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At least 991 records · Page 55
All sourcesNASA NTRSDOE OSTI
NASA NTRS1993

Influence of recreational activity and muscle strength on ulnar bending stiffness in men

Bone bending stiffness (modulus of elasticity [E] x moment of inertia [I]), a measure of bone strength, is related to its mineral content (BMC) and geometry and may be influenced by exercise. We evaluated the relationship of habitual recreational exercise and muscle strength to ulnar EI, width, and BMC in 51 healthy men, 28-61 yr of age. BMC and width were measured by single photon absorptiometry and EI by mechanical resistance tissue analysis. Maximum biceps strength was determined dynamically (1-RM) and grip strength isometrically. Subjects were classified as sedentary (S) (N = 13), moderately (M) (N = 18), or highly active (H) (N = 20) and exercised 0.2 +/- 0.2; 2.2 +/- 1.3; and 6.8 +/- 2.3 h.wk-1 (P < 0.001). H had greater biceps (P < 0.0005) and grip strength (P < 0.05), ulnar BMC (P < 0.05), and ulnar EI (P = 0.01) than M or S, who were similar. Amount of activity correlated with grip and biceps strength (r = 0.47 and 0.49; P < 0.001), but not with bone measurements, whereas muscle strength correlated with both EI and BMC (r = 0.40-0.52, P < 0.005). EI also correlated significantly with both BMC and ulnar width (P < 0.0001). Ulnar width and biceps strength were the only independent predictors of EI (r2 = 0.67, P < 0.0001). We conclude that levels of physical activity sufficient to increase arm strength influence ulnar bending stiffness.

NASA Discipline Musculoskeletal↗
DOE OSTI2021

How Useful are Conventional I–Vs for Performance Calibration of Single- and Two-Junction Perovskite Solar Cells? A Statistical Analysis of Performance Data on ≈200 Cells from 30 Global Sources

As perovskite photovoltaics (PV) advance from the laboratory to commercial prototypes, their accurate and reliable performance testing is becoming increasingly important. The well-documented dynamic response of perovskite solar cells to an external applied voltage has led to the development of steady-state performance measurement methods; however, these methods have not been widely adopted by the perovskite PV community. A key reason for this is that steady-state measurement methods take tens of minutes to complete, as opposed to conventional "fast" current-voltage (I-V) measurements usually lasting a few seconds. Fast I-Vs arise from a snapshot, almost always not a steady-state condition of the device; however, given their widespread use, the question arises: how do performance parameters of perovskite PV compare when measured with fast I-V and with a steady-state method? Results compiled from approximately 200 perovskite PV cells, including single junction, and two-terminal perovskite-perovskite and perovskite-Si tandems, show that fast I-Vs can provide a useful measure of the open-circuit voltage of the devices, while the short-circuit current and the overall efficiency can be widely misestimated. Here, the implications of these findings on performance testing protocols are discussed and possible options for fast and accurate testing of perovskite PV are proposed.

14 SOLAR ENERGY↗
DOE OSTI2023

Empirical probability and machine learning analysis of m , n = 2, 1 tearing mode onset parameter dependence in DIII-D H-mode scenarios

m, n = 2, 1 tearing mode onset empirical probability and machine learning analyses of a multiscenario DIII-D database of over 14 000 H-mode discharges show that the normalized plasma beta, the rotation profile, and the magnetic equilibrium shape have the strongest impact on the 2,1 tearing mode stability, in qualitative agreement with neoclassical tearing modes (m and n are the poloidal and toroidal mode numbers, respectively). In addition, 2,1 tearing modes are most likely to destabilize when n > 1 tearing modes are already present in the core plasma. The covariance matrix of tearing sensitive plasma parameters takes a nearly block-diagonal form, with the blocks incorporating thermodynamic, current and safety factor profile, separatrix shape, and plasma flow parameters, respectively. This suggests a number of paths to improved stability at fixed pressure and edge safety factor primarily by preserving a minimum of 1 kHz differential rotation, increasing the minimum safety factor above unity, using upper single null magnetic configuration, and reducing the core impurity radiation. In addition, lower triangularity, lower elongation, and lower pedestal pressure may also help to improve stability. Furthermore, the electron and ion temperature, collisionality, resistivity, internal inductance, and the parallel current gradient appear to only weakly correlate with the 2,1 tearing mode onsets in this database.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2025

