Analytical electron tomography

AbstractThe research leading to these results has received funding from the European Union Seventh Framework Programme under Grant Agreement 312483-ESTEEM2 (Integrated Infrastructure Initiative–I3), as well as from the European Research Council under the European Union’s Seventh Framework Programme (FP/2007-2013)/ERC grant agreement 291522-3DIMAGE. RKL acknowledges a Junior Research Fellowship at Clare College.This is the author accepted manuscript. The final version is available from Cambridge University Press via http://dx.doi.org/10.1557/mrs.2016.13

Directional sinogram inpainting for limited angle tomography

In this paper we propose a new joint model for the reconstruction of tomography data under limited angle sampling regimes. In many applications of Tomography, e.g. Electron Microscopy and Mammography, physical limitations on acquisition lead to regions of data which cannot be sampled. Depending on the severity of the restriction, reconstructions can contain severe, characteristic, artefacts. Our model aims to address these artefacts by inpainting the missing data simultaneously with the reconstruction. Numerically, this problem naturally evolves to require the minimisation of a non-convex and non-smooth functional so we review recent work in this topic and extend results to fit an alternating (block) descent framework. We illustrate the effectiveness of this approach with numerical experiments on two synthetic datasets and one Electron Microscopy dataset.Cantab Capital Institute for the Mathematics of Information PIHC innovation fund of the Technical Medical Centre of UT Dutch 4TU programme Precision Medicine Netherlands Organization for Scientific Research (NWO), project 639.073.506 Henslow Research Fellowship at Girton College, Cambridge Clare College Junior Research Fellowshi

Blind source separation aided characterization of the γ′ strengthening phase in an advanced nickel-based superalloy by spectroscopic 4D electron microscopy

The γ’ strengthening phase in an advanced nickel-based superalloy, ATI 718Plus, was characterized using a blind source separation applied to a four dimensional X-ray microanalysis dataset obtained by scanning transmission electron microscopy. Selected patterns in the X-ray spectra identified by independent component analysis were found to be spatially and chemically representative of the matrix (γ) and precipitate phases (γ’) present in the superalloy, enabling their size, shape and distribution to be determined. The three dimensional chemical reconstruction of the microstructure may provide insight into the role of the various alloying elements in the evolution of the microstructure at the nano-scale.The research leading to these results has received funding from the European Union Seventh Framework Programme under Grant Agreement 312483 - ESTEEM2 (Integrated Infrastructure Initiative-I3), as well as from the European Research Council under the European Union's Seventh Framework Programme (FP/2007-2013)/ERC grant agreement 291522 - 3DIMAGE. D.R. acknowledges support from the Royal Society’s Newton International Fellowship scheme. RKL acknowledges a Junior Research Fellowship at Clare College. RK acknowledges financial support from Rolls-Royce, EPSRC and the BMWi under EP/H022309/1, EP/H500375/1 and grant number 20T0813. F.d.l.P. and C.D. acknowledge 26 funding from the ERC under grant no. 259619 PHOTO EM. Special thanks to Giorgio Divitini and Lech Staniewicz for preparation of the FIB needle specimen and to Stephen A Croxall for SEM/FIB imaging.This is the final version of the article. It first appeared from Elsevier via http://dx.doi.org/10.1016/j.actamat.2016.01.04

Anomalous diffusion of single metal atoms on a graphene oxide support

Recent studies of single-atom catalysts open up the prospect of designing exceptionally active and environmentally efficient chemical processes. The stability and durability of such catalysts is governed by the strength with which the atoms are bound to their support and their diffusive behaviour. Here we use aberration-corrected STEM to image the diffusion of single copper adatoms on graphene oxide. We discover that individual atoms exhibit ano malous diffusion as a result of spatial and energetic disorder inherent in the support, and interpret the origins of this behaviour to develop a physical picture for the surface diffusion of single metal atoms

Entropic Comparison of Atomic-Resolution Electron Tomography of Crystals and Amorphous Materials

