bluuebunny/crossref_metadata_2025 huggingface dataset:
Revisiting “Steady-State” Monotonic and Cyclic Deformation: Emphasizing the Quasi-Stationary State of Deformation
Authors: Mughrabi Haël
Published: February 2020

High-temperature creep, cyclic deformation in saturation, and a number of technologically important processes are typical examples of the so-called “steady-state” deformation. These cases are usually defined in terms of the constancy of the mechanical parameters. Moreover, it is usually assumed that the deformation-induced microstructure undergoes no further changes. However, clear evidence shows that non-negligible microstructural changes continue to occur in the so-defined steady-state high-temperature creep and in cyclic saturation. It can be shown that the so-called “steady-state” deformation is actually a quasi-stationary deformation which is characterized by the initial development of a “mechanical steady state”, which is followed with a delay by a “microstructural steady state.” Only the latter can then be considered as a true steady state. A deeper analysis reveals a persistent slight increase of the dislocation density, with geometrically necessary dislocations in the cell walls/subgrain boundaries, causing the latter to transform gradually into sharper boundaries with higher misorientations. These findings, based on a detailed analysis of a wide range of experimental studies, are found to be almost identical for both high-temperature creep and cyclic deformation in saturation and are hence considered as characteristic of quasi-stationary deformation. The analysis clarifies, as a by-product, specific effects which arise from the increasing heterogeneity of the dislocation pattern (patterning). Thus, a marked decrease of the arrangement factor “alpha” in the Taylor flow stress is noted, as patterning proceeds, in agreement with predictions of the so-called composite model. Since this effect is compensated partially by the increase of the dislocation density, the flow stress remains rather insensitive to subtle microstructural changes. Based on these facts, the need for revision of current flow-stress formulations in future dislocation modeling is emphasized.
Metastatic Anaplastic Thyroid Carcinoma in Complete Remission: Morphological, Molecular, and Clinical Work-Up of a Rare Case
Authors: Stenman Adam , Hellgren L. Samuel , Jatta Kenbugul , Hysek Martin , Zemmler Maja , Altena Renske , Nilsson Inga-Lena , Bränström Robert , Zedenius Jan , Juhlin C. Christofer
Published: February 2020

Anaplastic thyroid carcinoma (ATC) exhibits an exceedingly poor prognosis, and the current treatment options are, for most cases, palliative by nature. Few reports of long-time survivors exist, although in these patients, tumors often were limited to the thyroid and/or regional lymph nodes. We describe a 64-year-old male who developed a rapidly growing mass in the left thyroid lobe. A fine-needle aspiration biopsy (FNAB) was consistent with ATC, and the patient underwent preoperative combined chemo- and radiotherapy followed by a hemithyroidectomy. The ensuing histopathological investigation was consistent with ATC adjoined by an oxyphilic well-differentiated lesion, likely a Hürthle cell carcinoma. Tumor margins were negative, and no extrathyroidal extension was noted. Focused next-generation sequencing analysis of the primary tumor tissue identified a TP53 gene mutation but could not identify any potential druggable targets. Additional Sanger sequencing detected a C228T TERT promoter mutation. The tumor was found to be microsatellite stable and displayed PDL1 expression in 80% of tumor cells. Following a CT scan 1 month postoperatively, metastatic deposits were suspected in the lung as well as in the left adrenal gland, of which FNAB verified the latter. Remarkably, upon radiological follow-up, the disease had gone into apparent complete remission. The patient is alive and well with no signs of residual disease after 12 months of follow-up. We here summarize the clinical, histological, and molecular data of this highly interesting patient case and review the literature for possible common denominators with other patients with disseminated ATC.
Synergistic effect of magnetic field and nanocomposite pour point depressant on the yield stress of waxy model oil
Authors: Huang Hui-Rong , Wang Wei , Peng Ze-Heng , Li Kai , Ding Yan-Fen , Yu Wei-Jie , Gan Dong-Ying , Wang Chuan-Shuo , Xue Yi-Han , Gong Jing
Published: February 2020

Yield stress, as the key parameter to characterize the network strength of waxy oil, is important to the petroleum pipeline safety. Reducing the yield stress of waxy oil is of great significance for flow assurance. In this study, the effect of alternating magnetic field (intensity, frequency) on the yield stress of a waxy model oil with nanocomposite pour point depressant (NPPD) is systematically investigated. An optimum magnetic field intensity and frequency is found for the reduction in yield stress. When adding with NPPD, the heterogeneous nucleation of NPPD contributes to the reduction in yield stress for waxy model oil. Interestingly, the magnetic field is helpful for the modification of yield stress at a lower frequency and intensity before the optimal value; however, the modification is found to be weakened when the magnetic field is further increased after the optimal value. Possible explanation is proposed that the aggregation morphology of wax crystal would be altered and results in the release of wrapped oil phase from the network structure under the magnetic field.
Nebivolol attenuates the anticonvulsant action of carbamazepine and phenobarbital against the maximal electroshock-induced seizures in mice
Authors: Borowicz-Reutt Kinga K. , Banach Monika , Rudkowska Monika
Published: February 2020

Background

Due to co-occurrence of seizures and cardiovascular disorders, nebivolol, a widely used selective β1-blocker with vasodilatory properties, may be co-administered with antiepileptic drugs. Therefore, we wanted to assess interactions between nebivolol and four conventional antiepileptic drugs: carbamazepine, valproate, phenytoin and phenobarbital in the screening model of tonic–clonic convulsions.

