Observation of a new Ds meson decaying to DK at a mass of 2.86 GeV/c2

We observe a new D_{s} meson with mass (2856.6+/-1.5_{stat}+/-5.0_{syst}) MeV/c;{2} and width (48+/-7_{stat}+/-10_{syst}) MeV/c;{2} decaying into D0K+ and D;{+}K_{S};{0}. In the same mass distributions, we also observe a broad structure with mass (2688+/-4_{stat}+/-3_{syst}) MeV/c;{2} and width (112+/-7_{stat}+/-36_{syst}) MeV/c;{2}. To obtain this result, we use 240 fb;{-1} of data recorded by the BABAR detector at the PEP-II asymmetric-energy e;{+}e;{-} storage rings at the Stanford Linear Accelerator Center running at center-of-mass energies near 10.6 GeV.     

Phonon thermal transport of URu2Si2: broken translational symmetry and strong-coupling of the "hidden order" to the lattice

A dramatic increase in the total thermal conductivity (kappa) is observed in the hidden order (HO) state of single crystal URu2Si2. Through measurements of the thermal Hall conductivity, we explicitly show that the electronic contribution to kappa is extremely small, so that this large increase in kappa is dominated by phonon conduction. An itinerant BCS or mean-field model describes this behavior well: the increase in kappa is associated with the opening of a large energy gap at the Fermi surface, thereby decreasing electron-phonon scattering. Our analysis implies that the "hidden order" parameter is strongly coupled to the lattice, suggestive of a broken symmetry involving charge degrees of freedom.     

Birefringence measurements on polymer melts in an axisymmetric flow cell

 The stress-optical rule relates birefringence to stress. Consequently, measurement of flow birefringence provides a non-intrusive technique of measuring stresses in complex flows. In this investigation we explore the use of an axisymmetric geometry to create a uniaxial elongational flow in polymer melts. In axisymmetric flows both birefringence and orientation angle change continuously along the path of the propagating light. The cumulative influence of the material's optical properties along the light's integrated path makes determination of local birefringence in the melt impossible. One can nevertheless use birefringence measurements to compare with predictions from computer simulations as a means of evaluating the constitutive equations for the stress. More specifically, in this investigation we compare the light intensity transmitted through the experimental set-up vs entry position, with the theoretically calculated transmitted intensity distribution as a means of comparing experiment and simulation. The main complication in our experiments is the use of a flow cell that necessarily consists of materials of different refractive indices. This introduces refraction and reflection effects that must be modeled before experimental results can be correctly interpreted. We describe how these effects are taken into account and test the accuracy of predictions against experiments. In addition, the high temperatures required to investigate polymer melts mean that a further complication is introduced by thermal stresses present in the flow cell glass. We describe how these thermal-stresses are also incorporated in the simulations. Finally, we present some preliminary results and evaluate the success of the overall method. Received: 2 April 2001 Accepted: 27 August 2001     

A ceric ammonium nitrate based oxidative cleavage pathway for the asymmetric aldol adducts of oxadiazinones derived from (1R,2S)-N-p-methoxybenzylnorephedrine

An N₄-p-methoxybenzyloxadiazinone has been prepared from (1R,2S)-norephedrine through a process of reductive amination, N-nitrosation, reduction, and cyclization. The oxadiazinone was acylated and employed in the asymmetric aldol addition reaction with aromatic and aliphatic aldehydes to yield aldol adducts in isolated yields ranging from 54% to 90%. Selected aldol adducts were treated with ceric ammonium nitrate in aqueous acetonitrile to afford the desired β-hydroxycarboxylic acids through a tandem process of oxidative cleavage of the N₄-p-methoxybenzyl group and acidic hydrolysis of the N₃-acyl side chain. The β-hydroxycarboxylic acids were recovered in high diastereomeric purity as determined by 500 MHz ¹H NMR spectroscopy and the absolute configuration was confirmed by polarimetry. The chiral auxiliary unit, the 3,4,5,6-tetrahydro-2H-1,3,4-oxadiazin-2-one (oxadiazinone), was converted into its corresponding 3,6-dihydro-2H-1,3,4-oxadiazin-2-one (oxadiazinone) through an oxidative pathway promoted by the ceric ammonium nitrate.     

