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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 1,459 records · Page 81
All sourcesNASA NTRSDOE OSTI
DOE OSTI2013

Structural characterization and low-temperature physical properties of p-type single-crystal K{sub 8}Ga{sub 8.5}Sn{sub 37.5} grown by self-flux method

Single-crystal K{sub 8}Ga{sub 8.5}Sn{sub 37.5} was synthesized employing a self-flux method where Ga and Sn were used as fluxes. Single-crystal X-ray diffraction analyses revealed that this composition crystallizes in a cubic structure with the Pm3{sup ¯}n space group (number sign 223, a=11.9345(16) Å, V=1699.9(4) Å{sup 3}, Z=1, and R/wR=0.0187/0.0382). A large dynamic disorder and anisotropic atomic displacement parameters were observed for K atoms inside the larger polyhedra in the crystal structure of K{sub 8}Ga{sub 8.5}Sn{sub 37.5}. Electrical properties measurements indicate p-type conduction with onset of minority charge carrier conduction at temperatures above 270 K. - Graphical abstract: Single-crystal K{sub 8}Ga{sub 8.5}Sn{sub 37.5} was synthesized via a double-flux method where Ga and Sn were used as fluxes. Large disorder for K inside the larger polyhedra in the crystal structure of K{sub 8}Ga{sub 8.5}Sn{sub 37.5} was observed. Measurements of the electronic properties indicate p-type conduction with the onset of minority charge carrier conduction at temperatures above 270 K. Highlights: • Single-crystal K{sub 8}Ga{sub 8.5}Sn{sub 37.5} synthesized for the first time, and fully structurally characterized. • Large disorder for K inside the larger polyhedra in the crystal structure of K{sub 8}Ga{sub 8.5}Sn{sub 37.5.} • Electronic properties indicate p-type conduction with relatively low thermal conductivity.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Scalable edge clustering of dynamic graphs via weighted line graphs

Timestamped relational datasets consisting of records (or connections) between pairs of entities are ubiquitous in network science. For applications like peer-to-peer communication, email, various social network interactions, and computer network security, it is useful to organize these records into groups based on how and when they are occurring. Weighted line graphs offer a natural way to model how records are related in such datasets but for large real-world graph topologies, building and utilizing the line graph is prohibitively expensive. Here, we present the framework to cluster the edges of a dynamic graph via the associated line graph that contains two major contributions. The first is a method to work with the line graph implicitly and the second is a distributed scale implementation of an agglomerative hierarchical graph clustering algorithm. We outline a novel hierarchical dynamic graph edge clustering approach that efficiently breaks massive relational datasets into small sets of edges containing events at various timescales. This is in stark contrast to traditional graph clustering algorithms that prioritize highly connected (clique-like) community structures. Our approach relies on constructing a sufficient subgraph of a weighted line graph and applying a hierarchical agglomerative clustering. This approach is related to scalable techniques from spatial clustering, nonlinear-dimension reduction, topological data analysis, and draws particular inspiration from HDBSCAN. As an edge clustering, this method yields an overlapping node clustering. Our algorithm is parallelizable and we demonstrate efficient clustering of a billion-scale, real-world dynamic graph into small edge sets that correlate in topology and time. The entire clustering process for a graph with tens of billions of edges takes just a few minutes of run time on 256 nodes of a distributed compute environment. We argue how the output of the edge clustering is useful for a multitude of data visualization and powerful machine learning tasks, both involving the original massive dynamic graph data and metadata associated with the nodes and edges. Finally, we describe how this approach can be extended to dynamic hypergraphs and dynamic graphs/hypergraphs with unstructured data living on vertices and edges.

