bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of incoming shear on unsteady wake in flow past surface mounted polygonal prism
Authors: Kumar Prashant , Tiwari Shaligram
Published: November 2019

Three-dimensional numerical investigations for flow past surface mounted finite height prisms of different cross sections (circular, square, and triangle with apex and base facing) have been carried out using Open Source Field Operation and Manipulation. A general code has been written to consider the effect of impinging shear flow using GroovyBC and is integrated with the existing solver. The effect of impinging shear at the inlet (shear intensity, K) on three-dimensional vortex structures has been explored using iso-Q surfaces for the varying Reynolds number (Re) ranging from 60 to 200 and fixed aspect ratio equal to 5. Three different vortex shedding regimes have been investigated based on values of Re and K, viz., steady flow, symmetric, and asymmetric modes of vortex shedding. Interwave and intrawave frequency modulations and their effects on wake oscillation have been illustrated using Hilbert spectra of transverse velocity signals in the wake. Effects of K and Re on wake oscillation frequency have been presented in terms of marginal spectra of the velocity signals. The extent of nonlinear fluctuations in the wake has been quantified in terms of “degree of stationarity.” Moreover, different modes with their associated frequencies and growth rates that are responsible for transition from the asymmetric to the symmetric mode have been discussed using the computational technique named “Dynamic Mode Decomposition.” Variation in the mean drag coefficient with the change in values of K and Re has also been reported.
High-performance all-solution-processed quantum dot near-infrared-to-visible upconversion devices for harvesting photogenerated electrons
Authors: Zhang Nan , Tang Haodong , Shi Kanming , Wang Weigao , Deng Weiqiao , Xu Bing , Wang Kai , Sun Xiao Wei
Published: November 2019

All-solution-processed quantum dot (QD) upconversion devices were realized by constructing a colloidal PbS QD near-infrared (NIR ∼ 1 μm)-sensitive layer on the cathode side of a red CdSe quantum dot light-emitting diode (QLED). Different from conventional upconversion devices, we utilized the photogenerated electrons rather than the holes created in the NIR-sensitive layer to inject into the QLED for visible light emission. Consequently, we obtained high-performance devices with a maximum photon-to-photon conversion efficiency of 3.35% and a luminance on-off ratio of approximately 8 × 103. The results indicate that the device structure could be used to realize low-cost and portable high-performance QD-based upconversion devices via solution-processing.
Forced convection in a fluid saturated anisotropic porous channel with isoflux boundaries
Authors: Karmakar Timir , Reza Motahar , Sekhar G. P. Raja
Published: November 2019

Fully developed forced convective flow inside a channel filled with a porous material bounded by two impermeable walls subject to a constant heat flux is considered. We consider the Brinkman-Forchheimer equation to govern the flow inside the porous medium, which accounts for the presence of the inertial term. We assume that the porous medium is anisotropic in nature and the permeability is varying along all the directions so that it appears as a positive semidefinite matrix in the momentum equation. We have obtained velocity, temperature, and Nusselt number numerically due to the presence of the nonlinear quadratic term in the momentum equation. Asymptotic solutions for small Darcy number (∼10−3) and high Darcy number (∼10) are obtained. The asymptotic behavior of the Nusselt number is discussed. The key purpose of this paper is to study the effect of anisotropic permeability ratio, anisotropic angle, and inertial parameter on the hydrodynamic quantities and heat transfer for the configuration considered. In particular, we observe that for the moderate range of Darcy number, 10−2 to 102, inertia plays a significant role in the Nusselt number. We observe that inclusion of anisotropic permeability enhances the relative heat transfer rate by almost 20% compared to the corresponding isotropic situation. We present a detailed analysis about the inclusion of the permeability matrix in the Brinkman-Forchheimer extended Darcy momentum equation.
Cassegrain metasurface for generation of orbital angular momentum of light
Authors: Liu Xuan , Deng Junhong , Jin Mingke , Tang Yutao , Zhang Xuecai , Li King Fai , Li Guixin
Published: November 2019

Light beams with a helical phase-front (optical vortices) carry orbital angular momentum (OAM), which provides an attractive degree of freedom for controlling light and developing a series of applications, such as optical tweezers, super-resolution imaging, optical communication, and quantum information processing. Recently, the versatile metasurfaces, two-dimensional arrays of subwavelength structures with space-variant phase responses, provide powerful and convenient approaches for OAM generation. We propose and experimentally demonstrate an efficient method to generate and focus the vortex beam with a planar Cassegrain metasurface. The required helical phase profile is imparted via the secondary reflective metasurface of the planar Cassegrain metasurface. The topological charge of the vortex beam is revealed by measuring the interference pattern at the focal plane of the planar Cassegrain metasurface with a reference Gaussian beam. The combination of OAM generation, Cassegrain system, and ultrathin flat metasurface renders this scheme very attractive for diverse applications at miniature scales.
Resonant free-carrier absorption in 2D hybrid organic-inorganic perovskites: The Rashba effect or small polarons?
Authors: Yu Zhi-Gang
Published: November 2019