Insights into distorted lamellar phases with small-angle scattering and machine learning

Lamellar phases are essential in various soft matter systems, with topological defects significantly influencing their mechanical properties. In this report, we present a machine-learning approach for quantitatively analyzing the structure and dynamics of distorted lamellar phases using scattering techniques. By leveraging the mathematical framework of Kolmogorov–Arnold networks, we demonstrate that the conformations of these distorted phases – expressed as superpositions of complex waves – can be reconstructed from small-angle scattering intensities. Through the contour analysis of wave field phase singularities, we obtain the statistics of the spatial distribution of topological defects. Furthermore, we establish that the temporal evolution of these defects can be derived from the time-dependent traveling wave field, informed by the dispersion relation of spectral components. This method opens new avenues for investigating the dynamics of distorted lamellar phases using various dynamic scattering techniques such as neutron spin echo and X-ray photon correlation spectroscopy. These findings enhance our microscopic understanding of how defects influence the physical properties of lamellar materials, with implications for both equilibrium and non-equilibrium states in general lamellar systems.

36 MATERIALS SCIENCE↗
DOE OSTI2018

The Development of the Corrosion Control Limits for Direct Feed Low-Activity Waste Melter-Off Gas Returns to Hanford Tank Farms - 18196

The Savannah River National Laboratory has been developing a corrosion model to facilitate implementation of Hanford's Direct Feed Low Waste (DFLAW) flowsheet. Laboratory testing and statistical analysis have been used to determine the necessary corrosion controls for returning effluent from the Hanford Waste Treatment and Immobilization Plant's Low Activity Waste Vitrification melter off-gas treatment system to the tank farms. The stream compositions are projected to contain components at relative concentrations that are significantly more corrosive toward carbon steel, specifically halide and sulfate anions, than the current waste compositions in the tank farms. Administrative programs are in place to mitigate potential corrosion mechanisms and thereby maintain the structural and leak integrity functions of these waste tanks throughout their intended service life. Waste chemistry and temperature control are the means by which corrosion degradation of the waste tanks is minimized. The current administrative specification for chemical composition and temperature for the underground carbon steel waste tanks is not designed to control the higher halide or sulfate composition. The content of the DFLAW waste streams will be diverse and depend on several factors, such as the melter feed composition and melter idle time. Other factors, such as effluent management of the off gas water collections, will impact the variability of the return streams even more. The work performed by the Savannah River National Laboratory has confirmed that the halide ions are the most aggressive species in the return stream compositions projected using a flowsheet simulation, and nitrite is the most effective inhibitor at pH 10 and 40 deg. C. This test program has employed statistically designed test matrices to determine the dependent variables and the interaction terms between the variables that are significant for the corrosion model and definition of the corrosion control specifications. The first phase of testing focused on identifying aggressive species in off-gas condensate return compositions that present a propensity for localized corrosion attack, namely pitting corrosion. The second phase of testing focused on developing a corrosion model from the interaction terms that will predict the susceptibility of pitting in the double shell tank system based on waste composition and the required amount of corrosion inhibitor. The data collected from this testing program in conjunction with other testing programs, both at the Savannah River Site and the Hanford Site, along with operations knowledge, has determined the chemistry ranges and chemical species requirements for corrosion control in the Hanford double-shell tank system for the effluents generated in the Hanford Waste Treatment and Immobilization Plant's Low Activity Waste facility during the DFLAW phase of operations. (authors)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2022

A novel methodology to integrate outcomes regarding perioperative pain experience into a composite score: Prediction model development and validation

