bluuebunny/crossref_metadata_2025 huggingface dataset:
AEM
Characterization of the products yielding from Chlorination Process to obtain
T
i
O
2 from natural Ilmenite
Authors: Montero Ludy Caceres , Solorzano Guillermo , Brocchi Eduardo A.
Published: December 2016

In the titanium industry, chlorination of ilmenite (FeOTiO
2
) at elevated temperatures in the presence of a reducing agent promotes formation of TiCl
4
in gaseous form, which can be subsequently selective condensed and then reduced to titanium metal or oxidized to producing TiO
2
[1]. Alternatively, in the absence of the reducing agent, the process becomes selective, favoring the formation of iron chlorides and promoting enrichment in content of TiO
2
obtained in the solid product of the reaction [2]. Therefore, the present study reports the observations by Analytical Electron microscopy (AEM) of principals characteristics of the TiO
2
polymorphs, anatase and rutile, obtained by chlorination with and without reducing agent respectively. The experimental analysis involved the as‐received material, the intermediate and final products, all sequentially characterized by means of X‐Ray Diffraction (XRD), X‐Ray Fluorescence (XRF), Scanning Electron Microscopy (SEM), Energy Dispersive Spectroscopy (EDS), and Transmission Electron Microscopy (TEM).

Fig. 1a., shows a low mag SEM image of the as‐received material constituted essentially by Ilmenita particles rich on Ti and Fe. Fig. 1b and 1c., are secondary electrons (SE) SEM images of the products after chlorination process for 60 minutes. While Fig 1b., corresponds to direct chlorination product shows faceted TiO
2
crystals, Fig 1b., corresponds to the product resulting from chlorination in the presence of carbon showing spheroidal TiO
2
anatase aggregates. The XR‐Difractograms shown in Fig 2., corroborated the crystal identification on each mentioned products. Fig 3.a and 3b., is TEM bright field (BF) ‐dark field (DF) pair of a robust single crystal of TiO
2
rutile and corresponding diffraction patron pointing in red the diffracted bean use for the DF image. Fig 4a., and 4b, is also BF and DF pair however of an anatase aggregates and the correspond diffraction patron in the Fig 4c., showing, namely in the DF imagen shaped nanocrystals about 10 nm in sizes. Interested to note in this aggregated nucleation rate of nanocrystals in a still shapeless aggregated. The same anatase product has been captured in the BF‐DF pair of Fig 5a and 5b and corresponding diffraction patron of Fig. 5c. These images correspond to a later state of nucleation and growth processes, configurating well‐defined spherical nanocrystalline aggregates of TiO
2
anatase in order to minimized of surface energy. After calcination of this product under N
2
atmosphere, it can seen the TiO
2
nanoparticles of about 10 nm in size have been more homogeneity distributed, mostly spheroidal and some exhibiting facets thereby implying in a thermodynamics states closer to the equilibrium.[2]
Microstructure of stainless steel produced by direct metal laser sintering
Authors: Labre Cilene , Pinto Andre , Solórzano Guillermo
Published: December 2016

Microstructure of stainless steel produced by direct metal laser sintering

C. Labre1, 2, A. L. Pinto1, G. Solórzano2

1
Brazilian Center of Physics Research, Rio de Janeiro, Brazil.

2
Department of Chemical and Materials Engineering, PUC‐Rio de Janeiro, Brazil.

Keywords: Additive manufacturing, direct metal laser sintering, 3D

Additive manufacturing or rapid prototyping is a layer‐by‐layer fabrication technique based on selective fusing and consolidating thin layers of loose powders with a scanning laser beam, for building three‐dimensional (3D) objects [1]. Among the various methods of additive manufacturing the direct metal laser sintering (DMLS) had a big progress in the recent years and as an alternative manufacturing route to produce components, it attracted great attention due to the easy processing, high process speed and capability of producing complex shaped metallic objects. The present study focuses on the microstructural characteristics of the 15‐5 PH stainless steel powder and a component built by DMLS from the same powder (composition: Cr 16,4wt%, Ni 4wt%, Cu 3,7 wt%, Mn 1,3wt%, Si 0,045wt%, Mo 0,5wt%, Nb 0,35wt%, C 0,045wt% and Fe (bal.)). For this purpose, JEOL JSM 7100FT scanning electron microscope (SEM), LYRA3 FEG SEM and electron backscattered diffraction (EBSD) have been used at Brazilian Center of Physics Research (CBPF).

Figure 1A shows that the 15‐5 PH powders are in spherical shape and the particle size are in the ranged of 20 to 50μm. Preliminary EBSD results of the slice view of Figure 1B show that the grains are randomly oriented (Figure 1C), each orientation is indicated by a specific color, and it has a higher concentration of grain size of up to 7μm (Figure 1D). Grain orientation map shows that there is not a preferential crystallographic orientation.

