Energy Research Articles

Improved electro-kinetics of new electrolyte composition for realizing high-performance zinc-bromine redox flow battery

Aqueous Redox Flow Batteries (ARFB) are the most prominent technology for large-scale energy storage applications. The energy density of the ARFBs is mainly determined by the electrolyte components, which highly influence the flow battery performance. In the present work, we acutely investigated the various electrolyte compositions and optimized the best electrolyte for realizing the high performance of Zn-Br2 ARFBs. The electrode kinetics, such as rate constant, exchange current density, conductivity, and diffusion coefficient, were analyzed using electrochemical techniques, cyclic voltammetry, and electrochemical impedance analysis. It was observed that zinc bromide (ZnBr2) + perchloric acid (HClO4) + 1-Ethyl-1-methylmorpholinium bromide (MEM) + N-ethyl-N-methylpyrrolidinium bromide (MEP) and ZnBr2 + zinc chloride (ZnCl2) + MEM + MEP electrolytes showed improved performance, where the redox kinetics of 2Br-/Br2 redox couple is greatly enhanced. The presence of perchloric acid unlocks the capacity of full electro-oxidation of bromide (Br-) to bromine (Br2) as it involves 1e- per Br-, which would be highly beneficial to attain high energy density. Further, Zn-Br2 RFB adopted with optimized electrolyte formulation ZnBr2 + HClO4 + MEM+ MEP shows a better round-trip efficiency and displays a stable long cycling performance over 200 cycles with an energy (EE) and coulombic efficiency (CE) of > 68% and > 92%, respectively.

Energy Partition between Submesoscale Internal Waves and Quasigeostrophic Vortical Motion in the Pycnocline

Abstract Shipboard ADCP velocity and towed CTD chain density measurements from the eastern North Pacific pycnocline are used to segregate energy between linear internal waves (IW) and linear vortical motion [quasigeostrophy (QG)] in 2D wavenumber space spanning submesoscale horizontal wavelengths λx ∼ 1–50 km and finescale vertical wavelengths λz ∼ 7–100 m. Helmholtz decomposition and a new Burger number (Bu) decomposition yield similar results despite different methodologies. While these wavelengths are conventionally attributed to internal waves, both QG and IW contribute significantly at all measured scales. Partition between IW and QG total energies depends on Bu. For Bu < 0.01, available potential energy EP exceeds horizontal kinetic energy EK and is contributed mostly by QG. In contrast, energy is nearly equipartitioned between QG and IW for Bu ≫ 1. For Bu < 2, EK is contributed mainly by IW, and EP by QG, while, for Bu > 2, contributions are reversed. Finescale near-inertial IW dominate vertical shear variance, implying negligible QG contribution to vertical shear instability. In contrast, both QG and IW at the smallest λx ∼ 1 km contribute large horizontal shear variance, so that both may lead to horizontal shear instability, while QG, with its longer time scales, likely dominates isopycnal stirring. Both QG and IW contribute to vortex stretching at small vertical scales. For QG, the relative vorticity contribution to linear potential vorticity anomaly increases with decreasing horizontal and increasing vertical scales.

Optimization of energy use efficiency and environmental assessment in soybean and peanut farming using the imperialist competitive algorithm

This study proposes using input-output analysis to improve energy use efficiency and assess environmental indicators in soybean and peanut farming. The research findings show that soybean production consumes 43170.20 MJ ha−1 of total energy and yields 40417.28 MJ ha−1 of output energy, while peanut production requires 28677.36 MJ ha−1 of total energy and produces 28677.36 MJ ha−1 of output energy. The LCA results indicate that on-farm emissions are associated with production inputs for both soybean and peanut systems, with diesel fuel and chemical fertilizers being the main contributors. Soybean farming shows higher levels of diesel fuel pollutants due to reduced usage, while peanuts have a higher prevalence of contaminants associated with diesel fuel. Using ICA to calculate optimized energy consumption results in 36672.77 MJ ha−1 for soybean production and 23485.45 MJ ha−1 for peanut production, leading to energy savings of 6075.33 MJ ha−1 and 5191.91 MJ ha−1, respectively. Additionally, the environmental impact category quantities for ICA analysis of soybean and peanut production reveal the resources per ton for soybean production to be 111.25 USD2013 and for peanut production to be 45.43 USD2013 in terms of energy use. The use of ICA demonstrates potential in maximizing energy efficiency and evaluating environmental indicators in soybean and peanut farming. By optimizing resource allocation and decision-making processes, ICA can help farmers reduce energy consumption and minimize environmental impact, ultimately leading to more sustainable and eco-friendly farming practices that benefit both the environment and the agricultural industry. Further research and implementation of ICA in farming practices have the potential to significantly improve energy efficiency and environmental sustainability in the soybean and peanut farming industry.

