bluuebunny/crossref_metadata_2025 huggingface dataset:
Estrogen receptor alpha mediated repression of PRICKLE1 destabilizes REST and promotes uterine fibroid pathogenesis
Authors: McWilliams Michelle M. , Koohestani Faezeh , Jefferson Wendy N. , Gunewardena Sumedha , Shivashankar Kavya , Wertenberger Riley A. , Williams Carmen J. , Rajendra Kumar T. , Chennathukuzhi Vargheese M.
Published: September 2024

Uterine fibroids (leiomyomas), benign tumors of the myometrial smooth muscle layer, are present in over 75% of women, often causing severe pain, menorrhagia and reproductive dysfunction. The molecular pathogenesis of fibroids is poorly understood. We previously showed that the loss of REST (RE-1SilencingTranscription factor), a tumor suppressor, in fibroids leads to activation of PI3K/AKT-mTOR pathway. We report here a critical link between estrogen receptor alpha (ERα) and the loss of REST,viaPRICKLE1. PRICKLE1 expression is markedly lower in leiomyomas, and the suppression of PRICKLE1 significantly down regulates REST protein levels. Conversely, overexpression of PRICKLE1 resulted in the restoration of REST in cultured primary leiomyoma smooth muscle cells (LSMCs). Crucially, mice exposed neonatally to environmental estrogens, proven risk factors for fibroids, expressed lower levels of PRICKLE1 and REST in the myometrium. Using mice that lack either endogenous estrogen (Lhb-/-mice) or ERα (Esr1-/-mice), we demonstrate thatPrickle1expression in the myometrium is suppressed by estrogen through ERα. Enhancer of zeste homolog 2 (EZH2) is known to participate in the repression of specific ERα target genes. Uterine leiomyomas express increased levels of EZH2 that inversely correlate with the expression of PRICKLE1. Using chromatin immunoprecipitation, we provide evidence for association of EZH2 with thePRICKLE1promoter and for hypermethylation of H3K27 within the regulatory region ofPRICKLE1in leiomyomas. Additionally, siRNA mediated knockdown of EZH2 leads to restoration of PRICKLE1 in LSMCs. Collectively, our results identify a novel link between estrogen exposure and PRICKLE1/REST-regulated tumorigenic pathways in leiomyomas.
Cost-effective solutions for high-throughput enzymatic DNA methylation sequencing
Authors: Longtin Amy , Watowich Marina M. , Sadoughi Baptiste , Petersen Rachel M. , Brosnan Sarah F. , Buetow Kenneth , Cai Qiuyin , Gurven Michael D. , Highland Heather M. , Huang Yi-Ting , Kaplan Hillard , Kraft Thomas S. , Lim Yvonne A. L. , Long Jirong , Melin Amanda D. , Roberson Jamie , Ng Kee-Seong , Stieglitz Jonathan , Trumble Benjamin C. , Venkataraman Vivek V. , Wallace Ian J. , Wu Jie , Snyder-Mackler Noah , Jones Angela , Bick Alexander G. , Lea Amanda J.
Published: September 2024

Characterizing DNA methylation patterns is important for addressing key questions in evolutionary biology, geroscience, and medical genomics. While costs are decreasing, whole-genome DNA methylation profiling remains prohibitively expensive for most population-scale studies, creating a need for cost-effective, reduced representation approaches (i.e., assays that rely on microarrays, enzyme digests, or sequence capture to target a subset of the genome). Most common whole genome and reduced representation techniques rely on bisulfite conversion, which can damage DNA resulting in DNA loss and sequencing biases. Enzymatic methyl sequencing (EM-seq) was recently proposed to overcome these issues, but thorough benchmarking of EM-seq combined with cost-effective, reduced representation strategies has not yet been performed. To do so, we optimized Targeted Methylation Sequencing protocol (TMS)—which profiles ∼4 million CpG sites—for miniaturization, flexibility, and multispecies use at a cost of ∼$80. First, we tested modifications to increase throughput and reduce cost, including increasing multiplexing, decreasing DNA input, and using enzymatic rather than mechanical fragmentation to prepare DNA. Second, we compared our optimized TMS protocol to commonly used techniques, specifically the Infinium MethylationEPIC BeadChip (n=55 paired samples) and whole genome bisulfite sequencing (n=6 paired samples). In both cases, we found strong agreement between technologies (R² = 0.97 and 0.99, respectively). Third, we tested the optimized TMS protocol in three non-human primate species (rhesus macaques, geladas, and capuchins). We captured a high percentage (mean=77.1%) of targeted CpG sites and produced methylation level estimates that agreed with those generated from reduced representation bisulfite sequencing (R² = 0.98). Finally, we applied our protocol to profile age-associated DNA methylation variation in two subsistence-level populations—the Tsimane of lowland Bolivia and the Orang Asli of Peninsular Malaysia—and found age-methylation patterns that were strikingly similar to those reported in high income cohorts, despite known differences in age-health relationships between lifestyle contexts. Altogether, our optimized TMS protocol will enable cost-effective, population-scale studies of genome-wide DNA methylation levels across human and non-human primate species.
SIRT6 loss causes intervertebral disc degeneration in mice by promoting senescence and SASP status
Authors: Ramteke Pranay , Watson Bahiyah , Toci Mallory , Tran Victoria A , Johnston Shira , Tsingas Maria , Barve Ruteja A. , Mitra Ramkrishna , Loeser Richard F. , Collins John A. , Risbud Makarand V.
Published: September 2024