Abstract Background An integrated score that globally assesses perioperative pain experience and rationally weights each component has not yet been developed. Methods A development dataset specific to adult Chinese patients undergoing orthopaedic surgery was obtained from PAIN OUT (1985 qualified patients of 2244). A more recent validation dataset obeying the same conditions was obtained from the Chinese Anaesthesia Shared‐database Platform (1004 qualified patients of 1032). Outcomes were assessed using the International Pain Outcomes Questionnaire (IPO‐Q), which comprises key patient‐level outcomes of perioperative pain management, including pain experience and perceptions of care. Using principal component analysis and regression models, a composite score (CS) was inferred to integrate pain experience. The discrimination of the CS for dissatisfaction and desire for more pain treatment was compared with that of the worst pain score. Results A CS was developed from the 12 items of the IPO‐Q regarding pain experience. The weight for calculating the CS was worst pain 11, least pain 17, time spent in severe pain 11, interference with activity in bed 9, interference with breathing deeply or coughing 10, interference with sleep 9, anxiety 12, helplessness 12, nausea 0, drowsiness 2, itch 5 and dizziness 2. In external validation, the CS indicated superior discrimination to the worst pain in predicting dissatisfaction ( p < 0.001) and desire for more pain treatment ( p < 0.001). Conclusions This study introduced a methodology to integrate outcomes regarding perioperative pain experience into a CS, which was based on the weight of each item. Significance This novel methodology sheds additional light on the riveting issue of carefully integrating several measures into a composite endpoint, which may be useful for quality improvement purposes when addressing the impact of a change in clinical practice.

Jiang, Bailin↗
DOE OSTI2021

A causal data fusion method for the general exposure and outcome

Abstract With the advent of the big data era, the need to combine multiple individual data sets to draw causal effects arises naturally in many medical and biological applications. Especially each data set cannot measure enough confounders to infer the causal effect of an exposure on an outcome. In this article, we extend the method proposed by a previous study to causal data fusion of more than two data sets without external validation and to a more general (continuous or discrete) exposure and outcome. Theoretically, we obtain the condition for identifiability of exposure effects using multiple individual data sources for the continuous or discrete exposure and outcome. The simulation results show that our proposed causal data fusion method has unbiased causal effect estimate and higher precision than traditional regression, meta‐analysis and statistical matching methods. We further apply our method to study the causal effect of BMI on glucose level in individuals with diabetes by combining two data sets. Our method is essential for causal data fusion and provides important insights into the ongoing discourse on the empirical analysis of merging multiple individual data sources.

Li, Hongkai↗
DOE OSTI2019

Can MRI be used to diagnose histologic grade in T1a (< 4 cm) clear cell renal cell carcinomas?

Objective: To assess whether MRI can differentiate low-grade from high-grade T1a cc-RCC. Materials and methods: With IRB approval, 49 consecutive solid < 4 cm cc-RCC (low grade [Grade 1 or 2] N = 38, high grade [Grade 3] N = 11) with pre-operative MRI before nephrectomy were identified between 2013 and 2018. Tumor size, apparent diffusion coefficient (ADC) histogram analysis, enhancement wash-in and wash-out rates, and chemical shift signal intensity index (SI index) were assessed by a blinded radiologist. Subjectively, two blinded Radiologists also assessed for (1) microscopic fat, (2) homogeneity (5-point Likert scale), and (3) ADC signal (relative to renal cortex); discrepancies were resolved by consensus. Outcomes were studied using Chi square, multivariate analysis, logistic regression modeling, and ROC. Inter-observer agreement was assessed using Cohen’s kappa. Results: Tumor size was 24 ± 7 (13–39) mm with no association to grade (p = 0.45). Among quantitative features studied, corticomedullary phase wash-in index (p = 0.015), SI index (p = 0.137), and tenth-centile ADC (p = 0.049) were higher in low-grade tumors. 36.8% (14/38) low-grade tumors versus zero high-grade tumors demonstrated microscopic fat (p = 0.015; Kappa = 0.67). Microscopic fat was specific for low-grade disease (100.0% [71.5–100.0]) with low sensitivity (36.8% [21.8–54.6]). Other subjective features did not differ between groups (p > 0.05). A logistic regression model combining microscopic fat + wash-in index + tenth-centile-ADC yielded area under ROC curve 0.98 (Confidence Intervals 0.94–1.0) with sensitivity/specificity 87.5%/100%. Conclusion: The combination of microscopic fat, higher corticomedullary phase wash-in and higher tenth-centile ADC is highly accurate for diagnosis of low-grade disease among T1a clear cell RCC.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2011

