Predicting Upscaled Behavior of Aqueous Reactants in Heterogeneous Porous Media

NASA Astrophysics Data System (ADS)

Wright, E. E.; Hansen, S. K.; Bolster, D.; Richter, D. H.; Vesselinov, V. V.

2017-12-01

When modeling reactive transport, reaction rates are often overestimated due to the improper assumption of perfect mixing at the support scale of the transport model. In reality, fronts tend to form between participants in thermodynamically favorable reactions, leading to segregation of reactants into islands or fingers. When such a configuration arises, reactions are limited to the interface between the reactive solutes. Closure methods for estimating control-volume-effective reaction rates in terms of quantities defined at the control volume scale do not presently exist, but their development is crucial for effective field-scale modeling. We attack this problem through a combination of analytical and numerical means. Specifically, we numerically study reactive transport through an ensemble of realizations of two-dimensional heterogeneous porous media. We then employ regression analysis to calibrate an analytically-derived relationship between reaction rate and various dimensionless quantities representing conductivity-field heterogeneity and the respective strengths of diffusion, reaction and advection.

Parameterization of subgrid-scale stress by the velocity gradient tensor

NASA Technical Reports Server (NTRS)

Lund, Thomas S.; Novikov, E. A.

1993-01-01

The objective of this work is to construct and evaluate subgrid-scale models that depend on both the strain rate and the vorticity. This will be accomplished by first assuming that the subgrid-scale stress is a function of the strain and rotation rate tensors. Extensions of the Caley-Hamilton theorem can then be used to write the assumed functional dependence explicitly in the form of a tensor polynomial involving products of the strain and rotation rates. Finally, use of this explicit expression as a subgrid-scale model will be evaluated using direct numerical simulation data for homogeneous, isotropic turbulence.

A Comparison of Change in the 0–10 Numeric Rating Scale to a Pain Relief Scale and Global Medication Performance Scale in a Short-term Clinical Trial of Breakthrough Pain Intensity

PubMed Central

Farrar, John T.; Polomano, Rosemary C.; Berlin, Jesse A.; Strom, Brian L.

2010-01-01

Background Pain intensity is commonly reported using a 0–10 numeric rating scale in breakthrough pain clinical trials. Analysis of the change on the Pain Intensity Numerical Rating Scale as a proportion as most consistently correlated with clinically important differences reported on the Patient Global Impression of Change. The analysis of data using a different global outcome measures and the pain relief scale will extend our understanding of these measures. Use of the pain relief scale is also explored in this study Methods Data came from the open titration phase of a multiple crossover, randomized, double-blind clinical trial comparing oral transmucosal fentanyl citrate to immediate-release oral morphine sulfate for treatment of cancer-related breakthrough pain. Raw and percent changes in the pain intensity scores on 1,307 from 134 oral transmucosal fentanyl citrate-naive patients were compared to the clinically relevant secondary outcomes of the pain relief verbal response scale and the global medication performance. The changes in raw and percent change were assessed over time and compared to the ordinal pain relief verbal response scale and global medication performance scales. Results The p-value of the interaction between the raw pain intensity difference was significant but not for the percent pain intensity difference score over 4 15 minute time periods (p = 0.034 and p = 0.26 respectively), in comparison with the ordinal pain relief verbal response scale (p = 0.0048 and p = 0.36 respectively), and global medication performance categories (p = 0.048 and p = 0.45 respectively). Conclusion The change in pain intensity in breakthrough pain was more consistent over time and when compared to both the pain relief verbal response scale and global medication performance scale when the percent change is used rather than raw pain intensity difference. PMID:20463579

A comparison of change in the 0-10 numeric rating scale to a pain relief scale and global medication performance scale in a short-term clinical trial of breakthrough pain intensity.

PubMed

Farrar, John T; Polomano, Rosemary C; Berlin, Jesse A; Strom, Brian L

2010-06-01

Pain intensity is commonly reported using a 0-10 Numeric Rating Scale in pain clinical trials. Analysis of the change on the Pain Intensity Numerical Rating Scale as a proportion has most consistently correlated with clinically important differences reported on the patient's global impression of change. The correlation of data from patients with breakthrough pain with a Pain Relief Scale and a different global outcome measures will extend our understanding of these measures. Data were obtained from the open titration phase of a multiple crossover, randomized, double-blind clinical trial comparing oral transmucosal fentanyl citrate with immediate-release oral morphine sulfate for the treatment of cancer-related breakthrough pain. Raw and percentage changes in the pain intensity scores from 1,307 episodes of pain in 134 oral transmucosal fentanyl citrate-naïve patients were correlated with the clinically relevant secondary outcomes of Pain Relief Verbal Response Scale and the global medication performance scale. The changes in raw and percentage change were assessed over time and compared with the ordinal Pain Relief Verbal Response Scale and Global Medication Performance Scale. The P value of the interaction between the raw pain intensity difference was significant (P = 0.034) for four 15-min time periods but not for the percentage pain intensity difference score (P = 0.26). We found similar results in comparison with the ordinal Pain Relief Verbal Response Scale (P = 0.0048 and P = 0.36 respectively) and global medication performance categories (P = 0.048 and P = 0.45, respectively). The change in pain intensity in breakthrough pain was more consistent over time and when compared with both the Pain Relief Verbal Response Scale and the Global Medication Performance Scale when the percentage change is used rather than raw pain intensity difference.

Pregabalin for painful HIV neuropathy

PubMed Central

Simpson, D. M.; Schifitto, G.; Clifford, D. B.; Murphy, T. K.; Durso-De Cruz, E.; Glue, P.; Whalen, E.; Emir, B.; Scott, G. N.; Freeman, R.

2010-01-01

Objective: Pregabalin is effective in several neuropathic pain syndromes. This trial evaluated its efficacy, safety, and tolerability for treatment of painful HIV-associated neuropathy. Methods: This randomized, double-blind, placebo-controlled, parallel-group trial included a 2-week double-blind dose-adjustment (150–600 mg/day BID) phase, a 12-week double-blind maintenance phase, and an optional 3-month open label extension phase. The primary efficacy measure was the mean Numeric Pain Rating Scale (NPRS) score, an 11-point numeric rating scale. Secondary measures included Patient Global Impression of Change (PGIC) and sleep measurements. Results: Baseline mean NPRS score was 6.93 for patients randomized to pregabalin (n = 151) and 6.72 for those to placebo (n = 151). Pregabalin average daily dosage (SD) was 385.7 (160.3) mg/d. At endpoint, pregabalin and placebo showed substantial reductions in mean NPRS score from baseline: −2.88 vs −2.63, p = 0.3941. Pregabalin had greater improvements in NPRS score relative to placebo at weeks 1 (−1.14 vs −0.69, p = 0.0131) and 2 (−1.92 vs −1.43, p = 0.0393), and at weeks 7 (−3.22 vs −2.53 p = 0.0307) and 8 (−3.33 vs −2.53, p = 0.0156). At all other time points, differences between groups were not significant. Sleep measurements and 7-item PGIC did not differ among treatment groups; however, collapsed PGIC scores showed 82.8% of pregabalin and 66.7% of placebo patients rated themselves in 1 of the 3 “improved” categories (p = 0.0077). Somnolence and dizziness were the most common adverse events with pregabalin. Conclusions: Pregabalin was well-tolerated, but not superior to placebo in the treatment of painful HIV neuropathy. Factors predicting analgesic response in HIV neuropathy warrant additional research. Classification of Evidence: This Class II trial showed that pregabalin is not more effective than placebo in treatment of painful HIV neuropathy. GLOSSARY AE = adverse events; ANCOVA = analysis of covariance; ARF = activity region finder; ARV = antiretroviral; GPS = Gracely Pain Scale; HADS = Hospital Anxiety and Depression Scale; HIV-DSP = HIV-associated distal sensory polyneuropathy; LOCF = last observation carried forward; mBPI-sf = modified Brief Pain Inventory–short form; NPRS = Numeric Pain Rating Scale; NPSI = Neuropathic Pain Symptom Inventory; NRS = Numeric Rating Scale; PGIC = Patient Global Impression of Change; VAS = visual analog scale. PMID:20124207

The effect of intra-operative transcutaneous electrical nerve stimulation on posterior neck pain following thyroidectomy.

PubMed

Park, C; Choi, J B; Lee, Y-S; Chang, H-S; Shin, C S; Kim, S; Han, D W

2015-04-01

Posterior neck pain following thyroidectomy is common because full neck extension is required during the procedure. We evaluated the effect of intra-operative transcutaneous electrical nerve stimulation on postoperative neck pain in patients undergoing total thyroidectomy under general anaesthesia. One hundred patients were randomly assigned to one of two groups; 50 patients received transcutaneous electrical nerve stimulation applied to the trapezius muscle and 50 patients acted as controls. Postoperative posterior neck pain and anterior wound pain were evaluated using an 11-point numerical rating scale at 30 min, 6 h, 24 h and 48 h following surgery. The numerical rating scale for posterior neck pain was significantly lower in the transcutaneous electrical nerve stimulation group compared with the control group at all time points (p < 0.05). There were no significant differences in the numerical rating scale for anterior wound pain at any time point. No adverse effects related to transcutaneous electrical nerve stimulation were observed. We conclude that intra-operative transcutaneous electrical nerve stimulation applied to the trapezius muscle reduced posterior neck pain following thyroidectomy. © 2014 The Association of Anaesthetists of Great Britain and Ireland.

Rupture dynamics along bimaterial interfaces: a parametric study of the coupling between interfacial sliding and normal traction perturbation

NASA Astrophysics Data System (ADS)

Scala, Antonio; Festa, Gaetano; Vilotte, Jean-Pierre

2017-04-01

Earthquake ruptures often develop along faults separating materials with dissimilar elastic properties. Due to the broken symmetry, the propagation of the rupture along the bimaterial interface is driven by the coupling between interfacial sliding and normal traction perturbations. We numerically investigate in-plane rupture growth along a planar interface, under slip weakening friction, separating two dissimilar isotropic linearly elastic half-spaces. We perform a parametric study of the classical Prakash-Clifton regularisation for different material contrasts. In particular mesh-dependence and regularisation-dependence of the numerical solutions are analysed in this parameter space. When regularisation involves a slip-rate dependent relaxation time, a characteristic sliding distance is identified below which numerical solutions no longer depend on the regularisation parameter, i.e. they are consistent solutions of the same physical problem. Such regularisation provides an adaptive high-frequency filter of the slip-induced normal traction perturbations, following the dynamic shrinking of the dissipation zone during the acceleration phase. In contrast, regularisation involving a constant relaxation time leads to numerical solutions that always depend on the regularisation parameter since it fails adapting to the shrinking of the process zone. Dynamic regularisation is further investigated using a non-local regularisation based on a relaxation time that depends on the dynamic length of the dissipation zone. Such reformulation is shown to provide similar results as the dynamic time scale regularisation proposed by Prakash-Clifton when slip rate is replaced by the maximum slip rate along the sliding interface. This leads to the identification of a dissipative length scale associated with the coupling between interfacial sliding and normal traction perturbations, together with a scaling law between the maximum slip rate and the dynamic size of the process zone during the rupture propagation. Dynamic time scale regularisation is show to provide mesh-independent and physically well-posed numerical solutions during the acceleration phase toward an asymptotic speed. When generalised Rayleigh wave does not exist, numerical solutions are shown to tend toward an asymptotic velocity higher than the slowest shear wave speed. When generalised Rayleigh wave speed exists, as numerical solutions tend toward this velocity, increasing spurious oscillations develop and solutions become unstable. In this regime regularisation dependent and unstable finite-size pulses may be generated. This instability is associated with the singular behaviour of the slip-induced normal traction perturbations, and of the slip rate at the rupture front, in relation with complete shrinking of the dissipation zone. This phase requires to be modelled either by more complex interface constitutive laws involving velocity-strengthening effects that may stabilize short wavelength interfacial propagating modes or by considering non-ideal interfaces that introduce a new length scale in the problem that may promote selection and stabilization of the slip pulses.

Numerical study of the small scale structures in Boussinesq convection

NASA Technical Reports Server (NTRS)

Weinan, E.; Shu, Chi-Wang

1992-01-01

Two-dimensional Boussinesq convection is studied numerically using two different methods: a filtered pseudospectral method and a high order accurate Essentially Nonoscillatory (ENO) scheme. The issue whether finite time singularity occurs for initially smooth flows is investigated. The numerical results suggest that the collapse of the bubble cap is unlikely to occur in resolved calculations. The strain rate corresponding to the intensification of the density gradient across the front saturates at the bubble cap. We also found that the cascade of energy to small scales is dominated by the formulation of thin and sharp fronts across which density jumps.

Incorporating a Nebulizer System Into High-Flow Nasal Cannula Improves Comfort in Infants With Bronchiolitis.

PubMed

Valencia-Ramos, Juan; Mirás, Alicia; Cilla, Amacia; Ochoa, Carlos; Arnaez, Juan

2018-07-01

High-flow nasal cannula (HFNC) is increasingly used to provide respiratory support in infants with bronchiolitis. The delivery of aerosol therapy through a jet nebulizer is widely indicated despite its controversial efficacy and poor tolerability. This randomized cross-over study aimed to evaluate the comfort and satisfaction of the delivery of aerosol therapy using a nebulization system integrated into HFNC compared with the standard practice of using a jet nebulizer with a face mask. The COMFORT-Behavior (COMFORT-B) scale, a visual analog scale, and a numeric rating scale were used by health professionals and caregivers to assess subjects' levels of comfort and satisfaction. A total of 113 nebulizations (64 via nebulizer with HFNC; 49 via jet nebulizer) were delivered to the 6 subjects included in the study. Use of the nebulizer with HFNC showed increased comfort and satisfaction during nebulization compared to use of the jet nebulizer, as measured by the COMFORT-B scale, the visual analog scale, and the numeric rating scale, with the following median (interquartile range) scores: 10.7 (7-16) versus 14.5 (10-20) ( P = .006), 8.5 (6-10) versus 7 (4-9) ( P = .02), and 3.84 (3.61-4.07) versus 1.83 (1.58-2.08) ( P < .001), respectively. Correlation between the COMFORT-B scale and the visual analog scale using Spearman's rho was -0.757 ( P < .001). The intraclass correlation coefficient for the COMFORT-B scale, visual analog scale, and numeric rating scale, as measured by 2 different nurses, was between 0.75 and 0.87. The use of a nebulizer incorporated into HFNC therapy results in an increased level of comfort and satisfaction compared to the use of a conventional jet nebulizer in subjects with bronchiolitis who required HFNC therapy. Further studies are needed to determine whether aerosol therapy delivered through HFNC improves the clinical course of this pathology. Copyright © 2018 by Daedalus Enterprises.

Time and length scales within a fire and implications for numerical simulation

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

TIESZEN,SHELDON R.

2000-02-02

A partial non-dimensionalization of the Navier-Stokes equations is used to obtain order of magnitude estimates of the rate-controlling transport processes in the reacting portion of a fire plume as a function of length scale. Over continuum length scales, buoyant times scales vary as the square root of the length scale; advection time scales vary as the length scale, and diffusion time scales vary as the square of the length scale. Due to the variation with length scale, each process is dominant over a given range. The relationship of buoyancy and baroclinc vorticity generation is highlighted. For numerical simulation, first principlesmore » solution for fire problems is not possible with foreseeable computational hardware in the near future. Filtered transport equations with subgrid modeling will be required as two to three decades of length scale are captured by solution of discretized conservation equations. By whatever filtering process one employs, one must have humble expectations for the accuracy obtainable by numerical simulation for practical fire problems that contain important multi-physics/multi-length-scale coupling with up to 10 orders of magnitude in length scale.« less

Assessment of dyspnoea in the emergency department by numeric and visual scales: A pilot study.

PubMed

Placido, Rui; Gigaud, Carine; Gayat, Etienne; Ferry, Axelle; Cohen-Solal, Alain; Plaisance, Patrick; Mebazaa, Alexandre; Laribi, Said

2015-04-01

Dyspnoea is a common and often debilitating symptom that affects up to 50% of patients admitted to acute tertiary care hospitals. The primary purpose of this study was to compare the numeric rating scale (NRS) and the visual analogue scale (VAS) for dyspnoea evaluation in the ED setting. This was a cohort study of patients admitted to the ED in a university hospital, with dyspnoea as the chief complaint. The agreement of the two dyspnoea scales was assessed using the intraclass correlation coefficient (ICC). One hundred and seventeen patients were included in this analysis. The median age for the whole study population was 67 years and 42% of patients were male. The aetiology of dyspnoea was acute heart failure (AHF) in 35% of patients. There was good agreement between the two scores (ICC=0.795; 95% CI=0.717-0.853; P<0.001). This pilot study demonstrated that numerical rating and visual analogue scales agree well when assessing the severity of dyspnoea in the ED. Further studies with larger cohorts of patients are needed to confirm these preliminary results. Copyright © 2015 Société française d’anesthésie et de réanimation (Sfar). All rights reserved.

Numerical Modeling of Propellant Boil-Off in a Cryogenic Storage Tank

NASA Technical Reports Server (NTRS)

Majumdar, A. K.; Steadman, T. E.; Maroney, J. L.; Sass, J. P.; Fesmire, J. E.

2007-01-01

A numerical model to predict boil-off of stored propellant in large spherical cryogenic tanks has been developed. Accurate prediction of tank boil-off rates for different thermal insulation systems was the goal of this collaboration effort. The Generalized Fluid System Simulation Program, integrating flow analysis and conjugate heat transfer for solving complex fluid system problems, was used to create the model. Calculation of tank boil-off rate requires simultaneous simulation of heat transfer processes among liquid propellant, vapor ullage space, and tank structure. The reference tank for the boil-off model was the 850,000 gallon liquid hydrogen tank at Launch Complex 39B (LC- 39B) at Kennedy Space Center, which is under study for future infrastructure improvements to support the Constellation program. The methodology employed in the numerical model was validated using a sub-scale model and tank. Experimental test data from a 1/15th scale version of the LC-39B tank using both liquid hydrogen and liquid nitrogen were used to anchor the analytical predictions of the sub-scale model. Favorable correlations between sub-scale model and experimental test data have provided confidence in full-scale tank boil-off predictions. These methods are now being used in the preliminary design for other cases including future launch vehicles

Evaluative measurement properties of the patient-specific functional scale for primary shoulder complaints in physical therapy practice.

PubMed

Koehorst, Marije L S; van Trijffel, Emiel; Lindeboom, Robert

2014-08-01

Clinical measurement, longitudinal. To assess the test-retest reliability, construct validity, and responsiveness of the Patient-Specific Functional Scale (PSFS) in patients with a primary shoulder complaint. Health measurement outcomes have become increasingly important for evaluating treatment. Patient-specific questionnaires are useful tools for determining treatment goals and evaluating treatment in individual patients. These questionnaires have not yet been validated in patients with nonspecific shoulder pain. Patients completed the PSFS, the numeric pain rating scale, and the Shoulder Pain and Disability Index at baseline, and after 1 week and 4 to 6 weeks. Test-retest reliability was determined using intraclass correlation coefficients. To assess convergent validity, change scores of the PSFS were correlated with the numeric pain rating scale and Shoulder Pain and Disability Index change scores. Responsiveness was assessed by calculating the area under the curve, the minimal clinically important change, and minimal detectable change, using the global rating of change as an external criterion. Fifty patients (37 men; mean age, 47.7 years) participated in the study. Reliability was high (intraclass correlation coefficient = 0.87; 95% confidence interval [CI]: 0.72, 0.94). The correlations between the change scores of the PSFS and those of the Shoulder Pain and Disability Index and numeric pain rating scale were 0.45 (95% CI: 0.17, 0.80) and 0.55 (95% CI: 0.29, 0.73), respectively. The area under the curve for the PSFS was 0.67 (95% CI: 0.51, 0.83). The minimal detectable change and minimal clinically important change were 0.97 and 1.29 points, respectively. These results suggest that the PSFS is a reliable, valid, and responsive instrument that can be used as an evaluative instrument in patients with a primary shoulder complaint.

Large-scale dynamo growth rates from numerical simulations and implications for mean-field theories

NASA Astrophysics Data System (ADS)

Park, Kiwan; Blackman, Eric G.; Subramanian, Kandaswamy

2013-05-01

Understanding large-scale magnetic field growth in turbulent plasmas in the magnetohydrodynamic limit is a goal of magnetic dynamo theory. In particular, assessing how well large-scale helical field growth and saturation in simulations match those predicted by existing theories is important for progress. Using numerical simulations of isotropically forced turbulence without large-scale shear with its implications, we focus on several additional aspects of this comparison: (1) Leading mean-field dynamo theories which break the field into large and small scales predict that large-scale helical field growth rates are determined by the difference between kinetic helicity and current helicity with no dependence on the nonhelical energy in small-scale magnetic fields. Our simulations show that the growth rate of the large-scale field from fully helical forcing is indeed unaffected by the presence or absence of small-scale magnetic fields amplified in a precursor nonhelical dynamo. However, because the precursor nonhelical dynamo in our simulations produced fields that were strongly subequipartition with respect to the kinetic energy, we cannot yet rule out the potential influence of stronger nonhelical small-scale fields. (2) We have identified two features in our simulations which cannot be explained by the most minimalist versions of two-scale mean-field theory: (i) fully helical small-scale forcing produces significant nonhelical large-scale magnetic energy and (ii) the saturation of the large-scale field growth is time delayed with respect to what minimalist theory predicts. We comment on desirable generalizations to the theory in this context and future desired work.

Large-scale dynamo growth rates from numerical simulations and implications for mean-field theories.

PubMed

Park, Kiwan; Blackman, Eric G; Subramanian, Kandaswamy

2013-05-01

Understanding large-scale magnetic field growth in turbulent plasmas in the magnetohydrodynamic limit is a goal of magnetic dynamo theory. In particular, assessing how well large-scale helical field growth and saturation in simulations match those predicted by existing theories is important for progress. Using numerical simulations of isotropically forced turbulence without large-scale shear with its implications, we focus on several additional aspects of this comparison: (1) Leading mean-field dynamo theories which break the field into large and small scales predict that large-scale helical field growth rates are determined by the difference between kinetic helicity and current helicity with no dependence on the nonhelical energy in small-scale magnetic fields. Our simulations show that the growth rate of the large-scale field from fully helical forcing is indeed unaffected by the presence or absence of small-scale magnetic fields amplified in a precursor nonhelical dynamo. However, because the precursor nonhelical dynamo in our simulations produced fields that were strongly subequipartition with respect to the kinetic energy, we cannot yet rule out the potential influence of stronger nonhelical small-scale fields. (2) We have identified two features in our simulations which cannot be explained by the most minimalist versions of two-scale mean-field theory: (i) fully helical small-scale forcing produces significant nonhelical large-scale magnetic energy and (ii) the saturation of the large-scale field growth is time delayed with respect to what minimalist theory predicts. We comment on desirable generalizations to the theory in this context and future desired work.

Fluoroscopy-guided Sacroiliac Joint Steroid Injection for Low Back Pain in a Patient with Osteogenesis Imperfecta.

PubMed

Dawson, P U; Rose, R E; Wade, N A

2015-09-01

Osteogenesis imperfecta, also known as 'brittle bone disease', is a genetic connective tissue disease. It is characterized by bone fragility and osteopenia (low bone density). In this case, a 57-year old female presented to the University Hospital of the West Indies (UHWI), Physical Medicine and Rehabilitation Clinic with left low back pain rated 6/10 on the numeric rating scale (NRS). Clinically, the patient had sacroiliac joint mediated pain although X-rays did not show the sacroiliac joint changes. Fluoroscopy-guided left sacroiliac joint steroid injection was done. Numeric rating scale and Oswestry Disability Index (ODI) questionnaire were used to evaluate outcome. This was completed at baseline, one week follow-up and at eight weeks post fluoroscopy-guided sacroiliac joint steroid injection. Numeric rating scale improved from 6/10 before the procedure to 0/10 post procedure, and ODI questionnaire score improved from a moderate disability score of 40% to a minimal disability score of 13%. Up to eight weeks, the NRS was 0/10 and ODI remained at minimal disability of 15%. Fluoroscopy-guided sacroiliac joint injection is a known diagnostic and treatment method for sacroiliac joint mediated pain. To our knowledge, this is the first case published on the use of fluoroscopy-guided sacroiliac joint steroid injection in the treatment of sacroiliac joint mediated low back pain in a patient with osteogenesis imperfecta.

A numerical study of the string function using a primitive equation ocean model

NASA Astrophysics Data System (ADS)

Tyler, R. H.; Käse, R.

We use results from a primitive-equation ocean numerical model (SCRUM) to test a theoretical 'string function' formulation put forward by Tyler and Käse in another article in this issue. The string function acts as a stream function for the large-scale potential energy flow under the combined beta and topographic effects. The model results verify that large-scale anomalies propagate along the string function contours with a speed correctly given by the cross-string gradient. For anomalies having a scale similar to the Rossby radius, material rates of change in the layer mass following the string velocity are balanced by material rates of change in relative vorticity following the flow velocity. It is shown that large-amplitude anomalies can be generated when wind stress is resonant with the string function configuration.

Minimum important differences for the patient-specific functional scale, 4 region-specific outcome measures, and the numeric pain rating scale.

PubMed

Abbott, J Haxby; Schmitt, John

2014-08-01

Multicenter, prospective, longitudinal cohort study. To investigate the minimum important difference (MID) of the Patient-Specific Functional Scale (PSFS), 4 region-specific outcome measures, and the numeric pain rating scale (NPRS) across 3 levels of patient-perceived global rating of change in a clinical setting. The MID varies depending on the external anchor defining patient-perceived "importance." The MID for the PSFS has not been established across all body regions. One thousand seven hundred eight consecutive patients with musculoskeletal disorders were recruited from 5 physical therapy clinics. The PSFS, NPRS, and 4 region-specific outcome measures-the Oswestry Disability Index, Neck Disability Index, Upper Extremity Functional Index, and Lower Extremity Functional Scale-were assessed at the initial and final physical therapy visits. Global rating of change was assessed at the final visit. MID was calculated for the PSFS and NPRS (overall and for each body region), and for each region-specific outcome measure, across 3 levels of change defined by the global rating of change (small, medium, large change) using receiver operating characteristic curve methodology. The MID for the PSFS (on a scale from 0 to 10) ranged from 1.3 (small change) to 2.3 (medium change) to 2.7 (large change), and was relatively stable across body regions. MIDs for the NPRS (-1.5 to -3.5), Oswestry Disability Index (-12), Neck Disability Index (-14), Upper Extremity Functional Index (6 to 11), and Lower Extremity Functional Scale (9 to 16) are also reported. We reported the MID for small, medium, and large patient-perceived change on the PSFS, NPRS, Oswestry Disability Index, Neck Disability Index, Upper Extremity Functional Index, and Lower Extremity Functional Scale for use in clinical practice and research.

Numerical analysis of two-fluid tearing mode instability in a finite aspect ratio cylinder

NASA Astrophysics Data System (ADS)

Ito, Atsushi; Ramos, Jesús J.

2018-01-01

The two-fluid resistive tearing mode instability in a periodic plasma cylinder of finite aspect ratio is investigated numerically for parameters such that the cylindrical aspect ratio and two-fluid effects are of order unity, hence the real and imaginary parts of the mode eigenfunctions and growth rate are comparable. Considering a force-free equilibrium, numerical solutions of the complete eigenmode equations for general aspect ratios and ion skin depths are compared and found to be in very good agreement with the corresponding analytic solutions derived by means of the boundary layer theory [A. Ito and J. J. Ramos, Phys. Plasmas 24, 072102 (2017)]. Scaling laws for the growth rate and the real frequency of the mode are derived from the analytic dispersion relation by using Taylor expansions and Padé approximations. The cylindrical finite aspect ratio effect is inferred from the scaling law for the real frequency of the mode.

Item Response Modeling of Forced-Choice Questionnaires

ERIC Educational Resources Information Center

Brown, Anna; Maydeu-Olivares, Alberto

2011-01-01

Multidimensional forced-choice formats can significantly reduce the impact of numerous response biases typically associated with rating scales. However, if scored with classical methodology, these questionnaires produce ipsative data, which lead to distorted scale relationships and make comparisons between individuals problematic. This research…

Validation of Scratching Severity as an Objective Assessment for Itch.

PubMed

Udkoff, Jeremy; Silverberg, Jonathan I

2018-05-01

There are currently no simple, standardized, objective assessments of itch for clinical trials and practice. We sought to validate and test the severity of scratching as an objective measure of itch (4-point ordinal scale ranging from 0 [not present] to 3 [very prominent] based on the observation of scratching lesions). We performed a prospective outpatient study using questionnaires and evaluations by a dermatologist in adults with atopic dermatitis (n = 261). Severity of scratching best correlated with patient-reported global atopic dermatitis severity (Kendall τ = 0.336, P < 0.0001), numeric rating scale of itch in the past 24 hours (τ = 0.266, P = 0.0010) and 3 days (τ = 0.296, P < 0.0001). Severity of scratching showed responsiveness over time. Patients experiencing improvement of scratching severity of 1 point or greater had significantly lower itch based on numeric rating scale in the past 3 days (Wilcoxon rank sum test, P = 0.0175), 5-D itch scale (P = 0.0146), and Patient-Oriented Eczema Measure scores (P = 0.0146). There was a significant decrease in scratching severity for patients experiencing itch improvement of 4 points or greater in the past 3 days on the numeric rating scale (Fisher exact test, P = 0.0026), Patient-Oriented Eczema Measure (P < 0.0001), and Dermatology Life Quality Index (P = 0.0285). Severity of scratching may be a useful endpoint in clinical trials and practice across the gamut of pruritic disorders. Future studies are needed to validate severity of scratching in other pruritic disease. Copyright © 2017 The Authors. Published by Elsevier Inc. All rights reserved.

When is best-worst best? A comparison of best-worst scaling, numeric estimation, and rating scales for collection of semantic norms.

PubMed

Hollis, Geoff; Westbury, Chris

2018-02-01

Large-scale semantic norms have become both prevalent and influential in recent psycholinguistic research. However, little attention has been directed towards understanding the methodological best practices of such norm collection efforts. We compared the quality of semantic norms obtained through rating scales, numeric estimation, and a less commonly used judgment format called best-worst scaling. We found that best-worst scaling usually produces norms with higher predictive validities than other response formats, and does so requiring less data to be collected overall. We also found evidence that the various response formats may be producing qualitatively, rather than just quantitatively, different data. This raises the issue of potential response format bias, which has not been addressed by previous efforts to collect semantic norms, likely because of previous reliance on a single type of response format for a single type of semantic judgment. We have made available software for creating best-worst stimuli and scoring best-worst data. We also made available new norms for age of acquisition, valence, arousal, and concreteness collected using best-worst scaling. These norms include entries for 1,040 words, of which 1,034 are also contained in the ANEW norms (Bradley & Lang, Affective norms for English words (ANEW): Instruction manual and affective ratings (pp. 1-45). Technical report C-1, the center for research in psychophysiology, University of Florida, 1999).

Scale-Dependent Rates of Uranyl Surface Complexation Reaction in Sediments

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

Liu, Chongxuan; Shang, Jianying; Kerisit, Sebastien N.

Scale-dependency of uranyl[U(VI)] surface complexation rates was investigated in stirred flow-cell and column systems using a U(VI)-contaminated sediment from the US Department of Energy, Hanford site, WA. The experimental results were used to estimate the apparent rate of U(VI) surface complexation at the grain-scale and in porous media. Numerical simulations using molecular, pore-scale, and continuum models were performed to provide insights into and to estimate the rate constants of U(VI) surface complexation at the different scales. The results showed that the grain-scale rate constant of U(VI) surface complexation was over 3 to 10 orders of magnitude smaller, dependent on themore » temporal scale, than the rate constant calculated using the molecular simulations. The grain-scale rate was faster initially and slower with time, showing the temporal scale-dependency. The largest rate constant at the grain-scale decreased additional 2 orders of magnitude when the rate was scaled to the porous media in the column. The scaling effect from the grain-scale to the porous media became less important for the slower sorption sites. Pore-scale simulations revealed the importance of coupled mass transport and reactions in both intragranular and inter-granular domains, which caused both spatial and temporal dependence of U(VI) surface complexation rates in the sediment. Pore-scale simulations also revealed a new rate-limiting mechanism in the intragranular porous domains that the rate of coupled diffusion and surface complexation reaction was slower than either process alone. The results provided important implications for developing models to scale geochemical/biogeochemical reactions.« less

Utility of numerical and visual analog scales for evaluating the post-operative pain in rural patients

PubMed Central

Mudgalkar, Nikhil; Bele, Samir D; Valsangkar, Sameer; Bodhare, Trupti N; Gorre, Mahipal

2012-01-01

Background: Visual analog scales (VAS) and numeric analog scales (NAS) are used to assess post-operative pain, but few studies indicate their usefulness in rural illiterate population in India. Aims: This study was designed to 1) Compare the impact of literacy on the ability to indicate pain rating on VAS and NAS in post-operative rural patients. 2) Assess the level of agreement between the pain scales. Setting and Design: Cross sectional, hospital based study. Methods: Informed consent was obtained from patients prior to undergoing surgical procedures in a teaching hospital. Post surgery, patients who were conscious and coherent, were asked to rate pain on both VAS and NAS. The pain ratings were obtained within 24 hours of surgery and within 5 minutes of each other. Statistical Methods: Percentages, chi square test, regression analysis. Results: A total of 105 patients participated in the study. 43 (41%) of the sample was illiterate. 82 (78.1%) were able to rate pain on VAS while 81 (77.1%) were able to rate pain on NAS. There was no significant association between pain ratings and type of surgery, duration of surgery and nature of anaesthesia. In multivariate analysis, age, sex and literacy had no significant association with the ability to rate pain on VAS (P value 0.652, 0.967, 0.328 respectively). Similarly, no significant association was obtained between age, sex and literacy and ability to rate pain on NAS (P value 0.713, 0.405, 0.875 respectively). Correlation coefficient between the scales was 0.693. Conclusion: VAS and NAS can be used interchangeably in Indian rural population as post-operative pain assessment tools irrespective of literacy status. PMID:23325940

Utility of numerical and visual analog scales for evaluating the post-operative pain in rural patients.

PubMed

Mudgalkar, Nikhil; Bele, Samir D; Valsangkar, Sameer; Bodhare, Trupti N; Gorre, Mahipal

2012-11-01

Visual analog scales (VAS) and numeric analog scales (NAS) are used to assess post-operative pain, but few studies indicate their usefulness in rural illiterate population in India. This study was designed to 1) Compare the impact of literacy on the ability to indicate pain rating on VAS and NAS in post-operative rural patients. 2) Assess the level of agreement between the pain scales. Cross sectional, hospital based study. Informed consent was obtained from patients prior to undergoing surgical procedures in a teaching hospital. Post surgery, patients who were conscious and coherent, were asked to rate pain on both VAS and NAS. The pain ratings were obtained within 24 hours of surgery and within 5 minutes of each other. Percentages, chi square test, regression analysis. A total of 105 patients participated in the study. 43 (41%) of the sample was illiterate. 82 (78.1%) were able to rate pain on VAS while 81 (77.1%) were able to rate pain on NAS. There was no significant association between pain ratings and type of surgery, duration of surgery and nature of anaesthesia. In multivariate analysis, age, sex and literacy had no significant association with the ability to rate pain on VAS (P value 0.652, 0.967, 0.328 respectively). Similarly, no significant association was obtained between age, sex and literacy and ability to rate pain on NAS (P value 0.713, 0.405, 0.875 respectively). Correlation coefficient between the scales was 0.693. VAS and NAS can be used interchangeably in Indian rural population as post-operative pain assessment tools irrespective of literacy status.

Divergent scaling of respiration rates to nitrogen and phosphorus across four woody seedlings between different growing seasons.

PubMed

Fan, Ruirui; Sun, Jun; Yang, Fuchun; Li, Man; Zheng, Yuan; Zhong, Quanlin; Cheng, Dongliang

2017-11-01

Empirical studies indicate that the exponents governing the scaling of plant respiration rates ( R ) with respect to biomass ( M ) numerically vary between three-fourth for adult plants and 1.0 for seedlings and saplings and are affected by nitrogen (N) and phosphorus (P) content. However, whether the scaling of R with respect to M (or N and P) varies among different phylogenetic groups (e.g., gymnosperms vs. angiosperms) or during the growing and dormant seasons remains unclear. We measured the whole-plant R and M , and N and P content of the seedlings of four woody species during the growing season (early October) and the dormant season (January). The data show that (i) the scaling exponents of R versus M , R versus N, and R versus P differed significantly among the four species, but (ii), not between the growing and dormant seasons for each of the four species, although (iii) the normalization constants governing the scaling relationships were numerically greater for the growing season compared to the dormant season. In addition, (iv) the scaling exponents of R versus M , R versus N, and R versus P were numerically larger for the two angiosperm species compared to those of the two gymnosperm species, (v) the interspecific scaling exponents for the four species were greater during the growing season than in the dormant season, and (vi), interspecifically, P scaled nearly isometric with N content. Those findings indicate that the metabolic scaling relationships among R , M , N, and P manifest seasonal variation and differ between angiosperm and gymnosperm species, that is, there is no single, canonical scaling exponent for the seedlings of woody species.

A rating system for the esthetics of bridges.

DOT National Transportation Integrated Search

1980-01-01

There is a need for a tangible way to evaluate the esthetic or visual characteristics of bridges. This report describes such a method based on a numerical experiential rating scale of -10 to +10. Negative values represent unpleasurable responses; pos...

Effective grid-dependent dispersion coefficient for conservative and reactive transport simulations in heterogeneous porous media

NASA Astrophysics Data System (ADS)

Cortinez, J. M.; Valocchi, A. J.; Herrera, P. A.

2013-12-01

Because of the finite size of numerical grids, it is very difficult to correctly account for processes that occur at different spatial scales to accurately simulate the migration of conservative and reactive compounds dissolved in groundwater. In one hand, transport processes in heterogeneous porous media are controlled by local-scale dispersion associated to transport processes at the pore-scale. On the other hand, variations of velocity at the continuum- or Darcy-scale produce spreading of the contaminant plume, which is referred to as macro-dispersion. Furthermore, under some conditions both effects interact, so that spreading may enhance the action of local-scale dispersion resulting in higher mixing, dilution and reaction rates. Traditionally, transport processes at different spatial scales have been included in numerical simulations by using a single dispersion coefficient. This approach implicitly assumes that the separate effects of local-dispersion and macro-dispersion can be added and represented by a unique effective dispersion coefficient. Moreover, the selection of the effective dispersion coefficient for numerical simulations usually do not consider the filtering effect of the grid size over the small-scale flow features. We have developed a multi-scale Lagragian numerical method that allows using two different dispersion coefficients to represent local- and macro-scale dispersion. This technique considers fluid particles that carry solute mass and whose locations evolve according to a deterministic component given by the grid-scale velocity and a stochastic component that corresponds to a block-effective macro-dispersion coefficient. Mass transfer between particles due to local-scale dispersion is approximated by a meshless method. We use our model to test under which transport conditions the combined effect of local- and macro-dispersion are additive and can be represented by a single effective dispersion coefficient. We also demonstrate that for the situations where both processes are additive, an effective grid-dependent dispersion coefficient can be derived based on the concept of block-effective dispersion. We show that the proposed effective dispersion coefficient is able to reproduce dilution, mixing and reaction rates for a wide range of transport conditions similar to the ones found in many practical applications.

Scale Invariance in Landscape Evolution Models Using Stream Power Laws

NASA Astrophysics Data System (ADS)

Kwang, J. S.; Parker, G.

2014-12-01

Landscape evolution models (LEM) commonly utilize stream power laws to simulate river incision with formulations such as E = KAmSn, where E is a vertical incision rate [L/T], K is an erodibility constant [L1-2m/T], A is an upstream drainage area [L2], S is a local channel gradient [-], and m and n are positive exponents that describe the basin hydrology. In our reduced complexity model, the landscape approached equilibrium by balancing an incision rate with a constant, uniform, vertical rock uplift rate at every location in the landscape. From our simulations, for a combination of m and n, the landscape exhibited scale invariance. That is, regardless of the size and scale of the basin, the relief and vertical structure of the landscape remained constant. Therefore, the relief and elevation profile of the landscape at equilibrium were only dependent on the coefficients for erodibility and uplift and an equation that described how upstream area, A, increased as the length of a stream increased. In our analytical 1D models, we utilized two equations that described upslope area, (a) A = Bl, where B is the profile width [L], and l is the stream length from the ridge [L] and (b) A = Clh, Hack's Law, where C is a constant [L2-h] and h is a positive exponent. With these equations, (a) m = n and (b) hm = n resulted in scale invariance. In our numerical 2D models, the relationship between A and l was inherent in the actual structure of the drainage network. From our numerical 2D results, scale invariance occurred when 2m = n. Additionally, using reasonable values from the literature for exponents, n, m and h, resulted in singularities at the ridges in the landscape, which caused truncation error. In consequence, the elevation of the ridge increased as the number of grid cells in the domain increased in the numerical model, and the model was unable to converge. These singularities at the ridges appeared when (a) m ≥ n and (b) hm ≥ n in the analytical model and 2m ≥ n in the numerical model. Here we present (1) 1D analytical solutions and (2) 2D numerical solutions that demonstrate scale invariance in LEMs and (3) the consequences of the singularity in 2D LEM numerical simulations. These results will help provide insight about the structure and dynamics of landscapes and drainage networks and shed light on geomorphological empirical relationships.

Psychometric properties of sleep and coping numeric rating scales in rheumatoid arthritis: a subanalysis of an etanercept trial.

PubMed

Avila-Ribeiro, Pedro; Brault, Yves; Dougados, Maxime; Gossec, Laure

2017-01-01

In rheumatoid arthritis, quality of sleep and ability to cope are important for patients; however their usefulness as outcome measures is not well established. Post-hoc analysis of an open-label 12-week trial of etanercept in biologic-naïve rheumatoid arthritis patients with visits at screening, baseline and over 12 weeks. Outcomes measured included Disease Activity Score 28 erythrocyte sedimentation rate (DAS28), numeric rating scales for sleep, coping, patient and physician-global assessment, pain and fatigue, and modified-HAQ. Reliability between screening and baseline visits by intra-class correlation, and responsiveness between baseline and 12 weeks by standardised response means were assessed for each outcome. In 108 patients, mean age 54 (standard deviation (SD) 13) years, mean disease duration 8 (SD 7) years, 75% women; disease activity was high at baseline: mean DAS28 5.5 (SD 0.8). Reliability intra-class correlation was 0.83[95% confidence interval: 0.77;0.88] for sleep, 0.81[0.74;0.87] for modified-HAQ, 0.80[0.71;0.86] for fatigue, 0.72[0.62;0.80] for physician-global assessment, 0.66[0.54;076] for coping, 0.65[0.53;0.75] for pain and 0.63[0.50;0.73] for patient-global assessment. Responsiveness standardised response means was 1.65[1.32;2.10] for physician-global assessment, 1.37[1.09;1.73] for pain, 1.36[1.08;1.73] for patient-global assessment, 1.15[0.95;1.41] for fatigue, 0.96[0.70;1.28] for coping, 0.92[0.73;1.15] for sleep and 0.86[0.69;1.07] for modified-HAQ. Numeric rating scales assessing sleep and coping were found to be generally as reliable as 'usual' outcomes in rheumatoid arthritis. Responsiveness was less high, indicating these domains of health may be less accessible to biologic treatment. When assessing the patient's perspective on treatment, it is feasible and valid to measure sleep and coping by numeric rating scales.

Anchoring effects in the judgment of confidence: semantic or numeric priming?

PubMed

Carroll, Steven R; Petrusic, William M; Leth-Steensen, Craig

2009-02-01

Over the last decade, researchers have debated whether anchoring effects are the result of semantic or numeric priming. The present study tested both hypotheses. In four experiments involving a sensory detection task, participants first made a relative confidence judgment by deciding whether they were more or less confident than an anchor value in the correctness of their decision. Subsequently, they expressed an absolute level of confidence. In two of these experiments, the relative confidence anchor values represented the midpoints between the absolute confidence scale values, which were either explicitly numeric or semantic, nonnumeric representations of magnitude. In two other experiments, the anchor values were drawn from a scale modally different from that used to express the absolute confidence (i.e., nonnumeric and numeric, respectively, or vice versa). Regardless of the nature of the anchors, the mean confidence ratings revealed anchoring effects only when the relative and absolute confidence values were drawn from identical scales. Together, the results of these four experiments limit the conditions under which both numeric and semantic priming would be expected to lead to anchoring effects.

Arthroscopic bursectomy for recalcitrant trochanteric bursitis after hip arthroplasty.

PubMed

Van Hofwegen, Christopher; Baker, Champ L; Savory, Carlton G; Baker, Champ L

2013-01-01

This study evaluated the use of arthroscopic bursectomy for pain relief in patients with trochanteric bursitis after hip arthroplasty. In this retrospective case series of 12 patients undergoing arthroscopic treatment of recalcitrant trochanteric bursitis after hip arthroplasty, outcomes were assessed via phone interview with a numeric pain rating scale from 1 to 10 and were compared with preoperative pain ratings. Patients were asked the percentage of time they had painless hip function and whether they would have the surgery again. At an average 36-month follow-up (range, 4-85 months), the average numeric pain scale rating improved from 9.3 to 3.3. At an average of 62% of the time, patients had painless use of the hip. Ten of 12 patients in the study felt the pain relief gained was substantial enough to warrant having procedure again. In these patients, arthroscopic bursectomy was a viable option for patients with recalcitrant bursitis after hip arthroplasty.

Nonideal Rayleigh–Taylor mixing

PubMed Central

Lim, Hyunkyung; Iwerks, Justin; Glimm, James; Sharp, David H.

2010-01-01

Rayleigh–Taylor mixing is a classical hydrodynamic instability that occurs when a light fluid pushes against a heavy fluid. The two main sources of nonideal behavior in Rayleigh–Taylor (RT) mixing are regularizations (physical and numerical), which produce deviations from a pure Euler equation, scale invariant formulation, and nonideal (i.e., experimental) initial conditions. The Kolmogorov theory of turbulence predicts stirring at all length scales for the Euler fluid equations without regularization. We interpret mathematical theories of existence and nonuniqueness in this context, and we provide numerical evidence for dependence of the RT mixing rate on nonideal regularizations; in other words, indeterminacy when modeled by Euler equations. Operationally, indeterminacy shows up as nonunique solutions for RT mixing, parametrized by Schmidt and Prandtl numbers, in the large Reynolds number (Euler equation) limit. Verification and validation evidence is presented for the large eddy simulation algorithm used here. Mesh convergence depends on breaking the nonuniqueness with explicit use of the laminar Schmidt and Prandtl numbers and their turbulent counterparts, defined in terms of subgrid scale models. The dependence of the mixing rate on the Schmidt and Prandtl numbers and other physical parameters will be illustrated. We demonstrate numerically the influence of initial conditions on the mixing rate. Both the dominant short wavelength initial conditions and long wavelength perturbations are observed to play a role. By examination of two classes of experiments, we observe the absence of a single universal explanation, with long and short wavelength initial conditions, and the various physical and numerical regularizations contributing in different proportions in these two different contexts. PMID:20615983

Numerical and experimental investigation of downdraft gasification of woody residues.

PubMed

Simone, Marco; Nicolella, Cristiano; Tognotti, Leonardo

2013-04-01

A pilot scale throated downdraft gasifier was operated with vine prunings as feedstock to assess the effect of biomass loading rate on process performance. A distributed 1D model of mass and heat transfer and reactions was applied to aid the interpretation of experimental evidence. The model takes into account peculiar gasifier design features (air inlets and throat) and it reproduces satisfactorily the temperature profiles and the mass fluxes of gaseous species at different biomass loading rates. The integration of pilot-scale experiments and numerical simulations provides sound indications for the gasifier operation. In particular, simulations performed at different loading rates and feedstock humidity show that steady state operation and stable performance of the gasifier rely on the thermal balance between the enthalpy of cold biomass moving downward and the counter-current radiative heat fluxes moving upward from the oxidation zone. This balance can be destabilized by high loading rate and moisture contents. Copyright © 2013 Elsevier Ltd. All rights reserved.

Efficacy and Safety of Oral Diclofenac Sustained release Versus Transdermal Diclofenac Patch in Chronic Musculoskeletal Pain: A Randomized, Open Label Trial.

PubMed

Shinde, Viraj Ashok; Kalikar, Mrunalini; Jagtap, Satyajeet; Dakhale, Ganesh N; Bankar, Mangesh; Bajait, Chaitali S; Motghare, Vijay M; Pashilkar, Ashlesha A; Raghute, Latesh B; Khamkar, Ajita D

2017-01-01

To compare the efficacy, safety, and tolerability of transdermal patches of diclofenac sodium with oral diclofenac sustained release (SR) in patients of chronic musculoskeletal MSK pain conditions. The eligible patients were given either transdermal diclofenac patch or tablet diclofenac SR. Pain was assessed at 2 and 4 weeks using a visual analog scale. Adverse events were recorded. Patients with 18-65 years old of either gender with score of ≥4 on a 11-item numeric rating scale-numeric version of visual analog scale for pain with diagnosis of primary osteoarthritis (OA) of the knee or hand of at least 3 months duration, with independent radiological confirmation of OA or having pain associated with other MSK conditions such as soft-tissue rheumatism, cervical and lumbar back pain, and fibromyalgia, of at least 3 months duration were included in this study. Transdermal diclofenac diethylamine patch and tablet diclofenac sodium sustained release (SR) do not significantly differ in the reduction of numerical rating scores at the end of 4 weeks (P = 0.8393). Transdermal diclofenac was equi-efficacious as tablet diclofenac sodium SR in reducing pain due to chronic MSK pain conditions.

The diagnostic value of the numeric pain rating scale in older postoperative patients.

PubMed

van Dijk, Jacqueline F M; Kappen, Teus H; van Wijck, Albert J M; Kalkman, Cor J; Schuurmans, Marieke J

2012-11-01

To measure the diagnostic value of the Numeric Rating Scale by comparing it to a Verbal Rating Scale in older patients. Pain management in older patients is an important challenge because of their greater susceptibility to adverse effects of analgesics. Nurses play an important role in applying guidelines for postoperative pain treatment. However, effective pain management is dependent upon valid and reliable pain assessment. Cross-sectional study. In total, 2674 older patients scored their postoperative pain on an 11-point numeric rating scale (NRS) and an adjective scale (VRS) including no pain, little pain, painful but bearable, considerable pain and terrible pain. The diagnostic value of different NRS cut-off values for administering analgesics is determined by an ROC curve. Sensitivity of NRS > 3 for 'unbearable' pain in older patients was 72% with a specificity of 97·2%. With a cut-off point NRS > 4, sensitivity increased to 83%, while specificity was 96·7%. With a cut-off point NRS > 5, sensitivity was 94%, while specificity was 85%. A high proportion (75%) of older old patients (≥ 75 years) with 'painful but bearable' considers NRS 4, 5 and 6 to this VRS category. Using an NRS cut-off point > 3 or > 4, a large group of older patients with 'bearable' pain would incorrectly classified as 'unbearable'. When we make the assumption that bearable pain means no wish for additional analgesics, this misclassification might result in overtreatment with analgesics, while 3% would be undertreated. With NRS cut-off point > 5, 6% have a risk of overtreatment and 15% of undertreatment. Nurses should not rely solely on the NRS score in determining pain treatment; they need to communicate with older patients about their pain, the need for analgesics and eventual misconceptions about analgesics. © 2012 Blackwell Publishing Ltd.

Scalar decay in two-dimensional chaotic advection and Batchelor-regime turbulence

NASA Astrophysics Data System (ADS)

Fereday, D. R.; Haynes, P. H.

2004-12-01

This paper considers the decay in time of an advected passive scalar in a large-scale flow. The relation between the decay predicted by "Lagrangian stretching theories," which consider evolution of the scalar field within a small fluid element and then average over many such elements, and that observed at large times in numerical simulations, associated with emergence of a "strange eigenmode" is discussed. Qualitative arguments are supported by results from numerical simulations of scalar evolution in two-dimensional spatially periodic, time aperiodic flows, which highlight the differences between the actual behavior and that predicted by the Lagrangian stretching theories. In some cases the decay rate of the scalar variance is different from the theoretical prediction and determined globally and in other cases it apparently matches the theoretical prediction. An updated theory for the wavenumber spectrum of the scalar field and a theory for the probability distribution of the scalar concentration are presented. The wavenumber spectrum and the probability density function both depend on the decay rate of the variance, but can otherwise be calculated from the statistics of the Lagrangian stretching history. In cases where the variance decay rate is not determined by the Lagrangian stretching theory, the wavenumber spectrum for scales that are much smaller than the length scale of the flow but much larger than the diffusive scale is argued to vary as k-1+ρ, where k is wavenumber, and ρ is a positive number which depends on the decay rate of the variance γ2 and on the Lagrangian stretching statistics. The probability density function for the scalar concentration is argued to have algebraic tails, with exponent roughly -3 and with a cutoff that is determined by diffusivity κ and scales roughly as κ-1/2 and these predictions are shown to be in good agreement with numerical simulations.

Evaluation of the numeric rating scale for perception of effort during isometric elbow flexion exercise.

PubMed

Lampropoulou, Sofia; Nowicky, Alexander V

2012-03-01

The aim of the study was to examine the reliability and validity of the numerical rating scale (0-10 NRS) for rating perception of effort during isometric elbow flexion in healthy people. 33 individuals (32 ± 8 years) participated in the study. Three re-test measurements within one session and three weekly sessions were undertaken to determine the reliability of the scale. The sensitivity of the scale following 10 min isometric fatiguing exercise of the elbow flexors as well as the correlation of the effort with the electromyographic (EMG) activity of the flexor muscles were tested. Perception of effort was tested during isometric elbow flexion at 10, 30, 50, 70, 90, and 100% MVC. The 0-10 NRS demonstrated an excellent test-retest reliability [intra class correlation (ICC) = 0.99 between measurements taken within a session and 0.96 between 3 consecutive weekly sessions]. Exploratory curve fitting for the relationship between effort ratings and voluntary force, and underlying EMG showed that both are best described by power functions (y = ax ( b )). There were also strong correlations (range 0.89-0.95) between effort ratings and EMG recordings of all flexor muscles supporting the concurrent criterion validity of the measure. The 0-10 NRS was sensitive enough to detect changes in the perceived effort following fatigue and significantly increased at the level of voluntary contraction used in its assessment (p < 0.001). These findings suggest the 0-10 NRS is a valid and reliable scale for rating perception of effort in healthy individuals. Future research should seek to establish the validity of the 0-10 NRS in clinical settings.

Search for subgrid scale parameterization by projection pursuit regression

NASA Technical Reports Server (NTRS)

Meneveau, C.; Lund, T. S.; Moin, Parviz

1992-01-01

The dependence of subgrid-scale stresses on variables of the resolved field is studied using direct numerical simulations of isotropic turbulence, homogeneous shear flow, and channel flow. The projection pursuit algorithm, a promising new regression tool for high-dimensional data, is used to systematically search through a large collection of resolved variables, such as components of the strain rate, vorticity, velocity gradients at neighboring grid points, etc. For the case of isotropic turbulence, the search algorithm recovers the linear dependence on the rate of strain (which is necessary to transfer energy to subgrid scales) but is unable to determine any other more complex relationship. For shear flows, however, new systematic relations beyond eddy viscosity are found. For the homogeneous shear flow, the results suggest that products of the mean rotation rate tensor with both the fluctuating strain rate and fluctuating rotation rate tensors are important quantities in parameterizing the subgrid-scale stresses. A model incorporating these terms is proposed. When evaluated with direct numerical simulation data, this model significantly increases the correlation between the modeled and exact stresses, as compared with the Smagorinsky model. In the case of channel flow, the stresses are found to correlate with products of the fluctuating strain and rotation rate tensors. The mean rates of rotation or strain do not appear to be important in this case, and the model determined for homogeneous shear flow does not perform well when tested with channel flow data. Many questions remain about the physical mechanisms underlying these findings, about possible Reynolds number dependence, and, given the low level of correlations, about their impact on modeling. Nevertheless, demonstration of the existence of causal relations between sgs stresses and large-scale characteristics of turbulent shear flows, in addition to those necessary for energy transfer, provides important insight into the relation between scales in turbulent flows.

IslandFAST: A Semi-numerical Tool for Simulating the Late Epoch of Reionization

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

Xu, Yidong; Chen, Xuelei; Yue, Bin

2017-08-01

We present the algorithm and main results of our semi-numerical simulation, islandFAST, which was developed from 21cmFAST and designed for the late stage of reionization. The islandFAST simulation predicts the evolution and size distribution of the large-scale underdense neutral regions (neutral islands), and we find that the late Epoch of Reionization proceeds very fast, showing a characteristic scale of the neutral islands at each redshift. Using islandFAST, we compare the impact of two types of absorption systems, i.e., the large-scale underdense neutral islands versus small-scale overdense absorbers, in regulating the reionization process. The neutral islands dominate the morphology of themore » ionization field, while the small-scale absorbers dominate the mean-free path of ionizing photons, and also delay and prolong the reionization process. With our semi-numerical simulation, the evolution of the ionizing background can be derived self-consistently given a model for the small absorbers. The hydrogen ionization rate of the ionizing background is reduced by an order of magnitude in the presence of dense absorbers.« less

Does format matter for comprehension of a facial affective scale and a numeric scale for pain by adults with Down syndrome?

PubMed

de Knegt, N C; Evenhuis, H M; Lobbezoo, F; Schuengel, C; Scherder, E J A

2013-10-01

People with intellectual disabilities are at high risk for pain and have communication difficulties. Facial and numeric scales for self-report may aid pain identification. It was examined whether the comprehension of a facial affective scale and a numeric scale for pain in adults with Down syndrome (DS) varies with presentation format. Adults with DS were included (N=106, mild to severe ID, mean age 37 years), both with (N=57) and without (N=49) physical conditions that may cause pain or discomfort. The Facial Affect Scale (FAS) and a numeric rating scale (NRS) were compared. One subgroup of participants (N=50) had to choose the two items within each format to indicate 'least pain' and 'most pain'. The other subgroup of participants (N=56) had to order three faces of the FAS from 'least pain' to 'most pain', and to answer questions about the magnitude of numbers for the NRS. Comprehension percentages were compared between two subgroups. More participants understood the FAS than the NRS, irrespective of the presentation format. The comprehension percentage for the FAS did not differ between the least-most extremities format and the ordering/magnitude format. In contrast, comprehension percentages for the NRS differed significantly between the least-most extremities format (61%) and the ordering/magnitude format (32%). The inclusion of ordering and magnitude in a presentation format is essential to assess thorough comprehension of facial and numeric scales for self-reported pain. The use of this format does not influence the number of adults with DS who pass the comprehension test for the FAS, but reduces the number of adults with DS who pass the comprehension test for the NRS. Copyright © 2013 Elsevier Ltd. All rights reserved.

Numerical heating in Particle-In-Cell simulations with Monte Carlo binary collisions

NASA Astrophysics Data System (ADS)

Alves, E. Paulo; Mori, Warren; Fiuza, Frederico

2017-10-01

The binary Monte Carlo collision (BMCC) algorithm is a robust and popular method to include Coulomb collision effects in Particle-in-Cell (PIC) simulations of plasmas. While a number of works have focused on extending the validity of the model to different physical regimes of temperature and density, little attention has been given to the fundamental coupling between PIC and BMCC algorithms. Here, we show that the coupling between PIC and BMCC algorithms can give rise to (nonphysical) numerical heating of the system, that can be far greater than that observed when these algorithms operate independently. This deleterious numerical heating effect can significantly impact the evolution of the simulated system particularly for long simulation times. In this work, we describe the source of this numerical heating, and derive scaling laws for the numerical heating rates based on the numerical parameters of PIC-BMCC simulations. We compare our theoretical scalings with PIC-BMCC numerical experiments, and discuss strategies to minimize this parasitic effect. This work is supported by DOE FES under FWP 100237 and 100182.

-> Air entrainment and bubble statistics in three-dimensional breaking waves

NASA Astrophysics Data System (ADS)

Deike, L.; Popinet, S.; Melville, W. K.

2016-02-01

Wave breaking in the ocean is of fundamental importance for quantifying wave dissipation and air-sea interaction, including gas and momentum exchange, and for improving air-sea flux parametrizations for weather and climate models. Here we investigate air entrainment and bubble statistics in three-dimensional breaking waves through direct numerical simulations of the two-phase air-water flow using the Open Source solver Gerris. As in previous 2D simulations, the dissipation due to breaking is found to be in good agreement with previous experimental observations and inertial-scaling arguments. For radii larger than the Hinze scale, the bubble size distribution is found to follow a power law of the radius, r-10/3 and to scale linearly with the time dependent turbulent dissipation rate during the active breaking stage. The time-averaged bubble size distribution is found to follow the same power law of the radius and to scale linearly with the wave dissipation rate per unit length of breaking crest. We propose a phenomenological turbulent bubble break-up model that describes the numerical results and existing experimental results.

Effects of forcing time scale on the simulated turbulent flows and turbulent collision statistics of inertial particles

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

Rosa, B., E-mail: bogdan.rosa@imgw.pl; Parishani, H.; Department of Earth System Science, University of California, Irvine, California 92697-3100

2015-01-15

In this paper, we study systematically the effects of forcing time scale in the large-scale stochastic forcing scheme of Eswaran and Pope [“An examination of forcing in direct numerical simulations of turbulence,” Comput. Fluids 16, 257 (1988)] on the simulated flow structures and statistics of forced turbulence. Using direct numerical simulations, we find that the forcing time scale affects the flow dissipation rate and flow Reynolds number. Other flow statistics can be predicted using the altered flow dissipation rate and flow Reynolds number, except when the forcing time scale is made unrealistically large to yield a Taylor microscale flow Reynoldsmore » number of 30 and less. We then study the effects of forcing time scale on the kinematic collision statistics of inertial particles. We show that the radial distribution function and the radial relative velocity may depend on the forcing time scale when it becomes comparable to the eddy turnover time. This dependence, however, can be largely explained in terms of altered flow Reynolds number and the changing range of flow length scales present in the turbulent flow. We argue that removing this dependence is important when studying the Reynolds number dependence of the turbulent collision statistics. The results are also compared to those based on a deterministic forcing scheme to better understand the role of large-scale forcing, relative to that of the small-scale turbulence, on turbulent collision of inertial particles. To further elucidate the correlation between the altered flow structures and dynamics of inertial particles, a conditional analysis has been performed, showing that the regions of higher collision rate of inertial particles are well correlated with the regions of lower vorticity. Regions of higher concentration of pairs at contact are found to be highly correlated with the region of high energy dissipation rate.« less

High Speed Dynamics in Brittle Materials

NASA Astrophysics Data System (ADS)

Hiermaier, Stefan

2015-06-01

Brittle Materials under High Speed and Shock loading provide a continuous challenge in experimental physics, analysis and numerical modelling, and consequently for engineering design. The dependence of damage and fracture processes on material-inherent length and time scales, the influence of defects, rate-dependent material properties and inertia effects on different scales make their understanding a true multi-scale problem. In addition, it is not uncommon that materials show a transition from ductile to brittle behavior when the loading rate is increased. A particular case is spallation, a brittle tensile failure induced by the interaction of stress waves leading to a sudden change from compressive to tensile loading states that can be invoked in various materials. This contribution highlights typical phenomena occurring when brittle materials are exposed to high loading rates in applications such as blast and impact on protective structures, or meteorite impact on geological materials. A short review on experimental methods that are used for dynamic characterization of brittle materials will be given. A close interaction of experimental analysis and numerical simulation has turned out to be very helpful in analyzing experimental results. For this purpose, adequate numerical methods are required. Cohesive zone models are one possible method for the analysis of brittle failure as long as some degree of tension is present. Their recent successful application for meso-mechanical simulations of concrete in Hopkinson-type spallation tests provides new insight into the dynamic failure process. Failure under compressive loading is a particular challenge for numerical simulations as it involves crushing of material which in turn influences stress states in other parts of a structure. On a continuum scale, it can be modeled using more or less complex plasticity models combined with failure surfaces, as will be demonstrated for ceramics. Models which take microstructural cracking directly into account may provide a more physics-based approach for compressive failure in the future.

On the efficient and reliable numerical solution of rate-and-state friction problems

NASA Astrophysics Data System (ADS)

Pipping, Elias; Kornhuber, Ralf; Rosenau, Matthias; Oncken, Onno

2016-03-01

We present a mathematically consistent numerical algorithm for the simulation of earthquake rupture with rate-and-state friction. Its main features are adaptive time stepping, a novel algebraic solution algorithm involving nonlinear multigrid and a fixed point iteration for the rate-and-state decoupling. The algorithm is applied to a laboratory scale subduction zone which allows us to compare our simulations with experimental results. Using physical parameters from the experiment, we find a good fit of recurrence time of slip events as well as their rupture width and peak slip. Computations in 3-D confirm efficiency and robustness of our algorithm.

Pre-emptive ice cube cryotherapy for reducing pain from local anaesthetic injections for simple lacerations: a randomised controlled trial.

PubMed

Song, JaeWoo; Kim, HyukHoon; Park, EunJung; Ahn, Jung Hwan; Yoon, Eunhui; Lampotang, Samsun; Gravenstein, Nikolaus; Choi, SangChun

2018-02-01

Subcutaneous local anaesthetic injection can be painful to patients in the ED. We evaluated the effect of cryotherapy by application of an ice cube to the injection site prior to injection in patients with simple lacerations. We conducted a prospective, randomised, controlled trial in consented patients with simple lacerations needing primary repair at a single emergency centre from April to July 2016. We randomly assigned patients undergoing repair for simple lacerations to either the cryotherapy group or the control group (standard care; no cryotherapy or other pretreatment of the injection site). In cryotherapy group subjects, we applied an ice cube (size: 1.5×1.5×1.5 cm) placed inside a sterile glove on the wound at the anticipated subcutaneous lidocaine injection site for 2 min prior to injection. The primary outcome was a subjective numeric rating (0-10 scale) of the perceived pain from the subcutaneous local anaesthetic injections. Secondary outcomes were (a) perceived pain on a numeric scale for cryotherapy itself, that is, pain from contact of the ice cube/glove with the skin and (b) the rate of complications after primary laceration repair. Fifty patients were enrolled, consented and randomised, with 25 in the cryotherapy group and 25 in the control group. The numeric rating scale for subcutaneous anaesthetic injections was median, IQR, 95% CI 2.0 (1 to 3.5), 1.81 to 3.47, respectively, in the cryotherapy group and 5.0 (3 to 7), 3.91 to 6.05 in the control group (Mann-Whitney U=147.50, p=0.001). No wound complications occurred in either group. The numeric rating scale for cryotherapy itself was median, IQR, 95% CI: 2.0 (1 to 3.5), 1.90 to 3.70. Pre-emptive topical injection site cryotherapy lasting 2 min before subcutaneous local anaesthetic injections can significantly reduce perceived pain from subcutaneous local anaesthetic injections in patients presenting for simple laceration repair. KCT0001990. © Article author(s) (or their employer(s) unless otherwise stated in the text of the article) 2018. All rights reserved. No commercial use is permitted unless otherwise expressly granted.

Characterizing Drainage Multiphase Flow in Heterogeneous Sandstones

NASA Astrophysics Data System (ADS)

Jackson, Samuel J.; Agada, Simeon; Reynolds, Catriona A.; Krevor, Samuel

2018-04-01

In this work, we analyze the characterization of drainage multiphase flow properties on heterogeneous rock cores using a rich experimental data set and mm-m scale numerical simulations. Along with routine multiphase flow properties, 3-D submeter scale capillary pressure heterogeneity is characterized by combining experimental observations and numerical calibration, resulting in a 3-D numerical model of the rock core. The uniqueness and predictive capability of the numerical models are evaluated by accurately predicting the experimentally measured relative permeability of N2—DI water and CO2—brine systems in two distinct sandstone rock cores across multiple fractional flow regimes and total flow rates. The numerical models are used to derive equivalent relative permeabilities, which are upscaled functions incorporating the effects of submeter scale capillary pressure. The functions are obtained across capillary numbers which span four orders of magnitude, representative of the range of flow regimes that occur in subsurface CO2 injection. Removal of experimental boundary artifacts allows the derivation of equivalent functions which are characteristic of the continuous subsurface. We also demonstrate how heterogeneities can be reorientated and restructured to efficiently estimate flow properties in rock orientations differing from the original core sample. This analysis shows how combined experimental and numerical characterization of rock samples can be used to derive equivalent flow properties from heterogeneous rocks.

Resolving the fine-scale structure in turbulent Rayleigh-Benard convection

NASA Astrophysics Data System (ADS)

Scheel, Janet; Emran, Mohammad; Schumacher, Joerg

2013-11-01

Results from high-resolution direct numerical simulations of turbulent Rayleigh-Benard convection in a cylindrical cell with an aspect ratio of one will be presented. We focus on the finest scales of convective turbulence, in particular the statistics of the kinetic energy and thermal dissipation rates in the bulk and the whole cell. These dissipation rates as well as the local dissipation scales are compared for different Rayleigh and Prandtl numbers. We also have investigated the convergence properties of our spectral element method and have found that both dissipation fields are very sensitive to insufficient resolution. We also demonstrate that global transport properties, such as the Nusselt number and the energy balances, are partly insensitive to insufficient resolution and yield consistent results even when the dissipation fields are under-resolved. Our present numerical framework is also compared with high-resolution simulations which use a finite difference method. For most of the compared quantities the agreement is found to be satisfactory.

Toward topology-based characterization of small-scale mixing in compressible turbulence

NASA Astrophysics Data System (ADS)

Suman, Sawan; Girimaji, Sharath

2011-11-01

Turbulent mixing rate at small scales of motion (molecular mixing) is governed by the steepness of the scalar-gradient field which in turn is dependent upon the prevailing velocity gradients. Thus motivated, we propose a velocity-gradient topology-based approach for characterizing small-scale mixing in compressible turbulence. We define a mixing efficiency metric that is dependent upon the topology of the solenoidal and dilatational deformation rates of a fluid element. The mixing characteristics of solenoidal and dilatational velocity fluctuations are clearly delineated. We validate this new approach by employing mixing data from direct numerical simulations (DNS) of compressible decaying turbulence with passive scalar. For each velocity-gradient topology, we compare the mixing efficiency predicted by the topology-based model with the corresponding conditional scalar variance obtained from DNS. The new mixing metric accurately distinguishes good and poor mixing topologies and indeed reasonably captures the numerical values. The results clearly demonstrate the viability of the proposed approach for characterizing and predicting mixing in compressible flows.

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

Stershic, Andrew J.; Dolbow, John E.; Moës, Nicolas

The Thick Level-Set (TLS) model is implemented to simulate brittle media undergoing dynamic fragmentation. This non-local model is discretized by the finite element method with damage represented as a continuous field over the domain. A level-set function defines the extent and severity of damage, and a length scale is introduced to limit the damage gradient. Numerical studies in one dimension demonstrate that the proposed method reproduces the rate-dependent energy dissipation and fragment length observations from analytical, numerical, and experimental approaches. In conclusion, additional studies emphasize the importance of appropriate bulk constitutive models and sufficient spatial resolution of the length scale.

Applications of Perron-Frobenius theory to population dynamics.

PubMed

Li, Chi-Kwong; Schneider, Hans

2002-05-01

By the use of Perron-Frobenius theory, simple proofs are given of the Fundamental Theorem of Demography and of a theorem of Cushing and Yicang on the net reproductive rate occurring in matrix models of population dynamics. The latter result, which is closely related to the Stein-Rosenberg theorem in numerical linear algebra, is further refined with some additional nonnegative matrix theory. When the fertility matrix is scaled by the net reproductive rate, the growth rate of the model is $1$. More generally, we show how to achieve a given growth rate for the model by scaling the fertility matrix. Demographic interpretations of the results are given.

Role of Hydrodynamic and Mineralogical Heterogeneities on Reactive Transport Processes.

NASA Astrophysics Data System (ADS)

Luquot, L.; Garcia-Rios, M.; soler Sagarra, J.; Gouze, P.; Martinez-Perez, L.; Carrera, J.

2017-12-01

Predicting reactive transport at large scale, i.e., Darcy- and field- scale, is still challenging considering the number of heterogeneities that may be present from nm- to pore-scale. It is well documented that conventional continuum-scale approaches oversimplify and/or ignore many important aspects of rock structure, chemical reactions, fluid displacement and transport, which, as a consequence, results in uncertainties when applied to field-scale operations. The changes in flow and reactive transport across the different spatial and temporal scales are of central concern in many geological applications such as groundwater systems, geo-energy, rock building heritage and geological storage... In this presentation, we will discuss some laboratory and numerical results on how local heterogeneities (structural, hydrodynamic and mineralogical) can affect the localization and the rate of the reaction processes. Different flow through laboratory experiments using various rock samples will be presented, from simple monomineral rocks such as limestone samples, and more complex rocks composed of different minerals with a large range of kinetic reactions. A new numerical approach based on multirate water mixing approach will be presented and applied to one of the laboratory experiment in order to analyze and distinguish the effect of the mineralogy distribution and the hydrodynamic heterogeneity on the total reaction rate.

Numerical calculation of protein-ligand binding rates through solution of the Smoluchowski equation using smooth particle hydrodynamics

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

Pan, Wenxiao; Daily, Michael D.; Baker, Nathan A.

2015-12-01

We demonstrate the accuracy and effectiveness of a Lagrangian particle-based method, smoothed particle hydrodynamics (SPH), to study diffusion in biomolecular systems by numerically solving the time-dependent Smoluchowski equation for continuum diffusion. The numerical method is first verified in simple systems and then applied to the calculation of ligand binding to an acetylcholinesterase monomer. Unlike previous studies, a reactive Robin boundary condition (BC), rather than the absolute absorbing (Dirichlet) boundary condition, is considered on the reactive boundaries. This new boundary condition treatment allows for the analysis of enzymes with "imperfect" reaction rates. Rates for inhibitor binding to mAChE are calculated atmore » various ionic strengths and compared with experiment and other numerical methods. We find that imposition of the Robin BC improves agreement between calculated and experimental reaction rates. Although this initial application focuses on a single monomer system, our new method provides a framework to explore broader applications of SPH in larger-scale biomolecular complexes by taking advantage of its Lagrangian particle-based nature.« less

Is pain assessment feasible as a performance indicator for Dutch nursing homes? A cross-sectional approach.

PubMed

Boerlage, Anneke A; Masman, Anniek D; Hagoort, Jacobus; Tibboel, Dick; Baar, Frans P M; van Dijk, Monique

2013-03-01

Quality of care gains transparency with the help of performance indicators. For Dutch nursing homes, the current set of performance indicators does not include pain. To determine the feasibility of pain assessment as performance indicator, information about pain prevalence and analgesic prescription in one nursing home was collected. Within the time span of 3 days, pain intensity was measured in 91% of the residents (201 out of 221), either with a numeric rating scale, a verbal rating scale, or the Rotterdam Elderly Pain Observation Scale (REPOS). Numerical rating was used for 72%, verbal rating for 3%, and REPOS observation for 25% of the residents. Pain was substantial in 65 residents (32%), who received the following analgesic prescription: World Health Organization (WHO) step 1, 45%; WHO step 3, 12%; and neuroactive agents, 5%. Thirty-eight percent of these residents were in pain and received no analgesics. Residents with substantial pain significantly more often received analgesics (p = .007). Results suggest that pain assessment is feasible in a nursing home and would stimulate staff attention to pain. Further investigation is necessary to find out if a pain algorithm is feasible and will lead to improved pain treatment. Copyright © 2013 American Society for Pain Management Nursing. Published by Elsevier Inc. All rights reserved.

Determining pain scale preference in a veteran population experiencing chronic pain.

PubMed

Douglas, Mary E; Randleman, Mary L; DeLane, Alice M; Palmer, Glen A

2014-09-01

The purpose of this study was to determine veteran pain scale preference of four common pain scales: the Faces Scale, the Visual Analog Scale, the Numeric Rating Scale, and the Mankoski Pain Scale. The study also examined the reliability and validity of the Mankoski Pain Scale with the other three scales. A sample of veterans (N = 200) with chronic pain receiving treatment in a residential rehabilitation treatment program (RRTP) and a surgical and specialty care (SSC) outpatient clinic at a Department of Veterans Affairs (VA) medical center participated in the study. There was a significant difference between scales in regard to preference, χ2(3) = 64.59, p < .001. A large percentage of the sample preferred the Mankoski Pain Scale (46%). Test-retest of the reliability was comparable for all the scales. Validity of the Mankoski scale was excellent, as it correlated very well with the Numeric (r = .84, p < .001), Analog (r = .83, p < .001), and Faces (r = .78, p < .001) scales. The findings indicate that the Mankoski Pain Scale is a valid and reliable tool for pain with veterans, and it was the preferred scale by veterans for use when describing pain. Published by Elsevier Inc.

New convergence results for the scaled gradient projection method

NASA Astrophysics Data System (ADS)

Bonettini, S.; Prato, M.

2015-09-01

The aim of this paper is to deepen the convergence analysis of the scaled gradient projection (SGP) method, proposed by Bonettini et al in a recent paper for constrained smooth optimization. The main feature of SGP is the presence of a variable scaling matrix multiplying the gradient, which may change at each iteration. In the last few years, extensive numerical experimentation showed that SGP equipped with a suitable choice of the scaling matrix is a very effective tool for solving large scale variational problems arising in image and signal processing. In spite of the very reliable numerical results observed, only a weak convergence theorem is provided establishing that any limit point of the sequence generated by SGP is stationary. Here, under the only assumption that the objective function is convex and that a solution exists, we prove that the sequence generated by SGP converges to a minimum point, if the scaling matrices sequence satisfies a simple and implementable condition. Moreover, assuming that the gradient of the objective function is Lipschitz continuous, we are also able to prove the {O}(1/k) convergence rate with respect to the objective function values. Finally, we present the results of a numerical experience on some relevant image restoration problems, showing that the proposed scaling matrix selection rule performs well also from the computational point of view.

Correlation between the pain numeric rating scale and the 12-item WHO Disability Assessment Schedule 2.0 in patients with musculoskeletal pain.

PubMed

Saltychev, Mikhail; Bärlund, Esa; Laimi, Katri

2018-03-01

The aim of this study was to assess the correlation between pain severity measured on a numeric rating scale and restrictions of functioning measured with the WHO Disability Assessment Schedule (WHODAS 2.0). This was a cross-sectional study of 1207 patients with musculoskeletal pain conditions. Correlation was assessed using Spearman's and Pearson tests. Although all the Spearman's rank correlations between WHODAS 2.0 items and pain severity were statistically significant, they were mostly weak, with only a few moderate associations for 'S2 household responsibilities', 'S8 washing', 'S9 dressing', and 'S12 day-to-day work'. The correlation between the WHODAS 2.0 total score and pain severity was also moderate: 0.41 [95% confidence interval (CI): 0.36-0.45] for average pain and 0.42 (95% CI: 0.37-0.46) for worst pain. The correlation between the WHODAS 2.0 total score and pain level was also assessed using Pearson's product-moment correlation, yielding figures that were similar to Spearman's correlation: 0.42 (P<0.0001, 95% CI: 0.37-0.46) for average pain and 0.39 (P<0.0001, 95% CI: 0.34-0.44) for worst pain. Among patients with chronic musculoskeletal pain, the correlation between pain severity measured by numeric rating scale and functioning level measured by WHODAS 2.0 was weak to moderate, with slightly stronger associations in physical domains of functioning.

Cooled radiofrequency denervation for treatment of sacroiliac joint pain: two-year results from 20 cases

PubMed Central

Ho, Kok-Yuen; Hadi, Mohamed Abdul; Pasutharnchat, Koravee; Tan, Kian-Hian

2013-01-01

Background Sacroiliac joint pain is a common cause of chronic low back pain. Different techniques for radiofrequency denervation of the sacroiliac joint have been used to treat this condition. However, results have been inconsistent because the variable sensory supply to the sacroiliac joint is difficult to disrupt completely using conventional radiofrequency. Cooled radiofrequency is a novel technique that uses internally cooled radiofrequency probes to enlarge lesion size, thereby increasing the chance of completely denervating the sacroiliac joint. The objective of this study was to evaluate the efficacy of cooled radiofrequency denervation using the SInergy™ cooled radiofrequency system for sacroiliac joint pain. Methods The charts of 20 patients with chronic sacroiliac joint pain who had undergone denervation using the SInergy™ cooled radiofrequency system were reviewed at two years following the procedure. Outcome measures included the Numeric Rating Scale for pain intensity, Patient Global Impression of Change, and Global Perceived Effect for patient satisfaction. Results Fifteen of 20 patients showed a significant reduction in pain (a decrease of at least three points on the Numeric Rating Scale). Mean Numeric Rating Scale for pain decreased from 7.4 ± 1.4 to 3.1 ± 2.5, mean Patient Global Impression of Change was “improved” (1.4 ± 1.5), and Global Perceived Effect was reported to be positive in 16 patients at two years following the procedure. Conclusion Cooled radiofrequency denervation showed long-term efficacy for up to two years in the treatment of sacroiliac joint pain. PMID:23869175

Test–retest reliability, validity, and minimum detectable change of visual analog, numerical rating, and verbal rating scales for measurement of osteoarthritic knee pain

PubMed Central

Alghadir, Ahmad H; Anwer, Shahnawaz; Iqbal, Amir; Iqbal, Zaheen Ahmed

2018-01-01

Objective Several scales are commonly used for assessing pain intensity. Among them, the numerical rating scale (NRS), visual analog scale (VAS), and verbal rating scale (VRS) are often used in clinical practice. However, no study has performed psychometric analyses of their reliability and validity in the measurement of osteoarthritic (OA) pain. Therefore, the present study examined the test–retest reliability, validity, and minimum detectable change (MDC) of the VAS, NRS, and VRS for the measurement of OA knee pain. In addition, the correlations of VAS, NRS, and VRS with demographic variables were evaluated. Methods The study included 121 subjects (65 women, 56 men; aged 40–80 years) with OA of the knee. Test–retest reliability of the VAS, NRS, and VRS was assessed during two consecutive visits in a 24 h interval. The validity was tested using Pearson’s correlation coefficients between the baseline scores of VAS, NRS, and VRS and the demographic variables (age, body mass index [BMI], sex, and OA grade). The standard error of measurement (SEM) and the MDC were calculated to assess statistically meaningful changes. Results The intraclass correlation coefficients of the VAS, NRS, and VRS were 0.97, 0.95, and 0.93, respectively. VAS, NRS, and VRS were significantly related to demographic variables (age, BMI, sex, and OA grade). The SEM of VAS, NRS, and VRS was 0.03, 0.48, and 0.21, respectively. The MDC of VAS, NRS, and VRS was 0.08, 1.33, and 0.58, respectively. Conclusion All the three scales had excellent test–retest reliability. However, the VAS was the most reliable, with the smallest errors in the measurement of OA knee pain. PMID:29731662

Hackneyed, Acned, or Just Plain Good: Perceiving Quality in Young Adult Fiction.

