Spectroscopic speciation of aqueous Am(iii)–oxalate complexes

Speciation, thermodynamic stability, and structural information of aqueous oxalato-Am(iii) complexes were resolved by combinatorial use of UV-Vis-LWCC, TRLFS, and DFT calculations.

Effect of ultrasound and heat on percutaneous absorption of l-ascorbic acid: human in vitro studies on Franz cell and Petri dish systems

OBJECTIVE

Percutaneous absorption of l-ascorbic acid (LAA) is limited due to its high hydrophilicity and low stability. Here, we investigated the effect of post-dosing sonophoresis (329 kHz, 20 mW cm^-2 ) and heat (36°C) on transdermal delivery of LAA.

METHODS

Ultrasound/heat, heat and control treatments were applied on skin surface for 2 and 5 min after topical application of C14-labelled LAA aqueous solution. After 15 min post-exposure, radioactivity was measured in tape-striped stratum corneum (TS-SC), epidermis, dermis and receptor fluid. As Franz diffusion cell model may have different acoustic response than in vivo human tissues, a novel Petri dish model was developed and compared with Franz cell model on the effects of ultrasound/heat treatment on the skin permeability.

RESULTS

Five-min ultrasound/heat treatment significantly accelerated skin absorption/penetration of LAA; 2-min treatment showed no enhancement effect on Franz diffusion cell model at the end of experiment. The use of Petri dish model significantly increased LAA concentrations in epidermis after 5 min of ultrasound/heat treatment, compared to the results of Franz cell model.

CONCLUSION

Combination of ultrasound (329 kHz, 20 mW cm^-2 ) and heat (36°C) significantly enhanced LAA transdermal penetration, when the time of treatment was sufficient (5 min). As Petri dish model was designed to simulate acoustic respond of dense human tissue to ultrasound, the difference between Franz cell and Petri dish models suggests that the enhancement effect of ultrasound/heat on skin penetration in vivo may be greater than that determined on in vitro Franz cell model.

Time-resolved laser fluorescence spectroscopy of UO2(CO3)3(4-)

The objective of the present study is to examine the luminescence characteristics of UO2(CO3)3(4-) in detail using time-resolved laser fluorescence spectroscopy. The peak wavelengths and lifetime of UO2(CO3)3(4-) were determined at room temperature using the two excitation laser wavelengths of 266 and 448 nm. The peak wavelengths in the luminescence spectrum exhibited hypsochromic shifts compared with those of UO2(2+). The lifetime determined from several samples containing various uranium concentrations was 8.9 ± 0.8 ns. Explanations for the hindrance to the observation of the luminescence spectrum of UO2(CO3)3(4-) in previous investigations are discussed. The representative experimental parameters, which might interrupt the measurement of weak luminescence, are the insertion delay time of the detection device, the overlapped luminescence of the background materials and the primary inner filter effect in the sample solution.

Spectroscopic studies on U(VI)-salicylate complex formation with multiple equilibria

This study investigates multiple equilibria related to the formation of the U(VI)-salicylate complex in a pH range of 3.0–5.5 using UV-Vis absorption and fluorescence measurement techniques. The absorbance changes at the characteristic charge-transfer bands of the complex were monitored, and the results indicated the presence of multiple equilibria and the formation of both 1:1 and 1:2 (U(VI):salicylate) complexes possessing bi-dentate chelate structures. The determined step-wise formation constants (log K 1:1 and log K 1:2) are as follows: 12.5 ± 0.1 and 11.4 ± 0.2 for salicylate, 11.2 ± 0.1 and 10.1 ± 0.2 for 5-sulfosalicylate, and 12.4 ± 0.1 and 11.4 ± 0.1 for 2,6-dihydroxybenzoate, respectively. The molar absorptivities of the complexes are also provided. Furthermore, time-resolved laser-induced luminescence spectra of U(VI) species demonstrate the presence of both a dynamic and static quenching process upon the addition of a salicylate ligand. Particularly for the luminescent hydroxouranyl species, a strong static quenching effect is observed. The results suggest that both the UO2(HSal)+ and the U(VI)–Sal chelate complexes serve as ground-state complexes that induce static quenching. The Stern–Volmer parameters were derived based on the measured luminescent intensity and lifetime data. The static quenching constants (log K S) obtained are 3.3 ± 0.1, 4.9 ± 0.1, and 4.4 ± 0.1 for UO2 2+, (UO2)2(OH)2 2+ and (UO2)3(OH)5 +, respectively.

