bluuebunny/crossref_metadata_2025 huggingface dataset:
A New Memory Perspective on the Sentence Comprehension Deficits of School-Age Children With Developmental Language Disorder: Implications for Theory, Assessment, and Intervention
Authors: Montgomery James W. , Gillam Ronald B. , Evans Julia L.
Published: April 2021

Purpose

The nature of the relationship between memory and sentence comprehension in school-age children with developmental language disorder (DLD) has been unclear. We present a novel perspective that highlights the relational influences of fluid intelligence, controlled attention, working memory (WM), and long-term memory (LTM) on sentence comprehension in children with and without DLD. This perspective has new and important implications for theory, assessment, and intervention.

Method

We review a large-scale study of children with and without DLD that focused on the connections between cognition, memory, and sentence comprehension. We also summarize a new model of these relationships.

Results

Our new model suggests that WM serves as a conduit through which syntactic knowledge in LTM, controlled attention, and general pattern recognition indirectly influence sentence comprehension in both children with DLD and typically developing children. For typically developing children, language-based LTM and fluid intelligence indirectly influence sentence comprehension. However, for children with DLD, controlled attention plays a larger indirect role.

Conclusions

WM plays a key role in children's ability to apply their syntactic knowledge when comprehending canonical and noncanonical sentences. Our new model has important implications for the assessment of sentence comprehension and for the treatment of larger sentence comprehension deficits.
A Bayesian method for point source polarisation estimation
Authors: Herranz D. , Argüeso F. , Toffolatti L. , Manjón-García A. , López-Caniego M.
Published: April 2021

The estimation of the polarisation P of extragalactic compact sources in cosmic microwave background (CMB) images is a very important task in order to clean these images for cosmological purposes –for example, to constrain the tensor-to-scalar ratio of primordial fluctuations during inflation– and also to obtain relevant astrophysical information about the compact sources themselves in a frequency range, ν ∼ 10–200 GHz, where observations have only very recently started to become available. In this paper, we propose a Bayesian maximum a posteriori approach estimation scheme which incorporates prior information about the distribution of the polarisation fraction of extragalactic compact sources between 1 and 100 GHz. We apply this Bayesian scheme to white noise simulations and to more realistic simulations that include CMB intensity, Galactic foregrounds, and instrumental noise with the characteristics of the QUIJOTE (Q U I JOint TEnerife) experiment wide survey at 11 GHz. Using these simulations, we also compare our Bayesian method with the frequentist filtered fusion method that has been already used in the Wilkinson Microwave Anisotropy Probe data and in the Planck mission. We find that the Bayesian method allows us to decrease the threshold for a feasible estimation of P to levels below ∼100 mJy (as compared to ∼500 mJy which was the equivalent threshold for the frequentist filtered fusion). We compare the bias introduced by the Bayesian method and find it to be small in absolute terms. Finally, we test the robustness of the Bayesian estimator against uncertainties in the prior and in the flux density of the sources. We find that the Bayesian estimator is robust against moderate changes in the parameters of the prior and almost insensitive to realistic errors in the estimated photometry of the sources.
A Virgo Environmental Survey Tracing Ionised Gas Emission (VESTIGE)
Authors: Junais  , Boissier S. , Boselli A. , Boquien M. , Longobardi A. , Roehlly Y. , Amram P. , Fossati M. , Cuillandre J.-C. , Gwyn S. , Ferrarese L. , Côté P. , Roediger J. , Lim S. , Peng E. W. , Hensler G. , Trinchieri G. , Koda J. , Prantzos N.
Published: April 2021

Context. The evolution of galaxies depends on their interaction with the surrounding environment. Ultra-diffuse galaxies (UDGs) have been found in large numbers in clusters. We detected a few star-forming blobs in the VESTIGE survey, located at ∼5 kpc from a UDG, namely NGVS 3543, in association with an HI gas cloud AGC 226178, suggesting a recent interaction between this low-surface-brightness system and the surrounding cluster environment.

Aims. We use a complete set of multi-frequency data including deep optical, UV, and narrow-band Hα imaging and HI data to understand the formation process that gave birth to this peculiar system.

Methods. For this purpose, we measured (i) the multi-wavelength radial surface brightness profiles of NGVS 3543 and compared them to the predictions of spectro-photometric models of galaxy evolution in rich clusters; and (ii) the aperture photometry of the blue regions in the vicinity of NGVS 3543 in order to determine their age and stellar mass.

Results. Comparisons of the observations with evolutionary models indicate that NGVS 3543 has undergone a ram-pressure stripping that peaked ∼100 Myr ago, transforming a blue gas-rich UDG into a red gas-poor UDG. Star formation has taken place in the ram pressure stripped gas, the mass of which is ∼108 M⊙, forming star complexes with a typical age of ∼20 Myr and a stellar mass of ∼104 M⊙.

