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A new experimental methodology is proposed which uses the electrostatic influence method (EIM) in scanning electron microscope (SEM) in order to estimate the second crossover energy E C2 for uncharged insulators. This experimental methodology based on simultaneous time measurement of the displacement and leakage currents, is approached to the short pulse irradiation technique but under stationary e-irradiation and allows determining the intrinsic secondary electron emission yield, σ 0 (σ 0 is the value of the total secondary electron yield just at the beginning of the irradiation before significant charge accumulation or before the formation of a surface potential). The obtained value of E C2 for soda-lime glass is confirmed by two additional experiments based on secondary electron imaging. This value is in good agreement with those previously obtained by other studies based on the surface potential measurement or the pulsed irradiation technique., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

Solution grown quantum dots (QD) are promising materials for photonic quantum science. These materials are strongly confined and further offer advantages in terms of customizability and scalability. In this review we describe the applications of these materials towards quantum science particularly as single photon emitters. We further compare the progress made towards realizing and functionalizing these materials with the current state of the art in epitaxially grown QDs. We particularly focus on charge injection to regulate electronic energy levels and optical emission, as well as effects of strain that are crucial for quantum information applications. This suggests several potential areas where the physical properties of these materials need to be better understood and controlled to fully realize their potential in quantum science. This article thus summarizes the state of the art in terms of solution grown QD development for quantum science and also outlines key areas where progress is expected before these materials become as developed as their solid-state counterparts., (© 2024 IOP Publishing Ltd. All rights, including for text and data mining, AI training, and similar technologies, are reserved.)

Great effort is put into making our mobility system more sustainable in order to mitigate climate change. One corner stone of this endeavour is the transition from internal combustion engines to electric engines for private cars. This transition, however, introduces new challenges, especially regarding the demand for electrical energy from renewable sources. One emerging phenomenon is the so-called charging rush hour, i.e. a sharp demand spike when many people arrive home and begin charging their electric cars. In this study we use an agent-based model calibrated with empirical data on mobility behaviour to investigate strategies for mitigating this charging rush hour. Studied counter strategies include telecommuting and the possibility to charge the car at work. Our findings show that the baseline peak of 65 MW per 100 000 people can only be reduced to 55 MW per 100 000 people even when combining multiple strategies. Thus the small incentives and policy changes investigated here are not enough to solve the problem of the charging rush hour and more disruptive changes to our mobility system are required., Competing Interests: The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: Milica Savanovic reports financial support was provided by Provincial Government of Styria. Lisa Goeberndorfer reports was provided by Provincial Government of Styria. If there are other authors, they declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (© 2024 The Author(s).)

The efficient dispersion of single-walled carbon nanotubes (SWCNTs) has been the subject of extensive research over the past decade. Despite these efforts, achieving individually dispersed SWCNTs at high concentrations remains challenging. In this study, we address the limitations associated with conventional methods, such as defect formation, excessive surfactant use, and the use of corrosive solvents. Our novel dispersion method utilizes the spontaneous charging of SWCNTs in a solvated electron system created by dissolving potassium in hexamethyl phosphoramide (HMPA). The resulting charged SWCNTs (c-SWCNTs) can be directly dispersed in the charging medium using only magnetic stirring, leading to defect-free c-SWCNT dispersions with high concentrations of up to 20 mg/mL. The successful dispersion of individual c-SWCNT strands is confirmed by their liquid-crystalline behavior. Importantly, the dispersion medium for c-SWCNTs exhibits no reactivity with metals, polymers, or other organic solvents. This versatility enables a wide range of applications, including electrically conductive free-standing films produced via conventional blade coating, wet-spun fibers, membrane electrodes, thermal composites, and core-shell hybrid microparticles.

Here we outline a vignette of the Bioscience Technology Facility (BTF) at the University of York as a singular exemplar of the Full Cost Recovery model. It is fully appreciated that every facility operates slightly differently, and each are subject to various rules at the institutional, regional and national level. Understanding the regulations that need to be followed for your cost recovery model may require discussion with your administrators to ensure compliance regulations for your Institution and governing bodies are followed. The below is almost a pick and mix of ways of working. It is, however, one of the few examples that is able to fully recover its operating costs within an academic environment and has sought and obtained full institutional and funders support. This model is now being much more widely adopted across the United Kingdom although again always with slightly different interpretations., (© 2023 The Authors. Journal of Microscopy published by John Wiley & Sons Ltd on behalf of Royal Microscopical Society.)

The demand for cooling applications increases severalfold; the integration of the CTES system will mitigate the demand and pollution caused by the building sectors. The objective of this study is to investigate the effect of grooving on the inner surface of the spherical capsule on the solidification characteristics of deionized (DI) water, which finds widespread use in the bed of cool thermal energy storage applications. Eight hemispheres made of mild steel of 100-mm diameter and 1-mm thickness are used to make four spherical capsules by the welding process for the study. Among the four capsules, one with a plain surface and the remaining with a groove depth of 0.3 mm, 0.5 mm, and 0.7 mm are made. The grooving in the hemispherical capsule is obtained by the turning operation. The experiments are conducted at various bath temperatures of - 6 °C, - 9 °C, and - 12 °C. The experimental result reveals that the surface modification leads to a significant reduction in solidification time, and in particular, the maximum percentage reduction in solidification time is achieved at - 6 °C. The provision of grooves makes the evaporator operate at - 6 °C instead of - 12 °C till the solidification of 75% mass and the predicted energy saving is 18 to 24%. As the enhancement of heat transfer rate techniques is carbon-free, the recycling of the PCM will have zero impact on environmental pollution., (© 2024. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Cryogenic electron microscopy can provide high-resolution reconstructions of macromolecules embedded in a thin layer of ice from which atomic models can be built de novo . However, the interaction between the ionizing electron beam and the sample results in beam-induced motion and image distortion, which limit the attainable resolutions. Sample charging is one contributing factor of beam-induced motions and image distortions, which is normally alleviated by including part of the supporting conducting film within the beam-exposed region. However, routine data collection schemes avoid strategies whereby the beam is not in contact with the supporting film, whose rationale is not fully understood. Here we characterize electrostatic charging of vitreous samples, both in imaging and in diffraction mode. We mitigate sample charging by depositing a single layer of conductive graphene on top of regular EM grids. We obtained high-resolution single-particle analysis (SPA) reconstructions at 2 Å when the electron beam only irradiates the middle of the hole on graphene-coated grids, using data collection schemes that previously failed to produce sub 3 Å reconstructions without the graphene layer. We also observe that the SPA data obtained with the graphene-coated grids exhibit a higher b factor and reduced particle movement compared to data obtained without the graphene layer. This mitigation of charging could have broad implications for various EM techniques, including SPA and cryotomography, and for the study of radiation damage and the development of future sample carriers. Furthermore, it may facilitate the exploration of more dose-efficient, scanning transmission EM based SPA techniques.

