UvHOS3-mediated histone deacetylation is essential for virulence and negatively regulates ustilaginoidin biosynthesis in Ustilaginoidea virens.

Ustilaginoidea virens is the causal agent of rice false smut, which has recently become one of the most important rice diseases worldwide. Ustilaginoidins, a major type of mycotoxins produced in false smut balls, greatly deteriorates grain quality. Histone acetylation and deacetylation are involved in regulating secondary metabolism in fungi. However, little is yet known on the functions of histone deacetylases (HDACs) in virulence and mycotoxin biosynthesis in U. virens. Here, we characterized the functions of the HDAC UvHOS3 in U. virens. The ΔUvhos3 deletion mutant exhibited the phenotypes of retarded growth, increased mycelial branches and reduced conidiation and virulence. The ΔUvhos3 mutants were more sensitive to sorbitol, sodium dodecyl sulphate and oxidative stress/H2 O2 . ΔUvhos3 generated significantly more ustilaginoidins. RNA-Seq and metabolomics analyses also revealed that UvHOS3 is a key negative player in regulating secondary metabolism, especially mycotoxin biosynthesis. Notably, UvHOS3 mediates deacetylation of H3 and H4 at H3K9, H3K18, H3K27 and H4K8 residues. Chromatin immunoprecipitation assays indicated that UvHOS3 regulates mycotoxin biosynthesis, particularly for ustilaginoidin and sorbicillinoid production, by modulating the acetylation level of H3K18. Collectively, this study deepens the understanding of molecular mechanisms of the HDAC UvHOS3 in regulating virulence and mycotoxin biosynthesis in phytopathogenic fungi.

Soil fungal community is more sensitive than bacterial community to modified materials application in saline-alkali land of Hetao Plain.

Soil salinization has become a major challenge that severely threatens crop growth and influences the productivity of agriculture. It is urgent to develop effective management measures to improve saline-alkali soil. Thus, in this study, soil properties, microbial communities, and function under desulfurization gypsum (DE), soil amendment (SA), farm manure (FA), and co-application of desulfurization gypsum, soil amendment, and farm manure (TA) in a field experiment were examined by high-throughput sequencing. The results showed that the application of modified materials is an effective approach in improving saline-alkali soil, especially TA treatment significantly increased the content of available phosphorus (AP), available potassium (AK), soil organic matter (SOM), and alkaline hydrolysis nitrogen (AHN) and decreased pH, bulk density (BD), and electrical conductivity (EC). The application of modified materials resulted in notable enhancement in fungal diversity and altered the composition and structure of the fungal community. Conversely, the effect on the bacterial community was comparatively minor, with changes limited to the structure of the community. Regarding the fungal community composition, Ascomycota, Mortierellomycota, and Basidiomycota emerged as the dominant phyla across all treatments. At each taxonomic level, the community composition exhibited significant variations in response to different modified materials, resulting in divergent soil quality. The TA treatment led to a decrease in Mortierellomycota and an increase in Ascomycota, potentially enhancing the ability to decompose organic matter and facilitate soil nutrient cycling. Additionally, the sensitivity of fungal biomarkers to modified materials surpassed that of the bacterial community. The impact of modified materials on soil microbial communities primarily stemmed from alterations in soil EC, AP, AK, and SOM. FUNGuild analysis indicated that the saprotroph trophic mode group was the dominant component, and the application of modified materials notably increased the symbiotroph group. PICRUSt analysis revealed that metabolism was the most prevalent functional module observed at pathway level 1. Overall, the application of modified materials led to a decrease in soil EC and an increase in nutrient levels, resulting in more significant alterations in the soil fungal community, but it did not dramatically change the soil bacterial community. Our study provides new insights into the application of modified materials in increasing soil nutrients and altering soil microbial communities and functions and provides a better approach for improving saline-alkali soil of Hetao Plain.

Dynamic Changes of Soil Microbial Communities During the Afforestation of Pinus Armandii in a Karst Region of Southwest China.

