Quantifying geometrically necessary dislocations in quartz using HR-EBSD: Application to chessboard subgrain boundaries

This study presents the first use of high-angular resolution electron backscatter diffraction (HR-EBSD) to quantitatively characterise geometrically necessary dislocations in quartz subgrain structures. HR-EBSD exploits cross-correlation of diffraction patterns to measure intragranular misorientations with precision on the order of 0.01° with well-constrained misorientation axes. We investigate the dislocation structures of chessboard subgrains in quartz within samples from the Greater Himalayan Sequence, Nepal. Our results demonstrate that chessboard subgrains are formed primarily from two sets of subgrain boundaries. One set consists primarily of {m}[c] edge dislocations, the other consists primarily of dislocations with Burgers vectors. Apparent densities of geometrically necessary dislocations vary from > 10^13 m−2 within some subgrain boundaries to < 10^12 m−2 within subgrain interiors. The results suggest that at pressures above approximately 10 kbar, chessboard subgrains may form within the α-quartz stability field. Most importantly, this study demonstrates the potential of HR-EBSD as an improved method for analysis of intragranular microstructures in quartz that are used as indicators of deformation conditions.D. Wallis and L.N. Hansen acknowledge support from the Natural Environment Research Council Grant NE/M000966/1. A.J. Parsons acknowledges support from the Natural Environment Research Council (training grant NE/J50001X/1)

Rotational predissociation of extremely weakly bound atom-molecule complexes produced by Feshbach resonance association

We study the rotational predissociation of atom - molecule complexes with very small binding energy. Such complexes can be produced by Feshbach resonance association of ultracold molecules with ultracold atoms. Numerical calculations of the predissociation lifetimes based on the computation of the energy dependence of the scattering matrix elements become inaccurate when the binding energy is smaller than the energy width of the predissociating state. We derive expressions that represent accurately the predissociation lifetimes in terms of the real and imaginary parts of the scattering length and effective range for molecules in an excited rotational state. Our results show that the predissociation lifetimes are the longest when the binding energy is positive, i.e. when the predissociating state is just above the excited state threshold.Comment: 17 pages, 5 figure

Dislocation interactions in olivine control postseismic creep of the upper mantle.

Changes in stress applied to mantle rocks, such as those imposed by earthquakes, commonly induce a period of transient creep, which is often modelled based on stress transfer among slip systems due to grain interactions. However, recent experiments have demonstrated that the accumulation of stresses among dislocations is the dominant cause of strain hardening in olivine at temperatures ≤600 °C, raising the question of whether the same process contributes to transient creep at higher temperatures. Here, we demonstrate that olivine samples deformed at 25 °C or 1150-1250 °C both preserve stress heterogeneities of ~1 GPa that are imparted by dislocations and have correlation lengths of ~1 μm. The similar stress distributions formed at these different temperatures indicate that accumulation of stresses among dislocations also provides a contribution to transient creep at high temperatures. The results motivate a new generation of models that capture these intragranular processes and may refine predictions of evolving mantle viscosity over the earthquake cycle

Development and evaluation of deep learning algorithms for assessment of acute burns and the need for surgery

Assessment of burn extent and depth are critical and require very specialized diagnosis. Automated image-based algorithms could assist in performing wound detection and classification. We aimed to develop two deep-learning algorithms that respectively identify burns, and classify whether they require surgery. An additional aim assessed the performances in different Fitzpatrick skin types. Annotated burn (n = 1105) and background (n = 536) images were collected. Using a commercially available platform for deep learning algorithms, two models were trained and validated on 70% of the images and tested on the remaining 30%. Accuracy was measured for each image using the percentage of wound area correctly identified and F1 scores for the wound identifier; and area under the receiver operating characteristic (AUC) curve, sensitivity, and specificity for the wound classifier. The wound identifier algorithm detected an average of 87.2% of the wound areas accurately in the test set. For the wound classifier algorithm, the AUC was 0.885. The wound identifier algorithm was more accurate in patients with darker skin types; the wound classifier was more accurate in patients with lighter skin types. To conclude, image-based algorithms can support the assessment of acute burns with relatively good accuracy although larger and different datasets are needed.Peer reviewe

Controls on the rheological properties of peridotite at a palaeosubduction interface: A transect across the base of the Oman-UAE ophiolite

Studies of experimentally deformed rocks and small-scale natural shear zones have demonstrated that volumetrically minor phases can control strain localisation by limiting grain growth and promoting grain-size sensitive deformation mechanisms. These small-scale studies are often used to infer a critical role for minor phases in the development of plate boundaries. However, the role of minor phases in strain localisation at an actual plate boundary remains to be tested by direct observation. In order to test the hypothesis that minor phases control strain localisation at plate boundaries, we conducted microstructural analyses of peridotite samples collected along a ~1 km transect across the base of the Oman-United Arab Emirates (UAE) ophiolite. The base of the ophiolite is marked by the Semail thrust, which represents the now exhumed contact between subducted oceanic crust and the overlying mantle wedge. As such, the base of the ophiolite provides the opportunity to directly examine a former plate boundary. Our results demonstrate that the mean olivine grain size is inversely proportional to the abundance of minor phases (primarily orthopyroxene, as well as clinopyroxene, hornblende, and spinel), consistent with suppression of grain growth by grain-boundary pinning. Our results also reveal that mean olivine grain size is proportional to CPO strength (both of which generally decrease towards the metamorphic sole), suggesting that the fraction of strain produced by different deformation mechanisms varied spatially. Experimentally-derived flow laws indicate that under the inferred deformation conditions, the viscosity of olivine was grain-size sensitive. As such, grain size, and thereby the abundance of minor phases, influenced viscosity during subduction-related deformation along the base of the mantle wedge. We calculate an order of magnitude decrease in the viscosity of olivine towards the base of the ophiolite, which suggests strain was localized near the subduction interface. Our data indicate that this rheological weakening was primarily the result of more abundant minor phases near the base of the ophiolite. Our interpretations are consistent with those of previous studies on experimentally deformed rocks and smaller-scale natural shear zones that indicate minor phases can exert the primary control on strain localisation. However, our study demonstrates for the first time that minor phases can control strain localisation at the scales relevant to a major plate boundar

