bluuebunny/crossref_metadata_2025 huggingface dataset:
Stochastic transitions: Paths over higher energy barriers can dominate in the early stages
Authors: Fitzgerald S. P. , Hass A. Bailey , Leines G. Díaz , Archer A. J.
Published: March 2023

The time evolution of many physical, chemical, and biological systems can be modeled by stochastic transitions between the minima of the potential energy surface describing the system of interest. We show that in cases where there are two (or more) possible pathways that the system can take, the time available for the transition to occur is crucially important. The well-known results of the reaction rate theory for determining the rates of transitions apply in the long-time limit. However, at short times, the system can, instead, choose to pass over higher energy barriers with a much higher probability, as long as the distance to travel in phase space is shorter. We construct two simple models to illustrate this general phenomenon. We also apply a version of the geometric minimum action method algorithm of Vanden-Eijnden and Heymann [J. Chem. Phys. 128, 061103 (2008)] to determine the most likely path at both short and long times.
Effect of oxidation on mechanical properties of copper nanowire: A ReaxFF (reactive force field) molecular dynamics study
Authors: Aral Gurcan , Islam Md Mahbubul
Published: March 2023

Nanostructures with high surface area to volume ratio, such as oxidized and coated Cu nanowires (NWs), exhibit unique mechanical properties due to their size and surface effects. Understanding the complex oxidation process of Cu NWs at nanoscale and quantifying its resulting effects on mechanical behavior and properties are significantly essential for effective usage of Cu NW devices in a wide range of applications in nanoelectronics. Here, we perform molecular dynamics simulations using ReaxFF (reactive force field) to investigate the oxidation process and mechanisms of [001]-oriented cylindrical Cu NWs and its contribution on the mechanical deformation behavior and material properties as a function of NW sizes. The relatively thin oxide CuxOy layer is formed on the surface of Cu NWs in an O2 environment, creating a core/shell (Cu/CuxOy) NW structure that played a key role in governing the overall tensile mechanical deformation behavior and properties of Cu NW. The formation of oxide layer effects, including the resulting interface and defects, leads to a reduction in the initial dislocation nucleation barrier, which facilitates the onset of plasticity and stress relaxation, ultimately resulting in a negative impact on the tensile strength, Young's modulus, yield stress and strain, and flow stress when compared to pristine counterparts. It is worth noting that the tensile mechanical response and properties of the Cu NWs are highly dependent on the pre-existing oxide shell layer associated with the size of NW, determining the overall mechanical performance and properties of Cu NWs.
Micro-mechanical insights into the stress transmission in strongly aggregating colloidal gel
Authors: Gadi Man Yezaz Ahmed , Dagur Divas Singh , Roy Saikat
Published: March 2023

Predicting the mechanical response of soft gel materials under external deformation is of paramount importance in many areas, such as foods, pharmaceuticals, solid–liquid separations, cosmetics, aerogels, and drug delivery. Most of the understanding of the elasticity of gel materials is based on the concept of fractal scaling with very few microscopic insights. Previous experimental observations strongly suggest that the gel material loses the fractal correlations upon deformation and the range of packing fraction up to which the fractal scaling can be applied is very limited. In addition, correctly implementing the fractal modeling requires identifying the elastic backbone, which is a formidable task. So far, there is no clear understanding of the gel’s elasticity at high packing fractions or the correct length scale that governs its mechanical response. In this work, we undertake extensive numerical simulations to elucidate the different aspects of stress transmission in gel materials. We observe the existence of two percolating networks of compressive and tensile normal forces close to the gel point. We also find that the probability distribution for the compressive and tensile parts normalized by their respective mean shows a universal behavior irrespective of various values of interaction potential and thermal energy and different particle size distributions. Interestingly, there are also a large number of contacts with zero normal force, and, consequently, a peak in the normal force distribution is observed at fn ≈ 0 even at higher pressures. We also identify the critical internal state parameters, such as the mean normal force, force anisotropies, and the average coordination number, and propose simple constitutive relations that relate different components of stress to internal state parameters. The agreement between our model prediction and the simulation observation is excellent. It is shown that the anisotropy in the force networks gives rise to the normal stress difference in soft gel materials. Our results strongly demonstrate that the mechanical response of the gel system is governed mainly by the particle length scale phenomena, with a complex interplay between the compressive and tensile forces at the particle contact.
The Aharonov–Anandan phase and geometric double-quantum excitation in strongly coupled nuclear spin pairs
Authors: Bengs Christian , Sabba Mohamed , Levitt Malcolm H.
Published: March 2023

The Aharonov–Anandan phase is a contribution to the phase acquired by the cyclic evolution of a quantum state, which depends only on the geometric properties of its trajectory. We report the study and the exploitation of the Aharonov–Anandan phase by nuclear magnetic resonance interferometry techniques in homonuclear spin-1/2 pairs in the near-equivalence limit. We introduce a new method for engineering effective zero-quantum Hamiltonians with an arbitrary phase in the transverse plane. We use this method to generate a variety of cyclic zero-quantum paths, enabling direct study of the geometric Aharonov–Anandan phase to probe the rotational characteristics of the zero-quantum subspace. We show that the geometric Aharonov–Anandan phase may be used for efficient double-quantum excitation in strongly coupled spin pairs. We find that geometric double-quantum excitation outperforms the standard method by a factor of 2 in experiments performed on a typical case involving near-equivalent spin pairs.
Nanoscale structure of a hybrid aqueous–nonaqueous electrolyte
Authors: Saboungi Marie-Louise , Borodin Oleg , Price David L. , Farago Bela , González Miguel A. , Kohara Shinji , Mangin-Thro Lucile , Wildes Andrew , Yamamuro Osamu
Published: March 2023

