155 research outputs found
Photoacoustic generation by a gold nanosphere: From linear to nonlinear thermoelastics in the long-pulse illumination regime
We investigate theoretically the photoacoustic generation by a gold
nanosphere in water in the thermoelastic regime. Specifically, we consider the
long-pulse illumination regime, in which the time for electron-phonon
thermalisation can be neglected and photoacoustic wave generation arises solely
from the thermo-elastic stress caused by the temperature increase of the
nanosphere or its liquid environment. Photoacoustic signals are predicted
computed based on the successive resolution of a thermal diffusion problem and
a thermoelastic problem, taking into account the finite size of the gold
nanosphere and the temperature-dependence of the thermal expansion coefficient
of water. For sufficiently high illumination fluences, this temperature
dependence yields a nonlinear relationship between the photoacoustic amplitude
and the fluence. For nanosecond pulses in the linear regime, we show that more
than 90 % of the emitted photoacoustic energy is generated in water, and the
thickness of the generating layer around the particle scales close to the
square root of the pulse duration. Our results demonstrate that the
point-absorber model introduced by Calasso et al.[17] significantly
overestimates the amplitude of photoacoustic waves in the nonlinear regime. We
therefore provide quantitative estimates of a critical energy, defined as the
absorbed energy required such that the nonlinear contribution is equal to that
of the linear contribution. Our results suggest that the critical energy scales
as the volume of water over which heat diffuses during the illumination pulse.
Moreover, thermal nonlinearity is shown to be expected only for sufficiently
high ultrasound frequency. Finally, we show that the relationship between the
photoacoustic amplitude and the equilibrium temperature at sufficiently high
fluence reflects the thermal diffusion at the nanoscale around the gold
nanosphere.Comment: Published in Physical Review B, 16 pages, 14 figure
Faux, falsification, pouvoir et société
La falsification â cantonnĂ©e pour lâessentiel Ă lâĂ©conomie â minerait les fondements des sociĂ©tĂ©s contemporaines ; elle aurait pour principal thĂ©Ăątre lâExtrĂȘme-Orient : de telles affirmations ont aujourdâhui valeur dâaxiome dans lâopinion courante et les mĂ©dias nâont de cesse dâappeler Ă la vigilance. La dimension marchande qui aujourdâhui domine lâapproche du faux se traduit par un consensus dans sa formulation juridique. Fruit du travail dâhistoriens et dâanthropologues, le prĂ©sent volume i..
Characterization of Blood Immune Cells in Patients With Decompensated Cirrhosis Including ACLF
Background and Aims: Patients with cirrhosis and acute-on-chronic liver failure (ACLF) have immunosuppression, indicated by an increase in circulating immune-deficient monocytes. The aim of this study was to investigate simultaneously the major blood-immune cell subsets in these patients. Material and Methods: Blood taken from 67 patients with decompensated cirrhosis (including 35 critically ill with ACLF in the intensive care unit), and 12 healthy subjects, was assigned to either measurements of clinical blood counts and microarray (genomewide) analysis of RNA expression in whole-blood; microarray (genomewide) analysis of RNA expression in blood neutrophils; or assessment of neutrophil antimicrobial functions. Results: Several features were found in patients with ACLF and not in those without ACLF. Indeed, clinical blood count measurements showed that patients with ACLF were characterized by leukocytosis, neutrophilia, and lymphopenia. Using the CIBERSORT method to deconvolute the whole-blood RNA-expression data, revealed that the hallmark of ACLF was the association of neutrophilia with increased proportions of macrophages M0-like monocytes and decreased proportions of memory lymphocytes (of B-cell, CD4 T-cell lineages), CD8 T cells and natural killer cells. Microarray analysis of neutrophil RNA expression revealed that neutrophils from patients with ACLF had a unique phenotype including induction of glycolysis and granule genes, and downregulation of cell-migration and cell-cycle genes. Moreover, neutrophils from these patients had defective production of the antimicrobial superoxide anion. Conclusions: Genomic analysis revealed that, among patients with decompensated cirrhosis, those with ACLF were characterized by dysregulation of blood immune cells, including increases in neutrophils (that had a unique phenotype) and macrophages M0-like monocytes, and depletion of several lymphocyte subsets (including memory lymphocytes). All these lymphocyte alterations, along with defective neutrophil superoxide anion production, may contribute to immunosuppression in ACLF, suggesting targets for future therapies
