bluuebunny/crossref_metadata_2025 huggingface dataset:
Seasonal movements and metapopulation structure of the Australian fairy tern in Western Australia
Authors: Dunlop James N. , Greenwell Claire N.
Published: July 2020

The Australian fairy tern metapopulation in Western Australian is distributed over an extensive stretch of coastline (≤2500km). Using mark–recapture and coordinated community-based resightings of marked birds, this study reveals important insights into the seasonal movement, interchange and key locations used by Australian fairy terns. The Western Australian metapopulation consists of a widely distributed, partially migratory spring/summer-breeding population and a smaller, winter-breeding, sedentary population on the Pilbara coast. The spring/summer-breeding population winters, primarily, around the northern islands of the Houtman Abrolhos, before migrating to breeding areas as far south as Point Malcolm on the eastern south coast and as far north as the Ningaloo coast (Exmouth). Thus, in Western Australia, Australian fairy terns from the same population reproduce in both tropical and temperate marine regions. Associations between birds, persisting over multiple seasons, suggest that group adherence may be an important behavioural trait of these small terns. Based on the recent use of breeding sites and the likely spatial extent of exchange of breeding adults and natal recruits, seven ‘neighbourhoods’ are proposed, which likely represent the best units to underpin a conservation strategy for this threatened coastal seabird. The combination of small population size, strong area fidelity and the potential for strong group adherence among individuals are important considerations for the development of effective conservation strategies in Western Australia. Maintaining the Australian fairy tern population size within the suggested management units is critical for the long-term conservation of this species.
Distribution and size of lipid droplets in oocytes recovered from young lamb and adult ovine ovaries
Authors: Abazarikia Amirhossein , Ariu Federica , Rasekhi Mahsa , Zhandi Mahdi , Ledda Sergio
Published: July 2020

This study evaluated the distribution and size of lipid droplets (LDs) in oocytes recovered from young and adult ovine ovaries. Collected oocytes were categorised on the basis of their major diameter (small (SO), 70–90 µm; medium (MO), >90–110 µm; large (LO), >110–130µm) and were stained with Nile red to detect LDs. In adult and young oocytes, a diffuse pattern distribution of LDs was dominant in all classes except adult LO and young SO and LO. Larger LDs (i.e. >3µm) were mostly present in young SO and LO, whereas smaller LDs (1–3µm) were detected in the other adult and young oocyte categories.
Bacteria-derived metabolite, methylglyoxal, modulates the longevity of
C. elegans
through TORC2/SGK-1/DAF-16 signaling
Authors: Shin Min-Gi , Lee Jae-Woong , Han Jun-Seok , Lee Bora , Jeong Jin-Hyuck , Park So-Hyun , Kim Jong-Hwan , Jang Sumi , Park Mooncheol , Kim Seon-Young , Kim Seokho , Yang Yong Ryoul , Kim Jeong-Yoon , Hoe Kwang-Lae , Park Chankyu , Lee Kwang-Pyo , Kwon Ki-Sun , Kwon Eun-Soo
Published: July 2020

Significance

The molecular mechanisms by which gut microbes modulate host longevity remain elusive. Using genome-wide lifespan screens and extensive interspecies genetic analysis, we identified that the gut microbe-derived metabolite methylglyoxal (MG) modulated host longevity. MG is a reactive carbonyl species involved in the formation of advanced glycation end products, which are implicated in various human pathologies. We identified that
Escherichia coli
producing reduced levels of MG increased the lifespan of
Caenorhabditis elegans
due to inhibition of TORC2/SGK-1 and activation of DAF-16. These findings challenge the current paradigm that MG is toxic due to the formation of glycation adducts on biomolecules. Instead, our results highlight the importance of gut microbe-derived MG in regulating the host TORC2/SGK-1/DAF-16 signaling pathway in the interspecies context.
A tiny ornithodiran archosaur from the Triassic of Madagascar and the role of miniaturization in dinosaur and pterosaur ancestry
Authors: Kammerer Christian F. , Nesbitt Sterling J. , Flynn John J. , Ranivoharimanana Lovasoa , Wyss André R.
Published: July 2020

Significance

Reptiles of the Mesozoic Era are known for their remarkable size: dinosaurs include the largest known land animals, and their relatives, the pterosaurs, include the largest creatures to ever fly. The origins of these groups are poorly understood, however. Here, we present a species (
Kongonaphon kely
) from the Triassic of Madagascar close to the ancestry of dinosaurs and pterosaurs, providing insight into the early evolution of those groups.
Kongonaphon
is a surprisingly small animal (estimated height, ∼10 cm). Analysis of ancestral body size indicates that there was a pronounced miniaturization event near the common ancestor of dinosaurs and pterosaurs. Tiny ancestral body size may help explain the origins of flight in pterosaurs and fuzzy integument in both groups.
Self-emitted surface corrugations in dynamic fracture of silicon single crystal
Authors: Wang Meng , Fourmeau Marion , Zhao Lv , Legrand Franck , Nélias Daniel
Published: July 2020

