Choosing a suitable sample size in qualitative research is an area of conceptual debate and practical uncertainty. That sample size principles, guidelines and tools have been developed to enable ...researchers to set, and justify the acceptability of, their sample size is an indication that the issue constitutes an important marker of the quality of qualitative research. Nevertheless, research shows that sample size sufficiency reporting is often poor, if not absent, across a range of disciplinary fields.
A systematic analysis of single-interview-per-participant designs within three health-related journals from the disciplines of psychology, sociology and medicine, over a 15-year period, was conducted to examine whether and how sample sizes were justified and how sample size was characterised and discussed by authors. Data pertinent to sample size were extracted and analysed using qualitative and quantitative analytic techniques.
Our findings demonstrate that provision of sample size justifications in qualitative health research is limited; is not contingent on the number of interviews; and relates to the journal of publication. Defence of sample size was most frequently supported across all three journals with reference to the principle of saturation and to pragmatic considerations. Qualitative sample sizes were predominantly - and often without justification - characterised as insufficient (i.e., 'small') and discussed in the context of study limitations. Sample size insufficiency was seen to threaten the validity and generalizability of studies' results, with the latter being frequently conceived in nomothetic terms.
We recommend, firstly, that qualitative health researchers be more transparent about evaluations of their sample size sufficiency, situating these within broader and more encompassing assessments of data adequacy. Secondly, we invite researchers critically to consider how saturation parameters found in prior methodological studies and sample size community norms might best inform, and apply to, their own project and encourage that data adequacy is best appraised with reference to features that are intrinsic to the study at hand. Finally, those reviewing papers have a vital role in supporting and encouraging transparent study-specific reporting.
The occurrence of microplastics (MPs) in wastewater has been studied in the last years. The high efficiency of their removal from wastewater is linked to their transfer to the sludge. In this work, ...the effect of high-density polyethylene (HDPE) on aerobic digestion was evaluated and these MPs were monitored, characterizing them by three different techniques. Two parallel batch digesters were monitored. AD-Control (meaning Aerobic Digester) operated as a reference, with no external HDPE particles, whereas these polymeric fragments were introduced to the second aerobic digester (AD-HDPE) using ring pulls as microplastic support. FTIR, Raman spectroscopies and fluorescence analysis of these microparticles showed some relevant results that should be highlighted. Higher fluorescence appeared after 7 days in the digester. It coincided with an increase of active volatile suspended solids (AVSS) in the AD-HDPE, which means that an increase of the microbial activity took place. Despite the presence of HDPE particles in the sludge, the digester performance was not compromised. Besides, the HDPE particles did not affect the microbial diversity (Shannon index) of the bacterial community at the end of the experiment compared to the bacterial community of the aerobic digester control tank. Based on the analysis of the relative abundances of microbial taxa, it was concluded that HDPE had selective effects on sludge microbial community, increasing the relative abundance of Bacteroridota phylum.
Display omitted
•HDPE microplastics enhanced biomass activity in aerobic digestion, aiding survival.•HDPE coexistence served as a survival means, revealing microbial adaptation strategies.•Fluorescence signalled increased activity while Raman showed progressive variation in HDPE spectra.•Consistent digestion performance: digestion was not compromised and TVS elimination remained unaffected.•Microbial community was selectively affected, rising relative abundance of Bacteroridota phylum.
Several thermostable proteases have been identified, yet only a handful have undergone the processes of cloning, comprehensive characterization, and full exploitation in various industrial ...applications. Our primary aim in this study was to clone a thermostable alkaline protease from a thermophilic bacterium and assess its potential for use in various industries. The research involved the amplification of the SpSKF4 protease gene, a thermostable alkaline serine protease obtained from the Geobacillus thermoglucosidasius SKF4 bacterium through polymerase chain reaction (PCR). The purified recombinant SpSKF4 protease was characterized, followed by evaluation of its possible industrial applications. The analysis of the gene sequence revealed an open reading frame (ORF) consisting of 1,206 bp, coding for a protein containing 401 amino acids. The cloned gene was expressed in Escherichia coli. The molecular weight of the enzyme was measured at 28 kDa using sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE). The partially purified enzyme has its highest activity at a pH of 10 and a temperature of 80℃. In addition, the enzyme showed a half-life of 15 h at 80℃, and there was a 60% increase in its activity at 10 mM Ca 2+ concentration. The activity of the protease was completely inhibited (100%) by phenylmethylsulfonyl fluoride (PMSF); however, the addition of sodium dodecyl sulfate (SDS) resulted in a 20% increase in activity. The enzyme was also stable in various organic solvents and in certain commercial detergents. Furthermore, the enzyme exhibited strong potential for industrial use, particularly as a detergent additive and for facilitating the recovery of silver from X-ray film.
