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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 OSTI2014

Uncertainty in least-squares fits to the thermal noise spectra of nanomechanical resonators with applications to the atomic force microscope

Thermal noise spectra of nanomechanical resonators are used widely to characterize their physical properties. These spectra typically exhibit a Lorentzian response, with additional white noise due to extraneous processes. Least-squares fits of these measurements enable extraction of key parameters of the resonator, including its resonant frequency, quality factor, and stiffness. Here, we present general formulas for the uncertainties in these fit parameters due to sampling noise inherent in all thermal noise spectra. Good agreement with Monte Carlo simulation of synthetic data and measurements of an Atomic Force Microscope (AFM) cantilever is demonstrated. These formulas enable robust interpretation of thermal noise spectra measurements commonly performed in the AFM and adaptive control of fitting procedures with specified tolerances.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2013

Bacterial community structure and functional contributions to emergence of health or necrotizing enterocolitis in preterm infants

Background: Preterm infants represent a unique patient population that is born functionally immature and must accomplish development under the influence of a hospital environment. Neonatal necrotizing enterocolitis (NEC) is an inflammatory intestinal disorder affecting preterm infants. The purpose of this study was to evaluate the progression of intestinal microbiota community development between preterm infants who remained healthy compared to preterm infants who developed NEC. Results: Weekly fecal samples from ten preterm infants, five with NEC and five matched healthy controls were obtained. Bacterial DNA from individual fecal samples was subjected to sequencing of 16S rRNA-based inventories using the 454 GS-FLX platform. Fecal samples from control infants demonstrated a temporal pattern in their microbiota, which converged toward that of a healthy full term breast-fed infant. Microbiota development in NEC patients diverged from controls beginning three weeks prior to diagnosis. Shotgun metagenomic sequencing was performed to identify functional differences in the respective microbiota of fecal samples from a set of twins in which one twin developed NEC and one did not. The majority of the differentially abundant genes in the NEC patient were associated with carbohydrate metabolism and mapped to members of the family Enterobacteriaceae. This may indicate an adaptation of the community to an altered profile of substrate availability for specific members as a first step towards the development of NEC. We propose that the microbial communities as a whole may metabolize milk differently, resulting in differential substrate availability for specific microbial groups. Additional differentially represented gene sets of interest were related to antibiotic resistance and vitamin biosynthesis. Conclusions: Our results suggest that there is a temporal component to microbiome development in healthy preterm infants. Thus, bacteriotherapy for the treatment or prevention of NEC must consider this temporal component of the microbial community in addition to its taxonomic composition and functional content.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2014

Evaluation of the Lawrence Livermore Microbal Detection Array at the Statens Serum Institut CRADA No. TC02189

This was a collaborative effort between Lawrence Livermore National Security, LLC as manager and operator of Lawrence Livermore National Laboratory (LLNL) and Statens Serum Institut to evaluate and transition the Lawrence Livermore Microarray Detection Array (LLMDA) analysis software package, the Composite Likelihood Maximization method (CLiMax) to the SSI. The SSI is a public enterprise under the Danish Ministry of Health that operates a microbiology reference laboratory for the Danish population and analyzes tens to thousands of human clinical samples annually. SSI has been collaborating with the LLNL team for several years to use the LLMDA to analyze viral and bacterial infections from human clinical samples. The collaboration has resulted in two joint publications thus far, describing improvements to LLMDA sample preparation, and the utility of the LLMDA for detecting emerging viruses in clinical samples. Under our previous collaboration, SSI has performed LLMDA experiments at their facility and then transferred the raw LLMDA data to LLNL for analysis. SSI had purchased LLMDA microarrays directly from the manufacturer, Roche NimbleGen. The main purpose of the current collaboration was to adapt the CLiMax analysis software so that it could run on a computer located at SSI. Additional effort was budgeted for LLNL staff to assist SSI with the transition and the operation of the software. The primary deliverable is the CLiMax software, installed on a computer at SSI.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2014

Solution Hybrid Selection Capture for the Recovery of Functional Full-Length Eukaryotic cDNAs From Complex Environmental Samples

