Single crystal growth and the elastic behaviour of In2Bi

Ultrasound velocities have been measured in In₂Bi crystals grown by zone-levelling. The elastic constants are reported. The elastic behaviour is remarkably isotropic: a pure shear and two almost pure waves propagate in all directions other than pure mode directions.     

Design of a new thin-film electro-optic switch

A new thin-film electro-optic switch employing two stable states of polarization is proposed and investigated. The design can be further employed to realize a TE-TM polarization converter by constructing a Mach-Zehnder type interferometer integrated optical switch. The limitations and design procedures for electro-optic devices are also discussed.     

Reply to comment on “variational formulation for the equilibrium condition of a conducting fluid in an electric field”

In this comment we respond to the several criticisms of the paper by Sujatha et al. raised by Kingham and Bell. In particular, we demonstrate that, contrary to their assertion, Taylor's solution for the electrostatic fields can never satisfy the boundary conditions for the actual experimental configurations involving field emission liquid metal ion sources and other experiments on electrostatically stressed conducting fluids. It is further argued that a careful analysis of Taylor's experimental procedure and observations suggests that although the observed static structures have a macroscopic axial-symmetry they have not the idealized conical shapes of prescribed angle. Furthermore, the formation of the Taylor cone structure is shown to be inconsistent with the principle of energy minimization.It is concluded that none of the criticism raised by Kingham and Bell invalidate any of the analysis or conclusions presented in the paper by Sujatha et al.This work has been supported in part by the Division of Materials Research, National Science Foundation, Grant No. DMR-81008829     

The photochemistry of sulfur dioxide excited within its first allowed band (3130 Å) and the “forbidden” band (3700–;4000 Å)

The quantum yields of SO₃ formation have been determined in pure SO₂ and in SO₂ mixtures with NO, CO₂, and O₂ using both flow and static systems. In separate series of experiments excitation of SO₂ was effected within the forbidden band, SO₂(³B₁) ← \documentclass{article}\pagestyle{empty}\begin{document}$$ {\rm SO}_2 (\tilde X,^1 A_1 ) $$\end{document}, and within the first allowed singlet band at 3130 Å. The values of Φ were found to be sensitive to the flow rate of the reactants. These results and the apparently divergent quantum yield results of Cox [10], Allen and coworkers [24, 26, 29], and Okuda and coworkers [11] were rationalized quantitatively in terms of the significant occurrence of the reactions SO + SO₃ → 2SO₂ (2), and 2SO → SO₂ + S [or (SO)₂] (3), in experiments of long residence time. From the present rate data, values of the rate constants were estimated, k₂=(1.2±0.7) × 10⁶; k₃=(5±4) × 10⁵ l˙/mole · sec. Φ values from triplet excitation experiments at high flow rates of NO? SO₂ and CO₂? SO₂ mixtures showed the sole reactant with SO₂ leading to SO₃ formation in this system to be SO₂(³B₁); SO₂(³B₁) + SO₂ → SO₃ + SO(³Σ^?) (la); k=(4.2±0.4) × 10⁷ l./mole · sec. With excitation of SO₂ at 3130 Å both singlet and triplet excited states play a role in SO₃ formation. If the reactive singlet state is ¹B₁, the long-lived fluorescent state, SO₂(¹B₁) + SO₂ → SO₃ + SO (¹ Δ or ³Σ^?) (lb), then k=(2.2±0.5) × 10⁹ l./mole · sec. From the observed inhibition of SO formation by added nitric oxide, it was found that the SO₃-forming triplet state, generated in this singlet excited SO₂ system, had a relative reactivity toward SO₂ and NO which was equal within the experimental error to that observed here for the SO₂(³B₁) species. Either SO₂(³B₁) molecules were created with an unexpectedly high efficiency in 3130 Å excited SO₂(¹B₁) quenching collisions, or another reactive triplet (presumably ³A₂ or ³B₂) of almost identical reactivity to SO₂(³B₁) was important here.     

Quantum critical scaling and the origin of non-fermi-liquid behavior in Sc1-xUxPd3

We used inelastic neutron scattering to study magnetic excitations of Sc1-xUxPd3 for U concentrations (x=0.25, 0.35) near the spin glass quantum critical point (QCP). The excitations are spatially incoherent, broad in energy (E=variant Planck's over 2piomega), and follow omega/T scaling at all wave vectors investigated. Since similar omega/T scaling has been observed for UCu5-xPdx and CeCu6-xAux near the antiferromagnetic QCP, we argue that the observed non-Fermi-liquid behavior in these f-electron materials arises from the critical phenomena near a T=0 K phase transition, irrespective of the nature of the transition.     

Surfactant free fabrication of polymeric nanoparticles by combined liquid-liquid phase separation and solvent/nonsolvent mixing technology

It is generally agreed that, in most cases, surfactants are required to obtain stable polymeric nanoparticle dispersions. Here, we report a method which can be used to produce surfactant free yet stable polymeric nanoparticle dispersions. This method is based on explored mechanism of selective solvation of nanoparticles and EPD (electron pair donor)/EPA (electron pair acceptor) complexes formed among solvent and nonsolvent molecules. Using polyimide P84 (copolyimide 3,3(') 4,4(')-benzophenone tetracarboxylic dianhydride and 80% methylphenylene diamine+20% methylene dianiline) as the model polymer, this mechanism was realized through a combined liquid-liquid phase separation and solvent/nonsolvent mixing technology. Surfactant-free polyimide nanoparticles (<100 nm) were produced. Experimental details and principles of this technology were given based on the ternary diffusion, the liquid-liquid phase separation and the advanced nucleation and growth theory. Two types of methods [denoted as the forward titration method and the backward titration (BT) method] were examined. It was found that the BT method is extremely helpful to prepare polyimide nanoparticles (<100 nm). As another important aspect, explored stabilization mechanism of the resultant nanoparticle dispersions was supported by the comparative experiments, implying that selective solvation of nanoparticles and EPD/EPA complexes may play key roles in stabilization.     

Neural stem cells express melatonin receptors and neurotrophic factors: colocalization of the MT<Subscript>1</Subscript>receptor with neuronal and glial markers

Background  

In order to optimize the potential benefits of neural stem cell (NSC) transplantation for the treatment of neurodegenerative disorders, it is necessary to understand their biological characteristics. Although neurotrophin transduction strategies are promising, alternative approaches such as the modulation of intrinsic neurotrophin expression by NSCs, could also be beneficial. Therefore, utilizing the C17.2 neural stem cell line, we have examined the expression of selected neurotrophic factors under different in vitro conditions. In view of recent evidence suggesting a role for the pineal hormone melatonin in vertebrate development, it was also of interest to determine whether its G protein-coupled MT₁ and MT₂ receptors are expressed in NSCs.