991 resultados para in-situ test


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Background Changes in the composition of gastrointestinal microbiota by dietary interventions using pro- and prebiotics provide opportunity for improving health and preventing disease. However, the capacity of lupin kernel fiber (LKFibre), a novel legume-derived food ingredient, to act as a prebiotic and modulate the colonic microbiota in humans needed investigation.

Aim of the study The present study aimed to determine the effect of LKFibre on human intestinal microbiota by quantitative fluorescent in situ hybridization (FISH) analysis.

Design A total of 18 free-living healthy males between the ages of 24 and 64 years consumed a control diet and a LKFibre diet (containing an additional 17–30 g/day fiber beyond that of the control—incorporated into daily food items) for 28 days with a 28-day washout period in a single-blind, randomized, crossover dietary intervention design.
Methods Fecal samples were collected for 3 days towards the end of each diet and microbial populations analyzed by FISH analysis using 16S rRNA gene-based oligonucleotide probes targeting total and predominant microbial populations.

Results Significantly higher levels of Bifidobacterium spp. (P = 0.001) and significantly lower levels of the clostridia group of C. ramosum, C. spiroforme and C. cocleatum (P = 0.039) were observed on the LKFibre diet compared with the control. No significant differences between the LKFibre and the control diet were observed for total bacteria, Lactobacillus spp., the Eubacterium spp., the C. histolyticum/C. lituseburense group and the Bacteroides–Prevotella group.
Conclusions Ingestion of LKFibre stimulated colonic bifidobacteria growth, which suggests that this dietary fiber may be considered as a prebiotic and may beneficially contribute to colon health.

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For free‐spawning organisms that release gametes into the sea, sperm limitation (too few sperm to fertilize all eggs) is a major factor limiting reproductive success. Given such circumstances, the presence of several mechanisms to prevent polyspermy (too many sperm) may seem paradoxical; however, a growing body of data suggests that natural fertilization levels, though variable, can routinely be high. Under such conditions, polyspermy is much more likely. The tension between sperm limitation and polyspermy represents sexual conflict because males, in competing to fertilize as many eggs as possible, can impose lethal costs on eggs if multiple sperm gain entry. Here we present data for a marine invertebrate indicating high levels of polyspermy under sperm‐limited conditions. When the sea urchin Evechinus chloroticus was induced to spawn in situ, mean rates of polyspermy were 17.3% ±3.4%, and polyspermy was recorded at rates as high as 62.7%. Polyspermy was nearly always present, even when fertilization rates were <50%, confirming predictions that it should be present under sperm‐limited conditions. Both sperm limitation and polyspermy imposed substantial reproductive costs, and we conclude that both sexual conflict related to polyspermy and sperm limitation have been simultaneous strong selective forces shaping the evolution of reproductive traits in the sea.

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High-yield multiwalled boron nitride (BN) nanotubes have been produced using a ball milling-annealing method. The BN nanotubes with a diameter less than 10 nm and a well-crystallized multiwalled structure were formed via an in situ nitriding reaction. The systematic investigation of the formation process at different annealing temperatures and for different times suggested that the formation of the unique multiwalled structure was attributed by a two-dimensional growth of the BN phase and a nonmetal catalytic growth.

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In situ neutron diffraction and Elasto-Plastic Self-Consistent (EPSC) polycrystal modelling have been employed to investigate which deformation mechanisms are involved in the plasticity of extruded AZ31 Mg alloy during the tensile loading along the extrusion direction. On the basis of this study we were able to determine the relative activity of the slip and twinning deformation modes. By tuning the parameters of the EPSC model (i.e. the critical resolved shear strengths and hardening parameters), excellent agreement with the experimental data has been achieved. It is shown that the strain in the crystallographic ⟨c ⟩direction is accommodated mainly by ⟨c + a ⟩ dislocation slip on second-order pyramidal planes. The results further indicate that either slip of ⟨a ⟩dislocations occurs on {10.1} pyramidal planes or cross-slip from basal and prismatic planes takes place.

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OBJECTIVE: We have previously shown in humans that local infusion of a nitric oxide synthase (NOS) inhibitor into the femoral artery attenuates the increase in leg glucose uptake during exercise without influencing total leg blood flow. However, rodent studies examining the effect of NOS inhibition on contraction-stimulated skeletal muscle glucose uptake have yielded contradictory results. This study examined the effect of local infusion of an NOS inhibitor on skeletal muscle glucose uptake (2-deoxyglucose) and capillary blood flow (contrast-enhanced ultrasound) during in situ contractions in rats.

RESEARCH DESIGN AND METHODS: Male hooded Wistar rats were anesthetized and one hindleg electrically stimulated to contract (2 Hz, 0.1 ms) for 30 min while the other leg rested. After 10 min, the NOS inhibitor NG-nitro-L-arginine methyl ester (L-NAME) (arterial concentration of 5 µmol/l) or saline was infused into the epigastric artery of the contracting leg.

