4,228 research outputs found
National Security Space Launch
The United States Space Forceās National Security Space Launch (NSSL) program, formerly known as the Evolved Expendable Launch Vehicle (EELV) program, was first established in 1994 by President William J. Clintonās National Space Transportation Policy. The policy assigned the responsibility for expendable launch vehicles to the Department of Defense (DoD), with the goals of lowering launch costs and ensuring national security access to space. As such, the United States Air Force Space and Missile Systems Center (SMC) started the EELV program to acquire more affordable and reliable launch capability for valuable U.S. military satellites, such as national reconnaissance satellites that cost billions per satellite. In March 2019, the program name was changed from EELV to NSSL, which reflected several important features: 1.) The emphasis on āassured access to space,ā 2.) transition from the Russian-made RD-180 rocket engine used on the Atlas V to a US-sourced engine (now scheduled to be complete by 2022), 3.) adaptation to manifest changes (such as enabling satellite swaps and return of manifest to normal operations both within 12 months of a need or an anomaly), and 4.) potential use of reusable launch vehicles. As of August 2019, Blue Origin, Northrop Grumman Innovation Systems, SpaceX, and United Launch Alliance (ULA) have all submitted proposals. From these, the U.S. Air Force will be selecting two companies to fulfill approximately 34 launches over a period of five years, beginning in 2022.
This paper will therefore first examine the objectives for the NSSL as presented in the 2017 National Security Strategy, Fiscal Year 2019, Fiscal Year 2020, and Fiscal Year 2021 National Defense Authorization Acts (NDAA), and National Presidential Directive No. 40. The paper will then identify areas of potential weakness and gaps that exist in space launch programs as a whole and explore the security implications that impact the NSSL specifically. Finally, the paper will examine how the trajectory of the NSSL program could be adjusted in order to facilitate a smooth transition into new launch vehicles, while maintaining mission success, minimizing national security vulnerabilities, and clarifying the defense acquisition process.No embargoAcademic Major: EnglishAcademic Major: International Studie
Citron binds to PSD-95 at glutamatergic synapses on inhibitory neurons in the hippocampus
Synaptic NMDA-type glutamate receptors are anchored to the second of three PDZ (PSD-95/Discs large/ZO-1) domains in the postsynaptic density (PSD) protein PSD-95. Here, we report that citron, a protein target for the activated form of the small GTP-binding protein Rho, preferentially binds the third PDZ domain of PSD-95. In GABAergic neurons from the hippocampus, citron forms a complex with PSD-95 and is concentrated at the postsynaptic side of glutamatergic synapses. Citron is expressed only at low levels in glutamatergic neurons in the hippocampus and is not detectable at synapses onto these neurons. In contrast to citron, p135 SynGAP, an abundant synaptic Ras GTPase-activating protein that can bind to all three PDZ domains of PSD-95, and Ca2+/calmodulin-dependent protein kinase II (CaM kinase II) are concentrated postsynaptically at glutamatergic synapses on glutamatergic neurons. CaM kinase II is not expressed and p135 SynGAP is expressed in less than half of hippocampal GABAergic neurons. Segregation of citron into inhibitory neurons does not occur in other brain regions. For example, citron is expressed at high levels in most thalamic neurons, which are primarily glutamatergic and contain CaM kinase II. In several other brain regions, citron is present in a subset of neurons that can be either GABAergic or glutamatergic and can sometimes express CaM kinase II. Thus, in the hippocampus, signal transduction complexes associated with postsynaptic NMDA receptors are different in glutamatergic and GABAergic neurons and are specialized in a way that is specific to the hippocampus
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Me and Earl and the Adapted Girl: Learning to Write a Young Adult Adaptation
Since the late 2000s, the movie industry has experienced a boom in Young Adult (YA) book-tomovie
adaptations, from the wildly popular Twilight series to romantic drama The Fault In Our
Stars. Having been an avid YA literature reader throughout my teenaged years, I found myself
consistently disappointed with the quality of these adaptations in the way they portrayed their
source material, often feeling that the cinematic qualities of the adaptation werenāt on par with the
literary. This frustration prompted me to wonder: How would I go about writing a YA adaptation?
