Elasticity of blood vessels makes them contract or dilate in regulating the body temperature to changes in external temperature changes such as air-conditioning. However, ageing makes them gradually lose elasticity, making it difficult for blood vessels to make adjustments. In this study, we propose the use of biospeckle Optical Coherence Tomography (b-OCT) to visualize the dynamic changes within the skin. A total of 20 subjects with equal number of male and female particpants with ten in their 20’s and the other ten subjects in their 30’s or older were subjected to heating of the palmar forearm of their dominant hand by a USB hot pad (40°C) for five minutes. A swept source OCT (SS-OCT) operating with a central wavelength of 1310nm, a bandwidth of 125 nm and a sweep frequency of 20kHz was used to obtain OCT structural images at 12fps. From the OCT structural images obtained before and after heating, biospeckle contrast was calculated from the temporal variation in the images and compared. Biospeckle contrast results were compared for the depth, gender, and age differences. With heating, a clear difference of increased contrast was observed at shallower depths in comparison to deeper regions for both genders, while, as a whole, a larger contrast difference was observed for male in comparison to female participants. Furthermore, in the age group larger than 30, the contrast change with change in environment was smaller, suggesting the loss of elasticity to adjust to the environmental changes.
In recent years, ultraviolet (UV) light therapy has been attracting attention as a treatment method for skin diseases such as atopic dermatitis, vitiligo, and psoriasis which have been considered difficult to treat. However, regarding the research on treatment, clinical studies have been the main research focus without much in-depth consideration into the radiative properties of UV light within the skin. Therefore, it is essential to know the optical properties, scattering and absorption coefficients, of the skin in the UV wavelength range to improve the treatment strategy. Our group has been developing a non-invasive method, reflection spatial profile method (RSPM), for measuring optical properties of skin and elucidated optical property differences arising out of cancer drugs[1]. In this study, we have developed a novel system that operates in the range of UV wavelengths irradiating the skin with a structured incoherent source and detecting the reflected light with a CCD camera. Measurements are being conducted with human subjects of different age groups. Based on results obtained from the forearm and hand measurements of 76 subjects consisting of 31 males and 45 females in their 20s~30s. UV light penetration depth can be estimated from the optical properties obtained. It was found that the amount of light absorption can vary up to 1.5 times at the same depth depending on gender, age, and site.
Microplastic pollution has become prevalent due to industrialization and the wide use of plastic. In this study, the individual and combined effects of polyethylene microplastic with Zn on lentil seed germination were monitored using Biospeckle Optical Coherence Tomography (bOCT), a technique established by authors to visualize the internal activity of biological objects. The results imply that both 100 mg L-1 heavy metal Zn or polyethylene microplastics (PEMPs) alone had a strong inhibitory effect on lentils. However, in combination with PEMPs, the Zn toxicity on lentils was reduced due to the reduction of Zn uptake by the seedlings through the interaction of Zn and MPs. These findings suggest that PEMPs could be able to mitigate the effect on the bioavailability and toxicity of Zn on lentils.
While artificial cultivation is gaining prominence due to rapid climate change, lighting costs remain a challenge. Therefore, research is needed to cultivate plants more efficiently. At the same time, it has been found that a mixture of far-red light (FR) and red light (R) also promotes growth through the action of phytochrome, a photoreceptor in the plant body. However, these studies require time and damaging of the plant to measure the dry mass and area of leaves, and immediate effects have not been investigated so far. Therefore, in this study, we propose laser biospeckle to evaluate the relationship between plant growth duration and FR response. Laser biospeckles are formed by light scattered from organelles in plant tissues by laser irradiation. The intensity of these speckles changes with time, and by examining these changes, the activity inside the plant can be evaluated. Biospeckles of arugula leaves were obtained by irradiating the leaves with laser light of wavelength 852 nm and simultaneously with LED light of wavelength 735 nm (FR) and 630 nm (R). Biospeckle movies under FR and non-irradiation were recorded by a CMOS camera at 15 frames/sec for 20 seconds. From the movie, correlation between the first frame and the subsequent frames were calculated. Experimental results showed that arugula at 1-month after seed planting showed an immediate FR response, while those at 3-month showed a sustained response. The relationship between biospeckle movement and plant growth behaviour is under investigation.
