Misconceptions about Atomic Models Amongst the Chemistry Students

Bohr’s model is a semi-classical model which involves both classical and quantum principles. Although more sophisticated Schrödinger model has been presented to students, the residual picture in their minds persists to consider Bohr’s model to be the closest to the physical reality. We included few questions about Bohr’s model in tests to assess the students’ understandings of realistic atomic models in general-chemistry courses offered for freshmen in two universities in the Middle-East (namely, Yarmouk University at Irbid, Jordan, and the United Arab Emirates University at Al-Ain, UAE, from both a statistical sample of 687 students was collected). The results reveal the existence of huge misconceptions amongst a large portion of the students’ sample (i.e., ≥ 85%). Alternative solutions are discussed and suggested to draw a strategy to better dissimilate the knowledge in order to overcome the existing learning difficulties

The Chemical Speciation of Trace-Metals in Street Dusts of Irbid, Jordan

Abstract Street dust samples were collected from different locations in Irbid city, Jordan. The concentrations of Pb, Cu, Zn, Cd, Ni, Mn, Cr and Al in these samples were determined usin

Combination of ICP-OES, XRF and XRD techniques for analysis of several dental ceramics and their identification using chemometrics

Abstract. In this paper dental ceramic samples from seven vendors were studied. The elemental composition for each type was investigated using the ICP-OES and the XRF. Assessment of the seven types of ceramic was also successfully achieved using the XRD spectral data and processed with Principal Component Analysis (PCA). Detecting possible adulteration in different mass percentages of ceramic was also possible by applying the XRD data for the adulterated samples to the original PCA model

Investigations on the Physical Structure and the Mechanism of Drug Release from an Enteric Matrix Microspheres with a Near-Zero-Order Release Kinetics Using SEM and Quantitative FTIR

The objectives of this study were to evaluate the physical structure and the release mechanisms of theophylline microspheres made of Eudragit S 100 polymer as an enteric polymer, combined with a nonerodible polymer, Eudragit RL 100. In the preparation process, polymer combinations (1:1) were dissolved in an organic solvent mixture composed of acetone and methanol at a specific ratio containing a theoretical drug loading of approximately 15%. Two microsphere formulations (LS1 and LS2) were prepared at two different total polymer concentrations (10% in LS1 and 12.7% in LS2). Dissolution studies were carried out using US Pharmacopeia Dissolution Apparatus II in an acidic medium for 8 h and in an acidic medium (2 h) followed by a slightly basic-buffered medium for 10 h. Both LS1 and LS2 microsphere formulations produced particles that were spherical in shape and had very narrow size distributions with one size fraction comprising 70–80% of the yield. Scanning electron microscopy and quantitative Fourier transform infrared were used for microsphere physical structure evaluation. Except for the absence of drug crystals, photomicrographs of both LS microspheres after dissolution in pH 1.2 and 7.2 buffer solutions were similar to those before dissolution. Dissolution results indicated the ability of LS microspheres to minimize drug release during the acid stage. However, in the slightly basic medium that followed the acidic stage, the drug release was sustained and controlled in its kinetics and data fitted to Peppas equation indicated a case II transport suggesting that the drug release is mainly through swelling/erosion mechanism

Use of Fluorometry to Differentiate Among Clipped Species in the Genera Astragalus, Oxytropis, and Pleuraphis

A rapid and reproducible method to determine botanical composition of forage is an ecological and economic goal for range animal ecologists. Multidimensional fluorometry previously demonstrated the possibility of a unique optical approach for accurately determining species composition of clipped and digested plant materials. Fluorometry may be used to detect toxic plants in standing crop as well as diets by using electronic transitions in chemical structures at wavelengths between 370 and 580 nm. Grass hay (genus Pleuraphis) and 6 clipped forbs (4 species of Astragalus and 2 species of Oxytropis) were examined. The resulting spectral signatures were evaluated for differences in the blue and green regions of the visible spectrum using Principal Component Analysis (PCA). This represents the first published data using chemometrics to differentiate among fluorophores from these plant extracts. It was possible to distinguish between the grass and forbs and among forbs. Further research will be required to evaluate these same plant species in mixed diets and fecal samples. The Rangeland Ecology & Management archives are made available by the Society for Range Management and the University of Arizona Libraries. Contact [email protected] for further information.Migrated from OJS platform August 2020Legacy DOIs that must be preserved: 10.2458/azu_jrm_v59i5_anderso

Microbiological analysis, antimicrobial activity, and heavy-metals content of Jordanian Ma'in hot-springs water

Ma'in hot springs are known as sites of balneotherapy. However, little is known about their microbiology and chemistry. In this study, we aim at evaluating the antimicrobial activity of Ma'in hot-springs water (MHSW), studying its microbiology, and determining its physicochemical properties including the heavy metals content. Therefore, water samples were collected from Ma'in hot springs and tested for antimicrobial activity using agar diffusion method. Water was then cultivated on nutrient agar to isolate and identify the dominant bacteria by chemical and molecular methods. The identified strains were tested by cross streak method to evaluate their antimicrobial activity against different clinical and standard strains. Finally, water samples were chemically analyzed and the heavy-metals content was assessed. Results revealed that MHSW was not active against any of the clinical isolates. Nevertheless, MHSW was found to be active against five standard bacterial strains, namely, Staphylococcus epidermidis ATCC 12228 (inhibition zone: 20 mm), Staphylococcus aureus ATCC 29213 (inhibition zone: 19 mm), Micrococcus luteus ATCC 9341 (inhibition zone: 15.3 mm), and Bacillus cereus ATCC 11778 (inhibition zone: 12.3 mm). After cultivation of MHSW, five bacterial isolates were obtained and identified based on 16S rRNA gene analysis as new strains of Anoxybacillus flavithermus (identity percentage ranges between 96–99%). Physicochemical analysis revealed that the in situ temperature was 59 °C, pH was 7.8, salinity was 1.6 ppt, and dissolved oxygen was 3.8 mg l−1. In respect to heavy-metals content in MHSW, the following metals were present in the order: Cr (0.571 ppm) > Mn(0.169 ppm) > Fe (0.124 ppm) > Zn (0.095) > Cu(0.070 ppm) > Ni(0.058 ppm) > Cd (0.023 ppm) > Pb (0 ppm). Cd, Cr, Ni and Mn were found to be higher than permissible levels set by international organizations and countries. This study highlights new chemical and microbiological data about Ma'in hot springs. Keywords: Ma'in hot springs, Antimicrobial activity, Heavy metals, Water microbiology, Thermophilic bacteria, Balneotherap