bluuebunny/crossref_metadata_2025 huggingface dataset:
Equine musculoskeletal development and performance: impact of the production system and early training
Authors: Rogers Chris W. , Bolwell Charlotte F. , Gee Erica K. , Rosanowski Sarah M.
Published: May 2020

The welfare debate around horse racing appears to be focussed on musculoskeletal injury and the racing of 2-year-olds. Much of this debate appears contrary to the evolutionary history of the horse as a cursorial animal and the capability of the equine musculoskeletal system to respond to the demands of race training. Epidemiological studies have reported that 2-year-old racehorses have a longer time period from entering training to the first race and a greater number of lost training days than older horses. However, this is, in part, due to the time taken to learn to train and the impact of dorsal metacarpal disease, which is due to loading of naïve as opposed to immature tissue. Across several racing jurisdictions and codes, it has been demonstrated that horses that train and race as 2-year-olds have longer, more successful, careers than those that start racing later in life. This positive trend has also been observed with horses starting in equestrian sport at an early age. The literature on the growth and development of the horse indicates that the musculoskeletal system is primed for activity and loading from an early age. Additional exercise for the young horse has a positive rather the negative effect, with many tissues having a sensitive period for ‘priming’ when the horse is a juvenile. This implies that under many modern management systems, the challenge to horse welfare is not ‘too much exercise too soon’ but ‘too little too late’. The current limitation in our understanding is the lack of knowledge of what is the correct exercise dose to optimise the musculoskeletal system. Modern management systems invariably provide too little exercise, but is the exercise data from feral horses the ‘gold standard’, or more a reflection of what the horse is capable of if resources such as food and water are limited? Further research is required to refine our understanding of the optimal exercise levels required and development of greater precision in identifying the sensitive periods for priming the musculoskeletal system.
The future of faecal microbiota transplantation in gastrointestinal illness
Authors: Reed Hayley , Begun Jakob
Published: May 2020

The gut microbiome is made up of hundreds of trillions of microorganisms that reside in a state of homeostatic balance within the healthy individual. Next generation sequencing has provided insight into the diversity of these microorganisms that reside within our gastrointestinal tract; despite developments in metabolomics and culturing techniques, the functions of many of these bacteria remain largely elusive. As such, research into the capacity of the gut microbiome to regulate immune homeostasis has revealed the importance of bacteria in human health, with the potential for exploiting these bacteria only now coming into focus.
Genetic characterisation of the spiny dogfish Squalus acanthias in the Adriatic Sea: evidence for high genetic diversity and an Atlantic–South Pacific origin
Authors: Gracan Romana , Lazar Bojan , Zupan Sara , Bužan Elena
Published: May 2020

Spiny dogfish Squalus acanthias is a widely distributed, highly migratory mesopredatory shark that is extremely sensitive to overexploitation. Because of unregulated targeted and incidental capture and a lack of enforceable management in the Mediterranean Sea, the spiny dogfish subpopulation has declined by at least 50% in the Mediterranean Sea over the past 75–105 years, and is regionally classified as endangered. In this study we sampled 124 spiny dogfish in the northern-most part of the Mediterranean (i.e. the Adriatic Sea) to: (1) assess levels of genetic diversity using 13 microsatellite loci and mitochondrial (mt)DNA (NADH dehydrogenase subunit 2 (ND2) gene); and (2) infer its evolutionary placement while assessing further possible genetic divergence across the Atlantic and Pacific Ocean basins based on ND2. Analysis of mtDNA revealed 12 unique haplotypes and a high level of genetic variation in the Mediterranean region, whereas results from microsatellite markers showed significant genetic heterogeneity and a fine-scale stock structuring involving both sexes. The findings support an Atlantic–South Pacific origin for the spiny dogfish in the Adriatic Sea, with little or no present-day connectivity with the Atlantic population. Consequently, this commercially exploited and regionally endangered coastal shark in the Adriatic Sea should be considered as a separate management unit, with implementation of regional protective management plans.
NIH funding and the pursuit of edge science
Authors: Packalen Mikko , Bhattacharya Jay
Published: May 2020

The National Institutes of Health (NIH) plays a critical role in funding scientific endeavors in biomedicine. Funding innovative science is an essential element of the NIH’s mission, but many have questioned the NIH’s ability to fulfill this aim. Based on an analysis of a comprehensive corpus of published biomedical research articles, we measure whether the NIH succeeds in funding work with novel ideas, which we term edge science. We find that edge science is more often NIH funded than less novel science, but with a delay. Papers that build on very recent ideas are NIH funded less often than are papers that build on ideas that have had a chance to mature for at least 7 y. We have three further findings. First, the tendency to fund edge science is mostly limited to basic science. Papers that build on novel clinical ideas are not more often NIH funded than are papers that build on well-established clinical knowledge. Second, novel papers tend to be NIH funded more often because there are more NIH-funded papers in innovative areas of investigation, rather than because the NIH funds innovative papers within research areas. Third, the NIH’s tendency to have funded papers that build on the most recent advances has declined over time. In this regard, NIH funding has become more conservative despite initiatives to increase funding for innovative projects. Given our focus on published papers, the results reflect both the funding preferences of the NIH and the composition of the applications it receives.
β-Oxidation and autophagy are critical energy providers during acute glucose depletion in S
accharomyces cerevisiae
Authors: Weber Carmen A. , Sekar Karthik , Tang Jeffrey H. , Warmer Philipp , Sauer Uwe , Weis Karsten
Published: May 2020

