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At least 523 records · Page 29
All sourcesNASA NTRSDOE OSTI
DOE OSTI2019

Integration of Local Knowledge is a Key for the Remediation Success of Legacy Uranium Mine Sites - 19564

A key to success, during all aspects of the remediation process on legacy uranium sites, and easily transferable between countries and projects, is the integration of local knowledge. However, before this knowledge can be integrated, local trust and project understanding must be developed. Local trust and project understanding can only be developed through a principle-centred approach to a shared project vision, two-way communication of knowledge, alignment of project goals, and understanding the local needs early in the remediation process. Once public confidence is obtained, local trust and project understanding must be maintained throughout the entirety of the remediation process. Project understanding is an ongoing endeavor that needs continuous communication and varied methods to succeed. During the management of assessment, remediation, and post remediation monitoring on the Saskatchewan Research Council's CLEANS project (remediation of 37 legacy uranium mine sites in Northern Saskatchewan, Canada), integration of local knowledge has been an instrumental tool attributing to success. During site assessment, integration of local knowledge has included the development and implementation of land use surveys to determine realistic travel and occupancy on and adjacent to these legacy sites, and site specific traditional knowledge and land use studies that have contributed to the development of a detailed knowledge of local land use, resource utilization, country food intake, and human history of the sites. The local knowledge gained during the assessment process is invaluable as it provides information required to support remediation planning, such as: valued ecosystem components, human trophic utilization, length of site occupancy, cultural value assessment, and future land use considerations. During remediation planning, local and traditional knowledge can also be incorporated through determination of plant species suitability for revegetation, development and selection of remediation options, and setting realistic sustainable development targets for local project inclusion. During site remediation operations, local involvement can be utilized through direct labour and equipment, cultural resource monitoring (i.e. archaeological and heritage protection), local logistics and historic information transfer, and stakeholder communications and engagement support. Post remediation, local involvement is an efficient mechanism for long-term monitoring, and care and maintenance activities. Although there may be differences between countries, regions and sites, the remediation process on legacy uranium mines can universally be more successful through the integration of local knowledge; while developing rights/stakeholder engagement and capacity building. (authors)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2011

State Enabling Legislation for Commercial-Scale Wind Power Siting and the Local Government Role

Siting of commercial-scale wind facilities (>5MW) is determined primarily by state laws. State laws either leave siting regulation to local governments, prescribe and constrain the role for local governments, establish state standards, or preempt local governance by having state institutions govern siting. Siting regulation is extremely important to the advancement of wind generation in the United States. Major siting decisions lie ahead for state and local governments as the nation diversifies its energy portfolio. An increase in the number of new wind facilities, siting in more locations and in more heavily populated areas, will require attention to the laws and regulations that govern siting. Local governments exercise some authority over commercial-scale wind facility siting in 48 of the 50 states. In 34 states, local governments have substantial autonomy to regulate the siting of most or all commercial-scale wind facilities. A few states authorize local governments to regulate wind facility siting, but make the scope of local regulation subject to limitations defined by state law. Eleven states set size thresholds for state regulatory involvement – with local governments in these states regulating smaller facilities and state boards regulating larger ones (either exclusively or concurrently with local governments). In just under a third of the states, siting of most or all commercial-scale wind facilities requires approval by both state and local government bodies. Only a few states reserve the regulation of siting of all or virtually all commercial-scale wind facilities to state boards and commissions. The content of the applicable regulations is more important, in general, than the level of government responsible for the decision. Several states that assign siting responsibilities to local governments have specified some of the content and the limits of local regulation. About 1/5 of the states have directed boards and commissions to develop statewide regulations to deal with wind facility siting issues subject to state approval. These requirements most often specify standards for setbacks, wildlife, noise, decommissioning, and other issues.

