Statolith Formation in Cnidaria: Effects of Cadmium on Aurelia Statoliths

Statolith formation in Cnidaria was reviewed with an emphasis on Aurelia statoliths. The review provides information on the chemical composition, mechanisms of initiation of mineralization, and effects of environmental factors on Cnidarian statolith formation. Environmental factors discussed include modified sea water ingredients, X-irradiation, clinostat rotation, and petroleum oil ingredients. A detailed account of the effects of cadmium on mineralization and demineralization of Aurelia statoliths is given. Cadmium at dosages of 2 to 4 μM significantly reduces statolith numbers in developing ephyrae. At a dosage of 3 μM, cadmium accelerates statolith loss in unfed ephyrae studied at 4 and 8 days following ephyra release from strobilae. Cadmium, therefore, is shown to reduce statolith numbers in developing ephyrae and to cause greater reduction of statolith numbers in unfed ephyrae after 4 and 8 days than occurred in controls. Supplementation of Cd2+-containing artificial sea water (ASW) with calcium (3X and 5X ASW calcium content) results in higher numbers of statoliths at day 4 as compared with cadmium-treated ephyrae. At 8 days only the 5X calcium supplemented ASW Js effective in enhancing statolith numbers in Cd2+-treated ephyrae. These results suggest that cadmium competes in some manner with calcium at the mineralizing sites of Aurelia

Engineering students' actions in a mathematical modelling task: Mediating mathematical understanding in a computer algebra system

Many engineering subjects rely on the interpretation of symbolic, numeric and graphic representations. Engineering students have challenges pertaining to their mathematical understanding of their actions with a computer algebra system (CAS). We investigated how a mathematical modelling task could mediate varied levels of mathematical understanding. When engineering students are exposed to a CAS environment, they habitually engage in programming activities without considering the computerised outputs. The purpose of this paper was to ascertain South African engineering students’ actions that can mediate broader levels of mathematical understanding in a CAS by utilising the Pirie- Kieren model of growth in mathematical understanding. Thirteen participants agreed to engage collaboratively in a mathematical modelling task. The task was analysed by means of content analysis following a deductive research approach. The findings disclosed that engineering students interdepend on paper-and-pen, computerised and reflective actions in their growth of mathematical understanding. Engineering students can be assisted in mediated and folding-back actions in order to fluctuate back and forth on their way to a more sound mathematical understanding. Explicit planning and sequence of subtasks can support engineering students to merge new levels of mathematics understanding with past comprehensions. Thoroughly planned modelling tasks can mediate novel levels of mathematical understanding when engineering students learn with a CAS

Mathematics teachers’ levels of technological pedagogical content knowledge and information and communication technology integration barriers

Abstract: Many mathematics teachers struggle to effectively integrate information and communication technology (ICT) in their teaching and need continuous professional development programmes to improve their technological pedagogical content knowledge (TPACK). This article aims to identify mathematics teachers’ levels of TPACK and barriers to integrating ICT as a means to inform their continuous professional development needs. The TPACK framework of Mishra and Koehler was used as a lens for this the study. Both quantitative and qualitative research methods were utilised. Ninety-three mathematics teachers, who completed a quantitative questionnaire, reported higher levels of content, pedagogical, and pedagogical content knowledge, with comparatively lower levels of technology, technological pedagogical, and technological content knowledge. Ten of these participants also participated in semi-structured interviews and revealed six primary barriers to integrating ICT in the classroom, namely curriculum-related time constraints, technological infrastructure, impact of ICT use on the learning process, ineffective professional development, teachers’ pedagogical beliefs and poor leadership. Continuous professional development programmes addressing specific ICTintegration barriers can effect significant changes in teachers’ TPACK, which may promote better teaching and learning of mathematics

Simulated computer adaptive testing method choices for ability estimation with empirical evidence

Computer adaptive testing (CAT) is a technological advancement for educational assessments that requires thorough feasibility studies through computer simulations to ensure strong testing foundations. This advancement is especially germane in Africa being adopters of technology, and this should not be done blindly without empirical evidence. A quasi-experimental design was adopted for this study to establish methodological choices for CAT ability estimation. Five thousand candidates were simulated with 100 items simulate through the three-parameter logistic model. The simulation design stipulated a fixed-length test of 30 items, while examinee characteristics were drawn from a normal distribution with a mean of 0 and a standard deviation of 1. Also, controls for the simulation were set not to control item exposure or to use the progressive restricted method. Data gathered were analyzed using descriptive statistics (mean and standard deviation) and inferential statistics (Two-way multivariate analysis of variance: MANOVA) for testing the generated hypotheses. This study provided empirical evidence for choosing ability estimation methods for CAT as part of the efforts geared towards designing accurate testing programs for use in higher education

Ptychographic ultrafast pulse reconstruction

We demonstrate a new ultrafast pulse reconstruction modality which is somewhat reminiscent of frequency resolved optical gating but uses a modified setup and a conceptually different reconstruction algorithm that is derived from ptychography. Even though it is a second order correlation scheme it shows no time ambiguity. Moreover, the number of spectra to record is considerably smaller than in most other related schemes which, together with a robust algorithm, leads to extremely fast convergence of the reconstruction.Comment: 4 pages, 4 figures, 3 references added, new figure 2, matches published versio

