Importance of phase unwrapping for the reconstruction of microwave tomographic images

Microwave image reconstruction is typically based on a regularized least-square minimization of either the complex-valued field difference between recorded and modeled data or the logarithmic transformation of these field differences. Prior work has shown anecdotally that the latter outperforms the former in limited surveys of simulated and experimental phantom results. In this paper, we provide a theoretical explanation of these empirical findings by developing closed form solutions for the field and the inverted electromagnetic property parameters in one dimension which reveal the dependency of the estimated permittivity and conductivity on the absolute (unwrapped) phase of the measured signal at the receivers relative to the source transmission. The analysis predicts the poor performance of complex-valued field minimization as target size and/or frequency and electromagnetic contrast increase. Such poor performance is avoided by logarithmic transformation and preservation of absolute measured signal phase. Two-dimensional experiments based on both synthetic and clinical data are used to confirm these findings. Robustness of the logarithmic transformation to variation in the initial guess of the reconstructed target properties is also shown. The results are generalizable to three dimensions and indicate that the minimization form with logarithmic transformation offers image reconstruction performance characteristics that are much more desirable for medial microwave imaging applications relative to minimizing differences in complex-valued field quantities.     

Filtering SAR interferometric phase noise using a split-window model

For interferometric synthetic aperture radar (InSAR) processing, the features of interferometric phase obtained in different coherence regions usually differ from each other. This is called region effect and exists in InSAR coherence map. When coherence value is used as a parameter to filter the phase noise, the result will be highly affected by this region effect. In this paper, we propose a new method of filtering InSAR phase noise using a split-window model. The idea of this method is to incorporate several filters into the model. Different filters will be used when dealing with phase noise locates in different coherence regions. The over-filtering or under-filtering caused by the coherence region effect can be eliminated in this method. As an example to demonstrate the superiority of this method, we incorporated an improved Goldstein filter and empirical mode decomposition filter into the current model. They were included to control phase noise level in the low- and high-coherence regions, respectively. The quantitative results obtained using a COnstellation of small Satellites for the Mediterranean basin Observation (COSMO-SkyMed) image pair over Kilauea volcano in Hawaiian demonstrate the advantages of the newly developed split-window model in filtering different types of noise.     

Synthesis and characterization of a single phase zeolite A using coal fly ash

Zeolitization of coal fly ash (CFA) provides a potential alternative for creating high-added-value products from this hazardous solid waste. In this work, a single phase zeolite A with high crystallinity was successfully synthesized from CFA via the alkali fusion hydrothermal method. X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray fluorescence (XRF), Fourier transform infrared (FT-IR) spectroscopy, N₂ physisorption, and solid-state MAS NMR spectra were applied to characterize as-synthesized zeolites. Results indicated that the type and purity of zeolite were closely related to the synthesis conditions and parameters. A well-defined cubic shape of zeolite A with a specific surface area of 43.7 m² g⁻¹ was obtained at a low temperature of 75 °C during hydrothermal treatment for 18 h. The ammonium cation exchange capacity (CEC) test showed an impressive value of 232.2 mmol 100 g⁻¹ over prepared zeolite A, which was about 22 times that of the original CFA and close to commercial zeolite A. These results pave the way for the exploitation and utilization of the CFA.

A single phase zeolite A with high CEC and crystallinity was synthesized by a simple hydrothermal method at low temperature.     

Electrokinetic measurement of cartilage using differential phase optical coherence tomography

When an electric field is applied to cartilage, current-generated stress gradients are produced and stress deformation occurs. Since differential phase optical coherence tomography (DP-OCT) is sensitive to tiny surface displacement, these tiny displacements are induced electrokinetically in cartilage and the electric-current-induced stress gradients were measured with DP-OCT. The electrokinetic surface displacement of cartilage was characterized by applying sinusoidal voltages with two amplitudes (5 and 10 V) and different frequencies (1.0, 0.5 and 0.2 Hz). The results show that by application of DP-OCT the surface displacement increased with increasing applied voltage and decreased with increasing excitation frequency. In the electrokinetic response of cartilage, measured optical phase delay between the surface displacement response and excitation waveform varies inversely with the excitation frequency. Since the streaming potential and other electrokinetic effects in cartilage are directly proportional to proteoglycan density, application of an electric field in cartilage combined with DP-OCT measurements may provide a sensitive indicator of cartilage viability.     

Large deformation monitoring over a coal mining region using pixel-tracking method with high-resolution Radarsat-2 imagery

Differential synthetic aperture radar interferometry (D-InSAR) is limited when exploited in high-intensity mining areas, because large deformation gradients lie beyond the maximum measurable value of the D-InSAR technique which breaks the prerequisite for successfully employing of the method. The SAR amplitude-based pixel-tracking method provides an alternative way to efficiently and robustly extract the large deformation distribution particularly when the D-InSAR technique is limited by loss of coherence. In addition, the deformation in the line-of-sight direction and the deformation along the azimuth direction are also presented in this paper with 24-day interval repeat-pass high-resolution Rardarsat-2 imagery. Combining both of these techniques can help to better understand the deformation mechanisms associated with underground mining activities. The accuracies of 0.12 m in slant-range direction and 0.19 m in the azimuth direction were achieved, respectively. Besides, the profiles across the maximum deformation region have verified that the deformation occurred during two acquisition periods is far beyond the theoretical maximum deformation gradient corresponding to high-resolution C-band SAR data. The obtained surface motion infers to the mining activities and assessed damage caused by the large deformation.     

