| 1. |
- Abolfathi, Bela, et al.
(author)
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The Fourteenth Data Release of the Sloan Digital Sky Survey : First Spectroscopic Data from the Extended Baryon Oscillation Spectroscopic Survey and from the Second Phase of the Apache Point Observatory Galactic Evolution Experiment
- 2018
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In: Astrophysical Journal Supplement Series. - : IOP Publishing Ltd. - 0067-0049 .- 1538-4365. ; 235:2
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Journal article (peer-reviewed)abstract
- The fourth generation of the Sloan Digital Sky Survey (SDSS-IV) has been in operation since 2014 July. This paper describes the second data release from this phase, and the 14th from SDSS overall (making this Data Release Fourteen or DR14). This release makes the data taken by SDSS-IV in its first two years of operation (2014-2016 July) public. Like all previous SDSS releases, DR14 is cumulative, including the most recent reductions and calibrations of all data taken by SDSS since the first phase began operations in 2000. New in DR14 is the first public release of data from the extended Baryon Oscillation Spectroscopic Survey; the first data from the second phase of the Apache Point Observatory (APO) Galactic Evolution Experiment (APOGEE-2), including stellar parameter estimates from an innovative data-driven machine-learning algorithm known as "The Cannon"; and almost twice as many data cubes from the Mapping Nearby Galaxies at APO (MaNGA) survey as were in the previous release (N = 2812 in total). This paper describes the location and format of the publicly available data from the SDSS-IV surveys. We provide references to the important technical papers describing how these data have been taken (both targeting and observation details) and processed for scientific use. The SDSS web site (www.sdss.org) has been updated for this release and provides links to data downloads, as well as tutorials and examples of data use. SDSS-IV is planning to continue to collect astronomical data until 2020 and will be followed by SDSS-V.
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| 2. |
- Blanton, Michael R., et al.
(author)
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Sloan Digital Sky Survey IV : Mapping the Milky Way, Nearby Galaxies, and the Distant Universe
- 2017
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In: Astronomical Journal. - : IOP Publishing Ltd. - 0004-6256 .- 1538-3881. ; 154:1
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Journal article (peer-reviewed)abstract
- We describe the Sloan Digital Sky Survey IV (SDSS-IV), a project encompassing three major spectroscopic programs. The Apache Point Observatory Galactic Evolution Experiment 2 (APOGEE-2) is observing hundreds of thousands of Milky Way stars at high resolution and. high signal-to-noise ratios in the near-infrared. The Mapping Nearby Galaxies at Apache Point Observatory (MaNGA) survey is obtaining spatially resolved spectroscopy for thousands of nearby galaxies (median z similar to 0.03). The extended Baryon Oscillation Spectroscopic Survey (eBOSS) is mapping the galaxy, quasar, and neutral gas distributions between z similar to 0.6 and 3.5 to constrain cosmology using baryon acoustic oscillations, redshift space distortions, and the shape of the power spectrum. Within eBOSS, we are conducting two major subprograms: the SPectroscopic IDentification of eROSITA Sources (SPIDERS), investigating X-ray AGNs. and galaxies in X-ray clusters, and the Time Domain Spectroscopic Survey (TDSS), obtaining spectra of variable sources. All programs use the 2.5 m Sloan Foundation Telescope at the. Apache Point Observatory; observations there began in Summer 2014. APOGEE-2 also operates a second near-infrared spectrograph at the 2.5 m du Pont Telescope at Las Campanas Observatory, with observations beginning in early 2017. Observations at both facilities are scheduled to continue through 2020. In keeping with previous SDSS policy, SDSS-IV provides regularly scheduled public data releases; the first one, Data Release 13, was made available in 2016 July.
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| 3. |
- Grumer, Jon, et al.
(author)
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Magnetic field induced transition rates in Ne- and Be-like ions for plasma diagnostics and E1M1 two-photon decay rate determination
- 2014
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In: XXVIII International Conference on Photonic, Electronic and Atomic Collisions (ICPEAC 2013). - : IOP Publishing. - 1742-6588 .- 1742-6596. ; 488, s. 152005-152005
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Journal article (other academic/artistic)abstract
- We report on theoretical results of magnetic field induced transitions (MITs) in Ne- and Be-like ions without nuclear spin for two applicalions. Firstly, MITs are promising candidates in the determination of magnetic fields in plasmas. In our work on Ne-like ions we present accurate theoretical MIT rates for 2p(6 1)S(O) - 2p(5)3s 3P(O),2 [11. Purthermore, for Be-like ions, it has been proposed to extract the rate of the BIM1 two-photon transition 2s(2 1)S(O) - 2s2p P-3(O) by measuring the lifetime of the 'Po state using a storage ring, which involves an external magnetic field. The MIT rates are carefully evaluated and shown to be of the same order as the ElMI rates [2].
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| 4. |
- Grumer, Jon, et al.
(author)
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Magnetic field induced transition rates in Ne- and Be-like ions for plasma diagnostics and E1M1 two-photon decay rate determination
- 2013
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In: Book of abstracts. - : Institute of Modern Physics, Chinese Academy of Sciences.
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Conference paper (other academic/artistic)abstract
- Synopsis We report on theoretical results of magnetic field induced transitions (MITs) in Ne- and Be-like ions without nuclear spin for two applications. Firstly, MITs are promising candidates in the determination of magnetic fields in plasmas. In our work on Ne-like ions we present accurate theoretical MIT rates for 2p6 1S0 − 2p53s 3P0 , 2 [1]. Furthermore, for Be-like ions, it has been proposed to extract the rate of the E1M1 two-photon transition 2s2 1S0 − 2s2p 3P0 by measuring the lifetime of the 3P0 state using a storage ring, which involves an external magnetic field. The MIT rates are carefully evaluated and shown to be of the same order as the E1M1 rates.
