A variable metric forward--backward method with extrapolation

Forward-backward methods are a very useful tool for the minimization of a functional given by the sum of a differentiable term and a nondifferentiable one and their investigation has experienced several efforts from many researchers in the last decade. In this paper we focus on the convex case and, inspired by recent approaches for accelerating first-order iterative schemes, we develop a scaled inertial forward-backward algorithm which is based on a metric changing at each iteration and on a suitable extrapolation step. Unlike standard forward-backward methods with extrapolation, our scheme is able to handle functions whose domain is not the entire space. Both {an ${\mathcal O}(1/k^2)$ convergence rate estimate on the objective function values and the convergence of the sequence of the iterates} are proved. Numerical experiments on several {test problems arising from image processing, compressed sensing and statistical inference} show the {effectiveness} of the proposed method in comparison to well performing {state-of-the-art} algorithms

Variable metric inexact line-search based methods for nonsmooth optimization

We develop a new proximal-gradient method for minimizing the sum of a differentiable, possibly nonconvex, function plus a convex, possibly non differentiable, function. The key features of the proposed method are the definition of a suitable descent direction, based on the proximal operator associated to the convex part of the objective function, and an Armijo-like rule to determine the step size along this direction ensuring the sufficient decrease of the objective function. In this frame, we especially address the possibility of adopting a metric which may change at each iteration and an inexact computation of the proximal point defining the descent direction. For the more general nonconvex case, we prove that all limit points of the iterates sequence are stationary, while for convex objective functions we prove the convergence of the whole sequence to a minimizer, under the assumption that a minimizer exists. In the latter case, assuming also that the gradient of the smooth part of the objective function is Lipschitz, we also give a convergence rate estimate, showing the O(1/k) complexity with respect to the function values. We also discuss verifiable sufficient conditions for the inexact proximal point and we present the results of a numerical experience on a convex total variation based image restoration problem, showing that the proposed approach is competitive with another state-of-the-art method

On the convergence of a linesearch based proximal-gradient method for nonconvex optimization

We consider a variable metric linesearch based proximal gradient method for the minimization of the sum of a smooth, possibly nonconvex function plus a convex, possibly nonsmooth term. We prove convergence of this iterative algorithm to a critical point if the objective function satisfies the Kurdyka-Lojasiewicz property at each point of its domain, under the assumption that a limit point exists. The proposed method is applied to a wide collection of image processing problems and our numerical tests show that our algorithm results to be flexible, robust and competitive when compared to recently proposed approaches able to address the optimization problems arising in the considered applications

Teachers who leave a mark. Personal biography and professional identity in memorable teachers

Fernández Cruz (1994), states that identity relates to the building of one-self in the interactionwith others. Professional identification in teaching is a slow process. Some people start undergoingthis process in childhood, some others with their professional practice. In this research advancewe analyze the life story of a university teacher from the Faculty of Architecture, Mar del PlataNational University (UNMdP) previously identified as a memorable professor by his students. Adeep cycle called biographical stimulated self theme (Kelchterman, 1993) in which the professor isled to reconstruct his biography and its sense, stems from the understanding and reconstruction ofhis professional life. This allows us to organize, focus, interpret, understand and validate what heis narrating. In this way tensions understood as categories emerge, associated to the meaning theprofessor himself gives to his own personal, professional experience and development

Life histories retold: reconceptualization of school biographies of trainee teachers

