Changes In Interference Pattern Research Articles

High temperature and pressure Gladstone–Dale coefficient measurements in air behind reflected shock waves

Understanding the optical properties of air is essential for the validation and characterization of plasmas and hypersonic flows. Beyond 6000 K, the dissociation of nitrogen and oxygen molecules, along with other reactions, alters the equilibrium composition of air, causing a temperature and pressure dependence in the Gladstone–Dale coefficient. Due to measurement complexities, there is currently very little experimental data to validate model predictions under these conditions. In this work, a unique quadrature fringe imaging interferometer technique is applied to high temperature and pressure measurements of air in the Sandia free-piston high enthalpy shock tube. The diagnostic method combines a narrowband and broadband source to capture large, nearly-discrete changes in the index of refraction by calibrating to interference pattern changes. For the experiments, the reflected shock front is used to generate temperatures between 6000 and 7800 K at pressures up to 300 psi (20 bars). Results behind the shock front exhibit complex flow bifurcation and tail shock feature before equilibrium conditions are reached. Measurements in these flows show close agreement with theoretical predictions of the nonconstant Gladstone–Dale coefficient at high temperatures and high pressures, providing new validation data for chemical equilibrium gas models.

Near-threshold photodetachment microscopy in the presence of a transverse magnetic field

Near-threshold photodetachment microscopy of mononegative ions is theoretically studied when a homogeneous transverse magnetic field $\mathrm{B}$ is superimposed to the static electric field $\mathrm{E}$. The electron flux distribution is obtained using two different approaches: the quantum source theory with the energy-Green function evaluated by means of the stationary phase approximation and the closed-orbit theory. Here we describe the physical ideas while developing the theory in detail. Both theoretical methods yield consistent descriptions for all field intensities and angular momentum of the detached electrons we have investigated and also reproduce reported experimental results. From our calculations, we have found that the presence of the transverse magnetic field leads to a global displacement of the recorded electron flux distribution along the $\mathrm{E}\ifmmode\times\else\texttimes\fi{}\mathrm{B}$ direction. Furthermore, we found that the shape of the recorded interference pattern changes from circular to elliptical as the magnetic field increases. We have theoretically characterized and quantified those effects on the interference pattern due to the presence of the transverse magnetic field.

Characterizing the SEMG patterns with myofascial pain using a multi-scale wavelet model through machine learning approaches

In this paper, we introduce a newly developed multi-scale wavelet model for the interpretation of surface electromyography (SEMG) signals and validate the model’s capability to characterize changes in neuromuscular activation in cases with myofascial pain syndrome (MPS) via machine learning methods. The SEMG data collected from normal (N = 30; 27 women, 3 men) and MPS subjects (N = 26; 22 women, 4 men) were adopted for this retrospective analysis. SMEGs were measured from the taut-band loci on both sides of the trapezius muscle on the upper back while he/she conducted a cyclic bilateral backward shoulder extension movement within 1 min. Classification accuracy of the SEMG model to differentiate MPS patients from normal subjects was 77% using template matching and 60% using K-means clustering. Classification consistency between the two machine learning methods was 87% in the normal group and 93% in the MPS group. The 2D feature graphs derived from the proposed multi-scale model revealed distinct patterns between normal subjects and MPS patients. The classification consistency using template matching and K-means clustering suggests the potential of using the proposed model to characterize interference pattern changes induced by MPS.

Supercurrent in Graphene Josephson Junctions with Narrow Trenches in the Quantum Hall Regime

ABSTRACTCoupling superconductors to quantum Hall edge states is the subject of intense investigation as part of the ongoing search for non-abelian excitations. Our group has previously observed supercurrents of hundreds of picoamperes in graphene Josephson junctions in the quantum Hall regime. One of the explanations of this phenomenon involves the coupling of an electron edge state on one side of the junction to a hole edge state on the opposite side. In our previous samples, these states are separated by several microns. Here, a narrow trench perpendicular to the contacts creates counterpropagating quantum Hall edge channels tens of nanometres from each other. Transport measurements demonstrate a change in the low-field Fraunhofer interference pattern for trench devices and show a supercurrent in both trench and reference junctions in the quantum Hall regime. The trench junctions show no enhancement of quantum Hall supercurrent and an unexpected supercurrent periodicity with applied field, suggesting the need for further optimization of device parameters.

