Layer Thickness Parameters Research Articles

Functional and morphological effects of systemic bevacizumab on cancer patients' eyes.

To evaluate the morphological and functional short-term effects of systemic bevacizumab on healthy eyes of cancer patients morphologically and functionally. The patients who underwent a chemotherapy regimen because of colon, lung, and breast cancer at the Department of Medical Oncology of the Gazi University School of Medicine between years 2010 and 2012 were included. All patients were administrated intravenous bevacizumab in three different dosages (5, 7.5, and 15 mg/kg per day) at 2- or 3-week intervals and a total of 6 to 18 courses in addition to regimens based on 5-fluorouracil, oxaliplatin, and irinotecan. After baseline ophthalmologic examination, patients were examined after the first course of chemotherapy and at the end of the protocol. Ophthalmologic evaluations included best-corrected visual acuity, color vision assessment, and ocular examinations with optical coherence tomography. Thirty-four eyes of 17 patients were enrolled. The mean (±SD) age of the patients was 53.64 (±11.09) years and median follow-up time was 9 months (range, 4 to 18 months). Seventy-six percent of the patients were diagnosed as having colon cancer and no significant change was identified in functional assessments such as best-corrected visual acuity or color vision or in morphological examinations with optical coherence tomography (central foveal thickness and retinal nerve fiber layer thickness parameters). Patients were divided into three groups based on the dosage of systemic bevacizumab infusions, and correlation between time-dependent changes in central foveal thickness, retinal nerve fiber layer thickness, and bevacizumab dosage was investigated and no significant correlation was detected. Repeated doses of systemic bevacizumab did not cause a deleterious effect on healthy eyes of cancer patients clinically, but further studies including histologic and biochemical analysis need to be conducted to reveal possible adverse effects.

Ocular outcomes evaluation in a 14-day head-down bed rest study.

We evaluated ocular outcomes in a 14-d head-down tilt (HDT) bed rest (BR) study designed to simulate the effects of microgravity on the human body. Healthy subjects were selected using NASA standard screening procedures. Standardized NASA BR conditions were implemented (e.g., strict sleep-wake cycle, standardized diet, 24-hour-a-day BR, continuous video monitoring). Subjects maintained a 6° HDT position for 14 consecutive days. Weekly ophthalmological examinations were performed in the sitting (pre/post-BR) and HDT (in-bed phase) positions. Equivalency tests with optimal-alpha techniques evaluated pre/post-BR differences in best-corrected visual acuity (BCVA), spherical equivalent, intraocular pressure (IOP), Spectral-domain OCT retinal nerve fiber layer thickness (RNFLT), optic disc and macular parameters. 16 subjects (12 men and 4 women) were enrolled. Nearly all ocular outcomes were within our predefined clinically relevant thresholds following HDTBR, except near BCVA (pre/post-BR mean difference: -0.06 logMAR), spherical equivalent (-0.30 D), Tonopen XL IOP (+3.03 mmHg) and Spectralis OCT average (+1.14 μm), temporal-inferior (+1.58 μm) and nasal-inferior RNFLT (+3.48 μm). Modified Amsler grid, red dot test, confrontational visual field, and color vision were within normal limits throughout. No changes were detected on stereoscopic color fundus photography. A few functional and structural changes were detected after 14-d HDTBR, notably an improved BCVA possibly due to learning effect and RNFL thickening without signs of optic disc edema. In general, 6° HDTBR determined a small nonprogressive IOP elevation, which returned to baseline levels post-BR. Further studies with different BR duration and/or tilt angle are warranted to investigate microgravity-induced ophthalmological changes.

