bluuebunny/crossref_metadata_2025_split huggingface dataset:
On the diffusion‐mediated cyclic coarsening and reversal coarsening in an advanced
Ni
‐based superalloy
Authors: Chen Yiqiang , Prasath Babu Rajan , Slater Thomas , Mitchell Robert , Ciuca Octav , Preuss Michael 
Published: December 2016

Polycrystalline nickel‐based superalloys for turbine disc applications typically employ complex alloy chemistry in order to produce a high volume fraction of gamma‐prime (γ′) precipitates for the optimisation of mechanical properties [1]. The precipitate coarsening causes a gradual loss of coherency between γ′ precipitates and γ matrix when materials serving elevated temperatures, therefore resulting in the degradation of its mechanical performance [2]. In this work, we report new experimental observations for diffusion‐mediated secondary γ′ precipitate coarsening (See Fig. 1) within a near‐zero misfit alloy RR1000 in a cyclic manner that these precipitates coarsen and split periodically [3].
Using absorption‐corrected energy‐dispersive X‐ray (EDX) spectroscopy within the scanning transmission electron microscope (STEM) [4], compositional variations for secondary γ′ precipitates as a function of coarsening behaviour under have been investigated. We have observed clear cyclic variations in the elemental concentrations of Co, Ti and Al within the secondary γ′ as a function of ageing time. STEM/EDX spectrum imaging and electron tomography on individual secondary γ′ have revealed local enrichment of Co within the core of secondary γ′ (See Fig. 2). STEM‐EDX analysis of the γ‐γ′ interface revealed nanoscale enrichment of Co and Cr and a depletion of Al and Ti within the γ matrix region near the γ‐γ′ interface (See Fig. 3). Our experimental results, coupled with complementary modelling and synchrotron X‐ray diffraction analysis, demonstrate the importance of elastic strain energy resulting from local compositional variations for influencing precipitate morphology. In particular, we show that elemental inhomogeneities, produced within both matrix and precipitates, are induced by complex interactions between thermodynamics and diffusion kinetics. These elemental inhomogeneities will likely affect the kinetics of coarsening and therefore must be taken into account when predicting the microstructure likely to be produced when the material is exposed to different heat treatment regimes. More generally, our findings suggest the importance of considering diffusion kinetics when attempting to understand the microstructural evolution of advanced superalloys. Our discovery renders the potential to retain the overall γ‐γ′ coherence in nickel‐based superalloys when exposed to elevated temperatures, and therefore to improve its creep properties.
A potential therapeutic effects of
BMN673
, a novel
PARP
inhibitor, on Triple Negative Breast Cancer
Authors: Eskiler Gamze Guney , Cecener Gulsah , Egeli Unal , Tunca Berrin 
Published: December 2016

Triple negative breast cancer (TNBC) is the most aggressive and lethal subtype of breast cancer due to a higher rate of early recurrence, distant metastases and also heterogeneity in the molecular levels. Thus, there is a urgent need for effective therapies. In the recent years, PARP inhibitors have drawn considerable attention for especially BRCA‐associated sporadic TNBC patients. In the present study, we aimed to determine the cytotoxic and apoptotic effects of BMN 673, which is a novel and highly potent PARP inhibitor, on TNBC cell line.
Triple‐negative BRCA1‐defective HCC1937 breast cancer cell line was treated with BMN673 and the cytoxoxicity effects was evaluated by WST‐1 analysis. The apoptotic effects was evaluated using Annexin V‐propidium iodide (PI) and cell cycle analysis. The double stained with acridine orange/ethidium bromide of these cells was observed under the fluorescence microscope.

Initial cytotoxicity screening showed that BMN673 displayed the anti‐proliferative effect, with in time (6–12 days) and dose‐dependent (0.01, 0.1, 1 and 10 nM) (p<0.05). The maximum inhibition rate was measured 19.54%, 24.21%, 49.91% and 58.0% at 0.01, 0.1, 1 and 10 nM of BMN673 at 12 days, respectively (p<0.05). There was an increase of apoptotic cell death and cell cycle progression in all concentrations compared to the untreated control. Treatment with doses of 0.01, 0.1, 1 and 10 nM BMN673 significantly induced total apoptotic cells (6.2%, 23.45%, 47.95% and 61.28%, respectively) and a significant block at the G
2
/M phase. Additionally, we observed a loss of membrane integrity, chromatin condensation and increasing vacuole formation in HCC1937 cells when treated with the maximum concentration of BMN673.

