bluuebunny/crossref_metadata_2025 huggingface dataset:
Understanding the degradation of
Pt
nanoparticles in a fuel cell electrode via identical location electron tomography
Authors: Rossouw David , Chinchilla Lidia , Trefz Tyler , Kremliakova Natalia , Botton Gianluigi
Published: December 2016

The degradation and high cost of electrodes materials used in proton exchange membrane fuel cells (PEMFCs) are major barriers limiting their commercialization in automotive vehicles [1]. The search for more affordable electrode materials has focused on controlling the surface structure and composition of novel multi‐metallic catalytic nanoparticles on high surface area support membrane [2]. During fuel cell operation, the catalyst nanoparticles can dissolve, re‐deposit and agglomerate, resulting in electrochemical surface area losses, and an associated decrease in catalyst activity [3]. It is therefore critical to understand the degradation mechanism of the nanoparticle catalysts during electrochemical aging in a fuel cell electrodes in order to improve the performance and lifetime of PEMFCs. Here we characterize a newly proposed fuel cell cathode material, comprised of nano‐particulate platinum on a NbO
x
‐carbon hybrid support, using identical location electron tomography. A full HAADF‐STEM tomographic tilt series of several representative clusters were obtained before and after acclerated stress tests (30,000 cycles from 0.6 to 1.0 V in an electrochemical cell).

Preliminary results are summarized in Figure 1. A three dimensional (3D) schematic of a simple PEMFC shows the overall structure and location of the cathode electrode catalyst material used in this study. Pt nanoparticles, a few nanometers in diameter, decorate the complex, 3D NbO
x
‐carbon hybrid support structure, imaged by HAADF STEM under identical conditions in (b) before and after electrochemical cycling and at two tilts separated by 40
0
. The 3D tomographic reconstructions of the structure are aligned and compared in (c). The high fidelity of the reconstructions and the relatively small overall changes observed in the structure enabled the semi‐automated matching of over 500 individual Pt nanoparticles before and after cycling (d). The semi‐automatized approach was accomplished with the aid of quantitative image analysis techniques including histogram normalization and maximum entropy thresholding, and alignment of the before and after reconstructions via a singular valued decomposition of the reconstructed Pt centroids matrix. Preliminary results suggest that a net leaching of the Pt into solution has occurred during cycling, indicated by the overall reduction in size of a vast majority of Pt nanoparticles (e). Analysis of 3D reconstructions obtained from Pt‐NbO
x
‐carbon hybrid structures differing in their Pt/NbO
x
ratio are underway to better elucidate the role of NbO
x
in the degradation of Pt.

Identical location electron tomography before and after electrochemical cycling has provided valuable insight into the degradation mechanism of the PEMFC electrode during cycling, enabling more informed decisions for the design of high‐performance durable electrode materials.
Structural insight into the function of full‐length human Fanconi Anemia
FANCD
2/
FANCI
complex by cryo‐electron microscopy
Authors: Li Zhuolun , Liang Chih‐Chao , Nicholson William , Cohn Martin , Venien‐Bryan Catherine
Published: December 2016

INTRODUCTION

At the center of the DNA damage Fanconi Anemia repair pathway is the FANCD2/FANCI complex, which is monoubiquitinated upon DNA damage, and this monoubiquitination is indispensable for activation of the pathway. However, neither FANCD2 nor FANCI have any recognizable domains, which results in limited understanding of the molecular functions of the complex. In this study, we have taken a structural approach to better understand the function of the human FANCD2/FANCI complex.

RESULTS

Experimental methods
The native full‐length human FANCD2/FANCI complex and the FANCD2/FANCI complex with the C‐terminus FANCD2 truncated were purified and subjected to cryo‐EM analysis. The activity of the complex was studied
in vivo
and
in vitro
using various assays.

Results

Here, we provide the first structural insight into the full‐length human FANCD2/FANCI complex utilizing cryo‐EM. The complex has a pocket‐like main body, a thumb‐like structure consisting of the C‐terminus of FANCI and a distinctive fork‐like tower consisting of the C‐terminus of FANCD2 (figure). Deletion of the C‐terminus of FANCD2 leads to defective DNA interstrand cross‐link repair (ICL repair). FANCD2 lacking the C‐terminus cannot be monoubiquitunated, while the
bona fide
monoubiquitination site (Lysine 561) is still present. Furthermore, the association with FANCI and the interaction between FANCD2 and the responsible E3 ligase complex, the FA core complex, remain unaffected in the mutant. The structure of the FANCD2/FANCI complex with the C‐terminus FANCD2 truncated was also studied using cryo‐EM, this truncated domain is located in the fork‐like tower (Figure )

Conclusion

Conclusion
A new domain of FANCD2 was discovered. The fork‐like tower domain in the C‐terminus of FANCD2 is required for its complete functions in the ICL repair. Interestingly, several disease‐causing mutations lie within this region, underscoring the importance of this domain.

Translational applicability

Our results contribute to uncover the mechanism of how the FANCD2/FANCI complex functions. A better understanding of the molecular mechanism underlying the FA pathway will increase our chances of developing better and more targeted modes of treatment.

