L. Peschier - Academia.edu (original) (raw)
Papers by L. Peschier
In the investigation of arson, evidence connecting a suspect to the fire scene may be obtained by... more In the investigation of arson, evidence connecting a suspect to the fire scene may be obtained by comparing the composition of ignitable liquid residues found at the crime scene to ignitable liquids found in possession of the suspect. Interpreting the result of such a comparison is hampered by processes at the crime scene that result in evaporation, matrix interference, and microbial degradation of the ignitable liquid. Most commonly, gasoline is used as a fire accelerant in arson. In the current scientific literature on gasoline comparison, classification studies are reported for unevaporated and evaporated gasoline residues. In these studies the goal is to discriminate between samples of several sources of gasoline, based on a chemical analysis. While in classification studies the focus is on discrimination of gasolines, for forensic purposes a likelihood ratio approach is more relevant. In this work, a first step is made towards the ultimate goal of obtaining numerical values for the strength of evidence for the inference of identity of source in gasoline comparisons. Three likelihood ratio methods are presented for the comparison of evaporated gasoline residues (up to 75% weight loss under laboratory conditions). Two methods based on distance functions and one multivariate method were developed. The performance of the three methods is characterized by rates of misleading evidence, an analysis of the calibration and an information theoretical analysis. The three methods show strong improvement of discrimination as compared with a completely uninformative method. The two distance functions perform better than the multivariate method, in terms of discrimination and rates of misleading evidence.
Journal of Magnetic Resonance, Series B, 1996
Water diffusion in poly [2-hydroxyethyl-methacrylate] hydrogels has been measured by PFG NMR tech... more Water diffusion in poly [2-hydroxyethyl-methacrylate] hydrogels has been measured by PFG NMR techniques, using both spin-echo and stimulated-echo methods. It is found that the results differ when evaluated using the standard equations for the echo attenuation. ...
International Journal of Pharmaceutics, 1989
In this study the thermal behaviour of human stratum cotneum is investigated using N-alkyl-azacyc... more In this study the thermal behaviour of human stratum cotneum is investigated using N-alkyl-azacycloheptan-2-one with a varying number of carbon atoms in the alkyl chain. Throughout this article these substances will be referred to as C, azones, in which n stands for the number of C atoms in the alkyl chain. The experiments have been carried out using differential thermal analysis (DTA). Untreated stratum corneum shows 4 transitions of which 3 are reversible and one is irreversible. The latter is due to protein denaturation, the former are due to gel-liquid state transitions of the lipids. Treatment with C, azones in combination with propylene glycol shifts the lipid transition peaks, normally found at 345K and 360K, to lower temperatures; treatment with C,, azone decreases the enthalpy involved in the transitions, whereas treatment with C, azone affects only the temperature of two transitions and not the enthalpy. A decrease in enthalpy is related to an increase in fluidity of the lipid bilayers; there seems to be a close parallel between the change in enthalpy and the change in permeability of stratum comeum.
Polymer, 1989
ABSTRACT A series of copolymers of 2-hydroxyethyl methacrylate (HEMA) and methacrylic acid (MAA) ... more ABSTRACT A series of copolymers of 2-hydroxyethyl methacrylate (HEMA) and methacrylic acid (MAA) were selected as possible carrier systems for controlled drug delivery. The tacticity of these copolymers averaged 60% syndiotacticity and 40% heterotacticity when prepared with 2,2,azobisisobutyronitrile (AIBN) at 70°C (pH c. 3.5). The presence of poly(ethylene glycol)400 (PEG 400) in the reaction mixture seemed to have only a minimal effect (at a low pH) on the polymerization reaction. In contrast, an increase in the pH gave a tendency towards heterotacticity and had an enormous effect on the reactivity ratios. The r values change from r(1) 1.50 and r(2) 0.67 to r(1) 13.8 and r(2) 0.07 for HEMA and MAA respectively. These changes affect the copolymer composition and thus the rate of drug release from the polymeric drug delivery systems made from these copolymers.
