3,068 research outputs found
The density of coronal plasma in active stellar coronae
No full textWe have analyzed high-resolution X-ray spectra of a sample of 22 active stars observed with the High Energy Transmission Grating Spectrometer on Chandra in order to investigate their coronal plasma density. Densities were investigated using the lines of the He-like ions O VII, Mg XI, and Si XIII. Si XIII lines in all stars of the sample are compatible with the low-density limit (i.e., ne1013 cm-3. Mg XI lines betray the presence of high plasma densities up to a few times 1012 cm-3 for most of the sources with higher X-ray luminosity (>~1030 ergs s-1) stars with higher LX and LX/Lbol tend to have higher densities at high temperatures. Ratios of O VII lines yield much lower densities of a few times 1010 cm-3, indicating that the ``hot'' and ``cool'' plasma resides in physically different structures. In the cases of EV Lac, HD 223460, Canopus, μ Vel, TY Pyx, and IM Peg, our results represent the first spectroscopic estimates of coronal density. No trends in density-sensitive line ratios with stellar parameters effective temperature and surface gravity were found, indicating that plasma densities are remarkably similar for stars with pressure scale heights differing by up to 3 orders of magnitude. Our findings imply remarkably compact coronal structures, especially for the hotter (~7 MK) plasma emitting the Mg XI lines characterized by the coronal surface filling factor, fMgXI, ranging from 10-4 to 10-1, while we find fOVII values from a few times 10-3 up to ~1 for the cooler (~2 MK) plasma emitting the O VII lines. We find that fOVII approaches unity at the same stellar surface X-ray flux level as characterizes solar active regions, suggesting that these stars become completely covered by active regions. At the same surface flux level, fMgXI is seen to increase more sharply with increasing surface flux. These results appear to support earlier suggestions that hot 107 K plasma in active coronae arises from flaring activity and that this flaring activity increases markedly once the stellar surface becomes covered with active regions. Comparison of our measured line fluxes with theoretical models suggests that significant residual model inaccuracies might be present and, in particular, that cascade contributions to forbidden and intercombination lines resulting from dielectronic recombination might be to blame
Rhagovelia excellentis Drake & Harris 1927
No full textRhagovelia excellentis Drake & Harris, 1927 Rhagovelia excellentis Drake & Harris, 1927: 134−135 (original description). Two paratypes are deposited in NMPC: PARATYPES (2 JJ apter.): ‘Dolores, Colo. / Aug. 15, 1925 / C. J. Drake // J [p] // PARATYPE [p] / Rhagovelia / excellentis / Drake + Harris [hw, red label]’. Current status. Junior synonym of Rhagovelia distincta Champion, 1898 (see GOULD 1931, SMITH 1988 a, POLHEMUS 1997, PADILLA- GIL & MOREIRA 2013).Published as part of Kment, Petr & Kolínová, Zdislava, 2013, Catalogue of type specimens of true bugs (Hemiptera: Heteroptera) deposited in the National Museum, Prague, Czech Republic, pp. 821-890 in Acta Entomologica Musei Nationalis Pragae 53 (2) on page 851, DOI: 10.5281/zenodo.574073
Trepobates vazquezae Drake & Hottes 1951
