New methods for bioimplant preparation: significance of biomineral structure research in marine avertebrates for further clarification of vertebrate mineralization processes

Unatoč dugogodišnjem istraživanju i upotrebi zamjenskih koštanih materijala, prirodni biomaterijali i dalje pokazuju najbolje rezultate. Uzimajući u obzir da kosti kralješnjaka kao zamjenski materijal predstavljaju potencijalni izvor zaraze, istraživači ispituju i druge biominerale manje srodnih organizama. Istraživanja provedena na morskim beskralješnjacima dovela su do razvoja i aplikacije implantata kao što je to Pro Osteon® ili Algipore®, koji postižu dobre kliničke rezultate. U ovom radu dan je prikaz najpoznatijih materijala dobivenih iz morskih organizama koji se već koriste u kliničkoj medicini ili imaju dobar potencijal za upotrebu. Navedene su i dodatne mogućnosti istraživanja morskih organizama u proučavanju patoloških procesa biomineralizacije u ljudskom organizmu.Despite years of bone replacement material research, most suitable implants still originate from natural resources. Considering the potential harmfulness of vertebrate bones as replacement materials, the attention of researchers has been oriented toward more diverse biomineral structures, like those extracted from marine invertebrates. Investigations of marine organisms have led to development and application of materials like Pro Osteon® or Algipore®, with good clinical results. The article presents a short overview of materials from marine invertebrates that are used in clinical medicine, or have good potential for medical application. Additional usage of marine invertebrates in human pathological biomineralization is also discussed

Monitoring and Guiding Pupils\u27 Problem Solving

This paper presents a discussion of the problem-solving approaches of primary and secondary school pupils in relation to the following issues: developing strategies, communicating, and receiving guidance. Guiding is the role of the teacher who should be sensitive enough to support pupils’ thinking, when necessary, but not direct it. A group of pupils (35 pupils between 10 and 19 years old) were given a geometrical problem that required them to define the number of parts created when a single plane was divided by straight lines. Each pupil tackled the problem individually, while prospective teachers from the Faculty of Education observed and guided them. After analysing the prospective teachers’ research reports on guiding pupils through the problem we came to the following conclusions: all the pupils needed guiding in order to make progress in problem solving towards general rule, most of the pupils need to learn about heuristics more systematically, prospective teachers got better inside view on thinking process for problem solving of different age groups of pupils. From the success at problem solving point of view we observed the following: until presented with a problem that required a geometrical approach, the differences among the age groups in terms of successful problem solving were not that noteworthy, the difference among age groups was observed in examples of more complex problem solving where a shift towards an arithmetical approach was needed.This paper presents a discussion of the problem-solving approaches of primary and secondary school pupils in relation to the following issues: developing strategies, communicating, and receiving guidance. Guiding is the role of the teacher who should be sensitive enough to support pupils’ thinking, when necessary, but not direct it. A group of pupils (35 pupils between 10 and 19 years old) were given a geometrical problem that required them to define the number of parts created when a single plane was divided by straight lines. Each pupil tackled the problem individually, while prospective teachers from the Faculty of Education observed and guided them. After analysing the prospective teachers’ research reports on guiding pupils through the problem we came to the following conclusions: all the pupils needed guiding in order to make progress in problem solving towards general rule, most of the pupils need to learn about heuristics more systematically, prospective teachers got better inside view on thinking process for problem solving of different age groups of pupils. From the success at problem solving point of view we observed the following: until presented with a problem that required a geometrical approach, the differences among the age groups in terms of successful problem solving were not that noteworthy, the difference among age groups was observed in examples of more complex problem solving where a shift towards an arithmetical approach was needed

Recent Advances in Catanionic Mixtures

Most surfactant mixtures display synergistic physicochemical properties, which have led to their extensive application in various technologies. Aqueous mixtures of two oppositely charged surfactants, so‐called catanionic surfactant mixtures, exhibit the strongest synergistic effect, which is manifested as high surface activity, enhanced adsorption and a low critical aggregation concentration. In addition, catanionic systems display rich phase behavior and a range of nano and microstructures, including small spherical micelles, rod‐like micelles as well as open and closed bilayers (vesicles). The spontaneous formation of catanionic vesicles is of special interest due to their various applications in nanotechnology and pharmaceutical formulations. In this chapter, the properties of catanionic mixtures of amphiphilic molecules with advantageous properties are discussed. Since numerous papers dealing with catanionic mixtures of monomeric surfactants already exist, the aim of this chapter is to summarize recent progress in mixtures of structurally different surfactants. At the end of the chapter, special emphasis is placed on applications of catanionic mixtures

