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The optimization of laser pulse shapes is of great importance and a major challenge for laser direct-drive implosions. In this paper, we propose an efficient intelligent method to perform laser pulse optimization via hydrodynamic simulations guided by the genetic algorithm and random forest algorithm. Compared to manual optimizations, the machine-learning guided method is able to efficiently improve the areal density by a factor of 63% and reduce the in-flight-aspect ratio by a factor of 30% at the same time. A relationship between the maximum areal density and ion temperature is also achieved by the analysis of the big simulation dataset. This design method has been successfully demonstrated by the 2021 summer double-cone ignition experiments conducted at the SG-II upgrade laser facility and has great prospects for the design of other inertial fusion experiments.
The vertebrate retina contains a large number of different types of neurons that can be distinguished by their morphological properties. Assuming that no location should be without a contribution from the circuitry and function linked to a specific type of neuron, it is expected that the dendritic trees of neurons belonging to a type will cover the retina in a regular manner. Thus, for most types of neurons, the contribution to visual processing is thought to be independent of the exact location of individual neurons across the retina. Here, we have investigated the distribution of AII amacrine cells in rat retina. The AII is a multifunctional amacrine cell found in mammals and involved in synaptic microcircuits that contribute to visual processing under both scotopic and photopic conditions. Previous investigations have suggested that AIIs are regularly distributed, with a nearest-neighbor distance regularity index of ~4. It has been argued, however, that this presumed regularity results from treating somas as points, without taking into account their actual spatial extent which constrains the location of other cells of the same type. When we simulated random distributions of cell bodies with size and density similar to real AIIs, we confirmed that the simulated distributions could not be distinguished from the distributions observed experimentally for AIIs in different regions and eccentricities of the retina. The developmental mechanisms that generate the observed distributions of AIIs remain to be investigated.
Hypertension represents one of the most common pre-existing conditions and comorbidities in Coronavirus disease 2019 (COVID-19) patients. To explore whether hypertension serves as a risk factor for disease severity, a multi-centre, retrospective study was conducted in COVID-19 patients. A total of 498 consecutively hospitalised patients with lab-confirmed COVID-19 in China were enrolled in this cohort. Using logistic regression, we assessed the association between hypertension and the likelihood of severe illness with adjustment for confounders. We observed that more than 16% of the enrolled patients exhibited pre-existing hypertension on admission. More severe COVID-19 cases occurred in individuals with hypertension than those without hypertension (21% vs. 10%, P = 0.007). Hypertension associated with the increased risk of severe illness, which was not modified by other demographic factors, such as age, sex, hospital geological location and blood pressure levels on admission. More attention and treatment should be offered to patients with underlying hypertension, who usually are older, have more comorbidities and more susceptible to cardiac complications.
Aggressive behaviour is common in animals and typically has lifetime consequences. As younger males have higher residual reproductive value than older males and lose more from injuries than older males do, the propensity for fighting tends to increase with age in many empirical reports and species. However, fighting patterns in those empirical reports cannot confirm the hypothesis that individuals cannot readily inflict injuries on their opponents. To address this shortcoming, a parasitoid wasp species, Anastatus disparis (Hymenoptera: Eupelmidae), was used as an experimental model to explore the characteristics of aggression from a life-history perspective; this wasp exhibits extreme fighting, resulting in contestants experiencing injury and death. Results showed that the energetic costs of fighting to injury significantly shortened life and caused the loss of most mating ability. Inconsistent with general predictions, the frequency and intensity of fighting in A. disparis significantly decreased with male age. Further study results showed significantly more young males were received by and successfully mated with virgin females, and most genes related to energy metabolism were downregulated in aged males. Our study provided supporting evidence that young A. disparis males show more aggression likely because of their resource holding potential and sexual attractiveness decline with age.
To determine whether a potassium dihydrogen phosphate (KDP) surface mitigated by micro-milling would potentially threaten downstream optics, we calculated the light-field modulation based on angular spectrum diffraction theory, and performed a laser damage test on downstream fused silica. The results showed that the downstream light intensification caused by a Gaussian mitigation pit of 800 μm width and 10 μm depth reached a peak value near the KDP rear surface, decreased sharply afterward, and eventually kept stable with the increase in downstream distance. The solved peak value of light intensification exceeded 6 in a range 8–19 mm downstream from the KDP rear surface, which is the most dangerous for downstream optics. Laser damage sites were then induced on the fused silica surface in subsequent laser damage tests. When the distance downstream was greater than 44 mm with a downstream light intensification of less than 3, there were no potential damage threats to downstream optics. The study proves that a mitigated KDP surface can cause laser damage to downstream optical components, to which attention should be paid in an actual application. Through this work, we find that the current manufacturing process and the mitigation index still need to be improved. The research methods and calculation models are also of great reference significance for related studies like optics mitigation and laser damage.