ERIC Educational Resources Information Center

Agee, Hugh

A rating scale was developed by Stephen Dunning for evaluating adolescent literature objectively. The distinguishing features of the scale's five categories are designed to produce a numerical score between 5 and 25 (each category a 1-to-5 ranking for poor/excellent quality), indicating the relative worth of a specific literary work. The first…

Efficacy and Safety of Oral Diclofenac Sustained release Versus Transdermal Diclofenac Patch in Chronic Musculoskeletal Pain: A Randomized, Open Label Trial

PubMed Central

Shinde, Viraj Ashok; Kalikar, Mrunalini; Jagtap, Satyajeet; Dakhale, Ganesh N.; Bankar, Mangesh; Bajait, Chaitali S.; Motghare, Vijay M.; Pashilkar, Ashlesha A.; Raghute, Latesh B.; Khamkar, Ajita D.

2017-01-01

Introduction: To compare the efficacy, safety, and tolerability of transdermal patches of diclofenac sodium with oral diclofenac sustained release (SR) in patients of chronic musculoskeletal MSK pain conditions. Materials and Methods: The eligible patients were given either transdermal diclofenac patch or tablet diclofenac SR. Pain was assessed at 2 and 4 weeks using a visual analog scale. Adverse events were recorded. Patients with 18–65 years old of either gender with score of ≥4 on a 11-item numeric rating scale-numeric version of visual analog scale for pain with diagnosis of primary osteoarthritis (OA) of the knee or hand of at least 3 months duration, with independent radiological confirmation of OA or having pain associated with other MSK conditions such as soft-tissue rheumatism, cervical and lumbar back pain, and fibromyalgia, of at least 3 months duration were included in this study. Results: Transdermal diclofenac diethylamine patch and tablet diclofenac sodium sustained release (SR) do not significantly differ in the reduction of numerical rating scores at the end of 4 weeks (P = 0.8393). Conclusion: Transdermal diclofenac was equi-efficacious as tablet diclofenac sodium SR in reducing pain due to chronic MSK pain conditions. PMID:29472748

Numerical Simulation of Self-gravitational Instability of Isothermal Gaseous Slab Under High External Pressure

NASA Astrophysics Data System (ADS)

Miyaji, S.; Umekawa, M.; Matsumoto, R.; Yoshida, T.

1996-05-01

Gaseous slab is formed with shock waves from super novae, collision of interstellar clouds, etc. When the mass in the Jeans scale is more than Jeans mass, the slab fragments into many clumps by gravitational instability. But in high external pressure environment, even the slab which is stable against Jeans mode can fragment(Elmegreen and Elmegreen 1978).This phenomenon results from incompressible mode instability(Lubow and Pringle 1993). These works are by linear analysis. We study numerically this isothermal gaseous slab which is formed by high external pressure and whose thickness is much smaller than its scale height. We assume self-gravitational fluid, and use two dimensional flux split method. Our model size is taken about the scale of linear maximum growth rate wave length and its five times length, which is an example of much longer than the maximum growth rate wave length. When the incompressible mode instability takes place, it becomes clumps. Each mass of the clumps is less than the Jeans mass. Then the clumps approach each other by gravitational interaction to form bigger clumps. In the presentation we will show results of numerical simulation and discuss about the interaction of fragments on star formation or initial mass function.

Validity of the Child Facial Coding System for the Assessment of Acute Pain in Children With Cerebral Palsy.

PubMed

Hadden, Kellie L; LeFort, Sandra; O'Brien, Michelle; Coyte, Peter C; Guerriere, Denise N

2016-04-01

The purpose of the current study was to examine the concurrent and discriminant validity of the Child Facial Coding System for children with cerebral palsy. Eighty-five children (mean = 8.35 years, SD = 4.72 years) were videotaped during a passive joint stretch with their physiotherapist and during 3 time segments: baseline, passive joint stretch, and recovery. Children's pain responses were rated from videotape using the Numerical Rating Scale and Child Facial Coding System. Results indicated that Child Facial Coding System scores during the passive joint stretch significantly correlated with Numerical Rating Scale scores (r = .72, P < .01). Child Facial Coding System scores were also significantly higher during the passive joint stretch than the baseline and recovery segments (P < .001). Facial activity was not significantly correlated with the developmental measures. These findings suggest that the Child Facial Coding System is a valid method of identifying pain in children with cerebral palsy. © The Author(s) 2015.

Open-label placebo treatment in chronic low back pain: a randomized controlled trial

PubMed Central

Carvalho, Cláudia; Caetano, Joaquim Machado; Cunha, Lidia; Rebouta, Paula; Kaptchuk, Ted J.; Kirsch, Irving

2016-01-01

Abstract This randomized controlled trial was performed to investigate whether placebo effects in chronic low back pain could be harnessed ethically by adding open-label placebo (OLP) treatment to treatment as usual (TAU) for 3 weeks. Pain severity was assessed on three 0- to 10-point Numeric Rating Scales, scoring maximum pain, minimum pain, and usual pain, and a composite, primary outcome, total pain score. Our other primary outcome was back-related dysfunction, assessed on the Roland–Morris Disability Questionnaire. In an exploratory follow-up, participants on TAU received placebo pills for 3 additional weeks. We randomized 97 adults reporting persistent low back pain for more than 3 months' duration and diagnosed by a board-certified pain specialist. Eighty-three adults completed the trial. Compared to TAU, OLP elicited greater pain reduction on each of the three 0- to 10-point Numeric Rating Scales and on the 0- to 10-point composite pain scale (P < 0.001), with moderate to large effect sizes. Pain reduction on the composite Numeric Rating Scales was 1.5 (95% confidence interval: 1.0-2.0) in the OLP group and 0.2 (−0.3 to 0.8) in the TAU group. Open-label placebo treatment also reduced disability compared to TAU (P < 0.001), with a large effect size. Improvement in disability scores was 2.9 (1.7-4.0) in the OLP group and 0.0 (−1.1 to 1.2) in the TAU group. After being switched to OLP, the TAU group showed significant reductions in both pain (1.5, 0.8-2.3) and disability (3.4, 2.2-4.5). Our findings suggest that OLP pills presented in a positive context may be helpful in chronic low back pain. PMID:27755279

Open-label placebo treatment in chronic low back pain: a randomized controlled trial.

PubMed

Carvalho, Cláudia; Caetano, Joaquim Machado; Cunha, Lidia; Rebouta, Paula; Kaptchuk, Ted J; Kirsch, Irving

2016-12-01

This randomized controlled trial was performed to investigate whether placebo effects in chronic low back pain could be harnessed ethically by adding open-label placebo (OLP) treatment to treatment as usual (TAU) for 3 weeks. Pain severity was assessed on three 0- to 10-point Numeric Rating Scales, scoring maximum pain, minimum pain, and usual pain, and a composite, primary outcome, total pain score. Our other primary outcome was back-related dysfunction, assessed on the Roland-Morris Disability Questionnaire. In an exploratory follow-up, participants on TAU received placebo pills for 3 additional weeks. We randomized 97 adults reporting persistent low back pain for more than 3 months' duration and diagnosed by a board-certified pain specialist. Eighty-three adults completed the trial. Compared to TAU, OLP elicited greater pain reduction on each of the three 0- to 10-point Numeric Rating Scales and on the 0- to 10-point composite pain scale (P < 0.001), with moderate to large effect sizes. Pain reduction on the composite Numeric Rating Scales was 1.5 (95% confidence interval: 1.0-2.0) in the OLP group and 0.2 (-0.3 to 0.8) in the TAU group. Open-label placebo treatment also reduced disability compared to TAU (P < 0.001), with a large effect size. Improvement in disability scores was 2.9 (1.7-4.0) in the OLP group and 0.0 (-1.1 to 1.2) in the TAU group. After being switched to OLP, the TAU group showed significant reductions in both pain (1.5, 0.8-2.3) and disability (3.4, 2.2-4.5). Our findings suggest that OLP pills presented in a positive context may be helpful in chronic low back pain.

Cavitation erosion prediction based on analysis of flow dynamics and impact load spectra

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

Mihatsch, Michael S., E-mail: michael.mihatsch@aer.mw.tum.de; Schmidt, Steffen J.; Adams, Nikolaus A.

2015-10-15

Cavitation erosion is the consequence of repeated collapse-induced high pressure-loads on a material surface. The present paper assesses the prediction of impact load spectra of cavitating flows, i.e., the rate and intensity distribution of collapse events based on a detailed analysis of flow dynamics. Data are obtained from a numerical simulation which employs a density-based finite volume method, taking into account the compressibility of both phases, and resolves collapse-induced pressure waves. To determine the spectrum of collapse events in the fluid domain, we detect and quantify the collapse of isolated vapor structures. As reference configuration we consider the expansion ofmore » a liquid into a radially divergent gap which exhibits unsteady sheet and cloud cavitation. Analysis of simulation data shows that global cavitation dynamics and dominant flow events are well resolved, even though the spatial resolution is too coarse to resolve individual vapor bubbles. The inviscid flow model recovers increasingly fine-scale vapor structures and collapses with increasing resolution. We demonstrate that frequency and intensity of these collapse events scale with grid resolution. Scaling laws based on two reference lengths are introduced for this purpose. We show that upon applying these laws impact load spectra recorded on experimental and numerical pressure sensors agree with each other. Furthermore, correlation between experimental pitting rates and collapse-event rates is found. Locations of high maximum wall pressures and high densities of collapse events near walls obtained numerically agree well with areas of erosion damage in the experiment. The investigation shows that impact load spectra of cavitating flows can be inferred from flow data that captures the main vapor structures and wave dynamics without the need for resolving all flow scales.« less

Evaluation of rotigotine transdermal patch for the treatment of depressive symptoms in patients with Parkinson's disease.

PubMed

Chung, Sun Ju; Asgharnejad, Mahnaz; Bauer, Lars; Ramirez, Francisco; Jeon, Beomseok

2016-08-01

To evaluate the dopamine receptor agonist, rotigotine, for improving depressive symptoms in patients with Parkinson's disease (PD). Patients were randomized 1:1 to rotigotine or placebo, titrated for ≤7 weeks, and maintained at optimal/maximum dose for 8-weeks. Primary efficacy variable: 17- item Hamilton Depression Rating Scale (HAM-D 17) total score change from baseline to end-of-maintenance. Secondary variables: changes in Beck Depression Inventory-II, Unified Parkinson's Disease Rating Scale (UPDRS) II (activities of daily living [ADL]) and III (motor) subscores, UPDRS II+III total, patient-rated Apathy Scale (AS), and Snaith-Hamilton Pleasure Scale. Of 380 patients randomized, 149/184 (81.0%) rotigotine-treated and 164/196 (83.7%) placebo-treated patients completed the study. mean (±SD) age 65.2 (±8.5) years; time since PD-diagnosis 2.74 (±3.08) years; 42.6% male. The treatment difference (LS mean [95% CI]) in change from baseline HAM-D 17 was -1.12 (-2.56, 0.33; p = 0.1286). UPDRS II, III, II+III and AS scores improved numerically with rotigotine versus placebo. Common adverse events with higher incidence with rotigotine: nausea, application/instillation site reactions, vomiting, and pruritus. Forty-one (10.8%) patients discontinued owing to adverse events (25 rotigotine/16 placebo). No statistically significant improvement in depressive symptoms were observed with rotigotine versus placebo. ADL, motor function, and patient-rated apathy improved numerically. ClinicalTrials.gov: NCT01523301.

Numerical Study of Pyrolysis of Biomass in Fluidized Beds

NASA Technical Reports Server (NTRS)

Bellan, Josette; Lathouwers, Danny

2003-01-01

A report presents a numerical-simulation study of pyrolysis of biomass in fluidized-bed reactors, performed by use of the mathematical model described in Model of Fluidized Bed Containing Reacting Solids and Gases (NPO-30163), which appears elsewhere in this issue of NASA Tech Briefs. The purpose of the study was to investigate the effect of various operating conditions on the efficiency of production of condensable tar from biomass. The numerical results indicate that for a fixed particle size, the fluidizing-gas temperature is the foremost parameter that affects the tar yield. For the range of fluidizing-gas temperatures investigated, and under the assumption that the pyrolysis rate exceeds the feed rate, the optimum steady-state tar collection was found to occur at 750 K. In cases in which the assumption was not valid, the optimum temperature for tar collection was found to be only slightly higher. Scaling up of the reactor was found to exert a small negative effect on tar collection at the optimal operating temperature. It is also found that slightly better scaling is obtained by use of shallower fluidized beds with greater fluidization velocities.

Short-term combined effects of thoracic spine thrust manipulation and cervical spine nonthrust manipulation in individuals with mechanical neck pain: a randomized clinical trial.

PubMed

Masaracchio, Michael; Cleland, Joshua A; Hellman, Madeleine; Hagins, Marshall

2013-03-01

Randomized clinical trial. To investigate the short-term effects of thoracic spine thrust manipulation combined with cervical spine nonthrust manipulation (experimental group) versus cervical spine nonthrust manipulation alone (comparison group) in individuals with mechanical neck pain. Research has demonstrated improved outcomes with both nonthrust manipulation directed at the cervical spine and thrust manipulation directed at the thoracic spine in patients with neck pain. Previous studies have not determined if thoracic spine thrust manipulation may increase benefits beyond those provided by cervical nonthrust manipulation alone. Sixty-four participants with mechanical neck pain were randomized into 1 of 2 groups, an experimental or comparison group. Both groups received 2 treatment sessions of cervical spine nonthrust manipulation and a home exercise program consisting of active range-of-motion exercises, and the experimental group received additional thoracic spine thrust manipulations. Outcome measures were collected at baseline and at a 1-week follow-up, and included the numeric pain rating scale, the Neck Disability Index, and the global rating of change. Participants in the experimental group demonstrated significantly greater improvements (P<.001) on both the numeric pain rating scale and Neck Disability Index at the 1-week follow-up compared to those in the comparison group. In addition, 31 of 33 (94%) participants in the experimental group, compared to 11 of 31 participants (35%) in the comparison group, indicated a global rating of change score of +4 or higher at the 1-week follow-up, with an associated number needed to treat of 2. Individuals with neck pain who received a combination of thoracic spine thrust manipulation and cervical spine nonthrust manipulation plus exercise demonstrated better overall short-term outcomes on the numeric pain rating scale, the Neck Disability Index, and the global rating of change.

Numerical Modeling of STARx for Ex Situ Soil Remediation

NASA Astrophysics Data System (ADS)

Gerhard, J.; Solinger, R. L.; Grant, G.; Scholes, G.

2016-12-01

Growing stockpiles of contaminated soils contaminated with petroleum hydrocarbons are an outstanding problem worldwide. Self-sustaining Treatment for Active Remediation (STAR) is an emerging technology based on smouldering combustion that has been successfully deployed for in situ remediation. STAR has also been developed for ex situ applications (STARx). This work used a two-dimensional numerical model to systematically explore the sensitivity of ex situ remedial performance to key design and operational parameters. First the model was calibrated and validated against pilot scale experiments, providing confidence that the rate and extent of treatment were correctly predicted. Simulations then investigated sensitivity of remedial performance to injected air flux, contaminant saturation, system configuration, heterogeneity of intrinsic permeability, heterogeneity of contaminant saturation, and system scale. Remedial performance was predicted to be most sensitive to the injected air flux, with higher air fluxes achieving higher treatment rates and remediating larger fractions of the initial contaminant mass. The uniformity of the advancing smouldering front was predicted to be highly dependent on effective permeability contrasts between treated and untreated sections of the contaminant pack. As a result, increased heterogeneity (of intrinsic permeability in particular) is predicted to lower remedial performance. Full-scale systems were predicted to achieve treatment rates an order of magnitude higher than the pilot scale for similar contaminant saturation and injected air flux. This work contributed to the large scale STARx treatment system that is being tested at a field site in Fall 2016.

Numerical determination of Paris law constants for carbon steel using a two-scale model

NASA Astrophysics Data System (ADS)

Mlikota, M.; Staib, S.; Schmauder, S.; Božić, Ž.

2017-05-01

For most engineering alloys, the long fatigue crack growth under a certain stress level can be described by the Paris law. The law provides a correlation between the fatigue crack growth rate (FCGR or da/dN), the range of stress intensity factor (ΔK), and the material constants C and m. A well-established test procedure is typically used to determine the Paris law constants C and m, considering standard specimens, notched and pre-cracked. Definition of all the details necessary to obtain feasible and comparable Paris law constants are covered by standards. However, these cost-expensive tests can be replaced by appropriate numerical calculations. In this respect, this paper deals with the numerical determination of Paris law constants for carbon steel using a two-scale model. A micro-model containing the microstructure of a material is generated using the Finite Element Method (FEM) to calculate the fatigue crack growth rate at a crack tip. The model is based on the Tanaka-Mura equation. On the other side, a macro-model serves for the calculation of the stress intensity factor. The analysis yields a relationship between the crack growth rates and the stress intensity factors for defined crack lengths which is then used to determine the Paris law constants.

The Thick Level-Set model for dynamic fragmentation

DOE PAGES

Stershic, Andrew J.; Dolbow, John E.; Moës, Nicolas

2017-01-04

The Thick Level-Set (TLS) model is implemented to simulate brittle media undergoing dynamic fragmentation. This non-local model is discretized by the finite element method with damage represented as a continuous field over the domain. A level-set function defines the extent and severity of damage, and a length scale is introduced to limit the damage gradient. Numerical studies in one dimension demonstrate that the proposed method reproduces the rate-dependent energy dissipation and fragment length observations from analytical, numerical, and experimental approaches. In conclusion, additional studies emphasize the importance of appropriate bulk constitutive models and sufficient spatial resolution of the length scale.

Pain Neurophysiology Education and Therapeutic Exercise for Patients With Chronic Low Back Pain: A Single-Blind Randomized Controlled Trial.

PubMed

Bodes Pardo, Gema; Lluch Girbés, Enrique; Roussel, Nathalie A; Gallego Izquierdo, Tomás; Jiménez Penick, Virginia; Pecos Martín, Daniel

2018-02-01

To assess the effect of a pain neurophysiology education (PNE) program plus therapeutic exercise (TE) for patients with chronic low back pain (CLBP). Single-blind randomized controlled trial. Private clinic and university. Patients with CLBP for ≥6 months (N=56). Participants were randomized to receive either a TE program consisting of motor control, stretching, and aerobic exercises (n=28) or the same TE program in addition to a PNE program (n=28), conducted in two 30- to 50-minute sessions in groups of 4 to 6 participants. The primary outcome was pain intensity rated on the numerical pain rating scale which was completed immediately after treatment and at 1- and 3-month follow-up. Secondary outcome measures were pressure pain threshold, finger-to-floor distance, Roland-Morris Disability Questionnaire, Pain Catastrophizing Scale, Tampa Scale for Kinesiophobia, and Patient Global Impression of Change. At 3-month follow-up, a large change in pain intensity (numerical pain rating scale: -2.2; -2.93 to -1.28; P<.001; d=1.37) was observed for the PNE plus TE group, and a moderate effect size was observed for the secondary outcome measures. Combining PNE with TE resulted in significantly better results for participants with CLBP, with a large effect size, compared with TE alone. Copyright © 2017 American Congress of Rehabilitation Medicine. Published by Elsevier Inc. All rights reserved.

GeV-scale hot sterile neutrino oscillations: a numerical solution

NASA Astrophysics Data System (ADS)

Ghiglieri, J.; Laine, M.

2018-02-01

The scenario of baryogenesis through GeV-scale sterile neutrino oscillations is governed by non-linear differential equations for the time evolution of a sterile neutrino density matrix and Standard Model lepton and baryon asymmetries. By employing up-to-date rate coefficients and a non-perturbatively estimated Chern-Simons diffusion rate, we present a numerical solution of this system, incorporating the full momentum and helicity dependences of the density matrix. The density matrix deviates significantly from kinetic equilibrium, with the IR modes equilibrating much faster than the UV modes. For equivalent input parameters, our final results differ moderately (˜50%) from recent benchmarks in the literature. The possibility of producing an observable baryon asymmetry is nevertheless confirmed. We illustrate the dependence of the baryon asymmetry on the sterile neutrino mass splitting and on the CP-violating phase measurable in active neutrino oscillation experiments.

A Simple and Accurate Rate-Driven Infiltration Model

NASA Astrophysics Data System (ADS)

Cui, G.; Zhu, J.

2017-12-01

In this study, we develop a novel Rate-Driven Infiltration Model (RDIMOD) for simulating infiltration into soils. Unlike traditional methods, RDIMOD avoids numerically solving the highly non-linear Richards equation or simply modeling with empirical parameters. RDIMOD employs infiltration rate as model input to simulate one-dimensional infiltration process by solving an ordinary differential equation. The model can simulate the evolutions of wetting front, infiltration rate, and cumulative infiltration on any surface slope including vertical and horizontal directions. Comparing to the results from the Richards equation for both vertical infiltration and horizontal infiltration, RDIMOD simply and accurately predicts infiltration processes for any type of soils and soil hydraulic models without numerical difficulty. Taking into account the accuracy, capability, and computational effectiveness and stability, RDIMOD can be used in large-scale hydrologic and land-atmosphere modeling.

Scaling of Foraminifera Parent and Offspring Size through the Phanerozoic

NASA Astrophysics Data System (ADS)

Guo, D.; Holme, F.; Payne, J.; Skotheim, J.

2011-12-01

Since before the 1940s, scientists have studied the scaling of body mass with metabolic rate, heart rate, fecundity, cardiac cycling rate, and numerous other traits. Like these traits, offspring mass scales with parent body mass for plants and animals. However, the relationship is not well documented in single-celled organisms. In our study, we examined how adult size scales with embryo size in fusulinid foraminifera. Fusulinids, and most other foraminifera, are an exceptional study group because the proloculus (the initial shell chamber) can be used to measure the size of the daughter cell at the time it became independent of its parent. We find that proloculus size increases with adult test size across fusulinid species. This pattern may result because the genomic sizes and the cellular machinery necessary for a larger adult size place limits on how small the initial daughter cell can be.

Direct Numerical Simulation of a Temporally Evolving Incompressible Plane Wake: Effect of Initial Conditions on Evolution and Topology

NASA Technical Reports Server (NTRS)

Sondergaard, R.; Cantwell, B.; Mansour, N.

1997-01-01

Direct numerical simulations have been used to examine the effect of the initial disturbance field on the development of three-dimensionality and the transition to turbulence in the incompressible plane wake. The simulations were performed using a new numerical method for solving the time-dependent, three-dimensional, incompressible Navier-Stokes equations in flows with one infinite and two periodic directions. The method uses standard Fast Fourier Transforms and is applicable to cases where the vorticity field is compact in the infinite direction. Initial disturbances fields examined were combinations of two-dimensional waves and symmetric pairs of 60 deg oblique waves at the fundamental, subharmonic, and sub-subharmonic wavelengths. The results of these simulations indicate that the presence of 60 deg disturbances at the subharmonic streamwise wavelength results in the development of strong coherent three-dimensional structures. The resulting strong three-dimensional rate-of-strain triggers the growth of intense fine scale motions. Wakes initiated with 60 deg disturbances at the fundamental streamwise wavelength develop weak coherent streamwise structures, and do not develop significant fine scale motions, even at high Reynolds numbers. The wakes which develop strong three-dimensional structures exhibit growth rates on par with experimentally observed turbulent plane wakes. Wakes which develop only weak three-dimensional structures exhibit significantly lower late time growth rates. Preliminary studies of wakes initiated with an oblique fundamental and a two-dimensional subharmonic, which develop asymmetric coherent oblique structures at the subharmonic wavelength, indicate that significant fine scale motions only develop if the resulting oblique structures are above an angle of approximately 45 deg.

Magnetic and velocity fields in a dynamo operating at extremely small Ekman and magnetic Prandtl numbers

NASA Astrophysics Data System (ADS)

Šimkanin, Ján; Kyselica, Juraj

2017-12-01

Numerical simulations of the geodynamo are becoming more realistic because of advances in computer technology. Here, the geodynamo model is investigated numerically at the extremely low Ekman and magnetic Prandtl numbers using the PARODY dynamo code. These parameters are more realistic than those used in previous numerical studies of the geodynamo. Our model is based on the Boussinesq approximation and the temperature gradient between upper and lower boundaries is a source of convection. This study attempts to answer the question how realistic the geodynamo models are. Numerical results show that our dynamo belongs to the strong-field dynamos. The generated magnetic field is dipolar and large-scale while convection is small-scale and sheet-like flows (plumes) are preferred to a columnar convection. Scales of magnetic and velocity fields are separated, which enables hydromagnetic dynamos to maintain the magnetic field at the low magnetic Prandtl numbers. The inner core rotation rate is lower than that in previous geodynamo models. On the other hand, dimensional magnitudes of velocity and magnetic fields and those of the magnetic and viscous dissipation are larger than those expected in the Earth's core due to our parameter range chosen.

Numerical calculation of protein-ligand binding rates through solution of the Smoluchowski equation using smoothed particle hydrodynamics

DOE PAGES

Pan, Wenxiao; Daily, Michael; Baker, Nathan A.

2015-05-07

Background: The calculation of diffusion-controlled ligand binding rates is important for understanding enzyme mechanisms as well as designing enzyme inhibitors. Methods: We demonstrate the accuracy and effectiveness of a Lagrangian particle-based method, smoothed particle hydrodynamics (SPH), to study diffusion in biomolecular systems by numerically solving the time-dependent Smoluchowski equation for continuum diffusion. Unlike previous studies, a reactive Robin boundary condition (BC), rather than the absolute absorbing (Dirichlet) BC, is considered on the reactive boundaries. This new BC treatment allows for the analysis of enzymes with “imperfect” reaction rates. Results: The numerical method is first verified in simple systems and thenmore » applied to the calculation of ligand binding to a mouse acetylcholinesterase (mAChE) monomer. Rates for inhibitor binding to mAChE are calculated at various ionic strengths and compared with experiment and other numerical methods. We find that imposition of the Robin BC improves agreement between calculated and experimental reaction rates. Conclusions: Although this initial application focuses on a single monomer system, our new method provides a framework to explore broader applications of SPH in larger-scale biomolecular complexes by taking advantage of its Lagrangian particle-based nature.« less

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.

Percolation transport theory and relevance to soil formation, vegetation growth, and productivity

NASA Astrophysics Data System (ADS)

Hunt, A. G.; Ghanbarian, B.

2016-12-01

Scaling laws of percolation theory have been applied to generate the time dependence of vegetation growth rates (both intensively managed and natural) and soil formation rates. The soil depth is thus equal to the solute vertical transport distance, the soil production function, chemical weathering rates, and C and N storage rates are all given by the time derivative of the soil depth. Approximate numerical coefficients based on the maximum flow rates in soils have been proposed, leading to a broad understanding of such processes. What is now required is an accurate understanding of the variability of the coefficients in the scaling relationships. The present abstract focuses on the scaling relationship for solute transport and soil formation. A soil formation rate relates length, x, and time, t, scales, meaning that the missing coefficient must include information about fundamental space and time scales, x0 and t0. x0 is proposed to be a fundamental mineral heterogeneity scale, i.e. a median particle diameter. to is then found from the ratio of x0 and a fundamental flow rate, v0, which is identified with the net infiltration rate. The net infiltration rate is equal to precipitation P less evapotranspiration, ET, plus run-on less run-off. Using this hypothesis, it is possible to predict soil depths and formation rates as functions of time and P - ET, and the formation rate as a function of depth, soil calcic and gypsic horizon depths as functions of P-ET. It is also possible to determine when soils are in equilibrium, and predict relationships of erosion rates and soil formation rates.

Universal nonlinear small-scale dynamo.

PubMed

Beresnyak, A

2012-01-20

We consider astrophysically relevant nonlinear MHD dynamo at large Reynolds numbers (Re). We argue that it is universal in a sense that magnetic energy grows at a rate which is a constant fraction C(E) of the total turbulent dissipation rate. On the basis of locality bounds we claim that this "efficiency of the small-scale dynamo", C(E), is a true constant for large Re and is determined only by strongly nonlinear dynamics at the equipartition scale. We measured C(E) in numerical simulations and observed a value around 0.05 in the highest resolution simulations. We address the issue of C(E) being small, unlike the Kolmogorov constant which is of order unity. © 2012 American Physical Society

Turbulent combustion in aluminum-air clouds for different scale explosion fields

NASA Astrophysics Data System (ADS)

Kuhl, Allen L.; Balakrishnan, Kaushik; Bell, John B.; Beckner, Vincent E.

2017-01-01

This paper explores "scaling issues" associated with Al particle combustion in explosions. The basic idea is the following: in this non-premixed combustion system, the global burning rate is controlled by rate of turbulent mixing of fuel (Al particles) with air. From similarity considerations, the turbulent mixing rates should scale with the explosion length and time scales. However, the induction time for ignition of Al particles depends on an Arrhenius function, which is independent of the explosion length and time. To study this, we have performed numerical simulations of turbulent combustion in unconfined Al-SDF (shock-dispersed-fuel) explosion fields at different scales. Three different charge masses were assumed: 1-g, 1-kg and 1-T Al-powder charges. We found that there are two combustion regimes: an ignition regime—where the burning rate decays as a power-law function of time, and a turbulent combustion regime—where the burning rate decays exponentially with time. This exponential dependence is typical of first order reactions and the more general concept of Life Functions that control the dynamics of evolutionary systems. Details of the combustion model are described. Results, including mean and rms profiles in combustion cloud and fuel consumption histories, are presented.

Multidimensional Assessment of Functional Outcomes in Schizophrenia: Results From QUALIFY, a Head-to-Head Trial of Aripiprazole Once-Monthly and Paliperidone Palmitate.

PubMed

Potkin, Steven G; Loze, Jean-Yves; Forray, Carlos; Baker, Ross A; Sapin, Christophe; Peters-Strickland, Timothy; Beillat, Maud; Nylander, Anna-Greta; Hertel, Peter; Nitschky Schmidt, Simon; Eramo, Anna; Hansen, Karina; Naber, Dieter

2017-01-01

QUALIFY was a 28-week, randomized, open-label, head-to-head trial that assessed improvements across multiple measures in stable patients with schizophrenia with aripiprazole once-monthly 400 mg vs paliperidone palmitate. Secondary effectiveness assessments included physician-rated readiness for work using the Work Readiness Questionnaire, the Clinical Global Impression-Severity and Clinical Global Impression-Improvement scales, and quality of life with the rater-blinded Heinrichs-Carpenter Quality of Life Scale. Patients assessed their treatment satisfaction and quality of life with Subjective Well-Being under Neuroleptic Treatment-short version and Tolerability and Quality of Life questionnaires. Odds of being ready for work at week 28 were significantly higher with aripiprazole once-monthly 400 mg vs paliperidone palmitate (adjusted odds ratio, 2.67; 95% CI, 1.39-5.14; P=.003). Aripiprazole once-monthly 400 mg produced numerically or significantly greater improvements from baseline vs paliperidone palmitate in all Quality of Life Scale items. With aripiprazole once-monthly 400 mg vs paliperidone palmitate at week 28, there were significantly more Clinical Global Impression-Severity and Clinical Global Impression-Improvement responders (adjusted odds ratio, 2.26; P=.010, and 2.51; P=.0032) and significantly better Clinical Global Impression-Improvement scores (least squares mean treatment difference, -0.326; 95% CI, -0.60 to -0.05; P=.020). Numerically larger improvements with aripiprazole once-monthly 400 mg vs paliperidone palmitate were observed for patient-rated scales Subjective Well-Being under Neuroleptic Treatment-short version and Tolerability and Quality of Life. Partial correlations were strongest among clinician-rated and among patient-rated scales but poorest between clinician and patient-rated scales. Consistently greater improvements were observed with aripiprazole once-monthly 400 mg vs paliperidone palmitate across all measures. Partial correlations between scales demonstrate the multidimensionality of various measures of improvement. More patients on aripiprazole once-monthly 400 mg were deemed ready to work by the study end. National Institutes of Health registry, NCT01795547, https://clinicaltrials.gov/ct2/results?id=NCT01795547). © The Author 2016. Published by Oxford University Press on behalf of CINP.

Development of the US3D Code for Advanced Compressible and Reacting Flow Simulations

NASA Technical Reports Server (NTRS)

Candler, Graham V.; Johnson, Heath B.; Nompelis, Ioannis; Subbareddy, Pramod K.; Drayna, Travis W.; Gidzak, Vladimyr; Barnhardt, Michael D.

2015-01-01

Aerothermodynamics and hypersonic flows involve complex multi-disciplinary physics, including finite-rate gas-phase kinetics, finite-rate internal energy relaxation, gas-surface interactions with finite-rate oxidation and sublimation, transition to turbulence, large-scale unsteadiness, shock-boundary layer interactions, fluid-structure interactions, and thermal protection system ablation and thermal response. Many of the flows have a large range of length and time scales, requiring large computational grids, implicit time integration, and large solution run times. The University of Minnesota NASA US3D code was designed for the simulation of these complex, highly-coupled flows. It has many of the features of the well-established DPLR code, but uses unstructured grids and has many advanced numerical capabilities and physical models for multi-physics problems. The main capabilities of the code are described, the physical modeling approaches are discussed, the different types of numerical flux functions and time integration approaches are outlined, and the parallelization strategy is overviewed. Comparisons between US3D and the NASA DPLR code are presented, and several advanced simulations are presented to illustrate some of novel features of the code.

Estimating 1 min rain rate distributions from numerical weather prediction

NASA Astrophysics Data System (ADS)

Paulson, Kevin S.

2017-01-01

Internationally recognized prognostic models of rain fade on terrestrial and Earth-space EHF links rely fundamentally on distributions of 1 min rain rates. Currently, in Rec. ITU-R P.837-6, these distributions are generated using the Salonen-Poiares Baptista method where 1 min rain rate distributions are estimated from long-term average annual accumulations provided by numerical weather prediction (NWP). This paper investigates an alternative to this method based on the distribution of 6 h accumulations available from the same NWPs. Rain rate fields covering the UK, produced by the Nimrod network of radars, are integrated to estimate the accumulations provided by NWP, and these are linked to distributions of fine-scale rain rates. The proposed method makes better use of the available data. It is verified on 15 NWP regions spanning the UK, and the extension to other regions is discussed.

The suitability of using dissolved gases to determine groundwater discharge to high gradient streams

USGS Publications Warehouse

Gleeson, Tom; Manning, Andrew H.; Popp, Andrea; Zane, Mathew; Clark, Jordan F.

2018-01-01

Determining groundwater discharge to streams using dissolved gases is known to be useful over a wide range of streamflow rates but the suitability of dissolved gas methods to determine discharge rates in high gradient mountain streams has not been sufficiently tested, even though headwater streams are critical as ecological habitats and water resources. The aim of this study is to test the suitability of using dissolved gases to determine groundwater discharge rates to high gradient streams by field experiments in a well-characterized, high gradient mountain stream and a literature review. At a reach scale (550 m) we combined stream and groundwater radon activity measurements with an in-stream SF6 tracer test. By means of numerical modeling we determined gas exchange velocities and derived very low groundwater discharge rates (∼15% of streamflow). These groundwater discharge rates are below the uncertainty range of physical streamflow measurements and consistent with temperature, specific conductance and streamflow measured at multiple locations along the reach. At a watershed-scale (4 km), we measured CFC-12 and δ18O concentrations and determined gas exchange velocities and groundwater discharge rates with the same numerical model. The groundwater discharge rates along the 4 km stream reach were highly variable, but were consistent with the values derived in the detailed study reach. Additionally, we synthesized literature values of gas exchange velocities for different stream gradients which show an empirical relationship that will be valuable in planning future dissolved gas studies on streams with various gradients. In sum, we show that multiple dissolved gas tracers can be used to determine groundwater discharge to high gradient mountain streams from reach to watershed scales.

The suitability of using dissolved gases to determine groundwater discharge to high gradient streams

NASA Astrophysics Data System (ADS)

Gleeson, Tom; Manning, Andrew H.; Popp, Andrea; Zane, Matthew; Clark, Jordan F.

2018-02-01

Determining groundwater discharge to streams using dissolved gases is known to be useful over a wide range of streamflow rates but the suitability of dissolved gas methods to determine discharge rates in high gradient mountain streams has not been sufficiently tested, even though headwater streams are critical as ecological habitats and water resources. The aim of this study is to test the suitability of using dissolved gases to determine groundwater discharge rates to high gradient streams by field experiments in a well-characterized, high gradient mountain stream and a literature review. At a reach scale (550 m) we combined stream and groundwater radon activity measurements with an in-stream SF6 tracer test. By means of numerical modeling we determined gas exchange velocities and derived very low groundwater discharge rates (∼15% of streamflow). These groundwater discharge rates are below the uncertainty range of physical streamflow measurements and consistent with temperature, specific conductance and streamflow measured at multiple locations along the reach. At a watershed-scale (4 km), we measured CFC-12 and δ18O concentrations and determined gas exchange velocities and groundwater discharge rates with the same numerical model. The groundwater discharge rates along the 4 km stream reach were highly variable, but were consistent with the values derived in the detailed study reach. Additionally, we synthesized literature values of gas exchange velocities for different stream gradients which show an empirical relationship that will be valuable in planning future dissolved gas studies on streams with various gradients. In sum, we show that multiple dissolved gas tracers can be used to determine groundwater discharge to high gradient mountain streams from reach to watershed scales.

Numerical simulations of sessile droplet evaporating on heated substrate

NASA Astrophysics Data System (ADS)

Chen, Xue; Chen, Paul G.; Ouazzani, Jalil; Liu, Qiusheng

2017-04-01

Motivated by the space project EFILE, a 2D axisymmetric numerical model in the framework of ALE method is developed to investigate the coupled physical mechanism during the evaporation of a pinned drop that partially wets on a heated substrate. The model accounts for mass transport in surrounding air, Marangoni convection inside the drop and heat conduction in the substrate as well as moving interface. Numerical results predict simple scaling laws for the evaporation rate which scales linearly with drop radius but follows a power-law with substrate temperature. It is highlighted that thermal effect of the substrate has a great impact on the temperature profile at the drop surface, which leads to a multicellular thermocapillary flow pattern. In particular, the structure of the multicellular flow behavior induced within a heated drop is mainly controlled by a geometric parameter (aspect ratio). A relationship between the number of thermal cells and the aspect ratio is proposed.

Validity, Sensitivity, and Responsiveness of the 11-Face Faces Pain Scale to Postoperative Pain in Adult Orthopedic Surgery Patients.

PubMed

Van Giang, Nguyen; Chiu, Hsiao-Yean; Thai, Duong Hong; Kuo, Shu-Yu; Tsai, Pei-Shan

2015-10-01

Pain is common in patients after orthopedic surgery. The 11-face Faces Pain Scale has not been validated for use in adult patients with postoperative pain. To assess the validity of the 11-face Faces Pain Scale and its ability to detect responses to pain medications, and to determine whether the sensitivity of the 11-face Faces Pain Scale for detecting changes in pain intensity over time is associated with gender differences in adult postorthopedic surgery patients. The 11-face Faces Pain Scale was translated into Vietnamese using forward and back translation. Postoperative pain was assessed using an 11-point numerical rating scale and the 11-face Faces Pain Scale on the day of surgery, and before (Time 1) and every 30 minutes after (Times 2-5) the patients had taken pain medications on the first postoperative day. The 11-face Faces Pain Scale highly correlated with the numerical rating scale (r = 0.78, p < .001). When the scores from each follow-up test (Times 2-5) were compared with those from the baseline test (Time 1), the effect sizes were -0.70, -1.05, -1.20, and -1.31, and the standardized response means were -1.17, -1.59, -1.66, and -1.82, respectively. The mean change in pain intensity, but not gender-time interaction effect, over the five time points was significant (F = 182.03, p < .001). Our results support that the 11-face Faces Pain Scale is appropriate for measuring acute postoperative pain in adults. Copyright © 2015 American Society for Pain Management Nursing. Published by Elsevier Inc. All rights reserved.

Advances in the management of multiple sclerosis symptoms: pathophysiology and assessment of spasticity in multiple sclerosis.

PubMed

Tintoré, Mar

2015-01-01

Spasticity is a prevalent and troublesome symptom for people with multiple sclerosis (MS). Common instruments to measure MS spasticity include the clinician-rated (modified) Ashworth scale and the patient-rated 0-10 spasticity Numerical Rating Scale (NRS). Current opinion is that measurement of MS spasticity should incorporate the patient's perspective. Other instruments to assess spasticity-associated symptoms such as the Penn spasms frequency scale, sleep quality NRS and pain NRS can assist in tracking MS spasticity evolution and inform management choices. Worsening spasticity reduces patient autonomy, impacts negatively on quality of life and increases health resource utilization and costs. Despite the wide range of issues associated with MS spasticity, undertreatment is common and standard treatment options (physiotherapy and classical oral therapies) often fail to provide adequate symptomatic control.

Correspondence of verbal descriptor and numeric rating scales for pain intensity: an item response theory calibration.

PubMed

Edelen, Maria Orlando; Saliba, Debra

2010-07-01

Assessing pain intensity in older adults is critical and challenging. There is debate about the most effective way to ask older adults to describe their pain severity, and clinicians vary in their preferred approaches, making comparison of pain intensity scores across settings difficult. A total of 3,676 residents from 71 community nursing homes across eight states were asked about pain presence. The 1,960 residents who reported pain within the past 5 days (53% of total, 70% female; age: M = 77.9, SD = 12.4) were included in analyses. Those who reported pain were also asked to provide a rating of pain intensity using either a verbal descriptor scale (VDS; mild, moderate, severe, and very severe and horrible), a numeric rating scale (NRS; 0 = no pain to 10 = worst pain imaginable), or both. We used item response theory (IRT) methods to identify the correspondence between the VDS and the NRS response options by estimating item parameters for these and five additional pain items. The sample reported moderate amounts of pain on average. Examination of the IRT location parameters for the pain intensity items indicated the following approximate correspondence: VDS mild approximately NRS 1-4, VDS moderate approximately NRS 5-7, VDS severe approximately NRS 8-9, and VDS very severe, horrible approximately NRS 10. This IRT calibration provides a crosswalk between the two response scales so that either can be used in practice depending on the preference of the clinician and respondent.

Work Environment Questionnaires and Army Unit Effectiveness and Satisfaction Measures

DTIC Science & Technology

1977-09-01

satisfaction indices (retention rates and disciplinary actions) and place more emphasis on these outcomes. In balance , the work environment and...last me a year"), and that "effective" supervisors and organizations planned carefully to stay within these constraints and balance expenditures over...scale was out of balance with its higher end. Most instruments reviewed used Likert scales with numerical anchors; very few provided specific descriptive

Efficient Simulation of Compressible, Viscous Fluids using Multi-rate Time Integration

NASA Astrophysics Data System (ADS)

Mikida, Cory; Kloeckner, Andreas; Bodony, Daniel

2017-11-01

In the numerical simulation of problems of compressible, viscous fluids with single-rate time integrators, the global timestep used is limited to that of the finest mesh point or fastest physical process. This talk discusses the application of multi-rate Adams-Bashforth (MRAB) integrators to an overset mesh framework to solve compressible viscous fluid problems of varying scale with improved efficiency, with emphasis on the strategy of timescale separation and the application of the resulting numerical method to two sample problems: subsonic viscous flow over a cylinder and a viscous jet in crossflow. The results presented indicate the numerical efficacy of MRAB integrators, outline a number of outstanding code challenges, demonstrate the expected reduction in time enabled by MRAB, and emphasize the need for proper load balancing through spatial decomposition in order for parallel runs to achieve the predicted time-saving benefit. This material is based in part upon work supported by the Department of Energy, National Nuclear Security Administration, under Award Number DE-NA0002374.

Perturbation solutions of combustion instability problems

NASA Technical Reports Server (NTRS)

Googerdy, A.; Peddieson, J., Jr.; Ventrice, M.

1979-01-01

A method involving approximate modal analysis using the Galerkin method followed by an approximate solution of the resulting modal-amplitude equations by the two-variable perturbation method (method of multiple scales) is applied to two problems of pressure-sensitive nonlinear combustion instability in liquid-fuel rocket motors. One problem exhibits self-coupled instability while the other exhibits mode-coupled instability. In both cases it is possible to carry out the entire linear stability analysis and significant portions of the nonlinear stability analysis in closed form. In the problem of self-coupled instability the nonlinear stability boundary and approximate forms of the limit-cycle amplitudes and growth and decay rates are determined in closed form while the exact limit-cycle amplitudes and growth and decay rates are found numerically. In the problem of mode-coupled instability the limit-cycle amplitudes are found in closed form while the growth and decay rates are found numerically. The behavior of the solutions found by the perturbation method are in agreement with solutions obtained using complex numerical methods.

Can stroke patients use visual analogue scales?

PubMed

Price, C I; Curless, R H; Rodgers, H

1999-07-01

Visual analogue scales (VAS) have been used for the subjective measurement of mood, pain, and health status after stroke. In this study we investigated how stroke-related impairments could alter the ability of subjects to answer accurately. Consent was obtained from 96 subjects with a clinical stroke (mean age, 72.5 years; 50 men) and 48 control subjects without cerebrovascular disease (mean age, 71.5 years; 29 men). Patients with reduced conscious level or severe dysphasia were excluded. Subjects were asked to rate the tightness that they could feel on the (unaffected) upper arm after 3 low-pressure inflations with a standard sphygmomanometer cuff, which followed a predetermined sequence (20 mm Hg, 40 mm Hg, 0 mm Hg). Immediately after each change, they rated the perceived tightness on 5 scales presented in a random order: 4-point rating scale (none, mild, moderate, severe), 0 to 10 numerical rating scale, mechanical VAS, horizontal VAS, and vertical VAS. Standard tests recorded deficits in language, cognition, and visuospatial awareness. Inability to complete scales with the correct pattern was associated with any stroke (P<0.001). There was a significant association between success using scales and milder clinical stroke subtype (P<0.01). Within the stroke group, logistic regression analysis identified significant associations (P<0.05) between impairments (cognitive and visuospatial) and inability to complete individual scales correctly. Many patients after a stroke are unable to successfully complete self-report measurement scales, including VAS.

Analgesia for total knee arthroplasty: a meta-analysis comparing local infiltration and femoral nerve block.

PubMed

Mei, ShuYa; Jin, ShuQing; Chen, ZhiXia; Ding, XiBing; Zhao, Xiang; Li, Quan

2015-09-01

Patients frequently experience postoperative pain after a total knee arthroplasty; such pain is always challenging to treat and may delay the patient's recovery. It is unclear whether local infiltration or a femoral nerve block offers a better analgesic effect after total knee arthroplasty.We performed a systematic review and meta-analysis of randomized controlled trials to compare local infiltration with a femoral nerve block in patients who underwent a primary unilateral total knee arthroplasty. We searched Pubmed, EMBASE, and the Cochrane Library through December 2014. Two reviewers scanned abstracts and extracted data. The data collected included numeric rating scale values for pain at rest and pain upon movement and opioid consumption in the first 24 hours. Mean differences with 95% confidence intervals were calculated for each end point. A sensitivity analysis was conducted to evaluate potential sources of heterogeneity.While the numeric rating scale values for pain upon movement (MD-0.62; 95%CI: -1.13 to -0.12; p=0.02) in the first 24 hours differed significantly between the patients who received local infiltration and those who received a femoral nerve block, there were no differences in the numeric rating scale results for pain at rest (MD-0.42; 95%CI:-1.32 to 0.47; p=0.35) or opioid consumption (MD 2.92; 95%CI:-1.32 to 7.16; p=0.18) in the first 24 hours.Local infiltration and femoral nerve block showed no significant differences in pain intensity at rest or opioid consumption after total knee arthroplasty, but the femoral nerve block was associated with reduced pain upon movement.

Analgesia for total knee arthroplasty: a meta-analysis comparing local infiltration and femoral nerve block

PubMed Central

Mei, ShuYa; Jin, ShuQing; Chen, ZhiXia; Ding, XiBing; Zhao, Xiang; Li, Quan

2015-01-01

Patients frequently experience postoperative pain after a total knee arthroplasty; such pain is always challenging to treat and may delay the patient's recovery. It is unclear whether local infiltration or a femoral nerve block offers a better analgesic effect after total knee arthroplasty. We performed a systematic review and meta-analysis of randomized controlled trials to compare local infiltration with a femoral nerve block in patients who underwent a primary unilateral total knee arthroplasty. We searched Pubmed, EMBASE, and the Cochrane Library through December 2014. Two reviewers scanned abstracts and extracted data. The data collected included numeric rating scale values for pain at rest and pain upon movement and opioid consumption in the first 24 hours. Mean differences with 95% confidence intervals were calculated for each end point. A sensitivity analysis was conducted to evaluate potential sources of heterogeneity. While the numeric rating scale values for pain upon movement (MD-0.62; 95%CI: -1.13 to -0.12; p=0.02) in the first 24 hours differed significantly between the patients who received local infiltration and those who received a femoral nerve block, there were no differences in the numeric rating scale results for pain at rest (MD-0.42; 95%CI:-1.32 to 0.47; p=0.35) or opioid consumption (MD 2.92; 95%CI:-1.32 to 7.16; p=0.18) in the first 24 hours. Local infiltration and femoral nerve block showed no significant differences in pain intensity at rest or opioid consumption after total knee arthroplasty, but the femoral nerve block was associated with reduced pain upon movement. PMID:26375568

Effects of turbulence on the collision rate of cloud droplets

NASA Astrophysics Data System (ADS)

Ayala, Orlando

This dissertation concerns effects of air turbulence on the collision rate of atmospheric cloud droplets. This research was motivated by the speculation that air turbulence could enhance the collision rate thereby help transform cloud droplets to rain droplets in a short time as observed in nature. The air turbulence within clouds is assumed to be homogeneous and isotropic, and its small-scale motion (1 mm to 10 cm scales) is computationally generated by direct numerical integration of the full Navier-Stokes equations. Typical droplet and turbulence parameters of convective warm clouds are used to determine the Stokes numbers (St) and the nondimensional terminal velocities (Sv) which characterize droplet relative inertia and gravitational settling, respectively. A novel and efficient methodology for conducting direct numerical simulations (DNS) of hydrodynamically-interacting droplets in the context of cloud microphysics has been developed. This numerical approach solves the turbulent flow by the pseudo-spectral method with a large-scale forcing, and utilizes an improved superposition method to embed analytically the local, small-scale (10 mum to 1 mm) disturbance flows induced by the droplets. This hybrid representation of background turbulent air motion and the induced disturbance flows is then used to study the combined effects of hydrodynamic interactions and airflow turbulence on the motion and collisions of cloud droplets. Hybrid DNS results show that turbulence can increase the geometric collision kernel relative to the gravitational geometric kernel by as much as 42% due to enhanced radial relative motion and preferential concentration of droplets. The exact level of enhancements depends on the Taylor-microscale Reynolds number, turbulent dissipation rate, and droplet pair size ratio. One important finding is that turbulence has a relatively dominant effect on the collision process between droplets close in size as the gravitational collision mechanism diminishes. A theory was developed to predict the radial relative velocity between droplets at contact. The theory agrees with our DNS results to within 5% for cloud droplets with strong settling. In addition, an empirical model is developed to quantify the radial distribution function. (Abstract shortened by UMI.)

A stochastic two-scale model for pressure-driven flow between rough surfaces

PubMed Central

Larsson, Roland; Lundström, Staffan; Wall, Peter; Almqvist, Andreas

2016-01-01

Seal surface topography typically consists of global-scale geometric features as well as local-scale roughness details and homogenization-based approaches are, therefore, readily applied. These provide for resolving the global scale (large domain) with a relatively coarse mesh, while resolving the local scale (small domain) in high detail. As the total flow decreases, however, the flow pattern becomes tortuous and this requires a larger local-scale domain to obtain a converged solution. Therefore, a classical homogenization-based approach might not be feasible for simulation of very small flows. In order to study small flows, a model allowing feasibly-sized local domains, for really small flow rates, is developed. Realization was made possible by coupling the two scales with a stochastic element. Results from numerical experiments, show that the present model is in better agreement with the direct deterministic one than the conventional homogenization type of model, both quantitatively in terms of flow rate and qualitatively in reflecting the flow pattern. PMID:27436975

A quantification method for numerical dissipation in quasi-DNS and under-resolved DNS, and effects of numerical dissipation in quasi-DNS and under-resolved DNS of turbulent channel flows

NASA Astrophysics Data System (ADS)

Komen, E. M. J.; Camilo, L. H.; Shams, A.; Geurts, B. J.; Koren, B.

2017-09-01

LES for industrial applications with complex geometries is mostly characterised by: a) a finite volume CFD method using a non-staggered arrangement of the flow variables and second order accurate spatial and temporal discretisation schemes, b) an implicit top-hat filter, where the filter length is equal to the local computational cell size, and c) eddy-viscosity type LES models. LES based on these three main characteristics is indicated as industrial LES in this paper. It becomes increasingly clear that the numerical dissipation in CFD codes typically used in industrial applications with complex geometries may inhibit the predictive capabilities of explicit LES. Therefore, there is a need to quantify the numerical dissipation rate in such CFD codes. In this paper, we quantify the numerical dissipation rate in physical space based on an analysis of the transport equation for the mean turbulent kinetic energy. Using this method, we quantify the numerical dissipation rate in a quasi-Direct Numerical Simulation (DNS) and in under-resolved DNS of, as a basic demonstration case, fully-developed turbulent channel flow. With quasi-DNS, we indicate a DNS performed using a second order accurate finite volume method typically used in industrial applications. Furthermore, we determine and explain the trends in the performance of industrial LES for fully-developed turbulent channel flow for four different Reynolds numbers for three different LES mesh resolutions. The presented explanation of the mechanisms behind the observed trends is based on an analysis of the turbulent kinetic energy budgets. The presented quantitative analyses demonstrate that the numerical errors in the industrial LES computations of the considered turbulent channel flows result in a net numerical dissipation rate which is larger than the subgrid-scale dissipation rate. No new computational methods are presented in this paper. Instead, the main new elements in this paper are our detailed quantification method for the numerical dissipation rate, the application of this method to a quasi-DNS and under-resolved DNS of fully-developed turbulent channel flow, and the explanation of the effects of the numerical dissipation on the observed trends in the performance of industrial LES for fully-developed turbulent channel flows.

Penetration of resonant magnetic perturbations in a rotating tokamak plasma with neoclassical poloidal viscosity

NASA Astrophysics Data System (ADS)

Wang, Jialei; Wang, Zheng-Xiong; Wei, Lai

2015-09-01

The penetration of time-dependant resonant magnetic perturbations (RMPs) is numerically studied by means of reduced magnetohydrodynamic simulations, taking into account the neoclassical poloidal viscosity (NPV) damping. It is found that with the increase of the RMP growth rate, the scalings of penetration threshold on resistivity as well as viscosity are significantly weakened in both viscoresistive and resistive-inertial regimes. In the high neoclassical viscosity regime, the scalings on neoclassical viscosity ν n c are numerically obtained in the cases of different RMP growth rate and viscosity ν. In the low neoclassical viscosity regime, ν n c almost has no effect on penetration threshold, which is unlike ν. Moreover, the synergistic effect of both ν n c and ν on the threshold is discussed as well. Finally, the role of the NPV in the torque balance is analysed. It is shown that the NPV tends to restore the velocity profile in the vicinity of the rational surface.

Clinical Decision Making in the Management of Patients With Cervicogenic Dizziness: A Case Series.

PubMed

Jung, Francis C; Mathew, Sherin; Littmann, Andrew E; MacDonald, Cameron W

2017-11-01

Study Design Case series. Background Although growing recognition of cervicogenic dizziness (CGD) is emerging, there is still no gold standard for the diagnosis of CGD. The purpose of this case series is to describe the clinical decision making utilized in the management of 7 patients presenting with CGD. Case Description Patients presenting with neck pain and accompanying subjective symptoms, including dizziness, unsteadiness, light-headedness, and visual disturbance, were selected. Clinical evidence of a temporal relationship between neck pain and dizziness, with or without sensorimotor disturbances, was assessed. Clinical decision making followed a 4-step process, informed by the current available best evidence. Outcome measures included the numeric rating scale for dizziness and neck pain, the Dizziness Handicap Inventory, Patient-Specific Functional Scale, and global rating of change. Outcomes Seven patients (mean age, 57 years; range, 31-86 years; 7 female) completed physical therapy management at an average of 13 sessions (range, 8-30 sessions) over a mean of 7 weeks. Clinically meaningful improvements were observed in the numeric rating scale for dizziness (mean difference, 5.7; 95% confidence interval [CI]: 4.0, 7.5), neck pain (mean difference, 5.4; 95% CI: 3.8, 7.1), and the Dizziness Handicap Inventory (mean difference, 32.6; 95% CI: 12.9, 52.2) at discontinuation. Patients also demonstrated overall satisfaction via the Patient-Specific Functional Scale (mean difference, 9) and global rating of change (mean, +6). Discussion This case series describes the physical therapist decision making, management, and outcomes in patients with CGD. Further investigation is warranted to develop a valid clinical decision-making guideline to inform management of patients with CGD. Level of Evidence Diagnosis, therapy, level 4. J Orthop Sports Phys Ther 2017;47(11):874-884. Epub 9 Oct 2017. doi:10.2519/jospt.2017.7425.

Numerical Study of Microstructural Evolution During Homogenization of Al-Si-Mg-Fe-Mn Alloys

NASA Astrophysics Data System (ADS)

Priya, Pikee; Johnson, David R.; Krane, Matthew J. M.

2016-09-01

Microstructural evolution during homogenization of Al-Si-Mg-Fe-Mn alloys occurs in two stages at different length scales: while holding at the homogenization temperature (diffusion on the scale of the secondary dendrite arm spacing (SDAS) in micrometers) and during quenching to room temperature (dispersoid precipitation at the nanometer to submicron scale). Here a numerical study estimates microstructural changes during both stages. A diffusion-based model developed to simulate evolution at the SDAS length scale predicts homogenization times and microstructures matching experiments. That model is coupled with a Kampmann Wagner Neumann-based precipitate nucleation and growth model to study the effect of temperature, composition, as-cast microstructure, and cooling rates during posthomogenization quenching on microstructural evolution. A homogenization schedule of 853 K (580 °C) for 8 hours, followed by cooling at 250 K/h, is suggested to optimize microstructures for easier extrusion, consisting of minimal α-Al(FeMn)Si, no β-AlFeSi, and Mg2Si dispersoids <1 μm size.

Hierarchical coarse-graining model for photosystem II including electron and excitation-energy transfer processes.

PubMed

Matsuoka, Takeshi; Tanaka, Shigenori; Ebina, Kuniyoshi

2014-03-01

We propose a hierarchical reduction scheme to cope with coupled rate equations that describe the dynamics of multi-time-scale photosynthetic reactions. To numerically solve nonlinear dynamical equations containing a wide temporal range of rate constants, we first study a prototypical three-variable model. Using a separation of the time scale of rate constants combined with identified slow variables as (quasi-)conserved quantities in the fast process, we achieve a coarse-graining of the dynamical equations reduced to those at a slower time scale. By iteratively employing this reduction method, the coarse-graining of broadly multi-scale dynamical equations can be performed in a hierarchical manner. We then apply this scheme to the reaction dynamics analysis of a simplified model for an illuminated photosystem II, which involves many processes of electron and excitation-energy transfers with a wide range of rate constants. We thus confirm a good agreement between the coarse-grained and fully (finely) integrated results for the population dynamics. Copyright © 2014 Elsevier Ireland Ltd. All rights reserved.

Ensemble solute transport in two-dimensional operator-scaling random fields

NASA Astrophysics Data System (ADS)

Monnig, Nathan D.; Benson, David A.; Meerschaert, Mark M.

2008-02-01

Motivated by field measurements of aquifer hydraulic conductivity (K), recent techniques were developed to construct anisotropic fractal random fields in which the scaling, or self-similarity parameter, varies with direction and is defined by a matrix. Ensemble numerical results are analyzed for solute transport through these two-dimensional "operator-scaling" fractional Brownian motion ln(K) fields. Both the longitudinal and transverse Hurst coefficients, as well as the "radius of isotropy" are important to both plume growth rates and the timing and duration of breakthrough. It is possible to create operator-scaling fractional Brownian motion fields that have more "continuity" or stratification in the direction of transport. The effects on a conservative solute plume are continually faster-than-Fickian growth rates, highly non-Gaussian shapes, and a heavier tail early in the breakthrough curve. Contrary to some analytic stochastic theories for monofractal K fields, the plume growth rates never exceed A. Mercado's (1967) purely stratified aquifer growth rate of plume apparent dispersivity proportional to mean distance. Apparent superstratified growth must be the result of other demonstrable factors, such as initial plume size.

Evaluation of validity and reliability of the Persian version of the functional index of hand osteoarthritis.

PubMed

Kordi Yoosefinejad, Amin; Motealleh, Alireza; Babakhani, Mohammad

2017-05-01

The Functional index of hand osteoarthritis (FIHOA) is a commonly used patient-reported outcome questionnaire designed to measure function in patients with hand osteoarthritis. The objective of this study was to evaluate the validity and reliability of the Persian version of the FIHOA. The Persian-translated version of FIHOA was administered to 72 native Persian-speaking patients in Iran with hand osteoarthritis. Thirty-six of the patients completed the questionnaire on two occasions 1 week apart. The physical component of the SF-36 and a numerical rating scale were used to evaluate the construct validity of the Persian version of FIHOA. Internal consistency was high (Cronbach's alpha = 0.89). Test-retest reliability for the total score was excellent (weighted kappa = 0.89, 95% CI 0.79-0.94). A significant positive correlation between total FIHOA score and numerical rating scale (r = 0.70) and a significant negative correlation between total FIHOA score and the physical component scale of the SF-36 (r = -0.76) were observed. The Persian version of the FIHOA showed adequate validity and reliability to evaluate functional disability in Persian-speaking patients with hand osteoarthritis.

A two-scale model for dynamic damage evolution

NASA Astrophysics Data System (ADS)

Keita, Oumar; Dascalu, Cristian; François, Bertrand

2014-03-01

This paper presents a new micro-mechanical damage model accounting for inertial effect. The two-scale damage model is fully deduced from small-scale descriptions of dynamic micro-crack propagation under tensile loading (mode I). An appropriate micro-mechanical energy analysis is combined with homogenization based on asymptotic developments in order to obtain the macroscopic evolution law for damage. Numerical simulations are presented in order to illustrate the ability of the model to describe known behaviors like size effects for the structural response, strain-rate sensitivity, brittle-ductile transition and wave dispersion.

Virtual reality rehabilitation of balance: assessment of the usability of the Nintendo Wii(®) Fit Plus.

PubMed

Meldrum, Dara; Glennon, Aine; Herdman, Susan; Murray, Deirdre; McConn-Walsh, Rory

2012-05-01

The aim of this study was to investigate the usability of the Nintendo Wii Fit Plus(®) (NWFP) in the treatment of balance impairment in vestibular and other neurological disease. This was a cross-sectional, quasi-experimental study. Participants (n = 26; mean age 43 ± 14, M13:F13) with quantified balance impairment took part in a 30-minute session on the NWFP using exercises and games that challenge balance. Outcomes included the System Usability Scale (SUS), a numerical rating scale of enjoyment and a post treatment questionnaire. The mean SUS score was high (mean 82 ± 18%) with only two participants rating below 50%. There was a negative correlation of age with SUS scores (r = -0.54; p = 0.004). Mean numerical rating scale score (/10) for enjoyment of the NWFP session was 8.4 ± 3. Of the participants, 88.5% said that they would like to use the NWFP in future treatment. Seventy-three percent reported more enjoyment and motivation than usual physiotherapy. No falls occurred during testing. This study has quantified the usability of the NWFP as a treatment for balance impairment showing high levels of usability and enjoyment with no serious adverse effects. The results of this study may assist physiotherapists in devising novel balance rehabilitation programmes. [Box: see text].

Comparison of parameterized nitric acid rainout rates using a coupled stochastic-photochemical tropospheric model

NASA Technical Reports Server (NTRS)

Stewart, Richard W.; Thompson, Anne M.; Owens, Melody A.; Herwehe, Jerold A.

1989-01-01

A major tropospheric loss of soluble species such as nitric acid results from scavenging by water droplets. Several theoretical formulations have been advanced which relate an effective time-independent loss rate for soluble species to statistical properties of precipitation such as the wet fraction and length of a precipitation cycle. In this paper, various 'effective' loss rates that have been proposed are compared with the results of detailed time-dependent model calculations carried out over a seasonal time scale. The model is a stochastic precipitation model coupled to a tropospheric photochemical model. The results of numerous time-dependent seasonal model runs are used to derive numerical values for the nitric acid residence time for several assumed sets of preciptation statistics. These values are then compared with the results obtained by utilizing theoretical 'effective' loss rates in time-independent models.

Coalescing colony model: Mean-field, scaling, and geometry

NASA Astrophysics Data System (ADS)

Carra, Giulia; Mallick, Kirone; Barthelemy, Marc

2017-12-01

We analyze the coalescing model where a `primary' colony grows and randomly emits secondary colonies that spread and eventually coalesce with it. This model describes population proliferation in theoretical ecology, tumor growth, and is also of great interest for modeling urban sprawl. Assuming the primary colony to be always circular of radius r (t ) and the emission rate proportional to r (t) θ , where θ >0 , we derive the mean-field equations governing the dynamics of the primary colony, calculate the scaling exponents versus θ , and compare our results with numerical simulations. We then critically test the validity of the circular approximation for the colony shape and show that it is sound for a constant emission rate (θ =0 ). However, when the emission rate is proportional to the perimeter, the circular approximation breaks down and the roughness of the primary colony cannot be discarded, thus modifying the scaling exponents.

A Pilot Study of the Correlation between the Numeric Rating Scale used to Evaluate "Geop" and Questionnaires on Pain Perception.

PubMed

Koo, Bon Sung; Jung, Myung Jin; Lee, Joon Ho; Jin, Hee Cheol; Lee, Jeong Seok; Kim, Yong Ik

2015-01-01

The word "geop" is a unique Korean term commonly used to describe fright, fear and anxiety, and similar concepts. The purpose of this pilot study is to examine the correlation between the Numeric Rating Scale (NRS) score of geop and three different questionnaires on pain perception. Patients aged 20 to 70 years who visited our outpatient pain clinics were evaluated. They were requested to rate the NRS score (range: 0-100) if they felt geop. Next, they completed questionnaires on pain perception, in this case the Korean version of the Pain Sensitivity Questionnaire (PSQ), the Pain Catastrophizing Scale (PCS), and the Pain Anxiety Symptoms Scale (PASS). The correlations among each variable were evaluated by statistical analyses. There was no statistically significant correlation between the NRS score of geop and the PSQ score (r = 0.075, P = 0.5605). The NRS score of geop showed a significant correlation with the PCS total score (r = 0.346, P = 0.0063). Among the sub-scales, Rumination (r = 0.338, P = 0.0077) and Magnification (r = 0.343, P = 0.0069) were correlated with the NRS score of geop. In addition, the NRS score of geop showed a significant correlation with the PASS total score (r = 0.475, P = 0.0001). The cognitive (r = 0.473, P = 0.0002) and fear factors (r = 0.349, P = 0.0063) also showed significant correlations with the NRS score of geop. This study marks the first attempt to introduce the concept of "geop." The NRS score of geop showed a moderate positive correlation with the total PCS and PASS score. However, further investigations are required before the "geop" concept can be used practically in clinical fields.

Laminar and Turbulent Dynamos in Chiral Magnetohydrodynamics. II. Simulations

NASA Astrophysics Data System (ADS)

Schober, Jennifer; Rogachevskii, Igor; Brandenburg, Axel; Boyarsky, Alexey; Fröhlich, Jürg; Ruchayskiy, Oleg; Kleeorin, Nathan

2018-05-01

Using direct numerical simulations (DNS), we study laminar and turbulent dynamos in chiral magnetohydrodynamics with an extended set of equations that accounts for an additional contribution to the electric current due to the chiral magnetic effect (CME). This quantum phenomenon originates from an asymmetry between left- and right-handed relativistic fermions in the presence of a magnetic field and gives rise to a chiral dynamo. We show that the magnetic field evolution proceeds in three stages: (1) a small-scale chiral dynamo instability, (2) production of chiral magnetically driven turbulence and excitation of a large-scale dynamo instability due to a new chiral effect (α μ effect), and (3) saturation of magnetic helicity and magnetic field growth controlled by a conservation law for the total chirality. The α μ effect becomes dominant at large fluid and magnetic Reynolds numbers and is not related to kinetic helicity. The growth rate of the large-scale magnetic field and its characteristic scale measured in the numerical simulations agree well with theoretical predictions based on mean-field theory. The previously discussed two-stage chiral magnetic scenario did not include stage (2), during which the characteristic scale of magnetic field variations can increase by many orders of magnitude. Based on the findings from numerical simulations, the relevance of the CME and the chiral effects revealed in the relativistic plasma of the early universe and of proto-neutron stars are discussed.

Study of neutron generation in the compact tokamak TUMAN-3M in support of a tokamak-based fusion neutron source

NASA Astrophysics Data System (ADS)

Kornev, V. A.; Askinazi, L. G.; Belokurov, A. A.; Chernyshev, F. V.; Lebedev, S. V.; Melnik, A. D.; Shabelsky, A. A.; Tukachinsky, A. S.; Zhubr, N. A.

2017-12-01

The paper presents DD neutron flux measurements in neutron beam injection (NBI) experiments aimed at the optimization of target plasma and heating beam parameters to achieve maximum neutron flux in the TUMAN-3M compact tokamak. Two ion sources of different design were used, which allowed the separation of the beam’s energy and power influence on the neutron rate. Using the database of experiments performed with the two ion sources, an empirical scaling was derived describing the neutron rate dependence on the target plasma and heating beam parameters. Numerical modeling of the neutron rate in the NBI experiments performed using the ASTRA transport code showed good agreement with the scaling.

Fast magnetic reconnection with large guide fields

DOE PAGES

Stanier, A.; Simakov, Andrei N.; Chacón, L.; ...

2015-01-09

We domonstrate, using two-fluid simulations, that low-βmagnetic reconnection remains fast, regardless of the presence of fast dispersive waves, which have been previously suggested to play a critical role. In order to understand these results, a discrete model is constructed that offers scaling relationships for the reconnection rate and dissipation region (DR) thickness in terms of the upstream magnetic field and DR length. Moreover, we verify these scalings numerically and show how the DR self-adjusts to process magnetic flux at the same rate that it is supplied to a larger region where two-fluid effects become important. The rate is therefore independentmore » of the DR physics and is in good agreement with kinetic results.« less

Effect of boundary conditions on thermal plume growth

NASA Astrophysics Data System (ADS)

Kondrashov, A.; Sboev, I.; Rybkin, K.

2016-07-01

We have investigated the influence of boundary conditions on the growth rate of convective plumes. Temperature and rate fields were studied in a rectangular convective cell heated by a spot heater. The results of the full-scale test were compared with the numerical data calculated using the ANSYS CFX software package. The relationship between the heat plume growth rate and heat boundary conditions, the width and height of the cell, size of heater for different kinds of liquid was established.

Elucidating the impact of micro-scale heterogeneous bacterial distribution on biodegradation

NASA Astrophysics Data System (ADS)

Schmidt, Susanne I.; Kreft, Jan-Ulrich; Mackay, Rae; Picioreanu, Cristian; Thullner, Martin

2018-06-01

Groundwater microorganisms hardly ever cover the solid matrix uniformly-instead they form micro-scale colonies. To which extent such colony formation limits the bioavailability and biodegradation of a substrate is poorly understood. We used a high-resolution numerical model of a single pore channel inhabited by bacterial colonies to simulate the transport and biodegradation of organic substrates. These high-resolution 2D simulation results were compared to 1D simulations that were based on effective rate laws for bioavailability-limited biodegradation. We (i) quantified the observed bioavailability limitations and (ii) evaluated the applicability of previously established effective rate concepts if microorganisms are heterogeneously distributed. Effective bioavailability reductions of up to more than one order of magnitude were observed, showing that the micro-scale aggregation of bacterial cells into colonies can severely restrict the bioavailability of a substrate and reduce in situ degradation rates. Effective rate laws proved applicable for upscaling when using the introduced effective colony sizes.

Interface-Resolving Simulation of Collision Efficiency of Cloud Droplets

NASA Astrophysics Data System (ADS)

Wang, Lian-Ping; Peng, Cheng; Rosa, Bodgan; Onishi, Ryo

2017-11-01

Small-scale air turbulence could enhance the geometric collision rate of cloud droplets while large-scale air turbulence could augment the diffusional growth of cloud droplets. Air turbulence could also enhance the collision efficiency of cloud droplets. Accurate simulation of collision efficiency, however, requires capture of the multi-scale droplet-turbulence and droplet-droplet interactions, which has only been partially achieved in the recent past using the hybrid direct numerical simulation (HDNS) approach. % where Stokes disturbance flow is assumed. The HDNS approach has two major drawbacks: (1) the short-range droplet-droplet interaction is not treated rigorously; (2) the finite-Reynolds number correction to the collision efficiency is not included. In this talk, using two independent numerical methods, we will develop an interface-resolved simulation approach in which the disturbance flows are directly resolved numerically, combined with a rigorous lubrication correction model for near-field droplet-droplet interaction. This multi-scale approach is first used to study the effect of finite flow Reynolds numbers on the droplet collision efficiency in still air. Our simulation results show a significant finite-Re effect on collision efficiency when the droplets are of similar sizes. Preliminary results on integrating this approach in a turbulent flow laden with droplets will also be presented. This work is partially supported by the National Science Foundation.

Magnetic flux concentrations from dynamo-generated fields

NASA Astrophysics Data System (ADS)

Jabbari, S.; Brandenburg, A.; Losada, I. R.; Kleeorin, N.; Rogachevskii, I.

2014-08-01

Context. The mean-field theory of magnetized stellar convection gives rise to two distinct instabilities: the large-scale dynamo instability, operating in the bulk of the convection zone and a negative effective magnetic pressure instability (NEMPI) operating in the strongly stratified surface layers. The latter might be important in connection with magnetic spot formation. However, as follows from theoretical analysis, the growth rate of NEMPI is suppressed with increasing rotation rates. On the other hand, recent direct numerical simulations (DNS) have shown a subsequent increase in the growth rate. Aims: We examine quantitatively whether this increase in the growth rate of NEMPI can be explained by an α2 mean-field dynamo, and whether both NEMPI and the dynamo instability can operate at the same time. Methods: We use both DNS and mean-field simulations (MFS) to solve the underlying equations numerically either with or without an imposed horizontal field. We use the test-field method to compute relevant dynamo coefficients. Results: DNS show that magnetic flux concentrations are still possible up to rotation rates above which the large-scale dynamo effect produces mean magnetic fields. The resulting DNS growth rates are quantitatively reproduced with MFS. As expected for weak or vanishing rotation, the growth rate of NEMPI increases with increasing gravity, but there is a correction term for strong gravity and large turbulent magnetic diffusivity. Conclusions: Magnetic flux concentrations are still possible for rotation rates above which dynamo action takes over. For the solar rotation rate, the corresponding turbulent turnover time is about 5 h, with dynamo action commencing in the layers beneath.

Predicting permeability of regular tissue engineering scaffolds: scaling analysis of pore architecture, scaffold length, and fluid flow rate effects.

PubMed

Rahbari, A; Montazerian, H; Davoodi, E; Homayoonfar, S

2017-02-01

The main aim of this research is to numerically obtain the permeability coefficient in the cylindrical scaffolds. For this purpose, a mathematical analysis was performed to derive an equation for desired porosity in terms of morphological parameters. Then, the considered cylindrical geometries were modeled and the permeability coefficient was calculated according to the velocity and pressure drop values based on the Darcy's law. In order to validate the accuracy of the present numerical solution, the obtained permeability coefficient was compared with the published experimental data. It was observed that this model can predict permeability with the utmost accuracy. Then, the effect of geometrical parameters including porosity, scaffold pore structure, unit cell size, and length of the scaffolds as well as entrance mass flow rate on the permeability of porous structures was studied. Furthermore, a parametric study with scaling laws analysis of sample length and mass flow rate effects on the permeability showed good fit to the obtained data. It can be concluded that the sensitivity of permeability is more noticeable at higher porosities. The present approach can be used to characterize and optimize the scaffold microstructure due to the necessity of cell growth and transferring considerations.

Upper Cervical Spinal Cord Stimulation as an Alternative Treatment in Trigeminal Neuropathy.

PubMed

Velásquez, Carlos; Tambirajoo, Kantharuby; Franceschini, Paulo; Eldridge, Paul R; Farah, Jibril Osman

2018-06-01

To describe the indications and outcomes of upper cervical cord stimulation in trigeminal neuropathy. A consecutive single-center series of patients was retrospectively reviewed. It included 12 patients with trigeminal neuropathy treated with upper cervical spinal cord stimulation. Clinical features, complications, and outcomes were reviewed. All patients had a successful trial before the definitive implantation of a spinal cord stimulator at the level of the craniocervical junction. The mean follow-up period was 4.4 years (range, 0.3-21.1 years). The average coverage in the pain zone was 72% and the median baseline, trial, and postoperative numeric rating scale (NRS) was 7, 3, and 3, respectively. When compared with the baseline, the mean reduction achieved in the postoperative average numeric rating scale was 4 points, accounting for a 57.1% pain reduction. The long-term failure rate was 25%. Despite there being enough evidence to consider upper cervical spinal cord stimulation as an effective treatment for patients with neuropathic trigeminal pain, a randomized controlled trial is needed to fully assess its indications and outcomes and compare it with other therapeutic approaches. Copyright © 2018 Elsevier Inc. All rights reserved.

The visual analogue thermometer and the graphic numeric rating scale: a comparison of self-report instruments for pain measurement in adults with burns.

PubMed

de Jong, A E E; Bremer, M; Hofland, H W C; Schuurmans, M J; Middelkoop, E; van Loey, N E E

2015-03-01

To evaluate the adequacy of pain management in burn care, pain measurement is essential. The visual analogue thermometer (VAT) and graphic numeric rating scale (GNRS) are frequently used self-report instruments for burn pain. To legitimise their interchangeable use in research and practice, we aimed to compare self-reports obtained by the VAT and GNRS, the ability of the scales to differentiate background from procedural pain, and to compare potential cutpoints. Adults with acute burns (N=319) participated in the study (67% male, mean age 40.3 years (SD 16), mean TBSA 9.9% (SD 10.4). Correlation coefficients between VAT and GNRS were 0.64 and 0.55 for, respectively, morning and afternoon background pain and 0.51 for procedural pain (p<0.01). VAT scores were lower than GNRS scores for all pain types (p<0.01). Both scales could differentiate background from procedural pain: procedural pain was higher (p<0.01). The standardized response mean was moderate (0.518 for VAT and 0.571 for GNRS). Self-reported thresholds for 'unacceptable pain' by GNRS were higher than by VAT (p<0.001). ROC analyses showed that the highest sensitivity was reached for pain score 2 for both scales. The results suggest that the instruments cannot be used interchangeably without taking their differences into account. Copyright © 2014 Elsevier Ltd and ISBI. All rights reserved.

Scale dependence of the alignment between strain rate and rotation in turbulent shear flow

NASA Astrophysics Data System (ADS)

Fiscaletti, D.; Elsinga, G. E.; Attili, A.; Bisetti, F.; Buxton, O. R. H.