Reference

1‐ Liang CC, Zhan B, Yoshikawa Y, Haas W, Gygi SP and Cohn MA. UHRF1 Is a Sensor for DNA Interstrand Crosslinks and Recruits FANCD2 to Initiate the Fanconi Anemia Pathway.
Cell reports
10
, 1947‐1956, doi:10.1016/j.celrep.2015.02.053 (2015
Multivariate‐aided mapping of solute partitioning in a rare‐earth magnesium alloy
Authors: Rossouw David , Langelier Brian , Scullion Andrew , Danaie Mohsen , Botton Gianluigi
Published: December 2016

The addition of trace rare‐earth alloying elements to wrought magnesium products can dramatically improve the formability of the base metal, leading to the development of the commercial Mg‐Zn‐Nd‐Zr alloy ZEK100 for lightweight vehicular components [1]. Of particular importance in rare‐earth alloy design is a greater understanding of the role of solute species to which the favourable texture and ductility are attributed [2,3]. Here we use an analytical transmission electron microscope, combined with electron tomography and multivariate statistical analysis (MSA), to study the microstructure and partitioning of the trace alloying elements in alloy ZEK100.

We observe three distinct precipitate populations in the matrix; large spherical neodymium rich precipitates decorate the microstructure at the micrometer length‐scale (Fig. 1a), and at the nanometer length scale, a fine dispersion of smaller round zinc‐rich and rod‐shaped zirconium rich intermetallic precipitates populations are present, as revealed by energy dispersive x‐ray analysis and electron energy loss spectroscopy (EELS). An electron tomographic reconstruction of a precipitate‐rich region (b) enabled the distinction between round and rod‐shaped precipitates and elucidation of the rod precipitate orientation distribution and preferred habit plane via principal component analysis (iii). By utilizing the high sensitivity of MSA when applied to EELS spectrum images, we interpret a weak component in the spectral dataset to represent the presence of zinc and neodymium rich shells, just a few monolayers thick, encapsulating the zirconium rich intermetallic precipitates (i,ii). This interpretation was supported by subsequent targeted analysis. An individual elongated precipitate was identified as a Zn
2
Zr
3
structure by lattice‐resolved HAADF‐STEM imaging (Fig. 2a, i), and a few monolayer thick shell is observed at the precipitate/matrix interface (ii). The partitioning of neodymium and zinc at a precipitate interface was also observed in a needle specimen of the same alloy by atom probe tomography (b), providing strong evidence in support of the MSA zinc and neodymium rich shell component interpretation.

The combination of EDX, EELS, electron tomography and MSA techniques enabled an efficient and targeted analysis of the complex microstructure in alloy ZEK100. In particular, the use of MSA enabled the detection of a subtle, few monolayer thick solute rich shell around the small rod‐shaped precipitates, which may have otherwise gone unnoticed using conventional data analysis techniques. The tendency of the rare‐earth solute Nd to encapsulate precipitates may affect its role as a texture‐modifying element, and could therefore be of great significance in optimizing the chemistry and processing of rare‐earth magnesium alloy systems.
FIB
patterning for position‐controlled nanowire growth
Authors: Mosberg Aleksander Buseth , Ren Dingding , Fimland Bjørn‐Ove , van Helvoort Antonius Theodorus Johannes
Published: December 2016

Semiconductor nanowire (NW) based heterostructures are a promising material system for next generation optoelectronic devices, such as flexible solar cells and light emitting diodes [1]. Their reduced contact area and surface strain relaxation allow for epitaxial growth on lattice‐mismatched substrates, a key advantage for integration of different III‐V semiconductors with existing silicon‐based technology.

Position‐controlled NWs can be grown in ordered arrays on Si to improve uniformity and device integration. This is commonly performed by using a SiO
2
thin film as a mask. Patterning of circular holes in the mask (Fig. 1(a)) allows for site‐specific NW growth in predefined patterns and positions. To date, this is performed using lithography techniques such as electron beam lithography or nanoimprint lithography [2]. Important processing parameters include oxide thickness, hole diameter and pattern pitch, requiring several steps to be optimized in order to achieve a high yield of uniform NWs [3]. Additionally, the catalytic particle is rarely centered in the hole, leading to undesirable asymmetry in the NW cross‐sections [4].

In this work, the parameter space for direct patterning of NW growth substrates by focused ion beam (FIB) is explored (Fig. 1). Self‐catalyzed GaAsSb NWs were grown using molecular beam epitaxy (MBE) on a FIB patterned Si(111) substrate with 40 nm thermal oxide, where hole size, dose and Ga‐beam overlap were systematically varied (Fig. 1(a‐c)). It is expected that a higher degree of flexibility and control can be attained using FIB compared to the conventionally used resist‐based patterning techniques. In addition, patterning by FIB leads to Ga implantation in both Si and SiO
2
, which could positively affect the self‐catalyzed NW growth and the properties of the NW‐substrate system in a unique way.