The ability to tolerate and thrive in diverse environments is paramount to all living organisms, and many organisms spend a large part of their lifetime in starvation. Upon acute glucose starvation, yeast cells undergo drastic physiological and metabolic changes and reestablish a constant—although lower—level of energy production within minutes. The molecules that are rapidly metabolized to fuel energy production under these conditions are unknown. Here, we combine metabolomics and genetics to characterize the cells’ response to acute glucose depletion and identify pathways that ensure survival during starvation. We show that the ability to respire is essential for maintaining the energy status and to ensure viability during starvation. Measuring the cells’ immediate metabolic response, we find that central metabolites drastically deplete and that the intracellular AMP-to-ATP ratio strongly increases within 20 to 30 s. Furthermore, we detect changes in both amino acid and lipid metabolite levels. Consistent with this, both bulk autophagy, a process that frees amino acids, and lipid degradation via β-oxidation contribute in parallel to energy maintenance upon acute starvation. In addition, both these pathways ensure long-term survival during starvation. Thus, our results identify bulk autophagy and β-oxidation as important energy providers during acute glucose starvation.
Low-frequency ultrasound-mediated cytokine transfection enhances T cell recruitment at local and distant tumor sites
Authors: Ilovitsh Tali , Feng Yi , Foiret Josquin , Kheirolomoom Azadeh , Zhang Hua , Ingham Elizabeth S. , Ilovitsh Asaf , Tumbale Spencer K. , Fite Brett Z. , Wu Bo , Raie Marina N. , Zhang Nisi , Kare Aris J. , Chavez Michael , Qi Lei S. , Pelled Gadi , Gazit Dan , Vermesh Ophir , Steinberg Idan , Gambhir Sanjiv S. , Ferrara Katherine W.
Published: May 2020

Robust cytotoxic T cell infiltration has proven to be difficult to achieve in solid tumors. We set out to develop a flexible protocol to efficiently transfect tumor and stromal cells to produce immune-activating cytokines, and thus enhance T cell infiltration while debulking tumor mass. By combining ultrasound with tumor-targeted microbubbles, membrane pores are created and facilitate a controllable and local transfection. Here, we applied a substantially lower transmission frequency (250 kHz) than applied previously. The resulting microbubble oscillation was significantly enhanced, reaching an effective expansion ratio of 35 for a peak negative pressure of 500 kPa in vitro. Combining low-frequency ultrasound with tumor-targeted microbubbles and a DNA plasmid construct, 20% of tumor cells remained viable, and ∼20% of these remaining cells were transfected with a reporter gene both in vitro and in vivo. The majority of cells transfected in vivo were mucin 1
+
/CD45
−
tumor cells. Tumor and stromal cells were then transfected with plasmid DNA encoding IFN-β, producing 150 pg/10
6
cells in vitro, a 150-fold increase compared to no-ultrasound or no-plasmid controls and a 50-fold increase compared to treatment with targeted microbubbles and ultrasound (without IFN-β). This enhancement in secretion exceeds previously reported fourfold to fivefold increases with other in vitro treatments. Combined with intraperitoneal administration of checkpoint inhibition, a single application of IFN-β plasmid transfection reduced tumor growth in vivo and recruited efficacious immune cells at both the local and distant tumor sites.
Habituation as a neural algorithm for online odor discrimination
Authors: Shen Yang , Dasgupta Sanjoy , Navlakha Saket
Published: May 2020

Habituation is a form of simple memory that suppresses neural activity in response to repeated, neutral stimuli. This process is critical in helping organisms guide attention toward the most salient and novel features in the environment. Here, we follow known circuit mechanisms in the fruit fly olfactory system to derive a simple algorithm for habituation. We show, both empirically and analytically, that this algorithm is able to filter out redundant information, enhance discrimination between odors that share a similar background, and improve detection of novel components in odor mixtures. Overall, we propose an algorithmic perspective on the biological mechanism of habituation and use this perspective to understand how sensory physiology can affect odor perception. Our framework may also help toward understanding the effects of habituation in other more sophisticated neural systems.
Pleiotropy complicates a trade-off between phage resistance and antibiotic resistance
Authors: Burmeister Alita R. , Fortier Abigail , Roush Carli , Lessing Adam J. , Bender Rose G. , Barahman Roxanna , Grant Raeven , Chan Benjamin K. , Turner Paul E.
Published: May 2020

Bacteria frequently encounter selection by both antibiotics and lytic bacteriophages. However, the evolutionary interactions between antibiotics and phages remain unclear, in particular, whether and when phages can drive evolutionary trade-offs with antibiotic resistance. Here, we describe
Escherichia coli
phage U136B, showing it relies on two host factors involved in different antibiotic resistance mechanisms: 1) the efflux pump protein TolC and 2) the structural barrier molecule lipopolysaccharide (LPS). Since TolC and LPS contribute to antibiotic resistance, phage U136B should select for their loss or modification, thereby driving a trade-off between phage resistance and either of the antibiotic resistance mechanisms. To test this hypothesis, we used fluctuation experiments and experimental evolution to obtain phage-resistant mutants. Using these mutants, we compared the accessibility of specific mutations (revealed in the fluctuation experiments) to their actual success during ecological competition and coevolution (revealed in the evolution experiments). Both
tolC
and LPS-related mutants arise readily during fluctuation assays, with
tolC
mutations becoming more common during the evolution experiments. In support of the trade-off hypothesis, phage resistance via
tolC
mutations occurs with a corresponding reduction in antibiotic resistance in many cases. However, contrary to the hypothesis, some phage resistance mutations pleiotropically confer increased antibiotic resistance. We discuss the molecular mechanisms underlying this surprising pleiotropic result, consideration for applied phage biology, and the importance of ecology in evolution of phage resistance. We envision that phages may be useful for the reversal of antibiotic resistance, but such applications will need to account for unexpected pleiotropy and evolutionary context.
Marginal zone SIGN-R1
+
macrophages are essential for the maturation of germinal center B cells in the spleen
Authors: Pirgova Gabriela , Chauveau Anne , MacLean Andrew J. , Cyster Jason G. , Arnon Tal I.
Published: May 2020

