Transient Head Research Articles

A U-Net architecture as a surrogate model combined with a geostatistical spectral algorithm for transient groundwater flow inverse problems

Characterizing groundwater flow parameters is crucial for understanding complex aquifer systems, and inverse techniques play a fundamental role in modeling hydrogeological parameters and assessing their uncertainties. Nonetheless, the use of a forward model in these methods can be highly time-consuming, especially with an increasing number of model parameters. To address this issue, we propose a surrogate model based on a U-Net architecture that replaces the transient groundwater flow model, reducing runtime and enabling a fast quantification of uncertainties related to key parameters, including heterogeneous hydraulic conductivity, boundary conditions, specific storage, and pumping rate. The surrogate is trained using limited evaluations of the forward model to learn the physical relationship between hydraulic conductivity fields and transient hydraulic heads measured on-site. The physical principles of the studied problem, including boundary conditions, specific storage, and source terms, are also mapped and introduced as inputs to the model to enhance its understanding of the governing equation of transient groundwater flow. To speed up learning using image–image regression, the previously predicted transient hydraulic heads also serve as an input to predict the transient heads at the current time step. Once the model is trained, we use a spectral geostatistical method to solve the inverse problem, a pumping test of 12 h, using the surrogate model in place of the forward model. Our study demonstrates that the trained U-Net accurately reproduces the state variables corresponding to a specific parameter field, and in terms of computational demand, using U-Net as a surrogate model reduces the required computational time by approximately an order of magnitude for the defined problem. The proposed approach offers an efficient and accurate method for groundwater flow parameter characterization and uncertainty quantification in complex aquifer systems.

Prediction model for energy conversion characteristics during transient processes in a mixed-flow pump

The global energy shortage is gradually intensifying. A pump is a versatile device with significant power consumption in energy conversion equipment. Of the world's total energy generated, pumps consume about 20%. With the continuous expansion of the application field, the pump's transient working characteristics are increasingly getting important for energy saving and consumption reduction. Due to ignoring the influence of impeller rotational acceleration and fluid inertia, traditional methods have significant errors in predicting transient energy conversion characteristics, which leads to improper design and unreasonable lectotype, resulting in low pump operation efficiency. Improving the prediction accuracy of transient energy characteristics and ultimately improving the pump operation efficiency is considered to be the key solution to reducing energy consumption. Therefore, this research paper proposes a prediction model of transient energy characteristics in a mixed-flow pump. Firstly, the dynamic hydraulic torque, an important parameter of energy growth during the start-up process was calculated according to the momentum moment equation. Secondly, based on the torque energy balance equation and the relative Bernoulli equation, the transient head expression during the start-up process of the mixed-flow pump is derived, and the saddle area correction is carried out. Finally, considering the additional shaft power loss caused by the pump's backflow and clearance leakage flow, a calculation method for the instantaneous energy conversion efficiency of the mixed-flow pump is established. The accuracy of the model is compared with traditional quasi-steady-state calculation results. The results show that the predicted head of the model is in good agreement with the test head, the head estimation error is reduced from 15% to 5%, and the modified head in the saddle area is closer to the test value. In addition, this study also shows the ability of the model to simulate different start-up modes and start-up times. The models presented in this paper help guide the transient hydraulic design and prediction of transient energy characteristics of pumps.

Theoretical prediction model of transient performance for a mixed flow pump under fast start-up conditions

There always appear unsteady characteristics during start-up periods of pumps, which can lead to instability of the entire system. However, the lack of a method for quickly and accurately predicting pump start-up performance makes it difficult to analyze the performance of the overall system during the period. To this end, a theoretical model to predict pump transient performance under fast start-up conditions is established in the present study. The theoretical prediction model for pump steady performance is built based on loss modeling first. Then, the balance between pump transient head and pipeline system is considered to determine transient pump performance. A time stepping algorithm is proposed to solve transient pump performance during start-up periods. The established theoretical model and the corresponding time stepping algorithm are applied to a mixed flow pump under fast start-up conditions with various acceleration time. The predicted evolution of pump head shows good agreement with experimental measurements, and average relative errors are within 10% for both steady and transient conditions. In addition, the theoretical model is applied to analyze the transient performance of oscillating curves and impact head. The mechanism for predicted oscillating results and the relation between peak impact head and the acceleration of rotation speed are revealed.

