Specification of initial connection handling in TCP using structured Petri nets

This paper uses structured Petri nets to specify how connection establishment is handled by the DoD Transmission Control Protocol. The purpose of this paper is to demonstrate an alternate specification technique by examining its application to a portion of a protocol of reasonable complexity.Initially we briefly present the semantics of structured Petri nets. Following this, a terse discussion of the problems of establishing connections in a network takes place. This discussion centers on the use of the three-way handshake, which is used by TCP, as a solution for many of these problems. Finally, the specification of the three-way handshake used in TCP is made. The specification is presented in three sections: first, a general set of notes concerning the nature of this particular specification is discussed; second, the data definitions of the specification are given; and, third, the actual nets themselves are presented.This paper is condensed from a portion of the author's dissertation, which is still in preparation. In the interests of brevity, some components of the specification, such a retransmission handling, have been omitted. Interested readers should contact the author for a more detailed paper

Low tech connections into the ARPA internet : the RawPacket split-gateway

This report describes a "low technology" method for connecting into the ARPA Internet. The use of a RawPacket interface in a system which supoprts IP makes possible the construction of a split-gateway between two hosts. The RawPacket interface permits a user-level process to introduce arbitrary packets into the IP layer, resulting in a virtual network interface. Since the split-gateway is implemented using a RawPacket interface, two networks may be connected together using a convenient medium which does not require explicit kernel support. Hence, split-gateways are well-suited for use as stub-gateways, connecting a local network to a long-haul network such as the ARPA backbone. In particular, the split-gateway discussed in this report achieves a reasonable level of connectivity for a comparatively small expenditure.This report details how the RawPacket software and split-gateways are implemented. In addition, various daemon configurations are presented, modifications to the operating environment are discussed, and some performance measurements are given

Embodied Knowledge: Writing Researchers’ Bodies Into Qualitative Health Research

After more than a decade of postpositivist health care research and an increase in narrative writing practices, social scientific, qualitative health research remains largely disembodied. The erasure of researchers’ bodies from conventional accounts of research obscures the complexities of knowledge production and yields deceptively tidy accounts of research. Qualitative health research could benefit significantly from embodied writing that explores the discursive relationship between the body and the self and the semantic challenges of writing the body by incorporating bodily details and experiences into research accounts. Researchers can represent their bodies by incorporating autoethnographic narratives, drawing on all of their senses, interrogating the connections between their bodily signifiers and research processes, and experimenting with the semantics of self and body. The author illustrates opportunities for embodiment with excerpts from an ethnography of a geriatric oncology team and explores implications of embodied writing for the practice of qualitative health research

Freezing of ridges and water networks preserves the Gamburtsev Subglacial Mountains for millions of years

Once an ice sheet grows beyond a critical thickness, the basal thermal regime favors melting and development of subglacial water networks. Subglacial water is necessary for bedrock erosion, but the exact mechanisms that lead to preservation of subglacial topography are unclear. Here we resolve the freezing mechanisms that lead to long-term, high-altitude preservation across the Gamburtsev Subglacial Mountains in East Antarctica. Analyses of a comprehensive geophysical data set reveal a large-scale water network along valley floors. The ice sheet often drives subglacial water up steep topography where it freezes along high ridges beneath thinner ice. Statistical tests of hypsometry show the Gamburtsevs resemble younger midlatitude mountains, indicating exceptional preservation. We conclude that the Gamburtsevs have been shielded from erosion since the latest Eocene (∼34 Ma). These freezing mechanisms likely account for the spatial and temporal patterns of erosion and preservation seen in other glaciated mountain ranges

Social representations and the politics of participation

Recent work has called for the integration of different perspectives into the field of political psychology (Haste, 2012). This chapter suggests that one possible direction that such efforts can take is studying the role that social representations theory (SRT) can play in understanding political participation and social change. Social representations are systems of common-sense knowledge and social practice; they provide the lens through which to view and create social and political realities, mediate people's relations with these sociopolitical worlds and defend cultural and political identities. Social representations are therefore key for conceptualising participation as the activity that locates individuals and social groups in their sociopolitical world. Political participation is generally seen as conditional to membership of sociopolitical groups and therefore is often linked to citizenship. To be a citizen of a society or a member of any social group one has to participate as such. Often political participation is defined as the ability to communicate one's views to the political elite or to the political establishment (Uhlaner, 2001), or simply explicit involvement in politics and electoral processes (Milbrath, 1965). However, following scholars on ideology (Eagleton, 1991; Thompson, 1990) and social knowledge (Jovchelovitch, 2007), we extend our understanding of political participation to all social relations and also develop a more agentic model where individuals and groups construct, develop and resist their own views, ideas and beliefs. We thus adopt a broader approach to participation in comparison to other political-psychological approaches, such as personality approaches (e.g. Mondak and Halperin, 2008) and cognitive approaches or, more recently, neuropsychological approaches (Hatemi and McDermott, 2012). We move away from a focus on the individual's political behaviour and its antecedents and outline an approach that focuses on the interaction between psychological and political phenomena (Deutsch and Kinnvall, 2002) through examining the politics of social knowledge

The \u3cem\u3eChlamydomonas\u3c/em\u3e Genome Reveals the Evolution of Key Animal and Plant Functions

Chlamydomonas reinhardtii is a unicellular green alga whose lineage diverged from land plants over 1 billion years ago. It is a model system for studying chloroplast-based photosynthesis, as well as the structure, assembly, and function of eukaryotic flagella (cilia), which were inherited from the common ancestor of plants and animals, but lost in land plants. We sequenced the ∼120-megabase nuclear genome of Chlamydomonas and performed comparative phylogenomic analyses, identifying genes encoding uncharacterized proteins that are likely associated with the function and biogenesis of chloroplasts or eukaryotic flagella. Analyses of the Chlamydomonas genome advance our understanding of the ancestral eukaryotic cell, reveal previously unknown genes associated with photosynthetic and flagellar functions, and establish links between ciliopathy and the composition and function of flagella