No full textTrepobates vazquezae Drake & Hottes, 1951 Trepobates vazquezae Drake & Hottes, 1951a: 141–143 (original description). Nine paratypes are deposited in NMPC: PARATYPES (4 JJ macr.): ‘Acapulco, Mex. / Aug. 3, 1951 / Drake & Hottes [p] // J [p] // Paratype [p] / Trepobates / vazquezae / D + H [hw, red label]’. PARATYPE (♀ apter.): ‘Acapulco, Mex. / Aug. 3, 1951 / Drake & Hottes [p] // ♀ [p] // Paratype [p] / Trepobates / vazquezae / D + H [hw, red label] // Trepobates / vazquezae / D. & H. [hw, white label with black frame submarginally]’. PARATYPES (4 ♀♀: 2♀♀ apter., 2 ♀♀ macr.):‘Acapulco, Mex./ Aug.3, 1951 / Drake & Hottes [p] // ♀ [p] // Paratype [p] / Trepobates / vazquezae / D + H [hw, red label]’. Current status. Valid species (see MATSUDA 1960; POLHEMUS & POLHEMUS 1995b, 2002).Published as part of Kment, Petr & Kolínová, Zdislava, 2013, Catalogue of type specimens of true bugs (Hemiptera: Heteroptera) deposited in the National Museum, Prague, Czech Republic, pp. 821-890 in Acta Entomologica Musei Nationalis Pragae 53 (2) on page 871, DOI: 10.5281/zenodo.574073
Microvelia arca Drake 1958
No full text<i>Microvelia arca</i> Drake, 1958 <p> <i>Microvelia arca</i> Drake, 1958: 59−60, Fig. 1 (original description).</p> <p>Three paratypes are deposited in NMPC:</p> <p>PARATYPES (2 JJ apter.): ‘Linha Facao / St. Catarina / Bras. [p] V [hw] 57 / F C. J. Drake / Coll. 1956 [p] // J [p] // PARATYPE / By C. J. Drake [p] / Microvelia / arca [hw,</p> <p>PARATYPE (1 ♀ apter.): ‘Linha Facao / St. Catarina / Bras. [p] V [hw] 57 / F. C. J. Drake / Coll. 1956 [p] // ♀ [p] // PARATYPE / By C. J. Drake [p] / Microvelia / arca [hw,</p> <p> <b>Current status.</b> Valid species, not attributed to any subgenus (2011, MOREIRA et al. 2011).</p>Published as part of <i>Kment, Petr & Kolínová, Zdislava, 2013, Catalogue of type specimens of true bugs (Hemiptera: Heteroptera) deposited in the National Museum, Prague, Czech Republic, pp. 821-890 in Acta Entomologica Musei Nationalis Pragae 53 (2)</i> on page 840, DOI: <a href="http://zenodo.org/record/5740731">10.5281/zenodo.5740731</a>
Rheumatobates clanis Drake & Harris 1932
No full textRheumatobates clanis Drake & Harris, 1932 Rheumatobates clanis Drake & Harris, 1932: 157−158 (original description). Five paratypes are deposited in NMPC: PARATYPES (2 JJ apter.): ‘Rio Grande / British Honduras / Nov. 1931 [p] // PARATYPE [p] / Rheumatobates / clanis / D+H [hw, red label] // J [p] // PARATYPUS / RHEUMATOBATES / CLANIS / Drake & Harris, 1932 / labelled: P. KMENT 2013 [p, red label]’. PARATYPE (♀ apter.): ‘Rio Grande / British Honduras / Nov. 1931 [p] // PARATYPE [p] / Rheumatobates / clanis / D+H [hw, red label] // ♀ [p]’. PARATYPES (2 ♀♀ apter.): ‘Rio Grande / British Honduras / Nov. 1931 [p] // PARATYPE [p] / Rheumatobates / clanis / D+H [hw, red label] // ♀ [p] // PARATYPUS / RHEUMATOBATES / CLANIS / Drake & Harris, 1932 / labelled: P. KMENT 2013 [p, red label]’. Current status. Valid species (see SMITH 1988b, CASTRO- VARGAS & MORALES- CASTAÑO 2011).Published as part of Kment, Petr & Kolínová, Zdislava, 2013, Catalogue of type specimens of true bugs (Hemiptera: Heteroptera) deposited in the National Museum, Prague, Czech Republic, pp. 821-890 in Acta Entomologica Musei Nationalis Pragae 53 (2) on page 868, DOI: 10.5281/zenodo.574073
Microvelia limaiana Drake 1951
No full text<i>Microvelia limaiana</i> Drake, 1951 <p> <i>Microvelia limaiana</i> Drake, 1951b: 79−80 (original description).</p> <p>Eight paratypes are deposited in NMPC:</p> <p>PARATYPE (J apter.): ‘Nova Teutonia / St. Catarina / Bras. [p] VI. 10 [hw] 1950 / Fritz Plaumann [p] / PARATYPE / By C. J. Drake [p] / Microvelia / limaiana [hw, red label] // Microvelia / limaiana / Drak. [hw, white label with black frame submarginally] // J|J|J [p]’.</p> <p>PARATYPES (5 JJ apter.): ‘Nova Teutonia / St. Catarina / Bras. [p] VI. 10 [hw] 1950 / Fritz Plaumann [p] // PARA- TYPE / By C. J. Drake [p] / Microvelia / limaiana [hw, red label] // J [p]’.</p> <p>PARATYPES (2 ♀♀: 1 ♀ apter., 1 ♀ macr.): ‘Nova Teutonia / St. Catarina / Bras. [p] VI. 10 [hw] 1950 / Fritz Plaumann [p] // PARATYPE / By C. J. Drake [p] / Microvelia / limaiana [hw, red label] // ♀ | ♀ | ♀ [p]’.</p> <p> <b>Current status.</b> Valid species, not attributed to any subgenus (see HECKMAN 2011, MOREIRA et al. 2011).</p>Published as part of <i>Kment, Petr & Kolínová, Zdislava, 2013, Catalogue of type specimens of true bugs (Hemiptera: Heteroptera) deposited in the National Museum, Prague, Czech Republic, pp. 821-890 in Acta Entomologica Musei Nationalis Pragae 53 (2)</i> on pages 844-845, DOI: <a href="http://zenodo.org/record/5740731">10.5281/zenodo.5740731</a>
