Parallel Glass Plates Research Articles

Evaporation-Driven Cellular Patterns in Confined Hyperelastic Hydrogels.

When a hyperelastic hydrogel confined between two parallel glass plates begins to dry from a lateral boundary, the volume lost by evaporation is accommodated by an inward displacement of the air-hydrogel interface that induces an elastic deformation of the hydrogel. Once a critical front displacement is reached, we observe intermittent fracture events initiated by a geometric instability resulting in localized bursts at the interface. These bursts relax the stresses and irreversibly form air cavities that lead to cellular networks. We show that the spatial extent of the strain field prior to a burst, influenced by the air-hydrogel interfacial tension and the confinement of the gel, determines the characteristic size of the cavities.

Dynamic imaging of three-dimensional temperature field via three-directional wavelength modulated lateral shearing interferometry

A three-directional wavelength modulated lateral shearing interference system was proposed for the dynamic three-dimensional visualization of a temperature field. The laser emitted from a distributed feedback (DFB) laser was divided into three beams by a fiber beam splitter. The beams were spatially expanded and passed through the flame in three directions of 0°, 120° and 240°, respectively. The three interferograms formed by reflections from the front and back surfaces of the parallel glass plates were spatially converged into the lens of a high-speed camera. Multiple plane mirrors were utilized to reflect the beams. The size of the region of interest (ROI) was −20 ∼ 20 mm in both x and z directions and 5 ∼ 30 mm in y direction, with a spatial resolution of 200 μm in all directions. A three-dimensional sensitivity matrix was modeled, and the simultaneous algebraic reconstruction technique (SART) was used for layer-by-layer imaging to achieve three-dimensional flame monitoring. Numerical simulations verified the effectiveness of the algorithm qualitatively and quantitatively. In experiments, the temperature distributions of four cases of flames, namely, steady diffused flame, partially blocked diffused flame, dynamic acoustically excited flame and the flame after ignition, were reconstructed at 1k frames per second (fps). The flame structures and temporal variations of temperature distributions were clearly visualized, demonstrating the ability of the system in fast monitoring of three-dimensional dynamic temperature fields.

Originating Point of Traveling Waves on a Spherical Field Dependent on the Nature of Substrate Surface

The Belousov–Zhabotinsky (BZ) reaction was investigated to understand how the direction of traveling waves (TWs) is determined in a spherical field. A cation-exchange resin bead loaded with the catalyst of the BZ reaction was placed on a glass plate coated with silicone greases with different surface densities. TWs were generated at the contact point between the bead and glass plate for a lower density silicone grease, and at the upper half of the bead for a higher density silicone grease. In addition, TWs were generated in the middle section of the bead, which was sandwiched between two parallel glass plates coated with a high-density silicone grease. The experimental results were qualitatively reproduced by numerical calculations. These results are discussed in relation to the adsorption of Br2 into the silicone grease as the source of the inhibitor.

A quasi-two-dimensional fluid experimental apparatus based on tank-in-tank configuration.

The fluid tank is an essential facility for experimental research on fluid mechanics. However, owing to the hydrostatic fluid pressure, a fine uniformity of the narrow channel is difficult to be maintained in a tall narrow-channel tank. To address this issue, we proposed a quasi-two-dimensional fluid experimental apparatus based on a "tank-in-tank" configuration and built with an outer tank and an inner tank. The outer tank was cuboid-shaped and used to load the fluid medium, while the inner tank, consisting of two parallel glass plates, was embedded into the outer tank and served as the experimental channel. The hydrostatic pressure acting on the channel was balanced so that a high level of uniformity was maintained over the whole channel. The available height and width of the channel were 2800 and 1500mm, respectively, while its gap distance could be adaptive from 0 to 120mm. Experimental research on motion characteristics of circular disks falling in the quasi-2D channel was implemented to investigate the effects of the falling environment and disk geometry. Four distinct falling types were observed, and the wake flow fields of the falling disks were visualized. The Reynolds numbers of falling disks ranged from 400 to 63 000 presently. Chaotic motion and regular motion were demarcated at Re ≈ 30 000. An analytical model was established to predict the final average falling velocity and Reynolds number. Finally, potential directions for future research and improvements to the apparatus were suggested.