Significance

When a moving crack front meets local material asperities, a persistent nonlinear propagating mode of the crack front can be triggered, which results in nontrivial fracture surface patterns. Unexpectedly, we report the continuous emergence of corrugation waves during high-speed crack propagation in asperity-free silicon single crystal. We reveal that these waves are driven by fracture energy fluctuation at critical crack speed. The corrugation waves are highly localized along the crack front. They twist the crack front and create fracture surface corrugations. Through meticulous quantitative characterization of the fracture surface markings, we evidence the nonlinear properties of these corrugation waves.
Flat latitudinal diversity gradient caused by the Permian–Triassic mass extinction
Authors: Song Haijun , Huang Shan , Jia Enhao , Dai Xu , Wignall Paul B. , Dunhill Alexander M.
Published: July 2020

Significance

The deep-time dynamics of the latitudinal diversity gradient (LDG), especially through dramatic events like mass extinctions, can provide invaluable insights into the biotic responses to global changes, yet they remain largely underexplored. Our study shows that the shape of marine LDGs changed substantially and rapidly during the Permian–Triassic mass extinction from a modern-like steep LDG to a flat LDG. The flat LDG lasted for ∼5 My and was likely a consequence of the extreme global environment, including extreme warming and ocean anoxia, which ensured harsh conditions prevailing from the tropics to the poles. Our findings highlight the fundamental role of environmental variations in concert with severe biodiversity loss in shaping the first-order biogeographic patterns.
Original antigenic sin priming of influenza virus hemagglutinin stalk antibodies
Authors: Arevalo Claudia P. , Le Sage Valerie , Bolton Marcus J. , Eilola Theresa , Jones Jennifer E. , Kormuth Karen A. , Nturibi Eric , Balmaseda Angel , Gordon Aubree , Lakdawala Seema S. , Hensley Scott E.
Published: July 2020

Significance

Humans are typically infected with influenza viruses in childhood and then continuously exposed to antigenically distinct influenza virus strains throughout life. Antibody responses elicited by initial influenza virus infections can be boosted upon subsequent exposures with antigenically drifted influenza virus strains. Here, we examined how initial influenza virus infections affect antibody responses against subsequent infections with an unrelated influenza virus subtype. We show that heterosubtypic infections in ferrets and humans boost hemagglutinin stalk antibodies that paradoxically do not bind effectively to the boosting influenza virus strain. We propose that hemagglutinin stalk antibody repertoires are shaped by the specific subtype of influenza virus that an individual encounters early in life, and that this affects susceptibility to heterosubtypic infections later in life.
Upper Midwest lakes are supersaturated with N
2
Authors: Loeks Brianna M. , Cotner James B.
Published: July 2020

Significance

Excess nitrogen (N) in freshwaters is problematic due to its impacts on eutrophication, biodiversity losses, and harmful algal blooms. Some microbial processes such as denitrification and anammox can remove N from systems while others such as N-fixation can add a usable form of N. However, not enough is known about when and where these competing processes are occurring in lakes, and understanding this can provide insight to management. Here, we determined that nearly all of the 34 lakes that we examined in the upper Midwest had a net loss of N
2
that must be compensated by watershed inputs to maintain steady state. These results suggest that N-fixation in these lakes was not enough to offset denitrification and anammox.
Genomic regions influencing aggressive behavior in honey bees are defined by colony allele frequencies
Authors: Avalos Arián , Fang Miaoquan , Pan Hailin , Ramirez Lluch Aixa , Lipka Alexander E. , Zhao Sihai Dave , Giray Tugrul , Robinson Gene E. , Zhang Guojie , Hudson Matthew E.
Published: July 2020

Significance

Honey bee colony defense is an emergent trait composed of individual aggressive responses. Here, we investigated the relationship between individual genotype, colony allele frequency, and aggression in individual bees. Our findings show that the colony-level defense response strongly correlates with colony-level allele frequency in a way that can be used to identify causative genomic regions. Importantly, we were able to validate a key associated region as also being under selection. As very similar allele frequency correlations are observed in both soldier and forager bees, we conclude that group genetics is more important than individual genetics in this case, giving further insight into the relationships between “nature,” “nurture,” and behavioral evolution.
Template-stabilized oxidic nickel oxygen evolution catalysts
Authors: Li Nancy , Keane Thomas P. , Veroneau Samuel S. , Hadt Ryan G. , Hayes Dugan , Chen Lin X. , Nocera Daniel G.
Published: July 2020

Significance

Metal-oxide catalysts that do not rely on the critical metals corrode immediately in nonbasic solutions. The development of self-healing offers a design principle to avert corrosion for typical metal oxides in neutral and near-neutral solutions. However, the stabilization of metal-oxide oxygen evolution catalysts (OECs) in acid remains to be a challenge that requires new design principles and strategies. We show here that high activity from OECs may be achieved in acid by embedding catalytic metal-oxide active sites within an acid-stable oxide framework. Specifically, we show that oxidic Ni OECs may be stabilized for extended periods of OER by embedding Ni in the acid-stable oxide framework of PbO
2
polymorphs.
Noninvasive acoustic manipulation of objects in a living body
Authors: Ghanem Mohamed A. , Maxwell Adam D. , Wang Yak-Nam , Cunitz Bryan W. , Khokhlova Vera A. , Sapozhnikov Oleg A. , Bailey Michael R.
Published: July 2020

Significance

The significance of this work is the development of a technique and technology to use a steerable beam from one source to safely lift and reposition a stone in a living body. The work has direct application to expelling kidney stones or manipulating an ingestible camera. Our work provides a framework for other medical applications, as well as nonmedical uses that require noninvasively moving sizable, dense objects in a free field or within a container.
Active photonic wireless power transfer into live tissues
Authors: Kim Juho , Seo Jimin , Jung Dongwuk , Lee Taeyeon , Ju Hunpyo , Han Junkyu , Kim Namyun , Jeong Jinmo , Cho Sungbum , Seol Jae Hun , Lee Jongho
Published: July 2020

