bluuebunny/crossref_metadata_2025 huggingface dataset:
Numerical 3D study on the influence of spanwise distribution of tubercles on wings for UAV applications
Authors: Papadopoulos Charalampos , Katsiadramis Vasilis , Yakinthos Kyros
Published: December 2019

In this work, a 3D numerical study on the influence of the spanwise distribution of tubercles for UAV applications is presented. The idea of using tubercles in aeronautics comes from the humpback whale (Megaptera novaeangliae) which has a characteristic flipper, with a spanwise scalloped leading edge, creating an almost sinusoidal shape, consisting of bumps called tubercles. Early experimental research showed a great potential in enhancing the 3D aerodynamic characteristics of a wing. Most of the existing experimental results concern infinite wings (2D) models and are accompanied with substantial loss in lift and increase in drag in pre–stall region. On the other hand, finite models (3D) have displayed a better overall aerodynamic performance (increased lift and moment, but also decreased drag). At a range of Reynolds number between 500,000 and 1,000,000 (based on the mean chord of the flipper), tubercles act as virtual fences, introducing a pair of counter rotating vortices that delays the stall of the flipper, a phenomenon that the whales use to perform sharp turns and catch their prey. The aforementioned Reynolds number range is the same as the operational Reynolds number for typical Unmanned Aerial Vehicles (UAV). To assess the influence of the tubercles installation on UAV wings, a full 3D computational study is carried-out, with the use of CFD tools that at a first phase are validated and calibrated with available in the literature experimental data. Then, computations are performed, for different spanwise tubercles distributions. The results show that there is a noticeable potential on controlling the flow on the wings of a UAV operating in a Reynolds number range between 500,000 and 1,000,000 (based on UAV’s wing mean chord), which can lead to an aerodynamic performance and efficiency increase.
Navigation architecture for hypersonic aircraft
Authors: Castigliola Luca , Causa Flavia , Grassi Michele
Published: December 2019

This paper aims at presenting an integrated navigation algorithm designed for estimating the navigation state of the STRATOFLY vehicle (LAPCAT–MR3). STRATOFLY project has been funded by the European Commission, under the framework of Horizon 2020 plan, with the aim of assessing the potential of high–speed transport vehicle. The complex interaction between elements of an air-breathing hypersonic vehicle represents a new paradigm in aircraft design. In particular, one of the needs for early GNC analysis in the case of LAPCAT–MR3 vehicle is the assessment of navigation performance over the reference trajectory. The navigation algorithm presented in this paper is based on an augmented state EKF data fusion algorithm exploiting inertial measurements provided by gyroscopes and accelerometers, heading estimates provided by a magnetometer and satellite-based measurements provided by a spaceborne GNSS receiver, considering GPS, GLONASS and GALILEO constellations.
Application SimInTech Software for Optimization Fuel System Parameters of the Perspective Helicopter
Authors: Satin Anatoly , Savelev Roman , Smagin Denis , Napreenko Konstantin , Neveshkina Anastasia
Published: December 2019

The possibility of applying optimization algorithms for mathematical modelling of the helicopter fuel system on the example of the advanced helicopter in Russian software complex SimInTech. The results of the fuel system parameters simplest optimization for the nominal operation mode are presented, examples of algorithms for the selection of the parameters of the units are shown.
Air traffic management based on 4D-trajectories: requirements and practical implementation
Authors: Rodríguez–Sanz Álvaro , Claramunt Puchol Cecilia , Gómez Comendador Fernando , Pérez-Castán Javier , Arnaldo Valdés Rosa , Serrano Martínez Francisco , Najar Godoy Mar
Published: December 2019

The current Air Traffic Management (ATM) functional approach is changing: ‘time’ is now integrated as an additional fourth dimension on trajectories. This notion will impose on aircraft the compliance of accurately arrival times over designated checkpoints, called Time Windows (TWs). In this context, we review the operational concept of 4D-trajectories, by initially developing an analysis of basic requirements for their implementation in the Communications, Navigation and Surveillance (CNS) systems and then by investigating their management in the future ATM context. We focus on defining the relationships between 4D-trajectories and other concepts and systems of the future ATM framework, and the needs that it will require for its application, detailing the main tools, programs and ATM/CNS systems that must be deployed. We appraise how 4D-trajectories must be managed and planned (negotiation, synchronization, modification and verification processes). Then, based on the degradation of a 4D-trajectory, we define and introduce the necessary corrective measures by evaluating the degradation tolerances and conditions.
Notes regarding the Modeling of the Angle of Attack
Authors: Moraru Laurentiu
Published: December 2019

Numerical integration has become routine for many decades and so has become the numerical integration of the aircraft’s equation of motion. Many numerical algorithms have been used in flight dynamics and the applications of the basic numerical methods to flight simulation have been included in textbooks for a long time. However, many design and/or optimization algorithms rely on analyzing large amounts of simulated data, so analytical algorithms that can provide expedite estimations of the fast varying parameters have been revaluated. The current paper discusses approximate analytical solutions for the angle of attack. Two types of such solutions are discussed. The first model considered originates in the classically linearized equations of motion. The second model discussed was obtained by simplifying the nonlinear equations of motion. The two models are compared against numerical results, provided by classical numerical integration algorithms.
Asymmetric Neber Reaction in the Synthesis of Chiral 2-(Tetrazol-5-yl)-2H-Azirines
Authors: Alves Cláudia , Grosso Carla , Barrulas Pedro , Paixão José A. , Cardoso Ana L. , Burke Anthony J. , Lemos Américo , Pinho e Melo Teresa M. V. D.
Published: December 2019

