2,132 research outputs found
Coarse-Graining and Self-Dissimilarity of Complex Networks
Can complex engineered and biological networks be coarse-grained into smaller
and more understandable versions in which each node represents an entire
pattern in the original network? To address this, we define coarse-graining
units (CGU) as connectivity patterns which can serve as the nodes of a
coarse-grained network, and present algorithms to detect them. We use this
approach to systematically reverse-engineer electronic circuits, forming
understandable high-level maps from incomprehensible transistor wiring: first,
a coarse-grained version in which each node is a gate made of several
transistors is established. Then, the coarse-grained network is itself
coarse-grained, resulting in a high-level blueprint in which each node is a
circuit-module made of multiple gates. We apply our approach also to a
mammalian protein-signaling network, to find a simplified coarse-grained
network with three main signaling channels that correspond to cross-interacting
MAP-kinase cascades. We find that both biological and electronic networks are
'self-dissimilar', with different network motifs found at each level. The
present approach can be used to simplify a wide variety of directed and
nondirected, natural and designed networks.Comment: 11 pages, 11 figure
Three Dimensional Electrical Impedance Tomography
The electrical resistivity of mammalian tissues varies widely and is correlated with physiological
function. Electrical impedance tomography (EIT) can be used to probe such variations in vivo, and offers a
non-invasive means of imaging the internal conductivity distribution of the human body. But the
computational complexity of EIT has severe practical limitations, and previous work has been restricted to
considering image reconstruction as an essentially two-dimensional problem. This simplification can limit
significantly the imaging capabilities of EIT, as the electric currents used to determine the conductivity variations will not in general be confined to a two-dimensional plane. A few studies have attempted three-dimensional EIT image reconstruction, but have not yet succeeded in generating images of a quality suitable for clinical applications. Here we report the development of a three-dimensional EIT system with greatly improved imaging capabilities, which combines our 64-electrode data-collection apparatus with customized matrix inversion techniques. Our results demonstrate the practical potential of EIT for clinical applications, such as lung or brain imaging and diagnostic screening
Life story and narrative approaches in the study of family lives
The chapter examines life story and narrative approaches and their application in the study of family lives. It begins with a brief history of some key figures in biographical research followed by an examination of some of the distinctions between the two approaches. The second part of the chapter presents and discusses a case of a grandfather and son drawn from an intergenerational study of fatherhood. The study’s method (the biographic-narrative interpretive method) demonstrates change and continuity in family life by situating lives in historical context and examining the cultural transmissions that are accepted and resisted by the younger generation. The chapter discusses the benefits of paying attention to the narrative form of life stories. In these ways biographical and narrative approaches produce a multi-layered analysis
Refining Lucy Mission Delta-V During Spacecraft Design Using Trajectory Optimization Within High-Fidelity Monte Carlo Maneuver Analysis
Recent advances linking medium-fidelity trajectory optimization and high-fidelity trajectory propagation/maneuver design software with Monte Carlo maneuver analysis and parallel processing enabled realistic statistical delta-V estimation well before launch. Completing this high-confidence, refined statistical maneuver analysis early enabled release of excess delta-V margin for increased dry mass margin for the Lucy Jupiter Trojan flyby mission. By 3.3 years before launch, 16 of 34 TCMs had 1000 re-optimized trajectory design samples, yielding tens of m/s lower 99%-probability delta-V versus targeting maneuvers to one optimal trajectory. One year later, 1000 re-optimized samples of all deterministic maneuvers and subsequent flybys further lowered estimated delta-V
“Let Me Do What I Please With It.. Don’t Decide My Identity For Me”: LGBTQ+ Youth Experiences of Social Media in Narrative Identity Development
Social media provides Lesbian Gay Bisexual Transgender Queer Plus (LGBTQ+) youth with daily access to a broader sociocultural dialogue that may shape narrative identity development. Through in-depth narrative interviews, this study sought to understand the lived experiences of 11 LGBTQ+ undergraduates (age range = 19-23) building narrative identities in the cultural context of social media and the role of social media within this process. Interviews were analyzed using an interpretative, individual analysis of personal stories. These experiences were then compared and contrasted through thematic analysis to identify four shared narrative themes. Narratives of merging safe spaces highlight how LGBTQ+ youth now have regular access to safe environments online/offline which facilitate more secure identity development. Narratives of external identity alignment describe social media as a tool for LGBTQ+ youth to seek out identities that match their preexisting sense of self. Narratives of multiple context-based identities encapsulate how adolescents’ identity markers are multiple and invoked in a context-dependent manner. Finally, narratives of individuality and autonomy characterize how LGBTQ+ youth perceive themselves as highly individualized members of a wider community. These findings highlight the complex role social media plays within LGBTQ+ youth identity development. The implications are discussed within
The Goldbeter-Koshland switch in the first-order region and its response to dynamic disorder
In their classical work (Proc. Natl. Acad. Sci. USA, 1981, 78:6840-6844),
Goldbeter and Koshland mathematically analyzed a reversible covalent
modification system which is highly sensitive to the concentration of
effectors. Its signal-response curve appears sigmoidal, constituting a
biochemical switch. However, the switch behavior only emerges in the
"zero-order region", i.e. when the signal molecule concentration is much lower
than that of the substrate it modifies. In this work we showed that the
switching behavior can also occur under comparable concentrations of signals
and substrates, provided that the signal molecules catalyze the modification
reaction in cooperation. We also studied the effect of dynamic disorders on the
proposed biochemical switch, in which the enzymatic reaction rates, instead of
constant, appear as stochastic functions of time. We showed that the system is
robust to dynamic disorder at bulk concentration. But if the dynamic disorder
is quasi-static, large fluctuations of the switch response behavior may be
observed at low concentrations. Such fluctuation is relevant to many biological
functions. It can be reduced by either increasing the conformation
interconversion rate of the protein, or correlating the enzymatic reaction
rates in the network.Comment: 23 pages, 4 figures, accepted by PLOS ON
What determines auditory similarity? The effect of stimulus group and methodology.
Two experiments on the internal representation of auditory stimuli compared the pairwise and grouping methodologies as means of deriving similarity judgements. A total of 45 undergraduate students participated in each experiment, judging the similarity of short auditory stimuli, using one of the methodologies. The experiments support and extend Bonebright's (1996) findings, using a further 60 stimuli. Results from both methodologies highlight the importance of category information and acoustic features, such as root mean square (RMS) power and pitch, in similarity judgements. Results showed that the grouping task is a viable alternative to the pairwise task with N > 20 sounds whilst highlighting subtle differences, such as cluster tightness, between the different task results. The grouping task is more likely to yield category information as underlying similarity judgements
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