Influence of structural parameters on the tribological properties of Al2O3/Mo laminated nanocomposites

High-performance Al2O3/Mo laminated nanocomposites are potential candidates for space vehicle bearing components because of their excellent self-lubricating ability and mechanical properties. The purpose of this study was to investigate how layer thickness and spacing parameters affected the sliding friction and wear of such Al2O3/Mo laminated composites against alumina. Eight types of Al2O3/Mo laminated nanocomposites with different microstructures were fabricated by hot-pressing. Analyses were carried to understand the effects on friction and wear of the number of Mo layers n, thickness ratio z, and the effective proportion of Mo real contact area. Results showed that the performance of the material was significantly improved by optimizing its microstructural design. By this method, the friction coefficient can be controlled in a stable range (0.34–0.50) in a high temperature environment. This friction coefficient is close to the value observed for pure Mo (0.37). Varying n, z and the contact area of Mo causes significant changes in the formation of effective lubricating oxide films (MoO3), thus enabling the best material performance. Furthermore, thicker molybdenum layers tend to improve the friction stability of the materials. Based on these analyses, a set of principles to design Al2O3/Mo laminated composites has been formulated.

The effect of myopic optic disc tilt on measurement of spectral-domain optical coherence tomography parameters

BackgroundTo compare the spectral-domain optical coherence tomography (SD-OCT) parameters, including ganglion cell-inner plexiform layer (GCIPL) thickness, retinal nerve fibre layer (RNFL) thickness and optic nerve head (ONH) parameters between glaucomatous...

Age-associated changes in the retinal nerve fiber layer and optic nerve head.

Optical coherence tomography (OCT) measures of the retinal nerve fiber layer (RNFL) thickness and neuroretinal rim (NRR) parameters are often used as a surrogate for retinal ganglion cell content. The purpose of this study was to investigate the relationship between these morphological measures and the aging effects on these structures. One hundred thirteen healthy individuals, aged 19 to 76 years, with no prior history of retinal of optic nerve head pathology were recruited. A circumpapillary and radial OCT scan centered on the optic nerve head (ONH) was used for data analysis. Transverse scaling was calculated for each subject using measures from optical biometry. Custom algorithms were used for morphological analysis of the ONH NRR and RNFL that included quantification of major retinal vascular contribution. There was a significant age-related loss of RNFL thickness (-0.23 μm/y, R(2) = 0.24, P < 0.01), major retinal vascular contribution (-0.03 μm/y, R(2) = 0.07, P = 0.01, neural rim volume (NRV, -0.004 mm(3)/y, R(2) = 0.15, P < 0.01), and minimum rim width (MRW, -1.77 μm/y, R(2) = 0.23, P < 0.01) before, and after, incorporating the Bruch's membrane opening size (sMRW, -1.86 μm/y, R(2) = 0.22, P < 0.01). When normalized, the rates of change for ONH NRR parameters (NRV, 0.69%/y and sMRW, 0.50%/y) exceeded that of RNFL thickness (0.19%/y, P < 0.01). Although both RNFL and ONH NRR parameters contain axons of retinal ganglion cells, there are differences in age-related changes in these measures that should be considered in clinical application.

Evaluation of Octopus Polar Trend Analysis for Detection of Glaucomatous Progression

To investigate the clinical usefulness of Polar Trend Analysis (PTA) of the Octopus Field Analysis software for detection of glaucoma progression in medically treated glaucoma. One eye each of 52 participants underwent Octopus Normal G2 perimetry and imaging with the RTVue-100 optical coherence tomograph at 6-month intervals (median follow-up 5 years). The eyes were classified as progressors or nonprogressors with PTA, which graphically presents pointwise linear regression analysis of focal defect at the corresponding nerve fiber angle at the disc margin. Polar Trend Analysis progression was defined as more than 1 significantly progressing test point location per sector. Progression of the retinal nerve fiber layer thickness (RNFLT) and ganglion cell complex (GCC) thickness parameters were evaluated with linear regression analysis. Seventeen eyes were classified as PTA progressors (all in the inferotemporal or superotemporal areas or in both), and 35 eyes as nonprogressors. Frequencies of statistically significant RNFLT and GCC progressions did not differ significantly between the groups for any peripapillary area (p&gt;0.05 for all comparisons). Significant inferior average RNFLT progression occurred in 50% of the PTA progressor eyes. Long-term measurement variability during the follow-up period was significantly higher in the PTA progressor group for inferior and superior GCC thickness and inferior average RNFLT (p&lt;0.001 for all comparisons). In glaucoma, PTA may indicate glaucomatous progression earlier than linear regression analysis of the RNFLT and GCC parameters. It may already draw attention to glaucomatous progression when the alteration of the corresponding structural parameters is represented only by increased long-term variability.

