Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “EYES”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 289 records · Page 16
All sourcesNASA NTRSDOE OSTI
DOE OSTI2014

WE-A-17A-12: The Influence of Eye Plaque Design On Dose Distributions and Dose- Volume Histograms

Purpose: To investigate the effect of slot design of the model EP917 plaque on dose distributions and dose-volume histograms (DVHs). Methods: The dimensions and orientation of the slots in EP917 plaques were measured. In the MCNP5 radiation simulation geometry, dose distributions on orthogonal planes and DVHs for a tumor and sclera were generated for comparisons. 27 slot designs and 13 plaques were evaluated and compared with the published literature and the Plaque Simulator clinical treatment planning system. Results: The dosimetric effect of the gold backing composition and mass density was < 3%. Slot depth, width, and length changed the central axis (CAX) dose distributions by < 1% per 0.1 mm in design variation. Seed shifts in the slot towards the eye and shifts of the {sup 125} I-coated Ag rod within the capsule had the greatest impact on CAX dose distribution, increasing by 14%, 9%, 4%, and 2.5% at 1, 2, 5, and 10 mm, respectively, from the inner sclera. Along the CAX, dose from the full plaque geometry using the measured slot design was 3.4% ± 2.3% higher than the manufacturer-provided geometry. D{sub 10} for the simulated tumor, inner sclera, and outer sclera for the measured plaque was also higher, but 9%, 10%, and 20%, respectively. In comparison to the measured plaque design, a theoretical plaque having narrow and deep slots delivered 30%, 37%, and 62% lower D{sub 10} doses to the tumor, inner sclera, and outer sclera, respectively. CAX doses at −1, 0, 1, and 2 mm were also lower by a factor of 2.6, 1.4, 1.23, and 1.13, respectively. Conclusion: The study identified substantial sensitivity of the EP917 plaque dose distributions to slot design. However, it did not identify substantial dosimetric variations based on radionuclide choice ({sup 125}I, {sup 103}Pd, or {sup 131}Cs). COMS plaques provided lower scleral doses with similar tumor dose coverage.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2015

SU-E-T-15: A Comparison of COMS and EP917 Eye Plaque Applicators Using Different Radionuclides

Purpose: To investigate the effect of plaque design and radionuclides on eye plaque dosimetry. Methods: The Monte Carlo N-particle Code version 6 (MCNP6) was used for radiation transport simulations. The 14 mm and 16 mm diameter COMS plaques and the model EP917 plaque were simulated using brachytherapy seeds containing I-125, Pd-103, and Cs-131 radionuclides. The origin was placed at the scleral inner surface. The central axis (CAX) doses of both COMS plaques at −1 mm, 0 mm, 1 mm, 2 mm, 5 mm, 10 mm, 15 mm, 20 mm, and 22.6 mm were compared to the model EP917 plaque. Dose volume histograms (DVHs) were also created for both COMS plaques for the tumor and outer sclera then compared to results for the model EP917 plaque. Results: For all radionuclides, the EP917 plaque delivered higher dose (max 343%) compared to the COMS plaques, except for the 14 mm COMS plaque with Cs-131 at 1 mm and 2 mm depths from outer sclera surface. This could be due to source design. For all radionuclides, the 14 mm COMS plaque delivered higher doses compared to the 16 mm COMS plaque for the depths up to 5 mm. Dose differences were not significant beyond depths of 10 mm due to ocular lateral scatter for the different plaque designs. Tumor DVHs for the 16 mm COMS plaque with Cs-131 provided better dose homogeneity and conformity compared to other COMS plaques with I-125 and Pd-103. Using Pd-103, DVHs for the 16 mm COMS plaque delivered less dose to outer sclera compared to other plaques. Conclusion: This study identified improved tumor homogeneity upon considering radionuclides and plaque designs, and found that scleral dose with the model EP917 plaque was higher than for the 16 mm COMS plaque for all the radionuclides studied.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2011