Plastic recycling is one of the most economical and environment-friendly solutions for effective plastic waste management. Triboelectric separation is one of beneficial methods to accomplish this. A method and device capable of analyzing the triboelectrification of materials with specific initial charges are proposed in this study. The process of triboelectrification is experimentally analyzed for various initial-charge conditions using the proposed method and device. The triboelectrification process can be divided into two groups depending on the initial-charge conditions. For the specific initial conditions, termed Group 2 in this work, it is observed that the initial charge of one material is first released into the control volume, following which the two materials exchange charges, unlike in the conventional triboelectrification process. This study is expected to provide valuable insights into triboelectrification analysis, thereby advancing the multistage plastic-separation processes., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier Ltd. All rights reserved.)

Each tRNA is aminoacylated (charged) with a genetic codon-specific amino acid. It remains unclear what factors are associated with tRNA charging and how tRNA charging is maintained. By using the individual tRNA acylation PCR method, we found that the charging ratio of tRNA Gln (CUG) reflects cellular glutamine level. When uncharged tRNA Gln (CUG) increased under amino acid starvation, the kinase GCN2, which is a key stimulator of the integrated stress response, was activated. Activation of GCN2 led to the upregulation of ubiquitin C (UBC) expression. Upregulated UBC, in turn, suppressed the further reduction in tRNA Gln (CUG) charging levels. Thus, tRNA charging is sensitive to intracellular nutrient status and is an important initiator of intracellular signaling., (© 2023 The Authors. FEBS Letters published by John Wiley & Sons Ltd on behalf of Federation of European Biochemical Societies.)

Bremsstrahlung spectra produced by 5 keV electrons incident on Al2O3 and MgO targets at air pressures of 30, 50, and 100 Pa have been compared with results produced using pyPENELOPE, a program designed to simulate electron microscopy. The comparisons showed that the experimental results were in good agreement with the results simulated using pyPENELOPE, except near the Duane-Hunt limit, where the bremsstrahlung amplitudes were consistently greater than PENEPMA predicted. The discrepancies may be due to charging effects, which are not simulated by PENEPMA, the Monte Carlo code on which pyPENELOPE is based. If so, the phenomena could potentially impact the accuracy of energy dispersive X-ray spectrometry measurements., Competing Interests: Conflict of interest The authors declare that they have no competing interest., (© The Author(s) 2023. Published by Oxford University Press on behalf of the Microscopy Society of America. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.)

Recently, owing to the high mobility and low cost of drones, drone-based delivery systems have shown considerable potential for ensuring flexible and reliable parcel delivery. Several crucial design issues must be considered to design such systems, including route planning, payload weight consideration, distance measurement, and customer location. In this paper, we present a survey of emerging drone routing algorithms for drone-based delivery systems, emphasizing three major drone routing aspects: trajectory planning, charging, and security. We focus on practical design considerations to ensure efficient, flexible, and reliable parcel delivery. We first discuss the potential issues arising when designing such systems. Next, we present a novel taxonomy based on the above-mentioned three aspects. We extensively review each algorithm for drone routing in terms of key features and operational characteristics. Furthermore, we compare the algorithms in terms of their main idea, advantages, limitations, and performance aspects. Finally, we present open research challenges to motivate further research in this field. In particular, we focus on the major aspects that researchers and engineers need to consider in order to design effective and reliable drone routing algorithms for drone-based delivery systems.

Recently, unmanned aerial vehicles (UAVs) or drones have emerged as a ubiquitous and integral part of our society. They appear in great diversity in a multiplicity of applications for economic, commercial, leisure, military and academic purposes. The drone industry has seen a sharp uptake in the last decade as a model to manufacture and deliver convergence, offering synergy by incorporating multiple technologies. It is due to technological trends and rapid advancements in control, miniaturization, and computerization, which culminate in secure, lightweight, robust, more-accessible and cost-efficient UAVs. UAVs support implicit particularities including access to disaster-stricken zones, swift mobility, airborne missions and payload features. Despite these appealing benefits, UAVs face limitations in operability due to several critical concerns in terms of flight autonomy, path planning, battery endurance, flight time and limited payload carrying capability, as intuitively it is not recommended to load heavy objects such as batteries. As a result, the primary goal of this research is to provide insights into the potentials of UAVs, as well as their characteristics and functionality issues. This study provides a comprehensive review of UAVs, types, swarms, classifications, charging methods and regulations. Moreover, application scenarios, potential challenges and security issues are also examined. Finally, future research directions are identified to further hone the research work. We believe these insights will serve as guidelines and motivations for relevant researchers., Competing Interests: Conflict of interestThe authors declare no conflict of interest., (© The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature 2023, Springer Nature or its licensor (e.g. a society or other partner) holds exclusive rights to this article under a publishing agreement with the author(s) or other rightsholder(s); author self-archiving of the accepted manuscript version of this article is solely governed by the terms of such publishing agreement and applicable law.)

Each transfer RNA (tRNA) is aminoacylated (charged) with a genetic codon-specific amino acid at its 3' end. Charged tRNAs are primarily used for translation, whereas fluctuations in charged tRNA fractions are known to reflect cellular response to stress. Here we report the development of individual tRNA-acylation using PCR (i-tRAP), a convenient PCR-based method that can specifically quantify individual tRNA charging ratio. In this i-tRAP method, demethylases remove base methylations which are problematic for reverse transcription reaction, and β-elimination reaction specifically removes the 3' end of adenine residue in uncharged tRNA. Subsequent TaqMan MGB qRT-PCR can distinguish between cDNA of charged tRNA and uncharged tRNA. By using this method, we revealed that the charging ratio of tRNAGln(CUG) was changed in response to amino acid starvation and also the charging ratio of tRNAGln(CUG) in senescent cells was lower than in young cells under starvation conditions. i-tRAP can be applicable to the quantification of charging ratio of various tRNAs, and provides a simple and convenient method for analyzing tRNA charging., (Published by Cold Spring Harbor Laboratory Press for the RNA Society.)

Capacity degradation and voltage fade of Li 2 MnO 3 during cycling are the limiting factors for its practical use as a high-capacity lithium-ion battery cathode. Here, the simulated amorphisation and recrystallisation (A + R) technique is used, for generating nanoporous Li 2 MnO 3 models of different lattice sizes (73 Å and 75 Å), under molecular dynamics (MD) simulations. Charging was carried out by removing oxygen and lithium ions, with oxygen charge compensated for, to restrain the release of oxygen, resulting in Li 2-x MnO 3-x composites. Detailed analysis of these composites reveals that the models crystallised into multiple grains, with grain boundaries increasing with decreasing Li/O content, and the complex internal microstructures depicted a wealth of defects, leading to the evolution of distorted cubic spinel LiMn 2 O 4 , Li 2 MnO 3 , and LiMnO 2 polymorphs. The X-ray diffraction (XRD) patterns for the simulated systems revealed peak broadening in comparison with calculated XRD, also, the emergence of peak 2Θ ~ 18-25° and peak 2Θ ~ 29° were associated with the spinel phase. Lithium ions diffuse better on the nanoporous 73 Å structures than on the nanoporous 75 Å structures. Particularly, the Li 1.00 MnO 2.00 shows a high diffusion coefficient value, compared to all concentrations. This study shed insights on the structural behaviour of Li 2 MnO 3 cathodes during the charging mechanism, involving the concurrent removal of lithium and oxygen.

