25,257 research outputs found
Multispectral Quantum Dots-in-a-Well Infrared Detectors Using Plasmon Assisted Cavities
We present the design, fabrication, and characterization, of multi-spectral quantum dots-in-a-well (DWELL) infrared detectors, by the integration of a surface plasmon assisted resonant cavity with the infrared detector. A square lattice and rectangular lattice cavity, formed by modifying the square lattice have been used in this design. By confining the resonant mode of the cavity to detector active region, the detector responsivity and detectivity have been improved by a factor of 5. A spectral tuning of 5.5 to 7.2 ÎŒm has been observed in the peak response of the detectors, by tuning the lattice constant of the cavity. Simulations indicate the presence of two modes of absorption, which have been experimentally verified. The use of a rectangular lattice predicts highly polarization sensitive modes in x- and y-direction, which are observed in fabricated detectors. A peak detectivity of 3.1 x 10^9 cm â(Hz)/W was measured at 77 K. This design offers a cost-effective and simple method of encoding spectral and polarization information, in infrared focal plane arrays
Histopathological image analysis : a review
Over the past decade, dramatic increases in computational power and improvement in image analysis algorithms have allowed the development of powerful computer-assisted analytical approaches to radiological data. With the recent advent of whole slide digital scanners, tissue histopathology slides can now be digitized and stored in digital image form. Consequently, digitized tissue histopathology has now become amenable to the application of computerized image analysis and machine learning techniques. Analogous to the role of computer-assisted diagnosis (CAD) algorithms in medical imaging to complement the opinion of a radiologist, CAD algorithms have begun to be developed for disease detection, diagnosis, and prognosis prediction to complement the opinion of the pathologist. In this paper, we review the recent state of the art CAD technology for digitized histopathology. This paper also briefly describes the development and application of novel image analysis technology for a few specific histopathology related problems being pursued in the United States and Europe
Optical properties of cubic boron arsenide
The ultrahigh thermal conductivity of boron arsenide makes it a promising
material for next-generation electronics and optoelectronics. In this work, we
report measured optical properties of cubic boron arsenide crystals including
the complex dielectric function, refractive index, and absorption coefficient
in the ultraviolet, visible, and near-infrared wavelength range. The data were
collected at room temperature using spectroscopic ellipsometry as well as
transmission and reflection spectroscopy. We further calculate the optical
response using density functional and many-body perturbation theory,
considering quasiparticle and excitonic corrections. The computed values for
the direct and indirect band gaps (4.25 eV and 2.07 eV) agree well with the
measured results (4.12 eV and 2.02 eV). Our findings contribute to the effort
of using boron arsenide in novel electronic and optoelectronic applications
that take advantage of its demonstrated ultrahigh thermal conductivity and
predicted high ambipolar carrier mobility
Thermoplasmonic effect of surface enhanced infrared absorption in vertical nanoantenna arrays
Thermoplasmonics is a method for increasing temperature remotely using focused visible or infrared laser beams interacting with plasmonic nanoparticles. Here, local heating induced by mid-infrared quantum cascade laser illumination of vertical gold-coated nanoantenna arrays embedded into polymer layers is investigated by infrared nanospectroscopy and electromagnetic/thermal simulations. Nanoscale thermal hotspot images are obtained by a photothermal scanning probe microscopy technique with laser illumination wavelength tuned at the different plasmonic resonances of the arrays. Spectral analysis indicates that both Joule heating by the metal antennas and surface-enhanced infrared absorption (SEIRA) by the polymer molecules located in the apical hotspots of the antennas are responsible for thermoplasmonic resonances, i.e. for strong local temperature increase. At odds with more conventional planar nanoantennas, the vertical antenna structure enables thermal decoupling of the hotspot at the antenna apex from the heat sink constituted by the solid substrate. The temperature increase was evaluated by quantitative comparison of data obtained with the photothermal expansion technique to the results of electromagnetic/ thermal simulations. In the case of strong SEIRA by the C=O bond of poly-methylmethacrylate at 1730 cm-1, for focused mid-infrared laser power of about 20 mW, the evaluated order of magnitude of the nanoscale temperature increase is of 10 K. This result indicates that temperature increases of the order of hundreds of K may be attainable with full mid-infrared laser power tuned at specific molecule vibrational fingerprints
NIR Calibrations for Soybean Seeds and Soy Food Composition Analysis: Total Carbohydrates, Oil, Proteins and Water Contents [v.2]
Conventional chemical analysis techniques are expensive, time consuming, and often destructive. The non-invasive Near Infrared (NIR) technology was introduced over the last decades for wide-scale, inexpensive chemical analysis of food and crop seed composition (see Williams and Norris, 1987; Wilcox and Cavins, 1995; Buning and Diller, 2000 for reviews of the NIR technique development stage prior to 1998, when Diode Arrays were introduced to NIR). NIR spectroscopic measurements obey Lambert and Beer’s law, and quantitative measurements can be successfully made with high speed and ease of operation. NIR has been used in a great variety of food applications. General applications of products analyzed come from all sectors of the food industry including meats, grains, and dairy products (Shadow, 1998).
