Scaling property of the critical hopping parameters for the Bose-Hubbard model

Recently precise results for the boundary between the Mott insulator phase and the superfluid phase of the homogeneous Bose-Hubbard model have become available for arbitrary integer filling factor g and any lattice dimension d > 1. We use these data for demonstrating that the critical hopping parameters obey a scaling relationship which allows one to map results for different g onto each other. Unexpectedly, the mean-field result captures the dependence of the exact critical parameters on the filling factor almost fully. We also present an approximation formula which describes the critical parameters for d > 1 and any g with high accuracy.Comment: 5 pages, 5 figures. to appear in EPJ

UPLC-MS-ESI-QTOF analysis and antifungal activity of the spondias tuberosa arruda leaf and root hydroalcoholic extracts

The aim of this study was to identify and evaluate the chemical compositions and effects of the S. tuberosa leaf and root hydroalcoholic extracts (HELST and HERST) against different strains of Candida. Chemical analysis was performed by Ultra-Performance Liquid Chromatography Coupled to Quadrupole/Time of Flight System (UPLC-MS-ESI-QTOF). The Inhibitory Concentration of 50% of the growth (IC50) as well as the intrinsic and combined action of the extracts with the antifungal fluconazole (FCZ) were determined by the microdilution method while the minimum fungicidal concentrations (MFCs) and the effect on fungal morphological transitions were analyzed by subculture and in humid chambers, respectively. From the preliminary phytochemical analysis, the phenols and flavonoids were the most abundant. The intrinsic IC50 values for HELST ranged from 5716.3 to 7805.8 \ub5g/mL and from 6175.4 to 51070.9 \ub5g/mL for the HERST, whereas the combination of the extracts with fluconazole presented IC50 values from 2.65 to 278.41 \ub5g/mL. The MFC of the extracts, individually, for all the tested strains was 6516384 \ub5g/mL. When fluconazole was combined with each extract, the MFC against CA URM 5974 was reduced (HELST: 2048 and HERST: 4096 \ub5g/mL). Synergism was observed against standard C. albicans (CA) and C. tropicalis (CT) strains and with the root extract against the CT isolate. The leaf extract inhibited the morphological transition of all strains while the root extract inhibited only CT strains

Internal Decoherence Of A Gaussian Wave Packet In A Harmonic Potential

We have studied the quantum dissipative problem of a Gaussian wave packet under the influence of a harmonic potential. A phenomenological approach to dissipation is adopted in the light of the well-known model in which the environment is composed of a bath of noninteracting harmonic oscillators. As one of the effects of the coupling to the bath is the evolution of an initially pure wave packet into a statistical mixture, we estimate the characteristic time elapsed for this to occur for different regimes of temperature, damping, and also different initial states.905Zurek, W.H., (2003) Rev. Mod. Phys., 75, p. 715. , RMPHAT 0034-6861Leggett, A.J., (2002) J. Phys.: Condens. Matter, 14, p. R415. , JCOMEL 0953-8984Zurek, W.H., (1981) Phys. Rev. D, 24, p. 1516. , 0556-2821Paz, J.P., Zurek, W.H., (1993) Phys. Rev. D, 48, p. 2728. , 0556-2821Caldeira, A.O., Leggett, A.J., (1985) Phys. Rev. A, 31, p. 1059. , 0556-2791Caldeira, A.O., Leggett, A.J., (1983) Physica A: Statistical Mechanics and Its Applications, 121, p. 587. , PHYADX 0378-4371Caldeira, A.O., Cerdeira, H.A., Ramaswamy, R., (1989) Phys. Rev. A, 40, p. 3438. , 0556-2791Rosenau Da Costa, M., Caldeira, A.O., Dutra, S.M., Westfahl, H., Jr., (2000) Phys. Rev. A, 61, p. 022107. , PLRAAN 1050-2947Zurek, W.H., Habib, S., Paz, J.P., (1993) Phys. Rev. Lett., 70, p. 1187. , PRLTAO 0031-9007Venugopalan, A., (1994) Phys. Rev. A, 50, p. 2742. , PLRAAN 1050-2947Hakim, V., Ambegaokar, V., (1985) Phys. Rev. A, 32, p. 423. , 0556-279