Conclusions. These results suggest that we are observing for the first time the ongoing transformation of a gas-rich UDG into a red and quiescent UDG under the effect of a ram-pressure stripping event. The same process could explain the lack of star-forming UDGs in rich environments observed in several nearby clusters.
Multiscale behaviour of stellar activity and rotation of the planet host Kepler-30
Authors: de Freitas D. B. , Lanza A. F. , da Silva Gomes F. O. , Das Chagas M. L.
Published: April 2021

Context. The Kepler-30 system consists of a G dwarf star with a rotation period of ~16 days and three planets orbiting almost coplanar with periods ranging from 29 to 143 days. Kepler-30 is a unique target with which to study stellar activity and rotation in a young solar-like star accompanied by a compact planetary system.

Aims. We use about 4 yr of high-precision photometry collected by the Kepler mission to investigate the fluctuations caused by photospheric convection, stellar rotation, and starspot evolution as a function of timescale. Our main goal is to apply methods for the analysis of time-series to find the timescales of the phenomena that affect the light variations. We correlate those timescales with periodicities in the star and the planetary system.

Methods. We model the flux rotational modulation induced by active regions using spot modelling and apply the Multifractal Detrending Moving Average algorithm in standard and multiscale versions to analyse the behaviour of variability and light fluctuations that can be associated with stellar convection and the evolution of magnetic fields on timescales ranging from less than 1 day up to about 35 days. The light fluctuations produced by stellar activity can be described by the multifractal Hurst index that provides a measure of their persistence.

Results. The spot modelling indicates a lower limit to the relative surface differential rotation of ΔΩ∕Ω ~ 0.02 ± 0.01 and suggests a short-term cyclic variation in the starspot area with a period of ~34 days, which is close to the synodic period of 35.2 days of the planet Kepler-30b. By subtracting the two time-series of the simple aperture photometry and pre-search data conditioning Kepler pipelines, we reduce the rotational modulation and find a 23.1-day period close to the synodic period of Kepler-30c. This period also appears in the multifractal analysis as a crossover of the fluctuation functions associated with the characteristic evolutionary timescales of the active regions in Kepler-30 as confirmed by spot modelling. These procedures and methods may be greatly useful for analysing current TESS and future PLATO data.
Stellar collisions in flattened and rotating Population III star clusters
Authors: Vergara M. Z. C. , Schleicher D. R. G. , Boekholt T. C. N. , Reinoso B. , Fellhauer M. , Klessen R. S. , Leigh N. W. C.
Published: April 2021

Fragmentation often occurs in disk-like structures, both in the early Universe and in the context of present-day star formation. Supermassive black holes (SMBHs) are astrophysical objects whose origin is not well understood; they weigh millions of solar masses and reside in the centers of galaxies. An important formation scenario for SMBHs is based on collisions and mergers of stars in a massive cluster with a high stellar density, in which the most massive star moves to the center of the cluster due to dynamical friction. This increases the rate of collisions and mergers since massive stars have larger collisional cross sections. This can lead to a runaway growth of a very massive star which may collapse to become an intermediate-mass black hole. Here we investigate the dynamical evolution of Miyamoto-Nagai models that allow us to describe dense stellar clusters, including flattening and different degrees of rotation. We find that the collisions in these clusters depend mostly on the number of stars and the initial stellar radii for a given radial size of the cluster. By comparison, rotation seems to affect the collision rate by at most 20%. For flatness, we compared spherical models with systems that have a scale height of about 10% of their radial extent, in this case finding a change in the collision rate of less than 25%. Overall, we conclude that the parameters only have a minor effect on the number of collisions. Our results also suggest that rotation helps to retain more stars in the system, reducing the number of escapers by a factor of 2−3 depending on the model and the specific realization. After two million years, a typical lifetime of a very massive star, we find that about 630 collisions occur in a typical models withN = 104,R = 100R⊙and a half-mass radius of 0.1 pc, leading to a mass of about 6.3 × 103 M⊙for the most massive object. We note that our simulations do not include mass loss during mergers or due to stellar winds. On the other hand, the growth of the most massive object may subsequently continue, depending on the lifetime of the most massive object.
Magnetic field inference in active region coronal loops using coronal rain clumps
Authors: Kriginsky M. , Oliver R. , Antolin P. , Kuridze D. , Freij N.
Published: April 2021

Aims. We aim to infer information about the magnetic field in the low solar corona from coronal rain clumps using high-resolution spectropolarimetric observations in the Ca II 8542 Å line obtained with the Swedish 1 m Solar Telescope.

Methods. The weak-field approximation (WFA) provides a simple tool to obtain the line-of-sight component of the magnetic field from spectropolarimetric observations. We adapted a method developed in a previous paper in order to assess the different conditions that must be satisfied in order to properly use the WFA for the data at hand. We also made use of velocity measurements in order to estimate the plane-of-the-sky magnetic field component, so that the magnetic field vector could be inferred.

