OR/MS methodology—A conceptual framework

Many authors deal, explicitly or implicitly, with OR/MS methodology and the term ‘methodology’ has gained such an inclusive connotation that it comes to denote nothing in particular. This has diluted the analytical precision of OR/MS ‘methodology’ as well as its practicability. Therefore an attempt to form a conceptual framework for OR/MS methodology will be presented. This framework consists of seven components addressing specific methodological aspects: each component has specific properties which distinguish it from the others; all of them together form a consistent hierarchy suitable to aid the successful development and implementation of OR/MS methods.     

Mitochondrial Dynamics in Cell Life and Death

Mitochondria are dynamic organelles that are able to change their morphology during cellular development and to meet the energetic needs of the cell, for example. During the past several years, knowledge about the molecular machinery involved in the control of mitochondrial shape has improved considerably. In August 2005, leading researchers in the field of mitochondrial dynamics met at the Venetian Institute of Molecular Medicine in Padova, Italy, to discuss novel and intriguing findings presented at the first workshop on "Mitochondrial Dynamics in Cell Life and Death." Some of the findings related to apoptosis and aging are described in this Perspective.     

Pooling operators with the marginalization property

In this paper, we consider the problem of combining a number of opinions which have been expressed as probability measures P₁, …, P_n, over some space. It is shown that a pooling formula which has the marginalization property of McConway (1981) must be of the form T = Σⁿ_i=₁W_i P_i + (1 - Σⁿ_i =₁W_i)Q, where Q is an arbitrary measure and W₁, …, W_n ϵ [—1,1] are weights such that| Σ_J Σ _j w_j | ≤ 1 for every subset J of {1, …, n}. If, in addition, T is required to preserve the independence of arbitrary events A and B whenever these events are independent under each P_i, then either T = P_i for some 1 ≤ i ≤ n or T = Q, in which case Q takes values in {0, l}.     

The two-sample t test versus satterthwaite's approximate f test

A comparison between the two-sample t test and Satterthwaite's approximate F test is made, assuming the choice between these two tests is based on a preliminary test on the variances. Exact formulas for the sizes and powers of the tests are derived. Sizes and powers are then calculated and compared for several situations.     

Sequential Pattern Analysis: A Statistical Investigation of Sequence Length and Support

In sequential pattern analysis, the frequency of patterns is evaluated by the support. While computed efficiently from large databases, we show that the support cannot be compared between different databases, since it is influenced by the actual sequence length distribution. Models for this sequence length distribution are surveyed. One of these models, the Good distribution, appears to be sufficiently flexible for practice. It is used to exemplify an approach for adjusting the relative support such that the resulting adjusted support values are better comparable between different databases. We illustrate our findings with texts from the bilingual FinDe corpus.     

Spatial approaches to social work – theoretical foundations and implications for practice and research

ABSTRACT

Spatial approaches have inspired and grounded the social sciences and social geography already for a longer time. Beyond these models, the theory discourse on social work developed innovative concepts and models of socio-spatial approaches. They set a special focus on aspects of individual and social development, the concept of acquirement and emancipatory approaches to spatial design. For interventions, special methods for socio-spatial analyses were developed. This article reflects the main approaches of this theory discourse and asks for its key implications for social work practice and research.     

Capturing Relatedness: Comprehensive Measures based on Secondary Data

This paper presents new measures of technological and customer‐side relatedness constructed from widely available secondary data. Relatedness is a concept central to predicting the existence and nature of a relationship between corporate diversification and firm performance. Yet, finding appropriate measures has been an ongoing struggle. The widely used SIC‐based entropy measure has low construct validity, and survey‐based measures are hard to replicate across firms and industries and over time. The measures we develop significantly outperform established measures in explaining variation in firm performance across firms and over time, and both sources of relatedness are found to be independent and significant explanations of firm performance.     

Rush and Be Wrong or Wait and Be Late? A Model of Information in Collaborative Processes

Business processes have become more simultaneous and collaborative in the recent past. In simultaneous processes, multiple parties must adapt to one another in real time as decisions evolve. For example, New Product Development (NPD) requires collaboration in the context of Concurrent Engineering, and Supply Chain Management (SCM) in the context of collaborative planning. In both cases, parties must modify decisions based on preliminary information, information that is not fully precise or stable, about what the other parties are doing. This article develops a generalized model of real‐time decision making based on preliminary information, which applies both to NPD and SCM. The model offers insights into when to commit to a course of action, and we derive seven principles that help in dealing with preliminary information.