[Predictive value of central venous-to-arterial carbon dioxide partial pressure difference for fluid responsiveness in septic shock patients: a prospective clinical study].

PubMed

Liu, Guangyun; Huang, Huibin; Qin, Hanyu; Du, Bin

2018-05-01

To evaluate the accuracy of central venous-to-arterial carbon dioxide partial pressure difference (Pcv-aCO 2 ) before and after rapid rehydration test (fluid challenge) in predicting the fluid responsiveness in patients with septic shock. A prospective observation was conducted. Forty septic shock patients admitted to medical intensive care unit (ICU) of Peking Union Medical College Hospital from October 2015 to June 2017 were enrolled. All of the patients received fluid challenge in the presence of invasive hemodynamic monitoring. Heart rate (HR), blood pressure, cardiac index (CI), Pcv-aCO 2 and other physiological variables were recorded at 10 minutes before and immediately after fluid challenge. Fluid responsiveness was defined as an increase in CI greater than 10% after fluid challenge, whereas fluid non-responsiveness was defined as no increase or increase in CI less than 10%. The correlation between Pcv-aCO 2 and CI was explored by Pearson correlation analysis. Receiver operating characteristic (ROC) curves were established to evaluate the discriminatory abilities of baseline and the changes after fluid challenge in Pcv-aCO 2 and other physiological variables to define the fluid responsiveness. The patients were separated into two groups according to the initial value of Pcv-aCO 2 . The cut-off value of 6 mmHg (1 mmHg = 0.133 kPa) was chosen according to previous studies. The discriminatory abilities of baseline and the change in Pcv-aCO 2 (ΔPcv-aCO 2 ) were assessed in each group. A total of 40 patients were finally included in this study. Twenty-two patients responded to the fluid challenge (responders). Eighteen patients were fluid non-responders. There was no significant difference in baseline physiological variable between the two groups. Fluid challenge could increase CI and blood pressure significantly, decrease HR notably and had no effect on Pcv-aCO 2 in fluid responders. In non-responders, blood pressure was increased significantly and CI, HR, Pcv-aCO 2 showed no change after fluid challenge. Pcv-aCO 2 was comparable in responders and non-responders. In 40 patients, CI and Pcv-aCO 2 was inversely correlated before fluid challenge (r = -0.391, P = 0.012) and the correlation between them weakened after fluid challenge (r = -0.301, P = 0.059). There was no significant correlation between the changes in CI and Pcv-aCO 2 after fluid challenge (r = -0.164, P = 0.312). The baseline Pcv-aCO 2 and ΔPcv-aCO 2 could not discriminate between responders and non-responders, with the area under ROC curve (AUC) of 0.50 [95% confidence interval (95%CI) = 0.32-0.69] and 0.51 (95%CI = 0.33-0.70), respectively. HR and blood pressure before fluid challenge and their changes after fluid challenge showed very poor discriminative performances. Before fluid challenge, 16 patients had a Pcv-aCO 2 > 6 mmHg. Their mean CI was significantly lower and Pcv-aCO 2 was significantly higher than that in 24 patients whose Pcv-aCO 2 ≤ 6 mmHg [n = 24; CI (mL×s -1 ×m -2 ): 48.3±11.7 vs. 65.0±18.3, P < 0.01; Pcv-aCO 2 (mmHg): 8.4±1.9 vs. 2.9±2.8, P < 0.01]. Pcv-aCO 2 was decreased significantly after fluid challenge in patients with an initial Pcv-aCO 2 > 6 mmHg and their ΔPcv-aCO 2 was notably different as compared with the patients whose baseline Pcv-aCO 2 ≤ 6 mmHg (mmHg: -3.8±3.4 vs. 0.9±2.9, P < 0.01). 68.8% (11/16) patients responded to the fluid challenge in patients with an initial Pcv-aCO 2 > 6 mmHg. The AUC of the baseline Pcv-aCO 2 and ΔPcv-aCO 2 to define fluid responsiveness was 0.85 (95%CI = 0.66-1.00) and 0.84 (95%CI = 0.63-1.00), respectively, and the positive predictive value was 1 when the cut-off value was 8.0 mmHg and -4.2 mmHg, respectively. 45.8% (11/24) patients responded to the fluid challenge in patients whose baseline Pcv-aCO 2 ≤ 6 mmHg. There was no predictive value of baseline Pcv-aCO 2 and ΔPcv-aCO 2 on fluid responsiveness. Pcv-aCO 2 and its change cannot serve as a surrogate of the change in cardiac output to define the response to fluid challenge in septic shock patients whose baseline Pcv-aCO 2 ≤ 6 mmHg, while the predictive values of baseline Pcv-aCO 2 and the change in Pcv-aCO 2 are presented in patients with the initial value of Pcv-aCO 2 > 6 mmHg. Clinical Trials, NCT01941472.

Nonlinear multimodal model for TLD of irregular tank geometry and small fluid depth

NASA Astrophysics Data System (ADS)

Love, J. S.; Tait, M. J.

2013-11-01

Tuned liquid dampers (TLDs) utilize sloshing fluid to absorb and dissipate structural vibrational energy. TLDs of irregular or complex tank geometry may be required in practice to avoid tank interference with fixed structural or mechanical components. The literature offers few analytical models to predict the response of this type of TLD, particularly when the fluid depth is small. In this paper, a multimodal model is developed utilizing a Boussinesq-type modal theory which is valid for small TLD fluid depths. The Bateman-Luke variational principle is employed to develop a system of coupled nonlinear ordinary differential equations which describe the fluid response when the tank is subjected to base excitation. Energy dissipation is incorporated into the model from the inclusion of damping screens. The fluid model is used to describe the response of a 2D structure-TLD system when the structure is subjected to external loading and the TLD tank geometry is irregular.

Socially cued seminal fluid gene expression mediates responses in ejaculate quality to sperm competition risk.

PubMed

Simmons, Leigh W; Lovegrove, Maxine

2017-08-30

There is considerable evidence that males will increase the number of sperm ejaculated in response to sperm competition risk. However, whether they have the capacity to adjust seminal fluid components of the ejaculate has received less attention. Male crickets ( Teleogryllus oceanicus ) have been shown to adjust the viability of sperm in their ejaculate in response to sperm competition risk. Here we show that socially mediated plasticity in sperm viability is probably due, at least in part, to male adjustments in the protein composition of the seminal fluid. Seven seminal fluid protein genes were found to have an increased expression in males exposed to rival calls. Increased expression of these genes was correlated with increased sperm viability in whole ejaculates, and gene knockdown confirmed that at least one of these proteins promotes sperm viability. Our results lend support for recent theoretical models that predict complex responses in male allocation to seminal fluid composition in response to sperm competition risk. © 2017 The Author(s).

Applying dynamic parameters to predict hemodynamic response to volume expansion in spontaneously breathing patients with septic shock

PubMed Central

Lanspa, Michael J.; Grissom, Colin K.; Hirshberg, Eliotte L.; Jones, Jason P.; Brown, Samuel M.

2013-01-01

Background Volume expansion is a mainstay of therapy in septic shock, although its effect is difficult to predict using conventional measurements. Dynamic parameters, which vary with respiratory changes, appear to predict hemodynamic response to fluid challenge in mechanically ventilated, paralyzed patients. Whether they predict response in patients who are free from mechanical ventilation is unknown. We hypothesized that dynamic parameters would be predictive in patients not receiving mechanical ventilation. Methods This is a prospective, observational, pilot study. Patients with early septic shock and who were not receiving mechanical ventilation received 10 ml/kg volume expansion (VE) at their treating physician's discretion after initial resuscitation in the emergency department. We used transthoracic echocardiography to measure vena cava collapsibility index (VCCI) and aortic velocity variation (AoVV) prior to VE. We used a pulse contour analysis device to measure stroke volume variation (SVV). Cardiac index was measured immediately before and after VE using transthoracic echocardiography. Hemodynamic response was defined as an increase in cardiac index ≥ 15%. Results 14 patients received VE, 5 of which demonstrated a hemodynamic response. VCCI and SVV were predictive (Area under curve = 0.83, 0.92, respectively). Optimal thresholds were calculated: VCCI ≥ 15% (Positive predictive value, PPV 62%, negative predictive value, NPV 100%, p = 0.03); SVV ≥ 17% (PPV 100%, NPV 82%, p = 0.03). AoVV was not predictive. Conclusions VCCI and SVV predict hemodynamic response to fluid challenge patients with septic shock who are not mechanically ventilated. Optimal thresholds differ from those described in mechanically ventilated patients. PMID:23324885

Evaluation of two real time PCR assays for the detection of bacterial DNA in amniotic fluid.

PubMed

Girón de Velasco-Sada, Patricia; Falces-Romero, Iker; Quiles-Melero, Inmaculada; García-Perea, Adela; Mingorance, Jesús

2018-01-01

The aim of this study was to evaluate two non-commercial Real-Time PCR assays for the detection of microorganisms in amniotic fluid followed by identification by pyrosequencing. We collected 126 amniotic fluids from 2010 to 2015 for the evaluation of two Real-Time PCR assays for detection of bacterial DNA in amniotic fluid (16S Universal PCR and Ureaplasma spp. specific PCR). The method was developed in the Department of Microbiology of the University Hospital La Paz. Thirty-seven samples (29.3%) were positive by PCR/pyrosequencing and/or culture, 4 of them were mixed cultures with Ureaplasma urealyticum. The Universal 16S Real-Time PCR was compared with the standard culture (81.8% sensitivity, 97.4% specificity, 75% positive predictive value, 98% negative predictive value). The Ureaplasma spp. specific Real-Time PCR was compared with the Ureaplasma/Mycoplasma specific culture (92.3% sensitivity, 89.4% specificity, 50% positive predictive value, 99% negative predictive value) with statistically significant difference (p=0.005). Ureaplasma spp. PCR shows a rapid response time (5h from DNA extraction until pyrosequencing) when comparing with culture (48h). So, the response time of bacteriological diagnosis in suspected chorioamnionitis is reduced. Copyright © 2017 Elsevier B.V. All rights reserved.

Predicting vibrational failure of flexible ducting

NASA Technical Reports Server (NTRS)

Henry, R. H.

1971-01-01

Technique applies to liquid or gas transfer through flexible ducting and proves valuable in high velocity fluid flow cases. Fluid mechanism responsible for free bellows vibrational excitation also causes flexible hose oscillation. Static pressure stress influences flexible ducting fatigue life and is considered separately.

Non-Ideal Compressible-Fluid Dynamics of Fast-Response Pressure Probes for Unsteady Flow Measurements in Turbomachinery

NASA Astrophysics Data System (ADS)

Gori, G.; Molesini, P.; Persico, G.; Guardone, A.

2017-03-01

The dynamic response of pressure probes for unsteady flow measurements in turbomachinery is investigated numerically for fluids operating in non-ideal thermodynamic conditions, which are relevant for e.g. Organic Rankine Cycles (ORC) and super-critical CO2 applications. The step response of a fast-response pressure probe is investigated numerically in order to assess the expected time response when operating in the non-ideal fluid regime. Numerical simulations are carried out exploiting the Non-Ideal Compressible Fluid-Dynamics (NICFD) solver embedded in the open-source fluid dynamics code SU2. The computational framework is assessed against available experimental data for air in dilute conditions. Then, polytropic ideal gas (PIG), i.e. constant specific heats, and Peng-Robinson Stryjek-Vera (PRSV) models are applied to simulate the flow field within the probe operating with siloxane fluid octamethyltrisiloxane (MDM). The step responses are found to depend mainly on the speed of sound of the working fluid, indicating that molecular complexity plays a major role in determining the promptness of the measurement devices. According to the PRSV model, non-ideal effects can increase the step response time with respect to the acoustic theory predictions. The fundamental derivative of gas-dynamic is confirmed to be the driving parameter for evaluating non-ideal thermodynamic effects related to the dynamic calibration of fast-response aerodynamic pressure probes.

Prediction of surface roughness and cutting force under MQL turning of AISI 4340 with nano fluid by using response surface methodology

NASA Astrophysics Data System (ADS)

Patole, Pralhad B.; Kulkarni, Vivek V.

2018-06-01

This paper presents an investigation into the minimum quantity lubrication mode with nano fluid during turning of alloy steel AISI 4340 work piece material with the objective of experimental model in order to predict surface roughness and cutting force and analyze effect of process parameters on machinability. Full factorial design matrix was used for experimental plan. According to design of experiment surface roughness and cutting force were measured. The relationship between the response variables and the process parameters is determined through the response surface methodology, using a quadratic regression model. Results show how much surface roughness is mainly influenced by feed rate and cutting speed. The depth of cut exhibits maximum influence on cutting force components as compared to the feed rate and cutting speed. The values predicted from the model and experimental values are very close to each other.

Computer simulations of postural change, water immersion and bedrest - An integrative approach for understanding the spaceflight response

NASA Technical Reports Server (NTRS)

Leonard, J. I.; Leach, C. S.; Rummel, J. A.

1982-01-01

Mathematical modeling techniques were used to simulate the fluid electrolyte (F-E) responses during gravity unloading. It is shown that the response to weightlessness can best be understood by separately examining the acute (hours to days) and chronic (days to weeks) phases, and assuming the presence of normal, although complex, feedback regulatory processes. Headward shifts of fluid are shown to be primarily responsible for acute body losses of extracellular F-E. Losses of body water are closely related to the volume of fluid shifts from the legs. A diuresis is predicted within the first several hours of hypogravity, and this may be obscured by a reduced F-E intake; on Skylab, early F-E losses occurred primarily by deficit intake.

Investigation on the forced response of a radial turbine under aerodynamic excitations

NASA Astrophysics Data System (ADS)

Ma, Chaochen; Huang, Zhi; Qi, Mingxu

2016-04-01

Rotor blades in a radial turbine with nozzle guide vanes typically experience harmonic aerodynamic excitations due to the rotor stator interaction. Dynamic stresses induced by the harmonic excitations can result in high cycle fatigue (HCF) of the blades. A reliable prediction method for forced response issue is essential to avoid the HCF problem. In this work, the forced response mechanisms were investigated based on a fluid structure interaction (FSI) method. Aerodynamic excitations were obtained by three-dimensional unsteady computational fluid dynamics (CFD) simulation with phase shifted periodic boundary conditions. The first two harmonic pressures were determined as the primary components of the excitation and applied to finite element (FE) model to conduct the computational structural dynamics (CSD) simulation. The computed results from the harmonic forced response analysis show good agreement with the predictions of Singh's advanced frequency evaluation (SAFE) diagram. Moreover, the mode superposition method used in FE simulation offers an efficient way to provide quantitative assessments of mode response levels and resonant strength.

Using functional hemodynamic indicators to guide fluid therapy.

PubMed

Bridges, Elizabeth

2013-05-01

Hemodynamic monitoring has traditionally relied on such static pressure measurements as pulmonary artery occlusion pressure and central venous pressure to guide fluid therapy. Over the past 15 years, however, there's been a shift toward less invasive or noninvasive monitoring methods, which use "functional" hemodynamic indicators that reflect ventilator-induced changes in preload and thereby more accurately predict fluid responsiveness. The author reviews the physiologic principles underlying functional hemodynamic indicators, describes how the indicators are calculated, and discusses when and how to use them to guide fluid resuscitation in critically ill patients.

Thermohydrodynamic analysis of cryogenic liquid turbulent flow fluid film bearings

NASA Technical Reports Server (NTRS)

Andres, Luis San

1993-01-01

A thermohydrodynamic analysis is presented and a computer code developed for prediction of the static and dynamic force response of hydrostatic journal bearings (HJB's), annular seals or damper bearing seals, and fixed arc pad bearings for cryogenic liquid applications. The study includes the most important flow characteristics found in cryogenic fluid film bearings such as flow turbulence, fluid inertia, liquid compressibility and thermal effects. The analysis and computational model devised allow the determination of the flow field in cryogenic fluid film bearings along with the dynamic force coefficients for rotor-bearing stability analysis.

Thermohydrodynamic Analysis of Cryogenic Liquid Turbulent Flow Fluid Film Bearings

NASA Technical Reports Server (NTRS)

San Andres, Luis

1996-01-01

This report describes a thermohydrodynamic analysis and computer programs for the prediction of the static and dynamic force response of fluid film bearings for cryogenic applications. The research performed addressed effectively the most important theoretical and practical issues related to the operation and performance of cryogenic fluid film bearings. Five computer codes have been licensed by the Texas A&M University to NASA centers and contractors and a total of 14 technical papers have been published.

[Research advances of fluid bio-mechanics in bone].

PubMed

Chen, Zebin; Huo, Bo

2017-04-01

It has been found for more than one century that when experiencing mechanical loading, the structure of bone will adapt to the changing mechanical environment, which is called bone remodeling. Bone remodeling is charaterized as two processes of bone formation and bone resorption. A large number of studies have confirmed that the shear stress is resulted from interstitial fluid flow within bone cavities under mechanical loading and it is the key factor of stimulating the biological responses of bone cells. This review summarizes the major research progress during the past years, including the biological response of bone cells under fluid flow, the pressure within bone cavities, the theoretical modeling, numerical simulation and experiments about fluid flow within bone, and finally analyzes and predicts the possible tendency in this field in the future.

Linear and nonlinear analysis of fluid slosh dampers

NASA Astrophysics Data System (ADS)

Sayar, B. A.; Baumgarten, J. R.

1982-11-01

A vibrating structure and a container partially filled with fluid are considered coupled in a free vibration mode. To simplify the mathematical analysis, a pendulum model to duplicate the fluid motion and a mass-spring dashpot representing the vibrating structure are used. The equations of motion are derived by Lagrange's energy approach and expressed in parametric form. For a wide range of parametric values the logarithmic decrements of the main system are calculated from theoretical and experimental response curves in the linear analysis. However, for the nonlinear analysis the theoretical and experimental response curves of the main system are compared. Theoretical predictions are justified by experimental observations with excellent agreement. It is concluded finally that for a proper selection of design parameters, containers partially filled with viscous fluids serve as good vibration dampers.

Prediction of inertial effects due to bone conduction in a 2D box model of the cochlea

NASA Astrophysics Data System (ADS)

Halpin, Alice A.; Elliott, Stephen J.; Ni, Guangjian

2015-12-01

A 2D box model of the cochlea has been used to predict the basilar membrane, BM, velocity and the fluid flow caused by two components of bone conduction: due to inertia of the middle ear and due to inertia of the cochlear fluids. A finite difference approach has been used with asymmetric fluid chambers, that enables an investigation of the effect of varying window stiffness, due to otosclerosis for example. The BM is represented as a series of locally reacting single degree of freedom systems, with graded stiffness along the cochlea to represent the distribution of natural frequencies and with a damping representative of the passive cochlea. The velocity distributions along the passive BM are similar for harmonic excitation via the middle ear inertia or via the fluid inertia, but the variation of the BM velocity magnitude with excitation frequency is different in the two cases. Excitation via the middle ear is suppressed if the oval window is assumed to be blocked, but the excitation via the cochlear fluids is still possible. By assuming a combined excitation due to both middle ear and fluid excitation, the difference between the overall response can be calculated with a flexible and a blocked oval window, which gives a reasonable prediction of Carhart's notch.

An experimental and finite element poroelastic creep response analysis of an intervertebral hydrogel disc model in axial compression.

PubMed

Silva, P; Crozier, S; Veidt, M; Pearcy, M J

2005-07-01

A hydrogel intervertebral disc (IVD) model consisting of an inner nucleus core and an outer anulus ring was manufactured from 30 and 35% by weight Poly(vinyl alcohol) hydrogel (PVA-H) concentrations and subjected to axial compression in between saturated porous endplates at 200 N for 11 h, 30 min. Repeat experiments (n=4) on different samples (N=2) show good reproducibility of fluid loss and axial deformation. An axisymmetric nonlinear poroelastic finite element model with variable permeability was developed using commercial finite element software to compare axial deformation and predicted fluid loss with experimental data. The FE predictions indicate differential fluid loss similar to that of biological IVDs, with the nucleus losing more water than the anulus, and there is overall good agreement between experimental and finite element predicted fluid loss. The stress distribution pattern indicates important similarities with the biological IVD that includes stress transference from the nucleus to the anulus upon sustained loading and renders it suitable as a model that can be used in future studies to better understand the role of fluid and stress in biological IVDs.

Aerothermal and aeroelastic response prediction of aerospace structures in high-speed flows using direct numerical simulation

NASA Astrophysics Data System (ADS)

Ostoich, Christopher Mark

Future high-speed air vehicles will be lightweight, flexible, and reusable. Ve- hicles fitting this description are subject to severe thermal and fluid dynamic loading from multiple sources such as aerothermal heating, propulsion sys- tem exhaust, and high dynamic pressures. The combination of low-margin design requirements and extreme environmental conditions emphasizes the occurrence of fluid-thermal-structural coupling. Numerous attempts to field such vehicles have been unsuccessful over the past half-century due par- tially to the inability of traditional design and analysis practices to predict the structural response in this flight regime. In this thesis, a high-fidelity computational approach is used to examine the fluid-structural response of aerospace structures in high-speed flows. The method is applied to two cases: one involving a fluid-thermal interaction problem in a hypersonic flow and the other a fluid-structure interaction study involving a turbulent boundary layer and a compliant panel. The coupled fluid-thermal investigation features a nominally rigid alu- minum spherical dome fixed to a ceramic panel holder placed in a Mach 6.59 laminar boundary layer. The problem was originally studied by Glass and Hunt in a 1988 wind tunnel experiment in the NASA Langley 8-Foot High Temperature Tunnel and is motivated by thermally bowed body panels designed for the National Aerospace Plane. In this work, the compressible Navier-Stokes equations for a thermally perfect gas and the transient heat equation in the structure are solved simultaneously using two high-fidelity solvers coupled at the solid-fluid interface. Predicted surface heat fluxes are within 10% of the measured values in the dome interior with greater differ- ences found near the dome edges where uncertainties concerning the exper- imental model's construction likely influence the thermal dynamics. On the flat panel holder, the local surface heat fluxes approach those on the wind- ward dome face due to a dome-induced horseshoe vortex scouring the panel's surface. Comparisons with reduced-order models of heat transfer indicate that they perform with varying levels of accuracy around some portions of the geometry while completely failing to predict significant heat loads in re- gions where the dome-influenced flow impacts the ceramic panel. Cumulative effects of flow-thermal coupling at later simulation times on the reduction of panel drag and surface heat transfer are quantified. The second fluid-structure study investigates the interaction between a thin metallic panel and a Mach 2.25 turbulent boundary layer with an ini- tial momentum thickness Reynolds number of 1200. A transient, non-linear, large deformation, 3D finite element solver is developed to compute the dynamic response of the panel. The solver is coupled at the fluid-structure interface with the compressible Navier-Stokes solver, the latter of which is used for a direct numerical simulation of the turbulent boundary layer. In this approach, no simplifying assumptions regarding the structural solution or turbulence modeling are made in order to get detailed solution data. It is found that the thin panel state evolves into a flutter type response char- acterized by high-amplitude, high-frequency oscillations into the flow. The oscillating panel disturbs the supersonic flow by introducing compression waves, modifying the turbulence, and generating fluctuations in the power exiting the top of the flow domain. The work in this thesis serves as a step forward in structural response prediction in high-speed flows. The results demonstrate the ability of high- fidelity numerical approaches to serve as a guide for reduced-order model improvement and as well as provide accurate and detailed solution data in scenarios where experimental approaches are difficult or impossible.

An Unstructured Finite Volume Approach for Structural Dynamics in Response to Fluid Motions.

PubMed

Xia, Guohua; Lin, Ching-Long

2008-04-01

A new cell-vortex unstructured finite volume method for structural dynamics is assessed for simulations of structural dynamics in response to fluid motions. A robust implicit dual-time stepping method is employed to obtain time accurate solutions. The resulting system of algebraic equations is matrix-free and allows solid elements to include structure thickness, inertia, and structural stresses for accurate predictions of structural responses and stress distributions. The method is coupled with a fluid dynamics solver for fluid-structure interaction, providing a viable alternative to the finite element method for structural dynamics calculations. A mesh sensitivity test indicates that the finite volume method is at least of second-order accuracy. The method is validated by the problem of vortex-induced vibration of an elastic plate with different initial conditions and material properties. The results are in good agreement with existing numerical data and analytical solutions. The method is then applied to simulate a channel flow with an elastic wall. The effects of wall inertia and structural stresses on the fluid flow are investigated.

Infections with the Sexually Transmitted Pathogen Nosema apis Trigger an Immune Response in the Seminal Fluid of Honey Bees (Apis mellifera).

PubMed

Grassl, Julia; Peng, Yan; Baer-Imhoof, Barbara; Welch, Mat; Millar, A Harvey; Baer, Boris

2017-01-06

Honey bee (Apis mellifera) males are highly susceptible to infections with the sexually transmitted fungal pathogen Nosema apis. However, they are able to suppress this parasite in the ejaculate using immune molecules in the seminal fluid. We predicted that males respond to infections by altering the seminal fluid proteome to minimize the risk to sexually transmit the parasite to the queen and her colony. We used iTRAQ isotopic labeling to compare seminal fluid proteins from infected and noninfected males and found that N. apis infections resulted in significant abundance changes in 111 of the 260 seminal fluid proteins quantitated. The largest group of proteins with significantly changed abundances consisted of 15 proteins with well-known immune-related functions, which included two significantly more abundant chitinases in the seminal fluid of infected males. Chitinases were previously hypothesized to be involved in honey bee antifungal activity against N. apis. Here we show that infection with N. apis triggers a highly specific immune response in the seminal fluid of honey bee males.

Computational Analysis of Arc-Jet Wedge Tests Including Ablation and Shape Change

NASA Technical Reports Server (NTRS)

Goekcen, Tahir; Chen, Yih-Kanq; Skokova, Kristina A.; Milos, Frank S.

2010-01-01

Coupled fluid-material response analyses of arc-jet wedge ablation tests conducted in a NASA Ames arc-jet facility are considered. These tests were conducted using blunt wedge models placed in a free jet downstream of the 6-inch diameter conical nozzle in the Ames 60-MW Interaction Heating Facility. The fluid analysis includes computational Navier-Stokes simulations of the nonequilibrium flowfield in the facility nozzle and test box as well as the flowfield over the models. The material response analysis includes simulation of two-dimensional surface ablation and internal heat conduction, thermal decomposition, and pyrolysis gas flow. For ablating test articles undergoing shape change, the material response and fluid analyses are coupled in order to calculate the time dependent surface heating and pressure distributions that result from shape change. The ablating material used in these arc-jet tests was Phenolic Impregnated Carbon Ablator. Effects of the test article shape change on fluid and material response simulations are demonstrated, and computational predictions of surface recession, shape change, and in-depth temperatures are compared with the experimental measurements.

Predicting tensorial electrophoretic effects in asymmetric colloids

NASA Astrophysics Data System (ADS)

Mowitz, Aaron J.; Witten, T. A.

2017-12-01

We formulate a numerical method for predicting the tensorial linear response of a rigid, asymmetrically charged body to an applied electric field. This prediction requires calculating the response of the fluid to the Stokes drag forces on the moving body and on the countercharges near its surface. To determine the fluid's motion, we represent both the body and the countercharges using many point sources of drag known as Stokeslets. Finding the correct flow field amounts to finding the set of drag forces on the Stokeslets that is consistent with the relative velocities experienced by each Stokeslet. The method rigorously satisfies the condition that the object moves with no transfer of momentum to the fluid. We demonstrate that a sphere represented by 1999 well-separated Stokeslets on its surface produces flow and drag force like a solid sphere to 1% accuracy. We show that a uniformly charged sphere with 3998 body and countercharge Stokeslets obeys the Smoluchowski prediction [F. Morrison, J. Colloid Interface Sci. 34, 210 (1970), 10.1016/0021-9797(70)90171-2] for electrophoretic mobility when the countercharges lie close to the sphere. Spheres with dipolar and quadrupolar charge distributions rotate and translate as predicted analytically to 4% accuracy or better. We describe how the method can treat general asymmetric shapes and charge distributions. This method offers promise as a way to characterize and manipulate asymmetrically charged colloid-scale objects from biology (e.g., viruses) and technology (e.g., self-assembled clusters).

Fluid Intelligence Predicts Novel Rule Implementation in a Distributed Frontoparietal Control Network.

PubMed

Tschentscher, Nadja; Mitchell, Daniel; Duncan, John

2017-05-03

Fluid intelligence has been associated with a distributed cognitive control or multiple-demand (MD) network, comprising regions of lateral frontal, insular, dorsomedial frontal, and parietal cortex. Human fluid intelligence is also intimately linked to task complexity, and the process of solving complex problems in a sequence of simpler, more focused parts. Here, a complex target detection task included multiple independent rules, applied one at a time in successive task epochs. Although only one rule was applied at a time, increasing task complexity (i.e., the number of rules) impaired performance in participants of lower fluid intelligence. Accompanying this loss of performance was reduced response to rule-critical events across the distributed MD network. The results link fluid intelligence and MD function to a process of attentional focus on the successive parts of complex behavior. SIGNIFICANCE STATEMENT Fluid intelligence is intimately linked to the ability to structure complex problems in a sequence of simpler, more focused parts. We examine the basis for this link in the functions of a distributed frontoparietal or multiple-demand (MD) network. With increased task complexity, participants of lower fluid intelligence showed reduced responses to task-critical events. Reduced responses in the MD system were accompanied by impaired behavioral performance. Low fluid intelligence is linked to poor foregrounding of task-critical information across a distributed MD system. Copyright © 2017 Tschentscher et al.

Plasmons and Polaritons in Low Dimensional Systems

NASA Astrophysics Data System (ADS)

Sun, Zhiyuan

Nearly everything relies on the electromagnetic (EM) force to be in its current form. Therefore, light-matter interaction is both a fundamental and a practical subject in physics. Focusing on the electromagnetic field, the matter degrees of freedom can be encoded into its response to the EM field in the form of charge density and urrent. Reshaped by the EM response, the photons in condensed matter systems appear as various collective modes. In this doctoral dissertation, I present our investigation of the linear and nonlinear EM response theory especially in the hydrodynamic regime of electron systems. Electrons in pristine solids behave as a hydrodynamic fluid in a certain range of temperatures and frequencies. We show that the response of such a fluid to electromagnetic field is different from what is predicted by the usual kinetic theory. Certain aspects of this response are universal, for example, a direct relation between the linear and second-order nonlinear optical conductivities. Discovery of this relation enriches our understanding of the light-matter interaction in diverse electron systems and new materials such as graphene. Subsequently, I study the properties of the charged collective modes, the plasmons and demons in 2D Dirac fluids, e.g., the electron-hole system in graphene. Under non-equilibrium situation, the amplitudes of these collective modes could possibly grow due to an effect of adiabatic amplification. I also present our study of the hyperbolic polaritons, the EM modes in hyperbolic materials. When confined in cavities, they develop isolated eigen modes which could be efficiently predicted by applying semi-classical quantization rules to fictitious particles. We demonstrate this Hamiltonian Optics analytically for cavities of spheroidal shapes, and predict novel geometric patterns of the electric field distribution due to classical periodic orbits.

Large area and low power dielectrowetting optical shutter with local deterministic fluid film breakup

NASA Astrophysics Data System (ADS)

Zhao, R.; Cumby, B.; Russell, A.; Heikenfeld, J.

2013-11-01

A large area (>10 cm2) and low-power (0.1-10 Hz AC voltage, ˜10's μW/cm2) dielectrowetting optical shutter requiring no pixelation is demonstrated. The device consists of 40 μm interdigitated electrodes covered by fluid splitting features and a hydrophobic fluoropolymer. When voltage is removed, the fluid splitting features initiate breakup of the fluid film into small droplets resulting in ˜80% transmission. Both the dielectrowetting and fluid splitting follow theory, allowing prediction of alternate designs and further improved performance. Advantages include scalability, optical polarization independence, high contrast ratio, fast response, and simple construction, which could be of use in switchable windows or transparent digital signage.

Aeroelastic Stability & Response of Rotating Structures

NASA Technical Reports Server (NTRS)

Keith, Theo G., Jr.; Reddy, T. S. R.

2001-01-01

A summary of the work performed under NASA grant NCC3-605 is presented. More details can be found in the cited references. This grant led to the development of relatively faster aeroelastic analyses methods for predicting flutter and forced response in fans, compressors, and turbines using computational fluid dynamic (CFD) methods.

High Cycle Fatigue Prediction for Mistuned Bladed Disks with Fully Coupled Fluid-Structural Interaction

DTIC Science & Technology

2006-06-01

response (time domain) structural vibration model for mistuned rotor bladed disk based on the efficient SNM model has been developed. The vi- bration...airfoil and 3D wing, unsteady vortex shedding of a stationary cylinder, induced vibration of a cylinder, forced vibration of a pitching airfoil, induced... vibration and flutter boundary of 2D NACA 64A010 transonic airfoil, 3D plate wing structural response. The predicted results agree well with benchmark

Intervertebral disc response to cyclic loading--an animal model.

PubMed

Ekström, L; Kaigle, A; Hult, E; Holm, S; Rostedt, M; Hansson, T

1996-01-01

The viscoelastic response of a lumbar motion segment loaded in cyclic compression was studied in an in vivo porcine model (N = 7). Using surgical techniques, a miniaturized servohydraulic exciter was attached to the L2-L3 motion segment via pedicle fixation. A dynamic loading scheme was implemented, which consisted of one hour of sinusoidal vibration at 5 Hz, 50 N peak load, followed by one hour of restitution at zero load and one hour of sinusoidal vibration at 5 Hz, 100 N peak load. The force and displacement responses of the motion segment were sampled at 25 Hz. The experimental data were used for evaluating the parameters of two viscoelastic models: a standard linear solid model (three-parameter) and a linear Burger's fluid model (four-parameter). In this study, the creep behaviour under sinusoidal vibration at 5 Hz closely resembled the creep behaviour under static loading observed in previous studies. Expanding the three-parameter solid model into a four-parameter fluid model made it possible to separate out a progressive linear displacement term. This deformation was not fully recovered during restitution and is therefore an indication of a specific effect caused by the cyclic loading. High variability was observed in the parameters determined from the 50 N experimental data, particularly for the elastic modulus E1. However, at the 100 N load level, significant differences between the models were found. Both models accurately predicted the creep response under the first 800 s of 100 N loading, as displayed by mean absolute errors for the calculated deformation data from the experimental data of 1.26 and 0.97 percent for the solid and fluid models respectively. The linear Burger's fluid model, however, yielded superior predictions particularly for the initial elastic response.

Comparative proteomics of cerebrospinal fluid reveals a predictive model for differential diagnosis of pneumococcal, meningococcal, and enteroviral meningitis, and novel putative therapeutic targets

PubMed Central

2015-01-01

Background Meningitis is the inflammation of the meninges in response to infection or chemical agents. While aseptic meningitis, most frequently caused by enteroviruses, is usually benign with a self-limiting course, bacterial meningitis remains associated with high morbidity and mortality rates, despite advances in antimicrobial therapy and intensive care. Fast and accurate differential diagnosis is crucial for assertive choice of the appropriate therapeutic approach for each form of meningitis. Methods We used 2D-PAGE and mass spectrometry to identify the cerebrospinal fluid proteome specifically related to the host response to pneumococcal, meningococcal, and enteroviral meningitis. The disease-specific proteome signatures were inspected by pathway analysis. Results Unique cerebrospinal fluid proteome signatures were found to the three aetiological forms of meningitis investigated, and a qualitative predictive model with four protein markers was developed for the differential diagnosis of these diseases. Nevertheless, pathway analysis of the disease-specific proteomes unveiled that Kallikrein-kinin system may play a crucial role in the pathophysiological mechanisms leading to brain damage in bacterial meningitis. Proteins taking part in this cellular process are proposed as putative targets to novel adjunctive therapies. Conclusions Comparative proteomics of cerebrospinal fluid disclosed candidate biomarkers, which were combined in a qualitative and sequential predictive model with potential to improve the differential diagnosis of pneumococcal, meningococcal and enteroviral meningitis. Moreover, we present the first evidence of the possible implication of Kallikrein-kinin system in the pathophysiology of bacterial meningitis. PMID:26040285

Comparative proteomics of cerebrospinal fluid reveals a predictive model for differential diagnosis of pneumococcal, meningococcal, and enteroviral meningitis, and novel putative therapeutic targets.

PubMed

Cordeiro, Ana Paula; Silva Pereira, Rosiane Aparecida; Chapeaurouge, Alex; Coimbra, Clarice Semião; Perales, Jonas; Oliveira, Guilherme; Sanchez Candiani, Talitah Michel; Coimbra, Roney Santos

2015-01-01

Meningitis is the inflammation of the meninges in response to infection or chemical agents. While aseptic meningitis, most frequently caused by enteroviruses, is usually benign with a self-limiting course, bacterial meningitis remains associated with high morbidity and mortality rates, despite advances in antimicrobial therapy and intensive care. Fast and accurate differential diagnosis is crucial for assertive choice of the appropriate therapeutic approach for each form of meningitis. We used 2D-PAGE and mass spectrometry to identify the cerebrospinal fluid proteome specifically related to the host response to pneumococcal, meningococcal, and enteroviral meningitis. The disease-specific proteome signatures were inspected by pathway analysis. Unique cerebrospinal fluid proteome signatures were found to the three aetiological forms of meningitis investigated, and a qualitative predictive model with four protein markers was developed for the differential diagnosis of these diseases. Nevertheless, pathway analysis of the disease-specific proteomes unveiled that Kallikrein-kinin system may play a crucial role in the pathophysiological mechanisms leading to brain damage in bacterial meningitis. Proteins taking part in this cellular process are proposed as putative targets to novel adjunctive therapies. Comparative proteomics of cerebrospinal fluid disclosed candidate biomarkers, which were combined in a qualitative and sequential predictive model with potential to improve the differential diagnosis of pneumococcal, meningococcal and enteroviral meningitis. Moreover, we present the first evidence of the possible implication of Kallikrein-kinin system in the pathophysiology of bacterial meningitis.

Heart rate responses and fluid balance of competitive cross-country hang gliding pilots.

PubMed

Morton, Darren P

2010-03-01

To evaluate the physiological challenges of competitive cross-country hang gliding. Seventeen experienced male pilots (age=41+/-9 y; mean+/-SD) were fitted with a monitor that recorded heart rate and altitude at 0.5 Hz throughout a competitive flight. Fluid losses were evaluated by comparing pilot pre- and postflight mass. The pilots' displacement was 88.4+/-43.7 km in 145.5+/-49.4 min. Mean flight altitude was 1902+/-427 m (range=1363-2601 m) with a maximum altitude of 2925+/-682 m (1870-3831 m). The mean in-flight heart rate of the pilots was 112+/-11 bpm (64+/-6% predicted HRmax). For all except one subject, heart rate was highest while launching (165+/-12 bpm, 93+/-7% predicted HRmax), followed by landing (154+/-13 bpm, 87+/-7% predicted HRmax). No statistically significant relationship was observed between heart rate during the launch and reported measures of state anxiety. Heart rate was inversely related (P<.01) to altitude for all pilots except one. Fluid loss during the flight was 1.32+/-0.70 L, which approximated 0.55 L/h, while mean in-flight fluid consumption was 0.39+/-0.44 L. Six pilots consumed no fluid during the flight. Even among experienced pilots, high heart rates are more a function of state anxiety than physical work demand. Fluid losses during flight are surprisingly moderate but pilots may still benefit from attending to fluid balance.

Thermally induced oscillations in fluid flow

NASA Technical Reports Server (NTRS)

Zuber, N.

1970-01-01

Theoretical investigation distinguishes the various mechanisms responsible for oscillations of pressure, temperature, and flow velocity, derives a quantitative description of the most troublesome mechanisms, and develops a capability to predict the occurrence of unstable flow.

Experiments and Simulations of Fully Hydro-Mechanically Coupled Response of Rough Fractures Exposed to High-Pressure Fluid Injection

NASA Astrophysics Data System (ADS)

Vogler, D.; Settgast, R. R.; Annavarapu, C.; Madonna, C.; Bayer, P.; Amann, F.

2018-02-01

In this work, we present the application of a fully coupled hydro-mechanical method to investigate the effect of fracture heterogeneity on fluid flow through fractures at the laboratory scale. Experimental and numerical studies of fracture closure behavior in the presence of heterogeneous mechanical and hydraulic properties are presented. We compare the results of two sets of laboratory experiments on granodiorite specimens against numerical simulations in order to investigate the mechanical fracture closure and the hydro-mechanical effects, respectively. The model captures fracture closure behavior and predicts a nonlinear increase in fluid injection pressure with loading. Results from this study indicate that the heterogeneous aperture distributions measured for experiment specimens can be used as model input for a local cubic law model in a heterogeneous fracture to capture fracture closure behavior and corresponding fluid pressure response.

Short-term responses of the kidney to high altitude in mountain climbers

PubMed Central

Goldfarb-Rumyantzev, Alexander S.; Alper, Seth L.

2014-01-01

In high-altitude climbers, the kidneys play a crucial role in acclimatization and in mountain sickness syndromes [acute mountain sickness (AMS), high-altitude cerebral edema, high-altitude pulmonary edema] through their roles in regulating body fluids, electrolyte and acid–base homeostasis. Here, we discuss renal responses to several high-altitude-related stresses, including changes in systemic volume status, renal plasma flow and clearance, and altered acid–base and electrolyte status. Volume regulation is considered central both to high-altitude adaptation and to maladaptive development of mountain sickness. The rapid and powerful diuretic response to the hypobaric hypoxic stimulus of altitude integrates decreased circulating concentrations of antidiuretic hormone, renin and aldosterone, increased levels of natriuretic hormones, plasma and urinary epinephrine, norepinephrine, endothelin and urinary adrenomedullin, with increased insensible fluid losses and reduced fluid intake. The ventilatory and hormonal responses to hypoxia may predict susceptibility to AMS, also likely influenced by multiple genetic factors. The timing of altitude increases and adaptation also modifies the body's physiologic responses to altitude. While hypovolemia develops as part of the diuretic response to altitude, coincident vascular leak and extravascular fluid accumulation lead to syndromes of high-altitude sickness. Pharmacological interventions, such as diuretics, calcium blockers, steroids, phosphodiesterase inhibitors and β-agonists, may potentially be helpful in preventing or attenuating these syndromes. PMID:23525530

Modeling and control of magnetorheological fluid dampers using neural networks

NASA Astrophysics Data System (ADS)

Wang, D. H.; Liao, W. H.

2005-02-01

Due to the inherent nonlinear nature of magnetorheological (MR) fluid dampers, one of the challenging aspects for utilizing these devices to achieve high system performance is the development of accurate models and control algorithms that can take advantage of their unique characteristics. In this paper, the direct identification and inverse dynamic modeling for MR fluid dampers using feedforward and recurrent neural networks are studied. The trained direct identification neural network model can be used to predict the damping force of the MR fluid damper on line, on the basis of the dynamic responses across the MR fluid damper and the command voltage, and the inverse dynamic neural network model can be used to generate the command voltage according to the desired damping force through supervised learning. The architectures and the learning methods of the dynamic neural network models and inverse neural network models for MR fluid dampers are presented, and some simulation results are discussed. Finally, the trained neural network models are applied to predict and control the damping force of the MR fluid damper. Moreover, validation methods for the neural network models developed are proposed and used to evaluate their performance. Validation results with different data sets indicate that the proposed direct identification dynamic model using the recurrent neural network can be used to predict the damping force accurately and the inverse identification dynamic model using the recurrent neural network can act as a damper controller to generate the command voltage when the MR fluid damper is used in a semi-active mode.

Mathematical model of renal elimination of fluid and small ions during hyper- and hypovolemic conditions.

PubMed

Gyenge, Christina C; Bowen, Bruce D; Reed, Rolf K; Bert, Joel L

2003-02-01

This study is concerned with the formulation of a 'kidney module' linked to the plasma compartment of a larger mathematical model previously developed. Combined, these models can be used to predict, amongst other things, fluid and small ion excretion rates by the kidney; information that should prove useful in evaluating values and trends related to whole-body fluid balance for different clinical conditions to establish fluid administration protocols and for educational purposes. The renal module assumes first-order, negative-feedback responses of the kidney to changes in plasma volume and/or plasma sodium content from their normal physiological set points. Direct hormonal influences are not explicitly formulated in this empiric model. The model also considers that the renal excretion rates of small ions other than sodium are proportional to the excretion rate of sodium. As part of the model development two aspects are emphasized (1): the estimation of parameters related to the renal elimination of fluid and small ions, and (2) model validation via comparisons between the model predictions and selected experimental data. For validation, model predictions of the renal dynamics are compared with new experimental data for two cases: plasma overload resulting from external fluid infusion (e.g. infusions of iso-osmolar solutions and/or hypertonic/hyperoncotic saline solutions), and untreated hypo volemic conditions that result from the external loss of blood. The present study demonstrates that the empiric kidney module presented above can provide good short-term predictions with respect to all renal outputs considered here. Physiological implications of the model are also presented. Copyright Acta Anaesthesiologica Scandinavica 47 (2003)

Fluid resuscitation in acute pancreatitis

PubMed Central

Aggarwal, Aakash; Manrai, Manish; Kochhar, Rakesh

2014-01-01

Acute pancreatitis remains a clinical challenge, despite an exponential increase in our knowledge of its complex pathophysiological changes. Early fluid therapy is the cornerstone of treatment and is universally recommended; however, there is a lack of consensus regarding the type, rate, amount and end points of fluid replacement. Further confusion is added with the newer studies reporting better results with controlled fluid therapy. This review focuses on the pathophysiology of fluid depletion in acute pancreatitis, as well as the rationale for fluid replacement, the type, optimal amount, rate of infusion and monitoring of such patients. The basic goal of fluid epletion should be to prevent or minimize the systemic response to inflammatory markers. For this review, various studies and reviews were critically evaluated, along with authors’ recommendations, for predicted severe or severe pancreatitis based on the available evidence. PMID:25561779

Acoustic-Structure Interaction in Rocket Engines: Validation Testing

NASA Technical Reports Server (NTRS)

Davis, R. Benjamin; Joji, Scott S.; Parks, Russel A.; Brown, Andrew M.

2009-01-01

While analyzing a rocket engine component, it is often necessary to account for any effects that adjacent fluids (e.g., liquid fuels or oxidizers) might have on the structural dynamics of the component. To better characterize the fully coupled fluid-structure system responses, an analytical approach that models the system as a coupled expansion of rigid wall acoustic modes and in vacuo structural modes has been proposed. The present work seeks to experimentally validate this approach. To experimentally observe well-coupled system modes, the test article and fluid cavities are designed such that the uncoupled structural frequencies are comparable to the uncoupled acoustic frequencies. The test measures the natural frequencies, mode shapes, and forced response of cylindrical test articles in contact with fluid-filled cylindrical and/or annular cavities. The test article is excited with a stinger and the fluid-loaded response is acquired using a laser-doppler vibrometer. The experimentally determined fluid-loaded natural frequencies are compared directly to the results of the analytical model. Due to the geometric configuration of the test article, the analytical model is found to be valid for natural modes with circumferential wave numbers greater than four. In the case of these modes, the natural frequencies predicted by the analytical model demonstrate excellent agreement with the experimentally determined natural frequencies.

Mesoscale atmospheric modeling for emergency response

NASA Astrophysics Data System (ADS)

Osteen, B. L.; Fast, J. D.

Atmospheric transport models for emergency response have traditionally utilized meteorological fields interpolated from sparse data to predict contaminant transport. Often these fields are adjusted to satisfy constraints derived from the governing equations of geophysical fluid dynamics, e.g. mass continuity. Gaussian concentration distributions or stochastic models are then used to represent turbulent diffusion of a contaminant in the diagnosed meteorological fields. The popularity of these models derives from their relative simplicity, ability to make reasonable short-term predictions, and, most important, execution speed. The ability to generate a transport prediction for an accidental release from the Savannah River Site in a time frame which will allow protective action to be taken is essential in an emergency response operation.

Bifurcations and Chaos of AN Immersed Cantilever Beam in a Fluid and Carrying AN Intermediate Mass

NASA Astrophysics Data System (ADS)

AL-QAISIA, A. A.; HAMDAN, M. N.

2002-06-01

The concern of this work is the local stability and period-doubling bifurcations of the response to a transverse harmonic excitation of a slender cantilever beam partially immersed in a fluid and carrying an intermediate lumped mass. The unimodal form of the non-linear dynamic model describing the beam-mass in-plane large-amplitude flexural vibration, which accounts for axial inertia, non-linear curvature and inextensibility condition, developed in Al-Qaisia et al. (2000Shock and Vibration7 , 179-194), is analyzed and studied for the resonance responses of the first three modes of vibration, using two-term harmonic balance method. Then a consistent second order stability analysis of the associated linearized variational equation is carried out using approximate methods to predict the zones of symmetry breaking leading to period-doubling bifurcation and chaos on the resonance response curves. The results of the present work are verified for selected physical system parameters by numerical simulations using methods of the qualitative theory, and good agreement was obtained between the analytical and numerical results. Also, analytical prediction of the period-doubling bifurcation and chaos boundaries obtained using a period-doubling bifurcation criterion proposed in Al-Qaisia and Hamdan (2001 Journal of Sound and Vibration244, 453-479) are compared with those of computer simulations. In addition, results of the effect of fluid density, fluid depth, mass ratio, mass position and damping on the period-doubling bifurcation diagrams are studies and presented.

Oscillatory fluid flow in deformable tubes: Implications for pore-scale hydromechanics from comparing experimental observations with theoretical predictions.

PubMed

Kurzeja, Patrick; Steeb, Holger; Strutz, Marc A; Renner, Jörg

2016-12-01

Oscillatory flow of four fluids (air, water, two aqueous sodium-tungstate solutions) was excited at frequencies up to 250 Hz in tubes of two materials (steel, silicone) covering a wide range in length, diameter, and thickness. The hydrodynamical response was characterized by phase shift and amplitude ratio between pressures in an upstream (pressure excitation) and a downstream reservoir connected by the tubes. The resulting standing flow waves reflect viscosity-controlled diffusive behavior and inertia-controlled wave behavior for oscillation frequencies relatively low and high compared to Biot's critical frequency, respectively. Rigid-tube theories correspond well with the experimental results for steel tubes filled with air or water. The wave modes observed for silicone tubes filled with the rather incompressible liquids or air, however, require accounting for the solid's shear and bulk modulus to correctly predict speed of pressure propagation and deformation mode. The shear mode may be responsible for significant macroscopic attenuation in porous materials with effective frame-shear moduli lower than the bulk modulus of the pore fluid. Despite notable effects of the ratio of densities and of acoustic and shear velocity of fluid and solid, Biot's frequency remains an approximate indicator of the transition from the viscosity to the inertia controlled regime.

An artificial intelligence tool to predict fluid requirement in the intensive care unit: a proof-of-concept study

PubMed Central

Celi, Leo Anthony; Hinske, L Christian; Alterovitz, Gil; Szolovits, Peter

2008-01-01

Introduction The goal of personalised medicine in the intensive care unit (ICU) is to predict which diagnostic tests, monitoring interventions and treatments translate to improved outcomes given the variation between patients. Unfortunately, processes such as gene transcription and drug metabolism are dynamic in the critically ill; that is, information obtained during static non-diseased conditions may have limited applicability. We propose an alternative way of personalising medicine in the ICU on a real-time basis using information derived from the application of artificial intelligence on a high-resolution database. Calculation of maintenance fluid requirement at the height of systemic inflammatory response was selected to investigate the feasibility of this approach. Methods The Multi-parameter Intelligent Monitoring for Intensive Care II (MIMIC II) is a database of patients admitted to the Beth Israel Deaconess Medical Center ICU in Boston. Patients who were on vasopressors for more than six hours during the first 24 hours of admission were identified from the database. Demographic and physiological variables that might affect fluid requirement or reflect the intravascular volume during the first 24 hours in the ICU were extracted from the database. The outcome to be predicted is the total amount of fluid given during the second 24 hours in the ICU, including all the fluid boluses administered. Results We represented the variables by learning a Bayesian network from the underlying data. Using 10-fold cross-validation repeated 100 times, the accuracy of the model in predicting the outcome is 77.8%. The network generated has a threshold Bayes factor of seven representing the posterior probability of the model given the observed data. This Bayes factor translates into p < 0.05 assuming a Gaussian distribution of the variables. Conclusions Based on the model, the probability that a patient would require a certain range of fluid on day two can be predicted. In the presence of a larger database, analysis may be limited to patients with identical clinical presentation, demographic factors, co-morbidities, current physiological data and those who did not develop complications as a result of fluid administration. By better predicting maintenance fluid requirements based on the previous day's physiological variables, one might be able to prevent hypotensive episodes requiring fluid boluses during the course of the following day. PMID:19046450

An artificial intelligence tool to predict fluid requirement in the intensive care unit: a proof-of-concept study.

PubMed

Celi, Leo Anthony; Hinske, L Christian; Alterovitz, Gil; Szolovits, Peter

2008-01-01

The goal of personalised medicine in the intensive care unit (ICU) is to predict which diagnostic tests, monitoring interventions and treatments translate to improved outcomes given the variation between patients. Unfortunately, processes such as gene transcription and drug metabolism are dynamic in the critically ill; that is, information obtained during static non-diseased conditions may have limited applicability. We propose an alternative way of personalising medicine in the ICU on a real-time basis using information derived from the application of artificial intelligence on a high-resolution database. Calculation of maintenance fluid requirement at the height of systemic inflammatory response was selected to investigate the feasibility of this approach. The Multi-parameter Intelligent Monitoring for Intensive Care II (MIMIC II) is a database of patients admitted to the Beth Israel Deaconess Medical Center ICU in Boston. Patients who were on vasopressors for more than six hours during the first 24 hours of admission were identified from the database. Demographic and physiological variables that might affect fluid requirement or reflect the intravascular volume during the first 24 hours in the ICU were extracted from the database. The outcome to be predicted is the total amount of fluid given during the second 24 hours in the ICU, including all the fluid boluses administered. We represented the variables by learning a Bayesian network from the underlying data. Using 10-fold cross-validation repeated 100 times, the accuracy of the model in predicting the outcome is 77.8%. The network generated has a threshold Bayes factor of seven representing the posterior probability of the model given the observed data. This Bayes factor translates into p < 0.05 assuming a Gaussian distribution of the variables. Based on the model, the probability that a patient would require a certain range of fluid on day two can be predicted. In the presence of a larger database, analysis may be limited to patients with identical clinical presentation, demographic factors, co-morbidities, current physiological data and those who did not develop complications as a result of fluid administration. By better predicting maintenance fluid requirements based on the previous day's physiological variables, one might be able to prevent hypotensive episodes requiring fluid boluses during the course of the following day.

Predicting Fluid Responsiveness by Passive Leg Raising: A Systematic Review and Meta-Analysis of 23 Clinical Trials.

PubMed

Cherpanath, Thomas G V; Hirsch, Alexander; Geerts, Bart F; Lagrand, Wim K; Leeflang, Mariska M; Schultz, Marcus J; Groeneveld, A B Johan

2016-05-01

Passive leg raising creates a reversible increase in venous return allowing for the prediction of fluid responsiveness. However, the amount of venous return may vary in various clinical settings potentially affecting the diagnostic performance of passive leg raising. Therefore we performed a systematic meta-analysis determining the diagnostic performance of passive leg raising in different clinical settings with exploration of patient characteristics, measurement techniques, and outcome variables. PubMed, EMBASE, the Cochrane Database of Systematic Reviews, and citation tracking of relevant articles. Clinical trials were selected when passive leg raising was performed in combination with a fluid challenge as gold standard to define fluid responders and non-responders. Trials were included if data were reported allowing the extraction of sensitivity, specificity, and area under the receiver operating characteristic curve. Twenty-three studies with a total of 1,013 patients and 1,034 fluid challenges were included. The analysis demonstrated a pooled sensitivity of 86% (95% CI, 79-92), pooled specificity of 92% (95% CI, 88-96), and a summary area under the receiver operating characteristic curve of 0.95 (95% CI, 0.92-0.98). Mode of ventilation, type of fluid used, passive leg raising starting position, and measurement technique did not affect the diagnostic performance of passive leg raising. The use of changes in pulse pressure on passive leg raising showed a lower diagnostic performance when compared with passive leg raising-induced changes in flow variables, such as cardiac output or its direct derivatives (sensitivity of 58% [95% CI, 44-70] and specificity of 83% [95% CI, 68-92] vs sensitivity of 85% [95% CI, 78-90] and specificity of 92% [95% CI, 87-94], respectively; p < 0.001). Passive leg raising retains a high diagnostic performance in various clinical settings and patient groups. The predictive value of a change in pulse pressure on passive leg raising is inferior to a passive leg raising-induced change in a flow variable.

Fluid flow in the osteocyte mechanical environment: a fluid-structure interaction approach.

PubMed

Verbruggen, Stefaan W; Vaughan, Ted J; McNamara, Laoise M

2014-01-01

Osteocytes are believed to be the primary sensor of mechanical stimuli in bone, which orchestrate osteoblasts and osteoclasts to adapt bone structure and composition to meet physiological loading demands. Experimental studies to quantify the mechanical environment surrounding bone cells are challenging, and as such, computational and theoretical approaches have modelled either the solid or fluid environment of osteocytes to predict how these cells are stimulated in vivo. Osteocytes are an elastic cellular structure that deforms in response to the external fluid flow imposed by mechanical loading. This represents a most challenging multi-physics problem in which fluid and solid domains interact, and as such, no previous study has accounted for this complex behaviour. The objective of this study is to employ fluid-structure interaction (FSI) modelling to investigate the complex mechanical environment of osteocytes in vivo. Fluorescent staining of osteocytes was performed in order to visualise their native environment and develop geometrically accurate models of the osteocyte in vivo. By simulating loading levels representative of vigorous physiological activity ([Formula: see text] compression and 300 Pa pressure gradient), we predict average interstitial fluid velocities [Formula: see text] and average maximum shear stresses [Formula: see text] surrounding osteocytes in vivo. Interestingly, these values occur in the canaliculi around the osteocyte cell processes and are within the range of stimuli known to stimulate osteogenic responses by osteoblastic cells in vitro. Significantly our results suggest that the greatest mechanical stimulation of the osteocyte occurs in the cell processes, which, cell culture studies have indicated, is the most mechanosensitive area of the cell. These are the first computational FSI models to simulate the complex multi-physics mechanical environment of osteocyte in vivo and provide a deeper understanding of bone mechanobiology.

Amniotic fluid index predicts the relief of variable decelerations after amnioinfusion bolus.

PubMed

Spong, C Y; McKindsey, F; Ross, M G

1996-10-01

Our purpose was to determine whether intrapartum amniotic fluid index before amnioinfusion can be used to predict response to therapeutic amnioinfusion. Intrapartum patients (n = 85) with repetitive variable decelerations in fetal heart rate that necessitated amnioinfusion (10 ml/min for 60 minutes) underwent determination of amniotic fluid index before and after bolus amnioinfusion. The fetal heart tracing was scored (scorer blinded to amniotic fluid index values) for number and characteristics of variable decelerations before and 1 hour after initiation of amnioinfusion. The amnioinfusion was considered successful if it resulted in a decrease of > or = 50% in total number of variable decelerations or a decrease of > or = 50% in the rate of atypical or severe variable decelerations after administration of the bolus. Spontaneous vaginal births before completion of administration of the bolus (n = 18) were excluded from analysis. The probability of success of amnioinfusion in relation to amniotic fluid index was analyzed with the chi(2) test for progressive sequence. The mean amniotic fluid index before amnioinfusion was 6.2 +/- 3.3 cm. An amniotic fluid index of < or = 5 cm was present in 40% of patients (27/67), and an amniotic fluid index of < or = 8 cm was present in 72% of patients (48/67). The probability of success of amnioinfusion decreased with increasing amniotic fluid index before amnioinfusion (76% [16/21] when initial amniotic fluid index was 0 to 4 cm, 63% [17/27] when initial amniotic fluid index was 4 to 8 cm, 44% [7/16] when initial amniotic fluid index was 8 to 12 cm, and 33% [1/3] when initial amniotic fluid index was > 12 cm, p = 0.03). The incidence of nuchal cords or true umbilical cord knots increased in relation to amniotic fluid index before amnioinfusion. Amniotic fluid index before amnioinfusion can be used to predict the success of amnioinfusion for relief of variable decelerations in fetal heart rate. Failure of amnioinfusion at a high amniotic fluid index before amnioinfusion may be explained by the increased prevalence of nuchal cords or true knots in the umbilical cord.

A New Methodology for Turbulence Modelers Using DNS Database Analysis

NASA Technical Reports Server (NTRS)

Parneix, S.; Durbin, P.

1996-01-01

Many industrial applications in such fields as aeronautical, mechanical, thermal, and environmental engineering involve complex turbulent flows containing global separations and subsequent reattachment zones. Accurate prediction of this phenomena is very important because separations influence the whole fluid flow and may have an even bigger impact on surface heat transfer. In particular, reattaching flows are known to be responsible for large local variations of the local wall heat transfer coefficient as well as modifying the overall heat transfer. For incompressible, non-buoyant situations, the fluid mechanics have to be accurately predicted in order to have a good resolution of the temperature field.

A 3D-CFD code for accurate prediction of fluid flows and fluid forces in seals

NASA Technical Reports Server (NTRS)

Athavale, M. M.; Przekwas, A. J.; Hendricks, R. C.

1994-01-01

Current and future turbomachinery requires advanced seal configurations to control leakage, inhibit mixing of incompatible fluids and to control the rotodynamic response. In recognition of a deficiency in the existing predictive methodology for seals, a seven year effort was established in 1990 by NASA's Office of Aeronautics Exploration and Technology, under the Earth-to-Orbit Propulsion program, to develop validated Computational Fluid Dynamics (CFD) concepts, codes and analyses for seals. The effort will provide NASA and the U.S. Aerospace Industry with advanced CFD scientific codes and industrial codes for analyzing and designing turbomachinery seals. An advanced 3D CFD cylindrical seal code has been developed, incorporating state-of-the-art computational methodology for flow analysis in straight, tapered and stepped seals. Relevant computational features of the code include: stationary/rotating coordinates, cylindrical and general Body Fitted Coordinates (BFC) systems, high order differencing schemes, colocated variable arrangement, advanced turbulence models, incompressible/compressible flows, and moving grids. This paper presents the current status of code development, code demonstration for predicting rotordynamic coefficients, numerical parametric study of entrance loss coefficients for generic annular seals, and plans for code extensions to labyrinth, damping, and other seal configurations.

Data Comparisons and Summary of the Second Aeroelastic Prediction Workshop

NASA Technical Reports Server (NTRS)

Heeg, Jennifer; Wieseman, Carol D.; Chwalowski, Pawel

2016-01-01

This paper presents the computational results generated by participating teams of the second Aeroelastic Prediction Workshop and compare them with experimental data. Aeroelastic and rigid configurations of the Benchmark Supercritical Wing (BSCW) wind tunnel model served as the focus for the workshop. The comparison data sets include unforced ("steady") system responses, forced pitch oscillations and coupled fluid-structure responses. Integrated coefficients, frequency response functions, and flutter onset conditions are compared. The flow conditions studied were in the transonic range, including both attached and separated flow conditions. Some of the technical discussions that took place at the workshop are summarized.

The Relationships of Working Memory, Secondary Memory, and General Fluid Intelligence: Working Memory is Special

PubMed Central

Shelton, Jill Talley; Elliott, Emily M.; Matthews, Russell A.; Hill, B. D.; Gouvier, Wm. Drew

2010-01-01

Recent efforts have been made to elucidate the commonly observed link between working memory and reasoning ability. The results have been inconsistent, with some work suggesting the emphasis placed on retrieval from secondary memory by working memory tests is the driving force behind this association (Mogle, Lovett, Stawski, & Sliwinski, 2008), while other research suggests retrieval from secondary memory is only partly responsible for the observed link between working memory and reasoning (Unsworth & Engle, 2006, 2007b). The present study investigates the relationship between processing speed, working memory, secondary memory, primary memory, and fluid intelligence. Although our findings show all constructs are significantly correlated with fluid intelligence, working memory, but not secondary memory, accounts for significant unique variance in fluid intelligence. Our data support predictions made by Unsworth and Engle, and suggest that the combined need for maintenance and retrieval processes present in working memory tests makes them “special” in their prediction of higher-order cognition. PMID:20438278

Plasma response measurements of non-axisymmetric magnetic perturbations on DIII-D via soft x-ray imaging

DOE PAGES

Shafer, Morgan W.; Unterberg, Ezekial A.; Wingen, Andreas; ...

2014-12-29

Recent observations on DIII-D have advanced the understanding of plasma response to applied resonant magnetic perturbations (RMPs) in both H-mode and L-mode plasmas. Three distinct 3D features localized in minor radius are imaged via filtered soft x-ray emission: (i) the formation of lobes extending from the unperturbed separatrix in the X-point region at the plasma boundary, (ii) helical kink-like perturbations in the steep-gradient region inside the separatrix, and (iii) amplified islands in the core of a low-rotation L-mode plasma. In this study, these measurements are used to test and to validate plasma response models, which are crucial for providing predictivemore » capability of edge-localized mode control. In particular, vacuum and two-fluid resistive magnetohydrodynamic(MHD) responses are tested in the regions of these measurements. At the plasma boundary in H-mode discharges with n = 3 RMPs applied, measurements compare well to vacuum-field calculations that predict lobe structures. Yet in the steep-gradient region, measurements agree better with calculations from the linear resistive two-fluid MHD code, M3D-C1. Relative to the vacuum fields, the resistive two-fluid MHD calculations show a reduction in the pitch-resonant components of the normal magnetic field (screening), and amplification of non-resonant components associated with ideal kink modes. However, the calculations still over-predict the amplitude of the measuredperturbation by a factor of 4. In a slowly rotating L-mode plasma with n = 1 RMPs, core islands are observed amplified from vacuum predictions. Finally, these results indicate that while the vacuum approach describes measurements in the edge region well, it is important to include effects of extended MHD in the pedestal and deeper in the plasma core.« less

Sound waves and resonances in electron-hole plasma

NASA Astrophysics Data System (ADS)

Lucas, Andrew

2016-06-01

Inspired by the recent experimental signatures of relativistic hydrodynamics in graphene, we investigate theoretically the behavior of hydrodynamic sound modes in such quasirelativistic fluids near charge neutrality, within linear response. Locally driving an electron fluid at a resonant frequency to such a sound mode can lead to large increases in the electrical response at the edges of the sample, a signature, which cannot be explained using diffusive models of transport. We discuss the robustness of this signal to various effects, including electron-acoustic phonon coupling, disorder, and long-range Coulomb interactions. These long-range interactions convert the sound mode into a collective plasmonic mode at low frequencies unless the fluid is charge neutral. At the smallest frequencies, the response in a disordered fluid is quantitatively what is predicted by a "momentum relaxation time" approximation. However, this approximation fails at higher frequencies (which can be parametrically small), where the classical localization of sound waves cannot be neglected. Experimental observation of such resonances is a clear signature of relativistic hydrodynamics, and provides an upper bound on the viscosity of the electron-hole plasma.

Analytical modeling and experimental validation of a magnetorheological mount

NASA Astrophysics Data System (ADS)

Nguyen, The; Ciocanel, Constantin; Elahinia, Mohammad

2009-03-01

Magnetorheological (MR) fluid has been increasingly researched and applied in vibration isolation devices. To date, the suspension system of several high performance vehicles has been equipped with MR fluid based dampers and research is ongoing to develop MR fluid based mounts for engine and powertrain isolation. MR fluid based devices have received attention due to the MR fluid's capability to change its properties in the presence of a magnetic field. This characteristic places MR mounts in the class of semiactive isolators making them a desirable substitution for the passive hydraulic mounts. In this research, an analytical model of a mixed-mode MR mount was constructed. The magnetorheological mount employs flow (valve) mode and squeeze mode. Each mode is powered by an independent electromagnet, so one mode does not affect the operation of the other. The analytical model was used to predict the performance of the MR mount with different sets of parameters. Furthermore, in order to produce the actual prototype, the analytical model was used to identify the optimal geometry of the mount. The experimental phase of this research was carried by fabricating and testing the actual MR mount. The manufactured mount was tested to evaluate the effectiveness of each mode individually and in combination. The experimental results were also used to validate the ability of the analytical model in predicting the response of the MR mount. Based on the observed response of the mount a suitable controller can be designed for it. However, the control scheme is not addressed in this study.

Hybrid Seminumerical Simulation Scheme to Predict Transducer Outputs of Acoustic Microscopes.

PubMed

Nierla, Michael; Rupitsch, Stefan J

2016-02-01

We present a seminumerical simulation method called SIRFEM, which enables the efficient prediction of high-frequency transducer outputs. In particular, this is important for acoustic microscopy where the specimen under investigation is immersed in a coupling fluid. Conventional finite-element (FE) simulations for such applications would consume too much computational power due to the required spatial and temporal discretization, especially for the coupling fluid between ultrasonic transducer and specimen. However, FE simulations are in most cases essential to consider the mode conversion at and inside the solid specimen as well as the wave propagation in its interior. SIRFEM reduces the computational effort of pure FE simulations by treating only the solid specimen and a small part of the fluid layer with FE. The propagation in the coupling fluid from transducer to specimen and back is processed by the so-called spatial impulse response (SIR). Through this hybrid approach, the number of elements as well as the number of time steps for the FE simulation can be reduced significantly, as it is presented for an axis-symmetric setup. Three B-mode images of a plane 2-D setup-computed at a transducer center frequency of 20 MHz-show that SIRFEM is, furthermore, able to predict reflections at inner structures as well as multiple reflections between those structures and the specimen's surface. For the purpose of a pure 2-D setup, the SIR of a curved-line transducer is derived and compared to the response function of a cylindrically focused aperture of negligible extend in the third spatial dimension.

Experimental Validation of a Coupled Fluid-Multibody Dynamics Model for Tanker Trucks

DTIC Science & Technology

2007-11-08

order to accurately predict the dynamic response of tanker trucks, the model must accurately account for the following effects : • Incompressible...computational code which uses a time- accurate explicit solution procedure is used to solve both the solid and fluid equations of motion. Many commercial...position vector, τ is the deviatoric stress tensor, D is the rate of deformation tensor, f r is the body force vector, r is the artificial

SPH modeling of fluid-solid interaction for dynamic failure analysis of fluid-filled thin shells

NASA Astrophysics Data System (ADS)

Caleyron, F.; Combescure, A.; Faucher, V.; Potapov, S.

2013-05-01

This work concerns the prediction of failure of a fluid-filled tank under impact loading, including the resulting fluid leakage. A water-filled steel cylinder associated with a piston is impacted by a mass falling at a prescribed velocity. The cylinder is closed at its base by an aluminum plate whose characteristics are allowed to vary. The impact on the piston creates a pressure wave in the fluid which is responsible for the deformation of the plate and, possibly, the propagation of cracks. The structural part of the problem is modeled using Mindlin-Reissner finite elements (FE) and Smoothed Particle Hydrodynamics (SPH) shells. The modeling of the fluid is also based on an SPH formulation. The problem involves significant fluid-structure interactions (FSI) which are handled through a master-slave-based method and the pinballs method. Numerical results are compared to experimental data.

Non-invasive measurements of pulse pressure variation and stroke volume variation in anesthetized patients using the Nexfin blood pressure monitor.

PubMed

Stens, Jurre; Oeben, Jeroen; Van Dusseldorp, Ab A; Boer, Christa

2016-10-01

Nexfin beat-to-beat arterial blood pressure monitoring enables continuous assessment of hemodynamic indices like cardiac index (CI), pulse pressure variation (PPV) and stroke volume variation (SVV) in the perioperative setting. In this study we investigated whether Nexfin adequately reflects alterations in these hemodynamic parameters during a provoked fluid shift in anesthetized and mechanically ventilated patients. The study included 54 patients undergoing non-thoracic surgery with positive pressure mechanical ventilation. The provoked fluid shift comprised 15° Trendelenburg positioning, and fluid responsiveness was defined as a concomitant increase in stroke volume (SV) >10 %. Nexfin blood pressure measurements were performed during supine steady state, Trendelenburg and supine repositioning. Hemodynamic parameters included arterial blood pressure (MAP), CI, PPV and SVV. Trendelenburg positioning did not affect MAP or CI, but induced a decrease in PPV and SVV by 3.3 ± 2.8 and 3.4 ± 2.7 %, respectively. PPV and SVV returned back to baseline values after repositioning of the patient to baseline. Bland-Altman analysis of SVV and PPV showed a bias of -0.3 ± 3.0 % with limits of agreement ranging from -5.6 to 6.2 %. The SVV was more superior in predicting fluid responsiveness (AUC 0.728) than the PVV (AUC 0.636), respectively. The median bias between PPV and SVV was different for patients younger [-1.5 % (-3 to 0)] or older [+2 % (0-4.75)] than 55 years (P < 0.001), while there were no gender differences in the bias between PPV and SVV. The Nexfin monitor adequately reflects alterations in PPV and SVV during a provoked fluid shift, but the level of agreement between PPV and SVV was low. The SVV tended to be superior over PPV or Eadyn in predicting fluid responsiveness in our population.

Haemodynamic coherence - The relevance of fluid therapy.

PubMed

Arnemann, Philip; Seidel, Laura; Ertmer, Christian

2016-12-01

The ultimate goal of fluid therapy is to improve the oxygenation of cells by improving the cardiac output, thus improving microcirculation by optimizing macrocirculation. This haemodynamic coherence is often altered in patients with haemorrhagic shock and sepsis. The loss of haemodynamic coherence is associated with adverse outcomes. It may be influenced by the mechanisms of the underlying disease and properties of different fluids used for resuscitation in these critically ill patients. Monitoring microcirculation and haemodynamic coherence may be an additional tool to predict the response to fluid administration. In addition, microcirculatory analysis may support the clinician in his decision to not administer fluids when microcirculatory blood flow is preserved. In future, the indication, guidance and termination of fluid therapy may be assessed by bedside microvascular analysis in combination with standard haemodynamic monitoring. Copyright © 2016 Elsevier Ltd. All rights reserved.

The reliability of the clinical examination in predicting hemodynamic status in acute febrile illness in a tropical, resource-limited setting.

PubMed

Moek, Felix; Poe, Poe; Charunwatthana, Prakaykaew; Pan-Ngum, Wirichada; Wattanagoon, Yupaporn; Chierakul, Wirongrong

2018-05-19

The clinical examination alone is widely considered unreliable when assessing fluid responsiveness in critically ill patients. Little evidence exists on the performance of the clinical examination to predict other hemodynamic derangements or more complex hemodynamic states. Patients with acute febrile illness were assessed on admission, both clinically and per non-invasive hemodynamic measurement. Correlations between clinical signs and hemodynamics patterns were analyzed, and the predictive capacity of the clinical signs was examined. Seventy-one patients were included; the most common diagnoses were bacterial sepsis, scrub typhus and dengue infection. Correlations between clinical signs and hemodynamic parameters were only statistically significant for Cardiac Index (r=0.75, p-value <0.01), Systemic Vascular Resistance Index (r=0.79, p-value <0.01) and flow time corrected (r=0.44, p-value 0.03). When assessing the predictive accuracy of clinical signs, the model identified only 62% of hemodynamic states correctly, even less if there was more than one hemodynamic abnormality. The clinical examination is not reliable to assess a patient's hemodynamic status in acute febrile illness. Fluid responsiveness, cardiodepression and more complex hemodynamic states are particularly easily missed.

Poroelastic properties of the Arbuckle Group in Oklahoma derived from well fluid level response to the 3 September 2016 Mw 5.8 Pawnee and 7 November 2016 Mw 5.0 Cushing earthquakes

USGS Publications Warehouse

Kroll, Kayla A.; Cochran, Elizabeth S.; Murray, Kyle E.

2017-01-01

The Arbuckle Group (Arbuckle) is a basal sedimentary unit that is the primary target for saltwater disposal in Oklahoma. Thus, the reservoir characteristics of the Arbuckle, including how the poroelastic properties change laterally and over time are of significant interest. We report observations of fluid level changes in two monitoring wells in response to the 3 September 2016 Mw 5.8 Pawnee and the 7 November 2016 Mw 5.0 Cushing earthquakes. We investigate the relationship between static strain resulting from these events and the fluid level changes observed in the wells. We model the fluid level response by estimating static strains from a set of earthquake source parameters and spatiotemporal poroelastic properties of the Arbuckle in the neighborhood of the monitoring wells. Results suggest that both the direction of the observed fluid level step and the amplitude can be predicted from the computed volumetric strain change and a reasonable set of poroelastic parameters. Modeling results indicate that poroelastic parameters differ at the time of the Pawnee and Cushing earthquakes, with a moderately higher Skempton’s coefficient required to fit the response to the Cushing earthquake. This may indicate that dynamic shaking resulted in physical alteration of the Arbuckle at distances up to ∼50  km from the Pawnee earthquake.

Application of the Spectral Element Method to Interior Noise Problems

NASA Technical Reports Server (NTRS)

Doyle, James F.

1998-01-01

The primary effort of this research project was focused the development of analytical methods for the accurate prediction of structural acoustic noise and response. Of particular interest was the development of curved frame and shell spectral elements for the efficient computational of structural response and of schemes to match this to the surrounding fluid.

Hydro-dynamic damping theory in flowing water

NASA Astrophysics Data System (ADS)

Monette, C.; Nennemann, B.; Seeley, C.; Coutu, A.; Marmont, H.

2014-03-01

Fluid-structure interaction (FSI) has a major impact on the dynamic response of the structural components of hydroelectric turbines. On mid-head to high-head Francis runners, the rotor-stator interaction (RSI) phenomenon always has to be considered carefully during the design phase to avoid operational issues later on. The RSI dynamic response amplitudes are driven by three main factors: (1) pressure forcing amplitudes, (2) excitation frequencies in relation to natural frequencies and (3) damping. The prediction of the two first factors has been largely documented in the literature. However, the prediction of fluid damping has received less attention in spite of being critical when the runner is close to resonance. Experimental damping measurements in flowing water on hydrofoils were presented previously. Those results showed that the hydro-dynamic damping increased linearly with the flow. This paper presents development and validation of a mathematical model, based on momentum exchange, to predict damping due to fluid structure interaction in flowing water. The model is implemented as an analytical procedure for simple structures, such as cantilever beams, but is also implemented in more general ways using three different approaches for more complex structures such as runner blades: a finite element procedure, a CFD modal work based approach and a CFD 1DOF approach. The mathematical model and all three implementation approaches are shown to agree well with experimental results.

