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•Amygdaloid administration of antioxidants or TRPA1 antagonists attenuated nociception and affective pain in neuropathy.•Blocking spinal 5-HT1A receptors prevented the antinociception ...induced by the amygdaloid drug treatments.•In neuropathy, amygdaloid oxidative stress driving TRPA1 suppressed serotonergic feedback-inhibition of nociception.•Antioxidants and TRPA1 antagonists in the amygdala disinhibited the serotonergic feedback-inhibition of nociception.
Earlier studies indicate that the central nucleus of the amygdala (CeA) contributes to neuropathic pain. Here we studied whether amygdaloid administration of antioxidants or antagonists of TRPA1 that is among ion channels activated by oxidative stress attenuates nociceptive or affective pain in experimental neuropathy, and whether this effect involves amygdaloid astrocytes or descending serotonergic pathways acting on the spinal 5-HT1A receptor. The experiments were performed in rats with spared nerve injury (SNI). Drugs were administered through a chronic cannula in the CeA or internal capsule (control site), and an intrathecal catheter. Nociception was assessed using monofilaments and affective pain using conditioned place-aversion. Antioxidants or TRPA1 antagonists in the CeA attenuated both nociceptive and affective pain in SNI animals but not in sham controls or in a control injection site. Drugs influencing astroglia (a gap junction decoupler or a D-amino acid oxidase inhibitor) in the CeA had no effect on SNI rats, whereas local anesthesia of the CeA attenuated nociception. Spinally administered 5-HT1A receptor antagonist at a dose that had no effect alone prevented the antinociceptive effect of amygdaloid TRPA1 blockers. The results suggest that injury-induced amygdaloid oxidative stress that drives TRPA1 promotes neuropathic pain behavior. This pronociceptive effect involves suppression of medullospinal serotonergic feedback-inhibition acting on the spinal 5-HT1A receptor. While the CeA is involved in mediating the nerve injury-induced pronociception, it may not be a critical relay for the recruitment of medullospinal feedback-inhibition.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
River and open-channel flows present complex three-dimensional (3D) structures in the water column and on the surface as a result of the existence of secondary currents driven by either centrifugal ...force or turbulence. This paper experimentally investigates secondary currents in a straight, turbulent, rough-bed open-channel flow; the effect of different channel width to flow depth ratios (12.25, 15, and 20) on secondary currents; and surface boils associated with secondary currents at moderate Reynolds numbers. Nearly instantaneous profiles of three components of flow velocity and turbulence characteristics in the water column were measured by using an acoustic Doppler velocity profiler (ADVP). Simultaneously, large-scale particle image velocimetry was used to measure the water surface velocities and turbulence structures. Mean velocity patterns in the water undulate across the channel, indicating the presence of secondary currents in the long-term average flow structure. Secondary currents affect the distribution of bed shear stress, Reynolds stress, and turbulence intensities across the channel. The aspect ratio determines the number of secondary cells in the water column. A mean multiband undulating surface velocity pattern in the transverse direction correlates with the secondary cell distribution in the water column below. The instantaneous position of the upwelling and downwelling regions on the surface may deviate from their long-term mean position, indicating a meandering of the surface pattern. Vortex structures are detected from instantaneous surface velocity maps, and vortex boil lines are identified. Boil vortices mainly occur in upwelling areas with high vorticity. The simultaneous detailed velocity measurements in the water column and on the free surface have shown a good agreement between the secondary cell patterns obtained by the two methods.
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DOBA, FGGLJ, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
A new radial time projection chamber based on Gas Electron Multiplier amplification layers was developed for the BONuS12 experiment in Hall B at Jefferson Lab. This device represents a significant ...evolutionary development over similar devices constructed for previous experiments, including cylindrical amplification layers constructed from single continuous GEM foils with less than 1% dead area. Particular attention had been paid to producing excellent geometric uniformity of all electrodes, including the very thin metalized polyester film of the cylindrical cathode. This manuscript describes the design, construction, and performance of this new detector.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
A stereoscopic particle image velocimetry (PIV) system for use in shallow (
${\sim }$
0.5 m deep) rivers was developed and deployed in the Urie River, Scotland, to study the interactions between ...turbulent flow and a Ranunculus penicillatus plant patch in its native environment. Statistical moments of the velocity field were calculated utilizing a new method of reducing the contribution of measurement noise, based on the measurement redundancy inherent in the stereoscopic PIV method. Reynolds normal and shear stresses, their budget terms, and higher-order moments of the velocity probability distribution in the wake of the plant patch were found to be dominated by the presence of a free shear layer induced by the plant drag. Plant motion, estimated from the PIV images, was characterized by travelling waves that propagate along the plant with a velocity similar to the eddy convection velocity, suggesting a direct coupling between turbulence and the plant motion. The characteristic frequency of the plant velocity fluctuations (
${\sim }$
1 Hz) may suggest that the plant motion is dominated by large eddies with scale similar to the flow depth or plant length. Plant and fluid velocity fluctuations were, in contrast, found to be strongly correlated only over a narrow (
${\sim }$
30 mm) elevation range above the top of the plant, supporting a contribution of the shear layer turbulence to the plant motion. Many aspects of flow–aquatic plant interactions remain to be clarified, and the newly developed stereoscopic field PIV system should prove valuable in future studies.