Intervertebral disc degeneration is a major risk factor contributing to chronic low back and neck pain. While the etiological factors for disc degeneration vary, age is still one of the most important risk factors. Recent studies have shown the promising role of SIRT6 in mammalian aging and skeletal tissue health, however its role in the intervertebral disc health remains unexplored. We investigated the contribution of SIRT6 to disc health by studying the age-dependent spinal phenotype of mice with conditional deletion ofSirt6in the disc (AcanCreERT2;Sirt6fl/fl). Histological studies showed a degenerative phenotype in knockout mice compared toSirt6fl/flcontrol mice at 12 months which became pronounced at 24 months. RNA-Seq analysis of NP and AF tissues, quantitative histone analysis, andin vitromultiomics employing RNA-seq with ATAC-seq revealed that SIRT6-loss resulted in changes in acetylation and methylation status of specific Histone 3 lysine residues, thereby affecting DNA accessibility and transcriptomic landscape. A decrease in autophagy and an increase in DNA damage were also noted inSirt6-deficient cells. Further mechanistic insights revealed that loss of SIRT6 increased senescence and SASP burden in the disc characterized by increased p21, γH2AX, IL-6, and TGF-β abundance. Taken together our study highlights the contribution of SIRT6 in modulating DNA damage, autophagy and cell senescence, and its importance in maintaining disc health during aging thereby underscoring it as a potential therapeutic target to treat intervertebral disc degeneration.
Applications of some artificial intelligence tools in the drug design of some compounds targeting the main viral protease of the Feline Infectious Peritonitis Virus (FIPV) in cats
Authors: Khan Mohd Yasir , Shah Abid Ullah , Duraisamy Nithyadevi , Moawad Nadine , ElAlaoui Reda Nacif , Cherkaoui Mohammed , Hemida Maged Gomaa
Published: September 2024

Feline infectious peritonitis virus (FIPV) is one of cats’ most serious viral infections. The FIPV infection induces a complicated syndrome in the affected cats, including immunosuppression and severe inflammatory conditions. Unfortunately, these vaccines cannot prevent cats from getting infected with these viral infections. There is ongoing research on preparing antiviral therapies against FIPV in cats. However, these are still in clinical trials and have not been fully approved by the drug authorities in many countries, including the USA. Targeting the main viral proteases is one of the promising trends in the drug design of many viral diseases, including coronaviruses. The main goal of the current study was to repurpose and test the efficacy of some known antiviral drugs to treat FIPV infection in cats by targeting the FIPV-main protease enzyme. To achieve these goals, we used the in-silico prediction and molecular docking tools to screen and identify some drugs targeting FIPV-MPro. We used the docking and binding energies as the main parameters for selecting target compounds (FIPV-MPro). Our results show that out of the 15 antiviral and immunomodulatory compounds, the top-ranked inhibitors for the FIPV-Mpro are (Michael acceptor inhibitors (N3), Sofosbuvir, and methotrexate).In conclusion, our results confirmed the potential applications of the predicted FIPV-Mpro inhibitors either independently or in combination with other immune-modulatory compounds. Further in vitro and in vivo studies are encouraged to test the efficacy of these identified compounds as potent inhibitors for the MPro of the FIPV in cats. This study will pave the way for the development of novel drugs that treat FIPV infection in cats.
Selective deuteration of an RNA:RNA complex for structural analysis using small-angle scattering
Authors: Munsayac Aldrex , Leite Wellington C. , Hopkins Jesse B. , Hall Ian , O’Neill Hugh M. , Keane Sarah C.
Published: September 2024

The structures of RNA:RNA complexes regulate many biological processes. Despite their importance, protein-free RNA:RNA complexes represent a tiny fraction of experimentally-determined structures. Here, we describe a joint small-angle X-ray and neutron scattering (SAXS/SANS) approach to structurally interrogate conformational changes in a model RNA:RNA complex. Using SAXS, we measured the solution structures of the individual RNAs in their free state and of the overall RNA:RNA complex. With SANS, we demonstrate, as a proof-of-principle, that isotope labeling and contrast matching (CM) can be combined to probe the bound state structure of an RNA within a selectively deuterated RNA:RNA complex. Furthermore, we show that experimental scattering data can validate and improve predicted AlphaFold 3 RNA:RNA complex structures to reflect its solution structure. Our work demonstrates thatin silicomodeling, SAXS, and CM-SANS can be used in concert to directly analyze conformational changes within RNAs when in complex, enhancing our understanding of RNA structure in functional assemblies.
Balancing limited resources in actin networks competition
Authors: Guérin Christophe , N'Diaye Anne-Betty , Gressin Laurène , Mogilner Alex , Théry Manuel , Blanchoin Laurent , Colin Alexandra
Published: September 2024

