2,300 research outputs found
Five-dimensional SYM from undeformed ABJM
We expand undeformed ABJM theory around the vacuum solution that was found in
arxiv:0909.3101. This solution can be interpreted as a circle-bundle over a
two-dimensional plane with a singularity at the origin. By imposing periodic
boundary conditions locally far away from the singularity, we obtain a local
fuzzy two-torus over which we have a circle fibration. By performing
fluctuation analysis we obtain five-dimensional SYM with the precise value on
the coupling constant that we would obtain by compactifying multiple M5 branes
on the vacuum three-manifold. In the resulting SYM theory we also find a
coupling to a background two-form.Comment: 23 page
Vaginal yeasts in the era of "over the counter" antifungals
OBJECTIVE: To establish whether there has been any rise in the prevalence of non-albicans
Candida species isolated from vaginal swabs since the introduction of “over the counter” antifungal
treatments.
METHOD: A retrospective review looking at all positive vaginal yeast isolates collected from
women attending one genitourinary medicine clinic during the 6 year period from 1993 to 1998
inclusive. All positive vaginal yeast isolates were included, regardless of whether or not the
patients were symptomatic. Isolates from HIV positive women were excluded from the analysis.
RESULT: No increase in non-albicans vaginal yeast isolates was shown during the period studied.
The proportion of non-albicans yeasts remained constant at approximately 5% of the total yeasts
isolated. The most common non-albicans yeast isolated was C glabrata.
CONCLUSION: There is no evidence from this study to suggest that the increasing use of “over the
counter” antifungal treatment has selected for atypical, possibly inherently azole resistant, strains
of vaginal yeasts in HIV seronegative women
Detecting THz current fluctuations in a quantum point contact using a nanowire quantum dot
We use a nanowire quantum dot to probe high-frequency current fluctuations in
a nearby quantum point contact. The fluctuations drive charge transitions in
the quantum dot, which are measured in real-time with single-electron detection
techniques. The quantum point contact (GaAs) and the quantum dot (InAs) are
fabricated in different material systems, which indicates that the interactions
are mediated by photons rather than phonons. The large energy scales of the
nanowire quantum dot allow radiation detection in the long-wavelength infrared
regime
Excited states and energy transfer among DNA bases in double helices
International audienceThe study of excited states and energy transfer in DNA double helices has recently gained new interest connected to the development of computational techniques and that of femtosecond spectroscopy. The present article points out contentious questions regarding the nature of the excited states and the occurrence of energy transfer and shows how they are currently approached. Using as example the polymer poly(dA)·poly(dT), composed of about 2000 adenine–thymine pairs, a model is proposed on the basis of time-resolved measurements (fluorescence decays, fluorescence anisotropy decays and fluorescence spectra, obtained with femtosecond resolution), associated to steady-state spectra. According to this qualitative model, excitation at 267 nm populates excited states that are delocalized over a few bases (excitons). Ultrafast internal conversion directs the excited state population to the lower part of the exciton band giving rise to fluorescence. Questions needing further investigations, both theoretical and experimental, are underlined with particular emphasis on delicate points related to the complexity and the plasticity of these systems
Time-resolved charge detection with cross-correlation techniques
We present time-resolved charge sensing measurements on a GaAs double quantum
dot with two proximal quantum point contact (QPC) detectors. The QPC currents
are analyzed with cross-correlation techniques, which enables us to measure dot
charging and discharging rates for significantly smaller signal-to-noise ratios
than required for charge detection with a single QPC. This allows to reduce the
current level in the detector and therefore the invasiveness of the detection
process and may help to increase the available measurement bandwidth in
noise-limited setups.Comment: 6 pages, 4 figure
Fluorescence of DNA Duplexes: From Model Helices to Natural DNA
International audienceRecent fluorescence studies of DNA duplexes with a simple repetitive base sequence have revealed important collective effects which are very sensitive to conformational disorder. In contrast to the monomeric chromophores, whose fluorescence lifetimes are shorter than 1 ps, the fluorescence decays of duplexes span several decades of time. The occurrence of excitation energy transfer, evidenced by the decay of the fluorescence anisotropy on the femtosecond time scale, is a common feature of all of the examined systems. It is explained by the existence of Franck-Condon exciton states, in line with the Vabsorption spectra. Understanding the nature of the long-lived excited states, whose emission dominates the steady-state fluorescence spectrum of natural DNA, will be one of the challenges for the years to come
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