Submicroscopic Level Research Articles

Material Characterization of Single Crystalline Cu Subjected to High Strain Rates and High Temperatures for Multiscale Simulation

The material characterization of single crystalline Cu columns was numerically carried out at the submicroscopic level. A molecular dynamics (MD) simulation was employed using the embedded-atom method (EAM) interatomic potential between a pair of Cu atoms to describe the interactions among Cu atoms. First, the relationship between mechanical properties and factors affecting their behavior were numerically investigated using a crystal structure including several defects. The factors were specimen size, strain rate, and temperature. As the specimen size increased the normalized yield stress decreased, which was similar to results obtained at other length-scale. The yield stress tended to lead to exponential strain rate-hardening and a linear temperature-softening. Next, material characterization was conducted based on these results. These computational results can lead to the development of an in silico platform to characterize material properties and MD simulation can lay the groundwork for multi-scale modeling and simulation. (Received June 16, 2017; Accepted June 29, 2017)

Utilização e avaliação de recursos digitais na elaboração conceitual sobre solubilidade de sais

O trabalho investigou a evolução das concepções de estudantes do segundo ano do Ensino Médio sobre “Solubilidade de Sais”, a partir da utilização do software educacional “Sais e Solubilidade” e após o contato formal dos estudantes com esse conteúdo. Partimos da hipótese de que os estudantes não se apropriam corretamente dos significados atribuídos ao conceito de solubilidade na dimensão submicroscópica, uma vez que estabelecem contato, na maioria das vezes, com a dimensão macroscópica (fenômeno) no cotidiano. Dessa forma, uma Situação de Ensino (SE) com o recurso do simulador possibilitou aos estudantes novos níveis de elaboração conceitual, mais próximos da dimensão submicroscópica. Realizamos o acompanhamento antes, durante e após a utilização do software e, com isso, foi possível a reorganização dos níveis explicativos e a análise da elaboração conceitual, pelos estudantes. Os resultados indicam que a utilização desse recurso propiciou melhores possibilidades de conceituação, com relação à dimensão submicroscópica.

Bruk av metaforer om kjemiske bindinger i kreativ skriving

The basis for this study is to use students' creative texts in science as a mean to gain insight into their conceptual ideas. Eight grade students' creative writing tasks (n = 26) were analyzed with respect to the conceptual metaphors that were used to describe the abstract concept chemical bonding. The conceptual metaphors were identified and sorted into two main categories; location event-structure conceptual metaphors and object event-structure conceptual metaphors. Results show that most metaphors can be categorized as location event-structure conceptual metaphors. Embodied concepts and everyday language rooted in senso-motoric experiences from students’ daily life as well as from former science education seem to play a central role when they attempt to make meaning of the abstract concept ‘chemical bonding’ within a creative writing context. Creative writing tasks in science may have an unutilized potential for both uncovering and developing understanding of abstract phenomena on sub-microscopic level, such as chemical bonding.

Analysis of Student’s Conception on Neutralisation: A Qualitative Study

Knowledge of chemistry involves abstract concepts and it should be explained in three representative levels, namely, macroscopic representative level, sub-microscopic representative level and symbolic representative level. The success of students in mastering the concepts of Chemistry is closely related to their ability to create relationships among the three levels of representation. Relying on this basis, the purpose of this study is to analyse the student’s conception of neutralisation according to these three representation level. The sample of the study constituted of 30 science stream students. The study was conducted by using Chemistry Achievement Test (CAT) as an instrument. The CAT is based on the multiple representations, developed according to the Malaysian context by the researcher. The data collected from the test were interpreted and analysed qualitatively. Based on the analysis carried out, a number of major difficulties and mistakes often experienced by the students at all the representation levels were identified. Among the mistakes were, the students could not relate between the number of particles which had reacted and that which had not during the neutralisation process. They also failed to determine the colour change of phenolphthalein on reaching the end point of the titration process. Other than that, the results also indicated that, the sub-microscopic level was the most problematic for them.