Methods

Seizure experiments were conducted in the electroconvulsive threshold and maximal electroshock tests in mice. The chimney test served as a method of assessing motor coordination, whereas long-term memory was evaluated in the computerized step-through passive-avoidance task. To exclude or confirm pharmacokinetic interactions, we measured brain concentrations of antiepileptic drugs using the fluorescence polarization immunoassay.

Results

It was shown that nebivolol applied at doses 0.5–15 mg/kg did not raise the threshold for electroconvulsions. However, nebivolol at the dose of 15 mg/kg reduced the anti-electroshock properties of carbamazepine. The effect of valproate, phenytoin, and phenobarbital remained unchanged by combination with the β-blocker. Nebivolol significantly decreased the brain concentration of valproate, but did not affect concentrations of remaining antiepileptic drugs. Therefore, contribution of pharmacokinetic interactions to the final effect of the nebivolol/carbamazepine combination seems not probable. Nebivolol alone and in combinations with antiepileptic drugs did not impair motor performance in mice. Nebivolol alone did not affect long-term memory of animals, and did not potentiate memory impairment induced by valproate and carbamazepine.

Conclusions

This study indicates that nebivolol attenuated effectiveness of some antiepileptic drugs. In case the results are confirmed in clinical settings, this β-blocker should be used with caution in epileptic patients.
Tribological study of mechanically milled graphite nanoparticles codeposited in electroless Ni-P coatings
Authors: Thakur I.S. , Pandey V.S. , Rao P.S. , Tyagi S. , Goyal Deepam
Published: February 2020

The present study focusses to enhance the wear resistance of electroless Ni-P coatings with the co-deposition of selflubricating nano graphite particles synthesized by mechanical milling using a high energy planetary ball mill. The coatings were developed on an aluminum substrate and nano graphite particles were co-deposited (4 g/l) into the Ni-P matrix using alkaline hypophosphite reduced electroless bath. Changes in properties after heat treatment at 220 °C for 4 h in vacuum have been correlated with morphological and microstructural changes shown by field emission scanning electron microscopy (FESEM) and X-ray diffraction (XRD) respectively. Energy dispersive analysis of X-ray (EDAX) determined the quality and elemental composition of coatings. Wear resistance, coefficient of friction (pin on disc) and microhardness of electroless Ni-P-graphite nanocomposite coatings were calculated and contrasted with Ni-P coatings. The outcomes reveal that the size of synthesized graphite nanoparticles is 20 nm. Microhardness and wear resistance of electroless coatings have improved after heat treatment. Excellent wear resistance has been observed at the cost of some hardness in Ni-P-graphite nanocomposite coatings over Ni-P coatings.
Towards a Cooperative Approach to Hobby Metal Detecting: The European Public Finds Recording Network (EPFRN) Vision Statement
Authors: Dobat Andres S. , Deckers Pieterjan , Heeren Stijn , Lewis Michael , Thomas Suzie , Wessman Anna
Published: February 2020

Hobby metal detecting is a controversial subject. Legal and policy approaches differ widely across national and regional contexts, and the attitudes of archaeologists and heritage professionals towards detectorists are often polarized and based on ethical or emotive arguments. We, the European Public Finds Recording Network (EPFRN), have implemented collaborative approaches towards detectorist communities in our respective contexts (Denmark, England and Wales, Finland, Flanders, and the Netherlands). Although our motivations are affected by our national circumstances, we base our work on an agreed set of goals, practices, and visions. This article presents the EPFRN's vision statement and provides insight into its underlying thoughts. We hope to create a debate on how to develop best practice approaches that acknowledge the inherent challenges of hobby metal detecting while realizing its potential.
Ephemeral species in the fossil record? Synchronous coupling of macroevolutionary dynamics in mid-Paleozoic zooplankton
Authors: Crampton James S. , Cooper Roger A. , Foote Michael , Sadler Peter M.
Published: February 2020

We document a positive and strong correlation between speciation and extinction rates in the Paleozoic zooplankton graptoloid clade, between 481 and 419 Ma. This correlation has a magnitude of ~0.35–0.45 and manifests at a temporal resolution of <50 kyr and, for part of our data set, <25 kyr. It cannot be explained as an artifact of the method used to measure rates, sampling bias, bias resulting from construction of the time series, autocorrelation, underestimation of species durations, or undetected phyletic evolution. Correlations are approximately equal during the Ordovician and Silurian, despite the very different speciation and extinction regimes prevailing during these two periods, and correlation is strongest in the shortest-lived cohorts of species.

