bluuebunny/crossref_metadata_2025 huggingface dataset:
Low-pass filtering compensation in common-path digital holographic microscopy
Authors: Dong Jie , Yetisen Ali K. , Dong Xingchen , Pöller Franziska , Jakobi Martin , Liu Zhanwei , Salazar Bloise Félix , Koch Alexander W.
Published: September 2020

A low-pass filtering compensation (LPFC) method is proposed to compensate for phase aberrations in point diffraction-based common-path digital holographic microscopy. This method estimates the phase aberration from the object hologram by Fourier transform and low-pass spatial filtering. The estimated phase aberration is subtracted from the object phase image to achieve single-hologram phase compensation. The accuracy and capability of LPFC for phase compensation were demonstrated by experiments on a Ronchi grating and a human blood smear. LPFC provides phase compensation for both smooth objects and objects containing abrupt edges, in the special case of a system with relatively high-frequency objects and low-frequency slight phase aberrations. LPFC operates without the need for fitting procedures, iterative steps, or prior knowledge of the optical parameters, which substantially simplifies the process of phase compensation in quantitative phase imaging.
How does three-dimensional canopy geometry affect the front propagation of a gravity current?
Authors: Zhou Jian , Venayagamoorthy Subhas K.
Published: September 2020

Large-eddy simulations are performed to investigate how three-dimensional canopy geometry affects the front propagation of an incoming gravity current under a given initial forcing. A regular array of rigid square cylinders are used to represent the distributed canopy elements. It is shown that the conventional geometrical parameter of submerged canopies in constant-density flows (ah, where a is the frontal area per canopy volume and h is the canopy height) is misleading when applied to buoyancy-driven flows due to the additional complexity arising from the internal density gradients. Instead, the present study suggests a new geometrical framework consisting of a canopy density (ϕ) and a canopy-to-current height ratio (h̃), which can jointly provide an unambiguous description of the state of the current–canopy interaction. Two propagation regimes of the gravity current are identified, either along the channel bed (through-flow) or above the canopy’s top boundary (over-flow). Our analysis reveals that ϕ and h̃ counteract each other’s effect on the transition of flow regimes. Large ϕ implies a strong suppression of horizontal advection within the canopy and thus promotes the through-to-over flow transition; in contrast, large h̃ tends to promote the over-to-through flow transition due to the lack of sufficient potential energy to overcome the height jump. The end product is a complex variation pattern of a propagation regime and front velocity in the two-dimensional ϕ–h̃ parameter space.
Structural and electronic properties of 2D (graphene, hBN)/H-terminated diamond (100) heterostructures
Authors: Mirabedini Pegah S. , Debnath Bishwajit , Neupane Mahesh R. , Alex Greaney P. , Glen Birdwell A. , Ruzmetov Dmitry , Crawford Kevin G. , Shah Pankaj , Weil James , Ivanov Tony. G.
Published: September 2020

We report a first-principles study of the structural and electronic properties of two-dimensional (2D) layer/hydrogen-terminated diamond (100) heterostructures. Both the 2D layers exhibit weak van-der-Waals (vdW) interactions and develop rippled configurations with the H-diamond (100) substrate to compensate for the induced strain. The adhesion energy of the hexagonal boron nitride (hBN) layer is slightly higher, and it exhibits a higher degree of rippling compared to the graphene layer. A charge transfer analysis reveals a small amount of charge transfer from the H-diamond (100) surface to the 2D layers, and most of the transferred charge was found to be confined within the vdW gap. In the graphene/H-diamond (100) heterostructure, the semi-metallic characteristic of the graphene layer is preserved. On the other hand, the hBN/H-diamond (100) heterostructure shows semiconducting characteristics with an indirect bandgap of 3.55 eV, where the hBN layer forms a Type-II band alignment with the H-diamond (100) surface. The resultant conduction band offset and valence band offset are 0.10 eV and 1.38 eV, respectively. A thin layer of hBN offers a defect-free interface with the H-diamond (100) surface and provides a layer-dependent tunability of electronic properties and band alignment for surface-doped diamond field effect transistors.
Transport phenomena in a differentially heated lid-driven cavity: A study using multi-relaxation-time thermal lattice Boltzmann modeling
Authors: Samanta Runa , Chattopadhyay Himadri , Guha Chandan
Published: September 2020

