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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 883 records · Page 49
All sourcesNASA NTRSDOE OSTI
DOE OSTI2015

DNA binding by FOXP3 domain-swapped dimer suggests mechanisms of long-range chromosomal interactions

FOXP3 is a lineage-specific transcription factor that is required for regulatory T cell development and function. In this study, we determined the crystal structure of the FOXP3 forkhead domain bound to DNA. The structure reveals that FOXP3 can form a stable domain-swapped dimer to bridge DNA in the absence of cofactors, suggesting that FOXP3 may play a role in long-range gene interactions. To test this hypothesis, we used circular chromosome conformation capture coupled with high throughput sequencing (4C-seq) to analyze FOXP3-dependent genomic contacts around a known FOXP3-bound locus, Ptpn22. Our studies reveal that FOXP3 induces significant changes in the chromatin contacts between the Ptpn22 locus and other Foxp3-regulated genes, reflecting a mechanism by which FOXP3 reorganizes the genome architecture to coordinate the expression of its target genes. Our results suggest that FOXP3 mediates long-range chromatin interactions as part of its mechanisms to regulate specific gene expression in regulatory T cells.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2021

Biotin attachment domain-containing proteins mediate hydroxy fatty acid-dependent inhibition of acetyl CoA carboxylase

Hundreds of naturally occurring specialized fatty acids (FAs) have potential as desirable chemical feedstocks if they could be produced at large scale by crop plants; however, transgenic expression of their biosynthetic genes has generally been accompanied by dramatic reductions in oil yield. For example, expression of castor (Ricinus communis) FA hydroxylase (FAH) in the Arabidopsis thaliana FA elongation mutant fae1 resulted in a 50% reduction of FA synthesis rate that was attributed to inhibition of acetyl-CoA carboxylase (ACCase) by an undefined mechanism. Here, we tested the hypothesis that the ricinoleic acid-dependent decrease in ACCase activity is mediated by biotin attachment domain-containing (BADC) proteins. BADCs are inactive homologs of biotin carboxy carrier protein that lack a biotin cofactor and can inhibit ACCase. Arabidopsis contains three BADC genes. To reduce expression levels of BADC1 and BADC3 in fae1/FAH plants, a homozygous badc1,3/fae1/FAH line was created. The rate of FA synthesis in badc1,3/fae1/FAH seeds doubled relative to fae1/FAH, restoring it to fae1 levels, increasing both native FA and HFA accumulation. Total FA per seed, seed oil content, and seed yield per plant all increased in badc1,3/fae1/FAH, to 5.8 µg, 37%, and 162 mg, respectively, relative to 4.9 µg, 33%, and 126 mg, respectively, for fae1/FAH. Transcript levels of FA synthesis-related genes, including those encoding ACCase subunits, did not significantly differ between badc1,3/fae1/FAH and fae1/FAH. These results demonstrate that BADC1 and BADC3 mediate ricinoleic acid-dependent inhibition of FA synthesis. We propose that BADC-mediated FAS inhibition as a general mechanism that limits FA accumulation in specialized FA-accumulating seeds.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2024

The effect of TiO2 nanoparticles on antral follicles is dependent on the nanoparticle internalization rate

Abstract Titanium dioxide nanoparticles (TiO2 NPs) are among the most widely produced metallic NPs due to commercial and industrial applications in products including food, cosmetics, paints, and plastics. TiO2 NPs are released into the environment posing health risks for humans and wildlife. Widespread uses have raised concerns about the potential toxicity of TiO2 NPs in reproduction. The ovary is an important endocrine organ responsible for sex steroid hormone production and folliculogenesis. NPs can reach the ovary, but limited information is available regarding NP toxicity and its effects on ovarian antral follicles. Thus, we tested the hypothesis that exposure to TiO2 NP affects sex hormone synthesis, oxidative stress, and antioxidant response in ovarian antral follicles in vitro. In addition, we characterized the NP internalization in the antral follicles over time to determine any association between NP internalization and effects on the antral follicle. Antral follicles were exposed to vehicle control or TiO2 NPs (5, 25, and 50 µg/ml) for 96 h. The lowest NP concentration (5 µg/ml) showed no internalization and no effects in antral follicles. The 25-µg/ml concentration had the highest internalization rate, leading to increased mRNA ratio of Bax to Bcl2. Interestingly, the highest concentration (50 µg/ml) showed lower internalization compared with the 25 µg/ml, with altered levels of steroidogenic involved genes and increased levels of progesterone and testosterone compared with control. In conclusion, these data suggest that TiO2 NP is internalized in antral follicles as the first step process in impairing follicle functions.

