Electron Transfer Photoinitiating Systems. The Effect of the Co‐Initiator Structure on the Photoinitiation Ability of a Photoredox Pair Containing Neutral Hemicyanine Dyes as Sensitizers

Summary: The photoinitiation ability of photoredox pairs composed of a neutral hemicyanine dye and different co‐initiators for the free radical polymerization of 2‐ethyl‐2‐(hydroxymethyl)propane‐1,3‐diol triacrylate is investigated. p‐(N,N‐dimethylaminostyryl)benzthiazole, p‐(N,N‐dimethylaminostyryl)benzoxazole, p‐(N,N‐dimethylaminostyryl)α‐naphthiazole are tested as dyes, and, as co‐initiators, an aromatic amino‐acid, an aromatic thio‐ and oxycarboxylic acid, and alkyltriphenylborate are applied as electron donors. N,N′‐dialkoxybipyridinium salts are used as ground‐state electron acceptors. The experimental results show that the photoinitiating ability of the tested photoredox pairs are controlled by both the driving force of the electron transfer process between an electron donor and an electron acceptor and the reactivity of the free radical that results from the secondary reactions occurring after the photoinduced electron transfer process. The greatest photoinitiation ability of free radical polymerization is observed when the tested dyes are applied as electron donors in their singlet excited states in combination with N,N′‐dialkoxybipyridinium salts acting as ground‐state electron acceptors.

Schematic of the investigated photoinitiation systems.     

BiNbO4-Based Glass–Ceramic Composites for Microwave Applications

The effect of a bespoke glass sintering aid, 0.3Bi₂O₃–0.3Nb₂O₅–0.3B₂O₃–0.1SiO₂ (BN1), developed from the base ceramic composition, BiNbO₄ (BN), on the sinterability, microstructure, and microwave (MW) dielectric properties of BN ceramics has been investigated. Densities >97% theoretical could be achieved at 1020°C for samples with up to 15% BN1 additions. The resulting microstructure was composed of BN laths surrounded by a residual glass phase that contained small fibrous crystals. Some evidence of dissolution of BN crystals was observed. Optimum properties were exhibited for samples with 15 wt% of glass addition sintered for 4 h at 1020°C with a relative permittivity ɛ_r=38, a MW quality factor Q × f ₀=17 353 at 5.6 GHz, and a temperature coefficient of resonant frequency τ_f=−10 ppm/°C. The high Q × f ₀, ɛ_r, and low τ_f, coupled with a relatively low sintering temperature, suggest that the use of bespoke glass sintering aids of this type may have great potential for the fabrication of MW ceramics.     

Application of different analytical methods used in the study of the cross‐linking of resins in intermediate‐product used in manufacturing of abrasive articles

Determining the degree of the crosslinking of resins in intermediate‐product used in the manufacturing of abrasive articles is difficult and complicated because of the presence of different components in the material. The abrasive articles consist of abrasive (e.g., fused alumina), filler (e.g., potassium fluoroborate–KBF₄, pyrite–FeS₂), wetting agent (e.g., resol), and binder (e.g., novolak). Proper hardening of intermediate‐product is a very important stage during production of abrasive tools. The hardening process depends on crosslinking of resins. Following were used to study crosslinking of resins: IGC, washing away method, NMR broad line, DSC, and FTIR methods. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Multi-walled carbon nanotube-supported tungsten oxide-containing multifunctional hybrid electrocatalytic system for oxygen reduction in acid medium

Combination of multi-walled carbon nanotubes, cobalt porphyrin and tungsten oxide in the film (deposited onto glassy carbon electrode substrate) produces an electrocatalytic system capable of effective reduction of oxygen in such acid medium as 0.5 mol dm⁻³ H₂SO₄.Co-existence of cobalt porphyrin and tungsten oxide, together with dispersed carbon nanotubes, leads to the enhancement effect evident from some positive shift in the oxygen reduction voltammetric potential and the significant increase of voltammetric currents (relative to those characteristic of the system free of carbon nanotubes and WO₃). The multi-component electrocatalytic film has also exhibited relatively higher activity towards reduction of hydrogen peroxide. It is reasonable to expect that the reduction of oxygen is initiated at the cobalt porphyrin redox centers, and the undesirable hydrogen peroxide intermediate is further reduced at the tungsten oxide support. An important function of carbon nanotubes is to improve transport of electrons within the electrocatalytic multi-component film.     