Significance

One of the highest demands in biomedical electronic implants is to provide a sustainable electrical power for extended healthy life without battery replacement surgeries. The reported technology enables providing sustainable power wirelessly through live tissues as demonstrated by a key biomedical function, i.e., electrical stimulation, of implantable medical electronics at the level of a full system. The approach capable of providing enough power (74.1 μW/cm
2
, active photovoltaic area: 11.1 mm
2
) indoor or outdoor during day and night should lead to developments of numerous medical electronic implants with advanced and diverse functions that are currently limited by a limited electrical power in live bodies.
Children drinking private well water have higher blood lead than those with city water
Authors: Gibson Jacqueline MacDonald , Fisher Michael , Clonch Allison , MacDonald John M. , Cook Philip J.
Published: July 2020

Significance

In the United States, 13% of households depend on an unregulated private well for their water. Compared with children in houses served by a regulated water utility, children in these homes have a 25% increased risk of elevated blood lead. Because lead is a neurotoxin, these children are at greater risk of experiencing irreversible cognitive damage, which can decrease their performance in school and increase their risks of behavioral problems. This study assesses associations between children’s blood lead and dependence on an unregulated private well for drinking water. It highlights the need for interventions to control lead corrosion from plumbing and well components (such as drop pipes, pump parts, and valves and fittings) in households depending on private wells.
A negative reciprocal regulatory axis between cyclin D1 and HNF4α modulates cell cycle progression and metabolism in the liver
Authors: Wu Heng , Reizel Yitzhak , Wang Yue J. , Lapiro Jessica L. , Kren Betsy T. , Schug Jonathan , Rao Shilpa , Morgan Ashleigh , Herman Adam , Shekels Laurie L. , Rassette Matthew S. , Lane Andrew N. , Cassel Teresa , Fan Teresa W. M. , Manivel Juan C. , Gunewardena Sumedha , Apte Udayan , Sicinski Piotr , Kaestner Klaus H. , Albrecht Jeffrey H.
Published: July 2020

Hepatocyte nuclear factor 4α (HNF4α) is a master regulator of liver function and a tumor suppressor in hepatocellular carcinoma (HCC). In this study, we explore the reciprocal negative regulation of HNF4α and cyclin D1, a key cell cycle protein in the liver. Transcriptomic analysis of cultured hepatocyte and HCC cells found that cyclin D1 knockdown induced the expression of a large network of HNF4α-regulated genes. Chromatin immunoprecipitation-sequencing (ChIP-seq) demonstrated that cyclin D1 inhibits the binding of HNF4α to thousands of targets in the liver, thereby diminishing the expression of associated genes that regulate diverse metabolic activities. Conversely, acute HNF4α deletion in the liver induces cyclin D1 and hepatocyte cell cycle progression; concurrent cyclin D1 ablation blocked this proliferation, suggesting that HNF4α maintains proliferative quiescence in the liver, at least, in part, via repression of cyclin D1. Acute cyclin D1 deletion in the regenerating liver markedly inhibited hepatocyte proliferation after partial hepatectomy, confirming its pivotal role in cell cycle progression in this in vivo model, and enhanced the expression of HNF4α target proteins. Hepatocyte cyclin D1 gene ablation caused markedly increased postprandial liver glycogen levels (in a HNF4α-dependent fashion), indicating that the cyclin D1-HNF4α axis regulates glucose metabolism in response to feeding. In AML12 hepatocytes, cyclin D1 depletion led to increased glucose uptake, which was negated if HNF4α was depleted simultaneously, and markedly elevated glycogen synthesis. To summarize, mutual repression by cyclin D1 and HNF4α coordinately controls the cell cycle machinery and metabolism in the liver.
Calibrating the coevolution of Ediacaran life and environment
Authors: Rooney Alan D. , Cantine Marjorie D. , Bergmann Kristin D. , Gómez-Pérez Irene , Al Baloushi Badar , Boag Thomas H. , Busch James F. , Sperling Erik A. , Strauss Justin V.
Published: July 2020

Significance

Our understanding of the interactions between animal evolution, biogeochemical cycling, and global tectonics during the Ediacaran Period (635 to 541 Ma) is severely hampered by lack of a robust temporal framework. The appearance and extinction of the earliest fossil animals are hypothesized to correlate with upheavals in biogeochemical cycles—foremost the Shuram carbon isotope excursion, possibly the largest known disturbance to the global carbon cycle. However, without age constraints on the excursion’s timing and duration, its driving mechanisms, global synchroneity, and role in Ediacaran geobiological evolution cannot be evaluated. We provide radioisotopic ages for the onset and termination of the Shuram, evaluate its global synchroneity, and show that it is divorced from the rise of the earliest preserved animal ecosystems.
Evolution of abiotic cubane chemistries in a nucleic acid aptamer allows selective recognition of a malaria biomarker
Authors: Cheung Yee-Wai , Röthlisberger Pascal , Mechaly Ariel E. , Weber Patrick , Levi-Acobas Fabienne , Lo Young , Wong Alvin W. C. , Kinghorn Andrew B. , Haouz Ahmed , Savage G. Paul , Hollenstein Marcel , Tanner Julian A.
Published: July 2020