In conlusion, this study has revealed that BMN673 inhibits cell proliferation and induces cell cycle progression and apoptosis within the minimum concentration. Thus, BMN673 could represent a potentially therapeutic strategy for especially, BRCA‐defective TNBC.
InAs/InSb
: From Nanowires to Nanomembranes
Authors: de la Mata María , Leturcq Renaud , Plissard Sébastien R. , Rolland Chloé , Magén César , Caroff Philippe , Arbiol Jordi 
Published: December 2016

The control over crystalline defects is of extreme importance when growing functional materials, since their presence may alter the final behavior (opto‐electronic properties) and evolution of the growing system (orientation and shape). In the present work we address both phenomena in the particular case of InSb related nanostructures.
On one hand, heterostructured architectures may show interfacial dislocations if reaching the coherency limit, which is dependent on geometrical constrictions of the systems in addition to the mismatch between phases. In this context, it is usually assumed that the mismatch strain in axial heterostructured nanowires is mainly relaxed by elastic distortion of the lattice, although theoretical calculations predict the formation of misfit dislocations[1]. It is remarkably important unveiling whether the partial/total lattice relaxation takes place through elastic and/or plastic mechanisms since both will affect the material performance. Interestingly, the location and shape of the heterointerfaces, as well as possible diffusion phenomena involved, may hinder the understanding of the actual relaxation mechanism, as we show in the case of axial InAs/InSb nanowires[2]. Contrary to most reported works, we find out the presence of misfit dislocations at the core of the system while there is a huge plane bending through the edges of the nanowires.
On the other hand, we correlate the systematic observation of a lateral twin boundary with the morphological transition from nanowires to membrane‐like systems, called nanosails. Based on the experimental data gathered, consisting on SEM and aberration‐corrected STEM measurements, including polarity determination[3], we are able to establish the underlying defect‐driving growth mechanism leading to the formation of membrane‐like structures growing aside InAs/InSb nanowires[4], showing excellent transport properties. Possible instabilities during the growth may promote the sinking of the catalytic droplet to wet one sidewall, leading to the nucleation of the lateral twin that opens the way for the broadening of the system.
The concept of quantum electron microscopy
Authors: Kruit Pieter , Berggren Karl , Hommelhoff Peter , Kasevich Mark 
Published: December 2016

Following a recent suggestion [1] that interaction‐free measurements are possible with electrons, we have analyzed the possibilities to use this concept for imaging of biological specimen with reduced damage. We have also made preliminary designs for an atomic resolution interaction‐free electron microscope, or “quantum electron microscope” [2], for one example see figure 1.
The idea of interaction‐free measurements follows Elitzur and Vaidman [3], who proposed that an opaque object may be observed by detecting a photon that did not interact with that object. This concept uses a Mach‐Zehnder interferometer in which one branch of the particle wave passes through the specimen (“specimen beam”) while the other part follows another path (“reference beam”). For a substantial reduction of the interaction, the amplitude of the wave passing through the specimen must be small and the interaction must be repeated many times. To implement this concept in an electron microscope would require a number of unique components not found in conventional transmission electron microscopes. These components include a coherent electron beam‐splitter or two‐state‐coupler, and a resonator structure to allow each electron to interrogate the specimen multiple times. A two‐state‐coupler has the function of moving the electron wave slowly between the reference beam and the specimen beam, as in a Rabi‐oscillation. We have come up with four different choices for this: a thin crystal, a grating mirror, a standing light wave and an electro‐dynamical pseudopotential.
Figures 2 shows a typical example of the theoretical output of a measurement, where for each pixel there is signal in the reference beam, the specimen beam and the inelastic channel, possibly detected in an energy loss measurement. Figure 3 shows the advantage of interaction free measurement in the detection of the presence of a dark pixel as compared to dark field microscopy. In the analysis of the image contrast that interaction‐free microscopy can create, our tentative conclusion is that transparent specimen can be detected, but different transparencies cannot be distinguished [4]. Other modes of operation of a microscope with multiple interactions with the specimen, however, may enable this.
In situ study of
Au‐Rh
nanoalloys
Authors: De Clercq Astrid , Piccolo Laurent , Giorgio Suzanne 
Published: December 2016

Introduction:

Au‐Rh nanoalloys were prepared from colloidal solution [1]. The growth mechanism was studied
in situ
by TEM in a graphene liquid cell [2‐3]. Then, in an environmental sample holder [4],the influence of oxygen or hydrogen adsorption on the structure of AuRh/TiO
2
catalysts was observed at a pressure of a few mbar and at room temperature.