Eukaryotic microbial communities play key functional roles in soil biology and potentially represent a rich source of natural products including biocatalysts. Culture-independent molecular methods are powerful tools to isolate functional genes from uncultured microorganisms. However, none of the methods used in environmental genomics allow for a rapid isolation of numerous functional genes from eukaryotic microbial communities. We developed an original adaptation of the solution hybrid selection (SHS) for an efficient recovery of functional complementary DNAs (cDNAs) synthesized from soil-extracted polyadenylated mRNAs. This protocol was tested on the Glycoside Hydrolase 11 gene family encoding endo-xylanases for which we designed 35 explorative 31-mers capture probes. SHS was implemented on four soil eukaryotic cDNA pools. After two successive rounds of capture, >90% of the resulting cDNAs were GH11 sequences, of which 70% (38 among 53 sequenced genes) were full length. Between 1.5 and 25% of the cloned captured sequences were expressed in Saccharomyces cerevisiae . Sequencing of polymerase chain reaction-amplified GH11 gene fragments from the captured sequences highlighted hundreds of phylogenetically diverse sequences that were not yet described, in public databases. This protocol offers the possibility of performing exhaustive exploration of eukaryotic gene families within microbial communities thriving in any type of environment.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2016

TU-H-CAMPUS-JeP3-02: Automated Dose Accumulation and Dose Accuracy Assessment for Online Or Offline Adaptive Replanning

Purpose: With introduction of high-quality treatment imaging during radiation therapy (RT) delivery, e.g., MR-Linac, adaptive replanning of either online or offline becomes appealing. Dose accumulation of delivered fractions, a prerequisite for the adaptive replanning, can be cumbersome and inaccurate. The purpose of this work is to develop an automated process to accumulate daily doses and to assess the dose accumulation accuracy voxel-by-voxel for adaptive replanning. Methods: The process includes the following main steps: 1) reconstructing daily dose for each delivered fraction with a treatment planning system (Monaco, Elekta) based on the daily images using machine delivery log file and considering patient repositioning if applicable, 2) overlaying the daily dose to the planning image based on deformable image registering (DIR) (ADMIRE, Elekta), 3) assessing voxel dose deformation accuracy based on deformation field using predetermined criteria, and 4) outputting accumulated dose and dose-accuracy volume histograms and parameters. Daily CTs acquired using a CT-on-rails during routine CT-guided RT for sample patients with head and neck and prostate cancers were used to test the process. Results: Daily and accumulated doses (dose-volume histograms, etc) along with their accuracies (dose-accuracy volume histogram) can be robustly generated using the proposed process. The test data for a head and neck cancer case shows that the gross tumor volume decreased by 20% towards the end of treatment course, and the parotid gland mean dose increased by 10%. Such information would trigger adaptive replanning for the subsequent fractions. The voxel-based accuracy in the accumulated dose showed that errors in accumulated dose near rigid structures were small. Conclusion: A procedure as well as necessary tools to automatically accumulate daily dose and assess dose accumulation accuracy is developed and is useful for adaptive replanning. Partially supported by Elekta, Inc.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2013

The Gemini NICI planet-finding campaign: The companion detection pipeline

We present high-contrast image processing techniques used by the Gemini NICI Planet-Finding Campaign to detect faint companions to bright stars. The Near-Infrared Coronographic Imager (NICI) is an adaptive optics instrument installed on the 8 m Gemini South telescope, capable of angular and spectral difference imaging and specifically designed to image exoplanets. The Campaign data pipeline achieves median contrasts of 12.6 mag at 0.''5 and 14.4 mag at 1'' separation, for a sample of 45 stars (V = 4.3-13.9 mag) from the early phase of the campaign. We also present a novel approach to calculating contrast curves for companion detection based on 95% completeness in the recovery of artificial companions injected into the raw data, while accounting for the false-positive rate. We use this technique to select the image processing algorithms that are more successful at recovering faint simulated point sources. We compare our pipeline to the performance of the Locally Optimized Combination of Images (LOCI) algorithm for NICI data and do not find significant improvement with LOCI.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2015

Magnetized interstellar molecular clouds – I. Comparison between simulations and Zeeman observations

