We theoretically studied how the electric filed effect can modify thermoelectric properties of intrinsic bismuth telluride nanowires, which are grown along [110] direction. The electronic structure and wave functions ...
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We theoretically studied how the electric filed effect can modify thermoelectric properties of intrinsic bismuth telluride nanowires, which are grown along [110] direction. The electronic structure and wave functions were calculated by solving the self-consistent system of the Schrodinger and Poisson equations by means of both the Thomas-Fermi approximation and the spectral element method. The thermoelectric parameters were determined using a constant relaxation-time approximation. The external electric field can increase the Seebeck coefficient of a nanowire with 7 – 15 nm lateral dimensions by nearly a factor of two, and enhance the figure of merit by an order of magnitude.
Magnetic manipulation, fluorescent tracking, and localized delivery of a drug payload to cancer cells in vitro is demonstrated, using nanostructured porous silicon microparticles as a carrier. The multifunctional micr...
Magnetic manipulation, fluorescent tracking, and localized delivery of a drug payload to cancer cells in vitro is demonstrated, using nanostructured porous silicon microparticles as a carrier. The multifunctional microparticles are prepared by electrochemical porosification of a silicon wafer in a hydrofluoric acid-containing electrolyte, followed by removal and fracture of the porous layer into particles using ultrasound. The intrinsically luminescent particles are loaded with superparamagnetic iron oxide nanoparticles and the anti-cancer drug doxorubicin. The drug-containing particles are delivered to human cervical cancer (HeLa) cells in vitro, under the guidance of a magnetic field. The high concentration of particles in the proximity of the magnetic field results in a high concentration of drug being released in that region of the Petri dish, and localized cell death is confirmed by cellular viability assay (Calcein AM).
The hardnesses of secondary cell wall laminae (SCWL) and compound corner middle lamellae (CCML) in wood were measured at indentation strain rates between approximately 7×10-4 s-1 and 20 s-1, using a new method ca...
The hardnesses of secondary cell wall laminae (SCWL) and compound corner middle lamellae (CCML) in wood were measured at indentation strain rates between approximately 7×10-4 s-1 and 20 s-1, using a new method called broadband nanoindentation creep. The wood was subsequently modified with ethylene glycol (EG) and the properties were re-measured. The SCWL and CCML responded differently to this modification: in the SCWL, hardness decreased uniformly by a factor of 3.7 ± 0.3 across all strain rates, whereas in CCML, the modification had a similar effect at low strain rates. However, at high strain rates, hardness was only lowered by a factor of 1.8. The EG modification also lowered elastic modulus of the SCWL and CCML, swelled the SCWL and CCML, and caused previously placed indents to disappear (CCML) or partly disappear (SCWL).
To investigate the local environment's effect on the lifetime and quantum yield of extended polymer chains in the absence of intra-and interchain aggregation, short, rodlike polymers of poly(2,5-di-n-octyloxy-1,4-...
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In this study, fracture toughness of North American elk (Cervus elaphus canadensis) antler and bovine femur were measured using four-point bending tests on single-edge notched compact samples (ASTM C1421). Tests were ...
In this study, fracture toughness of North American elk (Cervus elaphus canadensis) antler and bovine femur were measured using four-point bending tests on single-edge notched compact samples (ASTM C1421). Tests were conducted on crack growth directions longitudinal and transverse to the long axis of antler and bone in both dry and hydrated conditions to study the effects of fiber orientation and hydration. Fracture toughness results in the transverse orientation were much higher than that in the longitudinal orientation and increased with degree of hydration for both antler and bovine femur. The fracture toughness of antler was ∼ 50% higher than that of bovine femur. The highest fracture toughness value was obtained from the hydrated antler in the transverse orientation, which reached 10.31 MPa·m1/2 compared to that measured from bovine femur, which was 6.35 MPa·m1/2. The crack propagation and fracture surface were characterized using scanning electron microscopy. Toughening mechanisms, including crack deflection by osteons, uncracked ligament bridging, and microcracks formation, are observed and discussed. Comparisons between antler and bone are made.
The initial stage of polarization switching in ferroelectric thin films depends on phenomena that occur at characteristic time scales of tens to hundreds of nanoseconds, including the nucleation polarization domains a...
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The initial stage of polarization switching in ferroelectric thin films depends on phenomena that occur at characteristic time scales of tens to hundreds of nanoseconds, including the nucleation polarization domains and the propagation of domain walls. These long intrinsic times allow short-duration electric fields with magnitudes far above the low-frequency coercive electric field to be applied across capacitor devices without inducing switching. Using time-resolved x-ray microdiffraction, we have found that a series of 50 ns duration electric field pulses switches the polarization of a 35-nm-thick ferroelectric Pb(Zr,Ti)O3 film only at electric fields greater than 1.5 MV/cm, a factor of three higher than the low-frequency coercive field. There is no switching in response to a large number of short pulses with amplitudes lower than 1.5 MV/cm, even when the total duration reaches several milliseconds. In comparison, a series of microsecond-duration pulses causes cumulative changes in the area of switched polarization and eventually switches the entire capacitor. The difference between long- and short-duration electric field pulses arises from effects linked to domain nucleation and charge transport in the ferroelectric film. A phase-field model shows that the shrinking of the switched domain in the interval between pulses is a less important effect. This opportunity to apply large fields for short times without inducing switching by domain-wall motion raises the possibility that future experiments could reach the intrinsic coercive field of ferroelectric layers and provides a way to study the properties of materials under high electric fields.
We demonstrate a high sensitivity, high throughput microfabricated cell sorting device with the integrated piezoelectric actuator and optofluidic waveguide on a chip. For automated sorting, field-programmable-gate-arr...
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