Palladium catalysed aryl enol ether synthesis from vinyl triflates

Vinyl triflates can be efficiently converted into the corresponding aryl enol ethers by treatment with a phenol, NaO(t)Bu and a catalyst generated from Pd2dba3 and 2-(di-(t)Bu-phosphino)biphenyl.     

Two-kaon correlations in central Pb+Pb collisions at 158 a GeV/c

Two-particle interferometry of positive kaons is studied in Pb+Pb collisions at mean transverse momenta approximately 0.25 and 0.91 GeV/c. A three-dimensional analysis was applied to the lower p(T) data, while a two-dimensional analysis was used for the higher p(T) data. We find that the source-size parameters are consistent with the m(T) scaling curve observed in pion-correlation measurements in the same collisions, and that the duration time of kaon emission is consistent with zero within the experimental sensitivity.     

Factorization in finite-codimensional ideals of group algebras

Let G be a -compact, locally compact group and I be a closed2-sided ideal with finite codimension in L¹(G). It is shownthat there are a closed left ideal L having a right boundedapproximate identity and a closed right ideal R having a leftbounded approximate identity such that I = L + R. The proofuses ideas from the theory of boundaries of random walks ongroups. 2000 Mathematics Subject Classification: primary 43A20;secondary 42A85, 43A07, 46H10, 46H40, 60B11.     

Self-assembled structures of alkanethiols on gold-coated cantilever tips and substrates for atomic force microscopy: Molecular organisation and conditions for reproducible deposition

Measurements of surface-liquid interactions (contact-angle goniometry) and tip-surface adhesion forces (atomic force microscopy) combined with infrared spectroscopic studies have been used to investigate surface-preparation and solution-deposition conditions for the reproducible formation of self-assembled molecular structures on gold-coated tips and substrates for atomic force microscopy. Preliminary data show that surface-saturated self-assembled monolayers form reproducibly on prolonged (>20 h) exposure of gold-coated glass substrates to ethanolic solutions of ω-functionalised alkanethiols in the concentration range 80-160 mmol dm⁻³. The data also show that exposure for 16 h to alkanethiol concentrations in the range 160-240 mmol dm⁻³ promote bilayer formation whereas concentrations of 240-320 mmol dm⁻³ result in the deposition of multilayers, the average orientation of which is parallel to that of the first molecular layer; the use of parent 1-undecanethiol solutions at concentrations of 1-80 mmol dm⁻³ results in incomplete monolayer coverage.     

Synthesis and crystal structure of CuZrTiO5—A new crystal structure type

A new compound, CuZrTiO₅, was synthesized as strongly pleochroic green crystals from the oxides between 995 and 1010 °C, 1 atm. Its crystal structure was determined by single crystal XRD, resulting in R (F²>2σ(F²))=0.032 and wR (all data)=0.079). CuZrTiO₅ is orthorhombic, space group P2₁2₁2₁, a=3.5871(3) Å, b=6.6968(4) Å, c=14.6679(9) Å, V=352.35(4) Å³, Z=4. The structure is topologically similar to In₂TiO₅ but differs in space group and cation coordination. CuZrTiO₅ has relatively regular TiO₆ polyhedra, but coordination is 7+1 for Zr, and 4+2 for Cu due to the Jahn-Teller effect. Ordering of the long Cu-O bonds causes reduction in symmetry relative to In₂TiO₅. Layers of Cu alternate with Ti+Zr on (001), giving rise to a distinct cleavage. Bond valence sums on Ti and Zr are far from ideal, which appears due to the limited ability of this structural topology to avoid close next-nearest neighbour distances.     

Synthesis and Crystal Structure of Bis-(N,N′-dibenzylethane-1,2-diamine) cobalt(II) acetate

Abstract  

Bis-(N,N′-dibenzylethane-1,2-diamine) cobalt(II) acetate has been synthesized and the crystal structure determined. The compound crystallizes in the space group P2₁/c, a = 8.3212(6) ?, b = 11.8774(8) ?, c = 17.3643(12) ?, β = 98.1850(10)°, V = 1698.7(2) ?³, Z = 2. The complex occupies a crystallographic inversion center. The cobalt is in a distorted octahedral environment likely due to steric influences of the acetate groups.     

Spectral beam combining of 2 μm Tm fiber laser systems

Output beams from three independently frequency-stabilized thulium master-oscillator power-amplifier fiber laser systems were spectrally combined using a plane-ruled metal diffraction grating. Two laser channels were frequency-stabilized with guided mode resonance filters and the third was stabilized using a plane-ruled metal diffraction grating. The systems had output wavelengths between 1984 and 2015 nm, each with a spectral width of 100-450 pm and output powers between 40-120 W. The combined beam had powers up to 49 W and was 32% efficient with respect to the launched pump power.     

Voice Training and Changing Weight—Are They Reflected in Speaking Fundamental Frequency, Voice Range, and Pitch Breaks of 13-Year-Old Girls? A Longitudinal Study

Objective

Assessment of the voice-change progress of 20 girls (12–13 years) over 1 year by observing changes in speaking fundamental frequency (SFo), voice range, and register pitch breaks in the context of weight, height, voice training, and self-perception.

Study Design

One-year longitudinal collective case study.

Method

Twenty girls were recorded at the beginning and end of a year; nine girls were recorded another three times. SFo, vocal range, and characteristics were analyzed and interactions between these data assessed against weight and height to indicate pubertal development, and to test the hypothesis that changes in weight, height, SFo, and pitch breaks were related. Effects of training and the girls' self-perception of their voice use were also assessed.

Results

Vocal characteristics changed as the girls passed through different weight ranges. During 47.5–52.4 kg (called band 2) and 52.4–57.5 kg (band 3), there was progressive contraction of vocal range and in some girls a slight rise in SFo between recording times 1 and 5. Both high- and low-pitch breaks were present in 45% of girls' voices. Girls in band 4 (<57.5 kg) had an increased vocal range, and pitch breaks in vocal-range areas that indicated the development of adult vocal registers. In this study, voice-trained girls were heavier, had higher SFo, used wider speech-range inflection, had a higher vocal range, and greater voice-use confidence; all girls lost confidence in their voice use over the year.

Conclusions

In this longitudinal study of twenty 13-year-old girls, voice changes in SFo, vocal range, and pitch-break frequency were synchronous with certain weight ranges. Girls with training registered higher maximum phonational frequency and were more confident in their voice use than girls without training.