Catalogue Search | MBRL
Are you sure you want to remove the book from the shelf?
{{itemTitle}}
33,359
result(s) for
"Energy level"
Sort by:
Energy level transition and mode transition in a neuron
During continuous diffusion and propagation of intracellular ions, energy transition between electric and magnetic field is proceeded to present appropriate firing patterns. For theoretical neuron models, an equivalent Hamilton energy is derived by Helmholtz theorem. For neural circuits, the Hamilton energy can also be obtained by applying scale transformation on the field energy function. External stimuli injects energy into the neuron, and the energy level transition is induced accompanying with mode transition in the neuronal activity. On the flip side, large external stimuli can induce shape deformation of the cell and possible parameter shift occurs to keep neuron on appropriate energy level in the deterministic neuron models. In this letter, energy function for Hindmarh–Rose neuron is estimated and a criterion for transition between energy levels and firing modes is defined and explained. It provides possible clues for understanding the dependencies of pattern selection in discharge mode on energy level and adaptive controllability in neurons, and thus the neural activities in neurons and nervous system can be controlled by regulating energy flow.
Journal Article
Selective manipulation of electronically excited states through strong light–matter interactions
Strong coupling between light and matter leads to the spontaneous formation of hybrid light–matter states, having different energies than the uncoupled states. This opens up for new ways of modifying the energy landscape of molecules without changing their atoms or structure. Heavy metal-free organic light emitting diodes (OLED) use reversed intersystem crossing (RISC) to harvest light from excited triplet states. This is a slow process, thus increasing the rate of RISC could potentially enhance OLED performance. Here we demonstrate selective coupling of the excited singlet state of Erythrosine B without perturbing the energy level of a nearby triplet state. The coupling reduces the triplet–singlet energy gap, leading to a four-time enhancement of the triplet decay rate, most likely due to an enhanced rate of RISC. Furthermore, we anticipate that strong coupling can be used to create energy-inverted molecular systems having a singlet ground and lowest excited state.
Manipulating energy levels in molecules could allow applications such as improving organic LEDs. Here, the authors show evidence that reversed intersystem crossing can be enhanced in Erythrosine B coupled to a cavity by selectively manipulating the energy of the singlet state.
Journal Article
Broadband and strong visible-light-absorbing cuprous sensitizers for boosting photosynthesis
Rational construction of broadband and strong visible-light-absorbing (BSVLA) earth-abundant complexes is of great importance for efficient and sustainable solar energy utilization. Herein, we explore a universal Cu(I) center to couple with multiple strong visible-light-absorbing antennas to break the energy level limitations of the current noble-metal complexes, resulting in the BSVLA nonprecious complex (Cu-3). Systematic investigations demonstrate that double “ping-pong” energy-transfer processes in Cu-3 involving resonance energy transfer and Dexter mechanism enable a BSVLA between 430 and 620 nm and an antenna-localized long-lived triplet state for efficient intermolecular electron/energy transfer. Impressively, Cu-3 exhibited an outstanding performance for both energy- and electron-transfer reactions. Pseudo-first-order rate constant of photooxidation of 1,5-dihydroxynaphthalene with Cu-3 can achieve a record value of 190.8 × 10−3 min−1 among the molecular catalytic systems, over 30 times higher than that with a noble-metal photosensitizer (PS) [Ru(bpy)₃]2+. These findings pave the way to develop BSVLA earth-abundant PSs for boosting photosynthesis.
Journal Article
The controlled exciton transport of the Multi-chain system by cavity-dressed energy level crossings and anticrossings
The performance of various quantum devices is fundamentally linked to the control of exciton transport. To explore this, we study the exciton transport of the two-dimensional multi-chain systems with different coupling configurations in an optical cavity. Two types of the chains–the homogeneous and heterogeneous coupling chain, as well as two inter-chain coupling conformations—the square and triangular arrangements, are considered. The effects of the inter-chain coupling, the dimerization parameter, the cavity, the length and number of the chains on exciton transport are systematically investigated for different coupling configurations through the spectra, the Hopfield coefficients, and the steady-state dynamics of the system. The results show that in the absence of a cavity the exciton transport currents and efficiency are determined by the exciton distribution across the multi-chain system. However, when a cavity is introduced the exciton transport can be significantly enhanced or suppressed by the polariton formation at the cavity-dressed energy level crossings and anticrossings near zero-energy modes, where the coherent excitation and Landau–Zener transitions occur. Meanwhile, we discover that the discontinuous and extremal points in the second-order partial derivatives of the photon Hopfield coefficients with respect to the inter-chain coupling and the dimerization parameter correspond respectively to the crossings and anticrossings at the extreme points of the photon occupation number. Additionally, the exciton transport currents and efficiency present distinctly odd–even oscillation with chain length and number. This work provides critical insights into the exciton transport mechanism in multi-chain–cavity system and theoretical basis for designing high-performance excitonic devices with tunable transport properties.
