Site-specific Irradiation Research Articles

Automatic Identification and Monitoring of Plant Diseases Using Unmanned Aerial Vehicles: A Review

Disease diagnosis is one of the major tasks for increasing food production in agriculture. Although precision agriculture (PA) takes less time and provides a more precise application of agricultural activities, the detection of disease using an Unmanned Aerial System (UAS) is a challenging task. Several Unmanned Aerial Vehicles (UAVs) and sensors have been used for this purpose. The UAVs’ platforms and their peripherals have their own limitations in accurately diagnosing plant diseases. Several types of image processing software are available for vignetting and orthorectification. The training and validation of datasets are important characteristics of data analysis. Currently, different algorithms and architectures of machine learning models are used to classify and detect plant diseases. These models help in image segmentation and feature extractions to interpret results. Researchers also use the values of vegetative indices, such as Normalized Difference Vegetative Index (NDVI), Crop Water Stress Index (CWSI), etc., acquired from different multispectral and hyperspectral sensors to fit into the statistical models to deliver results. There are still various drifts in the automatic detection of plant diseases as imaging sensors are limited by their own spectral bandwidth, resolution, background noise of the image, etc. The future of crop health monitoring using UAVs should include a gimble consisting of multiple sensors, large datasets for training and validation, the development of site-specific irradiance systems, and so on. This review briefly highlights the advantages of automatic detection of plant diseases to the growers.

Irradiance, photosynthesis and elevated pCO2 effects on net calcification in tropical reef macroalgae

Calcifying tropical macroalgae produce sediment, build three-dimensional habitats, and provide substrate for invertebrate larvae on reefs. Thus, lower calcification rates under declining pH and increasing ocean pCO2, or ocean acidification, is a concern. In the present study, calcification rates were examined experimentally under predicted end-of-the-century seawater pCO2 (1116 μatm) and pH (7.67) compared to ambient controls (pCO2 409 μatm; pH 8.04). Nine reef macroalgae with diverse calcification locations, calcium carbonate structure, photophysiology, and site-specific irradiance were examined under light and dark conditions. Species included five from a high light patch reef on the Florida Keys Reef Tract (FKRT) and four species from low light reef walls on Little Cayman Island (LCI). Experiments on FKRT and LCI species were conducted at 500 and 50 μmol photons m−2 s−1 in situ irradiance, respectively. Calcification rates independent of photosystem-II (PSII) were also investigated for FKRT species. The most consistent negative effect of elevated pCO2 on calcification rates in the tropical macroalgae examined occurred in the dark. Most species (89%) had net calcification rates of zero or net dissolution in the dark at low pH. Species from the FKRT that sustained positive net calcification rates in the light at low pH also maintained ~30% of their net calcification rates without PSII at ambient pH. However, calcification rates in the light independent of PSII were not sustained at low pH. Regardless of these low pH effects, most FKRT species daily net calcification rates, integrating light/dark rates over a 24h period, were not significantly different between low and ambient pH. This was due to a 10-fold lower dark, compared to light, calcification rate, and a strong correspondence between calcification and photosynthetic rates. Interestingly, low-light species sustained calcification rates on par with high-light species without high rates of photosynthesis. Low-light species' morphology and physiology that promote high calcification rates at ambient pH, may increase their vulnerability to low pH. Our data indicate that the negative effect of elevated pCO2 and low pH on tropical macroalgae at the organismal level is their impact on dark net calcification, probably enhanced dissolution. However, elevated pCO2 and low pH effects on macroalgae daily calcification rates are greatest in species with lower net calcification rates in the light. Thus, macroalgae able to maintain high calcification rates in the light (high and low irradiance) at low pH, and/or sustain strong biotic control with high [H+] in the bulk seawater, are expected to dominate under global change.

MoS2 Memtransistors Fabricated by Localized Helium Ion Beam Irradiation.

Two-dimensional (2D) layered semiconductors have recently emerged as attractive building blocks for next-generation low-power nonvolatile memories. However, challenges remain in the controllable fabrication of bipolar resistive switching circuit components from these materials. Here, the experimental realization of lateral memtransistors from monolayer single-crystal molybdenum disulfide (MoS2) utilizing a focused helium ion beam is reported. Site-specific irradiation with the focused probe of a helium ion microscope creates a nanometer-scale defect-rich region, bisecting the MoS2 lattice. The reversible drift of these defects in the applied electric field modulates the resistance of the channel, enabling versatile memristive functionality. The device can reliably retain its resistance ratios and set/reset biases for 1180 switching cycles. Long-term potentiation and depression with sharp habituation are demonstrated. This work establishes the feasibility of ion irradiation for controllable fabrication of 2D memristive devices with promising key performance parameters, such as low power consumption. The applicability of these devices for synaptic emulation may address the demands of future neuromorphic architectures.

