The Experts below are selected from a list of 7578 Experts worldwide ranked by ideXlab platform

Sophie Dubacq - One of the best experts on this subject based on the ideXlab platform.

Jeffrey D Whyte - One of the best experts on this subject based on the ideXlab platform.

Maria M M Kaisar - One of the best experts on this subject based on the ideXlab platform.

  • improved diagnosis of trichuris trichiura by using a bead beating procedure on ethanol preserved stool samples prior to dna isolation and the performance of multiplex real time pcr for intestinal parasites
    Parasitology, 2017
    Co-Authors: Maria M M Kaisar, Eric A T Brienen, Yenny Djuardi, Erliyani Sartono, Taniawati Supali, Maria Yazdanbakhsh, Jaco J Verweij, Lisette Van Lieshout
    Abstract:

    For the majority of intestinal parasites, real-time PCR-based diagnosis outperforms microscopy. However, the data for Trichuris trichiura have been less convincing and most comparative studies have been performed in populations with low prevalence. This study aims to improve detection of T. trichuria DNA in human stool by evaluating four sample preparation methods. Faecal samples ( n = 60) were collected at Flores island, Indonesia and examined by microscopy. Aliquots were taken and a Bead-Beating procedure was used both on directly frozen stool and on material preserved with 96% ethanol. PCR on frozen samples showed 40% to be positive for T. trichiura , compared with 45% positive by microscopy. The percentage positive increased when using ethanol preservation (45·0%), Bead-Beating (51·7%) and a combination (55·0%) and all three methods showed significantly higher DNA loads. The various procedures had a less pronounced effect on the PCR results of nine other parasite targets tested. Most prevalent were Ascaris lumbricoides (≈60%), Necator americanus (≈60%), Dientamoeba fragilis (≈50%) and Giardia lamblia (≈12%). To validate the practicality of the procedure, Bead-Beating was applied in a population-based survey testing 910 stool samples. Findings confirmed Bead-Beating before DNA extraction to be a highly efficient procedure for the detection of T. trichiura DNA in stool.

Lisette Van Lieshout - One of the best experts on this subject based on the ideXlab platform.

  • improved diagnosis of trichuris trichiura by using a bead beating procedure on ethanol preserved stool samples prior to dna isolation and the performance of multiplex real time pcr for intestinal parasites
    Parasitology, 2017
    Co-Authors: Maria M M Kaisar, Eric A T Brienen, Yenny Djuardi, Erliyani Sartono, Taniawati Supali, Maria Yazdanbakhsh, Jaco J Verweij, Lisette Van Lieshout
    Abstract:

    For the majority of intestinal parasites, real-time PCR-based diagnosis outperforms microscopy. However, the data for Trichuris trichiura have been less convincing and most comparative studies have been performed in populations with low prevalence. This study aims to improve detection of T. trichuria DNA in human stool by evaluating four sample preparation methods. Faecal samples ( n = 60) were collected at Flores island, Indonesia and examined by microscopy. Aliquots were taken and a Bead-Beating procedure was used both on directly frozen stool and on material preserved with 96% ethanol. PCR on frozen samples showed 40% to be positive for T. trichiura , compared with 45% positive by microscopy. The percentage positive increased when using ethanol preservation (45·0%), Bead-Beating (51·7%) and a combination (55·0%) and all three methods showed significantly higher DNA loads. The various procedures had a less pronounced effect on the PCR results of nine other parasite targets tested. Most prevalent were Ascaris lumbricoides (≈60%), Necator americanus (≈60%), Dientamoeba fragilis (≈50%) and Giardia lamblia (≈12%). To validate the practicality of the procedure, Bead-Beating was applied in a population-based survey testing 910 stool samples. Findings confirmed Bead-Beating before DNA extraction to be a highly efficient procedure for the detection of T. trichiura DNA in stool.

Giulio Di Toro - One of the best experts on this subject based on the ideXlab platform.