Development of Teaching Material Oxidation-Reduction Reactions through Four Steps Teaching Material Development (4S TMD)

This research aims to develop oxidation-reduction reactions (redox) teaching material used the Four Steps Teaching Material Development (4S TMD) method consists of four steps: selection, structuring, characterization and didactical reduction. This paper is the first part of the development of teaching material that includes selection and structuring steps. At the selection step, the development of teaching material begins with the development concept of redox based on curriculum demands, then the development of fundamental concepts sourced from the international textbook, and last is the development of values or skills can be integrated with redox concepts. The results of this selection step are the subject matter of the redox concept and values can be integrated with it. In the structuring step was developed concept map that provide on the relationship between redox concepts; Macro structure that guide systematic on the writing of teaching material; And multiple representations which are the development of teaching material that connection between macroscopic, submicroscopic, and symbolic level representations. The result of the two steps in this first part of the study produced a draft of teaching material. Evaluation of the draft of teaching material is done by an expert lecturer in the field of chemical education to assess the feasibility of teaching material.

The Binary System Laboratory Activities Based on Students Mental Model

Generic science skills (GSS) are required to develop student conception in learning binary system. The aim of this research was to know the improvement of students GSS through the binary system labotoratory activities based on their mental model using hypothetical-deductive learning cycle. It was a mixed methods embedded experimental model research design. This research involved 15 students of a university in Papua, Indonesia. Essay test of 7 items was used to analyze the improvement of students GSS. Each items was designed to interconnect macroscopic, sub-microscopic and symbolic levels. Students worksheet was used to explore students mental model during investigation in laboratory. The increase of students GSS could be seen in their N-Gain of each GSS indicators. The results were then analyzed descriptively. Students mental model and GSS have been improved from this study. They were interconnect macroscopic and symbolic levels to explain binary systems phenomena. Furthermore, they reconstructed their mental model with interconnecting the three levels of representation in Physical Chemistry. It necessary to integrate the Physical Chemistry Laboratory into a Physical Chemistry course for effectiveness and efficiency.

A Novel Gametocyte Biomarker for Superior Molecular Detection of the Plasmodium falciparum Infectious Reservoirs.

Complete malaria eradication and optimal use of transmission-reducing interventions require knowledge of submicroscopic infectious reservoirs among asymptomatic individuals. Even submicroscopic levels of Plasmodium falciparum gametocytes can infect mosquitoes and promote onward transmission. Most efforts to identify gametocyte carriers use polymerase chain reaction amplification of the gametocyte-specific transcript Pfs25. To expand the repertoire of biomarkers available for superior gametocyte detection, we compared the gene expression profiles of gametocytes and asynchronous blood-stage P. falciparum parasites by microarray technology. This allowed the identification of 56 molecules abundantly expressed in the gametocyte stage of the parasite. The analytical sensitivity for gametocyte detection was evaluated for 25 genes with the highest expression levels. One candidate, Pfg17, exhibited superior analytical sensitivity against a panel of gametocyte-spiked whole blood, detecting 10 gametocytes/mL; in comparison, Pfs25 detected only 25.3 gametocytes/mL. Pfg17 also exhibited superior clinical sensitivity, identifying 19.1% more samples from blood-film microscopy-negative Ghanaian children and 40% more samples from asymptomatic adults as gametocyte positive. Cumulatively, our results suggest Pfg17 is an excellent biomarker for detecting asymptomatic infectious reservoirs otherwise missed by the most sensitive molecular method available. Our study has also improved the repertoire of transmission-stage antigens available for evaluation as candidate vaccines.