Monitoring Changes in Hepatic Venous Velocities Flow after a Fluid Challenge Can Identify Shock Patients Who Lack Fluid Responsiveness

PubMed Central

Du, Wei; Wang, Xiao-Ting; Long, Yun; Liu, Da-Wei

2017-01-01

Background: Evaluating the hemodynamic status and predicting fluid responsiveness are important in critical ultrasound assessment of shock patients. Transthoracic echocardiography with noninvasive diagnostic parameters allows the assessment of volume responsiveness. This study aimed to assess the hemodynamic changes in the liver and systemic hemodynamic changes during fluid challenge and during passive leg raising (PLR) by measuring hepatic venous flow (HVF) velocity. Methods: This is an open-label study in a tertiary teaching hospital. Shock patients with hypoperfusion who required fluid challenge were selected for the study. Patients <18 years old and those with contraindications to PLR were excluded from the study. Baseline values were measured, PLR tests were performed, and 500 ml of saline was infused over 30 min. Parameters associated with cardiac output (CO) in the left ventricular outflow tract were measured using the Doppler method. In addition, HVF velocity and right ventricular function parameters were determined. Results: Middle hepatic venous (MHV) S-wave velocity was positively correlated in all patients with CO at baseline (r = 0.706, P < 0.01) and after volume expansion (r = 0.524, P = 0.003). CO was also significantly correlated with MHV S-wave velocity in responders (r = 0.608, P < 0.01). During PLR, however, hepatic venous S-wave velocity did not correlate with CO. For the parameter ΔMHV D (increase in change in MHV D-wave velocity after volume expansion), defined as (MHV DafterVE − MHV DBaseline)/MHV DBaseline × 100%, >21% indicated no fluid responsiveness, with a sensitivity of 100%, a specificity of 71.2%, and an area under the receiver operating characteristic curve of 0.918. Conclusions: During fluid expansion, hepatic venous S-wave velocity can be used to monitor CO, whether or not it is increasing. ΔMHV D ≥21% indicated a lack of fluid responsiveness, thus helping to decide when to stop infusions. PMID:28485321

Puffing flame instability - Part II: Predicting the onset and frequency

NASA Astrophysics Data System (ADS)

Boettcher, Philipp; Shepherd, Joseph; Menon, Shyam; Blanquart, Guillaume

2011-11-01

Experiments and simulations have been performed on fuel rich n- hexane air mixtures in a closed vessel. Both experiments and simulations show a distinct cyclic combustion or ``puffing'' mode. The misalignment of buoyancy induced pressure gradients and density gradients across the flame front is responsible for the generation of vorticity and its subsequent roll-up into vortex rings. In the present work, a simplified model is proposed based on the fundamental interactions between fluid mechanical and chemical parameters. This simplified fluid mechanics model is based on dimensional analysis and is used to predict the onset and frequency of the puffing behavior. This work was sponsored by The Boeing Company through CTBA-GTA-1.

Oscillatory fluid flow induces the osteogenic lineage commitment of mesenchymal stem cells: The effect of shear stress magnitude, frequency, and duration.

PubMed

Stavenschi, Elena; Labour, Marie-Noelle; Hoey, David A

2017-04-11

A potent regulator of bone anabolism is physical loading. However, it is currently unclear whether physical stimuli such as fluid shear within the marrow cavity is sufficient to directly drive the osteogenic lineage commitment of resident mesenchymal stem cells (MSC). Therefore, the objective of the study is to employ a systematic analysis of oscillatory fluid flow (OFF) parameters predicted to occur in vivo on early MSC osteogenic responses and late stage lineage commitment. MSCs were exposed to OFF of 1Pa, 2Pa and 5Pa magnitudes at frequencies of 0.5Hz, 1Hz and 2Hz for 1h, 2h and 4h of stimulation. Our findings demonstrate that OFF elicits a positive osteogenic response in MSCs in a shear stress magnitude, frequency, and duration dependent manner that is gene specific. Based on the mRNA expression of osteogenic markers Cox2, Runx2 and Opn after short-term fluid flow stimulation, we identified that a regime of 2Pa shear magnitude and 2Hz frequency induces the most robust and reliable upregulation in osteogenic gene expression. Furthermore, long-term mechanical stimulation utilising this regime, elicits a significant increase in collagen and mineral deposition when compared to static control demonstrating that mechanical stimuli predicted within the marrow is sufficient to directly drive osteogenesis. Copyright © 2017. Published by Elsevier Ltd.

Setting the pace of microswimmers: when increasing viscosity speeds up self-propulsion

NASA Astrophysics Data System (ADS)

Pande, Jayant; Merchant, Laura; Krüger, Timm; Harting, Jens; Smith, Ana-Sunčana

2017-05-01

It has long been known that some microswimmers seem to swim counter-intuitively faster when the viscosity of the surrounding fluid is increased, whereas others slow down. This conflicting dependence of the swimming velocity on the viscosity is poorly understood theoretically. Here we explain that any mechanical microswimmer with an elastic degree of freedom in a simple Newtonian fluid can exhibit both kinds of response to an increase in the fluid viscosity for different viscosity ranges, if the driving is weak. The velocity response is controlled by a single parameter Γ, the ratio of the relaxation time of the elastic component of the swimmer in the viscous fluid and the swimming stroke period. This defines two velocity-viscosity regimes, which we characterize using the bead-spring microswimmer model and analyzing the different forces acting on the parts of this swimmer. The analytical calculations are supported by lattice-Boltzmann simulations, which accurately reproduce the two velocity regimes for the predicted values of Γ.

A review of turbomachinery blade-row interaction research

NASA Technical Reports Server (NTRS)

Smith, Todd E.

1988-01-01

Analytical and experimental research in the area of unsteady aerodynamics of turbomachinery has conventionally been applied to blading which oscillates when placed in a uniformly flowing fluid. Comparatively less effort has been offered for the study of blading which is subjected to nonuniformities within the flow field. The fluid dynamic environment of a blade-row embedded within multi-stage turbomachines is dominated by such highly unsteady fluid flow conditions. The production of wakes and circumferential pressure variations from adjacent blade-rows causes large unsteady energy transfers between the fluid and the blades. Determination of the forced response of a blade requires the ability to predict the unsteady loads which are induced by these aerodynamic sources. A review of research publications was done to determine recent investigations of the response of turbomachinery blading subjected to aerodynamic excitations. Such excitations are a direct result of the blade-row aerodynamic interaction which occurs between adjacent cascades of blades. The reports and papers reviewed have been organized into areas emphasizing experimental or analytical efforts.

Fluid Therapy: Double-Edged Sword during Critical Care?

PubMed Central

Benes, Jan; Kirov, Mikhail; Kuzkov, Vsevolod; Lainscak, Mitja; Molnar, Zsolt; Voga, Gorazd; Monnet, Xavier

2015-01-01

Fluid therapy is still the mainstay of acute care in patients with shock or cardiovascular compromise. However, our understanding of the critically ill pathophysiology has evolved significantly in recent years. The revelation of the glycocalyx layer and subsequent research has redefined the basics of fluids behavior in the circulation. Using less invasive hemodynamic monitoring tools enables us to assess the cardiovascular function in a dynamic perspective. This allows pinpointing even distinct changes induced by treatment, by postural changes, or by interorgan interactions in real time and enables individualized patient management. Regarding fluids as drugs of any other kind led to the need for precise indication, way of administration, and also assessment of side effects. We possess now the evidence that patient centered outcomes may be altered when incorrect time, dose, or type of fluids are administered. In this review, three major features of fluid therapy are discussed: the prediction of fluid responsiveness, potential harms induced by overzealous fluid administration, and finally the problem of protocol-led treatments and their timing. PMID:26798642

Fluid Therapy: Double-Edged Sword during Critical Care?

PubMed

Benes, Jan; Kirov, Mikhail; Kuzkov, Vsevolod; Lainscak, Mitja; Molnar, Zsolt; Voga, Gorazd; Monnet, Xavier

2015-01-01

Fluid therapy is still the mainstay of acute care in patients with shock or cardiovascular compromise. However, our understanding of the critically ill pathophysiology has evolved significantly in recent years. The revelation of the glycocalyx layer and subsequent research has redefined the basics of fluids behavior in the circulation. Using less invasive hemodynamic monitoring tools enables us to assess the cardiovascular function in a dynamic perspective. This allows pinpointing even distinct changes induced by treatment, by postural changes, or by interorgan interactions in real time and enables individualized patient management. Regarding fluids as drugs of any other kind led to the need for precise indication, way of administration, and also assessment of side effects. We possess now the evidence that patient centered outcomes may be altered when incorrect time, dose, or type of fluids are administered. In this review, three major features of fluid therapy are discussed: the prediction of fluid responsiveness, potential harms induced by overzealous fluid administration, and finally the problem of protocol-led treatments and their timing.

Prediction of interior noise due to random acoustic or turbulent boundary layer excitation using statistical energy analysis

NASA Technical Reports Server (NTRS)

Grosveld, Ferdinand W.

1990-01-01

The feasibility of predicting interior noise due to random acoustic or turbulent boundary layer excitation was investigated in experiments in which a statistical energy analysis model (VAPEPS) was used to analyze measurements of the acceleration response and sound transmission of flat aluminum, lucite, and graphite/epoxy plates exposed to random acoustic or turbulent boundary layer excitation. The noise reduction of the plate, when backed by a shallow cavity and excited by a turbulent boundary layer, was predicted using a simplified theory based on the assumption of adiabatic compression of the fluid in the cavity. The predicted plate acceleration response was used as input in the noise reduction prediction. Reasonable agreement was found between the predictions and the measured noise reduction in the frequency range 315-1000 Hz.

Changes in sensorimotor-related thalamic diffusion properties and cerebrospinal fluid hydrodynamics predict gait responses to tap test in idiopathic normal-pressure hydrocephalus.

PubMed

Tsai, Ping-Huei; Chen, Yung-Chieh; Chiang, Shih-Wei; Huang, Teng-Yi; Chou, Ming-Chung; Liu, Hua-Shan; Chung, Hsiao-Wen; Peng, Giia-Sheun; Ma, Hsin-I; Kao, Hung-Wen; Chen, Cheng-Yu

2018-05-07

To compare diffusion tensor (DT)-derived indices from the thalamic nuclei and cerebrospinal fluid (CSF) hydrodynamic parameters for the prediction of gait responsiveness to the CSF tap test in early iNPH patients. In this study, 22 patients with iNPH and 16 normal controls were enrolled with the approval of an institutional review board. DT imaging and phase-contrast magnetic resonance imaging were performed in patients and controls to determine DT-related indices of the sensorimotor-related thalamic nuclei and CSF hydrodynamics. Gait performance was assessed in patients using gait scale before and after the tap test. The Mann-Whitney U test and receiver operating characteristic (ROC) curve analysis were applied to compare group differences between patients and controls and assess the predictive performance of gait responsiveness to the tap test in the patients. Fractional anisotropy (FA) and axial diffusivity showed significant increases in the ventrolateral (VL) and ventroposterolateral (VPL) nuclei of the iNPH group compared with those of the control group (p < 0.05). The predictions of gait responsiveness of ventral thalamic FA alone (area under the ROC curve [AUC] < 0.8) significantly outperformed those of CSF hydrodynamics alone (AUC < 0.6). The AUC curve was elevated to 0.812 when the CSF peak systolic velocity and FA value were combined for the VPL nucleus, yielding the highest sensitivity (0.769) and specificity (0.778) to predict gait responses. Combined measurements of sensorimotor-related thalamic FA and CSF hydrodynamics can provide potential biomarkers for gait response to the CSF tap test in patients with iNPH. • Ventrolateral and ventroposterolateral thalamic FA may predict gait responsiveness to tap test. • Thalamic neuroplasticity can be assessed through DTI in idiopathic normal-pressure hydrocephalus. • Changes in the CST associated with gait control could trigger thalamic neuroplasticity. • Activities of sensorimotor-related circuits could alter in patients with gait disturbance. • Management of patients with iNPH could be more appropriate.

The fluid events model: Predicting continuous task action change.

PubMed

Radvansky, Gabriel A; D'Mello, Sidney; Abbott, Robert G; Morgan, Brent; Fike, Karl; Tamplin, Andrea K

2015-01-01

The fluid events model is a behavioural model aimed at predicting the likelihood that people will change their actions in ongoing, interactive events. From this view, not only are people responding to aspects of the environment, but they are also basing responses on prior experiences. The fluid events model is an attempt to predict the likelihood that people will shift the type of actions taken within an event on a trial-by-trial basis, taking into account both event structure and experience-based factors. The event-structure factors are: (a) changes in event structure, (b) suitability of the current action to the event, and (c) time on task. The experience-based factors are: (a) whether a person has recently shifted actions, (b) how often a person has shifted actions, (c) whether there has been a dip in performance, and (d) a person's propensity to switch actions within the current task. The model was assessed using data from a series of tasks in which a person was producing responses to events. These were two stimulus-driven figure-drawing studies, a conceptually driven decision-making study, and a probability matching study using a standard laboratory task. This analysis predicted trial-by-trial action switching in a person-independent manner with an average accuracy of 70%, which reflects a 34% improvement above chance. In addition, correlations between overall switch rates and actual switch rates were remarkably high (mean r = .98). The experience-based factors played a more major role than the event-structure factors, but this might be attributable to the nature of the tasks.

Early pleural fluid dynamics following video-assisted thoracoscopic lobectomy has limited clinical value

PubMed Central

Holbek, Bo Laksáfoss; Petersen, René Horsleben; Kehlet, Henrik

2017-01-01

The objective of this study was to evaluate the potential of predicting the pleural fluid output in patients after video-assisted thoracoscopic lobectomy of the lung. Detailed measurements of continuous fluid output were obtained prospectively using an electronic thoracic drainage device (Thopaz+™, Medela AG, Switzerland). Patients were divided into high (≥500 mL) and low (<500 mL) 24-hour fluid output, and detailed flow curves were plotted graphically to identify arithmetic patterns predicting fluid output in the early (≤24 hours) and later (24–48 hours) post-operative phase. Furthermore, multiple logistic regression analysis was used to predict high 24-hour fluid output using baseline data. Data were obtained from 50 patients, where 52% had a fluid output of <500 mL/24 hours. From visual assessment of flow curves, patients were grouped according to fluid output 6 hours postoperatively. An output ≥200 mL/6 hours was predictive of ‘high 24-hour fluid output’ (P<0.0001). However, 33% of patients with <200 mL/6 hours ended with a ‘high 24-hour fluid output’. Baseline data showed no predictive value of fluid production, and 24-hour fluid output had no predictive value of fluid output between 24 and 48 hours. Assessment of initial fluid production may predict high 24-hour fluid output (≥500 mL) but seems to lack clinical value in drain removal criteria. PMID:28840021

Water immersion and its computer simulation as analogs of weightlessness

NASA Technical Reports Server (NTRS)

Leonard, J. I.

1982-01-01

Experimental studies and computer simulations of water immersion are summarized and discussed with regard to their utility as analogs of weightlessness. Emphasis is placed on describing and interpreting the renal, endocrine, fluid, and circulatory changes that take place during immersion. A mathematical model, based on concepts of fluid volume regulation, is shown to be well suited to simulate the dynamic responses to water immersion. Further, it is shown that such a model provides a means to study specific mechanisms and pathways involved in the immersion response. A number of hypotheses are evaluated with the model related to the effects of dehydration, venous pressure disturbances, the control of ADH, and changes in plasma-interstitial volume. By inference, it is suggested that most of the model's responses to water immersion are plausible predictions of the acute changes expected, but not yet measured, during space flight. One important prediction of the model is that previous attempts to measure a diuresis during space flight failed because astronauts may have been dehydrated and urine samples were pooled over 24-hour periods.

Fluid Film Bearing Code Development

NASA Technical Reports Server (NTRS)

1995-01-01

The next generation of rocket engine turbopumps is being developed by industry through Government-directed contracts. These turbopumps will use fluid film bearings because they eliminate the life and shaft-speed limitations of rolling-element bearings, increase turbopump design flexibility, and reduce the need for turbopump overhauls and maintenance. The design of the fluid film bearings for these turbopumps, however, requires sophisticated analysis tools to model the complex physical behavior characteristic of fluid film bearings operating at high speeds with low viscosity fluids. State-of-the-art analysis and design tools are being developed at the Texas A&M University under a grant guided by the NASA Lewis Research Center. The latest version of the code, HYDROFLEXT, is a thermohydrodynamic bulk flow analysis with fluid compressibility, full inertia, and fully developed turbulence models. It can predict the static and dynamic force response of rigid and flexible pad hydrodynamic bearings and of rigid and tilting pad hydrostatic bearings. The Texas A&M code is a comprehensive analysis tool, incorporating key fluid phenomenon pertinent to bearings that operate at high speeds with low-viscosity fluids typical of those used in rocket engine turbopumps. Specifically, the energy equation was implemented into the code to enable fluid properties to vary with temperature and pressure. This is particularly important for cryogenic fluids because their properties are sensitive to temperature as well as pressure. As shown in the figure, predicted bearing mass flow rates vary significantly depending on the fluid model used. Because cryogens are semicompressible fluids and the bearing dynamic characteristics are highly sensitive to fluid compressibility, fluid compressibility effects are also modeled. The code contains fluid properties for liquid hydrogen, liquid oxygen, and liquid nitrogen as well as for water and air. Other fluids can be handled by the code provided that the user inputs information that relates the fluid transport properties to the temperature.

Numerical modeling of on-orbit propellant motion resulting from an impulsive acceleration

NASA Technical Reports Server (NTRS)

Aydelott, John C.; Mjolsness, Raymond C.; Torrey, Martin D.; Hochstein, John I.

1987-01-01

In-space docking and separation maneuvers of spacecraft that have large fluid mass fractions may cause undesirable spacecraft motion in response to the impulsive-acceleration-induced fluid motion. An example of this potential low gravity fluid management problem arose during the development of the shuttle/Centaur vehicle. Experimentally verified numerical modeling techniques were developed to establish the propellant dynamics, and subsequent vehicle motion, associated with the separation of the Centaur vehicle from the shuttle orbiter cargo bay. Although the shuttle/Centaur development activity was suspended, the numerical modeling techniques are available to predict on-orbit liquid motion resulting from impulsive accelerations for other missions and spacecraft.

Effects of exercise-heat acclimation on fluid, electrolyte, and endocrine responses during tilt and +Gz acceleration in women and men

NASA Technical Reports Server (NTRS)

Greenleaf, J. E.; Brock, P. J.; Sciaraffa, D.; Polese, A.; Elizondo, R.

1985-01-01

Two aspects of prolonged endurance training were investigated: (1) the effects of exercise-heat acclimation (on a cycle ergometer at 40 C, 42 rh) on orthostatic tolerance (70 deg head-up tilt) and on a +Gz (head-to-foot) acceleration tolerance of male and female subjects; and (2) comparison of their fluid-electrolyte shifts and hormonal (plasma epinephdrine, norepinephrine, renin, and vasopressin) responses during tilting and centrifugation. The adaptive responses during the 12 d, 2-h acclimation did not alter acceleration tolerance of either men or women, or the women's tilt tolerance, but did increase men's tilt tolerance from 30.4 min before to 58.3 min after acclimation. The patterns of fluid, electrolyte, and protein shifts at tolerance in acceleration and tilting tests were virtually the same in men and women. On the other hand, the hormonal plasma epinephrine, norepinephrine, renin, and vasopressin resonses displayed different shift patterns during acceleration and tilting. It is concluded that the responses to tilting cannot be used to predict responses to acceleration. Future experiments for relating the orthostatic and the acceleration tolerances, and the practical questions of the training regimens for future astronauts are discussed.

Analysis of Two-Phase Flow in Damper Seals for Cryogenic Turbopumps

NASA Technical Reports Server (NTRS)

Arauz, Grigory L.; SanAndres, Luis

1996-01-01

Cryogenic damper seals operating close to the liquid-vapor region (near the critical point or slightly su-cooled) are likely to present two-phase flow conditions. Under single phase flow conditions the mechanical energy conveyed to the fluid increases its temperature and causes a phase change when the fluid temperature reaches the saturation value. A bulk-flow analysis for the prediction of the dynamic force response of damper seals operating under two-phase conditions is presented as: all-liquid, liquid-vapor, and all-vapor, i.e. a 'continuous vaporization' model. The two phase region is considered as a homogeneous saturated mixture in thermodynamic equilibrium. Th flow in each region is described by continuity, momentum and energy transport equations. The interdependency of fluid temperatures and pressure in the two-phase region (saturated mixture) does not allow the use of an energy equation in terms of fluid temperature. Instead, the energy transport is expressed in terms of fluid enthalpy. Temperature in the single phase regions, or mixture composition in the two phase region are determined based on the fluid enthalpy. The flow is also regarded as adiabatic since the large axial velocities typical of the seal application determine small levels of heat conduction to the walls as compared to the heat carried by fluid advection. Static and dynamic force characteristics for the seal are obtained from a perturbation analysis of the governing equations. The solution expressed in terms of zeroth and first order fields provide the static (leakage, torque, velocity, pressure, temperature, and mixture composition fields) and dynamic (rotordynamic force coefficients) seal parameters. Theoretical predictions show good agreement with experimental leakage pressure profiles, available from a Nitrogen at cryogenic temperatures. Force coefficient predictions for two phase flow conditions show significant fluid compressibility effects, particularly for mixtures with low mass content of vapor. Under these conditions, an increase on direct stiffness and reduction of whirl frequency ratio are shown to occur. Prediction of such important effects will motivate experimental studies as well as a more judicious selection of the operating conditions for seals used in cryogenic turbomachinery.

Subharmonic Imaging and Pressure Estimation for Monitoring Neoadjuvant Chemotherapy

DTIC Science & Technology

2014-09-01

and therapy response [10]. However, the level of IFP has been shown to predict disease free survival for cervix cancer (34% disease free survival...p. 1951-1961. 11. Milosevic M, et al., Interstitial fluid pressure predicts survival in patients with cervix cancer independent of clinical...12b. DISTRIBUTION CODE 13. ABSTRACT (Maximum 200 Words) Neoadjuvant chemotherapy is currently the standard of care for locally advanced breast cancer

Multidisciplinary Modeling Software for Analysis, Design, and Optimization of HRRLS Vehicles

NASA Technical Reports Server (NTRS)

Spradley, Lawrence W.; Lohner, Rainald; Hunt, James L.

2011-01-01

The concept for Highly Reliable Reusable Launch Systems (HRRLS) under the NASA Hypersonics project is a two-stage-to-orbit, horizontal-take-off / horizontal-landing, (HTHL) architecture with an air-breathing first stage. The first stage vehicle is a slender body with an air-breathing propulsion system that is highly integrated with the airframe. The light weight slender body will deflect significantly during flight. This global deflection affects the flow over the vehicle and into the engine and thus the loads and moments on the vehicle. High-fidelity multi-disciplinary analyses that accounts for these fluid-structures-thermal interactions are required to accurately predict the vehicle loads and resultant response. These predictions of vehicle response to multi physics loads, calculated with fluid-structural-thermal interaction, are required in order to optimize the vehicle design over its full operating range. This contract with ResearchSouth addresses one of the primary objectives of the Vehicle Technology Integration (VTI) discipline: the development of high-fidelity multi-disciplinary analysis and optimization methods and tools for HRRLS vehicles. The primary goal of this effort is the development of an integrated software system that can be used for full-vehicle optimization. This goal was accomplished by: 1) integrating the master code, FEMAP, into the multidiscipline software network to direct the coupling to assure accurate fluid-structure-thermal interaction solutions; 2) loosely-coupling the Euler flow solver FEFLO to the available and proven aeroelasticity and large deformation (FEAP) code; 3) providing a coupled Euler-boundary layer capability for rapid viscous flow simulation; 4) developing and implementing improved Euler/RANS algorithms into the FEFLO CFD code to provide accurate shock capturing, skin friction, and heat-transfer predictions for HRRLS vehicles in hypersonic flow, 5) performing a Reynolds-averaged Navier-Stokes computation on an HRRLS configuration; 6) integrating the RANS solver with the FEAP code for coupled fluid-structure-thermal capability; and 7) integrating the existing NASA SRGULL propulsion flow path prediction software with the FEFLO software for quasi-3D propulsion flow path predictions, 8) improving and integrating into the network, an existing adjoint-based design optimization code.

Multicomponent model of deformation and detachment of a biofilm under fluid flow

PubMed Central

Tierra, Giordano; Pavissich, Juan P.; Nerenberg, Robert; Xu, Zhiliang; Alber, Mark S.

2015-01-01

A novel biofilm model is described which systemically couples bacteria, extracellular polymeric substances (EPS) and solvent phases in biofilm. This enables the study of contributions of rheology of individual phases to deformation of biofilm in response to fluid flow as well as interactions between different phases. The model, which is based on first and second laws of thermodynamics, is derived using an energetic variational approach and phase-field method. Phase-field coupling is used to model structural changes of a biofilm. A newly developed unconditionally energy-stable numerical splitting scheme is implemented for computing the numerical solution of the model efficiently. Model simulations predict biofilm cohesive failure for the flow velocity between and m s−1 which is consistent with experiments. Simulations predict biofilm deformation resulting in the formation of streamers for EPS exhibiting a viscous-dominated mechanical response and the viscosity of EPS being less than . Higher EPS viscosity provides biofilm with greater resistance to deformation and to removal by the flow. Moreover, simulations show that higher EPS elasticity yields the formation of streamers with complex geometries that are more prone to detachment. These model predictions are shown to be in qualitative agreement with experimental observations. PMID:25808342

Natural Attenuation of Nonionic Surfactants Used in Hydraulic Fracturing Fluids: Degradation Rates, Pathways, and Mechanisms.

PubMed

Heyob, Katie M; Blotevogel, Jens; Brooker, Michael; Evans, Morgan V; Lenhart, John J; Wright, Justin; Lamendella, Regina; Borch, Thomas; Mouser, Paula J

2017-12-05

Hydraulic fracturing fluids are injected into shales to extend fracture networks that enhance oil and natural gas production from unconventional reservoirs. Here we evaluated the biodegradability of three widely used nonionic polyglycol ether surfactants (alkyl ethoxylates (AEOs), nonylphenol ethoxylates (NPEOs), and polypropylene glycols (PPGs)) that function as weatherizers, emulsifiers, wetting agents, and corrosion inhibitors in injected fluids. Under anaerobic conditions, we observed complete removal of AEOs and NPEOs from solution within 3 weeks regardless of whether surfactants were part of a chemical mixture or amended as individual additives. Microbial enzymatic chain shortening was responsible for a shift in ethoxymer molecular weight distributions and the accumulation of the metabolite acetate. PPGs bioattenuated the slowest, producing sizable concentrations of acetone, an isomer of propionaldehyde. Surfactant chain shortening was coupled to an increased abundance of the diol dehydratase gene cluster (pduCDE) in Firmicutes metagenomes predicted from the 16S rRNA gene. The pduCDE enzymes are responsible for cleaving ethoxylate chain units into aldehydes before their fermentation into alcohols and carboxylic acids. These data provide new mechanistic insight into the environmental fate of hydraulic fracturing surfactants after accidental release through chain shortening and biotransformation, emphasizing the importance of compound structure disclosure for predicting biodegradation products.

Changes in arterial blood pressure induced by passive leg raising predict hypotension during the induction of sedation in critically ill patients without severe cardiac dysfunction.

PubMed

Yu, Tao; Pan, Chun; Guo, Feng-mei; Yang, Yi; Qiu, Hai-bo

2013-07-01

Hypotension due to the induction of sedation with dexmedetomidine infusion may be harmful in critically ill patients. Changes in pulse pressure induced by the passive leg raising test (PLR-ΔPP) as marker of fluid responsiveness, assessed prior to sedation, may predict hemodynamic changes. The present study was to investigate the power of the PLR test in critically ill patients in predicting hypotension induced by the induction of dexmedetomidine sedation. Fluid responsiveness was estimated by a passive leg raising (PLR) test before dexmedetomidine sedation. Patients were assigned to either the "Nonresponders" or "Responders" group according to their hemodynamic responses to the PLR test ("Nonresponders", PLR-ΔPP < 10.3%; "Responders", PLR-ΔPP ≥ 10.3%). Sedation was performed with a dexmedetomidine infusion (0.5 µg/kg over a 10-minute loading period, then 0.2 - 0.7 µg×kg(-1)×h(-1)) and titrated to maintain the target Richmond agitation sedation scale (RASS) score in the range of -2 to -1 and the bispectral index value in the range of 60 to 75. Radial artery pulse pressure, heart rate (HR), and central venous pressure (CVP) were measured at each phase of the study procedure. Hemodynamic fluctuations during the use of dexmedetomidine sedation were recorded and compared between the two groups. Fifty patients had a median (25% - 75% interquartile range) of 71 (61 - 78) years old were studied. At baseline, 39 of the 50 patients were "Nonresponders" and 11 were "Responders". Following dexmedetomidine sedation, patients classified as "Responders" had a significantly greater systolic blood pressure decrease during the induction of dexmedetomidine sedation than the "Nonresponders" ((-26.3 ± 6.8)% vs. -11.8 ± 8.5)%, P < 0.001). In addition, the "Responders" group required significantly more fluid boluses (8 vs. 3; P < 0.001) and vasopressors (2 vs. 0; P < 0.05) than the "Nonresponders" group to restore blood pressure. Finally, PLR-ΔPP was positively correlated with changes in systolic blood pressure (PLR-ΔSBP) (r(2) = 0.576; P < 0.001) and significantly correlated with dexmedetomidine infusion-induced changes in SBP (r(2) = 0.202; P < 0.05). AUC for PLR-ΔPP was 0.84 (95%CI 0.71 - 0.93). PLR-ΔPP predicted hypotension with a sensitivity of 73% and a specificity of 92%. The fluid responsiveness assessment pre-sedation was found to predict blood pressure fluctuation during the induction of dexmedetomidine sedation. The PLR test conducted prior to sedation may be a useful tool to identify patients with a high risk of hemodynamic events and may be used to indicate the need for prophylactic treatment.

The ability of pulse pressure variations obtained with CNAP™ device to predict fluid responsiveness in the operating room.

PubMed

Biais, Matthieu; Stecken, Laurent; Ottolenghi, Laetitia; Roullet, Stéphanie; Quinart, Alice; Masson, Françoise; Sztark, François

2011-09-01

Respiratory-induced pulse pressure variations obtained with an arterial line (ΔPP(ART)) indicate fluid responsiveness in mechanically ventilated patients. The Infinity® CNAP™ SmartPod® (Dräger Medical AG & Co. KG, Lübeck, Germany) provides noninvasive continuous beat-to-beat arterial blood pressure measurements and a near real-time pressure waveform. We hypothesized that respiratory-induced pulse pressure variations obtained with the CNAP system (ΔPP(CNAP)) predict fluid responsiveness as well as ΔPP(ART) predicts fluid responsiveness in mechanically ventilated patients during general anesthesia. Thirty-five patients undergoing vascular surgery were studied after induction of general anesthesia. Stroke volume (SV) measured with the Vigileo™/FloTrac™ (Edwards Lifesciences, Irvine, CA), ΔPP(ART), and ΔPP(CNAP) were recorded before and after intravascular volume expansion (VE) (500 mL of 6% hydroxyethyl starch 130/0.4). Subjects were defined as responders if SV increased by ≥15% after VE. Twenty patients responded to VE and 15 did not. The correlation coefficient between ΔPP(ART) and ΔPP(CNAP) before VE was r = 0.90 (95% confidence interval [CI] = 0.84-0.96; P < 0.0001). Before VE, ΔPP(ART) and ΔPP(CNAP) were significantly higher in responders than in nonresponders (P < 0.0001). The values of ΔPP(ART) and ΔPP(CNAP) before VE were significantly correlated with the percent increase in SV induced by VE (respectively, r(2) = 0.50; P < 0.0001 and r(2) = 0.57; P < 0.0001). Before VE, a ΔPP(ART) >10% discriminated between responders and nonresponders with a sensitivity of 90% (95% CI = 69%-99%) and a specificity of 87% (95% CI = 60%-98%). The area under the receiver operating characteristic (ROC) curve was 0.957 ± 0.035 for ΔPP(ART). Before VE, a ΔPP(CNAP) >11% discriminated between responders and nonresponders with a sensitivity of 85% (95% CI = 62%-97%) and a specificity of 100% (95% CI = 78%-100%). The area under the ROC curve was 0.942 ± 0.040 for ΔPP(CNAP). There was no significant difference between the area under the ROC curve for ΔPP(ART) and ΔPP(CNAP). A value of ΔPP(CNAP) >11% has a sensitivity of at least 62% in predicting preload-dependent responders to VE in mechanically ventilated patients during general anesthesia.

Third-order optical conductivity of an electron fluid

NASA Astrophysics Data System (ADS)

Sun, Zhiyuan; Basov, D. N.; Fogler, M. M.

2018-02-01

We derive the nonlinear optical conductivity of an isotropic electron fluid at frequencies below the interparticle collision rate. In this regime, governed by hydrodynamics, the conductivity acquires a universal form at any temperature, chemical potential, and spatial dimension. We show that the nonlinear response of the fluid to a uniform field is dominated by the third-order conductivity tensor σ(3 ) whose magnitude and temperature dependence differ qualitatively from those in the conventional kinetic regime of higher frequencies. We obtain explicit formulas for σ(3 ) for Dirac materials such as graphene and Weyl semimetals. We make predictions for the third-harmonic generation, renormalization of the collective-mode spectrum, and the third-order circular magnetic birefringence experiments.

Analytical Prediction of Turbulent Heat Transfer Parameters.

DTIC Science & Technology

1985-04-01

responsible for the observed whiplash motion of turbulent jets. The buckling theory predicts correctly the natural frequency of the whiplash motion and...number increases frcm % 102 to 10 , the whiplash motion of jets evolves from a sinusoid to a helix and eventually to a train of axisymmetric waves... whiplash and fluctuating motion of turbulent jets. The period of this fluctua- tion scales with the buckling time t. = A/V , i.e., with the time of fluid

Cytochrome P450 and ABCB1 genetics: association with quetiapine and norquetiapine plasma and cerebrospinal fluid concentrations and with clinical response in patients suffering from schizophrenia. A pilot study.

PubMed

Nikisch, Georg; Baumann, Pierre; Oneda, Beatrice; Kiessling, Bernhard; Weisser, Heike; Mathé, Aleksander A; Yoshitake, Takashi; Kehr, Jan; Wiedemann, Georg; Eap, Chin B

2011-07-01

Variability in response to atypical antipsychotic drugs is due to genetic and environmental factors. Cytochrome P450 (CYP) isoforms are implicated in the metabolism of drugs, while the P-glycoprotein transporter (P-gp), encoded by the ABCB1 gene, may influence both the blood and brain drug concentrations. This study aimed to identify the possible associations of CYP and ABCB1 genetic polymorphisms with quetiapine and norquetiapine plasma and cerebrospinal fluid (CSF) concentrations and with response to treatment. Twenty-two patients with schizophrenia receiving 600 mg of quetiapine daily were genotyped for four CYP isoforms and ABCB1 polymorphisms. Quetiapine and norquetiapine peak plasma and CSF concentrations were measured after 4 weeks of treatment. Stepwise multiple regression analysis revealed that ABCB1 3435C > T (rs1045642), 2677G > T (rs2032582) and 1236C > T (rs1128503) polymorphisms predicted plasma quetiapine concentrations, explaining 41% of the variability (p = 0.001). Furthermore, the ABCB1 polymorphisms predicted 48% (p = 0.024) of the variability of the Δ PANSS total score, with the non-carriers of the 3435TT showing higher changes in the score. These results suggest that ABCB1 genetic polymorphisms may be a predictive marker of quetiapine treatment in schizophrenia.

On the effect of acoustic coupling on random and harmonic plate vibrations

NASA Technical Reports Server (NTRS)

Frendi, A.; Robinson, J. H.

1993-01-01

The effect of acoustic coupling on random and harmonic plate vibrations is studied using two numerical models. In the coupled model, the plate response is obtained by integration of the nonlinear plate equation coupled with the nonlinear Euler equations for the surrounding acoustic fluid. In the uncoupled model, the nonlinear plate equation with an equivalent linear viscous damping term is integrated to obtain the response of the plate subject to the same excitation field. For a low-level, narrow-band excitation, the two models predict the same plate response spectra. As the excitation level is increased, the response power spectrum predicted by the uncoupled model becomes broader and more shifted towards the high frequencies than that obtained by the coupled model. In addition, the difference in response between the coupled and uncoupled models at high frequencies becomes larger. When a high intensity harmonic excitation is used, causing a nonlinear plate response, both models predict the same frequency content of the response. However, the level of the harmonics and subharmonics are higher for the uncoupled model. Comparisons to earlier experimental and numerical results show that acoustic coupling has a significant effect on the plate response at high excitation levels. Its absence in previous models may explain the discrepancy between predicted and measured responses.

Inter-device differences in monitoring for goal-directed fluid therapy.

PubMed

Thiele, Robert H; Bartels, Karsten; Gan, Tong-Joo

2015-02-01

Goal-directed fluid therapy is an integral component of many Enhanced Recovery After Surgery (ERAS) protocols currently in use. The perioperative clinician is faced with a myriad of devices promising to deliver relevant physiologic data to better guide fluid therapy. The goal of this review is to provide concise information to enable the clinician to make an informed decision when choosing a device to guide goal-directed fluid therapy. The focus of many devices used for advanced hemodynamic monitoring is on providing measurements of cardiac output, while other, more recent, devices include estimates of fluid responsiveness based on dynamic indices that better predict an individual's response to a fluid bolus. Currently available technologies include the pulmonary artery catheter, esophageal Doppler, arterial waveform analysis, photoplethysmography, venous oxygen saturation, as well as bioimpedance and bioreactance. The underlying mechanistic principles for each device are presented as well as their performance in clinical trials relevant for goal-directed therapy in ERAS. The ERAS protocols typically involve a multipronged regimen to facilitate early recovery after surgery. Optimizing perioperative fluid therapy is a key component of these efforts. While no technology is without limitations, the majority of the currently available literature suggests esophageal Doppler and arterial waveform analysis to be the most desirable choices to guide fluid administration. Their performance is dependent, in part, on the interpretation of dynamic changes resulting from intrathoracic pressure fluctuations encountered during mechanical ventilation. Evolving practice patterns, such as low tidal volume ventilation as well as the necessity to guide fluid therapy in spontaneously breathing patients, will require further investigation.

Determination of rock properties by low-frequency AC electrokinetics

NASA Astrophysics Data System (ADS)

Pengra, David B.; Xi Li, Sidney; Wong, Po-Zen

1999-12-01

In brine-saturated rock the existence of a mobile space charge at the fluid/solid interface leads to the electrokinetic phenomena of electroosmotic pressure and streaming potential. The coupling coefficients of these electrokinetic effects, when combined with the conductivity of the brine-saturated rock, determine the brine permeability of rock exactly. A sensitive low-frequency AC technique has been used to measure electrokinetic response of a collection of eight rock and four glass bead samples saturated with NaCl brine as a function of salt concentration (fluid conductivity of 0.5 to 6.38 S/m); the response of four of the original 12 samples has also been measured as a function of temperature from 0° to 50°C. All data verify the predicted permeability relationship. Additionally, the frequency response of the electroosmotic pressure signal alone can also be used to determine the permeability, given knowledge of experimental parameters. The concentration and temperature dependence of electroosmosis and streaming potential is found to mostly conform to the predictions of a simple model based on the Helmholtz-Smoluchowski equation, the Stern model of the electrochemical double layer, and an elementary theory of ionic conduction.

Finite-element model of the active organ of Corti

PubMed Central

Elliott, Stephen J.; Baumgart, Johannes

2016-01-01

The cochlear amplifier that provides our hearing with its extraordinary sensitivity and selectivity is thought to be the result of an active biomechanical process within the sensory auditory organ, the organ of Corti. Although imaging techniques are developing rapidly, it is not currently possible, in a fully active cochlea, to obtain detailed measurements of the motion of individual elements within a cross section of the organ of Corti. This motion is predicted using a two-dimensional finite-element model. The various solid components are modelled using elastic elements, the outer hair cells (OHCs) as piezoelectric elements and the perilymph and endolymph as viscous and nearly incompressible fluid elements. The model is validated by comparison with existing measurements of the motions within the passive organ of Corti, calculated when it is driven either acoustically, by the fluid pressure or electrically, by excitation of the OHCs. The transverse basilar membrane (BM) motion and the shearing motion between the tectorial membrane and the reticular lamina are calculated for these two excitation modes. The fully active response of the BM to acoustic excitation is predicted using a linear superposition of the calculated responses and an assumed frequency response for the OHC feedback. PMID:26888950

Unsteady Cascade Aerodynamic Response Using a Multiphysics Simulation Code

NASA Technical Reports Server (NTRS)

Lawrence, C.; Reddy, T. S. R.; Spyropoulos, E.

2000-01-01

The multiphysics code Spectrum(TM) is applied to calculate the unsteady aerodynamic pressures of oscillating cascade of airfoils representing a blade row of a turbomachinery component. Multiphysics simulation is based on a single computational framework for the modeling of multiple interacting physical phenomena, in the present case being between fluids and structures. Interaction constraints are enforced in a fully coupled manner using the augmented-Lagrangian method. The arbitrary Lagrangian-Eulerian method is utilized to account for deformable fluid domains resulting from blade motions. Unsteady pressures are calculated for a cascade designated as the tenth standard, and undergoing plunging and pitching oscillations. The predicted unsteady pressures are compared with those obtained from an unsteady Euler co-de refer-red in the literature. The Spectrum(TM) code predictions showed good correlation for the cases considered.

High frequency flow-structural interaction in dense subsonic fluids

NASA Technical Reports Server (NTRS)

Liu, Baw-Lin; Ofarrell, J. M.

1995-01-01

Prediction of the detailed dynamic behavior in rocket propellant feed systems and engines and other such high-energy fluid systems requires precise analysis to assure structural performance. Designs sometimes require placement of bluff bodies in a flow passage. Additionally, there are flexibilities in ducts, liners, and piping systems. A design handbook and interactive data base have been developed for assessing flow/structural interactions to be used as a tool in design and development, to evaluate applicable geometries before problems develop, or to eliminate or minimize problems with existing hardware. This is a compilation of analytical/empirical data and techniques to evaluate detailed dynamic characteristics of both the fluid and structures. These techniques have direct applicability to rocket engine internal flow passages, hot gas drive systems, and vehicle propellant feed systems. Organization of the handbook is by basic geometries for estimating Strouhal numbers, added mass effects, mode shapes for various end constraints, critical onset flow conditions, and possible structural response amplitudes. Emphasis is on dense fluids and high structural loading potential for fatigue at low subsonic flow speeds where high-frequency excitations are possible. Avoidance and corrective measure illustrations are presented together with analytical curve fits for predictions compiled from a comprehensive data base.

Wavelet based comparison of high frequency oscillations in the geodetic and fluid excitation functions of polar motion

NASA Astrophysics Data System (ADS)

Kosek, W.; Popinski, W.; Niedzielski, T.

2011-10-01

It has been already shown that short period oscillations in polar motion, with periods less than 100 days, are very chaotic and are responsible for increase in short-term prediction errors of pole coordinates data. The wavelet technique enables to compare the geodetic and fluid excitation functions in the high frequency band in many different ways, e.g. by looking at the semblance function. The waveletbased semblance filtering enables determination the common signal in both geodetic and fluid excitation time series. In this paper the considered fluid excitation functions consist of the atmospheric, oceanic and land hydrology excitation functions from ECMWF atmospheric data produced by IERS Associated Product Centre Deutsches GeoForschungsZentrum, Potsdam. The geodetic excitation functions have been computed from the combined IERS pole coordinates data.

Cerebrospinal Fluid Pressure: Revisiting Factors Influencing Optic Nerve Head Biomechanics

PubMed Central

Hua, Yi; Voorhees, Andrew P.; Sigal, Ian A.

2018-01-01

Purpose To model the sensitivity of the optic nerve head (ONH) biomechanical environment to acute variations in IOP, cerebrospinal fluid pressure (CSFP), and central retinal artery blood pressure (BP). Methods We extended a previously published numerical model of the ONH to include 24 factors representing tissue anatomy and mechanical properties, all three pressures, and constraints on the optic nerve (CON). A total of 8340 models were studied to predict factor influences on 98 responses in a two-step process: a fractional factorial screening analysis to identify the 16 most influential factors, followed by a response surface methodology to predict factor effects in detail. Results The six most influential factors were, in order: IOP, CON, moduli of the sclera, lamina cribrosa (LC) and dura, and CSFP. IOP and CSFP affected different aspects of ONH biomechanics. The strongest influence of CSFP, more than twice that of IOP, was on the rotation of the peripapillary sclera. CSFP had similar influence on LC stretch and compression to moduli of sclera and LC. On some ONHs, CSFP caused large retrolamina deformations and subarachnoid expansion. CON had a strong influence on LC displacement. BP overall influence was 633 times smaller than that of IOP. Conclusions Models predict that IOP and CSFP are the top and sixth most influential factors on ONH biomechanics. Different IOP and CSFP effects suggest that translaminar pressure difference may not be a good parameter to predict biomechanics-related glaucomatous neuropathy. CON may drastically affect the responses relating to gross ONH geometry and should be determined experimentally. PMID:29332130

Acoustic and mechanical response of reservoir rocks under variable saturation and effective pressure.

PubMed

Ravazzoli, C L; Santos, J E; Carcione, J M

2003-04-01

We investigate the acoustic and mechanical properties of a reservoir sandstone saturated by two immiscible hydrocarbon fluids, under different saturations and pressure conditions. The modeling of static and dynamic deformation processes in porous rocks saturated by immiscible fluids depends on many parameters such as, for instance, porosity, permeability, pore fluid, fluid saturation, fluid pressures, capillary pressure, and effective stress. We use a formulation based on an extension of Biot's theory, which allows us to compute the coefficients of the stress-strain relations and the equations of motion in terms of the properties of the single phases at the in situ conditions. The dry-rock moduli are obtained from laboratory measurements for variable confining pressures. We obtain the bulk compressibilities, the effective pressure, and the ultrasonic phase velocities and quality factors for different saturations and pore-fluid pressures ranging from normal to abnormally high values. The objective is to relate the seismic and ultrasonic velocity and attenuation to the microstructural properties and pressure conditions of the reservoir. The problem has an application in the field of seismic exploration for predicting pore-fluid pressures and saturation regimes.

Property Changes in Aqueous Solutions due to Surfactant Treatment of PCE: Implications to Geophysical Measurements

NASA Astrophysics Data System (ADS)

Werkema, D. D.

2007-12-01

Select physicochemical properties of aqueous solutions composed of surfactants, dye, and perchloroethylene (PCE) were evaluated through a response surface quadratic design model of experiment. Nine surfactants, which are conventionally used in the remediation of PCE, were evaluated with varying concentrations of PCE and indicator dyes in aqueous solutions. Two hundred forty experiments were performed using PCE as a numerical factor (coded A) from 0 to 200 parts per million (ppm), dye type (coded B) as a 3-level categorical factor, and surfactant type (coded C) as a 10-level categorical factor. Five responses were measured: temperature (°C), pH, conductivity (μS/cm), dissolved oxygen (DO, mg/L), and density (g/mL). Diagnostics proved a normally distributed predictable response for all measured responses except pH. The Box-Cox plot for transforms recommended a power transform for the conductivity response with lambda (λ) = 0.50, and for the DO response, λ =2.2. The overall mean of the temperature response proved to be a better predictor than the linear model. The conductivity response is best fitted with a linear model using significant coded terms B and C. Both DO and density also showed a linear model with coded terms A, B, and C for DO; and terms A and C for density. Some of the surfactant treatments of PCE significantly alter the conductivity, DO, and density of the aqueous solution. However, the magnitude of the density response is so small that it does not exceed the instrument tolerance. Results for the conductivity and DO responses provide predictive models for the surfactant treatment of PCE and may be useful in determining the potential for geophysically monitoring surfactant enhanced aquifer remediation (SEAR) of PCE. As the aqueous physicochemical properties change due to surfactant remediation efforts, so will the properties of the subsurface pore water which are influential factors in geophysical measurements. Geoelectrical methods are potentially the best suited to measure SEAR alterations in the subsurface because the conductivity of the pore fluid has the largest relative change. This research has provided predictive models for alterations in the physicochemical properties of the pore fluid to SEAR of PCE. Future investigations should address the contribution of the solid matrix in the subsurface and the solid-fluid interaction during SEAR of PCE contamination. Notice: Although this work was reviewed by EPA and approved for publication, it may not necessarily reflect official Agency policy. Mention of trade names or commercial products does not constitute endorsement or recommendation by EPA for use.

Hydrodynamic damping and stiffness prediction in Francis turbine runners using CFD

NASA Astrophysics Data System (ADS)

Nennemann, Bernd; Monette, Christine; Chamberland-Lauzon, Joël

2016-11-01

Fluid-structure interaction (FSI) has a major impact on the dynamic response of the structural components of hydroelectric turbines. On mid- to high-head Francis runners, the rotor-stator interaction (RSI) phenomenon has to be considered carefully during the design phase to avoid operational issues on the prototype machine. The RSI dynamic response amplitudes of the runner are driven by three main factors: (1) pressure forcing amplitudes, (2) excitation frequencies in relation to natural frequencies and (3) damping. All three of the above factors are significantly influenced by both mechanical and hydraulic parameters. The prediction of the first two factors has been largely documented in the literature. However, the prediction of hydro-dynamic damping has only recently and only partially been treated. Two mode-based approaches (modal work and coupled single degree of freedom) for the prediction of flow-added dynamic parameters using separate finite element analyses (FEA) in still water and unsteady computational fluid dynamic (CFD) analyses are presented. The modal motion is connected to the time resolved CFD calculation by means of dynamic mesh deformation. This approach has partially been presented in a previous paper applied to a simplified hydrofoil. The present work extends the approach to Francis runners under RSI loading. In particular the travelling wave mode shapes of turbine runners are considered. Reasonable agreement with experimental results is obtained in parts of the operating range.

A fiber matrix model for fluid flow and streaming potentials in the canaliculi of an osteon

NASA Technical Reports Server (NTRS)

Zeng, Y.; Cowin, S. C.; Weinbaum, S.

1994-01-01

A theoretical model is developed to predict the fluid shear stress and streaming potential at the surface of osteocytic processes in the lacunar-canalicular porosity of an osteon when the osteon is subject to mechanical loads that are parallel or perpendicular to its axis. The theory developed in Weinbaum et al. (31) for the flow through a proteoglycan matrix in a canaliculus is employed in a poroelastic model for the osteon. Our formulation is a generalization of that of Petrov et al. (17). Our model predicts that, in order to satisfy the measured frequency dependence of the phase and magnitude of the SGP in macroscopic bone samples, the fiber spacing in the fluid annulus must lie in the narrow range 6-7 nm typical of the spacing of GAG sidechains along a protein monomer. The model predictions for the local SGP profiles in the osteon agree with the experimental observations of Starkebaum et al. (24). The theory predicts that the pore pressure relaxation time, tau d, for a 150-300 microns diameter osteon with the foregoing matrix structure is approximately 0.03-0.13 sec, and that the amplitude of the mean fluid shear stress on the membrane of the osteocytic process at the mean areal radius of the osteon has a maximum at 28 Hz if tau d = 0.06 sec. This maximum, which is independent of the magnitude of the loading, could be important in vivo since the recent experiments of Turner et al. (28) and McLeod et al. (15) have a peak in the strain frequency spectrum between 20 and 30 Hz that also appears to be independent of the type (magnitude) of loading. Numerical predictions for the amplitude of the average fluid shear stress on the osteocytic membrane at the mean areal radius of the osteon show that the fluid shear stress associated with the low amplitude 20-30 Hz spectral strain component is at least as large as the average fluid shear stress associated with the high amplitude 1 Hz stride component, although the latter loading is an order of magnitude larger, and has a magnitude that lies within the middle of the range, 6-30 dynes/cm2, where fluid shear stresses in tissue culture studies with osteoblast monolayers have elicited an intracellular Ca++ response (31). The implications of these results for intracellular electrical communication are discussed.

Second-trimester amniotic fluid corticotropin-releasing hormone and urocortin in relation to maternal stress and fetal growth in human pregnancy.

PubMed

La Marca-Ghaemmaghami, Pearl; Dainese, Sara M; Stalla, Günter; Haller, Marina; Zimmermann, Roland; Ehlert, Ulrike

2017-05-01

This study explored the association between the acute psychobiological stress response, chronic social overload and amniotic fluid corticotropin-releasing hormone (CRH) and urocortin (UCN) in 34 healthy, second-trimester pregnant women undergoing amniocentesis. The study further examined the predictive value of second-trimester amniotic fluid CRH and UCN for fetal growth and neonatal birth outcome. The amniocentesis served as a naturalistic stressor, during which maternal state anxiety and salivary cortisol was measured repeatedly and an aliquot of amniotic fluid was collected. The pregnant women additionally completed a questionnaire on chronic social overload. Fetal growth parameters were obtained at amniocentesis using fetal ultrasound biometry and at birth from medical records. The statistical analyzes revealed that the acute maternal psychobiological stress response was unassociated with the amniotic fluid peptides, but that maternal chronic overload and amniotic CRH were positively correlated. Moreover, amniotic CRH was negatively associated with fetal size at amniocentesis and positively with growth in size from amniocentesis to birth. Hardly any studies have previously explored whether acute maternal psychological stress influences fetoplacental CRH or UCN levels significantly. Our findings suggest that (i) chronic, but not acute maternal stress may affect fetoplacental CRH secretion and that (ii) CRH is complexly involved in fetal growth processes as previously shown in animals.

Prevalence and Determinants of Physical Activity and Fluid Intake in Kidney Transplant Recipients

PubMed Central

Gordon, Elisa J.; Prohaska, Thomas R.; Gallant, Mary P.; Sehgal, Ashwini R.; Strogatz, David; Conti, David; Siminoff, Laura A.

2009-01-01

Background and Significance Self-care for kidney transplantation is recommended to maintain kidney function. Little is known about levels of self-care practices, and demographic, psychosocial, and health-related correlates. Aim We investigated patients’ self-reported exercise and fluid intake, demographic and psychosocial factors associated with these self-care practices, and health-related quality of life. Methods Eighty-eight of 158 kidney recipients from two academic medical centers completed a semi-structured interview and surveys 2 months post-transplant. Results Most patients were sedentary (76%) with a quarter exercising either regularly (11%) or not at current recommendations (13%). One third (35%) reported drinking the recommended three liters of fluid daily. Multivariate analyses indicated that private insurance, high self-efficacy, and better physical functioning were significantly associated with engaging in physical activity (p<0.05); while male gender, private insurance, high self-efficacy, and not attributing oneself responsible for transplant success were significant predictors of adherence to fluid intake (p<0.05). Despite the significance of these predictors, models for physical activity and fluid intake explained 10–15% of the overall variance in these behaviors. Multivariate analyses indicated that younger age, high value of exercise, and higher social functioning significantly (p<0.05) predicted high self-efficacy for physical activity, while being married significantly (p<0.05) predicted high self-efficacy for fluid intake. Conclusion Identifying patients at risk of inadequate self-care practice is essential for educating patients about the importance of self-care. PMID:19925468

Prevalence and determinants of physical activity and fluid intake in kidney transplant recipients.

PubMed

Gordon, Elisa J; Prohaska, Thomas R; Gallant, Mary P; Sehgal, Ashwini R; Strogatz, David; Conti, David; Siminoff, Laura A

2010-01-01

Self-care for kidney transplantation is recommended to maintain kidney function. Little is known about levels of self-care practices and demographic, psychosocial, and health-related correlates. To investigate patients' self-reported exercise and fluid intake, demographic and psychosocial factors associated with these self-care practices, and health-related quality of life. Eighty-eight of 158 kidney recipients from two academic medical centers completed a semi-structured interview and surveys 2 months post-transplant. Most patients were sedentary (76%) with a quarter exercising either regularly (11%) or not at current recommendations (13%). One-third (35%) reported drinking the recommended 3 L of fluid daily. Multivariate analyses indicated that private insurance, high self-efficacy, and better physical functioning were significantly associated with engaging in physical activity (p < 0.05); while male gender, private insurance, high self-efficacy, and not attributing oneself responsible for transplant success were significant predictors of adherence to fluid intake (p < 0.05). Despite the significance of these predictors, models for physical activity and fluid intake explained 10-15% of the overall variance in these behaviors. Multivariate analyses indicated that younger age, high value of exercise, and higher social functioning significantly (p < 0.05) predicted high self-efficacy for physical activity, while being married significantly (p < 0.05) predicted high self-efficacy for fluid intake. Identifying patients at risk of inadequate self-care practice is essential for educating patients about the importance of self-care.

Physics of field-responsive fluids

NASA Astrophysics Data System (ADS)

Wan, Tsz Kai Jones

Electrorheological (ER) fluid is a new class of material, which possesses a variety of potential applications, such as shock absorbers and clutches. It is formed by microparticles that are dispersed in a host fluid. The particles will form chains rapidly when we apply an electric field to the ER fluid. However, due to the inadequacy of knowledge, the proposed applications have not been commercialized yet. The prediction of the strength of the ER effect is the main concern in the theoretical investigation of ER fluids. The ER effect is originated from the induced interaction between the polarized particles in an ER fluid. Existing theories assume that the particles are at rest. In a realistic situation, the fluid flow exerts force and torque on the particles, setting the particles in both translational and rotational motions under these actions. Recent experiments showed that the induced forces between the rotating particles are markedly different from the values predicted by existing theories. To overcome the discrepancy between theory and experiment, we formulate a model to take the particle motion into account, and derive the dependence of forces on the angular velocity of the rotating particles. We develop first-principles methods to investigate the dynamic ER effects in which the suspended particles can have translational or rotational motions. A model based on the relaxation of polarization charge on the particle surfaces is proposed and solved for various experimental conditions. The method can be extended to study the ER effects of coated particles, crystalline particles, and to the magnetorheological effects of paramagnetic particles. Moreover, the nonlinear ER effects under a strong applied field will be studied by the same approach. The results may help in the preparation of materials for the design of ER fluids.

Predicting the amount of intraperitoneal fluid accumulation by computed tomography and its clinical use in patients with perforated peptic ulcer.

PubMed

Ishiguro, Toru; Kumagai, Youichi; Baba, Hiroyuki; Tajima, Yusuke; Imaizumi, Hideko; Suzuki, Okihide; Kuwabara, Koki; Matsuzawa, Takeaki; Sobajima, Jun; Fukuchi, Minoru; Ishibashi, Keiichiro; Mochiki, Erito; Ishida, Hideyuki

2014-01-01

The correlation between the amount of peritoneal fluid and clinical parameters in patients with perforated peptic ulcer (PPU) has not been investigated. The authors' objective was to derive a reliable formula for determining the amount of peritoneal fluid in patients with PPU before surgery, and to evaluate the correlation between the estimated amount of peritoneal fluid and clinical parameters. We investigated 62 consecutive patients who underwent emergency surgery for PPU, and in whom prediction of the amount of accumulated intraperitoneal fluid was possible by computed tomography (CT) using the methods described by Oriuchi et al. We examined the relationship between the predicted amount of accumulated intraperitoneal fluid and that measured during surgery, and the relationship between the amount of fluid predicted preoperatively or measured during surgery and several clinical parameters. There was a significant positive correlation between the amount of fluid predicted by CT scan and that measured during surgery. When patients with gastric ulcer and duodenal ulcer were analyzed collectively, the predicted amount of intraperitoneal fluid and the amount measured during surgery were each associated with the period from onset until CT scan, perforation size, the Mannheim peritoneal index, and the severity of postoperative complications according to the Clavien-Dindo classification. Our present results suggest that the method of Oriuchi et al is useful for predicting the amount of accumulated intraperitoneal fluid in patients with PPU, and that this would be potentially helpful for treatment decision-making and estimating the severity of postoperative complications.

Predicting the Amount of Intraperitoneal Fluid Accumulation by Computed Tomography and Its Clinical Use in Patients With Perforated Peptic Ulcer

PubMed Central

Ishiguro, Toru; Kumagai, Youichi; Baba, Hiroyuki; Tajima, Yusuke; Imaizumi, Hideko; Suzuki, Okihide; Kuwabara, Koki; Matsuzawa, Takeaki; Sobajima, Jun; Fukuchi, Minoru; Ishibashi, Keiichiro; Mochiki, Erito; Ishida, Hideyuki

2014-01-01

The correlation between the amount of peritoneal fluid and clinical parameters in patients with perforated peptic ulcer (PPU) has not been investigated. The authors' objective was to derive a reliable formula for determining the amount of peritoneal fluid in patients with PPU before surgery, and to evaluate the correlation between the estimated amount of peritoneal fluid and clinical parameters. We investigated 62 consecutive patients who underwent emergency surgery for PPU, and in whom prediction of the amount of accumulated intraperitoneal fluid was possible by computed tomography (CT) using the methods described by Oriuchi et al. We examined the relationship between the predicted amount of accumulated intraperitoneal fluid and that measured during surgery, and the relationship between the amount of fluid predicted preoperatively or measured during surgery and several clinical parameters. There was a significant positive correlation between the amount of fluid predicted by CT scan and that measured during surgery. When patients with gastric ulcer and duodenal ulcer were analyzed collectively, the predicted amount of intraperitoneal fluid and the amount measured during surgery were each associated with the period from onset until CT scan, perforation size, the Mannheim peritoneal index, and the severity of postoperative complications according to the Clavien–Dindo classification. Our present results suggest that the method of Oriuchi et al is useful for predicting the amount of accumulated intraperitoneal fluid in patients with PPU, and that this would be potentially helpful for treatment decision-making and estimating the severity of postoperative complications. PMID:25437594

Using regional pore-fluid pressure response following the 3 Sep 2016 M­­w5.8 Pawnee, Oklahoma earthquake to constrain far-field seismicity rate forecasts

NASA Astrophysics Data System (ADS)

Kroll, K.; Murray, K. E.; Cochran, E. S.

2016-12-01

The 3 Sep 2016 M­­w5.8 Pawnee, Oklahoma earthquake was the largest event to occur in recorded history of the state. Widespread shaking from the event was felt in seven central U.S. states and caused damage as far away as Oklahoma City ( 115 km SSW). The Pawnee earthquake occurred soon after the deployment of a subsurface pore-fluid pressure monitoring network in Aug 2016. Eight pressure transducers were installed downhole in inactive saltwater disposal wells that were completed in the basal sedimentary zone (the Arbuckle Group). The transducers are located in Alfalfa, Grant, and Payne Counties at distances of 48 to 140 km from the Pawnee earthquake. We observed coseismic fluid pressure changes in all monitoring wells, indicating a large-scale poroelastic response in the Arbuckle. Two wells in Payne County lie in a zone of volumetric compression 48-52 km SSE of the rupture and experienced a co-seismic rise in fluid pressures that we conclude was related to poroelastic rebound of the Arbuckle reservoir. We compare measurements of the pore-fluid pressure change to estimated values given by the product of the volumetric strain, a Skempton's coefficient of 0.33, and a Bulk modulus of 25 GPa for fractured granitic basement rocks. We explore the possibility that the small increase in pore-fluid pressure may increase the rate of seismicity in regions outside of the mainshock region. We test this hypothesis by supplementing the Oklahoma Geological Survey earthquake catalog by semi-automated detection smaller magnitude (<2.6 M) earthquakes on seismic stations that are located in the vicinity of the wells. Using the events that occur in the week before the mainshock (27 Aug to 3 Sep 2016) as the background seismicity rate and the estimated pore-fluid pressure increase, we use a rate-state model to predict the seismicity rate change in the week following the event. We then compare the model predictions to the observed seismicity in the week following the Pawnee earthquake. Prepared by LLNL under Contract DE-AC52-07NA27344.

A shock absorber model for structure-borne noise analyses

NASA Astrophysics Data System (ADS)

Benaziz, Marouane; Nacivet, Samuel; Thouverez, Fabrice

2015-08-01

Shock absorbers are often responsible for undesirable structure-borne noise in cars. The early numerical prediction of this noise in the automobile development process can save time and money and yet remains a challenge for industry. In this paper, a new approach to predicting shock absorber structure-borne noise is proposed; it consists in modelling the shock absorber and including the main nonlinear phenomena responsible for discontinuities in the response. The model set forth herein features: compressible fluid behaviour, nonlinear flow rate-pressure relations, valve mechanical equations and rubber mounts. The piston, base valve and complete shock absorber model are compared with experimental results. Sensitivity of the shock absorber response is evaluated and the most important parameters are classified. The response envelope is also computed. This shock absorber model is able to accurately reproduce local nonlinear phenomena and improves our state of knowledge on potential noise sources within the shock absorber.

Proteomic analysis of human follicular fluid in poor ovarian responders during in vitro fertilization.

PubMed

Oh, Jae Won; Kim, Seul Ki; Cho, Kyung-Cho; Kim, Min-Sik; Suh, Chang Suk; Lee, Jung Ryeol; Kim, Kwang Pyo

2017-03-01

Poor ovarian response (POR) in controlled ovarian stimulation is often observed during in vitro fertilization and embryo transfer cycles and it is a major problem. A POR has been found to be related to several factors, including advanced age, high body mass index, and history of ovarian or pelvic surgery. However, it is difficult to predict POR, as there are no specific biomarkers known. In this study, we used quantitative proteomic analyses to investigate potential biomarkers that can predict poor response during in vitro fertilization based on follicular fluid samples. A total of 1079 proteins were identified using a high-resolution orbitrap mass spectrometer coupled online to a nanoflow-LC system. It is notable that 65 upregulated and 66 downregulated proteins were found to be functionally enriched in poor responders. We also validated these differentially expressed proteins using a triple-quadrupole mass spectrometer for quantification of targeted proteins. Of the differentially expressed proteins, three proteins (pregnancy zone protein, renin, and sushi repeat-containing protein SRPX) were regarded as statistically significant (p < 0.05). © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Fluid Flow Phenomena during Welding

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, Wei

2011-01-01

MOLTEN WELD POOLS are dynamic. Liquid in the weld pool in acted on by several strong forces, which can result in high-velocity fluid motion. Fluid flow velocities exceeding 1 m/s (3.3 ft/s) have been observed in gas tungsten arc (GTA) welds under ordinary welding conditions, and higher velocities have been measured in submerged arc welds. Fluid flow is important because it affects weld shape and is related to the formation of a variety of weld defects. Moving liquid transports heat and often dominates heat transport in the weld pool. Because heat transport by mass flow depends on the direction andmore » speed of fluid motion, weld pool shape can differ dramatically from that predicted by conductive heat flow. Temperature gradients are also altered by fluid flow, which can affect weld microstructure. A number of defects in GTA welds have been attributed to fluid flow or changes in fluid flow, including lack of penetration, top bead roughness, humped beads, finger penetration, and undercutting. Instabilities in the liquid film around the keyhole in electron beam and laser welds are responsible for the uneven penetration (spiking) characteristic of these types of welds.« less

A 3D Culture Model to Study How Fluid Pressure and Flow Affect the Behavior of Aggregates of Epithelial Cells.

PubMed

Piotrowski-Daspit, Alexandra S; Simi, Allison K; Pang, Mei-Fong; Tien, Joe; Nelson, Celeste M

2017-01-01

Cells are surrounded by mechanical stimuli in their microenvironment. It is important to determine how cells respond to the mechanical information that surrounds them in order to understand both development and disease progression, as well as to be able to predict cell behavior in response to physical stimuli. Here we describe a protocol to determine the effects of interstitial fluid flow on the migratory behavior of an aggregate of epithelial cells in a three-dimensional (3D) culture model. This protocol includes detailed methods for the fabrication of a 3D cell culture chamber with hydrostatic pressure control, the culture of epithelial cells as an aggregate in a collagen gel, and the analysis of collective cell behavior in response to pressure-driven flow.

Application of the aeroacoustic analogy to a shrouded, subsonic, radial fan

NASA Astrophysics Data System (ADS)

Buccieri, Bryan M.; Richards, Christopher M.

2016-12-01

A study was conducted to investigate the predictive capability of computational aeroacoustics with respect to a shrouded, subsonic, radial fan. A three dimensional unsteady fluid dynamics simulation was conducted to produce aerodynamic data used as the acoustic source for an aeroacoustics simulation. Two acoustic models were developed: one modeling the forces on the rotating fan blades as a set of rotating dipoles located at the center of mass of each fan blade and one modeling the forces on the stationary fan shroud as a field of distributed stationary dipoles. Predicted acoustic response was compared to experimental data measured at two operating speeds using three different outlet restrictions. The blade source model predicted overall far field sound power levels within 5 dB averaged over the six different operating conditions while the shroud model predicted overall far field sound power levels within 7 dB averaged over the same conditions. Doubling the density of the computational fluids mesh and using a scale adaptive simulation turbulence model increased broadband noise accuracy. However, computation time doubled and the accuracy of the overall sound power level prediction improved by only 1 dB.

Predicted thermal response of a cryogenic fuel tank exposed to simulated aerodynamic heating profiles with different cryogens and fill levels

NASA Technical Reports Server (NTRS)

Hanna, Gregory J.; Stephens, Craig A.

1991-01-01

A two dimensional finite difference thermal model was developed to predict the effects of heating profile, fill level, and cryogen type prior to experimental testing the Generic Research Cryogenic Tank (GRCT). These numerical predictions will assist in defining test scenarios, sensor locations, and venting requirements for the GRCT experimental tests. Boiloff rates, tank-wall and fluid temperatures, and wall heat fluxes were determined for 20 computational test cases. The test cases spanned three discrete fill levels and three heating profiles for hydrogen and nitrogen.

Controversies in fluid therapy: Type, dose and toxicity

PubMed Central

McDermid, Robert C; Raghunathan, Karthik; Romanovsky, Adam; Shaw, Andrew D; Bagshaw, Sean M

2014-01-01

Fluid therapy is perhaps the most common intervention received by acutely ill hospitalized patients; however, a number of critical questions on the efficacy and safety of the type and dose remain. In this review, recent insights derived from randomized trials in terms of fluid type, dose and toxicity are discussed. We contend that the prescription of fluid therapy is context-specific and that any fluid can be harmful if administered inappropriately. When contrasting ‘‘crystalloid vs colloid’’, differences in efficacy are modest but differences in safety are significant. Differences in chloride load and strong ion difference across solutions appear to be clinically important. Phases of fluid therapy in acutely ill patients are recognized, including acute resuscitation, maintaining homeostasis, and recovery phases. Quantitative toxicity (fluid overload) is associated with adverse outcomes and can be mitigated when fluid therapy based on functional hemodynamic parameters that predict volume responsiveness and minimization of non-essential fluid. Qualitative toxicity (fluid type), in particular for iatrogenic acute kidney injury and metabolic acidosis, remain a concern for synthetic colloids and isotonic saline, respectively. Physiologically balanced crystalloids may be the ‘‘default’’ fluid for acutely ill patients and the role for colloids, in particular hydroxyethyl starch, is increasingly unclear. We contend the prescription of fluid therapy is analogous to the prescription of any drug used in critically ill patients. PMID:24834399

Detecting Rotational Superradiance in Fluid Laboratories

NASA Astrophysics Data System (ADS)

Cardoso, Vitor; Coutant, Antonin; Richartz, Mauricio; Weinfurtner, Silke

2016-12-01

Rotational superradiance was predicted theoretically decades ago, and is chiefly responsible for a number of important effects and phenomenology in black-hole physics. However, rotational superradiance has never been observed experimentally. Here, with the aim of probing superradiance in the lab, we investigate the behavior of sound and surface waves in fluids resting in a circular basin at the center of which a rotating cylinder is placed. We show that with a suitable choice for the material of the cylinder, surface and sound waves are amplified. Two types of instabilities are studied: one sets in whenever superradiant modes are confined near the rotating cylinder and the other, which does not rely on confinement, corresponds to a local excitation of the cylinder. Our findings are experimentally testable in existing fluid laboratories and, hence, offer experimental exploration and comparison of dynamical instabilities arising from rapidly rotating boundary layers in astrophysical as well as in fluid dynamical systems.

Modeling viscous dissipation during vocal fold contact: the influence of tissue viscosity and thickness with implications for hydration.

PubMed

Erath, Byron D; Zañartu, Matías; Peterson, Sean D

2017-06-01

The mechanics of vocal fold contact during phonation is known to play a crucial role in both normal and pathological speech production, though the underlying physics is not well understood. Herein, a viscoelastic model of the stresses during vocal fold contact is developed. This model assumes the cover to be a poroelastic structure wherein interstitial fluid translocates in response to mechanical squeezing. The maximum interstitial fluid pressure is found to generally increase with decreasing viscous dissipation and/or decreasing tissue elasticity. A global minimum in the total contact stress, comprising interstitial fluid pressure and elastic stress in the tissue, is observed over the studied dimensionless parameter range. Interestingly, physiologically reasonable estimates for the governing parameters fall within this global minimum region. The model is validated against prior experimental and computational work, wherein the predicted contact stress magnitude and impact duration agree well with published results. Lastly, observations of the potential relationship between vocal fold hydration and increased risk of tissue damage are discussed based upon model predictions of stress as functions of cover layer thickness and viscosity.

Tracking the dynamics of divergent thinking via semantic distance: Analytic methods and theoretical implications.

PubMed

Hass, Richard W

2017-02-01

Divergent thinking has often been used as a proxy measure of creative thinking, but this practice lacks a foundation in modern cognitive psychological theory. This article addresses several issues with the classic divergent-thinking methodology and presents a new theoretical and methodological framework for cognitive divergent-thinking studies. A secondary analysis of a large dataset of divergent-thinking responses is presented. Latent semantic analysis was used to examine the potential changes in semantic distance between responses and the concept represented by the divergent-thinking prompt across successive response iterations. The results of linear growth modeling showed that although there is some linear increase in semantic distance across response iterations, participants high in fluid intelligence tended to give more distant initial responses than those with lower fluid intelligence. Additional analyses showed that the semantic distance of responses significantly predicted the average creativity rating given to the response, with significant variation in average levels of creativity across participants. Finally, semantic distance does not seem to be related to participants' choices of their own most creative responses. Implications for cognitive theories of creativity are discussed, along with the limitations of the methodology and directions for future research.

Modelling Time and Length Scales of Scour Around a Pipeline

NASA Astrophysics Data System (ADS)

Smith, H. D.; Foster, D. L.

2002-12-01

The scour and burial of submarine objects is an area of interest for engineers, oceanographers and military personnel. Given the limited availability of field observations, there exists a need to accurately describe the hydrodynamics and sediment response around an obstacle using numerical models. In this presentation, we will compare observations of submarine pipeline scour with model predictions. The research presented here uses the computational fluid dynamics (CFD) model FLOW-3D. FLOW-3D, developed by Flow Science in Santa Fe, NM, is a 3-dimensional finite-difference model that solves the Navier-Stokes and continuity equations. Using the Volume of Fluid (VOF) technique, FLOW-3D is able to resolve fluid-fluid and fluid-air interfaces. The FAVOR technique allows for complex geometry to be resolved with rectangular grids. FLOW-3D uses a bulk transport method to describe sediment transport and feedback to the hydrodynamic solver is accomplished by morphology evolution and fluid viscosity due to sediment suspension. Previous investigations by the authors have shown FLOW-3D to well-predict the hydrodynamics around five static scoured bed profiles and a stationary pipeline (``Modelling of Flow Around a Cylinder Over a Scoured Bed,'' submit to Journal of Waterway, Port, Coastal, and Ocean Engineering). Following experiments performed by Mao (1986, Dissertation, Technical University of Denmark), we will be performing model-data comparisons of length and time scales for scour around a pipeline. Preliminary investigations with LES and k-ɛ closure schemes have shown that the model predicts shorter time scales in scour hole development than that observed by Mao. Predicted time and length scales of scour hole development are shown to be a function of turbulence closure scheme, grain size, and hydrodynamic forcing. Subsequent investigations consider variable wave-current flow regimes and object burial. This investigation will allow us to identify different regimes for the scour process based on dimensionless parameters such as the Reynolds number, the Keulegan-Carpenter number, and the sediment mobility number. This research is sponsored by the Office of Naval Research - Mine Burial Program.

Uterine and systemic inflammation influences ovarian follicular function in postpartum dairy cows

PubMed Central

Sá Filho, Ocilon G.; Absalon-Medina, Victor A.; Schneider, Augusto; Butler, W. R.; Gilbert, Robert O.

2017-01-01

The objective of this study was to determine the effects of uterine and systemic inflammatory responses to uterine bacterial contamination at calving in dairy cows on the growth and ovulatory outcomes of the first dominant follicle postpartum. Ovulatory capability of the first dominant follicle postpartum was predicted in 53 multiparous cows by using a combination of follicle growth characteristics and circulating estradiol concentrations. Endotoxin levels were assayed in follicular fluid samples that were aspirated the day after ovulatory outcome prediction. Plasma levels of haptoglobin, a proinflammatory acute phase protein, and paraoxonase, a negative acute phase protein were determined. Uterine bacteria and inflammation were evaluated in three uterine fluid samples from each cow collected on the day of calving, the day after follicle aspiration, and at 35 days postpartum. Cows that had a strong initial uterine inflammatory response (robust recruitment of polymorphonuclear leukocytes of ≥ 35% and cows with uterine pH < 8.5 on the day of calving) were more likely to have an ovulatory first dominant follicle. Follicular fluid endotoxin levels were higher in non-ovulatory cows compared with ovulatory cows. Endotoxin levels in circulation were not different between ovulatory groups but were higher prepartum than on day 7 and 14 postpartum. Systemic inflammation characterized by elevated haptoglobin concentrations was higher in non-ovulatory cows despite similar bacterial contamination and circulating endotoxin levels. Paraoxonase activity in follicular fluid was significantly associated with the paraoxonase activity in plasma, however, plasma paraoxonase concentrations were not different between non-ovulatory and ovulatory cows. Cows with a higher uterine bacterial load on the day of calving had slower ovarian follicle growth. In summary, a robust uterine inflammatory response on the day of calving was positively associated with ovarian function while elevated systemic inflammation during the early postpartum period was negatively associated with the ovulatory status of the first dominant follicle postpartum. PMID:28542500

Thermodynamic Predictions vs. Measured Fluid Chemistry: Lessons from Low-Temperature, Serpentinizing Fluids

NASA Astrophysics Data System (ADS)

Leong, J. M.; Howells, A. H.; Robinson, K. J.; Shock, E. L.