A new class of electrolytes have been reported, hybridizing aqueous with non-aqueous solvents, which combines non-flammability and non-toxicity characteristics of aqueous electrolytes with the superior electrochemical stability of non-aqueous systems. Here, we report measurements of the structure of an electrolyte composed of an equal-mass mixture of 21 m LiTFSI-water and 9 m LiTFSI-dimethyl carbonate using high-energy x-ray diffraction and polarized neutron diffraction with isotope substitution. Neutron structure factors from partially and fully deuterated samples exhibit peaks at low scattering vector Q that we ascribe to long-range correlations involving both solvent molecules and TFSI− anions. We compare both sets of measurements with results of molecular dynamics simulations based on a polarizable force field. The structures derived from simulations are generally in agreement with those measured, except that neutron structure factors predicted for two partially deuterated samples show very intense scattering increasing up to the low-Q limit of simulation, indicating a partial segregation between the two solvents not observed in experimental measurements.
Effect of surfactants on the elasticity of the liquid–liquid interface
Authors: Kikuchi Shunta , Watanabe Hiroshi
Published: March 2023

We investigated the effect of surfactants on an interface between two kinds of liquids by molecular dynamics (MD) simulation. We adopted the simple bead-spring model with two atoms as the surfactants. We controlled the interfacial tension of the surfactant adsorbed on the interface by changing the bond length. Although the interface’s structure changed depending on the magnitude of the interfacial tension, the interface was stable even under conditions where the interfacial tension was virtually zero. The Fourier spectrum of the fluctuations of the surface structure showed a crossover from q2 to q4 when the interfacial tension was almost zero, where q is the wavenumber. This crossover means that the bending rigidity is dominant for the restoring force when the surfactant molecules are sufficiently absorbed on the interface and the interfacial tension is almost zero, whereas the interfacial tension is dominant when the interfacial tension is a finite value.
The radiative surface hopping (RSH) algorithm: Capturing fluorescence events in molecular systems within a semi-classical non-adiabatic molecular dynamics framework
Authors: Pérez-Escribano Manuel , Jankowska Joanna , Granucci Giovanni , Escudero Daniel
Published: March 2023

In this article, we present the radiative surface hopping algorithm, which enables modeling fluorescence within a semi-classical non-adiabatic molecular dynamics framework. The algorithm has been tested for the photodeactivation dynamics of trans-4-dimethylamino-4′-cyanostilbene (DCS). By treating on equal footing the radiative and non-radiative processes, our method allows us to attain a complete molecular movie of the excited-state deactivation. Our dynamics rely on a semi-empirical quantum mechanical/molecular mechanical Hamiltonian and have been run for hundreds of picoseconds, both in the gas phase and in isopropyl ether. The proposed approach successfully captures the first fluorescence processes occurring in DCS, and it succeeds in reproducing the experimental fluorescence lifetime and quantum yield, especially in the polar solvent. The analysis of the geometrical features of the emissive species during the dynamics discards the hypothesis of a twisted intramolecular charge transfer state to be responsible for the dual emission observed experimentally in some polar solvents. In a nutshell, our method opens the way for theoretical studies on early fluorescence events occurring up to hundreds of picoseconds in molecular systems.
Electron-impact excitation of atoms or ions with the screened Coulomb potential
Authors: Chen Zhan-Bin
Published: March 2023

This paper reports the development of a novel distorted wave approach based on the relativistic configuration interaction theory for calculating atomic structures, radiative properties, and collision dynamics of atoms or ions under external confinement. Due to its physical interpretations, the Hulthén potential, valid for many important areas (widely plasma environments) in physics and chemistry, such as atomic physics, solid-state physics, nuclear physics, particle physics, and astrophysics, is used to include the effect of plasma background. The Breit interaction and quantum electromagnetic dynamics effects are perturbatively included in the multi-electron Hamiltonian. Wave functions of bound and continuous states are obtained, which are analyzed by means of the Dirac equations. Interparticle interactions in the scattering matrix element of the system are described by the screened Coulomb interactions. As a test desk, the present approach is applied to the calculation of atomic structures and collision dynamics of an exemplary He-like S14+ ion embedded in a plasma. The energy eigenvalues, transition probabilities, and excitation cross sections are analyzed in detail in terms of the screening parameter. The results of the verification cases are compared to references from the literature, which show a good agreement. The present study not only opens up an opportunity to provide a simple and effective way for understanding the plasma shielding models for many-electron systems but also has important implications for a wide range of applications in astrophysics and laboratory plasma experiments.
Functional group corrections to the GFN2-xTB and PM6 semiempirical methods for noncovalent interactions in alkanes and alkenes
Authors: Cabaleiro-Lago Enrique M. , Fernández Berta , Rodríguez-Fernández Roberto , Rodríguez-Otero Jesús , Vázquez Saulo A.
Published: March 2023

