48 research outputs found
Coupling motion of colloidal particles in quasi-twodimensional confinement
The Brownian motion of colloidal particles in quasi-two-dimensional (q2D)
confinement displays a distinct kinetic character from that in bulk. Here we
experimentally report dynamic coupling motion of Brownian particles in a
relatively long process (âŒ100 h), which displays a quasi-equilibrium state in the
q2D system. In the quasi-equilibrium state, the q2D confinement results in the
coupling of particle motions, which slowly damps the motion and interaction of
particles until the final equilibrium state is reached. The process of approaching
the equilibrium is a random relaxation of a many-body interaction system of
Brownian particles. As the relaxation proceeds for âŒ100 h, the system reaches
the equilibrium state in which the energy gained by the particles from the
stochastic collision in the whole system is counteracted by the dissipative energy
resulting from the collision. The relaxation time of this stochastic q2D system is
17.7 h. The theory is developed to explain coupling motions of Brownian particles
in q2D confinement
Discovery and regulation of chiral magnetic solitons: Exact solution from Landau-Lifshitz-Gilbert equation
The Landau-Lifshitz-Gilbert (LLG) equation has emerged as a fundamental and
indispensable framework within the realm of magnetism. However, solving the LLG
equation, encompassing full nonlinearity amidst intricate complexities,
presents formidable challenges. In this context, we develop a precise mapping
through geometric representation, establishing a direct linkage between the LLG
equation and an integrable generalized nonlinear Schr\"odinger equation. This
novel mapping provides accessibility towards acquiring a great number of exact
spatiotemporal solutions. Notably, exact chiral magnetic solitons, critical for
stability and controllability in propagation with and without damping effects
are discovered. Our formulation provides exact solutions for the long-standing
fully nonlinear problem, facilitating practical control through spin current
injection in magnetic memory applications.Comment: main text:5 pages, 4 figures, supplementary materials:5 pages, 2
figure
Onset of nonlinear electroosmotic flow under AC electric field
Nonlinearity of electroosmotic flows (EOFs) is ubiquitous and plays a crucial
role in the mass and energy transfer in ion transport, specimen mixing,
electrochemistry reaction, and electric energy storage and utilizing. When and
how the transition from a linear regime to a nonlinear one is essential for
understanding, prohibiting or utilizing nonlinear EOF. However, suffers the
lacking of reliable experimental instruments with high spatial and temporal
resolutions, the investigation of the onset of nonlinear EOF still stays in
theory. Herein, we experimentally studied the velocity fluctuations of EOFs
driven by AC electric field via ultra-sensitive fluorescent blinking tricks.
The linear and nonlinear AC EOFs are successfully identified from both the time
trace and energy spectra of velocity fluctuations. The critical electric field
() separating the two statuses is determined and is discovered by
defining a generalized scaling law with respect to the convection velocity
() and AC frequency () as ~. The
universal control parameters are determined with surprising accuracy for
governing the status of AC EOFs. We hope the current investigation could be
essential in the development of both theory and applications of nonlinear EOF
A fluidic platform for mobility evaluation of zebrafish with gene deficiency
IntroductionZebrafish is a suitable animal model for molecular genetic tests and drug discovery due to its characteristics including optical transparency, genetic manipulability, genetic similarity to humans, and cost-effectiveness. Mobility of the zebrafish reflects pathological conditions leading to brain disorders, disrupted motor functions, and sensitivity to environmental challenges. However, it remains technologically challenging to quantitively assess zebrafish's mobility in a flowing environment and simultaneously monitor cellular behavior in vivo.MethodsWe herein developed a facile fluidic device using mechanical vibration to controllably generate various flow patterns in a droplet housing single zebrafish, which mimics its dynamically flowing habitats.ResultsWe observe that in the four recirculating flow patterns, there are two equilibrium stagnation positions for zebrafish constrained in the droplet, i.e., the âsourceâ with the outward flow and the âsinkâ with the inward flow. Wild-type zebrafish, whose mobility remains intact, tend to swim against the flow and fight to stay at the source point. A slight deviation from streamline leads to an increased torque pushing the zebrafish further away, whereas zebrafish with motor neuron dysfunction caused by lipin-1 deficiency are forced to stay in the âsink,â where both their head and tail align with the flow direction. Deviation angle from the source point can, therefore, be used to quantify the mobility of zebrafish under flowing environmental conditions. Moreover, in a droplet of comparable size, single zebrafish can be effectively restrained for high-resolution imaging.ConclusionUsing the proposed methodology, zebrafish mobility reflecting pathological symptoms can be quantitively investigated and directly linked to cellular behavior in vivo
Label-free visualization of carbapenemase activity in living bacteria
