93 research outputs found
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Escape of DNA from a Weakly Biased Thin Nanopore: Experimental Evidence for a Universal Diffusive Behavior
We report experimental escape time distributions of double-stranded DNA molecules initially threaded halfway through a thin solid-state nanopore. We find a universal behavior of the escape time distributions consistent with a one-dimensional first passage formulation notwithstanding the geometry of the experiment and the potential role of complex molecule-liquid-pore interactions. Diffusion constants that depend on the molecule length and pore size are determined. Also discussed are the practical implications of long time diffusive molecule trapping in the nanopore.Engineering and Applied SciencesPhysic
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Correlated scattering of protons impinging as hydrogen molecules
The joint energy and angular-distribution function of protons transmitted through a thin foil when incident as 2-MeV H+2 has been measured. The experimental result is compared with simple calculations and satisfactory agreement is obtained.Physic
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Deduction of Continuum Potentials from Planar Channeling
A new method for determining planar continuum potentials from planar channeling data has been developed. Preliminary experiments have been done for 1.8-MeV α particles in [111] gold planar directions from which the continuum potential has been deduced.Physic
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Trapping DNA near a Solid-State Nanopore
We demonstrate that voltage biased solid-state nanopores can transiently localize DNA in an electrolyte solution. A double-stranded DNA (dsDNA) molecule is trapped when the electric field near the nanopore attracts and immobilizes a non-end segment of the molecule across the nanopore orifice without inducing a folded molecule translocation. In this demonstration of the phenomenon the ionic current through the nanopore decreases when the dsDNA molecule is trapped by the nanopore. By contrast, a translocating dsDNA molecule under the same conditions causes an ionic current increase. We also present finite element modeling results that predict this behavior for the conditions of the experiment.Physic
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Light emission from Er at the As-terminated Si(111) surface
Erbium atoms at an arsenic-terminated Si(111) surface can be made to emit light at the 1.55 mu m wavelength associated with an internal transition in the Er3+ ion. The As-terminated surface prepared under ultrahigh vacuum conditions has a surface recombination velocity of 50 cm s(-1) and partially suppresses competing nonradiative recombination mechanisms. Following the deposition of Er, its characteristic light emission is observed only after oxygen reacts with the surface. The intensity of the light emitted by Er increases significantly upon cooling from 310 to 215 K. No light emission was observed from Er atoms deposited on 7x7 or H-terminated surfaces.Physic
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Pressure–Voltage Trap for DNA near a Solid-State Nanopore
We report the formation of a tunable single DNA molecule trap near a solid-state nanopore in an electrolyte solution under conditions where an electric force and a pressure induced viscous flow force on the molecule are nearly balanced. Trapped molecules can enter the pore multiple times before escaping the trap by passing through the pore or by diffusing away. Statistical analysis of many individually trapped molecules yields a detailed picture of the fluctuation phenomena involved, which are successfully modeled by a one-dimensional first passage approach.Physic
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Observation of internal x-ray wave fields during Bragg diffraction with an application to impurity lattice location
By a simple extension of a previous experimental technique we demonstrate how the detailed standing-wave features of the internal x-ray wave field during the diffraction process may be observed even when a strong reflection occurs. The preliminary results reported here indicate that dynamical diffraction may be developed as a useful lattice-location technique in nearly perfect crystals.Physic
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Optical Absorption of DNA−Carbon Nanotube Structures
We measured the UV optical absorption of single-stranded DNA bound to single-walled carbon nanotubes (DNA/SWNT). The nucleotide absorbance from DNA/SWNT provides the first experimental confirmation that DNA binds to nanotubes through -stacking. Because the hypochromic absorbance typical of -stacked structures are expected to occur primarily for DNA dipole transitions that lie along the axis of the optically anisotropic SWNTs, the absorbance changes following binding of DNA to nanotubes reveal the preferred orientation assumed by each of the four bound nucleotides with respect to the nanotube's long axis.Engineering and Applied SciencesPhysic
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Critical analysis of the charge-state dependence of the energy loss of channeled ions
A critical analysis of channeled-ion energy-loss experiments is presented with the goal of commenting on the presence of the Barkas effect of Z31 corrections to the stopping power. Accurate charge-density values are obtained for silicon and used to evaluate Bloch and straggling effects in the data. The remaining contributions to the data show a clear Z31 dependence that can be explained with an electron-gas model for the Barkas effect.Physic
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X-Ray Evanescent-Wave Absorption and Emission
The presence and properties of x-ray evanescent waves are demonstrated detecting their absorption and their excitation in the vicinity of a target surface. The role of microscopic reversibility in relating the two cases is discussed and practical applications of the phenomena to probe interfaces are suggested.Physic
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