Fermion masses in a model for spontaneous parity breaking

In this paper we discuss a left-right symmetric model for elementary particles and their connection with the mass spectrum of elementary fermions. The model is based on the group $SU(2)_L\otimes SU(2)_R\otimes U(1)$. New mirror fermions and a minimal set of Higgs particles that breaks the symmetry down to $U(1)_{em}$ are proposed. The model can accommodate a consistent pattern for charged and neutral fermion masses as well as neutrino oscillations. An important consequence of the model is that the connection between the left and right sectors can be done by the neutral vector gauge bosons Z and a new heavy Z'.Comment: 7 pages, 3 figures. Accepted in Eur. Phys. J.

Dynamical complexity of discrete time regulatory networks

Genetic regulatory networks are usually modeled by systems of coupled differential equations and by finite state models, better known as logical networks, are also used. In this paper we consider a class of models of regulatory networks which present both discrete and continuous aspects. Our models consist of a network of units, whose states are quantified by a continuous real variable. The state of each unit in the network evolves according to a contractive transformation chosen from a finite collection of possible transformations, according to a rule which depends on the state of the neighboring units. As a first approximation to the complete description of the dynamics of this networks we focus on a global characteristic, the dynamical complexity, related to the proliferation of distinguishable temporal behaviors. In this work we give explicit conditions under which explicit relations between the topological structure of the regulatory network, and the growth rate of the dynamical complexity can be established. We illustrate our results by means of some biologically motivated examples.Comment: 28 pages, 4 figure

Inducing energy gaps in graphene monolayer and bilayer

In this paper we propose a mechanism for the induction of energy gaps in the spectrum of graphene and its bilayer, when both these materials are covered with water and ammonia molecules. The energy gaps obtained are within the range 20-30 meV, values compatible to those found in experimental studies of graphene bilayer. We further show that the binding energies are large enough for the adsorption of the molecules to be maintained even at room temperature

Sinovite Vilonodular Pigmentada: um desafio diagnóstico. Revisão de 8 casos

OBJECTIVE: Pigmented Villonodular Synovitis (PVNS) is a benign and uncommon clinical entity, characterized by excessive proliferation of synovial membrane of joints, tendon sheaths and bursas. The objective of this study was to evaluate demographic and clinical parameters, diagnostic and treatment procedures and the outcome of 28 patients with PVNS. MATERIAL AND METHODS: Retrospective study of the histologically proven cases of PVNS, diagnosed between January 1998 and April 2010 in the Orthopaedics Department of Coimbra University Hospital. Clinical data were reviewed for each patient and the following parameters were evaluated: gender, age at diagnosis, initial clinical symptoms and site of onset, symptom duration, main imaging findings (x-ray and magnetic resonance imaging of the involved structure), histological features of the lesion, treatment, follow-up duration, evidence of recurrence and time between surgery and recurrence. RESULTS: A total of 28 patients with histologically proven PVNS were included. The majority of patients were female (53.6%) and the mean age at the time of diagnosis was 39.2 ± 19.1 years (mean ± SD). The time between onset of symptoms and diagnosis was un- known in one patient and, in the other 27 patients, mean delay in diagnosis was 24.4 ± 20.5 months (mean ± SD). The knee was the most frequently affected site (75% of the cases). Pain and progressive local swelling sensation were the most frequent symptoms at onset (in 82.1% and 71.4% of the cases, respectively). Joint x-ray identified abnormalities in only 17.8% of the patients. Magnetic resonance imaging (MRI) of the affected structure identified the presence of synovial membrane proliferation in all cases and extra-articular extension of the lesion and bone erosions in 39.1% and 34.8%, respectively. Diagnosis was histologically proven in all cases (27 with synovial joint origin and 1 with tenosynovial origin). Subtotal synovectomy, total synovectomy, local excision of the lesion, synovectomy associated with arthroplasty and synovectomy associated with arthrodesis were performed in 53.6%, 21.4%, 10.7%, 7.1% and 3.6% of the cases, respectively. Local recurrence occurred in 25% of the patients, with a mean time of recurrence of 60.8 months after surgery. CONCLUSION: In PVNS patients, the non-specific symptoms often contribute to a delay in establishing a diagnosis. As in the majority of the reported studies, in this study the knee was also the most commonly affected articular site. Although the x-ray of the affected joint revealed abnormalities in just a few number of patients,MRI identified the presence of synovial membrane proliferation in all cases, proving its value in the diagnostic approach to this entity. However, only the histological study of the lesion allows establishing a definitive diagnosis