91 research outputs found
Runaway electrification of friable self-replicating granular matter
We establish that the nonlinear dynamics of collisions between particles
favors the charging of a insulating, friable, self-replicating granular
material that undergoes nucleation, growth, and fission processes; we
demonstrate with a minimal dynamical model that secondary nucleation produces a
positive feedback in an electrification mechanism that leads to runaway
charging. We discuss ice as an example of such a self-replicating granular
material: We confirm with laboratory experiments in which we grow ice from the
vapor phase in situ within an environmental scanning electron microscope that
charging causes fast-growing and easily breakable palm-like structures to form,
which when broken off may form secondary nuclei. We propose that thunderstorms,
both terrestrial and on other planets, and lightning in the solar nebula are
instances of such runaway charging arising from this nonlinear dynamics in
self-replicating granular matter
Revisión de la ordenación y plan técnico de ordenación del (nuevo) monte "Cortijo del Valle" T. M. Tarifa (Cádiz)
Se hace la 1ª revisión del Plan Técnico de Ordenación del Monte Cortijo el Valle, al que se añaden las fincas Valle II y Valle III y se redacta un nuevo Plan Técnico de Ordenación de todo el conjunto. Se estudian las mejoras que dicho nuevo Plan prevee en los pastizales, nuevos aprovechamientos corcheros, cinegético, así como en la red de caminos y en los cortafuegos
Effect of indirect composite treatment microtensile bond strength of self-adhesive resin cements
Background: No specific indications about the pre-treatment of indirect composite restorations is provided by the
manufacturers of most self-adhesive resin cements. The potential effect of silane treatment to the bond strength of
the complete tooth/indirect restoration complex is not available.The aim of this study was to determine the contribution of different surface treatments on microtensile bond strength of composite overlays to dentin using several
self-adhesive resin cements and a total-etch one.
Material and Methods: Composite overlays were fabricated and bonding surfaces were airborne-particle abraded
and randomly assigned to two different surface treatments: no treatment or silane application (RelyX Ceramic
Primer) followed by an adhesive (Adper Scotchbond 1 XT). Composite overlays were luted to flat dentin surfaces
using the following self-adhesive resin cements: RelyX Unicem, G-Cem, Speedcem, Maxcem Elite or Smartcem2,
and the total-etch resin cement RelyX ARC. After 24 h, bonded specimens were cut into sticks 1 mm thick and
stressed in tension until failure. Two-way ANOVA and SNK tests were applied at α=0.05.
Results: Bond strength values were significantly influenced by the resin cement used (
p
<0.001). However, composite surface treatment and the interaction between the resin cement applied and surface treatment did not significantly
affect dentin bond strength (
p
>0.05). All self-adhesive resin cements showed lower bond strength values than the
total-etch RelyX ARC. Among self-adhesive resin cements, RelyX Unicem and G-Cem attained statistically higher
bond strength values. Smartcem2 and Maxcem Elite exhibited 80-90% of pre-test failures.
Conclusions: The silane and adhesive application after indirect resin composite sandblasting did not improve the
bond strength of dentin-composite overlay complex. Selection of the resin cement seems to be a more relevant
factor when bonding indirect composites to dentin than its surface treatmen
Crystal growth as an excitable medium
Crystal growth has been widely studied for many years, and, since the
pioneering work of Burton, Cabrera and Frank, spirals and target patterns on
the crystal surface have been understood as forms of tangential crystal growth
mediated by defects and by two-dimensional nucleation. Similar spirals and
target patterns are ubiquitous in physical systems describable as excitable
media. Here, we demonstrate that this is not merely a superficial resemblance,
that the physics of crystal growth can be set within the framework of an
excitable medium, and that appreciating this correspondence may prove useful to
both fields. Apart from solid crystals, we discuss how our model applies to the
biomaterial nacre, formed by layer growth of a biological liquid crystal
Photonic and Nanobiophotonic Properties of Luminescent Lanthanide-Doped Hybrid Organic-Inorganic Materials
Research into lanthanide-doped organic–inorganic hybrid materials emerged in the 1990s with the
development of interesting materials for optics: high efficiency and stable solid-state lasers, new
fiber amplifiers and sensors, devices with upconversion, fast photochromic and non-linear
responses, etc. Their interest relies on the possibility of combining properties of sol–gel host
materials (shaping, tunable refractive index and mechanical properties, corrosion protection,
specific adhesion, etc.) and the well-known luminescence of lanthanide ions (Ln). The fast
development of photonic hybrids allowed the commercial exploitation of products with new or
enhanced characteristics (megajoule pulsed Nd-YAG laser, protective coatings of glasses, screens
or glasswares). However, recently, Ln-hybrid nanocomposites have found new applications in
bio-sensors, bio-analytics and even clinical imaging diagnostics. These applications make use of
the fluorescence properties of lanthanides that make luminescent hybrids ideal candidates for
time-resolved fluoroimmunoassays, DNA hybridation assays, fluorescence imaging microscopy,
or in vivo imaging. As a consequence, the goal of this review is twofold: (i) as a reminder of some
general considerations that must be taken into account to design new optically active Ln-doped
nanocomposites whatever the application field, and (ii) to show the most important advances
achieved in the past years in different areas, paying special attention to bio-medical application
Brinicles as a case of inverse chemical gardens
Brinicles are hollow tubes of ice from centimetres to metres in length that
form under floating sea ice in the polar oceans when dense, cold brine drains
downwards from sea ice into sea water close to its freezing point. When this
extremely cold brine leaves the ice it freezes the water it comes into contact
with; a hollow tube of ice --- a brinicle --- growing downwards around the
plume of descending brine. We show that brinicles can be understood as a form
of the self-assembled tubular precipitation structures termed chemical gardens,
plant-like structures formed on placing together a soluble metal salt, often in
the form of a seed crystal, and an aqueous solution of one of many anions,
often silicate. On one hand, in the case of classical chemical gardens, an
osmotic pressure difference across a semipermeable precipitation membrane that
filters solutions by rejecting the solute leads to an inflow of water and to
its rupture. The internal solution, generally being lighter than the external
solution, flows up through the break, and as it does so a tube grows upwards by
precipitation around the jet of internal solution. Such chemical-garden tubes
can grow to many centimetres in length. In the case of brinicles, on the other
hand, in floating sea ice we have porous ice in a mushy layer that filters out
water, by freezing it, and allows concentrated brine through. Again there is an
osmotic pressure difference leading to a continuing ingress of sea water in a
siphon pump mechanism that is sustained as long as the ice continues to freeze.
