The Effects of Off-Design Conditions on the Laminar-To-Turbulent Transition Location on a Slotted, Natural-Laminar-Flow Airfoil

The National Aeronautics and Space Administration (NASA) Aeronautics Research Mission Directorate (ARMD) vision for aeronautical research has defined the goal of creating an ultra-efficient subsonic transport flight vehicle. In order to create such a vehicle, the Advanced Aerodynamic Design Center for Ultra-Efficient Vehicles was established. This center is developing a new airfoil capable of maintaining laminar flow. At Texas A&M’s Computational Stability and Transition Laboratory, I am working to define the allowable sweep and twist for a new slotted, natural-laminar-flow (SNLF) airfoil, the S207. Setting the limits for these sweep and twist parameters will allow for proper implementation into Boeing’s subsonic ultra green aircraft configuration. The goal of this thesis is to identity the maximum sweep angle for which the crossflow instability does not negate the benefits of the natural-laminar-flow (NLF) design of the S207 airfoil, for a range of angles of attack. To determine this angle, the amplification of all expected disturbances is calculated using the Linear Parabolized Stability Equations (LPSE) on a multitude of sweep angles. In addition to sweep, the effects of angle of attack variation are also examined. For sweep angles ≥ 20◦ and cl ≈ 0.65, crossflow disturbances exceed their critical N-factor value of 5, and therefore crossflow is presumed to onset transition. Lowering the sweep angle to Λ = 15◦ and considering an angle of attack variation, the crossflow N-factors reach 4.6 units. This is below the critical value, but does not allow for much margin of error. Additionally, this critical value does not account for any interaction between the mechanisms, which lowers the N-factor necessary to induce transition. Therefore, a reduced sweep angle of 12.5◦ is analyzed. For a 12.5◦ sweep angle, the maximum N-factors achieved are well below the critical values, for all studied angles of attack. Considering the interaction between the Tollmien-Schlichting and crossflow mechanisms, flow over the 12.5◦ sweep case is still predicted to be laminar. Therefore, the crossflow instability does not appear to negate the benefits of the S207’s SNLF design for sweep angles up to and including 12.5◦ for an angle of attack range of -1.772◦ to -1.272

FoxP2 isoforms delineate spatiotemporal transcriptional networks for vocal learning in the zebra finch.

Human speech is one of the few examples of vocal learning among mammals yet ~half of avian species exhibit this ability. Its neurogenetic basis is largely unknown beyond a shared requirement for FoxP2 in both humans and zebra finches. We manipulated FoxP2 isoforms in Area X, a song-specific region of the avian striatopallidum analogous to human anterior striatum, during a critical period for song development. We delineate, for the first time, unique contributions of each isoform to vocal learning. Weighted gene coexpression network analysis of RNA-seq data revealed gene modules correlated to singing, learning, or vocal variability. Coexpression related to singing was found in juvenile and adult Area X whereas coexpression correlated to learning was unique to juveniles. The confluence of learning and singing coexpression in juvenile Area X may underscore molecular processes that drive vocal learning in young zebra finches and, by analogy, humans

Pricing European Options with a Log Student's t-Distribution: a Gosset Formula

The distribution of the returns for a stock are not well described by a normal probability density function (pdf). Student's t-distributions, which have fat tails, are known to fit the distributions of the returns. We present pricing of European call or put options using a log Student's t-distribution, which we call a Gosset approach in honour of W.S. Gosset, the author behind the nom de plume Student. The approach that we present can be used to price European options using other distributions and yields the Black-Scholes formula for returns described by a normal pdf.Comment: 12 journal pages, 9 figures and 3 tables (Submitted to Physica A

Accuracy of Medial Tibiofemoral Joint Space Palpation Among Second- Year Doctor of Physical Therapy Students Using Ultrasound Verification: An Observational Study

Background: Palpation skills are universally taught in physical therapy education programs worldwide. Accurate palpation is necessary for diagnosis and to guide interventional approaches. The primary purpose of this investigation was to measure ultrasonographic-confirmed palpation accuracy of the medial tibiofemoral joint space among second year Doctor of Physical Therapy students examining participants with characteristics representative of patients seen in clinical practice. Methods: Five second-year Doctor of Physical Therapy students served as examiners. Thirty-six participants contributed 67 knees for examination. The primary outcome was ultrasonographic-confirmed palpation accuracy, and the secondary outcomes evaluated the association between palpation accuracy and participant characteristics. Results: Pooled examiner accuracy was 39%. Chi-Square analyses revealed no association between pooled examiner palpation accuracy and BMI category (x2=1.46, p=0.48), age category (x2=0.21, p=0.65), sex (x2=1.47, p=0.23), skin tone (x2=0.06, p=0.81), or side of the examined knee (x2=0.27, p=0.61). Individual examiner palpation accuracy ranged from 14% to 75%, revealing a significant difference across examiners (x2=15.0, p=0.005). Two examiners had a combined accuracy of 64%, while the remaining 3 had a combined accuracy of 24%. Chi-Square analyses revealed no association between "successful" vs "unsuccessful" examiners and BMI category (x2=3.54, p=0.17), age category (x2=1.39, p=0.24), sex (x2=4.22, p=0.04), skin tone (x2=0.001, p=0.97), or side of the examined knee (x2=0.08, p=0.77). Conclusion: This investigation provides original data of ultrasonographic-confirmed palpation accuracy among secondyear Doctor of Physical Therapy students examining participants with characteristics representative of patients seen in clinical practice. Results may help inform instructional approaches and curricular design in physical therapy education

