Narratives of Continuity and Change: Changing Logics and Institutional Work in the United States Army

Institutional theorists have recently turned to the concept of institutional work to explain how the behavior of actors in organizational fields can establish, maintain, and transform the institutional logic that prevails in the field. In this paper I focus on the role of key actors in the process of changing field-level logics. Acknowledging that prior research efforts commonly study change `in the moment\u27 and leave relatively ignored the ongoing nature of the change process, I study the institutional work of key actors in the United States Army during a period of relative stability that follows the transition from a Cold War to a post-Cold War institutional logic. Analyzing a set of official stories provided by key actors in the U.S. Army, I expose the complex and contradictory nature of the institutional work that takes place after the logic that prevails in a given field is successfully replaced with a new logic. My findings support the contention that institutional work, and not the institutional logic that prevails, is responsible for the periods of relative stability that often follow successful change processes

The magnetic Bp star 36 Lyncis, I. Magnetic and photospheric properties

This paper reports the photospheric, magnetic and circumstellar gas characteristics of the magnetic B8p star 36 Lyncis (HD 79158). Using archival data and new polarised and unpolarised high-resolution spectra, we redetermine the basic physical properties, the rotational period and the geometry of the magnetic field, and the photospheric abundances of various elements.}{Based on magnetic and spectroscopic measurements, we infer an improved rotational period of $3.83475\pm 0.00002$ d. We determine a current epoch of the longitudinal magnetic field positive extremum (HJD 2452246.033), and provide constraints on the geometry of the dipole magnetic field (i\geq 56\degr, $3210 {\rm G}\leq B_{\rm d}\leq 3930$ G, $\beta$ unconstrained). We redetermine the effective temperature and surface gravity using the optical and UV energy distributions, optical photometry and Balmer line profiles ($T_{\rm eff}=13300\pm 300$ K, $\log g=3.7-4.2$), and based on the Hipparcos parallax we redetermine the luminosity, mass, radius and true rotational speed ($L=2.54\pm 0.16 L_\odot, M=4.0\pm 0.2 M_\odot, R=3.4\pm 0.7 R_\odot, v_{\rm eq}=45-61.5$ \kms). We measure photospheric abundances for 21 elements using optical and UV spectra, and constrain the presence of vertical stratification of these elements. We perform preliminary Doppler Imaging of the surface distribution of Fe, finding that Fe is distributed in a patchy belt near the rotational equator. Most remarkably, we confirm strong variations of the H$\alpha$ line core which we interpret as due to occultations of the star by magnetically-confined circumstellar gas.Comment: Accepted by Astronomy and Astrophysic

Optimizing SNR for multi-metabolite hyperpolarized carbon-13 MRI using a hybrid flip-angle scheme

Purpose: To improve the SNR of hyperpolarized carbon-13 MRI of [1-13C]pyruvate using a multispectral variable flip angle (msVFA) scheme in which the spectral profile and flip angle vary dynamically with time. Methods: Each image acquisition in a time-resolved imaging experiment used a unique spectrally varying RF pulse shape for msVFA. Therefore, the flip angle for every acquisition was optimized for pyruvate and each of its metabolites to yield the highest SNR across the acquisition. Multispectral VFA was compared with a spectrally varying constant flip-angle excitation model through simulations and in vivo. A modified broadband chemical shift-encoded gradient-echo sequence was used for in vivo experiments on six pregnant guinea pigs. Regions of interest placed in the placentae, maternal liver, and maternal kidneys were used as areas for SNR measurement. Results: In vivo experiments showed significant increases in SNR for msVFA relative to constant flip angle of up to 250% for multiple metabolites. Conclusion: Hyperpolarized carbon-13 imaging with msVFA excitation produces improved SNR for all metabolites in organs of interest

Revisiting the Rigidly Rotating Magnetosphere model for sigma Ori E. I. Observations and Data Analysis

We have obtained 18 new high-resolution spectropolarimetric observations of the B2Vp star sigma Ori E with both the Narval and ESPaDOnS spectropolarimeters. The aim of these observations is to test, with modern data, the assumptions of the Rigidly Rotating Magnetosphere (RRM) model of Townsend & Owocki (2005), applied to the specific case of sigma Ori E by Townsend et al. (2005). This model includes a substantially offset dipole magnetic field configuration, and approximately reproduces previous observational variations in longitudinal field strength, photometric brightness, and Halpha emission. We analyze new spectroscopy, including H I, He I, C II, Si III and Fe III lines, confirming the diversity of variability in photospheric lines, as well as the double S-wave variation of circumstellar hydrogen. Using the multiline analysis method of Least-Squares Deconvolution (LSD), new, more precise longitudinal magnetic field measurements reveal a substantial variance between the shapes of the observed and RRM model time-varying field. The phase resolved Stokes V profiles of He I 5876 A and 6678 A lines are fit poorly by synthetic profiles computed from the magnetic topology assumed by Townsend et al. (2005). These results challenge the offset dipole field configuration assumed in the application of the RRM model to sigma Ori E, and indicate that future models of its magnetic field should also include complex, higher-order components.Comment: 13 pages, 8 figures. Accepted for publication in MNRA