With this question in mind, I went on a personal discovery of what makes up my favorite literary
genre and how I would adapt it into a film. To understand the contextual and analytical background
of my question, I researched the state of the YA literature and movie industries, as well as looked at
film theory on adaptations. I then analyzed a case of what I consider to be a good YA adaptation ā
Me and Earl and the Dying Girl, a 2012 novel by Jesse Andrews and a 2015 movie directed by
Alfonso Gomez-Rejon ā to understand what qualities in particular I find important to adaptation.
In my final section, I put theory into practice by writing my own adapted screenplay based on
Please Ignore Vera Dietz, a 2010 novel by A.S. King, going on to discuss the problems I faced,
choices I made, and revelations I discovered in the writing process.Englis
A HIDDEN THEORY OF MIND IN JOUREY TO THE WEST
The essay demonstrates that āJourney to the Westā (JW) treats all Buddhist and Daoist scriptures as cannons for cultivating the mind. Since the novel explicitly states that Sun Wukong is resolved to cultivate Xuan (ē), Xuan should be interpreted as a faculty of the mind, which has never been done before. A hermeneutic reading of the novel and Dao De Jing (DDJ) under the constraint that all text are referring to minds gives rise to a tri-part model, which consists of an āemptyā mind state free of concepts, a mindful state filled with concepts, and a dualistic mind faculty that goes between the other two (Xuan). By this token, it can be established that the protagonist Tripitaka represented the āemptyā mind, while the protagonist Wukong represents the dualistic Xuan. This understanding thus makes it possible to explain the relationship between Daoism and Buddhism in JW. Without Buddhist Tripitaka, Wukong would be lost due to his desires that drive Xuan. Without Daoist Wukong, who had insight into the forms of the Way, Tripitaka would fall for distractions and misunderstandings. Thus, only when Buddhism and Daoism are combined, we can get the true Buddhist sutras. This analysis also makes it possible to understand the core debate between the southern and northern lineage of Daoism, and JWās stance on such debates
Carbon in Red Giants in Globular Clusters and Dwarf Spheroidal Galaxies
We present carbon abundances of red giants in Milky Way globular clusters and
dwarf spheroidal galaxies (dSphs). Our sample includes measurements of carbon
abundances for 154 giants in the clusters NGC 2419, M68, and M15 and 398 giants
in the dSphs Sculptor, Fornax, Ursa Minor, and Draco. This sample doubles the
number of dSph stars with measurements of [C/Fe]. The [C/Fe] ratio in the
clusters decreases with increasing luminosity above log(L/L_sun) ~= 1.6, which
can be explained by deep mixing in evolved giants. The same decrease is
observed in dSphs, but the initial [C/Fe] of the dSph giants is not uniform.
