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At least 1,657 records · Page 92Linked to original sources
PubMed1986

Homodyne interferometer for basilar membrane measurements.

Techniques available for measuring the mechanical response of the inner ear are compared. These include capacitive probe, Mössbauer and interferometric methods. The theory of a homodyne interferometer utilized for inner ear measurements is given. Experimental apparatus built to test the interferometer performance is described. Experimental results show that the measuring system can detect vibrations as low as 3 X 10(-12) cm. Its frequency response is flat within 1 dB from 0.1 to 40 kHz. It has a linear dynamic range of over 90 dB. Immunity of the interferometer to various disturbances is demonstrated.

Basilar Membrane↗
PubMed1986

Homodyne interferometer for basilar membrane vibration measurements. II. Hardware and techniques.

Selected mechanical features of the design of the homodyne interferometer are described. This interferometer was utilized for basilar membrane vibration measurements. The massive construction necessary to minimize mechanical vibration and noise is described. In order to measure basilar membrane vibrations, it was necessary to increase its reflectivity. Gold crystals were utilized as microscopic mirrors. The technique for fabrication of gold crystals is described. These crystals are small and fragile and required special handling. The method of picking up the crystals and placing them on a preselected location is described. In order to minimize the effect of the involuntary animal movements a reference mirror system is cemented to the skull. The design of the reference mirror system and the method of cementing it to the skull are described.

Animals↗
PubMed1986

Measurement of basilar membrane vibrations and evaluation of the cochlear condition.

The experimental procedure for measuring basilar membrane responses to acoustic signals is described. The surgical procedure developed for opening the cochlea with minimal trauma is presented. Each experiment included sound pressure level measurements to define the input signal, cochlear microphonic (CM) measurements to monitor the cochlear condition, interferometric measurements and histological evaluation of the cochleas. The characteristic frequency (CF) and the sensitivity at CF for the basilar membrane response is correlated with the change of CM response observed in six animals. It is demonstrated that both tuning characteristics are extremely sensitive to cochlear trauma as evidenced by changes of CM.

Animals↗
PubMed1987

Laser interferometric measurements on the dynamic behaviour of the cupula in the fish lateral line.

The motion of the cupula in the supra-orbital lateral line canal of the ruff in response to sinusoidal water movements was measured in vivo by means of a novel laser interferometer microscope. The interferometer utilized the laser light scattered back from a small bead (phi approximately equal to 1 micron) which was positioned under visual control on a selected location inside the cupula. The displacement of the cupula was measured in the range of 0.3 to 300 nm. The stimulus-response relation is found to be linear in this range. The frequency response of the cupula measured at the top is identical to that measured at the base near the sensory hair bundles. From this result it is concluded that the cupula is sliding over the sensory epithelium during motion in the physiological displacement range. A hydrodynamical model of cupular motion which incorporates a frequency dependent boundary layer around the cupula is presented. The model accurately describes the experimental data.

Animals↗
PubMed1989

Interferometric measurement of the amplitude and phase of tympanic membrane vibrations in cat.

The amplitude and phase of the tympanic membrane and malleus vibrations were measured over a wide frequency range with a homodyne interferometer. When sound pressure was maintained constant near the tympanic membrane, the malleus frequency response followed the typical pattern up to 10 kHz as measured by previous investigators. At higher frequencies the response changes dramatically. Instead of decreasing with frequency, between 10 and 20 kHz the vibration amplitude oscillates around a value which is only about 20 dB lower than the low frequency plateau level. Measurements of malleus vibration at several points along its length indicate that its mode of vibration changes at high frequencies, and no longer consists of a simple rotational component. All points on the tympanic membrane vibrate in phase with the malleus up to a frequency of 1 kHz. Above 5 kHz discrete resonances are observed, and the response varies strongly with position on the tympanic membrane.

Animals↗
PubMed1990

Heterodyne interferometer measurements of the frequency response of the manubrium tip in cat.

A heterodyne interferometer proved to be a very accurate tool to measure amplitude and phase of the malleus response during acoustical stimulation. It was shown that to obtain equal accuracy in the acoustical pressure measurements, pressure response must be remeasured at short time intervals. At frequencies above 4 kHz various gross resonances are apparent on the frequency response curves. The resonances are, depending on the animal, more or less pronounced. As a result of the improved accuracy changes of the malleus vibration response with time could clearly be discriminated. These changes can be related to shifts in frequency of the position of these resonances. Comparison of experimental frequency response and lumped parameter model predictions from literature shows that these resonances are not present in the model responses.