Potential new diagnostic tool for Alzheimer's disease using a linear discriminant function for Fourier domain optical coherence tomography.

We calculated and validated a linear discriminant function (LDF) for Fourier domain optical coherence tomography (OCT) to improve the diagnostic ability of retinal and retinal nerve fiber layer (RNFL) thickness parameters in the detection of Alzheimer's disease (AD). We enrolled AD patients (n = 151) and age-matched, healthy subjects (n = 61). The Cirrus and Spectralis OCT systems were used to obtain retinal measurements and circumpapillary RNFL thickness for each participant. An LDF was calculated using all retinal and RNFL OCT measurements. Receiver operating characteristic (ROC) curves were plotted and compared among the LDF and the standard parameters provided by OCT devices. Sensitivity and specificity were used to evaluate diagnostic performance. A validating set was used in an independent population to test the performance of the LDF. The optimal function was calculated using the RNFL thickness provided by Spectralis OCT, using the 768 points registered during peripapillary scan acquisition (grouped to obtain 24 uniformly divided locations): 18.325 + 0.056 × (315°-330°) - 0.122 × (300°-315°) - 0.041 × (285°-300°) + 0.091 × (255°-270°) + 0.041 × (225°-240°) + 0.183 × (195°-210°) - 0.108 × (150°-165°) - 0.092 × (75°-90°) + 0.051 × (30°-45°). The largest area under the ROC curve was 0.967 for the LDF. At 95% fixed specificity, the LDF yielded the highest sensitivity values. Measurements of RNFL thickness obtained with the Spectralis OCT device differentiated between healthy and AD individuals. Based on the area under the ROC curve, the LDF was a better predictor than any single parameter.

RETINA MEASUREMENTS FOR DIAGNOSIS OF PARKINSON DISEASE

To test the diagnostic ability of spectral domain optical coherence tomography for the detection of Parkinson disease using retinal nerve fiber layer and retinal thickness parameters. Retinal pigment epithelium produces levodopa. Patients with Parkinson disease (n = 111) and healthy subjects (n = 200) were enrolled. The Spectralis optical coherence tomography was used to obtain retinal nerve fiber layer thickness and retinal measurements. Two linear discriminant functions (LDFs) were developed, one using retinal nerve fiber layer parameters and another using retinal thickness. A validating set was used to test the performance of both LDFs. Receiver operating characteristic curves were plotted and compared with the standard parameters provided by optical coherence tomography for both LDFs. Sensitivity and specificity were used to evaluate diagnostic performance. The Retinal LDF combines only retinal thickness parameters and provided the best performance: 31.173 + 0.026 × temporal outer - 0.267 × superior outer + 0.159 × nasal outer - 0.197 × inferior outer - 0.060 × superior inner + 0.049 × foveal thickness. The largest areas under the receiver operating characteristic curve were 0.902 for Retinal LDF. The Retinal LDF yielded the highest sensitivity values. Measurements of retinal thickness differentiate between subjects who are healthy and those with advanced Parkinson disease.

Structure–Function Correlations in Glaucoma Using Matrix and Standard Automated Perimetry Versus Time-Domain and Spectral-Domain OCT Devices