We infer that this correlation reflects approximately synchronous coupling of speciation and extinction in the graptoloids on timescales of a few tens of thousands of years. Almost half of graptoloid species in our data set have durations of <0.5 Myr, and previous studies have demonstrated that, during times of background extinction, short-lived species were selectively targeted by extinction. These observations may be consistent with the model of ephemeral speciation, whereby new species are inferred to form constantly and at high rate, but most of them disappear rapidly through extinction or reabsorption into the ancestral lineage. Diversity dependence with a lag of ~1 Myr, also documented elsewhere, may reflect a subsequent and relatively slow, competitive dynamic that governed those species that dispersed beyond their originating water mass and escaped the ephemeral species filter.
Hypergeometric rational approximations to ζ(4)
Authors: Marcovecchio Raffaele , Zudilin Wadim
Published: February 2020

We give a new hypergeometric construction of rational approximations to ζ(4), which absorbs the earlier one from 2003 based on Bailey's 9F8 hypergeometric integrals. With the novel ingredients we are able to gain better control of the arithmetic and produce a record irrationality measure for ζ(4).
The Concept of Entitlement to an Exclusive Economic Zone as Reflected in International Judicial Decisions
Authors: Friedman Shani
Published: February 2020

The article seeks to shed light on a lacuna in the law and international adjudication regarding the entitlement of coastal states to the exclusive economic zone (EEZ), by analysing the implicit requirement in the UN Convention on the Law of the Sea of proclamation to establish such entitlement. The main argument of the article is that despite the requirement for proclamation, there is no definition of this act in international law that clarifies its legal status. Nonetheless, failure to heed the requirement to proclaim an EEZ can affect the establishment of the EEZ, which in turn affects the rights and jurisdictions of coastal states in the zone. It can also affect the competence of judicial institutions to decide on matters such as delimitation of overlapping zones.
Administrative Detention by Non-State Armed Groups: Legal Basis and Procedural Safeguards
Authors: Gavrilova Maria
Published: February 2020

The realities of contemporary armed conflicts with a complex interweaving net of actors are rarely reminiscent of classic combat scenarios envisaged by the drafters of the Geneva Conventions. The scarcity of conventional regulation of non-international armed conflicts (NIACs), coupled with the non-state character of the majority of detaining powers, lead to lack of clarity regarding the legal regime of detention of persons captured by non-state armed groups (NSAGs). In the absence of an explicit authorisation for internment under the international humanitarian law applicable to NIACs, recent developments in case law have induced a scholarly debate on what is the legal basis for administrative detention carried out by these actors. The article analyses key arguments presented by both sides of the debate, concluding that neither side can demonstrate either the existence or the absence of the authorisation in question, while the discussion itself has limited practical value in regulating the conduct of NSAGs. At the same time, the practice of states, although still ambivalent, points to the gradual transformation of mere legality, or the so-called ‘inherent power’ to intern, into a customary provision providing a legal basis for administrative detention by NSAGs.
ACAA2 and FASN polymorphisms affect the fatty acid profile of Chios sheep milk
Authors: Symeou Simoni , Tzamaloukas Ouranios , Banos Georgios , Miltiadou Despoina
Published: February 2020

The objective of the research reported in this research communication was the identification and association of single nucleotide polymorphisms (SNP) in the ovine DGAT1, FASN, SCD1 and ACAA2 genes with milk fat percentage and fatty acid (FA) content. Three consecutive monthly milk samplings were obtained from a total of 429 purebred Chios ewes during mid-lactation. Genotypic data were jointly analyzed with 1184 fat content and 37 718 FA percentage records using mixed models. The 3′ untranslated region (UTR) of the DGAT1 gene and the 5′ and 3′UTRs of the SCD1 gene appeared to be monomorphic. The FASN g.14777C>T SNP on exon 31 was associated with C13:0 and the ACAA2 g.2982T>C SNP on the 3′UTR was associated with C9:0, C11:0, C12:1 cis-9, C13:0 and the ω6/ω3 index, while fat percentage was not affected by the identified SNPs. The results could be useful for breeding programs aiming to improve the quality and nutritional value of ovine milk.
Gender, Family, and the Policing of the ‘Criminal Tribes’ in Nineteenth-Century North India
Authors: HINCHY JESSICA
Published: February 2020

In the South Asian setting, the fields of gender history and family history are still predominantly concerned with relatively elite social groups. Few studies have examined issues of gender and the family in the history of Dalit, low-caste, and socially marginalized communities, especially those that were labelled ‘criminal tribes’ from the mid-nineteenth century on. This article explores the ways in which gender patterned criminalized communities’ experiences of everyday colonial governance under Part I of the 1871 Criminal Tribes Act (CTA) in the first two decades that it was enforced in northern India. In this early period, the colonial government did not closely regulate marriage practices, domestic arrangements, or the gendered organization of labour within communities categorized as ‘criminal tribes’. Nevertheless, notions of sexuality and gender underlay colonial knowledge of the ‘criminal tribes’, which emerged in dialogue with middle-class Indian gender and caste politics. Moreover, the family unit was the central target of the CTA surveillance and policing regime, which aimed to produce ‘industrious’ families. Officially endorsed forms of labour had complex implications for criminalized communities in the context of North Indian gender norms and strategies of social mobility. Gender power dynamics also shaped criminalized peoples’ interpersonal, embodied interactions with British and Indian colonial officials on an everyday basis. Meanwhile, different forms of leverage and evasion were open to men and women to cope with their criminalization and so the colonial state was experienced in highly gendered ways.
Arthrobotrys cladodes and Pochonia chlamydosporia in the biological control of nematodiosis in extensive bovine production system
Authors: Vieira Ítalo Stoupa , Oliveira Isabela de Castro , Freitas Samuel Galvão , Campos Artur Kanadani , Araújo Jackson Victor de
Published: February 2020