In cells, multiple actin networks coexist in a dynamic manner. These networks compete for a common pool of actin monomers and actin-binding proteins. Interestingly, this competition does not result in the mere survival of the more consuming networks. Moreover, the co-existence of networks with various strengths is key to cell adaption to external changes. However, a comprehensive view of how these networks coexist in this competitive environment, where resources are limited, is still lacking. To address this question, we used a reconstituted system, in closed microwells, consisting of beads propelled by actin polymerization or micropatterns functionalized with lipids capable of initiating polymerization close to a membrane. This system enabled us to build dynamic actin architectures, competing for a limited pool of proteins, over a period of hours. We demonstrated the importance of protein turnover for the coexistence of actin networks, showing it ensures resource distribution between weak and strong networks. However, when competition becomes too intense, turnover alone is insufficient, leading to a selection process that favors the strongest networks. Consequently, we emphasize the importance of competition strength, which is defined by the turnover rate, the amount of available protein, and the number of competing structures. More generally, this work illustrates how turnover allows biological populations with various competition strengths to coexist despite resource constraints.
The landscape ofArabidopsistRNA aminoacylation
Authors: Ceriotti Luis F. , Warren Jessica M. , Virginia Sanchez-Puerta M. , Sloan Daniel B.
Published: September 2024

The function of tRNAs depends on enzymes that cleave primary transcript ends, add a 3′ CCA tail, introduce post-transcriptional base modifications, and charge (aminoacylate) mature tRNAs with the correct amino acid. Maintaining an available pool of the resulting aminoacylated tRNAs is essential for protein synthesis. High-throughput sequencing techniques have recently been developed to provide a comprehensive view of aminoacylation state in a tRNA-specific fashion. However, these methods have never been applied to plants. Here, we treatedArabidopsis thalianaRNA samples with periodate and then performed tRNA-seq to distinguish between aminoacylated and uncharged tRNAs. This approach successfully captured every tRNA isodecoder family and detected expression of additional tRNA-like transcripts. We found that estimated aminoacylation rates and CCA tail integrity were significantly higher on average for organellar (mitochondrial and plastid) tRNAs than for nuclear/cytosolic tRNAs. Reanalysis of previously published human cell line data showed a similar pattern. Base modifications result in nucleotide misincorporations and truncations during reverse transcription, which we quantified and used to test for relationships with aminoacylation levels. We also determined that theArabidopsistRNA-like sequences (t-elements) that are cleaved from the ends of some mitochondrial mRNAs have post-transcriptionally modified bases and CCA-tail addition. However, these t-elements are not aminoacylated, indicating that they are only recognized by a subset of tRNA-interacting enzymes and do not play a role in translation. Overall, this work provides a characterization of the baseline landscape of plant tRNA aminoacylation rates and demonstrates an approach for investigating environmental and genetic perturbations to plant translation machinery.
Causal Associations Between Imaging-derived Phenotypes and Risk of Alzheimer’s Disease and Other Neurodegenerative Disorders: A Mendelian Randomization Study
Authors: Chen Zhichun , Liu Jun , You Yong
Published: September 2024

Background

Accumulating observational studies have suggested associations between imaging-derived phenotypes (IDPs) and common neurodegenerative disorders, especially Alzheimer’s disease (AD). The goal of this study is to evaluate the causal associations between structural and functional IDPs and 4 neurodegenerative disorders, including AD, Parkinson’s disease (PD), Amyotrophic lateral sclerosis (ALS), and Multiple sclerosis (MS).

Methods

Bidirectional two-sample Mendelian randomization (MR) studies were conducted using summary statistics obtained from genome-wide association studies of 3909 IDPs from UK biobank and 4 neurodegenerative disorders.

Results

Forward MR analysis showed that volume of cerebral white matter in the left hemisphere was associated with increased risk of ALS (odds ratio [OR] = 1.15, 95% confidence interval [CI] = 1.09-1.22,P= 3.52 x 10-6). In reverse MR analysis, we revealed genetically determined risk of AD and MS were associated with multiple IDPs (allP< 1.28 x 10-5[0.05/3909], 9 IDPs in AD and 4 IDPs in MS). For example, genetically determined risk of AD was causally associated with reduced volume of gray matter in right ventral striatum (OR = 0.95, 95% CI = 0.93-0.97,P= 4.68 x 10-7) and lower rfMRI amplitudes in several nodes (ICA25 node 9, ICA25 node 8, and ICA100 node 11). Additionally, genetically determined risk of MS was causally associated with reduced volume in left putamen (OR = 0.97, 95% CI = 0.97-0.98,P= 4.47 x 10-7) and increased orientation dispersion index in right hippocampus (OR = 1.03, 95% CI = 1.01-1.04,P= 2.02 x 10-6).