The perception threshold of the vestibular Coriolis illusion.

The vestibular Coriolis illusion is a disorienting sensation that results from a transient head rotation about one axis during sustained body rotation about another axis. Although often used in spatial disorientation training for pilots and laboratory studies on motion sickness, little is known about the minimum required rotation rate to produce the illusion. This study determined the perception threshold associated with the Coriolis illusion. Nineteen participants performed a standardized pitching head movement during continuous whole-body yaw rotation at rates varying between 5 to 50 deg/s. The participants reported their motion sensation in relation to three hypothesized perception thresholds: 1) a sense of undefined self-motion, 2) a sense of rotation, and 3) a sense of rotation and its direction (i.e., the factual Coriolis illusion). The corresponding thresholds were estimated from curves fitted by a generalized linear model. On average threshold 1 was significantly lower (8 deg/s) than thresholds 2 and 3. The latter thresholds did not differ from each other and their pooled value was 10 deg/s. The Coriolis illusion is perceived at yaw rates exceeding 10 deg/s using a pitching head movement with 40 deg amplitude and 55 deg/s peak velocity. Model analysis shows that this corresponds to an internal rotation vector of 6 deg/s. With this vector the Coriolis perception threshold can be predicted for any other head movement.

Abstract WMP71: Sequential Detection Rates Of Intramural Hematoma For Diagnosing Spontaneous Intracranial Artery Dissection

Introduction: Spontaneous intracranial artery dissection (IAD) can be diagnosed with the detection of intramural hematoma (IMH). We previously reported that high-resolution 3-dimensional T1-weighted magnetic resonance imaging (HR-3D-T1WI) is useful to detect IMH. Limited evidence is available regarding sequential detection rates of IMH and appropriate timing of the detection. Methods: We retrieved data on consecutive patients from our prospective cohort databases from March 2011 to August 2018 who had definite, probable, or possible IAD based on the multidisciplinary expert consensus criteria. We detected IMH on initial and follow-up HR-3D-T1WI. We explored the association between detection of IMH and days from symptom onset to initial or follow-up HR-3D-T1WI. Results: A total of 104 patients (mean age 51 ± 13; 30 female; 68 patients, definite IAD; 31 patients; probable IAD, 5 patients; possible IAD) with at least initial HR-3D-T1WI data were included in the analysis. Clinical diagnoses included ischemic stroke (46%), subarachnoid hemorrhage (6%), transient ischemic attack (2%), and head or neck pain alone (46%). Age, Sex, vascular risk factors and modified Rankin Scale at 3 months were comparable between patients with IMH and without. Among them, follow-up HR-3D-T1WI was performed in 54 patients (52%). IMH was observed in 61 patients, 59% of all and 90% of definite IAD. The median days from symptom onset to initial or follow-up HR-3D-T1WI were 11 (interquartile range[IQR] 8–15) and 29 (IQR 19–57) days, respectively. The median days from symptom onset to first IMH detection were 12 (IQR range 8–17). The detection rate of IMH on initial HR-3D-T1WI was 55% overall, reaching 20% on day 3, 40% on day 7, and 50% on day 8–12 ( Figure ). Of the 23 patients who did not have an IMH on the initial HR-3D-T1WI, 4 (17%) had an IMH detected on the follow-up imaging. Conclusion: The detection rate of IMH on HR-3D-T1WI was approximately 60%, which reached the maximum in 1-2 weeks.

