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Peer Reviewed
See detailDiscrepancy between prolactin (PRL) messenger ribonucleic acid and PRL content in rat fetal pituitary cells: possible role of dopamine
Hooghe-Peters, E. L.; Belayew, A.; Herregodts, P. et al

in Molecular Endocrinology (1988), 2(12), 1163-8

Data are controversial concerning the time when PRL-synthesizing cells are detected for the first time in the rat pituitary. Using a very sensitive immunocytochemical technique, we could visualize only a ... [more ▼]

Data are controversial concerning the time when PRL-synthesizing cells are detected for the first time in the rat pituitary. Using a very sensitive immunocytochemical technique, we could visualize only a few PRL cells before day 10 after birth. At that time, pituitary PRL was still 200 times less abundant than in the adult (on a tissue weight basis) whereas PRL mRNA per mg total RNA was only 80 times lower than in the adult. However, by in situ hybridization, we could demonstrate the presence of PRL mRNA in cells from fetal day 18 on. We have also followed the expression of GH gene in rat pituitary cells during development. In contrast to results obtained with PRL cells, quantitative analysis of cDNA probe hybridization to GH mRNA correlated well with measurements of immunostained cells. We found that PRL was released in the blood from fetal day 19 onwards. Thus, at that time PRL is synthesized and secreted but not stored. We therefore measured brain dopamine levels, and the data support the idea that the rise in dopamine levels after birth contributes to PRL storage. We confirmed in vitro that newborn pituitary cells can store PRL when cultured in the presence of dopamine. [less ▲]

Detailed reference viewed: 11 (2 ULg)
See detailDiscrepancy in hemoglobin A1c results obtained by HPLC and CE: influence of carbamyl HB
Gougnard, Th; Chapelle, Jean-Paul ULg; Charlier, Corinne ULg et al

Poster (1997, October 18)

Detailed reference viewed: 15 (0 ULg)
See detailA discrete competitive facility location model with variable attractiveness
Kucukaydin, Hande ULg; Aras, Necati; Altinel, I. Kuban

Conference (2009, July 08)

We consider the discrete version of the competitive facility location problem in which new facilities have to be located by a new market entrant to compete against already existing ones that may belong to ... [more ▼]

We consider the discrete version of the competitive facility location problem in which new facilities have to be located by a new market entrant to compete against already existing ones that may belong to one or more competitors. The objective of the firm is to determine the locations of the new facilities and their attractiveness levels to maximize the profit. We formulate a mixed-integer nonlinear programming model for this problem and propose three methods for its solution: a Lagrangean heuristic, two branch-and-bound methods using Lagrangean and nonlinear programming relaxations. [less ▲]

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Peer Reviewed
See detailA discrete competitive facility location model with variable attractiveness
Kucukaydin, Hande ULg; Aras, Necati; Altinel, I. Kuban

in Journal of the Operational Research Society (2011), 62(9), 1726-1741

We consider the discrete version of the competitive facility location problem in which new facilities have to be located by a new market entrant firm to compete against already existing facilities that ... [more ▼]

We consider the discrete version of the competitive facility location problem in which new facilities have to be located by a new market entrant firm to compete against already existing facilities that may belong to one or more competitors. The demand is assumed to be aggregated at certain points in the plane and the new facilities can be located at predetermined candidate sites. We employ Huff’s gravity-based rule in modelling the behaviour of the customers where the probability that customers at a demand point patronize a certain facility is proportional to the facility attractiveness and inversely proportional to the distance between the facility site and demand point. The objective of the firm is to determine the locations of the new facilities and their attractiveness levels so as to maximize the profit, which is calculated as the revenue from the customers less the fixed cost of opening the facilities and variable cost of setting their attractiveness levels. We formulate a mixed-integer nonlinear programming model for this problem and propose three methods for its solution: a Lagrangean heuristic, a branch-and-bound method with Lagrangean relaxation, and another branch-and-bound method with nonlinear programming relaxation. Computational results obtained on a set of randomly generated instances show that the last method outperforms the others in terms of accuracy and efficiency and can provide an optimal solution in a reasonable amount of time. [less ▲]