2018-05-01

A combination of reaction-path, mixing, and sensitivity calculations was used to reconcile deviations between thermodynamic predictions and actual measurements of low-temperature serpentinizing fluid chemistry.

Role of bedside pancreatic scores and C-reactive protein in predicting pancreatic fluid collections and necrosis.

PubMed

Vinish, Doraiswami Babu; Abishek, Vishnu; Sujatha, K; Arulprakash, S; Solomon, Rajkumar; Ganesh, P

2017-01-01

Acute pancreatitis is a disease with variable outcome; the course of the disease can be modified by early aggressive management in patients with severe pancreatitis. Easily calculable pancreatic scores and investigations can help to triage these patients. We aimed to determine the role of bedside index for severity in acute pancreatitis (BISAP), harmless acute pancreatitis score (HAPS), and systemic inflammatory response syndrome (SIRS) scores on day of admission and C-reactive protein (CRP) at 48 h for predicting the presence of pancreatic fluid collection (PFC) and necrosis on CT scans done at 72 h. Of a total of 114 consecutively seen patients of pancreatitis, 64 with acute pancreatitis were enrolled in the study. All individuals had the pancreatitis predicting scores calculated at the time of admission, CRP at 48 h, and contrast-enhanced computed tomography (CECT) abdomen at 72 h from admission. The study population of 64 (55 male) had a mean (+SD) age of 37.7 ± 13 years. Alcohol was the most common (68.8%) etiology in these patients. Based on CECT, patients were divided into 2 groups; group 1 with 41 patients who had mild pancreatitis and group 2 with 23 patients who had pancreatic fluid collection with or without necrosis (PFCN). PFCN were seen in 19 (29.7%) of patients with 2 or more SIRS criteria, 17 (26.6%) of patients with BISAP score ≥3, and 16 patients (25.0%) with HAPS >0 respectively. All three scores were able to predict PFCN significantly. CRP >150 mg/L was noted in 23 patients and was able to predict the presence of fluid collections (p=0.0002) and pancreatic necrosis (p = 0.0004) on CT. BISAP, HAPS, and SIRS scores and CRP of 150 mg/L all correlated significantly with the occurrence of fluid collections and pancreatic necrosis on CT at 72 h. None of the scores was superior to the other in this respect.

Accidental release of chlorine in Chicago: Coupling of an exposure model with a Computational Fluid Dynamics model

NASA Astrophysics Data System (ADS)

Sanchez, E. Y.; Colman Lerner, J. E.; Porta, A.; Jacovkis, P. M.

2013-01-01

The adverse health effects of the release of hazardous substances into the atmosphere continue being a matter of concern, especially in densely populated urban regions. Emergency responders need to have estimates of these adverse health effects in the local population to aid planning, emergency response, and recovery efforts. For this purpose, models that predict the transport and dispersion of hazardous materials are as necessary as those that estimate the adverse health effects in the population. In this paper, we present the results obtained by coupling a Computational Fluid Dynamics model, FLACS (FLame ACceleration Simulator), with an exposure model, DDC (Damage Differential Coupling). This coupled model system is applied to a scenario of hypothetical release of chlorine with obstacles, such as buildings, and the results show how it is capable of predicting the atmospheric dispersion of hazardous chemicals, and the adverse health effects in the exposed population, to support decision makers both in charge of emergency planning and in charge of real-time response. The results obtained show how knowing the influence of obstacles in the trajectory of the toxic cloud and in the diffusion of the pollutants transported, and obtaining dynamic information of the potentially affected population and of associated symptoms, contribute to improve the planning of the protection and response measures.

Towards predicting coral calcification responses to ocean acidification: A combined modeling and experimental approach

NASA Astrophysics Data System (ADS)

Mollica, N. R.; Guo, W.; Cohen, A. L.; Foster, G. L.; Barkley, H.

2016-02-01

Experiments show that ocean acidification is detrimental to coral calcification. Nevertheless, coral sensitivities to OA vary and the mechanism(s) underlying these variable responses are not fully understood. One hypothesis is that ocean acidification affects the ability of coral's to regulate the pH of fluid at the site of calcification. We developed a numerical model of coral calcification that simulates corals' pH regulation based on physiochemical principles and predicts the rate of calcification [1]. Here we apply this model to Palauan corals, and seek to test the model's efficacy by comparing the predicted coral calcification responses with experimental measurements. Four coral cores were collected from two sites of different pH (7.84 and 8.04 respectively). Their bulk annual calcification rates, quantified from average density and extension rate measurements, vary from .83 to 1.39 g cm-2 year-1 for the low pH site and from 0.75 to 1.21 g cm-2 year-1for the high pH site. The higher bulk calcification rates observed in corals from the low pH site contrasts the expected general decrease in calcification in low pH seawater, and differs from our model prediction. We suspect this apparent discrepancy arises because fast-calcifying corals in low pH water are able to modulate the pH of fluid at the site of calcification. We test this hypothesis using boron isotope measurements from each coral. In addition, a more accurate measurement of instantaneous calcification, considering the number of corallites per measured area and the exact surface area of each polyp's 3-dimensional calcification site is applied. [1] Guo, W. (2014). AGU Fall Meeting, Abstract B41B-0033.

HANFORD DST THERMAL & SEISMIC PROJECT ANSYS BENCHMARK ANALYSIS OF SEISMIC INDUCED FLUID STRUCTURE INTERACTION IN A HANFORD DOUBLE SHELL PRIMARY TANK

DOE Office of Scientific and Technical Information (OSTI.GOV)

MACKEY, T.C.

M&D Professional Services, Inc. (M&D) is under subcontract to Pacific Northwest National Laboratories (PNNL) to perform seismic analysis of the Hanford Site Double-Shell Tanks (DSTs) in support of a project entitled ''Double-Shell Tank (DSV Integrity Project-DST Thermal and Seismic Analyses)''. The overall scope of the project is to complete an up-to-date comprehensive analysis of record of the DST System at Hanford in support of Tri-Party Agreement Milestone M-48-14. The work described herein was performed in support of the seismic analysis of the DSTs. The thermal and operating loads analysis of the DSTs is documented in Rinker et al. (2004). Themore » overall seismic analysis of the DSTs is being performed with the general-purpose finite element code ANSYS. The overall model used for the seismic analysis of the DSTs includes the DST structure, the contained waste, and the surrounding soil. The seismic analysis of the DSTs must address the fluid-structure interaction behavior and sloshing response of the primary tank and contained liquid. ANSYS has demonstrated capabilities for structural analysis, but the capabilities and limitations of ANSYS to perform fluid-structure interaction are less well understood. The purpose of this study is to demonstrate the capabilities and investigate the limitations of ANSYS for performing a fluid-structure interaction analysis of the primary tank and contained waste. To this end, the ANSYS solutions are benchmarked against theoretical solutions appearing in BNL 1995, when such theoretical solutions exist. When theoretical solutions were not available, comparisons were made to theoretical solutions of similar problems and to the results from Dytran simulations. The capabilities and limitations of the finite element code Dytran for performing a fluid-structure interaction analysis of the primary tank and contained waste were explored in a parallel investigation (Abatt 2006). In conjunction with the results of the global ANSYS analysis reported in Carpenter et al. (2006), the results of the two investigations will be compared to help determine if a more refined sub-model of the primary tank is necessary to capture the important fluid-structure interaction effects in the tank and if so, how to best utilize a refined sub-model of the primary tank. Both rigid tank and flexible tank configurations were analyzed with ANSYS. The response parameters of interest are total hydrodynamic reaction forces, impulsive and convective mode frequencies, waste pressures, and slosh heights. To a limited extent: tank stresses are also reported. The results of this study demonstrate that the ANSYS model has the capability to adequately predict global responses such as frequencies and overall reaction forces. Thus, the model is suitable for predicting the global response of the tank and contained waste. On the other hand, while the ANSYS model is capable of adequately predicting waste pressures and primary tank stresses in a large portion of the waste tank, the model does not accurately capture the convective behavior of the waste near the free surface, nor did the model give accurate predictions of slosh heights. Based on the ability of the ANSYS benchmark model to accurately predict frequencies and global reaction forces and on the results presented in Abatt, et al. (2006), the global ANSYS model described in Carpenter et al. (2006) is sufficient for the seismic evaluation of all tank components except for local areas of the primary tank. Due to the limitations of the ANSYS model in predicting the convective response of the waste, the evaluation of primary tank stresses near the waste free surface should be supplemented by results from an ANSYS sub-model of the primary tank that incorporates pressures from theoretical solutions or from Dytran solutions. However, the primary tank is expected to have low demand to capacity ratios in the upper wall. Moreover, due to the less than desired mesh resolution in the primary tank knuckle of the global ANSYS model, the evaluation of the primary tank stresses in the lower knuckle should be supplemented by results from a more refined ANSYS sub-model of the primary tank that incorporates pressures from theoretical solutions or from Dytran solutions.« less

Transport Phenomena of Water in Molecular Fluidic Channels

PubMed Central

Vo, Truong Quoc; Kim, BoHung

2016-01-01

In molecular-level fluidic transport, where the discrete characteristics of a molecular system are not negligible (in contrast to a continuum description), the response of the molecular water system might still be similar to the continuum description if the time and ensemble averages satisfy the ergodic hypothesis and the scale of the average is enough to recover the classical thermodynamic properties. However, even in such cases, the continuum description breaks down on the material interfaces. In short, molecular-level liquid flows exhibit substantially different physics from classical fluid transport theories because of (i) the interface/surface force field, (ii) thermal/velocity slip, (iii) the discreteness of fluid molecules at the interface and (iv) local viscosity. Therefore, in this study, we present the result of our investigations using molecular dynamics (MD) simulations with continuum-based energy equations and check the validity and limitations of the continuum hypothesis. Our study shows that when the continuum description is subjected to the proper treatment of the interface effects via modified boundary conditions, the so-called continuum-based modified-analytical solutions, they can adequately predict nanoscale fluid transport phenomena. The findings in this work have broad effects in overcoming current limitations in modeling/predicting the fluid behaviors of molecular fluidic devices. PMID:27650138

Clinical update on fluid therapy and nutritional support in acute pancreatitis.

PubMed

DiMagno, Matthew J

2015-01-01

The aim of this focused review is to provide a valuable and updated source of information for clinical practice on fluid therapy (FT) and nutritional support in acute pancreatitis (AP). The review encompasses important new clinical information that has become available for understanding and offering these specific treatments since the 2013 publication of two guidelines, both the joint International Association of Pancreatology and American Pancreatic Association and the American College of Gastroenterology. The 2015 Revised Japanese Guideline is discussed selectively. To this end, the review is divided into 7 sections, including timing and cause of mortality; severity classification systems; predicting severity; response to treatment; nutritional support; fluid therapy and steps for further research. In mild AP, begin oral feeding when nausea, vomiting and abdominal pain are improving. In (predicted) severe AP, feeding decisions should commence by 72 h, offering oral feeding if GI symptoms improve or enteral feeding if patients are symptomatic and/or intolerant to orals. All patients should be offered goal-directed FT during the first 6-12 h of presentation. Cautious FT is advised in those age >55 years or with preexisting organ failure or predictors of developing fluid sequestration. Copyright © 2015 IAP and EPC. Published by Elsevier India Pvt Ltd. All rights reserved.

Small Particle Response to Fluid Motion Using Tethered Particles to Simulate Microgravity

NASA Technical Reports Server (NTRS)

Trolinger, James; L'Esperance, Drew; Rangel, Roger; Coimbra, Carlos; Witherow, William K.; Rogers, Jan; Lal, Ravindra

2003-01-01

This paper reports on ground based work conducted to support the Spaceflight Definition project SHIVA (Spaceflight Holography Investigation in a Virtual Apparatus). SHIVA will advance our understanding of the movement of a particle in a fluid. Gravity usually dominates the equations of motion, but in microgravity as well as on earth other terms can become important. Through an innovative application of fractional differential equations, two members of our team produced the first analytical solution of a fundamental equation of motion, which had only been solved numerically or by approximation before. The general solution predicts that the usually neglected history term becomes important in particle response to a sinusoidal fluid movement when the characteristic viscous time is in the same order as the fluid oscillation period and peaks when the two times are equal. In this case three force terms, the Stokes drag, the added mass, and the history drag must all be included in predicting particle movement. We have developed diagnostic recording methods using holography to save all of the particle field data, allowing the experiment to essentially be transferred from space back to earth in what we call the virtual apparatus for on-earth microgravity experimentation. We can quantify precisely the three-dimensional motion of sets of particles, allowing us to test and apply the new analytical solutions. We are examining the response of particles up to 2 mm radius to fluid oscillation at frequencies up to 80 Hz with amplitudes up to 200 microns. Ground studies to support the flight development program have employed various schemes to simulate microgravity. One of the most reliable and meaningful methods uses spheres tethered to a fine hair suspended in the fluid. We have also investigated particles with nearly neutral buoyancy. Recordings are made at the peak amplitudes of vibration of the cell providing a measure of the ratio of fluid to particle amplitude. The experiment requires precise location of the particle to within microns during recording, and techniques for achieving this are one of the project challenges. Focused microscopic images and diffraction patterns are used. To make the experiment more versatile, the spaceflight system will record holograms both on film and electronically. A cross correlation procedure enables sub pixel accuracies for electronic recordings, partially accommodating the lower spatial resolution of CCDs. The electronic holograms can be down linked providing real time data. Results of the ground experiments, the flight experiment design, and data analysis procedures are reported.

Sound radiation from a water-filled pipe, radiation into light fluid.

PubMed

Liu, Bilong; Pan, Jie; Li, Xiaodong; Tian, Jing

2002-12-01

This paper is concerned with the sound radiation from a water-filled exhaust pipe. The pipe opening and a plate attached to it form a vibrating surface for this radiation. Fluid-structural coupling between the pipe and enclosed fluid is included in the system modeling, but light fluid assumption is used for sound radiation into the space above the vibrating surface. In this paper, a numerical study on the n = 0 mode in the pipe shows that the wave types associated with this mode have different characteristics in two regions of the nondimensional frequency omega. In the first region of 0

Particle sedimentation in a sheared viscoelastic fluid

NASA Astrophysics Data System (ADS)

Murch, William L.; Krishnan, Sreenath; Shaqfeh, Eric S. G.; Iaccarino, Gianluca

2017-11-01

Particle suspensions are ubiquitous in engineered processes, biological systems, and natural settings. For an engineering application - whether the intent is to suspend and transport particles (e.g., in hydraulic fracturing fluids) or allow particles to sediment (e.g., in industrial separations processes) - understanding and prediction of the particle mobility is critical. This task is often made challenging by the complex nature of the fluid phase, for example, due to fluid viscoelasticity. In this talk, we focus on a fully 3D flow problem in a viscoelastic fluid: a settling particle with a shear flow applied in the plane perpendicular to gravity (referred to as orthogonal shear). Previously, it has been shown that an orthogonal shear flow can reduce the settling rate of particles in viscoelastic fluids. Using experiments and numerical simulations across a wide range of sedimentation and shear Weissenberg number, this talk will address the underlying physical mechanism responsible for the additional drag experienced by a rigid sphere settling in a confined viscoelastic fluid with orthogonal shear. We will then explore multiple particle effects, and discuss the implications and extensions of this work for particle suspensions. This material is based upon work supported by the National Science Foundation Graduate Research Fellowship under Grant No. DGE-114747 (WLM).

From viscous to elastic sheets: Dynamics of smectic bubbles

NASA Astrophysics Data System (ADS)

Harth, Kirsten; Trittel, Torsten; van der Meer, Devaraj; Stannarius, Ralf

2015-11-01

Oscillations and rupture of bubbles composed of an inner fluid separated from an outer fluid by a membrane, represent an old but still immensely active field of research. Membrane properties apart from surface tension are often neglected for fluids (e.g. soap bubbles), whereas they govern the dynamics in systems with a rigid membrane (e.g. vesicles). Due to their layered phase structure, smectic liquid crystals can form stable, uniform and easy-to-handle fluid films of immense aspect ratios. Only recently, freely floating bubbles detached from a support could be prepared. We analyze their relaxation from strongly non-spherical shapes and the rupture using high-speed video recordings. Peculiar dynamics intermediate between simple viscous fluid films and an elastic response are observed: Fast oscillations, slowed relaxation and even the reversible formation of wrinkles and extrusions. Bubble rupture deviates qualitatively from previously observed behavior of simple Newtonian and other complex fluids. It becomes retarded by at least two orders of magnitude compared to the predictions of Taylor and Culick. A transition between fluid-like and elastic behavior is seen with increasing thickness. We give experimental results, an intuitive explanation and a novel hydrodynamic description.

Turbine Engine Hot Section Technology (HOST)

NASA Technical Reports Server (NTRS)

1982-01-01

Research and plans concerning aircraft gas turbine engine hot section durability problems were discussed. Under the topics of structural analysis, fatigue and fracture, surface protective coatings, combustion, turbine heat transfer, and instrumentation specific points addressed were the thermal and fluid environment around liners, blades, and vanes, material coatings, constitutive behavior, stress-strain response, and life prediction methods for the three components.

Prediction of Surface Ship Response to Severe Underwater Explosions Using a Virtual Underwater Shock Environment

DTIC Science & Technology

2003-06-01

output into LS-DYNA by using the following command: lsdyna keyword write The completed coupled fluid structure model is shown in Figure 110...be deleted to allow the model to be exported in LS-DYNA format. 3. LSDYNA KEYWORD WRITE: This exports the model in LS-DYNA keyword format. The

An evaluation and comparison of intraventricular, intraparenchymal, and fluid-coupled techniques for intracranial pressure monitoring in patients with severe traumatic brain injury.

PubMed

Vender, John; Waller, Jennifer; Dhandapani, Krishnan; McDonnell, Dennis

2011-08-01

Intracranial pressure measurements have become one of the mainstays of traumatic brain injury management. Various technologies exist to monitor intracranial pressure from a variety of locations. Transducers are usually placed to assess pressure in the brain parenchyma and the intra-ventricular fluid, which are the two most widely accepted compartmental monitoring sites. The individual reliability and inter-reliability of these devices with and without cerebrospinal fluid diversion is not clear. The predictive capability of monitors in both of these sites to local, regional, and global changes also needs further clarification. The technique of monitoring intraventricular pressure with a fluid-coupled transducer system is also reviewed. There has been little investigation into the relationship among pressure measurements obtained from these two sources using these three techniques. Eleven consecutive patients with severe, closed traumatic brain injury not requiring intracranial mass lesion evacuation were admitted into this prospective study. Each patient underwent placement of a parenchymal and intraventricular pressure monitor. The ventricular catheter tubing was also connected to a sensor for fluid-coupled measurement. Pressure from all three sources was measured hourly with and without ventricular drainage. Statistically significant correlation within each monitoring site was seen. No monitoring location was more predictive of global pressure changes or more responsive to pressure changes related to patient stimulation. However, the intraventricular pressure measurements were not reliable in the presence of cerebrospinal fluid drainage whereas the parenchymal measurements remained unaffected. Intraparenchymal pressure monitoring provides equivalent, statistically similar pressure measurements when compared to intraventricular monitors in all care and clinical settings. This is particularly valuable when uninterrupted cerebrospinal fluid drainage is desirable.

Thermoacoustic effects in supercritical fluids near the critical point: Resonance, piston effect, and acoustic emission and reflection

NASA Astrophysics Data System (ADS)

Onuki, Akira

2007-12-01

We present a general theory of thermoacoustic phenomena in one phase states of one-component fluids. Singular behavior is predicted in supercritical fluids near the critical point. In a one-dimensional geometry we start with linearized hydrodynamic equations taking into account the effects of heat conduction in the boundary walls and the bulk viscosity. We introduce a coefficient Z(ω) characterizing reflection of sound with frequency ω at the boundary in a rigid cell. As applications, we examine acoustic eigenmodes, response to time-dependent perturbations, and sound emission and reflection. Resonance and rapid adiabatic changes are noteworthy. In these processes, the role of the thermal diffusion layers is enhanced near the critical point because of the strong critical divergence of the thermal expansion.

Time-lapse 3-D seismic imaging of shallow subsurface contaminant flow.

PubMed

McKenna, J; Sherlock, D; Evans, B

2001-12-01

This paper presents a physical modelling study outlining a technique whereby buoyant contaminant flow within water-saturated unconsolidated sand was remotely monitored utilizing the time-lapse 3-D (TL3-D) seismic response. The controlled temperature and pressure conditions, along with the high level of acquisition repeatability attainable using sandbox physical models, allow the TL3-D seismic response to pore fluid movement to be distinguished from all other effects. TL3-D seismic techniques are currently being developed to monitor hydrocarbon reserves within producing reservoirs in an endeavour to improve overall recovery. However, in many ways, sandbox models under atmospheric conditions more accurately simulate the shallow subsurface than petroleum reservoirs. For this reason, perhaps the greatest application for analogue sandbox modelling is to improve our understanding of shallow groundwater and environmental flow mechanisms. Two fluid flow simulations were conducted whereby air and kerosene were injected into separate water-saturated unconsolidated sand models. In both experiments, a base 3-D seismic volume was recorded and compared with six later monitor surveys recorded while the injection program was conducted. Normal incidence amplitude and P-wave velocity information were extracted from the TL3-D seismic data to provide visualization of contaminant migration. Reflection amplitudes displayed qualitative areal distribution of fluids when a suitable impedance contrast existed between pore fluids. TL3-D seismic reflection tomography can potentially monitor the change in areal distribution of fluid contaminants over time, indicating flow patterns. However, other research and this current work have not established a quantifiable relationship between either normal reflection amplitudes and attenuation and fluid saturation. Generally, different pore fluids will have unique seismic velocities due to differences in compressibility and density. The predictable relationships that exist between P-wave velocity and fluid saturation can allow a quantitative assessment of contaminant migration.

Effects of resistivity and rotation on the linear plasma response to non-axisymmetric magnetic perturbations on DIII-D

DOE PAGES

Haskey, Shaun R.; Lanctot, Matthew J.; Liu, Y. Q.; ...

2015-01-05

Parameter scans show the strong dependence of the plasma response on the poloidal structure of the applied field highlighting the importance of being able to control this parameter using non-axisymmetric coil sets. An extensive examination of the linear single fluid plasma response to n = 3 magnetic perturbations in L-mode DIII-D lower single null plasmas is presented. The effects of plasma resistivity, toroidal rotation and applied field structure are calculated using the linear single fluid MHD code, MARS-F. Measures which separate the response into a pitch-resonant and resonant field amplification (RFA) component are used to demonstrate the extent to whichmore » resonant screening and RFA occurs. The ability to control the ratio of pitch-resonant fields to RFA by varying the phasing between upper and lower resonant magnetic perturbations coils sets is shown. The predicted magnetic probe outputs and displacement at the x-point are also calculated for comparison with experiments. Additionally, modelling of the linear plasma response using experimental toroidal rotation profiles and Spitzer like resistivity profiles are compared with results which provide experimental evidence of a direct link between the decay of the resonant screening response and the formation of a 3D boundary. As a result, good agreement is found during the initial application of the MP, however, later in the shot a sudden drop in the poloidal magnetic probe output occurs which is not captured in the linear single fluid modelling.« less

Controversies in pediatric anesthesia: sevoflurane and fluid management.

PubMed

Gueli, Sarah L; Lerman, Jerrold

2013-06-01

To explore the interrelationships among the pharmacokinetics of sevoflurane, epileptiform electroencephalographic (EEG) activity and awareness in children. To also describe the revised perioperative fluid management strategy espoused by Holliday and Segar and noninvasive measures that may predict who will respond positively to fluid loading. The depth of anesthesia during the early washin period with sevoflurane 8% is one-third less than during halothane. Eight percent sevoflurane rarely causes clinical seizures; more commonly, it causes epileptiform EEG activity that only weakly portends seizure activity. When preceded by nitrous oxide, midazolam or normocapnia, the risk of inducing epileptiform activity during spontaneous respiration is exceedingly small. Decreasing the inspired concentration of sevoflurane upon loss of the eyelash reflex to prevent epileptiform activity has not been shown to reduce the risk of clinical seizures, but more importantly, it may increase the risk of awareness if the child is stimulated. Isotonic intravenous solutions should be infused in volumes of 20-40 ml/kg over 2-4 h in children undergoing elective surgery. Postoperatively, these infusions may be continued at rates of 2/1/0.5 ml/kg/h; serum sodium concentration should be measured periodically. Noninvasive measures currently do not reliably identify those children who will respond positively to fluid boluses. Sevoflurane is a well tolerated induction agent that rarely causes seizures in children, but may cause awareness if the inspired concentration is prematurely reduced. Perioperative isotonic fluids should be infused at 20-40 ml/kg over 2-4 h during elective surgery. Noninvasive metrics do not predict a child's responsiveness to fluid loading.

Baseline neuropsychological profile and cognitive response to cerebrospinal fluid shunting for idiopathic normal pressure hydrocephalus.

PubMed

Thomas, George; McGirt, Matthew J; Woodworth, Graeme; Heidler, Jennifer; Rigamonti, Daniele; Hillis, Argye E; Williams, Michael A

2005-01-01

To evaluate neurocognitive changes and predict neurocognitive outcome after ventriculoperitoneal shunting for idiopathic normal pressure hydrocephalus (INPH). Reports of neurocognitive response to shunting have been variable and studies that predict cognitive outcomes after shunting are limited. We reviewed our experience with cognitive outcomes for INPH patients who were selected for shunting based on abnormal cerebrospinal fluid (CSF) pressure monitoring and positive response in any of the NPH symptoms following large volume CSF drainage. Forty-two INPH patients underwent neurocognitive testing and Folstein Mini-Mental State Examination (MMSE) prior to shunting. Neurocognitive testing or MMSEwere performed at least 3 months after shunt insertion. Significant improvement in a neurocognitive subtest was defined as improvement by one standard deviation (1 SD) for the patient's age, sex and education level. Significant improvement in overall neurocognitive outcome was defined as a 4-point improvement in MMSE or improvement by 1 SD in 50% of the administered neurocognitive subtests. Nonparametric tests were used to assess changes. Predictors of outcome were assessed via logistic regression analysis. Twenty-two patients (52.3%) showed overall neurocognitive improvement, and significant improvement was seen in tests of verbal memory and psychomotor speed. Predictive analysis showed that patients scoring more than 1 SD below mean at baseline on verbal memory immediate recall were fourfold less likely to show overall cognitive improvement, and sixfold less likely if also associated with visuoconstructional deficit or executive dysfunction. Verbal memory scores at baseline were higher in patients who showed overall cognitive improvement. Shunting INPH patients on the basis of CSF pressure monitoring and drainage response shows a significant rate of cognitive improvement, and baseline neurocognitive test scores may distinguish patients likely to respond to shunt surgery from those who will not. Copyright (c) 2005 S. Karger AG, Basel.

Prediction of ore fluid metal concentrations from solid solution concentrations in ore-stage calcite: Application to the Illinois-Kentucky and Central Tennessee Mississippi Valley-type districts

NASA Astrophysics Data System (ADS)

Smith-Schmitz, Sarah E.; Appold, Martin S.

2018-03-01

Knowledge of the concentrations of Zn and Pb in Mississippi Valley-type (MVT) ore fluids is fundamental to understanding MVT deposit origin. Most previous attempts to quantify the concentrations of Zn and Pb in MVT ore fluids have focused on the analysis of fluid inclusions. However, these attempts have yielded ambiguous results due to possible contamination from secondary fluid inclusions, interferences from Zn and Pb in the host mineral matrix, and uncertainties about whether the measured Zn and Pb signals represent aqueous solute or accidental solid inclusions entrained within the fluid inclusions. The purpose of the present study, therefore, was to try to determine Zn and Pb concentrations in MVT ore fluids using an alternate method that avoids these ambiguities by calculating Zn and Pb concentrations in MVT ore fluids theoretically based on their solid solution concentrations in calcite. This method was applied to the Illinois-Kentucky and Central Tennessee districts, which both contain ore-stage calcite. Experimental partition coefficient (D) values from Rimstidt et al. (1998) and Tsusue and Holland (1966), and theoretical thermodynamic distribution coefficient (KD) values were employed in the present study. Ore fluid concentrations of Zn were likely most accurately predicted by Rimstidt et al. (1998) D values, based on their success in predicting known fluid inclusion concentrations of Mg and Mn, and likely also most accurately predicted ore fluid concentrations of Fe. All four of these elements have a divalent ionic radius smaller than that of Ca2+ and form carbonate minerals with the calcite structure. For both the Illinois-Kentucky and the Central Tennessee district, predicted ore fluid Zn and Fe concentrations were on the order of up to 10's of ppm. Ore fluid concentrations of Pb could only be predicted using Rimstidt et al. (1998) D values. However, these concentrations are unlikely to be reliable, as predicted ore fluid concentrations of Sr and Ba, which like Pb also have a divalent ionic radius larger than that of Ca2+ and form carbonate minerals with the aragonite structure, did not consistently agree well with known concentrations of Sr and Ba in fluid inclusions. The ore fluid Zn concentrations predicted in the present study lie within the range of Zn concentrations typical of modern sedimentary brines and are high enough to allow deposition of the observed amounts of Zn in the Illinois-Kentucky and Central Tennessee districts within ranges of geologically reasonable times and ore fluid flow velocities. If the pH of the Illinois-Kentucky and Central pH ore fluids was as low as current evidence suggests to be possible, then these ore fluids could simultaneously have transported enough sulfide with their Zn to account for the observed amounts of sphalerite in the districts.

Aeroelastic Stability and Response of Rotating Structures

NASA Technical Reports Server (NTRS)

Keith, Theo G., Jr.; Reddy, Tondapu

2004-01-01

A summary of the work performed under NASA grant is presented. More details can be found in the cited references. This grant led to the development of relatively faster aeroelastic analysis methods for predicting flutter and forced response in fans, compressors, and turbines using computational fluid dynamic (CFD) methods. These methods are based on linearized two- and three-dimensional, unsteady, nonlinear aerodynamic equations. During the period of the grant, aeroelastic analysis that includes the effects of uncertainties in the design variables has also been developed.

High Performance Parallel Analysis of Coupled Problems for Aircraft Propulsion

NASA Technical Reports Server (NTRS)

Felippa, C. A.; Farhat, C.; Lanteri, S.; Maman, N.; Piperno, S.; Gumaste, U.

1994-01-01

In order to predict the dynamic response of a flexible structure in a fluid flow, the equations of motion of the structure and the fluid must be solved simultaneously. In this paper, we present several partitioned procedures for time-integrating this focus coupled problem and discuss their merits in terms of accuracy, stability, heterogeneous computing, I/O transfers, subcycling, and parallel processing. All theoretical results are derived for a one-dimensional piston model problem with a compressible flow, because the complete three-dimensional aeroelastic problem is difficult to analyze mathematically. However, the insight gained from the analysis of the coupled piston problem and the conclusions drawn from its numerical investigation are confirmed with the numerical simulation of the two-dimensional transient aeroelastic response of a flexible panel in a transonic nonlinear Euler flow regime.

The Esophagiome: concept, status, and future perspectives.

PubMed

Gregersen, Hans; Liao, Donghua; Brasseur, James G

2016-09-01

The term "Esophagiome" is meant to imply a holistic, multiscale treatment of esophageal function from cellular and muscle physiology to the mechanical responses that transport and mix fluid contents. The development and application of multiscale mathematical models of esophageal function are central to the Esophagiome concept. These model elements underlie the development of a "virtual esophagus" modeling framework to characterize and analyze function and disease by quantitatively contrasting normal and pathophysiological function. Functional models incorporate anatomical details with sensory-motor properties and functional responses, especially related to biomechanical functions, such as bolus transport and gastrointestinal fluid mixing. This brief review provides insight into Esophagiome research. Future advanced models can provide predictive evaluations of the therapeutic consequences of surgical and endoscopic treatments and will aim to facilitate clinical diagnostics and treatment. © 2016 New York Academy of Sciences.

Coral calcifying fluid pH dictates response to ocean acidification.

PubMed

Holcomb, M; Venn, A A; Tambutté, E; Tambutté, S; Allemand, D; Trotter, J; McCulloch, M

2014-06-06

Ocean acidification driven by rising levels of CO2 impairs calcification, threatening coral reef growth. Predicting how corals respond to CO2 requires a better understanding of how calcification is controlled. Here we show how spatial variations in the pH of the internal calcifying fluid (pHcf) in coral (Stylophora pistillata) colonies correlates with differential sensitivity of calcification to acidification. Coral apexes had the highest pHcf and experienced the smallest changes in pHcf in response to acidification. Lateral growth was associated with lower pHcf and greater changes with acidification. Calcification showed a pattern similar to pHcf, with lateral growth being more strongly affected by acidification than apical. Regulation of pHcf is therefore spatially variable within a coral and critical to determining the sensitivity of calcification to ocean acidification.

Gamma-oryzanol-loaded calcium pectinate microparticles reinforced with chitosan: optimization and release characteristics.

PubMed

Lee, Ji-Soo; Kim, Jong Soo; Lee, Hyeon Gyu

2009-05-01

Response surface methodology was used to optimize microparticle preparation conditions, including the ratio of pectin:gamma-oryzanol (OZ) (X(1)), agitation speed (X(2)), and the concentration of emulsifier (X(3)), for maximal entrapment efficiency (EE) of OZ-loaded Ca pectinate microparticles. The optimized values of X(1), X(2), and X(3) were found to be 2.72:5.28, 1143.5 rpm, and 2.61%, respectively. Experimental results obtained for the optimum formulation agreed favorably with the predicted results, indicating the usefulness of predicting models for EE. In order to evaluate the effect of chitosan-coating and blending on the release pattern of the entrapped OZ from microparticles, chitosan-coated and blended Ca pectinate microparticles were prepared. Release studies revealed that the chitosan treatments, especially the chitosan-coating, were effective in suppressing the release in both simulated gastric fluid (SGF) and intestinal fluid (SIF).

Age-related macular degeneration: using morphological predictors to modify current treatment protocols.

PubMed

Ashraf, Mohammed; Souka, Ahmed; Adelman, Ron A

2018-03-01

To assess predictors of treatment response in neovascular age-related macular degeneration (AMD) in an attempt to develop a patient-centric treatment algorithm. We conducted a systematic search using PubMed, EMBASE and Web of Science for prognostic indicators/predictive factors with the key words: 'age related macular degeneration', 'neovascular AMD', 'choroidal neovascular membrane (CNV)', 'anti-vascular endothelial growth factor (anti-VEGF)', 'aflibercept', 'ranibizumab', 'bevacizumab', 'randomized clinical trials', 'post-hoc', 'prognostic', 'predictive', 'response' 'injection frequency, 'treat and extend (TAE), 'pro re nata (PRN)', 'bi-monthly' and 'quarterly'. We only included studies that had an adequate period of follow-up (>1 year), a single predefined treatment regimen with a predetermined re-injection criteria, an adequate number of patients, specific morphological [optical coherence tomography (OCT)] criteria that predicted final visual outcomes and injection frequency and did not include switching from one drug to the other. We were able to identify seven prospective studies and 16 retrospective studies meeting our inclusion criteria. There are several morphological and demographic prognostic indicators that can predict response to therapy in wet AMD. Smaller CNV size, subretinal fluid (SRF), retinal angiomatous proliferation (RAP) and response to therapy at 12 weeks (visual, angiographic or OCT) can all predict good visual outcomes in patients receiving anti-VEGF therapy. Patients with larger CNV, older age, pigment epithelial detachment (PED), intraretinal cysts (IRC) and vitreomacular adhesion (VMA) achieved less visual gains. Patients having VMA/VMT required more intensive treatment with increased treatment frequency. Patients with both posterior vitreous detachment (PVD) and SRF require infrequent injections. Patients with PED are prone to recurrences of fluid activity with a reduction in visual acuity (VA). A regimen that involves less intensive therapy and extended follow-up intervals (4 weekly) can be suggested for patients who show adequate visual response and have both SRF and PVD at baseline. In addition, patients with poor prognostic indicators such as IRC, VMA, large CNV size, older age and poor response at 12 weeks should be extended very cautiously with the possibility of fixed monthly/bimonthly (every 2 months) treatments if they fail to achieve dryness. Patients with PED at baseline should receive monthly/bimonthly injections of anti-VEGF therapy or can be extended very cautiously (two weekly intervals) using a TAE protocol. © 2017 Acta Ophthalmologica Scandinavica Foundation. Published by John Wiley & Sons Ltd.

A design methodology of magentorheological fluid damper using Herschel-Bulkley model

NASA Astrophysics Data System (ADS)

Liao, Linqing; Liao, Changrong; Cao, Jianguo; Fu, L. J.

2003-09-01

Magnetorheological fluid (MR fluid) is highly concentrated suspension of very small magnetic particle in inorganic oil. The essential behavior of MR fluid is its ability to reversibly change from free-flowing, linear viscous liquids to semi-solids having controllable yield strength in milliseconds when exposed to magnetic field. This feature provides simple, quiet, rapid-response interfaces between electronic controls and mechanical systems. In this paper, a mini-bus MR fluid damper based on plate Poiseuille flow mode is typically analyzed using Herschel-Bulkley model, which can be used to account for post-yield shear thinning or thickening under the quasi-steady flow condition. In the light of various value of flow behavior index, the influences of post-yield shear thinning or thickening on flow velocity profiles of MR fluid in annular damping orifice are examined numerically. Analytical damping coefficient predictions also are compared via the nonlinear Bingham plastic model and Herschel-Bulkley constitutive model. A MR fluid damper, which is designed and fabricated according to design method presented in this paper, has tested by electro-hydraulic servo vibrator and its control system in National Center for Test and Supervision of Coach Quality. The experimental results reveal that the analysis methodology and design theory are reasonable and MR fluid damper can be designed according to the design methodology.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mukul M. Sharma; Steven L. Bryant; Carlos Torres-Verdin

The petrophysical properties of rocks, particularly their relative permeability and wettability, strongly influence the efficiency and the time-scale of all hydrocarbon recovery processes. However, the quantitative relationships needed to account for the influence of wettability and pore structure on multi-phase flow are not yet available, largely due to the complexity of the phenomena controlling wettability and the difficulty of characterizing rock properties at the relevant length scales. This project brings together several advanced technologies to characterize pore structure and wettability. Grain-scale models are developed that help to better interpret the electric and dielectric response of rocks. These studies allow themore » computation of realistic configurations of two immiscible fluids as a function of wettability and geologic characteristics. These fluid configurations form a basis for predicting and explaining macroscopic behavior, including the relationship between relative permeability, wettability and laboratory and wireline log measurements of NMR and dielectric response. Dielectric and NMR measurements have been made show that the response of the rocks depends on the wetting and flow properties of the rock. The theoretical models can be used for a better interpretation and inversion of standard well logs to obtain accurate and reliable estimates of fluid saturation and of their producibility. The ultimate benefit of this combined theoretical/empirical approach for reservoir characterization is that rather than reproducing the behavior of any particular sample or set of samples, it can explain and predict trends in behavior that can be applied at a range of length scales, including correlation with wireline logs, seismic, and geologic units and strata. This approach can substantially enhance wireline log interpretation for reservoir characterization and provide better descriptions, at several scales, of crucial reservoir flow properties that govern oil recovery.« less

Multiscale framework for predicting the coupling between deformation and fluid diffusion in porous rocks

DOE Office of Scientific and Technical Information (OSTI.GOV)

Andrade, José E; Rudnicki, John W

2012-12-14

In this project, a predictive multiscale framework will be developed to simulate the strong coupling between solid deformations and fluid diffusion in porous rocks. We intend to improve macroscale modeling by incorporating fundamental physical modeling at the microscale in a computationally efficient way. This is an essential step toward further developments in multiphysics modeling, linking hydraulic, thermal, chemical, and geomechanical processes. This research will focus on areas where severe deformations are observed, such as deformation bands, where classical phenomenology breaks down. Multiscale geometric complexities and key geomechanical and hydraulic attributes of deformation bands (e.g., grain sliding and crushing, and poremore » collapse, causing interstitial fluid expulsion under saturated conditions), can significantly affect the constitutive response of the skeleton and the intrinsic permeability. Discrete mechanics (DEM) and the lattice Boltzmann method (LBM) will be used to probe the microstructure---under the current state---to extract the evolution of macroscopic constitutive parameters and the permeability tensor. These evolving macroscopic constitutive parameters are then directly used in continuum scale predictions using the finite element method (FEM) accounting for the coupled solid deformation and fluid diffusion. A particularly valuable aspect of this research is the thorough quantitative verification and validation program at different scales. The multiscale homogenization framework will be validated using X-ray computed tomography and 3D digital image correlation in situ at the Advanced Photon Source in Argonne National Laboratories. Also, the hierarchical computations at the specimen level will be validated using the aforementioned techniques in samples of sandstone undergoing deformation bands.« less

Glassy dynamics in three-dimensional embryonic tissues

PubMed Central

Schötz, Eva-Maria; Lanio, Marcos; Talbot, Jared A.; Manning, M. Lisa

2013-01-01

Many biological tissues are viscoelastic, behaving as elastic solids on short timescales and fluids on long timescales. This collective mechanical behaviour enables and helps to guide pattern formation and tissue layering. Here, we investigate the mechanical properties of three-dimensional tissue explants from zebrafish embryos by analysing individual cell tracks and macroscopic mechanical response. We find that the cell dynamics inside the tissue exhibit features of supercooled fluids, including subdiffusive trajectories and signatures of caging behaviour. We develop a minimal, three-parameter mechanical model for these dynamics, which we calibrate using only information about cell tracks. This model generates predictions about the macroscopic bulk response of the tissue (with no fit parameters) that are verified experimentally, providing a strong validation of the model. The best-fit model parameters indicate that although the tissue is fluid-like, it is close to a glass transition, suggesting that small changes to single-cell parameters could generate a significant change in the viscoelastic properties of the tissue. These results provide a robust framework for quantifying and modelling mechanically driven pattern formation in tissues. PMID:24068179

Prediction of Body Fluids where Proteins are Secreted into Based on Protein Interaction Network

PubMed Central

Hu, Le-Le; Huang, Tao; Cai, Yu-Dong; Chou, Kuo-Chen

2011-01-01

Determining the body fluids where secreted proteins can be secreted into is important for protein function annotation and disease biomarker discovery. In this study, we developed a network-based method to predict which kind of body fluids human proteins can be secreted into. For a newly constructed benchmark dataset that consists of 529 human-secreted proteins, the prediction accuracy for the most possible body fluid location predicted by our method via the jackknife test was 79.02%, significantly higher than the success rate by a random guess (29.36%). The likelihood that the predicted body fluids of the first four orders contain all the true body fluids where the proteins can be secreted into is 62.94%. Our method was further demonstrated with two independent datasets: one contains 57 proteins that can be secreted into blood; while the other contains 61 proteins that can be secreted into plasma/serum and were possible biomarkers associated with various cancers. For the 57 proteins in first dataset, 55 were correctly predicted as blood-secrete proteins. For the 61 proteins in the second dataset, 58 were predicted to be most possible in plasma/serum. These encouraging results indicate that the network-based prediction method is quite promising. It is anticipated that the method will benefit the relevant areas for both basic research and drug development. PMID:21829572

Integrated Thermal Response Tool for Earth Entry Vehicles

NASA Technical Reports Server (NTRS)

Chen, Y.-K.; Milos, F. S.; Partridge, Harry (Technical Monitor)

2001-01-01

A system is presented for multi-dimensional, fully-coupled thermal response modeling of hypersonic entry vehicles. The system consists of a two-dimensional implicit thermal response, pyrolysis and ablation program (TITAN), a commercial finite-element thermal and mechanical analysis code (MARC), and a high fidelity Navier-Stokes equation solver (GIANTS). The simulations performed by this integrated system include hypersonic flow-field, fluid and solid interaction, ablation, shape change, pyrolysis gas generation and flow, and thermal response of heatshield and structure. The thermal response of the ablating and charring heatshield material is simulated using TITAN, and that of the underlying structural is simulated using MARC. The ablating heatshield is treated as an outer boundary condition of the structure, and continuity conditions of temperature and heat flux are imposed at the interface between TITAN and MARC. Aerothermal environments with fluid and solid interaction are predicted by coupling TITAN and GIANTS through surface energy balance equations. With this integrated system, the aerothermal environments for an entry vehicle and the thermal response of both the heatshield and the structure can be obtained simultaneously. Representative computations for a proposed blunt body earth entry vehicle are presented and discussed in detail.

Thermal Response Modeling System for a Mars Sample Return Vehicle

NASA Technical Reports Server (NTRS)

Chen, Y.-K.; Miles, Frank S.; Arnold, Jim (Technical Monitor)

2001-01-01

A multi-dimensional, coupled thermal response modeling system for analysis of hypersonic entry vehicles is presented. The system consists of a high fidelity Navier-Stokes equation solver (GIANTS), a two-dimensional implicit thermal response, pyrolysis and ablation program (TITAN), and a commercial finite-element thermal and mechanical analysis code (MARC). The simulations performed by this integrated system include hypersonic flowfield, fluid and solid interaction, ablation, shape change, pyrolysis gas eneration and flow, and thermal response of heatshield and structure. The thermal response of the heatshield is simulated using TITAN, and that of the underlying structural is simulated using MARC. The ablating heatshield is treated as an outer boundary condition of the structure, and continuity conditions of temperature and heat flux are imposed at the interface between TITAN and MARC. Aerothermal environments with fluid and solid interaction are predicted by coupling TITAN and GIANTS through surface energy balance equations. With this integrated system, the aerothermal environments for an entry vehicle and the thermal response of the entire vehicle can be obtained simultaneously. Representative computations for a flat-faced arc-jet test model and a proposed Mars sample return capsule are presented and discussed.

Thermal Response Modeling System for a Mars Sample Return Vehicle

NASA Technical Reports Server (NTRS)

Chen, Y.-K.; Milos, F. S.

2002-01-01

A multi-dimensional, coupled thermal response modeling system for analysis of hypersonic entry vehicles is presented. The system consists of a high fidelity Navier-Stokes equation solver (GIANTS), a two-dimensional implicit thermal response, pyrolysis and ablation program (TITAN), and a commercial finite element thermal and mechanical analysis code (MARC). The simulations performed by this integrated system include hypersonic flowfield, fluid and solid interaction, ablation, shape change, pyrolysis gas generation and flow, and thermal response of heatshield and structure. The thermal response of the heatshield is simulated using TITAN, and that of the underlying structural is simulated using MARC. The ablating heatshield is treated as an outer boundary condition of the structure, and continuity conditions of temperature and heat flux are imposed at the interface between TITAN and MARC. Aerothermal environments with fluid and solid interaction are predicted by coupling TITAN and GIANTS through surface energy balance equations. With this integrated system, the aerothermal environments for an entry vehicle and the thermal response of the entire vehicle can be obtained simultaneously. Representative computations for a flat-faced arc-jet test model and a proposed Mars sample return capsule are presented and discussed.

Flexibility Considerations on the Hydrodynamic Loading on a Vertical Wedge Drop

NASA Astrophysics Data System (ADS)

Ren, Zhongshu; Wang, Zhaoyuan; Judge, Carolyn; Stern, Fred; Ikeda, Christine

2017-11-01

High-speed craft operating at in waves frequently become airborne and slam into the water surface. This fluid-structure interaction problem is important to understand in order to increase the operating envelope of these craft. The goals of the current work are to investigate both the hydrodynamic loads and the resulting structural response on a planing hull. A V-shaped wedge is dropped vertically into calm water. The hydrodynamic pressure is measured using pressure sensors at discrete points on the hull. Two hulls are studied: one is rigid and one is flexible. Predictions of the hydrodynamic loading are made using Wagner's theory, Vorus's theory, and simulations in CFDShip Iowa. These predictions assume the structure is completely rigid. These predictions of the pressure coefficient match well with the rigid hull, as expected. The spray root is tracked in the rigid experimental set and compared with the theoretical and computational models. The pressure coefficient measured on the flexible hull shows discrepancies with the predictions due to the fluid-structure interaction. These discrepancies are quantified and interpreted in light of the structural flexibility. Funding for this work is from the Office of Naval Research Grant Number N00014-16-1-3188.

Serum Levels of Progranulin Do Not Reflect Cerebrospinal Fluid Levels in Neurodegenerative Disease.

PubMed

Wilke, Carlo; Gillardon, Frank; Deuschle, Christian; Dubois, Evelyn; Hobert, Markus A; Müller vom Hagen, Jennifer; Krüger, Stefanie; Biskup, Saskia; Blauwendraat, Cornelis; Hruscha, Michael; Kaeser, Stephan A; Heutink, Peter; Maetzler, Walter; Synofzik, Matthis

2016-01-01

Altered progranulin levels play a major role in neurodegenerative diseases, like Alzheimer's dementia (AD), frontotemporal dementia (FTD) and amyotrophic lateral sclerosis (ALS), even in the absence of GRN mutations. Increasing progranulin levels could hereby provide a novel treatment strategy. However, knowledge on progranulin regulation in neurodegenerative diseases remains limited. We here demonstrate that cerebrospinal fluid progranulin levels do not correlate with its serum levels in AD, FTD and ALS, indicating a differential regulation of its central and peripheral levels in neurodegeneration. Blood progranulin levels thus do not reliably predict central nervous progranulin levels and their response to future progranulin-increasing therapeutics.

Evaluation of space shuttle main engine fluid dynamic frequency response characteristics

NASA Technical Reports Server (NTRS)

Gardner, T. G.

1980-01-01

In order to determine the POGO stability characteristics of the space shuttle main engine liquid oxygen (LOX) system, the fluid dynamic frequency response functions between elements in the SSME LOX system was evaluated, both analytically and experimentally. For the experimental data evaluation, a software package was written for the Hewlett-Packard 5451C Fourier analyzer. The POGO analysis software is documented and consists of five separate segments. Each segment is stored on the 5451C disc as an individual program and performs its own unique function. Two separate data reduction methods, a signal calibration, coherence or pulser signal based frequency response function blanking, and automatic plotting features are included in the program. The 5451C allows variable parameter transfer from program to program. This feature is used to advantage and requires only minimal user interface during the data reduction process. Experimental results are included and compared with the analytical predictions in order to adjust the general model and arrive at a realistic simulation of the POGO characteristics.

Nanoscale viscoelasticity of extracellular matrix proteins in soft tissues: A multiscale approach.

PubMed

Miri, Amir K; Heris, Hossein K; Mongeau, Luc; Javid, Farhad

2014-02-01

It is hypothesized that the bulk viscoelasticity of soft tissues is determined by two length-scale-dependent mechanisms: the time-dependent response of the extracellular matrix (ECM) proteins at the nanometer scale and the biophysical interactions between the ECM solid structure and interstitial fluid at the micrometer scale. The latter is governed by poroelasticity theory assuming free motion of the interstitial fluid within the porous ECM structure. In a recent study (Heris, H.K., Miri, A.K., Tripathy, U., Barthelat, F., Mongeau, L., 2013. J. Mech. Behav. Biomed. Mater.), atomic force microscopy was used to measure the response of porcine vocal folds to a creep loading and a 50-nm sinusoidal oscillation. A constitutive model was calibrated and verified using a finite element model to accurately predict the nanoscale viscoelastic moduli of ECM. A generally good correlation was obtained between the predicted variation of the viscoelastic moduli with depth and that of hyaluronic acids in vocal fold tissue. We conclude that hyaluronic acids may regulate vocal fold viscoelasticity. The proposed methodology offers a characterization tool for biomaterials used in vocal fold augmentations. © 2013 Elsevier Ltd. All rights reserved.

Coping with treatment-related stress: effects on patient adherence in hemodialysis.

PubMed

Christensen, A J; Benotsch, E G; Wiebe, J S; Lawton, W J

1995-06-01

With a modified version of the Ways of Coping Checklist, the relation of coping to adherence among 57 hemodialysis patients was examined. The association of a particular type of coping to adherence was predicted to depend on the specific type of stressful encounter being considered. As predicted, coping efforts involving planful problem solving were associated with more favorable adherence when used in response to stressors involving a relatively controllable aspect of the hemodialysis context. For less controllable stressors, coping efforts involving emotional self-control were associated with more favorable adherence. The seeking of informational support in response to an uncontrollable encounter was associated with poorer fluid-intake adherence. Confrontive coping was associated with poorer adherence for both high- and low-control situations.

Drop formation, pinch-off dynamics and liquid transfer of simple and complex fluids

NASA Astrophysics Data System (ADS)

Dinic, Jelena; Sharma, Vivek

Liquid transfer and drop formation processes underlying jetting, spraying, coating, and printing - inkjet, screen, roller-coating, gravure, nanoimprint hot embossing, 3D - often involve formation of unstable columnar necks. Capillary-driven thinning of such necks and their pinchoff dynamics are determined by a complex interplay of inertial, viscous and capillary stresses for simple, Newtonian fluids. Micro-structural changes in response to extensional flow field that arises within the thinning neck give rise to additional viscoelastic stresses in complex, non- Newtonian fluids. Using FLOW-3D, we simulate flows realized in prototypical geometries (dripping and liquid bridge stretched between two parallel plates) used for studying pinch-off dynamics and influence of microstructure and viscoelasticity. In contrast with often-used 1D or 2D models, FLOW-3D allows a robust evaluation of the magnitude of the underlying stresses and extensional flow field (both uniformity and magnitude). We find that the simulated radius evolution profiles match the pinch-off dynamics that are experimentally-observed and theoretically-predicted for model Newtonian fluids and complex fluids.

Inner ear contribution to bone conduction hearing in the human.

PubMed

Stenfelt, Stefan

2015-11-01

Bone conduction (BC) hearing relies on sound vibration transmission in the skull bone. Several clinical findings indicate that in the human, the skull vibration of the inner ear dominates the response for BC sound. Two phenomena transform the vibrations of the skull surrounding the inner ear to an excitation of the basilar membrane, (1) inertia of the inner ear fluid and (2) compression and expansion of the inner ear space. The relative importance of these two contributors were investigated using an impedance lumped element model. By dividing the motion of the inner ear boundary in common and differential motion it was found that the common motion dominated at frequencies below 7 kHz but above this frequency differential motion was greatest. When these motions were used to excite the model it was found that for the normal ear, the fluid inertia response was up to 20 dB greater than the compression response. This changed in the pathological ear where, for example, otosclerosis of the stapes depressed the fluid inertia response and improved the compression response so that inner ear compression dominated BC hearing at frequencies above 400 Hz. The model was also able to predict experimental and clinical findings of BC sensitivity in the literature, for example the so called Carhart notch in otosclerosis, increased BC sensitivity in superior semicircular canal dehiscence, and altered BC sensitivity following a vestibular fenestration and RW atresia. Copyright © 2014 Elsevier B.V. All rights reserved.

Thermal and Fluid Modeling of the CRYogenic Orbital TEstbed (CRYOTE) Ground Test Article (GTA)

NASA Technical Reports Server (NTRS)

Piryk, David; Schallhorn, Paul; Walls, Laurie; Stopnitzky, Benny; Rhys, Noah; Wollen, Mark

2012-01-01

The purpose of this study was to anchor thermal and fluid system models to data acquired from a ground test article (GTA) for the CRYogenic Orbital TEstbed - CRYOTE. To accomplish this analysis, it was broken into four primary tasks. These included model development, pre-test predictions, testing support at Marshall Space Flight Center (MSFC} and post-test correlations. Information from MSFC facilitated the task of refining and correlating the initial models. The primary goal of the modeling/testing/correlating efforts was to characterize heat loads throughout the ground test article. Significant factors impacting the heat loads included radiative environments, multi-layer insulation (MLI) performance, tank fill levels, tank pressures, and even contact conductance coefficients. This paper demonstrates how analytical thermal/fluid networks were established, and it includes supporting rationale for specific thermal responses seen during testing.

Generating Inviscid and Viscous Fluid-Flow Simulations over an Aircraft Surface Using a Fluid-Flow Mesh

NASA Technical Reports Server (NTRS)

Rodriguez, David L. (Inventor); Sturdza, Peter (Inventor)

2013-01-01

Fluid-flow simulation over a computer-generated aircraft surface is generated using inviscid and viscous simulations. A fluid-flow mesh of fluid cells is obtained. At least one inviscid fluid property for the fluid cells is determined using an inviscid fluid simulation that does not simulate fluid viscous effects. A set of intersecting fluid cells that intersects the aircraft surface are identified. One surface mesh polygon of the surface mesh is identified for each intersecting fluid cell. A boundary-layer prediction point for each identified surface mesh polygon is determined. At least one boundary-layer fluid property for each boundary-layer prediction point is determined using the at least one inviscid fluid property of the corresponding intersecting fluid cell and a boundary-layer simulation that simulates fluid viscous effects. At least one updated fluid property for at least one fluid cell is determined using the at least one boundary-layer fluid property and the inviscid fluid simulation.

Fluid coupling in a discrete model of cochlear mechanics.

PubMed

Elliott, Stephen J; Lineton, Ben; Ni, Guangjian

2011-09-01

A discrete model of cochlear mechanics is introduced that includes a full, three-dimensional, description of fluid coupling. This formulation allows the fluid coupling and basilar membrane dynamics to be analyzed separately and then coupled together with a simple piece of linear algebra. The fluid coupling is initially analyzed using a wavenumber formulation and is separated into one component due to one-dimensional fluid coupling and one comprising all the other contributions. Using the theory of acoustic waves in a duct, however, these two components of the pressure can also be associated with a far field, due to the plane wave, and a near field, due to the evanescent, higher order, modes. The near field components are then seen as one of a number of sources of additional longitudinal coupling in the cochlea. The effects of non-uniformity and asymmetry in the fluid chamber areas can also be taken into account, to predict both the pressure difference between the chambers and the mean pressure. This allows the calculation, for example, of the effect of a short cochlear implant on the coupled response of the cochlea. © 2011 Acoustical Society of America

Magnetically Actuated Propellant Orientation Experiment, Controlling Fluid Motion With Magnetic Fields in a Low-Gravity Environment

NASA Technical Reports Server (NTRS)

Martin, J. J.; Holt, J. B.

2000-01-01

This report details the results of a series of fluid motion experiments to investigate the use of magnets to orient fluids in a low-gravity environment. The fluid of interest for this project was liquid oxygen (LO2) since it exhibits a paramagnetic behavior (is attracted to magnetic fields). However, due to safety and handling concerns, a water-based ferromagnetic mixture (produced by Ferrofluidics Corporation) was selected to simplify procedures. Three ferromagnetic fluid mixture strengths and a nonmagnetic water baseline were tested using three different initial fluid positions with respect to the magnet. Experiment accelerometer data were used with a modified computational fluid dynamics code termed CFX-4 (by AEA Technologies) to predict fluid motion. These predictions compared favorably with experiment video data, verifying the code's ability to predict fluid motion with and without magnetic influences. Additional predictions were generated for LO2 with the same test conditions and geometries used in the testing. Test hardware consisted of a cylindrical Plexiglas tank (6-in. bore with 10-in. length), a 6,000-G rare Earth magnet (10-in. ring), three-axis accelerometer package, and a video recorder system. All tests were conducted aboard the NASA Reduced-Gravity Workshop, a KC-135A aircraft.

Theoretical and experimental evaluation of the flow behavior of a magnetorheological damper using an extremely bimodal magnetic fluid

NASA Astrophysics Data System (ADS)

Iglesias, G. R.; Ahualli, S.; Echávarri Otero, J.; Fernández Ruiz-Morón, L.; Durán, J. D. G.

2014-08-01

The flow behavior of a magnetorheological (MR) fluid, consisting of iron particles dispersed in a ferrofluid carrier (‘MRFF’) in a commercial monotube MR shock absorber is studied. The magnetorheological properties of the MRFF suspensions are compared with those of a conventional oil-based MR fluid (‘MRF’). The mechanical behavior of the MR damper, filled with the MRFF or alternatively with the MRF, is characterized by means of different oscillatory force-displacement and force-velocity tests. The MR shock absorber has an internal electromagnet that generates a controlled magnetic field in the channels through which the MR suspensions flow under operation conditions. The results obtained indicate that the damper filled with MRFF shows a reliable and reproducible behavior. In particular, the response of the shock absorber can be controlled to a large extent by adjusting the electromagnetic current, showing a response that is independent of the mechanical and magnetic history of the MRFF. The non-linear hysteresis model proposed for predicting the damping force provides good agreement with the experimental results when the MRFF is employed. The improved response of the damper loaded with ferrofluid-based MRFF (instead of the conventional MRF) is explained considering the physical properties and the internal structure of the suspension.

Induced groundwater flux by increases in the aquifer's total stress.

PubMed

Chang, Ching-Min; Yeh, Hund-Der

2015-01-01

Fluid-filled granular soils experience changes in total stress because of earth and oceanic tides, earthquakes, erosion, sedimentation, and changes in atmospheric pressure. The pore volume may deform in response to the changes in stress and this may lead to changes in pore fluid pressure. The transient fluid flow can therefore be induced by the gradient in excess pressure in a fluid-saturated porous medium. This work demonstrates the use of stochastic methodology in prediction of induced one-dimensional field-scale groundwater flow through a heterogeneous aquifer. A closed-form of mean groundwater flux is developed to quantify the induced field-scale mean behavior of groundwater flow and analyze the impacts of the spatial correlation length scale of log hydraulic conductivity and the pore compressibility. The findings provided here could be useful for the rational planning and management of groundwater resources in aquifers that contain lenses with large vertical aquifer matrix compressibility values. © 2014, National Ground Water Association.

Interfacial profiles in fluid/liquid systems: a description based on the storing of elastic energy.

PubMed

Castellanos-Suárez, Aly J; Toro-Mendoza, Jhoan; García-Sucre, Máximo

2011-06-01

An analytical expression for the interfacial energy is found by solving a Poisson equation and assuming a Boltzmann distribution of volume elements forming the fluid/liquid system. Interfacial phenomena are treated as a result of the response of a liquid when it makes contact with other fluid phase, in order to reach thermal and mechanical equilibrium. This model gives a quantitative description of the interface, obtaining values for its molar, force and energy density profiles. Also, our model allows the determination of the proportion of the fluids present in the interfacial zone, the values of interfacial tension and thickness. In the case of water+n-alkanes systems, the tensions are in agreement with the behavior shown by the experimental data. Finally, the values for interfacial thickness predicted from molar density profiles are lower than the range of influence of the elastic energy and elastic field. Copyright © 2011 Elsevier Inc. All rights reserved.

Dynamic force response of spherical hydrostatic journal bearing for cryogenic applications

NASA Technical Reports Server (NTRS)

Sanandres, Luis

1994-01-01

Hydrostatic Journal Bearings (HJB's) are reliable and resilient fluid film rotor support elements ideal to replace roller bearings in cryogenic turbomachinery. HJB' will be used for primary space-power applications due to their long lifetime, low friction and wear, large load capacity, large direct stiffness, and damping force coefficients. An analysis for the performance characteristics of turbulent flow, orifice compensated, spherical hydrostatic journal bearings (HJB's) is presented. Spherical bearings allow tolerance for shaft misalignment without force performance degradation and have also the ability to support axial loads. The spherical HJB combines these advantages to provide a bearing design which could be used efficiently on high performance turbomachinery. The motion of a barotropic liquid on the thin film bearing lands is described by bulk-flow mass and momentum equations. These equations are solved numerically using an efficient CFD method. Numerical predictions of load capacity and force coefficients for a 6 recess, spherical HJB in a LO2 environment are presented. Fluid film axial forces and force coefficients of a magnitude about 20% of the radial load capacity are predicted for the case analyzed. Fluid inertia effects, advective and centrifugal, are found to affect greatly the static and dynamic force performance of the bearing studied.

Predictive models for pressure-driven fluid infusions into brain parenchyma

NASA Astrophysics Data System (ADS)

Raghavan, Raghu; Brady, Martin

2011-10-01

Direct infusions into brain parenchyma of biological therapeutics for serious brain diseases have been, and are being, considered. However, individual brains, as well as distinct cytoarchitectural regions within brains, vary in their response to fluid flow and pressure. Further, the tissue responds dynamically to these stimuli, requiring a nonlinear treatment of equations that would describe fluid flow and drug transport in brain. We here report in detail on an individual-specific model and a comparison of its prediction with simulations for living porcine brains. Two critical features we introduced into our model—absent from previous ones, but requirements for any useful simulation—are the infusion-induced interstitial expansion and the backflow. These are significant determinants of the flow. Another feature of our treatment is the use of cross-property relations to obtain individual-specific parameters that are coefficients in the equations. The quantitative results are at least encouraging, showing a high fraction of overlap between the computed and measured volumes of distribution of a tracer molecule and are potentially clinically useful. Several improvements are called for; principally a treatment of the interstitial expansion more fundamentally based on poroelasticity and a better delineation of the diffusion tensor of a particle confined to the interstitial spaces.

An EQT-cDFT approach to determine thermodynamic properties of confined fluids.

PubMed

Mashayak, S Y; Motevaselian, M H; Aluru, N R

2015-06-28

We present a continuum-based approach to predict the structure and thermodynamic properties of confined fluids at multiple length-scales, ranging from a few angstroms to macro-meters. The continuum approach is based on the empirical potential-based quasi-continuum theory (EQT) and classical density functional theory (cDFT). EQT is a simple and fast approach to predict inhomogeneous density and potential profiles of confined fluids. We use EQT potentials to construct a grand potential functional for cDFT. The EQT-cDFT-based grand potential can be used to predict various thermodynamic properties of confined fluids. In this work, we demonstrate the EQT-cDFT approach by simulating Lennard-Jones fluids, namely, methane and argon, confined inside slit-like channels of graphene. We show that the EQT-cDFT can accurately predict the structure and thermodynamic properties, such as density profiles, adsorption, local pressure tensor, surface tension, and solvation force, of confined fluids as compared to the molecular dynamics simulation results.

Ringin' the water bell: dynamic modes of curved fluid sheets

NASA Astrophysics Data System (ADS)

Kolinski, John; Aharoni, Hillel; Fineberg, Jay; Sharon, Eran

2015-11-01

A water bell is formed by fluid flowing in a thin, coherent sheet in the shape of a bell. Experimentally, a water bell is created via the impact of a cylindrical jet on a flat surface. Its shape is set by the splash angle (the separation angle) of the resulting cylindrically symmetric water sheet. The separation angle is altered by adjusting the height of a lip surrounding the impact point, as in a water sprinkler. We drive the lip's height sinusoidally, altering the separation angle, and ringin' the water bell. This forcing generates disturbances on the steady-state water bell that propagate forward and backward in the fluid's reference frame at well-defined velocities, and interact, resulting in the emergence of an interference pattern unique to each steady-state geometry. We analytically model these dynamics by linearizing the amplitude of the bell's response about the underlying curved geometry. This simple model predicts the nodal structure over a wide range of steady-state water bell configurations and driving frequencies. Due to the curved water bell geometry, the nodal structure is quite complex; nevertheless, the predicted nodal structure agrees extremely well with the experimental data. When we drive the bell beyond perturbative separation angles, the nodal locations surprisingly persist, despite the strikingly altered underlying water bell shape. At extreme driving amplitudes the water sheet assumes a rich variety of tortuous, non-convex shapes; nevertheless, the fluid sheet remains intact.

Stokes paradox in electronic Fermi liquids

NASA Astrophysics Data System (ADS)

Lucas, Andrew

2017-03-01

The Stokes paradox is the statement that in a viscous two-dimensional fluid, the "linear response" problem of fluid flow around an obstacle is ill posed. We present a simple consequence of this paradox in the hydrodynamic regime of a Fermi liquid of electrons in two-dimensional metals. Using hydrodynamics and kinetic theory, we estimate the contribution of a single cylindrical obstacle to the global electrical resistance of a material, within linear response. Momentum relaxation, present in any realistic electron liquid, resolves the classical paradox. Nonetheless, this paradox imprints itself in the resistance, which can be parametrically larger than predicted by Ohmic transport theory. We find a remarkably rich set of behaviors, depending on whether or not the quasiparticle dynamics in the Fermi liquid should be treated as diffusive, hydrodynamic, or ballistic on the length scale of the obstacle. We argue that all three types of behavior are observable in present day experiments.

The predictive value of external continuous lumbar drainage, with cerebrospinal fluid outflow controlled by medium pressure valve, in normal pressure hydrocephalus.

PubMed

Panagiotopoulos, V; Konstantinou, D; Kalogeropoulos, A; Maraziotis, T

2005-09-01

Although sporadic studies have described temporary external cerebrospinal fluid (CSF) lumbar drainage as a highly accurate test for predicting the outcome after ventricular shunting in normal pressure hydrocephalus (NPH) patients, a more recent study reports that the positive predictive value of external lumbar drainage (ELD) is high but the negative predictive value is deceptively low. Therefore, we conducted a prospective study in order to evaluate the predictive value of a continuous ELD, with CSF outflow controlled by medium pressure valve, in NPH patients. Twenty-seven patients with presumed NPH were admitted to our department and CSF drainage was carried out by a temporary (ELD) with CSF outflow controlled by a medium pressure valve for five days. All patients received a ventriculoperitoneal shunt using a medium pressure valve based upon preoperative clinical and radiographic criteria of NPH, regardless of ELD outcome. Clinical evaluation of gait disturbances, urinary incontinence and mental status, and radiological evaluation with brain CT was performed prior to and after ELD test, as well as three months after shunting. Twenty-two patients were finally shunted and included in this study. In a three-month follow-up, using a previously validated score system, overall improvement after permanent shunting correlated well to improvement after ELD test (Spearman's rho = 0.462, p = 0.03). When considering any degree of improvement as a positive response, ELD test yielded high positive predictive values for all individual parameters (gait disturbances 94%, 95% CI 71%-100%, urinary incontinence 100%, 95% CI 66%-100%, and mental status 100%, 95% CI 66%-100%) but negative predictive values were low (< 50%) except for cognitive impairment (85%, 95% CI 55%-98%). This study suggests that a positive ELD-valve system test should be considered a reliable criterion for preoperative selection of shunt-responsive NPH patients. In case of a negative ELD-valve system test, further investigation of the presumed NPH patients with additional tests should be performed.

[The assessment of ultrasonic measurement of superior vena cava blood flow for the volume responsiveness of patients with mechanical ventilation].

PubMed

Guo, Zhe; He, Wei; Hou, Jing; Li, Tong; Zhou, Hua; Xu, Yuan; Xi, Xiuming

2014-09-01

To approach the evaluative effect of respiratory variation of superior vena cava peak flow velocity measured using transthoracic echocardiography (TTE) on fluid responsiveness in patients with mechanical ventilation. A prospective cohort study was conducted. All mechanical ventilated critically ill patients whose fluid therapy was planned due to hypovolemia in Department of Critical Care Medicine of Beijing Tongren Hospital of Capital Medical University from April 2011 to April 2013 were enrolled. Volume expansion was performed with 500 mL Linger solution within 30 minutes. Patients were classified as responders if pulse pressure variation (PPV) increased ≥ 13% before volume expansion. The respiratory variation in superior vena cava peak velocity was calculated as the difference between maximum and minimum values of velocity in peak A, peak S and peak D over a single respiratory circle, and their variations (ΔA, ΔS, ΔD) were also calculated. The receiver operating characteristic curve (ROC curve) was plotted to assess the evaluative effect of respiratory variation of superior vena cava peak velocity on fluid responsiveness. Twenty-seven patients were enrolled in this study. Volume expansion increased PPV ≥ 13% happened in 14 patients (responders). The velocity of superior vena cava in peak A, peak S, peak D was significantly increased after volume expansion compared with that before volume expansion in responders [peak A (cm/s): 34.6 ± 2.2 vs. 31.3 ± 2.1, t=-2.493, P=0.027; peak S (cm/s): 39.1 ± 1.3 vs. 35.3 ± 2.1, t=-2.564, P=0.024; peak D (cm/s): 28.1 ± 1.2 vs. 23.3 ± 1.4, t=-4.995, P=0.000], but there was no significant difference in ΔA, ΔS and ΔD between before and after volume expansion. The ΔA, ΔS and ΔD were positively correlated with PPV (r=0.040, P=0.854; r=0.350, P=0.074; r=0.749, P=0.000). The area under ROC curve (AUC) of peak S was 0.36 [95% confidence interval (95%CI): 0.11-0.52], but the AUC of ΔS was 0.68 (95%CI 0.47-0.89), the AUC of peak D was 0.41 (95%CI 0.19-0.63), but the AUC of ΔD was 0.95 (95%CI 0.86-1.00), so the aberration rate of superior vena cava in respiration was better than the flow rate in superior vena cava. When the cut-off value of ΔS was 20.7% for predicting fluid responsiveness, the sensitivity was 78.6% and the specificity was 61.5%. When the cut-off value of ΔD was 12.7% for predicting fluid responsiveness, the sensitivity was 92.0% and the specificity was 92.3%. Respiratory variations in superior vena cava peak velocity measured by TTE could assess fluid responsiveness in patients with mechanical ventilation.

The Maternal Serological Response to Intrauterine Ureaplasma sp. Infection and Prediction of Risk of Pre-Term Birth

PubMed Central

Ireland, Demelza J.; Keelan, Jeffrey A.

2014-01-01

Pre-term birth (PTB) associated with intrauterine infection and inflammation (IUI) is the major cause of early PTB less than 32 weeks of gestation. Ureaplasma spp. are common commensals of the urogenital tract in pregnancy and are the most commonly identified microorganisms in amniotic fluid of pre-term pregnancies. While we have an understanding of the causal relationship between intra-amniotic infection, inflammation and PTB, we are still unable to explain why vaginal Ureaplasma sp. colonization is tolerated in some women but causes PTB in others. It is now known that placental tissues are frequently colonized by bacteria even in apparently healthy pregnancies delivered at term; usually this occurs in the absence of a significant local inflammatory response. It appears, therefore, that the site, nature, and magnitude of the immune response to infiltrating microorganisms are key in determining pregnancy outcome. Some evidence exists that the maternal serological response to Ureaplasma sp. colonization may be predictive of adverse pregnancy outcome, although issues such as the importance of virulence factors (serovars) and the timing, magnitude, and functional consequences of the immune response await clarification. This mini-review discusses the evidence linking the maternal immune response to risk of PTB and the potential applications of maternal serological analysis for predicting obstetric outcome. PMID:25538708

Neurocognitive Predictions of Performance.

DTIC Science & Technology

1987-09-25

feedback (see Section 1V.A). Many of these results, along with pilot analyses of intracerebral recordings using a. primate model, cannot be explained by...are subject to considerable distortion by the intervening media of cerebrum, cerebro -spinal fluid, skull, and scalp. The result is a smeaxing or...parietal component is consistent with evidence from primates and humans for neuronal firing in motor and somatost.nsory cortices prior to motor responses

The effect of dilatancy on the unloading behavior of Mt. Helen tuff

DOE Office of Scientific and Technical Information (OSTI.GOV)

Attia, A.V.; Rubin, M.B.

1993-11-01

In order to understand the role of rock dilatancy in modeling the response of partially saturated rock formations to underground nuclear explosions, we have developed a thermodynamically consistent model for a porous material, partially saturated with fluid. This model gives good predictions of the unloading behavior of dry, partially saturated, and fully saturated Mt. Helen tuff, as measured by Heard.

Direct differentiation of the quasi-incompressible fluid formulation of fluid-structure interaction using the PFEM

NASA Astrophysics Data System (ADS)

Zhu, Minjie; Scott, Michael H.

2017-07-01

Accurate and efficient response sensitivities for fluid-structure interaction (FSI) simulations are important for assessing the uncertain response of coastal and off-shore structures to hydrodynamic loading. To compute gradients efficiently via the direct differentiation method (DDM) for the fully incompressible fluid formulation, approximations of the sensitivity equations are necessary, leading to inaccuracies of the computed gradients when the geometry of the fluid mesh changes rapidly between successive time steps or the fluid viscosity is nonzero. To maintain accuracy of the sensitivity computations, a quasi-incompressible fluid is assumed for the response analysis of FSI using the particle finite element method and DDM is applied to this formulation, resulting in linearized equations for the response sensitivity that are consistent with those used to compute the response. Both the response and the response sensitivity can be solved using the same unified fractional step method. FSI simulations show that although the response using the quasi-incompressible and incompressible fluid formulations is similar, only the quasi-incompressible approach gives accurate response sensitivity for viscous, turbulent flows regardless of time step size.

Fault reactivation by fluid injection considering permeability evolution in fault-bordering damage zones

NASA Astrophysics Data System (ADS)

Yang, Z.; Yehya, A.; Rice, J. R.; Yin, J.

2017-12-01

Earthquakes can be induced by human activity involving fluid injection, e.g., as wastewater disposal from hydrocarbon production. The occurrence of such events is thought to be, mainly, due to the increase in pore pressure, which reduces the effective normal stress and hence the strength of a nearby fault. Change in subsurface stress around suitably oriented faults at near-critical stress states may also contribute. We focus on improving the modeling and prediction of the hydro-mechanical response due to fluid injection, considering the full poroelastic effects and not solely changes in pore pressure in a rigid host. Thus we address the changes in porosity and permeability of the medium due to the changes in the local volumetric strains. Our results also focus on including effects of the fault architecture (low permeability fault core and higher permeability bordering damage zones) on the pressure diffusion and the fault poroelastic response. Field studies of faults have provided a generally common description for the size of their bordering damage zones and how they evolve along their direction of propagation. Empirical laws, from a large number of such observations, describe their fracture density, width, permeability, etc. We use those laws and related data to construct our study cases. We show that the existence of high permeability damage zones facilitates pore-pressure diffusion and, in some cases, results in a sharp increase in pore-pressure at levels much deeper than the injection wells, because these regions act as conduits for fluid pressure changes. This eventually results in higher seismicity rates. By better understanding the mechanisms of nucleation of injection-induced seismicity, and better predicting the hydro-mechanical response of faults, we can assess methodologies and injection strategies to avoid risks of high magnitude seismic events. Microseismic events occurring after the start of injection are very important indications of when injection should be stopped and how to avoid major events. Our work contributes to the assessment or mitigation of seismic hazard and risk, and our long-term target question is: How to not make an earthquake?