Dual-task mobility among individuals with chronic stroke: changes in cognitive-motor interference patterns and relationship to difficulty level of mobility and cognitive tasks

Dual-task mobility performance is compromised after stroke. This study evaluated how the difficulty level of mobility and cognitive tasks influenced the cognitive-motor interference pattern among individuals with chronic stroke and whether it differed from age-matched control participants. A cross-sectional study. University laboratory. Individuals with chronic stroke and age-matched controls. Sixty-one individuals with chronic stroke (mean age: 62.9±7.8 years) and 32 controls (mean age: 61.0±7.3 years) performed three mobility tasks (forward walking, obstacle-crossing, backward walking) and two cognitive tasks (serial-3-subtractions, serial-7-subtractions) in single-task and dual-task conditions. time to complete the mobility tasks and correct response rates were recorded. Serial subtractions significantly increased the walking time compared to single-task walking (P<0.001) without decreasing the correct response rate (P>0.05) in both groups, indicating cognitive-related motor interference. As the difficulty of the walking task was increased (i.e., obstacle crossing), the dual-task effect on the walking time was similar to that observed during forward walking, but the correct response rate significantly decreased (P<0.05), indicating that more attentional resources were allocated to the mobility task. When the walking task difficulty level increased further (i.e., backward walking), an exaggerated increase in the walking time (P<0.001) was observed in both groups, but the stroke group also had a decreased correct response rate (P<0.001), indicative of a mutual interference pattern. The control group, however, maintained the correct response rate (P>0.05) despite the slowed walking speed in this condition (P<0.001). The degree of dual-task interference and task prioritization strategies are highly specific to the combinations of the walking and cognitive tasks used and are affected by the presence of stroke. The study results may provide the basis for establishing assessment tools and creating intervention programs that address dual-task mobility function post-stroke.

Determination of High-affinity Antibody-antigen Binding Kinetics Using Four Biosensor Platforms

Label-free optical biosensors are powerful tools in drug discovery for the characterization of biomolecular interactions. In this study, we describe the use of four routinely used biosensor platforms in our laboratory to evaluate the binding affinity and kinetics of ten high-affinity monoclonal antibodies (mAbs) against human proprotein convertase subtilisin kexin type 9 (PCSK9). While both Biacore T100 and ProteOn XPR36 are derived from the well-established Surface Plasmon Resonance (SPR) technology, the former has four flow cells connected by serial flow configuration, whereas the latter presents 36 reaction spots in parallel through an improvised 6 x 6 crisscross microfluidic channel configuration. The IBIS MX96 also operates based on the SPR sensor technology, with an additional imaging feature that provides detection in spatial orientation. This detection technique coupled with the Continuous Flow Microspotter (CFM) expands the throughput significantly by enabling multiplex array printing and detection of 96 reaction sports simultaneously. In contrast, the Octet RED384 is based on the BioLayer Interferometry (BLI) optical principle, with fiber-optic probes acting as the biosensor to detect interference pattern changes upon binding interactions at the tip surface. Unlike the SPR-based platforms, the BLI system does not rely on continuous flow fluidics; instead, the sensor tips collect readings while they are immersed in analyte solutions of a 384-well microplate during orbital agitation. Each of these biosensor platforms has its own advantages and disadvantages. To provide a direct comparison of these instruments' ability to provide quality kinetic data, the described protocols illustrate experiments that use the same assay format and the same high-quality reagents to characterize antibody-antigen kinetics that fit the simple 1:1 molecular interaction model.

Determination of High-affinity Antibody-antigen Binding Kinetics Using Four Biosensor Platforms

