| 1. |
- Niemi, MEK, et al.
(författare)
-
- 2021
-
swepub:Mat__t
|
|
| 2. |
- Kanai, M, et al.
(författare)
-
- 2023
-
swepub:Mat__t
|
|
| 3. |
- Barausse, Enrico, et al.
(författare)
-
Prospects for fundamental physics with LISA
- 2020
-
Ingår i: General Relativity and Gravitation. - : SPRINGER/PLENUM PUBLISHERS. - 0001-7701 .- 1572-9532. ; 52:8
-
Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- In this paper, which is of programmatic rather than quantitative nature, we aim to further delineate and sharpen the future potential of the LISA mission in the area of fundamental physics. Given the very broad range of topics that might be relevant to LISA,we present here a sample of what we view as particularly promising fundamental physics directions. We organize these directions through a "science-first" approach that allows us to classify how LISA data can inform theoretical physics in a variety of areas. For each of these theoretical physics classes, we identify the sources that are currently expected to provide the principal contribution to our knowledge, and the areas that need further development. The classification presented here should not be thought of as cast in stone, but rather as a fluid framework that is amenable to change with the flow of new insights in theoretical physics.
|
|
| 4. |
|
|
| 5. |
|
|
| 6. |
- Duffy, J. M. N., et al.
(författare)
-
Standardizing definitions and reporting guidelines for the infertility core outcome set: an international consensus development study
- 2020
-
Ingår i: Human Reproduction. - : Oxford University Press (OUP). - 0268-1161 .- 1460-2350. ; 35:12, s. 2735-2745
-
Tidskriftsartikel (refereegranskat)abstract
- STUDY QUESTION: Can consensus definitions for the core outcome set for infertility be identified in order to recommend a standardized approach to reporting? SUMMARY ANSWER: Consensus definitions for individual core outcomes, contextual statements and a standardized reporting table have been developed. WHAT IS KNOWN ALREADY: Different definitions exist for individual core outcomes for infertility. This variation increases the opportunities for researchers to engage with selective outcome reporting, which undermines secondary research and compromises clinical practice guideline development. STUDY DESIGN, SIZE, DURATION: Potential definitions were identified by a systematic review of definition development initiatives and clinical practice guidelines and by reviewing Cochrane Gynaecology and Fertility Group guidelines. These definitions were discussed in a face-to-face consensus development meeting, which agreed consensus definitions. A standardized approach to reporting was also developed as part of the process. PARTICIPANTS/MATERIALS, SETTING, METHODS: Healthcare professionals, researchers and people with fertility problems were brought together in an open and transparent process using formal consensus development methods. MAIN RESULTS AND THE ROLE OF CHANCE: Forty-four potential definitions were inventoried across four definition development initiatives, including the Harbin Consensus Conference Workshop Group and International Committee for Monitoring Assisted Reproductive Technologies, 12 clinical practice guidelines and Cochrane Gynaecology and Fertility Group guidelines. Twenty-seven participants, from 11 countries, contributed to the consensus development meeting. Consensus definitions were successfully developed for all core outcomes. Specific recommendations were made to improve reporting. LIMITATIONS, REASONS FOR CAUTION: We used consensus development methods, which have inherent limitations. There was limited representation from low- and middle-income countries. WIDER IMPLICATIONS OF THE FINDINGS: A minimum data set should assist researchers in populating protocols, case report forms and other data collection tools. The generic reporting table should provide clear guidance to researchers and improve the reporting of their results within journal publications and conference presentations. Research funding bodies, the Standard Protocol Items: Recommendations for Interventional Trials statement, and over 80 specialty journals have committed to implementing this core outcome set.
|
|
| 7. |
- Duffy, J. M. N., et al.
(författare)
-
Top 10 priorities for future infertility research: an international consensus development study
- 2020
-
Ingår i: Human Reproduction. - : Oxford University Press (OUP). - 0268-1161 .- 1460-2350. ; 35:12, s. 2715-2724
-
Tidskriftsartikel (refereegranskat)abstract
- STUDY QUESTION: Can the priorities for future research in infertility be identified? SUMMARY ANSWER: The top 10 research priorities for the four areas of male infertility, female and unexplained infertility, medically assisted reproduction and ethics, access and organization of care for people with fertility problems were identified. WHAT IS KNOWN ALREADY: Many fundamental questions regarding the prevention, management and consequences of infertility remain unanswered. This is a barrier to improving the care received by those people with fertility problems. STUDY DESIGN, SIZE, DURATION: Potential research questions were collated from an initial international survey, a systematic review of clinical practice guidelines and Cochrane systematic reviews. A rationalized list of confirmed research uncertainties was prioritized in an interim international survey. Prioritized research uncertainties were discussed during a consensus development meeting. Using a formal consensus development method, the modified nominal group technique, diverse stakeholders identified the top 10 research priorities for each of the categories male infertility, female and unexplained infertility, medically assisted reproduction and ethics, access and organization of care. PARTICIPANTS/MATERIALS, SETTING, METHODS: Healthcare professionals, people with fertility problems and others (healthcare funders, healthcare providers, healthcare regulators, research funding bodies and researchers) were brought together in an open and transparent process using formal consensus methods advocated by the James Lind Alliance. MAIN RESULTS AND THE ROLE OF CHANCE: The initial survey was completed by 388 participants from 40 countries, and 423 potential research questions were submitted. Fourteen clinical practice guidelines and 162 Cochrane systematic reviews identified a further 236 potential research questions. A rationalized list of 231 confirmed research uncertainties was entered into an interim prioritization survey completed by 317 respondents from 43 countries. The top 10 research priorities for each of the four categories male infertility, female and unexplained infertility (including age-related infertility, ovarian cysts, uterine cavity abnormalities and tubal factor infertility), medically assisted reproduction (including ovarian stimulation, IUI and IVF) and ethics, access and organization of care were identified during a consensus development meeting involving 41 participants from I I countries. These research priorities were diverse and seek answers to questions regarding prevention, treatment and the longer-term impact of infertility. They highlight the importance of pursuing research which has often been overlooked, including addressing the emotional and psychological impact of infertility, improving access to fertility treatment, particularly in lower resource settings and securing appropriate regulation. Addressing these priorities will require diverse research methodologies, including laboratory-based science, qualitative and quantitative research and population science. LIMITATIONS, REASONS FOR CAUTION: We used consensus development methods, which have inherent limitations, including the representativeness of the participant sample, methodological decisions informed by professional judgment and arbitrary consensus definitions. WIDER IMPLICATIONS OF THE FINDINGS: We anticipate that identified research priorities, developed to specifically highlight the most pressing clinical needs as perceived by healthcare professionals, people with fertility problems and others, will help research funding organizations and researchers to develop their future research agenda.
|
|
| 8. |
- Arzoumanian, Doris, et al.
