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At least 1,099 records · Page 61
All sourcesNASA NTRSDOE OSTI
DOE OSTI2025

Interpretation of wide-angle x-ray diffraction patterns from mesophase pitch-based carbon fibers – a simulation and experimental study

Carbon fiber is a critical material in a wide range of industries, where it is highly valued for its high specific strength/stiffness, excellent wear resistance, efficient electrical and thermal transport properties, chemical resistance, and low coefficient of thermal expansion. The properties of a specific carbon fiber are closely tied to its structural characteristics at all length scales. Here, in this work, we applied wide-angle x-ray diffraction to a set of heat-treated mesophase pitch-based carbon fibers, with the goal of elucidating the crystalline structures as a function of fiber orientation. To assist with analysis and interpretation of the experimental data, we employed diffraction pattern simulations using the scalar and vector forms of the Debye scattering equation to determine the influence of basal plane orientation, crystalline ordering (turbostratic-graphitic), and basal plane asymmetry on the diffraction patterns. The results presented here suggest that growth of the transverse crystallites in mesophase pitch-based carbon fiber is fixed until graphitization temperatures are reached. The work completed here provides a framework for the analysis of carbon fiber and other oriented carbon-based materials via diffraction.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Clustering and statistical analyses of air-conditioning intensity and use patterns in residential buildings

Energy conservation in residential buildings has gained increased attention due to its large portion of global energy use and potential of energy savings. Occupant behavior has been recognized as a key factor influencing the energy use and load diversity in buildings, therefore more realistic and accurate air-conditioning (AC) operating schedules are imperative for load estimation in equipment design and operation optimization. With the development of sensor technology, it became easier to access an increasing amount of heating/cooling data from thermal energy metering systems in residential buildings, which provides another possible way to understand building energy usage and occupant behaviors. However, except for cooling energy consumption benchmarking, there currently lacks effective and easy approaches to analyze AC usage and provide actionable insights for occupants. To fill this gap, this study proposes clustering analysis to identify AC use patterns of residential buildings, and develops new key performance indicators (KPIs) and data analytics to explore the AC operation characteristics using the long-term metered cooling energy use data, which is of great importance for inhabitants to understand their thermal energy use and save energy cost through adjustment of their AC use behavior. We demonstrate the proposed approaches in a residential district comprising 300 apartments, located in Zhengzhou, China. Main outcomes include: Representative AC use patterns are developed for three room types of residential buildings in the cold climate zone of China, which can be used as more realistic AC schedules to improve accuracy of energy simulation; Distributions of KPIs on household cooling energy usage are established, which can be used for household AC use intensity benchmarking and performance diagnoses.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗
DOE OSTI2025

Cataloging US state policy patterns towards microgrid deployment

Frequent extreme weather events have called for rigorous and timely efforts for alternative non-wire solutions. These efforts are getting more widespread to offer a perfect alternative as the conventional grid becomes progressively less resilient. One of these solutions is microgrids that can disconnect from the grid and offer grid resilience during an outage. While this technology is still finding its footing in the industry, states across the US are employing policy patterns and forms of instruments to support its deployment. This study includes a systemic review of the US by conducting a binary analysis of all 50 states (including Washington D.C, excluding other US territories) using seven variables. The results show four major policy approaches to microgrids: i) supporting microgrids through a definitive legislative activity leading to further policy action; ii) direct efforts from the public utilities commissions without a concrete legislative push; iii) initiatives from institutions other than the commissions; and lastly, iv) self-initiated community and private consumer efforts. The results help understand what policy instruments are being used in each of these patterns to support this niche technology that still faces regulatory challenges.