Lithium extraction from salt lake brine by four-stage ion-distillation of flow electrode capacitive deionization

Herein, a novel, highly efficient, and low-energy consumption four-stage ion-distillation of FCDI (ID-FCDI) device was developed that combined four commercial monovalent selective membranes with four flow electrode channels for high selectivity to extract Li+ ions from salt lake. It exhibited excellent separation factor (SMg2+Li+ = 11247.27), high enrichment ratio (4.95 times), super purity of Li+ ion solution (99.97 %), and low molar energy consumption (Em = 0.21 kWh mol−1) at mass ratio of Mg2+/Li+ = 1:1. The mathematical model calculation revealed that the excellent selective separation effectiveness of the as-proposed ID-FCDI system is due to the unique property of the monovalent selectivity membranes, in which the transmembrane rate of lithium ions is ten times that of magnesium ions under the same condition. Furthermore, the separation mechanism of the as-proposed ID-FCDI device for Li+/Mg2+ ions was determined by the high electrosorption capacity of the flow electrode for Li+ ions (1.14 times higher than Mg2+ ions), low diffusion resistance (1.413 Ω), and high diffusion coefficient of Li+ ions (2.83 times faster than Mg2+ ions) by electrochemical measurement. On this basis, 3.92 times of lithium was successfully enriched in the natural salt lake brine of Golmud (mass ratio of Mg2+/Li+ = 79.29), and the separation factor was 6307.17 with a 99.64 % purity of Li+ ion solution and an Em of 0.20 kWh mol−1. Finally, the Li2CO3 product (99.66 %) was precipitated via the reaction between Na2CO3 and the enriched Li+ ion solution, consequently fulfilling the battery-level application of the industrial purity requirements. These findings highlight that this device is promising and profitable for lithium extraction from salt lake in industrial production.

Statistical physics investigation of the docking process of fruity odorants on Machilis hrabei MhOR5: New microscopic interpretations

In this paper, the putative phenomenon of adsorption involved in the insect olfactory perception of four fruity odorants on Machilishrabei olfactory receptor MhOR5 was studied at a molecular scale. Thus, the experimental concentration–response curves of propyl acetate, butyl acetate, isobutyl acetate, and prenyl acetate on MhOR5 were adjusted using the monolayer model of ideal gas established using the powerful statistical physics approach, which was selected as the most appropriate model among the others. The fitted model parameters were applied to stereographic and energetic analyze the four olfactory systems. Indeed, the modeling results indicated that the tested fruity key food odorants (KFOs) were docked as 2- or 3-aggregated molecules on one MhOR5 binding site via a nonparallel position (i.e., multi-molecular adsorption mechanism). Energetic parameters were used to characterize the adsorption process involved in the studied systems via the determination of the molar adsorption energies (ranging from 12.91 to 17.52 kJ/mol). Hence, the values of the molar adsorption energies are positive and inferior to 40 kJ/mol; this means that the putative adsorption mechanism presented an exothermic character and a physical type. The docking simulation results proved that the adsorption of propyl acetate, butyl acetate, isobutyl acetate, and prenyl acetate on MhOR5 may occur via physical interactions (weak interactions) like alkyl, pi-alkyl, van der Waals, carbon hydrogen bond, and conventional hydrogen bond. The statistical physics theory may also be utilized to quantitatively characterize Machilishrabei MhOR5 activated by propyl acetate, butyl acetate, isobutyl acetate, and prenyl acetate odorants via the estimation of the different site size distributions (SSDs) and site energy distributions (SEDs).

