bluuebunny/crossref_metadata_2025 huggingface dataset:
Environmental Scanning Electron Microscopy applied to the identification of asbestos fibers in histological sections
Authors: Rinaudo Caterina , Croce Alessandro , Trincheri Nicol Francesca , Libener Roberta , Degiovanni Daniela , Grosso Federica
Published: December 2016

The strong relation between inhaled asbestos fibers and development of important respiratory diseases (asbestosis, pulmonary carcinoma, mesothelioma) is now demonstrated by many researches and accepted by the international community. The peculiarity of the minerals defined by the law “asbestos” is their growth as long and thin fibers that, as a consequence of the crystal habit, reach the respiratory apparatus, where may lie during long times –decades‐ displaying their carcinogenic effects. The longer asbestos fibers may be coated by iron‐proteins, forming the well‐known “ferruginous bodies”, which represent a way to isolate the fiber in the biological system [1]. It must be remarked that the observation of fibers or ferruginous bodies allow to prove exposure, environmental or working, to asbestos. Nevertheless “ferruginous bodies” may be formed also around elongated minerals/crystals, not belonging to asbestos group. In order to determine surely exposure to asbestos it appears therefore very important to recognize the chemical composition of the fiber inside the coating and identify the mineral phase. A new methodology allowing the sure identification of the mineral phase of a fiber coated in a “ferruginous body” [2], using Environmental Scanning Electron Microscopy (E‐SEM) coupled with Energy Dispersive Spectroscopy (EDS), will be presented.

Our University is placed near Casale Monferrato, a town of Piedmont, Italy, sadly famous for the high incidence of asbestos related diseases, in particular mesothelioma, as consequence of the presence of an Eternit factory working large contents of asbestos until 1985. In several patients suffering of mesothelioma also serious disorders of the biliary tract and/or of the gallbladder have been often diagnosed. Nevertheless, the seriousness of the damages to the respiratory system reduce the attention to other organs. In order to determine the presence of asbestos fibers in the gallbladder or in the biliary tract of patients suffering both of mesothelioma and of disorders in this gland, histological sections of gallbladder and of bile have been observed under E‐SEM/EDS. All the inorganic phases observed have been characterized under their morphological and chemical aspects [3]. By this work it can be proved the presence of asbestos fibers or bundles of asbestos fibers, as shown in the figure, in particular of crocidolite and chrysotile, in almost all the examined sections. The results obtained during this work will be presented and discussed.
Evaluation of feature‐based registration algorithms for the improvement of tilt‐series alignment in electron tomography
Authors: Verguet Amandine , Trepout Sylvain , Marco Sergio , Messaoudi Cédric
Published: December 2016

Despite the high performance achieved in goniometers‐control for tomographic tilt series recording, image alignment is mandatory to obtain accurate reconstructions. In addition, due to the high resolution currently expected from tomograms, the existing alignment methods (based on cross‐correlation, fiducial‐markers and landmarks) needs to be improved. Among the alternative methods presently proposed for general purpose image registration, Scale Invariant Feature Transform (SIFT) [1] has demonstrate its performance for the detection of common features occurring in several images. SIFT have been successfully used for panoramic stitching [2], object detection [1] and proposed as a method for image alignment in electron tomography [3].

We have implemented SIFT and two other feature‐based registration algorithms porposed since the publication of SIFT (ORB [4], BRISK [5]) in TomoJ [6] and evaluated their respective performances on tilt series data from different transmission electron microscopy (TEM) acquisition methods (TEM, EFTEM, STEM, and Cryo‐TEM). We will present here the results obtained validating the use of feature‐based registration algorithms on tilt series from the different acquisition modes.
I
n
A
s1‐x
S
bx /
A
l core‐shell nanowire epitaxy
Authors: Kanne Thomas , Gejl Aske , Sestoft Joachim , Johnson Erik , Simonsen Søren , Nygård Jesper , Krogstrup Peter
Published: December 2016

Hybrid materials with topological classification have received immense attention in recent years and become a focal point of condensed‐matter research [1‐2]. This development is to a large extent driven by the search for materials hosting Majorana bound states, proposed as building blocks for topologically protected quantum computation [3]. Recently, semi‐ and superconducting hybrid nanowires (NW) have been shown to be a feasible material combination, fulfilling the criteria of withstanding high magnetic fields while maintaining large spin‐orbit interaction of the semiconductors [4]. Prior growth studies of semiconducting InAs NWs with epitaxial superconducting Al shells have given detailed insight into the mechanisms of Al grain growth kinetics and especially how the growth evolution depends on the NW morphology [5]. In general, the quality of the interfaces have been shown to play an essential role in a variety of nanostructured device applications, ranging from photovoltaics to quantum transport, and is therefore an important hybrid material characteristics.