Ultrathin epitaxial Fe films in vicinal GaAs(001): A study by spin-resolved photoelectron spectroscopy

Thin epitaxial Fe films have been grown on vicinal GaAs(001) substrates and their remanent magnetic properties and the degree of substrate atom diffusion investigated using synchrotron-based photoelectron spectroscopy. The vicinal Fe films, though exhibiting greater As diffusion than their singular homologues, displayed better film quality both from the structural and the magnetic points of view. The spin-resolved valence spectra of the vicinal films resemble those for crystalline bulk Fe at lower film thicknesses than for singular films

A High-Throughput Gene Silencing Approach for Studying the Interaction Between Perennial Ryegrass (\u3cem\u3eLolium Perenne\u3c/em\u3e) and the Fungal Endophyte \u3cem\u3eNeotyphodium Lolii\u3cem\u3e

Perennial ryegrass (Lolium perenne L.) and its fungal endophyte (Neotyphodium lolii) are known to establish a mutualistic association that impacts on the agronomic productivity of endophyte-infected ryegrass pastures. To study this interaction at the molecular level, a genomic resource consisting of 13,964 endophyte ESTs has been generated. However, the functions of a large proportion of these genes remain to be elucidated. Recent work has demonstrated the potential for RNA-mediated gene silencing to suppress gene expression in a sequence specific manner thus allowing for the subsequent analysis of gene function

Risk perception and emergency experience: comparing a representative German sample with German emergency survivors

People’s perception of risk and its influencing factors has become an important element of research in past decades. The present paper investigated the influence of emergency experiences on risk perception and the impact of experience and gender on the accuracy of risk perception. A representative sample of the German population was subdivided into a general survivor group who had experienced at least one emergency previously (N = 165) and a general public group with no prior emergency experiences (N = 2248), which were compared to a German sample of survivors from the EU-funded Behavior, Security, and Culture (BeSeCu) international study of human behavior in emergency situations and evacuations (N = 201). The perceived risk of different emergencies – including larger-scale events like floods and other important but often overlooked events like domestic fires – was assessed with a questionnaire. Objective risk was also calculated for different emergencies and compared to the risk perceptions of each group to provide a measure of accuracy. The results of this study showed that emergency experiences increase perceived risk, for the experienced event in particular, and this outcome was evident regardless of whether the event was a large-scale one like a natural disaster or a smaller-scale one like a fire in one’s home. Additional data from the BeSeCu survivors identified several pre-, peri-, and post-event factors that might have influenced this outcome. Further results included the finding that gender is an important factor that moderates the accuracy of risk estimations but researchers should be mindful that the presence and pattern of any gender difference in perceived risk accuracy may vary across different types of event. Possible reasons and implications of the results are discussed

Contrasting motivation and learning strategies of ex-mathematics and ex-mathematical literacy students

Abstract: This inquiry contrasts motivation and learning strategies of ex-Mathematics (Maths) and ex-Mathematical Literacy (ML) students. ML ideally delivers candidates who can make sense of and actively participate in a world of numbers and numerical arguments, but ex-ML students are excluded from many undergraduate studies at most South African higher education institutions (HEIs). Institutions employ various strategies in enhancing student transition to higher education (HE), however, such options are rare for ex-ML students. A year-long foundation programme offered by a private HEI is one exception. This inquiry employed the Motivated Strategies for Learning Questionnaire and t-test, detecting significant differences in motivation and learning strategies between 111 ex-Maths and 81 ex-ML students. The intrinsic goal orientation, task value, self-efficacy, effort regulation and test anxiety-handling abilities of ex-Maths students were significantly superior. An integrated solution process addressing academic content and social-psychological attributes to improve the motivation of ex-ML students in support of their academic development is proffered

Isolation and Characterization of Novel BTB Domain Protein Encoding Genes from Fungal Grass Endophytes

Pasture grasses belonging to the Pooideae sub-family of the Poaceae family frequently host symbiotic fungal endophytes. These include the sexual Epichloë species and the anamorphic asexual Neotyphodium species, which are thought to have evolved from Epichloë species either by the direct loss of sexual reproduction or by interspecific hybridisation. The two key temperate pasture grasses, tall fescue (Festuca arundinacea Schreb) and perennial ryegrass (Lolium perenne L.) interact with the fungal endophytes N. coenophialum and N. lolii, respectively. Large insert genomic DNA libraries are valuable resources for the discovery and isolation of genes and their regulatory sequences, for physical mapping, map-based cloning of target genes as well as for whole genome sequencing. BTB (Bric-a-brac, tram-track, broad complex) domains are highly conserved motifs of 120 amino acids in length. The domains are rich in hydrophobic amino acids, and mediate protein-protein interaction that lead to homomeric dimerisation and in some cases heteromeric dimerisation of a large number of functionally diverse proteins. The presence of BTB domains defines a large family of genes involved in various biological processes, such as the regulation of transcription, DNA binding activity and structural organisation of macromolecular structures. Genes encoding BTB domain proteins (BDP) have previously been described in viruses, yeasts, plants, nematodes, insects, fish and mammals. However, BDP genes have not as yet been described for filamentous fungi