Santacruz-Márquez, Ramsés (ORCID:0000000225239064)↗
DOE OSTI2021

Seasonal trends in photosynthesis and leaf traits in scarlet oak

Understanding seasonal variation in photosynthesis is important for understanding and modelling plant productivity. Here, we used shotgun sampling to examine physiological, structural and spectral leaf traits of upper canopy, sun-exposed leaves in Quercus coccinea Münchh (scarlet oak) across the growing season in order to understand seasonal trends, explore the mechanisms underpinning physiological change, and investigate the impact of extrapolating measurements from a single date to the whole season. We tested the hypothesis that photosynthetic rates and capacities would peak at the summer solstice i.e., at the time of peak photoperiod. Contrary to expectations, our results reveal a late-season peak in both photosynthetic capacity and rate before the expected sharp decrease at the start of senescence. This late-season maximum occurred after the higher summer temperatures and VPD, and was correlated with the recovery of leaf water content and increased stomatal conductance. We modelled photosynthesis at the top of the canopy and found that the simulated results closely tracked the maximum carboxylation capacity of Rubisco. For both photosynthetic capacity and modelled top-of-canopy photosynthesis, the maximum value was therefore not observed at the summer solstice. Rather, in each case the measurements at and around the solstice were close to the overall seasonal mean, with values later in the season leading to deviations from the mean by up to 41% and 52% respectively. Overall, we found that the expected Gaussian pattern of photosynthesis was not observed. We conclude that an understanding of species- and environment-specific changes in photosynthesis across the season is essential for correct estimation of seasonal photosynthetic capacity.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2024

Preserving isohydricity: vertical environmental variability explains Amazon forest water-use strategies

Abstract Increases in hydrological extremes, including drought, are expected for Amazon forests. A fundamental challenge for predicting forest responses lies in identifying ecological strategies which underlie such responses. Characterization of species-specific hydraulic strategies for regulating water-use, thought to be arrayed along an ‘isohydric–anisohydric’ spectrum, is a widely used approach. However, recent studies have questioned the usefulness of this classification scheme, because its metrics are strongly influenced by environments, and hence can lead to divergent classifications even within the same species. Here, we propose an alternative approach positing that individual hydraulic regulation strategies emerge from the interaction of environments with traits. Specifically, we hypothesize that the vertical forest profile represents a key gradient in drought-related environments (atmospheric vapor pressure deficit, soil water availability) that drives divergent tree water-use strategies for coordinated regulation of stomatal conductance (gs) and leaf water potentials (ΨL) with tree rooting depth, a proxy for water availability. Testing this hypothesis in a seasonal eastern Amazon forest in Brazil, we found that hydraulic strategies indeed depend on height-associated environments. Upper canopy trees, experiencing high vapor pressure deficit (VPD), but stable soil water access through deep rooting, exhibited isohydric strategies, defined by little seasonal change in the diurnal pattern of gs and steady seasonal minimum ΨL. In contrast, understory trees, exposed to less variable VPD but highly variable soil water availability, exhibited anisohydric strategies, with fluctuations in diurnal gs that increased in the dry season along with increasing variation in ΨL. Our finding that canopy height structures the coordination between drought-related environmental stressors and hydraulic traits provides a basis for preserving the applicability of the isohydric-to-anisohydric spectrum, which we show here may consistently emerge from environmental context. Our work highlights the importance of understanding how environmental heterogeneity structures forest responses to climate change, providing a mechanistic basis for improving models of tropical ecosystems.