Label-free optical biosensors are powerful tools in drug discovery for the characterization of biomolecular interactions. In this study, we describe the use of four routinely used biosensor platforms in our laboratory to evaluate the binding affinity and kinetics of ten high-affinity monoclonal antibodies (mAbs) against human proprotein convertase subtilisin kexin type 9 (PCSK9). While both Biacore T100 and ProteOn XPR36 are derived from the well-established Surface Plasmon Resonance (SPR) technology, the former has four flow cells connected by serial flow configuration, whereas the latter presents 36 reaction spots in parallel through an improvised 6 x 6 crisscross microfluidic channel configuration. The IBIS MX96 also operates based on the SPR sensor technology, with an additional imaging feature that provides detection in spatial orientation. This detection technique coupled with the Continuous Flow Microspotter (CFM) expands the throughput significantly by enabling multiplex array printing and detection of 96 reaction sports simultaneously. In contrast, the Octet RED384 is based on the BioLayer Interferometry (BLI) optical principle, with fiber-optic probes acting as the biosensor to detect interference pattern changes upon binding interactions at the tip surface. Unlike the SPR-based platforms, the BLI system does not rely on continuous flow fluidics; instead, the sensor tips collect readings while they are immersed in analyte solutions of a 384-well microplate during orbital agitation.Each of these biosensor platforms has its own advantages and disadvantages. To provide a direct comparison of these instruments' ability to provide quality kinetic data, the described protocols illustrate experiments that use the same assay format and the same high-quality reagents to characterize antibody-antigen kinetics that fit the simple 1:1 molecular interaction model.

Effects of the groove-envelope phase in self-diffraction

If the laser-induced grating in a close-to-collinear two-beam geometry comprises only a few grooves, then the phase between the grooves of the grating and its envelope is decisive to nonlinear effects. Here it is shown that the groove-envelope phase, which can be altered through the delay between the pulses on a subcycle timescale, determines the interferences that arise in self-diffraction. The shape of the interference pattern changes as the laser intensity approaches the damage threshold in a thin dielectric solid, and simulations show that the shape depends on the mechanisms that lead to self-diffraction.

Birefringence manipulation in tapered polarization-maintaining photonic crystal fiber Mach-Zehnder interferometer for refractive index sensing

A temperature insensitive, compact and high resolution refractive index measurement system using tapered polarization maintaining photonic crystal fiber (PM-PCF) Mach-Zehnder interferometer (MZI) is proposed. The sensor exhibits sensitivity of 20.53nm/RIU with very high refractive index resolution of 1.2175×10−5 RIU and 252.6906dBm/RIU within the refractive index range from 1.33 to 1.37. The birefringence value varied from 1.90619×10−5 to 1.86978×10−5 with the corresponding change in refractive index. The core and clad having different propagation constant and the changes in the optical path length and hence a change in interference pattern is correlated with the minute changes in refractive index of the subjected sample.

3D TARGET DETECTION USING STACKED HOLOGRAM

A very popular technique of 3D vision now-a-days is holography which has many advantages over the stereoscopic 3D vision. The same technique can be implemented on RADAR to take high resolution 3D picture of the target and to track with very minute displacement. As this does not employ parallax method, so binocular antenna can be replaced by a single antenna. Again in this thesis another new concept, gated range, is implemented, i.e., the target can be detected within a certain range on spatial domain so that it can focus to the target and the clutter has no effect on it. Narrow virtual transmit pulses are synthesized by differencing long-duration, staggered pulse repetition interval (PRI) transmit pulses. PRI is staggered at an intermediate frequency IF. Echoes from virtual pulses form IF-modulated interference patterns with a reference wave. Samples of interference patterns are IF-filtered to produce high spatial resolution holographic data. PRI stagger can be very small, e.g., 1-ns, to produce a 1-ns virtual pulse from very long, staggered transmit pulses. Occupied Bandwidth (OBW) can be less than 10 MHz due to long RF pulses needed for holography, while spatial resolution can be very high, corresponding to ul tra-wideband (UWB) operation, due to short virtual pulses. X-Y antenna scanning can produce range-gated surface holograms from quadrature data. Multiple range gates can produce stacked-in-range holograms. Motion and vibration can be detected by changes in interference patterns within a range-gated zone.

Probing the topological charge of a vortex beam with dynamic angular double slits.

When a vortex beam with a spiral phase structure passes through dynamic angular double slits (ADS), the interference pattern changes alternatively between destructive and constructive at the angular bisector of the ADS. This change is due to their phase difference. Based on this property, we experimentally demonstrate a simple method to precisely and efficiently determine the topological charge of vortex beams. Furthermore, this scheme allows for the simultaneous determination of the modulus and the sign of the topological charge of the vortex beams.