Clarifying the response of soil microbial communities to vegetation restoration is essential to comprehend biogeochemical processes and ensure the long-term viability of forest development. To assess the variations in soil microbial communities throughout the growth of Pinus armandii plantations in the karst region, we utilized the "space instead of time" approach and selected four P. armandii stands with ages ranging from 10 to 47 years, along with a grassland control. The microbial community structure was determined by conducting Illumina sequencing of the 16 S rRNA gene and the ITS gene, respectively. The results demonstrated that afforestation with P. armandii significantly influenced soil microbial communities, as indicated by notable differences in bacterial and fungal composition and diversity between the plantations and the control. However, soil microbe diversity did not display significant variation across stand ages. Moreover, the bacterial community exhibited higher responsiveness to age gradients compared to the fungal community. Soil physicochemical factors play a critical role in elucidating microbial diversity and community composition variations during restoration processes. TN, AN, TP, AP, SOC, AK, and pH were the most significant influencing factors for the composition of bacterial community, while TC, SOC, pH, and TCa were the most significant influencing factors for the composition of fungal community. Our findings indicate substantial changes in soil bacterial and fungal communities across successive stages of development. Additionally, the changes in dominant bacteria and fungi characteristics across the age gradient were primarily attributed to variations in the prevailing soil conditions and chemical factors.

Prediction of death rates for cardiovascular diseases and cancers.

Background: To estimate cardiovascular and cancer death rates by regions and time periods. Design: Novel statistical methods were used to analyze clinical surveillance data. Methods: A multicenter, population-based medical survey was performed. Annual recorded deaths from cardiovascular diseases were analyzed for all 195 countries of the world. It is challenging to model such data; few mathematical models can be applied because cardiovascular disease and cancer data are generally not normally distributed. Results: A novel approach to assessing the biosystem reliability is introduced and has been found to be particularly suitable for analyzing multiregion environmental and healthcare systems. While traditional methods for analyzing temporal observations of multiregion processes do not deal with dimensionality efficiently, our methodology has been shown to be able to cope with this challenge. Conclusions: Our novel methodology can be applied to public health and clinical survey data.

Histone Deacetylase UvHST2 Is a Global Regulator of Secondary Metabolism in Ustilaginoidea virens.

Ustilaginoidea virens, the causal agent of rice false smut, produces a large amount of mycotoxins, including ustilaginoidins and sorbicillinoids. However, little is known about the regulatory mechanism of mycotoxin biosynthesis inU. virens. Here, we demonstrate that the NAD+-dependent histone deacetylase UvHST2 negatively regulates ustilaginoidin biosynthesis. UvHst2 knockout caused retarded hypha growth and reduced conidiation and pathogenicity inU. virens. Transcriptome analysis revealed that the transcription factor genes, transporter genes, and other tailoring genes in eight biosynthetic gene clusters (BGCs) including ustilaginoidin and sorbicillinoid BGCs were upregulated in ΔUvhst2. Interestingly, the UvHst2 deletion affects alternative splicing. Metabolomics revealed that UvHST2 negatively regulates the biosynthesis of various mycotoxins including ustilaginoidins, sorbicillin, ochratoxin B, zearalenone, and O-M-sterigmatocystin. Combined transcriptome and metabolome analyses uncover that UvHST2 positively regulates pathogenicity but negatively modulates the expression of BGCs involved in secondary metabolism. Collectively, UvHST2 functions as a global regulator of secondary metabolism inU. virens.

MiR-148a-3p attenuates apoptosis and inflammation by targeting CNTN4 in atherosclerosis.