Growth mechanism:

The colloidal solution was encapsulated in a graphene oxide liquid cell and directly observed in a standard electron microscope. The particle growth was initiated under the electron beam.
The same area was observed during about 80 s and images were recorded every 5 s. The average particle size increases until 4 nm. The density number plotted in fig. 1, indicates a maximal density after 25 s, then a drop after 50 s, corresponding to a growth mechanism by direct adsorption of the monomers. This process is followed by coalescence of the particles, as directly seen in fig. 2.

Segregation in hydrogen:

Au‐Rh nanoparticles with an homogeneous structure, and supported on rutile TiO
2
nanorods powders, were observed during oxidation‐ reduction cycles in an environmental sample holder. In the largest NPs, core‐ shell formation was clearly observed during hydrogen adsorption, as seen in figure 3. On the other hand, the observation of Au‐Rh NPs annealed
ex situ
in H
2
at 400 °C, also shows the core‐ shell contrast which was not visible before H
2
treatment.

The strong interaction between hydrogen and Rh is certainly responsible for the surface segregation of Rh.
Precision and application of atom location in
HAADF
and
ABF
Authors: Wang Yi , Zhou Dan , Sigle Wilfried , Suyolcu Y. Eren , Müller‐Caspary Knut , Krause Florian F , Rosenauer Andreas , van Aken Peter 
Published: December 2016

Precision and application of atom location in HAADF and ABF

Yi Wang
1
, Dan Zhou
1*
, Wilfried Sigle
1
, Y. E. Suyolcu
1
, Knut Müller‐Caspary
2
, Florian F. Krause
2
, Andreas Rosenauer
2
, Peter A. van Aken
1

1
Stuttgart Center for Electron Microscopy, Max Planck Institute for Solid State Research, Heisenbergstraße 1, 70569, Stuttgart, Germany

*
Current: Materials Science and Engineering, University of Wisconsin‐Madison, 1509 University Avenue, Madison, WI 53706, USA

2
Institut für Festkörperphysik, Universität Bremen, Otto‐Hahn‐Allee 1, 28359 Bremen, Germany

The multifaceted magnetic, electrical, and structural functionalities of perovskite oxides are underpinned by the distortions of the crystal lattice [1]. These distortions include the displacement of cations, deformation of oxygen octahedra (BO
6
, where B is a transition metal atom), and collective tilts of the octahedral network. Controlling and engineering these distortions in the constituent oxides are crucial in designing and fabricating heterostructures with novel functional properties that are absent in the bulk form. Atomistic understanding of these distortions and elucidation of their influence on the final properties requires imaging and measuring of atomic positions of both cations and oxygen. With the application of spherical aberration (
C
s
) correctors, sub‐Angstrom atomic resolution is nowadays regularly achievable in both TEM and STEM. The recent application of the annular bright‐field (ABF) imaging technique in perovskite oxides has become increasingly popular, as it enables simultaneous imaging of heavy and light elements and allows for simultaneous acquisition of other signals [2, 3].

Here, we report the development of a software tool, written in Digital Micrograph scripting language [4], to extract quantitative information of the crystal lattice and of oxygen octahedron distortions of perovskite oxides from high‐angle annular dark‐field (HAADF) and ABF STEM images. Center‐of‐mass and two‐dimensional (2D) Gaussian fitting methods are implemented to locate positions of individual atom columns. As shown in Fig.1, under daily reproducible working conditions, e.g. sample drift and contamination present, the precision is in the range of 3–4 pm. Applications of this tool will be presented.
The accuracy of atom location by ABF can be significantly influenced by atom‐column tilts introduced by inadequate alignment by the operator or by strain near crystal defects. The influence of such tilts was quantitatively analyzed using image simulations. Figure 2 shows exemplarily simulated HAADF and ABF images for 0 and 10 mrad tilt [5].
Covalent functionalization of Single‐Wall Carbon Nanotube by ferrocene derivatives : localisation and identification of a single molecule
Authors: Devaux Xavier , Allali Naoual , Mamane Victor , Dossot Manuel 
Published: December 2016

