n-octylamine and di-(2-ethylhexyl) phosphoric acid was analysed for three solvents in the presence or absence of 1-octanol. In the absence of 1-octanol, the stoichiometric ratio between the solute and tri-n-octylamine was 1:1 for dichloromethane, 1:2 for butyl acetate, and 1:4 for n-heptane. In the presence of 1-octanol, the formation of aminic adducts was restricted, the stoichiometries for the interfacial reaction between the acid and tri-n-octylamine becoming 1:1 for dichloromethane and butyl acetate, 1:2 for n-heptane. A similar effect has been observed for extraction with di-(2-ethylhexyl) phosphoric acid, the structure of the interfacial compound being changed for n-heptane and butyl acetate from HAE2 in the absence of 1-octanol to HAE by addition of this alcohol. The highest extraction constants were obtained when extractant associates were formed. However, when the extraction mechanism was the same, the increase in organic phase polarity influenced positively the value of extraction constant
Supermanifolds, symplectic geometry and curvature
We present a survey of some results and questions related to the notion of
scalar curvature in the setting of symplectic supermanifolds.Comment: Dedicated to Jaime Mu\~noz-Masqu\'e on occasion of his 65th birthda
Inelastic scattering of broadband electron wave packets driven by an intense mid-infrared laser field
Intense, 100 fs laser pulses at 3.2 and 3.6 um are used to generate, by
multi-photon ionization, broadband wave packets with up to 400 eV of kinetic
energy and charge states up to Xe+6. The multiple ionization pathways are well
described by a white electron wave packet and field-free inelastic cross
sections, averaged over the intensity-dependent energy distribution for (e,ne)
electron impact ionization. The analysis also suggests a contribution from a 4d
core excitation in xenon
Particle Collisions on Stringy Black Hole Background
The collision of two particles in the background of a Sen black hole is
studied. With the equations of motion of the particles, the center-of-mass
energy is investigated when the collision takes place at the horizon of a Sen
black hole. For an extremal Sen black hole, we find that the center-of-mass
energy will be arbitrarily high with two conditions: (1) spin and (2)
one of the colliding particles has the critical angular momentum
. For a nonextremal Sen black hole, we show that, in order to
obtain an unlimited center-of-mass energy, one of the colliding particles
should have the critical angular momentum ( is
the radius of the outer horizon for a nonextremal black hole). However, a
particle with the angular momentum could not approach the
black hole from outside of the horizon through free fall, which implies that
the collision with arbitrarily high center-of-mass energy could not take place.
Thus, there is an upper bound of the center-of-mass energy for the nonextremal
black hole. We also obtain the maximal center-of-mass energy for a
near-extremal black hole and the result implies that the Planck-scale energy is
hard to be approached. Furthermore, we also consider the back-reaction effects.
The result shows that, neglecting the gravitational radiation, it has a weak
effect on the center-of-mass energy. However, we argue that the maximum allowed
center-of-mass energy will be greatly reduced to below the Planck-scale when
the gravitational radiation is included.Comment: 17 pages, 4 figures, published versio
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