bluuebunny/crossref_metadata_2025_split huggingface dataset:
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.
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.
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.
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.
Kinetic Behavior of
Fe‐Ni‐C
Martensitic Steels during Aging at Room Temperature
Authors: Curelea Sergiu , Cazottes Sophie , Epicier Thierry , Danoix Frédéric , Zapolsky Héléna , Lavrskyi Mikola , Maugis Philippe , Chentouf Sara , Goune Mohamed 
Published: December 2016

The kinetic behavior of a Fe–24 Ni–0.4 C (weight percent) martensitic steel during aging at room temperature has been investigated by transmission electron microscopy. Electron diffraction, coupled with imaging techniques in a transmission electron microscope, including high resolution studies, have been used at various stages during the aging process, in order to characterize the microstructural features of the analyzed samples.

Rapid cooling (quenching) in liquid nitrogen of the austenitic state of the above‐mentioned material leads to the formation of a martensitic phase which, at room temperature (RT), begins to transform, through a process called spinodal decomposition. As a result of this process, a modulated structure is formed, in which carbon‐rich regions (precipitates) occur in a periodic manner throughout the matrix, leading to the presence of diffuse streaks or satellite spots around each fundamental (matrix) reflection on the electron diffraction patterns, see Figure1. This process is thus accompanied by a reduction of the tetragonality of the martensitic phase (
bct
), which evolves towards the formation of a cubic structure (
bcc
), see Figure2, corresponding to alpha‐iron (ferrite). After long ageing times, Fe3C is observed. The presence and structure of intermediate carbides is also studied.

The microstructure of the carbon‐rich phase is also analyzed by electron diffraction. The evolution of the tetragonality with time, translated as the c/a ratio, which is also function of the carbon composition, is studied. Moreover, the variation of the distance between the carbon‐rich precipitates (in fact, the periodicity of the modulated structure), along with the evolution of their width and length, are also observed.
Thanks are due to the Clym ( Centre Lyonnais de Microscopie) for the access to the TEM 2010F.
Influence of
Cu
content on the structural and morphological features of
TixCuy
intermetallic thin films for biosignals acquisition
Authors: Lopes Claudia , Koneti Siddhardha , Roiban Lucian , Borges Joel , Epicier Thierry , Vaz Filipe , Steyer Philippe 
Published: December 2016

Thin films synthesized by Physical Vapor Deposition (PVD) are currently studied to be used in different types of sensors [1,2]. Among these, sensors and electrodes used for biomedical devices are particularly important since they allow converting one or more measured signals of any living tissue into other quantities, usually an electrical signal. Beyond the electrical response, a biomedical sensor should also be biocompatible and totally innocuous for the patient. Additionally some degree of antibacterial effect is considered as a further asset for the sensor. The Ti‐Cu system perfectly meets such requirements, Ti being biocompatible, while Cu is relevant for its antibacterial character. Objective of this study is to deeply characterize the nature and microstructure of Ti‐Cu films in order to better understand and optimize the sensor response.
Films are deposited by a PVD magnetron sputtering process from a composite Ti‐Cu target. Their chemistry, morphology and fine microstructure are characterized by X‐Ray diffraction, Rutherford Backscattering Spectrometry, Scanning and Transmission Electron Microscopies.
Results show that three main zones were distinguished, in relation with the Cu/Ti atomic ratio into the films. SEM reveals that the morphology of micrometer‐ thick films changed from a columnar to an amorphous‐like microstructure. XRD diffraction indicated that the hcp‐Ti structure dominates for low Cu/Ti ratios. For higher Cu contents, formation of Ti‐Cu intermetallic phases was noticed which becomes more clear and obvious for the third zone (Cu contents above 75 at.%). HR‐TEM and STEM observations confirm the presence of nanocrystallites embedded into an amorphous matrix (Fig. 1). A further chemical characterisation allowed identifying the nature of intermetallics, which contributed to explain sensors' electrical behaviours (Fig. 2).
Probing structural and electronic properties of h‐
BN
by
HRTEM
and
STM
Authors: Mouhoub Ouafi , Ricolleau Christian , Wang Guillaume , Amara Hakim , Andrieux Amandine , Dorval Nelly , Fossard Frédéric , Lavenus Pierre , Lagoute Jerome , Pham Van Dong , Wu Pai Woei , Loiseau Annick , Alloyeau Damien 
Published: December 2016

After the discovery of graphene and its consequences in the field of nanoscience and nanomaterials, there has been a growing interest in 2D materials and also their vertical stacking due to unique properties and potential applications.[1] For instance, it was shown the transport properties of exfoliated graphene supported by hexagonal boron nitride (h‐BN) could approach the intrinsic graphene limits.[2] Nevertheless, studying the structural properties of 2D materials and 2D heterostructures is crucial to understand their physical and chemical properties. Our motivations have been to exploit state of the art aberration‐corrected high resolution transmission electron microscopy (HRTEM) and scanning tunneling microscopy (STM) to study the structure and electronic properties of graphene (G), h‐BN and G/h‐BN heterostructures.
HRTEM analyses were conducted with a JEOL ARM microscope equipped together with a cold FEG, an aberration corrector for the objective lens and a One view camera (Gatan). Notably, we used high‐speed atomic‐scale imaging to study with unprecedented dynamics (up to 25 fps) the nucleation and growth mechanisms of triangular holes in h‐BN under beam irradiation (Figure 1). The direct observation of B and N atom sputtering and surface reconstruction processes allow understanding how the triangular shape and orientation of holes are maintained during the growth. Interestingly, by studying the effects of the electron dose and the number of BN layers, we demonstrate that these atomic‐scale processes are simultaneously driven by kinetic and thermodynamic effects. Further works are in progress to study the stability of h‐BN/G stacking under electron‐beam irradiation.

STM analyses were carried out with low temperature STM at 4 K, on 2D heterostructures that consist in a few layers of graphene doped with nitrogen on thick exfoliated flakes of BN deposited on SiO
2
. Remarkably, we show that STM allows identifying and characterizing ionization defects within the BN flakes below the graphene layers (Figure 2). This study opens new avenues to probe the electronic interactions between this two stacked materials.