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PubMed1982

[Use of holographic interferometry in the analysis of the process of deformation of the base of the skull].

In order to reveal certain quantitative criteria on the skull basis deformities resulting from an injuring agent effect, an experimental investigation has been performed using the holographic interferometry method. Interferograms are registrated according to the scheme offered by Yu. N. Denisyuk at a gradual mechanical loading of the skull by means of a special device. A complicated picture of the skull basis deformity has been revealed under the effect of a successively increasing loading. When the external loading is comparatively small, a slight deformity of some bones appears and their dislocations regarding each other are distinctly seen. When the loading is as great as 90 kg (900 N), the mutual dislocation of the bones is stopped and a solid formation is resulted. If the loading is further increased, the curve of the whole skull basis is produced along the line passing through the foramen occipitale magnum region. The phenomena described correspond to an elastic skull deformity. Cracks and fractures begin forming when the resources of the mutual dislocation of the osseous fragments and the elastic deformity of separate bones are completely exhausted (in the experiments performed--at the loadings of 100 kg, that is 1,000 N and more). The greatest strain is observed in the area of the Turkish saddle, wings of the os sphenoidal, apices of the tample bone pyramids, that corresponds to clinical data on localization of fractures.

Cephalometry↗
PubMed1994

Holographic interferometry: a new technique for in vitro investigations of prosthetic heart valves.

At present there are many different prosthetic models available for heart valve replacement. Postimplant dysfunction resulting from material failure has been reported in several prostheses. The prime cause of these defects is hidden abnormalities in the valve construction or materials. In order to detect these defects before implantation, preoperative non-destructive testing of individual valves is proposed. For this purpose, holographic interferometry has been applied which is a non-contact, non-destructive, highly sensitive, three-dimensional measurement technique. Samples of different types of prosthetic heart valve, both mechanical and biological, were mounted in a specially developed test chamber with optical access from four sides. The valves were loaded with a static liquid pressure of 2.5-15 kPa. Deformations of the valves as a result of small pressure differences (0.5-15% of the static pressure) applied between two exposures were recorded by double-exposure holography. A fringe pattern superimposed on the image of the valve reconstructed from the hologram clearly indicates the presence of defects in the valve material.

Heart Valve Prosthesis↗
PubMed1993

Non-destructive evaluation of prosthetic heart valves by holographic interferometry.

Dysfunction of prosthetic heart valves is a common complication after heart valve replacement, affecting both biologic and mechanical prostheses. A preoperative, non-destructive test of each individual valve may help to prevent the implantation of a valve which has material weaknesses. To this end we developed a technique for testing heart valve prostheses by holographic interferometry. The advantage of this technique is that it provides a non-contact, non-destructive, highly sensitive three dimensional analysis of the valve under loading. Samples of several mechanical and biologic valve substitutes were investigated. Deformations of the valve, due to small pressure differences applied to the samples in a specially developed test chamber, were recorded by double exposure holography. A fringe pattern superimposed on the image of the valve reconstructed from the hologram clearly indicates the presence of even the slightest defect in the valve material. Our experimental results demonstrate the ability of non-destructive holographic screening testing to detect defects or weaknesses which may potentially lead to dysfunction in replacement valves.

Animals↗
PubMed1993

[Mechanism of the formation of orbital floor fractures. Holographic interferometry studies].

To date, it has not been possible to answer the question of whether in the classic blow-out fracture the orbital floor is fractured by hydraulic force exerted by the orbital contents or by force transmission within the bony structures of the skull. The aim of our investigation was therefore to reveal the nature of orbital deformation mediated solely by the bone. In holographic interferometry the holographic image of the unstrained object is superimposed on the image of the same object after deformation. The resulting image of the object contains a pattern of interference lines representing the extent of the deformation. This image can be visualized on a TV screen after digital processing of a picture registered by a video camera. This method was used to analyze the deformation of the bony orbit by contact force applied to several points along the orbital rim (each application consisting of 1 N) and by strain distributed evenly upon the orbital rim of the human skull. In all cases maximal deformation occurred in the medial part of the orbital floor no matter where the stress was applied. This finding coincides with the fact that the majority of clinically diagnosed fractures are found in this area. In conclusion, force transmission within the bone is considered as being one determining factor for occurrence of orbital floor fractures.

Biomechanical Phenomena↗
PubMed1996

[Prediction of functional recovery after surgery of macular epiretinal membranes. Value of interferometry using Lotmar's apparatus].

