New Penta(tetrathiafulvalenyl)[60]fullerenes for Supramolecular Materials

New penta(organo)fullerenes donor–acceptor systems bearing five tetrathiafulvalene recognition units have been synthesized to promote self‐assemblies similar in appearance to shuttlecocks nested into each other thanks to the conical host cavity created around the fullerene together with the π–π and electronic interactions.     

Higher valency ion substitution into the manganese oxide framework

A new route for higher valency ion substitution into the manganese oxide (OMS-2) framework is reported. Isomorphously substituted vanadium and niobium OMS-2 were hydrothermally synthesized at 200 degrees C for a period of 2 days. Characterization by XRD, elemental analysis, Raman spectroscopy, and resistivity studies proved that vanadium was incorporated into the manganese oxide structure. The presence of vanadium in the framework changes the electrical properties, making the material very attractive for water sensing applications.     

Yb-doped strictly all-fiber laser actively Q-switched by intermodal acousto-optic modulation

We show an actively Q-switched ytterbium-doped strictly all-fiber laser. Cavity loss modulation is achieved in a tapered optical fiber by core-to-cladding mode-coupling induced by travelling flexural acoustic waves. When the acoustical signal is switched-off, the optical power losses within the cavity are reduced, and then a laser pulse is emitted. Trains of Q-switched pulses were successfully obtained at repetition rates in the range 1–10 kHz, with pump powers between 59 and 88 mW, at the optical wavelength of 1064.1 nm. Best results were for laser pulses of 118 mW peak power, 1.8 μs of time width, with a pump power of 79 mW, at 7 kHz repetition rate.     

Time resolved visualization of structures of velocity gradients measured with near Kolmogorov-scale resolution in turbulent free-shear flows

A three-dimensional visualization of velocity gradients at the finest scales in a turbulent free-shear flow is obtained using a time-resolved scanning PIV system with near Kolmogorov-scale resolution. A minimal observation volume capable of capturing single velocity gradient structures is used. The structures are identified by iso-surfaces revealing four basic shapes in the makeup of the velocity gradients: sheets, tubes, square ribbons and spherical blobs. Their size is also obtained. The 3D local acceleration structure is visualized showing strong anti-alignment with the convective acceleration. The statistics of the velocity gradient, and higher order moments (skewness and kurtosis) are calculated and compared favorably with published experimental work and with homogeneous isotropic theory.     

Elucidating a particulate matter deposition episode by combining scanning electron microscopy and X-ray fluorescence spectrometry.

Multielemental composition and morphology of particulate matter samples were examined to detect the presence of two potential responsible pollutant emitters at four sites impacted during a pollution episode in the City of Campana, Argentina. Coke and smoke black are the main constituents associated to the industrial plants that were considered, a priori, as responsible pollutant emitters. Wavelength dispersive X-ray fluorescence (WDXRF) was employed for the analysis of metals in samples coming from both, suspected sources and four sites. On the basis of multielemental composition profiles, a screening analysis was undertaken for exploring similarities among sources and sample sites adopting the average concentration profile of the crustal rock as soil surrogate. Particle morphology was studied by scanning electron microscopy (SEM) in source samples and in those environmental samples selected through the screening analysis. Two types of collected samples were analyzed: 1) those with composition profiles closer to the potential sources and 2) those closer to the cluster rock. This strategy was adequate to identify the responsible source of the contamination episode.     

Syntheses and gas transport properties of polyarylates based on isophthalic and terephthalic acids and mixtures of bisphenol A and 1, 1 bi‐2‐naphthol