Acoustics↗
PubMed1991

Malleus vibration mode changes with frequency.

The mode of vibration of the cat manubrium is investigated by measuring its vibration in response to sound stimulus at four locations between the umbo and the processus lateralis with a heterodyne interferometer. The determination of mode requires high precision in measurement because amplitude differences between the points are small (about 20% at low audio-frequencies). Changes in the frequency response with time have been reported in an earlier paper. The nature and magnitude of this time change is analysed in detail: over a period of 1 h the average change in amplitude is about 5% and in phase 5 degrees. The malleus vibration at some frequencies is purely translational, it is rotational at others and mixed at most frequencies. When the motion is rotational the position of the axis of rotation shifts with frequency, the shifts are so large that the axis can lie near the umbo so that amplitudes at the processus lateralis are larger than at the umbo. The classical concept of the malleus rotating around a fixed axis running from the anterior mallar to the posterior incudal ligament fits our measurements only at low frequencies.

Animals↗
PubMed1992

Basilar membrane mechanics in the hook region of cat and guinea-pig cochleae: sharp tuning and nonlinearity in the absence of baseline position shifts.

A heterodyne laser interferometer was used to observe the movements of small (approximately 20 microns) stainless-steel beads placed on the basilar membrane in the hook region of cat and guinea-pig cochleae. In several preparations, the displacement patterns observed exhibited sharp nonlinear tuning; in one cat this tuning was comparable to that commonly observed in single auditory-nerve fibers. The most sensitive frequencies of the preparations ranged from 31-40 kHz in the cat, and 28-32 kHz in the guinea-pig. The sharp tuning and nonlinearity of the basilar membrane responses was not apparent in surgically or acoustically traumatized preparations. The response nonlinearities were susceptible to temporary threshold shifts and disappeared within a few minutes post-mortem. Stimulus-related shifts in the baseline position of the basilar membrane were not apparent at low stimulus levels. Such shifts were occasionally observed at higher stimulus levels (e.g., > 90 dB SPL), but never approached the fundamental (oscillatory) component of basilar membrane vibration in magnitude. These findings are discussed in relation to previous observations by other workers.

Acoustic Stimulation↗
PubMed1995

Shape and displacement patterns of the gerbil tympanic membrane in experimental otitis media with effusion.

This study assesses the visco-elastic properties of the tympanic membrane (TM) in isolated gerbilline temporal bones as a function of time after inducing experimental otitis media with effusion (OME). To do this we measured the TM displacements produced by application of sequences of static pressures across the TM, with a high resolution, real-time, differential moiré interferometer, and the results were compared with measurements on healthy ears. Two methods of producing OME were used: in one group tubal plugging was performed to produce mild OME (the 'TP group'); in the other group electro-cauterization of the nasopharyngeal orifice of the Eustachian tube was used to cause a severe form of OME (the 'EC group'). The measurements were performed from one day up to ten weeks after surgery. In the TP group the displacement fringe patterns were normal, i.e. qualitatively they resembled the patterns of the control group. Quantitatively there was a significant decrease of displacement for a given pressure on the first day after surgery, followed by a trend of increase with time; after seven to ten days the displacement was larger than in the control group. In the EC group the displacement was significantly reduced after half a week, followed by a trend of increase with time, similar to what was found in the TP group; at one week the displacement was larger than in the control group, and at ten weeks the largest displacement was recorded. In the EC group the displacement patterns were often irregular; in some cases with changes suggesting the presence of weak spots in the TM where retraction pockets most likely could develop. OME seems to affect the stiffness of the TM promptly so that it is a potential parameter for early diagnosis. The stiffness changes may, if measurable in the clinical situation, become prognostic parameters in the treatment of OME.

Acoustic Stimulation↗
PubMed1994

A method for determining three-dimensional vibration in the ear.