Bare quark stars or naked neutron stars? The case of RX J1856.5-3754
No full textIn a cool neutron star (T less than or similar to 10(6) K) endowed with a rather highmagnetic field (B greater than or similar to 10(13) G), a phase transition may occur in the outermost layers. As a consequence, the neutron star becomes "bare,'' i.e., no gaseous atmosphere sits on the top of the crust. The surface of a cooling, bare neutron star does not necessarily emit a blackbody spectrum because the emissivity is strongly suppressed at energies below the electron plasma frequency, omega(p). Since omega(p) approximate to 1 keV under the conditions typical of the dense electron gas in the condensate, the emission from a T similar to 100 eV bare neutron star will be substantially depressed with respect to that of a perfect Planckian radiator atmost energies. Here we present a detailed analysis of the emission properties of a bare neutron star. In particular, we derive the surface emissivity for an Fe composition in a range of magnetic fields and temperatures representative of cooling isolated neutron stars, like RX J1856.5 - 3754. We find that the emitted spectrum is strongly dependent on the electron conductivity in the solid surface layers. In the cold electron gas approximation ( no electron-lattice interactions), the spectrum turns out to be a featureless depressed blackbody in the 0.1 - 2 keV band with a steeper low-energy distribution. When damping effects due to collisions between electrons and the ion lattice ( mainly due to electron-phonon interactions) are accounted for, the spectrum is more depressed at low energies and spectral features may be present, depending on the magnetic field strength. Details of the emitted spectrum are found, however, to be strongly dependent on the assumed treatment of the transition from the external vacuum to the metallic surface. The implications of our results for RX J1856.5 - 3754 and other isolated neutron stars are discussed
Nidicola Harris & Drake 1941
No full text<i>Nidicola</i> Harris & Drake, 1941 <p>(Figs. 5, 22)</p> <p> <i>Nidicola</i> Harris & Drake, 1941: 343. Type species: <i>Nidicola marginata</i> Harris & Drake, 1941.</p> <p> <b>Diagnostic characters.</b> Small size (1.6–2.1 mm), oblong to obovate. Upper surface depressed. Head wider than long; eyes small; rostrum long, surpassing mid coxae. Pronotum much wider than long; anterior margin nearly straight; lateral margins widely explanate, carinated and straight, with anterior angles rounded; basal margin concave. Polymorphic wings, from well developed to not reaching the tip of abdomen, dense and finely punctured, especially in clavus; exocorium narrow. Legs moderately long, with short and slender hairs; femora not enlarged; fore coxae with four or five long setae; male fore tibiae with row of teeth on inner surface; fossula spongiosa small. Female with ovipositor reduced. Left paramere slender, long and slightly spiraled. Ostiolar peritreme (Fig. 22) gently curved forward, basal half a little wider than apical one (a little different to peritreme drawed in DRAKE & HERRING (1964) that is parallel-sided), and apically rounded with small excentric acute tip; median sulcus arises from top of peritreme; dorsal margin of metapleura smooth.</p> <p> <b>Studied material.