After MBE growth, three distinct growth regimes can be recognized, present in all arrays (Fig. 1(d‐e)): The smallest (10 nm pattern) diameter row features a high yield (≤ 80%) of straight NWs. As the hole diameter increases there is initially a transition to more parasitic crystal growth and finally multiple (2‐5) NWs grow within each hole. As the dose increases between arrays in each column, the patterned diameter for these transitions decreases proportionally. The results demonstrate that using FIB the parameter space can be mapped out efficiently within a single growth session and that growth can be tuned between aligned single NWs, 2D parasitic crystals and multiple NWs per hole. Transmission electron microscopy and electrical testing of single NWs directly on the growth substrate [5] will be used to refine the structural analysis and study the electrical properties of these NWs. It is expected that in addition to the flexibility of FIB patterning, III‐V NWs grown on FIB‐patterned Si will exhibit novel properties due to the implantation of Ga and the altered NW‐substrate interface.
New version of the
EELS
database: eelsdb.eu
Authors: Ewels Philip , Sikora Thierry , Serin Virginie , Ewels Chris P. , Lajaunie Luc
Published: December 2016

Since its creation at the end of the 1990's, the EELS and X‐ray Absorption Spectroscopy (XAS) database has gathered more than 220 spectra covering 37 elements of the periodic table, becoming the largest open‐access electronic repository of spectra from EELS and XAS experiments. The EELS database is now a common tool used by spectroscopists, theoreticians, students and private firms as a reference catalog for fine structures and data‐treatment analyzes
2‐4
and has been referenced by more than 30 papers. Much of this success is due to the open‐access nature of the database. The database depends on voluntary user contributions; to encourage these contributions, we have performed a major update of the website.

The EELS and XAS database has been completely rewritten, with an improved design, user interface and a number of new tools. The database is accessible at
https://eelsdb.eu/
(
Fig. 1
) and can now be used without registration. The submission process has been streamlined to encourage spectrum submissions (
Fig. 2
) and the new design gives greater emphasis on contributors' original work by highlighting their papers. With numerous new filters and a powerful search function, it is now simple to explore the database of several hundred of EELS and XAS spectra. Interactive plots allow spectra to be overlaid, facilitating online comparison. An application‐programming interface has been created, allowing external tools and software to easily access the information held within the database. In addition to the database itself, users can post and manage job adverts and read the latest news and events regarding the EELS and XAS communities. In accordance with the ongoing drive towards open access data increasingly demanded by funding bodies, the database will facilitate open access data sharing of EELS and XAS spectra.
5
Cryo
EM
offers novel insights into the nucleoprotein‐
RNA
interaction in the measles virus nucleocapsids
Authors: Gutsche Irina , Desfosses Ambroise , Effantin Gregory , Ling Wai Li , Ruigrok Rob WH , Sachse Carsten , Schoehn Guy
Published: December 2016

Measles a one of the most contagious human diseases. Last year we determined the structure of the helical nucleocapsid formed by the folded domain of the measles virus nucleoprotein encapsidating an RNA at 4.3 Å resolution (Gutsche et al, Science 2015). This structure revealed the molecular determinants of the nucleoprotein packing into a helix and provided first insights into the mode of nucleoprotein‐RNA interaction in the nucleocapsid. We will now present our most recent high resolution cryoEM dataobtained with the goal to gain more precise structural information about the rationale of the RNA encapsidation.
Ultra‐High Resolution
SEM
for Materials Analysis
Authors: Jiruše Jaroslav , Havelka Miloslav , Polster Jan
Published: December 2016

The need for increased SEM resolution and the simultaneous demand for enhanced analytical capability have led to the development of increasingly sophisticated instruments. Here we describe the design of a novel SEM column where recently‐developed high‐resolution optics [1] is brought together with traditional analytical capabilities. Combined with FIB it greatly enlarges the capability for 3D tomography inspection of a specimen especially when used in combination with other analytical techniques like EDS or EBSD.

The SEM column comprises a triple objective lens design. The first objective lens is optimized to yield an image resolution of less than 1.1 nm at 1 kV. The design retains a single‐pole lens [2] which creates a strong magnetic field around the sample, dramatically decreasing optical aberrations. However, the leaking magnetic field distorts ion trajectories of the FIB and causes beam splitting of ion‐isotopes. To overcome this, FIB processing is performed in a magnetic‐field‐free mode, where the second objective lens of a conventional type with a resolution of 2.5 nm is used. The third objective lens enables a large field of view. A combination of all three objective lenses allows for multiple display modes, e.g. for enlarged field of view, greater depth of field or optimizing resolution at high probe currents. To prevent thermal instability due to changes of lens excitation when switching between the imaging, analytical and other modes, the column works in a regime where constant thermal power dissipation is maintained independent of lens excitation. It significantly reduces image drift and enables stable, long‐term, automatic 3D analysis.

3D BSE tomography of an SERS‐active structure of gold‐coated, partially‐etched polystyrene spheres (Figure 1) was performed maintaining stable operation over a 13 hour period [3]. The sample was sliced using FIB and each cross‐section was automatically imaged at 2 kV using one of the three dedicated back‐scattered electrons (BSE) detectors to obtain the gold distribution on the polystyrene surface. InBeam BSE detector placed in the column acquires high‐angle BSE signal, whereas the two other detectors collect BSE with lower angles. The BSE detector triplet thus enables angle filtration. Furthermore, energy‐filtering of the BSE signal enhances material contrast, (Figure 2), where low‐loss 1.95‐2 keV BSEs reveal details not observable in the integral BSE signal.

