Numerical simulations of the discontinuous progression of cerebral aneurysms based on fluid-structure interactions study

Investigations into the characteristics of hemodynamics will provide a better understanding of the pathology of cerebral aneurysms for clinicians.In this work,a steady state discontinuous-growth model of the cerebral aneurysms was proposed.With the assumption of the fluid-structure interaction between the wall of blood vessel and blood,a fluid-structure coupling numerical simulation for this model was built using software ANSYS and CFX.The simulation results showed that as the aneurysm volume increased,a bl...     

Laser-conditioning mechanism of ZrO_2/SiO_2 HR films with fitting damage probability curves of laser-induced damage

<正>The method of fitting damage probability curves of laser-induced damage is introduced to investigate the laser-conditioning mechanism of ZrO_2/SiO_2 high reflection(HR) films.The laser-induced damage thresholds(LIDTs) of the sample are tested before and after the laser-conditioning scanning process.The parameters of the defects are obtained through the fitting process of the damage probability curve.It can be concluded that the roles of laser conditioning include two aspects:removing defects with lower threshold and producing new defects with higher threshold.The effect of laser conditioning is dependent on the competition of these two aspects.     

Kohlenhydrate

Ohne Zusammenfassung     

Reactions of the heavier group 14 element alkyne analogues Ar'EEAr' (Ar' = C6H3-2,6(C6H3-2,6-Pri2)2; E = Ge, Sn) with unsaturated molecules: probing the character of the EE multiple bonds

Reactions of the alkyne analogues Ar'EEAr' (Ar' = C6H3-2,6(C6H3-2,6-Pr(i)2)2; E = Ge (1); Sn (2)) with unsaturated molecules are described. Reaction of 1 and 2 with azobenzene afforded the new hydrazine derivatives Ar'E{(Ph)NN(Ph)}EAr' (E = Ge (3); Sn (4)). Treatment of 1 with Me3SiN3 gave the cyclic singlet diradicaloid Ar'Ge{mu2-(NSiMe3)}2GeAr' (5), whereas 2 afforded the monoimide bridged Ar'Sn{mu2-N(SiMe3)}SnAr' (6). Reaction of 1 with t-BuNC or PhCN yielded the adduct Ar'GeGe(CNBu(t))Ar' (7) or the ring compound (8). In contrast, the tin compound 2 did not react with either t-BuNC or PhCN. Treatment of 1 with N2CH(SiMe3) generated Ar'Ge{mu2-CH(SiMe3)}{mu2:eta2-N2CH(SiMe3)}{mu2-N2CH(SiMe3)}GeAr' (9) which contains ligands in three different bridging modes and no Ge-Ge bonding. Reaction of 1 with an excess of N(2)O gave a germanium peroxo species Ar'(HO)Ge(mu2-O)(mu2:eta2-O2)Ge(OH)Ar' (10) which features a ring. Oxidation of 1 by tetracyanoethylene (TCNE) led to cleavage of the Ge-Ge bond and formation of a large multiring system of formula Ar'Ge3+{(TCNE)2-}3{(GeAr')+}3. The digermyne 1 also reacted with 1 equiv of PhCPh to give the 1,2-digermacyclobutadiene 12, which has a ring, and with Me(3)SiCCH or PhCC-CCPh to activate a flanking C6H3-2,6-Pr(i)2 ring and give the tricyclic products 13 and 14. The "distannyne" 2 did not react with these acetylenes. Overall, the experiments showed that 1 is highly reactive toward unsaturated molecules, whereas the corresponding tin congener 2 is much less reactive. A possible explanation of the reactivity differences in terms of the extent of the singlet diradical character of the Ge-Ge and Sn-Sn bonds is discussed.     

The asymptotic Casimir–Polder potential from second-order perturbation theory and its generalization for anisotropic polarizabilities

It is shown how the leading term for very large R of the Casimir–Polder potential, that is the term varying as R^?7, arises in second-order perturbation theory applied to the interaction Hamiltonian ? \documentclass{article}\pagestyle{empty}\begin{document}$ - \sum\limits_\sigma {\frac{1}{2}\alpha (\sigma){\rm E}^{ \bot ^2 } (\sigma)} $\end{document}. The generalization to anisotropic molecules is calculated and the angular dependence of the long range intermolecular potential in this case is given explicitly in terms of the principal polarizabilities and their corresponding directions of the two molecules.     

A reversible valence equilibrium in a heavier main group compound

The addition of LiPh to Ar*SnCl (Ar* = C6H3-2,6-Trip2; Trip = C6H2-2,4,6-iPr3) at low temperature afforded the Sn(1)-Sn(III) species Ar*SnSnPh2Ar*, which exists in equilibrium with the Sn(II) compound Ar*SnPh. It is the first example of a room-temperature equilibrium of compounds involving main group elements in different oxidation states.     

Angular dependence of the retarded dispersion energy

The Casimir–Polder retarded dispersion energy is calculated for non-symmetric molecules and the energy is expressed in terms of body fixed axes for the dipole transition moments on each molecule. In the special case of molecules with cylindrical symmetry the potential energy is given in terms of the transverse and longitudinal polarizabilities and in terms of the angles defining the orientation of the axes of the molecules with respect to the intermolecular direction. In the limit of no retardation (R ? λ) the result becomes that of London and in the opposite limit of full retardation at large R the potential energy tends to that of Craig and Power.     