M2 high speed steel (HSS) samples were produced by an additive manufacturing (AM) process, selective laser melting (SLM). The observed microstructure from SEM and FIB was characterised by a ...continuous and homogeneous network of dendrites within two different phases. These phases were characterised to be bcc single crystals and fcc/bcc polycrystals from TEM-SADP. EBSD results also indicated that the bcc grains were randomly orientated. In addition, the lattice constants from two different SADPs of bcc crystal were calculated to be 2.892Å and 2.905Å, larger than high purity iron bcc structure of lattice constant 2.867Å. The elements V, Cr, Mo, W and Si were detected in the iron matrix with TEM-EDS. These elements were responsible for the enlargement of the lattice constant. TEM-EDS results also indicated that the network of dendrites were carbides. These results gave insights on the rapid solidification phenomenon in SLM.
•Microstructure of SLM M2 high speed steel was investigated through TEM.•A continuous and homogeneous network of carbide dendrites was observed.•Two distinct phases of bcc single crystals and fcc/bcc polycrystals were observed.•The iron bcc lattice constant calculated from TEM-SADP was larger.•Alloying elements V, Cr, Mo, W and Si were detected in the iron matrix by TEM-EDS.
Reactive iron minerals are crucial components of global nutrient cycles, directly controlling carbon transport and storage in marine sediments. Sequential selective extraction is frequently used for ...quantitatively characterising, and chemically isolating, individual Fe mineral phases. Reagent-specific mineral solubility is fundamental to the success of any sequential extraction, but is strongly affected by the varying physical and chemical morphology intrinsic to natural mineral samples. Natural sediment, rock, and soil samples often contain a mineral mixture, which further modifies solvent efficacy. 57Fe Mössbauer spectroscopy only probes the hyperfine interactions between next-nearest neighbouring atomic nuclei in the crystal lattice and is less affected by variation in mineral grain size and crystallinity than conventional, X-ray-based methods. In this study, we used Mössbauer spectroscopy in a novel context to cross-calibrate and optimise a popular, but frequently misused, sequential Fe extraction protocol. Our results showed that incomplete and premature removal of the target Fe minerals could occur at nearly every stage of the extraction and, in many cases, the leachate Fe content did not represent the target phase at all. Crystalline, natural siderite and amorphous, synthetic goethite were detected in the Mössbauer spectrum of the ammonium oxalate extraction for magnetite, after which all reactive Fe minerals should have been removed. Consistent with previous studies, and unlike many other clay minerals, nontronite was extracted as part of the highly reactive Fe pool, and in fact our data indicate that this mineral was extracted by the initial Na-acetate extraction that targets ‘carbonate-bound Fe’. Matrix effects appeared to cause variable yield efficiencies: synthetic goethite was successfully removed when present as an individual mineral yet persisted beyond its target extraction when present in an Fe mineral mixture. Although suitable for the quantification of operationally-defined Fe pools, we caution the unverified use of sequential Fe extraction protocols for mineral specific applications. The application of sequential Fe extractions to define the reactive Fe pools as a paleoredox proxy of depositional conditions appears relatively robust. The premature removal of 2-line ferrihydrite observed in this study (due to the use of the more aggressive Na-acetate extraction for crystalline siderite), does not limit the quantitative use of the sequential Fe extraction in ancient sediments, where such ‘easily reducible’ oxides are unlikely to persist. In contrast, attributing the outcomes of operationally-defined Fe pools to specific Fe minerals is precarious and potentially entirely erroneous. Where Fe mineral specificity or separation is required, we recommend post-extraction validation by another secondary technique. Mössbauer spectroscopy offers such a method that can independently verify extraction stages and assess mineral specificity.
