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At least 343 records · Page 19
All sourcesNASA NTRSDOE OSTI
DOE OSTI2025

51 V NMR evidence for interlayer-modulated charge order and a first-order low-temperature transition in CsV 3 ⁢Sb 5

Charge order in the kagome superconductor CsV 3 ⁢Sb 5 exhibits a complex three-dimensional organization and intermediate-temperature anomalies whose bulk character has remained unsettled. We use orientation-dependent 51 V NMR as a site-selective probe to determine the stacking of the charge density wave (CDW) state and its thermal evolution. Below 𝑇 CDW ≈ 94K, the field-linear splitting of the 51 V central transition together with the anisotropy of the Knight shift tensor identify an interlayer-modulated 3⁢𝑞 CDW whose local environments are consistent with a four-layer 2 × 2 × 4 stacking with mixed trihexagonal/Star-of-David distortions, in agreement with synchrotron x-ray determinations. For comparison, RbV 3 ⁢Sb 5 serves as a reference exhibiting a uniform trihexagonal 2 × 2 × 2 stacking, allowing us to isolate features unique to the 2 × 2 × 4 state in CsV 3 ⁢Sb 5 . With 𝐻 0 ∥ 𝑐, the 51 V quadrupolar satellites through the intermediate temperature scale near 𝑇 CO ≈ 65K reorganize into two well-resolved electric-field-gradient manifolds that coexist over a finite interval; their relative spectral weights interchange on cooling while the total integrated satellite intensity remains conserved and 𝜈 𝑄 within each manifold is nearly temperature independent. The coexistence without critical broadening, together with conserved intensity, provides bulk evidence consistent with a first-order charge-order transition near 𝑇 CO . Our measurements do not resolve whether this lower-temperature transition corresponds to a distinct in-plane order or a reorganization of the 3⁢𝑞 state; rather, they delimit this window and provide bulk, site-resolved constraints that connect prior reported anomalies to a thermodynamic first-order transition.

Wang, Xiaoling [California State Univ., East Bay, ↗
DOE OSTI2025

Impact of Module Configuration on Lithium-Ion Battery Performance and Degradation: Part I. Energy Throughput, Voltage Spread, and Current Distribution

Batteries are commonly connected in series and parallel to create modules that fulfill the power and energy requirements of specific applications. However, conclusions about battery performance and degradation under different conditions, as well as predictive models, are often derived from single cell cycling results. In this study, we evaluate the performance of six different series-parallel configurations of commercial lithium nickel manganese cobalt cells over hundreds of cycles. Each cell within the modules was individually instrumented for voltage, current, and temperature monitoring. We quantified the impact of module configuration on overall energy throughput, the voltage spread among series-connected cells, and the current heterogeneity in parallel-connected cells. This module cycling study, one of the broadest reported to date, supports systematic evaluation of the performance trade-offs, pack penalty, and safety implications of different module configurations.

25 ENERGY STORAGE↗
DOE OSTI2020

A New Scheme of Redundant Timing Crosschecking for Frontend Systems

In high energy physics experiments, frontend digitization modules are usually driven by a common clock. At the frontend electronics and digitization modules of the detector, a precise timing reference must establish in order to make a useful timing measurement. It would be very useful for the frontend digitization system to include a feature of redundant timing crosschecking. The inspiration for the timing crosschecking scheme came from the long-abandoned analog mean-timer schemes. In this scheme, several Front-end modules are connected together through a cable set with taps connected to the digitization modules. Pulses are driven from every FE modules alternately without overlapping. The arrival times of pulses sent from FE modules are digitized at the timing crosschecking module. The mean times will change as temperature changes, but their difference between two FE modules are cancelled mathematically. This feature enables easy achievement of good timing precision without the need for complex hardware.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2021

Integrated package of electron cyclotron emission imaging data processing and forward modeling in OMFIT

