Synthesis of pentacene nanotubes by melt-assisted template wetting

peer-reviewedno abstract availablePUBLISHEDpeer-reviewe

Spin instabilities and quantum phase transitions in integral and fractional quantum Hall states

The inter-Landau-level spin excitations of quantum Hall states at filling factors nu=2 and 4/3 are investigated by exact numerical diagonalization for the situation in which the cyclotron (hbar*omega_c) and Zeeman (E_Z) splittings are comparable. The relevant quasiparticles and their interactions are studied, including stable spin wave and skyrmion bound states. For nu=2, a spin instability at a finite value of epsilon=hbar*omega_c-E_Z leads to an abrupt paramagnetic to ferromagnetic transition, in agreement with the mean-field approximation. However, for nu=4/3 a new and unexpected quantum phase transition is found which involves a gradual change from paramagnetic to ferromagnetic occupancy of the partially filled Landau level as epsilon is decreased.Comment: 4 pages, 5 figures, submitted to Phys.Rev.Let

A method for defining human-machine micro-task workflows for gathering legal information

Series : Lecture notes in computer science, ISSN 0302-9743, vol. 8929With the growing popularity of micro-task crowdsourcing platforms, new workflow-based micro-task crowdsourcing approaches are starting to emerge. Such workflows occur in legal, political and conflict resolution do-mains as well, presenting new challenges, namely in micro-task specification and human-machine interaction, which result mostly from the flow of unstruc-tured data. Domain ontologies provide the structure and semantics required to describe the data flowing throughout the workflow in a way understandable to both humans and machines. This paper presents a method for the construction of micro-task workflows from legal domain ontologies. The method is currently being employed in the context of the UMCourt project in order to formulate in-formation retrieval and conflict resolution workflows.This work is part-funded by FEDER Funds, by the ERDF (Eu-ropean Regional Development Fund) through the COMPETE Programme (operation-al programme for competitiveness) and by National Funds through the FCT (Portu-guese Foundation for Science and Technology) within the project FCOMP-01-0124-FEDER-028980 (PTDC/EEI-SII/1386/2012). The work of Nuno Luz is supported by the doctoral grant SFRH/BD/70302/2010

Methylthiolate-induced reconstruction of Ag(1 1 1): A medium energy ion scattering study

Medium energy ion scattering (MEIS), using 100 keV H+ incident ions, has been used to investigate the structure of the Ag(1 1 1)(√7 × √7)R19° –CH3S surface phase. The results provide the first direct evidence that this structure does involve substantial reconstruction of the Ag surface layer. The measured absolute scattered ion yields and blocking curves are in generally good agreement with a specific structural model of the surface based on a reconstructed layer containing 3/7 ML Ag atoms, previously suggested on the basis of scanning tunnelling microscopy (STM) and normal incidence X-ray standing wave (NIXSW) studies. However, the MEIS data indicate that any rumpling of the thiolate layer, is small, and probably 0.2 Å. This value is smaller than the amplitude suggested in the STM and NIXSW studies, but could be entirely consistent with the earlier experimental data

Exploring CP Violation through Correlations in B --> pi K, B_d --> pi^+pi^-, B_s --> K^+K^- Observable Space

We investigate allowed regions in observable space of B --> pi K, B_d --> pi^+pi^- and B_s --> K^+K^- decays, characterizing these modes in the Standard Model. After a discussion of a new kind of contour plots for the $B\to\pi K$ system, we focus on the mixing- induced and direct CP asymmetries of the decays B_d --> pi^+pi^- and B_s--> K^+K^-. Using experimental information on the CP-averaged B_d --> pi^{+/-}K^{+/-} and B_d --> pi^+pi^- branching ratios, the relevant hadronic penguin parameters can be constrained,implying certain allowed regions in observable space. In the case of B_d --> pi^+pi^-, an interesting situation arises now in view of the recent B-factory measurements of CP violation in this channel, allowing us to obtain new constraints on the CKM angle gamma as a function of the B^0_d--\bar{B^0_d} mixing phase phi_d=2beta, which is fixed through A_{CP}^{mix}(B_d --> J/psi K_S) up to a twofold ambiguity. If we assume that A_{CP}^{mix}(B_d --> pi^+pi^-) is positive, as indicated by recent Belle data, and that phi_d is in agreement with the ``indirect'' fits of the unitarity triangle, also the corresponding values for gamma around 60 degrees can be accommodated. On the other hand, for the second solution of phi_d, we obtain a gap around gamma ~ 60 degrees. The allowed region in the space of A_{CP}^{mix}(B_s --> K^+K^-) and A_{CP}^{dir}(B_s --> K^+K^-) is very constrained in the Standard Model, thereby providing a narrow target range for run II of the Tevatron and the experiments of the LHC era.Comment: 34 pages, LaTeX, 12 figures. More detailed introduction and a few Comments added, conclusions unchanged. To appear in Phys. Rev.

