Energy Landscape Research Articles

Sleep Deprivation Effects on Brain State Dynamics Are Associated With Dopamine D2 Receptor Availability Via Network Control Theory

BackgroundSleep deprivation (SD) negatively affects brain function. Most brain imaging studies have investigated the effects of SD on static brain function. SD effects on functional brain dynamics and their relationship with molecular changes remain relatively unexplored. MethodsWe used functional magnetic resonance imaging to examine resting-brain state dynamics after one night of SD compared with rested wakefulness (N = 41) and assessed the association of brain state dynamics with striatal brain dopamine D2 receptor availability measured by positron emission tomography [11C]raclopride using network control theory. ResultsSD reduced dwell time and persistence probabilities, with the strongest effects in two brain states, one characterized by high default mode network and low dorsal attention network activity and the other by high frontoparietal network and low somatomotor network activity. Using network control theory, we showed that after SD, there was an overall increase in the control energy required for brain state transitions, with effects varying for different brain state transitions. Control energy requirement was negatively associated with transition probabilities under SD and restful wakefulness and accounted for SD-induced changes in transition probabilities. Alteration in the energy landscape was associated with SD-induced changes in striatal D2 receptor distribution. ConclusionsThese findings demonstrate altered occurrence of internally and externally oriented brain states following acute SD and suggest an association with energy requirements for brain state transitions modulated by striatal D2 receptors.

Context-dependent roles of mitochondrial LONP1 in orchestrating the balance between airway progenitor versus progeny cells

While all eukaryotic cells are dependent on mitochondria for function, in a complex tissue, which cell type and which cell behavior are more sensitive to mitochondrial deficiency remain unpredictable. Here, we show that in the mouse airway, compromising mitochondrial function by inactivating mitochondrial protease gene Lonp1 led to reduced progenitor proliferation and differentiation during development, apoptosis of terminally differentiated ciliated cells and their replacement by basal progenitors and goblet cells during homeostasis, and failed airway progenitor migration into damaged alveoli following influenza infection. ATF4 and the integrated stress response (ISR) pathway are elevated and responsible for the airway phenotypes. Such context-dependent sensitivities are predicted by the selective expression of Bok, which is required for ISR activation. Reduced LONP1 expression is found in chronic obstructive pulmonary disease (COPD) airways with squamous metaplasia. These findings illustrate a cellular energy landscape whereby compromised mitochondrial function could favor the emergence of pathological cell types.

Allosteric Control of the Catalytic Properties of Dipeptide-Based Supramolecular Assemblies.

Allostery, as seen in extant biology, governs the activity regulation of enzymes through the redistribution of conformational equilibria upon binding an effector. Herein, a minimal design is demonstrated where a dipeptide can exploit dynamic imine linkage to condense with simple aldehydes to access spherical aggregates as catalytically active states, which facilitates an orthogonal reaction due to the closer proximity of catalytic residues (imidazoles). The allosteric site (amine) of the minimal catalyst can concomitantly bind to an inhibitor via a dynamic exchange, which leads to the alternation of the energy landscape of the self-assembled state, resulting in downregulation of catalytic activity. Further, temporal control over allosteric regulation is realized via a feedback-controlled autonomous reaction network that utilizes the hydrolytic activity of the (in)active state as a function of time.

Functional Medium Entropy Alloys for Joint Replacement: An Atomistic Perspective of Material Deformation and a Correlation to Wear, Corrosion, and Biocompatibility

