Internal Friction and Vulnerability of Mixed Alkali Glasses

Based on a hopping model we show how the mixed alkali effect in glasses can be understood if only a small fraction c_V ofthe available sites for the mobile ions is vacant. In particular, we reproduce the peculiar behavior of the internal friction and the steep fall (''vulnerability'') of the mobility of the majority ion upon small replacements by the minority ion. The single and mixed alkali internal friction peaks are caused by ion-vacancy and ion-ion exchange processes. If c_V is small, they can become comparable in height even at small mixing ratios. The large vulnerability is explained by a trapping of vacancies induced by the minority ions. Reasonable choices of model parameters yield typical behaviors found in experiments.Comment: 4 pages, 4 figure

Paradoxes and Innovation in Family Firms: The Role of Paradoxical Thinking

Scholars stress that family firms are inherently paradoxical, and that tensions, such as tradition versus change, family liquidity versus business growth, and founder control versus successor autonomy, can both inhibit and foster innovation. Further, theorists propose that firms led by paradoxical thinkers are more likely to manage these tensions and fuel innovative behavior. Leveraging family business and organizational paradox literatures, this multi-stage exploratory study develops measures of paradoxical tensions and paradoxical thinking in family firms, and tests these propositions. Findings indicate that paradoxical tensions may stymie innovative behavior, but that leaders' paradoxical thinking is positively related to innovative behavior

Microfoundations of organizational paradox: The problem is how we think about the problem

Competing tensions and demands pervade our work lives. Accumulating research examines organizational and leadership approaches to leveraging these tensions. But what about individuals within firms? Although early paradox theory built upon micro-level insights from psychology and philosophy to understand the nature and management of varied competing demands, corresponding empirical studies are rare, offering scarce insights into why some individuals thrive with tensions while others struggle. In response, we contribute to the microfoundations of organizational paradox with a theoretical model and robust measures that help unpack individuals' varied approaches to tensions. Following rigorous scale development in Study 1, including samples from the US, UK, Israel, and China, we test our model in a large firm in the US using quantitative and qualitative methods. We identify resource scarcity (i.e. limited time and funding) as a source of tensions. We also demonstrate that a paradox mindset - the extent to which one is accepting of and energized by tensions - can help individuals leverage them to improve in-role job performance and innovation. Our results highlight paradox mindset as a key to unlocking the potential of everyday tensions

A Role for the Vacuolating Cytotoxin, VacA, in Colonization and Helicobacter pylori-Induced Metaplasia in the Stomach

Carriage of Helicobacter pylori strains producing more active (s1/i1) forms of VacA is strongly associated with gas-tric adenocarcinoma. To our knowledge, we are the first to determine effects of different polymorphic forms of VacA on inflammation and metaplasia in the mouse stomach. Bacteria producing the less active s2/i2 form of VacA colonized mice more efficiently than mutants null for VacA or producing more active forms of it, providing the first evidence of a positive role for the minimally active s2/i2 toxin. Strains producing more active toxin forms induced more severe and extensive metaplasia and in flammation in the mouse stomach than strains producing weakly active (s2/i2) toxin. We also examined the association in humans, controlling for cag PAI status. In human gastric biopsy specimens, the vacA i1 allele was strongly associated with precancerous intestinal metaplasia, with almost complete absence of intestinal metaplasia in subjects infected with i2-type strains, even in a vacA s1, cagA+ background

Identifying dynamical modules from genetic regulatory systems: applications to the segment polarity network

BACKGROUND It is widely accepted that genetic regulatory systems are 'modular', in that the whole system is made up of smaller 'subsystems' corresponding to specific biological functions. Most attempts to identify modules in genetic regulatory systems have relied on the topology of the underlying network. However, it is the temporal activity (dynamics) of genes and proteins that corresponds to biological functions, and hence it is dynamics that we focus on here for identifying subsystems. RESULTS Using Boolean network models as an exemplar, we present a new technique to identify subsystems, based on their dynamical properties. The main part of the method depends only on the stable dynamics (attractors) of the system, thus requiring no prior knowledge of the underlying network. However, knowledge of the logical relationships between the network components can be used to describe how each subsystem is regulated. To demonstrate its applicability to genetic regulatory systems, we apply the method to a model of the Drosophila segment polarity network, providing a detailed breakdown of the system. CONCLUSION We have designed a technique for decomposing any set of discrete-state, discrete-time attractors into subsystems. Having a suitable mathematical model also allows us to describe how each subsystem is regulated and how robust each subsystem is against perturbations. However, since the subsystems are found directly from the attractors, a mathematical model or underlying network topology is not necessarily required to identify them, potentially allowing the method to be applied directly to experimental expression data

