Biomedical subjects

L Dupont

Publications and source records attributed to L Dupont.

At least 19 recordsLinked to original sources

PubMed2006

Nano-polymer-dispersed liquid crystal as phase modulator for a tunable vertical-cavity surface-emitting laser at 1.55 mum.

We demonstrate what we believe is the first nonmechanical tunable vertical-cavity surface-emitting laser operating in the C band. This was achieved as a result of the combination of an InGaAs quantum well structure with a 6lambda thickness tunable index nano-polymer-dispersed liquid-crystal material. Experimental results exhibited a potential tunable range close to 10 nm, in the preliminary version, and excellent single mode locking due to the side-mode suppression ratio (more than 20 dB) over the whole spectral range. Another decisive advantage, compared to mechanical solutions, was the tuning response time of a few tens of microseconds (>30 micros) to scan the full spectral range (10 nm), making this device appropriate for some access network functions, as well as being robust and low cost. The voltage values are the main limitation to wavelength range extension. We present a first version of the device optically pumped. The next version will be electrically pumped as required for the access network applications targeted here.

Journal Article↗

PubMed2006

Explosion characteristics of synthesised biogas at various temperatures.

Biogas is considered as a valuable source of renewable energy. Indeed, it can be turned into useful energy (heat, electricity, fuel) and can contribute to reduce greenhouse gas emissions. Knowledge of its safety characteristics is a very important practical issue. Experimental investigation of synthesised biogas explosion characteristics was conducted in a 20-L sphere at various temperatures (30-70 degrees C) and at atmospheric pressure. The studied biogas was made of 50% methane (CH(4)) and 50% carbon dioxide (CO(2)). It was also saturated with humidity: this composition is frequently met in digesters during waste methanisation. There are two inert gases in biogas: water vapour and carbon dioxide. Its vapour water content rises along with temperature. The presence of these inert gases modifies considerably biogas characteristics compared to the ones of pure methane: explosion limits are lowered and beyond 70 degrees C, water vapour content is sufficient to inert the mixture. Furthermore, explosion violence (estimated with the maximum rate of pressure rise values, (dp/dt)(max)) is three times lower for biogas than for pure methane at ambient temperature.

Algorithms↗

PubMed2006

Listeria pleuritis 1 week after lung transplantation.

Listeria monocytogenes is an important bacterial pathogen in immunocompromised patients, the elderly, pregnant women and transplant patients, but until now it has not been reported in lung transplants. We report the first case of listeriosis in a lung transplant recipient who presented with a pleural effusion 8 days after transplantation. After the introduction of a thorax drain and the administration of intravenous antibiotics during 3 weeks, the patient recovered completely. This case highlights the increased risk for uncommon respiratory infections in lung transplant patients and examines the specific management of listeria pleuritis.

Ampicillin↗

PubMed2006

Gregariousness and protandry promote reproductive insurance in the invasive gastropod Crepidula fornicata: evidence from assignment of larval paternity.

According to the size-advantage hypothesis, protandric sequential hermaphroditism is expected when the increase in reproductive success with age or size is small for males but large for females. Interestingly, some protandrous molluscs have developed gregarious strategies that might enhance male reproductive success but at the cost of intraspecific competition. The gastropod Crepidula fornicata, a European invading species, is ideal for investigating mating patterns in a sequential hermaphrodite in relation to grouping behaviour because individuals of different size (age) live in perennial stacks, fertilization is internal and embryos are brooded. Paternity analyses were undertaken in stacks sampled in three close and recently invaded sites in Brittany, France. Paternity assignment of 239 larvae, sampled from a set of 18 brooding females and carried out using five microsatellite loci, revealed that 92% of the crosses occurred between individuals located in the same stack. These stacks thus function as independent mating groups in which individuals may reproduce consecutively as male and female over a short time period, a pattern explained by sperm storage capacity. Gregariousness and sex reversal are promoting reproductive insurance in this species. In addition, females are usually fertilized by several males (78% of the broods were multiply sired) occupying any position within the stack, a result reinforcing the hypothesis of sperm competition. Our study pointed out that mating behaviours and patterns of gender allocation varied in concert across sites suggesting that multiple paternities might enhance sex reversal depending on sperm competition intensity.