In this study we present compositional and structural control of InAs
1‐x
Sb
x
NWs grown by molecular beam epitaxy (MBE), ranging from pure InAs to pure InSb. We show that the hybrid system, InAs
1‐x
Sb
x
with epitaxial Al, offers new possibilities to form alternative epitaxially matched interfacial domains controlled by the Sb influence on the lattice parameter and the broken bond energy of the facets. By changing the molar fraction of Sb, the electrical properties of the semiconducting core can be tuned to desirable properties, which may be relevant for designing topological superconducting materials. An example of the InAs
1‐x
Sb
x
/Al hybrid system is shown in figure 1 with x = 0.34. Also presented in this study is a method to grow long and pure wurtzite (WZ) InAs
1‐x
Sb
x
NWs having a surprisingly high degree of epitaxial match between Al and the NWs.
In‐situ
TEM
growth of single‐layer boron nitride dome‐shaped nanostructures catalysed by iron clusters
Authors: La Torre A. , Åhlgren E. H. , Fay M. W. , Ben Romdhane F. , Skowron S. T. , Davies A. J. , Parmenter C. , Jouhannaud J. , Khlobystov A. N. , Pourroy G. , Besley E. , Brown P. D. , Banhart F.
Published: December 2016

We report on the growth and formation of single‐layer boron nitride dome‐shaped nanostructures mediated by small iron clusters located on flakes of hexagonal boron nitride. The nanostructures were synthesized
in situ
at high temperature inside a transmission electron microscope while the e‐beam was blanked (Figure 1). The formation process, typically originating at defective step‐edges on the boron nitride support, was investigated using a combination of transmission electron microscopy, electron energy loss spectroscopy and computational modelling. The
h‐
BN dome‐shaped nanostructure of Figure 1 was used to simulate images of BN protrusions at various angles relative to the incident electron beam, by adjusting effectively the beam direction. Figures 2 presents simulated images for beam angles of 0° (2a), 30° (2b,c) and 50° (2d), respectively, relative to the
h‐
BN plane normal, in comparison with experimentally observed features (Figures 2e‐h). The image simulations are in striking agreement with the experimental images, consistent with the circular features being protrusions formed normal to the
h‐
BN plane, whilst the hemispheres correspond to protrusions tilted with respect to the
h
‐BN plane. Computational modelling showed that the domes exhibit a nanotube‐like structure with flat circular caps (Figure 3) and that their stability was comparable to that of a single boron nitride layer.

Nanostructured carbon protrusions have been studied since 2001 [1–3], but the investigation of analogous BN structures has only just begun. In the present study, we have shown that even member rings are required for the formation of
h
‐BN dome‐shaped protrusions, but not in the form of active linear defects, containing B‐B and N‐N bonds, as observed recently in BN monolayers under electron beam irradiation [4]. Furthermore, according to our molecular simulations result the even members rings present in the half dome structure present B‐B and N‐N bonds (Figure 4). The BN dome‐shaped nanostructures represent a new material that perhaps by hosting metal atoms may unveil new optical, magnetic, electronic or catalytic properties, emerging from confinement effects.
Fine ultrastructure and composition of nuclear
PIP2
islets
Authors: Sobol Margarita , Lubovská Zuzana , Kalendová Alžběta , Yildirim Sukriye , Philimonenko Vlada , Marášek Pavel , Kalasová Ilona , Pastorek Lukáš , Fujimoto Toyoshi , Hozák Pavel
Published: December 2016

During the last decade importance of phosphoinositides in nucleus was uncovered. We defined previously unknown nuclear structures which occupy nearly 2% of nuclear volume and contain almost 30% of the nuclear pool of phosphatidylinositol 4,5‐bisphosphate (PIP2). These non‐membranous structures of 40 – 100 nm are decorated by PIP2, so we name them PIP2 islets. PIP2 islets are surrounded by phosphorus and nitrogen, hence proteins and nucleic acids are in their vicinity. We showed that PIP2 on the periphery of the islets is associated with Pol II transcription complex, nuclear myosin 1, chromatin and nascent RNA transcripts. We prove that PIP2 islets contribute to efficient DNA transcription. Further, we were interested in the fine ultrastructure and precise composition of the islets to clarify their role in the nuclear architecture.

PIP2 islets are filled by carbon‐rich compounds, however we were not able to identify these molecules by immunolabeling on either resin sections or Tokuyasu sections. The possible reason for this could be the high mobility of the lipids and their extraction during aldehyde fixation. To avoid problem of lipid fixation we are optimizing the method of quick‐ freeze fracture replica labelling for the interior of the cell nucleus. The samples are fixed physically – by high pressure freezing, and subsequently mechanically – by coating with carbon/platinum layer. This method enables a reliable fixation and immunolabeling of lipids in cellular membranes. The applicability of the method for the study of fine ultrastructure and immunolabeling of intranuclear non‐membranous lipidic structures will be discussed.
Phase formation and growth behavior of Co‐Ge thin films
Authors: Alvarez Carlos , Bertoglio Maxime , Hoummada Khalid , Portavoce Alain , Charai Ahmed
Published: December 2016

The potential use of germanide thin films as self‐aligned metallization in Ge‐based Complementary Metal‐Oxide Semiconductor (CMOS) technology has drawn interest in the solid‐state reactions of Ge and metal films [1‐3]. In order to integrate these germanide thin films as a contact material, a complete analysis of the solid‐state reactions of amorphous Ge (a‐Ge) and metals is required. The solid‐state reactions in the Co‐Ge thin films systems previously examined by
in situ
x‐ray diffracting annealing experiments only probed the crystal structures present in the film and did not identify the morphological variations of the process [1]. Furthermore, to the authors knowledge previous works Co‐Ge thin film systems have only analyzed systems with Ge in excess of Co.