</b> <i>Nidicola mitra</i> Drake & Herring, 1964: <b>NICARAGUA:</b> León, V. Telica, 4-IX-1991, 2 JJ 1 ♀, Nolo – González lgt., en nido de <i>Nasutitermes</i> sp. (MACN).</p> <p> <b>Remarks</b>. This genus includes a very peculiar group of species restricted to southwestern USA, Mexico and Central America. The long setae on fore coxae are probably related to a stridulatory function.</p>Published as part of <i>Carpintero, Diego Leonardo & Dellapé, Pablo Matías, 2012, Neotropical Scolopini (Hemiptera: Heteroptera: Anthocoridae): new taxa, diagnostic characters and a key to the genera of the tribe, pp. 49-66 in Acta Entomologica Musei Nationalis Pragae 52 (1)</i> on page 59, DOI: <a href="http://zenodo.org/record/5330417">10.5281/zenodo.5330417</a>
High-Resolution X-Ray Spectroscopy of the Post-T Tauri Star PZ Telescopii
No full textWe present an analysis of the Chandra High Energy Transmission Grating Spectrometer observation of the rapidly rotating (Prot=0.94days) post-T Tauri (~20 Myr old) star PZ Telescopii, in the Tucana association. Using two different methods, we have derived the coronal emission measure distribution EM(T) and chemical abundances. The EM(T) peaks at logT=6.9 and exhibits a significant emission measure at temperatures logT>7. The coronal abundances are generally ~0.5 times the solar photospheric values, which are presumed fairly representative of the composition of the underlying star. A minimum in abundance is seen at a first ionization potential (FIP) of 7-8 eV, with evidence for higher abundances at both lower and higher FIP, similar to patterns seen in other active stars. From an analysis of the He-like triplet of Mg XI, we have estimated electron densities of ~10^12-10^13 cm^-3. All the coronal properties found for PZ Tel are much more similar to those of AB Dor, which is slightly older than PZ Tel, than to those of the younger T Tauri star TW Hya. These results support earlier conclusions that the soft X-ray emission of TW Hya is likely dominated by accretion activity rather than by a magnetically heated corona. Our results also suggest that the coronae of pre-main-sequence stars rapidly become similar to those of older active main-sequence stars soon after the accretion stage has ended
The vanishing author in computer-generated works: a critical analysis of recent Australian case law
No full textAbstract
The use of software is ubiquitous in the creation of many copyright works, yet the requirement in copyright law that every work have a human author who engages in independent intellectual effort means that its use may prevent copyright subsistence. Several recent Australian cases have refocused attention on authorship as an essential criterion of copyright subsistence, and these cases suggest that much computer-produced output may be authorless and thus lack copyright protection. This article, the first in a two-part series, analyses how each case deals with the question of authorship of computer-produced works and why the use of software diminishes copyright protection for a significant number of computer-generated works. The article critiques the application of conventional notions of human authorship developed in the pre-computer age to modern productions and suggests alternative approaches to authorship that satisfy both the major objectives of copyright policy and the need to adapt to the computer age. The article argues that, without a broader judicial approach to authorship of computer-generated works, Parliament must remedy the lacuna in protection for these ‘authorless’ works. Possible solutions for reform are suggested. In a forthcoming article, the author comprehensively examines those reform proposals
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