Computer-aided Image Processing Research Articles

Ultrastructure of the membrane systems in the unicellular cyanobacterium Synechocystis sp. strain PCC 6803

Among prokaryotes, cyanobacteria are unique in having highly differentiated internal membrane systems. Like other Gram-negative bacteria, cyanobacteria such as Synechocystis sp. strain PCC 6803 have a cell envelope consisting of a plasma membrane, peptidoglycan layer, and outer membrane. In addition, these organisms have an internal system of thylakoid membranes where the electron transfer reactions of photosynthesis and respiration occur. A long-standing controversy concerning the cellular ultrastructures of these organisms has been whether the thylakoid membranes exist inside the cell as separate compartments, or if they have physical continuity with the plasma membrane. Advances in cellular preservation protocols as well as in image acquisition and manipulation techniques have facilitated a new examination of this topic. We have used a combination of electron microscopy techniques, including freeze-etched as well as freeze-substituted preparations, in conjunction with computer-aided image processing to generate highly detailed images of the membrane systems in Synechocystis cells. We show that the thylakoid membranes are in fact physically discontinuous from the plasma membrane in this cyanobacterium. Thylakoid membranes in Synechocystis sp. strain PCC 6803 thus represent bona fide intracellular organelles, the first example of such compartments in prokaryotic cells.

A DETECTIVE STUDY ON PARAXIAL DIGITAL HOLOGRAPHY IN ACQUIRING THE AMPLITUDE AND PHASE SIMULTANEOUSLY

A theoretical model to actualize digital holographic detection with the help of paraxial optical system based on the inverse calculation of diffraction is introduced briefly. In addition, we proposed a method to actualize the measurement when the measured object modulates the amplitude and the phase of object light simultaneously. The simulated experimental example will be illustrated with the help of numerical computation and computer-aided image processing techniques.

New Experimental Method for Measuring Gas Diffusivity in Heavy Oil by the Dynamic Pendant Drop Volume Analysis (DPDVA)

This paper presents a new experimental method and its computational scheme for measuring gas diffusivity in heavy oil at high pressures and elevated temperatures by the dynamic pendant drop volume analysis (DPDVA). In the experiment, a see-through windowed high-pressure cell is first filled with a test gas at a prespecified pressure and temperature. Then, a heavy oil sample is introduced by using a syringe pump to form a pendant drop inside the pressure cell. Due to the oil swelling effect, the subsequent dissolution of the gas into the pendant oil drop causes its volume to increase until the saturation state is reached. The sequential digital images of the dynamic pendant oil drop are acquired and analyzed by applying computer-aided image acquisition and processing techniques to measure the oil drop volumes at different times. A mass-transfer model is developed theoretically to describe the diffusion process of the gas into the pendant heavy oil drop. This model is numerically solved by applying the semidiscrete Galerkin finite element method. The volume of the dynamic pendant oil drop is calculated from the numerically predicted transient gas concentration distribution inside the pendant oil drop. The gas diffusivity in heavy oil and the swelling factor of gas-saturated heavy oil are, thus, determined by finding the best fit of the theoretically calculated volumes of the dynamic pendant oil drop to the experimentally measured data. This novel experimental technique is applied to measure CO2 diffusivities in a heavy oil sample and the swelling factors of a CO2-saturated heavy oil at P = 2, 3, 4, 5, and 6 MPa and T = 23.9 °C.

