bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of Octenylsuccinylation of Oxidized Cassava Starch on Grease Resistance and Waterproofing of Food Wrapping Paper
Authors: Zhong Li , Ding Yajie , Zhang Bin , Wang Zhigang , Li Chao , Fu Xiong , Huang Qiang
Published: January 2019

The surface of food wrapping paper is coated with octenylsuccinic anhydride (OSA)‐modified cassava starch to develop food packaging with high waterproofing and low grease permeability. Oxidized cassava starch is modified using various concentrations of OSA, and esterification is confirmed by Fourier transform infrared spectroscopy (FT‐IR) and 1H nuclear magnetic resonance spectroscopy (1H NMR). To explore the effects of OSA concentration, starch content, incubation time, and coating rate on oil resistance and hydrophobicity, grease and water barrier properties are quantified using the Tappi T559 pm‐96 method, Cobb's tests, and dynamic contact angle. The influence of octenylsuccinylation of oxidized cassava starch on the optical and physical properties of paper is also investigated. Conditions comprising 3% OSA, 20% starch concentration, a 20 min incubation time, and a coating speed of 15 mm s−1 achieved oil‐proof level 8 and a Cobb60 value of 17.6, which is much lower than that of the control method (27.5). Additionally, the surface roughness of paper is decreased, while tear strength, tensile strength, and folding strength are increased, meeting the strong oil‐proofing and mechanical property requirements of food packaging.
The Effects of Administration and Response Modes on Grade 1–2 Students’ Writing Performance
Authors: Kim Ahyoung Alicia , Lee Shinhye , Chapman Mark , Wilmes Carsten
Published: January 2019

This study aimed to investigate how Grade 1–2 English language learners (ELLs) differ in their performance on a writing test in two test modes: paper and online. Participants were 139 ELLs in the United States. They completed three writing tasks, representing three test modes: (1) a paper in which students completed their writing using a paper‐and‐pencil format, (2) online‐handwriting in which students viewed the prompt online and handwrote responses, and (3) online‐keyboarding in which learners viewed the prompt online and keyboarded responses. Up to 20 students were tested during each 90‐minute session, during which researchers observed two or three students to examine any differences in their writing behaviors across tasks. Immediately after students completed the tasks, researchers asked them about their preferred test modes. Students’ writings were analyzed quantitatively and qualitatively in terms of task completion, fluency, and complexity. Interview data were analyzed qualitatively. Findings suggest the handwriting task is the optimal mode for students in Grades 1–2. Yet the majority of ELLs observed said they preferred the keyboarding task over the handwriting tasks. Study results provide practical implications for writing test administration for K–12 ELLs.
Modeling the additive structure of stand biomass equations in climatic gradients of Eurasia
Authors: Usoltsev Vladimir Andreevich , Shobairi Seyed Omid Reza , Tsepordey Ivan Stepanovich , Chasovskikh Viktor Petrovich
Published: January 2019

It has been established that in cold climatic zones any increase in rainfall leads to a corresponding decrease in biomass volume and in warm zones an increase in rainfall leads to an increase in biomass value. Furthermore, in water‐rich areas (900 millimeters [mm] per year), a rise in temperature causes an increase of biomass values, whereas in arid areas (300 mm per year) it causes reductions. These statements confirm previously recognized results that other researchers documented at both local and regional levels. For natural and planted tree stands, these patterns follow suit, but in absolute terms plantation biomass shows annual increases in total biomass, roots, stems, needles, and branches, of 16, 18, 11, 2, and 3%, respectively, compared to natural stands. The percentage of change in the structure of biomass is related to the ratio of the two climatic indices—temperature and rainfall. In particular, for the central part of European Russia, the Russian Far East, and northeastern China, which are characterized by mean annual temperatures in January of –10 degrees Celsius (°C) and mean annual precipitation of 500 mm, any temperature increase of 1°C at a constant level of precipitation increases biomass of stands aged 100 years in total biomass, roots, stems, needles, and branches, by 2.2, 1.8, 2.5, 0.36, and 2.3%, respectively, regardless of the origin of the stands. In the same regions and with pine stands of the same age, a precipitation increase of 100 mm at an unchanged mean temperature reduces total biomass, roots, stems, and needles by 5.8, 2.3, 6.5, and 0.3%, respectively, and increases branch biomass by 0.3%. The development of such models for the basic forest‐forming species grown in Eurasia will make it possible to predict changes in the biological productivity of the forest cover of Eurasia related to climate change.
Diagnostic accuracy of saline contrast sonohysterography in detecting endometrial polyps in women with postmenopausal bleeding: systematic review and meta‐analysis
Authors: Vroom A. J. , Timmermans A. , Bongers M. Y. , van den Heuvel E. R. , Geomini P. M. A. J. , van Hanegem N.
Published: January 2019

Objective

In women with postmenopausal bleeding, endometrial polyps are a frequent finding and the risk of a focal (pre)malignancy in a polyp is up to 6%. Because of this reported risk, the detection of polyps in these women, preferably by a minimally invasive method, is important. The aim of this systematic review was to assess the accuracy of saline contrast sonohysterography (SCSH) for diagnosis of endometrial polyps in women with postmenopausal bleeding.

