bluuebunny/crossref_metadata_2025 huggingface dataset:
Prospectus on electron acceleration via magnetic reconnection
Authors: Dahlin J. T.
Published: October 2020

Many explosive plasma phenomena are powered by magnetic reconnection. Striking evidence of such events is found in short bursts of radiation from energetic electrons with energies much larger than what is typical of the ambient medium. Reconnection is a fundamentally multi-scale process that couples the global scale over which energy accumulates with small-scale dissipation. These macro- and micro-scales are bridged by a mesoscale of coherent magnetic structures that facilitate rapid energy conversion. Although there are many channels by which reconnection may release magnetic energy, a guiding-center approach distills electron energy gain into three basic mechanisms: parallel electric fields, Fermi reflection, and betatron acceleration. An efficient mechanism must scale strongly with the particle energy and operate over a globally significant region. These criteria favor the Fermi mechanism, which operates in volume-filling plasmoids. The guide field plays a critical role, facilitating three-dimensional transport that enables high-energy particles to continuously access acceleration sites, yet suppressing acceleration if the guide field is much larger than the reconnecting field. Open issues include the conditions necessary for power-law formation, the roles of scattering and plasma compression, and differences between the relativistic and nonrelativistic regimes. New high-resolution observations in the earth's magnetosphere offer a timely opportunity to test the predictions of numerical studies. On the other hand, understanding solar flares, where the global and dissipative scales are separated by many orders of magnitude, requires hybrid models that incorporate both the global evolution of the magnetic field and the self-consistent acceleration and feedback of energetic particles.
Energy transport and light propagation mechanisms in organic single crystals
Authors: Wittmann Bernd , Wiesneth Stephan , Motamen Sajedeh , Simon Laurent , Serein-Spirau Françoise , Reiter Günter , Hildner Richard
Published: October 2020

Unambiguous information about spatiotemporal exciton dynamics in three-dimensional nanometer- to micrometer-sized organic structures is difficult to obtain experimentally. Exciton dynamics can be modified by annihilation processes, and different light propagation mechanisms can take place, such as active waveguiding and photon recycling. Since these various processes and mechanisms can lead to similar spectroscopic and microscopic signatures on comparable time scales, their discrimination is highly demanding. Here, we study individual organic single crystals grown from thiophene-based oligomers. We use time-resolved detection-beam scanning microscopy to excite a local singlet exciton population and monitor the subsequent broadening of the photoluminescence (PL) signal in space and on pico- to nanosecond time scales. Combined with Monte Carlo simulations, we were able to exclude photon recycling for our system, whereas leakage radiation upon active waveguiding leads to an apparent PL broadening of about 20% compared to the initial excitation profile. Exciton–exciton annihilation becomes important at high excitation fluence and apparently accelerates the exciton dynamics leading to apparently increased diffusion lengths. At low excitation fluences, the spatiotemporal PL broadening results from singlet exciton diffusion with diffusion lengths of up to 210 nm. Surprisingly, even in structurally highly ordered single crystals, the transport dynamics is subdiffusive and shows variations between different crystals, which we relate to varying degrees of static and dynamic electronic disorders.
Admittance spectroscopy on single-crystal Cu2ZnSnSe4 solar cells: Back-contact effects and metastabilities
Authors: Lloyd Michael A. , Kuba Austin G. , McCandless Brian E. , Birkmire Robert
Published: October 2020

Admittance spectroscopy has become a commonly used device-level technique to probe the defect structure of kesterite materials. While this technique holds promise, phenomena such as current barriers and metastabilities cause difficulty in the interpretation of results. In this work, devices fabricated on single-crystalline CZTSe absorber layers are used to explore these effects in a more idealized system than thin films. Differences in behavior between admittance signatures of absorbers with Cu/Zn + Sn ratios of 0.86 and 0.77 are observed and mainly attributed to the formation of a low-temperature current barrier at the CZTSe/carbon-based back-contact interface in the more Cu-depleted devices. The effect of this barrier is significantly reduced by the implementation of higher-work function Au or MoO3−x back-contact material. Furthermore, distinct metastable doping densities are observed in each device type with the implementation of 3-h external bias conditioning of white, blue, or red light as well as 1 V applied forward bias. The origin of this behavior is attributed to a VSe–VCu defect complex that is predicted to exist in related chalcogenide materials.
The effects of monovalent metal cations on the crystal and electronic structures of Cs2MBiCl6 (M = Ag, Cu, Na, K, Rb, and Cs) perovskites
Authors: Shi Wenwu , Cai Tong , Wang Zhiguo , Chen Ou
Published: October 2020