The Rashba effect, which shifts the conduction band extremum from wavevector k = 0 to |k| = k0 ≠ 0 with an energy gain of ER, has been frequently invoked to explain outstanding optoelectronic properties in hybrid organic-inorganic perovskites (HOIPs). For two-dimensional (2D) layered HOIPs, the only direct experimental evidence of the Rashba effect to date is resonant free-carrier absorption (FCA), which has been attributed to direct optical transition between the Rashba subbands at |k| = k0 ≠ 0 with photon energy ℏω = 4ER. Here, we show that in layered perovskites, small polarons induced by a strong short-range coupling between electrons and optical phonons can also give rise to a resonant FCA at ℏω = 4Eb, with Eb being the polaron binding energy. The Rashba effect- and small-polaron-induced resonant FCA responses can be distinguished via an applied electric field, which moves the resonance peak to a higher or lower photon energy in the former but splits the peak into two in the latter, suggesting that electric-field-modulated FCA can help prove and quantify the Rashba effect and/or small polarons in layered perovskites.
Development and installation of a radio frequency quadrupole cooler test
Authors: Cavenago M. , Romé M. , Maero G. , Maggiore M. , Bellan L. , Cavaliere F. , Comunian M. , Galatà A. , Panzeri N. , Pisent A. , Pranovi L. , Porcellato A. M.
Published: November 2019

A Radio Frequency Quadrupole Cooler (RFQC) prototype was adapted for insertion into a high uniformity magnetic field, with Bz up to 0.2 T, to improve radial confinement. While the RFQC purpose is to reduce (by gas collisions) the energy spread and emittance of a beam of radioactive nuclei, to finely select ion mass in nuclear physics, the prototype is tested in a setup including a stable ion source, a pepper pot emittance meter, and two Faraday cups; this makes a precise characterization of the RFQC feasible. The ion extraction was studied in detail by simulations, both to match it to the emittance meter granularity and to verify the effect of the typical nonuniformity of the longitudinal electric field Ez inside the RFQC; an average motion description (including friction force from gas collisions) was used, introducing the ballistic and diffusive regimes. With a preliminary optimization of the electrode shape, buffer gas pressure pg, and radio frequency voltage, the ion beam can be extracted with a significant cooling margin.
Stabilization of ultrashort pulses by external pumping in an array of carbon nanotubes subject to piezoelectric effects
Authors: Konobeeva Natalia N. , Fedorov Eduard G. , Rosanov Nikolay N. , Zhukov Alexander V. , Bouffanais Roland , Belonenko Mikhail B.
Published: November 2019

We study the combined effects of electromagnetic pumping and piezoelectric damping on the propagation of ultrashort pulses in carbon nanotubes. Based on Maxwell’s equations, an effective equation is obtained for the vector potential of the electromagnetic field, which takes into account both the dissipation of the pulse field associated with piezoelectric effects due to the oscillations of the heavy nuclei of the medium and the pumping from an external electromagnetic wave. Our analysis shows that, when the dissipative piezoelectric effects are properly compensated through external pumping, a stable propagation of the ultrashort pulses is achievable. Specifically, we demonstrate the stability of the steady-state form of the electromagnetic pulse at long time scales with variations in various system parameters, including the absorption coefficient of heavy ions as well as the initial pulse field distribution. In addition, the stability of the pulse with respect to angular perturbations—breaking the axisymmetry of the pulse distribution—is substantiated.
Experimental study of protein translocation through MoS2 nanopores
Authors: Gu Chaoming , Yu Zhoubin , Li Xiaojie , Zhu Xin , Cao Zhen , Ye Zhi , Jin Chuanhong , Liu Yang
Published: November 2019

This experimental work studies the translocation of bovine serum albumin (BSA) proteins through MoS2 nanopores. A simple method of device fabrication is developed based on dry-transfer of exfoliated MoS2 membranes and subsequent TEM drilling, yielding MoS2 nanopores of a few monolayers thick and diameters as small as ∼11 nm. The current-voltage relation and low-frequency current noise of the devices are characterized. Typical BSA translocation signals that possibly correspond to various orientations are observed in the MoS2 devices, exhibiting enhanced amplitude and similar characteristics when compared to those from a silicon nitride (SiNx) control. Furthermore, the statistical data of the signal amplitude and dwell time at various biases are analyzed. These results show opportunities of single-molecular protein analysis using MoS2 nanopores.
Acceleration sensing with magnetically levitated oscillators above a superconductor
Authors: Timberlake Chris , Gasbarri Giulio , Vinante Andrea , Setter Ashley , Ulbricht Hendrik
Published: November 2019