Figure 2A shows a SEM image of the cross section of an object produced by DMLS. A laser scanning was repeated to build the subsequent layers until the objects is completed. Arrow indicates the building direction. The grain orientation map presents columnar grains randomly oriented melt pool boundaries (Figure 2B). The grain size distributions show a higher concentration of grain size below 5µm (Figure 1C). The grain size of the object is reduced comparing with the grain size of the original powder.
Low dose electron holography using direct‐electron detection camera
Authors: Chang Shery , Jin Lei , Barthel Juri , Dunin‐Borkowski Rafal , Dwyer Christian
Published: December 2016

The advent of commercially‐available direct detection cameras (DDCs) for transmission electron microscopy (TEM) offers the opportunity to reduce noise in images and diffraction patterns as well as providing fast frame rates for image recording. For sufficiently low dose rates, their design can enable significant improvements in detective quantum efficiency (DQE) and modulation transfer function (MTF) when compared to conventional charge‐coupled device (CCD) cameras. Existing literature on DDCs is focused predominantly on structural biological applications, where they provide clear advantages under low dose conditions, e.g., typically < 10 e
−
Å
−2
. Whereas the characteristics of DDCs at dose rates and spatial resolutions that are applicable to biological materials are already well established, in many other areas of TEM the dose rate can exceed 1000 e
−
Å
−2
, while the spatial resolution can vary from nanometers to better than 1 Å. In these contexts, the benefit of DDCs is less clear.

Here, we examine this question in the context of high‐resolution phase contrast imaging and off‐axis electron holography and demonstrate that the improved MTF and DQE of a DDC result in clear benefits over conventional CCD cameras. For electron holography, we find a significant improvement in the holographic interference fringe visibility and a reduction in statistical error in the phase of the reconstructed electron wavefunction. In addition, we show that at least three‐fold improvement in optimum phase resolution using the counting mode provided by DDC with four time less dose rate compared that of a conventional CCD camera (with a fringe spacing of 83pm in this case). Further improvement in SNR could be obtained by correlation and averaging over a series of holograms. As a result of the low camera noise, the correlation of individual hologram is robust even at low dose rates, and the averaging leads to an improvement in SNR that is close to the ideal root‐N behavior (N being the number of images).

Using BiFeO
3
on DyScO
3
substrate as an example, we demonstrate that both specimen and birpism fringe drift can be successfully correlated over 100 frames of hologram (total exposure of 20 sec at a dose rate of 10 e
−
per pixel per sec), as shown in Fig. 2. Our results show that DDCs are highly beneficial for electron holography (and similarly to high‐resolution TEM ) at low dose rates, thereby minimising potential specimen damage while maintaining an adequate SNR for analysis.
Image deconvolution for fast Tomography in Environmental Transmission Electron Microscopy
Authors: Feng Yue‐Meng , Tran Khanh , Koneti Siddardha , Roiban Lucian , Gay Anne‐Sophie , Langlois Cyril , Epicier Thierry , Grenier Thomas , Maxim Voichita
Published: December 2016

The development of environmental transmission electron microscopes (ETEM) as well as the environmental cells opens the way towards operando electron microscopy. In this respect, following the genesis of a catalyst or a chemical reaction in real time under gaseous environment and at high temperature becomes a possibly achievable goal. Performing such experiments in 2D has already been successful but reaching the 3D information in environmental mode is a challenge as it needs to acquire 2D projections fast enough in order to neglect the morphological evolution of the object during the chemical reaction, a required condition to reconstruct a 'correct' 3D object. Under environmental conditions, the motion and evolution of the objects might produce images corrupted by motion which will then exhibit possibly significant blurred features. These defaults might even be enhanced if one intends to acquire the image series rapidly. This contribution will address the possibility of using deconvolution methods to un‐blur such environmental microscopy images. Here we mainly focus on the motion blur correction of corrupted images: g(x,y)=(f*h)(x,y)+n(x,y)

where * denotes the convolution product,
f
is the ground truth image,
g
is the observed corrupted image,
h
is the degradation function of the acquisition system and n is the noise.

The Minimum Square Error (MSE) and the Constrained Least Square (CLS) filtering are used as image restauration processes as shown in figure 1. Both of them require the degradation function h as input and the parameter k related to the noise level which has to be optimized. Denoting
G
the Fourier transform of the corruptedimage, the Fourier transform of the reconstructed image is then given by one of the following relations:

F
MSE
(u,v)= G(u,v).H(u,v)
c
/ (|H(u,v)|
2
+k) and F
CLS
(u,v)= G(u,v).H(u,v)
c
/ (|H(u,v)|
2
+k.|P(u,v)|
2
),

where
H
is the Fourier transform of the convolution filter
h
,

H
c

is its complex conjugate,
P
is the Fourier transform of the Laplacian filter and |.| denotes the complex modulus. However, the degradation function is not known in practice and has to be estimated from the experimental images. The estimation of a parametric degradation function
h
is performed by image comparison: so far we manually determine the unknown parameters by comparing the blurred image with a similar one not affected by the motion blur. We will present perspectives of this work in terms of running an automatic estimation of the convolution kernel for in‐situ image processing of experimental micrographs.
Three dimesional nano‐ and interfacial structures in the
Si
rich
SiC
systems analysed by spectroscopic electron tomography
Authors: Xie Ling , Jarolimek Karol , Swaaij Rene Van , Leifer Klaus
Published: December 2016

