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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 289 records · Page 16
All sourcesNASA NTRSDOE OSTI
DOE OSTI2014

Quantum theory as the most robust description of reproducible experiments

It is shown that the basic equations of quantum theory can be obtained from a straightforward application of logical inference to experiments for which there is uncertainty about individual events and for which the frequencies of the observed events are robust with respect to small changes in the conditions under which the experiments are carried out. - Highlights: • It is shown that logical inference, that is, inductive reasoning, provides a rational explanation for the success of quantum theory. • The Schrödinger equation is obtained through logical inference applied to robust experiments. • The singlet and triplet states follow from logical inference applied to the Einstein-Podolsky-Rosen-Bohm experiment. • Robustness also leads to the quantum theoretical description of the Stern-Gerlach experiment.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2020

Reproducibility in G 0 W 0 calculations for solids

Ab initio many-body perturbation theory within the GW approximation is a Green's function formalism widely used in the calculation of quasiparticle excitation energies of solids. In what has become an increasingly standard approach, Kohn–Sham eigenenergies, generated from a DFT calculation with a strategically-chosen exchange–correlation functional “starting point”, are used to construct G and W, and then perturbatively corrected by the resultant GW self-energy. In practice, there are several ways to construct the GW self-energy, and these can lead to variations in predicted quasiparticle energies. For example, for ZnO and TiO 2 , the GW fundamental gaps reported in the literature can vary by more than 1 eV depending on the GW code used. In this work, we calculate and analyze GW quasiparticle (QP) energies of these and other systems with three different GW codes: BERKELEYGW, ABINIT and YAMBO. Through a systematic analysis of the GW implementation of these three codes, we identify the primary origin of major discrepancies between codes reported in prior literature to be the different implementations the Coulomb divergence in the Fock exchange term and the frequency integration scheme of the GW self-energy. We then eliminate these discrepancies by using common numerical methods and algorithms, demonstrating that the same quasiparticle energies for a given material can be obtained with different codes, within numerical differences ascribable to the technical details of the underling implementations. This work will be important for users and developers in assessing the precision of future GW applications and methods.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Assessing Single-Source Reproducibility of Human Head Hair Peptide Profiling from Different Regions of the Scalp

Neither microscopical hair comparisons nor mitochondrial DNA sequencing alone, or together, constitutes a basis for personal identification. Due to these limitations, a complementary technique to compare questioned and known hair shafts was investigated. Recently, scientists from Lawrence Livermore National Laboratory's Forensic Science Center and other collaborators developed a peptide profiling technique, which can infer non-synonymous single nucleotide polymorphisms (SNPs) preserved in hair shaft proteins as single amino acid polymorphisms (SAPs). In this study, peptide profiling was evaluated to determine if it can meet forensic expectations when samples are in limited quantities with the possibility that hair samples collected from different areas of a single donor’s scalp (i.e., single source) might not exhibit the same SAP profile. The average dissimilarity, percent differences in SAP profiles within each source, ranged from 0% difference to 29%. This pilot study suggests that more work is needed before peptide profiling of hair can be considered for forensic comparisons.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2011

Effect of Breast Volume on Treatment Reproducibility on a Tomotherapy Unit in the Treatment of Breast Cancer

Purpose: To determine whether the volume of a patient's breast is correlated with reliable daily setup in treatment of breast cancer with a helical tomotherapy treatment unit. Methods and Materials: Thirty-six consecutive patients with breast cancer were treated on a helical tomotherapy unit. During simulation, kilovoltage CT images were obtained for treatment planning. These were fused with daily megavoltage CT scans, and after setup based on skin marks and laser alignment the necessary shifts were carried out. The magnitude of daily shifts (in millimeters) was retrospectively obtained from the daily image fusions, and the breast volume was obtained from the treatment plan. A total of 873 fusion scans were reviewed. Random error for absolute and directional daily shifts was evaluated for correlation to volume. Variation over time was also evaluated. Results: Mean (SD) random shift for all patients in the lateral, longitudinal, and vertical directions was 2.7 (2.0), 3.1 (1.5), and 3.2 (2.6) mm, respectively. Mean (SD) absolute distance shifted was 6.0 (3.5) mm. There was no significant correlation between mean absolute or mean directional daily shift and breast volume (0.08, 0.08, 0.22, and 0.07, respectively). There was no correlation between setup variation and time. Conclusions: In this cohort, there was no correlation between breast volume and degree of daily shift. There was no correlation between time course and setup variation. Therefore, setup variation does not improve or degrade with repeated treatment setups.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2011

Local Setup Reproducibility of the Spinal Column When Using Intensity-Modulated Radiation Therapy for Craniospinal Irradiation With Patient in Supine Position

