Explicit Soliton for the Laplacian Co-Flow on a Solvmanifold

We apply the general Ansatz in geometric flows on homogeneous spaces proposed by Jorge Lauret for the Laplacian co-flow of invariant $G_2$-structures on a Lie group, finding an explicit soliton on a particular almost Abelian $7$-manifold.Comment: Minor corrections, proof's Lemma 4.1 modified. To appear in the S\~ao Paulo Journal of mathematical scienc

Harmonic G2G_2-structures on almost Abelian Lie groups

We consider left-invariant $G_2$-structures on $7$-dimensional almost Abelian Lie groups. Also, we characterise the associated torsion forms and the full torsion tensor according to the Lie bracket $A$ of the corresponding Lie algebra. In those terms, we establish the algebraic condition on $A$ for each of the possible $16$-torsion classes of a $G_2$-structure. In particular, we show that four of those torsion classes are not admissible, since $\tau_3=0$ implies $\tau_0=0$. Finally, we use the above results to provide the algebraic criteria on $A$, satisfying the harmonic condition $div T=0$, and this allows to identify which torsion classes are harmonic.Comment: 14 pages, no figures, comments are welcom

Kinematic analysis of a lower limb to determine the center of rotation of the knee at the sagittal plane.

En esta investigación se establece una metodología que permite describir el movimiento de miembros inferiores usando cadenas cinemáticas cerradas. Este análisis es realizado con el objetivo de determinar la posición del centro de rotación (CR) de la rodilla localizado en el plano sagital. Un paciente sano y sin antecedentes patológicos realizó pruebas de flexión-extensión con uno de sus miembros inferiores. Cuando el paciente realizo el movimiento articular (la flexo-extensión) un dispositivo de video y un programa (World In motion v4.0) determinan la posición de cuatro marcadores pasivos ubicados en el miembro inferior. Los datos obtenidos de los marcadores son utilizados en un modelo propuesto que permite localizar la posición del CR de la rodilla. En este estudio se concluye que el CR de la rodilla presenta movimiento relativo respecto a un punto fijo marcado en un miembro inferior. Los resultados comprueban que el CR de la rodilla delimitado en el plano sagital no presenta comportamiento de una junta completa (junta con un grado de libertad) como ha sido presentado en otros estudios. Abstract A methodology is established in this research which permits to describe the movement of a lower limb using closed kinematic chains. This analysis is developed with the aim to determine the location of the center of rotation (CR) of the knee joint in the sagittal plane. Flexion-extension tests were carried out on one of the lower limbs of a healthy patient without pathological antecedents. When the patient does articular movement (flexion-extension), a video equipment and a software determine the position of four passive markers installed on the lower limb. The information obtained from the markers is applied to the proposed model which allows to locate the center of rotation of the knee joint. Hence it was concluded that the CR of the knee joint undergoes a relative movement with respect to the fixed point marked on the lower limb. The results prove that the knee joint established in the sagittal plane does not show the behavior of a complete joint (a joint with one degree of freedom) as it has been described in other studies

G2_2-instantons on 22-step nilpotent Lie groups

We study the G$_2$-instanton condition for a family of metric connections arisen from the characteristic connection, on $7$-dimensional $2$-step nilpotent Lie groups with left-invariant coclosed G$_2$-structures. According to the dimension of the commutator subgroup, we establish necessary and sufficient conditions for the connection to be an instanton, in terms of the torsion of the G$_2$-structure, the torsion of the connection and the Lie group structure.Moreover, we show that in our setup, G$_2$-instantons define a naturally reductive structure on the simply connected $2$-step nilpotent Lie group with left-invariant Riemannian metric. Taking quotient by lattices, one obtains G$_2$-instantons on compact nilmanifolds.Comment: 36 pages. Comments are welcom