Effect of Tween and CTAB surfactants on aqueous solubility of the silibinin anticancer drug studied by using physicochemical properties at 310.15 K

The silibinin (SB) is an anticancer drug exhibits partial solubility in aqueous medium due to its slightly hydrophobic nature. In this context, the aqueous solubility of SB with Tween 40 (Tw 40), Tween 60 (Tw 60), Tween 80 (Tw 80) and Cetyltrimethylammonium bromide (CTAB) surfactants at 310.15 K are reported. The physicochemical properties (PCPs) such as density (ρ, g cm−3), Apparent Molar Volume (Vϕ, cm3·mol−1), viscosity (η, mPa.s), surface tension (γ, mNm−1), friccohesity (σ, s.m−1), activation energy (Δµ2*, kJ/mol), and molecular radii (r, nm) of SB with aqueous solution of Tw 40, Tw 60, Tw 80 and CTAB surfactants separately. The PCPs reflects the state of intermolecular forces (IMF) developed between SB and aqueous solutions of Tween (40, 60, 80) and CTAB surfactants with concentration varied from 25 to 150 µM (µM). This study focused on intermolecular interacting mechanism determined by using PCPs to evaluate self-aggregation potential of SB in aqueous surfactants solution. The PCPs data furnished interaction and structure breaking behavior of SB with surfactant molecules. The development of hydrogen bond (HB), hydrophilic, hydrophobic and electrostatic interactions of SB with surfactants which revealed that the structure dependent interacting activities enhances with increasing concentration of SB in aqueous surfactants.

Nova 1670 (CK Vulpeculae) was a merger of a red giant with a helium white dwarf

Context. Nova 1670 is a historical transient bearing strong similarities to a recently recognized type of stellar eruption known as the red nova, which is thought to be powered by stellar mergers. The remnant of the transient, CK Vul, is observable today mainly through cool circumstellar gas and dust, and recombining plasma, but we have no direct view on the stellar object. Aims. Within the merger hypothesis, we aim to infer the most likely configuration of the progenitor system that resulted in Nova 1670. Methods. We collected the literature data on the physical properties of the outburst and the remnant (including their energetics), and on the chemical composition of the circumstellar material (including elemental and isotopic abundances). These data, which result from optical and submillimeter observations of the circumstellar gas of CK Vul, are summarized here. We performed simple simulations to analyze the form and the level of mixing within the material associated with the merger. We identified products of nuclear burning, among which we find ashes of hydrogen burning in the CNO cycles and in the MgAl chain, as well as signs of partial helium burning. Results. Based primarily on the luminosity and chemical composition of the remnant, we find that the progenitor primary had to be an evolutionarily advanced red giant branch star of a mass of 1–2 M⊙. The secondary was either a very similar giant, or –more likely– a helium white dwarf. While the eruption event was mainly powered by accretion, we estimate that about 12% of total energy is likely to have come from helium burning activated during the merger. The coalescence of a first-ascent giant with a helium white dwarf created a star with a rather unique internal structure and composition, which resemble those of early R-type carbon stars. Conclusions. Nova 1670 is the result of a merger between a helium white dwarf and a first-ascent red giant and is likely now evolving to become an early R-type carbon star.

Interactions of adsorbing cosolutes with hydrophobic hydration shells.

The analysis of water density fluctuations in the hydration shell of nonpolar solutes provides insights into water-mediated interactions, especially hydrophobic interactions. These fluctuations are sensitive to small perturbations due to changes in thermodynamic conditions, such as temperature and pressure, but also to the presence of cosolutes, such as salts or small organic molecules. Herein, we investigate the effect of two classes of adsorbing cosolutes, using urea and methanol as representatives, on the fluctuations in energy and solvent density within the solvation shell of a model extended hydrophobic solute. We focus on the interactions of the cosolutes with the hydrophobic hydration shell, rather than with the solute itself, which though important remain largely unexplored. We calculate and analyze the interfacial partial molar energy of the cosolute, using a methodology based on the small system method. This approach provides correlated solvent density and energy fluctuations and allows us to decompose them into contributions due to interactions between the different components present in the solvation shell of the solute. The results show that adsorbed urea molecules interact more favorably with water than nonadsorbed urea molecules, which leads to the attenuation of interfacial density fluctuations and thus to the stabilization of the solvation shell. By contrast, the adsorbed methanol molecules interact preferably with other methanol molecules in the solvation shell, leading to a nano-phase segregated structure, which enhances interfacial fluctuations.