Analytical corrections were developed to improve the accuracy of the PM6 and GFN2-xTB semiempirical quantum mechanical methods for the evaluation of noncovalent interaction energies in alkanes and alkenes. We followed the approach of functional group corrections, wherein the atom–atom pair corrections depend on the nature of the interacting functional groups. The training set includes 21 alkane and 13 alkene complexes taken from the Donchev et al.’s database [Sci. Data 8, 55 (2021)], with interaction energies calculated at the CCSD(T)/CBS level, and our own data obtained for medium-size complexes (of 100 and 112 atoms). In general, for the systems included in the training and validation sets, the errors obtained with the PM6-FGC and xTB-FGC methods are within the chemical accuracy.
On the unusual Stokes shift in the smallest PPE dendrimer building block: Role of the vibronic symmetry on the band origin?
Authors: Galiana Joachim , Lasorne Benjamin
Published: March 2023

1,3-Bis(phenylethynyl)benzene is the primary chromophore of the light-harvesting polyphenylene ethynylene (PPE) dendrimers. It is experimentally known to share the same absorption spectrum as its pair of diphenylacetylene (aka. tolane) meta-substituted branches yet exhibits an unusual Stokes shift of about 2000 cm−1 with respect to its band origin (corresponding to the loss of one vibrational quantum within the antisymmetric acetylenic stretching) in its emission spectrum. We suggest, in the present work, the unusual but plausible involvement of molecular symmetry selection rules in a situation where the Born-Oppenheimer approximation is far to be valid. Our hypothesis is comforted with quantum dynamics simulations of absorption and emission UV-visible spectra based on the quantum chemistry data and a diabatic vibronic coupling Hamiltonian model.
Ultrafast laser induced charge migration with de- and re-coherences in polyatomic molecules: A general method with application to pyrene
Authors: Ma HuiMin , Manz Jörn , Wang HuiHui , Yan YiJing , Yang Yonggang
Published: March 2023

We develop a general method to study ultrafast laser induced charge migration in molecules, which includes both electronic and nuclear dynamics. The method can be applied to relatively large systems. A detailed analysis of charge migration in pyrene is performed. Decoherences and recoherences of charge migration in pyrene are found and explained in terms of nuclear motions.
On the interaction of Tollmien–Schlichting waves with a wall-embedded Helmholtz resonator
Authors: Michelis T. , de Koning C. , Kotsonis M.
Published: March 2023

The influence of a wall-embedded Helmholtz resonator on the development and stability of Tollmien–Schlichting (TS) waves is investigated numerically and experimentally for a range of frequencies extending from below to above resonance. Interactions are found to be limited in the near-wall region and toward the trailing edge of the resonator orifice while at the same time being linear nature. The dynamic response of the flow-excited resonator is shown to have a fixed phase relation with respect to the TS-waves, indicating that only amplification of the latter can be achieved. The same resonant behavior is maintained regardless of whether the resonator is flow-excited or acoustically excited. Thus, it is suggested that pressure perturbations propagate perpendicularly and acoustically within the resonator throat and cavity. The amplification observed in the vicinity of the resonator displays features typical of TS-wave scattering; however, it is confirmed that this is not solely the result of mean flow distortion due to the geometry and recirculation region. Instead, the results indicate that the phenomenology is a consequence of the combination of scattering, localized non-modal growth, and wall-forcing in the wall-normal direction due to resonance.
Probing the n → π* carbonyl–carbonyl interactions in the formaldehyde–trifluoroacetone dimer by rotational spectroscopy
Authors: Jin Yan , Wang Zhen , Li Wenqin , Xu Yugao , Feng Gang , Lesarri Alberto , Grabow Jens-Uwe
Published: March 2023

The non-covalent bonding features of carbonyl–carbonyl interactions have been investigated in the dimer of formaldehyde and trifluoroacetone using high resolution rotational spectroscopy combined with quantum chemical calculations. The observation of all possible isotopic substitutions for the heavy atoms in the complex enabled the determination of the accurate structure, characterized by the antiparallel arrangement of the two C=O bonds. The two moieties are connected through a dominant n → π* interaction enhanced by one weak C–H⋯O hydrogen bond, as revealed by supporting natural bond orbital analysis and symmetry-adapted perturbation theory analysis. Further computational investigations on 17 related adducts stabilized by carbonyl–carbonyl n → π* interactions show how the interaction strength is regulated by the incorporation of either electron-donating or withdrawing functional groups.
Role of ambient pressure on bouncing and coalescence of colliding jets
Authors: Li Minglei , Saha Abhishek , Sun Chao , Law Chung K.
Published: March 2023