In this study, investigation of mixed convection phenomena in a lid driven square cavity with heated side walls is carried out. The left and right walls are maintained at different constant temperatures, while the upper and bottom walls are thermally insulated. The left wall temperature is higher than the cavity fluid temperature, and the right wall is maintained at the initial fluid temperature. Transport phenomena inside the cavity within a wide parametric range are investigated. The parameters include the Reynolds number (10 ≤ Re ≤ 1000), the Prandtl number (0.01 ≤ Pr ≤ 50), and the Richardson number (0.01 ≤ Ri ≤ 10). It was observed that the flow is induced in the cavity by a shear force resulting from the motion of the upper lid combined with the buoyancy force due to the temperature difference in the cavity. The effects of Re, Pr, and Ri within the cavity were observed simultaneously. The numerical simulations were carried out using the thermal lattice Boltzmann method with multi-relaxation time collision model. The present investigation generates a benchmark dataset for the average Nusselt number (Nuavg) with varying Re, Pr, and Ri within the laminar flow regime. Results show that heat transfer from the side wall is not affected significantly by change in Pr in low levels of Ri, but as Ri increases, average Nu increases significantly. It is also observed that the average value of Nu increases with Pr and Re at a particular value of Ri. However, at a given Ri, for Re above 500 and Pr over 10, the Nu value remains unaffected by change in Re and Pr, which defines the limiting heat transfer in the laminar regime.
Enhancing sensitivity of lateral flow assay with application to SARS-CoV-2
Authors: Peng Tao , Liu Xiangpei , Adams L. Garry , Agarwal Girish , Akey Bruce , Cirillo Jeffrey , Deckert Volker , Delfan Sahar , Fry Edward , Han Zehua , Hemmer Philip , Kattawar George , Kim Moochan , Lee Ming-Che , Lu Chaoyang , Mogford Jon , Nessler Reed , Neuman Ben , Nie Xiaoyu , Pan Jianwei , Pryor Jane , Rajil Navid , Shih Yanhua , Sokolov Alexei , Svidzinsky Anatoly , Wang Dawei , Yi Zhenhuan , Zheltikov Aleksei , Scully Marlan
Published: September 2020

Lateral flow assay (LFA) has long been used as a biomarker detection technique. It has advantages such as low cost, rapid readout, portability, and ease of use. However, its qualitative readout process and lack of sensitivity are limiting factors. We report a photon-counting approach to accurately quantify LFAs while enhancing sensitivity. In particular, we demonstrate that the density of SARS-CoV-2 antibodies can be quantified and measured with an enhanced sensitivity using this simple laser optical analysis.
Molecular force fields with gradient-domain machine learning (GDML): Comparison and synergies with classical force fields
Authors: Sauceda Huziel E. , Gastegger Michael , Chmiela Stefan , Müller Klaus-Robert , Tkatchenko Alexandre
Published: September 2020

Modern machine learning force fields (ML-FF) are able to yield energy and force predictions at the accuracy of high-level ab initio methods, but at a much lower computational cost. On the other hand, classical molecular mechanics force fields (MM-FF) employ fixed functional forms and tend to be less accurate, but considerably faster and transferable between molecules of the same class. In this work, we investigate how both approaches can complement each other. We contrast the ability of ML-FF for reconstructing dynamic and thermodynamic observables to MM-FFs in order to gain a qualitative understanding of the differences between the two approaches. This analysis enables us to modify the generalized AMBER force field by reparametrizing short-range and bonded interactions with more expressive terms to make them more accurate, without sacrificing the key properties that make MM-FFs so successful.
Magnon-mediated spin currents in Tm3Fe5O12/Pt with perpendicular magnetic anisotropy
Authors: Vilela G. L. S. , Abrao J. E. , Santos E. , Yao Y. , Mendes J. B. S. , Rodríguez-Suárez R. L. , Rezende S. M. , Han W. , Azevedo A. , Moodera J. S.
Published: September 2020

The control of pure spin currents carried by magnons in magnetic insulator (MI) garnet films with a robust perpendicular magnetic anisotropy (PMA) is of great interest to spintronic technology as they can be used to carry, transport, and process information. Garnet films with PMA have labyrinth domain magnetic structures that enrich the magnetization dynamics and could be employed in more efficient wave-based logic and memory computing devices. In MI/non-magnetic (NM) bilayers, where NM is a normal metal providing a strong spin–orbit coupling, the PMA benefits the spin–orbit torque-driven magnetization switching by lowering the needed current and rendering the process faster, crucial for developing magnetic random-access memories. In this work, we investigated the magnetic anisotropies in thulium iron garnet (TIG) films with PMA via ferromagnetic resonance measurements, followed by the excitation and detection of magnon-mediated pure spin currents in TIG/Pt driven by microwaves and heat currents. TIG films presented a Gilbert damping constant of α ≈0.01, with resonance fields above 3.5 kOe and half linewidths broader than 60 Oe, at 300 K and 9.5 GHz. The spin-to-charge current conversion through TIG/Pt was observed as a microvoltage generated at the edges of the Pt film. The obtained spin Seebeck coefficient was 0.54 μV/K, also confirming the high interfacial spin transparency.
Structural and thermodynamic properties of hard-sphere fluids
Authors: Santos Andrés , Yuste Santos B. , López de Haro Mariano
Published: September 2020

This Perspective article provides an overview of some of our analytical approaches to the computation of the structural and thermodynamic properties of single-component and multicomponent hard-sphere fluids. For the structural properties, they yield a thermodynamically consistent formulation, thus improving and extending the known analytical results of the Percus–Yevick theory. Approximate expressions linking the equation of state of the single-component fluid to the one of the multicomponent mixtures are also discussed.
Hold On!
Authors: Newton Gina , Tribout Rachel
Published: September 2020

