Dielectric and Calorimetric Characteristics of Bound and Free Water in Surfactant-Based Systems

The hydration behavior of the system polyoxyethylene (10) oleylalcohol [C_18:1 (EO)₁₀ or Brij 97]/water/dodecane/butanol (model system B) was investigated along a dilution line for which the respective weight ratio of dodecane:butanol:Brij 97 is 3:3:4. Two experimental methods were applied: time domain dielectric spectroscopy (TDDS) and sub-zero temperature differential scanning calorimetry (SZT-DSC). Two types of bound water (with melting peaks at -25 and -11°C) were detected by SZT-DSC (using the endothermic mode), whereas TDDS revealed only one such type. Nevertheless, roughly the same total amount of bound water was estimated from these two techniques. The average number of bound water molecules per ethylene oxide (EO) group, N_W/EO is 2.3 (TDDS data) or 2.5 (SZT-DSC data) in good agreement with the observation that 1–2 water layers are formed in the hydration of ethoxylated surfactants. We have also shown that butanol is involved in the formation of the bound water that melts at -25°C. We suggest that butanol molecules occupy binding sites within the second hydration shell, thereby reducing the expected total bound water content.     

THE CHEMISTRY OF OPTICALLY ACTIVE SULFUR COMPOUNDS PART III

Abstract

The chemistry of optically active sulfur compounds has proven to be one of great interest and challenge as demonstrated by the prolific publications in this area. An ever larger number of different types of compounds with sulfur as center of chirality are being synthesized and it is expected that in future publications additional members of this group will be described. Thus far the following chiral sulfur compounds have been prepared:     

Crosslinked QA‐PEI nanoparticles: synthesis reproducibility,chemical modifications,and stability study

Quaternary ammonium polyethylenimine (QA‐PEI) nanoparticles were synthesized by PEI crosslinking and alkylation with octyliodide followed by quaternization by methyl iodide. The present study focuses on the reproducibility of particles formation with respect to particle size, positive charge, oxidative, thermal stability and antibacterial activity. The QA‐PEI‐based nanoparticles with particle size in the range of 160–190 nm were synthesized in high reproducibility and showed high chemical stability against environmental changes including exposure to different oxidizers and storage conditions. QA‐PEI nanoparticles incorporated in dental restorative resin composites at 2% w/w demonstrated strong antibacterial activity. Copyright © 2013 John Wiley & Sons, Ltd.     

Tungsten(VI) Complex of N‐Fused Porphyrin Absorbing Near‐Infrared Light beyond 1000 nm

Incorporating tungsten into the N3 core of a N‐fused porphyrin (NFP; 1 ) affords high‐valent tungsten(VI)‐NFP complexes, WClO₂‐1 and 21‐chlorinated WClO₂‐3 . The X‐ray structure of WClO₂‐1 reveals a distorted octahedral geometry with sitting atop metal coordination. The absorption spectrum of WClO₂‐1 displays bathochromically shifted Q‐like bands beyond 1000 nm, indicating an inherently narrow HOMO‐LUMO energy gap. DFT calculations show that the degeneracy of the LUMO and LUMO+1 pair of 1 is significantly resolved by the tungsten(VI) coordination. Conclusively, magnetic circular dichroism (MCD) spectroscopy and cyclic voltammetry provide a rationale for the narrow HOMO‐LUMO energy gap in the “16‐electron” d⁰ tungsten(VI)‐NFP complexes.     

Joint beamforming and power control in downlink multiuser multiple‐input multiple‐output systems

In this paper, we study joint beamforming and power control for downlink multiple‐input multiple‐output systems with multiple users and target values for signal‐to‐interference plus noise ratios (SINRs). We formulate this as a constrained optimization problem of minimizing total interference subject to constraints on the beamforming vector norms, target SINRs, and total transmit power. Necessary and sufficient conditions satisfied by the optimal beamformer and power allocation are presented, and a new algorithm for joint beamforming and power control is proposed. This adapts the beamforming vectors and transmit powers incrementally, and it stops when the specified SINR targets are achieved with minimum powers. The proposed algorithm is illustrated with numerical results obtained from simulations, which study its convergence and compare it with other similar algorithms. Copyright © 2013 John Wiley & Sons, Ltd.     

Solutions to fuzzy integral equations with arbitrary kernels

Using a parametric Riemann integral representation, a numerical algorithm for solving fuzzy Fredholm and Voltera integral equations of the second kind with arbitrary kernel is proposed and illustrated with examples.     

Total reflection X-ray fluorescence analysis of oral fluids of women affected by osteoporosis and osteopenia

Osteoporosis is a disease characterized by low bone mass and microarchitectural deterioration of bone tissue, leading to bone fragility and an increased susceptibility to fractures; the early stage of decreased bone density is called osteopenia. More than 200 million people are affected and about 50% of post-menopausic women are expected to develop the disease. Osteoporosis, osteopenia and periodontal disease have in common several risk factors, being hyperthyroidism and smoking habits the most important ones. There is scarce information in the literature about the association between periodontal disease and osteoporosis and/or osteopenia. Some works suggest that osteoporotic women are susceptible to a higher loss of periodontal insertion, alveolar bones, and teeth.     

Curriculum developers and problem solving: the case of Israeli elementary school projects

Problem solving has been a main focus in mathematics education for several decades, yet it seems that its definition and classroom implementation are far from being consensual. We explore the views and approaches of a small community: the project leaders of five elementary mathematics curriculum development projects in Israel, working within a centralized system, which dictates the syllabus. We describe and analyze their views along six categories: What are problems? What are not problems? Classification of problems, problem solving and individual differences, the ratio of problem solving tasks to other tasks in the project, and the role of heuristics and metacognition in teaching problem solving. We describe, exemplify, interpret and discuss the (few) points of convergence and the many different approaches. Finally, we reflect on the possible role of research in settling those differences. We speculate that our analysis and results go beyond the local and the idiosyncratic.