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Closed Unstretchable Knotless Ribbons and the Wunderlich Functional
Get PDFIn 1962, Wunderlich published the article "On a developable Mobius band," in which he attempted to determine the equilibrium shape of a free standing Mobius band. In line with Sadowsky's pioneering works on Mobius bands of infinitesimal width, Wunderlich used an energy minimization principle, which asserts that the equilibrium shape of the Mobius band has the lowest bending energy among all possible shapes of the band. By using the developability of the band, Wunderlich reduced the bending energy from a surface integral to a line integral without assuming that the width of the band is small. Although Wunderlich did not completely succeed in determining the equilibrium shape of the Mobius band, his dimensionally reduced energy integral is arguably one of the most important developments in the field. In this work, we provide a rigorous justification of the validity of the Wunderlich integral and fully formulate the energy minimization problem associated with finding the equilibrium shapes of closed bands, including both orientable and nonorientable bands with arbitrary number of twists. This includes characterizing the function space of the energy functional, dealing with the isometry and local injectivity constraints, and deriving the Euler-Lagrange equations. Special attention is given to connecting edge conditions, regularity properties of the deformed bands, determination of the parameter space needed to ensure that the deformation is surjective, reduction in isometry constraints, and deriving matching conditions and jump conditions associated with the Euler-Lagrange equations.journal articl
miR2118-dependent U-rich phasiRNA production in rice anther wall development
Get PDFReproduction-specific small RNAs are vital regulators of germline development in animals and plants. MicroRNA2118 (miR2118) is conserved in plants and induces the production of phased small interfering RNAs (phasiRNAs). To reveal the biological functions of miR2118, we describe here rice mutants with large deletions of the miR2118 cluster. Our results demonstrate that the loss of miR2118 causes severe male and female sterility in rice, associated with marked morphological and developmental abnormalities in somatic anther wall cells. Small RNA profiling reveals that miR2118-dependent 21-nucleotide (nt) phasiRNAs in the anther wall are U-rich, distinct from the phasiRNAs in germ cells. Furthermore, the miR2118-dependent biogenesis of 21-nt phasiRNAs may involve the Argonaute proteins OsAGO1b/OsAGO1d, which are abundant in anther wall cell layers. Our study highlights the site-specific differences of phasiRNAs between somatic anther wall and germ cells, and demonstrates the significance of miR2118/U-phasiRNA functions in anther wall development and rice reproduction.journal articl
Approaching isotropic transfer integrals in crystalline organic semiconductors
Get PDFDynamic disorders, which possess a finite charge delocalization, play a critical role in the charge transport properties of high-mobility molecular organic semiconductors. The use of two-dimensional (2D) charge transport in crystalline organic semiconductors can effectively facilitate reducing the sensitivity of charge carriers to thermal energetic disorders existing in even single crystals to enhance the carrier mobility. An isotropic transfer integral among adjacent molecules enables a dimensional transition from quasi-one-dimensional to 2D for charge transport among molecules. Herein, a tuned molecular packing, especially molecular rotation, was achieved in highly crystalline organic thin films via a brush-coating method. This tuned molecular packing was favorable for approaching isotropic transfer integrals. Consequently, high-performance organic transistors with a carrier mobility up to 21.5cm2V−1s−1 and low angle dependence were obtained. This work presents a unique modulation of molecular packing at the molecular scale to enable less sensitivity of the charge transport to dynamic disorders, providing an alternative route for enhancing the electrical performance of organic electronic devices.journal articl
Nickel Complexes of New Electron-Rich, Sterically-Hindered PNP Pincer Ligands
Get PDFOkinawa Institute of Science and Technology Graduate UniversityDoctor of PhilosophyThis thesis describes the synthesis, characterization and reactivity studies of nickel complexes of a new family of electron-rich, bulky PNP pincer ligands (PNP = 2,6-{R2PC(CH3)2}2-pyridine). The first chapter introduces the literature review of pincer complexes with a focus on nickel complexes and their applications. The second chapter introduces a new family of pyridine-based PNP pincer ligands that are based on the classic PNP framework, explores how the modified ligand influences the behavior of nickel complexes, and describes examples of mostly metal-based reactivity. This chapter mainly focuses on how this new family of PNP ligands can remain unreactive under specific reductive conditions, which allows the stabilization of complexes having unusual oxidation state of the metal center. The third chapter explores how it is possible to induce new types of ligand-based reactivity on the PNP pincer framework by blocking classical modes of metal-ligand cooperation, and how changes in the electronics and steric properties of the complex can lead to switching from metal-based reactivity to ligand-based reactivity
A claustrum in reptiles and its role in slow-wave sleep