Measure of attitude toward menopause using the semantic differential model

A semantic differential instrument that measures adult women's attitudes toward menopause was constructed and validated. A volunteer sample of 504 women, 18 years or older, completed the pilot instrument of 45 bipolar adjective scales. A principal components factor analysis revealed 20 scales that loaded on one dominant factor; this factor accounted for 60% of the variance for the 20 scales. Cronbach alpha reliability was .96. The revised 20-scale instrument was called the Menopause Attitude Scale (MAS). A second sample of 419 women completed the MAS and one additional instrument for assessment of convergent and discriminant validity. Convergent validity was demonstrated by a correlation of r = .63 for the MAS with the Attitudes Toward Menopause Scale. Discriminant validity was demonstrated by a correlation of r = .42 for the MAS with the Attitudes Toward Old People Scale and a correlation of r = -.04 for the MAS with the Attitudes Toward Women Scale. Factor analysis of MAS scores revealed that one factor accounted for 61.5% of the variance for the 20 scales. The test-retest reliability for 39 subjects was .87. Multiple regression analysis identified age and menopausal status as significant explanatory variables for MAS scores.     

Predicting osteoarthritic knee rehabilitation outcome by using a prediction model developed by data mining techniques

Artificial neural networks (ANN) have been applied to assist in clinical decision-making and prediction. While we consider possible effective treatments for patients with osteoarthritic knee such as Transcutaneous Electrical Nerve Stimulation (TENS), exercise, and TENS with exercise respectively, we have to select a treatment protocol for patients such that they would gain the best improvements according to their clinical conditions. To facilitate this functionality with the existing patient assessment, we hope to apply the ANN programming techniques to develop a computerized prediction system. A preliminary validation was performed to test the validity of the newly developed prediction protocol on knee rehabilitation. We input the key clinical attributes of 62 patients who have undergone the three above-mentioned knee treatments to the protocol. The expected pain improvement of each patient as predicted by the protocol was obtained. Spearman rank-order correlation was used to identify whether there was a significant correlation between the rankings of the observed and expected pain improvement. We found that the Spearman's rho was 0.424, which is statistically significant at p < 0.001. From this preliminary analysis, we are confident that this newly developed prediction protocol will be useful when deciding which treatment regime best suits a patient.     

PC-based differential model fitting as a support for clinical research

Summary A PC-based minimisation software written in C-language is described, which solves numerically both simple non-linear regression problems and problems expressed as systems of (unsolved) initial-value ordinary or partial differential equations. The software uses second-order iterated Runge-Kutta algorithm to approximate numerically the solution curves. It uses a quasi-Newton algorithm to minimize either sums of squares (weighted or unweighed) or NONMEM loss functions. Inverse Hessian approximation to the parameter dispersion and Monte Carlo generation of artificial samples are offered to test the robustness of the parameter values obtained.A real test problem is described, involving the hydrolysation of plasma Medium Chain Triglycerides to Free Fatty Acids and the uptake of these from plasma. Two competing models were evaluated, one involving linear terms for each transfer and one involving carrier-mediated, rate-limited hydrolysis and tissue absorption steps. The simpler linear model was found to be more robust and eventually used to describe the experimental data.     

A differential diagnostic medium for the isolation of bacteria of the Yersinia genus]

A formula of a solid differentiating diagnostic media for the isolation of Yersinia genus bacteria is suggested. The medium does not include components hard to get and is simple to prepare. No additional sterilization is necessary after the preparation, after the medium is poured into Petri dishes, it is dried in the air. The medium inhibits the growth of cocci and gram-negative contaminant microflora. Yersinia bacteria may be easily differentiated by the color and typical morphology of the colonies. Dishes with primary inoculation may be examined with a magnifying glass in 48 and 72 hrs incubation. The medium is highly sensitive. The results of its trials in examinations of washings off the environmental objects recommend it for practical studies.     

An improved selective and differential medium for the isolation of Burkholderia pseudomallei from clinical specimens

Isolation and culture of Burkholderia pseudomallei remains the main stay in the diagnosis of melioidosis. Thus, the search for selective and differential media for B. pseudomallei has been ongoing. A number of such media have been reported with varying efficacy. Ashdown medium is the most established selective medium for the isolation of B. pseudomallei. There are no reports of differential media differentiating B. pseudomallei from Burkholderia cepacia. This report documents such a selective and differentiating medium for B. pseudomallei. Of a total of 1042 clinical specimens containing mixed flora and gram-negative isolates that were tested on this medium, 16 of the specimens yielded B. pseudomallei. The isolation rate was found to be 1.5%. This medium was found to be simple and inexpensive, can be made by small laboratories, and called as Francis medium. Based on the colony morphology and color, a preliminary report can be made within 18-24 h for the presence of B. pseudomallei. Our study showed that this medium had an overall sensitivity of 78.4% with a specificity of 92.2%. The use of this medium as an early diagnostic tool will help to reduce mortality and morbidity of melioidosis patients.     