Cattle production in extensive systems favours the occurrence of gastrointestinal nematodes, and the use of nematophagous fungi complements the control strategies for these nematodes. The aim of this study was to evaluate the effectiveness of the fungi Arthrobotrys cladodes and Pochonia chlamydosporia in the biological control of gastrointestinal parasitic nematodes in grazing cattle. Twenty-four calves were randomly divided into four groups and allocated to independent paddocks from February 2018 to January 2019. In the first group, the animals received pellets containing P. chlamydosporia. In the second group, the animals received pellets containing A. cladodes. In the third group, the animals received pellets containing a combination of the fungi A. cladodes and P. chlamydosporia. In the control group, the animals received pellets without fungus. The combined use of A. cladodes and P. chlamydosporia showed greater efficacy in the biological control of bovine gastrointestinal parasitic nematodes than the same fungi used separately. The parasite load was lower and weight gain was greater (P ⩽ 0.05) in the groups of cattle treated with nematophagous fungi. Therefore, the use of A. cladodes and P. chlamydosporia is promising in the biological control of nematodiosis in cattle.
The contours of the development of non-living resources in Greenland
Authors: Takahashi Minori
Published: February 2020

In past discussions regarding development (of non-living resources) and indigenous people, a strong tendency existed to understand the act of development as a one-way impact from an outside society. This was often labelled as “environmental racism” and interpreted as a form of ethnic discrimination deeply intertwined with environmental issues. However, this view contained an element of confirmation bias regarding development and indigenous people. For example, it has been reported that in Alaska and elsewhere, indigenous people have taken initiative in developing non-living resources, making it clear that indigenous people are not necessarily passive subjects on whom development is unilaterally imposed. In this paper, after examining recent trends in the development of non-living resources, I shall take up the development of such resources in Greenland with the goal of sorting out and extrapolating the main arguments in the debate, especially within the self-rule government, regarding how the wealth obtained through the development of non-living resources should be enjoyed, while focusing on the notion of sustainable development and taking into consideration previous studies from the field of political science.
A NEW SPECIES OF ERIOCAULON (ERIOCAULACEAE) FROM THE SOUTHERN WESTERN GHATS OF KERALA, INDIA
Authors: Francis D. , Mohan V. , Venugopal D. K.
Published: February 2020

A new species of Eriocaulon, E. vamanae, is described from the southern Western Ghats of Kerala, India. It resembles Eriocaulon nepalense var. luzulifolium (Mart.) Praj. & J.Parn. but differs in the shape of its involucral bracts and receptacle, the fusion of the sepals in male flowers, the shape and indumentum of the sepals in female flowers, the size and indumentum of the petals in female flowers, and the seed coat appendages. Eriocaulon vamanae is so far known only from the type locality, Meesapulimala in Idukki District, Kerala, and is assessed as ‘Critically Endangered’ according to the IUCN’s Red List Categories and Criteria.
A note on the Brown–Erdős–Sós conjecture in groups
Authors: Long Jason
Published: February 2020

We show that a dense subset of a sufficiently large group multiplication table contains either a large part of the addition table of the integers modulo some k, or the entire multiplication table of a certain large abelian group, as a subgrid. As a consequence, we show that triples systems coming from a finite group contain configurations with t triples spanning
$ O(\sqrt t )$
vertices, which is the best possible up to the implied constant. We confirm that for all t we can find a collection of t triples spanning at most t + 3 vertices, resolving the Brown–Erdős–Sós conjecture in this context. The proof applies well-known arithmetic results including the multidimensional versions of Szemerédi’s theorem and the density Hales–Jewett theorem.

This result was discovered simultaneously and independently by Nenadov, Sudakov and Tyomkyn [5], and a weaker result avoiding the arithmetic machinery was obtained independently by Wong [11].
Water spreading weirs altering flood, nutrient distribution and crop productivity in upstream–downstream settings in dry lowlands of Afar, Ethiopia
Authors: Getnet Mezegebu , Amede Tilahun , Tilahun Gebeyaw , Legesse Gizachew , Gumma Murali Krishna , Abebe Hunegnaw , Gashaw Tadesse , Ketter Christina , Akker Elisabeth V.
Published: February 2020

Afar in Ethiopia is a drought prone area characterized by low rainfall, high temperature and suffering from flash flood emerging from adjacent mountains. We introduced a flood barrier, water spreading weirs (WSWs) in 2015 to convert floods to a productive use and assessed its effect in 2016 and 2017. WSWs resulted in deposition of sediments where sand deposition was higher in the upside of upstream weir whereas silt and clay deposition was prominent at the central location between the two weirs. There was a moisture gradient across farming fields with volumetric water content (VWC) at 20 cm depth varying between 10 and 22% depending on the relative position/distance of fields from the WSWs, consequently, effecting significant difference in yield between fields. There was a positive relationship between VWC made available by WSWs at planting and the yield (P < 0.001, r = 0.76) and biomass productivity (P < 0.005, r = 0.46). WSWs created differing farming zone following soil moisture regime, affecting grain and biomass yield. In good potential zones with high moisture content, the WSW-based farming enabled to produce up to 5 and 15 t ha−1 yr−1 of maize grain and biomass, respectively, while in low potential zones there was a complete crop grain failure. The system enabled pastoralists to produce huge amount of biomass and grain during Belg (short) and Meher (long) growing seasons that was stored and utilized during succeeding dry periods. Furthermore, the practice ensured a visible recovery of degraded rangelands. This was evident from the filling up of the riverbed as well as the two WSW wings with 1 m high and about 450 m length each with fertile sediment from Belg and Meher seasons of 2016 and 2017. Hence, future studies should analyze the sustainability and the potential of flood-based development at large scale.
Intercomparing Solar Spectral Irradiance From SORCE SIM
Authors: Mauceri Steffen , Pilewskie Peter , Woods Tom , Béland Stéphane , Richard Erik
Published: February 2020

