Vertex Operator Representation of the Soliton Tau Functions in the An(1)A_n^{(1)} Toda Models by Dressing Transformations

We study the relation between the group-algebraic approach and the dressing symmetry one to the soliton solutions of the $A_n^{(1)}$ Toda field theory in 1+1 dimensions. Originally solitons in the affine Toda models has been found by Olive, Turok and Underwood. Single solitons are created by exponentials of elements which ad-diagonalize the principal Heisenberg subalgebra. Alternatively Babelon and Bernard exploited the dressing symmetry to reproduce the known expressions for the fundamental tau functions in the sine-Gordon model. In this paper we show the equivalence between these two methods to construct solitons in the $A_n^{(n)}$ Toda models.Comment: 35 pages, LaTe

Effects of cell cycle noise on excitable gene circuits

We assess the impact of cell cycle noise on gene circuit dynamics. For bistable genetic switches and excitable circuits, we find that transitions between metastable states most likely occur just after cell division and that this concentration effect intensifies in the presence of transcriptional delay. We explain this concentration effect with a 3-states stochastic model. For genetic oscillators, we quantify the temporal correlations between daughter cells induced by cell division. Temporal correlations must be captured properly in order to accurately quantify noise sources within gene networks.Comment: 15 pages, 8 figure

Household food insecurity positively associated with increased hospital charges for infants

Objective: To test whether household food insecurity (HFI) was associated with total annual hospitalization charges, annual days hospitalized, and charges per day, among low-income infants (months) with any non-neonatal hospital stays. Methods: Administrative inpatient hospital charge data were matched to survey data from infants\u27 caregivers interviewed 1998-2005 in emergency departments in Boston and Little Rock. All study infants had been hospitalized at least once since birth; infants whose diagnoses were not plausibly related to nutrition were excluded from both groups. Log-transformed hospitalization charges were analyzed, controlling for site fixed effects. Results: 24% of infants from food-insecure households and 16% from food-secure households were hospitalized \u3e2 times (P=0.02). Mean annual inpatient hospital charges ($6,707 vs$5,735; P Conclusion: HFI was positively associated with annual inpatient charges among hospitalized low income infants. Average annual inpatient charges were almost $2,000 higher (inflation adjusted) for infants living in food-insecure households. Reducing or eliminating food insecurity could reduce health services utilization and expenditures for infants in low-income families, most of whom are covered by public health insurance

Teachers\u27 Efforts to Support Undocumented Students Within Ambiguous Policy Contexts

Although education scholars have recently focused greater attention on the experiences of undocumented youth in schools, few studies have examined educators\u27 perceptions of their roles and responsibilities with regards to this population. Since the 1982 Supreme Court decision Plyler v. Doe guaranteed education to this group and barred schools from inquiring about immigration status, little additional policy has offered guidance on how schools can support this group while also refraining from identifying it\u27s members. Policies are particularly lacking in new destination areas where there are fewer resources and less infrastructure for new immigrant populations. As increasingly harsh immigration enforcement policies amplify fear and anxiety among families, educators and other service providers are more in need of support than perhaps ever before. Some teachers in new destination areas, however, have found ways to create safe and empowering spaces for undocumented students. We conducted a qualitative case study to explore how such educators understand their roles amidst both this policy void and a political climate in which immigration has become an especially contentious and divisive issue. We interviewed 18 teachers of immigrant students in one new destination area in Virginia, a state experiencing an increase in the undocumented population. We found that teachers took actions to enhance students\u27 feelings of security and normalcy through curricular decisions, emotional support, and even the provision of basic needs. Teacher\u27s actions, which were often spontaneous, adaptive, and resourceful, could be described as agile advocacy. These actions ranged from providing information to families to pushing for school and district policy changes. However, the teachers also encountered many barriers and few supports in these efforts. They felt largely alone and frustrated by the incomprehensibility of the immigration system and the absence of building-and district-level leadership in support of undocumented students

Effects of Cell Cycle Noise on Excitable Gene Circuits

We assess the impact of cell cycle noise on gene circuit dynamics. For bistable genetic switches and excitable circuits, we find that transitions between metastable states most likely occur just after cell division and that this concentration effect intensifies in the presence of transcriptional delay. We explain this concentration effect with a three-states stochastic model. For genetic oscillators, we quantify the temporal correlations between daughter cells induced by cell division. Temporal correlations must be captured properly in order to accurately quantify noise sources within gene networks

A Mathematical Framework for Agent Based Models of Complex Biological Networks

Agent-based modeling and simulation is a useful method to study biological phenomena in a wide range of fields, from molecular biology to ecology. Since there is currently no agreed-upon standard way to specify such models it is not always easy to use published models. Also, since model descriptions are not usually given in mathematical terms, it is difficult to bring mathematical analysis tools to bear, so that models are typically studied through simulation. In order to address this issue, Grimm et al. proposed a protocol for model specification, the so-called ODD protocol, which provides a standard way to describe models. This paper proposes an addition to the ODD protocol which allows the description of an agent-based model as a dynamical system, which provides access to computational and theoretical tools for its analysis. The mathematical framework is that of algebraic models, that is, time-discrete dynamical systems with algebraic structure. It is shown by way of several examples how this mathematical specification can help with model analysis.Comment: To appear in Bulletin of Mathematical Biolog