Detailed reference viewed: 53 (3 ULg)
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See detailDiscrete Element Method Modeling of Ball Mills - Liner Wear Evolution
Boemer, Dominik ULg; Rycerski, Serge; Vis, Jean et al

in Oñate, E.; Bischoff, M.; Owen, D.R.J. (Eds.) et al Proceedings of the IV International Conference on Particle-Based Methods – Fundamentals and Applications (2015)

Detailed reference viewed: 23 (4 ULg)
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See detailDiscrete Element Method Modeling of Ball Mills - Liner Wear Evolution
Boemer, Dominik ULg

Master's dissertation (2015)

Ball mills, i.e. rotating cylindrical drums filled with a feed material and metal balls, also known as the charge, are a major category of grinding devices in mineral processing and cement production ... [more ▼]

Ball mills, i.e. rotating cylindrical drums filled with a feed material and metal balls, also known as the charge, are a major category of grinding devices in mineral processing and cement production. Since the grinding process is excessively energy-intensive and aggressive in terms of wear, a profiled and wear-resistant liner is installed in the mill to transfer energy to the grinding charge more efficiently and to protect the mill shell. Because of the harsh environment inside of the mill and the relatively long lifespan of its liner, the optimization of the liner by the classical way, i.e. experimental testing, is a difficult and slow process. In this thesis, a procedure for predicting the charge motion and the power draw of a ball mill based on the discrete element method (DEM) is calibrated and validated by means of photographs of the charge, and power draw measurements of a 1:5-scale laboratory mill, which were kindly provided by the company Magotteaux International S.A. . This computational method essentially renders future experimental testing unnecessary with respect to these characteristics. Based on this first method, a generic process for predicting the wear distribution and the progressive shape evolution of liner surfaces is developed and validated by the wear profiles of the shell liner in the first chamber of a 5.8 m diameter cement mill monitored during a decade by Magotteaux International S.A. . The energy dissipated by tangential damping defined by the linear spring-slider-damper DEM contact law was found to be the best fitting wear model with respect to the real wear data. The progressive update of the liner geometry by a multi-step procedure delivers relatively accurate results for liners without axial height variation while further investigations are still required for almost fully variable geometries. Nevertheless, detailed phenomena, like the creation of grooves in the liner, were for the first time numerically modeled in this thesis. [less ▲]

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Peer Reviewed
See detailDiscrete element modelling approach to assessment of granular properties in concrete
Stroeven, Piet; He, Huan ULg; Stroeven, Martijn

in Journal of Zhejiang University. Science A (2011), 12(5), 335-344

This paper presents the technological relevance of a concurrent algorithm-based discrete element modelling (DEM) system, HADES. This new system is the successor of SPACE that is limited to spherical ... [more ▼]

This paper presents the technological relevance of a concurrent algorithm-based discrete element modelling (DEM) system, HADES. This new system is the successor of SPACE that is limited to spherical grains only. It can realistically simulate the packing of arbitrary-shaped particles up to the fully compacted state. Generation of families of such particles, i.e., generally representing aggregate of fluvial origin and crushed rock, respectively, and the forming way of particulate structure are described. Similarly shaped particles are proposed for simulation of cement paste because of conformity with experimental results obtained by the X-ray tomography method. Technologically relevant territories inside and outside concrete technology are presently explored in this efficient, reliable, and economic way. Some results obtained by this DEM approach are presented. [less ▲]

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See detailDiscrete Event Production Simulation and Optimisation of Ship Block Erection Process
Caprace, Jean-David ULg; Trevisani Da Silva, Clarice; Rigo, Philippe ULg et al

in Proceeding of the 10th International Conference on Computer Applications and Information Technology in the Maritime Industries (2011, May)

