Analogue modeling of instabilities in crater lake hydrothermal systems.

International audienceWe carried out analogue experiments on two-phase boiling systems, using a porous vertical cylinder, saturated with water. The base of the cylinder was heated, and the top was cooled, as in a natural hydrothermal system. Previous work had shown that once the two-phase zone reached a certain level, thermal instabilities would develop. We made measurements of the acoustic energy related to boiling, and we found that high levels of acoustic noise were associated with the part of the cycle in which there was upward water movement. We repeated our experiments with a cooling water tank at the top of the system, representing a crater lake. This showed that periodic thermal instabilities still developed in this situation. We then compared our analogue measurements to two natural systems known to exhibit periodic behavior. There is good agreement between the thermal and acoustic cycling seen in our model and the observations made at Inferno Crater Lake in the Waimangu Geothermal area, New Zealand, whose level cycles by nearly 10 m, with a typical period of 38 days. Particularly notable is how in both systems high levels of acoustic noise are associated with rising water level. The much larger Ruapehu Crater Lake, also in New Zealand, cycled with a period of several months to a year for over a decade prior to the 1995 eruption. Strong acoustic and seismic energy usually occurred just before the lake temperature started to rise. This suggests a slightly different model, in which the increasing two-phase flow zone triggers more general convection once it reaches the base of the lake

NMR imaging of water flow in packed beds

Measurements by magnetic resonance imaging (MRI) of water flow within granular porous media are presented in this study. Our goal was not only to obtain visualizations of velocity field in porous media but rather to make accurate measurements of interstitial and averaged velocities in bead packs. Two situations were examined: the first for a packed bed with a large beads diameter where it was possible to visualize the interstitial velocities and the second with a packed bed with a small beads diameter where only averaged interstitial velocities were measured

Study of dispersion by NMR: comparison between NMR measurements and stochastic simulation

Dispersion remains, today, a highly topical subject. Our group has been interested in characterizing this phenomenon by pulsed-field-gradient NMR technique. Direct measurement of the dispersion coefficient can be done with a Pulsed Gradient Spin Echo (PGSE) sequence by assuming that the asymptotic regime is reached. In unsteady state, the propagator formalism is used. To better understand these measurements, the NMR experiment is modeled using a stochastic simulation (random walks) and compared with experimental results. The comparison is made for the simple case of Poiseuille flow in a circular tube (Taylor-Aris dispersion)

Study of dispersion by NMR: comparison between NMR measurements and stochastic simulation

Dispersion remains, today, a highly topical subject. Our group has been interested in characterizing this phenomenon by pulsed-field-gradient NMR technique. Direct measurement of the dispersion coefficient can be done with a Pulsed Gradient Spin Echo (PGSE) sequence by assuming that the asymptotic regime is reached. In unsteady state, the propagator formalism is used. To better understand these measurements, the NMR experiment is modeled using a stochastic simulation (random walks) and compared with experimental results. The comparison is made for the simple case of Poiseuille flow in a circular tube (Taylor-Aris dispersion)

Effect of silane coupling agents on basalt fiber-epoxidized vegetable oil matrix composite materials analyzed by the single fiber fragmentation technique