Bipolar disorder is a highly heritable polygenic disorder. Recent
enrichment analyses suggest that there may be true risk variants for
bipolar disorder in the expression quantitative trait loci (eQTL) in the
We sought to assess the impact of eQTL variants on bipolar disorder risk
by combining data from both bipolar disorder genome-wide association
studies (GWAS) and brain eQTL.
To detect single nucleotide polymorphisms (SNPs) that influence
expression levels of genes associated with bipolar disorder, we jointly
analysed data from a bipolar disorder GWAS (7481 cases and 9250 controls)
and a genome-wide brain (cortical) eQTL (193 healthy controls) using a
Bayesian statistical method, with independent follow-up replications. The
identified risk SNP was then further tested for association with
hippocampal volume (n = 5775) and cognitive performance
(n = 342) among healthy individuals.
Integrative analysis revealed a significant association between a brain
eQTL rs6088662 on chromosome 20q11.22 and bipolar disorder (log Bayes
factor = 5.48; bipolar disorder P =
5.85×10–5). Follow-up studies across multiple independent
samples confirmed the association of the risk SNP (rs6088662) with gene
expression and bipolar disorder susceptibility (P =
3.54×10–8). Further exploratory analysis revealed that
rs6088662 is also associated with hippocampal volume and cognitive
performance in healthy individuals.
Our findings suggest that 20q11.22 is likely a risk region for bipolar
disorder; they also highlight the informative value of integrating
functional annotation of genetic variants for gene expression in
advancing our understanding of the biological basis underlying complex
disorders, such as bipolar disorder.
In this work, sulfurizing metal precursors prepared by magnetron sputtering was applied in Cu2ZnSnS4 (CZTS) thin film fabrication. Three precursor structures, namely substrate/ Zn/(Cu&Sn), substrate/Zn/Cu/Sn/Cu and substrate/Zn/Sn/Cu, were compared for their synthesized CZTS film quality. It is notable that CZTS film made of the precursor structure of substrate/Zn/(Cu&Sn) has the best film quality with no obvious voids and biggest average grain size. When applying this precursor structure into device fabrication, a working CZTS device with an efficiency of 2.26% was made. The impact of metal precursors on the structural property of CZTS film were characterised by SEM, XRD, Raman and TEM. Thick MoS2 interfacial layer (∼200nm) between absorber and back Mo contact and ZnS formed in the front and back absorber regions are the possible reasons limiting short-circuit current and fill factor of the cell.
Secondary phases are likely to occur in the Cu2ZnSnS4 (CZTS) films since the CZTS is thermodynamically stable in only a narrow region of the phase diagram. The CZTS solar cell performance can be influenced by the existence and precipitated position of secondary phases. Therefore, locally investigate the distribution of secondary phases is important to further improve CZTS solar cell efficiency. In this study, two different kinds of transmission electron microscopy imaging techniques, bright field scanning TEM image (BF-STEM) and High-angle annular dark-field (HAADF) image, are applied to analyze the distribution of secondary phases. Due to the atomic number differences between CZTS and secondary phases, secondary phases are evident in the HAADF images. Therefore, HAADF image is a more powerful and convenient method to analyze the secondary phases than the BF-STEM image.
A simple empirical method that extracts the elastic moduli of both thin films and the underlying substrates is proposed and validated by both new nanoindentation experiments and published data. Deconvolution of thin film’s elastic properties from the substrate is achieved by statistical estimation, where a simple function relating the elastic moduli of the thin film and substrate to the film-substrate composite modulus is used to fit the experimental data plotted against the logarithmic indentation depth normalized by film thickness. Experimental data from a wide range of soft and hard films on substrate were used to demonstrate the deconvolution and validate the method. The estimated elastic moduli of thin films and substrates agree well with their corresponding standard values or values obtained by other methods. The advantages of this method are discussed, and recommendations are made on how to design experiments to obtain reliable data for this method.