Significance

Germinal centers (GCs) are critical for the generation of memory B cells and high-affinity antibody-producing cells. This process is important for protection from acute infections and for establishment of long-lasting immunity in response to vaccination. The microanatomic organization of distinct niches within lymphoid tissues is fundamental for GC responses, as it provides the basis for coordinated interactions between rare antigen-specific cells and antigen-presenting cells. Here we reveal a role for a specialized resident macrophage subset in maintaining positional regulation of a key antigen-presenting cell type within functional niches in the spleen. Our study demonstrates the importance of this regulation to humoral immunity.
Global reconstruction reduces the uncertainty of oceanic nitrous oxide emissions and reveals a vigorous seasonal cycle
Authors: Yang Simon , Chang Bonnie X. , Warner Mark J. , Weber Thomas S. , Bourbonnais Annie M. , Santoro Alyson E. , Kock Annette , Sonnerup Rolf E. , Bullister John L. , Wilson Samuel T. , Bianchi Daniele
Published: May 2020

Assessment of the global budget of the greenhouse gas nitrous oxide (

N

2

O) is limited by poor knowledge of the oceanic

N

2

O flux to the atmosphere, of which the magnitude, spatial distribution, and temporal variability remain highly uncertain. Here, we reconstruct climatological

N

2

O emissions from the ocean by training a supervised learning algorithm with over 158,000

N

2

O measurements from the surface ocean—the largest synthesis to date. The reconstruction captures observed latitudinal gradients and coastal hot spots of

N

2

O flux and reveals a vigorous global seasonal cycle. We estimate an annual mean

N

2

O flux of 4.2

±

1.0 Tg N

⋅

y

−
1

, 64% of which occurs in the tropics, and 20% in coastal upwelling systems that occupy less than 3% of the ocean area. This

N

2

O flux ranges from a low of 3.3

±

1.3 Tg N

⋅

y

−
1

in the boreal spring to a high of 5.5

±

2.0 Tg N

⋅

y

−
1

in the boreal summer. Much of the seasonal variations in global

N

2

O emissions can be traced to seasonal upwelling in the tropical ocean and winter mixing in the Southern Ocean. The dominant contribution to seasonality by productive, low-oxygen tropical upwelling systems (>75%) suggests a sensitivity of the global

N

2

O flux to El Niño–Southern Oscillation and anthropogenic stratification of the low latitude ocean. This ocean flux estimate is consistent with the range adopted by the Intergovernmental Panel on Climate Change, but reduces its uncertainty by more than fivefold, enabling more precise determination of other terms in the atmospheric

N

2

O budget.
Rational design principles for giant spin Hall effect in
5d
-transition metal oxides
Authors: Jadaun Priyamvada , Register Leonard F. , Banerjee Sanjay K.
Published: May 2020

Spin Hall effect (SHE), a mechanism by which materials convert a
charge
current into a
spin
current, invokes interesting physics and promises to empower transformative, energy-efficient memory technology. However, fundamental questions remain about the essential factors that determine SHE. Here, we solve this open problem, presenting a comprehensive theory of five rational design principles for achieving
giant
intrinsic SHE in transition metal oxides. Arising from our key insight regarding the inherently geometric nature of SHE, we demonstrate that two of these design principles are weak crystal fields and the presence of structural distortions. Moreover, we discover that antiperovskites are a highly promising class of materials for achieving giant SHE, reaching SHE values an
order of magnitude
larger than that reported for any oxide. Additionally, we derive three other design principles for enhancing SHE. Our findings bring deeper insight into the physics driving SHE and could help enhance and externally control SHE values.
Thermogenic carbon release from the Central Atlantic magmatic province caused major end-Triassic carbon cycle perturbations
Authors: Heimdal Thea H. , Jones Morgan T. , Svensen Henrik. H.
Published: May 2020

Significance

The Central Atlantic magmatic province (CAMP) is coincident with the end-Triassic extinction event and several negative carbon isotope excursions (CIEs). Sill emplacements in Brazil would have generated extensive volatiles and degassing due to the contact metamorphism of evaporites, organic-rich shales, and hydrocarbons. Thermogenic carbon release from contact metamorphism represents a plausible source for
12
C; however, this has not yet been explored from a carbon cycle approach. This study explores the effects of thermogenic carbon release from CAMP using carbon cycle modeling and shows that it represents a credible source for the negative CIEs at the end-Triassic. It strengthens the hypothesis that the subvolcanic part of a large igneous province is of major importance for understanding carbon cycle disruptions.
Learners’ perceptions of a Wiki-enhanced TBLT approach designed and implemented at the syllabus level
Authors: Zhang Shenglan
Published: May 2020

