Improving plant physiological performance and growth by increasing the efficiency of lighting systems

Plant cultivation in controlled environment has been grown considerably for commercial vegetable production in addition to research purposes in plant science. In a controlled environment, as well as in nature, light is a main factor affecting plant growth, development, and photosynthetic performance. Therefore, the yield and the quality of plant products are highly dependent on the amount of available light and its spectral composition. Light interaction with plants is not limited to photosynthesis. In addition to light intensity and quality, plants perceive also light direction which is essential in phototropic responses. Light is a major influential stimulus on plant tropisms, together with gravity force, and both compete and interact with each other. Considering plant cultivation in altered-gravity environment such as on the ISS, the moon or mars, light plays an unique role as an external stimulus in shaping the plant in a three-dimensional space through photomorphogenesis and phototropism. However, little is known about the interaction between plant tropisms, especially considering tropic responses of roots, and only recently advances in knowledge have been made thanks to the opportunities to experiment in absence of gravity on the ISS combining the use of LED technology. In this context, a deep understanding of plant responses to the different characteristics of light is needed and the peculiarities of LED technology provide promising opportunities for study and research in the field of plant science. The study and research activities carried out during this Ph.D. program were focused on plant responses to spectral composition of light by using LED technology. More specifically, the studies considered species suitable for plant production in controlled environment, with particular attention to red-leaf or reddish-leaf plants due to their contribution of antioxidant compounds to plant food. Given that the general aim of this Ph.D. was to improve plant cultivation in Space, in addition to studies specifically focused on the effect of light on plant growth, part of the research was dedicated to interactions between light and altered gravity. To perform experiments in altered-gravity conditions it was necessary to use specific facilities such as the International Space Station (ISS), the Large Diameter Centrifuge, and the Random Positioning Machine

Novel Approach to Ocular Photoscreening

Photoscreening is a technique that is typically applied in mass pediatric vision screening due to advantage of its objective, binocular, and cost-effective nature. Through the retinal reflex image, ocular alignment and refractive status are evaluated. In the USA, this method has screened millions of preschool children in the past years. Nevertheless, the efficiency of the screening has been contentious. In this dissertation, the technique is reviewed and reexamined. Revisions of photoscreening technique are developed to detect and quantify strabismus, refractive errors, and high-order ocular aberrations. These new optical designs overcome traditional design deficiencies in three areas: First, a Dynamic Hirschberg Test is conducted to detect strabismus. The test begins with both eyes following a moving fixation target under binocular viewing, and during the test each eye is designed to be unconscientiously occluded which forces refixation in strabismus subjects and reveals latent strabismus. Photoscreening images taken under monocular viewing are used to calculate deviations from the expected binocular eye movement path. A significant eye movement deviation from binocular to monocular viewing indicates the presence of strabismus. Second, a novel binocular adaptive photorefraction (APR) approach is developed to characterize the retinal reflex intensity profile according to the eye\u27s refractive state. This approach calculates the retinal reflex profile by integrating the retinal reflex intensity from a coaxial and several eccentric photorefraction images. Theoretical simulations evaluate the influence from several human factors. An experimental APR device is constructed with 21 light sources to increase the spherical refraction detection range. The additional light source angular meridians detect astigmatism. The experimentally measured distribution is characterized into relevant parameters to describe the ocular refraction state. Last, the APR design is further applied to detect vision problems that suffer from high-order aberrations (e.g. cataracts, dry eye, keratoconus). A monocular prototype APR device is constructed with coaxial and eccentric light sources to acquire 13 monocular photorefraction images. Light sources projected inside and along the camera aperture improve the detection sensitivity. The acquired reflex images are then decomposed into Zernike polynomials, and the complex reflex patterns are analyzed using the Zernike coefficient magnitudes

Aerospace medicine and biology: A continuing bibliography with indexes, supplement 118

This special bibliography lists 338 reports, articles, and other documents introduced into the NASA scientific and technical information system in July 1973