Methods

In August 2018, an electronic search was performed of MEDLINE, EMBASE and Web of Science databases to identify all diagnostic studies in which SCSH was used to detect endometrial polyps in postmenopausal women. Studies were included if SCSH was performed to detect endometrial polyps in women with postmenopausal bleeding and if detection of a polyp on hysteroscopy or diagnosis on histopathology was used as a reference standard. Two reviewers assessed methodological quality using the quality assessment of diagnostic accuracy studies (QUADAS‐2) tool. Two separate analyses were performed for each reference standard. Pooled sensitivity and specificity were calculated using the hierarchical summary receiver–operating characteristics (HSROC) model and HSROC curves were plotted.

Results

After selection and quality assessment, five studies were included. Using ‘polyps diagnosed with histopathology’ as the reference standard, the pooled sensitivity of SCSH was 86.5% (95% CI, 63.6–100%) and the pooled specificity was 91.1% (95% CI, 63.2–100%). Using ‘polyps seen on hysteroscopy’ as the reference standard, the pooled sensitivity of SCSH was 85.1% (95% CI, 66.9–100%) and the pooled specificity was 84.5% (95% CI, 68.1–100%). Excluding the one study that included women in whom the SCSH examination was reported to be suboptimal, the pooled sensitivity increased to 90.7% (95% CI, 72.8–100%) using hysteroscopy as the reference standard. The sensitivity of hysteroscopy to detect polyps, as reported in two studies, was 81–98%.

Conclusions

Provided that the SCSH examination is of optimal quality, it can be considered as a method to stratify women with postmenopausal bleeding for further diagnostic workup and treatment with hysteroscopy. In women without suspicion of a polypoid lesion on SCSH, and with a benign endometrial sample, expectant management should be considered. Copyright © 2019 ISUOG. Published by John Wiley & Sons Ltd.
Sequential improvement of rimocidin production in Streptomyces rimosus M527 by introduction of cumulative drug-resistance mutations
Authors: Zhao Yanfang , Song Zhangqing , Ma Zheng , Bechthold Andreas , Yu Xiaoping
Published: January 2019

Rimocidin is a polyene macrolide that exhibits a strong inhibitory activity against a broad range of plant-pathogenic fungi. In this study, fermentation optimization and ribosome engineering technology were employed to enhance rimocidin production in Streptomyces rimosus M527. After the optimization of fermentation, rimocidin production in S. rimosus M527 increased from 0.11 ± 0.01 to 0.23 ± 0.02 g/L during shake-flask experiments and reached 0.41 ± 0.05 g/L using 5-L fermentor. Fermentation optimization was followed by the generation of mutants of S. rimosus M527 through treatment of the strain with different concentrations of gentamycin (Gen) or rifamycin. One Genr mutant named S. rimosus M527-G37 and one Rifr mutant named S. rimosus M527-R5 showed increased rimocidin production. Double-resistant (Genr and Rifr) mutants were selected using S. rimosus M527-G37 and S. rimosus M527-R5, and subsequently tested. One mutant, S. rimosus M527-GR7, which was derived from M527-G37, achieved the greatest cumulative improvement in rimocidin production. In the 5-L fermentor, the maximum rimocidin production achieved by S. rimosus M527-GR7 was 25.36% and 62.89% greater than those achieved by S. rimosus M527-G37 and the wild-type strain S. rimosus M527, respectively. Moreover, in the mutants S. rimosus M527-G37 and S. rimosus M527-GR7 the transcriptional levels of ten genes (rimA  sr to rimK  sr) located in the gene cluster involved in rimocidin biosynthesis were all higher than those in the parental strain M527 to varying degrees. In addition, after expression of the single rimocidin biosynthetic genes in S. rimosus M527 a few recombinants showed an increase in rimocidin production. Expression of rimE led to the highest production.
Equilibrium configurations of drops or bubbles in an eccentric annulus
Authors: Beheshti Pour Negar , Thiessen David B.
Published: January 2019

The purpose of this paper is to find the zero-gravity equilibrium configurations of liquid drops or bubbles that have sufficient volume to form large-aspect-ratio bridging segments or occluding slugs in the eccentric annulus between two cylinders. In zero gravity, the static problem depends on the contact angle of the fluid segment on the solid support, and two geometric parameters: the radius ratio and the dimensionless distance between the cylinder centres. For both non-wetting and wetting liquids, we find regions of geometric parameter space where only occluding configurations occur, a bistable region where either configuration can occur, and a region where only the non-occluding bridging configuration can occur. For the non-occluding cases, we applied a large-aspect-ratio free-energy minimization approach to predict the cross-sectional shape of the liquid, and a finite element method was used to compute the interface shape of the occluding cases. A Surface Evolver model was used to simulate the three-dimensional shape of both occluding and non-occluding configurations. The simulation results support the theoretical predictions well. The fractional open area of the conduit was determined for both highly wetting and highly non-wetting minority phases. Optimization of the geometric parameters for a given wetting condition could facilitate the segregation and transport of two fluid phases in applications involving large aspect ratios and small pressure driving forces.
Three-dimensional small-scale instabilities of plane internal gravity waves
Authors: Ghaemsaidi Sasan John , Mathur Manikandan
Published: January 2019

