Browse Articles

Temperature-dependent local and global dynamics of atactic polystyrene: A coarse-grained molecular dynamics simulation study

A systematic coarse-grained (CG) model, as a promising and helpful tool to access the accurate knowledge of the local and global polymer dynamics of real polymers, is required to preserve structural, thermodynamic, and dynamic properties of the underlying atomistic model over a wide temperature range. In the present work, to explore the temperature-dependent local and global dynamic properties of atactic polystyrene (PS) as well as the dynamic consistency of a PS CG model constructed via a structure- and thermodynamics-based CG approach with the united-atom (UA) counterpart, we have investigated and compared the translational and rotational dynamics of the two models in the scale from a single monomer to a global chain in a broad temperature range. The CG model accurately reproduces the time-dependent translational diffusion scaling and the shift from a multistep relaxation to a single-step long-time decay process with increasing span of bond vectors as the UA model. There exists the coupling of the conformational relaxation and diffusion of the PS chains to the local structural α-relaxation. Both diffusion coefficients and relaxation times of the UA and CG models show the same temperature dependence and follow a power-law relationship of mode-coupling theory. These findings advance our understanding of the complex dynamics of atactic PS and give a sounder basis for the further development of CG PS models with the (time-dependent) frictional correction to perform a quantitative study of structural relaxation and dynamical heterogeneity near glass transition temperature.

SARS-CoV-2 virus lacking the envelope and membrane open-reading frames as a vaccine platform

Visual investigation of swelling and migration behavior of bentonite and kaolinite clays at elevated temperature using micromodels

Abstract Low-salinity waterflooding (LSWF) is an effective enhanced oil recovery (EOR) method, where injecting low-salinity brine disturbs the reservoir’s chemical balance to mobilize residual oil. However, clay minerals, abundant in sandstone reservoirs, pose challenges due to their tendency to swell and migrate, leading to permeability reduction and potential formation damage. While the impact of LSWF on clay-related damage is well studied, the role of temperature in exacerbating these effects remains insufficiently explored. This study investigates the effect of temperature on clay swelling and migration using a microfluidic oven and micromodels coated with bentonite and kaolinite. A series of injection tests were conducted under ambient and elevated temperatures, considering the influence of different cation types in the porous media. Image processing techniques were used to assess porosity, effective porosity, and permeability variations. The results indicate that temperature does not significantly affect clay swelling. However, higher temperatures greatly enhance clay migration for both bentonite and kaolinite, leading to severe pore throat clogging, an effect not observed at ambient temperature. These findings highlight the critical role of temperature in LSWF and its potential to exacerbate formation damage, emphasizing the need for careful reservoir management in high-temperature conditions.

Multiscale modeling of charge transfer in hole-transporting materials: Linking molecular morphology to charge mobility

Hole-transporting materials (HTMs) play a pivotal role in the performance and stability of organic electronic devices by enabling efficient hole transport. This study employs a multiscale approach to explore the relationship between molecular morphology and charge transfer properties in four HTM molecules. By combining quantum mechanical calculations, molecular dynamics simulations, and kinetic Monte Carlo modeling, we analyze key structural features such as radial distribution functions, principal axis orientations, and non-covalent interactions. Our findings reveal that molecular size and substituent effects significantly influence non-covalent interactions and molecular alignments, thereby affecting charge transport pathways. Charge transfer rates and energetic disorder were modeled using the master equation, and mobilities were computed, showing satisfactory agreement with experimental data. This comprehensive analysis provides valuable insights into the design of HTMs for organic electronic devices, emphasizing the importance of molecular architecture in optimizing charge mobility and minimizing energy losses.

Decarboxylative Cross-Acyl Coupling of Carboxylic Acids with Aldehydes Enabled by Nickel/Photoredox Catalysis

Embryonic macrophages orchestrate niche cell homeostasis for the establishment of the definitive hematopoietic stem cell pool

Abstract Embryonic macrophages emerge before the onset of definitive hematopoiesis, seed into discrete tissues and contribute to specialized resident macrophages throughout life. Presence of embryonic macrophages in the bone marrow and functional impact on hematopoietic stem cells (HSC) or the niche remains unclear. Here we show that bone marrow macrophages consist of two ontogenetically distinct cell populations from embryonic and adult origin. Newborn mice lacking embryonic macrophages have decreased HSC numbers in the bone marrow suggesting an important function for embryo-derived macrophages in orchestrating HSC trafficking around birth. The establishment of a normal cellular niche space in the bone marrow critically depends on embryonic macrophages that are important for the development of mesenchymal stromal cells, but not other non-hematopoietic niche cells, providing evidence for a specific role for embryo-derived macrophages in the establishment of the niche environment pivotal for the establishment of a normally sized HSC pool.