Ergonomics of the Operative Field in Paediatric Minimal Access Surgery

Imperial Users onl

The Distribution of Occlusal Load in the Human Mandible: A Photoelastic Study

This study is an investigation of the distribution of occlusal load in replicas of the dentate and edentulous human mandible by the method of three dimensional photoelastic stress analysis. The study was stimulated by an interest in the occlusion of the teeth and in the relationship between disorders of the occlusion and the development of pain or dysfunction in the stomatognathic system. A further interest was in the association of faults in the design of complete dentures with pain in the oral tissues underlying the denture base. The distribution of load in any bone is related to the form and structure of the bone and to the type of loading to which the bone is normally subjected. The anatomical and biomechanical techniques which may be used to investigate these factors were developed for the study of the long bones of the limbs and in particular for the study of the human femur. The methods have been outlined, their limitations highlighted and their results compared. The general agreement of the results is quite striking. The application of these methods to the structural analysis of the human mandible has demonstrated the way in which the bone is reinforced to meet the loads imposed by masticatory function. Relatively few studies have been reported in which the hypotheses developed from anatomical investigations have been tested by other methods. Photoelastic stress analysis was selected as a method which would provide a visual demonstration of the distribution of load in the mandible and which offered the additional benefit that stresses could be studied in sections cut from the photoelastic models. As one of the interests in this study was the distribution of load in replicas of the edentulous mandible when load was applied in a number of different ways to a mandibular complete denture base, the theories of complete denture design have been reviewed, with emphasis on the relationship between the design of the dentures and the transmission of forces to the underlying tissues. The anatomy of the mandible and of the muscles of mastication and the temporo-mandibular joint has also been described. In order to relate the experimental procedures in this study to the clinical conditions under which load is applied to the mandible, it was necessary to construct a frame in which the photoelastic models could be supported in a position simulating centric relation of the mandible to the cranium. The lines of action of these muscles were determined by radiographic and cephalometric methods and a supporting frame was constructed to represent the base of skull, with metal struts aligned to correspond to the angulation of the muscles. While the shortcomings of this method were recognised, the model system provided adequate support for the models and no movement of the models or of the supporting elements was observed during the loading cycle. The principles of polarisation, birefringence and photoelasticity have been explained in detail. The methods of photoelastic stress analysis have been outlined, the preparation of models described and the techniques of stress freezing and three dimensional stress analysis presented. A detailed description has then been given of the preparation of photoelastic replicas of a dentate and of an edentulous human mandible. Weights were suspended from the dentate replicas to simulate bilateral loading in the molar region, loading in the incisor region and unilateral loading in the molar region. The same loads were applied to the edentulous mandible through the medium of a complete denture base. The distribution of load beneath an underextended denture base and of a subperiosteal implant were also studied. Isochromatic fringe patterns were recorded on the right and left halves of each replica and on sections cut from selected areas of the mandibular body and ramus. Isoclinics were studied in sections from the neck of the mandible. Fringe patterns in the hemisectioned specimens of the dentate and edentulous replicas were basically similar and indicated that stress had been generated in those areas of the models corresponding to the sites of major reinforcement of the structure of the mandible. Changes in the manner of loading were reflected in alterations in the pattern of stress distribution which suggested that greater stresses were transmitted to the condylar region when load was applied in the incisor region or when unilateral loading was used. Sections through the edentulous models suggested that when the experimental conditions were in accord with accepted principles of complete denture construction, load was distributed to the outer portion of the model, corresponding to the thickened cortical areas of the mandible. The simulation of occlusal faults and the use of an underextended denture base produced unfavourable distribution of load and provided experimental confirmation of accepted techniques of complete denture construction. A strain gauge study was then undertaken to confirm the results of the photoelastic method and a study of the optical properties of bone was also made, which suggested that a pattern of birefringence exists in bone and that it may be modified by the application of load in a manner similar to that in which fringe patterns are generated in photoelastic models

Light Microscopy of Proteins in Their Ultrastructural Context

Fluorescence light microscopy is an essential tool in biomedical research. In immunofluorescence, fluorophore-conjugated antibodies are used to detect specific proteins of interest in a fixed biological sample. With recently developed nanoscopy techniques, whole cells can be imaged at an isotropic spatial resolution of ~10 nm, revealing accurate protein distributions on the nanoscale. However, most localized proteins are imaged against a dark background, which forbids seeing the overall subcellular compartments (ultrastructural context) that encompass them. Electron microscopy (EM), on the other hand, offers a complete cellular overview on the scale of a few nanometers. However, EM fails to reliably detect specific molecules of interest. To this end, correlated light and electron microscopy (CLEM) techniques have emerged to combine the high molecular contrast of fluorescence microscopy with the ultrastructural imaging capabilities of EM. Despite the merits of CLEM, sample preparation and image alignment are extremely laborious, limiting this correlative approach to only proof-of-concept biological experiments. This thesis poses this specific question: why is light microscopy alone incapable of resolving the ultrastructural context of cells, despite extraordinary improvements in spatial resolution? We argue that the limitation stems from the physical properties of fluorescent dyes: dyes are ~1 nm in diameter, a size comparable to the distance between proteins in the densely crowded cell. If labeled in bulk, fluorescent dyes would sterically hinder and self-quench via electron transfer and dipole-dipole interactions, which would limit the achievable staining density and thereby the sampling necessary to resolve the crowded cellular interior. This thesis made the conceptual realization that if the sample protein content is isotropically expanded up to 20-fold in all three dimensions, the relative size of fluorescent dyes would shrink by the same factor. Here, the relative radius of a fluorescent dye would approach ~50 pm, which is comparable to the size of an osmium atom (~200 pm) used in heavy metal EM staining. Bulk fluorescence staining of the decrowded cell will therefore no longer be limited by sampling and quenching restrictions, and ultrastructural details, previously accessible with only EM, can now be revealed on a standard light microscope. We call the underlying sample preparation technique pan-Expansion Microscopy (pan-ExM). pan-ExM combines the philosophy of bulk- (pan-) staining of the total protein content with a newly developed Expansion Microscopy (ExM) protocol capable of 20-fold linear sample expansion and protein retention. We first develop pan-ExM in cultured cells as a proof-of-concept demonstration. We then develop the technique in dissociated neuronal cultures and in thick (~70 μm) mouse brain tissue sections to establish its applicability in neurobiological research. Finally, in a method we call panception, we demonstrate that the conceptual advance of pan-staining is also applicable to transmitted light microscopy. Using polymers of varying refractive indices and light-scattering analogs of fluorescent dyes, we show that sample ultrastructure can be imaged with brightfield microscopy, and that sample microstructure can be revealed with the un-aided eye