Significance

We report the identification of a cubane-modified aptamer (cubamer) against the malaria biomarker
Plasmodium vivax
lactate dehydrogenase (PvLDH). The cubamer contains the benzene isostere cubane, which is entirely alien to biology. The crystal structure of the cubamer–protein complex reveals a binding mechanism involving the formation of an unprecedented cubane pocket and an unusual C–H⋅⋅⋅O hydrogen bond. Importantly, the cubamer is capable of distinguishing the PvLDH from the
Plasmodium falciparum
LDH despite a very high sequence homology, which is impossible for unmodified aptamers. Finally, we have used the cubamer to detect PvLDH in a mimetic clinical situation. This approach blending medicinal chemistry and Darwinian evolution can easily be extended to other nonnatural, exotic functional groups.
The emergent interactions that govern biodiversity change
Authors: Clark James S. , Scher C. Lane , Swift Margaret
Published: July 2020

Significance

Predicting how ecological communities respond to change requires an understanding of the direct effects of environment and the indirect effects that emerge when environment is propagated through food webs of interacting species. A probabilistic, dynamic framework for inference identifies these environment–species interactions. Results show how environmental effects translate into nonlinear responses, how they can be estimated from data, and the insight they provide on the relative importance of direct and indirect (through other species) responses to change. Because these effects include uncertainty from the model and data, they can guide management that has to weigh the utility of efforts to protect critical habitat (or not) against the risk for species that respond through the responses of others.
Characterizing soundscapes across diverse ecosystems using a universal acoustic feature set
Authors: Sethi Sarab S. , Jones Nick S. , Fulcher Ben D. , Picinali Lorenzo , Clink Dena Jane , Klinck Holger , Orme C. David L. , Wrege Peter H. , Ewers Robert M.
Published: July 2020

Significance

Human pressures are causing natural ecosystems to change at an unprecedented rate. Understanding these changes is important (e.g., to inform policy decisions), but we are hampered by the slow, labor-intensive nature of traditional ecological surveys. In this study, we show that automated analysis of the sounds of an ecosystem—its soundscape—enables rapid and scalable ecological monitoring. We used a neural network to calculate fingerprints of soundscapes from a variety of ecosystems. From these acoustic fingerprints we could accurately predict habitat quality and biodiversity across multiple scales and automatically identify anomalous sounds such as gunshots and chainsaws. Crucially, our approach generalized well across ecosystems, offering promise as a backbone technology for global monitoring efforts.
Functionally distinct Purkinje cell types show temporal precision in encoding locomotion
Authors: Chang Weipang , Pedroni Andrea , Hohendorf Victoria , Giacomello Stefania , Hibi Masahiko , Köster Reinhard W. , Ampatzis Konstantinos
Published: July 2020

Significance

Purkinje cells, the key cells for cerebellar computations, are thought to function similarly throughout the cerebellum and to comprise a uniform neuronal population. Here, we challenge this notion by providing detailed evidence that the Purkinje cells are organized into distinct types, each exhibiting specific activity patterns that are associated with a particular phase of the zebrafish swim cycle during locomotion. Connectivity experiments suggest that all the identified Purkinje cell types participate in orchestrating the cerebellar circuit ensembles, which are, therefore, highly heterogeneous.
The environmental stress response causes ribosome loss in aneuploid yeast cells
Authors: Terhorst Allegra , Sandikci Arzu , Keller Abigail , Whittaker Charles A. , Dunham Maitreya J. , Amon Angelika
Published: July 2020

Significance

Aneuploid cells experience significant cellular stress; however, the transcriptional consequences of aneuploidy remain highly debated. In aneuploid budding yeast, two opposing gene-expression patterns have been reported: the “environmental stress response” (ESR) and the “common aneuploidy gene-expression” (CAGE) signature, in which many ESR genes are oppositely regulated. Here we resolve this controversy. We show that the ESR represents a common response to aneuploidy and explain why the CAGE signature does not. Our data further suggest that activation of the ESR has profound consequences on the cellular physiology of aneuploid cells, leading to ribosome loss. Thus, our work provides critical insights into the coordination between cell division and macromolecule biosynthesis and a potential explanation for why aneuploid cells are less dense.
Antiresorptive activity of osteoprotegerin requires an intact heparan sulfate-binding site
Authors: Li Miaomiao , Xu Ding
Published: July 2020

Significance

Osteoprotegerin (OPG) plays an essential role in bone remodeling by inhibiting receptor activator of nuclear factor B ligand (RANKL), which drives osteoclastogenesis. While much is known about OPG–RANKL interaction, the exact biological function of the C-terminal domains of OPG remains a mystery. One likely function of the C-terminal domains of OPG is to interact with heparan sulfate (HS), a glycosaminoglycan that is abundantly expressed by osteoblast lineage cells. However, the physiological importance of OPG–HS interactions in bone remodeling remains uncertain. Here, by using two strains of transgenic mice, both of which have altered OPG–HS interactions, we have definitively shown that binding to osteoblast HS is indispensable for the antiresorptive function of OPG in bone remodeling.
Calpain inhibitor and ibudilast rescue β cell functions in a cellular model of Wolfram syndrome
Authors: Nguyen Lien D. , Fischer Tom T. , Abreu Damien , Arroyo Alfredo , Urano Fumihiko , Ehrlich Barbara E.
Published: July 2020