Direct observation of deformation of individual red blood cells in oscillatory fluid flow produced using a generator of precise sinusoidal shear flow

We report the development of a precision sinusoidal shear flow generator that creates an oscillatory shear flow in the narrow gap between two parallel glass plates moving in opposite directions, thereby allowing direct observation of the cyclical deformation and recovery of a single red blood cell (RBC). The system is used to demonstrate that RBCs change their shape with cyclical elongation and shape recovery and align with the fluid streamlines in the direction of laminar Couette shear flow. From six repetitions, it can be seen that the curvature showing the time series of the elongation index (EI) of an RBC in sinusoidal shear flow in the present device was highly symmetrical and there were no significant differences at a 95% confidence interval. Moreover, the system provides details about the deformation characteristics of an RBC, which have four phases: (i) low deformation, in which the EI is minimal and the RBC mostly retains its original circular shape; (ii) shape elongation, in which the RBC loaded with shear forces begins to change its shape dynamically from circular to oval; (iii) steady deformation, in which the EI is constant and the shape of the RBC is elliptical throughout; and (iv) shape recovery, in which the EI decreases and the RBC becomes oval with trailing endpoints. Along with this information, the developed measurement system has potential application in clinical and biological analyses of RBC deformability.

Experimental evaluation of Carbon Dioxide-Assisted Gravity Drainage process (CO2-AGD) to improve oil recovery in reservoirs with strong water drive

The Gas-Assisted Gravity Drainage (GAGD) process has been developed to improve and enhance oil production in both secondary and tertiary recovery stages. In the GAGD process, oil is produced through horizontal wells above the oil-water contact. Therefore, high levels of water cresting are probably happening, especially in reservoirs with active water aquifers. However, all the previous GAGD feasibility experimental studies have never been addressing the existence of active water aquifers. Consequently, the current research was conducted to test the immiscible GAGD process feasibility to improve oil recovery and minimize water cut in brown reservoirs with strong water coning tendencies.A Hele-Shaw model consists of two parallel glass plates packed with silica sand to visually discern the process performance. Specifically, the CO2-AGD process feasibility versus the Free Fall Gravity Drainage (FFGD) mechanism was investigated on the physical model with large, moderate, and without bottom water drive. The experimental results indicated that the GAGD process performance is higher performance than the FFGD in all runs because of its fast high oil recovery, especially when implemented on the reservoir without a bottom water drive. The immiscible CO2-AGD process is not only important in terms of increasing oil recovery, but it also significantly delays the gas breakthrough. The strength of the aquifer inversely impacts the gas breakthrough time as increasing the aquifer strength results in fast oil production and early gas breakthrough. Additionally, the immiscible GAGD experiments illustrated that oil recoveries in the FFGD and GAGD processes improved to 35% and 47% of OOIP for the model without bottom water drive, respectively. However, the oil recovery increased in the same FFGD and GAGD processes to 61% and 63% of OOIP for the model with a large bottom water drive, respectively. Specifically, the ultimate oil recovery during the GAGD process with a large bottom water drive was higher than the FFGD run with only 2%; while there is increasing in ultimate oil recovery for the model without the bottom water drive of about 12%. Consequently, the GAGD process is more efficient to improve oil recovery in reservoirs with limited or without bottom water drive.