A successful one-pot methodology for the synthesis of chiral 2-tetrazolyl-2H-azirines has been established, resorting to organocatalysis. The protocol involves the in situ tosylation of β-ketoxime-1H-tetrazoles followed by the Neber reaction, in the presence of chiral organocatalysts. Among the organocatalysts studied a novel thiourea catalyst derived from 6β-aminopenicillanic acid afforded excellent enantioselectivities.
Eye Movement Recordings: Practical Applications in Neurology
Authors: Rizzo John-Ross , Beheshti Mahya , Dai Weiwei , Rucker Janet C.
Published: December 2019

Accurate detection and interpretation of eye movement abnormalities often guides differential diagnosis, discussions on prognosis and disease mechanisms, and directed treatment of disabling visual symptoms and signs. A comprehensive clinical eye movement examination is high yield from a diagnostic standpoint; however, skillful recording and quantification of eye movements can increase detection of subclinical deficits, confirm clinical suspicions, guide therapeutics, and generate expansive research opportunities. This review encompasses an overview of the clinical eye movement examination, provides examples of practical diagnostic contributions from quantitative recordings of eye movements, and comments on recording equipment and related challenges.
Pediatric Idiopathic Intracranial Hypertension
Authors: Gaier Eric D. , Heidary Gena
Published: December 2019

The presentation of idiopathic intracranial hypertension (IIH) in pediatric populations has several important distinctions from that in adults, especially among prepubertal patients, in which there is no apparent association with gender or obesity. Pediatric patients are more likely to be asymptomatic or present with atypical symptoms than their adult counterparts, posing a diagnostic challenge in some cases. It is important to be aware of the ways in which diagnostic criteria for IIH are modified from that of adults. Ideal treatment practices and the natural history of pediatric IIH remain unclear. Acetazolamide is the mainstay of medical treatment, but some patients with significant visual loss may require surgical intervention. Multicenter studies to accrue a large number of cases and future prospective studies will help to better define pediatric IIH and to formulate consensus guidelines for treatment and management of these patients.
Kisspeptin and Prolactin
Authors: Grattan David R. , Szawka Raphael E.
Published: December 2019

The relationship between elevated prolactin and infertility has been known for a long time, but the specific mechanism by which prolactin inhibited reproduction had been uncertain. The discovery of kisspeptin has provided novel insights into how prolactin might cause infertility, with extensive evidence that elevated prolactin inhibits secretion of kisspeptin, resulting in hypogonadotropic hypogonadism, and infertility. More recent data suggest that a converse relationship might also exist, with evidence that kisspeptin influences prolactin secretion. This brief review will examine the relationship between kisspeptin and prolactin from each of these two perspectives: the well-characterized inhibitory effect of prolactin on kisspeptin neurons and the more recent concept that kisspeptin neurons are involved in the control of prolactin secretion.
Comparative investigation of the mechanical, electrical and thermal transport properties in graphene-like C3B and C3N
Authors: Wang Haifeng , Li Qingfang , Pan Hongzhe , Gao Yan , Sun Maozhu
Published: December 2019

By using state-of-the-art first-principles calculations based on density functional theory (DFT), we conduct a comparative study of the mechanical, electrical, and in-plane thermal transport properties of recently synthesized graphenelike C3B and C3N nanosheets. Our DFT results reveal that the monolayer C3B remarkably possesses a lower elastic modulus and in-plane stiffness as well as ultimate tensile strength compared to C3N, while obviously stronger anisotropy in failure behavior is found in C3B sheets. Both monolayer materials are found as semiconductors with indirect bandgaps of about 1.78 eV and 1.15 eV at the HSE06 level, and their carrier mobilities demonstrate remarkable anisotropy. Additionally, the electron mobility of C3B is found to be much higher than its hole mobility, while for C3N, the reverse is true. For the thermal transport properties, as expected, the intrinsic lattice thermal conductivity of the monolayer C3B (301 W/m K at 300 K) is also lower than that of C3N (380 W/m K at 300 K), while much great anisotropy of in-plane thermal conductivity is found in C3B. The underlying mechanisms governing the phonon thermal transport of these two graphenelike monolayers are thoroughly discussed and compared. Our research will benefit future theoretical research and practical application of these two novel boron-carbide and carbon-nitride materials.
Resonant ultrasound spectroscopy: The essential toolbox
Authors: Balakirev Fedor F. , Ennaceur Susan M. , Migliori Robert J. , Maiorov Boris , Migliori Albert
Published: December 2019

Resonant Ultrasound Spectroscopy (RUS) is an ultrasound-based minimal-effort high-accuracy elastic modulus measurement technique. RUS as described here uses the mechanical resonances (normal modes of vibration or just modes) of rectangular parallelepiped or cylindrical specimens with a dimension of from a fraction of a millimeter to as large as will fit into the apparatus. Provided here is all that is needed so that the reader can construct and use a state-of-the-art RUS system. Included are links to open-source circuit diagrams, links to download Los Alamos National Laboratory open-source data acquisition software, links to request free analysis software, procedures for acquiring measurements, considerations on building transducers, 3-D printed stage designs, and a full mathematical explanation of how the analysis software extracts elastic moduli from resonances.
Inclined hydromagnetic impact on tangent hyperbolic fluid flow over a vertical stretched sheet
Authors: Ali A. , Hussain R. , Maroof Misbah
Published: December 2019