2016-10-01

The scale dependence of the statistical alignment tendencies of the eigenvectors of the strain-rate tensor ei, with the vorticity vector ω , is examined in the self-preserving region of a planar turbulent mixing layer. Data from a direct numerical simulation are filtered at various length scales and the probability density functions of the magnitude of the alignment cosines between the two unit vectors | ei.ω ̂| are examined. It is observed that the alignment tendencies are insensitive to the concurrent large-scale velocity fluctuations, but are quantitatively affected by the nature of the concurrent large-scale velocity-gradient fluctuations. It is confirmed that the small-scale (local) vorticity vector is preferentially aligned in parallel with the large-scale (background) extensive strain-rate eigenvector e1, in contrast to the global tendency for ω to be aligned in parallel with the intermediate strain-rate eigenvector [Hamlington et al., Phys. Fluids 20, 111703 (2008), 10.1063/1.3021055]. When only data from regions of the flow that exhibit strong swirling are included, the so-called high-enstrophy worms, the alignment tendencies are exaggerated with respect to the global picture. These findings support the notion that the production of enstrophy, responsible for a net cascade of turbulent kinetic energy from large scales to small scales, is driven by vorticity stretching due to the preferential parallel alignment between ω and nonlocal e1 and that the strongly swirling worms are kinematically significant to this process.

Diffusion-limited mixing by incompressible flows

NASA Astrophysics Data System (ADS)

Miles, Christopher J.; Doering, Charles R.

2018-05-01

Incompressible flows can be effective mixers by appropriately advecting a passive tracer to produce small filamentation length scales. In addition, diffusion is generally perceived as beneficial to mixing due to its ability to homogenize a passive tracer. However we provide numerical evidence that, in cases where advection and diffusion are both actively present, diffusion may produce negative effects by limiting the mixing effectiveness of incompressible optimal flows. This limitation appears to be due to the presence of a limiting length scale given by a generalised Batchelor length (Batchelor 1959 J. Fluid Mech. 5 113–33). This length scale limitation may in turn affect long-term mixing rates. More specifically, we consider local-in-time flow optimisation under energy and enstrophy flow constraints with the objective of maximising the mixing rate. We observe that, for enstrophy-bounded optimal flows, the strength of diffusion may not impact the long-term mixing rate. For energy-constrained optimal flows, however, an increase in the strength of diffusion can decrease the mixing rate. We provide analytical lower bounds on mixing rates and length scales achievable under related constraints (point-wise bounded speed and rate-of-strain) by extending the work of Lin et al (2011 J. Fluid Mech. 675 465–76) and Poon (1996 Commun. PDE 21 521–39).

Does the Numeric Rating Scale (NRS) represent the optimal tool for evaluating pain in the triage process of patients presenting to the ED? Results of a muticenter study.

PubMed

Capponi, Rebecca; Loguercio, Valentina; Guerrini, Stefania; Beltrami, Giampietro; Vesprini, Andrea; Giostra, Fabrizio

2017-01-16

Pain evaluation at triage in Emergency Department (ED) is fundamental, as it influences significantly patients color code determination. Different scales have been proposed to quantify pain but they are not always reliable. This study aims to determine a) how important is for triage nurses pain measurement b) reliability of Numeric Rating Scale (NRS), the most used instrument to evaluate pain in Italian EDs, because it frequently shows higher pain scores than others scales. End point 1: a questionnaire was administered to triage nurses in some hospitals of northern Italy. End point 2: 250 patients arriving at the ED referring pain have been evaluated using, randomly, either the NRS or a fake "30-50" scale. End point 1: Triage nurses acknowledge to modify frequently the referred pain intensity. This for several reasons: nurses think that patients may exaggerate to obtain a higher priority color code; they may be influenced by specific patients categories (non EU citizens, drugs-addicted, elderly); the pain score referred by patients is not correspondent to nurse perception. End point 2: Data show that the mean value obtained with NRS is significantly (p<0.05) higher that the mean obtained with the "30-50" scale. Manipulation on pain evaluation performed by nurses might result in a dangerous underestimation of this symptom. At the same time, the use of NRS seems to allow patients to exaggerate pain perception with consequent altered attribution of color code at triage.

Application of the OMERACT filter to measures of core outcome domains in recent clinical studies of acute gout

PubMed Central

Taylor, William J; Redden, David; Dalbeth, Nicola; Schumacher, H Ralph; Edwards, N Lawrence; Simon, Lee S; John, Markus R; Essex, Margaret N; Watson, Douglas J; Evans, Robert; Rome, Keith; Singh, Jasvinder A

2014-01-01

Objective To determine the extent to which instruments that measure core outcome domains in acute gout fulfil the OMERACT filter requirements of truth, discrimination and feasibility. Methods Patient-level data from four randomised controlled trials of agents designed to treat acute gout and one observational study of acute gout were analysed. For each available measure construct validity, test-retest reliability, within-group change using effect size, between-group change using the Kruskall-Wallis statistic and repeated measures generalised estimating equations were assessed. Floor and ceiling effects were also assessed and MCID was estimated. These analyses were presented to participants at OMERACT 11 to help inform voting for possible endorsement. Results There was evidence for construct validity and discriminative ability for 3 measures of pain (0 to 4 Likert, 0 to 10 numeric rating scale, 0 to 100 mm visual analogue scale). Likewise, there appears to be sufficient evidence for a 4-point Likert scale to possess construct validity and discriminative ability for physician assessment of joint swelling and joint tenderness. There was some evidence for construct validity and within-group discriminative ability for the Health Assessment Questionnaire as a measure of activity limitations, but not for discrimination between groups allocated to different treatment. Conclusions There is sufficient evidence to support measures of pain (using Likert, numeric rating scale or visual analogue scales), joint tenderness and swelling (using Likert scale) as fulfilling the requirements of the OMERACT filter. Further research on a measure of activity limitations in acute gout clinical trials is required. PMID:24429178

Predicting Atomic Decay Rates Using an Informational-Entropic Approach

NASA Astrophysics Data System (ADS)

Gleiser, Marcelo; Jiang, Nan

2018-06-01

We show that a newly proposed Shannon-like entropic measure of shape complexity applicable to spatially-localized or periodic mathematical functions known as configurational entropy (CE) can be used as a predictor of spontaneous decay rates for one-electron atoms. The CE is constructed from the Fourier transform of the atomic probability density. For the hydrogen atom with degenerate states labeled with the principal quantum number n, we obtain a scaling law relating the n-averaged decay rates to the respective CE. The scaling law allows us to predict the n-averaged decay rate without relying on the traditional computation of dipole matrix elements. We tested the predictive power of our approach up to n = 20, obtaining an accuracy better than 3.7% within our numerical precision, as compared to spontaneous decay tables listed in the literature.

Predicting Atomic Decay Rates Using an Informational-Entropic Approach

NASA Astrophysics Data System (ADS)

Gleiser, Marcelo; Jiang, Nan

2018-02-01

We show that a newly proposed Shannon-like entropic measure of shape complexity applicable to spatially-localized or periodic mathematical functions known as configurational entropy (CE) can be used as a predictor of spontaneous decay rates for one-electron atoms. The CE is constructed from the Fourier transform of the atomic probability density. For the hydrogen atom with degenerate states labeled with the principal quantum number n, we obtain a scaling law relating the n-averaged decay rates to the respective CE. The scaling law allows us to predict the n-averaged decay rate without relying on the traditional computation of dipole matrix elements. We tested the predictive power of our approach up to n = 20, obtaining an accuracy better than 3.7% within our numerical precision, as compared to spontaneous decay tables listed in the literature.

GENERAL: Epidemic spreading on networks with vaccination

NASA Astrophysics Data System (ADS)

Shi, Hong-Jing; Duan, Zhi-Sheng; Chen, Guan-Rong; Li, Rong

2009-08-01

In this paper, a new susceptible-infected-susceptible (SIS) model on complex networks with imperfect vaccination is proposed. Two types of epidemic spreading patterns (the recovered individuals have or have not immunity) on scale-free networks are discussed. Both theoretical and numerical analyses are presented. The epidemic thresholds related to the vaccination rate, the vaccination-invalid rate and the vaccination success rate on scale-free networks are demonstrated, showing different results from the reported observations. This reveals that whether or not the epidemic can spread over a network under vaccination control is determined not only by the network structure but also by the medicine's effective duration. Moreover, for a given infective rate, the proportion of individuals to vaccinate can be calculated theoretically for the case that the recovered nodes have immunity. Finally, simulated results are presented to show how to control the disease prevalence.

Development and numerical/experimental characterization of a lab-scale flat flame reactor allowing the analysis of pulverized solid fuel devolatilization and oxidation at high heating rates

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

Lemaire, R., E-mail: romain.lemaire@mines-douai.fr; Menanteau, S.

2016-01-15

This paper deals with the thorough characterization of a new experimental test bench designed to study the devolatilization and oxidation of pulverized fuel particles in a wide range of operating conditions. This lab-scale facility is composed of a fuel feeding system, the functioning of which has been optimized by computational fluid dynamics. It allows delivering a constant and time-independent mass flow rate of fuel particles which are pneumatically transported to the central injector of a hybrid McKenna burner using a carrier gas stream that can be inert or oxidant depending on the targeted application. A premixed propane/air laminar flat flamemore » stabilized on the porous part of the burner is used to generate the hot gases insuring the heating of the central coal/carrier-gas jet with a thermal gradient similar to those found in industrial combustors (>10{sup 5} K/s). In the present work, results issued from numerical simulations performed a priori to characterize the velocity and temperature fields in the reaction chamber have been analyzed and confronted with experimental measurements carried out by coupling particle image velocimetry, thermocouple and two-color pyrometry measurements so as to validate the order of magnitude of the heating rate delivered by such a new test bench. Finally, the main features of the flat flame reactor we developed have been discussed with respect to those of another laboratory-scale system designed to study coal devolatilization at a high heating rate.« less

Development and numerical/experimental characterization of a lab-scale flat flame reactor allowing the analysis of pulverized solid fuel devolatilization and oxidation at high heating rates

NASA Astrophysics Data System (ADS)

Lemaire, R.; Menanteau, S.

2016-01-01

This paper deals with the thorough characterization of a new experimental test bench designed to study the devolatilization and oxidation of pulverized fuel particles in a wide range of operating conditions. This lab-scale facility is composed of a fuel feeding system, the functioning of which has been optimized by computational fluid dynamics. It allows delivering a constant and time-independent mass flow rate of fuel particles which are pneumatically transported to the central injector of a hybrid McKenna burner using a carrier gas stream that can be inert or oxidant depending on the targeted application. A premixed propane/air laminar flat flame stabilized on the porous part of the burner is used to generate the hot gases insuring the heating of the central coal/carrier-gas jet with a thermal gradient similar to those found in industrial combustors (>105 K/s). In the present work, results issued from numerical simulations performed a priori to characterize the velocity and temperature fields in the reaction chamber have been analyzed and confronted with experimental measurements carried out by coupling particle image velocimetry, thermocouple and two-color pyrometry measurements so as to validate the order of magnitude of the heating rate delivered by such a new test bench. Finally, the main features of the flat flame reactor we developed have been discussed with respect to those of another laboratory-scale system designed to study coal devolatilization at a high heating rate.

Plant allometry, leaf nitrogen and phosphorus stoichiometry, and interspecific trends in annual growth rates.

PubMed

Niklas, Karl J

2006-02-01

Life forms as diverse as unicellular algae, zooplankton, vascular plants, and mammals appear to obey quarter-power scaling rules. Among the most famous of these rules is Kleiber's (i.e. basal metabolic rates scale as the three-quarters power of body mass), which has a botanical analogue (i.e. annual plant growth rates scale as the three-quarters power of total body mass). Numerous theories have tried to explain why these rules exist, but each has been heavily criticized either on conceptual or empirical grounds. N,P-STOICHIOMETRY: Recent models predicting growth rates on the basis of how total cell, tissue, or organism nitrogen and phosphorus are allocated, respectively, to protein and rRNA contents may provide the answer, particularly in light of the observation that annual plant growth rates scale linearly with respect to standing leaf mass and that total leaf mass scales isometrically with respect to nitrogen but as the three-quarters power of leaf phosphorus. For example, when these relationships are juxtaposed with other allometric trends, a simple N,P-stoichiometric model successfully predicts the relative growth rates of 131 diverse C3 and C4 species. The melding of allometric and N,P-stoichiometric theoretical insights provides a robust modelling approach that conceptually links the subcellular 'machinery' of protein/ribosomal metabolism to observed growth rates of uni- and multicellular organisms. Because the operation of this 'machinery' is basic to the biology of all life forms, its allometry may provide a mechanistic explanation for the apparent ubiquity of quarter-power scaling rules.

Classical nucleation theory in the phase-field crystal model

NASA Astrophysics Data System (ADS)

Jreidini, Paul; Kocher, Gabriel; Provatas, Nikolas

2018-04-01

A full understanding of polycrystalline materials requires studying the process of nucleation, a thermally activated phase transition that typically occurs at atomistic scales. The numerical modeling of this process is problematic for traditional numerical techniques: commonly used phase-field methods' resolution does not extend to the atomic scales at which nucleation takes places, while atomistic methods such as molecular dynamics are incapable of scaling to the mesoscale regime where late-stage growth and structure formation takes place following earlier nucleation. Consequently, it is of interest to examine nucleation in the more recently proposed phase-field crystal (PFC) model, which attempts to bridge the atomic and mesoscale regimes in microstructure simulations. In this work, we numerically calculate homogeneous liquid-to-solid nucleation rates and incubation times in the simplest version of the PFC model, for various parameter choices. We show that the model naturally exhibits qualitative agreement with the predictions of classical nucleation theory (CNT) despite a lack of some explicit atomistic features presumed in CNT. We also examine the early appearance of lattice structure in nucleating grains, finding disagreement with some basic assumptions of CNT. We then argue that a quantitatively correct nucleation theory for the PFC model would require extending CNT to a multivariable theory.

Classical nucleation theory in the phase-field crystal model.

PubMed

Jreidini, Paul; Kocher, Gabriel; Provatas, Nikolas

2018-04-01

A full understanding of polycrystalline materials requires studying the process of nucleation, a thermally activated phase transition that typically occurs at atomistic scales. The numerical modeling of this process is problematic for traditional numerical techniques: commonly used phase-field methods' resolution does not extend to the atomic scales at which nucleation takes places, while atomistic methods such as molecular dynamics are incapable of scaling to the mesoscale regime where late-stage growth and structure formation takes place following earlier nucleation. Consequently, it is of interest to examine nucleation in the more recently proposed phase-field crystal (PFC) model, which attempts to bridge the atomic and mesoscale regimes in microstructure simulations. In this work, we numerically calculate homogeneous liquid-to-solid nucleation rates and incubation times in the simplest version of the PFC model, for various parameter choices. We show that the model naturally exhibits qualitative agreement with the predictions of classical nucleation theory (CNT) despite a lack of some explicit atomistic features presumed in CNT. We also examine the early appearance of lattice structure in nucleating grains, finding disagreement with some basic assumptions of CNT. We then argue that a quantitatively correct nucleation theory for the PFC model would require extending CNT to a multivariable theory.

Solution of the spatial neutral model yields new bounds on the Amazonian species richness

NASA Astrophysics Data System (ADS)

Shem-Tov, Yahav; Danino, Matan; Shnerb, Nadav M.

2017-02-01

Neutral models, in which individual agents with equal fitness undergo a birth-death-mutation process, are very popular in population genetics and community ecology. Usually these models are applied to populations and communities with spatial structure, but the analytic results presented so far are limited to well-mixed or mainland-island scenarios. Here we combine analytic results and numerics to obtain an approximate solution for the species abundance distribution and the species richness for the neutral model on continuous landscape. We show how the regional diversity increases when the recruitment length decreases and the spatial segregation of species grows. Our results are supported by extensive numerical simulations and allow one to probe the numerically inaccessible regime of large-scale systems with extremely small mutation/speciation rates. Model predictions are compared with the findings of recent large-scale surveys of tropical trees across the Amazon basin, yielding new bounds for the species richness (between 13100 and 15000) and the number of singleton species (between 455 and 690).

Rossby waves and two-dimensional turbulence in a large-scale zonal jet

NASA Technical Reports Server (NTRS)

Shepherd, Theodor G.

1987-01-01

Homogeneous barotropic beta-plane turbulence is investigated, taking into account the effects of spatial inhomogeneity in the form of a zonal shear flows. Attention is given to the case of zonal flows that are barotropically stable and of larger scale than the resulting transient eddy field. Numerical simulations reveal that large-scale zonal flows alter the picture of classical beta-plane turbulence. It is found that the disturbance field penetrates to the largest scales of motion, that the larger disturbance scales show a tendency to meridional rather than zonal anisotropy, and that the initial spectral transfer rate away from an isotropic intermediate-scale source is enhanced by the shear-induced transfer associated with straining by the zonal flow.

A model for managing sources of groundwater pollution

USGS Publications Warehouse

Gorelick, Steven M.

1982-01-01

The waste disposal capacity of a groundwater system can be maximized while maintaining water quality at specified locations by using a groundwater pollutant source management model that is based upon linear programing and numerical simulation. The decision variables of the management model are solute waste disposal rates at various facilities distributed over space. A concentration response matrix is used in the management model to describe transient solute transport and is developed using the U.S. Geological Survey solute transport simulation model. The management model was applied to a complex hypothetical groundwater system. Large-scale management models were formulated as dual linear programing problems to reduce numerical difficulties and computation time. Linear programing problems were solved using a numerically stable, available code. Optimal solutions to problems with successively longer management time horizons indicated that disposal schedules at some sites are relatively independent of the number of disposal periods. Optimal waste disposal schedules exhibited pulsing rather than constant disposal rates. Sensitivity analysis using parametric linear programing showed that a sharp reduction in total waste disposal potential occurs if disposal rates at any site are increased beyond their optimal values.

Effect of mean velocity shear on the dissipation rate of turbulent kinetic energy

NASA Technical Reports Server (NTRS)

Yoshizawa, Akira; Liou, Meng-Sing

1992-01-01

The dissipation rate of turbulent kinetic energy in incompressible turbulence is investigated using a two-scale DIA. The dissipation rate is shown to consist of two parts; one corresponds to the dissipation rate used in the current turbulence models of eddy-viscosity type, and another comes from the viscous effect that is closely connected with mean velocity shear. This result can elucidate the physical meaning of the dissipation rate used in the current turbulence models and explain part of the discrepancy in the near-wall dissipation rates between the current turbulence models and direct numerical simulation of the Navier-Stokes equation.

Computing generalized Langevin equations and generalized Fokker-Planck equations.

PubMed

Darve, Eric; Solomon, Jose; Kia, Amirali

2009-07-07

The Mori-Zwanzig formalism is an effective tool to derive differential equations describing the evolution of a small number of resolved variables. In this paper we present its application to the derivation of generalized Langevin equations and generalized non-Markovian Fokker-Planck equations. We show how long time scales rates and metastable basins can be extracted from these equations. Numerical algorithms are proposed to discretize these equations. An important aspect is the numerical solution of the orthogonal dynamics equation which is a partial differential equation in a high dimensional space. We propose efficient numerical methods to solve this orthogonal dynamics equation. In addition, we present a projection formalism of the Mori-Zwanzig type that is applicable to discrete maps. Numerical applications are presented from the field of Hamiltonian systems.

Stellar feedback in galaxies and the origin of galaxy-scale winds

NASA Astrophysics Data System (ADS)

Hopkins, Philip F.; Quataert, Eliot; Murray, Norman

2012-04-01

Feedback from massive stars is believed to play a critical role in driving galactic super-winds that enrich the intergalactic medium and shape the galaxy mass function, mass-metallicity relation and other global galaxy properties. In previous papers, we have introduced new numerical methods for implementing stellar feedback on sub-giant molecular cloud (sub-GMC) through galactic scales in numerical simulations of galaxies; the key physical processes include radiation pressure in the ultraviolet through infrared, supernovae (Type I and Type II), stellar winds ('fast' O star through 'slow' asymptotic giant branch winds), and H II photoionization. Here, we show that these feedback mechanisms drive galactic winds with outflow rates as high as ˜10-20 times the galaxy star formation rate. The mass-loading efficiency (wind mass-loss rate divided by the star formation rate) scales roughly as ? (where Vc is the galaxy circular velocity), consistent with simple momentum-conservation expectations. We use our suite of simulations to study the relative contribution of each feedback mechanism to the generation of galactic winds in a range of galaxy models, from Small Magellanic Cloud like dwarfs and Milky Way (MW) analogues to z˜ 2 clumpy discs. In massive, gas-rich systems (local starbursts and high-z galaxies), radiation pressure dominates the wind generation. By contrast, for MW-like spirals and dwarf galaxies the gas densities are much lower and sources of shock-heated gas such as supernovae and stellar winds dominate the production of large-scale outflows. In all of our models, however, the winds have a complex multiphase structure that depends on the interaction between multiple feedback mechanisms operating on different spatial scales and time-scales: any single feedback mechanism fails to reproduce the winds observed. We use our simulations to provide fitting functions to the wind mass loading and velocities as a function of galaxy properties, for use in cosmological simulations and semi-analytic models. These differ from typically adopted formulae with an explicit dependence on the gas surface density that can be very important in both low-density dwarf galaxies and high-density gas-rich galaxies.

Annual Research Briefs, 1998

NASA Technical Reports Server (NTRS)

Spinks, Debra (Compiler)

1998-01-01

The topics contained in this progress report are direct numerical simulation of turbulent non-premixed combustion with realistic chemistry; LES of non-premixed turbulent reacting flows with conditional source term estimation; measurements of the three-dimensional scalar dissipation rate in gas-phase planar turbulent jets; direct simulation of a jet diffusion flame; on the use of interpolating wavelets in the direct numerical simulation of combustion; on the use of a dynamically adaptive wavelet collocation algorithm in DNS (direct numerical simulation) of non-premixed turbulent combustion; 2D simulations of Hall thrusters; computation of trailing-edge noise at low mach number using LES and acoustic analogy; weakly nonlinear modeling of the early stages of bypass transition; interactions between freestream turbulence and boundary layers; interfaces at the outer boundaries of turbulent motions; largest scales of turbulent wall flows; the instability of streaks in near-wall turbulence; an implementation of the v(sup 2) - f model with application to transonic flows; heat transfer predictions in cavities; a structure-based model with stropholysis effects; modeling a confined swirling coaxial jet; subgrid-scale models based on incremental unknowns for large eddy simulations; subgrid scale modeling taking the numerical error into consideration; towards a near-wall model for LES of a separated diffuser flow; on the feasibility of merging LES with RANS (Reynolds Averaging Numerical simulation) for the near-wall region of attached turbulent flows; large-eddy simulation of a separated boundary layer; numerical study of a channel flow with variable properties; on the construction of high order finite difference schemes on non-uniform meshes with good conservation properties; development of immersed boundary methods for complex geometries; and particle methods for micro and macroscale flow simulations.

Emergence of Multiscaling in a Random-Force Stirred Fluid

NASA Astrophysics Data System (ADS)

Yakhot, Victor; Donzis, Diego

2017-07-01

We consider the transition to strong turbulence in an infinite fluid stirred by a Gaussian random force. The transition is defined as a first appearance of anomalous scaling of normalized moments of velocity derivatives (dissipation rates) emerging from the low-Reynolds-number Gaussian background. It is shown that, due to multiscaling, strongly intermittent rare events can be quantitatively described in terms of an infinite number of different "Reynolds numbers" reflecting a multitude of anomalous scaling exponents. The theoretically predicted transition disappears at Rλ≤3 . The developed theory is in quantitative agreement with the outcome of large-scale numerical simulations.

Postprocessing Algorithm for Driving Conventional Scanning Tunneling Microscope at Fast Scan Rates.

PubMed

Zhang, Hao; Li, Xianqi; Chen, Yunmei; Park, Jewook; Li, An-Ping; Zhang, X-G

2017-01-01

We present an image postprocessing framework for Scanning Tunneling Microscope (STM) to reduce the strong spurious oscillations and scan line noise at fast scan rates and preserve the features, allowing an order of magnitude increase in the scan rate without upgrading the hardware. The proposed method consists of two steps for large scale images and four steps for atomic scale images. For large scale images, we first apply for each line an image registration method to align the forward and backward scans of the same line. In the second step we apply a "rubber band" model which is solved by a novel Constrained Adaptive and Iterative Filtering Algorithm (CIAFA). The numerical results on measurement from copper(111) surface indicate the processed images are comparable in accuracy to data obtained with a slow scan rate, but are free of the scan drift error commonly seen in slow scan data. For atomic scale images, an additional first step to remove line-by-line strong background fluctuations and a fourth step of replacing the postprocessed image by its ranking map as the final atomic resolution image are required. The resulting image restores the lattice image that is nearly undetectable in the original fast scan data.

Influence of different propellant systems on ablation of EPDM insulators in overload state

NASA Astrophysics Data System (ADS)

Guan, Yiwen; Li, Jiang; Liu, Yang; Xu, Tuanwei

2018-04-01

This study examines the propellants used in full-scale solid rocket motors (SRM) and investigates how insulator ablation is affected by two propellant formulations (A and B) during flight overload conditions. An experimental study, theoretical analysis, and numerical simulations were performed to discover the intrinsic causes of insulator ablation rates from the perspective of lab-scaled ground-firing tests, the decoupling of thermochemical ablation, and particle erosion. In addition, the difference in propellant composition, and the insulator charring layer microstructure were analyzed. Results reveal that the degree of insulator ablation is positively correlated with the propellant burn rate, particle velocity, and aggregate concentrations during the condensed phase. A lower ratio of energetic additive material in the AP oxidizer of the propellant is promising for the reduction in particle size and increase in the burn rate and pressure index. However, the overall higher velocity of a two-phase flow causes severe erosion of the insulation material. While the higher ratio of energetic additive to the AP oxidizer imparts a smaller ablation rate to the insulator (under lab-scale test conditions), the slag deposition problem in the combustion chamber may cause catastrophic consequences for future large full-scale SRM flight experiments.

A Transition in the Cumulative Reaction Rate of Two Species Diffusion with Bimolecular Reaction

NASA Astrophysics Data System (ADS)

Rajaram, Harihar; Arshadi, Masoud

2015-04-01

Diffusion and bimolecular reaction between two initially separated reacting species is a prototypical small-scale description of reaction induced by transverse mixing. It is also relevant to diffusion controlled transport regimes as encountered in low-permeability matrix blocks in fractured media. In previous work, the reaction-diffusion problem has been analyzed as a Stefan problem involving a distinct moving boundary (reaction front), which predicts that front motion scales as √t, and the cumulative reaction rate scales as 1/√t-. We present a general non-dimensionalization of the problem and a perturbation analysis to show that there is an early time regime where the cumulative reaction rate scales as √t- rather than 1/√t. The duration of this early time regime (where the cumulative rate is kinetically rather than diffusion controlled) depends on the rate parameter, in a manner that is consistently predicted by our non-dimensionalization. We also present results on the scaling of the reaction front width. We present numerical simulations in homogeneous and heterogeneous porous media to demonstrate the limited influence of heterogeneity on the behavior of the reaction-diffusion system. We illustrate applications to the practical problem of in-situ chemical oxidation of TCE and PCE by permanganate, which is employed to remediate contaminated sites where the DNAPLs are largely dissolved in the rock matrix.

Scaling Relations for Intercalation Induced Damage in Electrodes

DOE PAGES

Chen, Chien-Fan; Barai, Pallab; Smith, Kandler; ...

2016-04-02

Mechanical degradation, owing to intercalation induced stress and microcrack formation, is a key contributor to the electrode performance decay in lithium-ion batteries (LIBs). The stress generation and formation of microcracks are caused by the solid state diffusion of lithium in the active particles. Here in this work, scaling relations are constructed for diffusion induced damage in intercalation electrodes based on an extensive set of numerical experiments with a particle-level description of microcrack formation under disparate operating and cycling conditions, such as temperature, particle size, C-rate, and drive cycle. The microcrack formation and evolution in active particles is simulated based onmore » a stochastic methodology. A reduced order scaling law is constructed based on an extensive set of data from the numerical experiments. The scaling relations include combinatorial constructs of concentration gradient, cumulative strain energy, and microcrack formation. Lastly, the reduced order relations are further employed to study the influence of mechanical degradation on cell performance and validated against the high order model for the case of damage evolution during variable current vehicle drive cycle profiles.« less

Diurnal Variation in the Basal Emission Rate of Isoprene

Treesearch

Jennifer Funk; Clive G. Jones; Christine J. Baker; Heather M. Fuller; Christian P. Giardina; Manuel T. Lerdua

2003-01-01

Isoprene is emitted from numerous plant species and profoundly influences tropospheric chemistry. Due to the short lifetime of isoprene in the atmosphere, developing an understanding of emission patterns at small time scales is essential for modeling regional atmospheric chemistry processes. Previous studies suggest that diurnal fluctuations in isoprene emission may be...

How IRT Can Solve Problems of Ipsative Data in Forced-Choice Questionnaires

ERIC Educational Resources Information Center

Brown, Anna; Maydeu-Olivares, Alberto

2013-01-01

In multidimensional forced-choice (MFC) questionnaires, items measuring different attributes are presented in blocks, and participants have to rank order the items within each block (fully or partially). Such comparative formats can reduce the impact of numerous response biases often affecting single-stimulus items (aka rating or Likert scales).…

Epidural labour analgesia using Bupivacaine and Clonidine

PubMed Central

Syal, K; Dogra, RK; Ohri, A; Chauhan, G; Goel, A

2011-01-01

Background: To compare the effects of addition of Clonidine (60 μg) to Epidural Bupivacaine (0.125%) for labour analgesia, with regard to duration of analgesia, duration of labour, ambulation, incidence of instrumentation and caesarean section, foetal outcome, patient satisfaction and side effects. Patients & Methods: On demand, epidural labour analgesia was given to 50 nulliparous healthy term parturients (cephalic presentation), divided in two groups randomly. Group I received bupivacaine (0.125%) alone, whereas Group II received bupivacaine (0.125%) along with Clonidine (60 μg). 10 ml of 0.125% bupivacaine was injected as first dose and further doses titrated with patient relief (Numerical Rating Scale <3). Top ups were given whenever Numerical Rating Scale went above 5. Results: There was statistically significant prolongation of duration of analgesia in Group II, with no difference in duration of labour, ambulation, incidence of instrumentation and caesarean section or foetal outcome. Also clonidine gave dose sparing effect to bupivacaine and there was better patient satisfaction without any significant side effects in Group II. Conclusion: Clonidine is a useful adjunct to bupivacaine for epidural labour analgesia and can be considered as alternative to opioids. PMID:21804714

Canonical Nonlinear Viscous Core Solution in pipe and elliptical geometry

NASA Astrophysics Data System (ADS)

Ozcakir, Ozge

2016-11-01

In an earlier paper (Ozcakir et al. (2016)), two new nonlinear traveling wave solutions were found with collapsing structure towards the center of the pipe as Reynolds number R -> ∞ , which were called Nonlinear Viscous Core (NVC) states. Asymptotic scaling arguments suggested that the NVC state collapse rate scales as R - 1 / 4 where axial, radial and azimuthal velocity perturbations from Hagen-Poiseuille flow scale as R - 1 / 2, R - 3 / 4 and R - 3 / 4 respectively, while (1 - c) = O (R - 1 / 2) where c is the traveling wave speed. The theoretical scaling results were roughly consistent with full Navier-Stokes numerical computations in the range 105 < R <106 . In the present paper, through numerical solutions, we show that the scaled parameter free canonical differential equations derived in Ozcakir et al. (2016) indeed has solution that satisfies requisite far-field conditions. We also show that these are in good agreement with full Navier-Stokes calculations in a larger R range than previously calculated (R upto 106). Further, we extend our study to NVC states for pipes with elliptical cross-section and identify similar canonical structure in these cases. National Science Foundation NSF-DMS-1515755, EPSRC Grant EP/1037948/1.

Musculoskeletal management of a patient with a history of chronic ankle sprains: identifying rupture of peroneal brevis and peroneal longus with diagnostic ultrasonography.

PubMed

Bruin, Dick B; von Piekartz, Harry

2014-09-01

The purpose of this case report is to describe the use of mobilization and eccentric exercise training for a patient with ankle pain and a history of chronic ankle sprains and discuss the course of diagnostic decision making when the patient did not respond to care. A 48-year-old police officer who had sustained multiple ankle sprains throughout his life presented with pain and restriction in his ability to walk, run, and work. The Global Rating of Change Scale score was - 6, the Numeric Pain Rating Scale score was 7/10, and the Lower Extremity Functional Scale score was - 33. Palpation of the peroneus longus and brevis muscles and inversion with overpressure reproduced the chief concern (Numeric Pain Rating Scale 7/10). The patient was initially diagnosed with chronic peroneal tendinopathy. Treatment included lateral translation mobilization of the talocrural joint combined with eccentric exercise using an elastic band for the peroneal muscles. The patient reported improvement in pain and function during the course of intervention but not as rapidly as expected. Therefore, follow-up ultrasonographic imaging and radiography were performed. These studies revealed partial rupture of the peroneal brevis muscle and total rupture of the peroneal longus muscle. A patient with long-term concerns of the foot complex with a diagnosis of peroneal tendinopathy showed slight improvement with eccentric exercises combined with manual therapy of the talocrural joint. After a course of treatment but minimal response, a diagnosis of tendon rupture was confirmed with diagnostic ultrasonography. Clinicians should be aware that when injuries do not improve with care, tendon rupture should be considered.

Structural and Practical Identifiability Issues of Immuno-Epidemiological Vector-Host Models with Application to Rift Valley Fever.

PubMed

Tuncer, Necibe; Gulbudak, Hayriye; Cannataro, Vincent L; Martcheva, Maia

2016-09-01

In this article, we discuss the structural and practical identifiability of a nested immuno-epidemiological model of arbovirus diseases, where host-vector transmission rate, host recovery, and disease-induced death rates are governed by the within-host immune system. We incorporate the newest ideas and the most up-to-date features of numerical methods to fit multi-scale models to multi-scale data. For an immunological model, we use Rift Valley Fever Virus (RVFV) time-series data obtained from livestock under laboratory experiments, and for an epidemiological model we incorporate a human compartment to the nested model and use the number of human RVFV cases reported by the CDC during the 2006-2007 Kenya outbreak. We show that the immunological model is not structurally identifiable for the measurements of time-series viremia concentrations in the host. Thus, we study the non-dimensionalized and scaled versions of the immunological model and prove that both are structurally globally identifiable. After fixing estimated parameter values for the immunological model derived from the scaled model, we develop a numerical method to fit observable RVFV epidemiological data to the nested model for the remaining parameter values of the multi-scale system. For the given (CDC) data set, Monte Carlo simulations indicate that only three parameters of the epidemiological model are practically identifiable when the immune model parameters are fixed. Alternatively, we fit the multi-scale data to the multi-scale model simultaneously. Monte Carlo simulations for the simultaneous fitting suggest that the parameters of the immunological model and the parameters of the immuno-epidemiological model are practically identifiable. We suggest that analytic approaches for studying the structural identifiability of nested models are a necessity, so that identifiable parameter combinations can be derived to reparameterize the nested model to obtain an identifiable one. This is a crucial step in developing multi-scale models which explain multi-scale data.

Phantom motor execution facilitated by machine learning and augmented reality as treatment for phantom limb pain: a single group, clinical trial in patients with chronic intractable phantom limb pain.

PubMed

Ortiz-Catalan, Max; Guðmundsdóttir, Rannveig A; Kristoffersen, Morten B; Zepeda-Echavarria, Alejandra; Caine-Winterberger, Kerstin; Kulbacka-Ortiz, Katarzyna; Widehammar, Cathrine; Eriksson, Karin; Stockselius, Anita; Ragnö, Christina; Pihlar, Zdenka; Burger, Helena; Hermansson, Liselotte

2016-12-10

Phantom limb pain is a debilitating condition for which no effective treatment has been found. We hypothesised that re-engagement of central and peripheral circuitry involved in motor execution could reduce phantom limb pain via competitive plasticity and reversal of cortical reorganisation. Patients with upper limb amputation and known chronic intractable phantom limb pain were recruited at three clinics in Sweden and one in Slovenia. Patients received 12 sessions of phantom motor execution using machine learning, augmented and virtual reality, and serious gaming. Changes in intensity, frequency, duration, quality, and intrusion of phantom limb pain were assessed by the use of the numeric rating scale, the pain rating index, the weighted pain distribution scale, and a study-specific frequency scale before each session and at follow-up interviews 1, 3, and 6 months after the last session. Changes in medication and prostheses were also monitored. Results are reported using descriptive statistics and analysed by non-parametric tests. The trial is registered at ClinicalTrials.gov, number NCT02281539. Between Sept 15, 2014, and April 10, 2015, 14 patients with intractable chronic phantom limb pain, for whom conventional treatments failed, were enrolled. After 12 sessions, patients showed statistically and clinically significant improvements in all metrics of phantom limb pain. Phantom limb pain decreased from pre-treatment to the last treatment session by 47% (SD 39; absolute mean change 1·0 [0·8]; p=0·001) for weighted pain distribution, 32% (38; absolute mean change 1·6 [1·8]; p=0·007) for the numeric rating scale, and 51% (33; absolute mean change 9·6 [8·1]; p=0·0001) for the pain rating index. The numeric rating scale score for intrusion of phantom limb pain in activities of daily living and sleep was reduced by 43% (SD 37; absolute mean change 2·4 [2·3]; p=0·004) and 61% (39; absolute mean change 2·3 [1·8]; p=0·001), respectively. Two of four patients who were on medication reduced their intake by 81% (absolute reduction 1300 mg, gabapentin) and 33% (absolute reduction 75 mg, pregabalin). Improvements remained 6 months after the last treatment. Our findings suggest potential value in motor execution of the phantom limb as a treatment for phantom limb pain. Promotion of phantom motor execution aided by machine learning, augmented and virtual reality, and gaming is a non-invasive, non-pharmacological, and engaging treatment with no identified side-effects at present. Promobilia Foundation, VINNOVA, Jimmy Dahlstens Fond, PicoSolve, and Innovationskontor Väst. Copyright © 2016 Elsevier Ltd. All rights reserved.

Radiative Extinction of Gaseous Spherical Diffusion Flames in Microgravity

NASA Technical Reports Server (NTRS)

Santa, K. J.; Chao, B. H.; Sunderland, P. B.; Urban, D. L.; Stocker, D. P.; Axelbaum, R. L.

2007-01-01

Radiative extinction of spherical diffusion flames was investigated experimentally and numerically. The experiments involved microgravity spherical diffusion flames burning ethylene and propane at 0.98 bar. Both normal (fuel flowing into oxidizer) and inverse (oxidizer flowing into fuel) flames were studied, with nitrogen supplied to either the fuel or the oxygen. Flame conditions were chosen to ensure that the flames extinguished within the 2.2 s of available test time; thus extinction occurred during unsteady flame conditions. Diagnostics included color video and thin-filament pyrometry. The computations, which simulated flow from a porous sphere into a quiescent environment, included detailed chemistry, transport and radiation, and yielded transient results. Radiative extinction was observed experimentally and simulated numerically. Extinction time, peak temperature, and radiative loss fraction were found to be independent of flow rate except at very low flow rates. Radiative heat loss was dominated by the combustion products downstream of the flame and was found to scale with flame surface area, not volume. For large transient flames the heat release rate also scaled with surface area and thus the radiative loss fraction was largely independent of flow rate. Peak temperatures at extinction onset were about 1100 K, which is significantly lower than for kinetic extinction. One observation of this work is that while radiative heat losses can drive transient extinction, this is not because radiative losses are increasing with time (flame size) but rather because the heat release rate is falling off as the temperature drops.

Theory of rumour spreading in complex social networks

NASA Astrophysics Data System (ADS)

Nekovee, M.; Moreno, Y.; Bianconi, G.; Marsili, M.

2007-01-01

We introduce a general stochastic model for the spread of rumours, and derive mean-field equations that describe the dynamics of the model on complex social networks (in particular, those mediated by the Internet). We use analytical and numerical solutions of these equations to examine the threshold behaviour and dynamics of the model on several models of such networks: random graphs, uncorrelated scale-free networks and scale-free networks with assortative degree correlations. We show that in both homogeneous networks and random graphs the model exhibits a critical threshold in the rumour spreading rate below which a rumour cannot propagate in the system. In the case of scale-free networks, on the other hand, this threshold becomes vanishingly small in the limit of infinite system size. We find that the initial rate at which a rumour spreads is much higher in scale-free networks than in random graphs, and that the rate at which the spreading proceeds on scale-free networks is further increased when assortative degree correlations are introduced. The impact of degree correlations on the final fraction of nodes that ever hears a rumour, however, depends on the interplay between network topology and the rumour spreading rate. Our results show that scale-free social networks are prone to the spreading of rumours, just as they are to the spreading of infections. They are relevant to the spreading dynamics of chain emails, viral advertising and large-scale information dissemination algorithms on the Internet.

Pain locations in the postoperative period after cardiac surgery: Chronology of pain and response to treatment.

PubMed

Roca, J; Valero, R; Gomar, C

Postoperative pain after cardiac surgery (CS) can be generated at several foci besides the sternotomy. Prospective descriptive longitudinal study on the chronological evolution of pain in 11 sites after CS including consecutive patients submitted to elective CS through sternotomy. The primary endpoints were to establish the main origins of pain, and to describe its chronological evolution during the first postoperative week. Secondary endpoints were to describe pain characteristics in the sternotomy area and to correlate pain intensity with other variables. Numerical Pain Rating Scale from 0 to 10 at rest and at movement on postoperative days 1, 2, 4 and 6. Numerical Pain Rating Scale>3 was considered moderate pain. Statistical analysis consisted in Mann-Whitney U-test, a Chi-squared, a Fisher exact text and Pearson's correlations. Forty-seven patients were enrolled. In 4 of 11 locations pain was reported as Numerical Pain Rating Scale>3 (sternotomy, oropharynx, saphenectomy and musculoskeletal pain in the back and shoulders). Maximum intensity of pain on postoperative days 1 and 2 was reported in the sternotomy area, while on postoperative days 4 and 6 it was reported at the saphenectomy. Pain at rest and at movement differed considerably in the sternotomy, saphenectomy and oropharynx. Pain at back and shoulders and at central venous catheter entry were not influenced by movement. Pain in the sternotomy was mainly described as oppressive. Patients with arthrosis and younger patients presented higher intensity of pain (P=.004; P=.049, respectively). Four locations were identified as the main sources of pain after CS: sternotomy, oropharynx, saphenectomy, and back and shoulders. Pain in different focuses presented differences in chronologic evolution and was differently influenced by movement. Copyright © 2017 Sociedad Española de Anestesiología, Reanimación y Terapéutica del Dolor. Publicado por Elsevier España, S.L.U. All rights reserved.

An upscaled rate law for magnesite dissolution in heterogeneous porous media

NASA Astrophysics Data System (ADS)

Wen, Hang; Li, Li

2017-08-01

Spatial heterogeneity in natural subsurface systems governs water fluxes and residence time in reactive zones and therefore determines effective rates of mineral dissolution. Extensive studies have documented mineral dissolution rates in natural systems, although a general rate law has remain elusive. Here we fill this gap by answering two questions: (1) how and to what extent does spatial heterogeneity affect water residence time and effectively-dissolving surface area? (2) what is the upscaled rate law that quantifies effective dissolution rates in natural, heterogeneous media? With data constraints from experimental work, 240 Monte-Carlo numerical experiments of magnesite dissolution within quartz matrix were run with spatial distributions characterized by a range of permeability variance σ2lnκ (0.5-6.0) and correlation length (2-50 cm). Although the total surface area and global residence time (τa) are the same in all experiments, the water fluxes through reactive magnesite zones varies between 0.7 and 72.8% of the total water fluxes. Highly heterogeneous media with large σ2lnκ and long λ divert water mostly into non-reactive preferential flow paths, therefore bypassing and minimizing flow in low permeability magnesite zones. As a result, the water residence time in magnesite zones (i.e., reactive residence time τa,r) is long and magnesite dissolution quickly reaches local equilibrium, which leads to small effective surface area and low dissolution rates. Magnesite dissolution rates in heterogeneous media vary from 2.7 to 100% of the rates in the equivalent homogeneous media, with effectively-dissolving surface area varying from 0.18 to 6.83 m2 (out of 51.71 m2 total magnesite surface area). Based on 240 numerical experiments and 45 column experiments, a general upscaled rate law in heterogeneous media, RMgCO3,ht =kAe,hm(1 - exp(-τa/τa,r))α, was derived to quantify effective dissolution rates. The dissolution rates in heterogeneous media are a function of the rate constants k being those measured under well-mixed conditions, effective surface area in equivalent homogeneous media Ae,hm, and the heterogeneity factor (1 - exp(-τa/τa,r))α. The heterogeneity factor quantify heterogeneity effects and depends on the relative magnitude of global residence time (τa) and reactive residence time (τa,r), as well as the shape factor α(= 5 σlnκ2) of the gamma distribution for reactive residence times. Exponential forms of rate laws have been used at the micro-scale describing direct interactions among water and mineral surface, and at the catchment scale describing weathering rates and concentration-discharge relationships. These observations highlight the key role of mineral-water contact time in determining dissolution rates at different scales. This work also emphasizes the importance of critical interfaces between reactive and non-reactive zones as determined by the details of spatial patterns and effective surface area as a scaling factor that quantifies dissolution rates in heterogeneous media across scales.

Reynolds number scaling of velocity increments in isotropic turbulence.

PubMed

Iyer, Kartik P; Sreenivasan, Katepalli R; Yeung, P K

2017-02-01

Using the largest database of isotropic turbulence available to date, generated by the direct numerical simulation (DNS) of the Navier-Stokes equations on an 8192^{3} periodic box, we show that the longitudinal and transverse velocity increments scale identically in the inertial range. By examining the DNS data at several Reynolds numbers, we infer that the contradictory results of the past on the inertial-range universality are artifacts of low Reynolds number and residual anisotropy. We further show that both longitudinal and transverse velocity increments scale on locally averaged dissipation rate, just as postulated by Kolmogorov's refined similarity hypothesis, and that, in isotropic turbulence, a single independent scaling adequately describes fluid turbulence in the inertial range.

Polyelectrolyte scaling laws for microgel yielding near jamming.

PubMed

Bhattacharjee, Tapomoy; Kabb, Christopher P; O'Bryan, Christopher S; Urueña, Juan M; Sumerlin, Brent S; Sawyer, W Gregory; Angelini, Thomas E

2018-02-28

Micro-scale hydrogel particles, known as microgels, are used in industry to control the rheology of numerous different products, and are also used in experimental research to study the origins of jamming and glassy behavior in soft-sphere model systems. At the macro-scale, the rheological behaviour of densely packed microgels has been thoroughly characterized; at the particle-scale, careful investigations of jamming, yielding, and glassy-dynamics have been performed through experiment, theory, and simulation. However, at low packing fractions near jamming, the connection between microgel yielding phenomena and the physics of their constituent polymer chains has not been made. Here we investigate whether basic polymer physics scaling laws predict macroscopic yielding behaviours in packed microgels. We measure the yield stress and cross-over shear-rate in several different anionic microgel systems prepared at packing fractions just above the jamming transition, and show that our data can be predicted from classic polyelectrolyte physics scaling laws. We find that diffusive relaxations of microgel deformation during particle re-arrangements can predict the shear-rate at which microgels yield, and the elastic stress associated with these particle deformations predict the yield stress.

Effects of Scale, Question Location, Order of Response Alternatives, and Season on Self-Reported Noise Annoyance Using ICBEN Scales: A Field Experiment.

PubMed

Brink, Mark; Schreckenberg, Dirk; Vienneau, Danielle; Cajochen, Christian; Wunderli, Jean-Marc; Probst-Hensch, Nicole; Röösli, Martin

2016-11-23

The type of noise annoyance scale and aspects of its presentation such as response format or location within a questionnaire and other contextual factors may affect self-reported noise annoyance. By means of a balanced experimental design, the effect of type of annoyance question and corresponding scale (5-point verbal vs. 11-point numerical ICBEN (International Commission on Biological Effects of Noise) scale), presentation order of scale points (ascending vs. descending), question location (early vs. late within the questionnaire), and survey season (autumn vs. spring) on reported road traffic noise annoyance was investigated in a postal survey with a stratified random sample of 2386 Swiss residents. Our results showed that early appearance of annoyance questions was significantly associated with higher annoyance scores. Questionnaires filled out in autumn were associated with a significantly higher annoyance rating than in the springtime. No effect was found for the order of response alternatives. Standardized average annoyance scores were slightly higher using the 11-point numerical scale whereas the percentage of highly annoyed respondents was higher based on the 5-point scale, using common cutoff points. In conclusion, placement and presentation of annoyance questions within a questionnaire, as well as the time of the year a survey is carried out, have small but demonstrable effects on the degree of self-reported noise annoyance.

Effects of Scale, Question Location, Order of Response Alternatives, and Season on Self-Reported Noise Annoyance Using ICBEN Scales: A Field Experiment

PubMed Central

Brink, Mark; Schreckenberg, Dirk; Vienneau, Danielle; Cajochen, Christian; Wunderli, Jean-Marc; Probst-Hensch, Nicole; Röösli, Martin

2016-01-01

The type of noise annoyance scale and aspects of its presentation such as response format or location within a questionnaire and other contextual factors may affect self-reported noise annoyance. By means of a balanced experimental design, the effect of type of annoyance question and corresponding scale (5-point verbal vs. 11-point numerical ICBEN (International Commission on Biological Effects of Noise) scale), presentation order of scale points (ascending vs. descending), question location (early vs. late within the questionnaire), and survey season (autumn vs. spring) on reported road traffic noise annoyance was investigated in a postal survey with a stratified random sample of 2386 Swiss residents. Our results showed that early appearance of annoyance questions was significantly associated with higher annoyance scores. Questionnaires filled out in autumn were associated with a significantly higher annoyance rating than in the springtime. No effect was found for the order of response alternatives. Standardized average annoyance scores were slightly higher using the 11-point numerical scale whereas the percentage of highly annoyed respondents was higher based on the 5-point scale, using common cutoff points. In conclusion, placement and presentation of annoyance questions within a questionnaire, as well as the time of the year a survey is carried out, have small but demonstrable effects on the degree of self-reported noise annoyance. PMID:27886110

Predicting SF-6D utility scores from the Oswestry disability index and numeric rating scales for back and leg pain.

PubMed

Carreon, Leah Y; Glassman, Steven D; McDonough, Christine M; Rampersaud, Raja; Berven, Sigurd; Shainline, Michael

2009-09-01

Cross-sectional cohort. The purpose of this study is to provide a model to allow estimation of utility from the Short Form (SF)-6D using data from the Oswestry Disability Index (ODI), Back Pain Numeric Rating Scale (BPNRS), and the Leg Pain Numeric Rating Scale (LPNRS). Cost-utility analysis provides important information about the relative value of interventions and requires a measure of utility not often available from clinical trial data. The ODI and numeric rating scales for back (BPNRS) and leg pain (LPNRS), are widely used disease-specific measures for health-related quality of life in patients with lumbar degenerative disorders. The purpose of this study is to provide a model to allow estimation of utility from the SF-6D using data from the ODI, BPNRS, and the LPNRS. SF-36, ODI, BPNRS, and LPNRS were prospectively collected before surgery, at 12 and 24 months after surgery in 2640 patients undergoing lumbar fusion for degenerative disorders. Spearman correlation coefficients for paired observations from multiple time points between ODI, BPNRS, and LPNRS, and SF-6D utility scores were determined. Regression modeling was done to compute the SF-6D score from the ODI, BPNRS, and LPNRS. Using a separate, independent dataset of 2174 patients in which actual SF-6D and ODI scores were available, the SF-6D was estimated for each subject and compared to their actual SF-6D. In the development sample, the mean age was 52.5 +/- 15 years and 34% were male. In the validation sample, the mean age was 52.9 +/- 14.2 years and 44% were male. Correlations between the SF-6D and the ODI, BPNRS, and LPNRS were statistically significant (P < 0.0001) with correlation coefficients of 0.82, 0.78, and 0.72, respectively. The regression equation using ODI, BPNRS,and LPNRS to predict SF-6D had an R of 0.69 and a root mean square error of 0.076. The model using ODI alone had an R of 0.67 and a root mean square error of 0.078. The correlation coefficient between the observed and estimated SF-6D score was 0.80. In the validation analysis, there was no statistically significant difference (P = 0.11) between actual mean SF-6D (0.55 +/- 0.12) and the estimated mean SF-6D score (0.55 +/- 0.10) using the ODI regression model. This regression-based algorithm may be used to predict SF-6D scores in studies of lumbar degenerative disease that have collected ODI but not utility scores.

Moderators of Effects of Internet-Delivered Exercise and Pain Coping Skills Training for People With Knee Osteoarthritis: Exploratory Analysis of the IMPACT Randomized Controlled Trial.

PubMed

Lawford, Belinda J; Hinman, Rana S; Kasza, Jessica; Nelligan, Rachel; Keefe, Francis; Rini, Christine; Bennell, Kim L

2018-05-09

Internet-delivered exercise, education, and pain coping skills training is effective for people with knee osteoarthritis, yet it is not clear whether this treatment is better suited to particular subgroups of patients. The aim was to explore demographic and clinical moderators of the effect of an internet-delivered intervention on changes in pain and physical function in people with knee osteoarthritis. Exploratory analysis of data from 148 people with knee osteoarthritis who participated in a randomized controlled trial comparing internet-delivered exercise, education, and pain coping skills training to internet-delivered education alone. Primary outcomes were changes in knee pain while walking (11-point Numerical Rating Scale) and physical function (Western Ontario and McMaster Universities Osteoarthritis Index function subscale) at 3 and 9 months. Separate regression models were fit with moderator variables (age, gender, expectations of outcomes, self-efficacy [pain], education, employment status, pain catastrophizing, body mass index) and study group as covariates, including an interaction between the two. Participants in the intervention group who were currently employed had significantly greater reductions in pain at 3 months than similar participants in the control group (between-group difference: mean 2.38, 95% CI 1.52-3.23 Numerical Rating Scale units; interaction P=.02). Additionally, within the intervention group, pain at 3 months reduced by mean 0.53 (95% CI 0.28-0.78) Numerical Rating Scale units per unit increase in baseline self-efficacy for managing pain compared to mean 0.11 Numerical Rating Scale units (95% CI -0.13 to 0.35; interaction P=.02) for the control group. People who were employed and had higher self-efficacy at baseline were more likely to experience greater improvements in pain at 3 months after an internet-delivered exercise, education, and pain coping skills training program. There was no evidence of a difference in the effect across gender, educational level, expectation of treatment outcome, or across age, body mass index, or tendency to catastrophize pain. Findings support the effectiveness of internet-delivered care for a wide range of people with knee osteoarthritis, but future confirmatory research is needed. Australian New Zealand Clinical Trials Registry ACTRN12614000243617; https://www.anzctr.org.au/Trial/Registration/TrialReview.aspx?id=365812&isReview=true (Archived by WebCite at http://www.webcitation.org/6z466oTPs). ©Belinda J Lawford, Rana S Hinman, Jessica Kasza, Rachel Nelligan, Francis Keefe, Christine Rini, Kim L Bennell. Originally published in the Journal of Medical Internet Research (http://www.jmir.org), 09.05.2018.

Pain point system scale (PPSS): a method for postoperative pain estimation in retrospective studies

PubMed Central

Gkotsi, Anastasia; Petsas, Dimosthenis; Sakalis, Vasilios; Fotas, Asterios; Triantafyllidis, Argyrios; Vouros, Ioannis; Saridakis, Evangelos; Salpiggidis, Georgios; Papathanasiou, Athanasios

2012-01-01

Purpose Pain rating scales are widely used for pain assessment. Nevertheless, a new tool is required for pain assessment needs in retrospective studies. Methods The postoperative pain episodes, during the first postoperative day, of three patient groups were analyzed. Each pain episode was assessed by a visual analog scale, numerical rating scale, verbal rating scale, and a new tool – pain point system scale (PPSS) – based on the analgesics administered. The type of analgesic was defined based on the authors’ clinic protocol, patient comorbidities, pain assessment tool scores, and preadministered medications by an artificial neural network system. At each pain episode, each patient was asked to fill the three pain scales. Bartlett’s test and Kaiser–Meyer–Olkin criterion were used to evaluate sample sufficiency. The proper scoring system was defined by varimax rotation. Spearman’s and Pearson’s coefficients assessed PPSS correlation to the known pain scales. Results A total of 262 pain episodes were evaluated in 124 patients. The PPSS scored one point for each dose of paracetamol, three points for each nonsteroidal antiinflammatory drug or codeine, and seven points for each dose of opioids. The correlation between the visual analog scale and PPSS was found to be strong and linear (rho: 0.715; P < 0.001 and Pearson: 0.631; P < 0.001). Conclusion PPSS correlated well with the known pain scale and could be used safely in the evaluation of postoperative pain in retrospective studies. PMID:23152699

Statistics of Magnetic Reconnection X-Lines in Kinetic Turbulence

NASA Astrophysics Data System (ADS)

Haggerty, C. C.; Parashar, T.; Matthaeus, W. H.; Shay, M. A.; Wan, M.; Servidio, S.; Wu, P.

2016-12-01

In this work we examine the statistics of magnetic reconnection (x-lines) and their associated reconnection rates in intermittent current sheets generated in turbulent plasmas. Although such statistics have been studied previously for fluid simulations (e.g. [1]), they have not yet been generalized to fully kinetic particle-in-cell (PIC) simulations. A significant problem with PIC simulations, however, is electrostatic fluctuations generated due to numerical particle counting statistics. We find that analyzing gradients of the magnetic vector potential from the raw PIC field data identifies numerous artificial (or non-physical) x-points. Using small Orszag-Tang vortex PIC simulations, we analyze x-line identification and show that these artificial x-lines can be removed using sub-Debye length filtering of the data. We examine how turbulent properties such as the magnetic spectrum and scale dependent kurtosis are affected by particle noise and sub-Debye length filtering. We subsequently apply these analysis methods to a large scale kinetic PIC turbulent simulation. Consistent with previous fluid models, we find a range of normalized reconnection rates as large as ½ but with the bulk of the rates being approximately less than to 0.1. [1] Servidio, S., W. H. Matthaeus, M. A. Shay, P. A. Cassak, and P. Dmitruk (2009), Magnetic reconnection and two-dimensional magnetohydrodynamic turbulence, Phys. Rev. Lett., 102, 115003.

Mapping Soil Age at Continental Scales

NASA Astrophysics Data System (ADS)

Slessarev, E.; Feng, X.

2017-12-01

Soil age controls the balance between weathered and unweathered minerals in soil, and thus strongly influences many of the biological, geochemical, and hydrological functions of the critical zone. However, most quantitative models of soil development do not represent soil age. Instead, they rely on a steady-state assumption: physical erosion controls the residence time of unweathered minerals in soil, and thus fixes the chemical weathering rate. This assumption may hold true in mountainous landscapes, where physical erosion rates are high. However, the steady-state assumption may fail in low-relief landscapes, where physical erosion rates have been insufficient to remove unweathered minerals left by glaciation and dust deposition since the Last Glacial Maximum (LGM). To test the applicability of the steady-state assumption at continental scales, we developed an empirical predictor for physical erosion, and then simulated soil development since LGM with a numerical model. We calibrated the physical erosion predictor using a compilation of watershed-scale sediment yield data, and in-situ 10Be denudation measurements corrected for weathering by Zr/Ti mass-balance. Physical erosion rates can be predicted using a power-law function of local relief and peak ground acceleration, a proxy for tectonic activity. Coupling physical erosion rates with the numerical model reveals that extensive low-relief areas of North America may depart from steady-state because they were glaciated, or received high dust fluxes during LGM. These LGM legacy effects are reflected in topsoil Ca:Al and Quartz:Feldspar ratios derived from United States Geological Survey data, and in a global compilation of soil pH measurements. Our results quantitatively support the classic idea that soils in the mid-high latitudes of the Northern Hemisphere are "young", in the sense that they are undergoing transient response to LGM conditions. Where they occur, such departures from steady-state likely increase mineral weathering rates and the supply of rock-derived nutrients to ecosystems.

Multi-scale calculation based on dual domain material point method combined with molecular dynamics

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

Dhakal, Tilak Raj

This dissertation combines the dual domain material point method (DDMP) with molecular dynamics (MD) in an attempt to create a multi-scale numerical method to simulate materials undergoing large deformations with high strain rates. In these types of problems, the material is often in a thermodynamically non-equilibrium state, and conventional constitutive relations are often not available. In this method, the closure quantities, such as stress, at each material point are calculated from a MD simulation of a group of atoms surrounding the material point. Rather than restricting the multi-scale simulation in a small spatial region, such as phase interfaces, or crackmore » tips, this multi-scale method can be used to consider non-equilibrium thermodynamic e ects in a macroscopic domain. This method takes advantage that the material points only communicate with mesh nodes, not among themselves; therefore MD simulations for material points can be performed independently in parallel. First, using a one-dimensional shock problem as an example, the numerical properties of the original material point method (MPM), the generalized interpolation material point (GIMP) method, the convected particle domain interpolation (CPDI) method, and the DDMP method are investigated. Among these methods, only the DDMP method converges as the number of particles increases, but the large number of particles needed for convergence makes the method very expensive especially in our multi-scale method where we calculate stress in each material point using MD simulation. To improve DDMP, the sub-point method is introduced in this dissertation, which provides high quality numerical solutions with a very small number of particles. The multi-scale method based on DDMP with sub-points is successfully implemented for a one dimensional problem of shock wave propagation in a cerium crystal. The MD simulation to calculate stress in each material point is performed in GPU using CUDA to accelerate the computation. The numerical properties of the multiscale method are investigated as well as the results from this multi-scale calculation are compared of particles needed for convergence makes the method very expensive especially in our multi-scale method where we calculate stress in each material point using MD simulation. To improve DDMP, the sub-point method is introduced in this dissertation, which provides high quality numerical solutions with a very small number of particles. The multi-scale method based on DDMP with sub-points is successfully implemented for a one dimensional problem of shock wave propagation in a cerium crystal. The MD simulation to calculate stress in each material point is performed in GPU using CUDA to accelerate the computation. The numerical properties of the multiscale method are investigated as well as the results from this multi-scale calculation are compared with direct MD simulation results to demonstrate the feasibility of the method. Also, the multi-scale method is applied for a two dimensional problem of jet formation around copper notch under a strong impact.« less

Numerical study of particle deposition and scaling in dust exhaust of cyclone separator

NASA Astrophysics Data System (ADS)

Xu, W. W.; Li, Q.; Zhao, Y. L.; Wang, J. J.; Jin, Y. H.

2016-05-01

The solid particles accumulation in the dust exhaust cone area of the cyclone separator can cause the wall wear. This undoubtedly prevents the flue gas turbine from long period and safe operation. So it is important to study the mechanism how the particles deposited and scale on dust exhaust cone area of the cyclone separator. Numerical simulations of gas-solid flow field have been carried out in a single tube in the third cyclone separator. The three-dimensionally coupled computational fluid dynamic (CFD) technology and the modified Discrete Phase Model (DPM) are adopted to model the gas-solid two-phase flow. The results show that with the increase of the operating temperature and processing capacity, the particle sticking possibility near the cone area will rise. The sticking rates will decrease when the particle diameter becomes bigger.

Fall prevention in the young old using an exoskeleton human body posturizer: a randomized controlled trial.

PubMed

Verrusio, W; Gianturco, V; Cacciafesta, M; Marigliano, V; Troisi, G; Ripani, M

2017-04-01

Fall risk in elderly has been related with physical decline, low quality of life and reduced survival. To evaluate the impact of exoskeleton human body posturizer (HBP) on the fall risk in the elderly. 150 subjects (mean age 64.85; 79 M/71 F) with mild fall risk were randomized into two groups: 75 for group treated with human body posturizer (HBP group) and 75 for physical training without HBP group (exercise group). The effects of interventions were assessed by differences in tests related to balance and falls. Medically eligible patients were screened with Tinetti balance and Gait evaluation scale, short physical performance battery and numeric pain rating scale to determine fall risk in elderly people. In the HBP group there was a significant improvement in short physical performance battery, Tinetti scale and Pain Numeric rating scale with a significant reduction in fall risk (p < 0.05). In the exercise group we observed only minimal variations in the test scores. The results at the sixth and twelfth months show a twofold positive effect in the HBP group reducing fall risk and improving quality of life by reducing pain. The use of exoskeleton human body posturizer seems to be a new significant device for prevention of fall in elderly patients. Further research should be carried out to obtain more evidence on effects of robotic technology for fall prevention in the elderly.

The effect of additional ankle and midfoot mobilizations on plantar fasciitis: a randomized controlled trial.

PubMed

Shashua, Anat; Flechter, Shlomo; Avidan, Liat; Ofir, Dani; Melayev, Alex; Kalichman, Leonid

2015-04-01

A single-blind randomized controlled trial. To evaluate the efficacy of ankle and midfoot mobilization on pain and function of patients with plantar fasciitis (PF). Plantar fasciitis is a degenerative process of the plantar fascia, with a lifetime prevalence of approximately 10%. Limited ankle dorsiflexion is a common finding and apparently acts as a contributing factor to the development of PF. Fifty patients with PF, aged 23 to 73 years, were randomly assigned to either the intervention or control group. Both groups received 8 treatments, twice a week, consisting of stretching exercises and ultrasound. In addition, the intervention group received mobilization of the ankle and midfoot joints. Dorsiflexion range of motion was measured at the beginning and at the end of treatment. The results were evaluated by 3 outcomes: the numeric pain-rating scale, Lower Extremity Functional Scale, and algometry. No significant difference was found between groups in any of the outcomes. Both groups showed a significant difference in the numeric pain-rating scale and Lower Extremity Functional Scale. Both groups significantly improved in dorsiflexion range of motion, with no difference between groups. The addition of ankle and foot joint mobilization aimed at improving dorsiflexion range of motion is not more effective than stretching and ultrasound alone in treating PF. The association between limited ankle dorsiflexion and PF is most probably due to soft tissue limitations, not the joints. Trial registered at ClinicalTrials.gov (registration number NCT01439932). Therapy, level 1b.

Exploring tectonomagmatic controls on mid-ocean ridge faulting and morphology with 3-D numerical models

NASA Astrophysics Data System (ADS)

Howell, S. M.; Ito, G.; Behn, M. D.; Olive, J. A. L.; Kaus, B.; Popov, A.; Mittelstaedt, E. L.; Morrow, T. A.

2016-12-01

Previous two-dimensional (2-D) modeling studies of abyssal-hill scale fault generation and evolution at mid-ocean ridges have predicted that M, the ratio of magmatic to total extension, strongly influences the total slip, spacing, and rotation of large faults, as well as the morphology of the ridge axis. Scaling relations derived from these 2-D models broadly explain the globally observed decrease in abyssal hill spacing with increasing ridge spreading rate, as well as the formation of large-offset faults close to the ends of slow-spreading ridge segments. However, these scaling relations do not explain some higher resolution observations of segment-scale variability in fault spacing along the Chile Ridge and the Mid-Atlantic Ridge, where fault spacing shows no obvious correlation with M. This discrepancy between observations and 2-D model predictions illuminates the need for three-dimensional (3-D) numerical models that incorporate the effects of along-axis variations in lithospheric structure and magmatic accretion. To this end, we use the geodynamic modeling software LaMEM to simulate 3-D tectono-magmatic interactions in a visco-elasto-plastic lithosphere under extension. We model a single ridge segment subjected to an along-axis gradient in the rate of magma injection, which is simulated by imposing a mass source in a plane of model finite volumes beneath the ridge axis. Outputs of interest include characteristic fault offset, spacing, and along-axis gradients in seafloor morphology. We also examine the effects of along-axis variations in lithospheric thickness and off-axis thickening rate. The main objectives of this study are to quantify the relative importance of the amount of magmatic extension and the local lithospheric structure at a given along-axis location, versus the importance of along-axis communication of lithospheric stresses on the 3-D fault evolution and morphology of intermediate-spreading-rate ridges.

Simple Kinematic Pathway Approach (KPA) to Catchment-scale Travel Time and Water Age Distributions

NASA Astrophysics Data System (ADS)

Soltani, S. S.; Cvetkovic, V.; Destouni, G.

2017-12-01

The distribution of catchment-scale water travel times is strongly influenced by morphological dispersion and is partitioned between hillslope and larger, regional scales. We explore whether hillslope travel times are predictable using a simple semi-analytical "kinematic pathway approach" (KPA) that accounts for dispersion on two levels of morphological and macro-dispersion. The study gives new insights to shallow (hillslope) and deep (regional) groundwater travel times by comparing numerical simulations of travel time distributions, referred to as "dynamic model", with corresponding KPA computations for three different real catchment case studies in Sweden. KPA uses basic structural and hydrological data to compute transient water travel time (forward mode) and age (backward mode) distributions at the catchment outlet. Longitudinal and morphological dispersion components are reflected in KPA computations by assuming an effective Peclet number and topographically driven pathway length distributions, respectively. Numerical simulations of advective travel times are obtained by means of particle tracking using the fully-integrated flow model MIKE SHE. The comparison of computed cumulative distribution functions of travel times shows significant influence of morphological dispersion and groundwater recharge rate on the compatibility of the "kinematic pathway" and "dynamic" models. Zones of high recharge rate in "dynamic" models are associated with topographically driven groundwater flow paths to adjacent discharge zones, e.g. rivers and lakes, through relatively shallow pathway compartments. These zones exhibit more compatible behavior between "dynamic" and "kinematic pathway" models than the zones of low recharge rate. Interestingly, the travel time distributions of hillslope compartments remain almost unchanged with increasing recharge rates in the "dynamic" models. This robust "dynamic" model behavior suggests that flow path lengths and travel times in shallow hillslope compartments are controlled by topography, and therefore application and further development of the simple "kinematic pathway" approach is promising for their modeling.

Numerical analysis of scalar dissipation length-scales and their scaling properties

NASA Astrophysics Data System (ADS)

Vaishnavi, Pankaj; Kronenburg, Andreas

2006-11-01

Scalar dissipation rate, χ, is fundamental to the description of scalar-mixing in turbulent non-premixed combustion. Most contributions to the statistics for χ come from the finest turbulent mixing-scales and thus its adequate characterisation requires good resolution. Reliable χ-measurement is complicated by the trade-off between higher resolution and greater signal-to-noise ratio. Thus, the present numerical study utilises the error-free mixture fraction, Z, and fluid mechanical data from the turbulent reacting jet DNS of Pantano (2004). The aim is to quantify the resolution requirements for χ-measurement in terms of easily measurable properties of the flow like the integral-scale Reynolds number, Reδ, using spectral and spatial-filtering [cf. Barlow and Karpetis (2005)] analyses. Analysis of the 1-D cross-stream dissipation spectra enables the estimation of the dissipation length scales. It is shown that these spectrally-computed scales follow the expected Kolmogorov scaling with Reδ-0.75 . The work also involves local smoothening of the instantaneous χ-field over a non-overlapping spatial-interval (filter-width, wf), to study the smoothened χ-value as a function of wf, as wf is extrapolated to the smallest scale of interest. The dissipation length-scales thus captured show a stringent Reδ-1 scaling, compared to the usual Kolmogorov-type. This concurs with the criterion of 'resolution adequacy' of the DNS, as set out by Sreenivasan (2004) using the theory of multi-fractals.

Mixing effects on apparent reaction rates and isotope fractionation during denitrification in a heterogeneous aquifer

USGS Publications Warehouse

Green, Christopher T.; Böhlke, John Karl; Bekins, Barbara A.; Phillips, Steven P.

2010-01-01

Gradients in contaminant concentrations and isotopic compositions commonly are used to derive reaction parameters for natural attenuation in aquifers. Differences between field‐scale (apparent) estimated reaction rates and isotopic fractionations and local‐scale (intrinsic) effects are poorly understood for complex natural systems. For a heterogeneous alluvial fan aquifer, numerical models and field observations were used to study the effects of physical heterogeneity on reaction parameter estimates. Field measurements included major ions, age tracers, stable isotopes, and dissolved gases. Parameters were estimated for the O2 reduction rate, denitrification rate, O2 threshold for denitrification, and stable N isotope fractionation during denitrification. For multiple geostatistical realizations of the aquifer, inverse modeling was used to establish reactive transport simulations that were consistent with field observations and served as a basis for numerical experiments to compare sample‐based estimates of “apparent” parameters with “true“ (intrinsic) values. For this aquifer, non‐Gaussian dispersion reduced the magnitudes of apparent reaction rates and isotope fractionations to a greater extent than Gaussian mixing alone. Apparent and true rate constants and fractionation parameters can differ by an order of magnitude or more, especially for samples subject to slow transport, long travel times, or rapid reactions. The effect of mixing on apparent N isotope fractionation potentially explains differences between previous laboratory and field estimates. Similarly, predicted effects on apparent O2threshold values for denitrification are consistent with previous reports of higher values in aquifers than in the laboratory. These results show that hydrogeological complexity substantially influences the interpretation and prediction of reactive transport.

Multi-scale continuum modeling of biological processes: from molecular electro-diffusion to sub-cellular signaling transduction

NASA Astrophysics Data System (ADS)

Cheng, Y.; Kekenes-Huskey, P.; Hake, J. E.; Holst, M. J.; McCammon, J. A.; Michailova, A. P.

2012-01-01

This paper presents a brief review of multi-scale modeling at the molecular to cellular scale, with new results for heart muscle cells. A finite element-based simulation package (SMOL) was used to investigate the signaling transduction at molecular and sub-cellular scales (http://mccammon.ucsd.edu/smol/, http://FETK.org) by numerical solution of the time-dependent Smoluchowski equations and a reaction-diffusion system. At the molecular scale, SMOL has yielded experimentally validated estimates of the diffusion-limited association rates for the binding of acetylcholine to mouse acetylcholinesterase using crystallographic structural data. The predicted rate constants exhibit increasingly delayed steady-state times, with increasing ionic strength, and demonstrate the role of an enzyme's electrostatic potential in influencing ligand binding. At the sub-cellular scale, an extension of SMOL solves a nonlinear, reaction-diffusion system describing Ca2+ ligand buffering and diffusion in experimentally derived rodent ventricular myocyte geometries. Results reveal the important role of mobile and stationary Ca2+ buffers, including Ca2+ indicator dye. We found that alterations in Ca2+-binding and dissociation rates of troponin C (TnC) and total TnC concentration modulate sub-cellular Ca2+ signals. The model predicts that reduced off-rate in the whole troponin complex (TnC, TnI, TnT) versus reconstructed thin filaments (Tn, Tm, actin) alters cytosolic Ca2+ dynamics under control conditions or in disease-linked TnC mutations. The ultimate goal of these studies is to develop scalable methods and theories for the integration of molecular-scale information into simulations of cellular-scale systems.

Numerical Simulation of nZVI at the Field Scale

NASA Astrophysics Data System (ADS)

Chowdhury, A. I.; Krol, M.; Sleep, B. E.; O'Carroll, D. M.

2014-12-01

Nano-scale zero valent iron (nZVI) has been used at a number of contaminated sites over the last decade. At most of these sites, significant decreases in contaminant concentrations have resulted from the application of nZVI. However, limited work has been completed investigating nZVI mobility at the field-scale. In this study a three dimensional, three phase, finite difference numerical simulator (CompSim) was used to simulate nZVI and polymer transport in a variably saturated site. The model was able to accurately predict the field observed head data without parameter fitting. In addition, the numerical simulator estimated the amount of nZVI delivered to the saturated and unsaturated zones as well as the phase of nZVI (i.e., attached or aqueous phase). The simulation results showed that the injected slurry migrated radially outward from the injection well, and therefore nZVI transport was governed by injection velocity as well as viscosity of the injected solution. A suite of sensitivity analyses was performed to investigate the impact of different injection scenarios (e.g. different volume and injection rate) on nZVI migration. Simulation results showed that injection of a higher volume of nZVI delivered more iron particles at a given distance; however, not necessarily to a greater distance proportionate to the increase in volume. This study suggests that on-site synthesized nZVI particles are mobile in the subsurface and the numerical simulator can be a valuable tool for optimum design of nZVI applications.

The decay of isotropic magnetohydrodynamics turbulence and the effects of cross-helicity

NASA Astrophysics Data System (ADS)

Briard, Antoine; Gomez, Thomas

2018-02-01

Decaying homogeneous and isotropic magnetohydrodynamics (MHD) turbulence is investigated numerically at large Reynolds numbers thanks to the eddy-damped quasi-normal Markovian (EDQNM) approximation. Without any background mean magnetic field, the total energy spectrum scales as -3/2$ in the inertial range as a consequence of the modelling. Moreover, the total energy is shown, both analytically and numerically, to decay at the same rate as kinetic energy in hydrodynamic isotropic turbulence: this differs from a previous prediction, and thus physical arguments are proposed to reconcile both results. Afterwards, the MHD turbulence is made imbalanced by an initial non-zero cross-helicity. A spectral modelling is developed for the velocity-magnetic correlation in a general homogeneous framework, which reveals that cross-helicity can contain subtle anisotropic effects. In the inertial range, as the Reynolds number increases, the slope of the cross-helical spectrum becomes closer to -5/3$ than -2$ . Furthermore, the Elsässer spectra deviate from -3/2$ with cross-helicity at large Reynolds numbers. Regarding the pressure spectrum P$ , its kinetic and magnetic parts are found to scale with -2$ in the inertial range, whereas the part due to cross-helicity rather scales in -7/3$ . Finally, the two rd laws for the total energy and cross-helicity are assessed numerically at large Reynolds numbers.

Finite Volume Numerical Methods for Aeroheating Rate Calculations from Infrared Thermographic Data

NASA Technical Reports Server (NTRS)

Daryabeigi, Kamran; Berry, Scott A.; Horvath, Thomas J.; Nowak, Robert J.

2003-01-01

The use of multi-dimensional finite volume numerical techniques with finite thickness models for calculating aeroheating rates from measured global surface temperatures on hypersonic wind tunnel models was investigated. Both direct and inverse finite volume techniques were investigated and compared with the one-dimensional semi -infinite technique. Global transient surface temperatures were measured using an infrared thermographic technique on a 0.333-scale model of the Hyper-X forebody in the Langley Research Center 20-Inch Mach 6 Air tunnel. In these tests the effectiveness of vortices generated via gas injection for initiating hypersonic transition on the Hyper-X forebody were investigated. An array of streamwise orientated heating striations were generated and visualized downstream of the gas injection sites. In regions without significant spatial temperature gradients, one-dimensional techniques provided accurate aeroheating rates. In regions with sharp temperature gradients due to the striation patterns two-dimensional heat transfer techniques were necessary to obtain accurate heating rates. The use of the one-dimensional technique resulted in differences of 20% in the calculated heating rates because it did not account for lateral heat conduction in the model.

Flow rate of transport network controls uniform metabolite supply to tissue

PubMed Central

Meigel, Felix J.

2018-01-01

Life and functioning of higher organisms depends on the continuous supply of metabolites to tissues and organs. What are the requirements on the transport network pervading a tissue to provide a uniform supply of nutrients, minerals or hormones? To theoretically answer this question, we present an analytical scaling argument and numerical simulations on how flow dynamics and network architecture control active spread and uniform supply of metabolites by studying the example of xylem vessels in plants. We identify the fluid inflow rate as the key factor for uniform supply. While at low inflow rates metabolites are already exhausted close to flow inlets, too high inflow flushes metabolites through the network and deprives tissue close to inlets of supply. In between these two regimes, there exists an optimal inflow rate that yields a uniform supply of metabolites. We determine this optimal inflow analytically in quantitative agreement with numerical results. Optimizing network architecture by reducing the supply variance over all network tubes, we identify patterns of tube dilation or contraction that compensate sub-optimal supply for the case of too low or too high inflow rate. PMID:29720455

Numerical study of two-dimensional wet foam over a range of shear rates

NASA Astrophysics Data System (ADS)

Kähärä, T.

2017-09-01

The shear rheology of two-dimensional foam is investigated over a range of shear rates with the numerical DySMaL model, which features dynamically deformable bubbles. It is found that at low shear rates, the rheological behavior of the system can be characterized by a yield stress power-law constitutive equation that is consistent with experimental findings and can be understood in terms of soft glassy rheology models. At low shear rates, the system rheology is also found to be subject to a scaling law involving the bubble size, the surface tension, and the viscosity of the carrier fluid. At high shear rates, the model produces a dynamic phase transition with a sudden change in the flow pattern, which is accompanied by a drop in the effective viscosity. This phase transition can be linked to rapid changes in the average bubble deformation and nematic order of the system. It is very likely that this phase transition is a result of the model dynamics and does not happen in actual foams.

Monitoring Academic and Social Skills in Elementary School: A Psychometric Evaluation of the Classroom Performance Survey

ERIC Educational Resources Information Center

Caldarella, Paul; Larsen, Ross A. A.; Williams, Leslie; Wehby, Joseph H.; Wills, Howard; Kamps, Debra

2017-01-01

Numerous well-validated academic progress monitoring tools are used in schools, but there are fewer behavioral progress monitoring measures available. Some brief behavior rating scales have been shown to be effective in monitoring students' progress, but most focus only on students' social skills and do not address critical academic-related…

Monitoring Academic and Social Skills in Elementary School: A Psychometric Evaluation of the Classroom Performance Survey

ERIC Educational Resources Information Center

Caldarella, Paul; Larsen, Ross A. A.; Williams, Leslie; Wehby, Joseph H.; Wills, Howard P.; Kamps, Debra M.