Lead-halide perovskites have attracted much attention over the past decade, while two main issues, i.e., the lead-induced toxicity and materials’ instability, limit their further practice in widespread applications. To overcome these limitations, an effective alternative is to design lead-free perovskite materials with the substitution of two divalent lead ions with a pair of monovalent and trivalent metal ions. However, fundamental physics and chemistry about how tuning material’s composition affects the crystal phase, electronic band structures, and optoelectronic properties of the material have yet to be fully understood. In this work, we conducted a series of density functional theory calculations to explore the mechanism that how various monovalent metal ions influence the crystal and electronic structures of lead-free Cs2MBiCl6 perovskites. We found that the Cs2MBiCl6 (M = Ag, Cu, and Na) perovskites preferred a cubic double perovskite phase with low carrier effective masses, while the Cs2MBiCl6 (M = K, Rb, and Cs) perovskites favored a monoclinic phase with relatively high carrier effective masses. The different crystal phase preferences were attributed to the different radii of monovalent metal cations and the orbital hybridization between the metal and Cl ions. The calculation showed that all Cs2MBiCl6 perovskites studied here exhibited indirect bandgaps. Smaller bandgap energies for the perovskites with a cubic phase were calculated than those of the monoclinic phase counterparts. Charge density difference calculation and electron localization functional analysis were also conducted and revealed that the carrier mobility can be improved via changing the characteristics of metal-halide bonds through compositional and, thus, crystal structure tuning. Our study shown here sheds light on the future design and fabrication of various lead-free perovskite materials for optoelectronic applications.
Near-field transmission and reflection spectroscopy for revealing absorption and scattering characteristics of single silver nanoplates
Authors: Mizobata Hidetoshi , Hasegawa Seiju , Tamura Mamoru , Iida Takuya , Imura Kohei
Published: October 2020

Near-field optical microscopy visualizes spatial characteristics of elementary excitations induced in metal nanostructures. However, the microscopy is not able to reveal the absorption and scattering characteristics of the object simultaneously. In this study, we demonstrate a method for revealing the absorption and scattering characteristics of silver nanoplate by using near-field transmission and reflection spectroscopy. Near-field transmission and reflection images show characteristic spatial features attributable to the excited plasmon modes. The near-field refection image near the resonance shows a reversed contrast depending on the observed wavelength. Near-field reflection spectra show unique positive and negative resonant features. We reveal that the optical characteristics and the wavelength dependency of the optical contrast originate from the scattering and absorption properties of the plasmons, with the aid of the electromagnetic simulations.
Fabrication and characteristics of flexible normally-off AlGaN/GaN HEMTs
Authors: Lin Runze , Zhao Desheng , Yu Guohao , Liu Xiaoyan , Wu Dongdong , Gu Erdan , Cui Xugao , Liu Ran , Zhang Baoshun , Tian Pengfei
Published: October 2020

In this paper, we present a method for removing a high electron mobility transistor (HEMT) silicon substrate using mechanical grinding and deep silicon etching technology and successfully transferred the epitaxial wafer to a PET substrate to achieve the flexible normally-off HEMT. By testing the output characteristics and transfer characteristics of the Si-substrate HEMT and PET-substrate HEMT, we have demonstrated that the PET-substrate HEMT has excellent performance and successfully achieved the mechanical flexibility. Furthermore, we analyzed the physical mechanisms of the change in PET-substrate and Si-substrate HEMT characteristics, as well as flexible HEMT performance under bent and flattened states. The flexible HEMT array demonstrates significant potential in integration with other flexible devices, such as GaN-based micro-LED arrays.
Machine learning interatomic potential developed for molecular simulations on thermal properties of β-Ga2O3
Authors: Liu Yuan-Bin , Yang Jia-Yue , Xin Gong-Ming , Liu Lin-Hua , Csányi Gábor , Cao Bing-Yang
Published: October 2020

The thermal properties of β-Ga2O3 can significantly affect the performance and reliability of high-power electronic devices. To date, due to the absence of a reliable interatomic potential, first-principles calculations based on density functional theory (DFT) have been routinely used to probe the thermal properties of β-Ga2O3. DFT calculations can only tackle small-scale systems due to the huge computational cost, while the thermal transport processes are usually associated with large time and length scales. In this work, we develop a machine learning based Gaussian approximation potential (GAP) for accurately describing the lattice dynamics of perfect crystalline β-Ga2O3 and accelerating atomic-scale simulations. The GAP model shows excellent convergence, which can faithfully reproduce the DFT potential energy surface at a training data size of 32 000 local atomic environments. The GAP model is then used to predict ground-state lattice parameters, coefficients of thermal expansion, heat capacity, phonon dispersions at 0 K, and anisotropic thermal conductivity of β-Ga2O3, which are all in excellent agreement with either the DFT results or experiments. The accurate predictions of phonon dispersions and thermal conductivities demonstrate that the GAP model can well describe the harmonic and anharmonic interactions of phonons. Additionally, the successful application of our GAP model to the phonon density of states of a 2500-atom β-Ga2O3 structure at elevated temperature indicates the strength of machine learning potentials to tackle large-scale atomic systems in long molecular simulations, which would be almost impossible to generate with DFT-based molecular simulations at present.
An efficient way to incorporate the geometric phase in the time-dependent wave packet calculations in a diabatic representation
Authors: Huang Jiayu , Zhang Dong H.
Published: October 2020

We present a new approach to incorporate the geometric phase in the time-dependent wave packet calculations based on the analytic diabatic potential energy matrices for two-state systems connecting via a conical intersection. The approach only requires information on the location of the conical intersection and the adiabatic potential energy surface of the ground electronic state and merely takes the same computational cost as a diabatic calculation. Demonstrations of the benchmark H + H2/HD reactions show that the new approach can accurately include the geometric phase in dynamics calculation and can be easily extended to the cold regime where the GP effects become more pronounced. Due to its simplicity and numerical efficiency, the new approach has the potential to extend the dynamics study of the geometric effects to a wide range of reaction systems.
Nitrous oxide emissions from applied nitrate fertiliser in commercial cherry orchards
Authors: Quin P. , Swarts N. , Oliver G. , Paterson S. , Friedl J. , Rowlings D.
Published: October 2020

