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At least 91 records · Page 5

Microscopic Behaviors of Tri-n-Butyl Phosphate, n-Dodecane and Their Mixtures at Air/Liquid and Liquid/Liquid Interfaces: An AMBER Polarizable Force Field Study

In solvent extraction processes for recovering metal ions from used nuclear fuel, as well as other industrial applications, a better understanding of the metal complex phase transfer phenomenon would greatly aid ligand design and process optimization. We have approached this challenge by utilizing classical molecular dynamics simulations technique to gain visual appreciation of the vapor/liquid and liquid/liquid interface between tri-n-butyl phosphate (TBP) and n-dodecane with air and water. In this study, we successfully reparameterized polarizable force fields for TBP and n-dodecane that accurately reproduced several of their thermophysical properties such as: density, heat of vaporization, and dipole moment. Our models were able to predict the surface and interfacial tension of different systems when compared to experimental results also performed by us. Through this study, we gained numerous atomistic understanding of the behaviors of TBP and n-dodecane at the interface against air and water, useful in further computational studies of such systems. Lastly, our studies indicate that the initial configuration of a simulation may have a large effect on the final result.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

Radiation defect dynamics in Si at room temperature studied by pulsed ion beams

The evolution of radiation defects after the thermalization of collision cascades often plays the dominant role in the formation of stable radiation disorder in crystalline solids of interest to electronics and nuclear materials applications. Here, we explore a pulsed-ion-beam method to study defect interaction dynamics in Si crystals bombarded at room temperature with 500 keV Ne, Ar, Kr, and Xe ions. The effective time constant of defect interaction is measured directly by studying the dependence of lattice disorder, monitored by ion channeling, on the passive part of the beam duty cycle. The effective defect diffusion length is revealed by the dependence of damage on the active part of the beam duty cycle. Results show that the defect relaxation behavior obeys a second order kinetic process for all the cases studied, with a time constant in the range of ∼4–13 ms and a diffusion length of ∼15–50 nm. Both radiation dynamics parameters (the time constant and diffusion length) are essentially independent of the maximum instantaneous dose rate, total ion dose, and dopant concentration within the ranges studied. However, both the time constant and diffusion length increase with increasing ion mass. This demonstrates that the density of collision cascades influences not only defect production and annealing efficiencies but also the defect interaction dynamics.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗

Epidemiological Studies of Low-Dose Ionizing Radiation and Cancer: Rationale and Framework for the Monograph and Overview of Eligible Studies

Abstract Whether low-dose ionizing radiation can cause cancer is a critical and long-debated question in radiation protection. Since the Biological Effects of Ionizing Radiation report by the National Academies in 2006, new publications from large, well-powered epidemiological studies of low doses have reported positive dose-response relationships. It has been suggested, however, that biases could explain these findings. We conducted a systematic review of epidemiological studies with mean doses less than 100 mGy published 2006–2017. We required individualized doses and dose-response estimates with confidence intervals. We identified 26 eligible studies (eight environmental, four medical, and 14 occupational), including 91 000 solid cancers and 13 000 leukemias. Mean doses ranged from 0.1 to 82 mGy. The excess relative risk at 100 mGy was positive for 16 of 22 solid cancer studies and 17 of 20 leukemia studies. The aim of this monograph was to systematically review the potential biases in these studies (including dose uncertainty, confounding, and outcome misclassification) and to assess whether the subset of minimally biased studies provides evidence for cancer risks from low-dose radiation. Here, we describe the framework for the systematic bias review and provide an overview of the eligible studies.