2017-01-01

Numerous well validated academic progress monitoring tools are used in schools, but there are fewer behavioral progress monitoring measures available. Some brief behavior rating scales have been shown to be effective in monitoring students' progress, but most focus only on students' social skills and do not address critical academic-related…

Phase 2a, randomized, double-blind, placebo-controlled, multicenter, parallel-group study of a H4 R-antagonist (JNJ-39758979) in Japanese adults with moderate atopic dermatitis.

PubMed

Murata, Yoko; Song, Michael; Kikuchi, Hisayuki; Hisamichi, Katsuya; Xu, Xie L; Greenspan, Andrew; Kato, Mai; Chiou, Chiun-Fang; Kato, Takeshi; Guzzo, Cynthia; Thurmond, Robin L; Ohtsuki, Mamitaro; Furue, Masutaka

2015-02-01

This trial was conducted to evaluate the safety and efficacy of the H4 R-antagonist JNJ-39758979 in adult Japanese patients with moderate atopic dermatitis (AD). Eligible patients were randomly assigned to JNJ-39758979 300 mg, 100 mg or placebo once daily for 6 weeks in this phase 2a, double-blind, multicenter, placebo-controlled study. Primary efficacy was assessed via week-6 Eczema Area and Severity Index (EASI) scores. Secondary efficacy assessments included Investigator's Global Assessment (IGA) and patient-reported outcome (PRO) pruritus assessments (Pruritus Categorical Response Scale [PCRS], Pruritus Numeric Rating Scales [PNRS], Pruritus Interference Numeric Rating Scale [PINRS] and Subject's Global Impressions of Change in Pruritus [SGICP]). Eighty-eight of 105 planned patients were randomized before the study was stopped and unblinded for safety reasons. The study did not meet the primary end-point. However, numerical improvements (i.e. decreases) in median EASI were observed with JNJ-39758979 100 mg (-3.7) and 300 mg (-3.0) versus placebo (-1.3) at week 6. Nominally significant improvements across PRO PCRS, PNRS and SGICP assessments were consistently observed, particularly with JNJ-39758979 300 mg. Safety, including adverse events (AE), was comparable between JNJ-39758979 and placebo with the exception of two patients (both receiving JNJ-39758979 300 mg) with serious AE of neutropenia, leading to premature study discontinuation. No deaths were reported. Except for neutropenia, no clinically relevant changes in laboratory values were observed. Although not conclusive, findings suggest H4 R-antagonism may be beneficial for AD, particularly in controlling pruritus. JNJ-39758979 appears to be associated with drug-induced agranulocytosis, likely an off-target effect. © 2014 Japanese Dermatological Association.

Assessing Behavioural Manifestations Prior to Clinical Diagnosis of Huntington Disease: "Anger and Irritability" and "Obsessions and Compulsions"

PubMed Central

Vaccarino, Anthony L; Anonymous; Anderson, Karen E.; Borowsky, Beth; Coccaro, Emil; Craufurd, David; Endicott, Jean; Giuliano, Joseph; Groves, Mark; Guttman, Mark; Ho, Aileen K; Kupchak, Peter; Paulsen, Jane S.; Stanford, Matthew S.; van Kammen, Daniel P; Watson, David; Wu, Kevin D; Evans, Ken

2011-01-01

The Functional Rating Scale Taskforce for pre-Huntington Disease (FuRST-pHD) is a multinational, multidisciplinary initiative with the goal of developing a data-driven, comprehensive, psychometrically sound, rating scale for assessing symptoms and functional ability in prodromal and early Huntington disease (HD) gene expansion carriers. The process involves input from numerous sources to identify relevant symptom domains, including HD individuals, caregivers, and experts from a variety of fields, as well as knowledge gained from the analysis of data from ongoing large-scale studies in HD using existing clinical scales. This is an iterative process in which an ongoing series of field tests in prodromal (prHD) and early HD individuals provides the team with data on which to make decisions regarding which questions should undergo further development or testing and which should be excluded. We report here the development and assessment of the first iteration of interview questions aimed to assess "Anger and Irritability" and "Obsessions and Compulsions" in prHD individuals. PMID:21826116

Completing the mechanical energy pathways in turbulent Rayleigh-Bénard convection.

PubMed

Gayen, Bishakhdatta; Hughes, Graham O; Griffiths, Ross W

2013-09-20

A new, more complete view of the mechanical energy budget for Rayleigh-Bénard convection is developed and examined using three-dimensional numerical simulations at large Rayleigh numbers and Prandtl number of 1. The driving role of available potential energy is highlighted. The relative magnitudes of different energy conversions or pathways change significantly over the range of Rayleigh numbers Ra ~ 10(7)-10(13). At Ra < 10(7) small-scale turbulent motions are energized directly from available potential energy via turbulent buoyancy flux and kinetic energy is dissipated at comparable rates by both the large- and small-scale motions. In contrast, at Ra ≥ 10(10) most of the available potential energy goes into kinetic energy of the large-scale flow, which undergoes shear instabilities that sustain small-scale turbulence. The irreversible mixing is largely confined to the unstable boundary layer, its rate exactly equal to the generation of available potential energy by the boundary fluxes, and mixing efficiency is 50%.

FAST MAGNETIC FIELD AMPLIFICATION IN THE EARLY UNIVERSE: GROWTH OF COLLISIONLESS PLASMA INSTABILITIES IN TURBULENT MEDIA

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

Falceta-Gonçalves, D.; Kowal, G.

2015-07-20

In this work we report on a numerical study of the cosmic magnetic field amplification due to collisionless plasma instabilities. The collisionless magnetohydrodynamic equations derived account for the pressure anisotropy that leads, in specific conditions, to the firehose and mirror instabilities. We study the time evolution of seed fields in turbulence under the influence of such instabilities. An approximate analytical time evolution of the magnetic field is provided. The numerical simulations and the analytical predictions are compared. We found that (i) amplification of the magnetic field was efficient in firehose-unstable turbulent regimes, but not in the mirror-unstable models; (ii) the growthmore » rate of the magnetic energy density is much faster than the turbulent dynamo; and (iii) the efficient amplification occurs at small scales. The analytical prediction for the correlation between the growth timescales and pressure anisotropy is confirmed by the numerical simulations. These results reinforce the idea that pressure anisotropies—driven naturally in a turbulent collisionless medium, e.g., the intergalactic medium, could efficiently amplify the magnetic field in the early universe (post-recombination era), previous to the collapse of the first large-scale gravitational structures. This mechanism, though fast for the small-scale fields (∼kpc scales), is unable to provide relatively strong magnetic fields at large scales. Other mechanisms that were not accounted for here (e.g., collisional turbulence once instabilities are quenched, velocity shear, or gravitationally induced inflows of gas into galaxies and clusters) could operate afterward to build up large-scale coherent field structures in the long time evolution.« less

Experimental and Numerical Observations of Hydrate Reformation during Depressurization in a Core-Scale Reactor

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

Seol, Yongkoo; Myshakin, Evgeniy

2011-01-01

Gas hydrate has been predicted to reform around a wellbore during depressurization-based gas production from gas hydrate-bearing reservoirs. This process has an adverse effect on gas production rates and it requires time and sometimes special measures to resume gas flow to producing wells. Due to lack of applicable field data, laboratory scale experiments remain a valuable source of information to study hydrate reformation. In this work, we report laboratory experiments and complementary numerical simulations executed to investigate the hydrate reformation phenomenon. Gas production from a pressure vessel filled with hydrate-bearing sand was induced by depressurization with and without heat fluxmore » through the boundaries. Hydrate decomposition was monitored with a medical X-ray CT scanner and pressure and temperature measurements. CT images of the hydrate-bearing sample were processed to provide 3-dimensional data of heterogeneous porosity and phase saturations suitable for numerical simulations. In the experiments, gas hydrate reformation was observed only in the case of no-heat supply from surroundings, a finding consistent with numerical simulation. By allowing gas production on either side of the core, numerical simulations showed that initial hydrate distribution patterns affect gas distribution and flow inside the sample. This is a direct consequence of the heterogeneous pore network resulting in varying hydraulic properties of the hydrate-bearing sediment.« less

Numerical evaluation of the scale problem on the wind flow of a windbreak

PubMed Central

Liu, Benli; Qu, Jianjun; Zhang, Weimin; Tan, Lihai; Gao, Yanhong

2014-01-01

The airflow field around wind fences with different porosities, which are important in determining the efficiency of fences as a windbreak, is typically studied via scaled wind tunnel experiments and numerical simulations. However, the scale problem in wind tunnels or numerical models is rarely researched. In this study, we perform a numerical comparison between a scaled wind-fence experimental model and an actual-sized fence via computational fluid dynamics simulations. The results show that although the general field pattern can be captured in a reduced-scale wind tunnel or numerical model, several flow characteristics near obstacles are not proportional to the size of the model and thus cannot be extrapolated directly. For example, the small vortex behind a low-porosity fence with a scale of 1:50 is approximately 4 times larger than that behind a full-scale fence. PMID:25311174

Numerical and experimental study of a high port-density WDM optical packet switch architecture for data centers.

PubMed

Di Lucente, S; Luo, J; Centelles, R Pueyo; Rohit, A; Zou, S; Williams, K A; Dorren, H J S; Calabretta, N

2013-01-14

Data centers have to sustain the rapid growth of data traffic due to the increasing demand of bandwidth-hungry internet services. The current intra-data center fat tree topology causes communication bottlenecks in the server interaction process, power-hungry O-E-O conversions that limit the minimum latency and the power efficiency of these systems. In this paper we numerically and experimentally investigate an optical packet switch architecture with modular structure and highly distributed control that allow configuration times in the order of nanoseconds. Numerical results indicate that the candidate architecture scaled over 4000 ports, provides an overall throughput over 50 Tb/s and a packet loss rate below 10(-6) while assuring sub-microsecond latency. We present experimental results that demonstrate the feasibility of a 16x16 optical packet switch based on parallel 1x4 integrated optical cross-connect modules. Error-free operations can be achieved with 4 dB penalty while the overall energy consumption is of 66 pJ/b. Based on those results, we discuss feasibility to scale the architecture to a much larger port count.

Numerical modeling of separated flows at moderate Reynolds numbers appropriate for turbine blades and unmanned aero vehicles

NASA Astrophysics Data System (ADS)

Castiglioni, Giacomo

Flows over airfoils and blades in rotating machinery, for unmanned and micro-aerial vehicles, wind turbines, and propellers consist of a laminar boundary layer near the leading edge that is often followed by a laminar separation bubble and transition to turbulence further downstream. Typical Reynolds averaged Navier-Stokes turbulence models are inadequate for such flows. Direct numerical simulation is the most reliable, but is also the most computationally expensive alternative. This work assesses the capability of immersed boundary methods and large eddy simulations to reduce the computational requirements for such flows and still provide high quality results. Two-dimensional and three-dimensional simulations of a laminar separation bubble on a NACA-0012 airfoil at Rec = 5x104 and at 5° of incidence have been performed with an immersed boundary code and a commercial code using body fitted grids. Several sub-grid scale models have been implemented in both codes and their performance evaluated. For the two-dimensional simulations with the immersed boundary method the results show good agreement with the direct numerical simulation benchmark data for the pressure coefficient Cp and the friction coefficient Cf, but only when using dissipative numerical schemes. There is evidence that this behavior can be attributed to the ability of dissipative schemes to damp numerical noise coming from the immersed boundary. For the three-dimensional simulations the results show a good prediction of the separation point, but an inaccurate prediction of the reattachment point unless full direct numerical simulation resolution is used. The commercial code shows good agreement with the direct numerical simulation benchmark data in both two and three-dimensional simulations, but the presence of significant, unquantified numerical dissipation prevents a conclusive assessment of the actual prediction capabilities of very coarse large eddy simulations with low order schemes in general cases. Additionally, a two-dimensional sweep of angles of attack from 0° to 5° is performed showing a qualitative prediction of the jump in lift and drag coefficients due to the appearance of the laminar separation bubble. The numerical dissipation inhibits the predictive capabilities of large eddy simulations whenever it is of the same order of magnitude or larger than the sub-grid scale dissipation. The need to estimate the numerical dissipation is most pressing for low-order methods employed by commercial computational fluid dynamics codes. Following the recent work of Schranner et al., the equations and procedure for estimating the numerical dissipation rate and the numerical viscosity in a commercial code are presented. The method allows for the computation of the numerical dissipation rate and numerical viscosity in the physical space for arbitrary sub-domains in a self-consistent way, using only information provided by the code in question. The method is first tested for a three-dimensional Taylor-Green vortex flow in a simple cubic domain and compared with benchmark results obtained using an accurate, incompressible spectral solver. Afterwards the same procedure is applied for the first time to a realistic flow configuration, specifically to the above discussed laminar separation bubble flow over a NACA 0012 airfoil. The method appears to be quite robust and its application reveals that for the code and the flow in question the numerical dissipation can be significantly larger than the viscous dissipation or the dissipation of the classical Smagorinsky sub-grid scale model, confirming the previously qualitative finding.

Postprocessing Algorithm for Driving Conventional Scanning Tunneling Microscope at Fast Scan Rates

PubMed Central

Zhang, Hao; Li, Xianqi; Park, Jewook; Li, An-Ping

2017-01-01

We present an image postprocessing framework for Scanning Tunneling Microscope (STM) to reduce the strong spurious oscillations and scan line noise at fast scan rates and preserve the features, allowing an order of magnitude increase in the scan rate without upgrading the hardware. The proposed method consists of two steps for large scale images and four steps for atomic scale images. For large scale images, we first apply for each line an image registration method to align the forward and backward scans of the same line. In the second step we apply a “rubber band” model which is solved by a novel Constrained Adaptive and Iterative Filtering Algorithm (CIAFA). The numerical results on measurement from copper(111) surface indicate the processed images are comparable in accuracy to data obtained with a slow scan rate, but are free of the scan drift error commonly seen in slow scan data. For atomic scale images, an additional first step to remove line-by-line strong background fluctuations and a fourth step of replacing the postprocessed image by its ranking map as the final atomic resolution image are required. The resulting image restores the lattice image that is nearly undetectable in the original fast scan data. PMID:29362664

Effect of Aromatherapy Massage on Chemotherapy-Induced Peripheral Neuropathic Pain and Fatigue in Patients Receiving Oxaliplatin: An Open Label Quasi-Randomized Controlled Pilot Study.

PubMed

Izgu, Nur; Ozdemir, Leyla; Bugdayci Basal, Fatma

2017-12-02

Patients receiving oxaliplatin may experience peripheral neuropathic pain and fatigue. Aromatherapy massage, a nonpharmacological method, may help to control these symptoms. The aim of this open-label, parallel-group, quasi-randomized controlled pilot study was to investigate the effect of aromatherapy massage on chemotherapy-induced peripheral neuropathic pain and fatigue in patients receiving oxaliplatin. Stratified randomization was used to allocate 46 patients to 2 groups: intervention (n = 22) and control (n = 24). Between week 1 and week 6, participants in the intervention group (IG) received aromatherapy massage 3 times a week. There was no intervention in weeks 7 and 8. The control group (CG) received routine care. Neuropathic pain was identified using the Douleur Neuropathique 4 Questions; severity of painful paresthesia was assessed with the numerical rating scale; fatigue severity was identified with the Piper Fatigue Scale. At week 6, the rate of neuropathic pain was significantly lower in the IG, when compared with the CG. The severity of painful paresthesia based on numerical rating scale in the IG was significantly lower than that in the CG at weeks 2, 4, and 6. At week 8, fatigue severity in the IG was significantly lower when compared with CG (P < .05). Aromatherapy massage may be useful in the management of chemotherapy-induced peripheral neuropathic pain and fatigue. This pilot study suggests that aromatherapy massage may be useful to relieve neuropathic pain and fatigue. However, there is a need for further clinical trials to validate the results of this study.

Pharmacodynamics and Pharmacokinetics of Morphine After Cardiac Surgery in Children With and Without Down Syndrome.

PubMed

Valkenburg, Abraham J; Calvier, Elisa A M; van Dijk, Monique; Krekels, Elke H J; O'Hare, Brendan P; Casey, William F; Mathôt, Ron A A; Knibbe, Catherijne A J; Tibboel, Dick; Breatnach, Cormac V

2016-10-01

To compare the pharmacodynamics and pharmacokinetics of IV morphine after cardiac surgery in two groups of children-those with and without Down syndrome. Prospective, single-center observational trial. PICU in a university-affiliated pediatric teaching hospital. Twenty-one children with Down syndrome and 17 without, 3-36 months old, scheduled for cardiac surgery with cardiopulmonary bypass. A loading dose of morphine (100 μg/kg) was administered after coming off bypass; thereafter, morphine infusion was commenced at 40 μg/kg/hr. During intensive care, nurses regularly assessed pain and discomfort with validated observational instruments (COMFORT-Behavior scale and Numeric Rating Scale-for pain). These scores guided analgesic and sedative treatment. Plasma samples were obtained for pharmacokinetic analysis. Median COMFORT-Behavior and Numeric Rating Scale scores were not statistically significantly different between the two groups. The median morphine infusion rate during the first 24 hours after surgery was 31.3 μg/kg/hr (interquartile range, 23.4-36.4) in the Down syndrome group versus 31.7 μg/kg/hr (interquartile range, 25.1-36.1) in the control group (p = 1.00). Population pharmacokinetic analysis revealed no statistically significant differences in any of the pharmacokinetic variables of morphine between the children with and without Down syndrome. This prospective trial showed that there are no differences in pharmacokinetics or pharmacodynamics between children with and without Down syndrome if pain and distress management is titrated to effect based on outcomes of validated assessment instruments. We have no evidence to adjust morphine dosing after cardiac surgery in children with Down syndrome.

The meaning of vaguely quantified frequency response options on a quality of life scale depends on respondents’ medical status and age

PubMed Central

Schneider, Stefan; Stone, Arthur A.

2017-01-01

Purpose Self-report items in quality of life (QoL) scales commonly use vague quantifiers like “sometimes” or “often” to measure the frequency of health-related experiences. This study examined whether the meaning of such vaguely quantified response options differs depending on people’s medical status and age, which may undermine the validity of QoL group comparisons. Methods Respondents (n = 600) rated the frequency of positive and negative QoL experiences using vague quantifiers (never, rarely, sometimes, often, always) and provided open-ended numeric frequency counts for the same items. Negative binomial regression analyses examined whether the numeric frequencies associated with each vague quantifier differed between medical status (no vs. one or more medical conditions) and age (18–40 years vs. 60+ years) groups. Results Compared to respondents without a chronic condition, those with a medical condition assigned a higher numeric frequency to the same vague quantifiers for negative QoL experiences; this effect was not evident for positive QoL experiences. Older respondents’ numeric frequencies were more extreme (i.e., lower at the low end and somewhat higher at the high end of the response range) than those of younger respondents. After adjusting for these effects, differences in QoL became somewhat more pronounced between medical status groups, but not between age groups. Conclusions The results suggest that people with different medical backgrounds and age do not interpret vague frequency quantifiers on a QoL scale in the same way. Open-ended numeric frequency reports may be useful to detect and potentially correct for differences in the meaning of vague quantifiers. PMID:27071685

Numerical Speed of Sound and its Application to Schemes for all Speeds

NASA Technical Reports Server (NTRS)

Liou, Meng-Sing; Edwards, Jack R.

1999-01-01

The concept of "numerical speed of sound" is proposed in the construction of numerical flux. It is shown that this variable is responsible for the accurate resolution of' discontinuities, such as contacts and shocks. Moreover, this concept can he readily extended to deal with low speed and multiphase flows. As a results, the numerical dissipation for low speed flows is scaled with the local fluid speed, rather than the sound speed. Hence, the accuracy is enhanced the correct solution recovered, and the convergence rate improved. We also emphasize the role of mass flux and analyze the behavior of this flux. Study of mass flux is important because the numerical diffusivity introduced in it can be identified. In addition, it is the term common to all conservation equations. We show calculated results for a wide variety of flows to validate the effectiveness of using the numerical speed of sound concept in constructing the numerical flux. We especially aim at achieving these two goals: (1) improving accuracy and (2) gaining convergence rates for all speed ranges. We find that while the performance at high speed range is maintained, the flux now has the capability of performing well even with the low: speed flows. Thanks to the new numerical speed of sound, the convergence is even enhanced for the flows outside of the low speed range. To realize the usefulness of the proposed method in engineering problems, we have also performed calculations for complex 3D turbulent flows and the results are in excellent agreement with data.

[A first step towards safer sedation and analgesia: A systematic evaluation of outcomes and level of sedation and analgesia in the mechanically ventilated critically ill patient].

PubMed

Frade-Mera, M J; Regueiro-Díaz, N; Díaz-Castellano, L; Torres-Valverde, L; Alonso-Pérez, L; Landívar-Redondo, M M; Muñoz-Pasín, R; Terceros-Almanza, L J; Temprano-Vázquez, S; Sánchez-Izquierdo-Riera, J Á

Safe analgesia and sedation strategies are necessary in order to avoid under or over sedation, as well as improving the comfort and safety of critical care patients. To compare and contrast a multidisciplinary protocol of systematic evaluation and management of analgesia and sedation in a group of critical care patients on mechanical ventilation with the usual procedures. A cohort study with contemporary series was conducted in a tertiary care medical-surgical ICU February to November during 2013 and 2014. The inclusion criteria were mechanical ventilation ≥ 24h and use of sedation by continuous infusion. Sedation was monitored using the Richmond agitation-sedation scale or bispectral index, and analgesia were measured using the numeric rating scale, or behavioural indicators of pain scale. The study variables included; mechanical ventilation time, weaning time, ventilation support time, artificial airway time, continuous sedative infusion time, daily dose and frequency of analgesic and sedative drug use, hospital stay, and ICU and hospital mortality, Richmond agitation-sedation scale, bispectral index, numeric rating scale, and behavioural indicators of pain scale measurements. Kruskal Wallis and Chi 2 , and a significance of p<.05 were used. The study included 153 admissions, 75 pre-intervention and 78 post-intervention, with a mean age of 55.7±13 years old, and 67% men. Both groups showed similarities in age, reason for admission, and APACHE. There were non-significant decreases in mechanical ventilation time 4 (1.4-9.2) and 3.2 (1.4-8.1) days, respectively; p= 0.7, continuous sedative infusion time 6 (3-11) and 5 (3-11) days; p= 0.9, length of hospital stay 29 (18-52); 25 (14-41) days; p= 0.1, ICU mortality (8 vs. 5%; p= 0.4), and hospital mortality (10.6 vs. 9.4%: p= 0.8). Daily doses of midazolam and remifentanil decreased 347 (227-479) mg/day; 261 (159-358) mg/day; p= 0.02 and 2175 (1427-3285) mcg/day; 1500 (715-2740) mcg/day; p= 0.02, respectively. There were increases in the use of remifentanil (32% vs. 51%; p= 0.01), dexmedetomidine (0 vs.6%; p= 0.02), dexketoprofen (60 vs. 76%; p= 0.03), and haloperidol (15 vs.28%; p= 0.04). The use of morphine decreased (71 vs. 54%; p= 0.03). There was an increase in the number of measurements and Richmond agitation-sedation scale scores 6 (3-17); 21 (9-39); p< 0.0001, behavioural indicators of pain scale 6 (3-18); 19(8-33); p< 0.001 and numeric rating scale 4 (2-6); 8 (6-17); p< 0.0001. The implementation of a multidisciplinary protocol of systematic evaluation of analgesia and sedation management achieved an improvement in monitoring and adequacy of dose to patient needs, leading to improved outcomes. Copyright © 2015 Elsevier España, S.L.U. y SEEIUC. All rights reserved.

Simulating spontaneous aseismic and seismic slip events on evolving faults

NASA Astrophysics Data System (ADS)

Herrendörfer, Robert; van Dinther, Ylona; Pranger, Casper; Gerya, Taras

2017-04-01

Plate motion along tectonic boundaries is accommodated by different slip modes: steady creep, seismic slip and slow slip transients. Due to mainly indirect observations and difficulties to scale results from laboratory experiments to nature, it remains enigmatic which fault conditions favour certain slip modes. Therefore, we are developing a numerical modelling approach that is capable of simulating different slip modes together with the long-term fault evolution in a large-scale tectonic setting. We extend the 2D, continuum mechanics-based, visco-elasto-plastic thermo-mechanical model that was designed to simulate slip transients in large-scale geodynamic simulations (van Dinther et al., JGR, 2013). We improve the numerical approach to accurately treat the non-linear problem of plasticity (see also EGU 2017 abstract by Pranger et al.). To resolve a wide slip rate spectrum on evolving faults, we develop an invariant reformulation of the conventional rate-and-state dependent friction (RSF) and adapt the time step (Lapusta et al., JGR, 2000). A crucial part of this development is a conceptual ductile fault zone model that relates slip rates along discrete planes to the effective macroscopic plastic strain rates in the continuum. We test our implementation first in a simple 2D setup with a single fault zone that has a predefined initial thickness. Results show that deformation localizes in case of steady creep and for very slow slip transients to a bell-shaped strain rate profile across the fault zone, which suggests that a length scale across the fault zone may exist. This continuum length scale would overcome the common mesh-dependency in plasticity simulations and question the conventional treatment of aseismic slip on infinitely thin fault zones. We test the introduction of a diffusion term (similar to the damage description in Lyakhovsky et al., JMPS, 2011) into the state evolution equation and its effect on (de-)localization during faster slip events. We compare the slip spectrum in our simulations to conventional RSF simulations (Liu and Rice, JGR, 2007). We further demonstrate the capability of simulating the evolution of a fault zone and simultaneous occurrence of slip transients. From small random initial distributions of the state variable in an otherwise homogeneous medium, deformation localizes and forms curved zones of reduced states. These spontaneously formed fault zones host slip transients, which in turn contribute to the growth of the fault zone.

Do inertial wave interactions control the rate of energy dissipation of rotating turbulence?

NASA Astrophysics Data System (ADS)

Cortet, Pierre-Philippe; Campagne, Antoine; Machicoane, Nathanael; Gallet, Basile; Moisy, Frederic

2015-11-01

The scaling law of the energy dissipation rate, ɛ ~U3 / L (with U and L the characteristic velocity and lengthscale), is one of the most robust features of fully developed turbulence. How this scaling is affected by a background rotation is still a controversial issue with importance for geo and astrophysical flows. At asymptotically small Rossby numbers Ro = U / ΩL , i.e. in the weakly nonlinear limit, wave-turbulence arguments suggest that ɛ should be reduced by a factor Ro . Such scaling has however never been evidenced directly, neither experimentally nor numerically. We report here direct measurements of the injected power, and therefore of ɛ, in an experiment where a propeller is rotating at a constant rate in a large volume of fluid rotating at Ω. In co-rotation, we find a transition between the wave-turbulence scaling at small Ro and the classical Kolmogorov law at large Ro . The transition between these two regimes is characterized from experiments varying the propeller and tank dimensions. In counter-rotation, the scenario is much richer with the observation of an additional peak of dissipation, similar to the one found in Taylor-Couette experiments.

CO 2 Leakage Into Shallow Aquifers: Modeling CO 2 Gas Evolution and Accumulation at Interfaces of Heterogeneity

DOE PAGES

Porter, Mark L.; Plampin, Michael; Pawar, Rajesh; ...

2014-12-31

The physicochemical processes associated with CO 2 leakage into shallow aquifer systems are complex and span multiple spatial and time scales. Continuum-scale numerical models that faithfully represent the underlying pore-scale physics are required to predict the long-term behavior and aid in risk analysis regarding regulatory and management decisions. This study focuses on benchmarking the numerical simulator, FEHM, with intermediate-scale column experiments of CO 2 gas evolution in homogeneous and heterogeneous sand configurations. Inverse modeling was conducted to calibrate model parameters and determine model sensitivity to the observed steady-state saturation profiles. It is shown that FEHM is a powerful tool thatmore » is capable of capturing the experimentally observed out ow rates and saturation profiles. Moreover, FEHM captures the transition from single- to multi-phase flow and CO 2 gas accumulation at interfaces separating sands. We also derive a simple expression, based on Darcy's law, for the pressure at which CO 2 free phase gas is observed and show that it reliably predicts the location at which single-phase flow transitions to multi-phase flow.« less

Cut points on 0-10 numeric rating scales for symptoms included in the Edmonton Symptom Assessment Scale in cancer patients: a systematic review.

PubMed

Oldenmenger, Wendy H; de Raaf, Pleun J; de Klerk, Cora; van der Rijt, Carin C D

2013-06-01

To improve the management of cancer-related symptoms, systematic screening is necessary, often performed by using 0-10 numeric rating scales. Cut points are used to determine if scores represent clinically relevant burden. The aim of this systematic review was to explore the evidence on cut points for the symptoms of the Edmonton Symptom Assessment Scale. Relevant literature was searched in PubMed, CINAHL®, Embase, and PsycINFO®. We defined a cut point as the lower bound of the scores representing moderate or severe burden. Eighteen articles were eligible for this review. Cut points were determined using the interference with daily life, another symptom-related method, or a verbal scale. For pain, cut point 5 and, to a lesser extent, cut point 7 were found as the optimal cut points for moderate pain and severe pain, respectively. For moderate tiredness, the best cut point seemed to be cut point 4. For severe tiredness, both cut points 7 and 8 were suggested frequently. A lack of evidence exists for nausea, depression, anxiety, drowsiness, appetite, well-being, and shortness of breath. Few studies suggested a cut point below 4. For many symptoms, there is no clear evidence as to what the optimal cut points are. In daily clinical practice, a symptom score ≥4 is recommended as a trigger for a more comprehensive symptom assessment. Until there is more evidence on the optimal cut points, we should hold back using a certain cut point in quality indicators and be cautious about strongly recommending a certain cut point in guidelines. Copyright © 2013 U.S. Cancer Pain Relief Committee. Published by Elsevier Inc. All rights reserved.

Detection of early landscape evolution through controlled experimentation, data analysis, and numerical modeling at the Landscape Evolution Observatory

NASA Astrophysics Data System (ADS)

Troch, Peter A.; Pangle, Luke; Niu, Guo-Yue; Dontsova, Katerina; Barron-Gafford, Greg; van Haren, Joost; Pavao-Zuckerman, Mitch

2014-05-01

The Landscape Evolution Observatory (LEO) at Biosphere 2-The University of Arizona consists of three identical, sloping, 333 m2 convergent landscapes inside a 5,000 m2 environmentally controlled facility. These engineered landscapes contain 1-meter depth of basaltic tephra, ground to homogenous loamy sand that will undergo physical, chemical, and mineralogical changes over many years. Each landscape contains a spatially dense sensor and sampler network capable of resolving meter-scale lateral heterogeneity and sub-meter scale vertical heterogeneity in moisture, energy and carbon states and fluxes. The density of sensors and frequency at which they can be polled allows for data collection at spatial and temporal scales that are impossible in natural field settings. Embedded solution and gas samplers allow for quantification of biogeochemical processes, and facilitate the use of chemical tracers to study water movement at very high spatial resolutions. Each ~600 metric ton landscape has load cells embedded into the structure to measure changes in total system mass with 0.05% full-scale repeatability (equivalent to less than 1 cm of precipitation). This facilitates the real time accounting of hydrological partitioning at the hillslope scale. Each hillslope is equipped with an engineered rain system capable of raining at rates between 3 and 45 mm/hr in a range of spatial patterns. The rain systems are capable of creating long-term steady state conditions or running complex simulations. The precipitation water supply storage system is flexibly designed to facilitate addition of tracers at constant or time-varying rates for any of the three hillslopes. This presentation will discuss detection of early landscape evolution in terms of hydrological, geochemical and microbial processes through controlled experimentation, data analysis, and numerical modeling during the commissioning phase of the first hillslope at LEO.

Quality Improvement Project: Replacing the Numeric Rating Scale with a Clinically Aligned Pain Assessment (CAPA) Tool.

PubMed

Topham, Debra; Drew, Debra

2017-12-01

CAPA is a multifaceted pain assessment tool that was adopted at a large tertiary Midwest hospital to replace the numeric scale for adult patients who could self-report their pain experience. This article describes the process of implementation and the effect on patient satisfaction scores. Use of the tool is supported by the premise that pain assessment entails more than just pain intensity and that assessment is an exchange of meaning between patients and clinicians dependent on internal and external factors. Implementation of the tool was a transformative process resulting in modest increases in patient satisfaction scores with pain management. Patient reports that "staff did everything to manage pain" had the biggest gains and were sustained for more than 2 years. The CAPA tool meets regulatory requirements for pain assessment. Copyright © 2017 American Society for Pain Management Nursing. Published by Elsevier Inc. All rights reserved.

Multirate Particle-in-Cell Time Integration Techniques of Vlasov-Maxwell Equations for Collisionless Kinetic Plasma Simulations

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

Chen, Guangye; Chacon, Luis; Knoll, Dana Alan

2015-07-31

A multi-rate PIC formulation was developed that employs large timesteps for slow field evolution, and small (adaptive) timesteps for particle orbit integrations. Implementation is based on a JFNK solver with nonlinear elimination and moment preconditioning. The approach is free of numerical instabilities (ω peΔt >>1, and Δx >> λ D), and requires many fewer dofs (vs. explicit PIC) for comparable accuracy in challenging problems. Significant gains (vs. conventional explicit PIC) may be possible for large scale simulations. The paper is organized as follows: Vlasov-Maxwell Particle-in-cell (PIC) methods for plasmas; Explicit, semi-implicit, and implicit time integrations; Implicit PIC formulation (Jacobian-Free Newton-Krylovmore » (JFNK) with nonlinear elimination allows different treatments of disparate scales, discrete conservation properties (energy, charge, canonical momentum, etc.)); Some numerical examples; and Summary.« less

Regional 3D Numerical Modeling of the Lithosphere-Mantle System: Implications for Continental Rift-Parallel Surface Velocities

NASA Astrophysics Data System (ADS)

Stamps, S.; Bangerth, W.; Hager, B. H.

2014-12-01

The East African Rift System (EARS) is an active divergent plate boundary with slow, approximately E-W extension rates ranging from <1-6 mm/yr. Previous work using thin-sheet modeling indicates lithospheric buoyancy dominates the force balance driving large-scale Nubia-Somalia divergence, however GPS observations within the Western Branch of the EARS show along-rift motions that contradict this simple model. Here, we test the role of mantle flow at the rift-scale using our new, regional 3D numerical model based on the open-source code ASPECT. We define a thermal lithosphere with thicknesses that are systematically changed for generic models or based on geophysical constraints in the Western branch (e.g. melting depths, xenoliths, seismic tomography). Preliminary results suggest existing variations in lithospheric thicknesses along-rift in the Western Branch can drive upper mantle flow that is consistent with geodetic observations.

Stochastic multi-scale models of competition within heterogeneous cellular populations: Simulation methods and mean-field analysis.

PubMed

Cruz, Roberto de la; Guerrero, Pilar; Spill, Fabian; Alarcón, Tomás

2016-10-21

We propose a modelling framework to analyse the stochastic behaviour of heterogeneous, multi-scale cellular populations. We illustrate our methodology with a particular example in which we study a population with an oxygen-regulated proliferation rate. Our formulation is based on an age-dependent stochastic process. Cells within the population are characterised by their age (i.e. time elapsed since they were born). The age-dependent (oxygen-regulated) birth rate is given by a stochastic model of oxygen-dependent cell cycle progression. Once the birth rate is determined, we formulate an age-dependent birth-and-death process, which dictates the time evolution of the cell population. The population is under a feedback loop which controls its steady state size (carrying capacity): cells consume oxygen which in turn fuels cell proliferation. We show that our stochastic model of cell cycle progression allows for heterogeneity within the cell population induced by stochastic effects. Such heterogeneous behaviour is reflected in variations in the proliferation rate. Within this set-up, we have established three main results. First, we have shown that the age to the G1/S transition, which essentially determines the birth rate, exhibits a remarkably simple scaling behaviour. Besides the fact that this simple behaviour emerges from a rather complex model, this allows for a huge simplification of our numerical methodology. A further result is the observation that heterogeneous populations undergo an internal process of quasi-neutral competition. Finally, we investigated the effects of cell-cycle-phase dependent therapies (such as radiation therapy) on heterogeneous populations. In particular, we have studied the case in which the population contains a quiescent sub-population. Our mean-field analysis and numerical simulations confirm that, if the survival fraction of the therapy is too high, rescue of the quiescent population occurs. This gives rise to emergence of resistance to therapy since the rescued population is less sensitive to therapy. Copyright © 2016 The Authors. Published by Elsevier Ltd.. All rights reserved.

Monitoring and modeling infiltration-recharge dynamics of managed aquifer recharge with desalinated seawater

NASA Astrophysics Data System (ADS)

Ganot, Yonatan; Holtzman, Ran; Weisbrod, Noam; Nitzan, Ido; Katz, Yoram; Kurtzman, Daniel

2017-09-01

We study the relation between surface infiltration and groundwater recharge during managed aquifer recharge (MAR) with desalinated seawater in an infiltration pond, at the Menashe site that overlies the northern part of the Israeli Coastal Aquifer. We monitor infiltration dynamics at multiple scales (up to the scale of the entire pond) by measuring the ponding depth, sediment water content and groundwater levels, using pressure sensors, single-ring infiltrometers, soil sensors, and observation wells. During a month (January 2015) of continuous intensive MAR (2.45 × 106 m3 discharged to a 10.7 ha area), groundwater level has risen by 17 m attaining full connection with the pond, while average infiltration rates declined by almost 2 orders of magnitude (from ˜ 11 to ˜ 0.4 m d-1). This reduction can be explained solely by the lithology of the unsaturated zone that includes relatively low-permeability sediments. Clogging processes at the pond-surface - abundant in many MAR operations - are negated by the high-quality desalinated seawater (turbidity ˜ 0.2 NTU, total dissolved solids ˜ 120 mg L-1) or negligible compared to the low-permeability layers. Recharge during infiltration was estimated reasonably well by simple analytical models, whereas a numerical model was used for estimating groundwater recharge after the end of infiltration. It was found that a calibrated numerical model with a one-dimensional representative sediment profile is able to capture MAR dynamics, including temporal reduction of infiltration rates, drainage and groundwater recharge. Measured infiltration rates of an independent MAR event (January 2016) fitted well to those calculated by the calibrated numerical model, showing the model validity. The successful quantification methodologies of the temporal groundwater recharge are useful for MAR practitioners and can serve as an input for groundwater flow models.

On beyond the standard model for high explosives: challenges & obstacles to surmount

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

Menikoff, Ralph Ds

2009-01-01

Plastic-bonded explosives (PBX) are heterogeneous materials. Nevertheless, current explosive models treat them as homogeneous materials. To compensate, an empirically determined effective burn rate is used in place of a chemical reaction rate. A significant limitation of these models is that different burn parameters are needed for applications in different regimes; for example, shock initiation of a PBX at different initial temperatures or different initial densities. This is due to temperature fluctuations generated when a heterogeneous material is shock compressed. Localized regions of high temperatures are called hot spots. They dominate the reaction for shock initiation. The understanding of hot spotmore » generation and their subsequent evolution has been limited by the inability to measure transients on small spatial ({approx} 1 {micro}m) and small temporal ({approx} 1 ns) scales in the harsh environment of a detonation. With the advances in computing power, it is natural to try and gain an understanding of hot-spot initiation with numerical experiments based on meso-scale simulations that resolve material heterogeneities and utilize realistic chemical reaction rates. However, to capture the underlying physics correctly, such high resolution simulations will require more than fast computers with a large amount of memory. Here we discuss some of the issues that need to be addressed. These include dissipative mechanisms that generate hot spots, accurate thermal propceties for the equations of state of the reactants and products, and controlling numerical entropy error from shock impedance mismatches at material interfaces. The later can generate artificial hot spots and lead to premature reaction. Eliminating numerical hot spots is critical for shock initiation simulations due to the positive feedback between the energy release from reaction and the hydrodynamic flow.« less

Short‐term time step convergence in a climate model

PubMed Central

Rasch, Philip J.; Taylor, Mark A.; Jablonowski, Christiane

2015-01-01

Abstract This paper evaluates the numerical convergence of very short (1 h) simulations carried out with a spectral‐element (SE) configuration of the Community Atmosphere Model version 5 (CAM5). While the horizontal grid spacing is fixed at approximately 110 km, the process‐coupling time step is varied between 1800 and 1 s to reveal the convergence rate with respect to the temporal resolution. Special attention is paid to the behavior of the parameterized subgrid‐scale physics. First, a dynamical core test with reduced dynamics time steps is presented. The results demonstrate that the experimental setup is able to correctly assess the convergence rate of the discrete solutions to the adiabatic equations of atmospheric motion. Second, results from full‐physics CAM5 simulations with reduced physics and dynamics time steps are discussed. It is shown that the convergence rate is 0.4—considerably slower than the expected rate of 1.0. Sensitivity experiments indicate that, among the various subgrid‐scale physical parameterizations, the stratiform cloud schemes are associated with the largest time‐stepping errors, and are the primary cause of slow time step convergence. While the details of our findings are model specific, the general test procedure is applicable to any atmospheric general circulation model. The need for more accurate numerical treatments of physical parameterizations, especially the representation of stratiform clouds, is likely common in many models. The suggested test technique can help quantify the time‐stepping errors and identify the related model sensitivities. PMID:27660669

Does postoperative 'M' technique massage with or without mandarin oil reduce infants' distress after major craniofacial surgery?

PubMed

de Jong, Marjan; Lucas, Cees; Bredero, Hansje; van Adrichem, Leon; Tibboel, Dick; van Dijk, Monique

2012-08-01

This article is a report of a randomized controlled trial of the effects of 'M' technique massage with or without mandarin oil compared to standard postoperative care on infants' levels of pain and distress, heart rate and mean arterial pressure after major craniofacial surgery. There is a growing interest in non-pharmacological interventions such as aromatherapy massage in hospitalized children to relieve pain and distress but well performed studies are lacking. This randomized controlled trial allocated 60 children aged 3-36 months after craniofacial surgery from January 2008 to August 2009 to one of three conditions; 'M' technique massage with carrier oil, 'M' technique massage with mandarin oil or standard postoperative care. Primary outcome measures were changes in COMFORT behaviour scores, Numeric Rating Scale pain and Numeric Rating Scale distress scores assessed from videotape by an observer blinded for the condition. In all three groups, the mean postintervention COMFORT behaviour scores were higher than the baseline scores, but differences were not statistically significant. Heart rate and mean arterial pressure showed a statistically significant change across the three assessment periods in all three groups. These changes were not related with the intervention. Results do not support a benefit of 'M' technique massage with or without mandarin oil in these young postoperative patients. Several reasons may account for this: massage given too soon after general anaesthesia, young patients' fear of strangers touching them, patients not used to massage. © 2011 Blackwell Publishing Ltd.

A new numerical formulation of gas leakage and spread into a residential space in terms of hazard analysis.

PubMed

Nagaosa, Ryuichi S

2014-04-30

This study proposes a new numerical formulation of the spread of a flammable gas leakage. A new numerical approach has been applied to establish fundamental data for a hazard assessment of flammable gas spread in an enclosed residential space. The approach employs an extended version of a two-compartment concept, and determines the leakage concentration of gas using a mass-balance based formulation. The study also introduces a computational fluid dynamics (CFD) technique for calculating three-dimensional details of the gas spread by resolving all the essential scales of fluid motions without a turbulent model. The present numerical technique promises numerical solutions with fewer uncertainties produced by the model equations while maintaining high accuracy. The study examines the effect of gas density on the concentration profiles of flammable gas spread. It also discusses the effect of gas leakage rate on gas concentration profiles. Copyright © 2014 The Authors. Published by Elsevier B.V. All rights reserved.

3D numerical simulations of multiphase continental rifting

NASA Astrophysics Data System (ADS)

Naliboff, J.; Glerum, A.; Brune, S.

2017-12-01

Observations of rifted margin architecture suggest continental breakup occurs through multiple phases of extension with distinct styles of deformation. The initial rifting stages are often characterized by slow extension rates and distributed normal faulting in the upper crust decoupled from deformation in the lower crust and mantle lithosphere. Further rifting marks a transition to higher extension rates and coupling between the crust and mantle lithosphere, with deformation typically focused along large-scale detachment faults. Significantly, recent detailed reconstructions and high-resolution 2D numerical simulations suggest that rather than remaining focused on a single long-lived detachment fault, deformation in this phase may progress toward lithospheric breakup through a complex process of fault interaction and development. The numerical simulations also suggest that an initial phase of distributed normal faulting can play a key role in the development of these complex fault networks and the resulting finite deformation patterns. Motivated by these findings, we will present 3D numerical simulations of continental rifting that examine the role of temporal increases in extension velocity on rifted margin structure. The numerical simulations are developed with the massively parallel finite-element code ASPECT. While originally designed to model mantle convection using advanced solvers and adaptive mesh refinement techniques, ASPECT has been extended to model visco-plastic deformation that combines a Drucker Prager yield criterion with non-linear dislocation and diffusion creep. To promote deformation localization, the internal friction angle and cohesion weaken as a function of accumulated plastic strain. Rather than prescribing a single zone of weakness to initiate deformation, an initial random perturbation of the plastic strain field combined with rapid strain weakening produces distributed normal faulting at relatively slow rates of extension in both 2D and 3D simulations. Our presentation will focus on both the numerical assumptions required to produce these results and variations in 3D rifted margin architecture arising from a transition from slow to rapid rates of extension.

The use of direct numerical simulation data in turbulence modeling

NASA Technical Reports Server (NTRS)

Mansour, N. N.

1991-01-01

Direct numerical simulations (DNS) of turbulent flows provide a complete data base to develop and to test turbulence models. In this article, the progress made in developing models for the dissipation rate equation is reviewed. New scaling arguments for the various terms in the dissipation rate equation were tested using data from DNS of homogeneous shear flows. Modifications to the epsilon-equation model that take into account near-wall effects were developed using DNS of turbulent channel flows. Testing of new models for flows under mean compression was carried out using data from DNS of isotropically compressed turbulence. In all of these studies the data from the simulations was essential in guiding the model development. The next generation of DNS will be at higher Reynolds numbers, and will undoubtedly lead to improved models for computations of flows of practical interest.

Convective dissolution of carbon dioxide in saline aquifers

NASA Astrophysics Data System (ADS)

Neufeld, Jerome A.; Hesse, Marc A.; Riaz, Amir; Hallworth, Mark A.; Tchelepi, Hamdi A.; Huppert, Herbert E.

2010-11-01

Geological carbon dioxide (CO2) storage is a means of reducing anthropogenic emissions. Dissolution of CO2 into the brine, resulting in stable stratification, increases storage security. The dissolution rate is determined by convection in the brine driven by the increase of brine density with CO2 saturation. We present a new analogue fluid system that reproduces the convective behaviour of CO2-enriched brine. Laboratory experiments and high-resolution numerical simulations show that the convective flux scales with the Rayleigh number to the 4/5 power, in contrast with a classical linear relationship. A scaling argument for the convective flux incorporating lateral diffusion from downwelling plumes explains this nonlinear relationship for the convective flux, provides a physical picture of high Rayleigh number convection in a porous medium, and predicts the CO2 dissolution rates in CO2 accumulations. These estimates of the dissolution rate show that convective dissolution can play an important role in enhancing storage security.

Scaling and intermittency in incoherent α-shear dynamo

NASA Astrophysics Data System (ADS)

Mitra, Dhrubaditya; Brandenburg, Axel

2012-03-01

We consider mean-field dynamo models with fluctuating α effect, both with and without large-scale shear. The α effect is chosen to be Gaussian white noise with zero mean and a given covariance. In the presence of shear, we show analytically that (in infinitely large domains) the mean-squared magnetic field shows exponential growth. The growth rate of the fastest growing mode is proportional to the shear rate. This result agrees with earlier numerical results of Yousef et al. and the recent analytical treatment by Heinemann, McWilliams & Schekochihin who use a method different from ours. In the absence of shear, an incoherent α2 dynamo may also be possible. We further show by explicit calculation of the growth rate of third- and fourth-order moments of the magnetic field that the probability density function of the mean magnetic field generated by this dynamo is non-Gaussian.

A Study of Criteria for the Evaluation of Secondary School Instrumentalists When Auditioning for Festival Bands. Final Report.

ERIC Educational Resources Information Center

Owen, Curtis D., Jr.

This study purposed to develop a means of evaluating student performance in auditions for festival bands which would minimize the inconsistencies of subjective judgment. Tape recordings of student auditions were played three times to judges. During the first audition, evaluators rated students on a continuum scale with numerical divisions, and…

Projected changes in diverse ecosystems from climate warming and biophysical drivers in northwest Alaska

Treesearch

Mark Torre Jorgenson; Bruce G. Marcot; David K. Swanson; Janet C. Jorgenson; Anthony R. DeGange

2015-01-01

Climate warming affects arctic and boreal ecosystems by interacting with numerous biophysical factors across heterogeneous landscapes. To assess potential effects of warming on diverse local-scale ecosystems (ecotypes) across northwest Alaska, we compiled data on historical areal changes over the last 25–50 years. Based on historical rates of change relative to time...

Turbulent Collapse of Gravitationally Bound Clouds

NASA Astrophysics Data System (ADS)

Murray, Daniel W.

In this dissertation, I explore the time-variable rate of star formation, using both numerical and analytic techniques. I discuss the dynamics of collapsing regions, the effect of protostellar jets, and development of software for use in the hydrodynamic code RAMSES. I perform high-resolution adaptive mesh refinement simulations of star formation in self-gravitating turbulently driven gas. I have run simulations including hydrodynamics (HD), and HD with protostellar jet feedback. Accretion begins when the turbulent fluctuations on largescales, near the driving scale, produce a converging flow. I find that the character of the collapse changes at two radii, the disk radius rd, and the radius r* where the enclosed gas mass exceeds the stellar mass. This is the first numerical work to show that the density evolves to a fixed attractor, rho(r, t) → rho( r), for rd < r < r*; mass flows through this structure onto a sporadically gravitationally unstable disk, and from thence onto the star. The total stellar mass M*(t) (t - t*)2, where (t - t *)2 is the time elapsed since the formation of the first star. This is in agreement with previous numerical and analytic work that suggests a linear rate of star formation. I show that protostellar jets change the normalization of the stellar mass accretion rate, but do not strongly affect the dynamics of star formation in hydrodynamics runs. In particular, M*(t) infinity (1 - f jet)2(t - t*) 2 is the fraction of mass accreted onto the protostar, where fjet is the fraction ejected by the jet. For typical values of fjet 0.1 - 0.3 the accretion rate onto the star can be reduced by a factor of two or three. However, I find that jets have only a small effect (of order 25%) on the accretion rate onto the protostellar disk (the "raw" accretion rate). In other words, jets do not affect the dynamics of the infall, but rather simply eject mass before it reaches the star. Finally, I show that the small scale structure--the radial density, velocity, and mass accretion profiles--are very similar in the jet and no-jet cases.

[Leeches, phytotherapy and physiotherapy in osteo-arthrosis of the knee--a geriatric case study].

PubMed

Teut, Michael; Warning, Albrecht

2008-10-01

Chronic pain is a serious problem for geriatric patients. Conventional pharmacotherapy with nonsteroidal anti-inflammatory drugs or opiates is often accompanied by serious side effects. An 87-year-old woman with severe joint pain due to osteoarthritis of the knee presented with side effects from fentanyl therapy. She was subsequently treated in an inpatient setting with leeches, phytotherapy, physiotherapy and three single doses of metamizol. Prospective single-case study. Pain reduction was assessed with a numeric rating scale (0-10; 0 = minimum; 10 = maximum), mobility by walking distance, and activities of daily living by Barthel index. The association between complementary therapy and the changes observed in the patient under treatment were evaluated using cognition-based medicine. Under complementary therapy, the patient experienced a clear reduction in pain (from 8 to 3 points on the numeric rating scale); regained the ability to walk (increase in walking distance from 0 to 70 m); and showed improvements in activities of daily living (increase in Barthel index from 45 to 65). An association between pain reduction and the complementary treatment setting seems likely. The role of complementary pain therapy in geriatric patients should be evaluated systematically. 2008 S. Karger AG, Basel

A feasible repetitive transcranial magnetic stimulation clinical protocol in migraine prevention.

PubMed

Zardouz, Shawn; Shi, Lei; Leung, Albert

2016-01-01

This case series was conducted to determine the clinical feasibility of a repetitive transcranial magnetic stimulation protocol for the prevention of migraine (with and without aura). Five patients with migraines underwent five repetitive transcranial magnetic stimulation sessions separated in 1- to 2-week intervals for a period of 2 months at a single tertiary medical center. Repetitive transcranial magnetic stimulation was applied to the left motor cortex with 2000 pulses (20 trains with 1s inter-train interval) delivered per session, at a frequency of 10 Hz and 80% resting motor threshold. Pre- and post-treatment numerical rating pain scales were collected, and percent reductions in intensity, frequency, and duration were generated. An average decrease in 37.8%, 32.1%, and 31.2% were noted in the intensity, frequency, and duration of migraines post-repetitive transcranial magnetic stimulation, respectively. A mean decrease in 1.9±1.0 (numerical rating pain scale ± standard deviation; range: 0.4-2.8) in headache intensity scores was noted after the repetitive transcranial magnetic stimulation sessions. The tested repetitive transcranial magnetic stimulation protocol is a well-tolerated, safe, and effective method for migraine prevention.

Interaction of monopoles, dipoles, and turbulence with a shear flow

NASA Astrophysics Data System (ADS)

Marques Rosas Fernandes, V. H.; Kamp, L. P. J.; van Heijst, G. J. F.; Clercx, H. J. H.

2016-09-01

Direct numerical simulations have been conducted to examine the evolution of eddies in the presence of large-scale shear flows. The numerical experiments consist of initial-value-problems in which monopolar and dipolar vortices as well as driven turbulence are superposed on a plane Couette or Poiseuille flow in a periodic two-dimensional channel. The evolution of the flow has been examined for different shear rates of the background flow and different widths of the channel. Results found for retro-grade and pro-grade monopolar vortices are consistent with those found in the literature. Boundary layer vorticity, however, can significantly modify the straining and erosion of monopolar vortices normally seen for unbounded domains. Dipolar vortices are shown to be much more robust coherent structures in a large-scale shear flow than monopolar eddies. An analytical model for their trajectories, which are determined by self-advection and advection and rotation by the shear flow, is presented. Turbulent kinetic energy is effectively suppressed by the shearing action of the background flow provided that the shear is linear (Couette flow) and of sufficient strength. Nonlinear shear as present in the Poiseuille flow seems to even increase the turbulence strength especially for high shear rates.

Direct numerical simulation of cellular-scale blood flow in microvascular networks

NASA Astrophysics Data System (ADS)

Balogh, Peter; Bagchi, Prosenjit

2017-11-01

A direct numerical simulation method is developed to study cellular-scale blood flow in physiologically realistic microvascular networks that are constructed in silico following published in vivo images and data, and are comprised of bifurcating, merging, and winding vessels. The model resolves large deformation of individual red blood cells (RBC) flowing in such complex networks. The vascular walls and deformable interfaces of the RBCs are modeled using the immersed-boundary methods. Time-averaged hemodynamic quantities obtained from the simulations agree quite well with published in vivo data. Our simulations reveal that in several vessels the flow rates and pressure drops could be negatively correlated. The flow resistance and hematocrit are also found to be negatively correlated in some vessels. These observations suggest a deviation from the classical Poiseuille's law in such vessels. The cells are observed to frequently jam at vascular bifurcations resulting in reductions in hematocrit and flow rate in the daughter and mother vessels. We find that RBC jamming results in several orders of magnitude increase in hemodynamic resistance, and thus provides an additional mechanism of increased in vivo blood viscosity as compared to that determined in vitro. Funded by NSF CBET 1604308.

A numerical and experimental comparison of human head phantoms for compliance testing of mobile telephone equipment.

PubMed

Christ, Andreas; Chavannes, Nicolas; Nikoloski, Neviana; Gerber, Hans-Ulrich; Poković, Katja; Kuster, Niels

2005-02-01

A new human head phantom has been proposed by CENELEC/IEEE, based on a large scale anthropometric survey. This phantom is compared to a homogeneous Generic Head Phantom and three high resolution anatomical head models with respect to specific absorption rate (SAR) assessment. The head phantoms are exposed to the radiation of a generic mobile phone (GMP) with different antenna types and a commercial mobile phone. The phones are placed in the standardized testing positions and operate at 900 and 1800 MHz. The average peak SAR is evaluated using both experimental (DASY3 near field scanner) and numerical (FDTD simulations) techniques. The numerical and experimental results compare well and confirm that the applied SAR assessment methods constitute a conservative approach.

The Impact of Frictional Healing on Stick-Slip Recurrence Interval and Stress Drop: Implications for Earthquake Scaling

NASA Astrophysics Data System (ADS)

Im, Kyungjae; Elsworth, Derek; Marone, Chris; Leeman, John

2017-12-01

Interseismic frictional healing is an essential process in the seismic cycle. Observations of both natural and laboratory earthquakes demonstrate that the magnitude of stress drop scales with the logarithm of recurrence time, which is a cornerstone of the rate and state friction (RSF) laws. However, the origin of this log linear behavior and short time "cutoff" for small recurrence intervals remains poorly understood. Here we use RSF laws to demonstrate that the back-projected time of null-healing intrinsically scales with the initial frictional state θi. We explore this behavior and its implications for (1) the short-term cutoff time of frictional healing and (2) the connection between healing rates derived from stick-slip sliding versus slide-hold-slide tests. We use a novel, continuous solution of RSF for a one-dimensional spring-slider system with inertia. The numerical solution continuously traces frictional state evolution (and healing) and shows that stick-slip cutoff time also scales with frictional state at the conclusion of the dynamic slip process θi (=Dc/Vpeak). This numerical investigation on the origins of stick-slip response is verified by comparing laboratory data for a range of peak slip velocities. Slower slip motions yield lesser magnitude of friction drop at a given time due to higher frictional state at the end of each slip event. Our results provide insight on the origin of log linear stick-slip evolution and suggest an approach to estimating the critical slip distance on faults that exhibit gradual accelerations, such as for slow earthquakes.

Predicting SF-6D utility scores from the Neck Disability Index and Numeric Rating Scales for Neck and Arm Pain

PubMed Central

Carreon, Leah Y.; Anderson, Paul A.; McDonough, Christine M.; Djurasovic, Mladen; Glassman, Steven D.

2010-01-01

Study Design Cross-sectional cohort Objective This study aims to provide an algorithm estimate SF-6D utilities using data from the NDI, neck pain and arm pain scores. Summary of Background Data Although cost-utility analysis is increasingly used to provide information about the relative value of alternative interventions, health state values or utilities are rarely available from clinical trial data. The Neck Disability Index (NDI) and numeric rating scales for neck and arm pain, are widely used disease-specific measures of symptoms, function and disability in patients with cervical degenerative disorders. The purpose of this study is to provide an algorithm to allow estimation of SF-6D utilities using data from the NDI, and numeric rating scales for neck and arm pain. Methods SF-36, NDI, neck and arm pain rating scale scores were prospectively collected pre-operatively, at 12 and 24 months post-operatively in 2080 patients undergoing cervical fusion for degenerative disorders. SF-6D utilities were computed and Spearman correlation coefficients were calculated for paired observations from multiple time points between NDI, neck and arm pain scores and SF-6D utility scores. SF-6D scores were estimated from the NDI, neck and arm pain scores using a linear regression model. Using a separate, independent dataset of 396 patients in which and NDI scores were available SF-6D was estimated for each subject and compared to their actual SF-6D. Results The mean age for those in the development sample, was 50.4 ± 11.0 years and 33% were male. In the validation sample the mean age was 53.1 ± 9.9 years and 35% were male. Correlations between the SF-6D and the NDI, neck and arm pain scores were statistically significant (p<0.0001) with correlation coefficients of 0.82, 0.62, and 0.50 respectively. The regression equation using NDI alone to predict SF-6D had an R2 of 0.66 and a root mean square error (RMSE) of 0.056. In the validation analysis, there was no statistically significant difference (p=0.961) between actual mean SF-6D (0.49 ± 0.08) and the estimated mean SF-6D score (0.49 ± 0.08) using the NDI regression model. Conclusion This regression-based algorithm may be a useful tool to predict SF-6D scores in studies of cervical degenerative disease that have collected NDI but not utility scores. PMID:20847713

Numerical approaches to combustion modeling. Progress in Astronautics and Aeronautics. Vol. 135

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

Oran, E.S.; Boris, J.P.

1991-01-01

Various papers on numerical approaches to combustion modeling are presented. The topics addressed include; ab initio quantum chemistry for combustion; rate coefficient calculations for combustion modeling; numerical modeling of combustion of complex hydrocarbons; combustion kinetics and sensitivity analysis computations; reduction of chemical reaction models; length scales in laminar and turbulent flames; numerical modeling of laminar diffusion flames; laminar flames in premixed gases; spectral simulations of turbulent reacting flows; vortex simulation of reacting shear flow; combustion modeling using PDF methods. Also considered are: supersonic reacting internal flow fields; studies of detonation initiation, propagation, and quenching; numerical modeling of heterogeneous detonations, deflagration-to-detonationmore » transition to reactive granular materials; toward a microscopic theory of detonations in energetic crystals; overview of spray modeling; liquid drop behavior in dense and dilute clusters; spray combustion in idealized configurations: parallel drop streams; comparisons of deterministic and stochastic computations of drop collisions in dense sprays; ignition and flame spread across solid fuels; numerical study of pulse combustor dynamics; mathematical modeling of enclosure fires; nuclear systems.« less

Numerical study of Tallinn storm-water system flooding conditions using CFD simulations of multi-phase flow in a large-scale inverted siphon

NASA Astrophysics Data System (ADS)

Kaur, K.; Laanearu, J.; Annus, I.

2017-10-01

The numerical experiments are carried out for qualitative and quantitative interpretation of a multi-phase flow processes associated with malfunctioning of the Tallinn storm-water system during rain storms. The investigations are focused on the single-line inverted siphon, which is used as under-road connection of pipes of the storm-water system under interest. A multi-phase flow solver of Computational Fluid Dynamics software OpenFOAM is used for simulating the three-phase flow dynamics in the hydraulic system. The CFD simulations are performed with different inflow rates under same initial conditions. The computational results are compared essentially in two cases 1) design flow rate and 2) larger flow rate, for emptying the initially filled inverted siphon from a slurry-fluid. The larger flow-rate situations are under particular interest to detected possible flooding. In this regard, it is anticipated that the CFD solutions provide an important insight to functioning of inverted siphon under a restricted water-flow conditions at simultaneous presence of air and slurry-fluid.

Numerical Investigation of a Novel Microscale Swirling Jet Reactor for Medical Sensor Applications

NASA Astrophysics Data System (ADS)

Ogus, G.; Baelmans, M.; Lammertyn, J.; Vanierschot, M.

2018-03-01

A microscale swirler and corresponding reactor for a recent detection and analysis tool for healthcare applications, Fiber optic-surface plasmon resonance (FO-SPR), is presented in this study. The sensor is a 400 μm diameter needle that works as a detector for certain particles. Currently, the detection process relies on diffusion of particles towards the sensor and hence diagnostic time is rather long. The aim of this study is to decrease that diagnostic time by introducing convective mixing in the reactor by means of a swirling inlet flow. This will increase the particle deposition on the FO-SPR sensor and hence an increase in detection rate, as this rate strongly depends on the aimed particle concentration near the sensor. As the flow rates are rather low and the length scales are small, the flow in such reactors is laminar. In this study, robustly controllable mixing features of a swirling jet flow is used to increase the particle concentration near the sensor. A numerical analysis (CFD) is performed to characterize the flow and a detailed analysis of flow structures depending on the flow rate are reported.

Epidemic spreading on one-way-coupled networks

NASA Astrophysics Data System (ADS)

Wang, Lingna; Sun, Mengfeng; Chen, Shanshan; Fu, Xinchu

2016-09-01

Numerous real-world networks (e.g., social, communicational, and biological networks) have been observed to depend on each other, and this results in interconnected networks with different topology structures and dynamics functions. In this paper, we focus on the scenario of epidemic spreading on one-way-coupled networks comprised of two subnetworks, which can manifest the transmission of some zoonotic diseases. By proposing a mathematical model through mean-field approximation approach, we prove the global stability of the disease-free and endemic equilibria of this model. Through the theoretical and numerical analysis, we obtain interesting results: the basic reproduction number R0 of the whole network is the maximum of the basic reproduction numbers of the two subnetworks; R0 is independent of the cross-infection rate and cross contact pattern; R0 increases rapidly with the growth of inner infection rate if the inner contact pattern is scale-free; in order to eradicate zoonotic diseases from human beings, we must simultaneously eradicate them from animals; bird-to-bird infection rate has bigger impact on the human's average infected density than bird-to-human infection rate.

Mean field model of acetylcholine mediated dynamics in the cerebral cortex.

PubMed

Clearwater, J M; Rennie, C J; Robinson, P A

2007-12-01

A recent continuum model of the large scale electrical activity of the cerebral cortex is generalized to include cholinergic modulation. In this model, dynamic modulation of synaptic strength acts over the time scales of nicotinic and muscarinic receptor action. The cortical model is analyzed to determine the effect of acetylcholine (ACh) on its steady states, linear stability, spectrum, and temporal responses to changes in subcortical input. ACh increases the firing rate in steady states of the system. Changing ACh concentration does not introduce oscillatory behavior into the system, but increases the overall spectral power. Model responses to pulses in subcortical input are affected by the tonic level of ACh concentration, with higher levels of ACh increasing the magnitude firing rate response of excitatory cortical neurons to pulses of subcortical input. Numerical simulations are used to explore the temporal dynamics of the model in response to changes in ACh concentration. Evidence is seen of a transition from a state in which intracortical inputs are emphasized to a state where thalamic afferents have enhanced influence. Perturbations in ACh concentration cause changes in the firing rate of cortical neurons, with rapid responses due to fast acting facilitatory effects of nicotinic receptors on subcortical afferents, and slower responses due to muscarinic suppression of intracortical connections. Together, these numerical simulations demonstrate that the actions of ACh could be a significant factor modulating early components of evoked response potentials.

Gigahertz dynamics of a strongly driven single quantum spin.

PubMed

Fuchs, G D; Dobrovitski, V V; Toyli, D M; Heremans, F J; Awschalom, D D

2009-12-11

Two-level systems are at the core of numerous real-world technologies such as magnetic resonance imaging and atomic clocks. Coherent control of the state is achieved with an oscillating field that drives dynamics at a rate determined by its amplitude. As the strength of the field is increased, a different regime emerges where linear scaling of the manipulation rate breaks down and complex dynamics are expected. By calibrating the spin rotation with an adiabatic passage, we have measured the room-temperature "strong-driving" dynamics of a single nitrogen vacancy center in diamond. With an adiabatic passage to calibrate the spin rotation, we observed dynamics on sub-nanosecond time scales. Contrary to conventional thinking, this breakdown of the rotating wave approximation provides opportunities for time-optimal quantum control of a single spin.

Numerical simulation of systems of shear bands in ductile metal with inclusions

NASA Astrophysics Data System (ADS)

Plohr, Jeeyeon

2017-06-01

We develop a method for numerical simulations of high strain-rate loading of mesoscale samples of ductile metal with inclusions. Because of its small-scale inhomogeneity, the composite material is prone to localized shear deformation. This method employs the Generalized Method of Cells to ensure that the micro mechanical behavior of the metal and inclusions is reflected properly in the behavior of the composite at the mesoscale. To find the effective plastic strain rate when shear bands are present, we extend and apply the analytic and numerical analysis of shear bands of Glimm, Plohr, and Sharp. Our tests of the method focus on the stress/strain response in uniaxial-strain flow, both compressive and tensile, of depleted uranium metal containing silicon carbide inclusions. In results, we verify the elevated temperature and thermal softening at shear bands in our simulations of pure DU and DU/SiC composites. We also note that in composites, due the asymmetry caused by the inclusions, shear band form at different times in different subcells. In particular, in the subcells near inclusions, shear band form much earlier than they do in pure DU.

Analytical and numerical treatment of drift-tearing modes in plasma slab

NASA Astrophysics Data System (ADS)

Mirnov, V. V.; Hegna, C. C.; Sovinec, C. R.; Howell, E. C.

2016-10-01

Two-fluid corrections to linear tearing modes includes 1) diamagnetic drifts that reduce the growth rate and 2) electron and ion decoupling on short scales that can lead to fast reconnection. We have recently developed an analytical model that includes effects 1) and 2) and important contribution from finite electron parallel thermal conduction. Both the tendencies 1) and 2) are confirmed by an approximate analytic dispersion relation that is derived using a perturbative approach of small ion-sound gyroradius ρs. This approach is only valid at the beginning of the transition from the collisional to semi-collisional regimes. Further analytical and numerical work is performed to cover the full interval of ρs connecting these two limiting cases. Growth rates are computed from analytic theory with a shooting method. They match the resistive MHD regime with the dispersion relations known at asymptotically large ion-sound gyroradius. A comparison between this analytical treatment and linear numerical simulations using the NIMROD code with cold ions and hot electrons in plasma slab is reported. The material is based on work supported by the U.S. DOE and NSF.

PPPC 4 DMν: a Poor Particle Physicist Cookbook for Neutrinos from Dark Matter annihilations in the Sun

NASA Astrophysics Data System (ADS)

Baratella, Pietro; Cirelli, Marco; Hektor, Andi; Pata, Joosep; Piibeleht, Morten; Strumia, Alessandro

2014-03-01

We provide ingredients and recipes for computing neutrino signals of TeV-scale Dark Matter (DM) annihilations in the Sun. For each annihilation channel and DM mass we present the energy spectra of neutrinos at production, including: state-of-the-art energy losses of primary particles in solar matter, secondary neutrinos, electroweak radiation. We then present the spectra after propagation to the Earth, including (vacuum and matter) flavor oscillations and interactions in solar matter. We also provide a numerical computation of the capture rate of DM particles in the Sun. These results are available in numerical form.

A numerical investigation of the crystallographic texture effect on the surface roughening in aluminum polycrystals

NASA Astrophysics Data System (ADS)

Romanova, V.; Balokhonov, R.; Batukhtina, E.; Zinovieva, O.; Bezmozgiy, I.

2015-10-01

The results of a numerical analysis of the mesoscale surface roughening in a polycrystalline aluminum alloy exposed to uniaxial tension are presented. A 3D finite-element model taking an explicit account of grain structure is developed. The model describes a constitutive behavior of the material on the grain scale, using anisotropic elasticity and crystal plasticity theory. The effects of the grain shape and texture on the deformation-induced roughening are investigated. Calculation results have shown that surface roughness is much higher and develops at the highest rate in a polycrystal with equiaxed grains where both the micro- and mesoscale surface displacements are observed.

Instantons in Quantum Annealing: Thermally Assisted Tunneling Vs Quantum Monte Carlo Simulations

NASA Technical Reports Server (NTRS)

Jiang, Zhang; Smelyanskiy, Vadim N.; Boixo, Sergio; Isakov, Sergei V.; Neven, Hartmut; Mazzola, Guglielmo; Troyer, Matthias

2015-01-01

Recent numerical result (arXiv:1512.02206) from Google suggested that the D-Wave quantum annealer may have an asymptotic speed-up than simulated annealing, however, the asymptotic advantage disappears when it is compared to quantum Monte Carlo (a classical algorithm despite its name). We show analytically that the asymptotic scaling of quantum tunneling is exactly the same as the escape rate in quantum Monte Carlo for a class of problems. Thus, the Google result might be explained in our framework. We also found that the transition state in quantum Monte Carlo corresponds to the instanton solution in quantum tunneling problems, which is observed in numerical simulations.

Tunnelling in Dante's Inferno

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

Furuuchi, Kazuyuki; Sperling, Marcus, E-mail: kazuyuki.furuuchi@manipal.edu, E-mail: marcus.sperling@univie.ac.at

2017-05-01

We study quantum tunnelling in Dante's Inferno model of large field inflation. Such a tunnelling process, which will terminate inflation, becomes problematic if the tunnelling rate is rapid compared to the Hubble time scale at the time of inflation. Consequently, we constrain the parameter space of Dante's Inferno model by demanding a suppressed tunnelling rate during inflation. The constraints are derived and explicit numerical bounds are provided for representative examples. Our considerations are at the level of an effective field theory; hence, the presented constraints have to hold regardless of any UV completion.

Numerical simulation of a plane turbulent mixing layer, with applications to isothermal, rapid reactions

NASA Technical Reports Server (NTRS)

Lin, P.; Pratt, D. T.

1987-01-01

A hybrid method has been developed for the numerical prediction of turbulent mixing in a spatially-developing, free shear layer. Most significantly, the computation incorporates the effects of large-scale structures, Schmidt number and Reynolds number on mixing, which have been overlooked in the past. In flow field prediction, large-eddy simulation was conducted by a modified 2-D vortex method with subgrid-scale modeling. The predicted mean velocities, shear layer growth rates, Reynolds stresses, and the RMS of longitudinal velocity fluctuations were found to be in good agreement with experiments, although the lateral velocity fluctuations were overpredicted. In scalar transport, the Monte Carlo method was extended to the simulation of the time-dependent pdf transport equation. For the first time, the mixing frequency in Curl's coalescence/dispersion model was estimated by using Broadwell and Breidenthal's theory of micromixing, which involves Schmidt number, Reynolds number and the local vorticity. Numerical tests were performed for a gaseous case and an aqueous case. Evidence that pure freestream fluids are entrained into the layer by large-scale motions was found in the predicted pdf. Mean concentration profiles were found to be insensitive to Schmidt number, while the unmixedness was higher for higher Schmidt number. Applications were made to mixing layers with isothermal, fast reactions. The predicted difference in product thickness of the two cases was in reasonable quantitative agreement with experimental measurements.

Multiphysics numerical modeling of the continuous flow microwave-assisted transesterification process.

PubMed

Muley, Pranjali D; Boldor, Dorin

2012-01-01

Use of advanced microwave technology for biodiesel production from vegetable oil is a relatively new technology. Microwave dielectric heating increases the process efficiency and reduces reaction time. Microwave heating depends on various factors such as material properties (dielectric and thermo-physical), frequency of operation and system design. Although lab scale results are promising, it is important to study these parameters and optimize the process before scaling up. Numerical modeling approach can be applied for predicting heating and temperature profiles including at larger scale. The process can be studied for optimization without actually performing the experiments, reducing the amount of experimental work required. A basic numerical model of continuous electromagnetic heating of biodiesel precursors was developed. A finite element model was built using COMSOL Multiphysics 4.2 software by coupling the electromagnetic problem with the fluid flow and heat transfer problem. Chemical reaction was not taken into account. Material dielectric properties were obtained experimentally, while the thermal properties were obtained from the literature (all the properties were temperature dependent). The model was tested for the two different power levels 4000 W and 4700 W at a constant flow rate of 840ml/min. The electric field, electromagnetic power density flow and temperature profiles were studied. Resulting temperature profiles were validated by comparing to the temperatures obtained at specific locations from the experiment. The results obtained were in good agreement with the experimental data.

Flow turbulence topology in regular porous media: From macroscopic to microscopic scale with direct numerical simulation

NASA Astrophysics Data System (ADS)

Chu, Xu; Weigand, Bernhard; Vaikuntanathan, Visakh

2018-06-01

Microscopic analysis of turbulence topology in a regular porous medium is presented with a series of direct numerical simulation. The regular porous media are comprised of square cylinders in a staggered array. Triply periodic boundary conditions enable efficient investigations in a representative elementary volume. Three flow patterns—channel with sudden contraction, impinging surface, and wake—are observed and studied quantitatively in contrast to the qualitative experimental studies reported in the literature. Among these, shear layers in the channel show the highest turbulence intensity due to a favorable pressure gradient and shed due to an adverse pressure gradient downstream. The turbulent energy budget indicates a strong production rate after the flow contraction and a strong dissipation on both shear and impinging walls. Energy spectra and pre-multiplied spectra detect large scale energetic structures in the shear layer and a breakup of scales in the impinging layer. However, these large scale structures break into less energetic small structures at high Reynolds number conditions. This suggests an absence of coherent structures in densely packed porous media at high Reynolds numbers. Anisotropy analysis with a barycentric map shows that the turbulence in porous media is highly isotropic in the macro-scale, which is not the case in the micro-scale. In the end, proper orthogonal decomposition is employed to distinguish the energy-conserving structures. The results support the pore scale prevalence hypothesis. However, energetic coherent structures are observed in the case with sparsely packed porous media.

Wettability effect on capillary trapping of supercritical CO2 at pore-scale: micromodel experiment and numerical modeling

NASA Astrophysics Data System (ADS)

Hu, R.; Wan, J.

2015-12-01

Wettability of reservoir minerals along pore surfaces plays a controlling role in capillary trapping of supercritical (sc) CO2 in geologic carbon sequestration. The mechanisms controlling scCO2 residual trapping are still not fully understood. We studied the effect of pore surface wettability on CO2 residual saturation at the pore-scale using engineered high pressure and high temperature micromodel (transparent pore networks) experiments and numerical modeling. Through chemical treatment of the micromodel pore surfaces, water-wet, intermediate-wet, and CO2-wet micromodels can be obtained. Both drainage and imbibition experiments were conducted at 8.5 MPa and 45 °C with controlled flow rate. Dynamic images of fluid-fluid displacement processes were recorded using a microscope with a CCD camera. Residual saturations were determined by analysis of late stage imbibition images of flow path structures. We performed direct numerical simulations of the full Navier-Stokes equations using a volume-of-fluid based finite-volume framework for the primary drainage and the followed imbibition for the micromodel experiments with different contact angles. The numerical simulations agreed well with our experimental observations. We found that more scCO2 can be trapped within the CO2-wet micromodel whereas lower residual scCO2 saturation occurred within the water-wet micromodels in both our experiments and the numerical simulations. These results provide direct and consistent evidence of the effect of wettability, and have important implications for scCO2 trapping in geologic carbon sequestration.

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

Walters, C.T.; Dulaney, J.L.; Campbell, B.E.

Demonstrations of operation of a compact neodymium glass laser with average output powers greater than 1 kW for several seconds are reported. The laser is based on the thermal inertia laser (TIL) concept wherein a neodymium-doped glass rod is pumped uniformly without cooling during a burst mode of laser operation. Design principles for TIL devices and scaling to 100 kW class lasers are discussed. Experimental results for a low repetition-rate proof-of-concept pulsed device (30 J, 0.2 Hz) and a high repetition-rate pulsed prototype (40 J, 36 Hz) are presented and compared to numerical solutions for the laser rate equations withmore » temperature dependent cross-sections.« less

Efficacy and safety of dextromethorphan/quinidine at two dosage levels for diabetic neuropathic pain: a double-blind, placebo-controlled, multicenter study.

PubMed

Shaibani, Aziz I; Pope, Laura E; Thisted, Ronald; Hepner, Adrian

2012-02-01

To evaluate dextromethorphan coadministered with quinidine as treatment of diabetic peripheral neuropathic pain. In a 13-week, phase 3, randomized controlled trial, 379 adults with daily symmetric diabetic peripheral neuropathy (DPN) leg pain for ≥3 months received double-blind placebo, dextromethorphan/quinidine (DMQ) 45/30 mg, or DMQ 30/30 mg, administered once daily for 7 days and twice daily thereafter. Efficacy measures included four pain rating scales applied daily using patient diaries, and another two applied at five clinic visits. On all six scales, DMQ 45/30 mg was significantly superior to placebo, including the primary efficacy analysis, which utilized mixed-effects modeling to test all scores on an 11-point numerical Pain Rating Scale (P < 0.0001). Sensitivity analyses gave consistent results. Efficacy vs placebo was also seen for diary ratings of present pain intensity, and pain interference with sleep and with activities (all P < 0.0001). Among clinic visit assessments, DMQ 45/30 mg demonstrated greater leg pain relief (P = 0.0002) and greater reduction of leg pain intensity (P = 0.0286) vs placebo. The efficacy of DMQ 30/30 mg was numerically less than for 45/30 mg but for most outcomes remained significantly greater vs placebo. Adverse events were mostly mild or moderate and of expected types. Discontinuation for adverse events in the DMQ groups was at least twice as common as placebo. Throughout a 13-week trial, DMQ was effective, with an acceptable safety profile, for treatment of DPN pain. Other fixed-dose combinations of DMQ should be studied to improve overall tolerability while maintaining significant efficacy. Wiley Periodicals, Inc.

Study and modeling of finite rate chemistry effects in turbulent non-premixed flames

NASA Technical Reports Server (NTRS)

Vervisch, Luc

1993-01-01

The development of numerical models that reflect some of the most important features of turbulent reacting flows requires information about the behavior of key quantities in well defined combustion regimes. In turbulent flames, the coupling between turbulent and chemical processes is so strong that it is extremely difficult to isolate the role played by one individual physical phenomenon. Direct numerical simulation (hereafter DNS) allows us to study in detail the turbulence-chemistry interaction in some restricted but completely defined situations. Globally, non-premixed flames are controlled by two limiting regimes: the fast chemistry case, where the turbulent flame can be pictured as a random distribution of local chemical equilibrium problems; and the slow chemistry case, where the chemistry integrates in time the turbulent fluctuations. The Damkoehler number, ratio of a mechanical time scale to chemical time scale, is used to distinguish between these regimes. Today most of the industrial computer codes are able to perform predictions in the hypothesis of local equilibrium chemistry using a presumed shape for the probability density function (pdt) of the conserved scalar. However, the finite rate chemistry situation is of great interest because industrial burners usually generate regimes in which, at some points, the flame is undergoing local extinction or at least non-equilibrium situations. Moreover, this variety of situations strongly influences the production of pollutants. To quantify finite rate chemistry effect, the interaction between a non-premixed flame and a free decaying turbulence is studied using DNS. The attention is focused on the dynamic of extinction, and an attempt is made to quantify the effect of the reaction on the small scale mixing process. The unequal diffusivity effect is also addressed. Finally, a simple turbulent combustion model based on the DNS observations and tractable in real flow configurations is proposed.