In the classical concept of the middle ear function the malleus rotates around a fixed axis which implies that at small amplitudes of vibration its displacement is essentially one dimensional. As a consequence malleus vibrations have been measured previously along a single viewing axis. As a first step in the study of the complete malleus motion we determined the three dimensional components at a single point (umbo) of the manubrium. To define 3-D motion it is in principle necessary to measure the vibrations from widely different observation angles. The viewing angles are limited however in our case by the ear canal geometry to about +/-15 degrees. In order to resolve the 3-D components under these conditions it is necessary to measure the vibration components with high accuracy. Amplitude and phase of the umbo vibrations were measured with a heterodyne interferometer over a wide frequency range (100 Hz to 20 kHz). The system included a two axis goniometer with the axes of rotation positioned at the focal plane of the interferometer objective lens. It was therefore possible to change the viewing angle in small increments around two orthogonal axes while keeping the same point in focus. From a redundant set of measurements the three orthogonal components of vibration were calculated by least squares fitting. The vector sum of the three components gives the three dimensional motion of the observed point. The vibration of the point on the umbo was found not to follow a straight line but an elliptical path instead. The shape of the ellipse and the inclination of the plane of the ellipse with respect to the stationary malleus position changed with frequency. These observations are consistent with our earlier findings that the mode of malleus vibration changes with frequency [Decraemer et al. (1991) Hear. Res. 54, 305-318].

Acoustic Stimulation↗
PubMed1995

Sound-induced displacement responses in the plane of the organ of Corti in the isolated guinea-pig cochlea.

Sound-induced displacement responses in the plane of the organ of Corti were studied in the apical turn in the isolated temporal-bone preparation of the guinea-pig cochlea. Swept sinusoidal sound stimuli (100-500 Hz) were delivered closed-field to the external auditory meatus. The surface of the organ of Corti was continuously monitored using a CCD video camera. Displacement responses in the plane of the organ of Corti were determined by analyzing the change of the location of the cells (pixel-by-pixel) within the visual field of the microscope. Displacement responses followed the stimulus amplitude and were observable at Hensen's cells, three rows of outer hair cells and inner hair cells. The most prominent displacement responses were over the outer hair cells; the maximum amplitude was 0.6-1.7 microns at 100 dB SPL. Tuned displacement responses were found; the Q10 dB was 1.3 +/- 0.6. The best frequency was tonotopically organized, decreasing toward the apex with a space constant of 0.4-0.9 mm/oct. The motion was directed either strial-apically or strial-basally in a frequency dependent manner. With the aid of laser interferometric measurements of the transverse displacement, it was concluded that sound stimulation does not induce slow DC motion in the organ of Corti for the isolated temporal-bone preparation.

Acoustic Stimulation↗
PubMed1994

Immunoreactivity of adsorbed anti human chorionic gonadotropin studied with an optical waveguide interferometric sensor.

A study on the immunoreactivity of adsorbed alpha hCG molecules as a function of substrate hydrophobicity and protein coverage is presented. The experiments were performed with a planar waveguide interferometrical immunosensor. The substrate hydrophobicity and the antibody density were found to be of major importance for the immunoreactivity of the adsorbed antibodies. A combination of a hydrophobic (contact angle > or = 80 degrees) substrate and only a fraction (approximately 0.3) of a monolayer of antibodies gives the highest immunoreactivity. However, the immunoreaction affinity constant of the active antibodies is found to be essentially independent of the substrate hydrophobicity. The experimental results indicate that the orientation and not the conformation of the active antibodies on the substrate is dependent on the substrate hydrophobicity.

Antibodies, Monoclonal↗
PubMed2004

Optical coherence tomography and confocal scanning laser tomography for assessment of macular edema.

PURPOSE: To compare optical coherence tomography (OCT) and confocal scanning laser tomography (cSLT) for quantitative retinal thickness mapping of the macula and their ability to detect macular edema. DESIGN: Prospective, comparative, clinical observational study. METHODS: The study population of 138 eyes (97 patients) was divided into a study group consisting of 45 (32.6%) eyes with macular edema and a control group consisting of 93 (67.4%) eyes without macular edema. All patients underwent OCT and cSLT of the macula. Retinal thickness measurements obtained by OCT were compared with signal width and edema index, determined by cSLT. RESULTS: The OCT measurements and cSLT edema index were significantly (P <.001) correlated with each other. Correlation coefficients decreased (P <.001) with increasing diameter of the measurement circle. In the macular edema group, correlation coefficients were significantly (P <.001) higher than in the control group. To separate the study and control groups, receiver operator characteristic curves covered a larger area for OCT measurements than for cSLT measurements. Retinal thickness measurements and edema index correlate with visual acuity (correlation coefficient r = -.653 for OCT, r = -.608 for cSLT; P <.001). CONCLUSIONS: Macular edema can be quantitatively mapped by OCT and cSLT. The retinal thickness and edema index measurements correlate with visual acuity. The fast and standard examination modes of OCT give similar measurements. Both OCT and cSLT can differentiate between eyes with and without macular edema, with OCT showing a higher predictive value.