Background: Atherosclerosis (AS) seriously affects human health. The role of microRNAs (miRNAs) in the pathogenesis and progression of AS has become a focus of research. Our goal was to identify the biological effect of differentially expressed miRNAs (DE-miRNAs) in AS. Methods: To analyze differentially expressed genes (DEGs), including differentially expressed mRNAs (DE-mRNAs) and DE-miRNAs, in AS by using the Gene Expression Omnibus (GEO) database and limma package. DEGs protein-protein interaction (PPI) network and functional enrichment analysis were constructed by using the search tool for the retrieval of interacting genes/proteins (STRING) database, Cytoscape software and Cytoscape plugin "ClueGO2.5.6". We established a coexpression network of dysregulated miRNAs and mRNAs to predict the function of miRNAs by using miRWalk database and Pearson correlation coefficient (PCC) analysis. Cellular experiments were used to validate the results of bioinformatics. Results: First, 69 common DEGs were obtained from datasets GSE43292 and GSE97210 using the limma package in R. Next, a DEG PPI network was constructed. Functional enrichment analysis of DEGs showed that 11 functional pathways were significantly enriched, such as positive regulation of monocyte chemotaxis. Seven common DE-miRNAs were obtained from the GSE99685 dataset and DE-mRNAs predicted miRNAs through the miRWalk database. The miRNA-mRNA network constructed using Cytoscape software suggested that miR-148a-3p targeted contactin 4 (CNTN4). Quantitative real-time polymerase chain reaction (qRT-PCR) assay results indicated that miR-148a-3p was downregulated and CNTN4 was upregulated in the THP-1 + phorbol 12-myristate 13-acetate (PMA) + oxidized low-density lipoprotein (oxLDL) group compared with the THP-1 + PMA group. qRT-PCR, flow cytometry, and enzyme-linked immunosorbent assay (ELISA) found that upregulated miR-148a-3p significantly inhibited the expression of CNTN4, cell apoptosis, and interleukin-6 (IL-6) and tumor necrosis factor-alpha (TNF-α) concentrations in oxLDL-induced THP-1 macrophages. In addition, a dual-luciferase reporter assay demonstrated that CNTN4 was a target gene of miR-148a-3p. Conclusions: Overall, these findings suggested that miR-148a-3p inhibited oxLDL-induced cell apoptosis and inflammation via targeting CNTN4 in THP-1 macrophages.

CircRNA_0050486 promotes cell apoptosis and inflammation by targeting miR-1270 in atherosclerosis.

Background: Atherosclerosis (AS) is a chronic inflammatory disease that plays a major role in cardiovascular disease. Circular RNAs (circRNAs) are related to the pathogenesis of AS, including the inflammatory response. This study aimed to explore the underlying mechanisms of circRNAs and how they regulate the inflammatory response in AS. Methods: Analyzed the expression profile of circRNAs in three oxidized low-density lipoprotein (oxLDL) treated macrophage samples and three macrophage control samples using bioinformatics methods. Expression and biological function of circRNA were verified in oxLDL-induced THP-1 macrophages. MiRNAs and target genes of circRNA were predicted by functional enrichment analysis. Expression and function of circRNA target miRNAs were explored in oxLDL-induced THP-1 macrophages. Finally, we predicted and analyzed the function of circRNAs-miRNAs target genes in AS. Results: We identified nine upregulated circRNAs and found that circ_0050486 was significantly upregulated in a THP-1 + PMA + oxLDL group compared with a THP-1 + PMA group. Additionally, circ_0050486 knockdown markedly inhibited IL-6 and TNF-α concentrations and the cell death rates in oxLDL-induced THP-1 macrophages. Furthermore, circ_0050486 targeted and inhibited miR-145 and miR-1270. Upregulated miR-1270 markedly inhibited IL-6 and TNF-α levels and the cell death rates in oxLDL-induced THP-1 macrophages. Finally, the target genes of miR-1270 and miR-145 were predicted by the miRDB, miRWalk, and Targetscan databases, and a functional analysis network of the target genes was constructed by Cytoscape GlueGO, including the regulation of the immune response and monocyte chemotaxis. The common target genes of miR-145 and miR-1270 were established by Cytoscape and included NF1A, among others. Conclusions: Our study suggested that circ_0050486 knockdown inhibited inflammation and apoptosis by targeting miR-1270 in oxLDL-induced THP-1 macrophages. This finding may provide a potential therapeutic target for atherosclerosis.

Higher water and nutrient use efficiencies in savanna than in rainforest lianas result in no difference in photosynthesis.

