Homogenization Model for Aberrant Crypt Foci

Several explanations can be found in the literature about the origin of colorectal cancer. There is however some agreement on the fact that the carcinogenic process is a result of several genetic mutations of normal cells. The colon epithelium is characterized by millions of invaginations, very small cavities, called crypts, where most of the cellular activity occurs. It is consensual in the medical community, that a potential first manifestation of the carcinogenic process, observed in conventional colonoscopy images, is the appearance of Aberrant Crypt Foci (ACF). These are clusters of abnormal crypts, morphologically characterized by an atypical behavior of the cells that populate the crypts. In this work an homogenization model is proposed, for representing the cellular dynamics in the colon epithelium. The goal is to simulate and predict, in silico, the spread and evolution of ACF, as it can be observed in colonoscopy images. By assuming that the colon is an heterogeneous media, exhibiting a periodic distribution of crypts, we start this work by describing a periodic model, that represents the ACF cell-dynamics in a two-dimensional setting. Then, homogenization techniques are applied to this periodic model, to find a simpler model, whose solution symbolizes the averaged behavior of ACF at the tissue level. Some theoretical results concerning the existence of solution of the homogenized model are proven, applying a fixed point theorem. Numerical results showing the convergence of the periodic model to the homogenized model are presented.Comment: 26 pages, 4 figure

Myelin figures: the buckling and flow of wet soap

Myelin figures are interfacial structures formed when certain surfactants swell in excess water. Here, I present data and model calculations suggesting myelin formation and growth is due to the fluid flow of surfactant, driven by the hydration gradient at the dry surfactant/water interface; a simple model based on this idea qualitatively reproduces the various myelin growth behaviors observed in different experiments. From a detailed experimental observation of how myelins develop from a planar precursor structure, I identify a mechanical instability that may underlie myelin formation. These results indicate the mixed mechanical character of the surfactant lamellar structure, where fluid and elastic properties coexist, is what enables the formation and growth of myelins.Comment: 11 pages, 10 figures, to appear in Phys. Rev. E. Corrected figures/typo

Single side damage simulations and detection in beam-like structures

Beam-like structures are the most common components in real engineering, while single side damage is often encountered. In this study, a numerical analysis of single side damage in a free-free beam is analysed with three different finite element models; namely solid, shell and beam models for demonstrating their performance in simulating real structures. Similar to experiment, damage is introduced into one side of the beam, and natural frequencies are extracted from the simulations and compared with experimental and analytical results. Mode shapes are also analysed with modal assurance criterion. The results from simulations reveal a good performance of the three models in extracting natural frequencies, and solid model performs better than shell while shell model performs better than beam model under intact state. For damaged states, the natural frequencies captured from solid model show more sensitivity to damage severity than shell model and shell model performs similar to the beam model in distinguishing damage. The main contribution of this paper is to perform a comparison between three finite element models and experimental data as well as analytical solutions. The finite element results show a relatively well performanc

Collaborating to Compete: A Search into Capabilities and Strategic Alliances in the Pharmaceutical Industry

Athough there is a profusion of studies related to strategic alliances and technological capacities which evaluate the issues individually, there is a scarcity of studies with empirical evidence relative to the implications of strategic alliances at the technological capacity configuration. Drawing on a scrutiny of specialised databases (Galé, Dialog, and Business & Industry) covering the 1993-2003 period, this article examines the entry and exit composition of innovative capabilities of 25 pharmaceutical companies’ capabilities involved in such alliances. They are organised in three groups: (i) large pharmaceutical companies (‘big-pharma’); (ii) large bio-pharmaceutical companies (‘bio-pharma’); and (iii) small and research-intensive companies. In terms of strategic alliance implications, a change was observed on the technological capacities’ configuration. The evidence suggests that the criteria for partner choice and technological capacity depend on the objectives and needs of each different group of company. Such type of evidence is important to provide researchers, corporate managers, and policy-makers with a concrete notion of the extent to which such division of innovative labour occurs and the actual changes going on the structure and organisation of innovative activities in the pharmaceutical industry.Titulo: Colaborando para Competir: Búsqueda Dentro de las Capacidades y Alianzas Estratégicas en la Industria Farmacéutica Pese a la existencia de muchos estudios relacionados a las evaluaciones individuales de las alianzas estratégicas y las capacidades tecnológicas, hay escasez de estudios con evidencia empírica relacionados con las implicaciones de las alianzas estratégicas en la configuración de las capacidades tecnológicas. Este artículo organiza un escrutinio de bases de datos (Galé, Dialog, and Business & Industry) entre los años del período 1993-2003, examinando la composición de entrada y salida de las capacidades innovativas de 25 compañías farmacéuticas involucradas en dichas alianzas. Las cuales se organizan en tres grupos (i)¨grandes compañías (grandes farmacéuticas); (ii)grandes compañías bio-farmacéuticas (bio-farma); y (iii) pequeñas compañías y compañías de investigación intensiva. En términos de las implicaciones de las alianzas estratégicas, se observa un cambio en la configuración de las capacidades tecnológicas. La evidencia sugiere que el criterio de para la elección de socios y de las capacidades tecnológicas depende de los objetivos y necesidades de los diversos grupos de compañías. Cada tipo de evidencia es de importancia para proveer a los investigadores, a los gerentes corporativos y los gestores con una noción concreta del grado de de importancia de cada división en las labores innovativas desarrolladas y en los cambio reales que se llevan a cabo en la estructura y la organización de las actividades innovativas en la industria farmacéutica .Athough there is a profusion of studies related to strategic alliances and technological capacities which evaluate the issues individually, there is a scarcity of studies with empirical evidence relative to the implications of strategic alliances at the technological capacity configuration. Drawing on a scrutiny of specialised databases (Galé, Dialog, and Business & Industry) covering the 1993-2003 period, this article examines the entry and exit composition of innovative capabilities of 25 pharmaceutical companies’ capabilities involved in such alliances. They are organised in three groups: (i) large pharmaceutical companies (‘big-pharma’); (ii) large bio-pharmaceutical companies (‘bio-pharma’); and (iii) small and research-intensive companies. In terms of strategic alliance implications, a change was observed on the technological capacities’ configuration. The evidence suggests that the criteria for partner choice and technological capacity depend on the objectives and needs of each different group of company. Such type of evidence is important to provide researchers, corporate managers, and policy-makers with a concrete notion of the extent to which such division of innovative labour occurs and the actual changes going on the structure and organisation of innovative activities in the pharmaceutical industry