Self-Similar Collapse Solutions for Cylindrical Cloud Geometries and Dynamic Equations of State

A self-similar formalism for the study of the gravitational collapse of molecular gas provides an important theoretical framework from which to explore the dynamics of star formation. Motivated by the presence of elongated and filamentary structures observed in giant molecular clouds, we build upon the existing body of work on cylindrical self-similar collapse flows by including dynamic equations of state that are different from the effective equation of state that produces the initial density distribution. We focus primarily on the collapse of initial states for which the gas is at rest and everywhere overdense from its corresponding hydrostatic equilibrium profile by a factor $\Lambda$, and apply our results toward the analysis of star formation within dense, elongated molecular cores. An important aspect of this work is the determination of the mass infall rates over a range of the parameters which define the overall state of the gas -- the overdensity parameter $\Lambda$, the index $\Gamma$ of the static equation of state, and the index $\gamma$ of the dynamic equation of state. While most of the parameter space explored in this work leads to solutions for which the underlying equations do not become singular, we do include a discussion on how to treat cases for which solutions pass smoothly through the singular surface. In addition, we also present a different class of collapse solutions for the special case $\gamma = 1$.Comment: Accepted for publication to PAS

Comprehensive Solution Structure Analysis of DNA Duplexes Containing Chemical Base Alterations

Most types of chemical modifications of DNA bases are endogenous processes which are sensitive to the intracellular conditions. For example, the enzymatically catalyzed methylation of canonical cytosine to 5-methylcytosine (5metC) is a key form of epigenetic regulation of gene expression patterns. This modification is catalyzed and controlled by DNA methyltransferases (DNMTs). Perturbed rates of enzymatic DNA methylation leads to hyper- or hypo-methylation, both of which are a common initiating step in several forms of cancer. In addition to epigenetics, DNA bases can be chemically altered, or damaged, in response to reactive oxygen species (ROS). The oxidation of DNA by ROS can lead to formation of various types of adducts, with 8-oxoguanine (oxoG) being one of the most prolific and toxic. oxoG is a deleterious modification which has been linked to cancer and neurological disorders. The first step in oxoG damage repair, oxoG glycosylase (hOGG1) recognizes and excises the oxidized base. Oxidation of guanine and methylation of cytosine can occur simultaneously within CpG sites. Moreover, in these sites the both enzymology of oxoG repair is compromised by the adjacent 5metC, and the enzymatic methylation of cytosine is altered by oxoG. This manuscript describes the structural study of the DNA substrates where oxoG and 5metC modifications are clustered in a CpG site to aid in the understanding of the enzymatic effects of such clustering. The NMR solution structure is shown of six of these proposed duplex DNA samples, two with a single oxidation, two with a single methylation, one sample with a fully methylated CpG site and a modified sample with both oxoG and 5metC occurring on opposing strands in one single base pair. No global structural changes are reported amongst these structures, with all of these structures featuring elements of right-handed A/B DNA. One local structural change was observed in all samples with oxoG, namely that oxoG causes the BII backbone conformation 3\u27 of the modification site. This BII backbone conformation may be the link between these modifications and lower enzymatic activity, as both hOGG1 and DNMT1 make direct contact with the 3\u27 backbone following an oxoG

Jodi Nunnari: Keeping an eye on mitochondrial inheritance

Nunnari is using cutting-edge microscopy techniques to explore mutations affecting mitochondrial fusion and fission in living cells and whole organisms

Small Airframe Manufacturer's Icing Perspective

This viewgraph presentation describes the icing effects, risk mitigation practices, and icing certifications for various Cessna small aircraft models. NASA's role in the development of simulation tools for icing certifications is also discussed

A mitochondrial-focused genetic interaction map reveals a scaffold-like complex required for inner membrane organization in mitochondria.

To broadly explore mitochondrial structure and function as well as the communication of mitochondria with other cellular pathways, we constructed a quantitative, high-density genetic interaction map (the MITO-MAP) in Saccharomyces cerevisiae. The MITO-MAP provides a comprehensive view of mitochondrial function including insights into the activity of uncharacterized mitochondrial proteins and the functional connection between mitochondria and the ER. The MITO-MAP also reveals a large inner membrane-associated complex, which we term MitOS for mitochondrial organizing structure, comprised of Fcj1/Mitofilin, a conserved inner membrane protein, and five additional components. MitOS physically and functionally interacts with both outer and inner membrane components and localizes to extended structures that wrap around the inner membrane. We show that MitOS acts in concert with ATP synthase dimers to organize the inner membrane and promote normal mitochondrial morphology. We propose that MitOS acts as a conserved mitochondrial skeletal structure that differentiates regions of the inner membrane to establish the normal internal architecture of mitochondria

From Napkin to Orbit in 9 Months; The TechEdSat Spacecraft Mission

The TechEdSat spacecraft mission saw one of the fastest turn around times for concept through launch of a CubeSat. On 26 October 2011, John Hines sketched on a brown paper napkin the outline for which components would be in this 1U CubeSat, and how they would be stacked; 269 days later that spacecraft launched from Tanegashima Space Center aboard the HTV-3 ISS resupply mission, with a total development time of only eight months. TechEdSat was among the first of five CubeSats deployed from the ISS. The goals of the TechEdSat mission were to explore the use of the Space Plug-n-Play Architecture (SPA) in a CubeSat, and to evaluate Commercial Off The Shelf (COTS) space-to-space communication solutions. TechEdSat featured an array of processors from AC Microtec including four NanoRTU's and the RTULite main processor, all communicating using the SPA-1 protocol. TechEdSat featured two primary payloads: an Iridium 9602 Modem, and a Quake Global Q1000 OrbComm modem. After a successful deployment on 4 October 2012 from the ISS, over 2000 packets of 122 bytes each (250 kB total) were received in the first four months of the mission. In this paper we discuss the challenges to rapid CubeSat development, the experience of having a CubeSat approved for deployment from the ISS, the ongoing results of the mission and lessons learned

Mitochondrial outer and inner membrane fusion requires a modified carrier protein

In yeast, three proteins are essential for mitochondrial fusion. Fzo1 and Mgm1 are conserved guanosine triphosphatases that reside in the outer and inner membranes, respectively. At each membrane, these conserved proteins are required for the distinct steps of membrane tethering and lipid mixing. The third essential component is Ugo1, an outer membrane protein in the mitochondrial transport protein family. We show that Ugo1 is a modified member of this family, containing three transmembrane domains and existing as a dimer, a structure that is critical for the fusion function of Ugo1. Our functional analysis of Ugo1 indicates that it is required distinctly for both outer and inner membrane fusion after membrane tethering, indicating that it operates at the lipid-mixing step of fusion. This role is distinct from the fusion dynamin-related proteins and thus demonstrates that at each membrane, a single fusion protein is not sufficient to drive the lipid-mixing step, but instead, this step requires a more complex assembly of proteins

Coassembly of Mgm1 isoforms requires cardiolipin and mediates mitochondrial inner membrane fusion

The soluble and membrane-anchored isoforms of Mgm1 are only active when they work together (in trans)