The Burden of Hard Atherosclerotic Plaques Does Not Promote Endoleak Development After Endovascular Aortic Aneurysm Repair: A Risk Stratification

Purpose: To objectify the influence of the atherosclerotic burden in the proximal landing zone on the development of endoleaks after endovascular abdominal aortic aneurysm repair (EVAR) or thoracic endovascular aneurysm repair (TEVAR) using objective aortic calcium scoring (ACS). Materials and Methods: This retrospective observation study included 267 patients who received an aortic endograft between 1997 and 2010 and for whom preoperative computed tomography (CT) was available to perform ACS using the CT-based V600 method. The mean follow-up period was 2 {+-} 2.3 years. Results: Type I endoleaks persisted in 45 patients (16.9%), type II in 34 (12.7%), type III in 8 (3%), and type IV or V in 3 patients, respectively (1.1% each). ACS in patients with type I endoleaks was not increased: 0.029 {+-} 0.061 ml compared with 0.075 {+-} 0.1349 ml in the rest of the patients, (p > 0.05; Whitney-Mann U-Test). There were significantly better results for the indication 'traumatic aortic rupture' than for the other indications (p < 0.05). In multivariate logistic regression analyses, age was an independent risk factor for the development of type I endoleaks in the thoracic aorta (Wald 9.5; p = 0.002), whereas ACS score was an independent protective factor (Wald 6.9; p = 0.009). In the abdominal aorta, neither age nor ACS influenced the development of endoleaks. Conclusion: Contrary to previous assumptions, TEVAR and EVAR can be carried out without increasing the risk of an endoleak of any type, even if there is a high atherosclerotic 'hard-plaque' burden of the aorta. The results are significantly better for traumatic aortic.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2012

Incidence and Cause of Hypertension During Adrenal Radiofrequency Ablation

Purpose: To evaluate the incidence and cause of hypertension prospectively during adrenal radiofrequency ablation (RFA). Methods: For this study, approved by our institutional review board, written informed consent was obtained from all patients. Patients who received RFA for adrenal tumors (adrenal ablation) and other abdominal tumors (nonadrenal ablation) were included in this prospective study. Blood pressure was monitored during RFA. Serum adrenal hormone levels including epinephrine, norepinephrine, dopamine, and cortisol levels were measured before and during RFA. The respective incidences of procedural hypertension (systolic blood pressure >200 mmHg) of the two patient groups were compared. Factors correlating with procedural systolic blood pressure were evaluated by regression analysis.ResultsNine patients underwent adrenal RFA and another 9 patients liver (n = 5) and renal (n = 4) RFA. Asymptomatic procedural hypertension that returned to the baseline by injecting calcium blocker was found in 7 (38.9%) of 18 patients. The incidence of procedural hypertension was significantly higher in the adrenal ablation group (66.7%, 6/9) than in the nonadrenal ablation group (11.1%, 1/9, P < 0.0498). Procedural systolic blood pressure was significantly correlated with serum epinephrine (R{sup 2} = 0.68, P < 0.0001) and norepinephrine (R{sup 2} = 0.72, P < 0.0001) levels during RFA. The other adrenal hormones did not show correlation with procedural systolic blood pressure. Conclusion: Hypertension occurs frequently during adrenal RFA because of the release of catecholamine.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2015

Can Early Computed Tomography Angiography after Endovascular Aortic Aneurysm Repair Predict the Need for Reintervention in Patients with Type II Endoleak?

