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At least 289 records · Page 16

Chemical Biology And Endomembrane Trafficking In Plants

Endomembrane trafficking is essential for coordinated growth and development in plants and response to environment. In particular, key plasma membrane proteins such as PIN auxin transporters and the BRI1 brassinosteroid receptor translocate dynamically between the endosomes and plasma membrane. We utilized a previously published large‐scale chemical library screening approach in which we identified small molecules that inhibited pollen germination or tube growth. This tip growth requires exocytosis, endocytosis and other endomembrane trafficking processes We then identified groups of small molecules that affect trafficking of PIN auxin transporters and other plasma membrane proteins in Arabidopsis roots. One of these compounds (ES2) targets the essential EXO70A1 component of the exocyst complex in Arabidopsis which is necessary for normal development. In Arabidopsis, there are 23 EXO70 genes (in mammals and yeast they are low copy number) where, among other roles, they appear to be involved in autophagy, cell division and pathogen responses. ES2 targets the exocyst complex in plants as well as mammals including humans where defective recycling/exocytosis have been correlated with disease. To our knowledge, ES2 is the first bioactive compound known to have this specificity. To examine exocytosis and its regulation in more detail, we have examined exo70 mutants, generated EXO70A1 structural data and are examining additional small molecules that may affect recycling/exocytosis. Support or Funding Information Acknowledgement: This work was supported by the US Department of Energy DE‐FG02‐02ER15295 (GRH, NVR).

Hicks, Glenn R.↗

Experimental Investigation on Additively Manufactured Transpiration and Film Cooling Structures

The last 50 years has witnessed significant improvement in film cooling technologies while transpiration cooling is still not implemented in turbine airfoil cooling. Although transpiration cooling could provide higher cooling efficiency with less coolant consumption compared to film cooling, the fine pore structure and high porosity in transpiration cooling metal media always raised difficulties in conventional manufacturing. Recently, the rapid development of additive manufacturing (AM) has provided a new perspective to address such challenge. With the capability of the innovative powder bed selective laser metal sintering (SLMS) AM technology, the complex geometries of transpiration cooling part could be precisely fabricated and endued with improved mechanical strength. This study utilized the SLMS AM technology to fabricate the transpiration cooling and film cooling structures with Inconel 718 superalloy. Five different types of porous media including two perforated plates with different hole pitches, metal sphere packing, metal wire mesh, and blood vessel shaped passages for transpiration cooling were fabricated by EOS M290 system. One laidback fan-shaped film cooling coupon was also fabricated with the same printing process as the control group. Heat transfer tests under three different coolant mass flow rates and four different mainstream temperatures were conducted to evaluate the cooling performance of the printed coupons. The effects of geometry parameters including porosity, surface outlet area ratio, and internal solid–fluid interface area ratio were investigated as well. The results showed that the transpiration cooling structures generally had higher cooling effectiveness than film cooling structure. The overall average cooling effectiveness of blood vessel-shaped transpiration cooling reached 0.35, 0.5, and 0.57, respectively, with low (1.2%), medium (2.4%), and high (3.6%) coolant injection ratios. The morphological parameters analysis showed the major factor that affected the cooling effectiveness most was the internal solid–fluid interface area ratio for transpiration cooling. This study showed that additive manufactured transpiration cooling could be a promising alternative method for turbine blade cooling and worthwhile for further investigations.

Engineering↗

Foreign object detection and removal to improve automated analysis of chest radiographs

Purpose: Chest radiographs commonly contain projections of foreign objects, such as buttons, brassier clips, jewellery, or pacemakers and wires. The presence of these structures can substantially affect the output of computer analysis of these images. An automated method is presented to detect, segment, and remove foreign objects from chest radiographs.Methods: Detection is performed using supervised pixel classification with a kNN classifier, resulting in a probability estimate per pixel to belong to a projected foreign object. Segmentation is performed by grouping and post-processing pixels with a probability above a certain threshold. Next, the objects are replaced by texture inpainting.Results: The method is evaluated in experiments on 257 chest radiographs. The detection at pixel level is evaluated with receiver operating characteristic analysis on pixels within the unobscured lung fields and an A{sub z} value of 0.949 is achieved. Free response operator characteristic analysis is performed at the object level, and 95.6% of objects are detected with on average 0.25 false positive detections per image. To investigate the effect of removing the detected objects through inpainting, a texture analysis system for tuberculosis detection is applied to images with and without pathology and with and without foreign object removal. Unprocessed, the texture analysis abnormality score of normal images with foreign objects is comparable to those with pathology. After removing foreign objects, the texture score of normal images with and without foreign objects is similar, while abnormal images, whether they contain foreign objects or not, achieve on average higher scores.Conclusions: The authors conclude that removal of foreign objects from chest radiographs is feasible and beneficial for automated image analysis.