In this Letter, the merging vs bouncing response of obliquely oriented colliding jets under elevated and reduced gaseous environment pressures was experimentally examined. Experiments with water and n-tetradecane confirmed that the collision outcome transitions from merging to bouncing and then to merging again, when the impact velocity was increased. This behavior which was previously reported for atmospheric pressure has now also been observed at elevated and reduced pressures. New results also show that there exists a critical pressure (0.9 bar for n-tetradecane and 5 bar for water) below which increasing pressure promotes bouncing (expands the bouncing regime), while beyond this, merging is promoted (reduces the bouncing regime) instead. This leads to a non-monotonic influence of pressure on the non-coalescence outcomes of collisional jets, which was not previously reported. The study provides evidence of new behaviors in colliding jets at reduced and elevated pressures, which differs from well-studied droplet–droplet collisions.
Reduced fire severity offers near-term buffer to climate-driven declines in conifer resilience across the western United States
Authors: Davis Kimberley T. , Robles Marcos D. , Kemp Kerry B. , Higuera Philip E. , Chapman Teresa , Metlen Kerry L. , Peeler Jamie L. , Rodman Kyle C. , Woolley Travis , Addington Robert N. , Buma Brian J. , Cansler C. Alina , Case Michael J. , Collins Brandon M. , Coop Jonathan D. , Dobrowski Solomon Z. , Gill Nathan S. , Haffey Collin , Harris Lucas B. , Harvey Brian J. , Haugo Ryan D. , Hurteau Matthew D. , Kulakowski Dominik , Littlefield Caitlin E. , McCauley Lisa A. , Povak Nicholas , Shive Kristen L. , Smith Edward , Stevens Jens T. , Stevens-Rumann Camille S. , Taylor Alan H. , Tepley Alan J. , Young Derek J. N. , Andrus Robert A. , Battaglia Mike A. , Berkey Julia K. , Busby Sebastian U. , Carlson Amanda R. , Chambers Marin E. , Dodson Erich Kyle , Donato Daniel C. , Downing William M. , Fornwalt Paula J. , Halofsky Joshua S. , Hoffman Ashley , Holz Andrés , Iniguez Jose M. , Krawchuk Meg A. , Kreider Mark R. , Larson Andrew J. , Meigs Garrett W. , Roccaforte John Paul , Rother Monica T. , Safford Hugh , Schaedel Michael , Sibold Jason S. , Singleton Megan P. , Turner Monica G. , Urza Alexandra K. , Clark-Wolf Kyra D. , Yocom Larissa , Fontaine Joseph B. , Campbell John L.
Published: March 2023

Increasing fire severity and warmer, drier postfire conditions are making forests in the western United States (West) vulnerable to ecological transformation. Yet, the relative importance of and interactions between these drivers of forest change remain unresolved, particularly over upcoming decades. Here, we assess how the interactive impacts of changing climate and wildfire activity influenced conifer regeneration after 334 wildfires, using a dataset of postfire conifer regeneration from 10,230 field plots. Our findings highlight declining regeneration capacity across the West over the past four decades for the eight dominant conifer species studied. Postfire regeneration is sensitive to high-severity fire, which limits seed availability, and postfire climate, which influences seedling establishment. In the near-term, projected differences in recruitment probability between low- and high-severity fire scenarios were larger than projected climate change impacts for most species, suggesting that reductions in fire severity, and resultant impacts on seed availability, could partially offset expected climate-driven declines in postfire regeneration. Across 40 to 42% of the study area, we project postfire conifer regeneration to be likely following low-severity but not high-severity fire under future climate scenarios (2031 to 2050). However, increasingly warm, dry climate conditions are projected to eventually outweigh the influence of fire severity and seed availability. The percent of the study area considered unlikely to experience conifer regeneration, regardless of fire severity, increased from 5% in 1981 to 2000 to 26 to 31% by mid-century, highlighting a limited time window over which management actions that reduce fire severity may effectively support postfire conifer regeneration.
Oligomerization of a plant helper NLR requires cell-surface and intracellular immune receptor activation
Authors: Feehan Joanna M. , Wang Junli , Sun Xinhua , Choi Jihyeon , Ahn Hee-Kyung , Ngou Bruno Pok Man , Parker Jane E. , Jones Jonathan D. G.
Published: March 2023

Plant disease resistance involves both detection of microbial molecular patterns by cell-surface pattern recognition receptors and detection of pathogen effectors by intracellular NLR immune receptors. NLRs are classified as sensor NLRs, involved in effector detection, or helper NLRs required for sensor NLR signaling. TIR-domain-containing sensor NLRs (TNLs) require helper NLRs NRG1 and ADR1 for resistance, and helper NLR activation of defense requires the lipase-domain proteins EDS1, SAG101, and PAD4. Previously, we found that NRG1 associates with EDS1 and SAG101 in a TNL activation-dependent manner [X. Sun
et al.
,
Nat. Commun.
12
, 3335 (2021)]. We report here how the helper NLR NRG1 associates with itself and with EDS1 and SAG101 during TNL-initiated immunity. Full immunity requires coactivation and mutual potentiation of cell-surface and intracellular immune receptor-initiated signaling [B. P. M. Ngou, H.-K. Ahn, P. Ding, J. D. G. Jones,
Nature
592
, 110–115 (2021), M. Yuan 
et al.
, 
Nature
592
, 105–109 (2021)]. We find that while activation of TNLs is sufficient to promote NRG1–EDS1–SAG101 interaction, the formation of an oligomeric NRG1–EDS1–SAG101 resistosome requires the additional coactivation of cell-surface receptor-initiated defense. These data suggest that NRG1–EDS1–SAG101 resistosome formation in vivo is part of the mechanism that links intracellular and cell-surface receptor signaling pathways.
On the rise of fear speech in online social media
Authors: Saha Punyajoy , Garimella Kiran , Kalyan Narla Komal , Pandey Saurabh Kumar , Meher Pauras Mangesh , Mathew Binny , Mukherjee Animesh
Published: March 2023