BACKGROUND: The predictability of the measurement of the macular function by white light interferometry was evaluated in a group of patients whose epiretinal membranes had been surgically removed. METHOD: Fifteen patients presenting either primitive or secondary epiretinal membranes were included. We used the apparatus described by W. Lotmar. The main evaluation criteria was the best corrected visual acuity (VA) chosen between the third month and the sixth month examinations. RESULTS: Preoperatively the mean visual acuity was 0.227 +/- 0.105. The mean final visual acuity was 0.507 +/- 0.198. The final visual acuity was predicted within an 0.1 interval in ten cases (67%). In two cases the predicted visual acuity was identical to the pre-operative VA and the final results confirmed the test. No improvement occurred. CONCLUSION: The Lotmar visometer is statistically predictive of the visual outcome after epi-retinal membranes surgery.

Female↗
PubMed2005

Development and validation of vertical scanning interferometry as a novel method for acquiring chondrocyte geometry.

Chondrocytes are sensitive to changes in shape which depend on the type of substrate, mechanical factors, or biochemical stimuli. Shape changes can cause metabolic and phenotypic alterations. Cell geometry is also important for mechanical models, determination of mechanical properties, and the study of cell attachment and spreading. In this study, a novel method called vertical scanning interferometry (VSI) was developed to allow rapid and straightforward determination of the height, diameter, surface area, volume, and curvature of single chondrocytes. The dimensions of single chondrocytes at 4 and 18 h were obtained and validated. Differences in the heights of zonal chondrocytes were found to be statistically significant. This method was also used to capture the geometry of a cell dehydrating as it was exposed to air. VSI has advantages over confocal microscopy and atomic force microscopy in terms of speed, ease of use, field of view, and precision. VSI quickly obtains and graphically represents the three-dimensional geometry of chondrocytes in a simple format. These methods could be expanded to image many types of cells on various biomaterials to assess biocompatibility and attachment and cell spreading characteristics.

Animals↗
PubMed2006

Electronic speckle pattern interferometry: a novel non-invasive tool for studying drug transport rate through free films.

In this work, Electronic Speckle Pattern Interferometry (ESPI) is presented as a non-invasive tool to study drug transport in controlled release systems. ESPI is shown to be a feasible tool to measure drug film permeability via comparison with an ordinary diaphragm cell. A specially designed cuvette was used in the release study: the polymeric film separated the donor and the receiving chambers of the cuvette to create a diffusion cell with no mixing in the two chambers. Thus, the cuvette mimicked a coated system immersed in a stagnant bulk liquid. Concentration profile data were obtained for the two compartments. Using these data, it was possible to visually discriminate between a film subject only to diffusion and a film subject to diffusion as well as osmotic effects. Moreover, using the concentration profile data collected at different time intervals, it was possible to follow the film properties in terms of drug permeability, thus studying how drug permeability depended on drug concentration. Compared to other measuring techniques, ESPI offers the advantages that no invasive measurements are needed, and that no sampling and calibration are required. Furthermore, the permeability can be measured with no influence of mass transfer in the boundary layers.

Benzyl Alcohols↗
PubMed2004

Resonance ultrasound spectroscopy with laser-Doppler interferometry for studying elastic properties of thin films.

We propose an advanced method to determine the elastic-stiffness coefficients Cij of thin films using resonance ultrasound spectroscopy (RUS). It uses free-vibration resonance frequencies of a film/substrate layered solid and derives inversely the film's Cij from the resonance frequencies. We develop a piezoelectric tripod consisting of two pinducers and one support to place the specimen on it and measure the resonance frequencies with high enough accuracy. Furthermore, we achieve mode identification by measuring deformation distributions on the vibrating specimen surface using laser-Doppler interferometry. Accurate measurements of frequencies and correct mode identification are the keys for deducing reliable Cij of the film. We applied this technique to copper thin films deposited of Si substrates. The resulting film's Cij are considerably smaller than the bulk's Cij and show anisotropy between the out-of-plane direction and in-plane direction.

Journal Article↗
PubMed2000

Chip-scale universal detection based on backscatter interferometry

An on-chip detector based on backscatter interferometry has been developed to perform subnanoliter-volume refractive index measurements. The detection system consists of a simple, folded optical train based on the interaction of a laser beam and an etched channel, consisting of two radii joined by a flat portion, thus defining a curved surface in the shape of a hemisphere in a silica (glass) plate. The backscattered light from the channel takes on the form of a high-contrast interference pattern that contains information related to the bulk properties of the fluid contained within the probe volume. Positional changes of the interference pattern (fringes) allow for the determination of deltan at the 10(-6) level, corresponding to 743 microM or 139 x 10(-15) mol or 12.8 x 10(-12) g of sucrose, in a probe volume of only 188 x 10(-12) L. A theoretical model of the on-chip backscatter interferometric detector has also been developed, evaluated, and found to be in agreement with experimental data. It is shown that the model can be used to predict general system performance for changes in the optical train such as the chip's wall thickness and channel diameter.

Journal Article↗
PubMed2006

Chemical gas sensor application of open-pore mesoporous thin films based on integrated optical polarimetric interferometry.

