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See detailDetection of influential observations on the error rate based on the generalized k-means clustering procedure
Ruwet, Christel ULg; Haesbroeck, Gentiane ULg

Conference (2009, October 14)

Cluster analysis may be performed when one wishes to group similar objects into a given number of clusters. Several algorithms are available in order to construct these clusters. In this talk, focus will ... [more ▼]

Cluster analysis may be performed when one wishes to group similar objects into a given number of clusters. Several algorithms are available in order to construct these clusters. In this talk, focus will be on the generalized k-means algorithm, while the data of interest are assumed to come from an underlying population consisting of a mixture of two groups. Among the outputs of this clustering technique, a classi cation rule is provided in order to classify the objects into one of the clusters. When classi cation is the main objective of the statistical analysis, performance is often measured by means of an error rate ER(F; Fm) where F is the distribution of the training sample used to set up the classi cation rule and Fm (model distribution) is the distribution under which the quality of the rule is assessed (via a test sample). Under contamination, one has to replace the distribution F of the training sample by a contaminated one, F(eps) say (where eps corresponds to the fraction of contamination). In that case, the error rate will be corrupted since it relies on a contaminated rule, while the test sample may still be considered as being distributed according to the model distribution. To measure the robustness of classification based on this clustering proce- dure, influence functions of the error rate may be computed. The idea has already been exploited by Croux et al. (2008) and Croux et al. (2008) in the context of linear and logistic discrimination. In this setup, the contaminated distribution takes the form F(eps)= (1-eps)*Fm + eps*Dx, where Dx is the Dirac distribution putting all its mass at x: After studying the influence function of the error rate of the generalized k- means procedure, which depends on the influence functions of the generalized k-means centers derived by Garcia-Escudero and Gordaliza (1999), a diagnostic tool based on its value will be presented. The aim is to detect observations in the training sample which can be influential for the error rate. [less ▲]

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See detailDetection of interstellar CH and CH(+) towards SN 1987a
Magain, Pierre ULg; Gillet, D.

in Astronomy and Astrophysics (1987), 184

The authors report the detection of interstellar CH and CH[SUP]+[/SUP] towards supernova 1987A. For both of these molecules, one component is detected at a heliocentric velocity of about 280 km/s ... [more ▼]

The authors report the detection of interstellar CH and CH[SUP]+[/SUP] towards supernova 1987A. For both of these molecules, one component is detected at a heliocentric velocity of about 280 km/s, corresponding to material inside the LMC. Some implications of the authors' results with regards to the H[SUB]2[/SUB]-to-dust ratio are briefly discussed. [less ▲]

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See detailDetection of irregularities in the TEC using GPS measurements. Application to a mid-latitude station
Warnant, René ULg

in Acta Geodaetica et Geophysica Hungarica (1998), 33(1), 121-128

Detailed reference viewed: 27 (2 ULg)
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See detailDetection of laminin receptor mRNA in human cancer cell lines and colorectal tissues by in situ hybridization.
Campo, E.; Monteagudo, C.; Castronovo, Vincenzo ULg et al

in American Journal of Pathology (1992), 141(5), 1073-83

The 67-kd high-affinity laminin receptor (67 LR) is a gene product whose expression appears to be associated with the invasive and metastatic phenotype of a variety of human cancer cells. Northern blot ... [more ▼]

