From Vlasov-Maxwell-Landau system with Coulomb potential to two-fluid incompressible Navier-Stokes-Fourier-Maxwell system with Ohm's law

In the diffusive regime, we obtain the uniform in Knudsen number estimate on the two-species Vlasov-Maxwell-Landau system with Coulomb potential around the global equilibrium. As a consequence, we justify the limit to the two-fluid incompressible Navier-Stokes-Fourier-Maxwell (NSFM) system with Ohm's law. This is the first result on the global in time uniform in Knudsen number estimate on the Boltzmann and Landau type equations with Coulomb potential coupled Vlasov-Maxwell equations.Comment: arXiv admin note: substantial text overlap with arXiv:2308.12607, arXiv:1905.0473

Hilbert expansion for kinetic equations with non-relativistic Coulomb collision

In this paper, we study the hydrodynamic limits of both the Landau equation and the Vlasov-Maxwell-Landau system in the whole space. Our main purpose is two-fold: the first one is to give a rigorous derivation of the compressible Euler equations from the Landau equation via the Hilbert expansion; while the second one is to prove, still in the setting of Hilbert expansion, that the unique classical solution of the Vlasov-Maxwell-Landau system converges, which is shown to be globally in time, to the resulting global smooth solution of the Euler-Maxwell system, as the Knudsen number goes to zero. The main ingredient of our analysis is to derive some novel interplay energy estimates on the solutions of the Landau equation and the Vlasov-Maxwell-Landau system which are small perturbations of both a local Maxwellian and a global Maxwellian, respectively. Our result solves an open problem in the hydrodynamic limit for the Landau-type equations with Coulomb potential and the approach developed in this paper can seamlessly be used to deal with the problem on the validity of the Hilbert expansion for other types of kinetic equations

Fine features of optical potential well induced by nonlinearity

Particles trapped by optical tweezers, behaving as mechanical oscillators in an optomechanical system, have found tremendous applications in various disciplines and are still arousing research interest in frontier and fundamental physics. These optically trapped oscillators provide compact particle confinement and strong oscillator stiffness. But these features are limited by the size of the focused light spot of a laser beam, which is typically restricted by the optical diffraction limit. Here, we propose to build an optical potential well with fine features assisted by the nonlinearity of the particle material, which is independent of the optical diffraction limit. We show that the potential well shape can have super-oscillation-like features and a Fano-resonance-like phenomenon, and the width of the optical trap is far below the diffraction limit. A particle with nonlinearity trapped by an ordinary optical beam provides a new platform with a sub-diffraction potential well and can have applications in high-accuracy optical manipulation and high-precision metrology.Comment: 4 pages, 5 figure

Association of gestational age at birth with subsequent suspected Developmental Coordination Disorder in early childhood

Importance. It remains unknown whether children born at different degrees of prematurity, early-term and post-term might have a higher risk of developing Developmental Coordination Disorder (DCD) compared to completely full-term children (39-40 gestational weeks). Objective. To differentiate between suspected DCD in children with different gestational ages based on a national representative sample in China. DESIGN, SETTING, AND PARTICIPANTS We conducted a retrospective cohort study in China from 2018 to 2019. A total of 152,433 children from 2,403 public kindergartens in 551 cities of China aged 3-5 years old were included in the final analysis. The association between gestational age and motor performance was investigated. A multi-level regression model was developed to determine the strength of association for different gestational ages associated with suspected DCD when considering kindergartens as clusters. Main outcomes and measures. Children’s motor performance was assessed using the Little Developmental Coordination Disorder Questionnaire (LDCDQ), completed by parents. Gestational age was determined according to the mother’s medical records. Results. Of the 152,433 children aged 3-5 years old, 80,370 (52.7%) were male, and 72,063 (47.3%) were female. There were 45,052 children aged 3 years old (29.6%), 59,796 aged 4 years old(39.2%), and 47,585 children aged 5 years old (31.2%). The LDCDQ total scores for very-preterm (β=-1.74, 95%CI: -1.98, 1.50; p<0.001), moderately-preterm (β=-1.24, 95%CI: -1.60, -0.89; p<0.001), late-preterm (β=-0.92, 95%CI: -1.08, -0.76; p<0.001), early-term (β=-0.36, 95%CI: -0.46, -0.25; p<0.001) and post-term children (β=-0.47, 95%CI: -0.67, -0.26; p<0.001) were significantly lower than full-term children when adjusting for child, family and maternal health characteristics. The very-preterm (OR=1.35, 95%CI: 1.23,1.48; p<0.001), moderately-preterm (OR=1.18, 95%CI: 1.02, 1.36; p<0.001), late-preterm (OR =1.24, 95%CI: 1.16,1.32; p<0.001), early-term (OR =1.11, 95%CI: 1.06,1.16; p<0.001) and post-term children (OR =1.167, 95%CI: 1.07, 1.27; p<0.001) were more likely to fall in the suspected Developmental Coordination Disorder (DCD) category on the LDCDQ compared with completely full-term children after adjusting for the same characteristics. The associations between different gestational ages and suspected DCD were stronger in boys and older (5 year old) children (each p<0.05). Conclusions and relevance. We found significant associations between every degree of prematurity at birth, early-term and post-term birth with suspected DCD when compared with full-term birth. Our findings have important implications for understanding motor development in children born at different gestational ages. Long-term follow-up and rehabilitation interventions should be considered for early- and post-term born children

Challenges and Perspectives for Biosensing of Bioaerosol Containing Pathogenic Microorganisms

As an important route for disease transmission, bioaerosols have received increasing attention. In the past decades, many efforts were made to facilitate the development of bioaerosol monitoring; however, there are still some important challenges in bioaerosol collection and detection. Thus, recent advances in bioaerosol collection (such as sedimentation, filtration, centrifugation, impaction, impingement, and microfluidics) and detection methods (such as culture, molecular biological assay, and immunological assay) were summarized in this review. Besides, the important challenges and perspectives for bioaerosol biosensing were also discussed

Microstructure and Crack Distribution of Fe-Based Amorphous Alloys Manufactured by Selective Laser Melting

In this study, Fe-based amorphous alloys with a length and width of 10 mm and height of 6 mm were prepared by selective laser melting (SLM). X-ray diffraction, Differential Thermal Analysis and Scanning Electron Microscope were used to investigated the effect of scan space and strategy on the crystallization, microstructure, crack distribution and density. The content of amorphous calculated by Differential Thermal Analysis is up to 93%. There is an obviously trend to lower crack distribution and higher density with an appropriate scan spaces and strategies. With the increasing scan space, the density increased first, then gradually decreased, while the crack decreased and then increasing with the scan space.Mechanical Engineerin