Differences in traits between lianas and trees in tropical forests have been studied extensively; however, few have compared the ecological strategies of lianas from different habitats. Here, we measured 25 leaf and stem traits concerning leaf anatomy, morphology, physiology and stem hydraulics for 17 liana species from a tropical seasonal rainforest and for 19 liana species from a valley savanna in south-west China. We found that savanna lianas had higher vessel density, wood density and lower hydraulically weighted vessel diameter and theoretical hydraulic conductivity than tropical seasonal rainforest lianas. Compared with tropical seasonal rainforest lianas, savanna lianas also showed higher leaf dry matter content, carbon isotope composition (δ13C), photosynthetic water use efficiency, ratio of nitrogen to phosphorus, photosynthetic phosphorus use efficiency and lower leaf size, stomatal conductance and nitrogen, phosphorus and potassium concentrations. Interestingly, no differences in light-saturated photosynthetic rate were found between savanna and tropical seasonal rainforest lianas either on mass or area basis. This is probably due to the higher water and nutrient use efficiencies of savanna lianas. A principal component analysis revealed that savanna and tropical seasonal rainforest lianas were significantly separated along the first axis, which was strongly associated with acquisitive or conservative resource use strategy. Leaf and stem functional traits were coordinated across lianas, but the coordination or trade-off was stronger in the savanna than in the tropical seasonal rainforest. In conclusion, a relatively conservative (slow) strategy concerning water and nutrient use may benefit the savanna lianas, while higher nutrient and water use efficiencies allow them to maintain similar photosynthesis as tropical seasonal rainforest species. Our results clearly showed divergences in functional traits between lianas from savanna and tropical seasonal rainforest, suggesting that enhanced water and nutrient use efficiencies might contribute to the distribution of lianas in savanna ecosystems.

Topography-related controls on N2O emission and CH4 uptake in a tropical rainforest catchment.

Forest soils in the warm-humid tropics significantly contribute to the regional greenhouse gas (GHG) budgets. However, spatial heterogeneity of GHG fluxes is often overlooked. Here, we present a study of N2O and CH4 fluxes over 1.5 years, along a topographic gradient in a rainforest catchment in Xishuangbanna, SW China. From the upper hillslope to the foot of the hillslope, and further to the flat groundwater discharge zone, we observed a decrease of N2O emission associated with an increase of soil water-filled-pore-space (WFPS), which we tentatively attribute to more complete denitrification to N2 at larger WFPS. In the well-drained soils on the hillslope, denitrification at anaerobic microsites or under transient water-saturation was the potential N2O source. Negative CH4 fluxes across the catchment indicated a net soil CH4 sink. As the oxidation of atmospheric CH4 is diffusion-limited, soil CH4 consumption rates were negatively related to WFPS, reflecting the topographic control. Our observations also suggest that during dry seasons N2O emission was significantly dampened (<10 µg N2O-N m-2 h-1) and CH4 uptake was strongly enhanced (83 µg CH4-C m-2 h-1) relative to wet seasons (17 µg N2O-N m-2 h-1 and 56 µg CH4-C m-2 h-1). In a post-drought period, several rain episodes induced exceptionally high N2O emissions (450 µg N2O-N m-2 h-1) in the groundwater discharge zone, likely driven by flushing of labile organic carbon accumulated during drought. Considering the global warming potential associated with both GHGs, we found that N2O emissions largely offset the C sink contributed by CH4 uptake in soils (more significant in the groundwater discharge zone). Our study illustrates important topographic controls on N2O and CH4 fluxes in forest soils. With projected climate change in the tropics, weather extremes may interact with these controls in regulating forest GHG fluxes, which should be accounted for in future studies.

Environmental and management controls of soil carbon storage in grasslands of southwestern China.

In order to predict the effects of climate change on the global carbon cycle, it is crucial to understand the environmental factors that affect soil carbon storage in grasslands. In the present study, we attempted to explain the relationships between the distribution of soil carbon storage with climate, soil types, soil properties and topographical factors across different types of grasslands with different grazing regimes. We measured soil organic carbon in 92 locations at different soil depth increments, from 0 to 100 cm in southwestern China. Among soil types, brown earth soils (Luvisols) had the highest carbon storage with 19.5 ±â€¯2.5 kg m-2, while chernozem soils had the lowest with 6.8 ±â€¯1.2 kg m-2. Mean annual temperature and precipitation, exerted a significant, but, contrasting effects on soil carbon storage. Soil carbon storage increased as mean annual temperature decreased and as mean annual precipitation increased. Across different grassland types, the mean carbon storage for the top 100 cm varied from 7.6 ±â€¯1.3 kg m-2 for temperate desert to 17.3 ±â€¯2.9 kg m-2 for alpine meadow. Grazing/cutting regimes significantly affected soil carbon storage with lowest value (7.9 ±â€¯1.5 kg m-2) recorded for cutting grass, while seasonal (11.4 ±â€¯1.3 kg m-2) and year-long (12.2 ±â€¯1.9 kg m-2) grazing increased carbon storage. The highest carbon storage was found in the completely ungrazed areas (16.7 ±â€¯2.9 kg m-2). Climatic factors, along with soil types and topographical factors, controlled soil carbon density along a soil depth in grasslands. Environmental factors alone explained about 60% of the total variation in soil carbon storage. The actual depth-wise distribution of soil carbon contents was significantly influenced by the grazing intensity and topographical factors. Overall, policy-makers should focus on reducing the grazing intensity and land conversion for the sustainable management of grasslands and C sequestration.

