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121.
This study was designed to investigate the effects of butyltins on yeast phagocytosis in vitro by haemocytes of the colonial ascidian Botryllus schlosseri. This species has been reported to be very sensitive to organotins. Results show that, in analogy to reports on mammalian leukocyte re-activity, butyltins exert inhibitory effects on phagocytosis in a concentration-dependent manner, mainly by influencing cellular calcium homeostasis by interacting with the calcium pump. As the immunosuppressant activity of organotins described in mammals and teleosteans also occurs in an invertebrate marine species, the latter may assume a role as a sensitive biosensor of butyltins as immunotoxins in aqueous ecosystems. 相似文献
122.
Giuliano Casale 《Queueing Systems》2008,60(3-4):193-202
We introduce the Conditional Mean Value Analysis (CMVA) algorithm, an exact solution method for product-form load-dependent closed queueing networks that provides a numerically stable solution of models where the load-dependent Mean Value Analysis (MVA) is numerically unstable. Similarly to the MVA algorithm for constant-rate queues, CMVA performs operations in terms of mean quantities only, i.e., queue-lengths, throughput, response times. Numerical stability derives from a new version of the MVA arrival theorem for load-dependent models which is expressed in terms of mean queue-lengths instead of marginal probabilities. The formula is obtained by the analysis of the conditional state spaces which describe network equilibrium as seen by jobs during their residence times at queues. We also provide a generalization of CMVA to multiclass models that preserves the numerical stability property. 相似文献
123.
Masuhiro Tsukada Giuliano Freddi John S. Crighton 《Journal of Polymer Science.Polymer Physics》1994,32(2):243-248
The structure and compatibility of poly(vinyl alcohol)-silk fibroin (PVA/SF) blend films were analyzed by differential scanning calorimetry (DSC), thermomechanical (TMA) and thermogravimetric (TGA) analysis, x-ray diffractometry, and scanning (SEM) and transmission (TEM) electron microscopy. DSC curves of PVA/SF blend films showed a major endothermic peak at 220°C, along with a peak at 280°C. These endotherms were assigned to the thermal decomposition of the ordered PVA elements and to the thermal degradation of silk fibroin, respectively. The PVA/SF blends behaved in a manner intermediate to the pure components, as suggested by both contraction expansion and sample weight retention properties recorded by TMA and TGA measurements. The IR absorption spectra of the blends were identified as purely a composite of the absorption bands characteristic of both PVA and SF pure polymers. The X-ray diffraction patterns of PVA/SF blends showed overlapping spacing due to PVA and SF. A dispersed phase formed by spherical particles of 3–7 μm diameter was observed by SEM and TEM. All these findings suggest that PVA and SF are incompatible. © 1994 John Wiley & Sons, Inc. 相似文献
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We calculate the oscillations of the dc conductance across a mesoscopic ring, simultaneously tuned by applied magnetic and electric fields orthogonal to the ring. The oscillations depend on the Aharonov-Bohm flux and of the spin-orbit coupling. They result from mixing of the dynamical phase, including the Zeeman spin splitting, and of geometric phases. By changing the applied fields, the geometric phase contribution to the conductance oscillations can be tuned from the adiabatic (Berry) to the nonadiabatic (Ahronov-Anandan) regime. To model a realistic device, we also include nonzero backscattering at the connection between ring and contacts, and a random phase for electron wave function, accounting for dephasing effects. 相似文献
127.
Lepareur N Mévellec F Noiret N Refosco F Tisato F Porchia M Bandoli G 《Dalton transactions (Cambridge, England : 2003)》2005,(17):2866-2875
Reduction-substitution reactions of [M(O)Cl(4)](-)(M=Re, (99)Tc) precursors with an excess of substituted dithiobenzoate ligands (R-PhCS(2))(-) in dichloromethane/methanol mixtures afford a series of six-coordinated neutral mixed-ligand complexes of the type M(III)(R-PhCS(3))(2)(R-PhCS(2))(M=Re; Rel--9; M=99)Tc; Tel--9). The coordination sphere is entirely filled by sulfur donor atoms, and the complexes adopt a distorted trigonal prismatic arrangement, as assessed by the X-ray crystal structure analysis of Re(4-Me-PhCS(3))(2)(4-Me-PhCS(2)), Re 2. These compounds show sharp proton and carbon NMR profiles, in agreement with the diamagnetism typical of low spin d(4) trigonal prismatic configurations. The red-ox processes involve reduction of the metal from Re(v) to Re(iii) and oxidation of dithiobenzoate to trithioperoxybenzoate. M2--9 complexes contain a substitution-inert [M(R-PhCS(3))(2)](+) moiety including the metal and two trithioperoxybenzoate fragments, while the third dithiobenzoate ligand is labile. The latter is efficiently replaced by reaction with better nucleophiles such as diethyldithiocarbamate giving a further class of mixed ligand complexes of the type M(III)(R-PhCS(3))(2)(Et(2)NCS(2))(M=Re; Re 10--18; M=(99)Tc; Tc--18), which retain the trigonal prismatic arrangement, as determined by the X-ray analyses of the representative compounds Re(PhCS(3))(2)(Et(2)NCS(2)), Re 10 and (99)Tc(PhCS(3))(2)(Et(2)NCS(2)), Tc 10. 相似文献
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G. Rapisarda B. Ginatempo G. M. Florio A. Stancanelli E. S. Giuliano 《Il Nuovo Cimento D》1990,12(10):1453-1463
Summary We have extended the well-known relativistic KKR-CPA theory up tol≤3 angular momentum, in order to make this framework suitable to deal with rare-earth alloys. However, such an extension has
also relevance in judging the convergence of the KKR-CPA calculations even for those atomic species with empty valencef-states. To do that we worked out the transformation from the usual real spherical harmonics to the cubic double-point group
representatin. We have tested the present theory and corresponding codes by computing the electronic structure of Cu0.75−Au0.25 and by comparing our results with earlierl≤2 R-KKR-CPA calculations. In order to reduce the large amount of computing time required, we have also used a new technique
for the Brillouin zone integration.
Work sponsored also by CRRN/SM. 相似文献