3-Methoxybutan-2-one as a sustainable bio-based alternative to chlorinated solvents

Methylation of acetoin with dimethyl carbonate was performed in a sustainable one-step process, with improved process mass intensity (PMI) and atom economy compared to previously published methods. The resulting product, 3-methoxybutan-2-one (MO) was successfully evaluated as a bio-based solvent, while both Kamlet–Taft solvatochromic parameters and Hansen solubility parameters demonstrate its potential viability in the substitution of chlorinated solvents. MO exhibited a low peroxide forming potential and a negative Ames mutagenicity test and was successfully used as a solvent in a Friedel–Crafts acylation (79% yield compared to 77% in dichloromethane) and for N-alkylations. MO is a renewable oxygenated solvent, with the potential ability to substitute carcinogenic halogenated solvents in some applications

The Uncertainty in Newton's Constant and Precision Predictions of the Primordial Helium Abundance

The current uncertainty in Newton's constant, G_N, is of the order of 0.15%. For values of the baryon to photon ratio consistent with both cosmic microwave background observations and the primordial deuterium abundance, this uncertainty in G_N corresponds to an uncertainty in the primordial 4He mass fraction, Y_P, of +-1.3 x 10^{-4}. This uncertainty in Y_P is comparable to the effect from the current uncertainty in the neutron lifetime, which is often treated as the dominant uncertainty in calculations of Y_P. Recent measurements of G_N seem to be converging within a smaller range; a reduction in the estimated error on G_N by a factor of 10 would essentially eliminate it as a source of uncertainty in the calculation of the primordial 4He abundance.Comment: 3 pages, no figures, fixed typos, to appear in Phys. Rev.

Negatively Charged Excitons and Photoluminescence in Asymmetric Quantum Well

We study photoluminescence (PL) of charged excitons ($X^-$) in narrow asymmetric quantum wells in high magnetic fields B. The binding of all $X^-$ states strongly depends on the separation $\delta$ of electron and hole layers. The most sensitive is the ``bright'' singlet, whose binding energy decreases quickly with increasing $\delta$ even at relatively small B. As a result, the value of B at which the singlet--triplet crossing occurs in the $X^-$ spectrum also depends on $\delta$ and decreases from 35 T in a symmetric 10 nm GaAs well to 16 T for $\delta=0.5$ nm. Since the critical values of $\delta$ at which different $X^-$ states unbind are surprisingly small compared to the well width, the observation of strongly bound $X^-$ states in an experimental PL spectrum implies virtually no layer displacement in the sample. This casts doubt on the interpretation of PL spectra of heterojunctions in terms of $X^-$ recombination

Effect of extended cefquinome treatment on clinical persistence or recurrence of environmental clinical mastitis

The effectiveness of antibiotic treatment of clinical mastitis (CM) is classically evaluated using bacteriological cure, which provides a concise and objective way of assessing efficacy but does not reflect the situation in the field where persistence or recurrence of clinical signs lead to perceived treatment failure. If clinical signs persist or recur, intramammary (IMM) treatment is often extended or supplemented with parenteral therapy in the expectation of a more efficient elimination of clinical signs or a lower probability of recurrence. The objective of this study was to evaluate the efficacy against clinical persistence or recurrence of three cefquinome treatment regimes, standard 1.5-day intramammary (SIMM), 5-day extended intramammary (EIMM) and combination of EIMM plus 5-day extended parenteral (ECOMBO) treatment. The study was conducted on three dairy farms with a high recurrence rate of environmental mastitis. Efficacy was evaluated using a multi-level model at the quarter and at the cow level, based on the persistence or recurrence of clinical signs at any time during a 105-day period following the end of the initial treatment, independent of pathogen. The most prevalent pathogens were E. coli (16.9%) and S. uberis (11.97%). EIMM and ECOMBO significantly decreased the persistence or recurrence of CM by 8% and 6% at the quarter level and by 9% and 8% at the cow level, respectively. ECOMBO may not reduce the persistence or recurrence of CM beyond EIMM. Whilst extended treatment regimens offered an improved outcome in this study, the producer and practitioner need to carefully consider such regimens from the perspective of prudent antibiotic use

Constraints upon the CKM angle phi_2 (alpha) from Belle and BaBar

The Belle and BaBar experiments have measured branching fractions and CP asymmetries in the charmless decay modes B0->pi+pi-, B0->rho+pi-/rho-pi+, and B0->rho+rho-. From these measurements, constraints upon the CKM angle phi_2 can be obtained. These constraints consistently indicate that phi_2 is around 100 degrees.Comment: 8 pages, 6 figures, 1 table, contribution to the 6th International Conference on Hyperons, Charm and Beauty Hadrons (BEACH 2004), Illinois Institute of Technology, 27 June - 3 July 2004. Final version with notation correction