Continuous Head Motion is a Greater Motor Control Challenge than Transient Head Motion in Patients with Loss of Vestibular Function

Background. The vestibular system is vital for gaze stability via the vestibulo-ocular reflex, which generates compensatory eye motion in the direction opposite to head motion. Consequently, individuals with peripheral vestibular loss demonstrate impaired gaze stability that reduces functional capacity and quality of life. To facilitate patients’ compensatory strategies, two classes of gaze stabilization exercises are often prescribed: (i) transient (eg, ballistic) and (ii) continuous. However, the relative benefits of these two classes of exercises are not well understood. Objective. To quantify head motion kinematics in patients with vestibular loss while they performed both classes of exercises. Methods. Using inertial measurement units, head movements of 18 vestibular schwannoma patients were measured before and after surgical deafferentation and compared with age-matched controls. Results. We found that the head movement during both classes of exercises paralleled those of natural head movement recorded during daily activities. However, head movement patterns were more informative for continuous than transient exercises in distinguishing patients from healthy controls. Specifically, we observed coupling between kinematic measures in control subjects that was absent in patients for continuous but not transient head motion exercises. In addition, kinematic measures (eg, cycle duration) were predictive of standard clinical measures for continuous but not transient head motion exercises. Conclusions. Our data suggest that performing continuous head motion is a greater motor control challenge than transient head motion in patients with less reliable vestibular feedback during the sub-acute stage of recovery, which may also prove to be a reliable measure of progression in vestibular rehabilitation protocols.

Factorized wave propagation model in tree-type pipe networks and its application to leak localization

In a leaky tree-structured pipe network, transient head and discharge at a measurement location arise from a superposition of the waves along the set of pipes linking the measurement location to each boundary node. Moreover, the solution can be split into a leak-free part and a term that accounts for the scattering from the leak, the latter varies linearly with leak size and nonlinearly with leak location. It is then shown that if the head adjacent to each boundary node is measured, any reasonably-sized leak can be uniquely and efficiently identified by the matched-field processing approach. The efficiency of the leak identification scheme stems from the linear dependence of wave scattering on leak size. The proposed method is successfully applied both numerically and to pilot data from a tree-structured system of viscoelastic pipes.

Mechanism and propagation characteristics of rotating stall in a mixed-flow pump

In order to explore mechanism and propagation characteristics of rotating stall, the unsteady flow characteristics of a mixed-flow pump are calculated based on SST turbulence model. Based on pressure fluctuation characteristics, number of stall cells and circumferential propagation velocity are calculated accurately under different stall conditions. With the circumferential evolution and transfer of stall cell, transient head shows a large periodic fluctuation. Pre-stall stage with weaken dissipation always occurs in the clockwise adjacent path of stall path. When a path is seriously disturbed by stall cell, the blocking effect will change the flow structure of rim flow and intensify the attack angle of downstream path, resulting in the formation of tip initial stall. Then the initial stall cell gradually propagates downstream, and experiences stages of development and attenuation. The fundamental reason for stall propagation is that the existence of stall vortices changes the trajectory of some fluids. The changing trajectory of rim flow is concentrated performance. Hence, distorted rim flow is the main inducement of pre-stall and tip initial stall. Through stall propagation mechanism, stages of flow paths at different time periods can be determined. The results could serve as reference to discover the stall mechanism under critical stall point.

Neural Mechanisms Underlying High-Frequency Vestibulocollic Reflexes In Humans And Monkeys.