The present study adopts a muti-facet approach to design bio inspired concentrated alloys for potential application as articulating surfaces in joint replacements. A series of equiatomic, Nb rich and Ti rich TiMoNbZr based medium entropy alloys (MEAs) were processed via arc melting and their mechanical, in-vitro corrosion, wear, and in vitro and in vivo biocompatibility were investigated. Equiatomic MEA had primarily bcc with minor hcp phases where the single bcc was achieved with the addition of Nb. The single bcc Nb rich alloy resulted in 13% elongation, much higher than equiatomic or Ti rich alloy. All the MEAs showed comparatively higher yield strength due to the climb of edge dislocations which is the main rate limiting mechanism at 300 K, as evident molecular dynamics (MD) simulation. The locally fluctuating energy landscape promotes kinks on edge dislocation, and at local minima nanoscale segments gets pinned. Upon yielding the entangled kink leaves a trail of vacancies/interstitials and escapes via climb motion to render high yield strength. The higher corrosion and pitting resistance of Nb enriched alloys can be attributed to the stable ZrO2, Nb2O5, TiO2, and MoO3 oxides, high polarization resistance (106-105 Ωcm−2), and low defect densities (1016-1018). In vitro cell-materials interaction using MC3T3-E1 showed bioinert but cytocompatible nature of the MEAs. The wear rate of the MEAs was in the range of 7-9×10−5 mm3N−1m−1. The wear debris did not show any tissue necrosis when implanted in rabbit femur rather new bone regeneration can be seen around the particles. Statement of SignificanceIn the present work, a noble Nb enriched MEAs with superior mechanical, in vitro wear, corrosion and cytocompatibility properties was designed for articulating surfaces in joint replacement.•Single bcc in Nb enriched MEAs resulted in 13 % elongation with high hardness and yield strength.•Climb of entangled edge segment is the rate limiting mechanism in controlling high yield strength of MEAs at 300 K.•High polarization resistance (106-105 Ωcm−2), and low defect densities (1016-1018) attributes to ZrO2, Nb2O5, TiO2, and MoO3 oxides enriched passive film.•Wet sliding wear rate ranged in order 7-9×10−5 mm3N−1m−1. In-situ generated wear debris when implanted in rabbit femur did not show any tissue necrosis rather new bone regeneration was observed around debris.

Effect of local chemical order on monovacancy diffusion in CoNiCrFe high-entropy alloy

High-entropy alloys (HEAs) are promising materials for nuclear applications. Understanding the influence of local chemical order (LCO) on defect diffusion and evolution in these alloys is crucial for enhancing their resistance to radiation damage. In this study, we used molecular dynamics simulation to investigate the effect of LCO on monovacancy diffusion in CoNiCrFe HEA. Alongside the Warren-Cowley parameter, which quantifies the degree of local elemental ordering, we propose a new parameter to characterize the spatial scale of LCOs. Based on their degree, LCO structures have been classified as either chemical medium-range order (CMRO) or chemical short-range order (CSRO). Our study reveals a non-monotonic variation in vacancy diffusion coefficients, transitioning from random solid solution to CSRO and then to CMRO structures. Moreover, we observe a preference for vacancy diffusion in low-energy Fe, Co-rich regions, with their spatial distribution and spatial connectivity significantly influencing the vacancy diffusion. Due to the spatial scale of the inhomogeneity introduced by LCO, both global average diffusion parameters and single migration barriers cannot fully reflect the actual diffusion dynamics. Therefore, our study emphasizes the importance of understanding the preferred diffusion pathways and the associated energy landscapes to fully assess the defect diffusion dynamics in HEAs. This deeper investigation into localized diffusion behaviors influenced by LCO is crucial for evaluating and enhancing the radiation damage tolerance of HEAs.

Incorporating public perception of Renewable Energy Landscapes in local spatial planning tools: A case study in Mediterranean countries

The European energy transition requirements have been posing many questions on the deployment of renewable energy sources. The development of renewable energy infrastructures entails landscape transformations affecting the perceived landscape quality and local acceptance. Sustainable energy spatial planning considers environmental, cultural, ecological needs but often neglect community perception of landscape transformations including both the physical landscape structures and the meanings associated to them. To address this issue, the paper aims to explore public perception and incorporate it in the planning tools. The research draws on a survey of residents of Arcos de la Frontera, Spain, conducted with the visual Q methodology, and on structured interviews with local experts. A selection of 36 different photovoltaic applications in urban and rural areas was evaluated by 21 citizens. The analysis identified four distinct viewpoints on photovoltaic applications in urban and rural landscapes. Local experts provided feedback on the current local spatial planning tools and on their consideration of landscape transformations. Considering both citizens and experts, we provided landscape integration strategies linked to siting and landscape design of solar power plants to be included in urban planning tools.