This study examines learners’ perceptions of an approach for improving Chinese-as-a-Foreign-Language learners’
language proficiency, especially their speaking ability. Built upon the Distributed Design Model, a wiki-enhanced, Task-Based
Language Teaching (TBLT) approach was designed at the syllabus level, taking into consideration various learning contexts. The
approach was implemented and evaluated. Findings show that the overall design of this approach and most of the different
components of the pre-task, core-task (interviews with native speakers, wiki-writing, and in-class presentations), and post-task
activities were very positively perceived by the students. All students liked this design and enjoyed the class. The main reasons
include (1) Students valued the opportunity to interact with native speakers outside the classroom; (2) The in-class presentations
gave them an opportunity to express their personalities; (3) They liked the fact that the wiki-essay writing was connected to the
in-class presentation because this helped them prepare the content of their presentation, also enabled them to develop writing and
speaking on a single topic so they could become more advanced in that topic; (4) They also liked the consistency in organization
and the eight units being procedurally similar. The learners held varying views on a few components of the pre-task and post-task
activities.
Minority positioning in physical and online spaces
Authors: Vuorsola Lasse
Published: May 2020

The study examines how a Sweden Finnish minority language activist group positions themselves by inserting
graffiti-like stickers into the Swedish Linguistic Landscape, and how the majority populations in Sweden and Finland react to
these revitalisation efforts. Protesting by placing stickers in physical environments is classified as an act of linguistic
citizenship (Isin 2009) and, from the majority’s point of view, these acts are a threat
to the shared cultural moral order. The data consists of pictures posted on Instagram that depict actual physical environments
where activists have placed stickers that encourage the minority to “speak their own language”. The activists utilise temporal,
spatial, textual, and multimodal elements in their discursive construction. As a theoretical framework, I apply Harré and Langehove’s (1991) positioning theory. The results show how minorities position
themselves in relation to the Swedish majority population with the aim of justifying their status and their right to exist.
The linguistic landscape of Nuuk, Greenland
Authors: Valijärvi Riitta-Liisa , Kahn Lily
Published: May 2020

The purpose of this article is to present and analyse public and private signs in the Linguistic Landscape of
Nuuk, the capital of Greenland. Nuuk is a trilingual environment including the indigenous language (West Greenlandic), the former
colonial language (Danish), and a global language (English). West Greenlandic is a somewhat unusual case among indigenous
languages in colonial and postcolonial settings because it is a statutory national language with a vigorous use. Our analysis
examines the use of West Greenlandic, Danish, and English from the theoretical perspective of centre vs. periphery, devoting
attention to the primary audiences (local vs. international) and chief functions (informational vs. symbolic) of the signs. As the
first investigation into the Greenlandic Linguistic Landscape, our analysis can contribute to research on signs in urban
multilingual indigenous language settings.
The complementizer layer in Standard Arabic revisited
Authors: Albuhayri Salem , Ouali Hamid
Published: May 2020

This paper revisits three issues related to the complementizer
layer (CP) in Standard Arabic. We reexamine them against the backdrop of Shlonsky’s 2000 analysis, and put forward a
new proposal couched in Rizzi’s 1997
split-CP hypothesis. First, we examine the apparent distributional and interpretive
differences between ʔinna and ʔanna, and
subsequently argue that the former is a lexical verum operator that projects a
VerumP in the middle of the split-CP field, whereas ʔanna is an
indicative force head. Second, the current work presents another view on the
elements analyzed as agreement clitics by Shlonsky (2000). We argue that they are not for agreement but rather are
expletive or resumptive pronouns. Evidence that they are not agreement derives
primarily from contexts where they appear in coordinated structures with overt DPs.
We then investigate extraction patterns for questions and focus in matrix clauses as
well as embedded clauses and propose that the preverbal subject DP in SVO is
externally merged in SpecTopP in the split CP while it binds a null
pro in SpecvP. This analysis captures the ban on
extraction across the subject in SVO in that it shows that this DP is already higher
in the structural hierarchy than the positions dedicated for focus and
wh-questions.
Phosphorylation of the microtubule-severing AAA+ enzyme Katanin regulates C. elegans embryo development
Authors: Joly Nicolas , Beaumale Eva , Van Hove Lucie , Martino Lisa , Pintard Lionel
Published: May 2020

The evolutionarily conserved microtubule (MT)-severing AAA-ATPase enzyme Katanin is emerging as a critical regulator of MT dynamics. In Caenorhabditis elegans, Katanin MT-severing activity is essential for meiotic spindle assembly but is toxic for the mitotic spindle. Here we analyzed Katanin dynamics in C. elegans and deciphered the role of Katanin phosphorylation in the regulation of its activity and stability. Katanin is abundant in oocytes, and its levels drop after meiosis, but unexpectedly, a significant fraction is present throughout embryogenesis, where it is dynamically recruited to the centrosomes and chromosomes during mitosis. We show that the minibrain kinase MBK-2, which is activated during meiosis, phosphorylates Katanin at multiple serines. We demonstrate unequivocally that Katanin phosphorylation at a single residue is necessary and sufficient to target Katanin for proteasomal degradation after meiosis, whereas phosphorylation at the other sites only inhibits Katanin ATPase activity stimulated by MTs. Our findings suggest that cycles of phosphorylation and dephosphorylation fine-tune Katanin level and activity to deliver the appropriate MT-severing activity during development.
Confounding factors from inducible systems for spatiotemporal gene expression regulation
Authors: Wüst Rob C.I. , Houtkooper Riekelt H. , Auwerx Johan
Published: May 2020