Get PDFThe mammalian claustrum, owing to its widespread connectivity with other forebrain structures, has been hypothesized to mediate functions that range from decision-making to consciousness(1). Here we report that a homologue of the claustrum, identified by single-cell transcriptomics and viral tracing of connectivity, also exists in a reptile-the Australian bearded dragon Pogona vitticeps. In Pogona, the claustrum underlies the generation of sharp waves during slow-wave sleep. The sharp waves, together with superimposed high-frequency ripples(2), propagate to the entire neighbouring pallial dorsal ventricular ridge (DVR). Unilateral or bilateral lesions of the claustrum suppress the production of sharp-wave ripples during slow-wave sleep in a unilateral or bilateral manner, respectively, but do not affect the regular and rapidly alternating sleep rhythm that is characteristic of sleep in this species(3). The claustrum is thus not involved in the generation of the sleep rhythm itself. Tract tracing revealed that the reptilian claustrum projects widely to a variety of forebrain areas, including the cortex, and that it receives converging inputs from, among others, areas of the mid- and hindbrain that are known to be involved in wake-sleep control in mammals(4-6). Periodically modulating the concentration of serotonin in the claustrum, for example, caused a matching modulation of sharp-wave production there and in the neighbouring DVR. Using transcriptomic approaches, we also identified a claustrum in the turtle Trachemys scripta, a distant reptilian relative of lizards. The claustrum is therefore an ancient structure that was probably already present in the brain of the common vertebrate ancestor of reptiles and mammals. It may have an important role in the control of brain states owing to the ascending input it receives from the mid- and hindbrain, its widespread projections to the forebrain and its role in sharp-wave generation during slow-wave sleep.journal articl
What is AI? Applications of artificial intelligence to dermatology
Get PDFIn the past, the skills required to make an accurate dermatological diagnosis have required exposure to thousands of patients over many years. However, in recent years, artificial intelligence (AI) has made enormous advances, particularly in the area of image classification. This has led computer scientists to apply these techniques to develop algorithms that are able to recognize skin lesions, particularly melanoma. Since 2017, there have been numerous studies assessing the accuracy of algorithms, with some reporting that the accuracy matches or surpasses that of a dermatologist. While the principles underlying these methods are relatively straightforward, it can be challenging for the practising dermatologist to make sense of a plethora of unfamiliar terms in this domain. Here we explain the concepts of AI, machine learning, neural networks and deep learning, and explore the principles of how these tasks are accomplished. We critically evaluate the studies that have assessed the efficacy of these methods and discuss limitations and potential ethical issues. The burden of skin cancer is growing within the Western world, with major implications for both population skin health and the provision of dermatology services. AI has the potential to assist in the diagnosis of skin lesions and may have particular value at the interface between primary and secondary care. The emerging technology represents an exciting opportunity for dermatologists, who are the individuals best informed to explore the utility of this powerful novel diagnostic tool, and facilitate its safe and ethical implementation within healthcare systems. What is already known about this topic? There is considerable interest in the application of artificial intelligence to medicine. Several publications in recent years have described computer algorithms that can diagnose melanoma or skin lesions. Multiple groups have independently evaluated algorithms for the diagnosis of melanoma and skin lesions. What does this study add? We combine an introduction to the field with a summary of studies comparing dermatologists against artificial intelligence algorithms with the aim of providing a comprehensive resource for clinicians. This review will equip clinicians with the relevant knowledge to critically appraise future studies, and also assess the clinical utility of this technology. A better informed and engaged cohort of clinicians will ensure that the technology is applied effectively and ethically.journal articl
Unravelling spiral cleavage
Get PDFSnails, earthworms and flatworms are remarkably different animals, but they all exhibit a very similar mode of early embryogenesis: spiral cleavage. This is one of the most widespread developmental programs in animals, probably ancestral to almost half of the animal phyla, and therefore its study is essential for understanding animal development and evolution. However, our knowledge of spiral cleavage is still in its infancy. Recent technical and conceptual advances, such as the establishment of genome editing and improved phylogenetic resolution, are paving the way for a fresher and deeper look into this fascinating early cleavage mode.journal articl
Effects of habitat loss on the genetic diversity of Embiratermes neotenicus (Isoptera) in a fragmented landscape of the Atlantic Forest, Brazil
Get PDF1. Connectivity loss during habitat fragmentation poses a serious threat to global biodiversity. The effects of this process depend on factors such as the dispersal ability and breeding systems of each species, the type of land use surrounding the habitat remnants and the position of fragments in the landscape.