17 WIND ENERGY↗
DOE OSTI2015

Causal localizations in relativistic quantum mechanics

Causal localizations describe the position of quantum systems moving not faster than light. They are constructed for the systems with finite spinor dimension. At the center of interest are the massive relativistic systems. For every positive mass, there is the sequence of Dirac tensor-localizations, which provides a complete set of inequivalent irreducible causal localizations. They obey the principle of special relativity and are fully Poincaré covariant. The boosters are determined by the causal position operator and the other Poincaré generators. The localization with minimal spinor dimension is the Dirac localization. Thus, the Dirac equation is derived here as a mere consequence of the principle of causality. Moreover, the higher tensor-localizations, not known so far, follow from Dirac’s localization by a simple construction. The probability of localization for positive energy states results to be described by causal positive operator valued (PO-) localizations, which are the traces of the causal localizations on the subspaces of positive energy. These causal Poincaré covariant PO-localizations for every irreducible massive relativistic system were, all the more, not known before. They are shown to be separated. Hence, the positive energy systems can be localized within every open region by a suitable preparation as accurately as desired. Finally, the attempt is made to provide an interpretation of the PO-localization operators within the frame of conventional quantum mechanics attributing an important role to the negative energy states.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2011

Multiple-copy state discrimination: Thinking globally, acting locally

We theoretically investigate schemes to discriminate between two nonorthogonal quantum states given multiple copies. We consider a number of state discrimination schemes as applied to nonorthogonal, mixed states of a qubit. In particular, we examine the difference that local and global optimization of local measurements makes to the probability of obtaining an erroneous result, in the regime of finite numbers of copies N, and in the asymptotic limit as N{yields}{infinity}. Five schemes are considered: optimal collective measurements over all copies, locally optimal local measurements in a fixed single-qubit measurement basis, globally optimal fixed local measurements, locally optimal adaptive local measurements, and globally optimal adaptive local measurements. Here an adaptive measurement is one in which the measurement basis can depend on prior measurement results. For each of these measurement schemes we determine the probability of error (for finite N) and the scaling of this error in the asymptotic limit. In the asymptotic limit, it is known analytically (and we verify numerically) that adaptive schemes have no advantage over the optimal fixed local scheme. Here we show moreover that, in this limit, the most naive scheme (locally optimal fixed local measurements) is as good as any noncollective scheme except for states with less than 2% mixture. For finite N, however, the most sophisticated local scheme (globally optimal adaptive local measurements) is better than any other noncollective scheme for any degree of mixture.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2014

Local quanta, unitary inequivalence, and vacuum entanglement

In this work we develop a formalism for describing localised quanta for a real-valued Klein–Gordon field in a one-dimensional box [0,R]. We quantise the field using non-stationary local modes which, at some arbitrarily chosen initial time, are completely localised within the left or the right side of the box. In this concrete set-up we directly face the problems inherent to a notion of local field excitations, usually thought of as elementary particles. Specifically, by computing the Bogoliubov coefficients relating local and standard (global) quantisations, we show that the local quantisation yields a Fock representation of the Canonical Commutation Relations (CCR) which is unitarily inequivalent to the standard one. In spite of this, we find that the local creators and annihilators remain well defined in the global Fock space F{sup G}, and so do the local number operators associated to the left and right partitions of the box. We end up with a useful mathematical toolbox to analyse and characterise local features of quantum states in F{sup G}. Specifically, an analysis of the global vacuum state |0{sub G}〉∈F{sup G} in terms of local number operators shows, as expected, the existence of entanglement between the left and right regions of the box. The local vacuum |0{sub L}〉∈F{sup L}, on the contrary, has a very different character. It is neither cyclic (with respect to any local algebra of operators) nor separating and displays no entanglement between left and right partitions. Further analysis shows that the global vacuum also exhibits a distribution of local excitations reminiscent, in some respects, of a thermal bath. We discuss how the mathematical tools developed herein may open new ways for the analysis of fundamental problems in local quantum field theory.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2018

Amide-linked local anesthetics preferentially target leukemia stem cell through inhibition of Wnt/β-catenin