The application of nitrate (NO3–) fertiliser is important worldwide in providing nitrogen (N) nutrition to perennial fruit trees. There is little information available on N losses to the environment from commercial cherry orchards, in relation to different timings of NO3– application. The emission of nitrous oxide (N2O) gas is an important greenhouse gas loss from NO3– application, being responsible for 6% of anthropogenic global warming and a catalyst for depletion of stratospheric ozone. In a commercial sweet-cherry orchard in southern Tasmania, we applied 373 g NO3–-N m–2 (equivalent to 90 kg NO3–-N ha–1) either pre- or post-harvest, or equally split between the two, to study the resultant N2O emissions. Emissions averaged 8.37 mg N2O-N m–2 day–1 during the pre-harvest period, primarily driven by a heavy rainfall event, and were significantly greater (P < 0.05) than the average 4.88 × 10–1 mg N2O-N m–2 day–1 from post-harvest NO3– application. Discounting the emissions related to the rainfall event, the resultant average 1.88 mg N2O-N m–2 day–1 for the rest of the pre-harvest emissions remained significantly greater (P < 0.05) than those post-harvest. Ongoing studies will help to build on these results and efforts to minimise N2O emissions in perennial tree cropping systems.
One health in history.
Authors: Bresalier Michael , Cassidy Angela , Woods Abigail
Published: October 2020

This chapter outlines the history of One Health. The first section of the chapter analyses intersections between human and animal health in the premodern era, to reveal how deeply animals and animal health were embedded within human medicine. The second section extends from the late 18th-century foundation of the veterinary profession until the turn of the 20th century. It tracks the evolving relationship between the veterinary and medical professions, and how, as scientific ideas and practices changed, new links were forged between human and animal bodies and diseases. The third section extends this analysis into the 20th century, focusing particularly on the changing status of animals within medical research, and on international efforts to develop comparative medicine and veterinary public health. The conclusion reflects on the importance of these findings for history and for One Health today.
Why one health?
Authors: Zinsstag Jakob , Waltner-Toews David , Tanner Marcel
Published: October 2020

This chapter discussed the foundational principles of One Health and highlights on the cultural differences in human-animal relations and their implications, animal ethical and welfare issues, and One Health as embedded in landscapes and transdisciplinarity.
Grappling with complexity: the context for one health and the ecohealth approach.
Authors: Bunch Martin J. , Waltner-Toews David
Published: October 2020

In this chapter, the nature of the problems that the ecohealth approach is intended to address were discussed and presents an overview of the ecosystem approach, a transdisciplinary conception of health, and principles and guidelines that bring these together in the ecosystem approach to health and well-being.
The role of social sciences in one health - reciprocal benefits.
Authors: Whittaker Maxine , Obrist Brigit , Berger-González Mónica
Published: October 2020

This chapter discusses the role of social sciences in developing a deeper understanding of diverse perspectives of health and illness in animals and humans, as well as in contributing to improve services and programmes using a One Health approach. Drawing on evaluated and ongoing examples from various countries, the authors demonstrate the added value of social sciences to address common local or global health problems using a One Health approach. The presentation and discussion of these examples allows for an exploration of various key aspects, ranging from diverse understandings of health risks, protection, responses, implementing interventions and health communications as well as questions of equity of access and benefit. Theories and approaches in anthropology and other social sciences frame the discussion. This analysis adds further value to social sciences' contribution to One Health and One Health's contribution to social sciences in research and in programme implementation.
Surveillance and response conducted in a one health context.
Authors: Aenishaenslin Cécile , Martins Sara Babo , Stärk Katharina D. C.
Published: October 2020

This chapter discussed the success of the One Health programme to reduce (i.e. mitigate) the impact of diseases on the health of people, animals and plants.
Animal-human transmission models.
Authors: Chitnis Nakul , Zinsstag Jakob , Fuhrimann Samuel , Hattendorf Jan
Published: October 2020

In this chapter the authors primarily focused on the diseases of the first categories (i.e. without human-to-human transmission or with limited human-to-human transmission), which clearly require an intervention in the animal reservoir and in food safety or improved sanitation in order to interrupt transmission to humans.
One health leadership and team building training.
Authors: Pelican Katharine , Blair Benjamin , Adisasmito Wiku , Allen Ian , Amir Vilda , Bazeyo William , Errecaborde Kaylee , Thi Huong Le , Mahero Michael , Wanzala Sylvia , Bender Jeffrey
Published: October 2020