Have you ever seen a fish that could do a handstand?
This is the story of a quirky and primitive little fish that is famous for two reasons: walking on its ‘hands’ (pectoral fins), and being one of the first marine fish in the world to be listed as Critically Endangered on the IUCN Red List of Threatened Species.
The Spotted Handfish has survived since the time of the dinosaurs – until now. Invasive seastars, pollution and climate change mean that this unique Australian is in serious trouble – hands up if you want to know more!
Hold On! Saving the Spotted Handfish is perfect for primary aged readers.
Sustainable use and preservation of biological resources
Authors: Kurtböke Ipek , Meyer Wieland , Sly Lindsay
Published: September 2020

Microorganisms, microbially derived biotechnological applications and as causative agents of human, animal and plant disease are becoming increasingly significant in national economies. However, there remains a significant information gap on their species, ecological and genetic diversity. Despite the recognition of their commercial value still little is known about their functional roles in sustaining global ‘life support systems’, such as in agriculture, forest, coastal and freshwater ecosystems as well as their detrimental roles in the environment. As a result, sustainable use, preservation of microbial resources and effective strategies to combat infections are of immense importance to mankind. Culture collections are thus the cornerstones of biotechnology, sustainable futures and infection control.
Vertical Transmission
Authors: Lyras Dena
Published: September 2020

I hope that this Vertical Transmission finds you and your families safe and well. At the time of writing, some of you are in parts of Australia with few or no COVID-19 infections, while those of you in Victoria are in Stage 4 lockdown and dealing with the confusion, anxiety and uncertainty of this pandemic. What is clear is that the work of our dedicated epidemiologists, microbiologists, medical scientists, nurses, GPs, hospital clinicians and researchers improves the lives and health of our community, and that approaching a complicated issue from many angles will enable us to find the solutions to carry us through this situation. On behalf of the ASM, I extend our sincere gratitude to all of you.
Early termination of the Shiga toxin transcript generates a regulatory small RNA
Authors: Sy Brandon M. , Lan Ruiting , Tree Jai J.
Published: September 2020

Significance

Enterohemorrhagic
E. coli
is a significant human pathogen that can cause severe disease due to the release of Shiga toxins. The toxins are encoded within lysogenic bacteriophage and controlled by antitermination of the phage late promoter, P
R′
. This promoter is always active, but terminated immediately downstream during lysogeny. A byproduct of antitermination regulation is transcription of a short RNA that is thought to be nonfunctional. Here we demonstrate that in Shiga toxin-encoding phages, this short RNA is a Hfq-binding regulatory small RNA. The small RNA represses toxin production threefold under lysogenic conditions and promotes high cell density growth. Lysogenic bacteriophages are highly abundant and our results suggest that antiterminated phage promoters may be a rich source of regulatory RNAs.
The TV and Movies corpora
Authors: Davies Mark
Published: September 2020

This paper discusses the creation and use of the TV Corpus (subtitles from 75,000 episodes, 325 million words, 6 English-speaking countries, 1950s-2010s) and the Movies Corpus (subtitles from 25,000 movies, 200 million words, 6 English-speaking countries, 1930s–2010s), which are available atEnglish-Corpora.org. The corpora compare well to the BNC-Conversation data in terms of informality, lexis, phraseology, and syntax. But at 525 million words in total size, they are more than 30 times as large as BNC-Conversation (both BNC1994 and BNC2014 combined), which means that they can be used to look at a wide range of linguistic phenomena. The TV and Movies corpora also allow useful comparisons of very informal language across time (containing texts from the 1930s and later for the movies, and from the 1950s onwards for TV shows) and between dialects of English (such as British and American English).
Environmental quality characteristics of the Apulian transitional waters. Case study: lagoons of Lesina and Varano (Italy)
Authors: Malcangio D. , Manella N. , Ungaro N.
Published: September 2020

Transitional waters are ecosystems of important naturalistic value and enjoy different forms of protection. They are often subject to the threat of pollution phenomena due to anthropic activities and therefore objects of research for the choice of good monitoring, control and management practices. This study deals with the environmental analysis, conducted with water quality measurement campaigns and subsequent analysis of the data collected, of two lagoons in southern Italy, the Lesina lagoon and the Varano lagoon. These fall into the category of transitional waters sensu the Directive 2000/60/EC. The anthropic pressures and their impacts were evaluated in order to assess the environmental quality objectives stated by the mentioned European Directive. As a result, this study showed a non-critical state of the lagoons, but they will certainly be kept under observation.
A methodology to evaluate the effects of river sediment withdrawal: The case study of the Amendolea River in southern Italy
Authors: Foti Giandomenico , Barbaro Giuseppe , Manti Andrea , Foti Pietro , La Torre Adriana , Geria Paolo Fantino , Puntorieri Pierfabrizio , Tramontana Nicola
Published: September 2020