Silicon (Si) nanopartcles (NPs) embedded in the insulating or semiconducting matrices has attracted much interest for the third generation of photovoltaics, so called “all‐Si” tandem solar cells. In this work, the amorphous Si rich silicon carbide (SRSC) absorber layers with 30% carbon content were deposited using plasma enhanced chemical vapour deposition (PECVD) on quartz substrate at 500 °C, and then the SRSC films were annealed at 1100 °C in nitrogen for 1 hour
1
. The thermal treatment leads to the SRSC films spinodally decomposed into a Si‐SiC nanocomposite. The nanostructures of the phase separated Si and SiC presented in the 15 minutes and 1 hour annealed SRSC films were investigated by two dimensional (2D) energy‐filtered transmission electron microscopy (EFTEM). After the thermal treatment, the coexistence of crystalline Si and SiC nanoparticles (NPs) were observed from the high resolution TEM (HRTEM) images and verified by the selected area diffraction (SAD) patterns. After 1 hour annealing, neither Si nor SiC phases are complelely crystallized, the detailed morphologies of Si and SiC nanostructures were studied by electron tomography. For the first time, we make use of EFTEM spectra‐imaging (SI) dataset to reveal the three dimensional distributions of Si, a‐SiC and c‐SiC in sub‐volumes. In particular, to obtain more detailed and quantitative information, we have fitted the plasmon spectra with reference plasmon peaks. This enables us to not only to get a quantitative 3D image of all components involved in the materials system in the final tomogram, but also to obtain information about hitherto undetected phases in this system. In such energy resolved plasmon tomograms, the 3D shape of a thin amorphous SiC layer (1) was observed at interface between the crystalline Si network like structure and crystalline SiC NPs. The appearance of the a‐SiC interfacial layer is expected from nucleation theory.
Probing the multiscale structure, composition and nanomechanical properties of lipids and biopolymers in natural systems: a few examples
Authors: Gaillard Cédric
Published: December 2016

The natural systems as plants or animal tissues possess a highly complex organisation of numerous components: micronutriments, proteins, polyssacharides, lipids, water, …. Their natural arrangement gives very fine structures that range from the nanometer up to few meters scale range (typically from the protein to the whole plant). Native architectures have a direct influence on the functional, chemical, organoleptic and nutritional macroscopic properties relevant for designing sustainable performant products for environmentally compatible food and non–food uses.

The development and application of experimental methodologies to probe the assemblies of lipids, biopolymers, mineral nutrients as well as structural water from the sub‐cellular to the molecular levels is then a permanent challenge. The parallel use of a set of complementary microscopy tools that provides relevant information may be needed to overcome the complexity of hydrated natural systems and to get both their structural, composition and nanomechanical properties. Most of the time, the experimental sample preparation is also a critical prerequisite to adapt the biological samples to the features of the analytical tool while keeping as most as possible the structures in their native shape. Thanks to this step, the microscopy tools can be operated through a direct or indirect correlation approach.

Using few applications we developed on biopolymer‐based nanoparticles as well as animal cells or plant tissues (see Figure 1), we will show how to probe the structure/composition/nanomechanical properties focusing on the strong complementarity of AFM imaging and force mapping, Raman mapping, SEM/EDX, and scanning transmission X‐ray spectrometry (STXM). We will also discuss about the samples preparation strategies, and about data processing in relation to the information expected.
Cryo‐electron microscopy from vitreous thin films in complement to
AFM
for understanding the multiscale supramolecular assemblies: a few examples
Authors: Gaillard Cédric
Published: December 2016

The considerable growth of nano‐technologies and nano‐sciences requires the implementation of very well adapted characterization tools and methods to combine both a nanometer resolution and a good preservation of the nano‐objects. This point is absolutely critical when the nanostructures are made of hydrated and organic compounds. Cryo‐electron microscopy (cryo‐TEM) made from vitrified thin films has proved to be a method of choice for characterizing the hierarchy of supramolecular assemblies of proteins and hydroxy fatty acids with maximum resolution and minimal damage.

We aim here to present a selection of applications of cryo‐TEM showing the characterization of dispersions of organic or hybrid organic/inorganic nanoparticles with a large range of sizes, shapes and composition (synthetic polymers, polysaccharides, proteins, lipids).

In particular, we will detail how cryo‐TEM helped to elucidate the supramolecular self‐assembling of fatty acids through a multiscale approach. The unique benefits as well as the limitations of cryo‐TEM will be discussed and compared with conventional SEM and TEM techniques as well as with liquid AFM.
Raman imaging of biology and soft matter samples: a few examples
Authors: Gaillard Cédric
Published: December 2016

Electron microscopy (SEM, TEM) is widely used to characterize the internal structures with micrometer spatial resolution. AFM is also commonly employed for analyzing the surface topography with a superior spatial resolution. However, confocal Raman microspectrometry is a unique way to complete such structural investigation by knowledge on chemical information. Raman imaging combines the spatial resolution of optical microscopy with the molecular analysis capabilities of Raman scattering. Then, it is very well adapted to provide direct information about conformation, structure and behavior of lipids and biopolymers (proteins, polysaccharides) from micronsized zones of interest.

Also, the mainly structure‐sensitive bands in protein and lipid spectra makes them suitable for multivariate analysis techniques such as principal component analysis (PCA) to deduce structural relationships.

Raman microspectrometry is then a method of choice for the compositional investigation with a high spectral resolution of hydrated biological systems of food interest along with the structural investigation performed conjointly with laser scanning confocal microscopy, AFM or electron microscopy with a superior spatial resolution.

