479 research outputs found
Phase diagram and complexity of mode-locked lasers: from order to disorder
We investigate mode-locking processes in lasers displaying a variable degree
of structural randomness, from standard optical cavities to multiple-scattering
media. By employing methods mutuated from spin-glass theory, we analyze the
mean-field Hamiltonian and derive a phase-diagram in terms of the pumping rate
and the degree of disorder. Three phases are found: i) paramagnetic,
corresponding to a noisy continuous wave emission, ii) ferromagnetic, that
describes the standard passive mode-locking, and iii) the spin-glass in which
the phases of the electromagnetic field are frozen in a exponentially large
number of configurations. The way the mode-locking threshold is affected by the
amount of disorder is quantified. The results are also relevant for other
physical systems displaying a random Hamiltonian, like Bose-Einstein
condensates and nonlinear optical beams.Comment: 4 pages, 2 figure
PRICKLE1-related early onset epileptic encephalopathy
The PRICKLE1 (Prickle Planar Cell Polarity Protein 1-MIM 608500) gene is involved in different phases of human development. The related diseases include autosomal recessive progressive myoclonus epilepsy - ataxia syndrome, neural tube defects associated with heterozygous mutations, agenesis of corpus callosum, polymicrogyria, and autistic spectrum disorder. Reported here is a young boy with a new variant (NM_153026.2:c.820G>A, p.Ala274Thr) presenting with an early infantile epileptic encephalopathy with developmental arrest
Static and dynamic glass-glass transitions: a mean-field study
The behavior of a family of mean-field glass models is reviewed. The models
are analyzed by means of a Langevin-based approach to the dynamics and a
Replica theory computation of the thermodynamics. We focus on the phase diagram
of a particular model case, where glass-to-glass transitions occur between
phases with a different number of characteristic time-scales for the relaxation
processes. The appearence of Johari-Goldstein processes as collective
reorganizations of sets of fast processes is discussed.Comment: Contribution to the Special Issue of Philosophical Magazine for the
11th International Workshop on Complex System
Genetic neonatal-onset epilepsies and developmental/epileptic encephalopathies with movement disorders: A systematic review
Despite expanding next generation sequencing technologies and increasing clinical in-terest into complex neurologic phenotypes associating epilepsies and developmental/epileptic encephalopathies (DE/EE) with movement disorders (MD), these monogenic conditions have been less extensively investigated in the neonatal period compared to infancy. We reviewed the medical literature in the study period 2000–2020 to report on monogenic conditions characterized by neonatal onset epilepsy and/or DE/EE and development of an MD, and described their electroclinical, genetic and neuroimaging spectra. In accordance with a PRISMA statement, we created a data collection sheet and a protocol specifying inclusion and exclusion criteria. A total of 28 different genes (from 49 papers) leading to neonatal-onset DE/EE with multiple seizure types, mainly featuring tonic and myoclonic, but also focal motor seizures and a hyperkinetic MD in 89% of conditions, with neonatal onset in 22%, were identified. Neonatal seizure semiology, or MD age of onset, were not always available. The rate of hypokinetic MD was low, and was described from the neonatal period only, with WW domain containing oxidoreductase (WWOX) pathogenic variants. The outcome is characterized by high rates of associated neurodevelopmental disorders and microcephaly. Brain MRI findings are either normal or nonspecific in most conditions, but serial imaging can be necessary in order to detect progressive abnormalities. We found high genetic heterogeneity and low numbers of described patients. Neurological phenotypes are complex, reflecting the involvement of genes necessary for early brain development. Future studies should focus on accurate neonatal epileptic phenotyping, and detailed description of semiology and time-course, of the associated MD, especially for the rarest conditions
Transition between localized and extended states in the hierarchical Anderson model
We present strong numerical evidence for the existence of a
localization-delocalization transition in the eigenstates of the 1-D Anderson
model with long-range hierarchical hopping. Hierarchical models are important
because of the well-known mapping between their phases and those of models with
short range hopping in higher dimensions, and also because the renormalization
group can be applied exactly without the approximations that generally are
required in other models. In the hierarchical Anderson model we find a finite
critical disorder strength Wc where the average inverse participation ratio
goes to zero; at small disorder W < Wc the model lies in a delocalized phase.
