947 research outputs found
Odd viscosity in chiral active fluids
Chiral active fluids are materials composed of self-spinning rotors that
continuously inject energy and angular momentum at the microscale.
Out-of-equilibrium fluids with active-rotor constituents have been
experimentally realized using nanoscale biomolecular motors, microscale active
colloids, or macroscale driven chiral grains. Here, we show how such chiral
active fluids break both parity and time-reversal symmetries in their steady
states, giving rise to a dissipationless linear-response coefficient called odd
viscosity in their constitutive relations. Odd viscosity couples pressure and
vorticity leading, for example, to density modulations within a vortex profile.
Moreover, chiral active fluids flow in the direction transverse to applied
compression as in shock propagation experiments. We envision that this
collective transverse response may be exploited to design self-assembled
hydraulic cranks that convert between linear and rotational motion in
microscopic machines powered by active-rotors fluids
THE COMPLEX POINT CLOUD FOR THE KNOWLEDGE OF THE ARCHITECTURAL HERITAGE. SOME EXPERIENCES
The present paper aims to present a series of experiences and experimentations that a group of PhD from the University of Naples Federico II conducted over the past decade. This work has concerned the survey and the graphic restitution of monuments and works of art, finalized to their conservation. The targeted query of complex point cloud acquired by 3D scanners, integrated with photo sensors and thermal imaging, has allowed to explore new possibilities of investigation. In particular, we will present the scientific results of the experiments carried out on some important historical artifacts with distinct morphological and typological characteristics. According to aims and needs that emerged during the connotative process, with the support of archival and iconographic historical research, the laser scanner technology has been used in many different ways. New forms of representation, obtained directly from the point cloud, have been tested for the elaboration of thematic studies for documenting the pathologies and the decay of materials, for correlating visible aspects with invisible aspects of the artifact
Grounding co-writing: An analysis of the theoretical basis of a new approach in mental health care
This contribution aims to highlight the theoretical and epistemological premises of the
co-writing experience, a practice where a clinician and a patient are mutually engaged
in jointly or collaboratively writing a narrative related to the patient’s experience.
Unlike a typical set of therapeutic techniques, co-writing is based on sharing perspectives and meanings about the experience of crisis, recovery, and the therapeutic
process. The paper identifies and briefly describes four non-clinical epistemological
paradigms on which it is grounded: ethnography, values-based practice, narrative
care, and phenomenology. Although they differ in several ways, at the same time,
they seem to share some common features that the paper investigates and comments.
For clinicians, nurses, researchers and Mental Health Service managers, attention
to the users and to the improvement of their active roles represents not only a strategy for the empowerment of results, but also the access door to a different perspective which relies on a renewed conceptualization of the mental disease nature that
may lead to overcoming the epistemic asymmetry between the ‘expert’ and the ‘other’
in favor of intersubjective dialogue
Anomalous coupling between topological defects and curvature
We investigate a counterintuitive geometric interaction between defects and
curvature in thin layers of superfluids, superconductors and liquid crystals
deposited on curved surfaces. Each defect feels a geometric potential whose
functional form is determined only by the shape of the surface, but whose sign
and strength depend on the transformation properties of the order parameter.
For superfluids and superconductors, the strength of this interaction is
proportional to the square of the charge and causes all defects to be repelled
(attracted) by regions of positive (negative) Gaussian curvature. For liquid
crystals in the one elastic constant approximation, charges between 0 and
are attracted by regions of positive curvature while all other charges
are repelled.Comment: 5 pages, 4 figures, minor changes, accepted for publication in Phys.
Rev. Let
Heat transport in model jammed solids
We calculate numerically the normal modes of vibrations in 3D jammed packings
of soft spheres as a function of the packing fraction and obtain the energy
diffusivity, a spectral measure of transport that controls sound propagation
and thermal conductivity. The crossover frequency between weak and strong
phonon scattering is controlled by the coordination and shifts to zero as the
system is decompressed towards the critical packing fraction at which rigidity
is lost. Below the crossover, the diffusivity displays a power-law divergence
with inverse frequency, which suggests that the vibrational modes are primarily
transverse waves, weakly scattered by disorder. Above it, a large number of
modes appear whose diffusivity plateaus at a nearly constant value independent
of the inter-particle potential, before dropping to zero above the Anderson
localization frequency. The thermal conductivity of a marginally jammed solid
just above the rigidity threshold is calculated and related to the one measured
experimentally at room temperature for most glasses.Comment: 15 pages, 7 figure
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