Search

A sensitive and reproducible screening analytical method is here proposed for the determination of six non dioxin-like polychlorinated biphenyls (NDL-PCBs, congener 28, 52, 101, 138, 153, 180) in chicken eggs based on accelerated solvent extraction (ASE) procedure for the fat extraction and determination, a solid phase extraction (SPE) sample clean-up process, and a gas chromatography – electron capture detection (GC-ECD) analysis. The optimized chromatographic separation, in less than 25 min, returned good responses for the six NDL-PCBs in the range of 2.5–60.0 µg L−1, with correlation coefficients always higher than 0.9995. Instrumental limits of detection were between 0.08–0.35 µg L−1, corresponding to 0.05 and 0.23 ng g−1 fat in the matrix, while method detection limits, calculated on spiked egg samples, ranged from 1.6 to 3.5 ng g−1 fat. The method has been extensively validated in terms of selectivity, sensitivity, recovery, precision, ruggedness and measurement uncertainty, following the European Directives. [ABSTRACT FROM AUTHOR]

We demonstrate a method to detect the spin resonance of Mn electrons at room temperature in paramagnetic samples of La1−xCaxMnO3 with x = 0.35, 0.40, and 0.45 using a simple magnetoimpedance (MI) measurement. The magnetic field dependent "ac" resistance and reactance were simultaneously measured at 300 K using a single-port impedance analyzer by passing a current of frequency f = 500 MHz–3 GHz directly through the sample. The magnetoresistance of each sample increased abruptly at a critical value of the applied magnetic field while the magnetoreactance displayed a dip. Both these features shifted linearly toward higher "dc" magnetic fields with increasing frequency of the current. We suggest that these anomalies in MI are imprints of spin resonance from the Mn electrons. Our results were also verified using a conventional broadband spectrometer (f = 2–10 GHz). Thus, the electrical detection of paramagnetic resonance using a low-cost impedance analyzer, as demonstrated here, can provide an alternate method to investigate magnetic resonances in various materials. [ABSTRACT FROM AUTHOR]

We demonstrate a method to detect the spin resonance of Mn electrons at room temperature in paramagnetic samples of La1−xCaxMnO3 with x = 0.35, 0.40, and 0.45 using a simple magnetoimpedance (MI) measurement. The magnetic field dependent "ac" resistance and reactance were simultaneously measured at 300 K using a single-port impedance analyzer by passing a current of frequency f = 500 MHz–3 GHz directly through the sample. The magnetoresistance of each sample increased abruptly at a critical value of the applied magnetic field while the magnetoreactance displayed a dip. Both these features shifted linearly toward higher "dc" magnetic fields with increasing frequency of the current. We suggest that these anomalies in MI are imprints of spin resonance from the Mn electrons. Our results were also verified using a conventional broadband spectrometer (f = 2–10 GHz). Thus, the electrical detection of paramagnetic resonance using a low-cost impedance analyzer, as demonstrated here, can provide an alternate method to investigate magnetic resonances in various materials. [ABSTRACT FROM AUTHOR]

We report the design and development of a compact electron and positron spectrometer based on tapered neodymium iron boron magnets to characterize the pairs generated in laser-matter experiments. The tapered design forms a gradient magnetic field component allowing energy dependent focusing of the dispersed charged particles along a chosen detector plane. The mirror symmetric design allows for simultaneous detection of pairs with energies from 2 MeV to 500 MeV with an accuracy of ≤10% in the wide energy range from 5 to 110 MeV for a parallel beam incident on a circular aperture of 20 mm. The energy resolution drops to ≤20% for 4–90 MeV range for a divergent beam originating from a point source at 20 cm away (i.e., a solid angle of ∼8 milli steradians), with ≤10% accuracy still maintained in the narrower energy range from 10 to 55 MeV. It offers higher solid angle acceptance, even for the divergent beam, compared to the conventional pinhole aperture-based spectrometers. The proposed gradient magnet is suitable for the detection of low flux and/or monoenergetic type electron/positron beams with finite transverse sizes and offers unparalleled advantages for gamma-ray spectroscopy in the intermediate MeV range. [ABSTRACT FROM AUTHOR]

Tandem repeat proteins exhibit native designability and represent potentially useful scaffolds for the construction of synthetic biomimetic assemblies. We have designed 2 synthetic peptides, HEAT_R1 and LRV_M3Δ1, based on the consensus sequences of single repeats of thermophilic HEAT (PBS_HEAT) and Leucine-Rich Variant (LRV) structural motifs, respectively. Self-assembly of the peptides afforded high-aspect ratio helical nanotubes. Cryo-electron microscopy with direct electron detection was employed to analyze the structures of the solvated filaments. The 3D reconstructions from the cryo-EM maps led to atomic models for the HEAT_R1 and LRV_M3Δ1 filaments at resolutions of 6.0 and 4.4 Å, respectively. Surprisingly, despite sequence similarity at the lateral packing interface, HEAT_R1 and LRV_M3Δ1 filaments adopt the opposite helical hand and differ significantly in helical geometry, while retaining a local conformation similar to previously characterized repeat proteins of the same class. The differences in the 2 filaments could be rationalized on the basis of differences in cohesive interactions at the lateral and axial interfaces. These structural data reinforce previous observations regarding the structural plasticity of helical protein assemblies and the need for high-resolution structural analysis. Despite these observations, the native designability of tandem repeat proteins offers the opportunity to engineer novel helical nanotubes. Moreover, the resultant nanotubes have independently addressable and chemically distinguishable interior and exterior surfaces that would facilitate applications in selective recognition, transport, and release. [ABSTRACT FROM AUTHOR]

Abstract Due to their very fast signal rise time in the order of 1 ns, Silicon-Photomultipliers have become of increasing interest for many experiments that require very good timing resolution. With the prospect of an application in medical imaging techniques like a Compton Camera or TOF-PET, a coincident detection of Cherenkov photons from electrons in the MeV range in PMMA has been performed. A 4 × 4 SiPM-array was used for this purpose and a timing resolution of 242 ps has been achieved. A spatial sensitivity for an electron source location could be shown using accumulated coincident light signals. The obtained results are in good agreement with theoretical calculations taking fundamental detector and set-up properties into account. These measurements constitute an important step towards the feasibility of a successful electron detection in a Compton Camera. [ABSTRACT FROM AUTHOR]