Key Points

Comparison of three correction methods applied to SORCE SIM is presented

Solar spectral irradiance trends differ in the ultraviolet
An Investigation Into the Origin of Nitrate in Arctic Sea Ice
Authors: Clark S. C. , Granger J. , Mastorakis A. , Aguilar‐Islas A. , Hastings M. G.
Published: February 2020

Atmospheric deposition has been suggested to be an important source of reactive nitrogen stored in Northern Hemisphere land‐fast ice, in contrast to Antarctic sea ice, where bulk nutrients originate predominantly from underlying seawater. A paucity of sea ice studies in the open Arctic Ocean limits our understanding of the potential for melting ice to contribute to primary production in N‐deplete waters of the Arctic. As part of the U.S. western Arctic GEOTRACES 2015 expedition, samples of pack ice, overlying snow, atmospheric aerosols, and underlying seawater were collected between 82°N and 89°N. To identify the provenance of N in sea ice, we measured a suite of tracers including the isotopic composition of nitrate, ammonium, water, and particulate N. Relatively low concentrations of nitrate and ammonium were detected in sea ice (0.1–8.2 and 0.6–1.2 μmol L−1, respectively), and in atmospheric samples (1.1–3.7 and 0.8–1.2 μmol L−1, respectively). Atmospheric nitrate in snow had characteristically high Δ17O and δ18O (Δ17ONO3 = δ17O − 0.52 × δ18O = 27.1–33.5‰ versus Vienna Standard Mean Ocean Water (VSMOW); δ18ONO3 = 70.8–87.8‰), and low δ15NNO3 (−5.9–2‰ versus N2). In contrast to the atmospheric samples, the sea ice δ15NNO3 was typically higher (−0.3–15.0‰) and the δ17ONO3 and δ18ONO3 much lower (Δ17ONO3 = 0–12.4‰; δ18ONO3 = 23.3–67.5‰). The presence of Δ17ONO3 in the sea ice indicated that 0–40% of the nitrate is sourced from the atmosphere, while the majority of the nitrate is non‐atmospheric (Δ17ONO3 = 0‰). Based upon concentration, isotopic observations, and dynamic box modeling with atmospheric deposition and biological processes, we find that the majority of nitrate can be explained by in‐situ biological nitrate production.
Wavenumber Spectra of Atmospheric Gravity Waves and Medium‐Scale Traveling Ionospheric Disturbances Based on More Than 10‐Year Airglow Images in Japan, Russia, and Canada
Authors: Tsuchiya Satoshi , Shiokawa Kazuo , Otsuka Yuichi , Nakamura Takuji , Yamamoto Mamoru , Connors Martin , Schofield Ian , Shevtsov Boris , Poddelsky Igor
Published: February 2020

We have studied atmospheric gravity waves (AGWs) and nighttime medium‐scale traveling ionospheric disturbances (MSTIDs) by applying three‐dimensional spectral analysis technique to 557.7‐ and 630.0‐nm airglow images at Shigaraki (SGK) (35°N, 136°E, 1999–2017) and Rikubetsu (RIK) (44°N, 144°E, 1999–2017), Japan, Athabasca (ATH), Canada, (55°N, 247°E, 2005–2017), and Magadan (MGD), Russia (60°N, 151°E, 2008–2017), focusing on their horizontal wavenumber spectra. For the AGWs in 557.7‐nm images, the power spectra in summer are stronger than in other seasons, probably due to stronger tropospheric convection. The highest energy content of the waves are mostly at wavelengths between 20 and 300 km at MGD, ATH, and RIK, while it is above 200 km at SGK. The largest power spectral density is obtained at RIK at wavelengths of 30–100 km and then ATH. The slopes of the horizontal wavenumber spectra varies from −2.77 to −3.22. From the MSTIDs in 630.0‐nm images, the power spectra in summer at RIK and SGK are stronger than those in other seasons regardless of solar activity. The power spectra in solar quiet time are stronger than those in solar active time at all four stations. These features can be explained by the Perkins instability with coupling between sporadic E and F layers. The spectral slope decreases with increasing latitudes. Weak positive correlations were obtained between the daily wave power of AGWs in 557.7‐nm images and MSTIDs in 630.0‐nm images, suggesting that the MSTIDs in the thermosphere may be partially generated by the AGWs from the mesopause region.
Dependence of Dayside Electron Densities at Venus on Solar Irradiance
Authors: Hensley K. , Withers P. , Girazian Z. , Pätzold M. , Tellmann S. , Häusler B.
Published: February 2020