Significance

Wolfram syndrome is a rare multisystem disease characterized by diabetes insipidus, diabetes mellitus, optic nerve atrophy, and deafness (DIDMOAD). It is primarily caused by mutations in the Wolfram syndrome 1 gene,
WFS1
. As a monogenetic disorder, Wolfram syndrome is a model for diabetes and neurodegeneration. There is no effective treatment for this invariably fatal disease. Here we characterize WFS1 as a regulator of calcium homeostasis and subsequently target calcium signaling to reverse deficits in a cellular model of Wolfram syndrome.
Assessment of energy availability and associated risk factors in professional female soccer players
Authors: Moss Samantha L. , Randell Rebecca K. , Burgess Darren , Ridley Stephanie , ÓCairealláin Cairbre , Allison Richard , Rollo Ian
Published: July 2020

This study aimed to assess energy availability (EA), alongside possible risk factors of reduced or low EA of professional female soccer players during a competitive season. Thirteen players (age: 23.7 ± 3.4 y, stature: 1.69 ± 0.08 m, body mass: 63.7 ± 7.0 kg) engaged in a 5‐day (two rest days, one light training, heavy training and match day) monitoring period. Energy intake (EI) and expenditure during exercise (EEE) were measured. EA was calculated and categorised as optimal, reduced or low (>45, 30‐45, <30 kcal·kg FFM−1·day−1, respectively). Relationships between EA and bone mineral density, resting metabolic rate (RMR), plasma micronutrient status, biochemical markers and survey data were assessed. EA was optimal for 15%, reduced for 62% and low for 23% of players. Higher EA was observed on rest days compared to others (P<0.05). EA was higher for the light compared to the heavy training day (P<0.001). EEE differed significantly between days (P<0.05). EI (2124 ± 444 kcal), carbohydrate (3.31 ± 0.64 g·kg·day−1) and protein (1.83 ± 0.41 g·kg·day−1) intake remained similar (P>0.05). Survey data revealed 23% scored 8 on the Low Energy Availability in Females Questionnaire and met criteria for low RMR (ratio <0.90). Relationships between EA and risk factors were inconclusive. Most players displayed reduced EA and did not alter EI or carbohydrate intake according to training or match demands. Although cases of low EA were identified, further work is needed to investigate possible long‐term effects and risk factors of low and reduced EA separately to inform player recommendations.
Rational design of a mutation to investigate the role of the brain protein TRIP8b in limiting the cAMP response of HCN channels in neurons
Authors: Porro Alessandro , Binda Anna , Pisoni Matteo , Donadoni Chiara , Rivolta Ilaria , Saponaro Andrea
Published: July 2020

TRIP8b (tetratricopeptide repeat–containing Rab8b-interacting protein) is the neuronal regulatory subunit of HCN channels, a family of voltage-dependent cation channels also modulated by direct cAMP binding. TRIP8b interacts with the C-terminal region of HCN channels and controls both channel trafficking and gating. The association of HCN channels with TRIP8b is required for the correct expression and subcellular targeting of the channel protein in vivo. TRIP8b controls HCN gating by interacting with the cyclic nucleotide-binding domain (CNBD) and competing for cAMP binding. Detailed structural knowledge of the complex between TRIP8b and CNBD was used as a starting point to engineer a mutant channel, whose gating is controlled by cAMP, but not by TRIP8b, while leaving TRIP8b-dependent regulation of channel trafficking unaltered. We found two-point mutations (N/A and C/D) in the loop connecting the CNBD to the C-linker (N-bundle loop) that, when combined, strongly reduce the binding of TRIP8b to CNBD, leaving cAMP affinity unaltered both in isolated CNBD and in the full-length protein. Proof-of-principle experiments performed in cultured cortical neurons confirm that the mutant channel provides a genetic tool for dissecting the two effects of TRIP8b (gating versus trafficking). This will allow the study of the functional role of the TRIP8b antagonism of cAMP binding, a thus far poorly investigated aspect of HCN physiology in neurons.
Reply to Comment on ‘A note on Purcell’s basic explanation of magnetic forces’
Authors: D’Abramo Germano
Published: July 2020

The article ‘Comment on “A note on Purcell’s basic explanation of magnetic forces”’ (2020 Eur. J. Phys.
41 068001) disputes the validity of the results presented in D’Abramo (2020 Eur. J. Phys.
41 025203). In this reply, we provide several arguments against that criticism and confirm the original conclusions.
EUV spectroscopy of Sn5+–Sn10+ ions in an electron beam ion trap and laser-produced plasmas
Authors: Bouza Z , Scheers J , Ryabtsev A , Schupp R , Behnke L , Shah C , Sheil J , Bayraktar M , López-Urrutia J R Crespo , Ubachs W , Hoekstra R , Versolato O O
Published: July 2020

