1,721,194 research outputs found
Elementary particle masses from a non-perturbative anomaly
Full text linkA novel dynamical mechanism of elementary particle mass generation has recently been conjectured and
numerically demonstrated by lattice simulations in a simple SU(3) gauge model where a SU(2) doublet
of strongly interacting fermions is coupled to a complex scalar field doublet through a Yukawa and a
Wilson-like term. As a first step towards building a natural (à la ’t-Hooft) extension of the Standard
Model, we argue that in the presence of weak gauge interactions the mechanism above, acting as a kind of
non-perturbative anomaly, yields for both elementary fermions and weak gauge bosons effective masses
proportional to the Λ–parameter of the theory, with particle–specific gauge coupling dependent prefactors
Pathogenesis of posterior capsular opacification. Part I. Epidemiological and clinico-statistical data
No full textWe examined 895 eves having extracapsular cataract surgery; 403 had an intraocular lens (IOL) implanted and 492 did not. The incidence of posterior capsular opacification was 7.69% in the eyes with an IOL and 14.23% in the eyes without an IOL. If we exclude complicated cataracts from the cases that did not have an IOL, the incidence of posterior capsular opacification decreases to 9.06%. Various models of implanted IOLs showed different incidences of posterior capsular opacification: For J-looped lenses the incidence was 11.02%; for Frezzotti-Caporossi lenses, 7.35%. The follow-up Nvas too short for soft lenses. The Frezzotti-Caporossi lens can he inserted with the convex side either anterior or posterior. A statistical evaluation shows that the reverse optic or posterior convex orientation in the bag caused a lower incidence of posterior capsular opacification (3.01%). © 1990, American Society of Cataract and Refractive Surgery. All rights reserved
Twisted-mass lattice QCD with mass non-degenerate quarks
No full textThe maximally twisted lattice QCD action of an SUf(2) doublet of mass degenerate Wilson quarks gives raise to a real positive fermion determinant and it is invariant under the product of standard parity times the change of sign of the coefficient of the Wilson term. The existence of this spurionic symmetry implies that O(a) improvement is either automatic or achieved through simple linear combinations of quantities taken with opposite external three-momenta. We show that in the case of maximal twist all these nice results can be extended to the more interesting case of a mass non-degenerate quark pair
Nonsupersymmetric model with unification of electroweak and strong interactions
No full textIn this paper, we show that adding to the standard model particle content a set of superstrongly interacting particles with appropriately chosen hypercharges leads to unification of strong and electroweak interactions at a level comparable to that of the minimal supersymmetric standard model
Cosmetic possibilities and problems in eyelid neurofibromas
No full textNeurofibromatosis type 1 (NF1) is an inherited systemic disease with frequent ocular involvement. A typical alteration observed in NF1 is the eyelid plexiform neurofibroma, often associated with facial homolateral hypertrophy. In such cases, surgical cosmetic results are rather unsatisfactory, since plexiform neurofibromas classically show a non-capsulated mass, with a marked tendency to local recurrence. The techniques for a cosmetic attempt are discussed on the basis of a personal series of eyelid reconstructions in NF1. The results can be considered satisfactory in some cases, when the orbital shape is preserved and the eyelid structure has not been excessively altered by the neurofibroma; in all other cases, the cosmetic outcome is inferior to the patient's and parents' expectations. The serious problem of recurrence is however a limitation to cosmetic surgery in eyelid neurofibromas
Uso della mappa di quota (ISOIPSE) nella stima ecografica della salienza sul piano retinico delle neoplasie oculari
No full textLa collezione degli strumenti di oculistica
No full textCollana del patrimonio storico scientifico dell'Università degli Studi di Siena "Mater.iali
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