Exploring the recovery capacity of recycling agents on atomic-scale energy properties of aged bitumen and their potential correlations with high-temperature rheological performance

This study implements molecular dynamics (MD) simulations to explore the atomic-level energy properties of rejuvenated bitumen, considering the influence of different recycling agent (RA) types, dosages and aging levels of bitumen. Moreover, the potential correlations between energy indices and high-temperature performance of rejuvenated bitumen are explored. Our findings show that recycling agents can effectively reinstate the cohesive energy density (CED) values of aged bitumen, correlating well with their high-temperature rheological properties. The results reveal that the energy parameters of potential energy (UVEP), kinetic energy (UWEK), non-bond energy (EN), total energy (UVET), diagonal energy (UNED), and cross-terms energy (ECT) can reflect the restoration level of recycling agents (RAs) on atomic-level energy characteristics of aged bitumen. Compared to rutting failure temperature (RFT), elastic recovery (R3.2), and creep compliance (Jnr3.2), the zero-shear viscosity (ZSV) greatly correlates with CED. Meanwhile, the UWEK index from MD simulations demonstrates a strong correlation with high-temperature rheological indicators of rejuvenated bitumen. With the rise in UWEK, there is a linear decrease in the RFT, Log(ZSV), and R3.2 values of rejuvenated bitumen. Conversely, the Log(Jnr3.2) exhibits a linear increasing trend. However, the correlation patterns between rheological indicators and either EN or ECT are contingent on the aging degree of bitumen. Based on the correlation coefficient, the UWEK stands out as the primary choice among all energy indices for predicting high-temperature rheological performance of rejuvenated bitumen.

Impact of Radiofrequency Exposure From Mobile Phones on the Risk of Developing Brain Tumors in Korean and Japanese Adolescents: A MOBI-Kids Case-control Study.

This study aimed to examine the association between risk of brain tumors and radiofrequency (RF) exposure from mobile phones among young people in Korea and Japan. This case-control study of brain tumors in young people was conducted in Korea and Japan under the framework of the international MOBI-Kids study. We included 118 patients diagnosed with brain tumors between 2011 and 2015 and 236 matched appendicitis controls aged 10-24 years. Information on mobile phone use was collected through face-to-face interviews. A detailed RF exposure algorithm, based on the MOBI-Kids algorithm and modified to account for the specificities of Japanese and Korean phones and networks, was used to calculate the odds ratios (ORs) for total cumulative specific energy using conditional logistic regression. The adjusted ORs in the highest tertile of cumulative call time at 1 year before the reference date were 1.61 (95% confidence interval [CI], 0.72-3.60) for all brain tumors and 0.70 (95% CI, 0.16-3.03) for gliomas, with no indication of a trend with exposure. The ORs for glioma specifically, were below 1 in the lowest exposure category. This study provided no evidence of a causal association between mobile phone use and risk of brain tumors as a whole or of glioma specifically. Further research will be required to evaluate the impact of newer technologies of communication in the future.

Effects of an Annular Baffle on Heat Transfer to an Immersed Coil Heat Exchanger in Thermally Stratified Tanks

