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Search Results: 1 - 10 of 297488 matches for " J Duchateau "
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Filamentation of ultrashort laser pulses in silica glass and KDP crystal: A comparative study
Jérémie Rolle,Luc Bergé,Guillaume Duchateau,Stefan Skupin
Physics , 2014, DOI: 10.1103/PhysRevA.90.023834
Abstract: Ionizing 800-nm femtosecond laser pulses propagating in silica glass and in potassium dihydrogen phosphate (KDP) crystal are investigated by means of a unidirectional pulse propagation code. Filamentation in fused silica is compared with the self-channeling of light in KDP accounting for the presence of defect states and electron-hole dynamics. In KDP, laser pulses produce intense filaments with higher clamping intensities up to 200 TW/cm$^2$ and longer plasma channels with electron densities above $10^{16}$ cm$^{-3}$. Despite these differences, the propagation dynamics in silica and KDP are almost identical at equivalent ratios of input power over the critical power for self-focusing.
The Relative Biologic Effectiveness versus Linear Energy Transfer Curve as a Cell Trait  [PDF]
Quoc T. Luu, Paul DuChateau
Applied Mathematics (AM) , 2013, DOI: 10.4236/am.2013.411A3004

The magnitude of biological response varies with different radiation types. Using Linear Energy Transfer (LET) to differentiate types of incident radiation beam, the Relative Biologic Effectiveness (RBE) as a function of LET (RBE-LET) was found to have a characteristic shape with a peak around LET values 100 - 200 eV/nm. This general feature is believed to be a property of the incident beam. Our systems engineering model, however, suggests that the shape of the RBE-LET curve is a cell trait, a property of the cell. Like any other trait, phenotypic variations result from interactions of the genes and their context. State-space block diagram of the differential equation model suggests the genes are those in the DNA double strand break (dsb) repair pathway; and the context is cellular stress responsing to DNA damage by both external stimuli and internal redox state. At a deeper level, the block diagram suggests cell using mathematical calculations in its decision-making when facing a stress signal. The MRN protein complex, in particular, may perform addition to count the degree of DNA twisting for the homeostatic regulation of DNA supercoiling. The ATM protein may act as a feedback amplifier.

Corticosteroids reduce neuron-specific-enolase liberation after cardiopulmonary bypass in men
D Schmartz, Y Tabardel, L Barvais, A d'Hollander, JM De Smet, J Duchateau
Critical Care , 2000, DOI: 10.1186/cc685
Abstract: After institutional approval, 45 patients scheduled for nonemergency coronary artery bypass grafting (CABG) with CPB were divided into four groups: the control group (CTRL; n = 17) received no corticosteroids; the DXM group (n = 7) received 2 mg/kg dexamethasone; and the MPS10 group (n = 14) received 10 mg/kg and the MPS30 (n = 7) group received 30 mg/kg methylprednisolone intravenously 2 h before surgery. CPB was conducted under moderate hypothermia (29-30 °C) using a cold crystalloid cardioplegia and a nonpulsatile flow. Anaesthesia consisted of a continuous infusion of sufentanil, midazolam and pancuronium. No aprotinin was used. We measured NSE levels before induction of anaesthesia and 4 h after CPB. For each patient we calculated the change in NSE concentration as follows: NSE (at 4 h)-NSE (baseline). We also measured tumor necrosis factor (TNF) and interleukin (IL)-8 at the same time. There were no differences between the groups regarding age, duration of CPB, aortic cross-clamping time or number of grafts.The CTRL group showed a significant increase in NSE after CPB, whereas in all three corticosteroid groups NSE was significantly lower (Fig. 1).TNF and IL-8 liberation were significantly and equally reduced in all three treatment groups. This suppression of the inflammatory response might lead to less neutrophil adhesion and migration, resulting in less tissue damage by proteolytic enzymes and oxygen-free radicals.Corticosteroids, even at moderate doses, are able to reduce the amount of NSE liberation during CPB. This may indicate less brain injury during CPB. Whether this reduction in NSE liberation translates into improved neurological outcome remains to be studied.
