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Chanlon S, Georges J. Pulsed-laser mode-mismatched crossed-beam thermal lens spectrometry within a small capillary tube: effect of flow rate and beam offset on the photothermal signal. SPECTROCHIMICA ACTA. PART A, MOLECULAR AND BIOMOLECULAR SPECTROSCOPY 2002; 58:1607-1613. [PMID: 12166732 DOI: 10.1016/s1386-1425(01)00612-6] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
Pulsed-laser crossed-beam thermal lens spectrometry within a small capillary tube has been investigated using static as well as flowing samples. It is shown that when both the excitation and probe beams are perfectly aligned, time-resolved and peak signals are adequately described by the theoretical relations previously reported for infinite samples. Depending on flow velocity and/or the lateral offset between excitation and probe beam axis, the optical element formed by the excitation beam may have a diverging or converging effect on the probe beam. However, optimization of the photothermal signal with pulsed excitation and flowing samples does not require offsetting the pump and probe beams and the peak signal is almost independent on the flow rate. The performance of the method has been checked with samples injected in a flowing stream. The response is linear over three orders of magnitude and the limit of detection obtained for cobalt nitrate in ethanol corresponds to an average absorbance of 5 x 10(-7) inside the capillary.
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Gove D, Georges J. Perspectives on legislation relating to the rights and protection of people with dementia in Europe. Aging Ment Health 2001; 5:316-21. [PMID: 11767978 DOI: 10.1080/13607860120080251] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/16/2022]
Abstract
This article focuses on the main legal provisions in Europe relating to the protection and rights of people with dementia. The information referred to was obtained in the framework of two EC funded projects, which involved the collection, translation and comparison of relevant legislation, and then the writing of legal recommendations to improve the legal rights and protection of people with dementia. The first project started in 1997 and was completed in 1999. The second project started in 1999 and was completed in November 2000. The article provides an overview of the main features of some of the laws in Europe on a few key issues, i.e. guardianship, coercive measures and bioethical issues. Some of the main differences between the systems in different countries are highlighted. An attempt is made to show how the adequacy and appropriateness of legal provisions differ vastly from one country to the next and also to identify the emergence of a few trends, which seem to reflect a movement towards a greater awareness of the nature of mental incapacity and hence a better provision for the rights and protection of people with dementia.
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Arnaud N, Georges J. Sensitive detection of tetracyclines using europium-sensitized fluorescence with EDTA as co-ligand and cetyltrimethylammonium chloride as surfactant. Analyst 2001; 126:694-7. [PMID: 11394316 DOI: 10.1039/b101525g] [Citation(s) in RCA: 56] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The determination of tetracyclines (TC) in aqueous solutions, based on europium-sensitized fluorescence, has been improved using EDTA as co-ligand and cetyltrimethylammonium chloride as surfactant. The method involves working in slightly alkaline solutions with the formation of a new chelate where the lanthanide ion is bound to the beta-diketone group. The method is about 6 times more sensitive than that with the Eu-TC-Triton system and LODs are 2.5 x 10(-10), 5 x 10(-10), 1.5 x 10(-9) and 2 x 10(-9) mol l-1 for TC, oxytetracycline, chlortetracycline and doxycycline, respectively. The method has been applied to the determination of TC in calf serum without sample pretreatment. The mean recovery was close to 102% and the lowest concentration attainable in serum samples was better than 0.1 microgram ml-1.
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Arnaud N, Georges J. Investigation of the thermal lens effect in water-ethanol mixtures: composition dependence of the refractive index gradient, the enhancement factor and the Soret effect. SPECTROCHIMICA ACTA. PART A, MOLECULAR AND BIOMOLECULAR SPECTROSCOPY 2001; 57:1295-1301. [PMID: 11419472 DOI: 10.1016/s1386-1425(00)00465-0] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
The thermal lens effect produced in binary mixtures of water and ethanol has been investigated. It is shown that the sensitivity of the thermal lens method upon the addition of ethanol in water varies as the temperature-dependent refractive index gradient to thermal conductivity ratio of the mixture. The dependence of k and dn/dT upon the ethanol volume fraction follows a second-order and fourth-order polynomial, respectively, and cannot be precisely predicted using the additive rule. Moreover, depending on the experimental conditions and the mixture composition, the temperature gradient produced subsequently to relaxation of the excited species induces mutual migration of the solvent molecules and the formation of a concentration gradient in the irradiated area. This effect, known as the Soret effect, can locally change the thermo-optical properties of the solution and produce an additional signal, especially when steady-state experiments are done. This may result in errors as large as 20% when quantitative informations have to be derived from experimental data.