The redesigned electron gun further enhances the analytical capabilities of the column. It allows probe currents as high as 400 nA for structural analysis and ten times faster beam energy alternation compared to the previous generation. The sharp conus of the objective pole‐piece enables FIB processing of large tilted samples, e.g. 8 inch wafers. The new SEM column will be used in the Mark II generation of the TESCAN MAIA electron microscope and the dual FIB‐SEM instruments GAIA and XEIA [4].
Correlation of interface morphology and composition in
GaInP/GaAs
with growth conditions
Authors: Han Han , Beyer Andreas , Belz Jürgen , König Alexander , Stolz Wolfgang , Volz Kerstin
Published: December 2016

Ternary (GaIn)P materials ststems grown on GaAs have attracted a lot of attention for laser applications, especially due to the low recombination velocities at the interface [1]. The physical properties of the interface are greatly influenced by the interface morphology, which can be controlled by either the growth temperature or growth interruptions or the introduction of interlayers, consisting e.g. of GaP. The interface morphologies of the semiconductor quantum wells can be characterized by the quantitative evaluation of high resolution high angle annular dark field (HAADF) images in scanning transmission electron microscopy (STEM). In the present work, quantitative evaluation of HAADF imaging in STEM is used to correlate the interface morphology and composition in (GaIn)P grown on GaAs with the growth conditions.

The (GaIn)P/GaAs QWs were grown with metal organic vapor phase epitaxy (MOVPE) on GaAs (001) substrate at temperatures of 525°C and 625 °C, respectively, with different growth interruption times with or without GaP interlayer. In order to be able to compare different samples, a carefully applied method to gain reliable results from high resolution STEM micrographs was used. Also, to derive the chemical composition maps, the chemical sensitive background intensity is subtracted after image normalization as shown in Figure 1. From the composition maps, the interface features are revealed and then correlated with the growth conditions. The growth interruptions can significantly affect the composition fluctuation and the interface morphology. At higher temperature of 625 °C, with the two GaP monolayers between (GaIn)P and GaAs substrate, shorter growth interruption time leads to intermixing at the interface while a longer growth interruption results in a sharp interface. Also, without the GaP buffer layer, platelet islands can be observed at the interface. At lower temperature of 525 °C the GaP buffer layer has less influence. Hence, the quantitative evaluation of HAADF STEM images can reveal the interface morphologies, which also have important influence on the optoelectronic properties.
Electron Tomography of entrapped iron nanoparticles in silicalite‐1 (Fischer‐Tropsch catalyst)
Authors: Koneti Siddardha , Roiban Lucian , Farrusseng David , Huve Joffrey , Epicier Thierry
Published: December 2016

It is known that Fischer‐Tropsch synthesis [1] is one of the best processes to convert syngas emitted from combusted of fossil fuels like coal and natural gas into liquid gas/ liquid fuels and other petro chemicals. Moreover, iron based catalysts are known to be efficient and active components of Fischer‐Tropsch catalyst. Encapsulating iron nanoparticles into mesosporous silica allows to provide a highly selective, active and stable Fe@silicalite‐1 catalyst [2]. Its architecture prevents the particles from sintering under reaction conditions, it does not show any activity to water‐gas‐shift reaction during FTS and it does not produce any CO
2
which is another advantage of this catalyst. These attributes made the Fe@silicalite‐1 catalyst extremely selective.

The 2D observation and analysis of iron nanoparticles on Silicate‐1 gives only partial information regarding the distribution and position of the particles making necessary electron nano‐tomography analyses. To understand the 3D position and size distribution of the iron nanoparticles in silica cages, high resolution electron tomography in bright field mode was performed in a FEI‐Titan ETEM using a Fischione tomographic holder. We worked in a low dose mode to avoid as much as possible any beam damage of silica. After the segmentation of reconstructed volumes, the quantification of the 3D models was made (Fig 1). It was found that a large majority of iron nanoparticles are encapsulated in the walls of silica. The Fe particles average size is of 3.5 nm (Fig 2) [3].
Electron microscopic characterization of thermally modified surface layers generated by electro‐discharge machining
Authors: Ehle Lisa , Schneider Sebastian , Schwedt Alexander , Richter Silvia , Mayer Joachim
Published: December 2016

Functional properties of construction components like wear resistance or fatigue strength heavily depend on their surface modifications like grain size, residual stresses, hardness, etc. Since these modifications are generated during machining, knowing about the resulting modifications beforehand is in high demand in industry. So far many time‐consuming iterative procedures are necessary to find the machining parameters that provide the desired surface integrity. Brinksmeier et al. [1, 2] introduced a new energy based approach called “Process Signatures” that is supposed to solve this problem. Process Signatures describe the relationship between internal material loads – like strain, temperature and their gradients – and the resulting material modifications for instance residual stresses, hardness and microstructure. Hence production processes are characterized by their mechanical, thermal and chemical loads or a combination of those instead of their machining parameters. The present work focuses on electro discharge machining (EDM), which is mainly characterized by thermal effects due to the high temperatures and temperature gradients arising from the generated spark plasma [3, 4].