An Electron Cyclotron Emission Imaging (ECEI) data analysis module has been developed for the OMFIT platform to accommodate the needs of users at the DIII-D tokamak for physics applications. The user can easily access the ECEI spatial observation windows in the plasma that are calculated based on the automatically retrieved hardware setup and available DIII-D equilibria, perform spectral analysis, and make 2D electron temperature fluctuation images. The module provides a powerful data post processing package for extracting important physics parameters from the 2D measurements, including the radial structure and poloidal mode number of Alfven Eigenmodes, as well as the frequency-vs-wavenumber dispersion relationship of broadband MHD. Lastly, the module propagates characterized synthetic fluctuations for the user, so one can perform forward modeling tasks with simple analytical fluctuations.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2021

Magnetic structure and multiferroicity of Sc-substituted hexagonal YbFeO 3

The hexagonal rare-earth ferrite RFeO 3 family represents a unique class of multiferroics exhibiting weak ferromagnetism, and a strong coupling between magnetism and structural trimerization is predicted. However, the hexagonal structure for RFeO 3 remains metastable in conventional conditions. We have succeeded in stabilizing the hexagonal structure of polycrystalline YbFeO 3 by partial Sc substitution of Yb. Using bulk magnetometry and neutron diffraction, we find that Yb 0.42 Sc 0.58 FeO 3 orders into a canted antiferromagnetic state with the Néel temperature T N ~ 165K, below which the Fe 3+ moments form the triangular configuration in the ab plane and their in-plane projections are parallel to the [100] axis, consistent with magnetic space group P6 3 c'm'. It is determined that the spin canting is aligned along the c axis, giving rise to the weak ferromagnetism. Furthermore, the Fe 3+ moments reorient toward a new direction below reorientation temperature T R ~ 40K, satisfying magnetic subgroup P6 3 , while the Yb 3+ moments order independently and ferrimagnetically along the c axis at the characteristic temperature T Yb ~ 15K. Interestingly, reproducible modulation of electric polarization induced by magnetic field at low temperature is achieved, suggesting that the delicate structural distortion associated with two-up/one-down buckling of the Yb/Sc planes and tilting of the FeO 5 bipyramids may mediate the coupling between ferroelectric and magnetic orders under magnetic field. Furthermore, the present work represents substantial progress to search for high-temperature multiferroics in hexagonal ferrites and related materials.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
NASA NTRS1976

Program to design, fabricate, test, and deliver a thermal control-mixing control device for the George C. Marshall Space Flight Center

The development and testing of a temperature sensor and pulse duration modulation (PDM) diverter valve for a thermal control-mixing control device are described. The temperature sensor selected for use uses a fluidic pin amplifier in conjunction with an expansion device. This device can sense changes of less than 0.25 F with greater than 15:1 signal to noise ratio when operating with a typical Freon pump supplied pressure. The pressure sensitivity of the sensor is approximately 0.0019 F/kPa. The valve which was selected was tested and performed with 100% flow diversion. In addition, the valve operates with a flow efficiency of at least 95%, with the possibility of attaining 100% if the vent flow of the PDM can be channeled through the last stage of the diverter valve. A temperature sensor which utilized an orifice bridge circuit and proportional-vortex combination mixing valve were also evaluated, but the concepts were rejected due to various problems.

Thurston, T. S.↗
NASA NTRS1981

Combined photovoltaic and thermal-storage module

Module uses phase change heat absorbing wax to reduce peak temperatures, increasing electrical efficiency. Wax makes module more cost effective than conventional thermomodules by also storing thermal energy for air and water heating.

Stultz, J. W.↗
DOE OSTI2023

Direct Observation of Enhanced Electron-Phonon Coupling in Copper Nanoparticles in the Warm-Dense Matter Regime