Novel Genetic-Neuro-Fuzzy Filter for Speckle Reduction from Sonography Images

Edge-preserving speckle noise reduction is essential to computer-aided ultrasound image processing and understanding. A new class of genetic-neuro-fuzzy filter is proposed to optimize the trade-off between speckle noise removal and edge preservation. The proposed approach combines the advantages of the fuzzy, neural, and genetic paradigms. Neuro-fuzzy approaches are very promising for nonlinear filtering of noisy images. Fuzzy reasoning embedded into the network structure aims at reducing errors while fine details are being processed. The learning method based on the real-time genetic algorithms (GAs) performs an effective training of the network from a collection of training data and yields satisfactory results after a few generations. The performance of the proposed filter has been compared with that of the commonly used median and Wiener filters in reducing speckle noises on ultrasound images. We evaluate this filter by passing the filter's output to the edge detection algorithm and observing its ability to detect edge pixels.Experimental results show that the proposed genetic-neuro-fuzzy technique is very effective in speckle noise reduction as well as detail preserving even in the presence of highly noise corrupted data, and it works significantly better than other well-known conventional methods in the literature.

Relationship between cavitation structures and cavitation damage

A study of visual and erosion effects of cavitation on simple single hydrofoil configurations in a cavitation tunnel was made. A two-dimensional hydrofoil with circular leading edge was used for the experiments. In addition, the hydrofoil geometry was modified to obtain some three-dimensional cavitation effects. A thin copper foil, applied to the surface of the hydrofoil, was used as an erosion sensor. Cavitation phenomenon above hydrofoils at different flow conditions (system pressure, water gas content) was observed. Images of vapour cavities from above and from side view were taken. A statistical evaluation of cavitation structures was made. Images of damaged copper coated hydrofoil surface were taken under sufficient magnification. A pit-count method, based on computer-aided image processing, was used for direct measurement of the cavitation erosion by evaluating the damage of the surface of the hydrofoil. A relation between characteristics of cavitation structures and cavitation damage was established.

Computer-aided tissue engineering: overview, scope and challenges.

Advances in computer-aided technology and its application with biology, engineering and information science to tissue engineering have evolved a new field of computer-aided tissue engineering (CATE). This emerging field encompasses computer-aided design (CAD), image processing, manufacturing and solid free-form fabrication (SFF) for modelling, designing, simulation and manufacturing of biological tissue and organ substitutes. The present Review describes some salient advances in this field, particularly in computer-aided tissue modeling, computer-aided tissue informatics and computer-aided tissue scaffold design and fabrication. Methodologies of development of CATE modelling from high-resolution non-invasive imaging and image-based three-dimensional reconstruction, and various reconstructive techniques for CAD-based tissue modelling generation will be described. The latest development in SFF to tissue engineering and a framework of bio-blueprint modelling for three-dimensional cell and organ printing will also be introduced.

Evaluation of Computer-assisted Image Enhancement in Minimal Invasive Endoscopic Surgery

This paper focuses on the evaluation of the usage of computer-aided image processing methods for minimal invasive surgery. During video endoscopy of visceral cavities the images are displayed directly on the monitor without further processing. In the course of the operation the former good quality of the images decreases due to typical disturbances like bleeding, smoke or flying particles. These disturbances can be reduced by using image processing methods like color normalization, temporal filtering or equalization. In this double-blinded analysis, 14 surgeons with different levels of experience evaluated 120 image pairs and 5 image sequences, directly comparing original and processed images or movies. Color normalization and equalization proved to significantly enhance video endoscopic images. With regard to temporal filtering, an improvement could be seen in the image sequences with filter size 5 being a greater enhancement than filter size 3. Comparing the state of experience and its influence on the results, it occurred that the experienced surgeons preferred the original color while altogether agreeing that the color-normalized images were better. The results obtained in the present evaluation show that the image processing methods which were used can significantly improve the quality of video endoscopic images. As a result of this, necessary lavages of the operated area are reduced and a better overview and orientation for the surgeon can be reached.

Automated Image Processing and Analysis of Fracture Surface Patterns Formed during Creep Crack Growth in Austenitic Heat-Resisting Steels with Different Microstructures.