In this study, the phase formation and crystallization behavior of a‐Ge and Co thin film layers are investigated by
ex situ
transmission electron microscopy (TEM) coupled with
in situ
x‐ray diffraction (XRD) annealing experiments. Four different specimens were prepared, alternating the stacking order and film thickness (200 nm and 30 nm), in order to explore the influence of the free surface on the crystallization and the phase reactions with Co in excess of a‐Ge. Thin film layers of a‐Ge and Co were deposited via electron beam evaporation onto (100) silicon wafers with the native oxide film present on the surface (~1–2 nm). The thin film specimens were characterized by TEM before and after annealing during the phase formation process. Bright field TEM images of the 200 nm Co on top of 30 nm a‐Ge stack are shown in Figure 1: (a) as‐deposited, (b) annealed at 280°C and (c) 400°C. Upon heating to 280°C, the a‐Ge layer reacts with the Co layer to form CoGe, which then undergoes an additional phase transformation to CoGe
2
with continued heating to 400°C.

The influence of the free surface (
fs
) on the crystallization process was examined on the 200 nm a‐Ge and 30 nm Co film stack. The scanning electron microscopy images of the specimens after annealing to 400°C are shown in Figure 2. (a) The specimen with a‐Ge at the free surface (a‐Ge
fs
) shows two distinct contrast indicating the presence of two different crystalline phases near the surface, while (b) the specimen with Co at the free surface (Co
fs
) shows a more homogeneous contrast throughout the surface. Both specimens have voids visible at the surface, which formed during annealing. By viewing the specimens in cross‐section, the presence of large voids is visible in (c) the specimen a‐Ge
fs
, but the voids are not present in (d) the specimen with Co
fs
. The resulting formation of voids in only one of two specimens indicates the free surface has a direct influence of the phase formation process.
In vitro/ex vivo behavior of a new optical imaging agent targeting αVβ3 integrin
Authors: Brioschi Chiara , Chianale Federica , Cordaro Alessia , Valbusa Giovanni , Maisano Federico , Tedoldi Fabio
Published: December 2016

Introduction
Integrin α
v
β
3
is usually expressed at low or undetectable levels in most adult epithelia, but it is highly upregulated in tumors and correlates with disease progression. Moreover, unlike in quiescent endothelium, α
v
β
3
is highly expressed in tumor‐associated vessels.

RGD (Arg‐Gly‐Asp) peptides carry the minimal integrin‐binding sequence and are well‐known to bind preferentially to α
v
β
3
. Thus, RGD‐based strategies have been widely adopted to design targeted molecules for cancer therapy and/or diagnosis.

We synthesized a new cyclic RGD‐based peptidomimetic conjugated with a NIR fluorophore intended for intrasurgical use during tumor resection, to allow proper identification of tumor margins and sparse metastases by optical imaging. We present here the
in vitro/ex vivo
characterization of this molecule, meant to define its specificity for the target receptor, its ability to enter the cells and its
in vivo
behavior after administration to mice. Cellular models were used to preliminarily characterize the effects and the fate of the molecule as it contacts the cells. Mouse tumor models were used to investigate the distribution of the molecule in tumors after
in vivo
administration.

Methods
Fluorescence microscopy, flow cytometry and immunofluorescence assays were used to define the features of the interaction of our molecule with cells expressing different α
v
β
3
levels.

Results
The
in vitro
characterization of the molecule in contact with adherent cells reveals that it is internalized into the endosomal compartment and that it interferes with α
v
β
3
‐mediated cell adhesion. The affinity to both α
v
β
3
and HSA of our fluorescent RGD‐based probe, demonstrated by flow cytometry and microscopy,is suitable for its intended use.

The
ex vivo
analyses of probe distribution in tumor tissues after
in vivo
administration highlight its ability to accumulate into the tumor mass and its specificity to delineate tumor margins.

Conclusions
Our fluorescent RGD‐based molecule is a promising optical imaging probe for fluorescence‐guided surgical resection of tumors characterized by variable expression of α
v
β
3
integrin.
In‐Situ Hydration of
MgO
Nanocrystals to amorphous
Mg(OH)2
using Liquid Cell Transmission Electron Microscopy
Authors: Vlug Wessel , Plümper Oliver , Kandianis Michael , van Blaaderen Alfons , van Huis Marijn
Published: December 2016

The hydration reaction of MgO to amorphous Mg(OH)
2
is a model hydration reaction and is important to diverse research fields, ranging from catalysis to Earth Sciences. Although the bulk thermodynamics and surface energies of these phases are well studied,[1,2] real time and real space analysis of the reaction at ambient pressure is lacking. In this study, the hydration of MgO nanocrystals is studied at the single particle level, both in real space and in diffraction space using
in‐situ
Transmission Electron Microscopy (TEM) at near‐ambient pressure and temperature. Upon exposure to water vapor and the electron beam, the MgO nanocrystals react with H
2
O and convert to amorphous Mg(OH)
2
.

Real‐time recordings of the hydration reaction reveal that the reaction starts at the MgO nanocrystal surface and proceeds inwards at a constant rate while the Mg(OH)
2
shell expands outwards. The growth rate is found to be constant throughout the reaction. Furthermore, as the applied dose rate is increased, the growth rate increases accordingly. Possible mechanisms for the beam‐promoted transformation are discussed, including the role of defect formation and migration at the interior and at the surface of the MgO nanocrystals, H
2
O diffusion towards the MgO surface, and the possible influence of beam‐generated H
2
O dissociation products. Assemblies of converting MgO/Mg(OH)
2
nanocrystals exhibited a reorganization of the assembly framework due to the solid volume increase (~100%) of each individual nanocrystal.
Improved Quantitative Compositional Analysis of γ′ and γ″ in Additively Manufactured Alloy 718 Using
STEM
X‐ray Energy Dispersive Spectrometry
Authors: Austin Wade C. , Bertali Giacomo , Withaar Thijs , Foord David , Freitag Bert , Burke Grace
Published: December 2016

