Complementary Surface Characterization of Chalcopyrite by Electron Microscopy, Electron Spectroscopy, and Optical Reflectance

Surface oxidation of polished natural specimens of chalcopyrite (CuFeS2) at temperature between 23°C and 300°C in air has been characterized by Auger electron and X-ray photoelectron spectroscopies. The reaction products consisted of an outer iron oxide layer and an intermediate copper rich sulfide layer. Several different oxides and sulfides were consistent with the electron spectroscopy data, so specimens were analyzed as a function of time and temperature at selected 20 μm diameter areas with an optical microreflectometer (OMR). Since the optical properties of a compound are unique, a reflectance model with three homogeneous layers was used to calculate reflectance curves by varying the compound in and thickness of each layer. The reaction products were modelled as Cu5FeS4 in contact with the CuFeS2 and Cu2S as an intermediate layer between Cu5FeS4 and the outer oxide. The outer oxide was most consistent with Fe3O4. Relative layer thicknesses were calculated from a series of balanced chemical equations, and Cu5FeS4 was much thicker than Cu2S with total thickness increasing with increasing temperature. The total film layer thicknesses calculated at 23°C were between 10nm and 35nm. At 200°C the film thickness varied from 8nm to 51nm with greater thicknesses associated with longer reaction times. Thicknesses at 300°C ranged from 12nm to 85nm

Optical Microreflectometry and Microscopy of Chalcopyrite Specimens: Reflectance Calculation and Comparison to Backscattered Electron Microscopy

A model was developed to calculate the optical reflectance of an absorbing substrate covered by multiple thin layers of absorbing materials. Both multiple homogeneous thin layers and thin surface layers of mixed phases were modeled. Reflectance versus wavelength was measured for polished chalcopyrite (CuFeS2) and compared to calculated data. The identity and thickness of surface compounds used to calculate reflectance curves were partially determined using X-ray photoelectron and Auger electron spectroscopies. Very good agreement between theoretical and experimental reflectance curves were observed as a function of surface composition. The hue (color) and luminosity (brightness) of the polished surface were also calculated from both experimental and theoretical curves and were found to also be valuable for evaluating surface composition. Contrast in optical photomicrographs resulting from both luminosity and hue was illustrated. Secondary and backscattered electron microscopy were also used to image chalcopyrite polished surfaces which were naturally oxidized by an exposure before and after ion etching. For a substrate covered with thin layers, the resulting backscattered coefficient was calculated as a function of the backscattered coefficient for the surface and the substrate, respectively. The variations of the relative difference between the effective backscattered coefficients vs the primary beam energy exhibited a maximum for a critical thickness difference of the surface layer. The dependence of the variations in thickness of the oxidized layer with the crystallographic orientation changes of the substrate as well as the resulting contrasts of the optical and electron images were discussed

Numerical study on diverging probability density function of flat-top solitons in an extended Korteweg-de Vries equation

We consider an extended Korteweg-de Vries (eKdV) equation, the usual Korteweg-de Vries equation with inclusion of an additional cubic nonlinearity. We investigate the statistical behaviour of flat-top solitary waves described by an eKdV equation in the presence of weak dissipative disorder in the linear growth/damping term. With the weak disorder in the system, the amplitude of solitary wave randomly fluctuates during evolution. We demonstrate numerically that the probability density function of a solitary wave parameter $\kappa$ which characterizes the soliton amplitude exhibits loglognormal divergence near the maximum possible $\kappa$ value.Comment: 8 pages, 4 figure

'Open Marxism' against and beyond the 'Great Enclosure'? Reflections on How (Not) to Crack Capitalism

The main purpose of this article is to provide an in-depth discussion of John Holloway’s recent book, Crack Capitalism. To this end, the paper offers a detailed account of the key strengths and weaknesses of Holloway’s version of ‘open Marxism’. The analysis is divided into two parts. The first part focuses on six significant strengths of Crack Capitalism: (1) its insistence upon the importance of autonomous forms of agenda-setting for both individual and collective emancipation; (2) its emphasis on the ordinary constitution of social struggles; (3) its fine-grained interpretation of the socio-ontological conditions underlying human agency; (4) its processual conception of radical social transformation; (5) its recognition of the elastic, adaptable, and integrative power of capitalism; and (6) its proposal for an alternative critical theory, commonly known as ‘open Marxism’ or ‘autonomous Marxism’. The second part of the study examines the principal weaknesses of Crack Capitalism: (1) the counterproductive implications of the preponderance of negativity, owing to a one-sided concern with critique, cracks, and crises; (2) conceptual vagueness; (3) an overuse of poetic and metaphorical language; (4) the absence of a serious engagement with the question of normativity; (5) a lack of substantive evidence; (6) a residual economic reductionism; (7) a simplistic notion of gender; (8) the continuing presence of various problematic ‘isms’; (9) the misleading distinction between ‘doing’ and ‘labour’; (10) a reductive understanding of capitalism; (11) an unrealistic view of society; and (12) socio-ontological idealis

