Effect of cavitation on velocity in the near-field of a diesel nozzle

The entire process of atomization of the fuel in an internal combustion engine plays a very important role in determining the overall efficiency of these engines. A good atomization process could help the fuel to mix with the air properly leading to its efficient combustion, thereby reducing the emitted pollutants as well. The recent trend followed by the engineers focused on designing fuel injectors for more efficient atomization is to increase the atomization pressure while decreasing the nozzle orifice diameter. A consequence of this is the development of cavitation (formation of vapor cavities or bubbles in the liquid) inside the injector close to the nozzle. The main reason behind this is the sudden changes in the pressure inside the injector and these cavities or bubbles are usually formed where the pressure is relatively low.This work mainly focuses on studying the formation of cavitation and its effect on the velocity of the spray in the near nozzle region using asymmetrical transparent nozzle equipped with a needle lift sensor with nozzle diameter of 0.35 mm at 300 bar of injection pressure. The experiment consists in recording of several image-pairs, which are separated by about 300 ns, capturing the dynamics of the spray, a few millimeters from the nozzle in the direction of the flow. These image-pairs are then used to compute the velocity from the displacement of the liquid structures and ligaments by correlating the first image with the second. About 200 of such velocity graphs are then averaged to obtain a velocity map and is compared with the similar average velocity maps obtained at different times from the start of the injection. The angular spread of the spray from each of these images is calculated as well. The images showing cavitation inside the injector are also recorded at these same instants of time so as to understand the effects of cavitation on the velocity and angular spread of the spray close to the nozzle.Comment: 13th International Conference on Liquid Atomization and Spray Systems, Aug 2015, Tainan, Taiwan. 2015, https://iclass2015.tw

Quantitative comparison of fuel spray images obtained using ultrafast coherent and incoherent double-pulsed illumination

We present a quantitative comparison between the high-pressure fuel spray images obtained experimentally using classical imaging with coherent and incoherent ultrafast illuminations recorded using a compatible CMOS camera. The ultrafast, incoherent illumination source was extracted from the supercontinuum generated by tightly focusing the femtosecond laser pulses in water. The average velocity maps computed using time-correlated image-pairs and spray edge complexity computed using the average curvature scale space maps are compared for the spray images obtained with the two illumination techniques and also for the numerically simulated spray using the coupled volume of fluid and level set method for interface tracking (direct numerical simulation or DNS). The spray images obtained with supercontinuum-derived, incoherent, ultrafast illumination are clearer, since the artifacts arising due to laser speckles and multiple diffraction effects are largely reduced and show a better correlation with the DNS results.Comment: 8 pages, 9 figures, Presented at the ILASS-Europe 2014, 26th Annual Conference on Liquid Atomization and Spray Systems held at Bremen, Germany from 8th to 10th September 201

Prevention by the CXCR2 antagonist SCH527123 of the calcification of porcine heart valve cusps implanted subcutaneously in rats

IntroductionCalcification is a main cause of bioprosthetic heart valves failure. It may be promoted by the inflammation developed in the glutaraldehyde (GA)-fixed cusps of the bioprosthesis. We tested the hypothesis that antagonizing the C-X-C chemokines receptor 2 (CXCR2) may prevent the calcification of GA-fixed porcine aortic valves.Materiel and methodsFour-week-old Sprague Dawley males were transplanted with 2 aortic valve cusps isolated from independent pigs and implanted into the dorsal wall. Four groups of 6 rats were compared: rats transplanted with GA-free or GA-fixed cusps and rats transplanted with GA-fixed cusps and treated with 1 mg/kg/day SCH5217123 (a CXCR2 antagonist) intraperitoneally (IP) or subcutaneously (SC) around the xenograft, for 14 days. Then, rats underwent blood count before xenografts have been explanted for histology and biochemistry analyses.ResultsA strong calcification of the xenografts was induced by GA pre-incubation. However, we observed a significant decrease in this effect in rats treated with SCH527123 IP or SC. Implantation of GA-fixed cusps was associated with a significant increase in the white blood cell count, an effect that was significantly prevented by SCH527123. In addition, the expression of the CD3, CD68 and CXCR2 markers was reduced in the GA-fixed cusps explanted from rats treated with SCH527123 as compared to those explanted from non-treated rats.ConclusionThe calcification of GA-fixed porcine aortic valve cusps implanted subcutaneously in rats was significantly prevented by antagonizing CXCR2 with SCH527123. This effect may partly result from an inhibition of the GA-induced infiltration of T-cells and macrophages into the xenograft

Association between metformin use and below-the-knee arterial calcification score in type 2 diabetic patients.