In this article, we report on the development of a time-of-flight based electron energy analyzer capable of measuring the 3-D momentum and energy distributions of very low energy (millielectronvolt-scale) photoemitted electrons. This analyzer is capable for measuring energy and 3-D momentum distributions of electrons with energies down to 1 meV with a sub-millielectronvolt energy resolution. This analyzer is an ideal tool for studying photoemission processes very close to the photoemission threshold and also for studying the physics of photoemission based electron sources. [ABSTRACT FROM AUTHOR]

Abstract We have developed multi-gap resistive plate chambers (MRPCs) with 2. 5 × 200 cm 2 readout strips for the time-of-flight (TOF) detector system of the LEPS2 experiment at SPring-8. These chambers consist of two float glass stacks with 5 gas gaps each, in a mirrored configuration. A time resolution of σ ≃ 80 ps was achieved for any position within a strip (at above 99% detection efficiency), improved to 60 ps after correcting for a relatively small time-charge slewing effect. This latter fact seems to stem from the suppression of modal dispersion, achieved through convenient design choices. [ABSTRACT FROM AUTHOR]

Surface charging by keV (kiloelectron Volt) electrons can pose a serious risk for satellites. There is a need for physical models with the correct and validated dynamical behavior. The 18.5‐month (2013–2015) output from the continuous operation online in real time as a nowcast of the Inner Magnetosphere Particle Transport and Acceleration Model (IMPTAM) is compared to the GOES 13 MAGnetospheric Electron Detector (MAGED) data for 40, 75, and 150 keV energies. The observed and modeled electron fluxes were organized by Magnetic Local Time (MLT) and IMPTAM driving parameters; the observed Interplanetary Magnetic Field (IMF) BZ, BY, and |B|; the solar wind speed VSW; the dynamic pressure PSW; and Kp and SYM‐H indices. The peaks for modeled fluxes are shifted toward midnight, but the ratio between the observed and modeled fluxes at around 06 MLT is close to 1. All the statistical patterns exhibit very similar features with the largest differences of about 1 order of magnitude at 18–24 MLT. Based on binary event analysis, 20–78% of threshold crossings are reproduced, but Heidke skill scores are low. The modeled fluxes are off by a factor of 2 in terms of the median symmetric accuracy. The direction of the error varies with energy: overprediction by 50% for 40 keV, overprediction by 2 for 75 keV, and underprediction by 18% for 150 keV. The revealed discrepancies are due to the boundary conditions developed for ions but used for electrons, absence of substorm effects, representations of electric and magnetic fields which can result in not enough adiabatic acceleration, and simple models for electron lifetimes. Key Points: IMPTAM performs well, with the ratio between the GOES MAGED and modeled keV electron fluxes at 06 MLT close to 1Peaks of IMPTAM fluxes are shifted toward midnight due to the background field models and the sources and losses used inside IMPTAMError is a factor of 2 based on median symmetric accuracy with largest difference of 1 order of magnitude; Heidke skill scores are low [ABSTRACT FROM AUTHOR]

Melanoma is the most aggressive skin tumour type. Although complete cure can be achieved when the whole tumour is resected, prognostic dramatically drops when melanoma cells reach deeper tissues and lymph nodes. Hence, there is an urgent need to develop accurate tools allowing (i) discriminating benign naevi from malignant tumours and (ii) being able to characterise melanoma infiltration. For that purpose, we exploited the paramagnetic properties of melanin by using electron paramagnetic resonance (EPR) spectroscopy to measure the melanin content in pigmented (B16F10 cancer cells) and non-pigmented melanomas (WM2664 cancer cells) inoculated intradermally in nude mice. Specifically, we took advantage of a new clinical EPR device (1 GHz), which provides sensitive measurements of radical species in vivo. Results showed that the melanin-specific EPR signal increased with tumour growth in pigmented tumours, whereas no EPR signal could be detected in achromic melanomas. These data plead for the development of new EPR spectrometers/imagers with an improved in-depth resolution for the detection of invasive melanomas. [ABSTRACT FROM AUTHOR]

Highlights • Pre-embedding labeling represents one of the easiest methods for molecule detection in electron microscopy. • Both peroxidase and gold labeling protocols can be used in pre-embedding procedure. • Pre-embedding offers vast opportunities to reveal and quantify molecular components at the ultrastructural level. Abstract Labeling of specific molecules for electron microscopy provides an extremely powerful tool to investigate subcellular distribution of proteins, lipids and sugars with resolution of a few nanometers. Moreover, this technology offers a unique opportunity to see how the pattern of these molecules changes in different physiological or pathological conditions. Pre-embedding labeling evolved as one of the easiest method for molecule detection in electron microscopy. It was named "pre-embedding" because the procedure involves a labeling step before the embedding of the specimen in the resin, its subsequent sectioning and analysis of sections under the electron microscope. Here we review different strategies and technical tips of the pre-embedding procedure, the potential of this method for detection and quantification of molecular components at the ultrastructural level, and the integration of the pre-embedding approach with rapidly developing light and electron microscopy technologies. [ABSTRACT FROM AUTHOR]

A new configuration of semiconductor detectors for backscattered electrons for a scanning electron microscope (SEM) is presented. The result of the optimization was the possibility to extract the information about the spatial relief (3D topology) of the sample and its subsurface structure (3D tomography) in the simplest way. The detector consists of 8 sensors-semiconductor plates, positioned in a certain way. The proposed method was tested on real structures having a surface micro relief or a subsurface volume structure. Experiments and simple calculations show increased effectiveness and a high signal-noise ratio in the proposed method. This is important, particularly for studying the radiation-sensitive biomedical tissue in SEM. [ABSTRACT FROM AUTHOR]

