Browsing
     by title


0-9 A B C D E F G H I J K L M N O P Q R S T U V W X Y Z

or enter first few letters:   
OK
Full Text
Peer Reviewed
See detailA local influence approach applied to binary data from a psychiatric study.
Jansen, Ivy; Molenberghs, Geert; Aerts, Marc et al

in Biometrics (2003), 59(2), 410-9

Recently, a lot of concern has been raised about assumptions needed in order to fit statistical models to incomplete multivariate and longitudinal data. In response, research efforts are being devoted to ... [more ▼]

Recently, a lot of concern has been raised about assumptions needed in order to fit statistical models to incomplete multivariate and longitudinal data. In response, research efforts are being devoted to the development of tools that assess the sensitivity of such models to often strong but always, at least in part, unverifiable assumptions. Many efforts have been devoted to longitudinal data, primarily in the selection model context, although some researchers have expressed interest in the pattern-mixture setting as well. A promising tool, proposed by Verbeke et al. (2001, Biometrics 57, 43-50), is based on local influence (Cook, 1986, Journal of the Royal Statistical Society, Series B 48, 133-169). These authors considered the Diggle and Kenward (1994, Applied Statistics 43, 49-93) model, which is based on a selection model, integrating a linear mixed model for continuous outcomes with logistic regression for dropout. In this article, we show that a similar idea can be developed for multivariate and longitudinal binary data, subject to nonmonotone missingness. We focus on the model proposed by Baker, Rosenberger, and DerSimonian (1992, Statistics in Medicine 11, 643-657). The original model is first extended to allow for (possibly continuous) covariates, whereafter a local influence strategy is developed to support the model-building process. The model is able to deal with nonmonotone missingness but has some limitations as well, stemming from the conditional nature of the model parameters. Some analytical insight is provided into the behavior of the local influence graphs. [less ▲]

Detailed reference viewed: 17 (3 ULg)
Peer Reviewed
See detailA Local Influence Approach to Sensitivity Analysis of Incomplete Longitudinal Ordinal Data
Van Steen, Kristel ULg; Molenberghs, G.; Verbeke, G. et al

in Statistical Modelling : An International Journal (2001), 1

Detailed reference viewed: 33 (12 ULg)
Full Text
Peer Reviewed
See detailLocal innovations and initiatives in the management of conflicts and health risks in agro-pastoral zones: The SAREL and PASEL projects in the Dakoro, department in Niger
Ibrahim, Habibou; Mormont, Marc ULg; Yamba, Boubacar

in Field Actions Science Report (2014), 7(11),

This article examines two projects concerned with livestock production in the Dakoro region of Niger. It highlights the results obtained in the management of conflicts between livestock producers and crop ... [more ▼]

This article examines two projects concerned with livestock production in the Dakoro region of Niger. It highlights the results obtained in the management of conflicts between livestock producers and crop farmers, and in the reduction of health risks by promoting the involvement and accountability of livestock producer associations in project activities. The collaboration of local stakeholders is an initiative and a local knowledge-sharing opportunity to promote peaceful conflict resolutions in the context of high land pressure and competing agro-pastoral land use. Such institutional, technical and social initiatives improve participatory governance and legitimise decisions at the grassroots level. They have made a significant contribution to prompting social change and to setting the scene for better security for mobile pastoral systems. [less ▲]

Detailed reference viewed: 37 (4 ULg)
See detailLocal ionospheric activity – nowcast and forecast services
Stankov, Stanimir; Warnant, René ULg; Stegen, Koen et al

Conference (2009)

Detailed reference viewed: 18 (0 ULg)
Full Text
Peer Reviewed
See detailLocal ionospheric electron density profile reconstruction in real time from simultaneous ground-based GNSS and ionosonde measurements
Stankov, Stanimir; Stegen, Koen; Muhtarov, Plamen et al

in Advances in Space Research (2011), 47(7), 1172-1180

Detailed reference viewed: 44 (6 ULg)
Full Text
Peer Reviewed
See detailLocal Knowledge in Policy Making
Schoenaers, Frédéric ULg; Delvaux, Bernard

in Policy and Society (2012), 31(2), 106-169

Detailed reference viewed: 50 (6 ULg)
See detailLocal mapping of dissipative vortex motion
Silhanek, Alejandro ULg

Conference (2013, May)

We have recently introduced an experimental technique which combines the spatial resolution of scanning Hall microscopy and sensitivity of ac-susceptibility measurements as a tool to probe the vortex ... [more ▼]