The ionosphere of Venus is a weakly ionized plasma layer embedded in the planet's upper atmosphere. Planetary ionospheres provide an excellent opportunity to study how our variable Sun affects the planets in our solar system. Because ionospheres are reservoirs from which atmospheric species can be lost to space, studying how ionospheres respond to changes in solar activity can help us understand how planetary atmospheres have evolved since their formation. While variations of the main and lower ionospheric peaks of Venus have been well studied, the behavior of the ionosphere above the altitude of the greatest electron density has not been fully constrained. To investigate the behavior of this region, we use electron density profiles obtained by the Venus Radio Science experiment aboard Venus Express. An increase in the response of the electron density to increasing solar irradiance with increasing altitude above the peak is readily apparent in these data. By using a one‐dimensional photochemical equilibrium model to investigate the factors that drive the variations of the ionosphere of Venus, we find that changes in the composition of the underlying neutral atmosphere are responsible for the observed increase in ionospheric response with altitude.
ULF Waves Generated Near the Plasmapause by the Magnetosphere‐Ionosphere Interactions
Authors: Streltsov Anatoly V. , Mishin Evgeny V.
Published: February 2020

Ultralow frequency (ULF) electromagnetic waves are regularly detected by satellites near the plasmapause during substorms. Usually, the small‐scale waves are observed embedded in the large‐scale, quasi‐stationary electric field. We suggest that the small‐scale waves are generated in the ionosphere by the interactions between the large‐scale field and irregularities in the ionospheric density/conductivity. Under certain conditions, these waves can be trapped in the global magnetospheric resonator and amplified by the positive feedback interactions with the ionosphere. To verify this hypothesis, we model with a two‐fluid magnetohydrodynamics code structure and amplitude of the ULF waves simultaneously observed near the plasmapause by the Defense Meteorological Satellite Program satellite at low altitudes and the Combined Release and Radiation Effects satellite at high altitudes. Simulations reproduce in good, quantitative detail the structure and amplitude of the observed waves. In particular, simulations reproduce a “spiky” character of the electric field observed by the Defense Meteorological Satellite Program satellite at low altitude, which is a characteristic feature of ULF waves produced by the ionospheric feedback instability.
Fast and Slow Water Ion Populations in the Enceladus Plume
Authors: Haythornthwaite R. P. , Coates A. J. , Jones G. H. , Waite J. H.
Published: February 2020

Ion velocities have been measured during the Enceladus E3 and E5 flybys using the Cassini Plasma Spectrometer (CAPS) instrument on the Cassini spacecraft. Data from three sensors in the CAPS instrument have been examined from two flybys that occurred during 2008. Positive ion measurements from the CAPS Ion Beam Spectrometer and Ion Mass Spectrometer have been used to measure positive ion velocities. The CAPS Electron Spectrometer has been used to complement the positive ion findings with measurements of negative ion velocities. Two velocities for the positive ions are found, with the fast ions (2.3–5.8 km/s) originating from the high‐speed neutral gas emission and slow ions (0.2–2.2 km/s) associated with the low‐speed thermal gas emission from Enceladus. Negative ions were found to be near stationary or northerly traveling, implying a deceleration mechanism within the plume. A tentative detection of fast negative ions was also recorded for one of the flybys. These findings will aid in future modeling of plume dynamics.
Suprathermal Fe in the Earth's Plasma Environment: Cluster RAPID Observations
Authors: Haaland S. , Daly P. W. , Vilenius E. , Krcelic P. , Dandouras I.
Published: February 2020

Baryonic matter in geospace is almost exclusively in a plasma state, with protons (H
) and to some extent ionized helium (He) and oxygen (O) being the dominant ion species. But also other heavier ion species and even molecular ions are present in geospace. The Research with Adaptive Particle Imaging Detectors (RAPID) on board the Cluster satellites can identify and characterize some of these ions by utilizing their measured time of flight and energy. Usually, the measurements are then assigned into three discrete species channels; protons (H
), helium (He), and a common channel for carbon, nitrogen, and oxygen (CNO), each with flux, energy, and angular information. But RAPID also has a Direct Event (DE) diagnostic mode in which the full time of flight and energy information for a limited number of incident particles are stored. With knowledge about energy losses in the various detector parts, it is then possible to derive the atomic mass of the incident particle. In this paper we report on results from a study of Cluster DE events during the years 2001–2018, with a particular emphasis of iron (Fe) ions. We show that suprathermal Fe ions can be found all over geospace covered by Cluster, and that the time variation is consistent with modulation by geomagnetic disturbances and solar activity. We do not find any clear correlations between detection of suprathermal Fe and meteor showers or sputtering off the moon.
Interhemispheric Asymmetry of Large‐Scale Electron Density Gradients in the Polar Cap Ionosphere: UT and Seasonal Variations
Authors: Jin Yaqi , Xiong Chao
Published: February 2020

The high‐latitude ionosphere is highly dynamical with significant irregularities and density gradients. However, the spatial and temporal distributions of density gradients and irregularities are very different between the Arctic and Antarctic. In this report, we study the interhemispheric asymmetry of the large‐scale (100 km) density gradients in both polar caps. Our results show that density gradients in the Arctic are enhanced during local winter (December solstice) with a peak around 19 UT. The UT and spatial distributions in the Antarctic local winter (June solstice) are similar to the Arctic except that they are reversed by 12 hr, which indicates a mirror symmetry between hemispheres. The 12‐hr difference in the peak density gradients can be explained by the displacements between the geographic and geomagnetic poles. The only asymmetry (anomaly) is the persistence of strong density gradients in the southern polar cap during local summer (December solstice).
The Climatological Horizontal Pattern of Energy Flux in the Tropical Atlantic as Identified by a Unified Diagnosis for Rossby and Kelvin Waves
Authors: Song Qingyang , Aiki Hidenori
Published: February 2020