Electron tomography bears promise for widespread determination of the three-dimensional arrangement of atoms in solids. However, it remains unclear whether methods successful for crystals are optimal for amorphous solids. Here, we explore the relative difficulty encountered in atomic-resolution tomography of crystalline and amorphous nanoparticles. We define an informational entropy to reveal the inherent importance of low-entropy zone-axis projections in the reconstruction of crystals. In turn, we propose considerations for optimal sampling for tomography of ordered and disordered materials.M. M. J. T is grateful for the support from the Leverhulme Trust and from the U.S. Department of Energy, Contract No. DE-AC02-06CH11357. R. K. L. acknowledges support from a Clare College Junior Research Fellowship. S. M. C. and P. A. M. acknowledge funding from the European Research Council under the European Union’s Seventh Framework Program (FP7/2007–2013)/ERC Grant Agreement No. 291522-3DIMAGE. C.-B. S. acknowledges support from the Leverhulme Trust project “Breaking the non-convexity barrier,” EPSRC Grant No. EP/M00483X/1, EPSRC Centre Grant No. EP/N014588/1, and CHiPS (the Horizon 2020 RISE project grant). R. T. acknowledges funding from EPSRC Grant No. EP/L016516/1 for the Cambridge Centre for Analysis. R. T. and C.-B. S. also acknowledge the Cantab Capital Institute for the Mathematics of Information. M. B. acknowledges the Isaac Newton Trust and the Leverhulme Trust Early Career Fellowship “Learning from mistakes: A supervised feedback-loop for imaging applications.

The breast cancer somatic 'muta-ome': tackling the complexity

Acquired somatic mutations are responsible for approximately 90% of breast tumours. However, only one somatic aberration, amplification of the HER2 locus, is currently used to define a clinical subtype, one that accounts for approximately 10% to 15% of breast tumours. In recent years, a number of mutational profiling studies have attempted to further identify clinically relevant mutations. While these studies have confirmed the oncogenic or tumour suppressor role of many known suspects, they have exposed complexity as a main feature of the breast cancer mutational landscape (the 'muta-ome'). The two defining features of this complexity are (a) a surprising richness of low-frequency mutants contrasting with the relative rarity of high-frequency events and (b) the relatively large number of somatic genomic aberrations (approximately 20 to 50) driving an average tumour. Structural features of this complex landscape have begun to emerge from follow-up studies that have tackled the complexity by integrating the spectrum of genomic mutations with a variety of complementary biological knowledge databases. Among these structural features are the growing links between somatic gene disruptions and those conferring breast cancer risk, mutually exclusive coexistence and synergistic mutational patterns, and a clearly non-random distribution of mutations implicating specific molecular pathways in breast tumour initiation and progression. Recognising that a shift from a gene-centric to a pathway-centric approach is necessary, we envisage that further progress in identifying clinically relevant genomic aberration patterns and associated breast cancer subtypes will require not only multi-dimensional integrative analyses that combine mutational and functional profiles, but also larger profiling studies that use second- and third-generation sequencing technologies in order to fill out the important gaps in the current mutational landscape

The Servant Leadership Survey: Development and Validation of a Multidimensional Measure

Purpose: The purpose of this paper is to describe the development and validation of a multi-dimensional instrument to measure servant leadership. Design/Methodology/Approach Based on an extensive literature review and expert judgment, 99 items were formulated. In three steps, using eight samples totaling 1571 persons from The Netherlands and the UK with a diverse occupational background, a combined exploratory and confirmatory factor analysis approach was used. This was followed by an analysis of the criterion-related validity. Findings: The final result is an eight-dimensional measure of 30 items: the eight dimensions being: standing back, forgiveness, courage, empowerment, accountability, authenticity, humility, and stewardship. The internal consistency of the subscales is good. The results show that the Servant Leadership Survey (SLS) has convergent validity with other leadership measures, and also adds unique elements to the leadership field. Evidence for criterion-related validity came from studies relating the eight dimensions to well-being and performance. Implications: With this survey, a valid and reliable instrument to measure the essential elements of servant leadership has been introduced. Originality/Value The SLS is the first measure where the underlying factor structure was developed and confirmed across several field studies in two countries. It can be used in future studies to test the underlying premises of servant leadership theory. The SLS provides a clear picture of the key servant leadership qualities and shows where improvements can be made on the individual and organizational level; as such, it may also offer a valuable starting point for training and leadership development