Pain relief assessment by aromatic essential oil massage on outpatients with primary dysmenorrhea: a randomized, double-blind clinical trial.

PubMed

Ou, Ming-Chiu; Hsu, Tsung-Fu; Lai, Andrew C; Lin, Yu-Ting; Lin, Chia-Ching

2012-05-01

This study assessed the effectiveness of blended essential oils on menstrual cramps for outpatients with primary dysmenorrhea and explored the analgesic ingredients in the essential oils. A randomized, double-blind clinical trial was conducted. Forty-eight outpatients were diagnosed with primary dysmenorrhea by a gynecologist and had 10-point numeric rating scales that were more than 5. The patients were randomly assigned to an essential oil group (n = 24) and a synthetic fragrance group (n = 24). Essential oils blended with lavender (Lavandula officinalis), clary sage (Salvia sclarea) and marjoram (Origanum majorana) in a 2:1:1 ratio was diluted in unscented cream at 3% concentration for the essential oil group. All outpatients used the cream daily to massage their lower abdomen from the end of the last menstruation continuing to the beginning of the next menstruation. Both the numeric rating scale and the verbal rating scale significantly decreased (P < 0.001) after one menstrual cycle intervention in the two groups. The duration of pain was significantly reduced from 2.4 to 1.8 days after aromatherapy intervention in the essential oil group. Aromatic oil massage provided relief for outpatients with primary dysmenorrhea and reduced the duration of menstrual pain in the essential oil group. The blended essential oils contain four key analgesic components that amount to as much as 79.29%; these analgesic constitutes are linalyl acetate, linalool, eucalyptol, and β-caryophyllene. This study suggests that this blended formula can serve as a reference for alternative and complementary medicine on primary dysmenorrhea. © 2012 The Authors. Journal of Obstetrics and Gynaecology Research © 2012 Japan Society of Obstetrics and Gynecology.

Efficacy and Safety of Pregabalin in the Treatment of Patients With Painful Diabetic Peripheral Neuropathy and Pain on Walking.

PubMed

Huffman, Cynthia; Stacey, Brett R; Tuchman, Michael; Burbridge, Claire; Li, Chunming; Parsons, Bruce; Pauer, Lynne; Scavone, Joseph M; Behar, Regina; Yurkewicz, Lorraine

2015-11-01

This randomized, double-blind, placebo-controlled, multicenter, 2-period crossover study (two 6-week treatment periods separated by a 2-week washout period) evaluated the efficacy and safety of pregabalin (150 to 300 mg/d) for treatment of pain and pain on walking in patients with painful diabetic peripheral neuropathy (DPN) who experienced pain while walking. Co-primary efficacy endpoints were: (1) mean pain score (last 7 daily pain diary scores, 0 to 10 numeric rating scale at end of each treatment period) and (2) DPN pain on walking (0 to 10 numeric rating scale immediately after walking 50 feet [15.2 m] on flat surface). Secondary endpoints included other pain parameters, patient-reported sleep, health-related quality of life, and safety measures. Two hundred three patients were treated (pregabalin, n=198; placebo, n=186), with no statistically significant treatment difference for pregabalin versus placebo in the co-primary efficacy endpoints, mean DPN pain (P=0.0656) and mean DPN pain on walking (P=0.412). A carryover effect was observed. Analysis of co-primary endpoints for period 1 showed significant treatment difference for DPN pain (P=0.034) and DPN pain on walking (P=0.001). Treatment with pregabalin resulted in significant improvements versus placebo on prespecified patient global impression of change (end of period 1; P=0.002), and sleep interference rating scale (end of period 2; P=0.011). Adverse events were more frequent with pregabalin than with placebo and caused discontinuation in 13 (6.6%) pregabalin patients versus 5 (2.7%) placebo patients. Failure to meet the co-primary objectives may be related to carryover effect from period 1 to period 2, lower pregabalin dose (150 to 300 mg/d), and/or placebo response in painful DPN.

A numerical investigation of the interplay between fireline length, geometry, and rate of spread

Treesearch

J. M. Canfield; R. R. Linn; J. A. Sauer; M. Finney; J. Forthofer

2014-01-01

The current study focuses on coupled dynamics and resultant geometry of fireline segments of various ignition lengths. As an example, for ignition lines of length scales typical for field experiments, fireline curvature is the result of a competition between the head fire and the flanks of the fire. A number of physical features (i.e. buoyancy and wind field divergence...

Long-time states of inverse cascades in the presence of a maximum length scale

NASA Technical Reports Server (NTRS)

Hossain, M.; Matthaeus, W. H.; Montgomery, D.

1983-01-01

It is shown numerically, both for the two-dimensional Navier-Stokes (guiding-center plasma) equations and for two-dimensional magnetohydrodynamics, that the long-time asymptotic state in a forced inverse-cascade situation is one in which the spectrum is completely dominated by its own fundamental. The growth continues until the fundamental is dissipatively limited by its own dissipation rate.

Multigrid preconditioned conjugate-gradient method for large-scale wave-front reconstruction.

PubMed

Gilles, Luc; Vogel, Curtis R; Ellerbroek, Brent L

2002-09-01

We introduce a multigrid preconditioned conjugate-gradient (MGCG) iterative scheme for computing open-loop wave-front reconstructors for extreme adaptive optics systems. We present numerical simulations for a 17-m class telescope with n = 48756 sensor measurement grid points within the aperture, which indicate that our MGCG method has a rapid convergence rate for a wide range of subaperture average slope measurement signal-to-noise ratios. The total computational cost is of order n log n. Hence our scheme provides for fast wave-front simulation and control in large-scale adaptive optics systems.

Spreading dynamics of a SIQRS epidemic model on scale-free networks

NASA Astrophysics Data System (ADS)

Li, Tao; Wang, Yuanmei; Guan, Zhi-Hong

2014-03-01

In order to investigate the influence of heterogeneity of the underlying networks and quarantine strategy on epidemic spreading, a SIQRS epidemic model on the scale-free networks is presented. Using the mean field theory the spreading dynamics of the virus is analyzed. The spreading critical threshold and equilibria are derived. Theoretical results indicate that the critical threshold value is significantly dependent on the topology of the underlying networks and quarantine rate. The existence of equilibria is determined by threshold value. The stability of disease-free equilibrium and the permanence of the disease are proved. Numerical simulations confirmed the analytical results.

Manifestations of drag reduction by polymer additives in decaying, homogeneous, isotropic turbulence.

PubMed

Perlekar, Prasad; Mitra, Dhrubaditya; Pandit, Rahul

2006-12-31

The existence of drag reduction by polymer additives, well established for wall-bounded turbulent flows, is controversial in homogeneous, isotropic turbulence. To settle this controversy, we carry out a high-resolution direct numerical simulation of decaying, homogeneous, isotropic turbulence with polymer additives. Our study reveals clear manifestations of drag-reduction-type phenomena: On the addition of polymers to the turbulent fluid, we obtain a reduction in the energy-dissipation rate, a significant modification of the fluid energy spectrum especially in the deep-dissipation range, a suppression of small-scale intermittency, and a decrease in small-scale vorticity filaments.

Control of dephasing in rotationally hot molecules

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

Bartram, David; Ivanov, Misha

We consider a rotationally hot diatomic molecule as an example of an open quantum system, where molecular vibrational wave packets are subject to dephasing due to rovibrational coupling. We report analytical and numerical results addressing whether the dephasing rate can be controlled by adjustment of the initial wave packet phases. It appears that over long time scales, phase-only control is not possible, but for earlier time scales the possibility of phase-only control of dephasing remains. In addition, we point out that the time dependence of the dephasing process depends significantly upon the degeneracy of the rotational environment states.

Measurement Properties of Performance-Specific Pain Ratings of Patients Awaiting Total Joint Arthroplasty as a Consequence of Osteoarthritis

PubMed Central

Stratford, Paul W.; Kennedy, Deborah M.; Woodhouse, Linda J.; Spadoni, Gregory

2008-01-01

Purpose: To estimate the test–retest reliability of the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) pain sub-scale and performance-specific assessments of pain, as well as the association between these measures for patients awaiting primary total hip or knee arthroplasty as a consequence of osteoarthritis. Methods: A total of 164 patients awaiting unilateral primary hip or knee arthroplasty completed four performance measures (self-paced walk, timed up and go, stair test, six-minute walk) and the WOMAC. Scores for 22 of these patients provided test–retest reliability data. Estimates of test–retest reliability (Type 2,1 intraclass correlation coefficient [ICC] and standard error of measurement [SEM]) and the association between measures were examined. Results: ICC values for individual performance-specific pain ratings were between 0.70 and 0.86; SEM values were between 0.97 and 1.33 pain points. ICC estimates for the four-item performance pain ratings and the WOMAC pain sub-scale were 0.82 and 0.57 respectively. The correlation between the sum of the pain scores for the four performance measures and the WOMAC pain sub-scale was 0.62. Conclusion: Reliability estimates for the performance-specific assessments of pain using the numeric pain rating scale were consistent with values reported for patients with a spectrum of musculoskeletal conditions. The reliability estimate for the WOMAC pain sub-scale was lower than typically reported in the literature. The level of association between the WOMAC pain sub-scale and the various performance-specific pain scales suggests that the scores can be used interchangeably when applied to groups but not for individual patients. PMID:20145758

Scaling and pedotransfer in numerical simulations of flow and transport in soils

USDA-ARS?s Scientific Manuscript database

Flow and transport parameters of soils in numerical simulations need to be defined at the support scale of computational grid cells. Such support scale can substantially differ from the support scale in laboratory or field measurements of flow and transport parameters. The scale-dependence of flow a...

Saturation of energetic-particle-driven geodesic acoustic modes due to wave-particle nonlinearity

NASA Astrophysics Data System (ADS)

Biancalani, A.; Chavdarovski, I.; Qiu, Z.; Bottino, A.; Del Sarto, D.; Ghizzo, A.; Gürcan, Ö.; Morel, P.; Novikau, I.

2017-12-01

The nonlinear dynamics of energetic-particle (EP) driven geodesic acoustic modes (EGAM) is investigated here. A numerical analysis with the global gyrokinetic particle-in-cell code ORB5 is performed, and the results are interpreted with the analytical theory, in close comparison with the theory of the beam-plasma instability. Only axisymmetric modes are considered, with a nonlinear dynamics determined by wave-particle interaction. Quadratic scalings of the saturated electric field with respect to the linear growth rate are found for the case of interest. As a main result, the formula for the saturation level is provided. Near the saturation, we observe a transition from adiabatic to non-adiabatic dynamics, i.e. the frequency chirping rate becomes comparable to the resonant EP bounce frequency. The numerical analysis is performed here with electrostatic simulations with circular flux surfaces, and kinetic effects of the electrons are neglected.

Turbulent properties under sloping Ice-wall in polar water

NASA Astrophysics Data System (ADS)

Mondal, Mainak; Gayen, Bishakhdatta; Griffiths, Ross W.; Kerr, Ross C.

2017-11-01

Ice-shelves around West Antarctic basins are the most vulnerable to melting in the presence of warmer continental shelf water. A large extent of slope exists under these ice-shelves, where turbulent transport of salt and heat into the ice wall drives a convective melt-water plume against it. Large scale ice-ocean models neglect the effect of convection which can lead to a wrong estimation of melt rate. We perform direct numerical simulations under sloping ice-shelves with realistic ambient conditions. We estimated the melt rates, boundary layer thicknesses and entrainment coefficients as a function of slope angle. The numerical results are further supported by theoretical predictions. Over the range of slope angles, different mechanisms are active for sustaining turbulence. For near vertical case, buoyancy production is the primary source of turbulent kinetic energy whereas for shallower angles turbulence is produced by velocity shear in the meltwater plume. Australian Research Council.

Evaluation of a strain-sensitive transport model in LES of turbulent nonpremixed sooting flames

NASA Astrophysics Data System (ADS)

Lew, Jeffry K.; Yang, Suo; Mueller, Michael E.

2017-11-01

Direct Numerical Simulations (DNS) of turbulent nonpremixed jet flames have revealed that Polycyclic Aromatic Hydrocarbons (PAH) are confined to spatially intermittent regions of low scalar dissipation rate due to their slow formation chemistry. The length scales of these regions are on the order of the Kolmogorov scale or smaller, where molecular diffusion effects dominate over turbulent transport effects irrespective of the large-scale turbulent Reynolds number. A strain-sensitive transport model has been developed to identify such species whose slow chemistry, relative to local mixing rates, confines them to these small length scales. In a conventional nonpremixed ``flamelet'' approach, these species are then modeled with their molecular Lewis numbers, while remaining species are modeled with an effective unity Lewis number. A priori analysis indicates that this strain-sensitive transport model significantly affects PAH yield in nonpremixed flames with essentially no impact on temperature and major species. The model is applied with Large Eddy Simulation (LES) to a series of turbulent nonpremixed sooting jet flames and validated via comparisons with experimental measurements of soot volume fraction.

Numerical Upscaling of Solute Transport in Fractured Porous Media Based on Flow Aligned Blocks

NASA Astrophysics Data System (ADS)

Leube, P.; Nowak, W.; Sanchez-Vila, X.

2013-12-01

High-contrast or fractured-porous media (FPM) pose one of the largest unresolved challenges for simulating large hydrogeological systems. The high contrast in advective transport between fast conduits and low-permeability rock matrix, including complex mass transfer processes, leads to the typical complex characteristics of early bulk arrivals and long tailings. Adequate direct representation of FPM requires enormous numerical resolutions. For large scales, e.g. the catchment scale, and when allowing for uncertainty in the fracture network architecture or in matrix properties, computational costs quickly reach an intractable level. In such cases, multi-scale simulation techniques have become useful tools. They allow decreasing the complexity of models by aggregating and transferring their parameters to coarser scales and so drastically reduce the computational costs. However, these advantages come at a loss of detail and accuracy. In this work, we develop and test a new multi-scale or upscaled modeling approach based on block upscaling. The novelty is that individual blocks are defined by and aligned with the local flow coordinates. We choose a multi-rate mass transfer (MRMT) model to represent the remaining sub-block non-Fickian behavior within these blocks on the coarse scale. To make the scale transition simple and to save computational costs, we capture sub-block features by temporal moments (TM) of block-wise particle arrival times to be matched with the MRMT model. By predicting spatial mass distributions of injected tracers in a synthetic test scenario, our coarse-scale solution matches reasonably well with the corresponding fine-scale reference solution. For predicting higher TM-orders (such as arrival time and effective dispersion), the prediction accuracy steadily decreases. This is compensated to some extent by the MRMT model. If the MRMT model becomes too complex, it loses its effect. We also found that prediction accuracy is sensitive to the choice of the effective dispersion coefficients and on the block resolution. A key advantage of the flow-aligned blocks is that the small-scale velocity field is reproduced quite accurately on the block-scale through their flow alignment. Thus, the block-scale transverse dispersivities remain in the similar magnitude as local ones, and they do not have to represent macroscopic uncertainty. Also, the flow-aligned blocks minimize numerical dispersion when solving the large-scale transport problem.

Large-Scale Hybrid Motor Testing. Chapter 10

NASA Technical Reports Server (NTRS)

Story, George

2006-01-01

Hybrid rocket motors can be successfully demonstrated at a small scale virtually anywhere. There have been many suitcase sized portable test stands assembled for demonstration of hybrids. They show the safety of hybrid rockets to the audiences. These small show motors and small laboratory scale motors can give comparative burn rate data for development of different fuel/oxidizer combinations, however questions that are always asked when hybrids are mentioned for large scale applications are - how do they scale and has it been shown in a large motor? To answer those questions, large scale motor testing is required to verify the hybrid motor at its true size. The necessity to conduct large-scale hybrid rocket motor tests to validate the burn rate from the small motors to application size has been documented in several place^'^^.^. Comparison of small scale hybrid data to that of larger scale data indicates that the fuel burn rate goes down with increasing port size, even with the same oxidizer flux. This trend holds for conventional hybrid motors with forward oxidizer injection and HTPB based fuels. While the reason this is occurring would make a great paper or study or thesis, it is not thoroughly understood at this time. Potential causes include the fact that since hybrid combustion is boundary layer driven, the larger port sizes reduce the interaction (radiation, mixing and heat transfer) from the core region of the port. This chapter focuses on some of the large, prototype sized testing of hybrid motors. The largest motors tested have been AMROC s 250K-lbf thrust motor at Edwards Air Force Base and the Hybrid Propulsion Demonstration Program s 250K-lbf thrust motor at Stennis Space Center. Numerous smaller tests were performed to support the burn rate, stability and scaling concepts that went into the development of those large motors.

Numerical Investigation of Earthquake Nucleation on a Laboratory-Scale Heterogeneous Fault with Rate-and-State Friction

NASA Astrophysics Data System (ADS)

Higgins, N.; Lapusta, N.

2014-12-01

Many large earthquakes on natural faults are preceded by smaller events, often termed foreshocks, that occur close in time and space to the larger event that follows. Understanding the origin of such events is important for understanding earthquake physics. Unique laboratory experiments of earthquake nucleation in a meter-scale slab of granite (McLaskey and Kilgore, 2013; McLaskey et al., 2014) demonstrate that sample-scale nucleation processes are also accompanied by much smaller seismic events. One potential explanation for these foreshocks is that they occur on small asperities - or bumps - on the fault interface, which may also be the locations of smaller critical nucleation size. We explore this possibility through 3D numerical simulations of a heterogeneous 2D fault embedded in a homogeneous elastic half-space, in an attempt to qualitatively reproduce the laboratory observations of foreshocks. In our model, the simulated fault interface is governed by rate-and-state friction with laboratory-relevant frictional properties, fault loading, and fault size. To create favorable locations for foreshocks, the fault surface heterogeneity is represented as patches of increased normal stress, decreased characteristic slip distance L, or both. Our simulation results indicate that one can create a rate-and-state model of the experimental observations. Models with a combination of higher normal stress and lower L at the patches are closest to matching the laboratory observations of foreshocks in moment magnitude, source size, and stress drop. In particular, we find that, when the local compression is increased, foreshocks can occur on patches that are smaller than theoretical critical nucleation size estimates. The additional inclusion of lower L for these patches helps to keep stress drops within the range observed in experiments, and is compatible with the asperity model of foreshock sources, since one would expect more compressed spots to be smoother (and hence have lower L). In this heterogeneous rate-and-state fault model, the foreshocks interact with each other and with the overall nucleation process through their postseismic slip. The interplay amongst foreshocks, and between foreshocks and the larger-scale nucleation process, is a topic of our future work.

Measuring IBS patient reported outcomes with an abdominal pain numeric rating scale: results from the proof cohort

PubMed Central

SPIEGEL, B.; BOLUS, R.; HARRIS, L. A.; LUCAK, S.; NALIBOFF, B.; ESRAILIAN, E.; CHEY, W. D.; LEMBO, A.; KARSAN, H.; TILLISCH, K.; TALLEY, J.; MAYER, E.; CHANG, L.

2009-01-01

Background Controversy exists about how to effectively measure patient reported outcomes in IBS clinical trials. Pain numeric rating scales (NRS) are widely used in the non-IBS pain literature. The FDA has proposed using the NRS in IBS. Aim To test the psychometrics of an abdominal pain NRS in IBS. Methods We analyzed data from a longitudinal cohort of Rome III IBS subjects. At entry, subjects completed a 10-point NRS, bowel symptoms, IBS severity measurements (IBSSS, FBDSI), health related quality of life indices (IBS-QOL, EQ5D), and the worker productivity activity index (WPAI). We repeated assessments at 3 months along with a response scale to calculate the minimal clinically important difference (MCID). Results There were 277 subjects (82% women; age=42±15) at baseline and 90 at 3 months. The NRS correlated cross-sectionally with IBSSS (r=0.60; p<0.0011), FBDSI (r=0.49; p<0.0001), IBS-QOL (r=0.43; p<0.0001), EQ5D (r=0.48; p<0.0001), presenteeism (r=0.39; p<0.0001), absenteeism (r=0.17; p=0.04), and distension (r=0.46; p<0.0001), but not stool frequency or form. The MCID was 2.2 points, correlating with a 29.5% reduction over time. Conclusions An abdominal pain NRS exhibits excellent validity and can be readily interpreted with an MCID in patients with IBS. These data support the use of the NRS in IBS clinical trials. PMID:19751360

The Worst Itch Numeric Rating Scale for patients with moderate to severe plaque psoriasis or psoriatic arthritis.

PubMed

Naegeli, April N; Flood, Emuella; Tucker, Jennifer; Devlen, Jennifer; Edson-Heredia, Emily

2015-06-01

Plaque psoriasis (PP) and psoriatic arthritis (PsA) are autoinflammatory chronic conditions associated with skin involvement. Pruritus, or itching, is a prevalent and bothersome symptom in patients with PP and is associated with reduced health-related quality of life. The Worst Itch Numeric Rating Scale (WI-NRS) has been developed as a simple, single item with which to assess the patient-reported severity of this symptom at its most intense during the previous 24-hour period. Qualitative research was undertaken to assess the content validity of the WI-NRS. Patients with moderate to severe PP and patients with PsA were recruited from clinical sites in the USA. The qualitative research entailed two-part interviews, which began with concept elicitation to gain understanding of patients' experiences of itching, followed by cognitive debriefing of the WI-NRS to assess the instrument's understandability, clarity, and degree of appropriateness from the patient's perspective. Twelve patients with PP and 22 with PsA participated in the study. Patients reported that itching was an important and relevant symptom of their psoriatic disease. The WI-NRS was reported to be complete and easy to understand; the recall period was considered appropriate, the response scale was familiar, and, overall, the instrument was found to be appropriate for assessing itching severity. Patient responses support the content validity of the WI-NRS. The psychometric properties of the tool will be evaluated in future studies. © 2014 The International Society of Dermatology.

Motor/Prefrontal Transcranial Direct Current Stimulation (tDCS) Following Lumbar Surgery Reduces Postoperative Analgesia Use.

PubMed

Glaser, John; Reeves, Scott T; Stoll, William David; Epperson, Thomas I; Hilbert, Megan; Madan, Alok; George, Mark S; Borckardt, Jeffrey J

2016-05-01

Randomized, controlled pilot trial. The present study is the first randomized, double-blind, sham-controlled pilot clinical trial of transcranial direct current stimulation (tDCS) for pain and patient-controlled analgesia (PCA) opioid usage among patients receiving spine surgery. Lumbar spinal surgeries are common, and while pain is often a complaint that precedes surgical intervention, the procedures themselves are associated with considerable postoperative pain lasting days to weeks. Adequate postoperative pain control is an important factor in determining recovery and new analgesic strategies are needed that can be used adjunctively to existing strategies potentially to reduce reliance on opioid analgesia. Several novel brain stimulation technologies including tDCS are beginning to demonstrate promise as treatments for a variety of pain conditions. Twenty-seven patients undergoing lumbar spine procedures at Medical University of South Carolina were randomly assigned to receive four 20-minute sessions of real or sham tDCS during their postsurgical hospital stay. Patient-administered hydromorphone usage was tracked along with numeric rating scale pain ratings. The effect of tDCS on the slope of the cumulative PCA curve was significant (P < 0.001) and tDCS was associated with a 23% reduction in PCA usage. In the real tDCS group a 31% reduction was observed in pain-at-its-least ratings from admission to discharge (P = 0.027), but no other changes in numeric rating scale pain ratings were significant in either group. The present pilot trial is the first study to demonstrate an opioid sparing effect of tDCS after spine surgical procedures. Although this was a small pilot trial in a heterogeneous sample of spinal surgery patients, a moderate effect-size was observed for tDCS, suggesting that future work in this area is warranted. 2.

Electrical high-frequency stimulation of the human thoracolumbar fascia evokes long-term potentiation-like pain amplification.

PubMed

Schilder, Andreas; Magerl, Walter; Hoheisel, Ulrich; Klein, Thomas; Treede, Rolf-Detlef

2016-10-01

Nociceptive long-term potentiation, a use dependent increase in synaptic efficacy in the dorsal horn of the spinal cord is thought to contribute to the development of persistent pain states. So far, no study has analyzed the effects of high-frequency stimulation (HFS) of afferents from deep tissues (muscle and fascia) on pain perception in the back in humans. In 16 healthy volunteers, the multifidus muscle and the overlying thoracolumbar fascia were stimulated with electrical high-frequency pulses (5 × 100 pulses at 100 Hz) through bipolar concentric needle electrodes placed at lumbar level (L3/L4). Electrical pain thresholds were lower (P < 0.001) and pain ratings were higher for fascia compared with muscle stimulation (P < 0.05). For both tissues, pain ratings increased significantly across the five 100 Hz trains (from 15 to 22 numerical rating scale for fascia, from 8 to 12 numerical rating scale for muscle; both P < 0.01). Fascia HFS increased fascia pain ratings 2.17 times compared with the unconditioned control site (P < 0.001), but had no significant effect on pain sensitivity of the muscle. The HFS in muscle had no significant effect on muscle pain, but decreased pain sensitivity of the overlying fascia by 20% (P < 0.05). In additional experiments using the same electrodes and followed over >60 minutes post-HFS, potentiation by fascia HFS was similar to that of skin HFS. These findings show that the spinal input from the fascia can induce long-term changes in pain sensitivity for at least 60 minutes making it a candidate potentially contributing to nonspecific low back pain.

Tetrahedron deformation and alignment of perceived vorticity and strain in a turbulent flow

NASA Astrophysics Data System (ADS)

Pumir, Alain; Bodenschatz, Eberhard; Xu, Haitao

2013-03-01

We describe the structure and dynamics of turbulence by the scale-dependent perceived velocity gradient tensor as supported by following four tracers, i.e., fluid particles, that initially form a regular tetrahedron. We report results from experiments in a von Kármán swirling water flow and from numerical simulations of the incompressible Navier-Stokes equation. We analyze the statistics and the dynamics of the perceived rate of strain tensor and vorticity for initially regular tetrahedron of size r0 from the dissipative to the integral scale. Just as for the true velocity gradient, at any instant, the perceived vorticity is also preferentially aligned with the intermediate eigenvector of the perceived rate of strain. However, in the perceived rate of strain eigenframe fixed at a given time t = 0, the perceived vorticity evolves in time such as to align with the strongest eigendirection at t = 0. This also applies to the true velocity gradient. The experimental data at the higher Reynolds number suggests the existence of a self-similar regime in the inertial range. In particular, the dynamics of alignment of the perceived vorticity and strain can be rescaled by t0, the turbulence time scale of the flow when the scale r0 is in the inertial range. For smaller Reynolds numbers we found the dynamics to be scale dependent.

Interacting scales and energy transfer in isotropic turbulence

NASA Technical Reports Server (NTRS)

Zhou, YE

1993-01-01

The dependence of the energy transfer process on the disparity of the interacting scales is investigated in the inertial and far-dissipation ranges of isotropic turbulence. The strategy for generating the simulated flow fields and the choice of a disparity parameter to characterize the scaling of the interactions is discussed. The inertial range is found to be dominated by relatively local interactions, in agreement with the Kolmogorov assumption. The far-dissipation is found to be dominated by relatively non-local interactions, supporting the classical notion that the far-dissipation range is slaved to the Kolmogorov scales. The measured energy transfer is compared with the classical models of Heisenberg, Obukhov, and the more detailed analysis of Tennekes and Lumley. The energy transfer statistics measured in the numerically simulated flows are found to be nearly self-similar for wave numbers in the inertial range. Using the self-similar form measured within the limited scale range of the simulation, an 'ideal' energy transfer function and the corresponding energy flux rate for an inertial range of infinite extent are constructed. From this flux rate, the Kolmogorov constant is calculated to be 1.5, in excellent agreement with experiments.

A new, objective, quantitative scale for measuring local skin responses following topical actinic keratosis therapy with ingenol mebutate.

PubMed

Rosen, Robert; Marmur, Ellen; Anderson, Lawrence; Welburn, Peter; Katsamas, Janelle

2014-12-01

Local skin responses (LSRs) are the most common adverse effects of topical actinic keratosis (AK) therapy. There is currently no method available that allows objective characterization of LSRs. Here, the authors describe a new scale developed to quantitatively and objectively assess the six most common LSRs resulting from topical AK therapy with ingenol mebutate. The LSR grading scale was developed using a 0-4 numerical rating, with clinical descriptors and representative photographic images for each rating. Good inter-observer grading concordance was demonstrated in peer review during development of the tool. Data on the use of the scale are described from four phase III double-blind studies of ingenol mebutate (n = 1,005). LSRs peaked on days 4 (face/scalp) or 8 (trunk/extremities), with mean maximum composite LSR scores of 9.1 and 6.8, respectively, and a rapid return toward baseline by day 15 in most cases. Mean composite LSR score at day 57 was generally lower than at baseline. The LSR grading scale is an objective tool allowing practicing dermatologists to characterize and compare LSRs to existing and, potentially, future AK therapies.

Validation of the Individualized Numeric Rating Scale (INRS): a pain assessment tool for nonverbal children with intellectual disability.

PubMed

Solodiuk, Jean C; Scott-Sutherland, Jennifer; Meyers, Margie; Myette, Beth; Shusterman, Christine; Karian, Victoria E; Harris, Sion Kim; Curley, Martha A Q

2010-08-01

Clinical observations suggest that nonverbal children with severe intellectual disability exhibit pain in a wide variety yet uniquely individual ways. Here, we investigate the feasibility and describe the initial psychometrics properties of the Individualized Numeric Rating Scale (INRS), a personalized pain assessment tool for nonverbal children with intellectual disability based on the parent's knowledge of the child. Parents of 50 nonverbal children with severe intellectual disability scheduled for surgery were able to complete the task of describing then rank ordering their child's usual and pain indicators. The parent, bedside nurse and research assistant (RA) triad then simultaneously yet independently scored the patient's post-operative pain using the INRS for a maximum of two sets of pre/post paired observations. A total of 170 triad assessments were completed before (n=85) and after (n=85) an intervention to manage the child's pain. INRS inter-rater agreement between the parents and research nurse was high (ICC 0.82-0.87) across all ratings. Parent and bedside nurse agreement (ICC 0.65-0.74) and bedside nurse and research nurse agreement (ICC 0.74-0.80) also suggest good reliability. A moderate to strong correlation (0.63-0.73) between INRS ratings and NCCPC-PV total scores provides evidence of convergent validity. These results provide preliminary data that the INRS is a valid and reliable tool for assessing pain in nonverbal children with severe intellectual disability in an acute care setting. Copyright (c) 2010 International Association for the Study of Pain. Published by Elsevier B.V. All rights reserved.

Reactive Fluid Flow and Applications to Diagenesis, Mineral Deposits, and Crustal Rocks

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

Rye, Danny M.; Bolton, Edward W.

2002-11-04

The objective is to initiate new: modeling of coupled fluid flow and chemical reactions of geologic environments; experimental and theoretical studies of water-rock reactions; collection and interpretation of stable isotopic and geochemical field data at many spatial scales of systems involving fluid flow and reaction in environments ranging from soils to metamorphic rocks. Theoretical modeling of coupled fluid flow and chemical reactions, involving kinetics, has been employed to understand the differences between equilibrium, steady-state, and non-steady-state behavior of the chemical evolution of open fluid-rock systems. The numerical codes developed in this project treat multi-component, finite-rate reactions combined with advective andmore » dispersive transport in multi-dimensions. The codes incorporate heat, mass, and isotopic transfer in both porous and fractured media. Experimental work has obtained the kinetic rate laws of pertinent silicate-water reactions and the rates of Sr release during chemical weathering. Ab-initio quantum mechanical techniques have been applied to obtain the kinetics and mechanisms of silicate surface reactions and isotopic exchange between water and dissolved species. Geochemical field-based studies were carried out on the Wepawaug metamorphic schist, on the Irish base-metal sediment-hosted ore system, in the Dalradian metamorphic complex in Scotland, and on weathering in the Columbia River flood basalts. The geochemical and isotopic field data, and the experimental and theoretical rate data, were used as constraints on the numerical models and to determine the length and time scales relevant to each of the field areas.« less

Fate of the antibiotic sulfadiazine in natural soils: Experimental and numerical investigations.

PubMed

Engelhardt, Irina; Sittig, Stephan; Šimůnek, Jirka; Groeneweg, Joost; Pütz, Thomas; Vereecken, Harry

2015-01-01

Based on small-scale laboratory and field-scale lysimeter experiments, the sorption and biodegradation of sulfonamide sulfadiazine (SDZ) were investigated in unsaturated sandy and silty-clay soils. Sorption and biodegradation were low in the laboratory, while the highest leaching rates were observed when SDZ was mixed with manure. The leaching rate decreased when SDZ was mixed with pure water, and was smallest with the highest SDZ concentrations. In the laboratory, three transformation products (TPs) developed after an initial lag phase. However, the amount of TPs was different for different mixing-scenarios. The TP 2-aminopyrimidine was not observed in the laboratory, but was the most prevalent TP at the field scale. Sorption was within the same range at the laboratory and field scales. However, distinctive differences occurred with respect to biodegradation, which was higher in the field lysimeters than at the laboratory scale. While the silty-clay soil favored sorption of SDZ, the sandy, and thus highly permeable, soil was characterized by short half-lives and thus a quick biodegradation of SDZ. For 2-aminopyrimidine, half-lives of only a few days were observed. Increased field-scale biodegradation in the sandy soil resulted from a higher water and air permeability that enhanced oxygen transport and limited oxygen depletion. Furthermore, low pH was more important than the organic matter and clay content for increasing the biodegradation of SDZ. A numerical analysis of breakthrough curves of bromide, SDZ, and its TPs showed that preferential flow pathways strongly affected the solute transport within shallow parts of the soil profile at the field scale. However, this effect was reduced in deeper parts of the soil profile. Due to high field-scale biodegradation in several layers of both soils, neither SDZ nor 2-aminopyrimidine was detected in the discharge of the lysimeter at a depth of 1m. Synthetic 50 year long simulations, which considered the application of manure with SDZ for general agricultural practices in Germany and humid climate conditions, showed that the concentration of SDZ decreased below 0.1 μg/L in both soils below the depth of 50 cm. Copyright © 2015 Elsevier B.V. All rights reserved.

Fate of the antibiotic sulfadiazine in natural soils: Experimental and numerical investigations

NASA Astrophysics Data System (ADS)

Engelhardt, Irina; Sittig, Stephan; Šimůnek, Jirka; Groeneweg, Joost; Pütz, Thomas; Vereecken, Harry

2015-06-01

Based on small-scale laboratory and field-scale lysimeter experiments, the sorption and biodegradation of sulfonamide sulfadiazine (SDZ) were investigated in unsaturated sandy and silty-clay soils. Sorption and biodegradation were low in the laboratory, while the highest leaching rates were observed when SDZ was mixed with manure. The leaching rate decreased when SDZ was mixed with pure water, and was smallest with the highest SDZ concentrations. In the laboratory, three transformation products (TPs) developed after an initial lag phase. However, the amount of TPs was different for different mixing-scenarios. The TP 2-aminopyrimidine was not observed in the laboratory, but was the most prevalent TP at the field scale. Sorption was within the same range at the laboratory and field scales. However, distinctive differences occurred with respect to biodegradation, which was higher in the field lysimeters than at the laboratory scale. While the silty-clay soil favored sorption of SDZ, the sandy, and thus highly permeable, soil was characterized by short half-lives and thus a quick biodegradation of SDZ. For 2-aminopyrimidine, half-lives of only a few days were observed. Increased field-scale biodegradation in the sandy soil resulted from a higher water and air permeability that enhanced oxygen transport and limited oxygen depletion. Furthermore, low pH was more important than the organic matter and clay content for increasing the biodegradation of SDZ. A numerical analysis of breakthrough curves of bromide, SDZ, and its TPs showed that preferential flow pathways strongly affected the solute transport within shallow parts of the soil profile at the field scale. However, this effect was reduced in deeper parts of the soil profile. Due to high field-scale biodegradation in several layers of both soils, neither SDZ nor 2-aminopyrimidine was detected in the discharge of the lysimeter at a depth of 1 m. Synthetic 50 year long simulations, which considered the application of manure with SDZ for general agricultural practices in Germany and humid climate conditions, showed that the concentration of SDZ decreased below 0.1 μg/L in both soils below the depth of 50 cm.

Modeling Long-Term Fluvial Incision : Shall we Care for the Details of Short-Term Fluvial Dynamics?

NASA Astrophysics Data System (ADS)

Lague, D.; Davy, P.

2008-12-01

Fluvial incision laws used in numerical models of coupled climate, erosion and tectonics systems are mainly based on the family of stream power laws for which the rate of local erosion E is a power function of the topographic slope S and the local mean discharge Q : E = K Qm Sn. The exponents m and n are generally taken as (0.35, 0.7) or (0.5, 1), and K is chosen such that the predicted topographic elevation given the prevailing rates of precipitation and tectonics stay within realistic values. The resulting topographies are reasonably realistic, and the coupled system dynamics behaves somehow as expected : more precipitation induces increased erosion and localization of the deformation. Yet, if we now focus on smaller scale fluvial dynamics (the reach scale), recent advances have suggested that discharge variability, channel width dynamics or sediment flux effects may play a significant role in controlling incision rates. These are not factored in the simple stream power law model. In this work, we study how these short- term details propagate into long-term incision dynamics within the framework of surface/tectonics coupled numerical models. To upscale the short term dynamics to geological timescales, we use a numerical model of a trapezoidal river in which vertical and lateral incision processes are computed from fluid shear stress at a daily timescale, sediment transport and protection effects are factored in, as well as a variable discharge. We show that the stream power law model might still be a valid model but that as soon as realistic effects are included such as a threshold for sediment transport, variable discharge and dynamic width the resulting exponents m and n can be as high as 2 and 4. This high non-linearity has a profound consequence on the sensitivity of fluvial relief to incision rate. We also show that additional complexity does not systematically translates into more non-linear behaviour. For instance, considering only a dynamical width without discharge variability does not induce a significant difference in the predicted long-term incision law and scaling of relief with incision rate at steady-state. We conclude that the simple stream power law models currently in use are false, and that details of short-term fluvial dynamics must make their way into long-term evolution models to avoid oversimplifying the coupled dynamics between erosion, tectonics and climate.

Microphysics of Magnetic Reconnection: Experiments on RSX and Simulation

NASA Astrophysics Data System (ADS)

Intrator, T. P.; Furno, I. G.; Hsu, S. C.; Lapenta, G.; Ricci, P.

2003-12-01

Using a unique LANL laboratory facility, the Reconnection Scaling Experiment (RSX), and a state-of-the-art LANL numerical code, CELESTE3D, we are beginning an experimental and numerical study of the microphysics of 2D and 3D "fast magnetic reconnection". RSX at Los Alamos National Laboratory is already operational and producing research plasmas. In RSX, the radial boundaries and thus the reconnection geometry are not constrained to two dimensions. It is capable of investigating 3D magnetic reconnection occurring in a free-boundary 3D linear geometry during the coalescence of two parallel current plasma channels, which are produced by using plasma gun technology. RSX can also scale the guide field (ion gyroradius) independently of other reconnection parameters. Frontier reconnection research invokes (1) `anomalous' microinstability-induced resistivity, which enhances dissipation rates inside the reconnection layer and (2) terms of the two-fluid generalized Ohm's law which introduce whistler and kinetic Alfvén wave dynamics. The two-fluid approach predicts (a) a two-spatial-scale spatial structure of the reconnection layer, with outer (inner) thickness equal to the ion (electron) skin depth and (b) Hall currents in the reconnection plane and out-of-plane magnetic field on the electron scale. We will show spatially resolved RSX experimental measurements of the dynamics of the reconnection layer, and take advantage of our scaling capabilities to address the applicability of the two-fluid approach.

Orthostatic intolerance and fatigue in the hypermobility type of Ehlers-Danlos Syndrome.

PubMed

De Wandele, Inge; Rombaut, Lies; De Backer, Tine; Peersman, Wim; Da Silva, Hellen; De Mits, Sophie; De Paepe, Anne; Calders, Patrick; Malfait, Fransiska

2016-08-01

To investigate whether orthostatic intolerance (OI) is a significant predictor for fatigue in Ehlers-Danlos Syndrome, hypermobility type (EDS-HT). Eighty patients with EDS-HT and 52 controls participated in the first part of the study, which consisted of questionnaires. Fatigue was evaluated using the Checklist Individual Strength (CIS). As possible fatigue determinants OI [Autonomic Symptom Profile (ASP)], habitual physical activity (Baecke), affective distress [Hospital Anxiety and Depression Scale (HADS)], pain (SF36), medication use and generalized hypermobility (5-point score of Grahame and Hakim regarding generalized joint hypermobility) were studied. Next, a 20 min head-up tilt (70°) was performed in a subsample of 39 patients and 35 controls, while beat-to-beat heart rate and blood pressure were monitored (Holter, Finometer Pro). Before and after tilt, fatigue severity was assessed using a numeric rating scale. Patients scored significantly higher on the CIS [total score: EDS: 98.2 (18.63) vs controls: 45.8 (16.62), P < 0.001] and on the OI domain of the ASP [EDS: 22.78 (7.16) vs controls: 6.5 (7.78)]. OI was prevalent in EDS-HT (EDS: 74.4%, controls: 34.3%, P = 0.001), and frequently expressed as postural orthostatic tachycardia (41.0% of the EDS group). Patients responded to tilt with a higher heart rate and lower total peripheral resistance (p < 0.001; p = 0.032). This altered response correlated with fatigue in daily life (CIS). In the EDS-HT group, tilt provoked significantly more fatigue [numeric rating scale increase: EDS: +3.1 (1.90), controls: +0.5 (1.24), P < 0.001]. Furthermore, the factors OI, pain, affective distress, decreased physical activity and sedative use explained 47.7% of the variance in fatigue severity. OI is an important determinant of fatigue in EDS-HT. © The Author 2016. Published by Oxford University Press on behalf of the British Society for Rheumatology. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Apparently abnormal Wechsler Memory Scale index score patterns in the normal population.

PubMed

Carrasco, Roman Marcus; Grups, Josefine; Evans, Brittney; Simco, Edward; Mittenberg, Wiley

2015-01-01

Interpretation of the Wechsler Memory Scale-Fourth Edition may involve examination of multiple memory index score contrasts and similar comparisons with Wechsler Adult Intelligence Scale-Fourth Edition ability indexes. Standardization sample data suggest that 15-point differences between any specific pair of index scores are relatively uncommon in normal individuals, but these base rates refer to a comparison between a single pair of indexes rather than multiple simultaneous comparisons among indexes. This study provides normative data for the occurrence of multiple index score differences calculated by using Monte Carlo simulations and validated against standardization data. Differences of 15 points between any two memory indexes or between memory and ability indexes occurred in 60% and 48% of the normative sample, respectively. Wechsler index score discrepancies are normally common and therefore not clinically meaningful when numerous such comparisons are made. Explicit prior interpretive hypotheses are necessary to reduce the number of index comparisons and associated false-positive conclusions. Monte Carlo simulation accurately predicts these false-positive rates.

On measurements and their quality. Paper 4: verbal anchors and the number of response options in rating scales.

PubMed

Beckstead, Jason W

2014-05-01

This is the last in a short series of papers on measurement theory and practice with particular relevance to intervention research in nursing, midwifery, and healthcare. Understanding how it is that people respond to the questions posed by researchers is fundamental to progress in the social and health sciences. For decades methodologists in psychology, marketing, education, and survey research have studied this issue. In this paper I review this diverse empirical literature to synthesize basic principles for creating rating scales which can reduce measurement error and increase the quality of resulting data. After introducing a theoretical framework known as the cognitive aspects of survey methods (CASM), I review the fundamentals of psychological scaling theory and discuss how it has been used to study the meanings of verbal response options and provide an illustration of how the quality of measurements may be influenced by our choice of the verbal phrases we present as response options. Next, I review the research on the optimal number of response options to use in various measurement situations and how verbal and numeric anchors can combine to influence data quality. Finally, I summarize the issues covered and present recommendations for best practice when creating and using rating scales in research. Copyright © 2013 Elsevier Ltd. All rights reserved.

Fast numerical methods for simulating large-scale integrate-and-fire neuronal networks.

PubMed

Rangan, Aaditya V; Cai, David

2007-02-01

We discuss numerical methods for simulating large-scale, integrate-and-fire (I&F) neuronal networks. Important elements in our numerical methods are (i) a neurophysiologically inspired integrating factor which casts the solution as a numerically tractable integral equation, and allows us to obtain stable and accurate individual neuronal trajectories (i.e., voltage and conductance time-courses) even when the I&F neuronal equations are stiff, such as in strongly fluctuating, high-conductance states; (ii) an iterated process of spike-spike corrections within groups of strongly coupled neurons to account for spike-spike interactions within a single large numerical time-step; and (iii) a clustering procedure of firing events in the network to take advantage of localized architectures, such as spatial scales of strong local interactions, which are often present in large-scale computational models-for example, those of the primary visual cortex. (We note that the spike-spike corrections in our methods are more involved than the correction of single neuron spike-time via a polynomial interpolation as in the modified Runge-Kutta methods commonly used in simulations of I&F neuronal networks.) Our methods can evolve networks with relatively strong local interactions in an asymptotically optimal way such that each neuron fires approximately once in [Formula: see text] operations, where N is the number of neurons in the system. We note that quantifications used in computational modeling are often statistical, since measurements in a real experiment to characterize physiological systems are typically statistical, such as firing rate, interspike interval distributions, and spike-triggered voltage distributions. We emphasize that it takes much less computational effort to resolve statistical properties of certain I&F neuronal networks than to fully resolve trajectories of each and every neuron within the system. For networks operating in realistic dynamical regimes, such as strongly fluctuating, high-conductance states, our methods are designed to achieve statistical accuracy when very large time-steps are used. Moreover, our methods can also achieve trajectory-wise accuracy when small time-steps are used.

Convective melting in a magma chamber: theory and numerical experiment.

NASA Astrophysics Data System (ADS)

Simakin, A.

2012-04-01

We present results of the numerical modeling of convective melting in a magma chamber in 2D. Model was pointed on the silicic system approximated with Qz-Fsp binary undersaturated with water. Viscosity was calculated as a function of the melt composition, temperature and crystal content and comprises for the pure melt 104.5-105.5 Pas. Lower boundary was taken thermally insulated in majority of the runs. Size of FEM (bilinear elements) grid for velocity is 25x25 cm and for the integration of the density term 8x8 cm. Melting of the chamber roof proceeds with the heat supply due to the chaotic thermo-compositional convection and conductive heat loose into melted substrate. We compare our numerical data with existing semi-analytical models. Theoretical studies of the assimilation rates in the magma chambers usually use theoretical semi-analytical model by Huppert and Sparks (1988) (e.g., Snyder, 2000). We find that this model has strong points: 1) Independence of the melting rate on the sill thickness (Ra>>Rac) 2) Independence of the convective heat transfer on the roof temperature 3) Determination of the exponential thermal boundary layer ahead of the melting front and weak points: 1) Ignoring the possibility of the crystallization without melting regime for narrow sills and dykes. 2)Neglecting of two-phase character of convection. 3)Ignoring of the strong viscosity variation near the melting front. Independence of convective flux from the sill size (at Ra>>Rac) allows reducing of computational domain to the geologically small size (10-15 m). Concept of exponential thermal boundary layer is also rather important. Length scale (L0) of this layer is related to the melting rate and thermal diffusivity coefficient kT as L0=kT/um and at the melting rate 10 m/yr becomes about 2 m. Such small scale implies that convective melting is very effective (small conductive heat loss) and part of the numerical domain filled with roof rocks can be taken small. In the H&S model conditions for the intruded magma to crystallize first and then switch to the roof melting or only crystallize were not defined. We did this in our numerical experiments in terms of the initial magma and roof rocks temperatures for particular sill size. Neglecting strong viscosity variation in the boundary layer at the melting front leads to the overestimation of the melting rate by H&S model on approximately 70% at Tm=940oC. At Tm =800oC effect of the crystals present in descending plumes compensates viscosity increase and numerical Um practically coincides with theoretical one (difference 8%). Some researchers (Huber et al., 2010) use empirical and scaling results obtained from stagnant-lid convection (Davaille and Jaupart, 1993). We find that the later model is not applicable to the melting problem since super-exponential dependence of the viscosity from temperature is valid providing full solidification below eutectic temperature Ts. "Melting temperature" at the stagnant-lid style of convection is defined by Arhenius rheological parameters and bulk melt temperature and can be less than Ts. Our numerical study was applied to the estimation of the possible time frame and efficiency of the remelting of the silicic pyroclastics by superheated rhyolites in the caldera environment (Simakin and Bindeman, 2012). Literature. 1)Davaille, A. and Jaupart, C. (1993) J. Fluid. Mech., 253: 141-166. 2) Huppert, H.E. and Sparks, R.S.J. (1988) J. Petrol., 29: 599-624. 3)Huber, C., Bachmann, O., Dufek, J. (2010) J. Volcanol. Geotherm. Res., 195: 97-105. 4)Jaupart, C. and Brandeis, G. (1986) Earth Planet. Sci. Lett. 80: 183-199. 5)Simakin, A.G. and Bindeman, I.N. (2012) Remelting in caldera and rift environments and the genesis of hot, "recycled" rhyolites. Earth Planet. Sci. Lett. (in review). 6) Snyder, D. (2000) Earth Planet. Sci. Lett. 175: 257-273.

Virtual Patterson Experiment - A Way to Access the Rheology of Aggregates and Melanges

NASA Astrophysics Data System (ADS)

Delannoy, Thomas; Burov, Evgueni; Wolf, Sylvie

2014-05-01

Understanding the mechanisms of lithospheric deformation requires bridging the gap between human-scale laboratory experiments and the huge geological objects they represent. Those experiments are limited in spatial and time scale as well as in choice of materials (e.g., mono-phase minerals, exaggerated temperatures and strain rates), which means that the resulting constitutive laws may not fully represent real rocks at geological spatial and temporal scales. We use the thermo-mechanical numerical modelling approach as a tool to link both experiments and nature and hence better understand the rheology of the lithosphere, by enabling us to study the behavior of polymineralic aggregates and their impact on the localization of the deformation. We have adapted the large strain visco-elasto-plastic Flamar code to allow it to operate at all spatial and temporal scales, from sub-grain to geodynamic scale, and from seismic time scales to millions of years. Our first goal was to reproduce real rock mechanics experiments on deformation of mono and polymineralic aggregates in Patterson's load machine in order to deepen our understanding of the rheology of polymineralic rocks. In particular, we studied in detail the deformation of a 15x15 mm mica-quartz sample at 750 °C and 300 MPa. This mixture includes a molten phase and a solid phase in which shear bands develop as a result of interactions between ductile and brittle deformation and stress concentration at the boundaries between weak and strong phases. We used digitized x-ray scans of real samples as initial configuration for the numerical models so the model-predicted deformation and stress-strain behavior can match those observed in the laboratory experiment. Analyzing the numerical experiments providing the best match with the press experiments and making other complementary models by changing different parameters in the initial state (strength contrast between the phases, proportions, microstructure, etc.) provides a number of new elements of understanding of the mechanisms governing the localization of the deformation across the aggregates. We next used stress-strain curves derived from the numerical experiments to study in detail the evolution of the rheological behavior of each mineral phase as well as that of the mixtures in order to formulate constitutive relations for mélanges and polymineralic aggregates. The next step of our approach would be to link the constitutive laws obtained at small scale (laws that govern the rheology of a polymineralic aggregate, the effect of the presence of a molten phase, etc.) to the large-scale behavior of the Earth by implementing them in lithosphere-scale models.

Resolving the fine-scale structure in turbulent Rayleigh-Bénard convection

NASA Astrophysics Data System (ADS)

Scheel, Janet D.; Emran, Mohammad S.; Schumacher, Jörg

2013-11-01

We present high-resolution direct numerical simulation studies of turbulent Rayleigh-Bénard convection in a closed cylindrical cell with an aspect ratio of one. The focus of our analysis is on the finest scales of convective turbulence, in particular the statistics of the kinetic energy and thermal dissipation rates in the bulk and the whole cell. The fluctuations of the energy dissipation field can directly be translated into a fluctuating local dissipation scale which is found to develop ever finer fluctuations with increasing Rayleigh number. The range of these scales as well as the probability of high-amplitude dissipation events decreases with increasing Prandtl number. In addition, we examine the joint statistics of the two dissipation fields and the consequences of high-amplitude events. We have also investigated the convergence properties of our spectral element method and have found that both dissipation fields are very sensitive to insufficient resolution. We demonstrate that global transport properties, such as the Nusselt number, and the energy balances are partly insensitive to insufficient resolution and yield correct results even when the dissipation fields are under-resolved. Our present numerical framework is also compared with high-resolution simulations which use a finite difference method. For most of the compared quantities the agreement is found to be satisfactory.

Sensitivities of Summertime Mesoscale Circulations in the Coastal Carolinas to Modifications of the Kain-Fritsch Cumulus Parameterization.

PubMed

Sims, Aaron P; Alapaty, Kiran; Raman, Sethu

2017-01-01

Two mesoscale circulations, the Sandhills circulation and the sea breeze, influence the initiation of deep convection over the Sandhills and the coast in the Carolinas during the summer months. The interaction of these two circulations causes additional convection in this coastal region. Accurate representation of mesoscale convection is difficult as numerical models have problems with the prediction of the timing, amount, and location of precipitation. To address this issue, the authors have incorporated modifications to the Kain-Fritsch (KF) convective parameterization scheme and evaluated these mesoscale interactions using a high-resolution numerical model. The modifications include changes to the subgrid-scale cloud formulation, the convective turnover time scale, and the formulation of the updraft entrainment rates. The use of a grid-scaling adjustment parameter modulates the impact of the KF scheme as a function of the horizontal grid spacing used in a simulation. Results indicate that the impact of this modified cumulus parameterization scheme is more effective on domains with coarser grid sizes. Other results include a decrease in surface and near-surface temperatures in areas of deep convection (due to the inclusion of the effects of subgrid-scale clouds on the radiation), improvement in the timing of convection, and an increase in the strength of deep convection.

Numerical Investigation of Dual-Mode Scramjet Combustor with Large Upstream Interaction

NASA Technical Reports Server (NTRS)

Mohieldin, T. O.; Tiwari, S. N.; Reubush, David E. (Technical Monitor)

2004-01-01

Dual-mode scramjet combustor configuration with significant upstream interaction is investigated numerically, The possibility of scaling the domain to accelerate the convergence and reduce the computational time is explored. The supersonic combustor configuration was selected to provide an understanding of key features of upstream interaction and to identify physical and numerical issues relating to modeling of dual-mode configurations. The numerical analysis was performed with vitiated air at freestream Math number of 2.5 using hydrogen as the sonic injectant. Results are presented for two-dimensional models and a three-dimensional jet-to-jet symmetric geometry. Comparisons are made with experimental results. Two-dimensional and three-dimensional results show substantial oblique shock train reaching upstream of the fuel injectors. Flow characteristics slow numerical convergence, while the upstream interaction slowly increases with further iterations. As the flow field develops, the symmetric assumption breaks down. A large separation zone develops and extends further upstream of the step. This asymmetric flow structure is not seen in the experimental data. Results obtained using a sub-scale domain (both two-dimensional and three-dimensional) qualitatively recover the flow physics obtained from full-scale simulations. All results show that numerical modeling using a scaled geometry provides good agreement with full-scale numerical results and experimental results for this configuration. This study supports the argument that numerical scaling is useful in simulating dual-mode scramjet combustor flowfields and could provide an excellent convergence acceleration technique for dual-mode simulations.

Untangling Slab Dynamics Using 3-D Numerical and Analytical Models

NASA Astrophysics Data System (ADS)

Holt, A. F.; Royden, L.; Becker, T. W.

2016-12-01

Increasingly sophisticated numerical models have enabled us to make significant strides in identifying the key controls on how subducting slabs deform. For example, 3-D models have demonstrated that subducting plate width, and the related strength of toroidal flow around the plate edge, exerts a strong control on both the curvature and the rate of migration of the trench. However, the results of numerical subduction models can be difficult to interpret, and many first order dynamics issues remain at least partially unresolved. Such issues include the dominant controls on trench migration, the interdependence of asthenospheric pressure and slab dynamics, and how nearby slabs influence each other's dynamics. We augment 3-D, dynamically evolving finite element models with simple, analytical force-balance models to distill the physics associated with subduction into more manageable parts. We demonstrate that for single, isolated subducting slabs much of the complexity of our fully numerical models can be encapsulated by simple analytical expressions. Rates of subduction and slab dip correlate strongly with the asthenospheric pressure difference across the subducting slab. For double subduction, an additional slab gives rise to more complex mantle pressure and flow fields, and significantly extends the range of plate kinematics (e.g., convergence rate, trench migration rate) beyond those present in single slab models. Despite these additional complexities, we show that much of the dynamics of such multi-slab systems can be understood using the physics illuminated by our single slab study, and that a force-balance method can be used to relate intra-plate stress to viscous pressure in the asthenosphere and coupling forces at plate boundaries. This method has promise for rapid modeling of large systems of subduction zones on a global scale.

Multiple time scale analysis of pressure oscillations in solid rocket motors

NASA Astrophysics Data System (ADS)

Ahmed, Waqas; Maqsood, Adnan; Riaz, Rizwan

2018-03-01

In this study, acoustic pressure oscillations for single and coupled longitudinal acoustic modes in Solid Rocket Motor (SRM) are investigated using Multiple Time Scales (MTS) method. Two independent time scales are introduced. The oscillations occur on fast time scale whereas the amplitude and phase changes on slow time scale. Hopf bifurcation is employed to investigate the properties of the solution. The supercritical bifurcation phenomenon is observed for linearly unstable system. The amplitude of the oscillations result from equal energy gain and loss rates of longitudinal acoustic modes. The effect of linear instability and frequency of longitudinal modes on amplitude and phase of oscillations are determined for both single and coupled modes. For both cases, the maximum amplitude of oscillations decreases with the frequency of acoustic mode and linear instability of SRM. The comparison of analytical MTS results and numerical simulations demonstrate an excellent agreement.

A review of numerical models to predict the atmospheric dispersion of radionuclides.

PubMed

Leelőssy, Ádám; Lagzi, István; Kovács, Attila; Mészáros, Róbert

2018-02-01

The field of atmospheric dispersion modeling has evolved together with nuclear risk assessment and emergency response systems. Atmospheric concentration and deposition of radionuclides originating from an unintended release provide the basis of dose estimations and countermeasure strategies. To predict the atmospheric dispersion and deposition of radionuclides several numerical models are available coupled with numerical weather prediction (NWP) systems. This work provides a review of the main concepts and different approaches of atmospheric dispersion modeling. Key processes of the atmospheric transport of radionuclides are emission, advection, turbulent diffusion, dry and wet deposition, radioactive decay and other physical and chemical transformations. A wide range of modeling software are available to simulate these processes with different physical assumptions, numerical approaches and implementation. The most appropriate modeling tool for a specific purpose can be selected based on the spatial scale, the complexity of meteorology, land surface and physical and chemical transformations, also considering the available data and computational resource. For most regulatory and operational applications, offline coupled NWP-dispersion systems are used, either with a local scale Gaussian, or a regional to global scale Eulerian or Lagrangian approach. The dispersion model results show large sensitivity on the accuracy of the coupled NWP model, especially through the description of planetary boundary layer turbulence, deep convection and wet deposition. Improvement of dispersion predictions can be achieved by online coupling of mesoscale meteorology and atmospheric transport models. The 2011 Fukushima event was the first large-scale nuclear accident where real-time prognostic dispersion modeling provided decision support. Dozens of dispersion models with different approaches were used for prognostic and retrospective simulations of the Fukushima release. An unknown release rate proved to be the largest factor of uncertainty, underlining the importance of inverse modeling and data assimilation in future developments. Copyright © 2017 Elsevier Ltd. All rights reserved.

Effect of Fentanyl Nasal Packing Treatment on Patients With Acute Postoperative Pain After Nasal Operation: A Randomized Double-Blind Controlled Trial.

PubMed

Kim, Kwan-Sub; Yeo, Nam-Kyung; Kim, Seong-Su; Park, Woong-Sub; Kwak, Su-Hyun; Cho, Sang-Hyeon; Sung, Gyu-Wan; Kim, Hae-Sook; Yi, Sang-Wook; Cho, Hae Jun

2018-05-01

Nasal packing is an option for bleeding control after endoscopic sinus surgery and septoplasty. Although new packing materials have been developed, patients still suffer from pain and require additional analgesics treatments. In this study, a prospective, randomized, and double-blind controlled trial was designed to evaluate the effect of fentanyl-soaked packing on pain after endoscopic sinus surgery and septoplasty. One hundred fifty-two patients who underwent nasal surgeries due to chronic rhinosinusitis or nasal septal deviation were enrolled in this study. At the end of operation, 50 mcg fentanyl-soaked biodegradable synthetic polyurethane foams packing Nasopore or Merocel were applied to a group of 79 patients, and saline-soaked ones were applied to another group of 73 patients. To evaluate the influence of fentanyl on postoperative nasal pain, patients' conditions were assessed via means of Numeric Rating Scale, patient satisfaction, and Ramsay Sedation Scale. In addition, symptoms of headache or sore throat and any signs of cardiopulmonary-relevant indicators were monitored. The fentanyl group had significantly decreased Numeric Rating Scale and increased patient satisfaction in every operation type for the majority of postoperative time periods ( P < .05) with reduced postoperative headache and sore throat compared to the control group. The fentanyl group showed a higher score on Ramsay Sedation Scale than the control group ( P < .05 in group including endoscopic sinus surgery). There were no significant differences in cardiopulmonary-relevant indicators between the 2 groups ( P > .05). Fentanyl group showed significantly reduced postoperative pain without serious adverse effects. We suggest that topical fentanyl application to nasal packs can be a useful method to reduce pain during the early postoperative period after endoscopic sinus surgery and septoplasty.

Large-scale numerical simulations of polydisperse particle flow in a silo

NASA Astrophysics Data System (ADS)

Rubio-Largo, S. M.; Maza, D.; Hidalgo, R. C.

2017-10-01

Very recently, we have examined experimentally and numerically the micro-mechanical details of monodisperse particle flows through an orifice placed at the bottom of a silo (Rubio-Largo et al. in Phys Rev Lett 114:238002, 2015). Our findings disentangled the paradoxical ideas associated to the free-fall arch concept, which has historically served to justify the dependence of the flow rate on the outlet size. In this work, we generalize those findings examining large-scale polydisperse particle flows in silos. In the range of studied apertures, both velocity and density profiles at the aperture are self-similar, and the obtained scaling functions confirm that the relevant scale of the problem is the size of the aperture. Moreover, we find that the contact stress monotonically decreases when the particles approach the exit and vanish at the outlet. The behavior of this magnitude is practically independent of the size of the orifice. However, the total and partial kinetic stress profiles suggest that the outlet size controls the propagation of the velocity fluctuations inside the silo. Examining this magnitude, we conclusively argue that indeed there is a well-defined transition region where the particle flow changes its nature. The general trend of the partial kinetic pressure profiles and the location of the transition region results the same for all particle types. We find that the partial kinetic stress is larger for bigger particles. However, the small particles carry a higher fraction of kinetic stress respect to their concentration, which suggest that the small particles have larger velocity fluctuations than the large ones and showing lower strength of correlation with the global flow. Our outcomes explain why the free-fall arch picture has served to describe the polydisperse flow rate in the discharge of silos.

“An Impediment to Living Life”: Why and How Should We Measure Stiffness in Polymyalgia Rheumatica?

PubMed Central

Mackie, Sarah Louise; Hughes, Rodney; Walsh, Margaret; Day, John; Newton, Marion; Pease, Colin; Kirwan, John; Morris, Marianne

2015-01-01

Objectives To explore patients’ concepts of stiffness in polymyalgia rheumatica (PMR), and how they think stiffness should be measured. Methods Eight focus groups were held at three centres involving 50 patients with current/previous PMR. Each group had at least one facilitator and one rapporteur making field notes. An interview schedule was used to stimulate discussion. Interviews were recorded, transcribed and analysed using an inductive thematic approach. Results Major themes identified were: symptoms: pain, stiffness and fatigue; functional impact; impact on daily schedule; and approaches to measurement. The common subtheme for the experience of stiffness was “difficulty in moving”, and usually considered as distinct from the experience of pain, albeit with a variable overlap. Some participants felt stiffness was the “overwhelming” symptom, in that it prevented them carrying out “fundamental activities” and “generally living life”. Diurnal variation in stiffness was generally described in relation to the daily schedule but was not the same as stiffness severity. Some participants suggested measuring stiffness using a numeric rating scale or a Likert scale, while others felt that it was more relevant and straightforward to measure difficulty in performing everyday activities rather than about stiffness itself. Conclusions A conceptual model of stiffness in PMR is presented where stiffness is an important part of the patient experience and impacts on their ability to live their lives. Stiffness is closely related to function and often regarded as interchangeable with pain. From the patients’ perspective, visual analogue scales measuring pain and stiffness were not the most useful method for reporting stiffness; participants preferred numerical rating scales, or assessments of function to reflect how stiffness impacts on their daily lives. Assessing function may be a pragmatic solution to difficulties in quantifying stiffness. PMID:25955770

Practical Dyspnea Assessment: Relationship Between the 0–10 Numerical Rating Scale and the Four-Level Categorical Verbal Descriptor Scale of Dyspnea Intensity

PubMed Central

Wysham, Nicholas G.; Miriovsky, Benjamin J.; Currow, David C.; Herndon, James E.; Samsa, Gregory P.; Wilcock, Andrew; Abernethy, Amy P.

2016-01-01

Context Measurement of dyspnea is important for clinical care and research. Objectives To characterize the relationship between the 0–10 Numerical Rating Scale (NRS) and four-level categorical Verbal Descriptor Scale (VDS) for dyspnea assessment. Methods This was a substudy of a double-blind randomized controlled trial comparing palliative oxygen to room air for relief of refractory breathlessness in patients with life-limiting illness. Dyspnea was assessed with both a 0–10 NRS and a four-level categorical VDS over the one-week trial. NRS and VDS responses were analyzed in cross section and longitudinally. Relationships between NRS and VDS responses were portrayed using descriptive statistics and visual representations. Results Two hundred twenty-six participants contributed responses. At baseline, mild and moderate levels of breathlessness were reported by 41.9% and 44.6% of participants, respectively. NRS scores demonstrated increasing mean and median levels for increasing VDS intensity, from a mean (SD) of 0.6 (±1.04) for VDS none category to 8.2 (1.4) for VDS severe category. The Spearman correlation coefficient was strong at 0.78 (P < 0.0001). Based on the distribution of NRS scores within VDS categories, we calculated test characteristics of two different cutpoint models. Both models yielded 75% correct translations from NRS to VDS; however, Model A was more sensitive for moderate or greater dyspnea, with fewer misses downcoded. Conclusion There is strong correlation between VDS and NRS measures for dyspnea. Proposed practical cutpoints for the relationship between the dyspnea VDS and NRS are 0 for none, 1–4 for mild, 5–8 for moderate, and 9–10 for severe. PMID:26004401

Dupilumab therapy provides clinically meaningful improvement in patient-reported outcomes (PROs): A phase IIb, randomized, placebo-controlled, clinical trial in adult patients with moderate to severe atopic dermatitis (AD).

PubMed

Simpson, Eric L; Gadkari, Abhijit; Worm, Margitta; Soong, Weily; Blauvelt, Andrew; Eckert, Laurent; Wu, Richard; Ardeleanu, Marius; Graham, Neil M H; Pirozzi, Gianluca; Sutherland, E Rand; Mastey, Vera

2016-09-01

Moderate to severe atopic dermatitis (AD) is associated with substantial patient burden despite current therapies. We sought to evaluate dupilumab treatment on patient-reported outcomes in adults with moderate to severe AD. Adults (N = 380) with moderate to severe AD inadequately controlled by topical medications were randomized to 16 weeks of double-blind, subcutaneous treatment with dupilumab 100 mg every 4 weeks, 200 mg every 2 weeks, 300 mg every 2 weeks, 300 mg once weekly, or placebo. Patient-reported outcomes included pruritus numeric rating scale; patient-reported sleep item on Scoring AD scale; Patient-Oriented Eczema Measure; Hospital Anxiety and Depression Scale; Dermatology Life Quality Index; and 5-dimension 3-level EuroQol. Dupilumab reduced peak itch at 16 weeks relative to placebo by 1.1 to 3.2 points on numeric rating scale (P < .0001 all doses, except 100 mg every 4 weeks P < .05); improved sleep and health-related quality of life on Dermatology Life Quality Index and 5-dimension 3-level EuroQol (P < .05 all doses, except 100 mg every 4 weeks); and reduced anxiety and depression symptoms (P < .05 all doses). Dupilumab's effects appeared early and achieved clinically relevant improvements without significant safety concerns. There are potential cultural differences affecting patient-reported outcome responses. Outcomes were secondary or exploratory end points. Dupilumab produced early and sustained patient-reported and clinically relevant improvements in sleep, mental health, and health-related quality of life; the two 300-mg dose regimens resulted in greatest benefits. Copyright © 2016 American Academy of Dermatology, Inc. Published by Elsevier Inc. All rights reserved.

Exact law for homogeneous compressible Hall magnetohydrodynamics turbulence

NASA Astrophysics Data System (ADS)

Andrés, N.; Galtier, S.; Sahraoui, F.

2018-01-01

We derive an exact law for three-dimensional (3D) homogeneous compressible isothermal Hall magnetohydrodynamic turbulence, without the assumption of isotropy. The Hall current is shown to introduce new flux and source terms that act at the small scales (comparable or smaller than the ion skin depth) to significantly impact the turbulence dynamics. The law provides an accurate means to estimate the energy cascade rate over a broad range of scales covering the magnetohydrodynamic inertial range and the sub-ion dispersive range in 3D numerical simulations and in in situ spacecraft observations of compressible turbulence. This work is particularly relevant to astrophysical flows in which small-scale density fluctuations cannot be ignored such as the solar wind, planetary magnetospheres, and the interstellar medium.

The tidal disruption of a star by a massive black hole

NASA Technical Reports Server (NTRS)

Evans, Charles R.; Kochanek, Christopher S.

1989-01-01

Results are reported from a three-dimensional numerical calculation of the tidal disruption of a low-mass main-sequence star on a parabolic orbit around a massive black hole (Mh = 10 to the 6th stellar mass). The postdisruption evolution is followed until hydrodynamic forces becomes negligible and the liberated gas becomes ballistic. Also given is the rate at which bound mass returns to pericenter after orbiting the hole once. The processes that determine the time scale to circularize the debris orbits and allow an accretion torus to form are discussed. This time scale and the time scales for radiative cooling and accretion inflow determine the onset and duration of the subsequent flare in the AGN luminosity.

Unconstrained handwritten numeral recognition based on radial basis competitive and cooperative networks with spatio-temporal feature representation.

PubMed

Lee, S; Pan, J J

1996-01-01

This paper presents a new approach to representation and recognition of handwritten numerals. The approach first transforms a two-dimensional (2-D) spatial representation of a numeral into a three-dimensional (3-D) spatio-temporal representation by identifying the tracing sequence based on a set of heuristic rules acting as transformation operators. A multiresolution critical-point segmentation method is then proposed to extract local feature points, at varying degrees of scale and coarseness. A new neural network architecture, referred to as radial-basis competitive and cooperative network (RCCN), is presented especially for handwritten numeral recognition. RCCN is a globally competitive and locally cooperative network with the capability of self-organizing hidden units to progressively achieve desired network performance, and functions as a universal approximator of arbitrary input-output mappings. Three types of RCCNs are explored: input-space RCCN (IRCCN), output-space RCCN (ORCCN), and bidirectional RCCN (BRCCN). Experiments against handwritten zip code numerals acquired by the U.S. Postal Service indicated that the proposed method is robust in terms of variations, deformations, transformations, and corruption, achieving about 97% recognition rate.

The growth of the tearing mode - Boundary and scaling effects

NASA Technical Reports Server (NTRS)

Steinolfson, R. S.; Van Hoven, G.

1983-01-01

A numerical model of resistive magnetic tearing is developed in order to verify and relate the results of the principal approximations used in analytic analyses and to investigate the solutions and their growth-rate scalings over a large range of primary parameters which include parametric values applicable to the solar atmosphere. The computations cover the linear behavior for a variety of boundary conditions, emphasizing effects which differentiate magnetic tearing in astrophysical situations from that in laboratory devices. Eigenfunction profiles for long and short wavelengths are computed and the applicability of the 'constant psi' approximation is investigated. The growth rate is computed for values of the magnetic Reynolds number up to a trillion and of the dimensionless wavelength parameter down to 0.001. The analysis predicts significant effects due to differing values of the magnetic Reynolds number.

Fast magnetic reconnection supported by sporadic small-scale Petschek-type shocks

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

Shibayama, Takuya, E-mail: shibayama@stelab.nagoya-u.ac.jp; Nakabou, Takashi; Kusano, Kanya

2015-10-15

Standard magnetohydrodynamic (MHD) theory predicts reconnection rate that is far too slow to account for a wide variety of reconnection events observed in space and laboratory plasmas. Therefore, it was commonly accepted that some non-MHD (kinetic) effects play a crucial role in fast reconnection. A recently renewed interest in simple MHD models is associated with the so-called plasmoid instability of reconnecting current sheets. Although it is now evident that this effect can significantly enhance the rate of reconnection, many details of the underlying multiple-plasmoid process still remain controversial. Here, we report results of a high-resolution computer simulation which demonstrate thatmore » fast albeit intermittent magnetic reconnection is sustained by numerous small-scale Petschek-type shocks spontaneously formed in the current sheet due to its plasmoid instability.« less

[Correlation of substrate structure and hydraulic characteristics in subsurface flow constructed wetlands].

PubMed

Bai, Shao-Yuan; Song, Zhi-Xin; Ding, Yan-Li; You, Shao-Hong; He, Shan

2014-02-01

The correlation of substrate structure and hydraulic characteristics was studied by numerical simulation combined with experimental method. The numerical simulation results showed that the permeability coefficient of matrix had a great influence on hydraulic efficiency in subsurface flow constructed wetlands. The filler with a high permeability coefficient had a worse flow field distribution in the constructed wetland with single layer structure. The layered substrate structure with the filler permeability coefficient increased from surface to bottom could avoid the short-circuited flow and dead-zones, and thus, increased the hydraulic efficiency. Two parallel pilot-scale constructed wetlands were built according to the numerical simulation results, and tracer experiments were conducted to validate the simulation results. The tracer experiment result showed that hydraulic characteristics in the layered constructed wetland were obviously better than that in the single layer system, and the substrate effective utilization rates were 0.87 and 0.49, respectively. It was appeared that numerical simulation would be favorable for substrate structure optimization in subsurface flow constructed wetlands.

Combining numerical simulations with time-domain random walk for pathogen risk assessment in groundwater

NASA Astrophysics Data System (ADS)

Cvetkovic, V.; Molin, S.

2012-02-01

We present a methodology that combines numerical simulations of groundwater flow and advective transport in heterogeneous porous media with analytical retention models for computing the infection risk probability from pathogens in aquifers. The methodology is based on the analytical results presented in [1,2] for utilising the colloid filtration theory in a time-domain random walk framework. It is shown that in uniform flow, the results from the numerical simulations of advection yield comparable results as the analytical TDRW model for generating advection segments. It is shown that spatial variability of the attachment rate may be significant, however, it appears to affect risk in a different manner depending on if the flow is uniform or radially converging. In spite of the fact that numerous issues remain open regarding pathogen transport in aquifers on the field scale, the methodology presented here may be useful for screening purposes, and may also serve as a basis for future studies that would include greater complexity.

Homogenization analysis of invasion dynamics in heterogeneous landscapes with differential bias and motility.

PubMed

Yurk, Brian P

2018-07-01

Animal movement behaviors vary spatially in response to environmental heterogeneity. An important problem in spatial ecology is to determine how large-scale population growth and dispersal patterns emerge within highly variable landscapes. We apply the method of homogenization to study the large-scale behavior of a reaction-diffusion-advection model of population growth and dispersal. Our model includes small-scale variation in the directed and random components of movement and growth rates, as well as large-scale drift. Using the homogenized model we derive simple approximate formulas for persistence conditions and asymptotic invasion speeds, which are interpreted in terms of residence index. The homogenization results show good agreement with numerical solutions for environments with a high degree of fragmentation, both with and without periodicity at the fast scale. The simplicity of the formulas, and their connection to residence index make them appealing for studying the large-scale effects of a variety of small-scale movement behaviors.

Investigations of the reliability of observational gait analysis for the assessment of lameness in horses.

PubMed

Hewetson, M; Christley, R M; Hunt, I D; Voute, L C

2006-06-24

The objectives of this study were to assess the reliability of a numerical rating scale (NRS) and a verbal rating scale (VRS) for the assessment of lameness in horses and to determine whether they can be used interchangeably. Sixteen independent observers graded the severity of lameness in 20 videotaped horses, and the agreement between and within observers, correlation and bias were determined for each scale. The observers agreed with each other in 56 per cent of the observations with the NRS and in 60 per cent of the observations with the VRS, and the associated Kendall coefficient of concordance was high. Similar trends were evident in the agreement between two observations by each observer. The correlation between and within observers was high for both scales. There were no significant differences (bias) among the observers' mean scores when using either scale. There was a significant correlation between the lameness scores attributed when using the two scales, but the differences between the scores when plotted against their overall mean were unacceptable for clinical purposes. The results indicate that the NRS and VRS are only moderately reliable when used to assess lameness severity in the horse, and that they should not be used interchangeably.

Optical Communications With A Geiger Mode APD Array

DTIC Science & Technology

2016-02-09

spurious fires from numerous sources, including crosstalk from other detectors in the same array . Additionally, after a 9 successful detection, the...be combined into arrays with large numbers of detectors , allowing for scaling of dynamic range with relatively little overhead on space and power...overall higher rate of dark counts than a single detector , this is more than compensated for by the extra detectors . A sufficiently large APD array could

Effect of concentration gradients on biodegradation in bench-scale sand columns with HYDRUS modeling of hydrocarbon transport and degradation.

PubMed

Horel, Agota; Schiewer, Silke; Misra, Debasmita

2015-09-01

The present research investigated to what extent results obtained in small microcosm experiments can be extrapolated to larger settings with non-uniform concentrations. Microbial hydrocarbon degradation in sandy sediments was compared for column experiments versus homogenized microcosms with varying concentrations of diesel, Syntroleum, and fish biodiesel as contaminants. Syntroleum and fish biodiesel had higher degradation rates than diesel fuel. Microcosms showed significantly higher overall hydrocarbon mineralization percentages (p < 0.006) than columns. Oxygen levels and moisture content were likely not responsible for that difference, which could, however, be explained by a strong gradient of fuel and nutrient concentrations through the column. The mineralization percentage in the columns was similar to small-scale microcosms at high fuel concentrations. While absolute hydrocarbon degradation increased, mineralization percentages decreased with increasing fuel concentration which was corroborated by saturation kinetics; the absolute CO2 production reached a steady plateau value at high substrate concentrations. Numerical modeling using HYDRUS 2D/3D simulated the transport and degradation of the investigated fuels in vadose zone conditions similar to those in laboratory column experiments. The numerical model was used to evaluate the impact of different degradation rate constants from microcosm versus column experiments.

Optimal volume of injectate for fluoroscopy-guided cervical interlaminar epidural injection in patients with neck and upper extremity pain

PubMed Central

Park, Jun Young; Kim, Doo Hwan; Lee, Kunhee; Choi, Seong-Soo; Leem, Jeong-Gil

2016-01-01

Abstract There is no study of optimal volume of contrast medium to use in cervical interlaminar epidural injections (CIEIs) for appropriate spread to target lesions. To determine optimal volume of contrast medium to use in CIEIs. We analyzed the records of 80 patients who had undergone CIEIs. Patients were divided into 3 groups according to the amount of contrast: 3, 4.5, and 6 mL. The spread of medium to the target level was analyzed. Numerical rating scale data were also analyzed. The dye had spread to a point above the target level in 15 (78.9%), 22 (84.6%), and 32 (91.4%) patients in groups 1 to 3, respectively. The dye reached both sides in 14 (73.7%), 18 (69.2%), and 23 (65.7%) patients, and reached the ventral epidural space in 15 (78.9%), 22 (84.6%), and 30 (85.7%) patients, respectively. There were no significant differences of contrast spread among the groups. There were no significant differences in the numerical rating scale scores among the groups during the 3 months. When performing CIEIs, 3 mL medication is sufficient volume for the treatment of neck and upper-extremity pain induced by lower cervical degenerative disease. PMID:27787378

Optimal volume of injectate for fluoroscopy-guided cervical interlaminar epidural injection in patients with neck and upper extremity pain.