[Display omitted] • Hydrogen-rich plastics is essential for promoting lignin co-pyrolysis. • Radical footprints in char/bio-oil reveals boosting effect of polypropylene behavior. • Products characterization confirms radical-mediated co-pyrolysis yielding more phenolics. • Mechanism of radical-mediated reactions in lignin/plastic co-pyrolysis is updated. Co-pyrolysis of lignin with representative waste plastics, including polypropylene (PP), acrylonitrile butadiene styrene (ABS), polystyrene (PS), and polyethylene terephthalate (PET), was investigated, focusing on radical-mediated reactions, with radical detection via electron paramagnetic resonance (EPR). During the co-pyrolysis of lignin with PP, favorable synergistic effects were observed, resulting in a significant 17 % enhancement in phenolic compound yields within the fixed-bed reactor, whereas the presence of other plastics led to exacerbated cross-linking carbonization in contrast. Furthermore, TOF-MS and FT-ICR-MS analyses corroborated that the bio-oil derived from lignin/PP exhibited a higher phenolic content and lower carbon number distribution. Additionally, the radical concentrations in bio-oil of lignin/PP were determined to be the lowest (1.07 × 1013 spins/µL), providing compelling evidence of the strong interaction between lignin and PP. Interestingly, EPR spectroscopy detected the resultant lowest spin concentrations (1.28 × 1019 spins/g) in lignin/PP char, in contrast to lignin in isolation or within other plastics, which strongly indicating that hydrogen-rich radicals originating from PP were responsible for inducing more effective quenching reactions with lignin intermediates. Moreover, the lignin/PP char demonstrated the highest carbon content (80.30 %) and the lowest I D /I G ratio (1.98), further affirming a highly effective interaction between lignin and PP. The perspective drawn from this study is that the abundant hydrogen source of PP can provide hydrogen-rich radicals to quench lignin intermediates and improve phenolic yield. This intriguing work provides a fresh perspective to evaluate the effect of plastic origin on lignin co-pyrolysis based on radical theory. [ABSTRACT FROM AUTHOR]

Raw ores are mixed with filling materials during mining, which makes it difficult to sort copper‑sulfur resources. Inductively coupled plasma analysis revealed that the primary dissolved metal ions from the filling materials were Ca2+ and Fe3+. Flotation solution chemistry, flotation tests, and X-ray photoelectron spectroscopy measurements confirmed that the dissolved calcium and iron materials were adsorbed onto the chalcopyrite surface in different component forms, which reduced chalcopyrite recovery. Moreover, zeta potential measurements, turbidity analysis, microscope observation, scanning electron microscopy detection, adsorption capacity measurements, and contact angle measurements revealed that the dissolved anions and cations from filling materials can change the surface zeta potential of chalcopyrite and filling materials, weaken the mutual repulsion energy, and strengthen the aggregation effect, thus reducing the adsorption of butyl xanthate on the chalcopyrite surface and its surface hydrophobics. The chalcopyrite recovery eventually decreased from 96.41% to 86.63%. [Display omitted] • The effect of filling materials on chalcopyrite flotation was firstly discussed. • The dissolved metal ions can be adsorbed on the surface of chalcopyrite in the form of hydrophilic hydroxide. • The dissolved materials can strengthen the aggregation between filling materials and chalcopyrite. • The addition of filling materials can weaken the flotation recovery of chalcopyrite. [ABSTRACT FROM AUTHOR]

• PEDOT wrapped CoWO4 MIP sensor was developed via simple synthetic route. • Sensor exhibited remarkable electrochemical performance and selectivity for phenacetin. • Detection mechanism revealed involvement of 2e- and a H + in oxidation of phenacetin. • Successful implementation of the sensor for pharmaceutical and homeopathic samples. A molecular imprinted polymeric (MIP) recognition system comprising of PEDOT swaddled CoWO 4 nanocapsules has been developed for the electrochemical detection of carcinogenic phenacetin drug. Facile hydrothermal route was employed to synthesize CoWO 4 whereas, EDOT was wrapped around under chemical polymerization at room temperature. A series of characterizations revealed that electrostatic interactions generated between thiophene sulfur of PEDOT and metal atoms of CoWO 4 have prompted the homogeneously wrapped molecularly imprinted nanocomposite. The obtained peak potential plotted against the CV scan rate revealed involvement of 2 electrons in the electroxidation detection process of phenacetin. The values of charge transfer coefficient α (0.69) and charge transfer rate constant k s (2.24 s−1) at electrode-electrolyte interface during the detection procedure were also evaluated. The nanoarchitecture of the designed MIP exhibited abundant imprinted sites to selectively bind the template molecule in terms of shape, size and functionalities resulted in significant augmentation in sensitivity (0.14 µA nM−1 cm−2) and a very low detection limit (0.091 nM). Phenacetin content in homeopathic and allopathic drug samples were successfully quantified with more than 95 % accuracy by employing the MIP modified electrode. The present research introduces new possibilities for identification of carcinogenic phenacetin used as adulterants in various narcotic drug samples. [Display omitted] Schematic representation for MIP fabrication and its utilization for electrochemical detection of phenacetin. [ABSTRACT FROM AUTHOR]