Furqan, Maham↗
DOE OSTI2018

A simple model for estimating changes in rainfall erosivity caused by variations in rainfall patterns

Highlights: • A simple relationship was developed for predicting daily erosivity in changing climates. • The relationship depends on precipitation amount and maximum 0.5-h intensity I{sub 0.5} . • The relationship was calibrated using measured climate data and had a R{sup 2} of 0.99. • Simulated daily and annual erosivities were predicted with a R{sup 2} of 0.99 using the relationship. • The relationship was tested using I{sub 24}, showing a R{sup 2} of 0.78 for the simulated data. A major challenge when coupling soil loss models with precipitation forecasts from Global Circulation Models (GCMs) is that their time resolutions do not generally agree. Precipitation forecasts from GCM must be scaled down; however, the distribution of the rainfall intensity, which can affect soil loss as much as precipitation amounts, is usually not considered in this process. Therefore, the objective of this study was to develop a statistical equation for computing event-based rainfall erosivity under changing precipitation patterns using the least amount of information possible. For this purpose, an empirical equation for predicting event-based rainfall erosivity was developed using the product of the total precipitation P and the maximum 0.5-h rainfall intensity, I{sub 0.5}. This equation was calibrated using measured precipitation data from 28 sites in Central Chile and then tested with simulated data with different rainfall patterns from the CLIGEN (CLImate GENerator) weather generator. More than 53,000 rainfall events were analyzed, where the equation consistently provided R{sup 2} values of 0.99 for every dataset used, revealing its robustness when used in potential climate change scenarios in the study site. However, because computing I{sub 0.5} requires estimating precipitation at a high time resolution, the relationship was recalibrated and tested using 1 through 24-h maximum rainfall intensities. Using these intensities, the equation provided erosivity estimates with R{sup 2} ranging from 0.78 to 0.99, where better results were obtained as the resolution of the data increased. This study provides the methodology for building and testing the proposed equation and discusses its advantages and limitations.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2023

In-depth analysis on parallel processing patterns for high-performance Dataframes

The Data Science domain has expanded monumentally in both research and industry communities during the past decade, predominantly owing to the Big Data revolution. Artificial Intelligence (AI) and Machine Learning (ML) are bringing more complexities to data engineering applications, which are now integrated into data processing pipelines to process terabytes of data. Typically, a significant amount of time is spent on data preprocessing in these pipelines, and hence improving its efficiency directly impacts the overall pipeline performance. The community has recently embraced the concept of Dataframes as the de-facto data structure for data representation and manipulation. However, the most widely used serial Dataframes today (R, pandas) experience performance limitations while working on even moderately large data sets. We believe that there is plenty of room for improvement by taking a look at this problem from a high-performance computing point of view. In a prior publication, we presented a set of parallel processing patterns for distributed dataframe operators and the reference runtime implementation, Cylon. In this paper, we are expanding on the initial concept by introducing a cost model for evaluating the said patterns. Furthermore, we evaluate the performance of Cylon on the ORNL Summit supercomputer.

97 MATHEMATICS AND COMPUTING↗
DOE OSTI2023

The physics of desiccation cracks 2: Modeling and prediction of the crack patterns

Here, this paper extends the experimental results of our companion paper by modeling and predicting the onset and pattern formation of desiccation cracks in geomaterials (Ruoyu et al., 2023). Thin-layer silt samples in controlled atmospheric conditions were tested to obtain the surface strain maps with the digital image correlation (DIC) method during dehydration. Support experiments, including consolidation and displacement-controlled triaxial tests, were conducted for the properties of geomaterials. These experimental results were used to validate a viscoplastic theoretical model by comparing cracks and singularities locations that distribute following the Cnoidal wave pattern. A critical value exists in the viscoplastic model that determines the number of singularities, which accurately predicts the number of cracks in the experiment. The critical values contain two crucial parameters: rate sensitivity and λ. Rate sensitivity describes the rate-dependent stress–strain relation, while λ shows the ability of pore pressure redistribution under the external mechanical loading rate. These results provide a new view to analyze the desiccation cracks considering the rate-dependent viscoplasticity.