Results. We have inferred the magnetic field vector from a data set totalling 100 spectral scans in the Ca II 8542 Å line, containing an off-limb view of the lower portion of catastrophically cooled coronal loops in an active region. Our results, albeit limited by the cadence and signal-to-noise ratio of the data, suggest that magnetic field strengths of hundreds of Gauss, even reaching up to 1000 G, are omnipresent at coronal heights below 9 Mm from the visible limb. Our results are also compatible with the presence of larger magnetic field values such as those reported by previous works. However, for large magnetic fields, the Doppler width from coronal rain is not that much larger than the Zeeman width, thwarting the application of the WFA. Furthermore, we have determined the temperature, T, and microturbulent velocity, ξ, of coronal rain clumps and off-limb spicules present in the same data set, and we have found that the former ones have narrower T and ξ distributions, their average temperature is similar, and coronal rain has microturbulent velocities smaller than those of spicules.
Wind suppression by X-rays in Cygnus X-3
Authors: Vilhu O. , Kallman T. R. , Koljonen K. I. I. , Hannikainen D. C.
Published: April 2021

Context. The radiatively driven wind of the primary star in wind-fed X-ray binaries can be suppressed by the X-ray irradiation of the compact secondary star. This causes feedback between the wind and the X-ray luminosity of the compact star.

Aims. We aim to estimate how the wind velocity on the face-on side of the donor star depends on the spectral state of the high-mass X-ray binary Cygnus X-3.

Methods. We modeled the supersonic part of the wind by computing the line force (force multiplier) with the Castor, Abbott & Klein formalism and XSTAR physics and by solving the mass conservation and momentum balance equations. We computed the line force locally in the wind considering the radiation fields from both the donor and the compact star in each spectral state. We solved the wind equations at different orbital angles from the line joining the stars and took the effect of wind clumping into account. Wind-induced accretion luminosities were estimated using the Bondi-Hoyle-Lyttleton formalism and computed wind velocities at the compact star. We compared them to those obtained from observations.

Results. We found that the ionization potentials of the ions contributing the most to the line force fall in the extreme-UV region (100–230 Å). If the flux in this region is high, the line force is weak, and consequently, the wind velocity is low. We found a correlation between the luminosities estimated from the observations for each spectral state of Cyg X-3 and the computed accretion luminosities assuming moderate wind clumping and a low mass of the compact star. For high wind clumping, this correlation disappears. We compared the XSTAR method used here with the comoving frame method and found that they agree reasonably well with each other.

Conclusions. We show that soft X-rays in the extreme-UV region from the compact star penetrate the wind from the donor star and diminish the line force and consequently the wind velocity on the face-on side. This increases the computed accretion luminosities qualitatively in a similar manner as observed in the spectral evolution of Cyg X-3 for a moderate clumping volume filling factor and a compact star mass of a few (2–3) solar masses.
Potential Development Strategy for Attraction and Community-based Agrotourism in Lebakmuncang Village
Authors: Djuwendah E , Karyani T , Wulandari E
Published: April 2021

Lebakmuncang is a tourism village in Ciwidey, Bandung, West Java, Indonesia, which has potential for natural and cultural resources supporting agro-tourism development. In recent years there has been a decline in tourist visits. The research objectives were to analyze the agro-tourism potential, to analyze visitor’s perceptions of the attractiveness of agro-tourism and agro-tourism development strategies. The research design used descriptive quantitative. Fifty tourists were selected by accidental sampling, and ten informants were selected purposively. Data analysis technique used Likert scale and SWOT matrix. The results showed Lebakmuncang village has variety agricultural commodities, dairy farming, and coffee processing business that have potential to support agro-tourism development; visitors’ perceptions of attraction and ancillary services was excellent. Visitors’ perception of amenities and accessibility was good. Strategies that can be carried out in developing agro-tourism are: (1) increasing community involvement, (2) adding animal husbandry attractions and coffee processing in tour packages, (3) adding supporting facilities that are not yet available, (4) synchronizing agro-tourism development programs with stakeholders, (5) training human resources in internet technology-based tourism management, (6) partnerships in promotion and marketing with travel agents, (7) improving service quality, (8) creating community-based and sustainable agro-tourism branding, and (9) promotional cooperation with other tourist objects..
The Impact of IUU Fishing Policy (Moratorium License of Fishery Commerce) to the level of Employment of Maritime and Fishery Vocational Schools Graduates
Authors: Susanto AB
Published: April 2021

The limited capacity of human resources (HR) that is competent in their field often causes the less than optimal utilization of the marine and fisheries resources in Indonesia. Maritime and Fishery Vocational Schools (MFVS) can be the solution to this problem, as they are expected to generate capable and competitive human resources; thus, utilizing and sustainably managing the vast marine resources in Indonesia, and in turn improving the efforts taken to advance Indonesian people’s welfare. However, the level of employment for MFVS graduates in Indonesia is still limited to large scale fishing activities. Additionally, since the launch of Moratorium License of Fishery Commerce of Fishery States in the Republic of Indonesia (56/PERMEN-KP/2014) by the Indonesian Ministry of Marine and Fisheries (IMMaF), most fishery companies have ceased to operate. The study aimed to determine the impact caused by this regulation against the level of employment of MFVS graduates, as well as the scheme of policies that should be applied to maximize the human resources in the field of marine and fisheries. This research used a qualitative method, where the descriptive analysis was used as a primary tool of analysis. The results of the analysis indicated that the trend of employment of MFVS graduates shifted after the enactment of this policy. The lack of synergy between policies in the field of marine and fisheries and policies in the field of education and transportation resulted in the difficulty of MFVS graduates to achieve a good career in this field..
Assessment tool to understand the readiness of Batik SMEs for Green Industry
Authors: Kusumawardani Sylvia D. A. , Sunardi  , Kurnani Tb Benito A.
Published: April 2021