Hay docentes que dejan en sus alumnos marcas profundas que perduran en el tiempo y que luego se manifiestan de diferentes maneras. Se trata de trazas dibujadas por experiencias que conmueven y perduran, que hacen que el alumno se retire de la clase pensando y sintiendo; nos referimos a las huellas que deja aquella práctica docente aggiornada, compleja y reflexiva, que va más allá de simplemente ofrecer un conjunto de hechos, datos y conceptos ya que tienen un entramado subyacente que les da sentido (Maggio, 2012). El presente artículo se desprende de una investigación de corte cualitativo que adopta un enfoque interpretativo, entendido como un proceso de comprensión de los significados cercanos de los propios actores involucrando también la construcción de una lectura constante e integrando los detalles inmediatos con la teoría relevada. Para explorar las huellas docentes en toda su variedad y complejidad, se adopta una perspectiva narrativa, que nos brinda una forma de co-construir la realidad abordándola desde diferentes planos. De esta manera, y mediante el análisis de los textos de campo la narrativa ofrece una particular reconstrucción de la experiencia, a partir de un proceso reflexivo que resignifica lo sucedido o vivido buscando responder el principal interrogante que motivó la investigación: ¿cuáles son aquellas enseñanzas que han dejado su traza en la construcción del perfil profesional de los alumnos del Profesorado de Inglés de la Universidad Nacional de Mar del Plata (UNMdP)?There are teachers who leave in their students deep marks that reveal themselves in different ways and last over time. These are traces drawn by experiences that move and last, that make the student leave the class thinking and feeling; we are referring to those traces left by updated, complex and reflective teaching practice, which goes beyond the simple fact of offering data and content as they have an underlying framework that gives them meaning (Maggio, 2012). This article follows a qualitative research that adopts an interpretative approach, perceived as a process of understanding the close meanings of the actors themselves, also involving the construction of a constant reading and integrating the immediate details with the relieved theory. To explore the teachers traces in all their variety and complexity, a narrative inquiry perspective is adopted, which gives us a way to co-construct reality by addressing it from different levels. In this way, and through the analysis of field texts, narrative inquiry offers a particular reconstruction of the experience, from a reflective process that resignifies what happened or was lived seeking answers to the main questions that motivated the research: which are those teachings experiences? who have left their trace in the construction of the professional profile of the students of the English Teaching Education Program of the National University of Mar del Plata (UNMdP)?Fil: Brandan, Silvia Antonia. Universidad Nacional de Mar del Plata. Facultad de Humanidades. Centro de Investigaciones Multidisciplinarias en Educación; ArgentinaFil: Porta Vazquez, Luis Gabriel. Universidad Nacional de Mar del Plata. Facultad de Humanidades. Centro de Investigaciones Multidisciplinarias en Educación; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata; Argentin

Silvia Porta Art Workshop - "From Home: What Causes The Pandemic"

Presentamos “Desde Casa: Lo que nos provoca la pandemia”, muestra colectiva con la participación de 26 artistas. Compartimos además el intercambio de audios entre artistas y maestra, que dan cuenta del proceso creativo en este contexto tan particular. En esta oportunidad, la consigna fue planteada a distancia: se les propuso que expresen los sentimientos de la cuarentena con los materiales que tenían en sus hogares. Hace 10 años Silvia Porta armó el Taller de Arte para niños y adolescentes en Villa Elisa (La Plata) En este espacio se han creado obras maravillosas de acuerdo con las propuestas temáticas, que se exhiben en muestras abiertas. Por las tardes, en el Taller pasan horas pensando en los proyectos, los materiales, buscando formas, texturas y colores. También realizan visitas a museos y exposiciones.Facultad de Periodismo y Comunicación Socia

La scelta della Fair Value Option nello IAS 40: evidenze empiriche sul settore Real Estate

The adoption of IAS/IFRS by the European Union has represented a key accounting change for European companies and offers a rich source of analysis to the scientific community. This thesis is part of the debate on-going on the choice between fair value and historical cost as the optimal evaluation criterium. The empirical research focuses on the accounting standard IAS 40, which is particularly suitable for this type of investigation as it is one of the few principles that allow the right to choose between the above mentioned assessment criteria (i.e., fair value and historical cost). In particular, IAS 40 deals with the accounting evaluation and representation of investment property in the financial statement. Investment property represents any fixed asset held for the purpose of obtaining profits in the form of rent or capital gains. The empirical investigation focuses on companies belonging to the real estate industry, because, as showed by previous research, companies belonging to this industry have significant investment properties as accounting entries on total assets. Therefore, the accounting choice between fair value and cost should have a greater impact on the balance sheet. A preference for a given option in connection with certain firm characteristics is expected. The empirical research is conducted on a sample of listed real estate companies based in four European countries (France, Germany, Sweden and Italy) that draw up consolidated financial statements. In particular, it investigates the determinants of the first-application choice between fair value and historical cost in 2005, when international accounting standards were adopted for the first time. By analyzing the firm characteristics in the four-year period preceding the choice (period 2001-2004), the thesis investigates the main determinants (financial position, leverage, return on investment and company size) of the “fair value vs cost” accounting choice. As control variables, the variables “sector” and “country” are included. The results show that financial position, leverage and return on investment do not drive the choice of opting for fair value rather than historical cost. This evidence may imply that the motivation underlying this choice is independent from accounting evaluations, but mainly oriented to the adequate development of corporate real assets by selecting the more suitable criteria. Moreover, it is found that the company size is lower for those firms that chose fair value rather than cost. This result can be due to the fact that, as the company size increases business complexity and, therefore, the so-called “agency costs”, companies might opt for the cost method to reduce agency costs. The cost method, indeed, is perceived more reliable and verifiable and companies might prefer it to the information relevance of the fair value. In addition, as expected, a positive relationship between the fair value adoption and medium-long term investment activities in the real estate is found. Finally, Swedish firms, that belong to an Anglo-Saxon context, are more likely to adopt fair value. In conclusion, this work provides a contribution to accounting regulatory bodies, suggesting that the choice of fair value does not seem driven by opportunistic considerations but rather by the assessment of the effective value of real estate investments