We aim here to review few examples of Raman imaging performed on different biological systems (algae, plant and animal tissues) and on soft‐matter based systems (highly diluted gels, dispersions) relevant in food industry, see Figures 1 and 2. We will focus on the complementarity with the other types of microscopy, and on the practical details concerning the sample preparation (choice of objectives, choice and influence of supports, smoothing or not of the surfaces,…).
Advanced Microstructure Characterization of β
Ti‐Nb‐Ta‐Fe
Alloys obtained by Powder Metallurgy
Authors: Afonso Conrado Ramos Moreira , Amigó A. M. , Amigó V.B.
Published: December 2016

In order to obtain advanced biomaterials, with low elastic modulus and acceptable mechanical strength titanium alloys with high contents of refractory materials are used. The addition of niobium, tantalum and molybdenum difficult the manufacturing processes of these alloys. One way to obtain these β‐Ti alloys is the powder metallurgy (P/M) that allow obtaining of customized materials. Although it presents intrinsic limitations, such as porosity, lack of diffusion and the increasing of grain size with sintering parameters. The objective of this work was the microstructure characterization of phases and mechanical properties of Ti35Nb10Ta alloy with Fe additions, using transmission electron microscopy (TEM) and selected area electron diffraction (SAD). The distribution of phases and grain orientation maps were determined with an Automatic Crystal Orientation Mapping (ACOM) system installed in a FEI Tecnai F20 TEM with LaB6 gun. An ASTAR NanoMegas system was used for ACOM diffraction data acquisition. The analyzed map step was 10 nm based on a rectangular grid (400 x 200 pixels). The identification of phases and orientations are obtained through image matching between experimental diffraction patterns and calculated templates. The microstructure obtained is composed mainly by β‐Ti phase (bcc) in β‐stabilizers rich areas (Nb, Ta, Fe), and α+β phase's region confirmed in TEM image (Fig. 1.a and 1.c) and SAD with orientation relationship ([0001]
a
//
[110]
β
) in β‐stabilizers poor areas (Ti rich). The a‐Ti (hcp) phase occurs mainly along the grain boundaries, growing inwards. In between it is possible to identify metastable w phase in nanometric scale, confirmed by TEM image (Fig. 1.b) and by spots with orientation relationship with β‐Ti matrix in the SAD zone axis [11‐20]
w
//
[1‐10]
β
(Fig. 1.d). Fig. 2 shows ACOM image of Ti35Nb10Ta alloy sintered at 1250ºC with virtual bright field (BF) combined with Reliability of α+β region (Fig. 2.a) and (b) PhaseMap combined with Virtual‐BF image of β (red) and α (green) region (Fig. 2.b). β‐Ti phase is mainly observed, with some α+β regions (β‐stabilizer poor elements concentration) and higher β‐Ti stabilization with Fe addition and sintering temperature. Nanometric ω phase was observed inside β‐Ti phase using TEM analysis. TEM and ASTAR provide complementary information both on phase constitution and orientation distribution in nanosized α phase precipitated inside β‐stabilizer poor regions.
Exchange‐coupled
Sm‐Co/Co
thin layers; structural and magnetic investigations
Authors: Hannachi Marwen , Belkacem Wajdi , Cabié Martiane , Bessais Lotfi , Mliki Najeh
Published: December 2016

Exchange‐coupled SmCo/Co hard/soft magnetic bilayers with different thicknesses of hard and soft phases were deposited on (100) silicon substrate, using Ultra High Vacuum (UHV) evaporation. Structural properties were investigated by transmission electron microscopy. Magnetic properties were measured, at room temperature, by Polar Magneto‐Optical Kerr Effect. Hysteresis loops show single‐phase magnetic behavior suggesting a strong exchange coupling between hard and soft phases. The magnetization ratio M
r
/M
s
and coercive field H
c
were found to increase with increasing hard layer thickness. The highest remanence (M
r
/M
s
= 1) and coercivity (H
c
=670 Oe) were obtained when SmCo and Co thicknesses are respectively 2.5 and 0.5 nm. The STEM‐HAADF images exhibit that this bilayer was not thoroughly continuous; it is composed of Co elliptical particles surrounded by SmCo. PMOKEimaging shows that themagnetization reversal process is dominated by wall propagation.
Analytical electron microscopy and atom probe tomography investigation of interfacial segregation
Authors: Danoix F. , Sauvage X. , Gouné M. , Gault B. , Cuvilly F.
Published: December 2016

The chemistry of internal interfaces plays a key role in modern physical metallurgy, in particular for the development of the new generations of steels. Despite the tremendous instrumental developments over the last decade, the atomic scale characterization of these interfaces in steels is still a very challenging problem.