Sediment deposition is an issue affecting many rivers. To oppose it, sediment withdrawals are often used. However, this practice can trigger further problems in river and coastal sections but, on the other hand, periodic removal of deposited sediments can reduce flooding risk. Also, these sediments can be used for beach nourishment. Therefore, before carrying out a sediment withdrawal, it is necessary to analyze the whole basin to evaluate the consequences for the sediment balance. This paper describes a methodology to evaluate the effects of river sediment withdrawals through a case study on the Amendolea River, a torrential river in southern Italy. In particular, the methodology is divided into three main phases. The first phase was developed with GIS software in order to perimeter and to morphometrically characterize the river basin and its hydraulically and sedimentologically homogeneous sub-basins. The second phase was developed using the HEC-HMS software in order to evaluate the hydrological balance of the basin and its sub-basins. The last phase was developed using the HEC-RAS software (through the SIAM model) in order to identify the areas in erosion, in deposition and in equilibrium. Moreover, through this model is possible to identify the sections where sediments can be withdrawn, and to estimate the possible morphological river changes due to withdrawals. In this case study, the sediments will be taken from the sections where the bottom has elevations near or above those of adjacent lands, such as to increase the flooding risk. Sediment withdrawals will be taken without eroding the bottom and at a distance from the river banks that does not unstabilize them. Finally, the methodology described in this paper is based on the joint use of various open source software and can be used in any other river with hydrological regime similar to the Amendolea River.
Analysis of the sea storm of 23rd-24th October 2017 offshore Bari (Italy)
Authors: Lusito Letizia , Francone Antonio , Strafella Davide , Leone Elisa , D’Alessandro Felice , Saponieri Alessandra , De Bartolo Samuele , Tomasicchio Giuseppe Roberto
Published: September 2020

Between the evening of October 23rd and the evening of October 24th 2017, a sea storm hit the city of Bari, along the Adriatic coast, in the south of Italy, causing widespread damages. Due to the absence of direct observations of wave characteristics, the present paper is aimed to (i) compare the development of the occurred sea storm as hindcasted by ’84 method with the predictions by atmosphere-ocean numerical models and satellite observations and (ii) estimate the most reliable value of the significant wave height, Hs, at the peak of the sea storm, with its associated return period. As a result, the ’84 showed the better agreement with the satellite observations in determining the value of Hs at the peak of the sea storm, compared with the predictions by more sophisticated atmosphere-ocean numerical models. In particular, the obtained value of Hs, equal to 6.58 m, makes the investigated sea storm an exceptional event.
Estimating remaining concentration-percentages of resuspended sediments via a non-local particle model for flocculation
Authors: Abdallah A. , Pasquali D. , Lisi I. , Di Risio M.
Published: September 2020

Maritime works often require sediment handling activities such as dredging and disposal, to maintain harbors and channels, nourish sandy beaches as well as to carefully remove and relocate contaminated materials from the bottom of estuarine and coastal areas. Such operations often lead to an increase in the concentration of suspended sediments in water columns, which in turn causes adverse effects on water quality and aquatic lives. Minimizing these detrimental impacts require designing such maritime works with care, by paying attention to the geometry of areas affected by the sediment resuspension. Numerical modeling has been recognized as a valuable tool to help designers and contractors to optimize such sediment handling works. In obtaining such, one of the most challenging aspects to be tackled is the estimation of the settling velocity of the fine-grained mixture that results from sediment resuspension. These settling velocities are affected by a phenomenon known as flocculation. In this paper, the concept of non-local interacting particles was used to formulate a one-dimensional model for the flocculation phenomenon. Also, a (deterministic) particle transport equation was formulated to reproduce the settling behavior of suspended sediments in a settling column. The proposed model was solved numerically. The simulation results provide an understanding of the mechanisms of flocculation and highlight how flocculation influences floccule-settling velocities and concentration percentages of sediments that remain in suspension.
Research Evidence, Knowledge Management and Educational Practice: early lessons from a systematic approach
Authors: Oakley Ann
Published: September 2020

'Evidence-informed' education is part of a general move internationally to found policy and practice on a more reliable scientific base. This paper describes a five-year initiative in this area funded by the English Department for Education and Skills in 2000. The paper describes the
background to the initiative, the infrastructure developed within it for supporting research synthesis, and some of the challenges experienced by the first review groups.
Against Privatizing Schools in the United Kingdom
Authors: Brighouse Harry
Published: September 2020

This paper argues against two models for privatizing schools in the UK: contracting out the management of schools to private companies, and voucher schemes. Contracting out cannot yield the efficiency benefits that are claimed for it, because the contracting process cannot be sufficiently
competitive and the government cannot have sufficient knowledge of what makes schools successful to manage the contracts well. Vouchers will not work because the private sector in the UK will not be willing to participate in a scheme which incorporates regulations designed to achieve a minimal
level of social justice.
How Education Makes Us Healthy[1]
Authors: Hammond Cathie
Published: September 2020

The evidence for positive correlations between years of education and health status is consistent. The patterns of causalities underlying these correlations are likely to be complex, but here the focus is upon one direction of causality; namely how education makes us healthy. If education
has the potential to improve health outcomes, then policy-makers and practitioners should understand the interrelated processes involved. As a first step towards this understanding, I suggest a typology of intermediate factors linking education to health outcomes, falling under four headings;
economic factors, access to health services, health-related practices, and coping with stress. Although the development of the typology was the purpose of the research, the process of doing so led to the identification of a number of policy-relevant issues or themes that apply to all groups
of intermediate factors: (1) immediate psychosocial outcomes of learning play a fundamental role in generating the behaviours, skills and personal attributes that have lasting effects upon health; (2) health benefits of education that apply to individuals do not always apply to communities;
(3) health benefits of education depend upon the nature of the learning experienced; and (4) they also depend upon the social and economic structures in which the learner is situated.
Durkheim, Vygotsky and the Curriculum of the Future
Authors: Young Michael F. D.
Published: September 2020