Numerical and experimental analysis of a focused reflected wave in a multi-layered material based on a ray model.

A focal probe is used for the acoustic measurement of a thin layer of a material with unknown sound velocity. This is now possible, because an algorithm, based on the focused ray model, has been found. However, there are still several problems such as the assumption that the half-aperture angle equals the incident angle, the identification of the longitudinal-wave focus, and the composition of the signal. In this work, we study the multi-mode wave focus numerically and experimentally to identify the focused longitudinal waves. A theoretical multilayered focusing model has been introduced based on geometrical acoustics. In addition, a phase differentiation theory is proposed to find the incident angle for the focus of the tilted rays, which is referred to as maximum half-aperture angle in other studies. The V(z,t) curve of a single layer, with a thickness of 1.5 mm and 2.0 mm, and a multi-layer are obtained using vertical translational movement. Both thickness and sound velocity are derived from the curve simultaneously. Our single layer experiments show that it is possible to focus multimode waves. The single and multi-layer experiments confirm the multi-layered focused ray model and phase differentiation theory. Furthermore, experiments are conducted to analyze the measured results.

Carbon exchanges and their responses to temperature and precipitation in forest ecosystems in Yunnan, Southwest China.

Forest ecosystems play an increasingly important role in the global carbon cycle. However, knowledge on carbon exchanges, their spatio-temporal patterns, and the extent of the key controls that affect carbon fluxes is lacking. In this study, we employed 29-site-years of eddy covariance data to observe the state, spatio-temporal variations and climate sensitivity of carbon fluxes (gross primary productivity (GPP), ecosystem respiration (Reco), and net ecosystem carbon exchange (NEE)) in four representative forest ecosystems in Yunnan. We found that 1) all four forest ecosystems were carbon sinks (the average NEE was -3.40tCha-1yr-1); 2) contrasting seasonality of the NEE among the ecosystems with a carbon sink mainly during the wet season in the Yuanjiang savanna ecosystem (YJ) but during the dry season in the Xishuangbanna tropical rainforest ecosystem (XSBN), besides an equivalent NEE uptake was observed during the wet/dry season in the Ailaoshan subtropical evergreen broad-leaved forest ecosystem (ALS) and Lijiang subalpine coniferous forest ecosystem (LJ); 3) as the GPP increased, the net ecosystem production (NEP) first increased and then decreased when the GPP>17.5tCha-1yr-1; 4) the precipitation determines the carbon sinks in the savanna ecosystem (e.g., YJ), while temperature did so in the tropical forest ecosystem (e.g., XSBN); 5) overall, under the circumstances of warming and decreased precipitation, the carbon sink might decrease in the YJ but maybe increase in the ALS and LJ, while future strength of the sink in the XSBN is somewhat uncertain. However, based on the redundancy analysis, the temperature and precipitation combined together explained 39.7%, 32.2%, 25.3%, and 29.6% of the variations in the NEE in the YJ, XSBN, ALS and LJ, respectively, which indicates that considerable changes in the NEE could not be explained by variations in the temperature and precipitation. Therefore, the effects of other factors (e.g., CO2 concentration, N/P deposition, aerosol and other variables) on the NEE still require extensive research and need to be considered seriously in carbon-cycle-models.

The effects of nitrogen fertilization on N2O emissions from a rubber plantation.