The greenhouse emissions are biggest challenge of the present era. The renewable power sources are required to have characteristics of good charge capacity, energy density with proven charging discharging cycles for energy storage and applications. Mg-air batteries (MABs) are an alternative renewable power source due to their inexpensive cost. In particular, the previous reports presented the metal-air battery structure, with a specific energy overall output of 765 W h kg -1 . This paper is focused mainly on the MAB, which employed nanocomposite polymeric electrodes with a proven energy density of 545 W h kg -1 and a charge capacity of 817 mA h g -1 when electrolyzed at a cycling current density of 7 mA cm -2 .

Triboelectrostatic separation (TES) has shown its great potential in dry fractionation of food ingredients. The principle of the TES technique is straightforward, i.e., charging particles through interactions of particle-particle and/or particle-wall of the contact material, followed by the effect of an electric field. However, optimization of TES efficiency is complex due to obscure understandings, unknowns, and inconsistencies in the charging mechanism between the tribocharger and the agro-food materials. To broaden the design and applications of the TES technique and shed some light on the charging mechanism, experiments were conducted in a vortex flow tribocharger made of three different materials (Copper, Stainless Steel, and PTFE) to investigate the chargeability of five type of selected pulses particles. A Faraday cup measurement system was applied to measure the electric charge of the particles collected at the core and wall regions of the tribocharger. The charges of the pulse particles induced by the vibratory feeder were also measured to verify the chargeability of the particles. Ideal charging material was suggested by comparing the specific charge of particles using the three vessels. A simple "wave propagation" mode based on the vortex flow dynamics has been proposed with an attempt to explore the role of particle-particle and particle-wall interactions on the triboelectrostatic charging., (Copyright © 2022 Elsevier Ltd. All rights reserved.)

The groundbreaking Unmanned Aerial Vehicles (UAVs) technology has gained significant attention from both academia and industrial experts due to several applications, such as military missions, power lines inspection, precision agriculture, remote sensing, delivery services, traffic monitoring and many more. UAVs are expected to become a mainstream delivery element by 2040 to address the ever-increasing demand for delivery services. Similarly, UAV-assisted monitoring approaches will automate the inspection process, lowering mission costs, increasing access to remote locations and saving time and energy. Despite the fact that unmanned aerial vehicles (UAVs) are gaining popularity in both military and civilian applications, they have a number of limitations and critical problems that must be addressed in order for missions to be effective. One of the most difficult and time-consuming tasks is charging UAVs. UAVs' mission length and travel distance are constrained by their low battery endurance. There is a need to study multi-UAV charging systems to overcome battery capacity limitations, allowing UAVs to be used for a variety of services while saving time and human resources. Wired and Wireless Power Transfer (WPT) systems have emerged as viable options to successfully solve this difficulty. In the past, several research surveys have focused on crucial aspects of wireless UAV charging. In this review, we have also examined the most emerging charging techniques for UAVs such as laser power transfer (LPT), distributed laser charging (DLC), simultaneous wireless information and power transfer (SWIPT) and simultaneous light wave information and power transfer (SLIPT). The classification and types of UAVs, as well as various battery charging methods, are all discussed in this paper. We've also addressed a number of difficulties and solutions for safe operation. In the final section, we have briefly discussed future research directions.

Metal-organic framework (MOF), an emerging class of porous hybrid inorganic-organic crystals, has been applied for various environmental remediation strategies including liquid and air filtration. In this study, the role of the zeolite imidazole framework-8 (ZIF-8) was explored on the charge trapping ability and its contribution to capturing the targeted pollutants of NaCl nanoparticles and SO 2 gas. Poly(lactic acid) fibers with controlled surface pores were electrospun using water vapor-induced phase separation, and the fiber surface was uniformly coated with ZIF-8 crystals via an in situ growth method. As a novel process approach, the corona charging process was applied to the ZIF-8 grown webs. The ZIF-8 promoted the charge trapping in the corona process, and the charged ZIF-8 web showed a significantly improved electrostatic filtration efficiency. Also, the charged ZIF-8 web showed an enhanced SO 2 capture ability, both in the static and dynamic air flow states, demonstrating the applicability as a bifunctional filter for both particulate and gaseous matters. The approach of this study is novel in that both particulate and gas capture capabilities were associated with the charge trapping ability of ZIF-8, implementing the corona charging process to the ZIF-8 webs.

Landing platforms' automation is aimed at servicing vertical take-off and landing UAVs between flights and maintaining their airworthiness. Over the last few years, different designs for the landing platforms have been proposed. This shows a strong development and establishment of automatic landing platforms with UAV positioning devices on the landing site. Positioning and safe fixation of the UAV are some of the main features of the landing platform, especially if it is mounted on a movable vehicle. This article focuses exclusively on the landing platform and its elements that provide the positioning of the UAV by affecting it during and after the landing. Both active devices and mechanisms and passive elements used for positioning are considered. This article, based on the review of recent patents and publications, gives the classification of positioning approaches used in landing stations with the analysis of the required landing precision, as well as the pros and cons of each type of approach.

Background: The process of manually recording the consumption of medical materials can be time consuming and prone to omission owing to its detailed and complicated nature. Implementing an information system will better improve work performance., Objective: The Information System Success Model was adopted as the theoretical foundation. The opinions of nursing staff were collected to verify the impact of the system intervention on their work performance., Methods: This cross-sectional study was conducted at a regional teaching hospital. Nursing staff were invited to participate in the field survey. A total of 296 questionnaires were collected, and of these, 284 (95.9%) were valid and returned., Results: The key findings showed that two critical factors ("subjective norm" and "system quality") had significant positive effects (both P<.001) on user satisfaction (R 2 =0.709). The path of "service quality" to "user satisfaction" showed marginal significance (P=.08) under the 92% CI. Finally, the explanatory power of the model reached 68.9%., Conclusions: Support from the top management, appointment of a nurse supervisor as the change agent, recruitment of seed members to establish a pioneer team, and promotion of the system through the influence of opinion leaders in small groups were critical success factors needed for implementing the system in the case hospital. The target system was proven to be able to improve work performance, and the time saved could be further used for patient care, thereby increasing the value of nursing work. The positive experiences gained from this study could lay the foundation for the further promotion of the new system, and this is for future studies to replicate. The example of the successful experience of the case hospital could also serve as a reference for other hospitals in developing countries like Taiwan with regard to the promotion of nursing informatization., (©Min-Chi Liao, I-Chun Lin. Originally published in JMIR mHealth and uHealth (http://mhealth.jmir.org), 25.03.2020.)