Novel Study Guides for Biochemistry Meaningful Learning in Biology: a Design-Based Research

One of the difficulties for biochemistry learning is the persistence of traditional teaching methods, based on transmission and memorization of abstract and detailed information, usually in a decontextualized way. Such scenario results in surface learning and content reproduction. In order to address these problems, three interventions in a discipline (Metabolism) for Biology majors were applied, in the form of innovative teaching tools (study guides). OBJECTIVES: The main goal is to evaluate the impact of these interventions on interest, motivation, and learning of the metabolic pathways. MATERIALS AND METHODS: We describe the development, application, and evaluation of two study guides – one created from a problem used as a contextual connection for glycogen metabolism study and another embedding an integrative view based on glutamate metabolism. Both materials were guided by broad themes like evolution, metabolic adaptation, and comparative biochemistry. The development of the study guides combined submicroscopic (molecular) and macroscopic (body, environment) levels, aiming to motivate reading and discussion. A design-based research with cycles of application and assessment was carried out, by means of classroom observation, grade analysis in written exams, and students’ interviews. RESULTS AND DISCUSSION: In general, based on in-class student feedback to professors and to the researcher in the interviews, the study guides arouse curiosity and fostered peer discussion. Final average grades indicate a good global performance in all proposed activities. Whole data from study guides’ application in classroom evidenced their impact on interest, motivation, and learning. The strategy of developing problem or integrative situation linking molecular (micro) and contextual (macro) levels were helpful to foster critical thinking and to value topics of scientific literacy. CONCLUSIONS: Analysis and interpretation of the results point to benefits for teaching and learning, with helpful information to guide elaboration and refinement of new teaching materials and to make active learning more meaningful.

IDENTIFICATION OF THE UNDERSTANDING OF THE STATES OF MATTER OF WATER AND AIR AMONG SLOVENIAN STUDENTS AGED 12, 14 AND 16 YEARS THROUGH SOLVING AUTHENTIC TASKS

The aim of the research was to identify how Slovenian primary and secondary school students of various age groups explain the particulate nature of the states of matter of water and air. The qualitative research included five 12, 14, and 16 year old students. A semi-structured interview including four computer-displayed tasks was used for the data collection. The research results show that all of the students correctly identified the states of matter of water at the particulate level, but not of air. It was found that the students had difficulty justifying their selection. The study confirmed the existence of: (a) misunderstanding regarding the interpretation of the particulate nature of matter, (b) a failure to distinguish between particle and matter, and (c) the inadequate description of submicroscopic level of matter with macroscopic level concept. The survey results provide an insight into the mindset of students and serve as a starting point for teachers’ lesson planning. Keywords: authentic tasks, macroscopic level, misunderstanding of pressure, states of matter, submicroscopic level.

A sensitive species-specific reverse transcription real-time PCR method for detection of Plasmodium falciparum and Plasmodium vivax

As the global burden of malaria decreases and countries strive towards disease elimination, there is a greater demand for sensitive diagnostics to target the submicroscopic reservoir of infection. We describe here a sensitive species-specific RT-qPCR method to differentiate between Plasmodium falciparum and P. vivax infections at the submicroscopic level. With amplification of the 18S rRNA genes from total nucleic acids (both DNA and RNA), we discern P. falciparum and P. vivax with a limit of detection of 10parasites/mL and 18copies/μL, respectively. This assay was validated with 519 blood samples, negative by thick-smear, from febrile and asymptomatic cohorts from Colombia. These results were directly compared to a qPCR-based method (DNA only) as the gold standard. Of the samples from patients who presented with fever (n=274), 34 infections were identified by RT-qPCR (16 P. falciparum, 15 P. vivax, and 3 mixed), of which only 10 infections were identified at the species level by qPCR. Within the asymptomatic cohort (n=245), 13 infections were identified by RT-qPCR (3 P. falciparum, 3 P. vivax, and 7 mixed), whereas the species for only one infection was determined by qPCR. We conclude that this species-specific RT-qPCR method provides a more sensitive tool for species identification compared to DNA based qPCR methods.

