SiO2 Nanoparticles-Acrylate Formulations for Core and Cladding in Planar Optical Waveguides.

A combination of acrylate formulations and SiO2 nanoparticles is investigated with the aim to improve the optical properties of low-refractive index polymers that are used for the fabrication of planar optical waveguides. A decrease in refractive index and also in the thermo-optic coefficient of nanocomposite materials is clearly demonstrated, while some formulations exhibit an increase in the glass transition temperature. The possibility of using these nanocomposite materials to fabricate waveguiding layers with low optical propagation losses at telecommunication wavelengths around 1550 nm is also shown. The nanomaterials can be applied in optical microchips on polymer platforms.

Ultra-stiff metallic glasses through bond energy density design.

The elastic properties of crystalline metals scale with their valence electron density. Similar observations have been made for metallic glasses. However, for metallic glasses where covalent bonding predominates, such as metalloid metallic glasses, this relationship appears to break down. At present, the reasons for this are not understood. Using high energy x-ray diffraction analysis of melt spun and thin film metallic glasses combined with density functional theory based molecular dynamics simulations, we show that the physical origin of the ultrahigh stiffness in both metalloid and non-metalloid metallic glasses is best understood in terms of the bond energy density. Using the bond energy density as novel materials design criterion for ultra-stiff metallic glasses, we are able to predict a Co33.0Ta3.5B63.5 short range ordered material by density functional theory based molecular dynamics simulations with a high bond energy density of 0.94 eV Å-3 and a bulk modulus of 263 GPa, which is 17% greater than the stiffest Co-B based metallic glasses reported in literature.

FLOWERING LOCUS T Triggers Early and Fertile Flowering in Glasshouse Cassava (Manihot esculenta Crantz).

Accelerated breeding of plant species has the potential to help challenge environmental and biochemical cues to support global crop security. We demonstrate the over-expression of ArabidopsisFLOWERING LOCUS T in Agrobacterium-mediated transformed cassava (Manihot esculenta Crantz; cultivar 60444) to trigger early flowering in glasshouse-grown plants. An event seldom seen in a glasshouse environment, precocious flowering and mature inflorescence were obtained within 4-5 months from planting of stem cuttings. Manual pollination using pistillate and staminate flowers from clonal propagants gave rise to viable seeds that germinated into morphologically typical progeny. This strategy comes at a time when accelerated crop breeding is of increasing importance to complement progressive genome editing techniques.

Electronic hybridisation implications for the damage-tolerance of thin film metallic glasses.

A paramount challenge in materials science is to design damage-tolerant glasses. Poisson's ratio is commonly used as a criterion to gauge the brittle-ductile transition in glasses. However, our data, as well as results in the literature, are in conflict with the concept of Poisson's ratio serving as a universal parameter for fracture energy. Here, we identify the electronic structure fingerprint associated with damage tolerance in thin film metallic glasses. Our correlative theoretical and experimental data reveal that the fraction of bonds stemming from hybridised states compared to the overall bonding can be associated with damage tolerance in thin film metallic glasses.

1-Alkenylcalcium iodide: synthesis and stability.

To enhance the scope of heavy calcium-based Grignard reagents, 1,2-dihydro-4-iodonaphthalene (1) was reduced with calcium in THF giving tetrakis(thf) (1,2-dihydronaphth-4-yl)calcium iodide (2). This derivative represents a 1-alkenylcalcium complex based on X-ray structure determination and NMR data. The stability of this compound is significantly reduced compared with the aromatic naphthylcalcium iodide.

Halide-free diarylcalcium complexes--syntheses, structures, and stability.

A general procedure was developed for the synthesis of diarylcalcium complexes by addition of KOtBu to arylcalcium iodides in THF. Intermediate arylcalcium tert-butanolate dismutates immediately leading to insoluble tert-butanolate precipitates of calcium. Depending on the steric demand and denticity of additional neutral aliphatic azabases, mononuclear or dinuclear complexes trans-[Ca(α-Naph)2(thf)4] (1), [Ca(ß-Naph)2(thf)4] (2), [Ca(Tol)2(tmeda)]2 (3), [Ca(Ph)2 (tmeda)]2 (4), [Ca(Ph)2(pmdta)(thf)] (5), [Ca(hmteta)(Ph)2] (6), and [Ca([18]C-6)(Ph)2] (7) were isolated (Naph=naphthyl; meda=N,N,N',N'-tetramethylethylenediamine; pmdta= N,N,N',N'',N''-pentamethyldiethylenetriamine; hmteta=N,N,N',N'',N''',N'''-hexamethyltriethylenetetramine). The Ca-C bond lengths vary between 250.8 and 263.5 pm, the ipso-carbon atoms show low-field-shifted resonances in the (13) C NMR spectra.