Journal Article
Effects of dietary energy levels on rumen bacterial community composition in Holstein heifers under the same forage to concentrate ratio condition
Background
The rumen bacterial community plays a critical role in feeds degradation and productivity. The effects of different forage to concentrate ratios on the ruminal microbial population structure have been studied extensively; however, research into changes in the ruminal bacterial community composition in heifers fed different energy level diets, with the same forage to concentrate ratio, has been very limited. The purpose of this study was to investigate the effects of different dietary energy levels, with the same forage to concentrate ratio, on ruminal bacterial community composition of heifers. Furthermore, we also determine the relationship between rumen bacteria and ruminal fermentation parameters.
Results
The 16S rRNA gene sequencing showed that, under the same forage to concentrate ratio of 50:50, an 8% difference in dietary energy level had no significant impact on the alpha diversity and the relative abundance of the major phyla and most of the major genera in heifers. In all the treatments groups,
Firmicutes
,
Bacteroidetes
, and
Proteobacteria
were the dominant phyla. Spearman correlation analysis between the relative abundances of the rumen bacteria at the genus level and the fermentation parameters showed that the relative abundances of
Prevotella
and BF311 were positively correlated with the ammonia nitrogen and butyrate concentrations, and these two genera were negatively correlated with the propionate and isovalerate concentrations, respectively, and the genus
Bifidobacterium
was positively correlated with the butyrate concentration and was negatively correlated with propionate and isovalerate concentration. The total volatile fatty acid concentration was positively correlated with BF311 abundances, and was negatively correlated with
Trichococcus
and
Facklamia
abundances.
Conclusions
Under the same forage to concentrate ratio condition of 50:50, an 8% difference in dietary energy levels had little impact on rumen bacterial community composition in heifers. The correlations between some genera of ruminal bacteria and the concentrations of volatile fatty acids and ammonia nitrogen might be indicative that the ruminal fermentation parameters are strongly influenced by the rumen bacterial community composition.
Journal Article
Unveiling Charge Carrier Recombination, Extraction, and Hot‐Carrier Dynamics in Indium Incorporated Highly Efficient and Stable Perovskite Solar Cells
Perovskite solar cells (PSCs) have been propelled into the limelight over the past decade due to the rapid‐growing power conversion efficiency (PCE). However, the internal defects and the interfacial energy level mismatch are detrimental to the device performance and stability. In this study, it is demonstrated that a small amount of indium (In3+) ions in mixed cation and halide perovskites can effectively passivate the defects, improve the energy‐level alignment, and reduce the exciton binding energy. Additionally, it is confirmed that In3+ ions can significantly elevate the initial carrier temperature, slow down the hot‐carrier cooling rate, and reduce the heat loss before carrier extraction. The device with 1.5% of incorporated In3+ achieves a PCE of 22.4% with a negligible hysteresis, which is significantly higher than that of undoped PSCs (20.3%). In addition, the unencapsulated PSCs achieve long‐term stability, which retain 85% of the original PCE after 3,000 h of aging in dry air. The obtained results demonstrate and promote the development of practical, highly efficient, and stable hot‐carrier‐enhanced PSCs. In this article, state‐of‐the‐art perovskite solar cells were reported with a small amount of incorporated indium (In3+) ions. The In3+ ions accumulate at the buried interface and align the energy level to the electron transport layer. Additionally, the charge carrier dynamics at and above the band edge in mixed cation and halide perovskites can be greatly affected.