We study the evolution of three-dimensional (3-D), small-scale, small-amplitude perturbations on a plane internal gravity wave using the local stability approach. The plane internal wave is characterised by its non-dimensional amplitude, $A$, and the angle the group velocity vector makes with gravity, $\unicode[STIX]{x1D6F7}$. For a given $(A,\unicode[STIX]{x1D6F7})$, the local stability equations are solved on the periodic fluid particle trajectories to obtain growth rates for all two-dimensional (2-D) and 3-D perturbation wave vectors. For small $A$, the local stability approach recovers previous results of 2-D parametric subharmonic instability (PSI) while offering new insights into 3-D PSI. Higher-order triadic resonances, and associated deviations from them, are also observed at small $A$. Moreover, for small $A$, purely transverse instabilities resulting from parametric resonance are shown to occur at select values of $\unicode[STIX]{x1D6F7}$. The possibility of a non-resonant instability mechanism for transverse perturbations at finite $A$ allows us to derive a heuristic, modified gravitational instability criterion. We then study the extension of small $A$ to finite $A$ internal wave instabilities, where we recover and build upon existing knowledge of small-scale, small-amplitude internal wave instabilities. Four distinct regions of the $(A,\unicode[STIX]{x1D6F7})$-plane based on the dominant instability modes are identified: 2-D PSI, 3-D oblique, quasi-2-D shear-aligned, and 3-D transverse. Our study demonstrates the local stability approach as a physically insightful and computationally efficient tool, with potentially broad utility for studies that are based on other theoretical approaches and numerical simulations of small-scale instabilities of internal waves in various settings.
A freely yawing axisymmetric bluff body controlled by near-wake flow coupling
Authors: Lambert Thomas J. , Vukasinovic Bojan , Glezer Ari
Published: January 2019

Flow-induced oscillations of a wire-mounted, freely yawing axisymmetric round bluff body and the induced loads are regulated in wind tunnel experiments (Reynolds number $60\,000<Re_{D}<200\,000$) by altering the reciprocal coupling between the body and its near wake. This coupling is controlled by exploiting the receptivity of the azimuthal separating shear layer at the body’s aft end to controlled pulsed perturbations effected by two diametrically opposed and independently controlled aft-facing rectangular synthetic jets. The model is supported by a thin vertical wire upstream of its centre of pressure, and prescribed modification of the time-dependent flow-induced loads enables active control of its yaw attitude. The dynamics of the interactions and coupling between the actuation and the cross-flow are investigated using simultaneous, time-resolved measurements of the body’s position and phase-locked particle image velocimetry measurements in the yawing plane. It is shown that the interactions between trains of small-scale actuation vortices and the local segment of the aft-separating azimuthal shear layer lead to partial attachment, and the ensuing asymmetric modifications of the near-wake vorticity field occur within 15 actuation cycles (approximately three convective time scales), which is in agreement with measurements of the flow loads in an earlier study. Open- and closed-loop actuation can be coupled to the natural, unstable motion of the body and thereby affect desired attitude control within 100 convective time scales, as is demonstrated by suppression or enhancement of the lateral motion.
Impact of coherence decay on wavepacket models for broadband shock-associated noise in supersonic jets
Authors: Wong Marcus H. , Jordan Peter , Honnery Damon R. , Edgington-Mitchell Daniel
Published: January 2019

Motivated by the success of wavepackets in modelling the noise from subsonic and perfectly expanded supersonic jets, we apply the wavepacket model to imperfectly expanded supersonic jets. Recent studies with subsonic jets have demonstrated the importance of capturing the ‘jitter’ of wavepackets in order to correctly predict the intensity of far-field sound. Wavepacket jitter may be statistically represented using a two-point coherence function; accurate prediction of noise requires identification of this coherence function. Following the analysis of Cavalieri & Agarwal (J. Fluid Mech., vol. 748, 2014. pp. 399–415), we extend their methodology to model the acoustic sources of broadband shock-associated noise in imperfectly expanded supersonic jets using cross-spectral densities of the turbulent and shock-cell quantities. The aim is to determine the relationship between wavepacket coherence-decay and far-field broadband shock-associated noise, using the model as a vehicle to explore the flow mechanisms at work. Unlike the subsonic case where inclusion of coherence decay amplifies the sound pressure level over the whole acoustic spectrum, we find that it does not play such a critical role in determining the peak sound amplitude for shock-cell noise. When higher-order shock-cell modes are used to reconstruct the acoustic spectrum at higher frequencies, however, the inclusion of a jittering wavepacket is necessary. These results suggest that the requirement for coherence decay identified in prior broadband shock-associated noise (BBSAN) models is in reality the statistical signature of jittering wavepackets. The results from this modelling approach suggest that nonlinear jittering effects of wavepackets need to be included in dynamic models for broadband shock-associated noise.
Characteristic path analysis of confinement influence on steady two-dimensional detonation propagation
Authors: Chiquete Carlos , Short Mark
Published: January 2019