42 ENGINEERING↗
DOE OSTI2014

Outcomes and Patterns of Failure for Grade 2 Meningioma Treated With Reduced-Margin Intensity Modulated Radiation Therapy

Purpose: The purpose of this study was to evaluate intracranial control and patterns of local recurrence (LR) for grade 2 meningiomas treated with intensity modulated radiation therapy (IMRT) with limited total margin expansions of ≤1 cm. Methods and Materials: We reviewed records of patients with a neuropathological diagnosis of grade 2 meningioma who underwent IMRT at our institution between 2002 and 2012. Actuarial rates were determined by the Kaplan-Meier method from the end of RT. LR was defined as in-field if ≥90% of the recurrence was within the prescription isodose, out-of-field (marginal) if ≥90% was outside of the prescription isodose, and both if neither criterion was met. Results: Between 2002 and 2012, a total of 54 consecutive patients underwent IMRT for grade 2 meningioma. Eight of these patients had total initial margins >1 cm and were excluded, leaving 46 patients for analysis. The median imaging follow-up period was 26.2 months (range, 7-107 months). The median dose for fractionated IMRT was 59.4 Gy (range, 49.2-61.2 Gy). Median clinical target volume (CTV), planning target volume (PTV), and total margin expansion were 0.5 cm, 0.3 cm, and 0.8 cm, respectively. LR occurred in 8 patients (17%), with 2-year and 3-year actuarial local control (LC) of 92% and 74%, respectively. Six of 8 patients (85%) had a known pattern of failure. Five patients (83%) had in-field LR; no patients had marginal LR; and 1 patient (17%) had both. Conclusions: The use of IMRT to treat grade 2 meningiomas with total initial margins (CTV + PTV) ≤1 cm did not appear to compromise outcomes or increase marginal failures compared with other modern retrospective series. Of the 46 patients who had margins ≤1 cm, none experienced marginal failure only. These results demonstrate efficacy and low risk of marginal failure after IMRT treatment of grade 2 meningiomas with reduced margins, warranting study within a prospective clinical trial.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2014

Failure Patterns After Hemithoracic Pleural Intensity Modulated Radiation Therapy for Malignant Pleural Mesothelioma

Purpose: We previously reported our technique for delivering intensity modulated radiation therapy (IMRT) to the entire pleura while attempting to spare the lung in patients with malignant pleural mesothelioma (MPM). Herein, we report a detailed pattern-of-failure analysis in patients with MPM who were unresectable or underwent pleurectomy/decortication (P/D), uniformly treated with hemithoracic pleural IMRT. Methods and Materials: Sixty-seven patients with MPM were treated with definitive or adjuvant hemithoracic pleural IMRT between November 2004 and May 2013. Pretreatment imaging, treatment plans, and posttreatment imaging were retrospectively reviewed to determine failure location(s). Failures were categorized as in-field (within the 90% isodose line), marginal (<90% and ≥50% isodose lines), out-of-field (outside the 50% isodose line), or distant. Results: The median follow-up was 24 months from diagnosis and the median time to in-field local failure from the end of RT was 10 months. Forty-three in-field local failures (64%) were found with a 1- and 2-year actuarial failure rate of 56% and 74%, respectively. For patients who underwent P/D versus those who received a partial pleurectomy or were deemed unresectable, the median time to in-field local failure was 14 months versus 6 months, respectively, with 1- and 2-year actuarial in-field local failure rates of 43% and 60% versus 66% and 83%, respectively (P=.03). There were 13 marginal failures (19%). Five of the marginal failures (38%) were located within the costomediastinal recess. Marginal failures decreased with increasing institutional experience (P=.04). Twenty-five patients (37%) had out-of-field failures. Distant failures occurred in 32 patients (48%). Conclusions: After hemithoracic pleural IMRT, local failure remains the dominant form of failure pattern. Patients treated with adjuvant hemithoracic pleural IMRT after P/D experience a significantly longer time to local and distant failure than patients treated with definitive pleural IMRT. Increasing experience and improvement in target delineation minimize the incidence of avoidable marginal failures.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2014

Are We Appropriately Selecting Therapy For Patients With Cervical Cancer? Longitudinal Patterns-of-Care Analysis for Stage IB-IIB Cervical Cancer