Highlights: • Local anaesthetics target malignant (LSC) and normal stem cells (HSC). • HSC are less sensitive than LSC to local anaesthetics. • Lidocaine and bupivacaine is more potent than ropivacaine. • Local anaesthetics acts on LSC and HSC via Wnt/β-catenin-dependent manner. The anti-cancer activities of amide-linked local anesthetics have been demonstrated in various types of bulky/differentiated cancer cells. However, whether these anesthetics also affect biological functions of cancer stem cells is largely unknown. In this study, we systematically investigated the effects of three commonly used amide-linked local anesthetics (ropivacaine, lidocaine and bupivacaine) on leukemia stem cell (LSC) derived from two different leukemia diseases (acute myeloid leukemia, n = 8 and chronic myeloid leukemia, n = 8) as well as normal hematopoietic stem cell (HSC) derived from cord blood donors (n = 8) as comparison. We show that all three local anesthetics at clinically achievable concentrations significantly inhibit colony formation and serial replating of LSC in a dose-dependent manner, suggesting their inhibitory effects on LSC differentiation, proliferation and self-renewal. In addition, lidocaine and bupivacaine are more potent than ropivacaine. However, local anesthetics at the same concentrations do not affect LSC and HSC survival, demonstrating the differentiation and self-renewal as the primary effects of local anesthetics on LSC and HSC. Interestingly, local anesthetics display certain selectivity between LSC and HSC by having higher efficacy on LSC than HSC. Mechanism studies using both pharmacological and genetic approaches demonstrate that these local anesthetics target LSC via inhibiting Wnt/β-catenin but not Hedgehog or NF-ĸB signaling. Our work is the first to demonstrate the possible influence of amide-linked local anesthetics on cancer as well as normal stem cells via inhibiting Wnt/β-catenin signaling. Our findings contribute to the comprehensive understanding of potential implication of amide-linked local aesthesis in tumor biology.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2017

Quantitative estimation of localization errors of 3d transition metal pseudopotentials in diffusion Monte Carlo

The necessarily approximate evaluation of non-local pseudopotentials in diffusion Monte Carlo (DMC) introduces localization errors. In this paper, we estimate these errors for two families of non-local pseudopotentials for the first-row transition metal atoms Sc–Zn using an extrapolation scheme and multideterminant wavefunctions. Sensitivities of the error in the DMC energies to the Jastrow factor are used to estimate the quality of two sets of pseudopotentials with respect to locality error reduction. The locality approximation and T-moves scheme are also compared for accuracy of total energies. After estimating the removal of the locality and T-moves errors, we present the range of fixed-node energies between a single determinant description and a full valence multideterminant complete active space expansion. The results for these pseudopotentials agree with previous findings that the locality approximation is less sensitive to changes in the Jastrow than T-moves yielding more accurate total energies, however not necessarily more accurate energy differences. For both the locality approximation and T-moves, we find decreasing Jastrow sensitivity moving left to right across the series Sc–Zn. The recently generated pseudopotentials of Krogel et al. reduce the magnitude of the locality error compared with the pseudopotentials of Burkatzki et al. by an average estimated 40% using the locality approximation. The estimated locality error is equivalent for both sets of pseudopotentials when T-moves is used. Finally, for the Sc–Zn atomic series with these pseudopotentials, and using up to three-body Jastrow factors, our results suggest that the fixed-node error is dominant over the locality error when a single determinant is used.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2024

Classifying photonic topology using the spectral localizer and numerical K -theory

Recently, the spectral localizer framework has emerged as an efficient approach for classifying topology in photonic systems featuring local nonlinearities and radiative environments. In nonlinear systems, this framework provides rigorous definitions for concepts such as topological solitons and topological dynamics, where a system’s occupation induces a local change in its topology due to nonlinearity. For systems embedded in radiative environments that do not possess a shared bulk spectral gap, this framework enables the identification of local topology and shows that local topological protection is preserved despite the lack of a common gap. However, as the spectral localizer framework is rooted in the mathematics of C*-algebras, and not vector bundles, understanding and using this framework requires developing intuition for a somewhat different set of underlying concepts than those that appear in traditional approaches for classifying material topology. In this tutorial, we introduce the spectral localizer framework from a ground-up perspective and provide physically motivated arguments for understanding its local topological markers and associated local measure of topological protection. In doing so, we provide numerous examples of the framework’s application to a variety of topological classes, including crystalline and higher-order topology. We then show how Maxwell’s equations can be reformulated to be compatible with the spectral localizer framework, including the possibility of radiative boundary conditions. To aid in this introduction, we also provide a physics-oriented introduction to multi-operator pseudospectral methods and numerical K-theory, two mathematical concepts that form the foundation for the spectral localizer framework. Finally, we provide some mathematically oriented comments on the C*-algebraic origins of this framework, including a discussion of real C*-algebras and graded C*-algebras that are necessary for incorporating physical symmetries. Looking forward, we hope that this tutorial will serve as an approachable starting point for learning the foundations of the spectral localizer framework.

