Rapid thermal cycling of solar array blanket coupons for Space Station Freedom

The NASA Lewis Research Center has been conducting rapid thermal cycling on blanket coupons for Space Station Freedom. This testing includes two designs (8 coupons total) of the solar array. Four coupons were fabricated as part of the Photovoltaic Array Environmental Protection Program (PAEP), NAS3-25079, at Lockheed Missiles and Space Company. These coupons began cycling in early 1989 and have completed 172,000 thermal cycles. Four other coupons were fabricated a year later and included several design changes; cycling of these began in early 1990 and has reached 90,000 cycles. The objective of this testing is to demonstrate the durability or operational lifetime (15 yrs.) of the welded interconnects within a low earth orbit (LEO) thermal cycling environment. The blanket coupons, design changes, test description, status to date including performance and observed anomalies, and any insights related to the testing of these coupons are described. The description of a third design is included

Women’s Experiences with Prenatal Care: A Mixed-Methods Study Exploring the Influence of the Social Determinants of Health

Background & Purpose: Racial and ethnic disparities pervade birth outcomes in the United States and the state of Connecticut. While Connecticut’s infant mortality rate is less than the national average, rates for the state’s Black/African American and Hispanic/Latino communities exceed it. This study explored how prenatal care in Connecticut may be enhanced to address these disparities. Methods: In spring 2013, seven focus groups and two semi-structured interviews were conducted (n=47). Participants also self-administered brief surveys. Recruited by local service providers, participants were 18 or older, pregnant and/or in the first year post-partum at the time. Most self-identified as non-white. Results: Even when care was perceived as strong quality, participants perceived a lack of patient-centeredness. Participants knew the importance of prenatal care and actively prioritized it even when experiencing challenges accessing healthcare services or barriers to broader conditions needed to be healthy. Participants also reported experiencing discrimination in healthcare. Conclusions & Implications: The women esteemed providers’ clinical advice, but felt unheard in their prenatal care experiences and faced structural challenges which may be addressed by changing institutional policies and procedures

The Quantum McKay Correspondence for polyhedral singularities

Let G be a polyhedral group, namely a finite subgroup of SO(3). Nakamura's G-Hilbert scheme provides a preferred Calabi-Yau resolution Y of the polyhedral singularity C^3/G. The classical McKay correspondence describes the classical geometry of Y in terms of the representation theory of G. In this paper we describe the quantum geometry of Y in terms of R, an ADE root system associated to G. Namely, we give an explicit formula for the Gromov-Witten partition function of Y as a product over the positive roots of R. In terms of counts of BPS states (Gopakumar-Vafa invariants), our result can be stated as a correspondence: each positive root of R corresponds to one half of a genus zero BPS state. As an application, we use the crepant resolution conjecture to provide a full prediction for the orbifold Gromov-Witten invariants of [C^3/G].Comment: Introduction rewritten. Issue regarding non-uniqueness of conifold resolution clarified. Version to appear in Inventione

Non-equilibrium dynamic critical scaling of the quantum Ising chain

We solve for the time-dependent finite-size scaling functions of the 1D transverse-field Ising chain during a linear-in-time ramp of the field through the quantum critical point. We then simulate Mott-insulating bosons in a tilted potential, an experimentally-studied system in the same equilibrium universality class, and demonstrate that universality holds for the dynamics as well. We find qualitatively athermal features of the scaling functions, such as negative spin correlations, and show that they should be robustly observable within present cold atom experiments.Comment: 4 pages + 2 page supplemen

The Functional Consequences of Variation in Transcription Factor Binding

One goal of human genetics is to understand how the information for precise and dynamic gene expression programs is encoded in the genome. The interactions of transcription factors (TFs) with DNA regulatory elements clearly play an important role in determining gene expression outputs, yet the regulatory logic underlying functional transcription factor binding is poorly understood. Many studies have focused on characterizing the genomic locations of TF binding, yet it is unclear to what extent TF binding at any specific locus has functional consequences with respect to gene expression output. To evaluate the context of functional TF binding we knocked down 59 TFs and chromatin modifiers in one HapMap lymphoblastoid cell line. We then identified genes whose expression was affected by the knockdowns. We intersected the gene expression data with transcription factor binding data (based on ChIP-seq and DNase-seq) within 10 kb of the transcription start sites of expressed genes. This combination of data allowed us to infer functional TF binding. On average, 14.7% of genes bound by a factor were differentially expressed following the knockdown of that factor, suggesting that most interactions between TF and chromatin do not result in measurable changes in gene expression levels of putative target genes. We found that functional TF binding is enriched in regulatory elements that harbor a large number of TF binding sites, at sites with predicted higher binding affinity, and at sites that are enriched in genomic regions annotated as active enhancers.Comment: 30 pages, 6 figures (7 supplemental figures and 6 supplemental tables available upon request to [email protected]). Submitted to PLoS Genetic

Sequential primed kinases create a damage-responsive phosphodegron on Eco1.

Sister-chromatid cohesion is established during S phase when Eco1 acetylates cohesin. In budding yeast, Eco1 activity falls after S phase due to Cdk1-dependent phosphorylation, which triggers ubiquitination by SCF(Cdc4). We show here that Eco1 degradation requires the sequential actions of Cdk1 and two additional kinases, Cdc7-Dbf4 and the GSK-3 homolog Mck1. These kinases recognize motifs primed by previous phosphorylation, resulting in an ordered sequence of three phosphorylation events on Eco1. Only the latter two phosphorylation sites are spaced correctly to bind Cdc4, resulting in strict discrimination between phosphates added by Cdk1 and by Cdc7. Inhibition of Cdc7 by the DNA damage response prevents Eco1 destruction, allowing establishment of cohesion after S phase. This elaborate regulatory system, involving three independent kinases and stringent substrate selection by a ubiquitin ligase, enables robust control of cohesion establishment during normal growth and after stress

The Calculus of Proportional alpha-Derivatives

We introduce a new proportional alpha-derivative with parameter alpha in [0,1], explore its calculus properties, and give several examples of our results. We begin with an introduction to our proportional alpha-derivative and some of its basic calculus properties. We next investigate the system of alpha-lines which make up our curved yet Euclidean geometry, as well as address traditional calculus concepts such as Rolle\u27s Theorem and the Mean Value Theorem in terms of our alpha-derivative. We also introduce a new alpha-integral to be paired with our alpha-derivative, which leads to proofs of the Fundamental Theorem of Calculus Parts I and II, as applied to our formulas. Finally, we provide instructions on how to locate alpha-maximum and alpha-minimum values as they are related to our type of Euclidean geometry, including an increasing and decreasing test, concavity test, and first and second alpha-derivative tests

Outreach and identity development: New perspectives on college student persistence

pre-printCollege student persistence continues to pose challenges for higher education institutions, despite over 40 years of research. Although persistence is studied from many different angles, the majority of studies examining the causes of and cures for students' departure from college reflect the importance of engagement in the higher education environment. An innovative type of engagement is involving college students in high school outreach. This article reports on a study involving 19 college students who participated in a National Science Foundation (NSF)-funded project intended to increase the enrollment and persistence of engineering students, specifically examining how engaging in outreach activities developed participants' views of themselves as engineers. We found that outreach activities incorporated several types of engagement and that participants engaged in outreach began to develop a professional engineering identity, both of which are linked to college student persistence. The study's implications for research and practice are discussed