465 research outputs found
Lattice perturbation theory for gluonic and fermionic actions
We calculate the two loop Landau mean links and the one loop renormalisation
of the anisotropy for Wilson and improved SU(3) gauge actions, using twisted
boundary conditions as a gauge invariant infrared regulator. We show these
accurately describe simulated results, and outline a method for generating
Feynman rules for general lattice field theories, in a form suitable for
efficient numerical calculation of perturbative loop diagrams.Comment: 6 pages of LaTeX. Two posters at Lattice2002(improve) combine
One-Dimensional Control System for a Linear Motor of a Two-Dimensional Nanopositioning Stage Using Commercial Control Hardware
A two-dimensional (2D) nanopositioning platform stage (NanoPla) is in development at the University of Zaragoza. To provide a long travel range, the actuators of the NanoPla are four Halbach linear motors. These motors present many advantages in precision engineering, and they are custom made for this application. In this work, a one-dimensional (1D) control strategy for positioning a Halbach linear motor has been developed, implemented, and experimentally validated. The chosen control hardware is a commercial Digital Motor Control (DMC) Kit from Texas Instruments that has been designed to control the torque or the rotational speed of rotative motors. Using a commercial control hardware facilitates the applicability of the developed control system. Nevertheless, it constrains the design, which needs to be adapted to the hardware and optimized. Firstly, a dynamic characterization of the linear motor has been performed. By leveraging the dynamic properties of the motor, a sensorless controller is proposed. Then, a closed-loop control strategy is developed. Finally, this control strategy is implemented in the control hardware. It was verified that the control system achieves the working requirements of the NanoPla. It is able to work in a range of 50 mm and perform a minimum incremental motion of 1 mu m
Addition Of Chiral And Achiral Allyltrichlorostannanes To Chiral α-alkoxy Aldehydes
Achiral and chiral allyltrichlorostannanes reacted with chiral α-alkoxy aldehydes to give the corresponding homoallylic alcohols with moderate to good levels of 1,4-syn-diastereoselection.204802812Fleming, I., Barbero, A., Walter, D., (1997) Chem. Rev., 97, p. 2063Nishigaichi, Y., Takuwa, A., Naruta, Y., Maruyama, K., (1993) Tetrahedron, 49, p. 7395Panek, J.S., Xu, F., Rondon, A.C., (1998) J. Am. Chem. Soc., 120, p. 4113Zhu, B., Panek, J.S., (2001) Eur. J. Org. Chem., 9, p. 1701Huang, H.B., Spande, T.F., Panek, J.S., (2003) J. Am. Chem. Soc., 125, p. 626Keck, G.E., Abbott, D.E., (1984) Tetrahedron Lett, 25, p. 1883Maguire, R.J., Mulzer, J., Bats, J.W., (1996) J. Org. Chem., 61, p. 6936Denmark, S.E., Stavenger, R.A., (1998) J. Org. Chem., 63, p. 9524Trost, B.M., Urabe, H., (1990) J. Org. Chem., 55, p. 3982Nishigaishi, Y., Takuwa, A., Jodai, A., (1991) Tetrahedron Lett, 32, p. 2383Almendros, P., Gruttadauria, M., Helliwell, M., Thomas, E.J., (1997) J. Chem. Soc. Perkin Trans. I, p. 2549Deka, D.C., Helliwell, M., Thomas, E.J., (2001) Tetrahedron, 57, p. 10017Martin, N., Thomas, E.J., (2001) Tetrahedron Lett, 42, p. 8373Kumar, P., Thomas, E.J., Tray, D.R., (2001) J. Braz. Chem. Soc., 12, p. 623Gruttadauria, M., Thomas, E.J., (1995) J. Chem. Soc. Perkin Trans. I, p. 1469Nishigaichi, Y., Kuramoto, H., Takuwa, A., (1995) Tetrahedron Lett, 36, p. 3353Dias, L.C., Giacomini, R., (1998) J. Braz. Chem. Soc., 9, p. 357Dias, L.C., Giacomini, R., (1998) Tetrahedron Lett, 39, p. 5343Dias, L.C., Meira, P.R.R., Ferreira, E., Org. Lett., 1999, p. 1335. , See also: "NMR Spectra and Structures of Organotin Compounds," V. S. Petrosyan, Progr. in NMR Spectr. 