The Macrophages-Microbiota Interplay in Colorectal Cancer (CRC)-Related Inflammation: Prognostic and Therapeutic Significance

Tumor-associated macrophages (TAMs) are the main population of myeloid cells infiltrating solid tumors and the pivotal orchestrators of cancer-promoting inflammation. However, due to their exceptional plasticity, macrophages can be also key effector cells and powerful activators of adaptive anti-tumor immunity. This functional heterogeneity is emerging in human tumors, colorectal cancer (CRC) in particular, where the dynamic co-existence of different macrophage subtypes influences tumor development, outcome, and response to therapies. Intestinal macrophages are in close interaction with enteric microbiota, which contributes to carcinogenesis and affects treatment outcomes. This interplay may be particularly relevant in CRC, one of the most prevalent and lethal cancer types in the world. Therefore, both macrophages and intestinal microbiota are considered promising prognostic indicators and valuable targets for new therapeutic approaches. Here, we discuss the current understanding of the molecular circuits underlying the interplay between macrophages and microbiota in CRC development, progression, and response to both conventional therapies and immunotherapies

Endothelial Tie1 regulates tumor angiogenesis, vascular abnormalization and metastatic dissemination

The Angiopoietin/Tie system is one of the most important vascular-tissue specific signaling pathways, essential during embryonic vascular development and maturation, and key regulator of adult homeostasis. The Tie receptors, Tie1 and Tie2, and their secreted angiopoietin (Ang) ligands, Ang1 and Ang2, have been identified as the main factors of the system. Ang1 is primarily produced by perivascular cells and acts in a paracrine fashion as strong Tie2 agonist that mediates endothelial cell (EC) survival and maturation signals. Ang2, expressed and stored in EC, functions primarily as an antagonist of Tie2 and promotes vascular destabilization. Nevertheless, it can act as a partial agonist of Tie2 in a context-dependent manner. Tie1 and Tie2 are both expressed by EC and share high similarities in their overall domain structure. Whereas Tie2 acts as the primary signal transducing receptor, Tie1 function as a holoreceptor is not completely understood: It does not activate signaling pathways on its own but rather modulates the Tie2 kinase activity. Tie1 is highly expressed in activated endothelial cells during embryogenesis and during pathological conditions, such as tumor progression and metastasis, but it is downregulated in the adult quiescent endothelium. Thus, Tie1 global deficiency in mice leads to embryonic lethality at late gestation due to perturbed vessel integrity, while its specific deletion in the growing tumor vasculature results in decreased blood vessel density. The combination of high expression in the tumor endothelium and low expression in the adult vasculature makes Tie1 an interesting molecule and a potential therapeutic target. Angiogenesis is one of the most critical steps during tumor growth and metastasis progression. Comparative tumor and metastasis experiments in wildtype and Tie1 endothelial-deficient mice were performed to mechanistically unravel the role of the orphan receptor during individual steps of tumor progression and metastasis. Analysis of the tumor vasculature demonstrated that Tie1 endothelial deletion induces no significant changes in the early steps of tumor growth but rather affects later steps of tumor progression. Endothelial-Tie1 deletion induces progressively normalization of primary tumor blood vessels accompanied by decreased microvessel density, increased mural cell coverage, improved vessel perfusion and reduced tumor cell intravasation into the blood stream as well as extravasation at secondary sites. These effects result in almost complete inhibition of post-surgical spontaneous lung metastasis and improved overall survival of Tie1-endothelial deleted mice. Mechanistically, Tie1 targeting in the primary tumor leads to vascular normalization and stabilization by increasing the proportion of Tie2-positive endothelial cells (stalk cells) and by potentiating the Ang1/Tie2 signaling axis which is primarily essential for the maintenance of endothelial quiescence and survival. The data establish a remarkable contribution of the orphan receptor Tie1 to primary tumor angiogenesis and to individual steps of metastatic cascade. These findings contribute to the mechanism-guided validation of Tie1 as a therapeutic target to sharpen the balance between triggering vascular regression and promoting vascular normalization

Silvia Porta Art Workshop - "From Home: What Causes The Pandemic"

Presentamos “Desde Casa: Lo que nos provoca la pandemia”, muestra colectiva con la participación de 26 artistas. Compartimos además el intercambio de audios entre artistas y maestra, que dan cuenta del proceso creativo en este contexto tan particular. En esta oportunidad, la consigna fue planteada a distancia: se les propuso que expresen los sentimientos de la cuarentena con los materiales que tenían en sus hogares.&nbsp