New ceramic-carbon composites for electrodes for electrochemical capacitors

A new class of composite materials is introduced. Fine powders of silica, titania, Y-modified zirconia, and three types of alumina were pressed and sintered to form porous monoliths with relatively uniform pore structure. Carbon was then deposited in the pores of such monoliths by thermal decomposition of dichloromethane, cyclohexene, and glucose. The structure of the carbon deposit was studied by low-temperature nitrogen adsorption and by thermal analysis. The composite materials were used as electrodes in electrochemical capacitors with 1-ethyl-3-methylimidazolium trifluoromethylsulfonate (a low-temperature ionic liquid) as the electrolyte. High capacitances were observed for glucose-derived materials, which had high specific surface areas.     

Synthesis of N-heterocyclic carbene precursors bearing biphenyl units and their use in ruthenium-catalyzed ring-opening metathesis polymerization

A range of new imidazolium and imidazolinium chlorides bearing biphenyl units on their nitrogen atoms was synthesized. They differed by the electron-withdrawing or -donating nature and the steric bulk of the substituents on their aromatic rings. These various N-heterocyclic carbene (NHC) precursors were combined with the [RuCl₂(p-cymene)]₂ dimer and potassium tert-butoxide to generate the corresponding ruthenium-arene complexes [RuCl₂(p-cymene)(NHC)] in situ. The catalytic activity of these species was investigated in the photoinduced ring-opening metathesis polymerization (ROMP) of cyclooctene. The results obtained confirmed the necessity of blocking the ortho-positions of the phenyl rings in the vicinity of the metal center in order to attain high catalytic efficiencies. They also showed that changing the steric and electronic properties of the substituents on the remote phenyl rings of the biphenyl units had no significant influence on the outcome of the polymerization.     

Synthesis of a new scaffold: the 7H,8H-pyrimido[1,6-b]pyridazin-6,8-dione nucleus

This paper describes a modified method of preparation of a number of alpha-aryl-alpha-(pyridazin-3-yl)-acetonitriles via the C-arylation reaction of the corresponding carbanionsof phenylacetonitriles using 3-chloropyridazine derivatives. KOH and DMSO were used inthe deprotonation process, which made the reaction very simple and safe to perform.Nitriles were obtained in the hydrolysis reaction to the corresponding alpha-aryl-alpha-(pyridazin-3-yl)-acetamide derivatives, which were next subjected to cyclization to afford the finalproducts. A number of new derivatives of 7H,8H-pyrimido[1,6-b]pyridazin-6,8-dione weresynthesized in the cyclocondensation reaction of respective alpha-aryl-alpha-(pyridazin-3-yl)-acetamides with diethyl carbonate in the presence of EtONa. The structure andcomposition of the new compounds were confirmed by IR, (1)H- and (13)C- NMR analysesand by elemental C, H and N analysis.     

The effect of parasitic boron doping on P-type piezoresistors

Absolute piezoresistive pressure sensors often use direct wafer bonding of SOI with the etched bulk silicon to provide us with sensitive membranes and sealed cavities. The advantage of such a process is that we can easily obtain a thin, monocrystalline silicon membrane with controlled thickness and a vacuum sealed cavity. However, few works have been reported on the electrical quality of this N-type membrane and its influence on performance of the P-type gauges. The problem of parasitic Boron appearance at the Si/SiO₂ interface was only recently shown in BESOI wafers, but it becomes much more significant when creating the component at the bottom side of the device layer, like in the case of an absolute piezoresistive pressure sensor.     

Study of 169Hf at high rotational frequency

High-spin properties of the nucleus ¹⁶⁹Hf have been studied through the fusion evaporation reaction ⁹⁶Zr(⁷⁶Ge,3n)¹⁶⁹Hf at a beam energy of 310 MeV. The known rotational bands have been extended considerably and 6 new bands have been established, four of which form coupled bands with pronounced M1 connections. Quasiparticle assignments are suggested for the new band structures, and it appears that coupling to vibrational degrees of freedom plays a role. Both coupled bands involve the excitation of quasiprotons. In the region of highest spin, a large alignment gain is interpreted in terms of a mixed crossing where an h _9/2 and an h _11/2 quasiproton provide the two signatures of the aligning configuration. Received: 23 March 2001 / Accepted: 20 September 2001     

Photophysical properties and photocytotoxicity of novel phthalocyanines - potentially useful for their application in photodynamic therapy

Two novel zinc(II) phthalocyanines bearing non-peripheral ester-alkyloxy substituents (Pc-4 and Pc-5) were synthesized, by a two-step procedure starting from 2,3-dicyanohydroquinone. Both sensitizers show promising photophysical properties, including solvatochromic study, qualitative evaluation of emission, aggregation behavior and singlet oxygen generation. It was proven that the photodynamic activity of the compounds studied depends on the molecular oxygen level. Comparison of the quantum yields of singlet oxygen generation as well as the oxidation rate constants using 1,3-diphenylisobenzofurane before and after deaeration proved the photodynamic effect of Pc-4 and Pc-5 to be governed by the photosensitization mechanism II. Changes in the quantities of the compounds exposed to irradiation were also estimated. Upon their exposure to light the changes in intensity of the Q band were monitored. The photodecomposition of Pc-4 and Pc-5 in DMSO or DMF solutions was found to proceed according to the first order kinetic reaction in two stages.The photosensitizing effect of Pc-4 in HSC-3 cells was significantly lower than that of ZnPc. Pc-4 was ineffective at 0.1 μM, while a low, approx. 15% photocytotoxicity was observed at 5 μM, at a distance of 5 and 10 cm. The efficacy of Pc-4 in photokilling of cultured cells is affected by hydrophobicity and the aggregation status of the photosensitizer.     

Mass spectrometry of 3-oxothiazolo[3,2-a] and [3,2-c]pyrimidin-5-ones. Correlation of the intensities of the M+. and the selected fragment ions

The mass spectral fragmentation of eight new 3-oxothiazolo[3,2-a] and [3,2-c]pyrimidin-5-ones were investigated. Fragmentation pathways are proposed on the basis of accurate mass and metastable transition measurements. The correlation between the intensities of M^+. and the selected fragment ions of these compounds is discussed. The data obtained created the basis for distinguishing isomers and metamers.