Optimization of Ti-6Al-4V and its foams for biomedical applications by field assisted sintering technique

The research aims to optimize the Ti6Al4V implants with mechanical properties matching that of human bones. Powder metallurgy processes were used to generate the alloy by the field assisted sintering technique combined with rapid cooling. It could be proven that the rapid cooling has an important effect on the microstructures, while maintaining the nanostructures of the raw materials. This allowed to improve the mechanical properties of the sintered alloys. Porous structures are designed to achieve implants with low elastic modulus to improve the fixation between the bone and the implants

New approaches to the measurement of chlorophyll, related pigments and productivity in the sea

In the 1984 SBIR Call for Proposals, NASA solicited new methods to measure primary production and chlorophyll in the ocean. Biospherical Instruments Inc. responded to this call with a proposal first to study a variety of approaches to this problem. A second phase of research was then funded to pursue instrumentation to measure the sunlight stimulated naturally occurring fluorescence of chlorophyll in marine phytoplankton. The monitoring of global productivity, global fisheries resources, application of above surface-to-underwater optical communications systems, submarine detection applications, correlation, and calibration of remote sensing systems are but some of the reasons for developing inexpensive sensors to measure chlorophyll and productivity. Normally, productivity measurements are manpower and cost intensive and, with the exception of a very few expensive multiship research experiments, provide no contemporaneous data. We feel that the patented, simple sensors that we have designed will provide a cost effective method for large scale, synoptic, optical measurements in the ocean. This document is the final project report for a NASA sponsored SBIR Phase 2 effort to develop new methods for the measurements of primary production in the ocean. This project has been successfully completed, a U.S. patent was issued covering the methodology and sensors, and the first production run of instrumentation developed under this contract has sold out and been delivered

Optimization of the holographic process for imaging and lithography

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2010.Cataloged from PDF version of thesis.Includes bibliographical references (p. 272-297).Since their invention in 1948 by Dennis Gabor, holograms have demonstrated to be important components of a variety of optical systems and their implementation in new fields and methods is expected to continue growing. Their ability to encode 3D optical fields on a 2D plane opened the possibility of novel applications for imaging and lithography. In the traditional form, holograms are produced by the interference of a reference and object waves recording the phase and amplitude of the complex field. The holographic process has been extended to include different recording materials and methods. The increasing demand for holographic-based systems is followed by a need for efficient optimization tools designed for maximizing the performance of the optical system. In this thesis, a variety of multi-domain optimization tools designed to improve the performance of holographic optical systems are proposed. These tools are designed to be robust, computationally efficient and sufficiently general to be applied when designing various holographic systems. All the major forms of holographic elements are studied: computer generated holograms, thin and thick conventional holograms, numerically simulated holograms and digital holograms. Novel holographic optical systems for imaging and lithography are proposed. In the case of lithography, a high-resolution system based on Fresnel domain computer generated holograms (CGHs) is presented. The holograms are numerically designed using a reduced complexity hybrid optimization algorithm (HOA) based on genetic algorithms (GAs) and the modified error reduction (MER) method. The algorithm is efficiently implemented on a graphic processing unit. Simulations as well as experimental results for CGHs fabricated using electron-beam lithography are presented. A method for extending the system's depth of focus is proposed. The HOA is extended for the design and optimization of multispectral CGHs applied for high efficiency solar concentration and spectral splitting. A second lithographic system based on optically recorded total internal reflection (TIR) holograms is studied. A comparative analysis between scalar and (cont.) vector diffraction theories for the modeling and simulation of the system is performed.A complete numerical model of the system is conducted including the photoresist response and first order models for shrinkage of the holographic emulsion. A novel block-stitching algorithm is introduced for the calculation of large diffraction patterns that allows overcoming current computational limitations of memory and processing time. The numerical model is implemented for optimizing the system's performance as well as redesigning the mask to account for potential fabrication errors. The simulation results are compared to experimentally measured data. In the case of imaging, a segmented aperture thin imager based on holographically corrected gradient index lenses (GRIN) is proposed. The compound system is constrained to a maximum thickness of 5mm and utilizes an optically recorded hologram for correcting high-order optical aberrations of the GRIN lens array. The imager is analyzed using system and information theories. A multi-domain optimization approach is implemented based on GAs for maximizing the system's channel capacity and hence improving the information extraction or encoding process. A decoding or reconstruction strategy is implemented using the superresolution algorithm. Experimental results for the optimization of the hologram's recording process and the tomographic measurement of the system's space-variant point spread function are presented. A second imaging system for the measurement of complex fluid flows by tracking micron sized particles using digital holography is studied. A stochastic theoretical model based on a stability metric similar to the channel capacity for a Gaussian channel is presented and used to optimize the system. The theoretical model is first derived for the extreme case of point source particles using Rayleigh scattering and scalar diffraction theory formulations. The model is then extended to account for particles of variable sizes using Mie theory for the scattering of homogeneous dielectric spherical particles. The influence and statistics of the particle density dependent cross-talk noise are studied. Simulation and experimental results for finding the optimum particle density based on the stability metric are presented. For all the studied systems, a sensitivity analysis is performed to predict and assist in the correction of potential fabrication or calibration errors.by José Antonio Domínguez-Caballero.Ph.D

