bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Airworthiness of Supersonic Aircraft
Authors: Black H. C. 
Published: June 2018

SummaryThe safety target for the Supersonic Transport has been set by the governments sponsoring the project. This is to achieve a safety level at least as good as that of subsonic aircraft at the same time. An analysis of present accident trends is used to give more precision to this statement. If the present rate of improvement in safety continues, the accident rate in the early 1970's can be expected to be some 20% to 25% below today's figures and the target for the SST must be for an improvement of at least 30%. To achieve improvements of this order in a safety record which is already good requires considerable effort by all concerned and necessitates a more scientific approach to safety requirements, especially airworthiness requirements. Some examples of the way this is being done in the United Kingdom and f ranee are given.
Rotary Inertia and Shear in Beam Vibration Treated by the Ritz Method
Authors: Dawson B. 
Published: June 2018

SummaryThe natural frequencies of vibration of a cantilever beam allowing for rotary inertia and shear deformation are obtained by the approximate Ritz method.The workability of the method is dependent upon the approximating functions chosen for the dynamic displacement curves. A series of characteristic functions representing the normal modes of vibration of cantilever beams in simple flexure is used as the approximating functions for both deflections due to flexure and shear deformation. Good agreement is shown between frequencies obtained by the Ritz method and those resulting from an analytical solution.The effect upon the natural frequencies of allowing for rotary inertia alone is shown and it is seen to increase rapidly with mode number.
Periodic solutions for indefinite singular perturbations of the relativistic acceleration
Authors: Bereanu Cristian , Zamora Manuel 
Published: June 2018

Using the Leray–Schauder degree, we study the existence of solutions for the following periodic differential equation with relativistic acceleration and singular nonlinearity:where μ > 1 and the weight h: [0, T] → ℝ is a continuous sign-changing function. There are no a priori estimates on the set of positive solutions (a condition used in general to apply the Leray–Schauder degree), and we prove that no solution of the equation appears on the boundary of an unbounded open set during the deformation to an autonomous problem.
Syndromic surveillance and its utilisation for mass gatherings
Authors: Berry A.C. 
Published: June 2018

AbstractTremendous advancements in syndromic surveillance strategies over the last two decades, and specifically from prior mass gatherings, have been incorporated into day-to-day healthcare analysis worldwide and have left a lasting indirect impact since their inception. Mass gatherings are a daily occurrence worldwide and provide a scenario ripe for public health aims and objectives utilising syndromic surveillance. Europe is less than a decade away from hosting a colossal worldwide gathering (2024 Summer Olympics) in likely a time when the global agreement is in flux. A call to arms is needed for additional surveillance strategies incorporating mobile application symptom checker data, telemedicine, social media and social data sensing. There remains a need for an optimal combination of real-time data sensing that captures the whole population, but to reach that goal we must incorporate new advancements into baseline epidemiologic data monitoring, otherwise we will be tracking real-time mass gathering events on top of inaccurate baseline epidemiologic data.
Suicide on Instagram – Content Analysis of a German Suicide-Related Hashtag
Authors: Arendt Florian 
Published: June 2018

Abstract. Background: Suicide is the second leading cause of death among 15–29-year-olds globally. Unfortunately, the suicide-related content on Instagram, a popular social media platform for youth, has not received the scholarly attention it deserves. Method: The present study provides a content analysis of posts tagged as #selbstmord, a German suicide-related hashtag. These posts were created between July 5 and July 11, 2017. Results: Approximately half of all posts included words or visuals related to suicide. Cutting was by far the most prominent method. Although sadness was the dominant emotion, self-hate and loneliness also appeared regularly. Importantly, inconsistency – a gap between one's inner mental state (e.g., sadness) and one's overtly expressed behavior (e.g., smiling) – was also a recurring theme. Conversely, help-seeking, death wishes, and professional awareness–intervention material were very rare. An explorative analysis revealed that some videos relied on very fast cutting techniques. We provide tentative evidence that users may be exposed to purposefully inserted suicide-related subliminal messages (i.e., exposure to content without the user's conscious awareness). Limitations: We only investigated the content of posts on one German hashtag, and the sample size was rather small. Conclusion: Suicide prevention organizations may consider posting more awareness–intervention materials. Future research should investigate suicide-related subliminal messages in social media video posts. Although tentative, this finding should raise a warning flag for suicide prevention scholars.
Why Are Some Rocky Mountain Lakes Ephemeral?
Authors: Liefert David T. , Shuman Bryan N. , Parsekian Andrew D. , Mercer Jason J. 
Published: June 2018

