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Search Results: 1 - 10 of 167839 matches for " E. Leblanc "
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Phosphate and Nitrate Release from Mucky Mineral Soils  [PDF]
Micha?l A. Leblanc, Léon E. Parent, Gilles Gagné
Open Journal of Soil Science (OJSS) , 2013, DOI: 10.4236/ojss.2013.32012
Abstract:

High-organic (mucky) mineral soils make a small proportion of the Canadian agricultural land but are highly productive, especially for organic farming. Although these high-quality soils may release large amounts of nitrate and phosphate to the environment, there is yet no reliable agro-environmental indicator for managing N and P compared to the adjacent mineral and organic soils. Our objective was to quantify the N mineralization and P environmental risks of mucky mineral soils. Nine Canadian soil series (eight Orthic Humic Gleysols and one Terric Humisol with three variants) were analyzed for texture, pH(CaCl2), total C and N, oxalate and Mehlich-III (M-III) extractable P, Al and Fe, and water extractable P (Pw). Soil texture varied from loamy sand to heavy clay, organic carbon (OC) content ranged from 14 to 392 g·OC·kg-1, total N from 1.21 to 16.38 g·N·kg-1, and degree of P saturation (DPSM-III) as molar (P/[Al + γFe])M-III percentage between 0.3% and 11.3%. After 100 d of incubation, soils released 31 to 340 mg·N·kg-1. The N mineralization rate was closely correlated to organic matter content (r = 0.91, p < 0.01). Sandy to loamy soils released 1.2 - 1.8 kg·N·ha-1·d-1 compared to 1.6 - 2.4 kg·N·ha-1·d-1 for clayey soils, 2.0

From skeletal to non skeletal: The intriguing roles of BMP-9: A literature review  [PDF]
E. Leblanc, G. Drouin, G. Grenier, N. Faucheux, R. Hamdy
Advances in Bioscience and Biotechnology (ABB) , 2013, DOI: 10.4236/abb.2013.410A4004
Abstract:

In the well-known superfamily of transforming growth factors beta (TGF-b), bone morphogenetic proteins (BMPs) are one of the most compelling cytokines for their major role in regulation of cell growth and differentiation in both embryonic and adult tissues. This subfamily was first described for its ability of potentiating bone formation, but nowadays, the power of BMPs is well beyond the bone healing scope. Some of the BMPs have been well studied and described in the literature, but the BMP9 is still worthy of attention. It has been shown by many authors that it is the most potent osteogenic BMP. Moreover, it has been described as one of the rare circulating BMPs. In this paper, we will review the recent literature on BMP9 and the different avenues for future research in that field. Our primary scope is to review its relation to bone formation and to elaborate on the available literature on other systems.

Levetiracetam-Associated Acute Kidney Injury and Drug Reaction with Eosinophilia and Systemic Symptoms (DRESS) Syndrome  [PDF]
Mathieu Leblanc, Martin Plaisance
Open Journal of Nephrology (OJNeph) , 2014, DOI: 10.4236/ojneph.2014.44022
Abstract:
DRESS syndrome is a severe drug induced reaction. Acute kidney injury (AKI) is sometimes present in the form of an acute interstitial nephritis. We present the case of a 75-year-old man with glioblastoma who developed a DRESS two months after starting levetiracetam and a few days after stopping dexamethasone. His skin and kidneys improved after removing levetiracetam and introducing again corticosteroids. DRESS has been reported more frequently with other antiepileptics, rarely with levetiracetam. Clinicians should add this drug to the list of potential causes of AKI.