Desplazamiento epifisario en niños con insuficiencia renal crónica

Para buscar la prevalencia y factores clínicos-bioquímicos implicados en el desarrollo de epifisiolisis en niños con insuficiencia renal crónica, estudiamos 48 pacientes de 8,1+4,2 años, 28 en tratamiento conservador y 20 sometidos a diálisis crónica. Se analizó edad cronológica y de aparición de la insuficiencia renal, años de evolución y de diálisis y enfermedad fundamental y se practicó estudio del metabolismo fosfocálcico y mapa óseo. Cuatro enfermos presentaron epifisiolisis, lo que supone una prevalencia en nuestro medio del 8,3%. Los 4 seguían tratamiento dialítico y la insuficiencia renal se presentó durante la lactancia por una enfermedad renal congenita o de aparición en período neonatal precoz. Bioquímicamente tenían el grado más severo de hiperparal iroidismo con cifras inapropiadamente bajas de calcio y fósforo a pesar de instauración del tratamiento sustitutivo mediante diálisis crónica.Clinical, biochemical and roentgenological features of 48 children with chronic renal failure have been analysed. The prevalence and factors implicated with slipped epiphysis outlined. Four of 48 patients (8.3%) shown roentgenological dates of epiphysiolysis. In this cases, the underlying renal disease was congenital or neonatal, developping renal failure in infancy (average 0.6 months) and had the most severe hyperparathyroidism associated with low calcium and phosphorus level in spite of dialytic treatment

Harmonic Sp(2)Sp(2)-invariant G2G_2-structures on the 77-sphere

We describe the $10$-dimensional space of $Sp(2)$-invariant $G_2$-structures on the homogeneous $7$-sphere $S^7=Sp(2)/Sp(1)$ as $\mathbb{R}^+\times Gl^+(3,\mathbb{R})$. In those terms, we formulate a general Ansatz for $G_2$-structures, which realises representatives in each of the $7$ possible isometric classes of homogeneous $G_2$-structures. Moreover, the well-known nearly parallel round and squashed metrics occur naturally as opposite poles in an $S^3$-family, the equator of which is a new $S^2$-family of coclosed $G_2$-structures satisfying the harmonicity condition $div T=0$. We show general existence of harmonic representatives of $G_2$-structures in each isometric class through explicit solutions of the associated flow and describe the qualitative behaviour of the flow. We study the stability of the Dirichlet gradient flow near these critical points, showing explicit examples of degenerate and nondegenerate local maxima and minima, at various regimes of the general Ansatz. Finally, for metrics outside of the Ansatz, we identify families of harmonic $G_2$-structures, prove long-time existence of the flow and study the stability properties of some well-chosen examples.Comment: 33 page

Marginal Bone Loss in Implants Placed in Grafted Maxillary Sinus

PurposeThe purpose of this study is to evaluate the vertical and horizontal graft bone resorption (GR) in grafted maxillary sinuses and the marginal bone loss (MBL) around implants placed in the sinuses with different prosthetic connections and to determine the effect of other clinical factors on these tissue responses at 6 and 18 months postloading.Material and MethodA total of 254 implants were placed in 150 grafted maxillary sinuses of 101 patients (51.5% female) with mean age of 52.2 years (range, 32–82 years). GR and MBL measurements were made in implants placed with two different prosthetic connections (internal and external) at 6 and 18 months postloading. The complex samples general linear model was used to analyze the influence of patient age, gender, smoking habit, history of periodontal disease, implantation timing (simultaneous vs deferred), and prosthetic abutment length on radiographic GR and MBL values.ResultsAt 18 months postloading, the MBL ranged from 0 mm to 5.89 mm; less than 1 mm was lost around 49.0% (mesial) and 44.3% (distal) of the implants, while no bone was lost around 32.9% (mesial) and 26.7% (distal). The GR was significantly affected by smoking, remnant alveolar bone height, graft length, graft height, gender, and age, and it significantly decreased over time. The MBL was influenced by the type of connection, implantation timing, and prosthetic abutment length. The MBL was greater with longer postloading interval and higher patient age and in smokers.ConclusionResorption of grafts that combine autogenous cortical bone with anorganic bovine bone is dependent on the anatomic features of the sinus and is not affected by the time elapsed after the first 6 months. The MBL in implants placed in these grafted areas is time dependent and mainly related to potentially modifiable clinical decisions and patient habits.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/110884/1/cid12092.pd

Soluble and insoluble dietary fibre intake and risk factors for metabolic syndrome and cardiovascular disease in middle-aged adults: The AWHS cohort