Batik industries in general are classified as Small Medium Enterprises (SMEs) with major problems related to environmental management and inefficiency of resource consumption. These problems cannot be solved by end of pipe approaches, instead, management since the upstream of the production process needs to be employed. The green industry is a concept that relevant to those problems since this prioritizes efficient resource use. The Indonesian government has developed the Green Industry Standard as a tool to assess the soundness of the industries and to promote the capability to compete in the global market. Globally, there are several concepts similar to the green industry, for example, eco-innovation and resource efficient and cleaner production (RECP) that have their own assessment tools to measure the readiness of the industries. This study aims to elaborate aspects in Green Industry Standard with other assessment tools to understand the readiness of Batik industries through Ministry of Industry Regulation Number 39 of 2019 regarding Green Industry Standard for Batik Industries. Finally, the new assessment tool was developed consisting of four major aspects, namely company characterization, description of the business model, analysis input and output, and readiness area. Each aspect included some criteria and required relevant data that need to be collected for assessment of the readiness of Batik SMEs in future research.
Using Daphnia magna Straus to monitor toxicity of sustainable oil sludge bio-phytoremediation
Authors: Rossiana Nia , Kaniawati Rosada Keukeu , Natasha Almapangesti Monica , Dhahiyat Yayat
Published: April 2021

Oil sludge (OS) is the toxic product of various oil refinery processes. Oil sludge biophytoremediation is sustainable remediation efforts were conducted to reduce OS toxicity level and they also need to be monitored through toxicity test. In this study, the toxicants were OS postbiophytoremediation for 24 months (OS24) and 40 months (OS40), and were tested to Daphnia magna. The toxicity test consisted of Range Finding Test, acute and chronic toxicity test. The purpose of this research is to obtain the LC50 value of each OS and the chronic effects shown by D. magna. The method in this study was experimental with Completely Randomized Design (CRD). The LC50-96 hours values were calculated from 50% of dead individuals while D. magna reproduction was calculated from the number of neonates (offspring) produced within three weeks. The LC50 of OS24 and OS40 were 0.042 ppm and 0.366 ppm respectively. Both were categorized as ‘extremely toxic’ refer to Swan, 1994, observed chronic effects were reproduction delays and a decrease in the number of neonates.
Feasibility Study of the Development of Grand Forest Park in Gunung Wayang, Bandung Regency, West Java, Indonesia
Authors: Qurrataayun R. , Parikesit  , Withaningsih S.
Published: April 2021

Gunung Wayang area is located inthe upstream part of the Citarum river basin. Forest preservation in the upper Citarum watershed is very important to maintain its sustainability. However, along with the increasing population and increasing demand for land, Gunung Wayang forest area faces increasing threats and disturbances from various deforestation activities, such as encroachment, illegal logging, and forest land conversion, which then worsening the condition of the Citarum watershed. One of the initiatives of the Government of Bandung Regency is the development of Grand Forest Park at Gunung Wayang. Therefore, this research aimed to identify, study, and analyze the feasibility of developing Grand Forest Park in this location. The method used was mixed-methods with a parallel convergent mixed approach. The results of the study indicate that there were several types of plants and animals with important conservation status. Grand Forest Park will increase many new economic opportunities and decrease deforestation activities. However, because nearly 70% of the people living around the area are farmers cultivating land in forest areas, therefore a comprehensive approach is needed to avoid conflicts related to land ownership.
Economic assessment of WECS for water pumping systems in the North Region of Cameroon
Authors: Kidmo Dieudonné Kaoga , Bogno Bachirou , Deli Kodji , Aillerie Michel , Ngoussandou Bello Pierre
Published: April 2021