Introduction: The work of veterinarians is continuously undergoing structural changes. A shift from purely curative individual animal care towards herd-health management is observed worldwide in the livestock sector. To illustrate the practical implementation with all its advantages and disadvantages, an online survey was conducted among all practicing livestock veterinarians in the Canton of Fribourg. A link to the survey was sent by email, it was voluntary and possible to complete the questionnaire anonymously. The survey focused on four topics: Demographic data, herd-health management, billing of counselling and use of antimicrobial drugs. Forty veterinarians from at least 79.2% (n = 19) of all veterinary practices located in the canton of Fribourg (n = 24) responded. Of these, 67.5% were practice owners or partner (n = 27) and 32.5% were employed veterinarians (n = 13). In Fribourg, only herd fertility management is included in the herd-health management on a regular basis. The quality and quantity of advanced trainings in herd-health management for veterinarians was assessed as moderate to poor. There are various options for charging herd-health management services. The amount charged was variable. The most frequently used options were hourly rates (100-300 CHF/h), "rate per cow per year excl. visit rate" (22-75 CHF/cow/year) or "rate per cow per year incl. visit rate" (85-98 CHF/ cow/year). Only one veterinarian (2.5%) charges for advisory activities not included in the the herd-health management service, which was asked for separately. However, the time required for counselling (excluding herd-health management) was estimated to be between 5.0-70.0% of the total working time (median 15.0%, interquartile range = 10.0-32.5%). Veterinarians in Fribourg are reHauptluctant to follow the international trend towards a regular, integrated herd-health management. The majority of them do not charge for consultancy outside the herdhealth management service. A nationwide survey should be considered to better assess the situation all over Switzerland.

A dedicated transmission helium ion microscope (THIM) for sub-50 keV helium has been constructed to investigate ion scattering processes and contrast mechanisms, aiding the development of new imaging and analysis modalities. Unlike a commercial helium ion microscope (HIM), the in-house built instrument allows full flexibility in experimental configuration. Here, we report projection imaging and intensity patterns obtained from powder and bulk crystalline samples using stationary broad-beam as well as convergent-beam illumination conditions in THIM. The He + ions formed unexpected spot patterns in the far field for MgO, BN and NaCl powder samples, but not for Au-coated MgO. The origin of the spot patterns in these samples was investigated. Surface diffraction of ions was excluded as a possible cause because the recorded scattering angles do not correspond to the predicted Bragg angles. Complementary secondary electron (SE) imaging in the HIM revealed that these samples charge significantly under He + ion irradiation. The spot patterns obtained in the THIM experiments are explained as artefacts related to sample charging. The results presented here indicate that factors other than channeling, blocking and surface diffraction of ions have an impact on the final intensity distribution in the far field. Hence, the different processes contributing to the final intensities will need to be understood in order to decouple and study the relevant ion-beam scattering and deflection phenomena.

Although charging is ubiquitous in electron microscopy, its effects are typically avoided or ignored. However, avoiding charging is not possible in some materials, e.g. lanthanide scandates with well-ordered surfaces positively charge immensely under electron beam illumination because of their electronic structure, and ignoring charging can leave new science undiscovered. In this work, a combination of rapidly acquired electron energy loss spectra and cross-correlation were used to understand and overcome charging effects in DyScO 3 . A 5.4 eV band gap was extracted from the charging-corrected loss spectrum, in good agreement with previously reported band gaps, and a 3.8 eV in-gap peak was attributed to surface states via comparison with density functional theory calculations. Additionally, ultraviolet photoelectron spectroscopy measurements indicated that under some conditions well-annealed DyScO 3 surfaces charge negatively causing upward band bending associated with occupied surface states in the gap. As was previously found in the case of positive charging under electron beam illumination with in-situ flexoelectric bending observations, the magnitude of negative charging under ultraviolet illumination is Zener tunneling limited in well-annealed DyScO 3 ., (Copyright © 2018 Elsevier B.V. All rights reserved.)

Marine sediment has a great potential to generate electricity with a bioelectrochemical system (BES) like the microbial fuel cell (MFC). In this study, we investigated the potential of marine sediment and activated carbon (AC) to generate and store electricity. Both internal and external energy supply was validated for storage behavior. Four types of anode electrode compositions were investigated. Two types were mixtures of different volumes of AC and Dutch Eastern Scheldt marine sediment (67% AC and 33% AC) and the others two were 100% AC or 100% marine sediment based. Each composition was duplicated. Operating these BES's under MFC mode with solely marine sediment as the anode electron donor resulted in the creation of a bio-battery. The recharge time of such bio-battery does depend on the fuel content and its usage. The results show that by usage of marine sediment and AC electricity was generated and stored. The 100% AC and the 67% AC mixed with marine sediment electrode were over long term potentiostatic controlled at -100 mV vs. Ag/AgCl which resulted in a cathodic current and an applied voltage. After switching back to the MFC operation mode at 1000 Ω external load, the electrode turned into an anode and electricity was generated. This supports the hypothesis that external supply electrical energy was recovered via bi-directional electron transfer. With open cell voltage experiments these AC marine bioanodes showed internal supplied electric charge storage up to 100 mC at short self-charging times (10 and 60 s) and up to 2.4°C (3,666 C/m 3 anode) at long charging time (1 h). Using a hypothetical cell voltage of 0.2 V, this value represents an internal electrical storage density of 0.3 mWh/kg AC marine anode. Furthermore it was remarkable that the BES with 100% marine sediment based electrode also acted like a capacitor similar to the charge storage behaviors of the AC based bioanodes with a maximum volumetric storage of 1,373 C/m 3 anode. These insights give opportunities to apply such BES systems as e.g., ex situ bio-battery to store and use electricity for off-grid purpose in remote areas.

How a heavily charged metal nanocrystal, and further a dual-nanocrystals system behavior with continuous electron charging? This refers to the electric dynamics in charged particles as well as the crystal growth for real metal particles, but it is still opening in experimental observations and interpretations. To this end, we performed an in-situ electron-beam irradiation study using transmission electron microscopy (TEM) on the Au nanocrystals that freely stand on the nitride boron nanotube (BNNT). Au nanocrystalline particles with sizes of 2⁻4 nm were prepared by a well-controlled sputtering method to stand on the BNNT surface without chemical bonding interactions. Au nanoparticles presented the surface atomic disorder, diffusion phenomena with continuous electron-beam irradiation, and further, the long-range motion that contains mainly the three stages: charging, activation, and adjacence, which are followed by final crystal growth. Firstly, the growth process undergoes the lattice diffusion and subsequently the surface-dominated diffusion mechanism. These abnormal phenomena and observations, which are fundamentally distinct from classic cases and previous reports, are mainly due to the overcharging of Au nanoparticle that produces a surface activation state in terms of high-energy plasma. This work therefore brings about new observations for both a single and dual-nanocrystals system, as well as new insights in understanding the resulting dynamics behaviors.