Recently, social media platforms are heavily moderated to prevent the spread of online hate speech, which is usually fertile in toxic words and is directed toward an individual or a community. Owing to such heavy moderation, newer and more subtle techniques are being deployed. One of the most striking among these is fear speech. Fear speech, as the name suggests, attempts to incite fear about a target community. Although subtle, it might be highly effective, often pushing communities toward a physical conflict. Therefore, understanding their prevalence in social media is of paramount importance. This article presents a large-scale study to understand the prevalence of 400K fear speech and over 700K hate speech posts collected from Gab.com. Remarkably, users posting a large number of fear speech accrue more followers and occupy more central positions in social networks than users posting a large number of hate speech. They can also reach out to benign users more effectively than hate speech users through replies, reposts, and mentions. This connects to the fact that, unlike hate speech, fear speech has almost zero toxic content, making it look plausible. Moreover, while fear speech topics mostly portray a community as a perpetrator using a (fake) chain of argumentation, hate speech topics hurl direct multitarget insults, thus pointing to why general users could be more gullible to fear speech. Our findings transcend even to other platforms (Twitter and Facebook) and thus necessitate using sophisticated moderation policies and mass awareness to combat fear speech.
Stratospheric chlorine processing after the 2020 Australian wildfires derived from satellite data
Authors: Wang Peidong , Solomon Susan , Stone Kane
Published: March 2023

The 2019 to 2020 Australian summer wildfires injected an amount of organic gases and particles into the stratosphere unprecedented in the satellite record since 2002, causing large unexpected changes in HCl and ClONO
2
. These fires provided a novel opportunity to evaluate heterogeneous reactions on organic aerosols in the context of stratospheric chlorine and ozone depletion chemistry. It has long been known that heterogeneous chlorine (Cl) activation occurs on the polar stratospheric clouds (PSCs; liquid and solid particles containing water, sulfuric acid, and in some cases nitric acid) that are found in the stratosphere, but these are only effective for ozone depletion chemistry at temperatures below about 195 K (i.e., largely in the polar regions during winter). Here, we develop an approach to quantitatively assess atmospheric evidence for these reactions using satellite data for both the polar (65 to 90°S) and the midlatitude (40 to 55°S) regions. We show that heterogeneous reactions apparently even happened at temperatures at 220 K during austral autumn on the organic aerosols present in 2020 in both regions, in contrast to earlier years. Further, increased variability in HCl was also found after the wildfires, suggesting diverse chemical properties among the 2020 aerosols. We also confirm the expectation based upon laboratory studies that heterogeneous Cl activation has a strong dependence upon water vapor partial pressure and hence atmospheric altitude, becoming much faster close to the tropopause. Our analysis improves the understanding of heterogeneous reactions that are important for stratospheric ozone chemistry under both background and wildfire conditions.
Social copying drives a tipping point for nonlinear population collapse
Authors: Oro Daniel , Alsedà Lluís , Hastings Alan , Genovart Meritxell , Sardanyés Josep
Published: March 2023

Sudden changes in populations are ubiquitous in ecological systems, especially under perturbations. The agents of global change may increase the frequency and severity of anthropogenic perturbations, but complex populations’ responses hamper our understanding of their dynamics and resilience. Furthermore, the long-term environmental and demographic data required to study those sudden changes are rare. Fitting dynamical models with an artificial intelligence algorithm to population fluctuations over 40 y in a social bird reveals that feedback in dispersal after a cumulative perturbation drives a population collapse. The collapse is well described by a nonlinear function mimicking social copying, whereby dispersal made by a few individuals induces others to leave the patch in a behavioral cascade for decision-making to disperse. Once a threshold for deterioration of the quality of the patch is crossed, there is a tipping point for a social response of runaway dispersal corresponding to social copying feedback. Finally, dispersal decreases at low population densities, which is likely due to the unwillingness of the more philopatric individuals to disperse. In providing the evidence of copying for the emergence of feedback in dispersal in a social organism, our results suggest a broader impact of self-organized collective dispersal in complex population dynamics. This has implications for the theoretical study of population and metapopulation nonlinear dynamics, including population extinction, and managing of endangered and harvested populations of social animals subjected to behavioral feedback loops.
Selective binding and periodic arrangement of magic boron clusters on monolayer borophene
Authors: Lv Haifeng , Chen Caiyun , Li Wenbin , Zhuo Zhiwen , Cheng Peng , Zhang Yi-Qi , Feng Baojie , Wu Kehui , Wu Xiaojun , Chen Lan
Published: March 2023