Generation of spatially dispersed irradiance time-series based on real cloud patterns

Clouds, being complex components of the atmosphere, have significant effects on power generation by photovoltaic (PV) systems. For example, shadows caused by the cloud coverage over a geographically distributed PV power plant may cause significant fluctuations in power generation by leaving a number of PV panels unable to generate power and contribute to power generation by the plant at each time instant. Thus, investigation of the mentioned effects on PV power generation requires realistic spatial irradiance information. Such information should be evaluated based on the existing real cloud coverage and its light transmission characteristics. This also provides the opportunity to select appropriate coping strategies against the mentioned negative effects of partial shading on PV plant’s power output. This paper presents a modeling approach which generates Spatially Dispersed Irradiance Profiles (SDIPs) for PV arrays based on existing cloud patterns derived from local sky images taken at the application sites. The model gets the direct, diffuse and global irradiance values incident on a horizontal surface, which are primarily obtained utilizing a solar irradiance model (the Morf (2013) model), along with local sky images captured at the application sites and cloud transmittance values, as input data and yields site-specific Spatially Dispersed Irradiance Profiles (SDIPs) incident on the surface of inclined PV panels within PV application areas, as a result of process of the inputs. Utilization of local sky images and cloud transmittance values for different cloud types creates the opportunity for precise analysis of interactions of sunlight with the existing cloud type and hence, obtaining unique and site-specific irradiance profiles according to the existing cloud type and distribution in the sky. The model firstly detects the cloudy and clear-sky parts in the sky image and then instantly utilizes the most appropriate ellipse on the cloud layer associated with each solar panel through which the beam irradiance is received by the panel. The model also considers the light transmission characteristics of different cloud types as the parameter affecting the beam irradiance. The diffuse and ground-reflected irradiance components are assumed to be spatially constant and thus identical for all solar panels. Cloud base heights, as provided in the International Cloud Atlas (1987), are also utilized to calculate the ground area covered by each sky image. Daily irradiance sequences for different observation points in a PV array are simulated under partly cloudy sky conditions using a set of sky images and utilized for validation purpose of the proposed algorithm. It is demonstrated that instantaneous irradiance values, as well as daily irradiance sequences, differ from point to point in a geographically distributed PV application site depending on the distribution of clouds in the sky. The mentioned variable characteristic of the irradiance sequences received at different observation points, as well as the model’s capability to reflect the mentioned variabilities, is verified using irradiance data derived from satellite observations. The performance of the proposed model is validated using variability index (VI) metric as a measure of irradiance variability during a day. The modeled VI values are validated against the measured VI values for a reference point located at the center point of the generated irradiance profiles. Daily VI values calculated for both measured and simulated 1-min global horizontal irradiance (GHI) data are compared for a population of totally 117 days during April – August time period. The results of comparison show statistics of mean bias error (MBE) of 0.16, root mean square error (RMSE) of 2.394, correlation coefficient of 0.94 and mean absolute error (MAE) of 1.91. The validation results demonstrate capability and accuracy of the proposed model for estimation of irradiance values under cloudy sky conditions.

Fluorescence imaging of reactive oxygen species byconfocal laser scanning microscopy for track analysis of synchrotron X-ray photoelectric nanoradiatordose: X-ray pump-optical probe.