Analytical electron microscopy (EDX and EELS in STEM mode) and atom probe tomography are the two techniques presenting spatial and analytical resolutions suitable for such characterizations. Their respective advantages and complementarity will be illustrated on the basis of quantitative determination of segregated amounts of interstitial and substitutional elements at interfaces, with particular emphasis on the intensive specimen preparation efforts required to reach their ultimate capabilities.
Multi‐technique approach to study the corrosion of plasma assisted surface treatments of 316L stainless steel
Authors: Escalada L , Owens A.S. Gasco , Soldera F. , Ávalos M. , Brühl S , Simison S
Published: December 2016

Different plasma assisted methods can be used to nitriding, carburizing, carbonitriding or to produce a coating over stainless steels. In order to preserve their excellent corrosion resistance is important to control these processes parameters, avoiding the chromium depletion of the steel matrix, produced mainly due to longer process time and/or higher temperatures. This work has the aim to analyze the corrosion morphology and behavior under certain test conditions using different characterization methods. For assessing the corrosion resistance, cyclic potentiodynamic anodic tests have been done. A three electrodes cell has been used, where the counter electrode is a platinum wire, the reference electrode is a saturated calomel electrode and the treated surface sample is the working electrode. When the current density reach an arbitrary value of 200 mA/cm2, the potential is registered as E
200
, and the potential is swept in reverse direction. This E
200
value is used as a parameter of comparison, obtaining the highest values for those samples with the thickest modified layers. The morphology observed for the nitrided and carburized AISI 316L samples, consists in pits located below the modified layer, and originated in some non‐metallic inclusions present in the “as received” alloy. SEM/FIB microscopy was used to identify and characterize this behavior. At present, there are some points of interest under research. The interphase between the modified layer and the steel seems to be a preferable site for pits to nucleate and grow. Atomic probe microscopy, TEM as well as EBSD were used to identify possible chemical and structural singularities in that place. The connection between the interphase and the electrolyte is produced by channels originated in the inclusions, but not all of them nucleate the attack. Different kind of inclusions have been observed and identified using TEM and EBSD.
Studying biological samples in their native liquid environment using electron microscopy
Authors: Hermannsdörfer Justus , Weatherup Robert , Hofmann Stephan , De Jonge Niels
Published: December 2016

It is now possible to study biological systems (e.g. eukaryotic cells) at nanometer spatial resolution in their native liquid environment using electron microscopy [1–3]. In contrast to conventional procedures, these new methods do not involve complex preparation steps like embedding, cutting, or freeze‐sectioning. It is further possible to minimize negative drying artifacts by adjusting experimental conditions that represent the native state as close as possible, i.e. the presence of water. Several different approaches meeting these requirements have been developed to study whole cells of different sizes:

Method 1: Two silicon microchips with electron transparent windows can be used to realize a microfluidic chamber that is sealed from the vacuum in the electron microscope (Figure 1). The chamber between the two microchips is thick enough to contain whole cells, yet thin enough to ensure a sufficient transmission of electrons. It is further possible to create bubbles in the liquid cell compartment by inducing a high density of electron dose on the sample. This increases the obtained contrast due to the minimized amount of scattering solvent. The liquid cell compartment can be used in a standard Transmission electron microscope (TEM). Method 2: Environmental scanning electron microscopy (ESEM) can be used to study cells covered in a thin layer of liquid surrounded by a saturated water atmosphere. The thickness of the liquid layer is controlled by adjusting the temperature and the environmental pressure within the vacuum chamber. Method 3: The wet sample is attached to an electron transparent support (e.g. graphene, carbon, silicon nitride) and covered with a thin membrane (e.g. mono or multilayer graphene) to realize a thin layer of liquid around the sample [4]. This method allows for high resolution imaging as the amount of solvent is reduced to a minimum. It can be used in any conventional TEM and SEM with scanning transmission electron microscopy (STEM) detection. The presence of water can be confirmed by beam‐induced bubbles.

Each of these three methods can be used to study the location and stoichiometry of transmembrane proteins within the intact plasma membrane [2, 3] with relevance to cancer research [5]. Nanoparticles, specifically attached to proteins, provide enough contrast for imaging (Figure 2). Also correlative light‐ and electron microscopy is readily possible, so that large numbers of cells can be screened, while selected regions can be studied with high resolution [5].
Structure and genome delivery mechanism of Staphylococcus aureus phage therapy agent phi812‐K1 determined by cryo‐electron microscopy
Authors: Nováček Jiří , Šiborová Marta , Benešík Martin , Pantůček Roman , Doškař Jiří , Plevka Pavel
Published: December 2016

Worldwide occurrence of multidrug‐resistant pathogenic bacteria has increased interest in alternative treatments including bacteriophage‐based therapy. Bacteriophage phi812 belongs to genus Twort‐like virus, subfamily
Spounavirinae
and can infect at least 75% of Methicilin‐resitant
S. aureus
strains (MRSA) and 95% of Methicillin‐sensitive
S. aureus
strains. We have employed cryo‐electron microscopy to determine structure and genome delivery mechanism for polyvalent staphylococcal backteriophage phi812‐K1. Phi812‐K1 has a 90 nm diameter isometric head and 240 nm long contractile tail ended by a double layered baseplate. The tail and baseplate of the native phage are dynamic. Therefore, a divide‐and‐conquer strategy was employed to separately determine the cryo‐EM reconstructions of the individual phage parts. The structure of the icosahedral head could be refined to 5.0 Å resolution and additional sub‐averaging within the T=16 icosahedral asymmetric unit allowed determination of the major capsid protein to 3.8 Å resolution. The structures of the native tail and baseplate were solved to 8 Å and 12 Å resolution, respectively. In order to examine the mechanism of the infection process, we determined the structure of the phage in the contracted state. The phage head is not altered after the DNA ejection. However, both the baseplate and tail undergo large reorganizations documented in their 6 Å and 8 Å resolution structures. Comparison of the tail and baseplate structures in the native and contracted conformation allowed us to determine the changes accompanying cell wall recognition and binding which is then followed by injection of the bacteriophage genome into the host bacteria.
Integrated microscopy: Matching scales and capabilities in light and electron microscopy
Authors: Hoogenboom Jacob
Published: December 2016