The surface potentials and dynamic charging properties of polymers subjected to electron irradiation in scanning electron microscopy are investigated by using a novel method applied in parallel with simulation and experimental methods. We perform our simulation through a parallel computing method with various microscopic parameters. The results show that under the given microscopic parameters, the charging time concomitantly decreases as the film thickness, electron mobility, trap cross and recombination rate increase. The surface potential decreases as electron energy, beam current density, capture cross section, sample thickness and electron-hole recombination rate increase and as electron mobility decreases. Charging time increases with increasing beam density, sample thickness, recombination rate and change in capture cross-section, and decreases with increasing electron mobility. The primary-electron energy exhibits an inflection point at 35 keV. This study offers an intuitive analytical and measurement method for understanding microscopic charge characteristics in electron-based surface microscopy., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

Recent advancements in electron microscope volume imaging, such as serial imaging using scanning electron microscopy (SEM), have facilitated the acquisition of three-dimensional ultrastructural information of biological samples. These advancements help build a comprehensive understanding of the functional structures in entire organelles, cells, organs and organisms, including large-scale wiring maps of neural circuitry in various species. Advanced volume imaging of biological specimens has often been limited by artifacts and insufficient contrast, which are partly caused by problems in staining, serial sectioning and electron beam irradiation. To address these issues, methods of sample preparation have been modified and improved in order to achieve better resolution and higher signal-to-noise ratios (SNRs) in large tissue volumes. These improvements include the development of new embedding media for electron microscope imaging that have desirable physical properties such as less deformation in the electron beam and higher stability for sectioning. The optimization of embedding media involves multiple resins and filler materials including biological tissues, metallic particles and conductive carbon black. These materials alter the physical properties of the embedding media, such as conductivity, which reduces specimen charge, ameliorates damage to sections, reduces image deformation and results in better ultrastructural data. These improvements and further studies to improve electron microscope volume imaging methods provide options for better scale, quality and throughput in the three-dimensional ultrastructural analyses of biological samples. These efforts will enable a deeper understanding of neuronal circuitry and the structural foundation of basic and higher brain functions.

The ability to control the charge state and ionization efficiency of lipids and hydrocarbons by means of in-source Paternò-Büchi functionalization in nano-electrospray ionization mass spectrometry experiments is investigated. Ultraviolet light irradiation of acetylpyridine filled nano-electrospray emitter tips, containing unsaturated analytes, generates protonated lipid and hydrocarbon ions. Comparison of reaction yields and fragment ion abundances of functionalized unsaturated fatty acids indicate that acetylpyridine Paternò-Büchi functionalization allows to readily detect fatty acids and determine double bond positions, but fragmentation efficiency and reactivity depend on double bond position and varies between different acetylpyridine isomers. Results for methyl oleate and olefins suggest that fragment ion abundances of unsaturated compounds depend on interactions between acetylpyridine and nearby functional groups. Paternò-Büchi functionalization with acetylpyridine was used to detect and assign double bond positions of mono- and polyunsaturated fatty acid, cholesterol ester, triglyceride, and hydrocarbon standards with ion abundances that are up to 631 times higher than abundances of the same compounds prior Paternò-Büchi reaction. To demonstrate the scope and analytical robustness of the newly developed method, free fatty acids in mouse brain as well as male Schistosoma mansoni extracts and hydrocarbons in an olefin mixture are investigated. For this complex set of analytes, charging and charge switching using acetylpyridine Paternò-Büchi functionalization enable double bond position assignment and relative quantification in positive ion mode. Graphical Abstract.

Electrophoretic mobility and time resolved light scattering are used to measure the effect on charging and aggregation of amidine and sulfate latex particles of different oxyanions namely, phosphate, arsenate, sulfate, and selenate. In the case of negatively charged sulfate latex particles oxyanions represent the coions, while they represent counterions in the case of the positively charged amidine latex. Repulsive interaction between the sulfate latex surface and the coions results in weak ion specific effects on the charging and aggregation. On the other hand the interaction of oxyanions with the amidine latex surface is highly specific. The monovalent dihydrogen phosphate ion strongly adsorbs to the positively charged surface and reverses the charge of the particle. This charge reversal leads also to the restabilization of the amidine latex suspension at the intermediate phosphate concentrations. In the case of dihydrogen arsenate the adsorption to amidine latex surface is weaker and no charge reversal and restabilization occurs. Similar differences are seen between the sulfate and selenate analogues, where selenate adsorbs more strongly to the surface as compared to the sulfate ion and invokes charge reversal. The present results indicate that ion specificity is much more pronounced in the case of counterions., (Copyright © 2018 Elsevier Inc. All rights reserved.)

Quantum dots (QDs) are steadily being implemented as down-conversion phosphors in market-ready display products to enhance color rendering, brightness, and energy efficiency. However, for adequate longevity, QDs must be encased in a protective barrier that separates them from ambient oxygen and humidity, and device architectures are designed to avoid significant heating of the QDs as well as direct contact between the QDs and the excitation source. In order to increase the utility of QDs in display technologies and to extend their usefulness to more demanding applications as, for example, alternative phosphors for solid-state lighting (SSL), QDs must retain their photoluminescence emission properties over extended periods of time under conditions of high temperature and high light flux. Doing so would simplify the fabrication costs for QD display technologies and enable QDs to be used as down-conversion materials in light-emitting diodes for SSL, where direct-on-chip configurations expose the emitters to temperatures approaching 100 °C and to photon fluxes from 0.1 W/mm 2 to potentially 10 W/mm 2 . Here, we investigate the photobleaching processes of single QDs exposed to controlled temperature and photon flux. In particular, we investigate two types of room-temperature-stable core/thick-shell QDs, known as "giant" QDs for which shell growth is conducted using either a standard layer-by-layer technique or by a continuous injection method. We determine the mechanistic pathways responsible for thermally-assisted photodegradation, distinguishing effects of hot-carrier trapping and QD charging. The findings presented here will assist in the further development of advanced QD heterostructures for maximum device lifetime stability.