PurposeThis study was designed to identify parameters on CT angiography (CTA) of type II endoleaks following endovascular aortic aneurysm repair (EVAR) for abdominal aortic aneurysm (AAA), which can be used to predict the subsequent need for reinterventions.MethodsWe retrospectively identified 62 patients with type II endoleak who underwent early CTA in mean 3.7 ± 1.9 days after EVAR. On the basis of follow-up examinations (mean follow-up period 911 days; range, 373–1,987 days), patients were stratified into two groups: those who did (n = 18) and those who did not (n = 44) require reintervention. CTA characteristics, such as AAA, endoleak, as well as nidus dimensions, patency of the inferior mesenteric artery, number of aortic branch vessels, and the pattern of endoleak appearance, were recorded and correlated with the clinical outcome.ResultsUnivariate and receiver operating characteristic curve regression analyses revealed significant differences between the two groups for the endoleak volume (surveillance group: 1391.6 ± 1427.9 mm{sup 3}; reintervention group: 3227.7 ± 2693.8 mm{sup 3}; cutoff value of 2,386 mm{sup 3}; p = 0.002), the endoleak diameter (13.6 ± 4.3 mm compared with 25.9 ± 9.6 mm; cutoff value of 19 mm; p < 0.0001), the number of aortic branch vessels (2.9 ± 1.2 compared with 4.2 ± 1.4 vessels; p = 0.001), as well as a “complex type” endoleak pattern (13.6 %, n = 6 compared with 44.4 %, n = 8; p = 0.02).ConclusionsEarly CTA can predict the future need for reintervention in patients with type II endoleak. Therefore, treatment decision should be based not only on aneurysm enlargement alone but also on other imaging characteristics.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2015

Image-Guided Cryoablation of the Spine in a Swine Model: Clinical, Radiological, and Pathological Findings with Light and Electron Microscopy

PurposeThis study was designed to present the feasibility of an in vivo image-guided percutaneous cryoablation of the porcine vertebral body.MethodsThe institutional animal care committee approved this study. Cone-beam computed tomography (CBCT)-guided vertebral cryoablations (n = 22) were performed in eight pigs with short, 2-min, single or double-freezing protocols. Protective measures to nerves included dioxide carbon (CO{sub 2}) epidural injections and spinal canal temperature monitoring. Clinical, radiological, and pathological data with light (n = 20) or transmission electron (n = 2) microscopic analyses were evaluated after 6 days of clinical follow-up and euthanasia.ResultsCBCT/fluoroscopic-guided transpedicular vertebral body cryoprobe positioning and CO{sub 2} epidural injection were successful in all procedures. No major complications were observed in seven animals (87.5 %, n = 8). A minor complication was observed in one pig (12.5 %, n = 1). Logistic regression model analysis showed the cryoprobe-spinal canal (Cp-Sc) distance as the most efficient parameter to categorize spinal canal temperatures lower than 19 °C (p < 0.004), with a significant Pearson’s correlation test (p < 0.041) between the Cp-Sc distance and the lowest spinal canal temperatures. Ablation zones encompassed pedicles and the posterior wall of the vertebral bodies with an inflammatory rim, although no inflammatory infiltrate was depicted in the surrounding neural structures at light microscopy. Ultrastructural analyses evidenced myelin sheath disruption in some large nerve fibers, although neurological deficits were not observed.ConclusionsCBCT-guided vertebral cryoablation of the porcine spine is feasible under a combination of a short freezing protocol and protective measures to the surrounding nerves. Ultrastructural analyses may be helpful assess the early modifications of the nerve fibers.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2017

Low Cerebral Blood Volume Identifies Poor Outcome in Stent Retriever Thrombectomy