In the present studies, scanning electron microscopy (SEM), electron backscatter diffraction (EBSD), electron probe microanalysis (EPMA) and transmission electron microscopy (TEM) have been used to analyze the surface modification of 42CrMo4 steels processed by EDM. According to the very high surface temperatures (above melting temperature) and high temperature gradients applied by EDM, the surface zone contains martensite and even dendrites (figure 1). Investigations on the carbon content in the surface zone reveal about 8 times higher carbon contents than in the matrix due to carbonization (figure 2). Carbonization occurs because of decomposition of the dielectric fluid and carbon diffusion results due to the high applied temperatures. The increase in carbon content also stabilizes the fcc crystal structure, as the EBSD phase map shows (figure 3). These surface modifications reveal information about the mechanisms and applied internal loads, since the internal loads, in particular temperature and temperature gradients, influence diffusion of carbon, generation of dendrites and martensitic transformation. Together with temperature measurements during processing and simulation of temperature evolution in the material, Process Signatures for EDM can be developed.
A precession electron diffraction study of ordered‐disordered phases in
Ni
‐
Cr
based alloys
Authors: Stephan Baptiste , Jacob Damien , Delabrouille Frederic
Published: December 2016

The alloy 690 is a nickel‐based alloy (60% Ni, 30% Cr, 10% Fe) used in nuclear Pressurized Water Reactors for different components (steam generator tubes, reactor vessel clevis etc.). These components are subjected to long thermal ageing for 40 to 60 years at 325 °C.

For these kind of alloys, thermal ageing can produce an order‐disorder transformation due to the formation of the Ni
2
Cr ordered phase by a nucleation growth mechanism. This transformation strongly modifies mechanical properties (strength increasing and ductility decreasing) as well as electrical properties when the orthorhombic ordered domains grow in the cubic disordered matrix.

In order to correlate the ordering state of these alloys to the evolution of their macroscopic properties, TEM studies are conducted. Ordered domains are generally very small (a few nanometers) so that imaging is not always feasible. Hence, ordering state is investigated using electron diffraction where we want to measure the intensity ratio between superlattice reflexions, related to the ordered domains, to the fundamental ones, related to both ordered domains and the disordered matrix (see figure 1). Indeed, in the kinematical approximation, the square of the order parameter s is proportional to Is/If, where Is and If are the intensities of the superlattice and fundamental reflections respectively. We want to appreciate the validity of this approach using Precession Electron Diffraction (PED) coupled to dynamical calculations of the intensities
1
. For this kind of quantitative study, PED is advantageous since it strongly reduces sensitivity to experimental parameters such as sample thickness and exact orientation, which renders comparison with intensity calculations much more reliable. Reflections of the <011> cubic matrix zone axis pattern are targeted. In this orientation, superlattice reflections come from only one of the six possible orientation variants of the ordered phase related to the disordered one (see figure 2). This particular type of zone axis thus gives the richest information about the ordered phase.

In the present study, model alloys with iron content of 0 to 3 wt. % Fe are aged between 24 and 20 000 h in the range of 325 to 500 °C. The precipitation of Ni
2
Cr ordered phase is detected by an increasing Vickers hardness and ThermoElectric Power (TEP) at the macroscopic scale.

We first need to validate our dynamical calculations on the fully ordered orthorhombic domains. In this attempt, specifically aged alloys are also studied, where ordered domains are well extended (a few tens of nanometers). Microdiffraction patterns are then collected on single domains and a systematic study of the intensity ratio Is/If as a function of the sample thickness is conducted in order to compare experimental and calculated data. Generalization of the procedure to the mixed alloys containing both ordered and disordered domains in various proportions will then be proposed.
Investigations of transition metal dichalcogenides with momentum‐resolved electron energy‐loss spectroscopy
Authors: Huang Michael R. S. , Wilfried Sigle , van Aken Peter A.
Published: December 2016

Investigations of transition metal dichalcogenides with momentum‐resolved electron energy‐loss spectroscopy

Michael R. S. Huang, Wilfried Sigle, and Peter A. van Aken

Max Planck Institute for Solid State Research, Stuttgart, Germany

When fast electrons pass through a thin film, various solid‐state excitations occur through mutual Coulomb interactions, which convey useful information relevant to the fundamental materials properties. Measurements by momentum‐dependent electron energy‐loss spectroscopy (q‐dependent EELS or ω ‐ q map) directly access the dispersion relation, enabling the physical origins of the intrinsic electronic excitations to be explored [1]. This research is concentrated on anisotropic titanium diselenide (TiSe2), a two‐dimensional material in the transition metal dichalcogenide group. The ω ‐ q maps were acquired in the Zeiss sub‐electron‐volt‐sub‐angstrom microscope (SESAM), which is equipped with a monochromator and the advanced in‐column Mandoline energy filter. To enhance the angular resolution, the specimen was purposely raised above the eucentric height, which significantly extends the effective camera length (ECL) beyond the originally achievable specification [2]. Figure 1 shows the characteristic dispersion of TiSe2 recorded along the momentum transfer parallel to the Γ‐K direction. The specific selection of scattering vector in reciprocal space is achieved through a narrow slit well positioned in the filter entrance pupil plane. With further increase of the ECL as well as in the spectral magnification, the details of the dispersion become clearly resolved (Figure 2). Similar to other layer‐ structured crystals such as graphite or molybdenite (MoS2) [3,4], the two dominant features at approximately 6.5 and 19.7 eV can be interpreted as the π and π + σ plasmons, which stem from the collective oscillations of the π and π + σ valence electrons, respectively. Moreover, another weak spectral feature at a lower energy of about 1.9 eV without significant dispersive behavior was also noticed. This excitation could probably be attributed either to the interband transition or to another plasmon resonance as a result of the negative real part of the dielectric function within this regime. However, more comprehensive investigations are required for clarity.
Efficient motor neuron targeting in adult mice by a single lumbar intrathecal r
AAV
9‐e
GFP
administration: application for motor neuron diseases
Authors: Bey Karim , Deniaud Johan , Carine Ciron , Dubreil Laurence , Aubourg Patrick , Colle Marie‐Anne
Published: December 2016

Spinal muscular atrophy (SMA) the second most common autosomal recessive disorder causes of childhood mortality affecting between 1/6000 to 1/10000 live births. SMA is due to deletion/mutations in the
Survival Motor Neuron 1
(SMN1) gene. The disease is characterized by degeneration of spinal motor neurons (MNs), atrophy of skeletal muscles, and generalized weakness. SMA is clinically classified into four main types (I, II, III and IV) based on the age of onset and clinical severity. Currently, no curative treatment exists for SMA type II/III SMA patients representing the majority currently awaiting treatment.

