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At least 415 records · Page 23Linked to original sources
PubMed1986

Evaluation of intrusive mechanics of the type "segmented arch" on a macerated human skull using the laser reflection technique and holographic interferometry.

Twelve different systems of intrusion, based on the principle of the "segmented arch," were evaluated on a macerated human skull. The number of teeth involved in the anterior unit and the location of the application points of intrusive force were considered to be variables. Initial displacements of the anterior teeth after loading were registered by means of the laser reflection technique and double exposure holographic recordings. An attempt was made to define "this" intrusive system, achieving the most genuine intrusion (for definition, see text) without flaring of the teeth. When two central incisors were incorporated in the sectional wire, strong torque forces appeared, especially when the intrusive forces seized more distally. When four or six anterior teeth were pinned in the sectional wire, tooth movement seemed to be under better control. When the six front teeth were incorporated in the sectional wire, the center of resistance (for definition, see text) was located more to the distal side of the canines. It seemed more difficult, however, to define the center of resistance of the four incisors; it was situated approximately distal to the lateral incisors. In some of the intrusive systems, the teeth underwent independent mesial or distal rotations. This was easily observed with the laser measuring techniques used.

Alveolar Process↗
PubMed1983

Rapid precision interferometry for the analytical ultracentrifuge. I. A laser controller based on a phase-lock-loop circuit.

This is the first of a series of manuscripts presenting methods to enable rapid reduction of data from the Rayleigh interference optical system of the Beckman Model E analytical ultracentrifuge. Here we present a pulsed laser controller for the ultracentrifuge. This laser controller uses a phase-lock-loop to provide properly timed light pulses over the speed range of 3000 to 60,000 rpm; it effectively resolves one rotor revolution into 4096 discrete angular positions. The circuit has been designed so that the laser light bursts occur at selectable angular positions of the rotor that are independent of rotor speed even under conditions of maximum acceleration or deceleration. We have used this controller in our laboratory over a 7-year period for both photographic and real-time collection at interferometric data from the ultracentrifuge.

Computers↗
PubMed1984

Rapid precision interferometry for the analytical ultracentrifuge. II. A laser controller based on a rate-multiplying circuit.

A laser controller that uses a fixed frequency clock and a digital rate-multiplying circuit to synchronize the triggering of a pulsed laser to the spinning of an analytical ultracentrifuge rotor has been designed. The circuit is simple, inexpensive, and virtually free of any adjustments. It tracks rotors undergoing full acceleration or deceleration. At constant rotor speed it provides triggering that is accurate and reproducible to better than 0.5 microseconds. The settings of this controller are independent of rotor speed over the full range of the ultracentrifuge.

Interferometry↗
PubMed1984

Rapid precision interferometry for the analytical ultracentrifuge. III. Determination of period of rotation, frequency of rotation, and elapsed time.

The approaches presented in this series of papers make possible rapid gathering, reduction, and analysis of data from the Rayleigh interference optical system of an analytical ultracentrifuge. Instrumentation described in this paper provides some of the timing and measurement circuits necessary for a microprocessor or minicomputer to determine the rotor frequency, rotor period, and elapsed time of an experiment. It includes simple but effective circuits to generate precise rotor timing pulses that are useful for synchronization of pulsed light sources. Circuits to control photographic operations in the ultracentrifuge are described briefly. All of these circuits are interfaced to a simple microcomputer address/data bus. An adapter between this bus and a Q-bus (for a DEC LSI-11/2 or LSI 11/23 microcomputer) is also described. The circuits presented have been used in this laboratory over a 3-year period. They have proven reliable and form an integral part of the real-time data acquisition systems that have been constructed.

Interferometry↗
PubMed1982

Microwatt ultrasonic power determination using laser interferometry.

A system using a water-immersed balance with laser interferometer for radiation force measurements has been developed which is capable of determining powers in the range of a few microwatts up to about 100 mW. High consistency of measuring values and low background noise levels are achieved by compensating thermal and atmospheric pressure drifts, shielding the balance system from convection currents and effective isolation from building vibrations. The sensitivity ascertained is 104 micrometer/mW or, expressed as interferometer steps (IS), 8740 IS/mW. The standard deviation for a power output of 100 mu W is less than 1% ; it increases to 11% for 3.5 mu W, the lowest value measured.

Interferometry↗
PubMed1986

The center of resistance of anterior teeth during intrusion using the laser reflection technique and holographic interferometry.

The aim of this investigation was to define the location of the center of resistance of various consolidated units of the maxillary anterior dentition using a dry human skull when subject to intrusive forces. The laser reflection technique and the holographic interferometric technique were employed to measure the displacement of the dentition to the applied forces. The units studied consisted of two central incisors, four incisors, and six anterior teeth. The incorporation of the lateral incisors into the upper incisor segment resulted in a small distal shift of the center of resistance (+/- 2 mm). However, when the canines were included into this unit, the center of resistance shifted distally by a significantly larger amount (+/- 7 mm). Increasing the magnitude of intrusive forces applied to the various units appeared to have no effect on the location of the center of resistance.