BackgroundMechanical thrombectomy (MT) is an efficient treatment of acute stroke caused by large-vessel occlusion. We evaluated the factors predicting poor clinical outcome (3-month modified Rankin Scale, mRS >2) although MT performed with modern stent retrievers.MethodsWe prospectively collected the clinical and imaging data of 105 consecutive anterior circulation stroke patients who underwent MT after multimodal CT imaging. Patients with occlusion of the internal carotid artery and/or middle cerebral artery up to the M2 segment were included. We recorded baseline clinical, procedural and imaging variables, technical outcome, 24-h imaging outcome and the clinical outcome. Differences between the groups were studied with appropriate statistical tests and binary logistic regression analysis.ResultsLow cerebral blood volume Alberta stroke program early CT score (CBV-ASPECTS) was associated with poor clinical outcome (median 7 vs. 9, p = 0.01). Lower collateral score (CS) significantly predicted poor outcome in regression modelling with CS = 0 increasing the odds of poor outcome 4.4-fold compared to CS = 3 (95% CI 1.27–15.5, p = 0.02). Lower CBV-ASPECTS significantly predicted poor clinical outcome among those with moderate or severe stroke (OR 0.82, 95% CI 0.68–1, p = 0.05) or poor collateral circulation (CS 0–1, OR 0.66, 95% CI 0.48–0.90, p = 0.009) but not among those with mild strokes or good collaterals.ConclusionsCBV-ASPECTS estimating infarct core is a significant predictor of poor clinical outcome among anterior circulation stroke patients treated with MT, especially in the setting of poor collateral circulation and/or moderate or severe stroke.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2018

Two-Step Estimation in a Heteroscedastic Linear Regression Model

We study the problem of estimating a parameter in some heteroscedastic linear regression model in the case where the regressors consist of all order statistics based on the sample of identically distributed not necessarily independent observations with finite second moment. It is assumed that the random errors depend on the parameter and distributions of the corresponding regressors. We propose a two-step procedure for finding explicit asymptotically normal estimators.

97 MATHEMATICS AND COMPUTING↗
DOE OSTI2019

Identification of Rate, Extent, and Mechanisms of Hot Metal Resulfurization with CaO-SiO{sub 2}-Na{sub 2}O Slag Systems

The resulfurization of hot metal has not been comprehensively studied in literature. This study presents an experimental and mathematical modeling study of resulfurization in thermodynamic and kinetic point of view. The rate, extent, and mechanisms of resulfurization were evaluated by analyzing concurrently the physical properties and sulfur-extracting ability of the slag. Experiments were conducted in a chamber furnace in an argon atmosphere, and the hot metal was sampled with pre-defined basis. The experiments were continued until the metal–slag system reached an apparent thermodynamic equilibrium. To obtain a quantitative measure on the effect of system properties on the rate and extent of resulfurization, the results of this study were combined with previous studies handling the sulfide capacities of Na{sub 2}O-SiO{sub 2} and CaO-SiO{sub 2}-Na{sub 2}O slag systems. The sulfide capacities of the slag and corresponding metal–slag sulfur partition ratios were mathematically modeled with data-driven techniques such as multiple linear and non-linear regression and artificial neural networks. Finally, with the help of these, to study the kinetics of resulfurization, a simple mechanistic reaction model was derived. The results suggest that resulfurization of hot metal follows 1st-order kinetics and that the rate and extent can be regulated through the control of the associated thermodynamic driving force and by modifying the physical properties of the slag. The rate-limiting factor was found to be determined by the morphology of the slag phase.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Complete revascularization determined by myocardial perfusion imaging could improve the outcomes of patients with stable coronary artery disease, compared with incomplete revascularization and no revascularization