(författare)
-
Dust polarized emission observations of NGC 6334: BISTRO reveals the details of the complex but organized magnetic field structure of the high-mass star-forming hub-filament network
- 2021
-
Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 647
-
Tidskriftsartikel (refereegranskat)abstract
- Context. Molecular filaments and hubs have received special attention recently thanks to new studies showing their key role in star formation. While the (column) density and velocity structures of both filaments and hubs have been carefully studied, their magnetic field (B-field) properties have yet to be characterized. Consequently, the role of B-fields in the formation and evolution of hub-filament systems is not well constrained. Aims. We aim to understand the role of the B-field and its interplay with turbulence and gravity in the dynamical evolution of the NGC 6334 filament network that harbours cluster-forming hubs and high-mass star formation. Methods. We present new observations of the dust polarized emission at 850 μm toward the 2 pc × 10 pc map of NGC 6334 at a spatial resolution of 0.09 pc obtained with the James Clerk Maxwell Telescope (JCMT) as part of the B-field In STar-forming Region Observations (BISTRO) survey. We study the distribution and dispersion of the polarized intensity (PI), the polarization fraction (PF), and the plane-of-The-sky B-field angle (χB_POS) toward the whole region, along the 10 pc-long ridge and along the sub-filaments connected to the ridge and the hubs. We derived the power spectra of the intensity and χBPOS along the ridge crest and compared them with the results obtained from simulated filaments. Results. The observations span 3 orders of magnitude in Stokes I and PI and 2 orders of magnitude in PF (from 0.2 to 20%). A large scatter in PI and PF is observed for a given value of I. Our analyses show a complex B-field structure when observed over the whole region ( 10 pc); however, at smaller scales (1 pc), χBPOS varies coherently along the crests of the filament network. The observed power spectrum of χBPOS can be well represented with a power law function with a slope of-1.33 ± 0.23, which is 20% shallower than that of I. We find that this result is compatible with the properties of simulated filaments and may indicate the physical processes at play in the formation and evolution of star-forming filaments. Along the sub-filaments, χBPOS rotates frombeing mostly perpendicular or randomly oriented with respect to the crests to mostly parallel as the sub-filaments merge with the ridge and hubs. This variation of the B-field structure along the sub-filaments may be tracing local velocity flows of infalling matter in the ridge and hubs. Our analysis also suggests a variation in the energy balance along the crests of these sub-filaments, from magnetically critical or supercritical at their far ends to magnetically subcritical near the ridge and hubs. We also detect an increase in PF toward the high-column density (NH2 â 1023 cm-2) star cluster-forming hubs. These latter large PF values may be explained by the increase in grain alignment efficiency due to stellar radiation from the newborn stars, combined with an ordered B-field structure. Conclusions. These observational results reveal for the first time the characteristics of the small-scale (down to 0.1 pc) B-field structure of a 10 pc-long hub-filament system. Our analyses show variations in the polarization properties along the sub-filaments that may be tracing the evolution of their physical properties during their interaction with the ridge and hubs. We also detect an impact of feedback from young high-mass stars on the local B-field structure and the polarization properties, which could put constraints on possible models for dust grain alignment and provide important hints as to the interplay between the star formation activity and interstellar B-fields.
|
|
| 9. |
- Eswaraiah, Chakali, et al.
(författare)
-
The JCMT BISTRO Survey: Revealing the Diverse Magnetic Field Morphologies in Taurus Dense Cores with Sensitive Submillimeter Polarimetry
- 2021
-
Ingår i: Astrophysical Journal Letters. - : American Astronomical Society. - 2041-8213 .- 2041-8205. ; 912:2
-
Tidskriftsartikel (refereegranskat)abstract
- We have obtained sensitive dust continuum polarization observations at 850 μm in the B213 region of Taurus using POL-2 on SCUBA-2 at the James Clerk Maxwell Telescope as part of the B-fields in STar-forming Region Observations (BISTRO) survey. These observations allow us to probe magnetic field (B-field) at high spatial resolution (∼2000 au or ∼0.01 pc at 140 pc) in two protostellar cores (K04166 and K04169) and one prestellar core (Miz-8b) that lie within the B213 filament. Using the Davis-Chandrasekhar-Fermi method, we estimate the B-field strengths in K04166, K04169, and Miz-8b to be 38 ± 14, 44 ± 16, and 12 ± 5 μG, respectively. These cores show distinct mean B-field orientations. The B-field in K04166 is well ordered and aligned parallel to the orientations of the core minor axis, outflows, core rotation axis, and large-scale uniform B-field, in accordance with magnetically regulated star formation via ambipolar diffusion taking place in K04166. The B-field in K04169 is found to be ordered but oriented nearly perpendicular to the core minor axis and large-scale B-field and not well correlated with other axes. In contrast, Miz-8b exhibits a disordered B-field that shows no preferred alignment with the core minor axis or large-scale field. We found that only one core, K04166, retains a memory of the large-scale uniform B-field. The other two cores, K04169 and Miz-8b, are decoupled from the large-scale field. Such a complex B-field configuration could be caused by gas inflow onto the filament, even in the presence of a substantial magnetic flux.
|
|
| 10. |
- Thiele, I., et al.
(författare)
-
A community-driven global reconstruction of human metabolism
- 2013
-
Ingår i: Nature Biotechnology. - : Springer Science and Business Media LLC. - 1087-0156 .- 1546-1696. ; 31:5, s. 419-
-
Tidskriftsartikel (refereegranskat)abstract
- Multiple models of human metabolism have been reconstructed, but each represents only a subset of our knowledge. Here we describe Recon 2, a community-driven, consensus 'metabolic reconstruction', which is the most comprehensive representation of human metabolism that is applicable to computational modeling. Compared with its predecessors, the reconstruction has improved topological and functional features, including similar to 2x more reactions and similar to 1.7x more unique metabolites. Using Recon 2 we predicted changes in metabolite biomarkers for 49 inborn errors of metabolism with 77% accuracy when compared to experimental data. Mapping metabolomic data and drug information onto Recon 2 demonstrates its potential for integrating and analyzing diverse data types. Using protein expression data, we automatically generated a compendium of 65 cell type-specific models, providing a basis for manual curation or investigation of cell-specific metabolic properties. Recon 2 will facilitate many future biomedical studies and is freely available at http://humanmetabolism.org/.
|
|
| 11. |
- Doi, Yasuo, et al.
(författare)
-
The JCMT BISTRO Survey: Magnetic Fields Associated with a Network of Filaments in NGC 1333
- 2020
-
Ingår i: Astrophysical Journal. - : American Astronomical Society. - 1538-4357 .- 0004-637X. ; 899:1
-
Tidskriftsartikel (refereegranskat)abstract
- We present new observations of the active star formation region NGC 1333 in the Perseus molecular cloud complex from the James Clerk Maxwell Telescope B-Fields In Star-forming Region Observations (BISTRO) survey with the POL-2 instrument. The BISTRO data cover the entire NGC 1333 complex (∼1.5 pc ? 2 pc) at 0.02 pc resolution and spatially resolve the polarized emission from individual filamentary structures for the first time. The inferred magnetic field structure is complex as a whole, with each individual filament aligned at different position angles relative to the local field orientation. We combine the BISTRO data with low- and high- resolution data derived from Planck and interferometers to study the multiscale magnetic field structure in this region. The magnetic field morphology drastically changes below a scale of ∼1 pc and remains continuous from the scales of filaments (∼0.1 pc) to that of protostellar envelopes (∼0.005 pc or ∼1000 au). Finally, we construct simple models in which we assume that the magnetic field is always perpendicular to the long axis of the filaments. We demonstrate that the observed variation of the relative orientation between the filament axes and the magnetic field angles are well reproduced by this model, taking into account the projection effects of the magnetic field and filaments relative to the plane of the sky. These projection effects may explain the apparent complexity of the magnetic field structure observed at the resolution of BISTRO data toward the filament network.
|
|
| 12. |
- Hwang, Jihye, et al.