The most accurate measurements of magnetic fields in star-forming gas are based on the Zeeman observations analysed by Crutcher et al. Here, we show that their finding that the 3D magnetic field scales approximately as density 0.65 can also be obtained from analysis of the observed line-of-sight fields. We present two large-scale adaptive-mesh-refinement magnetohydrodynamic simulations of several thousand M ⊙ of turbulent, isothermal, self-gravitating gas, one with a strong initial magnetic field (Alfven Mach number $\mathcal{M}_{A,0}=1$) and one with a weak initial field ($\mathcal{M}_{A,0}=10$). We construct samples of the 100 most massive clumps in each simulation and show that they exhibit a power-law relation between field strength and density ($\bar{n}_H$) in excellent agreement with the observed one. Our results imply that the average field in molecular clumps in the interstellar medium (ISM) is $\langle B_{tot}(\bar{n}_H)\rangle ≈ 43\bar{n}^{0.65}_{H,4}μG$. Furthermore, the median value of the ratio of the line-of-sight field to density 0.65 in the simulations is within a factor of about (1.3, 1.7) of the observed value for the strong- and weak-field cases, respectively. The median value of the mass-to-flux ratio, normalized to the critical value, is 70 per cent of the line-of-sight value. This is larger than the 50 per cent usually cited for spherical clouds because the actual mass-to-flux ratio depends on the volume-weighted field, whereas the observed one depends on the mass-weighted field. Our results indicate that the typical molecular clump in the ISM is significantly supercritical (! factor of 3). The results of our strong-field model are in very good quantitative agreement with the observations of Li et al., which show a strong correlation in field orientation between small and large scales. Because there is a negligible correlation in the weak-field model, we conclude that molecular clouds form from strongly magnetized (although magnetically supercritical) gas, in agreement with the conclusion of Li et al.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2020

A genome assembly and the somatic genetic and epigenetic mutation rate in a wild long-lived perennial Populus trichocarpa

Abstract Background Plants can transmit somatic mutations and epimutations to offspring, which in turn can affect fitness. Knowledge of the rate at which these variations arise is necessary to understand how plant development contributes to local adaption in an ecoevolutionary context, particularly in long-lived perennials. Results Here, we generate a new high-quality reference genome from the oldest branch of a wild Populus trichocarpa tree with two dominant stems which have been evolving independently for 330 years. By sampling multiple, age-estimated branches of this tree, we use a multi-omics approach to quantify age-related somatic changes at the genetic, epigenetic, and transcriptional level. We show that the per-year somatic mutation and epimutation rates are lower than in annuals and that transcriptional variation is mainly independent of age divergence and cytosine methylation. Furthermore, a detailed analysis of the somatic epimutation spectrum indicates that transgenerationally heritable epimutations originate mainly from DNA methylation maintenance errors during mitotic rather than during meiotic cell divisions. Conclusion Taken together, our study provides unprecedented insights into the origin of nucleotide and functional variation in a long-lived perennial plant.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2025

Designing an Optimal Sensor Network via Minimizing Information Loss

Optimal experimental design is a classic topic in statistics, with many well-studied problems, applications, and solutions. The design problem we study is the placement of sensors to monitor spatiotemporal processes, explicitly accounting for the temporal dimension in our modeling and optimization. We observe that recent advancements in computational sciences often yield large datasets based on physics-based simulations, which are rarely leveraged in experimental design. We introduce a novel model-based sensor placement criterion, along with a highly-efficient optimization algorithm, which integrates physics-based simulations and Bayesian experimental design principles to identify sensor networks that “minimize information loss” from simulated data. Our technique relies on sparse variational inference and (separable) Gauss-Markov priors, and thus may adapt many techniques from Bayesian experimental design. We validate our method through a case study monitoring air temperature in Phoenix, Arizona, using state-of-the-art physics-based simulations. Our results show our framework to be superior to random or quasi-random sampling, particularly with a limited number of sensors. We conclude by discussing practical considerations and implications of our framework, including more complex modeling tools and real-world deployments.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2017

A Multiple Flux-tube Solar Wind Model

We present a new model, MULTI-VP, which computes the three-dimensional structure of the solar wind and includes the chromosphere, the transition region, and the corona and low heliosphere. MULTI-VP calculates a large ensemble of wind profiles flowing along open magnetic field lines that sample the entire three-dimensional atmosphere or, alternatively, a given region of interest. The radial domain starts from the photosphere and typically extends to about 30 R{sub ⊙}. The elementary uni-dimensional wind solutions are based on a mature numerical scheme that was adapted in order to accept any flux-tube geometry. We discuss here the first results obtained with this model. We use Potential Field Source-surface extrapolations of magnetograms from the Wilcox Solar Observatory to determine the structure of the background magnetic field. Our results support the hypothesis that the geometry of the magnetic flux-tubes in the lower corona controls the distribution of slow and fast wind flows. The inverse correlation between density and speed far away from the Sun is a global effect resulting from small readjustments of the flux-tube cross-sections in the high corona (necessary to achieve global pressure balance and a uniform open flux distribution). In comparison to current global MHD models, MULTI-VP performs much faster and does not suffer from spurious cross-field diffusion effects. We show that MULTI-VP has the capability to predict correctly the dynamical and thermal properties of the background solar wind (wind speed, density, temperature, magnetic field amplitude, and other derived quantities) and to approach real-time operation requirements.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2012