Recently, the pollution caused by various hazardous chemicals has become a very serious problem. Currently, 200 million kinds of chemical substances are registered, and it is technically and costly very difficult or even impossible to analyse, identify each chemical individually and then evaluate their toxicity on the environment. On the other hand, bioassay has been getting a lot of attention where the toxicity of environmental toxicity is assessed based on the reaction of micro-organisms such as plankton without identifying each chemical individually. For this technique, a microscope observation is required to obtain critical features such as alive/dead status and swimming ability. With smaller microorganisms, microscope observation becomes more difficult due to the narrower focal depth of the imaging system. In our study, to overcome these difficulties, we proposed a novel technique for the micro-bioassay utilizing laser biospeckle in the diffraction field generated from plankton. Paramecium chilomonas of size 30-40 µm was exposed to different pH conditions from control 7.2 to gradually decreasing by 0.5 till 3.7. Results reveal the sensitivity of laser biospeckles in detecting the subtle changes in the swimming behavior, the health of the microbe with change in pH suggesting the potential for fast assessment the toxicity of an environment.
Heavy metals are one of the important components of water pollution. Heavy metals such as copper, zinc and cobalt are essential for the growth of living organisms as micronutrients. However, copper above critical levels can pose serious problems for the environment and human health. The biospeckle observed in OCT have the potential to map dynamic activities inside the plants. We propose biospeckle optical coherence tomography (bOCT) and demonstrate that the technique can monitor biological activity in plants. In bOCT, the temporal speckle contrast variation of the OCT reflection signal is used as a parameter to characterize the internal activities of the aquatic plant (Myriophyllum). Plant stems were observed using the bOCT technique after 7 days of exposure to copper solutions of three different copper concentrations to 0, 30, 100 mg/l. In addition, statistical Interferometry Technique (SIT) system that is also a very sensitive optical measurement technique developed in our lab. SIT enables the direct observation of short-term displacement or extension / shrinkage of plant surface with precision of nanometer scale and on a time scale of seconds. Compared with the bOCT technique, it takes short time. It does not require 7 days of exposure time. In just 3 hours of experiment time, we observed that the plants were receiving heavy metal stress in the copper solution. Under the same heavy metal exposure conditions (7 days), enzyme activities in plants were also measured and analyzed to demonstrate the reliability of our two laser measurement techniques. It can be seen that the increase of copper solution has a significant effect on the activity of plants. It was not possible to observe the effects of 7 days of heavy metal exposure on plants by measuring their length or the color of their leaves. Compared with traditional bioassay methods, SIT technology is the fastest, followed by bOCT technology. Both technologies are advanced and can be used as a new method for the determination of plant bioactivity.
Acid mine drainage (AMD) is generated during the mineral extraction process. AMD contaminates farmland and rivers, so it makes sense to study the effects of AMD on crops. Since the conventional methods for studying plant responses to environmental stress are damaging and time-consuming, we propose the Biospeckle OCT (bOCT) method to evaluate the response of plants to AMD in a rapid and non-invasive way. In this study, we selected rice plant and soybean as experimental subjects. The seeds were exposed to 40 and 80 ml/L of simulated AMD solution, and the seed condition was monitored by bOCT. OCT images of the seeds were obtained at a speed of 10 frames per second for a few tens of seconds. For each pixel of the OCT structural images, the contrast across the temporal axis was calculated to give bOCT images. Meanwhile, we measured the root shoot length of rice and soybean after growing in AMD as a comparison. It was found that bOCT images clearly distinguished the changes in biological activities of seeds due to 40 and 80 ml/L of AMD treatments from those of control within much shorter time, 48 hours and 72 hours for soybean and rice, respectively, compared to the conventional method that failed to show any changes within the same time. And The seedling growing status of soybean and rice after 7 and 10 days showed the same trend as the bOCT results, respectively. This suggests that the proposed bOCT method can reveal the different responses of soybean and rice to different concentrations of AMD at a very early stage. This technique may be able to provide a reference indicator for studying plant response to environmental stress, and it is efficient and non-invasive.
Seed germination rate and seedling growth differ based on environmental factors requiring non-invasive and non-contact seed screening techniques in agriculture. Moreover, the widespread usage and mismanagement of plastics have led to significant environmental problems affecting seed germination and seedling growth. Recently the attention of seed scientists and other biologists has been paid to optical sensing technologies-based measurements to observe the quality of seeds owing to the non-destructive and non-invasive detection capabilities. Moreover, the vigor of seeds is directly affected the crop yield. Therefore, here we propose to employ Biospeckle Optical Coherence Tomography (bOCT) in investigating the effect of polyethylene microplastics (PEMPs) on lentil seed germination. bOCT is a non-contact, nondestructive in vivo monitoring technique to visualize the change of internal activity of a biological object. Lentil seeds were exposed to PEMPs for 24 h bioassay with 10, 50, and 100 mg/L concentrations. The average speckle contrast was calculated after 0, 6, 12, and 24 h of exposure and statistically significant differences in bOCT contrast for all the treatments were observed just after 6 h of exposure. Thus, the results of the present study revealed that the presence of PEMPs significantly reduced the internal activity at the initial stages that could be visualized only because of the use of bOCT, in the early stage prior to the germination. Furthermore, this might be utilized as a trustworthy seed screening tool in the seed industry, which could save the screening time significantly compared to traditional approaches while assessing environmental pollution.