Animals↗

PubMed2006

Evaluating the "Leeds criteria" for Pseudomonas aeruginosa infection in a cystic fibrosis centre.

Four separate categories of chronic Pseudomonas aeruginosa (Pa) infection in children with cystic fibrosis (CF) have been previously defined, based on airway cultures taken over the previous year. The aim of the present study was to evaluate this definition in the current authors' paediatric and adult CF clinic using clinical, immunological and lung function parameters. During follow-up, out of 193 patients, 55 (34%) CF patients had never been infected with Pa, 27 (17%) were free of Pa, 29 (18%) were intermittently infected and 51 (31%) were chronically infected. Disease severity markers, such as lung function, were significantly worse in the chronic group, especially in the paediatric population. Differences in adult patients were smaller and no longer significant. Pa antibodies differed strongly between the groups, and were very high (mean+/-sd 55.4+/-5.5) and highly statistically significant from all other groups in the chronic group. They were low and different from all other groups in the never group (1.8+/-0.6). Pa antibodies did not differ between the free of Pa and the intermittent group. In conclusion, the current authors confirmed an agreement between Pseudomonas aeruginosa status according to the new definition and clinical status, as well as with the level of Pseudomonas aeruginosa antibodies.

Adolescent↗

PubMed2006

To transplant or not? The importance of psychosocial and behavioural factors before lung transplantation.

The gratifying results of lung transplantation in terms of survival and quality of life stimulate the referral of an ever-increasing number of patients with end-stage lung disease. This in turn compounds the organ shortage, which is the limiting factor in the transplantation rate. In the absence of good alternative treatment modalities, an evidence-based pretransplant screening process is a prerequisite to determine which patients will benefit most from transplantation. Within this evidence-based screening process, medical selection criteria are well established. There is a growing awareness that psychosocial and behavioural factors may determine outcome after transplantation as well. This paper reviews the available evidence for psychosocial and behavioural factors in the screening process for lung transplantation. The relation of various factors with post-transplant outcome was explored. Psychosocial characteristics before transplantation consist of 1) anxiety and depression, 2) personality disorders, 3) neurocognitive problems, and 4) lack of social support. Pretransplant behavioural factors include 1) noncompliance with medication, 2) alcohol abuse or dependence, 3) smoking, 4) noncompliance with dietary guidelines, and 5) noncompliance with monitoring of vital parameters and infections. It appears that the lack of rigorous studies limit the feasibility of an evidence-based screening process. Prospective studies are crucial to this further investigation of the relationship between psychosocial and behavioural determinants before transplantation and outcomes after transplantation, in terms of compliance, morbidity, and mortality. Identification of modifiable risk factors for poor outcome before transplantation is a first step in developing interventions.

Alcoholism↗

PubMed2005

Rapid screening of DOM's metal-binding ability using a fluorescence-based microplate assay.

This note describes the development of a method to rapidly quantify the metal-binding ability of low-volume DOM samples based on their fluorescence properties. The method uses 96-well microplates to screen the fluorescence quenching observed when increasing concentrations of various metals are added to the pH-buffered DOM sample. Only 1.6 mL of DOM sample is required to quantify the binding affinity for each metal and the result is obtained in a few minutes. This study presents results for a surface soil DOM sample for which binding was assessed for Cu2+, Fe2+, Ni2+ at pH 5 and 9.

Carbon↗

PubMed2005

Weakly acidic reflux in patients with chronic unexplained cough during 24 hour pressure, pH, and impedance monitoring.