Evaluating enzyme activity intracellularly on natural substrates is a significant experimental challenge in biomedical research. We report a labelâfree method for realâtime monitoring of the catalytic behavior of classâ
A, B, and D carbapenemases in live bacteria based on measurement of heat changes. By this means, novel biphasic kinetics for classâ
D OXAâ48 with imipenem as substrate is revealed, providing a new approach to detect OXAâ48âlike producers. This inâcell calorimetry approach offers major advantages in the rapid screening (10â
min) of carbapenemaseâproducing Enterobacteriaceae from 142 clinical bacterial isolates, with superior sensitivity (97â%) and excellent specificity (100â%) compared to conventional methods. As a general, labelâfree method for the study of living cells, this protocol has potential for application to a wider range and variety of cellular components and physiological processes
Coupling motion of colloidal particles in quasi-twodimensional confinement
The Brownian motion of colloidal particles in quasi-two-dimensional (q2D)
confinement displays a distinct kinetic character from that in bulk. Here we
experimentally report dynamic coupling motion of Brownian particles in a
relatively long process (âŒ100 h), which displays a quasi-equilibrium state in the
q2D system. In the quasi-equilibrium state, the q2D confinement results in the
coupling of particle motions, which slowly damps the motion and interaction of
particles until the final equilibrium state is reached. The process of approaching
the equilibrium is a random relaxation of a many-body interaction system of
Brownian particles. As the relaxation proceeds for âŒ100 h, the system reaches
the equilibrium state in which the energy gained by the particles from the
stochastic collision in the whole system is counteracted by the dissipative energy
resulting from the collision. The relaxation time of this stochastic q2D system is
17.7 h. The theory is developed to explain coupling motions of Brownian particles
in q2D confinement
Coupling motion of colloidal particles in quasi-twodimensional confinement
The Brownian motion of colloidal particles in quasi-two-dimensional (q2D)
confinement displays a distinct kinetic character from that in bulk. Here we
experimentally report dynamic coupling motion of Brownian particles in a
relatively long process (âŒ100 h), which displays a quasi-equilibrium state in the
q2D system. In the quasi-equilibrium state, the q2D confinement results in the
coupling of particle motions, which slowly damps the motion and interaction of
particles until the final equilibrium state is reached. The process of approaching
the equilibrium is a random relaxation of a many-body interaction system of
Brownian particles. As the relaxation proceeds for âŒ100 h, the system reaches
the equilibrium state in which the energy gained by the particles from the
stochastic collision in the whole system is counteracted by the dissipative energy
resulting from the collision. The relaxation time of this stochastic q2D system is
17.7 h. The theory is developed to explain coupling motions of Brownian particles
in q2D confinement
Formation of Circular Crack Pattern in Deposition Self-Assembled by Drying Nanoparticle Suspension
Curved cracks widely exist in nanoparticle (NP) deposition
produced
by drying colloidal suspension. Circular cracks, for example, initiate
and propagate along a circular trajectory. One feasible theoretical
explanation of a circular crack is the Xia-Hutchinson model, in which
a preexisting track (flaw loop) in the film is necessary for initiating
and propagating the crack on the circular path. Here, we report the
first experimental evidence of dried deposition to support this model.
Our results indicate that cracks along the circular trajectory can
surprisingly âpassâ across a 180 ÎŒm air gap. Moreover,
two arc-path cracks originate in different areas and propagate to
meet, forming a circular trajectory. These unexpected crack initiation
and propagation indicate that the crack propagates alone the âpreformedâ
track, experimentally confirming the hypothesis proposed by the XiaâHutchinson
model. The transition of the circular crack to a radial one indicates
that the deposition microstructure is the dominant factor for the
crack formation
Formation of Circular Crack Pattern in Deposition Self-Assembled by Drying Nanoparticle Suspension
Curved cracks widely exist in nanoparticle (NP) deposition
produced
by drying colloidal suspension. Circular cracks, for example, initiate
and propagate along a circular trajectory. One feasible theoretical
explanation of a circular crack is the Xia-Hutchinson model, in which
a preexisting track (flaw loop) in the film is necessary for initiating
and propagating the crack on the circular path. Here, we report the
first experimental evidence of dried deposition to support this model.
Our results indicate that cracks along the circular trajectory can
surprisingly âpassâ across a 180 ÎŒm air gap. Moreover,
two arc-path cracks originate in different areas and propagate to
meet, forming a circular trajectory. These unexpected crack initiation
and propagation indicate that the crack propagates alone the âpreformedâ
track, experimentally confirming the hypothesis proposed by the XiaâHutchinson
model. The transition of the circular crack to a radial one indicates
that the deposition microstructure is the dominant factor for the
crack formation