Red blood cell volume as a predictor of fatal reactions in cattle infected with Theileria parva Katete
P. Fandamu,T. Marcotty,J.R.A. Brandt,L. Duchateau
Onderstepoort Journal of Veterinary Research , 2010, DOI: 10.4102/ojvr.v74i1.138
Abstract: A comparison of mean corpuscular volume (MCV) and packed cell volume (PCV) was made between cattle undergoing lethal and non-lethal reactions following experimental infections with the apicomplexan protozoa, Theileria parva Katete. This work confirmed that anaemia occurs in infected animals. However, the fall in PCV was steeper in lethal reactions compared to non-lethal reactions. Our results show that animals with initially lower MCV values are more prone to fatal reaction, despite having normal PCV profiles. The study also found that small red blood cells are more likely to be infected with T. parva. These findings suggest that animals with a higher proportion of small red blood cells in circulation will be more likely to succumb to T. parva infections. The potential for using MCV as a predictor of the outcome of infection challenge is discussed.
Aprotinin does not influence the inflammatory reaction to cardiopulmonary bypass in humans
D Schmartz, Y Tabardel, JC Preiser, L Barvais, A d'Hollander, J Duchateau, JL Leclerc, JL Vincent
Critical Care , 1999, DOI: 10.1186/cc321
Abstract: After institutional approval and written informed consent, 60 male patients, scheduled for primary coronary artery bypass grafting, were enrolled in this prospective double-blinded study. The patients were randomized into three groups: Group high dose aprotinin (HD) received 2 × 106 KIU followed by 0.5 × 106 KIU/h and 2 × 106 KIU added to the pump prime; group low dose (LD) received half that dose and the control group (CTRL) received no aprotinin. No corticosteroids were given. Anesthesia consisted of a high dose sufentanil infusion. The CPB circuit was primed with gelatin and the flow rate was maintained at 2.4 l/min/m2 using a non-pulsatile flow. An anterograde, cold, crystalloid cardioplegic solution was used and mild hypothermia (30°C) was maintained during CPB. We measured tumor necrosis factor (TNF), interleukin 6, 8, 10 (IL6, IL8, IL10), endotoxin, prekallikrein, and prostaglandin D2 (PGD2) at the following time points: 30 min after study drug loading, 10min after beginning of CPB, before end of CPB, 4h after CPB, 1st postoperative day (POD1) and 2nd postoperative day (POD2). Data were analyzed using an analysis of variance for repeated measurements after logarithmic transformation to achieve normalization. There was no significant difference between groups in number of anastomosis, duration of CPB and aortic clamping. All three groups showed a significant inflammatory reaction characterized by an increase of TNF up to 46 pg/ml, IL6 up to 600 pg/ml, IL8 up to 27 pg/ml with no difference between the treatment and the placebo groups. This inflammatory reaction started at the beginning of CPB, was maximal 4 h post-CPB and resolved on POD1 and POD2. Endotoxin levels at end of CPB as well as the maximum increase were slightly lower in the treated than in the CTRL group. However, this difference was essentially due to one CTRL patient with very high endotoxin levels. The proinflammatory reaction was accompanied by a significant increase in the anti-inflammatory cy
Myocardial cell damage related to arterial switch operation in neonates with transposition of the great arteries
HH H?vels-Gürich, JF Vazquez-Jimenez, A Silvestri, K Schumacher, S Kreitz, J Duchateau, BJ Messmer, G von Bernuth, M-C Seghaye
Critical Care , 2001, DOI: 10.1186/cc1009