Characterization of five [C4H7O]+ Ion structures. Fragmentation of the 2-pentanone molecular ion

The [C₄H₇0]⁺ ions [CH₂?CH? C(?OH)CH₃]⁺ (1), [CH₃CH?CH? C(?OH)H]⁺ (2), [CH₂?C(CH₃)C(?OH)H]⁺ (3), [Ch₃CH₂CH₂C?O]⁺ (4) and [(CH₃)₂CHC?O]⁺ (5) have been characterized by their collision-induced dissociation (CID) mass spectra and charge stripping mass spectra. The ions 1–3 were prepared by gas phase protonation of the relevant carbonyl compounds while 4 and 5 were prepared by dissociative electron impact ionization of the appropriate carbonyl compounds. Only 2 and 3 give similar spectra and are difficult to distinguish from each other; the remaining ions can be readily characterized by either their CID mass spectra or their charge stripping mass spectra. The 2-pentanone molecular ion fragments by loss of the C(1) methyl and the C(5) methyl in the ratio 60:40 for metastable ions; at higher internal energies loss of the C(1) methyl becomes more favoured. Metastable ion characteristics, CID mass spectra and charge stripping mass spectra all show that loss of the C(1) methyl leads to formation of the acyl ion 4, while loss of the C(5) methyl leads to formation of protonated vinyl methyl ketone (1). These results are in agreement with the previously proposed potential energy diagram for the [C₅H₁₀O]⁺˙ system.     

Using hooves for high-resolution isotopic reconstruction of bovine dietary history

The objective of this study was to ascertain whether sequential sampling and isotopic analysis of bovine hooves could be used to reconstruct the dietary history of cattle. A controlled, on-farm experiment was conducted in which cattle were switched from a barley-based diet to an isotopically different diet incorporating maize, urea and seaweed (the isotopic spacing between diets was 13.6 per thousand for delta(13)C and 8.0 per thousand for delta(15)N) and maintained on that diet for 168 days. Postmortem sampling of the cleaned anterior wall of the lateral, left front claw was carried out on five individuals using a micro-drilling technique. From the first 60 mm of each claw, up to 41 samples with a spacing between them of less than 1 mm were collected. Bands were less than 1 mm deep and had a mean width of 1.2 mm. The hoof keratin showed a rapid increase followed by a slower increase in its delta(13)C and delta(15)N values following the diet switch, suggesting that C and N in hoof keratin originate from more than one pool. However, the response of the N isotope composition of the hoof was somewhat delayed compared with that of C. Estimated mean hoof growth rates for these cattle were 10.5 +/- 2.3 mm per month and 6.7 +/- 1.0 mm per month (+/-SD, n = 5) when receiving the barley-based transition diet and the maize-based experimental diet, respectively. These values are considerably higher than previous estimates obtained by visual methods and they suggest that diet may have a greater influence on hoof growth rates than seasonality. These results demonstrate that hooves are a suitable incremental tissue for high-resolution isotopic reconstruction of the dietary history of bovine animals.     

Hydrogen migrations in mass spectrometry. II—single and double hydrogen migrations in the electron impact fragmentation of n-propyl benzoate

The sources of the migrant hydrogen atom(s) in reactions (a) and (b) in the electron impact mass spectrum of n-propyl benzoate have been investigated: (a) [C₆H₅CO₂C₃H₇]⁺ →[C₆H₅CO₂H]⁺ + C₃H₆; (b) [C₆H₅CO₂C₃H₇]⁺ → [C₆H₅CO₂H₂]⁺ + C₃H₅^sdot;. Deuterium labelling of the propyl group showed that, for reaction (a) at 70 eV ionizing energy 3 ± 1% of the hydrogen originates from C-1 of the propyl group, 86 ± 4% from C-2 and 11 ± 3% from C-3. The specificity of the transfer from C-2 increases as the internal energy of the fragmenting ions decreases, indicating that the results cannot be rationalized in terms of H/D interchanges between positions in the propyl group, but rather that the reaction involves specific, competing, H transfer reactions from each propyl position, in contrast to the high site specificity characteristic of the McLafferty rearrangement. Reaction (b) involves, almost exclusively, transfer of one hydrogen from C-2 and one from C-3 with only very minor participation of C-1 hydrogens. The [C₆H₅COOH]⁺ ion produced in reaction (a) fragments further to [C₆H₅CO]⁺ + OH. and the labelling results indicate some interchange of the carboxylic hydrogen with (ortho) ring hydrogens for those ions fragmenting in the first drift region. The extent of interchange is less than that observed for fragmentation of the same ion produced by direct ionization of benzoic acid or by reaction (a) in ethyl benzoate.     

