3,393 research outputs found
Phase transitions in a gas of anyons
We continue our numerical Monte Carlo simulation of a gas of closed loops on
a 3 dimensional lattice, however now in the presence of a topological term
added to the action corresponding to the total linking number between the
loops. We compute the linking number using certain notions from knot theory.
Adding the topological term converts the particles into anyons. Using the
correspondence that the model is an effective theory that describes the
2+1-dimensional Abelian Higgs model in the asymptotic strong coupling regime,
the topological linking number simply corresponds to the addition to the action
of the Chern-Simons term. We find the following new results. The system
continues to exhibit a phase transition as a function of the anyon mass as it
becomes small \cite{mnp}, although the phases do not change the manifestation
of the symmetry. The Chern-Simons term has no effect on the Wilson loop, but it
does affect the {\rm '}t Hooft loop. For a given configuration it adds the
linking number of the 't Hooft loop with all of the dynamical vortex loops to
the action. We find that both the Wilson loop and the 't Hooft loop exhibit a
perimeter law even though there are no massless particles in the theory, which
is unexpected.Comment: 6 pages, 5 figure
A low-power recursive I/Q signal generator and current driver for bioimpedance applications
This brief presents a power-efficient quadrature signal generator and current driver application-specific integrated circuit (ASIC) for bioimpedance measurements in an electrical impedance tomography system for monitoring lung function. The signal generator is realized by a digital recursive signal oscillator with the ability of generating quadrature signals over a wide frequency range. The generated in-phase signal is applied to a current driver. It uses a balanced current-mode feedback architecture that monitors the output current through a feedback loop to minimize common-mode voltage build-up at the injection site. The quadrature signals can be used for I/Q demodulation of the measured bioimpedance. The ASIC was designed in TSMC 65 nm technology occupying an area of 0.21 mm2. The current driver can generate up to 0.7 mA current up to 200 kHz and consumes 2.7 mW power using ±0.8 V supplies
Newly forming bone graft: a novel surgical approach to the treatment of denuded roots
Many techniques have been proposed for root coverage. However, none of them presents predictable results in deep and wide recessions. OBJECTIVES: The aim of this case series report is to describe an alternative technique for root coverage at sites showing deep recessions and attachment loss >;4 mm at buccal sites. MATERIAL AND METHODS: Four patients presenting deep recession defects at buccal sites (>;4 mm) were treated by the newly forming bone graft technique, which consists in the creation of an alveolar socket at edentulous ridge and transferring of granulation tissue present in this socket to the recession defect after 21 days. Clinical periodontal parameters, including recession depth (RD), probing depth (PD), clinical attachment level (CAL), bleeding on probing (BOP), plaque index (PI) and keratinized gingiva width (KGW) were evaluated by a single examiner immediately before surgery and at 1, 3, 6 and 9 months postoperatively. RESULTS: All cases showed reduction in RD and PD, along with CAL gain, although no increase in KGW could be observed. These findings suggest that the technique could favor periodontal regeneration along with root coverage, especially in areas showing deep recessions and attachment loss
Penile Carcinoma: Risk Factors and Molecular Alterations
Penile carcinoma is a rare, male cancer. Although the incidence of penile carcinoma is very low in Western countries, in some countries, the incidence is significantly greater, with penile carcinoma accounting for ≤10% of all male malignancies. Greater insight has been gained in recent years as to its pathogenesis, the risk factors associated with its development, and the clinical and histological precursor lesions related to this disease. In this review, risk and conditions factors for penile carcinoma, molecular alterations in this type of cancer, histological types, and prognostic factors will be discussed in order to further our understanding of the biology and behavior of this cancer
Heavy metal levels in tissues (gonads and fillets) of Horse mackerel collected from Ghazaouet Bay (Western Mediterranean coast of Algeria)
The concentration levels of Zn, Pb, Cd and Cu were evaluated in the gonads and fillets of Horse mackerel (Trachurus trachurus) collected from Ghazaouet bay. The results showed the accumulation of Pb, Cd, Cu and Zn in the gonads and fillets. The metal concentrations in the fillets and gonads decreased in the following order: Zn >Cd >Pb >Cu and Zn >Cd >Cu >Pb, respectively. The levels of essential metals (zinc and copper) in both target organs generally complied with the recommended value for fish while the levels of non-essential metals like cadmium and lead, which are toxic and present in traces, greatly exceeded the recommended values in both target organs, which are ascribed mainly to the industrial pollution in Ghazaouet area. Therefore, it can be concluded that these heavy metals in different tissues of Horse mackerel, which is highly consumed in the Algerian coastal regions, could pose adverse health effects on consumers
SUSY Higgs at the LHC: Effects of light charginos and neutralinos
In view of the latest LEP data we consider the effects of charginos and
neutralinos on the two-photon and bbbar signatures of the Higgs at the LHC.