Abstract: Sixty-three neonates (age 2-28 [8.1 ± 4.6] days), who were operated on under combined deep hypothermic (15°C) circulatory arrest and low-flow cardiopulmonary bypass (CPB), were studied. Inclusion criteria were transposition of the great arteries with or without ventricular septal defect (VSD) that was suitable for arterial switch operation (VSD-; n = 53), and if necessary additional VSD closure (VSD+; n = 10). Patients were differentiated clinically into two groups by presence or absence of MD within 24 h after surgery. MD was defined as myocardial ischaemia after coronary reperfusion and/or myocardial hypocontractility as assessed by echocardiography. MD was related to clinical outcome parameters and to perioperative release of cardiac troponin-T (cTnT) and production of interleukin-6 and interleukin-8.MD was observed in 11 patients (17.5%). Two patients died early after surgery from myocardial infarction, and two died late after surgery (6.3%). CPB and cross-clamping, but not deep hypothermic circulatory arrest times, were correlated with MD; MD was more frequent in the VSD+ than in the VSD- group because of longer support times. Coronary status and age at surgery were not related to MD. Patients with MD had more frequently impaired cardiac, respiratory and renal functions. cTnT, interleukin-6 and interleukin-8 were significantly elevated at the end of CPB, and 4 and 24 h after surgery, as compared with preoperative values in both groups. Postoperative cTnT, interleukin-6 and interleukin-8 concentrations were significantly higher in MD patients than in the others. Multivariable analysis of independent risk factors for MD revealed interleukin-6 4 h after surgery to be significant (P = 0.04; odds ratio 1.24 [95% confidence interval 1.01-1.52] per 10 pg/ml). The cutoff point for prediction of MD was set at 500 pg/ml (specificity 95.4%, sensitivity 72.7%).Cardiac operations in neonates induce the production of the proinflammatory cytokines interelukin-6 and interleuki
Variation of inflammatory dynamics and mediators in primiparous cows after intramammary challenge with Escherichia coli
Adel Pezeshki, Philippe Stordeur, Hugues Wallemacq, Frédéric Schynts, Mieke Stevens, Philippe Boutet, Luc J Peelman, Bart De Spiegeleer, Luc Duchateau, Fabrice Bureau, Christian Burvenich
Veterinary Research , 2011, DOI: 10.1186/1297-9716-42-15
Abstract: The severity of coliform mastitis is of much more concern than its incidence [1]. Pathogen, cow and environment are three interdependent factors which influence the mastitis susceptibility [1]. From the various bacterial virulence factors studied during Escherichia coli mastitis [2], only a few have been found to play an important role in the outcome of the disease. It has been accepted that the type of E. coli strain is not the main factor in classification of severity. Preventive treatments which are efficient against contagious mastitis have been shown to be inefficient in the control of E. coli mastitis [3]. The severity of bovine E. coli mastitis is mainly determined by cow factors rather than by the pathogenecity of the invading pathogen and management [1]. It is known that the growth of E. coli in the udder cistern is specially related with the period of lactation and parity of cows. E. coli mastitis with severe clinical symptoms is more frequently observed around calving and during early lactation in dairy cows, whereas symptoms are mild to moderate during mid and late lactation. Because of hormonal, metabolic and nutritional alterations associated with pregnancy, immune system is compromised around calving (reviewed by Pezeshki et al. [4]). Cow parity is another important physiological factor that influences the severity of clinical coliform mastitis [5,6]. Clinical severe cases of coliform mastitis are mostly seen among multiparous cows rather than primiparous cows during early lactation. To our best knowledge the inflammatory status of primiparous cows ranking based on severity after intramammary infection of E. coli is poorly understood during early lactation. Physiological factors have been mainly studied in multiparous cows ranging from second lactation to sixth lactation [6-10].Thromboxanes (TX), prostaglandins (PG), leukotriens (LT) and lipoxines (LX) which are the enzymatically generated products of cyclooxygenases (COX) and lipoxygenases are genera
Regenerative Therapies for Equine Degenerative Joint Disease: A Preliminary Study
Sarah Broeckx, Marieke Zimmerman, Sara Crocetti, Marc Suls, Tom Mari?n, Stephen J. Ferguson, Koen Chiers, Luc Duchateau, Alfredo Franco-Obregón, Karin Wuertz, Jan H. Spaas