Spatiotemporally regulated targeted gene manipulation is a common way to study the effect of gene variants on phenotypic traits, but the Cre/loxP and Tet-On/Tet-Off systems can affect whole-organism physiology and function due to off-target effects. We highlight some of these adverse effects, including whole-body endocrinology and disturbances in the gut microbiome and in mitochondrial and metabolic function.
Synthesis of new silicene structure and its energy band properties*
Authors: Huang Wei-Qi , Liu Shi-Rong , Peng Hong-Yan , Li Xin , Huang Zhong-Mei
Published: May 2020

Silicene, silicon analogue to graphene which possesses a two-dimensional (2D) hexagonal lattice, has attracted increasing attention in the last few years due to predicted unique properties. However, silicon naturally possesses a three-dimensional (3D) diamond structure, so there seems to be not any natural solid phase of silicon similar to graphite. Here we report the synthesis of new silicene structure with a unique rectangular lattice by using a coherent electron beam to irradiate amorphous silicon nanofilm produced by pulsed laser deposition (PLD). Under the irradiation of coherent electron beam with proper kinetic energy, the surface layer of silicon nanofilm can be crystallized into silicene. The dynamic stability and the energy band properties of this new silicene structure are investigated by using first-principle calculations and density function theory (DFT) with the help of the observed crystalline structure and lattice constant. The new silicene structure has a real direct bandgap of 0.78 eV. Interestingly, the simulating calculation shows that the convex bond angle is 118° in the new silicene structure with rectangular lattices. The DFT simulations reveal that this new silicene structure has a Dirac-cone-like energy band. The experimental realization of silicene and the theoretically predicted properties shed light on the silicon material with potential applications in new devices.
Charge structure factors of doped armchair nanotubes in the presence of electron–phonon interaction
Authors: Rezania Hamed , Azizi Farshad
Published: May 2020

We present the behaviors of both dynamical and static charge susceptibilities of doped armchair nanotubes using the Green function approach in the context of Holstein-model Hamiltonian. Specially, the effects of magnetization and gap parameter on the the plasmon modes of armchair nanotube are investigated via calculating correlation function of charge density operators. Random phase approximation has been implemented to find the interacting dynamical charge susceptibility. The electrons in this systems interacts with each other by mediation of dispersionless Holstein phonons. Our results show that the increase of gap parameter leads to decreasing intensity of charge collective mode. Also the frequency position of the collective mode tends to higher frequencies due to the gap parameter. Furthermore the number of collective excitation mode decreases with chemical potential in the presence of electron–phonon interaction. Finally the temperature dependence of static charge structure factor of armchair nanotubes is studied. The effects of the gap parameter, magnetization and electron–phonon interaction on the static structure factor are addressed in details.
Regulation of microtubule array in its self-organized dense active crowds*
Authors: Jiang Xin-Chen , Ma Yu-Qiang , Shi Xiaqing
Published: May 2020

Microtubule self-organization under mechanical and chemical regulations plays a central role in cytokinesis and cellular transportations. In plant-cells, the patterns or phases of cortical microtubules organizations are the direct indicators of cell-phases. The dense nematic pattern of cortical microtubule array relies on the regulation of single microtubule dynamics with mechanical coupling to steric interaction among the self-organized microtubule crowds. Building upon previous minimal models, we investigate the effective microtubule width, microtubule catastrophe rate, and zippering angle as factors that regulate the self-organization of the dense nematic phase. We find that by incorporating the effective microtubule width, the transition from isotropic to the highly ordered nematic phase (N
I phase) with extremely long microtubules will be gapped by another nematic phase which consists of relative short microtubules (N
II phase). The N
II phase in the gap grows wider with the increase of the microtubule width. We further illustrate that in the dense phase, the collision-induced catastrophe rate and an optimal zippering angle play an important role in controlling the order–disorder transition, as a result of the coupling between the collision events and ordering. Our study shows that the transition to dense microtubule array requires the cross-talk between single microtubule growth and mechanical interactions among microtubules in the active crowds.
Progress on the 40Ca+ ion optical clock*
Authors: Zhang Baolin , Huang Yao , Zhang Huaqing , Hao Yanmei , Zeng Mengyan , Guan Hua , Gao Kelin
Published: May 2020

Progress of the 40Ca+ ion optical clock based on the 42S1/2 – 3d 2D5/2 electric quadrupole transition is reported. By setting the drive frequency to the “magic” frequency Ω
0, the frequency uncertainty caused by the scalar Stark shift and second-order Doppler shift induced by micromotion is reduced to the 10−19 level. By precisely measuring the differential static scalar polarizability Δα
0, the uncertainty due to the blackbody radiation (BBR) shift (coefficient) is reduced to the 10−19 level. With the help of a second-order integrating servo algorithm, the uncertainty due to the servo error is reduced to the 10−18 level. The total fractional uncertainty of the 40Ca+ ion optical clock is then improved to 2.2× 10−17, whereas this value is mainly restricted by the uncertainty of the BBR shift due to temperature fluctuations. The state preparation is introduced together with improvements in the pulse sequence, and furthermore, a better signal to noise ratio (SNR) and less dead time are achieved. The clock stability of a single clock is improved to

4.8
×

10

−
15

/

τ

(
in

seconds
)