Improvement of Varioptic's liquid lens based on electrowetting: how to obtain a short response time and its application in the design of a high resolution iris biometric system

NASA Astrophysics Data System (ADS)

Burger, Benjamin; Meimon, Serge C.; Petit, Cyril; Nguyen, Minh Chau

2015-02-01

This communication presents the results obtained for decreasing the response time of electrowetting-based real time focus correctors (liquid lenses). In order to provide a compact iris biometric system demonstrator, we have achieved a response time at 90% of 7.5 ms for a change in focalization from 0 diopter to 10 diopter with a liquid lens having an aperture of 1.9 mm. We have used a hydrodynamic fluid reorganization model to predict the features of these fast liquid lenses and evaluated the sensivity of the response time to the different conception parameters.

Non-Darcian flow of shear-thinning fluids through packed beads: Experiments and predictions using Forchheimer's law and Ergun's equation

NASA Astrophysics Data System (ADS)

Rodríguez de Castro, Antonio; Radilla, Giovanni

2017-02-01

The flow of shear-thinning fluids through unconsolidated porous media is present in a number of important industrial applications such as soil depollution, Enhanced Oil Recovery or filtration of polymeric liquids. Therefore, predicting the pressure drop-flow rate relationship in model porous media has been the scope of major research efforts during the last decades. Although the flow of Newtonian fluids through packs of spherical particles is well understood in most cases, much less is known regarding the flow of shear-thinning fluids as high molecular weight polymer aqueous solutions. In particular, the experimental data for the non-Darcian flow of shear-thinning fluids are scarce and so are the current approaches for their prediction. Given the relevance of non-Darcian shear-thinning flow, the scope of this work is to perform an experimental study to systematically evaluate the effects of fluid shear rheology on the flow rate-pressure drop relationships for the non-Darcian flow through different packs of glass spheres. To do so, xanthan gum aqueous solutions with different polymer concentrations are injected through four packs of glass spheres with uniform size under Darcian and inertial flow regimes. A total of 1560 experimental data are then compared with predictions coming from different methods based on the extension of widely used Ergun's equation and Forchheimer's law to the case of shear thinning fluids, determining the accuracy of these predictions. The use of a proper definition for Reynolds number and a realistic model to represent the rheology of the injected fluids results in the porous media are shown to be key aspects to successfully predict pressure drop-flow rate relationships for the inertial shear-thinning flow in packed beads.

Simulated digestion for testing the stability of edible vaccine based on Cucumber mosaic virus (CMV) chimeric particle display Hepatitis C virus (HCV) peptide.

PubMed

Vitti, Antonella; Nuzzaci, Maria; Condelli, Valentina; Piazzolla, Pasquale

2014-01-01

Edible vaccines must survive digestive process and preserve the specific structure of the antigenic peptide to elicit effective immune response. The stability of a protein to digestive process can be predicted by subjecting it to the in vitro assay with simulated gastric fluid (SGF) and simulated intestinal fluid (SIF). Here, we describe the protocol of producing and using chimeric Cucumber mosaic virus (CMV) displaying Hepatitis C virus (HCV) derived peptide (R9) in double copy as an oral vaccine. Its stability after treatment with SGF and SIF and the preservation of the antigenic properties were verified by SDS-PAGE and immuno western blot techniques.

Progress report on LBL's numerical modeling studies on Cerro Prieto

DOE Office of Scientific and Technical Information (OSTI.GOV)

Halfman-Dooley, S.E.; Lippman, M.J.; Bodvarsson, G.S.

1989-04-01

An exploitation model of the Cerro Prieto geothermal system is needed to assess the energy capacity of the field, estimate its productive lifetime and develop an optimal reservoir management plan. The model must consider the natural state (i.e., pre-exploitation) conditions of the system and be able to predict changes in the reservoir thermodynamic conditions (and fluid chemistry) in response to fluid production (and injection). This paper discusses the results of a three-dimensional numerical simulation of the natural state conditions of the Cerro Prieto field and compares computed and observed pressure and temperature/enthalpy changes for the 1973--1987 production period. 16 refs.,more » 24 figs., 2 tabs.« less

Prediction of Time Response of Electrowetting

NASA Astrophysics Data System (ADS)

Lee, Seung Jun; Hong, Jiwoo; Kang, Kwan Hyoung

2009-11-01

It is very important to predict the time response of electrowetting-based devices, such as liquid lenses, reflective displays, and optical switches. We investigated the time response of electrowetting, based on an analytical and a numerical method, to find out characteristic scales and a scaling law for the switching time. For this, spreading process of a sessile droplet was analyzed based on the domain perturbation method. First, we considered the case of weakly viscous fluids. The analytical result for the spreading process was compared with experimental results, which showed very good agreement in overall time response. It was shown that the overall dynamics is governed by P2 shape mode. We derived characteristic scales combining the droplet volume, density, and surface tension. The overall dynamic process was scaled quite well by the scales. A scaling law was derived from the analytical solution and was verified experimentally. We also suggest a scaling law for highly viscous liquids, based on results of numerical analysis for the electrowetting-actuated spreading process.

Analytical modeling for heat transfer in sheared flows of nanofluids.

PubMed

Ferrari, Claudio; Kaoui, Badr; L'vov, Victor S; Procaccia, Itamar; Rudenko, Oleksii; ten Thije Boonkkamp, J H M; Toschi, Federico

2012-07-01

We developed a model for the enhancement of the heat flux by spherical and elongated nanoparticles in sheared laminar flows of nanofluids. Besides the heat flux carried by the nanoparticles, the model accounts for the contribution of their rotation to the heat flux inside and outside the particles. The rotation of the nanoparticles has a twofold effect: it induces a fluid advection around the particle and it strongly influences the statistical distribution of particle orientations. These dynamical effects, which were not included in existing thermal models, are responsible for changing the thermal properties of flowing fluids as compared to quiescent fluids. The proposed model is strongly supported by extensive numerical simulations, demonstrating a potential increase of the heat flux far beyond the Maxwell-Garnett limit for the spherical nanoparticles. The road ahead, which should lead toward robust predictive models of heat flux enhancement, is discussed.

Acute toxicity of two generic drilling fluids and six additives, alone and combined, to mysids (Mysidopsis bahia)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Parrish, P.R.; Macauley, J.M.; Montgomery, R.M.

1988-01-01

Toxicity tests were conducted with two laboratory-prepared generic drilling fluids (muds) and six commonly used drilling-fluid additives to determine their toxicity, alone and combined, to mysids (Mysidopsis bahia). In 25 tests, the acute toxicity of combinations of one, two, or three of the drilling-fluid additives mixed with either drilling fluid was less than the toxicity predicted from the empirical 96-h LC50s for drilling fluid additive(s) and/or drilling fluid alone; the observed 96-h LC50s of the mixtures were from 1.3 to 23.6 times the values predicted from the presumption of additive toxicity.

Predicting optimal response to B-cell depletion with rituximab in multiple sclerosis using CXCL13 index, magnetic resonance imaging and clinical measures

PubMed Central

Alvarez, Enrique; Piccio, Laura; Mikesell, Robert J; Trinkaus, Kathryn; Parks, Becky J; Naismith, Robert T

2015-01-01

Background B-cell depleting drugs show promise for treating multiple sclerosis. Objective We sought predictors of optimal response to rituximab, a B-cell depleting antibody, to help guide therapy selection. Methods We performed a post hoc study of 30 relapsing multiple sclerosis patients with breakthrough disease while on beta-interferon or glatiramer acetate who were treated with add-on rituximab. Standardized neurologic examinations, brain magnetic resonance imaging, and cerebrospinal fluid were obtained before and after rituximab. Tissue biomarkers were measured. Optimal responders were defined as having no evidence of disease activity. Results At baseline, optimal responders with no evidence of disease activity had higher IgG indices (P = 0.041), and higher CXCL13 indices ((cerebrospinal fluid CXCL13/serum CXCL13)/albumin index; P = 0.024), more contrast enhancing lesions (P = 0.002), better 25 foot timed walk (P = 0.001), and Expanded Disability Status Scale (P = 0.002). Rituximab treatment led to reduced cerebrospinal fluid biomarkers of tissue destruction: myelin basic protein (P = 0.046), neurofilament light chain (P < 0.001), and of inflammation (CXCL13 index; P = 0.042). Conclusions Multiple sclerosis patients with optimal response to rituximab had higher cerebrospinal fluid IgG and CXCL13 indices, more gadolinium-enhancing lesions, and less disability at baseline. Rituximab treatment led to decreased markers of inflammation and tissue damage. If validated, these results will help identify multiple sclerosis patients who will respond optimally to B-cell depletion. PMID:28607711

Anisotropy and probe-medium interactions in the microrheology of nematic fluids.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cordoba, Andres; Stieger, Tillmann; Mazza, Marco G.

2016-01-01

A theoretical formalism is presented to analyze and interpret microrheology experiments in anisotropic fluids with nematic order. The predictions of that approach are examined in the context of a simple coarse-grained molecular model which is simulated using nonequilibrium molecular dynamics calculations. The proposed formalism is used to study the effect of confinement, the type of anchoring at the probe-particle surface, and the strength of the nematic field on the rheological response functions obtained from probe-particle active microrheology. As expected, a stronger nematic field leads to increased anisotropy in the rheological response of the material. It is also found that themore » defect structures that arise around the probe particle, which are determined by the type of anchoring and the particle size, have a significant effect on the rheological response observed in microrheology simulations. Independent estimates of the bulk dynamic modulus of the model nematic fluid considered here are obtained from small-amplitude oscillatory shear simulations with Lees Edwards boundary conditions. The results of simulations indicate that the dynamic modulus extracted from particle-probe microrheology is different from that obtained in the absence of the particle, but that the differences decrease as the size of the defect also decreases. Importantly, the results of the nematic microrheology theory proposed here are in much closer agreement with simulations than those from earlier formalisms conceived for isotropic fluids. As such, it is anticipated that the theoretical framework advanced in this study could provide a useful tool for interpretation of microrheology experiments in systems such as liquid crystals and confined macromolecular solutions or gels.« less

Review of a fluid resuscitation protocol: "fluid creep" is not due to nursing error.

PubMed

Faraklas, Iris; Cochran, Amalia; Saffle, Jeffrey

2012-01-01

Recent reviews of burn resuscitation have included the suggestion that "fluid creep" may be influenced by practitioner error. Our center uses a nursing-driven resuscitation protocol that permits titration of fluid based on hourly urine output, including the addition of colloid when patients fail to respond appropriately. The purpose of this study was to examine protocol compliance. We reviewed 140 patients (26 children) with burns of ≥20% TBSA who received protocol-directed resuscitation from 2005 to 2010. We compared each patient's actual hourly fluid infusion with that predicted by the protocol. Sixty-seven patients (48%) completed resuscitation using crystalloid alone, whereas 73 patients required colloid supplementation. Groups did not differ in age, gender, weight, or time from injury to admission. Patients requiring colloid had larger median total burns (33.0 vs 23.5% TBSA) and full-thickness burns (15.5 vs 4.5% TBSA) and more inhalation injuries (60.3 vs 28.4%; P < .001) than those who resuscitated with crystalloid alone. Because we included basic maintenance fluids in their regimen, patients had median predicted requirements of 5.4 ml/kg/%TBSA. Crystalloid-only patients required fluid volumes close to Parkland predictions (4.7 ml/kg/%TBSA), whereas patients who received colloid required more fluid than the predicted volume (7.5 ml/kg/%TBSA). However, the hourly difference between the predicted and received fluids was a median of only 1.0% (interquartile range: -6.1 to 11.1%) and did not differ between groups. Pediatric patients had greater calculated differences than adults. Crystalloid patients exhibited higher urine outputs than colloid patients until colloid was started, suggesting that early over-resuscitation did not contribute to fluid creep. Adherence to our protocol for burn shock resuscitation was excellent overall. Fluid creep exhibited by more seriously injured patients was not due to nurses' failure to follow the protocol. This review has illuminated some opportunities for practice improvement, possibly using a computerized decision support system.

Ideal glass transitions in thin films: An energy landscape perspective

NASA Astrophysics Data System (ADS)

Truskett, Thomas M.; Ganesan, Venkat

2003-07-01

We introduce a mean-field model for the potential energy landscape of a thin fluid film confined between parallel substrates. The model predicts how the number of accessible basins on the energy landscape and, consequently, the film's ideal glass transition temperature depend on bulk pressure, film thickness, and the strength of the fluid-fluid and fluid-substrate interactions. The predictions are in qualitative agreement with the experimental trends for the kinetic glass transition temperature of thin films, suggesting the utility of landscape-based approaches for studying the behavior of confined fluids.

Tendon exhibits complex poroelastic behavior at the nanoscale as revealed by high-frequency AFM-based rheology.

PubMed

Connizzo, Brianne K; Grodzinsky, Alan J

2017-03-21

Tendons transmit load from muscle to bone by utilizing their unique static and viscoelastic tensile properties. These properties are highly dependent on the composition and structure of the tissue matrix, including the collagen I hierarchy, proteoglycans, and water. While the role of matrix constituents in the tensile response has been studied, their role in compression, particularly in matrix pressurization via regulation of fluid flow, is not well understood. Injured or diseased tendons and tendon regions that naturally experience compression are known to have alterations in glycosaminoglycan content, which could modulate fluid flow and ultimately mechanical function. While recent theoretical studies have predicted tendon mechanics using poroelastic theory, no experimental data have directly demonstrated such behavior. In this study, we use high-bandwidth AFM-based rheology to determine the dynamic response of tendons to compressive loading at the nanoscale and to determine the presence of poroelastic behavior. Tendons are found to have significant characteristic dynamic relaxation behavior occurring at both low and high frequencies. Classic poroelastic behavior is observed, although we hypothesize that the full dynamic response is caused by a combination of flow-dependent poroelasticity as well as flow-independent viscoelasticity. Tendons also demonstrate regional dependence in their dynamic response, particularly near the junction of tendon and bone, suggesting that the structural and compositional heterogeneity in tendon may be responsible for regional poroelastic behavior. Overall, these experiments provide the foundation for understanding fluid-flow-dependent poroelastic mechanics of tendon, and the methodology is valuable for assessing changes in tendon matrix compressive behavior at the nanoscale. Copyright © 2017 Elsevier Ltd. All rights reserved.

A comparative study of the effects of cone-plate and parallel-plate geometries on rheological properties under oscillatory shear flow

NASA Astrophysics Data System (ADS)

Song, Hyeong Yong; Salehiyan, Reza; Li, Xiaolei; Lee, Seung Hak; Hyun, Kyu

2017-11-01

In this study, the effects of cone-plate (C/P) and parallel-plate (P/P) geometries were investigated on the rheological properties of various complex fluids, e.g. single-phase (polymer melts and solutions) and multiphase systems (polymer blend and nanocomposite, and suspension). Small amplitude oscillatory shear (SAOS) tests were carried out to compare linear rheological responses while nonlinear responses were compared using large amplitude oscillatory shear (LAOS) tests at different frequencies. Moreover, Fourier-transform (FT)-rheology method was used to analyze the nonlinear responses under LAOS flow. Experimental results were compared with predictions obtained by single-point correction and shear rate correction. For all systems, SAOS data measured by C/P and P/P coincide with each other, but results showed discordance between C/P and P/P measurements in the nonlinear regime. For all systems except xanthan gum solutions, first-harmonic moduli were corrected using a single horizontal shift factor, whereas FT rheology-based nonlinear parameters ( I 3/1, I 5/1, Q 3, and Q 5) were corrected using vertical shift factors that are well predicted by single-point correction. Xanthan gum solutions exhibited anomalous corrections. Their first-harmonic Fourier moduli were superposed using a horizontal shift factor predicted by shear rate correction applicable to highly shear thinning fluids. The distinguished corrections were observed for FT rheology-based nonlinear parameters. I 3/1 and I 5/1 were superposed by horizontal shifts, while the other systems displayed vertical shifts of I 3/1 and I 5/1. Q 3 and Q 5 of xanthan gum solutions were corrected using both horizontal and vertical shift factors. In particular, the obtained vertical shift factors for Q 3 and Q 5 were twice as large as predictions made by single-point correction. Such larger values are rationalized by the definitions of Q 3 and Q 5. These results highlight the significance of horizontal shift corrections in nonlinear oscillatory shear data.

Rotational response of suspended particles to turbulent flow: laboratory and numerical synthesis

NASA Astrophysics Data System (ADS)

Variano, Evan; Zhao, Lihao; Byron, Margaret; Bellani, Gabriele; Tao, Yiheng; Andersson, Helge

2014-11-01

Using laboratory and DNS measurements, we consider how aspherical and inertial particles suspended in a turbulent flow act to ``filter'' the fluid-phase vorticity. We use three approaches to predict the magnitude and structure of this filter. The first approach is based on Buckingham's Pi theorem, which shows a clear result for the relationship between filter strength and particle aspect ratio. Results are less clear for the dependence of filter strength on Stokes number; we briefly discuss some issues in the proper definition of Stokes number for use in this context. The second approach to predicting filter strength is based on a consideration of vorticity and enstrophy spectra in the fluid phase. This method has a useful feature: it can be used to predict the filter a priori, without need for measurements as input. We compare the results of this approach to measurements as a method of validation. The third and final approach to predicting filter strength is from the consideration of torques experienced by particles, and how the ``angular slip'' or ``spin slip'' evolves in an unsteady flow. We show results from our DNS that indicate different flow conditions in which the spin slip is more or less important in setting the particle rotation dynamics. Collaboration made possible by the Peder Sather Center.

Simulation model of converging-diverging (CD) nozzle to improve particle delivery system of deoxyribonucleic acid (DNA)

NASA Astrophysics Data System (ADS)

Sumarsono, Danardono A.; Ibrahim, Fera; Santoso, Satria P.; Sari, Gema P.

2018-02-01

Gene gun is a mechanical device which has been used to deliver DNA vaccine into the cells and tissues by increasing the uptake of DNA plasmid so it can generate a high immune response with less amount of DNA. Nozzle is an important part of the gene gun which used to accelerate DNA in particle form with a gas flow to reach adequate momentum to enter the epidermis of human skin and elicit immune response. We developed new designs of nozzle for gene gun to make DNA uptake more efficient in vaccination. We used Computational Fluid Dynamics (CFD) by Autodesk® Simulation 2015 to simulate static fluid pressure and velocity contour of supersonic wave and parametric distance to predict the accuracy of the new nozzle. The result showed that the nozzle could create a shockwave at the distance parametric to the object from 4 to 5 cm using fluid pressure varied between 0.8-1.2 MPa. This is indication a possibility that the DNA particle could penetrate under the mammalian skin. For the future research step, this new nozzle model could be considered for development the main component of the DNA delivery system in vaccination in vivo

Optimising the utility of pleural fluid adenosine deaminase for the diagnosis of adult tuberculous pleural effusion in Hong Kong.

PubMed

Chang, K C; Chan, M C; Leung, W M; Kong, F Y; Mak, C M; Chen, S Pl; Yu, W C

2018-02-01

Pleural fluid adenosine deaminase level can be applied to rapidly detect tuberculous pleural effusion. We aimed to establish a local diagnostic cut-off value for pleural fluid adenosine deaminase to identify patients with tuberculous pleural effusion, and optimise its utility. We retrospectively reviewed the medical records of consecutive adults with pleural fluid adenosine deaminase level measured by the Diazyme commercial kit (Diazyme Laboratories, San Diego [CA], United States) during 1 January to 31 December 2011 in a cluster of public hospitals in Hong Kong. We considered its level alongside early (within 2 weeks) findings in pleural fluid and pleural biopsy, with and without applying Light's criteria in multiple scenarios. For each scenario, we used the receiver operating characteristic curve to identify a diagnostic cut-off value for pleural fluid adenosine deaminase, and estimated its positive and negative predictive values. A total of 860 medical records were reviewed. Pleural effusion was caused by congestive heart failure, chronic renal failure, or hypoalbuminaemia caused by liver or kidney diseases in 246 (28.6%) patients, malignancy in 198 (23.0%), non-tuberculous infection in 168 (19.5%), tuberculous pleural effusion in 157 (18.3%), and miscellaneous causes in 91 (10.6%). All those with tuberculous pleural effusion had a pleural fluid adenosine deaminase level of ≤100 U/L. When analysis was restricted to 689 patients with pleural fluid adenosine deaminase level of ≤100 U/L and early negative findings for malignancy and non-tuberculous infection in pleural fluid, the positive predictive value was significantly increased and the negative predictive value non-significantly reduced. Using this approach, neither additionally restricting analysis to exudates by Light's criteria nor adding closed pleural biopsy would further enhance predictive values. As such, the diagnostic cut-off value for pleural fluid adenosine deaminase is 26.5 U/L, with a sensitivity of 87.3%, specificity of 93.2%, positive predictive value of 79.2%, negative predictive value of 96.1%, and accuracy of 91.9%. Sex, age, and co-morbidity did not significantly affect prediction of tuberculous pleural effusion using the cut-off value. We have established a diagnostic cut-off level for pleural fluid adenosine deaminase in the diagnosis of tuberculous pleural effusion by restricting analysis to a level of ≤100 U/L, and considering early pleural fluid findings for malignancy and non-tuberculous infection, but not Light's criteria.

Normal stresses in semiflexible polymer hydrogels

NASA Astrophysics Data System (ADS)

Vahabi, M.; Vos, Bart E.; de Cagny, Henri C. G.; Bonn, Daniel; Koenderink, Gijsje H.; MacKintosh, F. C.

2018-03-01

Biopolymer gels such as fibrin and collagen networks are known to develop tensile axial stress when subject to torsion. This negative normal stress is opposite to the classical Poynting effect observed for most elastic solids including synthetic polymer gels, where torsion provokes a positive normal stress. As shown recently, this anomalous behavior in fibrin gels depends on the open, porous network structure of biopolymer gels, which facilitates interstitial fluid flow during shear and can be described by a phenomenological two-fluid model with viscous coupling between network and solvent. Here we extend this model and develop a microscopic model for the individual diagonal components of the stress tensor that determine the axial response of semiflexible polymer hydrogels. This microscopic model predicts that the magnitude of these stress components depends inversely on the characteristic strain for the onset of nonlinear shear stress, which we confirm experimentally by shear rheometry on fibrin gels. Moreover, our model predicts a transient behavior of the normal stress, which is in excellent agreement with the full time-dependent normal stress we measure.

The Stokes-Einstein relation at moderate Schmidt number.

PubMed

Balboa Usabiaga, Florencio; Xie, Xiaoyi; Delgado-Buscalioni, Rafael; Donev, Aleksandar

2013-12-07

The Stokes-Einstein relation for the self-diffusion coefficient of a spherical particle suspended in an incompressible fluid is an asymptotic result in the limit of large Schmidt number, that is, when momentum diffuses much faster than the particle. When the Schmidt number is moderate, which happens in most particle methods for hydrodynamics, deviations from the Stokes-Einstein prediction are expected. We study these corrections computationally using a recently developed minimally resolved method for coupling particles to an incompressible fluctuating fluid in both two and three dimensions. We find that for moderate Schmidt numbers the diffusion coefficient is reduced relative to the Stokes-Einstein prediction by an amount inversely proportional to the Schmidt number in both two and three dimensions. We find, however, that the Einstein formula is obeyed at all Schmidt numbers, consistent with linear response theory. The mismatch arises because thermal fluctuations affect the drag coefficient for a particle due to the nonlinear nature of the fluid-particle coupling. The numerical data are in good agreement with an approximate self-consistent theory, which can be used to estimate finite-Schmidt number corrections in a variety of methods. Our results indicate that the corrections to the Stokes-Einstein formula come primarily from the fact that the particle itself diffuses together with the momentum. Our study separates effects coming from corrections to no-slip hydrodynamics from those of finite separation of time scales, allowing for a better understanding of widely observed deviations from the Stokes-Einstein prediction in particle methods such as molecular dynamics.

Multi-fluid modelling of pulsed discharges for flow control applications

NASA Astrophysics Data System (ADS)

Poggie, J.

2015-02-01

Experimental evidence suggests that short-pulse dielectric barrier discharge actuators are effective for speeds corresponding to take-off and approach of large aircraft, and thus are a fruitful direction for flow control technology development. Large-eddy simulations have reproduced some of the main fluid dynamic effects. The plasma models used in such simulations are semi-empirical, however, and need to be tuned for each flowfield under consideration. In this paper, the discharge physics is examined in more detail with multi-fluid modelling, comparing a five-moment model (continuity, momentum, and energy equations) to a two-moment model (continuity and energy equations). A steady-state, one-dimensional discharge was considered first, and the five-moment model was found to predict significantly lower ionisation rates and number densities than the two-moment model. A two-dimensional, transient discharge problem with an elliptical cathode was studied next. Relative to the two-moment model, the five-moment model predicted a slower response to the activation of the cathode, and lower electron velocities and temperatures as the simulation approached steady-state. The primary reason for the differences in the predictions of the two models can be attributed to the effects of particle inertia, particularly electron inertia in the cathode layer. The computational cost of the five-moment model is only about twice that of the simpler variant, suggesting that it may be feasible to use the more sophisticated model in practical calculations for flow control actuator design.

Free Vibration Response Comparison of Composite Beams with Fluid Structure Interaction

DTIC Science & Technology

2012-09-01

fluid damping to vibrating structures when in contact with a fluid medium such as water . The added mass effect changes the dynamic responses of the...200 words) The analysis of the dynamic response of a vibrating structure in contact with a fluid medium can be interpreted as an added mass effect...INTENTIONALLY LEFT BLANK v ABSTRACT The analysis of the dynamic response of a vibrating structure in contact with a fluid medium can be interpreted as

Supercritical fluid extraction of phenolic compounds and antioxidants from grape (Vitis labrusca B.) seeds.

PubMed

Ghafoor, Kashif; Al-Juhaimi, Fahad Y; Choi, Yong Hee

2012-12-01

Supercritical fluid extraction (SFE) technique was applied and optimized for temperature, CO₂ pressure and ethanol (modifier) concentration using orthogonal array design and response surface methodology for the extract yield, total phenols and antioxidants from grape (Vitis labrusca B.) seeds. Effects of extraction temperature and pressure were found to be significant for all these response variables in SFE process. Optimum SFE conditions (44 ~ 46 °C temperature and 153 ~ 161 bar CO₂ pressure) along with ethanol (<7 %) as modifier, for the maximum predicted values of extract yield (12.09 %), total phenols (2.41 mg GAE/ml) and antioxidants (7.08 mg AAE/ml), were used to obtain extracts from grape seeds. The predicted values matched well with the experimental values (12.32 % extract yield, 2.45 mg GAE/ml total phenols and 7.08 mg AAE/ml antioxidants) obtained at optimum SFE conditions. The antiradical assay showed that SFE extracts of grape seeds can scavenge more than 85 % of 1, 1-diphenyl-2-picrylhydrazyl (DPPH) radicals. The grape seeds extracts were also analyzed for hydroxybenzoic acids which included gallic acid (1.21 ~ 3.84 μg/ml), protocatechuic acid (3.57 ~ 11.78 μg/ml) and p-hydroxybenzoic acid (206.72 ~ 688.18 μg/ml).

Computation of dynamic seismic responses to viscous fluid of digitized three-dimensional Berea sandstones with a coupled finite-difference method.

PubMed

Zhang, Yang; Toksöz, M Nafi

2012-08-01

The seismic response of saturated porous rocks is studied numerically using microtomographic images of three-dimensional digitized Berea sandstones. A stress-strain calculation is employed to compute the velocities and attenuations of rock samples whose sizes are much smaller than the seismic wavelength of interest. To compensate for the contributions of small cracks lost in the imaging process to the total velocity and attenuation, a hybrid method is developed to recover the crack distribution, in which the differential effective medium theory, the Kuster-Toksöz model, and a modified squirt-flow model are utilized in a two-step Monte Carlo inversion. In the inversion, the velocities of P- and S-waves measured for the dry and water-saturated cases, and the measured attenuation of P-waves for different fluids are used. By using such a hybrid method, both the velocities of saturated porous rocks and the attenuations are predicted accurately when compared to laboratory data. The hybrid method is a practical way to model numerically the seismic properties of saturated porous rocks until very high resolution digital data are available. Cracks lost in the imaging process are critical for accurately predicting velocities and attenuations of saturated porous rocks.

A molecular Debye-Huckel theory of solvation in polar fluids: An extension of the Born model

DOE Office of Scientific and Technical Information (OSTI.GOV)

Xiao, Tiejun; Song, Xueyu

A dielectric response theory of solvation beyond the conventional Born model for polar fluids is presented. The dielectric response of a polar fluid is described by a Born response mode and a linear combination of Debye-Hückel-like response modes that capture the nonlocal response of polar fluids. The Born mode is characterized by a bulk dielectric constant, while a Debye-Hückel mode is characterized by its corresponding Debye screening length. Both the bulk dielectric constant and the Debye screening lengths are determined from the bulk dielectric function of the polar fluid. The linear combination coefficients of the response modes are evaluated inmore » a self-consistent way and can be used to evaluate the electrostatic contribution to the thermodynamic properties of a polar fluid. In conclusion, our theory is applied to a dipolar hard sphere fluid as well as interaction site models of polar fluids such as water, where the electrostatic contribution to their thermodynamic properties can be obtained accurately.« less

A molecular Debye-Huckel theory of solvation in polar fluids: An extension of the Born model

DOE PAGES

Xiao, Tiejun; Song, Xueyu

2017-12-06

A dielectric response theory of solvation beyond the conventional Born model for polar fluids is presented. The dielectric response of a polar fluid is described by a Born response mode and a linear combination of Debye-Hückel-like response modes that capture the nonlocal response of polar fluids. The Born mode is characterized by a bulk dielectric constant, while a Debye-Hückel mode is characterized by its corresponding Debye screening length. Both the bulk dielectric constant and the Debye screening lengths are determined from the bulk dielectric function of the polar fluid. The linear combination coefficients of the response modes are evaluated inmore » a self-consistent way and can be used to evaluate the electrostatic contribution to the thermodynamic properties of a polar fluid. In conclusion, our theory is applied to a dipolar hard sphere fluid as well as interaction site models of polar fluids such as water, where the electrostatic contribution to their thermodynamic properties can be obtained accurately.« less

A molecular Debye-Hückel theory of solvation in polar fluids: An extension of the Born model

NASA Astrophysics Data System (ADS)

Xiao, Tiejun; Song, Xueyu

2017-12-01

A dielectric response theory of solvation beyond the conventional Born model for polar fluids is presented. The dielectric response of a polar fluid is described by a Born response mode and a linear combination of Debye-Hückel-like response modes that capture the nonlocal response of polar fluids. The Born mode is characterized by a bulk dielectric constant, while a Debye-Hückel mode is characterized by its corresponding Debye screening length. Both the bulk dielectric constant and the Debye screening lengths are determined from the bulk dielectric function of the polar fluid. The linear combination coefficients of the response modes are evaluated in a self-consistent way and can be used to evaluate the electrostatic contribution to the thermodynamic properties of a polar fluid. Our theory is applied to a dipolar hard sphere fluid as well as interaction site models of polar fluids such as water, where the electrostatic contribution to their thermodynamic properties can be obtained accurately.

A molecular Debye-Hückel theory of solvation in polar fluids: An extension of the Born model.

PubMed

Xiao, Tiejun; Song, Xueyu

2017-12-07

A dielectric response theory of solvation beyond the conventional Born model for polar fluids is presented. The dielectric response of a polar fluid is described by a Born response mode and a linear combination of Debye-Hückel-like response modes that capture the nonlocal response of polar fluids. The Born mode is characterized by a bulk dielectric constant, while a Debye-Hückel mode is characterized by its corresponding Debye screening length. Both the bulk dielectric constant and the Debye screening lengths are determined from the bulk dielectric function of the polar fluid. The linear combination coefficients of the response modes are evaluated in a self-consistent way and can be used to evaluate the electrostatic contribution to the thermodynamic properties of a polar fluid. Our theory is applied to a dipolar hard sphere fluid as well as interaction site models of polar fluids such as water, where the electrostatic contribution to their thermodynamic properties can be obtained accurately.

Fluid manifold design for a solar energy storage tank

NASA Technical Reports Server (NTRS)

Humphries, W. R.; Hewitt, H. C.; Griggs, E. I.

1975-01-01

A design technique for a fluid manifold for use in a solar energy storage tank is given. This analytical treatment generalizes the fluid equations pertinent to manifold design, giving manifold pressures, velocities, and orifice pressure differentials in terms of appropriate fluid and manifold geometry parameters. Experimental results used to corroborate analytical predictions are presented. These data indicate that variations in discharge coefficients due to variations in orifices can cause deviations between analytical predictions and actual performance values.

Validation of model predictions of pore-scale fluid distributions during two-phase flow

NASA Astrophysics Data System (ADS)

Bultreys, Tom; Lin, Qingyang; Gao, Ying; Raeini, Ali Q.; AlRatrout, Ahmed; Bijeljic, Branko; Blunt, Martin J.

2018-05-01

Pore-scale two-phase flow modeling is an important technology to study a rock's relative permeability behavior. To investigate if these models are predictive, the calculated pore-scale fluid distributions which determine the relative permeability need to be validated. In this work, we introduce a methodology to quantitatively compare models to experimental fluid distributions in flow experiments visualized with microcomputed tomography. First, we analyzed five repeated drainage-imbibition experiments on a single sample. In these experiments, the exact fluid distributions were not fully repeatable on a pore-by-pore basis, while the global properties of the fluid distribution were. Then two fractional flow experiments were used to validate a quasistatic pore network model. The model correctly predicted the fluid present in more than 75% of pores and throats in drainage and imbibition. To quantify what this means for the relevant global properties of the fluid distribution, we compare the main flow paths and the connectivity across the different pore sizes in the modeled and experimental fluid distributions. These essential topology characteristics matched well for drainage simulations, but not for imbibition. This suggests that the pore-filling rules in the network model we used need to be improved to make reliable predictions of imbibition. The presented analysis illustrates the potential of our methodology to systematically and robustly test two-phase flow models to aid in model development and calibration.

Fluid Overload and Renal Angina Index at Admission Are Associated With Worse Outcomes in Critically Ill Children.

PubMed

Sethi, Sidharth K; Raghunathan, Veena; Shah, Shilpi; Dhaliwal, Maninder; Jha, Pranaw; Kumar, Maneesh; Paluri, Sravanthi; Bansal, Shyam; Mhanna, Maroun J; Raina, Rupesh

2018-01-01

Objectives: We investigated the association of fluid overload and oxygenation in critically sick children, and their correlation with various outcomes (duration of ventilation, ICU stay, and mortality). We also assessed whether renal angina index (RAI) at admission can predict mortality or acute kidney injury (AKI) on day 3 after admission. Design and setting: Prospective study, pediatric intensive care in a tertiary hospital. Duration: June 2013-June 2014. Patients: Patients were included if they needed invasive mechanical ventilation for >24 h and had an indwelling arterial catheter. Patients with congenital heart disease or those who received renal replacement therapy (RRT) were excluded. Methods: Oxygenation index, fluid overload percent (daily, cumulative), RAI at admission and pediatric logistic organ dysfunction (PELOD) score were obtained in all critically ill children. KDIGO classification was used to define AKI, using both creatinine and urine output criteria. Admission data for determination of RAI included the use of vasopressors, invasive mechanical ventilation, percent fluid overload, and change in kidney function (estimated creatinine clearance). Univariable and multivariable approaches were used to assess the relations between fluid overload, oxygenation index and clinical outcomes. An RAI cutoff >8 was used to predict AKI on day 3 of admission and mortality. Results: One hundred and two patients were recruited. Fluid overload predicted oxygenation index in all patients, independent of age, gender and PELOD score ( p < 0.05). Fluid overload was associated with longer duration of ventilation ( p < 0.05), controlled for age, gender, and PELOD score. Day-3 AKI rates were higher in patients with a RAI of 8 or more, and higher areas under the RAI curve had better prediction rates for Day-3 AKI. An RAI <8 had high negative predictive values (80-95%) for Day-3 AKI. RAI was better than traditional markers of pediatric severity of illness (PELOD) score for prediction of AKI on day 3. Conclusions: This study emphasizes that positive fluid balance adversely affects intensive care in critically ill children. Further, the RAI prediction model may help optimize treatment and improve clinical prediction of AKI.

Fluid Overload and Renal Angina Index at Admission Are Associated With Worse Outcomes in Critically Ill Children

PubMed Central

Sethi, Sidharth K.; Raghunathan, Veena; Shah, Shilpi; Dhaliwal, Maninder; Jha, Pranaw; Kumar, Maneesh; Paluri, Sravanthi; Bansal, Shyam; Mhanna, Maroun J.; Raina, Rupesh

2018-01-01

Objectives: We investigated the association of fluid overload and oxygenation in critically sick children, and their correlation with various outcomes (duration of ventilation, ICU stay, and mortality). We also assessed whether renal angina index (RAI) at admission can predict mortality or acute kidney injury (AKI) on day 3 after admission. Design and setting: Prospective study, pediatric intensive care in a tertiary hospital. Duration: June 2013-June 2014. Patients: Patients were included if they needed invasive mechanical ventilation for >24 h and had an indwelling arterial catheter. Patients with congenital heart disease or those who received renal replacement therapy (RRT) were excluded. Methods: Oxygenation index, fluid overload percent (daily, cumulative), RAI at admission and pediatric logistic organ dysfunction (PELOD) score were obtained in all critically ill children. KDIGO classification was used to define AKI, using both creatinine and urine output criteria. Admission data for determination of RAI included the use of vasopressors, invasive mechanical ventilation, percent fluid overload, and change in kidney function (estimated creatinine clearance). Univariable and multivariable approaches were used to assess the relations between fluid overload, oxygenation index and clinical outcomes. An RAI cutoff >8 was used to predict AKI on day 3 of admission and mortality. Results: One hundred and two patients were recruited. Fluid overload predicted oxygenation index in all patients, independent of age, gender and PELOD score (p < 0.05). Fluid overload was associated with longer duration of ventilation (p < 0.05), controlled for age, gender, and PELOD score. Day-3 AKI rates were higher in patients with a RAI of 8 or more, and higher areas under the RAI curve had better prediction rates for Day-3 AKI. An RAI <8 had high negative predictive values (80–95%) for Day-3 AKI. RAI was better than traditional markers of pediatric severity of illness (PELOD) score for prediction of AKI on day 3. Conclusions: This study emphasizes that positive fluid balance adversely affects intensive care in critically ill children. Further, the RAI prediction model may help optimize treatment and improve clinical prediction of AKI. PMID:29765932

Individual lipid encapsulated microbubble radial oscillations: Effects of fluid viscosity

PubMed Central

Helfield, Brandon; Chen, Xucai; Qin, Bin; Villanueva, Flordeliza S.

2016-01-01

Ultrasound-stimulated microbubble dynamics have been shown to be dependent on intrinsic bubble properties, including size and shell characteristics. The effect of the surrounding environment on microbubble response, however, has been less investigated. In particular, microbubble optimization studies are generally conducted in water/saline, characterized by a 1 cP viscosity, for application in the vasculature (i.e., 4 cP). In this study, ultra-high speed microscopy was employed to investigate fluid viscosity effects on phospholipid encapsulated microbubble oscillations at 1 MHz, using a single, eight-cycle pulse at peak negative pressures of 100 and 250 kPa. Microbubble oscillations were shown to be affected by fluid viscosity in a size- and pressure-dependent manner. In general, the oscillation amplitudes exhibited by microbubbles between 3 and 6 μm in 1 cP fluid were larger than in 4 cP fluid, reaching a maximum of 1.7-fold at 100 kPa for microbubbles 3.8 μm in diameter and 1.35-fold at 250 kPa for microbubbles 4.8 μm in diameter. Simulation results were in broad agreement at 250 kPa, however generally underestimated the effect of fluid viscosity at 100 kPa. This is the first experimental demonstration documenting the effects of surrounding fluid viscosity on microbubble oscillations, resulting in behavior not entirely predicted by current microbubble models. PMID:26827018

Physiologic mechanisms of circulatory and body fluid losses in weightlessness identified by mathematical modeling

NASA Technical Reports Server (NTRS)

Simanonok, K. E.; Srinivasan, R. S.; Charles, J. B.

1993-01-01

Central volume expansion due to fluid shifts in weightlessness is believed to activate adaptive reflexes which ultimately result in a reduction of the total circulating blood volume. However, the flight data suggests that a central volume overdistention does not persist, in which case some other factor or factors must be responsible for body fluid losses. We used a computer simulation to test the hypothesis that factors other than central volume overdistention are involved in the loss of blood volume and other body fluid volumes observed in weightlessness and in weightless simulations. Additionally, the simulation was used to identify these factors. The results predict that atrial volumes and pressures return to their prebedrest baseline values within the first day of exposure to head down tilt (HDT) as the blood volume is reduced by an elevated urine formation. They indicate that the mechanisms for large and prolonged body fluid losses in weightlessness is red cell hemoconcentration that elevates blood viscosity and peripheral resistance, thereby lowering capillary pressure. This causes a prolonged alteration of the balance of Starling forces, depressing the extracellular fluid volume until the hematocrit is returned to normal through a reduction of the red cell mass, which also allows some restoration of the plasma volume. We conclude that the red cell mass becomes the physiologic driver for a large 'undershoot' of the body fluid volumes after the normalization of atrial volumes and pressures.

On the Theory of Reactive Mixtures for Modeling Biological Growth

PubMed Central

Ateshian, Gerard A.

2013-01-01

Mixture theory, which can combine continuum theories for the motion and deformation of solids and fluids with general principles of chemistry, is well suited for modeling the complex responses of biological tissues, including tissue growth and remodeling, tissue engineering, mechanobiology of cells and a variety of other active processes. A comprehensive presentation of the equations of reactive mixtures of charged solid and fluid constituents is lacking in the biomechanics literature. This study provides the conservation laws and entropy inequality, as well as interface jump conditions, for reactive mixtures consisting of a constrained solid mixture and multiple fluid constituents. The constituents are intrinsically incompressible and may carry an electrical charge. The interface jump condition on the mass flux of individual constituents is shown to define a surface growth equation, which predicts deposition or removal of material points from the solid matrix, complementing the description of volume growth described by the conservation of mass. A formu-lation is proposed for the reference configuration of a body whose material point set varies with time. State variables are defined which can account for solid matrix volume growth and remodeling. Constitutive constraints are provided on the stresses and momentum supplies of the various constituents, as well as the interface jump conditions for the electrochem cal potential of the fluids. Simplifications appropriate for biological tissues are also proposed, which help reduce the governing equations into a more practical format. It is shown that explicit mechanisms of growth-induced residual stresses can be predicted in this framework. PMID:17206407

Interpreting electrically evoked emissions using a finite-element model of the cochlea

NASA Astrophysics Data System (ADS)

Deo, Niranjan V.; Grosh, Karl; Parthasarathi, Anand

2003-10-01

Electrically evoked otoacoustic emissions (EEOAEs) are used to investigate in vivo cochlear electromechanical function. Electrical stimulation through bipolar electrodes placed very close to the basilar membrane (in the scala vestibuli and scala tympani) gives rise to a narrow frequency range of EEOAEs, limited to around 20 kHz when the electrodes are placed near the 18-kHz best frequency place. Model predictions using a three-dimensional inviscid fluid model in conjunction with a middle ear model [S. Puria and J. B. Allen, J. Acoust. Soc. Am. 104, 3463-3481 (1998)] and a simple model for outer hair cell activity [S. Neely and D. Kim, J. Acoust. Soc. Am. 94, 137-146 (1993)] are used to interpret the experimental results. To estimate effect of viscosity, model results are compared with those obtained for a viscous fluid. The models are solved using a 2.5-D finite-element formulation. Predictions show that the high frequency limit of the excitation is determined by the spatial extent of the current stimulus. The global peaks in the EEOAE spectra are interpreted as constructive interference between electrically evoked backward traveling waves and forward traveling waves reflected from the stapes. Steady state response predictions of the model are presented.

Acoustic radiation damping of flat rectangular plates subjected to subsonic flows

NASA Technical Reports Server (NTRS)

Lyle, Karen Heitman

1993-01-01

The acoustic radiation damping for various isotropic and laminated composite plates and semi-infinite strips subjected to a uniform, subsonic and steady flow has been predicted. The predictions are based on the linear vibration of a flat plate. The fluid loading is characterized as the perturbation pressure derived from the linearized Bernoulli and continuity equations. Parameters varied in the analysis include Mach number, mode number and plate size, aspect ratio and mass. The predictions are compared with existing theoretical results and experimental data. The analytical results show that the fluid loading can significantly affect realistic plate responses. Generally, graphite/epoxy and carbon/carbon plates have higher acoustic radiation damping values than similar aluminum plates, except near plate divergence conditions resulting from aeroelastic instability. Universal curves are presented where the acoustic radiation damping normalized by the mass ratio is a linear function of the reduced frequency. A separate curve is required for each Mach number and plate aspect ratio. In addition, acoustic radiation damping values can be greater than or equal to the structural component of the modal critical damping ratio (assumed as 0.01) for the higher subsonic Mach numbers. New experimental data were acquired for comparison with the analytical results.

Fluid Shifts Before, During, and After Prolonged Space Flight and their Association with Intracranial Pressure and Visual Impairment

NASA Technical Reports Server (NTRS)

Stenger, M.; Lee, S.; Platts, S.; Macias, B.; Lui, J.; Ebert, D.; Sargsyan, A.; Dulchavsky, S.; Alferova, I.; Yarmanova, E.;

Lipocalin 2 in cerebrospinal fluid as a marker of acute bacterial meningitis

PubMed Central

2014-01-01

Background Early differential diagnosis between acute bacterial and viral meningitis is problematic. We aimed to investigate whether the detection of lipocalin 2, a protein of the acute innate immunity response, may be used as a marker for acute bacterial meningitis. Methods Transgenic mice expressing the human transferrin were infected by intraperitoneal route and were imaged. Cerebrospinal fluid (CSF) was sampled up to 48hours post- infection to measure lipocalin 2. We also tested a collection of 90 and 44 human CSF with confirmed acute bacterial or acute viral meningitis respectively. Results Lipocalin 2 was detected after 5 h in CSF during experimental infection in mice. Lipocalin 2 levels were significantly higher (p < 0.0001) in patients with confirmed acute bacterial meningitis (mean 125 pg/mL, range 106–145 pg/mL) than in patients with acute viral meningitis (mean 2 pg/mL, range 0–6 pg/mL) with a sensitivity of 81%, a specificity of 93%, a positive predictive value of 96% and a negative predictive value of 71% in diagnosing acute bacterial meningitis. Conclusions Increased levels of lipocalin 2 in cerebrospinal fluid may discriminate between acute bacterial and viral meningitis in patients with clinical syndrome of meningitis. PMID:24885531

Nonlinear modal resonances in low-gravity slosh-spacecraft systems

NASA Technical Reports Server (NTRS)

Peterson, Lee D.

1991-01-01

Nonlinear models of low gravity slosh, when coupled to spacecraft vibrations, predict intense nonlinear eigenfrequency shifts at zero gravity. These nonlinear frequency shifts are due to internal quadratic and cubic resonances between fluid slosh modes and spacecraft vibration modes. Their existence has been verified experimentally, and they cannot be correctly modeled by approximate, uncoupled nonlinear models, such as pendulum mechanical analogs. These predictions mean that linear slosh assumptions for spacecraft vibration models can be invalid, and may lead to degraded control system stability and performance. However, a complete nonlinear modal analysis will predict the correct dynamic behavior. This paper presents the analytical basis for these results, and discusses the effect of internal resonances on the nonlinear coupled response at zero gravity.

Nouvelles techniques pratiques pour la modelisation du comportement dynamique des systèmes eau-structure

NASA Astrophysics Data System (ADS)

Miquel, Benjamin

The dynamic or seismic behavior of hydraulic structures is, as for conventional structures, essential to assure protection of human lives. These types of analyses also aim at limiting structural damage caused by an earthquake to prevent rupture or collapse of the structure. The particularity of these hydraulic structures is that not only the internal displacements are caused by the earthquake, but also by the hydrodynamic loads resulting from fluid-structure interaction. This thesis reviews the existing complex and simplified methods to perform such dynamic analysis for hydraulic structures. For the complex existing methods, attention is placed on the difficulties arising from their use. Particularly, interest is given in this work on the use of transmitting boundary conditions to simulate the semi infinity of reservoirs. A procedure has been developed to estimate the error that these boundary conditions can introduce in finite element dynamic analysis. Depending on their formulation and location, we showed that they can considerably affect the response of such fluid-structure systems. For practical engineering applications, simplified procedures are still needed to evaluate the dynamic behavior of structures in contact with water. A review of the existing simplified procedures showed that these methods are based on numerous simplifications that can affect the prediction of the dynamic behavior of such systems. One of the main objectives of this thesis has been to develop new simplified methods that are more accurate than those existing. First, a new spectral analysis method has been proposed. Expressions for the fundamental frequency of fluid-structure systems, key parameter of spectral analysis, have been developed. We show that this new technique can easily be implemented in a spreadsheet or program, and that its calculation time is near instantaneous. When compared to more complex analytical or numerical method, this new procedure yields excellent prediction of the dynamic behavior of fluid-structure systems. Spectral analyses ignore the transient and oscillatory nature of vibrations. When such dynamic analyses show that some areas of the studied structure undergo excessive stresses, time history analyses allow a better estimate of the extent of these zones as well as a time notion of these excessive stresses. Furthermore, the existing spectral analyses methods for fluid-structure systems account only for the static effect of higher modes. Thought this can generally be sufficient for dams, for flexible structures the dynamic effect of these modes should be accounted for. New methods have been developed for fluid-structure systems to account for these observations as well as the flexibility of foundations. A first method was developed to study structures in contact with one or two finite or infinite water domains. This new technique includes flexibility of structures and foundations as well as the dynamic effect of higher vibration modes and variations of the levels of the water domains. Extension of this method was performed to study beam structures in contact with fluids. These new developments have also allowed extending existing analytical formulations of the dynamic properties of a dry beam to a new formulation that includes effect of fluid-structure interaction. The method yields a very good estimate of the dynamic behavior of beam-fluid systems or beam like structures in contact with fluid. Finally, a Modified Accelerogram Method (MAM) has been developed to modify the design earthquake into a new accelerogram that directly accounts for the effect of fluid-structure interaction. This new accelerogram can therefore be applied directly to the dry structure (i.e. without water) in order to calculate the dynamic response of the fluid-structure system. This original technique can include numerous parameters that influence the dynamic response of such systems and allows to treat analytically the fluid-structure interaction while keeping the advantages of finite element modeling.

The Prediction of Students' Academic Performance With Fluid Intelligence in Giving Special Consideration to the Contribution of Learning.

PubMed

Ren, Xuezhu; Schweizer, Karl; Wang, Tengfei; Xu, Fen

2015-01-01

The present study provides a new account of how fluid intelligence influences academic performance. In this account a complex learning component of fluid intelligence tests is proposed to play a major role in predicting academic performance. A sample of 2, 277 secondary school students completed two reasoning tests that were assumed to represent fluid intelligence and standardized math and verbal tests assessing academic performance. The fluid intelligence data were decomposed into a learning component that was associated with the position effect of intelligence items and a constant component that was independent of the position effect. Results showed that the learning component contributed significantly more to the prediction of math and verbal performance than the constant component. The link from the learning component to math performance was especially strong. These results indicated that fluid intelligence, which has so far been considered as homogeneous, could be decomposed in such a way that the resulting components showed different properties and contributed differently to the prediction of academic performance. Furthermore, the results were in line with the expectation that learning was a predictor of performance in school.

The Prediction of Students’ Academic Performance With Fluid Intelligence in Giving Special Consideration to the Contribution of Learning

PubMed Central

Ren, Xuezhu; Schweizer, Karl; Wang, Tengfei; Xu, Fen

2015-01-01

The present study provides a new account of how fluid intelligence influences academic performance. In this account a complex learning component of fluid intelligence tests is proposed to play a major role in predicting academic performance. A sample of 2, 277 secondary school students completed two reasoning tests that were assumed to represent fluid intelligence and standardized math and verbal tests assessing academic performance. The fluid intelligence data were decomposed into a learning component that was associated with the position effect of intelligence items and a constant component that was independent of the position effect. Results showed that the learning component contributed significantly more to the prediction of math and verbal performance than the constant component. The link from the learning component to math performance was especially strong. These results indicated that fluid intelligence, which has so far been considered as homogeneous, could be decomposed in such a way that the resulting components showed different properties and contributed differently to the prediction of academic performance. Furthermore, the results were in line with the expectation that learning was a predictor of performance in school. PMID:26435760

Response of a tethered aerostat to simulated turbulence

NASA Astrophysics Data System (ADS)

Stanney, Keith A.; Rahn, Christopher D.

2006-09-01

Aerostats are lighter-than-air vehicles tethered to the ground by a cable and used for broadcasting, communications, surveillance, and drug interdiction. The dynamic response of tethered aerostats subject to extreme atmospheric turbulence often dictates survivability. This paper develops a theoretical model that predicts the planar response of a tethered aerostat subject to atmospheric turbulence and simulates the response to 1000 simulated hurricane scale turbulent time histories. The aerostat dynamic model assumes the aerostat hull to be a rigid body with non-linear fluid loading, instantaneous weathervaning for planar response, and a continuous tether. Galerkin's method discretizes the coupled aerostat and tether partial differential equations to produce a non-linear initial value problem that is integrated numerically given initial conditions and wind inputs. The proper orthogonal decomposition theorem generates, based on Hurricane Georges wind data, turbulent time histories that possess the sequential behavior of actual turbulence, are spectrally accurate, and have non-Gaussian density functions. The generated turbulent time histories are simulated to predict the aerostat response to severe turbulence. The resulting probability distributions for the aerostat position, pitch angle, and confluence point tension predict the aerostat behavior in high gust environments. The dynamic results can be up to twice as large as a static analysis indicating the importance of dynamics in aerostat modeling. The results uncover a worst case wind input consisting of a two-pulse vertical gust.

Evidence for an Explanation Advantage in Naïve Biological Reasoning

PubMed Central

Legare, Cristine H.; Wellman, Henry M.; Gelman, Susan A.

2013-01-01

The present studies compare young children's explanations and predictions for the biological phenomenon of contamination. In Study 1, 36 preschoolers and 24 adults heard vignettes concerning contamination, and were asked either to make a prediction or to provide an explanation. Even 3-year-olds readily supplied contamination-based explanations, and most children mentioned an unseen mechanism (germs, contact through bodily fluids). Moreover, unlike adults who performed at ceiling across both explanation and prediction tasks, children were significantly more accurate with their explanations than their predictions. In Study 2, we varied the strength of cues regarding the desirability of the contaminated substance (N = 24 preschoolers). Although desirability affected responses, for both levels of desirability participants were significantly more accurate on explanation than prediction questions. Altogether, these studies demonstrate a significant “explanation advantage” for children's reasoning in the domain of everyday biology. PMID:18710700

The Generation of Harmonic Distortion and Distortion Products in a Computational Model of the Cochlea

NASA Astrophysics Data System (ADS)

Meaud, Julien; Li, Yizeng; Grosh, Karl

2011-11-01

It is generally agreed that the nonlinear response of the cochlea is due to the forward transduction of the outer hair cell (OHC) hair bundle (HB) and subsequent alteration of the active force applied to the cochlear structures, including the basilar membrane (BM). A mechanical-acoustical-electrical model of the cochlea with three-dimensional fluid representation, and feedback from OHC somatic motility coupled to nonlinear HB mechanotransduction is used to predict nonlinear distortion of the BM response to acoustic stimulus. An efficient alternating frequency time scheme is implemented to solve for the nonlinear stationary dynamics of the cochlea. The model is used to predict the location of maximum generation of nonlinear distortion during pure tone and two-tone stimulation as well as the propagation of the distortion components on the BM.

Method of calibrating a fluid-level measurement system

NASA Technical Reports Server (NTRS)

Woodard, Stanley E. (Inventor); Taylor, Bryant D. (Inventor)

2010-01-01

A method of calibrating a fluid-level measurement system is provided. A first response of the system is recorded when the system's sensor(s) is (are) not in contact with a fluid of interest. A second response of the system is recorded when the system's sensor(s) is (are) fully immersed in the fluid of interest. Using the first and second responses, a plurality of expected responses of the system's sensor(s) is (are) generated for a corresponding plurality of levels of immersion of the sensor(s) in the fluid of interest.

Predictors of Responses to Corticosteroids for Cancer-Related Fatigue in Advanced Cancer Patients: A Multicenter, Prospective, Observational Study.

PubMed

Matsuo, Naoki; Morita, Tatsuya; Matsuda, Yoshinobu; Okamoto, Kenichiro; Matsumoto, Yoshihisa; Kaneishi, Keisuke; Odagiri, Takuya; Sakurai, Hiroki; Katayama, Hideki; Mori, Ichiro; Yamada, Hirohide; Watanabe, Hiroaki; Yokoyama, Taro; Yamaguchi, Takashi; Nishi, Tomohiro; Shirado, Akemi; Hiramoto, Shuji; Watanabe, Toshio; Kohara, Hiroyuki; Shimoyama, Satofumi; Aruga, Etsuko; Baba, Mika; Sumita, Koki; Iwase, Satoru

2016-07-01

Although corticosteroids are widely used to relieve cancer-related fatigue (CRF), information regarding the factors predicting responses to corticosteroids remains limited. The aim of this study was to identify potential factors predicting responses to corticosteroids for CRF in advanced cancer patients. Inclusion criteria for this multicenter, prospective, observational study were patients who had metastatic or locally advanced cancer and had a fatigue intensity score of 4 or more on a 0-10 Numerical Rating Scale (NRS). Univariate and multivariate analyses were conducted to identify the factors predicting two-point reduction or more in NRS on day 3. Among 179 patients who received corticosteroids, 86 (48%; 95% CI 41%-56%) had a response with two-point reduction or more. Factors that significantly predicted responses were performance status score of 3 or more, Palliative Performance Scale score more than 40, absence of ascites, absence of drowsiness, absence of depression, serum albumin level greater than 3 mg/dL, serum sodium level greater than 135 mEq/L, and baseline NRS score greater than 5. A multivariate analysis showed that the independent factors predicting responses were baseline NRS score greater than 5 (odds ratio [OR] 6.6, 95% CI 2.8-15.4), Palliative Performance Scale score more than 40 (OR 4.4, 95% CI 2.1-9.3), absence of drowsiness (OR 3.4, 95% CI 1.7-6.9), absence of ascites (OR 2.3, 95% CI 1.1-4.7), and absence of pleural effusion (OR 2.2, 95% CI 1.0-5.0). Treatment responses to corticosteroids for CRF may be predicted by baseline symptom intensity, performance status, drowsiness, and severity of fluid retention symptoms. Larger prospective studies are needed to confirm these results. Copyright © 2016 American Academy of Hospice and Palliative Medicine. Published by Elsevier Inc. All rights reserved.

Dose-Response Evaluation of Braslet-M Occlusion Cuffs

NASA Technical Reports Server (NTRS)

Ebert, Douglas; Garcia, Kathleen; Sargsyan, Ashot E.; Ham, David; Hamilton, Douglas; Dulchavsky, Scott A.

2010-01-01

Introduction: Braslet-M is a set of special elasticized thigh cuffs used by the Russian space agency to reduce the effects of the head-ward fluid shift during early adaptation to microgravity by sequestering fluid in the lower extremities. Currently, no imaging modalities are used in the calibration of the device, and the pressure required to produce a predictable physiological response is unknown. This investigation intends to relate the pressure exerted by the cuffs to the extent of fluid redistribution and commensurate physiological effects. Materials and Methods: Ten healthy subjects with standardized fluid intake participated in the study. Data collection included femoral and internal jugular vein imaging in two orthogonal planes, pulsed Doppler of cervical and femoral vessels and middle cerebral artery, optic nerve imaging, and echocardiography. Braslet-M cuff pressure was monitored at the skin interface using pre-calibrated pressure sensors. Using 6 and 30 head-down tilt in two separate sessions, the effect of Braslet-M was assessed while incrementally tightening the cuffs. Cuffs were then simultaneously released to document the resulting hemodynamic change. Results: Preliminary analysis shows correlation between physical pressure exerted by the Braslet-M device and several parameters such as jugular and femoral vein cross-sections, resistivity of the lower extremity vascular bed, and others. A number of parameters reflect blood redistribution and will be used to determine the therapeutic range of the device and to prevent unsafe application. Conclusion: Braslet-M exerts a physical effect that can be measured and correlated with many changes in central and peripheral hemodynamics. Analysis of the full data set will be required to make definitive recommendations regarding the range of safe therapeutic application. Objective data and subjective responses suggest that a safer and equally effective use of Braslet can be achieved when compared with the current non-imaging calibration techniques.

Cell-line-specific stimulation of tumor cell aggressiveness by wound healing factors - a central role for STAT3.

PubMed

Ekblad, Lars; Lindgren, Gustaf; Persson, Emma; Kjellén, Elisabeth; Wennerberg, Johan

2013-01-25

Local recurrence is a major factor affecting survival after treatment for head and neck squamous cell carcinoma (HNSCC). It is possible that the normal processes involved in wound healing after surgical removal of a primary tumor can boost the regrowth of residual cancer cells, thereby contributing to the recurrent growth. In this work, we collected human wound fluids and used them to investigate the effect of wound healing factors on HNSCC cell lines in vitro. Wound fluids were collected from thyroidectomized patients diagnosed with benign disease and were included in assays of cell proliferation, migration, cell scattering, and invasion. The involvement of intracellular signaling pathways and membrane receptors were investigated by western blotting and the inclusion of specific inhibitors. One out of four cell lines was greatly stimulated in proliferation, migration, cell scattering, and invasion by the addition of wound fluid as compared with addition of fetal bovine or human serum. These effects were accompanied by a sharp increase in activation of signal transducer and activator of transcription 3 (STAT3). Inhibition of STAT3 activation abolished the wound fluid response, showing that STAT3 plays an important role in the wound healing response. Several of the observed phenotypic changes were epithelial-to-mesenchymal transition (EMT)-like, but the appropriate changes were not seen in any of the EMT markers investigated. The involvement of c-Met or epidermal growth factor receptor family members was excluded, while the interleukin-6 receptor was found to be partly responsible for the activation of STAT3. In conclusion, we found cell-line-specific effects of wound healing factors on HNSCC, setting the stage for therapy development and predictive opportunities.

Historical Review of Lower Body Negative Pressure Research in Space Medicine.

PubMed

Campbell, Mark R; Charles, John B

2015-07-01

Cephalad redistribution of intravascular and extravascular fluid occurs as a result of weightlessness during spaceflight. This provokes cardiovascular, cardiopulmonary, and autonomic nervous system responses. The resulting altered functional state can result in orthostatic hypotension and intolerance upon landing and return to a gravity environment. In-flight lower body negative pressure (LBNP) transiently restores normal body fluid distribution. Early in the U.S. space program, LBNP was devised as a way to test for orthostatic intolerance. With the development of the Skylab Program and longer duration spaceflight, it was realized that it could provide a method of monitoring orthostatic intolerance in flight and predicting the post-landing orthostatic response. LBNP was also investigated not only as an in-flight cardiovascular orthostatic stress test, but also as a countermeasure to cardiovascular deconditioning on Soviet space stations, Skylab, and the Shuttle. It is still being used by the Russian program on the International Space Station as an end-of-flight countermeasure.

The elasticity and failure of fluid-filled cellular solids: Theory and experiment

NASA Astrophysics Data System (ADS)

Warner, M.; Thiel, B. L.; Donald, A. M.

2000-02-01

We extend and apply theories of filled foam elasticity and failure to recently available data on foods. The predictions of elastic modulus and failure mode dependence on internal pressure and on wall integrity are borne out by photographic evidence of distortion and failure under compressive loading and under the localized stress applied by a knife blade, and by mechanical data on vegetables differing only in their turgor pressure. We calculate the dry modulus of plate-like cellular solids and the cross over between dry-like and fully fluid-filled elastic response. The bulk elastic properties of limp and aging cellular solids are calculated for model systems and compared with our mechanical data, which also show two regimes of response. The mechanics of an aged, limp beam is calculated, thus offering a practical procedure for comparing experiment and theory. This investigation also thereby offers explanations of the connection between turgor pressure and crispness and limpness of cellular materials.

Mechanical Properties Analysis of 4340 Steel Specimen Heat Treated in Oven and Quenching in Three Different Fluids

NASA Astrophysics Data System (ADS)

Fakir, Rachid; Barka, Noureddine; Brousseau, Jean

2018-03-01

This paper proposes a statistical approach to analyze the mechanical properties of a standard test specimen, of cylindrical geometry and in steel 4340, with a diameter of 6 mm, heat-treated and quenched in three different fluids. Samples were evaluated in standard tensile test to access their characteristic quantities: hardness, modulus of elasticity, yield strength, tensile strength and ultimate deformation. The proposed approach is gradually being built (a) by a presentation of the experimental device, (b) a presentation of the experimental plan and the results of the mechanical tests, (c) anova analysis of variance and a representation of the output responses using the RSM response surface method, and (d) an analysis of the results and discussion. The feasibility and effectiveness of the proposed approach leads to a precise and reliable model capable of predicting the variation of mechanical properties, depending on the tempering temperature, the tempering time and the cooling capacity of the quenching medium.

The elasticity and failure of fluid-filled cellular solids: theory and experiment.

PubMed

Warner, M; Thiel, B L; Donald, A M

2000-02-15

We extend and apply theories of filled foam elasticity and failure to recently available data on foods. The predictions of elastic modulus and failure mode dependence on internal pressure and on wall integrity are borne out by photographic evidence of distortion and failure under compressive loading and under the localized stress applied by a knife blade, and by mechanical data on vegetables differing only in their turgor pressure. We calculate the dry modulus of plate-like cellular solids and the cross over between dry-like and fully fluid-filled elastic response. The bulk elastic properties of limp and aging cellular solids are calculated for model systems and compared with our mechanical data, which also show two regimes of response. The mechanics of an aged, limp beam is calculated, thus offering a practical procedure for comparing experiment and theory. This investigation also thereby offers explanations of the connection between turgor pressure and crispness and limpness of cellular materials.

The elasticity and failure of fluid-filled cellular solids: Theory and experiment

PubMed Central

Warner, M.; Thiel, B. L.; Donald, A. M.

2000-01-01

We extend and apply theories of filled foam elasticity and failure to recently available data on foods. The predictions of elastic modulus and failure mode dependence on internal pressure and on wall integrity are borne out by photographic evidence of distortion and failure under compressive loading and under the localized stress applied by a knife blade, and by mechanical data on vegetables differing only in their turgor pressure. We calculate the dry modulus of plate-like cellular solids and the cross over between dry-like and fully fluid-filled elastic response. The bulk elastic properties of limp and aging cellular solids are calculated for model systems and compared with our mechanical data, which also show two regimes of response. The mechanics of an aged, limp beam is calculated, thus offering a practical procedure for comparing experiment and theory. This investigation also thereby offers explanations of the connection between turgor pressure and crispness and limpness of cellular materials. PMID:10660680

Ion association at discretely-charged dielectric interfaces: Giant charge inversion [Dielectric response controlled ion association at physically heterogeneous surfaces: Giant charge reversal

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Zhi -Yong; Wu, Jianzhong

2017-07-11

Giant charge reversal has been identified for the first time by Monte Carlo simulation for a discretely charged surface in contact with a trivalent electrolyte solution. It takes place regardless of the surface charge density under study and the monovalent salt. In stark contrast to earlier predictions based on the 2-dimensional Wigner crystal model to describe strong correlation of counterions at the macroion surface, we find that giant charge reversal reflects an intricate interplay of ionic volume effects, electrostatic correlations, surface charge heterogeneity, and the dielectric response of the confined fluids. While the novel phenomenon is yet to be confirmedmore » with experiment, the simulation results appear in excellent agreement with a wide range of existing observations in the subregime of charge inversion. Lastly, our findings may have far-reaching implications to understanding complex electrochemical phenomena entailing ionic fluids under dielectric confinements.« less

Prediction of pressure drop in fluid tuned mounts using analytical and computational techniques

NASA Technical Reports Server (NTRS)

Lasher, William C.; Khalilollahi, Amir; Mischler, John; Uhric, Tom

1993-01-01

A simplified model for predicting pressure drop in fluid tuned isolator mounts was developed. The model is based on an exact solution to the Navier-Stokes equations and was made more general through the use of empirical coefficients. The values of these coefficients were determined by numerical simulation of the flow using the commercial computational fluid dynamics (CFD) package FIDAP.

Hard sphere perturbation theory for fluids with soft-repulsive-core potentials

NASA Astrophysics Data System (ADS)

Ben-Amotz, Dor; Stell, George

2004-03-01

The thermodynamic properties of fluids with very soft repulsive-core potentials, resembling those of some liquid metals, are predicted with unprecedented accuracy using a new first-order thermodynamic perturbation theory. This theory is an extension of Mansoori-Canfield/Rasaiah-Stell (MCRS) perturbation theory, obtained by including a configuration integral correction recently identified by Mon, who evaluated it by computer simulation. In this work we derive an analytic expression for Mon's correction in terms of the radial distribution function of the soft-core fluid, g0(r), approximated using Lado's self-consistent extension of Weeks-Chandler-Andersen (WCA) theory. Comparisons with WCA and MCRS predictions show that our new extended-MCRS theory outperforms other first-order theories when applied to fluids with very soft inverse-power potentials (n⩽6), and predicts free energies that are within 0.3kT of simulation results up to the fluid freezing point.

A density functional theory for colloids with two multiple bonding associating sites.

PubMed

Haghmoradi, Amin; Wang, Le; Chapman, Walter G

2016-06-22

Wertheim's multi-density formalism is extended for patchy colloidal fluids with two multiple bonding patches. The theory is developed as a density functional theory to predict the properties of an associating inhomogeneous fluid. The equation of state developed for this fluid depends on the size of the patch, and includes formation of cyclic, branched and linear clusters of associated species. The theory predicts the density profile and the fractions of colloids in different bonding states versus the distance from one wall as a function of bulk density and temperature. The predictions from our theory are compared with previous results for a confined fluid with four single bonding association sites. Also, comparison between the present theory and Monte Carlo simulation indicates a good agreement.

Nonlinear rotordynamics analysis. [Space Shuttle Main Engine turbopumps

NASA Technical Reports Server (NTRS)

Noah, Sherif T.

1991-01-01

Effective analysis tools were developed for predicting the nonlinear rotordynamic behavior of the Space Shuttle Main Engine (SSME) turbopumps under steady and transient operating conditions. Using these methods, preliminary parametric studies were conducted on both generic and actual HPOTP (high pressure oxygen turbopump) models. In particular, a novel modified harmonic balance/alternating Fourier transform (HB/AFT) method was developed and used to conduct a preliminary study of the effects of fluid, bearing and seal forces on the unbalanced response of a multi-disk rotor in the presence of bearing clearances. The method makes it possible to determine periodic, sub-, super-synchronous and chaotic responses of a rotor system. The method also yields information about the stability of the obtained response, thus allowing bifurcation analyses. This provides a more effective capability for predicting the response under transient conditions by searching in proximity of resonance peaks. Preliminary results were also obtained for the nonlinear transient response of an actual HPOTP model using an efficient, newly developed numerical method based on convolution integration. Currently, the HB/AFT is being extended for determining the aperiodic response of nonlinear systems. Initial results show the method to be promising.

Shaded computer graphic techniques for visualizing and interpreting analytic fluid flow models

NASA Technical Reports Server (NTRS)

Parke, F. I.

1981-01-01

Mathematical models which predict the behavior of fluid flow in different experiments are simulated using digital computers. The simulations predict values of parameters of the fluid flow (pressure, temperature and velocity vector) at many points in the fluid. Visualization of the spatial variation in the value of these parameters is important to comprehend and check the data generated, to identify the regions of interest in the flow, and for effectively communicating information about the flow to others. The state of the art imaging techniques developed in the field of three dimensional shaded computer graphics is applied to visualization of fluid flow. Use of an imaging technique known as 'SCAN' for visualizing fluid flow, is studied and the results are presented.

Three-dimensional finite element modeling of pericellular matrix and cell mechanics in the nucleus pulposus of the intervertebral disk based on in situ morphology.

PubMed

Cao, Li; Guilak, Farshid; Setton, Lori A

2011-02-01

Nucleus pulposus (NP) cells of the intervertebral disk (IVD) have unique morphological characteristics and biologic responses to mechanical stimuli that may regulate maintenance and health of the IVD. NP cells reside as single cell, paired or multiple cells in a contiguous pericellular matrix (PCM), whose structure and properties may significantly influence cell and extracellular matrix mechanics. In this study, a computational model was developed to predict the stress-strain, fluid pressure and flow fields for cells and their surrounding PCM in the NP using three-dimensional (3D) finite element models based on the in situ morphology of cell-PCM regions of the mature rat NP, measured using confocal microscopy. Three-dimensional geometries of the extracellular matrix and representative cell-matrix units were used to construct 3D finite element models of the structures as isotropic and biphasic materials. In response to compressive strain of the extracellular matrix, NP cells and PCM regions were predicted to experience volumetric strains that were 1.9-3.7 and 1.4-2.1 times greater than the extracellular matrix, respectively. Volumetric and deviatoric strain concentrations were generally found at the cell/PCM interface, while von Mises stress concentrations were associated with the PCM/extracellular matrix interface. Cell-matrix units containing greater cell numbers were associated with higher peak cell strains and lower rates of fluid pressurization upon loading. These studies provide new model predictions for micromechanics of NP cells that can contribute to an understanding of mechanotransduction in the IVD and its changes with aging and degeneration.

Cerebrospinal fluid dynamics study in communicating hydrocephalus.

PubMed

Ramesh, Vengalathur Ganesan; Narasimhan, Vidhya; Balasubramanian, Chandramouli

2017-01-01

Communicating hydrocephalus often poses a challenge in diagnosis and management decisions. The objective of this study is to measure the opening pressure (P o ), pressure volume index (PVI), and cerebrospinal fluid outflow resistance (R out ), in patients with communicating hydrocephalus using bolus lumbar injection method and to evaluate its diagnostic and prognostic value. The study was conducted in 50 patients with communicating hydrocephalus, including normal pressure hydrocephalus (NPH) (19), post-meningitic hydrocephalus (23) and post-traumatic hydrocephalus (8). An improvised bolus lumbar injection method [the Madras Institute of Neurology (MIN) method] was used. In the NPH Group, the CSF dynamics studies correlated well with the clinico-radiological classification. The prediction of shunt responsiveness by CSF dynamics studies correlated with good outcome in 87.5%. In the post-meningitic hydrocephalus group, the value of CSF dynamics studies in predicting patients needing shunt was 89.5%. The CSF dynamics studies detected patients who needed shunt earlier than clinical or radiological indications. In the post-traumatic hydrocephalus group, 62.5% of patients improved with the treatment based on CSF dynamics studies. The improvised bolus lumbar injection method (MIN method) is a very simple test with fairly reliable and reproducible results. Study of CSF dynamics is a valuable tool in communicating hydrocephalus for confirmation of diagnosis and predicting shunt responsiveness. This is the first time that the value of CSF dynamics has been studied in patients with post-meningitic hydrocephalus. It was also useful for early selection of cases for shunting and for identifying patients with atrophic ventriculomegaly, thereby avoiding unnecessary shunt.

Cerebrospinal fluid dynamics study in communicating hydrocephalus

PubMed Central

Ramesh, Vengalathur Ganesan; Narasimhan, Vidhya; Balasubramanian, Chandramouli

2017-01-01

Context: Communicating hydrocephalus often poses a challenge in diagnosis and management decisions. Aims: The objective of this study is to measure the opening pressure (Po), pressure volume index (PVI), and cerebrospinal fluid outflow resistance (Rout), in patients with communicating hydrocephalus using bolus lumbar injection method and to evaluate its diagnostic and prognostic value. Materials and Methods: The study was conducted in 50 patients with communicating hydrocephalus, including normal pressure hydrocephalus (NPH) (19), post-meningitic hydrocephalus (23) and post-traumatic hydrocephalus (8). An improvised bolus lumbar injection method [the Madras Institute of Neurology (MIN) method] was used. Results: In the NPH Group, the CSF dynamics studies correlated well with the clinico-radiological classification. The prediction of shunt responsiveness by CSF dynamics studies correlated with good outcome in 87.5%. In the post-meningitic hydrocephalus group, the value of CSF dynamics studies in predicting patients needing shunt was 89.5%. The CSF dynamics studies detected patients who needed shunt earlier than clinical or radiological indications. In the post-traumatic hydrocephalus group, 62.5% of patients improved with the treatment based on CSF dynamics studies. Conclusions: The improvised bolus lumbar injection method (MIN method) is a very simple test with fairly reliable and reproducible results. Study of CSF dynamics is a valuable tool in communicating hydrocephalus for confirmation of diagnosis and predicting shunt responsiveness. This is the first time that the value of CSF dynamics has been studied in patients with post-meningitic hydrocephalus. It was also useful for early selection of cases for shunting and for identifying patients with atrophic ventriculomegaly, thereby avoiding unnecessary shunt. PMID:28484522

Methods of use for sensor based fluid detection devices

NASA Technical Reports Server (NTRS)

Lewis, Nathan S. (Inventor)

2001-01-01

Methods of use and devices for detecting analyte in fluid. A system for detecting an analyte in a fluid is described comprising a substrate having a sensor comprising a first organic material and a second organic material where the sensor has a response to permeation by an analyte. A detector is operatively associated with the sensor. Further, a fluid delivery appliance is operatively associated with the sensor. The sensor device has information storage and processing equipment, which is operably connected with the device. This device compares a response from the detector with a stored ideal response to detect the presence of analyte. An integrated system for detecting an analyte in a fluid is also described where the sensing device, detector, information storage and processing device, and fluid delivery device are incorporated in a substrate. Methods for use for the above system are also described where the first organic material and a second organic material are sensed and the analyte is detected with a detector operatively associated with the sensor. The method provides for a device, which delivers fluid to the sensor and measures the response of the sensor with the detector. Further, the response is compared to a stored ideal response for the analyte to determine the presence of the analyte. In different embodiments, the fluid measured may be a gaseous fluid, a liquid, or a fluid extracted from a solid. Methods of fluid delivery for each embodiment are accordingly provided.

