52 research outputs found
Crystal-to-crystal transition of ultrasoft colloids under shear
Ultrasoft colloids typically do not spontaneously crystallize, but rather
vitrify, at high concentrations. Combining in-situ rheo-SANS experiments and
numerical simulations we show that shear facilitates crystallization of
colloidal star polymers in the vicinity of their glass transition. With
increasing shear rate well beyond rheological yielding, a transition is found
from an initial bcc-dominated structure to an fcc-dominated one. This
crystal-to-crystal transition is not accompanied by intermediate melting but
occurs via a sudden reorganization of the crystal structure. Our results
provide a new avenue to tailor colloidal crystallization and crystal-to-crystal
transition at molecular level by coupling softness and shear
Uniform line fillings
Deterministic fabrication of random metamaterials requires filling of a space
with randomly oriented and randomly positioned chords with an on-average
homogenous density and orientation, which is a nontrivial task. We describe a
method to generate fillings with such chords, lines that run from edge to edge
of the space, in any dimension. We prove that the method leads to random but
on-average homogeneous and rotationally invariant fillings of circles, balls
and arbitrary-dimensional hyperballs from which other shapes such as rectangles
and cuboids can be cut. We briefly sketch the historic context of Bertrand's
paradox and Jaynes' solution by the principle of maximum ignorance. We analyse
the statistical properties of the produced fillings, mapping out the density
profile and the line-length distribution and comparing them to analytic
expressions. We study the characteristic dimensions of the space in between the
chords by determining the largest enclosed circles and balls in this pore
space, finding a lognormal distribution of the pore sizes. We apply the
algorithm to the direct-laser-writing fabrication design of optical
multiple-scattering samples as three-dimensional cubes of random but
homogeneously positioned and oriented chords.Comment: 10 pages, 12 figures; v3: restructured paper, more references, more
graph
Deterministic and controllable photonic scattering media via direct laser writing
Photonic scattering materials, such as biological tissue and white paper, are
made of randomly positioned nanoscale inhomogeneities in refractive index that
lead to multiple scattering of light. Typically these materials, both
naturally-occurring or man-made, are formed through self assembly of the
scattering inhomogeneities, which imposes challenges in tailoring the disorder
and hence the optical properties. Here, We report on the nanofabrication of
photonic scattering media using direct laser writing with deterministic design.
These deterministic scattering media consist of submicron thick polymer
nanorods that are randomly oriented within a cubic volume. We study the total
transmission of light as a function of the number density of rods and of the
sample thickness to extract the scattering and transport mean free paths using
radiative transfer theory. Such photonic scattering media with deterministic
and controllable properties are model systems for fundamental light scattering
in particular with strong anisotropy and offer new applications in solid-state
lighting and photovoltaics.Comment: 18 pages, 9 figure
Knowledge and behaviors regarding salt intake in Mozambique
Background/objectives: Health education and regulatory measures may contribute to lower population salt intake. Therefore, we aimed to describe knowledge and behaviors related to salt intake in Mozambique.
Subjects/methods: A cross-sectional evaluation of a representative sample of the population aged 15–64 years (n = 3116) was conducted in 2014/2015, following the Stepwise Approach to Chronic Disease Risk Factor Surveillance, including a 12-question module for evaluation of dietary salt.
Results: Three dimensions were identified in the questionnaire, named “self-reported salt intake”, “knowledge of health effects of salt intake”, and “behaviors for control of salt intake”. A total of 7.4% of the participants perceived that they consumed too much/far too much salt and 25.9% reported adding salt/salty seasoning often/always to prepared foods. The proportion considering that it was not important to decrease the salt contents of their diet was 8%, and 16.9% were not aware that high salt intake could be deleterious for health. Prevalences of lack of behaviors for reducing salt intake ranged from 74.9% for not limiting consumption of processed foods, to 95% for not buying low salt alternatives. There were few differences according to socio-demographic variables, but awareness of hypertension was, in general, associated with better knowledge and less frequent behaviors likely to contribute to a high salt intake.
Conclusions: Most Mozambicans were aware that high salt intake can cause health problems, but the self-reported salt intake and behaviors for its control show an ample margin for improvement. This study provides evidence to guide population level salt-reducing policies
Kinematics of the Southern Rhodope Core Complex (North Greece)
The Southern Rhodope Core Complex is a wide metamorphic dome exhumed in the northern Aegean as a result of large-scale extension
from mid-Eocene to mid-Miocene times. Its roughly triangular shape is bordered on the SW by the Jurassic and Cretaceous metamorphic
units of the Serbo-Macedonian in the Chalkidiki peninsula and on the N by the eclogite bearing gneisses of the Sideroneron
massif. The main foliation of metamorphic rocks is flat lying up to 100 km core complex width. Most rocks display a stretching
lineation trending NEâ SW. The Kerdylion detachment zone located at the SW controlled the exhumation of the core complex from
middle Eocene to mid-Oligocene. From late Oligocene to mid-Miocene exhumation is located inside the dome and is accompanied
by the emplacement of the synkinematic plutons of Vrondou and Symvolon. Since late Miocene times, extensional basin sediments
are deposited on top of the exhumed metamorphic and plutonic rocks and controlled by steep normal faults and flat-ramp-type
structures. Evidence from Thassos Island is used to illustrate the sequence of deformation from stacking by thrusting of the
metamorphic pile to ductile extension and finally to development of extensional Plio-Pleistocene sedimentary basin. Paleomagnetic
data indicate that the core complex exhumation is controlled by a 30� dextral rotation of the Chalkidiki block. Extensional
displacements are restored using a pole of rotation deduced from the curvature of stretching lineation trends at core complex
scale. It is argued that the Rhodope Core Complex has recorded at least 120 km of extension in the North Aegean, since the
last 40 My
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