BACKGROUND AND AIMS: Acid gastro-oesophageal reflux is one of the most important causes of chronic cough. The response to acid suppression in these patients is not as good as in patients with heartburn but improvement with antireflux surgery has been reported, suggesting the involvement of a non-acidic gastric component in the refluxate. Less acidic reflux may produce symptoms such as regurgitation or chest pain. We investigated whether chronic cough might be associated with weakly acidic reflux. METHODS: We studied 28 patients with chronic cough using 24 hour ambulatory pressure-pH-impedance monitoring. Manometry was used for precise recognition of cough and impedance-pHmetry to detect acid (pH <4), weakly acidic (pH 7-4), and weakly alkaline (impedance drops, pH >/=7) reflux. A symptom association probability (SAP) analysis was performed for each type of reflux. RESULTS: Analysis was completed in 22 patients with 24 cough events (5-92)/patient. The majority of cough events (69.4%) were considered "independent" of reflux whereas 30.6% occurred within two minutes of a reflux episode. Half of these (49%) were "reflux cough" sequences, involving acid (65%), weakly acidic (29%), and weakly alkaline (6%) reflux. Ten patients (45%) had a positive SAP between reflux and cough: five with acid, two with acid and weakly acidic, and three only with weakly acidic reflux. CONCLUSIONS: Ambulatory pressure-pH-impedance monitoring with SAP analysis allowed precise determination of the temporal association between cough and gastro-oesophageal reflux (acid, weakly acidic, and weakly alkaline) and identification of a subgroup of patients with chronic cough clearly associated with weakly acidic gastro-oesophageal reflux.

Adult↗

PubMed2004

Effects of spontaneously chosen crank rate variations on electromyographic responses in sub-maximal arm exercise in inexperienced subjects.

The aim of the present study was to compare electromyographic responses during arm exercises with a crank rate chosen spontaneously ( T(S)) or set at 20% below or above ( T(-20), T(+20)) the spontaneously chosen crank rate (SCCR). Ten male physical education students performed arm exercises with intensities ranging from 20% to 80% of maximal power. Muscular activity levels were analysed for the biceps brachii and the triceps brachii muscles using integrated rectified surface electromyography (iEMG). All values were presented as the mean and standard deviation. During T(S), the sum of iEMG for the two muscles studied was significantly ( P<0.05) lower than during T(+20) for each power output. No significant differences were observed in iEMG values between T(S) and T(-20). The hypothesis that SCCR relates to a minimisation of muscle activation during an upper body exercise was not confirmed. Variations superior or inferior to a 20% increase of the iEMG responses do not influence it. Moreover, the selection of crank rates depends on the power output and the SCCR increased significantly ( P<0.05) with increasing power output.

Adult↗

PubMed2003

A reversible copper extrusion-insertion electrode for rechargeable Li batteries.

Although widely used, the most promising Li-based technologies still suffer from a lack of suitable electrodes. There is therefore a need to seek new materials concepts to satisfy the increasing demands for energy storage worldwide. Here we report on a new layered electrode material, Cu(2.33)V(4)O(11), which shows a sustainable reversible capacity of 270 mA h g(-1) at a voltage of about 2.7 V, and electrochemically reacts with Li in an unusual and spectacular way. The reaction entails a reversible Li-driven displacement process leading to the growth and disappearance of Cu dendrites with a concomitant reversible decomposition and recrystallization of the initial electrode material. We show from structural considerations that the uniqueness of Cu(2.33)V(4)O(11) is rooted in the peculiar flexibility of the stacked [V(4)O(11)](n) layers, which is due to the presence of pivot oxygen atoms. Fully reversible displacement reactions could provide a new direction for developing an alternative class of higher energy density Li storage electrodes.

Copper↗

PubMed2003

Removal of hexavalent chromium with a lignocellulosic substrate extracted from wheat bran.

In this paper, a new recovery system of the toxic hexavalent chromium Cr(VI) is proposed that uses a lignocellulosic substrate derived from the industrial treatment process of wheat bran. We studied the adsorption mechanism of Cr(VI) onto the lignocellulosic substrate and showed that the adsorption reaction consumes a large amount of protons goes along the reduction of Cr(VI) into Cr(III). The oxidation of lignin moieties takes place concurrently to the chromium reduction and leads to the formation of hydroxyl and carboxyl functions. The latter contribute to an increase in the number of ion-exchange sites for the reduced chromium. The maximum adsorption capacity for hexavalent chromium was found at about 35 mg g(-1) in an acidic medium. This is comparable to other natural substrates and ordinary adsorbents.

Adsorption↗

PubMed2003

Metal ions binding onto a lignocellulosic substrate extracted from wheat bran: a NICA-Donnan approach.

