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Past research repeatedly revealed students' struggles to understand chemical equilibria, especially concerning their dynamic nature. Black-box simulations have proven to be helpful here. However, the effect is strongly dependent on the quality of teaching, the design principles of which are not yet fully known. One aspect of debate concerns the nature of supportive learning tasks, which require students to activate, construct and reflect on their mental models to foster conceptual understanding. In this paper, we investigate how drawing-assisted simulation-based learning promotes conceptual understanding of chemical equilibria in comparison to single-choice tasks. Both types of supporting tasks involve simulation-based activities according to the German instructional design SIMMS ("Simulation-based Instruction for Mental Modelling in School"), which requires students to construct their own explanations and predictions on a chemical system before exploring it "via" molecular dynamics simulations and revising their explanations and predictions retrospectively. In a quasi-experimental intervention study with 174 German high school students of ten chemistry courses (tenth grade), two treatment groups (drawing group and single-choice group) were compared with a control group, assessing the progress in conceptual understanding during simulation-based learning "via" drawings and explanations as well as pre- and post-intervention "via" questionnaire. Our findings reveal similar effects of drawing tasks and elaborate single-choice tasks on conceptual understanding of chemical equilibria. For equilibrium dynamics specifically, simulation-based settings featuring drawing tasks seem to be slightly more effective than simulation-based settings featuring elaborate single-choice-tasks in fostering understanding. What is more, simulation-based settings on the divergent phenomenon of Le Chatelier (where different final states emerge from the same initial state, depending on the nature of external perturbation) seem to be more efficient than those on the convergent nature of chemical equilibria (where several initial states with different educt/product ratios yield the same final state in equilibrium) in fostering student understanding irrespective of the mode of the supportive learning task.

The Environmental education navigates students towards environmentally friendly life style and securing a quality of life. The implementation of cross-section topics, including the Environmental education, into science classes, is possible through a variety of techniques. One of the least used methods is a real school experiment. The following paper presents the experiment, by which we simulate the combustion of PVC and observe the impact of combustion products on plants via UV-Vis spectrophotometry optical method. This method is suitable for qualification and analysis of vegetable pigments, i.e. chlorophylls, carotenoids, and anthocyanins. The experiment is integrated into the Techniques and Didactics of School Chemistry Experiments as a part of master degree course, which prepares students for the Chemistry teaching profession. The introduced experiment enables pedagogues to integrate the environmental education into teaching process and develop mathematical and science literacy of students in the Chemistry education.

A suitable combined laboratory experiment can involve more chemical disciplines and form students' views on practical connections. A laboratory experiment has been prepared focusing on the adsorption of the dangerous Co(II) ion using natural adsorbents representing waste material of a polysaccharide and keratin nature. Efficiency of Co(II) adsorption has been analyzed using an atomic adsorption spectroscopy method, and the adsorption results have been mutually compared. The students have acquired basic skills with an application of batch adsorption as well as with a spectral determination of the Co (II) adsorbate quantity. The importance of the experiment can be reflected in the context of the protection of the environment as well as circular economics.

The topic of "teacher professionalism" is one of the most crucial ones in quality education research. It has a potential to generate results that could inform and hence enhance the practice in classrooms. Thus, research in this field needs reliable instruments to measure the professional knowledge of our teachers to be able to generate reliable results for our research problems. Not many instruments have been developed with regard to this topic. At the same time, an adequate validation of the instrument developed is often missing (Schilling & Hill, 2007). Hence, in a bigger project "ProwiN" (German acronym for professional knowledge of science teachers), test instruments for measuring science teachers' pedagogical, pedagogical content and content knowledge (PK, PCK, and CK) were developed for the subjects biology, chemistry and physics. The present study tested the validity of some of these items which were used to measure the pedagogical content knowledge (PCK) of biology teachers. These items focused on measuring teachers' professional knowledge by analyzing 1) teachers' "knowledge about student understanding" (or lack of understanding) of several topics in biology and 2) "knowledge about instructional strategies" like the use of models or experiments. The content validity of these instruments was examined by think-aloud interviews with American and German Biology teachers (N = 11). This study shows a high content validity for these items. Furthermore, this paper demonstrates the scope for adapting the conceptual framework of these items to measure biology teachers' PCK in other countries.

