487 research outputs found
A Parametrical Finite Element Formulation of the Bloch-Torrey Equation for NMR Applications
We present a finite element formulation of the full Bloch-Torrey equation for nuclear magnetic resonance (NMR) applications. We obtained parametrical expressions that allow us to compute the involved matrices in a simple and fast way for any spatial convergence order. The framework here proposed is valid for many problems related to MR, as diffusion and perfusion MRI
Effetti della potatura sulla fisiologia dell'albero e sul microclima urbano
The presentation describes the effects of different pruning methods (i.e. reduction cut, removal cut, heading cut, and no pruning) on growth and physiology of two urban tree species. Also, the effects of improper pruning on microclimate are presented and discussed
Fully automatic detection of lung nodules in CT images using a hybrid feature set
Purpose: The aim of this study was to develop a novel technique for lung nodule detection using an optimized feature set. This feature set has been achieved after rigorous experimentation, which has helped in reducing the false positives significantly.
Method: The proposed method starts with preprocessing, removing any present noise from input images, followed by lung segmentation using optimal thresholding. Then the image is enhanced using multiscale dot enhancement filtering prior to nodule detection and feature extraction. Finally, classification of lung nodules is achieved using Support Vector Machine (SVM) classifier. The feature set consists of intensity, shape (2D and 3D) and texture features, which have been selected to optimize the sensitivity and reduce false positives. In addition to SVM, some other supervised classifiers like K‐Nearest‐Neighbor (KNN), Decision Tree and Linear Discriminant Analysis (LDA) have also been used for performance comparison. The extracted features have also been compared class‐wise to determine the most relevant features for lung nodule detection. The proposed system has been evaluated using 850 scans from Lung Image Database Consortium (LIDC) dataset and k‐fold cross‐validation scheme.
Results: The overall sensitivity has been improved compared to the previous methods and false positives per scan have been reduced significantly. The achieved sensitivities at detection and classification stages are 94.20% and 98.15%, respectively, with only 2.19 false positives per scan.
Conclusions: It is very difficult to achieve high performance metrics using only a single feature class therefore hybrid approach in feature selection remains a better choice. Choosing right set of features can improve the overall accuracy of the system by improving the sensitivity and reducing false positives
MicroRNA profile changes in human immunodeficiency virus type 1 (HIV-1) seropositive individuals
MicroRNAs (miRNAs) play diverse roles in regulating cellular and developmental functions. We have profiled the miRNA expression in peripheral blood mononuclear cells from 36 HIV-1 seropositive individuals and 12 normal controls. The HIV-1-positive individuals were categorized operationally into four classes based on their CD4+ T-cell counts and their viral loads. We report that specific miRNA signatures can be observed for each of the four classes
Nature based solutions to mitigate soil sealing in urban areas: Results from a 6-year study comparing permeable, porous, and impermeable pavements
A long-term research was started in 2011 to evaluate the effects on four different pavement systems on two woody species and on soil physical traits. 48 plants of Celtis australis and Fraxinus ornus were planted in a 1 m2 planting pit surrounded by 50 m2 of: 1- impermeable pavement (asphalt on concrete sub-base); 2- permeable pavement (pavers on a crushed rock sub-base); 3- porous pavement (monolithic porous pavement on a crushed rock sub-base); 4- no pavement (bare soil kept free of weeds by herbicides). Effects of the different pavements on growth and physiology of establishing trees have been described in a previous work. Trees have now fully established, showing most of their roots outside the planting pit, right under the pavements. The presentation will describe the results of the long-term measurements of tree growth (shoot and diameter growth, canopy size), phenology (leaf shedding, dormancy outbreak), and physiology (leaf gas exchange, water relations), which have been carried out on regular basis on 6 replicate trees per treatment. Effects observed on trees have been related to changes induced by pavements on soil characteristics (e.g. oxygen, CO2, water availability). Also, interestingly, the effect of pavements on the emission of volatile organic compounds (VOCs) by tree species has been investigated.
Results have shown that soil physical traits have been largely affected by impermeable pavements, with a significant reduction of evaporation of water from soil resulting in the onset of a subterranean urban heat island. On the contrary, porous pavements were extremely effective in maintaining soil temperature similar to that of unpaved soil. Furthermore, under impermeable pavements CO2 accumulates, with negative effects on root activity, but porous pavements can largely mitigate this CO2 enrichment. Indeed, the effects of the different on growth and physiology of ash and hackberry will be discussed in detail in the presentation
Alberi e pavimentazioni
La presentazione illustrer\ue0 gli effetti di una sperimentazione in corso dal 2011 finalizzata a studiare gli effetti di diverse tipologie di pavimentazioni sulla crescita e la fisiologia di due specie arboree, oltre che su alcuni parametri fisici del suolo. Verranno illustrate le principali problematiche derivanti dall'impermeabilizzazione del suolo e possibili metodo per porvi rimedio, tra cui pavimentazioni alternative e il verde urbano. Infine, sar\ue0 chiarito quali siano gli stress tipici che possono ridurre i servizi ecosistemici degli alberi in ambienti pavimentati
Detection of curved lines with B-COSFIRE filters: A case study on crack delineation
The detection of curvilinear structures is an important step for various
computer vision applications, ranging from medical image analysis for
segmentation of blood vessels, to remote sensing for the identification of
roads and rivers, and to biometrics and robotics, among others. %The visual
system of the brain has remarkable abilities to detect curvilinear structures
in noisy images. This is a nontrivial task especially for the detection of thin
or incomplete curvilinear structures surrounded with noise. We propose a
general purpose curvilinear structure detector that uses the brain-inspired
trainable B-COSFIRE filters. It consists of four main steps, namely nonlinear
filtering with B-COSFIRE, thinning with non-maximum suppression, hysteresis
thresholding and morphological closing. We demonstrate its effectiveness on a
data set of noisy images with cracked pavements, where we achieve
state-of-the-art results (F-measure=0.865). The proposed method can be employed
in any computer vision methodology that requires the delineation of curvilinear
and elongated structures.Comment: Accepted at Computer Analysis of Images and Patterns (CAIP) 201
Growth, Leaf Gas Exchange and Leaf Anatomy of three Ornamental Shrubs Grown under different Light Intensities
The aim of this work was to determine the long-term response of growth, leaf morphology and gas exchange of three widely grown shrubs to the level of irradiance. To this purpose, one-year-old uniform rooted cuttings of Camellia x williamsii W.W.Sm. 'Debbie', Photinia x fraseri Dress 'Red Robin' and Viburnum tinus L. 'Eve Price' grown in containers were placed for 2 years under different woven polypropylene fabrics that reduced light intensity by 60 % and 30 % and, as a control, plants were also grown in full sun. Plant dry weight, LAI, LAR, NAR, RGR, mean leaf area, number, ultrastructure and gas exchange were measured during the experiment. The species reacted in different ways to shading, indicating a strong genetic influence, even if some parameters as transpiration, leaf thickness, leaf size and stomatal frequency responded similarly to irradiance. Camellia showed a great adaptability to light conditions. Shading photinia greatly reduced root biomass but did not alter leaf gas exchange, thus is not a recommendable practice for this species. Viburnum increased leaves and stems biomass and increased net photosynthesis and water use efficiency under shaded conditions. In conclusion, effects of shading can positively affect plant growth and physiology, but response to shading is species-specific
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