The 67-kd high-affinity laminin receptor (67 LR) is a gene product whose expression appears to be associated with the invasive and metastatic phenotype of a variety of human cancer cells. Northern blot hybridization has been routinely used to quantify the level of 67 LR mRNA from total cellular RNA extracts of homogenized tissue specimens or in vitro grown cell populations. This technique is useful to assess the average expression of the 67 LR mRNA of a particular sample but does not provide information about expression in specific cell types nor about heterogeneity of expression from cell to cell. In this study, we analyzed the expression of 67 LR mRNA in four human cancer cell lines with varying degrees of expression of 67 LR protein (renal cancer A-704, breast carcinoma MCF-7/4 and MCF-7/7, and pancreatic cancer Panc-1) using in situ hybridization performed with 67 LR riboprobes. Total cellular RNA was simultaneously extracted from the cell lines and hybridized on Northern blots with a 67 LR cDNA probe to assess the validity of the mRNA detection by in situ hybridization. Sixty-seven LR mRNA expression was higher in Panc-1 and MCF-7/4 cells than in MCF-7/7 and renal carcinoma A-704. There was a direct correlation (R2 = 0.88) between the in situ hybridization analysis and the mRNA levels detected by Northern blot analysis. The in situ hybridization method showed a heterogeneous expression of the 67 LR mRNA in the four cell lines with different subpopulations of cells showing a range from negative to high levels of the message. Sixteen freshly frozen human colorectal tissues (seven adenocarcinomas, five matched normal mucosae, and four adenomas) were also analyzed by in situ hybridization. The 67 LR mRNA was localized in normal and neoplastic epithelial cells. Adenocarcinoma cells showed a 1.6- to 5-fold higher expression (P < 0.02 according to the Wilcoxon-Mann-Whitney test) than did epithelial colonic cells from normal mucosae or adenomas. The signal tended to be stronger in poorly differentiated carcinomas and carcinomas with metastases than in moderately differentiated and nonmetastatic tumors. We conclude that the high expression of 67 LR mRNA in colorectal tumors is due to an increased production by tumor cells. Furthermore, in situ hybridization is an effective method to detect the expression of LR mRNA in cultured cell lines as well as in frozen tissue sections. [less ▲]

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See detailDetection of left ventricular false tendons by two-dimensional echocardiography.
Pierard, Luc ULg; Henrard, L.; Noël, J.F.

in Acta cardiologica (1985), 40(2), 229-35

In a prospective series of 300 consecutive patients referred for a two-dimensional echocardiogram, the presence of left ventricular false tendons was searched. The diagnosis of a false tendon was made ... [more ▼]

In a prospective series of 300 consecutive patients referred for a two-dimensional echocardiogram, the presence of left ventricular false tendons was searched. The diagnosis of a false tendon was made when a clear linear echo was continuously observed within the left ventricular cavity from the septum to the free wall or to a papillary muscle. Using this criterion, a false tendon was detected in 9 of the 300 patients (incidence of 3%), frequently from an apical position. The precise sites of attachment of the false tendons were observed by slight rotation and/or angulation of the transducer from the classic views: the septum and the lateral papillary muscle were the most frequent sites of attachment. Associated congenital heart disease was present in only 1 patient. Most patients had moderate symptoms and a soft musical systolic murmur. Three patients had premature ventricular contractions disappearing with exercise. The possible relations of LV false tendons with a musical murmur, arrhythmia or abnormal LV geometry are discussed. [less ▲]

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See detailDetection of Local and Global Outliers in Spatial Data
Ernst, Marie ULg; Haesbroeck, Gentiane ULg

Conference (2013, July 11)

Spatial data are characterized by statistical units, with known geographical positions, on which non spatial attributes are measured. Two types of atypical observations can be defined: global and/or local ... [more ▼]

Spatial data are characterized by statistical units, with known geographical positions, on which non spatial attributes are measured. Two types of atypical observations can be defined: global and/or local outliers. The attribute values of a global outlier are outlying with respect to the values taken by the majority of the data points while the attribute values of a local outlier are extreme when compared to those of its neighbors. Classical outlier detection techniques may be used to find global outliers as the geographical positions of the data is not taken into account in this search. The detection of local outliers is more complex especially when there are more than one non spatial attribute. In this talk, existing techniques were outlined and two new procedures were defined. The first approach is to adapt an existing technique using in particular a regularized estimator of the covariance matrix. The second technique measures outlyingness using depth function. [less ▲]

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See detailDetection of micro-RNA/gene interactions involved in angiogenesis using machine learning techniques
Huynh-Thu, Vân Anh ULg; Hiard, Samuel ULg; Geurts, Pierre ULg et al

Poster (2007, September)

Motivation: Angiogenesis is the process responsible for the growth of new blood vessels from existing ones. It is also associated with the development of cancer, as tumors need to be irrigated by blood ... [more ▼]

