Modelling microstructure noise with mutually exciting point processes

International audienceWe introduce a new stochastic model for the variations of asset prices at the tick-by-tick level in dimension 1 (for a single asset) and 2 (for a pair of assets). The construction is based on marked point pro- cesses and relies on linear self and mutually exciting stochastic inten- sities as introduced by Hawkes. We associate a counting process with the positive and negative jumps of an asset price. By coupling suitably the stochastic intensities of upward and downward changes of prices for several assets simultaneously, we can reproduce microstructure noise (i.e. strong microscopic mean reversion at the level of seconds to a few minutes) and the Epps effect (i.e. the decorrelation of the increments in microscopic scales) while preserving a standard Brownian diffusion behaviour on large scales. More effectively, we obtain analytical closed-form formulae for the mean signature plot and the correlation of two price increments that enable to track across scales the effect of the mean-reversion up to the diffusive limit of the model. We show that the theoretical results are consistent with empirical fits on futures Euro-Bund and Euro-Bobl in several situations

Anaplastic oligodendrogliomas with 1p19q codeletion have a proneural gene expression profile

<p>Abstract</p> <p>Background</p> <p>In high grade gliomas, 1p19q codeletion and <it>EGFR </it>amplification are mutually exclusive and predictive of dramatically different outcomes. We performed a microarray gene expression study of four high grade gliomas with 1p19q codeletion and nine with <it>EGFR </it>amplification, identified by CGH-array.</p> <p>Results</p> <p>The two groups of gliomas exhibited very different gene expression profiles and were consistently distinguished by unsupervised clustering analysis. One of the most striking differences was the expression of normal brain genes by oligodendrogliomas with 1p19q codeletion. These gliomas harbored a gene expression profile that partially resembled the gene expression of normal brain samples, whereas gliomas with <it>EGFR </it>amplification expressed many genes in common with glioblastoma cancer stem cells. The differences between the two types of gliomas and the expression of neuronal genes in gliomas with 1p19q codeletion were both validated in an independent series of 16 gliomas using real-time RT-PCR with a set of 22 genes differentiating the two groups of gliomas (<it>AKR1C3</it>, <it>ATOH8</it>, <it>BMP2</it>, <it>C20orf42</it>, <it>CCNB1</it>, <it>CDK2</it>, <it>CHI3L1</it>, <it>CTTNBP2</it>, <it>DCX, EGFR, GALNT13, GBP1, IGFBP2, IQGAP1, L1CAM, NCAM1, NOG, OLIG2, PDPN, PLAT, POSTN, RNF135</it>). Immunohistochemical study of the most differentially expressed neuronal gene, alpha-internexin, clearly differentiated the two groups of gliomas, with 1p19q codeletion gliomas showing specific staining in tumor cells.</p> <p>Conclusion</p> <p>These findings provide evidence for neuronal differentiation in oligodendrogliomas with 1p19q codeletion and support the hypothesis that the cell of origin for gliomas with 1p19q codeletion could be a bi-potential progenitor cell, able to give rise to both neurons and oligodendrocytes.</p

Revisiting the loading dose of amikacin for patients with severe sepsis and septic shock

It has been proposed that doses of amikacin of >15 mg/kg should be used in conditions associated with an increased volume of distribution (Vd), such as severe sepsis and septic shock. The primary aim of this study was to determine whether 25 mg/kg (total body weight) of amikacin is an adequate loading dose for these patients.Clinical TrialJournal ArticleMulticenter StudyResearch Support, Non-U.S. Gov'tSCOPUS: ar.jinfo:eu-repo/semantics/publishe

CC chemokine CCL5 plays a central role impacting infarct size and post-infarction heart failure in mice

Aims The chemokine CCL5 plays a critical role as neutrophil and macrophage activator do in atherosclerosis and myocardial infarction. Thus, we investigated whether the treatment with a neutralizing monoclonal antibody (mAb) to mouse CCL5 would provide therapeutic benefit when provoking a coronary-associated ischaemic event. Methods and Results C57Bl/6 mice were submitted to left coronary artery permanent ligature. Then, various parameters were monitored for up to 21 days. At5 min and 3days after coronary occlusion, mice received one intravenous injection of the rat anti-mouse CCL5 mAb or isotype IgG control. Infarct size was assessed histologically and by measuring serum cardiac troponin I levels. Kinetics of CCL5 tissue expression, leucocyte infiltration, matrix metalloproteinase (MMP) levels, and collagen deposition were histologically assessed. Serum chemokine levels were measured by enzyme-linked immunosorbent assay. Cardiac function and dimensions were assessed by magnetic resonance imaging (MRI). Chronic ischaemia increased both circulating and intracardiac levels of CCL5. At 24 h, treatment with the anti-CCL5 mAb resulted in a smaller infarct size and reduced circulating levels of chemokines. This effect was associated with reduction of neutrophil and macrophage infiltration within the infarcted myocardium. After 3 days of chronic ischaemia, anti-CCL5 mAb treatment reduced cardiac MMP-9. At 7 days, collagen content was significantly lower. At 21 days, neutralizing CCL5 improved mouse survival, cardiac myocyte size, and cardiac function. Conclusion Treatment with anti-CCL5 mAb significantly reduced both infarct size and post-infarction heart failure in a mouse model of chronic cardiac ischaemia. Cardioprotective effects were associated with the reduction of leucocyte recruitment within infarcted heart

Sub-annual variability in historical water source use by Mediterranean riparian trees

This work was supported financially by a NERC PhD Studentship to CIS, Observatoire Hommes/Milieux Vallée du Rhône and the Department of Earth and Environmental Sciences at the University of St. AndrewsThe seasonal availability of water within a tree’s rooting zone may be an important determinant for individual tree growth and overall forest health, particularly in riparian corridors of Mediterranean climate zones that are vulnerable to water stress. Here, we present a new method that combines dendro-isotopes and isotope modelling for determining how water source use varies over 10 consecutive growing seasons (2000-2010) for co-occurring species Populus nigra and Fraxinus excelsior, along the Rhône River, south-eastern France. We conducted highly resolved δ18O analysis of cellulose micro-slices within tree rings and back-calculated the δ18O signature of source water available at the time of growth using a biochemical fractionation model. We related these patterns to inferred seasonal hydrologicalpartitioning through comparison with δ18O of waters from the vadose and phreatic zones, precipitation, and streamflow. The shallowly rooted Fraxinus displayed greater sub-annual source water variability, as well as greater isotopic enrichment, reflecting use of precipitation-derived vadose moisture. Its earlywood was formed mainly from winter rainfall(δ18O depleted) whilst the latewood was composed from growing season precipitation (δ18O enriched). In Populus, the sub-annual source water use was relatively depleted, suggesting use of hyporheic water and regional groundwater. From 2007, both species converged in their pattern of water source uptake which was attributed to a decline in phreatic water access for Populus. These results demonstrate that the seasonal variability in source water use can be identified retrospectively, a method which may prove important for anticipating the future consequences of climate-driven changes to the hydrological cycle.Publisher PDFPeer reviewe

Surrénalectomie laparoscopique pour incidentalome surrénalien (série consécutive de 133 patients)

REIMS-BU Santé (514542104) / SudocPARIS-BIUM (751062103) / SudocSudocFranceF

La déformation élastique artérielle au cours de la flexion articulaire : aspects biomécaniques et approche physiologique

REIMS-BU Santé (514542104) / SudocPARIS-BIUP (751062107) / SudocSudocFranceF

Traitement chirurgical du cancer du rectum. Experience Rémoise de 2000 à 2007

REIMS-BU Santé (514542104) / SudocSudocFranceF