Emission spectra from multiply-charged Sn5+–Sn10+ ions are recorded from an electron beam ion trap (EBIT) and from laser-produced plasma (LPP) in the extreme ultraviolet range relevant for nanolithographic applications. Features in the wavelength regime between 12.6 and 20.8 nm are studied. Using the Cowan code, emission line features of the charge-state-resolved Sn ion spectra obtained from the EBIT are identified. Emission features from tin LPP either from a liquid micro-droplet or planar solid target are subsequently identified and assigned to specific charge states using the EBIT data. For the planar solid tin target, the 4d–5p transitions of Sn8+–Sn10+ ions are shown to dominate the long-wavelength part of the measured spectrum and transitions of type 4d–4f + 4p–4d are visible in absorption. For the droplet target case, a clear increase in the charge state distribution with increasing laser intensity is observed. This qualitatively demonstrates the potential of using long-wavelength out-of-band emission features to probe the charge states contributing to the strong unresolved transition array at 13.5 nm relevant for nanolithography.
The physics of spontaneous parity-time symmetry breaking in the Kelvin–Helmholtz instability
Authors: Fu Yichen , Qin Hong
Published: July 2020

We show that the dynamical system of an inviscid fluid with velocity shear admits parity-time (PT) symmetry, which provides a physical explanation of the well-known observation that the spectrum of the perturbation eigenmodes of the system is symmetric with respect to the real axis. It is found that the Kelvin–Helmholtz instability is triggered when and only when the PT symmetry is spontaneously broken. The analysis of PT symmetry also reveals that the relative phase between parallel velocity and pressure perturbations needs to be locked at π/2 when the instability is suppressed.
Effect of electrical conduction on the electron emission properties of diamond needles
Authors: Blum Ivan , Borz Mario , Torresin Olivier , Mauchain Julien , Chalopin Benoit , Vella Angela
Published: July 2020

Single crystal diamond needles are promising structures as point electron sources. However, the low electrical conductivity of diamond limits their application as high brightness electron sources. Here we study experimentally and numerically the field emission behavior of single crystal diamond needles, in order to better explain the link between the low electrical conduction, the non-homogeneous field distribution in the needle, the evolution of the field enhancement factor and the saturation of the Fowler–Nordheim plot. Field emission current and voltage loss were measured as a function of the applied voltage. Numerical modelling was used to solve conduction, emission and Laplace equations taking into account the real geometry of the field emitter and its environment. The combination of experimental and numerical results shows that the conduction behavior and the field enhancement factor depend on the diamond geometry. Moreover, the Fowler–Nordheim plot saturation is shown to be affected by the electrostatic environment which can limit the range of voltage losses that can appear along the diamond needle and hence limit the field emission current. At the same time, the increase of the emission current at high field, which is sometimes argued to be caused by the breakdown of the field emitter, is here presented as a simple consequence of the conduction properties of the field emitter as it was already shown for silicon field emitters.
Physical processes in laser ablation into liquid and laser shock wave pinning
Authors: Anisimov S I , Inogamov N A , Khokhlov V A , Petrov Yu V , Zhakhovsky V V
Published: July 2020

The most important modern laser technologies include (i) the generation of colloid nanoparticles (NPs), laser ablation into a liquid (LAL—laser ablation in liquid) and (ii) surface hardening of products by laser pinning (LSP—laser shock peening). Significantly, with laser pinning, the surface to be treated is washed with water. Therefore, the physics of processes during ablation into a liquid and during pinning is common. True, the accents are different. If the ablation in the liquid actually forget about the shock wave (SW) generated by the impact, and leaving the thickness of the target, in the problem with pinning, on the contrary, the main question is about the impact. In addition, the role of water in LAL and LSP is different. In LAL, fluid contributes to the formation of NPs and adopts NPs, gently slowing them, whereas in LSP, water is needed to enhance the recoil and increase the amplitude of the hydrocarbon in the product. The complete picture, developed in the work, of course, should include both edges: the formation of ejection into the liquid as a result of ablation, i.e., LAL, and observation of the SW from the nucleation stage to its attenuation in the product volume, i.e., LSP.
Many-electron effects in secondary radiation generation during the interaction of atoms with intense laser pulses
Authors: Romanov A A , Silaev A A , Frolov M V , Sarantseva T S , Minina A A , Smirnova D A , Vvedenskii N V
Published: July 2020

A parallel program has been developed for numerically simulating the interaction of intense laser pulses with many-electron atoms based on non-stationary Kohn–Sham equations. With the use of this program, we calculate the nonlinear electron currents excited during ionization of argon atoms by intense two-color laser pulses. Based on the comparison with the solution of the time-dependent Schrödinger calculations for hydrogen atoms, the importance of taking into account many-electron effects in simulating the generation of secondary radiation in atomic gases under the action of ultrashort laser pulses is shown.
Study of plasma and particles flows from shock-loaded metal target with lateral lighting by argon explosive lamp
Authors: Kulish M I , Dudin S V , Ushnurtsev A E , Mintsev V B
Published: July 2020

Experimental estimates of the process of the ejection of particles and the formation of plasma during the shock wave exits on the free surface of the cooper sample studied were carried out. The radiation intensity was recorded by a three-channel pulsed pyrometer in an experimental assembly with lateral observation. When the impactor speed was about 5 km/s, a stream of particles and plasma flew from the target surface, the front speed of which reached 12.5 km/s.
Experimental study of spall strength of silicon rubber with microspheres under shock-wave action
Authors: Zubareva A N , Utkin A V , Mochalova V M , Efremov V P
Published: July 2020