Purpose: We performed a patterns-of-care analysis evaluating the effects of newer technology and recent research findings on treatment decisions over 26 years to determine whether patients with cervical cancer are being appropriately selected for treatment to optimize the therapeutic ratio. Methods and Materials: A retrospective analysis was conducted using the Surveillance, Epidemiology and End Results (SEER) program from 1983 to 2009. We identified 10,933 women with stage IB-IIB cervical carcinoma. Results: Of the 10,933 subjects identified, 40.1% received surgery, 26.8% received radiation (RT), and 33.1% received surgery plus RT. RT use increased after 2000 compared to prior to 2000, with a corresponding decrease in surgery and surgery plus RT. Among patients with risk factors including tumor size >4 cm, positive parametria, and positive lymph nodes, declining use of surgery plus RT was observed. However, 23% of patients with tumors >4 cm, 20% of patients with positive parametria, and 55% of node-positive patients continued to receive surgery plus RT as of 2009. Factors associated with increased use of surgery plus RT included patient age <50 and node-positive status. Conclusions: In this largest patterns-of-care analysis to date for patients with locally advanced cervical cancer, we found a substantial proportion of patients continue to undergo surgery followed by radiation, despite randomized data supporting the use of definitive radiation therapy, with lower morbidity than surgery and radiation.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2014

Extended Field Intensity Modulated Radiation Therapy With Concomitant Boost for Lymph Node–Positive Cervical Cancer: Analysis of Regional Control and Recurrence Patterns in the Positron Emission Tomography/Computed Tomography Era

Purpose: Positron emission tomography/computed tomography (PET/CT) is commonly used for nodal staging in locally advanced cervical cancer; however the false negative rate for para-aortic disease are 20% to 25% in PET-positive pelvic nodal disease. Unless surgically staged, pelvis-only treatment may undertreat para-aortic disease. We have treated patients with PET-positive nodes with extended field intensity modulated radiation therapy (IMRT) to address the para-aortic region prophylactically with concomitant boost to involved nodes. The purpose of this study was to assess regional control rates and recurrence patterns. Methods and Materials: Sixty-one patients with cervical cancer (stage IBI-IVA) diagnosed from 2003 to 2012 with PET-avid pelvic nodes treated with extended field IMRT (45 Gy in 25 fractions with concomitant boost to involved nodes to a median of 55 Gy in 25 fractions) with concurrent cisplatin and brachytherapy were retrospectively analyzed. The nodal location was pelvis-only in 41 patients (67%) and pelvis + para-aortic in 20 patients (33%). There were a total of 179 nodes, with a median number of positive nodes of 2 (range, 1-16 nodes) per patient and a median nodal size of 1.8 cm (range, 0.7-4.5 cm). Response was assessed by PET/CT at 12 to 16 weeks. Results: Complete clinical and imaging response at the first follow-up visit was seen in 77% of patients. At a mean follow-up time of 29 months (range, 3-116 months), 8 patients experienced recurrence. The sites of persistent/recurrent disease were as follows: cervix 10 (16.3%), regional nodes 3 (4.9%), and distant 14 (23%). The rate of para-aortic failure in patients with pelvic-only nodes was 2.5%. There were no significant differences in recurrence patterns by the number/location of nodes, largest node size, or maximum node standardized uptake value. The rate of late grade 3+ adverse events was 4%. Conclusions: Extended field IMRT was well tolerated and resulted in low regional recurrence in node-positive cervical cancer. The dose of 55 Gy in 25 fractions was effective in eradicating disease in involved nodes, with acceptable late adverse events. Distant metastasis is the predominant mode of failure, and the OUTBACK trial may challenge the presented paradigms.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2015

Radical Radiation Therapy After Lung-Sparing Surgery for Malignant Pleural Mesothelioma: Survival, Pattern of Failure, and Prognostic Factors

