Study of indicial aerodynamic forces of multistage space vehicle systems. Volume 1 - Application of theory to basic geometries and to the Saturn 5 Final report, 28 Jun. 1967 - 27 Sep. 1968

Potential theory for determining aerodynamic forces of axisymmetric vehicles and Saturn

Evolutionary History and Biological Regulation of CD93

CD93 is a transmembrane C-type lectin expressed on myeloid, endothelial, and B cells. First identified as a developmental B cell marker and a phagocytic C1q receptor, little is known about the role and mechanism of CD93 in efferocytosis (the phagocytosis of apoptotic cells). CD93 knockout mice develop chronic inflammatory diseases characterized by a lack of efferocytosis such as atherosclerosis and a lupus-like autoimmune disease. In humans, a cleaved form of CD93 (sCD93) is elevated during inflammation and autoimmune responses, and CD93 polymorphisms are associated with enhanced susceptibility to atherosclerosis and lupus. Despite these clinical associations, no comprehensive bioinformatic analysis of CD93’s evolution and regulation have been performed to date. To this end evolutionary analysis of CD93 was performed, demonstrating that CD93 evolution is characterized by conservation but with several amino acid residues showing recent positive selection. Promoter analysis of CD93 revealed several interactions with transcription factors involved in regulation of cell growth, differentiation, and apoptosis, consistent with the known expression profile of CD93 and cell types known to engage in efferocytosis. Shedding assays using human monocytes and monocyte-like THP-1 cells show that CD93 expression is lost during monocyte-to-macrophage differentiation and in response to PMA stimulation. The cleavage was not dependent on the TAPI-2-inhibitable proteases which includes select MMPs and other proteases such as ADAMs and ACE secretases. Importantly, apoptotic cell mimics opsonized with sCD93 containing supernatants show increased phagocytic uptake, suggesting that sCD93 acts as an opsonin for apoptotic cells

Is Trading Behavior Stable Across Contexts? Evidence from Style and Multi-Style Investors

In this paper we study priming of identity within the context of inherent vs. contextual financial decision making. We use a sample of individual trading accounts in equity-style funds taken from one fund family to test the hypothesis that trading styles are inherent vs. contextual. Our sample contains investors who invest either in a growth fund, a value fund, or both. We document behavioral differences between growth fund investors and value fund investors. We find that their trades depend on past returns in different ways: growth fund investors tend towards momentum trading and value fund investors tend towards contrarian trading. These differences may be due to inherent clientele characteristics, including beliefs about market prices, specific personality traits and cognitive strategies that cause them to self-select into one or the other style. We use a sample of investors that trade in both types of funds to test this proposition. Consistent with the contextual hypothesis, we find that investors who hold both types of funds trade growth fund shares differently than value fund shares

Individual vs. Aggregate Preferences: The Case of a Small Fish in a Big Pond

We study the relationship between the risk preferences of individuals and the risk preferences of the aggregate economy. To emphasize the vast differences that can occur between individual and market preferences brought about through aggregation, we assume an economy consisting entirely of risk seekers. We show that such individuals can lead to an aggregate economy that is risk averse. The converse is also true. An aggregate economy that exhibits risk aversion does not imply an economy of individual risk averters. An economy demanding a risk premium can be formed from individuals who do not demand such compensation. Understanding the relationship between the preferences of individuals and the preferences of the aggregate economy is crucial for understanding the connection between the behavioral finance literature, which focuses on individual preferences, and the asset-pricing literature, which focuses on aggregate prices. We discuss empirical implications of these results