In this work, porous media are studied using silicone rubber with glass microspheres as an example. There were investigated three types of silicon rubber samples featuring different concentrations and sizes of microspheres: non-porous silicon rubber, porous silicon rubber with calibrated glass microspheres and porous silicon rubber with glass microspheres having a wide range of sizes. The density of the samples was 0.99, 0.55 and 0.48 g/cm3, accordingly. Investigating spall strength under pulse tension shows that the destruction beginning threshold of the samples in question is quite low. For the non-porous sample, it is around 30 MPa, for the porous ones it is an order of magnitude lower. The spall plate does not come off the sample after the beginning of destruction. The ability of the free surface velocity to change in such a way is typical for materials with a low destruction threshold.
The study of the liquid metal drops fragmentation
Authors: Teplyakov I O , Ivochkin Yu P , Kubrikov K G
Published: July 2020

The main models of the fragmentation of liquid metal droplets in a steam explosion based on thermal stress, shock-acoustic effects and explosive boiling water inside the melt were analyzed. Experimental installations are described and research results are presented. The experiments were carried out with samples of various metals (tin, nickel, zinc, stainless steel), which were heated in levitation mode using an inductor. The maximum temperature for heating a sample of ball-bearing steel did not exceeded 1600 °C. Then, in the molten state, the samples (droplets) fell into a cell filled with distilled water at room temperature. In the experiments, the temperature of the melting sample was monitored and the crushing process was recorded. An experimental material indicating the diversity of the forms of the fragments being formed was obtained. The latter circumstance confirms the assumption of the existence of various fragmentation mechanisms, including the method of breaking drops under the action of intense sound waves caused by the collapse of vapor formations. The results of numerical estimates are given, which indicate that the rate of cooling of particles formed in the process of fragmentation can reach values from 109 to 1010 K/s. These values are quite sufficient for obtaining various alloys with an amorphous structure. The possibility of destruction of vapor shells around hot drops under the action of pressure pulses caused by the collapse of adjacent vapor-gas formations has been experimentally confirmed.
The formation of a detonation wave with multipoint initiation
Authors: Sosikov V A , Torunov S I , Dudin S V , Rapota D Yu , Sokolov N S
Published: July 2020

The results of experimental investigations of the formation of detonation waves with multipoint initiation for the case of a planar and converging cylindrical wave are presented. A special initiation system was used, where the main element was modeled for manufacturing on a three dimensional printer. A solution was found to form a smooth detonation wave for the planar case. Studies of a converging cylindrical detonation wave have shown the need to solve some fundamental issues related to the nonstationarity of such a wave.
Equation of state for rhenium at high pressures
Authors: Khishchenko K V
Published: July 2020

In this work, the equation of state for rhenium is proposed as a relationship between pressure, internal energy and density. The consistency of calculation results with experimental data at high energy densities is demonstrated. The equation of state can be used in numerical simulations of dynamic processes in this metal.
Interpretation of experiments on shock compression and isentropic expansion of uranium by quantum molecular dynamics simulations
Authors: Paramonov M A , Minakov D V , Levashov P R
Published: July 2020

In this work, results of quantum molecular dynamics calculations of thermodynamical properties of uranium are presented. The experiments on shock compression and subsequent isentropic expansion of porous samples of uranium are well described. Our first-principle calculations of the shock Hugoniot and release isentropes of uranium demonstrate good agreement with experimental measurements. In addition, unique information of temperature along experimental curves was obtained including supposed entries of isentropes into the two-phase liquid–gas region according to the hypothetical kinks on the experimental isentropes.
Numerical simulations of impact Taylor tests
Authors: Volkov G A , Bratov V A , Borodin E N , Evstifeev A D , Mikhailova N V
Published: July 2020

The finite element method is used for simulation of productivity in dynamic Taylor tests. Two different approaches for prediction of plastic deformation of finite element method is employed for numerical simulation of yielding under dynamic impact Taylor tests. Obtained results of modeling are compared with experimental ones. These are Johnson–Cook model and von Mises yielding criterion enhanced by incubation time approach. The simulation results have shown that the simplest method based on von Mises plasticity model provides good coincidence with experimental profiles of specimen shape in the course of deformation. The shortcoming is that the correct value of yield stress is depending on the loading rate and should be known beforehand. Thus, if there was a method to predict the value of dynamic yield stress to be used within von Mises criterion then this simple approach could be the optimal choice for simulation of dynamic plasticity in conditions of Taylor test.
Flow morphology of two-phase fluid in co-axial capillaries: Numerical simulation
Authors: Vagner S A , Patlazhan S A , Serra C A
Published: July 2020

The dynamic behavior of two-phase Newtonian fluid in co-flow coaxial capillaries was studied numerically. It was found that morphology of the dispersed phase is uniquely described by three non-dimensional parameters as capillary numbers and ratio of Reynolds numbers of the fluid components.
Fully implicit method with lower upper symmetric Gauss–Seidel preconditioner on multiple graphics processing units for hypersonic flows
Authors: Bocharov A N , Bityurin V A , Evstigneev N M , Fortov V E , Petrovskiy V P , Ryabkov O I , Teplyakov I O
Published: July 2020

In the paper, we present implementation and benchmarking for gas dynamic solver for hypersonic flow problems with fully implicit scheme. The aim of the paper is to verify and measure efficiency of the implicit method for computational architecture based on multiple graphics processing units. The verification is performed on a flow over the sphere-cone problem. We consider hypersonic flow regimes of Mach number around 20–30. New results are cross-compared with results of the previous version of the code for explicit time marching scheme.
Diffusion in ultracold strongly coupled multiply charged plasma: Calculation by molecular dynamics method
Authors: Bobrov A A , Bunkov A M , Bronin S Ya , Klyarfeld A B , Zelener B B , Zelener B V
Published: July 2020