AbstractSmall mountain lakes function as temporary storage basins for rain and snowmelt‐derived water. Many small lakes lose water seasonally, but questions remain about the processes involved and effects on watershed hydrology. Evaporation and groundwater outflow from lakes may influence baseflow in streams, hydrologic connections among lakes, and water fluxes from a watershed. To evaluate the role of small mountain lakes in watershed hydrology and the dominant pathways of water loss, we studied the water balances of four shallow, closed‐basin, subalpine lakes in southern Wyoming that lose up to 99% of their volumes between early summer and late fall. We tested the performance of seven evaporation models, compared observed rates of water loss with simulations of evaporation and drainage, and conducted geophysical surveys to evaluate the hydrologic environment between lakes. Our results show that groundwater outflow, rather than evaporation, can dominate water loss and cause closed‐basin mountain lakes to be ephemeral. Groundwater fluxes may contribute to varied rates and timing of water loss from the lakes. Evaporation accounted for 14% of water loss in a lake that overlays thin (<0.5 m) sediments and fractured bedrock and 83% in a lake underlain by >3 m of sediments and clay. Gradual recharge of groundwater (<18,000 m3·km−2·day−1) from each study lake likely helps sustain baseflow in streams once snowmelt has subsided. Total water loss from closed‐basin, subalpine lakes may therefore help to maintain baseflow of rivers in late summer, but their impact varies based on geological context and snowmelt availability.
The Seasonality of Physically Driven Export at Submesoscales in the Northeast Atlantic Ocean
Authors: Erickson Zachary K. , Thompson Andrew F. 
Published: June 2018

Submesoscale dynamics
(1–100 km) are associated with enhanced vertical velocities and evolve on a time scale similar to that of biological production (hours to days). Here we consider an annual cycle of submesoscale dynamics and their relation to productivity and export in a small (20 × 20 km) region of the northeast Atlantic Ocean. In this region, a springtime bloom is initiated by restratification of the mixed layer in June, although intermittent shoaling of the mixed layer maintains phytoplankton populations throughout the year. An optical community index suggests a dominance of large species (e.g., diatoms) during spring and picophytoplankton during the winter. We review three types of submesoscale instabilities—mixed layer (baroclinic), gravitational, and symmetric—and consider the impact of each on export of fixed carbon out of the surface layer. Mixed layer instabilities can potentially export material out of the mixed layer during winter, although the vertical velocity across the base of the mixed layer is sensitive to the parameterization scheme. Symmetric instabilities, in contrast, provide a clear mechanism for rapid export out of the mixed layer. A crucial factor determining export potential is the strength of the pycnocline at the base of the mixed layer. Export production is sensitive to the degree of overlap that exists between intense submesoscale activity associated with deep mixed layers in the winter and high productivity associated with the spring restratification, meaning that physically driven export of fixed carbon will likely happen over a short time window during spring.
Holocene Ice‐Flow Speedup in the Vicinity of the South Pole
Authors: Lilien David A. , Fudge T. J. , Koutnik Michelle R. , Conway Howard , Osterberg Erich C. , Ferris David G. , Waddington Edwin D. , Stevens C. Max 
Published: June 2018

AbstractThe South Pole Ice Core (SPICEcore) was drilled at least 180 km from an ice‐flow divide. Thus, the annual‐equivalent layer thicknesses in the core are affected by spatial variations in accumulation upstream in addition to temporal variations in regional accumulation. We use a new method to compare the SPICEcore accumulation record, derived by correcting measured layer thicknesses for thinning, with an accumulation record derived from new GPS and radar measurements upstream. When ice speeds are modeled as increasing by 15% since 10 ka, the upstream accumulation explains 77% of the variance in the SPICEcore‐derived accumulation (versus 22% without speedup). This result demonstrates that the ice‐flow direction and spatial pattern of accumulation were stable throughout the Holocene. The 15% speedup in turn suggests a slight (3–4%) steepening or thickening of the ice‐sheet interior and provides a new constraint on the evolution of the East Antarctic Ice Sheet following the glacial termination.
Insight Into Radio‐Isotope 129I Deposition in Fresh Snow at a Remote Glacier Basin of Northeast Tibetan Plateau, China
Authors: Dong Zhiwen , Shao Yaping , Qin Dahe , Zhang Luyuan , Hou Xiaolin , Wei Ting , Kang Shichang , Qin Xiang 
Published: June 2018

