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\"From New York Times bestselling author Susan Casey, an awe-inspiring portrait of the mysterious world beneath the waves, and the men and women who seek to uncover its secrets For all of human history, the deep ocean has been a source of wonder and terror, an unknown realm that evoked a singular, compelling question: What's down there? Unable to answer this for centuries, people believed the deep was a sinister realm of fiendish creatures and deadly peril. But now, cutting-edge technologies allow scientists and explorers to dive miles beneath the surface, and we are beginning to understand this strange and exotic underworld: A place of soaring mountains, smoldering volcanoes, and valleys 7,000 feet deeper than Everest is high, where tectonic plates collide and separate, and extraordinary life forms operate under different rules. Far from a dark void, the deep is a vibrant realm that's home to pink gelatinous predators and shimmering creatures a hundred feet long and ancient animals with glass skeletons and sharks that live for half a millennium-among countless other marvels. Susan Casey is our premiere chronicler of the aquatic world. For The Underworld she traversed the globe, joining scientists and explorers on dives to the deepest places on the planet, interviewing the marine geologists, marine biologists, and oceanographers who are searching for knowledge in this vast unseen realm. She takes us on a fascinating journey through the history of deep-sea exploration, from the myths and legends of the ancient world to storied shipwrecks we can now reach on the bottom, to the first intrepid bathysphere pilots, to the scientists who are just beginning to understand the mind-blowing complexity and ecological importance of the quadrillions of creatures who live in realms long thought to be devoid of life. Throughout this journey, she learned how vital the deep is to the future of the planet, and how urgent it is that we understand it in a time of increasing threats from climate change, industrial fishing, pollution, and the mining companies that are also exploring its depths. The Underworld is Susan Casey's most beautiful and thrilling book yet, a gorgeous evocation of the natural world and a powerful call to arms\"-- Provided by publisher.

In monolayer transition-metal dichalcogenides, localized strain can be used to design nanoarrays of single photon sources. Despite strong empirical correlation, the nanoscale interplay between excitons and local crystalline structure that gives rise to these quantum emitters is poorly understood. Here, we combine room-temperature nano-optical imaging and spectroscopic analysis of excitons in nanobubbles of monolayer WSe2 with atomistic models to study how strain induces nanoscale confinement potentials and localized exciton states. The imaging of nanobubbles in monolayers with low defect concentrations reveals localized excitons on length scales of around 10 nm at multiple sites around the periphery of individual nanobubbles, in stark contrast to predictions of continuum models of strain. These results agree with theoretical confinement potentials atomistically derived from the measured topographies of nanobubbles. Our results provide experimental and theoretical insights into strain-induced exciton localization on length scales commensurate with exciton size, realizing key nanoscale structure–property information on quantum emitters in monolayer WSe2.A combination of room-temperature nano-optical imaging and spectroscopy and atomistic theory reveals highly localized exciton states in nanobubbles of localized strain in monolayer WSe2.

Chiral nematic liquid crystals are self-organized helical superstructures in which the helices can stand or lie, and lie in either a uniform or a random way; here, the helices are reversibly driven from a standing arrangement to a uniform lying arrangement and then rotated in-plane—solely by light. Manipulation of cholesteric liquid crystals This paper reports the manipulation of the helix axis accompanied by handedness inversion of an optically tunable, self-organized helical superstructure (a cholesteric liquid crystal) in three dimensions. Practical applications of chiral nematic liquid crystals (also known as cholesteric liquid crystals), rely on variation of the pitch length of these helices, or switching the helical axis between parallel or perpendicular to a substrate. This is typically achieved application electric or magnetic fields. Quan Li and colleagues now report such a manipulation using only light as a stimulus. Using this method, they achieve two-dimensional beam steering without the need for complex, multicomponent integrated systems, and they also construct a photoswitchable diffraction grating using a bilayer cell design. Chiral nematic liquid crystals—otherwise referred to as cholesteric liquid crystals (CLCs)—are self-organized helical superstructures that find practical application in, for example, thermography 1 , reflective displays 2 , tuneable colour filters 3 , 4 and mirrorless lasing 5 , 6 . Dynamic, remote and three-dimensional control over the helical axis of CLCs is desirable, but challenging 7 , 8 . For example, the orientation of the helical axis relative to the substrate can be changed from perpendicular to parallel by applying an alternating-current electric field 9 , by changing the anchoring conditions of the substrate, or by altering the topography of the substrate’s surface 10 , 11 , 12 , 13 , 14 , 15 , 16 ; separately, in-plane rotation of the helical axis parallel to the substrate can be driven by a direct-current field 17 , 18 , 19 . Here we report three-dimensional manipulation of the helical axis of a CLC, together with inversion of its handedness, achieved solely with a light stimulus. We use this technique to carry out light-activated, wide-area, reversible two-dimensional beam steering—previously accomplished using complex integrated systems 20 and optical phased arrays 21 . During the three-dimensional manipulation by light, the helical axis undergoes, in sequence, a reversible transition from perpendicular to parallel, followed by in-plane rotation on the substrate surface. Such reversible manipulation depends on experimental parameters such as cell thickness, surface anchoring condition, and pitch length. Because there is no thermal relaxation, the system can be driven either forwards or backwards from any light-activated intermediate state. We also describe reversible photocontrol between a two-dimensional diffraction state, a one-dimensional diffraction state and a diffraction ‘off’ state in a bilayer cell.