RESULTS: Local NOS inhibition had no effect on blood pressure, heart rate, or muscle contraction force. Contractions increased (P < 0.05) skeletal muscle NOS activity, and this was prevented by L-NAME infusion. NOS inhibition caused a modest significant (P < 0.05) attenuation of the increase in femoral blood flow during contractions, but importantly there was no effect on capillary recruitment. NOS inhibition attenuated (P < 0.05) the increase in contraction-stimulated skeletal muscle glucose uptake by ~35%, without affecting AMP-activated protein kinase (AMPK) activation.

CONCLUSIONS: NOS inhibition attenuated increases in skeletal muscle glucose uptake during contraction without influencing capillary recruitment, suggesting that NO is critical for part of the normal increase in skeletal muscle fiber glucose uptake during contraction.

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This study investigated the tensile properties of a rotating or ballooning staple yarn. The results indicated that the effect of rotating speed on the tensile properties of a ballooning staple yarn was significant. As the yarn rotating speed increased, the tenacity of the rotating or ballooning yarn decreased, while the yarn breaking elongation increased. The effect of rotating speed on the tenacity of a ballooning staple yarn varied for different yarns. These results demonstrated that the breaking force of a ballooning yarn was much lower than the yarn breaking force obtained from normal tensile tests. These results provide new insight into the problems of yarn breakage in yarn spinning and twisting processes.

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An in situ laser-scanning confocal microscopy study has been undertaken into Widmanstätten ferrite formation in an Fe–C alloy, in combination with electron backscattered diffraction. It has been found for the first time that the sympathetic nucleation of Widmanstätten ferrite on grain boundary allotriomorphs can exhibit a step wise change in orientation and growth direction until the most favourable growth conditions are achieved.

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The adsorption of DNA on the Langmuir film of a cationic surfactant, dioctadecyldimethylammonium bromide (DODA·Br), and the change of the aggregation morphology of the composite monolayer with respect to surface pressure have been investigated by Brewster angle microscopy (BAM). In contrast with the case of DODA·Br on pure water subphase, when DNA was dispersed into subphase, its adsorption to the interface monolayer through electrostatic interaction decreases the charge density and therefore promotes the formation of domain at low surface pressure. In addition, the electrostatic interaction changed the phase morphology of DODA·Br Langmuir monolayer under different surface pressure, that is, from flower-shaped crystalline domain on the pure water subphase to circular domain on the subphase dispersed with DNA. The result also shows that the monolayer of the composite at air/water interface under the high pressure is not homogeneous, but consists of incompletely fused domains. For the Langmuir film of the surfactant with shorter alkyl-chains, similar morphology can be observed both under the high and low surface pressure. But the tight-stacked circular domain is no longer observed.

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An extensive study was made of the physical properties of a range of cementitiously stabilised materials to determine their suitability for use in in situ pavement construction. This process for recycling existing pavements has considerable environmental and cost benefits. Pavement models incorporating these materials were analysed to determine their structural behaviour.

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Investigates how first year biology undergraduates learn dissection when they have access to such interactive multimedia technology. Related design and developmental factors were evaluated in relation to how they helped students learn the content in the multimedia program. Through the use of interactive technology students can learn at their own pace without the need for actual animal dissection.

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Al/MgAl2O4 in situ metal matrix composites have been synthesized using value-added silica sources (microsilica and rice husk ash) containing ~97% SiO2 in Al-5 wt.% Mg alloy. The thermodynamics and kinetics of MgAl2O4 formation are discussed in detail. The MgO and MgAl2O4 phases were found to dominate in microsilica (MS) and rice husk ash (RHA) value-added composites, respectively, during the initial stage of holding the composites at 750 °C. A transition phase between MgO and MgAl2O4 was detected by the scanning electron microscopy and energy-dispersive spectroscopy (SEM–EDS) analysis of the particles extracted from the composite using 25% NaOH solution. This confirms that MgO is gradually transformed to MgAl2O4 by the reaction 3SiO2(s)+2MgO(s)+4Al(l)→2MgAl2O4(s)+3Si(l). The stoichiometry of MgAl2O4, n, computed by a new methodology is between 0.79 and 1.18. The reaction between the silica sources and the molten metal stopped after 55% of the silica source was consumed. A gradual increase in mean MgAl2O4 crystallite size, D, from 24 to 36 nm was observed in the samples held for 10 h.

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MgAl2O4 (spinel) is considered as a commercially important ceramic reinforcement in MMC fabrication because of the possible tailorable properties imparted with Al for many applications. Generally, any oxygen source, i.e., the dissolved oxygen, or pure oxygen atmosphere or atmospheric oxygen is sufficient for the formation of MgAl2O4 in Al–Mg alloy. Among all the reactive oxygen sources, the reactivity of SiO2 with Al alloy is found to be higher. Amorphous silica is highly reactive in nature compared to crystalline silica. The present study has examined the thermodynamics of MgAl2O4 formation in Al–Mg alloy by amorphous silica sources with the aid of differential thermal analyzer (DTA) and the simulated experiments. The dissolution of Si and the formation of MgAl2O4 are detected as the endothermic peak and the immediate exothermic peak respectively in DTA curves and the presence of MgAl2O4 is confirmed by the XRD of the simulated sample. The MgO formed due to the oxidation of Mg in Al–Mg alloy has been found to influence the MgAl2O4 formation.