Conclusions

Our study suggested plausible causal associations between risk of NDDs and brain IDPs. These findings might hold promise for identifying new disease mechanisms and developing novel preventative therapies for NDDs at the brain imaging levels.
Branched-chain amino acid metabolism is a crucial modulator of cellular senescence
Authors: Aramaki Yuma , Irie Kazuki , Obinata Hideru , Honda Shinya , Horii Takuro , Arakawa Satoko , Tsuchida Aiko , Hoshino Junki , Kobayashi Ryosuke , Izumi Takashi , Hatada Izuho , Shimizu Shigeomi , Minamishima Yoji A. , Konishi Akimitsu
Published: September 2024

Cellular senescence is a complex stress response that results in the permanent arrest of cell proliferation. The accumulation of senescent cells occurs during aging in living organisms, and contributes to tissue dysfunction. Although there are growing lines of evidence that various metabolic changes occur in senescent cells, the link between cellular metabolism and senescence is not yet fully understood. In this study, we demonstrate that alterations in the metabolism of branched-chain amino acids (BCAAs) play a crucial role in establishing cellular senescence. Furthermore, we identified mitochondrial BCAA transamination as a crucial step in this process. Our findings show that various types of cellular stress lead to a reduction in the expression of BCAA aminotransferase 2 (BCAT2), one of the BCAA catabolic enzymes, resulting in decreased catabolism of BCAAs and reduced synthesis of glutamate. The reduction of BCAA catabolites, together with the consequent limitation in glutathione production from glutamate, triggers cellular senescence. Furthermore, we demonstrate that a reduction in BCAT2 levels alone is sufficient to induce cellular senescence, both in cultured cells and in mice. Additionally, our results demonstrate that aging alters BCAA metabolism in both mice and humans. Our findings provide new insights into the metabolic mechanisms underlying cellular senescence, with a particular focus on the role of BCAAs.
The molecular origin of body temperature in homeothermic species
Authors: Artmann Gerhard Michael , Weiergraeber Oliver H. , Damiati Samar Abdullah M. , Firat Ipek Seda , Artmann Aysegul
Published: September 2024

We propose the Interfacial Water Quantum-transition model (IWQ model) explaining temperature-dependent functional transitions in proteins. The model postulates that measured critical temperatures, TC, correspond to reference temperatures, TW, defined by rotational quantum transitions of temporarily free water molecules at the protein-water interface. The model's applicability is demonstrated through transitions in hemoglobin and thermosensitive TRP channels. We suggest this mechanism also defines basal body temperatures in homeotherms, with TW=36.32 degrees C for humans. We demonstrate that human (mammal) and chicken (Aves) body temperatures align with specific reference temperatures, and correlate with pronounced transitions at TC in hemoglobin oxygen saturation. This suggests evolutionary adaptations in homeotherms involve an interplay between oxygen supply and water's rotational transition temperatures. The IWQ-model states that proteins sense and water sets critical physiological temperatures.
Anomaly detection in collider physics via factorized observables
Authors: Metodiev Eric M. , Thaler Jesse , Wynne Raymond
Published: September 2024

To maximize the discovery potential of high-energy colliders, experimental searches should be sensitive to unforeseen new physics scenarios. This goal has motivated the use of machine learning for unsupervised anomaly detection. In this paper, we introduce a new anomaly detection strategy called : factorized observables for regressing conditional expectations. Our approach is based on the inductive bias of factorization, which is the idea that the physics governing different energy scales can be treated as approximately independent. Assuming factorization holds separately for signal and background processes, the appearance of nontrivial correlations between low- and high-energy observables is a robust indicator of new physics. Under the most restrictive form of factorization, a machine-learned model trained to identify such correlations will in fact converge to the optimal new physics classifier. We test on a benchmark anomaly detection task for the Large Hadron Collider involving collimated sprays of particles called jets. By teasing out correlations between the kinematics and substructure of jets, our method can reliably extract percent-level signal fractions. This strategy for uncovering new physics adds to the growing toolbox of anomaly detection methods for collider physics with a complementary set of assumptions.

Published by the American Physical Society
2024
Dark branes for dark matter
Authors: Koutroulis Fotis , Megías Eugenio , Pokorski Stefan , Quirós Mariano
Published: September 2024

We propose a setup for the origin of dark matter based on spacetime with a warped extra dimension and three branes: the Planck brane, the TeV brane, at a (few) TeV scale ρT, and a dark brane, at a (sub-)GeV scale ρ1≲100  GeV≪ρT. The Standard Model (SM) is localized in the TeV brane, thus solving the Higgs hierarchy problem, while the dark matter χ, a Dirac fermion with mass mχ<ρ1, is localized in the dark brane. The radion, with mass mr<mχ, interacts strongly [∼mχ/ρ1∼O(1)] with dark matter and very weakly (

∼

m

f

ρ

1

/

ρ

T

2

≪

1

) with the Standard Model matter f. The generic conflict between the bounds on its detection signatures and its proper relic abundance is avoided as dark matter annihilation is p-wave suppressed. The former is determined by its very weak interactions with the SM and the latter by its much stronger annihilation into radions. Therefore, there is a vast range in the dark matter’s parameter space where the correct relic abundance is achieved consistently with the existing bounds. Moreover, for the dark brane with ρ1≲3  GeV, a confinement/deconfinement first order phase transition, where the radion condensates, produces a stochastic gravitational wave background at the nanohertz frequencies, which can be identified with the signal detected by the Pulsar Timing Array (PTA) experiments. In the PTA window, for 0.15≲mχ≲2  GeV the relic abundance is reproduced and all constraints are satisfied.

