1,851 research outputs found
Canonical Solution of Classical Magnetic Models with Long-Range Couplings
We study the canonical solution of a family of classical spin
models on a generic -dimensional lattice; the couplings between two spins
decay as the inverse of their distance raised to the power , with
. The control of the thermodynamic limit requires the introduction of
a rescaling factor in the potential energy, which makes the model extensive but
not additive. A detailed analysis of the asymptotic spectral properties of the
matrix of couplings was necessary to justify the saddle point method applied to
the integration of functions depending on a diverging number of variables. The
properties of a class of functions related to the modified Bessel functions had
to be investigated. For given , and for any , and lattice
geometry, the solution is equivalent to that of the model, where the
dimensionality and the geometry of the lattice are irrelevant.Comment: Submitted for publication in Journal of Statistical Physic
Density-Temperature-Softness Scaling of the Dynamics of Glass-forming Soft-sphere Liquids
The principle of dynamic equivalence between soft-sphere and hard-sphere
fluids [Phys. Rev. E \textbf{68}, 011405 (2003)] is employed to describe the
interplay of the effects of varying the density n, the temperature T, and the
softness (characterized by a softness parameter {\nu}^{-1}) on the dynamics of
glass-forming soft-sphere liquids in terms of simple scaling rules. The main
prediction is that the dynamic parameters of these systems, such as the
{\alpha}-relaxation time and the long-time self-diffusion coefficient, depend
on n, T, and {\nu} only through the reduced density n^\ast \equiv
n{\sigma}^{3}_{HS}(T, {\nu}),where the effective hard-sphere diameter
{\sigma}_{HS}(T, {\nu}) is determined, for example, by the
Andersen-Weeks-Chandler condition for soft-sphere-hard-sphere structural
equivalence. A number of scaling properties observed in recent simulations
involving glass-forming fluids with repulsive short range interactions are
found to be a direct manifestation of this general dynamic equivalence
principle. The self-consistent generalized Langevin equation (SCGLE) theory of
colloid dynamics is shown to accurately capture these scaling rule
Rab11-mediated trafficking and human cancers: An updated review
Many disorders block and subvert basic cellular processes in order to boost their pro-gression. One protein family that is prone to be altered in human cancers is the small GTPase RAB11 family, the master regulator of vesicular trafficking. RAB11 isoforms function as membrane organizers connecting the transport of cargoes towards the plasma membrane with the assembly of autophagic precursors and the generation of cellular protrusions. These processes dramatically impact normal cell physiology and their alteration significantly affects the survival, progression and metastatization as well as the accumulation of toxic materials of cancer cells. In this review, we dis-cuss biological mechanisms ensuring cargo recognition and sorting through a RAB11-dependent pathway, a prerequisite to understand the effect of RAB11 alterations in human cancers
Clinical insights into dermatofibrosarcoma protuberans
Dermatofibrosarcoma protuberans (DFSP) is a rare, locally aggressive cutaneous soft tissue sarcoma, it is the second most common skin sarcoma after Kaposi's sarcoma. The cause of DFSP remains unknown. The case of a 54-year-old female patient with a diagnosis of Dermatofibrosarcoma protuberans is presented, displaying a typical clinical presentation. It is characterized by an initial lesion in the form of a reddish spot on the anterior region of the chest, which showed slow growth until the development of a multinodular and irregular lesion with multiple recurrences. The lesion is resected, confined to the superficial layers of the skin, with 3 cm margins, confirming the histopathological diagnosis of dermatofibrosarcoma protuberans with clear margins. DFSP is an uncommon cutaneous sarcoma that is typically low- to intermediate-grade, and while it has a limited likelihood of metastasis, it exhibits a notable tendency for local recurrence. The risk of recurrence is closely linked to the extent of surgical resection
1-d gravity in infinite point distributions
The dynamics of infinite, asymptotically uniform, distributions of
self-gravitating particles in one spatial dimension provides a simple toy model
for the analogous three dimensional problem. We focus here on a limitation of
such models as treated so far in the literature: the force, as it has been
specified, is well defined in infinite point distributions only if there is a
centre of symmetry (i.e. the definition requires explicitly the breaking of
statistical translational invariance). The problem arises because naive
background subtraction (due to expansion, or by "Jeans' swindle" for the static