To gain the effects of N fertilizer applications on N2O emissions and local climate change in fertilized rubber (Hevea brasiliensis) plantations in the tropics, we measured N2O fluxes from fertilized (75 kg N ha(-1) yr(-1)) and unfertilized rubber plantations at Xishuangbanna in southwest China over a 2-year period. The N2O emissions from the fertilized and unfertilized plots were 4.0 and 2.5 kg N ha(-1) yr(-1), respectively, and the N2O emission factor was 1.96%. Soil moisture, soil temperature, and the area weighted mean ammoniacal nitrogen (NH4(+)-N) content controlled the variations in N2O flux from the fertilized and unfertilized rubber plantations. NH4(+)-N did not influence temporal changes in N2O emissions from the trench, slope, or terrace plots, but controlled spatial variations in N2O emissions among the treatments. On a unit area basis, the 100-year carbon dioxide equivalence of the fertilized rubber plantation N2O offsets 5.8% and 31.5% of carbon sink of the rubber plantation and local tropical rainforest, respectively. When entire land area in Xishuangbanna is considered, N2O emissions from fertilized rubber plantations offset 17.1% of the tropical rainforest's carbon sink. The results show that if tropical rainforests are converted to fertilized rubber plantations, regional N2O emissions may enhance local climate warming.

Automated anterior segment OCT image analysis for Angle Closure Glaucoma mechanisms classification.

BACKGROUND AND OBJECTIVES: Angle closure glaucoma (ACG) is an eye disease prevalent throughout the world. ACG is caused by four major mechanisms: exaggerated lens vault, pupil block, thick peripheral iris roll, and plateau iris. Identifying the specific mechanism in a given patient is important because each mechanism requires a specific medication and treatment regimen. Traditional methods of classifying these four mechanisms are based on clinically important parameters measured from anterior segment optical coherence tomography (AS-OCT) images, which rely on accurate segmentation of the AS-OCT image and identification of the scleral spur in the segmented AS-OCT images by clinicians. METHODS: In this work, a fully automated method of classifying different ACG mechanisms based on AS-OCT images is proposed. Since the manual diagnosis mainly based on the morphology of each mechanism, in this study, a complete set of morphological features is extracted directly from raw AS-OCT images using compound image transforms, from which a small set of informative features with minimum redundancy are selected and fed into a Naïve Bayes Classifier (NBC). RESULTS: We achieved an overall accuracy of 89.2% and 85.12% with a leave-one-out cross-validation and 10-fold cross-validation method, respectively. This study proposes a fully automated way for the classification of different ACG mechanisms, which is without intervention of doctors and less subjective when compared to the existing methods. CONCLUSIONS: We directly extracted the compound image transformed features from the raw AS-OCT images without any segmentation and parameter measurement. Our method provides a completely automated and efficient way for the classification of different ACG mechanisms.

Learning ECOC Code Matrix for Multiclass Classification with Application to Glaucoma Diagnosis.

Classification of different mechanisms of angle closure glaucoma (ACG) is important for medical diagnosis. Error-correcting output code (ECOC) is an effective approach for multiclass classification. In this study, we propose a new ensemble learning method based on ECOC with application to classification of four ACG mechanisms. The dichotomizers in ECOC are first optimized individually to increase their accuracy and diversity (or interdependence) which is beneficial to the ECOC framework. Specifically, the best feature set is determined for each possible dichotomizer and a wrapper approach is applied to evaluate the classification accuracy of each dichotomizer on the training dataset using cross-validation. The separability of the ECOC codes is maximized by selecting a set of competitive dichotomizers according to a new criterion, in which a regularization term is introduced in consideration of the binary classification performance of each selected dichotomizer. The proposed method is experimentally applied for classifying four ACG mechanisms. The eye images of 152 glaucoma patients are collected by using anterior segment optical coherence tomography (AS-OCT) and then segmented, from which 84 features are extracted. The weighted average classification accuracy of the proposed method is 87.65 % based on the results of leave-one-out cross-validation (LOOCV), which is much better than that of the other existing ECOC methods. The proposed method achieves accurate classification of four ACG mechanisms which is promising to be applied in diagnosis of glaucoma.

A new method for evaluating the degeneration of articular cartilage using pulse-echo ultrasound.

