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  • 1
    Electronic Resource
    Electronic Resource
    Edge-type misfit dislocations produced by thermal processing of pre-relaxed InxGa1−xAs/GaAs heterostructures (2000)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 88 (2000), S. 5975-5980 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Dislocation structures are presented for GaAs/InxGa1−xAs/GaAs heterostructures before and after thermal processing. Cathodoluminescence has allowed nondestructive examination of bulk specimens, while transmission electron microscopy has been used to establish the details of the dislocation configurations. In each as-grown specimen the thickness of the InxGa1−xAs layer was above its critical value, so 60° misfit dislocations were already present. It is shown that new pure edge, i.e., 90°, dislocations are formed at the interfaces by thermal processing at 1040 K. Their Burgers vectors are a/2〈101〉 perpendicular to their 〈010〉 directions. Although individual 90° misfit dislocations are more effective relievers of strain than 60° ones, the self-energy for an array of such dislocations is higher and hence 60° misfit dislocations form first. A model of the formation of 90° edge misfit dislocations is proposed in which the climb of vacancy-producing jogs on pre-existing 60° dislocations leaves a trailing dislocation dipole. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1315615
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  • 2
    Electronic Resource
    Electronic Resource
    Well-aligned carbon nitride nanotubes synthesized in anodic alumina by electron cyclotron resonance chemical vapor deposition (1999)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 74 (1999), S. 197-199 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Vertically aligned carbon nitride nanotubes with a uniform diameter of about 250 nm have been synthesized on a porous alumina membrane template (50–80 μm thick) in a microwave excited plasma of C2H2 and N2 using an electron cyclotron resonance chemical vapor deposition system. A negative dc bias voltage was applied to the substrate holder of graphite to promote the flow of ionic fluxes through the nanochannels of the alumina template. This allowed the physical, and subsequent chemical, absorption of species on the walls of the nanochannels that resulted in the formation of the carbon nitride nanotubes. The hollow structure and vertically aligned properties of the nanotubes have been clearly verified by field-emission scanning electron microscope images. The absorption band between 1250 and 1750 cm−1 in the Fourier transform infrared spectroscopy spectrum proves that nitrogen atoms have been incorporated into an amorphous network of carbon. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.123291
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  • 3
    Electronic Resource
    Electronic Resource
    The light curves for PG CV candidates - AAnS 34/2 (1993)225-232
    Amsterdam : Elsevier
    Chinese Astronomy and Astrophysics 17 (1993), S. 475 
    Details
    ISSN: 0275-1062
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Physics
    Type of Medium: Electronic Resource
    URL: http://linkinghub.elsevier.com/retrieve/pii/0275-1062(93)90024-J
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  • 4
    Electronic Resource
    Electronic Resource
    Calculation of the eigenvalues of pure quadrupole interaction in Mössbauer effect studies (1991)
    Springer
    Il nuovo cimento della Società Italiana di Fisica 13 (1991), S. 157-163 
    Details
    ISSN: 0392-6737
    Keywords: Mössbauer effect ; other γ-ray spectroscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Summary Two approximate formulae to calculate the eigenvalues of pure quadrupole interaction in Mössbauer effect studies have been proposed and the eigenvalue coefficients in the formulae have been given for various excited states and ground states of the nucleus with different spin. All the eigenvalues of pure quadrupole interaction between both excited state and ground state of nucleus with spinI=3/2÷9/2 and the electric-field gradient with different asymmetry parameter (η=0÷1.0) have been calculated by these formulae. The results show that the accuracies in all the calculations are more satisfactory or same in comparison with those obtained by the formula of Shenoy and Dunlap, especially when the asymmetry parameter of electric-field gradient is larger than 0.8 for the nucleus with spinI=5/2.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02463991
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  • 5
    Electronic Resource
    Electronic Resource
    Chemical Abundances of Planetary Nebulae: A UV to Far-IR Case Study of NGC 6153 (1997)
    Springer
    Astrophysics and space science 255 (1997), S. 499-505 
    Details
    ISSN: 1572-946X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1001515704001
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  • 6
    Electronic Resource
    Electronic Resource
    DMRG studies on interchain coupling model for quasi-one-dimensional organic magnet (2003)