Elimination of the Characterization of DWPF Pour Stream Sample and the Glass Fabrication and Testing of the DWPF Sludge Batch Qualification Sample

A recommendation to eliminate all characterization of pour stream glass samples and the glass fabrication and Product Consistency Test (PCT) of the sludge batch qualification sample was made by a Six-Sigma team chartered to eliminate non-value-added activities for the Defense Waste Processing Facility (DWPF) sludge batch qualification program and is documented in the report SS-PIP-2006-00030. That recommendation was supported through a technical data review by the Savannah River National Laboratory (SRNL) and is documented in the memorandums SRNL-PSE-2007-00079 and SRNL-PSE-2007-00080. At the time of writing those memorandums, the DWPF was processing sludge-only waste but, has since transitioned to a coupled operation (sludge and salt). The SRNL was recently tasked to perform a similar data review relevant to coupled operations and re-evaluate the previous recommendations. This report evaluates the validity of eliminating the characterization of pour stream glass samples and the glass fabrication and Product Consistency Test (PCT) of the sludge batch qualification samples based on sludge-only and coupled operations. The pour stream sample has confirmed the DWPF's ability to produce an acceptable waste form from Slurry Mix Evaporator (SME) blending and product composition/durability predictions for the previous sixteen years but, ultimately the pour stream analysis has added minimal value to the DWPF's waste qualification strategy. Similarly, the information gained from the glass fabrication and PCT of the sludge batch qualification sample was determined to add minimal value to the waste qualification strategy since that sample is routinely not representative of the waste composition ultimately processed at the DWPF due to blending and salt processing considerations. Moreover, the qualification process has repeatedly confirmed minimal differences in glass behavior from actual radioactive waste to glasses fabricated from simulants or batch chemicals. In contrast, the variability study has significantly added value to the DWPF's qualification strategy. The variability study has evolved to become the primary aspect of the DWPF's compliance strategy as it has been shown to be versatile and capable of adapting to the DWPF's various and diverse waste streams and blending strategies. The variability study, which aims to ensure durability requirements and the PCT and chemical composition correlations are valid for the compositional region to be processed at the DWPF, must continue to be performed. Due to the importance of the variability study and its place in the DWPF's qualification strategy, it will also be discussed in this report. An analysis of historical data and Production Records indicated that the recommendation of the Six Sigma team to eliminate all characterization of pour stream glass samples and the glass fabrication and PCT performed with the qualification glass does not compromise the DWPF's current compliance plan. Furthermore, the DWPF should continue to produce an acceptable waste form following the remaining elements of the Glass Product Control Program; regardless of a sludge-only or coupled operations strategy. If the DWPF does decide to eliminate the characterization of pour stream samples, pour stream samples should continue to be collected for archival reasons, which would allow testing to be performed should any issues arise or new repository test methods be developed.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2023

Rapid and efficient ambient temperature X-ray crystal structure determination at Turkish Light Source

High-resolution biomacromolecular structure determination is essential to better understand protein function and dynamics. Serial crystallography is an emerging structural biology technique which has fundamental limitations due to either sample volume requirements or immediate access to the competitive X-ray beamtime. Obtaining a high volume of well-diffracting, sufficient-size crystals while mitigating radiation damage remains a critical bottleneck of serial crystallography. As an alternative, we introduce the plate-reader module adapted for using a 72-well Terasaki plate for biomacromolecule structure determination at a convenience of a home X-ray source. We also present the first ambient temperature lysozyme structure determined at the Turkish light source (Turkish DeLight). The complete dataset was collected in 18.5 min with resolution extending to 2.39 Å and 100% completeness. Combined with our previous cryogenic structure (PDB ID: 7Y6A), the ambient temperature structure provides invaluable information about the structural dynamics of the lysozyme. Turkish DeLight provides robust and rapid ambient temperature biomacromolecular structure determination with limited radiation damage.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2025