Uncertainty analysis of calibration source with adjustable degree of polarization in a wide dynamic range

In order to satisfy the requirements of pre-launch laboratory calibration with high accuracy for polarization remote sensor, an innovative high precision polarimetric calibration instrument with adjustable degree of linear polarization (DoLP) in a wide dynamic range called adjustable polarization light source (APOLS) has been developed. APOLS consists of a collimated light source (CLS) and a polarization state adjuster (PSA). The PSA contains four parallel K9 glass plates, which can be orientated from 0° to 65° accurately controlled by electromechanical driving mechanism whose rotation accuracy is better than ±5″. Regarding the DoLP of APOLS, its adjustment range is from 0 to 0.72 within the spectral range from 460 to 2000 nm. The theoretical model of APOLS was established to describe the DoLP produced by multiple refraction of transmitted light. Meanwhile, the major systematic factors contributing to the DoLP uncertainty such as refractive index and absorption of K9 glass, incident angle, instability and parallelism of light source were analyzed. By using the spectro-polarimetric analyzer (SPOLA), the uncertainty evaluation experiments of APOLS were carried out. The results showed that when the DoLP value was in the range of 0.26 to 0.72, the uncertainty was less than 0.5%, and when the DoLP value was in the range of 0.003 to 0.26, the uncertainty was in the range of 8.5993% to 0.5534%. Moreover, the uncertainty was in the range of 0.0027% to 0.0032% when the uncertainty of the CLS was not considered. The consistency evaluation between APOLS and SPOLA ranged from -0.36 to 0.6 indicates the experimental results are satisfying. It can be concluded that the APOLS significantly improved the dynamic range and accuracy of the polarimetric calibration instrument.

Interferometric thickness measurement of glass plate by phase-shifting analysis using wavelength scanning with elimination of bias phase error

Phase-shifting fringe analysis using wavelength scanning has been broadly applied to the interferometric profiling of the thickness variation of glass plates. However, the nonlinear phase shifting can cause bias error during wavelength scanning. In this study, the bias error in the calculated phase was formulated by Taylor series expansion. Using the formulation, a novel 15-sample algorithm of a partially negative window was derived to enable compensation for the bias phase error. The new 15-sample algorithm was visualized by the algorithm polynomial on the complex plane and Fourier description in the frequency domain. The bias error suppression capability of the developed algorithm was examined by using the numerical simulation. Finally, the proposed algorithm was used in conjunction with a large-aperture Fizeau interferometer to examine the thickness variation of a glass parallel plate.

Comparative Evaluation of Flexural Strength of Two Newer Composite Resin Materials: An in Vitro Study

Objective: To evaluate in vitro the flexural strength of two newer composite resin materials . Material and Methods: Twenty-four samples were equally divided into two groups: G1 - Brilliant EverGlow and G2: Brilliant NG. The rectangular blocks of 25 mm in length, 2 mm in width and thickness were prepared from two composite materials. Blocks were created by applying composites to a customized split mold and formed between two parallel glass plates. Before light-curing, blocks were covered with Mylar strips and rinsed for 10 seconds in water. Subsequently, they were stored in distilled water for 24 hours at 37oC and 100% humidity before testing. Each sample was placed within a suitable framework of aluminum. The length of gap between the support was 21 mm and the speed of crosshead at 1 mm/minute. The data were subjected to an independent t-test. The level of significance was set at p <0.05. Results: A less flexural strength was observed in G1 (77.43 Mpa) compared to G2 (118.70 Mpa) (p<0.001). Conclusion: Universal nanohybrid composite resin material was found to have greater flexural strength than universal submicron hybrid composite material.

Wavelength-Tuning Common-Path Digital Holographic Microscopy for Quantitative Phase Imaging of Functional Micro-Optics Components

This study proposes a novel wavelength-tuning common-path digital holographic microscopy technique for quantitative phase imaging of functional micro-optics components. The proposed technique is immune to vibration and can reduce system error. In the proposed configuration, a parallel glass plate was inserted into the light path to create two identical test beams, which passed through a specially designed window filter. In this process, one beam serves as the object beam, while the other is diffracted to produce an ideal spherical wave front (the reference beam). A wavelength tunable laser was used as the light source to generate phase-shifting digital holograms. Structural information for the functional micro-optics components was then extracted using a classical four-step phase-shift algorithm. The viability of the proposed technique was assessed by measuring a micro-optics array.