Selective laser melting (SLM) is an additive manufacturing technique where successive laser beam passes are used to melt metal powder which forms a solid layer on solidification with high densification, little material waste, and large design freedom [1]. The application of SLM to repair high temperature components that often need reconditioning requires an understanding of the microstructural and compositional developments of the chosen material throughout the SLM process. Alloy 718 is a Ni‐Cr‐Fe‐Nb‐Ti‐Al alloy used in applications where high strength is needed while maintaining corrosion and creep resistance, making this alloy a prime candidate for SLM structural and compositional characterization. Precipitation hardening is one of the primary strengthening mechanisms of Alloy 718, where intermetallic phases of L1
2
‐ordered Ni
3(
Al, Ti) (γ′) or D2
00
‐ordered Ni
3
(Nb, Ti) (γ″) may form coherent precipitate particles in the face‐centered cubic matrix (γ) [2]. Additional phases that may be present in the microstructure of Alloy 718 include D0
a
‐ordered Ni
3
Nb (δ), MC, M
6
C, M
23
C
6
, and (Ni, Cr, Fe)
2
(Nb, Mo, Ti) Laves [3, 4]. The complex microstructures in this alloy system are further complicated by the multiple heating and cooling cycles present in the SLM process, thus requiring characterization on the nanoscale in order to understand the microstructural development during processing.

Analytical electron microscopy allows the identification of the particular microstructural components on the micro and nano scales. Alloy 718 is of particular interest in that the γ′ precipitates can nucleate on the (001) surface of γ″ precipitates in the as‐SLM condition. The structure and chemical composition of these precipitates was investigated through X‐ray energy dispersive spectrometry (XEDS) using an aberration‐corrected FEI Titan G2 ChemiSTEM equipped with the Super X EDX X‐ray detector configuration. Figure 1 shows a γ″ precipitate with γ′ precipitates on the two elongated sides of the γ″ in both scanning transmission electron microscopy (STEM) bright‐field (BF) and high‐angle annular dark‐field (HAADF) imaging modes. The understanding the formation of γ′/γ″ requires both structural information about the interface and chemical analysis across the interface of the two precipitates. Figure 2 displays 4 XEDS spectrum images of Ni, Nb, Ti, and Al showing the location of these elements throughout the precipitates present in the γ matrix. Quantitative XEDS analysis was performed on an as printed Alloy 718 specimen where the γ matrix composition was found to be 50.5 wt % Ni, 1.4 wt % Nb, 0.3 wt % Al, and 0.09 wt % Ti with γ′ and γ″ having compositions of 66.6 wt % Ni, 7.13 wt % Nb, 3.18 wt % Ti, and 2.4 wt % Al and 65.0 wt % Ni, 25.4 wt % Nb, 0.37 wt % Al and 3.6 wt % Ti, respectively.
In situ environmental
HRTEM
study of the restructuration under reducing atmosphere of small oxidized silver‐indium nanoparticles
Authors: Ramade Julien , Langlois Cyril , Pellarin Michel , Piccolo Laurent , Cottancin Emmanuel
Published: December 2016

In the form of alloyed or segregated structures, bimetallic nanoparticles (NPs) exhibit remarkable catalytic (activity, selectivity, stability) and optical (localized surface plasmon resonance, LSPR) properties, both depending on the morphology and the chemical configuration that they adopt. Moreover, the structure of these nanoparticles may evolve under specific environmental conditions (pressure, temperature, presence of reactants). It follows that structural and optical characterization techniques must be implemented in a controlled environment for probing these restructuring phenomena.

Here, we present an environmental TEM (ETEM) study on Ag‐In nanoparticles. These particles exhibit a reversible shift of their LSPR, after exposition to oxidizing (air, 25°C) and reducing (H
2
+N
2
, 500°C) atmospheres
[1]
. The particles were synthesized by Low Energy Cluster Beam Deposition (at PLYRA in Lyon), which allows an independent control of their size and composition. The microscope used was a FEI Titan ETEM operating at 300 kV, with a Cs corrector of the objective lens. HRTEM images and movies of the bimetallic nanoparticles were recorded at up to 500°C and under 10 mbar H
2
[2]
.

The starting chemical configuration of the particles is a core‐shell structure, with an Ag or Ag‐In alloyed core of 4–5 nm and an In
2
O
3
amorphous shell with a thickness of 1–2 nm. The nanoparticles were exposed in the ETEM to successive (H
2
pressure; temperature) couples, from (1 mbar H
2
; 25°C) to (10 mbar H
2
; 500°C). These particles were monitored both at the local (single nanoparticle tracking) and global (observations on large assemblies, under low magnification) scales. The structural changes observed at the atomic scale range from the almost complete extraction of the Ag‐rich core from the In
2
O
3
shell, leading to “Janus” nanoparticles, to the complete reduction of the indium oxide shell. In
2
O
3
reductions which occur at higher temperature than the melting point of indium (156°C) induce the competition between two behaviours: i) the melting or evaporation of reduced indium, and thus the decreasing thickness of the shell until its complete disappearance, ii) the diffusion from the shell to the core of reduced indium atoms, leading to a core growth (figure 1). This last point may be closely related to the evolution of the shell thickness during reduction. From these results, we constructed a (pressure, temperature) diagram highlighting the relationship between temperature and H
2
pressure in the reduction activation. These results provide new insights in both physical and chemical processes involved during reduction of oxidized metallic nanoparticles at the atomic scale.
Remnant states and magnetic coupling in Co/Cu multilayered nanowires observed by electron holography
Authors: Reyes David , Rodríguez Luis Alfredo , Warot‐Fonrose Bénédicte , Biziere Nicolas , Wade Travis , Gatel Christophe
Published: December 2016