Motivation: Angiogenesis is the process responsible for the growth of new blood vessels from existing ones. It is also associated with the development of cancer, as tumors need to be irrigated by blood vessels for growing. New cancer therapies appear that exploit angiogenesis inhibitors, also called angiostatic agents, to asphyxiate and starve the tumors. Better understanding the regulatory mechanisms that control angiogenesis is thus fundamental. Recently, short non-coding RNA molecules, called micro-RNAs, have been discovered that are involved in post- transcriptional regulation of gene expressions. These molecules bind to RNA messengers following the base pairing rules, preventing them from being translated into proteins and/or tagging them for degradation. The main goal of this work is to use computational approaches to identify micro-RNAs involved in angiogenesis. Method: In order to identify genes involved in angiogenesis, bovine endothelial cells were treated by a known angiogenesis inhibitor [1], prolactin 16K, and their gene expression profile was compared to the profile of untreated cells. The genes were then divided into three classes: up-regulated, down-regulated, and unaffected genes. The 3'UTR regions of these genes were then analysed by machine learning techniques. Different approaches were considered. First, we described each gene by a vector of motif counts in their 3'UTR regions and used machine learning techniques to rank the motifs according to their relevance for separating the genes into the different classes. We considered successively motifs corresponding to the seeds of known micro- RNAs and also all possible motifs of a given length. To rank the motifs, we compared ensemble of decision trees and linear support vector machines. Second, we considered an approach called Segment and Combine that was proposed in [2]. Finally, we also carried out an exhaustive search of all motifs of a given length that satisfy some constraints on specificity and coverage with respect to a given gene category. Results: The ability of the different approaches at identifying relevant motifs was first assessed on genes predicted to be the target of some known miRNAs. In this simple setting, most methods were able to identify the micro-RNA seed. The results obtained on the genes regulated by prolactin 16K are also very encouraging. We were able to identify one micro-RNA already known to play a role in angiogenesis and several motifs are predicted by different approaches as very specific of up- or down-regulation by prolactin 16K. Their relationship with known micro-RNAs is certainly worth exploring. Conclusion: Machine learning approaches are promising techniques for the identification of micro-RNA/gene interactions. Future work will concern the application of the same kind of techniques on promoters for the identification of transcription factor binding sites. [less ▲]

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See detailDetection of moulds growing on building materials by gas sensor arrays and pattern recognition
Kuske, Martyna; Padilla, M.; Romain, Anne-Claude ULg et al

in Technical digest of eurosensors : proceedings (2004)

This work explores the detection of moulds growing in different building materials by using a metal oxide sensor array Four mould species have been considered. Pattern Classification provides ... [more ▼]

This work explores the detection of moulds growing in different building materials by using a metal oxide sensor array Four mould species have been considered. Pattern Classification provides classification rates on the order of 80-90% for different species. Drift degrades slightyl these values subsequent test four months later. [less ▲]

Detailed reference viewed: 47 (6 ULg)
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See detailDetection of mRNA encoding an antibacterial-metalloprotein (MPII) by in situ hybridization with a cDNA probe generated by PCR in the worm nereis diversicolor
Salzet-Raveillon, B.; Rentier-Delrue, Françoise ULg; Dhainaut, A.

in Cellular and Molecular Biology (1993)

Based on partial amino acid sequence of an antibacterial-metalloprotein (MPII) consisting of a N-terminal fragment (1-33th) and an 43 amino acids long internal fragment, two oligonucleotides primers were ... [more ▼]

Based on partial amino acid sequence of an antibacterial-metalloprotein (MPII) consisting of a N-terminal fragment (1-33th) and an 43 amino acids long internal fragment, two oligonucleotides primers were synthesized and used to generate a cDNA fragment by the PCR method. The specificity of the PCR synthesized 220 bp fragment was verified by hybrid-arrest translation and sequencing. In situ hybridization performed with this cDNA fragment on Nereis diversicolor whole body defined two specific sites of recognition: a cluster of cells floating in the coelom and two types of muscles (perineural and oblique). Finally, the chronological expression of the MPII was postulated. [less ▲]