Chemistry is a school subject that is not viewed favorably among pupils. Before we can improve pupils' attitudes toward chemistry, it is important to find out the problem as to why the attitudes are relatively negative. The research was focused on Czech lower secondary and secondary grammar school pupils' attitudes to the subject of chemistry. Also, the difference between groups of variables (gender and grade) was examined. The sample size contained 931 Czech lower secondary and secondary grammar school pupils. The research tool was a questionnaire with 25 Likert type items. By the use of factor analysis, the items were distributed into four categories: 1) Popularity and difficulty of chemistry, 2) The relevance of chemistry, 3) Chemical aids and laboratory experiments, 4) The future life and chemistry. The overall score indicated neutral/slightly positive pupils' attitude toward chemistry. Girls received a lower score in comparison with boys in all grades, except the 1st grade, in secondary grammar schools. The opposite situation was among lower secondary school pupils, where girls achieved a slightly higher attitude score. It is possible to say that negative attitudes toward chemistry are also among lower secondary and secondary grammar school pupils, so it is needed to try to improve attitudes toward chemistry from the early age of pupils. The recommendations for the pedagogical practice are suggested in the conclusion.

A new concept for affordable supercapacitors based on Al aqueous electrolytes was proposed recently. This study provides a deeper insight into the cyclic performance of vine shoots-derived activated carbon using three different 1 M aqueous electrolytes: Al2(SO4)3, Al(NO3)3 and AlCl3. Cyclic voltammetry (CV), galvanostatic cycling and impedance measurements have shown that the type of anion causes the differences in the rate capability and long-term cyclability. Although CV deviation is provoked by aggravated sulphate penetration into pores upon switching at higher currents, Al2(SO4)3 emerged as the most promising electrolyte solution due to the best cycling stability of the 1.5 V full cell over 15,000 cycles. Intensive oxidation of the positive electrode during initial cycling, induced by nitrates reduction, is the main reason for the fastest capacitance drop observed in Al(NO3)3. Therefore, the capacitance values of the carbon cell measured after 5,000 cycles in Al(NO3)3 (75 F g-1) are two times lower than the corresponding values in Al2(SO4)3 and AlCl3 (131 and 127 F g-1, respectively). The oxidation becomes more pro­nounced only after 10,000 cycles in AlCl3, thus causing a notable capacitance drop, which is not evidenced in Al2(SO4)3. Al2(SO4)3-based cell can withstand 15,000 with good specific capacitance/energy retention.

Dynein, a motor protein, harnesses chemical energy from ATP hydrolysis to generate mechanical output as it travels along microtubular tracks. Essential to this process is the microtubule-binding domain (MTBD), which facilitates the interaction with and detachment from microtubules. Previous studies have proposed that the mechanism governing this interaction is primarily driven by the coiled-coil stalk attached to the MTBD. However, conflicting arguments suggest the presence of two-way communications, where the binding and unbinding mechanisms may also influence the nucleotide state of dynein. In this study, we employed all-atom explicit solvent simulations, enhanced sampling techniques, and coarse-grained methodologies to systematically investigate the effects of stalk and MT on the structural stabilities of different conformations of MTBD and their sequence of events during the transition from one to another. We found that the globular MTBD domain without stalk and MT predominantly resides in its weak binding configuration. Upon introduction of a limited length of stalk and interaction with MT, a balance between the strong and weak binding configurations is restored. Further introduction of the full-length stalk and interaction with MT strengthen the kinetic stability of these two configurations. We have also explored the sequence of events of the relevant transition between these two states using coarse-grained simulation protocols both in the presence and absence of interaction with MT. In the absence of MT interactions, we found a mixed conformational state of the system that corresponds to the already published crystal structure of Dynein. In the presence of MT, the conformational change of the stalk precedes the conformational change of the MTBD globular domain. Our findings support the view that the nucleotide state of the AAA+ ring determines the state of the MTBD domain through stalk, shedding light on the intricate mechanisms governing dynein's interaction with microtubules.