62 RADIOLOGY AND NUCLEAR MEDICINE↗

TH-E-18A-01: Developments in Monte Carlo Methods for Medical Imaging

Monte Carlo simulation methods are widely used in medical physics research and are starting to be implemented in clinical applications such as radiation therapy planning systems. Monte Carlo simulations offer the capability to accurately estimate quantities of interest that are challenging to measure experimentally while taking into account the realistic anatomy of an individual patient. Traditionally, practical application of Monte Carlo simulation codes in diagnostic imaging was limited by the need for large computational resources or long execution times. However, recent advancements in high-performance computing hardware, combined with a new generation of Monte Carlo simulation algorithms and novel postprocessing methods, are allowing for the computation of relevant imaging parameters of interest such as patient organ doses and scatter-to-primaryratios in radiographic projections in just a few seconds using affordable computational resources. Programmable Graphics Processing Units (GPUs), for example, provide a convenient, affordable platform for parallelized Monte Carlo executions that yield simulation times on the order of 10{sup 7} xray/ s. Even with GPU acceleration, however, Monte Carlo simulation times can be prohibitive for routine clinical practice. To reduce simulation times further, variance reduction techniques can be used to alter the probabilistic models underlying the x-ray tracking process, resulting in lower variance in the results without biasing the estimates. Other complementary strategies for further reductions in computation time are denoising of the Monte Carlo estimates and estimating (scoring) the quantity of interest at a sparse set of sampling locations (e.g. at a small number of detector pixels in a scatter simulation) followed by interpolation. Beyond reduction of the computational resources required for performing Monte Carlo simulations in medical imaging, the use of accurate representations of patient anatomy is crucial to the virtual generation of medical images and accurate estimation of radiation dose and other imaging parameters. For this, detailed computational phantoms of the patient anatomy must be utilized and implemented within the radiation transport code. Computational phantoms presently come in one of three format types, and in one of four morphometric categories. Format types include stylized (mathematical equation-based), voxel (segmented CT/MR images), and hybrid (NURBS and polygon mesh surfaces). Morphometric categories include reference (small library of phantoms by age at 50th height/weight percentile), patient-dependent (larger library of phantoms at various combinations of height/weight percentiles), patient-sculpted (phantoms altered to match the patient's unique outer body contour), and finally, patient-specific (an exact representation of the patient with respect to both body contour and internal anatomy). The existence and availability of these phantoms represents a very important advance for the simulation of realistic medical imaging applications using Monte Carlo methods. New Monte Carlo simulation codes need to be thoroughly validated before they can be used to perform novel research. Ideally, the validation process would involve comparison of results with those of an experimental measurement, but accurate replication of experimental conditions can be very challenging. It is very common to validate new Monte Carlo simulations by replicating previously published simulation results of similar experiments. This process, however, is commonly problematic due to the lack of sufficient information in the published reports of previous work so as to be able to replicate the simulation in detail. To aid in this process, the AAPM Task Group 195 prepared a report in which six different imaging research experiments commonly performed using Monte Carlo simulations are described and their results provided. The simulation conditions of all six cases are provided in full detail, with all necessary data on material composition, source, geometry, scoring and other parameters provided. The results of these simulations when performed with the four most common publicly available Monte Carlo packages are also provided in tabular form. The Task Group 195 Report will be useful for researchers needing to validate their Monte Carlo work, and for trainees needing to learn Monte Carlo simulation methods. In this symposium we will review the recent advancements in highperformance computing hardware enabling the reduction in computational resources needed for Monte Carlo simulations in medical imaging. We will review variance reduction techniques commonly applied in Monte Carlo simulations of medical imaging systems and present implementation strategies for efficient combination of these techniques with GPU acceleration. Trade-offs involved in Monte Carlo acceleration by means of denoising and “sparse sampling” will be discussed. A method for rapid scatter correction in cone-beam CT (<5 min/scan) will be presented as an illustration of the simulation speeds achievable with optimized Monte Carlo simulations. We will also discuss the development, availability, and capability of the various combinations of computational phantoms for Monte Carlo simulation of medical imaging systems. Finally, we will review some examples of experimental validation of Monte Carlo simulations and will present the AAPM Task Group 195 Report. Learning Objectives: Describe the advances in hardware available for performing Monte Carlo simulations in high performance computing environments. Explain variance reduction, denoising and sparse sampling techniques available for reduction of computational time needed for Monte Carlo simulations of medical imaging. List and compare the computational anthropomorphic phantoms currently available for more accurate assessment of medical imaging parameters in Monte Carlo simulations. Describe experimental methods used for validation of Monte Carlo simulations in medical imaging. Describe the AAPM Task Group 195 Report and its use for validation and teaching of Monte Carlo simulations in medical imaging.