Steady detonation in multi-dimensional flow is controlled by the chemical energy release that occurs in a subsonic elliptic flow region known as the detonation driving zone (DDZ). It is the region encompassing the detonation shock and sonic flow locus (in the frame of the detonation shock). A detonation that is strongly confined by material surrounding the explosive has the shock and sonic locus separated at the material interface. Information about the material boundary is traditionally believed to influence the DDZ structure via the subsonic flow on the boundary ahead of the sonic locus. A detonation that is weakly confined has the detonation shock and sonic locus intersecting at the material boundary. The sonic nature of the flow at the intersection point on the boundary is believed to isolate the DDZ structure from the material properties of the confinement. In this study, we examine the paths of characteristics propagating information about the confinement through the supersonic hyperbolic flow region that exists beyond the sonic locus, and determine whether these paths may impinge on the sonic locus and consequently influence the DDZ structure. Our configuration consists of a solid wall boundary deflected through a specified angle on detonation shock arrival, so that the streamline turning angle of the wall at the explosive edge is unambiguously defined. By varying the wall deflection angle from small through large values, we can systematically capture the evolution of the DDZ structure and the characteristic flow regions that influence its structure for strongly to weakly confined detonations. In all strong and weak confinement cases examined, we find that a subset of characteristics from the supersonic flow regions always impinge on the sonic locus. Limiting characteristics are identified that define the boundary between characteristics that impinge on the sonic surface and those that propagate information downstream of the sonic surface. In combination with an oblique-shock polar analysis, we show that the effects on the DDZ of characteristic impingement can be significant.
A NOTE ON NSOP1 IN ONE VARIABLE
Authors: RAMSEY NICHOLAS
Published: January 2019

We prove that, in order to establish that a theory is NSOP1, it suffices to show that no formula in a single free variable has SOP1.
Mobility and Memory: Maritime Crossings of the Storyteller in Marie-Célie Agnant’sLe livre d’EmmaGabriella Ghermandi’sRegina di fiori e di perle
Authors: Reid-Olds Tera
Published: January 2019

This article offers a comparative reading of Marie-Célie Agnant’sLe livre d’Emmaand Gabriella Ghermandi’sRegina di fiori e di perle. Acknowledging the distinct geographical and temporal contexts of the Francophone Caribbean and the Mediterranean, I argue that the authors’ employment of frame narratives and (ch)orality as a mode of collective remembrance and cultural transmission can be read as interventions in the debates on maritime perspectives and the figuration of the sea in contemporary literary studies. This argument is grounded in the mobility, fluidity, and dynamism of oral storytelling and the frame narrative’s pre-novelistic transnational path historically and in the present works, examining the authors’ stylistic and thematic practices as linked to the sea. By putting Agnant and Ghermandi in conversation, this article explores a maritime practice of reading and its potential application to other texts.
Liouville-Green expansions of exponential form, with an application to modified Bessel functions
Authors: Dunster T. M.
Published: January 2019

Linear second order differential equations of the form d2w/dz2 − {u2f(u, z) + g(z)}w = 0 are studied, where |u| → ∞ and z lies in a complex bounded or unbounded domain D. If f(u, z) and g(z) are meromorphic in D, and f(u, z) has no zeros, the classical Liouville-Green/WKBJ approximation provides asymptotic expansions involving the exponential function. The coefficients in these expansions either multiply the exponential or in an alternative form appear in the exponent. The latter case has applications to the simplification of turning point expansions as well as certain quantum mechanics problems, and new computable error bounds are derived. It is shown how these bounds can be sharpened to provide realistic error estimates, and this is illustrated by an application to modified Bessel functions of complex argument and large positive order. Explicit computable error bounds are also derived for asymptotic expansions for particular solutions of the nonhomogeneous equations of the form d2w/dz2 − {u2f(z) + g(z)}w = p(z).
Fixed points of multivalued maps under local Lipschitz conditions and applications
Authors: Gallegos Claudio A. , Henríquez Hernán R.
Published: January 2019

In this work we are concerned with the existence of fixed points for multivalued maps defined on Banach spaces. Using the Banach spaces scale concept, we establish the existence of a fixed point of a multivalued map in a vector subspace where the map is only locally Lipschitz continuous. We apply our results to the existence of mild solutions and asymptotically almost periodic solutions of an abstract Cauchy problem governed by a first-order differential inclusion. Our results are obtained by using fixed point theory for the measure of noncompactness.
Factoriality, Connes' type III invariants and fullness of amalgamated free product von Neumann algebras
Authors: Houdayer Cyril , Isono Yusuke
Published: January 2019

We investigate factoriality, Connes' type III invariants and fullness of arbitrary amalgamated free product von Neumann algebras using Popa's deformation/rigidity theory. Among other things, we generalize many previous structural results on amalgamated free product von Neumann algebras and we obtain new examples of full amalgamated free product factors for which we can explicitely compute Connes' type III invariants.
The Downfall of the Mandatory Death Penalty in Kenya
Authors: Chenwi Lilian
Published: January 2019

The retention and use of the death penalty, especially the mandatory death penalty, continues to be an issue of controversy and concern in Africa and elsewhere. Accordingly, African states are slowly but increasingly moving away from the death penalty, with many of them abolishing it either de facto or de jure, or limiting its use, with some finding its mandatory application to be unlawful. This article considers the recent Supreme Court of Kenya decision that declared the mandatory nature of the death penalty as provided for under the country's Penal Code to be unconstitutional. However, it argues that, while declaring the mandatory death penalty to be unconstitutional is commendable and a promising step on the path towards the abolition of the death penalty, the death penalty remains available as a punishment, with serious human rights implications if procedural safeguards are not followed.
The evolutionary correlation associated with seed mass and altitude on nutrient allocation of seeds
Authors: Bu Hai-Yan , Zhang Yan-Ming , Zhao Di , Wang Su-Yu , Jia Peng , Qi Wei , Liu Kun , Xu Dang-Hui , Ge Wen-Jing , Wang Xue-Jing
Published: January 2019

