Data-Driven Modeling of Landau Damping by Physics-Informed Neural Networks

Kinetic approaches are generally accurate in dealing with microscale plasma physics problems but are computationally expensive for large-scale or multiscale systems. One of the long-standing problems in plasma physics is the integration of kinetic physics into fluid models, which is often achieved through sophisticated analytical closure terms. In this study, we successfully construct a multi-moment fluid model with an implicit fluid closure included in the neural network using machine learning. The multi-moment fluid model is trained with a small fraction of sparsely sampled data from kinetic simulations of Landau damping, using the physics-informed neural network (PINN) and the gradient-enhanced physics-informed neural network (gPINN). The multi-moment fluid model constructed using either PINN or gPINN reproduces the time evolution of the electric field energy, including its damping rate, and the plasma dynamics from the kinetic simulations. For the first time, we introduce a new variant of the gPINN architecture, namely, gPINN$p$ to capture the Landau damping process. Instead of including the gradients of all the equation residuals, gPINN$p$ only adds the gradient of the pressure equation residual as one additional constraint. Among the three approaches, the gPINN$p$-constructed multi-moment fluid model offers the most accurate results. This work sheds new light on the accurate and efficient modeling of large-scale systems, which can be extended to complex multiscale laboratory, space, and astrophysical plasma physics problems.Comment: 11 pages, 7 figure

How Leadership Influences Open Government Data (OGD)-Driven Innovation: The Mediating Role of Organizational Commitment

Open government data (OGD) are considered a sustainable driver of firm innovation. Leadership is a crucial decision-maker for firms to employ OGD in innovation. The present study focuses on two of the most prominent leadership styles: transformational and transactional. Drawing on the Organizational Commitment Theory, we claim that affective and normative commitment are the two parallel mechanisms that explain how leadership promotes OGD-driven innovation in firms. Our results show that transformational leadership promotes OGD-driven radical innovation through affective commitment. In contrast, transactional leadership promotes OGD-driven incremental innovation through normative commitment. More importantly, we suggest that the OGD application stage moderates the effect of leadership on organizational commitment. Specifically, in the initial stage of the OGD application, higher transformational leadership triggers higher affective commitment in employees. In contrast, in the mature stage of OGD application, higher transactional leadership triggers higher normative commitment in employees

Combining viscosity-restricted intramolecular motion and mitochondrial targeting leads to selective tumor visualization

We report a novel fluorescent molecular conjugate, V-M1, enabling an accurate visualization of tumor tissues. The emission wavelength of V-M1 exceeds 650 nm, which is well within the near-infrared therapeutic window. Tumor accumulation of this cationic dye allows the visualization of cancerous cells as a function of mitochondrial viscosity.status: publishe

A Stimulated Emission Diagnostic Technique for Electron Temperature of the High Power Radio Wave Modified Ionosphere

We report observations of stimulated electromagnetic emission (SEE) induced by high power high frequency (HF) radio waves near the third electron gyroharmonic (3fce) at European Incoherent Scatter Radar (EISCAT). It is discovered that stimulated Brillouin scattering (SBS) spectrum behaves similarly as spectral ion lines of the incoherent scatter radar (ISR) for HF pumping frequency above 3fce. The SBS spectral width shows correlation with electron to ion temperature ratio Te/Ti. A new inversion method is proposed by incorporating the SBS spectral width within an artificial neural network approach to achieve electron temperature inversion for ionospheric turbulent plasmas. This work provides a potential new technique to diagnose parameters in the modified ionosphere when the ISR is not availabl

Microbial production of amino acid-modified spider dragline silk protein with intensively improved mechanical properties

<p>Spider dragline silk is a remarkably strong fiber with impressive mechanical properties, which were thought to result from the specific structures of the underlying proteins and their molecular size. In this study, silk protein 11R26 from the dragline silk protein of <i>Nephila clavipes</i> was used to analyze the potential effects of the special amino acids on the function of 11R26. Three protein derivatives, ZF4, ZF5, and ZF6, were obtained by site-directed mutagenesis, based on the sequence of 11R26, and among these derivatives, serine was replaced with cysteine, isoleucine, and arginine, respectively. After these were expressed and purified, the mechanical performance of the fibers derived from the four proteins was tested. Both hardness and average elastic modulus of ZF4 fiber increased 2.2 times compared with those of 11R26. The number of disulfide bonds in ZF4 protein was 4.67 times that of 11R26, which implied that disulfide bonds outside the poly-Ala region affect the mechanical properties of spider silk more efficiently. The results indicated that the mechanical performances of spider silk proteins with small molecular size can be enhanced by modification of the amino acids residues. Our research not only has shown the feasibility of large-scale production of spider silk proteins but also provides valuable information for protein rational design.</p

Convergent molecular evolution of thermogenesis and circadian rhythm in Arctic ruminants

The muskox and reindeer are the only ruminants that have evolved to survive in harsh Arctic environments. However, the genetic basis of this Arctic adaptation remains largely unclear. Here, we compared a de novo assembled muskox genome with reindeer and other ruminant genomes to identify convergent amino acid substitutions, rapidly evolving genes and positively selected genes among the two Arctic ruminants. We found these candidate genes were mainly involved in brown adipose tissue (BAT) thermogenesis and circadian rhythm. Furthermore, by integrating transcriptomic data from goat adipose tissues (white and brown), we demonstrated that muskox and reindeer may have evolved modulating mitochondrion, lipid metabolism and angiogenesis pathways to enhance BAT thermogenesis. In addition, results from co-immunoprecipitation experiments prove that convergent amino acid substitution of the angiogenesis-related gene hypoxia-inducible factor 2alpha (HIF2A), resulting in weakening of its interaction with prolyl hydroxylase domain-containing protein 2 (PHD2), may increase angiogenesis of BAT. Altogether, our work provides new insights into the molecular mechanisms involved in Arctic adaptation

A missense mutation in RRM1 contributes to animal tameness

The increased tameness to reduce avoidance of human in wild animals has been long proposed as the key step of animal domestication. The tameness is a complex behavior trait and largely determined by genetic factors. However, the underlying genetic mutations remain vague and how they influence the animal behaviors is yet to be explored. Behavior tests of a wild-domestic hybrid goat population indicate the locus under strongest artificial selection during domestication may exert a huge effect on the flight distance. Within this locus, only one missense mutation RRM1I241V which was present in the early domestic goat ~6500 years ago. Genome editing of RRM1I241V in mice showed increased tameness and sociability and reduced anxiety. These behavioral changes induced by RRM1I241V were modulated by the alternation of activity of glutamatergic synapse and some other synapse-related pathways. This study established a link between RRM1I241V and tameness, demonstrating that the complex behavioral change can be achieved by mutations under strong selection during animal domestication

Genetic basis of ruminant headgear and rapid antler regeneration

Ruminants are the only extant mammalian group possessing bony (osseous) headgear. We obtained 221 transcriptomes from bovids and cervids and sequenced three genomes representing the only two pecoran lineages that convergently lack headgear. Comparative analyses reveal that bovid horns and cervid antlers share similar gene expression profiles and a common cellular basis developed from neural crest stem cells. The rapid regenerative properties of antler tissue involve exploitation of oncogenetic pathways, and at the same time some tumor suppressor genes are under strong selection in deer. These results provide insights into the evolutionary origin of ruminant headgear as well as mammalian organ regeneration and oncogenesis