Photon and Fast Neutron Transmission Parameters of Metakaolin Doped Concrete

Radiation-shielding properties of metakaolin doped concrete samples wereinvestigated in this report. The gamma photon mass attenuation coefficientsand exposure buildup factor of the samples were determined theoreticallyusing WinXcom and EXABCal software respectively for the energyrange of 15 keV - 15 MeV and fast neutron removal cross section for theconcrete sample was evaluated. Results indicated that, oxides of silicon,aluminum, calcium and iron determined through the energy dispersiveX-ray fluorescence spectrometric analysis constitute more than 85% ofthe chemical composition of the concrete samples. The oxides contribute85.46, 86.47, 87.55, 88.75, and 86.15 % of the total chemical oxides inMK00, MK05, MK10, MK15, and MK20 respectively. Densities of theprepared MK doped concrete were in the range of 2.575-2.667 g/cm3 .Compressive stress of prepared MK doped concretes increased consistentlywith the curing period for each concrete sample. CS grew from 8.71 -10.63, 8.84 - 10.83, 9.44 - 11.22, 10.89 - 11.53, and 10.76 - 11.43 MPafor MK00, MK05, MK10, MK15, and MK20 respectively as the periodextends from 7 to 28 days. Mass attenuation coefficient decrease steadilywith an increase in energy up to about 0.1 MeV and the decrease becomesmaller beyond this energy with increasing energy for all the mixtures. Fastneutron removal cross section results indicate that MK10 (0.07693 cm-1)has the highest value of ΣR followed by MK15 (0.07628 cm-1) and MK20(0.07537 cm-1) while MK00 (0.07380 cm-1) and MK05 (0.07404 cm-1)have approximately the same value. It was found that MK10 concrete hasthe best gamma radiation and fast neutron shielding ability among the MKdoped concrete under study

Digital skills critical for education: Video analysis of students' technology use in Norwegian secondary English classrooms

Background: Globally, digital skills are a crucial aspect of education that schoolsshould develop systematically. Research on digital skills tends to be measured usingself-reports, performance tests or interventions. There is less knowledge about stu-dent and teacher uptake of technology in school, making it important to investigatethe actual use of technology and digital skills in authentic classroom settings. Objectives:This study contributes unique baseline data concerning students' use oftechnology and digital skills across mandatory English courses in real classroom set-tings in secondary schools in Norway over time. Methods:The study adapted a national framework for digital skills into an observa-tion protocol. With it, this study analysed videos from 60 naturally occurring Englishlessons in 13 English classes at seven lower secondary schools over two school years(grades 9 and 10), following 186 students (aged 13–15) and 10 teachers. Results and Conclusions:Students used digital skills critical for education in half ofthe video-recorded English lessons, with more digital skill use at some schools overtime. The main finding across classrooms and school years regards students' use ofbasic, not advanced, digital skills. Takeaways:Although teachers provide opportunities for students to use digital skillsin school, more advanced skills are needed. This work calls for continued use of videorecordings to provide systematic comparisons of potential shifts in students' digitalskills in real English secondary classroom settings over time.publishedVersio

Electronic excitations stabilized by a degenerate electron gas in semiconductors

Excitons in semiconductors and insulators consist of fermionic subsystems, electrons and holes, whose attractive interaction facilitates bound quasiparticles with quasi-bosonic character. In the presence of a degenerate electron gas, such excitons dissociate due to free carrier screening. Despite their absence, we found pronounced emission traces in the below-band-edge region of bulk, germanium-doped GaN up to a temperature of 100 K, mimicking sharp spectral features at high free electron concentrations (3.4E19–8.9E19 cm−3). Our interpretation of the data suggests that a degenerate, three-dimensional electron gas stabilizes a novel class of quasiparticles, which we name collexons. These many-particle complexes are formed by exchange of electrons with the Fermi gas. The potential observation of collexons and their stabilization with rising doping concentration is enabled by high crystal quality due to the almost ideal substitution of host atoms with dopants.DFG, 43659573, SFB 787: Semiconductor Nanophotonics: Materials, Models, Device

