bluuebunny/crossref_metadata_2025 huggingface dataset:
DEM analysis of passive failure state behind a rigid retaining wall: effect of boundary conditions
Authors: Altunbas Adlen , Soltanbeigi Behzad , Cinicioglu Ozer
Published: June 2019

Discrete Element Modelling (DEM) is a virtual testing method that enables multiscale studies on granular materials. DEM provides a well-controlled testing environment, which enables precise systematic evaluation of the factors influencing the bulk response. The current study focuses on the behaviour of cohesionless backfills while a passive state of stress is simulated (i.e. rigid retaining wall translates toward backfill). Though particle-scale properties (e.g. size, shape and cohesion) play an important role on the macro response, the main objective in this study is to highlight the extent by which boundary conditions are important. Thus, identical dense packings are subject to the following boundary conditions: smooth/rough retaining wall and smooth/rough/periodic sidewalls (necessary for maintaining plain-strain conditions). Based on the DEM results, the failure surface geometries, wall pressure distribution and dilative response of the specimens are evaluated. It is seen that a curvilinear slip surface, similar to that observed in experiments, is only obtained once a rough retaining wall and periodic sidewalls are available. The overall observations suggest that the mobilisation of the passive state of stress, for a cohesionless granular assembly, is highly sensitive to the considered various boundary conditions.
Modelling fracture formation and propagation in geo-materials
Authors: Maedo Michael A. , Sánchez Marcelo , Guimarães Leonardo , Manzoli Osvaldo , Cleto Pedro
Published: June 2019

The modelling of fracture formation and propagation in geo-materials is a subject of interest in several problems and applications. In this work, finite elements with high aspect ratio are used to study the hydraulic fracture process in the context of conventional continuum constitutive (stress-strain) relationships based on the damage theory. The deformable porous material is solved in a coupled manner by considering a fully hydro-mechanical approach. The adopted approach is explained and validated against analytical and numerical solutions.
Slope stability analysis: Barodesy vs linear elastic – perfectly plastic models
Authors: Tschuchnigg Franz , Medicus Gertraud , Schneider-Muntau Barbara
Published: June 2019

The results of slope stability analysis are not unique. Different factors of safety are obtained investigating the same slope. The differences result from different constitutive models including different failure surfaces. In this contribution, different strength reduction techniques for two different constitutive models (linear elastic - perfectly plastic model using a Mohr-Coulomb failure criterion and barodesy) have been investigated on slope stability calculations for two different slope inclinations. The parameters for Mohr – Coulomb are calibrated on peak states of element tests simulated with barodesy for different void ratios. For both slopes the predictions of the factors of safety are higher with barodesy than with Mohr-Coulomb. The difference is to some extend explained by the different shapes of failure surfaces and thus different values for peak strength under plane strain conditions. The plane strain predictions of Mohr-Coulomb are conservative compared to barodesy, where the failure surface coincides with Matsuoka-Nakai.
Vitamin D Replacement Mitigates Menopause-Associated Dyslipidaemia
and Atherogenic Indices in Ovariectomized Rats; A Biochemical
Study
Authors: Muhammad Marwa Hassan , Hussien Noha Ibrahim , Elwia Sania K.
Published: June 2019

Background & Aim Dyslipidaemia is highly prevalent among
postmenopausal women and its management represents a keystone in the
prevention of the worldwide increase in cardiovascular morbidity and
mortality. Therapy choices for menopause-associated dyslipidaemia are
limited and a matter of debate. So, it becomes prudent to search for natural
safe alternatives. Vitamin D (VD) has been acknowledged as an essential
factor in cardiovascular health. Thus, we aimed to illustrate the impact of
different VD status on dyslipidaemia and atherogenic indices.

Method 5 groups of rats were conducted; SHAM group fed control diet,
ovariectomized rats fed control diet (OVX), ovariectomized rats fed
VD-sufficient-high fat diet (HFD) (1 000 IU/ kg
diet), ovariectomized rats fed VD-deficient-HFD (25 IU/ kg
diet), and ovariectomized rats fed VD-replete-HFD
(10 000 IU/ kg diet) for 16 weeks.

Results Dyslipidaemia with an increased atherogenic index of plasma,
atherosclerosis coefficient, cardiac risk ratio, and aortic total
cholesterol accumulation in addition to reduced serum 25-hydroxy-VD levels
was observed in the OVX and VD-sufficient HFD versus SHAM. These findings
were aggravated by VD-deficient-HFD while reversed by VD-replete-HFD. The
VD-mediated abundance of aortic ATP-binding cassette transporter A1 (ABCA1)
expression, reduced activity of the inflammatory Jun N-terminal kinases
(JNK), and downregulation of aortic cluster of differentiation-36 (CD36)
receptors expression together with increased serum total antioxidant
capacity and reduced serum malondialdehyde were among the supposed
mechanisms.