We examined the structure-function relationship between two perimetric tests, the frequency doubling technology (FDT) matrix and standard automated perimetry (SAP), and two optical coherence tomography (OCT) devices (time-domain and spectral-domain). This cross-sectional study included 97 eyes from 29 healthy individuals, and 68 individuals with early, moderate, or advanced primary open-angle glaucoma. The correlations between overall and sectorial parameters of retinal nerve fiber layer thickness (RNFL) measured with Stratus and Spectralis OCT, and the visual field sensitivity obtained with FDT matrix and SAP were assessed. The relationship also was evaluated using a previously described linear model. The correlation coefficients for the threshold sensitivity measured with SAP and Stratus OCT ranged from 0.44 to 0.79, and those for Spectralis OCT ranged from 0.30 to 0.75. Regarding FDT matrix, the correlation ranged from 0.40 to 0.79 with Stratus OCT and from 0.39 to 0.79 with Spectralis OCT. Stronger correlations were found in the overall measurements and the arcuate sectors for both visual fields and OCT devices. A linear relationship was observed between FDT matrix sensitivity and the OCT devices. The previously described linear model fit the data from SAP and the OCT devices well, particularly in the inferotemporal sector. The FDT matrix and SAP visual sensitivities were related strongly to the RNFL thickness measured with the Stratus and Spectralis OCT devices, particularly in the overall and arcuate sectors.

Effect of change in macular birefringence imaging protocol on retinal nerve fiber layer thickness parameters using GDx VCC in eyes with macular lesions

This study evaluates the effect of two macular birefringence protocols (bow-tie retardation and irregular macular scan) using GDx VCC on the retinal nerve fiber layer (RNFL) thickness parameters in normal eyes and eyes with macular lesions. In eyes with macular lesions, the standard protocol led to significant overestimation of RNFL thickness which was normalized using the irregular macular pattern protocol. In eyes with normal macula, absolute RNFL thickness values were higher in irregular macular pattern protocols with the difference being statistically significant for all parameters except for inferior average thickness. This has implications for monitoring glaucoma patients who develop macular lesions during the course of their follow-up.

Detection of Early Glaucomatous Progression With Different Parameters of the RTVue Optical Coherence Tomograph

To investigate the ability of different parameters of the RTVue-100 Fourier-domain optical coherence tomograph (RTVue-OCT) to detect early glaucomatous progression. One eye of 17 healthy and 51 perimetric glaucoma patients was imaged prospectively at 6-month intervals for 1.5 to 3 years. Progression was determined by Octopus normal G2 visual field progression criteria. Ten of the 51 glaucoma eyes progressed based on visual field criteria. Median visual field mean defect change was -0.300 dB/y for the controls, -0.120 dB/y for all glaucoma eyes (P=0.461 vs. controls), and 1.231 dB/y for the 10 functionally progressing glaucoma eyes (P<0.001 vs. controls). Ganglion cell complex (GCC), focal loss volume, and GCC global loss volume showed significantly faster rate of progression in the glaucoma group than in controls (P=0.004 and P=0.001, respectively). No optic nerve head, retinal nerve fiber layer thickness, and average GCC parameter separated the rate of progression between the groups. Early structural progression of glaucoma may be better detected with pattern-based GCC parameters of the RTVue-OCT than with the optic nerve head, retinal nerve fiber layer thickness or average GCC parameters of the same instrument.

Retinal Nerve Fiber Layer Reflectance for Early Glaucoma Diagnosis

Compare performance of normalized reflectance index (NRI) and retinal nerve fiber layer thickness (RNFLT) parameters determined from optical coherence tomography (OCT) images for glaucoma and glaucoma suspect diagnosis. Seventy-five eyes from 71 human subjects were studied: 33 controls, 24 glaucomatous, and 18 glaucoma-suspects. RNFLT and NRI maps were measured using 2 custom-built OCT systems and the commercial instrument RTVue. Using area under the receiver operating characteristic curve, RNFLT and NRI measured in 7 RNFL locations were analyzed to distinguish between control, glaucomatous, and glaucoma-suspect eyes. The mean NRI of the control group was significantly larger than the means of glaucomatous and glaucoma-suspect groups in most RNFL locations for all 3 OCT systems (P<0.05 for all comparisons). NRI performs significantly better than RNFLT at distinguishing between glaucoma-suspect and control eyes using RTVue OCT (P=0.008). The performances of NRI and RNFLT for classifying glaucoma-suspect versus control eyes were statistically indistinguishable for PS-OCT-EIA (P=0.101) and PS-OCT-DEC (P=0.227). The performances of NRI and RNFLT for classifying glaucomatous versus control eyes were statistically indistinguishable (PS-OCT-EIA: P=0.379; PS-OCT-DEC: P=0.338; RTVue OCT: P=0.877). NRI is a promising measure for distinguishing between glaucoma-suspect and control eyes and may indicate disease in the preperimetric stage. Results of this pilot clinical study warrant a larger study to confirm the diagnostic power of NRI for diagnosing preperimetric glaucoma.