The synthesis and characterization of small boron clusters with unique size and regular arrangement are crucial for boron chemistry and two-dimensional borophene materials. In this study, together with theoretical calculations, the joint molecular beam epitaxy and scanning tunneling microscopy experiments achieve the formation of unique B
5
clusters on monolayer borophene (MLB) on a Cu(111) surface. The B
5
clusters tend to selectively bind to specific sites of MLB with covalent boron–boron bonds in the periodic arrangement, which can be ascribed to the charge distribution and electron delocalization character of MLB and also prohibits nearby co-adsorption of B
5
clusters. Furthermore, the close-packed adsorption of B
5
clusters would facilitate the synthesis of bilayer borophene, exhibiting domino effect-like growth mode. The successful growth and characterization of uniform boron clusters on a surface enrich the boron-based nanomaterials and reveal the essential role of small clusters during the growth of borophene.
OBSCN
restoration via
OBSCN-AS1
long-noncoding RNA CRISPR-targeting suppresses metastasis in triple-negative breast cancer
Authors: Guardia Talia , Zhang Yuqi , Thompson Keyata N. , Lee Se Jong , Martin Stuart S. , Konstantopoulos Konstantinos , Kontrogianni-Konstantopoulos Aikaterini
Published: March 2023

Mounting evidence implicates the giant, cytoskeletal protein obscurin (720 to 870 kDa), encoded by the
OBSCN
gene, in the predisposition and development of breast cancer. Accordingly, prior work has shown that the sole loss of
OBSCN
from normal breast epithelial cells increases survival and chemoresistance, induces cytoskeletal alterations, enhances cell migration and invasion, and promotes metastasis in the presence of oncogenic KRAS. Consistent with these observations, analysis of Kaplan–Meier Plotter datasets reveals that low
OBSCN
levels correlate with significantly reduced overall and relapse-free survival in breast cancer patients. Despite the compelling evidence implicating
OBSCN
loss in breast tumorigenesis and progression, its regulation remains elusive, limiting any efforts to restore its expression, a major challenge given its molecular complexity and gigantic size (~170 kb). Herein, we show that
OBSCN-Antisense RNA 1
(
OBSCN-AS1
), a novel nuclear long-noncoding RNA (lncRNA) gene originating from the minus strand of
OBSCN
, and
OBSCN
display positively correlated expression and are downregulated in breast cancer biopsies.
OBSCN-AS1
regulates
OBSCN
expression through chromatin remodeling involving H3 lysine 4 trimethylation enrichment, associated with open chromatin conformation, and RNA polymerase II recruitment. CRISPR-activation of
OBSCN-AS1
in triple-negative breast cancer cells effectively and specifically restores
OBSCN
expression and markedly suppresses cell migration, invasion, and dissemination from three-dimensional spheroids in vitro and metastasis in vivo. Collectively, these results reveal the previously unknown regulation of
OBSCN
by an antisense lncRNA and the metastasis suppressor function of the
OBSCN-AS1/OBSCN
gene pair, which may be used as prognostic biomarkers and/or therapeutic targets for metastatic breast cancer.
Inferring the disruption of rabies circulation in vampire bat populations using a betaherpesvirus-vectored transmissible vaccine
Authors: Griffiths Megan E. , Meza Diana K. , Haydon Daniel T. , Streicker Daniel G.
Published: March 2023

Transmissible vaccines are an emerging biotechnology that hold prospects to eliminate pathogens from wildlife populations. Such vaccines would genetically modify naturally occurring, nonpathogenic viruses (“viral vectors”) to express pathogen antigens while retaining their capacity to transmit. The epidemiology of candidate viral vectors within the target wildlife population has been notoriously challenging to resolve but underpins the selection of effective vectors prior to major investments in vaccine development. Here, we used spatiotemporally replicated deep sequencing to parameterize competing epidemiological mechanistic models of
Desmodus rotundus
betaherpesvirus (DrBHV), a proposed vector for a transmissible vaccine targeting vampire bat-transmitted rabies. Using 36 strain- and location-specific time series of prevalence collected over 6 y, we found that lifelong infections with cycles of latency and reactivation, combined with a high R
0
(6.9; CI: 4.39 to 7.85), are necessary to explain patterns of DrBHV infection observed in wild bats. These epidemiological properties suggest that DrBHV may be suited to vector a lifelong, self-boosting, and transmissible vaccine. Simulations showed that inoculating a single bat with a DrBHV-vectored rabies vaccine could immunize >80% of a bat population, reducing the size, frequency, and duration of rabies outbreaks by 50 to 95%. Gradual loss of infectious vaccine from vaccinated individuals is expected but can be countered by inoculating larger but practically achievable proportions of bat populations. Parameterizing epidemiological models using accessible genomic data brings transmissible vaccines one step closer to implementation.
Free-standing membrane incorporating single-atom catalysts for ultrafast electroreduction of low-concentration nitrate
Authors: Wang Xiaoxiong , Wu Xuanhao , Ma Wen , Zhou Xuechen , Zhang Shuo , Huang Dahong , Winter Lea R. , Kim Jae-Hong , Elimelech Menachem
Published: March 2023

