Evolutionary Dynamics and Optimization: Neutral Networks as Model-Landscapes for RNA Secondary-Structure Folding-Landscapes

We view the folding of RNA-sequences as a map that assigns a pattern of base pairings to each sequence, known as secondary structure. These preimages can be constructed as random graphs (i.e. the neutral networks associated to the structure $s$). By interpreting the secondary structure as biological information we can formulate the so called Error Threshold of Shapes as an extension of Eigen's et al. concept of an error threshold in the single peak landscape. Analogue to the approach of Derrida & Peliti for a of the population on the neutral network. On the one hand this model of a single shape landscape allows the derivation of analytical results, on the other hand the concept gives rise to study various scenarios by means of simulations, e.g. the interaction of two different networks. It turns out that the intersection of two sets of compatible sequences (with respect to the pair of secondary structures) plays a key role in the search for ''fitter'' secondary structures.Comment: 20 pages, uuencoded compressed postscript-file, Proc. of ECAL '95 conference, to appear., email: chris @ imb-jena.d

Voices from the margins: ‘Black’ Caribbean and Mexican heritage women educators in the rural south

This paper explores the ways in which immigrant and migrant women educators in the rural South understand and construct narratives of their lives. The ‘Black’ Caribbean and Mexican heritage women educators in this study experience and interpret events in their lives, as women, minorities, postcolonial ‘subjects,’ and outsiders in the rural South, a region traditionally dominated by white patriarchal norms and prejudices. We assert that from this position of multiple marginality they construct important insights into the nature of education in the rural South. As so-called “Third-World women” living in the “First World” of the United States, the interpretations that this group of immigrant and migrant women make of their lives illuminate the ‘real,’ yet fluid (Moya & Hames-Garcia, 2000), nature of identity and representation in this nation and in the “New” South. The experiences of these women clearly reveal that identity categories provide useful theoretical and practical understandings of often problematic constructs such as race, gender, social class and ethnicity and highlight the fact that experiences and interpretations vary within and across these identity categories. Thus, how these women respond to the South demonstrates the impact of significant continuities and discontinuities as these educators negotiate their identities in unfamiliar spaces

Secondary Sources: Top Ten

Secondary sources are a legal researcher\u27s best friend. They are a great place to begin researching a new topic as they provide a framework for understanding the subject. Not only will a good secondary source provide researchers with a way of approaching the topic, but it will also introduce beginning researchers to the language of the subject. Secondary sources also contain expert analysis, references to primary law such as cases, statutes, and regulations, and will also include such other resources as governmental reports, statistics, and other secondary sources. While secondary sources are an incredibly valuable research tool, they can offer such a wide array of options that researchers become overwhelmed with the sheer number of choices. This can strike anyone, even a fairly experienced researcher. Librarians, too, can become overwhelmed, especially when faced with teaching law students about the value of secondary sources and how to harness their power

WOW Factors in Secondary Science

Booklet of exciting practicals to do with Secondary school pupils. Each activity tested and written up by a Secondary PGCE or GTP student; some updated by other students in the following year. Templates all follow the same pattern and include risk assessments, materials needed, links to the curriculum et

Secondary globular cluster populations

Peer reviewe

Accessible Capacity of Secondary Users

A new problem formulation is presented for the Gaussian interference channels (GIFC) with two pairs of users, which are distinguished as primary users and secondary users, respectively. The primary users employ a pair of encoder and decoder that were originally designed to satisfy a given error performance requirement under the assumption that no interference exists from other users. In the scenario when the secondary users attempt to access the same medium, we are interested in the maximum transmission rate (defined as {\em accessible capacity}) at which secondary users can communicate reliably without affecting the error performance requirement by the primary users under the constraint that the primary encoder (not the decoder) is kept unchanged. By modeling the primary encoder as a generalized trellis code (GTC), we are then able to treat the secondary link and the cross link from the secondary transmitter to the primary receiver as finite state channels (FSCs). Based on this, upper and lower bounds on the accessible capacity are derived. The impact of the error performance requirement by the primary users on the accessible capacity is analyzed by using the concept of interference margin. In the case of non-trivial interference margin, the secondary message is split into common and private parts and then encoded by superposition coding, which delivers a lower bound on the accessible capacity. For some special cases, these bounds can be computed numerically by using the BCJR algorithm. Numerical results are also provided to gain insight into the impacts of the GTC and the error performance requirement on the accessible capacity.Comment: 42 pages, 12 figures, 2 tables; Submitted to IEEE Transactions on Information Theory on December, 2010, Revised on November, 201