Babesia divergens glycosylphosphatidylinositols modulate blood coagulation and induce Th2-biased cytokine profiles in antigen presenting cells
This work was supported by the the University of Tours (to IDP and FDG), the University of Montpellier (to SD and EC), the Deutsche Forschungsgemeinschaft (to RTS), the Wellcome Trust project grant 093228 (to TKS) and the Campus France/DAAD PHC PROCOPE 24931RE (to RTS and EC). The funding source has no involvement in the conduct of the research and preparation of the article.Glycosylphosphatidylinositols (GPIs) are glycolipids described as toxins of protozoan parasites due to their inflammatory properties in mammalian hosts characterized by the production of interleukin (IL)-1, IL-12 and tumor necrosis factor (TNF)-α. In the present work, we studied the cytokines produced by antigen presenting cells in response to ten different GPI species extracted from Babesia divergens, responsible for babesiosis. Interestingly, B. divergens GPIs induced the production of anti-inflammatory cytokines (IL-2, IL-5) and of the regulatory cytokine IL-10 by macrophages and dendritic cells. In contrast to all protozoan GPIs studied until now, GPIs from B. divergens did not stimulate the production of TNF-α and IL-12, leading to a unique Th1/Th2 profile. Analysis of the carbohydrate composition of the B. divergens GPIs indicated that the di-mannose structure was different from the evolutionary conserved tri-mannose structure, which might explain the particular cytokine profile they induce. Expression of major histocompatibility complex (MHC) molecules on dendritic cells and apoptosis of mouse peritoneal cells were also analysed. B. divergens GPIs did not change expression of MHC class I, but decreased expression of MHC class II at the cell surface, while GPIs slightly increased the percentages of apoptotic cells. During pathogenesis of babesiosis, the inflammation-coagulation auto-amplification loop can lead to thrombosis and the effect of GPIs on coagulation parameters was investigated. Incubation of B. divergens GPIs with rat plasma ex vivo led to increase of fibrinogen levels and to prolonged activated partial thromboplastin time, suggesting a direct modulation of the extrinsic coagulation pathway by GPIs.Publisher PDFPeer reviewe
J Clin Invest
Arterial cardiovascular events are the leading cause of death in patients with JAK2V617F myeloproliferative neoplasms (MPN). However, their mechanisms are poorly understood. The high prevalence of myocardial infarction without significant coronary stenosis or atherosclerosis in patients with MPN suggests that vascular function is altered. Consequences of JAK2V617F mutation on vascular reactivity are unknown. We observe here increased responses to vasoconstrictors in arteries from Jak2V617F mice, resulting from disturbed endothelial nitric oxide pathway and increased endothelial oxidative stress. This response was reproduced in wild-type mice by circulating microvesicles isolated from patients carrying JAK2V617F and by erythrocyte-derived microvesicles from transgenic mice. Microvesicles of other cellular origins had no effect. This effect was observed ex vivo on isolated aortas, but also in vivo on femoral arteries. Proteomic analysis of microvesicles derived from JAK2V617F erythrocytes identified increased expression of myeloperoxidase as the likely mechanism accounting for microvesicles effect. Myeloperoxidase inhibition in microvesicles derived from JAK2V617F erythrocytes supressed their effect on oxidative stress. Antioxidants, such as simvastatin and N-acetyl-cysteine, improved arterial dysfunction in Jak2V617F mice. In conclusion, JAK2V617F MPN are characterized by exacerbated vasoconstrictor responses resulting from increased endothelial oxidative stress caused by circulating erythrocyte-derived microvesicles. Simvastatin appears as promising therapeutic strategy in this setting
Evolution of coastal zone vulnerability to marine inundation in a global change context. Application to Languedoc Roussillon (France)