We have recently introduced an experimental technique which combines the spatial resolution of scanning Hall microscopy and sensitivity of ac-susceptibility measurements as a tool to probe the vortex dynamics in superconducting materials. This technique has proven to be particularly adequate to prospect the degree of mobility of each individual vortex, map the pinning landscape, visualize the intra-valley to inter-valley vortex hopping, and reveal the different mobility of vortices and antivortices created by magnetic dots. Furthermore, we have shown that using the phase sensitive character of the local ac-susceptibility technique it is possible to investigate the dissipative response of a single vortex. This technique opens new and exciting possibilities to locally study loss mechanisms in a variety of interesting magnetic systems such as magnetic domain walls. [less ▲]

Detailed reference viewed: 28 (2 ULg)
Full Text
Peer Reviewed
See detailLocal mapping of dissipative vortex motion
Raes, B; Van de Vondel, J; Silhanek, Alejandro ULg et al

in Physical Review. B : Condensed Matter (2012), 86

We explore, with unprecedented single vortex resolution, the dissipation and motion of vortices in a superconducting ribbon under the influence of an external alternating magnetic field. This is achieved ... [more ▼]

We explore, with unprecedented single vortex resolution, the dissipation and motion of vortices in a superconducting ribbon under the influence of an external alternating magnetic field. This is achieved by combining the phase sensitive character of ac susceptibility, allowing us to distinguish between the inductive and dissipative responses, with the local power of scanning Hall probe microscopy. Whereas the induced reversible screening currents contribute only inductively, the vortices do leave a fingerprint in the out-of-phase component. The observed large phase-lag demonstrates the dissipation of vortices at time scales comparable to the period of the driving force (i.e., 13 ms). These results indicate the presence of slow microscopic loss mechanisms mediated by thermally activated hopping transport of vortices between metastable states. [less ▲]

Detailed reference viewed: 43 (10 ULg)
Peer Reviewed
See detailLocal measurement system for optical and electro-optic characterization and homogeneity analysis of photorefractive sillenite crystals
Lemaire, Philippe ULg; Georges, Marc ULg

in Roosen, G.; Agullo-Lopez, F.; Schirmer, O. (Eds.) Proceedings of Symposium C on Photorefractive Materials of the 1994 E-MRS Spring Conference (1994, May)

Detailed reference viewed: 2 (0 ULg)
Full Text
Peer Reviewed
See detailLocal measurements of void fraction and liquid holdup in packed columns using X-ray computed tomography
Toye, Dominique ULg; Marchot, Pierre ULg; Crine, Michel ULg et al

in Chemical Engineering & Processing (1998), 37(6), 511-520

A 'tailor made' computed X-ray tomographic scanner has been developed as a tool for the analysis of the distribution of gas, liquid and solid phases in packed columns. The very good spatial resolution of ... [more ▼]

A 'tailor made' computed X-ray tomographic scanner has been developed as a tool for the analysis of the distribution of gas, liquid and solid phases in packed columns. The very good spatial resolution of the scanner has first been assessed by the imaging of objects of known shape and size, called 'physical' phantoms. Images have then been realized on a 0.6 m diameter and 2 m height column packed with Cascade Mini-Ring 1A packing elements, which is a random polypropylene packing designed to be used in absorption columns. The solid phase distribution, leading to the void fraction distribution, has been analyzed on cross-section images of the dry packed column (without any liquid flowrate). The measured value of the bed void fraction is equal to the value provided by the manufacturer. The analysis of the axial profile of void fraction shows that the 'end effect' may be neglected, whereas the analysis of the radial profile evidences the existence of a non negligible 'wall effect'. Images have then been carried out on the packed column irrigated by a liquid flowrate ranging between 0 and 6000 1 h(-1) (0-6.10(-3) m s(-1)). Hold-up values have been measured in different cross-sections of the column and averaged in order to obtain the total hold-up value in the bed. The computed values are in very good agreement with those reported in the literature for similar packing. The dependence of the liquid hold-up on the liquid superficial velocity can be expressed in terms of a power law. The fitted value of the exponent, equal to 0.65, is in the range of exponent values found in correlations of the literature. (C) 1998 Elsevier Science S.A. All rights reserved. [less ▲]

Detailed reference viewed: 122 (6 ULg)
Full Text
Peer Reviewed
See detailLocal Mechanical Stimuli Regulate Bone Formation and Resorption in Mice at the Tissue Level
Schulte, Friederike A.; Ruffoni, Davide ULg; Lambers, Floor M. et al

in PLOS ONE (2013), 8(4), 62172-12

Bone is able to react to changing mechanical demands by adapting its internal microstructure through bone forming and resorbing cells. This process is called bone modeling and remodeling. It is evident ... [more ▼]

