Continuous catalytic pyrolysis of oily sludge using U-shape reactor for producing saturates-enriched light oil

Continuous catalytic pyrolysis of oily sludge was carried out in a special U-shape reactor for producing saturates-enriched light oil. The sludge underwent thermal pyrolysis first and then catalytic pyrolysis. During the thermal pyrolysis, chain hydrocarbons were first cracked and further polymerized into aromatics. The effect of temperatures (400–800 °C) on the products was investigated and the maximum liquid yield (67.7%) was obtained at 500 °C. High temperature promoted polymerization, thus the distribution of aromatics in the liquid product was increased and was more concentrated in polyaromatics at 800 °C. In the catalytic upgrading stage, dolomite was used as catalyst and aromatics were adsorbed on it, either aggregated or decomposed. As a result, a light oil product with 57.0% saturates was obtained at the residence time of 8.9?s due to the conversion of aromatics and heavy hydrocarbons into light aliphatic hydrocarbons such as straight chain hydrocarbons. Compared with the oil phase in the raw sludge sample, the content of saturates was increased by 45.0% and that of the asphaltenes was reduced by 88.5%. Meanwhile, the inherent moisture in the oily sludge could participate in the steam reforming reaction, promoting the decomposition of aromatics and leading to an increase in the H₂ generation. Moreover, the release of H₂S was reduced from 0.132 to 0.005?mol per kg sludge and the sulfur content of the oil product was also decreased in the presence of dolomite. The deactivation of dolomite can be attributed to the carbonization of CaO and deposition of polyaromatic coke on the catalyst surface.     

Perfect-Fluid Sources for the Levi-Civita Metric II

A regular static interior solution of Einstein’s field equations representing a perfect fluid cylinder of finite radius is presented. The solution is matched to the Levi-Civita vacuum solution at a boundary where the pressure vanishes. The density and pressure are finite and positive inside the cylinder for a specific range of the mass parameter. The solution could thus represent a reasonable source for the Levi-Civita metric.     

Integrated photonic crystal spectrometers for sensing applications

A combination of negative refraction and diffraction compensation in a superprism-based photonic crystal structure is used to demonstrate a compact on-chip photonic crystal spectrometer. This structure provides strong dispersion and signal isolation, which are essential for forming an efficient and compact spectrometer. Performance of these spectrometers as spectral pattern detectors is discussed. The experimental results show that a PC structure with 80 μm × 220 μm dimension can locate a single spectral feature with better than 10 pm accuracy over a bandwidth of 50 nm around 1550 nm center wavelength at an output signal-to-noise ratio of 13 dB.     

Towards a synthetic glycoconjugate vaccine against Neisseria meningitidis A

Albumin conjugates of synthetic fragments of the capsular polysaccharide of the Gram-negative bacterium Neisseria meningitidis serogroup A were prepared. The fragments include monosaccharides 1 [alpha-D-ManpNAc-(1-->O)-(CH(2))(2)NH(2)] and 2 [6-O-P(O)(O(-))(2)-alpha-D-ManpNAc-(1-->O)-(CH(2))(2)NH(2)], disaccharide 3 [alpha-D-ManpNAc-[1-->O-P(O)(O(-))-->6]-alpha-D-ManpNAc-(1-->O)-(CH(2))(2)NH(2)], and trisaccharide 4 [alpha-D-ManpNAc-[1-->O-P(O)(O(-))-->6]-alpha-D-ManpNAc-[1-->O-P(O)(O(-))-->6]-alpha-D-ManpNAc-(1-->O)-(CH(2))(2)NH(2)]. Two monosaccharide blocks were employed as key intermediates. The reducing-end mannose unit featured the NHAc group at C-2, and contained the aminoethyl spacer as the aglycon for the final bioconjugation. The interresidual phosphodiester linkages were fashioned from an anomerically positioned H-phosphonate group in a 2-azido-mannose building block. The spacer-linked saccharides 1-4 were N-acylated with hepta-4,6-dienoic acid and the resulting conjugated diene-equipped saccharides were subjected to Diels-Alder-type addition with maleimidobutyryl-group functionalized human serum albumin to form covalent conjugates containing up to 26 saccharide haptens per albumin molecule. Complete (1)H, (13)C, and (31)P NMR assignments for 1-4 are given. Antigenicity of the neoglycoconjugates containing 1-4 was demonstrated by a double immunodiffusion assay which indicated that a fragment as small as a monosaccharide is recognized by a polyclonal meningococcus group A antiserum and that the O-acetyl group(s) present in the natural capsular material is not essential for antigenicity.     

Adsorption characteristics and the kinetics of the cation exchange of rhodamine-6G with Na+-montmorillonite

The adsorption and the kinetics of the cation exchange of rhodamine-6G (Rh-6G) with Na(+)-montmorillonite (Na(+)-MMT) have been studied. The binding parameters of Rh-6G have been determined by applying Freundlich and D-R isotherms. The enthalpy and the entropy of adsorption have been determined. The isosteric heat of adsorption has also been determined and decreases with increasing the concentration of Rh-6G. Increasing the concentration of Rh-6G led to a decrease in the adsorption capacity, which attributed to the formation of Rh-6G aggregates. Kinetic measurements of the cation exchange were followed up using a stopped-flow electrical conductivity detection unit. The cation-exchange process exhibited first-order kinetics with respect to the dye concentration and inversely proportional to the clay concentration. The measurements were accomplished at different temperatures and the activation parameters were determined. Increasing the Na(+)-MMT concentration led to a decrease in the rate constant. The latter is also affected by changing the exchangeable cation.     

Implications of $B \to \rho \gamma$ measurements in the standard model and supersymmetric theories

We study the implications of the recently improved upper limits on the branching ratios for the decays , expressed as . We work out the constraints that the current bound on implies on the parameters of the quark mixing matrix in the standard model (SM). Using the present profile of the unitarity triangle, we predict this ratio to lie in the range (at 95% C.L.), with the central value . We also work out the correlations involving , the isospin-violating ratio , and the direct CP-violating asymmetry in decays in the SM, in the minimal supersymmetric extension of the SM (MSSM), and in an extension of the MSSM involving an additional flavor-changing structure in transitions. Received: 19 August 2002 / Published online: 18 October 2002 RID="a" ID="a" e-mail: ali@mail.desy.de RID="b" ID="b" e-mail: lunghi@mail.desy.de     

Novel cycloartane saponins from Corchorus depressus L

Two novel bidesmosidic cycloartane-type glycosides, depressosides C and D were isolated from Corchorus depressus L. Their structures were elucidated as (22R)-16beta,22-epoxy-3beta,26-dihydroxy-9,19-cyclolanost-++ +24E-ene 3, 26-di-O-beta-D-glucopyranoside and (22R,24S)-22,25-epoxy-3beta,16beta,24-trihydroxy-9,19-cyclolano stane 3, 24-di-O-beta-glucopyranoside, respectively on the basis of chemical evidence and detailed spectroscopic studies.