The current research aims to examine the impact of a tangent hyperbolic fluid flow confined by a stretching sheet with the existence of variable thermal conductivity, mixed convection, and magneto hydrodynamics. A mathematical model is developed in the form of partial differential equations (PDEs) and then converted into ordinary differential equations by using self-felicitous transformations. The technique of BVP4C (MATLAB package) has been used to simplify these ordinary differential equations. The numerical solution of skin friction, mixed convection, Nusselt number, and velocity and temperature profiles for different values of the involved parameters is indicated through tables and graphs. It can be noticed that the velocity profile decreases when the Hartmann number increases. The effect of Weissenberg number, inclined angle, and power law index for velocity profiles is also identical to the Hartmann number. The temperature profile decays due to an increment in the Prandtl number. Skin friction and the Nusselt number have also been explained. The physical reasoning for growth or decay of these parameters has been discussed in detail.
Determining the complex Jones matrix elements of a chiral 3D optical metamaterial
Authors: Kilchoer Cédric , Abdollahi Narjes , Steiner Ullrich , Gunkel Ilja , Wilts Bodo D.
Published: December 2019

Due to their strong optical activity, chiral metamaterials are attractive optical elements for the control of the polarization of light. Efficient broadband circular polarizers can be implemented through chiral nanostructures that are periodic and possess certain spatial symmetries. Here, we demonstrate a new method to fully characterize any generalized chiral medium without the use of optical phase-retarding elements, such as quarter-wave plates. Using the advantage of symmetry considerations, all parameters of the complex Jones matrix associated with the metamaterial were determined by two linear-polarization experiments. A coordinate transformation then enabled the calculation of the gyro-optical response of the sample, i.e., its circular dichroism and circular polarization conversion, which is shown to be in good agreement with direct measurements. This approach is versatile, allowing to calculate the optical response in intensity and phase of any generalized chiral metamaterial upon linear, circular, or elliptical polarized illumination.
High cyclic stability of electrocaloric effect in relaxor poly(vinylidene fluoride-trifluoroethylene-chlorofluoroethylene) terpolymers in the absence of ferroelectric phase transition
Authors: Liu Yang , Zhang Guangzu , Haibibu Aziguli , Han Zhubing , Wang Qing
Published: December 2019

The incorporation of bulky defects into ferroelectric poly(vinylidene fluoride-trifluoroethylene) copolymers can result in a relaxor behavior, accompanied by outstanding electrocaloric properties near room temperature. However, it remains elusive whether ferroelectric transition occurs in relaxor terpolymers, which is critical for the design of electrocaloric cooling devices. In this work, we study the electrocaloric fatigue in poly(vinylidene fluoride-trifluoroethylene-chlorofluoroethylene) (61.8/30.4/7.8 mol. %) terpolymer, in which we revisit its controversial issue of the phase transition. We observe that the electrocaloric response of the terpolymers remains nearly constant (ΔS = 25.5 J K−1 kg−1, ΔT = 5.1 K at 100 MV m−1) within 50 cycles at different temperatures around room temperature. Moreover, we conduct temperature-dependent X-ray diffraction and Fourier-transform infrared spectroscopy measurements on the terpolymer to provide insights into the evolution in intermolecular lattice spacing and intramolecular conformation. We find no clear evidence of the ferroelectric-to-paraelectric phase transition near the temperature range, where differential scanning calorimeter measurement displays an endothermic peak.
Doping effect on the thermoelectric transport properties of HfTe5
Authors: Hu Junfeng , Yu Haiming , Ansermet Jean-Philippe
Published: December 2019

We studied the influence of doping HfTe5 with 5% Ti on electric (resistivity and the Hall effect) and thermoelectric transport properties (the Seebeck coefficient, magneto-thermoelectric power, and Nernst effect). The properties of 5% Ti-doped HfTe5 do not change much. Nernst coefficients larger than magneto-thermoelectric power were observed in a temperature range near the compensation temperature at which the Seebeck coefficient vanishes. This indicates that a two-carrier conduction model could describe our experimental results. Owing to the high thermoelectric performance, thermopiles were made on a printed circuit board based on doped and undoped HfTe5. A large Seebeck voltage was obtained at room temperature. It became even larger in a low temperature range and presented strong magnetic field dependence.
Upconverted excitonic photoluminescence from a two-dimensional lead-halide perovskite
Authors: Yamada Takumi , Aharen Tomoko , Kanemitsu Yoshihiko
Published: December 2019

Anti-Stokes photoluminescence (AS-PL) is an interesting optical phenomenon that can cause laser cooling in certain semiconductors where incident laser photons are efficiently converted into photons with higher energy. The underlying upconversion mechanism can be used to realize optical refrigerators, but suited materials need to be developed for actual applications. Here, we investigate the AS-PL properties of a two-dimensional (2D) perovskite PEA2PbI4 single crystal and compare them with those of a three-dimensional (3D) perovskite MAPbI3 single crystal. We find that, in the 2D perovskite PEA2PbI4, which has a large exciton binding energy, the free-exciton PL is dominant and that the measured upconversion gain spectra of both PEA2PbI4 and MAPbI3 crystals are similar. The AS-PL process in these perovskite single crystals is discussed.
A viscoplastic model for void growth under dynamic loading conditions
Authors: Zhao Fu-Qi , Pan Hao , Zhang Feng-Guo , Liu Jing-Xing
Published: December 2019

