Potential use of gamma irradiation in the production of mussel and oyster reference materials for paralytic shellfish poisoning toxins

Bivalve shellfish samples containing paralytic shellfish poisoning toxins were subjected to gamma irradiation dosage trials in order to assess the potential suitability of the technique in the production of toxin reference materials. Two candidate reference materials of tissue homogenates, mussels (Mytilus sp.) and native oysters (Ostrea edulis), were prepared in-house. Both were subjected to gamma irradiation at four different dose levels, 3.0, 6.0, 13.0 and 18.1 kGy. Bacterial levels were shown to be eliminated in the mussels and significantly reduced in the oysters following irradiation at all four dose levels. Paralytic shellfish poisoning (PSP) toxin concentrations were not significantly reduced in any of the samples indicating the treatment had no adverse affect on the initial stability of any of the PSP toxins monitored. Chromatographic results showed near-identical profiles for treated and non-treated samples inferring that no fluorescent toxin degradation products or matrix interferences were produced during the irradiation process. Results therefore proved that gamma irradiation treatment reduced bacterial levels within paralytic shellfish poisoning reference materials without compromising analyte content, with the subsequent potential to enhance the stability of future candidate reference materials treated in this manner.     

Effect of SiO2/Si3N4 dielectric distributed Bragg reflectors (DDBRs) for Alq3/NPB thin-film resonant cavity organic light emitting diodes

In this article, we report on the effect of SiO₂/Si₃N₄ dielectric distributed Bragg reflectors (DDBRs) for Alq₃/NPB thin-film resonant cavity organic light emitting diode (RCOLED) in increasing the light output intensity and reducing the linewidth of spontaneous emission spectrum. The optimum DDBR number is found as 3 pairs. The device performance will be bad by further increasing or decreasing the number of DDBR. As compared to the conventional Alq₃/NPB thin-film organic light emitting diode (OLED), the Alq₃/NPB thin-film RCOLED with 3-pair DDBRs has the superior electrical and optical characteristics including a forward voltage of 6 V, a current efficiency of 3.4 cd/A, a luminance of 2715 cd/m² under the injection current density of 1000 A/m², and a full width at half maximum (FWHM) of 12 nm for emission spectrum over the 5-9 V bias range. These results represent that the Alq₃/NPB thin-film OLED with DDBRs shows a potential as the light source for plastic optical fiber (POF) communication system.     

Optimal control of chaotic systems with input saturation using an input-state linearization scheme

Chaos is undesirable in many engineering applications since it causes a serious degradation of the system performance and restricts the system’s operating range. Therefore, the problem of controlling chaos has attracted intense interest in recent years. This paper proposes an approach for optimizing the control of chaotic systems with input saturation using an input-state linearization scheme. In the proposed approach, the optimal system gains are identified using the Nelder–Mead simplex algorithm. This algorithm does not require the derivatives of the cost function (or the performance index) to be optimized, and is therefore particularly applicable to problems with undifferentiable elements or discontinuities. Two numerical simulations are performed to demonstrate the feasibility and effectiveness of the proposed method.     

A structurally characterized Ni-Al methyl-bridged complex with catalytic ethylene oligomerization activity

A bimetallic Ni-Al (2.5087(15) A) complex with an agostic alpha-C-H, [eta-C5H4CH=N(C6F5)]Fe[eta-C5H4PPh2]Ni(AlMe3), has been isolated and crystallographically established. The complex is active towards ethylene oligomerization/polymerization under moderate conditions.     

Monitoring the coordination of aluminium during microporous oxide crystallisation by in situ soft X-ray absorption spectroscopy

An in situ cell, which is capable of obtaining time resolved soft X-ray data (200 eV < E < 3000 eV) under hydrothermal conditions has been developed and used to study the self-assembly processes occurring during microporous aluminophosphate crystallization.     

Flavin-based [2]rotaxanes

[reaction: see text] We report the synthesis of flavin-stoppered hydrogen bonded [2]rotaxanes 1 and 2. We also report the electrochemically controllable properties of these systems in solution, and for derivative 2, as an electropolymerized thin film.     

‘One-flask’ transformation of isocyanates and isothiocyanates to guanidines hydrochloride by using sodium bis(trimethylsilyl)amide

A ‘one-flask’ synthesis of guanidines was developed by reacting isocyanates and isothiocyanates with sodium bis(trimethylsilyl)amide followed by addition of primary or secondary amines with a catalytic amount of AlCl₃. The desired guanidines were obtained in good yields and the reaction was applicable to aliphatic and aromatic substrates. A plausible mechanism was proposed through the generation of cyanamide anion from isocyanates or isothiocyanates with sodium bis(trimethylsilyl)amide. Addition of amines and catalytic amount of AlCl₃ smoothly converted the cyanamides to the desired guanidines.     

One-pot ethynylation and catalytic desilylation in synthesis of mestranol and levonorgestrel

A one-pot ethylnylation and catalytic desilylation reaction was developed for the synthesis of mestranol and levonorgestrel. Addition of trimethylsilylacetylide to the carbonyl group at C-17 of the steroids yielded the C-17α-trimethylsilylacetylenyl adducts, which were desilylated with a catalytic amount of TBAF (0.050 equiv) in one pot to provide the corresponding mestranol and levonorgestrel both in 90% yields. A plausible mechanism was proposed for the catalytic desilylation through the regeneration of the fluoride ion from the reaction of alkoxide on the steroid with Me₃SiF. The one-pot ethynylation and catalytic desilylation methodology provided an alternative route and avoided the traditional use of flammable and explosive acetylene gas toward the synthesis of mestranol and levonorgestrel.     

Rate coefficients for the gas-phase reaction of hydroxyl radicals with 2-methoxyphenol (guaiacol) and related compounds

2-Methoxyphenol (guaiacol) and its derivatives are potential marker compounds for wood smoke emissions in the atmosphere. To investigate the atmospheric reactivity of this type of compounds, rate coefficients for their reactions with hydroxyl (OH) radicals have been determined at 294 ± 2 K and 1 atm using the relative rate method with gas chromatography for chemical analysis. The rate coefficients (in units of cm3 molecule?1 s?1) are: 2-methoxyphenol, (7.53 ± 0.41) × 10?11; 3-methoxyphenol, (9.80 ± 0.46) × 10?11; 4-methoxyphenol, (9.50 ± 0.55) × 10?11; 2-methoxy-4-methylphenol, (9.45 ± 0.59) × 10?11; and methoxybenzene, (2.20 ± 0.15) × 10?11. The estimated atmospheric lifetime for 2-methoxyphenol is ~2 h, indicating that it is too reactive to be used as a tracer for wood smoke emissions. The reactivity of the methoxyphenols is compared with other substituted aromatics and interpreted in relation to the type, number, and positions of the different substituents on the aromatic ring. The atmospheric implications of the reactions are also discussed.