De retibus socialibus et legibus momenti

Online Social Networks (OSNs) are a cutting edge topic. Almost everybody --users, marketers, brands, companies, and researchers-- is approaching OSNs to better understand them and take advantage of their benefits. Maybe one of the key concepts underlying OSNs is that of influence which is highly related, although not entirely identical, to those of popularity and centrality. Influence is, according to Merriam-Webster, "the capacity of causing an effect in indirect or intangible ways". Hence, in the context of OSNs, it has been proposed to analyze the clicks received by promoted URLs in order to check for any positive correlation between the number of visits and different "influence" scores. Such an evaluation methodology is used in this paper to compare a number of those techniques with a new method firstly described here. That new method is a simple and rather elegant solution which tackles with influence in OSNs by applying a physical metaphor.Comment: Changes made for third revision: Brief description of the dataset employed added to Introduction. Minor changes to the description of preparation of the bit.ly datasets. Minor changes to the captions of Tables 1 and 3. Brief addition in the Conclusions section (future line of work added). Added references 16 and 18. Some typos and grammar polishe

Cierre quirúrgico en flexión versus extensión en artroplastias totales de rodilla

Se ha realizado un estudio prospectivo de 44 pacientes con gonartrosis primaria que fueron intervenidos con artroplastia total de rodilla con el objeto de determinar las diferencies en cuanto a la movilidad final de la rodilla dependiendo del cierre quirúrgico en flexión o en extensión. Se formaron dos grupos con similares características de homogeneidad respecto al sexo, edad, peso corporal y arco de movilidad previa, no existiendo diferencies significativas entre los grupos en la valoración preoperatoria. En el primer grupo se incluyeron 22 pacientes donde se había realizado la sutura de la cápsula articular y del plano muscular y cutáneo en flexión de 70º a 90º; el segundo grupo estaba formado por otros 22 pacientes en los que se realizó la sutura con la rodilla en extensión completa. En todos los pacientes se implantó el mismo modelo artroplástico y todos siguieron el mismo protocolo de rehabilitación postoperatoria. La evaluación clínica se realizó en el momento del alta hospitalaria, al mes, tres y seis meses, siguiendo la escala del Hospital for Special Surgery. Se apreció un arco de movilidad y puntuación clínica mayor en el grupo de rodillas suturadas en extensión, con una diferencia estadísticamente significativa, en los controles realizados en el alta hospitalaria y al mes de la intervención. A los seis meses no se apreciaron diferencias entre ambos grupos. La posición de la rodilla en el cierre quirúrgico de una artroplastia no afecta a su funcionalidad.In a prospective study, 44 patients with primary osteoarthritis of the knee undergoing total knee arthroplasty were compared to determine whether surgical closure of the entire wound in flexion had any effect on the postoperative range of motion over a period of six months. In twenty-two patients the knee was surgically closed in 70º to 90º flexion. In the second group of 22 patients, knees were closed in extension. There was no significant difference between groups respect to age, gender, weight and preoperative range of motion. All of the patients were operated on by the same team of surgeons and with the same type of prosthesis. Both groups of patients received a standardized exercise program during their hospitalization. All patients were evaluated following the parameters of the Hospital for Special Surgery score at discharge from the hospital, at first month, third and sixth month after operation. At all the intervals, both the flexion measurements and function scores were better in the flexion closure group, although we only found statically significant difference at discharge and at the first month postoperatively. The position of the knee in the surgical closing of an arthroplasty doesn't affected o functionality

Fibromatosis agresiva en hueco popliteo: A propósito de un caso

Se presenta un caso de una masa indolora en región posterior de la pierna en un varón de 35 años de crecimiento rápido, consistencia firme y mal delimitada. La resonancia magnética mostraba infiltración de músculos y tejido cellar subcutáneo, siendo sugestiva de fibromatois, tumor neurogénico o sarcoma de partes blandas. La biopsia incisional confirmó el diagnóstico de fibromatiosis agresiva. La resección amplia es el tratamiento aconsejado por la mayoría de autores, aunque en algunos casos y debido al carácter infiltrativo de la lesión es difícil resecarla ampliamente. La radioterapia se aconseja en los casos de resección y en los casos de recidiva.We present a case of a 35 year-old man who presented a fast growing painless mass localized in the posterior leg, which had at physical examination poorly defined contour and firm consistency. Magnetic resonance imaging showed local infiltration of muscle and subcutaneous cellular tissue, being suggestive of fibromatosis, neurogenic tumour, or soft tissue sarcoma. The incision biopsy confirmed the diagnosis of aggressive fibromatosis. Wide resection is the treatment recommended by most authors, although in some cases and due to the infiltration tendency of the tumour, it is difficult to achieve wide margins. Post-operative radiotherapy is recommended in cases of marginal resection and in case of recurrence

Osteopoiquilia: A propósito de 2 casos

La osteopoiquilosis es una rara displasia ósea esclerosante. Su diagnóstico es normalmente hecho de forma accidental de radiografías que muestran múltiples áreas escleróticas en diversos huesos del esqueleto. Su diagnóstico diferencial se realiza con la melorreostosis, osteopatía estriada y metástasis osteobásticas, en base a la clínica, radiología y gammagrafía. Histológicamente aparecen condensaciones focales de hueso lamelar compacto dentro de la esponjosa. Nosotros recogemos 2 casos de osteopoiquilosis y se hace a su vez un recuerdo.Osteopoikilosis, is a rare sclerosing bone dysplasia. The diagnosis is usually made incidentally from radiographs with show multiple sclerotic areas in several bones of the body. The differential diagnosis from melorheostosis, osteophatia striata and specially from osteoblastic bone metastases, on the basis of the clinical, radiological and radionuclide scanning characteristics. Histologically, there are focal condensations of compact lamellar bone within the spongiosa. We report two case osteopoikilosis

The competition between incoming and outgoing fluxes in an elliptic problem

In this work we consider existence and uniqueness of positive solutions to the elliptic equation −∆u = λu in Ω, with the nonlinear boundary conditions ∂u ∂ν = u p on Γ1, ∂u ∂ν = −u q on Γ2, where Ω is a smooth bounded domain, ∂Ω = Γ1 ∪ Γ2, Γ1 ∩ Γ2 = ∅, ν is the outward unit normal, p, q > 0 and λ is a real parameter. We obtain a complete picture of the bifurcation diagram of the problem, depending on the values of p, q and the parameter λ. Our proofs are based on different techniques: variational arguments, bifurcation techniques or comparison arguments, depending on the range of parameters considered.Ministerio de Educación y CienciaFondo Europeo de Desarrollo Regiona

Using machining force feedback to quantify grain size in beta titanium

The fluctuating forces on the cutting tool generated during machining of β processed Ti-17 alloy are shown to contain sufficient information to enable measurement of β grain size to an equivalent accuracy of standard etching methods. Three orthogonal forces were gathered, cutting force tangential to the rotation, the force in the feed (radial) direction, and the normal force in the longitudinal axis. Each individual force produced a microstructure image with a high level of contrast but in some cases did not fully highlight all features as shown in the optical image of the equivalent area. By normalising and combining the three forces into a vector, followed by noise reduction, a high-resolution image with sufficient detail to undertake grain size measurements using the linear intercept was produced. The measured grain size differed by no more than 5% with respect the grain size measured in the etched micrograph. It is believed that the forces which have a higher proportion of elastic response in their total values, i.e., the feed and normal forces, produced the higher contrast images, indicating that elastic stresses produce the highest contrast between grains and plastic strains smear out the grain to grain variation