This paper is concerned with the principles on which the curriculum should be based. It argues that the fundamental issue is the relationship between the knowledge on which the curriculum is based and the everyday knowledge that learners bring to school or college. The approaches to
knowledge of two educational theorists, the French sociologist, Emile Durkheim, and the Russian psychologist, Lev Vygotsky, are discussed. While pointing out some of the limitations of their approaches, the paper argues that their attempts to integrate the objectivity and the historicity of
knowledge must remain at the heart of future curriculum debates.
Holocaust Education in the Primary School: some reflections on an emergent debate
Authors: Short Geoffrey
Published: September 2020

Recent years have witnessed the beginnings of a debate over whether the Holocaust should be taught in primary schools. In this article the claims advanced in favour of the proposal are shown to be plausible but lacking in empirical support, while the counter-claims are considered either
peripheral, contentious or contrary to established research. It is argued that some key omissions in the debate, such as the way primary school pupils conceptualise Jewish culture and identity, significantly strengthen the case against introducing young children to the Holocaust.
The GM-CSF–IRF5 signaling axis in eosinophils promotes antitumor immunity through activation of type 1 T cell responses
Authors: Arnold Isabelle C. , Artola-Boran Mariela , Gurtner Alessandra , Bertram Katrin , Bauer Michael , Frangez Ziva , Becher Burkhard , Kopf Manfred , Yousefi Shida , Simon Hans-Uwe , Tzankov Alexandar , Müller Anne
Published: September 2020

The depletion of eosinophils represents an efficient strategy to alleviate allergic asthma, but the consequences of prolonged eosinophil deficiency for human health remain poorly understood. We show here that the ablation of eosinophils severely compromises antitumor immunity in syngeneic and genetic models of colorectal cancer (CRC), which can be attributed to defective Th1 and CD8+ T cell responses. The specific loss of GM-CSF signaling or IRF5 expression in the eosinophil compartment phenocopies the loss of the entire lineage. GM-CSF activates IRF5 in vitro and in vivo and can be administered recombinantly to improve tumor immunity. IL-10 counterregulates IRF5 activation by GM-CSF. CRC patients whose tumors are infiltrated by large numbers of eosinophils also exhibit robust CD8 T cell infiltrates and have a better prognosis than patients with eosinophillow tumors. The combined results demonstrate a critical role of eosinophils in tumor control in CRC and introduce the GM-CSF–IRF5 axis as a critical driver of the antitumor activities of this versatile cell type.
Spatiotemporal restriction of endothelial cell calcium signaling is required during leukocyte transmigration
Authors: Dalal Prarthana J. , Sullivan David P. , Weber Evan W. , Sacks David B. , Gunzer Matthias , Grumbach Isabella M. , Heller Brown Joan , Muller William A.
Published: September 2020

Endothelial cell calcium flux is critical for leukocyte transendothelial migration (TEM), which in turn is essential for the inflammatory response. Intravital microscopy of endothelial cell calcium dynamics reveals that calcium increases locally and transiently around the transmigration pore during TEM. Endothelial calmodulin (CaM), a key calcium signaling protein, interacts with the IQ domain of IQGAP1, which is localized to endothelial junctions and is required for TEM. In the presence of calcium, CaM binds endothelial calcium/calmodulin kinase IIδ (CaMKIIδ). Disrupting the function of CaM or CaMKII with small-molecule inhibitors, expression of a CaMKII inhibitory peptide, or expression of dominant negative CaMKIIδ significantly reduces TEM by interfering with the delivery of the lateral border recycling compartment (LBRC) to the site of TEM. Endothelial CaMKII is also required for TEM in vivo as shown in two independent mouse models. These findings highlight novel roles for endothelial CaM and CaMKIIδ in transducing the spatiotemporally restricted calcium signaling required for TEM.
Non-linear spherical collapse in tachyon models and a comparison of collapse in tachyon and quintessence models of dark energy
Authors: Rajvanshi Manvendra Pratap , Bagla J S
Published: September 2020