2. Termites are abundant in tropical ecosystems, and within this group, soil-feeding species are the most sensitive to environmental degradation.
3. We investigated whether the fragmentation of the Atlantic Forest that occurred approximately 110 years ago because of sugarcane plantations in Northeast Brazil affected the genetic diversity of a population of Embiratermes neotenicus (Termitidae: Syntermitinae) in 14 fragments separated by 3–104 m over an extent of 20 km.
4. For 10 nests in each fragment, 10 individuals (n = 1400) were genotyped at five microsatellite loci. Our results show that the population exhibits weak genetic structure, with no relations between genetic variability and fragment features.
5. This result may be explained by the extraordinarily long lifespan of individual colonies, given this species’ peculiar breeding system, offering several opportunities for dispersal events and patch colonisation.
6. Landscape features such as the arrangement of forest fragments and seasonal nature of the sugarcane matrix could enable this species to maximise dispersal success and avoid local extinction.journal articl
TREEasy: An automated workflow to infer gene trees, species trees, and phylogenetic networks from multilocus data
Get PDFMultilocus genomic data sets can be used to infer a rich set of information about the evolutionary history of a lineage, including gene trees, species trees, and phylogenetic networks. However, user-friendly tools to run such integrated analyses are lacking, and workflows often require tedious reformatting and handling time to shepherd data through a series of individual programs. Here, we present a tool written in Python-TREEasy-that performs automated sequence alignment (with MAFFT), gene tree inference (with IQ-Tree), species inference from concatenated data (with IQ-Tree and RaxML-NG), species tree inference from gene trees (with ASTRAL, MP-EST, and STELLS2), and phylogenetic network inference (with SNaQ and PhyloNet). The tool only requires FASTA files and nine parameters as inputs. The tool can be run as command line or through a Graphical User Interface (GUI). As examples, we reproduced a recent analysis of staghorn coral evolution, and performed a new analysis on the evolution of the "WGD clade" of yeast. The latter revealed novel patterns that were not identified by previous analyses. TREEasy represents a reliable and simple tool to accelerate research in systematic biology (https://github.com/MaoYafei/TREEasy).journal articl
沖縄県におけるヒアリの侵入・蔓延時に推定される経済的損失
Get PDFハワイにヒアリSolenopsis invictaが侵入・定着した場合の経済的損失額を推定した既存文献をもとに、沖縄県にヒアリが侵入・蔓延した場合の経済的損失額を推定した。試算は、行政による根絶や分布拡大防止のための積極的な対策が行われず、ヒアリは沖縄県の生息可能な地域全域に拡大したと仮定して行った。その結果、市民生活や農業、インフラ整備、ゴルフ・リゾート等の娯楽に係る損害と、行政による最小限の対策費用を足し合わせた直接的な経済的損失は、約192億4,800万円と算出された。またヒアリによって阻害される、地域住民および旅行者による野外活動の経済的価値は、約246億1,000万円と算出された。合計で、年間の損失額は約438億5,800万円と推定された。本試算結果は、ヒアリ対策の必要性や予算を検討するにあたって、その経済的インパクトを評価する重要性を示すものである。ただし、日米間の社会構造の違いなどのため評価しきれなかった部分も多く、日本におけるより正確な被害額の推定のためにはさらなる精査が必要である。journal articl