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| 5. |
- Grumer, Jon, et al.
(author)
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The effect of an external magnetic field on the determination of E1M1 two-photon decay rates in Be-like ions
- 2013
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In: Physical Review A. Atomic, Molecular, and Optical Physics. - : American Physical Society. - 1050-2947 .- 1094-1622. ; 88
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Journal article (peer-reviewed)abstract
- In this work we report on ab initio theoretical results for the magnetic-field-induced 2s 2p 3P0 → 2s2 1S0 E1 transition for ions in the beryllium isoelectronic sequence between Z = 5 and 92. It has been proposed that the rate of the E1M1 two-photon transition 2s 2p 3P0 → 2s2 1S0 can be extracted from the lifetime of the 3P0 state in Be-like ions with zero nuclear spin by employing resonant recombination in a storage ring. This experimental approach involves a perturbing external magnetic field. The effect of this field needs to be evaluated in order to properly extract the two-photon rate from the measured decay curves. The magnetic-field-induced transition rates are carefully evaluated, and it is shown that, with a typical storage-ring field strength, it is dominant or of the same order as the E1M1 rate for low- and mid-Z ions. Results for several field strengths and ions are presented, and we also give a simple Z-dependent formula for the rate. We estimate the uncertainties of our model to be within 5% for low- and mid-Z ions and slightly larger for more highly charged ions. Furthermore we evaluate the importance of including both perturber states, 3P1 and 1P1, and it is s
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| 6. |
- Grumer, Jon, et al.
(author)
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Unexpected transitions induced by spin-dependent, hyperfine and external magnetic-field interactions
- 2014
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In: Physica Scripta. - : IOP Publishing. - 0031-8949 .- 1402-4896. ; 89:11
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Journal article (peer-reviewed)abstract
- Unexpected transitions are induced by weaker interactions not included in the gross structure model of the ion under investigation. We discuss different examples of such decay channels, starting with relativistic spin-induced transitions. These represented an important field of study a few decades ago, and we illustrate how some challenging cases can be treated very accurately with today's computational techniques, while close degeneracy sometimes still prevents ab initio methods from obtaining accurate results. For hyperfine induced transitions we review some recent results and discuss remaining challenges for experiment and theory. Finally, we discuss the newly opened field of accurate calculations for transitions induced by an external magnetic field and point to some examples of where these are accessible for experimental tests.
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| 7. |
- Hua, D., et al.
(author)
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A Novel Ferrofluid Rolling Robot : Design, Manufacturing, and Experimental Analysis
- 2021
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In: IEEE Transactions on Instrumentation and Measurement. - : IEEE. - 0018-9456 .- 1557-9662. ; 70
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Journal article (peer-reviewed)abstract
- With the increasing applications of magnetic robots in medical instruments, the research on different structures and locomotion approaches of magnetic robots has become a hotspot in recent years. A ferrofluid rolling robot (FRR) with magnetic actuation is proposed and enabled to realize a novel locomotion approach in this article. The drive performance of ferrofluid is elaborated, which is characterized by the magnetic torque of a rectangle-shaped object filled with ferrofluid under magnetic field. First, the proposed structure and locomotion mechanism of the FRR are detailed. Moreover, based on the established mathematical models of the FRR, the simulations with straight and turning locomotion are carried out, respectively. Finally, the FRR prototype is manufactured by 3-D printing, and experimental results demonstrate that the feasibility of straight and turning locomotion is verified. The locomotion performance of the FRR is in good agreement with the theoretical models where the root mean square (rms) value of displacement for experiments and simulations is 1.2 mm. In this work, the proposed FRR can automatically switch from straight to turning locomotion with a fast response in an external magnetic field, and does not has magnetism when without a magnetic field.
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| 8. |
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| 9. |
- Jönsson, Per, et al.
(author)
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An Introduction to Relativistic Theory as Implemented in GRASP
- 2023
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In: Atoms. - : MDPI. - 2218-2004. ; 11:1
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Journal article (peer-reviewed)abstract
- Computational atomic physics continues to play a crucial role in both increasing the understanding of fundamental physics (e.g., quantum electrodynamics and correlation) and producing atomic data for interpreting observations from large-scale research facilities ranging from fusion reactors to high-power laser systems, space-based telescopes and isotope separators. A number of different computational methods, each with their own strengths and weaknesses, is available to meet these tasks. Here, we review the relativistic multiconfiguration method as it applies to the General Relativistic Atomic Structure Package [grasp2018, C. Froese Fischer, G. Gaigalas, P. Jonsson, J. Bieron, Comput. Phys. Commun. (2018). DOI: 10.1016/j.cpc.2018.10.032]. To illustrate the capacity of the package, examples of calculations of relevance for nuclear physics and astrophysics are presented.
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| 10. |
- Jönsson, Per, et al.
(author)
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GRASP Manual for Users
- 2023
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In: Atoms. - : MDPI. - 2218-2004. ; 11:4
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Journal article (peer-reviewed)abstract
- grasp is a software package in Fortran 95, adapted to run in parallel under MPI, for research in atomic physics. The basic premise is that, given a wave function, any observed atomic property can be computed. Thus, the first step is always to determine a wave function. Different properties challenge the accuracy of the wave function in different ways. This software is distributed under the MIT Licence.
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