Patterns of change in cytochrome c oxidase redox status
Roy E. Gagnon,Andrew J. Macnab,Jacques G. LeBlanc
Spectroscopy: An International Journal , 2004, DOI: 10.1155/2004/605373
Abstract: Investigators using mono channel near infrared spectroscopy (NIRS) have reported different patterns of change in cytochrome c oxidase (Cyt) in similar studies of tissue ischaemia. We investigated whether there were distinctive differences in NIRS signals obtained simultaneously from different sampling sites during the same imposed physiological intervention within the same subject. Methods: Subjects were 36, healthy, 10 kg, commercial swine undergoing cardiopulmonary bypass to initiate 3 to 7 periods of 7.5 minutes of circulatory arrest. Each arrest was initiated at one of 81 combinations of high, normal, or low levels of core temperature, haematocrit, pH, and serum glucose. Each combination was repeated twice, yielding 162 NIRS data sets. Results: Six distinct patterns of change of Cyt were found. Typically, brain Cyt quickly became reduced shortly after the start of arrest, muscle Cyt did not start becoming reduced until after 3½ minutes of arrest, and spinal cord Cyt either did not change status or became gradually reduced throughout the period of arrest. The brain response may reflect strong oxygen dependence, while the muscle response may indicate a dependency buffered by myoglobin stores, and the spine response may indicate a low concentration of available Cyt that is too diffuse to be rapidly influenced by changes in oxygen availability. Conclusion: Multi?channel NIRS is needed for systemic evaluation of respiration at the cellular level in clinical settings. Distinctive Cyt patterns of change occur in different organs at the same time, in response to circulatory arrest.
Distribution of calcifying and silicifying phytoplankton in relation to environmental and biogeochemical parameters during the late stages of the 2005 North East Atlantic Spring Bloom
K. Leblanc,C. E. Hare,Y. Feng,G. M. Berg
Biogeosciences Discussions , 2009,
Abstract: The late stage of the North East Atlantic (NEA) spring bloom was investigated during June 2005 along a transect section from 45 to 66° N between 15 and 20° W in order to characterize the contribution of siliceous and calcareous phytoplankton groups and describe their distribution in relation to environmental factors. We measured several biogeochemical parameters such as nutrients, surface trace metals, algal pigments, biogenic silica (BSi), particulate inorganic carbon (PIC) or calcium carbonate, particulate organic carbon, nitrogen and phosphorus (POC, PON and POP, respectively), as well as transparent exopolymer particles (TEP). Results were compared with other studies undertaken in this area since the JGOFS NABE program. Characteristics of the spring bloom generally agreed well with the accepted scenario for the development of the autotrophic community. The NEA seasonal diatom bloom was in the late stages when we sampled the area and diatoms were constrained to the northern part of our transect, over the Icelandic Basin (IB) and Icelandic Shelf (IS). Coccolithophores dominated the phytoplankton community, with a large distribution over the Rockall-Hatton Plateau (RHP) and IB. The Porcupine Abyssal Plain (PAP) region at the southern end of our transect was the region with the lowest biomass, as demonstrated by very low chl-a concentrations and a community dominated by picophytoplankton. Early depletion of dissolved silicic acid (DSi) and increased stratification of the surface layer most likely triggered the end of the diatom bloom, leading to coccolithophore dominance. The chronic Si deficiency observed in the NEA could be linked to moderate Fe limitation, which increases the efficiency of the Si pump. TEP closely mirrored the distribution of both biogenic silica at depth and prymnesiophytes in the surface layer suggesting the sedimentation of the diatom bloom in the form of aggregates, but the relative contribution of diatoms and coccolithophores to carbon export in this area still needs to be resolved.
Specific heat of underdoped cuprates: RVB versus Fermi arcs
J. P. F. LeBlanc,E. J. Nicol,J. P. Carbotte
Physics , 2009, DOI: 10.1103/PhysRevB.80.060505
Abstract: A recent microscopic model of the pseudogap state, based on the resonating valence bond (RVB) spin liquid, has provided a simple ansatz for the electronic self energy in which a gap forms on the antiferromagnetic Brillouin zone as the limit of a Mott insulator is approached in the underdoped regime. Here, the ansatz is employed to calculate the electronic specific heat when a superconducting gap is also included. We find qualitative agreement with all experimental observations in the underdoped regime of the cuprates. We explore the relationship of the theory to two other purely phenomenological approaches, the nodal liquid and the Fermi arc model, and provide justification for their use on experimental data in light of this microscopic RVB theory.
