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Students’ experiences of teachers’ ways of unpacking visual representations in the context of intermolecular forces
(John Wiley and Sons Inc, 2026) Linder, Cedric; Patron, Emelie; Clark, Jonathan
This is the third article in a series, emanating from a project that used social semiotics and phenomenography to explore therole visual representations play in the teaching and learning of chemistry. Building on our earlier work that identified fivequalitatively different ways that teachers may use to unpack visual representations in their introductory classes at uppersecondary school when dealing with intermolecular forces, this article deals with how students describe their experience ofchemistry teachers’ unpacking of visual representations. The theoretical thematic analysis, grounded in phenomenography andsocial semiotics, foregrounds qualitative differences in students’ experiences of teachers’ representational work. The resultsshow that the ways of unpacking that we previously characterized as student‐centered were described by the students as beingparticularly valuable. Here, a key point from a student perspective is that the teacher reflects on how to verbally guide themthrough the unpacking process in ways that support them in their meaning‐making. We use these results to propose thatchemistry teacher practice and education can be modified to emphasize the importance of seeing the practice of unpackingfrom a semiotic perspective. Furthermore, based on our findings and previous research in the chemistry education field, weconclude by suggesting a strategy that can be used in teacher education and by in‐service teachers as a basis for planningchemistry lessons and reflecting on them, particularly with respect to the visual representations employed.
Comparative analysis of methamphetamine’s metabolic effects onblood-brain barrier endothelial cells: an in vitro recreational versus addictive simulation
(Taylor and Francis Ltd., 2026) Fick, Kelly; Fisher, David; Makhathini, Khayelihle Brian; Willemse, Chontrelle
Methamphetamine (Meth) neurotoxicity has traditionally been attributed to monoaminergicdisruption, yet growing evidence implicates early injury at the blood-brain barrier (BBB). the brainmicrovascular endothelial cells (BMVecs), which are the core cell type of the BBB and form thecerebral capillaries, contain the highest mitochondrial density of any endothelial population. thishigh mitochondrial density is essential for maintaining the highly selectively permeable propertiesof the BBB, leaving the BMVecs and the BBB susceptible to metabolic stress. to model the twostereotypical types of Meth users, recreational and addictive, bend.5 cells were exposed to Methat physiological (0.1, 1, 10, and 20 µM) and supraphysiological (100 µM) concentrations for 24 h only(acute exposure) or daily for 96 h (chronic exposure). succinate dehydrogenase (sDh) activity,mitochondrial membrane potential (ΔΨm), intracellular reactive oxygen species (ROs) levels, andendothelial monolayer integrity were assessed. acute Meth caused transient metabolic dysfunctionin BMVecs, marked by reduced sDh activity, ΔΨm depolarization, and increased intracellular ROsproduction with subsequent metabolic recovery, however, endothelial monolayer integrity remainedimpaired long-term. chronic Meth exposure, induced sustained ΔΨm depolarization, persistent ROselevation, and prolonged decreased endothelial monolayer integrity. these findings demonstratedistinct responses to acute and chronic Meth exposure and implicate mitochondrial dysfunction asa central mechanism driving BBB endothelium disruption, potential neuroinflammation, andincreased neurological vulnerability, shifting the focus beyond classical monoaminergic toxicity andhighlight the BBB endothelium as the central contributor to Meth-induced neuropathology.
Fabrication of iridium-gold nanocomposite for the detection of selective serotonin reuptake inhibitors
(International Association of Physical Chemists, 2026) Barry, Simone; Cupido, Candice; Pokpas, Keagan; Mulaudzi, Takalani; Ngece-Ajayi, Rachel Fanelwa
A comprehensive study of the development of a novel electrochemical sensor based on iridium-gold nanocomposite (IrAuNPs) modified electrodes for the detection of antidepressants, paroxetine (PRX) and citalopram (CIT) was conducted. The sensing platform, based on a glassy carbon electrode, was modified by drop-casting IrAuNPs, which allowed for enhanced conductivity. IrAuNPs, along with their counterparts iridium nanoparticles (IrNPs) and gold nanoparticles (AuNPs), were synthesized from coffee waste extract (CWE) via complete green chemistry. The physicochemical properties of synthesized nanomaterials were characterized using ultraviolet-visible spectroscopy, dynamic light scattering, highresolution transmission electron microscopy, Fourier-transform infrared spectroscopy, cyclic voltammetry and square wave voltammetry. Results showed that the CWE could reduce the respective metallic salts to form mostly near-spherical to spherical IrAuNPs, IrNPs and AuNPs with core sizes ranging from 2.02 nm to 13.27 nm. The electrochemical sensor could determine PRX and CIT in the concentration ranges of 20 to 200 nM and 1 to 10 µM, with detection limits of 0.072 nM and 0.085 µM, respectively. The sensor showed a recovery of 86 to 115.1 %. The proposed sensor demonstrated good precision and accuracy, with excellent sensitivity and selectivity for drug identification in a rapid analysis time, which is crucial for applications in biological matrices.