We experimentally demonstrate the stable trapping of a permanent magnet sphere above a lead superconductor, at vacuum pressures of 4×10−8 mbar. The levitating magnet behaves as a harmonic oscillator, with frequencies in the 4–31 Hz range detected, and shows promise to be an ultrasensitive acceleration sensor. We directly apply an acceleration to the magnet with a current carrying wire, which we use to measure a background noise of ∼10−10 m/Hz at 30.75 Hz frequency. With current experimental parameters, we find an acceleration sensitivity of Sa1/2=1.2±0.2×10−10 g/Hz, for a thermal noise limited system. By considering a 300 mK environment, at a background helium pressure of 1×10−10 mbar, acceleration sensitivities of Sa1/2∼3×10−15 g/Hz could be possible with ideal conditions and vibration isolation. To feasibly measure with such a sensitivity, feedback cooling must be implemented.
Shaping the zebrafish myotome by intertissue friction and active stress
Authors: Tlili S. , Yin J. , Rupprecht J.-F. , Mendieta-Serrano M. A. , Weissbart G. , Verma N. , Teng X. , Toyama Y. , Prost J. , Saunders T. E.
Published: November 2019

Significance

How do tissues self-organize to generate the complex organ shapes observed in vertebrates? Organ formation requires the integration of chemical and mechanical information, yet how this is achieved is poorly understood for most organs. Muscle compartments in zebrafish display a V shape, which is believed to be required for efficient swimming. We investigate how this structure emerges during zebrafish development, combining live imaging and quantitative analysis of cellular movements. We use theoretical modeling to understand how cell differentiation and mechanical interactions between tissues guide the emergence of a specific tissue morphology. Our work reveals how spatially modulating the mechanical environment around and within tissues can lead to complex organ shape formation.
Resolving seasonal rainfall changes in the Middle East during the last interglacial period
Authors: Orland Ian J. , He Feng , Bar-Matthews Miryam , Chen Guangshan , Ayalon Avner , Kutzbach John E.
Published: November 2019

Paleorainfall proxy records from the Middle East have revealed remarkable patterns of variability since the penultimate glacial period (140 ka), but the seasonality of this signal has been unresolvable. Here, seasonal-resolution oxygen isotope data from Soreq Cave speleothems suggest that summer monsoon rainfall periodically reaches as far north as Israel—well removed from the modern monsoon—at times (∼125, 105 ka) that overlap with evidence for some of the earliest modern human migrations out of Africa. These seasonal proxy data are corroborated by seasonal-resolution model output of the amount and oxygen-isotope ratio of rainfall from an isotope-enabled climate model. In contrast to the modern regional climate where rainfall is delivered predominantly in winter months along westerly storm tracks, the model suggests that during extreme peaks of summer insolation—as occurs during the last interglacial (e.g., 125, 105 ka)—regional rainfall increases due to both wetter winters and the incursion of summer monsoons. This interpretation brings clarity to regional paleoproxy records and provides important environmental context along one potential pathway of early modern human migration.
Biosynthesis of the nitrogenase active-site cofactor precursor NifB-co in
Saccharomyces cerevisiae
Authors: Burén Stefan , Pratt Katelin , Jiang Xi , Guo Yisong , Jimenez-Vicente Emilio , Echavarri-Erasun Carlos , Dean Dennis R. , Saaem Ishtiaq , Gordon D. Benjamin , Voigt Christopher A. , Rubio Luis M.
Published: November 2019

Significance

Nitrogen is a constituent of many essential biomolecules and plentiful on earth as inert N
2
gas. For its assimilation by eukaryotes, N
2
must be converted to a metabolically tractable form such as ammonium. Such conversion is catalyzed by nitrogenase, an enzyme produced by a select group of microorganisms called diazotrophs. Crop yields necessary to feed the world's population have critically depended on applying nitrogenous fertilizers. Incorporation of prokaryotic determinates required to produce active nitrogenase into crop plants would have enormous economic and environmental benefits. The active-site cofactors of all nitrogenases have a common metallocluster precursor synthesized by NifB. Here, we identify the genetic determinants for NifB function in mitochondria of
Saccharomyces cerevisiae
, thereby advancing prospects to generate N
2
-fixing crops.
Adaptational lag to temperature in valley oak (
Quercus lobata
) can be mitigated by genome-informed assisted gene flow
Authors: Browne Luke , Wright Jessica W. , Fitz-Gibbon Sorel , Gugger Paul F. , Sork Victoria L.
Published: November 2019

Climate change over the next century is predicted to cause widespread maladaptation in natural systems. This prediction, as well as many sustainable management and conservation practices, assumes that species are adapted to their current climate. However, this assumption is rarely tested. Using a large-scale common garden experiment combined with genome-wide sequencing, we found that valley oak (
Quercus lobata
), a foundational tree species in California ecosystems, showed a signature of adaptational lag to temperature, with fastest growth rates occurring at cooler temperatures than populations are currently experiencing. Future warming under realistic emissions scenarios was predicted to lead to further maladaptation to temperature and reduction in growth rates for valley oak. We then identified genotypes predicted to grow relatively fast under warmer temperatures and demonstrated that selecting seed sources based on their genotype has the potential to mitigate predicted negative consequences of future climate warming on growth rates in valley oak. These results illustrate that the belief of local adaptation underlying many management and conservation practices, such as using local seed sources for restoration, may not hold for some species. If contemporary adaptational lag is commonplace, we will need new approaches to help alleviate predicted negative consequences of climate warming on natural systems. We present one such approach, “genome-informed assisted gene flow,” which optimally matches individuals to future climates based on genotype–phenotype–environment associations.
How the phage T4 injection machinery works including energetics, forces, and dynamic pathway
Authors: Maghsoodi Ameneh , Chatterjee Anupam , Andricioaei Ioan , Perkins Noel C.
Published: November 2019

