Model of limestone weathering and damage in masonry : sedimentological and geotechnical controls in the Globigerina limestone formation (Miocene) of Malta

Five types and subtypes of stone used in construction in the Maltese Islands and three problematic stone types, mostly extracted from facies within the Oligo-Miocene Valletta Basin, are identified. Their nature and geotechnical behaviour is discussed in the context of specific use in masonry. These stone types represent end members of the variations in depositional and diagenetic environments in carbonates which control their level of physical heterogeneity, and ultimately affect the nature of damage seen in Globigerina limestone masonry. A model is presented linking the level of heterogeneity to the mode of salt weathering seen especially in ancient constructions.peer-reviewe

Syntectonic deposition of an oligo-miocene phosphorite conglomerate bed in Malta

A succession of Oligo-Miocene sediments at Sliema, Qawra and Migra Ferha includes a 1O-20cm phosphorite conglomerate bed capping the terminal hardground of the Lower Coralline Limestone Formation (Oligocene) which consists of carbonate platform sediments. The conglomerate bed always occurs in areas of significant thinning of the overlying Lower Globigerina Limestone. These palaeohighs have been linked to NNE-SSW trending lineaments. At Sliema, allochthonous phosphatised conglomerate infill NW-SE trending Neptunian dykes that dissect the platform sediments. These Oligo-Miocene syntectonic deposits were later cemented and vertically displaced by minor faulting trending NW-SE. Tectonic features at Sliema are linked to the regional N-S extensional regime and tentatively interpreted to have developed from stresses caused by displacement along the western margin of a NNE-SSW trending strike-slip fault. East of this fault, synclinal subsidence created the Valletta Basin and set conditions for current upwelling. Phosphatogenesis occurred along the basin margin swept by the prevailing westward currents. Phosphatised pebbles and ahermatypic corals were transported westward of palaeohigh margins in central and western Malta and deposited on the terminal hardground of the drowned Oligocene carbonate platform.peer-reviewe

CARBONATE FACIES, DEPOSITIONAL SEQUENCES AND TECTONOSTRATIGRAPHY OF THE PALAEOGENE MALTA PLATFORM

The break-up of Pangaea and the Late Mesozoic global sea-level rise drowned many Tethyan carbonate platforms although the resilient Malta Platform aggraded >4 km of carbonates along the North African passive margin where it was isolated from continental siliciclastics. Carbonate sedimentation was terminated by extensive Late Cretaceous to Early Paleogene depositional hiatuses, but renewed during the Oligocene, when basinward carbonate progradation began to drape over the >350 km long, cusp-shaped escarpment along the eastern margin of the isolated platform. This study sub-divides the Oligocene sediments of Malta into eight facies associations. The facies consist of carbonate grains of coral, coralline red algae and large benthic foraminifera which dominated sediments of the Late Rupelian to early Chattian, mid-Chattian and late Chattian, respectively. These successive carbonate factories produced the photozoan-heterozoan-photozoan triplet of carbonate grain associations which, when dated by benthic foraminiferal biozonation, correlates to the succession of carbonate grain associations in other Mediterranean carbonate platforms. The sedimentary triplet reflects abrupt changes in carbonate ecosystems that coincide with the last three of six surfaces that extend >80 km around Malta. The surfaces show evidence of the influence of meteoric water and pedogenic processes recognised by diagenetic features and isotopic excursions. These sequence boundaries sub-divide the succession into seven depositional sequences that reflect global third-order cyclic sea-level falls produced by glaciations with a periodicity of 1.2 Ma triggered by low-amplitude obliquity variations of the Earth’s axis combined with orbital eccentricity cycles. The periodic growth of the Antarctic ice-sheet during the Oligocene also affected Tethyan climate by shifting low latitude climate belts northwards. It is suggested that increased aridity over North Africa had reduced nutrient flux to the Tethys and favoured photozoan carbonate biota over the Malta Platform and other Tethyan carbonate platforms. The stepwise decrease in oxygen isotope ratio by the mid-Chattian reflects Antarctic deglaciation that increased both precipitation over North Africa and nutrient flux in the Tethys, favouring heterozoan ecosystems. The mid-Chattian transgressive heterozoan carbonates draped over structured bathymetry of an antecedent extensional regime that produced rotated fault-blocks. Highstand shedding of coralline red algae resulted in large clinoforms prograding into partly filled NNE trending half-graben (50 km-wide basin by lithospheric sagging over a failed Mesozoic rift. The late Chattian climatic optimum was reflected by a further decrease in the oxygen isotope ratio and aridity over North Africa and favoured a return to the photozoan association during the last phase of the Oligocene sedimentary triplet. Lepidocyclinids flourished in inner to mid-platform environments forming banks although the rate of accumulation of these hydrodynamic foraminifera did not keep up with sea-level rise. The shift to increased trophic resources by the end Oligocene terminated shallow marine carbonate sedimentation which resulted in the drowning of the Malta Platform

