608 research outputs found
Electronic and optical properties of electromigrated molecular junctions
Electromigrated nanoscale junctions have proven very useful for studying
electronic transport at the single-molecule scale. However, confirming that
conduction is through precisely the molecule of interest and not some
contaminant or metal nanoparticle has remained a persistent challenge,
typically requiring a statistical analysis of many devices. We review how
transport mechanisms in both purely electronic and optical measurements can be
used to infer information about the nanoscale junction configuration. The
electronic response to optical excitation is particularly revealing. We briefly
discuss surface-enhanced Raman spectroscopy on such junctions, and present new
results showing that currents due to optical rectification can provide a means
of estimating the local electric field at the junction due to illumination.Comment: 19 pages, 8 figures, invited paper for forthcoming special issue of
Journal of Physics: Condensed Matter. For other related papers, see
http://www.ruf.rice.edu/~natelson/publications.htm
Dark-pulse propagation in optical fibers
We report measurements of the reshaping of 0.3-psec dark pulses due to their passage through 10 m of single-mode optical fiber. The measurements were performed as a function of intensity and the observed strong reshaping agrees qualitatively with the predictions of the nonlinear Schrodinger equation which suggest that we have observed the formation of dark-pulse solitons.Peer reviewedElectrical and Computer Engineerin
Separate and combined effects of oligofructose and inulin on post-weaning coli bacillosis and weight gain: a preliminary study
Trends for a reduction in the use of dietary antibiotic growth promoters have caused increased interest in the use of alternative feed additives to maintain 'gut health' after weaning. Oligofructose and inulin are 'prebiotic' fructan-containing carbohydrates purported to enhance 'gut health' in newly-weaned pigs by altering microbial diversity (Konstantinov, et al., 2003). However, their effects using a challenge model of post-weaning colibacillosis (PWC) have never been examined. The aim of the present study was to compare the separate and combined effects of oligofructose and inulin supplementation on the occurrence of diarrhoea and the weight performance in piglets experimentally challenged with enterotoxigenic E. coli (ETEC)
Chiral Surface Plasmon Polaritons on Metallic Nanowires
Chiral surface plasmon polaritons (SPPs) can be generated by linearly
polarized light incident at the end of a nanowire, exciting a coherent
superposition of three specific nanowire waveguide modes. Images of chiral SPPs
on individual nanowires obtained from quantum dot fluorescence excited by the
SPP evanescent field reveal the chirality predicted in our theoretical model.
The handedness and spatial extent of the helical periods of the chiral SPPs
depend on the input polarization angle and nanowire diameter as well as the
dielectric environment. Chirality is preserved in the free-space output wave,
making a metallic nanowire a broad bandwidth subwavelength source of circular
polarized photons.Comment: 4 figure
QUARTERLY PROGRESS REPORT JANUARY, FEBRUARY, MARCH, 1968 REACTOR FUELS AND MATERIALS DEVELOPMENT PROGRAMS FOR FUELS AND MATERIALS BRANCH OF USAEC DIVISION OF REACTOR DEVELOPMENT AND TECHNOLOGY
Progress is reported in these areas: nuclear graphite; fuel development for gas-cooled reactors; HTGR graphite studies; nuclear ceramics; fast-reactor nitrides research; non-destructive testing; metallic fuels; basic swelling studies; ATR gas and water loop operation and maintenance; reactor fuels and materials; fast reactor dosimetry and damage analysis; and irradiation damage to reactor metals
Ultrafast light-controlled optical-fiber modulator
We report the ultrafast operation of a light-controlled optical-fiber modulator, driven by subpicosecond, compressed, and amplified (6000 A) dye laser pulses, controlling frequency doubled (5320 A) yttrium aluminum garnet laser pulses. The operation of the modulator is based on the optical Kerr effect, and its main component is 7 mm of single-mode optical fiber. Using this system as a light-controlled shutter, we produced either 0.4 ps green light pulses or 0.5 ps holes on the much longer duration second harmonic pulses.Peer reviewedElectrical and Computer Engineerin
Simultaneous optical pulse compression and wing reduction
We report the compression of picosecond optical pulses with a simultaneous reduction of the pulse wings by using a combination of both the self-phase modulation and nonlinear birefringence effects in a modified optical-fiber pulse compressor.Peer reviewedElectrical and Computer Engineerin
Manipulating infrared photons using plasmons in transparent graphene superlattices
Superlattices are artificial periodic nanostructures which can control the
flow of electrons. Their operation typically relies on the periodic modulation
of the electric potential in the direction of electron wave propagation. Here
we demonstrate transparent graphene superlattices which can manipulate infrared
photons utilizing the collective oscillations of carriers, i.e., plasmons of
the ensemble of multiple graphene layers. The superlattice is formed by
depositing alternating wafer-scale graphene sheets and thin insulating layers,
followed by patterning them all together into 3-dimensional
photonic-crystal-like structures. We demonstrate experimentally that the
collective oscillation of Dirac fermions in such graphene superlattices is
unambiguously nonclassical: compared to doping single layer graphene,
distributing carriers into multiple graphene layers strongly enhances the
plasmonic resonance frequency and magnitude, which is fundamentally different
from that in a conventional semiconductor superlattice. This property allows us
to construct widely tunable far-infrared notch filters with 8.2 dB rejection
ratio and terahertz linear polarizers with 9.5 dB extinction ratio, using a
superlattice with merely five graphene atomic layers. Moreover, an unpatterned
superlattice shields up to 97.5% of the electromagnetic radiations below 1.2
terahertz. This demonstration also opens an avenue for the realization of other
transparent mid- and far-infrared photonic devices such as detectors,
modulators, and 3-dimensional meta-material systems.Comment: under revie
The history of expansion of the genus Bursaphelenchus (Nematoda: Aphelenchida: Parasitaphelenchidae)
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