Predicting interface structure using the minima hopping method

Here, we adapt the minima hopping method (MHM) to the problem of interfacial structure prediction and apply it to study a canonical problem, the tilt grain boundaries in SrTiO 3 . Our method employs a hybrid approach by first exploring the potential energy surface (PES) of different grain boundary samplings with an empirical force field, among which the fifteen candidates with lower energies are then refined using ab initio density functional theory (DFT) calculations. During the exploratory stage, we bias the search using a local order parameter to primarily sample various reconstructions in the vicinity of the interface, while preserving the crystallinity of the bulk regions. We further enhance the search by incorporating initial structures with rigid body displacements to account for translational variations between bulk phases, enabling the MHM to effectively generate both stoichiometric and nonstoichiometric SrTiO 3 Σ⁢3(111)[110] and Σ⁢3(112)[110] grain boundaries. From an algorithmic standpoint, MHM outperforms earlier studies based on genetic algorithms (GA) by identifying more stable interfacial structures of several SrTiO 3 grain boundaries. The performance of the present implementation of the MHM approach is primarily limited by exploring an approximate description of the PES with a rather simple Buckingham potential. This limitation leads to variations in performance when compared to approaches utilizing more advanced surrogate PES models, such as direct DFT-PES sampling or GA with the embedded atom method (EAM). Despite the present limitations, the MHM approach is able to yield interfacial structures with comparable or lower interfacial energies in specific cases, such as Σ⁢3(111)[110] Γ=1, ±0.5 and Σ⁢3(112)[110] Γ= ±1, −2, underscoring the robustness of the MHM approach even with a simple approximation of the DFT PES. The MHM interfacial structure prediction method thus offers an efficient approach to understanding the grain boundaries and heterointerfaces at the atomic scale, providing an important prerequisite for effective materials design.

density functional theory↗
DOE OSTI2013

A Decision Theoretic Approach to Evaluate Radiation Detection Algorithms

There are a variety of sensor systems deployed at U.S. border crossings and ports of entry that scan for illicit nuclear material. In this work, we develop a framework for comparing the performance of detection algorithms that interpret the output of these scans and determine when secondary screening is needed. We optimize each algorithm to minimize its risk, or expected loss. We measure an algorithm’s risk by considering its performance over a sample, the probability distribution of threat sources, and the consequence of detection errors. While it is common to optimize algorithms by fixing one error rate and minimizing another, our framework allows one to simultaneously consider multiple types of detection errors. Our framework is flexible and easily adapted to many different assumptions regarding the probability of a vehicle containing illicit material, and the relative consequences of a false positive and false negative errors. Our methods can therefore inform decision makers of the algorithm family and parameter values which best reduce the threat from illicit nuclear material, given their understanding of the environment at any point in time. To illustrate the applicability of our methods, in this paper, we compare the risk from two families of detection algorithms and discuss the policy implications of our results.

Nobles, Mallory A.↗
DOE OSTI2020

Preliminary Test Design and Plan for a Canister Deposition Field Demonstration

This report provides a high-level test plan for deploying three commercial 32PTH2 spent nuclear fuel (SNF) canisters inside NUHOMS Advanced Horizontal Storage Modules (AHSM) from Orano (formerly Transnuclear Inc.). The details contained in this report represent the best designs and approaches explored for testing as of this publication. Given the rapidly developing nature of this test program, some of these plans may change to accommodate new objectives or adapt in response to conflicting requirements. The goal of the testing is to collect highly defensible and detailed surface deposition measurements from the surface of dry storage systems in a marine coastal environment to guide chloride-induced stress corrosion crack (CISCC) research. To facilitate surface sampling, the otherwise highly prototypic dry storage systems will not contain SNF but rather will be electrically heated to mimic the thermal-hydraulic environment. Instrumentation throughout the canister, storage module, and environment will provide an extensive amount of information for the use of model validation. Manual sampling over a comprehensive portion of the canister surface at regular time intervals will offer a high-fidelity quantification of the conditions experienced in a harsh yet realistic environment.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2020

Enabling Microscale Processing: Combined Raman and Absorbance Spectroscopy for Microfluidic On-Line Monitoring