We have analytically explored the thermodynamics of free Bose and Fermi gases for the entire range of temperature, and have extended the same for harmonically trapped cases. We have obtained approximate chemical potentials for the quantum gases in closed forms of temperature so that the thermodynamic properties of the quantum gases become plausible, especially in the intermediate regime between the classical and quantum limits. (Contains 3 figures.)

Nanoscience and nanotechnology currently represent one of the most rapidly developing fields of science and technology; therefore, the fundamental principles of nanoscience and nanotechnology should be understood by college and even high school students as well as by members of scientific communities. Silver, as the pioneer material in these fields, can be considered the appropriate guide on the voyage from the macro- to the nanoworld revealing the changes in fundamental properties of matter. We suggest a set of experiments that offer the preparation of silver mirror (macroscopic silver), submicroscopic "black" colloidal particles (less than 465 nm), and also nanoscopic "orange" particles (40 nm). Interestingly, all of these forms of silver can be prepared via the well-established Tollens reaction using just the variation in the initial concentrations of the reaction components. The macroscopic silver particles can be detected as a result of their typical metal shine. The colloidal and the nanoscopic silver particles, prepared in aqueous dispersions, can be simply detected with a laser pointer because of the Tyndall effect. However, more sophisticated methods like UV-vis absorption spectroscopy, dynamic light scattering, or transmission electron microscopy can be employed for the appropriate characterization of all of the prepared silver particles. (Contains 4 figures.)

The high-stakes Lebanese Brevet examinations are undertaken by almost all school students at the end of year 9 and include papers in Chemistry and Physics. This research presents an analysis of the 2007 examinations in these two science subjects using official statistics and response patterns arising from samples of candidate scripts. The examinations themselves appeared to be a significant source of student shortcomings, and recommendations are put forward to address their deficiencies and exploit their potential feedback functions.

This paper presents an original undergraduate student project in theoretical mechanics: a demonstration of theory and experiment agreement inspired by a recently theoretically treated mechanical problem of coupled rolling motion of two cylinders. The problem of a mechanical system subjected to non-holonomic constraints is theoretically and numerically solved. Subsequently, the solution is quantitatively verified by a simple and inexpensive experiment, originally proposed and constructed by the authors. The comparison of results of the theoretical study with experimental output shows that there are instruments to directly verify rather abstract mathematical theories even on the undergraduate level. Moreover, combining the theoretical description of the problem with an appropriate laboratory experiment and computational procedures gives students a more complex view of the physical problem as a whole. This paper can be used by physics teachers on the undergraduate university level as an inspiration for an interesting student project. Moreover, the theoretical part of this paper itself can be used by interested intermediate students themselves as a good exercise in theoretical mechanics. (Contains 1 footnote and 5 figures.)

Using electrocatalytic water reduction to produce hydrogen fuel offers significant potential for clean energy, yet its large-scale adoption depends on developing cost-effective, non-precious, and efficient catalysts to replace expensive Pt-based state-of-the-art HER catalysts. The catalytic HER performance of an active catalyst largely depends on the available catalytic active sites, conductivity, and intrinsic electrochemical kinetics, all of which can be altered by incorporating a heteroatom into the active catalyst structure. Herein, we synthesized a unique nitrogen-doped CuO@CuS (NCOS) core–shell-structured catalyst through a facile hydrothermal process followed by an efficacious nitrogenation process, and its electrochemical performance for the HER was systematically analyzed. The NCOS core–shell-structured catalyst exhibits a reduced overpotential (55 mV) and Tafel slope (107 mV dec−1) compared to the pure CuS (CS; 179 mV and 201 mV dec−1) catalyst at a current density of 10 mA cm−2. Moreover, the NCOS core–shell-structured catalyst demonstrates excellent endurance for up to 50 h of chronopotentiometric testing at a driving current density rate of 10 and 100 mA cm−2. This excellent catalytic HER activity is a result of an increased electron transfer rate and a greater number of accessible active sites, attributed to a change in structural properties and the high electronic conductivity aroused from nitrogen incorporation, as evidenced from the TOF and EIS curve analyses.