Abstract The effect of a cylindrical baffle on heat transfer to an immersed heat exchanger is investigated in initially thermally stratified tanks. The heat exchanger is located in the annular region created by the baffle and the tank wall. Three different cases of initial thermal stratification are explored, and in each case, experiments are conducted with and without the baffle in the stratified tank and in a comparable isothermal tank with the same initial energy, enabling exploration of the role of the baffle in a stratified tank and the role of stratification in tanks with or without the baffle. The baffle maintains the high initial temperature of the upper zone of the stratified tank for 10–16 min, as cool plumes that form on the heat exchanger are confined to the annular baffle region until they exit at the bottom of the tank. Regardless of stratification, the baffle always improves heat transfer to the immersed heat exchanger. In the isothermal tanks, the baffle increases total energy extracted in the first 30 min of discharge by over 20%. In stratified tanks, the baffle increases total energy extracted in 30 min of discharge by 9–16%. Initially, improvement in heat transfer in stratified tanks is due to the higher driving temperature differences around the heat exchanger. Later, after all the water from the hot zone has entered and flowed through the baffle, the tank is basically isothermal, and velocity increases as the fluid temperature drops, maintaining rates of heat transfer higher than that in the tank without the baffle. Stratification improves heat transfer in tanks without a baffle because, by design, the driving temperature difference between the heat exchanger wall and the surrounding fluid is considerably higher. However, in tanks with the baffle, stratification has only a modest positive effect on heat transfer to the immersed heat exchanger.

A Reinforcement Learning Approach for Flexible Job Shop Scheduling Problem With Crane Transportation and Setup Times.

Flexible job shop scheduling problem (FJSP) has attracted research interests as it can significantly improve the energy, cost, and time efficiency of production. As one type of reinforcement learning, deep Q-network (DQN) has been applied to solve numerous realistic optimization problems. In this study, a DQN model is proposed to solve a multiobjective FJSP with crane transportation and setup times (FJSP-CS). Two objectives, i.e., makespan and total energy consumption, are optimized simultaneously based on weighting approach. To better reflect the problem realities, eight different crane transportation stages and three typical machine states including processing, setup, and standby are investigated. Considering the complexity of FJSP-CS, an identification rule is designed to organize the crane transportation in solution decoding. As for the DQN model, 12 state features and seven actions are designed to describe the features in the scheduling process. A novel structure is applied in the DQN topology, saving the calculation resources and improving the performance. In DQN training, double deep Q-network technique and soft target weight update strategy are used. In addition, three reported improvement strategies are adopted to enhance the solution qualities by adjusting scheduling assignments. Extensive computational tests and comparisons demonstrate the effectiveness and advantages of the proposed method in solving FJSP-CS, where the DQN can choose appropriate dispatching rules at various scheduling situations.

In English

The total reorganization energy of the system and its components, the solvent reorganization energy and the transformation energy of reactants (water clusters [(H2O)nOH]-), during electrocatalytic hydrogen evolution on binary alloys of molybdenum with iron subgroup metals (Fe, Co, Ni) in an alkaline medium (30 wt. % NaOH solution) have been calculated. The calculated values of the solvent reorganization energy and the reorganization energy of water clusters are in agreement with the Marcus – Dogonadze – Kuznetsov theory. The dependence of the total reorganization energy of the system, the solvent reorganization energy, and the reorganization energy of discharging species (water clusters) on the electrolyte temperature has been calculated. It was shown that the total reorganization energy of the system and the activation energy of the electron-transfer reaction of electrocatalytic hydrogen evolution (HER) on binary alloys of molybdenum with iron subgroup metals in an alcaline vedium (30 wt. % NaOH solution) decrease linearly with increasing electrolyte temperature in the following order: Fe-54 at. % Mo > Ni-54 at. % Mo > Co-52 at. % Mo. The temperature dependences of the water cluster discharge reorganization energy and the activation energy on binary molybdenum alloys are linear and intersect in the boiling point region of 30 wt. % NaOH solution 384.7 K. At this temperature, the electrode process is limited by the diffusion of regenerating water clusters to the electrode surface. The calculated diffusion activation energy Ad is 9.9 kJ·mol–1. The value of the system reorganization energy lt is 39.8 kJ·mol–1, which is consistent with the theory of Markus – Dogonadze – Kuznetsov. Electrocatalytic activity of binary alloys of molybdenum with iron subgroup m

Classification of acoustic survey data: A comparison between seven teams of experts