AbstractWe present data of 129I deposition in fresh snow in the Laohugou glacier basin, northeast Tibetan Plateau, in summer 2016 and 2017, and trace its source and elevational distribution in the troposphere. Our results show that the 129I/127I atomic ratios in the fresh snow on the glacier surface are about 2 orders of magnitude larger than those in the Antarctic fresh snow and 4 orders the prenuclear level, indicating a predominantly anthropogenic source of the 129I in the mountain glacier environment of northeast Tibetan Plateau. The 129I level in the Laohugou glacier basin is 1–2 orders of magnitude lower than at representative European locations, and not significantly higher than that observed at other sites in Asia. The 129I/127I atomic ratio and 129I level show clear increases with elevation from 4,300 to 5,100 m above sea level. The 129I in the Laohugou glacier basin is probably deposited from the upper troposphere where there exists a local maximum of 129I. A conceptual model for interpretation of the observed 129I concentration and profile in Laohugou is provided. Thus, this work is of importance in providing a more complete view on the transport, dispersion, and removal of 129I in the atmosphere.
Ion and Electron κ Distribution Functions Along the Plasma Sheet
Authors: Espinoza C. M. , Stepanova M. , Moya P. S. , Antonova E. E. , Valdivia J. A. 
Published: June 2018

AbstractWe use kappa distributions to model thousands of ion and electron flux spectra along the plasma sheet and analyze the variation of the spectral index κ and the temperature T in this region. We find that κ distributions are ubiquitous and fit well ion and electron flux spectra during quiet times, and during the expansion and recovery phases of substorms. Near Earth, and up to ∼12 RE, the κ indices are different than the rest of the plasma sheet, both for ions (κi) and electrons (κe). There is a significant dawn‐dusk asymmetry in κi toward the tail, which is enhanced during substorms. The ions also exhibit a permanent temperature asymmetry, determined by a colder dawnside. The whole tail becomes hotter during substorms, but it appears that most of the energy is deposited near Earth.
Highly flexible, foldable, and rollable microsupercapacitors on an ultrathin polyimide substrate with high power density
Authors: Pu Juan , Wang Xiaohong , Xu Renxiao , Xu Sixing , Komvopoulos Kyriakos 
Published: June 2018

AbstractThe design and functionality of extremely flexible, foldable, and rollable microsupercapacitors (MSCs) with in-plane interdigital electrodes that consist of single-walled carbon nanotube (SWCNT) networks on an ultrathin polyimide substrate are demonstrated through experiments and finite element simulations. The all-solid-state MSCs can be reversibly bent, folded, and rolled purely elastically without degradation of their electrical performance. The simulation results confirm that the deformation in bent, folded, and rolled MSCs is purely elastic. The high power density (1125 W cm–3) and small time constant (1 ms) of the present MSCs are comparable to those of aluminum electrolytic capacitors. The MSCs operate at scan rates of up to 1000 V s–1, are characterized by a volumetric capacitance of 18 F cm–3 and an energy density of 1.6 mWh cm–3, and exhibit superior electrochemical stability with 96% capacity retention even after 100,000 charge/discharge cycles. The developed MSCs demonstrate high potential for integration in flexible and wearable electronic systems.
Quantitative spatial analysis of haematopoiesis-regulating stromal cells in the bone marrow microenvironment by 3D microscopy
Authors: Gomariz Alvaro , Helbling Patrick M. , Isringhausen Stephan , Suessbier Ute , Becker Anton , Boss Andreas , Nagasawa Takashi , Paul Grégory , Goksel Orcun , Székely Gábor , Stoma Szymon , Nørrelykke Simon F. , Manz Markus G. , Nombela-Arrieta César 
Published: June 2018