Significance

The virus bacteriophage T4 infects the bacterium
Escherichia coli
using an intriguing nanoscale injection machinery that employs a contractile tail. The injection machinery is responsible for recognizing and puncturing the bacterial host and transferring the viral genome into the host during infection. Fundamental questions remain concerning how this injection process unfolds in real time, a process that presently defies direct experimental observation. Using a combination of atomistic and continuum representations, this study contributes a system-level model of the entire bacteriophage T4 interacting with a host cell, and in doing so, it exposes the energetics, forces, and dynamical pathway associated with the injection process. The results have further implications for future nanotechnology devices for DNA transfection and experimental phage therapies.
Artificial turf infill associated with systematic toxicity in an amniote vertebrate
Authors: Xu Elvis Genbo , Lin Nicholas , Cheong Rachel S. , Ridsdale Charlotte , Tahara Rui , Du Trina Y. , Das Dharani , Zhu Jiping , Peña Silva Laura , Azimzada Agil , Larsson Hans C. E. , Tufenkji Nathalie
Published: November 2019

Significance

Athletes and children are playing on artificial turfs. However, the health risk associated with exposure to crumb rubber from artificial turfs is unknown for higher vertebrates. Here, we employed chicken embryo as a developing amniote vertebrate model to show that toxic leachate from artificial athletic turf infill impairs the early development of chicken, notably brain and cardiovascular system. This study triggers a scientific discussion as to whether crumb rubber is an appropriate infill material for artificial fields.
Replicator degrees of freedom allow publication of misleading failures to replicate
Authors: Bryan Christopher J. , Yeager David S. , O’Brien Joseph M.
Published: November 2019

In recent years, the field of psychology has begun to conduct replication tests on a large scale. Here, we show that “replicator degrees of freedom” make it far too easy to obtain and publish false-negative replication results, even while appearing to adhere to strict methodological standards. Specifically, using data from an ongoing debate, we show that commonly exercised flexibility at the experimental design and data analysis stages of replication testing can make it appear that a finding was not replicated when, in fact, it was. The debate that we focus on is representative, on key dimensions, of a large number of other replication tests in psychology that have been published in recent years, suggesting that the lessons of this analysis may be far reaching. The problems with current practice in replication science that we uncover here are particularly worrisome because they are not adequately addressed by the field’s standard remedies, including preregistration. Implications for how the field could develop more effective methodological standards for replication are discussed.
A critical role for microglia in maintaining vascular integrity in the hypoxic spinal cord
Authors: Halder Sebok K. , Milner Richard
Published: November 2019

Significance

We show that chronic mild hypoxia (CMH; 8% O
2
) induces transient vascular leak in spinal cord blood vessels that is associated with microglial clustering. Microglial depletion profoundly increased vascular leak during CMH, and this was associated with astrocyte-vascular uncoupling and loss of tight junction proteins. Microglial repair of blood vessels was blocked by a peptide that inhibits fibrinogen–Mac-1 interactions. These findings highlight a critical role for microglia in maintaining vascular integrity in the hypoxic spinal cord and suggest that a fibrinogen–Mac-1 interaction underpins this response. As relative hypoxia is experienced during lung disease, sleep apnea, and age-related central nervous system (CNS) ischemia, our findings have important implications regarding the critical role of microglia in maintaining CNS vascular integrity.
A structural basis for antibody-mediated neutralization of Nipah virus reveals a site of vulnerability at the fusion glycoprotein apex
Authors: Avanzato Victoria A. , Oguntuyo Kasopefoluwa Y. , Escalera-Zamudio Marina , Gutierrez Bernardo , Golden Michael , Kosakovsky Pond Sergei L. , Pryce Rhys , Walter Thomas S. , Seow Jeffrey , Doores Katie J. , Pybus Oliver G. , Munster Vincent J. , Lee Benhur , Bowden Thomas A.
Published: November 2019

Nipah virus (NiV) is a highly pathogenic paramyxovirus that causes frequent outbreaks of severe neurologic and respiratory disease in humans with high case fatality rates. The 2 glycoproteins displayed on the surface of the virus, NiV-G and NiV-F, mediate host-cell attachment and membrane fusion, respectively, and are targets of the host antibody response. Here, we provide a molecular basis for neutralization of NiV through antibody-mediated targeting of NiV-F. Structural characterization of a neutralizing antibody (nAb) in complex with trimeric prefusion NiV-F reveals an epitope at the membrane-distal domain III (DIII) of the molecule, a region that undergoes substantial refolding during host-cell entry. The epitope of this monoclonal antibody (mAb66) is primarily protein-specific and we observe that glycosylation at the periphery of the interface likely does not inhibit mAb66 binding to NiV-F. Further characterization reveals that a Hendra virus-F–specific nAb (mAb36) and many antibodies in an antihenipavirus-F polyclonal antibody mixture (pAb835) also target this region of the molecule. Integrated with previously reported paramyxovirus F−nAb structures, these data support a model whereby the membrane-distal region of the F protein is targeted by the antibody-mediated immune response across henipaviruses. Notably, our domain-specific sequence analysis reveals no evidence of selective pressure at this region of the molecule, suggestive that functional constraints prevent immune-driven sequence variation. Combined, our data reveal the membrane-distal region of NiV-F as a site of vulnerability on the NiV surface.
Photoperiodic and clock regulation of the vitamin A pathway in the brain mediates seasonal responsiveness in the monarch butterfly
Authors: Iiams Samantha E. , Lugena Aldrin B. , Zhang Ying , Hayden Ashley N. , Merlin Christine
Published: November 2019