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Arnaud N, Georges J. Thermal lens spectrometry in aqueous solutions of Brij 35: investigation of micelle effects on the time-resolved and steady-state signals. SPECTROCHIMICA ACTA. PART A, MOLECULAR AND BIOMOLECULAR SPECTROSCOPY 2001; 57A:1085-1092. [PMID: 11374568 DOI: 10.1016/s1386-1425(00)00425-x] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
This work investigates the effect of micelles on the time-resolved and steady-state thermal lens signals in aqueous solutions. The temperature gradient produced subsequently to non-radiative relaxation of the sample induces migration of micelles towards the colder region of the irradiated area along with an opposite flow of solute molecules. This phenomenon, known as the Soret effect, produces an additional probe beam signal with a rise time that is much longer than the thermal time constant and depends on the surfactant and solute concentrations. Extrapolation of the mass-diffusion constant at zero solute concentration allowed the determination of diffusion coefficients that are close to those derived by other methods for Brij 35 micelles in water. It is also shown that the surfactant has only a small effect on the thermal lens signal and that the enhancement produced by micelles with respect to pure water originates mainly firom the Soret effect. It follows that interpretation of experimental data without discriminating both components of the probe beam signal can lead to erroneous values of dn/dT.
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Brennetot R, Georges J. Investigation of chelate formation, intramolecular energy transfer and luminescence efficiency and lifetimes in the Eu-thenoyltrifluoroacetone-trioctylphosphine oxide-Triton X-100 system using absorbance, fluorescence and photothermal measurements. SPECTROCHIMICA ACTA. PART A, MOLECULAR AND BIOMOLECULAR SPECTROSCOPY 2000; 56:703-715. [PMID: 10794445 DOI: 10.1016/s1386-1425(99)00175-4] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
The formation and the photophysical properties of the europium-thenoyltrifluoroacetone (TTA) trioctylphosphine oxide (TOPO)-Triton X-100 chelate were investigated. When the medium is buffered with acetate, there is a strong competition between acetate and TTA for coordination with europium ions. When TOPO is added into the solution, the Eu-TTA-TOPO ternary chelate forms more easily, probably because the coligand acts as a synergic agent and would favour the formation of the enol form of TTA. Although the stoichiometric composition of the chelate is expected to be Eu(TTA)3(TOPO)2, the Eu-TTA and the Eu-TOPO mole ratios may be within 2-3 and 1-2, respectively, depending on the composition of the solution. However, the fluorescent properties of the chelate seem to be mainly dominated by its actual concentration into the solution rather than by its composition. Time resolution of europium emission spectra in the microsecond range has shown that energy transfer occurs from the TTA ligand to the 5D1 level of europium. Then, the emitting 5D0 level is populated through non-radiative deactivation of 5D1. The observed lifetimes of the 5D1 and 5D0 states are 1.25 and 860 micros, respectively. The overall fluorescence quantum yield of the chelate, measured by the photothermal method, is found to be 0.22. On the basis of the time-resolved photothermal experiments, the fluorescence quantum yield of the 5D0 state is expected to be > 0.8 and the energy transfer efficiency < 0.28.
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Arnaud N, Georges J. Improved detection of salicylic acids using terbium-sensitized luminescence in aqueous micellar solutions of cetyltrimethylammonium chloride. Analyst 1999; 124:1075-8. [PMID: 10736862 DOI: 10.1039/a902195g] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The determination of salicylic, p-aminosalicylic and 5-fluorosalicylic acids was investigated using terbium-sensitized luminescence in aqueous solutions. Formation of a ternary chelate between terbium, EDTA and the salicylic acid requires dissociation of the phenol group which is adjacent to the dissociated carboxylic group. The reaction is obtained in alkaline solutions and is enhanced in the presence of cetyltrimethylammonium chloride. As evidenced by absorbance and fluorescence measurements, the cationic surfactant plays an important role in the formation of the ternary chelate and then terbium luminescence depends mainly on the extent of chelate formation. Linearity is found over more than four orders of magnitude and detection limits are in the range (2-4) x 10(-10) mol l-1 for the three acids.