There is increased appreciation that dopamine neurons in the midbrain respond not only to reward 1 and reward-predicting cues 1 , 2 , but also to other variables such as the distance to reward 3 , movements 4 – 9 and behavioural choices 10 , 11 . An important question is how the responses to these diverse variables are organized across the population of dopamine neurons. Whether individual dopamine neurons multiplex several variables, or whether there are subsets of neurons that are specialized in encoding specific behavioural variables remains unclear. This fundamental question has been difficult to resolve because recordings from large populations of individual dopamine neurons have not been performed in a behavioural task with sufficient complexity to examine these diverse variables simultaneously. Here, to address this gap, we used two-photon calcium imaging through an implanted lens to record the activity of more than 300 dopamine neurons from the ventral tegmental area of the mouse midbrain during a complex decision-making task. As mice navigated in a virtual-reality environment, dopamine neurons encoded an array of sensory, motor and cognitive variables. These responses were functionally clustered, such that subpopulations of neurons transmitted information about a subset of behavioural variables, in addition to encoding reward. These functional clusters were spatially organized, with neighbouring neurons more likely to be part of the same cluster. Together with the topography between dopamine neurons and their projections, this specialization and anatomical organization may aid downstream circuits in correctly interpreting the wide range of signals transmitted by dopamine neurons. Two-photon calcium imaging of a large population of dopamine neurons in the ventral tegmental area of mice performing a virtual-reality navigation task reveals the organization principles of the dopamine system.

The circulation of the Southern Ocean connects ocean basins, links the deep and shallow layers of the ocean, and has a strong influence on global ocean circulation, climate, biogeochemical cycles and the Antarctic Ice Sheet. Processes that act on local and regional scales, which are often mediated by the interaction of the flow with topography, are fundamental in shaping the large-scale, three-dimensional circulation of the Southern Ocean. Recent advances provide insight into the response of the Southern Ocean to future change and the implications for climate, the carbon cycle and sea-level rise.

Vegetation composition shifts, and in particular, shrub expansion across the Arctic tundra are some of the most important and widely observed responses of high-latitude ecosystems to rapid climate warming. These changes in vegetation potentially alter ecosystem carbon balances by affecting a complex set of soil–plant–atmosphere interactions. In this review, we synthesize the literature on (a) observed shrub expansion, (b) key climatic and environmental controls and mechanisms that affect shrub expansion, (c) impacts of shrub expansion on ecosystem carbon balance, and (d) research gaps and future directions to improve process representations in land models. A broad range of evidence, including in-situ observations, warming experiments, and remotely sensed vegetation indices have shown increases in growth and abundance of woody plants, particularly tall deciduous shrubs, and advancing shrublines across the circumpolar Arctic. This recent shrub expansion is affected by several interacting factors including climate warming, accelerated nutrient cycling, changing disturbance regimes, and local variation in topography and hydrology. Under warmer conditions, tall deciduous shrubs can be more competitive than other plant functional types in tundra ecosystems because of their taller maximum canopy heights and often dense canopy structure. Competitive abilities of tall deciduous shrubs vs herbaceous plants are also controlled by variation in traits that affect carbon and nutrient investments and retention strategies in leaves, stems, and roots. Overall, shrub expansion may affect tundra carbon balances by enhancing ecosystem carbon uptake and altering ecosystem respiration, and through complex feedback mechanisms that affect snowpack dynamics, permafrost degradation, surface energy balance, and litter inputs. Observed and projected tall deciduous shrub expansion and the subsequent effects on surface energy and carbon balances may alter feedbacks to the climate system. Land models, including those integrated in Earth System Models, need to account for differences in plant traits that control competitive interactions to accurately predict decadal- to centennial-scale tundra vegetation and carbon dynamics.