In(8)(C(6)H(3)-2,6-Mes(2))(4) (Mes=C(6)H(2)-2,4,6-Me(3)): A Metal-Rich Main-Group Cluster with a Distorted Cubane Structure

A distorted In(8) cubane core (see picture) is present in the novel indium cluster In(8)(C(6)H(3)-2,6-Mes(2))(4) (Mes=C(6)H(2)-2,4,6-Me(3)), which was synthesized by the reaction of LiC(6)H(3)-2,6-Mes(2) with InCl. It has an average In-In bond length of 2.92 ? and represents a new addition to the range of heavier Group 13 element clusters.     

Structures,bonding, and reaction chemistry of the neutral organogallium(I) compounds (GaAr)n(n = 1 or 2) (Ar = terphenyl or related ligand): an experimental investigation of Ga-Ga multiple bonding

The synthesis, structure, and properties of several new organogallium(I) compounds are reported. The monovalent compounds GaAr* (Ar* = C(6)H(3)-2,6-Trip(2), Trip = C(6)H(2)-2,4,6-Pr(i)()(3), 1), GaAr# (Ar# = C(6)H(3)-2,6(Bu(t)Dipp)(2), Bu(t)Dipp = C(6)H(2)-2,6-Pr(i)(2)-4-Bu(t)(), 4), and the dimeric (GaAr')(2) (Ar' = C(6)H(3)-2,6-Dipp(2), Dipp = C(6)H(3)-2,6-Pr(i)(2), 6) were synthesized by the reaction of "GaI" with (Et(2)O)LiAr*, (Et(2)O)LiAr# (3), or (LiAr')(2). Compounds 1 and 4 were isolated as green crystals, whereas 6 was obtained as a brown-red crystalline solid. All three compounds dissolved in hydrocarbon solvents to give green solutions and almost identical UV/visible spectra. Cryoscopy of 1 and 6 showed that they were monomeric in cyclohexane. Crystals of 1 and 4 were unsuitable for X-ray crystal structure determinations, but an X-ray data set for 6 showed that it was weakly dimerized in the solid with a long Ga-Ga bond of 2.6268(7) A and a trans-bent CGaGaC core array. The 1,2-diiodo-1,2-diaryldigallane compounds [Ga(Ar*)I](2) (2), [Ga(Ar#)I](2) (5), and [Ga(Ar')I](2) (7) were isolated as byproducts of the synthesis of 1, 4, and 6. The crystal structures of 2 and 7 showed that they had planar ICGaGaCI core arrays with Ga-Ga distances near 2.49 A, consistent with Ga-Ga single bonding. Treatment of 1, 4, and 6 with B(C(6)F(5))(3) immediately afforded the 1:1 donor-acceptor complexes ArGa[B(C(6)F(5))(3)] (Ar = Ar*, 8; Ar#, 9; Ar', 10) that featured almost linear gallium coordination, Ga-B distances near the sum of the covalent radii of gallium and boron, as well as some close Ga...F contacts. Compound 1 also reacted with Fe(CO)(5) under ambient conditions to give Ar*GaFe(CO)(4) (11), which had been previously synthesized by the reaction of GaAr*Cl(2) with Na(2)Fe(CO)(4). Reaction of 1 with 2,3-dimethyl-1,3-butadiene afforded the compound [Ar*GaCH(2)C(Me)C(Me)CH(2)]2 (12) that had a 10-membered 1,5-Ga(2)C(8) ring with no Ga-Ga interaction. Stirring 1 or 6 with sodium readily gave Na(2)[Ar*GaGaAr*] (13) and Na(2)(Ar'GaGaAr') (14). The former species 13 had been synthesized previously by reduction of GaAr*Cl(2) with sodium and was described as having a Ga-Ga triple bond because of the short Ga-Ga distance and the electronic relationship between [Ar*GaGaAr*](2-) and the corresponding neutral group 14 alkyne analogues. Compound 14 has a similar structure featuring a trans-bent CGaGaC core, bridged by sodiums which were also coordinated to the flanking aryl rings of the Ar' ligands. The Ga-Ga bond length was found to be 2.347(1) A, which is slightly (ca. 0.02 A) longer than that reported for 13. Reaction of Ga[N(Dipp)C(Me)](2)CH, 15 (i.e., GaN(wedge)NDipp(2)), which is sterically related to 1, 4, and 6, with Fe(CO)(5) yielded Dipp(2)N(wedge)NGaFe(CO)(4) (16), whose Ga-Fe bond is slightly longer than that observed in 11. Reaction of the less bulky LiAr"(Ar"= C(6)H(3)-2,6-Mes(2)) with "GaI" afforded the new paramagnetic cluster Ga(11)Ar(4)" (17). The ready dissociation of 1, 4, and 6 in solution, the long Ga-Ga distance in 6, and the chemistry of these compounds showed that the Ga-Ga bonds are significantly weaker than single bonds. The reduction of 1 and 6 with sodium to give 13 and 14 supplies two electrons to the di-gallium unit to generate a single bond (in addition to the weak interaction in the neutral precursor) with retention of the trans-bent geometry. It was concluded that the stability of 13 and 14 depends on the matching size of the sodium ion, and the presence of Na-Ga and Na-Ar interactions that stabilize their Na(2)Ga(2) core structures.