Analysis and test evaluation of the dynamic response and stability of three advanced turboprop models

Results of dynamic response and stability wind tunnel tests of three 62.2 cm (24.5 in) diameter models of the Prop-Fan, advanced turboprop, are presented. Measurements of dynamic response were made with the rotors mounted on an isolated nacelle, with varying tilt for nonuniform inflow. One model was also tested using a semi-span wing and fuselage configuration for response to realistic aircraft inflow. Stability tests were performed using tunnel turbulence or a nitrogen jet for excitation. Measurements are compared with predictions made using beam analysis methods for the model with straight blades, and finite element analysis methods for the models with swept blades. Correlations between measured and predicted rotating blade natural frequencies for all the models are very good. The IP dynamic response of the straight blade model is reasonably well predicted. The IP response of the swept blades is underpredicted and the wing induced response of the straight blade is overpredicted. Two models did not flutter, as predicted. One swept blade model encountered an instability at a higher RPM than predicted, showing predictions to be conservative

Tunable Cavity Optomechanics with Ultracold Atoms

We present an atom-chip-based realization of quantum cavity optomechanics with cold atoms localized within a Fabry-Perot cavity. Effective sub-wavelength positioning of the atomic ensemble allows for tuning the linear and quadratic optomechanical coupling parameters, varying the sensitivity to the displacement and strain of a compressible gaseous cantilever. We observe effects of such tuning on cavity optical nonlinearity and optomechanical frequency shifts, providing their first characterization in the quadratic-coupling regime.Comment: 4 pages, 5 figure

Modal expansions and non-perturbative quantum field theory in Minkowski space

We introduce a spectral approach to non-perturbative field theory within the periodic field formalism. As an example we calculate the real and imaginary parts of the propagator in 1+1 dimensional phi^4 theory, identifying both one-particle and multi-particle contributions. We discuss the computational limits of existing diagonalization algorithms and suggest new quasi-sparse eigenvector methods to handle very large Fock spaces and higher dimensional field theories.Comment: new material added, 12 pages, 6 figure

Comparison of in situ and columnar aerosol spectral measurements during TexAQS-GoMACCS 2006: testing parameterizations for estimating aerosol fine mode properties

During the 2006 Texas Air Quality Study and Gulf of Mexico Atmospheric Composition and Climate Study (TexAQS-GoMACCS 2006), the optical, chemical and microphysical properties of atmospheric aerosols were measured on multiple mobile platforms and at ground based stations. In situ measurements of the aerosol light extinction coefficient (σ<sub>ep</sub>) were performed by two multi-wavelength cavity ring-down (CRD) instruments, one located on board the NOAA R/V <i>Ronald H. Brown</i> (RHB) and the other located at the University of Houston, Moody Tower (UHMT). An AERONET sunphotometer was also located at the UHMT to measure the columnar aerosol optical depth (AOD). The σ<sub>ep</sub> data were used to extract the extinction Ångström exponent (å<sub>ep</sub>), a measure of the wavelength dependence of σ<sub>ep</sub>. There was general agreement between the å<sub>ep</sub> (and to a lesser degree σ<sub>ep</sub>) measurements by the two spatially separated CRD instruments during multi-day periods, suggesting a regional scale consistency of the sampled aerosols. Two spectral models are applied to the σ<sub>ep</sub> and AOD data to extract the fine mode fraction of extinction (η) and the fine mode effective radius (<i>R</i><sub>eff,f</sub>). These two parameters are robust measures of the fine mode contribution to total extinction and the fine mode size distribution, respectively. The results of the analysis are compared to <i>R</i><sub>eff,f</sub> values extracted using AERONET V2 retrievals and calculated from in situ particle size measurements on the RHB and at UHMT. During a time period when fine mode aerosols dominated the extinction over a large area extending from Houston/Galveston Bay and out into the Gulf of Mexico, the various methods for obtaining <i>R</i><sub>eff,f</sub> agree qualitatively (showing the same temporal trend) and quantitatively (pooled standard deviation = 28 nm)

The Pictor technique: exploring experiences of collaborative working from the perspectives of generalist and specialist nurses

Interviews are widely used in qualitative research, and can take many different forms (see King and Horrocks, 2010). In this chapter, we will introduce a particular visual tool developed by the authors and colleagues for use in research interviews: the Pictor technique (e.g. King, Bravington, Brooks et al. 2013). The technique requires research participants to construct a ‘Pictor chart’ - a visual representation depicting their role and their work - which the researcher and participant can then use as a basis to explore potentially complex experiences in a research interview setting. We will present here an example from our own applied research to demonstrate how we have used Pictor in research interviews

Magnetoresistance and magnetic breakdown in the quasi-two-dimensional conductors (BEDT-TTF)2_2MHg(SCN)4_4[M=K,Rb,Tl]

The magnetic field dependence of the resistance of (BEDT-TTF)$_2$MHg(SCN)$_4$[M=K,Rb,Tl] in the density-wave phase is explained in terms of a simple model involving magnetic breakdown and a reconstructed Fermi surface. The theory is compared to measurements in pulsed magnetic fields up to 51 T. The value implied for the scattering time is consistent with independent determinations. The energy gap associated with the density-wave phase is deduced from the magnetic breakdown field. Our results have important implications for the phase diagram.Comment: 5 pages, RevTeX + epsf, 3 figures. To appear in Physical Review B, Rapid Communications, September 15, 199

Pluralism in qualitative research: the impact of different researchers and qualitative approaches on the analysis of qualitative data.