.
Perpendicular magnetization switching by large spin–orbit torques from sputtered Bi2Te3*
Authors: Zheng Zhenyi , Zhang Yue , Zhu Daoqian , Zhang Kun , Feng Xueqiang , He Yu , Chen Lei , Zhang Zhizhong , Liu Dijun , Zhang Youguang , Amiri Pedram Khalili , Zhao Weisheng
Published: May 2020

Spin–orbit torque (SOT) effect is considered as an efficient way to switch the magnetization and can inspire various high-performance spintronic devices. Recently, topological insulators (TIs) have gained extensive attention, as they are demonstrated to maintain a large effective spin Hall angle (

θ

SH

eff

), even at room temperature. However, molecular beam epitaxy (MBE), as a precise deposition method, is required to guarantee favorable surface states of TIs, which hinders the prospect of TIs towards industrial application. In this paper, we demonstrate that Bi2Te3 films grown by magnetron sputtering can provide a notable SOT effect in the heterostructure with perpendicular magnetic anisotropy CoTb ferrimagnetic alloy. By harmonic Hall measurement, a high SOT efficiency (8.7 ± 0.9 Oe/(109 A/m2)) and a large

θ

SH

eff

(3.3±0.3) are obtained at room temperature. Besides, we also observe an ultra-low critical switching current density (9.7×109 A/m2). Moreover, the low-power characteristic of the sputtered Bi2Te3 film is investigated by drawing a comparison with different sputtered SOT sources. Our work may provide an alternative to leverage chalcogenides as a realistic and efficient SOT source in future spintronic devices.
Preface: Key technologies for enhancing the performance of FAST
Authors: Jiang Peng , Shen Zhi-Qiang , Xu Ren-Xin
Published: May 2020

The Five-hundred-meter Aperture Spherical radio Telescope (FAST) passed its national acceptance inspection on 2020 January 11. This special issue includes a total of 15 papers, which are selected to introduce the status of FAST’s performance and demonstrate the key technologies applied to FAST. The presented performance parameters can provide an important reference for scientists to propose observations with FAST. The key technologies presented in these papers include design and implementation in the measurement and control system, electromagnetic compatibility system, and receiver system. Finally, scientific achievements obtained by FAST during the commissioning phase are also reported.
The fundamental performance of FAST with 19-beam receiver at L band
Authors: Jiang Peng , Tang Ning-Yu , Hou Li-Gang , Liu Meng-Ting , Krčo Marko , Qian Lei , Sun Jing-Hai , Ching Tao-Chung , Liu Bin , Duan Yan , Yue You-Ling , Gan Heng-Qian , Yao Rui , Li Hui , Pan Gao-Feng , Yu Dong-Jun , Liu Hong-Fei , Li Di , Peng Bo , Yan Jun
Published: May 2020

The Five-hundred-meter Aperture Spherical radio Telescope (FAST) has passed national acceptance and finished one pilot cycle of ‘Shared-Risk’ observations. It will start formal operation soon. In this context, this paper describes testing results of key fundamental parameters for FAST, aiming to provide basic support for observation and data reduction of FAST for scientific researchers. The 19-beam receiver covering 1.05–1.45 GHz was utilized for most of these observations. The fluctuation in electronic gain of the system is better than 1% over 3.5 hours, enabling enough stability for observations. Pointing accuracy, aperture efficiency and system temperature are three key parameters for FAST. The measured standard deviation of pointing accuracy is 7.9″, which satisfies the initial design of FAST. When zenith angle is less than 26.4°, the aperture efficiency and system temperature around 1.4 GHz are ∼0.63 and less than 24 K for central beam, respectively. The sensitivity and stability of the 19-beam backend are confirmed to satisfy expectation by spectral Hi observations toward NGC 672 and polarization observations toward 3C 286. The performance allows FAST to take sensitive observations for various scientific goals, from studies of pulsars to galaxy evolution.
Research on key technologies for installation and maintenance of reflector of FAST
Authors: Song Li-Qiang , Jiang Peng , Wang Qi-Ming , Yang Lei
Published: May 2020

The reflector of the Five-hundred-meter Aperture Spherical radio Telescope (FAST) consists of 4450 reflector units. Installation of the reflector faces the challenges of large span, complex terrain, serious interference, complex processes, high position and inability to use conventional equipment. The installation technology for the flexible reflector with a large span was specially studied and designed. Two half-span arc-moving cable cranes and two transfer trucks were jointly operated along a path that follows a circular beam. After installation of the reflector was completed, two half-span cable cranes were merged into a set of full-span cable cranes for maintenance of the reflector. Installation of the reflector combines features of unit and site topography of FAST. The installation technology follows scientific and reasonable practices, and is highly efficient and convenient. It represents a breakthrough in many key technologies in construction and maintenance techniques. It has promoted related technical progress in the construction and maintenance of complex projects. It has also provided an important reference for the construction and maintenance of similar projects, and has strong significance and applicability.
The design of China Reconfigurable ANalog-digital backEnd for FAST
Authors: Zhang Xin-Xin , Duan Ran , Yu Xin-Ying , Li Di , Tang Ning-Yu , Ching Tao-Chung
Published: May 2020