A particle swarm optimization method for fault localization and residue removal in digital microfluidic biochips

Second generation microfluidic biochip is known as digital microfluidic biochip (DMFB). DMFB performs different clinical pathological experimentation, DNA sequencing, air contamination detection and many other bio-chemical experiments based on appropriate bio-assay protocols. DMFB comprises two dimensional array of electrodes fabricated over two parallel glass plates, which is capable of performing miniaturized (nano/ pico liter volume) droplet dispensing, transportation and mixing through electro-wetting of dielectrics (EWOD). Droplet operations through EWOD are mostly managed by droplet scheduling algorithms which are NP hard in nature. At present reliability is a major concern for commercialization of operational DMFB. Reliable output of DMFB is mostly affected by different faults within electrodes. This further suffers from cross-contamination issues among different droplets due to repeated use of DMFB boards for different assay operations. Present work proposes a novel test droplet routing method based on adaptive weighted particle swarm optimization (PSO) model. This test droplet circulation method aims to identify defective electrodes and simultaneously performs residue removal. Experimental findings of the proposed model on some standard test benches and real life bio-assay samples reveal operational supremacy in terms of overall computational time and operational accuracy over some existing best known models.

Common-path spatial phase-shift speckle shearography using a glass plate

In this paper, a spatial phase shifting digital speckle pattern shearography setup based on a common path interferometer and modest components is proposed for direct measurement of dynamical deformation gradient of objects. The simplicity, stability, and efficiency of the setup are provided by employing a plane parallel glass plate as a shearing device. The desired field of view can easily be achieved by employing two lenses. Moreover, adjustable spatial carrier frequencies within the speckle pattern which is needed to evaluate the phase difference before and after deformation by Fourier transformation can easily be produced. Ultimately, the slope of the deformations on the test surface can be obtained with tunable sensitivity. To demonstrate our technique, the proposed setup is used to evaluate the phase change in a center-loaded aluminum plate. Experimental results for out of plane deformation gradient are presented and discussed.

Fast copolymer network liquid crystals for tunable birefringence colors.

A fast-switching, tunable color filter was found in a copolymer network liquid crystal (LC), which was in situ generated in a conventional LC test cell with parallel aligned glass plates and investigated with polarized light. Polarization filters were used to convert the tunable optical phase retardance of the test cells to birefringence colors as is always possible in a LC test cell with carefully adjusted cell gap and effective birefringence. The cell gap of the samples could be adjusted to a value of 9 μm, which is not easily possible in a polymer LC composite without creating defects. In these samples, the typical pastel colors seen frequently in birefringent samples could be avoided. The transmittance spectra were recorded and converted to CIE 1931 color coordinates, which showed that the colors seen had a reasonable distance to the white point. The electro-optic switching times of the samples were investigated: Fast responses of t on +t off <5 ms were found, which is an impressive speed for tunable birefringence colors in LCs and LC composites. Upon increasing addressing voltages, a blueshift of the peak seen in the transmittance spectra was observed. The samples consisted of copolymer network LC, generated from a reactive mixture with mesogenic monomer and nonmesogenic comonomer. The tunable color was seen selectively in samples with dodecyl acrylate as comonomer. The experiments show how even a straightforward electro-optic experiment still can result in unexpended findings, which may expand the use of LC composites in nondisplay applications. The polymer morphology in samples with a larger cell gap was investigated with scanning electron microscopy, and interdefect distances of ≈40 μm were found. The appearance of defects in test cells with a cell gap of 9 μm could be avoided because the cell gap was much smaller than the measured interdefect distances in test cells with a larger cell gap.

Experimental Study on Cellular Premixed Propane Flames in a Narrow Gap between Parallel Plates

ABSTRACTExperimental results on laminar propane flames propagating in a narrow gap between parallel glass plates are presented. Development and evolution of cellular flame structure is demonstrated by video and long-exposure photo recordings for stoichiometric and fuel-rich mixtures with equivalence ratio of 1.0:1.25. It is shown that in narrow gaps the lateral cell sizes by far exceed the gap width. Average flame propagation speed obtained for gap widths between 2.5 and 4.4 mm is shown to depend significantly on the gap width due to the effect of heat losses on the normal flame speed, as well as due to cooling of products behind the flame. Effect of gap width on the cellular structure is demonstrated, and statistical characteristics of the cells are obtained for two gap widths. Flame propagation patterns are also obtained for non-central ignition performed at one or simultaneously at two points.

