385 research outputs found
Collective behaviours: from biochemical kinetics to electronic circuits
In this work we aim to highlight a close analogy between cooperative
behaviors in chemical kinetics and cybernetics; this is realized by using a
common language for their description, that is mean-field statistical
mechanics. First, we perform a one-to-one mapping between paradigmatic
behaviors in chemical kinetics (i.e., non-cooperative, cooperative,
ultra-sensitive, anti-cooperative) and in mean-field statistical mechanics
(i.e., paramagnetic, high and low temperature ferromagnetic,
anti-ferromagnetic). Interestingly, the statistical mechanics approach allows a
unified, broad theory for all scenarios and, in particular, Michaelis-Menten,
Hill and Adair equations are consistently recovered. This framework is then
tested against experimental biological data with an overall excellent
agreement. One step forward, we consistently read the whole mapping from a
cybernetic perspective, highlighting deep structural analogies between the
above-mentioned kinetics and fundamental bricks in electronics (i.e.
operational amplifiers, flashes, flip-flops), so to build a clear bridge
linking biochemical kinetics and cybernetics.Comment: 15 pages, 6 figures; to appear on Scientific Reports: Nature
Publishing Grou
Percorsi a ‘sguardi multipli’: sfide e riflessioni sulla costruzione di pratiche decoloniali in università
‘Multiple Gaze’ Paths: Challenges and Reflections on the Construction of Decolonial
Practices in the University. Reconstructing dynamics that emerged from a project on literary texts
and racism in Italy, proposed in 2021 in the Department of Modern Languages, Literatures and
Cultures at the University of Bologna, the article aims to reflect on the positive aspects, limits and
critical issues of the path. The reflection will focus on specific aspects related to the project: the
methods and choices of developing the work carried out with students, colleagues and teachers; the
central role of the connection between text, body and experiences of racialized authors; the
questioning of the rigid opposition between artistic quality and political value of literary works; and the
need for cultural productions based on listening to historically marginalized voices. The proposed
analysis will also be connected to broader aspects: the gap between anti-racist and decolonial projects
and the real democratization of university; the question of responsibility, positioning and privilege in
the university; the challenges posed by the “professionalising” insertion of professors into the
neoliberal university system and the geopolitics of power in which this reality operates; and the
importance of continuing to enact practices of decolonizing teaching and research, while being aware
of the limits of these attempts. Finally, it will be proposed to interpret the university as a ‘crossing
space’ in order to deconstruct the rhetoric of belonging and permanence – namely, ‘being of the
university’ – and promote the idea of a space of connections that is open and capable of building
transformative networks and alliances
« si brusquement tu cesses d’exister » : neruda/minghella ; moment du poème, vacillement du traduire, l’instance du trouvé-créé, dans truly, madly, deeply
A partir d’un fragment de Neruda prononcé en stéréophonie dans une scène de traduction et de revenance qui est le pivot poétique et le kairos du film de Minghella, Truly, Madly, Deeply, cet article propose de montrer comment ce moment du poème, suspendu entre deux langues, fait brèche dans l’écriture du film, pour créer une ouverture par laquelle on spirale hors-récit et hors-langue vers le lieu de la lecture pure. Afin d’éclairer ce lieu sont posées les questions de l’adresse de l’absent(e), et celle de la destination de l’écrit. Ce moment poétique, d’un flottement, est le lieu de notre questionnement, un moment suspendu à la menace d’une perte de sens
Congenital mirror movements in a new Italian family
Mirror movements (MMs) occur on the contralateral side of a limb being used intentionally.
Because few families with congenital MMs and no other neurological signs have been reported, the underlying
mechanisms of MMs are still not entirely clear. We report on the clinical, genetic, neurophysiological and
neuroimaging findings of 10 of 26 living members of a novel four-generation family with congenital MMs. DCC
and RAD51 were sequenced in affected members of the family. Five of the ten subjects with MMs underwent
neurophysiological and neuroimaging evaluations. The neurophysiological evaluation consisted of
electromyographic (EMG) mirror recordings, investigations of corticospinal excitability, and analysis of
interhemispheric inhibition using transcranial magnetic stimulation techniques. The neuroimaging evaluation
included functional MRI during finger movements. Eight (all females) of the ten members examined presented
MMs of varying degrees at the clinical assessment. Transmission of MMs appears to have occurred according
to an autosomal-dominant fashion with variable expression. No mutation in DCC or RAD51 was identified. EMG
mirror activity was higher in MM subjects than in healthy controls. Short-latency interhemispheric inhibition
was reduced in MM subjects. Ipsilateral motor-evoked potentials were detectable in the most severe case.
The neuroimaging evaluation did not disclose any significant abnormalities in MM subjects. The variability of
the clinical features of this family, and the lack of known genetic abnormalities, suggests that MMs are
heterogeneous disorders. The pathophysiological mechanisms of MMs include abnormalities of transcallosal
inhibition and corticospinal decussatio
Replica symmetry breaking in mean field spin glasses trough Hamilton-Jacobi technique
During the last years, through the combined effort of the insight, coming
from physical intuition and computer simulation, and the exploitation of
rigorous mathematical methods, the main features of the mean field
Sherrington-Kirkpatrick spin glass model have been firmly established. In
particular, it has been possible to prove the existence and uniqueness of the
infinite volume limit for the free energy, and its Parisi expression, in terms
of a variational principle, involving a functional order parameter. Even the
expected property of ultrametricity, for the infinite volume states, seems to
be near to a complete proof. The main structural feature of this model, and
related models, is the deep phenomenon of spontaneous replica symmetry breaking
(RSB), discovered by Parisi many years ago. By expanding on our previous work,
the aim of this paper is to investigate a general frame, where replica symmetry
breaking is embedded in a kind of mechanical scheme of the Hamilton-Jacobi
type. Here, the analog of the "time" variable is a parameter characterizing the
strength of the interaction, while the "space" variables rule out
quantitatively the broken replica symmetry pattern. Starting from the simple
cases, where annealing is assumed, or replica symmetry, we build up a
progression of dynamical systems, with an increasing number of space variables,
which allow to weaken the effect of the potential in the Hamilton-Jacobi
equation, as the level of symmetry braking is increased. This new machinery
allows to work out mechanically the general K-step RSB solutions, in a
different interpretation with respect to the replica trick, and lightens easily
their properties as existence or uniqueness.Comment: 24 pages, no figure
Notes on the p-spin glass studied via Hamilton-Jacobi and Smooth-Cavity techniques
In these notes, we continue our investigation of classical toy models of
disordered statistical mechanics through various techniques recently developed
and tested mainly on the paradigmatic SK spin glass. Here we consider the
p-spin-glass model with Ising spins and interactions drawn from a normal
distribution N[0,1]. After a general presentation of its properties (e.g.