A computer program of automated image processing was developed for fractal analysis of creep fracture surface profiles in this study. Change in the creep fracture surface patterns during crack growth was examined by the computer-aided image processing and analysis. Fractal analysis was then made using software on the processed images. Creep crack growth experiments were carried out on the surface notched specimens of the austenitic 21Cr-4Ni-9Mn steel at 973 K. Creep crack growth rate was lower in the specimens with serrated grain boundaries than in those with straight grain boundaries. The fractal dimension of the grain-boundary fracture surface profiles was larger in the former specimens than in the latter ones. The fractal dimension was larger in the specimens tested under the lower stress, and decreased with increasing distance from notch root. Effects of grain-boundary microstructures and stress on the fracture patterns were correlated to the microstructure and stress dependence of the density of grain-boundary microcracks linked to the fracture surface. Quantitative evaluation of fracture surface patterns may give an important information about the fracture origin or crack growth direction.

Fast edge-preserving noise reduction for ultrasound images

Edge-preserving noise reduction is an essential operation for computer-aided ultrasound image processing and understanding. This paper describes a novel filter which is a two-dimensional (2-D) extension of the one-dimensional (1-D) Savitzky-Golay filter. The new filter, referred to as the 2-D weighted Savitzky-Golay filter, is based on the least squares fitting of a polynomial function to image intensities. The performance of the proposed filter has been compared with that of the commonly used median filter in reducing speckle noise on a synthetic image and an ultrasound thyroid image. Experimental results indicate that on these particular examples, the new filter can achieve at least the same level of noise reduction and edge preservation as that of the median filter, but with far less computation time. Since its complexity scales linearly with the problem size, the new filter is suitable for filtering problems with large windows. In addition, its performance also shows to be less sensitive to the size of the filtering window compared to the median filter.

Use of interferometric techniques for measuring the displacement field in the plane of a part-through crack existing in a plate

An experimental procedure based on holographic interferometry coupled with computer-aided image processing techniques was used to estimate the stress intensity factor (SIF) of a part-through crack in a plate. The loading consisted of a uniform remote tensile stress, leading to an opening and edge rotation displacement field along the crack plane. The evaluation of the crack opening displacements and edge rotations, carried out after the numerical interpretation of the fringe pattern, made possible an estimation of the SIF along the crack line, following the theoretical basis of the Line-Spring Model developed by Rice and Levy.

Computer-aided versus manual grain size assessment in a single phase material

The results of grain size assessment obtained using computer image analysis and manually are presented for comparison. Twelve images of austenitic steel structures of different grain size were examined. The most important grain size parameters, i.e., mean cross section and mean grain diameter were determined. To verify the proposed algorithms the results obtained for the same structures by using classical quantitative metallography are also presented. The algorithms based on significantly different methods for grain edge detection were used to demonstrate the relationships more clearly and to provide a more general view of computer-aided image processing. The measurements were also made manually by six independent observers. The comparison between different methods indicates an advantage of automatic techniques.

Improvement of calcium modified lead titanate piezoceramics by hot isostatic pressing

The hot isostatic pressing (HIP) is used in this work as a post-sintering treatment to obtain piezoelectric ceramics with very low contents of porosity. The method is applied to calcium modified lead titanate ceramics with a wide range of microstructures, corresponding to successive sintering stages. The effects of HIP on the various cases are quantitatively determined, checking the effectiveness of the treatment to reduce the porosity without further grain growth. A combination of computer-aided image processing and measurement with optical and scanning electron (SEM) micrographs and transmission electron microscopy (TEM) are used to characterise the microstructures. The effect of HIP on the porosity is different depending on the sintering stage of the ceramic. Their ferropiezoelectric behaviour is also evaluated in relation to the microstructural changes.

An Introduction to Geographical Information Systems

Beginning with the discussion of what is GIS, this article explains the concept of geographical data and spatial data models. Two software systems, viz computer-aided design and image processing have been identified as the close relatives of GIS and the similarities and differences between these systems and GIS are described. The operational functions of GIS are described under the categories of data input, analysis, spatial query and data output. Various application areas of GIS alongwith specialized applications of GIS are discussed. Some of the GIS software packages have been mentioned. A brief view has been taken of the state of GIS in India and the article is concluded.