The coastal system is likely to suffer increasing costal risk in a global change context. Its management implies to consider those risks in a holistic approach of the different vulnerability components of the coastal zone, by improving knowledge of hazard and exposure as well as analyzing and quantifying present day and future territory vulnerability. The ANR/VMC2007/MISEEVA project (2008-2011) has applied this approach on Languedoc Roussillon region in France. MISEEVA approach relies on several scenarios for 2030 and 2100, in terms of meteorology (driver of coastal hazard), sea level rise, and also considering further trends in demography and economy, and possible adaption strategies Hazard has been modeled (SWAN, MARS and SURFWB), on the base of the presentday situation, sea level rise hypotheses, and existing or modeled data, of extreme meteorological driving f. It allowed to assess the possible surges ranges and map coastal zone exposure to: - a permanent inundation (considering sea level rise in 2030 and 2100, - a recurrent inundation (considering sea level rise and extreme tidal range) - an exceptional inundation (adding extreme storm surge to sea level rise and tidal range). In 2030, exposure will be comparable to present day exposure. In 2100, extreme condition will affect a larger zone. Present days social and economic components of the coastal zone have been analyzed in terms of vulnerability and potential damaging. Adaptation capacity was approached by public inquiries and interviews of stakeholders and policy makers, based on existing planning documents The knowledge of the present day system is then compared to the possible management strategies that could be chosen in the future, so to imagine what would be the evolution of vulnerability to marine inundation, in regards to these possible strategies
Les Song (960-1279)Â : commentaire historique et numismatique
Tableau dâhistoire politique LâĂ©tude de la monnaie des Song du Nord (960-1127) et du Sud (1127-1279) ne saurait faire lâĂ©conomie dâun exposĂ© des grandes lignes de lâhistoire politique de la pĂ©riode. Ă lâorigine de la dynastie, Zhao Kuangyin è¶ćĄè€ (le futur empereur Taizu ć€Șç„, r. 927-976), issu dâune famille dâofficiers sous les Tang ćæ, parvenu au faĂźte de la hiĂ©rarchie militaire des Zhou postĂ©rieurs ćŸćš comme « commandant gĂ©nĂ©ral du palais » (dianqian du zongjian æźżćéœçžœæȘą), avait Ă©tĂ© nommĂ© grand ma..
La confrontation textes-terrain dans la construction des savoirs par LĂȘ QuĂœ ĂĂŽN, lettrĂ© vietnamien du xviiie siĂšcle
Ă premiĂšre vue, LĂȘ Quy ĂĂŽn pourrait apparaĂźtre comme un simple disciple de lâ« Ăcole des vĂ©rifications et des preuves », courant apparu en Chine Ă la charniĂšre des Ming et des Qing, qui dominera tout le xviiie siĂšcle. Si lâimpact de ce courant sur la rĂ©flexion du mandarin vietnamien ne saurait ĂȘtre minorĂ©, il apparaĂźt quâil entretient un rapport complexe avec la rĂ©flexion menĂ©e en Chine. Son itinĂ©raire intellectuel et gĂ©ographique est en effet marquĂ© par une tension entre deux pĂŽles : PĂ©kin et le terrain vietnamien. Dans la capitale chinoise, alors quâil est en ambassade, sa culture lettrĂ©e lui vaut la reconnaissance de ses pairs corĂ©ens et chinois, elle conforte sa lĂ©gitimitĂ© de lettrĂ©-fonctionnaire.Mais dans son rapport au ViĂȘt-Nam, cette culture classique chinoise est mise Ă lâĂ©preuve lorsque LĂȘ Quy ĂĂŽn entreprend un vaste programme de construction des savoirs en adĂ©quation avec la rĂ©alitĂ© locale. Il attache une importance particuliĂšre aux usages, aux animaux et aux plantes locales. Sa singularitĂ© rĂ©side dans une aptitude â rare dans le ViĂȘt-Nam du xviiie siĂšcle â Ă transcender le milieu lettrĂ© en diversifiant ses sources dâinformation.At first glance, LĂȘ Quy ĂĂŽn could appear as a mere follower of the so-called search of evidence which appeared in China at the turn of the Ming and Qing dynasties and dominated the whole eighteenth century. If the impact of this school on LĂȘ Quy ĂĂŽnâs thought cannot be underestimated, the Vietnamese scholar maintained a complex relationship with the debates that took place in China. His intellectual and geographical itinerary is indeed marked by a tension between two poles: Beijing and Vietnam. During his assignment at the Vietnamese embassy in China his literary culture earned him the recognition of his Korean and Chinese peers and reinforced his legitimacy as a scholar-official. However, this classical culture was challenged in Vietnam when LĂȘ Quy ĂĂŽn launched an extensive program of construction of knowledge whose aim was to build a body of knowledge in line with local reality
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