757 research outputs found
Depth dependent tetragonal distortion of a GaN epilayer with an AlN interlayer on Si(111) studied by Rutherford backscattering/channeling
No full textRutherford backscattering and channeling have been used to characterize the structure of an epitaxial GaN layer grown by metal-organic chemical vapor deposition on a Si(111) substrate. Using the channeling angular scan around an off-normal <1<(2)over bar>13> axis in the {10 (1) over bar0} plane of the GaN layer, the tetragonal distortion e(T), which is caused by the elastic strain in the epilayer, was determined. Moreover, the depth dependence of the e(T) was obtained by this technique. Our results show that the e(T) of the GaN epilayer is drastically reduced from 0.41% to 0.22% by inserting a 20 nm AlN interlayer. A fully relaxed (e(T)=0) GaN layer with a thickness of <1.5 mu m is expected. (C) 2014 Elsevier B.V. All rights reserved.Materials Science, MultidisciplinaryMaterials Science, Coatings & FilmsPhysics, AppliedPhysics, Condensed MatterSCI(E)[email protected]
'The Cloud of Unknowing': its inheritance and its inheritors
No full textThe thesis attempts a portrait of The Cloud in the context of its
position in the history of Christian mysticism. That the
anonymous work owed much to spiritual writers of the preceding
twelve hundred years is not debatable; what it owed maybe
slightly less obvious. The Cloud is essentially a work of
Dionysian mysticism, and various writers within that tradition
who may have influenced or affected the teaching of The Cloud are
examined. At the same time, however, the anonymous writer owes
much to the western tradition of Augustinian theology, and the
role of this, complementary to the Dionysian mysticism, is also
considered. In Chapter II we look at the theological doctrine
underlying the mystical doctrine of the Cloud corpus. Chapter
III has two major parts, both concerned with the influence of
The Cloud on the subsequent development of spiritual writing in
England. The first considers the relationship with Walter
Hilton. The second examines aspects of Puritan thought which may
indicate that the influence of The Cloud, after the Reformation,
was not restricted to Catholic thought
Modelling the magnetic activity and filtering radial velocity curves of young Suns : the weak-line T Tauri star LkCa 4
No full textSGG acknowledges support from the Science & Technology Facilities Council (STFC) via an Ernest Rutherford Fellowship [ST/J003255/1]. SHPA acknowledges financial support from CNPq, CAPES and Fapemig.We report results of a spectropolarimetric and photometric monitoring of the weak-line T Tauri star LkCa 4 within the Magnetic Topologies of Young Stars and the Survival of close-in giant Exoplanets (MaTYSSE) programme, involving ESPaDOnS at the Canada–France–Hawaii Telescope. Despite an age of only 2 Myr and a similarity with prototypical classical T Tauri stars, LkCa 4 shows no evidence for accretion and probes an interesting transition stage for star and planet formation. Large profile distortions and Zeeman signatures are detected in the unpolarized and circularly polarized lines of LkCa 4 using Least-Squares Deconvolution (LSD), indicating the presence of brightness inhomogeneities and magnetic fields at the surface of LkCa 4. Using tomographic imaging, we reconstruct brightness and magnetic maps of LkCa 4 from sets of unpolarized and circularly polarized LSD profiles. The large-scale field is strong and mainly axisymmetric, featuring a ≃2 kG poloidal component and a ≃1 kG toroidal component encircling the star at equatorial latitudes – the latter making LkCa 4 markedly different from classical T Tauri stars of similar mass and age. The brightness map includes a dark spot overlapping the magnetic pole and a bright region at mid-latitudes – providing a good match to the contemporaneous photometry. We also find that differential rotation at the surface of LkCa 4 is small, typically ≃5.5 times weaker than that of the Sun, and compatible with solid-body rotation. Using our tomographic modelling, we are able to filter out the activity jitter in the radial velocity curve of LkCa 4 (of full amplitude 4.3 km s−1) down to an rms precision of 0.055 km s−1. Looking for hot Jupiters around young Sun-like stars thus appears feasible, even though we find no evidence for such planets around LkCa 4.Peer reviewe