Is ‘no news’ really ‘good news’? Country visibility and FDI location choice

In choosing where to invest, firms seek out information on a set of possible locations. Information asymmetries may make country visibility particularly important in decisions to locate investment abroad. We develop a country visibility index based on international news stories in The Economist, and show that broad country visibility is at least as important in attracting foreign direct investment (FDI) as other specific investment promotion activities or proxies for information frictions. Controlling for standard gravity model determinants of FDI, we find that greater visibility of developing countries, in particular lower middle- and low-income countries, increases the investment that they receive from US multinational corporations. This is a postprint of the published article.Ye

Trade openness, income levels, and economic growth: the case of developing countries, 1970–2009.

This paper attempts to investigate the extent to which trade openness has had an impact on the levels of income and rates of growth in a sample of 115 developing countries for the period 1970–2009. Additionally, to assess whether there is an income level threshold for a country to benefit from international trade, the sample is broken down into three mutually exclusive groups of countries: low-income, lower middle-income, and upper middleincome countries. The main novelty of the paper lies on the use, on the one hand, of a new and better trade openness measure and, on the other hand, of non-stationary heterogeneous panel cointegration techniques to cope with the problem of cross-sectional dependence. The results show a positive bidirectional relationship between trade openness and income level in the long run, thus suggesting that trade openness is both a cause and a consequence of the level of income. The results for the short run, that is, the link between openness growth and economic growth, go in the same direction

Netrin-1 Peptide Is a Chemorepellent in \u3cem\u3eTetrahymena thermophila\u3c/em\u3e

Netrin-1 is a highly conserved, pleiotropic signaling molecule that can serve as a neuronal chemorepellent during vertebrate development. In vertebrates, chemorepellent signaling is mediated through the tyrosine kinase, src-1, and the tyrosine phosphatase, shp-2. Tetrahymena thermophila has been used as a model system for chemorepellent signaling because its avoidance response is easily characterized under a light microscope. Our experiments showed that netrin-1 peptide is a chemorepellent in T. thermophila at micromolar concentrations. T. thermophila adapts to netrin-1 over a time course of about 10 minutes. Netrin-adapted cells still avoid GTP, PACAP-38, and nociceptin, suggesting that netrin does not use the same signaling machinery as any of these other repellents. Avoidance of netrin-1 peptide was effectively eliminated by the addition of the tyrosine kinase inhibitor, genistein, to the assay buffer; however, immunostaining using an anti-phosphotyrosine antibody showed similar fluorescence levels in control and netrin-1 exposed cells, suggesting that tyrosine phosphorylation i s not required for signaling to occur. In addition, ELISA indicates that a netrin-like peptide is present in both whole cell extract and secreted protein obtained from Tetrahymena thermophila. Further study will be required in order to fully elucidate the signaling mechanism of netrin-1 peptide in this organism

Teacher training for political science PhD students in Europe: determinants of a tool for enhanced teaching in higher education

In this paper we examine the state of teacher training for political science PhD candidates in the European Union and make a comparison with the situation in the United States. We investigate the determinants of supply and demand of teacher training. On the supply side, we suggest that research orientation and quality assurance are factors that might enhance institutional willingness to provide training. On the demand side, we examine the influence of gender, career plans, year of study, and career status on student motivation to undergo teacher training. We find that about half of EU institutions offering PhD programs also provide some form of teacher training; this closely follows American trends. We also uncover that while research orientation has a significant positive effect on the willingness of universities to provide training in pedagogy, quality assurance does not. Of the four factors we put forward as potential influences on student demand for teacher training, only future plans have a significant effect. We argue that similarities in the situation of teacher training in the United States and the European Union make transatlantic dialogue in graduate education worthwhile. Moreover, the positive impact of teacher training on the quality of teaching and learning as well as the positive valuation of training by more than two-thirds of PhD students in our sample makes us conclude that teacher training should be more widely available