444 research outputs found
Bose-Einstein Correlations from Opaque Sources
Bose-Einstein correlations in relativistic heavy ion collisions are very
different for opaque sources than fortransparent ones. The Bose-Einstein radius
parameters measured in two-particle correlation functions depend sensitively on
the mean free path of the particles. In particular we find that the outward
radius for an opaque source is smaller than the sidewards radius for
sufficiently short duration of emission. A long duration of emission can
compensate the opacity reduction of the longitudinal radius parameter and
explain the experimental measurements of very similar side- and outward radius
parameters.Comment: additional material included, 8 pages, revtex, epsfig, 2 figure
included, manuscript also available at
http://www.nbi.dk/~vischer/publications.htm
Fluctuations and HBT Scales in Relativistic Nuclear Collisions
Bose-Einstein correlations in relativistic heavy ion collisions are examined
in a general model containing the essential features of hydrodynamical, cascade
as well as other models commonly employed for describing the particle
freeze-out. In particular the effects of longitudinal and transverse expansion,
emission from surfaces moving in time, the thickness of the emitting layer
varying from surface to volume emission and other effects are studied. Model
dependences of freeze-out sizes and times are discussed and compared to recent
data at 160AGeV.Comment: 9 pages, revtex, epsfig, 2 figure included, manuscript also available
at http://www.nbi.dk/~vischer/publications.htm
Visualization of SpoVAEa Protein Dynamics in Dormant Spores of <i>Bacillus cereus</i> and Dynamic Changes in Their Germinosomes and SpoVAEa during Germination
Bacillus cereus spores, like most Bacillus spores, can survive for years and germinate when their surroundings become suitable, and germination proteins play an important role in the initiation of germination. Because germinated spores lose the extreme resistance of dormant spores, information on the function of germination proteins could be useful in developing new strategies to control B. cereus spores. Prior work has shown that (i) the channel protein SpoVAEa exhibits high-frequency movement in the outer leaflet of the inner membrane (IM) in dormant B. subtilis spores and (ii) the formation of the foci termed germinosomes between two germination proteins, the germinant receptor GerR and the scaffold protein GerD, in developing B. cereus spores is slower than foci formation by GerR and GerD individually. However, the movement dynamics of SpoVAEa in B. cereus spores, and the behavior of the germinosome upon B. cereus spore germination, are not known. In this study, we found that SpoVAEa fluorescent foci in dormant B. cereus spores move on the IM, but slower than in B. subtilis spores, and they likely co-localize transiently with GerD-mScarlet-I in the germinosome. Our results further indicate that (i) the expression of GerR-SGFP2 and SpoVAEa-SGFP2 with GerD-mScarlet-I from a plasmid leads to more heterogeneity and lower efficiency of spore germination in B. cereus, and (ii) germinosome foci observed by Fluorescence resonance energy transfer (FRET) between GerR-SGFP2 and GerD-mScarlet-I can be lost soon after the spore-phase transition. However, this is not always the case, as some GerR-SGFP2 and GerD-mScarlet-I foci continued to exist, co-localize, and even show a weak FRET signal. These data highlight the heterogeneous behavior of spore germination protein complexes and indicate that some complexes may persist beyond the initiation of germination. IMPORTANCE Bacillus cereus is commonly present in soil and infects humans via contaminated food. In this study, we used B. cereus spores to investigate the movement of the spore-specific inner membrane (IM) channel protein SpoVAEa, the interaction between SpoVAEa and the germinosome scaffold protein GerD, and the dynamics of germinosomes with GerR and GerD in spore germination. Our results expand upon observations of interactions between specific B. cereus spore germination proteins, in particular the GerR germinant receptor A, B, and C subunits and GerD, as well as those between SpoVAEa and GerD. The approaches used in this work could also be used to examine the interactions between GerD and SpoVAEa and other germination proteins in spores of other Bacillus species
Properties of Exotic Matter for Heavy Ion Searches
We examine the properties of both forms of strange matter, small lumps of
strange quark matter (strangelets) and of strange hadronic matter (Metastable
Exotic Multihypernuclear Objects: MEMOs) and their relevance for present and
future heavy ion searches. The strong and weak decays are discussed separately
to distinguish between long-lived and short-lived candidates where the former
ones are detectable in present heavy ion experiments while the latter ones in
future heavy ion experiments, respectively. We find some long-lived strangelet
candidates which are highly negatively charged with a mass to charge ratio like
a anti deuteron (M/Z=-2) but masses of A=10 to 16. We predict also many
short-lived candidates, both in quark and in hadronic form, which can be highly
charged. Purely hyperonic nuclei are bound and have a negative charge while
carrying a positive baryon number. We demonstrate also that multiply charmed
exotics (charmlets) might be bound and can be produced at future heavy ion
colliders.Comment: 10 pages, 4 figures, uses IOP style and epsf.sty, to be published in
Journal of Physics, Proceedings of the International Symposium on Strangeness
in Quark Matter 1997, April 14-18, Thera (Santorini), Hellas. Corrected
typos, added comment about bag constant
Inhomogeneous Nucleation of Quark-Gluon Plasma in High Energy Nuclear Collisions
We estimate the probability that a hard nucleon-nucleon collision is able to
nucleate a seed of quark--gluon plasma in the surrounding hot and dense
hadronic matter formed during a central collision of two large nuclei at AGS
energies. The probability of producing at least one such seed is on the order
of 1-100\%. We investigate the influence of quark--gluon plasma formation on
the observed multiplicity distribution and find that it may lead to noticable
structure in the form of a bump or shoulder.Comment: 16 pages, latex and 12 ps figures available on reques
Nucleation of Quark--Gluon Plasma from Hadronic Matter
The energy densities achieved during central collisions of large nuclei at
Brookhaven's AGS may be high enough to allow the formation of quark--gluon
plasma. Calculations based on relativistic nucleation theory suggest that rare
events, perhaps one in every 10 or 10, undergo the phase transition.
Experimental ramifications may include an enhancement in the ratio of pions to
baryons, a reduction in the ratio of deuterons to protons, and a larger source
size as seen by hadron interferometry.Comment: 22 pages, 7 figures available upon request, NUC--MINN--94/5--
Scattering in the Presence of Electroweak Phase Transition Bubble Walls
We investigate the motion of fermions in the presence of an electro\-weak
phase transition bubble wall. We derive and solve the Dirac equation for such
fer\-mions, and compute the transmission and reflection coefficients for
fermions traveling from the symmetric to the asymmetric phases separated by the
domain wall.Comment: TPI--MINN--54, NUC--MINN--93/30--T, UMN--TH--1226/93, LaTex, 29 page
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