AbstractSinusoidal endothelial cells and mesenchymal CXCL12-abundant reticular cells are principal bone marrow stromal components, which critically modulate haematopoiesis at various levels, including haematopoietic stem cell maintenance. These stromal subsets are thought to be scarce and function via highly specific interactions in anatomically confined niches. Yet, knowledge on their abundance, global distribution and spatial associations remains limited. Using three-dimensional quantitative microscopy we show that sinusoidal endothelial and mesenchymal reticular subsets are remarkably more abundant than estimated by conventional flow cytometry. Moreover, both cell types assemble in topologically complex networks, associate to extracellular matrix and pervade marrow tissues. Through spatial statistical methods we challenge previous models and demonstrate that even in the absence of major specific interaction forces, virtually all tissue-resident cells are invariably in physical contact with, or close proximity to, mesenchymal reticular and sinusoidal endothelial cells. We further show that basic structural features of these stromal components are preserved during ageing.
Neuromorphic computing with multi-memristive synapses
Authors: Boybat Irem , Le Gallo Manuel , Nandakumar S. R. , Moraitis Timoleon , Parnell Thomas , Tuma Tomas , Rajendran Bipin , Leblebici Yusuf , Sebastian Abu , Eleftheriou Evangelos 
Published: June 2018

AbstractNeuromorphic computing has emerged as a promising avenue towards building the next generation of intelligent computing systems. It has been proposed that memristive devices, which exhibit history-dependent conductivity modulation, could efficiently represent the synaptic weights in artificial neural networks. However, precise modulation of the device conductance over a wide dynamic range, necessary to maintain high network accuracy, is proving to be challenging. To address this, we present a multi-memristive synaptic architecture with an efficient global counter-based arbitration scheme. We focus on phase change memory devices, develop a comprehensive model and demonstrate via simulations the effectiveness of the concept for both spiking and non-spiking neural networks. Moreover, we present experimental results involving over a million phase change memory devices for unsupervised learning of temporal correlations using a spiking neural network. The work presents a significant step towards the realization of large-scale and energy-efficient neuromorphic computing systems.
Molecular basis of Tousled-Like Kinase 2 activation
Authors: Mortuza Gulnahar B. , Hermida Dario , Pedersen Anna-Kathrine , Segura-Bayona Sandra , López-Méndez Blanca , Redondo Pilar , Rüther Patrick , Pozdnyakova Irina , Garrote Ana M. , Muñoz Inés G. , Villamor-Payà Marina , Jauset Cristina , Olsen Jesper V. , Stracker Travis H. , Montoya Guillermo 
Published: June 2018

AbstractTousled-like kinases (TLKs) are required for genome stability and normal development in numerous organisms and have been implicated in breast cancer and intellectual disability. In humans, the similar TLK1 and TLK2 interact with each other and TLK activity enhances ASF1 histone binding and is inhibited by the DNA damage response, although the molecular mechanisms of TLK regulation remain unclear. Here we describe the crystal structure of the TLK2 kinase domain. We show that the coiled-coil domains mediate dimerization and are essential for activation through ordered autophosphorylation that promotes higher order oligomers that locally increase TLK2 activity. We show that TLK2 mutations involved in intellectual disability impair kinase activity, and the docking of several small-molecule inhibitors of TLK activity suggest that the crystal structure will be useful for guiding the rationale design of new inhibition strategies. Together our results provide insights into the structure and molecular regulation of the TLKs.
An all-dielectric metasurface as a broadband optical frequency mixer
Authors: Liu Sheng , Vabishchevich Polina P. , Vaskin Aleksandr , Reno John L. , Keeler Gordon A. , Sinclair Michael B. , Staude Isabelle , Brener Igal 
Published: June 2018

AbstractA frequency mixer is a nonlinear device that combines electromagnetic waves to create waves at new frequencies. Mixers are ubiquitous components in modern radio-frequency technology and microwave signal processing. The development of versatile frequency mixers for optical frequencies remains challenging: such devices generally rely on weak nonlinear optical processes and, thus, must satisfy phase-matching conditions. Here we utilize a GaAs-based dielectric metasurface to demonstrate an optical frequency mixer that concurrently generates eleven new frequencies spanning the ultraviolet to near-infrared. The even and odd order nonlinearities of GaAs enable our observation of second-harmonic, third-harmonic, and fourth-harmonic generation, sum-frequency generation, two-photon absorption-induced photoluminescence, four-wave mixing and six-wave mixing. The simultaneous occurrence of these seven nonlinear processes is assisted by the combined effects of strong intrinsic material nonlinearities, enhanced electromagnetic fields, and relaxed phase-matching requirements. Such ultracompact optical mixers may enable a plethora of applications in biology, chemistry, sensing, communications, and quantum optics.
Excited-state vibrational dynamics toward the polaron in methylammonium lead iodide perovskite
Authors: Park Myeongkee , Neukirch Amanda J. , Reyes-Lillo Sebastian E. , Lai Minliang , Ellis Scott R. , Dietze Daniel , Neaton Jeffrey B. , Yang Peidong , Tretiak Sergei , Mathies Richard A. 
Published: June 2018