(författare)
-
The JCMT BISTRO Survey: A Spiral Magnetic Field in a Hub-filament Structure, Monoceros R2
- 2022
-
Ingår i: Astrophysical Journal. - : American Astronomical Society. - 1538-4357 .- 0004-637X. ; 941:1
-
Tidskriftsartikel (refereegranskat)abstract
- We present and analyze observations of polarized dust emission at 850 μm toward the central 1 × 1 pc hub-filament structure of Monoceros R2 (Mon R2). The data are obtained with SCUBA-2/POL-2 on the James Clerk Maxwell Telescope (JCMT) as part of the B-fields in Star-forming Region Observations survey. The orientations of the magnetic field follow the spiral structure of Mon R2, which are well described by an axisymmetric magnetic field model. We estimate the turbulent component of the magnetic field using the angle difference between our observations and the best-fit model of the underlying large-scale mean magnetic field. This estimate is used to calculate the magnetic field strength using the Davis–Chandrasekhar–Fermi method, for which we also obtain the distribution of volume density and velocity dispersion using a column density map derived from Herschel data and the C18O (J = 3 - 2) data taken with HARP on the JCMT, respectively. We make maps of magnetic field strengths and mass-to-flux ratios, finding that magnetic field strengths vary from 0.02 to 3.64 mG with a mean value of 1.0 ± 0.06 mG, and the mean critical mass-to-flux ratio is 0.47 ± 0.02. Additionally, the mean Alfvén Mach number is 0.35 ± 0.01. This suggests that, in Mon R2, the magnetic fields provide resistance against large-scale gravitational collapse, and the magnetic pressure exceeds the turbulent pressure. We also investigate the properties of each filament in Mon R2. Most of the filaments are aligned along the magnetic field direction and are magnetically subcritical.
|
|
| 13. |
- Tahani, Mehrnoosh, et al.
(författare)
-
JCMT BISTRO Observations: Magnetic Field Morphology of Bubbles Associated with NGC 6334
- 2023
-
Ingår i: Astrophysical Journal. - : American Astronomical Society. - 1538-4357 .- 0004-637X. ; 944:2
-
Tidskriftsartikel (refereegranskat)abstract
- We study the Hii regions associated with the NGC 6334 molecular cloud observed in the submillimeter and taken as part of the B-fields In STar-forming Region Observations Survey. In particular, we investigate the polarization patterns and magnetic field morphologies associated with these Hii regions. Through polarization pattern and pressure calculation analyses, several of these bubbles indicate that the gas and magnetic field lines have been pushed away from the bubble, toward an almost tangential (to the bubble) magnetic field morphology. In the densest part of NGC 6334, where the magnetic field morphology is similar to an hourglass, the polarization observations do not exhibit observable impact from Hii regions. We detect two nested radial polarization patterns in a bubble to the south of NGC 6334 that correspond to the previously observed bipolar structure in this bubble. Finally, using the results of this study, we present steps (incorporating computer vision; circular Hough transform) that can be used in future studies to identify bubbles that have physically impacted magnetic field lines.
|
|
| 14. |
- Bower, G. C., et al.
(författare)
-
THE ALLEN TELESCOPE ARRAY Pi GHz SKY SURVEY. I. SURVEY DESCRIPTION AND STATIC CATALOG RESULTS FOR THE BOOTES FIELD
- 2010
-
Ingår i: Astrophysical Journal. - : American Astronomical Society. - 1538-4357 .- 0004-637X. ; 725:2, s. 1792-1804
-
Tidskriftsartikel (refereegranskat)abstract
- The Pi GHz Sky Survey (PiGSS) is a key project of the Allen Telescope Array. PiGSS is a 3.1 GHz survey of radio continuum emission in the extragalactic sky with an emphasis on synoptic observations that measure the static and time-variable properties of the sky. During the 2.5 year campaign, PiGSS will twice observe similar to 250,000 radio sources in the 10,000 deg(2) region of the sky with b > 30 degrees to an rms sensitivity of similar to 1 mJy. Additionally, sub-regions of the sky will be observed multiple times to characterize variability on timescales of days to years. We present here observations of a 10 deg(2) region in the Bootes constellation overlapping the NOAO Deep Wide Field Survey field. The PiGSS image was constructed from 75 daily observations distributed over a 4 month period and has an rms flux density between 200 and 250 mu Jy. This represents a deeper image by a factor of 4-8 than we will achieve over the entire 10,000 deg(2). We provide flux densities, source sizes, and spectral indices for the 425 sources detected in the image. We identify similar to 100 new flat-spectrum radio sources; we project that when completed PiGSS will identify 10(4) flat-spectrum sources. We identify one source that is a possible transient radio source. This survey provides new limits on faint radio transients and variables with characteristic durations of months.
|
|
| 15. |
- Croft, S., et al.
(författare)
-
THE ALLEN TELESCOPE ARRAY TWENTY-CENTIMETER SURVEY-A 690 DEG(2), 12 EPOCH RADIO DATA SET. I. CATALOG AND LONG-DURATION TRANSIENT STATISTICS
- 2010
-
Ingår i: Astrophysical Journal. - 1538-4357 .- 0004-637X. ; 719:1, s. 45-58
-
Tidskriftsartikel (refereegranskat)abstract
- We present the Allen Telescope Array Twenty-centimeter Survey (ATATS), a multi-epoch (12 visits), 690 deg(2) radio image and catalog at 1.4 GHz. The survey is designed to detect rare, very bright transients as well as to verify the capabilities of the ATA to form large mosaics. The combined image using data from all 12 ATATS epochs has rms noise sigma = 3.94 mJy beam(-1) and dynamic range 180, with a circular beam of 150 '' FWHM. It contains 4408 sources to a limiting sensitivity of 5 sigma = 20 mJy beam(-1). We compare the catalog generated from this 12 epoch combined image to the NRAO VLA Sky Survey (NVSS), a legacy survey at the same frequency, and find that we can measure source positions to better than similar to 20 ''. For sources above the ATATS completeness limit, the median flux density is 97% of the median value for matched NVSS sources, indicative of an accurate overall flux calibration. We examine the effects of source confusion due to the effects of differing resolution between ATATS and NVSS on our ability to compare flux densities. We detect no transients at flux densities greater than 40 mJy in comparison with NVSS and place a 2 sigma upper limit of 0.004 deg(-2) on the transient rate for such sources. These results suggest that the greater than or similar to 1 Jy transients reported by Matsumara et al. may not be true transients, but rather variable sources at their flux density threshold.
|
|
| 16. |
|
|
| 17. |
|
|
| 18. |
|
|
| 19. |
- Abou-Zeid, M., et al.
(författare)
-
T-duality in (2,1) superspace
- 2019
-
Ingår i: Journal of High Energy Physics (JHEP). - : SPRINGER. - 1126-6708 .- 1029-8479. ; :6
-
Tidskriftsartikel (refereegranskat)abstract
- We find the T-duality transformation rules for 2-dimensional (2,1) supersymmetric sigma-models in (2,1) superspace. Our results clarify certain aspects of the (2,1) sigma model geometry relevant to the discussion of T-duality. The complexified duality transformations we find are equivalent to the usual Buscher duality transformations (including an important refinement) together with diffeomorphisms. We use the gauging of sigma-models in (2,1) superspace, which we review and develop, finding a manifestly real and geometric expression for the gauged action. We discuss the obstructions to gauging (2,1) sigma-models, and find that the obstructions to (2,1) T-duality are considerably weaker.
|
|
| 20. |
- Ching, Tao-Chung, et al.