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See detailDetection of Mycobacterium celatum in wild boars in Southern Belgium
Ceuleers, V; Vionnet, A; Grégoire, F et al

Conference (2013, August)

Detailed reference viewed: 4 (2 ULg)
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See detailDetection of myocardial ischemic memory using 99mTc-fucoidan: preclinical validation
Mikail, N; Louedec, L; Aid, R et al

Conference (2016, June)

Detailed reference viewed: 25 (1 ULg)
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See detailDetection of near-field, low permittivity layers with Ground Penetrating Radar: analytical estimation of the reflection coefficient
Van der Wielen, Audrey; Courard, Luc ULg; Nguyen, Frédéric ULg

in LAMBOT, Sébastien (Ed.) Proceedings of 15th International Conference on ground Penetrating Radar (2014)

The reflection coefficient of GPR waves encountering embedded thin layers is commonly estimated using a plane wave, far field approximation. But when the thin layer is situated in the near field of the ... [more ▼]

The reflection coefficient of GPR waves encountering embedded thin layers is commonly estimated using a plane wave, far field approximation. But when the thin layer is situated in the near field of the antenna, the spherical nature of the waves and the possible propagation of a lateral wave into the layer may have a strong influence on the measured reflected amplitude. In this work, we studied through 2D FDTD simulations the behavior of a radar wave interacting with thin layers of different thicknesses. The snapshots and radargrams showed a large influence of the layer thickness on the wave propagation. For the very thin layers, the evanescent wave plays a major role and the plane wave approximation gives a good estimation of the reflection coefficient. For thicker layers, the specific inclination of each multiple reflection has to be taken into account, as well as the lateral wave propagation. On the basis of these observations, we determined which analytical method should be used for the analytical prediction of the reflection coefficient, as a function of the layer thickness. [less ▲]

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See detailDetection of Neospora caninum in dog organs using real time PCR systems.
Ghalmi, F.; Losson, Bertrand ULg; Daube, Georges ULg et al

in Veterinary Parasitology (2008), 155

Neospora caninum is a parasite responsible for paresis in dogs. The dog can harbour enkysted parasites in several organs. The detection of N. caninum was performed using 3 different real time PCR systems ... [more ▼]

Neospora caninum is a parasite responsible for paresis in dogs. The dog can harbour enkysted parasites in several organs. The detection of N. caninum was performed using 3 different real time PCR systems all amplifying the NC5 DNA region. One system was based on Sybr1green, one on PlexorTM technology and the last on Taqman1 probe. Comparison of the three methods indicated that the detection limit was 1 equivalent genome on pure DNA but that this detection limit increased in the presence of foreign DNA using the Sybrgreen and Plexor systems. Therefore, the Taqman system was chosen to detect N. caninum in liver and spleen of naturally infected dogs. The overall prevalence was 32.2%. Comparison between PCR results and serological results using IFAT showed that among the 28 PCR positive dogs only 9 were seropositive and that 8 seropositive dogs were PCR negative. Therefore serology can underestimate the real carriage in dogs. However, PCR methods must be improved in terms of sensitivity and inhibition problems. [less ▲]

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See detailDetection of new biallelic polymorphisms in the human MxA gene
Tran Thi Duc, Tam; Farnir, Frédéric ULg; Michaux, Charles ULg et al

in Molecular Biology Reports (2012), 39(8), 8533-8538

The interferon-inducible human MxA protein plays an important role in innate defense against an array of viruses. One might expect allelic diversity at the MxA locus to influence the timing and magnitude ... [more ▼]

The interferon-inducible human MxA protein plays an important role in innate defense against an array of viruses. One might expect allelic diversity at the MxA locus to influence the timing and magnitude of its expression or even the range of viruses whose biological cycle is inhibited by the encoded product. Here we have collected 267 samples of genomic DNA from three distinct populations (European, Asian, and African) and have systematically sequenced the promoter of the MxA gene and its 17 exons in order to inventory its allelic variants. Fifteen single-nucleotide polymorphisms were detected, four of which had never been identified before. Two of these, located in the promoter (at positions -309 and -101 respectively), might affect the MxA expression pattern. The other two result in substitutions (Gly255Glu and Val268Met) in the protein’s N-terminal region that might directly affect its antiviral function. [less ▲]