In this study ion binding to solid organic matter was investigated. We used the NICA-Donnan model to describe the interaction between Cu(II), Pb(II), and Cd(II) ions and a lignocellulosic substrate extracted from wheat bran. Such a material represents a very cheap and flexible substrate, which can be used as a natural filter to remove toxic metal ions from industrial effluents or applied in the decontamination and rehabilitation of abandoned industrial sites. Moreover, such a material also represents a very simple model of natural organic matter derived from lignin and cellulose, for which there is now a lack of thermodynamic data as far as their interaction with toxic metal ions is concerned. Experimental results were obtained in various conditions of pH and ionic strength. In our modeling, we used the acidity constants and the concentration of sites that were determined in a previous work. The parameters deduced from the NICA-Donnan model were also compared to thermodynamic data available for other cases of natural organic matter, mainly humic substances.

Adsorption↗

PubMed2003

Maximal lactate steady state, respiratory compensation threshold and critical power.

Critical power (CP) and the second ventilatory threshold (VT(2)) are presumed to indicate the power corresponding to maximal lactate steady state (MLSS). The aim of this study was to investigate the use of CP and VT(2) as indicators of MLSS. Eleven male trained subjects [mean (SD) age 23 (2.9) years] performed an incremental test (25 W.min(-1)) to determine maximal oxygen uptake (.VO(2max)), maximal aerobic power (MAP) and the first and second ventilatory thresholds (VT(1) and VT(2)) associated with break points in minute ventilation (.V(E)), carbon dioxide production (.VCO(2)), .V(E)/.VCO(2) and .V(E)/.VO(2) relationships. Exhaustion tests at 90%, 95%, 100% and 110% of .VO(2max), and several 30-min constant work rates were performed in order to determine CP and MLSS, respectively. MAP and .VO(2max) values were 344 (29) W and 53.4 (3.7) ml.min(-1).kg(-1), respectively. CP [278 (22) W; 85.4 (4.8)% .VO(2max)] and VT(2) power output [286 (28) W; 85.3 (5.6)% .VO(2max)] were not significantly different (p=0.96) but were higher (p<0.05) than the MLSS work rate [239 (21) W; 74.3 (4.0)% .VO(2max)] and VT(1) power output [159 (23) W; 52.9 (6.9)% .VO(2max)]. MLSS work rate was significantly correlated (p<0.05) with those noted at VT(1) and VT(2) (r=0.74 and r=0.93, respectively). VT(2) overestimated MLSS by 10.9 (6.3)% .VO(2max), which was significantly higher than VT(1) [+21.4 (5.6)% .VO(2max); p<0.01]. CP calculated from a given range of exhaustion times does not correspond to MLSS.

Adaptation, Physiological↗

PubMed2003

Maximal lactate steady state does not correspond to a complete physiological steady state.

The purpose of this study was to verify whether the maximal lactate steady state (MLSS) corresponds to a physiological steady state. Eight male trained subjects performed a 30-min test on a cycle ergometer at a constant power corresponding to their own MLSS which had been previously determined. No significant variation was observed between the 10th and the 30th min for arterial lactate concentration, redox state, arterial oxygen pressure, arterial oxygen saturation, bicarbonates concentration, base excess, hematocrit, hemoglobin concentration, plasma volume, oxygen uptake, carbon dioxide output, gas exchange ratio, minute ventilation, ventilatory equivalents for oxygen and carbon dioxide, and arterial systolic blood pressure values. However, arterial carbon dioxide pressure and pH values were significantly different between the 10th and the 30th min (p < 0.01). Respiratory rate values and heart rate significantly increased (p < 0.01). These results indicate that MLSS does not correspond to a complete physiological steady state.

Adaptation, Physiological↗

PubMed2002

Characterization and comparison of two ligno-cellulosic substrates by (13)C CP/MAS NMR, XPS, conventional pyrolysis and thermochemolysis.

Ligno-cellulosic substrates (LCSs) isolated from wheat straw and bran exhibit high complexing capacities and may have important applications for metal removal from industrial effluents. These two LCSs were examined in the present work by spectroscopic and pyrolytic methods (solid state cross polarization magic angle spinning (CP/MAS) (13)C NMR, XPS, conventional Curie pyrolysis (Cupy)/GC/MS, and TMAH thermochemolysis/GC/MS). This combined study highlighted the limitation of some of the above methods when applied to ligno-cellulosic materials and the resulting biases and the usefulness of TMAH thermochemolysis. A large difference in composition was observed between bran- and straw-LCS due to a much higher contribution of alkyl moieties in the former. These moieties correspond to fatty acids esterified to the ligno-cellulosic macromolecular structure and such carboxylic functions should play an important role for metal complexation.