Pharmaceutisch Weekblad Scientific Edition, 1986
Pharmaceutisch Weekblad Scientific Edition, 1988
Journal of Controlled Release, 1989
A new coated controlled-release tablet for oxprenolol using microporous polypropylene powder (Acc... more A new coated controlled-release tablet for oxprenolol using microporous polypropylene powder (AccureF") as an excipient is presented. Core matrix tablets embedding the drug were dry coated by a mixture of microporous polypropylene powder and a small amount of oxprenolol as a loading dose. Due to the microporous coat the rate of release of oxprenolol could be accurately controlled. However, because of the hydrophobic nature of the polypropylene powder, both wetting problems and food interactions had to be solved. Sodium laurylsulphate (SLS) was selected as a wetting agent and was adsorbed on the surface of the porous polymeric powder. The amount of SLS adsorbed was quantified by both solution depletion and desorption experiments. The optimized tablets were tested in a new in vitro food simulation test, using well-defined medical liquid food as dissolution medium; they clearly showed the absence of food interactions. In order to properly validate the in vivo behaviour of the tablets the same liquid food was used in an in vivo pilot study in which six male volunteers took the new tablet with and without the liquid food. Both plasma and saliva samples were collected during the experiments. Neither the amount absorbed nor the calculated absorption profiles of oxprenolol were significantly affected by the presence of the liquid food. The bio-availability at 12 hours was 38 5 19% on an empty stomach and 37+20% for the food experiment. The absorption profiles together with the saliva samples implicate a continuation of the absorption beyond 12 hours, suggesting that oxprenolol is also absorbed from these tablets in the large intestines. The oxprenolol concentration in the saliva samples did not show any relationship to the plasma concentrations. Saliva samples are unfit for predicting oxprenolol plasma levels. 0168-3659/89/$03.50 0 1989 Elsevier Science Publishers B.V.
![Research paper thumbnail of Water mobility and structure in poly[2-hydroxyethylmethacrylate] hydrogels by means of the pulsed field gradient NMR technique](https://attachments.academia-assets.com/52401161/thumbnails/1.jpg)
](Biomaterials, 1993
(pHEMA) hydrogels, cross-linked with ethyleneglycoldimethac~iate, was studied by means of the pul... more (pHEMA) hydrogels, cross-linked with ethyleneglycoldimethac~iate, was studied by means of the pulsed field gradient (PFG) nuclear magnetic resonance (NMR) technique, which offers the opportunity to study the molecular displacements directly under well-defined equilibrium conditions, resulting in a determination of the self-diffusion coefficient. It is possible to check whether coexisting water phases with different mobilities (on a timescale of ca. 10 ms) are present. The dependence of the diffusion coefficient of water on the degree of hydration and the cross-linker concentration was measured. Magnetic interaction is found to cause cross-relaxation between the protons of water and those of the polymer matrix. This affects the data, rendering the evaluation by the standard equation invalid. An equation taking cross-relaxation into account has been derived. Amplitude measurements have shown that all the water in the gels contributes to the NMR signal. The PFG measurements have shown that the total water phase in a gel diffuses as one homogeneous phase, which can be characterized by a diffusion coefficient. The self-diffusion coefficient is strongly dependent on the degree of hydration of the gel; the cross-linker concentration has no measurable effect. The strong dependence of the diffusion of water on its concentration in the gel has consequences for the modelling of the swelling and drug-release dynamics of pHEMA and necessitates a revision of the present models describing these processes.
Science & justice : journal of the Forensic Science Society, 2014
In the investigation of arson, evidence connecting a suspect to the fire scene may be obtained by... more In the investigation of arson, evidence connecting a suspect to the fire scene may be obtained by comparing the composition of ignitable liquid residues found at the crime scene to ignitable liquids found in possession of the suspect. Interpreting the result of such a comparison is hampered by processes at the crime scene that result in evaporation, matrix interference, and microbial degradation of the ignitable liquid. Most commonly, gasoline is used as a fire accelerant in arson. In the current scientific literature on gasoline comparison, classification studies are reported for unevaporated and evaporated gasoline residues. In these studies the goal is to discriminate between samples of several sources of gasoline, based on a chemical analysis. While in classification studies the focus is on discrimination of gasolines, for forensic purposes a likelihood ratio approach is more relevant. In this work, a first step is made towards the ultimate goal of obtaining numerical values for...