BACKGROUND Vascular calcification (VC) is common in type 2 diabetes, and is associated with cardiovascular complications. Recent preclinical data suggest that metformin inhibits VC both in vitro and in animal models. However, metformin's effects in patients with diabetic VC have not previously been characterized. The present study investigated the association between metformin use and lower-limb arterial calcification in patients with type 2 diabetes and high cardiovascular risk. METHODS The DIACART cross-sectional cohort study included 198 patients with type 2 diabetes but without severe chronic kidney disease. Below-the-knee calcification scores were assessed by computed tomography and supplemented by colour duplex ultrasonography. Data on anti-diabetic drugs were carefully collected from the patients' medical records and during patient interviews. Biochemical and clinical data were studied as potential confounding factors. RESULTS Metformin-treated patients had a significantly lower calcification score than metformin-free patients (mean ± standard deviation: 2033 ± 4514 and 4684 ± 9291, respectively; p = 0.01). A univariate analysis showed that metformin was associated with a significantly lower prevalence of severe below-the-knee arterial calcification (p = 0.02). VC was not significantly associated with the use of other antidiabetic drugs, including sulfonylureas, insulin, gliptin, and glucagon like peptide-1 analogues. A multivariate logistic regression analysis indicated that the association between metformin use and calcification score (odds ratio [95% confidence interval] = 0.33 [0.11-0.98]; p = 0.045) was independent of age, gender, tobacco use, renal function, previous cardiovascular disease, diabetes duration, neuropathy, retinopathy, HbA1c levels, and inflammation. CONCLUSIONS In patients with type 2 diabetes, metformin use was independently associated with a lower below-the-knee arterial calcification score. This association may contribute to metformin's well-known vascular protective effect. Further prospective investigations of metformin's potential ability to inhibit VC in patients with and without type 2 diabetes are now needed to confirm these results

Etat actuel des connaissances sur les phyto-estrogènes

Les phyto-estrogènes sont des molécules d origine végétale capables de se fixer sur les récepteurs des estrogènes et douées d une activité agoniste et/ou antagoniste vis-à-vis des estrogènes, en fonction de leur concentration, des taux de stéroïdes endogènes et de l organe cible concerné. On distingue trois catégories principales: les isoflavones, retrouvées principalement dans le soja, les coumestanes, et les lignanes, présents dans le lin. A l heure où le bio est un phénomène de société de premier plan, les phyto-estrogènes suscitent un fort engouement. Les bouffées de chaleur et le cancer du sein sont en effet beaucoup moins fréquents dans les pays asiatiques où la consommation de soja est importante. On prêterait ainsi aux phyto-estrogènes des propriétés pour soulager certains troubles de la ménopause et un effet protecteur contre les maladies cardiovasculaires, l ostéoporose et certains cancers. L utilisation du soja, dans la nourriture ou sous forme de compléments alimentaires, est un phénomène en progression à une époque où augmentent les craintes suscitées par les traitements hormonaux. C est pourquoi de nombreuses études ont été menées afin de déterminer les bénéfices possibles et les risques éventuels liés à la consommation de phyto-estrogènes, et plus particulièrement d isoflavones de soja.AMIENS-BU Santé (800212102) / SudocSudocFranceF

Le mélanome cutané (traitements et prévention)

Le mélanome cutané est l un des cancers le moins répandu mais l un de ceux dont le taux d incidence est en constante évolution. Ceci est d autant plus inquiétant qu il n existe pas d autre moyen de lutte contre cette pathologie que la prévention. En effet, celle-ci demeure capitale car il existe très peu de traitements permettant d obtenir une rémission complète. A l heure où les tendances sont à une peau hâlée ou bronzée, il devient alors de plus en plus difficile de changer les mentalités sur les risques et les effets néfastes du soleil. C est alors que les professionnels de santé doivent intervenir ensemble afin d éduquer et de sensibiliser au mieux adultes et enfants.AMIENS-BU Santé (800212102) / SudocSudocFranceF

Effets in vitro de la quercétine et du kaempférol, deux flavonoïdes naturels, sur la résorption osseuse, l'apoptose et la différenciation des ostéoclastes

PARIS7-Bibliothèque centrale (751132105) / SudocSudocFranceF

Influence des cellules d'adénocarcinome mammaire sur la résorption osseuse et l'apoptose des ostéoclastes matures (rôle potentiel du M-CSF dans l'ostéolyse tumorale in vitro)

PARIS7-Bibliothèque centrale (751132105) / SudocSudocFranceF