Simultaneous enhancement of ductility and strength in AISI 1080 steel through a typical cyclic heat treatment

In view of obtaining high ductility along with reasonable strength through accelerated lamellar disintegration process, a typical cyclic heat treatment consisting of a short duration (6min) holding at 775°C (above A1) followed by air cooling (at two different rates, viz. still air cooling and forced air cooling at an air flow rate of 8.7m3h−1) is executed on an annealed AISI 1080 steel up to 4 cycles. Substantial enhancement in the kinetics of lamellar disintegration is observed with durations of 44min and 2h 26min under cyclic forced air cooling and cyclic still air cooling, respectively. In case of cyclic still air cooling, under relatively slower cooling rate, the ‘lamellar thickening’ and ‘divorced eutectoid growth’ are augmented which tend to increase the size (greater than 1µm) of fragmented cementite particles (up to 3 cycles) and promote the generation of more spheroids in divorced eutectoid region (DER) with progress of cyclic heat treatment. Accordingly, as %DER increases with number of heat treatment cycles, hardness and strength properties gradually decrease up to 3 cycles and remain almost unaltered thereafter on execution of 4th cycle; while ductility increases gradually up to 4 cycles. On contrary, by virtue of the generation of more lamellar faults (cooling rate being faster), an intense ‘lamellar disintegration’ is observed in case of cyclic forced air cooling. This tends to reduce the size of fragmented cementite particles (to submicroscopic level) with progress of cyclic heat treatment. Furthermore, faster cooling (more degree of undercooling) promotes the generation of more plate shaped (non-spheroid) cementite particles with progress of cyclic heat treatment. Accordingly, under cyclic forced air cooling, strength properties and ductility gradually increase simultaneously with number of heat treatment cycles that leads to a substantially high ductility (%Elongation=34) along with reasonable strength (UTS=942MPa) after 4 cycles.

A Study of Oil Viscosity Mental Model

There is no study regarding on how to learn viscosity of the liquid (e.g. oil) by interconnecting macroscopic, sub-microscopic and symbolic levels. Therefore, the purpose of this research was to study the mental model of the oil viscosity. Intermolecular attractive force of oil constituent on the sub-microscopic level is depicted in the form of mental models. In this research, the viscosity data for some types of oil was measured by using Hoppler method. Viscosity of mineral oil SAE 20W-50, mineral oil SAE 15W-40 and synthetic oil SAE 10W-40 were 1.75, 1.31, and 1.03 Pa s, and the densities of these oils were 908.64, 885.04, and 877.02 kg/m3, respectively. The results showed that the greater density of the mineral oil that is assumed to be composed of linear chains of hydrocarbons, the longer the chain of hydrocarbon linear. Consequently, there are stronger the London force and greater the oil viscosity. The density and viscosity of synthetic oil are lower than that of both mineral oils. Synthetic oil structurally forms polymers with large branching. This structure affects a lower synthetic oil viscosity. This study contributes to construct a mental model of pre-service chemistry teachers.

Prospective Primary School Teachers’ Understanding on States Of Matter and Their Changes

This study investigated Prospective Primary School Teachers (PPST)’ conceptual understandings on states of matter and their changes. Data were collected from 37 students Primary School Teacher Education Program. The students were given open-ended questions that explored their understandings on states of matter and their changes divided into macroscopic, submicroscopic and symbolic levels. Their understandings were divided into categories: understand, partial understand, misconception, and do not understand. The results showed that almost all students understood that matters are composed of particles. But most of them did not understand that between the particles exists “particle-free space”. Almost all students knew most of phenomena (macroscopic level) related to states of matter and their changes. However, most of them could not explain the phenomena at submicroscopic and symbolic levels. At these levels, their understandings were still largely in the categories of partial understanding, misconception, or do not understand. Given these results it can be concluded that most of the students did not have fully understandings on states of matter and their changes. These results imply the need for improving the teaching and learning quality on states of matter and their changes for PPST in Indonesia.