This paper analyses the potential utilization of wind electric pumping for water distribution in off-grid locations of the North Region of Cameroon (NRoC), using ground measured data as well as long-term satellite-derived data. Furthermore, this paper puts emphasis on statistical indexes of accuracy for the comparison of measured (2007–2012) and long-term satellite-derived (2005–2020) data. The outcome of this study clearly indicates that long-term satellite-derived data, obtained through the Prediction of Worldwide Renewable Energy Resources, can be considered as a viable alternative to missing site-specific data from ground stations, mainly in developing countries. The accuracy of satellite-based wind resource is deemed sufficient to provide a reasonable assessment in the initial phase of wind project planning, before in situ measurements with high accuracy are available. To model wind speeds characteristics, the energy pattern factor method (EPF) has been utilized as one of the reliable Weibull distribution methods for the assessment of wind energy potential at desired turbines heights in the selected locations. Five 20-kW pitch-controlled wind turbines (WT) with a hub height of 30 m, are considered to evaluate the power output and energy produced. Volumetric flow rates and costs of water produced are estimated. The results showed that, out of the eight chosen locations, Figuil shows the best combination of capacity factors (CF) and costs of energy (COE), while the site of Poli displays the worst values of CF and COE, no matter which of the five WT is employed. Thus, selecting WT for low wind speeds regimes, should require to combine location wind resource and WT characteristics such as lower cut-in wind speed (1.5 m/s) as well as lower rated wind speed (8.0 m/s) in order to successfully and affordably implement the wind technology in the NRoC.
Single-manufacturer and multi-retailer supply chain model with pre-payment based partial free transportation
Authors: Manna Amalesh Kumar , Mondal Rajan , Akbar Shaikh Ali , Ali Irfan , Bhunia Asoke Kumar
Published: April 2021

In this paper, a supply chain model between a manufacturing firm and a group of retailers has been developed. Manufacturing firm produces simultaneously both perfect and imperfect items which are separated by screening process. Then the perfect items are transferred to the retailers’ showroom/warehouse located in different places and a part of imperfect items are repaired by rework process. Retailers receive the products from the manufacturer with paying partial pre-payment to ensure the replenishment of order. On the other hand, the manufacturer provides partial free transportation facility to the retailers due to pre-payment. The corresponding problem has been formulated mathematically as a profit maximization problem and then solved it analytically. As an illustration of this supply chain model, three numerical examples have been considered and solved. Finally, post optimality analyses have been carried out to investigate the effects of changes of different parameters on the optimal policy.
Geomagnetically induced currents during the 07–08 September 2017 disturbed period: a global perspective
Authors: Clilverd Mark A. , Rodger Craig J. , Freeman Mervyn P. , Brundell James B. , Mac Manus Daniel H. , Dalzell Michael , Clarke Ellen , Thomson Alan W. P. , Richardson Gemma S. , MacLeod Finlay , Frame Ian
Published: April 2021

Measurements from six longitudinally separated magnetic observatories, all located close to the 53° mid-latitude contour, are analysed. We focus on the large geomagnetic disturbance that occurred during 7 and 8 September 2017. Combined with available geomagnetically induced current (GIC) data from two substations, each located near to a magnetic observatory, we investigate the magnetospheric drivers of the largest events. We analyse solar wind parameters combined with auroral electrojet indices to investigate the driving mechanisms. Six magnetic field disturbance events were observed at mid-latitudes with dH/dt > 60 nT/min. Co-located GIC measurements identified transformer currents >15 A during three of the events. The initial event was caused by a solar wind pressure pulse causing largest effects on the dayside, consistent with the rapid compression of the dayside geomagnetic field. Four of the events were caused by substorms. Variations in the Magnetic Local Time of the maximum effect of each substorm-driven event were apparent, with magnetic midnight, morning-side, and dusk-side events all occurring. The six events occurred over a period of almost 24 h, during which the solar wind remained elevated at >700 km s−1, indicating an extended time scale for potential GIC problems in electrical power networks following a sudden storm commencement. This work demonstrates the challenge of understanding the causes of ground-level magnetic field changes (and hence GIC magnitudes) for the global power industry. It also demonstrates the importance of magnetic local time and differing inner magnetospheric processes when considering the global hazard posed by GIC to power grids.
Acoustic lens can help generate longer and cleaner sound jets
Authors: Yiu Yuen
Published: April 2021

Using a 3D-printed generalized Luneburg lens, researchers created an acoustic lens that can generate sound jets twice as long as its competitors.
Element-specific investigations of ultrafast dynamics in photoexcited Cu2ZnSnS4 nanoparticles in solution
Authors: Rein Christian , Uhlig Jens , Carrasco-Busturia David , Khalili Khadijeh , Gertsen Anders S. , Moltke Asbjørn , Zhang Xiaoyi , Katayama Tetsuo , Lastra Juan Maria García , Nielsen Martin Meedom , Adachi Shin-Ichi , Haldrup Kristoffer , Andreasen Jens Wenzel
Published: April 2021

Ultrafast, light-induced dynamics in copper–zinc–tin–sulfide (CZTS) photovoltaic nanoparticles are investigated through a combination of optical and x-ray transient absorption spectroscopy. Laser-pump, x-ray-probe spectroscopy on a colloidal CZTS nanoparticle ink yields element-specificity, which reveals a rapid photo-induced shift of electron density away from Cu-sites, affecting the molecular orbital occupation and structure of CZTS. We observe the formation of a stable charge-separated and thermally excited structure, which persists for nanoseconds and involves an increased charge density at the Zn sites. Combined with density functional theory calculations, the results provide new insight into the structural and electronic dynamics of CZTS absorbers for solar cells.
Engineering plasmonic hot carrier dynamics toward efficient photodetection
Authors: Zhu Yisong , Xu Hongxing , Yu Peng , Wang Zhiming
Published: April 2021