In this chapter, The authors presented five case studies on OH leadership and team building programmes and approaches and then compare them to determine what competencies they are emphasizing as critical in their cultural and operational context. Case studies were selected to represent OH leadership and team building programmes within country and regional contexts. The cases discussed include the: (i) Global Health True Leaders (GHTL) programme in Indonesia; (ii) International Master of Public Health OH-oriented programme at Hanoi Medical University (HMU) in Vietnam; (iii) Engaging Intergovernmental Organizations (EIO)program at the University of Minnesota in the USA; (iv) One Health Systems Mapping and Analysis Resource Toolkit (OH-SMARTTM), implemented in 18 countries; and (v) multidisciplinary OH field attachments/placement programmes implemented by the One Health Central and Eastern Africa (OHCEA)university network in eight countries. All of these programmes were supported, in part, by the USAID One Health Workforce (OHW) Project. In presenting and analysing these case studies, this chapter provides examples of five field-validated programmes involving OH leadership and what competencies they identified as critical to OH leadership in their context.
Climate change: the ultimate one health challenge.
Authors: Stephen Craig , Duncan Colleen , Pollock Sue
Published: October 2020

This chapter provides an overview of the impacts of climate change and the shared benefits of diverse collaborations to adapt to this important threat to animal, man and environmental health.
Emergence of antimicrobial resistance and interaction between humans, animals and environment.
Authors: Szelecsenyi Arlette , Meier Helene , Spinner Keira , Vonaesch Pas Cale , Zinsstag Jakob , Widmer Andreas F.
Published: October 2020

This chapter discussed the management of antimicrobial resistance (AMR) under the One Health programme and presents examples of AMR in hospital germs circulating between animals and humans as well as discussed some evidences of environmental-animal-human AMR exchange.
Brucellosis surveillance and control: a case for one health.
Authors: Schelling Esther , Kasymbekov Joldoshbek , Baljinnyam Zolzaya , Roth Felix , Dean Anna , Zinsstag Jakob
Published: October 2020

This chapter describes a One Health approach to Brucella melitensis, B. abortus and B. suis for epidemiological assessments, surveillance and laboratory capacity, cross-sector economics and practical control options in Central Asia and Sahelian Africa.
Bovine tuberculosis at the human-livestock-wildlife interface in sub-Saharan Africa.
Authors: Tschopp Rea , Yahyaoui Hind
Published: October 2020

This chapter describes the epidemiology, prevalence, risk factors, transmission, the role of wild animals and the One Health approach to control bovine tuberculosis in sub-Saharan Africa.
One health into action: integrating global health governance with national priorities in a globalized world.
Authors: Okello Anna , Vandersmissen Alain , Welburn Susan C.
Published: October 2020

This chapter describes the evolution of global health governance (GHG), from the early years of international health diplomacy in the 19th century, to a discussion of the systems, actors and networks that currently hold a stake in GHG today. The various options, considerations and challenges that may be required to sustainably operationalize One Health on a global scale in the future are analysed, based on the changing relationships between health policy and practice.
Summary and outlook: one health in practice.
Authors: Zinsstag Jakob , Tanner Marcel
Published: October 2020

This chapter provides a comprehensive overview of what One Health entails, from its current positioning in the global and planetary health scene, by building on historical elements and providing key theoretical, methodological and practical issues of One Health.
Movement form of the overarm throw for children at 6, 10 and 14 years of age
Authors: Palmer Hannah A. , Newell Karl M. , Mulloy Franky , Gordon Dan , Smith Lee , Williams Genevieve K. R.
Published: October 2020

This study investigated overarm throwing technique at different developmental ages in children from the perspective of three distinct, though potentially complementary, approaches to motor skill acquisition. Children at 6, 10, and 14 years of age (N = 18), completed dominant overarm throws during which whole‐body kinematic data were collected. Firstly, application of Newell's ([1985]. Coordination, control and skill. In Advances in Psychology (Vol. 27, pp. 295–317). North‐Holland.) stages of learning identified three distinct age‐related coupling modes between forward motion of the centre‐of‐mass (CoM) and the wrist, which demonstrated a greater range of couplings for older children. Secondly, in line with Bernstein's ([1967]. The coordination and regulation of movement. London: Pergamon Press.) hypothesis of freezing before freeing degrees of freedom, a significantly smaller range of motion (ROM) at the ankle and knee joints, but greater ROM at the hip and upper limb joints was found for the 6 year old group compared to the 10 and 14 year old groups. Thirdly, based on the components model (Roberton & Halverson [1984]. Developing children‐their changing movement: A guide for teachers. Lea & Febiger.), the overarm throws demonstrated by 6 year olds were characterised as primitive to intermediate, where 10 and 14 year old's throws were characterised by the penultimate action level for each component. Characteristics of CoM‐wrist coupling more clearly identify children's age‐related technique and highlight the importance of posture‐ball release dynamics. The posture‐ball dynamics were supported by changes in ROM and the components model, revealing the complementary nature of the three approaches to the analysis of age‐related differences in overarm throwing action.
Basis and effects of ion migration on photovoltaic performance of perovskite solar cells
Authors: Zhou Wenke , Gu Juan , Yang Zhiqian , Wang Mingyang , Zhao Qing
Published: October 2020

