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See detailAnalytical solution of a simple artificial lighting scheme to test any lighting software
Embrechts, Jean-Jacques ULiege

in Light and Engineering (1998), 6(4)

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See detailAnalytical solution of a simple artificial lighting scheme to test any lighting software
Embrechts, Jean-Jacques ULiege

in Computer Modeling & Simulation in Engineering (1998), 3(3)

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See detailAnalytical Solution to Optimal Relocation of Satellite Formation Flying in Arbitrary Elliptic Orbits
Cho, Hancheol ULiege; Park, Sang-Young; Yoo, Sung-Moon et al

in Akella, Maruthi; Gearhart, James; Bishop, Robert (Eds.) et al AAS/AIAA Spaceflight Mechanics Meeting, Sedona 28 January - 1 February 2007 (2007, February)

The current paper presents and examines a general analytical solution to the optimal reconfiguration problem of satellite formation flying in an arbitrary eccentric orbit. The proposed approach does not ... [more ▼]

The current paper presents and examines a general analytical solution to the optimal reconfiguration problem of satellite formation flying in an arbitrary eccentric orbit. The proposed approach does not use any simplifying assumptions regarding the eccentricity of the reference orbit. For the fuel optimal reconfiguration problem, continuous and variable low-thrust accelerations can be represented by the Fourier series and summed into closed-form solutions. Initial and final boundary conditions are used to establish the constraints on the thrust functions. The analytical solution can be implicated by the Fourier coefficients that minimize propellant usage during the maneuver. This analytical solution is very useful for designing a reconfiguration controller for satellite formation flying in a general elliptical orbit. [less ▲]

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See detailAnalytical Solution to Optimal Relocation of Satellite Formation Flying in Arbitrary Elliptic Orbits
Cho, Hancheol ULiege; Park, Sang-Young; Yoo, Sung-Moon et al

in Aerospace Science and Technology (2013), 25(1), 161-176

The current paper presents and examines a general analytical solution to the optimal reconfiguration problem of satellite formation flying in an arbitrary elliptic orbit. The proposed approach does not ... [more ▼]

The current paper presents and examines a general analytical solution to the optimal reconfiguration problem of satellite formation flying in an arbitrary elliptic orbit. The proposed approach does not use any simplifying assumptions regarding the eccentricity of the reference orbit. For the fuel optimal reconfiguration problem, continuous and variable low-thrust accelerations can be represented by the Fourier series and summed into closed-form solutions. Initial and final boundary conditions are used to establish the constraints on the thrust functions. The analytical solution can be implicated by the Fourier coefficients that minimize propellant usage during the maneuver. This solution is found that compares favorably with numerical simulations. Also, this analytical solution is very useful for designing a reconfiguration controller for satellite formation flying in a general elliptic orbit. [less ▲]

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See detailAnalytical solutions for J 2-perturbed unbounded equatorial orbits
Martinusi, Vladimir ULiege; Gurfil, Pini

in Celestial Mechanics and Dynamical Astronomy (2013), 115

While solutions for bounded orbits about oblate spheroidal planets have been presented before, similar solutions for unbounded motion are scarce. This paper develops solutions for unbounded motion in the ... [more ▼]

While solutions for bounded orbits about oblate spheroidal planets have been presented before, similar solutions for unbounded motion are scarce. This paper develops solutions for unbounded motion in the equatorial plane of an oblate spheroidal planet, while taking into account only the J [SUB]2[/SUB] harmonic in the gravitational potential. Two cases are distinguished: A pseudo-parabolic motion, obtained for zero total specific energy, and a pseudo-hyperbolic motion, characterized by positive total specific energy. The solutions to the equations of motion are expressed using elliptic integrals. The pseudo-parabolic motion unveils a new orbit, termed herein the fish orbit, which has not been observed thus far in the perturbed two-body problem. The pseudo-hyperbolic solutions show that significant differences exist between the Keplerian flyby and the flyby performed under the the J [SUB]2[/SUB] zonal harmonic. Numerical simulations are used to quantify these differences. [less ▲]