REMOTE SENSING IN THE STUDY OF SIBERIA'S MOUNTAIN LANDSCAPES

A Russian geographer outlines several principal directions involving the application of remote sensing technologies to research on mountain systems in the Lake Baykal region of East Siberia. These include remote sensing applications involving: temporal comparison of images from different times; landscape forecasting and paleoland-scape reconstruction; determination of present-day dynamics; and computer-aided image processing. The paper describes how these and other methods were used to delineate the boundaries of a new Kodar National Park and in landscape/regional planning in the Goloustnaya River basin. Translated by Edward Torrey, Alexandria, VA from: Geografiya i prirodnyye resursy, 1998, No. 4, pp. 121-128.

Metal nanoparticles generated by laser ablation

We study a new method for producing ultrafine metal particles (nanopartides) that employs Laser Ablation of Microparticles (LAM). Pulsed excimer laser radiation at 248 nm wavelength was used to ablate ~2 μm feedstock of silver, gold, andpermalloy (Ni 81%:Fe 19%) under both normal atmospheric conditions and in other gases and pressures. A model for nanoparticle formation by LAM is proposed that includes plasma breakdown and shock-wave propagation through the initial microparticle. Behind the shock a large fraction of the original microparticle mass is converted to nanoparticles that diffuse to silicon substrates and TEM grids for collection and analysis. Nanoparticle morphologies are spherical except for gold nanoparticles >100 nm that are generally cubes. Electron micrographs of the samples were analyzed by computer-aided image processing to determine the effect of irradiation conditions on the nanoparticle size distribution. The results showed that mean particle diameters were normally in the range from 10 to 100 nm and that the particle size distributions were generally log-normal, with dispersion (diameter/standard deviation) ranging from 0.2 to 0.5. For metallic microparticle feedstock, the mean size of the produced nanoparticles generally increased with increasing laser fluence and were smallest for fluences not too far above the breakdown threshold.

Structural organization of the major subunits in cyanobacterial photosystem 1. Localization of subunits PsaC, -D, -E, -F, and -J.

Based on an improved isolation procedure using perfusion chromatography, trimeric Photosystem 1 (PS1) complexes have been isolated from various deletion mutants of the mesophilic cyanobacterium Synechocystis PCC 6803. These mutants are only deficient in the deleted subunits, which was carefully checked by high resolution gel electrophoresis in combination with immunoblotting. These highly purified and well characterized PS1 particles were then examined by electron microscopy, followed by computer-aided image processing with single particle averaging techniques as described earlier (Kruip, J., Boekema, E. J., Bald, D., Boonstra, A. F., and Rögner, M. (1993) J. Biol. Chem. 268, 23353-23360). This precise methodological approach allowed a confident localization of the PS1 subunits PsaC, -D, -E, -F, and -J; it also shows shape and size of these subunits once integrated in the PS1 complex. Subunits PsaC, -D, and -E form a ridge on the stromal site, with PsaE toward the edge of each monomer within the trimer and PsaD extending toward the trimeric center, leaving PsaC in between. PsaF (near PsaE) and PsaJ are close together on the outer edge of each monomer; their proximity is also supported by chemical cross-linking, using the zero-length cross-linker EDC. This localization of PsaF contradicts the position suggested by the published low resolution x-ray analysis and shows for the first time the existence of at least one transmembrane alpha-helix for PsaF. A topographic three-dimensional map has been drawn from this set of results showing the location of the major PS1 subunits (besides PsaA and PsaB). These data also led to the assignment of electron density in the recent medium resolution x-ray structure for PS1 (Krauss, N., Schubert, W.-D., Klukas, O., Fromme, P., Witt, H. T., Saenger, W. (1996) Nat. Struct. Biol. 3, 965-973).

