Monte Carlo Model for Studying the Effects of Melanin Concentrations on Retina Light Absorption

We developed a Monte Carlo model to calculate light absorption in human and mouse retinas. The retina was modeled as a five-layer spherical structure. The effects of melanin concentrations in the retinal pigment epithelium (RPE) and choroid layer were studied. Variations of blood content in choroid were also considered in the simulation. Our simulation results indicated that light absorption in neural retina was at least 20% higher in albino subjects than in pigmented subjects under both photobleaching and dark-adapted conditions. It can be four times higher at optical wavelengths corresponding to minimal hemoglobin absorption. The elevated absorption at neural retina was attributed to the light backscattered from the choroid and sclera layers. This simulation model may provide useful information in studying light-induced retina damage

Grain Pattern Characterization and Classification of Walnut by Image Processing

Grain pattern is an important characteristic of wood materials and it is usually assessed visually by trained workers. This paper presents results from a study to characterize walnut grain patterns by using image processing techniques. Grain streaks of the annual growth rings were segmented and labeled in walnut surface images. Grain pattern features were computed for each streak. The average elongation and average local contrast were used to classify 48 walnut samples into three visual grades. Three types of classification techniques were tested: linear discriminant analysis, quadratic discriminant analysis, and neural network classification. A hold-one-out procedure yielded correct classification rates of 71.4%, 61.9%, and 69.0%, respectively. The results establish the potential usefulness of image processing techniques in wood grain characterization and grading

On the Potential Usefulness of Fourier Spectra of Delayed Fluorescence from Plants

Delayed fluorescence (DF) from photosystem II (PSII) of plants can be potentially used as a biosensor for the detection of plant physiological status and environmental changes. It has been analyzed mainly in the time domain. Frequency-domain analysis through Fourier transform allows viewing a signal from another angle, but the usefulness of DF spectra has not been well studied. In this work, experiments were conducted to show the differences and similarities in DF spectra of different plants with short pulse excitation. The DF spectra show low-pass characteristics with first-order attenuation of high frequencies. The results also show that the low-frequency components differ while the high-frequency components are similar. These may imply the potential usefulness of Fourier spectra of DF to analyze photoelectron transport in plants and classify samples

Applications of Delayed Fluorescence from Photosystem II

While photosystem II (PSII) of plants utilizes light for photosynthesis, part of the absorbed energy may be reverted back and dissipated as long-term fluorescence (delayed fluorescence or DF). Because the generation of DF is coupled with the processes of forward photosynthetic activities, DF contains the information about plant physiological states and plant-environment interactions. This makes DF a potentially powerful biosensing mechanism to measure plant photosynthetic activities and environmental conditions. While DF has attracted the interest of many researchers, some aspects of it are still unknown because of the complexity of photosynthetic system. In order to provide a holistic picture about the usefulness of DF, it is meaningful to summarize the research on DF applications. In this short review, available literature on applications of DF from PSII is summarized

Modeling and simulation of phototransduction cascade in vertebrate rod photoreceptors

Abstract Background The activation of phototransduction cascade in rod photoreceptors has been well studied in literature, but there is a lack of a mature kinetic model structure covering both the activation and inactivation processes. Methods In this work, a kinetic model structure is developed to describe the major activation and inactivation processes in vertebrate rod photoreceptors with the electroretinogram (ERG) as output. Simulation was performed to validate developed model structure. Results The developed model structure could fit experimental data with small error. Conclusions The result indicated that the developed model structure could show the inactivation process of phototransduction cascades in the rod photoreceptors

Method and apparatus for plant drought stress management [abstract]

Physiologically based drought stress evaluation is desirable for sustainable biomass production and irrigation, but effective measurements and technologies are lacking. The present invention provides a method and apparatus to measure water deficiency (drought) by the primary physiological function of water, electron donation in photosystem II (PSII). Delayed fluorescence (DF) is measured as an output variable of the PSII phototransduction system and its dependence on the availability of electron donors (water) is modeled and analyzed. This yields an effective and immediate method to define and measure water availability or, conversely, the water deficiency (drought stress) according to the PSII photoelectron generation efficiency. Water deficiency is determined by the deficit from the maximum photoelectron generation efficiency available. Potential Areas of Applications: * Effective tool for irrigation optimization * Plant drought research Inventor(s): Jinglu Tan and Ya Guo Contact Info: Dr. Wayne McDaniel, Ph.D. ; [email protected] ; 573-884-330