Polyarylates based on isophthalic (IA) and terephthalic (TA) acids and an equimolar mixture of the diols Bisphenol A (BPA) and 1,1 bi‐2‐naphthol (BN) were synthesized to produce BPA‐BN/IA and BPA‐BN/TA polymers and to measure their gas permeability coefficients, P(i), at several pressures and 35 °C, to the gases O₂, N₂, CH₄, and CO₂. For the BPA‐BN/IA membranes, at a 2 atm up‐stream pressure, the P(O₂) and P(CO₂) are 0.93 and 4.0 Barrers with O₂/N₂ and CO₂/CH₄ ideal separation factors of 6.7 and 27. For the BPA‐BN/TA, at a 2 atm up‐stream pressure, the P(O₂) and P(CO₂) are 2.0 and 9.9 Barrers with O₂/N₂ and CO₂/CH₄ ideal separation factors of 5.6 and 21. Comparing the selectivity–permeability balance of properties shown by the BPA/TA membranes with that shown by the copolymer BPA‐BN/TA, the balance moves in the direction of higher selectivity and lower permeability because of the incorporation of BN, which is a more rigid monomer than BPA. However, when the balance of properties for the pair O₂/N₂ shown by BPA‐BN/TA is compared with the one shown by other membranes such as those based on mixtures of diols and diacids, that is the bisphenol A‐naphthalene/I‐T polymers reported in the literature, the balance moves up and to the right of the typical selectivity–permeability trade‐off observed in the BPA‐polyarylate family. Thus, simultaneous incorporations of flexible and rigid monomers in both the diols and the diacids lead to more productive and more selective membranes. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 256–263, 2006     

Antiphytopathogenic activity of Psoralea glandulosa (Fabaceae) against Botrytis cinerea and Phytophthora cinnamomi

The resinous exudate, three meroterpenes, namely bakuchiol (1), 3-hydroxybakuchiol (2), 12-hydroxyisobakuchiol (3), and one furanocoumarin, psoralen (4), were isolated from the leaves of culen (Psoralea glandulosa). In addition to these, two semi-synthetic derivatives, bakuchiol acetate (5) and bakuchiol methyl eter (6), were obtained from 1, and were subsequently evaluated in vitro for the inhibitory effect of resin and compounds on the mycelial growth of Botrytis cinerea Pers.: Fr. and Phytophthora cinnamomi Rands. The resinous exudate inhibited the mycelial growth of both the pathogens, while bakuchiol (1) exhibited an inhibitory effect on the mycelial growth of B. cinerea up to 94% at a concentration of 150 mg/L and psoralen (4) reduced the mycelial growth of P. cinnamomi up to 80% at a concentration of 150 mg/L. These compounds have the ability of blocking the development of mycelial growth and may be used as a potential biopesticide in the agricultural sector once the in vivo test results have been validated.     

Fast Electrochemical Characterization of Historical Glasses Using Carbon Screen‐Printed Electrodes and Ultrasonic Assisted Sampling

A new method for lead oxide (PbO) analysis in glasses, using a carbon screen printed electrode (SPE) is proposed. A suspension of the powdered glass sample in nitric acid is prepared using an ultrasonic probe, 100 µL of slurry are deposited on the SPE and the voltammetric measurement is carried out. Structural information of PbO in the glass matrix is obtained by CV. Lead quantification is performed by DPV. In the best conditions a LOD of 2.30 wt% of PbO was obtained. The method has been applied with good results in the analysis of historical glasses samples.     

Thermal effects on optical properties of silver ruby glass

2 O·10 CaO·74 SiO₂ mol%) glass doped with 0.11 and 0.35 wt.% silver are investigated. Heating treatments are carried out in a temperature range between 400 and 575 °C for times ranging from 30 to 300 min in different atmospheres and cooling rates. The starting glasses show a colourless and transparent appearance, but after thermal treatments under a reducing atmosphere become coloured, confirming the presence of silver colloids related to the 410-nm absorption band. On the other hand, the main effects of thermal treatments on the PL spectra concern those from samples treated in a reducing atmosphere. Thus, the intensity of both excitation and emission spectra chiefly diminishes in the 220–230 nm and 325–350 nm ranges, respectively. In addition, time-resolved spectra show the main ultraviolet (UV) emission centred above 330 nm upon excitation with 228-nm light. In contrast to the starting glass, we notice no shift or even slight shifts of the peak position to longer wavelengths with increasing delay time after pulse excitation, even for delay times as short as 0.01 ms. The results are discussed on the basis of transitions in which Ag⁺ ions are involved. Received: 6 February 1998/Accepted: 9 March 1998