A quantitative method to determine preservice chemistry teachers' perceptions of chemical representations

Chemical representations serve as a cornerstone to guide the teaching of chemistry concepts. The influence that a chemical representation has on instruction is largely dependent on how well the viewer interprets the information in the representation. Teachers serve as a guide to the students as they point out and make connections between the features present in a chemical representation. To influence how well the teacher serves as a guide it is important to develop teachers' pedagogical content knowledge as it relates to visualizations. As a first step towards developing this area of teaching expertise it is crucial to develop an understanding of how preservice chemistry teachers perceive a variety of chemical representations. To this end, this paper presents a novel card-sorting methodology that utilizes Johnstone's triangle as a continuum to determine how chemistry preservice teachers perceive representations relative to the presence of each of the three representational levels: macroscopic, submicroscopic, and symbolic. This study has determined that this methodology is both valid and reliable among a group of chemistry preservice teachers. The participants were able to effectively detect the presence or absence of the macroscopic domain. However, there was greater variance when the symbolic and submicroscopic levels were present. In addition, variance among the participants’ responses also increased dramatically when multiple levels were present in one representation. This was largely a result of what key features the participant focused on while viewing the card. The variance results of this study, along with the accompanying rationales for the placement of the cards, serve to inform the development of practices to further foster preservice chemistry teachers’ pedagogical-visual-content-knowledge (PVCK).

Plasmodium falciparum genotype and gametocyte prevalence in children with uncomplicated malaria in coastal Ghana.

Background Plasmodium falciparum gametocytes are vital to sustaining malaria transmission. Parasite densities, multiplicity of infection as well as asexual genotype are features that have been found to influence gametocyte production. Measurements of the prevalence of Plasmodium sp. gametocytes may serve as a tool to monitor the success of malaria eradication efforts.MethodsWhole blood was collected from 112 children aged between 6 months and 13 years with uncomplicated P. falciparum malaria attending three health facilities in southern Ghana from June to August, 2014 before (day 0) and 4 days after completion of anti-malaria drug treatment (day 7). Malaria parasites were observed by microscopy and polymerase chain reaction (PCR); submicroscopic gametocyte carriage was measured by a Pfs25 (PF3D7_1031000) mRNA real time reverse transcriptase polymerase chain reaction (RT-PCR). Parasite genotyping was performed on gDNA extracted from dried filter paper blood blots by amplification of the polymorphic regions of msp1 (PF3D7_0930300) and msp2 (PF3D7_0206800) using PCR.ResultsMicroscopy estimated 3.1% (3/96) of the total population to carry gametocytes on day 0, which decreased to 2.1% (2/96) on day 7. In contrast, reverse transcriptase-real time PCR (RT-PCR) analysis of a subset of 35 samples estimated submicroscopic gametocyte carriage to be as high as 77% (27/35) using primers specific for Pfs25 (CT < 35) on day 0 and by day 7 this only declined to 60% (21/35). Genotyping the msp2 gene identified higher levels of MOI than the msp1 gene.ConclusionsAlthough below detection by microscopy, gametocyte prevalence at submicroscopic levels are high in this region and emphasize the need for more effective elimination approaches like the development of transmission-blocking vaccines and safer gametocytocidal drugs.Electronic supplementary materialThe online version of this article (doi:10.1186/s12936-016-1640-8) contains supplementary material, which is available to authorized users.

Investigating How Science Teachers in South Africa Engage with all Three Levels of Representation in Selected Chemistry Topics

This article aims to investigate how science teachers engaged with the macroscopic, sub-microscopic and symbolic levels of representations in their Chemistry teaching. Data were collected in Limpopo province in South Africa from 15 ‘lead’ teachers and this paper reports on five lessons presented by the teachers during professional development workshops. The ‘lead’ teachers were selected by the Department of Education based on their qualifications, years of experience and results of their learners over the years. Data were gathered from video-recorded peer teaching lessons, field notes and post-lesson interviews. The findings show that the teachers in this study mainly focused on the symbolic and sub-microscopic level and did not engage with the content at all three levels, even though they participated in a professional development programme specifically geared towards the integration of all three levels. These findings, although they cannot be generalised because of the small sample size, indicate a need for changes in the pre-service and in-service teachers’ training, and in the curriculum in South Africa. The challenge facing the teaching of Chemistry in South Africa is to evolve suitable didactic practices to preserve the unity of Chemistry at all three levels of representation.