Berrington de Gonzalez, Amy↗

Synergetic Use of the WSR-88D Radars, GOES-R Satellites, and Lightning Networks to Study Microphysical Characteristics of Hurricanes

Abstract This study analyzes the microphysics and precipitation pattern of Hurricanes Harvey (2017) and Florence (2018) in both the eyewall and outer rainband regions. From the retrievals by a satellite red–green–blue scheme, the outer rainbands show a strong convective structure while the inner eyewall has less convective vigor (i.e., weaker upper-level reflectivities and electrification), which may be related to stronger vertical wind shear that hinders fast vertical motions. The WSR-88D column-vertical profiles further confirm that the outer rainband clouds have strong vertical motion and large ice-phase hydrometeor formation aloft, which correlates well with 3D Lightning Mapping Array source counts in height and time. From the results from this study, it is determined that the inner eyewall region is dominated by warm rain, whereas the external rainband region contains intense mixed-phase precipitation. External rainbands are defined here as those that reside outside of the main hurricane circulation, associated with surface tropical storm wind speeds. The synergy of satellite and radar dual-polarization parameters is instrumental in distinguishing between the key microphysical features of intense convective rainbands and the warm-rain-dominated eyewall regions within the hurricanes. Substantial amounts of ice aloft and intense updrafts in the external rainbands are indicative of heavy surface precipitation, which can have important implications for severe weather warnings and quantitative precipitation forecasts. The novel part of this study is to combine ground-based radar measurement with satellite observations to study hurricane microphysical structure from surface to cloud top so as to fill in the gaps between the two observational techniques.

Meteorology & Atmospheric Sciences↗

Space station Simulation Computer System (SCS) study for NASA/MSFC. Volume 5: Study analysis report

The Simulation Computer System (SCS) is the computer hardware, software, and workstations that will support the Payload Training Complex (PTC) at the Marshall Space Flight Center (MSFC). The PTC will train the space station payload scientists, station scientists, and ground controllers to operate the wide variety of experiments that will be on-board the Freedom Space Station. The further analysis performed on the SCS study as part of task 2-Perform Studies and Parametric Analysis-of the SCS study contract is summarized. These analyses were performed to resolve open issues remaining after the completion of task 1, and the publishing of the SCS study issues report. The results of these studies provide inputs into SCS task 3-Develop and present SCS requirements, and SCS task 4-develop SCS conceptual designs. The purpose of these studies is to resolve the issues into usable requirements given the best available information at the time of the study. A list of all the SCS study issues is given.

Source record↗

Space Transfer Vehicle Concepts and Requirements Study. Volume 2, Book 2: System and Program Requirements Trade Studies

During the 90-day study, support was provided to NASA in defining a point-of-departure space transfer vehicle (STV). The resulting STV concept was performance optimized with a two-stage LTV/LEV configuration. Appendix A reports on the effort during this period of the study. From the end of the 90-day study until the March Interim Review, effort was placed on optimizing the two-stage vehicle approach identified in the 90-day effort. After the March Interim Review, the effort was expanded to perform a full architectural trade study with the intent of developing a decision database to support STV system decisions in response to changing SEI infrastructure concepts. Several of the architecture trade studies were combined in a System Architecture Trade Study. In addition to this trade, system optimization/definition trades and analyses were completed and some special topics were addressed. Program- and system-level trade study and analyses methodologies and results are presented in this section. Trades and analyses covered in this section are: (1) a system architecture trade study; (2) evolution; (3) safety and abort considerations; (4) STV as a launch vehicle upper stage; and (5) optimum crew and cargo split.

Weber, Gary A.↗

Hindlimb Suspension (HLS) in Rodents for the Study of Intracranial Pressure, Molecular and Histologic Changes in the Eye, and CSF Production Regulation and Resorption: A Status Report of Two Studies