Conclusions Our study sheds light on alarming levels of VD deficiency
among ovariectomized rats. VD repletion improved the menopause-associated
dyslipidaemia and atherogenic indices through hypolipidemic, antioxidant,
and anti-inflammatory effects.
A Facile Access to Novel (5+5) Annellated Heterocycles: Synthesis of a Furopyrrole, an Imidazoimidazole and a Pyrroloimidazole
Authors: Zlatoidský Pavol , Martinelli Elisa , Svensson Emil , Pruvost Alexis
Published: June 2019

We describe the synthesis of an ethyl 3-aryl-6H-furo[2,3-b]pyrrole-5-carboxylate 2, a 5-aryl-1H-imidazo[1,2-a]imidazole 3, and an ethyl-1-aryl-1,4-dihydropyrrolo[2,3-d]imidazole-5-carboxylate 4 as new hinge-binding motifs for PI3K kinase inhibitors. A key reaction for the formation of 2 and 4 is the Hemmetsberger–Knittel cyclization of acryloazides. The core of 3 is accessible through reaction of an α-haloketone with 2-aminoimidazole.
Validity of Coagulation Activation Markers in Antiphospholipid Syndrome: A Systematic Review and Meta-analysis with a Short Data Report
Authors: Ames Paul R.J. , Bucci Tommaso , Iannaccone Luigi , Marottoli Vincenzo , Arcaro Alessia , Gentile Fabrizio , Ciampa Antonio
Published: June 2019

Prothrombin fragment F1 + 2 (F1 + 2) and thrombin–antithrombin (TAT) have been assessed in antiphospholipid syndrome (APS) but without evaluating a direct relationship with antiphospholipid (aPL) antibody titers. This article aims to investigate a direct relationship between aPL and F1 + 2 and perform a systematic review and meta-analysis of F1 + 2 and TAT in APS. Systematic search was performed using EMBASE and PubMed databases from January 1982 to December 2018 and random effects meta-analyses for continuous outcomes. This is a cross-sectional case–control study; immunoglobulin G/immunoglobulin M (IgG/IgM) anticardiolipin (aCL) anti-β2-glycoprotein-I, antiprothrombin (aPT) antibodies, F1 + 2, and lupus anticoagulants (LA) were measured in 25 thrombotic primary APS (PAPS), 9 nonthrombotic carriers of aPL, and 18 controls. The significant effect size (ES) for F1 + 2 between aPL +ve and aPL −ve systemic lupus erythematosus (SLE) and between aPL +ve SLE and control displayed high heterogeneity. The significant ES for F1 + 2 between aPL −ve SLE and controls displayed no heterogeneity. The ES for TAT between aPL +ve and aPL −ve SLE patients and between aPL −ve SLE and controls was low, without heterogeneity. Mean F1 + 2 was greater in PAPS (p < 0.0001), inversely correlated with IgG aCL, IgM aPT, and LA (p = 0.001, 0.03, and 0.01, respectively), though only IgG aCL negatively predicted F1 + 2 (p = 0.01). IgG aCL inversely predicts F1 + 2. IgG aCL positivity introduces heterogeneity in the F1 + 2 ES, whereas the lack of heterogeneity in the ES for TAT may indicate poor TAT formation in aPL +ve group. Thus, F1 + 2 measurements may be unfounded as already demonstrated for TAT in the 1990s.
Fake news game confers psychological resistance against online misinformation
Authors: Roozenbeek Jon , van der Linden Sander
Published: June 2019

The spread of online misinformation poses serious challenges to societies worldwide. In a novel attempt to address this issue, we designed a psychological intervention in the form of an online browser game. In the game, players take on the role of a fake news producer and learn to master six documented techniques commonly used in the production of misinformation: polarisation, invoking emotions, spreading conspiracy theories, trolling people online, deflecting blame, and impersonating fake accounts. The game draws on an inoculation metaphor, where preemptively exposing, warning, and familiarising people with the strategies used in the production of fake news helps confer cognitive immunity when exposed to real misinformation. We conducted a large-scale evaluation of the game with N = 15,000 participants in a pre-post gameplay design. We provide initial evidence that people’s ability to spot and resist misinformation improves after gameplay, irrespective of education, age, political ideology, and cognitive style.
(Ba0.85Ca0.15)(Ti0.9Zr0.1)O3 thin films prepared by PLD: Relaxor properties and complex microstructure
Authors: Piorra André , Hrkac Viktor , Wolff Niklas , Zamponi Christiane , Duppel Viola , Hadermann Joke , Kienle Lorenz , Quandt Eckhard
Published: June 2019

Ferroelectric lead-free thin films of the composition (Ba0.85Ca0.15)(Ti0.9Zr0.1)O3 (BCZT) were deposited by pulsed laser deposition on Pt/TiO2/SiO2/Si substrates using a ceramic BCZT target prepared by a conventional solid state reaction. The target material itself shows a piezoelectric coefficient of d33 = 640 pm/V. The (111) textured thin films possess a thickness of up to 1.1 μm and exhibit a clamped piezoelectric response d33,f of up to 190 pm/V, a dielectric coefficient of ɛr = 2000 at room temperature, and a pronounced relaxor behavior. As indicated by transmission electron microscopy, the thin films are composed of longitudinal micrometersized columns with ∼100 nm lateral dimension that are separated at twin- and antiphase boundaries. The superposition phenomena according to this columnar growth were simulated based on suitable supercells. The major structural component is described as a tetragonal distorted variant of the perovskite parent type; however, frequently coherently intergrown nanodomains were observed indicating a much more complex structure that is characterized by a 7-layer modulation along the growth direction of the films.
Temperature-dependent properties of magnetic CuFeS2 from first-principles calculations: Structure, mechanics, and thermodynamics
Authors: Khaledialidusti Rasoul , Mishra Abhishek Kumar , Barnoush Afrooz
Published: June 2019