Theoretical D* Optimization of N+-p Pb&amp;lt;sub&amp;gt;1-x&amp;lt;/sub&amp;gt;Sn&amp;lt;sub&amp;gt;x&amp;lt;/sub&amp;gt;Se Long-Wavelength (8 - 11 μm) Photovoltaic Detector at 77 K

In this work, the study of the influences of lifetime, doping concentration and absorption layer thickness to resistant- area product (R0A) and quantum efficiency of Pb1-xSnxSe photovoltaic detector are presented. Three fundamental current mechanisms including diffusion, generation-recombination, and tunneling models are considered. Using optimal doping concentration and absorption layer thickness parameters, the calculated detectivity (D*) of Pb1-xSnxSe photovoltaic detector is over 1012 cm Hz1/2/W.

Analysis of the machining performance and surface integrity in laser milling of polycrystalline diamonds

The increasing use of diamond cutting tools necessitates the development of compatible fabrication technologies for the diamond tools, especially for three-dimensional surfaces with micron scale accuracy and good surface quality. In this article, the formation mechanism of surfaces milled using a nanosecond pulsed laser on polycrystalline diamond and the effect of process parameters on the milling performance such as material removal rate and surface integrity are investigated based on a statistically designed experiment. It is shown that laser milling is a viable technology for three-dimensional processing of polycrystalline diamonds with good machining rates and acceptable surface quality. A microscopy analysis indicates that diamond graphitization can occur on the milled surfaces, and laser pulse energy and pulse overlap have a significant effect on the milled surface morphology. Characterization of the machined surface/subsurface is conducted using Raman spectroscopy, and the relationships between damaged surface layer thickness and process parameters are discussed. It is found that an optimum pulse overlap together with moderate pulse energy may be used, while the scan overlap should be selected in the vicinity of its optimum value at around 50% for a good surface quality while maintaining a high material removal rate.

Correlation of magnetic resonance imaging optic nerve parameters to optical coherence tomography and the visual field in glaucoma

To determine the viability of using magnetic resonance imaging measurement of optic nerve morphology as an objective analysis of glaucomatous damage. Retrospective study conducted at Tohoku University Hospital. Thirty-eight eyes of 19 patients with open-angle glaucoma. Patients were scanned with T2-weighted and 3-T diffusion tensor magnetic resonance imaging, and parameters of the optic nerve, including fractional anisotropy, apparent diffusion coefficient and cross-sectional area, were determined. Conventional parameters of glaucomatous damage, including circumpapillary and macular retinal nerve fibre layer thickness, and mean deviation and average total deviation of the central 16 test points from the Humphrey Field Analyzer, were then compared with the magnetic resonance imaging-derived parameters. Spearman's coefficient of correlation was calculated to determine the significance of the correlation. Correlation coefficient between the magnetic resonance imaging parameters and the parameters of glaucomatous damage. Mean deviation was significantly correlated with all magnetic resonance imaging parameters (fractional anisotropy: r = 0.53, apparent diffusion coefficient: r = -0.44, cross-sectional area: r = 0.70). Circumpapillary retinal nerve fibre layer thickness was significantly correlated with fractional anisotropy (r = 0.60) and cross-sectional area (r = 0.47), but not apparent diffusion coefficient (r = -0.29). Central macular function and macular retinal nerve fibre layer thickness were also significantly correlated with magnetic resonance imaging parameters. Optic nerve magnetic resonance imaging parameters were significantly correlated to glaucomatous damage. Magnetic resonance imaging analysis of the optic nerve may, thus, have value as an objective instrument to assess glaucomatous degeneration, including the function of the macula.