We present a dynamic theoretical viscoplastic model of voids subjected to external dynamic tensile loadings. The material viscosity and temperature are factors that are considered in the dynamic evolution of voids in viscoplastic materials. We focus on the thermal effect; the temperature affects the thermal softening of the material strength and also the material viscosity. Viscous flow is the dominant growth mechanism under high stresses and rates based on the results of the calculations for dynamic void growth predictions. The factors are independently studied, and the correlations are systematically analyzed.
Single-point structure tensors in turbulent channel flows with smooth and wavy walls
Authors: Yuan Junlin , Mishra Aashwin Ananda , Brereton Giles , Iaccarino Gianluca , Vartdal Magnus
Published: December 2019

A long-standing problem in turbulence modeling is that the Reynolds stress tensor alone is not necessarily sufficient to characterize the transient and nonequilibrium behaviors of turbulence under arbitrary mean deformation or frame rotation. A more complete single-point characterization of the flow can be obtained using the structure dimensionality, circulicity, and inhomogeneity tensors. These tensors are one-point correlations of local stream vector gradients and carry nonlocal information regarding the structure of the flow field. We explore the potential of these tensors to improve understanding of complex turbulent flows using direct numerical simulation of flows in channels with a smooth wall and a two-dimensional sinusoidal wavy wall. To enforce no-slip and no-penetration conditions at wavy-wall boundaries, an immersed boundary method for the stream vector Poisson equation was adopted within the framework of Stylianou, Pecnik, and Kassinos, “A general framework for computing the turbulence structure tensors,” Comput. Fluids 106, 54–66 (2015). The results show that the effects of wall waviness on the inclination and aspect ratio of the two-point velocity correlation near the wall are reproduced qualitatively by their corresponding single-point tensor representations. In the outer layer, good quantitative agreement is achieved for both parameters. Additional observations on the structural changes of turbulence due to wall waviness and their relevance to turbulence modeling with surface roughness are discussed. The findings of this investigation suggest that single-point structure tensors can be appended to the modeling basis for inhomogeneous flows with geometrically complex boundaries, such as rough-wall flows, to develop improved turbulence models.
Matrix isolation spectroscopy and spectral simulations of isotopically substituted C60 molecules
Authors: Wakabayashi Tomonari , Momose Takamasa , Fajardo Mario E.
Published: December 2019

Isotopically enriched (3.5% 13C) and depleted (0.5% 13C) fullerene C60 molecules are isolated in parahydrogen (pH2) solids at cryogenic temperatures and studied by high resolution (0.01–0.1 cm−1) infrared (IR) absorption measurements. Spectra of natural isotopic abundance (1.1% 13C) C60 molecules isolated in solid pH2, orthodeuterium (oD2), and Ne matrix hosts serve to identify the relatively minor spectral perturbations due to the trapping environments. Spectral features observed for the four IR-active T1u modes of threefold degeneracy in Ih symmetry, namely, T1u(1) at 529.77 cm−1, T1u(2) at 578.24 cm−1, T1u(3) at 1184.7 cm−1, and T1u(4) at 1432 cm−1, are assigned to the superpositions of matrix perturbed vibrational-mode spectra of a number of 13Cn12C60−n isotopologues. New molecular orbital calculations show the symmetry lowering effects of 13C substitution, namely, split vibrational frequencies and modified IR intensities. IR spectral patterns calculated for the 328 distinct isotopomers of 13Cn12C60−n up to n = 3 are used to satisfactorily simulate most of the observed absorption features. For the T1u(4) mode at 1432 cm−1, the observed splitting is insensitive to the 13C abundance, indicating spectral perturbations due to Fermi resonance. Weak absorption features at 1545 cm−1 are assigned to a combination of lower frequency modes. We discuss relative and absolute band strengths for the astrophysical application of estimating C60 abundances in planetary nebulae.
Global extrema of the Delange function, bounds for digital sums and concave functions
Authors: Galkin O. E. , Galkina S. Yu.
Published: December 2019

The sumsare defined by the equalityfor all positive integersand, whereis the sum of digits of the integerwritten in the system with base. In 1975 Delange generalised Trollope’s formula and proved that, whereandis the continuous nowhere differentiable Delange function. We find global extrema ofand, using this, obtain a precise bound for the difference. In the casethis becomes the bound for binary sums proved by Krüppel in 2008 and also earlier by other authors. We also evaluate the global extrema of some other continuous nowhere differentiable functions. We introduce the natural concave hull of a function and prove a criterion simplifying the evaluation of this hull. Moreover, we introduce the notion of an extreme subargument of a function on a convex set. We show that all points of global maximum of the difference, where the functionis strictly concave and some additional conditions hold, are extreme subarguments for. A similar result is obtained for functions of the form. We evaluate the global extrema and find extreme subarguments of the Delange function on the interval. The results in the paper are illustrated by graphs and tables.