Bone is able to react to changing mechanical demands by adapting its internal microstructure through bone forming and resorbing cells. This process is called bone modeling and remodeling. It is evident that changes in mechanical demands at the organ level must be interpreted at the tissue level where bone (re) modeling takes place. Although assumed for a long time, the relationship between the locations of bone formation and resorption and the local mechanical environment is still under debate. The lack of suitable imaging modalities for measuring bone formation and resorption in vivo has made it difficult to assess the mechanoregulation of bone three-dimensionally by experiment. Using in vivo micro-computed tomography and high resolution finite element analysis in living mice, we show that bone formation most likely occurs at sites of high local mechanical strain (p<0.0001) and resorption at sites of low local mechanical strain (p<0.0001). Furthermore, the probability of bone resorption decreases exponentially with increasing mechanical stimulus (R-2 = 0.99) whereas the probability of bone formation follows an exponential growth function to a maximum value (R-2 = 0.99). Moreover, resorption is more strictly controlled than formation in loaded animals, and ovariectomy increases the amount of non-targeted resorption. Our experimental assessment of mechanoregulation at the tissue level does not show any evidence of a lazy zone and suggests that around 80% of all (re) modeling can be linked to the mechanical microenvironment. These findings disclose how mechanical stimuli at the tissue level contribute to the regulation of bone adaptation at the organ level. [less ▲]

Detailed reference viewed: 17 (5 ULg)
Full Text
Peer Reviewed
See detailLocal modulation of steroid action: rapid control of enzymatic activity.
Charlier, Thierry D.; Cornil, Charlotte ULg; Patte-Mensah, Christine et al

in Frontiers in neuroscience (2015), 9

Estrogens can induce rapid, short-lived physiological and behavioral responses, in addition to their slow, but long-term, effects at the transcriptional level. To be functionally relevant, these effects ... [more ▼]

Estrogens can induce rapid, short-lived physiological and behavioral responses, in addition to their slow, but long-term, effects at the transcriptional level. To be functionally relevant, these effects should be associated with rapid modulations of estrogens concentrations. 17beta-estradiol is synthesized by the enzyme aromatase, using testosterone as a substrate, but can also be degraded into catechol-estrogens via hydroxylation by the same enzyme, leading to an increase or decrease in estrogens concentration, respectively. The first evidence that aromatase activity (AA) can be rapidly modulated came from experiments performed in Japanese quail hypothalamus homogenates. This rapid modulation is triggered by calcium-dependent phosphorylations and was confirmed in other tissues and species. The mechanisms controlling the phosphorylation status, the targeted amino acid residues and the reversibility seem to vary depending of the tissues and is discussed in this review. We currently do not know whether the phosphorylation of the same amino acid affects both aromatase and/or hydroxylase activities or whether these residues are different. These processes provide a new general mechanism by which local estrogen concentration can be rapidly altered in the brain and other tissues. [less ▲]

Detailed reference viewed: 143 (1 ULg)
Full Text
See detailLocal Operational Geomagnetic Index K Calculation (K-LOGIC) from digital ground-based magnetic measurements
Stankov, Stanimir; Stegen, Koen; Warnant, René ULg

Report (2011)

Detailed reference viewed: 40 (4 ULg)
Full Text
Peer Reviewed
See detailLocal order of the high-pressure metallic phase of liquid selenium: a diffraction study
Raty, Jean-Yves ULg; Gaspard, Jean-Pierre ULg; Le Bihan, T. et al

in Journal of Physics : Condensed Matter (1999), 11(50), 10243-1024910249

Liquid selenium undergoes a phase transition towards a metallic phase when sufficient pressure is applied. We performed an x-ray diffraction experiment at the 1D30 beamline of the ESRF at the wavelength ... [more ▼]

Liquid selenium undergoes a phase transition towards a metallic phase when sufficient pressure is applied. We performed an x-ray diffraction experiment at the 1D30 beamline of the ESRF at the wavelength of 0.149 Aring to investigate the local order of the metallic liquid. The diffraction pattern of liquid Se has been recorded with the large-volume Paris-Edinburgh cell between (20degC, 3 GPa) and (1650degC, 4.1 GPa). The local order of the metallic liquid selenium is found to be close to that of liquid tellurium. In particular, the coordination number Z increases with temperature from 2.6 to 3.0 [less ▲]