Data Analysis↗
DOE OSTI2014

Translation invariant time-dependent massive gravity: Hamiltonian analysis

The canonical structure of the massive gravity in the first order moving frame formalism is studied. We work in the simplified context of translation invariant fields, with mass terms given by general non-derivative interactions, invariant under the diagonal Lorentz group, depending on the moving frame as well as a fixed reference frame. We prove that the only mass terms which give 5 propagating degrees of freedom are the dRGT mass terms, namely those which are linear in the lapse. We also complete the Hamiltonian analysis with the dynamical evolution of the system.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2022

Wabash CarbonSAFE Static and Dynamic Modeling: Task 9.0 (Technical Report)

The objective of the Wabash CarbonSAFE project’s static and dynamic modeling task is to assess the feasibility of storing 50 million tonnes (1.67 million metric tonnes annually; MMTA) of industrially-sourced carbon dioxide (CO 2 ) in a commercial-scale geological storage complex at Wabash Valley Resources LLC (WVR) gasification facility near Terre Haute, Indiana over a period of 30 years. The targeted formations for storing CO 2 are: 1) Mt. Simon Sandstone (MSS) and the 2) Potosi Dolomite (Knox Group). All of the available data from the recently drilled Wabash #1 stratigraphic test well (now plugged and abandoned) were used in the construction of both the static and dynamic models. Geologic models were constructed to characterize both the Mt. Simon Sandstone and Potosi Dolomite storage complexes. Dynamic simulation models were constructed and used to assess the feasibility of injecting CO 2 into the Mt. Simon and Potosi formations. The geocellular models for the Potosi Dolomite and Mt. Simon Sandstone were built using Petrel™, Schlumberger’s reservoir modeling software. The dynamic simulations were run using Landmark’s Nexus ® reservoir simulation software.

29 ENERGY PLANNING, POLICY, AND ECONOMY↗
DOE OSTI2017

Spectroscopic Comparison of Metal-rich RRab Stars of the Galactic Field with their Metal-poor Counterparts

We investigate atmospheric properties of 35 stable RRab stars that possess the full ranges of period, light amplitude, and metal abundance found in Galactic RR Lyrae stars. Our results are derived from several thousand echelle spectra obtained over several years with the du Pont telescope of Las Campanas Observatory. Radial velocities of metal lines and the H α line were used to construct curves of radial velocity versus pulsation phase. From these we estimated radial velocity amplitudes for metal lines (formed near the photosphere) and H α Doppler cores (formed at small optical depths). We also measured H α emission fluxes when they appear during primary light rises. Spectra shifted to rest wavelengths, binned into small phase intervals, and co-added were used to perform model atmospheric and abundance analyses. The derived metallicities and those of some previous spectroscopic surveys were combined to produce a new calibration of the Layden abundance scale. We then divided our RRab sample into metal-rich (disk) and metal-poor (halo) groups at [Fe/H] = −1.0; the atmospheres of RRab families, so defined, differ with respect to (a) peak strength of H α emission flux, (b) H α radial velocity amplitude, (c) dynamical gravity, (d) stellar radius variation, (e) secondary acceleration during the photometric bump that precedes minimum light, and (f) duration of H α line-doubling. We also detected H α line-doubling during the “bump” in the metal-poor family, but not in the metal-rich one. Although all RRab probably are core helium-burning horizontal branch stars, the metal-rich group appears to be a species sui generis.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2013

Phase polymorphism of novel [Ru(NH{sub 3}){sub 6}](ClO{sub 4}){sub 3}—Comparison with [Ru(NH{sub 3}){sub 6}](BF{sub 4}){sub 3}. Part II

[Ru(NH{sub 3}){sub 6}](ClO{sub 4}){sub 3} undergoes two phase transitions at: T{sub C1}=290.3 K and T{sub C2}=74.8 K , thus exhibits three crystalline phases in the temperature range of 5–310 K. For the detected phase transitions, thermal effects were determined. Fourier transform far- and middle-infrared spectra (FT-FIR and FT-MIR), recorded at 8–350 K, suggest that reorientational motions of the NH{sub 3} ligands are very fast (τ{sub R}≈10{sup −12} s above T{sub C1}) and are significantly slowed down below T{sub C2}. X-ray single crystal diffraction (XRSCD) measurements revealed that in the high temperature phase (above T{sub C1}) the compound belongs to the cubic Fm3{sup ¯}m (No. 225) space group, whereas in the intermediate phase the unit cell parameter doubles and the space group is Ia3{sup ¯}(No. 206). {sup 1}H NMR studies revealed that the following reorientational motions are liberated during heating: three-fold reorientation of NH{sub 3} ligands, three-fold reorientation of the entire [Ru(NH{sub 3}){sub 6}]{sup 3+} cation, and isotropic reorientation of this cation. In the high temperature phase I the cations perform isotropic reorientations with the estimated activation energy equal to ca. 30.1 kJ mol{sup −1}. Comparison with adequate results obtained earlier for [Ru(NH{sub 3}){sub 6}](BF{sub 4}){sub 3} and for other similar compounds was made and general regularities were drawn. - Graphical abstract: Molar heat capacities obtained for [Ru(NH{sub 3}){sub 6}](ClO{sub 4}){sub 3} at temperatures between 5 and 310 K. Molecular structure of [Ru(NH{sub 3}){sub 6}]{sup 3+} and two types of ClO{sub 4}{sup -} varying in dynamic disorder at 293 K. Highlights: • Two solid phase transitions have been found in [Ru(NH{sub 3}){sub 6}](ClO{sub 4}){sub 3}. • The transitions are triggered by the hydrogen bond interactions between NH{sub 3} ligands and ClO{sub 4}{sup −} anions. • The complex is a highly dynamically disordered crystal across a wide temperature range.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2017

