Zur Trennung von Kobalt und Nickel

Ohne Zusammenfassung     

Localization of Dirac-like excitations in graphene in the presence of smooth inhomogeneous magnetic fields

The present paper discusses magnetic confinement of the Dirac excitations in graphene in the presence of inhomogeneous magnetic fields. In the first case a magnetic field directed along the z axis whose magnitude is proportional to 1/r is chosen. In the next case we choose a more realistic magnetic field which does not blow up at the origin and gradually fades away from the origin. The magnetic fields chosen do not have any finite/infinite discontinuity for finite values of the radial coordinate. The novelty of the two magnetic fields is related to the equations which are used to find the excited spectra of the excitations. It turns out that the bound state solutions of the two-dimensional hydrogen atom problem are related to the spectra of graphene excitations in the presence of the 1/r (inverse-radial) magnetic field. For the other magnetic field profile one can use the knowledge of the bound state spectrum of a two-dimensional cutoff Coulomb potential to dictate the excitation spectra of graphene. The spectrum of the graphene excitations in the presence of the inverse-radial magnetic field can be exactly solved while the other case cannot be. In the later case we give the localized solutions of the zero-energy states in graphene.     

Lewis Acid Catalyzed Selective Reactions of Donor–Acceptor Cyclopropanes with 2‐Naphthols

Lewis acid‐catalyzed reactions of 2‐substituted cyclopropane 1,1‐dicarboxylates with 2‐naphthols is reported. The reaction exhibits tunable selectivity depending on the nature of Lewis acid employed and proceed as a dearomatization/rearomatization sequence. With Bi(OTf)₃ as the Lewis acid, a highly selective dehydrative [3+2] cyclopentannulation takes place leading to the formation of naphthalene‐fused cyclopentanes. Interestingly, engaging Sc(OTf)₃ as the Lewis acid, a Friedel–Crafts‐type addition of 2‐naphthols to cyclopropanes takes place, thus affording functionalized 2‐naphthols. Both reactions furnished the target products in high regioselectivity and moderate to high yields.     

Aqueous Polymerization of Methyl Methacrylate Initiated by Potassium Peroxydisulfate-Ascorbic Acid Redox System

The aqueous polymerization of methyl methacrylate initiated by the redox system K₂S₂O₈-ascorbic acid has been studied at 35°C under the influence of oxygen. The rate of polymerization increases with increasing ascorbic acid concentration at low activator concentration, remains constant within the range 4.375 × 10^?3 to 11.25 × 10^?3 mole/liter, and at higher ascorbic acid concentration again decreases. The rate varies linearly with monomer concentration. The initial rate and the limiting conversion increase with increasing polymerization temperature. Organic solvents (water-miscible only) and small amounts of neutral salts like KC1 and Na₂SO₄ depress the initial rate and the maximum conversion. The addition of small amounts of salts like Cu²⁺ and Mn²⁺ increases the initial rate, but no appreciable increase in the limiting conversion is observed.     

Bicyclo [2.2.1]heptane as cyclopentane precursor. synthesis of benzhydropentalenes enroute to terpenoids

The synthesis of a bicyclo[2.2.l] heptane derivative and its transformation to two different cyclopentanoid derivatives and through intramolecular functionalisation is described for entry into diterpene and sesquiterpene.     

High pt and photon physics with ALICE at LHC

ALICE,A Large Ion Collider Experiment,is dedicated to study the QCD matter at extreme high temperature and density to understand the Quark Gluon Plasma (QGP) and phase transition.High-transversemomentum photons and neutral mesons from the initial hard scattering of partons can be measured with ALICE calorimeters,PHOS (PHOton Spectrometer) and EMCAL (ElectroMagnetic CALorimeter).Combing the additional central tracking detectors,the γ-jet and π 0-jet measurements thus can be accessed.These measurements offer us a sensitive tomography probe of the hot-dense medium generated in the heavy ion collisions.In this paper,high p T and photon physics is discussed and the ALICE calorimeters capabilities of high-transverse-momentum neutral mesons and γ-jet measurements are presented.     