This study investigates the horizontal distribution of wave energy flux in the tropical Atlantic Ocean using shallow‐water model experiments for three gravest baroclinic modes forced by climatological winds. This is the first attempt to apply a unified diagnostic scheme to the analysis of energy fluxes associated with both Rossby waves (RWs) and Kelvin waves (KWs) in the tropical Atlantic Ocean. Those analyses were difficult in previous studies owing to the difference of equatorial and quasigeostrophic dynamics. The scheme yields the transfer route (i.e., trajectories by group velocity vector) of wave energy originating from both local wind forcing and boundary reflection. The meridional flux of wave energy crossing two zonal sections (at 3°N and at 2°S) is examined for understanding where the equatorial and off‐equatorial regions interconnect. Equatorward energy fluxes into the basin interior are found mainly on the zonal section in the Northern Hemisphere (at 3°N), indicating the radiation of RWs from the Guinea coast. At the equator, seasonal transition in May from eastward wind anomaly to westward anomaly yields a significant energy input at the central basin that radiates both RWs and KWs. The energy flux of these RWs arrives at the western boundary in September, followed by reflection of KWs to yield eastward transbasin energy fluxes in October‐December. The analysis also identifies an unexpected wind input in May at 4°S which induces both RWs and inertial gravity waves.
Intense and Small Freshwater Pools From Rainfall Investigated During Spurs‐2 on 9 November 2017 in the Eastern Tropical Pacific
Authors: Reverdin G. , Supply A. , Drushka K. , Thompson E. J. , Asher W. E. , Lourenço A.
Published: February 2020

During the second Salinity Processes in the Upper Ocean Regional Study (SPURS‐2) 2017 tropical Pacific cruise, two drifters were deployed on 9 November. The drifters measured temperature and salinity in the top 36 cm, wave spectra, and the noise of rain drops. During a short nearly circular survey with a 1.8‐km radius around the drifters, the R/V Revelle measured air‐sea fluxes, as well as temperature and salinity stratification in the top 1 m from a towed surface salinity profiler (SSP). A C‐band weather radar measuring rain rate within 1‐ to 100‐km range of the ship observed discrete rain cells organized in a system moving from the southeast to the northwest. Some of the intense rain cells were small scale (1 km in diameter or less) with short lifetimes yet dropped more than 5 cm of water in half an hour near the drifters, whereas the ship measured short rain episodes totaling 1.3 cm of rainfall mostly accompanied by very low wind. The data indicate a large spatial heterogeneity in temperature and salinity, with near‐surface freshening of up to 9 psu measured at different times by the two drifters (separated by less than 500 m) and by the SSP. The drifters indicate deepening of the fresh and cool surface layer during the rain which then thinned during the following 40 min with very low wind speed (<2 m/s). Patchy surface‐trapped cold and fresh layers were also observed by the SSP east of the drifters. The high spatial and temporal variability of rainfall and surface‐trapped fresh pools is discussed.
Changes to the Appearance of Optical Lightning Flashes Observed From Space According to Thunderstorm Organization and Structure
Authors: Peterson Michael , Rudlosky Scott , Zhang Daile
Published: February 2020

Optical lightning observations from space reveal a wide range of flash structure. Lightning imagers such as the Geostationary Lightning Mapper and Lightning Imaging Sensor measure flash appearance by recording transient changes in cloud top illumination. The spatial and temporal optical energy distributions reported by these instruments depend on the physical structure of the flash and the distribution of hydrometeors within the thundercloud that scatter and absorb the optical emissions. This study explores how flash appearance changes according to the scale and organization of the parent thunderstorms with a focus on mesoscale convective systems. Clouds near the storm edge are frequently illuminated by large optical flashes that remain stationary between groups. These flashes appear large because their emissions can reflect off the exposed surfaces of nearby clouds to reach the satellite. Large stationary flashes also occur in small isolated thunderstorms. Optical flashes that propagate horizontally, meanwhile, are most frequently observed in electrified stratiform regions where extensive layered charge structures promote lateral development. Highly radiant “superbolts” occur in two scenarios: embedded within raining stratiform regions or in nonraining boundary/anvil clouds where optical emissions can take a relatively clear path to the satellite.
Connections Between Stratospheric Ozone Concentrations Over the Arctic and Sea Surface Temperatures in the North Pacific
Authors: Liu Meichen , Hu Dingzhu , Zhang Feng
Published: February 2020