In the investigation of arson, evidence connecting a suspect to the fire scene may be obtained by... more In the investigation of arson, evidence connecting a suspect to the fire scene may be obtained by comparing the composition of ignitable liquid residues found at the crime scene to ignitable liquids found in possession of the suspect. Interpreting the result of such a comparison is hampered by processes at the crime scene that result in evaporation, matrix interference, and microbial degradation of the ignitable liquid. Most commonly, gasoline is used as a fire accelerant in arson. In the current scientific literature on gasoline comparison, classification studies are reported for unevaporated and evaporated gasoline residues. In these studies the goal is to discriminate between samples of several sources of gasoline, based on a chemical analysis. While in classification studies the focus is on discrimination of gasolines, for forensic purposes a likelihood ratio approach is more relevant. In this work, a first step is made towards the ultimate goal of obtaining numerical values for the strength of evidence for the inference of identity of source in gasoline comparisons. Three likelihood ratio methods are presented for the comparison of evaporated gasoline residues (up to 75% weight loss under laboratory conditions). Two methods based on distance functions and one multivariate method were developed. The performance of the three methods is characterized by rates of misleading evidence, an analysis of the calibration and an information theoretical analysis. The three methods show strong improvement of discrimination as compared with a completely uninformative method. The two distance functions perform better than the multivariate method, in terms of discrimination and rates of misleading evidence.
Journal of Magnetic Resonance, Series B, 1996
Water diffusion in poly [2-hydroxyethyl-methacrylate] hydrogels has been measured by PFG NMR tech... more Water diffusion in poly [2-hydroxyethyl-methacrylate] hydrogels has been measured by PFG NMR techniques, using both spin-echo and stimulated-echo methods. It is found that the results differ when evaluated using the standard equations for the echo attenuation. ...
International Journal of Pharmaceutics, 1989
In this study the thermal behaviour of human stratum cotneum is investigated using N-alkyl-azacyc... more In this study the thermal behaviour of human stratum cotneum is investigated using N-alkyl-azacycloheptan-2-one with a varying number of carbon atoms in the alkyl chain. Throughout this article these substances will be referred to as C, azones, in which n stands for the number of C atoms in the alkyl chain. The experiments have been carried out using differential thermal analysis (DTA). Untreated stratum corneum shows 4 transitions of which 3 are reversible and one is irreversible. The latter is due to protein denaturation, the former are due to gel-liquid state transitions of the lipids. Treatment with C, azones in combination with propylene glycol shifts the lipid transition peaks, normally found at 345K and 360K, to lower temperatures; treatment with C,, azone decreases the enthalpy involved in the transitions, whereas treatment with C, azone affects only the temperature of two transitions and not the enthalpy. A decrease in enthalpy is related to an increase in fluidity of the lipid bilayers; there seems to be a close parallel between the change in enthalpy and the change in permeability of stratum comeum.
Polymer, 1989
ABSTRACT A series of copolymers of 2-hydroxyethyl methacrylate (HEMA) and methacrylic acid (MAA) ... more ABSTRACT A series of copolymers of 2-hydroxyethyl methacrylate (HEMA) and methacrylic acid (MAA) were selected as possible carrier systems for controlled drug delivery. The tacticity of these copolymers averaged 60% syndiotacticity and 40% heterotacticity when prepared with 2,2,azobisisobutyronitrile (AIBN) at 70°C (pH c. 3.5). The presence of poly(ethylene glycol)400 (PEG 400) in the reaction mixture seemed to have only a minimal effect (at a low pH) on the polymerization reaction. In contrast, an increase in the pH gave a tendency towards heterotacticity and had an enormous effect on the reactivity ratios. The r values change from r(1) 1.50 and r(2) 0.67 to r(1) 13.8 and r(2) 0.07 for HEMA and MAA respectively. These changes affect the copolymer composition and thus the rate of drug release from the polymeric drug delivery systems made from these copolymers.