Journal Article
Differential In Vitro Effects of SGLT2 Inhibitors on Mitochondrial Oxidative Phosphorylation, Glucose Uptake and Cell Metabolism
(1) The cardio-reno-metabolic benefits of the SGLT2 inhibitors canagliflozin (cana), dapagliflozin (dapa), ertugliflozin (ertu), and empagliflozin (empa) have been demonstrated, but it remains unclear whether they exert different off-target effects influencing clinical profiles. (2) We aimed to investigate the effects of SGLT2 inhibitors on mitochondrial function, cellular glucose-uptake (GU), and metabolic pathways in human-umbilical-vein endothelial cells (HUVECs). (3) At 100 µM (supra-pharmacological concentration), cana decreased ECAR by 45% and inhibited GU (IC5o: 14 µM). At 100 µM and 10 µM (pharmacological concentration), cana increased the ADP/ATP ratio, whereas dapa and ertu (3, 10 µM, about 10× the pharmacological concentration) showed no effect. Cana (100 µM) decreased the oxygen consumption rate (OCR) by 60%, while dapa decreased it by 7%, and ertu and empa (all 100 µM) had no significant effect. Cana (100 µM) inhibited GLUT1, but did not significantly affect GLUTs’ expression levels. Cana (100 µM) treatment reduced glycolysis, elevated the amino acids supplying the tricarboxylic-acid cycle, and significantly increased purine/pyrimidine-pathway metabolites, in contrast to dapa (3 µM) and ertu (10 µM). (4) The results confirmed cana´s inhibition of mitochondrial activity and GU at supra-pharmacological and pharmacological concentrations, whereas the dapa, ertu, and empa did not show effects even at supra-pharmacological concentrations. At supra-pharmacological concentrations, cana (but not dapa or ertu) affected multiple cellular pathways and inhibited GLUT1.
Journal Article
Review on the DFT computation of bulk heterojunction and dye-sensitized organic solar cell properties
Context
Organic solar cells (OSCs) represent a promising renewable energy technology due to their flexibility, low production cost, and environmental sustainability. To advance OSC efficiency and stability, density functional theory (DFT) has emerged as a powerful computational tool, enabling the prediction and optimization of critical properties at the molecular and device levels. This review highlights the key properties of bulk heterojunction solar (BHJ) solar cells and dye-sensitized solar cells (DSSCs) that can be accurately computed using DFT, including
electronic structure properties
(HOMO–LUMO energy levels, bandgap energies, and exciton binding energies, which influence charge separation and transport);
optical properties
(absorption spectra and light-harvesting efficiency, essential for maximizing photon capture);
charge transport properties
(reorganization energies, electron, and hole mobilities, and charge transfer rates that govern carrier dynamics within devices);
interfacial properties
(energy alignment at donor–acceptor interfaces, contributing to efficient charge separation and minimizing recombination); and
chemical reactivity descriptors
(ionization potential, electron affinity, chemical hardness, and electrophilicity, which facilitate material screening for OSC applications). We also show how to compute OSCs’ power conversion efficiency (PCE) from DFT.
Methods
The review also discusses the importance of selecting appropriate exchange–correlation functionals and basis sets to ensure the accuracy of DFT predictions. By providing reliable computational insights, DFT accelerates the rational design of OSC materials, guides experimental efforts, and reduces resource demands. This work underscores DFT’s pivotal role in optimizing OSC performance and fostering the development of next-generation photovoltaic technologies.
Journal Article
A database of water transitions from experiment and theory (IUPAC Technical Report)
The report and results of an IUPAC Task Group (TG) formed in 2004 on “A Database of Water Transitions from Experiment and Theory” (Project No. 2004-035-1-100) are presented. Energy levels and recommended labels involving exact and approximate quantum numbers for the main isotopologues of water in the gas phase, H
O, H
O, H
O, HD
O, HD
O, HD
O, D
O, D
O, and D
O, are determined from measured transition frequencies. The transition frequencies and energy levels are validated using first-principles nuclear motion computations and the MARVEL (measured active rotational–vibrational energy levels) approach. The extensive data including lines and levels are required for analysis and synthesis of spectra, thermochemical applications, the construction of theoretical models, and the removal of spectral contamination by ubiquitous water lines. These datasets can also be used to assess where measurements are lacking for each isotopologue and to provide accurate frequencies for many yet-to-be measured transitions. The lack of high-quality frequency calibration standards in the near infrared is identified as an issue that has hindered the determination of high-accuracy energy levels at higher frequencies. The generation of spectra using the MARVEL energy levels combined with transition intensities computed using high accuracy ab initio dipole moment surfaces are discussed. A recommendation of the TG is for further work to identify a single, suitable model to represent pressure- (and temperature-) dependent line profiles more accurately than Voigt profiles.
Journal Article