•The operational nature of sequential extractions is frequently misunderstood when used to identify specific mineral phases.•Sequential extraction results are often unverified. Incomplete and premature target mineral dissolution can occur throughout the Poulton and Canfield (2005) Fe extraction.•Grain size and matrix effects largely control the accuracy and the precision of many extraction stages.•Mössbauer spectroscopy combined with sequential extractions can quantitatively identify individual Fe minerals.
•U-isotopes are the main contributors to the radioactivity in CyL drinking waters.•Higher radioactivity content has been measured in samples from the CyL southwestern.•Radionuclide spatial ...distribution is related to the CyL hydrogeological formations.•>95% of the analysed samples did not pose a risk to human health (ID < 0.1 mSv/yr).•Alternative screening levels could be assessed to improve their predictive power.
Since the coming into force of the European Council Directive 51/2013 EURATOM and its transposition into the Spanish legislation, the presence of radioactive substances in drinking waters must be kept under surveillance to ensure that the health protection requirements are met. Driven by this regulatory framework, in an attempt to know the starting point from which to design surveillance plans, the groundwaters intended for human consumption of Castilla y León (Spain) have been radiologically characterised by using both low-level γ-ray and α-particle spectrometry to determine the activity concentration of the natural radionuclides needed to account for the indicative dose estimation. This extensive research has comprised the radiological characterisation of more than 400 drinking water samples from one of the European Union's largest regions. Furthermore, the gross α and gross β activities have been analysed. Results showed a high geographical variability that can be related to the hydrogeological formations where the groundwaters come from. The uranium isotopes, 234U and 238U, are the main radionuclides present in the analysed drinking waters reaching values up to 2000 mBq/L, in the southwestern and western of Castilla y León, where U-rich minerals are part of the host rock. High 210Pb and 226,228Ra occurrences are found in the low permeability igneous and metasedimentary hydrogeological formations of Salamanca province. From a public health protection point of view, 4.4% of the total drinking water samples from intakes exceeded the Indicative Dose parametric value of 0.1 mSv, which is a not negligible number of samples, being very likely related to granitic and metamorphosed host rock under specific local conditions. This fact highlights the need for research and consideration of special surveillance of the groundwaters from these areas.
Display omitted
The need to deliver high performant and miniaturised electrochemical sensors has boosted the use of carbon nanomaterials as smart modifiers of working electrode surface. Among the carbon ...nanomaterials, the common and cost-effective carbon black has recently attracted the attention from the scientific community for its outstanding features as electrode nanomodifier for analyte detection. Herein, we report the structural and morphological characterisation of several types of carbon blacks, namely HP 160, HS20, MTN 990, N115, N220, N375, N660, PL6, Super P, and XE2B, by means of Raman spectroscopy, transmission electron microscopy (TEM) and scanning electron microscopy (SEM) analyses. Furthermore, the electrochemical characterisation of screen-printed electrodes modified with these carbon blacks was carried out by cyclic voltammetry and electrochemical impedance spectroscopy with ferro/ferricyanide as redox probe, highlighting the advantage to use carbon black as nanomodifier in respect to the bare electrode. Among several tested carbon black types, the lowest peak-to-peak separation and resistance to electron transfer values were achieved using screen-printed electrodes modified with CB N115, N375, HP 160 and PL6. The electrodes modified with these types of CB were successively tested in cyclic voltammetry towards epinephrine, benzoquinone, ascorbic acid, cysteine, catechol, and caffeic acid, observing a remarkable improvement of electrochemical performances in respect to the bare electrode, even when the amperometric mode was used. The results obtained demonstrated that several types of CB can remarkably improve the electrochemical performances of the sensors in terms of the decrease of applied potential or peak-to-peak separation, the improvement of the peak intensity, and the decrease of the resistance of the electron transfer due to several key features, including nanodimensions, the onion-like carbon structure, and the high number of defect sites.