Nowadays, shipyards are making every effort to efficiently manage equipments and resources such as labourers, gantry cranes, transporters, steel and block stock yards, etc. The block erection scheduling ... [more ▼]

Nowadays, shipyards are making every effort to efficiently manage equipments and resources such as labourers, gantry cranes, transporters, steel and block stock yards, etc. The block erection scheduling of a gantry crane has thus far been manually performed by a manager of a shipyard. Such a scenario leads to undesirably long times for producing scheduling results. In addition, the quality of the scheduling results may not be optimal. To improve the overall process, block erection discrete event simulations have been developed in this study by using techniques of optimization. The first results presented in this paper are promising even if some future work must be realized. [less ▲]

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See detailDiscrete Event Production Simulation in Shipyard Workshops
Caprace, Jean-David ULg; Moreira Freire, Roberto; Assiss, Luiz Felipe et al

in Proceeding of the 21th COPINAVAL (2011, September)

Nowadays, shipyards are making huge effort to efficiently manage equipments and resources such as laborers, gantry cranes, transporters, steel and block stock yards, etc. Previously scheduling was ... [more ▼]

Nowadays, shipyards are making huge effort to efficiently manage equipments and resources such as laborers, gantry cranes, transporters, steel and block stock yards, etc. Previously scheduling was manually performed by an experienced manager of a shipyard. But such a scenario leads to undesirably long times for producing scheduling results. In addition, the quality of the scheduling results was usually not optimal. To improve the overall process, Discrete Event Simulations (DES) have been developed and recently use in shipbuilding industry. The use of simulation-based design and virtual reality technologies leads to higher efficiency in terms of work strategy planning, and offers, as a result, significant productivity gains. It gives computer-supported answers to the major questions: when and where to produce what and with which resources depending on the availability and restrictions of resources and materials. The first part of the paper presents a multi-criteria analysis to select the most appropriate DES software for shipyards. Then, the second part of the paper shows production simulation model focusing on block erection stage. Two different blocks splitting are compared and then the results are discussed. [less ▲]

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Peer Reviewed
See detailDiscrete finite element characterizations of source fields for volume and boundary constraints in electromagnetic problems
Henneron, Thomas; Clénet, Stéphane; Dular, Patrick ULg et al

in Journal of Computational & Applied Mathematics (2008), 215(2), 438-447

The consideration of electromagnetic field sources in potential formulations necessitates the definition of source fields. Such source fields are first defined for both volume and boundary constraints in ... [more ▼]

The consideration of electromagnetic field sources in potential formulations necessitates the definition of source fields. Such source fields are first defined for both volume and boundary constraints in static electromagnetic models. Then, automatic procedures are proposed to conveniently and efficiently characterize discrete source fields, with regard to their use in finite element formulations, their supports, their direct expression requiring no pre-computation, and their associated constraints. Two application examples are proposed to illustrate the approach. [less ▲]

Detailed reference viewed: 17 (0 ULg)
Peer Reviewed
See detailDiscrete Harmonic Oscillator: A Short Compendium of Formulas
Antippa, Adel F.; Dubois, Daniel ULg

in Dubois, Daniel (Ed.) COMPUTING ANTICIPATORY SYSTEMS (2010)

Since 2002, we have, in seven papers, studied the problem of the discrete harmonic oscillator, analytically, numerically, and graphically, and made progress on a number of fronts. We identified the ... [more ▼]

Since 2002, we have, in seven papers, studied the problem of the discrete harmonic oscillator, analytically, numerically, and graphically, and made progress on a number of fronts. We identified the natural frequency of oscillation of the dual incursive oscillators, studied the system bifurcation generated by incursive discretization, and the frequency dependent correlation between the resulting incursive oscillators. We also studied the synchronization of the discretizing time interval with the frequency of oscillation. From this analysis there emerged a nonlinear (or more precisely bilinear) formalism that is perfectly stable at all time scales, and fully conserves the total energy of the system. The formalism is applicable to the discrete harmonic oscillator specifically, and to discrete Hamiltonian systems in general. In retrospect the important themes and crucial steps can more easily be identified, and this is the purpose of this short note. In it we give, in a unified notation, a short compendium of the key formulas. This summary can serve as a guide for navigating through the seven papers, as well as a practical concise manual for using the formalism. [less ▲]