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See detailAnalytical solutions for the thick-walled cylinder problem modeled with an isotropic elastic second gradient constitutive equation
Collin, Frédéric ULiege; Caillerie, Denis; Chambon, René

in International Journal of Solids and Structures (2009), 46

Numerical modelling of localization phenomena shows that constitutive equations with internal length scale are necessary to properly model the post-localization behaviour. Moreover, these models allow an ... [more ▼]

Numerical modelling of localization phenomena shows that constitutive equations with internal length scale are necessary to properly model the post-localization behaviour. Moreover, these models allow an accurate description of the scale effects observed in some phenomena like micro indentation. This paper proposes some analytical results concerning a boundary value problem in a medium with microstructure. In addition to their own usefulness, such analytical solutions can be used in benchmark exercises for the validation of numerical codes. The paper focuses on the thick-walled cylinder problem, using a general small strain isotropic elastic second gradient model. The most general isotropic elastic model involving seven different constants is used and the expression of the analytical solutions is explicitly given. The influence of the microstructure is controlled by the internal length scale parameter. The classical macrostress is no more in equilibrium with the classical forces at the boundary. Double stresses are indeed also generated by the classical boundary conditions and, as far as the microstructure effects become predominant (i.e. the internal length scale is much larger than the thickness of the cylinder), the macrostresses become negligible. This leads to solutions completely different from classical elastic ones. [less ▲]

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See detailAnalytical strategies for the detection of counterfeit erectile dysfunction drugs
Sacré, Pierre-Yves ULiege

Doctoral thesis (2011)

Since the late eighties, when it was first mentioned, the worldwide phenomenon of pharmaceutical counterfeiting is growing. Belgian customs often encounter presumed counterfeited medical products in ... [more ▼]

Since the late eighties, when it was first mentioned, the worldwide phenomenon of pharmaceutical counterfeiting is growing. Belgian customs often encounter presumed counterfeited medical products in Belgian airports and ports because of their central position in Europe and their importance in the transit of goods. Further and deeper analyses are required to assess the counterfeit character of these goods and to provide a scientific basis for the eventual legal procedure. As reference laboratory for the federal agency for medicines and health products (FAMHP), the Scientific Institute of Public Health (IPH) frequently analyses illegal and counterfeit pharmaceutical preparations. The present research project was started with the objective of evaluating several existing methods and developing new analytical methods to detect counterfeit erectile dysfunction drugs. This thesis is focused on the analysis of illegal samples of phosphodiesterase type 5 inhibitors (PDE5-i) containing drugs because these are the most counterfeited pharmaceutical specialities in Belgium. The research was divided into a spectroscopic and a chromatographic part: Infrared based spectroscopies have already demonstrated their ability to detect counterfeit drugs. The first part of the study evaluates the capacity of each technique (mid-infrared (mid-IR), near-infrared (NIR) and Raman spectroscopy) separately and their combinations to discriminate genuine from illegal tablets. Then, the Classification And Regression Trees (CART) algorithm has been used to classify the different samples following the classification system of the Dutch National Institute for Public Health and the Environment (RIVM). The second spectroscopic approach used Raman microspectroscopy mapping to detect counterfeited Viagra®. This technique allows the detection of different compounds according to their Raman spectrum but also the study of the distribution of a selected ingredient among the core of a tablet. The chromatographic part consists of the development and validation of a new Ultra High Pressure Liquid Chromatography method coupled with a UV diode array detector (UHPLC-DAD) and compatible with mass spectrometry (MS) to detect and quantify the three authorised phosphodiesterase type 5 inhibitors (sildenafil, tadalafil and vardenafil) and five of their analogues in illegal pharmaceutical preparations. This method has been validated between +/- 5% acceptance limits using the total error approach and has been compared to the official Viagra® assay method. The ability of HPLC-UV impurity fingerprints to detect illegal samples and to predict whether a new unknown sample is genuine has also been evaluated. The developed analytical methods may be included in a general approach to detect counterfeit drugs containing PDE5-i. This generic approach may also be used to detect other types of counterfeited drugs but should therefore be adapted for each type of medicine. [less ▲]