60 APPLIED LIFE SCIENCES↗

MO-D-213-02: Quality Improvement Through a Failure Mode and Effects Analysis of Pediatric External Beam Radiotherapy

Purpose: To conduct a failure mode and effects analysis (FMEA) as per AAPM Task Group 100 on clinical processes associated with teletherapy, and the development of mitigations for processes with identified high risk. Methods: A FMEA was conducted on clinical processes relating to teletherapy treatment plan development and delivery. Nine major processes were identified for analysis. These steps included CT simulation, data transfer, image registration and segmentation, treatment planning, plan approval and preparation, and initial and subsequent treatments. Process tree mapping was utilized to identify the steps contained within each process. Failure modes (FM) were identified and evaluated with a scale of 1–10 based upon three metrics: the severity of the effect, the probability of occurrence, and the detectability of the cause. The analyzed metrics were scored as follows: severity – no harm = 1, lethal = 10; probability – not likely = 1, certainty = 10; detectability – always detected = 1, undetectable = 10. The three metrics were combined multiplicatively to determine the risk priority number (RPN) which defined the overall score for each FM and the order in which process modifications should be deployed. Results: Eighty-nine procedural steps were identified with 186 FM accompanied by 193 failure effects with 213 potential causes. Eighty-one of the FM were scored with a RPN > 10, and mitigations were developed for FM with RPN values exceeding ten. The initial treatment had the most FM (16) requiring mitigation development followed closely by treatment planning, segmentation, and plan preparation with fourteen each. The maximum RPN was 400 and involved target delineation. Conclusion: The FMEA process proved extremely useful in identifying previously unforeseen risks. New methods were developed and implemented for risk mitigation and error prevention. Similar to findings reported for adult patients, the process leading to the initial treatment has an associated high risk.

60 APPLIED LIFE SCIENCES↗

Dependence of Multiparticle Processes on the Interaction-Region Size in Collisions of High-Energy Protons and Nuclei

The problem of the dependence of multiparticle reaction-product formation on the interactionregion size is considered both at cosmic-ray and accelerator energies. In cosmic rays, a comparative analysis of interactions induced by protons and light nuclei was performed on the basis of data obtained by the Stratosphere Collaboration. At accelerator energies, the problem was studied by employing data of the EMU Collaboration. The results revealed a substantial distinction between the production processes in these event groups. An analysis of interactions between light nuclei, (C, O, Ne) + (C/N/O); between intermediate and light nuclei, (Si, S) + (C/N/O); and between heavy nuclei, (Au, Pb) + (Ag/Br), showed that there is a sizable enhancement of fluctuations as the size of the interaction region becomes smaller. A sharp growth of multiplicity and pseudorapidity correlations in the most central interactions, (C, O, Ne) + (C/N/O), is interpreted as a manifestation of internal virtual alpha-particle clustering of light nuclei.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

