We report the hyperspectral imaging system for the measurement of anthocyanin accumulations in ‘bok choy’ grown in the different environmental conditions in the indoor farms. Wavelength bandwidth from 400nm to 700nm that covers chlorophyll A, B, and anthocyanin absorption peaks was three dimensionally (wavelength vs intensity in the area of 100cm2) measured by hyperspectral imaging instrument. Estimated anthocyanin accumulations by hyperspectral imaging technique were compared with those measured by chemical (destructive) analysis. Coinciding results between hyperspectral and destructive analysis suggest that hyperspectral imaging system can be a valuable photonic instrument to replace previously used destructive analysis in agricultural researches. (Supported by 421035-04)
Microgravity, vacuum, and high-intensity ultraviolet waves are widely known characteristics of space. These different environments from the earth affect physical changes including ocular tissue changes while astronauts stay in the universe. The changes in ocular tissue in the space environment, also known as visual impairment intracranial pressure (VIIP) syndrome, including fundus optic disc edema, hyperopic drift, choroidal folds, cotton spots, and permanent fundus damage could influence astronauts’ vision system and ability of space operations. Especially, hyperopic drift by posterior flattening and folded retina by choroidal folds are reported to affect the retina's structures as a vision sensor directly. To investigate microgravity's effect on ocular tissues and vision, previous research on earth are used special facilities and various microgravity simulators, including head-down tilt bed-rest and random positioning machines. This study suggests that an experiment expose wild-type zebrafish to microgravity using a rotary cell culture system (RCCs) applied to experiments using cell and zebrafish's embryos in microgravity. Unlike previous research using zebrafish's embryos and larva, adult and growing zebrafish were employed in this study for observing ocular changes in simulated space environments. After exposing zebrafish to microgravity, in-vivo zebrafish's eye images were acquired by custom-built optical coherence tomography (OCT). This research for presenting the new method for small animal experiments in microgravity environments could be applied to investigate the influence of staying in the universe on an animal model with ophthalmic diseases.
Low-level light therapy, which is a red or near-infrared light-employed therapeutic methodology, can act to help the brain repair in cases of traumatic brain injury and stroke. In this paper, we investigate the effects of near-infrared light therapy (NILT) for the recovery of blood flow of mice with cerebral hypoperfusion, which is a key mechanism leading to vascular dementia, induced by bilateral common carotid artery stenosis (BCAS). The mice are divided into three groups of 4-5 mice per group: a normal group (without BCAS operation), a BCAS group (without NILT), or a BCAS/NILT group. The LED with a peak wavelength of 810 nm and a power of 20 mW is arranged to illuminate on the top of the mouse head. The mice receive treatment from the LED source 3 times per week for one month. After the treatment, positron emission tomography is used to quantify the effects of NILT on whole brain and regional cerebral blood flow in the cortex, striatum, and hippocampus.
Dermatologic patients have various skin characteristics such as skin tone and pigmentation color. However most studies on laser ablation and treatment only considered laser operating conditions like wavelength, output power and pulse duration. The laser ablation arises from photothermal effect by photon energy absorption. Chromophores like melanin exist as the absorber in the skin. In this study, we painted color to mimic chromophores on in-vivo and in-vitro skin models to demonstrate influence on the laser ablation by skin color. Water-based pens were used to paint color. Cross sectional images of the laser ablation were acquired by Fourier-domain optical coherence tomography (Fd-OCT). Light source to make ablation was a Q-switch diode-pumped Nd:YVO4 nanosecond laser (532nm central wavelength). Irradiated light energy dose of the laser could not make ablation craters in the control group. However experimental groups showed craters with same irradiation light energy dose. These results show painting on skin increased tissue damage by absorption in painted color without dyeing cells or tissues.
Glaucoma is a progressive optic neuropathy, characterized by the selective loss of retinal ganglion cells (RGCs). Therefore, monitoring the change of number or morphology of RGC is essential for the early detection as well as investigation of pathophysiology of glaucoma. Since RGC layer is transparent and hyporeflective, the direct optical visualization of RGCs has not been successful so far. Therefore, glaucoma evaluation mostly depends on indirect diagnostic methods such as the evaluation of optic disc morphology or retinal nerve fiber layer thickness measurement by optical coherence tomography.
We have previously demonstrated single photoreceptor cell imaging with differential interference contrast (DIC) microscopy. Herein, we successfully visualized single RGC using DIC microscopy. Since RGC layer is much less reflective than photoreceptor layer, various techniques including the control of light wavelength and bandwidth using a tunable band pass filter were adopted to reduce the chromatic aberration in z-axis for higher and clearer resolution. To verify that the imaged cells were the RGCs, the flat-mounted retina of Sprague-Dawley rat, in which the RGCs were retrogradely labeled with fluorescence, was observed by both fluorescence and DIC microscopies for direct comparison. We have confirmed that the cell images obtained by fluorescence microscopy were perfectly matched with cell images by DIC microscopy.
As conclusion, we have visualized single RGC with DIC microscopy, and confirmed with fluorescence microscopy.
In this study, we successfully generated the large bandwidth of supercontinuum spectra through hollow fibers filled with DNA. Also, by observing that spectra bandwidth was the widest in the order of the hollow core fiber filled with DNA modified by copper ion, the hollow core fiber with only DNA, and the bulk hollow core fiber, we demonstrated that DNA material modified with copper ions can further enhance the spectral bandwidth of supercontinuum. As a result, we anticipate that the SCG as a broadband light source can be used in analytical methods to demonstrate a wide range of biological and environmental questions.