Bibliography: 16 titles.
The gradient projection algorithm for a proximally smooth set and a function with Lipschitz continuous gradient
Authors: Balashov M. V.
Published: December 2019

We consider the minimization problem for a nonconvex function with Lipschitz continuous gradient on a proximally smooth (possibly nonconvex) subset of a finite-dimensional Euclidean space. We introduce the error bound condition with exponent

for the gradient mapping. Under this condition, it is shown that the standard gradient projection algorithm converges to a solution of the problem linearly or sublinearly, depending on the value of the exponent

. This paper is theoretical.

Bibliography: 23 titles.
Symmetries in left-invariant optimal control problems
Authors: Podobryaev A. V.
Published: December 2019

Left-invariant optimal control problems on Lie groups are considered. When studying the optimality of extreme trajectories, the crucial role is played by symmetries of the exponential map that are induced by symmetries of the conjugate subsystem of the Hamiltonian system of the Pontryagin maximum principle. A general construction is obtained for these symmetries of the exponential map for connected Lie groups with generic coadjoint orbits of codimension not exceeding one and with a connected stabilizer.

Bibliography: 32 titles.
High-density chemical cross-linking for modeling protein interactions
Authors: Mintseris Julian , Gygi Steven P.
Published: December 2019

Detailed mechanistic understanding of protein complex function is greatly enhanced by insights from its 3-dimensional structure. Traditional methods of protein structure elucidation remain expensive and labor-intensive and require highly purified starting material. Chemical cross-linking coupled with mass spectrometry offers an alternative that has seen increased use, especially in combination with other experimental approaches like cryo-electron microscopy. Here we report advances in method development, combining several orthogonal cross-linking chemistries as well as improvements in search algorithms, statistical analysis, and computational cost to achieve coverage of 1 unique cross-linked position pair for every 7 amino acids at a 1% false discovery rate. This is accomplished without any peptide-level fractionation or enrichment. We apply our methods to model the complex between a carbonic anhydrase (CA) and its protein inhibitor, showing that the cross-links are self-consistent and define the interaction interface at high resolution. The resulting model suggests a scaffold for development of a class of protein-based inhibitors of the CA family of enzymes. We next cross-link the yeast proteasome, identifying 3,893 unique cross-linked peptides in 3 mass spectrometry runs. The dataset includes 1,704 unique cross-linked position pairs for the proteasome subunits, more than half of them intersubunit. Using multiple recently solved cryo-EM structures, we show that observed cross-links reflect the conformational dynamics and disorder of some proteasome subunits. We further demonstrate that this level of cross-linking density is sufficient to model the architecture of the 19-subunit regulatory particle de novo.
Receding ice drove parallel expansions in Southern Ocean penguins
Authors: Cole Theresa L. , Dutoit Ludovic , Dussex Nicolas , Hart Tom , Alexander Alana , Younger Jane L. , Clucas Gemma V. , Frugone María José , Cherel Yves , Cuthbert Richard , Ellenberg Ursula , Fiddaman Steven R. , Hiscock Johanna , Houston David , Jouventin Pierre , Mattern Thomas , Miller Gary , Miskelly Colin , Nolan Paul , Polito Michael J. , Quillfeldt Petra , Ryan Peter G. , Smith Adrian , Tennyson Alan J. D. , Thompson David , Wienecke Barbara , Vianna Juliana A. , Waters Jonathan M.
Published: December 2019

Climate shifts are key drivers of ecosystem change. Despite the critical importance of Antarctica and the Southern Ocean for global climate, the extent of climate-driven ecological change in this region remains controversial. In particular, the biological effects of changing sea ice conditions are poorly understood. We hypothesize that rapid postglacial reductions in sea ice drove biological shifts across multiple widespread Southern Ocean species. We test for demographic shifts driven by climate events over recent millennia by analyzing population genomic datasets spanning 3 penguin genera (
Eudyptes
,
Pygoscelis
, and
Aptenodytes
). Demographic analyses for multiple species (macaroni/royal, eastern rockhopper, Adélie, gentoo, king, and emperor) currently inhabiting southern coastlines affected by heavy sea ice conditions during the Last Glacial Maximum (LGM) yielded genetic signatures of near-simultaneous population expansions associated with postglacial warming. Populations of the ice-adapted emperor penguin are inferred to have expanded slightly earlier than those of species requiring ice-free terrain. These concerted high-latitude expansion events contrast with relatively stable or declining demographic histories inferred for 4 penguin species (northern rockhopper, western rockhopper, Fiordland crested, and Snares crested) that apparently persisted throughout the LGM in ice-free habitats. Limited genetic structure detected in all ice-affected species across the vast Southern Ocean may reflect both rapid postglacial colonization of subantarctic and Antarctic shores, in addition to recent genetic exchange among populations. Together, these analyses highlight dramatic, ecosystem-wide responses to past Southern Ocean climate change and suggest potential for further shifts as warming continues.
Programmable active kirigami metasheets with more freedom of actuation
Authors: Tang Yichao , Li Yanbin , Hong Yaoye , Yang Shu , Yin Jie
Published: December 2019

