Evidence for two stages of mineralization in West Africa's largest gold deposit: Obuasi, Ghana

The supergiant Obuasi gold deposit is the largest deposit in the Paleoproterozoic Birimian terranes of West Africa with 62 Moz of gold (past production + resources). The deposit is hosted in the Paleoproterozoic Kumasi Group sedimentary rocks composed of carbonaceous phyllites, slates, psammites, and volcaniclastic rocks intruded by different generations of felsic dikes and granites. A three-stage deformation history is defined for the district. The D1Ob stage is weakly recorded in the sedimentary rocks as a layer-parallel fabric and indicates that bedding parallel shearing occurred during the early stage of deformation at Obuasi. The D2Ob is the main deformation stage affecting the Obuasi district and corresponds to a NW-SE shortening. Tight to isoclinal folding, as well as intense subhorizontal stretching, occurred during D2Ob, parallel with the plane of a pervasive NE-striking subvertical foliation (S2Ob). Finally, a N-S shortening event (D3Ob) refolded previously formed structures and formed a distinct ENE-striking, variably dipping S3Ob cleavage that is domainal in nature throughout the deposit. Two economic styles of mineralization occur at Obuasi and contribute equally to the gold budget. These are (1) gold-bearing sulfides, dominantly arsenopyrite, mainly disseminated in metasedimentary rocks and (2) native gold hosted in quartz veins that are as much as 25 m wide. Microstructural evidence, such as strain shadows surrounding gold-bearing arsenopyrite parallel with S2Ob, but folded by S3Ob, indicates that the sulfides were formed during D2Ob. Concentrations of as much as 700 ppm Au are present in the epitaxial growth zones of the arsenopyrite grains. Although the large mineralized quartz veins are boudinaged and refolded (indicating their formation during D2Ob), field and microanalytical observations demonstrate that the gold in the veins is hosted in microcracks controlled by D3Ob, where the S3Ob cleavage crosscuts the quartz veins in the main ore zones. Thus, these observations constitute the first evidence for multiple stages of gold deposition at the Obuasi deposit. Futhermore, three-dimensional modeling of stratigraphy, structure, and gold orebodies highlights three major controls on oreshoot location, which are (1) contacts between volcaniclastic units and pre-D1 felsic dikes, (2) fault intersections, and (3) F3Ob fold hinges. The maximum age for the older disseminated gold event is given by the age of the granites at 2105 ± 2 Ma, which is within error of hydrothermal rutile in the granites of 2098 ± 7 Ma; the absolute age of the younger gold event is not known

Quantitative Study of Geological Target Spotting with the use of Eye Tracking

In this paper we describe the use of eye tracking to quantitatively evaluate and analyse the variations in data interpretation performed by various geoscientists, measuring this against their ability to spot geological targets. We also describe an approach to evaluate the impact data preprocessing (i.e. enhancement) has on one's ability to perform the interpretation task. We adapted a mobile eye tracker to enable it to accurately map the point of gaze to the actual image coordinate instead of the forward facing eye tracker camera allowing the user to move their head as they view. Several visual interpretation tasks were performed by six geoscientists and the results are described in this paper

Substitution Program in Indonesia and Australia as Health Promotion Model at Schools

Obesity has been increasing as much as twice on age 6-12 years. The increase is happening both in Indonesia and Australia. The objective of this research is to construct a program model in Australia that can be substituted to be a health promotion model at School in effort to suppress child obesity. Research was conducted in 2014 with qualitative approach. Instruments used are as follow 1) Secondary data filling form 2) In depth interview guidence instrument 3) FGD (Focus Group Discussion) and BST (Brain Storming Technique). The informations were obtained by purposive and snowball technique. Data analysis by Miles and Huberman model. Substitution model is based on consideration that applied model has potential to be developed and other models whether internal or external ones in Indonesia. The model will be substituted by considering school condition and situation. School Health Unit (SKU) is a potential platform to promote health by these activities 1) Formal health education as taken place curricullum 2) Informal health education in forms of (1) health education information (2) Self health behaviour monitoring and control (3) Health promotion by doing healthy life (4) distribution of health education booklet to teachers and parents

Mobilisation of deep crustal sulfide melts as a first order control on upper lithospheric metallogeny