Assuming the usual GUT inspired relation between M_1 and M_2 we show that there
are only small regions with moderate tanbeta and large stop mixings that may be
dangerous. Pathological models not excluded by LEP which have degeneracy
between the sneutrino and the chargino are however a real danger because of
large branching fraction of the Higgs into invisibles. We have also studied
models where the gaugino masses are not unified at the GUT scale. We take
M_1=M_2/10 as an example where large reductions in the signal at the LHC can
occur. However we argue that such models with a very light neutralino LSP may
give a too large relic density unless the sleptons are light. We then combine
this cosmological constraint with neutralino production with light sfermions to
further reduce the parameter space that precludes observability of the Higgs at
the LHC. We still find regions of parameter space where the drops in the usual
Higgs signals at the LHC can be drastic. Nonetheless, in such scenarios where
Higgs may escape detection we show that one should be able to produce all
charginos and neutralinos. Although the heavier of these could cascade into the
Higgs, the rates are not too high and the Higgs may not always be recovered
this way.Comment: 37 pages, 17 figures, Latex file, Paper with high resolution figures
can be found at http://wwwlapp.in2p3.fr/web/lapp/preplapp/psth/LAPTH774.ps.g
The EROS2 search for microlensing events towards the spiral arms: the complete seven season results
The EROS-2 project has been designed to search for microlensing events
towards any dense stellar field. The densest parts of the Galactic spiral arms
have been monitored to maximize the microlensing signal expected from the stars
of the Galactic disk and bulge. 12.9 million stars have been monitored during 7
seasons towards 4 directions in the Galactic plane, away from the Galactic
center. A total of 27 microlensing event candidates have been found. Estimates
of the optical depths from the 22 best events are provided. A first order
interpretation shows that simple Galactic models with a standard disk and an
elongated bulge are in agreement with our observations. We find that the
average microlensing optical depth towards the complete EROS-cataloged stars of
the spiral arms is , a number that is
stable when the selection criteria are moderately varied. As the EROS catalog
is almost complete up to , the optical depth estimated for the
sub-sample of bright target stars with () is easier to interpret. The set of microlensing events
that we have observed is consistent with a simple Galactic model. A more
precise interpretation would require either a better knowledge of the distance
distribution of the target stars, or a simulation based on a Galactic model.
For this purpose, we define and discuss the concept of optical depth for a
given catalog or for a limiting magnitude.Comment: 22 pages submitted to Astronomy & Astrophysic
Parkinson's disease may disrupt overlapping subthalamic nucleus and pallidal motor networks.
There is an ongoing debate about differential clinical outcome and associated adverse effects of deep brain stimulation (DBS) in Parkinson's disease (PD) targeting the subthalamic nucleus (STN) or the globus pallidus pars interna (GPi). Given that functional connectivity profiles suggest beneficial DBS effects within a common network, the empirical evidence about the underlying anatomical circuitry is still scarce. Therefore, we investigate the STN and GPi-associated structural covariance brain patterns in PD patients and healthy controls. We estimate GPi's and STN's whole-brain structural covariance from magnetic resonance imaging (MRI) in a normative mid- to old-age community-dwelling cohort (n = 1184) across maps of grey matter volume, magnetization transfer (MT) saturation, longitudinal relaxation rate (R1), effective transversal relaxation rate (R2*) and effective proton density (PD*). We compare these with the structural covariance estimates in patients with idiopathic PD (n = 32) followed by validation using a reduced size controls' cohort (n = 32). In the normative data set, we observed overlapping spatially distributed cortical and subcortical covariance patterns across maps confined to basal ganglia, thalamus, motor, and premotor cortical areas. Only the subcortical and midline motor cortical areas were confirmed in the reduced size cohort. These findings contrasted with the absence of structural covariance with cortical areas in the PD cohort. We interpret with caution the differential covariance maps of overlapping STN and GPi networks in patients with PD and healthy controls as correlates of motor network disruption. Our study provides face validity to the proposed extension of the currently existing structural covariance methods based on morphometry features to multiparameter MRI sensitive to brain tissue microstructure
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