Warm-dense matter (WDM) is a highly-excited state that lies at the confluence of solids, plasmas, and liquids and that cannot be described by equilibrium theories. The transient nature of this state when created in a laboratory, as well as the difficulties in probing the strongly-coupled interactions between the electrons and the ions, make it challenging to develop a complete understanding of matter in this regime. Here in this work, by exciting isolated ~8 nm nanoparticles with a femtosecond laser below the ablation threshold, we create uniformly-excited WDM. We then use photoelectron spectroscopy to track the instantaneous electron temperature and directly extract the strongest electron-ion coupling observed experimentally to date. By directly comparing with state-of-the-art theories, we confirm that the superheated nanoparticles lie at the boundary between hot solids and plasmas, with associated strong electron-ion coupling. This is evidenced both by the fast energy loss of electrons to ions, as well as a strong modulation of the electron temperature by acoustic oscillations in the nanoparticle. This work demonstrates a new route for experimental exploration and theoretical validation of the exotic properties of WDM.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
NASA NTRS1987

An earth outgoing longwave radiation climate model. I - Clear sky radiation

An earth outgoing longwave radiation (OLWR) climate model is presented. The model uses the upward radiative transfer parameterization of Thompson and Warren (1982) for radiation calculations, and a climatologic dataset from Crutcher and Meserve (1970) and Taljaard et al. (1969) to provide data on temperature, dewpoint, and geopotential height for various altitudes. Using the model for a monthly average radiation budget study, clear sky cases of OLWR were calculated for the global average, zonal averages, and global distributions. The regional results on North and South America were compared with GOES data and were found to agree well. The clear sky case shows that the OLWR field is highly modulated by water vapor, especially in the tropics, where the strongest longitudinal variations in OLWR occur. In the high latitudes, where cold air contains less water vapor, OLWR is basically modulated by the surface temperature.

Yang, Shi-Keng↗
NASA NTRS1989

Thermal enclosures for electronically scanned pressure modules operating in cryogenic environments

Specific guidelines to design, construct, and test ESP thermal enclosures for applications at cryogenic temperatures are given. The enclosures maintain the ESP modules at a constant temperature (10 C plus or minus 1 C) to minimize thermal zero and sensitivity shifts, to minimize the frequency of expensive on-line calibrations, and to avoid adverse effects on tunnel and model boundary layers. The enclosures are constructed of a rigid closed-cell foam and are capable of withstanding the stagnation pressures to 932kPa (135 psia) without reduction in thermal insulation properties. This construction procedure has been used to construct several thermal packages which have been successfully used in National Transonic Facility.

Mitchell, Michael↗
NASA NTRS1984

Electronically-Scanned Pressure Sensors

Sensors not pneumatically switched. Electronic pressure-transducer scanning system constructed in modular form. Pressure transducer modules and analog to digital converter module small enough to fit within cavities of average-sized wind-tunnel models. All switching done electronically. Temperature controlled environment maintained within sensor modules so accuracy maintained while ambient temperature varies.

Coe, C. F.↗
NASA NTRS1980

Heart rate, multiple body temperature, long-range and long-life telemetry system for free-ranging animals

The design details and rationale for a versatile, long-range, long-life telemetry data acquisition system for heart rates and body temperatures at multiple locations from free-ranging animals are presented. The design comprises an implantable transmitter for short to medium range transmission, a receiver retransmitter collar to be worn for long-range transmission, and a signal conditioner interface circuit to assist in signal discrimination and demodulation of receiver or tape-recorded audio outputs. Implanted electrodes are used to obtain an ECG, from which R-wave characteristics are selected to trigger a short RF pulse. Pulses carrying heart rate information are interrupted periodically by a series of pulse interval modulated RF pulses conveying temperature information sensed at desired locations by thermistors. Pulse duration and pulse sequencing are used to discriminate between heart rate and temperature pulses as well as radio frequency interference. The implanted transmitter may be used alone for medium and short-range tracking, or with a receiver-transmitter collar that employs commercial tracking equipment for transmissions of up to 12 km. A system prototype has been tested on a dog.