Electrochemical Separation of Ag 2 S and Cu 2 S from Molten Sulfide Electrolyte

The production of precious metals from Cu-rich sources such as ore products or secondary sources is slow and complex largely due to limited solubility in aqueous electrolytes. This results in sequential processing with various electrolytes and chemistries, where first Cu is electrorefined, followed by Ag, followed by Au and the platinum group metals. These are separate processes, often conducted in separate electrorefining and electrowinning facilities. The chemical properties of molten sulfides, and their ability to operate at a temperature where liquid metal cathodes are used, suggest the possibility of an alternative, streamlined processing route for Cu and precious metals. Unfortunately, little thermodynamic or electrochemical information is available regarding the behavior of Cu and precious metal sulfides in molten sulfide electrolytes. Herein, the relative activity of the Cu 2 S-Ag 2 S pseudobinary dissolved in a BaS-La 2 S 3 supporting electrolyte is measured at 1523 K. It was found that the supporting electrolyte favors mixing with Ag 2 S over Cu 2 S. Molten sulfide electrolysis of Cu and Ag was conducted, with results in good agreement with the thermodynamic model. It is found that the Ag-Cu cathode chemistry will influence the electrochemical selectivity in the Ag-Cu-Ba-La-S system.

25 ENERGY STORAGE↗

CAD-centric Computation Management System for a Virtual TBM

HyPerComp Inc. in research collaboration with TEXCEL has set out to build a Virtual Test Blanket Module (VTBM) computational system to address the need in contemporary fusion research for simulating the integrated behavior of the blanket, divertor and plasma facing components in a fusion environment. Physical phenomena to be considered in a VTBM will include fluid flow, heat transfer, mass transfer, neutronics, structural mechanics and electromagnetics. We seek to integrate well established (third-party) simulation software in various disciplines mentioned above. The integrated modeling process will enable user groups to interoperate using a common modeling platform at various stages of the analysis. Since CAD is at the core of the simulation (as opposed to computational meshes which are different for each problem,) VTBM will have a well developed CAD interface, governing CAD model editing, cleanup, parameter extraction, model deformation (based on simulation,) CAD-based data interpolation. In Phase-I, we built the CAD-hub of the proposed VTBM and demonstrated its use in modeling a liquid breeder blanket module with coupled MHD and structural mechanics using HIMAG and ANSYS. A complete graphical user interface of the VTBM was created, which will form the foundation of any future development. Conservative data interpolation via CAD (as opposed to mesh-based transfer), the regeneration of CAD models based upon computed deflections, are among the other highlights of phase-I activity.

22 GENERAL STUDIES OF NUCLEAR REACTORS↗

Limiting Magnitude, τ, t eff , and Image Quality in DES Year 1

The Dark Energy Survey (DES) is an astronomical imaging survey being completed with the DECam imager on the Blanco telescope at CTIO. After each night of observing, the DES data management (DM) group performs an initial processing of that night's data, and uses the results to determine which exposures are of acceptable quality, and which need to be repeated. The primary measure by which we declare an image of acceptable quality is $\tau$, a scaling of the exposure time. This is the scale factor that needs to be applied to the open shutter time to reach the same photometric signal to noise ratio for faint point sources under a set of canonical good conditions. These conditions are defined to be seeing resulting in a PSF full width at half maximum (FWHM) of 0.9" and a pre-defined sky brightness which approximates the zenith sky brightness under fully dark conditions. Point source limiting magnitude and signal to noise should therefore vary with t in the same way they vary with exposure time. Measurements of point sources and $\tau$ in the first year of DES data confirm that they do. In the context of DES, the symbol $t_{eff}$ and the expression "effective exposure time" usually refer to the scaling factor, $\tau$, rather than the actual effective exposure time; the "effective exposure time" in this case refers to the effective duration of one second, rather than the effective duration of an exposure.

79 ASTRONOMY AND ASTROPHYSICS↗

SCALE MG Cross Section Processing for High Void BWR Using the AMPX 1,597-group Library

The CASL VERA neutronic simulator MPACT has been developed by Oak Ridge National Laboratory (ORNL) and University of Michigan for the pressurized water reactor applications. The MPACT capability is being extended for the boiling water reactor (BWR) analysis. Recent investigation showed that the MPACT multigroup (MG) library has limitations for high void BWR fuels because of the very coarse group structure. Since the MPACT MG library is generated with the AMPX/SCALE code package developed at ORNL, enhancement of the AMPX/SCALE code package and its MG library must be preceded to improve the accuracy of the MPACT MG library. Therefore, a new 1597-group structure was developed and an AMPX 1597-group library was generated. This ultra-fine group (UFG) library resulted in significant improvements in accuracy for fast spectrum systems compared to the AMPX 252-group results. However, the use of the AMPX 1597-group library requires significantly increased burden on memory and computing time.