Nonradiative decay of surface plasmons (SPs) is usually considered an unwanted process. However, recent studies have proven that hot carriers generated from nonradiative SP decay can be used for photodetection that circumvents the bandgap limitation in semiconductors. The major problem plaguing the plasmonic hot carrier photodetectors stems from the low quantum efficiency. In this review, we discuss recent progress of engineering plasmonic hot carrier dynamics and describe a host of plasmon-enhanced photodetectors, including optical antenna-based photodetectors, planar photodetectors, photodetectors coupled with 2D materials, functionalized photodetectors, photodetectors for integrated nanophotonics, and hot-hole photodetectors. Finally, we herein highlight some new directions in the plasmonic photodetection.
Hydrodynamical model of QED cascade expansion in an extremely strong laser pulse
Authors: Samsonov A. S. , Kostyukov I. Yu. , Nerush E. N.
Published: April 2021

The development of a self-sustained quantum electrodynamical (QED) cascade in a single strong laser pulse is studied analytically and numerically. A hydrodynamical approach is used to construct an analytical model of cascade evolution, which includes the key features of the cascade observed in 3D QED particle-in-cell (QED-PIC) simulations, such as the magnetic field dominance in the cascade plasma and laser energy absorption. The equations of the model are derived in closed form and solved numerically. Direct comparison between the solutions of the model equations and 3D QED-PIC simulations shows that our model is able to describe the complex nonlinear process of cascade development qualitatively well. Various regimes of the interaction based on the intensity of the laser pulse are revealed in both the solutions of the model equations and the results of the QED-PIC simulations.
Equilibrium approach for modeling erosional failure of granular dams
Authors: Roy Biswas Tirtha , Begam Sazeda , Dey Subhasish , Sen Dhrubajyoti
Published: April 2021

Erosional failure of granular dams by an overtopping body of water is investigated using a depth-averaged morphodynamic model. The transport of sediment by the flow assumes the sediment flux to remain in equilibrium with the local bed shear stress. Accordingly, the shallow-water hydrodynamic equations are coupled with the Exner equation for mass conservation of the sediment. The system of equations is solved using a fully coupled well-balanced finite volume method, second-order accurate in time and space. The effect of the steep bed slope of a dam face is incorporated into both the hydrodynamics and sediment transport equations, leading to improved predictions. Comparison with results obtained from nonequilibrium sediment transport models indicates that such models perform poorly while predicting the bed evolution near the toe of an eroding dam. Observations from experimental studies demonstrate that the amount of sediment entrained by the flow is not significant, except during the initial moments of failure. This suggests that the vertical exchange of mass between the bed and the flow layer, as assumed by the nonequilibrium models, may not be completely valid during the failure. The equilibrium model results, reproducing the key flow features of the overtopping failure process, are validated by experimental measurements. The study provides fresh insights into the sediment transport processes associated with the erosion of a granular dam by overtopping, establishes the appropriateness of the equilibrium approach for its numerical modeling, and proposes a well-balanced second-order accurate solution technique for solving the resulting coupled equations of flow and sediment transport.
Determination of Schottky barrier height of graphene electrode on AlGaN/GaN heterostructure
Authors: Pandit Bhishma , Kim Jaeho , Cho Jaehee
Published: April 2021

A graphene Schottky contact was fabricated on an AlGaN/GaN heterostructure and subsequently analyzed. The calculated and experimentally measured Schottky barrier heights (SBHs) determined using the theoretical Schottky–Mott model, the thermionic emission model, the temperature-dependent current–voltage measurement, and the capacitance–voltage measurement were observed to be inconsistent, which was attributed to the ambiguities in both the Schottky contact area and the Richardson constant. While excluding the effects of these two factors, an SBH of 0.15 eV was determined by the temperature-dependent Richardson plot. This result was confirmed by calculating the inverse of the square of the measured capacitance with consideration of the threshold voltage required to deplete the two-dimensional electron gas under the Schottky contact.
Spin reorientation transition in ultrathin Co films on the vicinal surface Au(788)
Authors: Rosa R. J. G. , Souza R. L. , Gomes G. F. M. , Paniago R. M. , Martins M. D.
Published: April 2021

In this work, we investigate the structural, morphological and magnetic properties of epitaxial Cobalt ultrathin films grown on the vicinal surface Au(788). The aim was to study the magnetization reversal and determine the influence of the regular arrangement of atomic steps, typical of a vicinal surface. The influence of the Co thickness on the spin reorientation from out-of-plane to in-plane magnetization were investigated by means of the magneto-optical Kerr effect (MOKE). Preparation and surface quality of the Co films were characterized using the surface experimental techniques LEED and STM. A smooth spin reorientation transition, between 8 and 12 atomic monolayers (ML) of Co, was observed from out-of-plane magnetization, between 5 ML and 12 ML of Co, to in-plane magnetization, above 13 ML of Co. Furthermore, the angular dependence of the magnetic hysteresis loops indicates uniaxial magnetic anisotropy parallel to the atomic steps in the surface plane of the system Au/Co/Au(788) for thicknesses between 13 ML and 20 ML of Co.
Epigenetic reprogramming of tumor cell–intrinsic STING function sculpts antigenicity and T cell recognition of melanoma
Authors: Falahat Rana , Berglund Anders , Putney Ryan M. , Perez-Villarroel Patricio , Aoyama Shota , Pilon-Thomas Shari , Barber Glen N. , Mulé James J.
Published: April 2021