Arrays of partially selective chemical sensors have been the focus of extensive research over the past decades because of their potential for widespread application in ambient air monitoring, health and safety, and biomedical diagnostics. Especially, vapor sensor arrays based on functionalized nanomaterials have shown great promise with their high sensitivity by dimensionality and outstanding electronic properties. Here, we introduce experiments where individual vapors and mixtures of them are examined by different chemical sensor arrays. The collected data from those sensor arrays are further analyzed by a principal component analysis (PCA) and targeted vapors are recognized based on prepared database.
Graphene is a promising material for its exceptional electrical and mechanical properties. Starting with the initial demonstration of isolating a single graphene sheet from graphite, much progress has been made in realizing graphene based devices for diverse applications. Here, we introduce an experiment in which the electrical properties of graphene are modified by coating different-sequence single-stranded deoxyribonucleic acid (ssDNA) molecules. We fabricated a graphene-field effect transistor (FET) by transferring CVD graphene on copper foil onto a Si/SiO2 wafer. A passivation layer opened up windows on the surface of the graphene to enable interaction with liquid buffers. ssDNA molecules with different base sequences were coated onto the active graphene channels. We observed a variation in the Dirac voltage of the ssDNA-coated graphene FETs according to the ssDNA base sequences. Electrical control of the graphene FET is obtained via gating effect of the deposited ssDNAs. We conduct a systematic study of this ssDNAinduced gating effect with different base sequences, concentrations, and lengths of molecules, leading to extraction of characteristic parameters of the graphene FET accordingly.
KEYWORDS: Graphene, Sensors, Principal component analysis, Humidity, NOx, Carbon monoxide, Molecules, Gas sensors, Field effect transistors, Chemical fiber sensors
Graphene is a promising material for vapor sensor applications because of its potential to be functionalized for specific chemical gases. In this work, we present a graphene gas sensor that uses single-stranded DNA (ssDNA) molecules as its sensing agent. We investigate the characteristics of graphene field effect transistors (FETs) coated with different ssDNAs. The sensitivity and recovery rate for a specific gas are modified according to the differences in the DNA molecules’ Guanine (G) and Cytosine (C) content. ssDNA-functionalized devices show a higher recovery rate compared to bare graphene devices. Pattern analysis of a 2-by-2 sensor array composed of graphene devices functionalized with different-sequence ssDNA enables identification of NH3, NO2, CO, SO2 using Principle Component Analysis (PCA).
The current study describes metal ion sensing with double crossover DNAs (DX1 and DX2), artificially designed as a platform of doping. The sample for sensing is prepared by a facile annealing method to grow the DXs lattice on a silicon/silicon oxide. Adding and incubating metal ion solution with the sensor substrate into the micro-tube lead the optical property change. Photoluminescence (PL) is employed for detecting the concentration of metal ion in the specimen. We investigated PL emission for sensor application with the divalent copper. In the range from 400 to 650 nm, the PL features of samples provide significantly different peak positions with excitation and emission detection. Metal ions contribute to modify the optical characteristics of DX with structural and functional change, which results from the intercalation of them into hydrogen bonding positioned at the center of double helix. The PL intensity is decreased gradually after doping copper ion in the DX tile on the substrate.
Surface-enhanced Raman scattering (SERS) has attracted considerable attention for chemical and biological agent detection through
the amplification of electromagnetic fields from localized surface plasmon resonance on a metal nanostructure. The fabrication of
metal nanostructure is the key issue for applications of SERS substrate. Particularly, well-ordered noble metal nanodot array can be
reproducibly fabricated using anodic aluminum oxide layer with uniform channels of nanometer dimensions. In this study, we report
the fabrication of Ag nanodot array on indium-tin-oxide (ITO) glass via the nanoporous alumina mask with through-holes and the
utilizing the array as a substrate for SERS application. Ag nanodot array with 55 nm diameter was fabricated in periodic pattern with
separation distance of 105 nm as a replica of the alumina mask. Optical property of Methylene Blue adsorption on Ag nanodot array
was examined by Raman spectroscopy. These results suggest that Ag nanodot array might be useful as a SERS platform for the future
application in sensitive detection of chemical materials.
We present polarization-sensitive full-field optical coherence tomography (PS-FF-OCT), which is based on a bi-stable polarization switch (BSPS) device. The proposed PS-FF-OCT is a Linnik type interferometer, and allows getting both the birefringence-induced phase retardation and the intensity images of specimens with high resolutions using a pair of micro objectives and a BSPS device. Two orthogonal polarization states are formed with a regular time interval by the BSPS device that changes the polarization direction of light in a short time by switching its optic axes. Therefore, both the horizontally polarized light signal and the vertically polarized light signal from the sample can be detected with a single CCD camera. For getting a phase retardation image in real-time, the BSPS device is phase-locked with the CCD camera. The proposed method makes easy implementation of the PS- FF-OCT system without the needs of complex alignment process of using two identical CCD cameras. The experimental results confirm the feasibility of the system.
For the faster switching speed and the lower power consumption, we optimized the structure of a fully depleted optical thyristor (DOT) by the depletion of charge at the lower negative voltage. The fabricated optical thyristor shows sufficient nonlinear s-shape I-V characteristics with the switching voltage of 2.85 V and the complete depletion voltage of -8.73 V. In this paper, using a finite difference method (FDM), we calculate the effects of parameters such as doping concentration and thickness of each layer to determine the optimized structure in the view of the fast and low-power-consuming operation.
We present mushroom-type TWEAM, which has improved velocity mismatch, with optimized impedance match compared to conventional modulators by reducing the distance between signal and ground metal line. In this paper, the layer structure of mushroom-type TW MQW EAM is designed for the operation of 1.55 um and optical index of active layer is designed to be 3.6. Also, we simulate an 1.55 um InGaAs/InGaAsP traveling-wave multiple quantum well electro- absorption modulator using 3D Finite Difference Time Domain method. Also, we investigate microwave characteristics in detail.
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