case), applied as in three dimensions, leaves an unregulated contribution to
the force due to surface mass fluctuations. Following a discussion by
Kiessling, we show that the problem may be resolved by defining the force in
infinite point distributions as the limit of an exponentially screened pair
interaction. We show that this prescription gives a well defined (finite) force
acting on particles in a class of perturbed infinite lattices, which are the
point processes relevant to cosmological N-body simulations. For identical
particles the dynamics of the simplest toy model is equivalent to that of an
infinite set of points with inverted harmonic oscillator potentials which
bounce elastically when they collide. We discuss previous results in the
literature, and present new results for the specific case of this simplest
(static) model starting from "shuffled lattice" initial conditions. These show
qualitative properties (notably its "self-similarity") of the evolution very
similar to those in the analogous simulations in three dimensions, which in
turn resemble those in the expanding universe.Comment: 20 pages, 8 figures, small changes (section II shortened, added
discussion in section IV), matches final version to appear in PR
Maturity related differences in body composition assessed by classic and specific bioimpedance vector analysis among male elite youth soccer players
The aim of this study was to analyze the efficiency of classic and specific bioelectrical impedance vector analysis (BIVA) in the assessment of maturity related differences in body composition among male elite youth soccer players, and to provide bioelectrical impedance reference data for this category. A group of 178 players (aged 12.1 \ub1 1.6 years) were registered in a professional Italian soccer team participating in the first division (Serie A). They were divided into three groups according to their maturity status while bioelectrical resistance and reactance were obtained. The classic and specific BIVA procedures were applied, which correct bioelectrical values for body height and body geometry, respectively. Percentage of fat mass (FM%) and total body water (TBW (L)) were estimated from bioelectrical values. Age-specific z-scores of the predicted age at peak height velocity identified 29 players as earlier-, 126 as on time-, and 23 as later-maturing. TBW was higher (p < 0.01) in adolescents classified as \u201cearly\u201d maturity status compared to the other two groups and classic BIVA confirmed these results. Conversely, no differences in FM% were found among the groups. Specific vector length showed a higher correlation (r = 0.748) with FM% compared with the classic approach (r = 0.493). Classic vector length showed a stronger association (r = 120.955) with TBW compared with specific (r = 120.263). Specific BIVA turns out to be accurate for the analysis of FM% in athletes, while classic BIVA shows to be a valid approach to evaluate TBW. An original data set of bioelectric impedance reference values of male elite youth soccer players was provided
Influence of hydrodynamics on many-particle diffusion in 2D colloidal suspensions
We study many-particle diffusion in 2D colloidal suspensions with full
hydrodynamic interactions through a novel mesoscopic simulation technique. We
focus on the behaviour of the effective scaled tracer and collective diffusion
coefficients and , where is the
single-particle diffusion coefficient, as a function of the density of the
colloids . At low Schmidt numbers , we find that
hydrodynamics has essentially no effect on the behaviour of . At
larger , is enhanced at all densities, although the
differences compared to the case without hydrodynamics are minor. The
collective diffusion coefficient, on the other hand, is much more strongly
coupled to hydrodynamical conservation laws and is distinctly different from
the purely dissipative case
Implications of the Unitarity Triangle `uc' for J, and elements
The Jarlskog rephasing invariant parameter is evaluated using one of
the six Unitarity Triangles involving well known CKM matrix elements \vud,
\vus,~\rub, ~\vcd, ~\vcs~ and ~\vcb. With PDG2000 values of \vud~ etc. as
input, we obtain , which in the PDG
representation of CKM matrix leads to the range for the CP
violating phase . The CKM matrix elements evaluated using this range of
are in agreement with the PDG CKM matrix. The implications of
refinements in the input on , and CKM matrix elements have also
been studied.Comment: 14 pages, 3 figures (eps), updated in the light of latest PDG2000
dat
Stability in microcanonical many-body spin glasses
We generalize the de Almeida-Thouless line for the many-body Ising spin glass
to the microcanonical ensemble and show that it coincides with the canonical
one. This enables us to draw a complete microcanonical phase diagram of this
model
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