Subtraction Approach Research Articles

Background Subtraction Approach Based on Independent Component Analysis

In this work, a new approach to background subtraction based on independent component analysis is presented. This approach assumes that background and foreground information are mixed in a given sequence of images. Then, foreground and background components are identified, if their probability density functions are separable from a mixed space. Afterwards, the components estimation process consists in calculating an unmixed matrix. The estimation of an unmixed matrix is based on a fast ICA algorithm, which is estimated as a Newton-Raphson maximization approach. Next, the motion components are represented by the mid-significant eigenvalues from the unmixed matrix. Finally, the results show the approach capabilities to detect efficiently motion in outdoors and indoors scenarios. The results show that the approach is robust to luminance conditions changes at scene.

Guided wave diffraction tomography within the born approximation

Detection and sizing of corrosion in pipelines and pressure vessels over large, partially accessible areas is of growing interest in the petrochemical industry. Low-frequency guided wave diffraction tomography is a potentially attractive technique to rapidly evaluate the thickness of large sections of partially accessible structures. Finite element simulations of a 64-element circular array on a plate show that when the scattering mechanism of the object to be reconstructed satisfies the Born approximation, the reconstruction of the thickness is accurate. However, the practical implementation is more challenging because the incident field is not known. This paper describes the baseline subtraction approach commonly used in structural health monitoring applications and proposes a new approach in which the measurement of the incident field is not required when using a circular array of transducers. Experimental results demonstrate that ultimately the scattering from the array of transducers is a major source of error in the tomographic reconstruction, but when there is no scattering from the array of transducers the reconstructions are very similar to the finite element simulations.

Pooled Sample Strategy in Conjunction with High-Resolution Liquid Chromatography−Mass Spectrometry-Based Background Subtraction to Identify Toxicological Markers in Dogs Treated with Ibipinabant

Metabolomics with chromatography-mass spectrometry is often challenging and relies on statistical tools to discern changes in a metabolome. A pooled sample strategy was proposed, consisting of (1) identification of potential marker candidates by detecting changes of metabolites in a few pooled samples between treated and control groups and (2) validation of markers of statistically significant changes with a large set of individual samples. This strategy was enabled by applying a thorough background subtraction approach based on high-resolution mass spectrometry. In a proof-of-principle study, plasma samples were generated and pooled in a 6-week investigational study to identify potential toxicological markers for an observed muscle toxicity associated with the treatment of ibipinabant in dogs. With pooled control samples as backgrounds, potential marker candidates were revealed in the background-subtracted profiles of the pooled ibipinabant-treated samples. After further cleaning with the use of mass defect filtering to exclude drug metabolites and the comparison of profiles between pooled treated samples to eliminate inconsistent peaks, the major biomarker candidates in the profiles were identified to be 19 acylcarnitines. A total of 3 of the 19 acylcarnitines were measured on the set of individual samples to allow for statistical analysis. The results confirmed the significance of acylcarnitine elevations in ibipinabant-treated dogs and indicated that the acylcarnitines could be early markers for the dog-specific toxicity. The advantages of the pooled sample strategy and its potential limitations for metabolomics are discussed.

Dark fringe operation and noise reduction with optical subtraction approach and power allocation

We demonstrate a technique to achieve the reduction of excess noise with dark fringe operation by optical subtraction and power allocation strategy. By performing the subtraction in optical way, the excess noise resulted from the photocurrent is eliminated and the phase information can be extracted with single photoreceiver. Meanwhile, by allocating more optical power to the probe beam, the DC background and the signal amplitude of the photocurrent become very small simultaneously so that the dark fringe operation is achieved. We compare the spectral distributions resulted from the proposed technique with that from the widely employed balanced detection and the modified balanced detection techniques which both are based on electronic subtraction. It is found that the experimental results closely agree to the theoretical predictions.

Validation of Alternative Formulations of Job Strain

To examine the construct validity of different formulations of job strain based on the demand-control(-support) model in the context of a hospital-based survey. We defined the best measure of job strain as the one that would be better predicted by professional status and job characteristics and better predict health outcomes, stress and back-pain leave. We received 1,298 responses from collaborators at the University Hospitals of Geneva who responded to a questionnaire survey including all the constructs cited above and the Job Content Questionnaire. The difference between decision latitude and psychological demands (strain by subtraction), corresponded to the definition of the best measure of job strain and significantly, albeit weakly, predicted all outcomes. The logarithmic approach was the second best measure of job strain and was in fact a better predictor of stress. We would encourage researchers to explore different formulations of job strain, in particular the subtraction approach, to compute strain from demands and decision latitude.