Gene therapy, restoring SMN1 activity in MNs, is a promising therapeutic strategy for SMA. In the moderate forms (type II/III) of the disease, no lesion is found in peripheral organs. Thus, a targeted therapy directly into the CNS should be more appropriate. We have, recently, demonstrated that a single administration of an rAAV9 vector into the cerebrospinal fluid leads to an efficient transduction of MNs in non‐human primates.

In order to treat our mouse model that can mimick the human pathology of type II/III SMA, the first main challenge was to develop an efficient and safety route of delivery that can target whole spinal cord and brain. In this context, we develop the lumbar intrathecal delivery (itlumb), by single percutaneous lumbar puncture. We demonstrate that a single lumbar intrathecal injection of rAAV9‐eGFP vector using specific neuronal promoter can efficiently and specifically target MNs from proximal to distal part of the spinal cord in adult mice, wherease, using rAAV9‐eGFP ubiquitous promoter, we observe both glial cells and MNs targeting
(figure a, b and c)
. Surprisingly, by lumbar administration, we efficiently reach the brain and target neurons and glial cells using rAAV9 ubiquitous promoter
(figure g)
.

Then, we compared the serotypes 9 and 10 of AAV vector in order to demonstrate which serotype is the most efficient to target MNs after intrathecal delivery. We used the Synapsin 1 (SYN1) promoter, that lead to specific expression in neuron cells population, in adult mice, by lumbar intrathecal administration. We observed a spectacular and specific MNs expression with the serotype 9 around 50% and 10 % in the lumbar and cervical spinal cord respectively. Wherease the serotype 10 transduce less significantly MNs cells (30% and 5 % in the lumbar and cervical spinal cord respectively).

This results, offer new perspectives for the treatment of motor neuron diseases such as moderate forms of spinal muscular atrophy.
Improving
3d
correlation in integrated correlated light and electron microscopy using confocal laser scanning microscopy
Authors: Sueters‐Di Meo Josey , Kruit Pieter , Hoogenboom Jacob
Published: December 2016

In CLEM experiments biological samples are typically first investigated by light microscopy (LM) to locate a region of interest. Next, nanometer‐scale imaging can be achieved by electron microscopy (EM). This results in identification of biomolecules within the ultrastructure and/or the possibility to correlate ultrastructure with preliminary live‐cell dynamics on biomolecules [1].

We have developed an integrated CLEM with which widefield fluorescence microscopy (WF‐FM) and EM can be performed in principle simultaneously [2]. Integration of these two modalities allows for fast ROI retrieval [3], optional fast switching between modalities increasing CLEM throughput, high (5 nm) correlation accuracy for the overlay [4], and novel imaging applications [5]. However, for WF‐FM the depth correlation for thick specimen or live cells contained in a dedicated liquids sample holder [6] is relatively poor. WF‐FM images through the entire sample and SEM only the upper ~100 nm (depending on e‐beam energy). We therefore integrated a Confocal Laser Scanning Microscope (CLSM) into a scanning electron microscope (SEM) via a Delmic Secom stage (Fig. 1‐4). This system will allow imaging with improved depth‐correlation by suppression of out‐of‐focus light contributions and will provide 3D optical information in CLEM.

We present our integrated CLSM SEM, using a commercial confocal scanner unit. We also demonstrate the procedure for alignment of the CLSM and SEM axes, needed to image the same area with both modalities. Lastly, the results of proof‐of‐principle experiments are presented, showing optical sectioning in thick specimen such as resin blocks or whole cells for improved LM‐SEM correlation along the axial direction.
Advanced
STEM
characterisation of composition controlled MoxW1 xS2 mixed transition metal dichalcogenide alloys grown by chemical vapour deposition
Authors: Murdock Adrian , Lozano Juan G , Prabakaran Arunvinay , Dillon Frank , Grobert Nicole
Published: December 2016

Nanoengineering of transition metal dichalcogenides (TMDs) (MX
2
: M= Mo, W, Nb; X= S, Se, Te) offers exciting new prospects for the production of two‐dimensional nanomaterials with tailored properties
1
. In particular, single layer TMD alloys, including Mo
x
W
1‐x
S
2
and MoSe
2(1‐x)
S
2x
(x=0‐1), have been shown to have a compositionally modulated electronic structure
5,6,7,8
, providing a tunable band gap that could be advantageous for new nanoelectronic, optoelectronic or photonic applications. Powders of such nanostructured materials may also offer improved catalytic capabilities due to optimised edge structures
9
. However, to date, synthesis of these ternary alloys has been limited to exfoliation of flakes from single crystals that are produced by vapour transport using bulk Mo, W, and S
5,6
or MoS
2
7
, offering limited prospects for large‐scale manufacturing in the future.