Open air O-arylation reaction of phenols with aryl halides catalyzed by polymer-anchored copper(II) complexes

Two copper complexes were synthesized from macroporous chloromethylated polystyrene beads. The first one was prepared by sequential attachment of imidazole and copper acetate with chloromethylated polystyrene-divinyl benzene copolymer, and the second one was prepared from 4-vinylpyridine and copper acetate with chloromethylated polystyrene-divinyl benzene copolymer. These catalysts showed excellent catalytic activity in O-arylation reaction of aryl halides with phenol in dimethylsulfoxide using potassium carbonate at 130 °C under open air conditions to give diaryl ethers in high yields. Less reactive aryl bromides and aryl chlorides have also been shown to react with phenols to give good yields of the diaryl ethers. The effects of various parameters such as solvent, catalyst from different copper salt and base on the reaction system were studied. The reaction is applicable to a wide variety of substituted aryl halides and phenols with different steric and electronic properties. These catalysts were recovered by simple filtration, and the reusability experiments showed that these catalysts can be used five times without much loss in the catalytic activity.     

Discrimination of speaker sex and size when glottal-pulse rate and vocal-tract length are controlled

A recent study [Smith and Patterson, J. Acoust. Soc. Am. 118, 3177-3186 (2005)] demonstrated that both the glottal-pulse rate (GPR) and the vocal-tract length (VTL) of vowel sounds have a large effect on the perceived sex and age (or size) of a speaker. The vowels for all of the "different" speakers in that study were synthesized from recordings of the sustained vowels of one, adult male speaker. This paper presents a follow-up study in which a range of vowels were synthesized from recordings of four different speakers--an adult man, an adult woman, a young boy, and a young girl--to determine whether the sex and age of the original speaker would have an effect upon listeners' judgments of whether a vowel was spoken by a man, woman, boy, or girl, after they were equated for GPR and VTL. The sustained vowels of the four speakers were scaled to produce the same combinations of GPR and VTL, which covered the entire range normally encountered in every day life. The results show that listeners readily distinguish children from adults based on their sustained vowels but that they struggle to distinguish the sex of the speaker.     

Heterohexanuclear (Cu3Fe3) Complexes of Substituted Hexaazatrinaphthylene (HATN) Ligands: Twofold BF4− Association in the Solid and Stepwise Oxidation (3e) or Reduction (2e) to Spectroelectrochemically Characterized Species

New tris(ferrocenylcopper) compounds [(μ₃‐dqp){Cu(dppf)}₃][X]₃ (dppf=1,1′‐bis(diphenylphosphinoferrocene), dqp=hexamethyl‐, hexachloro‐ or un‐substituted diquinoxalino[2,3‐a:2′,3′‐c]phenazine=hexaazatrinaphthylene (HATN), X^?=BF₄^? or PF₆^?) undergo at least two different, reversible one‐electron reductions and three very closely spaced one‐electron oxidations. While the latter are attributed to the stepwise ferrocene→ferrocenium conversions, the first electron addition occurs in the ligand bridge to yield EPR detectable radical complexes. X‐band EPR measurements at 9.5 GHz showed a partially resolved hyperfine structure, while high‐frequency EPR measurements at 95 or 115 GHz revealed a small but variable axial g tensor anisotropy. All reversible steps were investigated by optically transparent thin‐layer electrode (OTTLE) spectroelectrochemistry (UV/Vis/NIR regions), revealing very low energy transitions for the reduced forms in agreement with the frontier MO arrangement. A crystal structure of the compound with unsubstituted dqp shows notable deviation from the trigonal symmetry and the close association of two tetrafluoroborate anions with the complex trication along the quasi‐trigonal axis to yield [(μ₃‐dqp){Cu(dppf)}₃(BF₄)₂]BF₄.