The effect of shell thickness on the performance of all-inorganic quantum dot light-emitting diodes (QLEDs) is explored by employing a series of green quantum dots (QDs) (Zn x Cd 1- x Se/ZnS core/shell QDs with different ZnS shell thicknesses) as the emitters. ZnO nanoparticles and sol-gel NiO are employed as the electron and hole transport materials, respectively. Time-resolved and steady-state photoluminescence results indicate that positive charging processes might occur for the QDs deposited on NiO, which results in emission quenching of QDs and poor device performance. The thick shell outside the core in QDs not only largely suppresses the QD emission quenching but also effectively preserves the excitons in QDs from dissociation of electron-hole pairs when they are subjected to an electric field. The peak efficiency of 4.2 cd/A and maximum luminance of 4205 cd/m 2 are achieved for the device based on QDs with the thickest shells (∼4.2 nm). We anticipate that these results will spur progress toward the design and realization of efficient all-inorganic QLEDs as a platform for the QD-based full-colored displays.

The fluctuating granularity or "bee swarm" effect seen in highly defocussed transmission electron micrographs is caused by microscopic charge fluctuations in the specimen created by the illuminating beam. In the field of high-resolution single particle electron cryomicroscopy (cryoEM), there has been a concern that this fluctuating charge might cause defocus-dependent Thon ring fading which would degrade the final image. In this paper, we have analysed the 2.35 Å fringes from the (111) reflection in images of gold nanoparticles embedded in amorphous ice. We show that there is a small, yet detectable amount of defocus-dependent blurring of the lattice fringes when compared with those from a pure gold foil. The transverse electric field associated with the fluctuating charges on the insulating frozen water specimen deflects the electron beam locally and causes image blurring. The perturbation is small, decreasing the amplitude of the 2.35 Å reflection at 10 µm defocus by about 7% (intensity by 14%). For smaller defocus values in the range 2-4 µm and for resolutions that are typical in cryoEM, the effects of source incoherence and the bee swarm effect are negligible for all reasonable cryoEM imaging conditions, assuming that a field emission gun (FEG) is used for illumination. This leaves physical movement of the specimen due to radiation damage as the outstanding problem and the major source of contrast loss in cryoEM micrographs., (Copyright © 2018 MRC Laboratory of Molecular Biology. Published by Elsevier B.V. All rights reserved.)

When irradiated in a transmission electron microscope, plunge-frozen, amorphous water ice specimens accumulate a pattern of static charge that changes dynamically as the specimen is irradiated, and which can deflect the transmitted electrons and blur the resultant micrographs. Here we provide a physical description of this charge accumulation and characterise its dynamic behaviour in the context of low-dose electron cryomicroscopy (cryoEM). We observe the accumulation of positive charge in the primary irradiation area as expected from earlier work. To our surprise, we also observed a build-up of negative charge in nearby unirradiated regions of the specimen. Using a standard carbon support foil containing a pure water ice specimen, we collect a portion of this negative charge in the micrometer sized specimen holes which act as electrostatic lenses. These unusual, diverging micro-lenses are extremely sensitive charge detectors that allow us to directly measure the magnitude and dynamics of charge accumulation and neutralisation that occur during cryoEM imaging. Using these measurements, we find that the build-up of charge on the specimen saturates to a dynamic equilibrium at an electron fluence which is orders of magnitude lower than required for a typical low-dose micrograph. The measurements here will guide the development of optimal imaging conditions for biological specimens and contribute to a complete theory of information loss in electron cryomicroscopy., (Copyright © 2018 MRC Laboratory of Molecular Biology. Published by Elsevier B.V. All rights reserved.)

Contemporarily, serial block-face scanning electron microscopy (SBF-SEM) has emerged as an immensely powerful nanoscopic imaging technique, capable of generating large-volume three-dimensional information on a variety of biological specimens in a semiautomated manner. Despite the plethora of insights and advantages provided by SBF-SEM, a major challenge inherent to the technique is that of electron charging, which ultimately reduces attainable resolution and detracts from overall image quality. In this chapter, we describe a pre-embedding approach that involves infiltration of tissue with a highly conductive silver filler suspension following primary fixation. Such an approach is demonstrated to improve overall sample conductivity, resulting in the minimization of charging under high-vacuum conditions and an improvement in lateral resolution and image contrast. The strength of this sample preparation approach for SBF-SEM is illustrated on liver tissue.

The Safe-Range-Inventory (SRI) was constructed in order to help public authorities to improve the charging infrastructures for electric vehicles [1; 10.1016/j.trf.2017.04.011]. Specifically, the impact of fast (vs slow) charging stations on people's range anxiety was examined. Ninety-seven electric vehicle users from Germany (81 male; M age =12.1) were recruited to participate in the experimental design. Statistical analyses were conducted using ANOVA for repeated measures to test for interaction effects of available charging stations and remaining range with the dependent variable SD =12.1) were recruited to participate in the experimental design. Statistical analyses were conducted using ANOVA for repeated measures to test for interaction effects of available charging stations and remaining range with the dependent variable range anxiety . The full data set is publicly available via https://osf.io/bveyw/ (Carbon and Gebauer, 2017) [2].

Charge transport and electron emission properties in polypropylene and its nanocomposites filled with nanoclay particles submitted to an electron irradiation, in a Scanning Electron Microscope (SEM), are investigated using induced displacement and leakage currents. The measurements have been performed at various temperatures ranging from 20°C to 75°C at a primary beam energy of 20keV and a primary beam current of 1nA with the aim to highlight the effect of temperature and nanoclay content on these properties. The results show, at a given temperature, that the incorporation of clay in polypropylene (PP) matrix paradoxically leads to a concomitant increase in the electrical conductivity and the charge accumulated. In contrast, if the clay content is fixed, there is an increase in conductivity and a reduction of the charge accumulated when the temperature increases. The mobility of charge carriers and the corresponding activation energy are deduced from the measured leakage current during discharging step. The mobility was found to be an order of magnitude higher for the nanocomposites. The study of the influence of the temperature and nanoclay concentration on electron emission yield is also addressed., (Copyright © 2017 Elsevier Ltd. All rights reserved.)

Charging of a SiO2 particle induced by electron illumination was investigated by changing the illuminated area of the particle and its support film through control of the position of the mask plate inserted in a transmission electron microscope illumination system. The electric fields around the charged SiO2 particle were analyzed using electron holography. The amount of charge was evaluated quantitatively by comparing the reconstructed phase images with the simulated phase images. When the support film was not covered against the incident electron beam, secondary electrons emitted from the conductive support film were attracted to the charged particle, resulting in particle discharge. In contrast, when the support film was completely covered, secondary electrons were not emitted from the film, so that the particle remained positively charged., (© The Author 2017. Published by Oxford University Press on behalf of The Japanese Society of Microscopy. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.)