Seed reserves play vital roles in seed germination and seedling growth and their variation may be related to various environment factors, plant traits and phylogenetic history. Here, the evolutionary correlation associated with seed mass and altitude and carbon (C), nitrogen (N) and phosphorus (P) allocation of seeds among 253 alpine herbaceous plants was tested. In this study, phylogeny had strong limitations on nutrient allocation of seeds across species, and species from younger phylogenetic groups tended to have higher N and P contents, which might be considered as the evolutionary selection of seed plants. Higher seed N and P content would help seedlings to gain more survival chance and stronger competitive capacity, and their progeny would be more likely to be preserved. When phylogeny was considered, altitude only had a significant positive effect on P content, but the negative effects on seed mass were all expressed. The independent effects of altitude and seed mass suggest that the nutrient allocation of seeds might be affected by both environment and plant traits. In addition, altitude and seed mass displayed partial overlapping effects on nutrient allocation of seeds. The negative effects of seed mass were affected slightly by altitude, whereas altitude only had a significant positive effect on P content when seed mass was controlled. Above all, seed P content showed obvious and general correlations with seed mass, altitude and age of clade, which indicated that higher seed P content might be an adaptive selection of species associated with growth and survival of progeny.
The Neuropsychological Syndrome of Agenesis of the Corpus Callosum
Authors: Brown Warren S. , Paul Lynn K.
Published: January 2019

Background: Agenesis of the corpus callosum (AgCC) involves congenital absence of all or part of the corpus callosum. Because the disorder can only be firmly diagnosed via neuroradiology, it has a short research history, and only recently has the cognitive syndrome become clear. Purpose: Our purpose is to review the primary deficits in AgCC that constitute the core syndrome. Conclusions: The cores syndrome includes: (1) reduced interhemispheric transfer of sensory-motor information; (2) reduced cognitive processing speed; and (3) deficits in complex reasoning and novel problem-solving. These domains do not appear to reflect different neuroanatomical abnormalities, but rather different domains of expression of reduced interhemispheric communication from callosal absence. Implications: These core deficits are expressed across various domains of cognitive, behavioral, and social functioning. The impact of these deficits varies across development and may be moderated by individual factors such as co-occurrence of other neurodevelopmental conditions, general intellectual capacity, and environmental support. (JINS, 2019, 25, 324–330)
Revealing Short GRB Jet Structure and Dynamics with Gravitational Wave Electromagnetic Counterparts
Authors: Lamb Gavin P. , Kobayashi Shiho
Published: January 2019

Compact object mergers are promising candidates for the progenitor system of short gamma-ray bursts (GRBs). Using gravitational wave (GW) triggers to identify a merger, any electromagnetic (EM) counterparts from the jet can be used to constrain the dynamics and structure of short GRB jets. GW triggered searches could reveal a hidden population of optical transients associated with the short-lived jets from the merger object. If the population of merger-jets is dominated by low-Lorentz-factors, then a GW triggered search will reveal the on-axis orphan afterglows from these failed GRBs. By considering the EM counterparts from a jet, with or without the prompt GRB, the jet structure and dynamics can be constrained. By modelling the afterglow of various jet structures with viewing angle, we provide observable predictions for the on- and off- axis EM jet counterparts. The predictions provide an indication for the various features expected from the proposed jet structure models.
Observations of GW170817 by DESGW and the DECam GW-EM Collaboration
Authors: Annis James
Published: January 2019

On August 17, 2017 LIGO/Virgo detected a binary neutron star via gravitational waves. We observed 70 sq-degrees in the LIGO/Virgo spatial localization with the DECam on the 4m Blanco telescope covering 80% of the final map. Our group independently discovered an optical counterpart in NGC 4993. We searched our entire imaged region: the object in NGC 4993 was the only viable candidate. Our observations of NGC4993 show complicated morphology but simple star formation history. Our x-ray and radio observations indicate an off-axis jet as afterglow. Our high-cadence optical and infrared spectra show a source that must be described by at least two components, one of which is dominated by the r-process nucleosynthesis elements characteristic of a kilonova. Our modeling of the light curve demonstrates such a model in which 0.05 M⊙ of material is ejected from the system. Finally, we discuss the first standard siren measurement of H0.
Reanalysis of LIGO black-hole coalescences with alternative prior assumptions
Authors: Gerosa Davide , Vitale Salvatore , Haster Carl-Johan , Chatziioannou Katerina , Zimmerman Aaron
Published: January 2019

We present a critical reanalysis of the black-hole binary coalescences detected during LIGO’s first observing run under different Bayesian prior assumptions. We summarize the main findings of Vitale et al. (2017) and show additional marginalized posterior distributions for some of the binaries’ intrinsic parameters.

