Tootfinder

Permeation of hydrogen across graphdiyne: molecular dynamics vs. quantum simulations and role of membrane motion
Mateo Rodr\'iguez, Jos\'e Campos-Mart\'inez, Marta I. Hern\'andez
https://arxiv.org/abs/2603.24827 https://arxiv.org/pdf/2603.24827 https://arxiv.org/html/2603.24827
arXiv:2603.24827v1 Announce Type: new
Abstract: Previous research based on electronic structure calculations and molecular dynamics (MD) simulations have demonstrated that graphdiyne (GDY) is a very suitable two-dimensional membrane for the separation of small molecules in a gas mixture of different species. However, quantum effects may play a role in the dynamics of these permeation processes when light molecules are the ones involved in the crossing of the GDY subnanometric pores. In this work we report rigorous quantum-mechanical calculations together with equivalent MD simulations of the transport of H2 molecules through a static GDY membrane, as a case study for the validity of the application to these problems of classical dynamics. The force fields employed are based on an improved Lennard-Jones formulation, with parameters optimized by means of accurate ab initio calculations. It is found that, although quantum effects are still significant at the temperatures of interest (between 250 and 350 K), MD simulations are able to reasonably reproduce the dependence of the quantum permeances with the temperature. Moreover, MD permeances computed with quantum corrections through Feynman-Hibbs effective potentials provide a lower bound to quantum permeances, while the pure classical counterpart gives an upper bound, thus leading to a well delimited range of confidence of the permeation results. Furthermore, within MD simulations it is possible to incorporate the thermal motion of the GDY layer and in this situation it is observed an enhancement of the permeances with respect to the fixed membrane case, due to a significant reduction of the permeation barriers when the GDY atoms are allowed to vibrate. It seems apparent therefore, that modeling the membrane motion is crucial to provide reliable simulations of the gas transport features.
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Sequential Counterfactual Inference for Temporal Clinical Data: Addressing the Time Traveler Dilemma
Jingya Cheng, Alaleh Azhir, Jiazi Tian, Hossein Estiri
https://arxiv.org/abs/2602.21168 https://arxiv.org/pdf/2602.21168 https://arxiv.org/html/2602.21168
arXiv:2602.21168v1 Announce Type: new
Abstract: Counterfactual inference enables clinicians to ask "what if" questions about patient outcomes, but standard methods assume feature independence and simultaneous modifiability -- assumptions violated by longitudinal clinical data. We introduce the Sequential Counterfactual Framework, which respects temporal dependencies in electronic health records by distinguishing immutable features (chronic diagnoses) from controllable features (lab values) and modeling how interventions propagate through time. Applied to 2,723 COVID-19 patients (383 Long COVID heart failure cases, 2,340 matched controls), we demonstrate that 38-67% of patients with chronic conditions would require biologically impossible counterfactuals under naive methods. We identify a cardiorenal cascade (CKD -> AKI -> HF) with relative risks of 2.27 and 1.19 at each step, illustrating temporal propagation that sequential -- but not naive -- counterfactuals can capture. Our framework transforms counterfactual explanation from "what if this feature were different?" to "what if we had intervened earlier, and how would that propagate forward?" -- yielding clinically actionable insights grounded in biological plausibility.
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Nonlocal-coupling-based control of coherence resonance in an ensemble of non-excitable oscillators
Aleksey Ryabov, Vladimir V. Semenov
https://arxiv.org/abs/2603.24210 https://arxiv.org/pdf/2603.24210 https://arxiv.org/html/2603.24210
arXiv:2603.24210v1 Announce Type: new
Abstract: It is shown that nonlocal coupling provides for controlling the collective noise-induced dynamics of non-excitable oscillators in the regime of coherence resonance. This effect is demonstrated by means of numerical simulation on an example of coupled generalized Van der Pol oscillators near the saddle-node bifurcation of limit cycles. In particular, it has been established that increasing the coupling radius allows to enhance the effect of coherence resonance which is reflected in the evolution of the dependence of the correlation time on the noise intensity and the power spectrum transformations. Nonlocal coupling is considered as an intermediate option between local and global coupling topologies which are also discussed as a tool for controlling coherence resonance.
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Prandtl number dependence of rotating internally heated convection
Rodolfo Ostilla-M\'onico, Ali Arslan
https://arxiv.org/abs/2602.21860 https://arxiv.org/pdf/2602.21860 https://arxiv.org/html/2602.21860
arXiv:2602.21860v1 Announce Type: new
Abstract: We investigate the influence of the Prandtl number ($Pr$) on penetrative internally heated convection (IHC) in both non-rotating and rotating regimes using three-dimensional direct numerical simulations. By varying $Pr$ between 0.1 and 100, we show that the global mean temperature $\langle \overline{T} \rangle$ is not very sensitive to $Pr$, and is primarily controlled by the dynamics of the unstably stratified top boundary layer. In contrast, the Prandtl number dictates the behavior of the lower, stably stratified region and affects the vertical convective heat flux $\langle \overline{wT} \rangle$. In the non-rotating case, low $Pr$ fluids exhibit a ``symmetry recovery'' where turbulent stirring agitates the stable layer, whereas high $Pr$ fluids transition toward a ``dead zone'' of suppressed fluctuations. Under rotation, we find that $\langle \overline{wT} \rangle$ is enhanced across all Prandtl numbers, though global cooling efficiency, measured by the reduction in $\langle \overline{T} \rangle$, is only improved for $Pr\ge1$ due to the emergence of Ekman pumping. These results demonstrate that while IHC shares some scaling similarities with Rayleigh-B\'enard convection at the top boundary, the internal stratification creates a unique sensitivity to $Pr$ that is critical for understanding heat transport in planetary and stellar interiors.
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From a Falun Gong publication.
A suspected ransomware attack on China’s National Supercomputing Center (NSCC) in Tianjin has raised serious concerns about the security of sensitive research data linked to the country’s aerospace, defense, and scientific programs.
https:/…

