Growth of polydisperse aerosol in an adiabatic condensation nuclei counter (CNC) with finite expansion time

The diffusional growth of polydisperse aerosol was calculated as a function of expansion time, i.e.; time in which the temperature drop necessary for supersaturation-induced condensational growth is produced. At high nuclei concentrations and/or long expansion time only fractions of the ideal supersaturation (produced with small concentrations and fast expansion) are obtained. Large nuclei are activated earlier than smaller ones and consume so much vapor that smaller nuclei cannot possibly grow. This may cause a strong influence on the particle size detection limit. Therefore, great care is necessary to interpret condensation nuclei counter (CNC) measurements with concentrated polydisperse aerosols correctly.     

Peculiarities of performance of the spin valve for the superconducting current

The spin valve effect for the superconducting current based on the superconductor/ferromagnet proximity effect has been studied for a CoO _x /Fe1/Cu/Fe2/Cu/Pb multilayer. The magnitude of the effect ΔT _c = T _c ^AP ? T _c ^P , where T _c ^P and T _c ^AP are the superconducting transition temperatures for the parallel (P) and antiparallel (AP) orientation of magnetizations, respectively, has been measured for different thicknesses of the Fe1 layer d _Fe1. The obtained dependence of the effect on d _Fe1 reveals that ΔT _c can be increased in comparison with the case of a half-infinite Fe1 layer considered by the previous theory. A maximum of the spin valve effect occurs at d _Fe1 ～ d _Fe2. At the optimal value of d _Fe1 almost full switching from the normal to the superconducting state when changing the mutual orientation of magnetizations of the iron layers Fe1 and Fe2 from P to AP is demonstrated.     

C‐O Bond Cleavage of Diethyl Ether and Tetrahydrofurane by [(dpp‐BIAN)AlI(Et2O)] [dpp‐BIAN = 1,2‐bis[(2,6‐di‐iso‐propylphenyl)‐imino]acenaphthene]

At elevated temperatures, the aluminum complex [(dpp‐BIAN)AlI(Et₂O)] ( 1 ) splits the C‐O bonds of diethyl ether and tetrahydrofurane yielding the dimeric alkoxides [(dpp‐BIAN)AlOEt]₂ ( 2 ) and [(dpp‐BIAN)AlO(CH₂)₄I]₂ ( 3 ), respectively. Already at ambient temperatures, a cleavage of the C‐O bond of THF is to observe in the reaction of 1 with CpNa in THF as confirmed by the formation of [(dpp‐BIAN)AlO(CH₂)₄C₅H₅]₂ ( 4a ) and [(dpp‐BIAN)Al{O(CH₂)₄C₅H₅}(THF)] ( 4b ) in a molar ratio of 1:2. The reaction of 1 with t‐BuOK affords the monomeric alkoxide [(dpp‐BIAN)AlO‐t‐Bu(Et₂O)] ( 5 ). Compounds 2 , 3 , and 4a/b were characterized by elemental analyses and IR spectra. Additionally, the structures of 2 and 3 were determined by single crystal X‐ray diffraction.     

Ethylene polymerization with novel bridged tri- and tetranuclear titanocene/MAO systems

Two benzene centered tri- and tetracyclopentadienyl ligands C₆H₃(CH₂C₅H₅)₃-1,3,5 (1) and C₆H₂(CH₂C₅H₅)₄-1,2,4,5 (2) and their titanium complexes C₆H₃[CH₂C₅H₄Ti(C₅H₅)Cl₂]₃-1,3,5 (3), C₆H₃[CH₂C₅H₄Ti(C₅H₄CH₃)Cl₂]₃-1,3,5 (4), as well as C₆H₂[CH₂C₅H₄Ti(C₅H₅)Cl₂]₄-1,2,4,5 (5) were synthesized and characterized by mass and ¹H NMR spectra. In the presence of methylaluminoxane (MAO), 3, 4 and 5 are efficient catalysts for ethylene polymerization in toluene. The influence of the polymerization conditions such as catalyst concentration, MAO/Ti molar ratio, polymerization time and temperature were investigated in detail. 3, 4 and 5 produce linear polyethylene (PE) with broad molecular weight distributions (MWD) and a little lower molecular weight.     

Syntheses and structures of heterometallic clusters by the reaction of o-carboranyl cobaltadichalcogenolato complexes