A full subtraction approach for finite element method based source analysis using constrained Delaunay tetrahedralisation.

A full subtraction approach for finite element method based source analysis using constrained Delaunay tetrahedralisation.

Recognition of human activities using SVM multi-class classifier

Even great efforts have been made for decades, the recognition of human activities is still an unmature technology that attracted plenty of people in computer vision. In this paper, a system framework is presented to recognize multiple kinds of activities from videos by an SVM multi-class classifier with a binary tree architecture. The framework is composed of three functionally cascaded modules: (a) detecting and locating people by non-parameter background subtraction approach, (b) extracting various of features such as local ones from the minimum bounding boxes of human blobs in each frames and a newly defined global one, contour coding of the motion energy image (CCMEI), and (c) recognizing activities of people by SVM multi-class classifier whose structure is determined by a clustering process. The thought of hierarchical classification is introduced and multiple SVMs are aggregated to accomplish the recognition of actions. Each SVM in the multi-class classifier is trained separately to achieve its best classification performance by choosing proper features before they are aggregated. Experimental results both on a home-brewed activity data set and the public Schüldt’s data set show the perfect identification performance and high robustness of the system.

Magnetic Exchange Coupling in Actinide-Containing Molecules

Recent progress in the assembly of actinide-containing coordination clusters has generated systems in which the first glimpses of magnetic exchange coupling can be recognized. Such systems are of interest owing to the prospects for involving 5f electrons in stronger magnetic exchange than has been observed for electrons in the more contracted 4f orbitals of the lanthanide elements. Here, we survey the actinide-containing molecules thought to exhibit magnetic exchange interactions, including multiuranium, uranium-lanthanide, uranium-transition metal, and uranium-radical species. Interpretation of the magnetic susceptibility data for compounds of this type is complicated by the combination of spin-orbit coupling and ligand-field effects arising for actinide ions. Nevertheless, for systems where analogues featuring diamagnetic replacement components for the non-actinide spin centers can be synthesized, a data subtraction approach can be utilized to probe the presence of exchange coupling. In addition, methods have been developed for employing the resulting data to estimate lower and upper bounds for the exchange constant. Emphasis is placed on evaluation of the linear clusters (cyclam)M[(mu-Cl)U(Me(2)Pz)(4)](2) (M = Co, Ni, Cu, Zn; cyclam = 1,4,8,11-tetraazacyclotetradecane; Me(2)Pz(-) = 3,5-dimethylpyrazolate), for which strong ferromagnetic exchange with 15 cm(-1) < or = J < or = 48 cm(-1) is observed for the Co(II)-containing species. Owing to the modular synthetic approach employed, this system in particular offers numerous opportunities for adjusting the strength of the magnetic exchange coupling and the total number of unpaired electrons. To this end, the prospects of such modularity are discussed through the lens of several new related clusters. Ultimately, it is hoped that this research will be of utility in the development of electronic structure models that successfully describe the magnetic behavior of actinide compounds and will perhaps even lead to new actinide-based single-molecule magnets.

Hydrophilic interaction liquid chromatography – charged aerosol detection as a straightforward solution for simultaneous analysis of ascorbic acid and dehydroascorbic acid

Ascorbic acid (AA) and dehydroascorbic acid (DHA) are small polar molecules difficult to be retained in conventional chromatographic RP systems. Hydrophilic interaction liquid chromatography (HILIC) using Obelisk R (100 × 3.2 mm, 5 μm, Sielc) analytical column and isocratic elution by ammonium acetate buffer pH 4.2 was found to be successful at this task, while other tested HILIC columns – Obelisk N (100 × 3.2 mm, 5 μm, Sielc) and Luna HILIC (100 × 3.0 mm, 3 μm, Phenomenex) were unsuccessful for the purposes of analysis. Charged aerosol detection (CAD) has recently become a new alternative universal detection system in HPLC, and was extremely convenient for the simultaneous analysis of AA and DHA without the need of subtraction approach and oxidation/reduction step. CAD response was found linear in defined range in spite of the fact that CAD is designated as non-linear detection method. A simple and fast HILIC-CAD method was applied for the analysis of pharmaceutical preparations containing AA. Method validation was performed including parameters of precision, accuracy, linearity, limit of detection and limit of quantitation (LOQ). The method was fast, accurate and precise for both detectors with LOQ AA 5 μg/ml for UV detection and 10 μg/ml for CAD, respectively. DHA was detected only by CAD within tested concentration range with LOQ DHA 1 μg/ml.