PubMed

Park, Jun Young; Kim, Doo Hwan; Lee, Kunhee; Choi, Seong-Soo; Leem, Jeong-Gil

2016-10-01

There is no study of optimal volume of contrast medium to use in cervical interlaminar epidural injections (CIEIs) for appropriate spread to target lesions. To determine optimal volume of contrast medium to use in CIEIs. We analyzed the records of 80 patients who had undergone CIEIs. Patients were divided into 3 groups according to the amount of contrast: 3, 4.5, and 6 mL. The spread of medium to the target level was analyzed. Numerical rating scale data were also analyzed. The dye had spread to a point above the target level in 15 (78.9%), 22 (84.6%), and 32 (91.4%) patients in groups 1 to 3, respectively. The dye reached both sides in 14 (73.7%), 18 (69.2%), and 23 (65.7%) patients, and reached the ventral epidural space in 15 (78.9%), 22 (84.6%), and 30 (85.7%) patients, respectively. There were no significant differences of contrast spread among the groups. There were no significant differences in the numerical rating scale scores among the groups during the 3 months. When performing CIEIs, 3 mL medication is sufficient volume for the treatment of neck and upper-extremity pain induced by lower cervical degenerative disease.

Thalamic pain alleviated by stellate ganglion block: A case report.

PubMed

Liao, Chenlong; Yang, Min; Liu, Pengfei; Zhong, Wenxiang; Zhang, Wenchuan

2017-02-01

Thalamic pain is a distressing and treatment-resistant type of central post-stroke pain. Although stellate ganglion block is an established intervention used in pain management, its use in the treatment of thalamic pain has never been reported. A 66-year-old woman presented with a 3-year history of severe intermittent lancinating pain on the right side of the face and the right hand. The pain started from the ulnar side of the right forearm after a mild ischemic stroke in bilateral basal ganglia and left thalamus. Weeks later, the pain extended to the dorsum of the finger tips and the whole palmar surface, becoming more severe. Meanwhile, there was also pain with similar characteristics emerging on her right face, resembling atypical trigeminal neuralgia. Thalamic pain was diagnosed. After refusing the further invasive treatment, she was suggested to try stellate ganglion block. After a 3-day period of pain free (numerical rating scale: 0) postoperatively, she reported moderate to good pain relief with a numerical rating scale of about 3 to 4 lasting 1 month after the first injection. Pain as well as the quality of life was markedly improved with less dose of analgesic agents. Stellate ganglion block may be an optional treatment for thalamic pain.

Chiropractic management of a 47-year–old firefighter with lumbar disk extrusion

PubMed Central

Schwab, Matthew J.

2008-01-01

Abstract Objective This case report describes the effect of exercise-based chiropractic treatment on chronic and intractable low back pain complicated by lumbar disk extrusion. Clinical Features A 47-year–old male firefighter experienced chronic, unresponsive low back pain. Pre- and posttreatment outcome analysis was performed on numeric (0-10) pain scale, functional rating index, and the low back pain Oswestry data. Secondary outcome assessments included a 1-rep maximum leg press, balancing times, push-ups and sit-ups the patient performed in 60 seconds, and radiographic analysis. Intervention and Outcome The patient was treated with Pettibon manipulative and rehabilitative techniques. At 4 weeks, spinal decompression therapy was incorporated. After 12 weeks of treatment, the patient's self-reported numeric pain scale had reduced from 6 to 1. There was also overall improvement in muscular strength, balance times, self-rated functional status, low back Oswestry scores, and lumbar lordosis using pre- and posttreatment radiographic information. Conclusion Comprehensive, exercise-based chiropractic management may contribute to an improvement of physical fitness and to restoration of function, and may be a protective factor for low back injury. This case suggests promising interventions with otherwise intractable low back pain using a multimodal chiropractic approach that includes isometric strengthening, neuromuscular reeducation, and lumbar spinal decompression therapy. PMID:19646377

Effect of therapeutic exercises on pregnancy-related low back pain and pelvic girdle pain: Secondary analysis of a randomized controlled trial.

PubMed

Sklempe Kokic, Iva; Ivanisevic, Marina; Uremovic, Melita; Kokic, Tomislav; Pisot, Rado; Simunic, Bostjan

2017-03-06

To investigate the effect of a supervised, structured exercise programme on the occurrence and severity of pregnancy-related lumbopelvic pain. Randomized controlled trial. A total of 45 pregnant women were randomly assigned to 2 groups: an experimental group (n = 20; mean age 32.8 (standard deviation (SD) 3.6) years) and a control group (n = 22; mean age 32.2 years (SD 4.9)). Exercise intervention for the experimental group consisted of aerobic and resistance exercises performed bi-weekly from the date of inclusion into the study until the end of pregnancy, together with at least 30 min of brisk daily walks. A numeric rating scale, Roland-Morris Disability Questionnaire (RMDQ), and Pelvic Girdle Questionnaire (PGQ) were used to measure outcomes. The control group received only standard antenatal care. There were significant differences between the 2 groups on the numeric rating scale, PGQ and RMDQ scores in the 36th week of pregnancy (p = 0.017; p = 0.005; p < 0.001, respectively) in favour of the experimental group. The exercise programme had a beneficial effect on the severity of lumbopelvic pain in pregnancy, reducing the intensity of pain and the level of disability experienced as a result.

A prospective randomized, double-dummy trial comparing IV push low dose ketamine to short infusion of low dose ketamine for treatment of  pain in the ED.

PubMed

Motov, Sergey; Mai, Mo; Pushkar, Illya; Likourezos, Antonios; Drapkin, Jefferson; Yasavolian, Matthew; Brady, Jason; Homel, Peter; Fromm, Christian

2017-08-01

Compare adverse effects and analgesic efficacy of low-dose ketamine for acute pain in the ED administered either by single intravenous push (IVP) or short infusion (SI). Patients 18-65, presenting to ED with acute abdominal, flank, or musculoskeletal pain with initial pain score≥5, were randomized to ketamine 0.3mg/kg by either IVP or SI with placebo double-dummy. Adverse effects were evaluated by Side Effects Rating Scale for Dissociative Anesthetics (SERSDA) and Richmond Agitation-Sedation Scale (RASS) at 5, 15, 30, 60, 90, and 120min post-administration; analgesic efficacy was evaluated by Numerical Rating Scale (NRS). 48 patients enrolled in the study. IVP group had higher overall rates of feeling of unreality on SERSDA scale: 92% versus 54% (difference 37.5%; p=0.008; 95% CI 9.3-59.5%). At 5min median severity of feeling of unreality was 3.0 for IVP versus 0.0 for SI (p=0.001). IVP also showed greater rates of sedation on RASS scale at 5min: median RASS -2.0 versus 0.0 (p=0.01). Decrease in mean pain scores from baseline to 15min was similar across groups: 5.2±3.53 (95% CI 3.7-6.7) for IVP; 5.75±3.48 (95% CI 4.3-7.2) for SI. There were no statistically significant differences with respect to changes in vital signs and need for rescue medication. Low-dose ketamine given as a short infusion is associated with significantly lower rates of feeling of unreality and sedation with no difference in analgesic efficacy in comparison to intravenous push. Copyright © 2017 Elsevier Inc. All rights reserved.

A Phenotype Classification of Internet Use Disorder in a Large-Scale High-School Study.

PubMed

Lindenberg, Katajun; Halasy, Katharina; Szász-Janocha, Carolin; Wartberg, Lutz

2018-04-12

Internet Use Disorder (IUD) affects numerous adolescents worldwide, and (Internet) Gaming Disorder, a specific subtype of IUD, has recently been included in DSM-5 and ICD-11. Epidemiological studies have identified prevalence rates up to 5.7% among adolescents in Germany. However, little is known about the risk development during adolescence and its association to education. The aim of this study was to: (a) identify a clinically relevant latent profile in a large-scale high-school sample; (b) estimate prevalence rates of IUD for distinct age groups and (c) investigate associations to gender and education. N = 5387 adolescents out of 41 schools in Germany aged 11-21 were assessed using the Compulsive Internet Use Scale (CIUS). Latent profile analyses showed five profile groups with differences in CIUS response pattern, age and school type. IUD was found in 6.1% and high-risk Internet use in 13.9% of the total sample. Two peaks were found in prevalence rates indicating the highest risk of IUD in age groups 15-16 and 19-21. Prevalence did not differ significantly between boys and girls. High-level education schools showed the lowest (4.9%) and vocational secondary schools the highest prevalence rate (7.8%). The differences between school types could not be explained by academic level.

Microstructural evolution during the homogenization heat treatment of 6XXX and 7XXX aluminum alloys

NASA Astrophysics Data System (ADS)

Priya, Pikee

Homogenization heat treatment of as-cast billets is an important step in the processing of aluminum extrusions. Microstructural evolution during homogenization involves elimination of the eutectic morphology by spheroidisation of the interdendritic phases, minimization of the microsegregation across the grains through diffusion, dissolution of the low-melting phases, which enhances the surface finish of the extrusions, and precipitation of nano-sized dispersoids (for Cr-, Zr-, Mn-, Sc-containing alloys), which inhibit grain boundary motion to prevent recrystallization. Post-homogenization cooling reprecipitates some of the phases, changing the flow stress required for subsequent extrusion. These precipitates, however, are deleterious for the mechanical properties of the alloy and also hamper the age-hardenability and are hence dissolved during solution heat treatment. Microstructural development during homogenization and subsequent cooling occurs both at the length scale of the Secondary Dendrite Arm Spacing (SDAS) in micrometers and dispersoids in nanometers. Numerical tools to simulate microstructural development at both the length scales have been developed and validated against experiments. These tools provide easy and convenient means to study the process. A Cellular Automaton-Finite Volume-based model for evolution of interdendritic phases is coupled with a Particle Size Distribution-based model for precipitation of dispersoids across the grain. This comprehensive model has been used to study the effect of temperature, composition, as-cast microstructure, and cooling rates during post-homogenization quenching on microstructural evolution. The numerical study has been complimented with experiments involving Scanning Electron Microscopy, Energy Dispersive Spectroscopy, X-Ray Diffraction and Differential Scanning Calorimetry and a good agreement has with numerical results has been found. The current work aims to study the microstructural evolution during homogenization heat treatment at both length scales which include the (i) dissolution and transformation of the as-cast secondary phases; (ii) precipitation of dispersoids; and (iii) reprecipitation of some of the secondary phases during post-homogenization cooling. The kinetics of the phase transformations are mostly diffusion controlled except for the eta to S phase transformation in 7XXX alloys which is interface reaction rate controlled which has been implemented using a novel approach. Recommendations for homogenization temperature, time, cooling rates and compositions are made for Al-Si-Mg-Fe-Mn and Al-Zn-Cu-Mg-Zr alloys. The numerical model developed has been applied for a through process solidification-homogenization modeling of a Direct-Chill cast AA7050 cylindrical billet to study the radial variation of microstructure after solidification, homogenization and post-homogenization cooling.

CARMA: Software for continuous affect rating and media annotation

PubMed Central

Girard, Jeffrey M

2017-01-01

CARMA is a media annotation program that collects continuous ratings while displaying audio and video files. It is designed to be highly user-friendly and easily customizable. Based on Gottman and Levenson's affect rating dial, CARMA enables researchers and study participants to provide moment-by-moment ratings of multimedia files using a computer mouse or keyboard. The rating scale can be configured on a number of parameters including the labels for its upper and lower bounds, its numerical range, and its visual representation. Annotations can be displayed alongside the multimedia file and saved for easy import into statistical analysis software. CARMA provides a tool for researchers in affective computing, human-computer interaction, and the social sciences who need to capture the unfolding of subjective experience and observable behavior over time. PMID:29308198

Laboratory-scale in situ bioremediation in heterogeneous porous media: biokinetics-limited scenario.

PubMed

Song, Xin; Hong, Eunyoung; Seagren, Eric A

2014-03-01

Subsurface heterogeneities influence interfacial mass-transfer processes and affect the application of in situ bioremediation by impacting the availability of substrates to the microorganisms. However, for difficult-to-degrade compounds, and/or cases with inhibitory biodegradation conditions, slow biokinetics may also limit the overall bioremediation rate, or be as limiting as mass-transfer processes. In this work, a quantitative framework based on a set of dimensionless coefficients was used to capture the effects of the competing interfacial and biokinetic processes and define the overall rate-limiting process. An integrated numerical modeling and experimental approach was used to evaluate application of the quantitative framework for a scenario in which slow-biokinetics limited the overall bioremediation rate of a polycyclic aromatic hydrocarbon (naphthalene). Numerical modeling was conducted to simulate the groundwater flow and naphthalene transport and verify the system parameters, which were used in the quantitative framework application. The experiments examined the movement and biodegradation of naphthalene in a saturated, heterogeneous intermediate-scale flow cell with two layers of contrasting hydraulic conductivities. These experiments were conducted in two phases: Phase I, simulating an inhibited slow biodegradation; and Phase II, simulating an engineered bioremediation, with system perturbations selected to enhance the slow biodegradation rate. In Phase II, two engineered perturbations to the system were selected to examine their ability to enhance in situ biodegradation. In the first perturbation, nitrogen and phosphorus in excess of the required stoichiometric amounts were spiked into the influent solution to mimic a common remedial action taken in the field. The results showed that this perturbation had a moderate positive impact, consistent with slow biokinetics being the overall rate-limiting process. However, the second perturbation, which was to alleviate inhibition and increase the biodegradation rate, enhanced the overall biotransformation rate to a greater degree. Copyright © 2014 Elsevier B.V. All rights reserved.

Behaviors of susceptible-infected epidemics on scale-free networks with identical infectivity

NASA Astrophysics Data System (ADS)

Zhou, Tao; Liu, Jian-Guo; Bai, Wen-Jie; Chen, Guanrong; Wang, Bing-Hong

2006-11-01

In this paper, we propose a susceptible-infected model with identical infectivity, in which, at every time step, each node can only contact a constant number of neighbors. We implemented this model on scale-free networks, and found that the infected population grows in an exponential form with the time scale proportional to the spreading rate. Furthermore, by numerical simulation, we demonstrated that the targeted immunization of the present model is much less efficient than that of the standard susceptible-infected model. Finally, we investigate a fast spreading strategy when only local information is available. Different from the extensively studied path-finding strategy, the strategy preferring small-degree nodes is more efficient than that preferring large-degree nodes. Our results indicate the existence of an essential relationship between network traffic and network epidemic on scale-free networks.

Lagrangian model of copepod dynamics: Clustering by escape jumps in turbulence

NASA Astrophysics Data System (ADS)

Ardeshiri, H.; Benkeddad, I.; Schmitt, F. G.; Souissi, S.; Toschi, F.; Calzavarini, E.

2016-04-01

Planktonic copepods are small crustaceans that have the ability to swim by quick powerful jumps. Such an aptness is used to escape from high shear regions, which may be caused either by flow perturbations, produced by a large predator (i.e., fish larvae), or by the inherent highly turbulent dynamics of the ocean. Through a combined experimental and numerical study, we investigate the impact of jumping behavior on the small-scale patchiness of copepods in a turbulent environment. Recorded velocity tracks of copepods displaying escape response jumps in still water are here used to define and tune a Lagrangian copepod (LC) model. The model is further employed to simulate the behavior of thousands of copepods in a fully developed hydrodynamic turbulent flow obtained by direct numerical simulation of the Navier-Stokes equations. First, we show that the LC velocity statistics is in qualitative agreement with available experimental observations of copepods in turbulence. Second, we quantify the clustering of LC, via the fractal dimension D2. We show that D2 can be as low as ˜2.3 and that it critically depends on the shear-rate sensitivity of the proposed LC model, in particular it exhibits a minimum in a narrow range of shear-rate values. We further investigate the effect of jump intensity, jump orientation, and geometrical aspect ratio of the copepods on the small-scale spatial distribution. At last, possible ecological implications of the observed clustering on encounter rates and mating success are discussed.

A numerical study of a long flexible fiber in shear flow: dynamics and rheology

NASA Astrophysics Data System (ADS)

Zuk, Pawel; Perazzo, Antonio; Nunes, Janine; Stone, Howard

2017-11-01

Long slender particles can span the whole spectrum of stiffness: from very flexible particles such as globular proteins to extremely rigid particles, e.g. carbon nanotubes or β-amyloid fibers. The behavior of rigid particles is well understood, however there are only few recent experimental reports about long fibers of moderate flexibility. We present a numerical study of a single long flexible fiber in a shear flow. The fiber is simulated as a bead-spring model including hydrodynamic interactions in the Rotne-Prager-Yamakawa approximation. We analyze fiber shape, motion and stress induced in the fluid under the shear flow. We find that all of these properties appear to be related to the characteristic length scale of the kinks formed in the fibers. We present a scaling law for the kink size as a function of shear rate and the fiber parameters and justify it using elastic theory. The study suggests that local properties of a single fiber may condition the behavior of concentrated suspensions.

PILOT-SCALE EVALUATION OF ENGINEERED BARIER SYSTEMS FOR THE YUCCA MOUNTAIN PROJECT

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

S.W. Webb; J.T. George; R.E. Finley

This paper describes two quarter-scale experiments (1.4 m diameter) and associated numerical analyses on granular backfill engineered barrier systems in support of the Yucca Mountain Project for the potential repository. The two configurations include a sloped capillary barrier and a plain backfill. The tests involve application of dyed water as a constant line infiltration source along the top of the test set-up, monitoring water movement through the test, and measuring water exiting the experiments. A complete water balance estimate is made for each test, and observed water movement is compared with (1) detailed numerical analyses conducted using the TOUGH2 codemore » for unsaturated flow in porous media and (2) posttest observations. The results of the testing and analyses show that for the injection rates and configuration applied, the capillary barrier design diverts a significant amount of all injected water and the TOUGH2 pretest predictions show qualitative and quantitative agreement with the experimental data.« less

LES versus DNS: A comparative study

NASA Technical Reports Server (NTRS)

Shtilman, L.; Chasnov, J. R.

1992-01-01

We have performed Direct Numerical Simulations (DNS) and Large Eddy Simulations (LES) of forced isotropic turbulence at moderate Reynolds numbers. The subgrid scale model used in the LES is based on an eddy viscosity which adjusts instantaneously the energy spectrum of the LES to that of the DNS. The statistics of the large scales of the DNS (filtered DNS field or fDNS) are compared to that of the LES. We present results for the transfer spectra, the skewness and flatness factors of the velocity components, the PDF's of the angle between the vorticity and the eigenvectors of the rate of strain, and that between the vorticity and the vorticity stretching tensor. The above LES statistics are found to be in good agreement with those measured in the fDNS field. We further observe that in all the numerical measurements, the trend was for the LES field to be more gaussian than the fDNS field. Future research on this point is planned.

Evolution of Local Microstructures: Spatial Instabilities of Coarsening Clusters

NASA Technical Reports Server (NTRS)

Frazier, Donald O.

1999-01-01

This work examines the diffusional growth of discrete phase particles dispersed within a matrix. Engineering materials are microstructurally heterogeneous, and the details of the microstructure determine how well that material performs in a given application. Critical to the development of designing multiphase microstructures with long-term stability is the process of Ostwald ripening. Ripening, or phase coarsening, is a diffusion-limited process which arises in polydisperse multiphase materials. Growth and dissolution occur because fluxes of solute, driven by chemical potential gradients at the interfaces of the dispersed phase material, depend on particle size. The kinetics of these processes are "competitive," dictating that larger particles grow at the expense of smaller ones, overall leading to an increase of the average particle size. The classical treatment of phase coarsening was done by Todes, Lifshitz, and Slyozov, (TLS) in the limit of zero volume fraction, V(sub v), of the dispersed phase. Since the publication of TLS theory there have been numerous investigations, many of which sought to describe the kinetic scaling behavior over a 0 range of volume fractions. Some studies in the literature report that the relative increase in coarsening rate at low (but not zero) volume fractions compared to that predicted by TLS is proportional to v(sub v)(exp 1/2), whereas others suggcest V(sub v)(exp 1/3). This issue has been resolved recently by simulation studies at low volume fractions in three dimensions by members of the Rensselaer/MSFC team. Our studies of ripening behavior using large-scale numerical simulations suggest that although there are different circumstances which can lead to either scaling law, the most important length scale at low volume fractions is the diffusional analog of the Debye screening length. The numerical simulations we employed exploit the use of a recently developed "snapshot" technique, and identifies the nature of the coarsening dynamics at various volume fractions. Preliminary results of numerical and experimental investigations, focused on the growth of finite particle clusters, provide important insight into the nature of the transition between the two scaling regimes. The companion microgravity experiment centers on the growth within finite particle clusters, and follows the temporal dynamics driving microstructural evolution, using holography.

Continuum and crystal strain gradient plasticity with energetic and dissipative length scales

NASA Astrophysics Data System (ADS)

Faghihi, Danial

This work, standing as an attempt to understand and mathematically model the small scale materials thermal and mechanical responses by the aid of Materials Science fundamentals, Continuum Solid Mechanics, Misro-scale experimental observations, and Numerical methods. Since conventional continuum plasticity and heat transfer theories, based on the local thermodynamic equilibrium, do not account for the microstructural characteristics of materials, they cannot be used to adequately address the observed mechanical and thermal response of the micro-scale metallic structures. Some of these cases, which are considered in this dissertation, include the dependency of thin films strength on the width of the sample and diffusive-ballistic response of temperature in the course of heat transfer. A thermodynamic-based higher order gradient framework is developed in order to characterize the mechanical and thermal behavior of metals in small volume and on the fast transient time. The concept of the thermal activation energy, the dislocations interaction mechanisms, nonlocal energy exchange between energy carriers and phonon-electrons interactions are taken into consideration in proposing the thermodynamic potentials such as Helmholtz free energy and rate of dissipation. The same approach is also adopted to incorporate the effect of the material microstructural interface between two materials (e.g. grain boundary in crystals) into the formulation. The developed grain boundary flow rule accounts for the energy storage at the grain boundary due to the dislocation pile up as well as energy dissipation caused by the dislocation transfer through the grain boundary. Some of the abovementioned responses of small scale metallic compounds are addressed by means of the numerical implementation of the developed framework within the finite element context. In this regard, both displacement and plastic strain fields are independently discretized and the numerical implementation is performed in the finite element program ABAQUS/standard via the user element subroutine UEL. Using this numerical capability, an extensive study is conducted on the major characteristics of the proposed theories for bulk and interface such as size effect on yield and kinematic hardening, features of boundary layer formation, thermal softening and grain boundary weakening, and the effect of soft and stiff interfaces.

Multi-scale image segmentation and numerical modeling in carbonate rocks

NASA Astrophysics Data System (ADS)

Alves, G. C.; Vanorio, T.

2016-12-01

Numerical methods based on computational simulations can be an important tool in estimating physical properties of rocks. These can complement experimental results, especially when time constraints and sample availability are a problem. However, computational models created at different scales can yield conflicting results with respect to the physical laboratory. This problem is exacerbated in carbonate rocks due to their heterogeneity at all scales. We developed a multi-scale approach performing segmentation of the rock images and numerical modeling across several scales, accounting for those heterogeneities. As a first step, we measured the porosity and the elastic properties of a group of carbonate samples with varying micrite content. Then, samples were imaged by Scanning Electron Microscope (SEM) as well as optical microscope at different magnifications. We applied three different image segmentation techniques to create numerical models from the SEM images and performed numerical simulations of the elastic wave-equation. Our results show that a multi-scale approach can efficiently account for micro-porosities in tight micrite-supported samples, yielding acoustic velocities comparable to those obtained experimentally. Nevertheless, in high-porosity samples characterized by larger grain/micrite ratio, results show that SEM scale images tend to overestimate velocities, mostly due to their inability to capture macro- and/or intragranular- porosity. This suggests that, for high-porosity carbonate samples, optical microscope images would be more suited for numerical simulations.

Elevated atmospheric CO2 concentration leads to increased whole-plant isoprene emission in hybrid aspen (Populus tremula × Populus tremuloides).

PubMed

Sun, Zhihong; Niinemets, Ülo; Hüve, Katja; Rasulov, Bahtijor; Noe, Steffen M

2013-05-01

Effects of elevated atmospheric [CO2] on plant isoprene emissions are controversial. Relying on leaf-scale measurements, most models simulating isoprene emissions in future higher [CO2] atmospheres suggest reduced emission fluxes. However, combined effects of elevated [CO2] on leaf area growth, net assimilation and isoprene emission rates have rarely been studied on the canopy scale, but stimulation of leaf area growth may largely compensate for possible [CO2] inhibition reported at the leaf scale. This study tests the hypothesis that stimulated leaf area growth leads to increased canopy isoprene emission rates. We studied the dynamics of canopy growth, and net assimilation and isoprene emission rates in hybrid aspen (Populus tremula × Populus tremuloides) grown under 380 and 780 μmol mol(-1) [CO2]. A theoretical framework based on the Chapman-Richards function to model canopy growth and numerically compare the growth dynamics among ambient and elevated atmospheric [CO2]-grown plants was developed. Plants grown under elevated [CO2] had higher C : N ratio, and greater total leaf area, and canopy net assimilation and isoprene emission rates. During ontogeny, these key canopy characteristics developed faster and stabilized earlier under elevated [CO2]. However, on a leaf area basis, foliage physiological traits remained in a transient state over the whole experiment. These results demonstrate that canopy-scale dynamics importantly complements the leaf-scale processes, and that isoprene emissions may actually increase under higher [CO2] as a result of enhanced leaf area production. © 2013 The Authors. New Phytologist © 2013 New Phytologist Trust.

Regional Differences in Tropical Lightning Distributions.

NASA Astrophysics Data System (ADS)

Boccippio, Dennis J.; Goodman, Steven J.; Heckman, Stan

2000-12-01

Observations from the National Aeronautics and Space Administration Optical Transient Detector (OTD) and Tropical Rainfall Measuring Mission (TRMM)-based Lightning Imaging Sensor (LIS) are analyzed for variability between land and ocean, various geographic regions, and different (objectively defined) convective `regimes.' The bulk of the order-of-magnitude differences between land and ocean regional flash rates are accounted for by differences in storm spacing (density) and/or frequency of occurrence, rather than differences in storm instantaneous flash rates, which only vary by a factor of 2 on average. Regional variability in cell density and cell flash rates closely tracks differences in 85-GHz microwave brightness temperatures. Monotonic relationships are found with the gross moist stability of the tropical atmosphere, a large-scale `adjusted state' parameter. This result strongly suggests that it will be possible, using TRMM observations, to objectively test numerical or theoretical predictions of how mesoscale convective organization interacts with the larger-scale environment. Further parameters are suggested for a complete objective definition of tropical convective regimes.

Scaling rates of true polar wander in convecting planets and moons

NASA Astrophysics Data System (ADS)

Rose, Ian; Buffett, Bruce

2017-12-01

Mass redistribution in the convecting mantle of a planet causes perturbations in its moment of inertia tensor. Conservation of angular momentum dictates that these perturbations change the direction of the rotation vector of the planet, a process known as true polar wander (TPW). Although the existence of TPW on Earth is firmly established, its rate and magnitude over geologic time scales remain controversial. Here we present scaling analyses and numerical simulations of TPW due to mantle convection over a range of parameter space relevant to planetary interiors. For simple rotating convection, we identify a set of dimensionless parameters that fully characterize true polar wander. We use these parameters to define timescales for the growth of moment of inertia perturbations due to convection and for their relaxation due to true polar wander. These timescales, as well as the relative sizes of convective anomalies, control the rate and magnitude of TPW. This analysis also clarifies the nature of so called "inertial interchange" TPW events, and relates them to a broader class of events that enable large and often rapid TPW. We expect these events to have been more frequent in Earth's past.

Current Density Scaling in Electrochemical Flow Capacitors

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

Hoyt, NC; Wainright, JS; Savinell, RF

Electrochemical flow capacitors (EFCs) are a recently developed energy storage technology. One of the principal performance metrics of an EFC is the steady-state electrical current density that it can accept or deliver. Numerical models exist to predict this performance for specific cases, but here we present a study of how the current varies with respect to the applied cell voltage, flow rate, cell dimensions, and slurry properties using scaling laws. The scaling relationships are confirmed by numerical simulations and then subsequently by comparison to results from symmetric cell EFC experiments. This modeling approach permits the delimitation of three distinct operationalmore » regimes dependent on the values of two nondimensional combinations of the pertinent variables (specifically, a capacitive Graetz number and a conductivity ratio). Lastly, the models and nondimensional numbers are used to provide design guidance in terms of criteria for proper EFC operation. (C) The Author(s) 2015. Published by ECS. This is an open access article distributed under the terms of the Creative Commons Attribution 4.0 License (CC BY, http://creativecommons.org/licenses/by/4.0/), which permits unrestricted reuse of the work in any medium, provided the original work is properly cited. All rights reserved.« less

Border-Crossing Model for the Diffusive Coarsening of Wet Foams

NASA Astrophysics Data System (ADS)

Durian, Douglas; Schimming, Cody

For dry foams, the transport of gas from small high-pressure bubbles to large low-pressure bubbles is dominated by diffusion across the thin soap films separating neighboring bubbles. For wetter foams, the film areas become smaller as the Plateau borders and vertices inflate with liquid. So-called ``border-blocking'' models can explain some features of wet-foam coarsening based on the presumption that the inflated borders totally block the gas flux; however, this approximation dramatically fails in the wet/unjamming limit where the bubbles become close-packed spheres. Here, we account for the ever-present border-crossing flux by a new length scale defined by the average gradient of gas concentration inside the borders. We argue that it is proportional to the geometric average of film and border thicknesses, and we verify this scaling and the numerical prefactor by numerical solution of the diffusion equation. Then we show how the dA / dt =K0 (n - 6) von Neumann law is modified by the appearance of terms that depend on bubble size and shape as well as the concentration gradient length scale. Finally, we use the modified von Neumann law to compute the growth rate of the average bubble, which is not constant.

Accurate acceleration of kinetic Monte Carlo simulations through the modification of rate constants.

PubMed

Chatterjee, Abhijit; Voter, Arthur F

2010-05-21

We present a novel computational algorithm called the accelerated superbasin kinetic Monte Carlo (AS-KMC) method that enables a more efficient study of rare-event dynamics than the standard KMC method while maintaining control over the error. In AS-KMC, the rate constants for processes that are observed many times are lowered during the course of a simulation. As a result, rare processes are observed more frequently than in KMC and the time progresses faster. We first derive error estimates for AS-KMC when the rate constants are modified. These error estimates are next employed to develop a procedure for lowering process rates with control over the maximum error. Finally, numerical calculations are performed to demonstrate that the AS-KMC method captures the correct dynamics, while providing significant CPU savings over KMC in most cases. We show that the AS-KMC method can be employed with any KMC model, even when no time scale separation is present (although in such cases no computational speed-up is observed), without requiring the knowledge of various time scales present in the system.

Constraining the relative importance of raindrop- and flow-driven sediment transport mechanisms in postwildfire environments and implications for recovery time scales

USGS Publications Warehouse

McGuire, Luke; Kean, Jason W.; Staley, Dennis M.; Rengers, Francis K.; Wasklewicz, Thad A.

2016-01-01

Mountain watersheds recently burned by wildfire often experience greater amounts of runoff and increased rates of sediment transport relative to similar unburned areas. Given the sedimentation and debris flow threats caused by increases in erosion, more work is needed to better understand the physical mechanisms responsible for the observed increase in sediment transport in burned environments and the time scale over which a heightened geomorphic response can be expected. In this study, we quantified the relative importance of different hillslope erosion mechanisms during two postwildfire rainstorms at a drainage basin in Southern California by combining terrestrial laser scanner-derived maps of topographic change, field measurements, and numerical modeling of overland flow and sediment transport. Numerous debris flows were initiated by runoff at our study area during a long-duration storm of relatively modest intensity. Despite the presence of a well-developed rill network, numerical model results suggest that the majority of eroded hillslope sediment during this long-duration rainstorm was transported by raindrop-induced sediment transport processes, highlighting the importance of raindrop-driven processes in supplying channels with potential debris flow material. We also used the numerical model to explore relationships between postwildfire storm characteristics, vegetation cover, soil infiltration capacity, and the total volume of eroded sediment from a synthetic hillslope for different end-member erosion regimes. This study adds to our understanding of sediment transport in steep, postwildfire landscapes and shows how data from field monitoring can be combined with numerical modeling of sediment transport to isolate the processes leading to increased erosion in burned areas.

A catchment-scale groundwater model including sewer pipe leakage in an urban system

NASA Astrophysics Data System (ADS)

Peche, Aaron; Fuchs, Lothar; Spönemann, Peter; Graf, Thomas; Neuweiler, Insa

2016-04-01

Keywords: pipe leakage, urban hydrogeology, catchment scale, OpenGeoSys, HYSTEM-EXTRAN Wastewater leakage from subsurface sewer pipe defects leads to contamination of the surrounding soil and groundwater (Ellis, 2002; Wolf et al., 2004). Leakage rates at pipe defects have to be known in order to quantify contaminant input. Due to inaccessibility of subsurface pipe defects, direct (in-situ) measurements of leakage rates are tedious and associated with a high degree of uncertainty (Wolf, 2006). Proposed catchment-scale models simplify leakage rates by neglecting unsaturated zone flow or by reducing spatial dimensions (Karpf & Krebs, 2013, Boukhemacha et al., 2015). In the present study, we present a physically based 3-dimensional numerical model incorporating flow in the pipe network, in the saturated zone and in the unsaturated zone to quantify leakage rates on the catchment scale. The model consists of the pipe network flow model HYSTEM-EXTAN (itwh, 2002), which is coupled to the subsurface flow model OpenGeoSys (Kolditz et al., 2012). We also present the newly developed coupling scheme between the two flow models. Leakage functions specific to a pipe defect are derived from simulations of pipe leakage using spatially refined grids around pipe defects. In order to minimize computational effort, these leakage functions are built into the presented numerical model using unrefined grids around pipe defects. The resulting coupled model is capable of efficiently simulating spatially distributed pipe leakage coupled with subsurficial water flow in a 3-dimensional environment. References: Boukhemacha, M. A., Gogu, C. R., Serpescu, I., Gaitanaru, D., & Bica, I. (2015). A hydrogeological conceptual approach to study urban groundwater flow in Bucharest city, Romania. Hydrogeology Journal, 23(3), 437-450. doi:10.1007/s10040-014-1220-3. Ellis, J. B., & Revitt, D. M. (2002). Sewer losses and interactions with groundwater quality. Water Science and Technology, 45(3), 195-202. itwh (2002). Modellbeschreibung, Institut für technisch-wissenschaftliche Hydrologie GmbH, Hannover. Karpf, C. & Krebs, P. (2013). Modelling of groundwater infiltration into sewer systems. Urban Water Journal, 10:4, 221-229, DOI: 10.1080/1573062X.2012.724077. Kolditz, O., Bauer, S. et al. (2012). OpenGeoSys: an open source initiative for numerical simulation of thermo-hydro-mechanical/chemical (THM/C) processes in porous media. Env. Earth Sci. 67(2):589-599. Wolf, L., Held, I., Eiswirth, M., & Hötzl, H. (2004). Impact of leaky sewers on groundwater quality. Acta Hydrochimica et Hydrobiologica, 32(4-5), 361-373. doi:10.1002/aheh.200400538. Wolf, L. (2006). Influence of leaky sewer systems on groundwater resources beneath the city of Rastatt, Germany. Dissertation, University of Karlsruhe.

Modelling galaxy clustering on small scales to tighten constraints on dark energy and modified gravity

NASA Astrophysics Data System (ADS)

Wang, Yun

2017-01-01

We present a new approach to measuring cosmic expansion history and growth rate of large-scale structure using the anisotropic two-dimensional galaxy correlation function (2DCF) measured from data; it makes use of the empirical modelling of small-scale galaxy clustering derived from numerical simulations by Zheng et al. We validate this method using mock catalogues, before applying it to the analysis of the CMASS sample from the Sloan Digital Sky Survey Data Release 10 of the Baryon Oscillation Spectroscopic Survey. We find that this method enables accurate and precise measurements of cosmic expansion history and growth rate of large-scale structure. Modelling the 2DCF fully including non-linear effects and redshift space distortions in the scale range of 16-144 h-1 Mpc, we find H(0.57)rs(zd)/c = 0.0459 ± 0.0006, DA(0.57)/rs(zd) = 9.011 ± 0.073, and fg(0.57)σ8(0.57) = 0.476 ± 0.050, which correspond to precisions of 1.3 per cent, 0.8 per cent, and 10.5 per cent, respectively. We have defined rs(zd) to be the sound horizon at the drag epoch computed using a simple integral, fg(z) as the growth rate at redshift z, and σ8(z) as the matter power spectrum normalization on 8 h-1 Mpc scale at z. We find that neglecting the small-scale information significantly weakens the constraints on H(z) and DA(z), and leads to a biased estimate of fg(z). Our results indicate that we can significantly tighten constraints on dark energy and modified gravity by reliably modelling small-scale galaxy clustering.

Biodegradation modelling of a dissolved gasoline plume applying independent laboratory and field parameters

NASA Astrophysics Data System (ADS)

Schirmer, Mario; Molson, John W.; Frind, Emil O.; Barker, James F.

2000-12-01

Biodegradation of organic contaminants in groundwater is a microscale process which is often observed on scales of 100s of metres or larger. Unfortunately, there are no known equivalent parameters for characterizing the biodegradation process at the macroscale as there are, for example, in the case of hydrodynamic dispersion. Zero- and first-order degradation rates estimated at the laboratory scale by model fitting generally overpredict the rate of biodegradation when applied to the field scale because limited electron acceptor availability and microbial growth are not considered. On the other hand, field-estimated zero- and first-order rates are often not suitable for predicting plume development because they may oversimplify or neglect several key field scale processes, phenomena and characteristics. This study uses the numerical model BIO3D to link the laboratory and field scales by applying laboratory-derived Monod kinetic degradation parameters to simulate a dissolved gasoline field experiment at the Canadian Forces Base (CFB) Borden. All input parameters were derived from independent laboratory and field measurements or taken from the literature a priori to the simulations. The simulated results match the experimental results reasonably well without model calibration. A sensitivity analysis on the most uncertain input parameters showed only a minor influence on the simulation results. Furthermore, it is shown that the flow field, the amount of electron acceptor (oxygen) available, and the Monod kinetic parameters have a significant influence on the simulated results. It is concluded that laboratory-derived Monod kinetic parameters can adequately describe field scale degradation, provided all controlling factors are incorporated in the field scale model. These factors include advective-dispersive transport of multiple contaminants and electron acceptors and large-scale spatial heterogeneities.

Reactive transport of CO2-rich fluids in simulated wellbore interfaces: Experiments and models exploring behaviour on length scales of 1 to 6 m

NASA Astrophysics Data System (ADS)

Wolterbeek, T. K. T.; Raoof, A.; Peach, C. J.; Spiers, C. J.

2016-12-01

Defects present at casing-cement interfaces in wellbores constitute potential pathways for CO2 to migrate from geological storage systems. It is essential to understand how the transport properties of such pathways evolve when penetrated by CO2-rich fluids. While numerous studies have explored this problem at the decimetre length-scale, the 1-10-100 m scales relevant for real wellbores have received little attention. The present work addresses the effects of long-range reactive transport on a length scale of 1-6 m. This is done by means of a combined experimental and modelling study. The experimental work consisted of flow-through tests, performed on cement-filled steel tubes, 1-6 m in length, containing artificially debonded cement-interfaces. Four tests were performed, at 60-80 °C, imposing flow-through of CO2-rich fluid at mean pressures of 10-15 MPa, controlling the pressure difference at 0.12-4.8 MPa, while measuring flow-rate. In the modelling work, we developed a numerical model to explore reactive transport in CO2-exposed defects on a similar length scale. The formulation adopted incorporates fluid flow, advective and diffusive solute transport, and CO2-cement chemical reactions. Our results show that long-range reactive transport strongly affects the permeability evolution of CO2-exposed defects. In the experiments, sample permeability decreased by 2-4 orders, which microstructural observations revealed was associated with downstream precipitation of carbonates, possibly aided by migration of fines. The model simulations show precipitation in initially open defects produces a sharp decrease in flow rate, causing a transition from advection to diffusion-dominated reactive transport. While the modelling results broadly reproduce the experimental observations, it is further demonstrated that non-uniformity in initial defect aperture has a profound impact on self-sealing behaviour and system permeability evolution on the metre scale. The implication is that future reactive transport models and wellbore scale analyses must include defects with variable aperture in order to obtain reliable upscaling relations.

Error Rate Comparison during Polymerase Chain Reaction by DNA Polymerase

DOE PAGES

McInerney, Peter; Adams, Paul; Hadi, Masood Z.

2014-01-01

As larger-scale cloning projects become more prevalent, there is an increasing need for comparisons among high fidelity DNA polymerases used for PCR amplification. All polymerases marketed for PCR applications are tested for fidelity properties (i.e., error rate determination) by vendors, and numerous literature reports have addressed PCR enzyme fidelity. Nonetheless, it is often difficult to make direct comparisons among different enzymes due to numerous methodological and analytical differences from study to study. We have measured the error rates for 6 DNA polymerases commonly used in PCR applications, including 3 polymerases typically used for cloning applications requiring high fidelity. Error ratemore » measurement values reported here were obtained by direct sequencing of cloned PCR products. The strategy employed here allows interrogation of error rate across a very large DNA sequence space, since 94 unique DNA targets were used as templates for PCR cloning. The six enzymes included in the study, Taq polymerase, AccuPrime-Taq High Fidelity, KOD Hot Start, cloned Pfu polymerase, Phusion Hot Start, and Pwo polymerase, we find the lowest error rates with Pfu , Phusion, and Pwo polymerases. Error rates are comparable for these 3 enzymes and are >10x lower than the error rate observed with Taq polymerase. Mutation spectra are reported, with the 3 high fidelity enzymes displaying broadly similar types of mutations. For these enzymes, transition mutations predominate, with little bias observed for type of transition.« less

Small-scale anisotropy induced by spectral forcing and by rotation in non-helical and helical turbulence

NASA Astrophysics Data System (ADS)

Vallefuoco, Donato; Naso, Aurore; Godeferd, Fabien S.

2018-02-01

We study the effect of large-scale spectral forcing on the scale-dependent anisotropy of the velocity field in direct numerical simulations of homogeneous turbulence. ABC-type forcing and helical or non-helical Euler-type forcing are considered. We propose a scale-dependent characterisation of anisotropy based on a modal decomposition of the two-point velocity tensor spectrum. This produces direction-dependent spectra of energy, helicity and polarisation. We examine the conditions that allow anisotropy to develop in the small scales due to forcing and we show that the theoretically expected isotropy is not exactly obtained, even in the smallest scales, for ABC and helical Euler forcings. When adding rotation, the anisotropy level in ABC-forced simulations is similar to that of lower Rossby number Euler-forced runs. Moreover, even at low rotation rate, the natural anisotropy induced by the Coriolis force is visible at all scales, and two distinct wavenumber ranges appear from our fine-grained characterisation, not separated by the Zeman scale but by a scale where rotation and dissipation are balanced.

Measurement of Quality of Life II. From the Philosophy of Life to Science

PubMed Central

Ventegodt, Soren; Merrick, Joav; Andersen, Niels Jorgen

2003-01-01

We believe it should be possible to make operational the philosophical ideas of the good life in order to make it the object of scientific research. The Quality of Life Research Center in Copenhagen, Denmark has therefore spent the last several years with these questions and tried to find practical and evidence-based scientific solutions.This paper describes the theoretical road taken in moving from the abstract philosophy of life to the actual questionnaire. It presents an important aspect of our work with the quality-of-life (QOL) concept though the last decade. We have developed the quality-of-life philosophy; the SEQOL, QOL5, and QOL1 questionnaires; the quality-of-life theory; and the quality-of-life research methodology. We carried out quality-of-life population surveys and developed techniques for improving quality of life with the chronically sick patient. This paper presents the struggle to create a rating scale for the generic measurement of the global quality of life, based on quality-of-life theory, derived from quality-of-life philosophy. The developed rating scale is a ratio scale combining a Likert scale, a visual analogue scale, and a numerical scale, to a reduced combination scale. This allows for the extraction of as much information from the respondents as possible without exhausting them unduly or demanding more than can be reasonably expected. PMID:14570987

Measurement of quality of life II. From the philosophy of life to science.

PubMed

Ventegodt, Søren; Merrick, Joav; Andersen, Niels Jørgen

2003-10-13

We believe it should be possible to make operational the philosophical ideas of the good life in order to make it the object of scientific research. The Quality of Life Research Center in Copenhagen, Denmark has therefore spent the last several years with these questions and tried to find practical and evidence-based scientific solutions. This paper describes the theoretical road taken in moving from the abstract philosophy of life to the actual questionnaire. It presents an important aspect of our work with the quality-of-life (QOL) concept though the last decade. We have developed the quality-of-life philosophy; the SEQOL, QOL5, and QOL1 questionnaires; the quality-of-life theory; and the quality-of-life research methodology. We carried out quality-of-life population surveys and developed techniques for improving quality of life with the chronically sick patient. This paper presents the struggle to create a rating scale for the generic measurement of the global quality of life, based on quality-of-life theory, derived from quality-of-life philosophy. The developed rating scale is a ratio scale combining a Likert scale, a visual analogue scale, and a numerical scale, to a reduced combination scale. This allows for the extraction of as much information from the respondents as possible without exhausting them unduly or demanding more than can be reasonably expected.

Flow dynamics and salt transport in a coastal aquifer driven by a stratified saltwater body: Lab experiment and numerical modeling

NASA Astrophysics Data System (ADS)

Oz, Imri; Shalev, Eyal; Yechieli, Yoseph; Gavrieli, Ittai; Gvirtzman, Haim

2014-04-01

This paper examines the transient development and the steady-state configuration of groundwater within a coastal aquifer adjacent to a stratified saltwater body. Such systems consist of three different water types: the regional fresh groundwater, and low and high salinity brines forming the upper and lower water layers of the stratified water body, respectively. The dynamics, location and the geometry of the interfaces and the density-driven circulation flows that develop in the aquifer are examined using laboratory experiments and numerical modeling at the same scale. The results show that the transient intrusion of the different water bodies into the aquifer takes place at different rates, and that the locations of the interfaces between them change with time, before reaching steady-state. Under steady-state conditions both the model and the experiments show the existence of three interfaces between the three water types. The numerical model, which is calibrated against the salinity distribution and groundwater discharge rate in the laboratory experiments, allows the quantification of the flow rates and flow patterns within the aquifer. These flow patterns, which cannot be derived from laboratory experiments, show the transient development of three circulation cells which are confined between the three interfaces. These results confirm the hypothesis that has been previously suggested based solely on a steady-state numerical modeling defined by a conceptual understanding. Parametric analysis shows that the creation of three circulation cells and three interfaces is limited to certain conditions and defines the ranges for the creation of this unique system.

Numerical Study of Flow Augmented Thermal Management for Entry and Re-Entry Environments

NASA Technical Reports Server (NTRS)

Cheng, Gary C.; Neroorkar, Kshitij D.; Chen, Yen-Sen; Wang, Ten-See; Daso, Endwell O.

2007-01-01

The use of a flow augmented thermal management system for entry and re-entr environments is one method for reducing heat and drag loads. This concept relies on jet penetration from supersonic and hypersonic counterflowing jets that could significantly weaken and disperse the shock-wave system of the spacecraft flow field. The objective of this research effort is to conduct parametric studies of the supersonic flow over a 2.6% scale model of the Apollo capsule, with and without the counterflowing jet, using time-accurate and steady-state computational fluid dynamics simulations. The numerical studies, including different freestream Mach number angle of attack counterflowing jet mass flow rate, and nozzle configurations, were performed to examine their effect on the drag and beat loads and to explore the counternowing jet condition. The numerical results were compared with the test data obtained from transonic blow-down wind-tunnel experiments conducted independently at NASA MSFC.

Numerical Simulation of Polysilicon Solid-liquid Interface Transmogrification in Heat Transfer Process

NASA Astrophysics Data System (ADS)

Yang, Xi; Ma, Wenhui; Lv, Guoqiang; Zhang, Mingyu

2018-01-01

The shape of solid-liquid interface during the directional solidification process, which is difficult to be observed and measured in actual processes, controls the grain orientation and grain size of polysilicon ingot. We carried out numerical calculations of the directional solidification progress of polycrystalline silicon and invested the means to deal with the latent heat of solidification in numerical simulation. The distributions of the temperature field of the melt for the crystallization progress as well as the transformation of the solid-liquid interface were obtained. The simulation results are consistent with the experimental outcomes. The results show that the curvature of solid-liquid interface is small and stability, larger grain sized columnar crystal can be grown in the laboratory-scale furnace at a solidification rate of 10 μm•s-1. It shall provide important theoretical basis for metallurgical process and polysilicon production technology.

Correlation dimension and phase space contraction via extreme value theory

NASA Astrophysics Data System (ADS)

Faranda, Davide; Vaienti, Sandro

2018-04-01

We show how to obtain theoretical and numerical estimates of correlation dimension and phase space contraction by using the extreme value theory. The maxima of suitable observables sampled along the trajectory of a chaotic dynamical system converge asymptotically to classical extreme value laws where: (i) the inverse of the scale parameter gives the correlation dimension and (ii) the extremal index is associated with the rate of phase space contraction for backward iteration, which in dimension 1 and 2, is closely related to the positive Lyapunov exponent and in higher dimensions is related to the metric entropy. We call it the Dynamical Extremal Index. Numerical estimates are straightforward to obtain as they imply just a simple fit to a univariate distribution. Numerical tests range from low dimensional maps, to generalized Henon maps and climate data. The estimates of the indicators are particularly robust even with relatively short time series.

Effects of friction on forced two-dimensional Navier-Stokes turbulence.

PubMed

Blackbourn, Luke A K; Tran, Chuong V

2011-10-01

Large-scale dissipation mechanisms have been routinely employed in numerical simulations of two-dimensional turbulence to absorb energy at large scales, presumably mimicking the quasisteady picture of Kraichnan in an unbounded fluid. Here, "side effects" of such a mechanism--mechanical friction--on the small-scale dynamics of forced two-dimensional Navier-Stokes turbulence are elaborated by both theoretical and numerical analysis. Given a positive friction coefficient α, viscous dissipation of enstrophy has been known to vanish in the inviscid limit ν→0. This effectively renders the scale-neutral friction the only mechanism responsible for enstrophy dissipation in that limit. The resulting dynamical picture is that the classical enstrophy inertial range becomes a dissipation range in which the dissipation of enstrophy by friction mainly occurs. For each α>0, there exists a critical viscosity ν(c), which depends on physical parameters, separating the regimes of predominant viscous and frictional dissipation of enstrophy. It is found that ν(c)=[η'(1/3)/(Ck(f)(2))]exp[-η'(1/3)/(Cα)], where η' is half the enstrophy injection rate, k(f) is the forcing wave number, and C is a nondimensional constant (the Kraichnan-Batchelor constant). The present results have important theoretical and practical implications. Apparently, mechanical friction is a poor choice in numerical attempts to address fundamental issues concerning the direct enstrophy transfer in two-dimensional Navier-Stokes turbulence. Furthermore, as relatively strong friction naturally occurs on the surfaces and at lateral boundaries of experimental fluids as well as at the interfaces of shallow layers in geophysical fluid models, the frictional effects discussed in this study are crucial in understanding the dynamics of these systems.

Numerical analysis of field-scale transport of bromacil

NASA Astrophysics Data System (ADS)

Russo, David; Tauber-Yasur, Inbar; Laufer, Asher; Yaron, Bruno

Field-scale transport of bromacil (5-bromo-3- sec-butyl-6-methyluracil) was analyzed using two different model processes for local description of the transport. The first was the classical, one-region convection dispersion equation (CDE) model while the second was the two-region, mobile-immobile (MIM) model. The analyses were performed by means of detailed three-dimensional, numerical simulations of the flow and the transport [Russo, D., Zaidel, J. and Laufer, A., Numerical analysis of flow and transport in a three-dimensional partially saturated heterogeneous soil. Water Resour. Res., 1998, in press], employing local soil hydraulic properties parameters from field measurements and local adsorption/desorption coefficients and the first-order degradation rate coefficient from laboratory measurements. Results of the analyses suggest that for a given flow regime, mass exchange between the mobile and the immobile regions retards the bromacil degradation, considerably affects the distribution of the bromacil resident concentration, c, at relatively large travel times, slightly affects the spatial moments of the distribution of c, and increases the skewing of the bromacil breakthrough and the uncertainty in its prediction, compared with the case in which the soil contained only a single (mobile) region. Mean and standard deviation of the simulated concentration profiles at various elapsed times were compared with measurements from a field-scale transport experiment [Tauber-Yasur, I., Hadas, A., Russo, D. and Yaron, B., Leaching of terbuthylazine and bromacil through field soils. Water, Air Soil Poln., 1998, in press] conducted at the Bet Dagan site. Given the limitations of the present study (e.g. the lack of detailed field data on the spatial variability of the soil chemical properties) the main conclusion of the present study is that the field-scale transport of bromacil at the Bet Dagan site is better quantified with the MIM model than the CDE model.

Multidimensional Cyclic Voltammetry Simulations of Pseudocapacitive Electrodes with a Conducting Nanorod Scaffold

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

Mei, Bing-Ang; Li, Bin; Lin, Jie

This paper aims to understand the effect of nanoarchitecture on the performance of pseudocapacitive electrodes consisting of conducting scaffold coated with pseudocapacitive material. To do so, two-dimensional numerical simulations of ordered conducting nanorods coated with a thin film of pseudocapacitive material were performed. The simulations reproduced three-electrode cyclic voltammetry measurements based on a continuum model derived from first principles. Two empirical approaches commonly used experimentally to characterize the contributions of surface-controlled and diffusion-controlled charge storage mechanisms to the total current density with respect to scan rate were theoretically validated for the first time. Moreover, the areal capacitive capacitance, attributed tomore » EDL formation, remained constant and independent of electrode dimensions, at low scan rates. However, at high scan rates, it decreased with decreasing conducting nanorod radius and increasing pseudocapacitive layer thickness due to resistive losses. By contrast, the gravimetric faradaic capacitance, due to reversible faradaic reactions, decreased continuously with increasing scan rate and pseudocapacitive layer thickness but was independent of conducting nanorod radius. Note that the total gravimetric capacitance predicted numerically featured values comparable to experimental measurements. Finally, an optimum pseudocapacitive layer thickness that maximizes total areal capacitance was identified as a function of scan rate and confirmed by scaling analysis.« less

Multidimensional Cyclic Voltammetry Simulations of Pseudocapacitive Electrodes with a Conducting Nanorod Scaffold

DOE PAGES

Mei, Bing-Ang; Li, Bin; Lin, Jie; ...

2017-10-27

This paper aims to understand the effect of nanoarchitecture on the performance of pseudocapacitive electrodes consisting of conducting scaffold coated with pseudocapacitive material. To do so, two-dimensional numerical simulations of ordered conducting nanorods coated with a thin film of pseudocapacitive material were performed. The simulations reproduced three-electrode cyclic voltammetry measurements based on a continuum model derived from first principles. Two empirical approaches commonly used experimentally to characterize the contributions of surface-controlled and diffusion-controlled charge storage mechanisms to the total current density with respect to scan rate were theoretically validated for the first time. Moreover, the areal capacitive capacitance, attributed tomore » EDL formation, remained constant and independent of electrode dimensions, at low scan rates. However, at high scan rates, it decreased with decreasing conducting nanorod radius and increasing pseudocapacitive layer thickness due to resistive losses. By contrast, the gravimetric faradaic capacitance, due to reversible faradaic reactions, decreased continuously with increasing scan rate and pseudocapacitive layer thickness but was independent of conducting nanorod radius. Note that the total gravimetric capacitance predicted numerically featured values comparable to experimental measurements. Finally, an optimum pseudocapacitive layer thickness that maximizes total areal capacitance was identified as a function of scan rate and confirmed by scaling analysis.« less

Emergence of multi-scaling in fluid turbulence

NASA Astrophysics Data System (ADS)

Donzis, Diego; Yakhot, Victor

2017-11-01

We present new theoretical and numerical results on the transition to strong turbulence in an infinite fluid stirred by a Gaussian random force. The transition is defined as a first appearance of anomalous scaling of normalized moments of velocity derivatives (or dissipation rates) emerging from the low-Reynolds-number Gaussian background. It is shown that due to multi-scaling, strongly intermittent rare events can be quantitatively described in terms of an infinite number of different ``Reynolds numbers'' reflecting a multitude of anomalous scaling exponents. We found that anomalous scaling for high order moments emerges at very low Reynolds numbers implying that intense dissipative-range fluctuations are established at even lower Reynolds number than that required for an inertial range. Thus, our results suggest that information about inertial range dynamics can be obtained from dissipative scales even when the former does not exit. We discuss our further prediction that transition to fully anomalous turbulence disappears at Rλ < 3 . Support from NSF is acknowledged.

Solutions to a reduced Poisson–Nernst–Planck system and determination of reaction rates

PubMed Central

Li, Bo; Lu, Benzhuo; Wang, Zhongming; McCammon, J. Andrew

2010-01-01

We study a reduced Poisson–Nernst–Planck (PNP) system for a charged spherical solute immersed in a solvent with multiple ionic or molecular species that are electrostatically neutralized in the far field. Some of these species are assumed to be in equilibrium. The concentrations of such species are described by the Boltzmann distributions that are further linearized. Others are assumed to be reactive, meaning that their concentrations vanish when in contact with the charged solute. We present both semi-analytical solutions and numerical iterative solutions to the underlying reduced PNP system, and calculate the reaction rate for the reactive species. We give a rigorous analysis on the convergence of our simple iteration algorithm. Our numerical results show the strong dependence of the reaction rates of the reactive species on the magnitude of its far field concentration as well as on the ionic strength of all the chemical species. We also find non-monotonicity of electrostatic potential in certain parameter regimes. The results for the reactive system and those for the non-reactive system are compared to show the significant differences between the two cases. Our approach provides a means of solving a PNP system which in general does not have a closed-form solution even with a special geometrical symmetry. Our findings can also be used to test other numerical methods in large-scale computational modeling of electro-diffusion in biological systems. PMID:20228879

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

Rhinefrank, Kenneth E.; Lenee-Bluhm, Pukha; Prudell, Joseph H.

The most prudent path to a full-scale design, build and deployment of a wave energy conversion (WEC) system involves establishment of validated numerical models using physical experiments in a methodical scaling program. This Project provides essential additional rounds of wave tank testing at 1:33 scale and ocean/bay testing at a 1:7 scale, necessary to validate numerical modeling that is essential to a utility-scale WEC design and associated certification.

Effect of an Additional, Parallel Capacitor on Pulsed Inductive Plasma Accelerator Performance

NASA Technical Reports Server (NTRS)

Polzin, Kurt A.; Sivak, Amy D.; Balla, Joseph V.

2011-01-01

A model of pulsed inductive plasma thrusters consisting of a set of coupled circuit equations and a one-dimensional momentum equation has been used to study the effects of adding a second, parallel capacitor into the system. The equations were nondimensionalized, permitting the recovery of several already-known scaling parameters and leading to the identification of a parameter that is unique to the particular topology studied. The current rise rate through the inductive acceleration coil was used as a proxy measurement of the effectiveness of inductive propellant ionization since higher rise rates produce stronger, potentially better ionizing electric fields at the coil face. Contour plots representing thruster performance (exhaust velocity and efficiency) and current rise rate in the coil were generated numerically as a function of the scaling parameters. The analysis reveals that when the value of the second capacitor is much less than the first capacitor, the performance of the two-capacitor system approaches that of the single-capacitor system. In addition, as the second capacitor is decreased in value the current rise rate can grow to be twice as great as the rise rate attained in the single capacitor case.

Calculating Soil Wetness, Evapotranspiration and Carbon Cycle Processes Over Large Grid Areas Using a New Scaling Technique

NASA Technical Reports Server (NTRS)

Sellers, Piers

2012-01-01

Soil wetness typically shows great spatial variability over the length scales of general circulation model (GCM) grid areas (approx 100 km ), and the functions relating evapotranspiration and photosynthetic rate to local-scale (approx 1 m) soil wetness are highly non-linear. Soil respiration is also highly dependent on very small-scale variations in soil wetness. We therefore expect significant inaccuracies whenever we insert a single grid area-average soil wetness value into a function to calculate any of these rates for the grid area. For the particular case of evapotranspiration., this method - use of a grid-averaged soil wetness value - can also provoke severe oscillations in the evapotranspiration rate and soil wetness under some conditions. A method is presented whereby the probability distribution timction(pdf) for soil wetness within a grid area is represented by binning. and numerical integration of the binned pdf is performed to provide a spatially-integrated wetness stress term for the whole grid area, which then permits calculation of grid area fluxes in a single operation. The method is very accurate when 10 or more bins are used, can deal realistically with spatially variable precipitation, conserves moisture exactly and allows for precise modification of the soil wetness pdf after every time step. The method could also be applied to other ecological problems where small-scale processes must be area-integrated, or upscaled, to estimate fluxes over large areas, for example in treatments of the terrestrial carbon budget or trace gas generation.

Patient-controlled analgesia after coronary bypass: Remifentanil or sufentanil?

PubMed

Alavi, Seyed Mostafa; Ghoreishi, Seyed Mohammadmehran; Chitsazan, Mitra; Ghandi, Iman; Fard, Alireza Jahangiri; Hosseini, Seyed Saeed; Mahjoobifard, Maziar; Fani, Kamal

2014-07-01

adequate pain control after cardiac surgery is mandatory to reduce its remarkable morbidity. In this study, we aimed to compare the efficacy of patient-controlled analgesia with remifentanil or sufentanil for pain management after coronary artery bypass grafting. 249 patients who underwent coronary artery bypass were randomly assigned to receive patient-controlled analgesia with remifentanil or sufentanil during the first 24 h postoperatively. Pain intensity during patient-controlled analgesia was assessed using 4 different pain rating scales. patients given remifentanil had lower Visual Analog Scale scores at 24 h compared to those given sufentanil (p = 0.002). The Numeric Rating Scale at 24 h was also significantly lower in patients using remifentanil (p = 0.004). The Faces Pain Scale scores at 4, 18, and 24 h were significantly lower in patients using remifentanil compared to those using sufentanil (p = 0.045, 0.036, and 0.011, respectively). No significant differences between groups were seen in the pain intensity assessed by the Behavior Rating Scale at any time point during the first 24 h postoperatively. our study showed that both remifentanil and sufentanil patient-controlled analgesia can provide acceptable analgesia after coronary artery bypass. The difference between their efficacies was inconspicuous until 24 h postoperatively. Remifentanil seems to result in better pain relief at 24 h postoperatively. © The Author(s) 2013 Reprints and permissions: sagepub.co.uk/journalsPermissions.nav.

Image-based modelling of lateral magma flow: the Basement Sill, Antarctica

PubMed Central

Mirhadizadeh, Seyed

2017-01-01

The McMurdo Dry Valleys magmatic system, Antarctica, provides a world-class example of pervasive lateral magma flow on a continental scale. The lowermost intrusion (Basement Sill) offers detailed sections through the now frozen particle microstructure of a congested magma slurry. We simulated the flow regime in two and three dimensions using numerical models built on a finite-element mesh derived from field data. The model captures the flow behaviour of the Basement Sill magma over a viscosity range of 1–104 Pa s where the higher end (greater than or equal to 102 Pa s) corresponds to a magmatic slurry with crystal fractions varying between 30 and 70%. A novel feature of the model is the discovery of transient, low viscosity (less than or equal to 50 Pa s) high Reynolds number eddies formed along undulating contacts at the floor and roof of the intrusion. Numerical tracing of particle orbits implies crystals trapped in eddies segregate according to their mass density. Recovered shear strain rates (10−3–10−5 s−1) at viscosities equating to high particle concentrations (around more than 40%) in the Sill interior point to shear-thinning as an explanation for some types of magmatic layering there. Model transport rates for the Sill magmas imply a maximum emplacement time of ca 105 years, consistent with geochemical evidence for long-range lateral flow. It is a theoretically possibility that fast-flowing magma on a continental scale will be susceptible to planetary-scale rotational forces. PMID:28573002

Image-based modelling of lateral magma flow: the Basement Sill, Antarctica.

PubMed

Petford, Nick; Mirhadizadeh, Seyed

2017-05-01

The McMurdo Dry Valleys magmatic system, Antarctica, provides a world-class example of pervasive lateral magma flow on a continental scale. The lowermost intrusion (Basement Sill) offers detailed sections through the now frozen particle microstructure of a congested magma slurry. We simulated the flow regime in two and three dimensions using numerical models built on a finite-element mesh derived from field data. The model captures the flow behaviour of the Basement Sill magma over a viscosity range of 1-10 4  Pa s where the higher end (greater than or equal to 10 2  Pa s) corresponds to a magmatic slurry with crystal fractions varying between 30 and 70%. A novel feature of the model is the discovery of transient, low viscosity (less than or equal to 50 Pa s) high Reynolds number eddies formed along undulating contacts at the floor and roof of the intrusion. Numerical tracing of particle orbits implies crystals trapped in eddies segregate according to their mass density. Recovered shear strain rates (10 -3 -10 -5  s -1 ) at viscosities equating to high particle concentrations (around more than 40%) in the Sill interior point to shear-thinning as an explanation for some types of magmatic layering there. Model transport rates for the Sill magmas imply a maximum emplacement time of ca 10 5 years, consistent with geochemical evidence for long-range lateral flow. It is a theoretically possibility that fast-flowing magma on a continental scale will be susceptible to planetary-scale rotational forces.

Hierarchical calibration and validation framework of bench-scale computational fluid dynamics simulations for solvent-based carbon capture. Part 2: Chemical absorption across a wetted wall column: Original Research Article: Hierarchical calibration and validation framework of bench-scale computational fluid dynamics simulations

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

Wang, Chao; Xu, Zhijie; Lai, Kevin

Part 1 of this paper presents a numerical model for non-reactive physical mass transfer across a wetted wall column (WWC). In Part 2, we improved the existing computational fluid dynamics (CFD) model to simulate chemical absorption occurring in a WWC as a bench-scale study of solvent-based carbon dioxide (CO2) capture. To generate data for WWC model validation, CO2 mass transfer across a monoethanolamine (MEA) solvent was first measured on a WWC experimental apparatus. The numerical model developed in this work can account for both chemical absorption and desorption of CO2 in MEA. In addition, the overall mass transfer coefficient predictedmore » using traditional/empirical correlations is conducted and compared with CFD prediction results for both steady and wavy falling films. A Bayesian statistical calibration algorithm is adopted to calibrate the reaction rate constants in chemical absorption/desorption of CO2 across a falling film of MEA. The posterior distributions of the two transport properties, i.e., Henry's constant and gas diffusivity in the non-reacting nitrous oxide (N2O)/MEA system obtained from Part 1 of this study, serves as priors for the calibration of CO2 reaction rate constants after using the N2O/CO2 analogy method. The calibrated model can be used to predict the CO2 mass transfer in a WWC for a wider range of operating conditions.« less

Hierarchical calibration and validation framework of bench-scale computational fluid dynamics simulations for solvent-based carbon capture. Part 2: Chemical absorption across a wetted wall column: Original Research Article: Hierarchical calibration and validation framework of bench-scale computational fluid dynamics simulations

DOE PAGES

Wang, Chao; Xu, Zhijie; Lai, Kevin; ...

2017-10-24

Part 1 of this paper presents a numerical model for non-reactive physical mass transfer across a wetted wall column (WWC). In Part 2, we improved the existing computational fluid dynamics (CFD) model to simulate chemical absorption occurring in a WWC as a bench-scale study of solvent-based carbon dioxide (CO2) capture. To generate data for WWC model validation, CO2 mass transfer across a monoethanolamine (MEA) solvent was first measured on a WWC experimental apparatus. The numerical model developed in this work can account for both chemical absorption and desorption of CO2 in MEA. In addition, the overall mass transfer coefficient predictedmore » using traditional/empirical correlations is conducted and compared with CFD prediction results for both steady and wavy falling films. A Bayesian statistical calibration algorithm is adopted to calibrate the reaction rate constants in chemical absorption/desorption of CO2 across a falling film of MEA. The posterior distributions of the two transport properties, i.e., Henry's constant and gas diffusivity in the non-reacting nitrous oxide (N2O)/MEA system obtained from Part 1 of this study, serves as priors for the calibration of CO2 reaction rate constants after using the N2O/CO2 analogy method. The calibrated model can be used to predict the CO2 mass transfer in a WWC for a wider range of operating conditions.« less

Responses of heart rate variability to acute pain after minor spinal surgery: optimal thresholds and correlation with the numeric rating scale.

PubMed

Sesay, Musa; Robin, Georges; Tauzin-Fin, Patrick; Sacko, Oumar; Gimbert, Edouard; Vignes, Jean-Rodolphe; Liguoro, Dominique; Nouette-Gaulain, Karine

2015-04-01

The autonomic nervous system is influenced by many stimuli including pain. Heart rate variability (HRV) is an indirect marker of the autonomic nervous system. Because of paucity of data, this study sought to determine the optimal thresholds of HRV above which the patients are in pain after minor spinal surgery (MSS). Secondly, we evaluated the correlation between HRV and the numeric rating scale (NRS). Following institutional review board approval, patients who underwent MSS were assessed in the postanesthesia care unit after extubation. A laptop containing the HRV software was connected to the ECG monitor. The low-frequency band (LF: 0.04 to 0.5 Hz) denoted both sympathetic and parasympathetic activities, whereas the high-frequency band (HF: 0.15 to 0.4 Hz) represented parasympathetic activity. LF/HF was the sympathovagal balance. Pain was quantified by the NRS ranging from 0 (no pain) to 10 (worst imaginable pain). Simultaneously, HRV parameters were noted. Optimal thresholds were calculated using receiver operating characteristic curves with NRS>3 as cutoff. The correlation between HRV and NRS was assessed using the Spearman rank test. We included 120 patients (64 men and 56 women), mean age 51±14 years. The optimal pain threshold values were 298 ms for LF and 3.12 for LF/HF, with no significant change in HF. NRS was correlated with LF (r=0.29, P<0.005) and LF/HF (r=0.31, P<0.001) but not with HF (r=0.09, NS). This study suggests that, after MSS, values of LF>298 m and LF/HF>3.1 denote acute pain (NRS>3). These HRV parameters are significantly correlated with NRS.

The life of a meander bend: Connecting shape and dynamics via analysis of a numerical model

NASA Astrophysics Data System (ADS)

Schwenk, Jon; Lanzoni, Stefano; Foufoula-Georgiou, Efi

2015-04-01

Analysis of bend-scale meandering river dynamics is a problem of theoretical and practical interest. This work introduces a method for extracting and analyzing the history of individual meander bends from inception until cutoff (called "atoms") by tracking backward through time the set of two cutoff nodes in numerical meander migration models. Application of this method to a simplified yet physically based model provides access to previously unavailable bend-scale meander dynamics over long times and at high temporal resolutions. We find that before cutoffs, the intrinsic model dynamics invariably simulate a prototypical cutoff atom shape we dub simple. Once perturbations from cutoffs occur, two other archetypal cutoff planform shapes emerge called long and round that are distinguished by a stretching along their long and perpendicular axes, respectively. Three measures of meander migration—growth rate, average migration rate, and centroid migration rate—are introduced to capture the dynamic lives of individual bends and reveal that similar cutoff atom geometries share similar dynamic histories. Specifically, through the lens of the three shape types, simples are seen to have the highest growth and average migration rates, followed by rounds, and finally longs. Using the maximum average migration rate as a metric describing an atom's dynamic past, we show a strong connection between it and two metrics of cutoff geometry. This result suggests both that early formative dynamics may be inferred from static cutoff planforms and that there exists a critical period early in a meander bend's life when its dynamic trajectory is most sensitive to cutoff perturbations. An example of how these results could be applied to Mississippi River oxbow lakes with unknown historic dynamics is shown. The results characterize the underlying model and provide a framework for comparisons against more complex models and observed dynamics.

A quasi-Newton algorithm for large-scale nonlinear equations.

PubMed

Huang, Linghua

2017-01-01

In this paper, the algorithm for large-scale nonlinear equations is designed by the following steps: (i) a conjugate gradient (CG) algorithm is designed as a sub-algorithm to obtain the initial points of the main algorithm, where the sub-algorithm's initial point does not have any restrictions; (ii) a quasi-Newton algorithm with the initial points given by sub-algorithm is defined as main algorithm, where a new nonmonotone line search technique is presented to get the step length [Formula: see text]. The given nonmonotone line search technique can avoid computing the Jacobian matrix. The global convergence and the [Formula: see text]-order convergent rate of the main algorithm are established under suitable conditions. Numerical results show that the proposed method is competitive with a similar method for large-scale problems.

Chandra Survey of Nearby Galaxies: Testing the Accretion Model for Low-luminosity AGNs

NASA Astrophysics Data System (ADS)

She, Rui; Ho, Luis C.; Feng, Hua; Cui, Can

2018-06-01

From a Chandra sample of active galactic nuclei (AGNs) in nearby galaxies, we find that for low-luminosity AGNs, either the intrinsic absorption column density, or the fraction of absorbed AGNs, positively scales with the Eddington ratio for L bol/L Edd ≲ 10‑2. Such a behavior, along with the softness of the X-ray spectrum at low luminosities, is in good agreement with the picture that they are powered by hot accretion flows surrounding supermassive black holes. Numerical simulations find that outflows are inevitable with hot accretion flows, and the outflow rate is correlated with the innermost accretion rate in the low-luminosity regime. This agrees well with our results, suggesting that the X-ray absorption originates from, or is associated with, the outflow material. Gas and dust on larger scales may also produce the observed correlation. Future correlation analyses may help differentiate the two scenarios.

Disturbed cortisol secretion in man: contrasting Cushing's disease and endogenous depression.

PubMed

Voigt, K H; Bossert, S; Bretschneider, S; Bliestle, A; Fehm, H L

1985-08-01

A disturbed regulation of cortisol secretion is the principal pathology of Cushing's disease and is also the most widely reported neuroendocrine dysfunction in endogenous depression. Because additional clinical signs in both diseases indicated a hypothetical common pathway, we examined 17 patients suffering from Cushing's disease, following a protocol identical to that used in depressed patients (e.g., Hamilton Rating Scale for Depression, self-rating scales, and a clinical interview). Affective disorders, frequently observed in patients with Cushing's disease, were undetectable after surgical treatment (adrenalectomy or microadenomectomy of hypercortisolism). This was an unexpected result, since we found that recovered patients were still characterized by a disturbance of glucocorticoid feedback regulation, probably acting at the hypothalamic level. Our results, as well as numerous reports from others, failed to support the hypothesis that an impaired regulation of cortisol is directly linked to depressive illness.

The production of premixed flame surface area in turbulent shear flow

NASA Technical Reports Server (NTRS)

Trouve, A.

1993-01-01

In the present work, we use three-dimensional Direct Numerical Simulation (DNS) of premixed flames in turbulent shear flow to characterize the effect of a mean shear motion on flame surface production. The shear is uniform in the unburnt gas, and simulations are performed for different values of the mean shear rate, S. The data base is then used to estimate and compare the different terms appearing in the Sigma-equation as a function of S. The analysis gives in particular the relative weights f the turbulent flow and mean flow components, a(sub T) and A(sub T), of the flame surface production term. This comparison indicates whether the dominant effects of a mean flow velocity gradient on flame surface area are implicit and scale with the modified turbulent flow parameters, kappa and epsilon, or explicit and scale directly with the rate of deformation.

Topological defect formation and spontaneous symmetry breaking in ion Coulomb crystals.

PubMed

Pyka, K; Keller, J; Partner, H L; Nigmatullin, R; Burgermeister, T; Meier, D M; Kuhlmann, K; Retzker, A; Plenio, M B; Zurek, W H; del Campo, A; Mehlstäubler, T E

2013-01-01

Symmetry breaking phase transitions play an important role in nature. When a system traverses such a transition at a finite rate, its causally disconnected regions choose the new broken symmetry state independently. Where such local choices are incompatible, topological defects can form. The Kibble-Zurek mechanism predicts the defect densities to follow a power law that scales with the rate of the transition. Owing to its ubiquitous nature, this theory finds application in a wide field of systems ranging from cosmology to condensed matter. Here we present the successful creation of defects in ion Coulomb crystals by a controlled quench of the confining potential, and observe an enhanced power law scaling in accordance with numerical simulations and recent predictions. This simple system with well-defined critical exponents opens up ways to investigate the physics of non-equilibrium dynamics from the classical to the quantum regime.

Breakup process of cylindrical viscous liquid specimens after a strong explosion in the core

NASA Astrophysics Data System (ADS)

Bang, B. H.; Ahn, C. S.; Kim, D. Y.; Lee, J. G.; Kim, H. M.; Jeong, J. T.; Yoon, W. S.; Al-Deyab, S. S.; Yoo, J. H.; Yoon, S. S.; Yarin, A. L.

2016-09-01

Basic understanding and theoretical description of the expansion and breakup of cylindrical specimens of Newtonian viscous liquid after an explosion of an explosive material in the core are aimed in this work along with the experimental investigation of the discovered phenomena. The unperturbed motion is considered first, and then supplemented by the perturbation growth pattern in the linear approximation. It is shown that a special non-trivial case of the Rayleigh-Taylor instability sets in being triggered by the gas pressure differential between the inner and outer surfaces of the specimens. The spectrum of the growing perturbation waves is established, as well as the growth rate found, and the debris sizes evaluated. An experimental study is undertaken and both the numerical and analytical solutions developed are compared with the experimental data. A good agreement between the theory and experiment is revealed. It is shown that the debris size λ, the parameter most important practically, scales with the explosion energy E as λ ˜ E-1/2. Another practically important parameter, the number of fingers N measured in the experiments was within 6%-9% from the values predicted numerically. Moreover, N in the experiments and numerical predictions followed the scaling law predicted theoretically, N ˜ me 1 / 2 , with me being the explosive mass.

Study on Collapse Mechanism of Steel Frame Structure under High Temperature and Blast Loading

NASA Astrophysics Data System (ADS)

Baoxin, Qi; Yan, Shi; Bi, Jialiang

2018-03-01

Numerical simulation analysis for collapsing process and mechanism of steel frame structures under the combined effects of fire and explosion is performed in this paper. First of all, a new steel constitutive model considering fire (high temperature softening effect) and blast (strain rate effect) is established. On the basis of the traditional Johnson-Cook model and the Perzyna model, the relationship between strain and scaled distance as well as the EOUROCODE3 standard heating curve taking into account the temperature effect parameters is introduced, and a modified Johnson-Cook constitutive model is established. Then, the influence of considering the scaled distance is introduced in order to more effectively describe the destruction and collapse phenomena of steel frame structures. Some conclusions are obtained based on the numerical analysis that the destruction will be serious and even progressively collapse with decreasing of the temperature of the steel column for the same scaled distance under the combined effects of fire and blast; the damage will be serious with decreasing of the scaled distance of the steel column under the same temperature under the combined effects of fire and blast; in the case of the combined effects of fire and blast happening in the side-spans, the partial progressive collapse occurs as the scaled distance is less than or equal to 1.28; six kinds of damages which are no damage, minor damage, moderate damage, severe damage, critical collapse, and progressive collapse.

From minerals to hillslopes: Towards an integrated framework for interpreting chemical and physical erosion

NASA Astrophysics Data System (ADS)

Hahm, W.; Riebe, C. S.; Ferrier, K.; Kirchner, J. W.

2011-12-01

Traditional frameworks for conceptualizing hillslope denudation distinguish between the movement of mass in solution (chemical erosion) and mass moved via mechanical processes (physical erosion). At the hillslope scale, physical and chemical erosion rates can be quantified by combining measurements of regolith chemistry with cosmogenic nuclide concentrations in bedrock and sediment, while basin-scale rates are often inferred from riverine solute and sediment loads. These techniques integrate the effects of numerous weathering and erosion mechanisms and do not provide prima facie information about the precise nature and scale of those mechanisms. For insight into erosional process, physical erosion has been considered in terms of two limiting regimes. When physical erosion outpaces weathering front advance, regolith is mobilized downslope as soon as it is sufficiently loosened by weathering, and physical erosion rates are limited by rates of mobile regolith production. This is commonly termed weathering-limited erosion. Conversely, when weathering front advance outpaces erosion, the mobile regolith layer grows thicker over time, and physical erosion rates are limited by the efficiency of downslope transport processes. This is termed transport-limited erosion. This terminology brings the description of hillslope evolution closer to the realm of essential realism, to the extent that measurable quantities from the field can be cast in a process-based framework. An analogous process-limitation framework describes chemical erosion. In supply-limited chemical erosion, chemical weathering depletes regolith of its reactive phases during residence on a hillslope, and chemical erosion rates are limited by the supply of fresh minerals to the weathering zone. Alternatively, hillslopes may exhibit kinetic-limited chemical erosion, where physical erosion transports regolith downslope before weatherable phases are completely removed by chemical erosion. We show how supply- and kinetic-limited chemical erosion can be distinguished from one another using data from a global compilation of physical and chemical erosion rates. As a step towards understanding these rates at the level of essential realism, we explore how the hillslope-scale regimes of supply- and kinetic-limited chemical erosion relate to existing conceptual frameworks that interpret weathering rates in terms of transport- and kinetic-limitation at the mineral scale.

Respiration from the organ level to the stand

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

Sprugel, D.G.; Ryan, M.G.; Brooks, J.R.