The Enhancer of split complex arose prior to the diversification of schizophoran flies and is strongly conserved between Drosophila and stalk-eyed flies (Diopsidae)

Background: In Drosophila, the Enhancer of split complex (E(spl)-C) comprises 11 bHLH and Bearded genes that function during Notch signaling to repress proneural identity in the developing peripheral nervous system. Comparison with other insects indicates that the basal state for Diptera is a single bHLH and Bearded homolog and that the expansion of the gene complex occurred in the lineage leading to Drosophila. However, comparative genomic data from other fly species that would elucidate the origin and sequence of gene duplication for the complex is lacking. Therefore, in order to examine the evolutionary history of the complex within Diptera, we reconstructed, using several fosmid clones, the entire E(spl)-complex in the stalk-eyed fly, Teleopsis dalmanni and collected additional homologs of E(spl)-C genes from searches of dipteran EST databases and the Glossina morsitans genome assembly. Results: Comparison of the Teleopsis E(spl)-C gene organization with Drosophila indicates complete conservation in gene number and orientation between the species except that T. dalmanni contains a duplicated copy of E(spl)m5 that is not present in Drosophila. Phylogenetic analysis of E(spl)-complex bHLH and Bearded genes for several dipteran species clearly demonstrates that all members of the complex were present prior to the diversification of schizophoran flies. Comparison of upstream regulatory elements and 3’ UTR domains between the species also reveals strong conservation for many of the genes and identifies several novel characteristics of E(spl)-C regulatory evolution including the discovery of a previously unidentified, highly conserved SPS+A domain between E(spl)mg and E(spl)mb. Conclusion: Identifying the phylogenetic origin of E(spl)-C genes and their associated regulatory DNA is essential to understanding the functional significance of this well-studied gene complex. Results from this study provide numerous insights into the evolutionary history of the complex and will help refine the focus of studies examining the adaptive consequences of this gene expansion.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2015

Lens of Eye Dosimetry

An analysis of LANL occupational dose measurements was made with respect to lens of eye dose (LOE), in particular, for plutonium workers. Table 1 shows the reported LOE as a ratio of the “deep” (photon only) and “deep+neutron” dose for routine monitored workers at LANL for the past ten years. The data compares the mean and range of these values for plutonium workers* and non-routine plutonium workers. All doses were reported based on measurements with the LANL Model 8823 TLD.

61 RADIATION PROTECTION AND DOSIMETRY↗
NASA NTRS1999

Firing behavior of vestibular neurons during active and passive head movements: vestibulo-spinal and other non-eye-movement related neurons

The firing behavior of 51 non-eye movement related central vestibular neurons that were sensitive to passive head rotation in the plane of the horizontal semicircular canal was studied in three squirrel monkeys whose heads were free to move in the horizontal plane. Unit sensitivity to active head movements during spontaneous gaze saccades was compared with sensitivity to passive head rotation. Most units (29/35 tested) were activated at monosynaptic latencies following electrical stimulation of the ipsilateral vestibular nerve. Nine were vestibulo-spinal units that were antidromically activated following electrical stimulation of the ventromedial funiculi of the spinal cord at C1. All of the units were less sensitive to active head movements than to passive whole body rotation. In the majority of cells (37/51, 73%), including all nine identified vestibulo-spinal units, the vestibular signals related to active head movements were canceled. The remaining units (n = 14, 27%) were sensitive to active head movements, but their responses were attenuated by 20-75%. Most units were nearly as sensitive to passive head-on-trunk rotation as they were to whole body rotation; this suggests that vestibular signals related to active head movements were cancelled primarily by subtraction of a head movement efference copy signal. The sensitivity of most units to passive whole body rotation was unchanged during gaze saccades. A fundamental feature of sensory processing is the ability to distinguish between self-generated and externally induced sensory events. Our observations suggest that the distinction is made at an early stage of processing in the vestibular system.

Non-NASA Center↗