Magmatic arcs are terrestrial environments where lithospheric cycling and recycling of metals and volatiles is enhanced. However, the first-order mechanism permitting the episodic fluxing of these elements from the mantle through to the outer Earth’s spheres has been elusive. To address this knowledge gap, we focus on the textural and minero-chemical characteristics of metal-rich magmatic sulfides hosted in amphibole-olivine-pyroxene cumulates in the lowermost crust. We show that in cumulates that were subject to increasing temperature due to prolonged mafic magmatism, which only occurs episodically during the complex evolution of any magmatic arc, Cu-Au-rich sulfide can exist as liquid while Ni-Fe rich sulfide occurs as a solid phase. This scenario occurs within a ‘Goldilocks’ temperature zone at ~1100–1200 °C, typical of the base of the crust in arcs, which permits episodic fractionation and mobilisation of Cu-Au-rich sulfide liquid into permeable melt networks that may ascend through the lithosphere providing metals for porphyry and epithermal ore deposits

Intermediate filaments regulate tissue size and stiffness in the murine lens

PURPOSE. To define the contributions of the beaded filament (BF), a lens-specific intermediate filament (IF), to lens morphology and biomechanics. METHODS. Wild-type and congenic CP49 knockout (KO) mice were compared by using electrophysiological, biomechanical, and morphometric approaches, to determine changes that occurred because of the absence of this cytoskeletal structure. RESULTS. Electrophysiological assessment established that the fiber cells lacking the lens-specific IFs were indistinguishable from wild-type fiber cells. The CP49 KO mice exhibited lower stiffness, and an unexpected higher resilience than the wildtype lenses. The absence of these filaments resulted in lenses that were smaller, and exhibited a higher ratio of lens:lens nucleus size. Finally, lens shape differed as well, with the CP49 KO showing a higher ratio of axial:equatorial diameter. CONCLUSIONS. Previous work has shown that BFs are necessary in maintaining fiber cell and lens structural phenotypes with age, and that absence of these filaments results in a loss of lens clarity. This work demonstrates that several tissue-level properties that are critical to lens function are also dependent, at least in part, on the presence of these lens-specific IFs. (Invest Ophthalmol Vis Sci

Development and Microstructural Improvement of Spin Cast High-Speed Steel Rolls

A detailed microstructural analysis was conducted on a series of radial shell samples extracted from commercially produced centrifugally spin casted high-speed steel (HSS) work rolls for finishing hot strip mills (HSM). The systematic microstructural analysis was coupled with a numerical and experimental investigation to improve the life of HSS rolls. An integrated computational-experimental approach was developed to optimize the response of the HSS roll material that permitted the enhancement of the microstructure and properties of the HSS roll shell layer. Local continuous microstructural transformations through the thickness of the shell: carbide formation, precipitation, dissolution sequence and phase changes, were studied in great details. The analyses were conducted with the aid of advanced metallographic and experimental methods, finite-element (FE) analysis, and using commercial software systems to conduct thermodynamic-kinetics predictions. In order to analyze a response of the HSS roll to the hardening heat treatment (HT) and to control stress-strain evolution, a 3-D FE model was developed of the composite structure of the roll. The multilayered model considers nonlinear material properties of each individual layer as a function of temperature, based on measured chemical composition gradients through the HSS shell. Transient coupled thermal-stress analysis was performed, using actual measured surface temperatures as boundary conditions (BC) for the FE model. The allowable thermal stress-strain levels were established and compared with a) thermodynamically predicted high temperature mechanical properties and b) room temperature test results of the shear strengths for the shell, bonding and core. In addition, sub-structuring and image-based processing techniques were implemented to aid in the development of a meso-scale FE model to simulate the local response of a given microstructural constituents and matrix under particular thermal conditions. The fundamental interpretation of multilayered structure and multi-scale approach help to understand the kinetics phenomena associated with continuous local microstructural transformations due to nonlinear heat transfer. The results from the microstructural observations were in good agreement with the numerical predictions. The major impact of this work clearly indicated that a refined as-cast structure prior to the heat treatment promoted an increased precipitation of carbides during final hardening, which greatly improved strength and performance. A non-conventional HT was defined and implemented in order to provide an additional degree of microstructural pre-conditioning, which homogenized the matrix throughout the HSS shell. The new HT defined the austenitization temperatures and times to modify the morphology of brittle interdendritic eutectic carbide networks and, hence, facilitating the kinetics of dissolution of these carbides. This behavior caused an increase in the solute content of the matrix. As a result, the matrix hardness and strength were increased during subsequent hardening HT in comparison to the conventional HT routes used for as-cast HSS rolls. Reports about rolls with the new material that have been placed in service indicate that the rolls last 50-70% longer