This status report corresponds to two studies tied to an animal experiment being executed at the University of California Davis (Charles Fuller's laboratory). The animal protocol uses the well-documented rat hindlimb suspension (HLS) model, to examine the relationship between cephalic fluid shifts and the regulation of intracranial (ICP) and intraocular (IOP) pressures as well as visual system structure and function. Long Evans rats are subjected to HLS durations of 7, 14, 28 and 90 days. Subgroups of the 90-day animals are studied for recovery periods of 7, 14, 28 or 90 days. All HLS subjects have age-matched cage controls. Various animal cohorts are planned for this study: young males, young females and old males. In addition to the live measures (ICP by telemetry, IOP and retinal parameters by optical coherence tomography) which are shared with the Fuller study, the specific outcomes for this study include: -Gene expression analysis of the retina -Histologic analysis - Analysis of the microvasculature of retina flat mounts by NASA's VESsel GENeration Analysis (VESGEN) Software. To date, the young male and female cohorts are being completed. Due to the need to keep technical variation to a minimum, the histologic and genomic analyses have been delayed until all samples from each cohort are available and can be processed in a single batch per cohort. The samples received so far correspond to young males sacrificed at 7,14, 28 and 90 days of HLS and at 90 days of recovery; and from young females sacrificed at 7, 14 and 28 of HLS. A complementary study titled: "A gene expression and histologic approach to the study of cerebrospinal fluid (CSF) production and outflow in hindlimb suspended rats" seeks to study the molecular components of CSF production and outflow modulation as a result of HLS, bringing a molecular and histologic approach to investigate genome wide expression changes in the arachnoid villi and choroid plexus of HLS rats compared to rats in normal posture.

Theriot, C. A.↗

NICS (NASA Instrument Capabilities Study) Instrument Schedule and Cost Study

This paper summarizes work performed on the Flight Projects Directorate Planetary Science Projects Division (PSPD, Code 430) NICS (NASA Instrument Capabilities study) instrument schedule and cost study. Included are a short summary of the original NICS (NASA, 2008), and the design and approach, data collection, analysis, preliminary findings and recommendations from select areas of the current study. The NICS (2008) was chartered by then NASA Chief Engineer Michael Ryschkewitsch and chaired by Goddard Space Flight Center (GSFC) engineer, John Leon. The focus was to identify problem areas in instrument development and, if possible, to offer solutions. In the area of instrument developments, the NICS (2008) identified a lack of resources and authority to successfully manage to instrument cost and schedule requirements; and a lack of critical skills, expertise, and leadership to successfully implement unique (one-of-a-kind) high technology developments (NASA, 2008, pp. 51, 52). Additionally, the NICS (2008) found problems in requirements formulation, reviews and management; unrealistic caps and overly optimistic estimates; and externally directed changes which increased the likelihood of overrunning cost and schedule (NASA, 2008, pp.53, 54). It is noteworthy that NICS findings are consistent with previous studies at the mission level (Robbins, Schmidt & White, 2020). Five years later in 2013, the Instrument Projects Division (IPD) was established to implement and manage instrument projects greater than $20M. The IPD was known as Code 490. Its structure incorporated several of the NICS (2008) recommendations. To see if these incorporated recommendations made a difference, and to identify other potential challenges in instrument developments, two parallel studies were initiated. Originally led by the IPD, now led by the PSPD, and the Instrument and Payload Systems Engineering Branch (IPSE, Code 592), respectively, the instrument schedule and cost study and the instrument technical complexity study began in 2017. Data collection was initiated in 2020 and is on-going. This paper is limited to the IPD/PSPD study. Among other findings, preliminary data indicate IPD/PSPD project management support positively influenced instrument development as related to providing a dedicated level of support staff, including a deputy Instrument Project Manager (dIPM), reducing IPM leadership changes, and providing other project support. Next steps include continued data collection and analysis, and mapping to technical complexity data.

NICS implementation↗

Microbiome-wide association studies link dynamic microbial consortia to disease

Rapid advances in DNA sequencing, metabolomics, proteomics and computational tools are dramatically increasing access to the microbiome and identification of its links with disease. In particular, time-series studies and multiple molecular perspectives are facilitating microbiome-wide association studies, which are analogous to genome-wide association studies. Early findings point to actionable outcomes of microbiome-wide association studies, although their clinical application has yet to be approved. An appreciation of the complexity of interactions among the microbiome and the host's diet, chemistry and health, as well as determining the frequency of observations that are needed to capture and integrate this dynamic interface, is paramount for developing precision diagnostics and therapies that are based on the microbiome.