Atomic force microscopy reveals new biophysical markers for monitoring subcellular changes in oxidative injury: Neuroprotective effects of quercetin at the nanoscale

Oxidative stress has been recognised as an important pathological mechanism underlying the development of neurodegenerative diseases. The biomarkers for assessing the degree of oxidative stress have been attracting much interest because of their potential clinical relevance in understanding the cellular effects of free radicals and evaluation of the efficacy of drug treatment. Here, an interdisciplinary approach using atomic force microscopy (AFM) and cellular and biological molecular methods were used to investigate oxidative damage in P19 neurons and to reveal the underlying mechanism of protective action of quercetin. Biological methods demonstrated the oxidative damage of P19 neurons and showed that quercetin improved neuronal survival by preventing H2O2- induced p53 and Bcl-2 down-regulation and modulated Akt and ERK1/2 signalling pathways. For the first time, AFM was employed to evaluate morphologically (roughness, height, Feret dimension) and nanomechanical (elasticity) properties in H2O2-induced neuronal damage. The AFM analysis revealed that quercetin suppressed H2O2-provoked changes in cell membrane elasticity and morphological properties, thus confirming its neuroprotective activity. The obtained results indicate the potential of AFM-measured parameters as a biophysical markers of oxidative stress-induced neurodegeneration. In general, our study suggests that AFM can be used as a highly valuable tool in other biomedical applications aimed at screening and monitoring of drug- induced effects at cellular level

Amorphous Calcium Phosphate Formation and Aggregation Process Revealed by Light Scattering Techniques

Amorphous calcium phosphate (ACP) attracts attention as a precursor of crystalline calcium phosphates (CaPs) formation in vitro and in vivo as well as due to its excellent biological properties. Its formation can be considered to be an aggregation process. Although aggregation of ACP is of interest for both gaining a fundamental understanding of biominerals formation and in the synthesis of novel materials, it has still not been investigated in detail. In this work, the ACP aggregation was followed by two widely applied techniques suitable for following nanoparticles aggregation in general: dynamic light scattering (DLS) and laser diffraction (LD). In addition, the ACP formation was followed by potentiometric measurements and formed precipitates were characterized by Fourier transform infrared spectroscopy (FTIR), powder X- ray diffraction (PXRD), transmission electron microscopy (TEM), and atomic force microscopy (AFM). The results showed that aggregation of ACP particles is a process which from the earliest stages simultaneously takes place at wide length scales, from nanometers to micrometers, leading to a highly polydisperse precipitation system, with polydispersity and vol. % of larger aggregates increasing with concentration. Obtained results provide insight into developing a way of regulating ACP and consequently CaP formation by controlling aggregation on the scale of interest

Editorial

The teacher plays an important role in problem solving in school, with knowledge, problem selection and the way the problem situation is conveyed, as well as by guiding students through the process of solving the problem. The greater the teacher’s competence in problem solving, the greater the likelihood that s/he will include problem situations in mathematics instruction, and thus develop this competence in the students. A leading group in the field of researching problem-solving instruction and the inclusion of problem solving in mathematics instruction is ProMath, whose aim is to examine mathematicaldidactical questions concerning problem solving in mathematics education

Primary teacher studentsʼ understanding of fraction representational knowledge in Slovenia and Kosovo

The study of primary teacher students’ knowledge of fractions is very important because fractions present a principal and highly complex set of concepts and skills within mathematics. The present study examines primary teacher students’ knowledge of fraction representations in Slo - venia and Kosovo. According to research, there are five subconstructs of fractions: the part-whole subconstruct, the measure subconstruct, the quotient subconstruct, the operator subconstruct and the ratio sub - construct. Our research focused on the part-whole and the measure subconstructs of fractions, creating nine tasks that were represented by different modes of representation: area/region, number line and sets of objects. The sample consisted of 76 primary teacher students in Slovenia and 93 primary teacher students in Kosovo. Both similarities and differ - ences of the primary teacher students’ interpretations of the representa - tions across the two countries were revealed and compared. The find - ings suggest that primary teacher students from both countries need to upgrade their understanding of fractions. The analysis confirms that the formal mathematical knowledge acquired by primary teacher students is not necessarily adequate for teaching elementary concepts in school