Metallic micro/nanostructures are core components for building high-performance sensors and circuits. Nanoscratches on silicon (Si) surface have been demonstrated to induce the orientational deposition of metals; however, the effect of crystal defects on deposition remains unclear, which raises difficulties for preparing high-quality metallic micro/nanostructures. Herein, a site-controlled preparation strategy was proposed for obtaining high-grade Au micro/nanostructures on Si nanoscratches with the assistance of photoresist mask. The roles of Si oxide, amorphous Si (a-Si), and distorted Si were systematically investigated toward optimal preparation, and the involved mechanisms were further revealed based on surface conductivity detection and electron migration analysis. It was found that the scratch after removing top Si oxide and a-Si layers can facilitate the formation of compact Au structures. Further analysis indicated that Si oxide and a-Si can hinder electron migration in the scratched area, while distorted Si can promote electron migration which is more conducive to the redox reaction. The excellent practical applicability was demonstrated by detecting surface-enhanced Raman scattering spectra of malachite green molecules absorbed on the obtained Au line-structure arrays. Moreover, the prepared Au structures on Si can be mechanically transferred onto PDMS surface. This study opens a new road in the facile and cost-effective preparation of metallic micro/nanostructures, which are promising for extending microsensors applications. [Display omitted] • Site-controlled deposition of high-quality Au micro/nanostructures was achieved with the assistance of photoresist mask. • A-Si-free nanoscratches can induce the formation of compact Au structures. • The roles of crystal defects in orientational metal deposition were revealed. • Au line-structure arrays deposited on a-Si-free scratches present excellent Raman-enhanced performances. • Au micro/nanostructures prepared on Si can be mechanically transferred onto PDMS surface. [ABSTRACT FROM AUTHOR]

[Display omitted] • Pt/α-Fe 2 O 3 @RGO nanocomposite was successfully synthesized for selective detection of ornidazole. • The prepared Pt/α-Fe 2 O 3 @RGO/GCE electrode achieves excellent electrocatalytic conductivity towards ornidazole. • The developed sensor exhibits limit detection of 15 nM with a sensitivity of 0.277 µA µM−1 cm−2. The widespread use of antibiotics for humans and animals leads to the contamination of the water environments. ORD is one of the drugs widely used to treat anaerobic bacterial and protozoal infections. For that, their excessive doses or discharge erroneously be caused serious health issues and facilitate the development of antibiotic resistance in pathogens. Thus, several studies have been developed to monitor the contamination of environmental samples with pharmaceutical products. In this work, a Pt/α-Fe 2 O 3 @RGO nanocomposite was synthesized for the rapid and sensitive electrochemical detection of ORD. X-ray diffraction (XRD), Fourier transforms infrared spectroscopy (FT-IR), scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX) were used to characterize the prepared nanocomposite. The electrochemical performance of the constructed electrode was examined by electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV), and square wave voltammetry (SWV). The obtained results indicate that the Pt/α-Fe 2 O 3 @RGO nanocomposite achieves excellent electrocatalytic conductivity and rapid electron transfer for the detection of ORD, good reproducibility, storage stability, and reliable selectivity. Additionally, the detection limit of the developed sensor was 15 nM with a sensitivity of 0.277 µA µM−1 cm−2. [ABSTRACT FROM AUTHOR]

• A model FeReNC SAE allows demonstration on an electrochemically relevant material. • STEM-EELS and -EDS provide atomic-scale compositional and bonding information. • Direct electron detection EELS enables mapping of transition metal SAE sites. • Automation enables rapid simultaneous EELS/EDS probing of individual SAE sites. Single atom electrocatalysts (SAEs) are promising next-generation materials for promoting a variety of important reactions, such as the oxygen reduction, nitrogen reduction, and CO 2 reduction reactions. While bulk characterization techniques such as X-ray absorption spectroscopy and Mössbauer spectroscopy have significantly enhanced our understanding of these catalysts, direct probing of individual single metal atom sites at the atomic scale is necessary to understand local variations in the properties of these sites and accelerate design and synthesis of improved SAEs. Aberration-corrected scanning transmission electron microscopy (STEM) has become a powerful tool for providing this type of atomic-scale information about SAE metal sites. These sites are typically unstable under the electron beam, however, which, in combination with conventional acquisition methods and detectors, has limited the type and quantity of information obtainable by spectroscopic STEM techniques. Here, we map multiple individual SAE metal sites in a nitrogen-doped carbon containing atomically dispersed Fe and Re (FeReNC) at the atomic scale by direct electron detection electron energy-loss spectroscopy (EELS). Direct electron detection provides an improved signal-to-noise ratio over conventional scintillator-based detectors and enables detection and real space localization of weak signals. In addition, we demonstrate an automated method for identification of metal atom positions, placement of the probe on these sites, and simultaneous EELS and energy dispersive X-ray spectroscopic (EDS) signal acquisition. This simultaneous acquisition of EELS and EDS provides access to the composition and bonding of a wide range of SAE metal sites. Focusing the probe directly on the metal sites also increases the relevant data acquisition rate by more than an order of magnitude over two-dimensional mapping, enabling improved statistical measurements of site properties. The versatility, sensitivity, and speed that these techniques provide enhances our ability to probe the local elemental and chemical environment of a large number of individual SAE metal site structures at the atomic scale, enabling an improved understanding of the variations in the local properties of these electrocatalysts to be gained. As a result, significantly increased information about individual metal sites will be available to future electrochemical studies through these techniques, accelerating the development of advanced SAEs. [Display omitted] [ABSTRACT FROM AUTHOR]

• The extractable multi-dimensional information from the 4D-EELS technique. • Parallelly acquired phonon dispersion at nanoscale via 4D-EELS technique. • Visualizing local inhomogeneity by extracted momentum and energy filtered images. • The flexible mathematical combinations of spectra at different momentum via 4D-EELS. Recent advances in scanning transmission electron microscopy have enabled atomic-scale focused, coherent, and monochromatic electron probes, achieving nanoscale spatial resolution, meV energy resolution, sufficient momentum resolution, and a wide energy detection range in electron energy-loss spectroscopy (EELS). A four-dimensional EELS (4D-EELS) dataset can be recorded with a slot aperture selecting the specific momentum direction in the diffraction plane and the beam scanning in two spatial dimensions. In this paper, the basic principle of the 4D-EELS technique and a few examples of its application are presented. In addition to parallelly acquired dispersion with energy down to a lattice vibration scale, it can map the real space variation of any EELS spectrum features with a specific momentum transfer and energy loss to study various locally inhomogeneous scattering processes. Furthermore, simple mathematical combinations associating the spectra at different momenta are feasible from the 4D dataset, e.g., the efficient acquisition of a reliable electron magnetic circular dichroism (EMCD) signal is demonstrated. This 4D-EELS technique provides new opportunities to probe the local dispersion and related physical properties at the nanoscale. [ABSTRACT FROM AUTHOR]