Determination of the 3-dimensional atomic structure at internal interfaces by electron energy loss spectroscopy

The fine structure of a core-loss edge contains detailed information on the local atomic environment. It can be used as an extremely sensitive probe of the fluctuations in structure and bonding that can occur at internal interfaces. Interpretation of such fluctuations requires only a knowledge of the location of the electron probe when the spectrum is acquired and a means of interpreting the spectrum. The location of the probe can be controlled with atomic precision in the STEM by the use of the Z-contrast image, while the real space cluster methodology of multiple scattering analysis is ideally suited to the task of interpretation. This approach is used here to derive 3-dimensional models for tilt grain boundaries in TiO{sub 2} and SrTiO{sub 3}

Interfaces and defects in opto-electronic semiconductor films studies by atomic resolution stem

The growth of thin films on dissimilar substrates is of great technological importance for modern optoelectronic devices. However, device applications are currently limited by lattice mismatches between the film and substrate that invariably lead to defects detrimental to device performance. It is therefore of key importance that the mechanisms leading to the formation of these defects are understood on the fundamental atomic level. Correlated atomic resolution Z-contrast imaging and EELS in the STEM is a unique methodology by which this information can be obtained. In this paper, the application of this methodology to determine a novel graphoepitaxial growth mechanism for CdTe on (001)Si is demonstrated, and its potential for the study of GaN is discussed

‘Proper’ pro-nun-ſha- ſhun in eighteenth-century English: ECEP as a new tool for the study of historical phonology and dialectology

English historical linguists have often complained about the scholarly neglect of the phonology of the Late Modern English period; yet, the value of pronouncing dictionaries as rich and reliable evidence has been demonstrated (Beal, J. C., 1999, English Pronunciation in the Eighteenth Century: Thomas Spence’s Grand Repository of the English Language (1775). Oxford: Clarendon Press; Jones, C., 2006, English Pronunciation in the Eighteenth and Nineteenth Centuries. Basingstoke: Palgrave Macmillan). This article presents a new electronic, searchable database of ‘Eighteenth-Century English Phonology’ (ECEP) which aims to facilitate research on the social, regional, and lexical distribution of phonological variants in 18th-century English, as documented in contemporary pronouncing dictionaries. Taking Wells’ (1982, Accents of English. Cambridge: Cambridge University Press) lexical sets for the vowel system of present-day varieties of English as its reference, the database provides unicode IPA transcriptions for the relevant segment of each word given as an example of lexical (sub)set in his account of standard lexical sets, to which we have added some complementary consonant sets. These will be of use for comparative studies with 19th-century and present-day English. First, we describe the methodology and contents of ECEP: primary source selection, data input and annotation, the web-based interface. Second, we report on two case studies that demonstrate the value of evidence that can be systematically extracted from ECEP for the analysis of segmental and suprasegmental phonology; these are variations in the pronunciation of ‘wh’ in the set whale (/hw/∼/w/∼/h/), and the palatalization of alveolar consonants before /uː/. Thus, this article will demonstrate the viability of ECEP for historical phonology, dialectology, and sociolinguistics, and will help to promote the use of databases as key resources in historical linguistics

Splicing Modulation Results in Aberrant Isoforms and Protein Products of p53 Pathway Genes and the Sensitization of B Cells to Non-Genotoxic MDM2 Inhibition

Several molecular subtypes of cancer are highly dependent on splicing for cell survival. There is a general interest in the therapeutic targeting of splicing by small molecules. E7107, a first-in-class spliceosome inhibitor, showed strong growth inhibitory activities against a large variety of human cancer xenografts. Chronic lymphocytic leukaemia (CLL) is a clinically heterogeneous hematologic malignancy, with approximately 90% of cases being TP53 wild-type at diagnosis. An increasing number of studies are evaluating alternative targeted agents in CLL, including MDM2–p53 binding antagonists. In this study, we report the effect of splicing modulation on key proteins in the p53 signalling pathway, an important cell death pathway in B cells. Splicing modulation by E7107 treatment reduced full-length MDM2 production due to exon skipping, generating a consequent reciprocal p53 increase in TP53WT cells. It was especially noteworthy that a novel p21WAF1 isoform with compromised cyclin-dependent kinase inhibitory activity was produced due to intron retention. E7107 synergized with the MDM2 inhibitor RG7388, via dual MDM2 inhibition; by E7107 at the transcript level and by RG7388 at the protein level, producing greater p53 stabilisation and apoptosis. This study provides evidence for a synergistic MDM2 and spliceosome inhibitor combination as a novel approach to treat CLL and potentially other haematological malignancies