Magnetic nanowires (NWs) are of great interest due to their potential applications in technological devices and fundamental analysis in the spintronic field[1]–[3]. Among the wide diversity of NWs, the multilayered ones appear as good candidates for studying the spin torque phenomenon, and increasing the radio frequency (RF) output power by designing nano‐oscilators connected in series[4], [5]. For this propose the fundamental study of the magnetic states and coupling in cylindrical multilayered NWs is required. The resulting remanent states in these one‐dimensional multilayered systems will be the result of the competition between the shape anisotropy, crystal anisotropy, exchange interactions and the dipolar coupling that occurs due to the interlayer character.

In this work we have used electron holography (EH) technique to reveal the remnant states of Co/Cu multilayered NWs after applying a saturation magnetic field perpendicular (PP) and parallel (PL) to the wire axis. Cylindrical Co/Cu multilayered NWs were prepared by electrodeposition technique using the single bath method, and polycarbonate membrane to allow the wires growth. Local chemical analysis has been performed by energy‐filtered TEM (EFTEM) to distinguish and measure the thickness of the Co(Cu) layers founding 42 nm (46 nm) as its average value. Figure 1 c shows a EFTEM map with the positions of cobalt and copper layers for a wire with 80nm of diameter. For elucidating the different local remnant states along the wire, magnetic phase shift images retrieved by EH experiments were compared with those calculated from micromagnetic simulations (See Figs 1 a and b). We found that the resulting remnant states present a strong dependence with the local morphology of the layers (Co and Cu thicknesses, NW diameter, Co/Cu interface tilting) and the magnetic coupling between consecutives Co layers. Surprisingly only a weak effect due to the applied magnetic field direction was observed. For the studied nanowires, the ferromagnetic layers can present either a monodomain state perpendicularly to the NW axis, or a vortex state where the core orientation is determined by the layer morphology and the magnetic interaction with neighbors Co layers. This latter state is the most observed magnetic state. Thus, the remnant magnetic state of the multilayered NW is formed by a mixture of monodomain and vortex states. Figure 1 d shows the 3D representation of the simulation, in which there are two vortices with different chirality and polarization, the cores of the vortices are tilted respect to the Z axis.
Structure characteristic of Ni‐poly‐p‐xylylene nanocomposites synthesized by
VDP
Authors: Orekhov Anton , Vasiliev Alexsander , Ozerin Sergey , Vdovichenko Artem , Chvalun Sergey
Published: December 2016

The simplicity of synthesis of polymer nanocomposites together with elasticity and plasticity, make these materials attractive in the aspect of possible applications for different application, including electronics and sensors, like different rectifiers and switching devices based on their high nonlinear VAC (volt‐ampere characteristics) and tendency to form Schottky diodes, transistors, nanowires. Recent progress in spintronic and application of nanocomposites in that area have been shown in the work of Y. Liu,
et al.
[1,2]. Distinct attention in than and other investigations was attracted to the spin‐valves, which use the effect of giant or tunneling magnetoresistance. Typically these devices consist on three‐layer system: nonmagnetic layer is sandwiched between two ferromagnetic (hard and soft) of those. Based on these systems scanning heads of magnetic plates and magnetoresistance memory elements were produced. Usually the polymer materials were used as interlayer material between two ferromagnetic layers (hard and soft), while the adaptation of ferromagnetic polymer nanocomposites with embedded magnetic atoms (Ni, Co, Fe) will allow to construct spin‐valve structures based on the homogeneous material, introducing a number of technological advantages. For the fabrication of these heterostructures the study of physical properties, like magnetoresistive effects, including anomalous Hall effect demonstrating the evidence of spin polarization of charge carriers have to be performed together with the correlation between these effects and the structure of material. The coercive force can be changed by pinning of the ferromagnetic stage with antiferromagnetic inclusions.

In this work we present the results of electron microscopy and microanalysis study of Ni‐poly‐p‐xylylene nanocomposites stuffed with Ni nanoparticles in 5 ‐ 30 vol. % range of concentration. The magnetic and electrophysical properties for these samples are slightly above the percolation threshold and strongly above it.
The oxidation of gallium (
II
) sulphide
Authors: Long Edmund , Cucinotta Clotilde , Harvey Andrew , Downing Clive , Sanvito Stefano , Nicolosi Valeria
Published: December 2016

Introdution

Gallium (II) sulphide (GaS) is a III‐VI layered semiconductor, which has recently been exfoliated using liquid‐phase exfoliation. As a wide‐gap semiconductor it has potential in a range of applications including photodetectors, non‐linear optics, optoelectronics, Li ion battery anodes, but also as a catalyst for hydrogen evolution. However, early devices fabricated using GaS stopped functioning after a few weeks. Upon close inspection it was noted that the edges of exfoliated flakes were seen to have oxidised very shortly after exfoliation, and become amorphous, but the cause of device failure was unclear.