The vestibulocollic reflex is a compensatory response that stabilizes the head in space. During everyday activities, this stabilizing response is evoked by head movements that typically span frequencies from 0 to 30 Hz. Transient head impacts, however, can elicit head movements with frequency content up to 300-400 Hz, raising the question whether vestibular pathways contribute to head stabilization at such high frequencies. Here, we first established that electrical vestibular stimulation modulates human neck motor unit (MU) activity at sinusoidal frequencies up to 300 Hz, but that sensitivity increases with frequency up to a low-pass cutoff of ∼70-80 Hz. To examine the neural substrates underlying the low-pass dynamics of vestibulocollic reflexes, we then recorded vestibular afferent responses to the same electrical stimuli in monkeys. Vestibular afferents also responded to electrical stimuli up to 300 Hz, but in contrast to MUs their sensitivity increased with frequency up to the afferent resting firing rate (∼100-150 Hz) and at higher frequencies afferents tended to phase-lock to the vestibular stimulus. This latter nonlinearity, however, was not transmitted to neck motoneurons, which instead showed minimal phase-locking that decreased at frequencies >75 Hz. Similar to human data, we validated that monkey muscle activity also exhibited low-pass filtered vestibulocollic reflex dynamics. Together, our results show that neck MUs are activated by high-frequency signals encoded by primary vestibular afferents, but undergo low-pass filtering at intermediate stages in the vestibulocollic reflex. These high-frequency contributions to vestibular-evoked neck muscle responses could stabilize the head during unexpected head transients.SIGNIFICANCE STATEMENT Vestibular-evoked neck muscle responses rely on accurate encoding and transmission of head movement information to stabilize the head in space. Unexpected transient events, such as head impacts, are likely to push the limits of these neural pathways since their high-frequency features (0-300 Hz) extend beyond the frequency bandwidth of head movements experienced during everyday activities (0-30 Hz). Here, we demonstrate that vestibular primary afferents encode high-frequency stimuli through frequency-dependent increases in sensitivity and phase-locking. When transmitted to neck motoneurons, these signals undergo low-pass filtering that limits neck motoneuron phase-locking in response to stimuli >75 Hz. This study provides insight into the neural dynamics producing vestibulocollic reflexes, which may respond to high-frequency transient events to stabilize the head.

The 3D analysis and estimation of transient seepage in earth dams through PLAXIS 3D software: neural network

The issue of seepage and its management is essential in earth dams which if exceeded from a certain stage the destruction of dam is probable. Despite the studies run through consulting engineers, the hydraulic behaviors of both body and foundation cannot be predicted. To understand the function of such structures, the geotechnical software PLAXIS 3D based on FEM is applied to determine the transient seepage analysis on the subject earth dam for 1 year. The outputs in downstream drain are compared with the actual obtained results from seepage at the same points with 15-day intervals for 1 year as an experimental sample. The obtained data here thorough PLAXIS 3D in addition to available actual seepage, permeability coefficients in x, y, and z directions, transient head upstream, soil-specific gravity for both the wet and dry conditions, Poisson coefficient, c, ɸ, and elasticity modulus material are trained through a neural network algorithm. Here, an equation is yield through which the seepage is calculated in transient head upstream at any point of the subject earth dam. This equation has a great accuracy of (P value > 0.05), and is applied in calculating the actual seepage of earth dams in critical situations such as earth dam failure due to piping operation or dam body erosion.

Delineating Facies Spatial Distribution by Integrating Ensemble Data Assimilationand Indicator Geostatistics With Level‐Set Transformation

AbstractThe facies‐based approach has been widely adopted to delineate an aquifer into distinct geological units with unique distributions of hydraulic, physical, and/or chemical properties. The recent development in ensemble‐based data assimilation methods allows both the direct and indirect data to be used to improve facies delineation. A major difficulty in those applications is to honor the spatial continuity and avoid overfitting after data assimilation. We introduce a new facies delineation framework to integrate ensemble data assimilation with traditional transition probability‐based geostatistics. A level‐set concept is used to parametrize discrete facies indicators and for updating facies shape. During the iterative data assimilation process, we impose spatial continuity by conditioning facies field generation on points selected adaptively based on their sensitivity to observation data. This reconditioning step is a key step to maintain spatial continuity and overcome overfitting problems in inversion. We selected two examples to evaluate the performance of the new framework in estimating facies‐based permeability field. The first example is a two‐dimensional synthetic system with transient head data induced by pumping tests used for delineating two facies. The second example is a three‐dimensional case with three facies, conceptualized from a field tracer experiment within the Columbia River corridor in Washington State, USA. Both examples demonstrate that the new method can adequately capture the spatial pattern of hydrofacies with reconditioning, which leads to the improved prediction of system behaviors.