A QUADRIPOLAR EPISTEMIC PROPOSITION OF ENTREPRENEURSHIP CONSTRUCT

Este artigo aborda, à luz da proposição de Bruyne, Herman e Schouthute(1977) sobre os “quatro polos da prática metodológica: epistemológico, morfológico, teórico e técnico”, a forma pela qual vem se constituindo o Empreendedorismo nos estudos da Administração. Realizou-se uma análise bibliométrica a partir dos artigos publicados nos eventos vinculados à ANPAD. A seguir, fez-se a análise de conteúdo dos artigos selecionados, buscando identificar como se tem configurado o tema, considerando-se cada um dos polos. Verificou-se um excesso de pesquisas que privilegiam o polo técnico em detrimento dos demais, o que, provavelmente, está contribuindo para o esvaziamento da própria área na ANPAD. Nossas maiores contribuições se dão no polo técnico, aquele relacionado à coleta dos dados, e são inúmeros os estudos de caso encontrados. Na realidade, é para onde converge a maioria das pesquisas empíricas que abordam o empreendedorismo e seus temas relacionados. Aliada a essa discrepância está o fato de que a maioria das pesquisas também é resultado de estudos exploratório-descritivos. Há que lembrar que os estudos exploratório-descritivos estão no nível que Bruyne et al. (1977) denominam de “grau zero” de teorização.This article presents, based on the Bruyne, Herman and Schoutheete’s proposition (1977) on the “four poles of the methodological practice: epistemological, morphological, theoretical, and technical”, how entrepreneurship is being construed in Business Administration studies. We carried out a bibliometric analysis from articles published in events linked to ANPAD – National Association of graduate studies and research in business administration. Then we made a content analysis on selected articles in order to identify how the theme is approached considering each of the poles. There was an excess of researches favoring the technical pole comparing to the others, which is probably contributing with the emptying of ANPAD’s area itself. Our main contributions are given in the technical pole, related to data collection, and there are countless case studies. In reality it is where most empirical researches on entrepreneurship and related topics converge to. Allied to this discrepancy is the fact that most of researches are also the result of exploratory and descriptive studies. We must remember that the exploratory and descriptive studies are at the level that Bruyne et al. (1977) call the “ground zero” of theorization.Este artículo presenta, a la luz de la proposición de Bruyne at al. (1977), sobre los “cuatro polos de la práctica metodológica: epistemológico, morfológico, teórico y técnico”, como se viene constituyendo el Emprendedorismo en los estudios de Administración. Se realizó un análisis bibliométrico a partir de los artículos publicados en los eventos vinculados a la ANPAD. En seguida, se realizó el análisis de contenido en los artículos seleccionados, buscando identificar cómo se ha configurado el tema considerando cada uno de los polos. Se verificó un exceso de investigaciones que dan prioridad al polo técnico en perjuicio de los demás, lo que, probablemente, esté contribuyendo con el vaciado de la propia área en la ANPAD. Nuestras mayores contribuciones aparecen en el polo técnico, aquél relacionado a la colecta de los datos y son innumerables los estudios de caso encontrados. En realidad es para donde converge la mayoría de las investigaciones empíricas que abordan el emprendedorismo y sus temas relacionados. Aliada a esta discrepancia está el hecho de que la mayoría de las investigaciones también es resultado de estudios exploratorio-descriptivos. Hay que recordar que los estudios exploratorio-descriptivos están en el nivel que Bruyne et al. (1977) denominan de “grado cero” de teorización

Multi-scale modelling of concrete structures affected by alkali-silica reaction: Coupling the mesoscopic damage evolution and the macroscopic concrete deterioration

A finite-element approach based on the first-order FE 2 homogenisation technique is formulated to analyse the alkali-silica reaction-induced damage in concrete structures, by linking the concrete degradation at the macro-scale to the reaction extent at the meso-scale. At the meso-scale level, concrete is considered as a heterogeneous material consisting of aggregates embedded in a mortar matrix. The mechanical effects of the Alkali-Silica Reaction (ASR) are modelled through the application of temperature-dependent eigenstrains in several localised spots inside the aggregates and the mechanical degradation of concrete is modelled using continuous damage model, which is capable of reproducing the complex ASR crack networks. Then, the effective stiffness tensor and the effective stress tensor for each macroscopic finite element are computed by homogenising the mechanical response of the corresponding representative volume element (RVE), thus avoiding the use of phenomenological constitutive laws at the macro-scale. Convergence between macro- and meso-scales is achieved via an iterative procedure. A 2D model of an ASR laboratory specimen is analysed as a proof of concept. The model is able to account for the loading applied at the macro-scale and the ASR-product expansion at the meso-scale. The results demonstrate that the macroscopic stress state influences the orientation of damage inside the underlying RVEs. The effective stiffness becomes anisotropic in cases where damage is aligned inside the RVE