Forestry↗
DOE OSTI2018

Lack of acclimation of leaf area:sapwood area ratios in piñon pine and juniper in response to precipitation reduction and warming

The leaf area to sapwood area ratios of trees (A l :A S ) can shift to maintain homeostatic gas exchange per unit leaf area in response to climate variability. Here, we tested the hypothesis that trees alter their A l :A S ratios in response to long-term warming and reduced precipitation in order to maintain leaf-specific gas exchange rates under more stressful conditions. Whole-tree A l :A S was measured on mature piñon pine (Pinus edulis Engelm.) and one-seed juniper (Juniperus monosperma (Engelm.) Sarg.) trees after 5 years (2012–16) of chronic exposure to increased temperature (+4.8 °C), precipitation reduction (-45%), or both simultaneously. No difference was found in A l :A s among treatments for either species. Associated with this lack of shift in A l :A s were large changes in pre-dawn leaf water potential and stomatal conductance, consistent with theoretical expectations of interactions between leaf and whole-tree hydraulic supply. Finally, our results suggest that a lack of whole-tree acclimation in A l :A s results in the reductions in plant gas exchange and water status associated with long-term warming and reduced precipitation in semi-arid woodlands.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2019

Interrelationship between sex, age, blood volume and VO 2 max

Background Circulating blood volume (BV) and maximal oxygen uptake (VO 2 max) are physiological characteristics important for optimal human performance in aerospace and military operational environments. Addressing the interrelationships between BV, VO 2 max, sex, and age together is relevant to identifying those individuals with greatest risk of poor outcomes from hemorrhage, as well as assessing the levels of performance competence of individuals deployed in operational environments. In the present investigation, we report and compare for the first time BV and VO 2 max in a cohort of males and females together to test the hypothesis that BV and VO 2 max is lower in older people independent of sex. Methods To accomplish this, a ‘data mining’ effort of an historic database generated from NASA and U.S. Air Force experiments was conducted. BV, red cell volume, plasma volume, hematocrit, and VO 2 max were measured in 94 healthy individuals (28 females, 66 males) across an age range of 23 to 65 years to assess the interrelationship between sex, age, BV, and VO 2 max. Subjects were classified in age groups by < 40 years and ≥ 40 years; these groups identified females as pre‐ vs. post‐menopausal. Results Consistent with our hypothesis, comparisons revealed that males had higher (p < 0.01) BV, red cell volume, hematocrit, and VO 2 max than females when standardized for body size. Against expectations, BV was not different in older compared with younger males and females. VO 2 max was not different in older compared with younger females, while VO 2 max was lower in older males (p < 0.01). Conclusion We conclude that physiological mechanisms other than BV associated with aging appear to be responsible for a decline in VO 2 max of our older male subjects. Furthermore, factors other than menopause may also influence the control of BV in the female population. Our results provide evidence that aging may not compromise males or females in scenarios where BV can affect performance in aerospace and military environments. Support or Funding Information This research was supported in part by appointment of Ms. Koons to the Postgraduate Research Fellowship Program at the US Army Institute of Surgical Research administered by the Oak Ridge Institute for Science and Education through an interagency agreement between the US Department of Energy and USAMRMC. Study funding was provided by a grant from the US Army Combat Casualty Care Research Program (D‐009‐2014‐USAISR). This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal .

Convertino, Victor↗
DOE OSTI2019

Tracking DO 2 with Compensatory Reserve during Whole Blood Resuscitation in Baboons

