An efficient lasing action from pyrromethene 556 dye-doped organically modified silicates

Organically modified solid-state silicates (ORMOSILS) doped with a new laser dye 1,3,5,7,8-pentamethylpyrromethene-2,6-disulfonate-BF₂ complex (pyrromethene 556) have been synthesized by a sol-gel method and the compositional effects on pore characteristics, fluorescence and lasing properties have been investigated. It is found that the use of dimethylsulfoxide and γ-glycidoxypropyltrimethoxysilane could greatly change the structure properties of sol-gel derived ORMOSILS cage, and thus the fluorescence and lasing properties of the materials could improve significantly. A successful laser oscillation from this dye-doped ORMOSILS sample has been achieved upon pumping with a Q-switched frequency-doubled Nd:YAG laser at 532 nm. A slope efficiency of 54% with a useful lifetime greater than 10,000 shots has been demonstrated at a pump repetition rate of 1 Hz and a pump intensity of 1 J/cm² by using the new ORMOSILS cage on our newly designed laser system. Our results have shown that it is possible to obtain a high-efficiency with a long-lifetime for a compact new laser device by low cost dye-doped solid-state ORMOSILS.     

Ion pair charge-transfer complexes between anionic and cationic metal-dithiolenes [M(II) = Pd,Pt

New [M(R(2)pipdt)(2)](BF(4))(2) salts [R(2)pipdt = N,N'-dialkyl-piperazine-2,3-dithione; M = Pd(II), R = Me and M = Pt(II), R = Me, Et, Pr(i)] bearing redox-active cationic dithiolene complexes have been prepared and characterized. These cations react with the redox-active [M(mnt)(2)](2-) [M = Pd(II), Pt(II); mnt = maleonitrile-2,3-dithiolate] anionic dithiolenes to form salts describable as ion pair charge-transfer complexes. X-ray crystallographic studies have shown that [M(Me(2)pipdt)(2)][M(mnt)(2)] complexes, with M = Pd(II) and Pt(II), are isomorphous. Crystal data of the Pt salt (3a): triclinic, Ponemacr; (No. 2); Z = 1; T = 293(2) K; a = 6.784(7) A, b = 8.460(6) A, c = 13.510(5) A, alpha = 100.63(2) degrees, beta = 104.04(2) degrees, gamma = 96.90(2) degrees; R1 = 0.0691 [wR2 = 0.2187 (all data)]. Structural data show that approximately square-planar [Pt(Me(2)pipdt)(2)] dications and regular square-planar [Pt(mnt)(2)] dianions form an infinite anion-cation one-dimensional stack along axis a with a Pt...Pt a/2 distance of 3.392 A and a Pt...Pt...Pt angle of 180 degrees. Anions and cations arrange themselves face-to-face so as to take on a staggered arrangement. These salts exhibit strong absorptions in the visible-near-infrared region assigned to ion pair charge-transfer transitions. A relation between the optical and thermal electron transfer in the solid state is obtained using a "Marcus-Hush model", and a solid-state electrical conductivity in agreement with expectations is observed. Vibrational spectroscopy is in agreement with the existence of charge-transfer interactions between the cationic and anionic components of the salts.     

Interactions modes and physical properties in transition metal chalcogenolene-based molecular materials

Molecule-based materials are extremely versatile materials as they can be built from specifically designed building blocks with the desired size, shape, charge and electronic properties which determine their intermolecular interactions and, thus, their organization in the solid. The intermolecular interactions, therefore, in particular van der Waals interactions, π–π and π–d interactions, H-bonding, etc., play a crucial role in self-assembling these pre-designed molecular units and may provide a powerful way to afford layered mono- and multifunctional molecular materials with new or unknown physical properties. In this review the relationship between interaction modes and physical properties of organic/inorganic hybrids based on transition metal complexes with chalcogenolene ligands will be examined and an outlook will be proposed. With this goal, magnetic materials, highly conducting and metallic single-component materials containing dithiolene complex building blocks, multifunctional materials where the dithiolene complex is the magnetic or conducting component in addition to more complex systems involving other types of building block such as the metal oxalate complexes, will be discussed.     