These findings were presented at IAU Symposium 338, held on October 16-19, 2017 in Baton Rouge, LA, USA.
Supermassive Black Hole Binary Candidates from the Pan-STARRS1 Medium Deep Survey
Authors: Liu Tingting , Gezari Suvi
Published: January 2019

We conducted a systematic search for periodically varying quasars, which are predicted manifestations of sub-pc supermassive black hole binaries (SMBHBs), in the Pan-STARRS1 Medium Deep Survey (PS1 MDS). Since the normal variability of quasars can also mimic periodicity over a small number of cycles, we have extended the temporal baseline by monitoring the candidates with the Discovery Channel Telescope and the Las Cumbres Observatory telescopes. We have also adopted a more rigorous method to evaluate the significance of the periodic candidates, by considering in the light curves a “red noise” background modeled as the Damped Random Walk process. While none of the candidates can be resolved by the current pulsar timing arrays (PTAs) as individual gravitational wave sources, the Large Synoptic Survey Telescope is capable of finding more periodic candidates, some of which are likely to be detected by the PTA experiment with the Square Kilometre Array.
On the host galaxy properties of stellar binary black hole mergers
Authors: Lu Youjun , Cao Liang , Zhao Yuetong
Published: January 2019

We report our investigations on the host galaxy properties of stellar binary black holes (SBBHs) by implementing simple recipes for SBBH formation and merger into cosmological galaxy formation model. If the time delay between SBBH formation and merger ranges from Gyr to the Hubble time, SBBH mergers at redshift z < 0.3 occur preferentially in big galaxies with stellar mass M* > 2 × 1010M⊙ and metallicities Z peaking around ~0.6Z⊙. However, the host galaxy stellar mass distribution of heavy SBBH mergers (with total black hole mass >50M⊙) is bimodal with one peak at ~109M⊙ and the other peak at ~2 × 1010M⊙. The contribution fraction from metal-poor host galaxies (Z < 0.2Z⊙) to heavy mergers is much larger than that to less heavy mergers. If SBBHs were formed in the early universe, their mergers detected at z < 0.3 occur preferentially in even more massive galaxies with M* > 3 × 1010M⊙ and in galaxies with metallicities mostly >0.2Z⊙ and peaking at Z ~ 0.6Z⊙.
Cosmology with Gravitational Waves in DES and LSST
Authors: Herner Kenneth , Soares-Santos Marcelle , Annis James
Published: January 2019

Motivated by the prospect of the wealth of data arising from the inauguration of the era of gravitational wave detection by ground-based interferometers the DES collaboration, in partnership with members of the LIGO collaboration and members of the astronomical community at large, have established a research program to search for their optical counterparts and to explore their use as cosmological probes. In this talk we present the status of our program and discuss prospects for establishing this new probe as part of the portfolio of the Dark Energy research program in the future, in particular for the next generation survey, LSST.
Environmental Significance of the Chemical Composition of Sediments in Groundwater‐Recharged Lakes of the Badain Jaran Desert, NW China
Authors: Li Zhuolun , Chen Qiujie , Zhang Cheng , Yu Qiangjing , Dong Shipei , Zhao Liqiang , Wang Nai'ang
Published: January 2019

For lakes in desert hinterlands that are not recharged by river runoff, sediment is input solely by wind transport; however, the mechanisms that control the spatial variations in geochemical characteristics of sediments in such lakes remain unclear. Moreover, it remains uncertain whether some element ratios can be used as proxies for environmental characteristics. In this study, 100 surface sediment samples were collected from five lakes in the hinterland of the Badain Jaran Desert, NW China, and examined for their major, trace and rare earth element contents and mineral assemblages. Chemical composition and mineral components of the sediments differed significantly between lakes with different total dissolved solids (TDS). Geochemical characteristics of the lake sediments and their spatial variations are influenced by eolian sands, saline minerals, and sediment sorting. Eolian sands dominate the immobile and nonsoluble elements, whereas authigenic minerals are important in influencing variations in the mobile and soluble elements. Sediment sorting is reflected in the spatial variation of the sediment chemical composition. The positive relationship between the SiO2/Ti of sediment and lake area indicates that changes in the SiO2/Ti ratio can reveal approximate lake area. The Na2O/K2O ratio in sediments can reveal the TDS of salt lakes more effectively than can the Rb/Sr ratio. However, the key factors and mechanisms governing the chemical composition of sediments at different brine evolution stages vary among lakes with different TDS levels, which should be carefully considered when interpreting the environmental significance of the chemical composition as a proxy for paleoenviroment change.
Premonsoon/Postmonsoon Bay of Bengal Tropical Cyclones Intensity: Role of Air‐Sea Coupling and Large‐Scale Background State
Authors: Neetu S. , Lengaigne M. , Vialard J. , Samson G. , Masson S. , Krishnamohan K. S. , Suresh I.
Published: January 2019

The densely populated Bay of Bengal (BoB) rim witnesses the deadliest tropical cyclones (TCs) globally, before and after the summer monsoon. Previous studies indicated that enhanced salinity and reduced thermal stratification reduce cooling under BoB TCs after the monsoon, suggesting that air‐sea coupling may favor stronger TCs during that season. Using observations and simulations from a one fourth degree regional ocean‐atmosphere model, we show that BoB TCs are stronger before the monsoon due to a more favorable large‐scale background state (less vertical wind shear and higher sea surface temperature). Air‐sea coupling however alleviates this background state influence, by reducing the number of premonsoon intense TCs, because of larger cooling and reduced upward enthalpy fluxes below TCs during that season. As the impact of air‐sea interactions on BoB TCs is largest for intense TCs, it should be further investigated for Category 3 and above TCs, which are not reproduced at one fourth degree resolution.
Inertia Influences Pelagic Sargassum Advection and Distribution
Authors: Brooks Maureen T. , Coles Victoria J. , Coles William C.
Published: January 2019