Groundwater Estimation using Global Strong Form Collocation-based Meshfree Method in a Field like Synthetic Confined Aquifer Domain

Most of the groundwater simulation models are based on certain element (finite element method) or grid (finite difference method) formulation which is used for obtaining the transient head variation in the aquifer system. Since groundwater management scenarios often demand to call these simulation models several hundred times to deliver the acceptable decision variables, it is essential that an efficient and accurate system simulation technique should be adopted. In this paper, a recently developed global collocation approach based meshfree (Mfree) model is used as a groundwater state estimation tool. The developed model is first tested on a two-dimensional confined aquifer synthetic flow problem where the results are compared with the available analytical and numerical solutions. Different time steps and varied pumping schedules were also assessed for a performance check. Later the tested model is applied to a synthetic aquifer flow problem having a close analogy to real field variability. The results obtained through the projected Mfree model are the testimony of accuracy and successful application of the developed model.

A general analytical model for head response to oscillatory pumping in unconfined aquifers: effects of delayed gravity drainage and initial condition

Abstract. Oscillatory pumping tests (OPTs) provide an alternative to constant-head and constant-rate pumping tests for determining aquifer hydraulic parameters when OPT data are analyzed based on an associated analytical model coupled with an optimization approach. There are a large number of analytical models presented for the analysis of the OPT. The combined effects of delayed gravity drainage (DGD) and the initial condition regarding the hydraulic head are commonly neglected in the existing models. This study aims to develop a new model for describing the hydraulic head fluctuation induced by the OPT in an unconfined aquifer. The model contains a groundwater flow equation with the initial condition of a static water table, Neumann boundary condition specified at the rim of a partially screened well, and a free surface equation describing water table motion with the DGD effect. The solution is derived using the Laplace, finite-integral, and Weber transforms. Sensitivity analysis is carried out for exploring head response to the change in each hydraulic parameter. Results suggest that the DGD reduces to instantaneous gravity drainage in predicting transient head fluctuation when the dimensionless parameter a1=ϵSyb/Kz exceeds 500 with empirical constant ϵ, specific yield Sy, aquifer thickness b, and vertical hydraulic conductivity Kz. The water table can be regarded as a no-flow boundary when a1<10-2 and P<104 s, with P being the period of the oscillatory pumping rate. A pseudo-steady-state model without the initial condition causes a time-shift from the actual transient model in predicting simple harmonic motion of head fluctuation during a late pumping period. In addition, the present solution agrees well with head fluctuation data observed at the Savannah River site. Highlights. An analytical model of the hydraulic head due to oscillatory pumping in unconfined aquifers is presented. Head fluctuations affected by instantaneous and delayed gravity drainages are discussed. The effect of the initial condition on the phase of head fluctuation is analyzed. The present solution agrees well with head fluctuation data taken from field oscillatory pumping.

The unitary aqueduct method: a new tool for the preliminary design of air chambers

Modern aqueducts supply pressurized water from the available sources to the demanding urban-industrial or agricultural centers. Air chambers, in which air is stored at the pipeline pressure, are widely used in aqueducts, to reduce and to control the effects of the hydraulic transients produced immediately after the accidental or programmed stoppage of the pumps of the system. Dimensionless graphs have been proposed for the preliminary design of the air chambers: Allievi (1937), Angus (1937), Evans and Crawford (1954), Parmakian (1955), to name the classics. These graphs, obtained for the elastic and for the rigid column models of water hammer, allow the calculation of the initial air volume in the chamber and of the maximum and minimum pressures resulting from the hydraulic transients. However, dimensionless equations have not been proposed for the preliminary design of the air chambers. The method of the Unitary Aqueduct, for the preliminary design of the air chambers, is proposed in this paper, presenting dimensionless equations with only two dimensionless parameters, in which all aqueducts are represented, and design tables, from which the complete dimensions of the air chambers can be defined. The findings of this method are compared with the dimensions of a number of existing relevant aqueducts in Mexico, with very good correspondence. The Unitary Aqueduct is defined as a 10 km long aqueduct, with a flow of 2 m3/s, a water velocity of 2 m/s, and an absolute head of 110 m, typical of an aqueduct able to supply a city of 500 000 inhabitants. All possible aqueducts will be a multiple or a fraction of this aqueduct, and since a set of unitary air chambers for this unitary aqueduct can be completely pre-designed, for different relative minimum pressures, the design of an air chamber for a specific aqueduct will be a multiple or a fraction of one of the unitary air chambers of the prototype. Finally, the maximum possible upsurge is calculated and shown in a dimensionless figure. This maximum pressure can be compared with the maximum transient head desired, the difference between the two representing the head to be eliminated at the air chamber entrance or at the pipe connecting the returning flow with the air chamber. The method is also validated with the findings of a large number of experiments, carried out in an experimental installation.

