Corneal Biomechanics After Intrastromal Ring Surgery: Optomechanical In Silico Assessment

Purpose: To provide a biomechanical framework to better understand the postsurgical optomechanical behavior of the cornea after ring implantation. Methods: Calibrated in silico models were used to determine the corneal shape and stresses after ring implantation. After mechanical simulations, geometric ray-tracing was used to determine the change in spherical equivalent. The effect of the surgical procedure, circadian variation of intraocular pressure, or the biomechanical weakening introduced by keratoconus (KC) were evaluated for each intrastromal ring. Results: Models predicted the postsurgical optomechanical response of the cornea at a population level. The localized mechanical effect of the additional intrastromal volume introduced by the implants (size and diameter) drives the postsurgical corneal response. However, central corneal stresses did not increase more than 50%, and thus implants did not strengthen the cornea globally. Because of the biomechanical weakening introduced by laser pocketing, continuous implants in a pocket resulted in higher refractive corrections and in the relaxation of the anterior stroma, which could slow down KC progression. Implants can move within the stroma, acting as a dynamic pivot point that modifies corneal kinematics and flattens the corneal center. Changes in stromal mechanical properties did not impact on refraction for normal or pathological corneas. Conclusions: Implants do not stiffen the cornea but create a local bulkening effect that regularizes the corneal shape by modifying corneal kinematics without canceling corneal motion. Translational Relevance: In silico models can help to understand corneal biomechanics, to plan patient-specific interventions, or to create biomechanically driven nomograms

Fipronil/(S)-methoprene spot-on to control fleas on cats in a field trial in Spain

The study was conducted in order to evaluate the effect of a fipronil/(S)-methoprene formulation against fleas on naturally infested cats. The study involved a population of 89 cats distributed among 24 veterinary practices in 9 regions of Spain. The product was applied according to label instructions on days 0, 30 and 60. Animals underwent parasitological and clinical assessments on day 0 and thereafter in monthly intervals (every 30 days) until day 90. Ctenocephalides felis was the most abundant species (98.9% of all fleas collected), and flea abundance on Day 0 was associated with the hair type, the location of the household, and the time elapsed from the last anti-flea treatment. Fipronil/(S)-methoprene demonstrated high efficacy and induced the reduction of clinical signs related to the presence of fleas. Clinical signs and flea abundance decreased significantly throughout time (P=0.001) with an efficacy rate of 72.6% at Day 30, 88.4% at Day 60 and 93.9% at Day 90. A high level of flea control and a remission of the clinical signs related to presence of fleas were observed on cats following 3 monthly applications a fipronil/(S)-methoprene formulation

Physiological bases of bone regeneration I : Histology and physiology of bone tissue

Bone is the only body tissue capable of regeneration, allowing the restitutio ad integrum following trauma. In the event of a fracture or bone graft, new bone is formed, which following the remodeling process is identical to the pre-existing. Bone is a dynamic tissue in constant formation and resorption. This balanced phenomena, known as the remodeling process, allows the renovation of 5-15% of the total bone mass per year under normal conditions (1). Bone remodeling consists of the resorption of a certain amount of bone by osteoclasts, likewise the formation of osteoid matrix by osteoblasts, and its subsequent mineralization. This phenomenon occurs in small areas of the cortical bone or the trabecular surface, called ?Basic Multicellular Units? (BMU). Treatment in Traumatology, Orthopedics, Implantology, and Maxillofacial and Oral Surgery, is based on the biologic principals of bone regeneration, in which cells, extracellular matrix, and osteoinductive signals are involved. The aim of this paper is to provide an up date on current knowledge on the biochemical and physiological mechanisms of bone regeneration, paying particular attention to the role played by the cells and proteins of the bone matrix

Physiological bases of bone regeneration II : The remodeling process

Bone remodeling is the restructuring process of existing bone, which is in constant resorption and formation. Under normal conditions, this balanced process allows the renewal of 5 ? 10% of bone volume per year. At the microscopic level, bone remodeling is produced in basic multicellular units, where osteoclasts resorb a certain quantity of bone and osteoblasts form the osteoid matrix and mineralize it to fill the previously created cavity. These units contain osteoclasts, macrophages, preosteoblasts and osteoblasts, and are controlled by a series of factors, both general and local, allowing normal bone function and maintaining the bone mass. When this process becomes unbalanced then bone pathology appears, either in excess (osteopetrosis) or deficit (osteoporosis). The purpose of this study is to undertake a revision of current knowledge on the physiological and biological mechanisms of the bone remodeling process; highlighting the role played by the regulating factors, in particular that of the growth factor

Geometrical origin of the *-product in the Fedosov formalism

The construction of the *-product proposed by Fedosov is implemented in terms of the theory of fibre bundles. The geometrical origin of the Weyl algebra and the Weyl bundle is shown. Several properties of the product in the Weyl algebra are proved. Symplectic and abelian connections in the Weyl algebra bundle are introduced. Relations between them and the symplectic connection on a phase space M are established. Elements of differential symplectic geometry are included. Examples of the Fedosov formalism in quantum mechanics are given.Comment: LaTeX, 39 page