Seasonal adaptation to changes in light:dark regimes (i.e., photoperiod) allows organisms living at temperate latitudes to anticipate environmental changes. In nearly all animals studied so far, the circadian system has been implicated in measurement and response to the photoperiod. In insects, genetic evidence further supports the involvement of several clock genes in photoperiodic responses. Yet, the key molecular pathways linking clock genes or the circadian clock to insect photoperiodic responses remain largely unknown. Here, we show that inactivating the clock in the North American monarch butterfly using loss-of-function mutants for the circadian activators CLOCK and BMAL1 and the circadian repressor CRYPTOCHROME 2 abolishes photoperiodic responses in reproductive output. Transcriptomic approaches in the brain of monarchs raised in long and short photoperiods, summer monarchs, and fall migrants revealed a molecular signature of seasonal-specific rhythmic gene expression that included several genes belonging to the vitamin A pathway. We found that the rhythmic expression of these genes was abolished in clock-deficient mutants, suggesting that the vitamin A pathway operates downstream of the circadian clock. Importantly, we showed that a CRISPR/Cas9-mediated loss-of-function mutation in the gene encoding the pathway’s rate-limiting enzyme,
ninaB1
, abolished photoperiod responsiveness independently of visual function in the compound eye and without affecting circadian rhythms. Together, these results provide genetic evidence that the clock-controlled vitamin A pathway mediates photoperiod responsiveness in an insect. Given previously reported seasonal changes associated with this pathway in the mammalian brain, our findings suggest an evolutionarily conserved function of vitamin A in animal photoperiodism.
Fresnel drag in space–time-modulated metamaterials
Authors: Huidobro Paloma A. , Galiffi Emanuele , Guenneau Sébastien , Craster Richard V. , Pendry J. B.
Published: November 2019

Significance

Space–time-dependent electromagnetic media, whose constitutive parameters are directionally biased in space and time, are a topic of current enormous interest across physics. Here we address a problem of fundamental relevance: the similarities and differences between such modulated materials and the classic problem of moving media. We establish that, surprisingly, the Fresnel drag effect of light in moving media, dictated by special relativity, is also present in modulated media, fully resolving this paradox with an analytical approach. We discuss how nonreciprocity can emerge at vanishing frequency. While we focus on electromagnetism, our findings can be extended to other wave systems.
Topology optimization through stiffness/weight ratio analysis for a three-point bending test of additive manufactured parts
Authors: Garcia-Granada A A , Catafal-Pedragosa J , Lemu H G
Published: November 2019

Topology Optimization (TO) is a technique that allows for increasingly efficient designs and its objective is to maximize the performance of mechanical systems or structure in a variety of fields. Attempts to employ TO for parts manufactured with conventional methods such as casting, forging, injection moulding, CNC machining and the like could not lead to desired optimum results due to the existing manufacturing constraints regarding geometrical complexity. Currently, additive manufacturing (AM) techniques allow the fabrication of more complex shapes which in principle will lead to improved performances through application of the TO concept. This study focuses on structural optimization of additive manufactured parts of thermoplastic parts based on analysis of the stiffness/weight (mass) ratio for a beam subjected to a three-point bending load. The experimental work is done on optimization of parts manufactured by Fused Deposition Modelling (FDM) technology and finally compared with an identical model manufactured using Polyjet 3D printer. Different TO software are compared to conduct the optimization, and a module of SolidWorks 2018 from Dassault Systems is chosen for the topology optimization for the final experiment. The study focuses on the results on stiffness/mass ratios, paying attention to the influence of different printing parameters on the test results. An increase of stiffness/weight ratio of 31.7% was predicted by software while experiments showed an increase of just 27.04%.
State-of-the-art of crack propagation modelling in tubular joints
Authors: Atteya M , Mikkelsen O , Lemu H G
Published: November 2019

Offshore structures are conventionally designed for a service life between 20-30 years and mostly used beyond their service life. They are operated up to the point where costs of operations, maintenance and repair exceed the revenue generated by the offshore structure. The cyclic nature of environmental loading induces multi-axial stresses with high gradients in welded tubular joints that lead to fatigue cracks emanating from imperfections in the welded materials. Tubular joints may exhibit significant residual life after fatigue cracks formation due to crack propagating around the weld circumference. It is important to understand tubular joints behaviour and estimate the residual life beyond crack initiation as it promotes the safe operation of the offshore installation, inspection planning and life extension of the asset. This paper presents an overview of the residual life estimation of cracked tubular joints using numerical methods. The recent developments and possible enhancements to the modelling methods of cracked tubular joints are presented.
Impact from ice floes and icebergs on ships and offshore structures in Polar Regions
Authors: Amdahl J
Published: November 2019