X-ray Multiple Diffraction As A Probe To Determine All The Piezoelectric Coefficients Of A Crystal: Rochelle Salt Case

The x-ray multiple diffraction method, which allows us to determine the piezoelectric coefficients of a single crystal under an external electric field (E), was applied to Rochelle salt (dos Santos et al 2001 J. Phys.: Condens. Matter 13 10497) for E parallel to the piezoelectric Y direction. In this work, the theory was extended to consider an observed monoclinic-triclinic distortion under E application into the other two piezoelectric X and Z directions. Renninger scans carried out using the chosen (060) primary reflection have provided the four remaining coefficients through the measurement of the properly chosen secondary peaks. So that all eight piezoelectric coefficients (d14, d16, d21, d22, d23, d25, d34 and d36) for Rochelle salt were determined.154678357842Cady, W.G., (1964) Piezoelectricity, , (New York: Dover) (1946 revised edn)Jona, F., Shirane, G., (1962) Ferroelectric Crystals, , (Oxford: Pergamon) chapter VIIBeevers, A.C., Hughes, W., (1941) Proc. R. Soc. A, 117, p. 251Suzuki, E., Amamo, A., Nozaki, R., Shiozaki, Y., (1994) Ferroelectrics, 152, p. 385Irwin Vigness, C., (1934) Phys. Rev., 46, pp. 255-257Avanci, L.H., Cardoso, L.P., Girdwood, S.E., Pugh, D., Sherwood, J.N., Roberts, K.J., (1998) Phys. Rev. Lett., 81, p. 5426Avanci, L.H., Cardoso, L.P., Girdwood, S.E., Pugh, D., Roberts, K.J., Sasaki, J.M., Sherwood, J.N., (2000) Phys. Rev. B, 61, p. 6507Dos Santos, A.O., Yaegashi, W.H., Marcon, R., Li, B.B., Gelamo, R.V., Cardoso, L.P., Sasaki, J.M., Melo, F.E.E.A., (2001) J. Phys.: Condens. Matter, 13, p. 10497Nye, J.F., (1957) Physical Properties of Crystals, , (Oxford Science Publications) (Oxford: Clarendon)Voigt, W., (1910) Gött. Nachr., Lehrbuch der Kristallphysik 1st Edn, , (Leipzig: Teubner)Cole, H., Chambers, F.W., Dunn, H.M., (1962) Acta Crystallogr., 15, p. 138Shuvalov, L.A., (1988) Modern Crystallography IV, 37, p. 234. , (Berlin: Springer

Synchrotron radiation X-ray multiple diffraction in the study of KDP phase transition induced by electric field

In this work, the application of the X-ray multiple diffraction technique using synchrotron radiation at Laboratório Nacional de Luz Síncrotron (LNLS) to study KDP phase transition induced by electric field is discussed. A Huber three-axis (omega, phi, 2theta) diffractometer mounted on a table which rotates around the incident beam allows to measure Renninger scans (RS) at the XRD station of LNLS using the adequate polarization for the experiments. Prior results indicated (080) as the best choice for the KDP primary reflection and the (440)(<img src="http:/img/fbpe/mr/v4n1/quatro.gif" alt="quatro.gif (94 bytes)"> 40) four-beam case for the secondary. Two Bragg-surface diffraction (BSD) reflections, where the secondary beam is propagated parallel to the sample surface, are involved in this multiple diffraction case. A RS interval of 3.3° around phi = 0° position was measured while the electric field was increased up to 6 kV/cm. At this value, a phase transition was observed and the secondary peaks became narrower and changed their RS position indicating possible occurrence of a metastable ferroelectric phase