Ultrafast-optical-pump — structural-probe measurements, including ultrafast electron and x-ray scattering, provide direct experimental access to the fundamental timescales of atomic motion, and are thus foundational techniques for studying matter out of equilibrium. High-performance detectors are needed in scattering experiments to obtain maximum scientific value from every probe particle. We deploy a hybrid pixel array direct electron detector to perform ultrafast electron diffraction experiments on a WSe 2 /MoSe 2 2D heterobilayer, resolving the weak features of diffuse scattering and moiré superlattice structure without saturating the zero order peak. Enabled by the detector's high frame rate, we show that a chopping technique provides diffraction difference images with signal-to-noise at the shot noise limit. Finally, we demonstrate that a fast detector frame rate coupled with a high repetition rate probe can provide continuous time resolution from femtoseconds to seconds, enabling us to perform a scanning ultrafast electron diffraction experiment that maps thermal transport in WSe 2 /MoSe 2 and resolves distinct diffusion mechanisms in space and time. • We perform ultrafast electron diffraction on a WSe 2 /MoSe 2 heterobilayer • We denoise diffraction data with high frame rate direct electron detection • Diffraction data resolves a 10 nm periodicity moiré pattern • High dynamic range allows simultaneous measurement of atomic-scale Bragg peaks • Scanning micro-diffraction shows dynamics from angstrom to millimeter length scales [ABSTRACT FROM AUTHOR]

Highlights • A new type of angularly selective transmission electron detector is presented. • The detector is used to collect diffraction patterns in an SEM. • The detector is used to perform diffraction contrast transmission imaging in an SEM. Abstract A new type of angularly selective electron detector for use in a scanning electron microscope is presented. The detector leverages a digital micromirror device (DMD) to take advantage of the benefits of two-dimensional (2D) imaging detectors and high-bandwidth integrating detectors in a single optical system. The imaging detector provides direct access to the diffraction pattern, while the integrating detector can be synchronized to the microscope scan generator providing access to a real space image generated by integrating (pixel-by-pixel) a portion of the diffraction pattern as quantitatively defined by the DMD. The DMD, in effect, takes the place of the objective aperture in a transmission electron microscope (TEM) or an annular detector in a scanning transmission electron microscope (STEM), but has the distinct advantage that it can be programmed to take any shape in real time. Proof-of-principle data collected with the detector show diffraction contrast in samples ranging from a polycrystalline gold film to monolayer graphene. [ABSTRACT FROM AUTHOR]

Abstract The resolving power of the Timepix detector for wide-range charged particle detection has been examined and evaluated in defined radiation fields. The goal is to broadly characterize mixed-radiation fields consisting namely of X-rays and charged particles in terms of particle-types (species), spectral response (energy loss) and direction in wide field-of-view (essentially 2 π) with a single compact tracking detector. Tests and calibration measurements were performed with the same device at electron, proton and ion fields at various energies and incident directions. Event-by-event detection, together with pattern recognition analysis of the single particle tracks, are exploited to analyze events according to three degrees of freedom—the particle type (X-rays, light and heavy charged particles), energy range (low or high energy—depending on their range being smaller or larger than the pixel size of the detector semiconductor sensor) and direction (incident angle to the sensor plane). Characteristic values are determined for the cluster analysis morphology parameters, the particles stopping power or Linear Energy Transfer and derived correlated quantities. Ratios and correlations between selected parameters are analyzed including 2D-scatter plots. A physics-based wide-range classification is proposed for a total of 8 broad event groups—in terms of light charged particles (electrons, muons) of both low and high energy incident perpendicular (type 1, including X-rays) or high energy non-perpendicular (type 5), protons of low energy omnidirectional (type 2) and high energy non-perpendicular (type 6), alpha particles and light ions of low energy omnidirectional (type 3) and high energy non-perpendicular (type 7), and heavy ions of low energy omnidirectional (type 4) and high energy non-perpendicular (type 8). Highlights • Tests and calibration of response of Timepix detector. • Resolving power and dynamic range according particle type, energy, direction. • Physics-based classification of event types. • Intended for characterization of mixed radiation fields such as space radiation. [ABSTRACT FROM AUTHOR]

Abstract We report on the basis of density functional theory, the field emission properties of pristine and doped aluminum nanocone (Al-NC). We substituted the apex of the Al-NC with group IV and group V elements, namely arsenic (As), germanium (Ge) and phosphorous (P) atoms and had carried out studies on these nanocone structures. The density of states (DOS) spectrum gives a clear perception of the charge distribution over the Al-NC surface on doping. Furthermore, the Richardson-Dushman formula has been used to correlate the work function Φ and the charge density. We have observed that doping at the apex of Al-NC leads to the variation in work function Φ. The results show that the field emission properties of Al-NC can be improved with the substitution of As, Ge, and P at the apex of the structure. Our findings suggest that doping of the Al-NC with Ge, As and P leads to the improved field emission properties, which can be used for nanoelectronics and vacuum electronics. Graphical abstract Unlabelled Image Highlights • The electronic and field emission properties of aluminum nanocone (Al-NC) is studied. • The group IV and V atoms are substituted at the apex of aluminum nanocone to improve the field emission property. • The field emission properties are studied using work function and charge transfer of Al-NC. • The findings suggest that doped Al-NC is suitable to enhance the field emission property. • Doped Al-NC can be used in vacuum electronics, nanoelectronics and excitation of phosphor screen. [ABSTRACT FROM AUTHOR]