Here we investigate composition‐controlled Mo
x
W
1‐x
S
2
nanoflakes synthesised by atmospheric‐pressure chemical vapour deposition (CVD) using novel Mo and W containing precursors
10
. Conventional TEM and EDX analysis, supported by complementary XPS, where used to investigate the shape and thickness of the flakes and demonstrates that the W dopant composition can be varied from as little as a few percent (x=0.98), to over 86% (x=0.14). Through atomic‐resolution annular dark field scanning transmission electron microscopy (STEM) using a Cs probe corrected JEOL ARM200F we directly observe the substitution of W atoms for Mo atoms within the MoS
2
lattice. This confirms the synthesis of alloyed dichalcogenides rather than heterostructures, with W randomly distributed throughout the nanoflakes
11
. This new method for growth of ternary 2D TMD alloys offers improved composition control for application as industrial catalysts, while opening a new avenue for bandgap engineering of monolayers in the future.
TEMinvestigation of the effects of cycling on electrochemically stable hybridPt@NbOxnanocatalysts
Authors: Chinchilla Lidia , Rossouw David , Trefz Tyler , Kremliakova Natalia , Botton Gianluigi
Published: December 2016

Renewable energies and fuel cell technologies will likely play a major role in reducing our dependency on fossil fuels. In particular, proton exchange membrane fuel cells (PEMFCs) are suitable for use in both domestic and automotive applications. This sophisticated technology requires a functional nanostructured material that contains platinum to catalyse both the hydrogen oxidation reaction (HOR) and the oxygen reduction reaction (ORR) to produce water, electricity, and heat. [1] Unfortunately, in spite of their remarkable potential, the high cost and degradation of platinum‐based catalytic materials have been a barrier to widespread adoption of this type of technology. Reducing platinum content while simultaneously improving the durability will therefore require novel approaches in the catalyst design and its characterization at nanoscale level. [2]

Transmission Electron Microscopy (TEM) techniques have continued to play a major role in the design and characterization of PEMFC materials. Using an aberration‐corrected microscope (Titan cubed 80‐300), we investigated the structural stability over the lifetime of a proposed fuel cell cathode material containing nano‐particulate platinum on a NbOx‐carbon hybrid support. The characterization of this material included a series of ex‐situ TEM analyses before or after accelerated stress tests that cycled the sample 30,000 times between 0.6 and 1.0 V in an electrochemical cell.

The histograms shown in Fig1a and b reveal that some metal particle coarsening occurred during the 30,000‐cycle test. The as‐prepared catalyst contained 1–5 nm particles, the majority of which were determined to be bimetallic, as determined by electron energy loss spectroscopy (EELS), with some Pt‐rich particles and Nb‐rich grains (Fig. 1c). After 30,000 cycles, microanalysis data confirms that the cycling treatment caused some agglomeration of the small Pt‐rich particles. Analysis of the EELS oxygen K ionization edge indicates that multiple niobium oxidation states are present in the system, predominantly Nb(V) before electrochemical cycling (Fig 1c). Although conventional image comparisons between the initial and final state of the hybrid catalyst suggest that the Pt particle size increased marginally, in order to obtain an improved understanding of the material's degradation, morphological and structural evolution of the particles and hybrid support were tracked using the so‐called Identical Location TEM technique [3]. The results in figure 2 indicate that no large‐scale degradation of the hybrid support took place, suggesting carbon corrosion was minimized. In addition, only minor changes occurred to the average particle size, demonstrating the excellent stability of the metallic particles. These findings demonstrate that highly dispersed Pt/NbOxon carbon support material is a promising electrocatalyst for PEMFC.
Structural and chemical characterisation of novel
FeS
nanostructures for energy storage synthesised using a single‐source precursor
Authors: Lozano Juan G , Dillon Frank , Naylor Andy , Lee Lok Yi , Lippard Chris , Johnstone Duncan , Bruce Peter G , Grobert Nicole
Published: December 2016

Iron sulphide is an interesting material for a wide range of potential applications due to its number of possible phases, high abundance, low cost and non‐toxicity [1]. In particular, Fe‐S phases are capable of undergoing reversible electrochemical reactions with lithium‐ions making Fe‐S a potential material for anodes in lithium‐ion batteries [2]. Furthermore, by engineering the electrode materials to nanometre scale, there will be (a) a larger surface area of electrode material in contact with the electrolyte per unit mass, allowing a larger flux of Li‐ions between the two electrodes, resulting in faster charging and discharging of the battery; (b) shorter diffusion distances of Li‐ions which will result in a higher power density; (c) a better accommodation of strain following conversion reactions, thus resulting in longer cycling life. This advantages are even further strengthened if the nanostructures are synthesised in the two‐dimensional form, since then the accessible surface area of the materials is dramatically increased. Despite their superior properties, the scarce number of published reports on the synthesis on two‐dimensional FeS nanostructures is remarkable [3].