In addition to human activities, this study found that topography is also an important factor affecting land surface temperature (LST). In this paper, based on Landsat 8 OLI/TIRS remote sensing images, a radiative transfer model was adopted to retrieve the LST, and a maximum likelihood method was used to remove artificial environmental interference factors, such as water bodies and built-up lands. This paper aims to analyze the influence of topographic factors, such as elevation, slope, aspect and shaded relief, on the LST of Hangzhou. By means of a statistical analysis, we obtained the quantitative relationship between these factors and constructed a multiple linear regression model of terrain factors and LST. The research revealed the following findings: (1) in the study area, elevation and slope are negatively correlated with LST, and all the factors have linear relationships with LST. (2) The relationship between aspect and LST is not significant, and high values of LST are found on the southern, southeastern and southwestern slopes; the lowest values are found on the northern slopes. (3) There is a significant linear relationship between the values of the shaded relief map and LST, and the more shadows there are, the lower the LST value will be. (4) After comprehensive analysis of the influence of the abovementioned topographic factors on the LST, it is found that shaded relief has the greatest contribution and is positively correlated with LST. The influence of shaded relief on surface thermal environment should be paid more attention in the process of surface thermal environment work. The assessment of the influence degree of shaded relief and surface thermal environment should be the premise and basis for many other studies.

Developing adaptive materials with geometries that change in response to external stimuli provides fundamental insights into the links between the physical forces involved and the resultant morphologies and creates a foundation for technologically relevant dynamic systems 1 , 2 . In particular, reconfigurable surface topography as a means to control interfacial properties 3 has recently been explored using responsive gels 4 , shape-memory polymers 5 , liquid crystals 6 – 8 and hybrid composites 9 – 14 , including magnetically active slippery surfaces 12 – 14 . However, these designs exhibit a limited range of topographical changes and thus a restricted scope of function. Here we introduce a hierarchical magneto-responsive composite surface, made by infiltrating a ferrofluid into a microstructured matrix (termed ferrofluid-containing liquid-infused porous surfaces, or FLIPS). We demonstrate various topographical reconfigurations at multiple length scales and a broad range of associated emergent behaviours. An applied magnetic-field gradient induces the movement of magnetic nanoparticles suspended in the ferrofluid, which leads to microscale flow of the ferrofluid first above and then within the microstructured surface. This redistribution changes the initially smooth surface of the ferrofluid (which is immobilized by the porous matrix through capillary forces) into various multiscale hierarchical topographies shaped by the size, arrangement and orientation of the confining microstructures in the magnetic field. We analyse the spatial and temporal dynamics of these reconfigurations theoretically and experimentally as a function of the balance between capillary and magnetic pressures 15 – 19 and of the geometric anisotropy of the FLIPS system. Several interesting functions at three different length scales are demonstrated: self-assembly of colloidal particles at the micrometre scale; regulated flow of liquid droplets at the millimetre scale; and switchable adhesion and friction, liquid pumping and removal of biofilms at the centimetre scale. We envision that FLIPS could be used as part of integrated control systems for the manipulation and transport of matter, thermal management, microfluidics and fouling-release materials. By infusing a ferrofluid into a microstructured matrix and applying a magnetic field, dynamic, multiscale topographical reconfigurations emerge, enabling functions such as colloidal self-assembly, switchable adhesion and friction, and biofilm removal.

Analysis of precipitation is important to hydrologists and forecasters over mountain, especially in the arid and semi-arid regions of the world. The distribution of precipitation and rain days are analyzed based on 31 stations during the period from 1960 to 2018 in Tianshan Mountains. The results is show that the precipitation and precipitation days is significantly affected by topography in Tianshan mountains. The pattern of precipitation is increased from southern to northern, from eastern to western. High precipitation and precipitation days are located in the Ili Valley. The precipitation and precipitation days are increase with elevation increase decrease with longitude increase. But, the relationship is different between precipitation and rain days with latitude in south and north slope over Tianshan mountains.

Aiming at the characteristics of Dem and remote sensing images, this paper proposes a method for segmentation of Dem and remote sensing images based on region growing algorithm. First, using normalization and median filtering methods to preprocess the Dem image; secondly, setting appropriate seed points and thresholds based on the region growing algorithm to perform preliminary river recognition on the Dem image. Then, on this basis, constructing the circumscribed rectangle of the valley according to the length and width attributes of the valley. Finally, according to the valley information of Dem, we aligned, corrected and segmented the remote sensing image. The research results show that this method can realize the segmentation of valleys in Dem and remote sensing images, and provides a favorable data basis for the research of valley topography and characteristics.