Significance

Although cancer immunotherapies have shown potential in inducing durable tumor regression in patients with metastatic melanoma, their efficacy remains highly variable and patient specific. Here, we present one strategy to overcome resistance to T cell–based immunotherapies by pharmacologically modulating the STING pathway, a relatively common suppressed DNA-sensing pathway in human melanomas. We show that rescue of this pathway in human melanoma cells using a clinically available DNA methylation inhibitor can augment their antigenicity and recognition by tumor-infiltrating lymphocytes. These findings have important clinical implications for the development of optimal therapeutic protocols that consider the status of tumor-intrinsic STING activity and provide a strategy to design clinical interventions using T cell–based immunotherapies with appropriate patient selection in melanoma.
Learning loss due to school closures during the COVID-19 pandemic
Authors: Engzell Per , Frey Arun , Verhagen Mark D.
Published: April 2021

Significance

School closures have been a common tool in the battle against COVID-19. Yet, their costs and benefits remain insufficiently known. We use a natural experiment that occurred as national examinations in The Netherlands took place before and after lockdown to evaluate the impact of school closures on students’ learning. The Netherlands is interesting as a “best-case” scenario, with a short lockdown, equitable school funding, and world-leading rates of broadband access. Despite favorable conditions, we find that students made little or no progress while learning from home. Learning loss was most pronounced among students from disadvantaged homes.
One-step synthesis of fluorescence-enhanced carbon dots for Fe (III) on−off−on sensing, bioimaging and light-emitting devices
Authors: An Jia , Liu Guoyi , Chen Meizhu , Hu Yongqin , Chen Rubing , Lyu Ying , Zhang Chao , Liu Yufei
Published: April 2021

Carbon quantum dots (CDs), as one of the most potential fluorescent sensing materials, have attracted lots of attention in recent years. However, the low quantum yields, complicated separation and purification procedures have limited its application and large-scale production. In this paper, a facile and universal method was successfully developed to synthesize CDs-silica (SiO2) spheres composites (CS composites), which not only demonstrates 10-fold fluorescence enhancement compared with single CDs but also enables the purification with a simple centrifugation step. Meanwhile, fabricated composites also presented superior photoluminescence (PL) stability and high PL intensity, even in some tough environments such as acid/alkali aqueous solution, high/low temperature, and high ion concentration aqueous solution. This simple, fast, low-cost, and efficient synthesis method would potentially expand the application of CDs for clinical analysis, optical sensing (ferric ion (Fe3+) and pyrophosphate), bioimaging and light-emitting diodes (LEDs).
Structural, dielectric, magnetic and optical properties of double perovskite oxide Sm2NiMnO6 nanoparticles synthesized by a sol−gel process
Authors: Leng Kai , Xia Weiren , Tang Qingkai , Yang Li , Xie Yuting , Wu Zhiwei , Yi Kang , Zhu Xinhua
Published: April 2021

Here we report on the structural, dielectric, magnetic and optical properties of double perovskite Sm2NiMnO6 (SNMO) nanoparticles synthesized by a sol−gel method. Structural Reitveld refinements on x-ray powder diffraction data revealed that the SNMO nanoparticles crystallized in a monoclinic crystal structure with P21/n space group. SEM and (HR)TEM images revealed the phase purity and single-crystalline nature of the SNMO nanoparticles. XPS spectra confirmed the presence of Sm3+, Ni2+ and Mn4+ ions in the SNMO nanoparticles and oxygen in the forms of lattice oxygen and the hydroxyls species. SNMO ceramics exhibited relaxor-type dielectric behavior, well fitted by modified Curie−Weiss law. Such dielectric behavior originated from the interactions of random dipoles arisen from the B-site cations disorder accompanied with the variations in local electric fields and local strain fields due to the different radii of B-site cations, and/or the virtual electrons hopping between the Ni2+ and Mn4+ cations. Magnetic data demonstrate the variations of the magnetic transitions at low temperatures and the spin glass-like behavior below 11 K, which is attributed to the spin fluctuations induced by the competing interactions between the ferromagnetic (FM) and antiferromagnetic phases. Large positive Curie−Weiss temperature (θ
p) indicates the dominant FM super-exchange interactions in the SNMO samples. The SNMO nanoparticles have a direct optical band gap of 1.42 eV, close to 1.34 eV in a single junction solar cell. That enables the SNMO nanoparticles to be useful for solar cell absorbers.
TMP origami jumping mechanism with nonlinear stiffness
Authors: Sadeghi Sahand , Allison Samuel R , Bestill Blake , Li Suyi
Published: April 2021