GaN-based pin alpha-particle detectors grown on sapphire substrates have been subjected to 10 MeV electron irradiation over a cumulative dose range of 0 to 200 kGy. The pre- and post-irradiation detectors have been characterized with current–voltage and capacitance–voltage measurements, charge collection efficiency ( CCE ), and alpha-particle pulse-height spectroscopy. The results show that the performance of the detectors underwent significant changes due to enhanced carrier-hopping conductivity through defect states and deep-level traps in the space-charge region induced by the 10 MeV electron irradiation. Such detectors can be used for alpha detection with confidence in an environment of background high energy electrons, up to a dose of about 200 kGy, and the response can degrade rapidly if the dose exceeds 200 kGy. In this work, the maximum CCE was achieved in a detectors irradiated with a cumulative dose of 100 kGy. [ABSTRACT FROM AUTHOR]

The VSiPMT (Vacuum Silicon PhotoMultiplier Tube) is an original design for an innovative light detector we proposed with the aim to create new scientific instrumentation for future missions of exploration and observation of the universe. The idea behind this device is to replace the classical dynode chain of a photomultiplier tube with a silicon photomultiplier, the latter acting as an electron detector and amplifier. In this way we obtain a large area photodetector with an excellent photon counting, proper of the SiPMs, but with the dark noise of only one SiPM (1-inch is equivalent to  ∼ 54 SiPM 3 × 3 mm 2 ). From this point of view, the VSiPMT offers very attractive features and unprecedented performance in large area detection, such as: negligible power consumption, excellent SPE resolution, easy low-voltage-based stabilization and very good time performance. Hamamatsu realized for our group a 1-inch prototype. The results of the full characterization of the device are presented in this work. [ABSTRACT FROM AUTHOR]

A catalytic highly regioselective, diastereoselective, and enantioselective cyclopropanation of electron-deficient dienes and bromides via direct sulfide organocatalysis is reported. A variety of vinylcyclopropanes featuring a quaternary chiral center were synthesized in up to 99% yield and up to 98:2 enantiomeric ratio (er). These products could be facilely transformed to various interesting molecules with great structural diversity. [ABSTRACT FROM AUTHOR]

It is well known that plasma sheath presents a classic sheath structure when the dielectric-wall total electron emission coefficient Γ ≤ Γ c (<1). However, the structural transition of a classic sheath near a dielectric wall when Γ → Γ c is controversial about transiting to a space-charge limited (SCL) sheath or inverse sheath. In this study, the classic sheath between a Maxwellian low-temperature plasma source and a dielectric surface that emits secondary electrons is carefully investigated using a 1D3V, steady-state, kinetic sheath model within a broad range of plasma electron temperatures T e . Using the Monte Carlo method to simulate secondary electron emission (SEE) events that are based on the self-consistent primary electron velocity distribution function at the wall and a detailed SEE model, it is found that the total emitted electron velocity distribution function (EEVDF) perpendicular to the dielectric wall approximately satisfies a three-temperature Maxwellian distribution. Due to the relatively high average energy of this total EEVDF, for cases of T e with cold plasma ion assumption: (1) the critical SCL sheath does not exist; (2) Γ c reaches unit; (3) the sheath disappears when T e = T e c (i.e., Γ = 1); and (4) as T e increases, the classic sheath will transit to an inverse sheath structure. Further comparative calculations predict that the magnitude of emitted electrons' average energy may lead to different experimental results between thermionic emitting surfaces which have a “cold” half-Maxwellian EEVDF and SEE surfaces. However, when the finite plasma ion temperature is considered, at the transition point, the cold plasma ion assumption is expected to be invalid, and thus a fully kinetic sheath model should be built to reveal the potential new transition regime. [ABSTRACT FROM AUTHOR]

Nuclear fragmentation produced in 12 C ion therapeutic beams contributes significantly to the Relative Biological Effectiveness (RBE)—weighted dose in the distal edge of the Spread out Bragg Peak (SOBP) and surrounding tissues in out-of-field. Complex mixed radiation field originated by the therapeutic 12 C ion beam in a phantom is difficult to measure. This study presents a new method to characterise the radiation field produced in a 12 C ion beam using a monolithic Δ E-E telescope which provides the capability to identify the particle components of the mixed radiation field as well as the microdosimetric spectra that allows derivation of the RBE based on a radiobiological model. The response of the monolithic Δ E-E telescope to a 290 MeV/u 12 C ion beam at defined positions along the pristine Bragg Peak was studied using the Geant4 Monte Carlo toolkit. The microdosimetric spectra derived from the Δ E stage and the two-dimensional scatter plots of energy deposition in Δ E and E stages of the device in coincidence are presented, as calculated in-field and out-of-field. Partial dose weighted contribution to the microdosimetric spectra from nuclear fragments and recoils, such as 1 H, 4 He, 3 He, 7 Li, 9 Be and 11 B, have been analysed for each position. Comparison of simulation and experimental results are presented and demonstrates that the microdosimetric spectra changes dramatically within 0.5 mm depth increments close to and at the distal edge of the Bragg Peak which is impossible to identify using conventional Tissue Equivalent Proportional Counter (TEPC). [ABSTRACT FROM AUTHOR]

An event-counting method using a two-microchannel plate stack in a low-energy electron point projection microscope is implemented. 15 μm detector spatial resolution, i.e., the distance between first-neighbor microchannels, is demonstrated. This leads to a 7 times better microscope resolution. Compared to previous work with neutrons [Tremsin et al., Nucl. Instrum. Methods Phys. Res., Sect. A 592, 374 (2008)], the large number of detection events achieved with electrons shows that the local response of the detector is mainly governed by the angle between the hexagonal structures of the two microchannel plates. Using this method in point projection microscopy offers the prospect of working with a greater source-object distance (350 nm instead of 50 nm), advancing toward atomic resolution. [ABSTRACT FROM AUTHOR]

Radioactive xenon (mainly 131m Xe, 133 Xe, 133m Xe and 135 Xe) are tracked as markers of nuclear weapons testing. The CEA has developed the PIPSBox, a measurement cell able to detect electrons emitted by xenon nuclides. Combined with an ultra-low background γ spectrometer, electron detection capacities allow reaching minimum detectable activities (MDA) for a 3-day long measurement of about 0.5 mBq for the four xenon radionuclides. Compared to a classical measurement cell, MDAs are improved by a factor of 2–4. [ABSTRACT FROM AUTHOR]