Published by the American Physical Society
2024
Temperature fluctuations in a relativistic gas: Pressure corrections and possible consequences in the deconfinement transition
Authors: Castaño-Yepes Jorge David , Loewe Marcelo , Muñoz Enrique , Rojas Juan Cristóbal
Published: September 2024

In this work, we study the effects of random temperature fluctuations on the partition function of a quantum system by means of the . This picture provides a conceptual model for a quantum nonequilibrium system, depicted as an ensemble of subsystems at different temperatures, randomly distributed with respect to a given mean value. We then assume the temperature displays stochastic fluctuations T=T0+δT with respect to its ensemble average value T0, with zero mean δT¯=0 and standard deviation δT2¯=Δ. By means of the replica method, we obtain the average grand canonical potential, leading to the equation of state and the corresponding excess pressure caused by these fluctuations with respect to the equilibrium system at a uniform temperature. Our findings reveal an increase in pressure as the system’s ensemble average temperature T0 rises, consistently exceeding the pressure observed in an equilibrium state. We applied our general formalism to three paradigmatic physical systems; the relativistic Fermi gas, the ideal gas of photons, and a gas of non-Abelian gauge fields (gluons) in the noninteracting limit. Finally, we explore the implications for the deconfinement transition in the context of the simple bag model, where we show that the critical temperature decreases.

Published by the American Physical Society
2024
Nonlinearly charging the conformally dressed black holes preserving duality and conformal invariance
Authors: Ayón-Beato Eloy , Flores-Alfonso Daniel , Hassaine Mokhtar
Published: September 2024

We start this paper by concisely rederiving ModMax, which is nothing but the unique nonlinear extension of Maxwell’s equations preserving conformal and duality invariance. The merit of this new derivation is its transparency and simplicity since it is based on an approach where the elusive duality invariance is manifest. In the second part, we couple the ModMax electrodynamics to Einstein gravity with a cosmological constant together with a standard conformal scalar field, and new stationary spacetimes with dyonic charges are found. These solutions are later used as seed configurations to generate nonlinearly charged (super-)renormalizably dressed spacetimes by means of a known generating method that we extend to include any nonlinear conformal electrodynamics. We end by addressing the issue of how to generalize some of these results to include the recently studied non-Noetherian conformal scalar fields, whose equation of motion still enjoys conformal symmetry even though its action does not. It turns out that the static non-Noetherian conformally dressed black holes also become amenable to being charged by ModMax.

Published by the American Physical Society
2024
Nonequivalence of Carroll limits in relativistic string theory
Authors: Casalbuoni Roberto , Dominici Daniele , Gomis Joaquim
Published: September 2024

We construct new Carroll strings in flat space by considering the Carroll limit of equivalent relativistic string theories at the classical level. In the limit these Carroll strings are no longer equivalent and have different degrees of freedom. This fact is due to a general phenomenon that the configuration space and canonical Lagrangians are no longer equivalent after a singular redefinition of the variables and of the parameters of the starting Lagrangians.

Published by the American Physical Society
2024
Flexible quantum data bus for quantum networks
Authors: Freund Julia , Pirker Alexander , Dür Wolfgang
Published: September 2024

We consider multipath generation of Bell states in quantum networks, where a preprepared multipartite entangled two-dimensional cluster state serves as a resource to perform different tasks on demand. We show how to achieve parallel connections between multiple, freely chosen groups of parties by performing appropriate local measurements along a diagonal, staircase-shaped path on a two-dimensional cluster state. Remarkably, our measurement scheme preserves the entanglement structure of the cluster state such that the remaining state is again a two-dimensional cluster state. We demonstrate strategies for generating crossing, turning, and merging of multiple measurement lines along the two-dimensional cluster state. The results apply to local area as well as to long-distance networks.

Published by the American Physical Society
2024
Role of electrostatic doping on the resistance of metal and two-dimensional materials edge contacts
Authors: Brahma Madhuchhanda , Van de Put Maarten L. , Chen Edward , Fischetti Massimo V. , Vandenberghe William G.
Published: September 2024

In this theoretical study, we compare electrostatically doped metal-transition metal dichalcogenide (TMD) edge-contacts versus substitutionally doped edge-contacts in terms of their contact resistance. Our approach involves the utilization of electrostatic doping achieved by applying back-gate bias to the metal-TMD edge contacts, where carrier injection is primarily governed by the Schottky barrier at the interface. To analyze these contacts, we employ the Wentzel-Kramers-Brillouin (WKB) approximation to calculate the transmission coefficient and use density functional theory (DFT)-derived band structures. We numerically solve the Poisson equation to capture the electrostatic potential. We also account for the impact of the image force using Green's function for the Poisson equation with boundary conditions appropriate to our specific geometry. Our findings reveal that electrostatically doped TMD edge contacts exhibit higher contact resistance compared to impurity-doped edge contacts at equivalent carrier concentrations. At the same time, we find that, among the electrostatically doped edge contacts, a low-κ back-gate oxide in conjunction with low-κ top oxide is preferable in terms of improvement in contact resistance. For instance, in a metal-TMD edge contact scenario involving a monolayer MoS2 as the channel, SiO2 as the infinitely thick top oxide, and a SiO2 back-gate oxide with an equivalent oxide thickness (EOT) of 1nm, we demonstrate that it is possible to achieve an impressively low contact resistance of 50Ωµm when the back-gate bias exceeds or equals 2 V.