Metalladichalcogenolate cluster complexes [Cp'Co{E(2)C(2)(B(10)H(10))}]{Co2(CO)5} [Cp' = eta5-C5H5, E = S(3a), E = Se(3b); Cp' = eta5-C5(CH3)5, E = S(4a), E = Se(4b)], {CpCo[E(2)C(2)(B(10)H(10))]}(2)Mo(CO)2] [E = S(5a), Se(5b)], Cp*Co(micro2-CO)Mo(CO)(py)2[E(2)C(2)(B(10)H(10))] [E = S(6a), Se(6b)], Cp*Co[E(2)C(2)(B(10)H(10))]Mo(CO)2[E(2)C(2)(B(10)H(10))] [E = S(7a), Se(7b)], (Cp'Co[E(2)C(2)(B(10)H(10))]W(CO)2 [E(2)C(2)(B(10)H(10))] [Cp' = eta5-C5H5, E = S(8a), E = Se(8b); Cp' = eta5-C5(CH3)5, E = S(9a), E = Se(9b)], {CpCo[E(2)C(2)(B(10)H(10))]}(2)Ni [E = S(10a), Se(10b)] and 3,4-(PhCN(4)S)-3,1,2-[PhCN(4)SCo(Cp)S(2)]-3,1,2-CoC(2)B(9)H(8) 12 were synthesized by the reaction of [Cp'CoE(2)C(2)(B(10)H(10))] [Cp' = eta5-C5H5, E = S(1a), E = Se(1b); Cp' = eta5-C5(CH3)5, E = S(2a), E = Se(2b)] with Co2(CO)8, M(CO)3(py)3 (M = Mo, W), Ni(COD)2, [Rh(COD)Cl]2, and LiSCN4Ph respectively. Their spectrum analyses and crystal structures were investigated. In this series of multinuclear complexes, 3a,b and 4a,b contain a closed Co3 triangular geometry, while in complexes 5a-7b three different structures were obtained, the tungsten-cobalt mixed-metal complexes have only the binuclear structure, and the nickel-cobalt complexes were obtained in the trinuclear form. A novel structure was found in metallacarborane complex 12, with a B-S bond formed at the B(7) site. The molecular structures of 4a, 5a, 6a, 7b, 9a, 9b, 10a and 12 have been determined by X-ray crystallography.     

Methodenvariation mittels Dynamischer Geometrie—exemplarisch

Methods are mostly demonstrated using various mathematical topics or topics which can be mathematized instead of using various methods in order to explore topics. The causes for this domination are of curricular nature. A balance of these two basic patterns of mathematics teaching can be achieved by applying the spiral principle and the principle of computer-based variation of methods. This is demonstrated in the present contribution by means of dynamics geometry using “Rectangles with equal circumference or area” (grades 5–10) as an example. An argumentation on school algebra level for the computer-generated phenomenology is given. This contribution ends with a remark on necessary thematic extensions and unsolved interface problems when various media-specific methods are used.     

Gemischte Sandwichkomplexe der 4 f‐Elemente: Enantiomerenreine Cyclooctatetraenyl‐Cyclopentadienyl‐Komplexe des Samariums und Lutetiums mit donorfunktionalisierten Cyclopentadienylliganden

Organometallic Compounds of the Lanthanides. 139 Mixed Sandwich Complexes of the 4 f Elements: Enantiomerically Pure Cyclooctatetraenyl Cyclopentadienyl Complexes of Samarium and Lutetium with Donor‐Functionalized Cyclopentadienyl Ligands The reactions of [K{(S)‐C₅H₄CH₂CH(Me)OMe}], [K{(S)‐C₅H₄CH₂CH(Me)NMe₂}] and [K{(S)‐C₅H₄CH(Ph)CH₂NMe₂}] with the cyclooctatetraenyl lanthanide chlorides [(η⁸‐C₈H₈)Ln(μ‐Cl)(THF)]₂ (Ln = Sm, Lu) yield the mixed cyclooctatetraenyl cyclopentadienyl lanthanide complexes [(η⁸‐C₈H₈)Sm{(S)‐η⁵ : η¹‐C₅H₄CH₂CH(Me)OMe}] ( 1 a ), [(η⁸‐C₈H₈)Ln{(S)‐η⁵ : η¹‐C₅H₄CH₂CH(Me)NMe₂}] (Ln = Sm ( 2 a ), Lu ( 2 b )) and [(η⁸‐C₈H₈)Ln{(S)‐η⁵ : η¹‐C₅H₄CH(Ph)CH₂NMe₂}] (Ln = Sm ( 3 a ), Lu ( 3 b )). For comparison, the achiral compounds [(η⁸‐C₈H₈)Ln{η⁵ : η¹‐C₅H₄CH₂CH₂NMe₂}] (Ln = Sm ( 4 a ), Lu ( 4 b )) are synthesized in an analogous manner. ¹H‐, ¹³C‐NMR‐, and mass spectra of all new compounds as well as the X‐ray crystal structures of 3 b and 4 b are discussed.     

Der Einfluß der Koordinationssphäre von Samarocenen auf die Synthese von flüssigkristallinen Polymethacrylaten

The Influence of the Coordination Sphere of Samarocenes on the Synthesis of Liquid Crystalline Polymethacrylates (C₅Me₅)₂Sm(THF)₂ ( 1 ) reacts with 1,3‐Diisopropyl‐4,5‐dimethylimidazoline‐2‐ylidene C₃N₂Me₂iPr₂ (iPr‐carben) with formation of (C₅Me₅)₂Sm(iPr‐carben) ( 3 ). The reaction of (C₅Me₄Et)₂Sm(THF)₂ ( 2 ) with Al₂Me₆ in toluene yields [(C₅Me₄Et)₂Sm(CH₃)Al(CH₃)₃]₂ ( 6 ). 3 and 6 were characterized by single crystal X‐ray structure analysis. Via living polymerization of mesogenic methacrylates with the organosamarium complexes 1 , 2 , 3 , (C₅Me₅)₂Sm(C₃H₅) ( 4 ), (C₅Me₅)₂Sm(CH₃)(THF) ( 5 ), 6 , and (C₅Me₄Et)₂SmCH(SiMe₃)₂ ( 7 ), liquid crystalline homo‐ and blockcopolymers were obtained with narrow molecular mass distribution indexes in high yield. Partial competitive mechanisms are observed dependend of the structure of the catalyst and the polarity of the solvents.