Striatal GABA levels correlate with risk sensitivity in monetary loss.

Decision-making under risk is a common challenge. It is known that risk-taking behavior varies between contexts of reward and punishment, yet the mechanisms underlying this asymmetry in risk sensitivity remain unclear. This study used a monetary task to investigate neurochemical mechanisms and brain dynamics underpinning risk sensitivity. Twenty-eight participants engaged in a task requiring selection of visual stimuli to maximize monetary gains and minimize monetary losses. We modeled participant trial-and-error processes using reinforcement learning. Participants with higher subjective utility parameters showed risk preference in the gain domain (r = -0.59) and risk avoidance in the loss domain (r = -0.77). Magnetic resonance spectroscopy (MRS) revealed that risk avoidance in the loss domain was associated with γ-aminobutyric acid (GABA) levels in the ventral striatum (r = -0.42), but not in the insula (r = -0.15). Using functional magnetic resonance imaging (fMRI), we tested whether risk-sensitive brain dynamics contribute to participant risky choices. Energy landscape analyses demonstrated that higher switching rates between brain states, including the striatum and insula, were correlated with risk avoidance in the loss domain (r = -0.59), a relationship not observed in the gain domain (r = -0.02). These findings from MRS and fMRI suggest that distinct mechanisms are involved in gain/loss decision making, mediated by subcortical neurometabolite levels and brain dynamic transitions.

Navigating the Nuclear Renaissance Economic Viability, Zero Emissions, and the Future of Nuclear Energy with Generation IV Reactors and SMRs with Artificial Intelligence Integration

As global efforts intensify to combat climate change and achieve sustainable energy goals, nuclear power is re-emerging as a vital component of the energy mix. This article explores modern nuclear technologies' economic and environmental potential, focusing on the nuclear fuel cycle, Generation IV reactors, Small Modular Reactors (SMRs), and the transformative role of Artificial Intelligence (AI). The nuclear fuel cycle, encompassing fuel production, utilization, and disposal, is evolving to become more efficient and sustainable, reducing costs and environmental impacts. Generation IV reactors and SMRs represent significant advancements, offering enhanced safety, efficiency, and flexibility, making nuclear power more accessible and adaptable. AI integration revolutionizes nuclear operations by optimizing performance, predictive maintenance, and safety monitoring. These technologies collectively enhance nuclear power's economic viability and environmental benefits, positioning it as a cornerstone of global zero-emission strategies. The return on involvement in nuclear energy is substantial, driven by economic growth, energy security, and technological advancements. Continued investment and innovation in these areas are essential for realizing the full potential of nuclear energy in a sustainable and carbon-neutral future. This article underscores the importance of nuclear power in achieving global climate objectives and fostering a sustainable energy landscape.

Temperature-dependent ejection evolution arising from active and passive effects in DNA viruses

Recent experiments have demonstrated that the ejection velocity of different species of DNA viruses is temperature dependent, potentially influencing the cellular infection mechanisms of these viruses. However, due to the challenge in quantifying the multiscale characteristics of DNA virus systems, there is currently a lack of systematic theoretical research on the temperature-dependent evolution of ejection dynamics. This work presents a multiscale model to quantitatively explore the temperature-dependent mechanical properties during the virus ejection process, and unveil the underlying mechanisms. Two different assumptions of DNA structures, featuring two or single domains, are used for the early and later stages of ejection, respectively. Temperature is introduced as an influencing variable into the mesoscopic energy model by considering the temperature dependence of Debye length, DNA persistence length, molecular kinetic energy, and other parameters. The results indicate that temperature variations alter the energy landscape associated with DNA structure, leading to the changes in the energy minimum and corresponding DNA structure remaining in the capsid. These changes affect both the active ejection force and passive friction during the DNA ejection, ultimately leading to a significant increase in ejection velocity at higher temperatures. Furthermore, our model supports the previous hypothesis that temperature-induced changes in the size of viral portal pore could dramatically enhance DNA ejection velocity.