Accuracy and run-time comparison for different potential approaches and iterative solvers in finite element method based EEG source analysis

Accuracy and run-time play an important role in medical diagnostics and research as well as in the field of neuroscience. In Electroencephalography (EEG) source reconstruction, a current distribution in the human brain is reconstructed noninvasively from measured potentials at the head surface (the EEG inverse problem). Numerical modeling techniques are used to simulate head surface potentials for dipolar current sources in the human cortex, the so-called EEG forward problem. In this paper, the efficiency of algebraic multi-grid (AMG), incomplete Cholesky (IC) and Jacobi preconditioners for the conjugate gradient (CG) method are compared for iteratively solving the finite element (FE) method based EEG forward problem. The interplay of the three solvers with a full subtraction approach and two direct potential approaches, the Venant and the partial integration method for the treatment of the dipole singularity is examined. The examination is performed in a four-compartment sphere model with anisotropic skull layer, where quasi-analytical solutions allow for an exact quantification of computational speed versus numerical error. Specifically-tuned constrained Delaunay tetrahedralization (CDT) FE meshes lead to high accuracies for both the full subtraction and the direct potential approaches. Best accuracies are achieved by the full subtraction approach if the homogeneity condition is fulfilled. It is shown that the AMG-CG achieves an order of magnitude higher computational speed than the CG with the standard preconditioners with an increasing gain factor when decreasing mesh size. Our results should broaden the application of accurate and fast high-resolution FE volume conductor modeling in source analysis routine.

Degradation Kinetics of Carbohydrate Fractions of Ruminant Feeds Using Automated Gas Production Technique

The current ruminant feeding models require parameterization of the digestion kinetics of carbohydrate fractions in feed ingredients to estimate the supply of nutrients from a ration. Using an automated gas production technique, statistically welldefined digestion rate of carbohydrate, including soluble carbohydrate, can be estimated in a relatively easy way. In this study, the gas production during in vitro fermentation was measured and recorded by an automated gas production system to investigate degradation kinetics of carbohydrate fractions of a wide range of ruminant feeds: corn silage, rice straw, corn, soybean hull, soybean meal, and cell mass from lysine production (CMLP). The gas production from un-fractionated, ethanol insoluble residue and neutral detergent insoluble residue of the feed samples were obtained. The gas profiles of carbohydrate fractions on the basis of the carbohydrate scheme of the Cornell Net Carbohydrate and Protein System (A, B1, B2, B3 and C) were generated using a subtraction approach. After the gas profiles were plotted with time, a curve was fitted with a single-pool exponential equation with a discrete lag to obtain kinetic parameters that can be used as inputs for modern nutritional models. The fractional degradation rate constants (Kd) of corn silage were 11.6, 25.7, 14.8 and 0.8%/h for un-fractioned, A, B1 and B2 fractions, respectively. The values were statistically well estimated, assessed by high t-value (>12.9). The Kd of carbohydrate fractions in rice straw were 4.8, 21.1, 5.7 and 0.5%/h for un-fractioned, A, B1 and B2 fractions, respectively. Although the Kd of B2 fraction was poorly defined with a t-value of 4.4, the Kd of the other fractions showed tvalues higher than 21.9. The un-fractioned corn showed the highest Kd (18.2%/h) among the feeds tested, and the Kd of A plus B1 fraction was 18.7%/h. Soybean hull had a Kd of 6.0, 29.0, 3.8 and 13.8%/h for un-fractioned, A, B1 and B2, respectively. The large Kd of fraction B2 indicated that NDF in soybean hull was easily degradable. The t-values were higher than 20 except for the B1 fraction (5.7). The estimated Kd of soybean meal was 9.6, 24.3, 5.0%/h for un-fractioned, A and B1 fractions, respectively. A small amount of gas (5.6 ml at 48 ho of incubation) was produced from fermentation of CMLP which contained little carbohydrate. In summary, the automated gas production system was satisfactory for the estimation of well defined (t-value >12) kinetic parameters and Kd of soluble carbohydrate fractions of various feedstuffs that supply mainly carbohydrate. The subtraction approach, however, should be applied with caution for some concentrates, especially those which contain a high level of crude protein since nitrogen-containing compounds can interfere with gas production.