Background Hemorrhagic shock can be mitigated by timely and accurate resuscitation designed to restore adequate delivery of oxygen (DO 2 ) by increasing cardiac output (CO). However, standard care of using systolic blood pressure (SBP) as a guide for resuscitation has proven ineffective and can be associated with increased morbidity. We have developed a novel vital sign called the compensatory reserve (CRM) generated from analysis of arterial pulse waveform feature changes that has been validated in experimental and clinical models of hemorrhage. We tested the hypothesis that thresholds of DO 2 could be accurately defined by CRM while avoiding over resuscitation during whole blood resuscitation following a 25% hemorrhage in non‐human primates. Methods To accomplish this, adult male baboons (n=12) were exposed to a progressive controlled hemorrhage that resulted in an average (± SD) maximal reduction of 601 ± 18 ml of their estimated circulating blood volume of 1,262 ± 64 ml based on body weight. Values of DO 2 were calculated as the product of CO times O 2 carrying capacity of hemoglobin (i.e., Hb content × 1.34). Results Average (± SD) CRM increased from 6 ± 5 % at the end of hemorrhage to 70 ± 7 % at the end of resuscitation. DO 2 of 12.1, 10.3, and 7.0 ml O 2 ·kg −1 ·min −1 were calculated at 0% (baseline), 12.5% and 25% blood loss. By linear regression, CRM values of 6% (decompensation), 35%, and 68% corresponded to calculated DO 2 values of 6.0, 9.2, and 12.1 ml O 2 ·kg −1 ·min −1 during resuscitation. As such, return of CRM to baseline during resuscitation with only ~ 450 ml provided adequate DO 2 (12.5 ml O 2 ·kg −1 ·min −1 ) while total blood volume replacement (~600 ml) resulted in over resuscitation as indicated by an average increase in SBP (+17 mmHg) and CO (+0.1 L/min) over baseline values. Conclusion Consistent with our hypothesis, thresholds of DO 2 were associated with specific CRM values. A target resuscitation CRM value of 70% minimized the requirement for whole blood, while avoiding over resuscitation. Furthermore, CRM at 0% provided a noninvasive metric for determining critical DO 2 at approximately 5.4 ml O 2 ·kg −1 ·min −1 . Support or Funding Information This research was supported in part by appointment of Ms. Koons to the Postgraduate Research Fellowship Program at the US Army Institute of Surgical Research administered by the Oak Ridge Institute for Science and Education through an interagency agreement between the US Department of Energy and USAMRMC. Study funding was provided by a grant from the US Army Combat Casualty Care Research Program (D‐009‐2014‐USAISR). Linearregression of the relationship between DO 2 and compensatory reserve during whole blood resuscitation in baboons. Data are expressed as mean ± SE. image Linearregression of the relationship between DO 2 and compensatory reserve during whole blood resuscitation in baboons. Data are expressed as mean ± SE. This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal .

Koons, Natalie Jane↗
DOE OSTI2016

Predicting plant attractiveness to pollinators with passive crowdsourcing

Global concern regarding pollinator decline has intensified interest in enhancing pollinator resources in managed landscapes. These efforts frequently emphasize restoration or planting of flowering plants to provide pollen and nectar resources that are highly attractive to the desired pollinators. However, determining exactly which plant species should be used to enhance a landscape is difficult. Empirical screening of plants for such purposes is logistically daunting, but could be streamlined by crowdsourcing data to create lists of plants most probable to attract the desired pollinator taxa. People frequently photograph plants in bloom and the Internet has become a vast repository of such images. A proportion of these images also capture floral visitation by arthropods. Here, we test the hypothesis that the abundance of floral images containing identifiable pollinator and other beneficial insects is positively associated with the observed attractiveness of the same species in controlled field trials from previously published studies. We used Google Image searches to determine the correlation of pollinator visitation captured by photographs on the Internet relative to the attractiveness of the same species in common-garden field trials for 43 plant species. From the first 30 photographs, which successfully identified the plant, we recorded the number of Apis (managed honeybees), non-Apis (exclusively wild bees) and the number of bee-mimicking syrphid flies. We used these observations from search hits as well as bloom period (BP) as predictor variables in Generalized Linear Models (GLMs) for field-observed abundances of each of these groups. We found that non-Apis bees observed in controlled field trials were positively associated with observations of these taxa in Google Image searches (pseudo-R 2 of 0.668). Syrphid fly observations in the field were also associated with the frequency they were observed in images, but this relationship was weak. Apis bee observations were not associated with Internet images, but were slightly associated with BP. Our results suggest that passively crowdsourced image data can potentially be a useful screening tool to identify candidate plants for pollinator habitat restoration efforts directed at wild bee conservation. Increasing our understanding of the attractiveness of a greater diversity of plants increases the potential for more rapid and efficient research in creating pollinator-supportive landscapes.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2022

Spatial scales of competition and a growth–motility trade-off interact to determine bacterial coexistence