Objectives: To compare the outcomes among patients treated by complete coronary revascularization (CCR) or incomplete coronary revascularization (ICR) and no coronary revascularization (NCR) by myocardial perfusion imaging (MPI), as well as to evaluate the impact of severity of ischemia on patients with coronary artery disease (CAD) by different therapy strategies. Background: Using myocardial ischemia severity determined by MPI guiding treatment strategies for CAD patients still lacks strong clinical evidences. Methods: Consecutive patients (N = 286) underwent clinical stress-rest SPECT MPI and were retrospectively followed-up. For assessment of outcome of treatment, all patients were classified into three groups (CCR, ICR, and NCR), and further divided into two subgroups as mild ischemia (< 10% ischemic myocardium) and moderate-severe ischemia (≥ 10% ischemic myocardium). All-cause death was defined as the primary endpoint, and the composite of deaths, nonfatal myocardial infarction, and repeat revascularization (MACE) as the secondary endpoint. Results: Two-hundred eighty-six patients were followed-up for 46 ± 21 months. Thirty deaths and 65 MACEs were recorded. Patients treated by revascularization had significantly lower MACE (P < .001) but not mortality (P = .158) than patients treated by NCR. Outcomes of CCR related to mortality rate were greater than ICR and NCR (death: P = .019, MACE: P < .001). In patients with moderate-severe ischemia, CCR showed improved outcomes than ICR and NCR (death: P = .034; and MACE: P < .001). In patients with mild ischemia, the outcomes of CCR, ICR, and NCR had no significant difference (P > .05). Multivariate regression Cox analysis revealed that summed difference score [death: HR 1.09 (1.03, 1.15), P = .004] was an independent risk factor and CCR was an independent negative predictor [death: HR 0.31 (0.12, 0.81), P = .017; MACE: HR 0.30 (0.16, 0.57), P < .001]. Conclusions: Outcomes of patients treated by CCR were most likely more promising in comparison with treatment of ICR and NCR, especially when patients had over 10% ischemic myocardium.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2018

The parameter choice rules for weighted Tikhonov regularization scheme

The well-known approach to solve the ill-posed problem is Tikhonov regularization scheme. But, the approximate solution of Tikhonov scheme may not contain all the details of the exact solution. To circumference this problem, weighted Tikhonov regularization has been introduced. In this article, we propose two a posteriori parameter choice rules to choose the regularization parameter for weighted Tikhonov regularization and establish the optimal rate of convergence O(δ{sup ((α+1)/(α+2))}) for the scheme based on these proposed rules. The numerical results are documented to demonstrate the significance of the theoretical results.

97 MATHEMATICS AND COMPUTING↗
DOE OSTI2019

Advantage of multi-band solar-induced chlorophyll fluorescence to derive canopy photosynthesis in a temperate forest

When solar-induced chlorophyll fluorescence (SIF) is developed as a novel approach to quantify gross primary production (GPP), narrow SIF emission spectrum around the atmospheric oxygen absorption windows (˜ 761 nm and ˜687 nm) has been widely used to represent SIF and to derive GPP. As SIF is a continuous spectrum, deriving the full broadband SIF emission spectrum over 640–850 nm provides an opportunity to fully explore the potential of SIF in estimating GPP. Using high-frequency measurements of canopy carbon flux and SIF emissions at the atmospheric absorption bands, here we reconstruct the full SIF spectrum from SIF signals at the absorption bands, and then analyze correlations between the GPP and the selected single SIF bands and their combinations using both linear regression (LR) and Gaussian processes regression (GPR). Our results indicate that (1) the red SIF bands (640–700 nm) shows low correlation with GPP due to the strong (re)absorption of red SIF emissions by leaf chlorophyll; (2) the individual bands in near-infrared area (at 720 nm, 740 nm, and 761 nm) can determine about 60% and 62% of the variance in GPP with hourly scale by LR and GPR, respectively, and the combination of those SIF bands provide increased predictive power, explaining 66% and 76% variance in GPP with hourly scale by LR and GPR, respectively; (3) the solar radiation saturation, fraction of direct solar radiation, air temperature and leaf area index may have negative impacts on the SIF-GPP correlations when they are beyond optimal thresholds; and (4) the temporal aggregation of SIF-GPP (daily scale) enhances the correlations as compared with the hourly scale: the daily combination of SIF bands (at 687 nm, 720 nm, and 761 nm) can account for 80% and 93% of variance in daily daytime GPP by LR and GPR, respectively, suggesting that the combination of these three bands of SIF on the daily scale is the best proxy for GPP. Our results provide a new approach to analyze the SIF-GPP correlations using the ground-based full broadband SIF emission, suggesting that multi-bands SIF has a stronger capacity in predicting plant GPP than traditionally used signal band SIF data.

54 ENVIRONMENTAL SCIENCES↗