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See detailDetection of newly-synthetized RNAs in cell nuclei by a non-isotopic method using bromouridine
Nizet, S; Thiry, Marc ULg; Goessens, G

Poster (1997)

Detailed reference viewed: 6 (0 ULg)
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See detailDetection of nitric oxide by diaminofluorescein visualizes the skeleton in living zebrafish.
Renn, Jörg ULg; Pruvot, Benoist; Muller, Marc ULg

in Journal of Applied Ichthyology (2014), 30(4), 701706

Several in vivo stainings, such as Calcein, Alizarin Red and Quercetin are commonly used to visualize ossification in living teleost specimen. These staining techniques represent important tools for bone ... [more ▼]

Several in vivo stainings, such as Calcein, Alizarin Red and Quercetin are commonly used to visualize ossification in living teleost specimen. These staining techniques represent important tools for bone research in fish, but do not visualize cartilage. In the present study, we show that nitric oxide (NO) labelling by DAF-FM DA visualizes both bone and cartilage in vivo during zebrafish skeletogenesis. NO detection performed in Tg(osterix:mCherry) or in combination with Alizarin Red in wild-type zebrafish reveals that intense staining through NO labelling colocalizes with the appearance of osteoblasts and characterizes ossified structures. Cartilage structures are clearly distinguished in the living larvae, although the labelling is less intensive when compared to ossified structures. This method is the first and easy to handle alternative to cartilage and bone double stainings on fixed samples. In contrast to most live skeletal stainings, which only stain the mineralized bone structures, this protocol in addition allows in vivo visualization of cartilage. [less ▲]

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See detailDetection of nitrogen stress on winter wheat by multispectral machine vision
Marlier, Guillaume ULg; Gritten, Fanny; Leemans, Vincent ULg et al

Conference (2016, August 01)

Hand-held sensors (SPAD meter, N-Tester, …) used for detecting the leaves nitrogen concentration (Nc) present several drawbacks. The nitrogen concentration is gained by an indirect way through the ... [more ▼]

Hand-held sensors (SPAD meter, N-Tester, …) used for detecting the leaves nitrogen concentration (Nc) present several drawbacks. The nitrogen concentration is gained by an indirect way through the chlorophyll concentration and the leaves have to be fixed in a defined position for the measurements. These drawbacks could be overcome by an imaging device that measures the canopy reflectance. Hence, the objective of the paper is to analyse the potential of multispectral imaging for detecting nitrogen concentration. The tests were carried out on parcels submitted to nitrogen inputs varying from 0 to 180 kg N.ha-1. Reference Nc measurements were obtained by the Kjeldahl method and a Hydro N-Tester (Yara). The developed imaging system comprised a CMOS camera and a set of 22 interference filters ranging from 450 to 950 nm mounted on a wheel steered by a stepper motor. The image acquisition and the motor rotation were controlled by a program written in C++. The crop was imaged vertically at one meter height. The raw images presented 1280×1024 pixels covering an area of approximately 0.25 m² and were recorded with a 12-bit luminance resolution. To deal with the natural irradiance variability of the scene, a white reference was used and the integration time was automatically adjusted for each image. The image treatment included the segmentation of Photosynthetically Active Leaves (PAL) by using Bayes theorem and the computation of the mean PAL reflectance after correction of background and illumination fluctuations. Nc was estimated on the basis of the 22 filters by the Partial Least Square (PLS) method and by four filters selected by the Best Subset Selection (BSS) method. In comparison with the Kjeldahl method, the estimation of Nc by means of the Hydro N-Tester, the PLS method and the BSS method (filters 600-80, 950-100, 650-40 and 450-80 nm) gave determination coefficients equal to 0.53, 0.63, and 0.62, respectively. This indicated that the full multi-spectral approach gave significantly better Nc estimation than a portable device and suggested that a camera equipped with four filters would give similar results. [less ▲]

Detailed reference viewed: 86 (5 ULg)