Detailed reference viewed: 31 (1 ULg)
Peer Reviewed
See detailDiscrete Harmonic Oscillator: Evolution of Notation and Cumulative Erratum
Antippa, Adel F.; Dubois, Daniel ULg

in Dubois, Daniel (Ed.) COMPUTING ANTICIPATORY SYSTEMS (2010)

As the project on the discrete harmonic oscillator advanced, the notation evolved in parallel with our understanding of the problem, and it became progressively clear that a change of notation concerning ... [more ▼]

As the project on the discrete harmonic oscillator advanced, the notation evolved in parallel with our understanding of the problem, and it became progressively clear that a change of notation concerning the natural angular frequency of oscillation of the system, and related parameters, was required in order to conform to the spirit of the physics being developed. Specifically the notation needed to reflect the fact that the discrete harmonic oscillator is the more general entity, with the continuous harmonic oscillator being a special (and to some extent unrealistic) limiting case corresponding to dt-->0, where dt is the discretizing time interval. Furthermore, as the discrete nature of time (and eventually space), incursion (anticipation), system bifurcation, hyperincursion, frequency dependent correlation, and synchronization, where progressively integrated into the fabric of the discretizing algorithm, a new discrete, perfectly stable and energy conserving, formalism emerged, and with it evolved, in parallel, the expression for the total energy. In this short note we will focus on the evolution, throughout the project, of the notation for frequency, and the expression for the discrete total energy. We also provide a cumulative erratum for the seven papers in the project so far, as well as a table summarizing the evolution of the notation for the angular frequency and related parameters. [less ▲]

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See detailDiscrete Modeling: Thermidynamics Based on Shannon Entropy and Discrete States of Molecules
Pfleger, Martin; Wallek, Thomas; Pfennig, Andreas ULg

in Industrial and Engineering Chemistry (2015), 54

Thermodynamic modeling using the concept of Shannon entropy is a promising approach, especially in the field of describing fluid-phase behavior. This paper introduces the method of discrete modeling ... [more ▼]

Thermodynamic modeling using the concept of Shannon entropy is a promising approach, especially in the field of describing fluid-phase behavior. This paper introduces the method of discrete modeling, using the ideal-gas model as an illustrative example, and derives a general equation of state. Discrete modeling is based on discrete states of individual molecules. It utilizes the special characteristics of Shannon entropy to model the statistical behavior of systems by applying the maximum entropy principle to its constituents in a straightforward manner. The presented method and the general form of the equation of state thus obtained allow the derivation of equations of states for real fluids. As a novelty, it also allows for the description of the microscopic distribution of the mechanical states of individual molecules. Considering the kinetic states of the particles this includes the Maxwell−Boltzmann distribution, the caloric equation of state, and the heat capacity of the ideal gas. [less ▲]

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See detailDiscrete optimization
Louveaux, Quentin ULg

Poster (2005, September)

Have you ever wondered what is the shortest route to join the office? What is the best way to plan a trip through several cities? You have maybe already played with magical squares? Then you have met one ... [more ▼]

Have you ever wondered what is the shortest route to join the office? What is the best way to plan a trip through several cities? You have maybe already played with magical squares? Then you have met one of the nu- merous instances of discrete optimization. Discrete optimization is a field of mathematics which deals with any problem where parts of the solutions cannot be divided or fractional. And as one may guess, this is the case in many real-life problems. This poster is divided in three main topics. The first part focuses on formulating those problems. We will start from one of the industrial appli- cations and show how we can model it as a mathematical problem. In the second part we sketch the main tools and algorithms used to tackle those problems. In particular we point out the fact that requiring integrality leads to extremely hard problems to solve. We show that despite this fact, we are able to solve problems of substantial size. However there remain some problems that are hard to solve using the state-of-the-art techniques. In the third part we indicate what are the chal- lenges of the field. In particular we will give an overview of the research car- ried out in the universities supported by the Marie-Curie network ADONET. [less ▲]

