STS to Enhance Total Curriculum

Many nonscientists hold incorrect views of science. These incorrect views of science are rooted in fundamental problems with science education in schools. These problems are discussed in the context of their causes, including a dysfunctional working definition of science. The Science/Technology/Society (STS) movement is described and illustrated as a potential means to correct these problems. Examples derived from statewide efforts in Iowa are used as evidence that STS initiatives are paradigms for curriculum and instructional reform.     

Carbocyclic analogs of thymine nucleosides and related 1-substituted thymines

The carbocyclic analogs of thymidine (IXf), 1-β-ribofuranosylthymine (IXg), and 1-β-3′-deoxyribofuranosyl-thymine (IXe) were synthesized by incorporating modifications into the Shaw method of synthesizing 2,4-(1H,3H)pyrimidinediones via acryloylureas. Simpler analogs of thymine nucleosides were also prepared by this method. The carbocyclic analog of thymidine displayed modest activity against Leukemia L1210 in vivo. It differs from a compound prepared previously by a Prins reaction.     

Efficient, "tin-free" radical cyclization to aromatic systems. synthesis of 5,6,8,9,10,11-hexahydroindolo[2,1-a]isoquinolines

Efficient radical cyclization of alkyl iodides to various aromatic systems including pyrrole, indole, isoquinolone, pyridone, and benzene, mediated by dicumyl peroxide, is described. The methodology was used to provide access to 5,6,8,9,10,11-hexahydroindolo[2,1-a]isoquinoline derivatives.     

Determination of the inelastic mean-free-path and mean inner potential for AlAs and GaAs using off-axis electron holography and convergent beam electron diffraction.

The mean-free-paths for inelastic scattering of high-energy electrons (200 keV) for AlAs and GaAs have been determined based on a comparison of thicknesses as measured by electron holography and convergent-beam electron diffraction. The measured values are 77 +/- 4 nm and 67 +/- 4 nm for AlAs and GaAs, respectively. Using these values, the mean inner potentials of AlAs and GaAs were then determined, from a total of 15 separate experimental measurements, to be 12.1 +/- 0.7 V and 14.0 +/- 0.6 V, respectively. These latter measurements show good agreement with recent theoretical calculations within experimental error.     

Mikromethoden zur Bestimmung physikalischer Konstanten

Zusammenfassung Es wird darauf hingewiesen, daß die Methodik zur Bestimmung physikalischer Konstanten ein Teilgebiet der allgemeinen Mikrochemie ist, dessen planmäßiger Ausbau eine der vordringlichsten Aufgaben mikrochemischer Forschung ist.In einem historischen Rückblick wird gezeigt, daß diese Arbeitsrichtung in der TraditionEmichs und seiner Schule liegt.An einigen Beispielen eigener Arbeit werden die Probleme physikochemischer Mikromethodik erläutert.

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Summary It is pointed out that the methodology for the determination of physical constants is a partial province of general microchemistry, whose systematic development is one of the most pressing tasks of microchemical research. In an historical review, it is shown that this tendency is in the tradition ofEmich and his school. The problems of physico-chemical micromethodology are illustrated by several instances taken from the writer's own work.

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Résumé On montre que le mode opératoire pour déterminer les constantes physiques est un domaine partiel de la microchimie générale dont l'exécution méthodique est l'un des problèmes qui gagnent de plus de terrain dans la recherche microchimique. Au cours d'un aperçu historique, on prouve que ces directives de travail sont dans la tradition d'Emich et de son école. A l'aide de quelques exemples issus de travaux personnels, on présente les problèmes relatifs aux microméthodes physico-chimiques.