Production and characterization of xanthan gum by bacterial isolates

Xanthan gum is a microbial polymer synthesised by a plant pathogen of the Xanthomonas genus. Due to its rheological characteristics and water solubility, it is of enormous commercial significance and has been utilized as a thickening and stabilizing agent in a variety of industries. In this work, the potential for synthesizing xanthan gum in Xanthomonas species isolated from black rot spotted tomatoes, peppers, mango, and bananas was investigated. After washing the leaves in saline solution, a tenfold dilution was made, and aliquots (1 ml) were placed on a nutrient agar plate and incubated for 48 h at 25 °C. Gram staining was made on colonies that appeared yellow. An emulsification test was carried out on bacteria that were gram-negative rods. Potential xanthan gum producers include isolates displaying yellow colonies, gram-negative rods, and stable emulsions on carbon-enriched media. These requirements were satisfied by eight (61.5 %) of the isolates tested. Biochemical analysis of the isolates indicated that they were Xanthomonas species, and they were coded appropriately (BX2, BX3, PX4, MX6, PX7, MX8, TM9, TX11). The molecular analysis of the best two isolates (TM9 and BX3) revealed that they were Xanthomonas campestris and Stenotrophomonas maltophilia. After 96 h of incubation, Xanthomonas campestris and Stenotrophomonas maltophilia were the most effective xanthan gum producers, generating 2.10 g/l and 1.63 g/l of xanthan gum, respectively. The apparent viscosity (AV), emulsification index (IE24), scanning electron microscopy (SEM), thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC) were used to characterize the xanthan gums produced. The findings indicated little or no differences between commercially synthesized xanthan gum and produced xanthan gum. However, xanthan gum from Stenotrophomonas maltophilia has a higher apparent viscosity (660.6 mPas) that is above those of Xanthomonas campestris (526.1 mPas) and commercial xanthan gum (411.3 mPas), respectively. The gums showed structural similarities and exhibited good thermal stability. These findings indicate that Xanthomonas species are viable options for xanthan gum production

The lived experiences of nuclear medicine technologists during Covid-19 pandemic

This study presented the lived experiences of the nuclear medicine technologists (NMTs) during the COVID-19 pandemic. The participants of this study are nuclear medicine technologists working in healthcare facilities before and during the COVID-19 pandemic. A qualitative research design was used, specifically the phenomenological qualitative approach. The participants were chosen through purposive and snowball sampling. Based on the findings, it can be concluded that the experiences of the NMTs is an interplay of fear, sadness, and happiness. Fear of contacting COVID and/or spreading it to others has become a driving force to be more mindful of the infection control measures, specifically on the use of PPEs and appropriate physical distancing measures. The sadness, happiness, and fear felt by the participants have seemed to balance and helped the participants to cope with the pandemic. There had been notable changes in the personal-social (isolation from family and friends) and professional (workload change, redeployment) lives of the participants. Adaptation to the changes brought about by the pandemic has been evident in the participants. These reflect the resilience of the participants in the midst of the pandemi

PET brain imaging in HIV-associated neurocognitive disorders (HAND) in the era of combination antiretroviral therapy

Effective combination antiretroviral therapy (cART) has lead to a significant reduction in the prevalence and incidence of central nervous system (CNS) HIV-associated brain disease, particularly CNS opportunistic infections and HIV encephalitis. Despite this, cognitive deficits in people living with HIV, also known as HIV-associated neurocognitive disorders (HAND) have become more prevalent in recent years. The pathogenesis of HAND is likely to be multifactorial, however recent evidence suggests that brain microglial activation is the most likely pathogenic mechanism. Recent developments in positron emission tomography (PET) brain neuroimaging using novel brain radioligands targeting a variety of physiological changes in the brains of HIV-positive individuals have improved our understanding of the mechanisms associated with the development of HAND. This review will highlight recent PET brain neuroimaging studies in the cART era, focusing on physiological and neurochemical changes associated with HAND in people living with HIV

Strategic Transformations in the Media

Digital technologies have transformed the way many media organisations have conducted their business over the past two decades. This transformational context raises a number of important questions for media management researchers. Firstly, how have media firms adapted their strategies, resources and capabilities in response to the challenges presented by an increasingly digital environment? Secondly, how have these adaptive practices affected their corporate financial performance? This paper advances our theoretical understanding of media firm transformation by using a multi-disciplinary approach that draws on knowledge from corporate strategy, dynamic capabilities and firm performance. This integrated approach provides a more holistic view of strategic business transformation by understanding the strategic arguments that compel firm’s to reconfigure their resources and capabilities in a dynamic business environment