The Five-hundred-meter Aperture Spherical radio Telescope (FAST) was launched on 2016 September 25. From early 2017, we began to use the FAST wideband receiver, which was designed, constructed and installed on the FAST in Guizhou, China. The front end of the receiver is composed an uncooled Quad Ridge Flared Horn feed (QRFH) with the frequency range of 270 to 1620 MHz, and a cryostat operating at 10 K. We have cooperated with the Institute of Automation of the Chinese Academy of Sciences to develop the China Reconfigurable ANalog-digital backEnd (CRANE). The system covers the 3 GHz operating band of FAST. The hardware part of the backend includes an Analog Front-end Board, a wideband high precision Analog Digital Converter, and a FAST Digital Back-end. Analog circuit boards, field programmable gate arrays, and control computers form a set of hardware, software, and firmware platforms to achieve flexible bandwidth requirements through parameter changes. It is also suitable for the versatility of different astronomical observations, and can meet specific requirements. This paper briefly introduces the hardware and software of CRANE, as well as some observations of the system.
RFI measurements and mitigation for FAST
Authors: Zhang Hai-Yan , Wu Ming-Chang , Yue You-Ling , Gan Heng-Qian , Hu Hao , Huang Shi-Jie , Sun Jin-Hai , Peng Bo , Nan Ren-Dong , Collaboration FAST
Published: May 2020

Radio Frequency Interference (RFI) mitigation is essential for supporting the science output of Five-hundred-meter Aperture Spherical radio Telescope (FAST) due to its high sensitivity. In order to protect FAST from RFI, an Electromagnetic Compatibility (EMC) study has been carried out and the operation of a Radio Quiet Zone (RQZ) is ongoing. RFI measurements of the telescope instruments and monitoring of the active radio services outside the site have revealed the radiation properties of the RFI sources. Based on the measurement results and theoretical analysis, various EMC methods have been implemented for the telescope to decrease the RFIs. Meanwhile, the main RFI sources in the FAST RQZ, such as mobile stations, broadcast stations and navigation instruments, have been identified, and the technical measures have been adopted to protect the quiet radio environment around the site. The early science outputs of FAST have demonstrated the efficiency of RFI mitigation methods.
FAST interstellar scintillation observation of PSR B1929+10 and PSR B1842+14
Authors: Yao Ju-Mei , Zhu Wei-Wei , Wang Pei , Li Di , Lu Ji-Guang , Kou Fei-Fei , Yu Ye-Zhao , Peng Bo
Published: May 2020

In this paper, we present the Five-hundred-meter Aperture Spherical radio Telescope (FAST) observations of PSRs B1929+10 and B1842+14. Through analysis of the pulsars’ scintillation pattern, we detected the known scintillation arc from PSR B1929+10 and two previously undetected scintillation arcs from B1842+14. We find that the B1929+10 arc’s curvature scales with observing frequency as η
− ∝ ν
−2.1±0.1 and η
+ ∝ ν
−1.8±0.2, consistent with Arecibo results and the theoretical expectations of η ∝ ν
−2. From the arc curvature, we infer the scattering screen to be located at 0.20±0.02 kpc from the Earth, close to what was measured by RadioAstron at 324 MHz. From B1842+14, we find two scintillation arcs for the first time. The arcs’ curvatures imply that they are caused by two scattering screens located at a distance of 0.3±0.2 kpc and 1.6±0.6 kpc from the Earth, respectively. The screen distance uncertainties mainly come from the uncertainty in pulsar’s dispersion measure (DM)-derived distance. We present these FAST scintillation observations and discuss the future prospect of FAST pulsar scintillation study.
Pilot Hi survey of Planck Galactic Cold Clumps with FAST
Authors: Tang Ning-Yu , Zuo Pei , Li Di , Qian Lei , Liu Tie , Wu Yue-Fang , Krčo Marko , Liu Meng-Ting , Yue You-Ling , Zhu Yan , Liu Hong-Fei , Yu Dong-Jun , Sun Jing-Hai , Jiang Peng , Pan Gao-Feng , Li Hui , Gan Heng-Qian , Yao Rui , Liu Shu
Published: May 2020

We present a pilot Hi survey of 17 Planck Galactic Cold Clumps (PGCCs) with the Five-hundred-meter Aperture Spherical radio Telescope (FAST). Hi Narrow Self-Absorption (HINSA) is an effective method to detect cold Hi being mixed with molecular hydrogen H2 and improves our understanding of the atomic to molecular transition in the interstellar medium. HINSA was found in 58% PGCCs that we observed. The column density of HINSA was found to have an intermediate correlation with that of 13CO, following (N(HINSA)) = (0.52 ± 0.26) (N

13CO) + (10 ± 4.1). Hi abundance relative to total hydrogen [Hi]/[H] has an average value of 4.4 × 10–3, which is about 2.8 times of the average value of previous HINSA surveys toward molecular clouds. For clouds with total column density N
H > 5 × 1020 cm–2, an inverse correlation between HINSA abundance and total hydrogen column density is found, confirming the depletion of cold Hi gas during molecular gas formation in more massive clouds. Non-thermal line width of 13CO is about 0-0.5 km s−1 larger than that of HINSA. One possible explanation of narrower non-thermal width of HINSA is that HINSA region is smaller than that of 13CO. Based on an analytic model of H2 formation and H2 dissociation by cosmic ray, we found the cloud ages to be within 106.7 – 107.0 yr for five sources.
Perovskite semiconductors for direct X-ray detection and imaging
Authors: Su Yirong , Ma Wenbo , Yang Yang (Michael)
Published: May 2020