Herein, we describe three advanced techniques for cathodoluminescence (CL) spectroscopy that have recently been developed in our laboratories. The first is a new method to accurately determine the CL-efficiency of thin layers of phosphor powders. When a wide band phosphor with a band gap (E g > 5 eV) is bombarded with electrons, charging of the phosphor particles will occur, which eventually leads to erroneous results in the determination of the luminous efficacy. To overcome this problem of charging, a comparison method has been developed, which enables accurate measurement of the current density of the electron beam. The study of CL from phosphor specimens in a scanning electron microscope (SEM) is the second subject to be treated. A detailed description of a measuring method to determine the overall decay time of single phosphor crystals in a SEM without beam blanking is presented. The third technique is based on the unique combination of microscopy and spectrometry in the transmission electron microscope (TEM) of Brunel University London (UK). This combination enables the recording of CL-spectra of nanometre-sized specimens and determining spatial variations in CL emission across individual particles by superimposing the scanning TEM and CL-images.

For studying the electrical properties (charge trapping, transport and secondary electron emission) of the polypropylene-based nanocomposites with different contents of natural clay, the specimens were submitted to electron irradiation of a scanning electron microscope. A device, suitably mounted on the sample holder of the scanning electron microscope, was used to measure two currents (i.e. leakage and displacement currents) induced in the polypropylene-based nanocomposites (polymer nanocomposites) under electron irradiation. The evolution of trapped charge during irradiation for each type of studied polymer nanocomposites is deduced. The amount of trapped charge at the steady state is also determined by measuring the change of secondary electron image size associated to the electron trajectory simulation. It is found, surprisingly, that not only the leakage current increases as a function of clay loading level but also trapped charge. However, this could be related to the increase of conductivity in one hand and to proliferation of interfaces between nanoparticles and neighbouring materials on the other hand. These two processes play crucial role in controlling the carrier transport (through polymer nanocomposites or/and along its surface) closely related to the charge storage and leakage current. Additional experiment using dielectric spectroscopy were performed to show the effect of clay concentration in changing the dielectric relaxation behaviour and to evidence the existence of interfaces between nanoparticles and polymer. The secondary electron emission during electron irradiation is also studied through the total electron yield that is deduced by correlating the measured leakage and displacement currents., (© 2016 The Authors Journal of Microscopy © 2016 Royal Microscopical Society.)

Factors that influence the charging of protein ions formed by electrospray ionization from aqueous solutions in which proteins have native structures and function were investigated. Protein ions ranging in molecular weight from 12.3 to 79.7 kDa and pI values from 5.4 to 9.6 were formed from different solutions and reacted with volatile bases of gas-phase basicities higher than that of ammonia in the cell of a Fourier-transform ion cyclotron resonance mass spectrometer. The charge-state distribution of cytochrome c ions formed from aqueous ammonium or potassium acetate is the same. Moreover, ions formed from these two solutions do not undergo proton transfer to 2-fluoropyridine, which is 8 kcal/mol more basic than ammonia. These results provide compelling evidence that proton transfer between ammonia and protein ions does not limit protein ion charge in native electrospray ionization. Both circular dichroism and ion mobility measurements indicate that there are differences in conformations of proteins in pure water and aqueous ammonium acetate, and these differences can account for the difference in the extent of charging and proton-transfer reactivities of protein ions formed from these solutions. The extent of proton transfer of the protein ions with higher gas-phase basicity bases trends with how closely the protein ions are charged to the value predicted by the Rayleigh limit for spherical water droplets approximately the same size as the proteins. These results indicate that droplet charge limits protein ion charge in native mass spectrometry and are consistent with these ions being formed by the charged residue mechanism. Graphical Abstract ᅟ.

Charging of physical phase plates is a problem that has prevented their routine use in transmission electron microscopy of weak-phase objects. In theory, electrostatic phase plates are superior to thin-film phase plates since they do not attenuate the scattered electron beam and allow freely adjustable phase shifts. Electrostatic phase plates consist of multiple layers of conductive and insulating materials, and are thus more prone to charging than thin-film phase plates, which typically consist of only one single layer of amorphous material. We have addressed the origins of charging of Boersch phase plates and show how it can be reduced. In particular, we have performed simulations and experiments to analyze the influence of the insulating Si3N4 layers and surface charges on electrostatic charging. To optimize the performance of electrostatic phase plates, it would be desirable to fabricate electrostatic phase plates, which (i) impart a homogeneous phase shift to the unscattered electrons, (ii) have a low cut-on frequency, (iii) expose as little material to the intense unscattered beam as possible, and (iv) can be additionally polished by a focused ion-beam instrument to eliminate carbon contamination accumulated during exposure to the unscattered electron beam (Walter et al., 2012, Ultramicroscopy, 116, 62-72). We propose a new type of electrostatic phase plate that meets the above requirements and would be superior to a Boersch phase plate. It consists of three free-standing coaxial rods converging in the center of an aperture (3-fold coaxial phase plate). Simulations and preliminary experiments with modified Boersch phase plates indicate that the fabrication of a 3-fold coaxial phase plate is feasible., (Copyright © 2015 Elsevier B.V. All rights reserved.)

This is the fourth part of a series of tutorial papers discussing various causes of measurement uncertainty in scanned particle beam instruments, and some of the solutions researched and developed at NIST and other research institutions. Scanned particle beam instruments especially the scanning electron microscope (SEM) have gone through tremendous evolution to become indispensable tools for many and diverse scientific and industrial applications. These improvements have significantly enhanced their performance and made them far easier to operate. But, the ease of operation has also fostered operator complacency. In addition, the user-friendliness has reduced the apparent need for extensive operator training. Unfortunately, this has led to the idea that the SEM is just another expensive "digital camera" or another peripheral device connected to a computer and that all of the problems in obtaining good quality images and data have been solved. Hence, one using these instruments may be lulled into thinking that all of the potential pitfalls have been fully eliminated and believing that, everything one sees on the micrograph is always correct. But, as described in this and the earlier papers, this may not be the case. Care must always be taken when reliable quantitative data are being sought. The first paper in this series discussed some of the issues related to signal generation in the SEM, including instrument calibration, electron beam-sample interactions and the need for physics-based modeling to understand the actual image formation mechanisms to properly interpret SEM images. The second paper has discussed another major issue confronting the microscopist: specimen contamination and methods to eliminate it. The third paper discussed mechanical vibration and stage drift and some useful solutions to mitigate the problems caused by them, and here, in this the fourth contribution, the issues related to specimen "charging" and its mitigation are discussed relative to dimensional metrology.

