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At least 505 records · Page 28Linked to original sources
PubMed1995

Organic material concentration in auditory outer hair cells measured by laser interferometry.

Outer hair cells (OHC) of the mammalian cochlea are quasicylindrical cells of different length, which play a major role in hearing at threshold. Their particular shape allows the use of a noninvasive laser interferometric technique of isolated cells in vitro in order to measure the organic material concentration (OMC), hence the density of each cell body. In most (95%) of the OHCs isolated from the same guinea pig, when the cell diameter is normalized, the results show that the cell body OMC does not vary with cell length. In different animals, the respective normalized OMC mean values can vary between 70 kg/m3 and 103 kg/m3. A few OHCs with morphological particularities often possess cell body OMCs > 103 kg/m3. The results of the interferometric measurements in isolated OHCs confirm that density variations in the cell bodies are not involved in a sound frequency coding. The in vitro OMC variations of the OHCs could be related to the isolation procedure; however, they could also correlate with actual in vivo OMC variations.

Animals↗
PubMed1996

Trace analysis of pollutants in water using the photothermal interferometry as HPLC detector.

A new procedure including high performance liquid chromatography in combination with photothermal interference spectroscopy as detection device (HPLC/PIS) has been proposed, optimized and its figures of merit for pesticide residue analysis are shown. The flowing sample under study is set in one arm of a Mach-Zehnder interferometer, and its refractive index is modulated by a periodically chopped continuous wave argon ion laser. As chopper, an acousto optical modulator has been introduced to switch the excitation laser beam between different lines (457 nm, 488 nm, 514 nm) simultaneously. Thus a multi component analysis can be realized either by using an HPLC-system in front of the PIS device or by a multi line Ar(+)-laser, directly. The limit of detection of the HPLC/PIS system reached 71 microg/l of the pesticide di-nitro-ortho-cresol (DNOC).

Journal Article↗
PubMed1998

Two-dimensional tracking of ncd motility by back focal plane interferometry.

A technique for detecting the displacement of micron-sized optically trapped probes using far-field interference is introduced, theoretically explained, and used to study the motility of the ncd motor protein. Bead motions in the focal plane relative to the optical trap were detected by measuring laser intensity shifts in the back-focal plane of the microscope condenser by projection on a quadrant diode. This detection method is two-dimensional, largely independent of the position of the trap in the field of view and has approximately 10-micros time resolution. The high resolution makes it possible to apply spectral analysis to measure dynamic parameters such as local viscosity and attachment compliance. A simple quantitative theory for back-focal-plane detection was derived that shows that the laser intensity shifts are caused primarily by a far-field interference effect. The theory predicts the detector response to bead displacement, without adjustable parameters, with good accuracy. To demonstrate the potential of the method, the ATP-dependent motility of ncd, a kinesin-related motor protein, was observed with an in vitro bead assay. A fusion protein consisting of truncated ncd (amino acids 195-685) fused with glutathione-S-transferase was adsorbed to silica beads, and the axial and lateral motions of the beads along the microtubule surface were observed with high spatial and temporal resolution. The average axial velocity of the ncd-coated beads was 230 +/- 30 nm/s (average +/- SD). Spectral analysis of bead motion showed the increase in viscous drag near the surface; we also found that any elastic constraints of the moving motors are much smaller than the constraints due to binding in the presence of the nonhydrolyzable nucleotide adenylylimidodiphosphate.

Calibration↗
PubMed2000

Leaky wave detection at air-solid interfaces by laser interferometry

A recently developed optical heterodyne interferometer is proved to be sensitive to detect ultrasonic waves leaking out from metals (and from non-metals as well) several centimeters away from the metal surface in air. This measurement is based on the detection of the optical index variation in air due to the leaky wave. Experiments were carried out using both ultrasonic leaky Rayleigh and leaky Lamb waves in the low-megahertz region. Optical measurements of these leaky wave velocities in semi-infinite materials and plates, which are related to elastic constants of the materials, showed a good correlation to the predicted values. Optical measurements of the amplitude of the leaky waves were used to obtain attenuation coefficients, which correlate to the structural integrity of the materials. Surface and near-surface defects were also detected. This optical method can be used for metals with low-reflectivity surfaces. Thus, it can be used for non-polished surfaces and can be extended for non-contact, non-destructive evaluation applications.