Since the brine that is pumped out is denser than the sea water, and descends
rather rises, a brinicle is a downwards growing tube of ice; an inverse
chemical garden
Lanthanide doped ZnS quantum dots dispersed in silica glasses: an easy one pot sol–gel synthesis for obtaining novel photonic materials
Silica glasses containing both ZnS quantum dots (QDs) and luminescent lanthanide ions are attractive
candidates to develop new lighting displays, sensor devices or laser emitters. This work reports an easy
sol–gel method to prepare Eu3+-doped and Eu3+,Mn2+-codoped ZnS nanocrystals dispersed in
a transparent silica matrix. Semiconductor nanocrystals with an average size of 5–6 nm and exhibiting
both cubic and hexagonal phases were obtained at low temperature. The luminescent interactions
between ZnS QDs, Eu3+ and Mn2+ ions provided materials with different optical responses but also
gave information about the organization of the different species in the nanocomposite. Indeed, Eu ions
were found to be both dispersed within the silica and located at the surface of the nanochalcogenide, the
latter providing a ZnS/Eu3+ energy transfer. Incorporation of Mn2+ into the ZnS lattice induced the
appearance of defect states that enhance the blue luminescence of the nanocomposite. These results
underline the sensitivity of optical processes to the nature and organization of the active species, which
is of vital importance for the design of photonic material
The African swine fever virus dynein-binding protein p54 induces infected cell apoptosis
AbstractA specific interaction of ASFV p54 protein with 8 kDa light chain cytoplasmic dynein (DLC8) has been previously characterized and this interaction is critical during virus internalization and transport to factory sites. During early phases of infection, the virus induces the initiation of apoptosis triggering activation of caspase-9 and -3. To analyze the role of the structural protein p54 in apoptosis, transient expression experiments of p54 in Vero cells were carried out which resulted in effector caspase-3 activation and apoptosis. Interestingly, p54 mutants, lacking the 13 aa dynein-binding motif lose caspase activation ability and pro-death function of p54. This is the first reported ASFV protein which induces apoptosis
From chemical gardens to chemobrionics
Chemical gardens are perhaps the best example in chemistry of a
self-organizing nonequilibrium process that creates complex
structures. Many different chemical systems and materials can
form these self-assembling structures, which span at least 8
orders of magnitude in size, from nanometers to meters. Key to
this marvel is the self-propagation under fluid advection of
reaction zones forming semipermeable precipitation membranes
that maintain steep concentration gradients, with osmosis and
buoyancy as the driving forces for fluid flow. Chemical gardens
have been studied from the alchemists onward, but now in the
21st century we are beginning to understand how they can lead
us to a new domain of self-organized structures of semipermeable
membranes and amorphous as well as polycrystalline solids
produced at the interface of chemistry, fluid dynamics, and
materials science. We propose to call this emerging field
chemobrionics
Genetic Association of a Gain-of-Function IFNGR1 Polymorphism and the Intergenic Region LNCAROD/DKK1 With Behcet's Disease
Objective. Behçet’s disease is a complex systemic inflammatory vasculitis of incompletely understood etiology. This study was undertaken to investigate genetic associations with Behçet’s disease in a diverse multiethnic population.Methods. A total of 9,444 patients and controls from 7 different populations were included in this study. Genotyping was performed using an Infinium ImmunoArray- 24 v.1.0 or v.2.0 BeadChip. Analysis of expression data from stimulated monocytes, and epigenetic and chromatin interaction analyses were performed.Results. We identified 2 novel genetic susceptibility loci for Behçet’s disease, including a risk locus in IFNGR1(rs4896243) (odds ratio [OR] 1.25; P = 2.42 × 10−9) and within the intergenic region LNCAROD/DKK1 (rs1660760) (OR 0.78; P = 2.75 × 10−8). The risk variants in IFNGR1 significantly increased IFNGR1 messenger RNA expression in lipopolysaccharide- stimulated monocytes. In addition, our results replicated the association (P 30 genetic susceptibility loci with a suggestive level of association (P < 5 × 10−5), which will require replication. Finally, functional annotation of genetic susceptibility loci in Behçet’s disease revealed their possible regulatory roles and suggested potential causal genes and molecular mechanisms that could be further investigated.Conclusion. We performed the largest genetic association study in Behçet’s disease to date. Our findings reveal novel putative functional variants associated with the disease and replicate and extend the genetic associations in other loci across multiple ancestries
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