The Ability of Macular Parameters and Circumpapillary Retinal Nerve Fiber Layer by Three SD-OCT Instruments to Diagnose Highly Myopic Glaucoma

To compare the ability of circumpapillary retinal nerve fiber layer (cpRNFL) thickness and macular parameters obtained by three spectral-domain optical coherence tomography (SD-OCT) instruments to detect highly myopic glaucoma. In this study, 84 glaucomatous eyes, 53 normal eyes with high myopia, and 86 normal eyes (not highly myopic) were enrolled. Each participant was imaged using Cirrus, RTVue, and 3D OCT to evaluate the average and quadrant cpRNFL thicknesses. The macular retinal nerve fiber layer (mRNFL), ganglion cell layer + inner plexiform layer (GCL/IPL), and mRNFL + GCL/IPL (GCC) thicknesses were analyzed. The areas under the receiver operating characteristic curves (AUCs) were compared between the instruments. In addition, the best parameters for the AUC were compared between the cpRNFL parameters and macular parameters in each instrument. These analyses revealed similar AUCs for the average cpRNFL and GCC thicknesses between the instruments. RTVue displayed a significantly higher AUC in the nasal cpRNFL thickness than both Cirrus (P = 0.0004) and 3D OCT (P = 0.0006). 3D OCT showed higher AUCs than Cirrus in the mRNFL parameters. There were no significant differences between the best cpRNFL parameters and macular parameters in each instrument. The average cpRNFL and GCC thicknesses that were measured using these OCT instruments exhibited similar abilities for diagnosing highly myopic glaucoma, and RTVue exhibited better diagnostic abilities than Cirrus and 3D OCT for nasal cpRNFL. 3D OCT had better ability than Cirrus in the mRNFL. Both cpRNFL and GCC in each instrument were comparable, and their measurements offered good ability for diagnosing glaucoma with high myopia. (http://www.umin.ac.jp/ctr/index/htm9, UMIN000006900.).

An efficient cost function for the optimization of an n-layered isotropic cloaked cylinder

In this paper, we present an efficient cost function for optimizing n-layered isotropic cloaked cylinders. Cost function efficiency is achieved by extracting the expression for the angle independent scatterer contribution of an associated Green's function. Therefore, since this cost function is not a function of angle, accounting for every bistatic angle is not necessary and thus more efficient than other cost functions. With this general and efficient cost function, isotropic cloaked cylinders can be optimized for many layers and material parameters. To demonstrate this, optimized cloaked cylinders made of 10, 20 and 30 equal thickness layers are presented for TE and TM incidence. Furthermore, we study the effect layer thickness has on optimized cloaks by optimizing a 10 layer cloaked cylinder over the material parameters and individual layer thicknesses.The optimized material parameters in this effort do not exhibit the dual nature that is evident in the ideal transformation optics design. This indicates that the inevitable field penetration and subsequent PEC boundary condition at the cylinder must be taken into account for an optimal cloaked cylinder design. Furthermore, a more effective cloaked cylinder can be designed by optimizing both layer thickness and material parameters than by additional layers alone.

Comparative Assessment for the Ability of Cirrus, RTVue, and 3D-OCT to Diagnose Glaucoma