Climate models underestimate dynamic cloud feedbacks in the tropics

We acknowledge funding from the UK Natural Environment Research Council for the CIRCULATES project (Grant NE/T006315/1). Mark Webb was supported by the Met Office Hadley Centre Climate Programme funded by BEIS and Defra. We also acknowledge the World Climate Research Programme, which, through its Working Group on Coupled Modelling, coordinated and promoted CMIP6.Cloud feedbacks are the leading cause of uncertainty in climate sensitivity. The complex coupling between clouds and the large-scale circulation in the tropics contributes to this uncertainty. To address this problem, the coupling between clouds and circulation in the latest generation of climate models is compared to observations. Significant biases are identified in the models. The implications of these biases are assessed by combining observations of the present day with future changes predicted by models to calculate observationally constrained feedbacks. For the dynamic cloud feedback (i.e., due to changes in circulation), the observationally constrained values are consistently larger than the model-only values. This is due to models failing to capture a nonlinear minimum in cloud brightness for weakly descending regimes. Consequently, while the models consistently predict that these regimes increase in frequency in association with a weakening tropical circulation, they underestimate the positive cloud feedback associated with this increase.Publisher PDFPeer reviewe

Disability interactions in digital games: From accessibility to inclusion

Digital games are a hugely popular activity enjoyed for the diverse experiences and relationships that they offer players. In 2019, games are more accessible to an increasingly diverse audience of disabled players through both new gaming technology and in-game options that allow people to tune their experiences. As a significant cultural medium, it is also challenging perceptions of disability in how characters are depicted. In this workshop, we aim to understand better the research challenges in making games for and with disabled players. We explore opportunities in games and disability through the lens of the new Disability Interaction (DIX) manifesto

Melt movement through the Icelandic crust.

We use both seismology and geobarometry to investigate the movement of melt through the volcanic crust of Iceland. We have captured melt in the act of moving within or through a series of sills ranging from the upper mantle to the shallow crust by the clusters of small earthquakes it produces as it forces its way upward. The melt is injected not just beneath the central volcanoes, but also at discrete locations along the rift zones and above the centre of the underlying mantle plume. We suggest that the high strain rates required to produce seismicity at depths of 10-25 km in a normally ductile part of the Icelandic crust are linked to the exsolution of carbon dioxide from the basaltic melts. The seismicity and geobarometry provide complementary information on the way that the melt moves through the crust, stalling and fractionating, and often freezing in one or more melt lenses on its way upwards: the seismicity shows what is happening instantaneously today, while the geobarometry gives constraints averaged over longer time scales on the depths of residence in the crust of melts prior to their eruption. This article is part of the Theo Murphy meeting issue 'Magma reservoir architecture and dynamics'

Energy efficient engine. High pressure compressor detail design report

A compressor optimization study defined a 10-stage configuration with a 22.6:1 pressure ratio, and adiabatic efficiency goal of 86.1%, and a polytropic efficiency of 90.6%; the corrected airflow is 53.5 kg/sec. Subsequent component testing included three full-scale tests: a six-stage rig test, and another 10-stage rig test completed in the second quarter of 1982. Information from these tests is being used to select the configuration for a core engine test scheduled for July 1982 and an integrated core/low spool test slated for early 1983. The test results will also provide data base for the flight propulsion system

Face-to-face: Social work and evil

The concept of evil continues to feature in public discourses and has been reinvigorated in some academic disciplines and caring professions. This article navigates social workers through the controversy surrounding evil so that they are better equipped to acknowledge, reframe or repudiate attributions of evil in respect of themselves, their service users or the societal contexts impinging upon both. A tour of the landscape of evil brings us face-to-face with moral, administrative, societal and metaphysical evils, although it terminates in an exhortation to cultivate a more metaphorical language. The implications for social work ethics, practice and education are also discussed

A Preliminary Study to Understand How Mainstream Accessibility and Digital Assistive Technologies Reaches People in Lower- and Middle-Income Countries

Accessibility to mainstream digital devices and the use of Digital Assistive Technologies (Digital AT) facilitates participation and improves function and independece of people with disabilities in these regions. However, mainstream access is not fully realised in LMICs and there are multiple barriers in the way for the uptake and use of Digital AT. Through a thematic analysis of interviews with eight expert professionals in the domain of provisioning Digital AT and its related services in LMICs, we discuss five steps or barriers for the uptake and use of Digital AT and have identified three practical strategies that have shown evidence to overcome these barriers. Developers of Digital AT will find these insights useful and the same will provide an understanding of the market to business strategists to deliver pathways to better accessibility services and new Digital AT