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See detailAnalytical strategies for the detection of counterfeit erectile dysfunction drugs.
Sacre, Pierre-Yves ULiege; Deconinck, Eric; De Beer, Jacques

in Wang, Perry; Wertheimer, Albert (Eds.) Counterfeit Medicines Volume II: Detection, Identification and Analysis (2013)

Among all classes of drugs, the type 5 phosphodiesterase inhibitors (PDE5-i) (sildenafil, vardenafil and tadalafil) are the most counterfeited and copied in industrialized countries. This is why it is ... [more ▼]

Among all classes of drugs, the type 5 phosphodiesterase inhibitors (PDE5-i) (sildenafil, vardenafil and tadalafil) are the most counterfeited and copied in industrialized countries. This is why it is very important for regulatory agencies to have a panel of analytical methods to analyse these drugs and to be able to detect counterfeit or substandard medicines. During this chapter, several analytical techniques will be described and discussed. Among spectroscopic techniques, Raman, NIR, FT-IR and chemical imaging techniques will be envisaged. Their ability to detect counterfeits and predict if a new sample is genuine or not will be presented. Other techniques such as XRay powder diffraction and NMR spectroscopies will be briefly presented. Chromatographic impurity fingerprints will be considered and described for the analysis of suspect samples of Cialis® and Viagra®. Once again, the possibility to predict the authenticity of a new sample by the mean of this technique is envisaged. Finally, a MS-compatible UHPLC-UV method for the analysis of the three authorised PDE5-i and some of their analogues will be shortly described. This technique has been validated using spiked placebo samples in a vegetal matrix representing a suspect sample with a complex matrix. As a conclusion, a generic strategy for the detection and quality evaluation of counterfeit drugs will be presented. [less ▲]

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See detailAnalytical strategies for ultra-trace measurement of dioxins and related compounds in biological matrices
L'Homme, Benjamin ULiege

Doctoral thesis (2015)

The human exposure to persistent organic pollutants (POPs) is a concern since these compounds are ubiquitous in the environment. This class of compounds group different families such as the ... [more ▼]

The human exposure to persistent organic pollutants (POPs) is a concern since these compounds are ubiquitous in the environment. This class of compounds group different families such as the polychlorodibenzo-p-dioxins (PCDDs), the polychlorodibenzofurans (PCDFs), the polychlorinated biphenyls (PCBs), the organochlorine pesticides (OCPs), and the halogenated flame-retardants (HFRs). Their use, their release in the environment, their presence in foodstuffs, as well as in various goods on the market are mostly regulated through international conventions, like the Stockholm convention on POPs, and at the European and national levels. Despite the proactive approach in order to reduce the overall exposure to POPs, levels of contaminants (even banned) are still found in the environment and in the human body. In this thesis, we developed several methods of analysis of POPs in different samples. The first was a confirmatory method for PCDD/Fs and PCBs analysis in food and feed following a new European Regulation No 709/2014 that recently allowed the use of gas chromatography (GC) coupled to triple quadrupole mass spectrometry (GC-QQQMS/MS) for this purpose. We fully validated the method on vegetable oil matrix around the maximum level of 1.50 ng WHO2005TEQ/kg. We showed that all analytical criteria, specific to this instrumentation, laid down by the Regulation were met, which indicates that the QQQMS/MS can successfully be used in the legal context for confirmatory purposes and could be an alternative to high-resolution sector field mass spectrometry (HRMS) in this context. The proper establishment of limits of quantitation was a key point in the discussion along with other analytical criteria proposed in the European Regulation, as new interpretations were necessary for the use of triple quadrupole mass spectrometry due to its different features from the HRMS. In addition, we developed in parallel a method for the analysis of Dechloranes in food. The measurement of ultra-trace levels of compounds from this emerging class of flame-retardants was possible after optimization of the injections parameters by means of experimental design, and of fragmentation pathways. Eventually, we reported relatively low levels in various food matrices and preliminary data about the significance of this route of exposure for humans. Besides food analysis, we developed a screening method to quickly assess levels of contaminants in human blood, involving a minimally invasive sampling technique and a couple of drops of blood. The instrumentation was first based on cryogenic zone compression (CZC) hyphenated to high-resolution time of flight mass spectrometry (HRTOFMS) applied to the analysis of two markers of exposure in regular dried-blood spots (DBS) typically used for newborn sampling. The second approach was based on GC-QQQMS/MS applied to the analysis of a broader range of OCPs and NDL-PCBs (30 analytes) in 40 µL blood. The blood was however collected using a novel Volumetric Absorptive MicroSampling (VAMS) method, directly inspired by the DBS but offering a control on the volume of blood sampled, hence opening the door to quantitation. The sample preparation of the VAMS dried sample was miniaturized and only 2 mL of solvents were necessary to prepare a sample, which makes it environmentally friendly. The focus was especially drawn to maximize the sensitivity via the optimization of the ionization energy and the electron multiplier voltage in order to reach appropriate low limits of quantitation. In this context of ultra-low volume of blood, background levels arose as the limitation of the method owing to the small signals coming from samples and closing the gap with blanks. Nevertheless, this patient-friendly approach is perfectly suitable for fast screening of population and could be useful in the context of UNEP campaigns where samples are hardly collected. [less ▲]

