325 research outputs found
Kinetic arrest of the first order ferromagnetic to antiferromagnetic transition in Ce(FeRu) : formation of a magnetic-glass
We present results of dc magnetization and magnetic relaxation study showing
the kinetic arrest of a first order ferromagnetic to antiferromagnetic
transition in Ce(FeRu). This leads to the formation of a
non-ergodic glass-like magnetic state. The onset of the magnetic-glass
transformation is tracked through the slowing down of the magnetization
dynamics. This glassy state is formed with the assistance of an external
magnetic field and this is distinctly different from the well known
'spin-glass' state.Comment: 10 pages of text and 4 figure
Studies on Magnetic-field induced first-order transitions
We shall discuss magnetization and transport measurements in materials
exhibiting a broad first-order transition. The phase transitions would be
caused by varying magnetic field as well as by varying temperature, and we
concentrate on ferromagnetic to antiferromagnetic transitions in magnetic
materials. We distinguish between metastable supercooled phases and metastable
glassy phase.Comment: 50th Golden Jubilee Solid State Physics Symposium during Dec.5-9
(2005) in Mumbai - manuscript of Invited tal
Strong pressure-energy correlations in van der Waals liquids
Strong correlations between equilibrium fluctuations of the configurational
parts of pressure and energy are found in the Lennard-Jones liquid and other
simple liquids, but not in hydrogen-bonding liquids like methanol and water.
The correlations, that are present also in the crystal and glass phases,
reflect an effective inverse power-law repulsive potential dominating
fluctuations, even at zero and slightly negative pressure. In experimental data
for supercritical Argon, the correlations are found to be approximately 96%.
Consequences for viscous liquid dynamics are discussed.Comment: Phys. Rev. Lett., in pres
Excess specific heat and evidence of zero point entropy in magnetic glassy state of half-doped manganites
We show that specific heat C has non-Debye behavior for glassy states in
half-doped manganites. Irrespective of the magnetic order or electronic states,
these magnetic glasses have higher C compared to their equilibrium
counterparts. The excess C contributed by the glassy state varies linearly
with temperature similar to conventional glasses indicating tunneling in the
two-level systems. These glassy states show signature of zero point entropy.
Magnetic glasses can be produced simply by different field cooling protocols
and may be considered ideal magnetic counterpart of the conventional glass
p-Adic description of characteristic relaxation in complex systems
This work is a further development of an approach to the description of
relaxation processes in complex systems on the basis of the p-adic analysis. We
show that three types of relaxation fitted into the Kohlrausch-Williams-Watts
law, the power decay law, or the logarithmic decay law, are similar random
processes. Inherently, these processes are ultrametric and are described by the
p-adic master equation. The physical meaning of this equation is explained in
terms of a random walk constrained by a hierarchical energy landscape. We also
discuss relations between the relaxation kinetics and the energy landscapes.Comment: AMS-LaTeX (+iopart style), 9 pages, submitted to J.Phys.
Programmable models of growth and mutation of cancer-cell populations
In this paper we propose a systematic approach to construct mathematical
models describing populations of cancer-cells at different stages of disease
development. The methodology we propose is based on stochastic Concurrent
Constraint Programming, a flexible stochastic modelling language. The
methodology is tested on (and partially motivated by) the study of prostate
cancer. In particular, we prove how our method is suitable to systematically
reconstruct different mathematical models of prostate cancer growth - together
with interactions with different kinds of hormone therapy - at different levels
of refinement.Comment: In Proceedings CompMod 2011, arXiv:1109.104
Minimal model for beta relaxation in viscous liquids
Contrasts between beta relaxation in equilibrium viscous liquids and glasses
are rationalized in terms of a double-well potential model with
structure-dependent asymmetry, assuming structure is described by a single
order parameter. The model is tested for tripropylene glycol where it accounts
for the hysteresis of the dielectric beta loss peak frequency and magnitude
during cooling and reheating through the glass transition.Comment: Phys. Rev. Lett. (in press
Model for the alpha and beta shear-mechanical properties of supercooled liquids and its comparison to squalane data
This paper presents data for supercooled squalane's frequency-dependent shear
modulus covering frequencies from 10 mHz to 30 kHz and temperatures from 168 K
to 190 K; measurements are also reported for the glass phase down to 146 K. The
data reveal a strong mechanical beta process. A model is proposed for the shear
response of supercooled liquids. The model is an electrical equivalent-circuit
characterized by additivity of the dynamic shear compliances of the alpha and
beta processes. The nontrivial parts of the alpha and beta processes are
represented by a "Cole-Cole retardation element", resulting in the Cole-Cole
compliance function well-known from dielectrics. The model, which assumes that
the high-frequency decay of the alpha shear compliance loss varies with angular
frequency as , has seven parameters. Assuming time-temperature
superposition for the alpha and the beta processes separately, the number of
parameters varying with temperature is reduced to four. From the temperature
dependence of the best-fit model parameters the following conclusions are
drawn: 1) the alpha relaxation time conforms to the shoving model; 2) the beta
relaxation loss-peak frequency is almost temperature independent; 3) the alpha
compliance magnitude, which in the model equals the inverse of the
instantaneous shear modulus, is only weakly temperature dependent; 4) the beta
compliance magnitude decreases by a factor of three upon cooling in the
temperature range studied. The final part of the paper briefly presents
measurements of the dynamic adiabatic bulk modulus covering frequencies from 10
mHz to 10 kHz in the temperature range 172 K to 200 K. The data are
qualitatively similar to the shear data by having a significant beta process. A
single-order-parameter framework is suggested to rationalize these
similarities
Time-temperature superposition in viscous liquids
Dielectric relaxation measurements on supercooled triphenyl phosphite show
that at low temperatures time-temperature superposition (TTS) is accurately
obeyed for the primary (alpha) relaxation process. Measurements on 6 other
molecular liquids close to the calorimetric glass transition indicate that TTS
is linked to an high-frequency decay of the alpha loss, while
the loss peak width is nonuniversal.Comment: 4 page
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