1995-07-01

The status of efforts to estimate respiration of conifers varies sharply from one tissue to another. There have been numerous measurements of foliage respiration in conifers, but relatively few measurements of within-stand variation in reference to parameters that might be used for scaling. However, a number of logical models for scaling have been proposed (e.g., light, age, or N) and general directions for future research seem well established. There are far fewer measurements of woody-tissue respiration that might be useful for scaling, but some consensus seems to have developed that the use of sapwood biomass and growth rates as indicesmore » may provide the key to scaling woody-tissue respiration up to the stand level. Root respiration is still bogged down by a plurality of methods, each of which seems to have some serious disadvantages, so that even the nature of within-stand variation is poorly known. Successful and believable scaling of root respiration from tissue-specific measurements to the stand level seems to be far in the future. Finally, proxy measurements such as litterfall and N concentration can and have been used to estimate respiration for whole stands without measuring tissue-specific rates at all, but all of these techniques require assumptions that need further testing before they will be generally accepted.« less

Can a numerically stable subgrid-scale model for turbulent flow computation be ideally accurate?: a preliminary theoretical study for the Gaussian filtered Navier-Stokes equations.

PubMed

Ida, Masato; Taniguchi, Nobuyuki

2003-09-01

This paper introduces a candidate for the origin of the numerical instabilities in large eddy simulation repeatedly observed in academic and practical industrial flow computations. Without resorting to any subgrid-scale modeling, but based on a simple assumption regarding the streamwise component of flow velocity, it is shown theoretically that in a channel-flow computation, the application of the Gaussian filtering to the incompressible Navier-Stokes equations yields a numerically unstable term, a cross-derivative term, which is similar to one appearing in the Gaussian filtered Vlasov equation derived by Klimas [J. Comput. Phys. 68, 202 (1987)] and also to one derived recently by Kobayashi and Shimomura [Phys. Fluids 15, L29 (2003)] from the tensor-diffusivity subgrid-scale term in a dynamic mixed model. The present result predicts that not only the numerical methods and the subgrid-scale models employed but also only the applied filtering process can be a seed of this numerical instability. An investigation concerning the relationship between the turbulent energy scattering and the unstable term shows that the instability of the term does not necessarily represent the backscatter of kinetic energy which has been considered a possible origin of numerical instabilities in large eddy simulation. The present findings raise the question whether a numerically stable subgrid-scale model can be ideally accurate.

Temperament, Beliefs About Pain Control, and Pain Intensity in Endometriosis Patients.

PubMed

Bylinka, Joanna; Oniszczenko, Włodzimierz

2016-12-01

This correlational study investigated the relationships between temperament, beliefs about pain control, and pain intensity ratings in a group of 103 women diagnosed with endometriosis. Temperament traits were assessed using the Formal Characteristics of Behaviour-Temperament Inventory. Beliefs about pain control were measured using the Polish version of the Beliefs about Pain Control Questionnaire. The Numerical Rating Scale (NRS-11) was used to measure pain intensity. There was a high negative correlation between the temperament trait of endurance and pain intensity ratings. Moderate negative correlations with pain intensity were found for internal beliefs about pain control. Hierarchical multiple regression analysis indicated that the endurance trait and internal beliefs about pain control accounted for 33 % of the variance in pain intensity ratings in women with endometriosis.

Resonance-modulated wavelength scaling of high-order-harmonic generation from H2+

NASA Astrophysics Data System (ADS)

Wang, Baoning; He, Lixin; Wang, Feng; Yuan, Hua; Zhu, Xiaosong; Lan, Pengfei; Lu, Peixiang

2018-01-01

Wavelength scaling of high-order harmonic generation (HHG) in a non-Born-Oppenheimer treatment of H2+ is investigated by numerical simulations of the time-dependent Schrödinger equation. The results show that the decrease in the wavelength-dependent HHG yield is reduced compared to that in the fixed-nucleus approximation. This slower wavelength scaling is related to the charge-resonance-enhanced ionization effect, which considerably increases the ionization rate at longer driving laser wavelengths due to the relatively larger nuclear separation. In addition, we find an oscillation structure in the wavelength scaling of HHG from H2+. Upon decreasing the laser intensity or increasing the nuclear mass, the oscillation structure will shift towards a longer wavelength of the laser pulse. These results permit the generation of an efficient harmonic spectrum in the midinfrared regime by manipulating the nuclear dynamics of molecules.

Recent topographic evolution and erosion of the deglaciated Washington Cascades inferred from a stochastic landscape evolution model

NASA Astrophysics Data System (ADS)

Moon, Seulgi; Shelef, Eitan; Hilley, George E.

2015-05-01

In this study, we model postglacial surface processes and examine the evolution of the topography and denudation rates within the deglaciated Washington Cascades to understand the controls on and time scales of landscape response to changes in the surface process regime after deglaciation. The postglacial adjustment of this landscape is modeled using a geomorphic-transport-law-based numerical model that includes processes of river incision, hillslope diffusion, and stochastic landslides. The surface lowering due to landslides is parameterized using a physically based slope stability model coupled to a stochastic model of the generation of landslides. The model parameters of river incision and stochastic landslides are calibrated based on the rates and distribution of thousand-year-time scale denudation rates measured from cosmogenic 10Be isotopes. The probability distributions of those model parameters calculated based on a Bayesian inversion scheme show comparable ranges from previous studies in similar rock types and climatic conditions. The magnitude of landslide denudation rates is determined by failure density (similar to landslide frequency), whereas precipitation and slopes affect the spatial variation in landslide denudation rates. Simulation results show that postglacial denudation rates decay over time and take longer than 100 kyr to reach time-invariant rates. Over time, the landslides in the model consume the steep slopes characteristic of deglaciated landscapes. This response time scale is on the order of or longer than glacial/interglacial cycles, suggesting that frequent climatic perturbations during the Quaternary may produce a significant and prolonged impact on denudation and topography.

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

McInerney, Peter; Adams, Paul; Hadi, Masood Z.

As larger-scale cloning projects become more prevalent, there is an increasing need for comparisons among high fidelity DNA polymerases used for PCR amplification. All polymerases marketed for PCR applications are tested for fidelity properties (i.e., error rate determination) by vendors, and numerous literature reports have addressed PCR enzyme fidelity. Nonetheless, it is often difficult to make direct comparisons among different enzymes due to numerous methodological and analytical differences from study to study. We have measured the error rates for 6 DNA polymerases commonly used in PCR applications, including 3 polymerases typically used for cloning applications requiring high fidelity. Error ratemore » measurement values reported here were obtained by direct sequencing of cloned PCR products. The strategy employed here allows interrogation of error rate across a very large DNA sequence space, since 94 unique DNA targets were used as templates for PCR cloning. The six enzymes included in the study, Taq polymerase, AccuPrime-Taq High Fidelity, KOD Hot Start, cloned Pfu polymerase, Phusion Hot Start, and Pwo polymerase, we find the lowest error rates with Pfu , Phusion, and Pwo polymerases. Error rates are comparable for these 3 enzymes and are >10x lower than the error rate observed with Taq polymerase. Mutation spectra are reported, with the 3 high fidelity enzymes displaying broadly similar types of mutations. For these enzymes, transition mutations predominate, with little bias observed for type of transition.« less

Self-similarity of waiting times in fracture systems

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

Niccolini, G.; Bosia, F.; Carpinteri, A.

2009-08-15

Experimental and numerical results are presented for a fracture experiment carried out on a fiber-reinforced element under flexural loading, and a statistical analysis is performed for acoustic emission waiting-time distributions. By an optimization procedure, a recently proposed scaling law describing these distributions for different event magnitude scales is confirmed by both experimental and numerical data, thus reinforcing the idea that fracture of heterogeneous materials has scaling properties similar to those found for earthquakes. Analysis of the different scaling parameters obtained for experimental and numerical data leads us to formulate the hypothesis that the type of scaling function obtained depends onmore » the level of correlation among fracture events in the system.« less

Horizontal heat fluxes over complex terrain computed using a simple mixed-layer model and a numerical model

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

Kimura, Fujio; Kuwagata, Tuneo

1995-02-01

The thermally induced local circulation over a periodic valley is simulated by a two-dimensional numerical model that does-not include condensational processes. During the daytime of a clear, calm day, heat is transported from the mountainous region to the valley area by anabatic wind and its return flow. The specific humidity is, however, transported in an inverse manner. The horizontal exchange rate of sensible heat has a horizontal scale similarity, as long as the horizontal scale is less than a critical width of about 100 km. The sensible heat accumulated in an atmospheric column over an arbitrary point can be estimatedmore » by a simple model termed the uniform mixed-layer model (UML). The model assumes that the potential temperature is both vertically and horizontally uniform in the mixed layer, even over the complex terrain. The UML model is valid only when the horizontal scale of the topography is less than the critical width and the maximum difference in the elevation of the topography is less than about 1500 m. Latent heat is accumulated over the mountainous region while the atmosphere becomes dry over the valley area. When the horizontal scale is close to the critical width, the largest amount of humidity is accumulated during the late afternoon over the mountainous region. 18 refs., 15 figs., 1 tab.« less

Evaluation of deconvolution modelling applied to numerical combustion

NASA Astrophysics Data System (ADS)

Mehl, Cédric; Idier, Jérôme; Fiorina, Benoît

2018-01-01

A possible modelling approach in the large eddy simulation (LES) of reactive flows is to deconvolve resolved scalars. Indeed, by inverting the LES filter, scalars such as mass fractions are reconstructed. This information can be used to close budget terms of filtered species balance equations, such as the filtered reaction rate. Being ill-posed in the mathematical sense, the problem is very sensitive to any numerical perturbation. The objective of the present study is to assess the ability of this kind of methodology to capture the chemical structure of premixed flames. For that purpose, three deconvolution methods are tested on a one-dimensional filtered laminar premixed flame configuration: the approximate deconvolution method based on Van Cittert iterative deconvolution, a Taylor decomposition-based method, and the regularised deconvolution method based on the minimisation of a quadratic criterion. These methods are then extended to the reconstruction of subgrid scale profiles. Two methodologies are proposed: the first one relies on subgrid scale interpolation of deconvolved profiles and the second uses parametric functions to describe small scales. Conducted tests analyse the ability of the method to capture the chemical filtered flame structure and front propagation speed. Results show that the deconvolution model should include information about small scales in order to regularise the filter inversion. a priori and a posteriori tests showed that the filtered flame propagation speed and structure cannot be captured if the filter size is too large.

A scale space based algorithm for automated segmentation of single shot tagged MRI of shearing deformation.

PubMed

Sprengers, Andre M J; Caan, Matthan W A; Moerman, Kevin M; Nederveen, Aart J; Lamerichs, Rolf M; Stoker, Jaap

2013-04-01

This study proposes a scale space based algorithm for automated segmentation of single-shot tagged images of modest SNR. Furthermore the algorithm was designed for analysis of discontinuous or shearing types of motion, i.e. segmentation of broken tag patterns. The proposed algorithm utilises non-linear scale space for automatic segmentation of single-shot tagged images. The algorithm's ability to automatically segment tagged shearing motion was evaluated in a numerical simulation and in vivo. A typical shearing deformation was simulated in a Shepp-Logan phantom allowing for quantitative evaluation of the algorithm's success rate as a function of both SNR and the amount of deformation. For a qualitative in vivo evaluation tagged images showing deformations in the calf muscles and eye movement in a healthy volunteer were acquired. Both the numerical simulation and the in vivo tagged data demonstrated the algorithm's ability for automated segmentation of single-shot tagged MR provided that SNR of the images is above 10 and the amount of deformation does not exceed the tag spacing. The latter constraint can be met by adjusting the tag delay or the tag spacing. The scale space based algorithm for automatic segmentation of single-shot tagged MR enables the application of tagged MR to complex (shearing) deformation and the processing of datasets with relatively low SNR.

A Constructive Mean-Field Analysis of Multi-Population Neural Networks with Random Synaptic Weights and Stochastic Inputs

PubMed Central

Faugeras, Olivier; Touboul, Jonathan; Cessac, Bruno

2008-01-01

We deal with the problem of bridging the gap between two scales in neuronal modeling. At the first (microscopic) scale, neurons are considered individually and their behavior described by stochastic differential equations that govern the time variations of their membrane potentials. They are coupled by synaptic connections acting on their resulting activity, a nonlinear function of their membrane potential. At the second (mesoscopic) scale, interacting populations of neurons are described individually by similar equations. The equations describing the dynamical and the stationary mean-field behaviors are considered as functional equations on a set of stochastic processes. Using this new point of view allows us to prove that these equations are well-posed on any finite time interval and to provide a constructive method for effectively computing their unique solution. This method is proved to converge to the unique solution and we characterize its complexity and convergence rate. We also provide partial results for the stationary problem on infinite time intervals. These results shed some new light on such neural mass models as the one of Jansen and Rit (1995): their dynamics appears as a coarse approximation of the much richer dynamics that emerges from our analysis. Our numerical experiments confirm that the framework we propose and the numerical methods we derive from it provide a new and powerful tool for the exploration of neural behaviors at different scales. PMID:19255631

Multiphase flow modelling of volcanic ash particle settling in water using adaptive unstructured meshes

NASA Astrophysics Data System (ADS)

Jacobs, C. T.; Collins, G. S.; Piggott, M. D.; Kramer, S. C.; Wilson, C. R. G.

2013-02-01

Small-scale experiments of volcanic ash particle settling in water have demonstrated that ash particles can either settle slowly and individually, or rapidly and collectively as a gravitationally unstable ash-laden plume. This has important implications for the emplacement of tephra deposits on the seabed. Numerical modelling has the potential to extend the results of laboratory experiments to larger scales and explore the conditions under which plumes may form and persist, but many existing models are computationally restricted by the fixed mesh approaches that they employ. In contrast, this paper presents a new multiphase flow model that uses an adaptive unstructured mesh approach. As a simulation progresses, the mesh is optimized to focus numerical resolution in areas important to the dynamics and decrease it where it is not needed, thereby potentially reducing computational requirements. Model verification is performed using the method of manufactured solutions, which shows the correct solution convergence rates. Model validation and application considers 2-D simulations of plume formation in a water tank which replicate published laboratory experiments. The numerically predicted settling velocities for both individual particles and plumes, as well as instability behaviour, agree well with experimental data and observations. Plume settling is clearly hindered by the presence of a salinity gradient, and its influence must therefore be taken into account when considering particles in bodies of saline water. Furthermore, individual particles settle in the laminar flow regime while plume settling is shown (by plume Reynolds numbers greater than unity) to be in the turbulent flow regime, which has a significant impact on entrainment and settling rates. Mesh adaptivity maintains solution accuracy while providing a substantial reduction in computational requirements when compared to the same simulation performed using a fixed mesh, highlighting the benefits of an adaptive unstructured mesh approach.

Wide-range simulation of elastoplastic wave fronts and failure of solids under high-speed loading

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

Saveleva, Natalia, E-mail: saveleva@icmm.ru; Bayandin, Yuriy, E-mail: buv@icmm.ru; Naimark, Oleg, E-mail: naimark@icmm.ru

2015-10-27

The aim of this paper is numerical study of deformation processes and failure of vanadium under shock-wave loading. According developed statistical theory of solid with mesoscopic defects the constitutive equations were proposed in terms of two structural variables characterizing behavior of defects ensembles: defect density tensor and structural scaling parameter. On the basis of wide-range constitutive equations the mathematical model of deformation behavior and failure of vanadium was developed taking into account the bond relaxation mechanisms, multistage of fracture and nonlinearity kinetic of defects. Results of numerical simulation allow the description of the major effects of shock wave propagation (elasticmore » precursor decay, grow of spall strength under grow strain rate)« less

Cancer symptom scale preferences: does one size fit all?

PubMed

Jeter, Kirby; Blackwell, Siobhan; Burke, Lucy; Joyce, David; Moran, Catherine; Conway, Emma Victoria; Cremen, Iseult; O'Connor, Brenda; Ui Dhuibhir, Pauline; Walsh, Declan

2018-06-01

Patients with advanced cancer do not report all symptoms, so assessment is best done systematically. However, for such patients, completion rates of some symptom instruments are <50%. Symptoms can be quantified by various scales including the Categorical Response Scale (CRS), Numerical Rating Scale (NRS) and Visual Analogue Scale (VAS). Patient preferences for CRS, NRS and VAS in symptom assessment and their clinical utility in 3 cancer symptoms: pain, tiredness and appetite loss were determined. A prospective survey was conducted involving cancer admissions to a 36-bed palliative care unit. 100 inpatients were recruited, aged 38-93 years (x̅ =71 years; SD=11.6), with median Eastern Cooperative Oncology Group (ECOG) scores of 2 (range 0-4). VAS was the least preferred measure. 52% of patients choose the same scale for all 3 symptoms and 44% for 2, with 4% choosing a different individual scale per symptom. There was moderate agreement between participant scale preference and observer determined ease of scale completion (loss of appetite: κ=0.36; pain: κ=0.49; tiredness: κ=0.45). Participants preferred CRS for appetite loss (48%) and tiredness (40%) and NRS for pain (44%). VAS was the least favoured scale and should be used cautiously in this population. Most participants had a scale preference with high intrapatient consistency between scales. CRS was preferred for appetite loss and tiredness and NRS for pain. Consideration should be given to individualised cancer symptom assessment according to patient scale preference. Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://www.bmj.com/company/products-services/rights-and-licensing/.

The scaling of oblique plasma double layers

NASA Technical Reports Server (NTRS)

Borovsky, J. E.

1983-01-01

Strong oblique plasma double layers are investigated using three methods, i.e., electrostatic particle-in-cell simulations, numerical solutions to the Poisson-Vlasov equations, and analytical approximations to the Poisson-Vlasov equations. The solutions to the Poisson-Vlasov equations and numerical simulations show that strong oblique double layers scale in terms of Debye lengths. For very large potential jumps, theory and numerical solutions indicate that all effects of the magnetic field vanish and the oblique double layers follow the same scaling relation as the field-aligned double layers.

A study of the topology of dissipating motions in direct numerical simulations of time-developing compressible and incompressible mixing layers

NASA Technical Reports Server (NTRS)

Chen, J. H.; Chong, M. S.; Soria, J.; Sondergaard, R.; Perry, A. E.; Rogers, M.; Moser, R.; Cantwell, B. J.

1990-01-01

A preliminary investigation of the geometry of flow patterns in numerically simulated compressible and incompressible mixing layers was carried out using 3-D critical point methodology. Motions characterized by high rates of kinetic energy dissipation and/or high enstrophy were of particular interest. In the approach the partial derivatives of the velocity field are determined at every point in the flow. These are used to construct the invariants of the velocity gradient tensor and the rate-of-strain tensor (P, Q, R, and P(sub s), Q(sub s), R(sub s) respectively). For incompressible flow the first invariant is zero. For the conditions of the compressible simulation, the first invariant is found to be everywhere small, relative to the second and third invariants, and so in both cases the local topology at a point is mainly determined by the second and third invariants. The data at every grid point is used to construct scatter plots of Q versus R and Q(sub s) versus R(sub s). Most points map to a cluster near the origin in Q-R space. However, fine scale motions, that is motions which are characterized by velocity derivatives which scale with the square root of R(sub delta), tend to map to regions which lie far from the origin. Definite trends are observed for motions characterized by high enstrophy and/or high dissipation. The observed trends suggest that, for these motions, the second and third invariants of the velocity gradient and rate-of-strain tensors are strongly correlated. The second and third invariants of the rate-of-strain tensor are related by K(-Q(sub s))(exp 3/2), which is consistent with the above scaling of velocity derivatives. The quantity K appears to depend on Reynolds number with an upper limit K = 2(the square root of 3)/9 corresponding to locally axisymmetric flow. For both the compressible and incompressible mixing layer, regions corresponding to high rates of dissipation are found to be characterized by comparable magnitudes of R(sub ij)R(sub ij) and S(sub ij)S(sub ij). For the incompressible mixing layer, regions characterized by the highest values of enstrophy are found to have relatively low strain rates.

Coupling a Reactive Transport Code with a Global Land Surface Model for Mechanistic Biogeochemistry Representation: 1. Addressing the Challenge of Nonnegativity

DOE PAGES

Tang, Guoping; Yuan, Fengming; Bisht, Gautam; ...

2016-01-01

Reactive transport codes (e.g., PFLOTRAN) are increasingly used to improve the representation of biogeochemical processes in terrestrial ecosystem models (e.g., the Community Land Model, CLM). As CLM and PFLOTRAN use explicit and implicit time stepping, implementation of CLM biogeochemical reactions in PFLOTRAN can result in negative concentration, which is not physical and can cause numerical instability and errors. The objective of this work is to address the nonnegativity challenge to obtain accurate, efficient, and robust solutions. We illustrate the implementation of a reaction network with the CLM-CN decomposition, nitrification, denitrification, and plant nitrogen uptake reactions and test the implementation atmore » arctic, temperate, and tropical sites. We examine use of scaling back the update during each iteration (SU), log transformation (LT), and downregulating the reaction rate to account for reactant availability limitation to enforce nonnegativity. Both SU and LT guarantee nonnegativity but with implications. When a very small scaling factor occurs due to either consumption or numerical overshoot, and the iterations are deemed converged because of too small an update, SU can introduce excessive numerical error. LT involves multiplication of the Jacobian matrix by the concentration vector, which increases the condition number, decreases the time step size, and increases the computational cost. Neither SU nor SE prevents zero concentration. When the concentration is close to machine precision or 0, a small positive update stops all reactions for SU, and LT can fail due to a singular Jacobian matrix. The consumption rate has to be downregulated such that the solution to the mathematical representation is positive. A first-order rate downregulates consumption and is nonnegative, and adding a residual concentration makes it positive. For zero-order rate or when the reaction rate is not a function of a reactant, representing the availability limitation of each reactant with a Monod substrate limiting function provides a smooth transition between a zero-order rate when the reactant is abundant and first-order rate when the reactant becomes limiting. When the half saturation is small, marching through the transition may require small time step sizes to resolve the sharp change within a small range of concentration values. Our results from simple tests and CLM-PFLOTRAN simulations caution against use of SU and indicate that accurate, stable, and relatively efficient solutions can be achieved with LT and downregulation with Monod substrate limiting function and residual concentration.« less

Experimental quantification of decoherence via the Loschmidt echo in a many spin system with scaled dipolar Hamiltonians

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

Buljubasich, Lisandro; Dente, Axel D.; Levstein, Patricia R.

2015-10-28

We performed Loschmidt echo nuclear magnetic resonance experiments to study decoherence under a scaled dipolar Hamiltonian by means of a symmetrical time-reversal pulse sequence denominated Proportionally Refocused Loschmidt (PRL) echo. The many-spin system represented by the protons in polycrystalline adamantane evolves through two steps of evolution characterized by the secular part of the dipolar Hamiltonian, scaled down with a factor |k| and opposite signs. The scaling factor can be varied continuously from 0 to 1/2, giving access to a range of complexity in the dynamics. The experimental results for the Loschmidt echoes showed a spreading of the decay rates thatmore » correlate directly to the scaling factors |k|, giving evidence that the decoherence is partially governed by the coherent dynamics. The average Hamiltonian theory was applied to give an insight into the spin dynamics during the pulse sequence. The calculations were performed for every single radio frequency block in contrast to the most widely used form. The first order of the average Hamiltonian numerically computed for an 8-spin system showed decay rates that progressively decrease as the secular dipolar Hamiltonian becomes weaker. Notably, the first order Hamiltonian term neglected by conventional calculations yielded an explanation for the ordering of the experimental decoherence rates. However, there is a strong overall decoherence observed in the experiments which is not reflected by the theoretical results. The fact that the non-inverted terms do not account for this effect is a challenging topic. A number of experiments to further explore the relation of the complete Hamiltonian with this dominant decoherence rate are proposed.« less

Modeling solute transport in a heterogeneous unsaturated porous medium under dynamic boundary conditions on different spatial scales

NASA Astrophysics Data System (ADS)

Cremer, Clemens; Neuweiler, Insa; Bechtold, Michel

2013-04-01

Understanding transport of solutes/contaminants through unsaturated soil in the shallow subsurface is vital to assess groundwater quality, nutrient cycling or to plan remediation projects. Alternating precipitation and evaporation conditions causing upward and downward flux with differing flow paths, changes in saturation and related structural heterogeneity make the description of transport in the unsaturated zone near the soil-surface a complex problem. Preferential flow paths strongly depend, among other things, on the saturation of a medium. Recent studies (e.g. Bechtold et al., 2011) showed lateral flow and solute transport during evaporation conditions (upward flux) in vertically layered sand columns. Results revealed that during evaporation water and solute are redistributed laterally from coarse to fine media deeper in the soil, and towards zones of lowest hydraulic head near to the soil surface. These zones at the surface can be coarse or fine grained depending on saturation status and evaporation flux. However, if boundary conditions are reversed and precipitation is applied, the flow field is not reversed in the same manner, resulting in entirely different transport patterns for downward and upward flow. Therefore, considering net-flow rates alone is misleading when describing transport in the shallow unsaturated zone. In this contribution, we analyze transport of a solute in the shallow subsurface to assess effects resulting from the superposition of heterogeneous soil structures and dynamic flow conditions on various spatial scales. Two-dimensional numerical simulations of unsaturated flow and transport in heterogeneous porous media under changing boundary conditions are carried out using a finite-volume code coupled to a particle tracking algorithm to quantify solute transport and leaching rates. In order to validate numerical simulations, results are qualitatively compared to those of a physical experiment (Bechtold et al., 2011). Numerical simulations differ in lateral scale reaching from 0.2 m to 1.5 m, while the height of the domain is kept constant to 1.5m. Strong material heterogeneity is realized through vertical layers of coarse and fine sand. Both materials remain permanently under liquid-flow-dominated ('stage1') evaporation conditions. Spatial moments as well as the dilution index (Kitanidis, 1994) are used for quantification of transport behaviour. Results show that, while all simulations led to anomalous transport, infiltration-evaporation cycles lead to faster solute leaching rates than solely infiltration at the same net-infiltration rate in both homogeneous and heterogeneous media. Flow and transport-paths significantly differed between infiltration and evaporation, resulting in lateral water fluxes and hence lateral solute transport. Variation of the width of the model domain shows faster leaching rates for domains with small horizontal extent.

An empirical and model study on automobile market in Taiwan

NASA Astrophysics Data System (ADS)

Tang, Ji-Ying; Qiu, Rong; Zhou, Yueping; He, Da-Ren

2006-03-01

We have done an empirical investigation on automobile market in Taiwan including the development of the possession rate of the companies in the market from 1979 to 2003, the development of the largest possession rate, and so on. A dynamic model for describing the competition between the companies is suggested based on the empirical study. In the model each company is given a long-term competition factor (such as technology, capital and scale) and a short-term competition factor (such as management, service and advertisement). Then the companies play games in order to obtain more possession rate in the market under certain rules. Numerical simulation based on the model display a competition developing process, which qualitatively and quantitatively agree with our empirical investigation results.

Scaling methane oxidation: From laboratory incubation experiments to landfill cover field conditions

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

Abichou, Tarek, E-mail: abichou@eng.fsu.edu; Mahieu, Koenraad; Chanton, Jeff

2011-05-15

Evaluating field-scale methane oxidation in landfill cover soils using numerical models is gaining interest in the solid waste industry as research has made it clear that methane oxidation in the field is a complex function of climatic conditions, soil type, cover design, and incoming flux of landfill gas from the waste mass. Numerical models can account for these parameters as they change with time and space under field conditions. In this study, we developed temperature, and water content correction factors for methane oxidation parameters. We also introduced a possible correction to account for the different soil structure under field conditions.more » These parameters were defined in laboratory incubation experiments performed on homogenized soil specimens and were used to predict the actual methane oxidation rates to be expected under field conditions. Water content and temperature corrections factors were obtained for the methane oxidation rate parameter to be used when modeling methane oxidation in the field. To predict in situ measured rates of methane with the model it was necessary to set the half saturation constant of methane and oxygen, K{sub m}, to 5%, approximately five times larger than laboratory measured values. We hypothesize that this discrepancy reflects differences in soil structure between homogenized soil conditions in the lab and actual aggregated soil structure in the field. When all of these correction factors were re-introduced into the oxidation module of our model, it was able to reproduce surface emissions (as measured by static flux chambers) and percent oxidation (as measured by stable isotope techniques) within the range measured in the field.« less

Evolution of porosity and diffusivity associated with chemical weathering of a basalt clast

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

Navarre-Sitchler, A.; Steefel, C.I.; Yang, L.

Weathering of rocks as a result of exposure to water and the atmosphere can cause significant changes in their chemistry and porosity. In low-porosity rocks, such as basalts, changes in porosity, resulting from chemical weathering, are likely to modify the rock's effective diffusivity and permeability, affecting the rate of solute transport and thus potentially the rate of overall weathering to the extent that transport is the rate limiting step. Changes in total porosity as a result of mineral dissolution and precipitation have typically been used to calculate effective diffusion coefficients through Archie's law for reactive transport simulations of chemical weathering,more » but this approach fails to account for unconnected porosity that does not contribute to transport. In this study, we combine synchrotron X-ray microcomputed tomography ({mu}CT) and laboratory and numerical diffusion experiments to examine changes in both total and effective porosity and effective diffusion coefficients across a weathering interface in a weathered basalt clast from Costa Rica. The {mu}CT data indicate that below a critical value of {approx}9%, the porosity is largely unconnected in the basalt clast. The {mu}CT data were further used to construct a numerical pore network model to determine upscaled, effective diffusivities as a function of total porosity (ranging from 3 to 30%) for comparison with diffusivities determined in laboratory tracer experiments. By using effective porosity as the scaling parameter and accounting for critical porosity, a model is developed that accurately predicts continuum-scale effective diffusivities across the weathering interface of the basalt clast.« less

Microphysically Derived Expressions for Rate-and-State Friction Parameters, a, b, and Dc

NASA Astrophysics Data System (ADS)

Chen, Jianye; Niemeijer, A. R.; Spiers, Christopher J.

2017-12-01

Rate-and-state friction (RSF) laws are extensively applied in fault mechanics but have a largely empirical basis reflecting only limited understanding of the underlying physical mechanisms. We recently proposed a microphysical model describing the frictional behavior of a granular fault gouge undergoing deformation in terms of granular flow accompanied by thermally activated creep and intergranular sliding at grain contacts. Numerical solutions reproduced typical experimental results well. Here we extend our model to obtain physically meaningful, analytical expressions for the steady state frictional strength and standard RSF parameters, a, b, and Dc. The frictional strength contains two components, namely, grain boundary friction and friction due to intergranular dilatation. The expressions obtained for a and b linearly reflect the rate dependence of these two terms. Dc scales with slip band thickness and varies only slightly with velocity. The values of a, b, and Dc predicted show quantitative agreement with previous experimental results, and inserting their values into classical RSF laws gives simulated friction behavior that is consistent with the predictions of our numerically implemented model for small departures from steady state. For large velocity steps, the model produces mixed RSF behavior that falls between the Slowness and Slip laws, for example, with an intermediate equivalent slip(-weakening) distance d0. Our model possesses the interesting property not only that a and b are velocity dependent but also that Dc and d0 scale differently from classical RSF models, potentially explaining behaviour seen in many hydrothermal friction experiments and having substantial implications for natural fault friction.

Bounded energy states in homogeneous turbulent shear flow - An alternative view

NASA Technical Reports Server (NTRS)

Bernard, P. S.; Speziale, C. G.

1992-01-01

The equilibrium structure of homogeneous turbulent shear flow is investigated from a theoretical standpoint. Existing turbulence models, in apparent agreement with physical and numerical experiments, predict an unbounded exponential time growth of the turbulent kinetic energy and dissipation rate; only the anisotropy tensor and turbulent time scale reach a structural equilibrium. It is shown that if a residual vortex stretching term is maintained in the dissipation rate transport equation, then there can exist equilibrium solutions, with bounded energy states, where the turbulence production is balanced by its dissipation. Illustrative calculations are presented for a k-epsilon model modified to account for net vortex stretching.

A second-order theory for transverse ion heating and momentum coupling due to electrostatic ion cyclotron waves

NASA Technical Reports Server (NTRS)

Miller, Ronald H.; Winske, Dan; Gary, S. P.

1992-01-01

A second-order theory for electrostatic instabilities driven by counterstreaming ion beams is developed which describes momentum coupling and heating of the plasma via wave-particle interactions. Exchange rates between the waves and particles are derived, which are suitable for the fluid equations simulating microscopic effects on macroscopic scales. Using a fully kinetic simulation, the electrostatic ion cyclotron instability due to counterstreaming H(+) beams has been simulated. A power spectrum from the kinetic simulation is used to evaluate second-order exchange rates. The calculated heating and momentum loss from second-order theory is compared to the numerical simulation.

The evolution of active region loop plasma

NASA Technical Reports Server (NTRS)

Krall, K. R.; Antiochos, S. K.

1980-01-01

The adjustment of coronal active-region loops to changes in their heating rate is investigated numerically. The one-dimensional hydrodynamic equations are solved subject to boundary conditions in which heat flux-induced mass exchange between coronal and chromospheric components is allowed. The calculated evolution of physical parameters suggests that (1) mass supplied during chromospheric evaporation is much more effective in moderating coronal temperature excursions than when downward heat flux is dissipated by a static chromosphere, and (2) the method by which the chromosphere responds to changing coronal conditions can significantly influence coronal readjustment time scales. Observations are cited which illustrate the range of possible fluctuations in the heating rates.

A Discrete Velocity Kinetic Model with Food Metric: Chemotaxis Traveling Waves.

PubMed

Choi, Sun-Ho; Kim, Yong-Jung

2017-02-01

We introduce a mesoscopic scale chemotaxis model for traveling wave phenomena which is induced by food metric. The organisms of this simplified kinetic model have two discrete velocity modes, [Formula: see text] and a constant tumbling rate. The main feature of the model is that the speed of organisms is constant [Formula: see text] with respect to the food metric, not the Euclidean metric. The uniqueness and the existence of the traveling wave solution of the model are obtained. Unlike the classical logarithmic model case there exist traveling waves under super-linear consumption rates and infinite population pulse-type traveling waves are obtained. Numerical simulations are also provided.

The Use of DNS in Turbulence Modeling

NASA Technical Reports Server (NTRS)

Mansour, Nagi N.; Merriam, Marshal (Technical Monitor)

1997-01-01

The use of Direct numerical simulations (DNS) data in developing and testing turbulence models is reviewed. The data is used to test turbulence models at all levels: algebraic, one-equation, two-equation and full Reynolds stress models were tested. Particular examples on the development of models for the dissipation rate equation are presented. Homogeneous flows are used to test new scaling arguments for the various terms in the dissipation rate equation. The channel flow data is used to develop modifications to the equation model that take into account near-wall effects. DNS of compressible flows under mean compression are used in testing new compressible modifications to the two-equation models.

Gas-Driven Fracturing of Saturated Granular Media

NASA Astrophysics Data System (ADS)

Campbell, James M.; Ozturk, Deren; Sandnes, Bjørnar

2017-12-01

Multiphase flows in deformable porous materials are important in numerous geological and geotechnical applications; however, the complex flow behavior makes subsurface transport processes difficult to control—or even characterize. Here, we study gas-driven (pneumatic) fracturing of a wet unconsolidated granular packing confined in a Hele-Shaw cell, and we present an in-depth analysis of both pore-scale phenomena and large-scale pattern formation. The process is governed by a complex interplay among pressure, capillary, frictional, and viscous forces. At low gas-injection rates, fractures grow in a stick-slip fashion and branch out to form a simply connected network. We observe the emergence of a characteristic length scale—the separation distance between fracture branches—creating an apparent uniform spatial fracture density. We conclude that the well-defined separation distance is the result of local compaction fronts surrounding fractures and keeping them apart. A scaling argument is presented that predicts fracture density as a function of granular friction, grain size, and capillary interactions. We study the influence of the gas-injection rate and find that the system undergoes a fluidization transition above a critical injection rate, resulting in directional growth of the fractures, and a fracture density that increases with an increasing rate. A dimensionless fluidization number F is defined as the ratio of viscous to frictional forces, and our experiments reveal a frictional regime for F <1 characterized by stick-slip, rate-independent growth, with a transition to a viscous regime (F >1 ) characterized by continuous growth in several fracture branches simultaneously.

Power-law behaviour evaluation from foreign exchange market data using a wavelet transform method

NASA Astrophysics Data System (ADS)

Wei, H. L.; Billings, S. A.

2009-09-01

Numerous studies in the literature have shown that the dynamics of many time series including observations in foreign exchange markets exhibit scaling behaviours. A simple new statistical approach, derived from the concept of the continuous wavelet transform correlation function (WTCF), is proposed for the evaluation of power-law properties from observed data. The new method reveals that foreign exchange rates obey power-laws and thus belong to the class of self-similarity processes.

Basic numerical competences in large-scale assessment data: Structure and long-term relevance.

PubMed

Hirsch, Stefa; Lambert, Katharina; Coppens, Karien; Moeller, Korbinian

2018-03-01

Basic numerical competences are seen as building blocks for later numerical and mathematical achievement. The current study aimed at investigating the structure of early numeracy reflected by different basic numerical competences in kindergarten and its predictive value for mathematical achievement 6 years later using data from large-scale assessment. This allowed analyses based on considerably large sample sizes (N > 1700). A confirmatory factor analysis indicated that a model differentiating five basic numerical competences at the end of kindergarten fitted the data better than a one-factor model of early numeracy representing a comprehensive number sense. In addition, these basic numerical competences were observed to reliably predict performance in a curricular mathematics test in Grade 6 even after controlling for influences of general cognitive ability. Thus, our results indicated a differentiated view on early numeracy considering basic numerical competences in kindergarten reflected in large-scale assessment data. Consideration of different basic numerical competences allows for evaluating their specific predictive value for later mathematical achievement but also mathematical learning difficulties. Copyright © 2017 Elsevier Inc. All rights reserved.

Psychometric Properties of the Pain Numeric Rating Scale When Applied to Multiple Body Regions among Professional Musicians.

PubMed

Saltychev, Mikhail; Vastamäki, Heidi; Mattie, Ryan; McCormick, Zachary; Vastamäki, Martti; Laimi, Katri

2016-01-01

Despite the broad popularity of a numeric rating scale (NRS) its psychometric properties are not well known. The objective was to determine if there is any difference in the discrimination ability of the NRS when used for measuring pain severity separately in different body regions. Cross-sectional survey study of 630 professional musicians. Item Response Theory (IRT) was used to define the psychometric properties of the NRS. The discrimination ability of the pain NRS was dependent on the body area to which it was applied. The discrimination was low 0.5 (95% CI 0.4. to 0.7) for the hand region and perfect for the shoulder and upper part of the neck- 3.2 (95% CI 1.2 to 5.2) and 10.5 (95% CI 10.0 to 10.9), respectively. Both shoulder and neck NRSs showed a great shift towards higher levels of pain severity meaning that the ability of the NRS to discriminate low levels of pain is poor. NRS scores obtained from all other regions did not demonstrate any discrimination ability. The pain NRS might have different psychometric properties depending on the body area to which it is applied. Overall, the modest discrimination ability of the pain NRS implies that it should be used in screening questionnaires with some reservations.

Psychometric Properties of the Pain Numeric Rating Scale When Applied to Multiple Body Regions among Professional Musicians

PubMed Central

2016-01-01

Background Despite the broad popularity of a numeric rating scale (NRS) its psychometric properties are not well known. The objective was to determine if there is any difference in the discrimination ability of the NRS when used for measuring pain severity separately in different body regions. Methods Cross-sectional survey study of 630 professional musicians. Item Response Theory (IRT) was used to define the psychometric properties of the NRS. Results The discrimination ability of the pain NRS was dependent on the body area to which it was applied. The discrimination was low 0.5 (95% CI 0.4. to 0.7) for the hand region and perfect for the shoulder and upper part of the neck– 3.2 (95% CI 1.2 to 5.2) and 10.5 (95% CI 10.0 to 10.9), respectively. Both shoulder and neck NRSs showed a great shift towards higher levels of pain severity meaning that the ability of the NRS to discriminate low levels of pain is poor. NRS scores obtained from all other regions did not demonstrate any discrimination ability. Conclusions The pain NRS might have different psychometric properties depending on the body area to which it is applied. Overall, the modest discrimination ability of the pain NRS implies that it should be used in screening questionnaires with some reservations. PMID:27603011

Reliability and relationship of the fear-avoidance beliefs questionnaire with the shoulder pain and disability index and numeric pain rating scale in patients with shoulder pain.

PubMed

Riley, Sean P; Tafuto, Vincent; Cote, Mark; Brismée, Jean-Michel; Wright, Alexis; Cook, Chad

2018-03-20

The purpose of this study was to determine: 1) the test-retest reliability of Fear-Avoidance Beliefs Questionnaire (FABQ) Work (FABQW) subscale, FABQ Physical Activity (FABQPA) subscale, Shoulder Pain and Disability Index (SPADI) Pain subscale, SPADI Disability subscale, and Numeric Pain Rating scale (NPRS); and 2) the relationship between the FABQPA, FABQW, SPADI pain, SPADI disability, and NPRS after 4 weeks of pragmatically applied physical therapy (PT) in patients with shoulder pain. Prospective, single-group observational design. Data were collected at initial evaluation, the first follow-up visit prior to the initiation of treatment, and after 4 weeks of treatment. Statistically significant Intraclass Correlation Coefficient (ICC 2,1 ) values were reported for the FABQPA, FABQW, SPADI Pain, SPADI Disability, and NPRS. A statistically significant moderate relationship between the FABQPA subscale, SPADI subscale, and NPRS could not be established prior to and after 4 weeks of pragmatically applied PT. Statistically significant differences were observed between the initial evaluation and four-week follow-up for the FABQPA, SPADI Pain, SPADI Disability, and NPRS (p < 0.01). Since a meaningful relationship between the FABQ, SPADI, and NPRS did not exist, it suggests that the FABQPA may be measuring a metric other than pain. This study suggests that the FABQW may not be sensitive to change over time.

Numerical Modeling of Artificial Recharge: Determining Spatial/Temporal Sampling Resolution to Quantify Infiltration Rates and Effective Hydraulic Conductivity

NASA Astrophysics Data System (ADS)

Glose, T. J.; Hausner, M. B.; Lowry, C.

2016-12-01

The accurate, fine scale quantification of groundwater-surface water (GW-SW) interactions over large expanses in hydrologic systems is a fundamental need in order to accurately characterize critical zones of biogeochemical transformation and fluxes, as well as to provide insight into near-surface geologic heterogeneity. Paired fiber-optic distributed temperature sensing (FO-DTS) is a tool that is capable of synoptically sampling hydrologic systems, allowing GW-SW interactions to be examined at a fine scale over large distances. Within managed aquifer recharge (MAR) sites, differential recharge dynamics controlled by bed clogging and subsurface heterogeneity dictate the effectiveness of these sites at infiltrating water. Numerical modeling indicates that the use of paired FO-DTS in an MAR site can provide accurate quantification of flux at the GW-SW interface, as well as provide insight to the areal extent of geologic heterogeneity in the subsurface. However, the lateral and vertical separation of the fiber-optic cables is of vital importance. Here we present a 2-D, fully coupled groundwater flow and heat transport model with prescribed heterogeneity. Following a forward modeling approach, realizations simulating varying fiber-optic cable positioning, differential bed clogging, and hydraulic conductivity variability were analyzed over a suite of scenarios. The results from the model were then used as observations to calculate groundwater recharge rates and calibration targets for an inverse model to estimate subsurface heterogeneity.

Clinical evaluation of the WOMAC 3.0 OA Index in numeric rating scale format using a computerized touch screen version.

PubMed

Theiler, R; Spielberger, J; Bischoff, H A; Bellamy, N; Huber, J; Kroesen, S

2002-06-01

The Western Ontario and McMaster Universities (WOMAC) Osteoarthritis Index is a previously described self-administered questionnaire covering three domains: pain, stiffness and function. It has been validated in patients with osteoarthritis (OA) of the hip or knee in a paper-based format. To validate the WOMAC 3.0 using a numerical rating scale in a computerized touch screen format allowing immediate evaluation of the questionnaire. In the computed version cartoons, written and audio instruments were included in order facilitate application. Fifty patients, demographically balanced, with radiographically proven primary hip or knee OA completed the classical paper and the new computerized WOMAC version. Subjects were randomized either to paper format or computerized format first to balance possible order effects. The intra-class correlation coefficients for pain, stiffness and function values were 0.915, 0.745 and 0.940, respectively. The Spearman correlation coefficients for pain, stiffness and function were 0.88, 0.77 and 0.87, respectively. These data indicate that the computerized WOMAC OA index 3.0 is comparable to the paper WOMAC in all three dimensions. The computerized version would allow physicians to get an immediate result and if present a direct comparison with a previous exam. Copyright 2002 OsteoArthritis Research Society International. Published by Elsevier Science Ltd. All rights reserved.

The cross-cultural adaptation of the DASH questionnaire in Thai (DASH-TH).

PubMed

Tongprasert, Siam; Rapipong, Jeeranan; Buntragulpoontawee, Montana

2014-01-01

Clinical measurement. Currently there are no self-report questionnaires in Thai to evaluate disability levels in patients suffering from upper extremity musculoskeletal disorders. To translate and cross-cultural adaptation the disabilities of the arm, shoulder and hand (DASH) questionnaire to Thai version and to evaluate content validity, construct validity and internal consistency of the questionnaire. The DASH-TH was produced by following cross-cultural adaptation guidelines stated by the Institute for Work and Health (IWH). Forty Thai patients with arm, shoulder or hand problems participated in field testing of the questionnaire. Content validity was determined by obtaining the item-objective congruence (IOC) value for each questionnaire item. Correlation between the DASH-TH score and numeric rating scale was used to assess construct validity. Internal consistency of DASH-TH was measured using Cronbach's alpha coefficient. Forty patients (14 males, 26 females) with arm, shoulder or hand problems enrolled in the present study. The average age of patients was 44.8 years. The index of item-objective congruence (IOC) of each item ranged from 0.7 to 1.0. The Cronbach's alpha coefficient of the questionnaire was 0.938. There was no correlation between DASH-TH score and numeric rating scale. The DASH-TH has high content validity and internal consistency. N/A. Copyright © 2014 Hanley & Belfus. Published by Elsevier Inc. All rights reserved.

Diode Laser Clinical Efficacy and Mini-Invasivity in Surgical Exposure of Impacted Teeth.

PubMed

Migliario, Mario; Rizzi, Manuela; Lucchina, Alberta Greco; Renò, Filippo

2016-11-01

The gold standard to arrange impacted teeth in the dental arch is represented by a surgical approach followed by orthodontic traction force application. In the literature, many surgical approaches are proposed to reach such a scope. The aim of the present study is to demonstrate how laser technique could positively assist surgical approaches.Study population was composed by 16 patients undergoing orthodontic treatment of 20 impacted teeth. In 10 patients (population A) surgical exposure of the impacted teeth was performed using a 980 nm diode laser, while in the other 10 patients (population B), surgical incision was performed using a traditional lancet.Only 3 patients of the population A needed local anesthesia for surgical procedure while the remaining 7 patients reported only faint pain during surgery. Two patients referred postsurgical pain (numerical rating scale average value = 2) and needed to take analgesics. None of the patients showed other postsurgical side effects (bleeding, edema).All population B patients needed infiltrative anesthesia and referred postsurgical pain (numerical rating scale average value >4) treated with analgesics. Moreover, in such population, 4 patients referred lips edema while 4 showed bleeding and 6 needed surgical sutures of soft tissues.The lack of side effects of laser surgical approach to expose impacted teeth must persuade dental practitioners to choose such a clinical approach to closed surgical approach every time it is possible.

A Lagrangian model of Copepod dynamics in turbulent flows

NASA Astrophysics Data System (ADS)

Ardeshiri, Hamidreza; Benkeddad, Ibtissem; Schmitt, Francois G.; Souissi, Sami; Toschi, Federico; Calzavarini, Enrico

2016-04-01

Planktonic copepods are small crustaceans that have the ability to swim by quick powerful jumps. Such an aptness is used to escape from high shear regions, which may be caused either by flow perturbations, produced by a large predator such as fish larave, or by the inherent highly turbulent dynamics of the ocean. Through a combined experimental and numerical study, we investigate the impact of jumping behaviour on the small-scale patchiness of copepods in a turbulent environment. Recorded velocity tracks of copepods displaying escape response jumps in still water are used to define and tune a Lagrangian Copepod (LC) model. The model is further employed to simulate the behaviour of thousands of copepods in a fully developed hydrodynamic turbulent flow obtained by direct numerical simulation of the Navier-Stokes equations. First, we show that the LC velocity statistics is in qualitative agreement with available experimental observations of copepods in turbulence. Second, we quantify the clustering of LC, via the fractal dimension D2. We show that D2 can be as low as 2.3, corresponding to local sheetlike aggregates, and that it critically depends on the shear-rate sensitivity of the proposed LC model. We further investigate the effect of jump intensity, jump orientation and geometrical aspect ratio of the copepods on the small-scale spatial distribution. Possible ecological implications of the observed clustering on encounter rates and mating success are discussed.

Comparing Trigger Point Dry Needling and Manual Pressure Technique for the Management of Myofascial Neck/Shoulder Pain: A Randomized Clinical Trial.

PubMed

De Meulemeester, Kayleigh E; Castelein, Birgit; Coppieters, Iris; Barbe, Tom; Cools, Ann; Cagnie, Barbara

2017-01-01

The aim of this study was to investigate short-term and long-term treatment effects of dry needling (DN) and manual pressure (MP) technique with the primary goal of determining if DN has better effects on disability, pain, and muscle characteristics in treating myofascial neck/shoulder pain in women. In this randomized clinical trial, 42 female office workers with myofascial neck/shoulder pain were randomly allocated to either a DN or MP group and received 4 treatments. They were evaluated with the Neck Disability Index, general numeric rating scale, pressure pain threshold, and muscle characteristics before and after treatment. For each outcome parameter, a linear mixed-model analysis was applied to reveal group-by-time interaction effects or main effects for the factor "time." No significant differences were found between DN and MP. In both groups, significant improvement in the Neck Disability Index was observed after 4 treatments and 3 months (P < .001); the general numerical rating scale also significantly decreased after 3 months. After the 4-week treatment program, there was a significant improvement in pain pressure threshold, muscle elasticity, and stiffness. Both treatment techniques lead to short-term and long-term treatment effects. Dry needling was found to be no more effective than MP in the treatment of myofascial neck/shoulder pain. Copyright © 2016. Published by Elsevier Inc.

Tsunami hazard maps of spanish coast at national scale from seismic sources

NASA Astrophysics Data System (ADS)

Aniel-Quiroga, Íñigo; González, Mauricio; Álvarez-Gómez, José Antonio; García, Pablo

2017-04-01

Tsunamis are a moderately frequent phenomenon in the NEAM (North East Atlantic and Mediterranean) region, and consequently in Spain, as historic and recent events have affected this area. I.e., the 1755 earthquake and tsunami affected the Spanish Atlantic coasts of Huelva and Cadiz and the 2003 Boumerdés earthquake triggered a tsunami that reached Balearic island coast in less than 45 minutes. The risk in Spain is real and, its population and tourism rate makes it vulnerable to this kind of catastrophic events. The Indian Ocean tsunami in 2004 and the tsunami in Japan in 2011 launched the worldwide development and application of tsunami risk reduction measures that have been taken as a priority in this field. On November 20th 2015 the directive of the Spanish civil protection agency on planning under the emergency of tsunami was presented. As part of the Spanish National Security strategy, this document specifies the structure of the action plans at different levels: National, regional and local. In this sense, the first step is the proper evaluation of the tsunami hazard at National scale. This work deals with the assessment of the tsunami hazard in Spain, by means of numerical simulations, focused on the elaboration of tsunami hazard maps at National scale. To get this, following a deterministic approach, the seismic structures whose earthquakes could generate the worst tsunamis affecting the coast of Spain have been compiled and characterized. These worst sources have been propagated numerically along a reconstructed bathymetry, built from the best resolution available data. This high-resolution bathymetry was joined with a 25-m resolution DTM, to generate continuous offshore-onshore space, allowing the calculation of the flooded areas prompted by each selected source. The numerical model applied for the calculation of the tsunami propagations was COMCOT. The maps resulting from the numerical simulations show not only the tsunami amplitude at coastal areas but also the run-up and inundation length from the coastline. The run-up has been calculated with numerical model, complemented with an alternative method, based on interpolation on a tsunami run-up database created ad hoc. These estimated variables allow the identification of the most affected areas in case of tsunami and they are also the base for the local authorities to evaluate the necessity of new higher resolution studies at local scale on specific areas.

What Can Modern River Profiles Tell Us about Orogenic Processes and Orogen Evolution?

NASA Astrophysics Data System (ADS)

Whipple, K. X.

2008-12-01

Numerous lines of evidence from theory, numerical simulations, and physical experiments suggest that orogen evolution is strongly coupled to atmospheric processes through the interrelationships among climate, topography, and erosion rate. In terms of orogenic processes and orogen evolution, these relationships are most important at the regional scale (mean topographic gradient, mean relief above surrounding plains) largely because crustal deformation is most sensitive to erosional unloading averaged over sufficiently long wavelengths. For this reason, and because above moderate erosion rates (> 0.2 mm/yr) hillslope form becomes decoupled from erosion rate, attention has focused on the river network, and even on particularly large rivers. We now have data that demonstrates a monotonic relationship between erosion rate and the channel steepness index (slope normalized for differences in drainage area) in a variety of field settings. Consequently, study of modern river profiles can yield useful information on recent and on-going patterns of rock uplift. It is not yet possible, however, to quantitatively isolate expected climatic and lithologic influences on this relationship. A combination of field studies and theoretical analyses are beginning to reveal the timescale of landscape response, and thus the topographic memory of past conditions. At orogen scale, river profile response to a change in rock uplift rate is on the order of 1-10 Myr. Because of these long response times, the modern profiles of large rivers and their major tributaries can potentially preserve an interpretable record of rock uplift rates since the Miocene and are insensitive to short-term climatic fluctuations. Only significant increases in rock uplift rate, however, are likely to leave a clear topographic signature. Strategies have been developed to differentiate between temporal and spatial (tectonic, climatic, or lithologic) influences on channel profile form, especially where spatially distributed data on recent incision rates is available. A more difficult question is one of cause and effect. Only in some circumstances is it possible to determine whether rivers are steep in response to localized rock uplift or whether localized rock uplift occurs in response to rapidly incising steep rivers.

A model of return intervals between earthquake events

NASA Astrophysics Data System (ADS)

Zhou, Yu; Chechkin, Aleksei; Sokolov, Igor M.; Kantz, Holger

2016-06-01

Application of the diffusion entropy analysis and the standard deviation analysis to the time sequence of the southern California earthquake events from 1976 to 2002 uncovered scaling behavior typical for anomalous diffusion. However, the origin of such behavior is still under debate. Some studies attribute the scaling behavior to the correlations in the return intervals, or waiting times, between aftershocks or mainshocks. To elucidate a nature of the scaling, we applied specific reshulffling techniques to eliminate correlations between different types of events and then examined how it affects the scaling behavior. We demonstrate that the origin of the scaling behavior observed is the interplay between mainshock waiting time distribution and the structure of clusters of aftershocks, but not correlations in waiting times between the mainshocks and aftershocks themselves. Our findings are corroborated by numerical simulations of a simple model showing a very similar behavior. The mainshocks are modeled by a renewal process with a power-law waiting time distribution between events, and aftershocks follow a nonhomogeneous Poisson process with the rate governed by Omori's law.

Citizen Science Data and Scaling

NASA Astrophysics Data System (ADS)

Henderson, S.; Wasser, L. A.

2013-12-01

There is rapid growth in the collection of environmental data by non experts. So called ';citizen scientists' are collecting data on plant phenology, precipitation patterns, bird migration and winter feeding, mating calls of frogs in the spring, and numerous other topics and phenomena related to environmental science. This data is generally submitted to online programs (e.g Project BudBurst, COCORaHS, Project Feederwatch, Frogwatch USA, etc.)and is freely available to scientists, educators, land managers, and decisions makers. While the data is often used to address specific science questions, it also provides the opportunity to explore its utility in the context of ecosystem scaling. Citizen science data is being collected and submitted at an unprecedented rate and is of a spatial and temporal scale previously not possible. The amount of citizen science data vastly exceeds what scientists or land managers can collect on their own. As such, it provides opportunities to address scaling in the environmental sciences. This presentation will explore data from several citizen science programs in the context of scaling.

Combined Experimental and Numerical Investigation of Electric-Arc Airspikes For Blunt Body at Mach 3

NASA Astrophysics Data System (ADS)

Misiewicz, C.; Myrabo, L. N.; Shneider, M. N.; Raizer, Y. P.

2005-04-01

Electric-arc airspike experiments were performed with a 1.25-inch diameter blunt body in the vacuum-driven Mach 3 wind tunnel at Rensselaer Polytechnic Institute. Schlieren movies at 30-Hz frame rate were recorded of the airspike flowfields, revealing substantial evolution over the 6-second run durations. Arc powers up to 2-kW were delivered into the airspike by an arc-welding power supply, using zirconiated tungsten electrodes. Aerodynamic drag was measured with a piezo-electric load cell, revealing reductions up to 70% when the airspike was energized. The test article was a small-scale model of the Mercury lightcraft, a laser-propelled transatmospheric vehicle designed to transport one-person into orbit. Numerical modeling of this airspike is based on the Euler gasdynamic equations for conditions identical to those tested in the RPI supersonic tunnel. Excellent agreement between the shock wave shapes given by first-order asymptotic theory, numerical modeling, and experiment is demonstrated. Results of the numerical modeling confirm both the significant drag reduction potential and the energy efficiency of the airspike concept.

Observation of the development of secondary features in a Richtmyer–Meshkov instability driven flow

DOE PAGES

Bernard, Tennille; Truman, C. Randall; Vorobieff, Peter; ...

2014-09-10

Richtmyer–Meshkov instability (RMI) has long been the subject of interest for analytical, numerical, and experimental studies. In comparing results of experiment with numerics, it is important to understand the limitations of experimental techniques inherent in the chosen method(s) of data acquisition. We discuss results of an experiment where a laminar, gravity-driven column of heavy gas is injected into surrounding light gas and accelerated by a planar shock. A popular and well-studied method of flow visualization (using glycol droplet tracers) does not produce a flow pattern that matches the numerical model of the same conditions, while revealing the primary feature ofmore » the flow developing after shock acceleration: the pair of counter-rotating vortex columns. However, visualization using fluorescent gaseous tracer confirms the presence of features suggested by the numerics; in particular, a central spike formed due to shock focusing in the heavy-gas column. Furthermore, the streamwise growth rate of the spike appears to exhibit the same scaling with Mach number as that of the counter-rotating vortex pair (CRVP).« less

A numerical study on the thermal initiation of a confined explosive in 2-D geometry.

PubMed

Aydemir, Erdoğan; Ulas, Abdullah

2011-02-15

Insensitive munitions design against thermal stimuli like slow or fast cook-off has become a significant requirement for today's munitions. In order to achieve insensitive munitions characteristics, the response of the energetic material needs to be predicted against heating stimuli. In this study, a 2D numerical code was developed to simulate the slow and fast cook-off heating conditions of confined munitions and to obtain the response of the energetic materials. Computations were performed in order to predict the transient temperature distribution, the ignition time, and the location of ignition in the munitions. These predictions enable the designers to have an idea of when and at which location the energetic material ignites under certain adverse surrounding conditions. In the paper, the development of the code is explained and the numerical results are compared with available experimental and numerical data in the literature. Additionally, a parametric study was performed showing the effect of dimensional scaling of munitions and the heating rate on the ignition characteristics. Copyright © 2010 Elsevier B.V. All rights reserved.

Mineral trapping of CO2 in operated geothermal reservoirs - Numerical simulations on various scales

NASA Astrophysics Data System (ADS)

Kühn, Michael; Stanjek, Helge; Peiffer, Stefan; Clauser, Christoph

2013-04-01

A novel approach to store CO2 not only by hydrodynamic trapping within a reservoir, but to convert dissolved CO2 into the geochemically more stable form of calcite in a reaction with calcium obtained from dissolution of sulphates and alkalinity from feldspars or fly ashes is described here. The presentation gives answers to the key questions: • Where are potential geothermal reservoirs with anhydrite abundant? • Does the transfer of anhydrite into calcite work at all and what are the reaction rates? • What are probable alkalinity sources and how fast are they available? Numerical simulation is a means to quantify the entire process of CO2 storage and to deepen the understanding of the detailed chemical processes. We performed numerical simulations on multiple scales. The relevant scales reach from the micro or thin section scale (ca. 1 cm) to the reservoir scale (ca. 10 km). The idea is to provide constraints for smaller scale models from the larger scale and derive functionality from smaller scale models of processes which cannot be resolved in larger scale models, due to restrictions of discretization of the applied numerical mesh. With regard to the 3 questions above we can conclude that the combination of CO2 storage and geothermal energy production is generally feasible because candidate sites are available, anhydrite is transformable into calcite and alkalinity can be provided by fly ashes (Back et al. 2010) or even in-situ (Kühn and Clauser 2006). Based on our laboratory investigations and numerical studies we are able to estimate the storage potential for mineral trapping of CO2 in geothermal reservoirs (Kühn et al. 2009). On the one hand the maximum is unfortunately less than a million tons over the life time of a geothermal heating plant. On the other hand significant storage capacities are available in geological formations with regard to hydrodynamic trapping for millions of tonnes of carbon dioxide. This is why under the current circumstances the combination of geothermal energy production and CO2 storage is not economical. Acknowledgements: The work presented here was part of the CO2Trap project in the research and development program GEOTECHNOLOGIEN funded by the German Ministry of Education and Research (BMBF) and the German Research Foundation (DFG) (grant 03G0614A-C). References Back M., Kühn M., Stanjek H., Peiffer S. (2008) Reactivity of alkaline lignite fly ashes towards CO2 in water. Environmental Science & Technology 42(12), 4520-4526, doi: 10.1021/es702760v. Kühn M., Clauser C. (2006) Mineral trapping of CO2 in geothermal reservoirs. Chemie Ingenieur Technik 78(4), 425-434, doi: 10.1002/cite.200600019 (in German). Kühn M., Clauser C., Vosbeck K., Stanjek H., Meyn V., Back M., Peiffer S. (2009) Mineral trapping of CO2 in operated hydrogeothermal reservoirs. In: Grobe M., Pashin J. C., Dodge R. L. (eds.) Carbon dioxide sequestration in geological media—State of the science: AAPG Studies in Geology 59, p. 545-552.

Numerical Modeling and Experimental Analysis of Scale Horizontal Axis Marine Hydrokinetic (MHK) Turbines

NASA Astrophysics Data System (ADS)

Javaherchi, Teymour; Stelzenmuller, Nick; Seydel, Joseph; Aliseda, Alberto

2013-11-01

We investigate, through a combination of scale model experiments and numerical simulations, the evolution of the flow field around the rotor and in the wake of Marine Hydrokinetic (MHK) turbines. Understanding the dynamics of this flow field is the key to optimizing the energy conversion of single devices and the arrangement of turbines in commercially viable arrays. This work presents a comparison between numerical and experimental results from two different case studies of scaled horizontal axis MHK turbines (45:1 scale). In the first case study, we investigate the effect of Reynolds number (Re = 40,000 to 100,000) and Tip Speed Ratio (TSR = 5 to 12) variation on the performance and wake structure of a single turbine. In the second case, we study the effect of the turbine downstream spacing (5d to 14d) on the performance and wake development in a coaxial configuration of two turbines. These results provide insights into the dynamics of Horizontal Axis Hydrokinetic Turbines, and by extension to Horizontal Axis Wind Turbines in close proximity to each other, and highlight the capabilities and limitations of the numerical models. Once validated at laboratory scale, the numerical model can be used to address other aspects of MHK turbines at full scale. Supported by DOE through the National Northwest Marine Renewable Energy Center.

Management of postoperative pain: experience of the Niamey National Hospital, Niger

PubMed Central

Chaibou, Maman Sani; Sanoussi, Samuila; Sani, Rachid; Toudou, Nouhou A; Daddy, Hadjara; Madougou, Moussa; Abdou, Idrissa; Abarchi, Habibou; Chobli, Martin

2012-01-01

Objective The aim of this study was to evaluate the management of postoperative pain at the Niamey National Hospital. Methods A prospective study was conducted in the Department of Anesthesiology and Intensive Care at the Niamey National Hospital from March to June, 2009. Data collected included age, sex, literacy, American Society of Anesthesiologists (ASA) physical status classification, type of anesthesia, type of surgery, postoperative analgesics used, and the cost of analgesics. Three types of pain assessment scale were used depending on the patient’s ability to describe his or her pain: the verbal rating scale (VRS), the numerical rating scale (NRS), or the visual analog scale (VAS). Patients were evaluated during the first 48 hours following surgery. Results The sample included 553 patients. The VRS was used for the evaluation of 72% of patients, the NRS for 14.4%, and the VAS for 13.6%. Of the VRS group, 33.9%, 8.3%, and 2.1% rated their pain as 3 or 4 out of 4 at 12, 24, and 48 hours postoperatively, respectively. For the NRS group, 33.8%, 8.8%, and 2.5% rated their pain as greater than 7 out of 10 at 12, 24, and 48 hours postoperatively, respectively. For the VAS group, 29.3%, 5.4%, and 0% rated their pain as greater than 7 out of 10 at 12, 24, and 48 hours postoperatively, respectively. Conclusion Postoperative pain assessment and management in developing countries has not been well described. Poverty, illiteracy, and inadequate training of physicians and other health personnel contribute to the underutilization of postoperative analgesia. Analysis of the results gathered at the Niamey National Hospital gives baseline data that can be the impetus to increase training in pain management and to establish standardized protocols. PMID:23271923

Management of postoperative pain: experience of the Niamey National Hospital, Niger.

PubMed

Chaibou, Maman Sani; Sanoussi, Samuila; Sani, Rachid; Toudou, Nouhou A; Daddy, Hadjara; Madougou, Moussa; Abdou, Idrissa; Abarchi, Habibou; Chobli, Martin

2012-01-01

The aim of this study was to evaluate the management of postoperative pain at the Niamey National Hospital. A prospective study was conducted in the Department of Anesthesiology and Intensive Care at the Niamey National Hospital from March to June, 2009. Data collected included age, sex, literacy, American Society of Anesthesiologists (ASA) physical status classification, type of anesthesia, type of surgery, postoperative analgesics used, and the cost of analgesics. Three types of pain assessment scale were used depending on the patient's ability to describe his or her pain: the verbal rating scale (VRS), the numerical rating scale (NRS), or the visual analog scale (VAS). Patients were evaluated during the first 48 hours following surgery. The sample included 553 patients. The VRS was used for the evaluation of 72% of patients, the NRS for 14.4%, and the VAS for 13.6%. Of the VRS group, 33.9%, 8.3%, and 2.1% rated their pain as 3 or 4 out of 4 at 12, 24, and 48 hours postoperatively, respectively. For the NRS group, 33.8%, 8.8%, and 2.5% rated their pain as greater than 7 out of 10 at 12, 24, and 48 hours postoperatively, respectively. For the VAS group, 29.3%, 5.4%, and 0% rated their pain as greater than 7 out of 10 at 12, 24, and 48 hours postoperatively, respectively. Postoperative pain assessment and management in developing countries has not been well described. Poverty, illiteracy, and inadequate training of physicians and other health personnel contribute to the underutilization of postoperative analgesia. Analysis of the results gathered at the Niamey National Hospital gives baseline data that can be the impetus to increase training in pain management and to establish standardized protocols.

Radiative Kähler moduli stabilization

NASA Astrophysics Data System (ADS)

Kobayashi, Tatsuo; Omoto, Naoya; Otsuka, Hajime; Tatsuishi, Takuya H.

2018-05-01

We propose a new type of Kähler moduli stabilization mechanisms in type IIB superstring theory on Calabi-Yau manifolds with the positive Euler number. The overall Kähler modulus can be perturbatively stabilized by radiative corrections due to sparticles. Its minimum is the anti-de Sitter vacuum, where supersymmetry is broken. We can uplift it to the de Sitter vacuum by introducing anti-D-branes, keeping the modulus stabilized. Although our numerical results depend on the choice of the cutoff scale and degeneracies of sparticles, at any rate there exist the parameter spaces where the masses of Kaluza-Klein and stringy modes are larger than the cutoff scale. Furthermore, this stabilization scenario predicts an ultralight axion.

Numerical dissipation vs. subgrid-scale modelling for large eddy simulation

NASA Astrophysics Data System (ADS)

Dairay, Thibault; Lamballais, Eric; Laizet, Sylvain; Vassilicos, John Christos

2017-05-01

This study presents an alternative way to perform large eddy simulation based on a targeted numerical dissipation introduced by the discretization of the viscous term. It is shown that this regularisation technique is equivalent to the use of spectral vanishing viscosity. The flexibility of the method ensures high-order accuracy while controlling the level and spectral features of this purely numerical viscosity. A Pao-like spectral closure based on physical arguments is used to scale this numerical viscosity a priori. It is shown that this way of approaching large eddy simulation is more efficient and accurate than the use of the very popular Smagorinsky model in standard as well as in dynamic version. The main strength of being able to correctly calibrate numerical dissipation is the possibility to regularise the solution at the mesh scale. Thanks to this property, it is shown that the solution can be seen as numerically converged. Conversely, the two versions of the Smagorinsky model are found unable to ensure regularisation while showing a strong sensitivity to numerical errors. The originality of the present approach is that it can be viewed as implicit large eddy simulation, in the sense that the numerical error is the source of artificial dissipation, but also as explicit subgrid-scale modelling, because of the equivalence with spectral viscosity prescribed on a physical basis.

Up-Scaling Geochemical Reaction Rates for Carbon Dioxide (CO2) in Deep Saline Aquifers

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

Peters, Catherine A

2013-02-28

Geochemical reactions in deep subsurface environments are complicated by the consolidated nature and mineralogical complexity of sedimentary rocks. Understanding the kinetics of these reactions is critical to our ability to make long-term predictions about subsurface processes such as pH buffering, alteration in rock structure, permeability changes, and formation of secondary precipitates. In this project, we used a combination of experiments and numerical simulation to bridge the gap between our knowledge of these reactions at the lab scale and rates that are meaningful for modeling reactive transport at core scales. The focus is on acid-driven mineral dissolution, which is specifically relevantmore » in the context of CO2-water-rock interactions in geological sequestration of carbon dioxide. The project led to major findings in three areas. First, we modeled reactive transport in pore-network systems to investigate scaling effects in geochemical reaction rates. We found significant scaling effects when CO2 concentrations are high and reaction rates are fast. These findings indicate that the increased acidity associated with geological sequestration can generate conditions for which proper scaling tools are yet to be developed. Second, we used mathematical modeling to investigate the extent to which SO2, if co-injected with CO2, would acidify formation brines. We found that there exist realistic conditions in which the impact on brine acidity will be limited due to diffusion rate-limited SO2 dissolution from the CO2 phase, and the subsequent pH shift may also be limited by the lack of availability of oxidants to produce sulfuric acid. Third, for three Viking sandstones (Alberta sedimentary basin, Canada), we employed backscattered electron microscopy and energy dispersive X-ray spectroscopy to statistically characterize mineral contact with pore space. We determined that for reactive minerals in sedimentary consolidated rocks, abundance alone is not a good predictor of mineral accessible surface area, and should not be used in reactive transport modeling. Our work showed that reaction rates would be overestimated by three to five times.« less

Field test comparison of two dermal tolerance assessment methods of hand hygiene products.

PubMed

Girard, R; Carré, E; Pires-Cronenberger, S; Bertin-Mandy, M; Favier-Bulit, M C; Coyault, C; Coudrais, S; Billard, M; Regard, A; Kerhoas, A; Valdeyron, M L; Cracco, B; Misslin, P

2008-06-01

This study aimed to compare the sensitivity and workload requirement of two dermal tolerance assessment methods of hand hygiene products, in order to select a suitable pilot testing method for field tests. An observer-rating method and a self-assessment method were compared in 12 voluntary hospital departments (autumn/winter of 2005-2006). Three test-periods of three weeks were separated by two-week intervals during which the routine products were reintroduced. The observer rating method scored dryness and irritation on four-point scales. In the self-assessment method, the user rated appearance, intactness, moisture content, and sensation on a visual analogue scale which was converted into a 10-point numerical scale. Eleven products (soaps) were tested (223/250 complete reports for observer rating, 131/251 for self-assessment). Two products were significantly less well tolerated than the routine product according to the observers, four products according to the self-assessments. There was no significant difference between the two methods when products were classified according to tolerance (Fisher's test: P=0.491). For the symptom common to both assessment methods (dryness), there is a good correlation between the two methods (Spearman's Rho: P=0.032). The workload was higher for observer rating method (288 h of observer time plus 122 h of prevention team and pharmacist time compared with 15 h of prevention team and pharmacist time for self-assessment). In conclusion, the self-assessment method was considered more suitable for pilot testing, although further time should be allocated for educational measures as the return rate of complete self-assessment forms was poor.

Instability and turbulent mixing of shocked `V' shaped interface

NASA Astrophysics Data System (ADS)

Li, Long; Sun, Yutao

Based on the mass fraction model of multicomponent mixture, the interaction between weak shock wave and `V' shaped air/ interface with different vertex angles are numerical simulated using high resolution finite volume method with minimized dispersion and controllable dissipation (MDCD) scheme. It is observed that the baroclinic vorticity is deposited near the interface due to the misalignment of the density and pressure gradient, leading to the formation of vortical structures along the interface. The predicted leftmost interface displacement and interface width growth rate in the early stage of interface evolution agree well with experimental results. The numerical results indicate that with the evolution of the interfacial vortical structures, the array of vortices begins to merge. As the result, the vortices accumulate at several distinct regions. It is in these regions, the multi-scale structures are generated because of the interaction between vortices. It is observed that due to the different scaling with Reynolds number of upper bound and lower bound, an uncoupled inertial range appears, and the mixing transition occurs with the appearance of an inertial range of scales. The classical Kolmogorov -5/3 power laws are shown in the energy fluctuation spectrum, which means the inertial range is just beginning to form and the flow field near the material interface will develop to turbulence.

Particle Clogging in Filter Media of Embankment Dams: A Numerical and Experimental Study

NASA Astrophysics Data System (ADS)

Antoun, T.; Kanarska, Y.; Ezzedine, S. M.; Lomov, I.; Glascoe, L. G.; Smith, J.; Hall, R. L.; Woodson, S. C.

2013-12-01

The safety of dam structures requires the characterization of the granular filter ability to capture fine-soil particles and prevent erosion failure in the event of an interfacial dislocation. Granular filters are one of the most important protective design elements of large embankment dams. In case of cracking and erosion, if the filter is capable of retaining the eroded fine particles, then the crack will seal and the dam safety will be ensured. Here we develop and apply a numerical tool to thoroughly investigate the migration of fines in granular filters at the grain scale. The numerical code solves the incompressible Navier-Stokes equations and uses a Lagrange multiplier technique which enforces the correct in-domain computational boundary conditions inside and on the boundary of the particles. The numerical code is validated to experiments conducted at the US Army Corps of Engineering and Research Development Center (ERDC). These laboratory experiments on soil transport and trapping in granular media are performed in constant-head flow chamber filled with the filter media. Numerical solutions are compared to experimentally measured flow rates, pressure changes and base particle distributions in the filter layer and show good qualitative and quantitative agreement. To further the understanding of the soil transport in granular filters, we investigated the sensitivity of the particle clogging mechanism to various parameters such as particle size ratio, the magnitude of hydraulic gradient, particle concentration, and grain-to-grain contact properties. We found that for intermediate particle size ratios, the high flow rates and low friction lead to deeper intrusion (or erosion) depths. We also found that the damage tends to be shallower and less severe with decreasing flow rate, increasing friction and concentration of suspended particles. This work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344 and was sponsored by the Department of Homeland Security (DHS), Science and Technology Directorate, Homeland Security Advanced Research Projects Agency (HSARPA).

Numerical Simulation of The Mediterranean Sea Using Diecast: Interaction Between Basin, Sub-basin and Local Scale Features and Natural Variability.

NASA Astrophysics Data System (ADS)

Fernández, V.; Dietrich, D. E.; Haney, R. L.; Tintoré, J.

In situ and satellite data obtained during the last ten years have shown that the circula- tion in the Mediterranean Sea is extremely complex in space, with significant features ranging from mesoscale to sub-basin and basin scale, and highly variable in time, with mesoscale to seasonal and interannual signals. Also, the steep bottom topography and the variable atmospheric conditions from one sub-basin to another, make the circula- tion to be composed of numerous energetic and narrow coastal currents, density fronts and mesoscale structures that interact at sub-basin scale with the large scale circula- tion. To simulate numerically and better understand these features, besides high grid resolution, a low numerical dispersion and low physical dissipation ocean model is required. We present the results from a 1/8z horizontal resolution numerical simula- tion of the Mediterranean Sea using DieCAST ocean model, which meets the above requirements since it is stable with low general dissipation and uses accurate fourth- order-accurate approximations with low numerical dispersion. The simulations are carried out with climatological surface forcing using monthly mean winds and relax- ation towards climatological values of temperature and salinity. The model reproduces the main features of the large basin scale circulation, as well as the seasonal variabil- ity of sub-basin scale currents that are well documented by observations in straits and channels. In addition, DieCAST brings out natural fronts and eddies that usually do not appear in numerical simulations of the Mediterranean and that lead to a natural interannual variability. The role of this intrinsic variability in the general circulation will be discussed.

Recent Advances in our Understanding of Debris-covered Glacier Response to Climate

NASA Astrophysics Data System (ADS)

Pellicciotti, F.

2016-12-01

Debris-covered glaciers are relevant in many mountainous regions, but both modelling and observational studies are less numerous compared to those on traditional "clean" glaciers. A number of conjectures about their behaviour and response to climate have been made. First, it is assumed that in a warming climate debris cover would increase because of slope instability and increased meltout of englacial debris. Second, large-scale remote sensing studies have suggested that their thinning rates are comparable to those of debris-free glaciers, in spite of the insulating effect of a debris mantle. This apparent anomaly has been explained conceptually through high rates of energy absorption at supraglacial cliffs and ponds, but no evidence for this argument exists at the glacier scale. We validate each of these assumptions based on numerical modelling, analysis of satellite data and field observations from High Mountain Asia and the well monitored Langtang catchment in the Himalaya, in particular. First, no change in debris-covered area is apparent for regions of stable or positive mass balance such as the Karakoram, in line with the reasoning that sustained negative mass balance triggers an increase in debris. Second, results from an ensemble of DEM differences for the Langtang glaciers show that thinning rates of the debris-covered glaciers are not equivalent to those of the debris-free glaciers, contradicting results from the large-scale studies. However, thinning rates are higher than would be expected for a debris-covered surface, and can be explained through physically-based models of cliffs and lakes. These dynamic features form on low-gradient glacier sections between stagnant and dynamic zones, evolve in time and can survive or disappear depending on their characteristics. Ablation from cliffs and lakes is very high and can account between 10 to 30% of mass losses from the glaciers, despite covering a small percentage of the glacier area. Among the mechanisms controlling their persistence and relationship to climate, a key finding is that coupling of cliffs and ponds is a prerequisite for their long term survival. Our study provides a significant step towards a better understanding of the response of debris-covered glaciers to climate change, and highlights avenues of future research.

The flow of a dust particle by highly collisional drifting plasma

NASA Astrophysics Data System (ADS)

Grach, Veronika; Semenov, Vladimir; Trakhtengerts, Victor

We present the study of the flow of a dust particle by a weakly ionized highly collisional drifting plasma. The charging of a conductive sphere and wake formation downstream and upstream of it is analyzed in the case of a strong external field l0 = E0 /(4πen0 ) λD a (E0 is the magnitude of the external field, n0 is plasma density, λD is Debye length and a is a radius of the sphere). Under such conditions, the effects of the space charge field and ionization-recombination processes play crucial role. The sphere charge and the spatial distributions of plasma ions and electrons are calculated nu-merically; analytical expressions are obtained for some limiting cases. We obtain that the size of the wake is determined by the external field and the recombination rate. At low recombination rates (α/(4πµ+,- ) 1, where α is the recombination coefficient, µ+,- are mobilities of positive and negative plasma particles) the longitudinal scale of wake is about 20l0 , at high recombina-tion rates the longitudinal scale is about l0 . The transverse scale of the wake is determined by the ratio of the mobilities and can reach several dust particle radii. It was also shown that the absolute value of the dust particle charge decreases with increasing recombination rate. The total electric charge (the sphere charge plus the plasma space charge) is shown to be zero in accordance with predictions of the theory of static currents in a conducting medium. On the basis of the obtained spatial distributions of charged plasma particles, the electrostatic potential around the sphere is calculated numerically. The interaction potential between two systems "particle+wake" is analyzed for arbitrary locations of such systems. We obtain that the potential can be attractive at moderate and large distances, if the particles are not aligned in the direction perpendicular to the external electric field. The results can be important in understanding intergrain interactions in weakly ionized highly collisional anisotropic dusty plasmas.

An Analytical Model for Basin-scale Glacier Erosion as a Function of Climate and Topography

NASA Astrophysics Data System (ADS)

Jaffrey, M.; Hallet, B.