Gilbert, Jack A.↗

Lunar Science Conference, 7th, Houston, Tex., March 15-19, 1976, Proceedings. Volume 1 - Regolith studies. Volume 2 - Petrogenetic studies of mare and highland rocks. Volume 3 - The moon and other bodies

Attention is given to lunar core studies (multi-core, deep drill, and drive tube), surface soil studies (petrography and geochemistry, light and volatile element studies, and agglutinate related studies), and surfaces process studies. Also considered are mare basalts, with emphasis on mineralogy and petrology, chemical and isotopic studies, and constraints and models of basalt evolution, along with breccia and highland samples with attention given to geochronology, boulders and consortium studies and the formation of highland samples. Remote sensing and photogeology of the moon, crustal bombardment, physical properties of the moon, and comparative planetology are also discussed.

Merrill, R. B.↗

Space station Simulation Computer System (SCS) study for NASA/MSFC. Volume 6: Study issues report

The Simulation Computer System (SCS) is the computer hardware, software, and workstations that will support the Payload Training Complex (PTC) at the Marshall Space Flight Center (MSFC). The PTC will train the space station payload specialists and mission specialists to operate the wide variety of experiments that will be on-board the Freedom Space Station. This simulation Computer System (SCS) study issues report summarizes the analysis and study done as task 1-identify and analyze the CSC study issues- of the SCS study contract.This work was performed over the first three months of the SCS study which began in August of 1988. First issues were identified from all sources. These included the NASA SOW, the TRW proposal, and working groups which focused the experience of NASA and the contractor team performing the study-TRW, Essex, and Grumman. The final list is organized into training related issues, and SCS associated development issues. To begin the analysis of the issues, a list of all the functions for which the SCS could be used was created, i.e., when the computer is turned on, what will it be doing. Analysis was continued by creating an operational functions matrix of SCS users vs. SCS functions to insure all the functions considered were valid, and to aid in identification of users as the analysis progressed. The functions will form the basis for the requirements, which are currently being developed under task 3 of the SCS study.

Source record↗

Mission Study for Generation-X: A Large Area and High Angular Observatory to Study the Early Universe

In this report we provide a summary of the technical progress achieved during the last year Generation-X Vision Mission Study. In addition, we provide a brief programmatic status. The Generation-X (Gen-X) Vision Mission Study investigates the science requirements, mission concepts and technology drivers for an X-ray telescope designed to study the new frontier of astrophysics: the birth and evolution of the first stars, galaxies and black holes in the early Universe. X-ray astronomy offers an opportunity to detect these via the activity of the black holes, and the supernova explosions and gamma-ray burst afterglows of the massive stars. However, such objects are beyond the grasp of current missions which are operating or even under development. Our team has conceived a Gen-X Vision Mission based on an X-ray observatory with 100 m2 collecting area at 1 keV (1000 times larger than Chandra) and 0.1 arcsecond angular resolution (several times better than Chandra and 50 times better than the Constellation-X resolution goal). Such a high energy observatory will be capable of detecting the earliest black holes and galaxies in the Universe, and will also study extremes of density, gravity, magnetic fields, and kinetic energy which cannot be created in laboratories. In our study we develop the mission concept and define candidate technologies and performance requirements for Gen-X. The baseline Gen-X mission involves four 8 m diameter X-ray telescopes operating at Sun-Earth L2. We trade against an alternate concept of a single 26 m diameter telescope with focal plane instruments on a separate spacecraft. A telescope of this size will require either robotic or human-assisted in-flight assembly. The required effective area implies that extremely lightweight grazing incidence X-ray optics must be developed. To achieve the required areal density of at least 100 times lower than for Chandra, we study 0.2 mm thick mirrors which have active on-orbit figure control. We also study the suite of required detectors, including a large FOV high angular resolution imager, a cryogenic imaging spectrometer and a reflection grating spectrometer.