Chalcopyrite (CuFeS2) is an antiferromagnetic semiconductor with promising magnetic and electrical properties, although these properties are not yet completely understood. The structural, magnetic, and electronic properties of bulk CuFeS2 were studied via first-principles plane-wave pseudopotential calculations based on density functional theory (DFT) using DFT+U and hybrid functional B3LYP methodology. The temperature-dependent structural, thermal, and mechanical properties of tetragonal CuFeS2 were also investigated via density functional perturbation theory. Furthermore, the structural parameters, elastic constants, bulk and shear moduli, volume expansion, and specific heats as a function of temperature were evaluated. Tetragonal CuFeS2 was found to exhibit negative thermal expansion behavior at temperatures lower than 100 K. A comprehensive comparison of the various calculated parameters with earlier published studies is also presented along with available experimental data and used as a basis to critically discuss the various properties of CuFeS2.
Mapping the structural transitions controlled by the trilinear coupling in Ca3-xSrxTi2O7
Authors: Kratochvilova Marie , Huang Fei-Ting , Diaz Maria-Teresa Fernandez , Klicpera Milan , Day Sarah J. , Thompson Stephen P. , Oh Yoon-Seok , Gao Bin , Cheong Sang-Wook , Park Je-Geun
Published: June 2019

We present the results of the high-temperature neutron and x-ray diffraction experiments on the Ca3–xSrxTi2O7 (x = 0.5, 0.8, 0.85, 0.9) compounds. The ferro- to paraelectric transition in these hybrid improper ferroelectric materials arises from the so-called trilinear coupling. Depending on the strontium content, various structures and phase transitions, different from theoretical predictions, emerge. The in situ x-ray powder diffraction indicates a direct ferro- to paraelectric transition between the orthorhombic A21am and the tetragonal undistorted I4/mmm phase for x ≤ 0.6. We identified a reduction in the trilinear coupling robustness by increasing the Sr-doping level to lead to the emergence of the intermediate tetragonal P42/mnm phase and the gradual suppression of the orthorhombic phase. The observed character of the structure transitions and the Ca3–xSrxTi2O7 phase diagram are discussed in the framework of theoretical models of other related hybrid improper ferroelectric systems.
Characterization of a microwave argon plasma column at atmospheric pressure by optical emission and absorption spectroscopy coupled with collisional-radiative modelling
Authors: Durocher-Jean Antoine , Desjardins Edouard , Stafford Luc
Published: June 2019

Optical emission and absorption spectroscopy of argon 2p-1s transitions (Paschen notation) combined with collisional-radiative (CR) modeling of argon 2p states are developed and used to determine the neutral gas temperature, the Ar 1s number density, and the electron temperature along a microwave argon plasma column at atmospheric pressure. The CR model, designed specifically for atmospheric-pressure and optically thick plasma conditions, is fully detailed and validated by comparing the relative line emission intensities of argon 2p-to-1s transitions measured experimentally with the ones predicted by the CR model using the electron temperature as the only adjustable parameter. Subsequently, the neutral gas temperature (∼1300–1600 K; obtained from the broadening of argon 2p2-1s2 and 2p3-1s2 emission lines), the Ar 1s5 number density (1–2 × 1018 m−3; obtained from absorption spectroscopy of the argon 2p9-1s5 transition using a tunable laser diode), and the electron temperature (∼1.4 eV; obtained from the comparison between the measured and simulated 2p-to-1s emission line intensities) are reported as a function of the axial distance along the microwave plasma column. The values and behaviors reveal a good agreement with those reported in previous experimental and modeling studies.
Flow structures of a lobed mixer and effects of streamwise vortices on mixing enhancement
Authors: Fang Xin-xin , Shen Chi-bing , Sun Ming-bo , Sandberg Richard D. , Wang Peng
Published: June 2019

Large-scale vortices downstream of a lobed mixer are investigated experimentally using a nanoparticle-based planar laser scattering experimental system. The results are contrasted with additional measurements of a flat plate and a convoluted plate. Three streamwise vortices form downstream of the lobed mixer due to the pressure difference between the peak and trough regions of the trailing edge. This is not the case for the convoluted plate, where the streamwise structures are suppressed and do not appear downstream. Comparison of vortex sizes indicates that streamwise vortices contribute almost 80% of mixing enhancement, which is substantially higher than what could be expected from the increase of the interfacial surface area, especially in the far field of the present compressible mixing layer. It is also quite different from the effects of streamwise vortices on the mixing enhancement in incompressible mixing layers. That no streamwise vortices appear downstream of the convoluted plate indicates that the pressure difference around the corners of the peak and trough regions in the lobed mixer plays an important role for the appearance of the streamwise vortices. Three-dimensional views of the streamwise vortices show that a significant amount of fluid is entrained from the lower stream to the upper stream, resulting in the development of the streamwise vortices for the lobed mixer. The interaction of the streamwise and spanwise vortices then leads to the formation of a large number of small-scale vortices. These two mechanisms enlarge the interfacial surface area of the two streams greatly and substantially improve the turbulent mixing prominently. In addition, the presence of vortex clusters and T-shape vortices in the mixing layer indicate that they are common topological structures in such flows.
Groove-structured meta-surface for patterned sub-diffraction sound focusing
Authors: Chen Jian , Sun Zeqing , Fan Zheng
Published: June 2019