Photoluminescence of Y2O3:Eu thin film phosphors by sol-gel deposition and rapid thermal annealing

Y₂O₃:Eu³⁺ phosphor films have been developed by using the sol-gel process. Comprehensive characterization methods such as Photoluminescent (PL) spectroscopy, X-ray diffraction (XRD) and Fourier Transform Infrared (FTIR) spectroscopy were used to characterize the Y₂O₃:Eu³⁺ phosphor films. In this experiment, the XRD profiles show that the Y₂O₃:Eu³⁺ phosphor films crystallization temperature and optimum annealing temperature occur at about 650 and 750 °C, respectively. The optimum dopant concentration is 12 mol% Eu³⁺ and the critical transfer distance (R_c) among Eu³⁺ ions is calculated to be about 0.84 nm. Vacuum environment is more efficient than oxygen and nitrogen to eliminate the OH content and hence yields higher luminescent phosphor films. The PL emission intensity of Y₂O₃:Eu³⁺ phosphor films is also dependent on the annealing time. It was found that the H₂O impurities were effectively eliminated after annealing time of 25 s at 750 °C in vacuum environment. From the experiment results, the schematic energy band diagram of Y₂O₃:Eu³⁺ phosphor films is constructed.     

5nsec Dead time multichannel scaling system for Mössbauer spectrometer

A PC programmable and fast multichannel scaling module has been designed to use a commercial Mössbauer spectrometer. This module is based on a 10$ single chip 8 bits microcomputer (MC6805) and on a 35$ fast ALU, which allows a high performance and low cost system. The module can operate in a stand-alone mode. Data analysis are performed in real time display, on XT/AT IBM PC or compatibles. The channels are ranged between 256 and 4096, the maximum number of counts is 2³²?1 per channel, the dwell time is 3 μsec and the dead time between channels is 5 nsec. A friendly software display the real time spectrum and offers menues with different options at each state.     

Evaluation and evidence of natural gangliosides with two unsaturated bonds in the ceramide structure obtained by a combination of MALDI-MS and NMR spectroscopy

Gangliosides are membrane-associated glycosphingolipids. N-Acetyl GM3 and N-glycolyl GM3 are two tumor-associated antigens expressed in cancer tissues such as melanoma and mammalian cancer. In order to use these antigens in GM3-based vaccines for patients with early stage cancer, the synthetic version is recommended to avoid the risk of animal virus transmission from the source. However, the isolation of natural gangliosides is of comparative value for the structural characterization. The structures of N-acetyl and N-glycolyl GM3 extracted from dog and horse erythrocytes were evaluated by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry and nuclear magnetic resonance techniques; additionally, the natural N-acetyl ganglioside was compared to a synthetic one. In addition to the main compound with C24:0 fatty acid chain, a minor component with an additional unsaturation in the ceramide chain was detected, in both the dog and the horse gangliosides. This paper shows spectroscopic evidence of the aforementioned compounds.     

On the coset laws for skew lattices

Skew lattices are a noncommutative generalization of lattices. In the paper we study the varieties of symmetric, strongly symmetric and cancellative skew lattices, and characterize them in terms of certain laws regarding the coset structure of a skew lattice. As a consequence, combinatorial results connecting powers of D{\mathcal{D}}-classes and indices are derived.     

Azaphenanthrene alkaloids with antitumoral activity from Anaxagorea dolichocarpa Sprague & Sandwith (Annonaceae)

Phytochemical investigation of Anaxagorea dolichocarpa Sprague & Sandwith led to isolation of three azaphenanthrene alkaloids: eupolauramine, sampangine and imbiline 1. Their chemical structures were established on the basis of spectroscopic data from IR, HR-ESI-MS, NMR (including 2D experiments) and comparison with the literature. Sampangine and imbiline 1 are being described in the Anaxagorea genus for the first time. Eupolauramine and sampangine show concentration-dependent antitumoral activity in leukemic cells K562 with IC(50) of 18.97 and 10.95 μg/mL, respectively.     

Coherent structures in the near field of round jets

The present paper reports measurements of axial and radial velocities obtained with laser-Doppler anemometry in the transitional region of a round jet. The predominant frequencies of the coherent structures detected in the non-artificially excited jet, correspond to Strouhal numbers, around 0.33 and 0.55 and an interpretation of these observations is made. The use of external excitation can modify some characteristics of the jets disturbing the balance between the different flow structures, namely those corresponding to the two values of St. The jet diameter was 30.0 mm and the velocities ranged from near zero up to 15 m/s, corresponding to Reynolds number of 2.87 × 10⁴.To obtain the velocity probability distributions, power spectral distributions and auto-correlations, together with mean and rms velocities a LDA with double Bragg cell system was used. The Doppler signal was analysed with a counter interfaced to an Apple II microcomputer and a Racal magnetic tape.