This paper presents a novel nondestructive ultrasonic technique for measuring the sound speed and acoustic impedance of articular cartilage using the pulsed Vz,t technique. Vz,t data include a series of pulsed ultrasonic echoes collected using different distances between the ultrasonic transducer and the specimen. The 2D Fourier transform is applied to the Vz,t data to reconstruct the 2D reflection spectrum Rθ,ω. To obtain the reflection coefficient of articular cartilage, the Vz,t data from a reference specimen with a well-known reflection coefficient are obtained to eliminate the dependence on the general system transfer function. The ultrasound-derived aggregate modulus (Ha) is computed based on the measured reflection coefficient and the sound speed. In the experiment, 32 cartilage-bone samples were prepared from bovine articular cartilage, and 16 samples were digested using 0.25% trypsin solution. The sound speed and Ha of these cartilage samples were evaluated before and after degeneration. The magnitude of the sound speed decreased with trypsin digestion (from 1663 ± 5.6 m/s to 1613 ± 5.3 m/s). Moreover, the Young's modulus in the corresponding degenerative state was measured and was correlated with the ultrasound-derived aggregate modulus. The ultrasound-derived aggregate modulus was determined to be highly correlated with the Young's modulus (n = 16, r>0.895, p<0.003, Pearson correlation test for each measurement). The results demonstrate the effectiveness of using the proposed method to assess the changes in sound speed and the ultrasound-derived aggregate modulus of cartilage after degeneration.

Reliable feature selection for automated angle closure glaucoma mechanism detection.

Glaucoma is an eye disease where a loss of vision occurs as a result of progressive optic nerve damage usually associates with high intraocular pressure. A subtype of glaucoma called primary angle-closure glaucoma (PACG) has been observed to be the result of one or more mechanisms such as Pupil block, Plateau iris, Peripheral iris roll, and Lens in the anterior segment of the eye. Reliable features in anterior segment images are important for determining the specific mechanisms involved in PACG. In this paper, first the discriminant features are selected by several feature selection algorithms in the context of PACG detection based on anterior segment optical coherence tomography (AS-OCT) images, and then a novel criteria is proposed to further select more reliable features. Our approach is based on selecting the top-ranked features in each algorithm and its rank combination for selection of the best features. Compared with the features selected by the individual feature selection methods, the features selected by our method achieves the best performance in terms of the accuracy of classification of the four PACG mechanisms by using AdaBoost classifier.

Simultaneously measuring thickness, density, velocity and attenuation of thin layers using V(z,t) data from time-resolved acoustic microscopy.

To meet the need of efficient, comprehensive and automatic characterization of the properties of thin layers, a nondestructive method using ultrasonic testing to simultaneously measure thickness, density, sound velocity and attenuation through V(z,t) data, recorded by time-resolved acoustic microscopy is proposed. The theoretical reflection spectrum of the thin layer at normal incidence is established as a function of three dimensionless parameters. The measured reflection spectrum R(θ,ω) is obtained from V(z,t) data and the measured thickness is derived from the signals when the lens is focused on the front and back surface of the thin layer, which are picked up from the V(z,t) data. The density, sound velocity and attenuation are then determined by the measured thickness and inverse algorithm utilizing least squares method to fit the theoretical and measured reflection spectrum at normal incidence. It has the capability of simultaneously measuring thickness, density, sound velocity and attenuation of thin layer in a single V(z,t) acquisition. An example is given for a thin plate immersed in water and the results are satisfactory. The method greatly simplifies the measurement apparatus and procedures, which improves the efficiency and automation for simultaneous measurement of basic mechanical and geometrical properties of thin layers.

Determination of the multiple local properties of thin layer with high lateral resolution by scanning acoustic microscopy.

Simultaneous determination of the multiple local acoustic and geometrical properties of the thin layer with a high lateral resolution is of great interest in ultrasonic non-destructive evaluation. In this paper, we propose a technique based on the V(z, t) data to simultaneously determine the four local properties of the thin layer, namely, the thickness, the sound velocity, the acoustic impedance, and the density. First, the V(z, t) data are collected from both the thin layer and the reference material. Then the sound velocity and the thickness are calculated by focusing the point-focusing transducer on the front and back surfaces of the thin layer, with the confocal positions determined by averaging the peak positions in the V(z) curves at different frequencies. Second, the acoustic impedance of the thin layer is obtained based on the experimental and theoretical two-dimensional reflection spectrum using the echo from the front surface of the layer. Finally, the density can be obtained by dividing the acoustic impedance by the sound velocity. The four local properties of an aluminum layer are accurately obtained using our method. The largest relative error of determining the four properties is around 1%. This technique opens a new way of simultaneously measuring the multiple local acoustic and geometrical properties of thin layers.