    Springer
    The European physical journal 35 (2003), S. 365-370 
    Details
    ISSN: 1434-6036
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract. We carry out Density Matrix Renormalization Group (DMRG) calculations on the interchain coupling model for the quasi-one-dimensional organic ferromagnets under open boundary condition. Considering the topology of the system, the two-step DMRG technique is adopted. It is found that in the high spin ground state of the system the interchain coupling is in favor of the stability of ferromagnetic state, and the on-site electron-electron repulsive interaction has the same effect. However the inter-site electron-electron interaction causes a charge density distribution along the main chain and weakens the stability of the ferromagnetic ground state. The lattice distortion along the main chain is also discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1140/epjb/e2003-00296-x
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  • 7
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    HST and LAMOST discover a dual active galactic nucleus in J0038+4128 (2014)
    Oxford University Press
    Details
    Publication Date: 2014-03-21
    Description: We report the discovery of a kiloparsec-scale dual active galactic nucleus (AGN) in J0038+4128. From the Hubble Space Telescope ( HST ) Wide Field Planetary Camera 2 (WFPC2) images, we find two optical nuclei with a projection separation of 4.7 kpc (3.44 arcsec). The southern component (J0038+4128S) is spectroscopically observed with the HST Goddard High Resolution Spectrograph in the UV range and is found to be a Seyfert 1 galaxy with a broad Lyα emission line. The northern component (J0038+4128N) is spectroscopically observed during the Large Sky Area Multi-Object Fibre Spectroscopic Telescope (also named the Guoshoujing Telescope) pilot survey in the optical range. The observed line ratios as well as the consistency of redshift of the nucleus emission lines and the host galaxy's absorption lines indicate that J0038+4128N is a Seyfert 2 galaxy with narrow lines only. These results thus confirm that J0038+4128 is a Seyfert 1–Seyfert 2 AGN pair. The HST WFPC2 F 336 W / U -band image of J0038+4128 also reveals for the first time for a dual AGN system two pairs of bi-symmetric arms, as are expected from the numerical simulations of such system. Being one of a few confirmed kiloparsec-scale dual AGNs exhibiting a clear morphological structure of the host galaxies, J0038+4128 provides a unique opportunity to study the co-evolution of the host galaxies and their central supermassive black holes undergoing a merging process.
    Print ISSN: 0035-8711
    Electronic ISSN: 1365-2966
    Topics: Physics
    Published by Oxford University Press
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  • 8
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    Hunting for extremely faint planetary nebulae in the SDSS spectroscopic database (2013)
    Oxford University Press
    Details
    Publication Date: 2013-10-29
    Description: Using ~1700 000 target- and sky-fibre spectra from the Sloan Digital Sky Survey (SDSS), we have carried out a systematic search for Galactic planetary nebulae (PNe) via detections of the [O iii ] 4959, 5007 lines. Thanks to the excellent sensitivity of the SDSS spectroscopic surveys, this is by far the deepest search for PNe ever taken, reaching a surface brightness of the [O iii ] 5007 line down to about 29.0 mag arcsec –2 . The search leads to the recovery of 13 previously known PNe in the Northern and Southern Galactic Caps. In total, 44 new PN candidates are identified, including seven candidates of multiple detections and 37 candidates of single detection. The seven candidates of multiple detections are all extremely large (between 21 and 154 arcmin) and faint, located mostly in the low Galactic latitude region and with a kinematics similar to disc stars. After checking their images in Hα and other bands, three of them are probably H ii regions, one is probably associated with a new supernova remnant, another one is possibly a true PN and the remaining two could be either PNe or supernova remnants. Based on sky positions and kinematics, seven candidates of single detection probably belong to the halo population. If confirmed, they will increase the number of known PNe in the Galactic halo significantly. All the newly identified PN candidates are very faint, with a surface brightness of the [O iii ] 5007 line between 27.0–30.0 mag arcsec –2 , and very challenging to be discovered with previously employed techniques (e.g. slitless spectroscopy, narrow-band imaging), and thus may greatly increase the number of ‘missing’ faint PNe. Our results demonstrate the power of large-scale fibre spectroscopy in hunting for ultrafaint PNe and other types of emission line nebulae. Combining the large spectral data bases provided by the SDSS and other on-going projects (e.g. the LAMOST Galactic surveys), it is possible to build a statistically meaningful sample of ultrafaint, large, evolved PNe, thus, improving the census of Galactic PNe.