PLOS ONE , 2014, DOI: 10.1371/journal.pone.0085917
Abstract: Degenerative joint disease (DJD) is a major cause of reduced athletic function and retirement in equine performers. For this reason, regenerative therapies for DJD have gained increasing interest. Platelet-rich plasma (PRP) and mesenchymal stem cells (MSCs) were isolated from a 6-year-old donor horse. MSCs were either used in their native state or after chondrogenic induction. In an initial study, 20 horses with naturally occurring DJD in the fetlock joint were divided in 4 groups and injected with the following: 1) PRP; 2) MSCs; 3) MSCs and PRP; or 4) chondrogenic induced MSCs and PRP. The horses were then evaluated by means of a clinical scoring system after 6 weeks (T1), 12 weeks (T2), 6 months (T3) and 12 months (T4) post injection. In a second study, 30 horses with the same medical background were randomly assigned to one of the two combination therapies and evaluated at T1. The protein expression profile of native MSCs was found to be negative for major histocompatibility (MHC) II and p63, low in MHC I and positive for Ki67, collagen type II (Col II) and Vimentin. Chondrogenic induction resulted in increased mRNA expression of aggrecan, Col II and cartilage oligomeric matrix protein (COMP) as well as in increased protein expression of p63 and glycosaminoglycan, but in decreased protein expression of Ki67. The combined use of PRP and MSCs significantly improved the functionality and sustainability of damaged joints from 6 weeks until 12 months after treatment, compared to PRP treatment alone. The highest short-term clinical evolution scores were obtained with chondrogenic induced MSCs and PRP. This study reports successful in vitro chondrogenic induction of equine MSCs. In vivo application of (induced) MSCs together with PRP in horses suffering from DJD in the fetlock joint resulted in a significant clinical improvement until 12 months after treatment.
Femtosecond laser pulse train interaction with dielectric materials
O. Dematteo Caulier,K. Mishchik,B. Chimier,S. Skupin,A. Bourgeade,C. Javaux Léger,R. Kling,C. H?nninger,J. Lopez,V. Tikhonchuk,G. Duchateau
Physics , 2015, DOI: 10.1063/1.4935119
Abstract: We investigate the interaction of trains of femtosecond microjoule laser pulses with dielectric materials by means of a multi-scale model. Our theoretical predictions are directly confronted with experimental observations in soda-lime glass. We show that due to the low heat conductivity, a significant fraction of the laser energy can be accumulated in the absorption region. Depending on the pulse repetition rate, the material can be heated to high temperatures even though the single pulse energy is too low to induce a significant material modification. Regions heated above the glass transition temperature in our simulations correspond very well to zones of permanent material modifications observed in the experiments.
Coulomb-Volkov approach of ionization by extreme ultraviolet laser pulses in the subfemtosecond regime
Guillaume Duchateau,Eric Cormier,Robert Gayet
Physics , 2002, DOI: 10.1103/PhysRevA.66.023412
Abstract: In conditions where the interaction betweeen an atom and a short high-frequency extreme ultraviolet laser pulse is a perturbation, we show that a simple theoretical approach, based on Coulomb-Volkov-type states, can make reliable predictions for ionization. To avoid any additional approximation, we consider here a standard case : the ionization of hydrogen atoms initially in their ground state. For any field parameter, we show that the method provides accurate energy spectra of ejected electrons, including many above threshold ionization peaks, as long as the two following conditions are simultaneously fulfilled : (i) the photon energy is greater than or equal to the ionization potential ; (ii) the ionization process is not saturated. Thus, ionization of atoms or molecules by the high order harmonic laser pulses which are generated at present may be addressed through this Coulomb-Volkov treatment.
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