self-averaging of the free energy, existence of a suitable thermodynamic
limit), we study its equilibrium behavior within the Hamilton-Jacobi framework
and the smooth cavity approach. Through the former we find both the RS and the
1RSB expressions for the free energy, coupled with their self-consistent
relations for the overlaps. Through the latter, we recover these results as
irreducible expression, and we study the generalization of the overlap
polynomial identities suitable for this model; a discussion on their deep
connection with the structure of the internal energy and the entropy closes the
investigation.Comment: To appear on JM
Biocompounds recovery from Spirulina by conventional and ohmic heating methodologies: chemical and biological properties
Extracting the totality of bio-compounds with industrial interest from Cyanobacterium is often prevented by
the intrinsic rigidity of its cell wall. In this sense, the present study focuses on evaluating the influence thermal
batch extraction (conventional extraction technologies) and ohmic heating (OH) assisted extraction
(considered a greener alternative technology) in blue green microalgae Arthrospira platensis (Spirulina) cell
disruption for bioactive fractions recovery.
The proximal composition of Spirulina was initially determined. The maximum protein content (i.e., CPhycocyanin),
total carbohydrates (TC) and total phenolic compounds (TPC) extracted in water at different
times (30-120 min) and temperatures (30-51 ºC) was quantified after the conventional and OH- assisted
extraction. The freeze-thawing process was used as control. The antioxidant activity (i.e., FRAP and DPPH
assays) of the obtained extracts was assessed.
Results showed that with the freeze-thawing process, traditionally used for the recovery of bio- compounds
from Spirulina, the concentration of C-phycocyanin was approx. 42 mg/g of Spirulina, 26 mgGlcE/g Spirulina
of TC and 9 mgGAE/g Spirulina of TPC. Using OH-assisted extraction, the maximum of C-Phycocyanin
content obtained was 45 mg/g of Spirulina (obtained at 37 ºC, 30 min), the maximum carbohydrates content
was 40 mgGlcE/g Spirulina and the maximum TPC was 10 mgGAE/g Spirulina. On the other hand, using
conventional thermal treatment it can be observed that, under the same conditions, the bioactive compounds
recovery decreased to 35 mg/g, 20 mgGlcE/g Spirulina for C-phycocyanin concentration and TC (p<0.05),
respectively. The concentration in phenolic compounds is not so affected, but even so the ohmic heating
potentiates the extraction of these secondary metabolites.
The antioxidant activity of the extracts there was not different between conventional treatments andOH.
Thus, the results indicated that OH is a good alternative to conventional methods aiming at the extraction of
intracellular components with a decrease in processing time and energy costs associated with the extraction
process, which together with an easy upscale make OH an interesting methodology for use in the industrial
production of microalgae colorants and bioactive supplements.info:eu-repo/semantics/publishedVersio
The Impact of a Community-Based Childhood Obesity Prevention Program on Children’s Physical Activity and Fitness
The purpose of this study is to determine the effects of South County Food, Fitness and Fun (SCFFF), a 16-week community-based obesity prevention program, on children’s moderate to vigorous physical activity (MVPA), physical fitness, body mass index (BMI), and BMI z-score. A non-randomized pre-test and post-test study design was used to assess changes in MVPA, physical fitness, BMI and BMI z-score from baseline to program end. MVPA was measured by accelerometer, physical fitness measured by Fitnessgram, and height and weight were measured by stadiometer and scale and used to calculate BMI. The analytic sample for this study included 53 children from nine SCFFF programs conducted between 2011-2016. There was a significant increase in the percentage of time children spent participating in MVPA (1.12%; p=0.022), curl-ups (p\u3c0.001) and trunk lifts (p=0.004). BMI z-score decreased (p\u3c0.001). Results reinforce the importance of offering community-based interventions that include caregivers to prevent excess weight gain in children
Ferromagnetic models for cooperative behavior: Revisiting Universality in complex phenomena
Ferromagnetic models are harmonic oscillators in statistical mechanics.
Beyond their original scope in tackling phase transition and symmetry breaking
in theoretical physics, they are nowadays experiencing a renewal applicative
interest as they capture the main features of disparate complex phenomena,
whose quantitative investigation in the past were forbidden due to data
lacking. After a streamlined introduction to these models, suitably embedded on
random graphs, aim of the present paper is to show their importance in a
plethora of widespread research fields, so to highlight the unifying framework
reached by using statistical mechanics as a tool for their investigation.
Specifically we will deal with examples stemmed from sociology, chemistry,
cybernetics (electronics) and biology (immunology).Comment: Contributing to the proceedings of the Conference "Mathematical
models and methods for Planet Heart", INdAM, Rome 201
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