(författare)
-
The JCMT BISTRO-2 Survey: Magnetic Fields of the Massive DR21 Filament
- 2022
-
Ingår i: Astrophysical Journal. - : American Astronomical Society. - 1538-4357 .- 0004-637X. ; 941:2
-
Tidskriftsartikel (refereegranskat)abstract
- We present 850 mu m dust polarization observations of the massive DR21 filament from the B-fields In STar-forming Region Observations (BISTRO) survey, using the POL-2 polarimeter and the SCUBA-2 camera on the James Clerk Maxwell Telescope. We detect ordered magnetic fields perpendicular to the parsec-scale ridge of the DR21 main filament. In the subfilaments, the magnetic fields are mainly parallel to the filamentary structures and smoothly connect to the magnetic fields of the main filament. We compare the POL-2 and Planck dust polarization observations to study the magnetic field structures of the DR21 filament on 0.1-10 pc scales. The magnetic fields revealed in the Planck data are well-aligned with those of the POL-2 data, indicating a smooth variation of magnetic fields from large to small scales. The plane-of-sky magnetic field strengths derived from angular dispersion functions of dust polarization are 0.6-1.0 mG in the DR21 filament and similar to 0.1 mG in the surrounding ambient gas. The mass-to-flux ratios are found to be magnetically supercritical in the filament and slightly subcritical to nearly critical in the ambient gas. The alignment between column density structures and magnetic fields changes from random alignment in the low-density ambient gas probed by Planck to mostly perpendicular in the high-density main filament probed by James Clerk Maxwell Telescope. The magnetic field structures of the DR21 filament are in agreement with MHD simulations of a strongly magnetized medium, suggesting that magnetic fields play an important role in shaping the DR21 main filament and subfilaments.
|
|
| 21. |
- Karoly, Janik, et al.
(författare)
-
The JCMT BISTRO Survey: Studying the Complex Magnetic Field of L43
- 2023
-
Ingår i: Astrophysical Journal. - 1538-4357 .- 0004-637X. ; 952:1
-
Tidskriftsartikel (refereegranskat)abstract
- We present observations of polarized dust emission at 850 mu m from the L43 molecular cloud, which sits in the Ophiuchus cloud complex. The data were taken using SCUBA-2/POL-2 on the James Clerk Maxwell Telescope as a part of the BISTRO large program. L43 is a dense (N-H2 similar to 10(22) - 10(23) cm(-2)) complex molecular cloud with a submillimeter-bright starless core and two protostellar sources. There appears to be an evolutionary gradient along the isolated filament that L43 is embedded within, with the most evolved source closest to the Sco OB2 association. One of the protostars drives a CO outflow that has created a cavity to the southeast. We see a magnetic field that appears to be aligned with the cavity walls of the outflow, suggesting interaction with the outflow. We also find a magnetic field strength of up to similar to 160 +/- 30 mu G in the main starless core and up to similar to 90 +/- 40 mu G in the more diffuse, extended region. These field strengths give magnetically super- and subcritical values, respectively, and both are found to be roughly trans-Alfvenic. We also present a new method of data reduction for these denser but fainter objects like starless cores.
|
|
| 22. |
- Kwon, Woojin, et al.
(författare)
-
B-fields in Star-forming Region Observations (BISTRO): Magnetic Fields in the Filamentary Structures of Serpens Main
- 2022
-
Ingår i: Astrophysical Journal. - : American Astronomical Society. - 1538-4357 .- 0004-637X. ; 926:2
-
Tidskriftsartikel (refereegranskat)abstract
- We present 850 mu m polarimetric observations toward the Serpens Main molecular cloud obtained using the POL-2 polarimeter on the James Clerk Maxwell Telescope as part of the B-fields In STar-forming Region Observations survey. These observations probe the magnetic field morphology of the Serpens Main molecular cloud on about 6000 au scales, which consists of cores and six filaments with different physical properties such as density and star formation activity. Using the histogram of relative orientation (HRO) technique, we find that magnetic fields are parallel to filaments in less-dense filamentary structures where NH2 < 0.93 x 10(22) cm(-2) (magnetic fields perpendicular to density gradients), while they are perpendicular to filaments (magnetic fields parallel to density gradients) in dense filamentary structures with star formation activity. Moreover, applying the HRO technique to denser core regions, we find that magnetic field orientations change to become perpendicular to density gradients again at NH2 approximate to 4.6 x 10(22) NH2 approximate to 16 x 10(22) cm(-2), magnetic fields change back to being parallel to density gradients once again, which can be understood to be due to magnetic fields being dragged in by infalling material. In addition, we estimate the magnetic field strengths of the filaments (B-POS = 60-300 mu G)) using the Davis-Chandrasekhar-Fermi method and discuss whether the filaments are gravitationally unstable based on magnetic field and turbulence energy densities.
|
|
| 23. |
- Leszczynska, M., et al.
(författare)
-
Thermal Variation of Structure and Electrical Conductivity in Bi4YbO7.5
- 2013
-
Ingår i: Chemistry of Materials. - : American Chemical Society (ACS). - 1520-5002 .- 0897-4756. ; 25:3, s. 326-336
-
Tidskriftsartikel (refereegranskat)abstract
- The thermal behavior of the oxide ion-conducting solid electrolyte Bi4YbO7.5 was investigated using a combination of variable temperature X-ray and neutron powder diffraction, thermal analysis (DTA and TGA), and ac impedance spectroscopy. The title compound shows a fluorite-type structure throughout the measured temperature range (20-850 degrees C), with a phase separation at ca. 600 degrees C into a cubic delta-type phase and an orthorhombic phase of assumed stoichiometry Bi17Yb7O36. This type of transition is a relatively common feature in bismuth oxide-based systems and can limit their practical application. Here, the transition was carefully studied using isothermal measurements, which showed that it is accompanied by changes in oxide-ion stoichiometry, as well as significant disorder in the oxide ion sublattice in the delta-type phase. These results correlate with the observed electrical behavior. Analysis of the total neutron scattering through reverse Monte Carlo (RMC) modeling reveals details of the coordination environments for both cations. The oxide-ion vacancy distribution seems to be consistent with a favoring of vacancy pairs, although vacancy pairs exhibit the highest frequency as they have the maximum likelihood. A vacancy ordering model based on three vacancies per cell is presented.
|
|
| 24. |
|
|
| 25. |
- Oka, M., et al.