Transient, Isolated Head Tremor in "Unaffected" Individuals: Is Essential Tremor an Even More Prevalent Disease Than We Suppose?

Background: Mild and transient head tremor may sometimes be observed in otherwise tremor-free relatives of essential tremor (ET) cases, although its prevalence is unclear. A diagnostic question is whether this transient, isolated head tremor, often observed as no more than a wobble, is an early manifestation of ET or whether it is a normal finding. A direct comparison with controls is needed.Methods: Two hundred and forty-one first-degree relatives of ET cases (FD-ET) and 77 spousal controls (Co) were enrolled in a study of ET. Each underwent a detailed evaluation that included a tremor history and videotaped neurological examination. None of the enrollees reported tremor, had a prior diagnosis of ET, or had significant tremor on screening spirals. All videotaped examinations were initially reviewed by a movement disorder neurologist blinded to subject type, and among those with head tremor on examination, co-reviewed by two additional movement disorders neurologists.Results: Twenty-six (10.8, 95% Confidence interval [CI] = 7.5–15.3%) of 241 FD-ET vs. 2 (2.6, 95% CI = 0.7–9.0%) of 77 Co had isolated, transient head tremor (odds ratio = 4.54, 95% CI = 1.05–19.57, p = 0.04). No enrollee had significant upper extremity tremor and none met inclusion criteria for ET based on the presence of upper extremity tremor. With one exception, head tremor occurred during or after phonation. It was always transient (generally a single back and forth wobble) and rare (observed briefly on one or two occasions during the videotaped examination) and had a faster frequency, lower amplitude and a different quality than voluntary head shaking.Conclusion: The basis for the observed isolated head tremor is unknown, but it could be an early feature of ET in ET families.Indeed, one-in-ten otherwise unaffected first-degree relatives of ET cases exhibited such tremor. To a far lesser extent it was also observed in “unaffected” controls. In both, it is likely a sign of early, emerging, undiagnosed ET, although follow-up studies are needed to confirm this. If it were ET, it would indicate that the prevalence of ET may be considerably higher than previously suspected.

Analysis of groundwater flow and stream depletion in L-shaped fluvial aquifers

Abstract. Understanding the head distribution in aquifers is crucial for the evaluation of groundwater resources. This article develops a model for describing flow induced by pumping in an L-shaped fluvial aquifer bounded by impermeable bedrocks and two nearly fully penetrating streams. A similar scenario for numerical studies was reported in Kihm et al. (2007). The water level of the streams is assumed to be linearly varying with distance. The aquifer is divided into two subregions and the continuity conditions of the hydraulic head and flux are imposed at the interface of the subregions. The steady-state solution describing the head distribution for the model without pumping is first developed by the method of separation of variables. The transient solution for the head distribution induced by pumping is then derived based on the steady-state solution as initial condition and the methods of finite Fourier transform and Laplace transform. Moreover, the solution for stream depletion rate (SDR) from each of the two streams is also developed based on the head solution and Darcy's law. Both head and SDR solutions in the real time domain are obtained by a numerical inversion scheme called the Stehfest algorithm. The software MODFLOW is chosen to compare with the proposed head solution for the L-shaped aquifer. The steady-state and transient head distributions within the L-shaped aquifer predicted by the present solution are compared with the numerical simulations and measurement data presented in Kihm et al. (2007).