Methods

A combination of ab initio Density Functional Theory (DFT) calculations and High Resolution Scanning Transmission Electron Microscopy (HRSTEM) has been used to study the initiation and progression of oxidation from two potential species: O
2
and H
2
O ‐ the latter of particular importance due to potential effects on hydrogen evolution. DFT was implemented in the CP2K code, modelling GaS as monolayer nanoribbons with various edge terminations to explore potential reaction sites and pathways.

Experimentally, GaS was exfoliated in IPA using ultrasonication, resulting in flakes several layers thick. The dispersion was drop‐cast onto Au TEM grids, and then aged in two environments: ambient and under de‐ionised water, to explore the effect we have observed stark contrasts between flakes exposed to air (Figure 1) and those exposed to water (Figure 2). During ageing, they were investigated with HRSTEM combining high spatial resolution imaging with pixel‐by‐pixel energy dispersed X‐ray (EDX) mapping.

Results

O
2
seems to react with the edges of the flake, substituting into sulphur sites, resulting in a loss of crystalline structure. However this reaction, while initially exothermic at all edges, ceases progressing the oxidation after the first few nm of the edge leaving the rest of the flake pristine, even after over 100 days.

Exposure to DI H
2
O, on the other hand, resulted in significant changes after only a couple of weeks. The resulting HAADF contrast was mottled, with small crystallite regions remaining. The brighter regions (corresponding to thicker regions) contain higher concentrations of sulphur, but seem localised more towards edges, although overall there is an increase in the amount of sulphur relative to gallium. This suggests that GaS undergoes a reaction with water resulting in the loss of gallium from the flakes, and our theory is that remaining sulphur redeposits at the step edges.
In situ study of the degradation phenomena induced by lithiation/delithiation cycle of a composite
S
i‐based anode by the mean of
X
‐ray tomography
Authors: Vanpeene Victor , Maire Eric , Etiemble Aurélien , Roué Lionel , Bonnin Anne
Published: December 2016

In the context of increasing energy density of lithium‐ion batteries, silicon is of high interest with his high theoretical gravimetric capacity, ten times higher than the commonly used carbon. However the use of silicon is faced to huge hurdles such as poor life time of those electrodes and not sufficient sustainability versus high current density (commonly used in EVs and HEVs).

The poor cycle life of Si‐based electrodes is mainly due to their large volume variation upon cycling, inducing electrical disconnections and instability of the solid electrolyte interface (SEI). The study of the morphological variation of Si‐based electrodes upon cycling is thus highly relevant to evaluate their degradation and to optimize their formulation and architecture. However, this is challenging considering their complex three‐dimensional structure and their major evolution with cycling. Furthermore, samples are fragile and reactive and therefore difficult to prepare for bulk observations. In this context, X‐ray tomography appears as an effective non‐destructive and 3D observation tool.

In this communication, in‐situ synchrotron X‐ray tomography analyses are performed on Si‐based electrodes prepared from a pH3 buffered slurry of ball‐milled Si powder + carbon black + carboxymethylcellulose (CMC) (80/12/8) loaded into a carbon paper (AvCarb EP40) by impregnation, in order to get a clear view of the 3D architecture of the electrode with cycling. From the initial state, represented in Fig. 1, to fully lithiated and then fully delithiated state, X‐ray scans were performed each thirty minutes to continuously follow the morphological evolution of the electrode structure.

After an appropriate image reconstruction and segmentation procedure, phase identification has been achieved. Moreover the separation of a void porosity and an electrolyte phase was possible and the quantifying of the pore size distribution evolution with cycling, as shown in Fig. 2.

Also key morphological parameters of these Si‐based electrodes and their evolution with cycling are determined, such as the electrode thickness and volume fraction of the pores as shown in Fig. 3. Those results may greatly enlighten the understanding of degradation phenomena in the Si‐based electrodes and help develop new composite electrodes formulation for sustainable applications.
Structural transformations revealed by in‐situ
HRTEM
observations
Authors: Zhang Zaoli
Published: December 2016

With the recent advance of TEM,
in‐situ
observations have become a very essential technique to understand the structure – property relationship of materials. Here, a few examples are shown. 1) Metal silicides are widely used in microelectronics as ohmic contact due to their low resistivity and the existence of phases that are thermodynamically stable over a wide range of temperatures. The fundamental mechanisms about the silicide film formation remains unclear. The formation mechanism of Pd silicide is carefully explored by
in–situ
HRTEM/ STEM observations in a Cs‐corrected TEM, and combined with atomic quantitative analysis (
Figure 1
). By
in‐situ
STEM imaging observations, it is found that Pd
2
Si is initially formed at the tripe junction at the interfaces, and the formation process is advanced by Pd atom intrusion into Si lattice leading to the Si lattice change. Pd
2
Si silicide phase transformation process also induces the strain changes. In addition, the Pd silicide phase transformation process is discussed by the thermodynamics analysis. 2) Simultaneous chemistry and structural transitions are also demonstrated in nanocrystalline materials. Bulk Cu‐Cr nanostructures subjected to annealing are shown by in‐situ tracking microstructural and compositions enabled with EELS analysis. It is found that the destabilization process of nanostructured materials can initiate at a very low temperature [1], and dynamic process can be well revealed once the composition information is in‐situ tracked.
Interface study of metal nitride films on
MgO
and
Al2O3
substrate using
CS
‐corrected
TEM
Authors: Zhang Zaoli
Published: December 2016

Transition metal nitrides have found wide‐spread applications in the cutting‐ and machining‐tool industry due to their extreme hardness, thermal stability and resistance to corrosion. The increasing demand of these nitrides requires an in‐depth understanding of their structures at the atomic level. This has led to some experimental and theoretical researches [1‐6].