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See detailAnalytical study of the interaction between bending and axial force in bolted joints
Boissonnade, N.; Jaspart, Jean-Pierre ULiege; Muzeau, J. P. et al

in Proceedings of the Third European Conference on Steel Structures (EUROSTEEL) (2002)

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See detailAnalytical study of three cystatin C assays and their impact on cystatin C-based GFR-prediction equations.
Delanaye, Pierre ULiege; Pieroni, Laurence; Abshoff, Christelle et al

in Clinica Chimica Acta (2008), 398(1-2), 118-24

BACKGROUND: Cystatin C-based equations are used to estimate GFR. However, three cystatin C immunoassays are on the market. Difference in cystatin C assays could have strong consequences on the accuracy ... [more ▼]

BACKGROUND: Cystatin C-based equations are used to estimate GFR. However, three cystatin C immunoassays are on the market. Difference in cystatin C assays could have strong consequences on the accuracy and precision of cystatin C-based equations. We have performed an analytical study of these three assays and studied potential differences between assays on the precision of cystatin C-based equations. METHODS: We have studied imprecision, recovery, linearity and interferences of the three immunoassays (nephelometric assay from Siemens and turbidimetric assays from Dako and Gentian). The impact of differences in cystatin C assays has been studied for the equations published by Levey (Siemens assay) and Grubb (Dako assay). RESULTS: Analytical performance of the Dako assay is slightly less high. For cystatin C values below 2.5 mg/L, no statistical difference is found between results given by the Dako and the Gentian assays. So, both assays can be used in the Grubb equation. Cystatin C results are different with the Siemens assay. The Levey equation, built with the Siemens assay, can only be used with cystatin C values measured with this assay. Using the Dako or Gentian assay results in the Levey equation can lead to differences in estimating GFR up to 6 mL/min/1.73 m2. Differences can reach 9.5 mL/min/1.73 m2 if the Siemens assay is used in the Grubb equation. CONCLUSION: The Siemens and Gentian assays seem analytically more valid than the Dako assay for cystatin C determination. Differences in cystatin C assays can lead to significant differences in cystatin C-based equations. However, these differences seem less important than the differences observed with creatinine and creatinine-based equations. [less ▲]

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See detailAnalytical study of “La Famille Soler” by Picasso: from the Blue Period to Cubism
Defeyt, Catherine ULiege; Vekemans, Bart; Vandenabeele, Peter et al

Poster (2013, September 23)

Detailed reference viewed: 43 (6 ULiège)
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See detailAnalytical technologies and tolls for drug purity testing
Crommen, Jacques ULiege; Chiap, Patrice ULiege; Ceccato, Attilio ULiege et al

Conference (1996)

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See detailAnalytical Tools and Strategic Approach to Detect Poor Quality Medicines, Identify Unknown Components, and Timely Alerts for Appropriate Measures: Case Study of Antimalarial Medicines
Habyalimana, Védaste ULiege; Mbinze Kindenge, Jérémie; Kalenda Tshilombo, Nicodème ULiege et al

in American Journal of Analytical Chemistry (2015), 6

Nowadays, the circulation of poor quality medicines is becoming an alarming worldwide phenomenon with serious public health and socio-economic concerns. The situation is particularly critical in ... [more ▼]