Stabilization of Single Metal Atoms on Graphitic Carbon Nitride

Graphitic carbon nitride (g-C$_{3}$N$_{4}$) exhibits unique properties as a support for single-atom heterogeneous catalysts (SAHCs). Understanding how the synthesis method, carrier properties, and metal identity impact the isolation of metal centers is essential to guide their design. This study compares the effectiveness of direct and postsynthetic routes to prepare SAHCs by incorporating palladium, silver, iridium, platinum, or gold in g-C$_{3}$N$_{4}$ of distinct morphology (bulk, mesoporous and exfoliated). The speciation (single atoms, dimers, clusters, or nanoparticles), distribution, and oxidation state of the supported metals are characterized by multiple techniques including extensive use of aberration-corrected electron microscopy. SAHCs are most readily attained via direct approaches applying copolymerizable metal precursors and employing high surface area carriers. In contrast, although post-synthetic routes enable improved control over the metal loading, nanoparticle formation is more prevalent. Comparison of the carrier morphologies also points toward the involvement of defects in stabilizing single atoms. The distinct metal dispersions are rationalized by density functional theory and kinetic Monte Carlo simulations, highlighting the interplay between the adsorption energetics and diffusion kinetics. Evaluation in the continuous three-phase semihydrogenation of 1-hexyne identifies controlling the metal-carrier interaction and exposing the metal sites at the surface layer as key challenges in designing efficient SAHCs.The authors are grateful to the following people for support: Dr. G. Vilé for fruitful discussion, Dr. R. Verel for NMR measurements, Dr. C. Zaubitzer for TEM training, and Dr. J. Barnard for assistance with microscopy studies. ScopeM at ETH Zurich for use of their facilities. This research has received funding from the Swiss National Science Foundation (grant number 200021_169679) and the European Union’s Seventh Framework Programme (grant numbers 291522 - 3DIMAGE and 31 2483 - ESTEEM2). R.K.L. acknowledges a Junior Research Fellowship from Clare College. The SuperSTEM Laboratory is the UK National Facility for Aberration - Corrected STEM, supported by the Engineering and Physical Sciences Research Council (EPSRC). Thanks to BSC - RES for providing generous computational resources

Microfluidization of Graphite and Formulation of Graphene-Based Conductive Inks

We report the exfoliation of graphite in aqueous solutions under high shear rate [∼ 10$^{8}$ s$^{-1}$] turbulent flow conditions, with a 100% exfoliation yield. The material is stabilized without centrifugation at concentrations up to 100 g/L using carboxymethylcellulose sodium salt to formulate conductive printable inks. The sheet resistance of blade coated films is below ∼2Ω/□. This is a simple and scalable production route for conductive inks for large-area printing in flexible electronics.We acknowledge funding from EU Graphene Flagship, ERCs grants Hetero2D, HiGRAPHINK, 3DIMAGEEPSRC, ESTEEM2, BIHSNAM, KNOTOUGH, and SILKENE, EPSRC grants EP/K01711X/1, EP/K017144/1, and EP/N010345/1, a Vice Chancellor award from the University of Cambridge, a Junior Research Fellowship from Clare College and the Cambridge NanoCDT and Graphene Technology CDT. We thank Chris Jones for useful discussions, and Imerys Graphite and Carbon for graphite powders

Whole-genome cancer analysis as an approach to deeper understanding of tumour biology

Recent advances in DNA sequencing technology are providing unprecedented opportunities for comprehensive analysis of cancer genomes, exomes, transcriptomes, as well as epigenomic components. The integration of these data sets with well-annotated phenotypic and clinical data will expedite improved interventions based on the individual genomics of the patient and the specific disease