10,675 research outputs found
Metabolic and Chaperone Gene Loss Marks the Origin of Animals: Evidence for Hsp104 and Hsp78 Sharing Mitochondrial Clients
The evolution of animals involved acquisition of an emergent gene repertoire
for gastrulation. Whether loss of genes also co-evolved with this developmental
reprogramming has not yet been addressed. Here, we identify twenty-four genetic
functions that are retained in fungi and choanoflagellates but undetectable in
animals. These lost genes encode: (i) sixteen distinct biosynthetic functions;
(ii) the two ancestral eukaryotic ClpB disaggregases, Hsp78 and Hsp104, which
function in the mitochondria and cytosol, respectively; and (iii) six other
assorted functions. We present computational and experimental data that are
consistent with a joint function for the differentially localized ClpB
disaggregases, and with the possibility of a shared client/chaperone
relationship between the mitochondrial Fe/S homoaconitase encoded by the lost
LYS4 gene and the two ClpBs. Our analyses lead to the hypothesis that the
evolution of gastrulation-based multicellularity in animals led to efficient
extraction of nutrients from dietary sources, loss of natural selection for
maintenance of energetically expensive biosynthetic pathways, and subsequent
loss of their attendant ClpB chaperones.Comment: This is a reformatted version from the recent official publication in
PLoS ONE (2015). This version differs substantially from first three arXiV
versions. This version uses a fixed-width font for DNA sequences as was done
in the earlier arXiv versions but which is missing in the official PLoS ONE
publication. The title has also been shortened slightly from the official
publicatio
Analyzing inter-organizational systems from a power and interest perspective
Inter-organizational systems (IOS) are ICT-based systems that enable organizations to share information and to electronically conduct business across organizational boundaries. Especially since the increasing availability of the Internet, there have been less technological barriers to implement IOS. However, that does not imply that IOS-possibilities are implemented successfully in all occasions: other barriers may remain. Innovation is not only a technical process of ?solving problems?, it also involves economic and political processes in which interests are articulated, alliances are built and outcomes are struggled over. To explore this observation, this paper presents a model that helps to describe and analyze IOS from a power and interest perspective of multiple parties. To illustrate this model, eight case studies of IOS are discussed, of which two in more depth. After that, we will put the findings of the analysis in a broader perspective. The paper concludes with the assertion that the scope for the design of an effective IOS depends on a combination of technical, economic and social
Microphase separation in thin block copolymer films: a weak segregation mean-field approach
In this paper we consider thin films of AB block copolymer melts confined
between two parallel plates. The plates are identical and may have a preference
for one of the monomer types over the other. The system is characterized by
four parameters: the Flory-Huggins chi-parameter, the fraction f of A-monomers
in the block copolymer molecules, the film thickness d, and a parameter h
quantifying the preference of the plates for the monomers of type A. In certain
regions of parameter space, the film will be microphase separated. Various
structures have been observed experimentally, each of them characterized by a
certain symmetry, orientation, and periodicity. We study the system
theoretically using the weak segregation approximation to mean field theory. We
restrict our analysis to the region of the parameter space where the film
thickness d is close to a small multiple of the natural periodicity. We will
present our results in the form of phase diagrams in which the absolute value
of the deviation of the film thickness from a multiple of the bulk periodicity
is placed along the horizontal axis, and the chi-parameter is placed along the
vertical axis; both axes are rescaled with a factor which depends on the
A-monomer fraction f. We present a series of such phase diagrams for increasing
values of the surface affinity for the A-monomers. We find that if the film
thickness is almost commensurate with the bulk periodicity, parallel
orientations of the structures are favoured over perpendicular orientations. We
also predict that on increasing the surface affinity, the region of stability
of the bcc phase shrinks.Comment: 35 pages, 20 figure
Realtime system control by means of path expressions
A high-level, algebraic programming method for the online control of actions in a real-time, parallel processing environment is described. The method is based on the interaction of path expressions. On the basis of a set of path expressions, evocation of actions can be controlled in real-time in a fully automated way. It is shown how intelligent system behavior can be obtained by a combination of rules given as path expressions. Each of these rules specifies some partial behavior to which the system must comply. The control system operates as a rule-based action planning system that works online in an asynchronous environment. The development of the prototype system PBOS (Path Based Operating System) has demonstrated that path expression specification naturally integrates with a real-time, multitasking control syste
Energy from streaming current and potential
It is investigated how much energy can be delivered by a streaming current source. A streaming current and subsequent streaming potential originate when double layer charge is transported by hydrodynamic flow. Theory and a network model of such a source is presented and initial experimental results are given, showing a supplied power of 20 nW obtained by a pressure difference of 1 atm over a glass porous plug, using a 1-mM KCl solution. It is indicated how the rather low mechanical-to-electrical energy conversion efficiency can be increased
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