Microfluidics have many potential applications including characterization of chemical processes on a reduced scale, spanning the study of reaction kinetics using on-chip liquid–liquid extractions, sample pretreatment to simplify off-chip analysis, and for portable spectroscopic analyses. The use of in situ characterization of process streams from laboratory-scale and microscale experiments on the same chemical system can provide comprehensive understanding and in-depth analysis of any similarities or differences between process conditions at different scales. A well-characterized extraction of Nd(NO 3 ) 3 from an aqueous phase of varying NO 3– (aq) concentration with tributyl phosphate (TBP) in dodecane was the focus of this microscale study and was compared to an earlier laboratory-scale study utilizing counter current extraction equipment. Here, we verify that this same extraction process can be followed on the microscale using spectroscopic methods adapted for microfluidic measurement. Concentration of Nd (based on UV–vis) and nitrate (based on Raman) was chemometrically measured during the flow experiment, and resulting data were used to determine the distribution ratio for Nd. Extraction distributions measured on the microscale were compared favorably with those determined on the laboratory scale in the earlier study. Both micro-Raman and micro-UV–vis spectroscopy can be used to determine fundamental parameters with significantly reduced sample size as compared to traditional laboratory-scale approaches. This leads naturally to time, cost, and waste reductions.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2015

Elementary Energy Transfer Pathways in Allochromatium vinosum Photosynthetic Membranes

Allochromatium vinosum (formerly Chromatium vinosum) purple bacteria are known to adapt their light-harvesting strategy during growth according to environmental factors such as temperature and average light intensity. Under low light illumination or low ambient temperature conditions, most of the LH2 complexes in the photosynthetic membranes form a B820 exciton with reduced spectral overlap with LH1. To elucidate the reason for this light and temperature adaptation of the LH2 electronic structure, we performed broadband femtosecond transient absorption spectroscopy as a function of excitation wavelength in A. vinosum membranes. A target analysis of the acquired data yielded individual rate constants for all relevant elementary energy transfer (ET) processes. We found that the ET dynamics in high-light-grown membranes was well described by a homogeneous model, with forward and backward rate constants independent of the pump wavelength. Thus, the overall B800→B850→B890→ Reaction Center ET cascade is well described by simple triexponential kinetics. In the low-light-grown membranes, we found that the elementary backward transfer rate constant from B890 to B820 was strongly reduced compared with the corresponding constant from B890 to B850 in high-light-grown samples. The ET dynamics of low-light-grown membranes was strongly dependent on the pump wavelength, clearly showing that the excitation memory is not lost throughout the exciton lifetime. The observed pump energy dependence of the forward and backward ET rate constants suggests exciton diffusion via B850→ B850 transfer steps, making the overall ET dynamics nonexponential. Our results show that disorder plays a crucial role in our understanding of low-light adaptation in A. vinosum.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2025

Interactions between macro‐ and micro‐climate: Effects on phenolic compound production in Nardus stricta at high elevations

Abstract Phenolic compounds are key to plant defence, offering protection as antioxidants, UV shields, and antimicrobials. Their production is largely shaped by environmental conditions. It is believed that plants at lower elevations increase phenolic content to counter herbivory, while those at higher elevations rely on phenolics to manage abiotic stresses, such as climate variability. Microhabitat warming also affects phenolic levels, but responses differ, depending on broader climatic contexts: plants in warmer, lower‐elevation environments show limited adaptability, whereas high‐elevation plants demonstrate greater plasticity. Despite the importance of these environmental interactions, many small‐scale abiotic studies lack sufficient spatial replication across broader gradients like elevation or latitude, while large‐scale studies frequently overlook microscale factors. This study investigated the effects of macroclimate factors and microhabitat warming on phenolic production in Nardus stricta across five semi‐natural grassland sites (1546–1875 m a.s.l.) in Portugal's Serra da Estrela. Warming was simulated using open‐top chambers over two growing seasons, after which leaf samples were analysed for phenolic compounds, and soil nutrients were measured. The N. stricta plants at the highest elevation site contained significantly higher leaf flavonoid concentrations. Microhabitat warming led to a significant decrease in flavonoid concentrations, but only at the highest elevation site. These effects occurred independently of soil nutrient levels, suggesting direct thermal effects or stress responses might be involved. Our findings highlight the complex interactions between macro‐ and microenvironmental factors in shaping plant chemistry, underscoring critical considerations for plant resilience in the face of climate change. This understanding is essential for developing strategies to support plant and ecosystem adaptation to changing climates.

Moreira, X. [Misión Biológica de Galicia (MBG‐CSIC↗