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931.
932.
Calza P Medana C Baiocchi C Branca P Pelizzetti E 《Journal of chromatography. A》2004,1049(1-2):115-125
Mepanipyrim, a widely used pyrimidinic fungicide, has been photocatalytically degraded in aqueous solution on TiO2. The purpose of this study is to artificially produce degradation compounds similar to those formed in the environment. Numerous intermediates have been identified and characterised through a MSn spectra analysis, allowing us to give insight into the early steps of the degradation process. Several concomitant pathways occur concerning both reductive and/or oxidative attacks; the main steps involve the cleavage of triple bond, mono and bihydroxylation of the parent molecule, loss of benzene moiety and/or propynylic chain. All these structures are easily degraded themselves, so that the only species recognised to endure in the investigated times is guanidine. A mechanism of transformation accounting for the identified intermediates is proposed. 相似文献
933.
Claudio?FernándezEmail author Georgi. D.?RaikovEmail author 《Annales Henri Poincare》2004,5(2):381-403
We consider the three-dimensional Schrödinger operators
and
where
, A is a magnetic potential generating a constant magnetic
field of strength
, and
where
decays fast enough at infinity. Then, A. Pushnitskis representation of the spectral shift function (SSF)
for the pair of operators
is well defined for energies
We study the behaviour of the associated representative of the equivalence class
determined by the SSF, in a neighbourhood of the Landau levels
Reducing our analysis to the study of the eigenvalue asymptotics for a family of
compact operators of Toeplitz type, we establish a relation between the type of the
singularities of the SSF at the Landau levels and the decay rate of V at infinity.
Communicated by Bernard HelfferSubmitted 23/09/03, accepted 15/01/04 相似文献
934.
We show that it is impossible to determine the state equation of quintessence models on the basis of pure observational SNIa data. An independent estimate of
M0 is necessary. Also in this most favourable case the situation can be problematic. 相似文献
935.
The ammonium removal efficiency (ARE) and cell viability was investigated in freshly isolated rat hepatocytes exposed to increasing ammonium loads (0.1-2.0 mM). No difference was observed in both ARE and cell viability at the different ammonium concentrations tested. Storage of hepatocytes at 0 degrees C for 72 hours inhibited ammonium removal and urea synthesis. Rewarming of cells at 37 degrees C for 120 min was followed by an ARE fully comparable to freshly isolated hepatocytes. These data indicated that cold preservation of rat hepatocytes for 3 days in UW followed by a rewarming is associated with normal ammonium detoxification efficiency. 相似文献
936.
937.
Di Tullio A D'Acquarica I Gasparrini F Desiderio P Giannessi F Muck S Piccirilli F Tinti MO Villani C 《Chemical communications (Cambridge, England)》2002,(5):474-475
The enantiomers of carnitine are converted on-line in the injection port of a gas chromatograph into beta-hydroxy-gamma-butyrolactones and are separated on a derivatized beta-cyclodextrin chiral stationary phase. 相似文献
938.
We describe a novel macrocyclic minireceptor that is assembled from a chiral 1,2-diamine and 5-allyloxyisophthalic acid. After immobilization on HPLC silica, the chiral macrocycle preferentially binds the L-enantiomers of simple amino acid derivatives, with enantioselectivities values up to 3.0 kcal/mol. [structure: see text] 相似文献
939.
Barbieri R Bertini I Cavallaro G Lee YM Luchinat C Rosato A 《Journal of the American Chemical Society》2002,124(19):5581-5587
Lanthanides may substitute calcium in calcium-binding proteins, such as, for instance, EF-hand proteins. Paramagnetic lanthanides are capable of orienting the protein in high magnetic fields to an extent similar to that obtained by using orienting devices, and each lanthanide orients according to its magnetic susceptibility tensor. Here, Ce(3+), Tb(3+), Dy(3+), Ho(3+), Er(3+), Tm(3+), Yb(3+) in the C-terminal site of calbindin D(9k) have been investigated. Such systems provide (1)H-(15)N residual dipolar couplings (rdc) which can be used for solution structure determinations. Within the frame of optimizing the use of residual dipolar couplings for efficient solution structure determination, it is proposed here to use a number of lanthanides (e.g., >2) to obtain the orientations of the internuclear vectors with respect to an arbitrary reference system. This is facilitated by the independent knowledge of the magnetic susceptibility anisotropy tensor of each metal, obtained from the analysis of the pseudocontact shifts. A further module of the program PARAMAGNETIC-DYANA, called RDCDYANA-ANGLES, is developed to efficiently incorporate such rdc-derived orientations, instead of the rdc themselves, as constraints in the solution structure calculation. This strategy is absolutely general and can be extended to any other pair of dipole-dipole coupled nuclei. The effect of mobility is also assessed. In principle, information on the mobility can be obtained with a number of lanthanide ions >5, or by combining a smaller number of lanthanide ions with a few orienting devices. 相似文献
940.
Very High Specific Activity RadioNuclides, HSARN, are a powerful tool to label a wide variety of chemical elements and compounds present in the biosphere in ultra-trace amounts. Medium and high Z radionuclides, can be produced by irradiation in light-ions accelerator and sometimes nuclear reactor. If the nuclear reaction product has atomic number different from irradiated target, it is possible separating the radioactive nuclide from irradiated target, without addition of isotopic carrier. These kinds of radionuclides are named No Carrier Added, NCA, and their specific activity is very high and can reach values close to the theoretical Carrier Free one. The true specific activity must be determined by use of very sensitive radioanalytical techniques. If a low isotopic dilution factor is obtained, these radiotracers are used to label inorganic species and complexes of elements, which are presently introduced into the echo-systems by human activities. New production methods for NCA Pt, Ir, Au, Cu and Ga radiotracers are presented, with some details on radiochemistry and quality controls. 相似文献