Development of the FITS tools package for multiple software environments

The HEASARC is developing a package of general purpose software for analyzing data files in FITS format. This paper describes the design philosophy which makes the software both machine-independent (it runs on VAXs, Suns, and DEC-stations) and software environment-independent. Currently the software can be compiled and linked to produce IRAF tasks, or alternatively, the same source code can be used to generate stand-alone tasks using one of two implementations of a user-parameter interface library. The machine independence of the software is achieved by writing the source code in ANSI standard Fortran or C, using the machine-independent FITSIO subroutine interface for all data file I/O, and using a standard user-parameter subroutine interface for all user I/O. The latter interface is based on the Fortran IRAF Parameter File interface developed at STScI. The IRAF tasks are built by linking to the IRAF implementation of this parameter interface library. Two other implementations of this parameter interface library, which have no IRAF dependencies, are now available which can be used to generate stand-alone executable tasks. These stand-alone tasks can simply be executed from the machine operating system prompt either by supplying all the task parameters on the command line or by entering the task name after which the user will be prompted for any required parameters. A first release of this FTOOLS package is now publicly available. The currently available tasks are described, along with instructions on how to obtain a copy of the software

No Evidence for Orbital Loop Currents in Charge Ordered YBa2_2Cu3_3O6+x_{6+x} from Polarized Neutron Diffraction

It has been proposed that the pseudogap state of underdoped cuprate superconductors may be due to a transition to a phase which has circulating currents within each unit cell. Here, we use polarized neutron diffraction to search for the corresponding orbital moments in two samples of underdoped YBa$_2$Cu$_3$O$_{6+x}$ with doping levels $p=0.104$ and 0.123. In contrast to some other reports using polarized neutrons, but in agreement with nuclear magnetic resonance and muon spin rotation measurements, we find no evidence for the appearance of magnetic order below 300 K. Thus, our experiment suggests that such order is not an intrinsic property of high-quality cuprate superconductor single crystals. Our results provide an upper bound for a possible orbital loop moment which depends on the pattern of currents within the unit cell. For example, for the CC-$\theta_{II}$ pattern proposed by Varma, we find that the ordered moment per current loop is less than 0.013 $\mu_B$ for $p=0.104$.Comment: Comments in arXiv:1710.08173v1 fully addresse

Closure statistics in interferometric data

Interferometric visibilities, reflecting the complex correlations between signals recorded at antennas in an interferometric array, carry information about the angular structure of a distant source. While unknown antenna gains in both amplitude and phase can prevent direct interpretation of these measurements, certain combinations of visibilities called closure phases and closure amplitudes are independent of antenna gains and provide a convenient set of robust observables. However, these closure quantities have subtle noise properties and are generally both linearly and statistically dependent. These complications have obstructed the proper use of closure quantities in interferometric analysis, and they have obscured the relationship between analysis with closure quantities and other analysis techniques such as self calibration. We review the statistics of closure quantities, noting common pitfalls that arise when approaching low signal-to-noise due to the nonlinear propagation of statistical errors. We then develop a strategy for isolating and fitting to the independent degrees of freedom captured by the closure quantities through explicit construction of linearly independent sets of quantities along with their noise covariance in the Gaussian limit, valid for moderate signal-to-noise, and we demonstrate that model fits have biased posteriors when this covariance is ignored. Finally, we introduce a unified procedure for fitting to both closure information and partially calibrated visibilities, and we demonstrate both analytically and numerically the direct equivalence of inference based on closure quantities to that based on self calibration of complex visibilities with unconstrained antenna gains.Comment: 31 pages, 17 figure

Risk Aversion and Clientele Effects

We use traded options on growth and value indices to test for clientele differences in risk preferences. Value investors appear to have exhibited a higher average level of risk aversion than growth investors for two different time periods in the late 1990’s and early 2000’s. We construct a model of time-varying clientele preferences that allows investors with different levels of risk-aversion to switch between investment styles conditional upon the evolution of returns and risk. The model makes predictions about the autocorrelations structure of measured risk parameters and also about the autocorrelation and cross-autocorrelation of fund flows by style. Empirical tests of the model provide evidence consistent with the existence of style switchers—investors who move funds between growth and value securities. We construct trading strategies in the value and growth index options markets that effectively buy risk from one clientele and sell it to another. These strategies generated modest positive returns over the period of study