Recent and not quite so recent books and conference proceedings on electron microscopy and related topics are surveyed. A few books on very different subjects are included to lighten the dough. [ABSTRACT FROM AUTHOR]

A method for increasing compositional or material contrast of a standard semiconductor BSE detector in a scanning electron microscope (SEM) by compensation of the topographic contrast component is proposed. Compensation is based on the physical properties of backscattered electron emission and topography information of the specimen's surface. Three analytical and semi-empirical compensation algorithms employing different physical models and approximations are implemented and compared to conventional BSE signals to show the effectivity of the proposed compensation approach. [ABSTRACT FROM AUTHOR]

Level lifetimes provide key insight into the structure of atomic nuclei and serve as stringent tests of theoretical descriptions. Though several methods for determining level lifetimes exist for both reaction measurements and decay studies, here the focus is on techniques involving the direct measurement of time differences between population and subsequent depopulation of excited states. The techniques presented herein are broadly applicable across multiple timing ranges, but the approach is specifically described for the β γ timing method. A multi-step, amplitude-dependent time walk correction and timing resolution corrections were employed to address the data analysis complications that arise from using thick scintillators for electron detection. Subsequently, a new Monte Carlo method utilizing measured detector responses obtained from the data, coupled with chi-square minimization, is presented for extracting excited state lifetimes ≳ 100 picoseconds. The framework of this Monte Carlo method is developed for the decay of a state in 68Zn with a known 1.6 ps half life, which is considered prompt given the detection sensitivity of the technique, and then benchmarked using two other excited states in neutron-rich Ni isotopes with 120(34) ps and 1.05(3) ns half lives. Using this new method which takes into account the thick scintillator used, these same half lives were measured to be 135(10) ps and 1.04(24) ns, respectively. The overall good agreement demonstrates the validity of the technique. [ABSTRACT FROM AUTHOR]

The visible camera system EDICAM (Event Detection Intelligent Camera), recently installed on JT-60SA, is simulated to assess whether it can be used for measuring synchrotron radiation from relativistic runaway electrons. In this simulation, the SOFT synthetic synchrotron diagnostic framework is used to compute the synthetic synchrotron camera images from a JT-60SA-like disruption modelled with the DREAM disruption simulation code. In the studied scenario, a large amount of argon is added to the plasma, and a disruption is simulated by starting a prescribed exponential temperature drop and finishing with further cooling provided by the argon in a self-consistent simulation of the current quench. The background plasma evolution is calculated by DREAM self-consistently with the fast electron population, which is modelled kinetically. The resulting runaway electron distribution function along with the parameters of the EDICAM visible camera system are used as an input to the SOFT framework to assess the feasibility of the camera for runaway electron detection. We find that the runaway electron beam formed in the disruption can produce synchrotron radiation observable by the EDICAM system, thus enabling the use of the EDICAM for the characterization of runaway electron beams. • EDICAM visible camera system on the JT-60SA tokamak used for synchrotron radiation detection. • Disruption runaway electron generation modelling for JT-60SA. • Synchrotron radiation image simulated with the EDICAM parameters. • EDICAM can be used for runaway electron detection. [ABSTRACT FROM AUTHOR]

The MeV region of antineutrino energy is of special interest for physics research and for monitoring nuclear nonproliferation. Whereas liquid scintillation detectors are typically used to detect the Inverse Beta Decay (IBD), it has recently been proposed to detect it with a liquid-organic Time Projection Chamber, which could allow a full reconstruction of the particle tracks of the IBD final state. We present the first simulation-based statistical analysis of the expected signatures. Their unequivocal signature could enable a background-minimized detection of electron antineutrinos using information on energy, location and direction of all final state particles. We show that the positron track reflects the antineutrino's vertex. It can also be used to determine the initial neutrino energy. In addition, we investigate the possibility to reconstruct the antineutrino direction on an event-by-event basis by the energy deposition of the neutron-induced proton recoils. Our simulations indicate that this could be a promising approach which should be further studied through experiments with a detector prototype. [ABSTRACT FROM AUTHOR]

The article discusses the collaboration between Japan Electron Optics Laboratory Co., Ltd (JEOL) and Scintacor Ltd to develop a high sensitivity, low noise, fiber coupling CMOS camera called SightSKY 1 for Transmission Electron Microscopes (TEM). TEM is a microscopy technique that uses a beam of electrons to produce high-resolution images of biological specimens or samples. Scintacor's phosphor coating optimized the sensitivity and resolution of the camera while maintaining a low noise level. The collaboration between the two companies resulted in the successful development of the camera, exceeding initial expectations. [Extracted from the article]

• Durability and fatigue of RG7 bronze. • Relationship between the method of loading and the topography of the fracture surface. • Influence of load type and its size on surface quality. • Fractal dimension to describe the surface of fatigue fracture. The paper presents the results of fatigue cyclic tests performed on MZGS stand of RG7 bronze under symmetric bending, symmetric torsion, and the combination of proportional symmetric bending and torsion, where τ a = σ a and τ a = 0.5σ a. Causes of damage were determined by scanning electron microscopic observation. The fracture images were observed using a Tescan Vega 4 Scanning Electron Microscope operating at 20 kV. Secondary electron detection (SE) was used to obtain SEM images. For topographic analysis, an optical profilometer by Sensofar 3D S neox was used, which includes modern software for surface analysis by Digital Surf Mountains Map. Fatigue crack analysis was performed by observing samples for each combination under the following scheme: one with a low load level with a lifetime of 1,000,000 cycles and the other with a high load level and a lifetime of 30,000 cycles. [ABSTRACT FROM AUTHOR]

Most of the particles assigned as (corona)viruslike particles represent coated vesicles (Figure 1K-O and 2J-M), whereas Figure 1 R shows an unidentifiable structure that does not reveal sufficient features of coronavirus particles. In addition, false-positive electron microscopy data have often been used to validate other in situ virus detection methods such as immunohistochemistry and in situ hybridization, which detect virus molecules rather than the intact virus particle and can provide nonspecific results. The putative virus particles are termed "coronavirus-like particles" or "virus-like particles.". [Extracted from the article]

