Models and Representation

Models are of central importance in many scientific contexts. We study models and thereby discover features of the phenomena they stand for. For this to be possible models must be representations: they can instruct us about the nature of reality only if they represent the selected parts or aspects of the world we investigate. This raises an important question: In virtue of what do scientific models represent their target systems? In this chapter we first disentangle five separate questions associated with scientific representation and offer five conditions of adequacy that any successful answer to these questions must meet. We then review the main contemporary accounts of scientific representation – similarity, isomorphism, inferentialist, and fictionalist accounts – through the lens of these questions. We discuss each of their attributes and highlight the problems they face. We finally outline our own preferred account, and suggest that it provides the most promising way of addressing the questions raised at the beginning of the chapter

Überlebensfaktoren in der Therapie erblicher Netzhautdegenerationen

Zusammenfassung: In genetisch bedingten Netzhautdystrophien sterben die Photorezeptoren durch Apoptose. Dies ist ein Prozess, dem komplexe molekulare Abläufe zugrunde liegen und der iniziiert wird, wenn proapoptotische Signale in der individuellen Zelle die Oberhand gewinnen. Die Identifizierung der beteiligten Faktoren und deren Wirkungen schuf die Basis dafür, diejenigen mit antiapoptotischem Potenzial in Tiermodellen für vererbte Netzhautdegenerationen auszutesten. Etliche dieser Faktoren waren in der Lage, den Gang der Degeneration zu verlangsamen. Ein Aufhalten oder gar ein Verhindern des Krankheitsverlaufs ist jedoch bis dato nicht realisiert. Zudem zeigte sich, dass der Erhalt der Morphologie nicht mit dem Erhalt der Funktion im ERG korrelieren muss. Vertiefte Einsichten in die pro- und antiapoptotischen Netzwerke sind klar vonnöten, damit antiapoptotische Therapien mit Überlebensfaktoren den Weg zur Applikation beim Menschen finden. Im Vergleich dazu konnte in einem Hundemodell für Leber-Amaurose durch elektive Gentherapie die retinale Funktion hergestellt und somit der Nachweis der Wirksamkeit der Methode erbracht werde

The turn of the valve: representing with material models

Many scientific models are representations. Building on Goodman and Elgin’s notion of representation-as we analyse what this claim involves by providing a general definition of what makes something a scientific model, and formulating a novel account of how they represent. We call the result the DEKI account of representation, which offers a complex kind of representation involving an interplay of, denotation, exemplification, keying up of properties, and imputation. Throughout we focus on material models, and we illustrate our claims with the Phillips-Newlyn machine. In the conclusion we suggest that, mutatis mutandis, the DEKI account can be carried over to other kinds of models, notably fictional and mathematical models

Exploring modularity in biological networks

Network theoretical approaches have shaped our understanding of many different kinds of biological modularity. This essay makes the case that to capture these contributions, it is useful to think about the role of network models in exploratory research. The overall point is that it is possible to provide a systematic analysis of the exploratory functions of network models in bioscientific research. Using two examples from molecular and developmental biology, I argue that often the same modelling approach can perform one or more exploratory functions, such as introducing new directions of research, offering a complementary set of concepts, methods and algorithms for individuating important features of natural phenomena, generating proofs of principle demonstrations and potential explanations for phenomena of interest and enlarging the scope of certain research agendas. This article is part of the theme issue 'Unifying the essential concepts of biological networks: biological insights and philosophical foundations'

An Alternative Interpretation of Statistical Mechanics

In this paper I propose an interpretation of classical statistical mechanics that centers on taking seriously the idea that probability measures represent complete states of statistical mechanical systems. I show how this leads naturally to the idea that the stochasticity of statistical mechanics is associated directly with the observables of the theory rather than with the microstates (as traditional accounts would have it). The usual assumption that microstates are representationally significant in the theory is therefore dispensable, a consequence which suggests interesting possibilities for developing non-equilibrium statistical mechanics and investigating inter-theoretic answers to the foundational questions of statistical mechanics

PrP-dependent association of prions with splenic but not circulating lymphocytes of scrapie-infected mice.

An intact immune system, and particularly the presence of mature B lymphocytes, is crucial for mouse scrapie pathogenesis in the brain after peripheral exposure. Prions are accumulated in the lymphoreticular system (LRS), but the identity of the cells containing infectivity and their role in neuroinvasion have not been determined. We show here that although prion infectivity in the spleen is associated with B and T lymphocytes and to a lesser degree with the stroma, no infectivity could be detected in lymphocytes from blood. In wild-type mice, which had been irradiated and reconstituted with PrP-deficient lymphohaematopoietic stem cells and inoculated with scrapie prions, infectivity in the spleen was present in the stroma but not in lymphocytes. Therefore, splenic B and T lymphocytes can either synthesize prions or acquire them from another source, but only when they express PrP