Superresolution techniques have pushed the resolution of fluorescence microscopy (FM) towards that of electron microscopy (EM)[1]. Meanwhile, developments in scanning EM (SEM) are revolutionizing EM, moving lateral image dimensions to typical FM fields‐of‐view[2] and extending imaging capability into the third dimension[3] and the live‐cell regime[4]. By correlating data from both techniques[5], molecules can be localized within the context of cells and tissue and with reference to their live dynamics, but throughput and quantification are hindered by elaborate, expert procedures involving separate microscopes. In this presentation, I will show an integrated approach, with high‐numerical aperture FM in a SEM, such that the electron beam can be positioned anywhere within the fluorescence field of view[6, 7]. Using electron‐beam excited cathodoluminescence from the transparent sample substrate, we achieve automated FM‐EM image registration (Fig. 1) with an accuracy that can be pushed to 5 nm, i.e. equalling biomolecular length scales. Besides integrated correlation microscopy, I will show our progress towards novel applications bridging fluorescence and electron microscopy, such as fluorescence‐guided live‐cell EM[8], and electron‐beam identification and localization of labels, molecules, and cells.
Electron microscopy approaches to studying lipid‐protein interactions
Authors: Walz Thomas
Published: December 2016

Membrane proteins play crucial roles in many cellular processes such as signaling, nutrient uptake and cell adhesion. Although the lipid bilayer influences many aspects of membrane protein function, our understanding of lipid–protein interactions is limited. In the first part of my talk, I will describe how electron crystallography of the water channel aquaporin‐0 reconstituted with lipids into two‐dimensional crystals can be used to address very basic questions in membrane biology, such as the driving forces that define lipid–protein interactions and the effects of hydrophobic mismatch. In the second part, I will discuss how we use membrane proteins reconstituted into nanodiscs to make it possible to study lipid–protein interactions by single‐particle cryo‐electron microscopy. In particular, I will discuss how the mechanosensitive channel MscS adapts to different lipid bilayers.
Electrical properties of atomic carbon chains measured by in‐situ TEM
Authors: Banhart Florian , La Torre Alessandro , Ben Romdhane Ferdaous , Cretu Ovidiu , Botello‐Mendez Andrés , Charlier Jean‐Christophe
Published: December 2016

Carbon in the

sp
1

hybridization (carbyne) is able to form atomic chains that constitute the elementary one‐dimensional phase of carbon [1]. Despite many efforts, the synthesis of carbon chains in appreciable quantities remains difficult and even the existence of bulk carbyne is subject of an ongoing controversy. However, the existence of individual carbon chains is undisputed since they have been observed in
in‐situ
TEM studies. The present work allowed, for the first time, to measure the electrical properties of carbon chains by using a dedicated specimen stage for establishing electrical contacts in the TEM.

Carbon chains are unusual conductors that may occur either as metallic cumulene with double bonds or as semiconducting polyyne with alternating single and triple bonds. Now, as it became possible to characterize them electrically, these two electronic configurations can be distinguished. A piezo‐driven tip (Nanofactory), integrated into the specimen holder of a TEM, allowed to establish contacts to graphenic material and, by controlled retraction of the electrodes, to unravel chains of carbon atoms (fig. 1a). At the same time, the electrical properties could be measured [2, 3]. By recording current‐voltage curves of individual carbon chains, both cumulene and polyyne were identified (fig. 1b). It was found experimentally and by quantum conductance calculations (fig. 1c) that transport through narrow resonant states makes the conductivity much lower than predicted in previous theoretical work. At high applied bias, however, a sudden rise in current occurs, showing the absence of conduction channels at lower energy and their presence at higher energy.

When the 1D system is under strain, the chains exhibit a semiconducting behavior, corresponding to polyyne. Conversely, when the chain is unstrained, an ohmic behavior, corresponding to cumulene, is observed (fig. 1b) [4]. This confirms a recent theoretical prediction, namely that the Peierls distortion, which would stabilize polyyne, is suppressed by zero‐point vibrations in an unstrained chain so that cumulene is the stable configuration. In the presence of strain, however, polyyne is favoured by the Peierls instability. Thus, a metal‐insulator transition can be induced by adjusting the strain. Furthermore, it is shown that these atomic chains can act as rectifying diodes when they are in a non‐symmetric contact configuration, i.e., between a carbon and a metal contact or between two carbon contacts of different type.
The effect of tau hyperphosphorylation on Pin1 expression in primary cortical neurons: in okadaic acid induced
AD
model
Authors: Metin Derya , Ak Duygu Gezen , Dursun Erdinç , Atasoy İrem , Yılmazer Selma , Korkmaz Arzu Karabay , Ozturk Melek
Published: December 2016

Hyperphosphorylation of tau leading to neurofibrillary tangles (NFT) is a key pathological hallmarks in neurodegenerative disorders such as Alzheimer's disease (AD) (1). Peptidyl‐prolyl cis‐trans isomerase (Pin1) regulates the phosphorylation of Ser/Thr sites of tau protein, and promote microtubule assembly (2). In this study, we aimed to determine the interaction between Pin1 expression and tau hyperphosphorylation in primary cortical neurons using okadaic acid (OKA) model (3) utilized to study AD.