Lund, G. F.↗
DOE OSTI2021

A Catastrophic Charge Density Wave in BaFe 2 Al 9

Charge density waves (CDWs) are modulations of the electron density and the atomic lattice that develop in some crystalline materials at low temperatures. We report an unusual example of a CDW in BaFe 2 Al 9 below 100 K. In contrast to the canonical CDW phase transition, temperature-dependent physical properties of single crystals reveal a first-order phase transition. This is accompanied by a discontinuous change in the size of the crystal lattice. In fact, this large strain has catastrophic consequences for the crystals causing them to physically shatter. Single-crystal X-ray diffraction reveals superlattice peaks in the low-temperature phase signaling the development of a CDW lattice modulation. No similar low-temperature transitions are observed in BaFe 2 Al 9 . Electronic structure calculations provide one hint to the different behavior of these two compounds; the d-orbital states in the Fe compound are not completely filled. Iron compounds are renowned for their magnetism, and partly filled d-states play a key role. Finally, it is therefore surprising that BaFe 2 Al 9 develops a structural modulation at low temperature instead of magnetic order.

36 MATERIALS SCIENCE↗
NASA NTRS1993

Mechanosensory calcium-selective cation channels in epidermal cells

This paper explores the properties and likely functions of an epidermal Ca(2+)-selective cation channel complex activated by tension. As many as eight or nine linked or linkable equivalent conductance units or co-channels can open together. Open time for co-channel quadruplets and quintuplets tends to be relatively long with millimolar Mg2+ (but not millimolar Ca2+) at the cytosolic face of excised plasma membrane. Sensitivity to tension is regulated by transmembrane voltage and temperature. Under some circumstances channel activity is sychronized in rhythmic pulses. Certain lanthanides and a cytoskeleton-disturbing herbicide that inhibit gravitropic reception act on the channel system at low concentrations. Specifically, ethyl-N-phenylcarbamate promotes tension-dependent activity at micromolar levels. With moderate suction, Gd3+ provided at about 0.5 micromole at the extracellular face of the membrane promotes for several seconds but may then become inhibitory. Provision at 1-2 micromoles promotes and subsequently inhibits more vigorously (often abruptly and totally), and at high levels inhibits immediately. La3+, a poor gravitropic inhibitor, acts similarly but much more gradually and only at much higher concentrations. These properties, particularly these susceptibilities to modulation, indicate that in vivo the mechanosensitive channel must be mechanosensory and mechanoregulatory. It could serve to transduce the shear forces generated in the integrated wall-membrane-cytoskeleton system during turgor changes and cell expansion as well as transducing the stresses induced by gravity, touch and flexure. In so far as such transduction is modulated by voltage and temperature, the channels would also be sensors for these modalities as long as the wall-membrane-cytoskeleton system experiences mechanical stress.

NASA Discipline Number 40-50↗
NASA NTRS2000

Long-term Global Morphology of Gravity Wave Activity Using UARS Data

An extensive body of research this quarter is documented. Further methodical analysis of temperature residuals in Cryogenic Limb Array Etalon Spectrometer (CLAES) Version 8 level 3AT data show signatures during December 1992 at middle and high northern latitudes that, when compared to Naval Research Laboratory/Mountain Wave Forecast Model (NRL)/(MWFM) mountain wave hindcasts, reveal evidence of long mountain waves in these data over Eurasia, Greenland, Scandinavia and North America. The explicit detection of gravity waves in limb-scanned Cryogenic Infrared Spectrometers and Telescopes for the Atmosphere (CRISTA) temperatures is modeled at length, to derive visibility functions. These insights are used to convert CRISTA gravity wave temperature residuals into data that more closely resemble gravity wave fluctuations detected in data from other satellite instruments, such as Microwave Limb Sounder (MLS), Limb Infrared Monitor of the Stratosphere (LIMS) and Global Positioning System/Meteorology (GPS)/(MET). Finally, newly issued mesospheric temperatures from inversion of CRISTA 15gin emissions are analyzed using a new method that uses separate Kalman fits to the ascending and descending node data. This allows us to study global gravity wave amplitudes at two local times, 12 hours apart. In the equatorial mesosphere, where a large diurnal tidal temperature signal exists, we see modulations of gravity wave activity that are consistent with gravity wave-tidal interactions produced by tidal temperature variability.