The coexistence of competing species is a long-lasting puzzle in evolutionary ecology research. Despite abundant experimental evidence showing that the opportunity for coexistence decreases as niche overlap increases between species, bacterial species and strains competing for the same resources are commonly found across diverse spatially heterogeneous habitats. We thus hypothesized that the spatial scale of competition may play a key role in determining bacterial coexistence, and interact with other mechanisms that promote coexistence, including a growth–motility trade-off. To test this hypothesis, we let two Pseudomonas putida strains compete at local and regional scales by inoculating them either in a mixed droplet or in separate droplets in the same Petri dish, respectively. We also created conditions that allow the bacterial strains to disperse across abiotic or fungal hyphae networks. We found that competition at the local scale led to competitive exclusion while regional competition promoted coexistence. When competing in the presence of dispersal networks, the growth–motility trade-off promoted coexistence only when the strains were inoculated in separate droplets. Our results provide a mechanism by which existing laboratory data suggesting competitive exclusion at a local scale is reconciled with the widespread coexistence of competing bacterial strains in complex natural environments with dispersal.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2012

Nature and function of insulator protein binding sites in the Drosophila genome

Chromatin insulator elements and associated proteins have been proposed to partition eukaryotic genomes into sets of independently regulated domains. Here we test this hypothesis by quantitative genome-wide analysis of insulator protein binding to Drosophila chromatin. We find distinct combinatorial binding of insulator proteins to different classes of sites and uncover a novel type of insulator element that binds CP190 but not any other known insulator proteins. Functional characterization of different classes of binding sites indicates that only a small fraction act as robust insulators in standard enhancer-blocking assays. We show that insulators restrict the spreading of the H3K27me3 mark but only at a small number of Polycomb target regions and only to prevent repressive histone methylation within adjacent genes that are already transcriptionally inactive. RNAi knockdown of insulator proteins in cultured cells does not lead to major alterations in genome expression. Taken together, these observations argue against the concept of a genome partitioned by specialized boundary elements and suggest that insulators are reserved for specific regulation of selected genes.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2026

Revisiting the three-kaon interaction and its relation with 𝐾⁡(1460)

Here, we test the hypothesis of 𝐾⁡(1460) being a hadronic 𝐽 𝑃 = 0 − molecule through nonperturbative 𝑆-wave $KK\bar{⁢K}$, 𝐾⁢𝜋⁢𝜋, 𝐾⁢𝜋⁢𝜂 coupled-channel dynamics in a three-body unitary isobar approach. The scalar two-body coupled-channel resonances 𝑓 0 ⁡(500), 𝑓 0 ⁡(980), 𝑎 0 ⁡(980), and 𝐾$^*_0$⁡(700) are generated in the subsytems in amplitudes that match phase shifts from experiment. In a first step, previous results in the limit of mass-degenerate, stable 𝑓 0 and 𝑎 0 isobars are reproduced. Once the full seven-coupled channel model is switched on, other 𝑆-matrix effects obscure and modify the resonance signal, including complex thresholds, a two-body cusp, and a triangle singularity at threshold.

Döring, M. [George Washington Univ., Washington, D↗
DOE OSTI2026

(Ir)Relevance of Disorder for Superconductivity in Cuprates

In cuprates that exhibit high-temperature superconductivity (HTS), as the doping level 𝑝 is increased beyond the optimal value, the superfluid density 𝑛 𝑠⁢0 decreases and eventually vanishes, closely tracking the critical temperature 𝑇 𝑐 . This has been interpreted using a dirty-𝑑-wave extension of the Bardeen-Cooper-Schrieffer theory, assuming that 𝑇 𝑐 and 𝑛 𝑠⁢0 decrease with increasing disorder and pair breaking. Here, to test this hypothesis, we tuned the doping level in overdoped La 2-x ⁢Sr x ⁢CuO 4−𝛿 films by electrolyte gating, measured several parameters used to quantify the level of disorder (the residual resistivity ratio RRR, the mean free path 𝑙 0 , and the electron mobility 𝜇), and studied how 𝑇 𝑐 and 𝑛 𝑠⁢0 scale with these. The experimentally measured dependence turned out to be the opposite of the expected—𝑇 𝑐 and 𝑛 𝑠⁢0 increased with increasing disorder. This brings the question of the true origin of the demise of 𝑇 𝑐 and 𝑛 𝑠⁢0 with overdoping back to the center stage of the quest to decipher the HTS enigma.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2021

Heat transport in liquid water from first-principles and deep neural network simulations