We compared the ability of circumpapillary retinal nerve fiber layer (cpRNFL) thickness and macular parameters obtained by three spectral-domain optical coherence tomography (SD-OCT) instruments to detect glaucoma. We enrolled 87 normal eyes and 145 glaucomatous eyes (75 early glaucomatous eyes (EGs), mean deviation > -6 dB). Each participant was imaged using Cirrus, RTVue, and 3D-OCT to evaluate the average and quadrant cpRNFL thicknesses. The macular retinal nerve fiber layer (mRNFL), ganglion cell layer plus inner plexiform layer (GCL/IPL), and mRNFL + GCL/IPL (ganglion cell complex [GCC]) thicknesses were analyzed. The areas under the receiver operating characteristic curves (AUCs) were compared among the instruments. These instruments revealed similar AUCs for the average cpRNFL and GCC thicknesses in EGs, and total all-stage glaucomatous eyes (TGs). RTVue showed better performance in the nasal cpRNFL thickness than Cirrus and 3D-OCT, and better performance in the temporal cpRNFL thickness than 3D-OCT in TGs. RTVue had a higher AUC for the superior GCC thickness compared to Cirrus and 3D-OCT in EGs, and TGs. Cirrus had higher AUCs for GCL/IPL parameters in TGs, and lower AUCs for the mRNFL parameters in EGs and TGs compared to 3D-OCT. The average cpRNFL and GCC thicknesses measured using these OCT instruments exhibited similar abilities in the diagnosis of glaucoma, and RTVue exhibited better diagnostic abilities than Cirrus and 3D-OCT for nasal cpRNFL, and superior GCC thicknesses. The diagnostic performance of Cirrus and 3D-OCT was different for GCL/IPL and mRNFL parameters. (http://www.umin.ac.jp/ctr number, UMIN000006900.)

Free vibration and dynamic response of a fluid-coupled double elliptical plate system using Mathieu functions

A three-dimensional analytic model involving products of angular and radial Mathieu functions is developed for the exact free vibration analysis and transient acousto–structural response of two parallel elliptical plates, coupled with an internal bounded inviscid and compressible fluid medium, and under general external transverse loads of arbitrary temporal and spatial variations. Extensive numerical data are presented in an orderly fashion for the first ten symmetric/anti-symmetric system natural frequencies as a function of fluid layer thickness parameter for selected plate aspect ratios. Also, the occurrences of frequency veering phenomena between various modes of the same symmetry group and the interchange of associated mode shapes in the veering region are noted and discussed. Moreover, selected fluid-coupled structural deformation mode shapes are presented in vivid graphical form and the issue of mode localization is examined. The Laplace transform with respect to the time variable is subsequently invoked and a linear system of coupled algebraic equations is ultimately obtained, which is truncated and then solved by implementing Durbin's Laplace inversion algorithm accompanied with special solution convergence enhancement techniques for eradication of spurious oscillations (Gibbs' phenomenon). Numerical simulations are conducted for the displacement time histories of water-coupled double aluminum plates of selected aspect ratios and fluid depths, subjected to external loads of practical interest (i.e., an impulsive point load, a concentrated pulse load, and a uniformly distributed blast load). Validity of the results is established through computations made by using a commercial finite element package as well as by comparison with the data available in literature.

Optic disc and retinal nerve fiber layer parameters as indicators of neurodegenerative brain changes in patients with obstructive sleep apnea syndrome

Retina is a unique part of the central nervous system (CNS) for visualizing the processes of axonal and neuronal degeneration. Optical coherence tomography (OCT) allows direct visualization and measurement of retinal nerve fiber layer (RNFL) thickness, macular volume, and optic disc (OD) parameters. One of the disorders associated with atrophy in different brain regions is obstructive sleep apnea syndrome (OSAS). In the present study, we aimed to determine OD and RNFL changes measured by OCT for investigating the progress of neurodegeneration development in OSAS, excluding all the other conditions that can directly affect RNFL thickness and optic nerve parameters. Both eyes of 101 patients with OSAS and 20 controls were investigated by OCT. Full-night polysomnography (PSG) and ophthalmologic examination including automated visual field (VF) examination and OCT were performed in all of the patients. According to the OSAS grading, patients were grouped as mild (n=15), moderate (n=27), and severe (n=59). We found significant decrease in RNFL thickness only in the patients with severe OSAS compared with the other groups and decreased macular ganglion cell thickness in the severe OSAS group compared with the control group. VF parameters were significantly worsened in all the OSAS subgroups compared to the control group. We found different data such as normal or increased optic nerve parameters as result of subtle OD edema, which may mask possible peripapillar axonal loss. We think that evaluation of neurodegeneration in OSAS is not always possible by examining OD and RNFL because there are difficulties due to the confounding issues of cerebral atrophy and OD edema.