Biological impacts of TiO<Subscript>2</Subscript> on human lung cell lines A549 and H1299: particle size distribution effects

Increasing use of titanium dioxide (TiO₂) nanoparticles in many commercial applications has led to emerging concerns regarding the safety and environmental impact of these materials. In this study, we have investigated the biological impact of nano-TiO₂ (with particle primary size of 20 nm Aeroxide P25) on human lung cell lines in vitro and also the effect of particle size distribution on the particle uptake and apparent toxicity. The biological impact of nano-TiO₂ is shown to be influenced by the concentration and particle size distribution of the TiO₂ and the impact was shown to differ between the two cell lines (A549 and H1299) investigated herein. A549 cell line was shown to be relatively resistant to the total amount of TiO₂ particles uptaken, as measured by cell viability and metabolic assays, while H1299 had a much higher capacity to ingest TiO₂ particles and aggregates, with consequent evidence of impact at concentrations as low as 30–150 μg/mL TiO₂. Evidence gathered from this study suggests that both viability and metabolic assays (measuring metabolic and mitochondrial activities and also cellular ATP level) should be carried out collectively to gain a true assessment of the impact of exposure to TiO₂ particles.     

Bi-directional terahertz emission from gold-coated nanogratings by excitation via femtosecond laser pulses

We report on the investigation of terahertz (THz) emission from gold-coated nanogratings (500 nm grating constant) upon femtosecond laser irradiation (785?nm, 150?fs, 1?kHz, ??1?mJ/pulse). Unlike common assumptions, THz emission is not only observed in case of rear side irradiation (through substrate (Welsh et al. in Phys. Rev. Lett. 98:026803, 2007; Welsh and Wynne in Opt. Express 17:2470?C2480, 2009)) of the nanograting, but also in case of front side excitation (through air). Furthermore in both cases, THz emission propagates in the direction of laser beam propagation and reverse. Based on these findings, we suggest a new approach to describe the newly observed phenomena. Using a highly sensitive and fast superconducting transition edge sensor (TES) as calorimeter, it was possible to directly measure the absolute energy of the emitted THz pulses in a defined spectral and spatial range, enabling for the first time a quantitative analysis of the THz emission process.     

Charge-density-wave phase of 1T-TiSe2: the influence of conduction band population

The charge-density-wave phase of TiSe(2) was studied by angle-resolved photoelectron spectroscopy and resistivity measurements investigating the influence of the band gap size and of a varying population of the conduction band. A gradual suppression of the charge-density-wave-induced electronic superstructure is observed for a variation of the band gap in the ternary compounds TiC(x)Se(2-x) with C=(S,Te) as well as for an occupation of only the conduction band by H(2)O adsorption-induced band bending. These observations point to an optimum band gap and support an excitonic driving force for the charge-density wave.     

Phosphorbestimmungsmethoden

Ohne Zusammenfassung     

Cycloadditions of Bifunctional Vinyl Ethers with Electrophilic Alkenes through Tetramethylene Zwitterion Intermediates

Bifunctional vinyl ethers react with electron‐poor alkenes to cyclobutanes in good yields. The second C?C bond reacted with neither the cyclobutane nor its zwitterion intermediate, even on heating. Cyclobutanes formed from ‘tetracyanoethylene’ ( 8 ) were transformed into tetrahydropyridines by reaction of the corresponding zwitterion with MeCN as the solvent. In contrast, cyclobutanes formed from dimethyl (dicyanomethylidene)propanedioate ( 9 ) did not react with MeCN, which is ascribed to diminished stabilization of the zwitterion intermediate, and increased steric effects. These results extend the classical studies of Huisgen and his co‐workers.     

Stable Algebraic Topology and Stable Topological Algebra

Algebraic topology is a young subject, and its foundations arenot yet firmly in place. I shall give some history, examplesand modern developments in that part of the subject called stablealgebraic topology, or stable homotopy theory. This is by farthe most calculationally accessible part of algebraic topology,although it is also the least intuitively grounded in visualizablegeometric objects. It has a great many applications to othersubjects such as algebraic geometry and geometric topology.Time will not allow me to say as much as I would like aboutthat. Rather, I shall emphasize some foundational issues thathave been central to this part of algebraic topology since theearly 1960s, but that have been satisfactorily resolved onlyin the last few years. 1991 Mathematics Subject Classification55P42, 55N20.     

205T1-NMR and UV-Visible spectroscopic determination of the formation constants of aqueous thallium(I) hydroxo-complexes

The hydrolysis of T1(I) has been studied at 25°C using²⁰⁵T1-NMR spectroscopy and UV-Vis spectrophotometry in aqueous solutions with ionic strengths maintained by NaC10₄ at 2, 4, 6, and 8M. The formation constant and the spectral characteristics for the hydroxo complex, T10Hℴ have been determined. At high hydroxide ion concentrations there is clear evidence from the UV-Vis data for the formation of a T1(OH)₂-species. The spectrum and an estimated formation constant for this second hydroxo complex are also reported.