Measurements of Picosecond Energy Equilibration in Isochorically Heated Materials

In this Final Report we present the results of our DOE/FES-sponsored research on rapidly heated materials. The research focused on the details of picosecond energy equilibration and material response to isochoric heating by relativistic (or “hot”) electrons. The major goal was to improve the understanding of these processes by making time-resolved extreme ultraviolet (XUV) measurements of ultrafast energy deposition and blast-wave formation for testing impulsive-heating models in extreme thermodynamic conditions. Major achievements of the project include the design, fabrication, deployment, and use of two XUV spectrometers on the Multi-Terawatt (MTW) Laser System at the University of Rochester’s Laboratory for Laser Energetics. One of the spectrometers is coupled to an x-ray charge-coupled device (CCD) for time-integrated measurements; the other is coupled to an ultrafast x-ray streak camera for time-resolved measurements. Working together, these instruments provide absolutely calibrated data on the emitted XUV spectrum from an isochoric heated target. The new diagnostic system was used to measure and infer the time-resolved rear-surface temperature and density for different target materials and different target-interaction conditions. Experiments with laser-heated metal foils measured the ultrafast dynamics and energy deposition from hot electrons into plasma heating and blast-wave formation. The blast wave was observed emerging from the rear surface of the laser-irradiated target. The time between the prompt emission (electron-driven x-ray emission) and the blast-wave arrival was used to estimate the energy deposition into the wave. The data are consistent with a Sedov–Taylor blast wave, with energy transfer from the laser to the blast of up to 20 mJ. The data represent the first quantitative assessment of the blast-wave energy in a metal following heating by a short burst of high-intensity laser-generated hot electrons. The funding from this grant provided significant opportunities for training and professional development. The grant supported or partially supported a graduate student, a postdoctoral research associate, and a senior staff scientist. This support included bringing together a dedicated group of individuals with a niche set of experimental and theoretical skills for studying advanced material properties experiments and ultrafast radiation conditions. The team dynamic fostered training and knowledge transfer across the whole spectrum of research activities through shared experiences in advanced laboratory techniques, data analysis, modeling, and the development of new ideas, techniques, presentations, and publications. The results of this work, which significantly improve the understanding of rapid energy deposition in solid matter, have been widely disseminated to communities of interest through invited talks, contributed talks, and peer-reviewed journals.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2015

Atomic-scale cation dynamics in a monolayer VO X /α-Fe 2 O 3 catalyst

Catalytic reactions are associated with dynamical changes in the catalyst that include the oxidation state and local structural variations. The understanding of such dynamics, particularly at the atomic-scale, is of great importance for revealing the activity and selectivity of the catalyst in numerous reactions. Combining in situ X-ray absorption spectroscopy with in situ diffuse reflectance infrared Fourier transform spectroscopy, we studied the redox-induced dynamical changes for a VO X monolayer catalyst supported on a α-Fe 2 O 3 powder. The results show that several co-existing VO X species reversibly change their V oxidation states between +5 and +4, in concurrence with a structural change from two-dimensional chains to well connected V–O–V networks. These changes are also associated with the breaking and formation of the V &#9552 O vanadyl group. This combined study provides new insight into how VO X species change during catalytic reactions, which leads to proposed atomic-scale models for the redox-induced dynamics of the catalyst.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2017