No detection of large-scale magnetic fields at the surfaces of Am and HgMn stars

We investigate the magnetic dichotomy between Ap/Bp and other A-type stars by carrying out a deep spectropolarimetric study of Am and HgMn stars. Using the NARVAL spectropolarimeter at the Telescope Bernard Lyot (Observatoire du Pic du Midi, France), we obtained high-resolution circular polarisation spectroscopy of 12 Am stars and 3 HgMn stars. Using Least Squares Deconvolution (LSD), no magnetic field is detected in any of the 15 observed stars. Uncertaintiies as low as 0.3 G (respectively 1 G) have been reached for surface-averaged longitudinal magnetic field measurements for Am (respectively HgMn) stars. Associated with the results obtained previously for Ap/Bp stars, our study confirms the existence of a magnetic dichotomy among A-type stars. Our data demonstrate that there is at least one order of magnitude difference in field strength between Zeeman detected stars (Ap/Bp stars) and non Zeeman detected stars (Am and HgMn stars). This result confirms that the spectroscopically-defined Ap/Bp stars are the only A-type stars harbouring detectable large-scale surface magnetic fields.Comment: 6 pages, 3 figures, accepted for publication in A&

Model Based Definition: Finally, the Engineering Drawing Killer?

The Engineering drawing has stood as the universal method of translating design intent since the first standard was formalized in 1927 as BS308. Further development of national and international standards has been informed by advances in CADCAM technology and the need for transfer of complex yet unambiguous definition between organisations. The emergence of model based definition (MBD) has driven a new workflow where the engineering drawing is no longer required. Instead, the dataset includes semantic, machine readable, tolerancing of surfaces and features for integration into manufacturing and metrology procedures. Despite the advantages of MBD, it has been largely ignored in UK Higher Education. However MBD is the ideal method for teaching and learning geometrical tolerancing since it ignores the theoretically exact dimensions and housekeeping, concentrating on the functional limits. Further, it utilises the 3D workspace that students are increasingly familiar with

The magnetic field and confined wind of the O star θ1\theta^1~Orionis~C

In this paper we confirm the presence of a globally-ordered, kG-strength magnetic field in the photosphere of the young O star $\theta^1$~Orionis~C, and examine the properties of its optical line profile variations. A new series of high-resolution MuSiCoS Stokes $V$ and $I$ spectra has been acquired which samples approximately uniformly the rotational cycle of $\theta^1$~Orionis~C. Using the Least-Squares Deconvolution (LSD) multiline technique, we have succeeded in detecting variable Stokes $V$ Zeeman signatures associated with the LSD mean line profile. These signatures have been modeled to determine the magnetic field geometry. We have furthermore examined the profi le variations of lines formed in both the wind and photosphere using dynamic spectra. Based on spectrum synthesis fitting of the LSD profiles, we determine that the polar strength of the magnetic dipole component is 1150 \la B_{\rm d}\la 1800~G and that the magnetic obliquity is 27\degr \la \beta \la 68\degr, assuming i=45\pm 20\degr. The best-fit values for i=45\degr are $B_{\rm d} = 1300 \pm 150 (1\sigma)$~G and \beta = 50\degr \pm 6\degr (1\sigma). Our data confirm the previous detection of a magnetic field in this star, and furthermore demonstrate the sinusoidal variability of the longitudinal field and accurately determine the phases and intensities of the magnetic extrema. The analysis of ``photospheric'' and ``wind'' line profile variations supports previous reports of the optical spectroscopic characteristics, and provides evidence for infall of material within the magnetic equatorial plane

The component masses of the cataclysmic variable V347 Puppis

We present time-resolved spectroscopy and photometry of the double-lined eclipsing cataclysmic variable V347 Pup (=LB 1800). There is evidence of irradiation on the inner hemisphere of the secondary star, which we correct for using a model to give a secondary-star radial velocity of KR= 198 ± 5 km s−1. The rotational velocity of the secondary star in V347 Pup is found to be v sin i= 131 ± 5 km s−1 and the system inclination is i= 840 ± 23. From these parameters we obtain masses of M1= 0.63 ± 0.04 M⊙ for the white dwarf primary and M2= 0.52 ± 0.06 M⊙ for the M0.5V secondary star, giving a mass ratio of q= 0.83 ± 0.05. On the basis of the component masses, and the spectral type and radius of the secondary star in V347 Pup, we find tentative evidence for an evolved companion. V347 Pup shows many of the characteristics of the SW Sex stars, exhibiting single-peaked emission lines, high-velocity S-wave components and phase-offsets in the radial velocity curve. We find spiral arms in the accretion disc of V347 Pup and measure the disc radius to be close to the maximum allowed in a pressureless disc