Brissenden, Roger↗

Ethical, legal and social implications of human genome studies in radiation research: a workshop report for studies on atomic bomb survivors at the Radiation Effects Research Foundation

The Radiation Effects Research Foundation (RERF) is the primary organization in Japan dedicated to studying the health consequences of the Hiroshima and Nagasaki atomic bombings in World War II. In December 2020, RERF held a virtual international workshop on the ethical, legal and social implications (ELSI) of genome studies. In this workshop, the ELSI considerations of future human genome studies on radiation research including atomic bomb survivors and their families were discussed. Since genome sequencing (GS) is now practical and affordable, RERF now plans GS of parents/child trios to examine genetic effects of atomic bomb radiation. As such studies may engender some novel risks and benefits, ethics review and engagement with families (including consent) need to be considered. These include protection of individual privacy, use of samples from deceased prior participants, return of results to the participants, public sharing of genome data and advance science and social welfare. Specifically with regard to social welfare, the results of such studies may have implications for public and government decision-making regarding social benefits of victims and other important questions. Based on these broad-ranging discussions we have developed the following concepts to guide this work: “trust,” “compromise” and “relationship building,” inclusive of the concerned stakeholders, scientific aims and Japanese society at large. We conclude that in order to realize, establish and maintain these concepts, it is essential to put procedures into place to ensure the successful, consensus-based implementation of the RERF studies.

63 RADIATION, THERMAL, AND OTHER ENVIRON. POLLUTAN↗

Studying Response to Light in Offices: A Literature Review and Pilot Study

Researchers have been exploring the influence of light on health in office settings for over two decades; however, a greater understanding of physiological responses and technology advancements are shifting the way researchers study the influence of light in realistic environments. New technologies paired with Ecological Momentary Assessments (EMAs) administered via smartphones provide ways to collect information about individual light exposure and occupant response throughout the day. The study aims to document occupant response to tunable lighting in a real office environment, including potential beneficial or adverse health and well-being effects. Twenty-three office employees agreed to participate in a twelve-week study examining occupant response to two lighting conditions (static vs. dynamic). No significant differences were observed for any of the measures, highlighting the importance and complexity of in-situ studies conducted in realistic environments. While prior office studies have shown a significant influence on daytime sleepiness and sleep quality, research has not shown mood or stress to be significantly impacted by lighting conditions. Correlation analyses regarding lighting satisfaction, environmental satisfaction, and visual comfort demonstrate a significant relationship between certain items that may inform future studies. Further, the high correlation means it is reasonable to assume that many environmental factors in offices can influence occupant behavior and well-being.

60 APPLIED LIFE SCIENCES↗

A Ni(II) Bis(diphosphine)-Hydride Complex Containing Proton Relays - Structural Characterization and Electrocatalytic Studies

The syntheses of the new 1,5-diphenyl-3,7-di(isopropyl)-1,5-diaza-3,7-diphosphacyclooctane ligand, PiPr2NPh2, is reported. The two equivalents of the ligand react with [Ni(CH3CN)6](BF4)2 to form the bis-diphosphine Ni(II)-complex [Ni(PiPr2NPh2)2](BF4)2, which acts as a proton reduction electrocatalyst. In addition to [Ni(PiPr2NPh2)2]2+, we report the syntheses and structural characterization of the Ni(0)-complex Ni(PiPr2NPh2)2, and the Ni(II)-hydride complex [HNi(PiPr2NPh2)2]BF4. The [HNi(PiPr2NPh2)2]BF4 complex represents the first Ni(II)-hydride in the [Ni(PR2NR'2)2]2+ family of compounds to be isolated and structurally characterized. In addition to the experimental data, the mechanism of electrocatalysis facilitated by [Ni(PiPr2NPh2)2]2+ is analyzed using linear free energy relationships recently established for the [Ni(PR2NR'2)2]2+ family. We thank Dr. Aaron Appel, Dr. Simone Raugei and Dr. Eric Wiedner for helpful discussions. This research was supported as part of the Center for Molecular Electrocatalysis, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences. Mass spectrometry was provided at W. R. Wiley Environmental Molecular Sciences Laboratory (EMSL), a national scientific user facility sponsored by the Department of Energy’s office of Biological and Environmental Research located at Pacific Northwest National Laboratory. Pacific Northwest National Laboratory is operated by Battelle for the U.S. Department of Energy.

diphosphine↗