5,672 research outputs found
Genetically encoded fluorescent redox probes.
Redox processes are involved in almost every cell of the body as a consequence of aerobic life. In the past decades, redox biology has been increasingly recognized as one of the key themes in cell signaling. The progress has been accelerated by development of fluorescent probes that can monitor redox conditions and dynamics in cells and cell compartments. This short paper focuses on fluorescent redox probes that are genetically encoded, and discusses their properties, molecular mechanism, advantages and pitfalls. Our recent work on reaction-based encoded probes that are responsive to particular redox signaling molecules is also reviewed. Future challenges and directions are also commented
Competition of spatial and temporal instabilities under time delay near codimension-two Turing-Hopf bifurcations
Competition of spatial and temporal instabilities under time delay near the
codimension-two Turing-Hopf bifurcations is studied in a reaction-diffusion
equation. The time delay changes remarkably the oscillation frequency, the
intrinsic wave vector, and the intensities of both Turing and Hopf modes. The
application of appropriate time delay can control the competition between the
Turing and Hopf modes. Analysis shows that individual or both feedbacks can
realize the control of the transformation between the Turing and Hopf patterns.
Two dimensional numerical simulations validate the analytical results.Comment: 13 pages, 6 figure
Exciton diffusion in semiconducting single-wall carbon nanotubes studied by transient absorption microscopy
Spatiotemporal dynamics of excitons in isolated semiconducting single-walled
carbon nanotubes are studied using transient absorption microscopy.
Differential reflection and transmission of an 810-nm probe pulse after
excitation by a 750-nm pump pulse are measured. We observe a bi-exponentially
decaying signal with a fast time constant of 0.66 ps and a slower time constant
of 2.8 ps. Both constants are independent of the pump fluence. By spatially and
temporally resolving the differential reflection, we are able to observe a
diffusion of excitons, and measure a diffusion coefficient of 200 cm2/s at room
temperature and 300 cm2/s at lower temperatures of 10 K and 150 K.Comment: 6 pages, 4 figure
Thermoelectric property studies on thallium-doped lead telluride prepared by ball milling and hot pressing
Thallium doping into lead telluride has been demonstrated to increase the dimensionless thermoelectric figure-of-merit (ZT) by enhancing Seebeck coefficient due to the creation of resonant states close to Fermi level without affecting the thermal conductivity. However, the process is tedious, energy consuming, and small in quantities since it involves melting, slow cooling for crystal growth, long time annealing, post-crushing and hot pressing. Here we show that a similar ZT value about 1.3 at 400βΒ°C is achieved on bulk samples with grain sizes of 3β7βΞΌm by ball milling a mixture of elemental thallium, lead, and tellurium and then hot pressing the ball milled nanopowders
Superconductivity and local-moment magnetism in Eu(FeCo)As
We report the measurements of resistivity and magnetization under magnetic
fields parallel and perpendicular to the basal plane, respectively, on a
cobalt-doped Eu(FeCo)As single crystal. We
observed a resistivity drop at 21 K, which shifts toward lower
temperatures under external fields, suggesting a superconducting transition.
The upper critical fields near show large anisotropy, in contrast with
those of other '122' FeAs-based superconductors. Low-field magnetic
susceptibility data also show evidence of superconductivity below 21 K. Instead
of expected zero-resistance below , however, a resistivity reentrance
appears at 17 K under zero field, coincident with the magnetic ordering of
Eu moments. Based on the temperature and field dependences of
anisotropic magnetization, a helical magnetic structure for the Eu spins
is proposed. External magnetic fields easily changes the helimagnetism into a
ferromagnetism with fully polarized Eu spins, accompanying by
disappearance of the resistivity reentrance. Therefore, superconductivity
coexists with ferromagnetic state of Eu spins under relatively low
magnetic field. The magnetic and superconducting phase diagrams are finally
summarized for both and .Comment: 8 pages, 10 figure
Evidence for Two Gaps and Breakdown of the Uemura Plot in BaKFeAs Single Crystals
We report a detailed investigation on the lower critical field of
the superconducting BaKFeAs (FeAs-122) single crystals.
A pronounced kink is observed on the curve, which is attributed to
the existence of two superconducting gaps. By fitting the data to
the two-gap BCS model in full temperature region, a small gap of
meV and a large gap of meV
are obtained. The in-plane penetration depth is estimated to
be 105 nm corresponding to a rather large superfluid density, which points to
the breakdown of the Uemura plot in FeAs-122 superconductors.Comment: 5 pages, 4 figure
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