In this paper, we will present our recent results on the atomic and electronic structures of the interface between various metal nitride thin films (CrN, VN and TiN) on MgO and Al
2
O
3
substrate using C
S
‐corrected HRTEM and STEM, EELS/EDXS, quantitative atomic measurement and diffraction analysis as well as theoretical calculations. Interfacial detailed atomic and electronic structures are revealed and compared. Interface induced phenomena between nitride films and substrates are unveiled [1‐4].

Figure 1
shows two typical interfacial atomic structures, frequently accompanied by interface atom reconstruction and interface dislocations to accommodate the misfit strains between two lattices. Particular studies on the effects of N defects in the metal nitride (CrN) film have been carried out. Combining the image analysis and spectrum analysis, some generalized conclusions are derived. (i) a relationship between the lattice constant and N vacancy concentration in CrN is established [5], (ii) the ionicity of CrN crystal is correlated with the N vacancy concentration; (iii) especially, a direct relationship between electronic structure change (L
3
/L
2
ratio) and elastic deformation (lattice constants) in CrN films has been experimentally deduced, indicating that the elastic deformation may trigger a noticeable change in the fine structure of Cr‐L
2,3
edge (
Figure2
). The experiment demonstrates an indirect approach to acquire electronic structure changes during the elastic deformation. The effect of randomly distributed defects in the films has been explored in a quantitative way using electron diffraction, complemented with HRTEM and EELS analysis. Some quantitative relations are also established [5].
Nanometric localization of synaptic proteins by combining single‐molecule localization imaging with scanning electron microscopy
Authors: Luccardini Camilla , Perret Manon , Markert Sebastian , Stigloher Christian , Burdin Béatrice , Bessereau Jean‐Louis
Published: December 2016

Synapses are compartmentalized organelles containing thousands of proteins. Their precise localization at both pre‐ and post‐ synaptic elements is essential for a correct processing and transfer of information between excitable cells. To decipher cellular and molecular mechanisms that regulate and maintain neurotransmitter receptors at synapses we are using
C. elegans
neuromuscular junction (NMJ) as a model of synapse. In particular, we are interested in a novel mechanism of clustering acetylcholine and GABA
A
receptors based on extracellular scaffolding proteins in the synaptic cleft. The transparency and simple morphology of
C. elegans
combined with the ease of genomic engineering to tag endogenous proteins, provide a means to address the localization and organization of these extracellular scaffolding proteins.

We used 2D and 3D direct Stochastic Optical Reconstruction Microscopy (dSTORM) on immuno‐stained worms and we found that acetylcholine receptor (AChR) clusters are close but not in perfect register with presynaptic boutons. We then built a knock‐in strain expressing AChR tagged with the photoswitchable protein Eos and used PALM to analyze AChR content at individual synapses. We found that the number of AChRs is variable depending on synaptic size but the density or receptors is remarkably constant. We are now mapping protein distribution on synaptic ultrastructure by combining the tomo‐array technique with STORM/PALM imaging.
Lipidic structures in the cell nucleus ‐ role of lamins?
Authors: Philimonenko Vlada , Sobol Margarita , Jarolimová Lenka , Lubovská Zuzana , Schrenková Jana , Kalendová Alžběta , Philimonenko Anatoly , Šmíd Ondřej , Hozák Pavel
Published: December 2016

Spatial ordering of the cell nucleus is critical for controlling fundamental nuclear processes such as gene expression, DNA replication, and RNA processing. So far, mostly protein complexes have been found as important for this ordering. We describe novel structures containing phosphatidylinositol 4,5‐bisphosphate (PIP2) which seem to contribute as well. Ultrastructural studies demonstrate the PIP2‐positive structures propagating through the nucleolus and stretching into the nucleoplasm where PIP2 is enriched in interchromatin granules, and also form previously undescribed 50‐100 nm roundish “lipid islets”. We show that PIP2 islets are evolutionary conserved structures enriched in carbon‐rich compounds and surrounded by nucleic acids and protein‐containing constituents. By means of electron microscopy and super‐resolution light microscopy, we show that at the periphery of the islets, PIP2 co‐localizes or is located in the immediate vicinity with nascent transcripts, lamin A, LAP2α, and markers of transcriptionally active and inactive chromatin. We demonstrate that PIP2 islets are sensitive to RNase treatment, while their disruption affects the level of transcription. Direct binding and mobility assays also revealed nucleoplasmic interactions between PIP2 and nuclear myosin 1 (NM1), which is a part of chromatin remodelling complex B‐WICH and promotes Pol I and Pol II transcription. Furthermore, PIP2‐dependent recruitment of lamin A into an NM1‐bound lipo‐protein complex was demonstrated. We analysed the lamin A/NMI/PIP2 complex in more detail and revealed some specific lamin isoforms as components of this complex. Based also on the results of microscopic localization and NMI PIP2‐dependent mobility, we hypothesize that this complex participates in the formation of intranuclear domains involved in fine‐tuning of gene expression patterns.
Imaging photon camera with high spatiotemporal resolution
Authors: Glazenborg Rene , Marr James , Martin Adrian , Ortega Raquel , Schyns Emile , Siegmund Oswald , Vallerga John
Published: December 2016

Photon counting detectors with high spatiotemporal resolution levels are key tools of new super‐resolution imaging techniques, as required for time resolved single molecule imaging. PHOTONIS Imaging Photon Counter, IPC, is a wide field (18 mm active area) camera able to detect individual incoming photons with 2 dimensional spatial resolution < 40 µm FWHM and < 100 ps timing resolution. The IPC consists of a dual microchannel plate detector equipped with a cross strip anode and high speed electronics that allows global count rates up to 5 MHz. The PHOTONIS IPC comes with a user‐friendly plug‐and‐play GUI for operation and data acquisition. The 1 Gbps Ethernet interface provides the connection to a computer for data storage and analysis.

