485 research outputs found
2D Superconductivity: Classification of Universality Classes by Infinite Symmetry
I consider superconducting condensates which become incompressible in the
infinite gap limit. Classical 2D incompressible fluids possess the dynamical
symmetry of area-preserving diffeomorphisms. I show that the corresponding
infinite dynamical symmetry of 2D superconducting fluids is the coset
, with
the chiral algebra of quantum area-preserving diffeomorphisms
and I derive its minimal models. These define a discrete set of 2D
superconductivity universality classes which fall into two main categories:
conventional superconductors with their vortex excitations and unconventional
superconductors. These are characterized by a broken symmetry and are labeled by an integer level . They
possess neutral spinon excitations of fractional spin and statistics which carry also an isospin
quantum number; this hidden symmetry implies that these anyon
excitations are non-Abelian. The simplest unconventional superconductor is
realized for : in this case the spinon excitations are semions
(half-fermions). My results show that spin-charge separation in 2D
superconductivity is a universal consequence of the infinite symmetry of the
ground state. This infinite symmetry and its superselection rules realize a
quantum protectorate in which the neutral spinons can survive even as soft
modes on a rigid, spinless charge condensate.Comment: Revised version to appear in Nuclear Physics
Classification of Quantum Hall Universality Classes by $\ W_{1+\infty}\ $ symmetry
We show how two-dimensional incompressible quantum fluids and their
excitations can be viewed as edge conformal field theories,
thereby providing an algebraic characterization of incompressibility. The
Kac-Radul representation theory of the algebra leads then to
a purely algebraic complete classification of hierarchical quantum Hall states,
which encompasses all measured fractions. Spin-polarized electrons in
single-layer devices can only have Abelian anyon excitations.Comment: 11 pages, RevTeX 3.0, MPI-Ph/93-75 DFTT 65/9
Morbidity of central neck dissection for papillary thyroid cancer
Thyroid cancer has a very well-known propensity for nodal involvement, either in the central and lateral neck compartments. Neck dissection addressing the central compartment may be performed with an elective or therapeutic intent, the former concomitantly to a thyroidectomy whereas the latter may be accomplished also as a revision procedure for recurrent disease. In this paper complications of central compartment neck dissection will be described, analyzing separately primary and revision procedures
Radioguided Parathyroidectomy with Portable Mini Gamma-Camera for the Treatment of Primary Hyperparathyroidism
Background. A proper localisation of pathological parathyroid glands is essential for a minimally invasive approach in the surgical treatment of primary hyperparathyroidism (PHP). The recent introduction of portable mini gamma-cameras (pMGCs) enabled intraoperative scintigraphic scanning. The aim of our study is to evaluate the efficacy of this new method and compare it with the preoperative localisation surveys. Methods. 20 patients were studied; they were evaluated preoperatively by neck ultrasound and Tc-sestaMIBI-scintigraphy and intraoperatively with the pMGC IP Guardian 2. The results obtained from the three evaluations were compared. Results. The pMGC presented a sensitivity of 95%, a specificity of 98.89%, and a diagnostic accuracy of 98.18%, which were higher than those of preoperative ultrasound (sensitivity 55%; specificity 95%; diagnostic accuracy 87%) and scintigraphy with Tc-sestaMIBI (sensitivity 73.68%; specificity 96.05%; diagnostic accuracy 91.58%). Conclusions. The pMGC can be used effectively as an intraoperative method to find the correct location of the pathological parathyroid glands. The pMGC is more reliable than the currently used preoperative and intraoperative localisation techniques
Predicting gene expression levels from DNA sequences and post-transcriptional information with transformers
Background and objectives: In the latest years, the prediction of gene expression levels has been crucial due to its potential applications in the clinics. In this context, Xpresso and others methods based on Convolutional Neural Networks and Transformers were firstly proposed to this aim. However, all these methods embed data with a standard one-hot encoding algorithm, resulting in impressively sparse matrices. In addition, post-transcriptional regulation processes, which are of uttermost importance in the gene expression process, are not considered in the model.Methods: This paper presents Transformer DeepLncLoc, a novel method to predict the abundance of the mRNA (i.e., gene expression levels) by processing gene promoter sequences, managing the problem as a regression task. The model exploits a transformer-based architecture, introducing the DeepLncLoc method to perform the data embedding. Since DeepLncloc is based on word2vec algorithm, it avoids the sparse matrices problem.Results: Post-transcriptional information related to mRNA stability and transcription factors is included in the model, leading to significantly improved performances compared to the state-of-the-art works. Transformer DeepLncLoc reached 0.76 of R-2 evaluation metric compared to 0.74 of Xpresso.Conclusion: The Multi-Headed Attention mechanisms which characterizes the transformer methodology is suitable for modeling the interactions between DNA's locations, overcoming the recurrent models. Finally, the integration of the transcription factors data in the pipeline leads to impressive gains in predictive power. (C) 2022 Elsevier B.V. All rights reserved
Conformal Symmetry and Universal Properties of Quantum Hall States
The low-lying excitations of a quantum Hall state on a disk geometry are edge
excitations. Their dynamics is governed by a conformal field theory on the
cylinder defined by the disk boundary and the time variable. We give a simple
and detailed derivation of this conformal field theory for integer filling,
starting from the microscopic dynamics of -dimensional non-relativistic
electrons in Landau levels. This construction can be generalized to describe
Laughlin's fractional Hall states via chiral bosonization, thereby making
contact with the effective Chern-Simons theory approach. The conformal field
theory dictates the finite-size effects in the energy spectrum. An experimental
or numerical verification of these universal effects would provide a further
confirmation of Laughlin's theory of incompressible quantum fluids.Comment: 39 pages, 7 figures (not included, they are mailed on request),
harvmac CERN-TH 6702/9
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