Novel NIR calibrations for rapid, reliable and accurate composition analysis of a variety of several soy based foods and bulk soybean seeds were developed and validated in a six-year collaborative project with a large number of different samples (N >~12, 000). The availability of such calibrations is important for establishing NIR as a secondary method for composition analysis of foods and soybeans both in applications and fundamental research
NIR Calibrations for Soybean Seeds and Soy Food Composition Analysis: Total Carbohydrates, Oil, Proteins and Water Contents
Conventional chemical analysis techniques are expensive, time consuming, and often destructive. The non-invasive Near Infrared (NIR) technology was introduced over the last decades for wide-scale, inexpensive chemical analysis of food and crop seed composition (see Williams and Norris, 1987; Wilcox and Cavins, 1995; Buning and Diller, 2000 for reviews of the NIR technique development stage prior to 1998, when Diode Arrays were introduced to NIR). NIR spectroscopic measurements obey Lambert and Beer’s law, and quantitative measurements can be successfully made with high speed and ease of operation. NIR has been used in a great variety of food applications. General applications of products analyzed come from all sectors of the food industry including meats, grains, and dairy products (Shadow, 1998)
The 'nanobig rods' class of gold nanorods: optimized dimensions for improved in vivo therapeutic and imaging efficacy
Currently, gold nanorods can be synthesized in a wide range of sizes.
However, for intended biological applications gold nanorods with approximate
dimensions 50 nm x 15 nm are used. We investigate by computer simulation the
effect of particle dimensions on the optical and thermal properties in the
context of the specific applications of photoacoustic imaging. In addition we
discuss the influence of particle size in overcoming the following biophysical
barriers when administrated in vivo: extravasation, avoidance of uptake by
organs of the reticuloendothelial system, penetration through the interstitium,
binding capability and uptake by the target cells. Although more complex
biological influences can be introduced in future analysis, the present work
illustrates that larger gold nanorods, designated by us as "nanobig rods", may
perform relatively better at meeting the requirements for successful in vivo
applications compared to their smaller counterparts which are conventionally
used
Plasmon Resonance in Multilayer Graphene Nanoribbons
Plasmon resonance in nanopatterned single layer graphene nanoribbon (SL-GNR),
double layer graphene nanoribbon (DL-GNR) and triple layer graphene nanoribbon
(TL-GNR) structures is studied both experimentally and by numerical
simulations. We use 'realistic' graphene samples in our experiments to identify
the key bottle necks in both experiments and theoretical models. The existence
of electrical tunable plasmons in such stacked multilayer GNRs was first
experimentally verified by infrared microscopy. We find that the strength of
the plasmonic resonance increases in DL-GNR when compared to SL-GNRs. However,
we do not find a further such increase in TL-GNRs compared to DL-GNRs. We
carried out systematic full wave simulations using finite element technique to
validate and fit experimental results, and extract the carrier scattering rate
as a fitting parameter. The numerical simulations show remarkable agreement
with experiments for unpatterned SLG sheet, and a qualitative agreement for
patterned graphene sheet. We believe that further improvements such as
introducing a bandgap into the numerical model could lead to a better
quantitative agreement of numerical simulations with experiments. We also note
that such advanced modeling would first require better quality graphene samples
and accurate measurements
Thermoplasmonic effect of surface enhanced infrared absorption in vertical nanoantenna arrays
Thermoplasmonics is a method for increasing temperature remotely using focused visible or infrared laser beams interacting with plasmonic nanoparticles. Here, local heating induced by mid-infrared quantum cascade laser illumination of vertical gold-coated nanoantenna arrays embedded into polymer layers is investigated by infrared nanospectroscopy and electromagnetic/thermal simulations. Nanoscale thermal hotspot images are obtained by a photothermal scanning probe microscopy technique with laser illumination wavelength tuned at the different plasmonic resonances of the arrays. Spectral analysis indicates that both Joule heating by the metal antennas and surface-enhanced infrared absorption (SEIRA) by the polymer molecules located in the apical hotspots of the antennas are responsible for thermoplasmonic resonances, i.e. for strong local temperature increase. At odds with more conventional planar nanoantennas, the vertical antenna structure enables thermal decoupling of the hotspot at the antenna apex from the heat sink constituted by the solid substrate. The temperature increase was evaluated by quantitative comparison of data obtained with the photothermal expansion technique to the results of electromagnetic/ thermal simulations. In the case of strong SEIRA by the C=O bond of poly-methylmethacrylate at 1730 cm-1, for focused mid-infrared laser power of about 20 mW, the evaluated order of magnitude of the nanoscale temperature increase is of 10 K. This result indicates that temperature increases of the order of hundreds of K may be attainable with full mid-infrared laser power tuned at specific molecule vibrational fingerprints
- âŠ