Significance

Kirigami is an emerging approach to construct 3-dimensional (3D) structures by simply cutting and folding thin sheets. Sole slits lead to expanded 3D structures through buckling to open the cuts. Compared to homogenous shape shifting through thin sheets with sole cuts, adding folds into cuts provides potential for programmable structure reconfiguration in kirigami sheets with excised holes. However, folding often closes the cutouts in such kirigami sheets, resulting in compact 3D pop-up structures. Here, we combine a universal fold design and slits in kirigami sheets to realize both expanded and compact structures, allowing reprogrammability in both 2D and 3D through folding-induced opening and reclosing of slits. We demonstrate thermal actuation of programmable kirigami metastructures and machines through cuts-guided directional folding.
Scaling the risk landscape drives optimal life-history strategies and the evolution of grazing
Authors: Bhat Uttam , Kempes Christopher P. , Yeakel Justin D.
Published: December 2019

Significance

Consumer species assume diverse life-history and foraging strategies in part to mitigate the risks imparted by spatially variable resources. By deriving a mechanistic model of energy allocation, we show how fitness-optimizing strategies are tied to resource variability and that population stability depends on the scaling of resource variability with consumer body size and diet. These relationships offer insight into the evolutionary trend toward larger body size, known as Cope’s rule, and the mammalian transition from browsing to grazing following the advent of grasslands in the mid-to-late Miocene.
A formula for the value of a stochastic game
Authors: Attia Luc , Oliu-Barton Miquel
Published: December 2019

Significance

Stochastic games were introduced by the Nobel Memorial Prize winner Lloyd Shapley in 1953 to model dynamic interactions in which the environment changes in response to the players’ behavior. The theory of stochastic games and its applications have been studied in several scientific disciplines, including economics, operations research, evolutionary biology, and computer science. In addition, mathematical tools that were used and developed in the study of stochastic games are used by mathematicians and computer scientists in other fields. This paper contributes to the theory of stochastic games by providing a tractable formula for the value of finite competitive stochastic games. This result settles a major open problem which remained unsolved for nearly 40 y.
Corazonin signaling integrates energy homeostasis and lunar phase to regulate aspects of growth and sexual maturation in
Platynereis
Authors: Andreatta Gabriele , Broyart Caroline , Borghgraef Charline , Vadiwala Karim , Kozin Vitaly , Polo Alessandra , Bileck Andrea , Beets Isabel , Schoofs Liliane , Gerner Christopher , Raible Florian
Published: December 2019

The molecular mechanisms by which animals integrate external stimuli with internal energy balance to regulate major developmental and reproductive events still remain enigmatic. We investigated this aspect in the marine bristleworm,
Platynereis dumerilii
, a species where sexual maturation is tightly regulated by both metabolic state and lunar cycle. Our specific focus was on ligands and receptors of the gonadotropin-releasing hormone (GnRH) superfamily. Members of this superfamily are key in triggering sexual maturation in vertebrates but also regulate reproductive processes and energy homeostasis in invertebrates. Here we show that 3 of the 4
gnrh-like
(
gnrhl
) preprohormone genes are expressed in specific and distinct neuronal clusters in the
Platynereis
brain. Moreover, ligand–receptor interaction analyses reveal a single
Platynereis
corazonin receptor (CrzR) to be activated by CRZ1/GnRHL1, CRZ2/GnRHL2, and GnRHL3 (previously classified as AKH1), whereas 2 AKH-type hormone receptors (GnRHR1/AKHR1 and GnRHR2/AKHR2) respond only to a single ligand (GnRH2/GnRHL4).
Crz1/gnrhl1
exhibits a particularly strong up-regulation in sexually mature animals, after feeding, and in specific lunar phases. Homozygous
crz1/gnrhl1
knockout animals exhibit a significant delay in maturation, reduced growth, and attenuated regeneration. Through a combination of proteomics and gene expression analysis, we identify enzymes involved in carbohydrate metabolism as transcriptional targets of CRZ1/GnRHL1 signaling. Our data suggest that
Platynereis
CRZ1/GnRHL1 coordinates glycoprotein turnover and energy homeostasis with growth and sexual maturation, integrating both metabolic and developmental demands with the worm’s monthly cycle.
Geographically divergent evolutionary and ecological legacies shape mammal biodiversity in the global tropics and subtropics
Authors: Rowan John , Beaudrot Lydia , Franklin Janet , Reed Kaye E. , Smail Irene E. , Zamora Andrew , Kamilar Jason M.
Published: December 2019

Significance

Research in ecology and biogeography often assumes that ecological communities are shaped primarily by recent drivers, such as current climate and human activity. Here we analyze a comprehensive dataset of 515 large mammal communities across the Earth’s tropics and subtropics and show that present-day diversity patterns are codetermined by both past and present factors. Although current climate is important, paleoclimatic influences are strong. Likewise, while post-Industrial Revolution human impacts have affected mammal diversity patterns, imprints of prehistoric human-driven extinctions over the last ∼100,000 y are also evident. The influence of past versus present climate and human impacts varies markedly around the world, highlighting the importance of regionally unique evolutionary and ecological histories in shaping global patterns of biodiversity.
Insights into the mechanism and regulation of the CbbQO-type Rubisco activase, a MoxR AAA+ ATPase
Authors: Tsai Yi-Chin Candace , Ye Fuzhou , Liew Lynette , Liu Di , Bhushan Shashi , Gao Yong-Gui , Mueller-Cajar Oliver
Published: December 2019

