We employ a new laterally coupled, vertical double dot with a tunable tunnel-coupling gate in a parallel configuration to study the electron spin and orbital dependence of quantum mechanical tunnel coupling on the size of the honeycomb vertices in the small electron numbers regime. We find a transition from the weak coupling regime, where fluctuations in tunnel coupling due to varying electron configuration dominate the anticrossings, to a regime where the two dots coalesce. We apply a magnetic field to ascertain the orbital angular momenta of the Fermi surface eigenstates, which correlate with anticrossing size, and we identify spin pairs with congruent behavior.

The structure of a C-symmetric epidithiodiketopiperazine alkaloid, SCH 64874, was determined by semisynthesis. The relative stereochemistry of the β-hydroxy carboxylic acid chain having three chiral centers was determined by comparison of the NMR data of the four possible diastereomeric β-hydroxy carboxylic acid fragments with those of SCH 64874. Condensation of the (-)-deacetylaranotin core with two enantiomeric β-hydroxy carboxylic acids revealed the relative stereochemistry of SCH 64874. The relative stereochemistry of the β-keto carboxylic acid chain of the analogous alkaloid hirsutellomycin was determined in a stepwise manner. The C4'-C6' syn relationships were predicted by comparing the NMR data of the corresponding ester fragments with that of hirsutellomycin. The relative stereochemistry of the whole molecule, including the epimerizable C2' stereocenter, was determined by introduction of four possible side chains into the bisdethiodi(methylthio)deacetylaranotin core. We found that the stereochemistry of C2' converged with that of the thermodynamically stable form influenced by the core structure.

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Thin polycrystalline zinc-doped indium oxide (In 2 O 3 -ZnO) films were prepared by post-annealing amorphous films with various weight concentrations x of ZnO in the range 0 x 0.06. We have studied the dependences of the resistivity ρ and Hall coefficient on temperature T and magnetic field H in the range 0.5 T 300 K, H 6 Tfor 350 nm films annealed in air. Films with 0 x 0.03 show the superconducting resistive transition. The transition temperature T c is below 3.3 K and the carrier density n is about 10 25 -10 26 m −3 . The annealed In 2 O 3 -ZnO films were examined by transmission electron microscopy and x-ray diffraction analysis revealing that the crystallinity of the films depends on the annealing time. We studied the upper critical magnetic field H c2 (T ) for the film with x = 0.01. From the slope of dH c2 /dT , we obtain the coherence length ξ(0) ≈ 10 nm at T = 0 K and a coefficient of electronic heat capacity that is small compared with those of other oxide materials.

Since 1995, Cu has been shown to be a good base element for bulk glass-forming alloys, with fully glassy sections up to 7 mm being reported. [1] For instance, Lin and Johnson [2] produced 4 mm thick glassy strips of Cu 47 Ti 34 Zr 11 Ni 8 alloy by copper die injection casting. The introduction of 1 at.% Si increased the critical thickness for glass formation to 7 mm. [1] Binary Cu -(Zr or Hf) alloys have been found to form an amorphous phase [3][4] over a wide composition range. However, addition of Ti in both these binary systems greatly increased the glass forming ability (GFA), [5][6][7][8] with the critical diameter for fully amorphous rods being at least 4 mm for Cu 60 Zr 30 Ti 10 , Cu 60 Hf 20 Ti 20 and Cu 55 Hf 25 Ti 20 . On the other hand, it has been shown that small additions of B and Y [7] and of Nb, Ta and Mo [9] reduce the GFA for Cu-Hf-Ti alloys.One of the empirical rules for high GFA in a metallic alloy is that the heat of formation from the constituent elements is negative. Nevertheless, although addition of alloying elements with positive enthalpy of solution should reduce the GFA, there have been some reports that the addition of elements with positive heats of mixing enhances GFA, [10][11][12][13] though Xu et al. [10] show that this occurs only when they decrease the melting temperature of the alloy. The objective of the present study was to investigate the effects of small concentrations of Al, Mo, Si and V on the GFA and thermal stability for Cu-Hf-Ti-based alloys.Cu-based alloy ingots of composition Cu 55-x Hf 25 Ti 20 M x (M = Al, Mn, Si, V, where v = 1, 2, 4 and 7 at.%) were prepared by argon arc melting mixtures of Cu (99.99 % pure), Hf (99.8 % pure), Ti (99.98 % pure), Al (99.99 % pure) Mn (99.99 % pure) Si (99.99 % pure) and V (99.98 % pure). The alloy compositions represent the nominal values but the weight losses in melting were negligible (< 0.1 %). The alloy ingots were inverted on the hearth and re-melted several times, to ensure compositional homogeneity. Conical alloy shapes, of length ∼ 50 mm and having a minimum diameter of 1 mm and a maximum of 10 mm, were produced by copper mould suction-casting within the argon arc furnace. [6] Additionally, ribbon samples of each alloy, with cross sections of typically 0.03 mm × 2.0 mm, were produced by chill-block melt spinning in a sealed argon atmosphere. The structures of the conical and ribbon samples were studied by XRD and the glass transition (T g ) and crystallisation (T x ) temperatures determined by DSC (using a Perkin Elmer DSC-7) at a heating rate of 0.33 K/s. The initial melting (T m ) and liquidus (T l ) temperatures were measured by DTA (Perkin Elmer DTA-7) at a heating rate of 0.33 K/s. Both, the DSC and the DTA instruments were calibrated at the respective heating rates using the known melting temperatures of pure metals. The measured T l corresponding to the completion of the melting transformation were adjusted to allow for thermal lag, using a correction factor determined earlier by Donald and Davies. [14] Initiall...

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