Advanced composites structural concepts and materials technologies for primary aircraft structures. Structural response and failure analysis: ISPAN modules users manual

The ISPAN Program (Interactive Stiffened Panel Analysis) is an interactive design tool that is intended to provide a means of performing simple and self contained preliminary analysis of aircraft primary structures made of composite materials. The program combines a series of modules with the finite element code DIAL as its backbone. Four ISPAN Modules were developed and are documented. These include: (1) flat stiffened panel; (2) curved stiffened panel; (3) flat tubular panel; and (4) curved geodesic panel. Users are instructed to input geometric and material properties, load information and types of analysis (linear, bifurcation buckling, or post-buckling) interactively. The program utilizing this information will generate finite element mesh and perform analysis. The output in the form of summary tables of stress or margins of safety, contour plots of loads or stress, and deflected shape plots may be generalized and used to evaluate specific design

ISPAN (Interactive Stiffened Panel Analysis): A tool for quick concept evaluation and design trade studies

Interactive Stiffened Panel Analysis (ISPAN) modules, written in FORTRAN, were developed to provide an easy to use tool for creating finite element models of composite material stiffened panels. The modules allow the user to interactively construct, solve and post-process finite element models of four general types of structural panel configurations using only the panel dimensions and properties as input data. Linear, buckling and post-buckling solution capability is provided. This interactive input allows rapid model generation and solution by non finite element users. The results of a parametric study of a blade stiffened panel are presented to demonstrate the usefulness of the ISPAN modules. Also, a non-linear analysis of a test panel was conducted and the results compared to measured data and previous correlation analysis

Using nestedness and species-accumulation analyses to strengthen a conservation plan for littoral forest birds in south-eastern Madagascar

The littoral forests of south-eastern Madagascar are among the most threatened ecosystems on the island. A conservation plan has been developed for the region due to a proposed mining venture. Here, we provide a novel methodology to assess if the planned conservation measures would effectively conserve the bird diversity inhabiting these forests. Bird community composition within 30 littoral forest fragments was quantified with each fragment characterized by measures of fragment area, isolation, and internal habitat complexity. A nestedness and cumulative species–area analysis was conducted to ascertain the contribution of forest fragments of different sizes in capturing the overall bird species richness. Datasets representing the overall and forest-dependent bird assemblages were found to be significantly nested. The pattern of nestedness appeared to be driven by fragment size. However, cumulative species–area analyses showed that the assemblages were imperfectly nested with ten species displaying idiosyncratic distribution patterns. When a modest conservation target was set (the occurrence of a bird species in three or more fragments), the proposed conservation plan would only protect approximately half the species found in the littoral forests. We show that protecting an additional four large patches would mean that the proportion of forest-birds captured in three or more patches would increase to 70%

A Distributed Multilevel Force-directed Algorithm

The wide availability of powerful and inexpensive cloud computing services naturally motivates the study of distributed graph layout algorithms, able to scale to very large graphs. Nowadays, to process Big Data, companies are increasingly relying on PaaS infrastructures rather than buying and maintaining complex and expensive hardware. So far, only a few examples of basic force-directed algorithms that work in a distributed environment have been described. Instead, the design of a distributed multilevel force-directed algorithm is a much more challenging task, not yet addressed. We present the first multilevel force-directed algorithm based on a distributed vertex-centric paradigm, and its implementation on Giraph, a popular platform for distributed graph algorithms. Experiments show the effectiveness and the scalability of the approach. Using an inexpensive cloud computing service of Amazon, we draw graphs with ten million edges in about 60 minutes.Comment: Appears in the Proceedings of the 24th International Symposium on Graph Drawing and Network Visualization (GD 2016