Purpose: To prospectively assess the survival, patterns of failure, and prognostic factors in a large cohort of patients with malignant pleural mesothelioma who had undergone a novel trimodal therapeutic approach, including lung-sparing surgery, chemotherapy, and subsequent treatment with high doses of intensity modulated radiation therapy (IMRT) to the whole hemithorax. Methods and Materials: The analysis was conducted on the data from 69 patients. Of the 69 patients, 35 underwent extended pleurectomy/decortication (P/D), with resection of the entire pleura, along with portions of the pericardium and diaphragm and 34, partial pleurectomy, defined as partial removal of parietal or visceral pleura for diagnostic purposes, leaving gross tumor behind in all cases. All patients received cisplatin/pemetrexed chemotherapy. Postoperative IMRT was delivered to the entire hemithorax, excluding the intact lung. The IMRT dose was 50 Gy in 25 fractions. Any fluorodeoxyglucose-avid areas or regions of particular concern for residual disease were given a simultaneous boost to 60 Gy. Results: The median follow-up duration was 19 months. No difference was seen in overall survival and locoregional control between the extended P/D group and the partial pleurectomy group. The 2-year overall survival was 65% and 58% in the extended P/D and partial pleurectomy groups, respectively (P=.94). Locoregional control at 2 years was 65% and 64% in the extended P/D and partial pleurectomy groups, respectively (P=.75). The predominant pattern of failure was distant: 19 patients (27.5%) developed distant metastases as the first site of relapse. Gross residual disease after surgery was significantly associated with overall survival (hazard ratio 3.45). One fatal pneumonitis was reported; 14 cases (20%) of grade 2 to 3 pneumonitis were documented. Conclusions: Radical IMRT after lung-sparing surgery and chemotherapy for malignant pleural mesothelioma leads to promising survival results and acceptable toxicity rates. The similarity of survival between patients treated with extended P/D or partial pleurectomy observed in our study is intriguing.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2016

Patterns of Local-Regional Management Following Neoadjuvant Chemotherapy in Breast Cancer: Results From ACOSOG Z1071 (Alliance)

Purpose: American College of Surgeons Oncology Group Z1071 was a prospective trial evaluating the false negative rate of sentinel lymph node (SLN) surgery after neoadjuvant chemotherapy (NAC) in breast cancer patients with initial node-positive disease. Radiation therapy (RT) decisions were made at the discretion of treating physicians, providing an opportunity to evaluate variability in practice patterns following NAC. Methods and Materials: Of 756 patients enrolled from July 2009 to June 2011, 685 met all eligibility requirements. Surgical approach, RT, and radiation field design were analyzed based on presenting clinical and pathologic factors. Results: Of 401 node-positive patients, mastectomy was performed in 148 (36.9%), mastectomy with immediate reconstruction in 107 (26.7%), and breast-conserving surgery (BCS) in 146 patients (36.4%). Of the 284 pathologically node-negative patients, mastectomy was performed in 84 (29.6%), mastectomy with immediate reconstruction in 69 (24.3%), and BCS in 131 patients (46.1%). Bilateral mastectomy rates were higher in women undergoing reconstruction than in those without (66.5% vs 32.2%, respectively, P<.0001). Use of internal mammary RT was low (7.8%-11.2%) and did not differ between surgical approaches. Supraclavicular RT rate ranged from 46.6% to 52.2% and did not differ between surgical approaches but was omitted in 193 or 408 node-positive patients (47.3%). Rate of axillary RT was more frequent in patients who remained node-positive (P=.002). However, 22% of patients who converted to node-negative still received axillary RT. Post-mastectomy RT was more frequently omitted after reconstruction than mastectomy (23.9% vs 12.1%, respectively, P=.002) and was omitted in 19 of 107 patients (17.8%) with residual node-positive disease in the reconstruction group. Conclusions: Most clinically node-positive patients treated with NAC undergoing mastectomy receive RT. RT is less common in patients undergoing reconstruction. There is wide variability in RT fields. These practice patterns conflict with expert recommendations and ongoing trial guidelines. There is a significant need for greater uniformity and guidelines regarding RT following NAC.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2017

Histologic Subtype in Core Lung Biopsies of Early-Stage Lung Adenocarcinoma is a Prognostic Factor for Treatment Response and Failure Patterns After Stereotactic Body Radiation Therapy