Edible insects have been officially classified as food in the European Union since 2015. Currently, four insect species are approved for food use. However, no official method for detecting insects in food has been recognized to date. To establish a simple analytical method for insect detection in food, we developed an indirect sandwich (enzyme-linked lectin sorbent assay) ELLA specific for N-acetylglucosamine in chitin and chitosan polymers. The validation of the method demonstrated that the ELLA developed in this study is reliable for insect detection. The limit of detection (LOD) and quantification (LOQ) were 0.006 and 0.028 mg/mL, respectively. Intra-day precision ranged from 2.45% to 30.29%, and inter-day precision from 0.36% to 12.87%. Significant differences in the total amount of chitin and chitosan were observed among the insect products, processed insect products, and samples without any insect addition (p < 0.05).

Summary: Here, we present a protocol for the synthesis of dibenzo[c,e]oxepin-5(7H)-ones starting from 2′-alkyl-[1,1′-biphenyl]-2-carboxylic acids. This technique uses two copper(0)-catalyzed benzylic C(sp3)−H activation strategies taking either di-tertbutyl peroxide or gaseous oxygen as an oxidant. We detail a photocatalytic thermal approach for copper powder-catalyzed reaction with oxygen. We also describe a procedure for catalyst recycling in both the strategies. The product has been successfully synthesized both in mmol and gram scale.For complete details on the use and execution of this protocol, please refer to Nandi et al. (2022). : Publisher’s note: Undertaking any experimental protocol requires adherence to local institutional guidelines for laboratory safety and ethics.

In this study, a new series of aliphatic, cyclic, and heterocyclic derivatives of haemanthamine was designed and synthesized to enhance its inhibitory effect on the proliferation and viability of cancer cells. A library of haemanthamine derivatives was subjected to 10 μM single-dose cytotoxicity screening against a panel of human cell lines of various histotypes. Initial cytotoxicity evaluation of the parent haemanthamine (1) and a series of twenty-nine (2–30) semisynthetic analogues showed that for some of the newly formed derivatives, a certain cytotoxic effect was observed, in one case even higher than that of the parent compound. Specifically, 11-O-(4-chloro-3-nitrobenzoyl)haemanthamine (21) showed an enhanced antiproliferative effect, where the mean growth percent (GP) value was 5% compared to haemanthamine, leading to a decrease in the GP to 25%. Among ten cell lines tested, derivative 21, bearing a substituted aromatic ester bond via C-11 of haemanthamine, had excellent activity for inhibiting the growth of HeLa (IC50 = 0.2 ± 0.1 μM), A549 (IC50 = 1.7 ± 0.1 μM) and HT-29 (IC50 = 2.2 ± 0.1 μM) cells. When evaluating response kinetics, we found that 21 and haemanthamine dose- and time-dependently suppressed the proliferation of A549 cells. In contrast to haemanthamine (1), Trypan blue and lactate dehydrogenase (LDH) release assay revealed that 21 was capable of reducing the survival of A549 cells.

Summary: Selective C‒H functionalization in a pool of proximal C‒H bonds, predictably altering their innate reactivity is a daunting challenge. We disclose here, an expedient synthesis of privileged seven-membered lactones, dibenzo[c,e]oxepin-5(7H)-one through a highly chemoselective benzylic C(sp3)‒H activation. Remarkably, the formation of widely explored six-membered lactone via C(sp2)‒H activation is suppressed under the present conditions. The reaction proceeds smoothly on use of inexpensive metallic copper catalyst and di-tert-butyl peroxide (DTBP). Owing to the hazards of stoichiometric DTBP, further, we have developed a sustainable metallic copper/rose bengal dual catalytic system coupled with molecular oxygen replacing DTBP. A 1,5-aryl migration through Smiles rearrangement was realized from the corresponding diaryl ether substrates instead of expected eight-membered lactones. The present methodology is scalable, applied to the total synthesis of cytotoxic and neuroprotective natural product alterlactone. The catalyst is recyclable and the reaction can be performed in a copper bottle without any added catalyst.