We study evolution of perturbations in dark matter and dark energy for spherical collapse using a completely self consistent, relativistic approach. We study tachyon models of dark energy using the approach outlined in Rajvanshi and Bagla (2018). We work with models that are allowed by current observations. We find that as with quintessence models allowed by observations, dark energy perturbations do not affect evolution of perturbations in dark matter in a significant manner. Perturbations in dark energy remain small for such models. We then take two different Lagrangians for dark energy: tachyon and quintessence models, reconstruct potentials to have same expansion history and then compare if two can be distinguished in the nonlinear regime. Any variations we find are only due to a different Lagrangian density, and allow a comparison of different classes of models in a fair manner. We find that dark matter perturbations carry no imprint of the class of dark energy models for the same expansion history: this is significant in that we can work with any convenient model to study clustering of dark matter. We find that the evolution of dark energy perturbations carries an imprint of the class of models and dark energy perturbations grow differently in tachyon models and quintessence models for the same expansion history. However, the difference between these diminishes for (1 + w) ≪ 1 and hence prospects for differentiating between models using characteristics of perturbations are limited in our Universe.
High-performance solid-state photon-enhanced thermionic emission solar energy converters with graded bandgap window-layer
Authors: Yang Yang , Xu Peng , Cao Weiwei , Zhu Bingli , Wang Bo , Bai Yonglin , Qin Junjun , Bai Xiaohong , Chen Zhen
Published: September 2020

To realize a high-performance solid-state photon-enhanced thermionic emission (SPETE) solar energy converter, in this study, a graded bandgap window layer is therefore adopted, throughout which the bandgap gradation is generated via the variation of Al composition in the

A

l

x

G

a

1
−
x

As

layer in the SPETE converter with a GaAs absorber. Based on one-dimension steady-state equation, an analytical model is formed in analyzing performance of the proposed device in our study. Theoretical simulation results indicate that not only are the losses of contact surface recombination being decreased via the bandgap-gradation-induced build-in electric field of the window layer, but also the photon-generated electrons are effectively collected, thereby improving the conversion efficiency. Moreover, the effect of bandgap energy of the contact surface and the width of the window layer on device performance is discussed. A trade-off of high-efficient SPETE converters is therefore realized between large contact surface bandgap and thin window layer width, to which the rationale lies in the improved process of electron collection facilitated by the enhanced build-in electric field rather than reducing the photon absorption in the window layer. Threshold values for barrier height at the emitting interface are presented to guarantee the ideal voltage-current characteristic. It is found that the threshold values of barrier increase with the increase in temperatures.
Electron transport parameters in CO2: a comparison of two experimental systems and measured data
Authors: Vass Máté , Egüz Eda , Chachereau Alise , Hartmann Péter , Korolov Ihor , Hösl Andreas , Bošnjaković Danko , Dujko Saša , Donkó Zoltán , Franck Christian M
Published: September 2020

Two experimental apparatuses used to obtain electron transport coefficients in gases are compared based on measurements in CO2 over a wide range of E/N-values. The operation principles of the two experimental systems as well as their data acquisition methods are different. One operates under the time of flight (TOF) principle, where the transport coefficients are obtained by fitting the theoretical form of the electron density of a swarm in an unbounded region, n(x, t), to the measured current at different values of the drift length, I(L, t). The other experimental apparatus operates in the Pulsed Townsend (PT) mode, where the electron transport coefficients are obtained by fitting the spatial integral of n(x, t) over the drift region to the measured, time-dependent current signal, I(t). In both apparatuses, the measured E/N range was extended as much as possible to allow a large overlap for the comparison of the results. The bulk drift velocity, W, obtained by the two systems agrees well (within a few %) over a wide range of E/N values (100 Td ≤ E/N ≤ 1000 Td). The agreement between the data sets for the longitudinal component of the bulk diffusion tensor,

D

L

, is less satisfactory, the TOF data show systematically higher values (by 10–50% depending on E/N) than the PT measurements. Significant differences are also found below 100 Td in case of the effective ionisation frequency,

ν

e
f
f

, and the (steady state) Townsend ionisation coefficient,

α

e
f
f

, where the TOF apparatus is unable to give accurate results. Our comparison justifies the correctness of the measured data over the range of agreement and also indicates the interval in E/N where the data obtained by each of the experimental systems can be taken to be reliable. The limits of the operating regimes of the two setups, stemming from the hardware and from the physical limits, are discussed.
Se diffusion in CdTe thin films for photovoltaics
Authors: Colegrove Eric , Zheng Xin , Ablekim Tursun , Duenow Joel N , Perkins Craig L , Moutinho Helio R , Metzger Wyatt K
Published: September 2020

Manipulating CdSeTe bandgrading to enhance photocurrent and carrier lifetime is an essential part of high-performance CdTe photovoltaics (PVs). In this work, we examine Se diffusion kinetics in single-crystal and polycrystalline CdTe during deposition, thermal annealing, and CdCl2 treatments. Se distributions are determined by dynamic secondary-ion-mass spectroscopy and Auger electron spectroscopy depth profiling and coupled with electron backscatter diffraction images of the crystalline structure. Effective bulk and grain boundary diffusion coefficients are determined by analytical models and discussed in the context of processing and film morphology. Se is found to diffuse in CdTe at much higher rates during CdCl2 treatments than with thermal processing alone. GB diffusion also occurs at a significantly faster rate than bulk diffusion. As a result of these two effects, the near interface bulk and GB Se diffusion during CdCl2 treatments dominates the bandgrading profiles in CdTe PVs.
Thermal magnetic fluctuations of a ferroelectric quantum critical point
Authors: Khaetskii Alexander , Juričič Vladimir , Balatsky Alexander V
Published: September 2020

