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Although the importance of nonphotochemical quenching (NPQ) on photosynthetic biomass production and crop yields is well established, the in vivo operation of the individual mechanisms contributing to overall NPQ is still a matter of controversy. In order to investigate the timescale and activation dynamics of specific quenching mechanisms, we have developed a technique called snapshot transient absorption (TA) spectroscopy, which can monitor molecular species involved in the quenching response with a time resolution of 30 s. Using intact thylakoid membrane samples, we show how conventional TA kinetic and spectral analyses enable the determination of the appropriate wavelength and time delay for snapshot TA experiments. As an example, we show how the chlorophyll-carotenoid charge transfer and excitation energy transfer mechanisms can be monitored based on signals corresponding to the carotenoid (Car) radical cation and Car S1 excited state absorption, respectively. The use of snapshot TA spectroscopy together with the previously reported fluorescence lifetime snapshot technique (Sylak-Glassman et al. in Photosynth Res 127:69-76, 2016) provides valuable information such as the concurrent appearance of specific quenching species and overall quenching of excited Chl. Furthermore, we show that the snapshot TA technique can be successfully applied to completely intact photosynthetic organisms such as live cells of Nannochloropsis. This demonstrates that the snapshot TA technique is a valuable method for tracking the dynamics of intact samples that evolve over time, such as the photosynthetic system in response to high-light exposure.

The rapid response of photosynthetic organisms to fluctuations in ambient light intensity is incompletely understood at both the molecular and membrane levels. In this review, we describe research from our group over a 10-year period aimed at identifying the photophysical mechanisms used by plants, algae and mosses to control the efficiency of light harvesting by photosystem II on the seconds-to-minutes time scale. To complement the spectroscopic data, we describe three models capable of describing the measured response at a quantitative level. The review attempts to provide an integrated view that has emerged from our work, and briefly looks forward to future experimental and modelling efforts that will refine and expand our understanding of a process that significantly influences crop yields.

Nonphotochemical quenching (NPQ) is a proxy for photoprotective thermal dissipation processes that regulate photosynthetic light harvesting. The identification of NPQ mechanisms and their molecular or physiological triggering factors under in vivo conditions is a matter of controversy. Here, to investigate chlorophyll (Chl)-zeaxanthin (Zea) excitation energy transfer (EET) and charge transfer (CT) as possible NPQ mechanisms, we performed transient absorption (TA) spectroscopy on live cells of the microalga Nannochloropsis oceanica We obtained evidence for the operation of both EET and CT quenching by observing spectral features associated with the Zea S1 and Zea●+ excited-state absorption (ESA) signals, respectively, after Chl excitation. Knockout mutants for genes encoding either violaxanthin de-epoxidase or LHCX1 proteins exhibited strongly inhibited NPQ capabilities and lacked detectable Zea S1 and Zea●+ ESA signals in vivo, which strongly suggests that the accumulation of Zea and active LHCX1 is essential for both EET and CT quenching in N. oceanica.

Decarbonizing the glass industry requires alternative melting technology, as current industrial melting practices rely heavily on fossil fuels. Hydrogen has been proposed as an alternative to carbon‐based fuels, but the ensuing consequences on the mechanical behavior of the glass remain to be clarified. A critical distinction between hydrogen and carbon‐based fuels is the increased generation of water during combustion, which raises the equilibrium solubility of water in the melt and alters the behavior of the resulting glass. A series of five silicate glasses with 80% silica and variable [Na2O]/([H2O] + [Na2O]) ratios were simulated using molecular dynamics to elucidate the effects of water on fracture. Several fracture toughness calculation methods were used in combination with atomistic fracture simulations to examine the effects of hydroxyl content on fracture behavior. This study reveals that the crack propagation pathway is a key metric to understanding fracture toughness. Notably, the fracture propagation path favors hydrogen sites over sodium sites, offering a possible explanation of the experimentally observed effects of water on fracture properties. [ABSTRACT FROM AUTHOR]