Karyotype analysis of Helianthus annuus using Giemsa banding and fluorescence in situ hybridization.

The karyotype of H. annuus was analysed by computer-aided image processing with respect to the chromosome length, arm ratio, occurrence and chromosomal position of intercalary heterochromatin and the location of 18S/25S and 5S ribosomal RNA genes. The karyotype was subdivided into a group of four acrocentric chromosome pairs, of which two were distinguishable by HKG (HCl, KOH, Giemsa) banding and a group of 13 meta- to submetacentric pairs. The latter could be subdivided into seven pairs with one and six pairs with two HKG bands. Three pairs of submetacentric satellite chromosomes revealed 18S/25S rDNA loci after fluorescence in situ hybridization (FISH) and silver staining. A fourth, smaller and possibly inactive, locus occurred in the terminal position on a metacentric pair. One submetacentric satellite chromosome pair revealed a 5S rRNA gene locus in the pericentromeric position; a second locus marked a submetacentric pair with one HKG band. The C-banding technique marks exclusively centromeric heterochromatin. Measurements of chromosomes in combination with Giemsa banding and FISH enabled the discrimination of most chromosome pairs of the sunflower.

Photoviscoelastic Stress Analysis near Contact Regions under Complex Loads

This study discusses several types of contact, involving compression andsliding, between a time-dependent material and a rigid body. Itdemonstrates a useful application of a new hybrid method forphotoviscoelastic stress analysis under non-proportional loadingconditions, in which the principal axes of stress, strain, andbirefringence are not aligned with each other. Using a computer-aidedimage processing technique, the distribution of fringe order andbirefringent principal axes in the vicinity of the contact surface areevaluated from a few photoviscoelastic images through a plane polariscopeby using the well known diagonal summation theorem. The variation of theprincipal stress and/or strain differences as well as their directions areeasily obtainable over a wide time range by use of the opticalconstitutive equations of photoviscoelasticity and the characteristicmaterial properties functions.

Determination of Interfacial Tension from the Profile of a Pendant Drop Using Computer-Aided Image Processing: 1. Theoretical

A method of profile optimization for determining the surface and interfacial tension (IFT) of liquid–fluid systems from the profile of a pendant drop is described. A new, versatile routine for estimating the drop shape parameter is introduced. The factors that affect the available accuracy of the method have been analyzed using theoretical simulations. It was found that the tilt of the drop profiles may lead to large errors in the resultant IFT values if the tilt was not corrected before or during the optimization procedure. This effect could be reduced drastically if a profile were averaged between its two sides and the mean profile were used for optimization. The aspect ratio of a drop image (or profile) can be determined reliably by considering it one of the parameters to be optimized. The dependence of the error in the resultant IFT value on the error in the aspect ratio was found to be highly sensitive to drop shape. The available accuracy of IFT determination using this method depends strongly on the precision of the determination of the drop profiles. After error analysis using theoretical simulations a 95% confidence interval of ca. 0.05 and 0.12% was estimated for this method for the profiles determined with maximum statistical error of 3.5 and 7.0 μm, respectively.

Determination of Interfacial Tension from the Profile of a Pendant Drop Using Computer-Aided Image Processing: 2. Experimental

The reliability of the method described in the preceding paper (B. Song and J. Springer,J. Colloid Interface Sci.183,in press, 1996) for the determination of surface and interfacial tension (IFT) of liquid–fluid systems from the profile of a pendant drop has been studied experimentally. Influences on the resultant IFT values from factors such as the location of the drop profile and illumination conditions are considered. The reproducibility and accuracy of the measurement method were examined by measuring the time dependence of polyethylene glycol (PEG600)/air and water/air systems and by determining the temperature dependence of the polyethylene glycol (PEG6000)/N2and LD (low-density) polyethylene/N2systems. The effect of drop vibrations on the accuracy of the method is discussed.