  • dislocation motion and the microphysics of flash heating and weakening of faults during earthquakes
    Crystals, 2016
    Co-Authors: Elena Spagnuolo, Marie Violay, Oliver Plümper, Andrea Cavallo, Giulio Di Toro
    Abstract:

    Earthquakes are the result of slip along faults and are due to the decrease of rock frictional strength (dynamic weakening) with increasing slip and slip rate. Friction experiments simulating the abrupt accelerations (>>10 m/s2), slip rates (~1 m/s), and normal stresses (>>10 MPa) expected at the passage of the earthquake rupture along the front of fault patches, measured large fault dynamic weakening for slip rates larger than a critical velocity of 0.01–0.1 m/s. The dynamic weakening corresponds to a decrease of the friction coefficient (defined as the ratio of shear stress vs. normal stress) up to 40%–50% after few millimetres of slip (flash weakening), almost independently of rock type. The microstructural evolution of the sliding interfaces with slip may yield hints on the microphysical processes responsible for flash weakening. At the microscopic scale, the frictional strength results from the interaction of micro- to nano-scale surface irregularities (asperities) which deform during fault sliding. During flash weakening, the visco-plastic and brittle work on the asperities results in abrupt frictional heating (flash heating) and grain size reduction associated with mechano-chemical reactions (e.g., decarbonation in CO2-bearing minerals such as calcite and dolomite; dehydration in water-bearing minerals such as clays, serpentine, etc.) and phase transitions (e.g., flash melting in silicate-bearing rocks). However, flash weakening is also associated with grain size reduction down to the nanoscale. Using focused ion beam scanning and transmission electron microscopy, we studied the micro-physical mechanisms associated with flash heating and nanograin formation in carbonate-bearing fault rocks. Experiments were conducted on pre-cut Carrara marble (99.9% calcite) cylinders using a rotary shear apparatus at conditions relevant to seismic rupture propagation. Flash heating and weakening in calcite-bearing rocks is associated with a shock-like stress release due to the migration of fast-moving dislocations and the conversion of their kinetic energy into heat. From a review of the current natural and experimental observations we speculate that this mechanism tested for calcite-bearing rocks, is a general mechanism operating during flash weakening (e.g., also precursory to flash melting in the case of silicate-bearing rocks) for all fault rock types undergoing fast slip acceleration due to the passage of the seismic rupture front.

  • Dislocation Motion and the Microphysics of Flash Heating and Weakening of Faults during Earthquakes
    Crystals, 2016
    Co-Authors: Elena Spagnuolo, Aurora Cavallo, Marie Violay, Oliver Plümper, Giulio Di Toro
    Abstract:

    © 2016 by the authors; licensee MDPI, Basel, Switzerland.Earthquakes are the result of slip along faults and are due to the decrease of rock frictional strength (dynamic weakening) with increasing slip and slip rate. Friction experiments simulating the abrupt accelerations (>>10 m/s2), slip rates (~1 m/s), and normal stresses (>>10 MPa) expected at the passage of the earthquake rupture along the front of fault patches, measured large fault dynamic weakening for slip rates larger than a critical velocity of 0.01–0.1 m/s. The dynamic weakening corresponds to a decrease of the friction coefficient (defined as the ratio of shear stress vs. normal stress) up to 40%–50% after few millimetres of slip (flash weakening), almost independently of rock type. The microstructural evolution of the sliding interfaces with slip may yield hints on the microphysical processes responsible for flash weakening. At the microscopic scale, the frictional strength results from the interaction of micro- to nano-scale surface irregularities (asperities) which deform during fault sliding. During flash weakening, the visco-plastic and brittle work on the asperities results in abrupt frictional heating (flash heating) and grain size reduction associated with mechano-chemical reactions (e.g., decarbonation in CO2-bearing minerals such as calcite and dolomite; dehydration in water-bearing minerals such as clays, serpentine, etc.) and phase transitions (e.g., flash melting in silicate-bearing rocks). However, flash weakening is also associated with grain size reduction down to the nanoscale. Using focused ion beam scanning and transmission electron microscopy, we studied the micro-physical mechanisms associated with flash heating and nanograin formation in carbonate-bearing fault rocks. Experiments were conducted on pre-cut Carrara marble (99.9% calcite) cylinders using a rotary shear apparatus at conditions relevant to seismic rupture propagation. Flash heating and weakening in calcite-bearing rocks is associated with a shock-like stress release due to the migration of fast-moving dislocations and the conversion of their kinetic energy into heat. From a review of the current natural and experimental observations we speculate that this mechanism tested for calcite-bearing rocks, is a general mechanism operating during flash weakening (e.g., also precursory to flash melting in the case of silicate-bearing rocks) for all fault rock types undergoing fast slip acceleration due to the passage of the seismic rupture front.