Plasmonic modulator based on gain-assisted metal–semiconductor–metal waveguide

We investigate plasmonic modulators with gain material to be implemented as ultra-compact and ultra-fast active nanodevices in photonic integrated circuits. We analyze metal–semiconductor–metal (MSM) waveguides with InGaAsP-based active material layers as ultra-compact plasmonic modulators. The modulation is performed by changing the gain of the core, that results in different transmittance through the waveguides. A MSM waveguide enables high field localization and therefore high modulation speed. Bulk semiconductor, quantum wells and quantum dots, arranged in either horizontal or vertical layout, are considered as the core of the MSM waveguide. Dependences on the waveguide core size and gain values of various active materials are studied. The designs consider also practical aspects like n- and p-doped layers and barriers in order to obtain close to reality results. The effective propagation constants in the MSM waveguides are calculated numerically. Their changes in the switching process are considered as a figure of merit. We show that a MSM waveguide with electrical current control of the gain incorporates compactness and deep modulation along with having a reasonable level of transmittance.     

Simultaneous TG/DTG–DSC–FTIR characterization of collagen in inert and oxidative atmospheres

In this paper, a TG/DTG–DSC–FTIR study of type I collagen extracted from bovine Achilles tendon both in inert (nitrogen) and oxidative atmosphere (synthetic air and oxygen) from room temperature to 700 °C was performed. The thermal analysis results have shown that after initial dehydration, collagen exhibits a single decomposition step in nitrogen (due to pyrolysis), while in air and oxygen two steps are observed due to thermo-oxidative decomposition, the latter being highly exothermic. The CO₂ bands dominate the FTIR spectra of evolved gases in all atmospheres (especially in air and oxygen), along with the characteristic bands of ammonia, water, HNCO, methane. In nitrogen, the bands of pyrrole, HCN, and ethane were also identified, while in oxidative atmospheres, nitrogen oxides and CO are released. A study was also performed by comparing the DTG and gas evolution curves observed for the three atmospheres.     

Catalyst development for organocatalytic hydrosilylation of aromatic ketones and ketimines

A new family of Lewis basic 2-pyridyl oxazolines have been developed, which can act as efficient organocatalysts for the enantioselective reduction of prochiral aromatic ketones and ketimines with trichlorosilane, a readily available and inexpensive reagent. 1-Isoquinolyl oxazoline, derived from mandelic acid, was identified as the most efficient catalyst of the series, capable of delivering high enantioselectivities in the reduction of both ketones (up to 94% ee) and ketimines (up to 89% ee).     

Comparative analysis of lipophilic compounds in eggs of organically raised ISA Brown and Araucana hens

Hens?? eggs represent a rich source of important nutrients, including lipids and carotenoids. The lipid composition of hens?? eggs is influenced by genetic factors, age, and diet. The aim of this study was to compare the fatty acids, cholesterol, and carotenoids content of the egg yolk of ISA Brown and Araucana hens grown in free-range housing systems. Fatty acids and cholesterol were analysed by GC-FID and GC-MS and carotenoids were quantified by RP-HPLC-PDA. The Araucana egg yolk has a higher lipid content and higher egg-to-albumen ratio than the ISA Brown yolk, while the total cholesterol, carotenoids content and profile are not significantly different. The lipids of the Araucana egg yolk have a higher content of mono-unsaturated fatty acids (MUFAs), eicosapentaenoic acid (EPA), and docosahexaenoic acid (DHA) and a better n-6/n-3 ratio than the ISA Brown egg yolk lipids. The major carotenoids were lutein and zeaxanthin, which account for more than 83 % in egg yolk. Eggs of both breeds, when raised organically, represent very good sources of highly bio-available lutein and zeaxanthin, pigments which are related to lower risk of age-related macular degeneration. We report for the first time on the fatty acids composition in lipid fractions and the profile and content of carotenoids of the Araucana egg yolk.     

Surprising acid/base and ion-sequestration chemistry of Sn9(4-): HSn9(3-), Ni@HSn9(3-), and the Sn9(3-) ion revisited

K(4)Sn(9) dissolves in ethylenediamine (en) to give equilibrium mixtures of the diamagnetic HSn(9)(3-) ion along with K(x)Sn(9)((4-x)-) ion pairs, where x = 0, 1, 2, 3. The HSn(9)(3-) cluster is formed from the deprotonation of the en solvent and is the conjugate acid of Sn(9)(4-). DFT studies show that the structure is quite similar to the known isoelectronic RSn(9)(3-) ions (e.g., R = i-Pr). The hydrogen atom of HSn(9)(3-) (δ = 6.18 ppm) rapidly migrates among all nine Sn atoms in an intramolecular fashion; the Sn(9) core is also highly dynamic on the NMR time scale. The HSn(9)(3-) cluster reacts with Ni(cod)(2) to give the Ni@HSn(9)(3-) ion containing a hydridic hydrogen (δ = -28.3 ppm) that also scrambles across the Sn(9) cluster. The Sn(9)(4-) ion competes effectively with 2,2,2-crypt for binding K(+) in en solutions, and the pK(a) of HSn(9)(3-) is similar to that of en (i.e., Sn(9)(4-) is a very strong Br?nsted base with a pK(b) comparable to that of the NH(2)CH(2)CH(2)NH(-) anion). Competition studies show that the HSn(9)(3-) ? Sn(9)(4-) + H(+) equilibrium is fully reversible. The HSn(9)(3-) anion is present in significant concentrations in en solutions containing 2,2,2-crypt, yet it has gone undetected for over 30 years.