Low-pressure gas chromatography (LPGC) has been known to be advantageous compared to standard GC since Giddings first described the concept in 1962, but a practical solution for its use eluded [...]

Nanomaterials are promising in the development of innovative therapeutic options that include tissue and organ replacement, as well as bone repair and regeneration. The expansion of new nanoscaled biomaterials is based on progress in the field of nanotechnologies, material sciences, and biomedicine. In recent decades, nanomaterial systems have bridged the line between the synthetic and natural worlds, leading to the emergence of a new science called nanomaterial design for biological applications. Nanomaterials replicating bone properties and providing unique functions help in bone tissue engineering. This review article is focused on nanomaterials utilized in or being explored for the purpose of bone repair and regeneration. After a brief overview of bone biology, including a description of bone cells, matrix, and development, nanostructured materials and different types of nanoparticles are discussed in detail.

In the environment the weathering of plastic debris is one of the main sources of secondary microplastic (MP). It is distinct from primary MP, as it is not intentionally engineered, and presents a highly heterogeneous analyte composed of plastic fragments in the size range of 1 μm−1 mm. To detect secondary MP, methods must be developed with appropriate reference materials. These should share the characteristics of environmental MP which are a broad size range, multitude of shapes (fragments, spheres, films, fibers), suspensibility in water, and modified particle surfaces through aging (additional OH, C=O, and COOH). To produce such a material, we bring forward a rapid sonication-based fragmentation method for polystyrene (PS), polyethylene terephthalate (PET), and polylactic acid (PLA), which yields up to 105/15 mL dispersible, high purity MP particles in aqueous media. To satisfy the claim of a reference material, the key properties—composition and size distribution to ensure the homogeneity of the samples, as well as shape, suspensibility, and aging —were analyzed in replicates (N = 3) to ensure a robust production procedure. The procedure yields fragments in the range of 100 nm−1 mm (

As polymeric materials are already used in many industries, the range of their applications is constantly expanding. Therefore, their preparation procedures and the resulting properties require considerable attention. In this work, we designed the surface of polyethylene naphthalate (PEN) introducing copper nanowires. The surface of PEN was transformed into coherent ripple patterns by treatment with a KrF excimer laser. Then, Cu deposition onto nanostructured surfaces by a vacuum evaporation technique was accomplished, giving rise to nanowires. The morphology of the prepared structures was investigated by atomic force microscopy and scanning electron microscopy. Energy dispersive spectroscopy and X-ray photoelectron spectroscopy revealed the distribution of Cu in the nanowires and their gradual oxidation. The optical properties of the Cu nanowires were measured by UV-Vis spectroscopy. The sessile drop method revealed the hydrophobic character of the Cu/PEN surface, which is important for further studies of biological responses. Our study suggests that a combination of laser surface texturing and vacuum evaporation can be an effective and simple method for the preparation of a Cu/polymer nanocomposite with potential exploitation in bioapplications; however, it should be borne in mind that significant post-deposition oxidation of the Cu nanowire occurs, which may open up new strategies for further biological applications.