(författare)
-
Electron Scattering by High-frequency Whistler Waves at Earth's Bow Shock
- 2017
-
Ingår i: Astrophysical Journal Letters. - : Institute of Physics Publishing (IOPP). - 2041-8205 .- 2041-8213. ; 842:2
-
Tidskriftsartikel (refereegranskat)abstract
- Electrons are accelerated to non-thermal energies at shocks in space and astrophysical environments. While different mechanisms of electron acceleration have been proposed, it remains unclear how non-thermal electrons are produced out of the thermal plasma pool. Here, we report in situ evidence of pitch-angle scattering of nonthermal electrons by whistler waves at Earth's bow shock. On 2015 November 4, the Magnetospheric Multiscale (MMS) mission crossed the bow shock with an Alfvn Mach number similar to 11 and a shock angle similar to 84 degrees. In the ramp and overshoot regions, MMS revealed bursty enhancements of non-thermal (0.5-2 keV) electron flux, correlated with high-frequency (0.2-0.4 Omega(ce), where Omega(ce) is the cyclotron frequency) parallel-propagating whistler waves. The electron velocity distribution (measured at 30 ms cadence) showed an enhanced gradient of phase-space density at and around the region where the electron velocity component parallel to the magnetic field matched the resonant energy inferred from the wave frequency range. The flux of 0.5 keV electrons (measured at 1 ms cadence) showed fluctuations with the same frequency. These features indicate that non-thermal electrons were pitch-angle scattered by cyclotron resonance with the high-frequency whistler waves. However, the precise role of the pitch-angle scattering by the higher-frequency whistler waves and possible nonlinear effects in the electron acceleration process remains unclear.
|
|
| 26. |
- Schiebel, Ralf, et al.
(författare)
-
Advances in planktonic foraminifer research : New perspectives for paleoceanography
- 2018
-
Ingår i: Revue de Micropaleontologie. - : Elsevier BV. - 0035-1598 .- 1873-4413. ; 61:3-4, s. 113-138
-
Forskningsöversikt (refereegranskat)abstract
- Planktonic foraminifer tests are major archives of environmental change and provide a multitude of proxies in paleoceanography and paleoclimatology. The application of such proxies is contingent upon a collaborative effort to better understand how the living organisms record the properties of their environment and how the resulting signals are recorded in marine sediments. In this contribution, we provide a review of the rapidly developing sub-fields of research, where new advances have been made possibleby technological developments, and by cross-disciplinary work of the scientific community. Following brief historical overviews of the sub-fields, we discuss the latest advances in planktonic foraminifer research and highlight the resulting new perspectives in ocean and climate research. Natural classification based on consistent species concepts forms the basis for analysis of any foraminifer-derived proxy. New approaches in taxonomy and phylogeny of Cenozoic planktonic foraminifers (Section 2) are presented, highlighting new perspectives on sensitivity and response of planktonic foraminifers to the changing climate and environment (Section 4). Calibration of foraminifer-specific data and environmental parameters is improving along with the technical development of probes and the access to samples from the natural environment (Section 3), enhancing our understanding of the ever-changing climate and ocean system. Comprehension of sedimentation and flux dynamics facilitates maximum gain of information from fossil assemblages (Section 5). Subtle changes in the physical (e.g., temperature), chemical (e.g., pH), and biological (e.g., food) conditions of ambient seawater affect the abundance of species and composition of assemblages as well as the chemical composition of the foraminifer shell and provide increasingly-detailed proxy data on paleoenvironments (Section 6).
|
|
| 27. |
- Terenius, Olle, et al.
(författare)
-
RNA interference in Lepidoptera : An overview of successful and unsuccessful studies and implications for experimental design
- 2011
-
Ingår i: Journal of insect physiology. - : Elsevier BV. - 0022-1910 .- 1879-1611. ; 57:2, s. 231-245
-
Tidskriftsartikel (refereegranskat)abstract
- Gene silencing through RNA interference (RNAi) has revolutionized the study of gene function, particularly in non-model insects. However, in Lepidoptera (moths and butterflies) RNAi has many times proven to be difficult to achieve. Most of the negative results have been anecdotal and the positive experiments have not been collected in such a way that they are possible to analyze. In this review, we have collected detailed data from more than 150 experiments including all to date published and many unpublished experiments. Despite a large variation in the data, trends that are found are that RNAi is particularly successful in the family Saturniidae and in genes involved in immunity. On the contrary, gene expression in epidermal tissues seems to be most difficult to silence. In addition, gene silencing by feeding dsRNA requires high concentrations for success. Possible causes for the variability of success in RNAi experiments in Lepidoptera are discussed. The review also points to a need to further investigate the mechanism of RNAi in lepidopteran insects and its possible connection to the innate immune response. Our general understanding of RNAi in Lepidoptera will be further aided in the future as our public database at http://insectacentral.org/RNAi will continue to gather information on RNAi experiments.
|
|
| 28. |
- Wolever, Thomas M S, et al.
(författare)
-
Measuring the glycemic index of foods: interlaboratory study.
- 2008
-
Ingår i: The American journal of clinical nutrition. - 0002-9165 .- 1938-3207. ; 87:1
-
Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: Many laboratories offer glycemic index (GI) services. OBJECTIVE: We assessed the performance of the method used to measure GI. DESIGN: The GI of cheese-puffs and fruit-leather (centrally provided) was measured in 28 laboratories (n=311 subjects) by using the FAO/WHO method. The laboratories reported the results of their calculations and sent the raw data for recalculation centrally. RESULTS: Values for the incremental area under the curve (AUC) reported by 54% of the laboratories differed from central calculations. Because of this and other differences in data analysis, 19% of reported food GI values differed by >5 units from those calculated centrally. GI values in individual subjects were unrelated to age, sex, ethnicity, body mass index, or AUC but were negatively related to within-individual variation (P=0.033) expressed as the CV of the AUC for repeated reference food tests (refCV). The between-laboratory GI values (mean+/-SD) for cheese-puffs and fruit-leather were 74.3+/-10.5 and 33.2+/-7.2, respectively. The mean laboratory GI was related to refCV (P=0.003) and the type of restrictions on alcohol consumption before the test (P=0.006, r2=0.509 for model). The within-laboratory SD of GI was related to refCV (P<0.001), the glucose analysis method (P=0.010), whether glucose measures were duplicated (P=0.008), and restrictions on dinner the night before (P=0.013, r2=0.810 for model). CONCLUSIONS: The between-laboratory SD of the GI values is approximately 9. Standardized data analysis and low within-subject variation (refCV<30%) are required for accuracy. The results suggest that common misconceptions exist about which factors do and do not need to be controlled to improve precision. Controlled studies and cost-benefit analyses are needed to optimize GI methodology. The trial was registered at clinicaltrials.gov as NCT00260858.
|
|
| 29. |
|
|
| 30. |
|
|
| 31. |
- Haynes, R.J., et al.
(författare)
-
New high temperature gas flow cell developed at ISIS
- 2009
-
Ingår i: Journal of Physics: Conference Series. - : IOP Publishing. - 1742-6588 .- 1742-6596. ; 251:1, s. Art. no. 012090-
-
Konferensbidrag (refereegranskat)abstract
- A flow-through quartz gas cell, together with a gas flow control and monitoring system, has been designed and constructed at ISIS. This equipment allows neutron powder diffraction data to be collected on samples at temperatures up to around 1300 K when exposed to user chosen mixtures of O2, Ar, CO2, and CO. By exploiting the sensitivity of neutrons to the presence of light atoms such as oxygen, it is possible to probe the crystal structure of oxide materials as a function of oxygen partial pressures down to log 10p(O2) of about -20. The resultant structural information can then be correlated with the bulk properties of the materials, whose research and technological interests lie in fields such as energy production, storage materials, catalysis, and earth science.
|
|
| 32. |
- Hull, C. M., et al.