97 MATHEMATICS AND COMPUTING↗
DOE OSTI2018

Maximally-localized position, Euclidean path-integral, and thermodynamics in GUP quantum mechanics

In dealing with quantum mechanics at very high energies, it is essential to adapt to a quasiposition representation using the maximally-localized states because of the generalized uncertainty principle. In this paper, we look at maximally-localized states as eigenstates of the operator ξ=X+iβP that we refer to as the maximally-localized position. We calculate the overlap between maximally-localized states and show that the identity operator can be expressed in terms of the maximally-localized states. Furthermore, we show that the maximally-localized position is diagonal in momentum-space and that the maximally-localized position and its adjoint satisfy commutation and anti-commutation relations reminiscent of the harmonic oscillator commutation and anti-commutation relations. As application, we use the maximally-localized position in developing the Euclidean path-integral and introduce the compact form of the propagator for maximal localization. The free particle momentum-space propagator and the propagator for maximal localization are analytically evaluated up to quadratic-order in β. Finally, we obtain a path-integral expression for the partition function of a thermodynamic system using the maximally-localized states. The partition function of a gas of noninteracting particles is evaluated. At temperatures exceeding the Planck energy, we obtain the gas’ maximum internal energy N∕2β and recover the zero heat capacity of an ideal gas.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2015

Cdc6 localizes to S- and G2-phase centrosomes in a cell cycle-dependent manner

Highlights: • Cdc6 protein is a component of the pre-replicative complex required for chromosomal replication initiation. • Cdc6 localized to centrosomes of S and G2 phases in a cell cycle-dependent manner. • The centrosomal localization was governed by centrosomal localization signal sequences of Cdc6. • Deletions or substitution mutations on the centrosomal localization signal interfered with centrosomal localization of the Cdc6 proteins. - Abstract: The Cdc6 protein has been primarily investigated as a component of the pre-replicative complex for the initiation of chromosome replication, which contributes to maintenance of chromosomal integrity. Here, we show that Cdc6 localized to the centrosomes during S and G2 phases of the cell cycle. The centrosomal localization was mediated by Cdc6 amino acid residues 311–366, which are conserved within other Cdc6 homologues and contains a putative nuclear export signal. Deletions or substitutions of the amino acid residues did not allow the proteins to localize to centrosomes. In contrast, DsRed tag fused to the amino acid residues localized to centrosomes. These results indicated that a centrosome localization signal is contained within amino acid residues 311–366. The cell cycle-dependent centrosomal localization of Cdc6 in S and G2 phases suggest a novel function of Cdc6 in centrosomes.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2017

Cellular localization of ATBF1 protein and its functional implication in breast epithelial cells

ATBF1, a large transcription factor, was normally localized in nuclei, and its mislocalization to cytoplasm was reported in multiple cancers. However, localization of ATBF1 in breast epithelial cells and its potential functions were unknown. Here, we investigated ATBF1 localization via immunofluorescence staining in different kinds of breast epithelial cells. In MCF10A cells and normal mice mammary gland tissues, ATBF1 was mainly localized in nuclei. Knockdown of ATBF1 expression in MCF10A cells by siRNA promoted cell proliferation. Moreover, ATBF1 was co-localized with chromosome during mitosis, indicating its potential function in mitosis. In an estrogen receptor (ER)-positive breast cancer cell line (MCF7), estrogen induced ATBF1 translocation from cytoplasm to nuclei in an ER dependent pathway. In ER-negative cells (Hs578T and MDA-MB-231), ATBF1 was co-localized with GM130 in cytoplasm, indicating ATBF1 localization was associated with protein modification in golgi body. The results were beneficial for intensive investigation of ATBF1's function with different cellular localization in breast cancer. - Highlights: • Cellular localization of ATBF1 is correlated with its function in breast cancer. • Nuclear ATBF1 was co-localized with chromosome during mitosis normally. • Estrogen induced translocation of cytoplasmic ATBF1 to nuclei in MCF7. • Translocation of ATBF1 in ER{sup +} breast cancer cells was ER dependent. • Cytoplasmic ATBF1 was co-localized with golgi body in ER{sup −} breast cancer cells.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2011

Local Setup Errors in Image-Guided Radiotherapy for Head and Neck Cancer Patients Immobilized With a Custom-Made Device