Noninvasive PET quantitative myocardial blood flow with regadenoson for assessing cardiac allograft vasculopathy in orthotopic heart transplantation patients

Background: Risk stratification and early detection of cardiac allograft vasculopathy (CAV) is essential in orthotopic heart transplantation (OHT) patients. This study assesses the changes in myocardial blood flow (MBF) noninvasively in OHT patients using quantitative cardiac PET with regadenoson. Methods: Twelve patients (Group 1) (8 males, 4 females, mean age 55 ± 7 years) with no history of post OHT myocardial ischemia were enrolled 5.4 ± 2.0 years after OHT. Fifteen patients (Group 2) (9 males, 6 females, mean age 71 ± 9 years) with intermediate pretest probability but not documented evidence for coronary artery disease (CAD) were also included to serve as control. Global and regional MBFs were assessed using dynamic {sup 13}N-NH{sub 3} PET at rest and during regadenoson-induced hyperemia. The coronary flow reserve (CFR) was also calculated as the ratio of hyperemic to resting MBF. Results: Mean regadenoson-induced rate-pressure products were similar in both groups, while there was an increase in resting rate-pressure product in Group 1 patients. Both mean and median values of resting MBF were higher in Group 1 than Group 2 patients (1.33 ± 0.31 and 1.01 ± 0.21 mL/min/g for Groups 1 and 2, respectively, P < .001), while mean hyperemic MBF values were similar in both Groups (2.68 ± 0.84 and 2.64 ± 0.94 mL/min/g, P = NS) but median hyperemic MBF values were lower in Group 1 than Group 2 patients (2.0 vs. 2.60 mL/min/g, P = .018). Both mean and median CFR values demonstrated a significant reduction for Group 1 compared to Group 2 patients (2.07 ± 0.74 vs 2.63 ± 0.48, P = .025). Conclusions: This study suggests that the MBF in OHT patients may be abnormal at resting state with diminished CFR. This hints that the epicardial and microvascular coronary subsystem may be exacerbated after OHT leading to the gradual progression of CAV. [French] French Abstract: Contexte: Cette étude pilote par tomographie a positrons évalue de manière quantitative les changements de perfusion myocardique et le risque de vasculopathie coronaire après transplantation cardiaque chez l’être humain. Méthodes: Douze patients (groupe 1) (8 hommes, 4 femmes, âge moyen 55 ± 7 ans) sans antécédents d'ischémie myocardique post-chirurgicale ont été étudiés après 5,4 ± 2,0 ans après transplantation cardiaque. Quinze patients (groupe 2) (9 hommes, 6 femmes, âge moyen 71 ± 9 ans) avec une probabilité intermédiaire mais sans signes objectifs de maladie coronarienne ont servi de contrôles. Les donnes de perfusion myocardique globales et régionales ont été évaluées par tomographie à positrons l'aide de{sup 13}N-NH3 au repos et durant l'hyperémie induite par le vasodilatateur coronarien régadénoson. La réserve de flux coronarien a été calculée sur base du rapport entre le flux myocardique hyperhémique induit par le régadénoson et le flux myocardique au repos. Résultats: les double produits (fréquence cardiaque x tension artérielle) moyens après régadénoson furent similaires chez les deux groups de patients. Par contre le double produit au repos était plus élevé dans le groupe de patient transplantés. Les valeurs moyennes et médianes de perfusion myocardique globale au repos ont été calculées à 1.33 ± 0.31 ml/min/g dans le groupe de patients transplantés et 1.01 ± 0.21 ml/min/g dans le groupe control (P < 0.001). Après régadénoson, les valeurs moyennes de perfusion myocardique se sont avérées similaires dans les deux groupes (2,68 ± 0,84 et 2,64 ± 0,94 ml/min/g, P > 0.05). Néanmoins les valeurs médianes se sont avérées inferieures dans le groupe 1 