The chromatin‐regulatory principles of histone post‐translational modifications (PTMs) are discussed with a focus on the potential alterations in chromatin functional state due to steric and mechanical constraints imposed by bulky histone modifications such as ubiquitin and SUMO. In the classical view, PTMs operate as recruitment platforms for histone “readers,” and as determinants of chromatin array compaction. Alterations of histone charges by “small” chemical modifications (e.g., acetylation, phosphorylation) could regulate nucleosome spontaneous dynamics without globally affecting nucleosome structure. These fluctuations in nucleosome (...) wrapping can be exploited by chromatin‐processing machinery. In contrast, ubiquitin and SUMO are comparable in size to histones, and it seems logical that these PTMs could conflict with canonical nucleosome organization. An experimentally testable hypothesis that by adding sterical bulk these PTMs can robustly alter nucleosome primary structure is proposed. The model presented here stresses the diversity of mechanisms by which histone PTMs regulate chromatin dynamics, primary structure and, hence, functionality. (shrink)

This book is devoted to the problems of the growth of science. These prob lems, neglected for a long time by the philosophers of science, have become in the 60's and 70's a subject of vivid discussion. There are philosophers who stress only the dependence of science upon various sociological, psycho logical and other factors and deny any internal laws of the development of knowledge, like approaching the truth. The majority rejects such nihilism and searches for the laws of the (...) growth of science. However, they often overlook the role of the Correspondence Principle which connects the suc cessive scientific theories. On the other hand, some authors, while stressing the role of this principle, overlook logical difficulties connected with it, e. g. the problem of the incompatibility of successive theories, of the falsity of some of their assumptions, etc. I believe the Correspondence Principle to be a basic principle of the pro gress of contemporary physics and, probably, of every advanced science. How ever, this principle must be properly interpreted and the above-mentioned logical difficulties must be solved. Their solution requires, as it seems, revealing the idealizational nature of the basic laws of science, in any case of the quantitative laws of advanced sciences. This point has been recently emphasized by some Polish philosophers, especially in Poznan. (shrink)

The paper is a sketch of a conception of approximative truth (or verisimilitude). The concepts of relative error, and degree of inadequacy are introduced. By means of them the concept of truth-content of quantitative facts-statements, laws and theories is defined. Laws and theories accepted in science have a high truth-content, i.e. they are approximately true.

Abstract The problem of the existence of the objects of knowledge is the main problem in the controversy between realism and anti?realism. This controversy appears on three levels: (i) perceptions, (ii) concepts, (iii) scientific theories. According to perception?realism, things exist objectively; according to subjective idealism, they are only bundles of impressions. According to conceptual realism, genera (classes) exist objectively; according to nominalism, they do not exist (there are only general names). According to scientific realism, the objects of confirmed theories, including (...) unobservable entities, exist objectively; according to phenomenalism, only observable bodies exist. On each level a naive realism and a critical realism is distinguished. On the level of scientific theories direct objects (ideal models) are distinguished from ultimate objects (real entities). (shrink)

This paper considers the method of idealization and factualization as the main method of all advanced empirical science. The procedure is as follows. Some idealizing conditions are assumed: the vanishing of factors $(p_{i}=0)$ which never vanish in the real world. An idealization law is formulated -- a law which is exactly (non-vacuously) fulfilled only in an ideal model, not in any real system. Then the idealizing assumptions are abrogated one by one-it is a process of gradual factualization, of the transition (...) to the factual laws which are fulfilled in real systems. These laws may be directly applied and tested by experience. (shrink)

There are two concepts of the scope of a law: 1) the set of bodies (in our world) in which the law is fulfilled, 2) the set of models of the law, or the set of possible worlds in which it is fulfilled. Their use leads to opposite answers to the question which law is broader than the other.

Abstract Three main concepts of model in science are distinguished: (1) semantical model of a theory; (2) real model of another real thing; (3) mathematical model of a real thing. The last concept is the most important for the empirical sciences. The mathematical model is not identical with a theory: it is an ideal object which is directly described by the theory. We have here an intermediate level between reality and theory.

There are three main kinds of causal connections between two events: the transfer of energy, the transfer of information and the triggering of the transfer of one of them or both. There are also other kinds of causal connections.

Władysław Krajewski criticizes frontally Kałuszyńska's argumentation on behalf of anti-realism.

INTRODUCTION The aim of the present volume is to introduce prominent Polish philosophers of the 20th century as well as their significant accomplishments in ...

There is one fundamental and many non-fundamental kinds of existence. Things (material bodies) exist fundamentally. Many other objects exist non-fundamentally: properties, events, relations, states; abstracts (universals), laws of Nature; possible states, virtual particles; minds, mental processes; ideal objects created by minds (Popperian "World 3"). All of them are always based on material bodies, but they exist really.