In forest management settings, disturbance resets forests to earlier successional stages, typically improving forage conditions for mule deer. Examining how forest disturbance influences mule deer behavior is important for guiding forest and wildlife management. We used GPS collar data collected between 2017 and 2019 from 136 adult female mule deer in three populations throughout western Montana, United States, to investigate how disturbance from burns (wildfire and prescribed fire) and timber harvest influenced three aspects of space‐use behaviors: (1) probability of migration from winter range to summer range, (2) home range (second‐order) selection by migrants on summer range, and (3) within‐home range (third‐order) selection. We hypothesized that deer would maximize use of disturbances during summer for nutritional benefits, predicting that deer with higher proportionate disturbance in their winter home range would be less likely to migrate away from those disturbances during summer. We predicted that migrants would select disturbances at the second and third orders. We found that proportionate disturbance in winter home ranges had no effect on the probability of migration. Among migrants, deer generally selected burns, timber harvests, and open‐canopy habitat at the second order in all study areas, with particularly strong selection for 6‐ to 15‐year‐old disturbances. At population levels, selection for disturbances ceased at the third order. At individual levels, however, third‐order selection for burns increased with availability, whereas selection for harvests decreased, suggesting burns may satisfy more resource needs than harvests. Our results emphasize how space‐use fidelity constrains mule deer habitat selection. During summer, adherence to migratory strategies constrains the habitat available for second‐order selection, preventing deer from exploiting disturbances that would otherwise be available had they remained resident in wintering areas. Second‐order selection then determines disturbance availability within home ranges, affecting third‐order behaviors. Although variance in selection behaviors among individuals was high, population‐level patterns were remarkably similar among study areas, suggesting these responses may be generalizable to mule deer throughout the northern Rocky Mountains. Forest management practices like timber harvest, prescribed burns, and wildfire management within higher elevation areas of summer range used by migrants could yield the greatest nutritional benefits for mule deer. [ABSTRACT FROM AUTHOR]

Opioid-seeking behaviors depend on glutamatergic plasticity in the nucleus accumbens core (NAcc). Here we investigated whether the behavioral and synaptic effects of opioids are influenced by acid-sensing ion channel 1A (ASIC1A). We tested the effects of ASIC1A on responses to several opioids and found that Asic1a−/− mice had elevated behavioral responses to acute opioid administration as well as opioid seeking behavior in conditioned place preference (CPP). Region-restricted restoration of ASIC1A in NAcc was sufficient to reduce opioid CPP, suggesting NAcc is an important site of action. We next tested the effects of oxycodone withdrawal on dendritic spines in NAcc. We found effects of oxycodone and ASIC1A that contrasted with changes previously described following cocaine withdrawal. Finally, we examined α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor-mediated and N-methyl-D-aspartic acid (NMDA) receptor-mediated synaptic currents in NAcc. Oxycodone withdrawal, like morphine withdrawal, increased the AMPAR/NMDAR ratio in Asic1a+/+ mice, whereas oxycodone withdrawal reduced the AMPAR/NMDAR ratio in Asic1a−/− mice. A single dose of oxycodone was sufficient to induce this paradoxical effect in Asic1a−/− mice, suggesting an increased sensitivity to oxycodone. We conclude that ASIC1A plays an important role in the behavioral and synaptic effects of opioids and may constitute a potential future target for developing novel therapies. [ABSTRACT FROM AUTHOR]