The effect of inertia (resistance to a change in velocity of buoyant finite‐sized objects) on the advection of pelagic Sargassum, a macroalgae, is a function of the size and density of natural Sargassum rafts. Here we present observations of Sargassum density and an approach for estimating an effective radius of Sargassum rafts from remote‐sensing observations. This allows the existing theoretical framework for Lagrangian modeling of inertial effects on spherical particles to be applied to Sargassum. Accounting for inertia yields up to a 20% increase in Sargassum export from the Sargasso Sea southward and provides a return pathway to the tropics that may be important to maintaining a self‐sustaining population. Resolving inertial effects also leads to increases in retention in the Gulf of Mexico and Caribbean Sea, where Sargassum inundation events are increasingly common. Including inertial effects in models of Sargassum advection could improve predictions of these events.
Local Generation of High‐Frequency Plasmaspheric Hiss Observed by Van Allen Probes
Authors: He Zhaoguo , Chen Lunjin , Liu Xu , Zhu Hui , Liu Si , Gao Zhonglei , Cao Yong
Published: January 2019

The generation of a high‐frequency plasmaspheric hiss (HFPH) wave observed by Van Allen Probes is studied in this letter for the first time. The wave has a moderate power spectral density (∼10−6 nT2/Hz), with a frequency range extended from 2 to 10 kHz. The correlated observations of waves and particles indicate that HFPH is associated with the enhancement of electron flux during the substorm on 6 January 2014. Calculations of the wave linear growth rate driven by the fitted electron phase space density show that the electron distribution after the substorm onset is efficient for the HFPH generation. The energy of the contributing electrons is about 1–2 keV, which is consistent with the observation. These results support that the observed HFPH is likely to be generated locally inside the plasmasphere due to the instability of injected kiloelectron volt electrons.
A Numerical Model for the Effect of Permeability Change on Faulting During Fluid Injection
Authors: Zhang Xi , Jeffrey Robert G. , He Changrong
Published: January 2019

Slip and slip zone development during constant‐rate fluid injection into a permeable fault in an infinite, impermeable elastic rock is studied here numerically using a hydromechanical fracture model. The interplay of slip zone growth and fault dilatancy is assumed to be affected by linear slip weakening of frictional strength and slip‐induced dilation. The discretization error is minimized by using element sizes based on a mesh sensitivity study to obtain accurate slipping and pressurized lengths. Comparisons with published results for large and zero fault permeability cases demonstrate the validity of the numerical results. Dimensional analysis is used to identify five parameters that control slip development, including the slip‐induced dilatancy factor, initial fault permeability, the product of fluid viscosity and injection rate, the background shear to normal stress ratio, and the residual coefficient of friction. Conditions leading a quasi‐static stable slip to either continue as stable aseismic slip or accelerate are discussed. Acceleration of slip occurs on less permeable faults characterized by a hybrid tensile‐shear fracture subject to higher pressure, while prolonged aseismic slip occurs along a more permeable fault subject to lower pressure. During long‐duration aseismic slip the pressure varies slightly around the value that equalizes the fault shear strength and the background shear stress. A permeability perturbation in the form of a sinusoidal fault aperture distribution does not change the tendency of the slip to be slow and stable. Like preexisting permeability, slip‐induced dilation responses play a role in limiting pressure level and extending the slow slip period.
Azimuthal Seismic Anisotropy of 70‐Ma Pacific‐Plate Upper Mantle
Authors: Mark H. F. , Lizarralde D. , Collins J. A. , Miller N. C. , Hirth G. , Gaherty J. B. , Evans R. L.
Published: January 2019

Plate formation and evolution processes are predicted to generate upper mantle seismic anisotropy and negative vertical velocity gradients in oceanic lithosphere. However, predictions for upper mantle seismic velocity structure do not fully agree with the results of seismic experiments. The strength of anisotropy observed in the upper mantle varies widely. Further, many refraction studies observe a fast direction of anisotropy rotated several degrees with respect to the paleospreading direction, suggesting that upper mantle anisotropy records processes other than 2‐D corner flow and plate‐driven shear near mid‐ocean ridges. We measure 6.0 ± 0.3% anisotropy at the Moho in 70‐Ma lithosphere in the central Pacific with a fast direction parallel to paleospreading, consistent with mineral alignment by 2‐D mantle flow near a mid‐ocean ridge. We also find an increase in the strength of anisotropy with depth, with vertical velocity gradients estimated at 0.02 km/s/km in the fast direction and 0 km/s/km in the slow direction. The increase in anisotropy with depth can be explained by mechanisms for producing anisotropy other than intrinsic effects from mineral fabric, such as aligned cracks or other structures. This measurement of seismic anisotropy and gradients reflects the effects of both plate formation and evolution processes on seismic velocity structure in mature oceanic lithosphere, and can serve as a reference for future studies to investigate the processes involved in lithospheric formation and evolution.
Klinkenberg Effect and Effective Pressure for Gas Permeability of Tight Sandstones
Authors: Xiao Wenlian , Bernabé Yves , Evans Brian , Mok Ulrich , Zhao Jinzhou , Ren Xiyao , Chen Meng
Published: January 2019