The release of wastewaters containing relatively low levels of nitrate (NO
3
−
) results in sufficient contamination to induce harmful algal blooms and to elevate drinking water NO
3
−
concentrations to potentially hazardous levels. In particular, the facile triggering of algal blooms by ultra-low concentrations of NO
3
−
necessitates the development of efficient methods for NO
3
−
destruction. However, promising electrochemical methods suffer from weak mass transport under low reactant concentrations, resulting in long treatment times (on the order of hours) for complete NO
3
−
destruction. In this study, we present flow-through electrofiltration via an electrified membrane incorporating nonprecious metal single-atom catalysts for NO
3
−
reduction activity enhancement and selectivity modification, achieving near-complete removal of ultra-low concentration NO
3
−
(10 mg-N L
−1
) with a residence time of only a few seconds (10 s). By anchoring Cu single atoms supported on N-doped carbon in a carbon nanotube interwoven framework, we fabricate a free-standing carbonaceous membrane featuring high conductivity, permeability, and flexibility. The membrane achieves over 97% NO
3
−
removal with high N
2
selectivity of 86% in a single-pass electrofiltration, which is a significant improvement over flow-by operation (30% NO
3
−
removal with 7% N
2
selectivity). This high NO
3
−
reduction performance is attributed to the greater adsorption and transport of nitric oxide under high molecular collision frequency coupled with a balanced supply of atomic hydrogen through H
2
dissociation during electrofiltration. Overall, our findings provide a paradigm of applying a flow-through electrified membrane incorporating single-atom catalysts to improve the rate and selectivity of NO
3
−
reduction for efficient water purification.
Dissolved gases in the deep North Atlantic track ocean ventilation processes
Authors: Seltzer Alan M. , Nicholson David P. , Smethie William M. , Tyne Rebecca L. , Le Roy Emilie , Stanley Rachel H. R. , Stute Martin , Barry Peter H. , McPaul Katelyn , Davidson Perrin W. , Chang Bonnie X. , Rafter Patrick A. , Lethaby Paul , Johnson Rod J. , Khatiwala Samar , Jenkins William J.
Published: March 2023

Gas exchange between the atmosphere and ocean interior profoundly impacts global climate and biogeochemistry. However, our understanding of the relevant physical processes remains limited by a scarcity of direct observations. Dissolved noble gases in the deep ocean are powerful tracers of physical air-sea interaction due to their chemical and biological inertness, yet their isotope ratios have remained underexplored. Here, we present high-precision noble gas isotope and elemental ratios from the deep North Atlantic (~32°N, 64°W) to evaluate gas exchange parameterizations using an ocean circulation model. The unprecedented precision of these data reveal deep-ocean undersaturation of heavy noble gases and isotopes resulting from cooling-driven air-to-sea gas transport associated with deep convection in the northern high latitudes. Our data also imply an underappreciated and large role for bubble-mediated gas exchange in the global air-sea transfer of sparingly soluble gases, including O
2
, N
2
, and SF
6
. Using noble gases to validate the physical representation of air-sea gas exchange in a model also provides a unique opportunity to distinguish physical from biogeochemical signals. As a case study, we compare dissolved N
2
/Ar measurements in the deep North Atlantic to physics-only model predictions, revealing excess N
2
from benthic denitrification in older deep waters (below 2.9 km). These data indicate that the rate of fixed N removal in the deep Northeastern Atlantic is at least three times higher than the global deep-ocean mean, suggesting tight coupling with organic carbon export and raising potential future implications for the marine N cycle.
Biolistic delivery of liposomes protected in metal-organic frameworks
Authors: Kumari Sneha , Wijesundara Yalini H. , Howlett Thomas S. , Waliullah Mohammad , Herbert Fabian C. , Raja Arun , Trashi Ikeda , Bernal Rodrigo A. , Gassensmith Jeremiah J.
Published: March 2023

Needle-and-syringe-based delivery has been the commercial standard for vaccine administration to date. With worsening medical personnel availability, increasing biohazard waste production, and the possibility of cross-contamination, we explore the possibility of biolistic delivery as an alternate skin-based delivery route. Delicate formulations like liposomes are inherently unsuitable for this delivery model as they are fragile biomaterials incapable of withstanding shear stress and are exceedingly difficult to formulate as a lyophilized powder for room temperature storage. Here we have developed a approach to deliver liposomes into the skin biolistically—by encapsulating them in a nano-sized shell made of Zeolitic Imidazolate Framework-8 (ZIF-8). When encapsulated within a crystalline and rigid coating, the liposomes are not only protected from thermal stress, but also shear stress. This protection from stressors is crucial, especially for formulations with cargo encapsulated inside the lumen of the liposomes. Moreover, the coating provides the liposomes with a solid exterior that allows the particles to penetrate the skin effectively. In this work, we explored the mechanical protection ZIF-8 provides to liposomes as a preliminary investigation for using biolistic delivery as an alternative to syringe-and-needle–based delivery of vaccines. We demonstrated that liposomes with a variety of surface charges could be coated with ZIF-8 using the right conditions, and this coating can be just as easily removed—without causing any damage to the protected material. The protective coating prevented the liposomes from leaking cargo and helped in their effective penetration when delivered into the agarose tissue model and porcine skin tissue.
Greed communication predicts the approval and reach of US senators’ tweets
Authors: Mercadante Eric J. , Tracy Jessica L. , Götz Friedrich M.
Published: March 2023