Confining acoustic fields in subwavelength volumes is of fundamental interest in wave-energy harvesting and high-resolution imaging. Phononic crystals have been shown to be capable of superfocusing but are highly limited by their very large dimensions. Acoustic metasurfaces can yield similar functionality with unit cells significantly smaller than the wavelength. However, they are studied mostly under effective medium theory and cannot manipulate evanescent waves directly to control near-field focusing. Here, we use a microscopic approach to study acoustic metasurfaces for subdiffraction focusing of reflected waves, which consist of an array of deep-subwavelength sized and spaced grooves. We further show that the focusing pattern can be tailored by the designer. To validate the effectiveness of our scheme, two representative metasurfaces are designed theoretically, proved numerically, and confirmed experimentally for subdiffraction sound focusing with different patterns. We hope that our approach can work as a general guideline to shape near-field signals in the broad field of acoustics.
Carrier densities of Sn-doped In2O3 nanoparticles and their effect on X-ray photoelectron emission
Authors: Jia Junjun , Takaya Ai , Yonezawa Takehiro , Yamasaki Kazuhiko , Nakazawa Hiromi , Shigesato Yuzo
Published: June 2019

Sn-doped In2O3 (ITO) nanoparticles with various Sn doping concentrations were successfully fabricated using a liquid phase coprecipitation method. Similar to sputtered ITO thin films, Sn doping reaches a maximum carrier density (1.52×1021cm−3) at 10 at. % in ITO nanoparticles, which was estimated from the bulk plasmon energy based on a scanning ellipsometry (SE) simulation. Interestingly, the X-ray photoelectron emission spectra (XPS) of In 3d core levels show a clear asymmetric peak with a shoulder on the high-binding-energy side for degenerated ITO nanoparticles, which may be associated with the influence of the surface plasmon or plasmonic coupling. Our results suggest that combining the SE simulation and XPS measurements effectively provides a new way to understand the difference between bulk plasmons and surface plasmons for transparent conductive oxide nanoparticles.
Bifurcation diagram and dynamic response of a MEMS resonator with a 1:3 internal resonance
Authors: Czaplewski David A. , Strachan Scott , Shoshani Oriel , Shaw Steven W. , López Daniel
Published: June 2019

The dynamic response of a nonlinear resonator in the presence of resonant mode coupling is studied experimentally and theoretically. For the case of a clamped-clamped beam resonator in the presence of a 1:3 internal resonance, we show that at the onset of internal resonance, steady state oscillations cannot be sustained. At higher drive levels, stable oscillations can be maintained but the resonator amplitude undergoes amplitude modulated responses. We use these dynamic responses to build a bifurcation diagram that can be described remarkably well with a simple model consisting of a Duffing resonator coupled to a linear one.
Quantum simulation of ferromagnetic and anti-ferromagnetic tunneling anisotropic magnetoresistance in a single-molecule-magnet dimer tunnel-junction
Authors: Zhang Chao , Yao Hui , Nie Yi-Hang , Liang Jiu-Qing
Published: June 2019

In this work, we simulate the tunneling anisotropic magnetoresistance (TAMR) in a single-molecule-magnet (SMM) dimer tunnel-junction with metal and ferromagnetic (FM) electrodes. The non-collinear polarization of electrode with respect to the uniaxial anisotropy-axis of magnet results in both the FM and anti-ferromagnetic (AFM) TAMR respectively for the FM and AFM inter-molecule couplings. In terms of the spin coherent state representation of electron spin the non-collinear tunneling is able to be analyzed with the usual rate equation approach in a sequential tunneling regime. The ferromagnetic TAMR varies with the non-collinear angle and the tunneling magnetoresistance (TMR) is just a special case of the angle θ = π. With the FM dimer we obtain the higher TMR up to 400% and the high polarization rate (79%) of spin current as well. The angle dependence of TAMR for the AFM dimer is also presented along with the spin current.
Link prediction for tree-like networks
Authors: Shang Ke-ke , Li Tong-chen , Small Michael , Burton David , Wang Yan
Published: June 2019

Link prediction is the problem of predicting the location of either unknown or fake links from uncertain structural information of a network. Link prediction algorithms are useful in gaining insight into different network structures from partial observations of exemplars. However, existing link prediction algorithms only focus on regular complex networks and are overly dependent on either the closed triangular structure of networks or the so-called preferential attachment phenomenon. The performance of these algorithms on highly sparse or treelike networks is poor. In this letter, we proposed a method that is based on the network heterogeneity. We test our algorithms for three real large sparse networks: a metropolitan water distribution network, a Twitter network, and a sexual contact network. We find that our method is effective and performs better than traditional algorithms, especially for the Twitter network. We further argue that heterogeneity is the most obvious defining pattern for complex networks, while other statistical properties failed to be predicted. Moreover, preferential attachment based link prediction performed poorly and hence we infer that preferential attachment is not a plausible model for the genesis of many networks. We also suggest that heterogeneity is an important mechanism for online information propagation.
High-gain leaky surface acoustic wave amplifier in epitaxial InGaAs on lithium niobate heterostructure
Authors: Hackett L. , Siddiqui A. , Dominguez D. , Douglas J. K. , Tauke-Pedretti A. , Friedmann T. , Peake G. , Arterburn S. , Eichenfield M.
Published: June 2019