The surface tension of liquid copper

The surface tension of liquid copper of 99.999 mass per cent purity has been measured by the sessile drop method in the temperature range 1373 to 1861 K. The least-squares equation expressing the surface tension σ as a function of temperature T is:

$\text{σ(}\text{Cu}\text{)/}\text{mN m}{}^{\mathrm{?}}\text{= (1552±35) ? (0.176±0.023)T/}\text{K}$

The linear correlation of excess surface enthalpy $\text{H}{}^{\mathrm{\sigma }}\text{A}{}^{\mathrm{\sigma }}$ and excess surface entropy $\text{S}{}^{\mathrm{\sigma }}\text{A}{}^{\mathrm{\sigma }}$ per unit area among σ(T) from the literature is also demonstrated. Estimation of $\text{S}{}^{\mathrm{\sigma }}\text{A}{}^{\mathrm{\sigma }}$ via the statistical electron-gas theory of Zadumkin and Pugachewich yields an equation for the calculation of recommended values for the surface tension of molten copper as a function of temperature:

$\text{σ(}\text{Cu}\text{)/}\text{mN m}{}^{\mathrm{?}}\text{= 1497 ? 0.174(T/}\text{K}\text{)}$

.     

Substituent effects on ion abundances and energetics in substituted acetophenones

Based on the quasi-equilibrium theory of mass spectra it is shown that the intensity ratio [A]⁺/[M]⁺, where [A]⁺ is a fragment ion and [M]⁺ is the molecular ion, is given by [A]⁺/[M]⁺ = f′ (k₁/k_t) ((1/f) ? 1), where f is the fraction of molecular ions with insufficient energy to fragment, f′ is the fraction of [A]⁺ ions with insufficient energy to fragment, and k₁/k_t is the fraction of fragmenting molecular ions which form [A]⁺. For substituted acetophenones it is shown that f depends on the substituent present and that f′ k₁/k_t is also substituent dependent for formation of both [CH₃CO]⁺ and [YC₆H₄CO]⁺. It is also shown that no direct information concerning the effect of a substituent on the rate of a particular fragmentation reaction can be obtained from intensity studies. The ionization potentials of the parent molecules and the appearance potentials of the [YC₆H₄CO]⁺ fragment ions have been measured for fifteen substituted acetophenones and the correlations with substituent constants are discussed.     

Structural studies in main group chemistry : XXII. Structural and tin-119 mössbauer studies of some five-coordinate triorganotin anions

The structures of two complexes, [Ph₃PCH₂Ph]⁺[Bu₃SnCl₂⁻]⁻ and [Ph₃AsCH₂COPh]⁺[Ph₃SnCl₂]⁻, have been determined by X-ray diffraction. Both materials are monoclinic, space group P2_1/c. Unit cell data for [Ph₃PCH₂Ph]⁺−[Bu₃SnCl₂]⁻ are a 9.8521(6), b 16.9142(4), c 22.3517(7) Å, β 91.4235(9)°; and for [Ph₃AsCH₂COPh]⁺[Ph₃SnCl₂]⁻ a 34.9760(3), b 11.1290(5), c 24.2410(2) Å, β 108.56(2)°, and both consist of the component ionic species. The organotin anions each have trigonal bipyramidal geometry with equatorial organic groups and axial halogens. In the [Ph₃SnCl₂]⁻ anion the two Sn---Cl bond distances are the same (2.58(1) and 2.60(1) Å), but in [Bu₃SnCl₂]⁻, as in [Me₃SnCl₂]⁻, they are substantially different (2.573(7) and 2.689(6) Å). The Sn---C bond distances also vary: [Ph₃SnCl₂]⁻ 2.15(4), 2.16(3) and 2.25(5); [Bu₃SnCl₂]⁻ 2.21(1), 2.20(2) and 2.29(2) Å. Tin-119 Mössbauer data for these and several other similar complexes are also reported.