Abstract
Hydro-abrasive erosion on hydraulic turbines is economically and energetically important. To better understand the causes and consequences of turbine erosion and to further develop ...mitigation measures, the suspended sediment concentration (
SSC
) and size distribution of mineral particles in the turbine water of the 64 MW high-head run-of-river hydropower plant (HPP) Fieschertal, Switzerland, have been continuously measured since 2012. An innovative combination of measuring techniques is used: turbidimeters, single-frequency acoustics, densimetry, laser diffraction and gravimetric analysis of water samples. Automatic warnings have been defined in the HPP’s control system to allow for systematic HPP shutdowns when the
SSC
in the valve chamber exceeds the threshold value of 10 g/l for at least 15 minutes. During the flood of July 29 and 30, 2017 with an
SSC
peak of 110 g/l, the intake was closed and the HPP was shut down for half a day. This prevented about 8000 tons of fine sediment from entering the HPP, which corresponds to 9 % of the turbines’ annual suspended sediment load (
SSL
) in 2017, or 12 % of the
SSL
in an average year without a significant flood. If the intake had been closed one hour earlier, the
SSL
could have been further reduced by about 3000 tons. For an earlier closing of the intake in case of floods, the turbidimeter at the intake shall be complemented by an additional instrument capable of measuring also medium to high
SSC
. Apart from the described flood event,
SSC
peaks in the range of 5 to 20 g/l occurring typically in late summer were attributed to re-suspension events in the storage tunnel due to HPP operation.
Hydro-abrasive erosion of hydraulic turbines is an economically important issue due to maintenance costs and production losses, in particular at high- and medium-head run-of- river hydropower plants ...(HPPs) on sediment laden rivers. In this paper, research and development in this field over the last century are reviewed. Facilities for sediment exclusion, typically sand traps, as well as turbine design and materials have been improved considerably. Since the 1980s, hard-coatings have been applied on Francis and Pelton turbine parts of erosion-prone HPPs and became state-of-the-art. These measures have led to increased times between overhauls and smaller efficiency reductions. Analytical, laboratory and field investigations have contributed to a better processes understanding and quantification of sediment-related effects on turbines. More recently, progress has been made in numerical modelling of turbine erosion. To calibrate, validate and further develop prediction models, more measurements from both physical model tests in laboratories and real-scale data from HPPs are required. Significant improvements to mitigate hydro-abrasive erosion have been achieved so far and development is ongoing. A good collaboration between turbine manufacturers, HPP operators, measuring equipment suppliers, engineering consultants, and research institutes is required. This contributes to the energy- and cost-efficient use of the worldwide hydropower potential.
Intensive theoretical and experimental efforts over the past decade have aimed at explaining the discrepancy between data for the proton electric to magnetic form factor ratio, G(E)/G(M), obtained ...separately from cross section and polarization transfer measurements. One possible explanation for this difference is a two-photon-exchange contribution. In an effort to search for effects beyond the one-photon-exchange or Born approximation, we report measurements of polarization transfer observables in the elastic H(eover →,e(')pover →) reaction for three different beam energies at a Q(2)=2.5 GeV(2), spanning a wide range of the kinematic parameter ε. The ratio R, which equals μ(p)G(E)/G(M) in the Born approximation, is found to be independent of ε at the 1.5% level. The ε dependence of the longitudinal polarization transfer component P(ℓ) shows an enhancement of (2.3±0.6)% relative to the Born approximation at large ε.
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CMK, CTK, FMFMET, IJS, NUK, PNG, UM
At medium- and high-head hydropower plants (HPPs) on sediment-laden rivers, hydro-abrasive erosion in turbines is an important economic issue. In HPPs with headwater storage, reservoir sedimentation ...is another problem related to fine sediment. On the one hand, turbine erosion is mitigated by reducing the sediment load in power waterways. On the other hand, reservoir sedimentation may be mitigated by conveying more fine sediment through power waterways to downstream river reaches. To optimize the operation of HPP schemes on the long-term, it is recommended to find a balance between these options based on real-time data using available monitoring techniques. An operational measure to mitigate turbine erosion is to close intakes and switch-off turbines in periods of high suspended sediment concentration (SSC) and coarse particles, typically during floods. Prerequisites for such operation are (i) there is no obligation to generate electricity, (ii) real-time SSC measurements are available, and (iii) the value of the 'switch-off SSC' is known. In a case study at the high-head HPP Fieschertal, a switch-off SSC of 10 g/l was estimated. The economic analysis showed that it would have been clearly profitable to practice such a switch-off during the major flood in 2012 which had an SSC peak of 50 g/l.
Fine sediments are important in the design and operation of hydropower plants (HPPs), in particular with respect to sediment management and hydro-abrasive erosion in hydraulic machines. Therefore, ...there is a need for reliable real-time measurements of suspended sediment mass concentration (SSC) and particle size distribution (PSD). The following instruments for SSC measurements were investigated in a field study during several years at the HPP Fieschertal in the Swiss Alps: (1) turbidimeters, (2) a Laser In-Situ Scattering and Trans- missometry instrument (LISST), (3) a Coriolis Flow and Density Meter (CFDM), (4) acoustic transducers, and (5) pressure sensors. LISST provided PSDs in addition to concentrations. Reference SSCs were obtained by gravimetrical analysis of automatically taken water samples. In contrast to widely used turbidimeters and the single-frequency acoustic method, SSCs obtained from LISST, the CFDM or the pressure sensors were less or not affected by particle size variations. The CFDM and the pressure sensors allowed measuring higher SSC than the optical or the acoustic techniques (without dilution). The CFDM and the pressure sensors were found to be suitable to measure SSC ≥ 2 g/l. In this paper, the measuring techniques, instruments, setup, methods for data treatment, and selected results are presented and discussed.
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