Active surface acoustic wave components have the potential to transform RF front ends by consolidating functionalities that currently occur across multiple chip technologies, leading to reduced insertion loss from converting back and forth between acoustic and electronic domains in addition to improved size and power efficiency. This letter demonstrates a significant advance in these active devices with a compact, high-gain, and low-power leaky surface acoustic wave amplifier based on the acoustoelectric effect. Devices use an acoustically thin semi-insulating InGaAs surface film on a YX lithium niobate substrate to achieve exceptionally high acoustoelectric interaction strength via an epitaxial In0.53Ga0.47As(P)/InP quaternary layer structure and wafer-scale bonding. We demonstrate 1.9 dB of gain per acoustic wavelength and power consumption of 90 mW for 30 dB of electronic gain. Despite the strong intrinsic leaky propagation loss, 5 dB of terminal gain is obtained for a semiconductor that is only 338 μm long due to state-of-the-art heterogenous integration and an improved material platform.
CuO-CeO2 nanocomposite catalysts produced by mechanochemical synthesis
Authors: Borchers Ch. , Martin M. L. , Vorobjeva G. A. , Morozova O. S. , Firsova A. A. , Leonov A. V. , Kurmaev E. Z. , Kukharenko A. I. , Zhidkov I. S. , Cholakh S. O.
Published: June 2019

Mechanochemical synthesis based on ball-milling of individual oxides was applied as a one-step preparation technique for CuO-CeO2 catalyst for preferential CO oxidation in H2 excess. The mechanical energy dose transferred to the original powder mixture determines both the catalyst composition and activity. It is found that after 90 min of milling (corresponding to a dose of 372 kJ mol–1), a mixture of 10 wt.% CuO-CeO2 powder exhibits a CO conversion of 97% at 423 K. Four active oxygen states, which are not observed in case of pure CeO2, were detected in the nanocomposite lattice and attributed to the presence of Cu in surface sites as well as in subsurface bulk sites of CeO2, in nearest neighbor and next nearest neighbor positions. Correspondingly, oxidation of CO to CO2 was found to occur in a two-stage process with Tmax = 395/460 K, and oxidation of H2 to H2O likewise in a four-stage process with Tmax = 426/448/468/516 K. The milled powder consists of CeO2 crystallites sized 8–10 nm agglomerated to somewhat larger aggregates, with CuO dispersed on the surface of the CeO2 crystallites, and to a lesser extent present as Cu2O.
Space charge suppression in environment-friendly PP nanocomposites by employing freeze-dried MgO with foam nanostructure for high-voltage power cable insulation
Authors: Zha Jun-Wei , Wang Ying , Wang Si-Jiao , Zheng Ming-Sheng , Bian Xingming , Dang Zhi-Min
Published: June 2019

Space charge accumulation along insulation thickness is still regarded as a critical issue during the operation of high-voltage direct current transmission cables, which will result in the distortion of the partial electric field, seriously causing the degradation or aging of the main insulation. Polypropylene (PP) environment-friendly thermoplastic cables without cross-linking have shown great potential, which tend to gradually substitute the traditional unrecyclable extruded cross-linked polyethylene cables. Here, the styrene-ethylene-butylene-styrene block copolymer is selected to optimize the mechanical properties of PP. An extremely small amount of MgO with a foam nanostructure synthesized through a designed freeze-drying process is introduced to suppress the accumulation of space charge and further improve the electrical properties of PP insulation. With a very low concentration of foamed MgO (0.2 phr), it is found that the injection and accumulation of space charge could be largely suppressed under 60 kV/mm and the DC conductivity of PP composites remains as low as ∼1.6 × 10−15 S/m. Besides, the DC breakdown strength of the composites is up to 315 kV/mm. Therefore, the PP-matrix composites can be considered as potential high-performance insulating materials in the non-cross-linking environment-friendly thermoplastic high-voltage power cable.
Dopamine-like STDP modulation in nanocomposite memristors
Authors: Nikiruy K. E. , Emelyanov A. V. , Demin V. A. , Sitnikov A. V. , Minnekhanov A. A. , Rylkov V. V. , Kashkarov P. K. , Kovalchuk M. V.
Published: June 2019

The development of memristor-based spiking neuromorphic systems (NS) has been essentially driven by the hope to replicate the extremely high energy efficiency of biological systems. Spike-timing-dependent plasticity (STDP) mechanism is considered as one of the most promising learning rules for NS. STDP learning has been observed in different types of biological synapses in presence of neuromodulators, e.g. dopamine, and is believed to be an enabling phenomenon for important biological functions such as associative and reinforcement learning. However, the direct STDP window change under dopamine-like modulation has not been yet demonstrated in memristive synapses. In this study, we experimentally demonstrate a simple way for the STDP window shape modulation by introducing the coefficients controlling the neuron spike amplitudes. In such a way the STDP window shape could be modulated from a classical asymmetric shape to a bell-shaped, as well as to anti-STDP and to anti-bell-shaped. The experiments have been carried out with (Co0.4Fe0.4B0.2)x(LiNbO3)1−x nanocomposite-based memristors. Memristive characteristics of the nanocomposite structures with different metal content are also comprehensively studied. Obtained results give every hope for bio-inspired operation of the future large memristor-based NS with reinforcement learning ability.
Special Topic on Nonlinear Optics in 2D Materials
Authors: Vermeulen Nathalie , Palomba Stefano
Published: June 2019

Over the past decade, graphene and other two-dimensional (2D) materials have been widely recognized as promising media for establishing nonlinear light-matter interactions. The scope of this Special Topic is to present new insights in the nonlinear-optical characteristics of these 2D crystals, both from a theoretical and an experimental point of view, and to address their potential for practical applications. Particular attention is paid to the role of intraband and interband transitions, the dynamics of the photocarriers excited in the materials, the analogies and differences between graphene and its 3D and 1D counterparts, and the combination of 2D materials with waveguiding and/or resonance structures. This editorial concludes with a general outlook for future research in the field.
Properties of factorization operators in boundary crossing problems for random walks
Authors: Lotov V. I.
Published: June 2019

