9,881 research outputs found
Can the nuclear symmetry potential at supra-saturation densities be negative?
In the framework of an Isospin-dependent Boltzmann-Uehling-Uhlenbeck (IBUU)
transport model, for the central Au+Au reaction at an incident
beam energy of 400 MeV/nucleon, effect of nuclear symmetry potential at
supra-saturation densities on the pre-equilibrium clusters emission is studied.
It is found that for the positive symmetry potential at supra-saturation
densities the neutron to proton ratio of lighter clusters with mass number
() is larger than that of the weighter clusters with
mass number (), whereas for the negative symmetry potential
at supra-saturation densities the is \emph{smaller} than that
of the . This may be considered as a probe of the negative
symmetry potential at supra-saturation densities.Comment: 5 pages, 3 figures, 1 table, to be publishe
Understanding thio-effects in simple phosphoryl systems : role of solvent effects and nucleophile charge.
Recent experimental work (J. Org. Chem., 2012, 77, 5829) demonstrated pronounced differences in measured thio-effects for the hydrolysis of (thio)phosphodichloridates by water and hydroxide nucleophiles. In the present work, we have performed detailed quantum chemical calculations of these reactions, with the aim of rationalizing the molecular bases for this discrimination. The calculations highlight the interplay between nucleophile charge and transition state solvation in SN2(P) mechanisms as the basis of these differences, rather than a change in mechanism
World history and world outlook
La historia mundial es una forma particularmente adecuada para hacer frente al etnocentrismo. Los textos sobre historia general existentes hasta la fecha mencionan a China en uno o dos capĂtulos, mientras que dedican el resto de su tiempo a Europa. ÂżEs esto debido a que solo Europa ha cambiado, a que solo han tenido lugar acontecimientos en Europa? Cualquiera que haya estudiado la historia de China le dirá que esto no es cierto. La historia de la cultura china es para la humanidad mundial moderna prácticamente tan importante, desde un punto de vista internacional, como lo es la historia de Europa. Sin embargo, cuando leemos “historia mundial”, leemos principalmente sobre Europa.World history has a value in breaking down our ethnocentrism. The up-to-date general histories mention China in one or two chapters, whereas they spend all the rest of their time on Europe. Is this because only Europe has changed, only Europe has had things happen? Anyone who has studied the history of China will tell you this is not true. The history of Chinese culture is as important, from an international point of view, to modern world humanity as is the history of Europe. Yet when we read “world history” we read chiefly of Europe
Large QCD at non-zero chemical potential
The general issue of large QCD at nonzero chemical potential is
considered with a focus on understanding the difference between large QCD
with an isospin chemical potential and large QCD with a baryon chemical
potential. A simple diagrammatic analysis analogous to `t Hooft's analysis at
implies that the free energy with a given baryon chemical potential is
equal to the free energy with an isospin chemical potential of the same value
plus corrections. Phenomenologically, these two systems behave quite
differently. A scenario to explain this difference in light of the diagrammatic
analysis is explored. This scenario is based on a phase transition associated
with pion condensation when the isospin chemical potential exceeds ;
associated with this transition there is breakdown of the expansion--in
the pion condensed phase there is a distinct expansion including a
larger set of diagrams. While this scenario is natural, there are a number of
theoretical issues which at least superficially challenge it. Most of these can
be accommodated. However, the behavior of quenched QCD which raises a number of
apparently analogous issues cannot be easily understood completely in terms of
an analogous scenario. Thus, the overall issue remains open
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