A spectroscopic and computational study of Al(III) complexes in sodium cryolite melts: Ionic composition in a wide range of cryolite ratios

The structure of sodium cryolite melts was studied using Raman spectroscopy and quantum chemical calculations performed at the density functional theory level. The existence of bridged forms in the melts was argued first from the analysis of experimental Raman spectra. In the quantum chemical modelling emphasis was put on the construction of potential energy surfaces describing the formation/dissociation of certain complex species. Effects of the ionic environment were found to play a crucial role in the energetics of model processes. The structure of the simplest possible polymeric forms involving two Al centres linked through F atoms (“dimers”) was thoroughly investigated. The calculated equilibrium constants and model Raman spectra yield additional evidence in favour of the dimers. This agrees with a self-consistent analysis of a series of Raman spectra for a wide range of the melt composition.     

[Zn3(PO4)2(H2O)0.8(NH3)1.2]

The structure of the title compound, ammineaquadi‐μ₅‐phosphato‐trizinc(II), [Zn₃(PO₄)₂(H₂O)_0.8(NH₃)_1.2], consists of two parts: (i) PO₄ and ZnO₄ vertex‐sharing tetrahedra arranged in layers parallel to (100) and (ii) ZnO₂(N/O)₂ tetrahedra located between the layers. Elemental analysis establishes the ammine‐to‐water ratio as 3:2. ZnO₂(N/O)₂ tetrahedra are located at special position 4e (site symmetry 2) in C2/c. The two O atoms of ZnO₂(N/O)₂ are bonded to neighbouring P atoms, forming two Zn—O—P linkages and connecting ZnO₂(N/O)₂ tetrahedra with two adjacent bc plane layers. A noteworthy feature of the structure is the presence of NH₃ and H₂O at the same crystallographic position and, consequently, qualitative changes in the pattern of hydrogen bonding and weaker N/O—H...O electrostatic interactions, as compared to two closely related structures.     

Wavelength tunable high power laser using a double-clad Er:Yb doped fiber

We experimentally demonstrated a stable, wavelength-tunable fiber laser using a polarization-maintaining, double-clad Er:Yb doped fiber amplifier in the cavity. The output wavelength is tunable over the range from 1535 to 1567 nm using a fixed grating and the dichroic mirror placed on a rotational mount; under rotation of the dichroic mirror the tuning ratio of 50 nm/deg was found. We studied the wavelength tuning range dependence on the amplifier fiber length and achieved a maximal output power of 850 mW. This configuration can be Q-switched for high peak power and its narrow bandwidth is suitable for nonlinear optics applications, such as parametric teraherthz generator.     

Apatite type lanthanum silicate and composite anode half cells

Apatite type rare earth silicates are being extensively studied as electrolyte material for intermediate temperature solid oxide fuel cells (SOFC). In this paper we presents results on synthesis of Al and/or Fe-doped ATLS, the design of compatible anode materials, thermal expansion properties and co-sintering of half-cells from expansion matched materials using the advanced pulsed electric current sintering (PECS) technique. The issues related to the co-sintering of half cells have been addressed successfully by the combined use of nano powders and PECS.     

Development of an Instrument to Assess Attitudes Toward Science,Technology, Engineering,and Mathematics (STEM)

There is a need for more students to be interested in science, technology, engineering, and mathematics (STEM) careers to advance U.S. competitiveness and economic growth. A consensus exists that improving STEM education is necessary for motivating more students to pursue STEM careers. In this study, a survey to measure student (grades 4–6) attitudes toward STEM and STEM careers was developed and administered to 662 students from two STEM‐focused and three comprehensive (non‐STEM‐focused) schools. Cronbach's alphas for the whole survey and subscales indicated a high internal consistency. Statistically significant difference in means between students attending the STEM‐focused and comprehensive schools on the two subscales of the survey and the overall survey were found. However, the explained variance for these results was approximately 1%. The survey is a useful tool to assess efficacy of STEM education programs on student attitudes toward STEM and STEM careers.     