In this work, we compute the thermal conductivity of water within linear response theory from equilibrium molecular dynamics simulations, by adopting two different approaches. In one, the potential energy surface (PES) is derived on the fly from the electronic ground state of density functional theory (DFT) and the corresponding analytical expression is used for the energy flux. In the other, the PES is represented by a deep neural network (DNN) trained on DFT data, whereby the PES has an explicit local decomposition and the energy flux takes a particularly simple expression. By virtue of a gauge invariance principle, established by Marcolongo, Umari, and Baroni, the two approaches should be equivalent if the PES were reproduced accurately by the DNN model. We test this hypothesis by calculating the thermal conductivity, at the GGA (PBE) level of theory, using the direct formulation and its DNN proxy, finding that both approaches yield the same conductivity, in excess of the experimental value by approximately 60%. Besides being numerically much more efficient than its direct DFT counterpart, the DNN scheme has the advantage of being easily applicable to more sophisticated DFT approximations, such as meta-GGA and hybrid functionals, for which it would be hard to derive analytically the expression of the energy flux. We find in this way that a DNN model, trained on meta-GGA (SCAN) data, reduces the deviation from experiment of the predicted thermal conductivity by about 50%, leaving the question open as to whether the residual error is due to deficiencies of the functional, to a neglect of nuclear quantum effects in the atomic dynamics, or, likely, to a combination of the two.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2022

High-pressure control of optical nonlinearity in the polar Weyl semimetal TaAs

The transition metal monopnictide family of Weyl semimetals recently has been shown to exhibit anomalously strong second-order optical nonlinearity, which is theoretically attributed to a highly asymmetric polarization distribution induced by their polar structure. We experimentally test this hypothesis by measuring optical second harmonic generation (SHG) from TaAs across a pressure-tuned polar-to-nonpolar structural phase transition. Despite the high-pressure structure remaining noncentrosymmetric, the SHG yield is reduced by more than 60% by 20 GPa as compared to the ambient pressure value. By examining the pressure dependence of distinct groups of SHG susceptibility tensor elements, we find that the yield is primarily controlled by a single element that governs the response along the polar axis. Furthermore, our results confirm a connection between the polar axis and the giant optical nonlinearity of Weyl semimetals and demonstrate pressure as a means to tune this effect in situ.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2022

Information content of the differences in the charge radii of mirror nuclei

Differences in the charge radii of mirror nuclei have been recently suggested to contain information on the slope of the symmetry energy L. To test this hypothesis, we perform statistical correlation analysis using quantified energy density functionals that are consistent with our previous knowledge on global nuclear observables such as binding energies and charge radii. We conclude that the difference in charge radii between a mirror pair, $ΔR$$^{mir}_{ch}$, is an inferior isovector indicator compared to other observables, such at the neutron skin or electric dipole polarizability α D . In particular, this quantity correlates poorly with both the neutron skin and L. Here, we demonstrate that $ΔR$$^{mir}_{ch}$ is influenced by pairing correlations in the presence of low-lying proton continuum in the proton-rich mirror-partner nucleus. Considering the large theoretical uncertainties on $ΔR$$^{mir}_{ch}$, we conclude that the precise data on mirror charge radii cannot provide a stringent constraint on L.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2024

Quantum electrodynamics mediated by a photon with continuous spin

In recent work with Zhou, we studied classical interactions of matter with a “continuous spin” field, whose excitations have zero mass but nonzero spin Casimir (spin scale) ρ . We reported evidence that such theories are a calculable infrared deformation of familiar massless theories including electromagnetism. Building on the aforementioned work, this paper presents rules for computing scattering amplitudes involving charged scalar matter and continuous spin photons with nonzero spin scale. As a concrete example, we compute the pair annihilation and Compton scattering amplitudes in this theory and comment on their physical properties, including unitarity and scaling behavior at small and large ρ . Like the classical physics and soft factors studied in prior work, these amplitudes exhibit “helicity correspondence,” recovering familiar amplitudes at energy scales ≫ ρ , but with calculable deviations that could be experimentally tested. These results bolster the conjecture that continuous spin particles with a very small ρ could mediate long-range forces in nature (e.g., the photon could be a continuous spin particle), and extend the range of physical effects that could be used to test this hypothesis. Published by the American Physical Society 2024

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