Sound has been established to play an essential role in plant growth. Sound of a particular frequency has been proven to increase yield and immunity. In this study, we have considered the possibility of functional Optical Coherence Tomography (fOCT) in investigating the changes in the internal structures in response to sounds of different frequencies, 100 Hz and 10kHz. Results showed a clear dependence of the fOCT signal on the sound frequency, with 100 Hz showing an increase while 10kHz showing a decrease. Our results extend the possibility of the application of OCT to the field of plant photonics.
Existing method of surveying supermicroplastics (fragments ≤ 350 µm) in sea remains a challenge. To this end, we propose a new method based on laser speckles and two submersible spheres. In simulation experiments, a 630 nm laser illuminated a cuvette containing polystyrene particles and zooplanktons producing speckles recorded by a CMOS camera. Speckles were analyzed to discriminate different sized polystyrene spheres (2 μm, 20 μm and 200 μm) and zooplanktons. As discrimination algorithms, difference of subsequent frames of the speckle movie and deep learning were investigated. Deep learning was found to be capable of distinguishing speckles from different particle sizes.
Statistical interferometer technique (SIT) is a highly sensitive optical interferometer developed by us capable of measuring sub-nanometer displacements and when applied to plant growth studies revealed nanometric intrinsic fluctuations (NIF). NIF observed in minimum time scale of several tens of seconds is strongly influenced by the environmental conditions. Our earlier experiments with rice under ozone or heavy metal stress, such as cadmium even for a short duration of one hour decreased NIF. In contrast, having a micronutrient, such as zinc increased NIF. Therefore, presence of NIF is found to be a novel phenomenon characterizing plant condition that could appear only under sub-nanometric measurement. In this study, we report the effects of adding a plant growth hormone called auxin. Roots of rice seedlings were exposed to auxin solutions of different concentrations of 0, 1, and 4 μM for 24 hours. Significant increment was seen in NIF for a concentration of 1 μM while a significant reduction was seen in NIF for 4 μM within an hour after immersion of the roots. Application of an inhibitor to auxin called TIBA also resulted in almost immediate reduction of NIF. Current results suggest for NIF affected by the enodgenous hormones to be related to growth, as the action of a growth-related endogenous hormone auxin is chemically inactivated. Thus, NIF not only could be applied to investigate and speedily assess the effects of environmental agents on plant elongation or shrinkage but also could be implicated as one of the possible mechanisms for the origin of NIF itself.
In recent years, it has been found that sound also has effect on plant growth and its yield with certain sound directing the seedling of corn toward the sound source and its ability in distinguishing stuttering of larvae from other sounds. However, methods investigating the effects of sound either take a long time or destructive. Here, we have used laser biospeckle, a non-destructive and non-contact technique to investigate the activities of an arugula plant (2-4 weeks old) under sounds of different frequencies of 0 Hz or control, 100 Hz, 1 kHz, 10 kHz. Laser biospeckle has been proved to be valid for investigating the aging of fruits, believed to be due to the movement of water, organelles etc.. Biospeckle activities were recorded for 20 sec at 15 fps following exposure to sounds for 1min. The correlation parameter (r) of biospeckle activity was used to characterize the activity of the plant with r being 1 for highly active and 0 for reduced plant activity. Sound level of 100 dB was the same for all frequencies. There was a clear difference in r between the control and other frequencies and r was lower than that of control indicating a reduction in the activity. Moreover, r for 100 Hz was found to be closer to control while at higher frequencies, r was much lower indicating a dependence of the activity on the frequency.
Using statistical interferometry technique (SIT), a highly sensitive interferometry technique developed in our laboratory, we reported about the existence of nanometric intrinsic fluctuations (NIF) in a variety of plants. SIT permits noncontact, noninvasive, and fast detection of plant growth fluctuations in subnanometer scale. We propose the application of NIF to investigate the effect of heavy metal, cadmium, on growth dynamics of Chinese chive (Allium tuberosum). NIFs of leaves were observed for 3 days under four different concentrations of CdCl2: 0, 0.001, 0.01, and 0.1 mM. Results showed significant reduction of NIFs within 4 h for all Cd concentrations, and there was a further decrease with the exposure time of Cd under 0.1 and 0.01 mM. In addition, under 0.001 mM, a significant recovery could be observed after a rapid reduction in the first 4 h. As a comparison, measured antioxidative enzymes increased with increasing Cd concentration. However, no significant increase could be seen within the initial 4 h under a smaller concentration of 0.001 mM as seen for NIFs. The results imply that NIF can be used as an indicator for heavy metal stress on plants as well as it can be more sensitive to detect the influence of smaller Cd amounts on plants at an early stage.