Bases fisiológicas de la regeneración ósea II: el proceso de remodelado

El remodelado óseo es un proceso de reestructuración del hueso existente, que está en constante formación y reabsorción. Este fenómeno equilibrado permite, en condiciones normales, la renovación de un 5-10% del hueso total al año. A nivel microscópico el remodelado óseo se produce en las unidades básicas multicelulares, donde los osteoclastos reabsorben una cantidad determinada de hueso y los osteoblastos forman la matriz osteoide y la mineralizan para rellenar la cavidad previamente creada. En estas unidades hay osteoclastos, macrófagos, preosteoblastos y osteoblastos y están regidos por una serie de factores, tanto generales como locales, permitiendo el normal funcionamiento del hueso y el mantenimiento de la masa ósea. Cuando este proceso se desequilibra aparece la patología ósea, bien por exceso (osteopetrosis) o por defecto (osteoporosis). El propósito de este trabajo es realizar una revisión de los conocimientos actuales sobre los mecanismos bioquímicos y fisiológicos del proceso de remodelado óseo, resaltando de manera especial el papel de los factores reguladores del mismo, entre los que destacan los factores de crecimiento.Bone remodeling is the restructuring process of existing bone, which is in constant resorption and formation. Under normal conditions, this balanced process allows the renewal of 5 ' 10% of bone volume per year. At the microscopic level, bone remodeling is produced in basic multicellular units, where osteoclasts resorb a certain quantity of bone and osteoblasts form the osteoid matrix and mineralize it to fill the previously created cavity. These units contain osteoclasts, macrophages, preosteoblasts and osteoblasts, and are controlled by a series of factors, both general and local, allowing normal bone function and maintaining the bone mass. When this process becomes unbalanced then bone pathology appears, either in excess (osteopetrosis) or deficit (osteoporosis). The purpose of this study is to undertake a revision of current knowledge on the physiological and biological mechanisms of the bone remodeling process; highlighting the role played by the regulating factors, in particular that of the growth factors

Bases fisiológicas de la regeneración ósea I: histología y fisiología del tejido óseo

El hueso es el único tejido del organismo capaz de regenerarse, permitiendo la restitutio ad integrum tras el trauma. Cuando se produce una fractura, se coloca un implante osteointegrado o se realiza un injerto para aumentar el sustrato óseo antes de la inserción de implantes, lo que se pretende es la regeneración ósea, es decir, la formación de hueso nuevo que, tras un proceso de remodelado, sea idéntico al preexistente. El hueso es un tejido dinámico en constante formación y reabsorción. Este fenómeno equilibrado, denominado proceso de remodelado, permite la renovación de un 5-15 % del hueso total al año en condiciones normales (1). El remodelado óseo consiste en la reabsorción de una cantidad determinada de hueso llevada a cabo por los osteoclastos, así como la formación de la matriz osteoide por los osteoblastos y su posterior mineralización. Este fenómeno tiene lugar en pequeñas áreas de la cortical o de la superficie trabecular, llamadas 'unidades básicas de remodelado óseo'. La actuación terapéutica en los campos de la Traumatología y Ortopedia, Cirugía Oral y Maxilofacial e Implantología, se asienta sobre los principios biológicos de la regeneración ósea, en los que están implicados células, matriz extracelular y señales osteoinductivas. El objetivo de este trabajo es realizar una puesta al día de los conocimientos actuales sobre los mecanismos bioquímicos y fisiológicos de la regeneración ósea, resaltando de manera especial el papel que en ella juegan las células y las proteínas de la matriz ósea.Bone is the only body tissue capable of regeneration, allowing the restitutio ad integrum following trauma. In the event of a fracture or bone graft, new bone is formed, which following the remodeling process is identical to the pre-existing. Bone is a dynamic tissue in constant formation and resorption. This balanced phenomena, known as the remodeling process, allows the renovation of 5-15% of the total bone mass per year under normal conditions (1). Bone remodeling consists of the resorption of a certain amount of bone by osteoclasts, likewise the formation of osteoid matrix by osteoblasts, and its subsequent mineralization. This phenomenon occurs in small areas of the cortical bone or the trabecular surface, called 'Basic Multicellular Units' (BMU). Treatment in Traumatology, Orthopedics, Implantology, and Maxillofacial and Oral Surgery, is based on the biologic principals of bone regeneration, in which cells, extracellular matrix, and osteoinductive signals are involved. The aim of this paper is to provide an up date on current knowledge on the biochemical and physiological mechanisms of bone regeneration, paying particular attention to the role played by the cells and proteins of the bone matrix

Cooperative CPU, GPU, and FPGA heterogeneous execution with EngineCL

Heterogeneous systems are the core architecture of most of the high-performance computing nodes, due to their excellent performance and energy efficiency. However, a key challenge that remains is programmability, specifically, releasing the programmer from the burden of managing data and devices with different architectures. To this end, we extend EngineCL to support FPGA devices. Based on OpenCL, EngineCL is a high-level framework providing load balancing among devices. Our proposal fully integrates FPGAs into the framework, enabling effective cooperation between CPU, GPU, and FPGA. With command overlapping and judicious data management, our work improves performance by up to 96% compared with single-device execution and delivers energy-delay gains of up to 37%. In addition, adopting FPGAs does not require programmers to make big changes in their applications because the extensions do not modify the user-facing interface of EngineCL

A geometrically defined stiffness contact for finite element models of wood joints

Finite element models tend to overestimate the actual elastic response of structural timber connections. The paper shows how such overprediction relates to the modelling of the contact between fasteners and timber. The use of a control parameter called stiffness contact is proposed. After an experimental campaign, a method to determine it, based only on the geometry of a rectangular contact area, is proposed. The modeling adequacy is demonstrated by applying it to dowel embedment and moment resistant wood joint tests. The obtained results show good agreement with the experimental test series

Metric Properties of the Fuzzy Sphere

The fuzzy sphere, as a quantum metric space, carries a sequence of metrics which we describe in detail. We show that the Bloch coherent states, with these spectral distances, form a sequence of metric spaces that converge to the round sphere in the high-spin limit.Comment: Slightly shortened version, no major changes, two new references, version to appear on Letters in Mathematical Physic