Retrieval of the thickness and refractive index dispersion of parallel plate from a single interferogram recorded in both spectral and angular domains

The principle of retrieving the thickness and refractive index dispersion of a parallel glass plate is reported based on single interferogram recording and phase analysis. With the parallel plate illuminated by a convergent light sheet, the transmitted light interfering in both spectral and angular domains is recorded. The phase recovered from the single interferogram by Fourier analysis is used to retrieve the thickness and refractive index dispersion without periodic ambiguity. Experimental results of an optical substrate standard show that the accuracy of refractive index dispersion is less than 2.5 × 10−5 and the relative uncertainty of thickness is 6 × 10−5 (3σ). This method is confirmed to be robust against the intensity noises, indicating the capability of stable and accurate measurement.

Wavelength measurement by Fourier analysis of interference fringes through a plane parallel plate

When a diverging laser beam passed through a plane parallel glass plate, interference fringes were observed; analysis of these fringes provided accurate estimation of the source wavelength. The fringes had a unique angular range of uniform fringe density. Fourier transform of the fringes in this range directly provided wavelength information. Reference lasers were used to establish a calibration between the fringe density and wavenumber, with which we estimated the wavelength of a test laser. An accuracy of 4.5×10-5 was obtained, which is better than that of conventional grating spectrometers, while providing a much broader free spectral range. Our method has unique features, such as extreme simplicity of the setup, fast analysis, and low cost, which are great advantages in practical wavelength meter applications.

A simple technique for measuring the optical propagation losses in thin films

ABSTRACTA simple method for measuring the light propagation losses in thin films deposited on an transparent plane parallel substrate is described. It consists on measuring the scattered light intensity from a plane parallel waveguiding substrate on which the optical propagation loss measured thin film is deposited. The method is simple to set up and to operate. It allows to measure relatively large propagation losses. It is illustrated by measuring very large propagation losses in chromophore doped deoxyribonucleic – surfactant complex thin film deposited on a plane parallel glass plate. The method is particularly interesting for measuring large propagation losses.

Dual-wavelength common-path digital holographic microscopy for quantitative phase imaging of biological cells

Biological cells are usually transparent with a small refractive index gradient. Digital holographic interferometry can be used in the measurement of biological cells. We propose a dual-wavelength common-path digital holographic microscopy for the quantitative phase imaging of biological cells. In the proposed configuration, a parallel glass plate is inserted in the light path to create the lateral shearing, and two lasers with different wavelengths are used as the light source to form the dual-wavelength composite digital hologram. The information of biological cells for different wavelengths is separated and extracted in the Fourier domain of the hologram, and then combined to a shorter wavelength in the measurement process. This method could improve the system’s temporal stability and reduce speckle noises simultaneously. Mouse osteoblastic cells and peony pollens are measured to show the feasibility of this method.

An interferometric system for measuring thickness of parallel glass plates without 2π ambiguity using phase analysis of quadrature Haidinger fringes.

An interferometric system is proposed for measuring the thickness of parallel glass plates by analyzing Haidinger fringes. Although a conventional Haidinger interferometer can measure thickness without 2π ambiguity using positions of peak and valley points in the interferogram, measurement accuracy is directly affected by the number of these points involved in the calculation. The proposed method obtains phase values over the entire interferogram by analyzing the quadrature Haidinger fringes generated by a current modulated laser diode. Therefore, it can achieve high speed measurement and nanometric resolution without mechanical rotation and thickness limitation of specimens. In the experiments, the standard deviation of repeated thickness measurement was evaluated as less than 0.3 nm, and the measured thickness profile of the proposed system agreed with that of a conventional thickness interferometer within ±15 nm. We also discussed the required accuracy of refractive index of specimens to implement the proposed method successfully and presented an exemplary measurement result of a multi-layer coated sample having a discontinuous thickness profile.