We compared mercury bioaccumulation in triploid and diploid walleye (Sander vitreus) in Narraguinnep Reservoir, Colorado, USA, and made several hypotheses that sex- and ploidy-specific differences in the allocation of energy towards reproductive development would affect mercury bioaccumulation. We tested our hypotheses with linear regression and a bioenergetics model informed by field data. We found diploid walleye had 28%-31% higher mercury concentrations on average than triploids, but there were no differences between sexes of the same ploidy. Triploids of mature age exhibited minimal gonadal development when compared to diploids. After accounting for reproductive investment, the bioenergetics model accounted for most of the observed difference in average mercury concentration between ploidies for females. Conversely, the energetic cost of producing testes was low, and gonadal development could not explain observed patterns for males. Costs associated with elevated swimming activity and metabolism by diploid males relative to other groups could explain the difference but requires further investigation. The use of triploid fish in stocking programs could prove useful for reducing mercury in fish destined for human consumption. Nous comparons la bioaccumulation de mercure dans des dores jaunes (Sander vitreus) triploides et diploides dans le reservoir Narraguinnep (Colorado, Etats-Unis) et formulons plusieurs hypotheses a l'effet que des differences selon le sexe et la ploidie sur le plan de l'affectation de ressources energetiques au developpement des organes reproducteurs auraient une incidence sur la bioaccumulation de mercure. Nous validons ces hypotheses a l'aide de la regression lineaire et d'un modele bioenergetique alimente de donnees de terrain. Nous constatons que les dores diploides presentent des concentrations de mercure de 28 % a 31 % plus importantes, en moyenne, que les triploides, mais aucune difference n'est relevee entre les sexes de meme ploidie. Les triploides d'age mature presentent un developpement gonadique minimal comparativement aux diploides. Une fois pris en compte l'investissement dans le systeme reproducteur, le modele bioenergetique explique la majeure partie des differences observees des concentrations de mercure moyennes entre femelles de ploidies differentes. A l'inverse, le cout energetique de la production de testicules est faible, et le developpement des gonades ne peut expliquer les motifs observes chez les males. Les couts associes a une activite de nage et un metabolisme plus eleves chez les males diploides par rapport aux autres groupes pourraient expliquer la difference, mais cela necessite un examen plus approfondi. L'utilisation de poissons triploides dans les programmes d'empoissonnement pourrait s'averer utile pour reduire les concentrations de mercure dans les poissons destines a la consommation humaine. [Traduit par la Redaction], Introduction Induced triploidy is commonly used in aquaculture operations (Piferrer et al. 2009), for biocontrol of aquatic vegetation (Allen and Wattendorf 1987), and increasingly as a stocking option for recreational [...]

Experimental electrochemistry offers unique opportunities for interactive instruction at all levels of education; however, widespread adoption in curricula is hindered by high costs associated with electrochemical instrumentation. Thus, the development of affordable instruments represents an essential step toward making electrochemistry accessible to everyone. While numerous commercially available three-electrode potentiostats exist, two-electrode potentiostats provide a simple and inexpensive alternative. Herein, we present the two-electrode SweepStat as a low-cost option capable of performing voltammetry and amperometry with comparable data acquisition to commercially available potentiostats valued from $4,000-40,000 USD. Additionally, the SweepStat's design facilitates current measurements in the nanoampere regime, permitting experiments with ultramicroelectrodes (UMEs; r[subscript electrode] < 25 [mu]). The fabrication, programming, and testing of this device constitute a valuable experimental exercise at the intersection of circuit design and construction, computer programing, and electrochemical analysis. A set of simple electrochemical experiments are presented for both macroelectrodes and UMEs, highlighting key electrochemical techniques, equations, and concepts. Furthermore, finite element modeling and commercial potentiostat comparisons are used to verify the efficacy of the SweepStat platform. The open-source nature of the SweepStat coupled with the wealth of electrochemical techniques and experiments that can be implemented with a simple two-electrode circuit offers an unparalleled opportunity for electrochemical instruction with extensive method development driven by student research.

Nonphotochemical quenching (NPQ) provides an essential photoprotection in plants, assuring safe dissipation of excess energy as heat under high light. Although excitation energy transfer (EET) between chlorophyll (Chl) and carotenoid (Car) molecules plays an important role in NPQ, detailed information on the EET quenching mechanism under in vivo conditions, including the triggering mechanism and activation dynamics, is very limited. Here, we observed EET between the Chl Q y state and the Car S1 state in high-light-exposed spinach thylakoid membranes. The kinetic and spectral analyses using transient absorption (TA) spectroscopy revealed that the Car S1 excited state absorption (ESA) signal after Chl excitation has a maximum absorption peak around 540 nm and a lifetime of ∼8 ps. Snapshot TA spectroscopy at multiple time delays allowed us to track the Car S1 ESA signal as the thylakoid membranes were exposed to various light conditions. The obtained snapshots indicate that maximum Car S1 ESA signal quickly rose and slightly dropped during the initial high-light exposure (