In the development of MAVs, there are three main approaches, which are based on flapping-wings, rotating wings, and fixed wings for generating lift. We focus on the fixed, flexible-wing aerodynamics in this chapter. It is well known that flying animals typically have flexible wings to adapt to the flow environment. Birds have different layers of feathers, all flexible and often connected to each other. Hence, they can adjust the wing planform for a particular flight mode. The flapping modes of bats are more complicated than those of birds. Bats have more than two dozen independently controlled joints in the wing (Swartz, 1997) and highly deforming bones (Swartz et al., 1992) that enable them to fly at either a positive or a negative AoA, to dynamically change wing camber, and to create a complex 3D wing topology to achieve extraordinary flight performance. Bats have compliant thin-membrane surfaces, and their flight is characterized by highly unsteady and 3D wing motions (Figure 3.1). Measurements by Tian et al. (2006) have shown that bats exhibit highly articulated motion, in complete contrast to the relatively simple flapping motion of birds and insects. They have shown that bats can execute a 180° turn in a compact and fast manner: flying in and turning back in the space of less than one half of its wingspan and accomplishing the turn within three wing beats with turn rates exceeding 200°/s.
Low Reynolds number aerodynamics is important to a number of natural and man-made flyers. Birds, bats, and insects have been of interest to biologists for years, and active study in the aerospace engineering community, motivated by interest in micro air vehicles (MAVs), has been increasing rapidly. The focus of this book is the aerodynamics associated with fixed and flapping wings. The book considers both biological flyers and MAVs, including a summary of the scaling laws which relate the aerodynamics and flight characteristics to a flyer's sizing on the basis of simple geometric and dynamics analyses, structural flexibility, laminar-turbulent transition, airfoil shapes, and unsteady flapping wing aerodynamics. The interplay between flapping kinematics and key dimensionless parameters such as the Reynolds number, Strouhal number, and reduced frequency is highlighted. The various unsteady lift enhancement mechanisms are also addressed.
Low Reynolds number aerodynamics is important to a number of natural and manmade flyers. Birds, bats, and insects have been of interest to biologists for years, and active study in the aerospace engineering community has been increasing rapidly. Part of the reason is the advent of micro air vehicles (MAVs). With a maximal dimension of 15 cm and nominal flight speeds of around 10 m/s, MAVs are capable of performing missions such as environmental monitoring, survelliance, and assessment in hostile environments. In contrast to civilian transport and many military flight vehicles, these small flyers operate in the low Reynolds number regime of 105 or lower. It is well established that the aerodynamic characteristics, such as the lift-to-drag ratio of a flight vehicle, change considerably between the low and high Reynolds number regimes. In particular, flow separation and laminar–turbulent transition can result in substantial change in effective airfoil shape and reduce aerodynamic performance. Because these flyers are lightweight and operate at low speeds, they are sensitive to wind gusts. Furthermore, their wing structures are flexible and tend to deform during flight. Consequently, the aero/fluid and structural dynamics of these flyers are closely linked to each other, making the entire flight vehicle difficult to analyze.
The primary focus of this book is on the aerodynamics associated with fixed and flapping wings. Chapter 1 offers a general introduction to low Reynolds number flight vehicles, considering both biological flyers and MAVs, followed by a summary of the scaling laws, which relate the aerodynamics and flight characteristics to a flyer's size on the basis of simple geometric and dynamics analyses.
Bird, bat, and insect flight has fascinated humans for many centuries. As enthusiastically observed by Dial (1994), most species of animals fly. There are nearly a million species of flying insects, and of the living 13,000 warm-blooded vertebrate species (i.e., birds and mammals), 10,000 (9000 birds and 1000 bats) have taken to the skies. With respect to maneuvering a body efficiently through space, birds represent one of nature's finest locomotion experiments. Although aeronautical technology has advanced rapidly over the past 100 years, nature's flying machines, which have evolved over 150 million years, are still impressive. Considering that humans move at top speeds of 3–4 body lengths per second, a race horse runs approximately 7 body lengths per second, a cheetah accomplishes 18 body lengths per second (Norberg, 1990), a supersonic aircraft such as the SR-71, “Blackbird,” traveling near Mach 3 (~2000 mph) covers about 32 body lengths per second, it is amazing that a common pigeon (Columba livia) frequently attains speeds of 50 mph, which converts to 75 body lengths per second. A European starling (Sturnus vulgaris) is capable of flying at 120 body lengths per second, and various species of swifts are even more impressive, over 140 body lengths per second. The roll rate of highly aerobatic aircraft (e.g., the A-4 Skyhawk) is approximately 720°/s, and a Barn Swallow (Hirundo rustics) has a roll rate in excess of 5000°/s. The maximum positive G-forces permitted in most general aviation aircraft is 4–5 G and select military aircraft withstand 8–10 G.