146 research outputs found
Annihilation Diagrams in Two-Body Nonleptonic Decays of Charmed Mesons
In the pole-dominance model for the two-body nonleptonic decays of charmed
mesons and , it is shown that the
contributions of the intermediate pseudoscalar and the axial-vector meson poles
cancel each other in the annihilation diagrams in the chiral limit. In the same
limit, the annihilation diagrams for the decays vanish
independently.Comment: 9 pages (+ 3 figures available upon request), UR-1316, ER-40685-766,
IC/93/21
Bulk and edge excitations of a Hall ferromagnet
In this article, we shall focus on the collective dynamics of the fermions in
a quantum Hall droplet. Specifically, we propose to look at the
quantum Hall ferromagnet. In this system, the electron spins are ordered in the
ground state due to the exchange part of the Coulomb interaction and the Pauli
exclusion principle. The low energy excitations are ferromagnetic magnons. In
order to obtain an effective Lagrangian for these magnons, we shall introduce
bosonic collective coordinates in the Hilbert space of many-fermion systems.
These collective coordinates describe a part of the fermionic Hilbert space.
Using this technique, we shall interpret the magnons as bosonic collective
excitations in the Hilbert space of the many-electron Hall system. Furthermore,
by considering a Hall droplet of finite extent, we shall also obtain the
effective Lagrangian governing the spin collective excitations at the edge of
the sample.Comment: 30 pages, plain TeX, no figure
Axial Anomaly Effect in Chiral p-wave Superconductor
We analyze the chiral p-wave superconductor in the low temperature region.
The superconductor has a epsilon_{x} p_{x} + i epsilon_{y} p_{y}-wave gap in
two dimensional space (2D). Near the second superconducting transition point,
the system could be described by a quasi-1D chiral p-wave model in 2D. The
axial anomaly occurs in such a model and causes an accumulation of the
quasiparticle in an inhomogeneous magnetic field. The effect is related to the
winding number of the gap.Comment: 12 pages, 1 figure, RevTex. The final version is accepted for
publication in J. Phys. Soc. Jp
Genotypic variability and antifungal susceptibility of Candida spp. isolated from hospital surfaces and hands of healthcare professionals
Objectives Candida spp. are responsible for 9095% of hematogenous fungal infections. In Brazil and Latin America, C. albicans is the most common specie, followed by C. parapsilosis and C. tropicalis. Infections caused by Candida spp. may have their origin in exogenous sources, transmitted to patients via contaminated infusions, biomedical devices or even by the hands of the hospital staff members. Molecular biology techniques such as Randomly Amplified Polymorphic DNA (RAPD) can show that the strains found in anatomical sites or abi- otic surfaces have the same pattern genome.Moreover, in the last decades it has been observed increasing the number of yeasts isolated from hospital environment resistant to antifungals. Thus, the aim of this study was to determine the susceptibility to antifungals and intraspecies similarity among isolates of different hospital surfaces and hands of healthcare professionals.
Methods The study was conducted with 25 isolates of Candida spp.: 5 strains of C. albicans and 5 strains of C. parapsilosis isolated from hospital surfaces. 5 strains of C. albicans, 5 strains of C. parapsilosis and 5 strains of C. tropicalis isolated from hands of healthcare professionals. Professionals and surfaces belonged to intensive care units. The minimal inhibitory concentration (MIC) was determined to voriconazole (VOR), fluconazole (FLZ), amphotericin B (AMB) and micafungin (MFG) according to M27-A3 of the Clinical and Labora- tory Standards Institute (CLSI). To determine the intra-species similarity, 3 primers were used: P4 (50 -AAGAGCCCGT-30 ), OPA-18 (50AGCTGACCGT30) and OPE-18 (50GGACTGCAGA 30). RAPD pro- files were analyzed using BioNumerics software version 4.6. The study was approved by the Ethics in research involving human subjects, CAAE 0448.0.093.000-11 protocol.
Results In relation to susceptibility testing (Table 1), it is important to highlight that C. parapsilosis showed 80% of MFG resistance. C. albicans and C. tropicalis showed reduced susceptibility to VOR, and resistence of the AMB was observed for C. albicans (20%). All amplifi- cations revealed distinct polymorphic bands. Genetic distances between each of the isolates were calculated and cluster analysis was used to generate a dendrogram showing relationships between them. The analysis of all primers showed similarity greater than 80% between strains of hands and hospital surfaces for intraspecies. Conclusion Our work shows that, healthy people and hospital surfaces may be colonized by different species yeast. Furthermore, the strains studied had relative resistance to antifungal drugs most frequently used in clinical practice. Finally, there was a high similarity between samples from hands (hospital staff members) and surfaces, providing an infection risk to susceptible individuals. Healthy people working in hospitals can carry yeasts on their hands with the same potential virulence, and which therefore offer the same risk of infection. This information should be considered when preventive measures are established. Attention to the colonization of hands and surfaces should not be restricted to high-risk units such as NICUs, but should also include other sections of hospitals
Assessment of in vitro biofilm formation and antifungal susceptibility of Candida albicans isolates from vulvovaginal candidiasis
Objectives Vulvovaginal candidiasis (VVC) is an inflammation of the genital mucosa, which mainly affects the vulva and vagina. Candida spp. are considered commensal fungus, however, when there is imbalance in the microbiota or the host immune system is compromised, these can become pathogenic. C. albicans is responsible for most cases of VVC and is able of expressing mechanisms which allow the colonization or infection in the host. These factors related yeasts, including the growth of strains resistant to antifungal agents and virulence attributes (such as biofilm formation) are important in the development of VVC. In this sense, the objective of this study was to evaluate the in vitro biofilm formation and susceptibility to antifungal of C. albicans isolates from patients with vulvovaginal candidiasis. Methods For the study were analyzed 30 clinical isolates of Candida albicans. The clinical isolates were separated in groups of 10 samples of the according to symptoms presented by the patients: asymptomatic (AS), vulvovaginal candidiasis (VVC) and recurrent vulvo- vaginal candidiasis (RVVC). For all isolates were analyzed biofilm formation and minimal inhibitory concentration (MIC) for fluconazole and nystatin. The MIC was performed according to M27-A3 protocol of the Clinical Laboratory Standards Institute. Biofilm forming ability was assessed through quantification of total biomass by crystal violet (CV) staining, performed on 96-well microplates containing a cellular suspension of 1 9 107 cells ml1 and incubated for 24 h at 37°C.