Halide perovskite materials, which are emerging as some of the most promising candidates for photovoltaics, have been widely studied and have been certified as demonstrating a comparable efficiency to single-crystal silicon solar cells. However, their low stability poses a challenge for commercialization. External impediments, like moisture, heat, and UV light, can be addressed by strict encapsulation; nevertheless, ion migration remains. The migrated ions will bring in a growing number of charged defects and phase segregation to bulk perovskite; they will cause interfacial band doping and degradation of the carrier transport layer, which will greatly hinder carrier transportation. Those effects are the origins of perovskite intrinsic instability. Thus, a thorough understanding of the operational mechanism of ion migration is urgent for the fabrication of perovskite solar cells (PSCs) with improved stability. Here, we systemically summarize the factors governing ion migration in perovskite film and the associated impact on the performance of PSCs. Light illumination, organic cations, grain boundaries, residue lattice strain and moisture have been found to make ion migration easier. Strategies developed to suppress the ion migration are also interspersed in each section.
Real-time observation of ion migration in halide perovskite by photoluminescence imaging microscopy
Authors: Zhang Jing , Li Cheng , Chen Mengyu , Huang Kai
Published: October 2020

The stability issue of organometal halide perovskite optoelectronic devices, e.g. the current–voltage –hysteresis effect and the degradation of the device performance under external light/electric field, are closely related to the ionic movement inside perovskite materials. However, our understanding of ionic properties is still at a relatively preliminary stage, and the detailed dynamic process of ionic movement in perovskite materials is controversial. Photoluminescence (PL) imaging microscopy, as a versatile real-time observation and characterization method, has become a powerful tool to explore the ionic movement in different material systems. This review firstly summarizes the development of PL imaging microscopy for ion migration characterization in perovskite materials. Secondly, combined with the wide-field PL imaging microscope, the dynamic process of ion migration in halide perovskite materials is further discussed. Thirdly, the observations of the degradation process and the ion migration suppression in different perovskite optoelectronic devices characterized by PL imaging microscopy are also introduced. This methodology is of significance for the deep understanding of the interaction between carriers/defect ions in perovskite materials, and provides guidance to further improve the stability and efficiency of perovskite optoelectronic devices.
Chemistry of ruthenium as an electrode for metal–insulator–metal capacitor application
Authors: Jung Eui Young , Bang Jeongil , Hwang Ji Hyeon , Han Dong Hee , Kim Youngjin , Kim Haeryong , Jeon Woojin
Published: October 2020

Notwithstanding its excellent properties such as high work function and low resistance, Ru has not been widely applied in the preparation of electrodes for various electronic devices. This is because of the occurrence of severe morphological degradation in the actual devices employing Ru. Herein, we investigated Ru chemistry for electrode application and the degradation mechanism of Ru during subsequent processes such as thin film deposition or thermal annealing. We revealed that subsurface oxygen induces Ru degradation owing to the alteration of Ru chemistry by the pretreatment under various gas ambient conditions and due to the growth behavior of TiO2 deposited via atomic layer deposition (ALD). The degradation of Ru is successfully ameliorated by conducting an appropriate pretreatment prior to ALD. The TiO2 thin film deposited on the pretreated Ru electrode exhibited a rutile-phased crystal structure and smooth surface morphology, thereby resulting in excellent electrical properties. This paper presents an important development in the application of Ru as the electrode that can facilitate the development of various next-generation electronic devices.
Geometrically self-similar ion acceleration in collisionless plasma beam expansion
Authors: Hu Yuan , Wang Joseph , Sun Quanhua
Published: October 2020

Fully kinetic particle-in-cell simulations are carried out to study ion acceleration in a geometrically expanding plasma beam. The ion acceleration is demonstrated to be essentially self-similar. An analytical model is developed for ion acceleration evaluation. The plasma plume is found to be fully expanded after about 20 times of the beam radius (R
0) downstream of the beam exit, where the ion velocity reaches the maximum. The maximum ion velocity increase is about twice of the initial ion acoustic speed. Hence, to minimize the facility effects on plasma plume experiments in a vacuum chamber, the chamber needs to provide a plume expansion region of at least 20R
0 along the beam direction so the expansion process is not terminated prematurely.
The local kinetic energy density revisited
Authors: Jiang Hao
Published: October 2020

Kinetic energy density (KED) plays a fundamental role in density functional theory, chemical bonding, etc. As a basic quantity, its definition is ambiguous, which will inevitably exert unpredictable adverse effects on application. We derive another form of local total energy density (ED) and KED based on the perturbation theory. Contrary to popular belief, our study reveals that energy is only distributed inside the potential well and exactly fills the entire potential well. It seems that the ambiguity of the quantum definition of total ED is eliminable by the stability of energy distribution, and there is a one-to-one correspondence between this form of KED and total ED. As a result, the ambiguity of the KED is also eliminable. Moreover, this new form of local KED ‘selectively’ agrees well with the key regions of other commonly used ones. However, it is much less localized than other forms. Its locality features imply that it may provide a native way to describe the strong correlation and the van der Waals interactions.
Quantum geometric machine learning for quantum circuits and control
Authors: Perrier Elija , Tao Dacheng , Ferrie Chris
Published: October 2020