Evaluating drywells for stormwater management and enhanced aquifer recharge.

Drywells are increasingly used for stormwater management and enhanced aquifer recharge, but only limited research has quantitatively determined the performance of drywells. Numerical and field scale experiments were, therefore, conducted to improve our understanding and ability to characterize the drywell behavior. In particular, HYDRUS (2D/3D) was modified to simulate transient head boundary conditions for the complex geometry of the Maxwell Type IV drywell; i.e., a sediment chamber, an overflow pipe, and the variable geometry and storage of the drywell system with depth. Falling-head infiltration experiments were conducted on drywells located at the National Training Center in Fort Irwin, California (CA) and a commercial complex in Torrance, CA to determine in situ soil hydraulic properties (the saturated hydraulic conductivity, Ks , and the retention curve shape parameter, α) for an equivalent uniform soil profile by inverse parameter optimization. A good agreement between the observed and simulated water heights in wells was obtained for both sites as indicated by the coefficient of determination 0.95-0.99-%, unique parameter fits, and small standard errors. Fort Irwin and Torrance drywells had very distinctive soil hydraulic characteristics. The fitted value of Ks =1.01 × 10-3 m min-1 at the Torrance drywell was consistent with the sandy soil texture at this site and the default value for sand in the HYDRUS soil catalog. The drywell with this Ks = 1.01 × 10-3 m min-1 could easily infiltrate predicted surface runoff from a design rain event (∼51.3 m3) within 5760 min (4 d). In contrast, the fitted value of Ks=2.25 × 10-6 m min-1 at Fort Irwin was very low compared to the Torrance drywell and more than an order of magnitude smaller than the default value reported in the HYDRUS soil catalog for sandy clay loam at this site, likely due to clogging. These experiments and simulations provide useful information to characterize effective soil hydraulic properties in situ, and to improve the design of drywells for enhanced recharge.

Effect of M-current modulation on mammalian vestibular responses to transient head motion.

The precise role and mechanisms underlying efferent modulation of peripheral vestibular afferent function are not well understood in mammals. Clarifying the details of efferent action may lead to new strategies for clinical management of debilitating disturbances in vestibular and balance function. Recent evidence in turtle indicates that efferent modulation of M-currents is likely one mechanism for modifying afferent discharge. M-currents depend in part on KCNQ potassium conductances (Kv7), which can be adjusted through efferent activation of M1, M3, and/or M5 muscarinic acetylcholine receptors (mAChRs). How KCNQ channels and altered M-currents affect vestibular afferent function in vivo is unclear, and whether such a mechanism operates in mammals is unknown. In this study we used the KCNQ antagonist XE991 and the KCNQ activator retigabine in anesthetized mice to evaluate the effects of M-current modulation on peripheral vestibular responses to transient head motion. At low doses of XE991, responses were modestly enhanced, becoming larger in amplitude and shorter in latency. Higher doses of XE991 produced transient response enhancement, followed by steady-state suppression where latencies and thresholds increased and amplitudes decreased. Retigabine produced opposite effects. Auditory function was also impacted, based on results of companion auditory brain stem response testing. We propose that closure of KCNQ channels transforms vestibular afferent behavior by suppressing responses to transient high-frequency stimuli while simultaneously enhancing responses to sustained low-frequency stimulation. Our results clearly demonstrate that KCNQ channels are critical for normal mammalian vestibular function and suggest that efferent action may utilize these mechanisms to modulate the dynamic characteristics and gain of vestibular afferent responses.NEW & NOTEWORTHY The role of calyceal KCNQ channels and associated M-current in normal mammalian vestibular function is unknown. Our results show that calyceal KCNQ channels are critical for normal vestibular function in the intact mammal. The findings provide evidence that efferent modulation of M-currents may act normally to differentially adjust the sensitivity of vestibular neurons to transient and tonic stimulation and that such mechanisms may be targeted to achieve effective clinical management of vestibular disorders.