The first PHOTONIS IPC was installed at the National Institute of Standards and Technology (NIST) in 2015; the IPC is being used in a new single‐molecule super‐resolution fluorescence lifetime imaging microscope at the Center for Nanoscale Science and Technology at NIST.

PHOTONIS launched in Q1 2016 a new low‐noise and high quantum efficiency cathode technology that boosts the detection efficiency and dual resolution of the next IPC generation.
TEM
Characterization of Indium Phosphide Nano‐Flags Growth
Authors: Kauffmann Yaron , Kelrich Alexander , Ritter Dan
Published: December 2016

Quasi two‐dimensional (2D) semiconductor materials are desirable for electronic, photonic, and energy conversion applications and have stimulated extensive research on their synthesis
1‐3
and applications
4‐6
. One such example is the growth of indium phosphide flag‐like nanostructures (Fig. 1) by epitaxial growth on a nanowire template
7
. By the intentional incorporation of defects, control of the nano‐flag location along the nanowire was achieved. Long InP nanowires with inherent high defect density in the top area of the flagpole, which pins the catalyst, resulted in top flag geometry (Fig. 1a). Intentional defect creation in the middle section of the flagpole produced middle nanoflags (Fig. 1b). Bottom flags were created by growing defect free primary nanowires under high phosphine flow (Fig. 1c).

Detailed investigation, using aberration corrected high resolution TEM (FEI Titan 80‐300), high angle annular dark field STEM and electron diffraction, of the flag‐like nano‐structures at different stages of the growth provided valuable details about the growth mechanism and the resulting morphology of such nano‐structures.

The main conclusion from the TEM observations is that the growth process involves a few stages. The first stage consists of asymmetrical dissolution of the nanowire (NW) tip into the catalyst (Fig. 2a), followed by the Au catalyst unpinning from the top of the nanowire, and its induced migration along the nanowire sidewall. The final position of the catalyst is determined by the position of structural defects (such as stacking faults ‐ Fig. 2b) along the NW (i.e. the “flagpole”). The next stage involves the epitaxial growth of a pure Wurtzite nano‐flag on one of the facets of the “flagpole” resulting in a two dimensional nano‐membrane on a one dimensional NW sidewall template (Fig. 2c‐d).

The comprehensive understanding of the growth process may help improve the synthesis of similar nano‐structures. It may allow for better control on the growth process of more complex structures and also help achieving similar nanostructures in a variety of III‐V semiconductor material systems with potential applications such as active nanophotonics.
Ferroelectric/dielectric composite tunnel junctions: influence of the stacking sequence on their microstructure
Authors: Pailloux Frédéric , Bugnet Matthieu , Crassous Arnaud , Fusil Stéphane , Garcia Vincent , Bibes Manuel , Botton Gianluigi , Barthélémy Agnès , Pacaud Jéröme
Published: December 2016

Increasing the tunnel electroresistance of ferroelectric tunnel junctions can be achieved by replacing the single ferroelectric barrier by a ferroelectric/dielectric bilayer. For a given thickness of the layers, the stacking sequence (ferroelectric/dielectric or dielectric/ferroelectric) can lead to different resistivity.

In this paper, we study composite tunnel junctions based on the Mn‐BiFeO3/SrTiO3 bilayer, deposited on a LaSrMnO3 (LSMO) buffer, grown on (001)‐oriented SrTiO3 (STO) substrates (fig. 1). The samples were grown by PLD. The nominal thicknesses are 0.8nm for SrTiO3 and 2.8 nm for Mn‐BiFeO3 (BFO).

TEM/HRTEM micrographs reveal the homogeneity of the bilayers. The sharpness and roughness of the interfaces are then studied by mean of Cs‐corrected HAADF‐STEM for both stacking sequences.

STO/BFO/LSMO (fig. 1a): for this configuration, both BFO/LSMO and STO/BFO interfaces appear flat, suggesting a homogeneous thickness of the BFO layer of 2.8 nm. The top surface of STO exhibits steps of half perovskite‐cell height leading to an effective STO thickness of about three to four unit‐cell; somewhat thicker than the awaited one.

BFO/STO/LSMO (fig. 1b): whereas the STO/LSMO interface looks flat and sharp, the BFO/STO interface exhibits a roughness of the order of one perovskite unit‐cell, indicating that the effective STO layer thickness is somewhat inhomogeneous, but close to the awaited 0.8nm thickness. The BFO surface looks flat, suggesting that the effective BFO thickness varies along the bilayer but also remains close to the 2.8nm awaited thickness.

Deeper insights on the interfaces sharpness are further obtained by ELNES measurements at the Mn L23 , Fe L23 , Ti L23 and O‐K edges. Peculiar fingerprints of the Fe and Ti L23‐edges are observed at the bilayer interfaces suggesting slight changes of the crystal field in their vicinity.