(författare)
-
Geometry of the N=2 supersymmetric sigma model with Euclidean worldsheet
- 2009
-
Ingår i: Journal of High Energy Physics (JHEP). - : Springer Science and Business Media LLC. - 1126-6708 .- 1029-8479. ; :7, s. 078-
-
Tidskriftsartikel (refereegranskat)abstract
- We investigate the target space geometry of supersymmetric sigma models in two dimensions with Euclidean signature, and the conditions for N = 2 supersymmetry. For a real action, the geometry for the N = 2 model is not the generalized Kahler geometry that arises for Lorentzian signature, but is an interesting modification of this which is not a complex geometry.
|
|
| 33. |
- Hull, C. M., et al.
(författare)
-
Topological sigma models with H-flux
- 2008
-
Ingår i: Journal of High Energy Physics (JHEP). - : Springer Science and Business Media LLC. - 1126-6708 .- 1029-8479. ; :9, s. 057-
-
Tidskriftsartikel (refereegranskat)abstract
- We investigate the topological theory obtained by twisting the N = (2, 2) supersymmetric nonlinear sigma model with target a bihermitian space with torsion. For the special case in which the two complex structures commute, we show that the action is a Q-exact term plus a quasi-topological term. The quasi-topological term is locally given by a closed two-form which corresponds to a flat gerbe-connection and generalises the usual topological term of the A-model. Exponentiating it gives a Wilson surface, which can be regarded as a generalization of a Wilson line. This makes the quantum theory globally well-defined.
|
|
| 34. |
|
|
| 35. |
- Lebedkin, S., et al.
(författare)
-
Dimerization of C70 under high pressure : thermal dissociation and photophysical properties of the dimer C140
- 2000
-
Ingår i: Electronic properties od novel materials-molecular nanostructures. - Meville, NY : American Institute of Physics (AIP). - 1563969734 ; , s. 77-80
-
Konferensbidrag (refereegranskat)abstract
- We have recently shown that solid C70 efficiently converts into a cap-to-cap dimer C2hC140 at pressure of ~1 GPa and temperature of ~200 °C [1]. Here we report on measurements of the thermal dissociation of C140 (purified by chromatography) at ambient pressure and its photophysical properties, in particular photogeneration of singlet oxygen (1O2). The kinetics of dissociation of C140 in the solid state between 130 and 200 °C is well described by a simple first-order process, with an activation energy of 1.6±0.03 eV (compare to 1.75±0.05 eV for the C60 dimer C120 [2]). In contrast, the thermal dissociation of C140 dissolved in o-dichlorobenzene shows different, non-Arrhenius behavior, suggesting a strong influence of the molecular surroundings. The quantum efficiency of 1O2 generation in solutions of C140 and C120 is close to unity, i.e. similar to that of C70 and C60.
|
|
| 36. |
- Lebedkin, S., et al.
(författare)
-
Structure and properties of the fullerene dimer C140 produced by pressure treatment of C70
- 2000
-
Ingår i: Journal of Physical Chemistry B. - : American Chemical Society (ACS). - 1520-6106 .- 1520-5207. ; 104:17, s. 4101-4110
-
Tidskriftsartikel (refereegranskat)abstract
- A [2+2] cycloaddition cap-to-cap C70 dimer with C2h molecular symmetry was synthesized in high yield by pressure treatment of polycrystalline C70 at 1 GPa and 200° C. It was separated from unreacted monomers by chromatography and characterized by 13C NMR, Raman, and infrared spectroscopy, and other methods. Remarkably, only one isomer was produced out of the five possible [2+2] cycloaddition products which have equally low formation energies according to semiempirical modeling calculations. The dimer obtained is the one favored when C70 molecules adopt an ordered packing with parallel D5 axes. The intercage bonding in C140, its thermal stability, and intercage vibrational modes are similar to those found for the C60 dimer, C120. Both dimers photodissociate to the monomers in solution, probably via excited triplet states. The UV absorption and fluorescence properties of C140 are not very different from those of C70, suggesting only weak electronic interactions between the two cages of C140. In comparison, the pressure-induced dimerization of C60, under the conditions used for C70, results mainly in C60 oligomers and polymeric chains, but the dimer C120 could be isolated at low yield when short reaction times (≤5 min) were used.
|
|
| 37. |
- Leszczynska, M., et al.
(författare)
-
Oxide ion distribution, vacancy ordering and electrical behaviour in the Bi3NbO7-Bi3YbO6 pseudo-binary system
- 2014
-
Ingår i: Journal of Materials Chemistry A. - : Royal Society of Chemistry (RSC). - 2050-7488 .- 2050-7496. ; 2:43, s. 18624-18634
-
Tidskriftsartikel (refereegranskat)abstract
- Oxide ion distribution, vacancy ordering and electrical conductivity has been examined in the Nb/Yb double substituted bismuth oxide based system Bi3Nb1-xYbxO7-x, using X-ray and neutron powder diffraction, reverse Monte Carlo modelling of total neutron scattering data and a. c. impedance spectroscopy. Transference number measurements confirm the system to be predominantly ionically conducting above ca. 450 degrees C. Niobium rich compositions show incommensurate ordering of the fluorite subcell, while increasing ytterbium content results in a commensurate fluorite, with fully disordered cation and anion sublattices. Oxide ion distribution shows both compositional and thermal dependencies. The latter is discussed with respect to its effect on the thermal variation of cubic lattice parameter. Substitution of bismuth by niobium and ytterbium in the cation sublattice of bismuth oxide leads to the creation of Frenkel interstitial oxide ions, which increase the tetrahedral vacancy concentration. The high vacancy concentration is confirmed in both Rietveld and RMC analyses of neutron data. Examination of vacancy ordering, in the x - 0.6 composition, indicates a favouring of vacancy pair alignment.
|
|
| 38. |
- Leszczynska, M., et al.
(författare)
-
Total scattering analysis of cation coordination and vacancy pair distribution in Yb substituted delta-Bi2O3
- 2013
-
Ingår i: Journal of Physics Condensed Matter. - : IOP Publishing. - 0953-8984 .- 1361-648X. ; 25:45
-
Tidskriftsartikel (refereegranskat)abstract
- Reverse Monte Carlo (RMC) modelling of neutron total scattering data, combined with conventional Rietveld analysis of x-ray and neutron data, has been used to describe the cation coordination environments and vacancy pair distribution in the oxide ion conducting electrolyte Bi3YbO6. The thermal variation of the cubic fluorite unit cell volume, monitored by variable temperature x-ray and neutron experiments, reveals significant curvature, which is explained by changes in the oxide ion distribution. There is a significant increase in tetrahedral oxide ion vacancy concentration relative to delta-Bi2O3, due to the creation of Frenkel defects associated with the Yb3+ cation. The tetrahedral oxide ion vacancy concentration increases from room temperature to 800 degrees C, but little change is observed in the vacancy pair distribution with temperature. The vacancy pair distributions at both temperatures are consistent with a favouring of vacancy pairs.
|
|
| 39. |
- Lyo, A-Ran, et al.