Magnetic activity and hot Jupiters of young Suns : the weak-line T Tauri stars V819 Tau and V830 Tau
No full textSGG acknowledges support from the Science & Technology Facilities Council (STFC) via an Ernest Rutherford Fellowship [ST/J003255/1]. SHPA acknowledges financial support from CNPq, CAPES and Fapemig. AAV acknowledges support from the Swiss National Science Foundation (SNSF) via the allocation of an Ambizione Followship. Date of Acceptance: 06/08/2015We report results of a spectropolarimetric and photometric monitoring of the weak-line T Tauri stars (wTTSs) V819 Tau and V830 Tau within the MaTYSSE (Magnetic Topologies of Young Stars and the Survival of close-ingiant Exoplanets) programme, involving the ESPaDOnS spectropolarimeter at the Canada-France-Hawaii Telescope. At ≃3 Myr, both stars dissipated their discs recently and are interesting objects for probing star and planet formation. Profile distortions and Zeeman signatures are detected in the unpolarized and circularly polarized lines, whose rotational modulation we modelled using tomographic imaging, yielding brightness and magnetic maps for both stars. We find that the large-scale magnetic fields of V819 Tau and V830 Tau are mostly poloidal and can be approximated at large radii by 350-400 G dipoles tilted at≃30° to the rotation axis. They are significantly weaker than the field of GQ Lup, an accreting classical T Tauri star (cTTS) with similar mass and age which can be used to compare the magnetic properties of wTTSs and cTTSs. The reconstructed brightness maps of both stars include cool spots and warm plages. Surface differential rotation is small, typically ≃4.4 times smaller than on the Sun, in agreement with previous results on wTTSs. Using our Doppler images to model the activity jitter and filter it out from the radial velocity(RV) curves, we obtain RV residuals with dispersions of 0.033 and 0.104km s-1 for V819 Tau and V830 Tau, respectively. RV residuals suggest that a hot Jupiter may be orbiting V830 Tau, though additional data are needed to confirm this preliminary result. We find no evidence for close-in giant planet around V819 Tau.Peer reviewe
Depth dependence of the tetragonal distortion of a GaN layer on Si(111) studied by Rutherford backscattering/channeling
No full textRutherford backscattering and channeling have been used to characterize the structure of a GaN layer grown on a Si(111) substrate. The results show that a 1.26 mum GaN epitaxial layer with a rather abrupt interface and a good crystalline quality (chi(min)=3.4%) can be grown on a Si(111) substrate. Using the channeling angular scan around an off-normal <1 (2) over bar 13> axis in the {10 (1) over bar0} plane of the GaN layer, the tetragonal distortion e(T), which is caused by the elastic strain in the epilayer, can be determined. Moreover, the depth dependence of the e(T) can be obtained using this technique. A fully relaxed (e(T)=0) GaN layer for a thickness <2.8 mum is expected. (C) 2002 American Institute of Physics.Physics, AppliedSCI(E)EI23ARTICLE224130-41328
Chas. White, author of Story of Australian bushranging ; Dr. Pechey, present at Keightly episode ... [picture] /
No full textIncludes portrait of Captain Starlight from: Robbery under arms / by Rolf Boldrewood.; Exhibited: "Bushrangers and Bandits", National Museum of Australia, June 2002 - June 2003.; Exhibited: "In the Line of Duty: Policing in Australia 1788 - 2006", Old Parliament House, August 2006 - February 2007. AuCNL. Portraits and inscriptions (top L to R): Chas. White author of Story of Australian bushranging; Dr. Pechey present at Keightly episode; Hipkiss gave Ben Hall first death wound at Billabong 5th May -65; Ver. Rev. Dr. Gibney heroic rescue at Glenrowen [Glenrowan]; Superintnt Hare author of Last of the bushrangers; Ben Hall; Lowry; Starlight; T. Clarke; Rutherford; Martin Cash Tasmanian outlaw after sentence lived a respected farmer; Const. Bracken escaped from Kellys Glenrowen [Glenrowan]; Insr Stephenson daring capture & shooting of Lowry; McKinley [McKinlay?], Burns & Day daring shooting & capture of Angel & Thurston; J. Hawthorne now a squatter Wee Waa daring capture of Dunne