comparativement au groupe control (2,0 versus 2,60 ml/min/g; P = 0,018). Les valeurs moyennes et médianes de réserve de flux myocardique mesurées étaient significativement réduites chez les patient transplantés (2,07 ± 0,74) en comparaison aux patients du groupe 2 (2,63 ± 0,48; P = 0.025). Conclusion: La perfusion myocardique au repos peut s’avérer anormale après transplantation cardiaque et s’accompagner d’une diminution de la réserve du flux coronaire. Cette étude pilote suggère que les vaisseaux épicardiques et la micro-vascularisation du myocarde peuvent être atteints après transplantation et conduire à la maladie coronaire du greffon. [Spanish] Spanish Abstract: Antecedentes: la estratificación de riesgo y detección temprana de la vasculopatía del aloinjerto cardiaco (VAC) es esencial en los pacientes con trasplante cardiaco ortotópico (TCO). El presente estudio evalúa de forma no invasiva los cambios en el flujo sanguíneo miocárdico (FSM) en pacientes con TCO utilizando el PET cardiaco cuantitativo con regadenoson. Métodos: Doce pacientes (Grupo 1) (8 hombres, 4 mujeres, edad promedio 55 ± 7 años) sin historia de isquemia miocárdica posterior al TCO fueron incluidos después de 5.4 ± 2.0 años de ser trasplantados. Quince pacientes (Grupo 2) (9 hombres, 6 mujeres, edad promedio 71 ± 9 años) con probabilidad pre-prueba intermedia pero sin evidencia documentada de enfermedad arterial coronaria (EAC) fueron incluidos como grupo control. El FSM global y regional fueron evaluados utilizando el estudio PET dinámico con {sup 13}N-NH{sub 3} en reposo y durante la inducción de hiperemia con regadenoson. La reserva de flujo coronario (RFC) también fue calculada como la proporción entre el FSM hiperémico y el de reposo. Resultados: el producto de velocidad-presión promedio inducido por regadenoson fue similar en ambos grupos, mientras que existió un incremento de este producto velocidad-presión durante el reposo en el Grupo 1 de pacientes. Los valores de la media y mediana del FSM de reposo fueron mayores en el Grupo 1 que el Grupo 2 de pacientes (1.33 ± 0.31 y 1.01 ± 0.21 mL/min/g para los Grupos 1 y 2, respectivamente, P < 0.001). La media de los valores del FSM hiperémico fueron similares en ambos grupos (2.68 ± 0.84 and 2.64 ± 0.94 mL/min/g, P = NS), sin embargo la mediana fue menor en el Grupo 1 que en el Grupo 2 (2.0 vs. 2.60 mL/min/g, P = .018). Tanto la media como la mediana para los valores de la RFC demostraron una disminución significativa en el Grupo 1 comparada con el Grupo 2 (2.07 ± 0.74 vs. 2.63 ± 0.48, P = 0.025). Conclusiones: El presente estudio sugiere que el FSM en pacientes con TCO puede estar alterado en reposo con una RFC disminuida. Esto indica que los sistemas coronarios epicardico y microvascular pudieran estar inflamados posterior al TCO conduciendo a una progresión gradual de la VAC. [Chinese] Chinese Abstract: 背景: 对于原位心脏移植 (OHT) 病人, 早期检测移植心脏血管病变 (CAV) 和进行危险分层是必要的。 本研究拟通过类伽腺苷定 心脏 PET 显像, 非侵入性地评估 OHT 病人心肌血流 (MBF) 的变化。 方法: 研究对象分为两组。 第一组, 12个病人 (8 男, 4女, 平均 55 ± 7岁), OHT 后 5.4 ± 2.0 年, 没有 OHT 后心肌缺血。 第二组 (对照组), 15 个病人 (9 男, 6 女, 平均 71 ± 9 岁), 中等冠心病可能, 但尚未确诊。 分别于静息及类伽腺苷药物负荷下, 动态采集 {sup 13}N-NH{sub 3} PET 图像, 获得整体和局部 MBF。冠脉血流储备 (CFR) 通过负荷 MBF /静息 MBF 计算而得。 结果: 类伽腺苷负荷时, 反映心肌耗氧 的心率血压乘积在两组间没有差异, 但在静息时, 第一组明显高于第二组。静息时, 第一组 MBF 的平均值高于第二组 (1.33 ± 0.31 vs. 1.01 ± 0.21 mL/min/g, P < 0.001); 负荷时, 两组 MBF 的平均值无差异 (2.68 ± 0.84 vs. 2.64 ± 0.94 mL/min/g, P = NS), 但 MBF 的中位数第一组要低于第二组 (2.0 vs. 2.60 mL/min/g, P = 0.018), 且第一组 CFR 的平均值明显低于第二组 (2.07 ± 0.74 vs. 2.63 ± 0.48, P = 0.025)。 结论: 在原位心脏移植病人中, 冠脉血流储备以及静息心肌血流 均呈现明显异常。提示原位心脏移植后, 冠状动脉心外膜血管与微小血管功能均受损, 进而将逐渐导致移植心脏血管病变。 关键词: 动态PET, 类伽腺苷, 冠状动脉血流储备, 原位心脏移植, 移植心脏血管病变。.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2020