The vast majority of biological carbon dioxide fixation relies on the function of ribulose 1,5-bisphosphate carboxylase/oxygenase (Rubisco). In most cases the enzyme exhibits a tendency to become inhibited by its substrate RuBP and other sugar phosphates. The inhibition is counteracted by diverse molecular chaperones known as Rubisco activases (Rcas). In some chemoautotrophic bacteria, the CbbQO-type Rca Q2O2 repairs inhibited active sites of hexameric form II Rubisco. The 2.2-Å crystal structure of the MoxR AAA+ protein CbbQ2 from
Acidithiobacillus ferrooxidans
reveals the helix 2 insert (H2I) that is critical for Rca function and forms the axial pore of the CbbQ hexamer. Negative-stain electron microscopy shows that the essential CbbO adaptor protein binds to the conserved, concave side of the CbbQ2 hexamer. Site-directed mutagenesis supports a model in which adenosine 5′-triphosphate (ATP)-powered movements of the H2I are transmitted to CbbO via the concave residue L85. The basal ATPase activity of Q2O2 Rca is repressed but strongly stimulated by inhibited Rubisco. The characterization of multiple variants where this repression is released indicates that binding of inhibited Rubisco to the C-terminal CbbO VWA domain initiates a signal toward the CbbQ active site that is propagated via elements that include the CbbQ α4-β4 loop, pore loop 1, and the presensor 1-β hairpin (PS1-βH). Detailed mechanistic insights into the enzyme repair chaperones of the highly diverse CO
2
fixation machinery of Proteobacteria will facilitate their successful implementation in synthetic biology ventures.
Kinetics and mechanism of planar nanowire growth
Authors: Rothman Amnon , Dubrovskii Vladimir G. , Joselevich Ernesto
Published: December 2019

Significance

Surface-guided growth of planar nanowires is an attractive way of creating aligned arrays of nanowires to enable their large-scale integration into practical devices, but the kinetics and mechanism of planar vs. regular nonplanar growth are poorly controlled and understood. We present kinetic data for planar nanowire growth supported by a theoretical model. Planar vs. nonplanar nanowire growth rates show different power dependence on nanowire diameter attributed to the dimensionality of precursor material diffusion. Whereas the regular nonplanar growth is dominated by surface diffusion over the nanowire sidewalls, planar growth is found to be dominated by surface diffusion over the substrate. This knowledge enables much higher control over the diameter and length distribution of surface-guided nanowires in different material systems.
Human activities have opposing effects on distributions of narrow-ranged and widespread plant species in China
Authors: Xu Wu-Bing , Svenning Jens-Christian , Chen Guo-Ke , Zhang Ming-Gang , Huang Ji-Hong , Chen Bin , Ordonez Alejandro , Ma Ke-Ping
Published: December 2019

Significance

Human activities can drive both species’ range contractions and expansions. Species’ responses to human activities are suggested to be influenced by their geographic range sizes. Here, we test the idea that human impacts cause range declines in small-range species but promote range expansion of common species, using distribution data for 9,701 plants across China to examine the relation of human activities to the degree to which species fill their climatic potential ranges. We found that narrow-ranged and widespread species indeed exhibited opposing responses to human activities, with their range filling decreasing and increasing with human influence, respectively. These findings suggest that human activities have reduced ranges of narrow-ranged species but expanded those of widespread species, causing biotic homogenization across China.
SIRT5 stabilizes mitochondrial glutaminase and supports breast cancer tumorigenesis
Authors: Greene Kai Su , Lukey Michael J. , Wang Xueying , Blank Bryant , Druso Joseph E. , Lin Miao-chong J. , Stalnecker Clint A. , Zhang Chengliang , Negrón Abril Yashira , Erickson Jon W. , Wilson Kristin F. , Lin Hening , Weiss Robert S. , Cerione Richard A.
Published: December 2019

Significance

The mitochondrial enzyme glutaminase (GLS) is frequently up-regulated in cancer cells, and a GLS-selective inhibitor is being evaluated in clinical trials. Previous screens identified succinylated lysine residues on GLS, but the functional consequences of these posttranslational modifications have remained unclear. Here, we report that the mitochondrial desuccinylase SIRT5 stabilizes GLS. Both GLS and SIRT5 are upregulated during cellular transformation, and high expression of SIRT5 in human breast tumors correlates with poor patient prognosis. Mechanistically, SIRT5-mediated desuccinylation of residue K164 protects GLS from ubiquitination at K158 and from subsequent degradation. These findings reveal an important role for SIRT5 in mammary tumorigenesis and establish a posttranslational mechanism regulating GLS levels. Collectively, they support further investigation of SIRT5 as a potential therapeutic target.
Retroviruses drive the rapid evolution of mammalianAPOBEC3genes
Authors: Ito Jumpei , Gifford Robert J. , Sato Kei
Published: December 2019

APOBEC3(A3) genes are members of theAID/APOBECgene family that are found exclusively in mammals.A3genes encode antiviral proteins that restrict the replication of retroviruses by inducing G-to-A mutations in their genomes and have undergone extensive amplification and diversification during mammalian evolution. Endogenous retroviruses (ERVs) are sequences derived from ancient retroviruses that are widespread mammalian genomes. In this study we characterize theA3repertoire and use the ERV fossil record to explore the long-term history of coevolutionary interaction between A3s and retroviruses. We examine the genomes of 160 mammalian species and identify 1,420AID/APOBEC-related genes, including representatives of previously uncharacterized lineages. We show thatA3genes have been amplified in mammals and that amplification is positively correlated with the extent of germline colonization by ERVs. Moreover, we demonstrate that the signatures of A3-mediated mutation can be detected in ERVs found throughout mammalian genomes and show that in mammalian species with expandedA3repertoires, ERVs are significantly enriched for G-to-A mutations. Finally, we show thatA3amplification occurred concurrently with prominent ERV invasions in primates. Our findings establish that conflict with retroviruses is a major driving force for the rapid evolution of mammalianA3genes.
Elastic avalanches reveal marginal behavior in amorphous solids
Authors: Shang Baoshuang , Guan Pengfei , Barrat Jean-Louis
Published: December 2019