    Print ISSN: 0035-8711
    Electronic ISSN: 1365-2966
    Topics: Physics
    Published by Oxford University Press
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  • 9
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    Exploration of spin-down rate of neutron stars in high-mass X-ray binaries (2016)
    Oxford University Press
    Details
    Publication Date: 2016-02-28
    Description: We use the evolutionary population synthesis method to investigate the statistical properties of the wind-fed neutron-star (NS) compact ( P orb 〈 10 d) high-mass X-ray binaries (HMXBs) in our Galaxy, based on different spin-down models. Model 1 assumes that the surrounding material is treated as forming a quasi-static atmosphere. Model 2 assumes that the characteristic velocity of matter and the typical Alfvén velocity of material in the magnetospheric boundary layer are comparable to the sound speed in the external medium. We find that the spin-down rate in the supersonic propeller phase in either model 1 or model 2 is too low to produce the observed number of compact HMXBs. Model 3 assumes that the infalling material is ejected with the corotation velocity at the magnetospheric radius when the magnetospheric radius is larger than the corotation radius. Model 4 uses simple integration of the magnetic torque over the magnetosphere. Both models 3 and 4 have a larger spin down rate than that given by model 1 or 2. We also find that models 3 and 4 can predict a reasonable number of observed wind-fed NS compact HMXBs. By comparing our calculated results with the observed particular distributions of wind-fed NS compact HMXBs in a P s versus P orb diagram, we find that the subsonic propeller phase may not exist at all. However, the spin-down rates in models 3 and 4 both seem reasonable to produce the observed distribution of wind-fed NS compact HMXBs in the P s versus P orb diagram. We cannot find which spin-down rate seems more reasonable from our calculations.
    Print ISSN: 0035-8711
    Electronic ISSN: 1365-2966
    Topics: Physics
    Published by Oxford University Press
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  • 10
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    The SDSS spectroscopic catalogue of white dwarf-main-sequence binaries: new identifications from DR 9-12 (2016)
    Oxford University Press
    Details
    Publication Date: 2016-04-07
    Description: We present an updated version of the spectroscopic catalogue of white dwarf-main-sequence (WDMS) binaries from the Sloan Digital Sky Survey (SDSS). We identify 938 WDMS binaries within the data releases (DR) 9–12 of SDSS plus 40 objects from DR 1–8 that we missed in our previous works, 646 of which are new. The total number of spectroscopic SDSS WDMS binaries increases to 3294. This is by far the largest and most homogeneous sample of compact binaries currently available. We use a decomposition/fitting routine to derive the stellar parameters of all systems identified here (white dwarf effective temperatures, surface gravities and masses, and secondary star spectral types). The analysis of the corresponding stellar parameter distributions shows that the SDSS WDMS binary population is seriously affected by selection effects. We also measure the Na I   8183.27, 8194.81 absorption doublet and H α emission radial velocities (RV) from all SDSS WDMS binary spectra identified in this work. 98 objects are found to display RV variations, 62 of which are new. The RV data are sufficient enough to estimate the orbital periods of three close binaries.
    Print ISSN: 0035-8711
    Electronic ISSN: 1365-2966
    Topics: Physics
    Published by Oxford University Press
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