We study the properties of operators arising in the calculation of double Laplace–Stieltjes transforms of distributions in various boundary crossing problems for random walks. Such operators are defined in terms of the components of the Wiener–Hopf factorization. We give bounds for the norms of these operators and prove continuity theorems.
Systematic mapping of cell wall mechanics in the regulation of cell morphogenesis
Authors: Davì Valeria , Chevalier Louis , Guo Haotian , Tanimoto Hirokazu , Barrett Katia , Couturier Etienne , Boudaoud Arezki , Minc Nicolas
Published: June 2019

Significance

The cell wall is a thin polymeric layer encasing the membrane of bacterial, fungal, and vegetal cells, which supports viability and defines cell shape and the mode of growth and division. The material properties of the cell wall are thus key for understanding morphogenesis, but remain difficult to quantify. We introduce a systematic method to map subcellular values of cell wall thickness and bulk elasticity in large populations of yeast cells with unprecedented accuracy. By screening libraries of mutants with defects in cell shapes, we demonstrate that cell walls are stiffer in larger cells or larger cell portions. This size-dependent stiffening constrains cell size definition and promotes cell mechanical integrity.
The VEGF receptor neuropilin 2 promotes homologous recombination by stimulating YAP/TAZ-mediated Rad51 expression
Authors: Elaimy Ameer L. , Amante John J. , Zhu Lihua Julie , Wang Mengdie , Walmsley Charlotte S. , FitzGerald Thomas J. , Goel Hira Lal , Mercurio Arthur M.
Published: June 2019

Significance

VEGF signaling mediated by the NRPs impacts tumor cells, independently of its function in angiogenesis and vascular permeability. VEGF–NRP2 signaling in tumor cells is associated with poor prognosis and therapy resistance in TNBC patients. In light of these observations the question arises, How does VEGF–NRP2 contribute to therapy resistance in TNBC? We discovered that autocrine VEGF–NRP2 signaling contributes to HR DNA repair and therapy resistance in TNBC cells by promoting YAP/TAZ-dependent Rad51 transcription. We also demonstrated that Rad51 is a YAP/TAZ target gene and that VEGF–NRP2–YAP/TAZ–mediated cisplatin resistance occurs through downstream Rad51 expression. These observations establish functions of VEGF–NRP2 signaling and YAP/TAZ in tumor biology and provide an integrated mechanism that governs Rad51 expression and HR in TNBC.
Chronic, sublethal effects of high temperatures will cause severe declines in southern African arid-zone birds during the 21st century
Authors: Conradie Shannon R. , Woodborne Stephan M. , Cunningham Susan J. , McKechnie Andrew E.
Published: June 2019

Significance

We synthesized physiological and behavioral data to evaluate the risks of acute, lethal effects of extreme heat events versus the sublethal costs of chronic exposure to sustained hot weather for birds inhabiting southern Africa’s Kalahari Desert over the course of the 21st century. The risk of mass mortality events similar to those predicted for the American southwest and sometimes observed in Australia will remain low for Kalahari birds. However, the sublethal costs of chronic exposure, manifested as progressive loss of body condition, delayed fledging, reduced fledging size, and outright breeding failure, will likely drive major population declines. We anticipate that much of the Kalahari’s avian biodiversity will be lost by the end of the century.
Axonal pathology in hPSC-based models of Parkinson’s disease results from loss of Nrf2 transcriptional activity at the Map1b gene locus
Authors: Czaniecki Christopher , Ryan Tammy , Stykel Morgan G. , Drolet Jennifer , Heide Juliane , Hallam Ryan , Wood Shalandra , Coackley Carla , Sherriff Keith , Bailey Craig D. C. , Ryan Scott D.
Published: June 2019

Significance

Neurological dysfunction in Parkinson’s disease (PD) is highly associated with pathological deposits of aggregated α-synuclein (α-syn) in the brain, and yet an understanding of how early α-syn deposits bring about neuronal dysfunction remains elusive. This study exploits stem cell technology to model PD using two human isogenic stem cell models of the disease. Using these systems, we have identified a mechanism whereby mutant α-syn inhibits the antioxidant response, which, in turn, leads to axonal pathology through loss of expression of microtubule stabilizing proteins. We show that reactivation of this pathway can rescue axonal neuropathology. This is a demonstration of modulation of cytoskeletal elements as a potential therapy against PD, providing a previously unknown link between α-syn mutation and the antioxidant pathway.
The combination of
TPL2
knockdown and TNFα causes synthetic lethality via caspase-8 activation in human carcinoma cell lines
Authors: Serebrennikova Oksana B. , Paraskevopoulou Maria D. , Aguado-Fraile Elia , Taraslia Vasiliki , Ren Wenying , Thapa Geeta , Roper Jatin , Du Keyong , Croce Carlo M. , Tsichlis Philip N.
Published: June 2019

Significance

Tumor necrosis factor α (TNFα) fails to induce apoptosis in most tumor cells. Defining the mechanism(s) responsible for the protection of these cells from TNFα-induced apoptosis may have significant therapeutic implications. Here, we show that tumor progression locus-2 (TPL2), a MAP3 kinase activated by TNFα, protects from TNFα-induced apoptosis by preventing the activation of caspase-8, and that the combination of
TPL2
knockdown and TNFα treatment induces synthetic lethality. More important, sensitivity to synthetic lethality can be predicted from the gene expression profiles of the tumor cells. In addition to their therapeutic potential, these results identify an important node in TNFα signaling.
Single-cell genomics unveiled a cryptic cyanobacterial lineage with a worldwide distribution hidden by a dinoflagellate host
Authors: Nakayama Takuro , Nomura Mami , Takano Yoshihito , Tanifuji Goro , Shiba Kogiku , Inaba Kazuo , Inagaki Yuji , Kawata Masakado
Published: June 2019