KEYWORDS: Ozone, Optical coherence tomography, Coherence imaging, Ions, Mirrors, Imaging systems, Data acquisition, Humidity, In vivo imaging, Signal detection
In this study, Optical Coherence Tomography (OCT) was used to investigate the effect of short term ozone exposure
on both front and back surfaces of the leaves of Allium tuberosum plant. Plant leaves were subjected to treat with
240ppb level of ozone, and imaging data were acquired from back and front surfaces of the leaves. Variations of the
biological activations were monitored based on the biospeckles. Standard deviations (SD) of OCT temporal signal at
each point were calculated and used to visualize the effect of ozone exposure. Leaf back surface showed higher SDs in
biospeckle OCT signal in comparison to these of the front surface. These observations prove that the short term
ozone stress on plant can be investigated successively with biospeckle OCT imaging technique.
Optical intrinsic signal imaging (OISI) provides the surface activation map of brain and has provided many insights. In this study, we show that the optical coherence tomography (OCT) can indeed provide depth resolved functional map of cat visual cortex. Activation profile obtained by integrating OCT signal across depth correlates well with that determined by the OISI. Functional OCT (fOCT) promises to be a valid technique for revealing unexplored organization inside the brain at a micro system level.
We report the application of Optical coherence tomography (OCT) for visualizing a one dimensional depth resolved functional structure of cat brain in vivo. The OCT system is based on the known fact that neural activation induces structural changes such as capillary dilation and cellular swelling. Detecting these changes as an amplitude change of the scattered light, an OCT signal reflecting neural activity i.e., fOCT (functional OCT) could be obtained. Experiments have been done to obtain a depth resolved stimulus-specific profile of activation in cat visual cortex. Our results in one dimension indicate that indeed an orientation dependent functional signal could be obtained. Further, we show that this depth resolved fOCT signal is well correlated with the stimulus dependent column determined by OISI. Based on the results, the smallest functional unit in depth, resolved by the proposed system is around 40 micrometers . We are extending our system to perform two dimensional functional imaging.
We propose a optical coherence tomographic (OCT) system for imaging functional organization of brain. To enhance the reflectivity of OCT signal, simulation studies have been done with iron particles as the tracer elements. It has been found that by proper choice of the size of the particles, the OCT signal can be greatly enhanced.
We present the observation results of a single string DNA (deoxy ribo nucleic acid) obtained by collection mode near- field optical microscopy operated under constant distance mode with the optical near field intensity as the feedback signal. The observed width of the narrowest string is 4 nm. To our knowledge, this is not only the successful optical observation of a single string DNA by purely optical means but also under such high resolving capability. These are attributed to the special care taken during the sample preparation to avoid unwanted scattered light and to the probe which were specially designed to enhance the local near field interaction. All these factors make the probe picks up efficiently the high spatial frequency components of the scattered near field at the same time rejecting effectively the lower spatial frequency components.
In spite of the very wide applications of a near-field optical microscope (NOM) in various fields such as observation of biological specimens, optical storage etc. [1,2], a systematic analysis of the images with respect to resolution and contrast is lacking. In this work using 20 nm gold particles (calibrated by electron microscope) fixed on a glass plate as the observation object, we have evaluated the transfer function of NOM.
In this presentation, we describe about the high resolution imaging of flagellar filaments of a salmonella with a diameter of 25 nm by a photon scanning tunneling microscope (PSTM). In our PSTM system, we have used a metal coated fiber probe with a nanometric dielectric protrusion fabricated by indigenous technique developed by us. By using this probe, flagellar filaments could be imaged as having a full width at half maximum of 50 nm. Obtained images strongly depended on the separation of the sample and to the probe, and the diameter of the aperture polarization of the irradiated light.
A theoretical and experimental investigation on the far-field diffraction patterns of a dot array with Gaussian random fluctuations has been done quantitatively by means of a generalized fluctuation parameter. It has been found that the exposure condition strongly influences the nature of the observed photographic pattern and hence the observation of the light-depletion phenomenon first reported by Stark and later, analyzed by Martin and Aime.
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