Physical Bond Breaking in Associating Copolymer Liquids

We combine ideas from polymer and glassy liquid physics to construct a new model for the bond breaking time scale of attractive sticker groups in associating copolymer liquids that form transient networks. The activated event is argued to be a two-step process, involving first the release of the non-sticker dynamic caging constraints that defines the primary alpha relaxation, followed by attractive stickers surmounting an association free energy barrier subject to a local frictional resistance which can be strongly affected by relaxation-diffusion decoupling. Here, the ideas embedded in the model produce a consistent and good description of the bond breaking timescale for diverse polymer chemistries and architectures as a function of temperature and fraction of sticky groups. Chemically sensible values for association free energies are deduced. In strong contrast, the existing phenomenological models are shown to incur qualitative failures.

36 MATERIALS SCIENCE↗
DOE OSTI2019

A biradical-tagged phospholipid as a polarizing agent for solid-state MAS Dynamic Nuclear Polarization NMR of membrane proteins

We report a novel Dynamic Nuclear Polarization (DNP) NMR polarizing agent ToSMTSL-PTE representing a phospholipid with a biradical TOTAPOL tethered to the polar head group has been synthesized, characterized, and employed to enhance solid-state Nuclear Magnetic Resonance (SSNMR) signal of a lipid-reconstituted integral membrane protein proteorhodopsin (PR). A matrix-free PR formulation for DNP improved the absolute sensitivity of NMR signal by a factor of ca. 4 compared to a conventional preparation with TOTAPOL dispersed in a glassy glycerol/water matrix. DNP enhancements measured at 400 MHz/263 GHz and 600 MHz/395 GHz showed a strong field dependence but remained moderate at both fields, and comparable to those obtained for PR covalently modified with ToSMTSL. Additional continuous wave (CW) X-band electron paramagnetic resonance (EPR) experiments with ToSMTSL-PTE in solutions and in lipid bilayers revealed that an unfavorable conformational change of the linker connecting mononitroxides could be one of the reasons for moderate DNP enhancements. Further, differential scanning calorimetry (DSC) and CW EPR experiments indicated an inhomogeneous distribution and/or a possibility of a partial aggregation of ToSMTSL-PTE in DMPC:DMPA bilayers when the concentration of the polarizing agent was increased to 20 mol% to maximize the DNP enhancement. Thus, conformational changes and an inhomogeneous distribution of the lipid-based biradicals in lipid bilayers emerged as important factors to consider for further development of this matrix-free approach for DNP of membrane proteins.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2018