Bursts of emissions of low-energy electrons, including interatomic Coulomb decay electrons and Auger electrons (0-1000 eV), as well as X-ray fluorescence produced by irradiation of large-Z element nanoparticles by either X-ray photons or high-energy ion beams, is referred to as the nanoradiator effect. In therapeutic applications, this effect can damage pathological tissues that selectively take up the nanoparticles. Herein, a new nanoradiator dosimetry method is presented that uses probes for reactive oxygen species (ROS) incorporated into three-dimensional gels, on which macrophages containing iron oxide nanoparticles (IONs) are attached. This method, together with site-specific irradiation of the intracellular nanoparticles from a microbeam of polychromatic synchrotron X-rays (5-14 keV), measures the range and distribution of OH radicals produced by X-ray emission or superoxide anions ({\rm{O}}_2^-) produced by low-energy electrons. The measurements are based on confocal laser scanning of the fluorescence of the hydroxyl radical probe 2-[6-(4'-amino)phenoxy-3H-xanthen-3-on-9-yl] benzoic acid (APF) or the superoxide probe hydroethidine-dihydroethidium (DHE) that was oxidized by each ROS, enabling tracking of the radiation dose emitted by the nanoradiator. In the range 70 µm below the irradiated cell, ^\bullet{\rm{OH}} radicals derived mostly from either incident X-ray or X-ray fluorescence of ION nanoradiators are distributed along the line of depth direction in ROS gel. In contrast, {\rm{O}}_2^- derived from secondary electron or low-energy electron emission by ION nanoradiators are scattered over the ROS gel. ROS fluorescence due to the ION nanoradiators was observed continuously to a depth of 1.5 mm for both oxidized APF and oxidized DHE with relatively large intensity compared with the fluorescence caused by the ROS produced solely by incident primary X-rays, which was limited to a depth of 600 µm, suggesting dose enhancement as well as more penetration by nanoradiators. In conclusion, the combined use of a synchrotron X-ray microbeam-irradiated three-dimensional ROS gel and confocal laser scanning fluorescence microscopy provides a simple dosimetry method for track analysis of X-ray photoelectric nanoradiator radiation, suggesting extensive cellular damage with dose-enhancement beyond a single cell containing IONs.

Photo-Activatable Substrates for Site-Specific Differentiation of Stem Cells.

In this report, a UV sensitive, PEGylated PFSSTKTC (Pro-Phe-Ser-Ser-Thr-Lys-Thr-Cys) peptide was modified on quartz substrate to investigate the spatial controlled differentiation of stem cells. This substrate could restrict the cell adhesion due to the steric hindrance of PEG shell. With UV irradiation, PFSSTKTC became exposed owing to the breakage of o-nitrobenzyl group with the detachment of PEG shell. The irradiation boundary on substrate was stable in the long term. The in vitro osteogenic differentiation results revealed that under the site-specific irradiation, the mesenchymal stem cells (MSCs) could specifically differentiate into osteoblast under the induction of PFSSTKTC peptide. This photoactivatable biomaterial shows great potential for region controllable and precise MSCs differentiation.

Microbeam irradiation of C. elegans nematode in microfluidic channels

To perform high-throughput studies on the biological effects of ionizing radiation in vivo, we have implemented a microfluidic tool for microbeam irradiation of Caenorhabditis elegans. The device allows the immobilization of worms with minimal stress for a rapid and controlled microbeam irradiation of multiple samples in parallel. Adapted from an established design, our microfluidic clamp consists of 16 tapered channels with 10-μm-thin bottoms to ensure charged particle traversal. Worms are introduced into the microfluidic device through liquid flow between an inlet and an outlet, and the size of each microchannel guarantees that young adult worms are immobilized within minutes without the use of anesthesia. After site-specific irradiation with the microbeam, the worms can be released by reversing the flow direction in the clamp and collected for analysis of biological endpoints such as repair of radiation-induced DNA damage. For such studies, minimal sample manipulation and reduced use of drugs such as anesthetics that might interfere with normal physiological processes are preferable. By using our microfluidic device that allows simultaneous immobilization and imaging for irradiation of several whole living samples on a single clamp, here we show that 4.5-MeV proton microbeam irradiation induced DNA damage in wild-type C. elegans, as assessed by the formation of Rad51 foci that are essential for homologous repair of radiation-induced DNA damage.

Review of therapeutic strategies for osteosarcoma, chondrosarcoma, and Ewing’s sarcoma

SummaryThe most prevalent forms of bone cancer are osteosarcoma, chondrosarcoma, and Ewing’s sarcoma. Although chemotherapy and radiotherapy have replaced traditional surgical treatments, survival rates have undergone only marginal improvements. Current knowledge of the molecular pathways involved in each type of cancer has led to better approaches in cancer treatment. A number of cell signaling molecules are involved in tumorigenesis, and specific targets have been identified based on these signal transducers. This review highlights some of the important cellular pathways and potential therapeutic targets, tumor site-specific irradiation techniques, and novel drug delivery systems used to administer these drugs.