A nanoporous carbon material was synthesized by heating potassium citrate without using a template or an activating agent. It is shown to represent a viable coating for use in solid-phase microextraction. The material is thermally stable and mainly consists of amorphous sheets of sp2-bonded carbon. It has an extensive pore structure and a surface area as large as 1236 m²⋅g-1. The nanoporous carbon was deposited on the surface of steel wires, and the resulting fibers were applied to the extraction of trace levels of chlorobenzenes in water samples. Following extraction by absorbing, the chlorobenzenes were quantified by gas chromatograph in combination with electron capture detection. Extraction temperature and time, and desorption temperature were optimized (80 °C, 10 min and 310 °C). Under optimized conditions, the calibration plots are linear in the following concentration ranges: 2.5 to 100 ng⋅g-1 (pentachlorobenzene), 5 to 200 ng⋅g-1 (1,2,3,4-tetrachlorobenzene), 10 to 100 ng⋅g-1 (hexachlorobenzene) and 10 to 500 ng⋅g-1 (1,2,3-trichlorobenzene, 1,2,4-trichlorobenzene, 1,3,5-trichlorobenzene). Other figures of merit include (a) high enrichment factors (8324 to 9920), (b) low limits of detection (0.10-1.03 ng⋅g-1), and (c) good reproducibility (relative standard deviations including intra-day and inter-day with a single fiber and fiber-to-fiber were below 6.4% at a mixed concentration level of 2.5, 5, and 10 ng⋅g-1 respectively in ultra-water). This method was successfully applied to the determination of chlorobenzenes in (spiked) lake waters where it gave recoveries between 82.3% and 104.5%. [ABSTRACT FROM AUTHOR]

A new Combined System for high-efficiency detection of Secondary and Backscattered Electrons (CSSBE) in the ESEM consists of three detectors: an ionisation SE detector, an improved scintillation BSE detector, and a new Ionisation Secondary Electron Detector with an electrostatic Separator (ISEDS). The ISEDS optimizes conditions for electron-gas ionisation phenomena in the ESEM to achieve a strongly amplified signal from the secondary electrons with a minimal contribution from backscattered and beam electrons. For this purpose, it is originally equipped with an electrostatic separator, which focuses signal electrons towards a detection electrode and controls the concentration of positive ions above the sample. The working principle of the ISEDS is explained by simulations of signal electron trajectories in gas using the EOD program with our Monte Carlo module. The ability to detect the signal electrons in a selected range of energies is described with Geant4 Monte Carlo simulations of electron-solid interactions and proven by experimental results. High-efficiency detection of the ISEDS is demonstrated by imaging a low atomic number sample under a reduced beam energy of 5 keV, very low beam currents of up to 0.2 pA, and gas pressure of hundreds of Pa. [ABSTRACT FROM AUTHOR]

Quantitative analyses produce important information concerning the microstructural characteristics of materials, which are reflected in the main properties of the materials. The secondary and backscattered electron modes represent the two main techniques most used in scanning electron microscopy, to produce images and, consequently, realize a quantitative analysis. However, each technique has its advantages and problems. The present work proposed evaluate what is the best SEM technique to quantify secondary phases in a cladding of Inconel 686, which can be extended to the other classes of nickel based alloys rich in Mo. It was performed a quantitative analysis of several images to characterize the microstructure of Inconel 686 weld cladding. The images were obtained using three modes: secondary electron (SE), Z contrast backscattered electron (BSE) and topographic backscattered electron (BSE). The segmentation and quantify of secondary phases was performed by SVRNA software. The statistical results revealed differences between the techniques. The secondary electron mode included several artefacts that reduced the precision of the quantification study. The BSE modes are shown to be the best techniques for quantification. [ABSTRACT FROM AUTHOR]

In situ transmission electron microscopy (TEM) with the ability to reveal materials dynamic processes with high spatial and temporal resolution has attracted significant interest. The recent advances in in situ methods, including liquid and gas sample environment, pump-probe ultrafast microscopy, nanomechanics and ferroelectric domain switching the aberration corrected electron optics as well as fast electron detector has opened new opportunities to extend the impact of in situ TEM in broad areas of research ranging from materials science to chemistry, physics and biology. In this article, we highlight the development of liquid environment electron microscopy and its applications in the study of colloidal nanoparticle growth, electrochemical processes and others; in situ study of topological vortices in ferroelectric and ferromagnetic materials. At the end, perspectives of future in situ TEM are provided. [ABSTRACT FROM AUTHOR]

Space assets are continuously bathed by charged particles making their components susceptible to the effects of spacecraft charging. While their orbits are not embedded within the radiation belts, low earth orbiting assets with high inclinations do pass through the horns of these belts during each polar crossing, transiting through potentially dangerous charged particle populations many times per day. Occasionally, these low altitude horns include significant populations of energetic ~1 MeV electrons, which can penetrate typical spacecraft shielding and accumulate within dielectric materials and on ungrounded conductors, a process known as internal charging. The National Oceanic and Atmospheric Administration Polar Operational Environmental Satellites (POES) have experienced on-orbit anomalies in the boost voltage regulator (BVR) that is suspected to be associated with the accumulation and discharge of ~800 keV electrons. We have used observations from the Medium Energy Proton and Electron Detector (MEPED) instrument and a first principles model of charge accumulation [11] to develop estimates of electron internal charge (IC) accumulation over the lifetime of each POES and Metop spacecraft for a range of typical discharge time constants. With the advantage afforded by a larger database of anomalies, we are able to show that these BVR anomalies are generally not attributable in a simple way to the accumulation and subsequent discharge from >800 keV nor a higher fluence of lower energy >300 keV electrons. To the best of our knowledge, this paper presents the first long-term estimates of IC for spacecraft in highly inclined low earth orbits. [ABSTRACT FROM PUBLISHER]