Purpose: Stereotactic body radiation therapy (SBRT) has emerged as an effective treatment for early-stage lung cancer. The histologic subtype of surgically resected lung adenocarcinoma is recognized as a prognostic factor, with the presence of solid or micropapillary patterns predicting poor outcomes. We describe the outcomes after SBRT for early-stage lung adenocarcinoma stratified by histologic subtype. Methods and Materials: We identified 119 consecutive patients (124 lesions) with stage I to IIA lung adenocarcinoma who had undergone definitive SBRT at our institution from August 2008 to August 2015 and had undergone core biopsy. Histologic subtyping was performed according to the 2015 World Health Organization classification. Of the 124 tumors, 37 (30%) were a high-risk subtype, defined as containing a component of solid and/or micropapillary pattern. The cumulative incidences of local, nodal, regional, and distant failure were compared between the high-risk and non–high-risk adenocarcinoma subtypes using Gray's test, and multivariable-adjusted hazard ratios (HRs) were estimated from propensity score–weighted Cox regression models. Results: The median follow-up for the entire cohort was 17 months and for surviving patients was 21 months. The 1-year cumulative incidence of and adjusted HR for local, nodal, regional, and distant failure in high-risk versus non–high-risk lesions was 7.3% versus 2.7% (HR 16.8; 95% confidence interval [CI] 3.5-81.4), 14.8% versus 2.6% (HR 3.8; 95% CI 0.95-15.0), 4.0% versus 1.2% (HR 20.9; 95% CI 2.3-192.3), and 22.7% versus 3.6% (HR 6.9; 95% CI 2.2-21.1), respectively. No significant difference was seen with regard to overall survival. Conclusions: The outcomes after SBRT for early-stage adenocarcinoma of the lung correlate highly with histologic subtype, with micropapillary and solid tumors portending significantly higher rates of locoregional and metastatic progression. In this context, the histologic subtype determined from core biopsies is a prognostic factor and could have important implications for patient selection, adjuvant treatment, biopsy methods, and clinical trial design.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2017

Prognostic Relevance of Treatment Failure Patterns in Pediatric High-Grade Glioma: Is There a Role for a Revised Failure Classification System?

Purpose: We sought to investigate the pattern of treatment failure with respect to anatomic extent, radiation dose, and criteria for failure according to the Response Assessment in Neuro-Oncology (RANO). We evaluated the corresponding prognostic significance of these factors in patients with pediatric high-grade glioma (pHGG). Methods and Materials: Fifty-six patients with pHGG were enrolled in an institutional phase 1 to 2 prospective trial that included maximal safe resection and radiation therapy with concurrent and adjuvant erlotinib. The radiation therapy dose administered was 54 to 59.4 Gy at 1.8 Gy/d. Tumor progression was defined according to clinical symptoms and imaging features and was classified in relation to the original extent of the tumor, radiation prescription target volume coverage, and RANO criteria (RANOc). Results: With a median follow-up period of 90 months (range, 70-124 months), progression occurred in 48 patients (85.7%) while 8 (14.3%) were without progression. Central failure represented 42.6% of the total cohort, while in-field, marginal, and distant failures occurred in 7.4%, 9.3%, and 22.2%, respectively. Patients with biopsy or subtotal resection had increased rates of central failure and represented 14.81% and 16.67% of the total cohort, respectively. Tumor progression was classified as local, local plus distant, or distant. Among patients with local failure as a component of failure, 5 were considered to have marginal failure. Patients with frontal, temporal, and parietal disease had the highest rates of multifocal failure. A comparison between responses defined by RANOc demonstrated varied time to death (TTD) from progression. Conclusions: Pediatric high-grade glioma was shown to have high rates of central failure, particularly in cases with limited resection. Patients with central failure had a trend toward more prolonged TTD from failure relative to other failure patterns. The low marginal failure rates seen in this group suggest that less conservative radiation target margins may be possible. TTD from failure varied according to RANO type, suggesting that adult RANOc require modification before being applied to pHGG.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2022

Variation in Proton Craniospinal Irradiation Practice Patterns in the United States: A Pediatric Proton Consortium Registry (PPCR) Study

Craniospinal irradiation (CSI) is commonly used for pediatric brain tumors with a propensity for spread in craniospinal fluid, principally medulloblastoma. Evolving technology has led to the use of highly conformal radiation therapy (RT) techniques for CSI, including proton therapy. Target delineation and plan coverage are critical for CSI, but there is ongoing controversy and variability in these realms, with little available data on practice patterns. We sought to characterize proton CSI practice patterns in the United States by examining CSI plans in the Pediatric Proton/Photon Consortium Registry (PPCR).