User-cooperative dynamic resource allocation for backscatter-aided wireless-powered MEC network

Non-uniform Brillouin zone sampling for thermal transport in layered materials

Lattice thermal conductivity in layered materials is typically dominated by long-wavelength phonon modes and is traditionally computed by uniform phonon sampling in the Brillouin zone, which is often computationally demanding. In this work, we develop and implement a non-uniform Brillouin zone sampling approach to efficiently predict the thermal conductivity of layered materials within the Boltzmann transport equation framework. Using single-layer graphene and bulk MoS2 as case studies, our method optimizes phonon sampling through two key parameters: grid cutoff distance, which defines a dense phonon mesh near the Γ-point, and grid ratio, which sets the resolution of the coarser grid in the remaining regions. This selective sampling reduces the computational cost involved in phonon scattering calculation by a factor of 10 while maintaining thermal conductivity prediction accuracy within 12% compared with the uniform grid approach.

Technology innovation and environmental outcomes of road transportation policy instruments

Abstract Road transportation policies can drive innovation in more environmentally sustainable vehicle and fuel technologies but may have unintended consequences. To assess their impacts on technology innovation, greenhouse gas emissions, air pollution, and land use, we systematically review and analyze evidence on the outcomes of 14 road transportation policy instruments, including fuel economy and low-carbon fuel standards, biofuel and zero-emission vehicle mandates, and fuel and vehicle taxes. We find that the effects of these policy instruments depend on their interactions, design, choice, and sequencing. We identify six types of relationships between policy instruments and highlight design features that have inadvertently increased vehicle emissions. We trace the evolution of electric vehicles through policy milestones shaped by experimentation and competition among influential jurisdictions based on their domestic priorities, industrial structure, and incumbent industry resistance. We show that policy instruments promoting first-generation biofuels have in some cases inhibited innovation in advanced biofuels.

Drill pipe detection and counting based on improved YOLOv11 and Savitzky-Golay

Theoretical investigation of vibrational energy transfer of water at the gas/liquid interface around 3400 cm−1

Using molecular dynamics simulations based on neural network potentials and a mixed quantum/classical approach, we theoretically explore vibrational energy transfer pathways for OH groups around 3400 cm−1 at interfaces. Our calculations show that intramolecular vibrational energy transfer has a time constant of 369.2 fs, aligning with experimental findings. The reorientation time is 1624 fs. The intermolecular vibrational energy transfer rate is slower due to weak couplings between water molecules. Our results suggest that intramolecular energy transfer is the main driver of vibrational energy transfer for OH groups around 3400 cm−1 at the gas/water interface.

Configurable kinetics of polarization switching via ion migration in ferroionic CuInP2S6

Intranasal delivery of blackberry-loaded Chitosan nanoparticles for antipsychotic potential in Ketamine-induced schizophrenia in rats

Abstract Schizophrenia is a neuropsychiatric disorder with limited treatment options that have unwanted side effects. Clozapine, an atypical antipsychotic, has been used for resistant schizophrenia. This study investigated the effect of anthocyanin-rich extract from Rubus fruticosus (RFE) loaded into chitosan nanoparticles against ketamine-induced schizophrenia in rats. The extract’s phenolic and flavonoid content was measured using UPLC-ESI-MS/MS, revealing 9.42 ± 0.5 mg of gallic acid equivalent and 2.54 ± 0.02 mg of quercetin equivalent per g of extract, with 19 identified compounds, predominantly anthocyanin glycosides. Chitosan nanoparticles were prepared with chitosan and sodium tripolyphosphate at a ratio of 3:1 with particle size 194.49 ± 5.69 nm and encapsulation efficiency of 64.6 ± 1.12%. Rats were treated with ketamine to induce schizophrenia-like symptoms, and various groups received different treatments, including control, ketamine, ketamine + clozapine, ketamine + RFE, and a combination of clozapine/RFE. Clozapine and RFE treatments were initiated from day 8 to day 14. RFE treatment ameliorated positive, negative, and cognitive symptoms of schizophrenia while mitigating clozapine-induced side effects such as weight gain, hyperglycemia, hyperlipidemia, agranulocytosis, and liver dysfunction. RFE corrected oxidative stress as evidenced by its effect on catalase activity and reduced glutathione level. Additionally, RFE hindered neuroinflammation induced by ketamine and reduced the levels of Tumor Necrosis Factor-α. RFE also increased BDNF levels. This study demonstrates that RFE-loaded chitosan nanoparticles exhibit potent antipsychotic properties and enhance clozapine’s therapeutic efficacy while minimizing its adverse effects. This could shed light on the integration of the use of natural products and advanced nano-based formulations to manage schizophrenia patients worldwide.