Chemical gas sensors that employ integrated optical polarimetric interferometry were fabricated by the sol-gel synthesis of transparent mesoporous thin films of TiO2-P2O5 nanocomposite on tapered layers of TiO2 sputtered on tin-diffused glass waveguides. Atomic force microscopy images of the mesoporous thin film clearly show the open pore mouths on the film surface that favor rapid diffusion and adsorption of gas-phase analytes within the entire film. Adsorption of gas and vapor induces changes (Deltan) in the refractive index of the mesoporous thin film that lead to shifts in the phase difference between the fundamental transverse electric and magnetic modes simultaneously excited in the glass waveguide via single-beam incidence. Upon exposure to NH3 gas at concentrations as low as 100 ppb in dry air at room temperature, the sensor exhibits a reversible change in the phase difference with the response and recovery times of less than 60 and 90 s, respectively. It is unexpected that the sensor is unresponsive to either NO2 or C6H6 vapor, leading to a somewhat selective sensitivity to NH3. Determination of Deltan was carried out with a combination of the experimental results and the theoretical calculations. The sensor design represents a novel, effective, and easily accessible approach to mesoporous thin-film-based integrated optical chemical sensors.

Journal Article↗
PubMed2006

Nonlinear wave-packet interferometry and molecular state reconstruction in a vibrating and rotating diatomic molecule.

We formulate two-color nonlinear wave-packet interferometry (WPI) for application to a diatomic molecule in the gas phase and show that this form of heterodyne-detected multidimensional electronic spectroscopy will permit the reconstruction of photoinduced rovibrational wave packets from experimental data. Using two phase-locked pulse pairs, each resonant with a different electronic transition, nonlinear WPI detects the quadrilinear interference contributions to the population of an excited electronic state. Combining measurements taken with different phase-locking angles isolates various quadrilinear interference terms. One such term gives the complex overlap between a propagated one-pulse target wave packet and a variable three-pulse reference wave packet. The two-dimensional interferogram in the time domain specifies the complex-valued overlap of the given target state with a collection of variable reference states. An inversion procedure based on singular-value decomposition enables reconstruction of the target wave packet from the interferogram without prior detailed characterization of the nuclear Hamiltonian under which the target propagates. With numerically calculated nonlinear WPI signals subject to Gaussian noise, we demonstrate the reconstruction of a rovibrational wave packet launched from the A state and propagated in the E state of Li2.

Journal Article↗
PubMed2006

Immobilization of enamel matrix derivate protein onto polypeptide multilayers. Comparative in situ measurements using ellipsometry, quartz crystal microbalance with dissipation, and dual-polarization interferometry.

The buildup of biodegradable poly(L-glutamic acid) (PGA) and poly(L-lysine) (PLL) multilayers on silica and titanium surfaces and the immobilization of enamel matrix derivate (EMD) protein was followed by utilizing in situ ellipsometry, quartz crystal microbalance with dissipation, and dual-polarization interferometry (DPI). The use of the relatively new DPI technique validated earlier published ellipsometry measurements of the PLL-PGA polypeptide films. The hydrophobic aggregating EMD protein was successfully immobilized both on top of and within the multilayer structures at pH 5.0. DPI measurements further indicated that the immobilization of EMD is influenced by the flow pattern during adsorption. The formed polypeptide-EMD multilayer films are of interest since it is known that EMD is able to trigger cell response and induce biomineralization. The multilayer films thus have potential to be useful as bioactive and biodegradable coatings for future dental implants.

Animals↗
PubMed2000

Widespread uplift and 'trapdoor' faulting on Galápagos volcanoes observed with radar interferometry.

Volcanic uplift, caused by the accumulation of magma in subsurface reservoirs, is a common precursor to eruptions. But, for some volcanoes, uplift of metres or more has not yet led to an eruption. Here we present displacement maps of volcanoes in the Galápagos Islands, constructed using satellite radar interferometry, that might help explain this dichotomy. We show that all but one of the seven volcanoes on the islands of Isabela and Fernandina deformed during 1992-99. Cerro Azul and Fernandina erupted during the observation period and show evidence of inflation, co-eruptive deflation and shallow dyke intrusion. In contrast, the largest volcano, Sierra Negra, has not erupted, yet exhibits spatially and temporally variable deformation, with a maximum uplift of 2.7 m between 1992 and 1999, which can be modelled by a shallow inflating sill. Inflation during 1997-98, however, was accompanied by 'trapdoor' faulting on a steeply dipping fracture system within the caldera. Repeated trapdoor faulting over geological time has formed an arcuate intra-caldera ridge within Sierra Negra and may have acted to relax stresses above the magma chamber, inhibiting summit eruptions. Similar processes may help explain large uplift unaccompanied by eruptive activity at other volcanoes.