Halide perovskites have emerged as the next generation of optoelectronic materials and their remarkable performances have been attractive in the fields of solar cells, light-emitting diodes, photodetectors, etc. In addition, halide perovskites have been reported as an attractive new class of X-ray direct detecting materials recently, owning to the strong X-ray stopping capacity, excellent carrier transport, high sensitivity, and cost-effective manufacturing. Meanwhile, perovskite based direct X-ray imagers have been successfully demonstrated as well. In this review article, we firstly introduced some fundamental principles of direct X-ray detection and imaging, and summarized the advances of perovskite materials for these purposes and finally put forward some needful and feasible directions.
The application of halide perovskites in memristors
Authors: Cao Gang , Cheng Chuantong , Zhang Hengjie , Zhang Huan , Chen Run , Huang Beiju , Yan Xiaobing , Pei Weihua , Chen Hongda
Published: May 2020

New neuromorphic architectures and memory technologies with low power consumption, scalability and high-speed are in the spotlight due to the von Neumann bottleneck and limitations of Moore's law. The memristor, a two-terminal synaptic device, shows powerful capabilities in neuromorphic computing and information storage applications. Active materials with high defect migration speed and low defect migration barrier are highly promising for high-performance memristors. Halide perovskite (HP) materials with point defects (such as gaps, vacancies, and inversions) have strong application potential in memristors. In this article, we review recent advances on HP memristors with exceptional performances. First, the working mechanisms of memristors are described. Then, the structures and properties of HPs are explained. Both electrical and photonic HP-based memristors are overviewed and discussed. Different fabrication methods of HP memristor devices and arrays are described and compared. Finally, the challenges in integrating HP memristors with complementary metal oxide semiconductors (CMOS) are briefly discussed. This review can assist in developing HP memristors for the next-generation information technology.
I/P interface modification for stable and efficient perovskite solar cells
Authors: Zhang Jie , Hou Shixin , Li Renjie , Chen Bingbing , Hou Fuhua , Cui Xinghua , Liu Jingjing , Wang Qi , Wang Pengyang , Zhang Dekun , Zhao Ying , Zhang Xiaodan
Published: May 2020

Interface engineering has played an increasingly essential role in the development of perovskite solar cells (PSCs). Herein, we adopted an effective and simple one-step interface passivation method on a FA-based perovskite to fabricate efficient and stable planar PSCs. The surface defects are reduced by the perovskite interface passivation layer incorporated between the hole transport and perovskite absorber layers, and then non-radiative recombination is suppressed while interfacial carrier extraction is enhanced. The passivated planar PSCs demonstrates 20.83% power conversion efficiency (PCE), which is caused by the simultaneous enhancement of the fill factor and open-circuit voltage. In addition, the device also shows great ambient and thermal stability. It retains 94% of its original PCE after 1000 h under ambient air without encapsulation as well as 90% of its initial efficiency after 400 h under continuous heating at 65 °C with encapsulation. This research provides a strategy for the development of efficient and stable PSCs.
Light-emitting diodes based on all-inorganic copper halide perovskite with self-trapped excitons
Authors: Liu Nian , Zhao Xue , Xia Mengling , Niu Guangda , Guo Qingxun , Gao Liang , Tang Jiang
Published: May 2020

Light-emitting diodes based on lead halide perovskite have attracted great attention due to their outstanding performance. However, their application is plagued by the toxicity of Pb and the poor stability. Herein novel copper-based all inorganic perovskite CsCu2I3 with much enhanced stability has been reported with a potential photoluminescence quantum yield (PLQY) over 20% and self-trapped excitons (STE). By taking advantage of its extraordinary thermal stability, we successfully fabricate high-quality CsCu2I3 film through direct vacuum-based deposition (VBD) of CsCu2I3 powder. The resulting film shows almost the same PLQY with the synthesized powder, as well as excellent uniformity and stability. The perovskite light-emitting diodes (Pe-LED) based on the evaporated CsCu2I3 emitting layer achieve a luminescence of 10 cd/m2 and an external quantum efficiency (EQE) of 0.02%. To the best of our knowledge, this is the first CsCu2I3 Pe-LED fabricated by VBD with STE property, which offers a new avenue for lead-free Pe-LED.
Giant efficiency and color purity enhancement in multicolor inorganic perovskite light-emitting diodes via heating-assisted vacuum deposition
Authors: Han Boning , Shan Qingsong , Zhang Fengjuan , Song Jizhong , Zeng Haibo
Published: May 2020

Inorganic perovskites (CsPbX3 (X = I, Br, Cl)) have broad prospection in the field of high-definition displaying due to its excellent optoelectronic characteristics. The vacuum deposition process possesses advantages and competitiveness in the industrialized production. However, the performance of light emitting diodes (LEDs) based on vacuum-deposited is incredibly low. Herein, we proposed a heating-assisted vacuum deposition (HAVD) method to construct inorganic perovskite LEDs (PeLEDs) with enhanced performance. The roughness and crystallinity of perovskite film were improved by regulating the heating treatment of substrates. And the perovskite film exhibited largely rise in luminescence, with decreasing defect density. Consequently, with the optimized temperature, the green PeLEDs exhibited 100-fold improvement of external quantum efficiency (EQE) with the luminance of up to 11 941 cd/m2, and the full width at half-maximum (FWHM) of the electroluminescence (EL) spectra was decreased from 25 to 17 nm. At the same time, the red and blue PeLEDs also exhibited obvious enhancement in EQE and luminance by HAVD method, and both the FWHM of EL spectra dropped below 20 nm, exhibiting excellent high color purity. HAVD strategy has a huge potential to be a new commonly used method for low-cost fabrication of displays and lighting.