The application of machine learning techniques to solve problems in quantum control together with established geometric methods for solving optimisation problems leads naturally to an exploration of how machine learning approaches can be used to enhance geometric approaches for solving problems in quantum information processing. In this work, we review and extend the application of deep learning to quantum geometric control problems. Specifically, we demonstrate enhancements in time-optimal control in the context of quantum circuit synthesis problems by applying novel deep learning algorithms in order to approximate geodesics (and thus minimal circuits) along Lie group manifolds relevant to low-dimensional multi-qubit systems, such as SU(2), SU(4) and SU(8). We demonstrate the superior performance of greybox models, which combine traditional blackbox algorithms with whitebox models (which encode prior domain knowledge of quantum mechanics), as means of learning underlying quantum circuit distributions of interest. Our results demonstrate how geometric control techniques can be used to both (a) verify the extent to which geometrically synthesised quantum circuits lie along geodesic, and thus time-optimal, routes and (b) synthesise those circuits. Our results are of interest to researchers in quantum control and quantum information theory seeking to combine machine learning and geometric techniques for time-optimal control problems.
Laser-plasma proton acceleration with a combined gas-foil target
Authors: Levy Dan , Bernert Constantin , Rehwald Martin , Andriyash Igor A. , Assenbaum Stefan , Kluge Thomas , Kroupp Eyal , Obst-Huebl Lieselotte , Pausch Richard , Schulze-Makuch Alexander , Zeil Karl , Schramm Ulrich , Malka Victor
Published: October 2020

Laser-plasma proton acceleration was investigated in the target normal sheath acceleration regime with a target composed of a gas layer and a thin foil. The laser’s shape, duration, energy and frequency are modified as it propagates in the gas, altering the laser-solid interaction leading to proton acceleration. The modified properties of the laser were assessed by both numerical simulations and by measurements. The 3D particle-in-cell simulations have shown that a nearly seven-fold increase in peak intensity at the foil plane is possible. In the experiment, maximum proton energies showed high dependence on the energy transmission of the laser through the gas and a lesser dependence on the size and shape of the pulse. At high gas densities, where high intensity was expected, laser energy depletion and pulse distortion suppressed proton energies. At low densities, with the laser focused far behind the foil, self-focusing was observed and the gas showed a positive effect on proton energies. The promising results of this first exploration motivate further study of the target.
Effects of elastic softening and helium accumulation kinetics on surface morphological evolution of plasma-facing tungsten
Authors: Chen Chao-Shou , Dasgupta Dwaipayan , Weerasinghe Asanka , Wirth Brian D. , Maroudas Dimitrios
Published: October 2020

Based on a continuous-domain model, capable of accessing the spatiotemporal scales relevant to fuzz formation on the surface of plasma-facing component (PFC) tungsten, we report self-consistent simulation results that elucidate the effects of elastic softening and helium (He) accumulation kinetics on the surface morphological response of PFC tungsten. The model accounts for the softening of the elastic moduli in the near-surface region of PFC tungsten, including both thermal softening at high temperature and softening due to He accumulation upon He implantation. The dependence of the elastic moduli on the He content follows an exponential scaling relation predicted by molecular-dynamics simulations, while the He content in the near-surface region of PFC tungsten evolves according to a first-order saturation kinetics, consistent with experimental and simulation results reported in the literature. We establish that this elastic softening accelerates both nanotendril growth on the PFC surface and the onset of fuzz formation. We also explore the role of the rate of He accumulation to a saturation level in the near-surface region of irradiated tungsten in the onset of fuzz formation. For PFC tungsten surfaces such as W(110) where, under typical irradiation conditions, the characteristic time scale for stress-driven surface diffusion is comparable to the characteristic time scale for He accumulation, we find that accelerating the rate of He accumulation accelerates the growth rate of nanotendrils emanating from the surface. Additionally, we present a systematic parametric study of the PFC surface morphological response to explore its dependence on the He accumulation kinetics that is controlled by the irradiation conditions for low-energy implantation. Finally, we introduce an incubation time for nanotendril growth on the PFC surface, a concept equivalent to that of incubation fluence discussed in the literature, to predict and explain the minimum exposure time required to observe fuzz formation on PFC tungsten surfaces.
Influence of non-magnetic Zn-doping on the structural and the magnetic properties of magnesium ferrite
Authors: Mahale Vinay , Raut A V , Surashe V K , Vinayak V , Dorik R G , Shengule D R
Published: October 2020

Spinel ferrites are the important class of soft magnetic material and are of interest to many researchers due to their excellent electrical and magnetic properties. Magnesium ferrite (MgFe2O4) is one such spinel ferrite with great potential technological applications. In the present study, the magnesium ferrite (Mg0.8Zn0.2Fe2O4) samples were prepared by well-known sol-gel auto-combustion method. The influence of Zn-doping on the structural and magnetic properties was investigated by X-ray diffraction and magnetization studies. The room temperature X-ray diffraction studies of the pure MgFe2O4 and Zn-doped Mg-Fe2O4 (Mg0.8Zn0.2Fe2O4) revealed the formation of single phase cubic spinel structure. The crystallite size obtained from Sherrer’s formula indicated that the Zn-doped and undoped shows nanocrystalline nature with crystallite size 22 nm and 24 nm respectively. The lattice constant (?) was found to be increased after Zn doping. Several other structural parameters are also increased after Zn doping. The magnetic properties were investigated by means of pulse field hysteresis loop technic. The M-H plot exhibits typical ferrimegnetic nature. The saturaturation magnetization increases after Zn doping. The observed magnetic behaviour of Mg0.8Zn0.2Fe2O4 nanocrystalline ferrite was on the basis of theoretical model.
Studies on Synthesis and Structural Properties of Nickel Ferrite before and after Gamma Irradiation
Authors: Kalunge Santosh , Surase Anand , Sapate D. R. , Nimbhore S. R. , Barote V. K. , Pandit A. A.
Published: October 2020