Via numerical simulation and experimental assessment, this study examines the use of origami folding to develop robotic jumping mechanisms with tailored nonlinear stiffness to improve dynamic performance. We propose a multifunctional structure where the load-carrying skeleton of the structure acts as the energy-storage medium at the same time. Specifically, we use Tachi–Miura polyhedron (TMP) bellow origami—which exhibits a nonlinear ‘strain-softening’ force-displacement curve—as a jumping robotic skeleton with embedded energy storage. TMP’s nonlinear stiffness allows it to store more energy than a linear spring and offers improved jumping height and airtime. Moreover, the nonlinearity can be tailored by directly changing the underlying TMP crease geometry. A critical challenge is to minimize the TMP’s hysteresis and energy loss during its compression stage right before jumping. So we used the plastically annealed lamina emergent origami (PALEO) concept to modify the TMP creases. PALEO increases the folding limit before plastic deformation occurs, thus improving the overall strain energy retention. Jumping experiments confirmed that a nonlinear TMP mechanism achieved roughly 9% improvement in air time and a 13% improvement in jumping height compared to a ‘control’ TMP sample with a relatively linear stiffness. This study’s results validate the advantages of using origami in robotic jumping mechanisms and demonstrate the benefits of utilizing nonlinear spring elements for improving jumping performance. Therefore, they could foster a new family of energetically efficient jumping mechanisms with optimized performance in the future.
Polarized QED cascades
Authors: Seipt Daniel , Ridgers Christopher P , Del Sorbo Dario , Thomas Alec G R
Published: April 2021

By taking the spin and polarization of the electrons, positrons and photons into account in the strong-field QED processes of nonlinear Compton emission and pair production, we find that the growth rate of QED cascades in ultra-intense laser fields can be substantially reduced. While this means that fewer particles are produced, we also found them to be highly polarized. We further find that the high-energy tail of the particle spectra is polarized opposite to that expected from Sokolov–Ternov theory, which cannot be explained by just taking into account spin-asymmetries in the pair production process, but results significantly from ‘spin-straggling’. We employ a kinetic equation approach for the electron, positron and photon distributions, each of them spin/polarization-resolved, with the QED effects of photon emission and pair production modelled by a spin/polarization dependent Boltzmann-type collision operator. For photon-seeded cascades, depending on the photon polarization, we find an excess or a shortage of particle production in the early stages of cascade development, which provides a path towards a controlled experiment. Throughout this paper we focus on rotating electric field configuration, which represent an idealized model and allows for a straightforward interpretation of the observed effects.
On interplay of surface tension and inertial stabilization mechanisms in the stable and unstable interface dynamics with the interfacial mass flux
Authors: Ilyin D V , Goddard W A , Abarzhi I I , Abarzhi S I
Published: April 2021

Non-equilibrium dynamics of interfaces and mixing are omnipresent in fluids, plasmas and materials, in nature and technology, at astrophysical and at molecular scales. This work investigates dynamics of an interface separating fluids of different densities and having interfacial mass flux, and being influenced by the acceleration and the surface tension. We derive solutions for the interface dynamics conserving mass, momentum and energy, find the critical acceleration values separating stable and unstable regimes, and reveal the macroscopic inertial mechanism as primary mechanism of the interface stabilization. We show that while the surface tension influences only the interface, its presence leads to formation of vortical structures in the bulk. For large accelerations the conservative dynamics is unstable, leading to the growth of interface perturbations and the growth of the interface velocity. This new instability can be unambiguously discerned from other instabilities; for strong accelerations it has the fastest growth-rate and the largest stabilizing surface tension value when compared to Landau-Darrieus and Rayleigh-Taylor instabilities. We further find the values of initial perturbation wavelengths at which the conservative dynamics can be stabilized and at which it has the fastest growth. Our results agree with existing observations, identify extensive theory benchmarks for future experiments and simulations, and outline perspectives for application problems in nature and technology.
Nonlinear propagation dynamics of Gaussian beams in fractional Schrödinger equation
Authors: Jiao Ruiyun , Zhang Wenqian , Dou Lichao , Liu Bing , Zhan Kaiyun , Jiao Zhiyong
Published: April 2021

We investigated theoretically the nonlinear propagation dynamics of Gaussian beams in the fractional Schrödinger equation (FSE). When the nonlinearity is introduced into FSE without invoking an external potential, the evolution behaviors of incident Gaussian beams are modulated regularly and some novel phenomena arise. In the one-dimensional case, by changing the values of Kerr or saturated nonlinear coefficient, specific localized or diffracted phenomena appear in the corresponding intensity region, where the splitting angle of one-dimensional incident beam will be modulated flexibly to become larger or smaller in weak nonlinear region, besides, when the self-focusing strength is moderate, the energy of the beam is highly concentrated to form a breathing soliton structure. For two-dimensional case, Kerr or saturated nonlinearity will modulate the energy to the middle or edge in a certain nonlinear region, corresponding to the decrease or increase of the conical diffraction radius, it should be noted that there are two evolution periods under the saturated self-focusing nonlinearity. The work may provide more possibilities for beam modulation in FSE from a nonlinear perspective.