Cyanobacteria are one of the most important contributors to oceanic primary production and survive in a wide range of marine habitats. Much effort has been made to understand their ecological features, diversity, and evolution, based mainly on data from free-living cyanobacterial species. In addition, symbiosis has emerged as an important lifestyle of oceanic microbes and increasing knowledge of cyanobacteria in symbiotic relationships with unicellular eukaryotes suggests their significance in understanding the global oceanic ecosystem. However, detailed characteristics of these cyanobacteria remain poorly described. To gain better insight into marine cyanobacteria in symbiosis, we sequenced the genome of cyanobacteria collected from a cell of a pelagic dinoflagellate that is known to host cyanobacterial symbionts within a specialized chamber. Phylogenetic analyses using the genome sequence revealed that the cyanobacterium represents an underdescribed lineage within an extensively studied, ecologically important group of marine cyanobacteria. Metagenomic analyses demonstrated that this cyanobacterial lineage is globally distributed and strictly coexists with its host dinoflagellates, suggesting that the intimate symbiotic association allowed the cyanobacteria to escape from previous metagenomic studies. Furthermore, a comparative analysis of the protein repertoire with related species indicated that the lineage has independently undergone reductive genome evolution to a similar extent as
Prochlorococcus
, which has the most reduced genomes among free-living cyanobacteria. Discovery of this cyanobacterial lineage, hidden by its symbiotic lifestyle, provides crucial insights into the diversity, ecology, and evolution of marine cyanobacteria and suggests the existence of other undiscovered cryptic cyanobacterial lineages.
Structural bases for F plasmid conjugation and F pilus biogenesis in
Escherichia coli
Authors: Hu Bo , Khara Pratick , Christie Peter J.
Published: June 2019

Bacterial conjugation systems are members of the large type IV secretion system (T4SS) superfamily. Conjugative transfer of F plasmids residing in the
Enterobacteriaceae
was first reported in the 1940s, yet the architecture of F plasmid-encoded transfer channel and its physical relationship with the F pilus remain unknown. We visualized F-encoded structures in the native bacterial cell envelope by in situ cryoelectron tomography (CryoET). Remarkably, F plasmids encode four distinct structures, not just the translocation channel or channel-pilus complex predicted by prevailing models. The F1 structure is composed of distinct outer and inner membrane complexes and a connecting cylinder that together house the envelope-spanning translocation channel. The F2 structure is essentially the F1 complex with the F pilus attached at the outer membrane (OM). Remarkably, the F3 structure consists of the F pilus attached to a thin, cell envelope-spanning stalk, whereas the F4 structure consists of the pilus docked to the OM without an associated periplasmic density. The traffic ATPase TraC is configured as a hexamer of dimers at the cytoplasmic faces of the F1 and F2 structures, where it respectively regulates substrate transfer and F pilus biogenesis. Together, our findings present architectural renderings of the DNA conjugation or “mating” channel, the channel–pilus connection, and unprecedented pilus basal structures. These structural snapshots support a model for biogenesis of the F transfer system and allow for detailed comparisons with other structurally characterized T4SSs.
Structures of the cGMP-dependent protein kinase in malaria parasites reveal a unique structural relay mechanism for activation
Authors: El Bakkouri Majida , Kouidmi Imène , Wernimont Amy K. , Amani Mehrnaz , Hutchinson Ashley , Loppnau Peter , Kim Jeong Joo , Flueck Christian , Walker John R. , Seitova Alma , Senisterra Guillermo , Kakihara Yoshito , Kim Choel , Blackman Michael J. , Calmettes Charles , Baker David A. , Hui Raymond
Published: June 2019

The cyclic guanosine-3′,5′-monophosphate (cGMP)-dependent protein kinase (PKG) was identified >25 y ago; however, efforts to obtain a structure of the entire PKG enzyme or catalytic domain from any species have failed. In malaria parasites, cooperative activation of PKG triggers crucial developmental transitions throughout the complex life cycle. We have determined the cGMP-free crystallographic structures of PKG from
Plasmodium falciparum
and
Plasmodium vivax
, revealing how key structural components, including an N-terminal autoinhibitory segment (AIS), four predicted cyclic nucleotide-binding domains (CNBs), and a kinase domain (KD), are arranged when the enzyme is inactive. The four CNBs and the KD are in a pentagonal configuration, with the AIS docked in the substrate site of the KD in a swapped-domain dimeric arrangement. We show that although the protein is predominantly a monomer (the dimer is unlikely to be representative of the physiological form), the binding of the AIS is necessary to keep
Plasmodium
PKG inactive. A major feature is a helix serving the dual role of the N-terminal helix of the KD as well as the capping helix of the neighboring CNB. A network of connecting helices between neighboring CNBs contributes to maintaining the kinase in its inactive conformation. We propose a scheme in which cooperative binding of cGMP, beginning at the CNB closest to the KD, transmits conformational changes around the pentagonal molecule in a structural relay mechanism, enabling PKG to orchestrate rapid, highly regulated developmental switches in response to dynamic modulation of cGMP levels in the parasite.
Allosteric modulation of a human protein kinase with monobodies
Authors: Zorba Adelajda , Nguyen Vy , Koide Akiko , Hoemberger Marc , Zheng Yuejiao , Kutter Steffen , Kim Chansik , Koide Shohei , Kern Dorothee
Published: June 2019