Harvesting the power of the oceans: Advancements, challenges, and the promising future of wave energy

This dissertation explores the pivotal domain of wave energy, delving into its historical evolution, technological advancements, and economic prospects. In response to escalating environmental challenges and the imperative to address climate change, the pursuit of sustainable and ecologically benign energy sources has gained prominence. Wave energy emerges as a compelling frontier within the realm of renewable energy, tapping into the perpetual undulations of oceans. The study traces the conceptual antecedents of wave energy from the 19th century to its current status as a burgeoning renewable energy source. Significant strides in technology during the 1990s and 2010s marked a shift towards optimizing energy conversion efficiencies, exploring novel materials, and refining wave energy converter designs. The dissertation analyzes diverse wave energy converter types, their operational principles, and their potential applications. Despite challenges such as environmental impact, operational reliability, and high capital costs, the unwavering commitment of researchers positions Wave Energy as a sanguine contender in the renewable energy landscape. The economic outlook for wave energy is promising, with global potential estimated at 2 billion kilowatts, fostering socio-economic benefits and contributing to carbon emission reduction. By presenting a comprehensive examination of wave energy, this dissertation underscores its significance in the pursuit of sustainable, environmentally friendly, and reliable energy solutions.

Protonation Effects on the Benzoxazine Formation Pathways and Products Distribution.

The effect of acidic media on the formation of the 3,4-dihydro-2H-3-phenyl-1,3-benzoxazine Bz is evaluated, focusing on the differentiation of intermediates and products formed by the distinct pathways observed in the presence and absence of acid. The use of real-time mass spectrometry (PSI-ESI-MS) coupled to tandem mass spectrometry and infrared multiple photon dissociation (IRMPD) allowed the differentiation of the species observed during the synthesis of benzoxazines in these different conditions. The results suggest that formic acid promotes the formation of aniline and phenol condensation products (IC and IIC) by protecting the aniline amino group and enhancing the formaldehyde electrophilicity. The results also suggest that although the presence of acid allow a more efficient potential energy landscape to be accessed, the last cyclization step for the formation of benzoxazines cannot be mediated by the protonation route intermediate (ROP Bz). Overall, the conclusions presented here provide important information about the synthesis of benzoxazines under acidic conditions, allowing the development of optimal reaction conditions.

Marine fungal diversity unlocks potent antivirals against monkeypox through methyltransferase inhibition revealed by molecular dynamics and free energy landscape

The escalating threat posed by the Monkeypox virus (MPXV) to global health necessitates the urgent discovery of effective antiviral agents, as there are currently no specific drugs available for its treatment, and existing inhibitors are hindered by toxicity and poor pharmacokinetic profiles. This study aimed to identify potent MPXV inhibitors by screening a diverse library of small molecule compounds derived from marine fungi, focusing on the viral protein VP39, a key methyltransferase involved in viral replication. An extensive virtual screening process identified four promising compounds—CMNPD15724, CMNPD28811, CMNPD30883, and CMNPD18569—alongside a control molecule. Rigorous evaluations, including re-docking, molecular dynamics (MD) simulations, and hydrogen bond analysis, were conducted to assess their inhibitory potential against MPXV VP39. CMNPD15724 and CMNPD30883, in particular, demonstrated a superior binding affinity and stable interactions within the target protein's active site throughout the MD simulations, suggesting a capacity to overcome the limitations associated with sinefungin. The stability of these VP39-compound complexes, corroborated by MD simulations, provided crucial insights into the dynamic behavior of these interactions. Furthermore, Principal Component Analysis (PCA) based free energy landscape assessments offered a detailed understanding of the dynamic conformational changes and energetic profiles underlying these compounds' functional disruption of VP39. These findings establish CMNPD15724, CMNPD28811, CMNPD30883, and CMNPD18569 as promising MPXV inhibitors and highlight marine fungi as a valuable source of novel antiviral agents. These compounds represent potential candidates for further experimental validation, advancing the development of safer and more effective therapeutic options to combat this emerging viral infection.