22 GENERAL STUDIES OF NUCLEAR REACTORS↗

Essay: Bob Siemann-SLC Days at SLAC

Bob Siemann was a great experimentalist and an excellent teacher.We will greatly miss him. Bob came to SLAC in early 1991 to work on the Stanford Linear Collider (SLC). The SLC was a challenging accelerator which began operating in the late 1980's but still had numerous obstacles to be overcome years into operation. One of the compounding difficulties was making reproducible measurements, since the stability of the collider was poor and the diagnostics were insufficient. Bob dove into this challenge and helped design experiments and diagnostics that provided further clarity. I first got to know Bob while I was still a graduate student, trying to finish my thesis and performing some experimental studies on the SLC, which, at the time, was proving to be very difficult. Most of my expertise had been in beam theory and simulation. Dealing with the real issues of the accelerator was challenging. Bob helped me understand the difference between systematic and statistical errors, and separate operational issues from the fundamental physics. His way of teaching was not to provide an explanation but to ask enough questions so that I could find the answer on my own - this was the best way to learn. I later asked Bob to be a reader on my thesis. As in all things, he took this role extremely seriously. He read through the draft and marked every page to the point where I was regretting my decision. However, his questions again helped me understand my own work better and greatly improved my thesis. Bob was also the de facto leader of an effort focused on the damping rings and the bunch compressors. He was great to work with. He made people think for themselves and refused to simply provide answers. He also worked hard himself, expressing real interest and curiosity. After the studies of the SLC damping rings identified a sawtooth instability due to the vacuum chamber impedance as a source of many downstream fluctuations, Bob took charge of upgrading the rings. As part of this program, I suggested an extensive upgrade that also replaced the dipoles with combined function magnets which might have reduced the horizontal emittance another factor of 3. Although he was extremely busy, Bob helped me develop the proposal and understand the magnetic limitations as well as the potential impacts on the beam dynamics. He helped me consider issues well beyond my initial scope. While the proposal never went anywhere and I think Bob had been aware that there was no funding to pursue the option, he saw that it would be a great learning experience for me and it was. In the early 1990's I had simulated a new regime for the beam-ion instability and, with Frank Zimmermann, I developed a model for the effect which was predicted to occur within the high current, low emittance bunch trains in future storage rings or linear colliders. I thought this was pretty good work but Bob convinced me that the next step had to be confirming the theory with measurements. Because the growth rate was inversely dependent on beam sizes and proportional to the vacuum pressure, measurements required significantly increasing the vacuum pressure in existing facilities. Most people discounted trying such an experiment, but with Bob's urging and suggestions and John Byrd's excitement, we managed to make the measurements at the Advanced Light Source (ALS) at Berkeley. By the mid-1990's Bob was completely focused on advanced acceleration concepts and I was not interacting with him as often. At the time, SLAC was putting together a large effort in designing and documenting a design for the Next Linear Collider (NLC) while constructing the NLC Test Accelerator. Bob was worried that a straightforward extrapolation of the microwave technology would be difficult to bring to fruition because of the cost. He wanted to focus on more cost-effective approaches that could enable future accelerators for high energy physics. As usual, he was correct. The experimental programs that he started in direct laser acceleration and plasma-wakefield acceleration have made great progress. He accomplished this with lots of hard work and by engaging the people around him, especially students and postdocs. In the process, he created a group of extremely talented people which has enabled these technologies to be developed to the point where it seems likely that they are viable and will offer two cost-effective approaches to high-gradient acceleration.