Remarks Concerning the Study of Four-Jet Events from Hadronic Decays of the Z0
H. Jeremie,P. Leblanc,E. Lefebvre,D. Davignon,G. Karapetian;
Physics , 2006, DOI: 10.1139/P06-048
Abstract: The angular correlations of four-jet events from hadronic decays of the Z0 have been studied in the past mainly to extract from them the fundamental constants of quantum chromodynamics called colour factors. Previous studies have used all the available phase-space in order to maximize statistics. In this note we want to point out the possibility that significant differences between experiment and theory in restricted regions of phase-space might have escaped detection. Such differences could be a harbinger of the existence of new particles. Some preliminary results are presented.
Signatures of superconducting gap inhomogeneities in optical properties
J. P. F. LeBlanc,E. J. Nicol,J. P. Carbotte
Physics , 2008, DOI: 10.1103/PhysRevB.78.094513
Abstract: Scanning tunneling spectroscopy applied to the high-$T_{c}$ cuprates has revealed significant spatial inhomogeneity on the nanoscale. Regions on the order of a coherence length in size show variations of the magnitude of the superconducting gap of order $\pm20%$ or more. An important unresolved question is whether or not these variations are also present in the bulk, and how they influence superconducting properties. As many theories and data analyses for high-$T_{c}$ superconductivity assume spatial homogeneity of the gap magnitude, this is a pressing question. We consider the far-infrared optical conductivity and evaluate, within an effective medium approximation, what signatures of spatial variations in gap magnitude are present in various optical quantities. In addition to the case of d-wave superconductivity, relevant to the high-$T_c$ cuprates, we have also considered s-wave gap symmetry in order to provide expected signatures of inhomogeneities for superconductors in general. While signatures of gap inhomogeneities can be strongly manifested in s-wave superconductors, we find that the far-infrared optical conductivity in d-wave is robust against such inhomogeneity.
Emergence of Plasmaronic Structure in the Near Field Optical Response of Graphene
J. P. Carbotte,J. P. F. LeBlanc,E. J. Nicol
Physics , 2012, DOI: 10.1103/PhysRevB.85.201411
Abstract: The finite momentum optical response $\sigma({\boldsymbol{q}},\omega)$ of graphene can be probed with the innovative technique of infrared nanoscopy where mid-infrared radiation is confined by an atomic force microscope cantilever tip. In contrast to conventional $q\sim 0$ optical absorption which primarily involves Dirac fermions with momentum near the Fermi momentum, $k\sim k_F$, for finite $q$, $\sigma({\boldsymbol{q}},\omega)$ has the potential to provide information on many body renormalizations and collective phenomena which have been found at small $k< k_F$ near the Dirac point in electron-doped graphene. For electron-electron interactions, the low energy excitation spectrum characterizing the incoherent part of the quasiparticle spectral function of Dirac electrons with $k\sim k_F$ consists of a flat, small amplitude background which scales with chemical potential and Fermi momentum. However, probing of the states with $k$ near $k=0$ will reveal plasmarons, a collective state of a charge carrier and a plasmon. These collective modes in graphene have recently been seen in angle-resolved photoemission spectroscopy and here we describe how they manifest in near field optics.
Signatures of Fermi surface reconstruction in Raman spectra of underdoped cuprates
J. P. F. Leblanc,J. P. Carbotte,E. J. Nicol
Physics , 2009, DOI: 10.1103/PhysRevB.81.064504
Abstract: We have calculated the Raman B$_{1g}$ and B$_{2g}$ spectra as a function of temperature, as well as doping, for the underdoped cuprates, using a model based on the resonating valence-bond spin-liquid. We discuss changes in intensity and peak position brought about by the presence of a pseudogap and the implied Fermi surface reconstruction, which are elements of this model. Signatures of Fermi surface reconstruction are evident as a sharp rise in the doping dependence of the antinodal to nodal peak ratio which occurs below the quantum critical point. The temperature dependence of the B$_{1g}$ polarization can be used to determine if the superconducting gap is limited to the Fermi pocket, as seen in angle resolved photoemission spectroscopy, or extends beyond. We find that the slope of the linear low energy B$_{2g}$ spectrum maintains its usual d-wave form, but with an effective gap which reflects the gap amplitude projected on the Fermi pocket. Our calculations capture the main qualitative features revealed in the extensive data set available on the HgBa$_2$CuO$_{4+\delta}$ (Hg-1201) cuprate.
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