A full subtraction approach for finite element method based source analysis using constrained Delaunay tetrahedralisation

A mathematical dipole is widely used as a model for the primary current source in electroencephalography (EEG) source analysis. In the governing Poisson-type differential equation, the dipole leads to a singularity on the right-hand side, which has to be treated specifically. In this paper, we will present a full subtraction approach where the total potential is divided into a singularity and a correction potential. The singularity potential is due to a dipole in an infinite region of homogeneous conductivity. The correction potential is computed using the finite element (FE) method. Special care is taken in order to evaluate the right-hand side integral appropriately with the objective of achieving highest possible convergence order for linear basis functions. Our new approach allows the construction of transfer matrices for fast computation of the inverse problem for anisotropic volume conductors. A constrained Delaunay tetrahedralisation (CDT) approach is used for the generation of high-quality FE meshes. We validate the new approach in a four-layer sphere model with a highly conductive cerebrospinal fluid (CSF) and an anisotropic skull compartment. For radial and tangential sources with eccentricities up to 1 mm below the CSF compartment, we achieve a maximal relative error of 0.71% in a CDT-FE model with 360 k nodes which is not locally refined around the source singularity and therefore useful for arbitrary dipole locations. The combination of the full subtraction approach with the high quality CDT meshes leads to accuracies that, to the best of the author's knowledge, have not yet been presented before.

Algorithm for Thorough Background Subtraction of High-Resolution LC/MS Data: Application to Obtain Clean Product Ion Spectra from Nonselective Collision-Induced Dissociation Experiments

Nonselective collision-induced dissociation (CID) is a technique for producing fragmentation products for all ions generated in an ion source. It is typical of liquid chromatography/mass spectrometry (LC/MS) analysis of complex samples that matrix-related components may contribute to the resulting product ion spectra and confound the usefulness of this technique for structure interpretation. In this proof-of-principle study, a high-resolution LC/MS-based background subtraction algorithm was used to process the nonselective CID data to obtain clean product ion spectra for metabolites in human plasma samples. With buspirone and clozapine metabolites in human plasma as examples, this approach allowed for not only facile detection of metabolites of interest but also generation of their respective product ion spectra that were clean and free of matrix-related interferences. This was demonstrated with both an MS(E) technique (where E represents collision energy) with a quadrupole time-of-flight (QTOF) instrument and an in-source fragmentation technique with an LTQ Orbitrap instrument. The combined nonselective CID and background subtraction approach should allow for detection and structural interpretation of other types of sample analyses where control samples are obtained.

How size evaluation of lymph node is protocol dependent in MRI when using ultrasmall superparamagnetic iron oxide nanoparticles

In this study, the volume of susceptibility artifact was evaluated in T1 and T2-weighted spin echo (SE) and gradient echo (GRE) images at various parameters using registration and subtraction methods. In order to state an important misinterpretation problem in lymphography, it was demonstrated that a lymph node size may be enlarged approximately 10 times when a T2*-weighted GRE protocol is used. To overcome this problem a technical consideration using multisequence (GRE and SE) paradigm was suggested to ensure both lymph node detection and metastasis identification in lymphatic system. The paradigm was also extended by post-processing manipulation of the SE images using a registration and subtraction approach for detection of lymphatic lesions.

Statistical Background Subtraction Using Spatial Cues

Most statistical background subtraction techniques are based on the analysis of temporal color/intensity distribution. However, learning statistics on a series of time frames can be problematic, especially when no frame absent of moving objects is available or when the available memory is not sufficient to store the series of frames needed for learning. In this letter, we propose a spatial variation to the traditional temporal framework. The proposed framework allows statistical motion detection with methods trained on one background frame instead of a series of frames as is usually the case. Our framework includes two spatial background subtraction approaches suitable for different applications. The first approach is meant for scenes having a nonstatic background due to noise, camera jitter or animation in the scene (e.g.,waving trees, fluttering leaves). This approach models each pixel with two PDFs: one unimodal PDF and one multimodal PDF, both trained on one background frame. In this way, the method can handle backgrounds with static and nonstatic areas. The second spatial approach is designed to use as little processing time and memory as possible. Based on the assumption that neighboring pixels often share similar temporal distribution, this second approach models the background with one global mixture of Gaussians.