2017-12-01

Knowledge about glacier erosion has advanced considerably over the last few decades with the emergence of a firm mechanistic understanding of abrasion and quarrying, the growing sophistication of complex numerical models of glacial erosion and the evolution of glacial landforms, and the increase in data from field studies of erosion rates. Interest in glacial erosion has also intensified and diversified substantially as it is increasingly recognized as a key process affecting the heights of mountains, the overall evolution of mountain belts, and the coupling of climate, erosion, and tectonics. Yet, the general controls of glacier erosion rates have not been addressed theoretically, and the large range of published basin-scale erosion rates, covering more than 3 orders of magnitude, remains poorly understood. To help gain insight into glacier erosion rates at the scale of glacier basins, the only scale for which extensive data exist, we develop analytically a simple budget of the total mechanical energy per unit time, the power, dissipated by a steady state glacier in sliding, S, and viscous deformation, V. We hypothesize that the power for the work of erosion derives solely from S and that the basin wide erosion rate scales with S averaged over the basin. We solve the power budget directly in terms of climatic and topographic parameters, showing explicitly that the source of power to drive both S and V is the gravitational power supplied by the net snow accumulation (mass balance). The budget leads to the simple metric φ=mbΔz2 for the basin average of S with Δz being the glacier basin relief and mb the gradient of the mass balance with elevation. The dependence of φ on the square of the relief arises from both the mass balance's and potential energy's linear increases with elevation. We validate φ using results from a comprehensive field study of erosion rates paired with glaciological data along a transect extending from Southern Patagonia to the Antarctic Peninsula (Koppes et al. 2015. Nature, 526(7571), 100). Along this transect, φ accounts for 75% ± 12% of the variation in reported erosion rates. The power budget model illuminates the role of climate and topography in basin scale erosion rates with direct implications for the broad community interested in ice masses and their interconnections with climate and topography.

Microbiological-enhanced mixing across scales during in-situ bioreduction of metals and radionuclides at Department of Energy Sites

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

Valocchi, Albert; Werth, Charles; Liu, Wen-Tso

Bioreduction is being actively investigated as an effective strategy for subsurface remediation and long-term management of DOE sites contaminated by metals and radionuclides (i.e. U(VI)). These strategies require manipulation of the subsurface, usually through injection of chemicals (e.g., electron donor) which mix at varying scales with the contaminant to stimulate metal reducing bacteria. There is evidence from DOE field experiments suggesting that mixing limitations of substrates at all scales may affect biological growth and activity for U(VI) reduction. Although current conceptual models hold that biomass growth and reduction activity is limited by physical mixing processes, a growing body of literaturemore » suggests that reaction could be enhanced by cell-to-cell interaction occurring over length scales extending tens to thousands of microns. Our project investigated two potential mechanisms of enhanced electron transfer. The first is the formation of single- or multiple-species biofilms that transport electrons via direct electrical connection such as conductive pili (i.e. ‘nanowires’) through biofilms to where the electron acceptor is available. The second is through diffusion of electron carriers from syntrophic bacteria to dissimilatory metal reducing bacteria (DMRB). The specific objectives of this work are (i) to quantify the extent and rate that electrons are transported between microorganisms in physical mixing zones between an electron donor and electron acceptor (e.g. U(IV)), (ii) to quantify the extent that biomass growth and reaction are enhanced by interspecies electron transport, and (iii) to integrate mixing across scales (e.g., microscopic scale of electron transfer and macroscopic scale of diffusion) in an integrated numerical model to quantify these mechanisms on overall U(VI) reduction rates. We tested these hypotheses with five tasks that integrate microbiological experiments, unique micro-fluidics experiments, flow cell experiments, and multi-scale numerical models. Continuous fed-batch reactors were used to derive kinetic parameters for DMRB, and to develop an enrichment culture for elucidation of syntrophic relationships in a complex microbial community. Pore and continuum scale experiments using microfluidic and bench top flow cells were used to evaluate the impact of cell-to-cell and microbial interactions on reaction enhancement in mixing-limited bioactive zones, and the mechanisms of this interaction. Some of the microfluidic experiments were used to develop and test models that considers direct cell-to-cell interactions during metal reduction. Pore scale models were incorporated into a multi-scale hybrid modeling framework that combines pore scale modeling at the reaction interface with continuum scale modeling. New computational frameworks for combining continuum and pore-scale models were also developed« less

Direct Numerical Simulations of Multiphase Flows

NASA Astrophysics Data System (ADS)

Tryggvason, Gretar

2013-03-01

Many natural and industrial processes, such as rain and gas exchange between the atmosphere and oceans, boiling heat transfer, atomization and chemical reactions in bubble columns, involve multiphase flows. Often the mixture can be described as a disperse flow where one phase consists of bubbles or drops. Direct numerical simulations (DNS) of disperse flow have recently been used to study the dynamics of multiphase flows with a large number of bubbles and drops, often showing that the collective motion results in relatively simple large-scale structure. Here we review simulations of bubbly flows in vertical channels where the flow direction, as well as the bubble deformability, has profound implications on the flow structure and the total flow rate. Results obtained so far are summarized and open questions identified. The resolution for DNS of multiphase flows is usually determined by a dominant scale, such as the average bubble or drop size, but in many cases much smaller scales are also present. These scales often consist of thin films, threads, or tiny drops appearing during coalescence or breakup, or are due to the presence of additional physical processes that operate on a very different time scale than the fluid flow. The presence of these small-scale features demand excessive resolution for conventional numerical approaches. However, at small flow scales the effects of surface tension are generally strong so the interface geometry is simple and viscous forces dominate the flow and keep it simple also. These are exactly the conditions under which analytical models can be used and we will discuss efforts to combine a semi-analytical description for the small-scale processes with a fully resolved simulation of the rest of the flow. We will, in particular, present an embedded analytical description to capture the mass transfer from bubbles in liquids where the diffusion of mass is much slower than the diffusion of momentum. This results in very thin mass-boundary layers that are difficult to resolve, but the new approach allows us to simulate the mass transfer from many freely evolving bubbles and examine the effect of the interactions of the bubbles with each other and the flow. We will conclude by attempting to summarize the current status of DNS of multiphase flows. Support by NSF and DOE (CASL)

Decadal-scale rates of reef erosion following El Niño-related mass coral mortality.

PubMed

Roff, George; Zhao, Jian-Xin; Mumby, Peter J

2015-12-01

As the frequency and intensity of coral mortality events increase under climate change, understanding how declines in coral cover may affect the bioerosion of reef frameworks is of increasing importance. Here, we explore decadal-scale rates of bioerosion of the framework building coral Orbicella annularis by grazing parrotfish following the 1997/1998 El Niño-related mass mortality event at Long Cay, Belize. Using high-precision U-Th dating and CT scan analysis, we quantified in situ rates of external bioerosion over a 13-year period (1998-2011). Based upon the error-weighted average U-Th age of dead O. annularis skeletons, we estimate the average external bioerosion between 1998 and 2011 as 0.92 ± 0.55 cm depth. Empirical observations of herbivore foraging, and a nonlinear numerical response of parrotfish to an increase in food availability, were used to create a model of external bioerosion at Long Cay. Model estimates of external bioerosion were in close agreement with U-Th estimates (0.85 ± 0.09 cm). The model was then used to quantify how rates of external bioerosion changed across a gradient of coral mortality (i.e., from few corals experiencing mortality following coral bleaching to complete mortality). Our results indicate that external bioerosion is remarkably robust to declines in coral cover, with no significant relationship predicted between the rate of external bioerosion and the proportion of O. annularis that died in the 1998 bleaching event. The outcome was robust because the reduction in grazing intensity that follows coral mortality was compensated for by a positive numerical response of parrotfish to an increase in food availability. Our model estimates further indicate that for an O. annularis-dominated reef to maintain a positive state of reef accretion, a necessity for sustained ecosystem function, live cover of O. annularis must not drop below a ~5-10% threshold of cover. © 2015 John Wiley & Sons Ltd.

Comparison of entrainment rates from a tank experiment with results using the one-dimensional turbulence model.

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

Kerstein, Alan R.; Sayler, B. J.; Wunsch, S.

2010-05-01

Recent work suggests that cloud effects remain one of the largest sources of uncertainty in model-based estimates of climate sensitivity. In particular, the entrainment rate in stratocumulus-topped mixed layers needs better models. More than thirty years ago a clever laboratory experiment was conducted by McEwan and Paltridge to examine an analog of the entrainment process at the top of stratiform clouds. Sayler and Breidenthal extended this pioneering work and determined the effect of the Richardson number on the dimensionless entrainment rate. The experiments gave hints that the interaction between molecular effects and the one-sided turbulence seems to be crucial formore » understanding entrainment. From the numerical point of view large-eddy simulation (LES) does not allow explicitly resolving all the fine scale processes at the entrainment interface. Direct numerical simulation (DNS) is limited due to the Reynolds number and is not the tool of choice for parameter studies. Therefore it is useful to investigate new modeling strategies, such as stochastic turbulence models which allow sufficient resolution at least in one dimension while having acceptable run times. We will present results of the One-Dimensional Turbulence stochastic simulation model applied to the experimental setup of Sayler and Breidenthal. The results on radiatively induced entrainment follow quite well the scaling of the entrainment rate with the Richardson number that was experimentally found for a set of trials. Moreover, we investigate the influence of molecular effects, the fluids optical properties, and the artifact of parasitic turbulence experimentally observed in the laminar layer. In the simulations the parameters are varied systematically for even larger ranges than in the experiment. Based on the obtained results a more complex parameterization of the entrainment rate than currently discussed in the literature seems to be necessary.« less

Non-equilibrium relaxation in a stochastic lattice Lotka-Volterra model

NASA Astrophysics Data System (ADS)

Chen, Sheng; Täuber, Uwe C.

2016-04-01

We employ Monte Carlo simulations to study a stochastic Lotka-Volterra model on a two-dimensional square lattice with periodic boundary conditions. If the (local) prey carrying capacity is finite, there exists an extinction threshold for the predator population that separates a stable active two-species coexistence phase from an inactive state wherein only prey survive. Holding all other rates fixed, we investigate the non-equilibrium relaxation of the predator density in the vicinity of the critical predation rate. As expected, we observe critical slowing-down, i.e., a power law dependence of the relaxation time on the predation rate, and algebraic decay of the predator density at the extinction critical point. The numerically determined critical exponents are in accord with the established values of the directed percolation universality class. Following a sudden predation rate change to its critical value, one finds critical aging for the predator density autocorrelation function that is also governed by universal scaling exponents. This aging scaling signature of the active-to-absorbing state phase transition emerges at significantly earlier times than the stationary critical power laws, and could thus serve as an advanced indicator of the (predator) population’s proximity to its extinction threshold.

Self-reported pain intensity with the numeric reporting scale in adult dengue.

PubMed

Wong, Joshua G X; Gan, Victor C; Ng, Ee-Ling; Leo, Yee-Sin; Chan, Siew-Pang; Choo, Robin; Lye, David C

2014-01-01

Pain is a prominent feature of acute dengue as well as a clinical criterion in World Health Organization guidelines in diagnosing dengue. We conducted a prospective cohort study to compare levels of pain during acute dengue between different ethnicities and dengue severity. Demographic, clinical and laboratory data were collected. Data on self-reported pain was collected using the 11-point Numerical Rating Scale. Generalized structural equation models were built to predict progression to severe disease. A total of 499 laboratory confirmed dengue patients were recruited in the Prospective Adult Dengue Study at Tan Tock Seng Hospital, Singapore. We found no statistically significant differences between pain score with age, gender, ethnicity or the presence of co-morbidity. Pain score was not predictive of dengue severity but highly correlated to patients' day of illness. Prevalence of abdominal pain in our cohort was 19%. There was no difference in abdominal pain score between grades of dengue severity. Dengue is a painful disease. Patients suffer more pain at the earlier phase of illness. However, pain score cannot be used to predict a patient's progression to severe disease.

Towards Forming a Primordial Protostar in a Cosmological AMR Simulation

NASA Astrophysics Data System (ADS)

Turk, Matthew J.; Abel, Tom; O'Shea, Brian W.

2008-03-01

Modeling the formation of the first stars in the universe is a well-posed problem and ideally suited for computational investigation.We have conducted high-resolution numerical studies of the formation of primordial stars. Beginning with primordial initial conditions appropriate for a ΛCDM model, we used the Eulerian adaptive mesh refinement code (Enzo) to achieve unprecedented numerical resolution, resolving cosmological scales as well as sub-stellar scales simultaneously. Building on the work of Abel, Bryan and Norman (2002), we followed the evolution of the first collapsing cloud until molecular hydrogen is optically thick to cooling radiation. In addition, the calculations account for the process of collision-induced emission (CIE) and add approximations to the optical depth in both molecular hydrogen roto-vibrational cooling and CIE. Also considered are the effects of chemical heating/cooling from the formation/destruction of molecular hydrogen. We present the results of these simulations, showing the formation of a 10 Jupiter-mass protostellar core bounded by a strongly aspherical accretion shock. Accretion rates are found to be as high as one solar mass per year.

solveME: fast and reliable solution of nonlinear ME models.

PubMed

Yang, Laurence; Ma, Ding; Ebrahim, Ali; Lloyd, Colton J; Saunders, Michael A; Palsson, Bernhard O

2016-09-22

Genome-scale models of metabolism and macromolecular expression (ME) significantly expand the scope and predictive capabilities of constraint-based modeling. ME models present considerable computational challenges: they are much (>30 times) larger than corresponding metabolic reconstructions (M models), are multiscale, and growth maximization is a nonlinear programming (NLP) problem, mainly due to macromolecule dilution constraints. Here, we address these computational challenges. We develop a fast and numerically reliable solution method for growth maximization in ME models using a quad-precision NLP solver (Quad MINOS). Our method was up to 45 % faster than binary search for six significant digits in growth rate. We also develop a fast, quad-precision flux variability analysis that is accelerated (up to 60× speedup) via solver warm-starts. Finally, we employ the tools developed to investigate growth-coupled succinate overproduction, accounting for proteome constraints. Just as genome-scale metabolic reconstructions have become an invaluable tool for computational and systems biologists, we anticipate that these fast and numerically reliable ME solution methods will accelerate the wide-spread adoption of ME models for researchers in these fields.

Large scale Direct Numerical Simulation of premixed turbulent jet flames at high Reynolds number

NASA Astrophysics Data System (ADS)

Attili, Antonio; Luca, Stefano; Lo Schiavo, Ermanno; Bisetti, Fabrizio; Creta, Francesco

2016-11-01

A set of direct numerical simulations of turbulent premixed jet flames at different Reynolds and Karlovitz numbers is presented. The simulations feature finite rate chemistry with 16 species and 73 reactions and up to 22 Billion grid points. The jet consists of a methane/air mixture with equivalence ratio ϕ = 0 . 7 and temperature varying between 500 and 800 K. The temperature and species concentrations in the coflow correspond to the equilibrium state of the burnt mixture. All the simulations are performed at 4 atm. The flame length, normalized by the jet width, decreases significantly as the Reynolds number increases. This is consistent with an increase of the turbulent flame speed due to the increased integral scale of turbulence. This behavior is typical of flames in the thin-reaction zone regime, which are affected by turbulent transport in the preheat layer. Fractal dimension and topology of the flame surface, statistics of temperature gradients, and flame structure are investigated and the dependence of these quantities on the Reynolds number is assessed.

Mixing of a passive scalar in isotropic and sheared homogeneous turbulence

NASA Technical Reports Server (NTRS)

Shirani, E.; Ferziger, J. H.; Reynolds, W. C.

1981-01-01

In order to calculate the velocity and scalar fields, the three dimensional, time-dependent equations of motion and the diffusion equation were solved numerically. The following cases were treated: isotropic, homogeneous turbulence with decay of a passive scalar; and homogeneous turbulent shear flow with a passive scalar whose mean varies linearly in the spanwise direction. The solutions were obtained at relatively low Reynolds numbers so that all of the turbulent scales could be resolved without modeling. Turbulent statistics such as integral length scales, Taylor microscales, Kolmogorov length scale, one- and two-point correlations of velocity-velocity and velocity-scalar, turbulent Prandtl/Schmidt number, r.m.s. values of velocities, the scalar quantity and pressure, skewness, decay rates, and decay exponents were calculated. The results are compared with the available expermental results, and good agreement is obtained.

Generalized activity equations for spiking neural network dynamics.

PubMed

Buice, Michael A; Chow, Carson C

2013-01-01

Much progress has been made in uncovering the computational capabilities of spiking neural networks. However, spiking neurons will always be more expensive to simulate compared to rate neurons because of the inherent disparity in time scales-the spike duration time is much shorter than the inter-spike time, which is much shorter than any learning time scale. In numerical analysis, this is a classic stiff problem. Spiking neurons are also much more difficult to study analytically. One possible approach to making spiking networks more tractable is to augment mean field activity models with some information about spiking correlations. For example, such a generalized activity model could carry information about spiking rates and correlations between spikes self-consistently. Here, we will show how this can be accomplished by constructing a complete formal probabilistic description of the network and then expanding around a small parameter such as the inverse of the number of neurons in the network. The mean field theory of the system gives a rate-like description. The first order terms in the perturbation expansion keep track of covariances.

Renormalization group theory outperforms other approaches in statistical comparison between upscaling techniques for porous media

NASA Astrophysics Data System (ADS)

Hanasoge, Shravan; Agarwal, Umang; Tandon, Kunj; Koelman, J. M. Vianney A.

2017-09-01

Determining the pressure differential required to achieve a desired flow rate in a porous medium requires solving Darcy's law, a Laplace-like equation, with a spatially varying tensor permeability. In various scenarios, the permeability coefficient is sampled at high spatial resolution, which makes solving Darcy's equation numerically prohibitively expensive. As a consequence, much effort has gone into creating upscaled or low-resolution effective models of the coefficient while ensuring that the estimated flow rate is well reproduced, bringing to the fore the classic tradeoff between computational cost and numerical accuracy. Here we perform a statistical study to characterize the relative success of upscaling methods on a large sample of permeability coefficients that are above the percolation threshold. We introduce a technique based on mode-elimination renormalization group theory (MG) to build coarse-scale permeability coefficients. Comparing the results with coefficients upscaled using other methods, we find that MG is consistently more accurate, particularly due to its ability to address the tensorial nature of the coefficients. MG places a low computational demand, in the manner in which we have implemented it, and accurate flow-rate estimates are obtained when using MG-upscaled permeabilities that approach or are beyond the percolation threshold.

Bounded energy states in homogeneous turbulent shear flow: An alternative view

NASA Technical Reports Server (NTRS)

Bernard, Peter S.; Speziale, Charles G.

1990-01-01

The equilibrium structure of homogeneous turbulent shear flow is investigated from a theoretical standpoint. Existing turbulence models, in apparent agreement with physical and numerical experiments, predict an unbounded exponential time growth of the turbulent kinetic energy and dissipation rate; only the anisotropy tensor and turbulent time scale reach a structural equilibrium. It is shown that if vortex stretching is accounted for in the dissipation rate transport equation, then there can exist equilibrium solutions, with bounded energy states, where the turbulence production is balanced by its dissipation. Illustrative calculations are present for a k-epsilon model modified to account for vortex stretching. The calculations indicate an initial exponential time growth of the turbulent kinetic energy and dissipation rate for elapsed times that are as large as those considered in any of the previously conducted physical or numerical experiments on homogeneous shear flow. However, vortex stretching eventually takes over and forces a production-equals-dissipation equilibrium with bounded energy states. The validity of this result is further supported by an independent theoretical argument. It is concluded that the generally accepted structural equilibrium for homogeneous shear flow with unbounded component energies is in need of re-examination.

Simulation of substrate degradation in composting of sewage sludge

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

Zhang Jun; Gao Ding, E-mail: gaod@igsnrr.ac.c; Chen Tongbin

2010-10-15

To simulate the substrate degradation kinetics of the composting process, this paper develops a mathematical model with a first-order reaction assumption and heat/mass balance equations. A pilot-scale composting test with a mixture of sewage sludge and wheat straw was conducted in an insulated reactor. The BVS (biodegradable volatile solids) degradation process, matrix mass, MC (moisture content), DM (dry matter) and VS (volatile solid) were simulated numerically by the model and experimental data. The numerical simulation offered a method for simulating k (the first-order rate constant) and estimating k{sub 20} (the first-order rate constant at 20 {sup o}C). After comparison withmore » experimental values, the relative error of the simulation value of the mass of the compost at maturity was 0.22%, MC 2.9%, DM 4.9% and VS 5.2%, which mean that the simulation is a good fit. The k of sewage sludge was simulated, and k{sub 20}, k{sub 20s} (first-order rate coefficient of slow fraction of BVS at 20 {sup o}C) of the sewage sludge were estimated as 0.082 and 0.015 d{sup -1}, respectively.« less

Numerical investigation of the influence of electromagnetic treatment on calcium carbonate scaling rate in non-isothermal pipe flow

NASA Astrophysics Data System (ADS)

Kireev, Victor; Kovaleva, Liana; Isakov, Andrey; Alimbekova, Sofya

2017-11-01

In the present paper, an attempt to explain the mechanisms of the electromagnetic field influence on the process of formation and deposition of calcium carbonate from supersaturated brine solution has been made using numerical modeling. The one-dimensional mathematical model of the brine laminar flow through a cylindrical tube with non-uniform temperature field is written in the form of the system of transient convection-diffusion-reaction partial differential equations describing temperature field and chemical components concentrations (Ca2+, HCO3-, CaCO3). The influence of the temperature on the kinetics of formation of calcium carbonate is taken into account and it is described in accordance with the Arrhenius equation. The kinetics of the calcium carbonate precipitation on the wall of the pipe is given on the basis of the Henry isotherm. It has been established that the electromagnetic treatment of brine solution leads to a decrease of the adsorption rate constant and Henry's constant but it does not significantly influence on the chemical reaction rate of calcium carbonate formation. It also has been shown that treatment with electromagnetic field significantly reduces the amount of calcium carbonate deposits on the wall of the pipe.

Effect of surface roughness on the heating rates of large-angled hypersonic blunt cones

NASA Astrophysics Data System (ADS)

Irimpan, Kiran Joy; Menezes, Viren

2018-03-01

Surface-roughness caused by the residue of an ablative Thermal Protection System (TPS) can alter the turbulence level and surface heating rates on a hypersonic re-entry capsule. Large-scale surface-roughness that could represent an ablated TPS, was introduced over the forebody of a 120° apex angle blunt cone, in order to test for its influence on surface heating rates in a hypersonic freestream of Mach 8.8. The surface heat transfer rates measured on smooth and roughened models under the same freestream conditions were compared. The hypersonic flow-fields of the smooth and rough-surfaced models were visualized to analyse the flow physics. Qualitative numerical simulations and pressure measurements were carried out to have an insight into the high-speed flow physics. Experimental observations under moderate Reynolds numbers indicated a delayed transition and an overall reduction of 17-46% in surface heating rates on the roughened model.

Quantitative X-ray - UV Line and Continuum Spectroscopy with Application to AGN: State-Specific Hydrogenic Recombination Cooling Coefficients for a Wide Range of Conditions

NASA Technical Reports Server (NTRS)

LaMothe, J.; Ferland, Gary J.

2002-01-01

Recombination cooling, in which a free electron emits light while being captured to an ion, is an important cooling process in photoionized clouds that are optically thick or have low metallicity. State specific rather than total recombination cooling rates are needed since the hydrogen atom tends to become optically thick in high-density regimes such as Active Galactic Nuclei. This paper builds upon previous work to derive the cooling rate over the full temperature range where the process can be a significant contributor in a photoionized plasma. We exploit the fact that the recombination and cooling rates are given by intrinsically similar formulae to express the cooling rate in terms of the closely related radiative recombination rate. We give an especially simple but accurate approximation that works for any high hydrogenic level and can be conveniently employed in large-scale numerical simulations.

The Analysis, Numerical Simulation, and Diagnosis of Extratropical Weather Systems

DTIC Science & Technology

1999-09-30

The Analysis, Numerical Simulation, and Diagnosis of Extratropical Weather Systems Dr. Melvyn A. Shapiro NOAA/Environmental Technology Laboratory...formulation, and numerical prediction of the life cycles of synoptic-scale and mesoscale extratropical weather systems, including the influence of planetary...scale inter-annual and intra-seasonal variability on their evolution. These weather systems include: extratropical oceanic and land-falling cyclones

Parallel Simulation of Unsteady Turbulent Flames

NASA Technical Reports Server (NTRS)

Menon, Suresh

1996-01-01

Time-accurate simulation of turbulent flames in high Reynolds number flows is a challenging task since both fluid dynamics and combustion must be modeled accurately. To numerically simulate this phenomenon, very large computer resources (both time and memory) are required. Although current vector supercomputers are capable of providing adequate resources for simulations of this nature, the high cost and their limited availability, makes practical use of such machines less than satisfactory. At the same time, the explicit time integration algorithms used in unsteady flow simulations often possess a very high degree of parallelism, making them very amenable to efficient implementation on large-scale parallel computers. Under these circumstances, distributed memory parallel computers offer an excellent near-term solution for greatly increased computational speed and memory, at a cost that may render the unsteady simulations of the type discussed above more feasible and affordable.This paper discusses the study of unsteady turbulent flames using a simulation algorithm that is capable of retaining high parallel efficiency on distributed memory parallel architectures. Numerical studies are carried out using large-eddy simulation (LES). In LES, the scales larger than the grid are computed using a time- and space-accurate scheme, while the unresolved small scales are modeled using eddy viscosity based subgrid models. This is acceptable for the moment/energy closure since the small scales primarily provide a dissipative mechanism for the energy transferred from the large scales. However, for combustion to occur, the species must first undergo mixing at the small scales and then come into molecular contact. Therefore, global models cannot be used. Recently, a new model for turbulent combustion was developed, in which the combustion is modeled, within the subgrid (small-scales) using a methodology that simulates the mixing and the molecular transport and the chemical kinetics within each LES grid cell. Finite-rate kinetics can be included without any closure and this approach actually provides a means to predict the turbulent rates and the turbulent flame speed. The subgrid combustion model requires resolution of the local time scales associated with small-scale mixing, molecular diffusion and chemical kinetics and, therefore, within each grid cell, a significant amount of computations must be carried out before the large-scale (LES resolved) effects are incorporated. Therefore, this approach is uniquely suited for parallel processing and has been implemented on various systems such as: Intel Paragon, IBM SP-2, Cray T3D and SGI Power Challenge (PC) using the system independent Message Passing Interface (MPI) compiler. In this paper, timing data on these machines is reported along with some characteristic results.

Numerical simulation of systems of shear bands in ductile metal with inclusions

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

Plohr, JeeYeon N., E-mail: jplohr@lanl.gov; Plohr, Bradley J.

2016-02-15

We develop a method for numerical simulations of high strain-rate loading of mesoscale samples of ductile metal with inclusions. Because of its small-scale inhomogeneity, the composite material is prone to localized shear deformation (adiabatic shear bands). This method employs the Generalized Method of Cells of Paley and Aboudi [Mech. Materials, vol. 14, pp. 127–139, 1992] to ensure that the micro mechanical behavior of the metal and inclusions is reflected properly in the behavior of the composite at the mesoscale. To find the effective plastic strain rate when shear bands are present, we extend and apply the analytic and numerical analysismore » of shear bands of Glimm, Plohr, and Sharp [Mech. Materials, vol. 24, pp. 31–41, 1996]. Our tests of the method focus on the stress/strain response in uniaxial-strain flow, both compressive and tensile, of depleted uranium metal containing silicon carbide inclusions. We use the Preston-Tonks-Wallace viscoplasticity model [J. Appl. Phys., vol. 93, pp. 211–220, 2003], which applies to the high strain-rate regime of an isotropic viscoplastic solid. In results, we verify the elevated temperature and thermal softening at shear bands in our simulations of pure DU and DU/SiC composites. We also note that in composites, due the asymmetry caused by the inclusions, shear band form at different times in different subcells. In particular, in the subcells near inclusions, shear band form much earlier than they do in pure DU.« less

Numerical simulation of systems of shear bands in ductile metal with inclusions

NASA Astrophysics Data System (ADS)

Plohr, JeeYeon N.; Plohr, Bradley J.

2016-02-01

We develop a method for numerical simulations of high strain-rate loading of mesoscale samples of ductile metal with inclusions. Because of its small-scale inhomogeneity, the composite material is prone to localized shear deformation (adiabatic shear bands). This method employs the Generalized Method of Cells of Paley and Aboudi [Mech. Materials, vol. 14, pp. 127-139, 1992] to ensure that the micro mechanical behavior of the metal and inclusions is reflected properly in the behavior of the composite at the mesoscale. To find the effective plastic strain rate when shear bands are present, we extend and apply the analytic and numerical analysis of shear bands of Glimm, Plohr, and Sharp [Mech. Materials, vol. 24, pp. 31-41, 1996]. Our tests of the method focus on the stress/strain response in uniaxial-strain flow, both compressive and tensile, of depleted uranium metal containing silicon carbide inclusions. We use the Preston-Tonks-Wallace viscoplasticity model [J. Appl. Phys., vol. 93, pp. 211-220, 2003], which applies to the high strain-rate regime of an isotropic viscoplastic solid. In results, we verify the elevated temperature and thermal softening at shear bands in our simulations of pure DU and DU/SiC composites. We also note that in composites, due the asymmetry caused by the inclusions, shear band form at different times in different subcells. In particular, in the subcells near inclusions, shear band form much earlier than they do in pure DU.

Numerical Issues Associated with Compensating and Competing Processes in Climate Models: an Example from ECHAM-HAM

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

Wan, Hui; Rasch, Philip J.; Zhang, Kai

2013-06-26

The purpose of this paper is to draw attention to the need for appropriate numerical techniques to represent process interactions in climate models. In two versions of the ECHAM-HAM model, different time integration methods are used to solve the sulfuric acid (H2SO4) gas evolution equation, which lead to substantially different results in the H2SO4 gas concentration and the aerosol nucleation rate. Using convergence tests and sensitivity simulations performed with various time stepping schemes, it is confirmed that numerical errors in the second model version are significantly smaller than those in version one. The use of sequential operator splitting in combinationmore » with long time step is identified as the main reason for the large systematic biases in the old model. The remaining errors in version two in the nucleation rate, related to the competition between condensation and nucleation, have a clear impact on the simulated concentration of cloud condensation nuclei in the lower troposphere. These errors can be significantly reduced by employing an implicit solver that handles production, condensation and nucleation at the same time. Lessons learned in this work underline the need for more caution when treating multi-time-scale problems involving compensating and competing processes, a common occurrence in current climate models.« less

Tetrahedral-Mesh Simulation of Turbulent Flows with the Space-Time Conservative Schemes

NASA Technical Reports Server (NTRS)

Chang, Chau-Lyan; Venkatachari, Balaji; Cheng, Gary C.

2015-01-01

Direct numerical simulations of turbulent flows are predominantly carried out using structured, hexahedral meshes despite decades of development in unstructured mesh methods. Tetrahedral meshes offer ease of mesh generation around complex geometries and the potential of an orientation free grid that would provide un-biased small-scale dissipation and more accurate intermediate scale solutions. However, due to the lack of consistent multi-dimensional numerical formulations in conventional schemes for triangular and tetrahedral meshes at the cell interfaces, numerical issues exist when flow discontinuities or stagnation regions are present. The space-time conservative conservation element solution element (CESE) method - due to its Riemann-solver-free shock capturing capabilities, non-dissipative baseline schemes, and flux conservation in time as well as space - has the potential to more accurately simulate turbulent flows using unstructured tetrahedral meshes. To pave the way towards accurate simulation of shock/turbulent boundary-layer interaction, a series of wave and shock interaction benchmark problems that increase in complexity, are computed in this paper with triangular/tetrahedral meshes. Preliminary computations for the normal shock/turbulence interactions are carried out with a relatively coarse mesh, by direct numerical simulations standards, in order to assess other effects such as boundary conditions and the necessity of a buffer domain. The results indicate that qualitative agreement with previous studies can be obtained for flows where, strong shocks co-exist along with unsteady waves that display a broad range of scales, with a relatively compact computational domain and less stringent requirements for grid clustering near the shock. With the space-time conservation properties, stable solutions without any spurious wave reflections can be obtained without a need for buffer domains near the outflow/farfield boundaries. Computational results for the isotropic turbulent flow decay, at a relatively high turbulent Mach number, show a nicely behaved spectral decay rate for medium to high wave numbers. The high-order CESE schemes offer very robust solutions even with the presence of strong shocks or widespread shocklets. The explicit formulation in conjunction with a close to unity theoretical upper Courant number bound has the potential to offer an efficient numerical framework for general compressible turbulent flow simulations with unstructured meshes.

Ultra-Long Time Dynamics of Contaminant Plume Mixing Induced by Transient Forcing Factors in Geologic Formations

NASA Astrophysics Data System (ADS)

Rajabi, F.; Battiato, I.

2016-12-01

Long term predictions of the impact of anthropogenic stressors on the environment is essential to reduce the risks associated with processes such as CO2 sequestration and nuclear waste storage in the subsurface. On the other hand, transient forcing factors (e.g. time-varying injection or pumping rate) with evolving heterogeneity of time scales spanning from days to years can influence transport phenomena at the pore scale. A comprehensive spatio-temporal prediction of reactive transport in porous media under time-dependent forcing factors for thousands of years requires the formulation of continuum scale models for time-averages. Yet, as every macroscopic model, time-averaged models can loose predictivity and accuracy when certain conditions are violated. This is true whenever lack of temporal and spatial scale separation occurs and it makes the continuum scale equation a poor assumption for the processes at the pore scale. In this work, we consider mass transport of a dissolved species undergoing a heterogeneous reaction and subject to time-varying boundary conditions in a periodic porous medium. By means of homogenization method and asymptotic expansion technique, we derive a macro-time continuum-scale equation as well as expressions for its effective properties. Our analysis demonstrates that the dynamics at the macro-scale is strongly influenced by the interplay between signal frequency at the boundary and transport processes at the pore level. In addition, we provide the conditions under which the space-time averaged equations accurately describe pore-scale processes. To validate our theoretical predictions, we consider a thin fracture with reacting walls and transient boundary conditions at the inlet. Our analysis shows a good agreement between numerical simulations and theoretical predictions. Furthermore, our numerical experiments show that mixing patterns of the contaminant plumes at the pore level strongly depend on the signal frequency.

Strategies for efficient numerical implementation of hybrid multi-scale agent-based models to describe biological systems

PubMed Central

Cilfone, Nicholas A.; Kirschner, Denise E.; Linderman, Jennifer J.

2015-01-01

Biologically related processes operate across multiple spatiotemporal scales. For computational modeling methodologies to mimic this biological complexity, individual scale models must be linked in ways that allow for dynamic exchange of information across scales. A powerful methodology is to combine a discrete modeling approach, agent-based models (ABMs), with continuum models to form hybrid models. Hybrid multi-scale ABMs have been used to simulate emergent responses of biological systems. Here, we review two aspects of hybrid multi-scale ABMs: linking individual scale models and efficiently solving the resulting model. We discuss the computational choices associated with aspects of linking individual scale models while simultaneously maintaining model tractability. We demonstrate implementations of existing numerical methods in the context of hybrid multi-scale ABMs. Using an example model describing Mycobacterium tuberculosis infection, we show relative computational speeds of various combinations of numerical methods. Efficient linking and solution of hybrid multi-scale ABMs is key to model portability, modularity, and their use in understanding biological phenomena at a systems level. PMID:26366228

The clinical importance of changes in the 0 to 10 numeric rating scale for worst, least, and average pain intensity: analyses of data from clinical trials of duloxetine in pain disorders.

PubMed

Farrar, John T; Pritchett, Yili L; Robinson, Michael; Prakash, Apurva; Chappell, Amy

2010-02-01

Data on 1,700 patients pooled from 5 randomized, placebo-controlled duloxetine studies (3 in diabetic peripheral neuropathic pain and 2 in fibromyalgia) were analyzed to determine clinically important differences (CIDs) in the 0 to 10 Numeric Rating Scale-Pain Intensity (NRS-PI) for patient-reported "worst" and "least" pain intensity while validating the previously published level for "average" pain. The correspondence between the baseline-to-endpoint raw and percentage change in the NRS-PI for the worst, least, and average pain were compared to patients' perceived improvements at endpoint as measured by the 7-point Patient Global Impression of Improvement (PGI-I) scales. Stratification by baseline pain separated the raw but not the percent change scores. The PGI-I category of "much better" or above was our a priori definition of a CID. Cutoff points for the NRS-PI change scores were determined using a receiver operator curve analysis. A consistent relationship between the worst and average NRS-PI percent change and the PGI-I was demonstrated regardless of the study, pain type, age, sex, or treatment group with a reduction of approximately 34%. The least pain item CID was slightly higher at 41%. Raw change CID cutoff points were approximately -2, -2.5 and -3 for least, average, and worst pain respectively. We determined an anchor-based value for the change in the worst, least, and average pain intensity items of the Brief Pain Inventory that best represents a clinically important difference. Our findings support a standard definition of a clinically important difference in clinical trials of chronic-pain therapies. Copyright 2010 American Pain Society. Published by Elsevier Inc. All rights reserved.

Progress towards Continental River Dynamics modeling

NASA Astrophysics Data System (ADS)

Yu, Cheng-Wei; Zheng, Xing; Liu, Frank; Maidment, Daivd; Hodges, Ben

2017-04-01

The high-resolution National Water Model (NWM), launched by U.S. National Oceanic and Atmospheric Administration (NOAA) in August 2016, has shown it is possible to provide real-time flow prediction in rivers and streams across the entire continental United States. The next step for continental-scale modeling is moving from reduced physics (e.g. Muskingum-Cunge) to full dynamic modeling with the Saint-Venant equations. The Simulation Program for River Networks (SPRNT) provides a computational approach for the Saint-Venant equations, but obtaining sufficient channel bathymetric data and hydraulic roughness is seen as a critical challenge. However, recent work has shown the Height Above Nearest Drainage (HAND) method can be applied with the National Elevation Dataset (NED) to provide automated estimation of effective channel bathymetry suitable for large-scale hydraulic simulations. The present work examines the use of SPRNT with the National Hydrography Dataset (NHD) and HAND-derived bathymetry for automated generation of rating curves that can be compared to existing data. The approach can, in theory, be applied to every stream reach in the NHD and thus provide flood guidance where none is available. To test this idea we generated 2000+ rating curves in two catchments in Texas and Alabama (USA). Field data from the USGS and flood records from an Austin, Texas flood in May 2015 were used as validation. Large-scale implementation of this idea requires addressing several critical difficulties associated with numerical instabilities, including ill-posed boundary conditions generated in automated model linkages and inconsistencies in the river geometry. A key to future progress is identifying efficient approaches to isolate numerical instability contributors in a large time-space varying solution. This research was supported in part by the National Science Foundation under grant number CCF-1331610.

Hierarchical calibration and validation framework of bench-scale computational fluid dynamics simulations for solvent-based carbon capture. Part 2: Chemical absorption across a wetted wall column: Original Research Article: Hierarchical calibration and validation framework of bench-scale computational fluid dynamics simulations

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

Wang, Chao; Xu, Zhijie; Lai, Kevin

The first part of this paper (Part 1) presents a numerical model for non-reactive physical mass transfer across a wetted wall column (WWC). In Part 2, we improved the existing computational fluid dynamics (CFD) model to simulate chemical absorption occurring in a WWC as a bench-scale study of solvent-based carbon dioxide (CO2) capture. To generate data for WWC model validation, CO2 mass transfer across a monoethanolamine (MEA) solvent was first measured on a WWC experimental apparatus. The numerical model developed in this work has the ability to account for both chemical absorption and desorption of CO2 in MEA. In addition,more » the overall mass transfer coefficient predicted using traditional/empirical correlations is conducted and compared with CFD prediction results for both steady and wavy falling films. A Bayesian statistical calibration algorithm is adopted to calibrate the reaction rate constants in chemical absorption/desorption of CO2 across a falling film of MEA. The posterior distributions of the two transport properties, i.e., Henry’s constant and gas diffusivity in the non-reacting nitrous oxide (N2O)/MEA system obtained from Part 1 of this study, serves as priors for the calibration of CO2 reaction rate constants after using the N2O/CO2 analogy method. The calibrated model can be used to predict the CO2 mass transfer in a WWC for a wider range of operating conditions.« less

Hierarchical calibration and validation framework of bench-scale computational fluid dynamics simulations for solvent-based carbon capture. Part 2: Chemical absorption across a wetted wall column: Original Research Article: Hierarchical calibration and validation framework of bench-scale computational fluid dynamics simulations

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

Wang, Chao; Xu, Zhijie; Lai, Kevin

Part 1 of this paper presents a numerical model for non-reactive physical mass transfer across a wetted wall column (WWC). In Part 2, we improved the existing computational fluid dynamics (CFD) model to simulate chemical absorption occurring in a WWC as a bench-scale study of solvent-based carbon dioxide (CO 2) capture. In this study, to generate data for WWC model validation, CO 2 mass transfer across a monoethanolamine (MEA) solvent was first measured on a WWC experimental apparatus. The numerical model developed in this work can account for both chemical absorption and desorption of CO 2 in MEA. In addition,more » the overall mass transfer coefficient predicted using traditional/empirical correlations is conducted and compared with CFD prediction results for both steady and wavy falling films. A Bayesian statistical calibration algorithm is adopted to calibrate the reaction rate constants in chemical absorption/desorption of CO 2 across a falling film of MEA. The posterior distributions of the two transport properties, i.e., Henry's constant and gas diffusivity in the non-reacting nitrous oxide (N 2O)/MEA system obtained from Part 1 of this study, serves as priors for the calibration of CO 2 reaction rate constants after using the N 2O/CO 2 analogy method. Finally, the calibrated model can be used to predict the CO 2 mass transfer in a WWC for a wider range of operating conditions.« less

Effects of herbal medicine for dysmenorrhea treatment on accompanied acne vulgaris: a study protocol for a randomized controlled trial.

PubMed

Kim, Kwan-Il; Nam, Hae Jeong; Kim, Mia; Lee, Junhee; Kim, Kyuseok

2017-06-17

The incidence of preadolescent acne among women is increasing. Acne deteriorates the quality of life; conventional treatment options are limited and have not been effective against acne, particularly acne associated with menstruation. Despite evidence that acne associated with menstruation abnormalities naturally improves when menstruation recovers to normal, there have only been few studies on the effects of dysmenorrhea treatment on acne. Therefore- we designed this study to assess the effects of gyejibokryung-hwan (GBH) and dangguijagyag-san (DJS), which are widely used in dysmenorrhea treatment, on acne associated with menstruation cycle. This is a protocol for a randomized, double-blind, parallel-group, placebo-controlled and multicenter trial. One hundred and sixteen participants with dysmenorrhea accompanied by acne vulgaris will be recruited at three centers and randomized into two groups, the herbal treatment group and placebo group. The participants will receive GBH or DJS based on pattern identification or placebo granules thrice daily for 8 weeks, with an 8-week follow up. The primary outcome will be the mean percentage change in the count of inflammatory acne lesions. The secondary outcomes would be based on dysmenorrhea numeric rating scale, verbal multidimensional scoring system for dysmenorrhea, acne numeric rating scale, investigator's static global assessment scale of facial acne vulgaris, and safety testing. Adverse events will also be reported. The effects of GBH or DJS used in dysmenorrhea treatment on acne associated with the menstrual cycle will be evaluated. The findings of this trial will provide evidence regarding the effect of herbal medicine in improving acne vulgaris associated with menstruation in women. Korean Clinical Trial Registry ( http://cris.nih.go.kr ; registration number: KCT0002259). Date of registration: March 10, 2017.

Identification of a constitutive law for trabecular bone samples under remodeling in the framework of irreversible thermodynamics

NASA Astrophysics Data System (ADS)

Louna, Zineeddine; Goda, Ibrahim; Ganghoffer, Jean-François

2018-01-01

We construct in the present paper constitutive models for bone remodeling based on micromechanical analyses at the scale of a representative unit cell (RUC) including a porous trabecular microstructure. The time evolution of the microstructure is simulated as a surface remodeling process by relating the surface growth remodeling velocity to a surface driving force incorporating a (surface) Eshelby tensor. Adopting the framework of irreversible thermodynamics, a 2D constitutive model based on the setting up of the free energy density and a dissipation potential is identified from FE simulations performed over a unit cell representative of the trabecular architecture obtained from real bone microstructures. The static and evolutive effective properties of bone at the scale of the RUC are obtained by combining a methodology for the evaluation of the average kinematic and static variables over a prototype unit cell and numerical simulations with controlled imposed first gradient rates. The formulated effective growth constitutive law at the scale of the homogenized set of trabeculae within the RUC is of viscoplastic type and relates the average growth strain rate to the homogenized stress tensor. The postulated model includes a power law function of an effective stress chosen to depend on the first and second stress invariants. The model coefficients are calibrated from a set of virtual testing performed over the RUC subjected to a sequence of loadings. Numerical simulations show that overall bone growth does not show any growth kinematic hardening. The obtained results quantify the strength and importance of different types of external loads (uniaxial tension, simple shear, and biaxial loading) on the overall remodeling process and the development of elastic deformations within the RUC.

Hierarchical calibration and validation framework of bench-scale computational fluid dynamics simulations for solvent-based carbon capture. Part 2: Chemical absorption across a wetted wall column: Original Research Article: Hierarchical calibration and validation framework of bench-scale computational fluid dynamics simulations

DOE PAGES

Wang, Chao; Xu, Zhijie; Lai, Kevin; ...

2017-10-24

Part 1 of this paper presents a numerical model for non-reactive physical mass transfer across a wetted wall column (WWC). In Part 2, we improved the existing computational fluid dynamics (CFD) model to simulate chemical absorption occurring in a WWC as a bench-scale study of solvent-based carbon dioxide (CO 2) capture. In this study, to generate data for WWC model validation, CO 2 mass transfer across a monoethanolamine (MEA) solvent was first measured on a WWC experimental apparatus. The numerical model developed in this work can account for both chemical absorption and desorption of CO 2 in MEA. In addition,more » the overall mass transfer coefficient predicted using traditional/empirical correlations is conducted and compared with CFD prediction results for both steady and wavy falling films. A Bayesian statistical calibration algorithm is adopted to calibrate the reaction rate constants in chemical absorption/desorption of CO 2 across a falling film of MEA. The posterior distributions of the two transport properties, i.e., Henry's constant and gas diffusivity in the non-reacting nitrous oxide (N 2O)/MEA system obtained from Part 1 of this study, serves as priors for the calibration of CO 2 reaction rate constants after using the N 2O/CO 2 analogy method. Finally, the calibrated model can be used to predict the CO 2 mass transfer in a WWC for a wider range of operating conditions.« less

Apparent Dependence of Rate- and State-Dependent Friction Parameters on Loading Velocity and Cumulative Displacement Inferred from Large-Scale Biaxial Friction Experiments

NASA Astrophysics Data System (ADS)

Urata, Yumi; Yamashita, Futoshi; Fukuyama, Eiichi; Noda, Hiroyuki; Mizoguchi, Kazuo

2017-06-01

We investigated the constitutive parameters in the rate- and state-dependent friction (RSF) law by conducting numerical simulations, using the friction data from large-scale biaxial rock friction experiments for Indian metagabbro. The sliding surface area was 1.5 m long and 0.5 m wide, slid for 400 s under a normal stress of 1.33 MPa at a loading velocity of either 0.1 or 1.0 mm/s. During the experiments, many stick-slips were observed and those features were as follows. (1) The friction drop and recurrence time of the stick-slip events increased with cumulative slip displacement in an experiment before which the gouges on the surface were removed, but they became almost constant throughout an experiment conducted after several experiments without gouge removal. (2) The friction drop was larger and the recurrence time was shorter in the experiments with faster loading velocity. We applied a one-degree-of-freedom spring-slider model with mass to estimate the RSF parameters by fitting the stick-slip intervals and slip-weakening curves measured based on spring force and acceleration of the specimens. We developed an efficient algorithm for the numerical time integration, and we conducted forward modeling for evolution parameters ( b) and the state-evolution distances (L_{{c}}), keeping the direct effect parameter ( a) constant. We then identified the confident range of b and L_{{c}} values. Comparison between the results of the experiments and our simulations suggests that both b and L_{{c}} increase as the cumulative slip displacement increases, and b increases and L_{{c}} decreases as the loading velocity increases. Conventional RSF laws could not explain the large-scale friction data, and more complex state evolution laws are needed.

The evolution of a binary in a retrograde circular orbit embedded in an accretion disk

NASA Astrophysics Data System (ADS)

Ivanov, P. B.; Papaloizou, J. C. B.; Paardekooper, S.-J.; Polnarev, A. G.

2015-04-01

Aims: Supermassive black hole binaries may form as a consequence of galaxy mergers. Both prograde and retrograde orbits have been proposed. We study a binary with a small mass ratio, q, in a retrograde orbit immersed in and interacting with a gaseous accretion disk in order to estimate the time scales for inward migration that leads to coalescence and the accretion rate to the secondary component. Methods: We employed both semi-analytic methods and two-dimensional numerical simulations, focusing on the case where the binary mass ratio is small but large enough to significantly perturb the disk. Results: We develop the theory of type I migration in this case and go on to determine the conditions for gap formation. We find that when this happens inward migration occurs on a time scale equal to the time required for one half of the secondary mass to be accreted through the unperturbed accretion disk. The accretion rate onto the secondary itself is found to only play a minor role in the orbital evolution as it is of the order of q1/3 of that to the primary. We obtain good general agreement between the semi-analytic and fully numerical approaches and note that the former can be applied to disks with a wide dynamic range on long time scales. Conclusions: We conclude that inward migration induced by interaction with the disk can enable the binary to migrate inwards, alleviating the so-called final parsec problem. When q is sufficiently small, there is no well-pronounced cavity inside the binary orbit, unlike the prograde case. The accretion rate to the secondary does not influence the binary orbital evolution much, but can lead to some interesting observational consequences, provided the accretion efficiency is sufficiently large. In this case the binary may be detected as, for example, two sources of radiation rotating around each other. However, the study should be extended to consider orbits with significant eccentricity and the effects of gravitational radiation at small length scales. Also, torques acting between a circumbinary accretion disk, which has a non-zero inclination with respect to a retrograde binary orbit at large distances, may cause the inclination to increase on a time scale that can be similar to, or smaller than, the time scale of orbital evolution, depending on the disk parameters and binary mass ratio. This is also an aspect for future study. The movies are available in electronic form at http://www.aanda.org

Numerical models for fluid-grains interactions: opportunities and limitations

NASA Astrophysics Data System (ADS)

Esteghamatian, Amir; Rahmani, Mona; Wachs, Anthony

2017-06-01

In the framework of a multi-scale approach, we develop numerical models for suspension flows. At the micro scale level, we perform particle-resolved numerical simulations using a Distributed Lagrange Multiplier/Fictitious Domain approach. At the meso scale level, we use a two-way Euler/Lagrange approach with a Gaussian filtering kernel to model fluid-solid momentum transfer. At both the micro and meso scale levels, particles are individually tracked in a Lagrangian way and all inter-particle collisions are computed by a Discrete Element/Soft-sphere method. The previous numerical models have been extended to handle particles of arbitrary shape (non-spherical, angular and even non-convex) as well as to treat heat and mass transfer. All simulation tools are fully-MPI parallel with standard domain decomposition and run on supercomputers with a satisfactory scalability on up to a few thousands of cores. The main asset of multi scale analysis is the ability to extend our comprehension of the dynamics of suspension flows based on the knowledge acquired from the high-fidelity micro scale simulations and to use that knowledge to improve the meso scale model. We illustrate how we can benefit from this strategy for a fluidized bed, where we introduce a stochastic drag force model derived from micro-scale simulations to recover the proper level of particle fluctuations. Conversely, we discuss the limitations of such modelling tools such as their limited ability to capture lubrication forces and boundary layers in highly inertial flows. We suggest ways to overcome these limitations in order to enhance further the capabilities of the numerical models.

A fundamental discussion of what triggers localized deformation in geological materials

NASA Astrophysics Data System (ADS)

Peters, Max; Paesold, Martin; Poulet, Thomas; Herwegh, Marco; Regenauer-Lieb, Klaus; Veveakis, Manolis

2015-04-01

Discontinuous or localized structures are often marked by the transition from a homogeneously deforming into a highly localized mode. This transition has extensively been described in ductile shear zones, folding and pinch-and-swell boudinage, in natural examples, rock deformation experiments and numerical simulations, at various scales. It is conventionally assumed that ductile instabilities, which act as triggers for localized deformation, exclusively arise from structural heterogeneities, i.e. geometric interactions or material imperfections. However, Hansen et al. (2012) concluded from recent laboratory experiments that localized deformation might arise out of steady-state conditions, where the size of initial perturbations was either insufficiently large to trigger localization, or these heterogeneities were simply negligible at the scale of observation. We therefore propose the existence of a principal localization phenomenon, which is based on the material-specific rate-dependency of deformation at elevated temperatures. The concept of strain localization out of a mechanical steady state in a homogeneous material at a critical material parameter and/or deformation rate has previously been discussed for engineering materials (Gruntfest, 1963) and frictional faults (Veveakis et al., 2010). We expand this theory to visco-plastic carbonate rocks, considering deformation conditions and mechanisms encountered in naturally deformed rocks. In the numerical simulation, we implement a grain-size evolution based on the Paleowattmeter scaling relationship of Austin & Evans (2007), which takes both grain size sensitive (diffusion) and insensitive (dislocation) creep combined with grain growth into account (Herwegh et al., 2014). Based on constant strain rate simulations carried out under isothermal boundary conditions, we explore the parameter space in order to obtain the criteria for localization. We determine the criteria for the onset of localization, i.e. the critical amount of dissipative work translated into heat over the diffusive capacity of the system by an instability study designed for such materials (Gruntfest, 1963). With respect to our numerical experiments, this critical parameter determines the timing when the entire amount of deformation energy translated into heat cannot be diffusively transported out of the system anymore. The resulting local temperature rise then induces strain localization. In contrast to classical shear heating scenarios with (catastrophic) thermal runaways, temperature variations of less than 1 K are sufficient for this localization mode to occur due to the balance between heat producing (e.g. dislocation creep) and consuming (grain growth) processes in the present setup. We demonstrate that this rise in latent heat is sufficient to provoke grain growth, operating as an endothermic reaction, stabilizing the simulated localized structure in turn. Various localized ductile structures, such as folded or boudinaged layers, can therefore be placed at the same material failure mode due to fundamental energy bifurcations triggered by dissipative work out of homogeneous state. Finally, we will discuss situations, in which structural heterogeneities are considered negligible and where the energy theory described here plays an underlying role by means of a comparison between numerical experiments and natural examples. REFERENCES Austin, N. and Evans, B. (2007). Paleowattmeters: A scaling relation for dynamically recrystallized grain size. Geology, 35. Gruntfest, I.J. (1963). Thermal feedback in liquid flow, plane shear at constant stress. Transactions of the Society of Rheology, 7. Hansen, L.N. and Zimmermann, M.E. and Dillman, A.M. and Kohlstedt, D.L (2012). Strain localization in olivine aggregates at high temperature: a laboratory comparison of constant-strain-rate and constant-stress boundary conditions. Earth and Planetary Science Letters, 333-334. Herwegh, M., Poulet, T., Karrech, A. and Regenauer-Lieb, K. (2014). From transient to steady state deformation and grain size: A thermodynamic approach using elasto-visco-plastic numerical modeling. Journal of Geophysical Research, 119. Veveakis, E., Alevizos, S. and Vardoulakis, I. (2010). Chemical reaction capping of thermal instability during shear of frictional faults. Journal of Mechanics and Physics of Solids, 58.

Measurement Properties of the Brazilian-Portuguese Version of the Lumbar Spine Instability Questionnaire.

PubMed

Araujo, Amanda Costa; da Cunha Menezes Costa, Lucíola; de Oliveira, Crystian Bittencourt Soares; Morelhão, Priscila Kalil; de Faria Negrão Filho, Rúben; Pinto, Rafael Zambelli; Costa, Leonardo Oliveira Pena

2017-07-01

Cross-cultural adaptation and analysis of measurement properties. To translate and cross-culturally adapt the Lumbar Spine Instability Questionnaire (LSIQ) into Brazilian-Portuguese and to test its measurement properties in Brazilian patients with low back pain. The selection of subgroup of patients that respond better to specific interventions is the top research priority in the field of back pain. The LSIQ is a tool able to stratify patients with low back pain who responds better to motor control exercises. There is no Brazilian-Portuguese version of the LSIQ available. The original version of the LSIQ was translated and cross-culturally adapted. We collected data from 100 patients with low back pain. In addition to LSIQ, we also collected information about physical activity levels (measured by the International Physical Activity Questionnaire short version), disability (measured by the Roland Morris Disability Questionnaire), pain intensity (measured by the Pain numerical Rating Scale), kinesiophobia (measured by the Tampa Scale of Kinesiophobia), and depression (measured by the Beck Depression Inventory). The measurement properties tested were internal consistency, reproducibility (reliability and agreement), construct validity, and ceiling and floor effects. The Brazilian-Portuguese version of the LSIQ showed good measurement properties with a Cronbach alpha of 0.79, an intraclass correlation coefficient of 0.75, a standard error of measurement of 1.65 points, and a minimal detectable change of 3.54 points. We did not detect ceiling and floor effects. The construct validity analysis was observed a moderate correlation between the LSIQ and Pain Numerical Rating Scale r = 0.46, Roland Morris Disability Questionnaire r = 0.66, Tampa Scale of Kinesiophobia r = 0.49, and Beck Depression Inventory r = 0.44. The Brazilian-Portuguese version of LIQ has adequate measurement properties and can be used in clinical practice and research. NA.

A priori testing of subgrid-scale models for large-eddy simulation of the atmospheric boundary layer

NASA Astrophysics Data System (ADS)

Juneja, Anurag; Brasseur, James G.

1996-11-01

Subgrid-scale models are generally developed assuming homogeneous isotropic turbulence with the filter cutoff lying in the inertial range. In the surface layer and capping inversion regions of the atmospheric boundary layer, the turbulence is strongly anisotropic and, in general, influenced by both buoyancy and shear. Furthermore, the integral scale motions are under-resolved in these regions. Herein we perform direct numerical simulations of shear and buoyancy-generated homogeneous anisotropic turbulence to compute and analyze the actual subgrid-resolved-scale (SGS-RS) dynamics as the filter cutoff moves into the energy-containing scales. These are compared with the SGS-RS dynamics predicted by Smagorinsky-based models with a focus on motivating improved closures. We find that, in general, the underlying assumption of such models, that the anisotropic part of the subgrid stress tensor be aligned with the resolved strain rate tensor, is a poor approximation. Similarly, we find poor alignment between the actual and predicted stress divergence, and find low correlations between the actual and modeled subgrid-scale contribution to the pressure and pressure gradient. Details will be given in the talk.

Nonhelical inverse transfer of a decaying turbulent magnetic field.

PubMed

Brandenburg, Axel; Kahniashvili, Tina; Tevzadze, Alexander G

2015-02-20

In the presence of magnetic helicity, inverse transfer from small to large scales is well known in magnetohydrodynamic (MHD) turbulence and has applications in astrophysics, cosmology, and fusion plasmas. Using high resolution direct numerical simulations of magnetically dominated self-similarly decaying MHD turbulence, we report a similar inverse transfer even in the absence of magnetic helicity. We compute for the first time spectral energy transfer rates to show that this inverse transfer is about half as strong as with helicity, but in both cases the magnetic gain at large scales results from velocity at similar scales interacting with smaller-scale magnetic fields. This suggests that both inverse transfers are a consequence of universal mechanisms for magnetically dominated turbulence. Possible explanations include inverse cascading of the mean squared vector potential associated with local near two dimensionality and the shallower k^{2} subinertial range spectrum of kinetic energy forcing the magnetic field with a k^{4} subinertial range to attain larger-scale coherence. The inertial range shows a clear k^{-2} spectrum and is the first example of fully isotropic magnetically dominated MHD turbulence exhibiting weak turbulence scaling.

Orogen-scale uplift in the central Italian Apennines drives episodic behaviour of earthquake faults

PubMed Central

Cowie, P. A.; Phillips, R. J.; Roberts, G. P.; McCaffrey, K.; Zijerveld, L. J. J.; Gregory, L. C.; Faure Walker, J.; Wedmore, L. N. J.; Dunai, T. J.; Binnie, S. A.; Freeman, S. P. H. T.; Wilcken, K.; Shanks, R. P.; Huismans, R. S.; Papanikolaou, I.; Michetti, A. M.; Wilkinson, M.

2017-01-01

Many areas of the Earth’s crust deform by distributed extensional faulting and complex fault interactions are often observed. Geodetic data generally indicate a simpler picture of continuum deformation over decades but relating this behaviour to earthquake occurrence over centuries, given numerous potentially active faults, remains a global problem in hazard assessment. We address this challenge for an array of seismogenic faults in the central Italian Apennines, where crustal extension and devastating earthquakes occur in response to regional surface uplift. We constrain fault slip-rates since ~18 ka using variations in cosmogenic 36Cl measured on bedrock scarps, mapped using LiDAR and ground penetrating radar, and compare these rates to those inferred from geodesy. The 36Cl data reveal that individual faults typically accumulate meters of displacement relatively rapidly over several thousand years, separated by similar length time intervals when slip-rates are much lower, and activity shifts between faults across strike. Our rates agree with continuum deformation rates when averaged over long spatial or temporal scales (104 yr; 102 km) but over shorter timescales most of the deformation may be accommodated by <30% of the across-strike fault array. We attribute the shifts in activity to temporal variations in the mechanical work of faulting. PMID:28322311

Orogen-scale uplift in the central Italian Apennines drives episodic behaviour of earthquake faults.

PubMed

Cowie, P A; Phillips, R J; Roberts, G P; McCaffrey, K; Zijerveld, L J J; Gregory, L C; Faure Walker, J; Wedmore, L N J; Dunai, T J; Binnie, S A; Freeman, S P H T; Wilcken, K; Shanks, R P; Huismans, R S; Papanikolaou, I; Michetti, A M; Wilkinson, M

2017-03-21

Many areas of the Earth's crust deform by distributed extensional faulting and complex fault interactions are often observed. Geodetic data generally indicate a simpler picture of continuum deformation over decades but relating this behaviour to earthquake occurrence over centuries, given numerous potentially active faults, remains a global problem in hazard assessment. We address this challenge for an array of seismogenic faults in the central Italian Apennines, where crustal extension and devastating earthquakes occur in response to regional surface uplift. We constrain fault slip-rates since ~18 ka using variations in cosmogenic 36 Cl measured on bedrock scarps, mapped using LiDAR and ground penetrating radar, and compare these rates to those inferred from geodesy. The 36 Cl data reveal that individual faults typically accumulate meters of displacement relatively rapidly over several thousand years, separated by similar length time intervals when slip-rates are much lower, and activity shifts between faults across strike. Our rates agree with continuum deformation rates when averaged over long spatial or temporal scales (10 4  yr; 10 2  km) but over shorter timescales most of the deformation may be accommodated by <30% of the across-strike fault array. We attribute the shifts in activity to temporal variations in the mechanical work of faulting.

Assessment of the face validity of two pain scales in Kenya: a validation study using cognitive interviewing

PubMed Central

2012-01-01

Background Patients in sub-Saharan Africa commonly experience pain, which often is un-assessed and undertreated. One hindrance to routine pain assessment in these settings is the lack of a single-item pain rating scale validated for the particular context. The goal of this study was to examine the face validity and cultural acceptability of two single-item pain scales, the Numerical Rating Scale (NRS) and the Faces Pain Scale-Revised (FPS-R), in a population of patients on the medical, surgical, and pediatric wards of Moi Teaching and Referral Hospital in Kenya. Methods Swahili versions of the NRS and FPS-R were developed by standard translation and back-translation. Cognitive interviews were performed with 15 patients at Moi Teaching and Referral Hospital in Eldoret, Kenya. Interview transcripts were analyzed on a question-by-question basis to identify major themes revealed through the cognitive interviewing process and to uncover any significant problems participants encountered with understanding and using the pain scales. Results Cognitive interview analysis demonstrated that participants had good comprehension of both the NRS and the FPS-R and showed rational decision-making processes in choosing their responses. Participants felt that both scales were easy to use. The FPS-R was preferred almost unanimously to the NRS. Conclusions The face validity and acceptability of the Swahili versions of the NRS and FPS-R has been demonstrated for use in Kenyan patients. The broader application of these scales should be evaluated and may benefit patients who currently suffer from pain. PMID:22512923

A continuum dislocation dynamics framework for plasticity of polycrystalline materials

NASA Astrophysics Data System (ADS)

Askari, Hesam Aldin

The objective of this research is to investigate the mechanical response of polycrystals in different settings to identify the mechanisms that give rise to specific response observed in the deformation process. Particularly the large deformation of magnesium alloys and yield properties of copper in small scales are investigated. We develop a continuum dislocation dynamics framework based on dislocation mechanisms and interaction laws and implement this formulation in a viscoplastic self-consistent scheme to obtain the mechanical response in a polycrystalline system. The versatility of this method allows various applications in the study of problems involving large deformation, study of microstructure and its evolution, superplasticity, study of size effect in polycrystals and stochastic plasticity. The findings from the numerical solution are compared to the experimental results to validate the simulation results. We apply this framework to study the deformation mechanisms in magnesium alloys at moderate to fast strain rates and room temperature to 450 °C. Experiments for the same range of strain rates and temperatures were carried out to obtain the mechanical and material properties, and to compare with the numerical results. The numerical approach for magnesium is divided into four main steps; 1) room temperature unidirectional loading 2) high temperature deformation without grain boundary sliding 3) high temperature with grain boundary sliding mechanism 4) room temperature cyclic loading. We demonstrate the capability of our modeling approach in prediction of mechanical properties and texture evolution and discuss the improvement obtained by using the continuum dislocation dynamics method. The framework was also applied to nano-sized copper polycrystals to study the yield properties at small scales and address the observed yield scatter. By combining our developed method with a Monte Carlo simulation approach, the stochastic plasticity at small length scales was studied and the sources of the uncertainty in the polycrystalline structure are discussed. Our results suggest that the stochastic response is mainly because of a) stochastic plasticity due to dislocation substructure inside crystals and b) the microstructure of the polycrystalline material. The extent of the uncertainty is correlated to the "effective cell length" in the sampling procedure whether using simulations and experimental approach.

Validation and properties of the verbal numeric scale in children with acute pain.

PubMed

Bailey, Benoit; Daoust, Raoul; Doyon-Trottier, Evelyne; Dauphin-Pierre, Sabine; Gravel, Jocelyn

2010-05-01

Although the verbal numeric scale (VNS) is used frequently at patients' bedsides, it has never been formally validated in children with acute pain. In order to validate this scale, a prospective cohort study was performed in children between 8 and 17years presenting to a pediatric emergency department (ED) with acute pain. Pain was graded using the VNS, the visual analogue scale (VAS), and the verbal rating scale (VRS). A second assessment was done before discharge. We determined a priori that in order to be valid, the VNS would need to: correlate with the VAS (concurrent validity); decrease after intervention to reduce pain (construct validity); and be associated with the VRS categories (content validity). The VNS interchangeability with the VAS, its minimal clinically significant difference, and test-retest reliability were also determined. A total of 202 patients (mean age: 12.2+/-2.6years) were enrolled. The VNS correlated with the VAS: r(ic)=0.93, p<0.001. There were differences in the VNS before versus after interventions (p<0.001), and between VRS categories (mild versus moderate, p<0.001; moderate versus severe, p<0.001). The 95% limits of agreement (interchangeability) between VNS/VAS were outside the a priori set limit of +/-2.0: -1.8, 2.5. The VNS minimal clinically significant difference was 1. The VNS had good test-retest reliability with 95% limits of agreement of -0.9 and 1.2. In conclusion, the VNS provides a valid and reliable scale to evaluate acute pain in children aged 8-17years but is not interchangeable with the VAS. Copyright 2009 International Association for the Study of Pain. Published by Elsevier B.V. All rights reserved.

Analysis of Low-Frequency Unsteadiness in Shock and Turbulent Boundary Layer Interactions Using Direct Numerical Simulation Data

DTIC Science & Technology

2011-02-09

1991; Beresh , Clemens, & Dolling, 2002; Ganapathisubramani, Clemens & Dolling, 2007) and (b) the downstream separated flow (Thomas, Putnam & Chu...Ferziger, J.H., Reynolds, W.C. (1980) “Improved subgrid-scale models for large eddy simulation,” AIAA Paper 1980-1357. 5. Beresh , S.J., Clemens, N.T...AIAA Journal 25, 5, 668-675. 34. Lempert, W.R., Wu, and Miles, R.B. (1997) “Filtered Rayleigh scattering measurements using a MHz rate pulse

Numerical Field Model Simulation of Full Scale Fire Tests in a Closed Vessel

DTIC Science & Technology

1986-12-01

is assumed to be dilTuse. 42 1. The Method for Calculating the Radiant Heat Transfer. The net radiosity method for the interchange of radiation between... radiosity B^ is the rate at which radiant energy leaves a surface and equals the radiation emitted plus the radiation reflected. ^1 = ^1^ V "^ Pi^i...H; can be defined as the sum of the radiosities B: for each of the surfaces in the enclosure multiphed by the shape factor F- where F-; is the

Correlations in electrically coupled chaotic lasers.

PubMed

Rosero, E J; Barbosa, W A S; Martinez Avila, J F; Khoury, A Z; Rios Leite, J R

2016-09-01

We show how two electrically coupled semiconductor lasers having optical feedback can present simultaneous antiphase correlated fast power fluctuations, and strong in-phase synchronized spikes of chaotic power drops. This quite counterintuitive phenomenon is demonstrated experimentally and confirmed by numerical solutions of a deterministic dynamical system of rate equations. The occurrence of negative and positive cross correlation between parts of a complex system according to time scales, as proved in our simple arrangement, is relevant for the understanding and characterization of collective properties in complex networks.

Cooperative emission of light by an ensemble of dipoles near a metal nanoparticle: the plasmonic Dicke effect.

PubMed

Pustovit, Vitaliy N; Shahbazyan, Tigran V

2009-02-20

We identify a new mechanism for cooperative emission of light by an ensemble of N dipoles near a metal nanostructure supporting a surface plasmon. The cross talk between emitters due to the virtual plasmon exchange leads to the formation of three plasmonic superradiant modes whose radiative decay rates scale with N, while the total radiated energy is thrice that of a single emitter. Our numerical simulations indicate that the plasmonic Dicke effect survives nonradiative losses in the metal.

Effective Power-Law Dependence of Lyapunov Exponents on the Central Mass in Galaxies

NASA Technical Reports Server (NTRS)

Delis, N.; Efthymiopoulos, C.; Kalapotharakos, C.

2015-01-01

Using both numerical and analytical approaches, we demonstrate the existence of an effective power-law relation L alpha m(sup p) between themean Lyapunov exponent L of stellar orbits chaotically scattered by a supermassive black hole (BH) in the centre of a galaxy and the mass parameter m, i.e. ratio of the mass of the BH over the mass of the galaxy. The exponent p is found numerically to obtain values in the range p approximately equals 0.3-0.5. We propose a theoretical interpretation of these exponents, based on estimates of local 'stretching numbers', i.e. local Lyapunov exponents at successive transits of the orbits through the BH's sphere of influence. We thus predict p = 2/3 - q with q approximately equaling 0.1-0.2. Our basic model refers to elliptical galaxy models with a central core. However, we find numerically that an effective power-law scaling of L with m holds also in models with central cusp, beyond a mass scale up to which chaos is dominated by the influence of the cusp itself. We finally show numerically that an analogous law exists also in disc galaxies with rotating bars. In the latter case, chaotic scattering by the BH affects mainly populations of thick tube-like orbits surrounding some low-order branches of the x(sub 1) family of periodic orbits, as well as its bifurcations at low-order resonances, mainly the inner Lindblad resonance and the 4/1 resonance. Implications of the correlations between L and m to determining the rate of secular evolution of galaxies are discussed.

A multi-scalar PDF approach for LES of turbulent spray combustion

NASA Astrophysics Data System (ADS)

Raman, Venkat; Heye, Colin

2011-11-01

A comprehensive joint-scalar probability density function (PDF) approach is proposed for large eddy simulation (LES) of turbulent spray combustion and tests are conducted to analyze the validity and modeling requirements. The PDF method has the advantage that the chemical source term appears closed but requires models for the small scale mixing process. A stable and consistent numerical algorithm for the LES/PDF approach is presented. To understand the modeling issues in the PDF method, direct numerical simulation of a spray flame at three different fuel droplet Stokes numbers and an equivalent gaseous flame are carried out. Assumptions in closing the subfilter conditional diffusion term in the filtered PDF transport equation are evaluated for various model forms. In addition, the validity of evaporation rate models in high Stokes number flows is analyzed.

The effect of graphical and numerical presentation of hypothetical prenatal diagnosis results on risk perception.

PubMed

Siegrist, Michael; Orlow, Pascale; Keller, Carmen

2008-01-01

To evaluate various formats for the communication of prenatal test results. In study 1 (N=400), female students completed a questionnaire assessing risk perception, affect, and perceived usefulness of prenatal test results. A randomized, 2 (risk level; low, high) x 4 (format; ratio with numerator 1, ratio with denominator 1000, Paling Perspective Scale, pictograms) design was used. Study 2 (N=200) employed a 2 (risk level; low, high) x 2 (format; Paling Perspective Scale, risk comparisons in numerical format) design. In study 1, the Paling Perspective Scale resulted in a higher level of perceived risk across different risk levels compared with the other formats. Furthermore, participants in the low-risk group perceived the test results as less risky compared with participants in the high-risk group (P < 0.001) when the Paling Perspective Scale was used. No significant differences between low and high risks were observed for the other 3 formats. In study 2, the Paling Perspective Scale evoked higher levels of perceived risks relative to the numerical presentation of risk comparisons. For both formats, we found that participants confronted with a high risk perceived test results as more risky compared with participants confronted with a low risk. The Paling Perspective Scale resulted in a higher level of perceived risk compared with the other formats. This effect must be taken into account when choosing a graphical or numerical format for risk communication.

Validation Study of Unnotched Charpy and Taylor-Anvil Impact Experiments using Kayenta

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

Kamojjala, Krishna; Lacy, Jeffrey; Chu, Henry S.

2015-03-01

Validation of a single computational model with multiple available strain-to-failure fracture theories is presented through experimental tests and numerical simulations of the standardized unnotched Charpy and Taylor-anvil impact tests, both run using the same material model (Kayenta). Unnotched Charpy tests are performed on rolled homogeneous armor steel. The fracture patterns using Kayenta’s various failure options that include aleatory uncertainty and scale effects are compared against the experiments. Other quantities of interest include the average value of the absorbed energy and bend angle of the specimen. Taylor-anvil impact tests are performed on Ti6Al4V titanium alloy. The impact speeds of the specimenmore » are 321 m/s and 393 m/s. The goal of the numerical work is to reproduce the damage patterns observed in the laboratory. For the numerical study, the Johnson-Cook failure model is used as the ductile fracture criterion, and aleatory uncertainty is applied to rate-dependence parameters to explore its effect on the fracture patterns.« less

Numerical investigation of solid mixing in a fluidized bed coating process

NASA Astrophysics Data System (ADS)

Kenche, Venkatakrishna; Feng, Yuqing; Ying, Danyang; Solnordal, Chris; Lim, Seng; Witt, Peter J.

2013-06-01

Fluidized beds are widely used in many process industries including the food and pharmaceutical sectors. Despite being an intensive research area, there are no design rules or correlations that can be used to quantitatively predict the solid mixing in a specific system for a given set of operating conditions. This paper presents a numerical study of the gas and solid dynamics in a laboratory scale fluidized bed coating process used for food and pharmaceutical industries. An Eulerian-Eulerian model (EEM) with kinetic theory of granular flow is selected as the modeling technique, with the commercial computational fluid dynamics (CFD) software package ANSYS/Fluent being the numerical platform. The flow structure is investigated in terms of the spatial distribution of gas and solid flow. The solid mixing has been evaluated under different operating conditions. It was found that the solid mixing rate in the horizontal direction is similar to that in the vertical direction under the current design and operating conditions. It takes about 5 s to achieve good mixing.

Computation of the sound generated by isotropic turbulence

NASA Technical Reports Server (NTRS)

Sarkar, S.; Hussaini, M. Y.

1993-01-01

The acoustic radiation from isotropic turbulence is computed numerically. A hybrid direct numerical simulation approach which combines direct numerical simulation (DNS) of the turbulent flow with the Lighthill acoustic analogy is utilized. It is demonstrated that the hybrid DNS method is a feasible approach to the computation of sound generated by turbulent flows. The acoustic efficiency in the simulation of isotropic turbulence appears to be substantially less than that in subsonic jet experiments. The dominant frequency of the computed acoustic pressure is found to be somewhat larger than the dominant frequency of the energy-containing scales of motion. The acoustic power in the simulations is proportional to epsilon (M(sub t))(exp 5) where epsilon is the turbulent dissipation rate and M(sub t) is the turbulent Mach number. This is in agreement with the analytical result of Proudman (1952), but the constant of proportionality is smaller than the analytical result. Two different methods of computing the acoustic power from the DNS data bases yielded consistent results.

Salinization of aquifers at the regional scale by marine transgression: Time scales and processes

NASA Astrophysics Data System (ADS)

Armandine Les Landes, A.; Davy, P.; Aquilina, L.

2014-12-01

Saline fluids with moderate concentrations have been sampled and reported in the Armorican basement at the regional scale (northwestern France). The horizontal and vertical distributions of high chloride concentrations (60-1400mg/L) at the regional scale support the marine origin and provide constraints on the age of these saline fluids. The current distribution of fresh and "saline" groundwater at depth is the result mostly of processes occurring at geological timescales - seawater intrusion processes followed by fresh groundwater flushing -, and only slightly of recent anthropogenic activities. In this study, we focus on seawater intrusion mechanisms in continental aquifers. We argue that one of the most efficient processes in macrotidal environments is the gravity-driven downconing instability below coastal salinized rivers. 2-D numerical experiments have been used to quantify this process according to four main parameter types: (1) the groundwater system permeability, (2) the salinity degree of the river, (3) the river width and slope, and (4) the tidal amplitude. A general expression of the salinity inflow rates have been derived, which has been used to estimate groundwater salinization rates in Brittany, given the geomorphological and environmental characteristics (drainage basin area, river widths and slopes, tidal range, aquifer permeability). We found that downconing below coastal rivers entail very high saline rates, indicating that this process play a major role in the salinization of regional aquifers. This is also likely to be an issue in the context of climate change, where sea-level rise is expected.

Patient-reported outcomes in neurofibromatosis and schwannomatosis clinical trials.

PubMed

Wolters, Pamela L; Martin, Staci; Merker, Vanessa L; Gardner, Kathy L; Hingtgen, Cynthia M; Tonsgard, James H; Schorry, Elizabeth K; Baldwin, Andrea

2013-11-19

Neurofibromatosis (NF) is a genetic disease with multiple clinical manifestations that can significantly impact quality of life (QOL). Clinical trials should include patient-reported outcomes (PROs) as endpoints to assess treatment effects on various aspects of QOL, but there is no consensus on the selection and use of such measures in NF. This article describes the PRO Working Group of the Response Evaluation in Neurofibromatosis and Schwannomatosis (REiNS) Collaboration, its main goals, methods for identifying appropriate PRO measures for NF clinical trials, and recommendations for assessing pain intensity. The REiNS PRO group selected core endpoint domains important to assess in NF. The members developed criteria to rate PRO measures, including patient characteristics, psychometric properties, and feasibility, and utilized a systematic process to evaluate PROs for NF clinical trials. Within the subdomain of pain intensity, the group reviewed the Numerical Rating Scale-11 (NRS-11), the Visual Analogue Scale, and the Faces Pain Scale-Revised using this process. Based on the review criteria, each of these pain intensity scales is brief, reliable, valid, and widely used. However, the NRS-11 was given the highest rating for use in NF clinical trials due to recommendations from pain experts and other consensus groups, its extensive use in research, strong psychometric data including sensitivity to change, and excellent feasibility in ages ≥ 8 years. The systematic review criteria and process are effective for identifying appropriate PRO measures and provide information utilized by the REiNS Collaboration to achieve consensus regarding PROs in NF clinical trials.

Star Formation and Gas Dynamics in Galactic Disks: Physical Processes and Numerical Models

NASA Astrophysics Data System (ADS)

Ostriker, Eve C.

2011-04-01

Star formation depends on the available gaseous ``fuel'' as well as galactic environment, with higher specific star formation rates where gas is predominantly molecular and where stellar (and dark matter) densities are higher. The partition of gas into different thermal components must itself depend on the star formation rate, since a steady state distribution requires a balance between heating (largely from stellar UV for the atomic component) and cooling. In this presentation, I discuss a simple thermal and dynamical equilibrium model for the star formation rate in disk galaxies, where the basic inputs are the total surface density of gas and the volume density of stars and dark matter, averaged over ~kpc scales. Galactic environment is important because the vertical gravity of the stars and dark matter compress gas toward the midplane, helping to establish the pressure, and hence the cooling rate. In equilibrium, the star formation rate must evolve until the gas heating rate is high enough to balance this cooling rate and maintain the pressure imposed by the local gravitational field. In addition to discussing the formulation of this equilibrium model, I review the current status of numerical simulations of multiphase disks, focusing on measurements of quantities that characterize the mean properties of the diffuse ISM. Based on simulations, turbulence levels in the diffuse ISM appear relatively insensitive to local disk conditions and energetic driving rates, consistent with observations. It remains to be determined, both from observations and simulations, how mass exchange processes control the ratio of cold-to-warm gas in the atomic ISM.