Purpose: To evaluate the local positioning uncertainties during fractionated radiotherapy of head-and-neck cancer patients immobilized using a custom-made fixation device and discuss the effect of possible patient correction strategies for these uncertainties. Methods and Materials: A total of 45 head-and-neck patients underwent regular control computed tomography scanning using an in-room computed tomography scanner. The local and global positioning variations of all patients were evaluated by applying a rigid registration algorithm. One bounding box around the complete target volume and nine local registration boxes containing relevant anatomic structures were introduced. The resulting uncertainties for a stereotactic setup and the deformations referenced to one anatomic local registration box were determined. Local deformations of the patients immobilized using our custom-made device were compared with previously published results. Several patient positioning correction strategies were simulated, and the residual local uncertainties were calculated. Results: The patient anatomy in the stereotactic setup showed local systematic positioning deviations of 1-4 mm. The deformations referenced to a particular anatomic local registration box were similar to the reported deformations assessed from patients immobilized with commercially available Aquaplast masks. A global correction, including the rotational error compensation, decreased the remaining local translational errors. Depending on the chosen patient positioning strategy, the remaining local uncertainties varied considerably. Conclusions: Local deformations in head-and-neck patients occur even if an elaborate, custom-made patient fixation method is used. A rotational error correction decreased the required margins considerably. None of the considered correction strategies achieved perfect alignment. Therefore, weighting of anatomic subregions to obtain the optimal correction vector should be investigated in the future.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2014

Predictors of Individual Tumor Local Control After Stereotactic Radiosurgery for Non-Small Cell Lung Cancer Brain Metastases

Purpose: To evaluate local control rates and predictors of individual tumor local control for brain metastases from non-small cell lung cancer (NSCLC) treated with stereotactic radiosurgery (SRS). Methods and Materials: Between June 1998 and May 2011, 401 brain metastases in 228 patients were treated with Gamma Knife single-fraction SRS. Local failure was defined as an increase in lesion size after SRS. Local control was estimated using the Kaplan-Meier method. The Cox proportional hazards model was used for univariate and multivariate analysis. Receiver operating characteristic analysis was used to identify an optimal cutpoint for conformality index relative to local control. A P value <.05 was considered statistically significant. Results: Median age was 60 years (range, 27-84 years). There were 66 cerebellar metastases (16%) and 335 supratentorial metastases (84%). The median prescription dose was 20 Gy (range, 14-24 Gy). Median overall survival from time of SRS was 12.1 months. The estimated local control at 12 months was 74%. On multivariate analysis, cerebellar location (hazard ratio [HR] 1.94, P=.009), larger tumor volume (HR 1.09, P<.001), and lower conformality (HR 0.700, P=.044) were significant independent predictors of local failure. Conformality index cutpoints of 1.4-1.9 were predictive of local control, whereas a cutpoint of 1.75 was the most predictive (P=.001). The adjusted Kaplan-Meier 1-year local control for conformality index ≥1.75 was 84% versus 69% for conformality index <1.75, controlling for tumor volume and location. The 1-year adjusted local control for cerebellar lesions was 60%, compared with 77% for supratentorial lesions, controlling for tumor volume and conformality index. Conclusions: Cerebellar tumor location, lower conformality index, and larger tumor volume were significant independent predictors of local failure after SRS for brain metastases from NSCLC. These results warrant further investigation in a prospective setting.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2017

Magnitude of pseudopotential localization errors in fixed node diffusion quantum Monte Carlo

Growth in computational resources has lead to the application of real space diffusion quantum Monte Carlo to increasingly heavy elements. Although generally assumed to be small, we find that when using standard techniques, the pseudopotential localization error can be large, on the order of an electron volt for an isolated cerium atom. We formally show that the localization error can be reduced to zero with improvements to the Jastrow factor alone, and we define a metric of Jastrow sensitivity that may be useful in the design of pseudopotentials. We employ an extrapolation scheme to extract the bare fixed node energy and estimate the localization error in both the locality approximation and the T-moves schemes for the Ce atom in charge states 3+/4+. The locality approximation exhibits the lowest Jastrow sensitivity and generally smaller localization errors than T-moves although the locality approximation energy approaches the localization free limit from above/below for the 3+/4+ charge state. We find that energy minimized Jastrow factors including three-body electron-electron-ion terms are the most effective at reducing the localization error for both the locality approximation and T-moves for the case of the Ce atom. Less complex or variance minimized Jastrows are generally less effective. Finally, our results suggest that further improvements to Jastrow factors and trial wavefunction forms may be needed to reduce localization errors to chemical accuracy when medium core pseudopotentials are applied to heavy elements such as Ce.