Journal Article↗
PubMed2005

Spatial quantum noise interferometry in expanding ultracold atom clouds.

In a pioneering experiment, Hanbury Brown and Twiss (HBT) demonstrated that noise correlations could be used to probe the properties of a (bosonic) particle source through quantum statistics; the effect relies on quantum interference between possible detection paths for two indistinguishable particles. HBT correlations--together with their fermionic counterparts--find numerous applications, ranging from quantum optics to nuclear and elementary particle physics. Spatial HBT interferometry has been suggested as a means to probe hidden order in strongly correlated phases of ultracold atoms. Here we report such a measurement on the Mott insulator phase of a rubidium Bose gas as it is released from an optical lattice trap. We show that strong periodic quantum correlations exist between density fluctuations in the expanding atom cloud. These spatial correlations reflect the underlying ordering in the lattice, and find a natural interpretation in terms of a multiple-wave HBT interference effect. The method should provide a useful tool for identifying complex quantum phases of ultracold bosonic and fermionic atoms.

Journal Article↗
PubMed2005

Molecular wave packet interferometry and quantum entanglement.

We study wave packet interferometry (WPI) considering the laser pulse fields both classical and quantum mechanically. WPI occurs in a molecule after subjecting it to the interaction with a sequence of phase-locked ultrashort laser pulses. Typically, the measured quantity is the fluorescence of the molecule from an excited electronic state. This signal has imprinted the interference of the vibrational wave packets prepared by the different laser pulses of the sequence. The consideration of the pulses as quantum entities in the analysis allows us to study the entanglement of the laser pulse states with the molecular states. With a simple model for the molecular system, plus several justified approximations, we solve for the fully quantum mechanical molecule-electromagnetic field state. We then study the reduced density matrices of the molecule and the laser pulses separately. We calculate measurable corrections to the case where the fields are treated classically.

Journal Article↗
PubMed2006

Wave packet interferometry and quantum state reconstruction by acousto-optic phase modulation.

Studies of wave packet dynamics often involve phase-selective measurements of coherent optical signals generated from sequences of ultrashort laser pulses. In wave packet interferometry (WPI), the separation between the temporal envelopes of the pulses must be precisely monitored or maintained. Here we introduce a new (and easy to implement) experimental scheme for phase-selective measurements that combines acousto-optic phase modulation with ultrashort laser excitation to produce an intensity-modulated fluorescence signal. Synchronous detection, with respect to an appropriately constructed reference, allows the signal to be simultaneously measured at two phases differing by 90 degrees. Our method effectively decouples the relative temporal phase from the pulse envelopes of a collinear train of optical pulse pairs. We thus achieve a robust and high signal-to-noise scheme for WPI applications, such as quantum state reconstruction and electronic spectroscopy. The validity of the method is demonstrated, and state reconstruction is performed, on a model quantum system--atomic Rb vapor. Moreover, we show that our measurements recover the correct separation between the absorptive and dispersive contributions to the system susceptibility.

Journal Article↗
PubMed1995

Very-long-baseline radio interferometry surveys of the compact structure in active galactic nuclei.

Very-long-baseline radio interferometry (VLBI) imaging surveys have been undertaken since the late 1970s. The sample sizes were initially limited to a few tens of objects but the snapshot technique has now allowed samples containing almost 200 sources to be studied. The overwhelming majority of powerful compact sources are asymmetric corejects of one form or another, most of which exhibit apparent superluminal motion. However 5-10% of powerful flat-spectrum sources are 100-parsec (pc)-scale compact symmetric objects; these appear to form a continuum with the 1-kpc-scale double-lobed compact steep-spectrum sources, which make up 15-20% of lower frequency samples. It is likely that these sub-galactic-size symmetric sources are the precursors to the large-scale classical double sources. There is a surprising peak around 90 degrees in the histogram of misalignments between the dominant source axes on parsec and kiloparsec scales; this seems to be associated with sources exhibiting a high degree of relativistic beaming. VLBI snapshot surveys have great cosmological potential via measurements of both proper motion and angular size vs. redshift as well as searches for gravitational "millilensing."

Journal Article↗
PubMed1995

Possible links between BL Lacertae objects and quasars from very long baseline interferometry radio data.

Systematic differences in the very long baseline interferometry (VLBI) radio polarization structure and average VLBI component speeds of BL Lacertae objects and quasars support the view that the observational distinction between these classes, based in large part on the strength of their optical line emission, is meaningful; in other words, this distinction reflects significant differences in the physical conditions in these sources. Possible models providing a link between the optical and VLBI properties of BL Lacertae objects and quasars are discussed. Most VLBI polarization observations to date have been global observations made at 6 cm; recent results suggest that the VLBI polarization structure of some sources may change dramatically on scales smaller than those probed by these 6-cm observations.

Journal Article↗