Mechanical deformation of amorphous solids can be described as consisting of an elastic part in which the stress increases linearly with strain, up to a yield point at which the solid either fractures or starts deforming plastically. It is well established, however, that the apparent linearity of stress with strain is actually a proxy for a much more complex behavior, with a microscopic plasticity that is reflected in diverging nonlinear elastic coefficients. Very generally, the complex structure of the energy landscape is expected to induce a singular response to small perturbations. In the athermal quasistatic regime, this response manifests itself in the form of a scale-free plastic activity. The distribution of the corresponding avalanches should reflect, according to theoretical mean-field calculations [S. Franz and S. Spigler,
Phys. Rev. E
95, 022139 (2017)], the geometry of phase space in the vicinity of a typical local minimum. In this work, we characterize this distribution for simple models of glass-forming systems, and we find that its scaling is compatible with the mean-field predictions for systems above the jamming transition. These systems exhibit marginal stability, and scaling relations that hold in the stationary state are examined and confirmed in the elastic regime. By studying the respective influence of system size and age, we suggest that marginal stability is systematic in the thermodynamic limit.
In situ self-assembling Au-DNA complexes for targeted cancer bioimaging and inhibition
Authors: Wang Maonan , Chen Yun , Cai Weijuan , Feng Huan , Du Tianyu , Liu Weiwei , Jiang Hui , Pasquarelli Alberto , Weizmann Yossi , Wang Xuemei
Published: December 2019

Significance

Although many efforts have been devoted to localize and monitor cancer progression, it is still difficult to precisely evaluate the development of cancers for efficient targeted treatments. Herein, we demonstrate a straightforward strategy using in situ self-assembly of gold nanocluster–DNA complexes. In combination with the tumor suppressor gene-phosphatase and tensin homolog (PTEN), the gold nanocluster-PTEN complexes could realize targeted bioimaging and identification of cancers and simultaneously inhibit the effect of relevant oncogenes. Meanwhile, these biocompatible self-assembling gold nanocluster–PTEN complexes cannot only facilitate safe and targeted therapeutics, but can also avoid the side effects of conventional DNA transfection. This strategy allows the possibility of establishing a multimode platform for accurately targeted cancer theranostics to eradicate tumors and vascularized metastases.
Assessment of the manganese cluster’s oxidation state via photoactivation of photosystem II microcrystals
Authors: Cheah Mun Hon , Zhang Miao , Shevela Dmitry , Mamedov Fikret , Zouni Athina , Messinger Johannes
Published: December 2019

Knowledge of the manganese oxidation states of the oxygen-evolving Mn
4
CaO
5
cluster in photosystem II (PSII) is crucial toward understanding the mechanism of biological water oxidation. There is a 4 decade long debate on this topic that historically originates from the observation of a multiline electron paramagnetic resonance (EPR) signal with effective total spin of S = 1/2 in the singly oxidized S
2
state of this cluster. This signal implies an overall oxidation state of either Mn(III)
3
Mn(IV) or Mn(III)Mn(IV)
3
for the S
2
state. These 2 competing assignments are commonly known as “low oxidation (LO)” and “high oxidation (HO)” models of the Mn
4
CaO
5
cluster. Recent advanced EPR and Mn K-edge X-ray spectroscopy studies converge upon the HO model. However, doubts about these assignments have been voiced, fueled especially by studies counting the number of flash-driven electron removals required for the assembly of an active Mn
4
CaO
5
cluster starting from Mn(II) and Mn-free PSII. This process, known as photoactivation, appeared to support the LO model since the first oxygen is reported to evolve already after 7 flashes. In this study, we improved the quantum yield and sensitivity of the photoactivation experiment by employing PSII microcrystals that retained all protein subunits after complete manganese removal and by oxygen detection via a custom built thin-layer cell connected to a membrane inlet mass spectrometer. We demonstrate that 9 flashes by a nanosecond laser are required for the production of the first oxygen, which proves that the HO model provides the correct description of the Mn
4
CaO
5
cluster’s oxidation states.
Social media-predicted personality traits and values can help match people to their ideal jobs
Authors: Kern Margaret L. , McCarthy Paul X. , Chakrabarty Deepanjan , Rizoiu Marian-Andrei
Published: December 2019

Work is thought to be more enjoyable and beneficial to individuals and society when there is congruence between one’s personality and one’s occupation. We provide large-scale evidence that occupations have distinctive psychological profiles, which can successfully be predicted from linguistic information unobtrusively collected through social media. Based on 128,279 Twitter users representing 3,513 occupations, we automatically assess user personalities and visually map the personality profiles of different professions. Similar occupations cluster together, pointing to specific sets of jobs that one might be well suited for. Observations that contradict existing classifications may point to emerging occupations relevant to the 21st century workplace. Findings illustrate how social media can be used to match people to their ideal occupation.