In the present work nanocrystalline NiFe2O4 samples were prepared by the sol-gel auto combustion technique. The synthesis was carried out by taking citric acid as fuel with metal nitrate to fuel ratio as 1:3. The obtained powder was annealed at 5500C for 4 h and then used for structural and magnetic investigations. Prepared nickel ferrite samples have been irradiated by gamma-ray (60Co) to examine the changes that occurred in structural properties. Structural properties of nickel ferrite nanoparticles before and after gamma irradiation were carried out by X-ray diffraction (XRD) technique. From the XRD pattern, it was observed that all the Braggs planes reveal cubic spinel structure before and after gamma irradiation. A close examination of the XRD pattern revealed the crystallite size of 21 nm and 19 nm for nickel ferrite samples before and after gamma irradiation respectively. The obtained results help in providing interesting and useful study for various applications of nickel ferrites.
Structural Morphological and Infrared Properties of Cd2+ Substitutes Nickel Ferrite Particles
Authors: Devmunde B. H. , Bhalerao P.S. , Solunke M.B.
Published: October 2020

The Structural properties of cadmium substituted nickel ferrite with general formula Ni1-xCdxFe2O4 (x=0.0, 0.1, 0.2, 0.3, 0.4 and 0.5) were synthesized by using Sol-gel auto combustion method. All the chemicals used for preparations was high purity (99.9% Sigma-Aldrich).The prepared nanoparticles samples were investigated by characterizing them through X-ray diffraction, scanning electron microscopy and infrared spectroscopy. From XRD results, it is observed prepared samples were in the nano size having cubic spinel structure with single phase. Lattice constant is found increasing with Cd2+ concentration. The average grain size obtained from SEM in the range of 45-58 nm. The EDAX plot gives the evidence of presence of Ni2+, Cd2+, Fe3+, and O2- ions with proper ratio confirming the desired stoichiometric composition. IR spectra exhibit two distinct absorption bands hear about 400 cm−1 and 600 cm−1
Effect of Magnetic Field on Thermal Conductivity of the Cobalt Ferrite Magnetic Nanofluids
Authors: Kharat Prashant B. , Somvanshi Sandeep B. , Khirade Pankaj P. , Jadhav K. M.
Published: October 2020

Stable magnetic nanofluids of cobalt ferrite nanoparticles were synthesized by chemical co-precipitation method. The structural, morphological and magnetic properties were characterized by the X-ray diffraction (XRD), Transmission Electron Microscopy (TEM), and Vibrating Sample Magnetometer (VSM) respectively. The XRD study revealed the spinel structure of the prepared cobalt ferrite nanoparticles with Fd-3m space group. Prepared nanoparticles were found to be spherical in nature with average particles size of 10 nm. The prepared cobalt ferrite nanoparticles were exhibit near superparamagnetic behavior. These superparamagnetic cobalt ferrite nanoparticles used for the preparation of the magnetic nanofluids in ethylene glycol with various volume fraction concentrations viz. 0.2%, 0.4%, 0.6%, 0.8%, and 1%. The thermal conductivity of the ethylene glycol was significantly enhanced by dispersing the cobalt ferrite nanoparticles. The thermal conductivity of the prepared cobalt ferrite / ethylene glycol (COEG) magnetic nanofluid were also responded to the magnetic field intensity and shows increasing trend with increasing magnetic field intensity.
Effect of vacuum thermal annealing on optical properties of amorphous (Se80Te20)94Ag6 chalcogenide thin films prepared by thermal evaporation technique
Authors: Gupta Anubha , Malik K , Parvinder  , Kumar R
Published: October 2020

Amorphous (Se80Te20)94Ag6 thin films are prepared at room temperature by using thermal evaporation technique. The as-prepared thin films are annealed both at higher and lower temperatures than glass transition temperature Tg. X-ray diffraction of annealed film above Tg confirms the presence of different phases. The glass transition temperature of as-prepared glass is evaluated with the help of DSC measurement. Transmittance measurements are used to find the value of optical parameters and optical band gap Eg. Refractive index and extinction coefficient increases with increase in annealing temperature. The band gap show an increase for the annealing temperature less than Tg and decrease for the temperature greater than Tg. Mott and Davis Model forms the basis for the explanation of change in optical band gap.
Multifunctional Magnetic Nano-platforms for Advanced Biomedical applications: A Brief Review
Authors: Kharat Prashant B. , Somvanshi Sandeep B. , Jadhav K. M.
Published: October 2020