Effect of Surface Nonequilibrium Thermochemistry in Simulation of Carbon Based Ablators

NASA Technical Reports Server (NTRS)

Chen, Yih-Kang; Gokcen, Tahir

2012-01-01

This study demonstrates that coupling of a material thermal response code and a flow solver using finite-rate gas/surface interaction model provides time-accurate solutions for multidimensional ablation of carbon based charring ablators. The material thermal response code used in this study is the Two-dimensional Implicit Thermal Response and Ablation Program (TITAN), which predicts charring material thermal response and shape change on hypersonic space vehicles. Its governing equations include total energy balance, pyrolysis gas momentum conservation, and a three-component decomposition model. The flow code solves the reacting Navier-Stokes equations using Data Parallel Line Relaxation (DPLR) method. Loose coupling between material response and flow codes is performed by solving the surface mass balance in DPLR and the surface energy balance in TITAN. Thus, the material surface recession is predicted by finite-rate gas/surface interaction boundary conditions implemented in DPLR, and the surface temperature and pyrolysis gas injection rate are computed in TITAN. Two sets of gas/surface interaction chemistry between air and carbon surface developed by Park and Zhluktov, respectively, are studied. Coupled fluid-material response analyses of stagnation tests conducted in NASA Ames Research Center arc-jet facilities are considered. The ablating material used in these arc-jet tests was a Phenolic Impregnated Carbon Ablator (PICA). Computational predictions of in-depth material thermal response and surface recession are compared with the experimental measurements for stagnation cold wall heat flux ranging from 107 to 1100 Watts per square centimeter.

Effect of Non-Equilibrium Surface Thermochemistry in Simulation of Carbon Based Ablators

NASA Technical Reports Server (NTRS)

Chen, Yih-Kanq; Gokcen, Tahir

2012-01-01

This study demonstrates that coupling of a material thermal response code and a flow solver using non-equilibrium gas/surface interaction model provides time-accurate solutions for the multidimensional ablation of carbon based charring ablators. The material thermal response code used in this study is the Two-dimensional Implicit Thermal-response and AblatioN Program (TITAN), which predicts charring material thermal response and shape change on hypersonic space vehicles. Its governing equations include total energy balance, pyrolysis gas mass conservation, and a three-component decomposition model. The flow code solves the reacting Navier-Stokes equations using Data Parallel Line Relaxation (DPLR) method. Loose coupling between the material response and flow codes is performed by solving the surface mass balance in DPLR and the surface energy balance in TITAN. Thus, the material surface recession is predicted by finite-rate gas/surface interaction boundary conditions implemented in DPLR, and the surface temperature and pyrolysis gas injection rate are computed in TITAN. Two sets of nonequilibrium gas/surface interaction chemistry between air and the carbon surface developed by Park and Zhluktov, respectively, are studied. Coupled fluid-material response analyses of stagnation tests conducted in NASA Ames Research Center arc-jet facilities are considered. The ablating material used in these arc-jet tests was Phenolic Impregnated Carbon Ablator (PICA). Computational predictions of in-depth material thermal response and surface recession are compared with the experimental measurements for stagnation cold wall heat flux ranging from 107 to 1100 Watts per square centimeter.

Control of the induced microgravity environment of the Man Tended Free Flyer (MTFF)

NASA Technical Reports Server (NTRS)

Schlund, Juergen

1988-01-01

Induced disturbance sources have been identified on board the Man Tended Free Flyer (MTFF). Vibration responses at sensitive payload/spacecraft interfaces have been predicted by the application of an empirically found spacecraft dynamic transfer function. Vibrations from fluid loops (Freon, water) and of reaction wheels are assessed to be the main contributors to the induced microgravity environment. The expected payload acceleration response amplitudes presented here are more than one hundred times higher than the admissible values given by the MTFF system requirement, not considering the structural striction-friction effects which could be avoided by appropriate design. Real responses will be significantly lower because the derivation of excitation and transmission functions are based on worst case assumptions. The results indicate that future activities must be concentrated on equipment design improvement and the implementation of vibration reduction along the disturbance transmission path. The activities must be accompanied by early equipment and assembly development tests and transmissibility measurements with the integrated spacecraft engineering and structural models in order to improve the accuracy of payload response predictions.

Thermal/Fluid Analysis of a Composite Heat Exchanger for Use on the RLV Rocket Engine

NASA Technical Reports Server (NTRS)

Nguyen, Dalton

2002-01-01

As part of efforts to design a regeneratively cooled composite nozzle ramp for use on the reusable vehicle (RLV) rocket engine, an C-SiC composites heat exchanger concept was proposed for thermal performance evaluation. To test the feasibility of the concept, sample heat exchanger panels were made to fit the Glenn Research Center's cell 22 for testing. Operation of the heat exchanger was demonstrated in a combustion environment with high heat fluxes similar to the RLV Aerospike Ramp. Test measurements were reviewed and found to be valuable for the on going fluid and thermal analysis of the actual RLV composite ramp. Since the cooling fluid for the heat exchanger is water while the RLV Ramp cooling fluid is LH2, fluid and thermal models were constructed to correlate to the specific test set-up. The knowledge gained from this work will be helpful for analyzing the thermal response of the actual RLV Composite Ramp. The coolant thermal properties for the models are taken from test data. The heat exchanger's cooling performance was analyzed using the Generalized Fluid System Simulation Program (GFSSP). Temperatures of the heat exchanger's structure were predicted in finite element models using Patran and Sinda. Results from the analytical models and the tests show that RSC's heat exchanger satisfied the combustion environments in a series of 16 tests.

Thermal/Fluid Analysis of a Composite Heat Exchanger for Use on the RLV Rocket Engine

NASA Technical Reports Server (NTRS)

Nguyen, Dalton; Turner, Larry D. (Technical Monitor)

2001-01-01

As part of efforts to design a regeneratively cooled composite nozzle ramp for use on the reusable vehicle (RLV) rocket engine, a C-SiC composite heat exchanger concept was proposed for thermal performance evaluation. To test the feasibility of the concept, sample heat exchanger panels were made to fit the Glenn Research Center's cell 22 for testing. Operation of the heat exchanger was demonstrated in a combustion environment with high heat fluxes similar to the RLV Aerospike Ramp. Test measurements were reviewed and found to be valuable for the on-going fluid and thermal analysis of the actual RLV composite ramp. Since the cooling fluid for the heat exchanger is water while the RLV Ramp cooling fluid is LH2, fluid and therma models were constructed to correlate to the specific test set-up. The knowledge gained from this work will be helpful for analyzing the thermal response of the actual RLV Composite Ramp. The coolant thermal properties for the models are taken from test data. The heat exchanger's cooling performance was analyzed using the Generalized Fluid System Simulation Program (GFSSP). Temperatures of the heat exchanger's structure were predicted in finite element models using Patran and Sinda. Results from the analytical models and the tests show that RSC's heat exchanger satisfied the combustion environments in a series of 16 tests.

Investigating Response from Attached and Separated Flow Excitations on a Real Launch Vehicle using SEA

NASA Technical Reports Server (NTRS)

Harrison, Phil; LaVerde, Bruce; Teague,David

2009-01-01

Statistical Energy Analysis (SEA) response has been fairly well anchored to test observations for Diffuse Acoustic Field (DAF) loading by others. Meanwhile, not many examples can be found in the literature anchoring the SEA vehicle panel response results to Turbulent Boundary Layer (TBL) fluctuating pressure excitations. This deficiency is especially true for supersonic trajectories such as those required by this nation s launch vehicles. Response and excitation data from vehicle flight measurements gathered during the development flight era of the Space Shuttle have been used in a trial to assess the sensitivity of response analysis to certain known and unknown parameters of the flight. This assessment compares vibration response predictions for TBL excitations produced by the SEA tool to flight measurements. A secondary, but perhaps more important objective, is to provide more clarity concerning the accuracy and conservatism that can be expected from response estimates to TBL-excited vehicle models in SEA. What range of parameters must be included in such an analysis in order to land on the conservative side in response predictions? What is the variability produced in the results with changes in these parameters? The TBL fluid structure loading model used for this study is provided from the SEA module of the commercial code VA One.

Nonlinear oscillatory rheology and structure of wormlike micellar solutions and colloidal suspensions

NASA Astrophysics Data System (ADS)

Gurnon, Amanda Kate

The complex, nonlinear flow behavior of soft materials transcends industrial applications, smart material design and non-equilibrium thermodynamics. A long-standing, fundamental challenge in soft-matter science is establishing a quantitative connection between the deformation field, local microstructure and macroscopic dynamic flow properties i.e., the rheology. Soft materials are widely used in consumer products and industrial processes including energy recovery, surfactants for personal healthcare (e.g. soap and shampoo), coatings, plastics, drug delivery, medical devices and therapeutics. Oftentimes, these materials are processed by, used during, or exposed to non-equilibrium conditions for which the transient response of the complex fluid is critical. As such, designing new dynamic experiments is imperative to testing these materials and further developing micromechanical models to predict their transient response. Two of the most common classes of these soft materials stand as the focus of the present research; they are: solutions of polymer-like micelles (PLM or also known as wormlike micelles, WLM) and concentrated colloidal suspensions. In addition to their varied applications these two different classes of soft materials are also governed by different physics. In contrast, to the shear thinning behavior of the WLMs at high shear rates, the near hard-sphere colloidal suspensions are known to display increases, sometimes quite substantial, in viscosity (known as shear thickening). The stress response of these complex fluids derive from the shear-induced microstructure, thus measurements of the microstructure under flow are critical for understanding the mechanisms underlying the complex, nonlinear rheology of these complex fluids. A popular micromechanical model is reframed from its original derivation for predicting steady shear rheology of polymers and WLMs to be applicable to weakly nonlinear oscillatory shear flow. The validity, utility and limits of this constitutive model are tested by comparison with experiments on model WLM solutions. Further comparisons to the nonlinear oscillatory shear responses measured from colloidal suspensions establishes this analysis as a promising, quantitative method for understanding the underlying mechanisms responsible for the nonlinear dynamic response of complex fluids. A new experimental technique is developed to measure the microstructure of complex fluids during steady and transient shear flow using small-angle neutron scattering (SANS). The Flow-SANS experimental method is now available to the broader user communities at the NIST Center for Neutron Research, Gaithersburg, MD and the Institut Laue-Langevin, Grenoble, France. Using this new method, a model shear banding WLM solution is interrogated under steady and oscillatory shear. For the first time, the flow-SANS methods identify new metastable states for shear banding WLM solutions, thus establishing the method as capable of probing new states not accessible using traditional steady or linear oscillatory shear methods. The flow-induced three-dimensional microstructure of a colloidal suspension under steady and dynamic oscillatory shear is also measured using these rheo- and flow-SANS methods. A new structure state is identified in the shear thickening regime that proves critical for defining the "hydrocluster" microstructure state of the suspension that is responsible for shear thickening. For both the suspensions and the WLM solutions, stress-SANS rules with the measured microstructures define the individual stress components arising separately from conservative and hydrodynamic forces and these are compared with the macroscopic rheology. Analysis of these results defines the crucial length- and time-scales of the transient microstructure response. The novel dynamic microstructural measurements presented in this dissertation provide new insights into the complexities of shear thickening and shear banding flow phenomena, which are effects observed more broadly across many different types of soft materials. Consequently, the microstructure-rheology property relationships developed for these two classes of complex fluids will aid in the testing and advancement of micromechanical constitutive model development, smart material design, industrial processing and fundamental non-equilibrium thermodynamic research of a broad range of soft materials.

Predicting Athletes' Pre-Exercise Fluid Intake: A Theoretical Integration Approach.

PubMed

Li, Chunxiao; Sun, Feng-Hua; Zhang, Liancheng; Chan, Derwin King Chung

2018-05-21

Pre-exercise fluid intake is an important healthy behavior for maintaining athletes’ sports performances and health. However, athletes’ behavioral adherence to fluid intake and its underlying psychological mechanisms have not been investigated. This prospective study aimed to use a health psychology model that integrates the self-determination theory and the theory of planned behavior for understanding pre-exercise fluid intake among athletes. Participants ( n = 179) were athletes from college sport teams who completed surveys at two time points. Baseline (Time 1) assessment comprised psychological variables of the integrated model (i.e., autonomous and controlled motivation, attitude, subjective norm, perceived behavioral control, and intention) and fluid intake (i.e., behavior) was measured prospectively at one month (Time 2). Path analysis showed that the positive association between autonomous motivation and intention was mediated by subjective norm and perceived behavioral control. Controlled motivation positively predicted the subjective norm. Intentions positively predicted pre-exercise fluid intake behavior. Overall, the pattern of results was generally consistent with the integrated model, and it was suggested that athletes’ pre-exercise fluid intake behaviors were associated with the motivational and social cognitive factors of the model. The research findings could be informative for coaches and sport scientists to promote athletes’ pre-exercise fluid intake behaviors.

Droplet breakup driven by shear thinning solutions in a microfluidic T-junction

NASA Astrophysics Data System (ADS)

Chiarello, Enrico; Gupta, Anupam; Mistura, Giampaolo; Sbragaglia, Mauro; Pierno, Matteo

2017-12-01

Droplet-based microfluidics turned out to be an efficient and adjustable platform for digital analysis, encapsulation of cells, drug formulation, and polymerase chain reaction. Typically, for most biomedical applications, the handling of complex, non-Newtonian fluids is involved, e.g., synovial and salivary fluids, collagen, and gel scaffolds. In this study, we investigate the problem of droplet formation occurring in a microfluidic T-shaped junction, when the continuous phase is made of shear thinning liquids. At first, we review in detail the breakup process, providing extensive, side-by-side comparisons between Newtonian and non-Newtonian liquids over unexplored ranges of flow conditions and viscous responses. The non-Newtonian liquid carrying the droplets is made of Xanthan solutions, a stiff, rodlike polysaccharide displaying a marked shear thinning rheology. By defining an effective Capillary number, a simple yet effective methodology is used to account for the shear-dependent viscous response occurring at the breakup. The droplet size can be predicted over a wide range of flow conditions simply by knowing the rheology of the bulk continuous phase. Experimental results are complemented with numerical simulations of purely shear thinning fluids using lattice Boltzmann models. The good agreement between the experimental and numerical data confirm the validity of the proposed rescaling with the effective Capillary number.

Changes in Ultrasonic Velocity from Fluid Substitution, Calculated with Laboratory Methods, Digital Rock Physics, and Biot Theory

NASA Astrophysics Data System (ADS)

Goldfarb, E. J.; Ikeda, K.; Tisato, N.

2017-12-01

Seismic and ultrasonic velocities of rocks are function of several variables including fluid saturation and type. Understanding the effect of each variable on elastic waves can be valuable when using seismic methods for subsurface modeling. Fluid type and saturation are of specific interest to volcanology, water, and hydrocarbon exploration. Laboratory testing is often employed to understand the effects of fluids on elastic waves. However, laboratory testing is expensive and time consuming. It normally requires cutting rare samples into regular shapes. Fluid injection can also destroy specimens as removing the fluid after testing can prove difficult. Another option is theoretical modeling, which can be used to predict the effect of fluids on elastic properties, but it is often inaccurate. Alternatively, digital rock physics (DRP) can be used to investigate the effect of fluid substitution. DRP has the benefit of being non invasive, as it does not require regular sample shapes or fluid injection. Here, we compare the three methods for dry and saturated Berea sandstone to test the reliability of DRP. First, ultrasonic velocities were obtained from laboratory testing. Second, for comparison, we used a purely theoretical approach - i.e., Hashin-Shtrikman and Biot theory - to estimate the wave speeds at dry and wet conditions. Third, we used DRP. The dry sample was scanned with micro Computed Tomography (µCT), and a three dimensional (3D) array was recorded. We employed a segmentation-less method to convert each 3D array value to density, porosity, elastic moduli, and wave speeds. Wave propagation was simulated numerically at similar frequency as the laboratory. To simulate fluid substitution, we numerically substituted air values for water and repeated the simulation. The results from DRP yielded similar velocities to the laboratory, and accurately predicted the velocity change from fluid substitution. Theoretical modeling could not accurately predict velocity, and under-predicted the velocity change from fluid substitution. The mathematical approach proved to be a poor comparison for the laboratory measurement. DRP proved to be effective, and could be used in future with drill cuttings, perhaps to limit the use of expensive cores. DRP could also limit the requirement for physically testing fluid substitution.

The prediction of self-care behaviors in end-stage renal disease patients using Leventhal's Self-Regulatory Model.

PubMed

O'Connor, Susan M; Jardine, Alan G; Millar, Keith

2008-08-01

To assess the utility of Leventhal's Self-Regulatory Model (SRM) to predict self-care behavior with regard to dietary, medication, and fluid regimes in end-stage renal disease (ESRD) patients. In a prospective study, ESRD patients treated via hospital-based haemodialysis (N=73) were screened for cognitive deficits and completed questionnaires that enquired about illness perceptions, coping strategies, knowledge of kidney disease, and psychological distress at Time 1. Physiological proxy measures of self-care behaviors regarding diet (serum potassium levels), fluid intake (mean and standard deviation of interdialytic weight gain), and medication (serum phosphate levels) regimes were collected 3 weeks later at Time 2. Illness representations (emotional and timeline perceptions) predicted self-care behaviors with regard to diet and medication. Emotion-focused coping strategies predicted higher levels of variation in adherence to fluid restrictions. Younger males were less likely to adhere to the fluid restrictions. The SRM has predictive utility. Psychological interventions should focus on alleviating disease-specific distress and challenging erroneous timeline perceptions in order to increase adherence to dietary and medication regimes in ESRD patients. A more specific measure of coping for ESRD is required to clarify the role of coping strategies in this population. Younger, male patients should be targeted for extra support with fluid restrictions.

The fluid mechanics of the inner-ear disorder BPPV

NASA Astrophysics Data System (ADS)

Weidman, Michael; Squires, Todd; Stone, Howard

2001-11-01

The inner ear of mammals contains fluid-filled semi-circular canals with a flexible sensory membrane (called a cupula) which detects rotational acceleration. Benign Paroxysmal Positional Vertigo (BPPV) is one of the most common disorders of this system diagnosed today, and is characterized by symptoms of dizziness and nausea brought on by sudden changes in head orientation. BPPV is believed to have a mechanical (rather than nervous) origin, in which dense particles called otoconia settle into the canals and trigger false sensations of rotational acceleration. Several qualitative mechanisms have been proposed by the medical community, which we examine from a fluid mechanical standpoint. Traditionally, the semicircular canal and the cupula are modeled as an over-damped torsional pendulum with a driving force provided by rotational acceleration. We extend this model to include the time-dependent mechanical response owing to sedimentation of the otoconia. We make qualitative and quantitative predictions associated with the proposed mechanisms, with an eye towards differentiating between them and perhaps towards more effective diagnostic and therapeutic methods.

DNA methylation-based age prediction from various tissues and body fluids

PubMed Central

Jung, Sang-Eun; Shin, Kyoung-Jin; Lee, Hwan Young

2017-01-01

Aging is a natural and gradual process in human life. It is influenced by heredity, environment, lifestyle, and disease. DNA methylation varies with age, and the ability to predict the age of donor using DNA from evidence materials at a crime scene is of considerable value in forensic investigations. Recently, many studies have reported age prediction models based on DNA methylation from various tissues and body fluids. Those models seem to be very promising because of their high prediction accuracies. In this review, the changes of age-associated DNA methylation and the age prediction models for various tissues and body fluids were examined, and then the applicability of the DNA methylation-based age prediction method to the forensic investigations was discussed. This will improve the understandings about DNA methylation markers and their potential to be used as biomarkers in the forensic field, as well as the clinical field. PMID:28946940

Bartter syndrome prenatal diagnosis based on amniotic fluid biochemical analysis.

PubMed

Garnier, Arnaud; Dreux, Sophie; Vargas-Poussou, Rosa; Oury, Jean-François; Benachi, Alexandra; Deschênes, Georges; Muller, Françoise

2010-03-01

Bartter syndrome is an autosomic recessive disease characterized by severe polyuria and sodium renal loss. The responsible genes encode proteins involved in electrolyte tubular reabsorption. Prenatal manifestations, mainly recurrent polyhydramnios because of fetal polyuria, lead to premature delivery. After birth, polyuria leads to life-threatening dehydration. Prenatal genetic diagnosis needs an index case. The aim of this study was to analyze amniotic fluid biochemistry for the prediction of Bartter syndrome. We retrospectively studied 16 amniotic fluids of Bartter syndrome-affected fetuses diagnosed after birth, only six of them being genetically proven. We assayed total proteins, alpha-fetoprotein, and electrolytes and defined a Bartter index corresponding to the multiplication of total protein and of alpha-fetoprotein. Results were compared with two control groups matched for gestational age-non-Bartter polyhydramnios (n = 30) and nonpolyhydramnios (n = 60). In Bartter syndrome, we observed significant differences (p < 0.0001) for protein amniotic fluid levels when compared with the two control groups (1.55 g/L, 3.9 g/L, and 5.2 g/L, respectively) and low Bartter index (0.16, 0.82, and 1.0, respectively). No statistical difference was observed for electrolytes. In conclusion, Bartter syndrome can be prenatally suspected on amniotic fluid biochemistry (sensitivity 93% and specificity 100%), allowing appropriate management before and after birth.

Computational fluid dynamics (CFD) insights into agitation stress methods in biopharmaceutical development.

PubMed

Bai, Ge; Bee, Jared S; Biddlecombe, James G; Chen, Quanmin; Leach, W Thomas

2012-02-28

Agitation of small amounts of liquid is performed routinely in biopharmaceutical process, formulation, and packaging development. Protein degradation commonly results from agitation, but the specific stress responsible or degradation mechanism is usually not well understood. Characterization of the agitation stress methods is critical to identifying protein degradation mechanisms or specific sensitivities. In this study, computational fluid dynamics (CFD) was used to model agitation of 1 mL of fluid by four types of common laboratory agitation instruments, including a rotator, orbital shaker, magnetic stirrer and vortex mixer. Fluid stresses in the bulk liquid and near interfaces were identified, quantified and compared. The vortex mixer provides the most intense stresses overall, while the stir bar system presented locally intense shear proximal to the hydrophobic stir bar surface. The rotator provides gentler fluid stresses, but the air-water interfacial area and surface stresses are relatively high given its low rotational frequency. The orbital shaker provides intermediate-level stresses but with the advantage of a large stable platform for consistent vial-to-vial homogeneity. Selection of experimental agitation methods with targeted types and intensities of stresses can facilitate better understanding of protein degradation mechanisms and predictability for "real world" applications. Copyright © 2011 Elsevier B.V. All rights reserved.

Matrix metalloproteinase and tissue inhibitor of metalloproteinase in serum and synovial fluid of osteoarthritic dogs.

PubMed

Salinardi, B J; Roush, J K; Schermerhorn, T; Mitchell, K E

2006-01-01

To better understand the mechanisms responsible for the pathological processes of osteoarthritis (OA) and to potentially identify a profile of changes that could be predictive of early OA, matrix metalloproteinase-1 (MMP-1) and tissue inhibitor of matrix metalloproteinase-2 (TIMP-2) in the synovial fluid and serum of normal and osteoarthritic dogs were examined. The concentration of MMP-1 in the synovial fluid of osteoarthritic dogs (0.62 +/- 0.16), as measured by densitometry, was significantly higher than that found in control dogs (0.42 +/- 0.19) (P = 0.03). The concentration of MMP-1 in the serum of osteoarthritic dogs (0.74 +/- 0.16) was significantly less than that found in control dogs (0.87 +/- 0.08) (P = 0.05). The concentration of TIMP-2 in the synovial fluid of osteoarthritic dogs (46.2 +/- 21.9 ng/ml) was significantly less than that of control dogs (122.0 +/- 66.5 ng/ml) (P = 0.009). The concentration of TIMP-2 in the serum of osteoarthritic dogs (116.2 +/- 43.1 ng/ml) was not significantly different than that of control dogs (95.1 +/- 94.4 ng/ml) (P = 0.554). In addition, a phospho-tyrosine immunoprecipitation and mass spectrometry were used to isolate and identify interferon-alpha in canine synovial fluid.

Orientational dynamics of a triaxial ellipsoid in simple shear flow: Influence of inertia.

PubMed

Rosén, Tomas; Kotsubo, Yusuke; Aidun, Cyrus K; Do-Quang, Minh; Lundell, Fredrik

2017-07-01

The motion of a single ellipsoidal particle in simple shear flow can provide valuable insights toward understanding suspension flows with nonspherical particles. Previously, extensive studies have been performed on the ellipsoidal particle with rotational symmetry, a so-called spheroid. The nearly prolate ellipsoid (one major and two minor axes of almost equal size) is known to perform quasiperiodic or even chaotic orbits in the absence of inertia. With small particle inertia, the particle is also known to drift toward this irregular motion. However, it is not previously understood what effects from fluid inertia could be, which is of highest importance for particles close to neutral buoyancy. Here, we find that fluid inertia is acting strongly to suppress the chaotic motion and only very weak fluid inertia is sufficient to stabilize a rotation around the middle axis. The mechanism responsible for this transition is believed to be centrifugal forces acting on fluid, which is dragged along with the rotational motion of the particle. With moderate fluid inertia, it is found that nearly prolate triaxial particles behave similarly to the perfectly spheroidal particles. Finally, we also are able to provide predictions about the stable rotational states for the general triaxial ellipsoid in simple shear with weak inertia.

Fluid Flow Characteristics and Porosity Behavior in Full Penetration Laser Welding of a Titanium Alloy

NASA Astrophysics Data System (ADS)

Chang, Baohua; Allen, Chris; Blackburn, Jon; Hilton, Paul; Du, Dong

2015-04-01

In this paper, a computational fluid mechanics model is developed for full penetration laser welding of titanium alloy Ti6Al4V. This has been used to analyze possible porosity formation mechanisms, based on predictions of keyhole behavior and fluid flow characteristics in the weld pool. Numerical results show that when laser welding 3 mm thickness titanium alloy sheets with given laser beam focusing optics, keyhole depth oscillates before a full penetration keyhole is formed, but thereafter keyhole collapses are not predicted numerically. For lower power, lower speed welding, the fluid flow behind the keyhole is turbulent and unstable, and vortices are formed. Molten metal is predicted to flow away from the center plane of the weld pool, and leave a gap or void within the weld pool behind the keyhole. For higher power, higher speed welding, fluid flow is less turbulent, and such vortices are not formed. Corresponding experimental results show that porosity was absent in the melt runs made at higher power and higher welding speed. In contrast, large pores were present in melt runs made at lower power and lower welding speed. Based on the combination of experimental results and numerical predictions, it is proposed that porosity formation when keyhole laser welding may result from turbulent fluid flow behind the keyhole, with the larger the value of associated Reynolds number, the higher the possibility of porosity formation. For such fluid flow controlled porosities, measures to decrease Reynolds number of the fluid flow close to the keyhole could prove effective in reducing or avoiding porosity.

Seismicity rate surge on faults after shut-in: poroelastic response to fluid injection

NASA Astrophysics Data System (ADS)

Chang, K. W.; Yoon, H.; Martinez, M. J.

2017-12-01

Subsurface energy activities such as geological CO2 storage and wastewater injection require injecting large amounts of fluid into the subsurface, which will alter the states of pore pressure and stress in the storage formation. One of the main issues for injection-induced seismicity is the post shut-in increases in the seismicity rate, often observed in the fluid-injection operation sites. The rate surge can be driven by the following mechanisms: (1) pore-pressure propagation into distant faults after shut-in and (2) poroelastic stressing caused by well operations, depending on fault geometry, hydraulic and mechanical properties of the formation, and injection history. We simulate the aerial view of the target reservoir intersected by strike-slip faults, in which injection-induced pressure buildup encounters the faults directly. We examine the poroelastic response of the faults to fluid injection and perform a series of sensitivity tests considering: (1) permeability of the fault zone, (2) locations and the number of faults with respect to the injection point, and (3) well operations with varying the injection rate. Our analysis of the Coulomb stress change suggests that the sealing fault confines pressure diffusion which stabilizes or weakens the nearby conductive fault depending on the injection location. We perform the sensitivity test by changing injection scenarios (time-dependent rates), while keeping the total amount of injected fluids. Sensitivity analysis shows that gradual reduction of the injection rate minimizes the Coulomb stress change and the least seismicity rates are predicted. Sandia National Laboratories is a multimission laboratory managed and operated by National Technology and Engineering Solutions of Sandia, LLC., a wholly owned subsidiary of Honeywell International, Inc., for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-NA-0003525.

Correlation between CD64 and PCT levels in cerebrospinal fluid and degree of hearing impairment sequelae in neonates with purulent meningitis.

PubMed

Liu, Cui; Zhao, Dongchi

2017-12-01

This study investigated the possible correlation between the degree of hearing impairment caused by neonatal purulent meningitis and the levels of CD64 and PCT in cerebrospinal fluid of patients, and assessed the prognostic value of such levels. We recorded data from 156 cases of neonatal purulent meningitis retrospectively. All the patients received brainstem response audiometry, and cerebrospinal fluid samples were collected within the first day after admission through lumbar puncture. Flow cytometry was used to detect CD64 levels and enzyme-linked fluorescent assay was used to detect PCT levels. The children with hearing impairment were followed up for 1 year and brainstem response audiometry was performed again in them. We found that 43.59% of the children showed different degrees of hearing impairment, and 55% of them did not fully recover. The levels of PCT and CD64 in cerebrospinal fluid of children with hearing impairment were significantly higher than those of children with normal hearing (P<0.01). The levels of PCT and CD64 in mild, moderate and severe hearing impaired children increased gradually with higher degrees of impairment, and the differences between groups were significant (P<0.01). During the follow-up, it was found that the levels of PCT and CD64 in children correlated well with the degree of hearing recovery, and the differences between groups were significant (P<0.01). In our study, approximately 1/4 children with purulent meningitis showed long-term hearing impairment. Based on our analyses, the levels of CD64 and PCT in cerebrospinal fluid can be used to predict the degree and long-term prognosis of hearing impairment caused by purulent meningitis in children.

Dissertation Defense Computational Fluid Dynamics Uncertainty Analysis for Payload Fairing Spacecraft Environmental Control Systems

NASA Technical Reports Server (NTRS)

Groves, Curtis Edward

2014-01-01

Spacecraft thermal protection systems are at risk of being damaged due to airflow produced from Environmental Control Systems. There are inherent uncertainties and errors associated with using Computational Fluid Dynamics to predict the airflow field around a spacecraft from the Environmental Control System. This paper describes an approach to quantify the uncertainty in using Computational Fluid Dynamics to predict airflow speeds around an encapsulated spacecraft without the use of test data. Quantifying the uncertainty in analytical predictions is imperative to the success of any simulation-based product. The method could provide an alternative to traditional "validation by test only" mentality. This method could be extended to other disciplines and has potential to provide uncertainty for any numerical simulation, thus lowering the cost of performing these verifications while increasing the confidence in those predictions. Spacecraft requirements can include a maximum airflow speed to protect delicate instruments during ground processing. Computational Fluid Dynamics can be used to verify these requirements; however, the model must be validated by test data. This research includes the following three objectives and methods. Objective one is develop, model, and perform a Computational Fluid Dynamics analysis of three (3) generic, non-proprietary, environmental control systems and spacecraft configurations. Several commercially available and open source solvers have the capability to model the turbulent, highly three-dimensional, incompressible flow regime. The proposed method uses FLUENT, STARCCM+, and OPENFOAM. Objective two is to perform an uncertainty analysis of the Computational Fluid Dynamics model using the methodology found in "Comprehensive Approach to Verification and Validation of Computational Fluid Dynamics Simulations". This method requires three separate grids and solutions, which quantify the error bars around Computational Fluid Dynamics predictions. The method accounts for all uncertainty terms from both numerical and input variables. Objective three is to compile a table of uncertainty parameters that could be used to estimate the error in a Computational Fluid Dynamics model of the Environmental Control System /spacecraft system. Previous studies have looked at the uncertainty in a Computational Fluid Dynamics model for a single output variable at a single point, for example the re-attachment length of a backward facing step. For the flow regime being analyzed (turbulent, three-dimensional, incompressible), the error at a single point can propagate into the solution both via flow physics and numerical methods. Calculating the uncertainty in using Computational Fluid Dynamics to accurately predict airflow speeds around encapsulated spacecraft in is imperative to the success of future missions.

Dissertation Defense: Computational Fluid Dynamics Uncertainty Analysis for Payload Fairing Spacecraft Environmental Control Systems

NASA Technical Reports Server (NTRS)

Groves, Curtis Edward

2014-01-01

Spacecraft thermal protection systems are at risk of being damaged due to airflow produced from Environmental Control Systems. There are inherent uncertainties and errors associated with using Computational Fluid Dynamics to predict the airflow field around a spacecraft from the Environmental Control System. This paper describes an approach to quantify the uncertainty in using Computational Fluid Dynamics to predict airflow speeds around an encapsulated spacecraft without the use of test data. Quantifying the uncertainty in analytical predictions is imperative to the success of any simulation-based product. The method could provide an alternative to traditional validation by test only mentality. This method could be extended to other disciplines and has potential to provide uncertainty for any numerical simulation, thus lowering the cost of performing these verifications while increasing the confidence in those predictions.Spacecraft requirements can include a maximum airflow speed to protect delicate instruments during ground processing. Computational Fluid Dynamics can be used to verify these requirements; however, the model must be validated by test data. This research includes the following three objectives and methods. Objective one is develop, model, and perform a Computational Fluid Dynamics analysis of three (3) generic, non-proprietary, environmental control systems and spacecraft configurations. Several commercially available and open source solvers have the capability to model the turbulent, highly three-dimensional, incompressible flow regime. The proposed method uses FLUENT, STARCCM+, and OPENFOAM. Objective two is to perform an uncertainty analysis of the Computational Fluid Dynamics model using the methodology found in Comprehensive Approach to Verification and Validation of Computational Fluid Dynamics Simulations. This method requires three separate grids and solutions, which quantify the error bars around Computational Fluid Dynamics predictions. The method accounts for all uncertainty terms from both numerical and input variables. Objective three is to compile a table of uncertainty parameters that could be used to estimate the error in a Computational Fluid Dynamics model of the Environmental Control System spacecraft system.Previous studies have looked at the uncertainty in a Computational Fluid Dynamics model for a single output variable at a single point, for example the re-attachment length of a backward facing step. For the flow regime being analyzed (turbulent, three-dimensional, incompressible), the error at a single point can propagate into the solution both via flow physics and numerical methods. Calculating the uncertainty in using Computational Fluid Dynamics to accurately predict airflow speeds around encapsulated spacecraft in is imperative to the success of future missions.

Computational Fluid Dynamics Uncertainty Analysis for Payload Fairing Spacecraft Environmental Control Systems

NASA Technical Reports Server (NTRS)

Groves, Curtis E.

2013-01-01

Spacecraft thermal protection systems are at risk of being damaged due to airflow produced from Environmental Control Systems. There are inherent uncertainties and errors associated with using Computational Fluid Dynamics to predict the airflow field around a spacecraft from the Environmental Control System. This proposal describes an approach to validate the uncertainty in using Computational Fluid Dynamics to predict airflow speeds around an encapsulated spacecraft. The research described here is absolutely cutting edge. Quantifying the uncertainty in analytical predictions is imperative to the success of any simulation-based product. The method could provide an alternative to traditional"validation by test only'' mentality. This method could be extended to other disciplines and has potential to provide uncertainty for any numerical simulation, thus lowering the cost of performing these verifications while increasing the confidence in those predictions. Spacecraft requirements can include a maximum airflow speed to protect delicate instruments during ground processing. Computationaf Fluid Dynamics can be used to veritY these requirements; however, the model must be validated by test data. The proposed research project includes the following three objectives and methods. Objective one is develop, model, and perform a Computational Fluid Dynamics analysis of three (3) generic, non-proprietary, environmental control systems and spacecraft configurations. Several commercially available solvers have the capability to model the turbulent, highly three-dimensional, incompressible flow regime. The proposed method uses FLUENT and OPEN FOAM. Objective two is to perform an uncertainty analysis of the Computational Fluid . . . Dynamics model using the methodology found in "Comprehensive Approach to Verification and Validation of Computational Fluid Dynamics Simulations". This method requires three separate grids and solutions, which quantify the error bars around Computational Fluid Dynamics predictions. The method accounts for all uncertainty terms from both numerical and input variables. Objective three is to compile a table of uncertainty parameters that could be used to estimate the error in a Computational Fluid Dynamics model of the Environmental Control System /spacecraft system. Previous studies have looked at the uncertainty in a Computational Fluid Dynamics model for a single output variable at a single point, for example the re-attachment length of a backward facing step. To date, the author is the only person to look at the uncertainty in the entire computational domain. For the flow regime being analyzed (turbulent, threedimensional, incompressible), the error at a single point can propagate into the solution both via flow physics and numerical methods. Calculating the uncertainty in using Computational Fluid Dynamics to accurately predict airflow speeds around encapsulated spacecraft in is imperative to the success of future missions.

Cerebrospinal fluid pulse pressure amplitude during lumbar infusion in idiopathic normal pressure hydrocephalus can predict response to shunting

PubMed Central

2010-01-01

Background We have previously seen that idiopathic normal pressure hydrocephalus (iNPH) patients having elevated intracranial pressure (ICP) pulse amplitude consistently respond to shunt surgery. In this study we explored how the cerebrospinal fluid pressure (CSFP) pulse amplitude determined during lumbar infusion testing, correlates with ICP pulse amplitude determined during over-night ICP monitoring and with response to shunt surgery. Our goal was to establish a more reliable screening procedure for selecting iNPH patients for shunt surgery using lumbar intrathecal infusion. Methods The study population consisted of all iNPH patients undergoing both diagnostic lumbar infusion testing and continuous over-night ICP monitoring during the period 2002-2007. The severity of iNPH was assessed using our NPH grading scale before surgery and 12 months after shunting. The CSFP pulse was characterized from the amplitude of single pressure waves. Results Totally 62 iNPH patients were included, 45 of them underwent shunt surgery, in whom 78% were shunt responders. Among the 45 shunted patients, resistance to CSF outflow (Rout) was elevated (≥ 12 mmHg/ml/min) in 44. The ICP pulse amplitude recorded over-night was elevated (i.e. mean ICP wave amplitude ≥ 4 mmHg) in 68% of patients; 92% of these were shunt responders. In those with elevated overnight ICP pulse amplitude, we found also elevated CSFP pulse amplitude recorded during lumbar infusion testing, both during the opening phase following lumbar puncture and during a standardized period of lumbar infusion (15 ml Ringer over 10 min). The clinical response to shunting after 1 year strongly associated with the over-night ICP pulse amplitude, and also with the pulsatile CSFP during the period of lumbar infusion. Elevated CSFP pulse amplitude during lumbar infusion thus predicted shunt response with sensitivity of 88 and specificity of 60 (positive and negative predictive values of 89 and 60, respectively). Conclusions In iNPH patients, shunt response can be anticipated in 9/10 patients with elevated overnight ICP pulse amplitude, while in only 1/10 with low ICP pulse amplitude. Additionally, the CSFP pulse amplitude during lumbar infusion testing was elevated in patients with elevated over-night ICP pulse amplitude. In particular, measurement of CSFP pulse amplitude during a standardized infusion of 15 ml Ringer over 10 min was useful in predicting response to shunt surgery and can be used as a screening procedure for selection of iNPH patients for shunting. PMID:20205911

Stimuli Responsive/Rheoreversible Hydraulic Fracturing Fluids for Enhanced Geothermal Energy Production (Part II)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bonneville, Alain; Jung, Hun Bok; Shao, Hongbo

We have used an environmentally friendly and recyclable hydraulic fracturing fluid - diluted aqueous solutions of polyallylamine or PAA – for reservoir stimulation in Enhanced Geothermal System (EGS). This fluid undergoes a controlled and large volume expansion with a simultaneous increase in viscosity triggered by CO2 at EGS temperatures. We are presenting here the results of laboratory-scale hydraulic fracturing experiment using the fluid on small cylindrical rock cores (1.59 cm in diameter and 5.08 cm in length) from the Coso geothermal field in California. Rock samples consisted of Mesozoic diorite metamorphosed to greenschist facies. The experiments were conducted on 5more » samples for realistic ranges of pressures (up to 275 bar) and temperatures (up to 210 °C) for both the rock samples and the injected fluid. After fracturing, cores were subjected to a CO2 leakage test, injection of KI solution, and X-ray microtomography (XMT) scanning to examine the formation and distribution of fractures. The design and conduct of these experiments will be presented and discussed in details. Based on the obtained XMT images, Computational Fluid Dynamics (CFD) simulations were then performed to visualize hydraulic fractures and compute the bulk permeability. OpenFOAM (OpenCFD Ltd., Reading, UK), was used to solve the steady state simulation. The flow predictions, based upon the laminar, 3-D, incompressible Navier-Stokes equations for fluid mass and momentum, show the remarkable stimulation of the permeability in the core samples and demonstrate the efficiency of such a CO2 triggered fluid in EGS.« less

Predicting low-temperature free energy landscapes with flat-histogram Monte Carlo methods

NASA Astrophysics Data System (ADS)

Mahynski, Nathan A.; Blanco, Marco A.; Errington, Jeffrey R.; Shen, Vincent K.

2017-02-01

We present a method for predicting the free energy landscape of fluids at low temperatures from flat-histogram grand canonical Monte Carlo simulations performed at higher ones. We illustrate our approach for both pure and multicomponent systems using two different sampling methods as a demonstration. This allows us to predict the thermodynamic behavior of systems which undergo both first order and continuous phase transitions upon cooling using simulations performed only at higher temperatures. After surveying a variety of different systems, we identify a range of temperature differences over which the extrapolation of high temperature simulations tends to quantitatively predict the thermodynamic properties of fluids at lower ones. Beyond this range, extrapolation still provides a reasonably well-informed estimate of the free energy landscape; this prediction then requires less computational effort to refine with an additional simulation at the desired temperature than reconstruction of the surface without any initial estimate. In either case, this method significantly increases the computational efficiency of these flat-histogram methods when investigating thermodynamic properties of fluids over a wide range of temperatures. For example, we demonstrate how a binary fluid phase diagram may be quantitatively predicted for many temperatures using only information obtained from a single supercritical state.

Turbine Engine Hot Section Technology, 1984

NASA Technical Reports Server (NTRS)

1984-01-01

Presentations were made concerning the hot section environment and behavior of combustion liners, turbine blades, and waves. The presentations were divided into six sessions: instrumentation, combustion, turbine heat transfer, structural analysis, fatigue and fracture, and surface properties. The principal objective of each session was to disseminate research results to date, along with future plans. Topics discussed included modeling of thermal and fluid flow phenomena, structural analysis, fatigue and fracture, surface protective coatings, constitutive behavior, stress-strain response, and life prediction methods.

Observation of a new surface mode on a fluid-saturated permeable solid

NASA Astrophysics Data System (ADS)

Nagy, Peter B.

1992-06-01

Almost ten years ago, S. Feng and D. L. Johnson predicted the presence of a new surface mode on a fluid/fluid-saturated porous solid interface with closed surface pores [J. Acoust. Soc. Am. 74, 906 (1983)]. We found that, due to surface tension, practically closed-pore boundary conditions can prevail at an interface between a nonwetting fluid (e.g., air) and a porous solid saturated with a wetting fluid (e.g., water or alcohol). Surface wave velocity and attenuation measurements were made on alcohol-saturated porous sintered glass at 100 kHz. The experimental results show clear evidence of the new ``slow'' surface mode predicted by Feng and Johnson.

Fluid sampling device

NASA Technical Reports Server (NTRS)

Studenick, D. K. (Inventor)

1977-01-01

An inlet leak is described for sampling gases, more specifically, for selectively sampling multiple fluids. This fluid sampling device includes a support frame. A plurality of fluid inlet devices extend through the support frame and each of the fluid inlet devices include a longitudinal aperture. An opening device that is responsive to a control signal selectively opens the aperture to allow fluid passage. A closing device that is responsive to another control signal selectively closes the aperture for terminating further fluid flow.

Male Mating Rate Is Constrained by Seminal Fluid Availability in Bedbugs, Cimex lectularius

PubMed Central

Reinhardt, Klaus; Naylor, Richard; Siva-Jothy, Michael T.

2011-01-01

Sexual selection, differences in reproductive success between individuals, continues beyond acquiring a mating partner and affects ejaculate size and composition (sperm competition). Sperm and seminal fluid have very different roles in sperm competition but both components encompass production costs for the male. Theoretical models predict that males should spend ejaculate components prudently and differently for sperm and seminal fluid but empirical evidence for independent variation of sperm number and seminal fluid volume is scarce. It is also largely unknown how sperm and seminal fluid variation affect future mating rate. In bedbugs we developed a protocol to examine the role of seminal fluids in ejaculate allocation and its effect on future male mating rate. Using age-related changes in sperm and seminal fluid volume we estimated the lowest capacity at which mating activity started. We then showed that sexually active males allocate 12% of their sperm and 19% of their seminal fluid volume per mating and predicted that males would be depleted of seminal fluid but not of sperm. We tested (and confirmed) this prediction empirically. Finally, the slightly faster replenishment of seminal fluid compared to sperm did not outweigh the faster decrease during mating. Our results suggest that male mating rate can be constrained by the availability of seminal fluids. Our protocol might be applicable to a range of other organisms. We discuss the idea that economic considerations in sexual conflict research might benefit from distinguishing between costs and benefits that are ejaculate dose-dependent and those that are frequency-dependent on the mating rate per se. PMID:21779378

Developing an effective means to reduce 5-hydroxymethyl-2-furfural from caramel colour.

PubMed

Guan, Yongguang; Chen, Mingshun; Yu, Shujuan; Tang, Qiang; Yan, He

2014-01-15

Supercritical carbon dioxide fluid extraction was used to extract 5-hydroxymethyl-2-furfural from caramel colour (solid content was about 75%). The procedure was carried out by response surface methodology using a quadratic polynomial model. Extraction pressure, time, temperature and ethanol content were selected as the independent variables. Conditions to obtain the highest extraction ratio of 5-hydroxymethyl-2-furfural were determined to be an extraction pressure of 21.65MPa, time of 46.7min, temperature of 35°C and 70% ethanol content of caramel colour. The predicted 5-hydroxymethyl-2-furfural extraction ratio was 87.42%. Under the conditions stated above, the experimental value of 5-hydroxymethyl-2-furfural extraction ratio was 86.98%, which was similar to the predicted value by the model. This study indicated that supercritical carbon dioxide fluid extraction can effectively reduce 5-hydroxymethyl-2-furfural from caramel colour, which can help food industry to improve the safety of the food material, as well as provide more healthy caramel colour for human beings. Copyright © 2013 Elsevier Ltd. All rights reserved.

First and second sound in cylindrically trapped gases.

PubMed

Bertaina, G; Pitaevskii, L; Stringari, S

2010-10-08

We investigate the propagation of density and temperature waves in a cylindrically trapped gas with radial harmonic confinement. Starting from two-fluid hydrodynamic theory we derive effective 1D equations for the chemical potential and the temperature which explicitly account for the effects of viscosity and thermal conductivity. Differently from quantum fluids confined by rigid walls, the harmonic confinement allows for the propagation of both first and second sound in the long wavelength limit. We provide quantitative predictions for the two sound velocities of a superfluid Fermi gas at unitarity. For shorter wavelengths we discover a new surprising class of excitations continuously spread over a finite interval of frequencies. This results in a nondissipative damping in the response function which is analytically calculated in the limiting case of a classical ideal gas.

Inferior vena cava collapsibility detects fluid responsiveness among spontaneously breathing critically-ill patients.

PubMed

Corl, Keith A; George, Naomi R; Romanoff, Justin; Levinson, Andrew T; Chheng, Darin B; Merchant, Roland C; Levy, Mitchell M; Napoli, Anthony M

2017-10-01

Measurement of inferior vena cava collapsibility (cIVC) by point-of-care ultrasound (POCUS) has been proposed as a viable, non-invasive means of assessing fluid responsiveness. We aimed to determine the ability of cIVC to identify patients who will respond to additional intravenous fluid (IVF) administration among spontaneously breathing critically-ill patients. Prospective observational trial of spontaneously breathing critically-ill patients. cIVC was obtained 3cm caudal from the right atrium and IVC junction using POCUS. Fluid responsiveness was defined as a≥10% increase in cardiac index following a 500ml IVF bolus; measured using bioreactance (NICOM™, Cheetah Medical). cIVC was compared with fluid responsiveness and a cIVC optimal value was identified. Of the 124 participants, 49% were fluid responders. cIVC was able to detect fluid responsiveness: AUC=0.84 [0.76, 0.91]. The optimum cutoff point for cIVC was identified as 25% (LR+ 4.56 [2.72, 7.66], LR- 0.16 [0.08, 0.31]). A cIVC of 25% produced a lower misclassification rate (16.1%) for determining fluid responsiveness than the previous suggested cutoff values of 40% (34.7%). IVC collapsibility, as measured by POCUS, performs well in distinguishing fluid responders from non-responders, and may be used to guide IVF resuscitation among spontaneously breathing critically-ill patients. Copyright © 2017 Elsevier Inc. All rights reserved.

Measurement and prediction of flow through a replica segment of a mildly atherosclerotic coronary artery of man

NASA Technical Reports Server (NTRS)

Back, L. H.; Radbill, J. R.; Cho, Y. I.; Crawford, D. W.

1986-01-01

Pressure distributions were measured along a hollow vascular axisymmetric replica of a segment of the left circumflex coronary artery of man with mildly atherosclerotic diffuse disease. A large range of physiological Reynolds numbers from about 60 to 500, including hyperemic response, was spanned in the flows investigation using a fluid simulating blood kinematic viscosity. Predicted pressure distributions from the numerical solution of the Navier-Stokes equations were similar in trend and magnitude to the measurements. Large variations in the predicted velocity profiles occurred along the lumen. The influence of the smaller scale multiple flow obstacles along the wall (lesion variations) led to sharp spikes in the predicted wall shear stresses. Reynolds number similarity was discussed, and estimates of what time averaged in vivo pressure drop and shear stress might be were given for a vessel segment.

Feedback control of an electrorheological long-stroke vibration damper

NASA Astrophysics Data System (ADS)

Sims, Neil D.; Stanway, Roger; Johnson, Andrew R.; Peel, David J.; Bullough, William A.

1999-06-01

It is widely acknowledged that the inherent non-linearity of smart fluid dampers is inhibiting the development of effective control regimes, and mass-production devices. In an earlier publication, an innovative solution to this problem was presented -- using a simple feedback control strategy to linearize the response. The study used a quasi-steady model of a long-stroke Electrorheological damper, and showed how proportional feedback control could linearize the simulated response. However, this initial research did not consider the dynamics of the damper's behavior, and so the development of a more advanced model has been necessary. In this article, the authors present an extension to this earlier study, using a model of the damper's response that is capable of accurately predicting the dynamic response of the damper. To introduce the topic, the electrorheological long-stroke damper test rig is described, and an overview of the earlier study is given. The advanced model is then derived, and its predictions are compared to experimental data from the test rig. This model is then incorporated into the feedback control simulations, and it is shown how the control strategy is still able to linearize the response in simulations.

Fluid Shifts

NASA Technical Reports Server (NTRS)

Stenger, M. B.; Hargens, A.; Dulchavsky, S.; Ebert, D.; Lee, S.; Laurie, S.; Garcia, K.; Sargsyan, A.; Martin, D.; Lui, J.;

Fluid inclusions in Ebelyakh diamonds: Evidence of CO2 liberation in eclogite and the effect of H2O on diamond habit

NASA Astrophysics Data System (ADS)

Smith, Evan M.; Kopylova, Maya G.; Frezzotti, Maria Luce; Afanasiev, Valentin P.

2015-02-01

Fluid inclusions were studied in six octahedrally-grown, eclogitic diamonds from the Ebelyakh River mine, northern Russia, using microthermometry and Raman spectroscopy. The fluids are CO2-N2 mixtures with 40 ± 4 mol% N2, which are trapped along fractures that healed in the diamond stability field. The CO2-rich composition of the fluids provides the first empirical evidence that CO2 can be liberated as a free phase in eclogite in the diamond stability field of the lithospheric mantle, as has been previously predicted from theory. This finding means that the interpretation of carbon isotopes in eclogitic diamonds should not overlook isotopic fractionation due to CO2 liberation from carbonatitic diamond-forming media as it percolates through eclogites. Preferential nucleation of CO2 bubbles in eclogite compared to peridotite may lead to a rock type-specific fracturing mechanism and sampling bias that would help explain the overabundance of eclogite xenoliths in kimberlites. Fluid inclusions in octahedrally-grown, non-fibrous diamonds from both the studied Ebelyakh diamonds and those from other cratons do not show detectable amounts of water. In comparison, fibrous diamond fluid inclusions typically contain 10-25 wt.% water. The absence of "dry" fluids in fibrous diamonds and the presence of these in octahedrally-grown diamonds may indicate different compositions of fluids equilibrated with these two types of diamonds. If there is variability in the water content in diamond-forming fluids, it should affect diamond growth morphology. Water could be responsible for causing fibrous diamond growth, by inhibiting the advancement of growth steps within octahedral faces.

Digestive kinetics determines bioavailability of pollutants. Final report, 1 July 1993--30 September 1998

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mayer, L.M.

1998-09-30

The bioavailability of sedimentary contaminants to animals in harbor sediments was addressed by studying the mechanisms by which animals solubilize contaminants during feeding and digestion. Digestive physiology work on many different animal species revealed patterns of enzymes, surfactants and dissolved organic matter that correlate with feeding mode, phyletic position, and diet. Incubation of digestive fluids to dissolve contaminants from polluted sediments was developed to provide numerical estimates of bioavailability, and showed that much higher fractions of total contaminant loading are available than predicted by currently established, aqueous equilibrium approaches. The kinetics of reactions are slow enough that variations in feedingmore » rates will influence overall bioavailability. Experimental manipulations showed mechanisms of bioavailability. Dissolved amino acids, in the form of enzyme proteins and hydrolyzed food, are responsible for solubilization of metals such as copper. At high levels, copper can inactivate digestive enzymes. Metals in sedimentary sulfide minerals were largely impervious to digestive fluid attack. Surfactants are responsible for most solubilization of polycyclic aromatic hydrocarbons (PAH), though other agents also appear to play a role. Bioavailability of both metals and PAH can be limited by saturating the digestive agents responsible for their dissolution.« less

Permeability generation and resetting of tracers during metamorphic fluid flow: implications for advection-dispersion models

NASA Astrophysics Data System (ADS)

Cartwright, Ian

Advection-dispersion fluid flow models implicitly assume that the infiltrating fluid flows through an already fluid-saturated medium. However, whether rocks contain a fluid depends on their reaction history, and whether any initial fluid escapes. The behaviour of different rocks may be illustrated using hypothetical marble compositions. Marbles with diverse chemistries (e.g. calcite + dolomite + quartz) are relatively reactive, and will generally produce a fluid during heating. By contrast, marbles with more restricted chemistries (e.g. calcite + quartz or calcite-only) may not. If the rock is not fluid bearing when fluid infiltration commences, mineralogical reactions may produce a reaction-enhanced permeability in calcite + dolomite + quartz or calcite + quartz, but not in calcite-only marbles. The permeability production controls the pattern of mineralogical, isotopic, and geochemical resetting during fluid flow. Tracers retarded behind the mineralogical fronts will probably be reset as predicted by the advection-dispersion models; however, tracers that are expected to be reset ahead of the mineralogical fronts cannot progress beyond the permeability generating reaction. In the case of very unreactive lithologies (e.g. pure calcite marbles, cherts, and quartzites), the first reaction to affect the rocks may be a metasomatic one ahead of which there is little pervasive resetting of any tracer. Centimetre-scale layering may lead to the formation of self-perpetuating fluid channels in rocks that are not fluid saturated due to the juxtaposition of reactants. Such layered rocks may show patterns of mineralogical resetting that are not predicted by advection-dispersion models. Patterns of mineralogical and isotopic resetting in marbles from a number of terrains, for example: Chillagoe, Marulan South, Reynolds Range (Australia); Adirondack Mountains, Old Woman Mountains, Notch Peak (USA); and Stephen Cross Quarry (Canada) vary as predicted by these models.

Ventral striatal prediction error signaling is associated with dopamine synthesis capacity and fluid intelligence

PubMed Central

Schlagenhauf, Florian; Rapp, Michael A.; Huys, Quentin J. M.; Beck, Anne; Wüstenberg, Torsten; Deserno, Lorenz; Buchholz, Hans-Georg; Kalbitzer, Jan; Buchert, Ralph; Kienast, Thorsten; Cumming, Paul; Plotkin, Michail; Kumakura, Yoshitaka; Grace, Anthony A.; Dolan, Raymond J.; Heinz, Andreas

2013-01-01

Fluid intelligence represents the capacity for flexible problem solving and rapid behavioral adaptation. Rewards drive flexible behavioral adaptation, in part via a teaching signal expressed as reward prediction errors in the ventral striatum, which has been associated with phasic dopamine release in animal studies. We examined a sample of 28 healthy male adults using multimodal imaging and biological parametric mapping with 1) functional magnetic resonance imaging during a reversal learning task and 2) in a subsample of 17 subjects also with positron emission tomography using 6-[18F]fluoro-L-DOPA to assess dopamine synthesis capacity. Fluid intelligence was measured using a battery of nine standard neuropsychological tests. Ventral striatal BOLD correlates of reward prediction errors were positively correlated with fluid intelligence and, in the right ventral striatum, also inversely correlated with dopamine synthesis capacity (FDOPA Kinapp). When exploring aspects of fluid intelligence, we observed that prediction error signaling correlates with complex attention and reasoning. These findings indicate that individual differences in the capacity for flexible problem solving may be driven by ventral striatal activation during reward-related learning, which in turn proved to be inversely associated with ventral striatal dopamine synthesis capacity. PMID:22344813

Fluid resuscitation following a burn injury: implications of a mathematical model of microvascular exchange.

PubMed

Bert, J; Gyenge, C; Bowen, B; Reed, R; Lund, T

1997-03-01

A validated mathematical model of microvascular exchange in thermally injured humans has been used to predict the consequences of different forms of resuscitation and potential modes of action of pharmaceuticals on the distribution and transport of fluid and macromolecules in the body. Specially, for 10 and/or 50 per cent burn surface area injuries, predictions are presented for no resuscitation, resuscitation with the Parkland formula (a high fluid and low protein formulation) and resuscitation with the Evans formula (a low fluid and high protein formulation). As expected, Parkland formula resuscitation leads to interstitial accumulation of excess fluid, while use of the Evans formula leads to interstitial accumulation of excessive amounts of proteins. The hypothetical effects of pharmaceuticals on the transport barrier properties of the microvascular barrier and on the highly negative tissue pressure generated postburn in the injured tissue were also investigated. Simulations predict a relatively greater amelioration of the acute postburn edema through modulation of the postburn tissue pressure effects.

COMPARING SIMULATED AND EXPERIMENTAL HYSTERETIC TWO- PHASE TRANSIENT FLUID FLOW PHENOMENA

EPA Science Inventory

A hysteretic model for two-phase permeability (k)-saturation (S)-pressure (P) relations is outlined that accounts for effects of nonwetting fluid entrapment. The model can be employed in unsaturated fluid flow computer codes to predict temporal and spatial fluid distributions. Co...

Computing Thermal Effects of Cavitation in Cryogenic Liquids

NASA Technical Reports Server (NTRS)

Hosangadi, Ashvin; Ahuja, Vineet; Dash, Sanford M.

2005-01-01

A computer program implements a numerical model of thermal effects of cavitation in cryogenic fluids. The model and program were developed for use in designing and predicting the performances of turbopumps for cryogenic fluids. Prior numerical models used for this purpose do not account for either the variability of properties of cryogenic fluids or the thermal effects (especially, evaporative cooling) involved in cavitation. It is important to account for both because in a cryogenic fluid, the thermal effects of cavitation are substantial, and the cavitation characteristics are altered by coupling between the variable fluid properties and the phase changes involved in cavitation. The present model accounts for both thermal effects and variability of properties by incorporating a generalized representation of the properties of cryogenic fluids into a generalized compressible-fluid formulation for a cavitating pump. The model has been extensively validated for liquid nitrogen and liquid hydrogen. Using the available data on the properties of these fluids, the model has been shown to predict accurate temperature-depression values.

Thermal Ablation Modeling for Silicate Materials

NASA Technical Reports Server (NTRS)

Chen, Yih-Kanq

2016-01-01

A general thermal ablation model for silicates is proposed. The model includes the mass losses through the balance between evaporation and condensation, and through the moving molten layer driven by surface shear force and pressure gradient. This model can be applied in the ablation simulation of the meteoroid and the glassy ablator for spacecraft Thermal Protection Systems. Time-dependent axisymmetric computations are performed by coupling the fluid dynamics code, Data-Parallel Line Relaxation program, with the material response code, Two-dimensional Implicit Thermal Ablation simulation program, to predict the mass lost rates and shape change. The predicted mass loss rates will be compared with available data for model validation, and parametric studies will also be performed for meteoroid earth entry conditions.

Development of a cryogenic mixed fluid J-T cooling computer code, 'JTMIX'

NASA Technical Reports Server (NTRS)

Jones, Jack A.

1991-01-01

An initial study was performed for analyzing and predicting the temperatures and cooling capacities when mixtures of fluids are used in Joule-Thomson coolers and in heat pipes. A computer code, JTMIX, was developed for mixed gas J-T analysis for any fluid combination of neon, nitrogen, various hydrocarbons, argon, oxygen, carbon monoxide, carbon dioxide, and hydrogen sulfide. When used in conjunction with the NIST computer code, DDMIX, it has accurately predicted order-of-magnitude increases in J-T cooling capacities when various hydrocarbons are added to nitrogen, and it predicts nitrogen normal boiling point depressions to as low as 60 K when neon is added.

Study of journal bearing dynamics using 3-dimensional motion picture graphics

NASA Technical Reports Server (NTRS)

Brewe, D. E.; Sosoka, D. J.

1985-01-01

Computer generated motion pictures of three dimensional graphics are being used to analyze journal bearings under dynamically loaded conditions. The motion pictures simultaneously present the motion of the journal and the pressures predicted within the fluid film of the bearing as they evolve in time. The correct prediction of these fluid film pressures can be complicated by the development of cavitation within the fluid. The numerical model that is used predicts the formation of the cavitation bubble and its growth, downstream movement, and subsequent collapse. A complete physical picture is created in the motion picture as the journal traverses through the entire dynamic cycle.

A method to adapt thoracic impedance based on chest geometry and composition to assess congestion in heart failure patients.

PubMed

Cuba-Gyllensten, Illapha; Gastelurrutia, Paloma; Bonomi, Alberto G; Riistama, Jarno; Bayes-Genis, Antoni; Aarts, Ronald M

2016-04-14

Multi-frequency trans-thoracic bioimpedance (TTI) could be used to track fluid changes and congestion of the lungs, however, patient specific characteristics may impact the measurements. We investigated the effects of thoracic geometry and composition on measurements of TTI and developed an equation to calculate a personalized fluid index. Simulations of TTI measurements for varying levels of chest circumference, fat and muscle proportion were used to derive parameters for a model predicting expected values of TTI. This model was then adapted to measurements from a control group of 36 healthy volunteers to predict TTI and lung fluids (fluid index). Twenty heart failure (HF) patients treated for acute HF were then used to compare the changes in the personalized fluid index to symptoms of HF and predicted TTI to measurements at hospital discharge. All the derived body characteristics affected the TTI measurements in healthy volunteers and together the model predicted the measured TTI with 8.9% mean absolute error. In HF patients the estimated TTI correlated well with the discharged TTI (r=0.73,p <0.001) and the personalized fluid index followed changes in symptom levels during treatment. However, 37% (n=7) of the patients were discharged well below the model expected value. Accounting for chest geometry and composition might help in interpreting TTI measurements. Copyright © 2016 IPEM. Published by Elsevier Ltd. All rights reserved.

Reduced viscosity interpreted for fluid/gas mixtures

NASA Technical Reports Server (NTRS)

Lewis, D. H.

1981-01-01

Analysis predicts decrease in fluid viscosity by comparing pressure profile of fluid/gas mixture with that of power-law fluid. Fluid is taken to be viscous, non-Newtonian, and incompressible; the gas to be ideal; the flow to be inertia-free, isothermal, and one dimensional. Analysis assists in design of flow systems for petroleum, coal, polymers, and other materials.

What is the impact of the fluid challenge technique on diagnosis of fluid responsiveness? A systematic review and meta-analysis.

PubMed

Toscani, Laura; Aya, Hollmann D; Antonakaki, Dimitra; Bastoni, Davide; Watson, Ximena; Arulkumaran, Nish; Rhodes, Andrew; Cecconi, Maurizio

2017-08-04

The fluid challenge is considered the gold standard for diagnosis of fluid responsiveness. The objective of this study was to describe the fluid challenge techniques reported in fluid responsiveness studies and to assess the difference in the proportion of 'responders,' (PR) depending on the type of fluid, volume, duration of infusion and timing of assessment. Searches of MEDLINE and Embase were performed for studies using the fluid challenge as a test of cardiac preload with a description of the technique, a reported definition of fluid responsiveness and PR. The primary outcome was the mean PR, depending on volume of fluid, type of fluids, rate of infusion and time of assessment. A total of 85 studies (3601 patients) were included in the analysis. The PR were 54.4% (95% CI 46.9-62.7) where <500 ml was administered, 57.2% (95% CI 52.9-61.0) where 500 ml was administered and 60.5% (95% CI 35.9-79.2) where >500 ml was administered (p = 0.71). The PR was not affected by type of fluid. The PR was similar among patients administered a fluid challenge for <15 minutes (59.2%, 95% CI 54.2-64.1) and for 15-30 minutes (57.7%, 95% CI 52.4-62.4, p = 1). Where the infusion time was ≥30 minutes, there was a lower PR of 49.9% (95% CI 45.6-54, p = 0.04). Response was assessed at the end of fluid challenge, between 1 and 10 minutes, and >10 minutes after the fluid challenge. The proportions of responders were 53.9%, 57.7% and 52.3%, respectively (p = 0.47). The PR decreases with a long infusion time. A standard technique for fluid challenge is desirable.

Relationships between self-diffusivity, packing fraction, and excess entropy in simple bulk and confined fluids.

PubMed

Mittal, Jeetain; Errington, Jeffrey R; Truskett, Thomas M

2007-08-30

Static measures such as density and entropy, which are intimately connected to structure, have featured prominently in modern thinking about the dynamics of the liquid state. Here, we explore the connections between self-diffusivity, density, and excess entropy for two of the most widely used model "simple" liquids, the equilibrium Lennard-Jones and square-well fluids, in both bulk and confined environments. We find that the self-diffusivity data of the Lennard-Jones fluid can be approximately collapsed onto a single curve (i) versus effective packing fraction and (ii) in appropriately reduced form versus excess entropy, as suggested by two well-known scaling laws. Similar data collapse does not occur for the square-well fluid, a fact that can be understood on the basis of the nontrivial effects that temperature has on its static structure. Nonetheless, we show that the implications of confinement for the self-diffusivity of both of these model fluids, over a broad range of equilibrium conditions, can be predicted on the basis of knowledge of the bulk fluid behavior and either the effective packing fraction or the excess entropy of the confined fluid. Excess entropy is perhaps the most preferable route due to its superior predictive ability and because it is a standard, unambiguous thermodynamic quantity that can be readily predicted via classical density functional theories of inhomogeneous fluids.

Analyzing Flows In Rocket Nuclear Reactors

NASA Technical Reports Server (NTRS)

Clark, J. S.; Walton, J. T.; Mcguire, M.

1994-01-01

CAC is analytical prediction program to study heat-transfer and fluid-flow characteristics of circular coolant passage. Predicts, as function of time, axial and radial fluid conditions, temperatures of passage walls, rates of flow in each coolant passage, and approximate maximum material temperatures. Written in ANSI standard FORTRAN 77.

Dehydration, hemodynamics and fluid volume optimization after induction of general anesthesia.

PubMed

Li, Yuhong; He, Rui; Ying, Xiaojiang; Hahn, Robert G

2014-01-01

Fluid volume optimization guided by stroke volume measurements reduces complications of colorectal and high-risk surgeries. We studied whether dehydration or a strong hemodynamic response to general anesthesia increases the probability of fluid responsiveness before surgery begins. Cardiac output, stroke volume, central venous pressure and arterial pressures were measured in 111 patients before general anesthesia (baseline), after induction and stepwise after three bolus infusions of 3 ml/kg of 6% hydroxyethyl starch 130/0.4 (n=86) or Ringer's lactate (n=25). A subgroup of 30 patients who received starch were preloaded with 500 ml of Ringer's lactate. Blood volume changes were estimated from the hemoglobin concentration and dehydration was estimated from evidence of renal water conservation in urine samples. Induction of anesthesia decreased the stroke volume to 62% of baseline (mean); administration of fluids restored this value to 84% (starch) and 68% (Ringer's). The optimized stroke volume index was clustered around 35-40 ml/m2/beat. Additional fluid boluses increased the stroke volume by ≥10% (a sign of fluid responsiveness) in patients with dehydration, as suggested by a low cardiac index and central venous pressure at baseline and by high urinary osmolality, creatinine concentration and specific gravity. Preloading and the hemodynamic response to induction did not correlate with fluid responsiveness. The blood volume expanded 2.3 (starch) and 1.8 (Ringer's) times over the infused volume. Fluid volume optimization did not induce a hyperkinetic state but ameliorated the decrease in stroke volume caused by anesthesia. Dehydration, but not the hemodynamic response to the induction, was correlated with fluid responsiveness.

Fluid, solid and fluid-structure interaction simulations on patient-based abdominal aortic aneurysm models.

PubMed

Kelly, Sinead; O'Rourke, Malachy

2012-04-01

This article describes the use of fluid, solid and fluid-structure interaction simulations on three patient-based abdominal aortic aneurysm geometries. All simulations were carried out using OpenFOAM, which uses the finite volume method to solve both fluid and solid equations. Initially a fluid-only simulation was carried out on a single patient-based geometry and results from this simulation were compared with experimental results. There was good qualitative and quantitative agreement between the experimental and numerical results, suggesting that OpenFOAM is capable of predicting the main features of unsteady flow through a complex patient-based abdominal aortic aneurysm geometry. The intraluminal thrombus and arterial wall were then included, and solid stress and fluid-structure interaction simulations were performed on this, and two other patient-based abdominal aortic aneurysm geometries. It was found that the solid stress simulations resulted in an under-estimation of the maximum stress by up to 5.9% when compared with the fluid-structure interaction simulations. In the fluid-structure interaction simulations, flow induced pressure within the aneurysm was found to be up to 4.8% higher than the value of peak systolic pressure imposed in the solid stress simulations, which is likely to be the cause of the variation in the stress results. In comparing the results from the initial fluid-only simulation with results from the fluid-structure interaction simulation on the same patient, it was found that wall shear stress values varied by up to 35% between the two simulation methods. It was concluded that solid stress simulations are adequate to predict the maximum stress in an aneurysm wall, while fluid-structure interaction simulations should be performed if accurate prediction of the fluid wall shear stress is necessary. Therefore, the decision to perform fluid-structure interaction simulations should be based on the particular variables of interest in a given study.

Modeling Electrically Evoked Otoacoustic Emissions

NASA Astrophysics Data System (ADS)

Grosh, K.; Deo, N.; Parthasarathi, A. A.; Nuttall, A. L.; Zheng, J. F.; Ren, T. Y.

2003-02-01

Electrical evoked otoacoustic emissions (EEOAE) are used to investigate in vivo cochlear electromechanical function. Round window electrical stimulation gives rise to a broad frequency EEOAE response, from 100 Hz or below to 40 kHz in guinea pigs. Placing bipolar electrodes very close to the basilar membrane (in the scala vestibuli and scala tympani) gives rise to a much narrower frequency range of EEOAE, limited to around 20 kHz when the electrodes are placed near the 18 kHz best frequency place. Model predictions using a three dimensional fluid model in conjunction with a simple model for outer hair cell (OHC) activity are used to interpret the experimental results. The model is solved using a 2.5D finite-element formulation. Predictions show that the high-frequency limit of the excitation is determined by the spatial extent of the current stimulus (also called the current spread). The global peaks in the EEOAE spectra are interpreted as constructive interference between electrically evoked backward traveling waves and forward traveling waves reflected from the stapes. Steady-state response predictions of the model are presented.

On the prediction of the human response: a recycled mechanistic pharmacokinetic/pharmacodynamic approach.

PubMed

Meno-Tetang, Guy M L; Lowe, Philip J

2005-03-01

Although it is routine to predict the blood or plasma pharmacokinetics of compounds for man based upon preclinical studies, the real value of such predictions only comes when linked to drug effects. In the first example, the immunomodulator, FTY720, the first sphingosine-1-phosphate receptor agonist, stimulates the sequestration of lymphocytes into lymph nodes thus removing cells from blood circulation. A prior physiology-based pharmacokinetic model fitted the concentration-time course of FTY720 in rats. This was connected to an indirect response model of the lymphocyte system to characterise the cell trafficking effects. The IC(50) of FTY720 was different in the rat compared with the monkey; man was assumed to be similar to the monkey. The systemic lymphocyte half-lives were also different between species. To make predictions of the pharmacodynamic behaviour for man, two elements are required, i) systemic exposure, in this case from an upscaled physiology based model, and ii) an estimate of lymphocyte turnover in man, gained from the literature from other drug treatments. Predictions compared well with clinical results. The second example is the monoclonal antibody Xolair, designed to bind immunoglobulin E for atopic diseases. A mechanism based two-site binding model described the kinetics of both Xolair and endogenous IgE. This model has been reused for other monoclonal antibodies designed to bind fluid-phase ligands. Sensitivity analysis shows that if differences across species in the kinetics of the endogenous system are not accounted for, then pharmacokinetic/pharmacodynamic models may give misleading predictions of the time course and extent of the response.

Diet-induced obesity reprograms the inflammatory response of the murine lung to inhaled endotoxin

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tilton, Susan C., E-mail: susan.tilton@pnnl.gov; Waters, Katrina M.; Karin, Norman J.

The co-occurrence of environmental factors is common in complex human diseases and, as such, understanding the molecular responses involved is essential to determine risk and susceptibility to disease. We have investigated the key biological pathways that define susceptibility for pulmonary infection during obesity in diet-induced obese (DIO) and regular weight (RW) C57BL/6 mice exposed to inhaled lipopolysaccharide (LPS). LPS induced a strong inflammatory response in all mice as indicated by elevated cell counts of macrophages and neutrophils and levels of proinflammatory cytokines (MDC, MIP-1γ, IL-12, RANTES) in the bronchoalveolar lavage fluid. Additionally, DIO mice exhibited 50% greater macrophage cell counts,more » but decreased levels of the cytokines, IL-6, TARC, TNF-α, and VEGF relative to RW mice. Microarray analysis of lung tissue showed over half of the LPS-induced expression in DIO mice consisted of genes unique for obese mice, suggesting that obesity reprograms how the lung responds to subsequent insult. In particular, we found that obese animals exposed to LPS have gene signatures showing increased inflammatory and oxidative stress response and decreased antioxidant capacity compared with RW. Because signaling pathways for these responses can be common to various sources of environmentally induced lung damage, we further identified biomarkers that are indicative of specific toxicant exposure by comparing gene signatures after LPS exposure to those from a parallel study with cigarette smoke. These data show obesity may increase sensitivity to further insult and that co-occurrence of environmental stressors result in complex biosignatures that are not predicted from analysis of individual exposures. - Highlights: ► Obesity modulates inflammatory markers in BAL fluid after LPS exposure. ► Obese animals have a unique transcriptional signature in lung after LPS exposure. ► Obesity elevates inflammatory stress and reduces antioxidant capacity in the lung. ► Toxicant-specific biomarkers predict exposure independent of systemic inflammation.« less

Resonances, radiation pressure and optical scattering phenomena of drops and bubbles

NASA Technical Reports Server (NTRS)

Marston, P. L.; Goosby, S. G.; Langley, D. S.; Loporto-Arione, S. E.

1982-01-01

Acoustic levitation and the response of fluid spheres to spherical harmonic projections of the radiation pressure are described. Simplified discussions of the projections are given. A relationship between the tangential radiation stress and the Konstantinov effect is introduced and fundamental streaming patterns for drops are predicted. Experiments on the forced shape oscillation of drops are described and photographs of drop fission are displayed. Photographs of critical angle and glory scattering by bubbles and rainbow scattering by drops are displayed.

Thermal Protection System Cavity Heating for Simplified and Actual Geometries Using Computational Fluid Dynamics Simulations with Unstructured Grids

NASA Technical Reports Server (NTRS)

McCloud, Peter L.

2010-01-01

Thermal Protection System (TPS) Cavity Heating is predicted using Computational Fluid Dynamics (CFD) on unstructured grids for both simplified cavities and actual cavity geometries. Validation was performed using comparisons to wind tunnel experimental results and CFD predictions using structured grids. Full-scale predictions were made for simplified and actual geometry configurations on the Space Shuttle Orbiter in a mission support timeframe.