Cuspid↗
PubMed2004

High-speed label-free detection by spinning-disk micro-interferometry.

Spinning-disk interferometers are a new class of analytic sensors to detect immobilized biomolecules with high speed and high sensitivity. The disks are composed of a large number of surface-normal self-referencing interferometers, analogous to an optical CD, but operating on the principle of microdiffraction quadrature that achieves sensitive linear detection of bound molecules. The surface-normal structures have a small footprint of only 20 microm each, allowing potential integration to over a million interferometric elements per disk. We have fabricated interferometric microstructures on silicon and on dielectric mirror disks to demonstrate the basic principles of the BioCD. We have detected the presence of immobilized anti-mouse IgG and the specific binding of 10 femtomol of mouse IgG at a sampling rate of 100 kilo-samples/s, while also demonstrating negligible non-specific binding. This technique provides a label-free method that could potentially screen hundreds to thousands of proteins per disk.

Biosensing Techniques↗
PubMed1985

Laser interferometry and visual prognosis in uveitis.

Forty-six eyes in 26 patients with active, intermediate, and/or posterior uveitis with decreased visual acuity were evaluated with the laser interferometer before treatment with systemic cyclosporine. Pretreatment visual acuity (ETDRS), pretreatment laser interferometric visual acuity, and the best visual acuity obtained while under treatment were compared. Eighty-six percent of patients in whom the laser interferometer predicted an improvement of three or more lines did improve. In contrast, 52% of patients in whom no improvement was predicted improved three or more lines with therapy. There was a moderate correlation (R = 0.59) (P less than 0.001) between the number of lines of improvement predicted and the number of lines of improvement obtained. If the laser visual acuity is three or more lines better than the eye chart acuity, the prognosis for vision improvement after cyclosporine therapy is good, even in those patients with cystoid macula edema.

Humans↗
PubMed2003

Comparison of biometric measurements using partial coherence interferometry and applanation ultrasound.

PURPOSE: To compare and contrast axial length (AL) measurements assessed by ultrasound biometry and optical biometry. SETTING: Department of Ophthalmology, Johannes Gutenberg-University, Mainz, Germany. METHODS: Optical biometry and ultrasound biometry were performed in 360 eyes to measure AL. RESULTS: In eyes with a clear-appearing crystalline lens, there was a statistically significant median difference in AL measurements between the 2 methods in eyes with a normal or long length. In eyes with cataract, there was a statistically significant median difference in AL measurements in eyes with a normal or short length. In these cases, optical biometry produced larger readings than ultrasound biometry. In eyes with a posterior chamber intraocular lens, there was no statistically significant difference between the 2 methods in eyes of all lengths. In all eyes, the 2 methods produced reliable measurements. CONCLUSIONS: These results show that optical biometry and ultrasound applanation biometry give statistically significant differences in AL measurement in patients with cataract and normal lenses. In these cases, optical biometry provided clinically relevant larger values than ultrasound applanation. Optical biometry provides an alternative to ultrasound biometry. However, ultrasound biometry may be indicated in certain complex cases.

Biometry↗
PubMed1993

Reverse transduction measured in the isolated cochlea by laser Michelson interferometry.

It is thought that the sensitivity of mammalian hearing depends on amplification of the incoming sound within the cochlea by a select population of sensory cells, the outer hair cells. It has been suggested that these cells sense displacements and feedback forces which enhance the basilar membrane motion by reducing the inherent damping of the cochlear partition. In support of this hypothesis, outer hair cells show membrane-potential-induced length changes at acoustic rates. This process has been termed 'reverse transduction'. For amplification, the forces should be large enough to move the basilar membrane. Using a displacement-sensitive interferometer, we tested this hypothesis in an isolated cochlea while stimulating the outer hair cells with current passed across the partition. We show here that the cochlear partition distorts under the action of electrically driven hair cell length changes and produces place-specific vibration of the basilar membrane of a magnitude comparable to that observed near auditory threshold (about 1 nm). Such measurements supply direct evidence that cochlear amplification arises from the properties of the outer hair cell population.

Animals↗
PubMed1990

White light interferometry in amblyopic children--a pilot study.

Interferometric acuity using the IRAS white light interferometer was compared with Snellen acuity in nine amblyopic children between the ages of five and nine years, and nine aged matched controls. All of the amblyopic eyes achieved better grating acuities than Snellen acuities. Fifty-seven per cent of the amblyopes with a best corrected Snellen acuity of 6/18 or less in their amblyopic eye, achieved grating acuities indistinguishable from normal. The hand held white light interferometer may have a role in the assessment of meridional amblyopia and in children with high astigmatic errors.

Amblyopia↗