The accuracy of flap thickness and diameter in LASIK using a femtosecond laser

PURPOSE: To evaluate the resultant thickness of the WaveLight FS200 (Alcon Vision, LLC) created LASIK flap compared to intended thickness at the surgical visit, using the WaveLight EX500 (Alcon Vision, LLC) pachymeter and the resultant flap diameter compared to intended diameter. METHODS: This single arm, prospective, single surgeon study assessed the accuracy of the intended flap thickness and diameter, after successful bilateral LASIK surgery. The WaveLight FS200 femtosecond laser was used to create all flaps with an intended thickness of 120 μm. Flap thickness was calculated by subtracting the stromal bed thickness after flap lift from the preoperative corneal thickness using the WaveLight EX500 on-board optical pachymeter. Flap diameter was determined using digital analysis. RESULTS: A total of 58 subjects (116 eyes) completed the study. The calculated mean flap thickness was 120.6 ± 9.0 μm (range 102 to 143 μm) using the EX500 pre- and post-flap pachymetry measurements. There was no statistically significant difference between the planned and achieved flap thickness (p \u3e 0.05). The mean difference in flap diameter between planned and actual was 0.02 ± 0.05 mm. Corneal thickness measured by Pentacam at up to 2 months preoperatively versus EX500 just prior to surgery was similar, with EX500 measuring 2 μm less on average than the Pentacam. CONCLUSION: The results suggest that the WaveLight FS200 laser is reliable for LASIK flap thickness and diameter and accurately created flaps at the intended thickness and the intended diameter

Review and Evaluation of the Gibson Dome High Level Nuclear Waste Repository Environmental Assessment: Geohydrologic Issues

Introduction: Background/Authorization: This report is meant to provide a technical review and evaluation of Department of Energy documents concerning groundwater, radionuclide travel time and monitoring issues relative to siting a high level nuclear waste repository in the Gibson Dome area in Southern Utah. in so doing we have, during a relatively short period of time, examined in detail the Department of Energy Guidelines concerning high level nuclear waste disposal (1983) including revisions (1984), and each draft of the Environmental Assessments for Davis and Lavender Canyon, up to and including the fifth draft (dated July 27, 1984). In addition, a large body of supporting DOE documents and relavant published research literature was carefully examined and incorporated into this report. Our approach to the review and evaluation process has been to examine the assumptions analysis procedures, conclusions and supporting data regarding groundwater, radionuclide travel time and monitoring issues for the Davis and Lavender Canyon Environmental Assessments, and to provide independent appraisal of the DOE approach and assessment of these issues. This work is carried out under a contract with the State of Utah Office of Planning and Budget (Contract No. 85-0205)

A comparison of attitudes toward cognitive enhancement and legalized doping in sport in a community sample of Australian adults

Background: This article compares public attitudes toward the use of prescription drugs for cognitive enhancement with the use of performance enhancing drugs in sport. We explore attitudes toward the acceptability of both practices; the extent to which familiarity with cognitive enhancement is related to its perceived acceptability; and relationships between the acceptability of cognitive enhancement and legalized doping in sport. Methods: A survey was administered through a computer-assisted telephone interviewing system to members of the Australian general public aged 18-101 years in the state of Queensland. Results: Of 1,265 participants, 7% agreed that cognitive enhancement is acceptable; 2.4% of the total sample said they had taken prescription drugs to enhance their concentration or alertness in the absence of a diagnosed disorder, and a further 8% said they knew someone who had done so. These participants were twice as likely to think cognitive enhancement was acceptable. Only 3.6% of participants agreed that people who play professional sport should be allowed to use performance-enhancing drugs if they wanted to. Participants who found cognitive enhancement acceptable were 9.5 times more likely to agree with legalized doping. Conclusions: Policies that facilitated the use of prescription drugs by healthy people for cognitive enhancement or permitted performance-enhancing drugs in sport would be at odds with the attitudes of the vast majority of our participants. Furthermore, our findings do not support media claims that the use of prescription drugs for cognitive enhancement is widespread in all sectors of society

Public attitudes towards the acceptability of using drugs to treat depression and ADHD

Objective: This paper examines public attitudes towards the acceptability of using prescription drugs to treat depression and attention deficit hyperactivity disorder (ADHD), and whether attitudes are influenced by familiarity with the use of pharmacological treatments for these disorders

Freight Commodity Flow in Kentucky

The primary objectives of this project were to further the understanding of freight flows throughout Kentucky and to make recommendations on the potential value of freight commodity flow data as an input for statewide transportation planning models. Freight flow data are difficult to accumulate and to convert to common units for use. However, the data available from Reebie Associates that were developed with the Federal Highway Administration have proved useful. The database itself was found to be consistent with other sources of aggregate freight data for Kentucky except for airports. The data assigned to the highway network was in general agreement with weigh station counts and previous research conducted by Morehead State University. However, modeled truck volumes were found to have poor correspondence with the 1996 KYTC classification counts particularly for non-freeway routes. These errors are attributed to the large zone size (3-digit zip code) used in the model as well as the representation of Tennessee as a single zone. Specific recommendations are made for KYTC\u27s consideration for future freight transportation planning efforts

Fundamentals of Protein Adsorption at the Solid-Liquid Interface over Short Time Periods