HCO3− secretion and CaCO3 precipitation play major roles in intestinal water absorption in marine teleost fish in vivo

PubMed Central

Cooper, Christopher A.; Wilson, Rod W.

2010-01-01

The intestine of marine teleosts must effectively absorb fluid from ingested seawater to avoid dehydration. This fluid transport has been almost exclusively characterized as driven by NaCl absorption. However, an additional feature of the osmoregulatory role of the intestine is substantial net HCO3− secretion. This is suggested to drive additional fluid absorption directly (via Cl−/HCO3− exchange) and indirectly by precipitating ingested Ca2+ as CaCO3, thus creating the osmotic gradient for additional fluid absorption. The present study tested this hypothesis by perfusing the intestine of the European flounder in vivo with varying [Ca2+]: 10 (control), 40, and 90 mM. Fractional fluid absorption increased from 47% (control) to 73% (90 mM Ca2+), where almost all secreted HCO3− was excreted as CaCO3. This additional fluid absorption could not be explained by NaCl cotransport. Instead, a significant positive relationship between Na+-independent fluid absorption and total HCO3− secretion was consistent with the predicted roles for anion exchange and CaCO3 precipitation. Further analysis suggested that Na+-independent fluid absorption could be accounted for by net Cl− and H+ absorption (from Cl−/HCO3− exchange and CO2 hydration, respectively). There was no evidence to suggest that CaCO3 alone was responsible for driving fluid absorption. However, by preventing the accumulation of luminal Ca2+ it played a vital role by dynamically maintaining a favorable osmotic gradient all along the intestine, which permits substantially higher rates of solute-linked fluid absorption. To overcome the resulting hyperosmotic and highly acidic absorbate, it is proposed that plasma HCO3− buffers the absorbed H+ (from HCO3− production), and consequently reduces the osmolarity of the absorbed fluid entering the body. PMID:20130226

Validation of a Solid Rocket Motor Internal Environment Model

NASA Technical Reports Server (NTRS)

Martin, Heath T.

2017-01-01

In a prior effort, a thermal/fluid model of the interior of Penn State University's laboratory-scale Insulation Test Motor (ITM) was constructed to predict both the convective and radiative heat transfer to the interior walls of the ITM with a minimum of empiricism. These predictions were then compared to values of total and radiative heat flux measured in a previous series of ITM test firings to assess the capabilities and shortcomings of the chosen modeling approach. Though the calculated fluxes reasonably agreed with those measured during testing, this exercise revealed means of improving the fidelity of the model to, in the case of the thermal radiation, enable direct comparison of the measured and calculated fluxes and, for the total heat flux, compute a value indicative of the average measured condition. By replacing the P1-Approximation with the discrete ordinates (DO) model for the solution of the gray radiative transfer equation, the radiation intensity field in the optically thin region near the radiometer is accurately estimated, allowing the thermal radiation flux to be calculated on the heat-flux sensor itself, which was then compared directly to the measured values. Though the fully coupling the wall thermal response with the flow model was not attempted due to the excessive computational time required, a separate wall thermal response model was used to better estimate the average temperature of the graphite surfaces upstream of the heat flux gauges and improve the accuracy of both the total and radiative heat flux computations. The success of this modeling approach increases confidence in the ability of state-of-the-art thermal and fluid modeling to accurately predict SRM internal environments, offers corrections to older methods, and supplies a tool for further studies of the dynamics of SRM interiors.

Predictions of the near edge transport shortfall in DIII-D L-mode plasmas using the trapped gyro-Landau-fluid model [Predictions of the near edge transport shortfall in DIII-D L-mode plasmas using the TGLF model

DOE PAGES

Kinsey, Jon E.; Staebler, Gary M.; Candy, Jefferey M.; ...

2015-01-14

Previous studies of DIII-D L-mode plasmas have shown that a transport shortfall exists in that our current models of turbulent transport can significantly underestimate the energy transport in the near edge region. In this paper, the Trapped Gyro-Landau-Fluid (TGLF) drift wave transport model is used to simulate the near edge transport in a DIII-D L-mode experiment designed to explore the impact of varying the safety factor on the shortfall. We find that the shortfall systematically increases with increasing safety factor and is more pronounced for the electrons than for the ions. Within the shortfall dataset, a single high current casemore » has been found where no transport shortfall is predicted. Reduced neutral beam injection power has been identified as the key parameter separating this discharge from other discharges exhibiting a shortfall. Further analysis shows that the energy transport in the L-mode near edge region is not stiff according to TGLF. Unlike the H-mode core region, the predicted temperature profiles are relatively more responsive to changes in auxiliary heating power. In testing the fidelity of TGLF for the near edge region, we find that a recalibration of the collision model is warranted. A recalibration improves agreement between TGLF and nonlinear gyrokinetic simulations performed using the GYRO code with electron-ion collisions. As a result, the recalibration only slightly impacts the predicted shortfall.« less

An investigation of the open-loop amplification of a Reynolds number dependent process by wave distortion

NASA Technical Reports Server (NTRS)

Ventrice, M. B.; Purdy, K. R.

1974-01-01

The response of a constant-temperature hot-wire anemometer to sinusoidal and distorted sinusoidal acoustic oscillations is examined. The output of the anemometer is dependent upon the Reynolds number of the flow over the wire. The response is a measure of the interaction between the anemometer output and the acoustic pressure in the neighborhood of the wire. It is an open-loop prediction of the characteristics of actual closed-loop operation of a system. If the open-loop response is large enough, unstable closed-loop operation is predicted. The study was motivated by a need to investigate the stability limits of liquid-propellant rockets when perturbed by pressure oscillations. The sinusoidal and distorted sinusoidal acoustic oscillations used for this study are the same as those characteristic of unstable rocket combustion. Qualitatively, the results are similar--the response of the system to pure sinusoidal acoustic vibration of the fluid surrounding the wire is small, even when the magnitude of the acoustic pressure is quite large; but the response can be increased by as much as an order of magnitude with respect to the sinusoidal case by the addition of distortion. The amplitude and phase of the distortion component, relative to the fundamental component, are the dominant factors in the increase in the response.

The measurement of ultrasound scattering from individual micron-sized objects and its application in single cell scattering.

PubMed

Falou, Omar; Rui, Min; El Kaffas, Ahmed; Kumaradas, J Carl; Kolios, Michael C

2010-08-01

The measurement of the ultrasound backscatter from individual micron-sized objects such as cells is required for various applications such as tissue characterization. However, performing such a measurement remains a challenge. For example, the presence of air bubbles in a suspension of cells during the measurements may lead to the incorrect interpretation of the acoustic signals. This work introduces a technique for measuring the ultrasound backscatter from individual micron-sized objects by combining a microinjection system with a co-registered optical microscope and an ultrasound imaging device. This allowed the measurement of the ultrasound backscatter response from a single object under optical microscope guidance. The optical and ultrasonic data were used to determine the size of the object and to deduce its backscatter responses, respectively. In order to calibrate the system, the backscatter frequency responses from polystyrene microspheres were measured and compared to theoretical predictions. A very good agreement was found between the measured backscatter responses of individual microspheres and theoretical predictions of an elastic sphere. The backscatter responses from single OCI-AML-5 cells were also investigated. It was found that the backscatter responses from AML cells are best modeled using the fluid sphere model. The advantages, limitations, and future applications of the developed technique are discussed.

A multiscale quasi-continuum theory to determine thermodynamic properties of fluid mixtures in nanochannels

NASA Astrophysics Data System (ADS)

Motevaselian, Mohammad Hossein; Mashayak, Sikandar Y.; Aluru, Narayana R.

2015-11-01

We present an empirical potential-based quasi-continuum theory (EQT) that seamlessly integrates the interatomic potentials into a continuum framework such as the Nernst-Planck equation. EQT is a simple and fast approach, which provides accurate predictions of potential of mean force (PMF) and density distribution of confined fluids at multiple length-scales, ranging from few Angstroms to macro meters. The EQT potentials can be used to construct the excess free energy functional in the classical density functional theory (cDFT). The combination of EQT and cDFT (EQT-cDFT), allows one to predict the thermodynamic properties of confined fluids. Recently, the EQT-cDFT framework was developed for single component LJ fluids confined in slit-like graphene channels. In this work, we extend the framework to confined LJ fluid mixtures and demonstrate it by simulating a mixture of methane and hydrogen molecules inside slit-like graphene channels. We show that the EQT-cDFT predictions for the structure of the confined fluid mixture compare well with the MD simulations. In addition, our results show that graphene nanochannels exhibit a selective adsorption of methane over hydrogen.

Determination of shelf heat transfer coefficients along the shelf flow path of a freeze dryer using the shelf fluid temperature perturbation approach.

PubMed

Kuu, Wei Y; Nail, Steven L; Hardwick, Lisa M

2007-01-01

The spatial distribution of local shelf heat transfer coefficients, Ks, was determined by mapping the transient temperature response of the shelf surface along the serpentine internal channels of the shelf while the temperature of the heat transfer fluid was ramped from -40 degrees to 40 degrees C. The solution of a first-order non-steady-state differential equation resulted in a predicted shelf surface temperature as a function of the shelf fluid temperature at any point along the flow path. During the study, the shelf surfaces were maintained under a thermally insulated condition so that the heat transfers by gas conduction and radiation were negligible. To minimize heat conduction by gas, the chamber was evacuated to a low pressure, such as 100 mTorr. To minimize heat transfers between shelves, shelves were moved close together, with a gap of approximately 3 mm between any two shelves, because the shelf surface temperatures at corresponding vertical locations of two shelves are virtually equal. In addition, this also provides a shielding from radiation heat transfer from shelf to walls. Local heat transfer coefficients at the probed locations h(x) ( approximately Ks) were calculated by fitting the experimental shelf temperature response to the theoretical value. While the resulting values of K(s) are in general agreement with previously reported values, the values of Ks close to the inlet are significantly higher than those of other locations of the shelf channel. This observation is most likely attributed to the variation of the flow pattern of heat transfer fluid within the channels.

Thin-Film Magnetic-Field-Response Fluid-Level Sensor for Non-Viscous Fluids

NASA Technical Reports Server (NTRS)

Woodard, Stanley E.; Shams, Qamar A.; Fox, Robert L.; Taylor, Bryant D.

2008-01-01

An innovative method has been developed for acquiring fluid-level measurements. This method eliminates the need for the fluid-level sensor to have a physical connection to a power source or to data acquisition equipment. The complete system consists of a lightweight, thin-film magnetic-field-response fluid-level sensor (see Figure 1) and a magnetic field response recorder that was described in Magnetic-Field-Response Measurement-Acquisition System (LAR-16908-1), NASA Tech Briefs, Vol. 30, No. 6 (June 2006), page 28. The sensor circuit is a capacitor connected to an inductor. The response recorder powers the sensor using a series of oscillating magnetic fields. Once electrically active, the sensor responds with its own harmonic magnetic field. The sensor will oscillate at its resonant electrical frequency, which is dependent upon the capacitance and inductance values of the circuit.

Suspension restraint - Induced hypokinesia and antiorthostasis as a simulation of weightlessness

NASA Technical Reports Server (NTRS)

Musacchia, X. J.; Steffen, J. M.; Deavers, D. R.

1982-01-01

Muscle, renal, fluid and electrolyte responses were measured in suspended rats; the hind limbs are non-load bearing and the front limbs can be used for feeding and grooming. Hind limb hypokinesia reverses after removal from the suspension harness. This suspension system is adjustable for a head-down tilt to produce antiorthostatic responses which are also reversible. Responses to hypokinesia or antiorthostatic hypokinesia for up to 14 days were measured, e.g., muscle atrophy: soleus greater than gastrocnemius equals plantaris greater than extensor digitorum longus, kaliuresis, and increased excretion of urea, NH3, and 3 methylhistidine. Muscle protein loss, a response to a reduction in RNA, is also reversible. A head-down tilt for 7-14 days results in diuresis and natriuresis. These changes are reversed within 24 hours after removal from the restraint harness. Physiological effects of suspension restraint can be used to simulate and predict responses to microgravity exposure.

Hybrid multiphase CFD simulation for liquid-liquid interfacial area prediction in annular centrifugal contactors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wardle, K.E.

2013-07-01

Liquid-liquid contacting equipment used in solvent extraction processes has the dual purpose of mixing and separating two immiscible fluids. Consequently, such devices inherently encompass a wide variety of multiphase flow regimes. A hybrid multiphase computational fluid dynamics (CFD) solver which combines the Eulerian multi-fluid method with VOF (volume of fluid) sharp interface capturing has been developed for application to annular centrifugal contactors. This solver has been extended to enable prediction of mean droplet size and liquid-liquid interfacial area through a single moment population balance method. Simulations of liquid-liquid mixing in a simplified geometry and a model annular centrifugal contactor aremore » reported with droplet breakup/coalescence models being calibrated versus available experimental data. Quantitative comparison is made for two different housing vane geometries and it is found that the predicted droplet size is significantly smaller for vane geometries which result in higher annular liquid holdup.« less

Continuum Model of Gas Uptake for Inhomogeneous Fluids

DOE PAGES

Ihm, Yungok; Cooper, Valentino R.; Vlcek, Lukas; ...

2017-07-20

We describe a continuum model of gas uptake for inhomogeneous fluids (CMGIF) and use it to predict fluid adsorption in porous materials directly from gas-substrate interaction energies determined by first principles calculations or accurate effective force fields. The method uses a perturbation approach to correct bulk fluid interactions for local inhomogeneities caused by gas substrate interactions, and predicts local pressure and density of the adsorbed gas. The accuracy and limitations of the model are tested by comparison with the results of Grand Canonical Monte Carlo simulations of hydrogen uptake in metal-organic frameworks (MOFs). We show that the approach provides accuratemore » predictions at room temperature and at low temperatures for less strongly interacting materials. As a result, the speed of the CMGIF method makes it a promising candidate for high-throughput materials discovery in connection with existing databases of nano-porous materials.« less

Fluid Shifts

NASA Technical Reports Server (NTRS)

Stenger, Michael; Hargens, A.; Dulchavsky, S.; Ebert, D.; Lee, S.; Sargsyan, A.; Martin, D.; Lui, J.; Macias, B.; Arbeille, P.;

Fluid Shifts

NASA Technical Reports Server (NTRS)

Stenger, M.; Hargens, A.; Dulchavsky, S.; Ebert, D.; Lee, S.; Lauriie, S.; Garcia, K.; Sargsyan, A.; Martin, D.; Ribeiro, L.;

Hunger and thirst numeric rating scales are not valid estimates for gastric content volumes: a prospective investigation in healthy children.

PubMed

Buehrer, Sabin; Hanke, Ursula; Klaghofer, Richard; Fruehauf, Melanie; Weiss, Markus; Schmitz, Achim

2014-03-01

A rating scale for thirst and hunger was evaluated as a noninvasive, simple and commonly available tool to estimate preanesthetic gastric volume, a surrogate parameter for the risk of perioperative pulmonary aspiration, in healthy volunteer school age children. Numeric scales with scores from 0 to 10 combined with smileys to rate thirst and hunger were analyzed and compared with residual gastric volumes as measured by magnetic resonance imaging and fasting times in three settings: before and for 2 h after drinking clear fluid (group A, 7 ml/kg), before and for 4 vs 6 h after a light breakfast followed by clear fluid (7 ml/kg) after 2 vs 4 h (crossover, group B), and before and for 1 h after drinking clear fluid (crossover, group C, 7 vs 3 ml/kg). In 30 children aged 6.4-12.8 (median 9.8) years, participating on 1-5 (median two) study days, 496 sets of scores and gastric volumes were determined. Large inter- and intra-individual variations were seen at baseline and in response to fluid and food intake. Significant correlations were found between hunger and thirst ratings in all groups, with children generally being more hungry than thirsty. Correlations between scores and duration of fasting or gastric residual volumes were poor to moderate. Receiver operating characteristic (ROC) analysis revealed that thirst and hunger rating scales cannot predict gastric content. Hunger and thirst scores vary considerably inter- and intra-individually and cannot predict gastric volume, nor do they correlate with fasting times in school age children. © 2013 John Wiley & Sons Ltd.

Forced responses on a radial turbine with nozzle guide vanes

NASA Astrophysics Data System (ADS)

Liu, Yixiong; Yang, Ce; Ma, Chaochen; Lao, DaZhong

2014-04-01

Radial turbines with nozzle guide vanes are widely used in various size turbochargers. However, due to the interferences with guide vanes, the blades of impellers are exposed to intense unsteady aerodynamic excitations, which cause blade vibrations and lead to high cycle failures (HCF). Moreover, the harmonic resonance in some frequency regions are unavoidable due to the wide operation conditions. Aiming to achieve a detail insight into vibration characteristics of radial flow turbine, a numerical method based on fluid structure interaction (FSI) is presented. Firstly, the unsteady aerodynamic loads are determined by computational fluid dynamics (CFD). And the fluctuating pressures are transformed from time domain to frequency domain by fast Fourier-transform (FFT). Then, the entire rotor model is adopted to analyze frequencies and mode shapes considering mistuning in finite element (FE) method. Meanwhile, harmonic analyses, applying the pressure fluctuation from CFD, are conducted to investigate the impeller vibration behavior and blade forced response in frequency domain. The prediction of the vibration dynamic stress shows acceptable agreement to the blade actual damage in consistent tendency.

Concepts and methods for describing critical phenomena in fluids

NASA Technical Reports Server (NTRS)

Sengers, J. V.; Sengers, J. M. H. L.

1977-01-01

The predictions of theoretical models for a critical-point phase transistion in fluids, namely the classical equation with third-degree critical isotherm, that with fifth-degree critical isotherm, and the lattice gas, are reviewed. The renormalization group theory of critical phenomena and the hypothesis of universality of critical behavior supported by this theory are discussed as well as the nature of gravity effects and how they affect cricital-region experimentation in fluids. The behavior of the thermodynamic properties and the correlation function is formulated in terms of scaling laws. The predictions of these scaling laws and of the hypothesis of universality of critical behavior are compared with experimental data for one-component fluids and it is indicated how the methods can be extended to describe critical phenomena in fluid mixtures.

Marital Conflict, Allostatic Load, and the Development of Children's Fluid Cognitive Performance

PubMed Central

Hinnant, J. Benjamin; El-Sheikh, Mona; Keiley, Margaret; Buckhalt, Joseph A.

2013-01-01

Relations between marital conflict, children’s respiratory sinus arrhythmia (RSA), and fluid cognitive performance were examined over three years to assess allostatic processes. Participants were 251 children reporting on marital conflict, baseline RSA and RSA reactivity to a lab challenge were recorded, and fluid cognitive performance was measured using the Woodcock-Johnson III. A cross-lagged model showed that higher levels of marital conflict at age 8 predicted weaker RSA-R at age 9 for children with lower baseline RSA. A growth model showed that lower baseline RSA in conjunction with weaker RSA-R predicted the slowest development of fluid cognitive performance. Findings suggest that stress may affect development of physiological systems regulating attention, which are tied to the development of fluid cognitive performance. PMID:23534537

[Latest advances in acute pancreatitis].

PubMed

de-Madaria, Enrique

2013-10-01

The present article analyzes the main presentations on acute pancreatitis (AP) in Digestive Disease Week 2013. Perfusion computed tomography allows early diagnosis of pancreatic necrosis. Neutrophil gelatinase-associated lipocalin predicts the development of acute renal failure, severe AP and death. Factors associated with greater fluid sequestration in AP are alcoholic etiology, an elevated hematocrit, and the presence of criteria of systemic inflammatory response syndrome; fluid sequestration is associated with a worse outcome. True pseudocysts (fluid collections without necrosis for more than 4 weeks) are a highly infrequent complication in AP. Patients with necrotic collections have a poor prognosis, especially if associated with infection. A meta-analysis on fluid therapy suggests that early aggressive fluid administration is associated with higher mortality and more frequent respiratory complications. According to a meta-analysis, enteral nutrition initiated within 24 hours of admission improves the outcome of AP compared with later initiation of enteral nutrition. Pentoxifylline could be a promising alternative in AP; a double-blind randomized study showed that this drug reduced the length of hospital and intensive care unit stay, as well as the need for intensive care unit admission. The association of octreotide and celecoxib seems to reduce the frequency of organ damage compared with octreotide alone. Mild AP can be managed in the ambulatory setting through hospital-at-home units after a short, 24-hour admission. Copyright © 2013 Elsevier España, S.L. All rights reserved.

Ion association at discretely-charged dielectric interfaces: Giant charge inversion

NASA Astrophysics Data System (ADS)

Wang, Zhi-Yong; Wu, Jianzhong

2017-07-01

Giant charge reversal has been identified for the first time by Monte Carlo simulation for a discretely charged surface in contact with a trivalent electrolyte solution. It takes place regardless of the surface charge density under study and the monovalent salt. In stark contrast to earlier predictions based on the 2-dimensional Wigner crystal model to describe strong correlation of counterions at the macroion surface, we find that giant charge reversal reflects an intricate interplay of ionic volume effects, electrostatic correlations, surface charge heterogeneity, and the dielectric response of the confined fluids. While the novel phenomenon is yet to be confirmed with experiment, the simulation results appear in excellent agreement with a wide range of existing observations in the subregime of charge inversion. Our findings may have far-reaching implications to understanding complex electrochemical phenomena entailing ionic fluids under dielectric confinements.

Acute coagulopathy of trauma: balancing progressive catecholamine induced endothelial activation and damage by fluid phase anticoagulation.

PubMed

Johansson, P I; Ostrowski, S R

2010-12-01

Acute coagulopathy of trauma predicts a poor clinical outcome. Tissue trauma activates the sympathoadrenal system resulting in high circulating levels of catecholamines that influence hemostasis dose-dependently through immediate effects on the two major compartments of hemostasis, i.e., the circulating blood and the vascular endothelium. There appears to be a dose-dependency with regards to injury severity and the hemostatic response to trauma evaluated in whole blood by viscoelastic assays like thrombelastography (TEG), changing from normal to hypercoagulable, to hypocoagulable and finally hyperfibrinolytic in severely injured patients. Since high catecholamine levels may directly damage the endothelium and thereby promote systemic coagulation activation, we hypothesize that the progressive hypocoagulability and ultimate hyperfibrinolysis observed in whole blood with increasing injury severity, is an evolutionary developed response that counterbalances the injury and catecholamine induced endothelial activation and damage. Given this, the rise in circulating catecholamines in trauma patients may favor a switch from hyper- to hypocoagulability in the blood to keep the progressively more procoagulant microvasculature open. The hypothesis delineated in the present paper thus infers that the state of the fluid phase, including its cellular elements, is a consequence of the degree of the tissue injury and importantly, critically related to the degree of endothelial damage, with a progressively more procoagulant endothelium inducing a gradient of increasing anticoagulation towards the fluid phase. The implications of this hypothesis may include targeted treatment strategies according to the degree of sympathoadrenal response as evaluated by whole blood viscoelastical hemostatic assays in trauma patients. Copyright © 2010 Elsevier Ltd. All rights reserved.

Immune Response Augmentation in Metastasized Breast Cancer by Localized Therapy Utilizing Biocompatible Magnetic Fluids

DTIC Science & Technology

2008-08-01

SUBJECT TERMS Cancer therapy by localized immune response, Magneto -rehological Fluids 16. SECURITY CLASSIFICATION OF: 17. LIMITATION OF ABSTRACT...Metastasized Breast Cancer by Localized Therapy utilizing Biocompatible Magnetic Fluids PRINCIPAL INVESTIGATOR: Cahit Evrensel...2008 4. TITLE AND SUBTITLE 5a. CONTRACT NUMBER Immune Response Augmentation in Metastasized Breast Cancer by Localized Therapy utilizing

Emerging biomarkers in breast cancer care.

PubMed

Napieralski, Rudolf; Brünner, Nils; Mengele, Karin; Schmitt, Manfred

2010-08-01

Currently, decision-making for breast cancer treatment in the clinical setting is mainly based on clinical data, histomorphological features of the tumor tissue and a few cancer biomarkers such as steroid hormone receptor status (estrogen and progesterone receptors) and oncoprotein HER2 status. Although various therapeutic options were introduced into the clinic in recent decades, with the objective of improving surgery, radiotherapy, biochemotherapy and chemotherapy, varying response of individual patients to certain types of therapy and therapy resistance is still a challenge in breast cancer care. Therefore, since breast cancer treatment should be based on individual features of the patient and her tumor, tailored therapy should be an option by integrating cancer biomarkers to define patients at risk and to reliably predict their course of the disease and/or response to cancer therapy. Recently, candidate-marker approaches and genome-wide transcriptomic and epigenetic screening of different breast cancer tissues and bodily fluids resulted in new promising biomarker panels, allowing breast cancer prognosis, prediction of therapy response and monitoring of therapy efficacy. These biomarkers are now subject of validation in prospective clinical trials.

Microwave fluid flow meter

DOEpatents

Billeter, Thomas R.; Philipp, Lee D.; Schemmel, Richard R.

1976-01-01

A microwave fluid flow meter is described utilizing two spaced microwave sensors positioned along a fluid flow path. Each sensor includes a microwave cavity having a frequency of resonance dependent upon the static pressure of the fluid at the sensor locations. The resonant response of each cavity with respect to a variation in pressure of the monitored fluid is represented by a corresponding electrical output which can be calibrated into a direct pressure reading. The pressure drop between sensor locations is then correlated as a measure of fluid velocity. In the preferred embodiment the individual sensor cavities are strategically positioned outside the path of fluid flow and are designed to resonate in two distinct frequency modes yielding a measure of temperature as well as pressure. The temperature response can then be used in correcting for pressure responses of the microwave cavity encountered due to temperature fluctuations.

Computational Modeling of Space Physiology for Informing Spaceflight Countermeasure Design and Predictions of Efficacy

NASA Technical Reports Server (NTRS)

Lewandowski, B. E.; DeWitt, J. K.; Gallo, C. A.; Gilkey, K. M.; Godfrey, A. P.; Humphreys, B. T.; Jagodnik, K. M.; Kassemi, M.; Myers, J. G.; Nelson, E. S.;

Plasma genetic and genomic abnormalities predict treatment response and clinical outcome in advanced prostate cancer.

PubMed

Xia, Shu; Kohli, Manish; Du, Meijun; Dittmar, Rachel L; Lee, Adam; Nandy, Debashis; Yuan, Tiezheng; Guo, Yongchen; Wang, Yuan; Tschannen, Michael R; Worthey, Elizabeth; Jacob, Howard; See, William; Kilari, Deepak; Wang, Xuexia; Hovey, Raymond L; Huang, Chiang-Ching; Wang, Liang

2015-06-30

Liquid biopsies, examinations of tumor components in body fluids, have shown promise for predicting clinical outcomes. To evaluate tumor-associated genomic and genetic variations in plasma cell-free DNA (cfDNA) and their associations with treatment response and overall survival, we applied whole genome and targeted sequencing to examine the plasma cfDNAs derived from 20 patients with advanced prostate cancer. Sequencing-based genomic abnormality analysis revealed locus-specific gains or losses that were common in prostate cancer, such as 8q gains, AR amplifications, PTEN losses and TMPRSS2-ERG fusions. To estimate tumor burden in cfDNA, we developed a Plasma Genomic Abnormality (PGA) score by summing the most significant copy number variations. Cox regression analysis showed that PGA scores were significantly associated with overall survival (p < 0.04). After androgen deprivation therapy or chemotherapy, targeted sequencing showed significant mutational profile changes in genes involved in androgen biosynthesis, AR activation, DNA repair, and chemotherapy resistance. These changes may reflect the dynamic evolution of heterozygous tumor populations in response to these treatments. These results strongly support the feasibility of using non-invasive liquid biopsies as potential tools to study biological mechanisms underlying therapy-specific resistance and to predict disease progression in advanced prostate cancer.

Using Mason number to predict MR damper performance from limited test data

NASA Astrophysics Data System (ADS)

Becnel, Andrew C.; Wereley, Norman M.

2017-05-01

The Mason number can be used to produce a single master curve which relates MR fluid stress versus strain rate behavior across a wide range of shear rates, temperatures, and applied magnetic fields. As applications of MR fluid energy absorbers expand to a variety of industries and operating environments, Mason number analysis offers a path to designing devices with desired performance from a minimal set of preliminary test data. Temperature strongly affects the off-state viscosity of the fluid, as the passive viscous force drops considerably at higher temperatures. Yield stress is not similarly affected, and stays relatively constant with changing temperature. In this study, a small model-scale MR fluid rotary energy absorber is used to measure the temperature correction factor of a commercially-available MR fluid from LORD Corporation. This temperature correction factor is identified from shear stress vs. shear rate data collected at four different temperatures. Measurements of the MR fluid yield stress are also obtained and related to a standard empirical formula. From these two MR fluid properties - temperature-dependent viscosity and yield stress - the temperature-corrected Mason number is shown to predict the force vs. velocity performance of a full-scale rotary MR fluid energy absorber. This analysis technique expands the design space of MR devices to high shear rates and allows for comprehensive predictions of overall performance across a wide range of operating conditions from knowledge only of the yield stress vs. applied magnetic field and a temperature-dependent viscosity correction factor.

Outcome prediction in monochorionic diamniotic twin pregnancies with moderately discordant amniotic fluid.

PubMed

Van Mieghem, T; Eixarch, E; Gucciardo, L; Done, E; Gonzales, I; Van Schoubroeck, D; Lewi, L; Gratacos, E; Deprest, J

2011-01-01

The aim of this study was to identify predictors of twin-to-twin transfusion syndrome (TTTS) and selective intrauterine growth restriction (sIUGR) in monochorionic diamniotic (MCDA) twin pregnancies with moderate amniotic fluid discordance (mAFD). Monochorionic twins with mAFD (n = 45; gestational age, 15-29 weeks) were assessed for extent of fluid discordance, fetal growth discordance and fetal cardiac dysfunction, and were followed longitudinally. A prediction algorithm was constructed for TTTS and sIUGR and validated in an unrelated cohort (n = 52). Cardiac dysfunction could not predict TTTS or sIUGR. Twins below 20 weeks of gestation with a fluid discordance of ≥ 3.1 cm had a risk of TTTS of 85.7%. Sensitivity for TTTS was nevertheless only 55%. An intertwin weight discordance of ≥ 25% had 63% sensitivity and 76% specificity for sIUGR without TTTS. The outcome of MCDA twins with mAFD remains unpredictable, yet high-risk and low-risk subgroups for TTTS can be identified based on severity of fluid discordance and gestational age.

Processes in the development of mathematics in kindergarten children from Title 1 schools.

PubMed

Foster, Matthew E; Anthony, Jason L; Clements, Doug H; Sarama, Julie H

2015-12-01

This study examined how well nonverbal IQ (or fluid intelligence), vocabulary, phonological awareness (PA), rapid autonomized naming (RAN), and phonological short-term memory (STM) predicted mathematics outcomes. The 208 participating kindergartners were administered tests of fluid intelligence, vocabulary, PA, RAN, STM, and numeracy in the fall of kindergarten, whereas tests of numeracy and applied problems were administered in the spring of kindergarten. Fall numeracy scores accounted for substantial variation in spring outcomes (R(2) values = .49 and .32 for numeracy and applied problems, respectively), which underscores the importance of preschool math instruction and screening for mathematics learning difficulties on entry into kindergarten. Fluid intelligence and PA significantly predicted unique variation in spring numeracy scores (ΔR(2) = .05) after controlling for autoregressive effects and classroom nesting. Fluid intelligence, PA, and STM significantly predicted unique variation in spring applied problems scores (ΔR(2) = .14) after controlling for autoregressive effects and classroom nesting. Although the contributions of fluid intelligence, PA, and STM toward math outcomes were reliable and arguably important, they were small. Copyright © 2015 Elsevier Inc. All rights reserved.

Influence of mantle viscosity structure and mineral grain size on fluid migration pathways in the mantle wedge.

NASA Astrophysics Data System (ADS)

Cerpa, N. G.; Wada, I.; Wilson, C. R.; Spiegelman, M. W.

2016-12-01

We develop a 2D numerical porous flow model that incorporates both grain size distribution and matrix compaction to explore the fluid migration (FM) pathways in the mantle wedge. Melt generation for arc volcanism is thought to be triggered by slab-derived fluids that migrate into the hot overlying mantle and reduce its melting temperature. While the narrow location of the arcs relative to the top of the slab ( 100±30 km) is a robust observation, the release of fluids is predicted to occur over a wide range of depth. Reconciling such observations and predictions remains a challenge for the geodynamic community. Fluid transport by porous flow depends on the permeability of the medium which in turn depends on fluid fraction and mineral grain size. The grain size distribution in the mantle wedge predicted by laboratory derived laws was found to be a possible mechanism to focusing of fluids beneath the arcs [Wada and Behn, 2015]. The viscous resistance of the matrix to the volumetric strain generates compaction pressure that affects fluid flow and can also focus fluids towards the arc [Wilson et al, 2014]. We thus have developed a 2D one-way coupled Darcy's-Stokes flow model (solid flow independent of fluid flow) for the mantle wedge that combines both effects. For the solid flow calculation, we use a kinematic-dynamic approach where the system is driven by the prescribed slab velocity. The solid rheology accounts for both dislocation and diffusion creep and we calculate the grain size distribution following Wada and Behn [2015]. In our fluid flow model, the permeability of the medium is grain size dependent and the matrix bulk viscosity depends on solid shear viscosity and fluid fraction. The fluid influx from the slab is imposed as a boundary condition at the base of the mantle wedge. We solve the discretized governing equations using the software package TerraFERMA. Applying a range of model parameter values, including slab age, slab dip, subduction rate, and fluid influx, we quantify the combined effects of grain size and compaction on fluid flow paths.

The reliability of the physical examination to guide fluid therapy in adults with severe falciparum malaria: an observational study.

PubMed

Hanson, Josh; Lam, Sophia W K; Alam, Shamsul; Pattnaik, Rajyabardhan; Mahanta, Kishore C; Uddin Hasan, Mahatab; Mohanty, Sanjib; Mishra, Saroj; Cohen, Sophie; Day, Nicholas; White, Nicholas; Dondorp, Arjen

2013-10-01

Adults with severe malaria frequently require intravenous fluid therapy to restore their circulating volume. However, fluid must be delivered judiciously as both under- and over-hydration increase the risk of complications and, potentially, death. As most patients will be cared for in a resource-poor setting, management guidelines necessarily recommend that physical examination should guide fluid resuscitation. However, the reliability of this strategy is uncertain. To determine the ability of physical examination to identify hypovolaemia, volume responsiveness, and pulmonary oedema, clinical signs and invasive measures of volume status were collected independently during an observational study of 28 adults with severe malaria. The physical examination defined volume status poorly. Jugular venous pressure (JVP) did not correlate with intravascular volume as determined by global end diastolic volume index (GEDVI; r(s) = 0.07, p = 0.19), neither did dry mucous membranes (p = 0.85), or dry axillae (p = 0.09). GEDVI was actually higher in patients with decreased tissue turgor (p < 0.001). Poor capillary return correlated with GEDVI, but was present infrequently (7% of observations) and, therefore, insensitive. Mean arterial pressure (MAP) correlated with GEDVI (rs = 0.16, p = 0.002), but even before resuscitation patients with a low GEDVI had a preserved MAP. Anuria on admission was unrelated to GEDVI and although liberal fluid resuscitation led to a median hourly urine output of 100 ml in 19 patients who were not anuric on admission, four (21%) developed clinical pulmonary oedema subsequently. MAP was unrelated to volume responsiveness (p = 0.71), while a low JVP, dry mucous membranes, dry axillae, increased tissue turgor, prolonged capillary refill, and tachycardia all had a positive predictive value for volume responsiveness of ≤50%. Extravascular lung water ≥11 ml/kg indicating pulmonary oedema was present on 99 of the 353 times that it was assessed during the study, but was identified on less than half these occasions by tachypnoea, chest auscultation, or an elevated JVP. A clear chest on auscultation and a respiratory rate <30 breaths/minute could exclude pulmonary oedema on 82% and 72% of occasions respectively. Findings on physical examination correlate poorly with true volume status in adults with severe malaria and must be used with caution to guide fluid therapy. Clinicaltrials.gov identifier: NCT00692627.

Prediction of space sickness in astronauts from preflight fluid, electrolyte, and cardiovascular variables and Weightless Environmental Training Facility (WETF) training

NASA Technical Reports Server (NTRS)

Simanonok, K.; Mosely, E.; Charles, J.

1992-01-01

Nine preflight variables related to fluid, electrolyte, and cardiovascular status from 64 first-time Shuttle crewmembers were differentially weighted by discrimination analysis to predict the incidence and severity of each crewmember's space sickness as rated by NASA flight surgeons. The nine variables are serum uric acid, red cell count, environmental temperature at the launch site, serum phosphate, urine osmolality, serum thyroxine, sitting systolic blood pressure, calculated blood volume, and serum chloride. Using two methods of cross-validation on the original samples (jackknife and a stratefied random subsample), these variables enable the prediction of space sickness incidence (NONE or SICK) with 80 percent sickness and space severity (NONE, MILD, MODERATE, of SEVERE) with 59 percent success by one method of cross-validation and 67 percent by another method. Addition of a tenth variable, hours spent in the Weightlessness Environment Training Facility (WETF) did not improve the prediction of space sickness incidences but did improve the prediction of space sickness severity to 66 percent success by the first method of cross-validation of original samples and to 71 percent by the second method. Results to date suggest the presence of predisposing physiologic factors to space sickness that implicate fluid shift etiology. The data also suggest that prior exposure to fluid shift during WETF training may produce some circulatory pre-adaption to fluid shifts in weightlessness that results in a reduction of space sickness severity.

Fluid therapy and perfusional considerations during resuscitation in critically ill patients with intra-abdominal hypertension.

PubMed

Regli, Adrian; De Keulenaer, Bart; De Laet, Inneke; Roberts, Derek; Dabrowski, Wojciech; Malbrain, Manu L N G

2015-01-01

Intra-abdominal hypertension (IAH) and abdominal compartment syndrome (ACS) are consistently associated with morbidity and mortality among the critically ill or injured. Thus, avoiding or potentially treating these conditions may improve patient outcomes. With the aim of improving the outcomes for patients with IAH/ACS, the World Society of the Abdominal Compartment Syndrome recently updated its clinical practice guidelines. In this article, we review the association between a positive fluid balance and outcomes among patients with IAH/ACS and how optimisation of fluid administration and systemic/regional perfusion may potentially lead to improved outcomes among this patient population.Evidence consistently associates secondary IAH with a positive fluid balance. However, despite increased research in the area of non-surgical management of patients with IAH and ACS, evidence supporting this approach is limited. Some evidence exists to support implementing goal-directed resuscitation protocols and restrictive fluid therapy protocols in shocked and recovering critically ill patients with IAH. Data from animal experiments and clinical trials has shown that the early use of vasopressors and inotropic agents is likely to be safe and may help reduce excessive fluid administration, especially in patients with IAH. Studies using furosemide and/or renal replacement therapy to achieve a negative fluid balance in patients with IAH are encouraging. The type of fluid to be administered in patients with IAH remains far from resolved. There is currently insufficient evidence to recommend the use of abdominal perfusion pressure as a resuscitation endpoint in patients with IAH. However, it is important to recognise that IAH either abolishes or increases threshold values for pulse pressure variation and stroke volume variation to predict fluid responsiveness, while the presence of IAH may also result in a false negative passive leg raising test.Correct fluid therapy and perfusional support during resuscitation form the cornerstone of medical management in patients with abdominal hypertension. Controlled studies determining whether the above medical interventions may improve outcomes among those with IAH/ACS are urgently required.

Growth and nonlinear response of driven water bells

NASA Astrophysics Data System (ADS)

Kolinski, John M.; Aharoni, Hillel; Fineberg, Jay; Sharon, Eran

2017-04-01

A water bell forms when a fluid jet impacts upon a target and separates into a two-dimensional sheet. Depending on the angle of separation from the target, the sheet can curve into a variety of different geometries. We show analytically that harmonic perturbations of water bells have linear wave solutions with geometry-dependent growth. We test the predictions of this model experimentally with a custom target system, and observe growth in agreement with the model below a critical forcing amplitude. Once the critical forcing amplitude is exceeded, a nonlinear transcritical bifurcation occurs; the response amplitude increases linearly with increasing forcing amplitude, albeit with a fundamentally different spatial form, and distinct nodes appear in the amplitude envelope.

Anaerobic biodegradation of aircraft deicing fluid in UASB reactors.

PubMed

Tham, P T Pham thi; Kennedy, K J Kevin J

2004-05-01

A central composite design was employed to methodically investigate anaerobic treatment of aircraft deicing fluid (ADF) in bench-scale Upflow Anaerobic Sludge Blanket (UASB) reactors. A total of 23 runs at 17 different operating conditions (0.8% 1.6% ADF (6000-12,000mg/L COD), 12-56h HRT, and 18-36gVSS/L) were conducted in continuous mode. The development of four empirical models describing process responses (i.e. COD removal efficiency, biomass-specific acetoclastic activity, methane production rate, and methane production potential) as functions of ADF concentration, hydraulic retention time, and biomass concentration is presented. Model verification indicated that predicted responses (COD removal efficiencies, biomass-specific acetoclastic activity, and methane production rates and potential) were in good agreement with experimental results. Biomass-specific acetoclastic activity was improved two-fold from 0.23gCOD/gVSS/d for inoculum to a maximum of 0.55gCOD/gVSS/d during ADF treatment in UASB reactors. For the design window, COD removal efficiencies were higher than 90%. The predicted methane production potentials were close to theoretical values, and methane production rates increased as the organic loading rate is increased. ADF toxicity effects were evident for 1.6% ADF at medium organic loadings (SOLR above 0.5gCOD/gVSS/d). In contrast, good reactor stability and excellent COD removal efficiencies were achieved at 1.2% ADF for reactor loadings approaching that of highly loaded systems (0.73gCOD/gVSS/d).

Preliminary Design Optimization For A Supersonic Turbine For Rocket Propulsion

NASA Technical Reports Server (NTRS)

Papila, Nilay; Shyy, Wei; Griffin, Lisa; Huber, Frank; Tran, Ken; McConnaughey, Helen (Technical Monitor)

2000-01-01

In this study, we present a method for optimizing, at the preliminary design level, a supersonic turbine for rocket propulsion system application. Single-, two- and three-stage turbines are considered with the number of design variables increasing from 6 to 11 then to 15, in accordance with the number of stages. Due to its global nature and flexibility in handling different types of information, the response surface methodology (RSM) is applied in the present study. A major goal of the present Optimization effort is to balance the desire of maximizing aerodynamic performance and minimizing weight. To ascertain required predictive capability of the RSM, a two-level domain refinement approach has been adopted. The accuracy of the predicted optimal design points based on this strategy is shown to he satisfactory. Our investigation indicates that the efficiency rises quickly from single stage to 2 stages but that the increase is much less pronounced with 3 stages. A 1-stage turbine performs poorly under the engine balance boundary condition. A portion of fluid kinetic energy is lost at the turbine discharge of the 1-stage design due to high stage pressure ratio and high-energy content, mostly hydrogen, of the working fluid. Regarding the optimization technique, issues related to the design of experiments (DOE) has also been investigated. It is demonstrated that the criteria for selecting the data base exhibit significant impact on the efficiency and effectiveness of the construction of the response surface.

Modeling of classical swirl injector dynamics

NASA Astrophysics Data System (ADS)

Ismailov, Maksud M.

The knowledge of the dynamics of a swirl injector is crucial in designing a stable liquid rocket engine. Since the swirl injector is a complex fluid flow device in itself, not much work has been conducted to describe its dynamics either analytically or by using computational fluid dynamics techniques. Even the experimental observation is limited up to date. Thus far, there exists an analytical linear theory by Bazarov [1], which is based on long-wave disturbances traveling on the free surface of the injector core. This theory does not account for variation of the nozzle reflection coefficient as a function of disturbance frequency, and yields a response function which is strongly dependent on the so called artificial viscosity factor. This causes an uncertainty in designing an injector for the given operational combustion instability frequencies in the rocket engine. In this work, the author has studied alternative techniques to describe the swirl injector response, both analytically and computationally. In the analytical part, by using the linear small perturbation analysis, the entire phenomenon of unsteady flow in swirl injectors is dissected into fundamental components, which are the phenomena of disturbance wave refraction and reflection, and vortex chamber resonance. This reveals the nature of flow instability and the driving factors leading to maximum injector response. In the computational part, by employing the nonlinear boundary element method (BEM), the author sets the boundary conditions such that they closely simulate those in the analytical part. The simulation results then show distinct peak responses at frequencies that are coincident with those resonant frequencies predicted in the analytical part. Moreover, a cold flow test of the injector related to this study also shows a clear growth of instability with its maximum amplitude at the first fundamental frequency predicted both by analytical methods and BEM. It shall be noted however that Bazarov's theory does not predict the resonant peaks. Overall this methodology provides clearer understanding of the injector dynamics compared to Bazarov's. Even though the exact value of response is not possible to obtain at this stage of theoretical, computational, and experimental investigation, this methodology sets the starting point from where the theoretical description of reflection/refraction, resonance, and their interaction between each other may be refined to higher order to obtain its more precise value.

Technology of forced flow and once-through boiling: A survey. [pressure distribution

NASA Technical Reports Server (NTRS)

Poppendieck, H. F.; Sabin, C. M.

1975-01-01

Representative boiling heat transfer and pressure drop information obtained primarily from past NASA and AEC programs is presented which is applicable to forced flow and once-through boiler systems. The forced convection boiler has a number of advantages: little possibility of flow mal-distribution; heat transfer characteristics are usually consistent; and conductances are predictable, so that higher heat fluxes may be employed with safety (which leads to more compact, lighter weight equipment). It was found that in gas-fired systems particularly, the controlling heat transfer resistance may be on the hot side, so that increased fluxes would require extended surfaces. If in a power generation system the working fluid is very expensive, a forced flow boiler can be designed especially for small holdup volume. If the fluid is temperature sensitive, the boiling side wall temperatures can be tailored to maintain maximum heat transfer rates without overheating the fluid. The forced flow and once-through configurations may be the only type which can satisfy a specific need (such as the automotive Rankine cycle power plant design having a very short time-response boiler).

CRYogenic Orbital TEstbed Ground Test Article Thermal Analysis

NASA Technical Reports Server (NTRS)

Piryk, David; Schallhorn, Paul; Walls, Laurie; Stopnitzky, Benny; Rhys, Noah; Wollen, Mark

2012-01-01

The purpose of this study was to anchor thermal and fluid system models to CRYOTE ground test data. The CRYOTE ground test artide was jointly developed by Innovative Engineering Solutions, United Launch Alliance and NASA KSC. The test article was constructed out of a titanium alloy tank, Sapphire 77 composite skin (similar to G10), an external secondary payload adapter ring, thermal vent system, multi layer insulation and various data acquisition instrumentation. In efforts to understand heat loads throughout this system, the GTA (filled with liquid nitrogen for safety purposes) was subjected to a series of tests in a vacuum chamber at Marshall Space Flight Center. By anchoring analytical models against test data, higher fidelity thermal environment predictions can be made for future flight articles which would eventually demonstrate critical cryogenic fluid management technologies such as system chilldown, transfer, pressure control and long term storage. Significant factors that influenced heat loads included radiative environments, multi-layer insulation performance, tank fill levels and pressures and even contact conductance coefficients. This report demonstrates how analytical thermal/fluid networks were established and includes supporting rationale for specific thermal responses.

Contention between supply of hydrothermal fluid and conduit obstruction: inferences from numerical simulations

NASA Astrophysics Data System (ADS)

Tanaka, Ryo; Hashimoto, Takeshi; Matsushima, Nobuo; Ishido, Tsuneo

2018-05-01

We investigate a volcanic hydrothermal system using numerical simulations, focusing on change in crater temperature. Both increases and decreases in crater temperature have been observed before phreatic eruptions. We follow the system's response for up to a decade after hydrothermal fluid flux from the deep part of the system is increased and permeability is reduced at a certain depth in a conduit. Our numerical simulations demonstrate that: (1) changes in crater temperature are controlled by the magnitude of the increase in hydrothermal fluid flux and the degree of permeability reduction; (2) significant increases in hydrothermal flux with decreases in permeability induce substantial pressure changes in shallow depths in the edifice and decreases in crater temperature; (3) the location of maximum pressure change differs between the mechanisms. The results of this study imply that it is difficult to predict eruptions by crater temperature change alone. One should be as wary of large eruptions when crater temperature decreases as when crater temperature increases. It is possible to clarify the implications of changes in crater temperature with simultaneous observation of ground deformation.[Figure not available: see fulltext.

Optimal design of disc-type magneto-rheological brake for mid-sized motorcycle: experimental evaluation

NASA Astrophysics Data System (ADS)

Sohn, Jung Woo; Jeon, Juncheol; Nguyen, Quoc Hung; Choi, Seung-Bok

2015-08-01

In this paper, a disc-type magneto-rheological (MR) brake is designed for a mid-sized motorcycle and its performance is experimentally evaluated. The proposed MR brake consists of an outer housing, a rotating disc immersed in MR fluid, and a copper wire coiled around a bobbin to generate a magnetic field. The structural configuration of the MR brake is first presented with consideration of the installation space for the conventional hydraulic brake of a mid-sized motorcycle. The design parameters of the proposed MR brake are optimized to satisfy design requirements such as the braking torque, total mass of the MR brake, and cruising temperature caused by the magnetic-field friction of the MR fluid. In the optimization procedure, the braking torque is calculated based on the Herschel-Bulkley rheological model, which predicts MR fluid behavior well at high shear rate. An optimization tool based on finite element analysis is used to obtain the optimized dimensions of the MR brake. After manufacturing the MR brake, mechanical performances regarding the response time, braking torque and cruising temperature are experimentally evaluated.

ESTIMATION OF FREE HYDROCARBON VOLUME FROM FLUID LEVELS IN MONITORING WELLS

EPA Science Inventory

Under the assumption of local vertical equilibrium, fluid pressure distributions specified from well fluid levels in monitoring wells may be used to predict water and hydrocarbon saturation profiles given expressions for air-water-hydrocarbon saturation-pressure relations. Verti...

Shadowgraph Study of Gradient Driven Fluctuations

NASA Technical Reports Server (NTRS)

Cannell, David; Nikolaenko, Gennady; Giglio, Marzio; Vailati, Alberto; Croccolo, Fabrizio; Meyer, William

2002-01-01

A fluid or fluid mixture, subjected to a vertical temperature and/or concentration gradient in a gravitational field, exhibits greatly enhanced light scattering at small angles. This effect is caused by coupling between the vertical velocity fluctuations due to thermal energy and the vertically varying refractive index. Physically, small upward or downward moving regions will be displaced into fluid having a refractive index different from that of the moving region, thus giving rise to the enhanced scattering. The scattered intensity is predicted to vary with scattering wave vector q, as q(sup -4), for sufficiently large q, but the divergence is quenched by gravity at small q. In the absence of gravity, the long wavelength fluctuations responsible for the enhanced scattering are predicted to grow until limited by the sample dimensions. It is thus of interest to measure the mean-squared amplitude of such fluctuations in the microgravity environment for comparison with existing theory and ground based measurements. The relevant wave vectors are extremely small, making traditional low-angle light scattering difficult or impossible because of stray elastically scattered light generated by optical surfaces. An alternative technique is offered by the shadowgraph method, which is normally used to visualize fluid flows, but which can also serve as a quantitative tool to measure fluctuations. A somewhat novel shadowgraph apparatus and the necessary data analysis methods will be described. The apparatus uses a spatially coherent, but temporally incoherent, light source consisting of a super-luminescent diode coupled to a single-mode optical fiber in order to achieve extremely high spatial resolution, while avoiding effects caused by interference of light reflected from the various optical surfaces that are present when using laser sources. Results obtained for a critical mixture of aniline and cyclohexane subjected to a vertical temperature gradient will be presented. The sample was confined between two horizontal parallel sapphire plates with a vertical spacing of 1 mm. The temperatures of the sapphire plates were controlled by independent circulating water loops that used Peltier devices to add or remove heat from the room air as required. For a mixture with a temperature gradient, two effects are involved in generating the vertical refractive index gradient, namely thermal expansion and the Soret effect, which generates a concentration gradient in response to the applied temperature gradient. For the aniline/cyclohexane system, the denser component (aniline) migrates toward the colder surface. Consequently, when heating from above, both effects result in the sample density decreasing with altitude and are stabilizing in the sense that no convective motion occurs regardless of the magnitude of the applied temperature gradient. The Soret effect is strong near a binary liquid critical point, and thus the dominant effect is due to the induced concentration gradient. The results clearly show the divergence at low q and the predicted gravitational quenching. Results obtained for different applied temperature gradients at varying temperature differences from the critical temperature, clearly demonstrate the predicted divergence of the thermal diffusion ratio. Thus, the more closely the critical point is approached, the smaller becomes the temperature gradient required to generate the same signal. Two different methods have been used to generate pure concentration gradients. In the first, a sample cell was filled with a single fluid, ethylene glycol, and a denser miscible fluid, water, was added from below thus establishing a sharp interface to begin the experiment. As time went on the two fluids diffused into each other, and large amplitude fluctuations were clearly observed at low q. The effects of gravitational quenching were also evident. In the second method, the aniline/cyclohexane sample was used, and after applying a vertical temperature gradient for several hours, the top and bottom temperatures were set equal and the thermal gradient died on a time scale of seconds, leaving the Soret induced concentration gradient in place. Again, large-scale fluctuations were observed and died away slowly in amplitude as diffusion destroyed the initial concentration gradient.

Investigating Response from Turbulent Boundary Layer Excitations on a Real Launch Vehicle using SEA

NASA Technical Reports Server (NTRS)

Harrison, Phillip; LaVerde,Bruce; Teague, David

2009-01-01

Statistical Energy Analysis (SEA) response has been fairly well anchored to test observations for Diffuse Acoustic Field (DAF) loading by others. Meanwhile, not many examples can be found in the literature anchoring the SEA vehicle panel response results to Turbulent Boundary Layer (TBL) fluctuating pressure excitations. This deficiency is especially true for supersonic trajectories such as those required by this nation s launch vehicles. Space Shuttle response and excitation data recorded from vehicle flight measurements during the development flights were used in a trial to assess the capability of the SEA tool to predict similar responses. Various known/measured inputs were used. These were supplemented with a range of assumed values in order to cover unknown parameters of the flight. This comparison is presented as "Part A" of the study. A secondary, but perhaps more important, objective is to provide more clarity concerning the accuracy and conservatism that can be expected from response estimates of TBL-excited vehicle models in SEA (Part B). What range of parameters must be included in such an analysis in order to land on the conservative side in response predictions? What is the sensitivity of changes in these input parameters on the results? The TBL fluid structure loading model used for this study is provided by the SEA module of the commercial code VA One.

Understanding heat and fluid flow in linear GTA welds

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zacharia, T.; David, S.A.; Vitek, J.M.

1992-01-01

A transient heat flow and fluid flow model was used to predict the development of gas tungsten arc (GTA) weld pools in 1.5 mm thick AISI 304 SS. The welding parameters were chosen so as to correspond to an earlier experimental study which produced high-resolution surface temperature maps. The motivation of the present study was to verify the predictive capability of the computational model. Comparison of the numerical predictions and experimental observations indicate good agreement.

Understanding heat and fluid flow in linear GTA welds

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zacharia, T.; David, S.A.; Vitek, J.M.

1992-12-31

A transient heat flow and fluid flow model was used to predict the development of gas tungsten arc (GTA) weld pools in 1.5 mm thick AISI 304 SS. The welding parameters were chosen so as to correspond to an earlier experimental study which produced high-resolution surface temperature maps. The motivation of the present study was to verify the predictive capability of the computational model. Comparison of the numerical predictions and experimental observations indicate good agreement.

Upper Stage Tank Thermodynamic Modeling Using SINDA/FLUINT

NASA Technical Reports Server (NTRS)

Schallhorn, Paul; Campbell, D. Michael; Chase, Sukhdeep; Piquero, Jorge; Fortenberry, Cindy; Li, Xiaoyi; Grob, Lisa

2006-01-01

Modeling to predict the condition of cryogenic propellants in an upper stage of a launch vehicle is necessary for mission planning and successful execution. Traditionally, this effort was performed using custom, in-house proprietary codes, limiting accessibility and application. Phenomena responsible for influencing the thermodynamic state of the propellant have been characterized as distinct events whose sequence defines a mission. These events include thermal stratification, passive thermal control roll (rotation), slosh, and engine firing. This paper demonstrates the use of an off the shelf, commercially available, thermal/fluid-network code to predict the thermodynamic state of propellant during the coast phase between engine firings, i.e. the first three of the above identified events. Results of this effort will also be presented.

Portable vapor diffusion coefficient meter

DOEpatents

Ho, Clifford K [Albuquerque, NM

2007-06-12

An apparatus for measuring the effective vapor diffusion coefficient of a test vapor diffusing through a sample of porous media contained within a test chamber. A chemical sensor measures the time-varying concentration of vapor that has diffused a known distance through the porous media. A data processor contained within the apparatus compares the measured sensor data with analytical predictions of the response curve based on the transient diffusion equation using Fick's Law, iterating on the choice of an effective vapor diffusion coefficient until the difference between the predicted and measured curves is minimized. Optionally, a purge fluid can forced through the porous media, permitting the apparatus to also measure a gas-phase permeability. The apparatus can be made lightweight, self-powered, and portable for use in the field.

Using Fiber Optic Distributed Acoustic Sensing to Measure Hydromechanics in a Crystalline Rock Aquifer

NASA Astrophysics Data System (ADS)

Ciervo, C.; Becker, M.; Cole, M. C.; Coleman, T.; Mondanos, M.

2016-12-01

Measuring hydromechanical behavior in fractured rock is important for hydraulic fracturing and stimulation in petroleum reservoirs, predicting thermal effects in geothermal fields, and monitoring geologic carbon sequestration injection. We present a new method for measuring geomechanical response to fluid pressure in fractures that employs fiber optic Distributed Acoustic Sensing (DAS). DAS was designed to measure acoustic and seismic signals, often in petroleum wells. DAS seismic monitoring has been proposed as a particularly useful tool for performing seismic testing for carbon sequestration and geothermal projects because fiber optic cable is able to withstand high temperatures and pressures. DAS measures seismic vibration in the Hz to kHz frequency range by measuring strain rate in the fiber optic cable. We adapted this technology to measure rock strain in response to periodic hydraulic pulses in the mHz frequency range. A field experiment was conducted in a low-permeability fractured crystalline bedrock to test the ability of DAS to measure hydromechanical response to periodic pumping and injection. The fiber optic cable was coupled to the borehole wall using a flexible liner designed with an air coupled transducer to measure fluid pressure. Both strain and pressure were measured across a known fracture zone hydraulically connected to the pumping/injection well 30 m away. Periodic strain with amplitudes as small as 50 nm were measured in response to head amplitudes of 2 mm. Clean strain signals were detected at all tested periods of hydraulic oscillation ranging from 2 to 18 minutes. A non-linear relationship was found between opening and closing of the fracture (as measured by cable strain) and fluid pressure in the fracture. The response was also sensitive to the fiber optic cable design. This field test suggests potential for measuring hydraulic connectivity and hydromechanical behavior in fractured formations through cementing fiber optic cable in wellbores outside of well casings.

Zones of life in the subsurface of hydrothermal vents: A synthesis

NASA Astrophysics Data System (ADS)

Larson, B. I.; Houghton, J.; Meile, C. D.

2011-12-01

Subsurface microbial communities in Mid-ocean Ridge (MOR) hydrothermal systems host a wide array of unique metabolic strategies, but the spatial distribution of biogeochemical transformations is poorly constrained. Here we present an approach that reexamines chemical measurements from diffuse fluids with models of convective transport to delineate likely reaction zones. Chemical data have been compiled from bare basalt surfaces at a wide array of mid-ocean ridge systems, including 9°N, East Pacific Rise, Axial Seamount, Juan de Fuca, and Lucky Strike, Mid-Atlantic Ridge. Co-sampled end-member fluid from Ty (EPR) was used to constrain reaction path models that define diffuse fluid compositions as a function of temperature. The degree of mixing between hot vent fluid (350 deg. C) and seawater (2 deg. C) governs fluid temperature, Fe-oxide mineral precipitation is suppressed, and aqueous redox reactions are prevented from equilibrating, consistent with sluggish kinetics. Quartz and pyrite are predicted to precipitate, consistent with field observations. Most reported samples of diffuse fluids from EPR and Axial Seamount fall along the same predicted mixing line only when pyrite precipitation is suppressed, but Lucky Strike fluids do not follow the same trend. The predicted fluid composition as a function of temperature is then used to calculate the free energy available to autotrophic microorganisms for a variety of catabolic strategies in the subsurface. Finally, the relationships between temperature and free energy is combined with modeled temperature fields (Lowell et al., 2007 Geochem. Geophys., Geosys.) over a 500 m x 500 m region extending downward from the seafloor and outward from the high temperature focused hydrothermal flow to define areas that are energetically most favorable for a given metabolic process as well as below the upper temperature limit for life (~120 deg. C). In this way, we can expand the relevance of geochemical model predictions of bioenergetics by predicting functionally-defined 'Zones of Life' and placing them spatially within the boundary of the 120 deg. C isotherm, estimating the extent of subsurface biosphere beneath mid-ocean ridge hydrothermal systems. Preliminary results indicate that methanogenesis yields the most energy per kg of vent fluid, consistent with the elevated CH4(aq) seen at all three sites, but may be constrained by temperatures too hot for microbial life while available energy from the oxidation of Fe(II) peaks near regions of the crust that are more hospitable.

The Contribution of Mathematical Modeling to Understanding Dynamic Aspects of Rumen Metabolism

PubMed Central

Bannink, André; van Lingen, Henk J.; Ellis, Jennifer L.; France, James; Dijkstra, Jan

2016-01-01

All mechanistic rumen models cover the main drivers of variation in rumen function, which are feed intake, the differences between feedstuffs and feeds in their intrinsic rumen degradation characteristics, and fractional outflow rate of fluid and particulate matter. Dynamic modeling approaches are best suited to the prediction of more nuanced responses in rumen metabolism, and represent the dynamics of the interactions between substrates and micro-organisms and inter-microbial interactions. The concepts of dynamics are discussed for the case of rumen starch digestion as influenced by starch intake rate and frequency of feed intake, and for the case of fermentation of fiber in the large intestine. Adding representations of new functional classes of micro-organisms (i.e., with new characteristics from the perspective of whole rumen function) in rumen models only delivers new insights if complemented by the dynamics of their interactions with other functional classes. Rumen fermentation conditions have to be represented due to their profound impact on the dynamics of substrate degradation and microbial metabolism. Although the importance of rumen pH is generally acknowledged, more emphasis is needed on predicting its variation as well as variation in the processes that underlie rumen fluid dynamics. The rumen wall has an important role in adapting to rapid changes in the rumen environment, clearing of volatile fatty acids (VFA), and maintaining rumen pH within limits. Dynamics of rumen wall epithelia and their role in VFA absorption needs to be better represented in models that aim to predict rumen responses across nutritional or physiological states. For a detailed prediction of rumen N balance there is merit in a dynamic modeling approach compared to the static approaches adopted in current protein evaluation systems. Improvement is needed on previous attempts to predict rumen VFA profiles, and this should be pursued by introducing factors that relate more to microbial metabolism. For rumen model construction, data on rumen microbiomes are preferably coupled with knowledge consolidated in rumen models instead of relying on correlations with rather general aspects of treatment or animal. This helps to prevent the disregard of basic principles and underlying mechanisms of whole rumen function. PMID:27933039

Evaluation of Computational Fluid Dynamics and Coupled Fluid-Solid Modeling for a Direct Transfer Preswirl System.

PubMed

Javiya, Umesh; Chew, John; Hills, Nick; Dullenkopf, Klaus; Scanlon, Timothy

2013-05-01

The prediction of the preswirl cooling air delivery and disk metal temperature are important for the cooling system performance and the rotor disk thermal stresses and life assessment. In this paper, standalone 3D steady and unsteady computation fluid dynamics (CFD), and coupled FE-CFD calculations are presented for prediction of these temperatures. CFD results are compared with previous measurements from a direct transfer preswirl test rig. The predicted cooling air temperatures agree well with the measurement, but the nozzle discharge coefficients are under predicted. Results from the coupled FE-CFD analyses are compared directly with thermocouple temperature measurements and with heat transfer coefficients on the rotor disk previously obtained from a rotor disk heat conduction solution. Considering the modeling limitations, the coupled approach predicted the solid metal temperatures well. Heat transfer coefficients on the rotor disk from CFD show some effect of the temperature variations on the heat transfer coefficients. Reasonable agreement is obtained with values deduced from the previous heat conduction solution.

Flow of two immiscible fluids in a periodically constricted tube: Transitions to stratified, segmented, churn, spray or segregated flow

NASA Astrophysics Data System (ADS)

Tsamopoulos, John; Fraggedakis, Dimitris; Dimakopoulos, Yiannis

2015-11-01

We study the flow of two immiscible, Newtonian fluids in a periodically constricted tube driven by a constant pressure gradient. Our Volume-of-Fluid algorithm is used to solve the governing equations. First the code is validated by comparing its predictions to previously reported results for stratified and pulsing flow. Then it is used to capture accurately all the significant topological changes that take place. Initially, the fluids have a core-annular arrangement, which is found to either remain the same or change to a different arrangement depending on the fluid properties, the pressure driving the flow or the flow geometry. The flow-patterns that appear are the core-annular, segmented, churn, spray and segregated flow. The predicted scalings near pinching of the core fluid concur with similarity predictions and earlier numerical results (Cohen et al. (1999)). Flow-pattern maps are constructed in terms of the Reynolds and Weber numbers. Our results provide deeper insights in the mechanism of the pattern transitions and are in agreement with previous studies on core-annular flow (Kouris & Tsamopoulos (2001 & 2002)), segmented flow (Lac & Sherwood (2009)) and churn flow (Bai et al. (1992)). GSRT of Greece through the program ``Excellence'' (Grant No. 1918, entitled ``FilCoMicrA'').

The Need for Deeper Hydrology

NASA Astrophysics Data System (ADS)

Fogg, G. E.

2016-12-01

Hydrologists often compartmentalize subsurface fluid systems into soil, vadose zone, and groundwater even though such entities are all part of a dynamic continuum. Similarly, hydrogeologists mainly study the fresh groundwater that is essential to water resources upon which humans and ecosystems depend. While vast amounts of these fresh groundwater resources are in sedimentary basins, many of those basins contain vast amounts of saline groundwater and petroleum underneath the freshwater. Contrary to popular assumptions in the hydrogeology and petroleum communities, the saline groundwater and petroleum resources are not stagnant, but migrate in response to Tothian, topographically driven flow as well as other driving forces controlled by thermal, density and geomechanical processes. Importantly, the transition between fresh and saline groundwater does not necessarily represent a boundary between deep, stagnant groundwater and shallower, circulating groundwater. The deep groundwater is part of the subsurface fluid continuum, and exploitation of saline aquifer systems for conventional and unconventional (e.g., fracking) petroleum production or for injection of waste fluids should be done with some knowledge of the integrated fresh and saline water hydrogeologic system. Without sufficient knowledge of the deep and shallow hydrogeology, there will be significant uncertainty about the possible impacts of injection and petroleum extraction activities on overlying fresh groundwater quality and quantity. When significant uncertainty like this exists in science, public and scientific perceptions of consequences swing wildly from one extreme to another. Accordingly, professional and lay opinions on fracking range from predictions of doom to predictions of zero impact. This spastic range of opinions stems directly from the scientific uncertainty about hydrogeologic interactions between shallow and deep hydrogeologic systems. To responsibly manage both the fresh and saline, petroliferous groundwater resources, a new era of whole-system characterization is needed that integrates deep and shallow geologic and hydrogeologic models and data, including aquifer-aquitard frameworks, head and pressure in space and time, and hydrogeochemistry.

Prediction of Shock-Induced Cavitation in Water

NASA Astrophysics Data System (ADS)

Brundage, Aaron

2013-06-01

Fluid-structure interaction problems that require estimating the response of thin structures within fluids to shock loading has wide applicability. For example, these problems may include underwater explosions and the dynamic response of ships and submarines; and biological applications such as Traumatic Brain Injury (TBI) and wound ballistics. In all of these applications the process of cavitation, where small cavities with dissolved gases or vapor are formed as the local pressure drops below the vapor pressure due to shock hydrodynamics, can cause significant damage to the surrounding thin structures or membranes if these bubbles collapse, generating additional shock loading. Hence, a two-phase equation of state (EOS) with three distinct regions of compression, expansion, and tension was developed to model shock-induced cavitation. This EOS was evaluated by comparing data from pressure and temperature shock Hugoniot measurements for water up to 400 kbar, and data from ultrasonic pressure measurements in tension to -0.3 kbar, to simulated responses from CTH, an Eulerian, finite volume shock code. The new EOS model showed significant improvement over pre-existing CTH models such as the SESAME EOS for capturing cavitation. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy/NNSA under contract DE-AC04-94AL85000.

Maneuvering a reentry body via magneto-gasdynamic forces

NASA Astrophysics Data System (ADS)

Ohare, Leo Patrick

1992-04-01

Some of the characteristics of the interaction of an electrically conducting fluid with a non-uniform applied magnetic field and a potential magnetogasdynamic control system which may be used on future aerospace vehicles are presented. The flow through a two dimensional channel is predicted by numerically solving the magnetogasdynamic equations using a time marching technique. The fluid was modeled as a compressible, inviscid, supersonic gas with finite electrical conductivity. Development of the algorithm provided a means to predict and analyze phenomena associated with magnetogasdynamic flows which had not been previously explored using numerical methods. One such phenomena was the prediction of oblique waves resulting from the interaction of an electrically conducting fluid with a non-uniform applied magnetic field. Development of this tool provided a means to explore an application which might have potential use for future aerospace vehicle missions. In order to appreciate the significance of this technology, predictions were made of the pitching moment about a slender blunted cone, generated by a system relying on the fluid-magnetic interaction. These moments were compared to predictions of a pitching moment generated by a deflecting control surface on the same vehicle. It was shown that the proposed magnetogasdynamic system could produce moments which were on the same order as the moments produced by the flap systems at low deflection angles.

Effects of fluid-rock interaction on friction and slip stability of gouge-filled faults (Invited)

NASA Astrophysics Data System (ADS)

Spiers, C. J.

2013-12-01

Understanding the effects of fluid-rock interaction on fault friction is central not only to understanding natural seismogenesis but also to evaluating the risks of fault reactivation and induced seismicity posed by subsurface resources production and by geological storage of CO2. Microstructural studies on natural fault rocks deformed in the mid and upper crust, including those sampled in fault drilling projects, frequently show evidence for i) fluid-related reactions forming an anastomosing phyllosilicate network, ii) pressure solution and cataclasis of clast phases, and iii) dilatation and cementation of fractures, cracks and pores. Moreover, decades of friction experiments on simulated granitic, gabroic, quartz and more recently calcite and phyllosilicate-quartz gouges, have shown that the presence of an aqueous pore fluid, or even water vapour, strongly influences the frictional behaviour of these materials. This has long been recognised to point to the operation of fluid-assisted deformation mechanisms, such as stress corrosion cracking or pressure solution. Indeed, recent low velocity friction experiments performed at Utrecht on evaporite and quartz gouges, with varying amounts of phyllosilicate, indicate that fluid-assisted deformation of the clast phases is a requirement for velocity-weakening slip capable of causing stick-slip. Supercritical carbon dioxide, on the other hand, has little effect on the frictional behaviour of either dry or wet gouges. An important trend emerging from all gouges containing quartz, and tested at hydrothermal conditions and sliding velocities below 100 μm/s, is a transition from velocity strengthening at low temperatures, to velocity weakening at intermediate temperatures, and back to velocity strengthening at high temperatures, delineating three regimes of steady state frictional behaviour. Where dilation has been measured or estimated, the velocity weakening regime is further characterised by porosity development. This all leads to the conclusion that a micromechanism-based description of the frictional behaviour of gouge-filled faults, under mid and upper crustal conditions, needs to account for pressure solution and stress corrosion cracking of clast phases, and for both dilatant and non-dilatant slip on intervening, weak phyllosilicates. First attempts to do this, assuming pressure solution as the fluid-assisted clast deformation mechanism, successfully predict the three-regime behaviour seen in experiments on phyllosilicate-quartz gouges, as well as other key observations. Both steady state and transient frictional behaviour similar to that seen in experiments can be predicted. The key factor here controlling both frictional response (i.e a, b, a-b and Dc in the terminology of RSF modelling) and porosity turns out to be competition between dilatation due to intergranular slip on phyllosillicates versus flow and compaction by pressure solution. In particular, velocity-weakening slip, hence rupture nucleation, are predicted to be caused by the effects of the fluid phase in promoting compaction by pressure solution during dilatant shear.

Computational modelling of the mechanics of trabecular bone and marrow using fluid structure interaction techniques.

PubMed

Birmingham, E; Grogan, J A; Niebur, G L; McNamara, L M; McHugh, P E

2013-04-01

Bone marrow found within the porous structure of trabecular bone provides a specialized environment for numerous cell types, including mesenchymal stem cells (MSCs). Studies have sought to characterize the mechanical environment imposed on MSCs, however, a particular challenge is that marrow displays the characteristics of a fluid, while surrounded by bone that is subject to deformation, and previous experimental and computational studies have been unable to fully capture the resulting complex mechanical environment. The objective of this study was to develop a fluid structure interaction (FSI) model of trabecular bone and marrow to predict the mechanical environment of MSCs in vivo and to examine how this environment changes during osteoporosis. An idealized repeating unit was used to compare FSI techniques to a computational fluid dynamics only approach. These techniques were used to determine the effect of lower bone mass and different marrow viscosities, representative of osteoporosis, on the shear stress generated within bone marrow. Results report that shear stresses generated within bone marrow under physiological loading conditions are within the range known to stimulate a mechanobiological response in MSCs in vitro. Additionally, lower bone mass leads to an increase in the shear stress generated within the marrow, while a decrease in bone marrow viscosity reduces this generated shear stress.

Modelling fluid accumulation in the neck using simple baseline fluid metrics: implications for sleep apnea.

PubMed

Vena, Daniel; Yadollahi, A; Bradley, T Douglas

2014-01-01

Obstructive sleep apnea (OSA) is a common respiratory disorder among adults. Recently we have shown that sedentary lifestyle causes an increase in diurnal leg fluid volume (LFV), which can shift into the neck at night when lying down to sleep and increase OSA severity. The purpose of this work was to investigate various metrics that represent baseline fluid retention in the legs and examine their correlation with neck fluid volume (NFV) and to develop a robust model for predicting fluid accumulation in the neck. In 13 healthy awake non-obese men, LFV and NFV were recorded continuously and simultaneously while standing for 5 minutes and then lying supine for 90 minutes. Simple regression was used to examine correlations between baseline LFV, baseline neck circumference (NC) and change in LFV with the outcome variables: change in NC (ΔNC) and in NFV (ΔNFV90) after lying supine for 90 minutes. An exhaustive grid search was implemented to find combinations of input variables which best modeled outcomes. We found strong positive correlations between baseline LFV (supine and standing) and ΔNFV90. Models developed for predicting ΔNFV90 included baseline standing LFV, baseline NC combined with change in LFV after lying supine for 90 minutes. These correlations and the developed models suggest that a greater baseline LFV might contribute to increased fluid accumulation in the neck. These results give more evidence that sedentary lifestyle might play a role in the pathogenesis of OSA by increasing the baseline LFV. The best models for predicting ΔNC include baseline LFV and NC; they improved accuracies of estimating ΔNC over individual predictors, suggesting that a combination of baseline fluid metrics is a good predictor of the change in NC while lying supine. Future work is aimed at adding additional baseline demographic features to improve model accuracy and eventually use it as a screening tool to predict severity of OSA prior to sleep.

Cyst fluid telomerase activity predicts the histologic grade of cystic neoplasms of the pancreas

PubMed Central

Hata, Tatsuo; Molin, Marco Dal; Suenaga, Masaya; Yu, Jun; Pittman, Meredith; Weiss, Matthew; Canto, Marcia I.; Wolfgang, Christopher; Lennon, Anne Marie; Hruban, Ralph H; Goggins, Michael

2016-01-01

Purpose Pancreatic cysts frequently pose clinical dilemmas. On one hand, cysts with high-grade dysplasia offer opportunities for cure, on the other hand, those with low-grade dysplasia are easily over treated. Cyst fluid markers have the potential to improve the evaluation of these cysts. Since telomerase activity is commonly activated in malignant cells, we evaluated the diagnostic performance of cyst fluid telomerase activity measurements for predicting histologic grade. Experimental design Telomerase activity was measured using telomerase repeat amplification with digital-droplet PCR in surgically-aspirated cyst fluid samples from 219 patients who underwent pancreatic resection for a cystic lesion (184, discovery, 35 validation) and 36 patients who underwent endoscopic ultrasound fine needle aspiration. Methodological and clinical factors associated with telomerase activity were examined. Results Telomerase activity was reduced in samples that had undergone prior thawing. Among 119 samples not previously thawed, surgical cyst fluids from cystic neoplasms with high-grade dysplasia +/− associated invasive cancer had higher telomerase activity (median [interquartile range], 1158 [295.9–13033] copies/μL of cyst fluid than those without (19.74 [2.58–233.6] copies/μL) (P < 0.001). Elevated cyst fluid telomerase activity had a diagnostic accuracy for invasive cancer/high-grade dysplasia of 88.1% (discovery), 88.6% (validation), and 88.2% (merged). Among cysts classified preoperatively as having “worrisome features”, cyst fluid telomerase activity had high diagnostic performance (sensitivity 73.7%, specificity 90.6%, accuracy, 86.1%). In multivariate analysis, telomerase activity independently predicted the presence of invasive cancer/high-grade dysplasia. Conclusion Cyst fluid telomerase activity can be a useful predictor of the neoplastic grade of pancreatic cysts. PMID:27230749

Flow of two immiscible fluids in a periodically constricted tube: Transitions to stratified, segmented, churn, spray, or segregated flow

NASA Astrophysics Data System (ADS)

Fraggedakis, D.; Kouris, Ch.; Dimakopoulos, Y.; Tsamopoulos, J.