43 PARTICLE ACCELERATORS↗

Thermal neutron detector and gamma-ray spectrometer utilizing a single material

A combined thermal neutron detector and gamma-ray spectrometer system, including: a detection medium including a lithium chalcopyrite crystal operable for detecting thermal neutrons in a semiconductor mode and gamma-rays in a scintillator mode; and a photodetector coupled to the detection medium also operable for detecting the gamma rays. Optionally, the detection medium includes a .sup.6LiInSe.sub.2 crystal. Optionally, the detection medium comprises a compound formed by the process of: melting a Group III element; adding a Group I element to the melted Group III element at a rate that allows the Group I and Group III elements to react thereby providing a single phase I-III compound; and adding a Group VI element to the single phase I-III compound and heating; wherein the Group I element includes lithium.

36 MATERIALS SCIENCE↗

A 2D/1D coupling neutron transport method based on the matrix MOC and NEM methods

A new 2D/1D coupling method based on the matrix MOC method (MMOC) and nodal expansion method (NEM) is proposed for solving the three-dimensional heterogeneous neutron transport problem. The MMOC method, used for radial two-dimensional calculation, constructs a response matrix between source and flux with only one sweep and then solves the linear system by using the restarted GMRES algorithm instead of the traditional trajectory sweeping process during within-group iteration for angular flux update. Long characteristics are generated by using the customization of commercial software AutoCAD. A one-dimensional diffusion calculation is carried out in the axial direction by employing the NEM method. The 2D and ID solutions are coupled through the transverse leakage items. The 3D CMFD method is used to ensure the global neutron balance and adjust the different convergence properties of the radial and axial solvers. A computational code is developed based on these theories. Two benchmarks are calculated to verify the coupling method and the code. It is observed that the corresponding numerical results agree well with references, which indicates that the new method is capable of solving the 3D heterogeneous neutron transport problem directly. (authors)

97 MATHEMATICS AND COMPUTING↗

Determination of Activity of Neodymium(III) in Molten Eutectic LiCl-KCl using Electrochemical Methods

The pyrochemical recycling of actinides is a promising option for closing the nuclear fuel cycle. The technology is particularly attractive for recycle of metallic and molten salt fuels. The Republic of Korea is also taking a serious look at the application of pyrochemical treatment of used oxide fuel from Pressurized Water Reactors (PWR). The science behind pyrochemical recycling is being actively studied at the various national labs and universities. The Rare Earth Drawdown process is proposed to be included in a commercial pyrochemical recycling facility in order to minimize the amount of waste generated from the processing that will require permanent disposal in a geological repository. This process involves selective extraction of rare earth elements from electro-refiner salt. The salt can then be further processed to selectively remove Group I-II active metals and eventually be recycled back to the electro-refiner. The preferred method of separation of the rare earths from the salt is using electrolysis due to its inherent selectivity and ease of operation. The purpose of this study is to evaluate the effects of the presence of cesium (Group I) on the electrochemical behavior of neodymium in a molten eutectic LiCl-KCl salt. The activity and by extension the activity coefficient of a species determines many of the key electrochemical properties such as apparent reduction potential. In this study, we have undertaken a series of experiments to experimentally determine the activity coefficient of the dissolved neodymium(III) ions as a function of concentration, both in the presence and absence of cesium. This was done using a first of its kind electrochemical cell. Previously, activity of dissolved species has been determined using electrochemical cells in which equilibrium potentials are measured for the Nd/Nd(III) versus a Ag/AgCl reference electrode. There are several issues associated with such an approach. These electrodes are associated with several sources of errors; indeterminate values of Standard Reduction Potentials of (E{sup θ}) for Ag and Nd in molten salts, unknown liquid junction potentials and potential drifts. These uncertainties contribute errors to the experimental measurements. For this study, we employed a Nd/LiCl-KCl-NdCl{sub 3(Saturatedelectrode)}. There are several advantages with using such an electrode. If the expanded Nernst Equation is written for the aforementioned electrochemical cell, all of the terms cancel out except the activity term. This enables us to directly experimentally measure the activity of the species in solution. When we use a saturated NdCl{sub 3} reference electrode, the activity that is measured is defined as the activity versus a 'Saturated Solid State'. To determine the activity coefficients, we need to determine the activity versus the 'Liquid Standard Sate'. To convert the activity from solid standard state to liquid standard state, we correct for it using the hypothetical Gibbs free energy of fusion for neodymium chloride. (authors)

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