Local hydrodynamic investigation of the aeration in a submerged hollow fibre membranes cassette

The better understanding of the effective air distribution inside a membrane cassette is a particular challenge in submerged membrane bioreactor. The present study is the first one that investigates the hydrodynamics of the coarse bubbles flow inside a hollow fibre membranes cassette. The experimental investigations were carried out in a reactor equipped with commercial modules from ZENON ZeeWeed^® 500d. A bi-optical probe was used to measure the bubble size, the bubble velocity and the gas hold-up at different locations between the modules and for three different gas flow rates. These local measurements gave significant information about the lateral distribution of the air and its evolution with the height on the surface of the membrane modules, which can impact on the filtration performance and are the first step to an optimisation of the aeration system and module geometry.     

Fabrication and Tribological Properties of Pb Nanoparticles

In this paper, we describe a surfactant-assisted solution dispersion method to obtain metal nanoparticles, which involves dispersing and stabilizing metal droplets in an appropriate solvent. This method has been successfully used to prepare Pb nanoparticles from bulk Pb. The X-ray powder diffraction and transmission electron microscopy investigations show the formation of Pb nanoparticles possessing the same crystal structure as bulk metal and an average particle diameter of 40 nm. Thermal analysis indicates that Pb nanoparticles have organic shell, which is in agreement with the excellent oil-solubility. In addition, the tribological properties of Pb nanoparticles as additive in oil are discussed.     

Dependence of photoemission efficiency on the pulsed laser cleaning of Tungsten photocathodes, part 1: Experimental

3+ :YAG laser with 5^th harmonic generator, generating 16 ps duration pulses at 213 nm, with energies up to 0.5 mJ. Experimental results concerning the action of laser pulses, as well as the effects of residual pressure on the cleanliness of the photocathodes surface are presented and discussed. Influence of laser pulses and residual pressure on the work function of the metal are also investigated. Received: 15 April 1996/Accepted: 5 November 1996     

Iterative method for solving a nonlinear boundary value problem

In this paper, a boundary value problem for a nonlinear second-order ordinary differential equation is studied. By means of the maximum principle we established the existence and the uniqueness of a solution of the problem. Then for finding the solution an iterative method is proposed. It is proved that this method converges much faster than the Picar successive approximations and in a particular case it gives two-sided monotone approximations to the exact solution of the problem. Finally, some illustrative examples are considered to confirm the efficiency of the method.     

Low-temperature photoluminescence spectra of highly excited quantum wires

Optical spectra of highly excited quantum wires at low temperatures have been studied within the dynamical screening approximation. We found a strong Fermi-edge singularity (FES) in the photoluminescence spectra. The spectral shape and FES intensity strongly depend on temperature in agreement with recent experimental results.     

One step Pd(0)-catalyzed synthesis, X-ray analysis, and photophysical properties of cyclopent[hi]aceanthrylene: fullerene-like properties in a nonalternant cyclopentafused aromatic hydrocarbon.

A simple procedure for the synthesis of cyclopentafused polycyclic aromatic hydrocarbons (CP-PAH) with Pd(PPh(3))(2)Cl(2) catalyst has been applied to the one-pot palladium(0)-catalyzed coupling of 9,10-dibromoanthracene (1) with 2-methyl-3-butyn-2-ol. Reactions carried out in refluxing benzene in the presence of CuSO(4)/Al(2)O(3) yielded 9,10-dialkynylanthracene 2a, alkynyl aceanthrylene 2b, and 2,7-disubstituted cyclopent[hi]aceanthrylene 2c in 13%, 23%, and 19% purified yields, respectively, with total conversions of 80-90%. Sealed tube reactions without copper at 110 degrees C improved the yield of 2c up to >75%. Single-crystal X-ray analyses of 2a and 2c reveal a three-dimensional hydrogen bonding network, producing a unique crystal packing. The packing structure of 2b is dominated by pi-pi stacking interactions between two aceanthrylene molecules. CP-PAHs 2b and 2c have potentially interesting fullerene-like photophysics. While the UV-vis and fluorescence spectra of 2a (Phi(F) = 0.87) show the characteristic vibronic structure of anthracene, the UV-vis spectra of ruby-red aceanthrylene 2b and greenish-black cyclopent[hi]aceanthrylene 2c extend well into the visible range. Isomers 2b and 2c showed no detectable fluorescence emission. Unlike fullerenes, compounds 2b and 2c are poor singlet oxygen sensitizers with measured (1)O(2) quantum yields of 0.02 and 0.06, respectively. As expected from a simple Hückel analysis, 2c has relatively low two-electron reduction potentials as determined by cyclic voltammetry.     

Thorium in human blood serum,clot, and urine comparison with ICRP excretion model

Neutron activation followed by a simple radio-chemical separation procedure was employed to determine the concentrations of thorium (²³²Th) in human blood serum, clot, and urine of normal subjects and three groups of occupationally exposed persons. The thorium concentrations in the blood serum, clot, and urine samples of the exposed groups were distinctly higher than those of the other study groups and were found to increase with increasing occupational length of the persons. Daily urinary excretion is correlated with serum thorium burden and it is estimated that the daily excreted thorium is about 15% of the thorium in the serum pool.     

Anti-apoptotic and neuroprotective effects of Tetramethylpyrazine following spinal cord ischemia in rabbits

Background  

Tetramethylpyrazine (TMP) is one of the most important active ingredients of a Chinese herb Ligusticum wallichii Franchat, which is widely used in many ischemia disorders treatments. However, the exact mechanism by which TMP protects the spinal cord ischemia/reperfusion (I/R) injury is still unknown. For this purpose, rabbits were randomly divided into sham group, control group and TMP group. After the evaluation of neurologic function, the spinal cords were immediately removed for biochemical and histopathological analysis. Apoptosis was measured quantitatively by the terminal transferase UTP nick end-labeling (TUNEL) method and confirmed by electron microscopic examination, the expression of Bax and Bcl-2 was immunohistochemically evaluated and quantified by Western blot analysis.