2015-08-01

We study the flow of two immiscible, Newtonian fluids in a periodically constricted tube driven by a constant pressure gradient. Our volume-of-fluid algorithm is used to solve the governing equations. First, the code is validated by comparing its predictions to previously reported results for stratified and pulsing flow. Then, it is used to capture accurately all the significant topological changes that take place. Initially, the fluids have a core-annular arrangement, which is found to either remain the same or change to a different arrangement depending on the fluid properties, the pressure driving the flow, or the flow geometry. The flow-patterns that appear are the core-annular, segmented, churn, spray, and segregated flow. The predicted scalings near pinching of the core fluid concur with similarity predictions and earlier numerical results [I. Cohen et al., "Two fluid drop snap-off problem: Experiments and theory," Phys. Rev. Lett. 83, 1147-1150 (1999)]. Flow-pattern maps are constructed in terms of the Reynolds and Weber numbers. Our result provides deeper insights into the mechanism of the pattern transitions and is in agreement with previous studies on core-annular flow [Ch. Kouris and J. Tsamopoulos, "Core-annular flow in a periodically constricted circular tube, I. Steady state, linear stability and energy analysis," J. Fluid Mech. 432, 31-68 (2001) and Ch. Kouris et al., "Comparison of spectral and finite element methods applied to the study of interfacial instabilities of the core-annular flow in an undulating tube," Int. J. Numer. Methods Fluids 39(1), 41-73 (2002)], segmented flow [E. Lac and J. D. Sherwood, "Motion of a drop along the centreline of a capillary in a pressure-driven flow," J. Fluid Mech. 640, 27-54 (2009)], and churn flow [R. Y. Bai et al., "Lubricated pipelining—Stability of core annular-flow. 5. Experiments and comparison with theory," J. Fluid Mech. 240, 97-132 (1992)].

A Summary of Data and Findings from the First Aeroelastic Prediction Workshop

NASA Technical Reports Server (NTRS)

Schuster, David M.; Chwalowski, Pawel.; Heeg, Jennifer; Wieseman, Carol D.

2012-01-01

This paper summarizes data and findings from the first Aeroelastic Prediction Workshop (AePW) held in April, 2012. The workshop has been designed as a series of technical interchange meetings to assess the state of the art of computational methods for predicting unsteady flowfields and static and dynamic aeroelastic response. The goals are to provide an impartial forum to evaluate the effectiveness of existing computer codes and modeling techniques to simulate aeroelastic problems, and to identify computational and experimental areas needing additional research and development. For this initial workshop, three subject configurations have been chosen from existing wind tunnel data sets where there is pertinent experimental data available for comparison. Participant researchers analyzed one or more of the subject configurations and results from all of these computations were compared at the workshop. Keywords: Unsteady Aerodynamics, Aeroelasticity, Computational Fluid Dynamics, Transonic Flow, Separated Flow.

Resolving the mystery of transport within internal transport barriersa)

NASA Astrophysics Data System (ADS)

Staebler, G. M.; Kinsey, J. E.; Belli, E. A.; Candy, J.; Waltz, R. E.; Greenfield, C. M.; Lao, L. L.; Smith, S. P.; Grierson, B. A.; Chrystal, C.

2014-05-01

The Trapped Gyro-Landau Fluid (TGLF) quasi-linear model [G. M. Staebler, et al., Phys. Plasmas 12, 102508 (2005)], which is calibrated to nonlinear gyrokinetic turbulence simulations, is now able to predict the electron density, electron and ion temperatures, and ion toroidal rotation simultaneously for internal transport barrier (ITB) discharges. This is a strong validation of gyrokinetic theory of ITBs, requiring multiple instabilities responsible for transport in different channels at different scales. The mystery of transport inside the ITB is that momentum and particle transport is far above the predicted neoclassical levels in apparent contradiction with the expectation from the theory of suppression of turbulence by E ×B velocity shear. The success of TGLF in predicting ITB transport is due to the inclusion of ion gyro-radius scale modes that become dominant at high E ×B velocity shear and to improvements to TGLF that allow momentum transport from gyrokinetic turbulence to be faithfully modeled.

Resolving the mystery of transport within internal transport barriers

DOE PAGES

Staebler, Gary M.; Kinsey, Jon E.; Belli, Emily A.; ...

2014-05-02

Here, the Trapped Gyro-Landau Fluid (TGLF) quasi-linear model, which is calibrated to nonlinear gyrokinetic turbulence simulations, is now able to predict the electron density, electron and ion temperatures and ion toroidal rotation simultaneously for internal transport barrier (ITB) discharges. This is a strong validation of gyrokinetic theory of ITBs, requiring multiple instabilities responsible for transport in different channels at different scales. The mystery of transport inside the ITB is that momentum and particle transport is far above the predicted neoclassical levels in apparent contradiction with the expectation from the theory of suppression of turbulence by E × B velocity shear.more » The success of TGLF in predicting ITB transport is due to the inclusion of ion gyro-radius scale modes that become dominant at high E × B velocity shear and to improvements to TGLF that allow momentum transport from gyrokinetic turbulence to be faithfully modeled.« less

Response to a pure tone in a nonlinear mechanical-electrical-acoustical model of the cochlea.

PubMed

Meaud, Julien; Grosh, Karl

2012-03-21

In this article, a nonlinear mathematical model is developed based on the physiology of the cochlea of the guinea pig. The three-dimensional intracochlear fluid dynamics are coupled to a micromechanical model of the organ of Corti and to electrical potentials in the cochlear ducts and outer hair cells (OHC). OHC somatic electromotility is modeled by linearized piezoelectric relations whereas the OHC hair-bundle mechanoelectrical transduction current is modeled as a nonlinear function of the hair-bundle deflection. The steady-state response of the cochlea to a single tone is simulated in the frequency domain using an alternating frequency time scheme. Compressive nonlinearity, harmonic distortion, and DC shift on the basilar membrane (BM), tectorial membrane (TM), and OHC potentials are predicted using a single set of parameters. The predictions of the model are verified by comparing simulations to available in vivo experimental data for basal cochlear mechanics. In particular, the model predicts more amplification on the reticular lamina (RL) side of the cochlear partition than on the BM, which replicates recent measurements. Moreover, small harmonic distortion and DC shifts are predicted on the BM, whereas more significant harmonic distortion and DC shifts are predicted in the RL and TM displacements and in the OHC potentials. Copyright © 2012 Biophysical Society. Published by Elsevier Inc. All rights reserved.

Assessment of computational prediction of tail buffeting

NASA Technical Reports Server (NTRS)

Edwards, John W.

1990-01-01

Assessments of the viability of computational methods and the computer resource requirements for the prediction of tail buffeting are made. Issues involved in the use of Euler and Navier-Stokes equations in modeling vortex-dominated and buffet flows are discussed and the requirement for sufficient grid density to allow accurate, converged calculations is stressed. Areas in need of basic fluid dynamics research are highlighted: vorticity convection, vortex breakdown, dynamic turbulence modeling for free shear layers, unsteady flow separation for moderately swept, rounded leading-edge wings, vortex flows about wings at high subsonic speeds. An estimate of the computer run time for a buffeting response calculation for a full span F-15 aircraft indicates that an improvement in computer and/or algorithm efficiency of three orders of magnitude is needed to enable routine use of such methods. Attention is also drawn to significant uncertainties in the estimates, in particular with regard to nonlinearities contained within the modeling and the question of the repeatability or randomness of buffeting response.

Computational fluid dynamics tools can be used to predict the progression of coronary artery disease

NASA Astrophysics Data System (ADS)

Coşkun, A. Ümit; Chen, Caixia; Stone, Peter H.; Feldman, Charles L.

2006-03-01

Atherosclerosis is focal and individual plaques evolve in an independent manner. The endothelium regulates arterial behavior by responding to its local shear stress. In vitro studies indicate that low endothelial shear stress (ESS) upregulates the genetic and molecular responses leading to the initiation and progression of atherosclerosis and promotes inflammation and formation of other features characteristic of vulnerable plaque. Physiologic ESS is vasculoprotective and fosters quiescence of the endothelium and vascular wall. High ESS promotes platelet aggregation. ESS and vascular wall morphology along the course of human coronary arteries can now be characterized in vivo, and may predict the focal areas in which atherosclerosis progression occurs. Rapidly evolving methodologies are able to characterize the arterial wall and the local hemodynamic factors likely responsible for progression of coronary disease in man. These new diagnostic modalities allow for identification of plaque progression. Accurate identification of arterial segments at high-risk for progression may permit pre-emptive intervention strategies to avoid adverse coronary events.

Perturbative tests of theoretical transport models using cold pulse and modulated electron cyclotron heating experiments

NASA Astrophysics Data System (ADS)

Kinsey, J. E.; Waltz, R. E.; DeBoo, J. C.

1999-05-01

It is difficult to discriminate between various tokamak transport models using standardized statistical measures to assess the goodness of fit with steady-state density and temperature profiles in tokamaks. This motivates consideration of transient transport experiments as a technique for testing the temporal response predicted by models. Results are presented comparing the predictions from the Institute for Fusion Studies—Princeton Plasma Physics Laboratory (IFS/PPPL), gyro-Landau-fluid (GLF23), Multi-mode (MM), Current Diffusive Ballooning Mode (CDBM), and Mixed-shear (MS) transport models against data from ohmic cold pulse and modulated electron cyclotron heating (ECH) experiments. In ohmically heated discharges with rapid edge cooling due to trace impurity injection, it is found that critical gradient models containing a strong temperature ratio (Ti/Te) dependence can exhibit behavior that is qualitatively consistent both spatially and temporally with experimental observation while depending solely on local parameters. On the DIII-D tokamak [J. L. Luxon and L. G. Davis, Fusion Technol. 8, 441 (1985)], off-axis modulated ECH experiments have been conducted in L-mode (low confinement mode) and the perturbed electron and ion temperature response to multiple heat pulses has been measured across the plasma core. Comparing the predicted Fourier phase of the temperature perturbations, it is found that no single model yielded agreement with both electron and ion phases for all cases. In general, it was found that the IFS/PPPL, GLF23, and MS models agreed well with the ion response, but not with the electron response. The CDBM and MM models agreed well with the electron response, but not with the ion response. For both types of transient experiments, temperature coupling between the electron and ion transport is found to be an essential feature needed in the models for reproducing the observed perturbative response.

Effects of gonadotropin-releasing hormone agonist/recombinant follicle-stimulating hormone versus gonadotropin-releasing hormone antagonist/recombinant follicle-stimulating hormone on follicular fluid levels of adhesion molecules during in vitro fertilization.

PubMed

Fornaro, Felice; Cobellis, Luigi; Mele, Daniela; Tassou, Argyrò; Badolati, Barbara; Sorrentino, Simona; De Lucia, Domenico; Colacurci, Nicola

2007-01-01

To compare the effects of GnRH-agonist/recombinant rFSH versus GnRH-antagonist/recombinant FSH stimulation on follicular fluid levels of soluble intercellular adhesion molecule (sICAM)-1 and vascular cell adhesion molecule-1 (sVCAM-1) during in vitro fertilization (IVF). Prospective, randomized study. University hospital. Seventy-three women underwent IVF. GnRH-agonist/rFSH or GnRH-antagonist/rFSH administration and collection of follicular fluid from 3 small (11-14 mm in diameter) and 3 large (18-21 mm in diameter) follicles on the day of oocyte retrieval. Follicular fluid levels of sICAM-1 and sVCAM-1 and intrafollicular estradiol and progesterone were also measured. Women who underwent GnRH-agonist/rFSH showed higher concentrations of sICAM-1 in both small and large follicles were compared with patients who received GnRH-antagonist/rFSH treatment; follicular fluid levels of sVCAM-1 were similar between the 2 stimulation protocols. Content of sICAM-1 in small and large follicles positively correlated with the number of follicles of > or =15 mm and the number of oocytes that were retrieved in both study groups. Concentrations of follicular fluid sVCAM-1 and progesterone were higher in large than in small follicles and were correlated positively to each other in both follicular classes. In IVF, GnRH-agonist/rFSH is associated with higher follicular fluid levels of sICAM-1 compared with GnRH-antagonist/rFSH regimen. Intrafollicular sICAM-1 content may predict ovarian response, and sVCAM-1 appears as an indicator of the degree of follicular luteinization.

Compressibility effects on rotor forces in the leakage path between a shrouded pump impeller and its housing

NASA Technical Reports Server (NTRS)

Cao, Nhai The

1993-01-01

A modified approach to Childs' previous work on fluid-structure interaction forces in the leakage path between an impeller shroud and its housing is presented in this paper. Three governing equations consisting of continuity, path-momentum, and circumferential-momentum equations were developed to describe the leakage path inside a pump impeller. Radial displacement perturbations were used to solve for radial and circumferential force coefficients. In addition, impeller-discharge pressure disturbances were used to obtain pressure oscillation responses due to precessing impeller pressure wave pattern. Childs' model was modified from an incompressible model to a compressible barotropic-fluid model (the density of the working fluid is a function of the pressure and a constant temperature only). Results obtained from this model yielded interaction forces for radial and circumferential force coefficients. Radial and circumferential forces define reaction forces within the impeller leakage path. An acoustic model for the same leakage path was also developed. The convective, Coriolis, and centrifugal acceleration terms are removed from the compressible model to obtain the acoustics model. A solution due to impeller discharge pressure disturbances model was also developed for the compressible and acoustics models. The results from these modifications are used to determine what effects additional perturbation terms in the compressible model have on the acoustic model. The results show that the additional fluid mechanics terms in the compressible model cause resonances (peaks) in the force coefficient response curves. However, these peaks only occurred at high values of inlet circumferential velocity ratios greater than 0.7. The peak pressure oscillation was shown to occur at the wearing ring seal. Introduction of impeller discharge disturbances with n = 11 diametral nodes showed that maximum peak pressure oscillations occurred at nondimensional precession frequencies of f = 6.4 and f = 7.8 for this particular pump. Bolleter's results suggest that for peak pressure oscillations to occur at the wearing ring seal, the nondimensional excitation frequency should be on the order of f = 2.182 for n = 11. The resonances found in this research do not match the excitation frequencies predicted by Bolleter. At the predicted peak excitation frequencies given by Bolleter, the compressible model shows an attenuation of the pressure oscillations at the seal exit. The compressibility of the fluid does not have a significant influence on the model at low values of nondimensional excitation frequency. At high values of nondimensional frequency, the effects of compressibility become more significant. For the acoustic analysis, the convective, Coriolis, and centrifugal acceleration terms do affect the results to a limited extent for precession excitation and to a large extent for a pressure excitation when the fluid operates at relatively high Mach numbers.

An integrated physiology model to study regional lung damage effects and the physiologic response

PubMed Central

2014-01-01

Background This work expands upon a previously developed exercise dynamic physiology model (DPM) with the addition of an anatomic pulmonary system in order to quantify the impact of lung damage on oxygen transport and physical performance decrement. Methods A pulmonary model is derived with an anatomic structure based on morphometric measurements, accounting for heterogeneous ventilation and perfusion observed experimentally. The model is incorporated into an existing exercise physiology model; the combined system is validated using human exercise data. Pulmonary damage from blast, blunt trauma, and chemical injury is quantified in the model based on lung fluid infiltration (edema) which reduces oxygen delivery to the blood. The pulmonary damage component is derived and calibrated based on published animal experiments; scaling laws are used to predict the human response to lung injury in terms of physical performance decrement. Results The augmented dynamic physiology model (DPM) accurately predicted the human response to hypoxia, altitude, and exercise observed experimentally. The pulmonary damage parameters (shunt and diffusing capacity reduction) were fit to experimental animal data obtained in blast, blunt trauma, and chemical damage studies which link lung damage to lung weight change; the model is able to predict the reduced oxygen delivery in damage conditions. The model accurately estimates physical performance reduction with pulmonary damage. Conclusions We have developed a physiologically-based mathematical model to predict performance decrement endpoints in the presence of thoracic damage; simulations can be extended to estimate human performance and escape in extreme situations. PMID:25044032

Immersed Boundary Methods for Optimization of Strongly Coupled Fluid-Structure Systems

NASA Astrophysics Data System (ADS)

Jenkins, Nicholas J.

Conventional methods for design of tightly coupled multidisciplinary systems, such as fluid-structure interaction (FSI) problems, traditionally rely on manual revisions informed by a loosely coupled linearized analysis. These approaches are both inaccurate for a multitude of applications, and they require an intimate understanding of the assumptions and limitations of the procedure in order to soundly optimize the design. Computational optimization, in particular topology optimization, has been shown to yield remarkable results for problems in solid mechanics using density interpolations schemes. In the context of FSI, however, well defined boundaries play a key role in both the design problem and the mechanical model. Density methods neither accurately represent the material boundary, nor provide a suitable platform to apply appropriate interface conditions. This thesis presents a new framework for shape and topology optimization of FSI problems that uses for the design problem the Level Set method (LSM) to describe the geometry evolution in the optimization process. The Extended Finite Element method (XFEM) is combined with a fictitiously deforming fluid domain (stationary arbitrary Lagrangian-Eulerian method) to predict the FSI response. The novelty of the proposed approach lies in the fact that the XFEM explicitly captures the material boundary defined by the level set iso-surface. Moreover, the XFEM provides a means to discretize the governing equations, and weak immersed boundary conditions are applied with Nitsche's Method to couple the fields. The flow is predicted by the incompressible Navier-Stokes equations, and a finite-deformation solid model is developed and tested for both hyperelastic and linear elastic problems. Transient and stationary numerical examples are presented to validate the FSI model and numerical solver approach. Pertaining to the optimization of FSI problems, the parameters of the discretized level set function are defined as explicit functions of the optimization variables, and the parameteric optimization problem is solved by nonlinear programming methods. The gradients of the objective and constrains are computed by the adjoint method for the global monolithic fluid-solid system. Two types of design problems are explored for optimization of the fluid-structure response: 1) the internal structural topology is varied, preserving the fluid-solid interface geometry, and 2) the fluid-solid interface is manipulated directly, which leads to simultaneously configuring both internal structural topology and outer mold shape. The numerical results show that the LSM-XFEM approach is well suited for designing practical applications, while at the same time reducing the requirement on highly refined mesh resolution compared to traditional density methods. However, these results also emphasize the need for a more robust embedded boundary condition framework. Further, the LSM can exhibit greater dependence on initial design seeding, and can impede design convergence. In particular for the strongly coupled FSI analysis developed here, the thinning and eventual removal of structural members can cause jumps in the evolution of the optimization functions.

A Comprehensive Prediction Model of Hydraulic Extended-Reach Limit Considering the Allowable Range of Drilling Fluid Flow Rate in Horizontal Drilling.

PubMed

Li, Xin; Gao, Deli; Chen, Xuyue

2017-06-08

Hydraulic extended-reach limit (HERL) model of horizontal extended-reach well (ERW) can predict the maximum measured depth (MMD) of the horizontal ERW. The HERL refers to the well's MMD when drilling fluid cannot be normally circulated by drilling pump. Previous model analyzed the following two constraint conditions, drilling pump rated pressure and rated power. However, effects of the allowable range of drilling fluid flow rate (Q min  ≤ Q ≤ Q max ) were not considered. In this study, three cases of HERL model are proposed according to the relationship between allowable range of drilling fluid flow rate and rated flow rate of drilling pump (Q r ). A horizontal ERW is analyzed to predict its HERL, especially its horizontal-section limit (L h ). Results show that when Q min  ≤ Q r  ≤ Q max (Case I), L h depends both on horizontal-section limit based on rated pump pressure (L h1 ) and horizontal-section limit based on rated pump power (L h2 ); when Q min  < Q max  < Q r (Case II), L h is exclusively controlled by L h1 ; while L h is only determined by L h2 when Q r  < Q min  < Q max (Case III). Furthermore, L h1 first increases and then decreases with the increase in drilling fluid flow rate, while L h2 keeps decreasing as the drilling fluid flow rate increases. The comprehensive model provides a more accurate prediction on HERL.

Emergency department management of gastro-enteritis in Australia and New Zealand.

PubMed

Schutz, Jacquie; Babl, Franz E; Sheriff, Nisa; Borland, Meredith

2008-10-01

Comparison of clinical practice guideline (CPG) recommendations and reported physician management of gastro-enteritis at Paediatric Research in Emergency Departments International Collaborative (PREDICT) network sites as a baseline for further randomised controlled trials. Two part survey comprising: (i) review of CPGs from PREDICT sites for gastro-enteritis; and (ii) survey of senior emergency department physicians regarding the management of gastro-enteritis. All 11 PREDICT sites participated. Nine CPGs were available with three sites using a common CPG. For moderate dehydration, eight CPGs advocated nasogastric (NG) rehydration in preference to intravenous (IV) rehydration. The IV route was reserved for severe dehydration or failed NG rehydration. In the second component of the survey, 78 of 83 (94%) physicians responded. In moderate dehydration, 82% of respondents used NG rehydration. In severe dehydration, 86% used IV fluids; 12% used NG and 3% an initial IV bolus followed by NG fluid. Serum electrolytes were measured universally with IV fluid use and by 22% using NG rehydration. The IV fluid bolus was with normal saline (86%). Fifty-four per cent used anti-emetics 'rarely' or 'sometimes'. The commonest agents were ondansetron (60%) and metoclopramide (29%). CPG recommendations and physician practice for the management of gastro-enteritis were similar across PREDICT sites with a focus on NG for moderate dehydration and IV for severe dehydration. A variety of fluids and administration rates were used. Anti-emetics were used infrequently. The efficacy and safety of newer anti-emetics should be explored in collaborative studies. Collaborative development of new CPGs should be considered to simplify fluid regimens.

Conductivity dependence of seismoelectric wave phenomena in fluid-saturated sediments

NASA Astrophysics Data System (ADS)

Block, Gareth I.; Harris, John G.

2006-01-01

Seismoelectric phenomena in sediments arise from acoustic wave-induced fluid motion in the pore space, which perturbs the electrostatic equilibrium of the electric double layer on the grain surfaces. Experimental techniques and the apparatus built to study the conductivity dependence of the electrokinetic (EK) effect are described, and outcomes for studies in loose glass microspheres and medium-grain sand are presented. By varying the NaCl concentration in the pore fluid, we measured the conductivity dependence of two kinds of EK behavior: (1) the electric fields generated within the samples by the passage of transmitted acoustic waves and (2) the electromagnetic waves produced at the fluid-sediment interface by the incident acoustic wave. Both phenomena are caused by relative fluid motion in the sediment pores; this feature is characteristic of poroelastic (Biot) media but is not predicted by either viscoelastic fluid or solid models. A model of plane wave reflection from a fluid-sediment interface using EK-Biot theory leads to theoretical predictions that compare well to the experimental data for both loose glass microspheres and medium-grain sand.

The Eighth Industrial Fluids Properties Simulation Challenge

PubMed Central

Schultz, Nathan E.; Ahmad, Riaz; Brennan, John K.; Frankel, Kevin A.; Moore, Jonathan D.; Moore, Joshua D.; Mountain, Raymond D.; Ross, Richard B.; Thommes, Matthias; Shen, Vincent K.; Siderius, Daniel W.; Smith, Kenneth D.

2016-01-01

The goal of the eighth industrial fluid properties simulation challenge was to test the ability of molecular simulation methods to predict the adsorption of organic adsorbates in activated carbon materials. In particular, the eighth challenge focused on the adsorption of perfluorohexane in the activated carbon BAM-109. Entrants were challenged to predict the adsorption in the carbon at 273 K and relative pressures of 0.1, 0.3, and 0.6. The predictions were judged by comparison to a benchmark set of experimentally determined values. Overall good agreement and consistency were found between the predictions of most entrants. PMID:27840542

Computation of Coupled Thermal-Fluid Problems in Distributed Memory Environment

NASA Technical Reports Server (NTRS)

Wei, H.; Shang, H. M.; Chen, Y. S.

2001-01-01

The thermal-fluid coupling problems are very important to aerospace and engineering applications. Instead of analyzing heat transfer and fluid flow separately, this study merged two well-accepted engineering solution methods, SINDA for thermal analysis and FDNS for fluid flow simulation, into a unified multi-disciplinary thermal fluid prediction method. A fully conservative patched grid interface algorithm for arbitrary two-dimensional and three-dimensional geometry has been developed. The state-of-the-art parallel computing concept was used to couple SINDA and FDNS for the communication of boundary conditions through PVM (Parallel Virtual Machine) libraries. Therefore, the thermal analysis performed by SINDA and the fluid flow calculated by FDNS are fully coupled to obtain steady state or transient solutions. The natural convection between two thick-walled eccentric tubes was calculated and the predicted results match the experiment data perfectly. A 3-D rocket engine model and a real 3-D SSME geometry were used to test the current model, and the reasonable temperature field was obtained.

Validation of metabolomics analysis of human perilymph fluid using liquid chromatography-mass spectroscopy.

PubMed

Mavel, Sylvie; Lefèvre, Antoine; Bakhos, David; Dufour-Rainfray, Diane; Blasco, Hélène; Emond, Patrick

2018-05-22

Although there is some data from animal studies, the metabolome of inner ear fluid in humans remains unknown. Characterization of the metabolome of the perilymph would allow for better understanding of its role in auditory function and for identification of biomarkers that might allow prediction of response to therapeutics. There is a major technical challenge due to the small sample of perilymph fluid available for analysis (sub-microliter). The objectives of this study were to develop and validate a methodology for analysis of perilymph metabolome using liquid chromatography-high resolution mass spectrometry (LC-HRMS). Due to the low availability of perilymph fluid; a methodological study was first performed using low volumes (0.8 μL) of cerebrospinal fluid (CSF) and optimized the LC-HRMS parameters using targeted and non-targeted metabolomics approaches. We obtained excellent parameters of reproducibility for about 100 metabolites. This methodology was then used to analyze perilymph fluid using two complementary chromatographic supports: reverse phase (RP-C18) and hydrophilic interaction liquid chromatography (HILIC). Both methods were highly robust and showed their complementarity, thus reinforcing the interest to combine these chromatographic supports. A fingerprinting was obtained from 98 robust metabolites (analytical variability <30%), where amino acids (e.g., asparagine, valine, glutamine, alanine, etc.), carboxylic acids and derivatives (e.g., lactate, carnitine, trigonelline, creatinine, etc.) were observed as first-order signals. This work lays the foundations of a robust analytical workflow for the exploration of the perilymph metabolome dedicated to the research of biomarkers for the diagnosis/prognosis of auditory pathologies. Copyright © 2018 Elsevier B.V. All rights reserved.

The assessment of circulating volume using inferior vena cava collapse index and carotid Doppler velocity time integral in healthy volunteers: a pilot study.

PubMed

Peachey, Tom; Tang, Andrew; Baker, Elinor C; Pott, Jason; Freund, Yonathan; Harris, Tim

2016-09-02

Assessment of circulating volume and the requirement for fluid replacement are fundamental to resuscitation but remain largely empirical. Passive leg raise (PLR) may determine fluid responders while avoiding potential fluid overload. We hypothesised that inferior vena cava collapse index (IVCCI) and carotid artery blood flow would change predictably in response to PLR, potentially providing a non-invasive tool to assess circulating volume and identifying fluid responsive patients. We conducted a prospective proof of concept pilot study on fasted healthy volunteers. One operator measured IVC diameter during quiet respiration and sniff, and carotid artery flow. Stroke volume (SV) was also measured using suprasternal Doppler. Our primary endpoint was change in IVCCI after PLR. We also studied changes in IVCCI after "sniff", and correlation between carotid artery flow and SV. Passive leg raise was associated with significant reduction in the mean inferior vena cava collapsibility index from 0.24 to 0.17 (p < 0.01). Mean stroke volume increased from 56.0 to 69.2 mL (p < 0.01). There was no significant change in common carotid artery blood flow. Changes in physiology consequent upon passive leg raise normalised rapidly. Passive leg raise is associated with a decrease of IVCCI and increase in stroke volume. However, the wide range of values observed suggests that factors other than circulating volume predominate in determining the proportion of collapse with respiration. In contrast to other studies, we did not find that carotid blood flow increased with passive leg raise. Rapid normalisation of post-PLR physiology may account for this.

Investigate the complex process in particle-fluid based surface generation technology using reactive molecular dynamics method

NASA Astrophysics Data System (ADS)

Han, Xuesong; Li, Haiyan; Zhao, Fu

2017-07-01

Particle-fluid based surface generation process has already become one of the most important materials processing technology for many advanced materials such as optical crystal, ceramics and so on. Most of the particle-fluid based surface generation technology involves two key process: chemical reaction which is responsible for surface softening; physical behavior which is responsible for materials removal/deformation. Presently, researchers cannot give a reasonable explanation about the complex process in the particle-fluid based surface generation technology because of the small temporal-spatial scale and the concurrent influence of physical-chemical process. Molecular dynamics (MD) method has already been proved to be a promising approach for constructing effective model of atomic scale phenomenon and can serve as a predicting simulation tool in analyzing the complex surface generation mechanism and is employed in this research to study the essence of surface generation. The deformation and piles of water molecule is induced with the feeding of abrasive particle which justifies the property mutation of water at nanometer scale. There are little silica molecule aggregation or materials removal because the water-layer greatly reduce the strength of mechanical interaction between particle and materials surface and minimize the stress concentration. Furthermore, chemical effect is also observed at the interface: stable chemical bond is generated between water and silica which lead to the formation of silconl and the reaction rate changes with the amount of water molecules in the local environment. Novel ring structure is observed in the silica surface and it is justified to be favored of chemical reaction with water molecule. The siloxane bond formation process quickly strengthened across the interface with the feeding of abrasive particle because of the compressive stress resulted by the impacting behavior.

Synovial fluid progenitors expressing CD90+ from normal but not osteoarthritic joints undergo chondrogenic differentiation without micro-mass culture.

PubMed

Krawetz, Roman J; Wu, Yiru Elizabeth; Martin, Liam; Rattner, Jerome B; Matyas, John R; Hart, David A

2012-01-01

Mesenchymal progenitor cells (MPCs) can differentiate into osteoblasts, adipocytes, and chondrocytes, and are in part responsible for maintaining tissue integrity. Recently, a progenitor cell population has been found within the synovial fluid that shares many similarities with bone marrow MPCs. These synovial fluid MPCs (sfMPCs) share the ability to differentiate into bone and fat, with a bias for cartilage differentiation. In this study, sfMPCs were isolated from human and canine synovial fluid collected from normal individuals and those with osteoarthritis (human: clinician-diagnosed, canine: experimental) to compare the differentiation potential of CD90+ vs. CD90- sfMPCs, and to determine if CD90 (Thy-1) is a predictive marker of synovial fluid progenitors with chondrogenic capacity in vitro. sfMPCs were derived from synovial fluid from normal and OA knee joints. These cells were induced to differentiate into chondrocytes and analyzed using quantitative PCR, immunofluorescence, and electron microscopy. The CD90+ subpopulation of sfMPCs had increased chondrogenic potential compared to the CD90- population. Furthermore, sfMPCs derived from healthy joints did not require a micro-mass step for efficient chondrogenesis. Whereas sfMPCs from OA synovial fluid retain the ability to undergo chondrogenic differentiation, they require micro-mass culture conditions. Overall, this study has demonstrated an increased chondrogenic potential within the CD90+ fraction of human and canine sfMPCs and that this population of cells derived from healthy normal joints do not require a micro-mass step for efficient chondrogenesis, while sfMPCs obtained from OA knee joints do not differentiate efficiently into chondrocytes without the micro-mass procedure. These results reveal a fundamental shift in the chondrogenic ability of cells isolated from arthritic joint fluids, and we speculate that the mechanism behind this change of cell behavior is exposure to the altered milieu of the OA joint fluid, which will be examined in further studies.

On hydrodynamic phase field models for binary fluid mixtures

NASA Astrophysics Data System (ADS)

Yang, Xiaogang; Gong, Yuezheng; Li, Jun; Zhao, Jia; Wang, Qi

2018-05-01

Two classes of thermodynamically consistent hydrodynamic phase field models have been developed for binary fluid mixtures of incompressible viscous fluids of possibly different densities and viscosities. One is quasi-incompressible, while the other is incompressible. For the same binary fluid mixture of two incompressible viscous fluid components, which one is more appropriate? To answer this question, we conduct a comparative study in this paper. First, we visit their derivation, conservation and energy dissipation properties and show that the quasi-incompressible model conserves both mass and linear momentum, while the incompressible one does not. We then show that the quasi-incompressible model is sensitive to the density deviation of the fluid components, while the incompressible model is not in a linear stability analysis. Second, we conduct a numerical investigation on coarsening or coalescent dynamics of protuberances using the two models. We find that they can predict quite different transient dynamics depending on the initial conditions and the density difference although they predict essentially the same quasi-steady results in some cases. This study thus cast a doubt on the applicability of the incompressible model to describe dynamics of binary mixtures of two incompressible viscous fluids especially when the two fluid components have a large density deviation.

Intelligence moderates reinforcement learning: a mini-review of the neural evidence

PubMed Central

2014-01-01

Our understanding of the neural basis of reinforcement learning and intelligence, two key factors contributing to human strivings, has progressed significantly recently. However, the overlap of these two lines of research, namely, how intelligence affects neural responses during reinforcement learning, remains uninvestigated. A mini-review of three existing studies suggests that higher IQ (especially fluid IQ) may enhance the neural signal of positive prediction error in dorsolateral prefrontal cortex, dorsal anterior cingulate cortex, and striatum, several brain substrates of reinforcement learning or intelligence. PMID:25185818

Intelligence moderates reinforcement learning: a mini-review of the neural evidence.

PubMed

Chen, Chong

2015-06-01

Our understanding of the neural basis of reinforcement learning and intelligence, two key factors contributing to human strivings, has progressed significantly recently. However, the overlap of these two lines of research, namely, how intelligence affects neural responses during reinforcement learning, remains uninvestigated. A mini-review of three existing studies suggests that higher IQ (especially fluid IQ) may enhance the neural signal of positive prediction error in dorsolateral prefrontal cortex, dorsal anterior cingulate cortex, and striatum, several brain substrates of reinforcement learning or intelligence. Copyright © 2015 the American Physiological Society.

Method for a microfluidic weaklink device

DOEpatents

Shepodd, Timothy J [Livermore, CA; Duncan, Matthew P [Augusta, GA

2009-12-01

The present invention relates to an electrokinetic (EK) pump capable of creating high pressures electroosmotically, and capable of retaining high pressures. Both pressure creation and retention are accomplished without the need for moving parts. The EK pump uses a polymerizable fluid that creates the pressure-retaining seal within the EK pump when polymerization is initiated, typically by exposure to UV radiation. Weaklink devices are advantageously constructed including such a pressure-retaining EK pump since, among other advantages, the response of the weaklink device relies on predictable and reliable chemical polymerization reactions.

Preliminary Numerical Simulations of Nozzle Formation in the Host Rock of Supersonic Volcanic Jets

NASA Astrophysics Data System (ADS)

Wohletz, K. H.; Ogden, D. E.; Glatzmaier, G. A.

2006-12-01

Recognizing the difficulty in quantitatively predicting how a vent changes during an explosive eruption, Kieffer (Kieffer, S.W., Rev. Geophys. 27, 1989) developed the theory of fluid dynamic nozzles for volcanism, utilizing a highly developed predictive scheme used extensively in aerodynamics for design of jet and rocket nozzles. Kieffer's work shows that explosive eruptions involve flow from sub to supersonic conditions through the vent and that these conditions control the erosion of the vent to nozzle shapes and sizes that maximize mass flux. The question remains how to predict the failure and erosion of vent host rocks by a high-speed, multiphase, compressible fluid that represents an eruption column. Clearly, in order to have a quantitative model of vent dynamics one needs a robust computational method for a turbulent, compressible, multiphase fluid. Here we present preliminary simulations of fluid flowing from a high-pressure reservoir through an eroding conduit and into the atmosphere. The eruptive fluid is modeled as an ideal gas, the host rock as a simple incompressible fluid with sandstone properties. Although these simulations do not yet include the multiphase dynamics of the eruptive fluid or the solid mechanics of the host rock, the evolution of the host rock into a supersonic nozzle is clearly seen. Our simulations show shock fronts both above the conduit, where the gas has expanded into the atmosphere, and within the conduit itself, thereby influencing the dynamics of the jet decompression.

Computational Fluid Dynamics Uncertainty Analysis for Payload Fairing Spacecraft Environmental Control Systems

NASA Technical Reports Server (NTRS)

Groves, Curtis; Ilie, Marcel; Schallhorn, Paul

2014-01-01

Spacecraft components may be damaged due to airflow produced by Environmental Control Systems (ECS). There are uncertainties and errors associated with using Computational Fluid Dynamics (CFD) to predict the flow field around a spacecraft from the ECS System. This paper describes an approach to estimate the uncertainty in using CFD to predict the airflow speeds around an encapsulated spacecraft.

Depth dependent stress revealed by aftershocks

NASA Astrophysics Data System (ADS)

Narteau, C.; Shebalin, P.

2017-12-01

Aftershocks occur in response to perturbations of the state of stress induced either by earthquakes or human activities. Along major strike-slip fault segments of the San Andreas fault system, the time-delay before the onset of the power-law aftershock decay rate (the c-value) varies by three orders of magnitude in the first twenty kilometers below the surface. Despite the influence of the lithostatic stress, there is no continuous change in c-value with respect to depth. Instead, two decay phases are separated by an abrupt increase at an intermediate depth range of 2 to 5 km. This transitional regime is the only one observed in fluid-injection-induced seismic areas. This provides strong evidence for the role of fluid and a porosity reduction mechanism at depth of few kilometers in active fault zones. Aftershock statistics can then be used to predict the evolution the differential shear stress with depth until the brittle-ductile transition is reached.

Development of a Physiologically-Based Pharmacokinetic Model of the Rat Central Nervous System

PubMed Central

Badhan, Raj K. Singh; Chenel, Marylore; Penny, Jeffrey I.

2014-01-01

Central nervous system (CNS) drug disposition is dictated by a drug’s physicochemical properties and its ability to permeate physiological barriers. The blood–brain barrier (BBB), blood-cerebrospinal fluid barrier and centrally located drug transporter proteins influence drug disposition within the central nervous system. Attainment of adequate brain-to-plasma and cerebrospinal fluid-to-plasma partitioning is important in determining the efficacy of centrally acting therapeutics. We have developed a physiologically-based pharmacokinetic model of the rat CNS which incorporates brain interstitial fluid (ISF), choroidal epithelial and total cerebrospinal fluid (CSF) compartments and accurately predicts CNS pharmacokinetics. The model yielded reasonable predictions of unbound brain-to-plasma partition ratio (Kpuu,brain) and CSF:plasma ratio (CSF:Plasmau) using a series of in vitro permeability and unbound fraction parameters. When using in vitro permeability data obtained from L-mdr1a cells to estimate rat in vivo permeability, the model successfully predicted, to within 4-fold, Kpuu,brain and CSF:Plasmau for 81.5% of compounds simulated. The model presented allows for simultaneous simulation and analysis of both brain biophase and CSF to accurately predict CNS pharmacokinetics from preclinical drug parameters routinely available during discovery and development pathways. PMID:24647103

Prediction of fingering in porous media

NASA Astrophysics Data System (ADS)

Wang, Zhi; Feyen, Jan; Elrick, David E.

1998-09-01

Immiscible displacement, involving two fluids in a porous medium, can be unstable and fingered under certain conditions. In this paper, the original linear instability criterion of Chuoke et al. [1959] is generalized, considering wettability of two immiscible fluids to the porous medium. This is then used to predict 24 specific flow and porous medium conditions for the onset of wetting front instability in the subsurface. Wetting front instability is shown to be a function of the driving fluid wettability to the medium, differences in density and viscosity of the fluids, the magnitude of the interfacial tension, and the direction of flow with respect to gravity. Scenarios of water and nonaqueous-phase liquid infiltration into the vadose zone are examined to predict preferential flow and contamination of groundwater. The mechanisms of finger formation, propagation, and persistence in the vadose zone are reviewed, and the existing equations for calculating the size, the number and velocity of fingers are simplified for field applications. The analyses indicate that fingers initiate and propagate according to spatial and temporal distribution of the dynamic breakthrough (water- or air-entry) pressures in the porous medium. The predicted finger size and velocity are in close agreement with the experimental results.

Spatiotemporal and geometric optimization of sensor arrays for detecting analytes fluids

DOEpatents

Lewis, Nathan S.; Freund, Michael S.; Briglin, Shawn M.; Tokumaru, Phil; Martin, Charles R.; Mitchell, David T.

2006-10-17

Sensor arrays and sensor array systems for detecting analytes in fluids. Sensors configured to generate a response upon introduction of a fluid containing one or more analytes can be located on one or more surfaces relative to one or more fluid channels in an array. Fluid channels can take the form of pores or holes in a substrate material. Fluid channels can be formed between one or more substrate plates. Sensor can be fabricated with substantially optimized sensor volumes to generate a response having a substantially maximized signal to noise ratio upon introduction of a fluid containing one or more target analytes. Methods of fabricating and using such sensor arrays and systems are also disclosed.

Spatiotemporal and geometric optimization of sensor arrays for detecting analytes in fluids

DOEpatents

Lewis, Nathan S [La Canada, CA; Freund, Michael S [Winnipeg, CA; Briglin, Shawn S [Chittenango, NY; Tokumaru, Phillip [Moorpark, CA; Martin, Charles R [Gainesville, FL; Mitchell, David [Newtown, PA

2009-09-29

Sensor arrays and sensor array systems for detecting analytes in fluids. Sensors configured to generate a response upon introduction of a fluid containing one or more analytes can be located on one or more surfaces relative to one or more fluid channels in an array. Fluid channels can take the form of pores or holes in a substrate material. Fluid channels can be formed between one or more substrate plates. Sensor can be fabricated with substantially optimized sensor volumes to generate a response having a substantially maximized signal to noise ratio upon introduction of a fluid containing one or more target analytes. Methods of fabricating and using such sensor arrays and systems are also disclosed.

Superfluidity, Bose-Einstein condensation, and structure in one-dimensional Luttinger liquids

NASA Astrophysics Data System (ADS)

Vranješ Markić, L.; Vrcan, H.; Zuhrianda, Z.; Glyde, H. R.

2018-01-01

We report diffusion Monte Carlo (DMC) and path integral Monte Carlo (PIMC) calculations of the properties of a one-dimensional (1D) Bose quantum fluid. The equation of state, the superfluid fraction ρS/ρ0 , the one-body density matrix n (x ) , the pair distribution function g (x ) , and the static structure factor S (q ) are evaluated. The aim is to test Luttinger liquid (LL) predictions for 1D fluids over a wide range of fluid density and LL parameter K . The 1D Bose fluid examined is a single chain of 4He atoms confined to a line in the center of a narrow nanopore. The atoms cannot exchange positions in the nanopore, the criterion for 1D. The fluid density is varied from the spinodal density where the 1D liquid is unstable to droplet formation to the density of bulk liquid 4He. In this range, K varies from K >2 at low density, where a robust superfluid is predicted, to K <0.5 , where fragile 1D superflow and solidlike peaks in S (q ) are predicted. For uniform pore walls, the ρS/ρ0 scales as predicted by LL theory. The n (x ) and g (x ) show long range oscillations and decay with x as predicted by LL theory. The amplitude of the oscillations is large at high density (small K ) and small at low density (large K ). The K values obtained from different properties agree well verifying the internal structure of LL theory. In the presence of disorder, the ρS/ρ0 does not scale as predicted by LL theory. A single vJ parameter in the LL theory that recovers LL scaling was not found. The one body density matrix (OBDM) in disorder is well predicted by LL theory. The "dynamical" superfluid fraction, ρSD/ρ0 , is determined. The physics of the deviation from LL theory in disorder and the "dynamical" ρSD/ρ0 are discussed.

Beyond the standard two-film theory: Computational fluid dynamics simulations for carbon dioxide capture in a wetted wall column

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Chao; Xu, Zhijie; Lai, Canhai

The standard two-film theory (STFT) is a diffusion-based mechanism that can be used to describe gas mass transfer across liquid film. Fundamental assumptions of the STFT impose serious limitations on its ability to predict mass transfer coefficients. To better understand gas absorption across liquid film in practical situations, a multiphase computational fluid dynamics (CFD) model fully equipped with mass transport and chemistry capabilities has been developed for solvent-based carbon dioxide (CO 2) capture to predict the CO 2 mass transfer coefficient in a wetted wall column. The hydrodynamics is modeled using a volume of fluid method, and the diffusive andmore » reactive mass transfer between the two phases is modeled by adopting a one-fluid formulation. We demonstrate that the proposed CFD model can naturally account for the influence of many important factors on the overall mass transfer that cannot be quantitatively explained by the STFT, such as the local variation in fluid velocities and properties, flow instabilities, and complex geometries. The CFD model also can predict the local mass transfer coefficient variation along the column height, which the STFT typically does not consider.« less

Beyond the standard two-film theory: Computational fluid dynamics simulations for carbon dioxide capture in a wetted wall column

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Chao; Xu, Zhijie; Lai, Canhai

The standard two-film theory (STFT) is a diffusion-based mechanism that can be used to describe gas mass transfer across liquid film. Fundamental assumptions of the STFT impose serious limitations on its ability to predict mass transfer coefficients. To better understand gas absorption across liquid film in practical situations, a multiphase computational fluid dynamics (CFD) model fully equipped with mass transport and chemistry capabilities has been developed for solvent-based carbon dioxide (CO2) capture to predict the CO2 mass transfer coefficient in a wetted wall column. The hydrodynamics is modeled using a volume of fluid method, and the diffusive and reactive massmore » transfer between the two phases is modeled by adopting a one-fluid formulation. We demonstrate that the proposed CFD model can naturally account for the influence of many important factors on the overall mass transfer that cannot be quantitatively explained by the STFT, such as the local variation in fluid velocities and properties, flow instabilities, and complex geometries. The CFD model also can predict the local mass transfer coefficient variation along the column height, which the STFT typically does not consider.« less

Beyond the standard two-film theory: Computational fluid dynamics simulations for carbon dioxide capture in a wetted wall column

DOE PAGES

Wang, Chao; Xu, Zhijie; Lai, Canhai; ...

2018-03-27

The standard two-film theory (STFT) is a diffusion-based mechanism that can be used to describe gas mass transfer across liquid film. Fundamental assumptions of the STFT impose serious limitations on its ability to predict mass transfer coefficients. To better understand gas absorption across liquid film in practical situations, a multiphase computational fluid dynamics (CFD) model fully equipped with mass transport and chemistry capabilities has been developed for solvent-based carbon dioxide (CO 2) capture to predict the CO 2 mass transfer coefficient in a wetted wall column. The hydrodynamics is modeled using a volume of fluid method, and the diffusive andmore » reactive mass transfer between the two phases is modeled by adopting a one-fluid formulation. We demonstrate that the proposed CFD model can naturally account for the influence of many important factors on the overall mass transfer that cannot be quantitatively explained by the STFT, such as the local variation in fluid velocities and properties, flow instabilities, and complex geometries. The CFD model also can predict the local mass transfer coefficient variation along the column height, which the STFT typically does not consider.« less

Compression in Working Memory and Its Relationship With Fluid Intelligence.

PubMed

Chekaf, Mustapha; Gauvrit, Nicolas; Guida, Alessandro; Mathy, Fabien

2018-06-01

Working memory has been shown to be strongly related to fluid intelligence; however, our goal is to shed further light on the process of information compression in working memory as a determining factor of fluid intelligence. Our main hypothesis was that compression in working memory is an excellent indicator for studying the relationship between working-memory capacity and fluid intelligence because both depend on the optimization of storage capacity. Compressibility of memoranda was estimated using an algorithmic complexity metric. The results showed that compressibility can be used to predict working-memory performance and that fluid intelligence is well predicted by the ability to compress information. We conclude that the ability to compress information in working memory is the reason why both manipulation and retention of information are linked to intelligence. This result offers a new concept of intelligence based on the idea that compression and intelligence are equivalent problems. Copyright © 2018 Cognitive Science Society, Inc.

Regression analysis of traction characteristics of traction fluids

NASA Technical Reports Server (NTRS)

Loewenthal, S. H.; Rohn, D. A.

1983-01-01

Traction data for Santotrac 50 and TDF-88 over a wide range of operating conditions were analyzed. An eight term correlation equation to predict the maximum traction coefficient and a six term correlation equation to predict the initial slope of the traction curve were developed. The slope correlation was corrected for size effect considering the compliance of the disks. The effects of different operating conditions on the traction performance of each traction fluid were studied. Both fluids exhibited a loss in traction with increases in spin, but the losses with the TDF-88 fluid were not as severe as those with Santotrac 50. Overall, both fluids exhibited similar performance, showing an increase in traction with contact pressure up to about 2.0 GPa, and a reduction in traction with higher surface speeds up to about 100 m/sec. The apparent stiffness of the traction contact, that is, film disk combination, increases with contact pressure and decreases with speed.

Prediction of global vapor-liquid equilibria for mixtures containing polar and associating components with improved renormalization group theory.

PubMed

Mi, Jianguo; Tang, Yiping; Zhong, Chongli; Li, Yi-Gui

2005-11-03

Our recently improved renormalization group (RG) theory is further reformulated within the context of density functional theory. To improve the theory for polar and associating fluids, an explicit and complete expression of the theory is derived in which the density fluctuation is expanded up to the third-order term instead of the original second-order term. A new predictive equation of state based on the first-order mean spherical approximation statistical associating fluid theory (FMSA-SAFT) and the newly improved RG theory is proposed for systems containing polar and associating fluids. The calculated results for both pure fluids and mixtures are in good agreement with experimental data both inside and outside the critical region. This work demonstrates that the RG theory incorporated with the solution of FMSA is a promising route for accurately describing the global phase behavior of complex fluids and mixtures.

The Effect of Age in the Alteration in Fluid Balance of Rats in Response to Centrifugation

NASA Technical Reports Server (NTRS)

Fuller, Charles A.

2000-01-01

With an increase in gravity load induced by centrifugation or upon return to Earth following spaceflight, there is a period of adjustment in fluid balance in rats. With centrifugation there is a reduced fluid intake with maintenance of the rate of urine excretion. Following spaceflight there is an increase in urine output and maintenance of fluid intake. The initial period of acclimation to hypergravity is associated with a net loss of fluids. In the present study in response to centrifugation at 2.0 G this period of acclimation is present in mature rats for a longer period of time, about 24 hours. Following this initial response a period of over compensation has previously been reported. In the present study this was not observed. The net effect of these alterations in water intake and output in response to centrifugation for 14 days was slight increase in the percent total body water, with effective compensation seen in both young and mature rats. Older rats have been shown to have a reduced relative thirst and compensatory renal function in response to hypohydration, hyperosmolality and pharmacological stimuli. Responsiveness to these stimuli are delayed and/or attenuated in older animals. Similar findings were noted in the present study in the initial response to centrifugation. The older animal had a delayed return of fluid intake to control levels. The delay of one day did not appear to effect long-term fluid homeostasis, as there was difference in the response of percent total body water at the end of 14 days of centrifugation with both age groups having a slight but significant increase. This increase has been attributed to the increase in lean body mass induced by centrifugation.

Time-dependent deformation of gas shales - role of rock framework versus reservoir fluids

NASA Astrophysics Data System (ADS)

Hol, Sander; Zoback, Mark

2013-04-01

Hydraulic fracturing operations are generally performed to achieve a fast, drastic increase of permeability and production rates. Although modeling of the underlying short-term mechanical response has proven successful via conventional geomechanical approaches, predicting long-term behavior is still challenging as the formation interacts physically and chemically with the fluids present in-situ. Recent experimental work has shown that shale samples subjected to a change in effective stress deform in a time-dependent manner ("creep"). Although the magnitude and nature of this behavior is strongly related to the composition and texture of the sample, also the choice of fluid used in the experiments affects the total strain response - strongly adsorbing fluids result in more, recoverable creep. The processes underlying time-dependent deformation of shales under in-situ stresses, and the long-term impact on reservoir performance, are at present poorly understood. In this contribution, we report triaxial mechanical tests, and theoretical/thermodynamic modeling work with the aim to identify and describe the main mechanisms that control time-dependent deformation of gas shales. In particular, we focus on the role of the shale solid framework versus the type and pressure of the present pore fluid. Our experiments were mainly performed on Eagle Ford Shale samples. The samples were subjected to cycles of loading and unloading, first in the dry state, and then again after equilibrating them with (adsorbing) CO2 and (non-adsorbing) He at fluid pressures of 4 MPa. Stresses were chosen close to those persisting under in-situ conditions. The results of our tests demonstrate that likely two main types of deformation mechanisms operate that relate to a) the presence of microfractures as a dominating feature in the solid framework of the shale, and b) the adsorbing potential of fluids present in the nanoscale voids of the shale. To explain the role of adsorption in the observed compaction creep, we postulate a serial coupling between 1) stress-driven desorption of the fluid species, 2) diffusion of the desorbed species out of the solid, and 3) consequent shrinkage. We propose a model in which the total shrinkage of the solid (Step 3) that is measured as bulk compaction, is driven by a change in stress state (Step 1), and evolves in time controlled by the diffusion characteristics of the system (Step 2). Our experimental and modeling study shows that both the nature of the solid framework of the shale, as well as the type and pressure of pore fluids affect the long-term in-situ mechanical behavior of gas shale reservoirs.

Effect of bodily fluids from honey bee (Apis mellifera) larvae on growth and genome-wide transcriptional response of the causal agent of American Foulbrood disease (Paenibacillus larvae).

PubMed

De Smet, Lina; De Koker, Dieter; Hawley, Alyse K; Foster, Leonard J; De Vos, Paul; de Graaf, Dirk C

2014-01-01

Paenibacillus larvae, the causal agent of American Foulbrood disease (AFB), affects honey bee health worldwide. The present study investigates the effect of bodily fluids from honey bee larvae on growth velocity and transcription for this Gram-positive, endospore-forming bacterium. It was observed that larval fluids accelerate the growth and lead to higher bacterial densities during stationary phase. The genome-wide transcriptional response of in vitro cultures of P. larvae to larval fluids was studied by microarray technology. Early responses of P. larvae to larval fluids are characterized by a general down-regulation of oligopeptide and sugar transporter genes, as well as by amino acid and carbohydrate metabolic genes, among others. Late responses are dominated by general down-regulation of sporulation genes and up-regulation of phage-related genes. A theoretical mechanism of carbon catabolite repression is discussed.

Modeling and measuring non-Newtonian shear flows of soft interfaces

NASA Astrophysics Data System (ADS)

Lopez, Juan; Raghunandan, Aditya; Underhill, Patrick; Hirsa, Amir

2017-11-01

Soft interfaces of polymers, particles, and proteins between fluid phases are ubiquitous in industrial and natural processes. The flow response of such systems to deformation is often not linear, as one would expect for Newtonian interfaces. The resistance to (pure shear) flow of interfaces is generally characterized by a single intrinsic material property, the surface shear viscosity. Predicted shear responses of Newtonian interfaces have achieved consensus across a wide range of flow conditions and measurement devices, when the nonlinear hydrodynamic coupling to the bulk phase is correctly accounted for. However, predicting the flows of sheared non-Newtonian interfaces remains a challenge. Here, we introduce a computational model that incorporates a non-Newtonian constitutive equation for the sheared interface and properly accounts for the coupled interfacial and bulk phase flows. We compare predictions to experiments performed with a model phospholipid system, DPPC - the main constituent of mammalian lung surfactant. Densely packed films of DPPC are directly sheared in a knife-edge surface viscometer. Yield-stress and shear thinning behaviors are shown to be accurately captured across hydrodynamic regimes straddling the Stokes flow limit to inertia dominated flows. Supported by NASA Grant NNX13AQ22G.

Analyses of ACPL thermal/fluid conditioning system

NASA Technical Reports Server (NTRS)

Stephen, L. A.; Usher, L. H.

1976-01-01

Results of engineering analyses are reported. Initial computations were made using a modified control transfer function where the systems performance was characterized parametrically using an analytical model. The analytical model was revised to represent the latest expansion chamber fluid manifold design, and systems performance predictions were made. Parameters which were independently varied in these computations are listed. Systems predictions which were used to characterize performance are primarily transient computer plots comparing the deviation between average chamber temperature and the chamber temperature requirement. Additional computer plots were prepared. Results of parametric computations with the latest fluid manifold design are included.

Protein kinases as mediators of fluid shear stress stimulated signal transduction in endothelial cells: a hypothesis for calcium-dependent and calcium-independent events activated by flow.

PubMed

Berk, B C; Corson, M A; Peterson, T E; Tseng, H

1995-12-01

Fluid shear stress regulates endothelial cell function, but the signal transduction mechanisms involved in mechanotransduction remain unclear. Recent findings demonstrate that several intracellular kinases are activated by mechanical forces. In particular, members of the mitogen-activated protein (MAP) kinase family are stimulated by hyperosmolarity, stretch, and stress such as heat shock. We propose a model for mechanotransduction in endothelial cells involving calcium-dependent and calcium-independent protein kinase pathways. The calcium-dependent pathway involves activation of phospholipase C, hydrolysis of phosphatidylinositol 4,5-bisphosphate (PIP2), increases in intracellular calcium and stimulation of kinases such as calcium-calmodulin and C kinases (PKC). The calcium-independent pathway involves activation of a small GTP-binding protein and stimulation of calcium-independent PKC and MAP kinases. The calcium-dependent pathway mediates the rapid, transient response to fluid shear stress including activation of nitric oxide synthase (NOS) and ion transport. In contrast, the calcium-independent pathway mediates a slower response including the sustained activation of NOS and changes in cell morphology and gene expression. We propose that focal adhesion complexes link the calcium-dependent and calcium-independent pathways by regulating activity of phosphatidylinositol 4-phosphate (PIP) 5-kinase (which regulates PIP2 levels) and p125 focal adhesion kinase (FAK, which phosphorylates paxillin and interacts with cytoskeletal proteins). This model predicts that dynamic interactions between integrin molecules present in focal adhesion complexes and membrane events involved in mechanotransduction will be integrated by calcium-dependent and calcium-independent kinases to generate intracellular signals involved in the endothelial cell response to flow.

Langevin dynamics encapsulate the microscopic and emergent macroscopic properties of midge swarms

PubMed Central

2018-01-01

In contrast to bird flocks, fish schools and animal herds, midge swarms maintain cohesion but do not possess global order. High-speed imaging techniques are now revealing that these swarms have surprising properties. Here, I show that simple models found on the Langevin equation are consistent with this wealth of recent observations. The models predict correctly that large accelerations, exceeding 10 g, will be common and they predict correctly the coexistence of core condensed phases surrounded by dilute vapour phases. The models also provide new insights into the influence of environmental conditions on swarm dynamics. They predict that correlations between midges increase the strength of the effective force binding the swarm together. This may explain why such correlations are absent in laboratory swarms but present in natural swarms which contend with the wind and other disturbances. Finally, the models predict that swarms have fluid-like macroscopic mechanical properties and will slosh rather than slide back and forth after being abruptly displaced. This prediction offers a promising avenue for future experimentation that goes beyond current quasi-static testing which has revealed solid-like responses. PMID:29298958

Abrupt contraction flow of magnetorheological fluids

NASA Astrophysics Data System (ADS)

Kuzhir, P.; López-López, M. T.; Bossis, G.

2009-05-01

Contraction and expansion flows of magnetorheological fluids occur in a variety of smart devices. It is important therefore to learn how these flows can be controlled by means of applied magnetic fields. This paper presents a first investigation into the axisymmetric flow of a magnetorheological fluid through an orifice (so-called abrupt contraction flow). The effect of an external magnetic field, longitudinal or transverse to the flow, is examined. In experiments, the pressure-flow rate curves were measured, and the excess pressure drop (associated with entrance and exit losses) was derived from experimental data through the Bagley correction procedure. The effect of the longitudinal magnetic field is manifested through a significant increase in the slope of the pressure-flow rate curves, while no discernible yield stress occurs. This behavior, observed at shear Mason numbers 10

Mechanotransduction in bone: osteoblasts are more responsive to fluid forces than mechanical strain

NASA Technical Reports Server (NTRS)

Owan, I.; Burr, D. B.; Turner, C. H.; Qiu, J.; Tu, Y.; Onyia, J. E.; Duncan, R. L.

1997-01-01

Mechanical force applied to bone produces two localized mechanical signals on the cell: deformation of the extracellular matrix (substrate strain) and extracellular fluid flow. To study the effects of these stimuli on osteoblasts, MC3T3-E1 cells were grown on type I collagen-coated plastic plates and subjected to four-point bending. This technique produces uniform levels of physiological strain and fluid forces on the cells. Each of these parameters can be varied independently. Osteopontin (OPN) mRNA expression was used to assess the anabolic response of MC3T3-E1 cells. When fluid forces were low, neither strain magnitude nor strain rate was correlated with OPN expression. However, higher-magnitude fluid forces significantly increased OPN message levels independently of the strain magnitude or rate. These data indicate that fluid forces, and not mechanical stretch, influence OPN expression in osteoblasts and suggest that fluid forces induced by extracellular fluid flow within the bone matrix may play an important role in bone formation in response to mechanical loading.

Fluid overpressures and strength of the sedimentary upper crust

NASA Astrophysics Data System (ADS)

Suppe, John

2014-12-01

The classic crustal strength-depth profile based on rock mechanics predicts a brittle strength σ1 -σ3 = κ(ρbar gz -Pf) that increases linearly with depth as a consequence of [1] the intrinsic brittle pressure dependence κ plus [2] an assumption of hydrostatic pore-fluid pressure, Pf = ρwgz. Many deep borehole stress data agree with a critical state of failure of this form. In contrast, fluid pressures greater than hydrostatic ρbar gz >Pf >ρw gz are normally observed in clastic continental margins and shale-rich mountain belts. Therefore we explore the predicted shapes of strength-depth profiles using data from overpressured regions, especially those dominated by the widespread disequilibrium-compaction mechanism, in which fluid pressures are hydrostatic above the fluid-retention depth zFRD and overpressured below, increasing parallel to the lithostatic gradient ρbar gz . Both brittle crustal strength and frictional fault strength below the zFRD must be constant with depth because effective stress (ρbar gz -Pf) is constant, in contrast with the classic linearly increasing profile. Borehole stress and fluid-pressure measurements in several overpressured deforming continental margins agree with this constant-strength prediction, with the same pressure-dependence κ as the overlying hydrostatic strata. The role of zFRD in critical-taper wedge mechanics and jointing is illustrated. The constant-strength approximation is more appropriate for overpressured crust than classic linearly increasing models.

The Influence of Dynamic Contact Angle on Wetting Dynamics

NASA Technical Reports Server (NTRS)

Rame, Enrique; Garoff, Steven

2005-01-01

When surface tension forces dominate, and regardless of whether the situation is static or dynamic, the contact angle (the angle the interface between two immiscible fluids makes when it contacts a solid) is the key parameter that determines the shape of a fluid-fluid interface. The static contact angle is easy to measure and implement in models predicting static capillary surface shapes and such associated quantities as pressure drops. By contrast, when the interface moves relative to the solid (as in dynamic wetting processes) the dynamic contact angle is not identified unambiguously because it depends on the geometry of the system Consequently, its determination becomes problematic and measurements in one geometry cannot be applied in another for prediction purposes. However, knowing how to measure and use the dynamic contact angle is crucial to determine such dynamics as a microsystem throughput reliably. In this talk we will present experimental and analytical efforts aimed at resolving modeling issues present in dynamic wetting. We will review experiments that show the inadequacy of the usual hydrodynamic model when a fluid-fluid meniscus moves over a solid surface such as the wall of a small tube or duct. We will then present analytical results that show how to parametrize these problems in a predictive manner. We will illustrate these ideas by showing how to implement the method in numerical fluid mechanical calculations.

Fluid mechanics of slurry flow through the grinding media in ball mills

DOE Office of Scientific and Technical Information (OSTI.GOV)

Songfack, P.K.; Rajamani, R.K.

1995-12-31

The slurry transport within the ball mill greatly influences the mill holdup, residence time, breakage rate, and hence the power draw and the particle size distribution of the mill product. However, residence-time distribution and holdup in industrial mills could not be predicted a priori. Indeed, it is impossible to determine the slurry loading in continuously operating mills by direct measurement, especially in industrial mills. In this paper, the slurry transport problem is solved using the principles of fluid mechanics. First, the motion of the ball charge and its expansion are predicted by a technique called discrete element method. Then themore » slurry flow through the porous ball charge is tackled with a fluid-flow technique called the marker and cell method. This may be the only numerical technique capable of tracking the slurry free surface as it fluctuates with the motion of the ball charge. The result is a prediction of the slurry profile in both the radial and axial directions. Hence, it leads to the detailed description of slurry mass and ball charge within the mill. The model predictions are verified with pilot-scale experimental work. This novel approach based on the physics of fluid flow is devoid of any empiricism. It is shown that the holdup of industrial mills at a given feed percent solids can be predicted successfully.« less

Prediction of the characteristics of two types of pressure waves in the cochlea: Theoretical considerations

NASA Astrophysics Data System (ADS)

Andoh, Masayoshi; Wada, Hiroshi

2004-07-01

The aim of this study was to predict the characteristics of two types of cochlear pressure waves, so-called fast and slow waves. A two-dimensional finite-element model of the organ of Corti (OC), including fluid-structure interaction with the surrounding lymph fluid, was constructed. The geometry of the OC at the basal turn was determined from morphological measurements of others in the gerbil hemicochlea. As far as mechanical properties of the materials within the OC are concerned, previously determined mechanical properties of portions within the OC were adopted, and unknown mechanical features were determined from the published measurements of static stiffness. Time advance of the fluid-structure scheme was achieved by a staggered approach. Using the model, the magnitude and phase of the fast and slow waves were predicted so as to fit the numerically obtained pressure distribution in the scala tympani with what is known about intracochlear pressure measurement. When the predicted pressure waves were applied to the model, the numerical result of the velocity of the basilar membrane showed good agreement with the experimentally obtained velocity of the basilar membrane documented by others. Thus, the predicted pressure waves appeared to be reliable. Moreover, it was found that the fluid-structure interaction considerably influences the dynamic behavior of the OC at frequencies near the characteristic frequency.

Predictors of Response to Multiple Sclerosis Therapeutics in Individual Patients.

PubMed

Hegen, Harald; Auer, Michael; Deisenhammer, Florian

2016-10-01

Multiple sclerosis (MS) is a chronic inflammatory disorder of the central nervous system. Several disease-modifying therapies have been shown to ameliorate the disease course; however, the individual treatment response and the occurrence of adverse events remain highly unpredictable. In the last 2 decades, a multitude of studies have aimed to identify biomarkers that enable treatment allocation in the individual patient or subgroup of patients with regard to treatment efficacy and safety profile. Following a PubMed database search, we provide an overview on what is presently known about body fluid markers for the prediction of response to the currently approved MS therapeutics. We also discuss the potential use of biomarkers with regard to drug-induced adverse events. To date, only a few molecules have been introduced in clinical routine: anti-drug antibodies against interferon (IFN)-β and natalizumab that are associated with abolished drug levels and treatment failure; anti-JC virus (JCV) antibody index that allows risk stratification for the development of progressive multifocal leukoencephalopathy (PML), a rare but severe adverse event during natalizumab treatment; and serostatus of varicella zoster virus as screening examination prior to fingolimod therapy to prevent the infection. A few candidate biomarkers still need closer examination, such as type I IFN signature and T-helper cell (Th)-17 reactivity for prediction of IFN-β treatment response, L-selectin expression for prediction of natalizumab-associated PML, interleukin (IL)-21 levels for prediction of secondary autoimmunity after exposure to alemtuzumab, lymphocyte count with regard to PML risk while receiving dimethyl fumarate or N-terminal-pro-B-type natriuretic peptide (NT-proBNP) for monitoring of cardiac side effects during mitoxantrone therapy.

Early- or mid-trimester amniocentesis biomarkers for predicting preterm delivery: a meta-analysis.

PubMed

Liu, Yinglin; Liu, Yukun; Zhang, Rui; Zhu, Liqiong; Feng, Ziya

2017-02-01

To determine the value of early- or mid-trimester amniotic fluid levels of interleukin-6 (IL-6), matrix metalloproteinase-8 (MMP-8), and glucose for predicting preterm delivery. Randomized controlled trials and two-arm prospective, retrospective, cohorts, and case-controlled studies in which patients received early- or mid-trimester amniocentesis for karyotyping, and biomarker testing of the amniotic fluid was performed and delivery data were available were included in the analysis. Outcome measures were the associations of amniotic fluid IL-6, MMP-8, and glucose levels with preterm delivery. Differences in means with 95% confidence intervals (CIs) were calculated. Of 288 articles identified, 14 were included in the meta-analysis with a total of 675 patients who had preterm birth and 2518 patients who had term births. The preterm-delivery group had significantly higher amniotic fluid IL-6 and MMP-8 levels, and a significantly lower glucose level than the term delivery group (IL-6: difference in means = 0.32, 95% CI: 0.22-0.43, p < 0.001; MMP-8: difference in means = 4.47, 95% CI: 0.83-8.11), p = 0.016; glucose: difference in means = -5.22, 95% CI: -8.19 to -2.26, p = 0.001) Conclusion: Early- or mid-trimester amniotic fluid IL-6, MMP-8, and glucose levels are useful for predicting the risk of preterm delivery. KEY MESSAGES Median amniotic fluid ferritin and IL-6 levels, and mean amniotic fluid ALP levels were higher in the preterm group. The preterm-delivery group had significantly higher amniotic fluid IL-6 and MMP-8 levels, and a significantly lower glucose level than the term-delivery group.

Physics Simulation Software for Autonomous Propellant Loading and Gas House Autonomous System Monitoring

NASA Technical Reports Server (NTRS)

Regalado Reyes, Bjorn Constant

2015-01-01

1. Kennedy Space Center (KSC) is developing a mobile launching system with autonomous propellant loading capabilities for liquid-fueled rockets. An autonomous system will be responsible for monitoring and controlling the storage, loading and transferring of cryogenic propellants. The Physics Simulation Software will reproduce the sensor data seen during the delivery of cryogenic fluids including valve positions, pressures, temperatures and flow rates. The simulator will provide insight into the functionality of the propellant systems and demonstrate the effects of potential faults. This will provide verification of the communications protocols and the autonomous system control. 2. The High Pressure Gas Facility (HPGF) stores and distributes hydrogen, nitrogen, helium and high pressure air. The hydrogen and nitrogen are stored in cryogenic liquid state. The cryogenic fluids pose several hazards to operators and the storage and transfer equipment. Constant monitoring of pressures, temperatures and flow rates are required in order to maintain the safety of personnel and equipment during the handling and storage of these commodities. The Gas House Autonomous System Monitoring software will be responsible for constantly observing and recording sensor data, identifying and predicting faults and relaying hazard and operational information to the operators.

Spatial relationship between bone formation and mechanical stimulus within cortical bone: Combining 3D fluorochrome mapping and poroelastic finite element modelling.

PubMed

Carrieroa, A; Pereirab, A F; Wilson, A J; Castagno, S; Javaheri, B; Pitsillides, A A; Marenzana, M; Shefelbine, S J

2018-06-01

Bone is a dynamic tissue and adapts its architecture in response to biological and mechanical factors. Here we investigate how cortical bone formation is spatially controlled by the local mechanical environment in the murine tibia axial loading model (C57BL/6). We obtained 3D locations of new bone formation by performing 'slice and view' 3D fluorochrome mapping of the entire bone and compared these sites with the regions of high fluid velocity or strain energy density estimated using a finite element model, validated with ex-vivo bone surface strain map acquired ex-vivo using digital image correlation. For the comparison, 2D maps of the average bone formation and peak mechanical stimulus on the tibial endosteal and periosteal surface across the entire cortical surface were created. Results showed that bone formed on the periosteal and endosteal surface in regions of high fluid flow. Peak strain energy density predicted only the formation of bone periosteally. Understanding how the mechanical stimuli spatially relates with regions of cortical bone formation in response to loading will eventually guide loading regime therapies to maintain or restore bone mass in specific sites in skeletal pathologies.

Estimation of the full-field dynamic response of a floating bridge using Kalman-type filtering algorithms

NASA Astrophysics Data System (ADS)

Petersen, Ø. W.; Øiseth, O.; Nord, T. S.; Lourens, E.

2018-07-01

Numerical predictions of the dynamic response of complex structures are often uncertain due to uncertainties inherited from the assumed load effects. Inverse methods can estimate the true dynamic response of a structure through system inversion, combining measured acceleration data with a system model. This article presents a case study of full-field dynamic response estimation of a long-span floating bridge: the Bergøysund Bridge in Norway. This bridge is instrumented with a network of 14 triaxial accelerometers. The system model consists of 27 vibration modes with natural frequencies below 2 Hz, obtained from a tuned finite element model that takes the fluid-structure interaction with the surrounding water into account. Two methods, a joint input-state estimation algorithm and a dual Kalman filter, are applied to estimate the full-field response of the bridge. The results demonstrate that the displacements and the accelerations can be estimated at unmeasured locations with reasonable accuracy when the wave loads are the dominant source of excitation.

Exploring the Use of Molecular Biomarkers for Precision Medicine in Age-Related Macular Degeneration.

PubMed

Lorés-Motta, Laura; de Jong, Eiko K; den Hollander, Anneke I

2018-06-01

Precision medicine aims to improve patient care by adjusting medication to each patient's individual needs. Age-related macular degeneration (AMD) is a heterogeneous eye disease in which several pathways are involved, and the risk factors driving the disease differ per patient. As a consequence, precision medicine holds promise for improved management of this disease, which is nowadays a main cause of vision loss in the elderly. In this review, we provide an overview of the studies that have evaluated the use of molecular biomarkers to predict response to treatment in AMD. We predominantly focus on genetic biomarkers, but also include studies that examined circulating or eye fluid biomarkers in treatment response. This involves studies on treatment response to dietary supplements, response to anti-vascular endothelial growth factor, and response to complement inhibitors. In addition, we highlight promising new therapies that have been or are currently being tested in clinical trials and discuss the molecular studies that can help identify the most suitable patients for these upcoming therapeutic approaches.

Numerical investigations of the fluid flows at deep oceanic and arctic permafrost-associated gas hydrate deposits

NASA Astrophysics Data System (ADS)

Frederick, Jennifer Mary

Methane hydrate is an ice-like solid which sequesters large quantities of methane gas within its crystal structure. The source of methane is typically derived from organic matter broken down by thermogenic or biogenic activity. Methane hydrate (or more simply, hydrate) is found around the globe within marine sediments along most continental margins where thermodynamic conditions and methane gas (in excess of local solubility) permit its formation. Hydrate deposits are quite possibly the largest reservoir of fossil fuel on Earth, however, their formation and evolution in response to changing thermodynamic conditions, such as global warming, are poorly understood. Upward fluid flow (relative to the seafloor) is thought to be important for the formation of methane hydrate deposits, which are typically found beneath topographic features on the seafloor. However, one-dimensional models predict downward flow relative to the seafloor in compacting marine sediments. The presence of upward flow in a passive margin setting can be explained by fluid focusing beneath topography when sediments have anisotropic permeability due to sediment bedding layers. Even small slopes (10 degrees) in bedding planes produce upward fluid velocity, with focusing becoming more effective as slopes increase. Additionally, focusing causes high excess pore pressure to develop below topographic highs, promoting high-angle fracturing at the ridge axis. Magnitudes of upward pore fluid velocity are much larger in fractured zones, particularly when the surrounding sediment matrix is anisotropic in permeability. Enhanced flow of methane-bearing fluids from depth provides a simple explanation for preferential accumulation of hydrate under topographic highs. Models of fluid flow at large hydrate provinces can be constrained by measurements of naturally-occurring radioactive tracers. Concentrations of cosmogenic iodine, 129-I, in the pore fluid of marine sediments often indicate that the pore fluid is much older than the host sediment. Old pore fluid age may reflect complex flow patterns, such a fluid focusing, which can cause significant lateral migration as well as regions where downward flow reverses direction and returns toward the seafloor. Longer pathlines can produce pore fluid ages much older than that expected with a one-dimensional compaction model. For steady-state models with geometry representative of Blake Ridge (USA), a well-studied hydrate province, pore fluid ages beneath regions of topography and within fractured zones can be up to 70 Ma old. Results suggest that the measurements of 129-I/127-I reflect a mixture of new and old pore fluid. However, old pore fluid need not originate at great depths. Methane within pore fluids can travel laterally several kilometers, implying an extensive source region around the deposit. Iodine age measurements support the existence of fluid focusing beneath regions of seafloor topography at Blake Ridge, and suggest that the methane source at Blake Ridge is likely shallow. The response of methane hydrate reservoirs to warming is poorly understood. The great depths may protect deep oceanic hydrates from climate change for the time being because transfer of heat by conduction is slow, but warming will eventually be felt albeit in the far future. On the other hand, unique permafrost-associated methane hydrate deposits exist at shallow depths within the sediments of the circum-Arctic continental shelves. Arctic hydrates are thought to be a relict of cold glacial periods, aggrading when sea levels are much lower and shelf sediments are exposed to freezing air temperatures. During interglacial periods, rising sea levels flood the shelf, bringing dramatic warming to the permafrost- and hydrate-bearing sediments. Permafrost-associated methane hydrate deposits have been responding to warming since the last glacial maximum ~18 kaBP as a consequence of these natural glacial cycles. This `experiment,' set into motion by nature itself, allows us a unique opportunity to study the response of methane hydrate deposits to warming. Gas hydrate stability in the Arctic and the permeability of the shelf sediments to gas migration is thought to be closely linked with relict submarine permafrost. Submarine permafrost extent depends on several environmental factors, such as the shelf lithology, sea level variations, mean annual air temperature, ocean bottom water temperature, geothermal heat flux, groundwater hydrology, and the salinity of the pore water. Effects of submarine groundwater discharge, which introduces fresh terrestrial groundwater off-shore, can freshen deep marine sediments and is an important control on the freezing point depression of ice and methane hydrate. While several thermal modeling studies suggest the permafrost layer should still be largely intact near-shore, many recent field studies have reported elevated methane levels in Arctic coastal waters. The permafrost layer is thought to create an impermeable barrier to fluid and gas flow, however, talik formation (unfrozen regions within otherwise continuous permafrost) below paleo-river channels can create permeable pathways for gas migration from depth. This is the first study of its kind to make predictions of the methane gas flux to the water column from the Arctic shelf sediments using a 2D multi-phase fluid flow model. Model results show that the dissociation of methane hydrate deposits through taliks can supersaturate the overlying water column at present-day relative to equilibrium with the atmosphere when taliks are large (> 1 km width) or hydrate saturation is high within hydrate layers (> 50% pore volume). Supersaturated waters likely drive a net flux of methane into the atmosphere, a potent greenhouse gas. Effects of anthropogenic global warming will certainly increase gas venting rates if ocean bottom water temperatures increase, but likely won't have immediately observable impacts due to the long response times.