Cortical neurons were obtained from embryonic day 16(E16) Sprague Dawley rat embryos. The neurons were treated with 25 nM OKA on day 7 of culture. Then at 4, 8 and 24 hours after treatment OKA, tau phosphorylation was analyzed by western blot using anti‐tau antibodies including Thr231 and Tau‐1. Immunocytochemistry was used for Pin1 protein expression and localization. Pin1 mRNA expression was determined by qRT‐PCR at 4, 8 and 24 hours. For cytotoxicity LDH analysis was performed by ELISA. At 8 hours with OKA, tau phosphorylation at Thr231 was increased and non‐phosphorylated Tau‐1 was decreased compared with the untreated control. Pin1 mRNA expression levels at both 4 and 8 hours post‐OKA treatment were lower than the control group. No significant differences at Pin1 mRNA and protein expression levels were observed between the OKA‐treated group and the untreated control group at 24 hours of treatment. Pin1 was mainly localized in the nucleus of control groups, whereas was found in cytoplasm of OKA‐treated group. Apoptotic nuclear morphology in OKA‐treated group was detected more than the control neurons. In OKA‐treated group the LDH release was not significantly different than the other groups at 4 and 8 hours, whereas it significantly increased at 24 hours.

Our study indicates that OKA induces the tau‐hyperphosphorylation, affects Pin‐1 expression, and causes to translocation of Pin‐1 proteins into cytoplasm from nucleus. This study will provide a new approach for AD molecular pathophysiology of in OKA‐ induced AD model.
Electron Tomography at the Frontiers of Materials Chemistry
Authors: Leary Rowan
Published: December 2016

This presentation will follow two themes. The first considers recent contributions of electron tomography in materials chemistry, with particular focus on rationally designed multi‐scale and multi‐component systems. Second, developments and future prospects in electron tomographic methodology will be discussed.

Summarised in Figures 1 and 2, for example, is a recent study of Au nanorpisms decorated with Pt nanoparticles of size relevant for catalysis [1]. The tomographic analyses disclosed otherwise ambiguous details of the multi‐component architecture, revealing that both pseudospherical protrusions and dendritic Pt nanoparticles grow on all faces of the nanoprisms, the faceted or occasionally twisted morphologies of which were also revealed, and shedding light on alignment of the Pt nanoparticles. Complementary electron energy‐loss spectrum imaging showed that the Au nanoprisms support multiple localized surface plasmon resonances despite the presence of pendant Pt nanoparticles. These insights suggest potential applications in plasmon‐enhanced catalysis and in situ monitoring of chemical processes via surface‐enhanced spectroscopy, and pave the way toward comprehensive engineering of such multi‐functional nanostructures.

With the widespread adoption of scanning transmission electron microscopy and high‐angle annular‐dark field imaging, structural electron tomographic studies have reached a consistently high standard. The fidelity of such studies has also been raised significantly by the development of advanced reconstruction algorithms, such as those based on compressed sensing [2]. These are undergoing continual evolution to address the range of contexts and challenges faced in contemporary nanoscale investigations, including quantitative, low‐dose and analytical electron tomography.

Significant advances in hardware, such as fast and efficient X‐ray and electron energy‐loss spectrometers, and new camera technologies, have opened the flood gates to analytical electron tomography [3]. New ‘big data’ challenges are faced in the processing and analysis of multi‐dimensional tomography data sets. In this regard,
post facto
‘computational microscopy’ is becoming increasingly important; and versatile computational approaches can yield rich rewards. Indeed, computational analysis combined with advanced reconstruction can enable capture of the salient information content in a powerful and efficient manner. Computational modelling also offers the opportunity to utilise signals that have traditionally been thought unsuitable for tomography. Combined, hardware and computational advances are enabling a new era of analytical electron tomography, providing sophisticated 3D mapping at the nanoscale, spanning composition, crystallography, chemical, optical and electronic properties.
Probing cell behavior: Combining
MEMS
(microelectromechanical systems) technology with high resolution live cell imaging
Authors: Geitmann Anja
Published: December 2016

