Type III and IV deformation twins in minerals and metals

Type IV twins are defined and shown to exist in triclinic crystal systems, as well as in some monoclinic and trigonal systems. Here, we focus on Pericline twins in triclinic plagioclase as an example. Type IV twins are associated with the irrationality of one of the twinning elements that is rational for a type II twin. The formation of type IV twins is accomplished through the shear on a K2 plane produced by the motion of twinning disconnections on a K1 plane, followed by rotational partitioning. The same systems where type IV twins are present also have type III twins instead of type I. Without using the correct type IV analysis, one would deduce the wrong magnitude and direction of shear associated with the twinning process, the magnitude of which would increase with greater triclinicity. Types I and II twins form if and only if there are rational lattice translation vectors lying in the plane of distortion/shear. Otherwise, the twins are types III and IV. Historically, two types of twins (I and II) have been categorized for twinning in minerals and metals. When analyzed by the topological model, a crystallographic construction used to define the defect structure of interfaces, triclinic and some other lowsymmetry crystals do not fall into either category and instead form two new twinning types, namely, III and IV. Aside from accurately describing twin structures, these concepts are important for understanding the deformation of minerals such as plagioclase and for deriving constitutive models for the deformation

Factor Substitution and Unobserved Factor Quality in Nursing Homes

This paper studies factor substitution in one important sector: the nursing home industry. Specifically, we measure the extent to which nursing homes substitute materials for labor when labor becomes relatively more expensive. From a policy perspective, factor substitution in this market is important because materials-intensive methods of care are associated with greater risks of morbidity and mortality among nursing home residents. Studying longitudinal data from 1991-1998 on nearly every nursing home in the United States, we use the method of instrumental variables (IV) to address the potential endogeneity of nursing home wages. The results from the IV models are consistent with the theory of factor substitution: higher nursing home wages are associated with lower staffing, greater use of materials (specifically, physical restraints), and a higher proportion of residents with pressure ulcers. A comparison of OLS and IV results suggests that empirical studies of factor substitution should take into account unobserved heterogeneity in factor quality.

Winter Quarter Commencement Address

Commencement address given by John Price Hirth, Professor in the Department of Metallurgical Engineering, to the Winter 1987 graduating class of The Ohio State University, St. John Arena, Columbus, Ohio, March 20, 1987

Atomic displacements accompanying deformation twinning: shears and shuffles

Deformation twins grow by the motion of disconnections along their interfaces, thereby coupling shear with migration. Atomic-scale simulations of this mechanism have advanced to the point where the trajectory of each atom can be followed as it transits from a site in the shrinking grain, through the interface, and onwards to a site in the growing twin. Historically, such trajectories have been factorised into shear and shuffle components according to some defined convention. In the present article, we introduce a method of factorisation consistent with disconnection motion. This procedure is illustrated for the case of {10-12} twinning in hcp materials, and shown to agree with simulated atomic trajectories for Zr.Peer ReviewedPostprint (published version

Mice Transgenic for the Human Carcinoembryonic Antigen Gene Maintain Its Spatiotemporal Expression Pattern

The tumor marker carcinoembryonic antigen (CEA) is predominantly expressed in epithelial cells along the gastrointestinal tract and in a variety of adenocarcinomas. As a basis for investigating its in vivo regulation and for establishing an animal model for tumor immunotherapy, transgenic mice were generated with a 33-kilobase cosmid clone insert containing the complete human CEA gene and flanking sequences. CEA was found in the tongue, esophagus, stomach, small intestine, cecum, colon, and trachea and at low levels in the lung, testis, and uterus of adult mice of independent transgenic strains. CEA was first detected at day 10.5 of embryonic development (embryonic day 10.5) in primary trophoblast giant cells and was found in the developing gut, urethra, trachea, lung, and nucleus pulposus of the vertebral column from embryonic day 14.5 onwards. From embryonic day 16.5 CEA was also visible in the nasal mucosa and tongue. Because this spatiotemporal expression pattern correlates well with that known for humans, it follows that the transferred genomic region contains all of the regulatory elements required for the correct expression of CEA. Furthermore, although mice apparently lack an endogenous CEA gene, the entire repertoire of transcription factors necessary for correct expression of the CEA transgene is conserved between mice and humans. After tumor induction, these immunocompetent mice will serve as a model for optimizing various forms of immunotherapy, using CEA as a target antigen

Implementation of the Integrated Approach in Different Types of Exposure Scenarios

The ICRP recognises three types of exposure situations (planned, existing and emergency). In all three situations, the release of radionuclides into the natural environment leads to exposures of non-human biota, as well as the potential for exposures of the public. This paper describes how the key principles of the ICRP system of radiological protection apply to non-human biota and members of the public in each of these exposure situations. Current work in this area within ICRP Task Group (TG) 105 is highlighted. For example, how simplified numeric criteria may be used in planned exposure situations that are protective of both the public and non-human biota. In emergency exposure situations, the initial response will always be focused on human protection however, understanding the potential impacts of radionuclide releases on non-human biota will likely become important in terms of communication as governments and the public seek to understand the exposures that are occurring. For existing exposure situations, we need to better understand the potential impacts of radionuclides on animals and plants especially when deciding on protective actions. Understanding the comparative impacts from radiological, non-radiological and physical aspects is often important in managing remediating legacy sites. The TG is making use of case studies of how exposure situations have been managed in the past to provide additional guidance and advice for the protection of non-human biota

Azimuthal seismic anisotropy of 70-ma Pacific-plate upper mantle.