Purpose: To evaluate the repeatability and reproducibility of QSM of the liver via single breath‐hold chemical shift–encoded MRI at both 1.5 T and 3 T in a multicenter, multivendor study in subjects with iron overload. Methods: This prospective study included four academic medical centers with three different MRI vendors at 1.5 T and 3 T. Subjects with known or suspected liver iron overload underwent multi‐echo spoiled gradient‐recalled‐echo scans at each field strength. A subset received repeatability testing at either 1.5 T or 3 T. Susceptibility and R2*$$ {\mathrm{R}}_2^{\ast } $$ maps were reconstructed from the multi‐echo images and analyzed at a single center. QSM‐measured susceptibility was compared with R2*$$ {\mathrm{R}}_2^{\ast } $$ and a commercial R2‐based liver iron concentration method across centers and field strengths using linear regression and F‐tests on the intercept and slope. Field‐strength reproducibility and test/retest repeatability were evaluated using Bland–Altman analysis. Results: A total of 155/80 data sets (test/retest) were available at 1.5 T, and 159/70 data sets (test/retest) were available at 3 T. Calibrations across sites were reproducible, with some variability (e.g., susceptibility slope with liver iron concentration ranged from 0.102 to 0.123 g/[mg·$$ \cdotp $$ppm] across centers at 1.5 T). Field strength reproducibility was good (concordance correlation coefficient = 0.862), and test/retest repeatability was excellent (intraclass correlation coefficient = 0.951). Conclusion: QSM as an imaging biomarker of liver iron overload is feasible and repeatable across centers and MR vendors. It may be complementary with R2*$$ {\mathrm{R}}_2^{\ast } $$ as they are obtained from the same acquisition. Although good reproducibility was observed, liver QSM may benefit from standardization of acquisition parameters. Overall, QSM is a promising method for liver iron quantification. [ABSTRACT FROM AUTHOR]

Background: Non‐septic tenosynovitis is a clinically relevant and often performance limiting musculoskeletal injury in the horse. Objectives: To review the published literature to determine which tendon sheaths are commonly affected by non‐septic tenosynovitis and to describe the most frequently reported pathological lesions, outcomes, and surgical complications in equine non‐septic tenosynovitis. Study design: Systematic review. Methods: Literature searches were conducted in July 2021 from the online search engines PubMed, Scopus, Web of Science Core, VetMed Resource and ProQuest Theses & Dissertations. The inclusion criteria followed a participants, interventions, comparisons, outcome and study design (PICOS) approach. For inclusion, studies had to include live equids with non‐septic tenosynovitis of any tendon sheath. Studies were excluded if they only described non‐equine species, if they included data only on non‐tendon sheath structures, or if they included data exclusively on cases of septic or contaminated tendon sheaths. Determination of non‐sepsis relied on the diagnosis of the original authors; however, if non‐sepsis was not explicitly specified, then cases that had a history of contamination of the sheath, a wound near the sheath or a positive bacterial culture were excluded from analysis. Data analysed included the distribution of structures affected by non‐septic tenosynovitis, the most common pathological lesions identified within each sheath, and the most frequently reported surgical complications of non‐septic tenosynovitis. The quality of each study was assessed using a methodological quality analysis. Results: A total of 85 studies describing non‐septic tenosynovitis in the horse were included. Across all 85 studies, there were a total of 2449 tendon sheaths in 2101 horses reported to be affected by non‐septic tenosynovitis. The digital flexor sheath was the most reported structure to be diagnosed with non‐septic tenosynovitis: 41/85 (48%) studies examined the digital flexor sheath exclusively, followed by the carpal flexor sheath, tarsal flexor sheath, carpal extensor sheaths, tarsal extensor sheaths, and one case of biceps brachii non‐septic tenosynovitis. For most tendon sheaths, the most common pathological lesion was an intrathecal tear of a soft tissue structure, including tears of the deep digital flexor tendon and tears of the manica flexoria. Bilateral disease was most common in the carpal flexor sheath, where distal radial physeal exostoses were the most common pathological lesions. Less common causes of non‐septic tenosynovitis included neoplasia, fracture of a bone adjacent to a tendon sheath, and mineralisation of an intrathecal tendon. The likelihood of return to previous level of athletic function following non‐septic tenosynovitis of most structures was approximately 50%, and the most common complication was persistent effusion following tenoscopy. While iatrogenic infection following surgery was uncommon, it was most likely following tenoscopy of the digital flexor sheath. Conclusion: Non‐septic tenosynovitis is commonly reported in equine athletes, with intra‐thecal tears of the deep digital flexor tendon, superficial digital flexor tendon and manica flexoria frequently reported. Directions for future research include more thorough assessment of and reporting of complications following non‐septic tenosynovitis and correlation of characteristics of intrathecal pathological lesions with clinical outcomes. [ABSTRACT FROM AUTHOR]