Social media are at the forefront of modern political campaigning. They allow politicians to communicate directly with constituents and constituents to endorse politicians’ messages and share them with their networks. Analyzing every tweet of all US senators holding office from 2013 to 2021 (861,104 tweets from 140 senators), we identify a psycholinguistic factor, greed communication, that robustly predicts increased approval (favorites) and reach (retweets). These effects persist when tested against diverse established psycholinguistic predictors of political content dissemination on social media and various other psycholinguistic variables. We further find that greed communication in the tweets of Democratic senators is associated with greater approval and retweeting compared to greed communication in the tweets of Republican senators, especially when those tweets also mention political outgroups.
Steering CO
2
electroreduction pathway toward ethanol via surface-bounded hydroxyl species-induced noncovalent interaction
Authors: Zhang Jiawei , Zeng Gangming , Zhu Shangqian , Tao Haolan , Pan Yue , Lai Wenchuan , Bao Jun , Lian Cheng , Su Dong , Shao Minhua , Huang Hongwen
Published: March 2023

Selective electroreduction of carbon dioxide (CO
2
RR) into ethanol at an industrially relevant current density is highly desired. However, it is challenging because the competing ethylene production pathway is generally more thermodynamically favored. Herein, we achieve a selective and productive ethanol production over a porous CuO catalyst that presents a high ethanol Faradaic efficiency (FE) of 44.1 ± 1.0% and an ethanol-to-ethylene ratio of 1.2 at a large ethanol partial current density of 501.0 ± 15.0 mA cm
−2
, in addition to an extraordinary FE of 90.6 ± 3.4% for multicarbon products. Intriguingly, we found a volcano-shaped relationship between ethanol selectivity and nanocavity size of porous CuO catalyst in the range of 0 to 20 nm. Mechanistic studies indicate that the increased coverage of surface-bounded hydroxyl species (*OH) associated with the nanocavity size-dependent confinement effect contributes to the remarkable ethanol selectivity, which preferentially favors the *CHCOH hydrogenation to *CHCHOH (ethanol pathway) via yielding the noncovalent interaction. Our findings provide insights in favoring the ethanol formation pathway, which paves the path toward rational design of ethanol-oriented catalysts.
Dissection of 3D chromosome organization in
Streptomyces coelicolor
A3(2) leads to biosynthetic gene cluster overexpression
Authors: Deng Liang , Zhao Zhihu , Liu Lin , Zhong Zhiyu , Xie Wenxinyu , Zhou Fan , Xu Wei , Zhang Yubo , Deng Zixin , Sun Yuhui
Published: March 2023

The soil-dwelling filamentous bacteria,
Streptomyces,
is widely known for its ability to produce numerous bioactive natural products. Despite many efforts toward their overproduction and reconstitution, our limited understanding of the relationship between the host’s chromosome three dimension (3D) structure and the yield of the natural products escaped notice. Here, we report the 3D chromosome organization and its dynamics of the model strain,
Streptomyces coelicolor
, during the different growth phases. The chromosome undergoes a dramatic global structural change from primary to secondary metabolism, while some biosynthetic gene clusters (BGCs) form special local structures when highly expressed. Strikingly, transcription levels of endogenous genes are found to be highly correlated to the local chromosomal interaction frequency as defined by the value of the frequently interacting regions (FIREs). Following the criterion, an exogenous single reporter gene and even complex BGC can achieve a higher expression after being integrated into the chosen loci, which may represent a unique strategy to activate or enhance the production of natural products based on the local chromosomal 3D organization.
Regressive changes in sizes of somatosensory cuneate nucleus after sensory loss in primates
Authors: Qi Hui-Xin , Reed Jamie L. , Liao Chia-Chi , Kaas Jon H.
Published: March 2023

Neurons in the early stages of processing sensory information suffer transneuronal atrophy when deprived of their activating inputs. For over 40 y, members of our laboratory have studied the reorganization of the somatosensory cortex during and after recovering from different types of sensory loss. Here, we took advantage of the preserved histological material from these studies of the cortical effects of sensory loss to evaluate the histological consequences in the cuneate nucleus of the lower brainstem and the adjoining spinal cord. The neurons in the cuneate nucleus are activated by touch on the hand and arm, and relay this activation to the contralateral thalamus, and from the thalamus to the primary somatosensory cortex. Neurons deprived of activating inputs tend to shrink and sometimes die. We considered the effects of differences in species, type and extent of sensory loss, recovery time after injury, and age at the time of injury on the histology of the cuneate nucleus. The results indicate that all injuries that deprived part or all of the cuneate nucleus of sensory activation result in some atrophy of neurons as reflected by a decrease in nucleus size. The extent of the atrophy is greater with greater sensory loss and with longer recovery times. Based on supporting research, atrophy appears to involve a reduction in neuron size and neuropil, with little or no neuron loss. Thus, the potential exists for restoring the hand to cortex pathway with brain–machine interfaces, for bionic prosthetics, or biologically with hand replacement surgery.
Stability in inverse problem of an elastic plate with a curved middle surface
Authors: Fu Song-Ren , Yao Peng-Fei
Published: March 2023

We consider stability in an inverse problem of determining three spatially varying functions including the source term and the mass density for a curved plate by the Riemannian geometrical approach. The stability is derived by the Carleman estimates and observability inequalities. Two kinds of boundary conditions are considered: one is the hinged boundary conditions and the other is the clamped boundary conditions. In particular, the case of the Euler–Bernoulli plate is included.