The fiber-matrix interfacial shear strength (IFSS) of biobased epoxy composites reinforced with basalt fiber was investigated by the fragmentation method. Basalt fibers were modified with four different silanes, (3-aminopropyl)trimethoxysilane, [3-(2-aminoethylamino)propyl]-trimethoxysilane, trimethoxy[2-(7-oxabicyclo[4.1.0]hept-3-yl)ethyl]silane and (3-glycidyloxypropyl)trimethoxysilane to improve the adhesion between the basalt fiber and the resin. The analysis of the fiber tensile strength results was performed in terms of statistical parameters. The tensile strength of silane-treated basalt fiber is higher than the tensile strength of the untreated basalt fiber; this behavior may be due to flaw healing effect on the defected fiber surfaces. The IFSS results on the composites confirm that the interaction between the fiber modified with coupling agents and the bio-based epoxy resin was much stronger than that with the untreated basalt fiber. POLYM. COMPOS., 36:1205-1212, 2015. (c) 2014 Society of Plastics EngineersContract grant sponsor: Programme Support Research and Development (Polytechnic University of Valencia); contract grant number: PAID-00-12.Samper Madrigal, MD.; Petrucci, R.; Sánchez Nacher, L.; Balart Gimeno, RA.; Kenny, JM. (2015). Effect of silane coupling agents on basalt fiber-epoxidized vegetable oil matrix composite materials analyzed by the single fiber fragmentation technique. Polymer Composites. 36(7):1205-1212. https://doi.org/10.1002/pc.23023S12051212367Lopattananon, N., Kettle, A. P., Tripathi, D., Beck, A. J., Duval, E., France, R. M., … Jones, F. R. (1999). Interface molecular engineering of carbon-fiber composites. Composites Part A: Applied Science and Manufacturing, 30(1), 49-57. doi:10.1016/s1359-835x(98)00109-2Nishikawa, M., Okabe, T., & Takeda, N. (2008). Determination of interface properties from experiments on the fragmentation process in single-fiber composites. Materials Science and Engineering: A, 480(1-2), 549-557. doi:10.1016/j.msea.2007.07.067Rao, V., Herrera-franco, P., Ozzello, A. D., & Drzal, L. T. (1991). A Direct Comparison of the Fragmentation Test and the Microbond Pull-out Test for Determining the Interfacial Shear Strength. The Journal of Adhesion, 34(1-4), 65-77. doi:10.1080/00218469108026506Doan, T.-T.-L., Brodowsky, H., & Mäder, E. (2012). Jute fibre/epoxy composites: Surface properties and interfacial adhesion. Composites Science and Technology, 72(10), 1160-1166. doi:10.1016/j.compscitech.2012.03.025Koyanagi, J., Nakatani, H., & Ogihara, S. (2012). Comparison of glass–epoxy interface strengths examined by cruciform specimen and single-fiber pull-out tests under combined stress state. Composites Part A: Applied Science and Manufacturing, 43(11), 1819-1827. doi:10.1016/j.compositesa.2012.06.018Johnson, A. C., Hayes, S. A., & Jones, F. R. (2012). 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Tensile properties of fibre-reinforced metals: Copper/tungsten and copper/molybdenum. Journal of the Mechanics and Physics of Solids, 13(6), 329-350. doi:10.1016/0022-5096(65)90035-9Altuna, F. I., Espósito, L. H., Ruseckaite, R. A., & Stefani, P. M. (2010). Thermal and mechanical properties of anhydride-cured epoxy resins with different contents of biobased epoxidized soybean oil. Journal of Applied Polymer Science, 120(2), 789-798. doi:10.1002/app.33097Harry-O’kuru, R. E., Mohamed, A., Gordon, S. H., & Xu, J. (2012). Syntheses of Novel Protein Products (Milkglyde, Saliglyde, and Soyglyde) from Vegetable Epoxy Oils and Gliadin. Journal of Agricultural and Food Chemistry, 60(7), 1688-1694. doi:10.1021/jf204701tPan, X., Sengupta, P., & Webster, D. C. (2011). High Biobased Content Epoxy–Anhydride Thermosets from Epoxidized Sucrose Esters of Fatty Acids. 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LRRK2 protein levels are determined by kinase function and are crucial for kidney and lung homeostasis in mice

Mutations in leucine-rich repeat kinase 2 (LRRK2) cause late-onset Parkinson's disease (PD), but the underlying pathophysiological mechanisms and the normal function of this large multidomain protein remain speculative. To address the role of this protein in vivo, we generated three different LRRK2 mutant mouse lines. Mice completely lacking the LRRK2 protein (knock-out, KO) showed an early-onset (age 6 weeks) marked increase in number and size of secondary lysosomes in kidney proximal tubule cells and lamellar bodies in lung type II cells. Mice expressing a LRRK2 kinase-dead (KD) mutant from the endogenous locus displayed similar early-onset pathophysiological changes in kidney but not lung. KD mutants had dramatically reduced full-length LRRK2 protein levels in the kidney and this genetic effect was mimicked pharmacologically in wild-type mice treated with a LRRK2-selective kinase inhibitor. Knock-in (KI) mice expressing the G2019S PD-associated mutation that increases LRRK2 kinase activity showed none of the LRRK2 protein level and histopathological changes observed in KD and KO mice. The autophagy marker LC3 remained unchanged but kidney mTOR and TCS2 protein levels decreased in KD and increased in KO and KI mice. Unexpectedly, KO and KI mice suffered from diastolic hypertension opposed to normal blood pressure in KD mice. Our findings demonstrate a role for LRRK2 in kidney and lung physiology and further show that LRRK2 kinase function affects LRRK2 protein steady-state levels thereby altering putative scaffold/GTPase activity. These novel aspects of peripheral LRRK2 biology critically impact ongoing attempts to develop LRRK2 selective kinase inhibitors as therapeutics for PD

High LRRK2 Levels Fail to Induce or Exacerbate Neuronal Alpha-Synucleinopathy in Mouse Brain

The G2019S mutation in the multidomain protein leucine-rich repeat kinase 2 (LRRK2) is one of the most frequently identified genetic causes of Parkinson’s disease (PD). Clinically, LRRK2(G2019S) carriers with PD and idiopathic PD patients have a very similar disease with brainstem and cortical Lewy pathology (α-synucleinopathy) as histopathological hallmarks. Some patients have Tau pathology. Enhanced kinase function of the LRRK2(G2019S) mutant protein is a prime suspect mechanism for carriers to develop PD but observations in LRRK2 knock-out, G2019S knock-in and kinase-dead mutant mice suggest that LRRK2 steady-state abundance of the protein also plays a determining role. One critical question concerning the molecular pathogenesis in LRRK2(G2019S) PD patients is whether α-synuclein (aSN) has a contributory role. To this end we generated mice with high expression of either wildtype or G2019S mutant LRRK2 in brainstem and cortical neurons. High levels of these LRRK2 variants left endogenous aSN and Tau levels unaltered and did not exacerbate or otherwise modify α-synucleinopathy in mice that co-expressed high levels of LRRK2 and aSN in brain neurons. On the contrary, in some lines high LRRK2 levels improved motor skills in the presence and absence of aSN-transgene-induced disease. Therefore, in many neurons high LRRK2 levels are well tolerated and not sufficient to drive or exacerbate neuronal α-synucleinopathy