Cell biological experimentation has benefitted from the development of microdevices based on microfluidics and MEMS (microelectromechanical systems) technology. These devices exploit the possibility to create microscopic 3D structures that can be used to manipulate single cells. Furthermore, microdevices can be used to miniaturize laboratory functions (Lab‐on‐a‐Chip). We developed an experimental platform with the specific aim to study tip growing cells, the TipChip [1]. The device allows positioning of single cells such as pollen grains or fungal spores at the entrances of serially arranged microchannels harboring microscopic experimental setups. The transport of the cells is mediated by fluid‐flow. Once positioned in the device, the tip growing cells, pollen tubes, filamentous yeast or fungal hyphae, can be exposed to chemical gradients, microstructural features, integrated biosensors or directional triggers. The device is compatible with Nomarski optics and fluorescence microscopy and can thus be used for live cell imaging. Using the TipChip platform we investigated the growth mechanism in pollen tubes. The pollen tube is a cellular transport system that is generated to connect the male gametophyte with its female counterpart. Through this catheter‐like protuberance the sperm cells are delivered from the pollen grain to the ovule nestled deep within the pistillar tissues. To be competitive, the pollen tube elongates extremely rapidly and it has to do so against the impedance of the apoplast of the transmitting tissue and through the maze of pistillar cells that separate the pollen grain from the ovule. Using calibrated micro‐cantilevers we quantified the invasive force of the pollen tube and we found that sperm cell discharge can be triggered by mechanical constriction [2]. Further applications include exposure of cells to precisely calibrated electric fields and micron‐sharp, tunable chemical gradients. The TipChip is therefore a highly versatile tool for the combined quantitative biophysical and optical investigation of polar growth in plant cells.
3D
imaging via
FIB‐SEM
tomography at nanoscale for tissue engineering applications
Authors: Urszula Stachewicz , Szewczyk Piotr , Kruk Adam , Barber Asa , Czyrska‐Filemonowicz Aleksandra
Published: December 2016

The use of electrospun nanofibers for guided bone regeneration or bone scaffolds are becoming increasingly important in tissue engineering for next‐generation healthcare. However, understanding the interaction between the nanofiber scaffolds that organize into complex 3D organizations and cells for optimized growth is a recurrent problem yet to be overcome.

In this study we exploit high resolution 3D imaging using scanning electron microscopy (SEM) and focussed ion beam (FIB) microscopy to evaluate cryo‐prepared electrospun nanofiber scaffolds. Specifically, a biodegradable electrospun nanofiber membrane fabricated from poly(D,L‐lactide‐co‐glycolide) (PLGA) is used for guided bone regeneration for orthopaedic applications. The electrospun scaffolds are produced with randomly oriented and aligned nanofibers, creating a range of void sizes, which are crucial for controlling cells penetration into electrospun scaffolds. The secondary electron imaging in Figure 1 and 2 demonstrates osteoblasts spreading over the random and aligned nanofiber mat surface respectively and within the fibrous membrane after 4 days in culture. Osteoblasts tend to growth both along the principal fiber axis and migrate in all directions towards neighboring fibrous filopodia, localized at the edges of osteoblasts, help the sheets of cells to align in the nanofiber direction and participate in cell‐cell adhesion. It is presumed that these filopodia–like–protrusions are responsible for osteoblast elongation and migration into the 3D network of the electrospun nanofiber mat.

The interaction between osteoblasts and osteoblast‐derived mineralized nodule formation on the nanofiber membrane is visualized using 3D FIB‐SEM imaging based on a ‘slice‐and‐view’ approach. The 3D imaging highlights a coherent interface at small length scales between osteoblasts and nanofiber surfaces through connections between osteoblast, their filopodia and the nanofibers that promote cell growth. These imaging results are supported by biochemical approaches that indicate the formation of proteins responsible for focal adhesion in osteoblasts.
1
The presented 3D tomography therefore presents a new approach in high resolution visualization the cell growth on electrospun nanofibers, and potentially other biomaterials, that will develop and design new biomaterials for a range of clinically important applications including orthopaedics of this work.
A closer look at high‐resolution electron holography
Authors: Niermann Tore , Lehmann Michael
Published: December 2016

In the recent years high‐resolution off‐axis electron holography made huge advancements. Electron microscopes with increased numbers of electron optical biprisms and electron lenses allow more flexible ray paths. Due to the combination of double biprism holography and higher magnification at the lower biprism, holograms in the high resolution regime are now recorded with negligible artifacts [1]. Furthermore, smart averaging schemes for hologram series allow to prolong the effective exposure time for a hologram to time scales, where the experimental errors are not dominated by the shot noise anymore [2].

One of the advantages of holography is the posterior correction of residual aberrations. However, the aberrations still have to be sufficiently known. By quantitative comparison of reconstructed wave functions with calculations the imaging parameters can be retrieved with sufficient precision allowing the reconstruction of aberration corrected exit‐wave functions. Thus nowadays holograms with (sub‐)angstrom resolution can be obtained on a regular basis.

In off‐axis holography only the side‐band channel of the information recorded in the hologram is reconstructed. As hologram series are recorded and the reconstructed wave function can be propagated to arbitrary defocus values anyway, also focal series of conventional images (center‐band) can be obtained in the same measurement.

In the figures the reconstructed exit waves of a GaAs wedge, obtained by inline and off‐axis holography are shown [3, 4]. While differences in the low‐frequency reconstruction are expected, also significant differences in thicker specimen parts are found. The latter can be easily recognized on the left side of the linescan profiles, where the amplitudes signals at the columns positions exhibit different behaviours. There are several possible reasons for this discrepancy. The numerical inversion of the imaging process within the inline method becomes worse conditioned since the thicker parts exhibit stronger non‐linear imaging. Thus the reconstruction algorithm might converge in a wrong minimum of the overall error figure. Also, any changes of the object during the acquisition of the series will exhibit different behaviour in the measurement. Furthermore, both channels (side‐band and center‐band) refer to different parts of the density matrix due to the different quantum‐mechanical nature of the underlying interference experiment.