Securitized Optical Fiber Communication and Sensor Systems Using Mode-Selective Couplers

In this paper, we report the results of testing a securitized hybrid sensing/communication system. A long-period grating sensor operating in the 1550 nm range along a bidirectional communication link at 1310 nm is securitized against intrusion by launching visible light at 650 nm through a splitter. The arising few-mode interference pattern changes are monitored and the responses to a variety of deformations on the fiber link are investigated. It is shown that the intrusion sensing channel is activated by even the weakest deformations imposed on the fiber with no losses on the channel being incurred. Analysis of the intermodal pattern changes make it possible to discern the types of deformations imposed on the sensor-communication channel.

Change of interference pattern using fundamental and second-harmonic wavelengths by phase shift of a beam

Interference pattern of two different wavelengths, forming a four-sided pyramid consisting of eight beams, is discussed. Synchronization between two wavelengths having a multiple relationship, which corresponds to mixing of fundamental and second-harmonic generation wavelengths, forms a stationary interference pattern successfully. Phase shift variation of a beam changes the basic pattern of interference. This technique can be a new scheme for multi-wavelength material processing with periodic structure and will increase the variation of meta-atoms fabricated by interfering femtosecond laser processing.

Research on Temperature Detection Based on Spectrum Analysis of the Speckle Pattern Interferometry

To improve the accuracy of the transient temperature detection system, Transient temperature inversion processing algorithms is proposed based on spectrum analysis of speckle pattern interferometry. The interference fringes is formed by speckle interferometry in the system, and due to transient temperature changes cause the material strain, so that the speckle interference pattern changes. the interference fringes on the measured surface is obtained by the area array CCD collection before and after deformation. The corresponding spectrum density function will changes by the changes of transient temperature, and the amplitude changes of center wavelength is inverted by the speckle pattern interferometry. Through detecting and calculating the ratio of the amplitude of the center wavelength, the transient temperature can be obtained by spectrum analysis. In the analysis and calculation for the function of transient temperature and material strain, material strain and interference fringes, derived the amplitude and phase function of the transient temperature change and interference fringes, so as to provide the necessary conditions for detecting the use of spectral density function temperature. Experiment using 660nm laser diode, SI6600 type area CCD detector to obtain the speckle pattern interference fringes, system extracts the amplitude ratio of the central wavelength from spectral distribution function, and by calculation and calibration the detection accuracy of temperature can be achieved of 2°C. Compared to traditional methods that is direct detection for interference fringes changes, the new methods improve the accuracy by nearly an order of magnitude. It is more accurate detection and better uniformity, better stability.

Effect of Thin Metallic Layers on the Refractive Index of a Multilayer System

We present a simplified structure made of periodic metallic layers on a glass substrate, which offers a potentially simpler approach to building photonic crystals. Using microwave experiments and Fresnel formulas, we investigate the refractive index properties of these structures. We make both transmission and reflection measurements and find that the refractive index of a periodic layered media decreases depending on the periodicity of the geometric arrangement, dielectric contrast and filling fraction of metallic layers. It is shown that metallic layers lead to a substantial change of interference pattern which can be interpreted as a result of interference in a uniform medium with a refractive index smaller than 1.

Detection of deoxynivalenol using biolayer interferometry

Biolayer interferometry allows for the real time monitoring of the interactions between molecules without the need for reagents with enzymatic, fluorescent, or radioactive labels. The technology is based upon the changes in interference pattern of light reflected from the surface of an optical fiber when materials bind to the tip of the fiber. The technique represents an alternative to technologies such as surface plasmon resonance, with an advantage in that the flow of extracts through small capillaries is not required. In this report, a deoxynivalenol-bovine serum albumin (DON-BSA) conjugate was non-covalently immobilized to the surface of aminopropylsilane sensors and the change in interference pattern resulting from the binding of DON-specific antibodies was measured. The basis for the assay was the competition between DON and the immobilized DON-BSA for binding to limited amounts of antibody. The technique was used to measure DON in extracts of spiked whole wheat flour, with a limit of detection of 0.10mg DON/kg. Matrix interferences were an issue, and adequate quantification required using matrix-matched standards. When samples were tested with sensors that had not been conditioned to remove loosely attached DON-BSA, the recoveries at five spiking levels over the range from 0.2 to 5mg/kg averaged 108.8% [relative standard deviation (RSD) 16.0%]. Using sensors that had been conditioned lowered the average recovery (101.4%) and improved the RSD (13.2%). This suggests that conditioning the sensors helped reduce a bias in the assay towards overestimation. These results, and the ease with which assays can be conducted, suggest further exploration of this technology for detection of mycotoxins is warranted.