Author Posting. © American Geophysical Union, 2019. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research-Solid Earth 124(2), (2019):1889-1909, doi:10.1029/2018JB016451.Plate formation and evolution processes are predicted to generate upper mantle seismic anisotropy and negative vertical velocity gradients in oceanic lithosphere. However, predictions for upper mantle seismic velocity structure do not fully agree with the results of seismic experiments. The strength of anisotropy observed in the upper mantle varies widely. Further, many refraction studies observe a fast direction of anisotropy rotated several degrees with respect to the paleospreading direction, suggesting that upper mantle anisotropy records processes other than 2‐D corner flow and plate‐driven shear near mid‐ocean ridges. We measure 6.0 ± 0.3% anisotropy at the Moho in 70‐Ma lithosphere in the central Pacific with a fast direction parallel to paleospreading, consistent with mineral alignment by 2‐D mantle flow near a mid‐ocean ridge. We also find an increase in the strength of anisotropy with depth, with vertical velocity gradients estimated at 0.02 km/s/km in the fast direction and 0 km/s/km in the slow direction. The increase in anisotropy with depth can be explained by mechanisms for producing anisotropy other than intrinsic effects from mineral fabric, such as aligned cracks or other structures. This measurement of seismic anisotropy and gradients reflects the effects of both plate formation and evolution processes on seismic velocity structure in mature oceanic lithosphere, and can serve as a reference for future studies to investigate the processes involved in lithospheric formation and evolution.We thank the Captain and crew of the R/V Marcus G. Langseth and the engineers and technicians from the Scripps Institution of Oceanography and the Woods Hole Oceanographic Institution, who provided the instruments through the National Science Foundation's Ocean Bottom Seismograph Instrument Pool (OBSIP). The professionalism and expertise of these individuals were key to the success of this experiment. We also thank Donna Blackman, Tom Brocher, Philip Skemer, and an anonymous reviewer for their thoughtful comments which greatly improved this paper. The OBS data described here are archived at the IRIS Data Management Center (http://www.iris.edu) under network code ZA 2011–2013. The travel time picks are archived in the Marine‐Geo Digital Library (http://www.marine‐geo.org/library/) with the DOI 10.1594/IEDA/324643. This work was supported by NSF grant OCE‐0928663 to D. Lizarralde, J. Collins, and R. Evans; NSF grant OCE‐0927172 to G. Hirth; NSF grant OCE‐0928270 to J. Gaherty; and an NSF Graduate Research Fellowship to H. Mark.2019-07-2

Nucleation and growth of platelets in hydrogen-ion-implanted silicon

H ion implantation into crystalline Si is known to result in the precipitation of planar defects in the form of platelets. Hydrogen-platelet formation is critical to the process that allows controlled cleavage of Si along the plane of the platelets and subsequent transfer and integration of thinly sliced Si with other substrates. Here we show that H-platelet formation is controlled by the depth of the radiation-induced damage and then develop a model that considers the influence of stress to correctly predict platelet orientation and the depth at which platelet nucleation density is a maximum.This work was supported by the U.S. Department of Energy, Office of Basic Energy Sciences

Microstructural and geochemical constraints on the evolution of deep arc lithosphere

Mantle xenoliths from the Sierra Nevada, California, USA, sampled a vertical column (60–120 km) of lithosphere that formed during Mesozoic continental arc magmatism. This lithosphere experienced an anticlockwise P-T-t path resulting in rapid cooling that effectively “quenched in” features inherited from earlier high-temperature conditions. Here we combine new mineral chemistry data (water, trace element, and major element concentrations) with mineral crystallographic preferred orientations (CPOs) to investigate the relationship between melt infiltration and deformation. The peridotites record a refertilization trend with increasing depth, starting from shallow, coarse-protogranular, less-melt-infiltrated spinel peridotite with strong, orthorhombic olivine CPO to deep, fine-porphyroclastic, highly melt-infiltrated garnet peridotite with weak, axial-[010] olivine CPO. In contrast to the observed axial-[010] CPOs, subgrain boundary orientations and misorientation axes suggest the dominant activation of the (001)[100] slip system, suggesting deformation under moderately hydrous conditions. After accounting for effects of subsolidus cooling, we see coherent trends between mineral trace element abundance and water content, indicating that melt infiltration led to an increase in water content of the peridotites. However, measured olivine and pyroxene water contents in all peridotites (5–10 and 30–500 wt ppm, respectively) are lower than that required to promote dominant (001)[100] slip system observed in both natural and experimental samples. These results suggest that deformation occurred earlier along the P-T path, probably during or shortly after hydrous melt infiltration. Subsequent rapid cooling at 90 Ma led to water loss from olivine (owing to decreased solubility at low temperature), leaving behind a deep arc lithosphere that remained viscously coupled to the Farallon slab until the opening of the slab window in the late Cenozoic