36 MATERIALS SCIENCE↗
DOE OSTI2011

Feasibility of using cone-beam CT to verify and reposition the optically guided target localization of linear accelerator based stereotactic radiosurgery

Purpose: The optically guided target localization had been developed for linear accelerator based stereotactic radiosurgery (SRS). Unlike the traditional laser localization, the optical guided target localization utilizes a digital system to position patient. Although the system has been proven accurate and robust, it takes away the capability of physicist to directly double check the target position prior to irradiation. Any error from system calibration, data transformation, or head ring position maintenance will not be caught. The purpose of this work is to investigate the possibility of using cone-beam CT (CBCT) to double check the optically guided SRS target localization and reposition the patient. Methods: A SRS quality assurance (QA) phantom was used in the study. The phantom mounted with SRS head frame was scanned by computer tomography (CT) and planned according to the SRS radiation treatment planning process. A target isocenter is defined and transferred to the optically guided target localization system. The phantom was then transported to the linear accelerator room and localized at the initial position agreed by the optically guided target localization system and the CBCT system. Tests were conducted by moving/rotating the phantom to a set of preset offsets and taking CBCT images. Shifts detected by CBCT were compared with the preset offsets. Agreements between them were studied to see how well the CBCT was in discovering the optically guided target localization error. Results: Experiment results demonstrated good agreement between the CBCT detected phantom shift and the preset offset, when the offset is above 1 mm shift or 0.2 degree rotation. Offset less than 1 mm shift or 0.2 degree rotation was not detectable by CBCT. Conclusions: The study concludes that the CBCT is able to discover the optically guided target localization error due to the system calibration or had ring migration. It is a valuable second check tool for SRS target localization quality assurance. The accuracy of CBCT in estimating patient positioning deviation satisfies the SRS procedures with generous tumor size and margin that can tolerate 1 mm or 0.2 degree accuracy. This avoids sending patient home without treatment. CBCT can be neither used as a primary SRS target localization nor can it be used to reposition the patient that cannot tolerate 1 mm shift or 0.2 degree rotation.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2016

SU-G-IeP2-05: Effect of Localizer Type and Patient Off-Centering On CT Radiation Dose with Use of Automatic Tube Current Modulation

Purpose: Apparent patient size in CT localizers varies with localizer type and patient positioning, resulting in variation in effective mAs as guided by Tube Current Modulation (TCM). Our aim was to investigate the effects of vertical off-centering on CTDI-vol when using different localizer types and TCM strengths. Methods: A CTDI body phantom was scanned using an abdominal protocol with three TCM strengths (Siemens Definition AS40, CAREDose4D; very weak, average, very strong). Data was acquired at 11 table height positions; with phantom center at isocenter and at 10 other positions between 142mm below and 53mm above. At each position, scans were acquired using 5 different localizer types: PA, AP, Lateral, PA+Lateral, and Lateral+PA. CTDI-vol was recorded for the 165 combinations of table height, localizer type, and TCM strength, and magnification factors measured from localizer images. Results: Magnification factors from AP and PA localizers ranged from 0.79–1.11 and 1.35–0.91, respectively from lowest to highest positions (highest with phantom located closest to X-ray tube), with a smaller impact when using Lateral, PA+Lateral, Lateral+PA localizer types, all of which behaved similarly. For an average TCM strength and PA localizer, CTDI-vol ranged from 75% higher to 12% lower than the isocenter value for the lowest to highest table positions, respectively. For table positions ranging from lowest to highest, CTDI-vol ranged from −23% to 17% for AP, from −8% to 0.3% for lateral and from −7% to 1% for a combination of PA and Lateral in either order. Similar behavior was found for different TCM strengths, but effects were more pronounced for very strong compared with very weak modulation strengths. Conclusion: Patient off-centering substantially impacts radiation dose, which depends on the amount of vertical offcentering and type of the localizer used. The combination of PA and Lateral localizers is most robust against effects of patient off-centering.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2024