Entanglement of two different quantum orders is of an interest of the modern condensed matter physics. One of the examples is the dynamical multiferroicity, where fluctuations of electric dipoles lead to magnetization. We investigate this effect at finite temperature and demonstrate an elevated magnetic response of a ferroelectric near the ferroelectric quantum critical point (FE QCP). We calculate the magnetic susceptibility of a bulk sample on the paraelectric side of the FE QCP at finite temperature and find enhanced magnetic susceptibility near the FE QCP. We propose quantum paraelectric strontium titanate as a candidate material to search for dynamic multiferroicity. We estimate the magnitude of the magnetic susceptibility for this material and find that it is detectable experimentally.
First principles investigation of electron correlation and Lifshitz transition within iron polynitrides
Authors: Feng Qingguo
Published: September 2020

Metal poly-nitrogen compounds are gaining great interests as potential high energy density materials. Several iron polynitrides have been recently synthesized and investigated under high pressure (2018 Nature Communications
9 2756). In this work the electron correlations within these iron poly-nitrogen compounds were self-consistently determined, benchmarked with those obtained from linear response approach. Along with the increase of the concentration of nitrogen, the Coulomb interaction strengths show a monotonic decrease, where FeN and FeN2 are antiferromagnetic and the others are ferromagnetic. Then the electron correlation is studied along with the pressure, where the electrons are more delocalized as pressure becomes higher. One electronic topological transition was found for FeN2, owing to a breaking of symmetry of spin and a transition of magnetism induced by a structural change. The band structure, densities of states, Fermi surface and absorption spectra were calculated and discussed.
New image reconstruction algorithm for CCERT: LBP + Gaussian mixture model (GMM) clustering
Authors: Wang Yuxin , He Xuekai , Jiang Yandan , Wang Baoliang , Ji Haifeng , Huang Zhiyao
Published: September 2020

This work focuses on the study of the image reconstruction algorithm of capacitively coupled electrical resistance tomography (CCERT). With the combination of a linear back projection (LBP) algorithm and an unsupervised Gaussian mixture model (GMM) algorithm, a new image reconstruction algorithm for CCERT is proposed. The LBP algorithm is used to implement the initial image reconstruction. The GMM algorithm is adopted to acquire the gray level threshold which will be used for the establishment of the gray level threshold filter. The final reconstructed image can be obtained with the thresholding operation. With a developed 12-electrode CCERT prototype system, the new image reconstruction algorithm is tested in image reconstruction experiments. The experimental results show that the proposed new image reconstruction algorithm is effective. The image reconstruction results are satisfactory. Compared with the conventional image reconstruction algorithms, the new image reconstruction algorithm (LBP + GMM) can obtain better reconstructed images with smaller relative image errors. It can obtain the reconstructed images with fewer empirical preset parameters and less manual intervention. In addition, with the introduction of the GMM algorithm, a relatively more suitable and reasonable gray level threshold can be obtained because the GMM algorithm implements the clustering process by utilizing both mean and variance information on the gray level distribution. Thus, better image reconstruction results can be obtained.
Monitoring corrosion-induced thickness loss of stainless steel plates using the electromechanical impedance technique
Authors: Liu Yang , Feng Xin
Published: September 2020

Stainless steel plates are widely used in steel structures. Corrosion damage of a stainless steel plate can induce the thickness and mass loss of the stainless steel plate. The corrosion-induced thickness loss (CITL) is one of the main reasons for the degradation of the stiffness and bearing capacity of the stainless steel plate, which endangers the safety of the structure and causes economic losses. Therefore, effective monitoring of the CITL of the stainless steel plate can help to ensure the safety of steel structures. In this study, a novel monitoring method for the CITL of the stainless steel plate based on the electromechanical impedance (EMI) technique is presented. The effective mechanical admittance (EMA) of a simply supported thin stainless steel plate under the excitation of a single surface-bonded piezoelectric transducer is derived theoretically; the resonance frequency shift (

Δ
f

) of the bending vibration mode in the admittance signature is extracted as the CITL-sensitive feature to identify the CITL of the stainless steel plate. The quantitative relationship between

Δ
f

and CITL, based on the EMA, is established theoretically for monitoring the CITL of the stainless steel plate. The effectiveness of the proposed method is verified by experiments. The experimental results demonstrate that the proposed method can sensitively identify, accurately quantify and predict the CITL of the stainless steel plate, and has excellent stability and reliability. This method can not only overcome the limitation of the existing statistics-based EMI methods that cannot quantify the CITL, but also compensate for the weakness of commonly-used non-destructive testing methods that cannot quantitatively predict CITL in an on-line monitoring manner. The proposed method provides an effective monitoring and tracking tool for the CITL of the stainless steel plate.
Magnetic mesoporous silica nanospheres with dual probe & release fluorescent functionality
Authors: Tancredi Pablo , Rivas-Rojas Patricia C , Veiga Lionel S , Garate Octavio , Socolovsky Leandro M , Muraca Diego , Ybarra Gabriel
Published: September 2020