This is the fourth part of a series of tutorial papers discussing various causes of measurement uncertainty in scanned particle beam instruments, and some of the solutions researched and developed at NIST and other research institutions. Scanned particle beam instruments, especially the scanning electron microscope (SEM), have gone through tremendous evolution to become indispensable tools for many and diverse scientifc and industrial applications. These improvements have significantly enhanced their performance and made them far easier to operate. But, the ease of operation has also fostered operator complacency. In addition, the user-friendliness has reduced the apparent need for extensive operator training. Unfortunately, this has led to the idea that the SEM is just another expensive "digital camera" or another peripheral device connected to a computer and that all of the problems in obtaining good quality images and data have been solved. Hence, one using these instruments may be lulled into thinking that all of the potential pitfalls have been fully eliminated and believing that, everything one sees on the micrograph is always correct. But, as described in this and the earlier papers, this may not be the case. Care must always be taken when reliable quantitative data are being sought. The first paper in this series discussed some of the issues related to signal generation in the SEM, including instrument calibration, electron beam-sample interactions and the need for physics-based modeling to understand the actual image formation mechanisms to properly interpret SEM images. The second paper has discussed another major issue confronting the microscopist: specimen contamination and methods to eliminate it. The third paper discussed mechanical vibration and stage drift and some useful solutions to mitigate the problems caused by them, and here, in this the fourth contribution, the issues related to specimen "charging" and its mitigation are discussed relative to dimensional metrology.

CdSe/Zn1-X CdX S core/shell heterostructured quantum dots (QDs) with varying shell thicknesses are studied as the active material in a series of electroluminescent devices. "Giant" CdSe/Zn1-X CdX S QDs (e.g., CdSe core radius of 2 nm and Zn1-X CdX S shell thickness of 6.3 nm) demonstrate a high device efficiency (peak EQE = 7.4%) and a record-high brightness (>100 000 cd m(-2) ) of deep-red emission, along with improved device stability., (© 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Internal sample conductivity in scanning electron microscopy can be a valuable alternative to metal coating. Proton conductivity may be used for this purpose. Many solid materials with active hydrogen atoms, such as hydrogen- and ammonium-salts, organic acids, and even ice, are protonic conductors or semiconductors. Here we present a method to generate proton conductivity in dry biological materials. A simple treatment with hydrogen chloride gas or hydrochloric acid vapour for a few minutes provides sufficient conductivity for many samples. After a removal of excess hydrogen chloride vapour with a vacuum desiccator, the objects may be examined in the SEM without metal coating. The use of internally conductive samples extends the range of easy-to-perform SEM preparation techniques. It is advantageous for material contrast imaging of uncoated samples, and it can be used in combination with metal coating to enhance conductivity on difficult samples with complex overlapping surfaces, where simple metal coating does not reliably eliminate charging problems., (© 2014 The Authors Journal of Microscopy © 2014 Royal Microscopical Society.)

As shown by Matsumoto and Tonomura, the phase shift imposed on an electron beam by an electrostatic phase plate is constant for all (straight) electron trajectories passing through a circular aperture, provided that (1) the electric field goes to zero at distances far above and below the aperture and (2) the value of the phase shift at the boundary (i.e. perimeter of the aperture) is constant [5]. We now point out that the result can be valid for any shape of the hole in the aperture, and, furthermore, it requires only that the electric field is equal and opposite at large distances above and below the aperture, respectively. We also point out that the conditions of validity of the Matsumoto-Tonomura approximation constrain the phase shift across the open aperture to a quadratic algebraic form when the phase shift is not constant around the perimeter. Finally, it follows that the projection approximation for calculating the phase shift must fail for strong phase shifts of higher than quadratic form. These extensions of the original result of Matsumoto and Tonomura give further insight to the analysis of charging phenomena observed with apertures that are designed to produce contrast in in-focus images of weak phase objects., (© 2013 Published by Elsevier B.V.)

Microfabricated devices designed to provide phase contrast in the transmission electron microscope must be free of phase distortions caused by unexpected electrostatic effects. We find that such phase distortions occur even when a device is heated to 300 °C during use in order to avoid the formation of polymerized, carbonaceous contamination. Remaining factors that could cause unwanted phase distortions include patchy variations in the work function of a clean metal surface, radiation-induced formation of a localized oxide layer, and creation of a contact potential between an irradiated area and the surround due to radiation-induced structural changes. We show that coating a microfabricated device with evaporated carbon apparently eliminates the problem of patchy variation in the work function. Furthermore, we show that a carbon-coated titanium device is superior to a carbon-coated gold device, with respect to radiation-induced electrostatic effects. A carbon-coated, hybrid double-sideband/single-sideband aperture is used to record in-focus, cryo-EM images of monolayer crystals of streptavidin. Images showing no systematic phase error due to charging are achievable under conditions of low-dose data collection. The contrast in such in-focus images is sufficient that one can readily see individual streptavidin tetramer molecules. Nevertheless, these carbon-coated devices perform well for only a limited length of time, and the cause of failure is not yet understood., (© 2013 Elsevier B.V. All rights reserved.)

Images of radiation-sensitive specimens obtained by electron microscopy suffer a reduction in quality beyond that expected from radiation damage alone due to electron beam-induced charging or movement of the specimen. For biological specimens, charging and movement are most severe when they are suspended in an insulating layer of vitreous ice, which is otherwise optimal for preserving hydrated specimens in a near native state. We image biological specimens, including a single particle protein complex and a lipid-enveloped virus in thin, vitreous ice films over suspended sheets of unmodified graphene. We show that in such preparations, the charging of ice, as assessed by electron-optical perturbation of the imaging beam, is eliminated. We also use the same specimen supports to record high resolution images at liquid nitrogen temperature of monolayer paraffin crystals grown over graphene., (Copyright © 2013 The Authors. Published by Elsevier Inc. All rights reserved.)

Combined effects of sample parameters on polymer charging due to electron irradiation are explored by a novel approach of contour in parallel computing. Transient processes of negative charging of a Kapton film sample irradiated by 10 keV electrons are simulated with a simultaneous scattering-transport model and the existing experimental secondary electron current. As a function of sample thickness and electron mobility, the contour maps are then presented of the steady-state leakage current and surface potential and the total charge accumulated in a charging process. It is found that the leakage current and surface potential behave similarly in the contour form, and the total charge has the local maximum with respect to the sample thickness. Generally, the sample thickness affects the charging process more than the electron mobility, but both have less influence in very strong and weak charging states. Accompanied by discussion of charge dissipation effects, this study offers a comprehensive insight into complicated charging phenomena in electron-based surface microscopy, analysis and measurement., (Copyright © 2013 Elsevier Ltd. All rights reserved.)

Using first-principles simulations on PbS and CdSe colloidal quantum dots, we find that surface defects form in response to electronic doping and charging of the nanoparticles. We show that electronic trap states in nanocrystals are dynamic entities, in contrast with the conventional picture wherein traps are viewed as stable electronic states that can be filled or emptied, but not created or destroyed. These traps arise from the formation or breaking of atomic dimers at the nanoparticle surface. The dimers' energy levels can reside within the bandgap, in which case a trap is formed. Fortunately, we are also able to identify a number of shallow-electron-affinity cations that stabilize the surface, working to counter dynamic trap formation and allowing for trap-free doping.