TiO2 Nanoparticles with High Photocatalytic Activity Under Visible Light

TiO₂ nanoparticles (C-TNT) with high visible light activity were obtained by carbonization of titania nanotubes (TNT) in an ethanol atmosphere under elevated pressure at 180 and 220 °C. New material was characterised by means of UV–Vis/DR, FTIR/DRS, TEM, and XRD. The photocatalytic activity was tested during monoazo dye decomposition under artificial solar light irradiation. Modified photocatalyst (220 °C, 4 h) had higher photocatalytic activity than both the pristine and commercial P25 catalysts.     

Fat content and fatty acids profile of colostrum and milk of primitive Konik horses ( Equus caballus gmelini Ant.) during six months of lactation

The effect of the stage of lactation, the number of foals and age of the mare on changes in the fat content and fatty acid composition of colostrum and milk of primitive Konik horses was investigated. Colostrum and milk samples from 12 lactating mares were collected at the beginning of lactation, on the days 1 and 2 after foaling and then, starting from the first month of lactation, at 4-week intervals up to the sixth month of lactation. Significant differences were observed in fat content as well as the composition of some analysed fatty acids between colostrum and milk of mares of the Konik breed. The number of foalings and the age of mares did not have a statistically significant effect on the fat content in milk and had only a slight effect on the fatty acid composition. Milk produced by mares of the Konik breed is characterized by a considerable content of polyene fatty acids with 18 carbon atoms, a low ratio of n-6 fatty acids to n-3 fatty acids as well as low, highly advantageous values of atherogenic and thrombogenic indices.     

Immunologic function of the harderian gland in chickens

1. The pharmacokinetics of methyldopa after oral and intravenous administration was studied in hypertensive and normotensive patients. After intravenous administration methyldopa plasma concentrations decayed according to a two-compartment open model. 2. For intravenous administration the overall elimination constant Ke1 was 0.56 +/- 0.03 h-1, the volume of distribution of the central compartment 0.29 +/- 0.80 1 kg-1 and the plasma clearance rate 11.2 +/- 0.6 1 h-1. 3. Plasma half-times during the beta-phase of the methyldopa plasma decay curve following intravenous and oral administration were 2.8 +/- 1.3 and 2.1 +/- 0.7 h, respectively. 4. Maximal plasma levels in hypertensive out-patients show great variation and range from 0 to 1.9 microgram ml-1. 5. No relationships were found between maximal methyldopa plasma levels in patients under treatment and control of hypertension.     

Ion-release, dissolution and buffering by zinc phosphate dental cements

The interaction of zinc phosphate dental cement with aqueous solutions has been studied in order to elucidate the relationship between pH change and ion release (dissolution). For each storage medium (deionized water, lactic acid at pH 2.7 and lactate buffer at pH 2.2) five cylindrical specimens of zinc phosphate cement (6 mm diameter×12 mm height) were prepared and weighed. They were stored individually in 8 cm³ of solution for a week, then the pH was determined and the specimens reweighed. The solutions were replaced and the specimens stored for a further week, then the pH and the weight were again measured. This was repeated for four weeks. For each storage solution at each time interval, the concentration of ions leached (Na, Mg, Al, Zn and P) were determined using ICP-OES. The lactate buffer was particularly erosive and reduced specimens to 4.1% (±0.9%) of their original mass after 4 weeks. The lactic acid was also erosive, but in water, specimens showed no significant mass change after 4 weeks. In all media, Na, Al, Mg, Zn and P ions were released, with mole ratios varying at each time interval. In all cases, the pH shifted towards neutral, but the relationship between ion release and solution pH was not straightforward. From the mole ratios of ions, estimates could be made of the relative proportions of attack at matrix to attack at filler, and this showed attack at filler predominated in most solutions at most time intervals.