An explainable variational autoencoder model for three-dimensional acoustic emission source localization in hollow cylindrical structures

We introduce an explainable variational autoencoder for three-dimensional (3D) localization of acoustic emission sources in hollow cylindrical structures, with an unsupervised approach. This research capitalizes on multi-arrival waveforms generated by helical path propagation in cylindrical geometries to enable efficient two-receiver localization. By integrating the modal characteristics of Lamb modes under multi-path conditions, we demonstrate that two sets of time-of-arrival differences and peak amplitudes extracted from one receiver can serve as effective localization features. This initial approach identifies four potential source locations, highlighting the feasibility of two-receiver source localization using traditional feature extraction methods. However, direct extraction can be challenging when mode overlaps occur, complicating the localization process. To address this, our work proposes a novel waveform-based method. This method leverages the consistent dispersion characteristics within isotropic materials, where each unique combination of mode arrival times and peak amplitudes constructs a distinct waveform. This distinctiveness overcomes the ambiguities associated with mode overlaps, significantly enhancing the method’s precision and robustness. Our approach adopts a data-driven strategy for waveform-based localization using variational autoencoder (VAE). VAE discerns waveform patterns for localization, while also addressing data uncertainties. The VAE’s encoder and decoder networks capture the localization process and the source’s influence on waveform generation, respectively, guiding latent variables to segregate waveforms by source in the latent space. The design of the learning process focuses on specific localization characteristics to enhance result explainability. Localization predictions are generated by projecting test waveforms, not included in the training set, onto a trained latent space. The prediction is determined using a nearest-neighbor approach based on the closest latent representation of a source. Validation with pencil-lead-break tests on a metallic pipe confirmed our method’s effectiveness, achieving an averaged 3D localization accuracy of 0.84.

Lee, Guan-Wei↗
DOE OSTI2018

Systematic Quantum Cluster Typical Medium Method for the Study of Localization in Strongly Disordered Electronic Systems

Great progress has been made in recent years towards understanding the properties of disordered electronic systems. In part, this is made possible by recent advances in quantum effective medium methods which enable the study of disorder and electron-electronic interactions on equal footing. They include dynamical mean-field theory and the Coherent Potential Approximation, and their cluster extension, the dynamical cluster approximation. Despite their successes, these methods do not enable the first-principles study of the strongly disordered regime, including the effects of electronic localization. The main focus of this review is the recently developed typical medium dynamical cluster approximation for disordered electronic systems. This method has been constructed to capture disorder-induced localization and is based on a mapping of a lattice onto a quantum cluster embedded in an effective typical medium, which is determined self-consistently. Unlike the average effective medium-based methods mentioned above, typical medium-based methods properly capture the states localized by disorder. The typical medium dynamical cluster approximation not only provides the proper order parameter for Anderson localized states, but it can also incorporate the full complexity of Density-Functional Theory (DFT)-derived potentials into the analysis, including the effect of multiple bands, non-local disorder, and electron-electron interactions. After a brief historical review of other numerical methods for disordered systems, we discuss coarse-graining as a unifying principle for the development of translationally invariant quantum cluster methods. Together, the Coherent Potential Approximation, the Dynamical Mean-Field Theory and the Dynamical Cluster Approximation may be viewed as a single class of approximations with a much-needed small parameter of the inverse cluster size which may be used to control the approximation. We then present an overview of various recent applications of the typical medium dynamical cluster approximation to a variety of models and systems, including single and multiband Anderson model, and models with local and off-diagonal disorder. We then present the application of the method to realistic systems in the framework of the DFT and demonstrate that the resulting method can provide a systematic first-principles method validated by experiment and capable of making experimentally relevant predictions. We also discuss the application of the typical medium dynamical cluster approximation to systems with disorder and electron-electron interactions. Most significantly, we show that in the limits of strong disorder and weak interactions treated perturbatively, that the phenomena of 3D localization, including a mobility edge, remains intact. However, the metal-insulator transition is pushed to larger disorder values by the local interactions. We also study the limits of strong disorder and strong interactions capable of producing moment formation and screening, with a non-perturbative local approximation. Here, we find that the Anderson localization quantum phase transition is accompanied by a quantum-critical fan in the energy-disorder phase diagram.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