Sweat chloride analysis is one of the important approaches in cystic fibrosis diagnosis. The commonly used Macroduct method to acquire sweat samples is semi-invasive, time consuming and expensive. Furthermore, this method often fails to collect a sufficient amount of sweat in newborns due to the insufficient sweating rate. In this work, we present a novel, simple, 3D-printed sampling device that is used to collect sweat specimens completely noninvasively in less than one minute. The device has a flow-through channel adjacent to the skin surface, through which 500 µL of deionized water is flushed and the spontaneously formed sweat on the skin in the channel area is washed into a plastic vial. The developed skin-wash procedure is a single step operation, is completely noninvasive and it always produces a sweat specimen. The ions from the skin-wash are subsequently analyzed by capillary electrophoresis with contactless conductivity detection and selected ion ratio (Cl−/K+) or ((Cl− + Na+)/K+) is used as a cut-off value to diagnose cystic fibrosis patients with sensitivity and specificity comparable to the conventional Macroduct method.

Nanoparticles (NPs) represent an emerging platform for diagnosis and treatment of various diseases such as cancer, where they can take advantage of enhanced permeability and retention (EPR) effect for solid tumor accumulation. To improve their colloidal stability, prolong their blood circulation time and avoid premature entrapment into reticuloendothelial system, coating with hydrophilic biocompatible polymers is often essential. Most studies, however, employ just one type of coating polymer. The main purpose of this study is to head-to-head compare biological behavior of three leading polymers commonly used as “stealth” coating materials for biocompatibilization of NPs poly(ethylene oxide), poly(2-ethyl-2-oxazoline) and poly[N-(2-hydroxypropyl)methacrylamide] in an in vivo animal solid tumor model. We used radiolabeled biodegradable hydroxyapatite NPs as a model nanoparticle core within this study and we anchored the polymers to the NPs core by hydroxybisphosphonate end groups. The general suitability of polymers for coating of NPs intended for solid tumor accumulation is that poly(2-ethyl-2-oxazoline) and poly(ethylene oxide) gave comparably similar very good results, while poly[N-(2-hydroxypropyl)methacrylamide] was significantly worse. We did not observe a strong effect of molecular weight of the coating polymers on tumor and organ accumulation, blood circulation time, biodistribution and biodegradation of the NPs.

High-chromium ferritic stainless steels strengthened by Laves phase precipitates were developed for a high-temperature application in steam power plants. The impact of tungsten content on the precipitation of the intermetallic Laves phase during the newly developed thermomechanical process route was investigated. Due to rapid thermomechanically induced precipitation, a considerable reduction in processing time in comparison to the conventional solely thermal two-step processing of high chromium ferritic steels was achieved. Nevertheless, comparable mechanical properties at room temperature, i.e., the ultimate tensile strength of 712 MPa and the yield strength of 434 MPa, were obtained. The microstructure was analyzed by scanning electron microscopy (SEM) in combination with digital particle analysis, to estimate the particle size and the phase fraction of the Laves phase. The mean particle size of 52 nm and the volume fraction of 4.11% were achieved. Due to the tungsten content, an increase in the volume fraction and particle size was observed, giving rise to the higher strengthening effect.

This work presents a comprehensive and detailed ab initio study of interactions between the tilt Σ5(210) grain boundary (GB), impurities X (X = Al, Si) and vacancies (Va) in ferromagnetic fcc nickel. To obtain reliable results, two methods of structure relaxation were employed: the automatic full relaxation and the finding of the minimum energy with respect to the lattice dimensions perpendicular to the GB plane and positions of atoms. Both methods provide comparable results. The analyses of the following phenomena are provided: the influence of the lattice defects on structural properties of material such as lattice parameters, the volume per atom, interlayer distances and atomic positions; the energies of formation of particular structures with respect to the standard element reference states; the stabilization/destabilization effects of impurities (in substitutional (s) as well as in tetragonal (iT) and octahedral (iO) interstitial positions) and of vacancies in both the bulk material and material with GBs; a possibility of recombination of Si(i)+Va defect to Si(s) one with respect to the Va position; the total energy of formation of GB and Va; the binding energies between the lattice defects and their combinations; impurity segregation energies and the effect of Va on them; magnetic characteristics in the presence of impurities, vacancies and GBs. As there is very little experimental information on the interaction between impurities, vacancies and GBs in fcc nickel, most of the present results are theoretical predictions, which may motivate future experimental work.