Purpose: To evaluate local positioning errors of the lumbar spine during fractionated intensity-modulated radiotherapy of patients treated with craniospinal irradiation and to assess the impact of rotational error correction on these uncertainties for one patient setup correction strategy. Methods and Materials: 8 patients (6 adults, 2 children) treated with helical tomotherapy for craniospinal irradiation were retrospectively chosen for this analysis. Patients were immobilized with a deep-drawn Aquaplast head mask. Additionally to daily megavoltage control computed tomography scans of the skull, once-a-week positioning of the lumbar spine was assessed. Therefore, patient setup was corrected by a target point correction, derived from a registration of the patient's skull. The residual positioning variations of the lumbar spine were evaluated applying a rigid-registration algorithm. The impact of different rotational error corrections was simulated. Results: After target point correction, residual local positioning errors of the lumbar spine varied considerably. Craniocaudal axis rotational error correction did not improve or deteriorate these translational errors, whereas simulation of a rotational error correction of the right-left and anterior-posterior axis increased these errors by a factor of 2 to 3. Conclusion: The patient fixation used allows for deformations between the patient's skull and spine. Therefore, for the setup correction strategy evaluated in this study, generous margins for the lumbar spinal target volume are needed to prevent a local geographic miss. With any applied correction strategy, it needs to be evaluated whether or not a rotational error correction is beneficial.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2012

Validating the RTOG-Endorsed Brachial Plexus Contouring Atlas: An Evaluation of Reproducibility Among Patients Treated by Intensity-Modulated Radiotherapy for Head-and-Neck Cancer

Purpose: To evaluate interobserver variability for contouring the brachial plexus as an organ-at-risk (OAR) and to analyze its potential dosimetric consequences in patients treated with intensity-modulated radiotherapy (IMRT) for head-and-neck cancer. Methods and Materials: Using the Radiation Therapy Oncology Group (RTOG)-endorsed brachial plexus contouring atlas, three radiation oncologists independently delineated the OAR on treatment planning computed-tomography (CT) axial scans from 5 representative patients undergoing IMRT to a prescribed dose of 70 Gy for head-and-neck cancer. Dose-volume histograms for the brachial plexus were calculated, and interobserver differences were quantified by comparing various dosimetric statistics. Qualitative analysis was performed by visually assessing the overlapping contours on a single beam's eye view. Results: Brachial plexus volumes for the 5 patients across observers were 26 cc (18-35 cc), 25 cc (21-30 cc), 29 cc (28-32 cc), 29 cc (23-38 cc), and 29 cc (23-34 cc). On qualitative analysis, minimal variability existed except at the inferolateral portion of the OAR, where slight discrepancies were noted among the physicians. Maximum doses to the brachial plexus ranged from 71.6 to 72.6 Gy, 75.2 to 75.8 Gy, 69.1 to 71.0 Gy, 76.4 to 76.9 Gy, and 70.6 to 71.4 Gy. Respective volumes receiving doses greater than 60 Gy (V60) were 8.6 to 10.9 cc, 6.2 to 8.1 cc, 8.2 to 11.6 cc, 8.3 to 10.5 cc, and 5.6 to 9.8 cc. Conclusion: The RTOG-endorsed brachial plexus atlas provides a consistent set of guidelines for contouring this OAR with essentially no learning curve. Adoption of these contouring guidelines in the clinical setting is encouraged.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2012

Day-to-Day Reproducibility of Prostate Intrafraction Motion Assessed by Multiple kV and MV Imaging of Implanted Markers During Treatment

Purpose: When one is performing online setup correction for prostate positioning displacements prior to daily dose delivery, intrafraction motion can become a limiting factor to prostate targeting accuracy. The aim of this study was to quantify and characterize prostate intrafraction motion assessed by multiple kilovoltage (kV) and megavoltage (MV) imaging of implanted markers during treatment in a large patient group. Methods and Materials: Intrafraction motion in the sagittal plane was studied by retrospective analysis of displacements of implanted gold markers on (nearly) lateral kV and MV images obtained at various time points during the treatment fractions (mean, 27 per patient) in 108 consecutive patients. The effective prostate motion in a fraction was defined as the time-weighted mean displacement. Results: Prostate displacements in the sagittal plane increased during the fraction (mean, 0.2 {+-} 0.2 mm/min). Forty percent of patients had a systematic (i.e., appearing in all fractions) effective displacement in the sagittal plane greater than 2 mm. Observed effective population mean-of-means ({mu}eff) +/- systematic ({Sigma}eff) intrafraction motion ({mu}{sub eff} {+-} {Sigma}{sub eff}) was 0.9 {+-} 1.1 mm and 0.6 {+-} 1.0 mm for the anterior-posterior and superior inferior directions, respectively. Corresponding random motion ({sigma}{sub eff}) was 1.2 mm and 1.1 mm. Mean effective prostate motion in the first 5 fractions was predictive for mean effective displacement in the remaining fractions (p < 0.001). Conclusion: For a large subgroup of patients, the systematic component of intrafraction prostate motion was substantial. Intrafraction motion correction prior to each beam delivery or offline corrections could likely be beneficial for the subgroup of patients with significant motion. The systematic component is well predicted by measurements in the initial fractions.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2015