Despite being the subject of intense effort and scrutiny, kinases have proven to be consistently challenging targets in inhibitor drug design. A key obstacle has been promiscuity and consequent adverse effects of drugs targeting the ATP binding site. Here we introduce an approach to controlling kinase activity by using monobodies that bind to the highly specific regulatory allosteric pocket of the oncoprotein Aurora A (AurA) kinase, thereby offering the potential for more specific kinase modulators. Strikingly, we identify a series of highly specific monobodies acting either as strong kinase inhibitors or activators via differential recognition of structural motifs in the allosteric pocket. X-ray crystal structures comparing AurA bound to activating vs inhibiting monobodies reveal the atomistic mechanism underlying allosteric modulation. The results reveal 3 major advantages of targeting allosteric vs orthosteric sites: extreme selectivity, ability to inhibit as well as activate, and avoidance of competing with ATP that is present at high concentrations in the cells. We envision that exploiting allosteric networks for inhibition or activation will provide a general, powerful pathway toward rational drug design.
The effects of instructional focus and task type on pre-vocational learners’ ability in EFL oral interaction
Authors: van Batenburg Eline , Oostdam Ron , van Gelderen Amos , Fukkink Ruben , de Jong Nivja
Published: June 2019

Little is known about the effect of diverging pedagogies on the development of interactional oral skills in a foreign language. In a controlled study, we evaluated three newly developed instructional programmes that were situated in the same training context, but that differed in instructional focus and type of task. These were compared to the effects of business-as-usual instruction. Multilevel analysis revealed that all experimental groups outperformed the ‘business-as-usual’ control group on oral interaction skills (N = 199), with similar results for the programmes. Positive effects were found on interaction skills for trained contexts of use only. No transfer was found to tasks in other contexts of use. We conclude that receiving contextualised oral interaction instruction is beneficial to the development of pre-vocational learners’ interaction skills.
Rescue of DNA damage after constricted migration reveals a mechano-regulated threshold for cell cycle
Authors: Xia Yuntao , Pfeifer Charlotte R. , Zhu Kuangzheng , Irianto Jerome , Liu Dazhen , Pannell Kalia , Chen Emily J. , Dooling Lawrence J. , Tobin Michael P. , Wang Mai , Ivanovska Irena L. , Smith Lucas R. , Greenberg Roger A. , Discher Dennis E.
Published: June 2019

Migration through 3D constrictions can cause nuclear rupture and mislocalization of nuclear proteins, but damage to DNA remains uncertain, as does any effect on cell cycle. Here, myosin II inhibition rescues rupture and partially rescues the DNA damage marker γH2AX, but an apparent block in cell cycle appears unaffected. Co-overexpression of multiple DNA repair factors or antioxidant inhibition of break formation also exert partial effects, independently of rupture. Combined treatments completely rescue cell cycle suppression by DNA damage, revealing a sigmoidal dependence of cell cycle on excess DNA damage. Migration through custom-etched pores yields the same damage threshold, with ∼4-µm pores causing intermediate levels of both damage and cell cycle suppression. High curvature imposed rapidly by pores or probes or else by small micronuclei consistently associates nuclear rupture with dilution of stiff lamin-B filaments, loss of repair factors, and entry from cytoplasm of chromatin-binding cGAS (cyclic GMP-AMP synthase). The cell cycle block caused by constricted migration is nonetheless reversible, with a potential for DNA misrepair and genome variation.
Aeromagnetic noise reduction and interpretation by Multifractal Singular Value Decomposition
Authors: Ma M , Yang K , Feng G A , Wang C H , Li X , Gao Q
Published: June 2019

The aeromagnetic signal often has a minority of noise in it, which may be composed of random noise caused by the aircraft itself, fringe pattern noise caused by the differences between the aircraft airlines, or linear features aligned along the declination direction after reduction to the pole, which are usually hard to distinguish visually but will make useful information submerged In this paper, the aeromagnetic data of a polymetallic deposit-accumulated area in Inner Mongolia Province, northwest China, is taken as an example, from which the aeromagnetic noise is extracted by multifractal singular value decomposition (MSVD), the singular values are automatically fitted into limited number of fractal straight lines according to their inflection points and minimum fitting error, each line represents a certain kind of noise or signal, the noises are chosen and removed in this way. The last two decomposed components are usually a band pass and a low pass filter that can be used for tectonic faults and geological bodies’ interpretation, respectively.
Improving marine soils by different consolidation methods for stability of harbour structures
Authors: Houssam Khelalfa
Published: June 2019

Marine geotechnics is one of the most difficult specialties and is part of coastal engineering. The geotechnician is interested in soils as these are the main element of the context in which the stability of a structure will be designed. The methods of improvement of vibroflotation (VF), dynamic compaction (DC) and the pre-loading took a scale in Algeria these last years, they are applied at the port of DjenDjen in Jijel province, object of our study, in the framework of its extension and its development, in order to improve the support soil which will receive the foundations of the protections structures and the container terminal in caissons. The main objective is to establish numerical studies of the stability of the protection structure realized on the improved soil which was itself taken into consideration in the modelling, while respecting also the real phasing of construction of this structure. However, soil improvement was checked before and after treatment to verify its influence on the stability of the harbour structures.