Depending on the rolling vector, single‐wall carbon nanotubes (SWCNTs) can present metallic or semi‐conducting properties, which is of strong interest for potential applications in electronic devices and sensors. Consequently, SWCNTs have been recognized as interesting candidates for developing electrochemical biosensors for several years. They are described as promoters of electron transfer between electrode and target molecules, increasing reaction rate and decreasing electrode response time [1,2]. To realise efficient bio‐electrochemical sensor of D‐glucose, ferrocene derivatives were covalently grafted on purified SWCNTs. Ferrocene active electrochemical center was separated from carbon nanotube by polyethylene glycol linkers of different chain length (3 to 5 etoxy links).
The functionalized SWCNTs were studied using an aberration‐corrected STEM working at accelerating voltage of 80 kV (Jeol ARM200) to assess the efficiency of the functionalization and explore the selectivity of the grafting.
High‐resolution HAADF and BF images were simultaneously recorded to determine the structure of the SWCNTs. By analysing the Fourier‐transform of the images the chiral indices of a SWCNT can be determined using the same method than for ED pattern [3]. The comparison of information obtained from HAADF and BF images at different focus and simulations using QSTEM [4] shows that the chiral indices of a SWCNT can be assigned by measuring the tube diameter on HAADF and the chiral angle from BF images, for a focus range of a few nm. The simultaneous use of both detectors may allow for a lowering the dose of electrons for the recording of relevant data and so limit the irradiation damages, especially for small‐diameter SWCNTs.

On HAADF, the strong signature of atoms heavier than carbon, at the end of a tiny over‐contrast of about 1.4 nm long can be seen on some SWCNTs, as it is shown in the figure, in the red square. The structure of this SWCNT of 1.1 nm in diameter was determined as a chiral tube with (11,6) indices. QSTEM simulation of a single ferrocene‐polyethylene‐glycol molecule grafted on (11,6) CNT shows contrasts that match well with that of the experimental image. EELS spectrum images were realised to track oxygen K and iron L2‐3 signals. As it can be seen in the figure, two iron atoms were detected in the area of analysis. Their localisation corresponds to that of the two strong contrasts in the HAADF image. In the EELS spectra the energy of the Fe L
2‐3
edges (close to 708 eV and 721 eV) is consistent to that usually recorded with XPS for Fe (II) in ferrocene groups [5]. Oxygen signal was also detected along the chain that links the iron atom to the SWCNT. The analysis of about thirty SWCNTs shows that the functionalization method affects both semiconducting and metallic tubes.
Analysis of semipolarInxGa1‐xN/GaNheterostructures byWBDFandHRTEMimaging
Authors: Chen Xiaodan , Qi Haoyuan , Li Yueliang , Meisch Tobias , Scholz Ferdinand , Kaiser Ute 
Published: December 2016