     

Transmission electron microscopy study of Ruddlesden-Popper Can+1MnnO3n+1n=2 and 3 compounds

Two Ruddlesden-Popper compounds Ca_n+1Mn_nO_3n+1 with n=2 and 3 synthesized by a citrate gel technique have been studied by TEM. The structure of Ca₄Mn₃O₁₀ is consistent with the previously determined structure having the space group Pbca and a⁻ a⁻ c⁺/a⁻ a⁻ c⁺ tilt system. The presence of defects suggests the possible high-temperature phase transition from untilted I4/mmm to Pbca. The structure of Ca₃Mn₂O₇ was found to be different from the previously suggested I4/mmm symmetry. Ca₃Mn₂O₇ forms with an orthorhombic structure with either Cmcm or Cmc2₁ space group. A structural model for Cmc2₁ based on the tilting of almost-rigid octahedra with a⁺ c⁻ c⁻/a⁺ c⁻ c⁻ tilt system is proposed. The lamellar defects were shown to be twin variants of the Cmc2₁ structure with the (001)_t interfaces, which suggests the possible tilting phase transition from the ideal I4/mmm to Cmc2₁ following the maximal group-subgroup symmetry tree: I4/mmm→Fmmm→Bbmm(Cmcm)→Bb2₁m(Cmc2₁).     

Aromatic bromination versus oxidation of indolylmalonates by bromine

The reactions of 5-substituted indolylmalonates (2a-e), carrying an electron-withdrawing group at the N(1) position, with bromine in CCl(4) or AcOH are reported. These substrates undergo oxidation in competition with the well-known aromatic bromination. Under the two sets of conditions, with parent indolylmalonate (2a), chemospecific oxidation is observed, whereas with 5-hydroxyindolylmalonate (2c), bromination at the 4- and 6-position is the dominating reaction. Investigation of the products composition of several 5-substituted indolylmalonates revealed the following trend: with a 5-substituted electron-withdrawing group like fluorine, the indolylmalonate undergoes oxidation rather than bromination. In contrast, with a 5-substituted electron-donating group, like a hydroxyl group, the ring bromination occurs preferentially over the oxidation. When the 5-substituent is an alkoxyl group, a significant amount of brominated-oxidized products is obtained. Monitoring the oxidation reaction by mass spectrometry allowed the characterization of the 2-bromoindolylidenemalonate intermediate. A bromonium ion is considered as possible pathway in the formation of this intermediate. The conformation of unsymmetrical methoxyl and benzyloxyl substituents was determined from (1)H NMR spectra, single-crystal X-ray diffraction and ab initio calculations.     

The influence of nanoparticle fillers on the morphology of a spin-cast thin film polymer blend

Polymer/nanoparticle composite films are receiving growing attention thanks to their potential for application in ultra-thin electronic and optical devices. Polymer blend demixing has been shown to be a suitable technique for the structuring of polymer thin films and the patterning of nanoparticles (NP) within them. In this work we show that the morphology of thin polymer films made by spin-casting a polymer blend solution containing NP fillers on a surface depends strongly on the concentration of NP fillers. More specifically, polystyrene/polymethylmethacrylate (PS/PMMA) films formed from a toluene solution, and which demix following a nucleation and growth mechanism, were studied. It was found that both the height and the surface density of PMMA domains increased as the concentration of CoPt:Cu NPs in the film was increased. We find that similar effects are induced in a NP-free PS/PMMA demixed film upon increasing the molecular weight of the PS molecules. This suggests that under certain conditions the NPs and the polymer molecules in the blend do not behave as separate species but form aggregates.     

Controlling open‐shell loading in norbornene‐based radical polymers modulates the solid‐state charge transport exponentially

Radical polymers are an emerging class of electronically active macromolecules; however, the fundamental mechanism by which charge is transferred in these polymers has yet to be established in full. To address this issue, well‐defined norbornene‐based nitroxide radical polymers were synthesized using the controlled ring‐opening metathesis polymerization technique. These polymers were blended in solution with a quenched, electrically insulating hydroxylamine derivative to dilute the radical content of the system. Electron paramagnetic resonance spectroscopy data were used to characterize the radical content as well as to reveal that hydrogen atom transfer occurred between the open‐shell and closed‐shell polynorbornene derivatives when they were blended in solution. Using these platform macromolecules, we demonstrate that the systematic manipulation of the radical content in open‐shell macromolecules leads to exponential changes in the macroscopic electrical conductivity. When coupled with the fact that these materials show a clear temperature‐independent charge transport behavior, a picture emerges that charge transfer in radical polymers is dictated by a tunneling mechanism between localized donor and acceptor sites within the redox‐active thin films. These results constitute the first experimental insight into the mechanism of solid‐state electrical conduction in radical polymers, and this provides a design paradigm for open‐shell macromolecular charge transport. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2017 , 55, 1516–1525