1978, 11, 115Dias, L.C., Meira, P.R.R., (2000) Synlett, p. 37Dias, L.C., Ferreira, E., (2001) Tetrahedron Lett, 42, p. 7159Dias, L.C., Ferreira, A.A., Diaz, G., (2002) Synlett, p. 1845Dias, L.C., Diaz, G., Ferreira, A.A., Meira, P.R.R., Ferreira, E., (2003) Synthesis, p. 603Dias, L.C., Giacomini, R., Meira, P.R.R., Ferreira, E., Ferreira, A.A., Diaz, G., dos Santos, D.R., Steil, L.J., (2003) Arkivoc, 10, p. 240Dias, L.C., dos Santos, D.R., Steil, L.J., (2003) Tetrahedron Lett, 44, p. 6861(2002) Org. Lett., 4, p. 4325. , We have recently described a very efficient, synthetically useful 1, 4-anti-1, 5-anti boron-mediated aldol reaction of chiral α-methyl-ÎČ-alkoxy methyl ketone with achiral aldehydes: Dias, L.C., BaĂș, R.Z., de Sousa, M.A., Zukerman-Schpector, JDenmark, S.E., Wilson, T., Willson, T.M., (1988) J. Am. Chem. Soc., 110, p. 984Denmark, S.E., Weber, E.J., Wilson, T., Willson, T.M., (1989) Tetrahedron, 45, p. 1053Denmark, S.E., Almstead, N.G., (1992) Tetrahedron, 48, p. 5565Denmark, S.E., Almstead, N.G., (1993) J. Am. Chem. Soc., 115, p. 3133Dias, L.C., Fattori, J., Perez, C.C., (2008) Tetrahedron Lett, 49, p. 557Dias, L.C., Fattori, J., Perez, C.C., Oliveira, V.M., Aguilar, A.M., (2008) Tetrahedron, 64, p. 5891Kim, D., Lee, J., Shim, P.J., Lim, J.I., Doi, T., Kim, S., (2002) J. Org. Chem., 67, p. 772noteShambayati, S., Schreiber, S.L., Blake, J.F., Wierschke, S.G., Jorgensen, W.L., (1990) J. Am. Chem. Soc., 112, p. 697noteChĂ©rest, M., Felkin, H., Prudent, N., (1968) Tetrahedron Lett, 18, p. 2199Anh, N.T., Eisenstein, O., (1977) Nouv. J. Chem., 1, p. 61noteBatey, R.A., Thadani, A.N., Smil, D.V., Lough, A.J., (2000) Synthesis, 7, p. 990Heathcock, C.H., Pirrung, M.C., Sohn, J.E., (1979) J. Org. Chem., 44, p. 4294Landmann, B., Hoffmann, R.W., (1987) Chem. Ber., 120, p. 331Dias, L.C., Ferreira, M.A.B., Tormena, C.F., (2008) J. Phys. Chem. A, 112, p. 232Sames, D., Liu, Y., De Young, L., Polt, R., (1995) J. Org. Chem., 60, p. 2153Lombardo, M., Morganti, S., Trombini, C., (2003) J. Org. Chem., 68, p. 997notenotenot
Automated analysis of atrial late gadolinium enhancement imaging that correlates with endocardial voltage and clinical outcomes: A 2-center study
This work was supported by the British Heart Foundation PG/10/37/28347, RG/10/11/28457, NIHR Biomedical Research Centre funding, and the ElectroCardioMaths Programme of the Imperial BHF Centre of Research Excellence
A model based on the combination of ifn-Îł, ip-10, ferritin and 25-hydroxyvitamin d for discriminating latent from active tuberculosis in children
Altres ajuts: This work was supported by grants from: (i) the Isolana Foundation, (ii) the Maria Francisca de Roviralta Foundation expedient AT/MA 1-19/07/2017, AT/MA 70-27/04/2016, and AT/MA 3-22/10/2014 and (vi) FundaciĂł Recerca i DocĂšncia MĂștua Terrassa.In recent years, pediatric research on tuberculosis (TB) has focused on addressing new biomarkers with the potential to be used as immunological non-sputum-based methods for the diagnosis of TB in children. The aim of this study was to characterize a set of cytokines and a series of individual factors (ferritin, 25-hydroxyvitamin D [25(OH)D], parasite infections, and nutritional status) to assess different patterns for discriminating between active TB and latent TB infection (LTBI) in children. The levels of 13 cytokines in QuantiFERON-TB Gold In-Tube (QFT-GIT) supernatants were analyzed in 166 children: 74 with active TB, 37 with LTBI, and 55 uninfected controls. All cytokines were quantified using Luminex or ELISA. Ferritin and 25(OH)D were also evaluated using CLIA, and Toxocara canis Ig-G antibodies were detected with a commercial ELISA kit. The combination of IP-10, IFN-Îł, ferritin, and 25(OH)D achieved the best diagnostic performance to discriminate between active TB and LTBI cases in children in relation to the area under receiver operating characteristic (ROC) curve 0.955 (confidence interval 95%: 0.91-1.00), achieving optimal sensitivity and specificity for the development of a new test (93.2 and 90.0%, respectively). Children with TB showed higher ferritin levels and an inverse correlation between 25(OH)D and IFN-Îł levels. The model proposed includes a combination of biomarkers for discriminating between active TB and LTBI in children to improve the accuracy of TB diagnosis in children. This combination of biomarkers might have potential for identifying the onset of primary TB in children
Thermal noise properties of two aging materials
In this lecture we review several aspects of the thermal noise properties in
two aging materials: a polymer and a colloidal glass.