Published by the American Physical Society
2024
Interaction-enhanced nesting in spin-fermion and Fermi-Hubbard models
Authors: Rossi R. , IV F. Šimkovic , Ferrero M. , Georges A. , Tsvelik A. M. , Prokof'ev N. V. , Tupitsyn I. S.
Published: September 2024

The spin-fermion (SF) model postulates that the dominant coupling between low-energy fermions in near critical metals is mediated by collective spin fluctuations (paramagnons) peaked at the Néel wave vector, QN, connecting hot spots on opposite sides of the Fermi surface. It has been argued that strong correlations at hot spots lead to a Fermi surface deformation (FSD) featuring flat regions and increased nesting. This conjecture was confirmed in the perturbative self-consistent calculations when the paramagnon propagator dependence on momentum deviation from QN is given by χ−1∝|Δq|. Using diagrammatic Monte Carlo (diagMC) technique we show that such a dependence holds only at temperatures orders of magnitude smaller than any other energy scale in the problem, indicating that a different mechanism may be at play. Instead, we find that a χ−1∝|Δq|2 dependence yields a robust finite-T scenario for achieving FSD. To link phenomenological and microscopic descriptions, we applied the connected determinant diagMC method to the (t−t′) Hubbard model and found that at large U/t>5.5 before the formation of electron and hole pockets (i) the FSD defined as a maximum of the spectral function is not very pronounced; instead, it is the lines of zeros of the renormalized dispersion relation that deforms toward nesting, and (ii) the static spin susceptibility is well described by χ−1∝|Δq|2. Flat FS regions yield a nontrivial scenario for realizing a non-Fermi liquid state.

Published by the American Physical Society
2024
Role of the constriction angle on the clogging by bridging of suspensions of particles
Authors: Vani Nathan , Escudier Sacha , Jeong Deok-Hoon , Sauret Alban
Published: September 2024

Confined flows of particles can lead to clogging, and therefore failure, of various fluidic systems across many applications. As a result, design guidelines need to be developed to ensure that clogging is prevented or at least delayed. In this Letter, we investigate the influence of the angle of reduction in the cross section of the channel on the bridging of semidilute and dense non-Brownian suspensions of spherical particles. We observe a decrease of the clogging probability with the reduction of the constriction angle. This effect is more pronounced for dense suspensions close to the maximum packing fraction where particles are in contact in contrast to semidilute suspensions. We rationalize this difference in terms of arch selection. We describe the role of the constriction angle and the flow profile, providing insights into the distinct behavior of semidilute and dense suspensions.

Published by the American Physical Society
2024
Continuous Coherent Quantum Feedback with Time Delays: Tensor Network Solution
Authors: Vodenkova Kseniia , Pichler Hannes
Published: September 2024

In this paper, we develop a novel method to solve problems involving quantum optical systems coupled to coherent quantum feedback loops featuring time delays. Our method is based on exact mappings of such non-Markovian problems to equivalent Markovian driven dissipative quantum many-body problems. In this work, we show that the resulting Markovian quantum many-body problems can be solved (numerically) exactly and efficiently using tensor network methods for a series of paradigmatic examples, consisting of driven quantum systems coupled to waveguides at several distant points. In particular, we show that our method allows solving problems in so far inaccessible regimes, including problems with arbitrary long time delays and arbitrary numbers of excitations in the delay lines. We obtain solutions for the full real-time dynamics as well as the steady state in all these regimes. Finally, motivated by our results, we develop a novel mean-field approach, which allows us to find the solution semianalytically, and we identify parameter regimes where this approximation is in excellent agreement with our tensor network results.

Published by the American Physical Society
2024
Superconducting Qubits above 20 GHz Operating over 200 mK
Authors: Anferov Alexander , Harvey Shannon P. , Wan Fanghui , Simon Jonathan , Schuster David I.
Published: September 2024

Current state-of-the-art superconducting microwave qubits are cooled to extremely low temperatures to avoid sources of decoherence. Higher qubit operating temperatures would significantly increase the cooling power available, which is desirable for scaling up the number of qubits in quantum computing architectures and integrating qubits in experiments requiring increased heat dissipation. To operate superconducting qubits at higher temperatures, it is necessary to address both quasiparticle decoherence (which becomes significant for aluminum junctions above 160 mK) and dephasing from thermal microwave photons (which are problematic above 50 mK). Using low-loss niobium-trilayer junctions, which have reduced sensitivity to quasiparticles due to the higher superconducting transition temperature of niobium, we fabricate transmons with higher frequencies than previously studied, up to 24 GHz. We measure decoherence and dephasing times of about 1μs, corresponding to average qubit quality factors of approximately 105, and find that decoherence is unaffected by quasiparticles up to 1K. Without relaxation from quasiparticles, we are able to explore dephasing from purely thermal sources, finding that our qubits can operate up to approximately 250mK while maintaining similar performance. The thermal resilience of these qubits creates new options for scaling up quantum processors, enables hybrid quantum experiments with high heat-dissipation budgets, and introduces a material platform for even-higher-frequency qubits.

