5,280 research outputs found
Failed "nonaccelerating" models of prokaryote gene regulatory networks
Much current network analysis is predicated on the assumption that important
biological networks will either possess scale free or exponential statistics
which are independent of network size allowing unconstrained network growth
over time. In this paper, we demonstrate that such network growth models are
unable to explain recent comparative genomics results on the growth of
prokaryote regulatory gene networks as a function of gene number. This failure
largely results as prokaryote regulatory gene networks are "accelerating" and
have total link numbers growing faster than linearly with network size and so
can exhibit transitions from stationary to nonstationary statistics and from
random to scale-free to regular statistics at particular critical network
sizes. In the limit, these networks can undergo transitions so marked as to
constrain network sizes to be below some critical value. This is of interest as
the regulatory gene networks of single celled prokaryotes are indeed
characterized by an accelerating quadratic growth with gene count and are size
constrained to be less than about 10,000 genes encoded in DNA sequence of less
than about 10 megabases. We develop two "nonaccelerating" network models of
prokaryote regulatory gene networks in an endeavor to match observation and
demonstrate that these approaches fail to reproduce observed statistics.Comment: Corrected error in biological input parameter: 13 pages, 9 figure
Inherent size constraints on prokaryote gene networks due to "accelerating" growth
Networks exhibiting "accelerating" growth have total link numbers growing
faster than linearly with network size and can exhibit transitions from
stationary to nonstationary statistics and from random to scale-free to regular
statistics at particular critical network sizes. However, if for any reason the
network cannot tolerate such gross structural changes then accelerating
networks are constrained to have sizes below some critical value. This is of
interest as the regulatory gene networks of single celled prokaryotes are
characterized by an accelerating quadratic growth and are size constrained to
be less than about 10,000 genes encoded in DNA sequence of less than about 10
megabases. This paper presents a probabilistic accelerating network model for
prokaryotic gene regulation which closely matches observed statistics by
employing two classes of network nodes (regulatory and non-regulatory) and
directed links whose inbound heads are exponentially distributed over all nodes
and whose outbound tails are preferentially attached to regulatory nodes and
described by a scale free distribution. This model explains the observed
quadratic growth in regulator number with gene number and predicts an upper
prokaryote size limit closely approximating the observed value.Comment: Corrected error in biological input parameter: 15 pages, 10 figure
High effectiveness liquid droplet/gas heat exchanger for space power applications
A high-effectiveness liquid droplet/gas heat exchanger (LDHX) concept for thermal management in space is described. Heat is transferred by direct contact between fine droplets (approx. 100 to 300 micron diameter) of a suitable low vapor pressure liquid and an inert working gas. Complete separation of the droplet and gas media in the zero-g environment is accomplished by configuring the LDHX as a vortex chamber. The large heat transfer area presented by the small droplets permits heat exchanger effectiveness of 0.9 to 0.95 in a compact, lightweight geometry which avoids many of the limitations of conventional plate and fin or tube and shell heat exchangers, such as their tendency toward single point failure. The application of the LDHX in a high temperature Bryaton cycle is discussed to illustrate the performance and operational characteristics of this heat exchanger concept
General Campus Climate from a Conservative Student Perspective
Campus Climate Research studies how students and others in a college community feel about the climate of their institutions, especially how the climate facilitates learning, growth, and expression. Typically, this research has been applied to diversity concerns, especially in the decades after affirmative action became a common practice in higher education admissions. My research adds to this literature, because in the midst of creating a campus community and campus climate that is sensitive and in alliance with the needs of marginalized students, institutions will often find that a struggle occurs between the needs of marginalized students and the perceived neglect towards conservative students (or traditionally privileged students). My study uses the lens of Campus Climate Research to explore the extent to which conservative or conservative-leaning students at Ohio Wesleyan feel that they can comfortably interact with other OWU community members. I utilized Campus Climate Research measures to conduct an anonymous survey that asked a series of questions about the students’ academic and social perceptions regarding fairness and equity. I found that while most students take courses that challenge their personal opinions, it is often the case that conservative students still do not feel comfortable speaking out in class or with their professors due to the negative responses of students and occasionally professors. However, this does not mean that faculty are failing at creating an optimum learning environment. It is often said that, compared to non-academic social interactions students experience, OWU professors are good at making sure that conversations stay civil. Not surprisingly, students are in disagreement over their perceptions on restricted freedom of speech — some believing that we are restricted and others believing that we are not. Conservative students also reported they felt that political views are being left out of discussions about open mindedness and acceptance
Generic Polynomials
In Galois theory one is interested in finding a polynomial over a field that has a given Galois group. A more desirable polynomial is one that parametrizes all such polynomials with that given group as its corresponding Galois group. These are called generic polynomials and we provide detailed proofs of two theorems that give methods for constructing such polynomials. Furthermore, we construct generic polynomials for Sn, C3, V , C4, C6, D3, D4, and D6
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