Pharmaceutisch Weekblad Scientific Edition, 1986
Pharmaceutisch Weekblad Scientific Edition, 1988
Journal of Controlled Release, 1989
A new coated controlled-release tablet for oxprenolol using microporous polypropylene powder (Acc... more A new coated controlled-release tablet for oxprenolol using microporous polypropylene powder (AccureF") as an excipient is presented. Core matrix tablets embedding the drug were dry coated by a mixture of microporous polypropylene powder and a small amount of oxprenolol as a loading dose. Due to the microporous coat the rate of release of oxprenolol could be accurately controlled. However, because of the hydrophobic nature of the polypropylene powder, both wetting problems and food interactions had to be solved. Sodium laurylsulphate (SLS) was selected as a wetting agent and was adsorbed on the surface of the porous polymeric powder. The amount of SLS adsorbed was quantified by both solution depletion and desorption experiments. The optimized tablets were tested in a new in vitro food simulation test, using well-defined medical liquid food as dissolution medium; they clearly showed the absence of food interactions. In order to properly validate the in vivo behaviour of the tablets the same liquid food was used in an in vivo pilot study in which six male volunteers took the new tablet with and without the liquid food. Both plasma and saliva samples were collected during the experiments. Neither the amount absorbed nor the calculated absorption profiles of oxprenolol were significantly affected by the presence of the liquid food. The bio-availability at 12 hours was 38 5 19% on an empty stomach and 37+20% for the food experiment. The absorption profiles together with the saliva samples implicate a continuation of the absorption beyond 12 hours, suggesting that oxprenolol is also absorbed from these tablets in the large intestines. The oxprenolol concentration in the saliva samples did not show any relationship to the plasma concentrations. Saliva samples are unfit for predicting oxprenolol plasma levels. 0168-3659/89/$03.50 0 1989 Elsevier Science Publishers B.V.
Biomaterials, 1993
(pHEMA) hydrogels, cross-linked with ethyleneglycoldimethac~iate, was studied by means of the pul... more (pHEMA) hydrogels, cross-linked with ethyleneglycoldimethac~iate, was studied by means of the pulsed field gradient (PFG) nuclear magnetic resonance (NMR) technique, which offers the opportunity to study the molecular displacements directly under well-defined equilibrium conditions, resulting in a determination of the self-diffusion coefficient. It is possible to check whether coexisting water phases with different mobilities (on a timescale of ca. 10 ms) are present. The dependence of the diffusion coefficient of water on the degree of hydration and the cross-linker concentration was measured. Magnetic interaction is found to cause cross-relaxation between the protons of water and those of the polymer matrix. This affects the data, rendering the evaluation by the standard equation invalid. An equation taking cross-relaxation into account has been derived. Amplitude measurements have shown that all the water in the gels contributes to the NMR signal. The PFG measurements have shown that the total water phase in a gel diffuses as one homogeneous phase, which can be characterized by a diffusion coefficient. The self-diffusion coefficient is strongly dependent on the degree of hydration of the gel; the cross-linker concentration has no measurable effect. The strong dependence of the diffusion of water on its concentration in the gel has consequences for the modelling of the swelling and drug-release dynamics of pHEMA and necessitates a revision of the present models describing these processes.
Science & justice : journal of the Forensic Science Society, 2014
In the investigation of arson, evidence connecting a suspect to the fire scene may be obtained by... more In the investigation of arson, evidence connecting a suspect to the fire scene may be obtained by comparing the composition of ignitable liquid residues found at the crime scene to ignitable liquids found in possession of the suspect. Interpreting the result of such a comparison is hampered by processes at the crime scene that result in evaporation, matrix interference, and microbial degradation of the ignitable liquid. Most commonly, gasoline is used as a fire accelerant in arson. In the current scientific literature on gasoline comparison, classification studies are reported for unevaporated and evaporated gasoline residues. In these studies the goal is to discriminate between samples of several sources of gasoline, based on a chemical analysis. While in classification studies the focus is on discrimination of gasolines, for forensic purposes a likelihood ratio approach is more relevant. In this work, a first step is made towards the ultimate goal of obtaining numerical values for...