The principles for ULS design and ALS design for offshore structures are discussed. The use of pressure-area curve versus force-area curves for analysis for estimation of ALS impacts is deliberated. Aspects of local and global shape of the ice feature are discussed in view of external mechanics (demand for energy dissipation) and internal mechanics (local damage). Simplified methods for structural damage assessment are reviewed for ice loads that may move both transverse to and along the shell plating. Material modelling of ice for nonlinear finite element analysis (NLFEA) of ice-structure interaction is reviewed. The material models must be calibrated against design curves and the sensitivity of the material parameters with respect to mesh size is investigated. Results from simulation of impacts of ice with different shapes on the column of a floating platform are presented, and the critical shape for penetration of the front plating for the present structural configuration is identified.
Remote inspection by the magnetic tomography method (MTM) to prevent the risks imposed by exploitation of Arctic offshore pipelines
Authors: Kamaeva S S , Kolesnikov I S , Eremin N A , Khusnutdinov L A
Published: November 2019

Cold climate areas that provide opportunities for the remote inspection of pipelines include the Barents Sea, the Russian Arctic, the Alaskan Chukchi Sea, the Beaufort Sea and the Canadian Arctic offshore. First, an analysis of several actual projects of contactless diagnostics using the magnetic tomography method of pipelines in Arctic conditions is done. Second, the Risk-Based Inspection methodology for Arctic offshore pipelines is discussed. It involves ensuring pipeline reliability on the basis of data on the technical condition of the metal in actual operating conditions. The magnetic tomography method allows not only to remotely identify areas of anomalies with metal defects, but also to register mechanical stress levels taking into account actual loads. This reduces the risk for the structure to come to the critical state in terms of exceeding local loads. Finally, magnetic tomography technology allows managing risks in cases of local corrosion, stress cracking or loss of stability of underwater pipelines in areas with free spanning. The qualitative indicators of the inspection include the probabilities of identifying, interpreting the degree of danger, missing a dangerous defect. The pipeline diagnostics report provides the parameters of reliability forecasting: the period of incident-free operation, safe working pressure, and pressure coefficient.
About a method of acoustic impact on high viscosity oil fields
Authors: Alisheva Z N , Eremin N A , Metaksa G P
Published: November 2019

The report describes the method of the acoustic impact on the oil reservoir. Chemical decomposition of formation water molecules occurs with the help of energy-accumulating substances. Water becomes a supplier of hydrogen and oxygen. This allows the processes of hydrogenation and synthesis of new compounds. The decomposition of water is carried out using activated aluminum. As a result of the reaction, hydrogen is released, which provides the reaction of hydrogenation of all fractions of heavy oils. Industrial tests of the new method of acoustic impact were carried out at one of the fields with high viscosity of the Embamunaigas company in 2016. Pilot tests revealed an increase in the flowability of heavy oil during the hydrogenation of its components. The increase in well productivity was recorded during the first days of testing a new method. The negative side of the tests was the colmatation of the well with the released aluminum oxide. Physical and chemical processes on the surface of the reacting components were studied. In the course of the research, the state of the phase interface was studied. The spectral composition of the responses at the phase interface was measured. The report presents the results of measurements of the spectral response of water to external influences. The test results of the new acoustic method showed the need for additional research.
Feasibility study for utilization of solar energy in the arctic areas
Authors: Tamrakar S , Mustafa M , Riise R
Published: November 2019

This research investigates a solar thermal system and a solar photovoltaic system which produces local energy, by incoming solar radiation, to meet the energy consumption demand of a residential building in the arctic region. The study on the use of the solar systems in the arctic areas is rare and often doubted. So, to analyze the potential of solar energy, a study case of an existing building block in Narvik, Norway was selected. The performance and function of both the systems were studied and achieved by calculation and simulation models of the thermal system and the PV system separately. The solar systems met the energy demand of DHW and space heating during summer due to the availability of the sun for long hours. However, in winter, especially in December and January, the energy production was zero due to snow accumulation and minimum sunlight. The results showed that the solar thermal collector produced about 14315 kWh throughout a year, whereas, the PV system generated an annual energy output of 18640 kWh. Thus, the results suggest considerable potential for solar utilization, however in the current context cost can be a limitation.
The future incidence, prevalence and costs of stroke in the UK
Authors: King Derek , Wittenberg Raphael , Patel Anita , Quayyum Zahid , Berdunov Vladislav , Knapp Martin
Published: November 2019

Background

we project incidence and prevalence of stroke in the UK and associated costs to society to 2035. We include future costs of health care, social care, unpaid care and lost productivity, drawing on recent estimates that there are almost 1 million people living with stroke and the current cost of their care is £26 billion.