Gas permeability kg of tight sandstones was measured while cycling pore pressure, Pf, and confining pressure, Pc, using two different procedures. First, we cycled the pore pressure from a minimum value close to atmospheric pressure to a maximum one slightly lower than Pc, while keeping the Pc constant. Second, Pf and Pc were simultaneously varied so as to keep the difference, Pc − Pf, constant. Significant effects owing to slip flow were observed when the gas pressure was lower than about 5 MPa. Klinkenberg plots showed that, under constant Pc, gas permeability kg decreased linearly for high values of 1/Pf, reached a minimum and then sharply increased as 1/Pf approached zero. Under constant Pc − Pf, kg again decreased linearly in the high limit of 1/Pf and showed additional decrease in the low 1/Pf limit. The linear segments in both procedures indicate that kg in tight sandstones was subject to slip flow at low values of Pf, while the curved segments revealed the sensitivity of permeability to effective pressure when Pf became comparable in magnitude to confining pressure. The effective pressure coefficient α was estimated and generally appeared to be a well‐defined decreasing function of the pressure difference Pc − Pf. We modified the Walsh permeability model for fissured rocks to include slip flow effects and obtained satisfactory fits to the experimental data for the samples with the lowest porosities and the highest pressure sensitivities. This observation suggests that the intrinsic permeability of these rocks was controlled by intergranular and/or intragranular crack‐like pores.
Long‐Lasting Evolution of Layer 2A in the Western South Atlantic: Evidence for Low‐Temperature Hydrothermal Circulation in Old Oceanic Crust
Authors: Kardell Dominik A. , Christeson Gail L. , Estep Justin D. , Reece Robert S. , Carlson Richard L.
Published: January 2019

Previous seismic studies suggest that hydrothermal processes are active only within young oceanic crust (<10–16 Ma). However, differences between measured and predicted heat flow at the ocean floor indicate that hydrothermal fluids may be transporting heat advectively in crust up to ages of 65 Ma. We report on seismic velocities of 0–71 Ma slow to intermediate spreading rate upper crust in the western South Atlantic. Thirteen high‐resolution 2‐D velocity models were built using traveltime tomography on downward continued streamer data acquired during the Crustal Reflectivity Experiment Southern Transect. In the Crustal Reflectivity Experiment Southern Transect area, velocities at the top of seismic layer 2A increase rapidly from ~2.4 km/s at 0 Ma to ~4.2 km/s at 6 Ma and then undergo a more gradual increase to ~4.9 km/s at 58 Ma. These new results resolve the long‐standing debate about the duration of interaction between ocean crust and seawater, providing seismic evidence for hydrothermal circulation continuing to crustal ages predicted by heat flow studies. Seismic layer 2B does not show a systematic off‐axis velocity trend but has an average value of 5.15 km/s. We interpret this result to indicate that the hydrothermal system becomes too shallow to affect the physical properties of layer 2B shortly after crustal accretion. Upper crustal heterogeneity in ridge‐parallel profile orientation is more pronounced for crust accreted at slow spreading rates, compared to intermediate rates. This result is consistent with shorter magmatic segments at slower spreading rates, increasing the frequency of tectonic and magmatic accretion alternately occurring along the ridge.
Shallow and Deep Eastern Boundary Currents in the South Atlantic at 34.5°S: Mean Structure and Variability
Authors: Kersalé Marion , Perez Renellys C. , Speich Sabrina , Meinen Christopher S. , Lamont Tarron , Le Hénaff Matthieu , van den Berg Marcel A. , Majumder Sudip , Ansorge Isabelle J. , Dong Shenfu , Schmid Claudia , Terre Thierry , Garzoli Silvia L.
Published: January 2019

The first in situ continuous full‐water‐column observations of the eastern boundary currents (EBCs) at 34.5°S in the South Atlantic are obtained using 23 months of data from a line of Current and Pressure recording Inverted Echo Sounders (CPIES) spanning the Cape Basin. The CPIES are used to evaluate the mean structure of the EBC, the associated water masses, and the volume transport variability. The estimated northward time‐mean Benguela Current absolute geostrophic transport is 24 Sv, with a temporal standard deviation of 17 Sv. Beneath this current the time‐mean transport is southward, indicating the presence of a deep‐EBC (DEBC), with a time‐mean transport of 12 Sv, and a standard deviation of 17 Sv. Offshore of these currents, the shallow and deep flows are more variable with weak time means, likely influenced by Agulhas Rings transiting through the region. Hydrographic data collected along the CPIES line demonstrate that the DEBC is carrying recently ventilated North Atlantic Deep Water, as it flows along the continental slope. This is consistent with a previously hypothesized interior pathway bringing recently ventilated North Atlantic Deep Water from the Deep Western Boundary Current across the Atlantic to the Cape Basin. The observations further indicate that much of the DEBC must recirculate within the basin. Spectral analyses of the shallow and deep EBC transport time series demonstrate that the strongest variability occurs on timescales ranging from 30 to 90 days, associated with the propagation of Agulhas Rings.