(författare)
-
The JCMT BISTRO Survey: An 850/450 mu m Polarization Study of NGC 2071IR in Orion B
- 2021
-
Ingår i: Astrophysical Journal. - : American Astronomical Society. - 1538-4357 .- 0004-637X. ; 918:2
-
Tidskriftsartikel (refereegranskat)abstract
- We present the results of simultaneous 450 mu m and 850 mu m polarization observations toward the massive star-forming region NGC 2071IR, a target of the BISTRO (B-fields in STar-forming Region Observations) Survey, using the POL-2 polarimeter and SCUBA-2 camera mounted on the James Clerk Maxwell Telescope. We find a pinched magnetic field morphology in the central dense core region, which could be due to a rotating toroidal disklike structure and a bipolar outflow originating from the central young stellar object IRS 3. Using the modified Davis-Chandrasekhar-Fermi method, we obtain a plane-of-sky magnetic field strength of 563 +/- 421 mu G in the central similar to 0.12 pc region from 850 mu m polarization data. The corresponding magnetic energy density of 2.04 x 10(-8) erg cm(-3) is comparable to the turbulent and gravitational energy densities in the region. We find that the magnetic field direction is very well aligned with the whole of the IRS 3 bipolar outflow structure. We find that the median value of polarization fractions is 3.0% at 450 mu m in the central 3 ' region, which is larger than the median value of 1.2% at 850 mu m. The trend could be due to the better alignment of warmer dust in the strong radiation environment. We also find that polarization fractions decrease with intensity at both wavelengths, with slopes, determined by fitting a Rician noise model of 0.59 +/- 0.03 at 450 mu m and 0.36 +/- 0.04 at 850 mu m, respectively. We think that the shallow slope at 850 mu m is due to grain alignment at the center being assisted by strong radiation from the central young stellar objects.
|
|
| 40. |
- Ngoc, Nguyen Bich, et al.
(författare)
-
Observations of Magnetic Fields Surrounding LkH alpha 101 Taken by the BISTRO Survey with JCMT-POL-2
- 2021
-
Ingår i: Astrophysical Journal. - : American Astronomical Society. - 1538-4357 .- 0004-637X. ; 908:1
-
Tidskriftsartikel (refereegranskat)abstract
- We report the first high spatial resolution measurement of magnetic fields surrounding LkH alpha 101, part of the Auriga-California molecular cloud. The observations were taken with the POL-2 polarimeter on the James Clerk Maxwell Telescope within the framework of the B-fields In Star-forming Region Observations (BISTRO) survey. Observed polarization of thermal dust emission at 850 mu m is found to be mostly associated with the redshifted gas component of the cloud. The magnetic field displays a relatively complex morphology. Two variants of the Davis-Chandrasekhar-Fermi method, unsharp masking and structure function, are used to calculate the strength of magnetic fields in the plane of the sky, yielding a similar result of B-POS similar to 115 mu G. The mass-to-magnetic-flux ratio in critical value units, lambda similar to 0.3, is the smallest among the values obtained for other regions surveyed by POL-2. This implies that the LkH alpha 101 region is subcritical, and the magnetic field is strong enough to prevent gravitational collapse. The inferred delta B/B-0 similar to 0.3 implies that the large-scale component of the magnetic field dominates the turbulent one. The variation of the polarization fraction with total emission intensity can be fitted by a power law with an index of alpha = 0.82 0.03, which lies in the range previously reported for molecular clouds. We find that the polarization fraction decreases rapidly with proximity to the only early B star (LkH alpha 101) in the region. Magnetic field tangling and the joint effect of grain alignment and rotational disruption by radiative torques can potentially explain such a decreasing trend.
|
|
| 41. |
- von der Lieth, Claus-Wilhelm, et al.
(författare)
-
EUROCarbDB : an open-access platform for glycoinformatics
- 2011
-
Ingår i: Glycobiology. - : Oxford University Press (OUP). - 0959-6658 .- 1460-2423. ; 21:4, s. 493-502
-
Tidskriftsartikel (refereegranskat)abstract
- The EUROCarbDB project is a design study for a technical framework, which provides sophisticated, freely accessible, open-source informatics tools and databases to support glycobiology and glycomic research. EUROCarbDB is a relational database containing glycan structures, their biological context and, when available, primary and interpreted analytical data from high-performance liquid chromatography, mass spectrometry and nuclear magnetic resonance experiments. Database content can be accessed via a web-based user interface. The database is complemented by a suite of glycoinformatics tools, specifically designed to assist the elucidation and submission of glycan structure and experimental data when used in conjunction with contemporary carbohydrate research workflows. All software tools and source code are licensed under the terms of the Lesser General Public License, and publicly contributed structures and data are freely accessible. The public test version of the web interface to the EUROCarbDB can be found at http://www.ebi.ac.uk/eurocarb.
|
|
| 42. |
- Abrahams, I., et al.
(författare)
-
A Combined Total Scattering and Simulation Approach to Analyzing Defect Structure in Bi3YO6
- 2010
-
Ingår i: Chemistry of Materials. - : American Chemical Society (ACS). - 1520-5002 .- 0897-4756. ; 22:15, s. 4435-4445
-
Tidskriftsartikel (refereegranskat)abstract
- The defect structure and electrical properties of the fast oxide ion-conducting solid electrolyte delta-Bi3YO6 have been studied using a combination of total neutron scattering analysis, energy minimization methods, and AC impedance spectroscopy. Conventional structural analysis using the Rietveld method reveals the oxide ions to be distributed over three crystallographic sites at room temperature, with a small change in this distribution at 800 degrees C. Analysis of short-range correlations using a total neutron scattering approach yields information on Bi and Y coordination environments. Careful analysis of the angular distribution functions derived from reverse Monte Carlo modeling of the total scattering data reveals physical evidence for a predominance of vacancy ordering in this system. This ordering is confirmed as the lowest energy configuration in parallel energy minimization simulations.
|
|
| 43. |
- Biendicho, J. J., et al.
(författare)
-
Synthesis and characterization of perovskite-type Sr(x)Y1-xFeO(3-delta) (0.63 <= x < 1.0) and Sr0.75Y0.25Fe1-yMyO3-delta (M=Cr, Mn, Ni), (y=0.2, 0.33, 0.5)
- 2013
-
Ingår i: Journal of Solid State Chemistry. - : Elsevier BV. - 0022-4596 .- 1095-726X. ; 200, s. 30-38
-
Tidskriftsartikel (refereegranskat)abstract
- Oxygen-deficient ferrates with the cubic perovskite structure SrxY1-xFeO3-delta were prepared in air (0.71 <= x <= 0.91) as well as in N-2 (x=0.75 and 0.79) at 1573 K. The oxygen content of the compounds prepared in air increases with increasing strontium content from 3-delta=2.79(2) for x=0.75 to 3-delta=2.83(2) for x=0.91. Refinement of the crystal structure of Sr0.25Y0.25FeO2.29 using TOP neutron powder diffraction (NPD) data shows high anisotropic atomic displacement parameter (ADP) for the oxygen atom resulting from a substantial cation and anion disorder. Electron diffraction (ED) and highresolution electron microscopy (HREM) studies of Sr0.75Y0.25FeO2.79 reveal a modulation along (1 0 0)(p) with G +/- similar to 0.4(1 0 0)(p) indicating a local ordering of oxygen vacancies. Magnetic susceptibility measurements at 5-390 K show spin-glass behaviour with dominating antiferromagnetic coupling between the magnetic moments of Fe cations. Among the studied compositions, Sr0.75Y0.25Fe02.79 shows the lowest thermal expansion coefficient (TEC) of 10.5 ppm/K in air at 298-673 K. At 773-1173 K TEC increases up to 17.2 ppm/K due to substantial reduction of oxygen content. The latter also results in a dramatic decrease of the electrical conductivity in air above 673 K. Partial substitution of Fe by Cr, Mn and Ni according to the formula Sr0.75Y0.25Fe1-yMyO3-delta (y=0.2, 0.33, 0.5) leads to cubic perovskites for all substituents with y=0.2. Their TECs are higher in comparison with un-doped Sr0.75Y0.25Fe02.79. Only M=Ni has increased electrical conductivity compared to un-doped Sr0.75Y0.25Fe02.79.
|
|
| 44. |
- Biendicho, Jordi Jacas, et al.