Methods

we developed a model to produce projections, building on earlier work to estimate the costs of stroke care by age, gender and other characteristics. Our cell-based simulation model uses the 2014-based Office for National Statistics population projections; future trends in incidence and prevalence rates of stroke derived from an expert consultation exercise; and data from the Office for Budget Responsibility on expected future changes in productivity and average earnings.

Results

between 2015 and 2035, the number of strokes in the UK per year is projected to increase by 60% and the number of stroke survivors is projected to more than double. Under current patterns of care, the societal cost is projected to almost treble in constant prices over the period. The greatest increase is projected to be in social care costs—both public and private—which we anticipate will rise by as much as 250% between 2015 and 2035.

Conclusion

the costs of stroke care in the UK are expected to rise rapidly over the next two decades unless measures to prevent strokes and to reduce the disabling effects of strokes can be successfully developed and implemented.
Exposure to Organophosphate Pesticides and Menstrual Cycle Characteristics in Chinese Preconceptional Women
Authors: Zhang Yan , Ji Lin , Hu Yi , Tse Lap Ah , Wang Yiwen , Qin Kaili , Ding Guodong , Zhou Yijun , Yu Xiaodan , Ouyang Fengxiu , Zhang Jun , Gao Yu , Tian Ying ,   for the Shanghai Birth Cohort Study
Published: November 2019

Organophosphates (OPs) are the most heavily used pesticides in China. The Chinese population, including preconceptional women, is highly exposed, yet little is known regarding the associations between OP exposure and menstruation in humans. We conducted a cross-sectional analysis in women preparing for pregnancy to investigate the relationship between biomarkers of OP exposure and menstrual cycle characteristics. From 2013 to 2015, 627 women visiting free preconception-care clinics at 2 maternity hospitals in Shanghai, China, were included. Information on menstrual cycle characteristics was obtained through questionnaires. OP exposure was assessed by measuring urine concentrations of 6 dialkylphosphate metabolites (dimethylphosphate, dimethylthiophosphate, dimethyldithiophosphate, diethylphosphate, diethylthiophosphate, and diethyldithiophosphate). The relationship between concentrations of dialkylphosphate metabolites and menstrual cycle characteristics was analyzed using multiple linear regression models and logistic regression models. Log-transformed levels of diethyl phosphate metabolites (the sum of diethylphosphate and diethylthiophosphate levels) were related to a higher risk of irregularity of menstrual cycles (adjusted odds ratio = 2.36, 95% confidence interval: 1.28, 4.34). Subjects with a higher concentration of diethyl phosphate metabolites (log-transformed) had a shorter duration of menstrual bleeding (adjusted β = −0.33, 95% confidence interval: −0.64, −0.02). The findings suggest that OP exposure may be associated with alterations in menstrual function in preconceptional women.
Bedtimes and Blood Pressure: A Prospective Cohort Study of Mexican Adolescents
Authors: Jansen Erica C , Dunietz Galit Levi , Matos-Moreno Amilcar , Solano Maritsa , Lazcano-Ponce Eduardo , Sánchez-Zamorano Luisa María
Published: November 2019

INTRODUCTION

Hypertension affects up to 5% of children worldwide and predicts later cardiovascular morbidity. Associations of short sleep and hypertension have been frequently reported in adults but less consistently in children. This study aims to examine the role of late bedtimes, a marker of short sleep duration, and potentially misaligned circadian rhythms, on incident elevated blood pressure (BP) in a large cohort of Mexican children.

METHODS

Participants included 2,033 adolescents recruited from public schools in Morelos, Mexico, free from elevated BP (<90th sex, age, and height-standardized percentile). Fourteen months later, all adolescents had a second BP assessment. We abstracted baseline habitual bedtimes from questionnaires to evaluate the association between bedtime and elevated BP incidence (≥90th percentile). Risk ratios and 95% confidence intervals were estimated with discrete-time mixed survival models, adjusting for potential confounders and accounting for clustering by school.

RESULTS

Participants were 12.5 (SD = 0.6) years old at baseline. At the follow-up visit 10% of adolescents had developed elevated BP. Compared to participants with a habitual weekday bedtime between 9 and 10 pm, those with a weekday bedtime 11 pm or later had a 1.87 times higher risk of developing elevated BP over the follow-up period (95% CI = 1.09, 2.21), after accounting for confounders. Participants with earlier weekday bedtimes also had a higher risk of elevated BP (RR = 1.96; 95% CI = 1.27, 3.01). The associations persisted after accounting for wake time.