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Peer Reviewed
See detailA discrete population of squamocolumnar junction cells implicated in the pathogenesis of cervical cancer.
Herfs, Michael ULg; Yamamoto, Yusuke; Laury, Anna et al

in Proceedings of the National Academy of Sciences of the United States of America (2012), 109(26), 10516-21

Infection by carcinogenic human papillomaviruses (HPV) results in precancers [cervical intraepithelial neoplasia (CIN)] and cancers near the ectoendocervical squamocolumnar (SC) junction of the cervix ... [more ▼]

Infection by carcinogenic human papillomaviruses (HPV) results in precancers [cervical intraepithelial neoplasia (CIN)] and cancers near the ectoendocervical squamocolumnar (SC) junction of the cervix. However, the specific cells targeted by HPV have not been identified and the cellular origin of cervical cancer remains elusive. In this study, we uncovered a discrete population of SC junctional cells with unique morphology and gene-expression profile. We also demonstrated that the selected junctional biomarkers were expressed by a high percentage of high-grade CIN and cervical cancers associated with carcinogenic HPVs but rarely in ectocervical/transformation zone CINs or those associated with noncarcinogenic HPVs. That the original SC junction immunophenotype was not regenerated at new SC junctions following excision, not induced by expression of viral oncoproteins in foreskin keratinocytes, and not seen in HPV-related precursors of the vagina, vulva, and penis further support the notion that junctional cells are the source of cervical cancer. Taken together, our findings suggest that carcinogenic HPV-related CINs and cervical cancers are linked to a small, discrete cell population that localizes to the SC junction of the cervix, expresses a unique gene expression signature, and is not regenerated after excision. The findings in this study uncover a potential target for cervical cancer prevention, provide insight into the risk assessment of cervical lesions, and establish a model for elucidating the pathway to cervical cancer following carcinogenic HPV infection. [less ▲]

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See detailA Discrete Sequence Associated with Mixed Finite Elements and its Gauge Condition for Vector Potentials
Dular, Patrick ULg; Nicolet, André; Genon, André et al

in IEEE Transactions on Magnetics (1995), 31(3), 1356-1359

A sequence of finite element spaces built on tetrahedra, hexahedra and prisms, is presented, and a gauge condition for vector potentials is shown to be well defined in these spaces. Results are presented ... [more ▼]

A sequence of finite element spaces built on tetrahedra, hexahedra and prisms, is presented, and a gauge condition for vector potentials is shown to be well defined in these spaces. Results are presented for a modified vector potential formulation for 3D eddy current problems. [less ▲]

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See detailDiscrete symmetries in the three-Higgs-doublet model
Ivanov, Igor ULg; Vdovin, Evgeny

in Physical Review. D : Particles and Fields (2012), 86(9), 0950305

N-Higgs-doublet models (NHDM) are among the most popular examples of electroweak symmetry breaking mechanisms beyond the Standard Model. Discrete symmetries imposed on the NHDM scalar potential play a ... [more ▼]

N-Higgs-doublet models (NHDM) are among the most popular examples of electroweak symmetry breaking mechanisms beyond the Standard Model. Discrete symmetries imposed on the NHDM scalar potential play a pivotal role in shaping the phenomenology of the model, and various symmetry groups have been studied so far. However, in spite of all efforts, the classification of finite Higgs-family symmetry groups realizable in NHDM for any N>2 is still missing. Here, we solve this problem for the three-Higgs-doublet model by making use of Burnside’s theorem and other results from pure finite group theory which are rarely exploited in physics. Our method and results can also be used beyond high-energy physics, for example, in the study of possible symmetries in three-band superconductors. [less ▲]

Detailed reference viewed: 13 (3 ULg)