Reduced adiposity by compensatory WAT browning upon iBAT removal in mice

Highlights: • Prolonged time course for cold exposure was utilized to elucidate dynamic changes in BAT and in WAT browning in mice. • Loss of classic iBAT enhanced WAT browning due to compensatorily increased sympathetic WAT input in mice. • Significantly reduced adiposity in the iBAT removal group compared with the control group in mice. The strong effects of classic brown adipose tissue (BAT) and recruited beige adipocytes in treatment of obesity and metabolic syndrome have been attracting increasing research interest. Cold treatment is an effective, convenient approach to stimulate BAT activity and induce white adipose tissue (WAT) browning. Here, we utilized prolonged cold exposure (from 2 h to 2 weeks in a 4° cold chamber) to elucidate dynamic changes in BAT and in WAT browning during acute and chronic cold exposure in mice. BAT mass decreased quickly, with reduced lipid droplet sizes within 8 h of cold exposure owing to the utilization of BAT pre-storage triglycerides, and subsequently increased during prolonged cold exposure. These dynamic morphological changes in BAT were confirmed by gene expression changes in ADRB3 and PGC1α, while UCP1 and ELOVL3 expression was continuously up-regulated throughout the entire cold exposure period. Additionally, cold treatment increased BAT secretion of FGF21, which has been reported to activate beige adipocyte formation. Thus, to illustrate potential crosstalk between secreted BAT proteins (so-called BATokines) and beige adipogenesis during cold stress, we performed an interscapular BAT (iBAT) removal experiment in mice. Surprisingly, loss of classic iBAT enhanced WAT browning due to compensatorily increased sympathetic WAT input. Unexpectedly, we observed significantly reduced adiposity in the iBAT removal group compared with the control group. These results further suggest that WAT browning plays an important role in whole-body energy metabolism during cold acclimation, even without iBAT. Furthermore, our data imply that enhanced WAT browning may be an efficient therapeutic tool to combat obesity and related syndromes.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2020

Block orbital-selective Mott insulators: A spin excitation analysis

We present a comprehensive study of the spin excitations—as measured by the dynamical spin structure factor S(q,ω)—of the so-called block-magnetic state of low-dimensional orbital-selective Mott insulators. We realize this state via both a multi-orbital Hubbard model and a generalized Kondo-Heisenberg Hamiltonian. Due to various competing energy scales present in the models, the system develops periodic ferromagnetic islands of various shapes and sizes, which are antiferromagnetically coupled. The 2×2 particular case was already found experimentally in the ladder material BaFe2Se3 that becomes superconducting under pressure. Here we discuss the electronic density as well as Hubbard and Hund coupling dependence of S(q,ω) using density matrix renormalization group method. Several interesting features were identified: (1) An acoustic (dispersive spin-wave) mode develops. (2) The spin-wave bandwidth establishes a new energy scale that is strongly dependent on the size of the magnetic island and becomes abnormally small for large clusters. (3) Optical (dispersionless spin excitation) modes are present for all block states studied here. In addition, a variety of phenomenological spin Hamiltonians have been investigated but none matches entirely our results that were obtained primarily at intermediate Hubbard U strengths. Our comprehensive analysis provides theoretical guidance and motivation to crystal growers to search for appropriate candidate materials to realize the block states, and to neutron scattering experimentalists to confirm the exotic dynamical magnetic properties unveiled here, with a rich mixture of acoustic and optical features.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2015

The unusual and dynamic character of PX-DNA

PX-DNA is a four-stranded DNA structure that has been implicated in the recognition of homology, either continuously, or in an every-other-half-turn fashion. Some of the structural features of the molecule have been noted previously, but the structure requires further characterization. Here, we report atomic force microscopic characterization of PX molecules that contain periodically placed biotin groups, enabling the molecule to be labeled by streptavidin molecules at these sites. In comparison with conventional double stranded DNA and with antiparallel DNA double crossover molecules, it is clear that PX-DNA is a more dynamic structure. Moreover, the spacing between the nucleotide pairs along the helix axis is shorter, suggesting a mixed B/A structure. Circular dichroism spectroscopy indicates unusual features in the PX molecule that are absent in both the molecules to which it is compared.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2023

Maintaining Microstructure – The Path to Successful Technology Maturation in Fluidized Systems

Scaling circulating fluidized bed risers has been a point of contention for nearly a century. There have been numerous attempts to define various methodologies. These have all fallen short of providing a robust approach, primarily due to a lack of maintaining microstructure dynamics – a key factor in maintain interphase heat and mass transfer. Recent work by the author put forward an approach based up maintaining dynamic similarity at different scales by ensuring that the microstructure remained similar by maintaining statistical and chaotic parameters across the scale. That work relied on a dimensionless regime map in which the x-axis was defined by the ratio of the solids flux to the saturation carrying capacity. This latter property was only good within the range of the data and it became evident that extrapolation beyond the limits of the data could induce unrealistic conditions. Therefore, literature was reviewed to develop a better correlation for the saturation carrying capacity. In doing so, a critical diameter concept was developed and applied to the correlations for both Geldart Group A and B materials. The critical diameter for Geldart Group A and B materials is 0.2 m and 0.3 m, respectively. The paper then gives examples on how to use the scaling approach to maintain dynamic similarity across the scales.<br>