We present the results of calculations of electron and ion diffusion by the method of molecular dynamics in an ultracold multiply charged plasma. The calculations were carried out in a wide range of Coulomb coupling parameter. The problems of similarity for a Coulomb multiply charged plasma are discussed. It is shown that in a multiply charged classical plasma for the diffusion coefficients in a wide range of coupling parameter, the similarity assumption is valid.
On dusty plasma formation in Martian ionosphere
Authors: Reznichenko Yu S , Dubinskii A Yu , Popel S I
Published: July 2020

A self-consistent model for the formation and evolution of dusty plasmas in the Martian ionosphere is developed. The effects of the initial distributions of dust particles, as well as condensation and absorption of carbon dioxide and water molecules by dust particles, are studied. Theory values of characteristic sizes of dust grains and their charges are obtained. The theoretical values of the sizes are in agreement with the data of observations. The possibility of the formation of dusty plasma structures in the Martian ionosphere which are analogous to noctilucent clouds in the atmosphere of the Earth is discussed.
Inhomogeneity of a one-dimensional Yukawa system in a trap
Authors: Nikolaev V S , Timofeev A V
Published: July 2020

A system of like charges interacting with a weak repulsive Yukawa potential and confined in a one-dimensional parabolic electrostatic trap is under consideration. It is shown that inter-particle distance in this system grows from the center of the structure to its periphery. The same effect takes place for the mean square displacement of particles from their equilibrium positions, which corresponds to the amplitude of thermal oscillations, and for the value of Lindemann parameter. This leads to different degrees of order for particles located at different distances from the center of the structure. This result might be important for the study of phase transitions in dusty, colloidal and one-component plasmas.
The influence of magnetic field on the geometrical dimensions of dusty structure in striations
Authors: Pavlov S I , Dzlieva E S , Ermolenko M A , Novikov L A , Karasev V Yu
Published: July 2020

The onset of magnetic field on the glow discharge results in the redistribution of plasma flows, which in turn may cause the change of the charge of dust particles levitating in strata. Upon that dusty structure changes its geometric form and inner ordering of particles. In this work, we present the investigation of the influence of magnetic field on dusty structures formed in striation of glow discharge. We detected the variation of geometrical dimensions of structures with magnetic field, and the behavior of interparticle distance was determined. There was obtained the dependence of the concentration of dust particles in normal to vector B cross section of structure on the magnetic induction. Corresponding graph was compared to one of rotation speed, which has three characteristic diapasons. First one is characterized by negative projection of angular velocity Ω on B, two other diapasons are characterized by positive Ω projection and the slope of Ω(B) graph.
Study of plasma jets in plasma focus using the snow-plough model
Authors: Baronova E O , Vikhrev V V , Stepanenko A M , Nikulin V Ya , Silin P V
Published: July 2020

Development of plasma jets (PJ) generated in plasma focus machine is investigated numerically by the snow-plough model. It is shown that axial speed of PJ, V = 5 × 107 cm/s, few times exceeds the speed of thermal plasma expansion. It means that long distance transportation of plasma jets can be achieved. Results of calculations are in good agreement with experimental data obtained by interferometry.
Surface barrier discharge pre-sowing treatment of winter wheat seeds in a three-electrode arrangement with dc bias
Authors: Lazukin A V , Gundareva S V , Nikitin A M , Serdykov J A , Krivov S A
Published: July 2020

In the present work, the experimental results of reaction of morphological indicators (sprout and root length, number of roots, 3-day germination) of seedlings of high quality winter wheat seeds treated by plasma byproducts in the three-electrode system of surface dielectric barrier discharge with dc bias on the third electrode in humid air of atmospheric pressure at different polarity of the bias voltage are shown. The treatment was carried out for 15 min in a strip electrode system (eight 1 mm width strips with 4 mm distance between them, a sinusoidal voltage of 2.7 kV (rms) with a frequency 23 kHz) made on a corundum ceramic barrier (1 mm thickness) with the additional third electrode which is a stainless steel grid distant 10 mm from the surface of the dielectric barrier. Direct-current bias of 8 kV of positive or negative polarity was applied to the third electrode. Seeds were located on the surface of the third electrode. The treatment was also carried out with vibration of the system (the imitation of seeds movement along the third electrode). It is shown that the efficiency of treatment depends on the month of carrying it out. It was succeeded to get a reliable stimulation with weak control. With strong control (potential sowing months) it was not obtained. The imposing of dc bias in any considered case is less efficient than plasma products affection without bias. The vibration of electrode system leads to seeds damage during the treatment and notable germination reduction.
Thermocouple and electric probe measurements in a cold atmospheric-pressure microwave plasma jet
Authors: Chepelev V M , Chistolinov A V , Khromov M A , Antipov S N , Gadzhiev M Kh
Published: July 2020

A cold atmospheric-pressure plasma jet was studied using the novel microwave plasmatron recently developed. Cold plasma jet was generated in Ar flow by electrode 2.45 GHz discharge of up to 200 W power in the portable plasmatron burner (torch) with 2.5 cm diameter outlet. Oscillograms and floating potential dependences on distance from the torch outlet were measured by planar electric probe. Axial and radial distributions of gas temperature in a cold plasma jet were obtained by means of thermocouple method.