The measurements have been performed after a quench for the polymer and
during the transition from a fluid-like to a solid-like state for the gel. Two
kind of noise has been measured: the electrical noise and the mechanical noise.
For both materials we have observed that the electric noise is characterized
by a strong intermittency, which induces a large violation of the Fluctuation
Dissipation Theorem (FDT) during the aging time, and may persist for several
hours at low frequency. The statistics of these intermittent signals and their
dependance on the quench speed for the polymer or on sample concentration for
the gel are studied. The results are in a qualitative agreement with recent
models of aging, that predict an intermittent dynamics. For the mechanical
noise the results are unclear. In the polymer the mechanical thermal noise is
still intermittent whereas for the gel the violation of FDT, if it exists, is
extremely small.Comment: to be published in the Proceedings of the XIX Sitges Conference on
''Jammming, Yielding and Irreversible Deformation in Condensed Matter'',
M.-C.Miguel and M. Rubi eds.,Springer Verlag, Berli
Wear and damage transitions of wheel and rail materials under various contact conditions
This study discusses a TÎł/A method of plotting wear data from a twin-disc machine for identifying the wear and damage transitions of wheel and rail materials. As found in previous work, three wear regimes (mild wear, severe wear and catastrophic wear) of U71Mn rail material were identified in dry rolling-sliding contact tests. It was determined that the damage mechanism transforms in the different wear regimes. Here earlier studies were extended to establish wear behavior for the presence of a number of third body materials (oil, water, friction enhancers) and a rail cladding process designed to make wheels and rails more durable. This has provided much needed data for Multi-Body Dynamics (MBD) simulations, and will allow better predictions of profile evolution of wheel and rail over a wider range of conditions
Advances in ab-initio theory of Multiferroics. Materials and mechanisms: modelling and understanding
Within the broad class of multiferroics (compounds showing a coexistence of
magnetism and ferroelectricity), we focus on the subclass of "improper
electronic ferroelectrics", i.e. correlated materials where electronic degrees
of freedom (such as spin, charge or orbital) drive ferroelectricity. In
particular, in spin-induced ferroelectrics, there is not only a {\em
coexistence} of the two intriguing magnetic and dipolar orders; rather, there
is such an intimate link that one drives the other, suggesting a giant
magnetoelectric coupling. Via first-principles approaches based on density
functional theory, we review the microscopic mechanisms at the basis of
multiferroicity in several compounds, ranging from transition metal oxides to
organic multiferroics (MFs) to organic-inorganic hybrids (i.e. metal-organic
frameworks, MOFs)Comment: 22 pages, 9 figure
Adsorption of mono- and multivalent cat- and anions on DNA molecules
Adsorption of monovalent and multivalent cat- and anions on a deoxyribose
nucleic acid (DNA) molecule from a salt solution is investigated by computer
simulation. The ions are modelled as charged hard spheres, the DNA molecule as
a point charge pattern following the double-helical phosphate strands. The
geometrical shape of the DNA molecules is modelled on different levels ranging
from a simple cylindrical shape to structured models which include the major
and minor grooves between the phosphate strands. The densities of the ions
adsorbed on the phosphate strands, in the major and in the minor grooves are
calculated. First, we find that the adsorption pattern on the DNA surface
depends strongly on its geometrical shape: counterions adsorb preferentially
along the phosphate strands for a cylindrical model shape, but in the minor
groove for a geometrically structured model. Second, we find that an addition
of monovalent salt ions results in an increase of the charge density in the
minor groove while the total charge density of ions adsorbed in the major
groove stays unchanged. The adsorbed ion densities are highly structured along
the minor groove while they are almost smeared along the major groove.
Furthermore, for a fixed amount of added salt, the major groove cationic charge
is independent on the counterion valency. For increasing salt concentration the
major groove is neutralized while the total charge adsorbed in the minor groove
is constant. DNA overcharging is detected for multivalent salt. Simulations for
a larger ion radii, which mimic the effect of the ion hydration, indicate an
increased adsorbtion of cations in the major groove.Comment: 34 pages with 14 figure
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