Phase Change Material Thermal Power Generator

NASA Technical Reports Server (NTRS)

Jones, Jack A. (Inventor); Chao, Yi (Inventor); Valdez, Thomas I. (Inventor)

2014-01-01

An energy producing device, for example a submersible vehicle for descending or ascending to different depths within water or ocean, is disclosed. The vehicle comprises a temperature-responsive material to which a hydraulic fluid is associated. A pressurized storage compartment stores the fluid as soon as the temperature-responsive material changes density. The storage compartment is connected with a hydraulic motor, and a valve allows fluid passage from the storage compartment to the hydraulic motor. An energy storage component, e.g. a battery, is connected with the hydraulic motor and is charged by the hydraulic motor when the hydraulic fluid passes through the hydraulic motor. Upon passage in the hydraulic motor, the fluid is stored in a further storage compartment and is then sent back to the area of the temperature-responsive material.

Phase change material thermal power generator

NASA Technical Reports Server (NTRS)

Jones, Jack A. (Inventor); Chao, Yi (Inventor); Valdez, Thomas I. (Inventor)

2011-01-01

An energy producing device, for example a submersible vehicle for descending or ascending to different depths within water or ocean, is disclosed. The vehicle comprises a temperature-responsive material to which a hydraulic fluid is associated. A pressurized storage compartment stores the fluid as soon as the temperature-responsive material changes density. The storage compartment is connected with a hydraulic motor, and a valve allows fluid passage from the storage compartment to the hydraulic motor. An energy storage component, e.g. a battery, is connected with the hydraulic motor and is charged by the hydraulic motor when the hydraulic fluid passes through the hydraulic motor. Upon passage in the hydraulic motor, the fluid is stored in a further storage compartment and is then sent back to the area of the temperature-responsive material.

Vanadium oxide-carbon nanotube composite electrodes for energy storage by supercritical fluid deposition: experiment design and device performance

NASA Astrophysics Data System (ADS)

Do, Quyet H.; Fielitz, Thomas R.; Zeng, Changchun; Arda Vanli, O.; Zhang, Chuck; Zheng, Jim P.

2013-08-01

Vanadium pentoxide (V2O5) deposited on porous multiwalled carbon nanotube (MWCNT) buckypaper using supercritical fluid CO2(scCO2) deposition shows excellent performance for electrochemical capacitors. However, the low weight loading of V2O5 is one of the main problems. In this paper, design of experiments and response surface methods were employed to explore strategies for improving the active material loading by increasing the organo-vanadium precursor adsorption. A second-order response surface model was fitted to the designed experiments to predict the loading of the vanadium precursors onto carbon nanotube buckypaper as a function of time, temperature and pressure of CO2, buckypaper functionalization, precursor type, initial precursor mass and stir speed. Operation conditions were identified by employing a model that led to a precursor loading of 19.33%, an increase of 72.28% over the initial screening design. CNTs-V2O5 composite electrodes fabricated from deposited samples using the optimized conditions demonstrated outstanding electrochemical performance (947.1 F g-1 of V2O5 at a high scan rate 100 mV s-1). The model also predicted operation conditions under which light precursor aggregation took place. The V2O5 from aggregated precursor still possessed considerable specific capacitance (311 F g-1 of V2O5 at a scan rate 100 mV s-1), and the significantly higher V2O5 loading (˜81%) contributed to an increase in overall electrode capacitance.

Assessing the Impact of Germination and Sporulation Conditions on the Adhesion of Bacillus Spores to Glass and Stainless Steel by Fluid Dynamic Gauging

PubMed Central

Xu Zhou, Ke; Li, Nan; Christie, Graham

2017-01-01

Abstract The adhesion of spores of 3 Bacillus species with distinctive morphologies to stainless steel and borosilicate glass was studied using the fluid dynamic gauging technique. Marked differences were observed between different species of spores, and also between spores of the same species prepared under different sporulation conditions. Spores of the food‐borne pathogen B. cereus were demonstrated to be capable of withstanding shear stresses greater than 1500 Pa when adhered to stainless steel, in contrast to spores of Bacillus subtilis and Bacillus megaterium, which detached in response to lower shear stress. An extended DLVO model was shown to be capable of predicting the relative differences in spore adhesion between spores of different species and different culture conditions, but did not predict absolute values of force of adhesion well. Applying the model to germinating spores showed a significant reduction in adhesion force shortly after triggering germination, indicating a potential strategy to achieve enhanced removal of spores from surfaces in response to shear stress, such as during cleaning‐in‐place procedures. Practical Application Spore‐forming bacteria are a concern to the food industry because they have the potential to cause food‐borne illness and product spoilage, while being strongly adhesive to processing surfaces and resistant to cleaning‐in‐place procedures. This work is of significance to the food processors and manufacturers because it offers insight to the properties of spore adhesion and identifies a potential strategy to facilitate the removal of spores during cleaning procedures. PMID:29125641

A review of shear wave splitting in the crack-critical crust

NASA Astrophysics Data System (ADS)

Crampin, Stuart; Chastin, Sebastien

2003-10-01

Over the last 15 years, it has become established that crack-induced stress-aligned shear wave splitting, with azimuthal anisotropy, is an inherent characteristic of almost all rocks in the crust. This means that most in situ rocks are pervaded by fluid-saturated microcracks and consequently are highly compliant. The evolution of such stress-aligned fluid-saturated grain-boundary cracks and pore throats in response to changing conditions can be calculated, in some cases with great accuracy, using anisotropic poro-elasticity (APE). APE is tightly constrained with no free parameters, yet dynamic modelling with APE currently matches a wide range of phenomena concerning anisotropy, stress, shear waves and cracks. In particular, APE has allowed the anisotropic response of a reservoir to injection to be calculated (predicted with hindsight), and the time and magnitude of an earthquake to be correctly stress-forecast. The reason for this calculability and predictability is that the microcracks in the crust are so closely spaced that they form critical systems. This crack-critical crust leads to a new style of geophysics that has profound implications for almost all aspects of pre-fracturing deformation of the crust and for solid-earth geophysics and geology. We review past, present and speculate about the future of shear wave splitting in the crack-critical crust. Shear wave splitting is seen to be a dynamic measure of the deformation of the rock mass. There is some good news and some bad news for conventional geophysics. Many accepted phenomena are no longer valid at high spatial and temporal resolution. A major effect is that the detailed crack geometry changes with time and varies from place to place in response to very small previously negligible changes. However, at least in some circumstances, the behaviour of the rock in the highly complex inhomogeneous Earth may be calculated and the response predicted, opening the way to possible control by feedback. The need is to devise ways to exploit these new opportunities in the crack-critical crust. Recent observations from the SMSITES Project at Húsavík in Northern Iceland, gathered while this review was being written, display the extraordinarily sensitivity of in situ rock to small changes at great distances. The effects are far too large to occur in a conventional elastic brittle crust, and their presence confirms the highly compliant nature of the crack-critical crust.

Incorporating Dynamic Assessment of Fluid Responsiveness Into Goal-Directed Therapy: A Systematic Review and Meta-Analysis

PubMed Central

Fridfinnson, Jason A.; Kumar, Anand; Blanchard, Laurie; Rabbani, Rasheda; Bell, Dean; Funk, Duane; Turgeon, Alexis F.; Abou-Setta, Ahmed M.; Zarychanski, Ryan

2017-01-01

Objective: Dynamic tests of fluid responsiveness have been developed and investigated in clinical trials of goal-directed therapy. The impact of this approach on clinically relevant outcomes is unknown. We performed a systematic review and meta-analysis to evaluate whether fluid therapy guided by dynamic assessment of fluid responsiveness compared with standard care improves clinically relevant outcomes in adults admitted to the ICU. Data Sources: Randomized controlled trials from MEDLINE, EMBASE, CENTRAL, clinicaltrials.gov, and the International Clinical Trials Registry Platform from inception to December 2016, conference proceedings, and reference lists of relevant articles. Study Selection: Two reviewers independently identified randomized controlled trials comparing dynamic assessment of fluid responsiveness with standard care for acute volume resuscitation in adults admitted to the ICU. Data Extraction: Two reviewers independently abstracted trial-level data including population characteristics, interventions, clinical outcomes, and source of funding. Our primary outcome was mortality at longest duration of follow-up. Our secondary outcomes were ICU and hospital length of stay, duration of mechanical ventilation, and frequency of renal complications. The internal validity of trials was assessed in duplicate using the Cochrane Collaboration’s Risk of Bias tool. Data Synthesis: We included 13 trials enrolling 1,652 patients. Methods used to assess fluid responsiveness included stroke volume variation (nine trials), pulse pressure variation (one trial), and stroke volume change with passive leg raise/fluid challenge (three trials). In 12 trials reporting mortality, the risk ratio for death associated with dynamic assessment of fluid responsiveness was 0.59 (95% CI, 0.42–0.83; I2 = 0%; n = 1,586). The absolute risk reduction in mortality associated with dynamic assessment of fluid responsiveness was –2.9% (95% CI, –5.6% to –0.2%). Dynamic assessment of fluid responsiveness was associated with reduced duration of ICU length of stay (weighted mean difference, –1.16 d [95% CI, –1.97 to –0.36]; I2 = 74%; n = 394, six trials) and mechanical ventilation (weighted mean difference, –2.98 hr [95% CI, –5.08 to –0.89]; I2 = 34%; n = 334, five trials). Three trials were adjudicated at unclear risk of bias; the remaining trials were at high risk of bias. Conclusions: In adult patients admitted to intensive care who required acute volume resuscitation, goal-directed therapy guided by assessment of fluid responsiveness appears to be associated with reduced mortality, ICU length of stay, and duration of mechanical ventilation. High-quality clinical trials in both medical and surgical ICU populations are warranted to inform routine care. PMID:28817481

Comprehensive computational model for combining fluid hydrodynamics, light transport and biomass growth in a Taylor vortex algal photobioreactor: Lagrangian approach.

PubMed

Gao, Xi; Kong, Bo; Vigil, R Dennis

2017-01-01

A comprehensive quantitative model incorporating the effects of fluid flow patterns, light distribution, and algal growth kinetics on biomass growth rate is developed in order to predict the performance of a Taylor vortex algal photobioreactor for culturing Chlorella vulgaris. A commonly used Lagrangian strategy for coupling the various factors influencing algal growth was employed whereby results from computational fluid dynamics and radiation transport simulations were used to compute numerous microorganism light exposure histories, and this information in turn was used to estimate the global biomass specific growth rate. The simulations provide good quantitative agreement with experimental data and correctly predict the trend in reactor performance as a key reactor operating parameter is varied (inner cylinder rotation speed). However, biomass growth curves are consistently over-predicted and potential causes for these over-predictions and drawbacks of the Lagrangian approach are addressed. Copyright © 2016 Elsevier Ltd. All rights reserved.

Laboratory study on the kinetics of the warming of cold fluids-A hot topic.

PubMed

Mendibil, Alexandre; Jost, Daniel; Thiry, Aurélien; Garcia, Delphine; Trichereau, Julie; Frattini, Benoit; Dang-Minh, Pascal; Maurin, Olga; Margerin, Sylvie; Domanski, Laurent; Tourtier, Jean-Pierre

2016-10-01

In case of mild therapeutic hypothermia after an out-of-hospital cardiac arrest, several techniques could limit the cold fluid rewarming during its perfusion. We aimed to evaluate cold fluid temperature evolution and to identify the factors responsible for rewarming in order to suggest a prediction model of temperature evolution. This was a laboratory experimental study. We measured temperature at the end of the infusion line tubes (ILT). A 500ml saline bag at 4°C was administered at 15 and 30ml/min, with and without cold packs applied to the cold fluid bag or to the ILT. Cold fluid temperature was integrated in a linear mixed model. Then we performed a mathematical modelization of the thermal transfer across the ILT. The linear mixed model showed that the mean temperature of the cold fluid was 1°C higher (CI 95%: [0.8-1.2]) with an outflow rate of 15 versus 30ml/min (P<0.001). Similarly, the mean temperature of the cold fluid was 0.7°C higher (CI 95%: [0.53-0.9]) without cold pack versus with cold packs (P<0.001). Mathematical modelization of the thermal transfer across the ILT suggested that the cold fluid warming could be reduced by a shorter and a wider ILT. As expected, use of CP has also a noticeable influence on warning reduction. The combination of multiple parameters working against the rewarming of the solution should enable the infusion of a solute with retained caloric properties. By limiting this "ILT effect," the volume required for inducing mild therapeutic hypothermia could be reduced, leading to a safer and a more efficient treatment. Copyright © 2016 Société française d'anesthésie et de réanimation (Sfar). Published by Elsevier Masson SAS. All rights reserved.

Experimental validation of a novel stictionless magnetorheological fluid isolator

NASA Astrophysics Data System (ADS)

Kelso, Shawn P.; Denoyer, Keith K.; Blankinship, Ross M.; Potter, Kenneth; Lindler, Jason E.

2003-07-01

Magnetorheological (MR) fluid damper design typically constitutes a piston/dashpot configuration. During reciprocation, the fluid is circulated through the device with the generated pressure providing viscous damping. In addition, the damper is also intended to accommodate off-axis loading; i.e., rotation moments and lateral loads orthogonal to the axis of operation. Typically two sets of seals, one where the piston shaft enters and exits the device and one between the piston and the cylinder wall, maintain alignment of the damper and seal the fluid from leaking. With MR fluid, these seals can act as sources of non-linear friction effects (stiction) and oftentimes possess a shorter lifespan due to the abrasive nature of the ferrous particles suspended in the fluid. Intelligently controlling damping forces must also accommodate the non-linear stiction behavior, which degrades performance. A new, unique MR fluid isolator was designed, fabricated and tested that directly addresses these concerns. The goal of this research was the development of a stiction-free MR isolator whose damping force can be predicted and precisely controlled. This paper presents experimental results for a prototype device and compares those results to model predictions.

4D ERT-based calibration and prediction of biostimulant induced changes in fluid conductivity

NASA Astrophysics Data System (ADS)

Johnson, T. C.; Versteeg, R. J.; Day-Lewis, F. D.; Major, W. R.; Wright, K. E.

2008-12-01

In-situ bioremediation is an emerging and cost-effective method of removing organic contaminants from groundwater. The performance of bioremedial systems depends on the adequate delivery and distribution of biostimulants to contaminated zones. Monitoring the distribution of biostimulants using monitoring wells is expensive, time consuming, and provides inadequate information between sampling wells. We discuss a Hydrogeophysical Performance Monitoring System (HPMS) deployed to monitor bioremediation efforts at a TCE-contaminated Superfund site in Brandywine MD. The HPMS enables autonomous electrical geophysical data acquisition, processing, quality-assurance/quality-control, and inversion. Our objective is to demonstrate the feasibility and cost effectiveness of the HPMS to provide near real-time information on the spatiotemporal behavior of injected biostimulants. As a first step, we use time-lapse electrical resistivity tomography (ERT) to estimate changes in bulk conductivity caused by the injectate. We demonstrate how ERT-based bulk conductivity estimates can be calibrated with a small number of fluid conductivity measurements to produce ERT-based estimates of fluid conductivity. The calibration procedure addresses the spatially variable resolution of the ERT tomograms. To test the validity of these estimates, we used the ERT results to predict the fluid conductivity at tens of points prior to field sampling of fluid conductivity at the same points. The comparison of ERT-predicted vs. observed fluid conductivity displays a high degree of correlation (correlation coefficient over 0.8), and demonstrates the ability of the HPMS to estimate the four-dimensional (4D) distribution of fluid conductivity caused by the biostimulant injection.

Application of Biot Theory to the Study of Acoustic Reflection from Sediments

DTIC Science & Technology

1992-09-08

of bottom loss at all frequencies. To predict propagation loss, a multipath expansion propagation model [15] was used. The sound velocity profile in...public release; distribution unlimited. 13. AISTRACT (Maximum 200 wovov Wave Propagation in fluid-saturated poroelastic media may be described using...of grazing angle and frequency is compared against the more common fluid-fluid and fluid-solid interface models . Finally, shallow water propagation

The Effect of Viscosity of a Fluid on the Frequency Response of a Viscoelastic Plate Loaded by This Fluid

NASA Astrophysics Data System (ADS)

Zamanov, A. D.; Ismailov, M. I.; Akbarov, S. D.

2018-03-01

A hydroviscoelastic system consisting of a viscoelastic plate and a half-plane filled with a viscous fluid is considered. The effect of viscosity of the fluid on the frequency response of the system and its dependence on the rheological parameters of plate material are estimated. The problem on forced vibrations of the system in the plane strain state is investigated using the exact equations of viscoelastodynamics for describing the motion of the plate and linearized Navier-Stokes equations for describing the flow of the fluid. The results found in the cases of nonviscous compressible and Newtonian compressible viscous fluids are compared.

The reliability of the physical examination to guide fluid therapy in adults with severe falciparum malaria: an observational study

PubMed Central

2013-01-01

Background Adults with severe malaria frequently require intravenous fluid therapy to restore their circulating volume. However, fluid must be delivered judiciously as both under- and over-hydration increase the risk of complications and, potentially, death. As most patients will be cared for in a resource-poor setting, management guidelines necessarily recommend that physical examination should guide fluid resuscitation. However, the reliability of this strategy is uncertain. Methods To determine the ability of physical examination to identify hypovolaemia, volume responsiveness, and pulmonary oedema, clinical signs and invasive measures of volume status were collected independently during an observational study of 28 adults with severe malaria. Results The physical examination defined volume status poorly. Jugular venous pressure (JVP) did not correlate with intravascular volume as determined by global end diastolic volume index (GEDVI; rs = 0.07, p = 0.19), neither did dry mucous membranes (p = 0.85), or dry axillae (p = 0.09). GEDVI was actually higher in patients with decreased tissue turgor (p < 0.001). Poor capillary return correlated with GEDVI, but was present infrequently (7% of observations) and, therefore, insensitive. Mean arterial pressure (MAP) correlated with GEDVI (rs = 0.16, p = 0.002), but even before resuscitation patients with a low GEDVI had a preserved MAP. Anuria on admission was unrelated to GEDVI and although liberal fluid resuscitation led to a median hourly urine output of 100 ml in 19 patients who were not anuric on admission, four (21%) developed clinical pulmonary oedema subsequently. MAP was unrelated to volume responsiveness (p = 0.71), while a low JVP, dry mucous membranes, dry axillae, increased tissue turgor, prolonged capillary refill, and tachycardia all had a positive predictive value for volume responsiveness of ≤50%. Extravascular lung water ≥11 ml/kg indicating pulmonary oedema was present on 99 of the 353 times that it was assessed during the study, but was identified on less than half these occasions by tachypnoea, chest auscultation, or an elevated JVP. A clear chest on auscultation and a respiratory rate <30 breaths/minute could exclude pulmonary oedema on 82% and 72% of occasions respectively. Conclusions Findings on physical examination correlate poorly with true volume status in adults with severe malaria and must be used with caution to guide fluid therapy. Trial registration Clinicaltrials.gov identifier: NCT00692627 PMID:24079262

Biological markers of intermediate outcomes in studies of indoor air and other complex mixtures.

PubMed Central

Wilcosky, T C

1993-01-01

Biological markers of intermediate health outcomes sometimes provide a superior alternative to traditional measures of pollutant-related disease. Some opportunities and methodologic issues associated with using markers are discussed in the context of exposures to four complex mixtures: environmental tobacco smoke and nitrogen dioxide, acid aerosols and oxidant outdoor pollution, environmental tobacco smoke and radon, and volatile organic compounds. For markers of intermediate health outcomes, the most important property is the positive predictive value for clinical outcomes of interest. Unless the marker has a known relationship with disease, a marker response conveys no information about disease risk. Most markers are nonspecific in that various exposures cause the same marker response. Although nonspecificity can be an asset in studies of complex mixtures, it leads to problems with confounding and dilution of exposure-response associations in the presence of other exposures. The timing of a marker's measurement in relation to the occurrence of exposure influences the ability to detect a response; measurements made too early or too late may underestimate the response's magnitude. Noninvasive markers, such as those measured in urine, blood, or nasal lavage fluid, are generally more useful for field studies than are invasive markers. However, invasive markers, such as those measured in bronchoalveolar lavage fluid or lung specimens from autopsies, provide the most direct evidence of pulmonary damage from exposure to air pollutants. Unfortunately, the lack of basic information about marker properties (e.g., sensitivity, variability, statistical link with disease) currently precludes the effective use of most markers in studies of complex mixtures. PMID:8206030

Modelling and validation of magnetorheological brake responses using parametric approach

NASA Astrophysics Data System (ADS)

Z, Zainordin A.; A, Abdullah M.; K, Hudha

2013-12-01

Magnetorheological brake (MR Brake) is one x-by-wire systems which performs better than conventional brake systems. MR brake consists of a rotating disc that is immersed with Magnetorheological Fluid (MR Fluid) in an enclosure of an electromagnetic coil. The applied magnetic field will increase the yield strength of the MR fluid where this fluid was used to decrease the speed of the rotating shaft. The purpose of this paper is to develop a mathematical model to represent MR brake with a test rig. The MR brake model is developed based on actual torque characteristic which is coupled with motion of a test rig. Next, the experimental are performed using MR brake test rig and obtained three output responses known as angular velocity response, torque response and load displacement response. Furthermore, the MR brake was subjected to various current. Finally, the simulation results of MR brake model are then verified with experimental results.

Fluid challenge: tracking changes in cardiac output with blood pressure monitoring (invasive or non-invasive).

PubMed

Lakhal, Karim; Ehrmann, Stephan; Perrotin, Dominique; Wolff, Michel; Boulain, Thierry

2013-11-01

To assess whether invasive and non-invasive blood pressure (BP) monitoring allows the identification of patients who have responded to a fluid challenge, i.e., who have increased their cardiac output (CO). Patients with signs of circulatory failure were prospectively included. Before and after a fluid challenge, CO and the mean of four intra-arterial and oscillometric brachial cuff BP measurements were collected. Fluid responsiveness was defined by an increase in CO ≥10 or ≥15% in case of regular rhythm or arrhythmia, respectively. In 130 patients, the correlation between a fluid-induced increase in pulse pressure (Δ500mlPP) and fluid-induced increase in CO was weak and was similar for invasive and non-invasive measurements of BP: r² = 0.31 and r² = 0.29, respectively (both p < 0.001). For the identification of responders, invasive Δ500mlPP was associated with an area under the receiver-operating curve (AUC) of 0.82 (0.74-0.88), similar (p = 0.80) to that of non-invasive Δ500mlPP [AUC of 0.81 (0.73-0.87)]. Outside large gray zones of inconclusive values (5-23% for invasive Δ500mlPP and 4-35% for non-invasive Δ500mlPP, involving 35 and 48% of patients, respectively), the detection of responsiveness or unresponsiveness to fluid was reliable. Cardiac arrhythmia did not impair the performance of invasive or non-invasive Δ500mlPP. Other BP-derived indices did not outperform Δ500mlPP. As evidenced by large gray zones, BP-derived indices poorly reflected fluid responsiveness. However, in our deeply sedated population, a high increase in invasive pulse pressure (>23%) or even in non-invasive pulse pressure (>35%) reliably detected a response to fluid. In the absence of a marked increase in pulse pressure (<4-5%), a response to fluid was unlikely.

Effect of ovine hydatid cyst fluid on the cardiovascular and respiratory systems in sheep.

PubMed

Tabatabai, M; Ismaili, M H; Sami, M; Fardin, R; Kadivar, R

1975-01-01

Rupture of the hydatid cyst in man brings about mild to severe toxic reactions including death. The present study was undertaken to investigate some of the responses resulting from administration of the ovine hydatid fluid to the sheep, which, like man, is an intermediate host of the Echinococcus granulosus. In 50 sodium pentobarbital-anesthetized sheep, the arterial blood pressure (A.B.P.), central venous pressure (C.V.P.), respiration and electrocardiogram were recorded. Intraveonus administration of 5-10 ml hydatid fluid brought about moderate to severe fall in A.B.P. and rapid respiration with or without transient apnea or permanent repiratory cessation in 80 percent of the animals. Fifty percent of the sheep died of circulatory and respiratory failure after the first injection of the hydatid fluid. Boiled hydatid fluid did not lose its potency to evoke the above responses. Pretreatment of the aminals with atropine sulfate, 0,5 mg/kg subcutaneously, did not block the reactions. Administration of the antihistamine chlorpheniramine, 4 mg/kg intravenously, caused partial prevention of the reactions in 6 out of 10 responsive sheep. The cardiovascular and respiratory responses to ovine hydatid fluid may be due to antigen-antibody reactions or some toxic component of the fluid.

Comparison of microdialysis sampling perfusion fluid components on the foreign body reaction in rat subcutaneous tissue.

PubMed

Keeler, Geoffrey D; Durdik, Jeannine M; Stenken, Julie A

2014-06-16

Microdialysis sampling is a commonly used technique for collecting solutes from the extracellular space of tissues in laboratory animals and humans. Large molecular weight solutes can be collected using high molecular weight cutoff (MWCO) membranes (100kDa or greater). High MWCO membranes require addition of high molecular weight dextrans or albumin to the perfusion fluid to prevent fluid loss via ultrafiltration. While these perfusion fluid additives are commonly used during microdialysis sampling, the tissue response to the loss of these compounds across the membrane is poorly understood. Tissue reactions to implanted microdialysis sampling probes containing different microdialysis perfusion fluids were compared over a 7-day time period in rats. The base perfusion fluid was Ringer's solution supplemented with either bovine serum albumin (BSA), rat serum albumin (RSA), Dextran-70, or Dextran-500. A significant inflammatory response to Dextran-70 was observed. No differences in the tissue response between BSA and RSA were observed. Among these agents, the BSA, RSA, and Dextran-500 produced a significantly reduced inflammatory response compared to the Dextran-70. This work demonstrates that use of Dextran-70 in microdialysis sampling perfusion fluids should be eliminated and replaced with Dextran-500 or other alternatives. Copyright © 2013 Elsevier B.V. All rights reserved.

Links between fluid circulation, temperature, and metamorphism in subducting slabs

USGS Publications Warehouse

Spinelli, G.A.; Wang, K.

2009-01-01

The location and timing of metamorphic reactions in subducting lithosph??re are influenced by thermal effects of fluid circulation in the ocean crust aquifer. Fluid circulation in subducting crust extracts heat from the Nankai subduction zone, causing the crust to pass through cooler metamorphic faci??s than if no fluid circulation occurs. This fluid circulation shifts the basalt-to-eclogite transition and the associated slab dehydration 14 km deeper (35 km farther landward) than would be predicted with no fluid flow. For most subduction zones, hydrothermal cooling of the subducting slab will delay eclogitization relative to estimates made without considering fluid circulation. Copyright 2009 by the American Geophysical Union.

Intrinsically safe moisture blending system

DOEpatents

Hallman Jr., Russell L.; Vanatta, Paul D.

2012-09-11

A system for providing an adjustable blend of fluids to an application process is disclosed. The system uses a source of a first fluid flowing through at least one tube that is permeable to a second fluid and that is disposed in a source of the second fluid to provide the adjustable blend. The temperature of the second fluid is not regulated, and at least one calibration curve is used to predict the volumetric mixture ratio of the second fluid with the first fluid from the permeable tube. The system typically includes a differential pressure valve and a backpressure control valve to set the flow rate through the system.

An Artificial Intelligence Approach for Modeling and Prediction of Water Diffusion Inside a Carbon Nanotube

PubMed Central

2009-01-01

Modeling of water flow in carbon nanotubes is still a challenge for the classic models of fluid dynamics. In this investigation, an adaptive-network-based fuzzy inference system (ANFIS) is presented to solve this problem. The proposed ANFIS approach can construct an input–output mapping based on both human knowledge in the form of fuzzy if-then rules and stipulated input–output data pairs. Good performance of the designed ANFIS ensures its capability as a promising tool for modeling and prediction of fluid flow at nanoscale where the continuum models of fluid dynamics tend to break down. PMID:20596382

Coiling of viscous jets

NASA Astrophysics Data System (ADS)

Ribe, Neil M.

2004-11-01

A stream of viscous fluid falling from a sufficient height onto a surface forms a series of regular coils. I use a numerical model for a deformable fluid thread to predict the coiling frequency as a function of the thread's radius, the flow rate, the fall height, and the fluid viscosity. Three distinct modes of coiling can occur: viscous (e.g. toothpaste), gravitational (honey falling from a moderate height) and inertial (honey falling from a great height). When inertia is significant, three states of steady coiling with different frequencies can exist over a range of fall heights. The numerically predicted coiling frequencies agree well with experimental measurements in the inertial coiling regime.

Prediction of mass transfer coefficients in non-Newtonian fermentation media using first-principles methods.

PubMed

Radl, Stefan; Khinast, Johannes G

2007-08-01

Bubble flows in non-Newtonian fluids were analyzed using first-principles methods with the aim to compute and predict mass transfer coefficients in such fermentation media. The method we used is a Direct Numerical Simulation (DNS) of the reactive multiphase flow with deformable boundaries and interfaces. With this method, we are able for the first time to calculate mass transfer coefficients in non-Newtonian liquids of different rheologies without any experimental data. In the current article, shear-thinning fluids are considered. However, the results provide the basis for further investigations, such as the study of viscoelastic fluids. (c) 2007 Wiley Periodicals, Inc.

Progress Towards a Microgravity CFD Validation Study Using the ISS SPHERES-SLOSH Experiment

NASA Technical Reports Server (NTRS)

Storey, Jedediah M.; Kirk, Daniel; Marsell, Brandon (Editor); Schallhorn, Paul (Editor)

2017-01-01

Understanding, predicting, and controlling fluid slosh dynamics is critical to safety and improving performance of space missions when a significant percentage of the spacecrafts mass is a liquid. Computational fluid dynamics simulations can be used to predict the dynamics of slosh, but these programs require extensive validation. Many CFD programs have been validated by slosh experiments using various fluids in earth gravity, but prior to the ISS SPHERES-Slosh experiment1, little experimental data for long-duration, zero-gravity slosh existed. This paper presents the current status of an ongoing CFD validation study using the ISS SPHERES-Slosh experimental data.

An Artificial Intelligence Approach for Modeling and Prediction of Water Diffusion Inside a Carbon Nanotube.

PubMed

Ahadian, Samad; Kawazoe, Yoshiyuki

2009-06-04

Modeling of water flow in carbon nanotubes is still a challenge for the classic models of fluid dynamics. In this investigation, an adaptive-network-based fuzzy inference system (ANFIS) is presented to solve this problem. The proposed ANFIS approach can construct an input-output mapping based on both human knowledge in the form of fuzzy if-then rules and stipulated input-output data pairs. Good performance of the designed ANFIS ensures its capability as a promising tool for modeling and prediction of fluid flow at nanoscale where the continuum models of fluid dynamics tend to break down.

Progress Towards a Microgravity CFD Validation Study Using the ISS SPHERES-SLOSH Experiment

NASA Technical Reports Server (NTRS)

Storey, Jed; Kirk, Daniel (Editor); Marsell, Brandon (Editor); Schallhorn, Paul (Editor)

2017-01-01

Understanding, predicting, and controlling fluid slosh dynamics is critical to safety and improving performance of space missions when a significant percentage of the spacecrafts mass is a liquid. Computational fluid dynamics simulations can be used to predict the dynamics of slosh, but these programs require extensive validation. Many CFD programs have been validated by slosh experiments using various fluids in earth gravity, but prior to the ISS SPHERES-Slosh experiment, little experimental data for long-duration, zero-gravity slosh existed. This paper presents the current status of an ongoing CFD validation study using the ISS SPHERES-Slosh experimental data.

Investigation of SSME alternate high pressure fuel turbopump lift-off seal fluid and structural dynamic interaction

NASA Technical Reports Server (NTRS)

Elrod, David A.

1989-01-01

The Space Shuttle main engine (SSME) alternate turbopump development program (ATD) high pressure fuel turbopump (HPFTP) design utilizes an innovative lift-off seal (LOS) design that is located in close proximity to the turbine end bearing. Cooling flow exiting the bearing passes through the lift-off seal during steady state operation. The potential for fluid excitation of lift-off seal structural resonances is investigated. No fluid excitation of LOS resonances is predicted. However, if predicted LOS natural frequencies are significantly lowered by the presence of the coolant, pressure oscillations caused by synchronous whirl of the HPFTP rotor may excite a resonance.

Elastic contact mechanics: percolation of the contact area and fluid squeeze-out.

PubMed

Persson, B N J; Prodanov, N; Krick, B A; Rodriguez, N; Mulakaluri, N; Sawyer, W G; Mangiagalli, P

2012-01-01

The dynamics of fluid flow at the interface between elastic solids with rough surfaces depends sensitively on the area of real contact, in particular close to the percolation threshold, where an irregular network of narrow flow channels prevails. In this paper, numerical simulation and experimental results for the contact between elastic solids with isotropic and anisotropic surface roughness are compared with the predictions of a theory based on the Persson contact mechanics theory and the Bruggeman effective medium theory. The theory predictions are in good agreement with the experimental and numerical simulation results and the (small) deviation can be understood as a finite-size effect. The fluid squeeze-out at the interface between elastic solids with randomly rough surfaces is studied. We present results for such high contact pressures that the area of real contact percolates, giving rise to sealed-off domains with pressurized fluid at the interface. The theoretical predictions are compared to experimental data for a simple model system (a rubber block squeezed against a flat glass plate), and for prefilled syringes, where the rubber plunger stopper is lubricated by a high-viscosity silicon oil to ensure functionality of the delivery device. For the latter system we compare the breakloose (or static) friction, as a function of the time of stationary contact, to the theory prediction.

A two-phase debris-flow model that includes coupled evolution of volume fractions, granular dilatancy, and pore-fluid pressure

USGS Publications Warehouse

George, David L.; Iverson, Richard M.

2011-01-01

Pore-fluid pressure plays a crucial role in debris flows because it counteracts normal stresses at grain contacts and thereby reduces intergranular friction. Pore-pressure feedback accompanying debris deformation is particularly important during the onset of debrisflow motion, when it can dramatically influence the balance of forces governing downslope acceleration. We consider further effects of this feedback by formulating a new, depth-averaged mathematical model that simulates coupled evolution of granular dilatancy, solid and fluid volume fractions, pore-fluid pressure, and flow depth and velocity during all stages of debris-flow motion. To illustrate implications of the model, we use a finite-volume method to compute one-dimensional motion of a debris flow descending a rigid, uniformly inclined slope, and we compare model predictions with data obtained in large-scale experiments at the USGS debris-flow flume. Predictions for the first 1 s of motion show that increasing pore pressures (due to debris contraction) cause liquefaction that enhances flow acceleration. As acceleration continues, however, debris dilation causes dissipation of pore pressures, and this dissipation helps stabilize debris-flow motion. Our numerical predictions of this process match experimental data reasonably well, but predictions might be improved by accounting for the effects of grain-size segregation.

Aging and free surface flow of a thixotropic fluid

NASA Astrophysics Data System (ADS)

Huynh, H. T.; Roussel, N.; Coussot, P.

2005-03-01

Free surface flows of thixotropic fluids such as paints, self-compacting concrete, or natural mudflows are of noticeable practical interest. Here we study the basic characteristics of the uniform flow of a layer of thixotropic fluid under gravity. A theoretical approach relying on a simple thixotropy constitutive equation shows that after some time at rest over a small slope angle the fluid layer should start to flow rather abruptly beyond a new, larger, critical slope angle. The theory also predicts that the critical time at which the layer velocity should significantly increase is proportional to the duration of the preliminary rest and tends to infinity when the new slope approaches the critical slope. Experiments carried out with different suspensions show that the qualitative trends of the flows are in very good agreement with the theoretical predictions, except that the critical time for flow start appears to be proportional to a power 0.6 of the time of rest whereas the theory predicts a linear dependence. We show that this indicates a restructuration process at rest differing from the restructuration process under flow.

Prediction of the low-velocity distribution from the pore structure in simple porous media

NASA Astrophysics Data System (ADS)

de Anna, Pietro; Quaife, Bryan; Biros, George; Juanes, Ruben

2017-12-01

The macroscopic properties of fluid flow and transport through porous media are a direct consequence of the underlying pore structure. However, precise relations that characterize flow and transport from the statistics of pore-scale disorder have remained elusive. Here we investigate the relationship between pore structure and the resulting fluid flow and asymptotic transport behavior in two-dimensional geometries of nonoverlapping circular posts. We derive an analytical relationship between the pore throat size distribution fλ˜λ-β and the distribution of the low fluid velocities fu˜u-β /2 , based on a conceptual model of porelets (the flow established within each pore throat, here a Hagen-Poiseuille flow). Our model allows us to make predictions, within a continuous-time random-walk framework, for the asymptotic statistics of the spreading of fluid particles along their own trajectories. These predictions are confirmed by high-fidelity simulations of Stokes flow and advective transport. The proposed framework can be extended to other configurations which can be represented as a collection of known flow distributions.

Solubility Limits in Lennard-Jones Mixtures: Effects of Disparate Molecule Geometries.

PubMed

Dyer, Kippi M; Perkyns, John S; Pettitt, B Montgomery

2015-07-23

In order to better understand general effects of the size and energy disparities between macromolecules and solvent molecules in solution, especially for macromolecular constructs self-assembled from smaller molecules, we use the first- and second-order exact bridge diagram extensions of the HNC integral equation theory to investigate single-component, binary, ternary, and quaternary mixtures of Lennard-Jones fluids. For pure fluids, we find that the HNCH3 bridge function integral equation (i.e., exact to third order in density) is necessary to quantitatively predict the pure gas and pure liquid sides of the coexistence region of the phase diagram of the Lennard-Jones fluid. For the mixtures, we find that the HNCH2 bridge function integral equation is sufficient to qualitatively predict solubility in the binary, ternary, and quaternary mixtures, up to the nominal solubility limit. The results, as limiting cases, should be useful to several problems, including accurate phase diagram predictions for complex mixtures, design of self-assembling nanostructures via solvent controls, and the solvent contributions to the conformational behavior of macromolecules in complex fluids.

Modelling of sea floor spreading initiation and rifted continental margin formation

NASA Astrophysics Data System (ADS)

Tymms, V. J.; Isimm Team

2003-04-01

Recent observations of depth dependent (heterogeneous) stretching where upper crustal extension is much less than that of the lower crust and lithospheric mantle at both non-volcanic and volcanic margins plus the discovery of broad domains of exhumed continental mantle at non-volcanic rifted margins are not predicted by existing quantitative models of rifted margin formation which are usually based on intra-continental rift models subjected to very large stretching factors. New conceptual and quantitative models of rifted margin formation are required. Observations and continuum mechanics suggest that the dominant process responsible for rifted continental margin formation is sea-floor spreading of the young ocean ridge, rather than pre-breakup intra-continental rifting. Simple fluid flow models of ocean ridge processes using analytical iso-viscous corner-flow demonstrate that the divergent motion of the upwelling mantle beneath the ocean ridge, when viewed in the reference frame of the young continental margin, shows oceanward flow of the lower continental crust and lithospheric mantle of the young rifted margin giving rise to depth dependent stretching as observed. Single-phase fluid-models have been developed to model the initiation of sea-floor spreading and the thermal, stretching and thinning evolution of the young rifted continental margin. Finite element fluid-flow modelling incorporating the evolving temperature dependent viscosity field on the fluid flow also show depth dependent stretching of the young continental margin. Two-phase flow models of ocean ridges incorporating the transport of both solid matrix and melt fluid (Spiegelman &Reynolds 1999) predict the divergent motion of the asthenosphere and lithosphere matrix, and the focusing of basaltic melt into the narrow axial zone spreading centre at ocean ridges. We are adapting two-phase flow models for application to the initiation of sea-floor spreading and rifted continental margin formation. iSIMM investigators are V Tymms, NJ Kusznir, RS White, AM Roberts, PAF Christie, N Hurst, Z Lunnon, CJ Parkin, AW Roberts, LK Smith, R Spitzer, A. Davies and A. Surendra, with funding from NERC, DTI, Agip UK, BP, Amerada Hess Ltd., Anadarko, Conoco, Phillips, Shell, Statoil, and WesternGeco.

A practical tool for estimating subsurface LNAPL distributions and transmissivity using current and historical fluid levels in groundwater wells: Effects of entrapped and residual LNAPL

NASA Astrophysics Data System (ADS)

Lenhard, R. J.; Rayner, J. L.; Davis, G. B.

2017-10-01

A model is presented to account for elevation-dependent residual and entrapped LNAPL above and below, respectively, the water-saturated zone when predicting subsurface LNAPL specific volume (fluid volume per unit area) and transmissivity from current and historic fluid levels in wells. Physically-based free, residual, and entrapped LNAPL saturation distributions and LNAPL relative permeabilities are integrated over a vertical slice of the subsurface to yield the LNAPL specific volumes and transmissivity. The model accounts for effects of fluctuating water tables. Hypothetical predictions are given for different porous media (loamy sand and clay loam), fluid levels in wells, and historic water-table fluctuations. It is shown the elevation range from the LNAPL-water interface in a well to the upper elevation where the free LNAPL saturation approaches zero is the same for a given LNAPL thickness in a well regardless of porous media type. Further, the LNAPL transmissivity is largely dependent on current fluid levels in wells and not historic levels. Results from the model can aid developing successful LNAPL remediation strategies and improving the design and operation of remedial activities. Results of the model also can aid in accessing the LNAPL recovery technology endpoint, based on the predicted transmissivity.

A new model of cavern diameter based on a validated CFD study on stirring of a highly shear-thinning fluid.

PubMed

Story, Anna; Jaworski, Zdzisław

2017-01-01

Results of numerical simulations of momentum transfer for a highly shear-thinning fluid (0.2% Carbopol) in a stirred tank equipped with a Prochem Maxflo T type impeller are presented. The simulation results were validated using LDA data and both tangential and axial force measurements in the laminar and early transitional flow range. A good agreement between the predicted and experimental results of the local fluid velocity components was found. From the predicted and experimental values of both tangential and axial forces, the power number, Po , and thrust number, Th , were also calculated. Values of the absolute relative deviations were below 4.0 and 10.5%, respectively, for Po and Th , which confirms a satisfactory agreement with experiments. An intensive mixing zone, known as cavern, was observed near the impeller. In this zone, the local values of fluid velocity, strain rate, Metzner-Otto coefficient, shear stress and intensity of energy dissipation were all characterized by strong variability. Based on the results of experimental study a new model using non-dimensional impeller force number was proposed to predict the cavern diameter. Comparative numerical simulations were also carried out for a Newtonian fluid (water) and their results were similarly well verified using LDA measurements, as well as experimental power number values.

Smart Fluid System Dually Responsive to Light and Electric Fields: An Electrophotorheological Fluid.

PubMed

Yoon, Chang-Min; Jang, Yoonsun; Noh, Jungchul; Kim, Jungwon; Jang, Jyongsik

2017-10-24

Electrophotorheological (EPR) fluids, whose rheological activity is dually responsive to light and electric fields (E fields), is formulated by mixing photosensitive spiropyran-decorated silica (SP-sSiO 2 ) nanoparticles with zwitterionic lecithin and mineral oil. A reversible photorheological (PR) activity of the EPR fluid is developed via the binding and releasing mechanism of lecithin and merocyanine (MC, a photoisomerized form of SP) under ultraviolet (UV) and visible (VIS) light applications. Moreover, the EPR fluid exhibits an 8-fold higher electrorheological (ER) performance compared to the SP-sSiO 2 nanoparticle-based ER fluid (without lecithin) under an E field, which is attributed to the enhanced dielectric properties facilitated by the binding of the lecithin and SP molecules. Upon dual application of UV light and an E field, the EPR fluid exhibits high EPR performance (ca. 115.3 Pa) that far exceeds its separate PR (ca. 0.8 Pa) and ER (ca. 57.5 Pa) activities, because of the synergistic contributions of the PR and ER effects through rigid and fully connected fibril-like structures. Consequently, this study offers a strategy on formulation of dual-stimuli responsive smart fluid systems.

Ex-Vivo Lymphatic Perfusion System for Independently Controlling Pressure Gradient and Transmural Pressure in Isolated Vessels

PubMed Central

Kornuta, Jeffrey A.; Dixon, J. Brandon

2015-01-01

In addition to external forces, collecting lymphatic vessels intrinsically contract to transport lymph from the extremities to the venous circulation. As a result, the lymphatic endothelium is routinely exposed to a wide range of dynamic mechanical forces, primarily fluid shear stress and circumferential stress, which have both been shown to affect lymphatic pumping activity. Although various ex-vivo perfusion systems exist to study this innate pumping activity in response to mechanical stimuli, none are capable of independently controlling the two primary mechanical forces affecting lymphatic contractility: transaxial pressure gradient, ΔP, which governs fluid shear stress; and average transmural pressure, Pavg, which governs circumferential stress. Hence, the authors describe a novel ex-vivo lymphatic perfusion system (ELPS) capable of independently controlling these two outputs using a linear, explicit model predictive control (MPC) algorithm. The ELPS is capable of reproducing arbitrary waveforms within the frequency range observed in the lymphatics in vivo, including a time-varying ΔP with a constant Pavg, time-varying ΔP and Pavg, and a constant ΔP with a time-varying Pavg. In addition, due to its implementation of syringes to actuate the working fluid, a post-hoc method of estimating both the flow rate through the vessel and fluid wall shear stress over multiple, long (5 sec) time windows is also described. PMID:24809724

Blood Pressure Responses and Mineral Ocorticoid Levels in the Suspended Rat Model for Weightlessness

NASA Technical Reports Server (NTRS)

Musacchia, X. J.; Steffen, J. M.

1985-01-01

Cardiovascular responses and fluid/electrolyte shifts seen during space flight are attributed to cephalad redistribution of vascular fluid. The antiorthostatic (AO) rat (suspended head down tilted, 15-20 deg) is used to model these responses. Current studies show that elevated blood pressures in A0 rats are sustained for periods up to seven days. Comparisons are made with presuspension rats. Increased blood pressure in head down tilted subjects suggests a specific response to A0 positioning, potentially relatable to cephalad fluid shift. To assess a role for hormonal regulation of sodium excretion, serum aldosterone levels were measured.

Damping effects of magnetic fluids of various saturation magnetization (abstract)

NASA Astrophysics Data System (ADS)

Chagnon, Mark

1990-05-01

Magnetic fluids have been widely accepted for use in loudspeaker voice coil gaps as viscous dampers and liquid coolants. When applied properly to a voice coil in manufacturing of the loudspeaker, dramatic improvement in frequency response and power handling is observed. Over the past decade, a great deal of study has been given to the effects of damping as a function of fluid viscosity. It is known that the apparent viscosity of a magnetic fluid increases as a function of applied magnetic field, and that the viscosity versus field relationship approximate that of the magnetization versus applied field. At applied magnetic field strength sufficient to cause magnetic saturation of the fluid, no further increase in viscosity with increased magnetic field is observed. In order to provide a better understanding of the second order magnetoviscous damping effects in magnetic fluids used in voice coils and to provide a better loudspeaker design criterion using magnetic fluids, we have studied the effect on damping of several magnetic fluids of the same O field viscosity and of varying saturation magnetization. Magnetic fluids with saturation magnetization ranging from 50 to 450 G and 100 cps viscosity at O applied field were injected into the voice coil gap of a standard midrange loudspeaker. The frequency response over the entire dynamic range of the speaker was measured. The changes in frequency response versus fluid magnetization are reported.

An analytical model to predict interstitial lubrication of cartilage in migrating contact areas.

PubMed

Moore, A C; Burris, D L

2014-01-03

For nearly a century, articular cartilage has been known for its exceptional tribological properties. For nearly as long, there have been research efforts to elucidate the responsible mechanisms for application toward biomimetic bearing applications. It is now widely accepted that interstitial fluid pressurization is the primary mechanism responsible for the unusual lubrication and load bearing properties of cartilage. Although the biomechanics community has developed elegant mathematical theories describing the coupling of solid and fluid (biphasic) mechanics and its role in interstitial lubrication, quantitative gaps in our understanding of cartilage tribology have inhibited our ability to predict how tribological conditions and material properties impact tissue function. This paper presents an analytical model of the interstitial lubrication of biphasic materials under migrating contact conditions. Although finite element and other numerical models of cartilage mechanics exist, they typically neglect the important role of the collagen network and are limited to a specific set of input conditions, which limits general applicability. The simplified approach taken in this work aims to capture the broader underlying physics as a starting point for further model development. In agreement with existing literature, the model indicates that a large Peclet number, Pe, is necessary for effective interstitial lubrication. It also predicts that the tensile modulus must be large relative to the compressive modulus. This explains why hydrogels and other biphasic materials do not provide significant interstitial pressure under high Pe conditions. The model quantitatively agrees with in-situ measurements of interstitial load support and the results have interesting implications for tissue engineering and osteoarthritis problems. This paper suggests that a low tensile modulus (from chondromalacia or local collagen rupture after impact, for example) may disrupt interstitial pressurization, increase shear stresses, and activate a condition of progressive surface damage as a potential precursor of osteoarthritis. © 2013 Elsevier Ltd. All rights reserved.

Group contribution methodology based on the statistical associating fluid theory for heteronuclear molecules formed from Mie segments.

PubMed

Papaioannou, Vasileios; Lafitte, Thomas; Avendaño, Carlos; Adjiman, Claire S; Jackson, George; Müller, Erich A; Galindo, Amparo

2014-02-07

A generalization of the recent version of the statistical associating fluid theory for variable range Mie potentials [Lafitte et al., J. Chem. Phys. 139, 154504 (2013)] is formulated within the framework of a group contribution approach (SAFT-γ Mie). Molecules are represented as comprising distinct functional (chemical) groups based on a fused heteronuclear molecular model, where the interactions between segments are described with the Mie (generalized Lennard-Jonesium) potential of variable attractive and repulsive range. A key feature of the new theory is the accurate description of the monomeric group-group interactions by application of a high-temperature perturbation expansion up to third order. The capabilities of the SAFT-γ Mie approach are exemplified by studying the thermodynamic properties of two chemical families, the n-alkanes and the n-alkyl esters, by developing parameters for the methyl, methylene, and carboxylate functional groups (CH3, CH2, and COO). The approach is shown to describe accurately the fluid-phase behavior of the compounds considered with absolute average deviations of 1.20% and 0.42% for the vapor pressure and saturated liquid density, respectively, which represents a clear improvement over other existing SAFT-based group contribution approaches. The use of Mie potentials to describe the group-group interaction is shown to allow accurate simultaneous descriptions of the fluid-phase behavior and second-order thermodynamic derivative properties of the pure fluids based on a single set of group parameters. Furthermore, the application of the perturbation expansion to third order for the description of the reference monomeric fluid improves the predictions of the theory for the fluid-phase behavior of pure components in the near-critical region. The predictive capabilities of the approach stem from its formulation within a group-contribution formalism: predictions of the fluid-phase behavior and thermodynamic derivative properties of compounds not included in the development of group parameters are demonstrated. The performance of the theory is also critically assessed with predictions of the fluid-phase behavior (vapor-liquid and liquid-liquid equilibria) and excess thermodynamic properties of a variety of binary mixtures, including polymer solutions, where very good agreement with the experimental data is seen, without the need for adjustable mixture parameters.

Flow of a Casson fluid through a locally-constricted porous channel: a numerical study

NASA Astrophysics Data System (ADS)

Amlimohamadi, Haleh; Akram, Maryammosadat; Sadeghy, Kayvan

2016-05-01

Flow of a Casson fluid through a two-dimensional porous channel containing a local constriction is numerically investigated assuming that the resistance offered by the porous medium obeys the Darcy's law. Treating the constriction as another porous medium which obeys the Darcy-Forcheimer model, the equations governing fluid flow in the main channel and the constriction itself are numerically solved using the finite-volume method (FVM) based on the pseudo-transient SIMPLE algorithm. It is shown that an increase in the porosity of the channel decreases the shear stress exerted on the constriction. On the other hand, an increase in the fluid's yield stress is predicted to increase the maximum shear stress experienced by the constriction near its crest. The porosity of the constriction itself is predicted to have a negligible effect on the plaque's shear stress. But, the momentum of the weak flow passing through the constriction is argued to lower the bulk fluid from separating downstream of the constriction.

Scaling and modeling of turbulent suspension flows

NASA Technical Reports Server (NTRS)

Chen, C. P.

1989-01-01

Scaling factors determining various aspects of particle-fluid interactions and the development of physical models to predict gas-solid turbulent suspension flow fields are discussed based on two-fluid, continua formulation. The modes of particle-fluid interactions are discussed based on the length and time scale ratio, which depends on the properties of the particles and the characteristics of the flow turbulence. For particle size smaller than or comparable with the Kolmogorov length scale and concentration low enough for neglecting direct particle-particle interaction, scaling rules can be established in various parameter ranges. The various particle-fluid interactions give rise to additional mechanisms which affect the fluid mechanics of the conveying gas phase. These extra mechanisms are incorporated into a turbulence modeling method based on the scaling rules. A multiple-scale two-phase turbulence model is developed, which gives reasonable predictions for dilute suspension flow. Much work still needs to be done to account for the poly-dispersed effects and the extension to dense suspension flows.

Hot soup! Correlating the severity of liquid scald burns to fluid and biomedical properties.

PubMed

Loller, Cameron; Buxton, Gavin A; Kerzmann, Tony L

2016-05-01

Burns caused by hot drinks and soups can be both debilitating and costly, especially to pediatric and geriatric patients. This research is aimed at better understanding the fluid properties that can influence the severity of skin burns. We use a standard model which combines heat transfer and biomedical equations to predict burn severity. In particular, experimental data from a physical model serves as the input to our numerical model to determine the severity of scald burns as a consequence of actual fluid flows. This technique enables us to numerically predict the heat transfer from the hot soup into the skin, without the need to numerically estimate the complex fluid mechanics and thermodynamics of the potentially highly viscous and heterogeneous soup. While the temperature of the soup is obviously is the most important fact in determining the degree of burn, we also find that more viscous fluids result in more severe burns, as the slower flowing thicker fluids remain in contact with the skin for longer. Furthermore, other factors can also increase the severity of burn such as a higher initial fluid temperature, a greater fluid thermal conductivity, or a higher thermal capacity of the fluid. Our combined experimental and numerical investigation finds that for average skin properties a very viscous fluid at 100°C, the fluid must be in contact with the skin for around 15-20s to cause second degree burns, and more than 80s to cause a third degree burn. Copyright © 2015 Elsevier Ltd and ISBI. All rights reserved.

Heat Flux and Fluid Flow in the Terrebonne Basin, Northern Gulf of Mexico

NASA Astrophysics Data System (ADS)

Meazell, K.; Flemings, P. B.

2016-12-01

We use a three-dimensional seismic survey to map the gas hydrate stability zone within a mid-slope salt-withdrawal minibasin in the northern Gulf of Mexico and identify anomalous regions within the basin where fluids may modify the hydrate stability zone. A discontinuous bottom-simulating reflector (BSR) marks the base of the hydrate stability zone and suggests an average geothermal gradient of 18.1 C/km based on the calculated temperature at the BSR assuming seawater salinity, hydrostatic pressure, and a seafloor temperature of 4 C. When compared to our model of the predicted base of gas hydrate stability assuming a basin-wide geothermal gradient of 18.1 C, two anomalies are found where the BSR is observed significantly shallower than expected. The southern anomaly has a lateral influence of 1500 m from the salt, and a maximum shoaling of 800 m. This anomaly is likely the result of increased salinity or heat from a rising salt diapir along the flank of the basin. A local geothermal gradient of 67.31 C/km or a salinity of 17.5 wt % can explain the observed position of the BSR at the southern anomaly. The northern anomaly is associated with active cold seep vents. In this area, the pluming BSR is crescent shaped, which we interpret as the result of warm and or salty fluids migrating up through a fault. This anomaly has a lateral influence of 1500 m, and a maximum shoaling of 600 m above the predicted base of gas hydrate stability. A local geothermal gradient of 35.45 C/km or a salinity of 14.7 wt % is required to adjust the position of the BSR to that which is observed at the northern anomaly. Active fluid migration suggests a combination of both heat and salinity is responsible for the altered position of the BSR.

Assessment of disintegration of rapidly disintegrating tablets by a visiometric liquid jet-mediated disintegration apparatus.

PubMed

Desai, Parind M; Liew, Celine V; Heng, Paul W S

2013-02-14

The aim of this study was to develop a responsive disintegration test apparatus that is particularly suitable for rapidly disintegrating tablets (RDTs). The designed RDT disintegration apparatus consisted of disintegration compartment, stereomicroscope and high speed video camera. Computational fluid dynamics (CFD) was used to simulate 3 different designs of the compartment and to predict velocity and pressure patterns inside the compartment. The CFD preprocessor established the compartment models and the CFD solver determined the numerical solutions of the governing equations that described disintegration medium flow. Simulation was validated by good agreement between CFD and experimental results. Based on the results, the most suitable disintegration compartment was selected. Six types of commercial RDTs were used and disintegration times of these tablets were determined using the designed RDT disintegration apparatus and the USP disintegration apparatus. The results obtained using the designed apparatus correlated well to those obtained by the USP apparatus. Thus, the applied CFD approach had the potential to predict the fluid hydrodynamics for the design of optimal disintegration apparatus. The designed visiometric liquid jet-mediated disintegration apparatus for RDT provided efficient and precise determination of very short disintegration times of rapidly disintegrating dosage forms. Copyright © 2012 Elsevier B.V. All rights reserved.

Application of response surface methodology to optimise supercritical carbon dioxide extraction of essential oil from Cyperus rotundus Linn.

PubMed

Wang, Hongwu; Liu, Yanqing; Wei, Shoulian; Yan, Zijun

2012-05-01

Supercritical fluid extraction with carbon dioxide (SC-CO2 extraction) was performed to isolate essential oils from the rhizomes of Cyperus rotundus Linn. Effects of temperature, pressure, extraction time, and CO2 flow rate on the yield of essential oils were investigated by response surface methodology (RSM). The oil yield was represented by a second-order polynomial model using central composite rotatable design (CCRD). The oil yield increased significantly with pressure (p<0.0001) and CO2 flow rate (p<0.01). The maximum oil yield from the response surface equation was predicted to be 1.82% using an extraction temperature of 37.6°C, pressure of 294.4bar, extraction time of 119.8 min, and CO2 flow rate of 20.9L/h. Copyright © 2011 Elsevier Ltd. All rights reserved.

Rheological effects on friction in elastohydrodynamic lubrication

NASA Technical Reports Server (NTRS)

Trachman, E. G.; Cheng, H. S.

1973-01-01

An analytical and experimental investigation is presented of the friction in a rolling and sliding elastohydrodynamic lubricated contact. The rheological behavior of the lubricant is described in terms of two viscoelastic models. These models represent the separate effects of non-Newtonian behavior and the transient response of the fluid. A unified description of the non-Newtonian shear rate dependence of the viscosity is presented as a new hyperbolic liquid model. The transient response of viscosity, following the rapid pressure rise encountered in the contact, is described by a compressional viscoelastic model of the volume response of a liquid to an applied pressure step. The resulting momentum and energy equations are solved by an iterative numerical technique, and a friction coefficient is calculated. The experimental study was performed, with two synthetic paraffinic lubricants, to verify the friction predictions of the analysis. The values of friction coefficient from theory and experiment are in close agreement.

Neonatal Responsiveness to the Odor of Amniotic and Lacteal Fluids: A Test of Perinatal Chemosensory Continuity.

ERIC Educational Resources Information Center

Marlier, Luc; Schaal, Benoist; Soussignan, Robert

1998-01-01

Studied head-orientation response of breast-feeding neonates in paired-choice odor tests. Found that 2-day olds detected amniotic fluid and colostrum, treating them as similar sensorily and/or hedonically. Four-day olds exhibited a preference for breast milk. Three-day olds oriented longer toward the odor of their own amniotic fluid than alien…

Immune Response Augmentation in Metastasized Breast Cancer by Localized Therapy Utilizing Biocompatible Magnetic Fluids. Addendum

DTIC Science & Technology

2009-08-01

Metastasized Breast Cancer by Localized Therapy Utilizing Biocompatible Magnetic Fluids PRINCIPAL INVESTIGATOR: Cahit A. Evrensel...AND SUBTITLE 5a. CONTRACT NUMBER Immune Response Augmentation in Metastasized Breast Cancer by Localized Therapy Utilizing Biocompatible... Magneto -rheological Fluid (MRF) iron nano-particles were synthesized using the reverse micelle technique and coated with poly(NIPAAm). The size

Impact of plasma response on plasma displacements in DIII-D during application of external 3D perturbations

DOE PAGES

Wingen, Andreas; Ferraro, Nathaniel M.; Shafer, Morgan W.; ...

2014-05-23

The effects of applied non-axisymmetric resonant magnetic perturbations (RMPs) are predicted without and with self-consistent plasma response by modeling of the magnetic field structure and two-fluid MHD simulations, respectively. A synthetic diagnostic is used to simulate soft X-ray (SXR) emission within the steep gradient region of the pedestal, 0.98 > ψ > 0.94. The entire pedestal and edge region is characterized by large changes in plasma rotation and current density. Those parameters are expected to strongly affect the plasma response to RMPs. The M3D-C1 code takes into account this response self-consistently. The plasma response is investigated in detail and usedmore » in the forward modeling of the simulated local SXR emission, within the framework of the synthetic diagnostic. The resulting synthetic emission is compared to measured SXR data. The latter clearly shows helical m = 11 ± 1 displacements around the 11/3 rational surface of sizes up to 5 cm, which change with the poloidal angle. The synthetic emission with plasma response is used to explain the nature of the measured displacements. Different approaches are tested. One approach is based on the magnetic field structure to simulate local emission, which shows additional structures at the separatrix, that are caused by the lobes. Especially without plasma response, almost only separatrix structures are generated while no significant displacements are found further inside. Another approach to model local emission uses the fluid quantities electron density and temperature, as calculated by M3D-C1. Compared to the previous approach, based on the magnetic field structure, the emission simulated by the fluid approach with plasma response shows better agreement with the measured SXR data. To be specific, it has comparable displacements in the steep gradient region and no lobe structures at all. The helical displacements around the 11/3 surface are identified to be directly related to the kink response, caused by non-resonant amplification of various poloidal RMP modes due to plasma response. Regarding the latter, the role of different plasma parameters is investigated, but it appears that the electron rotation plays a key role in the formation of screening and resonant amplification, while the kinking appears to be sensitive to the edge current density. As a result, it is also hypothesised that the strength of the kink response is also correlated to edge-localized-mode (ELM) stability.« less

Microfluidic-based Broadband Measurements of Fluid Permittivity and Permeability to 100 GHz

NASA Astrophysics Data System (ADS)

Little, Charles A. E.

This dissertation concerns the development of unique microfluidic microwave devices and associated microwave calibrations to quantitatively extract the broadband permittivity and permeability of fluids between 100 kHz and 110 GHz. The devices presented here consist of SU-8- and PDMS-based microfluidic channels integrated lithographically with coplanar waveguides (CPWs), measured via an external vector network analyzer (VNA). By applying our hybrid set of microwave calibrations to the raw data we extract distributed circuit parameters, representative of the electromagnetic response of the microfluidic channel. We then correlate these parameters to the permittivity and permeability of the fluid within the channels. We are primarily focused on developing devices, calibrations, and analyses to characterize various chemical and biological systems. The small fluid volumes and overall scale of our devices lends the technique to point-of-care blood and cell analysis, as well as to the analysis of high-value chemicals. Broadband microwave microfluidics is sensitive to three primary categories of phenomena: Ionic, dipolar, and magnetic resonances. All three can occur in complex fluids such as blood, proteins and particle suspensions. In order to make quantitative measurements, we need to be able to model and separate all three types of responses. Here we first measure saline solutions (NaCl and water) as an ideal system to better understanding both the ionic and dipolar response. Specifically, we are targeting the electrical double-layer (EDL) response, an ionic effect, which dominates over the intrinsic fluid response at lower frequencies. We have found that the EDL response for saline obeys a strict Debye-type relaxation model, the frequency response of which is dependent solely on the conductivity of the solution. To develop a better understanding of the magnetic response, we first measure magnetic nanoparticles; showing it is possible to detect the magnetic resonances of magnetic nanoparticle in a fluid environment using the broad-band approach, and that the response matches cavity-based measurements. In addition, we demonstrate the complicated intermixing that occurs between magnetic and electrical responses in CPW-type measurements through both numerical modeling, and empirical measurements of impeded embedded permalloy devices.

A comprehensive Guyton model analysis of physiologic responses to preadapting the blood volume as a countermeasure to fluid shifts

NASA Technical Reports Server (NTRS)

Simanonok, K. E.; Srinivasan, R. S.; Myrick, E. E.; Blomkalns, A. L.; Charles, J. B.

1994-01-01

The Guyton model of fluid, electrolyte, and circulatory regulation is an extensive mathematical model capable of simulating a variety of experimental conditions. It has been modified for use at NASA to simulate head-down tilt, a frequently used analog of weightlessness. Weightlessness causes a headward shift of body fluids that is believed to expand central blood volume, triggering a series of physiologic responses resulting in large losses of body fluids. We used the modified Guyton model to test the hypothesis that preadaptation of the blood volume before weightless exposure could counteract the central volume expansion caused by fluid shifts, and thereby attenuate the circulatory and renal responses that result in body fluid losses. Simulation results show that circulatory preadaptation, by a procedure resembling blood donation immediately before head-down bedrest, is effective in damping the physiologic responses to fluid shifts and reducing body fluid losses. After 10 hours of head-down tilt, preadaptation also produces higher blood volume, extracellular volume, and total body water for 20 to 30 days of bedrest, compared with non-preadapted control. These results indicate that circulatory preadaptation before current Space Shuttle missions may be beneficial for the maintenance of reentry and postflight orthostatic tolerance in astronauts. This paper presents a comprehensive examination of the simulation results pertaining to changes in relevant physiologic variables produced by blood volume reduction before a prolonged head-down tilt. The objectives were to study and develop the countermeasure theoretically, to aid in planning experimental studies of the countermeasure, and to identify potentially disadvantageous physiologic responses that may be caused by the countermeasure.

Structural and optical behavior due to thermal effects in end-pumped Yb:YAG disk lasers.

PubMed

Sazegari, Vahid; Milani, Mohammad Reza Jafari; Jafari, Ahmad Khayat

2010-12-20

We employ a Monte Carlo ray-tracing code along with the ANSYS package to predict the optical and structural behavior in end-pumped CW Yb:YAG disk lasers. The presence of inhomogeneous temperature, stress, and strain distributions is responsible for many deleterious effects for laser action through disk fracture, strain-induced birefringence, and thermal lensing. The thermal lensing, in turn, results in the optical phase distortion in solid-state lasers. Furthermore, the dependence of optical phase distortion on variables such as the heat transfer coefficient, the cooling fluid temperature, and crystal thickness is discussed.

Unconventional Rotor Power Response to Yaw Error Variations

DOE PAGES

Schreck, S. J.; Schepers, J. G.

2014-12-16

Continued inquiry into rotor and blade aerodynamics remains crucial for achieving accurate, reliable prediction of wind turbine power performance under yawed conditions. To exploit key advantages conferred by controlled inflow conditions, we used EU-JOULE DATA Project and UAE Phase VI experimental data to characterize rotor power production under yawed conditions. Anomalies in rotor power variation with yaw error were observed, and the underlying fluid dynamic interactions were isolated. Unlike currently recognized influences caused by angled inflow and skewed wake, which may be considered potential flow interactions, these anomalies were linked to pronounced viscous and unsteady effects.

Effects of a vertical magnetic field on particle confinement in a magnetized plasma torus.

PubMed

Müller, S H; Fasoli, A; Labit, B; McGrath, M; Podestà, M; Poli, F M

2004-10-15

The particle confinement in a magnetized plasma torus with superimposed vertical magnetic field is modeled and measured experimentally. The formation of an equilibrium characterized by a parallel plasma current canceling out the grad B and curvature drifts is described using a two-fluid model. Characteristic response frequencies and relaxation rates are calculated. The predictions for the particle confinement time as a function of the vertical magnetic field are verified in a systematic experimental study on the TORPEX device, including the existence of an optimal vertical field and the anticorrelation between confinement time and density.

Representative equations for the thermodynamic and transport properties of fluids near the gas-liquid critical point

NASA Technical Reports Server (NTRS)

Sengers, J. V.; Basu, R. S.; Sengers, J. M. H. L.

1981-01-01

A survey is presented of representative equations for various thermophysical properties of fluids in the critical region. Representative equations for the transport properties are included. Semi-empirical modifications of the theoretically predicted asymtotic critical behavior that yield simple and practical representations of the fluid properties in the critical region are emphasized.

Active Learning in Fluid Mechanics: Youtube Tube Flow and Puzzling Fluids Questions

ERIC Educational Resources Information Center

Hrenya, Christine M.

2011-01-01

Active-learning exercises appropriate for a course in undergraduate fluid mechanics are presented. The first exercise involves an experiment in gravity-driven tube flow, with small groups of students partaking in a contest to predict the experimental flow rates using the mechanical energy balance. The second exercise takes the form of an…

Measuring and predicting reservoir heterogeneity in complex deposystems: The fluvial-deltaic Big Injun sandstone in West Virginia

DOE Office of Scientific and Technical Information (OSTI.GOV)

Patchen, D.G.; Hohn, M.E.; Aminian, K.

1993-04-01

The purpose of this research is to develop techniques to measure and predict heterogeneities in oil reservoirs that are the products of complex deposystems. The unit chosen for study is the Lower Mississippian Big Injun sandstone, a prolific oil producer (nearly 60 fields) in West Virginia. This research effort has been designed and is being implemented as an integrated effort involving stratigraphy, structural geology, petrology, seismic study, petroleum engineering, modeling and geostatistics. Sandstone bodies are being mapped within their regional depositional systems, and then sandstone bodies are being classified in a scheme of relative heterogeneity to determine heterogeneity across depositionalmore » systems. Facies changes are being mapped within given reservoirs, and the environments of deposition responsible for each facies are being interpreted to predict the inherent relative heterogeneity of each facies. Structural variations will be correlated both with production, where the availability of production data will permit, and with variations in geologic and engineering parameters that affect production. A reliable seismic model of the Big Injun reservoirs in Granny Creek field is being developed to help interpret physical heterogeneity in that field. Pore types are being described and related to permeability, fluid flow and diagenesis, and petrographic data are being integrated with facies and depositional environments to develop a technique to use diagenesis as a predictive tool in future reservoir development. Another objective in the Big Injun study is to determine the effect of heterogeneity on fluid flow and efficient hydrocarbon recovery in order to improve reservoir management. Graphical methods will be applied to Big Injun production data and new geostatistical methods will be developed to detect regional trends in heterogeneity.« less

Measuring and predicting reservoir heterogeneity in complex deposystems: The fluvial-deltaic Big Injun sandstone in West Virginia. Annual report, September 20, 1991--September 20, 1992

DOE Office of Scientific and Technical Information (OSTI.GOV)

Patchen, D.G.; Hohn, M.E.; Aminian, K.

1993-04-01

The purpose of this research is to develop techniques to measure and predict heterogeneities in oil reservoirs that are the products of complex deposystems. The unit chosen for study is the Lower Mississippian Big Injun sandstone, a prolific oil producer (nearly 60 fields) in West Virginia. This research effort has been designed and is being implemented as an integrated effort involving stratigraphy, structural geology, petrology, seismic study, petroleum engineering, modeling and geostatistics. Sandstone bodies are being mapped within their regional depositional systems, and then sandstone bodies are being classified in a scheme of relative heterogeneity to determine heterogeneity across depositionalmore » systems. Facies changes are being mapped within given reservoirs, and the environments of deposition responsible for each facies are being interpreted to predict the inherent relative heterogeneity of each facies. Structural variations will be correlated both with production, where the availability of production data will permit, and with variations in geologic and engineering parameters that affect production. A reliable seismic model of the Big Injun reservoirs in Granny Creek field is being developed to help interpret physical heterogeneity in that field. Pore types are being described and related to permeability, fluid flow and diagenesis, and petrographic data are being integrated with facies and depositional environments to develop a technique to use diagenesis as a predictive tool in future reservoir development. Another objective in the Big Injun study is to determine the effect of heterogeneity on fluid flow and efficient hydrocarbon recovery in order to improve reservoir management. Graphical methods will be applied to Big Injun production data and new geostatistical methods will be developed to detect regional trends in heterogeneity.« less

Preface: Current perspectives in modelling, monitoring, and predicting geophysical fluid dynamics

NASA Astrophysics Data System (ADS)

Mancho, Ana M.; Hernández-García, Emilio; López, Cristóbal; Turiel, Antonio; Wiggins, Stephen; Pérez-Muñuzuri, Vicente

2018-02-01

The third edition of the international workshop Nonlinear Processes in Oceanic and Atmospheric Flows was held at the Institute of Mathematical Sciences (ICMAT) in Madrid from 6 to 8 July 2016. The event gathered oceanographers, atmospheric scientists, physicists, and applied mathematicians sharing a common interest in the nonlinear dynamics of geophysical fluid flows. The philosophy of this meeting was to bring together researchers from a variety of backgrounds into an environment that favoured a vigorous discussion of concepts across different disciplines. The present Special Issue on Current perspectives in modelling, monitoring, and predicting geophysical fluid dynamics contains selected contributions, mainly from attendants of the workshop, providing an updated perspective on modelling aspects of geophysical flows as well as issues on prediction and assimilation of observational data and novel tools for describing transport and mixing processes in these contexts. More details on these aspects are discussed in this preface.

Experimental investigation of leaky lamb modes by an optically induced grating.

PubMed

Van de Rostyne, Kris; Glorieux, Christ; Gao, Weimin; Lauriks, Walter; Thoen, Jan

2002-09-01

By removing the symmetry of a free plate configuration, fluid loading significantly modifies the nature of acoustic waves travelling along a plate, and it even gives existence to new acoustic modes. We present theoretical predictions for the existence, dispersive behavior, and spatial distribution of leaky Lamb waves in a fluid-loaded film. Although Lamb modes are often investigated by studying the radiated fluid waves resulting from their leakage, here their properties are assessed by detecting the wave displacements directly using laser beam deflection. By using crossed laser beam excitation, the detection and analysis of the different modes is done at a fixed wavelength, allowing one to verify the existence, the velocity, and the damping of each predicted mode in a simple and unambiguous way. Our theoretical predictions for the nature of the modes in a water-loaded Plexiglas film, including parts of looping modes, are experimentally confirmed.

Porosity variations in and around normal fault zones: implications for fault seal and geomechanics

NASA Astrophysics Data System (ADS)

Healy, David; Neilson, Joyce; Farrell, Natalie; Timms, Nick; Wilson, Moyra

2015-04-01

Porosity forms the building blocks for permeability, exerts a significant influence on the acoustic response of rocks to elastic waves, and fundamentally influences rock strength. And yet, published studies of porosity around fault zones or in faulted rock are relatively rare, and are hugely dominated by those of fault zone permeability. We present new data from detailed studies of porosity variations around normal faults in sandstone and limestone. We have developed an integrated approach to porosity characterisation in faulted rock exploiting different techniques to understand variations in the data. From systematic samples taken across exposed normal faults in limestone (Malta) and sandstone (Scotland), we combine digital image analysis on thin sections (optical and electron microscopy), core plug analysis (He porosimetry) and mercury injection capillary pressures (MICP). Our sampling includes representative material from undeformed protoliths and fault rocks from the footwall and hanging wall. Fault-related porosity can produce anisotropic permeability with a 'fast' direction parallel to the slip vector in a sandstone-hosted normal fault. Undeformed sandstones in the same unit exhibit maximum permeability in a sub-horizontal direction parallel to lamination in dune-bedded sandstones. Fault-related deformation produces anisotropic pores and pore networks with long axes aligned sub-vertically and this controls the permeability anisotropy, even under confining pressures up to 100 MPa. Fault-related porosity also has interesting consequences for the elastic properties and velocity structure of normal fault zones. Relationships between texture, pore type and acoustic velocity have been well documented in undeformed limestone. We have extended this work to include the effects of faulting on carbonate textures, pore types and P- and S-wave velocities (Vp, Vs) using a suite of normal fault zones in Malta, with displacements ranging from 0.5 to 90 m. Our results show a clear lithofacies control on the Vp-porosity and the Vs-Vp relationships for faulted limestones. Using porosity patterns quantified in naturally deformed rocks we have modelled their effect on the mechanical stability of fluid-saturated fault zones in the subsurface. Poroelasticity theory predicts that variations in fluid pressure could influence fault stability. Anisotropic patterns of porosity in and around fault zones can - depending on their orientation and intensity - lead to an increase in fault stability in response to a rise in fluid pressure, and a decrease in fault stability for a drop in fluid pressure. These predictions are the exact opposite of the accepted role of effective stress in fault stability. Our work has provided new data on the spatial and statistical variation of porosity in fault zones. Traditionally considered as an isotropic and scalar value, porosity and pore networks are better considered as anisotropic and as scale-dependent statistical distributions. The geological processes controlling the evolution of porosity are complex. Quantifying patterns of porosity variation is an essential first step in a wider quest to better understand deformation processes in and around normal fault zones. Understanding porosity patterns will help us to make more useful predictive tools for all agencies involved in the study and management of fluids in the subsurface.