Role of interaction mode of phenanthrene derivatives as selective PDE5 inhibitors using molecular dynamics simulations and quantum chemical calculations.

Phosphodiesterase type 5 (PDE5) inhibitors play a crucial role in blocking PDE5 to improve erectile dysfunction (ED). However, most PDE5 drugs revealed side effects including the loss of vision due to the PDE6 inhibition. Phenanthrene derivatives isolated from E. macrobulbon were previously reported as PDE5 inhibitors. Two phenanthrene derivatives (cpds 1-2) revealed better inhibition to PDE5 than PDE6 and cpd 1 is more selective to PDE5 than cpd 2. To elucidate why the phenanthrene derivatives could inhibit PDE5 and PDE6, their binding modes were investigated using molecular dynamics simulations and quantum chemical calculations, as compared to the PDE5 drugs. From the results, all four drugs and phenanthrene derivatives revealed similar π-π interactions to Phe820 in PDE5. Additional H-bond interaction to Gln817 in PDE5 resulted in better PDE5 inhibition of vardenafil and tadalafil. Moreover, cpds 1-2 were able to form the H-bond interaction with Asp764 in PDE5. In the case of the PDE6, the loss of π-π interaction to Phe776 and H-bond interaction to Gln773 indicated the important points for losing the PDE6 inhibition. In conclusion, to develop the new potent PDE5 inhibitors, not only the important interaction with PDE5 but also the interaction with PDE6 should be considered. In phenanthrene derivatives, the middle ring was significant to form π-π interactions to Phe820 in PDE5 and hydroxyl substituent was also the key part to form the H-bond interaction with Asp764 in PDE5. Principal component analysis (PCA) and free energy landscape (FEL) analysis indicated the stability of the system. The bioavailability, drug-likeness, and pharmacokinetics of phenanthrene derivatives were also predicted. These derivatives revealed good drug-likeness and GI absorption. The obtained results showed that phenanthrene derivatives could be interesting for the development of PDE5 inhibitors in the future.

Fundamental Thermodynamic, Kinetic, and Mechanical Properties of Lithium and Its Alloys.

Lithium alloying reactions are beneficial in promoting uniform plating and stripping of lithium metal in all-solid-state batteries. First-principles calculations are performed to predict thermodynamic, kinetic, and mechanical properties of lithium and several important Li-M alloys (M = Mg, Ag, Zn, Al, Ga, In, Sn, Sb, and Bi). While the Li-Mg binary system forms a solid solution, most other lithium-metal alloys prefer stoichiometric intermetallic compounds with common local motifs that enable fast Li diffusion. Lithium and Li-rich alloys exhibit an unusually flat energy landscape along paths that connect BCC to close-packed structures like FCC and HCP, with important implications for mechanical properties. Very low migration barriers for Li diffusion that rival those of superion conductors are predicted, both in pure Li and in Li-M intermetallics. However, vacancy concentration, which is crucial for substitutional diffusion, is predicted to be low in metallic Li and most Li-M intermetallics. Compounds such as B32 LiAl and LiGa as well as D03 Li3Sb and Li3Bi exhibit structural vacancies at higher ends of their voltage windows, which together with low migration barriers leads to exceptionally high Li mobilities. In the Li-Mg solid solution, the addition of Mg is found to decrease the vacancy tracer diffusion coefficient by an order of magnitude.