The combination of different nanomaterials through step-by-step synthesis procedures has turned into a promising alternative to fabricate high-quality nanosystems in order to satisfy the increasingly demanding requirements of the biomedical field. In this work, we report a detailed study on the synthesis and characterization of a complex nanosystem composed of nanoparticles with a single magnetic nanoparticle core and a shell of dense and mesoporous silica arranged in layers. The procedure designed to fabricate these systems lead us to the formation of a dispersion of non-agglomerated spherical nanoparticles of nearly 100 nm. The structural characterization performed over the final samples confirmed both the prevalence of single-core systems and the presence of the mesoporous silica shell in the outer layer. The performance of the nanosystem in a specific technological application was tested by sequentially loading two different fluorescents molecules by covalent and non-covalent bonding strategies. Due to the distinct loading strategies, the resulting nanosystem presented a magnetically-assisted probe & release functionality as analyzed in a magnetophoretic experiment.
Study of adhesion and migration dynamics in ubiquitin E3A ligase (UBE3A)-silenced SYSH5Y neuroblastoma cells by micro-structured surfaces
Authors: Mezzena R , Masciullo C , Antonini S , Cremisi F , Scheffner M , Cecchini M , Tonazzini I
Published: September 2020

During neuronal development, neuronal cells read extracellular stimuli from the micro/nano-environment within which they exist, retrieving essential directionality and wiring information. Here, focal adhesions (FAs-protein clusters anchoring integrins to cytoskeleton) act as sensors, by integrating signals from both the extracellular matrix environment and chemotactic factors, contributing to the final neuronal pathfinding and migration. In the processes that orchestrate neuronal development, the important function of ubiquitin E3A ligase (UBE3A) is emerging. UBE3A has crucial functions in the brain and changes in its expression levels lead to neurodevelopmental disorders: the lack of UBE3A leads to Angelman syndrome (AS, OMIN 105830), while its increase causes autisms (Dup15q-autism). By using nano/micro-structured anisotropic substrates we previously showed that UBE3A-deficient neurons have deficits in contact guidance (Tonazzini et al, Mol Autism 2019).

Here, we investigate the adhesion and migration dynamics of UBE3A-silenced SH-SY5Y neuroblastoma cells in vitro by exploiting nano/micro-grooved substrates. We analyze the molecular processes regulating the development of FAs by transfection with EGFP-vector encoding for paxillin, a protein of FA clusters, and by live-cell total-internal-reflection-fluorescence microscopy. We show that UBE3A-silenced SH-SY5Y cells have impaired FA morphological development and pathway activation, which lead to a delayed adhesion and also explain the defective contact guidance in response to directional topographical stimuli. However, UBE3A-silenced SH-SY5Y cells show an overall normal migration behavior, in terms of speed and ability to follow the GRs directional stimulus. Only the collective cell migration upon cell gaps was slightly delayed for UBE3Ash SHs. Overall, the deficits of UBE3Ash SHS-SY5Y cells in FA maturation/sensing and in collective migration may have patho-physiological implications, in AS condition, considering the much more complex stimuli that neurons find in vivo during the neurodevelopment.
Electron beam evaporated Au islands as a nanoscale etch mask on few-layer MoS2 and fabrication of top-edge hybrid contacts for field-effect transistors
Authors: Walter Timothy N , Oliver Nailah , Mohney Suzanne E
Published: September 2020

Metal contacts to two-dimensional layered semiconductors are crucial to the performance of field-effect transistors (FETs) and other applications of layered materials in nanoelectronics and beyond. In this work, the wetting behavior of very thin Au films on exfoliated MoS2 flakes was studied and evaluated as a nanoscale, self-assembled dry etch mask. Etching nanoscale pits into MoS2 flakes prior to metallization from the top of the flake forms edge sites that contribute some fraction of edge contacts in addition to top contacts for additional carrier injection and lower contact resistance. The morphology and thickness of Au islands and MoS2 were studied with scanning electron microscopy and atomic force microscopy before and after etching with low-power plasmas. A Cl2 plasma etch of 10 s with a Au island mask of 6 nm (nominal) showed the best resulting morphology among the plasma conditions studied. Back-gated MoS2-based FETs on SiO2/p
+-Si with Ti/Au contacts were fabricated using a Cl2 etch of only the contact regions, and they yielded devices with ON currents of 100s µA/µm, ON/OFF ratios ⩾106, and contact resistance <10 kΩ µm. The best set of devices had a very low contact resistance of ∼1 kΩ µm with almost no dependence of contact resistance on gating. Using nanoscale etch masks made from metal islands could be highly customizable and shows promise for engineering FETs with low contact resistance.
Investigating chirping steel balls: a novel set-up
Authors: Chua Xian Wei
Published: September 2020

The International Young Physicists’ Tournament (IYPT) is a worldwide, annual competition for high school students. This paper is adapted from the author’s investigation into problem 4, Ball Sound, of the 27th IYPT. A novel set-up is proposed to investigate the unusual ‘chirping’ sound produced when two hard steel balls, or similar, are brought gently into contact with each other. It is shown that the decreasing time interval between rapid successive ball collisions, and not surface acceleration, is responsible for the chirping phenomenon. The proposed set-up simulates the collision of steel balls using our hands, and provides effective physical insights into the mechanism of chirp production.