This result is based on numerical calculation of the inverse participation
ratio in the infinite volume limit using an exact renormalization group
approach facilitated by the model's hierarchical structure. Our results are
consistent with the presence of an Anderson transition in short-range models
with D > 2 dimensions, which was predicted using renormalization group
arguments. Our finding should stimulate interest in the hierarchical Anderson
model as a simplified and tractable model of the Anderson localization
transition which occurs in finite-dimensional systems with short-range hopping.Comment: 7 pages, 7 figure
Approaches, Strategies and Theoretical and Practice-Based Research Methods to investigate and archive video art:Some reflections from the REWIND projects
This paper will discuss methodologies, approaches and issues, emerging out of three major research projects that have investigated early histories of video art in Europe: REWIND (2004 ongoing), REWINDItalia (2011-2014) and EWVA (2015-2018). The paper will discuss how the projects have engaged with the history of the apparatus, the identity and status of the artworks, preservation methods, and the legacy of these video artworks today. A particular focus will be on semi-structured questionnaires for interviews structured to capture oral histories, memories and recollections, that in some cases would have been otherwise lost to future knowledge and the uncovering of lost artworks and their available documentation. The speakers directly involved in the projects - will discuss solutions, risks and experiences encountered in the projects and future research perspectives for re-covering, collecting, archiving and narrating the histories of early video art in Europe. The paper will discuss also different practice-based research methods, platforms and engagement strategies, including re-installation and re-enactment
Marginal States in Mean Field Glasses
We study mean field systems whose free energy landscape is dominated by
marginally stable states. We review and develop various techniques to describe
such states, elucidating their physical meaning and the interrelation between
them. In particular, we give a physical interpretation of the two-group replica
symmetry breaking scheme and confirm it by establishing the relation to the
cavity method and to the counting of solutions of the Thouless-Anderson-Palmer
equations. We show how these methods all incorporate the presence of a soft
mode in the free energy landscape and interpret the occurring order parameter
functions in terms of correlations between the soft mode and the local
magnetizations. The general formalism is applied to the prototypical case of
the Sherrington-Kirkpatrick-model where we re-examine the physical properties
of marginal states under a new perspective.Comment: 27 pages, 8 figure
Non-equilibrium thermodynamics. IV: Generalization of Maxwell, Claussius-Clapeyron and Response Functions Relations, and the Prigogine-Defay Ratio for Systems in Internal Equilibrium
We follow the consequences of internal equilibrium in non-equilibrium systems
that has been introduced recently [Phys. Rev. E 81, 051130 (2010)] to obtain
the generalization of Maxwell's relation and the Clausius-Clapeyron relation
that are normally given for equilibrium systems. The use of Jacobians allow for
a more compact way to address the generalized Maxwell relations; the latter are
available for any number of internal variables. The Clausius-Clapeyron relation
in the subspace of observables show not only the non-equilibrium modification
but also the modification due to internal variables that play a dominant role
in glasses. Real systems do not directly turn into glasses (GL) that are frozen
structures from the supercooled liquid state L; there is an intermediate state
(gL) where the internal variables are not frozen. Thus, there is no single
glass transition. A system possess several kinds of glass transitions, some
conventional (L \rightarrow gL; gL\rightarrow GL) in which the state change
continuously and the transition mimics a continuous or second order transition,
and some apparent (L\rightarrow gL; L\rightarrow GL) in which the free energies
are discontinuous so that the transition appears as a zeroth order transition,
as discussed in the text. We evaluate the Prigogine-Defay ratio {\Pi} in the
subspace of the observables at these transitions. We find that it is normally
different from 1, except at the conventional transition L\rightarrow gL, where
{\Pi}=1 regardless of the number of internal variables.Comment: 42 pages, 3 figures, citations correcte
Monte Carlo studies of the ordering of the one-dimensional Heisenberg spin glass with long-range power-law interactions
The nature of the ordering of the one-dimensional Heisenberg spin-glass model
with a long-range power-law interaction is studied by extensive Monte Carlo
simulations, with particular attention to the issue of the spin-chirality
decoupling/coupling. Large system sizes up to are studied. With
varying the exponent describing the power-law interaction, we observe
three distinct types of ordering regimes. For smaller , the spin and
the chirality order at a common finite temperature with a common
correlation-length exponent, exhibiting the standard spin-chirality coupling
behavior. For intermediate , the chirality orders at a temperature
higher than the spin, exhibiting the spin-chirality decoupling behavior. For
larger , both the spin and the chirality order at zero temperature. We
construct a phase diagram in the versus the temperature plane, and
discuss implications of the results. Critical properties associated with both
the chiral-glass and the spin-glass transitions are also determined.Comment: 28 pages, 26 figures, to appear in J. Phys. Soc. Jp
Missense PDSS1 mutations in CoenzymeQ10 synthesis cause optic atrophy and sensorineural deafness
CoenzymeQ10 is one of the main cellular antioxidants and an essential lipid involved in numerous cell reactions, such as energy production and apoptosis modulation. A large number of enzymes are involved in CoQ10 biosynthesis. Mutations in the genes encoding for these enzymes cause a CoQ10 deficiency, characterized by neurological and systemic symptoms. Here we describe two young sisters with sensorineural deafness followed by optic atrophy, due to a novel homozygous pathogenic variant in PDSS1. The visual system seems to be mainly involved when the first steps of CoQ10 synthesis are impaired (PDSS1, PDSS2, and COQ2 deficiency)
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