GaN‐based optoelectronic structures have been successfully applied in the fabrication of blue light emitting diodes (LEDs) and laser diodes [1]. The fabrication of high‐efficient green LEDs remains challenging which is referred to as the “green gap”. In GaN‐based green LEDs, the active region consists of InxGa1‐xN quantum wells (QWs) and GaN barrier layers (BLs) where the emitting wavelength is controlled by theIncontent (x). However,Inincorporation often results in inferior crystal quality due to the miscibility gap and lattice mismatch when theIncontent is increased [2]. Although conventionalc‐plane InxGa1‐xN /GaN QWs have demonstrated the highest crystal quality, the quantum efficiency remains low as a result of the polarization field along thec‐axis which tilts the conduction and valence bands thus reducing the recombination probability (i.e., quantum confined Stark effect, QCSE). Semipolar InxGa1‐xN/GaN structures, on the other hand, offer a good compromise between reduced QCSE and acceptable crystal quality [3].In this study, we investigated the crystal quality of two sets of InxGa1‐xN/GaN structures grown on (11‐22) and (10‐11)‐semipolar planes. The samples were grown on sapphire by using metalorganic vapor phase epitaxy (MOVPE). The weak‐beam dark‐field technique (WBDF) was applied to investigate the distribution of the threading dislocations (TDs). Figure 1 shows the WBDF images of a (11‐22)‐semipolar sample. The GaN growth starts on thec‐plane‐like facets by MOVPE, forming triangular shaped stripes. The stripes subsequently coalesce forming a closed {11‐22}‐semipolar surface. TDs originate from the inclined c‐plane‐like GaN/sapphire interface and propagate inc‐direction and then bend 90° to thea‐directions. Most of the dislocations accumulate around the coalescence area and penetrate the QWs. The bending phenomenon is related to the triangular shape of the original GaN stripes and the SiNxinterlayers deposited during the growth of GaN.By using high‐resolution TEM, we characterized the local structures of the QWs. Figure 2 shows the experimental HRTEM images of a (10‐11)‐semipolar sample acquired from the active region. Structural factors, such as the thickness of the QWs, the interfacial sharpness between the QWs and the BLs and the stacking faults formed with in the active region, can be analyzed with atomic resolution. Stacking faults are observed and confirmed to be the I2intrinsic type. [4]
FIB
characterisation of cell/device interface
Authors: Panaitov Gregory , Neumann Elmar , Offenhäusser Andreas 
Published: December 2016

Cryo‐preparation of biological samples for electron microscopy has many advantages against the chemical fixation. Cryo‐fixation is extremely rapid which can inhibit, within milliseconds, the intracellular movements of macromolecules and other substances. Due to its rapidity, it may even allow the detection of the processes of contacting between the vesicles and the membrane in the cells. One can try to capture the processes at synapse contact, which would be impossible with much slower chemical fixation.
The problems may arrive if the biological sample is contacting to the solids for example at the interface of biological sensor. Due to different thermal expansion coefficient of the solid and biological materials, it may lead to unwonted artefacts at the interface area.
We will present the information about the interface between our structurally modified biosensors and biological cells of different preparation techniques. We have used cryo‐fixation, standard chemical fixation with critical point drying and epoxy embedding. For characterisation of the interface, we apply SEM and FIB (FEI Helios NanoLab DualBeam) sectioning at cryo‐ and room temperatures.
Optical quantitative phase imaging by focal series reconstruction with partially coherent illumination
Authors: Mueller Johannes , Blessing Katharina , Koch Christoph 
Published: December 2016

Optical phase imaging has many applications, it allows to image transparent objects like cells without staining, which is a huge benefit in biology, and also allows to measure the phase from reflecting objects to determine their topography. Furthermore, there are many applications in life science, material science, healthcare and industry for optical phase imaging.
There exist different methods to image phases, phase contrast microscopy converts the phase information into amplitude contrast, but is difficult to interpret quantitatively, quantitative phase microscopy (QPM) on the other hand tries to determine the phase information quantitatively. Several full‐field QPM methods exist, they can be divided in off‐axis approaches and inline approaches. Off‐axis approaches need a special microscope due to the reference beam and suffer from the high coherence of the illumination resulting in phase noise. Inline approaches could be divided in phase‐shifting methods, common‐path methods, digital inline holography, ptychography, Shack–Hartmann wave front sensors and focal series reconstruction, e.g. from the transport of intensity equation (TIE). Some of these approaches need special equipment, like laser illumination, gratings or spatial light modulators, which makes them expensive or introduces artefacts from the experimental setup or from the reconstruction algorithm.
Focal series reconstruction has the advantage, that it only needs a standard optical microscope plus a computer and no additional equipment, this makes quantitative phase imaging from focal series reconstruction both an easy and a low‐cost method.
Figs. 1 & 2 present results obtained by our current approach to optical quantitative phase imaging, where we use focal series reconstruction with partially coherent illumination (a green LED source). The images were aquired using a Zeiss Axiovert 200M microscope and a pco edge sCMOS camera by varying the object height (z = 0µm is the focal plane). We apply our flux‐preserving iterative reconstruction algorithm [1] and combine it with a TIE‐like approach [2]. It aligns the images during reconstruction and applies gradient‐flipping regularization [3]. This full‐resolution inline holography (FRIH) algorithm [2] was originally developed for electron microscopy, but here we apply it to optical microscopy. We will discuss the validity of the reconstruction, especially with respect to artefacts and present the algorithm and the results in more detail.