Study of depth-dependent tetragonal distortion of quaternary AlInGaN epilayer by Rutherford backscattering/channeling
No full textA 240-nm thick Al(0.4)In(0.02)Ga(0.58)N layer is grown by metal organic chemical vapour deposition, with an over 1-mu m thick GaN layer used as a buffer layer on a substrate of sapphire (0001). Rutherford backscattering and channeling are used to characterize the microstructure of AlInGaN. The results show a good crystalline quality of AlInGaN (chi(min) = 1.5%) with GaN buffer layer. The channeling angular scan around an off-normal < 1 (2) over bar 13 > axis in the {10 (1) over bar0} plane of the AlInGaN layer is used to determine tetragonal distortion e(T), which is caused by the elastic strain in the AlInGaN. The resulting AlInGaN is subjected to an elastic strain at interfacial layer, and the strain decreases gradually towards the near-surface layer. It is expected that an epitaxial AlInGaN thin film with a thickness of 850 nm will be fully relaxed (e(T) = 0).Physics, MultidisciplinarySCI(E)EI中国科技核心期刊(ISTIC)中国科学引文数据库(CSCD)2ARTICLE8null1
Tetragonal distortion of InAsPSb film grown on InAs substrate studied by Rutherford backscattering/channeling and synchrotron X-ray diffraction
No full textRutherford backscattering/channeling spectrometry and synchrotron X-ray diffraction are employed to characterize the structural properties of the InAsPSb epilayer grown on the InAs substrate. The results indicate that a 975-nm thick InAs0.668P0.219Sb0.113 layer has a quite good crystalline quality (chi(min)=6.1%). The channeling angular scan around an off-normal < 1 1 1 > axis in the (0 1) plane of the sample is used to determine the tetragonal distortion e(T), which is caused by elastic strain in the layer. The results show that the InAsPSb layer is subjected to an elastic strain at the interfacial layer, and the strain decreases gradually moving towards the near-surface layer. It is expected that an epitaxial InAsPSb layer with the thickness of around 1700 nm will be fully relaxed (e(T)=0). The magnitude difference of e(T) deduced from angular scans and X-ray diffraction implies some structure (like dislocations) may play a role. (C) 2011 Elsevier B.V. All rights reserved.Physics, Condensed MatterSCI(E)EI0ARTICLE173219-322140
Depth distribution of the strain in the GaN layer with low-temperature AlN interlayer on Si(111) substrate studied by Rutherford backscattering/channeling
No full textThe depth distribution of the strain-related tetragonal distortion e(T) in the GaN epilayer with low-temperature AlN interlayer (LT-AlN IL) on Si(111) substrate is investigated by Rutherford backscattering and channeling. The samples with the LT-AlN IL of 8 and 16 nm thickness are studied, which are also compared with the sample without the LT-AlN IL. For the sample with 16-nm-thick LT-AlN IL, it is found that there exists a step-down of e(T) of about 0.1% in the strain distribution. Meanwhile, the angular scan around the normal GaN <0001> axis shows a tilt difference about 0.01degrees between the two parts of GaN separated by the LT-AlN IL, which means that these two GaN layers are partially decoupled by the AlN interlayer. However, for the sample with 8-nm-thick LT-AlN IL, neither step-down of e(T) nor the decoupling phenomenon is found. The 0.01degrees decoupled angle in the sample with 16-nm-thick LT-AlN IL confirms the relaxation of the LT-AlN IL. Thus the step-down of e(T) should result from the compressive strain compensation brought by the relaxed AlN interlayer. It is concluded that the strain compensation effect will occur only when the thickness of the LT-AlN IL is beyond a critical thickness. (C) 2004 American Institute of Physics.Physics, AppliedSCI(E)EI7ARTICLE235562-55648
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