Hackers Claim Breach of China’s Supercomputing Hub, Stealing 10PB of Sensitive Military Data - Vision Times
A group of hackers claim to have breached China’s National Supercomputing Center in Tianjin and stolen more than 10 petabytes of research data, including sensitive aerospace and military simulations

Easily forgotten in this time: #Iran is still controlled by horrible criminals with no respect for the truth, human lives or dignity.
#IranProtests #IranWar

RE: https://journa.host/@samlitzinger/116256632271821780
Fetterman continues to be the biggest disappointment of a human being of this century.

A New Old Musical, Now Available in Book Form
I have written a new musical. It is also, simultaneously, an old musical. The story happened in 1537. Shakespeare wrote the central character in 1595 and disappeared him from the text in the same scene that introduced him. My piece sits in Renaissance dramatic verse arranged into two acts with song cues a composer can set for voice and chamber orchestra.

A New Old Musical, Now Available in Book Form | David Boles, Blogs
I have written a new musical. It is also, simultaneously, an old musical. The story happened in 1537. Shakespeare wrote the central character in 1595 and disappeared him from the text in the same s…

"Hot-dry extremes could hit 28% of humanity five times more often by end of century"
#Climate #ClimateChange
https://

Hot-dry extremes could hit 28% of humanity five times more often by end of century
In their current state, climate policies around the world could leave a significant chunk of the global population exposed to simultaneous extreme heat and drought over five times more often by the end of this century than during the mid-to-late 20th century.

Two-dimensional IR-Raman spectroscopy of vibrational polaritons: Role of dipole surfaces
Xinwei Ji, Tomislav Begusic, Tao E. Li
https://arxiv.org/abs/2603.24521 https://arxiv.org/pdf/2603.24521 https://arxiv.org/html/2603.24521
arXiv:2603.24521v1 Announce Type: new
Abstract: Nonlinear spectroscopy provides a unique perspective to understand time-resolved molecular dynamics under vibrational strong coupling (VSC). Herein, equilibrium-nonequilibrium cavity molecular dynamics simulations are performed to compute the two-dimensional (2D) infrared-infrared-Raman (IIR) spectroscopy of liquid water under VSC. In conventional computational chemistry practices, accurate molecular spectra are often constructed by using an advanced molecular dipole or polarizability model to post-process molecular dynamics trajectories evolved under a computationally efficient potential. By contrast, this work highlights the necessity of employing a consistent dipole surface model in both CavMD simulations and spectroscopic post-processing. While utilizing inconsistent dipole models only mildly influences the linear polariton spectrum, it severely distorts 2D spectra in wide frequency regions. With a consistent dipole-induced-dipole model, compared to the outside-cavity molecular 2D-IIR spectrum, the cavity 2D-IIR spectrum splits the OH stretch band to a pair of polariton branches along only the IR (not Raman) axis, while fading molecular signals at other frequency regions. This work provides the foundation for employing direct CavMD simulations to construct 2D spectra of realistic molecules under VSC.
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