Journal Article↗
PubMed1982

Laser interferometry as a prognostic tool in pseudophakic rhegmatogenous retinal detachment.

A group of patients have been studied whose retinas had been surgically reattached. The early macular function as measured by the laser interferometer is usually better than the Snellen visual acuity, and corresponds with the final Snellen visual acuity obtained in six to twelve months after surgery. A reasonable theory is proposed to explain this Snellen acuity-retinal acuity disparity.

Humans↗
PubMed2005

Dual-capillary backscatter interferometry for high-sensitivity nanoliter-volume refractive index detection with density gradient compensation.

A simple, stable, ultrasensitive dual-capillary dual-bicell (DCDB) microinterferometic backscattering detection (MIBD) system was developed. In DCDB MIBD, a He-Ne laser beam passes through a half-wave plate onto the cross section of two capillaries, one for reference and another for sensing analyte. The position of the backscattered fringe from each capillary, which are in proximity or essentially identical thermal environments, was detected with matched bicell photodetectors. The configuration was found to effectively compensate for thermal drift, which is normally the major source of noise in refractive index (RI) detection systems. It is shown that passive environmental compensation leads to greatly enhanced signal in nanoscale refractometry preformed by MIBD. An order of magnitude improvement in detection limits over single channel configurations is possible. Performance reaches the 10(-9) RIU level for like solvents in the presence in extremely large thermally induced RI gradients. At this level of detectability, DCDB MIBD could facilitate nanoliter-volume, femtomole-level universal detection in applications ranging from mu-HPLC and on-chip CE to scanning microcalorimetry.

Journal Article↗
PubMed2003

Violation of a Bell-like inequality in single-neutron interferometry.

Non-local correlations between spatially separated systems have been extensively discussed in the context of the Einstein, Podolsky and Rosen (EPR) paradox and Bell's inequalities. Many proposals and experiments designed to test hidden variable theories and the violation of Bell's inequalities have been reported; usually, these involve correlated photons, although recently an experiment was performed with (9)Be(+) ions. Nevertheless, it is of considerable interest to show that such correlations (arising from quantum mechanical entanglement) are not simply a peculiarity of photons. Here we measure correlations between two degrees of freedom (comprising spatial and spin components) of single neutrons; this removes the need for a source of entangled neutron pairs, which would present a considerable technical challenge. A Bell-like inequality is introduced to clarify the correlations that can arise between observables of otherwise independent degrees of freedom. We demonstrate the violation of this Bell-like inequality: our measured value is 2.051 +/- 0.019, clearly above the value of 2 predicted by classical hidden variable theories.

Journal Article↗
PubMed1998

Collective membrane motions of high and low amplitude, studied by dynamic light scattering and micro-interferometry.

Undulations of lipid bilayers were experimentally studied for the two limiting cases of high and weak lateral tension using two well established model systems: freely suspended planar lipid bilayers, so-called black lipid membranes (BLM) for high-tension studies and large unilamellar vesicles (LUV) for measurements at weak tension. This variation in tension results in changes of undulation amplitudes from several hundred nm (LUV) down to 1 nm (BLM), thus requiring different physical methods for their detection. We have employed microinterferometric techniques (RICM) for studying the regime of weak tension and dynamic light scattering (DLS) for that of high tension. The dedicated DLS set-up allowed the measurements of undulations over a wide wave vector range of 250 < q/cm-1 < 35,000 cm-1. This enabled the observation of collective membrane modes in two regimes, the oscillating one at low q and the overdamped regime at high q. The transition between both regimes at the bifurcation point is rather abrupt and depends on the lateral tension of the bilayer, as is demonstrated by comparing the dispersion curves of pure lipid and of lipid-cholestrol BLMs over the same q-range. The DLS measurements allowed a critical test of a hydrodynamic theory of the dispersion behaviour of membrane collective modes under tension. The DLS measurements are compared with RICM results of undulatory excitations of giant vesicles weakly adhering to substrates in the 10(-6)-2.5 x 10(-7) m wavelength regime and at low frequencies (0.1-25 Hz). Experimental evidence for the strong decrease in the relaxation rate by the hydrodynamic coupling of the membrane with the wall is established.

Animals↗