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Brennetot R, Georges J. Transient absorption of the probe beam by the erythrosine triplet in pulsed-laser thermal lens spectrometry: the influence of the solvent, oxygen and dye concentration. Chem Phys Lett 1998. [DOI: 10.1016/s0009-2614(98)00385-6] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
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Jullien Y, Georges J, Sindt M, Schneider M, Mieloszynski JL, Paquer D. SYNTHÈSES D'ESTERS DITHIOPHOSPHORIQUES COMPORTANT LES FONCTIONS -SO2-OH ET-O-SO2-OH. PHOSPHORUS SULFUR 1998. [DOI: 10.1080/10426509808043594] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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Jullien Y, Georges J, Sindt M, Schneider M, Mieloszynski J, Paquer D. Synthèses D'esters Dithiophosphoriques Comportant Les Fonctions -SO 2-OH ET -O-SO 2-OH. PHOSPHORUS SULFUR 1998. [DOI: 10.1080/10426509808545458] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
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Fischer M, Georges J. Fluorescence quantum yield of rhodamine 6G in ethanol as a function of concentration using thermal lens spectrometry. Chem Phys Lett 1996. [DOI: 10.1016/0009-2614(96)00838-x] [Citation(s) in RCA: 281] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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Fischer M, Georges J. Prediction of the calibration curves for the analysis of high absorbances using mode-mismatched dual-beam thermal lens spectrometry with chopped continuous wave laser excitation. Anal Chim Acta 1996. [DOI: 10.1016/0003-2670(95)00531-5] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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38
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Georges J. Investigation of fluorescence efficiency in the europium-thenoyltrifluoroacetone chelate in aqueous and ethanolic solutions by laser-induced fluorescence and photothermal spectroscopic methods. Anal Chim Acta 1995. [DOI: 10.1016/0003-2670(95)00385-1] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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39
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Georges J. A single and simple mathematical expression of the signal for cw-laser thermal lens spectrometry. Talanta 1994; 41:2015-23. [DOI: 10.1016/0039-9140(94)00200-2] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/1994] [Accepted: 06/24/1994] [Indexed: 11/29/2022]
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Jarrett M, Heitkemper MM, Bond EF, Georges J. Comparison of diet composition in women with and without functional bowel disorder. Gastroenterol Nurs 1994; 16:253-8. [PMID: 8075160 DOI: 10.1097/00001610-199406000-00004] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
Nurses are often involved in helping patients alleviate chronic distressing gastrointestinal symptoms such as those associated with irritable bowel syndrome or functional bowel disorder. One therapeutic strategy is to increase dietary fiber intake and to eliminate gastrointestinal (GI) irritants such as caffeine, alcohol, and tobacco smoking. However, little work has been done to establish a relationship between dietary factors and chronic GI symptoms. In this article, the authors: (a) describe and compare caloric and dietary constituent intake in symptomatic (n = 18) and asymptomatic (n = 37) women, and (b) examine the relationships among diet, GI symptoms, and stool characteristics in the two groups. In particular, total calories, fiber, fat, protein, and carbohydrates as well as alcohol and caffeine intakes were compared in women who do not smoke. Because menstrual cycle phase modulates both symptoms and appetite, women were studied during the follicular phase. Groups had similar caloric, fat, and protein intakes. Fiber intakes were similar and similar to national norms in both groups. When compared with asymptomatic women, the symptomatic women consumed more refined carbohydrates. Relationships were observed among dietary intake of refined carbohydrates, fiber, GI symptoms, and stool characteristics in women with functional bowel disorder.
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Arnaud N, Drevet S, Georges J. Effect of surfactants in the determination of orotic acid in aqueous solutions by sensitized terbium fluorescence. Analyst 1994. [DOI: 10.1039/an9941902453] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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42
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Chartier A, Georges J. Liquid chromatographic determination of carotenoids using dual-beam continuous-wave laser thermal lens detection. Anal Chim Acta 1993. [DOI: 10.1016/0003-2670(93)85315-b] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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43
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Georges J, Ghazarian S. Study of europium-sensitized fluorescence of tetracycline in a micellar solution of Triton X-100 by fluorescence and thermal lens spectrometry. Anal Chim Acta 1993. [DOI: 10.1016/0003-2670(93)80411-d] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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44
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Chartier A, Fox CG, Georges J. Evaluation of thermal lens detection in flow injection with high background absorbance. Analyst 1993. [DOI: 10.1039/an9931800157] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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45
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Georges J. Lanthanide-sensitized luminescence and applications to the determination of organic analytes. A review. Analyst 1993. [DOI: 10.1039/an9931801481] [Citation(s) in RCA: 127] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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46
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Chartier A, Georges J, Mermet J. Limitation of the thermal-lens method in fluorescence quantum-yield measurements. Chem Phys Lett 1990. [DOI: 10.1016/0009-2614(90)85375-m] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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47
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Chartier A, Georges J, Mermet J. Abnormal signals in thermal lens spectrophotometry: Determination of the triplet lifetime of erythrosine. ACTA ACUST UNITED AC 1990. [DOI: 10.1016/0584-8539(90)80245-t] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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48
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Georges J, Chen JW. Microemulsions studies: Correlation between viscosity, electrical conductivity and electrochemical and fluorescent probe measurements. Colloid Polym Sci 1986. [DOI: 10.1007/bf01410641] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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49
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Georges J, Desmettre S, PORTHAULT M. PHYSICO-CHEMICAL AND TRANSPORT PROPERTIES OF DODECANE-IN-WATER EMULSIONS STABILIZED WITH IONIC AND NONIONIC SURFACTANTS. J DISPER SCI TECHNOL 1986. [DOI: 10.1080/01932698608943447] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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50
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Georges J, Mermet M. Simultaneous determination of tin and lead by anodic stripping voltammetry with addition of surfactant. Anal Chim Acta 1986. [DOI: 10.1016/0003-2670(86)80068-x] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
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