Interpretation of refraction images in synchrotron based imaging techniques using growth plate injury specimens in an animal model

Typical clinical radiography uses the variable absorption of x-radiation of different tissues within the object to produce contrast in the image. The interpretation of this image is based on understanding the anatomy and pathology as well as understanding how the image is produced. One needs to understand what features of the image are representative of the anatomy/pathology, what is inherent to the imaging process and what is artefact. The correlation of contrast in the image with absorption contrast in the object is fairly intuitive. Diffraction Enhanced Imaging (DEI) uses the bending or refraction of radiation as it passes through a tissue interface to produce the contrast in the image in addition to absorption. The ability to interpret the refraction contrast image is not as intuitive as the absorption image. Edges are enhanced and tissues with different densities can look similar. Understanding the image acquisition of refraction based radiography also is not as intuitive as typical absorption radiography. One potential advantage of DEI is the ability to visualize small structures that may not be visible using absorption radiography. The growth plate of long bones and the premature closure or bone bridge/bar formation across the growth plate associated with a fracture was targeted as a study sample. An animal model (juvenile rat) was used for inducing a fracture through the proximal metaphysis of the tibia. The animal was then sacrificed at variable times of healing which is described below. The specimens were then imaged using DEI techniques at Brookhaven National Lab, Upton, New York, at the Biomedical Imaging and Therapy (BMIT) beamline at the Canadian Light Source and using a laboratory based DEI system at Nesch, LLC, Crown Point, Indiana. High resolution absorption images were obtained using a SkyScan micro-CT from Prof. Cooper’s laboratory for comparison of DEI and absorption images. Histological slides were also prepared for correlation of image anatomy. The reason for imaging these specimens using different techniques was to determine potential translation of synchrotron based techniques with lab based or conventional techniques as well as determining what features of imaging could be uniquely done at a synchrotron. Since access to synchrotron biomedical imaging facilities is limited, the potential for some work to be done outside of synchrotron facilities would make research progress more efficient. A detailed analysis of the images was performed. The detail of the bone as well as the fracture was exquisite with the CT data. With the planar images the orientation of the trabeculae of the bone relative to the direction of the analyser crystal (direction of diffraction) changes the appearance and texture of the bone image. It was hoped to visualize the layers of the growth plate (variable calcification) and perhaps the initiation of bone spicules leading to bone bridges across the growth plates at the site of fracture. However, the small size of the object limited observable detail. This work was originally intended to apply a unique imaging technique for the study of growth plate fracture pathophysiology. However, it became clear that the technical image production and interpretation was more important to the project than the individual analysis of each specimen. As a result not all specimens were used, but those selected were used to refine the technique and interpret the synchrotron based images compared to conventional images. The use of DEI for assessing bone bridge formation was promising, but the specimen size limited detail and resolution. This has led to the conclusion that a larger animal model would be more appropriate for this type of study. Further, it was discovered that the bone (growth plate) orientation affected the planar image contrast of the bone / cartilage interface based on long axis orientation relative to the refraction sensitive direction of the DEI system. To more fully exploit this effect, more images at different object orientations would be necessary for interpretation in future work with larger animal models