Journal Article↗

PubMed2002

Use of a NICA-Donnan approach for analysis of proton binding to a lignocellulosic substrate extracted from wheat bran.

The acid-base properties of a lignocellulosic substrate extracted from wheat bran have been investigated. The lignocellulosic substrate was first studied by use of FTIR, XPS, and solid-state 13C NMR to characterize the surface-active groups. Major contributions arise from the presence of carboxylic and phenolic sites. The former are associated with long-chain fatty acids and the latter are constituent units of lignin. All ionizable sites were quantified by use of the Ca-acetate method and by potentiometric titrations in non-aqueous media. Results were compared with those from conductimetric titrations in water and in the presence of barium ions. Protometric titration curves for the lignocellulosic substrate were obtained at several ionic strengths. Data were also treated with the NICA-Donnan model to determine the intrinsic ionization parameters.

Cellulose↗

PubMed2002

Spontaneously chosen crank rate variations in submaximal arm exercise with inexperienced subjects. Effects on cardiorespiratory and efficiency parameters.

The aim of the present study was to compare the physiological responses during arm exercises when the crank rate was chosen spontaneously (TS) or set at +/- 20 % (T-20, T+ 20) of the spontaneously chosen crank rate (SCCR). Eight physical education male students, aged 22 +/- 3.2 years, performed an upper body exercise in which intensities ranged from unload to 80 % of maximal power. No significant difference was observed in oxygen uptake, ventilation, gross and net efficiency values between TS and T+ 20 or T-20. Nevertheless, oxygen uptake and ventilation were significantly (p < 0.05) lower and gross and net efficiencies higher (p < 0.05) during T-20 than T+ 20. No significant difference was noticed for heart rate, delta and work efficiency between TS, T-20 and T+ 20. The hypothesis that SCCR is the most economical one according to the efficiency parameters was not quite verified. However, crank rates lower than SCCR could be interesting because they increase gross efficiency compared to higher crank rates. Moreover, the selection of crank rates depends on power output. Indeed, SCCR increased significantly (p < 0.05) with power output. In the physical reconditioning of injured or handicapped subjects, the latter are very sensitive to the power output, and the crank rate could be another constraint.

Adult↗

PubMed2001

Original 2-alkylamino-6-halogenoquinazolin-4(3H)-ones and K(ATP) channel activity.

A series of 6-substituted 2-alkylaminoquinazolin-4(3H)-ones structurally related to 3-alkylamino-4H-pyrido[4,3-e]-1,2,4-thiadiazine 1,1-dioxides were synthesized and tested as putative K(ATP) channel openers on isolated pancreatic endocrine tissue as well as on isolated vascular, intestinal, and uterine smooth muscle. Most of the 6-halogeno-2-alkylaminoquinazolin-4(3H)-ones were found to inhibit insulin release from pancreatic B-cells and to exhibit vasorelaxant properties. In contrast to their pyridothiadiazine dioxide isosteres previously described as more active on the endocrine than on the smooth muscle tissue, quinazolinones cannot be considered as tissue selective compounds. Biological investigations, including measurements of (86)Rb, (45)Ca efflux from pancreatic islet cells and measurements of vasodilator potency in rat aortic rings exposed to 30 or 80 mM KCl in the presence or the absence of glibenclamide, were carried out with 6-chloro- and 6-iodo-3-isopropylaminoquinazolin-4(3H)-ones. Such experiments showed that, depending on the tissue, these new compounds did not always express the pharmacological profile of pure K(ATP) channel openers. Analyzed by X-ray crystallography, one example of quinazolinones appeared to adopt a double conformation. This only suggests a partial analogy between the 2-alkylaminoquinazolin-4(3H)-ones and the 3-alkylamino-4H-pyrido[4,3-e]-1,2,4-thiadiazine 1,1-dioxides. In conclusion, the newly synthesized quinazolinones interfere with insulin secretion and smooth muscle contractile activity. Most of the compounds lack tissue selectivity, and further investigations are required to fully elucidate their mechanism(s) of action.

Adenosine Triphosphate↗