Acoustic surveys of mixed fish aggregations often rely on manual allocation of acoustic energy to target species, with auxiliary information such as trawl catches and target strength distributions aiding interpretation. However, different teams of experts may use the same auxiliary data differently. In this experiment, seven teams of experts interpreted the same acoustic data, and we compared their classification to target categories to quantify uncertainty in the manual classification process. The teams largely agreed on the total acoustic energy attributable to organisms, but there was significant variation in how the teams split this energy on different target categories. This was caused by differences in applied thresholds for separating plankton and fish, as well as disagreements in species classification. For all target categories, the variation due to teams was lower than the overall variability across acoustic segments, but when scaled up to the number of segments in a typical survey, the team effect either dominated or was of similar magnitude as the segment variability. These results imply a need for further standardisation and uncertainty estimation of expert evaluations in acoustic surveys involving manual interpretation of echo sounder data.

Analysis of the exergy performances of a glazed and unglazed PV/T collector under different conditions

The exergy performances of the hybrid PV/T solar collector using different heat transfer fluids was numerically investigated. The mathematical model is based on the energy balance equations applied to each collector element as well as exergy balance founded on the second law of thermodynamics. The governing equations are discretized and solved using Finite difference method based on alternating directions implicit scheme. A comparative study of the exergy performances of the hybrid collector with and without glass cover using nanofluid Cu−water, distilled water and water-EG mixture as transfer fluids is conducted. The results showed that Cu−water nanofluid enhances the total exergy of the collector by 1.6% and 2.7% highest than water and water-EG respectively. However, regarding the thermal exergy, water-EG mixture is the best fluid which allows to improve the collector production by 17% and 28.5% than water and Cu−water respectively. The maximum energy and exergy efficiencies reached over the day are around 70% and 15% respectively. In addition, it is found that the overall exergy produced by the unglazed system is 6.45% higher than the collector with glass cover. While, the total energy yield of this latter is 26% higher than the system without cover. The effect of operating parameters on the collector exergy effectiveness is analyzed and discussed in this work.

Mapping the Evolution of Green Finance Research and Development in Emerging Green Economies

Research on green and sustainable finance is increasing, crucial for advancing a green financial system and economic growth. Utilizing a Scopus database, this paper collects data and, through bibliometric analysis in R studio, visually explores research trends, hotspots, and fronts in green finance and sustainable development across top emerging green economies. From 2001 to 2022, publications in this field have grown annually, with China leading globally. Significant hotspots include urban total factor energy efficiency, reducing carbon emissions, regional economic development, climate adaptation, technological progress, green innovation, and transitioning from linear to circular economy models. The study anticipates future research to focus on refining industrial and financial structures that align sustainable, green development with superior ecological environment protection, highlighting the evolving nature of green finance research and its impact on promoting sustainable economic practices.

Applications of the Peach-Koehler force in liquid crystals

ABSTRACT In solids, external stress induces the Peach-Koehler force, which drives dislocations to move. Similarly, in liquid crystals, an external angular stress creates an analogous force, which drives disclinations to move. In this work, we develop a method to calculate the relevant angular stress either analytically or numerically, and hence to determine the force on a disclination. We demonstrate this method by applying the Peach-Koehler force theory to four problems: (a) Single disclination in a liquid crystal cell between two uniform in-plane alignments perpendicular to each other. (b) Array of disclinations in a liquid crystal cell with patterned substrates. (c) Pair of disclinations in a long capillary tube with homeotropic anchoring. (d) Radial hedgehog or disclination loop inside a sphere with homeotropic anchoring, and its response to an applied magnetic field. In all of these problems, the Peach-Koehler force theory predicts the equilibrium defect structure, and the predictions are consistent with the results of minimising the total free energy.