EFFECT OF HYDROGEL MECHANICS ON IN-SITU CARTILAGE INTEGRATION

Purpose: Successful tissue engineering matrices need to integrate strongly and stably with native tissues to maintain the integrity of the regenerating tissue since poor integration can cause an altered property of the implant and ultimately its degradation. Autologous chondrocyte implantation in combination with three-dimensional biocompatible substrates represents an approach to in-situ repair of relatively large cartilage lesions, which is known as matrix-assisted chondrocyte transplantation (MACT). However, current investigations on how substrate properties influence its integration with native articular cartilage are still limited. This study aimed to evaluate the effects of hydrogel stiffness on MACT-based cartilage tissue integration. Methods: Human articular chondrocytes were harvested from expired, but non-diseased osteochondral grafts extracted from corpses. Isolated cells were passaged twice and then pooled from three donors. Hydrogel precursor solutions were prepared by dissolving type VII agarose in ultrapure water at 0.5%, 1%, 2.5%, 5% and 7.5%, w/v. Each of the solutions was casted between two parallel glass plates separated by a ∼2-mm thick spacer and allowed to solidify on an ice pack for 1–3 minutes. The physical properties of the formed hydrogels were determined. An in-vitro disc-ring human cartilage explant model was employed to study cartilage integration, which allows for easy analysis of integration strength and cell migration. Briefly, human articular cartilage was devitalized through freeze-thaw cycles to eliminate potential cellular activities and preserve extracellular matrix structure. Devitalized cartilage was shaped into Ø8 mm × 2 mm thick discs by aseptically removing both superficial and deep zone cartilage tissues. A Ø4-mm central core was then punched out of each disc and the hole was filled with one of the hydrogel precursor solutions containing 40 x 106 chondrocytes per mL, followed by gelation. (The central hole was filled with 0.5% and 7.5% agarose gels shown in yellow and green colors, respectively.) Hydrogel-cartilage composites were individually cultivated in 24-well plates with the complete chondrocyte medium. At weeks 6 and 12, the composites were harvested for evaluation. A push-through test in which the hydrogel implant of a composite was gradually pushed out by a 1/8’’ plunger at a rate of 10 μm/s while the composite was placed on a custom-designed rigid annular ring with a 5-mm center hole was performed to quantify the adhesive strength at the integration interface. Statistical analyses were performed by one-way or two-way ANOVA in conjunction with the Bonferroni post test for multiple comparisons with significance at p < 0.05. Results: Hydrogel stiffness tested ranged from 0.5 to 15 kPa (n = 14). At week 6, there was no statistical significance observed in tissue integration. At week 12, adhesive stress in the 5% and 7.5% groups remained low whereas the 1% and 2.5% values were significantly higher than the corresponding 6-week values (ˆp < 0.05) with the strongest integration in the 2.5% group. After the push-through test, the hydrogel constructs were collected and evaluated mechanically. The construct stiffness remained similar after week 6 in both of the 5% and 7.5% groups while the hydrogel constructs in the other three groups continued to develop over time. For comparison, free-swelling hydrogel constructs without an outer cartilage annulus were cultured in parallel under identical conditions. Yet, similar tissue properties were determined in free-swelling and push-out samples within the same groups at each time point, suggesting that the presence of the devitalized outer cartilage ring does not significantly influence construct development. Conclusions: This study demonstrated that integration of implanted chondrocyte-laden agarose hydrogels with native human cartilage is significantly affected by substrate mechanics. An optimal hydrogel stiffness that yielded superior integration strength without compromising development of tissue-engineered constructs was identified (2.5% agarose). This work not only provides valuable information to surgeons who perform MACT in the future, but also opens a new avenue towards improvement in designing hydrogel platforms suitable for clinical uses.