3,435 research outputs found
A comparative study of peroxisomal structures in Hansenula polymorpha pex mutants
In a recent study, we performed a systematic genome analysis for the conservation of genes involved in peroxisome biogenesis (PEX genes) in various fungi. We have now performed a systematic study of the morphology of peroxisome remnants (‘ghosts’) in Hansenula polymorpha pex mutants (pex1–pex20) and the level of peroxins and matrix proteins in these strains. To this end, all available H. polymorpha pex strains were grown under identical cultivation conditions in glucose-limited chemostat cultures and analyzed in detail. The H. polymorpha pex mutants could be categorized into four distinct groups, namely pex mutants containing: (1) virtually normal peroxisomal structures (pex7, pex17, pex20); (2) small peroxisomal membrane structures with a distinct lumen (pex2, pex4, pex5, pex10, pex12, pex14); (3) multilayered membrane structures lacking apparent matrix protein content (pex1, pex6, pex8, pex13); and (4) no peroxisomal structures (pex3, pex19).
On Witten multiple zeta-functions associated with semisimple Lie algebras IV
In our previous work, we established the theory of multi-variable Witten
zeta-functions, which are called the zeta-functions of root systems. We have
already considered the cases of types , , , and . In
this paper, we consider the case of -type. We define certain analogues of
Bernoulli polynomials of -type and study the generating functions of them
to determine the coefficients of Witten's volume formulas of -type. Next
we consider the meromorphic continuation of the zeta-function of -type and
determine its possible singularities. Finally, by using our previous method, we
give explicit functional relations for them which include Witten's volume
formulas.Comment: 22 pag
Time and length scales in spin glasses
We discuss the slow, nonequilibrium, dynamics of spin glasses in their glassy
phase. We briefly review the present theoretical understanding of the
spectacular phenomena observed in experiments and describe new numerical
results obtained in the first large-scale simulation of the nonequilibrium
dynamics of the three dimensional Heisenberg spin glass.Comment: Paper presented at "Highly Frustrated Magnetism 2003", Grenoble,
August 200
Field-Shift Aging Protocol on the 3D Ising Spin-Glass Model: Dynamical Crossover between the Spin-Glass and Paramagnetic States
Spin-glass (SG) states of the 3-dimensional Ising Edwards-Anderson model
under a static magnetic field are examined by means of the standard Monte
Carlo simulation on the field-shift aging protocol at temperature . For each
process with (T; \tw, h), \tw being the waiting time before the field is
switched on, we extract the dynamical crossover time, \tcr(T; \tw, h). We
have found a nice scaling relation between the two characteristic length scales
which are properly determined from \tcr and \tw and then are normalized by
the static field crossover length introduced in the SG droplet theory. This
scaling behavior implies the instability of the SG phase in the equilibrium
limit even under an infinitesimal . In comparison with this numerical result
the field effect on real spin glasses is also discussed.Comment: 4 pages, 5 figures, jpsj2, Changed conten
Real space application of the mean-field description of spin glass dynamics
The out of equilibrium dynamics of finite dimensional spin glasses is
considered from a point of view going beyond the standard `mean-field theory'
versus `droplet picture' debate of the last decades. The main predictions of
both theories concerning the spin glass dynamics are discussed. It is shown, in
particular, that predictions originating from mean-field ideas concerning the
violations of the fluctuation-dissipation theorem apply quantitatively,
provided one properly takes into account the role of the spin glass coherence
length which plays a central role in the droplet picture. Dynamics in a uniform
magnetic field is also briefly discussed.Comment: 4 pages, 4 eps figures. v2: published versio
Aging dynamics in reentrant ferromagnet: CuCoCl-FeCl graphite bi-intercalation compound
Aging dynamics of a reentrant ferromagnet
CuCoCl-FeCl graphite bi-intercalation compound has
been studied using AC and DC magnetic susceptibility. This compound undergoes
successive transitions at the transition temperatures ( K) and
( K). The relaxation rate exhibits a characteristic
peak at close to a wait time below , indicating that
the aging phenomena occur in both the reentrant spin glass (RSG) phase below
and the ferromagnetic (FM) phase between and . The
relaxation rate () in the FM phase
exhibits two peaks around and a time much shorter than under
the positive -shift aging, indicating a partial rejuvenation of domains. The
aging state in the FM phase is fragile against a weak magnetic-field
perturbation. The time () dependence of around is well approximated by a stretched exponential relaxation:
. The exponent depends on
, , and . The relaxation time () exhibits a
local maximum around 5 K, reflecting a chaotic nature of the FM phase. It
drastically increases with decreasing temperature below .Comment: 16 pages,16 figures, submitted to Physical Review
A generalized Macdonald operator
We present an explicit difference operator diagonalized by the Macdonald
polynomials associated with an (arbitrary) admissible pair of irreducible
reduced crystallographic root systems. By the duality symmetry, this gives rise
to an explicit Pieri formula for the Macdonald polynomials in question. The
simplest examples of our construction recover Macdonald's celebrated difference
operators and associated Pieri formulas pertaining to the minuscule and
quasi-minuscule weights. As further by-products, explicit expansions and
Littlewood-Richardson type formulas are obtained for the Macdonald polynomials
associated with a special class of small weights.Comment: 11 pages. To appear in Int. Math. Res. Not. IMR
Helicon waves and efficient plasma production
Helicon waves generated by radio-frequency (rf) waves are experimentally demonstrated to have the characteristics of Landau damping, as predicted theoretically, and fully ionized plasmas are realized by this efficient coupling of rf powers to plasmas. Excited waves are identified as a helicon wave by measuring wavelengths in the plasma along the magnetic field and comparing with the dispersion relation. Good agreement is found between experimental and theoretical results
Temperature shifts in the Sinai model: static and dynamical effects
We study analytically and numerically the role of temperature shifts in the
simplest model where the energy landscape is explicitely hierarchical, namely
the Sinai model. This model has both attractive features (there are valleys
within valleys in a strict self similar sense), but also one important
drawback: there is no phase transition so that the model is, in the large size
limit, effectively at zero temperature. We compute various static chaos
indicators, that are found to be trivial in the large size limit, but exhibit
interesting features for finite sizes. Correspondingly, for finite times, some
interesting rejuvenation effects, related to the self similar nature of the
potential, are observed. Still, the separation of time scales/length scales
with temperatures in this model is much weaker that in experimental
spin-glasses.Comment: 19 pages, Revtex4, eps figure
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