Aged↗
PubMed2004

Direct measurements of the compressive properties of single proteoglycan aggregates.

Proteoglycan aggregate is a major component of the extracellular matrix in articular cartilage and is considered to be responsible for the resistance to compression of this tissue. The reduced stiffness of articular cartilage due to the loss of proteoglycan aggregate has been reported in osteoarthritis. In order to understand the mechanical properties of extracellular matrix in articular cartilage at molecular level, the compressive properties of 36 single molecules of proteoglycan aggregate were directly measured using a laser tweezers/interferometer system. The proteoglycan aggregates showed resistance when compressed to approximately 30% of their contour length. The stiffness of proteoglycan aggregates increased non-linearly from 2.6+/-3.8 pN/microm (compressed to 30-35% of their contour length) to 115.5+/-30.9 pN/microm (compressed to 2.5-5% of their contour length).

Compressive Strength↗
PubMed2005

Laser interference lithography as a new and efficient technique for micropatterning of biopolymer surface.

Laser interference lithography (LIL) is a straightforward technique to prepare linear micropatterns for regulating cellular adhesion behaviors on polymer substratum. This process is based on selective laser ablation directly duplicating the interference patterns of two or more coherent laser beams onto the polymer surface. Micropatterns prepared by LIL on poly(ethylene terephthalate) and Thermanox were characterized using atomic force microscopy (AFM) and white light interferometer while the chemical surface modification induced by laser was analyzed by X-ray photoelectron spectroscopy (XPS). The AFM photographs show that the micropatterns are well-defined and of great consistency. Polymer properties and laser parameters related to LIL as well as laser ablation mechanisms are discussed in this technical note.

Biocompatible Materials↗
PubMed2005

Integration of microfluidics with a four-channel integrated optical Young interferometer immunosensor.

This report describes an optical sensing hybrid system obtained by bonding a microfluidic system to an integrated optical (IO) four-channel Young interferometer (YI) chip. The microfluidic system implemented into a glass plate consists of four microchannels with cross-sectional dimensions of 200 microm x 15 microm. The microfluidic system is structured in such a way that after bonding to the IO chip, each microchannel addresses one sensing window in the four-channel YI sensor. Experimental tests show that the implementation of the microfluidics reduces the response time of the sensor from 100s, as achieved with a bulky cuvette, to 4s. Monitoring the anti-human serum albumine/human serum albumine (alpha-HSA/HSA) immunoreaction demonstrates the feasibility to use the microfluidic sensing system for immunosensing applications. In this case, a better discrimination between the bulk refractive index change and the layer formation can be made, resulting into higher accuracy and offering the prospect of being able to use the kinetics of the immunoreaction. The microfluidic sensing system shows an average phase resolution of 7 x 10(-5) x 2pi for different pairs of channels, which at the given interaction length of 4 mm corresponds to a refractive index resolution of 6 x 10(-8), being equivalent to a protein mass coverage resolution of 20 fg/mm2.

Antibodies↗
PubMed2005

Porous silicon-based optical microsensor for the detection of L-glutamine.

The molecular binding between the glutamine-binding protein (GlnBP) from Escherichia coli and L-glutamine (Gln) is optically transduced by means of a biosensor based on porous silicon nano-technology. The sensor operates by the measurement of the interferometric fringes in the reflectivity spectrum of a porous silicon Fabry-Perot layer. The binding event is revealed as a shift in wavelength of the fringes. Due to the hydrophobic interaction with the Si-H terminated surface of the porous silicon, the GlnBP protein, which acts as a molecular probe for Gln, penetrates and links into the pores of the porous silicon matrix. We can thus avoid any preliminary functionalization process of the porous layer surface, which is also prevented from oxidation, at least for few cycles of wet measurements. The binding of Gln to GlnBP has also been investigated at different concentration of GlnBP.

Biosensing Techniques↗