41 research outputs found
Wrinkling instability of vesicles in steady linear flow
We present experimental observations and numerical simulations of a wrinkling
instability that occurs at sufficiently high strain rates in the trembling
regime of vesicle dynamics in steady linear flow. Spectral and statistical
analysis of the data shows similarities and differences with the wrinkling
instability observed earlier for vesicles in transient elongation flow. The
critical relevance of thermal fluctuations for this phenomenon is revealed by a
simple model using coupled Langevin equations that reproduces the experimental
observations quite well.Comment: 6 pages, 9 figures + 2 video
Fluid Vesicles in Flow
We review the dynamical behavior of giant fluid vesicles in various types of
external hydrodynamic flow. The interplay between stresses arising from
membrane elasticity, hydrodynamic flows, and the ever present thermal
fluctuations leads to a rich phenomenology. In linear flows with both
rotational and elongational components, the properties of the tank-treading and
tumbling motions are now well described by theoretical and numerical models. At
the transition between these two regimes, strong shape deformations and
amplification of thermal fluctuations generate a new regime called trembling.
In this regime, the vesicle orientation oscillates quasi-periodically around
the flow direction while asymmetric deformations occur. For strong enough
flows, small-wavelength deformations like wrinkles are observed, similar to
what happens in a suddenly reversed elongational flow. In steady elongational
flow, vesicles with large excess areas deform into dumbbells at large flow
rates and pearling occurs for even stronger flows. In capillary flows with
parabolic flow profile, single vesicles migrate towards the center of the
channel, where they adopt symmetric shapes, for two reasons. First, walls exert
a hydrodynamic lift force which pushes them away. Second, shear stresses are
minimal at the tip of the flow. However, symmetry is broken for vesicles with
large excess areas, which flow off-center and deform asymmetrically. In
suspensions, hydrodynamic interactions between vesicles add up to these two
effects, making it challenging to deduce rheological properties from the
dynamics of individual vesicles. Further investigations of vesicles and similar
objects and their suspensions in steady or time-dependent flow will shed light
on phenomena such as blood flow.Comment: 13 pages, 13 figures. Adv. Colloid Interface Sci., 201
Characteristic spatial scale of vesicle pair interactions in a plane linear flow
We report the experimental studies on interaction of two vesicles trapped in
a microfluidic analog of four-roll mill, where a plane linear flow is realized.
We found that the dynamics of a single vesicle is significantly altered by the
presence of another vesicle at separation distances up to about 3.2 \div 3.7
times of effective radius of the vesicles. This is supported by direct
measurements of a single vesicle back-reaction on the velocity field. Thus, the
experiment provides the lower bound for the interaction scale of vesicles and
so the corresponding upper bound for the volume fraction \phi=0.08 \div 0.13 of
non-interacting vesicle suspensions.Comment: 5 pages, 8 figures, PRE accepted for publicatio
Dopamine D2 receptor function is compromised in the brain of the methionine sulfoxide reductase A knockout mouse
Previous research suggests that brain oxidative stress and altered rodent locomotor behavior are linked. We observed bio-behavioral changes in methionine sulfoxide reductase A knockout mice associated with abnormal dopamine signaling. Compromised ability of these knockout mice to reduce methionine sulfoxide enhances accumulation of sulfoxides in proteins. We examined the dopamine D2-receptor function and expression, which has an atypical arrangement and quantity of methionine residues. Indeed, protein expression levels of dopamine D2-receptor were higher in knockout mice compared with wild-type. However, the binding of dopamine D2-receptor agonist was compromised in the same fractions of knockout mice. Coupling efficiency of dopamine D2-receptors to G-proteins was also significantly reduced in knockout mice, supporting the compromised agonist binding. Furthermore, pre-synaptic dopamine release in knockout striatal sections was less responsive than control sections to dopamine D2-receptor ligands. Behaviorally, the locomotor activity of knockout mice was less responsive to the inhibitory effect of quinpirole than wild-type mice. Involvement of specific methionine residue oxidation in the dopamine D2-receptor third intracellular loop is suggested by in vitro studies. We conclude that ablation of methionine sulfoxide reductase can affect dopamine signaling through altering dopamine D2-receptor physiology and may be related to symptoms associated with neurological disorders and diseases
Estas son algunas de las habilidades blandas demandadas en Colombia
Este producto forma parte de una serie de infografías de divulgación científica que buscan reseñar algunas de las investigaciones más importantes en las que ha tenido participación la Universidad EAFIT, publicadas en las revistas especializadas más prestigiosas del mund
Fast Prototyping of Silica Glass Microfluidic Chips: The Sol-Gel Route
International audienceA combination of material, patterning, and sealing method is introduced to replicate and assemble monolithic microfluidic chips made of hybrid silica glass (HSG). First, it is shown how to prepare sols suited to the replication of complex geometries out of range of conventional etching methods. Second, it is shown how to tailor the surface properties of HSG devices. The performances and the simplicity of this fast prototyping method are demonstrated using quantitative mechanical, optical, and physicochemical characterization techniques and benchmark microfluidic experiments. Finally, the high potential of HSG microfluidics to oil-recovery and chemistry applications in benchmark experiments on crude oils is established
Parallel FPGA implementation of RSA with residue number systems – can side-channel threats be avoided
Abstract. In this paper, we present a new parallel architecture to avoid side-channel analyses such as: timing attack, simple/differential power analysis, fault induction attack and simple/differential electromagnetic analysis. We use a Montgomery Multiplication based on Residue Number Systems. Thanks to RNS, we develop a design able to perform an RSA signature in parallel on a set of identical and independent coprocessors. Of independent interest, we propose a new DPA countermeasure in the framework of RNS. It is only (slightly) memory consuming (1.5 KBytes). Finally, we synthesized our new architecture on FPGA and it presents promising performance results. Even if our aim is to sketch a secure architecture, the RSA signature is performed in less than 160 ms, with competitive hardware resources. To our knowledge, this is the first proposal of an architecture counteracting electromagnetic analysis apart from hardware countermeasures reducing electromagnetic radiations