Detailed reference viewed: 13 (0 ULg)
Full Text
See detailLocal order, dynamics and stability of C and N doped phase change materials
Hippert, Françoise; Raty, Jean-Yves ULg; Noé, Pierre et al

Conference (2013, July 26)

Doping Chalcogenide Phase Change Materials, such as Ge2Sb2Te5 and GeTe used in non-volatile phase change memories, was shown to improve the stability of the amorphous phase and to strongly increase the ... [more ▼]

Doping Chalcogenide Phase Change Materials, such as Ge2Sb2Te5 and GeTe used in non-volatile phase change memories, was shown to improve the stability of the amorphous phase and to strongly increase the crystallization temperature. We combined total X-ray scattering experiments [1], Fourier Transform InfraRed (FTIR) spectroscopy and ab initio Molecular Dynamics simulations to address the stabilization of the amorphous phase of GeTe doped with Carbon or Nitrogen. The comparison between the simulation and exp erimental results allows in depth understanding of the role of dopants. They deeply modify the structure of the amorphous phase by introducing tetrahedral units centered on C or N, triangular environments and short C chains in C-doped GeTe, N-Ge3 pyramids and N2 molecules in N-doped GeTe. One major difference between N and C doping is the fact that C can form short bonds with Te, although in smaller proportion than C-Ge, while short N-Te bonds are absent in N-doped GeTe. The inclusion of C or N leads to an increase in high frequency vibrational modes, to a reduction of the density of floppy vibrational modes that drive the crystallization and to an increase of the rigidity. This stabilization mechanism could apply more generally to various GST materials as well as to other iono-covalent glasses. [1] G.E. Ghezzi, J.Y.Raty, S. Maitrejean, A. Roule, E. Elkaim and F. Hippert, Appl. Phys. Lett. 99 (2011) 151906 [less ▲]

Detailed reference viewed: 75 (3 ULg)
Full Text
Peer Reviewed
See detailLocal ordering and magnetism in Ga0.9Fe3.1N
Burghaus, Jens; Sougrati, Moulay T.; Moechel, Anne et al

in Journal of Solid State Chemistry (2011), 184(9), 2315-2321

Prior investigations of the ternary nitride series Ga1-xFe3+xN (0 <= x 1) have indicated a transition from ferromagnetic gamma'-Fe4N to antiferromagnetic ``GaFe3N''. The ternary nitride ``GaFe3N'' has ... [more ▼]

Prior investigations of the ternary nitride series Ga1-xFe3+xN (0 <= x 1) have indicated a transition from ferromagnetic gamma'-Fe4N to antiferromagnetic ``GaFe3N''. The ternary nitride ``GaFe3N'' has been magnetically and spectroscopically reinvestigated in order to explore the weakening of the ferromagnetic interactions through the gradual incorporation of gallium into gamma'-Fe4N. A hysteretic loop at RI reveals the presence of a minority phase of only 0.1-0.2 at\%, in accord with the sound two-step synthesis. The composition of the gallium-richest phase ``GaFe3N'' was clarified by Prompt Gamma-ray Activation Analysis and leads to the berthollide formula Ga0.91(1)Fe3.09(10)N1.05(7). Magnetic measurements indicate a transition around 8 K, further supported by Mossbauer spectral data. The weakening of the ferromagnetic coupling through an increasing gallium concentration is explained by a simple Stoner argument. In Ga0.9Fe3.1N the presence of iron on the gallium site affects the magnetism by the formation of 13-atom iron clusters. (C) 2011 Elsevier Inc. All rights reserved. [less ▲]

Detailed reference viewed: 18 (2 ULg)
Full Text
Peer Reviewed
See detailLocal orders in II-VI liquid compounds
Gaspard, Jean-Pierre ULg; Raty, Jean-Yves ULg; Ceolin, R. et al

in Journal of Non-Crystalline Solids (1996), 205-207

The structure of liquid CdTe, HgTe and ZnTe is studied by neutron scattering. Upon melting, drastically different behaviors are found: CdTe and ZnTe keep their fourfold coordination in the melt and remain ... [more ▼]

The structure of liquid CdTe, HgTe and ZnTe is studied by neutron scattering. Upon melting, drastically different behaviors are found: CdTe and ZnTe keep their fourfold coordination in the melt and remain semiconductors, whereas HgTe becomes sixfold coordinated and metallic. This dissimilarity is discussed in terms of the electronegativity difference and of the repulsive potential hardness. Entropic aspects are also discussed [less ▲]

Detailed reference viewed: 44 (0 ULg)