Breault, Ronald↗
DOE OSTI2015

Dynamics of copper-phthalocyanine molecules on Au/Ge(001)

Spatially resolved current-time scanning tunneling spectroscopy combined with current-distance spectroscopy has been used to characterize the dynamic behavior of copper-phthalocyanine (CuPc) molecules adsorbed on a Au-modified Ge(001) surface. The analyzed CuPc molecules are adsorbed in a “molecular bridge” configuration, where two benzopyrrole groups (lobes) are connected to a Au-induced nanowire, whereas the other two lobes are connected to the adjacent nanowire. Three types of lobe configurations are found: a bright lobe, a dim lobe, and a fuzzy lobe. The dim and fuzzy lobes exhibit a well-defined switching behavior between two discrete levels, while the bright lobe shows a broad oscillation band. The observed dynamic behavior is induced by electrons that are injected into the LUMO+1 orbital of the CuPc molecule. By precisely adjusting the tip-molecule distance, the switching frequency of the lobes can be tuned accurately.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2019

Structural Analysis of Peripheral Organs of the Immune System in the Assessment of Grippol Vaccine Safety

The safety of Grippol vaccine was assessed by macro- and microscopic methods in the experiment. The morphological features of group lymphoid nodules of the small intestine were studied on days 4, 7, 14 and 30 after vaccination. The structural morphological dynamics of lymphoid tissue under these conditions is shown. Because of the use of the vaccine, the lymphocytopoietic processes in the body are activated, which indicates the formation of an immune response.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2020

Shifting modes of iron sulfidization at the onset of OAE-2 drive regional shifts in pyrite δ 34 S records

We report total reduced inorganic S isotope ratios (δ 34 S CRS ) shift toward more negative values across much of the southern North Atlantic just before the onset of the Cenomanian-Turonian Ocean Anoxic Event (OAE-2). At the same time, there is no parallel isotopic change in the significantly larger pool of kerogen (organic) S, which indicates that the distribution and S-isotope composition of sulfide in the environment likely did not drive the change in δ 34 S CRS . Here, we investigate possible explanations for the negative shift in δ 34 S CRS values and their divergence from organic S by isolating iron sulfides for morphological identification and grain-specific isotopic analysis using secondary ion mass spectrometry (SIMS). In pre- and syn-OAE-2 sedimentary rocks from Demerara Rise, we find four distinct morphologies of iron sulfides: pyrite framboids (1–20 μm diameter), irregular pyrite aggregates (1–38 μm diameter), large cemented pyrite aggregates (~60 μm diameter), and irregular and cemented aggregates of the pyrite polymorph marcasite (1–45 μm diameter). These different textural groups have distinct S-isotopic compositions that are largely consistent through the onset of OAE-2. As such, the secular change in bulk δ 34 S CRS values likely reflects the changing proportions of these phases stratigraphically across OAE-2. All textural groups feature resolvable intra-grain δ 34 S variability, suggesting that the environments in which they formed were characterized by dynamic sulfide δ 34 S values and/or by partial closed-system distillation. We use grain-specific δ 34 S distributions to rule out shoaling of the chemocline within the sediments as a mechanism for the observed decrease in δ 34 S CRS . Instead, we propose that changes in the reactivity of the iron species delivered to Demerara Rise over the ~200 kyr leading up to the onset of OAE-2 impacted the relative contributions of pyrite with S-isotope signatures reflecting the water column, shallow sediments, and deeper sediments to the bulk sedimentary δ 34 S CRS value. Specifically, the change in iron reactivity at the onset of OAE-2 favored the production of 34 S-depleted large, cemented aggregates and framboids at the expense of more 34 S-enriched irregular aggregates. Our results underscore that bulk δ 34 S CRS measurements integrate multiple reduced phases that form via distinct reaction mechanisms and potentially in different parts of the depositional environment. Grain-specific SIMS analyses dramatically enrich our ability to interpret pyrite isotopic patterns in the geologic record.

58 GEOSCIENCES↗