Eckermann, Stephen D.↗
DOE OSTI2026

QTL Mapping of Seed Fatty Acid Contents in Camelina sativa Under Heat Stress

Heat stress alters oil quality in oilseed crops, yet its genetic underpinnings in Camelina sativa remain unclear. This study investigated the genetic basis of heat-induced changes in seed fatty acids using a recombinant inbred line (RIL) population derived from a cross between two camelina varieties, Suneson and Pryzeth. Exposure to high temperature during reproductive growth led to increased proportions of saturated (C16:0, C18:0) and monounsaturated (C18:1) fatty acids, whereas polyunsaturated C18:3, total unsaturated fatty acids (UFA) and the PUFA/MUFA ratio were decreased, suggesting an inhibition of the C18:1 → C18:2 → C18:3 desaturation pathway. A high-density linkage map (4981 bins across 20 chromosomes) was built, and 25 QTLs for fatty acids were detected, with hotspots on chromosomes 1, 9, 12, 13, 16, and 20. A major QTL on chromosome 1 (~ 80 cM) explained the largest variance component for PUFA/MUFA under heat. Three desaturase genes (FAD2, FAD7, FAD8) were located within key QTL intervals, nominating them as candidates for modulating unsaturation under elevated temperature. These results provide a genetic basis for fine mapping and functional validation, supporting future molecular and breeding efforts to stabilize oil quality under warming conditions.

Camelina↗
DOE OSTI2023

Thermo-acoustoelastic effect of Rayleigh wave: Theory and experimental verification

Previous studies showed that the thermally-induced ultrasonic bulk wave velocity change could be used to measure acoustoelastic coefficients and third-order elastic constants of elastic materials. This method is naturally immune from the ambient temperature effect and has improved sensitivity and a simpler test setup than the conventional acoustoelastic test. However, Rayleigh wave is preferred for thick components or structures with only one accessible surface. In this work, the thermo-hyperelastic constitutive equation, along with acoustoelastic theory, is used to derive the expression of the thermo-acoustoelastic coefficient (TAEC) of Rayleigh wave. The numerical relationship between the TAEC of Rayleigh wave and Murnaghan constants ( l, m and n ) are given for common metals. Further, the TAEC expressions for Rayleigh wave and shear wave are similar, and both are dominated by the constant m . The TAEC of Rayleigh wave was measured on an aluminum 6061 specimen using the thermal modulation experiment in a temperature range of 22 ~ 35°C. The measured TAEC shows good agreement with the theoretical calculation. Then the third-order elastic constants were calculated based on TAECs of bulk waves and Rayleigh wave.

42 ENGINEERING↗
NASA NTRS2018

The Atmosphere-Ocean Interface Layer of NASA's Goddard Earth Observing System Model and Data Assimilation System Volume 51

The Goddard Earth Observing System (GEOS) general circulation model (GCM) includes modules for sea surface temperature (SST) diurnal warming and cool-skin layers. To support the application of a coupled atmosphere-ocean data assimilation capability, the GCM needs to be flexible enough to support both coupled atmosphere ocean general circulation model (AOGCM) and atmosphere-only (AGCM) configurations, with only minor configuration changes at the user interface. This document presents a formulation of an atmosphere-ocean interface layer (AOIL) that serves this purpose. Previous work by Akella et al. (2017) described a version of a model for near-surface temperature variations, including both both diurnal warming and cool-skin effects, that has been used since 2017 in the near-real-time GEOS FP (forward processing) weather analysis and forecasting system. The diurnal cycle of SST in that version of the GEOS atmospheric data assimilation system (ADAS) undergoes a sharp decay in the late afternoon (local time). The updated AOIL presented here includes a modification of the similarity function used in the diurnal warming model. Results from offline model runs illustrate an improvement in the near-surface (less than 0:5m depth) diurnal cycle compared to the original formulation. The new formulation requires minimal parameter tuning, and the improvements are robust across long (several month) simulation periods. This new model formulation, however, retains some deficiences from the previous module, such as a small warm bias in calm wind conditions for water depths below 1m. Our future work would include surface salinification and sea-ice into the AOIL.

Koster, Randal D.↗