1,721,465 research outputs found
ROTC Cadets and CSM George C. Hogan
No full textJacksonville State University CSM George C. Hogan, Ranger program supervisor, and cadets Jamie Martin and Don Owens are shown outside during training.https://digitalcommons.jsu.edu/rotc_photos/1477/thumbnail.jp
Analysis of temporal length limitations in XeCl lasers
No full textExperimental observations of the development of constrictions in rare-gas halide laser discharges are reported. The onset of constriction is related to the premature termination of both spontaneous emission and laser pulses in a discharge excited XeCl laser. A mechanism is proposed to account for the onset of constriction in this laser, which may be more generally applicable to other discharge-excited devices
Anarchival Practices
Full text linkLaunch of the publication series ‘Worlding Public Cultures: The Arts and Social Innovation’, featuring Carine Zaayman (author of the premiering WPC book, Anarchival Practices: The Clanwilliam Arts Project as Re-imagining Custodianship of the Past, WPC / ICI Berlin Press 2022) in conversation with Wesley C. Hogan In this chapbook, Carine Zaayman instantiates the Anarchive as a means to reimagine how custodianship of the past is practiced. The Anarchive constellates archives and the absences that attend them in a manner that both centralizes the vastness of absence, and leaves it unreconstructed. The chapbook articulates the implications of the Anarchival constellation for scholarship and artistic practices that draw on archival material. Her argument is founded on an engagement with colonial archives that hold strands of Southern African pasts, and demonstrate its implications by examining the Clanwilliam Arts Project. Through an analysis of this case study, she argues that the Anarchive facilitates a privileging of decolonial forms of custodianship of the past that can lead to communal, co-designed and embodied forms of historical narration
Patrick C. Hogan, “How Authors’ Minds Make Stories”, New York: Cambridge University Press, 2013, 227 s. [recenzja]
Full text linkRecenzja książki: Patrick C. Hogan, "How Authors’ Minds Make Stories", New
York: Cambridge University Press, 2013, 227 s. Twarda oprawa,
publikacja anglojęzyczna
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Role of surface structural motifs on the stability and reflectance anisotropy spectra of Sb-rich GaSb(001) reconstructions
Full text linkThe structure of the technologically important-but still mostly unknown-GaSb(001)-c(2 x 6) surface reconstruction is investigated by means of ab initio simulations of reflectance anisotropy spectroscopy (RAS) and total energy calculations. A large number of reconstruction models for the GaSb(001) surface in the Sb-rich coverage regime are considered. The influence of each single surface structural motif on the RAS spectra is studied in detail, as well as their role in the surface stability with regard to application of the electron counting rule (ECR). We interpret the features of the RAS data measured for this reconstruction and suggest a new model for the c(2 x 6) phase. In this model a few Sb atoms in the second layer are randomly substituted by Ga, forming surface antisite defects. When used to fulfill the ECR, this "doping" effect considerably lowers the total energy of the long chain c(2 x 6) reconstruction model, making it competitive with the more stable short-chain (4 x 3) reconstructions. Formation of the surface antisites occurs spontaneously in the presence of dynamical negative charge fluctuations and is favored by the excellent matching between GaSb(001) and metallic Sb and by the natural softness of the Ga-Sb bonds. Calculations of the reflectance anisotropy spectra confirm that this structure is a major component of a largely disordered surface, where motifs of the stable (4 x 3) reconstructions are also present
Spontaneous Formation of Surface Antisite Defects in the Stabilization of the Sb-Rich GaSb(001) Surface
No full textThis Letter solves the long-standing puzzle [Phys. Rev. Lett. 79, 693 (1997)] of why GaSb(001) apparently violates the electron counting rule (ECR) in forming a reconstruction featuring long Sb-dimer chains, rather than the c(4 x 4) reconstruction found in all other arsenide and antimonide III-V compounds in the V-rich regime. We find that an alternative strategy, that in fact satisfies the ECR, is followed by the Sb-rich GaSb(001) surface, whereby long Sb-dimer chains are stabilized by randomly distributed subsurface Ga antisite defects. The excess of surface Sb drives the defect formation that in turn stabilizes the surface in a metastable phase. The transition to the c(4 x 4) reconstruction, where the ECR is instead satisfied through missing dimers, is therefore inhibited. Our conclusions are supported by ab initio simulations of experimental reflectance anisotropy spectra
Optical properties of GaSb(001)--c(2x6): the role of surface antisite defects
No full textWe consider the formation of surface antisite defects on a previously proposed model for the GaSb(001)-c(2 x 6) surface. Based on ab initio total energy calculations, we show how these defects stabilize the otherwise metallic surface and how their formation is driven by the excess charge associated with the Sb-rich surface conditions. The surface-sensitive optical technique of reflectance anisotropy spectroscopy is shown to be crucial for detecting the defects, and computation of spectra yields a good agreement with experiment when defects are included in the surface reconstruction
Optical Properties of real surfaces from microscopic calculations of the dielectric function of finite atomic slabs
No full textWe present a critical analysis of the procedures and approximations which are generally used to obtain the optical properties of a real solid surface starting from microscopic calculations of the dielectric function of a finite atomic slab. We show that relatively thin slabs-often the only ones accessible to modern ab initio methods-are indeed adequate provided that the proper procedure is followed for the extraction of the actual surface contributions, and we point out some possible sources of artifacts that should be avoided
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