Analysis of the effect of component size and demand pattern on the final price for a green hydrogen production system

Hydrogen emerges as a pivotal energy carrier, shaping the future of the energy landscape. This study explores the potential of utilizing solar energy for green hydrogen production, presenting a promising avenue for low-carbon energy generation. Despite its potential, uncertainties stemming from the intermittent nature of solar energy, demand fluctuations, and economic considerations pose challenges to its widespread adoption. The paper delves into the performance of a power-to-hydrogen system, employing solid oxide electrolyzers to convert electricity from solar arrays into green hydrogen. Two distinct system architectures are proposed: the dedicated configuration, where the owner of the solar array and power-to-hydrogen facilities are the same, and the non-dedicated configuration, where the power-to-hydrogen system purchases solar electricity from the owner of the solar power plant. Simulation results from the case study reveal that the non-dedicated system offers superior economic performance compared to the dedicated system. Considering different hydrogen demand levels and electrolyzer sizes, the levelized cost of hydrogen in the non-dedicated scheme is below 2 $/kg, demonstrating competitive pricing within the realm of renewable technologies. However, solar-assisted green hydrogen faces tough competition with traditional sources of hydrogen production when considering economic aspects.

Arrhythmogenic cardiomyopathy-related cadherin variants affect desmosomal binding kinetics

Cadherins are calcium dependent adhesion proteins that establish and maintain the intercellular mechanical contact by bridging the gap between adjacent cells. Desmoglein-2 (Dsg2) and desmocollin-2 (Dsc2) are tissue specific cadherin isoforms of the cell-cell contact in cardiac desmosomes. Mutations in the DSG2-gene and in the DSC2-gene are related to arrhythmogenic right ventricular cardiomyopathy (ARVC) a rare but severe heart muscle disease. Here, several possible homophilic and heterophilic binding interactions of wild-type Dsg2, wild-type Dsc2, as well as one Dsg2- and two Dsc2-variants, each associated with ARVC, are investigated. Using single molecule force spectroscopy (SMFS) with atomic force microscopy (AFM) and applying Jarzynski's equality the kinetics and thermodynamics of Dsg2/Dsc2 interaction can be determined. The free energy landscape of Dsg2/Dsc2 dimerization exposes a high activation energy barrier, which is in line with the proposed strand-swapping binding motif. Although the binding motif is not affected by any of the mutations, the binding kinetics of the interactions differ significantly from the wild-type. While wild-type cadherins exhibit an average complex lifetime of approx. 0.3 s interactions involving a variant consistently show - lifetimes that are substantially larger. The lifetimes of the wild-type interactions give rise to the picture of a dynamic adhesion interface consisting of continuously dissociating and (re)associating molecular bonds, while the delayed binding kinetics of interactions involving an ARVC-associated variant might be part of the pathogenesis. Our data provide a comprehensive and consistent thermodynamic and kinetic description of cardiac cadherin binding, allowing detailed insight into the molecular mechanisms of cell adhesion.

Impacts of hydrogen fraction and equivalence ratio on the explosion characteristics of ethanol/hydrogen mixtures

With the anticipated widespread integration of biofuels and hydrogen fuels within the future energy landscape, the potential explosion hazards after their release within confined spaces under the atmospheric are deserving of heightened attention. The present work takes the mixtures of ethanol and hydrogen as the objects and experimentally studies the impacts of hydrogen fraction and equivalence ratio on the explosion characteristics in a constant-volume explosion vessel at 0.10 MPa and 400 K. The data reveals that an increase in the hydrogen fraction leads to a rise in the maximum explosion pressure during lean explosions but causes a decrease during rich explosions. Nonetheless, the duration of the explosion decreases with the increase of hydrogen fraction in all the explosions. In consideration of explosion pressure, the maximum pressure rise is found to be exponential in relation to the maximum explosion pressure. However, the confidence level diminishes significantly with an increase in the hydrogen fraction. Conversely, the maximum rate of pressure rise during an explosion appears to be a function of the duration of the explosion, suggesting that the reaction rate plays a more pivotal role in determining the hazardous level. Meanwhile, the duration of fast combustion steadily occupies approximately 83 % of the explosion duration. Furthermore, the deflagration index is no more than 30 MPa*m/s, namely, ethanol/hydrogen mixture is a promising fuel with mild hazardous potential.