In-situ measurements of sound propagating over extensive green roofs

In this study, in-situ measurements of sound propagating over flat, extensive green roofs are presented for 5 cases. Measurements were performed just before and just after the placement of the green roof (under dry conditions) with an identical source-receiver configuration in both situations, allowing a direct estimate of the acoustical effect. Situations involving a single and double diffraction over the green roof were considered, for substrate thicknesses ranging from 20–30 mm to 180 mm, and for vegetation cover ranging from absence to 100%. The green roof acoustic effect was analyzed for propagation path lengths interacting with the roofs ranging from 2.5 m to 25 m. Measurements show that green roofs might lead to consistent and significant sound reduction at locations where only diffracted sound waves arrive relative to common, non-vegetated roofs. A single diffraction case with an acoustic green roof improvement exceeding 10 dB was found for sound frequencies between 400 Hz and 1250 Hz, although the green roof interaction path length was only 4.5 m. For less shielded receivers, a change in interference pattern might be observed, leading to positive or negative effects, relative to a non-vegetated roof top. For the double diffraction cases the green roof improvement is less frequency-dependent and a case with positive effects up to 10 dB was found.

Modal interferometer based on hollow-core photonic crystal fiber for strain and temperature measurement

In this work, sensitivity to strain and temperature of a sensor relying on modal interferometry in hollow-core photonic crystal fibers is studied. The sensing structure is simply a piece of hollow-core fiber connected in both ends to standard single mode fiber. An interference pattern that is associated to the interference of light that propagates in the hollow core fundamental mode with light that propagates in other modes is observed. The phase of this interference pattern changes with the measurand interaction, which is the basis for considering this structure for sensing. The phase recovery is performed using a white light interferometric technique. Resolutions of +/- 1.4 microepsilon and +/- 0.2 degrees C were achieved for strain and temperature, respectively. It was also found that the fiber structure is not sensitive to curvature.

Five beam holographic lithography for simultaneous fabrication of three dimensional photonic crystal templates and line defects using phase tunable diffractive optical element

This paper demonstrates an approach for laser holographic patterning of three-dimensional photonic lattice structures using a single diffractive optical element. The diffractive optical element is fabricated by recording gratings in a photosensitive polymer using a two-beam interference method and has four diffraction gratings oriented with four-fold symmetry around a central opening. Four first-order diffracted beams from the gratings and one non-diffracted central beam overlap and form a three-dimensional interference pattern. The phase of one side beam is delayed by inserting a thin piece of microscope glass slide into the beam. By rotating the glass slide, thus tuning the phase of the side beam, the five beam interference pattern changes from face-center tetragonal symmetry into diamond-like lattice symmetry with an optimal bandgap. Three-dimensional photonic crystal templates are produced in a photoresist and show the phase tuning effect for bandgap optimization. Furthermore, by integrating an amplitude mask in the central opening, line defects are produced within the photonic crystal template. This paper presents the first experimental demonstration on the holographic fabrication approach of three-dimensional photonic crystal templates with functional defects by a single laser exposure using a single optical element.

공초점 방식을 이용한 기판 사이의 공기갭 측정

공초점 방식을 이용하여 두 기판사이의 얇은 공기갭의 두께를 측정하는 방법을 제안하였다. 공기갭이 약 200 nm 이내 일때는 두 기판면이 초점의 레일리 영역 안에 있으므로 완전한 간섭신호를 측정할 수 있었다. 또 초점영역 근처에서의 간섭무늬만 측정되므로 다층 박막중에 존재하는 공기갭이라도 측정할 수 있는 장점이 있다. 간섭무늬 변화가 작은 영역을 제외하면 1 nm 이내의 안정도를 가진다. A confocal technique was demonstrated for measuring the absolute value of an air gap between substrates. Since the two surfaces were in Rayleigh range of the laser focus for air gaps less than 200 nm, complete interference patterns were observed. And since interference patterns were obtained only from the area of focus, it was an advantage of this method that air gaps between multiple thin films could be measured. Stability is less than 1 nm except in the range where the interference pattern changes slowly.