Here we report structural and chemical characterisation of iron sulphide nanoparticles and two‐dimensional nanosheets synthesised using a one‐pot, fast and facile single source precursor method. This synthesis method offers the possibility of tailoring the design of the nanostructures with slight variations of the synthesis conditions. Conventional transmission electron microscopy (TEM), high resolution TEM, and selected area electron diffraction patterns confirmed that the nanoparticles consisted of high‐crystalline quality troilite FeS; while the nanosheets are made of small crystallites with random rotations while still lying on their (0001) basal plane. Scanning‐transmission electron microscopy (STEM) and electron energy‐loss spectroscopy confirmed that the majority of the crystallites in the nanosheets are troilite FeS, with some residual pyrite also present; and no oxides were formed during synthesis. Electrochemical tests also indicate that the nanosheets show much larger capacities compared with the nanoparticles.
Analytical Atomic‐Resolution Microscopy of Oxygen Deficient
Ca2Mn3O8‐d
Authors: Mazarío‐Fernández Ángel , Torres‐Pardo Almudena , Cortés‐gil Raquel , Varela Aurea , Parras Marina , Hernando Maria , González‐Calbet Jose María
Published: December 2016

Manganese related perovskites (AMnO
3
, A=alkaline earth) present a wide range of fascinating functional properties due to the ability of Mn to adopt several oxidation states and different coordination polyhedra. Regarding their catalytic behaviour, CaMnO
3‐δ
selectively oxidizes, at least on a laboratory scale, propene to benzene and 2‐methyl propene
[1]
. Moreover, the Ca‐Mn‐O system presents a great variety of oxides with different Ca/Mn ratio and crystalline structure and a particular behaviour: their reduction process leads to a rock‐salt type structure which, in most cases, can be again oxidized to the starting material
[2]
.

Here we show the combination of oxygen engineering performed under adequate controlled atmosphere with local characterization techniques like atomic resolution electron microscopy associated to Energy Electron Loss Spectroscopy (EELS) to provide a complete characterization of other member of the Ca‐Mn‐O system. In particular, Ca
2
Mn
3
O
8
crystallizes in a monoclinic layered structure
[3]
with sheets of Mn
IV
in octahedral coordination held together by Ca
2+
cations alternately stacked along a axis (Fig. 1). The total reduction process of this material leads to Ca
2
Mn
3
II
O
5
with rock‐salt type structure.

By means of partial reduction, different samples have been stabilized in the Ca
2
Mn
3
O
8‐
d
system. Among them, Ca
2
Mn
3
O
6.5
, a new layered calcium manganese oxide with only Mn
3+
, has been stabilized. The different samples obtained in the Ca
2
Mn
3
O
8‐δ
system have been characterized by using High Angle Annular Dark Field (HAADF) and Annular Bright Field (ABF) imaging associated to EELS and Energy Dispersive Spectroscopic (EDS) in an aberration‐corrected JEOL JEMARM200cF electron microscope. The structural evolution and the local variation of the Mn oxidation state in different phases with different anionic composition will be discussed.
Visualization of Dengue virus like particles interacting with antibodies
Authors: Deliot Aurelie , Nicolai Marie‐Claire , Ronzon Frederic , Lecouturier Valerie , Nemecek Daniel
Published: December 2016

Dengue virus (DENV) is one of the most important arthropod‐borne viruses that infect humans. Approximately 400 million people are infected annually in tropical and sub‐tropical regions worldwide [1]. In 2015, Sanofi Pasteur released the first commercialized and approved tetravalent vaccine that is protective against the four DENV serotypes [2].

In the context of developing a better understanding of the interaction of dengue antigen with the immune system, it is important to fully understand the structure and accessibility of specific epitopes. Particularly in the case of the dengue virus, viral capsids bud into the host endoplasmic reticulum and acquire structural proteins prM and E embedded in the membrane. The prM and E proteins are assembled as trimers as part of an immature icosahedral shell and undergo significant structural rearrangement during viral exit via the Golgi apparatus. In the Golgi, Host furin‐type proteases concomitantly cleave the pr peptide triggering rearrangement of the trimers into dimers, which is necessary for infectivity of the viral particle [3]. However, maturation of DENV virions is not efficient and partly immature particles are released during DENV infection as well. It has been hypothesized that these particles function as decoys to avoid neutralization of the infectious mature particles by the immune system [4].

Recombinant antigens in the form of virus‐like particles are attractive as reagents for understanding antigen‐antibody interactions. Here, we investigated the molecular architecture of virus like particles (VLPs) made of dengue structural subunits, which are produced by The Native Antigen Company (Oxfordshire, UK). We found by SDS‐PAGE and confirmed by Western blot that DENV‐2 and DENV‐3 VLPs contain a significant fraction of uncleaved prM subunits. To assess the molecular architecture and conformation of subunits in the VLP particles, we determined 3D structure of individual particles by cryo‐electron tomography. The particles have a spherical (DENV‐2 VLPs) or elongated (DENV‐3 VLPs) outer shell with short spikes and an internal cavity (Figure 1). The spikes exhibit the same morphology as the prM/E subunits in the immature dengue viral particles. We additionally imaged and reconstructed the 3D structure of VLP particles mixed with monoclonal antibodies specific to the mature conformation of DENV. We identified bound antibodies to individual particles in subtomograms after subtraction of the VLP shell (Figure 2). Binding of the antibodies to the VLP particles was subsequently confirmed by Western blot and immunogenicity assays suggesting that these VLPs could adopt a mixed conformation with mature dimers and immature trimers on the same particles, as previously described for DEN virions or adopt a specific new conformation of mature prME specific to VLPs.

This study was funded by Sanofi Pasteur using equipment installed at Sanofi Pasteur.