Household energy resilience in extreme weather events: An investigation of energy service importance, HVAC usage behaviors, and willingness to pay

Household energy resilience, particularly maintaining essential energy services within an acceptable and affordable level, is critical during extreme weather events (e.g., winter storms, heat waves) with power shortages or outages. However, the research on the importance and acceptable compromise levels of energy services, HVAC usage behavior changes, and willingness to pay (WTP) for energy services during disasters is limited. Therefore, this study investigates the importance and compromise of household energy services, HVAC usage behaviors, and WTP, as three key dimensions of household energy resilience, in both normal days and disaster scenarios through surveys (n = 485). First, 12 common residential end-uses are grouped into high, mid, and low-priority services using hierarchical clustering, in which high-priority services (perceived as important and un-compromisable) include food cooking and storage (refrigerator and freezer) and thermal comfort (space heating and cooling), mid-priority services involve water heating and lighting, while low-priority services are mostly related to entertainment and housework (e.g., TV, laundry). Also, HVAC use patterns demonstrate that occupants become more energy conservative during disasters, e.g., reducing durations of running HVAC and adjusting temperature setpoints to save energy. In terms of energy cost, approximately 60% of respondents are willing to pay more to maintain energy services during disasters, although only 13% are prepared to pay over double the normal energy prices. The regression models further reveal that household energy resilience varies across different socio-demographic groups (e.g., age, income, family size) and is impacted by disaster experience and beliefs in clean energy and climate. These research findings provide important perspectives to understand household energy resilience and inform measures for disaster adaptation of households in extreme weather events.

Applicability of Ratings of Perceived Exertion as a Measure of Subjective Fatigue in First Responders: An Exploratory Study

Introduction: Many researchers use Ratings of Perceived Exertion (RPE) as an indicator of subjective fatigue. Recent findings suggest that energy and fatigue are two distinct unipolar moods. Methods: Eleven first responders (FR) participated in a 90-minute strenuous exercise battery where they ended the protocol by completing a graded VO2max test where they were asked to perform until volitional fatigue, measured through RPE. Subjective feelings of mental energy (ME) and fatigue (MF) and physical energy (PE) and fatigue (PF) were measured before the beginning of the protocol and right after. Data was not normally distributed and presented in median and interquartile ranges. Spearman correlation coefficients were calculated for RPE, post mood state, and changes in mood states. Results: Participants’ self-reported RPE at the conclusion of the VO2max test was 18.27 [18.00,19.00]. Post PE (r=-0.012, p=0.97), PF (r=-0.036, p=0.92), ME (r=-0.13, p=0.69), and MF (r=0.43, p=0.19) displayed insignificant correlations with RPE. Similarly, insignificant correlations were observed between changes in PE (r=0.26, p=0.44), PF (r=0.46, p=0.15), ME (r=0.35, p=0.30), MF (r=-0.43, p=0.19), and RPE. Five participants reported an increase in feelings of PE (15.00 [13.00,19.00]) and seven participants reported lower feelings of PF (-12.00 [-19.50,-8.00]) post assessment. Seven participants reported improvements in ME (22.00 [8.00,68.00]) and three reported a reduction in MF (-13.00 [-27.00, -7.00]). Conclusions: Our findings suggests that self-reported RPE may not be a reliable measure of subjective fatigue in FR populations during acute strenuous exercise. Further our findings support previous work that ME, MF, PE, and PF are four distinct unipolar moods, and researchers seeking to assess fatigue in FR should use RPE with caution as it seems to be a measure of subjective perception of exercise intensity instead of a true measure of subjective fatigue.

Conformer-Selective Photoelectron Circular Dichroism.

Conformational flexibility and chirality both play a key role in molecular recognition. It is therefore very useful to develop spectroscopic methods that simultaneously probe both properties. It has been theoretically predicted that photoelectron circular dichroism (PECD) should be very sensitive to conformational isomerism. However, experimental proof has been less forthcoming and only exists for a very few favorable cases. Here, we present a new PECD scheme based on resonance-enhanced two-photon ionization (RE2PI) using UV/Vis nanosecond laser excitations. The spectral resolution obtained thereby guarantees conformer-selectivity by inducing resonant conformer-specific ππ* S1←S0 transitions. We apply this experimental scheme to the study of chiral 1-indanol, which exists in two conformers linked by a ring inversion and defined by the position of the hydroxyl group, namely axial and equatorial. We show that the PECD of the equatorial and axial forms considerably differ in sign, magnitude and shape. We also discuss the influence of the total ionization energy, vibronic excitation of intermediate and final states, and relative polarization of the excitation and ionization lasers. Conformer-specificity adds a new dimension to the applications of PECD in analytical chemistry addressing now the general case of floppy systems.