Purpose: To directly measure the quantity and degree of denaturation of biomaterial- adsorbed proteins over short time periods. Methods: Contact lenses were used as model biomaterials as they are widely used, readily available, and have a wide variety of material properties. The proteins lysozyme, lactoferrin, and albumin were investigated, as they are major protein components of bodily fluids, notably tears. Time points within the first few minutes of protein-material interactions were concentrated on. • A novel technique to measure the activity of surface adsorbed lysozyme was developed (Chapter 3) • Direct comparison of traditional extraction procedures and the novel surface technique for measuring the activity of adsorbed lysozyme (Chapter 4) • The effect of competitive adsorption between lysozyme and lactoferrin and the effect on lysozyme activity (Chapter 5) • Investigations of using I125 radiolabeling for protein adsorption experiments with contact lenses (Chapter 6) • The effect of competitive adsorption of an artificial tear solution to the deposition of lysozyme, lactoferrin, and albumin (Chapter 7) Results: Using the novel technique, the activity of surface adsorbed lysozyme and any biologically relevant lysozyme can be measured and distinguished within the first few minutes of lysozyme-material interaction. Using the novel technique in conjunction with protein extraction provides detailed activity information about deposited biologically relevant adsorbed lysozyme and lysozyme which is in underlying protein layers or in the bulk of the material. Lactoferrin co-adsorption with lysozyme did not affect the surface activity of lysozyme, but did decrease the activity of desorbed lysozyme. Radiochemical experiments using I125 can provide sensitive measurements of protein adsorption to contact lens materials, but extra steps need to be taken to limit and measure the amount of unbound I125 in solution and to quantify the ‘apparent mass’ adsorbed unbound I125 represents. Lotrafilcon B was the only lens material to show decreased protein adsorption due to competitive adsorption effects. This effect occurred when lysozyme and lactoferrin were competing and when lysozyme, lactoferrin, and albumin were competing with components from the artificial tear solution. Conclusions: This thesis has developed and refined methods to measure biomaterial- adsorbed proteins over short time periods. These techniques can be utilized in the future to measure both the quantity and degree of denaturation of adsorbed proteins to contact lenses and other biomaterials

Effects of Fault Dip and Slip Rake Angles on Near-Source Ground Motions: Why Rupture Directivity Was Minimal in the 1999 Chi-Chi, Taiwan, Earthquake

We study how the fault dip and slip rake angles affect near-source ground velocities and displacements as faulting transitions from strike-slip motion on a vertical fault to thrust motion on a shallow-dipping fault. Ground motions are computed for five fault geometries with different combinations of fault dip and rake angles and common values for the fault area and the average slip. The nature of the shear-wave directivity is the key factor in determining the size and distribution of the peak velocities and displacements. Strong shear-wave directivity requires that (1) the observer is located in the direction of rupture propagation and (2) the rupture propagates parallel to the direction of the fault slip vector. We show that predominantly along-strike rupture of a thrust fault (geometry similar in the Chi-Chi earthquake) minimizes the area subjected to large-amplitude velocity pulses associated with rupture directivity, because the rupture propagates perpendicular to the slip vector; that is, the rupture propagates in the direction of a node in the shear-wave radiation pattern. In our simulations with a shallow hypocenter, the maximum peak-to-peak horizontal velocities exceed 1.5 m/sec over an area of only 200 km^2 for the 30°-dipping fault (geometry similar to the Chi-Chi earthquake), whereas for the 60°- and 75°-dipping faults this velocity is exceeded over an area of 2700 km^2. These simulations indicate that the area subjected to large-amplitude long-period ground motions would be larger for events of the same size as Chi-Chi that have different styles of faulting or a deeper hypocenter

Dynamic Earthquake Ruptures in the Presence of Lithostatic Normal Stresses: Implications for Friction Models and Heat Production

We simulate dynamic ruptures on a strike-slip fault in homogeneous and layered half-spaces and on a thrust fault in a layered half-space. With traditional friction models, sliding friction exceeds 50% of the fault normal compressive stress, and unless the pore pressures approach the lithostatic stress, the rupture characteristics depend strongly on the depth, and sliding generates large amounts of heat. Under application of reasonable stress distributions with depth, variation of the effective coefficient of friction with the square root of the shear modulus and the inverse of the depth creates distributions of stress drop and fracture energy that produce realistic rupture behavior. This ad hoc friction model results in (1) low-sliding friction at all depths and (2) fracture energy that is relatively independent of depth. Additionally, friction models with rate-weakening behavior (which form pulselike ruptures) appear to generate heterogeneity in the distributions of final slip and shear stress more effectively than those without such behavior (which form cracklike ruptures). For surface rupture on a thrust fault, the simple slip-weakening friction model, which lacks rate-weakening behavior, accentuates the dynamic interactions between the seismic waves and the rupture and leads to excessively large ground motions on the hanging wall. Waveforms below the center of the fault (which are associated with waves radiated to teleseismic distances) indicate that source inversions of thrust events may slightly underestimate the slip at shallow depths

Computer Simulation of Flows in a Channel with Extremely Irregular Bed Topography

Source: ICHE Conference Archive - https://mdi-de.baw.de/icheArchiv