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2025

Modeling the microplastic distribution along the Delaware River Estuary: Accumulation patterns and hydrodynamic influences

Microplastic pollution is an escalating environmental concern, particularly in densely populated estuary regions, where it poses significant threats to aquatic life and human health. The dispersion patterns of microplastic particles along estuaries are influenced and complicated by multiple environmental factors such as river flow, tidal mixing, salt intrusion, and estuarine circulation. This study examines the accumulation and dispersion patterns by modeling three typical classes of microplastics in the Delaware River Estuary: synthetic fibers, sinking plastic films, and rising plastic pellets. Our findings reveal specific areas with high microplastic accumulation for each type. Notably, the upper estuary regions exhibit significant retention of rising microplastics, associated with a region with reduced along-thalweg velocities downstream of Trenton, NJ and upstream of Philadelphia, PA. Conversely, synthetic fibers and sinking plastic films accumulate in the flow convergence zone near the bottom salinity front, typically downstream of Philadelphia. All of the microplastic accumulation hot spot locations are controlled by the balance of river discharge and salinity intrusions. During the dry season, microplastic accumulation hot spots shift upstream in the estuary, whereas in the wet season, the strong river discharge pushes them downstream. Furthermore, on the other hand, tidal mixing, settling, and resuspension processes strongly impact the spreading of microplastics along the river.

Delaware River Estuary↗
DOE OSTI2014

X-ray microstructural analysis of nanocrystalline TiZrN thin films by diffraction pattern modeling

A detailed microstructural characterization of nanocrystalline TiZrN thin films grown at different substrate temperatures (T{sub S}) was carried out by X-ray diffraction (XRD). Total diffraction pattern modeling based on more meaningful microstructural parameters, such as crystallite size distribution and dislocation density, was performed to describe the microstructure of the thin films more precisely. This diffraction modeling has been implemented and used mostly to characterize powders, but the technique can be very useful to study hard thin films by taking certain considerations into account. Nanocrystalline films were grown by using the cathodic pulsed vacuum arc technique on stainless steel 316L substrates, varying the temperature from room temperature to 200 °C. Further surface morphology analysis was performed to study the dependence of grain size on substrate temperature using atomic force microscopy (AFM). The crystallite and surface grain sizes obtained and the high density of dislocations observed indicate that the films underwent nanostructured growth. Variations in these microstructural parameters as a function of T{sub S} during deposition revealed a competition between adatom mobility and desorption processes, resulting in a specific microstructure. These films also showed slight anisotropy in their microstructure, and this was incorporated into the diffraction pattern modeling. The resulting model allowed for the films' microstructure during synthesis to be better understood according to the experimental results obtained. - Highlights: • Mobility and desorption competition generates a critical temperature. • A microstructure anisotropy related to the local strain was observed in thin films. • Adatom mobility and desorption influence grain size and microstrain.

36 MATERIALS SCIENCE↗
DOE OSTI2017

Element-resolved Kikuchi pattern measurements of non-centrosymmetric materials

Angle-resolved electron Rutherford backscattering (ERBS) measurements using an electrostatic electron energy analyser can provide unique access to element-resolved crystallographic information. We present Kikuchi pattern measurements of the non-centrosymmetric crystal GaP, separately resolving the contributions of electrons backscattered from Ga and P. In comparison to element-integrated measurements like in the method of electron backscatter diffraction (EBSD), the effect of the absence of a proper 4-fold rotation axis in the point group of GaP can be sensed with a much higher visibility via the element-resolved Ga to P intensity ratio. These element-resolved measurements make it possible to experimentally attribute the previously observed point-group dependent effect in element-integrated EBSD measurements to the larger contribution of electrons scattered from Ga compared to P. - Highlights: •Element specific Kikuchi patterns are presented for GaP. •Absence of a proper four-fold rotation axis is demonstrated. •Ga and P intensity variations after 90 degree rotation have opposite phase. •The asymmetry in the total intensity distribution resembles that of Ga.

36 MATERIALS SCIENCE↗