Published by the American Physical Society
2024
Solving Boolean Satisfiability Problems With The Quantum Approximate Optimization Algorithm
Authors: Boulebnane Sami , Montanaro Ashley
Published: September 2024

One of the most prominent application areas for quantum computers is solving hard constraint satisfaction and optimization problems. However, detailed analyses of the complexity of standard quantum algorithms have suggested that outperforming classical methods for these problems would require extremely large and powerful quantum computers. The quantum approximate optimization algorithm (QAOA) is designed for near-term quantum computers, yet previous work has shown strong limitations on the ability of QAOA to outperform classical algorithms for optimization problems. Here we instead apply QAOA to hard constraint satisfaction problems, where both classical and quantum algorithms are expected to require exponential time. We analytically characterize the average success probability of QAOA on a constraint satisfaction problem commonly studied using statistical physics methods: random k-SAT at the threshold for satisfiability, as the number of variables n goes to infinity. We complement these theoretical results with numerical experiments on the performance of QAOA for small n, which match the limiting theoretical bounds closely. We then compare QAOA with leading classical solvers. For random 8-SAT, we find that for more than 14 quantum circuit layers, QAOA achieves more efficient scaling than the highest-performance classical solver we tested, WalkSATlm. Our results suggest that near-term quantum algorithms for solving constraint satisfaction problems may outperform their classical counterparts.

Published by the American Physical Society
2024
Heavy fuel preparation effects on the operation of a spark ignition unmanned aerial vehicle engine
Authors: Hooper Peter
Published: September 2024

Purpose

This paper aims to conduct an experimental and theoretical investigation into fuel pre-delivery effects for a heavy fuel crankcase scavenged spark ignition two-stroke cycle engine for unmanned aerial vehicle application.

Design/methodology/approach

One-dimensional computational fluid dynamic modelling of the engine system using WAVE software supported by experimental dynamometer testing of the subject engine with kerosene JET A-1 and gasoline and fuels.

Findings

The experimental research has shown performance improvements using fuel preheating via use of auxiliary transfer port fuel injection. Computational simulation has allowed comparisons with auxiliary transfer port injection and direct in-cylinder injection to be made.

Practical implications

While some heavy fuel engines are now available for unmanned aerial vehicles the best solution to meet the military equipment single fuel policy remains an area of evolving research. The findings within this study show possibilities for fuel pre-treatment.

Originality/value

One-dimensional computational fluid dynamic modelling of the engine system using WAVE software supported by experimental dynamometer testing of the subject engine with kerosene JET A-1 and gasoline fuels.
Beeyond Foods: creating a sweet honey revolution
Authors: Boppolige Archana Anand , Fernandez Cledwyn , Saggurti Suneetha
Published: September 2024

Learning outcomes

After completion of the case study, the students will be able to[1] review the industry analysis using Porter’s five forces and strength, weakness, opportunities, threats framework and understand how a firm can achieve a competitive advantage, analyze the stakeholder theory and the salience of stakeholder mapping for enterprises with large number of stakeholders, apply the Mendelow framework of stakeholder mapping in this context and integrate it with stakeholder engagement for small enterprises and examine and evaluate how new age enterprises can engage better with stakeholders to provide a higher value creation.

Case overview/synopsis

Ayushi Srivastava started her enterprise, Beeyond Foods, in early 2021 with the aim to provide unadulterated, raw honey to consumers. She also wanted to help the beekeeping community by providing the beekeepers with a fair price for the procurement of honey from the bee hives. Beeyond Foods was a small enterprise in India that sold two variants of honey to consumers. The first variant was sourced from the Himalayan region of India, whereas the second was sourced from the Western Ghats of India. The primary distribution channel was trade fairs, where Srivastava would assemble her stall and sell honey to potential customers. Furthermore, a part of the sales was also driven by an electronic channel, which was through the company website. Customers could place their orders, and the honey would directly be delivered to their homes. With a successful start to the business, Srivastava was interested to scale her business and reach more customers. However, she was mindful that there were multiple stakeholders involved in the business. Srivastava had to study the values and needs of each stakeholder, while simultaneously formulate a strategy to expand her reach. This case study is designed to teach the concept of stakeholder value creation for small business enterprises.

Complexity academic level

This case study is well suited for an entrepreneurship and strategy course at the postgraduate (Master of Business Administration) level. This case study can also be taught in a marketing course.

Supplementary materials

Teaching notes are available for educators only.

Subject code

CSS3: Entrepreneurship.
ESG and firm performance: do stakeholder engagement, financial constraints and religiosity matter?
Authors: Ho Ly , Nguyen Van Ha , Dang Tung Lam
Published: September 2024

Purpose

This study revisits the relationship between environmental, social and governance (ESG) activities and firm performance. More importantly, it tests whether this relationship is moderated by critical yet underexplored factors such as stakeholder engagement, financial constraints, and religiosity.