Display omitted
The understanding of relationships between processing, microstructure and mechanical properties in laser powder bed fusion is currently incomplete. Microstructure-property relations in 316L stainless ...steel are revealed in this study using isothermal heat treatments as an investigative tool. As-built material was heat treated to selectively remove microstructural features such as melt pool boundaries, microsegregations and the as-built grain structure to evaluate their influence on yield and failure behaviour. Anisotropic yield behaviour was found to be caused by microstructural features alone and not influenced by porosity. However, ductility and failure were dominated by lack of fusion porosity. The alignment of pores between tracks along layer boundaries was found to cause anisotropic ductility. Three strengthening mechanisms in as-built material were identified as grain boundaries, chemical segregation and dislocation density. Heat treatments were categorised into three regimes: recovery, homogenisation and annealing. The findings of this study show that the shape, size, orientation and distribution of pores are crucial parameters for evaluating the structural integrity of parts produced by laser powder bed fusion.
Display omitted
•Laser powder bed fusion 316L samples are heat treated and characterised.•Microstructural features are related to anisotropic yield behaviour.•Anisotropic ductility is related to the shape, size and orientation of porosity.•Heat treatments are categorised by recovery, homogenisation and annealing regimes.
Selective laser melting (SLM) can produce complex hierarchical architectures paving the way for highly customisable biodegradable load-bearing bone scaffolds. For the first time, an in-depth analysis ...on the performance of SLM-manufactured iron-manganese bone scaffolds suitable for load-bearing applications is presented. Microstructural, mechanical, corrosion and biological characterisations were performed on SLM-manufactured iron-manganese scaffolds. The microstructure of the scaffold consisted primarily of γ-austenite, leading to high ductility. The mechanical properties of the scaffold were sufficient for load-bearing applications even after 28 days immersion in simulated body fluids. Corrosion tests showed that the corrosion rate was much higher than bulk pure iron, attributed to a combination of the manufacturing method, the addition of Mn to the alloy and the design of the scaffold. In vitro cell testing showed that the scaffold had good biocompatibility and viability towards mammalian cells. Furthermore, the presence of filopodia showed good osteoblast adhesion. In vivo analysis showed successful bone integration with the scaffold, with new bone formation observed after 4 weeks of implantation. Overall the SLM manufactured porous Fe-35Mn implants showed promise for biodegradable load-bearing bone scaffold applications.
Biodegradable iron scaffolds are emerging as a promising treatment for critical bone defects. Within this field, selective laser melting (SLM) has become a popular method of manufacturing bespoke scaffolds. There is limited knowledge on SLM-manufactured iron bone scaffolds, and no knowledge on their application for load-bearing situations. The current manuscript is the first study to characterise SLM manufactured iron-manganese bone scaffolds for load-bearing applications and also the first study to perform In vivo testing on SLM produced biodegradable iron scaffolds. In this study, for the first time, the mechanical, corrosion and biological properties of an iron-manganese scaffold manufactured using SLM were investigated. In summary the SLM-manufactured porous iron-manganese implants displayed great potential for biodegradable load-bearing bone scaffolds.
Display omitted
Central to future electronic device developments in diamond is the provision of smooth, low defect density substrate materials. This review examines plasma treatments of diamond to enable smoothing ...of rough surfaces, the removal of damage created by various non-plasma polishing processes previously applied and for patterning into device structures. The favoured reported plasma treatments for surface smoothing are detailed. The characterisation, effectiveness and other fabrication considerations of each plasma process are discussed. Despite significant recent progress the processing technology associated with plasma-etching diamond remains immature when compared to those used for conventional semiconductor materials.
Display omitted
•Substrate polishing and patterning are key to diamond device applications.•Polishing in known to introduce considerable substrate damage•Diamond is notoriously difficult to etch with conventional methods.•Recent progress with etching means low damage substrates and effective patterning approaches are emerging.•This review paper offers the reader and overview of the current state-of-the-art.
PDF