In this concise survey, we have introduced overview and features on biomedical utilizations of a class of metal nanoparticles including magnetic nanoparticles. Their most significant related materials are additionally examined for biomedical applications for treating different cancer like diseases. At present, physicochemical techniques have been demonstrated fruitful to orchestrate, shape, control, and produce metal and oxide based homogeneous frameworks, e.g., nano and micro scale particles. In this way, we have principally centred around useful magnetic nanoparticles for nano-medication as a result of their high bio-flexibility to the organs inside human body. Here, bio-conjugation procedures are extremely urgent to interface nanoparticles with customary medications, nano-drugs, bio-particles or polymers for biomedical applications. Bio-functionalization of tailored nanoparticles for biomedicine is demonstrated separate to in vitro and in vivo investigation conventions that commonly incorporate medication conveyance, hyperthermia treatment, magnetic resonance imaging (MRI). The last can be particularly applied utilizing magnetic nanoparticles, for example, spinel ferrite oxide nanoparticles for diagnostic and treatment of malignancies. Significantly, nano scale-frameworks or micro scale-frameworks or half breed micro-nano scale frameworks are shortly brought into nano-medication.
Synthesis of Goblet shape defected ground slotted microstrip patch antenna
Authors: Chauhan E S , Khandka S , Kumar A
Published: October 2020

This paper presented for investigation, how the defects as well as slots of different shapes and sizes on the ground of microstrip patch antenna (MPA) improve its characteristics like VSWR, Return Loss, efficiency, etc. This has been done by cutting a rectangular shape of defect on the ground and cut a slot on the goblet shaped patch of designed antenna structure. This microstrip antenna is suitable for tracking data, satellite communication, etc. The performance and advantages of microstrip antenna such as low cost, low profile, low weight made them the perfect choice for communication systems. In the proposed defected ground microstrip patch antenna (DG - MP A), a rectangular slot (1.25mm × 3.75mm) is cut on the Goblet Patch (10.71mm ×41. 5mm ×1. 5mm) of the structure. An inset feed (-11mm x 6mm) is introduced in this microstrip antenna. The antenna designed to function at 2.2 GHz. The proposed antenna not only operate at 2.2 GHz frequency, but also offers Return loss -26.86, VSWR 0.78, with frequency 12.85 GHz (Ku - band).
Lindau Nobel Laureate Meetings: Bridging the Generations of Scientists
Authors: Somvanshi Sandeep B.
Published: October 2020

“Educate, Inspire, Connect” is the motto of yearly Lindau Nobel Laureate Meetings which completely replicates what this gathering is all about. Since 1951, Nobel laureates have assembled in the pleasant town of Lindau, Germany, to discuss the progression of science. Beginning in 1953, the gatherings integrated young scientist from all over the world to ingrain in them enthusiasm and acquaintance on science, while likewise giving an environment for fruitful collaborations. From June 30 to July 5, 2019, around 580 young scientist representing 89 nations accumulated in this small town on the shores of Lake Constance to directly interact with 41 Nobel prize winners. In light of this year’s theme dedicated to Physics, it was an incredible benefit to go to this gathering as a young materials scientist. In spite of the fact that it was an overall gathering of physicist, a considerable insights into current advancement and development in materials science was offered by the many Nobel laureates. My objective in this article is to share these experiences and to increase awareness of this interesting and unique scientific meeting.
Synthesis and Photoluminescence study of Strontium salts with 2-Methyl-8-Hydroxyquinoline and 8-Hydroxyquinoline
Authors: Ruchir Kumar C. , Nimje Y. M. , Anwane S. W.
Published: October 2020

The pure green and turquoise green-emitting organometallic complex of strontium(II) with 8-Hydroxyquinoline and 2-methyl-8-hydroxyquinoline were synthesized by using Co-precipitation method. The structure of Sr(8-Hq)2 and Sr(2-Me-8Hq)2 was studied with Fourier transform infrared spectroscopy, and the vibrational peak of the Sr-O bond was found at 503 cm−1 and 499 cm−1 respectively. The X-Ray diffraction spectra are taken and compared with XRD data of raw materials to confirm the formation of the complex. Further UV-Absorption was studied, and the optical band gap is 2.813eV and 2.852eV, respectively, by using Taucs plot method. The photoluminescent study carried out in solution medium, and the emission wavelength found at 526nm and 509nm, and the color is confirmed using the CIE plot method, and the emission color is pure green and turquoise green. The complex may have significant applications as emitters in organic optoelectronic devices.
VUV investigation of blue emitting MAl12O19: Eu (M = Ca, Sr, Ba) phosphors synthesized by combustion method
Authors: Korpe R. G. , Koparkar K. A. , Bajaj N. S. , Omanwar S. K.
Published: October 2020

. Abstract Synthesis of europium doped alkaline earth aluminates MAl12O19 [M=Ca, Sr, Ba] by low temperatures (500ºC) solution combustion method. It corresponds to maintain the ratio of metal nitrate and urea solution mixtures. The characterization of Eu doped MAl12O19 [M=Ca, Sr, Ba] materials were done by X-ray diffraction, scanning electron microscope analysis and the optical properties were studied under 147 nm and 172 nm from synchrotron radiation excitation. The Eu-doped MAl12O19 phosphor shows broad and strong absorption in VUV region and exhibits intensive emission in blue region. The CaAl12O19: Eu2+ shows strong blue emission band at 414 nm while in SrAl12O19:Eu2+ two emission peaks are observed at about 395 nm and another around 418 nm. Both CaAl12O19: Eu2+ and SrAl12O19:Eu2+ display two very weak red emission bands at 592, 613 and 591, 613 nm respectively due to co-existence of Eu3+. BaAl12O19: Eu2+ phosphor shows emission around 440 nm in the blue region of the spectrum.