Design/methodology/approach

A wide range of estimation techniques, including pooled ordinary least squares (OLS), fixed effects, system generalized method of moments (GMM) and propensity score matching-difference-in-differences (PSM-DiD), are employed to investigate such issues in a large sample of firms from 31 countries.

Findings

ESG performance has a positive and significant impact on firm performance. While stakeholder engagement positively moderates this relationship, financial constraints and religiosity negatively moderate it. Interestingly, this positive linkage is driven by environmental and social performance rather than governance performance.

Practical implications

Firms should proactively engage in ESG initiatives and consider the intervening influences of stakeholder engagement, financial constraints and religiosity in making decisions to invest in ESG activities. Furthermore, our findings can help policymakers understand the financial consequences of ESG practices, which can be helpful in designing new policies to further promote corporate engagement in ESG practices.

Originality/value

First, our research findings help reconcile the long-standing debate about the value impact of ESG. Second, our paper investigates relatively new aspects of the ESG-firm performance relationship. Third, our study offers more insight into the ESG literature by showing that not all ESG dimensions equally impact firm performance.
Does export promotion enhance firm-level intensive margin of exports? Evidence from a meta-regression analysis
Authors: Demena Binyam Afewerk
Published: September 2024

Purpose

The impact of export promotion programs (EPPs) on the intensive margin of exports remains somewhat uncertain. This study tackles a crucial question: does export promotion enhance firm-level intensive margin of exports?

Design/methodology/approach

We draw upon comprehensive empirical research conducted up to 2023. We collected 951 estimates, constructed 22 variables, captured diverse contexts and employed a meta-analytical approach to scrutinize the considerable variation in findings.

Findings

The overall meta-effect, after filtering out publication bias, is positive and statistically significant. Firms receiving EPP support exhibit an export intensity that is 1–9% higher than firms not participating in such programs. Assessing the mechanisms through which EPPs bolster this, we observe that support in the form of various services plays a more substantial role compared to assistance in the form of financial resources.

Research limitations/implications

Evaluating EPPs and their activities in terms of social welfare falls beyond the scope of this paper, which specifically focuses on the benefits of EPPs to export intensity. Subsequent research should undertake a comprehensive evaluation, considering both economic impacts and costs for accurate assessments of welfare. We also suggest that future meta-analyses explore other dimensions of firm-level performance linked to EPPs.

Practical implications

Publication bias distorts the impacts of EPPs, leading to an overstatement of their actual effects. Adjusting for publication bias, the practical significance of EPPs for a country’s trade intensity appears to be limited. Additionally, the provision of diverse activities and services primarily contributes to the amplification of export margins as compared to subsidies and grants. While larger firms initially benefit more from EPPs, these effects are found to be transitory.

Originality/value

This is the first meta-analysis scrutinizing the impact of EPPs, specifically concentrating on the firm-level intensive margin of exports.
Second language writing anxiety and ChatGPT adoption as an automated writing evaluation tool
Authors: Liu Zhifang
Published: September 2024

Purpose

This study examines the relationship between the writing anxiety experienced by English second language learners and their intention to employ ChatGPT for their academic writing as an automated writing evaluation tool. This research integrates writing anxiety as an additional variable to understand how much writing anxiety affects the perceived usefulness of ChatGPT as an automated writing evaluation tool, perceived ease of use of ChatGPT, and attitude towards using ChatGPT as an automated writing evaluation tool for their academic writing with the technology acceptance model (TAM) as a theoretical framework.

Design/methodology/approach

This is a cross-sectional study, with SEM PLS to analysis data collected from 639 undergraduate students.

Findings

This study found that writing anxiety significantly affects perceived ease of use of ChatGPT as an automated writing evaluation tool, and attitude towards using ChatGPT. Altogether they both influence students’ intention to use the ChatGPT as an automated writing evaluation tool.

Originality/value

This study contributes to the understanding of students intention to use ChatGPT as an automated writing evaluation tool when they suffer from writing anxiety.
Valeant pharmaceuticals fraud
Authors: Belanger Maude , Hounwanou Dossa Charles , Menah Koffi Sanvee , Sauvageau Isabelle , Smaili Nadia
Published: September 2024

Purpose

The aim of this study is to examine the patterns of fraud present in Valeant’s 2014 and 2015 financial statements and determine through a risk management analysis whether these frauds could have been prevented. This analysis provides the opportunity to more effectively prevent financial statement fraud.

Design/methodology/approach

Data were collected from Valeant pharmaceuticals annual reports, financial statements reports and financial authority documentation. Based on these documents, this paper analyzes the different fraud schemes and investigate whether fraud could have been detected earlier by governance actors. In particular, this paper examines the firm’s financial statements three years before the fraud was detected by the Securities and Exchange Commission.

Findings

The analysis of financial statements reveals few clues and no alarming red flags three years before detection of the fraud. However, financial statement analyses were complex because of the many acquisitions the firm made in the years before.

Originality/value

This paper aims to contribute to the literature on fraud by investigating a case of financial statement fraud.