Investigation on transient behavior of residual heat removal pumps in 1000 MW nuclear power plant using a 1D-3D coupling methodology during start-up period

Residual heat removal pumps (RHRPs) are the key equipment in nuclear power plants, and their transient performances can sensitively affect the stability and reliability of pump system. A 1D-3D coupling methodology has been developed to investigate the instantaneous flow characteristics of the pump system during start-up period. In this methodology, the flow in the RHRPs was considered to be three-dimensional (3D) flow and the flow in pipe system was simplified to be one-dimensional (1D) flow. Due to the influence of the impeller structure displacement was taken into account, the SST k-ω turbulence model was selected to calculate the 3D flow field in the RHRPs. At the same time, the structure response caused by the flow loads was also obtained by using Fluid-structure interaction method. The 1D flow in the pipe system was calculated by Euler equations. The boundary condition at the shared interface was properly updated by the code MpCCI which was used to exchange the information between the two domains. Meanwhile, the head of the RHRP, the stress of impeller structure and the displacement of impeller were also obtained. The results show that the transient head is distinctly impacted during the startup period. Additionally, the stress of impeller structure rapidly increases with the increase of the rotating speed, and then the impact effect is found. These imply that instability phenomenon occurring during the startup process. Furthermore, the total displacement of impeller is increasing and its distribution is asymmetrical along the impeller radial. Finally, the maximum displacement occurs at the impeller hub where which is near the rim between two blades, due to the centrifugal force at the rim is larger than that in other regions and the relative low impeller rigidity.

Venous Sinus Stenting in Idiopathic Intracranial Hypertension: Results of a Prospective Trial.

Our goal was to evaluate the safety and efficacy of stenting of venous sinus stenosis (VSS) in patients with medically-refractory, medically-intolerant or fulminant idiopathic intracranial hypertension (IIH) in a prospective, observational study. Thirteen patients with IIH who were refractory or intolerant to medical therapy or who presented with fulminant visual field (VF) loss underwent stenting of VSS at the transverse-sinus sigmoid sinus junction, using a Precise Pro carotid stent system (Cordis). Inclusion criteria included papilledema-related VF loss with mean deviation (MD) worse than or equal to -6.00 dB, elevated opening pressure (OP) on lumbar puncture (LP), VSS (either bilateral or unilateral in a dominant sinus), and an elevated (≥8 mm Hg) trans-stenotic gradient (TSG). The main outcome measures were pre- to post-stent change in symptoms related to intracranial hypertension, MD (in dB) on automated (Humphrey) VFs, grade of papilledema (1-5), retinal nerve fiber layer (RNFL) thickness as measured by spectral domain optical coherence tomography (SD-OCT), TSG (mm Hg), and OP on LP (cm H20). Improvement or resolution of headaches occurred in 84.7% of patients, pulse-synchronous tinnitus in 100%, diplopia in 100%, and transient visual obscuration in 100%. Out of 26 eyes, 21 showed an improvement in MD, with an average improvement of +5.40 dB. Of 24 eyes with initial papilledema, 20 showed an improvement in Frisen grade, (mean change in grade of 1.90). Of 23 eyes undergoing SD-OCT, 21 (91.3%) demonstrated a reduction in RNFL thickness, with a poststent mean thickness of 90.48 μm. Mean change in OP was -20 cm H2O (reduction in mean from 42 to 22 cm H20) with all subjects demonstrating a reduction, although a second stenting procedure was necessary in one patient. Complications of the stenting procedure included one small, self-limited retroperitoneal hemorrhage, transient head or pelvic pain, and one allergic reaction to contrast. No serious adverse events occurred. Stenting of VSS is safe and results in reduction of intracranial pressure in patients with IIH. This is associated with improvement in papilledema, RNFL thickness, VF parameters, and symptoms associated with intracranial hypertension.