Management of infantile hemangiomas during the COVID pandemic

This article is made available for unrestricted research re-use and secondary analysis in any form or by any means with acknowledgement of the original source. These permissions are granted for the duration of the World Health Organization (WHO) declaration of COVID-19 as a global pandemic.The COVID‐19 pandemic has caused significant shifts in patient care including a steep decline in ambulatory visits and a marked increase in the use of telemedicine. Infantile hemangiomas (IH) can require urgent evaluation and risk stratification to determine which infants need treatment and which can be managed with continued observation. For those requiring treatment, prompt initiation decreases morbidity and improves long‐term outcomes. The Hemangioma Investigator Group has created consensus recommendations for management of IH via telemedicine. FDA/EMA‐approved monitoring guidelines, clinical practice guidelines, and relevant, up‐to‐date publications regarding initiation and monitoring of beta‐blocker therapy were used to inform the recommendations. Clinical decision‐making guidelines about when telehealth is an appropriate alternative to in‐office visits, including medication initiation, dosage changes, and ongoing evaluation, are included. The importance of communication with caregivers in the context of telemedicine is discussed, and online resources for both hemangioma education and propranolol therapy are provided

LSD1 activation promotes inducible EMT programs and modulates the tumour microenvironment in breast cancer

Complex regulatory networks control epithelial-to-mesenchymal transition (EMT) but the underlying epigenetic control is poorly understood. Lysine-specific demethylase 1 (LSD1) is a key histone demethylase that alters the epigenetic landscape. Here we explored the role of LSD1 in global epigenetic regulation of EMT, cancer stem cells (CSCs), the tumour microenvironment, and therapeutic resistance in breast cancer. LSD1 induced pan-genomic gene expression in networks implicated in EMT and selectively elicits gene expression programs in CSCs whilst repressing non-CSC programs. LSD1 phosphorylation at serine-111 (LSD1-s111p) by chromatin anchored protein kinase C-theta (PKC-θ), is critical for its demethylase and EMT promoting activity and LSD1-s111p is enriched in chemoresistant cells in vivo. LSD1 couples to PKC-θ on the mesenchymal gene epigenetic template promotes LSD1-mediated gene induction. In vivo, chemotherapy reduced tumour volume, and when combined with an LSD1 inhibitor, abrogated the mesenchymal signature and promoted an innate, M1 macrophage-like tumouricidal immune response. Circulating tumour cells (CTCs) from metastatic breast cancer (MBC) patients were enriched with LSD1 and pharmacological blockade of LSD1 suppressed the mesenchymal and stem-like signature in these patient-derived CTCs. Overall, LSD1 inhibition may serve as a promising epigenetic adjuvant therapy to subvert its pleiotropic roles in breast cancer progression and treatment resistance.T. Boulding, R.D. McCuaig, A. Tan, K. Hardy, F. Wu, J. Dunn, M. Kalimutho, C.R. Sutton, J.K. Forwood, A.G. Bert, G.J. Goodall, L. Malik, D. Yip, J.E. Dahlstrom, A. Zafar, K.K. Khanna, S. Ra

Stress and psychological health: testing the mediating role of cognitive appraisal

This study tested the mediating role of primary (e.g., threat and challenge perceptions) and secondary (e.g., coping potential and control perception) cognitive appraisal in the relationship between occupational stress and psychological health. This mediation was tested using a cross-sectional study based on self-reported measures. The total sample consisted of 2,302 nurses, 1,895 females (82.3%) and 407 males (17.7%), who completed an evaluation protocol with measures of occupational stress, cognitive appraisal, and psychological health. To test the mediating role of cognitive appraisal in the relationship between cognitive appraisal and psychological health, we used Structural Equation Modeling (SEM). The results confirmed that primary and secondary cognitive appraisals partially mediated the relationship between occupational stress and psychological health; however, the direct effects of stress on psychological health cannot be ignored. The findings indicated that cognitive appraisal is an important underlying mechanism in explaining adaptation at work.This study was conducted at Psychology Research Centre (UID/PSI/01662/2013), University of MInho, and supported by the Portuguese Foundation for Science and Technology and the Portuguese Ministry of Science, Technology and Higher Education through national funds and co-financed by FEDER through COMPETE2020 under the PT2020 Partnership Agreement (POCI-01-0145-FEDER-007653)