CONCLUSION

These data showed a U-shaped association between weekday bedtime and elevated/high BP risk among Mexican adolescents.
Individual signatures outweigh social group identity in contact calls of a communally nesting parrot
Authors: Smith-Vidaurre Grace , Araya-Salas Marcelo , Wright Timothy F
Published: November 2019

Despite longstanding interest in the evolutionary origins and maintenance of vocal learning, we know relatively little about how social dynamics influence vocal learning processes in natural populations. The “signaling group membership” hypothesis proposes that socially learned calls evolved and are maintained as signals of group membership. However, in fission–fusion societies, individuals can interact in social groups across various social scales. For learned calls to signal group membership over multiple social scales, they must contain information about group membership over each of these scales, a concept termed “hierarchical mapping.” Monk parakeets (Myiopsitta monachus), small parrots native to South America, exhibit vocal mimicry in captivity and fission–fusion social dynamics in the wild. We examined patterns of contact call acoustic similarity in Uruguay to test the hierarchical mapping assumption of the signaling group membership hypothesis. We also asked whether geographic variation patterns matched regional dialects or geographic clines that have been documented in other vocal learning species. We used visual inspection, spectrographic cross-correlation and random forests, a machine learning approach, to evaluate contact call similarity. We compared acoustic similarity across social scales and geographic distance using Mantel tests and spatial autocorrelation. We found high similarity within individuals, and low, albeit significant, similarity within groups at the pair, flock and site social scales. Patterns of acoustic similarity over geographic distance did not match mosaic or graded patterns expected in dialectal or clinal variation. Our findings suggest that monk parakeet social interactions rely more heavily upon individual recognition than group membership at higher social scales.
Hippocampal vascular reserve associated with cognitive performance and hippocampal volume
Authors: Perosa Valentina , Priester Anastasia , Ziegler Gabriel , Cardenas-Blanco Arturo , Dobisch Laura , Spallazzi Marco , Assmann Anne , Maass Anne , Speck Oliver , Oltmer Jan , Heinze Hans-Jochen , Schreiber Stefanie , Düzel Emrah
Published: November 2019

Medial temporal lobe dependent cognitive functions are highly vulnerable to hypoxia in the hippocampal region, yet little is known about the relationship between the richness of hippocampal vascular supply and cognition. Hippocampal vascularization patterns have been categorized into a mixed supply from both the posterior cerebral artery and the anterior choroidal artery or a single supply by the posterior cerebral artery only. Hippocampal arteries are small and affected by pathological changes when cerebral small vessel disease is present. We hypothesized, that hippocampal vascularization patterns may be important trait markers for vascular reserve and modulate (i) cognitive performance; (ii) structural hippocampal integrity; and (iii) the effect of cerebral small vessel disease on cognition. Using high-resolution 7 T time-of-flight angiography we manually classified hippocampal vascularization patterns in older adults with and without cerebral small vessel disease in vivo. The presence of a mixed supplied hippocampus was an advantage in several cognitive domains, including verbal list learning and global cognition. A mixed supplied hippocampus also was an advantage for verbal memory performance in cerebral small vessel disease. Voxel-based morphometry showed higher anterior hippocampal grey matter volume in mixed, compared to single supply. We discuss that a mixed hippocampal supply, as opposed to a single one, may increase the reliability of hippocampal blood supply and thereby provide a hippocampal vascular reserve that protects against cognitive impairment.
Safety and Efficacy of Fidaxomicin and Vancomycin in Children and Adolescents with Clostridioides (Clostridium) difficile Infection: A Phase 3, Multicenter, Randomized, Single-blind Clinical Trial (SUNSHINE)
Authors: Wolf Joshua , Kalocsai Krisztina , Fortuny Claudia , Lazar Stefan , Bosis Samantha , Korczowski Bartosz , Petit Arnaud , Bradford Daniel , Croos-Dabrera Rodney , Incera Elodie , Melis Joost , van Maanen Rob
Published: November 2019

Background

Fidaxomicin, a narrow-spectrum antibiotic approved for Clostridioides (Clostridium) difficile infection (CDI) in adults, is associated with lower rates of recurrence than vancomycin; however, pediatric data are limited. This multicenter, investigator-blind, phase 3, parallel-group trial assessed the safety and efficacy of fidaxomicin in children.

Methods

Patients aged <18 years with confirmed CDI were randomized 2:1 to 10 days of treatment with fidaxomicin (suspension or tablets, twice daily) or vancomycin (suspension or tablets, 4 times daily). Safety assessments included treatment-emergent adverse events. The primary efficacy end point was confirmed clinical response (CCR), 2 days after the end of treatment (EOT). Secondary end points included global cure (GC; CCR without CDI recurrence) 30 days after EOT (end of study; EOS). Plasma and stool concentrations of fidaxomicin and its active metabolite OP-1118 were measured.

Results

Of 148 patients randomized, 142 were treated (30 <2 years old). The proportion of participants with treatment-emergent adverse events was similar with fidaxomicin (73.5%) and vancomycin (75.0%). Of 3 deaths in the fidaxomicin arm during the study, none were CDI or treatment related. The rate of CCR at 2 days after EOT was 77.6% (76 of 98 patients) with fidaxomicin and 70.5% (31 of 44) with vancomycin, whereas the rate of GC at EOS was significantly higher in participants receiving fidaxomicin (68.4% vs 50.0%; adjusted treatment difference, 18.8%; 95% confidence interval, 1.5%–35.3%). Systemic absorption of fidaxomicin and OP-1118 was minimal, and stool concentrations were high.

Conclusions

Compared with vancomycin, fidaxomicin was well tolerated and demonstrated significantly higher rates of GC in children and adolescents with CDI.

Clinical Trials Registration

NCT02218372