Nowadays, the circulation of poor quality medicines is becoming an alarming worldwide phenomenon with serious public health and socio-economic concerns. The situation is particularly critical in developing countries where drug quality assurance and regulatory systems for drug manufacturing, importation, distribution and sales are weak. A sustained vigilance on poor quality medicines that regroup counterfeit/falsified, substandard and degraded medicines is therefore required to ensure patient safety and genuine medicines integrity. A case situation is illustrated including a strategic approach and analytical tools that were found useful to detect poor quality medicines, identify unknown components, and timely alerts for appropriate measures against the spread of those harmful products. Several suspected medicines randomly sampled in several strategic Rwandan areas were firstly check-controlled by means of visual inspection and then applying several analytical techniques from simple to more complex ones. The following medicines were studied: quinine sulfate tablets, artemisinin-based combination tablets, and artesunate powders for injection. Taking into account the pharmaceutical forms and the chemical characteristics, the following tests were applied: uniformity of mass, friability, disintegration, fluorescence, identification and assay. They were followed by more complex analytical techniques that allowed more comprehension of abnormal findings among which the presence of a wrong active pharmaceutical ingredient in quinine sulfate tablets which is mainly discussed in this paper to illustrate a strategic approach and various analytical tools that can be used in detecting and identifying unknown component in poor quality medicines. [less ▲]

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See detailAnalytical tools to fight against counterfeit medicines
Marini Djang'Eing'A, Roland ULiege; Mbinze Kindenge, J.; Montes, M. L. A. et al

in Chimica Oggi = Chemistry Today (2010), 28(5), 10-14

Counterfeiting has been dramatically increasing this last decade throughout the world and particularly in developing countries, with many consequences such as adverse impacts on public health, economics ... [more ▼]

Counterfeiting has been dramatically increasing this last decade throughout the world and particularly in developing countries, with many consequences such as adverse impacts on public health, economics and negative reputation for the pharmaceutical industry. Recognizing the magnitude of the issue, health authorities at national, regional and international levels are trying to fight against this scourge using various strategies including the setting-up of effective quality control that need to be reinforced through generic, fast and specific detection methods. To illustrate this topic, we will present several analytical tools, including liquid chromatography, low cost capillary electrophoresis and near infrared spectroscopy, developed and applied to the detection and quantification of counterfeit drugs. [less ▲]

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See detailAnalytical validation based on total error measurement and cut-off interpretation of a neonatal screening TSH-immunoassay.
Boemer, François ULiege; Bours, Vincent ULiege; Schoos, Roland ULiege et al

in Journal of Chromatography. B : Analytical Technologies in the Biomedical & Life Sciences (2009), 877

To prevent the severe developmental and physical morbidities associated with congenital hypothyroidism, we developed a home-made Enzyme-Linked Immunosorbent Assay (ELISA) method to quantify Thyroid ... [more ▼]

To prevent the severe developmental and physical morbidities associated with congenital hypothyroidism, we developed a home-made Enzyme-Linked Immunosorbent Assay (ELISA) method to quantify Thyroid Stimulating Hormone (TSH) levels on newborn dried blood spots. In order to agree with actual clinical laboratory quality referential (ISO 15189), we desired to update our analytical validation protocol. For this purpose, an approach using accuracy profiles based on tolerance intervals for the total error measurement was for first time applied to an immunological assay. According to acceptance limits fixed at +/-30%, the method was found accurate over a concentration range from 17.48 to 250mIU/L. Based on 99.5 percentile of a 16,459 newborn population, cut-off was fixed at 20.1mIU/L and validated against normal and pathologic neonatal populations. Additionally, uncertainty regions around this value were obtained applying four different approaches. Finally, we demonstrated here our in-house immunological technique fulfils criterions of a neonatal screening policy. [less ▲]

Detailed reference viewed: 128 (27 ULiège)