Virtual Laboratory in the Role of Dynamic Visualisation for Better Understanding of Chemistry in Primary School

Understanding chemistry includes the ability to think on three levels: the macroscopic level, the symbolic level, and the level of particles – sub-microscopic level. Pupils have the most difficulty when trying to understand the sub-microscopic level because it is outside their range of experience. A virtual laboratory enables a simultaneous demonstration of all three levels of a chemical concept along with dynamic visualisation at the submicroscopic level. This study presents the effective usage of a virtual laboratory that can overcome the gap between the previously-mentioned conceptual levels. We carried out a didactic experiment to test the effectiveness of a virtual laboratory that enables dynamic visualisation. The experiment involved seventh-grade pupils (N = 109) from five different primary schools in Slovenia. We asked ourselves the question as to whether the learning outcomes of pupils are better when they use a virtual laboratory rather than in science classes without a virtual laboratory where dynamic visualisation at the submicroscopic and sub-micro levels are only explained by means of static demonstrations. A virtual laboratory has many significant advantages. The results of the didactic experiment showed that, in terms of knowledge acquisition, using a virtual laboratory is better than science classes without visualisation elements.

Polymers and Cross-Linking: A CORE Experiment To Help Students Think on the Submicroscopic Level

The Polymers and Cross-Linking experiment is presented via a new three phase learning cycle: CORE (Chemical Observations, Representations, Experimentation), which is designed to model productive chemical inquiry and to promote a deeper understanding about the chemistry operating at the submicroscopic level. The experiment is built on two familiar activities often used in public outreach: mixing solutions of poly(vinyl alcohol) and sodium borate, producing the substance known as “slime”, and linking paper clips as an analogy to represent polymers. In phase 1 of the CORE experiment, students prepare slime, and explore the properties of the separate solutions and slime. In phase 2, students use analogical reasoning to think about a representation for considering the chemistry at the submicroscopic level. The analogy activity includes using an Analog to Target Worksheet to carefully consider similarities and differences between the analog (paper clip chains) and target (polymers). Phase 3 begins with pairs of...

Hyperspectral backscatter imaging: a label-free approach to cytogenetics.

Current techniques for chromosome analysis need to be improved for rapid, economical identification of complex chromosomal defects by sensitive and selective visualisation. In this paper, we present a straightforward method for characterising unstained human metaphase chromosomes. Backscatter imaging in a dark-field setup combined with visible and short near-infrared spectroscopy is used to monitor morphological differences in the distribution of the chromosomal fine structure in human metaphase chromosomes. The reasons for the scattering centres in the fine structure are explained. Changes in the scattering centres during preparation of the metaphases are discussed. FDTD simulations are presented to substantiate the experimental findings. We show that local scattering features consisting of underlying spectral modulations of higher frequencies associated with a high variety of densely packed chromatin can be represented by their scatter profiles even on a sub-microscopic level. The result is independent of the chromosome preparation and structure size. This analytical method constitutes a rapid, cost-effective and label-free cytogenetic technique which can be used in a standard light microscope. Graphical abstract Hyperspectral backscatter imaging for label-free characterization.

Incorporating measurable (‘minimal’) residual disease-directed treatment strategies to optimize outcomes in adults with acute myeloid leukemia

Curative-intent therapy leads to complete remissions in many adults with acute myeloid leukemia (AML), but relapse remains common. Numerous studies have unequivocally demonstrated that the persistence of measurable (‘minimal’) residual disease (MRD) at the submicroscopic level during morphologic remission identifies patients at high risk of disease recurrence and short survival. This association has provided the impetus to customize anti-leukemia therapy based on MRD data, a strategy that is now routinely pursued in acute promyelocytic leukemia (APL). While it is currently uncertain whether this approach will improve outcomes in AML other than APL, randomized studies have validated MRD-based risk-stratified treatment algorithms in acute lymphoblastic leukemia. Here, we review the available studies examining MRD-directed therapy in AML, appraise their strengths and limitations, and discuss avenues for future investigation.