We examined the relationship between sea surface temperatures (SSTs) in the North Pacific and the concentration of stratospheric ozone in the northern hemisphere in February–March from 1980 to 2017 using reanalysis and satellite datasets. Our results show that the concentration of stratospheric ozone can be modulated by the principle mode of the North Pacific SSTs—that is, there are negative and zonally asymmetrical ozone anomalies in the Arctic stratosphere, but positive ozone anomalies in the lower stratosphere at mid‐latitudes during the positive phases of the North Pacific SSTs. The North Pacific SST anomalies account for about 20% of the linear variance of ozone concentrations in the lower stratosphere over the Arctic. Negative SST anomalies in the central North Pacific tend to result in a strengthened Western‐Pacific like teleconnection, which favors the propagation of more planetary wavenumber‐1 and ‐2 waves into the stratosphere. The North Pacific SSTs‐related upwelling branch of the Brewer–Dobson circulation in the mid‐latitude stratosphere strengthens, but its downwelling branch in the Arctic stratosphere weakens. This results in decreased ozone anomalies in the lower stratosphere over the Arctic and increased ozone anomalies in the lower stratosphere at mid‐latitudes. The zonally asymmetrical distribution of ozone related to the positive phase of SSTs over the North Pacific may be related to the shifting and strengthening of the stratospheric Arctic vortex.
Toward a Data Assimilation System for Seamless Sea Ice Prediction Based on the AWI Climate Model
Authors: Mu Longjiang , Nerger Lars , Tang Qi , Loza Svetlana N. , Sidorenko Dmitry , Wang Qiang , Semmler Tido , Zampieri Lorenzo , Losch Martin , Goessling Helge F.
Published: February 2020

This paper describes and evaluates the assimilation component of a seamless sea ice prediction system, which is developed based on the fully coupled Alfred Wegener Institute, Helmholtz Center for Polar and Marine Research Climate Model (AWI‐CM, v1.1). Its ocean/ice component with unstructured‐mesh discretization and smoothly varying spatial resolution enables seamless sea ice prediction across a wide range of space and time scales. The model is complemented with the Parallel Data Assimilation Framework to assimilate observations in the ocean/ice component with an Ensemble Kalman Filter. The focus here is on the data assimilation of the prediction system. First, the performance of the system is tested in a perfect‐model setting with synthetic observations. The system exhibits no drift for multivariate assimilation, which is a prerequisite for the robustness of the system. Second, real observational data for sea ice concentration, thickness, drift, and sea surface temperature are assimilated. The analysis results are evaluated against independent in situ observations and reanalysis data. Further experiments that assimilate different combinations of variables are conducted to understand their individual impacts on the model state. In particular, assimilating sea ice drift improves the sea ice thickness estimate, and assimilating sea surface temperature is able to avert a circulation bias of the free‐running model in the Arctic Ocean at middepth. Finally, we present preliminary results obtained with an extended system where the atmosphere is constrained by nudging toward reanalysis data, revealing challenges that still need to be overcome to adapt the ocean/ice assimilation. We consider this system a prototype on the way toward strongly coupled data assimilation across all model components.
Secretin release after Roux-en-Y gastric bypass reveals a population of glucose-sensitive S cells in distal small intestine
Authors: Modvig Ida M. , Andersen Daniel B. , Grunddal Kaare V. , Kuhre Rune E. , Martinussen Christoffer , Christiansen Charlotte B. , Ørskov Cathrine , Larraufie Pierre , Kay Richard G. , Reimann Frank , Gribble Fiona M. , Hartmann Bolette , Bojsen-Møller Kirstine N. , Madsbad Sten , Wewer Albrechtsen Nicolai J. , Holst Jens J.
Published: February 2020

Objectives

Gastrointestinal hormones contribute to the beneficial effects of Roux-en-Y gastric bypass surgery (RYGB) on glycemic control. Secretin is secreted from duodenal S cells in response to low luminal pH, but it is unknown whether its secretion is altered after RYGB and if secretin contributes to the postoperative improvement in glycemic control. We hypothesized that secretin secretion increases after RYGB as a result of the diversion of nutrients to more distal parts of the small intestine, and thereby affects islet hormone release.

Methods

A specific secretin radioimmunoassay was developed, evaluated biochemically, and used to quantify plasma concentrations of secretin in 13 obese individuals before, 1 week after, and 3 months after RYGB. Distribution of secretin and its receptor was assessed by RNA sequencing, mass-spectrometry and in situ hybridization in human and rat tissues. Isolated, perfused rat intestine and pancreas were used to explore the molecular mechanism underlying glucose-induced secretin secretion and to study direct effects of secretin on glucagon, insulin, and somatostatin secretion. Secretin was administered alone or in combination with GLP-1 to non-sedated rats to evaluate effects on glucose regulation.

Results

Plasma postprandial secretin was more than doubled in humans after RYGB (P < 0.001). The distal small intestine harbored secretin expressing cells in both rats and humans. Glucose increased the secretion of secretin in a sodium-glucose cotransporter dependent manner when administered to the distal part but not into the proximal part of the rat small intestine. Secretin stimulated somatostatin secretion (fold change: 1.59,P < 0.05) from the perfused rat pancreas but affected neither insulin (P = 0.2) nor glucagon (P = 0.97) secretion. When administered to rats in vivo, insulin secretion was attenuated and glucagon secretion increased (P = 0.04), while blood glucose peak time was delayed (from 15 to 45 min) and gastric emptying time prolonged (P = 0.004).

Conclusions

Glucose-sensing secretin cells located in the distal part of the small intestine may contribute to increased plasma concentrations observed after RYGB. The metabolic role of the distal S cells warrants further studies.