Imaging the photochemical dynamics of cyclobutanone with MeV ultrafast electron diffraction

We study the photoinduced chemical dynamics of cyclobutanone upon excitation at 200 nm to the 3s Rydberg state using MeV ultrafast electron diffraction (UED). We observe both the elastic scattering signal, which contains information about the structural dynamics, and the inelastic scattering signal, which encodes information about the electronic state. Our results suggest a sub-picosecond timescale for the photodissociation dynamics and an excited state lifetime of about 230 femtoseconds. The dissociation is found to be dominated by the C3 channel, where cyclopropane and CO are produced. The branching ratio of the C3 channel to the C2 channel, where ethene and ketene are produced, is estimated to be ∼5:3. Our data suggest that the C3 and C2 channels account for ∼80% of the photoproducts, with the remaining 20% exhibiting ring-opened structures. It is found that the timescale associated with the dissociation process in the C2 channel is shorter compared to that in the C3 channel. Leveraging the enhanced temporal resolution of MeV UED, our results provide a real-time mapping of the nuclear wave packet dynamics, capturing the complete photochemical dynamics from S2 minimum through the S1/S0 conical intersection and finally to the dissociation. Our experimental results provide new insights into the Norrish type I reaction and can be used to benchmark non-adiabatic dynamics simulations.

Effectiveness of tirzepatide in patients with HFpEF using a target trial emulation retrospective cohort study

Geospatial analysis of trace metal pollution and ecological risks in river sediments from agrochemical sources in Morocco’s Sebou basin

Facile synthesis of carbon-coated silicon nanocomposite with tremella-like porous structure for superior lithium-ion storage

Silicon/carbon (Si/C) composites have been envisaged as one of the most promising anode materials for the next-generation lithium-ion batteries (LIBs) with high energy density, and constructing reasonable and cross-scale structures is crucial adjective for high-performance Si/C electrodes. Herein, a facile synthesis strategy was developed by combining gel coating, carbonization, and molten salt-assisted magnesiothermic reduction (MSA-MR), and a unique tremella-like Si/C composite with internal void structure (IV-Si/C) was successfully prepared. The working mechanisms of both sodium alginate (SA) and molten salt (NaCl) on the successful preparation of the target IV-Si/C nanocomposite were also investigated in detail. It was demonstrated that, α-L-guluronic (G) blocks in SA can be cross-linked with cations to promote the interactions with silicon dioxide (SiO2) particles, boosting uniform distribution of nanosized Si particles in the SA-derived carbon matrix. Meanwhile, NaCl generated from SA not only effectively boosted the crystallization of SiO2 during the high-temperature carbonization process but also can effectively inhibit the formation of inert SiC and strengthen reduction of carbon during the MSA-MR treatment, resulting in successful preparation of the tremella-like Si/C composite with abundant internal voids. Benefitting from its unique structure, when used as an alternative anode material for electrochemical lithium storage, the as-obtained IV-Si/C nanocomposite delivered a high reversible specific capacity of 1899.6 mAh g−1 with an initial Coulomb efficiency of 75.96% and superior rate capability and long-term cycling stability. This facile and low-cost synthesis strategy may shed light on the controllable preparation of functional nanomaterials with unique structures, especially high-performance Si/C anode materials for their large-scale application in LIBs.

Aqueous secondary formation substantially contributes to hydrophilic organophosphate esters in aerosols

Correction: Analyzing cost impacts across the entire process of prefabricated building components from design to application

Terahertz waves facilitate capsaicin expulsion from TRPV1

Transient receptor potential vanilloid 1 (TRPV1) is a critical non-selective cation channel involved in various biological and physiological processes, making it a promising drug target for treating multiple diseases. Capsaicin, a TRPV1 agonist, is widely used to relieve pain by desensitizing the TRPV1 with persistent stimulation. However, the initially intolerable burning sensation due to TRPV1 activation necessitates the use of antagonists to deactivate TRPV1 and mitigate discomfort, which yet causes thermoregulation disorders. In this study, molecular dynamics simulations reveal that frequency-specific terahertz (THz) waves can promote capsaicin unbinding from TRPV1, suggesting a spatiotemporally controlled approach for TRPV1 deactivation. The THz wave resonates with the hydroxyl group in the capsaicin head, increasing its rotational kinetic energy and promoting its rotation. This disrupts the key hydrogen bond between the hydroxyl group and TRPV1 residue E570, significantly reducing capsaicin’s affinity for TRPV1. Our findings suggest that THz waves could mimic TRPV1 antagonists in a more flexible way, offering temporal control over capsaicin recruitment and expulsion (i.e., TRPV1 activation, desensitization, and deactivation) for more comfortable pain relief. In addition, this work enlightens a THz-based, pill-free strategy to control the pain induced by inflammatory ligands activated TRPV1.