A High‐Quality Professional Development for Teachers of Grades 3–6 for Implementing Engineering into Classrooms

With the increasing emphasis on integrating engineering into K‐12 classrooms to help meet the needs of our complex and multidisciplinary society, there is an urgent need to investigate teachers' engineering‐focused professional development experiences as they relate to teacher learning, implementation, and student achievement. This study addresses this need by examining the effects of a professional development program focused on engineering integration, and how teachers chose to implement engineering in their classrooms as a result of the professional development. 198 teachers in grades 3–6 from 43 schools in 17 districts participated in a yearlong professional development program designed to help integrate the new state science standards, with a focus on engineering, into their teaching. Posters including lesson plans and student artifacts were used to assess teachers' engineering practices and the implementation in their classrooms. Results indicated that the majority of the teachers who participated in the professional development were able to effectively implement engineering design lessons in their classrooms suggesting that the teachers' success in implementing engineering lessons in their classroom was closely related to the structure of the professional development program.     

The influence of substrate surface roughness on microstrip transmission line loss using conventional analyses and length‐scale fractal analysis

Two components of conductor topography can impact conductor loss for signals in the GHz frequency range: conductor–ceramic interface roughness and conductor edge angle. This study is an experimental investigation of the influence of these conductor topographies on conductor loss in microstrip circuits produced by thick‐film technology. The aluminum nitride ceramic substrates have different surface roughnesses due to different surface finish processes. The substrate surfaces were characterized using conventional and length‐scale fractal analysis. The conductor–ceramic interface was measured with a contact profilometer. The conductor edge angle and conductor edge profile were measured optically. It was found that there is a direct correlation between conductor loss and conductor edge angle, whereas there is an inverse correlation between loss and substrate roughness or relative length of the conductor–ceramic interface. This is the opposite result to the conventional expectation of surface roughness effects on conductor loss. There is also a negative correlation between conductor edge angle and surface roughness or relative length. The loss behavior can be explained by the interaction of the conductor paste with the surfaces during processing. The paste tends to spread more on the smoother surfaces, and thus creates an elongated edge of diminishing cross‐section and a small edge angle. This leads to greater conductor loss. Copyright © 2009 John Wiley & Sons, Ltd.     

The reduction of Ag(I) by α‐silylamines R2NCH2SiX3

The introduction of the organosilicon substituent into the α‐position of an amino group results in cardinal change of the amine reactivity irrespective of the coordination state of silicon. Amines R₂NCH₂SiX₃ [R = Me, Et, PhCH₂, CH₂SiX₃; SiX₃ = SiMe₃, Si(OEt)₃, Si(OCH₂CH₂)₃N] easily react with AgNO₃, to give the corresponding ammonium salts (R₂NH⁺ CH₂SiX₃)·NO₃^?. At the same time, Ag(I) is reduced to Ag(0). The interaction of N‐methyl‐N,N‐bis(silatranylmethyl)amine with AgNO₃ has been investigated by EPR spectroscopy. It was proven that the reaction involved a single electron transfer stage with the formation of cation radical of this amine. A mechanism of the reaction is proposed. Copyright © 2006 John Wiley & Sons, Ltd.     

The application of homodyne spectroscopy to the study of low-frequency microturbulence in the TEXT tokamak

Summary The wave propagation direction of microturbulence in a tokamak plasma has been accurately measured by application of a new homodyne spectroscopy technique. This method has been used in conjunction with a collective far-infrared laser scattering experiment on TEXT. The low-frequency density fluctuations are observed to propagate primarily in the electron diamagnetic drift direction, however, the broadband spectra also possess an appreciable level of fluctuations traveling in the ion drift direction. Application of the homodyne spectroscopy technique represents an inexpensive and easily implemented alternative to the more technically demanding heterodyne schemes available in the far-infrared.