AbstractHybrid organic–inorganic perovskites have attractive optoelectronic properties including exceptional solar cell performance. The improved properties of perovskites have been attributed to polaronic effects involving stabilization of localized charge character by structural deformations and polarizations. Here we examine the Pb–I structural dynamics leading to polaron formation in methylammonium lead iodide perovskite by transient absorption, time-domain Raman spectroscopy, and density functional theory. Methylammonium lead iodide perovskite exhibits excited-state coherent nuclear wave packets oscillating at ~20, ~43, and ~75 cm−1 which involve skeletal bending, in-plane bending, and c-axis stretching of the I–Pb–I bonds, respectively. The amplitudes of these wave packet motions report on the magnitude of the excited-state structural changes, in particular, the formation of a bent and elongated octahedral PbI64− geometry. We have predicted the excited-state geometry and structural changes between the neutral and polaron states using a normal-mode projection method, which supports and rationalizes the experimental results. This study reveals the polaron formation via nuclear dynamics that may be important for efficient charge separation.
Doping-induced structural phase transition in cobalt diselenide enables enhanced hydrogen evolution catalysis
Authors: Zheng Ya-Rong , Wu Ping , Gao Min-Rui , Zhang Xiao-Long , Gao Fei-Yue , Ju Huan-Xin , Wu Rui , Gao Qiang , You Rui , Huang Wei-Xin , Liu Shou-Jie , Hu Shan-Wei , Zhu Junfa , Li Zhenyu , Yu Shu-Hong 
Published: June 2018

AbstractTransition metal dichalcogenide materials have been explored extensively as catalysts to negotiate the hydrogen evolution reaction, but they often run at a large excess thermodynamic cost. Although activating strategies, such as defects and composition engineering, have led to remarkable activity gains, there remains the requirement for better performance that aims for real device applications. We report here a phosphorus-doping-induced phase transition from cubic to orthorhombic phases in CoSe2. It has been found that the achieved orthorhombic CoSe2 with appropriate phosphorus dopant (8 wt%) needs the lowest overpotential of 104 mV at 10 mA cm−2 in 1 M KOH, with onset potential as small as −31 mV. This catalyst demonstrates negligible activity decay after 20 h of operation. The striking catalysis performance can be attributed to the favorable electronic structure and local coordination environment created by this doping-induced structural phase transition strategy.
Long-haul optical transmission link using low-noise phase-sensitive amplifiers
Authors: Olsson Samuel L.I. , Eliasson Henrik , Astra Egon , Karlsson Magnus , Andrekson Peter A. 
Published: June 2018

AbstractThe capacity and reach of long-haul fiber optical communication systems is limited by in-line amplifier noise and fiber nonlinearities. Phase-sensitive amplifiers add 6 dB less noise than conventional phase-insensitive amplifiers, such as erbium-doped fiber amplifiers, and they can provide nonlinearity mitigation after each span. Realizing a long-haul transmission link with in-line phase-sensitive amplifiers providing simultaneous low-noise amplification and nonlinearity mitigation is challenging and to date no such transmission link has been demonstrated. Here, we demonstrate a multi-channel-compatible and modulation-format-independent long-haul transmission link with in-line phase-sensitive amplifiers. Compared to a link amplified by conventional erbium-doped fiber amplifiers, we demonstrate a reach improvement of 5.6 times at optimal launch powers with the phase-sensitively amplified link operating at a total accumulated nonlinear phase shift of 6.2 rad. The phase-sensitively amplified link transmits two data-carrying waves, thus occupying twice the bandwidth and propagating twice the total power compared to the phase-insensitively amplified link.