SYNCHROTRON‐BASED ANGIOGRAPHY FOR INVESTIGATION OF THE REGULATION OF VASOMOTOR FUNCTION IN THE MICROCIRCULATION IN VIVO

1. Real-time imaging of the vascular networks of any organ system in vivo is possible with synchrotron radiation (SR) angiography. In this review, we discuss the advantages of SR angiography over clinical X-ray imaging and other non-ionizing imaging modalities. Current limitations are also described. 2. The usefulness of dual-energy and temporal subtraction approaches to K-edge iodine imaging are compared. 3. High-resolution images of the microcirculation in small animals are now being collected routinely by multiple research groups through public access research programmes at synchrotrons worldwide. Such images are permitting unrivalled insights into vasomotor regulation deep within intact organ systems, such as the brain, kidney, lung and heart. For example, recent observations indicate changes in vascular control mechanisms in pulmonary hypertension that are specific to certain branching segments of the pulmonary circulation. 4. New possibilities for non-iodinated contrast agents in SR angiography are briefly described. 5. High-resolution angiography in vivo using SR will now allow us to identify vessels with localized or non-uniform vasoconstriction in states such as diabetes or to characterize the extent of endothelial dysfunction in the circulation following hypertension or ischaemic-reperfusion injury. In the near future, this research is expected to reveal the contribution of resistance vessel dysfunction to diverse pathophysiological states, such as stroke, hypertension and ischaemic heart disease.

Dissociating functional brain networks by decoding the between-subject variability

In this study we illustrate how the functional networks involved in a single task (e.g. the sensory, cognitive and motor components) can be segregated without cognitive subtractions at the second-level. The method used is based on meaningful variability in the patterns of activation between subjects with the assumption that regions belonging to the same network will have comparable variations from subject to subject. fMRI data were collected from thirty nine healthy volunteers who were asked to indicate with a button press if visually presented words were semantically related or not. Voxels were classified according to the similarity in their patterns of between-subject variance using a second-level unsupervised fuzzy clustering algorithm. The results were compared to those identified by cognitive subtractions of multiple conditions tested in the same set of subjects. This illustrated that the second-level clustering approach (on activation for a single task) was able to identify the functional networks observed using cognitive subtractions (e.g. those associated with vision, semantic associations or motor processing). In addition the fuzzy clustering approach revealed other networks that were not dissociated by the cognitive subtraction approach (e.g. those associated with high- and low-level visual processing and oculomotor movements). We discuss the potential applications of our method which include the identification of “hidden” or unpredicted networks as well as the identification of systems level signatures for different subgroupings of clinical and healthy populations.

Stabilisation of feedback linearisable uncertain nonlinear systems with time delay using scaled sliding surface

The authors consider a stabilisation problem of a class of feedback linearisable nonlinear systems with uncertainty and a delay in the input. In the considered system, the nonlinear function cannot be directly cancelled by the input due to a time delay. Thus, the traditional idea of cancelling and subtraction approach cannot be used. The authors design a stabilising controller by utilising a scaled sliding surface and show that the control results are such that any finite delay can be allowed in the input. This is an improved result over the existing results and an example is provided for comparison and verification.

Wavelet-Based Speech Enhancement Using Time-Adapted Noise Estimation

Spectral subtraction is commonly used for speech enhancement in a single channel system because of the simplicity of its implementation. However, this algorithm introduces perceptually musical noise while suppressing the background noise. We propose a wavelet-based approach in this paper for suppressing the background noise for speech enhancement in a single channel system. The wavelet packet transform, which emulates the human auditory system, is used to decompose the noisy signal into critical bands. Wavelet thresholding is then temporally adjusted with the noise power by time-adapted noise estimation. The proposed algorithm can efficiently suppress the noise while reducing speech distortion. Experimental results, including several objective measurements, show that the proposed wavelet-based algorithm outperforms spectral subtraction and other wavelet-based denoising approaches for speech enhancement for nonstationary noise environments.

Influence of syllable complexity and frequency

Functional imaging studies have delineated a „minimal network for overt speech production“, encompassing mesiofrontal structures (supplementary motor area, anterior cingulate gyrus), bilateral pre- and postcentral convolutions, extending rostrally into posterior parts of the inferior frontal gyrus (IFG) of the language-dominant hemisphere, left anterior insula as well as bilateral components of the basal ganglia, the cerebellum, and the thalamus. In order to further elucidate the specific contribution of these cerebral regions to speech motor planning, subjects were asked to read aloud visually presented bisyllabic pseudowords during functional magnetic resonance imaging (fMRI). The test stimuli systematically varied in onset complexity (CCV versus CV) and frequency of occurence (high frequency, HF, versus low frequency, LF) of the initial syllable. A cognitive subtraction approach revealed a significant main effect of syllable onset complexity (CCV versus CV) at the level of left posterior IFG, left anterior insula and both cerebellar hemispheres. Conceivably, these areas closely cooperate in the sequencing of subsyllabic aspects of the sound structure of verbal utterances. A significant main effect of syllable frequency (LF versus HF), by contrast, did not emerge. However, calculation of the time series of hemodynamic activation within the various cerebral structures engaged in speech motor control revealed this factor to enhance functional connectivity between Broca's area and ipsilateral anterior insula.