Understanding the spatiotemporal variation of water quality and phytoplankton biomass in subtropical reservoir using the blue–sky multispectral data
(John Wiley and Sons Ltd, 2025) Dube, Timothy; Dalu, Tatenda; Muthivhi, Faith F.
Chlorophyll-a (chl-a) is an optically active compound used as a proxy for phytoplankton biomass to determine the trophic states of aquatic ecosystems. Blue–sky remote sensing technologies present low-cost and effective monitoring techniques for water quality on a large scale. This study was aimed at using readily available Landsat multispectral images to assess the spatial and temporal variation of phytoplankton biomass in Nandoni reservoir, Limpopo Province, and at examining the relationships that exist between the physicochemical variables and chl-a concentration. Landsat 7 ETM+ and Landsat 8 OLI images for June (dry) and December (wet), for the years 2008–2020, were used to derive the distribution of chl-a concentration. Using regression techniques, in situ measured chl-a showed a strong and perfectly linear relationship to the predicted Landsat chl-a in the Nandoni reservoir. There was a negative significant correlation between land use and land cover and water quality variables. Using permutational multivariate analysis of variance (PERMANOVA) analysis, we uncovered significant differences for chl-a concentration in sites, seasons and zones. A significant positive correlation was observed between water temperature and chl-a concentration. In contrast, a strong negative significant correlation was observed for chl-a with salinity and total dissolved solids. chl-a concentration in the Nandoni reservoir was derived using Landsat remote sensing images, suggesting that the Landsat data is suitable for monitoring small reservoirs in a short timescale. The results of this study suggest that remote sensing techniques can be used to control the development of an early warning system for this study and other reservoirs. Furthermore, the results highlight the role of using analysis ready Landsat series data in monitoring phytoplankton biomass and chl-a abundance in freshwater systems.
Crafts for H i cosmology. I. Data processing pipeline and validation tests
(American Astronomical Society, 2025) Hu, Wenkai; Yang, Wenxiu; Wolz, Laura
We present the calibration procedures and validation of source measurement with the data of the Commensal Radio Astronomy FAST Survey for H i intensity mapping by the Five-hundred-meter Aperture Spherical Radio Telescope. Using a 70 hr drift-scan observation with the L-band (1.05-1.45 GHz) 19 beam receiver, we obtain the data covering a 270 deg2 sky area. We employ both the pulsar backend and the spectrum backend to calibrate the spectral time-ordered data (TOD) before projecting them onto HEALPix maps. We produce calibrated TOD with a frequency resolution of 30 kHz and time resolution of 1 s and the map data cube with a frequency resolution of 30 kHz and spatial resolution of 2.95 arcmin2. We examine the pointing errors, noise overflow, radio-frequency interference (RFI) contamination, and their effect on the data quality. The resulting noise level is ∼5.7 mJy for the calibrated TOD and 1.6 mJy for the map, consistent with the theoretical predictions within 5% at RFI-free channels. We also validate the data by principal component analysis and find that the residual map looks thermal noise dominated after removing 30 modes. We identify 447 isolated bright continuum sources in our data matching the NRAO VLA Sky Survey catalog, with relative flux error of 8.3% for TOD and 6.6% for the map level. We also measure the H i emission of 90 galaxies with redshift z < 0.07 and compare them with H i-MaNGA spectra, yielding an overall relative H i integral flux error of 16.7%. These results provide an important first step in assessing the feasibility of conducting cosmological H i detection with CRAFTS.