Qualitative approaches to research in psychology and the social sciences are increasingly used. The variety of approaches incorporates different epistemologies, theoretical traditions and practices with associated analysis techniques spanning a range of theoretical and empirical frameworks. Despite the increase in mixed method approaches it is unusual for qualitative methods to be used in combination with each other. The Pluralism in Qualitative Research project (PQR) was developed in order to investigate the benefits and creative tensions of integrating diverse qualitative approaches. Amongst other objectives it seeks to interrogate the contributions and impact of researchers and methods on data analysis. The paper presents our pluralistic analysis of a single semi-structured interview transcript. Analyses were carried out by different researchers using grounded theory, Foucauldian discourse analysis, interpretative phenomenological analysis and narrative analysis. We discuss the variation and agreement in the analysis of the data. The implications of the findings on the conduct, writing and presentation of qualitative research are discussed

CD4+ T-cell responses to Epstein-Barr virus (EBV) latent-cycle antigens and the recognition of EBV-transformed lymphoblastoid cell lines

There is considerable interest in the potential of Epstein-Barr virus (EBV) latent antigen-specific CD4$^+$ T cells to act as direct effectors controlling EBV-induced B lymphoproliferations. Such activity would require direct CD4$^+$ T-cell recognition of latently infected cells through epitopes derived from endogenously expressed viral proteins and presented on the target cell surface in association with HLA class II molecules. It is therefore important to know how often these conditions are met. Here we provide CD4$^+$ epitope maps for four EBV nuclear antigens, EBNA1, -2, -3A, and -3C, and establish CD4$^+$ T-cell clones against 12 representative epitopes. For each epitope we identify the relevant HLA class II restricting allele and determine the efficiency with which epitope-specific effectors recognize the autologous EBV-transformed B-lymphoblastoid cell line (LCL). The level of recognition measured by gamma interferon release was consistent among clones to the same epitope but varied between epitopes, with values ranging from 0 to 35% of the maximum seen against the epitope peptide-loaded LCL. These epitope-specific differences, also apparent in short-term cytotoxicity and longer-term outgrowth assays on LCL targets, did not relate to the identity of the source antigen and could not be explained by the different functional avidities of the CD4$^+$ clones; rather, they appeared to reflect different levels of epitope display at the LCL surface. Thus, while CD4$^+$ T-cell responses are detectable against many epitopes in EBV latent proteins, only a minority of these responses are likely to have therapeutic potential as effectors directly recognizing latently infected target cells

On vertex coloring without monochromatic triangles

We study a certain relaxation of the classic vertex coloring problem, namely, a coloring of vertices of undirected, simple graphs, such that there are no monochromatic triangles. We give the first classification of the problem in terms of classic and parametrized algorithms. Several computational complexity results are also presented, which improve on the previous results found in the literature. We propose the new structural parameter for undirected, simple graphs -- the triangle-free chromatic number $\chi_3$. We bound $\chi_3$ by other known structural parameters. We also present two classes of graphs with interesting coloring properties, that play pivotal role in proving useful observation about our problem. We give/ask several conjectures/questions throughout this paper to encourage new research in the area of graph coloring.Comment: Extended abstrac

Correlation between Fermi surface transformations and superconductivity in the electron-doped high-TcT_c superconductor Nd2−x_{2-x}Cex_xCuO4_4

Two critical points have been revealed in the normal-state phase diagram of the electron-doped cuprate superconductor Nd$_{2-x}$Ce$_x$CuO$_4$ by exploring the Fermi surface properties of high quality single crystals by high-field magnetotransport. First, the quantitative analysis of the Shubnikov-de Haas effect shows that the weak superlattice potential responsible for the Fermi surface reconstruction in the overdoped regime extrapolates to zero at the doping level $x_c = 0.175$ corresponding to the onset of superconductivity. Second, the high-field Hall coefficient exhibits a sharp drop right below optimal doping $x_{\mathrm{opt}} = 0.145$ where the superconducting transition temperature is maximum. This drop is most likely caused by the onset of long-range antiferromagnetic ordering. Thus, the superconducting dome appears to be pinned by two critical points to the normal state phase diagram.Comment: 9 pages; 7 figures; 1 tabl