Substrate deformability and applied normal force are coupled to change nanoscale friction.

Amonton's law of friction states that the friction force is proportional to the normal force in magnitude, and the slope gives a constant friction coefficient. In this work, with molecular dynamics simulation, we study how the kinetic friction at the nanoscale deviates qualitatively from the relation. Our simulation demonstrates that the friction behavior between a nanoscale AFM tip and an elastic graphene surface is regulated by the coupling of the applied normal force and the substrate deformability. First, it is found that the normal load-induced substrate deformation could lower friction at low load while increasing it at high load. In addition, when the applied force exceeds a certain threshold another abrupt change in friction behavior is observed, i.e., the stick-slip friction changes to the paired stick-slip friction. The unexpected change in friction behavior is then ascribed to the change of the microscopic contact states between the two surfaces: the increase in normal force and the substrate deformability together lead to a change in the energy landscape experienced by the tip. Finally, the Prandtl-Tomlinson model also validates that the change in friction behavior can be interpreted in terms of the energy landscape.

Nanoparticle agglomeration in molten salt nanofluids: Free energy landscape and its impacts on thermal transport property degradation

The nanofluids consisting of molten salt and nanoparticles can gain enhanced thermal performance for heat transfer and energy storage processes. Agglomeration of nanoparticles is ubiquitous in this colloidal dispersion, deteriorating the dispersed states of the nanocomposite interiors, and its microscopic mechanisms are unsatisfactorily explored. In this work, molecular dynamics simulations combined with umbrella sampling technique to capture the relative dispersion state of nanoparticles in molten salts effectively were performed to reveal the free energy landscape of agglomeration and its influence on heat transport. The dominant deep minima in the free energy surface demonstrates that the agglomeration of MgO nanoparticles in the molten NaCl salt is principally induced by van der Waals attractions between MgO nanoparticles and aggravated by large surface area. The unstable dispersion of nanoparticles is the most fatal problem for enhanced thermal conductivity during agglomeration, and the relative distance of MgO nanoparticles has less impacts on the thermal conductivity of the melt. The stronger adsorption of ions around nanoparticles can improve their relative dispersion, and utilize interfacial effects to enhance the thermal conductivity. Combined with the benefit of ordered ionic layer on the surface, the MgO nanoparticles of 10 Å diameter (specific surface area of ∼ 938.80 m2/g) become the optimal choice for molten NaCl. With the mechanisms of interfacial microstructures preventing agglomerated nanoparticles and improving heat transfer of molten salts revealed, this work can enlighten the selection or feasible modification for nanoparticles in various high-temperature molten salts, since the mechanisms are universal to other nanofluids, especially for ionic liquid based nanofluids.

Vibrational Energy Landscapes and Energy Flow in GPCRs.

We construct and analyze disconnectivity graphs to provide the first graphical representation of the vibrational energy landscape of a protein, in this study β2AR, a G-protein coupled receptor (GPCR), in active and inactive states. The graphs, which indicate the relative free energy of each residue and the minimum free energy barriers for energy transfer between them, reveal important composition, structural and dynamic properties that mediate the flow of energy. Prolines and glycines, which contribute to GPCR plasticity and function, are identified as bottlenecks to energy transport along the backbone from which alternative pathways for energy transport via nearby noncovalent contacts emerge, seen also in the analysis of first passage time (FPT) distributions presented here. Striking differences between the disconnectivity graphs and FPT distributions for the inactive and active states of β2AR are found where structural and dynamic changes occur upon activation, contributing to allosteric regulation.