Simple model of evapotranspiration by Eucalyptus plantations for data poor areas and tested using water balance data from a small catchment in Guangxi,China

ABSTRACT

Measurements of catchment and stand water balance were made in a small, upland catchment in Guangxi province, China that was covered with a plantation of a Eucalyptus urophylla × Eucalyptus grandis hybrid. These data were used to investigate the relationship between streamflow and the net stand water balance and to test the efficacy of a relationship between the crop factor (ratio of evapotranspiration to potential evaporation) and relative plant available soil water for predicting evapotranspiration. The model was then used to quantify the effect of afforestation with Eucalyptus plantations on the water balance of (1) upland catchments with shallow soils and (2) catchments with deeper soil profiles such as those that can occur in lowland catchments in Guangxi.

During the experiment, the plantation experienced a dry year in 2014, when rainfall was 1095 mm, and a year with approximately average rainfall in 2015 (1493 mm). In 2014, plantation evapotranspiration was 779 mm or 71% of rainfall while during 2015 the annual plantation evapotranspiration was 931 mm or 61% of rainfall. Measured streamflow for a full year was only 18 mm (2%) less than the difference between rainfall and estimated evapotranspiration. The relationship between measured streamflow and the net stand water balance was also strong (r² = 0.8) and unbiased (slope of 1.006).

A model that predicted the crop factor as a function of relative plant available soil water explained more than 78% of the variation in observed evapotranspiration and had a model efficiency of 0.73. It also provided an unbiased prediction of monthly evapotranspiration. When used to model the effect of a change from grassland to a plantation of E. urophylla, it predicted an average annual decrease in drainage of 70 mm and a 5% increase in the number of months with zero flow.     

fMRI activation in a visual-perception task: network of areas detected using the general linear model and independent components analysis.

The Motor-Free Visual Perception Test, revised (MVPT-R), provides a measure of visual perceptual processing. It involves different cognitive elements including visual discrimination, spatial relationships, and mental rotation. We adapted the MVPT-R to an event-related functional MRI (fMRI) environment to investigate the brain regions involved in the interrelation of these cognitive elements. Two complementary analysis methods were employed to characterize the fMRI data: (a) a general linear model SPM approach based upon a model of the time course and a hemodynamic response estimate and (b) independent component analysis (ICA), which does not constrain the specific shape of the time course per se, although we did require it to be at least transiently task-related. Additionally, we implemented ICA in a novel way to create a group average that was compared with the SPM group results. Both methods yielded similar, but not identical, results and detected a network of robustly activated visual, inferior parietal, and frontal eye-field areas as well as thalamus and cerebellum. SPM appeared to be the more sensitive method and has a well-developed theoretical approach to thresholding. The ICA method segregated functional elements into separate maps and identified additional regions with extended activation in response to presented events. The results demonstrate the utility of complementary analyses for fMRI data and suggest that the cerebellum may play a significant role in visual perceptual processing. Additionally, results illustrate functional connectivity between frontal eye fields and prefrontal and parietal regions.     

Gastric transitional zones,areas where Helicobacter treatment fails: results of a treatment trial using the Sydney strain mouse model

Current combination therapies cure Helicobacter pylori infection in 75 to 85% of cases. However, many treatment failures are not explained by antibiotic resistance. Our goal was to explore treatment failures under in vivo conditions by using the H. pylori Sydney strain (SS1) mouse model. Mice infected with H. pylori (SS1) were treated with monotherapies or combination therapies used in human trials. Bacterial levels and distribution of organisms within the stomach were assessed 24 h after treatment to determine clearance and location of treatment failures and 29 days after treatment to determine cure rates. Except for treatment with metronidazole, mono- and dual therapies did not cure infection but resulted in decreases in bacterial levels and differences in distribution within the stomach. In cases of treatment failure when clarithromycin was used, omeprazole and dual therapy with omeprazole and amoxicillin resulted in organisms being cleared from the antrum, but organisms remained in the antrum-body transitional zone. The triple therapies of OMC and bismuth subcitrate, metronidazole, and tetracycline were successful in eradicating infection. Except for metronidazole monotherapy and triple therapy with OAC, there was good correlation between the Sydney strain mouse model and humans with respect to the success of antimicrobial therapy. The antrum-body transitional zone was identified as a sanctuary site in treatment failure. This could result from antimicrobial agents not functioning effectively at this site or bacteria in this location expressing products that protect them against antimicrobial agents. This is the first demonstration of a possible sanctuary site as a reason for failure of therapy.