Spectroscopic study on the mononuclear hydrolysis species of Pu(VI) under oxidation conditions

The formation constants of mononuclear hydrolysis species of Pu(VI) were determined by absorption spectroscopy under carefully designed experimental conditions. In order to exclude the formation of polynuclear hydrolysis species, the concentration of plutonium was diluted below 50 μM. To maintain the oxidation state of Pu(VI), NaOCl was applied as an oxidant. The trace amount of Pu(V) was monitored by the measurement of redox potential and absorption spectroscopy by using a liquid waveguide capillary cell with the optical path length of 100 cm. The determined molar absorption coefficients (ε, M−1 cm−1) were 272±26 and 436±33 for PuO2(OH)+ and PuO2(OH)2(aq) species, respectively. The formation constants of mononuclear hydrolysis species of Pu(VI) at ionic strength of 0.01 M NaClO4 were determined as follows:

logߙ*β′ 1 ߙ(for PuO2(OH)+) = −5.8±0.3,

logߙ*β′ 2 ߙ(for PuO2(OH)2(aq)) = −13.4±0.2

and

logߙ*β′ 3ߙ(for PuO2(OH)3 −) = −24.3±0.8.

Effect of reduction on the stability of Pu(VI) hydrolysis species

The chemical speciation of aqueous plutonium species has been performed by spectrophotometry. The main focus was concentrated on the effect of Pu(V) produced by the reduction of Pu(VI) on the stability of the Pu(VI) hydrolysis species. In order to detect the trace amounts of PuO2 + ions, a liquid waveguide capillary cell with an optical path length of 100 cm was connected to a spectrophotometer. As a consequence of the improved detection sensitivity, an absorption band at 569 nm being indicative of Pu(V) was observed within one day after the sample preparation from the pure Pu(VI) solution. The first hydrolysis species was (PuO2)2(OH)2 2+, at plutonium concentrations of 0.1–0.12 mM and at weak acidic conditions (pH 5–6). The formation constant of (PuO2)2(OH)2 2+ was determined to be log*β′22=−7.34±0.22 at 0.01 M NaClO4. This dinuclear hydroxide species was unstable and disappeared within one month after the sample preparation at the present experimental condition. In the neutral pH range, the second hydrolysis species was formed and remained for over one year. The samples showed different behavior for the reduction of Pu(VI). The time dependent distribution of plutonium species and their characteristic features in the absorption spectra are reported.

Ternary complex formation of Eu(III) with o-phthalate in aqueous solutions

Ternary hydroxo complex formation of Eu(III) with o-phthalate was investigated by potentiometry and fluorescence spectrophotometry. Curves of the equilibrium pH versus the amount of NaOH added showed that the pH value starting to form a Eu(III) precipitate was decreased due to the formation of a ternary hydroxo complex, EuOHL(s) (L = phthalate). The formation of EuOHL(s) was qualitatively confirmed by the enhancement of the fluorescence intensity of Eu(III) in the precipitate with the light absorbed by phthalate, and was quantitatively confirmed by the measurement of the amounts of Eu(III), OH(-) and phthalate included in the precipitate. The solubility product of EuOHL(s) was determined as pK(sp)(0) = 15.6+/-0.4. Characteristic features in the fluorescence spectra and the solubility product of the Eu(III)-phthalate complex were compared with those of the Eu(III)-PDA (PDA = pyridine-2,6-dicarboxylate) complex. The fluorescence intensity of the EuL(+) complex of L = PDA was about 11 times stronger than that of L = phthalate. The origin of the difference in the fluorescence intensity is discussed based on the intramolecular energy transfer effect from the lowest triplet energy level of the ligand to the resonance energy level of Eu(III).

Tunable stimulated-Brillouin-scattering resonator started by feedback provided by Bragg scattering from the dynamic grating within an active medium

We report a tunable stimulated-Brillouin-scattering resonator that does not require a starting mirror or a wavelength selector. The resonator is based on the Bragg scattering from the dynamic grating within the active medium itself. The laser dye (Rhodamine 6G dissolved in ethanol) was utilized as the active medium and was pumped by a frequency-doubled Nd:YAG laser. The quality factor (M(2)) of the output beam was 2.2. A single short pulse (<1 ns) with a pumping efficiency of ~4% was observed.

Keratosis lichenoides chronica: marked response to calcipotriol ointment

Keratosis lichenoides chronica (KCL) is a rare dermatosis characterized by a distinctive seborrheic dermatitis-like facial eruption, together with violaceous, papular, and nodular lesions on the extremities and trunk, typically arranged in a linear and reticulate pattern. KLC is resistant to therapy, although spontaneous remission has been reported. We describe a 35-year-old woman with KLC who had the typical features of widespread violaceous, reticulate, and striae-like eruptions with a prominent keratotic component over a nine-year period and who responded well to treatment with calcipotriol ointment. The immunohistochemical profiles are presented in addition to typical histopathologic features.

Simplified holographic associative memory using enhanced nonlinear processing with a thermoplastic plate

A simplified holographic associative memory by enhanced nonlinear recording using a thermoplastic plate is described. The system is based on two new concepts: The system utilizes the second-order diffraction instead of the first-order diffraction, and to enhance the second-order diffraction efficiency, a novel angle-tuning recording using a thermoplastic plate is employed. As a result, the size of the system is reduced by one half with a remarkable increase (as much as approximately 100 times) in light efficiency compared with that of the conventional systems, and the need for critical alignment is eliminated. Experimental results demonstrating the performance of the system are provided.