Prospective, Multicenter Validation Study of Magnetic Resonance Volumetry for Response Assessment After Preoperative Chemoradiation in Rectal Cancer: Can the Results in the Literature be Reproduced?

Purpose: To review the available literature on tumor size/volume measurements on magnetic resonance imaging for response assessment after chemoradiotherapy, and validate these cut-offs in an independent multicenter patient cohort. Methods and Materials: The study included 2 parts. (1) Review of the literature: articles were included that assessed the accuracy of tumor size/volume measurements on magnetic resonance imaging for tumor response assessment. Size/volume cut-offs were extracted; (2) Multicenter validation: extracted cut-offs from the literature were tested in a multicenter cohort (n=146). Accuracies were calculated and compared with reported results from the literature. Results: The review included 14 articles, in which 3 different measurement methods were assessed: (1) tumor length; (2) 3-dimensonial tumor size; and (3) whole volume. Study outcomes consisted of (1) complete response (ypT0) versus residual tumor; (2) tumor regression grade 1 to 2 versus 3 to 5; and (3) T-downstaging (ypT<cT). In the multicenter cohort, best results were obtained for the validation of the whole-volume measurements, in particular for the outcome ypT0 (accuracy 44%-80%), with the optimal cut-offs being 1.6 cm{sup 3} (after chemoradiation therapy) and a volume reduction of Δ80% to 86.6%. Accuracies for whole-volume measurements to assess tumor regression grade 1 to 2 were 52% to 61%, and for T-downstaging 51% to 57%. Overall accuracies for tumor length ranged between 48% and 53% and for 3D size measurement between 52% and 56%. Conclusions: Magnetic resonance volumetry using whole-tumor volume measurements can be helpful in rectal cancer response assessment with selected cut-off values. Measurements of tumor length or 3-dimensional tumor size are not helpful. Magnetic resonance volumetry is mainly accurate to assess a complete tumor response (ypT0) after chemoradiation therapy (accuracies up to 80%).

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2015

Coprecipitation of nickel zinc malonate: A facile and reproducible synthesis route for Ni{sub 1−x}Zn{sub x}O nanoparticles and Ni{sub 1−x}Zn{sub x}O/ZnO nanocomposites via pyrolysis

Nanoparticles of Ni{sub 1−x}Zn{sub x}O and Ni{sub 1−x}Zn{sub x}O/ZnO, which can be good candidates for selective gas sensors, were successfully obtained via a two-step synthetic route, in which the nickel zinc malonate precursor was first synthesized by co-precipitation from an aqueous solution, followed by pyrolysis in air at a relatively low temperature (~500 °C). The precursor was characterized by ICP-AES, FTIR and TG and the results indicate the molecular structure of the precursor to be compatible with Ni{sub 1−x}Zn{sub x}(OOCCH{sub 2}COO)·2H{sub 2}O. The decomposition product, characterized using various techniques (FTIR, XRD, ToF-SIMS, SEM, TEM and XPS), was established to be a doped nickel oxide (Ni{sub 1−x}Zn{sub x}O for 0.01≤x≤0.1) and a composite material (Ni{sub 1−x}Zn{sub x}O/ZnO for 0.2≤x≤0.5). To elucidate the form in which the Zn is present in the NiO structure, three analytical techniques were employed: ToF-SIMS, XRD and XPS. While ToF SIMS provided a direct evidence of the presence of Zn in the NiO crystal structure, XRD showed that Zn actually substitutes Ni in the structure and XPS is a bit more specific by indicating that the Zn is present in the form of Zn{sup 2+} ions. - Highlights: • Coprecipitation synthesis of nickel zinc malonate single bath precursor was achieved. • The as synthesized precursors are an homogeneous mixture of nickel and zinc malonate. • XRD, ToF-SIMS, XPS, SEM and TEM was used to characterized decomposition products. • Ni{sub 1−x}Zn{sub x}O nanoparticles (0.01≤x≤0.1) formed after pyrolysis (~500 °C) of precursor. • Ni{sub 1−x}Zn{sub x}O/ZnO nanocomposite (0.2≤x≤0.5) formed after pyrolysis at 500 °C of precursor.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