Stars in dSphs at lower metallicities have larger [C/Fe] ratios. We hypothesize
that [C/Fe] (corrected to the initial carbon abundance) declines with
increasing [Fe/H] due to the metallicity dependence of the carbon yield of
asymptotic giant branch stars and due to the increasing importance of Type Ia
supernovae at higher metallicities. We also identified 11 very carbon-rich
giants (8 previously known) in three dSphs. However, our selection biases
preclude a detailed comparison to the carbon-enhanced fraction of the Milky Way
stellar halo. Nonetheless, the stars with [C/Fe] < +1 in dSphs follow a
different [C/Fe] track with [Fe/H] than the halo stars. Specifically, [C/Fe] in
dSphs begins to decline at lower [Fe/H] than in the halo. The difference in the
metallicity of the [C/Fe] "knee" adds to the evidence from [alpha/Fe]
distributions that the progenitors of the halo had a shorter timescale for
chemical enrichment than the surviving dSphs.Comment: accepted to ApJ; 20 pages, 11 figures, 2 machine-readable table
An Exonic Splicing Enhancer within a Bidirectional Coding Sequence Regulates Alternative Splicing of an Antisense mRNA
The discovery of increasing numbers of genes with overlapping sequences highlights the problem of expression in the context of constraining regulatory elements from more than one gene. This study identifies regulatory sequences encompassed within two genes that overlap in an antisense orientation at their 3ā ends. The genes encode the Ī±-thyroid hormone receptor gene (TRĪ± or NR1A1) and Rev-erbĪ± (NR1D1). In mammals TRĪ± pre-mRNAs are alternatively spliced to yield mRNAs encoding functionally antagonistic proteins: TRĪ±1, an authentic thyroid hormone receptor; and TRĪ±2, a non-hormone-binding variant that acts as a repressor. TRĪ±2-specific splicing requires two regulatory elements that overlap with Rev-erbĪ± sequences. Functional mapping of these elements reveals minimal splicing enhancer elements that have evolved within the constraints of the overlapping Rev-erbĪ± sequence. These results provide insight into the evolution of regulatory elements within the context of bidirectional coding sequences. They also demonstrate the ability of the genetic code to accommodate multiple layers of information within a given sequence, an important property of the code recently suggested on theoretical grounds
Stress Resistance Screen in a Human Primary Cell Line Identifies Small Molecules That Affect Aging Pathways and Extend Caenorhabditis elegans' Lifespan.
Increased resistance to environmental stress at the cellular level is correlated with the longevity of long-lived mutants and wild-animal species. Moreover, in experimental organisms, screens for increased stress resistance have yielded mutants that are long-lived. To find entry points for small molecules that might extend healthy longevity in humans, we screened ā¼100,000 small molecules in a human primary-fibroblast cell line and identified a set that increased oxidative-stress resistance. Some of the hits fell into structurally related chemical groups, suggesting that they may act on common targets. Two small molecules increased C. elegans' stress resistance, and at least 9 extended their lifespan by ā¼10-50%. We further evaluated a chalcone that produced relatively large effects on lifespan and were able to implicate the activity of two, stress-response regulators, NRF2/skn-1 and SESN/sesn-1, in its mechanism of action. Our findings suggest that screening for increased stress resistance in human cells can enrich for compounds with promising pro-longevity effects. Further characterization of these compounds may reveal new ways to extend healthy human lifespan
Resonant Scattering of Surface Plasmon Polaritons by Dressed Quantum Dots
The resonant scattering of surface plasmon-polariton waves by embedded
semiconductor quantum dots above the dielectric/metal interface is explored in
the strong-coupling regime. In contrast to non-resonant scattering by a
localized dielectric surface defect, a strong resonant peak in the scattering
field spectrum is predicted and accompanied by two side valleys. The peak
height depends nonlinearly on the amplitude of surface plasmon-polariton waves,
reflecting the feedback dynamics from a photon-dressed electron-hole plasma
inside the quantum dots. This unique behavior in the scattering field peak
strength is correlated with the occurrence of a resonant dip in the absorption
spectrum of surface plasmon-polariton waves due to interband photon-dressing
effect. Our result on the scattering of surface plasmon-polariton waves may be
experimentally observable and applied to spatially selective illumination and
imaging of individual molecules.Comment: 15 pages, 3 figure
Controlling quantum-dot light absorption and emission by a surface-plasmon field
The possibility for controlling the probe-field optical gain and absorption
switching and photon conversion by a surface-plasmon-polariton near field is
explored for a quantum dot above the surface of a metal. In contrast to the
linear response in the weak-coupling regime, the calculated spectra show an
induced optical gain and a triply-split spontaneous emission peak resulting
from the interference between the surface-plasmon field and the probe or
self-emitted light field in such a strongly-coupled nonlinear system. Our
result on the control of the mediated photon-photon interaction, very similar
to the `gate' control in an optical transistor, may be experimentally
observable and applied to ultra-fast intrachip/interchip optical interconnects,
improvement in the performance of fiber-optic communication networks and
developments of optical digital computers and quantum communications.Comment: 7 pages, 15 figure
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