Introduction: The Westernization of the Mediterranean lifestyle has led to a modification of certain dietary habits such as a decrease in the consumption of dietary fibre-rich foods. The impact of these changes on cardiovascular diseases (CVD) has been studied over the last few years and the effect of the different sources of fibre on cardiovascular risk parameters and coronary heart disease (CHD) continues to create controversy. Objective: To evaluate the association between the source of dietary fibre and the prevalence of metabolic syndrome (MetS) and other cardiovascular risk factors in a Spanish working population. Subjects and methods: The study was carried out in a sample of 1592 Spanish workers free of CVD (40-55 years old) within the Aragon Workers' Health Study (AWHS) cohort. Sociodemographic, anthropometric, clinical and biochemical data were collected. Fibre intake was assessed by means of a validated 136-items semiquantitative food-frequency questionnaire. MetS was defined by using the modified National Cholesterol Education Programme-Adult Treatment Panel III (NCEP-ATP III) definition. Results: After adjusting for possible confounding factors, we found an inverse association between insoluble fibre intake and systolic and diastolic blood pressure, total cholesterol, triglycerides, apolipoprotein B100 and ratio TG/HDL. Soluble fibre was inversely associated with triglycerides and apolipoprotein B100. Furthermore, prevalence of MetS was found to be lower (OR 0.62, 95% CI: 0.40-0.96) in those participants in the highest quartile of insoluble fibre intake. Conclusion: A higher intake of insoluble fibre could play an important role in the control and management of hypertension, lipid profile and MetS. Introducción: La occidentalización del estilo de vida mediterráneo ha dado lugar a una modificación de ciertos hábitos dietéticos, tales como una disminución en el consumo de alimentos ricos en fibra dietética. El impacto de estos cambios sobre las enfermedades cardiovasculares (ECV) se ha estudiado en los últimos años y el efecto de las diferentes fuentes de fibra en los parámetros de riesgo cardiovascular y en la enfermedad coronaria sigue creando controversia. Objetivo: Evaluar la asociación entre la fuente de fibra dietética y la prevalencia de síndrome metabólico (SM) y otros factores de riesgo cardiovascular en una población laboral española. Sujetos y métodos: El estudio se llevó a cabo en una muestra de 1592 trabajadores españoles libres de ECV (40-55 años) pertenecientes a la cohorte del Estudio de la Salud de los Trabajadores de Aragón (AWHS). Se recogieron datos sociodemográficos, antropométricos, clínicos y bioquímicos. La ingesta de fibra se evaluó por medio de un cuestionario semicuantitativo de frecuencia de consumo de alimentos de 136-items previamente validado. Para la definición de SM se siguieron los criterios del Programa Nacional de Educación del Colesterol en el marco del III Panel de Tratamiento de Adultos (NCEPATP III). Resultados: Se encontró una asociación inversa entre el consumo de fibra insoluble y la presión arterial sistólica y diastólica, colesterol total, triglicéridos, apolipoproteína B100 y la relación TG/HDL, tras ajustar por posibles factores de confusión. Así mismo, la fibra soluble se asoció inversamente con triglicéridos y apolipoproteína B100. Además, se encontró una menor prevalencia de SM (OR 0.62, IC del 95%: 0.40 a 0.96) en aquellos participantes en el cuartil más alto de consumo de fibra insoluble. Conclusión: Una mayor ingesta de fibra insoluble puede desempeñar un papel importante en el control y manejo de la hipertensión, el perfil lipídico y el SM

Desarrollo de una herramienta de ayuda a la enseñanza de heurísticas

En el presente trabajo se presenta una aplicación desarrollada en entornos gráficos interactivos que permite simular, paso a paso, el desarrollo de heurísticas. Esta herramienta facilita la docencia al profesor de la asignatura optativa Heurísticas que se imparte en la Ingeniería Técnica en Informática de Gestión de la Universidad de La Laguna y permite al alumno comprender y asimilar conceptos, y mejorar el conocimiento práctico de estas técnicas

Discrete Particle Swarm Optimization for the minimum labelling Steiner tree problem

Particle Swarm Optimization is an evolutionary method inspired by the social behaviour of individuals inside swarms in nature. Solutions of the problem are modelled as members of the swarm which fly in the solution space. The evolution is obtained from the continuous movement of the particles that constitute the swarm submitted to the effect of the inertia and the attraction of the members who lead the swarm. This work focuses on a recent Discrete Particle Swarm Optimization for combinatorial optimization, called Jumping Particle Swarm Optimization. Its effectiveness is illustrated on the minimum labelling Steiner tree problem: given an undirected labelled connected graph, the aim is to find a spanning tree covering a given subset of nodes, whose edges have the smallest number of distinct labels