The nomination committee in Maltese listed companies

The aim of this study is to examine the Nomination Committee (NC) in Maltese listed companies. The study achieves this by assessing the Maltese regulatory framework relating to this Committee, as well as its roles, status and effectiveness. A predominantly qualitative mixed methodology was employed to achieve these objectives. Twenty-five semi-structured interviews were held with two financial analysts, two MFSA representatives, eight audit firm representatives and 13 representatives of Maltese Listed Companies (MLCs) Research findings show that the NC is not as yet not well established among MLCs. There is a particular lack of insistence on the part of local regulatory authorities, as well as substantial resistance from listed companies, with regard to the adoption of this committee. Furthermore, most NCs in such companies are not performing all of the roles listed in their Code while the roles currently performed may need to be carried out in a more structured manner. Yet it is highly worthwhile for such companies to devote more attention to the NC, this being one of the best possible bastions of appropriate corporate governance. The change in the status of the NC from being merely recommended by the Code of Principles of Good Corporate Governance to becoming mandatory by the Listing Rules is increasingly called for. In this way, Maltese listed companies will need to embrace such a change. It is hoped that this study will contribute towards fostering more awareness about the NC and the corporate governance of Maltese listed companies.peer-reviewe

Heritability of cognitive and emotion processing during functional MRI in a twin sample

Despite compelling evidence that brain structure is heritable, the evidence for the heritability of task-evoked brain function is less robust. Findings from previous studies are inconsistent possibly reflecting small samples and methodological variations. In a large national twin sample, we systematically evaluated heritability of task-evoked brain activity derived from functional magnetic resonance imaging. We used established standardised tasks to engage brain regions involved in cognitive and emotional functions. Heritability was evaluated across a conscious and nonconscious Facial Expressions of Emotion Task (FEET), selective attention Oddball Task, N-back task of working memory maintenance, and a Go-NoGo cognitive control task in a sample of Australian adult twins (N ranged from 136 to 226 participants depending on the task and pairs). Two methods for quantifying associations of heritability and brain activity were utilised; a multivariate independent component analysis (ICA) approach and a univariate brain region-of-interest (ROI) approach. Using ICA, we observed that a significant proportion of task-evoked brain activity was heritable, with estimates ranging from 23% to 26% for activity elicited by nonconscious facial emotion stimuli, 27% to 34% for N-back working memory maintenance and sustained attention, and 32% to 33% for selective attention in the Oddball task. Using the ROI approach, we found that activity of regions specifically implicated in emotion processing and selective attention showed significant heritability for three ROIs, including estimates of 33%–34% for the left and right amygdala in the nonconscious processing of sad faces and 29% in the medial superior prefrontal cortex for the Oddball task. Although both approaches show similar levels of heritability for the Nonconscious Faces and Oddball tasks, ICA results displayed a more extensive network of heritable brain function, including additional regions beyond the ROI analysis. Furthermore, multivariate twin modelling of both ICA networks and ROI activation suggested a mix of common genetic and unique environmental factors that contribute to the associations between networks/regions. Together, the results indicate a complex relationship between genetic factors and environmental interactions that ultimately give rise to neural activation underlying cognition and emotion