Results Antifungal susceptibility testing is showed in table 1. The isolates were tested to the two antifungals. The MIC raging from 0.125 to 2 lg ml1 for fluconazole and 1 to 4 lg ml1 to nystatin. The figure 1 show the quantification of the total biomass. It was evident that all the C. albicans isolates were able to form biofilm, although differences occurred depending on the isolated and consequently the group. Importantly it was noted that, in general, VVC and RVVC groups had similar capacity biofilm formation. On the other hand, these groups had less total biomass (average Abs = 1,091 ` 0.88) compared with AS group (average Abs = 1,521 ` 1.32).
Conclusion Although all the samples analyzed are sensitive to anti- fungals tested research of resistant strains is relevant, since recurrences are related to cases of VVC. Nystatin and fluconazole were effective in small concentrations for the isolates analysed. All samples were able to form biofilm and the average of the group of asymptomatic patients greater than the others. Thus, the capacity to form- ing biofilm is an important virulence factor in the persistence of microorganisms in infectious processes and represent an increase in resistance to antifungal and host defense
Ultracold Gases of Ytterbium: Ferromagnetism and Mott States in an SU(6) Fermi System
It is argued that ultracold quantum degenerate gas of ytterbium Yb
atoms having nuclear spin exhibits an enlarged SU symmetry.
Within the Landau Fermi liquid theory, stability criteria against Fermi liquid
(Pomeranchuk) instabilities in the spin channel are considered. Focusing on the
SU generalizations of ferromagnetism, it is shown within mean-field
theory that the transition from the paramagnet to the itinerant ferromagnet is
generically first order. On symmetry grounds, general SU itinerant
ferromagnetic ground states and their topological excitations are also
discussed. These SU ferromagnets can become stable by increasing the
scattering length using optical methods or in an optical lattice. However, in
an optical lattice at current experimental temperatures, Mott states with
different filling are expected to coexist in the same trap, as obtained from a
calculation based on the SU Hubbard model.Comment: 4+ pages, 1 figure; v2: Improved discussion of the SU(6)
symmetry-breaking patterns; v3: added further discussion on the order of the
transition. Added Reference
Chiral Anomaly and Spin Gap in One-Dimensional Interacting Fermions
Semiclassical approach has been developed for the one-dimensional interacting
fermion systems. Starting from the incommensurate spin density wave (SDW) mean
field state for the repulsive Hubbard model in 1D, the non-Abelian bosonized
Lagrangian describing the spin-charge separation is obtained. The Berry phase
term is derived from the chiral anomaly, and we obtain the massless
Tomonaga-Luttinger liquid in the single chain case while the spin gap opens in
the double-chain system. This approach offers a new method to identify the
strong-coupling fixed point, and its relation to the Abelian bosonization
formalism is discussed on the spin gap state. The generalization to higher
dimensions is also discussed.Comment: Revised and enlarged version. 16 pages in REVTE
Hall coefficient of LaYSrCuO () at low temperatures under high magnetic fields
The Hall coefficient in the low-temperature tetragonal phase and the
mid-temperature orthorhombic phase of LaYSrCuO
() single crystals is measured under high magnetic fields up to 9 T
in order to investigate the detailed behavior of the transport properties at
low temperatures in the stripe phase. When the superconductivity is suppressed
by high magnetic fields, the Hall coefficient has negative values in low
temperatures, and the temperature region of the negative values spreads as
increasing magnetic fields. This result indicates that the Hall coefficient in
the stripe phase around is a finite negative value, not zero.Comment: 4 pages, 4 figures. to be published to Physical Review
Exact Renormalization Group and Loop Equation
We propose a gauge invariant formulation of the exact renormalization group
equation for nonsupersymmetric pure U(N) Yang-Mills theory, based on the
construction by Tim Morris. In fact we show that our renormalization group
equation amounts to a regularized version of the loop equation, thereby
providing a direct relation between the exact renormalization group and the
Schwinger-Dyson equations. We also discuss a possible implication of our
formulation to the holographic correspondence of the bulk gravity and the
boundary gauge theory.Comment: 13 pages, Latex, References added. An error in eq. (6) fixed and a
few corrrections accordingly. Results unchange
Heavy quark supermultiplet excitations
Lorentz covariant wave functions for meson and baryon supermultiplets are
simply derived by boosting representations corresponding to
multiquark systems at rest.Comment: 12 pages (Revtex), UTAS-PHYS-93-4
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