Aberrant axon initial segment plasticity and intrinsic excitability of ALS hiPSC motor neurons

Dysregulated neuronal excitability is a hallmark of amyotrophic lateral sclerosis (ALS). We sought to investigate how functional changes to the axon initial segment (AIS), the site of action potential generation, could impact neuronal excitability in ALS human induced pluripotent stem cell (hiPSC) motor neurons. We find that early TDP-43 and C9orf72 hiPSC motor neurons show an increase in the length of the AIS and impaired activity-dependent AIS plasticity that is linked to abnormal homeostatic regulation of neuronal activity and intrinsic hyperexcitability. In turn, these hyperactive neurons drive increased spontaneous myofiber contractions of in vitro hiPSC motor units. In contrast, late hiPSC and postmortem ALS motor neurons show AIS shortening, and hiPSC motor neurons progress to hypoexcitability. At a molecular level, aberrant expression of the AIS master scaffolding protein ankyrin-G and AIS-specific voltage-gated sodium channels mirror these dynamic changes in AIS function and excitability. Our results point toward the AIS as an important site of dysfunction in ALS motor neurons

Community-acquired pneumonias in SARS-CoV-2 negative patients admitted at Mater Dei Hospital and their subsequent follow-up

BACKGROUND: Community-acquired pneumonia refers to an acute infection of the lung parenchyma acquired within the community, and its management depends on the severity of symptoms and method of presentation. The aim of this audit is to evaluate community-acquired pneumonias in SARS-CoV-2 negative patients admitted at Mater Dei Hospital and their subsequent follow-up.METHODS: In this observational audit, demographic data was collected from 200 patients between June and September 2020. Follow-up of these patients was audited to assess whether local current practice is being adhered to as per British Thoracic Society recommendations.RESULTS: From our sample of 200 patients, 25.5% who were being treated for community-acquired pneumonia passed away during their admission. The age range of our patients varied from 18 to 99 years with the majority being over the age of 75. 31 out of 149 surviving patients (20.8%) had both imaging and medical outpatient follow-up booked, 18 patients (12.08%) had only a chest x-ray follow-up whilst 19 patients (12.75%) had medical outpatient follow-up only. In total 68 patients (45.63%) had imaging or medical outpatient follow-up, or both.CONCLUSION: Any patient admitted and treated for a community-acquired pneumonia should receive a follow-up appointment to assess for resolution of symptoms, and/or follow-up imaging to assess for resolution of changes. Non-resolution of these changes may necessitate discussion at a multi-disciplinary level to conclude how to further investigate such a patient.peer-reviewe

Genetic correlations between wellbeing, depression and anxiety symptoms and behavioral responses to the emotional faces task in healthy twins

© 2018 Elsevier BV. This manuscript version is made available under the CC-BY-NC-ND 4.0 license: http://creativecommons.org/licenses/by-nc-nd/4.0/ This author accepted manuscript is made available following 12 month embargo from date of publication (March 2018) in accordance with the publisher’s archiving policyCurrently there is a very limited understanding of how mental wellbeing versus anxiety and depression symptoms are associated with emotion processing behaviour. For the first time, we examined these associations using a behavioural emotion task of positive and negative facial expressions in 1668 healthy adult twins. Linear mixed model results suggested faster reaction times to happy facial expressions was associated with higher wellbeing scores, and slower reaction times with higher depression and anxiety scores. Multivariate twin modelling identified a significant genetic correlation between depression and anxiety symptoms and reaction time to happy facial expressions, in the absence of any significant correlations with wellbeing. We also found a significant negative phenotypic relationship between depression and anxiety symptoms and accuracy for identifying neutral emotions, although the genetic or environment correlations were not significant in the multivariate model. Overall, the phenotypic relationships between speed of identifying happy facial expressions and wellbeing on the one hand, versus depression and anxiety symptoms on the other, were in opposing directions. Twin modelling revealed a small common genetic correlation between response to happy faces and depression and anxiety symptoms alone, suggesting that wellbeing and depression and anxiety symptoms show largely independent relationships with emotion processing at the behavioral level