(författare)
-
Synthesis and characterization of perovskite-type SrxY1−xFeO3−δ (0.63≤x<1.0) and Sr0.75Y0.25Fe1−yMyO3−δ (M=Cr, Mn, Ni), (y=0.2, 0.33, 0.5)
- 2013
-
Ingår i: Journal of Solid State Chemistry. - : Elsevier BV. - 0022-4596 .- 1095-726X. ; 200, s. 30-38
-
Tidskriftsartikel (refereegranskat)abstract
- Oxygen-deficient ferrates with the cubic perovskite structure SrxY1-xFeO3-d were prepared in air (0.71 ≤ x ≤ 0.91) as well as in N2 (x=0.75 and 0.79) at 1573K. The oxygen content of the compounds prepared in air increases with increasing strontium content from 3-δ=2.79(2) for x=0.75 to 3-δ=2.83(2) for x=0.91. Refinement of the crystal structure of Sr0.75Y0.25FeO2.79 using TOF neutron powder diffraction (NPD) data shows high anisotropic atomic displacement parameter (ADP) for the oxygen atom resulting from a substantial cation and anion disorder. Electron diffraction (ED) and high-resolution electron microscopy (HREM) studies of Sr0.75Y0.25FeO2.79 reveal a modulation along <100>p with G± ~0.4<100>p indicating a local ordering of oxygen vacancies. Magnetic susceptibility measurements at 5-390K show spin-glass behaviour with dominating antiferromagnetic coupling between the magnetic moments of Fe cations. Among the studied compositions, Sr0.75Y0.25FeO2.79 shows the lowest thermal expansion coefficient (TEC) of 10.5 ppm K-1 in air at 298-673K. At 773-1173K TEC increases up to 17.2 ppm K-1 due to substantial reduction of oxygen content. The latter also results in a dramatic decrease of the electrical conductivity in air above 673K. Partial substitution of Fe by Cr, Mn and Ni according to the formula Sr0.75Y0.25Fe1-yMyO3-δ (y=0.2, 0.33, 0.5) leads to cubic perovskites for all substituents with y=0.2. Their TECs are higher in comparison with un-doped Sr0.75Y0.25FeO2.79. Only M=Ni has increased electrical conductivity compared to un-doped Sr0.75Y0.25FeO2.79.
|
|
| 45. |
- Boettcher, Erin, et al.
(författare)
-
VV 655 and NGC 4418: Implications of an interaction for the evolution of a LIRG
- 2020
-
Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 637
-
Tidskriftsartikel (refereegranskat)abstract
- Context. VV655, a dwarf irregular galaxy with HI tidal debris, is a companion to the lenticular luminous infrared galaxy (LIRG) NGC4418. NGC4418 stands out among nearby LIRGs due to its dense central concentration of molecular gas and the dusty, bi-polar structures along its minor axis suggestive of a wind driven by a central starburst and possible nuclear activity. Aims. We seek to understand the consequences of the ongoing minor interaction between VV655 and NGC4418 for the evolution of the LIRG. Specifically, we consider the origin of the gas supply responsible for the unusual nuclear properties of NGC4418. Methods. We investigate the structural, kinematic, and chemical properties of VV655 and NGC4418 by analyzing archival imaging data and optical spectroscopic observations from the SDSS-III and new spectra from SALT-RSS. We characterize their gas-phase metal abundances and spatially resolved, ionized gas kinematics to better understand whether gas transfer between VV655 and NGC4418 resulted in the highly obscured nucleus of the LIRG. Results. The gas-phase metallicity in NGC4418 significantly exceeds that in VV655. No kinematic disturbances in the ionized gas are observed along the minor axis of NGC4418, but we see evidence for ionized gas outflows from VV655 that may increase the cross-section for gas stripping in grazing collisions. A faint, asymmetric outer arm is detected in NGC4418 of the type normally associated with galaxy-galaxy interactions. Conclusions. The simplest model suggests that the minor interaction between VV655 and NGC4418 produced the unusual nuclear properties of the LIRG via tidal torquing of the interstellar medium of NGC4418 rather than through a significant gas transfer event. In addition to inducing a central concentration of gas in NGC4418, this interaction also produced an enhanced star formation rate and an outer tidal arm in the LIRG. The VV655-NGC 4418 system offers an example of the potential for minor collisions to alter the evolutionary pathways of giant galaxies.
|
|
| 46. |
- Burbano, M., et al.
(författare)
-
A dipole polarizable potential for reduced and doped CeO2 obtained from first principles
- 2011
-
Ingår i: Journal of Physics Condensed Matter. - : IOP Publishing. - 0953-8984 .- 1361-648X. ; 23:25
-
Tidskriftsartikel (refereegranskat)abstract
- In this paper we present the parameterization of a new interionic potential for stoichiometric, reduced and doped CeO2. We use a dipole polarizable potential (DIPPIM: the dipole polarizable ion model) and optimize its parameters by fitting them to a series of density functional theory calculations. The resulting potential was tested by calculating a series of fundamental properties for CeO2 and by comparing them against experimental values. The values for all the calculated properties (thermal and chemical expansion coefficients, lattice parameters, oxygen migration energies, local crystalline structure and elastic constants) are within 10-15% of the experimental ones, an accuracy comparable to that of ab initio calculations. This result suggests the use of this new potential for reliably predicting atomic scale properties of CeO2 in problems where ab initio calculations are not feasible due to their size limitations.
|
|
| 47. |
- Burbano, M., et al.
(författare)
-
Oxygen Vacancy Ordering and the Conductivity Maximum in Y(2)O(3)-Doped CeO(2)
- 2012
-
Ingår i: Chemistry of Materials. - : American Chemical Society (ACS). - 1520-5002 .- 0897-4756. ; 24:1, s. 222-229
-
Tidskriftsartikel (refereegranskat)abstract
- The defect structure and ionic diffusion processes within the anion-deficient, fluorite structured system Ce(1-x)Y(x)O(2-x/2) have been investigated at high temperatures (873 K-1073 K) as a function of dopant concentration, x, using a combination of neutron diffraction studies, impedance spectroscopy measurements, and molecular dynamics (MD) simulations using interionic potentials developed from ab initio calculations. Particular attention is paid to the short-range ion-ion correlations, with no strong evidence that the anion vacancies prefer, at high temperature, to reside in the vicinity of either cationic species. However, the vacancy-vacancy interactions play a more important role, with preferential ordering of vacancy pairs along the directions, driven by their strong repulsion at closer distances, becoming dominant at high values of x. This effect explains the presence of a maximum in the ionic conductivity in the intermediate temperature range as a function of increasing x. The wider implications of these conclusions for understanding the structure property relationships within anion-deficient fluorite structured oxides are briefly discussed, with reference to complementary studies of yttria and/or scandia doped zirconia published previously.
|
|
| 48. |
|
|
| 49. |
|
|
| 50. |
- Grady, Christine, et al.
(författare)
-
Broad Consent for Research With Biological Samples : Workshop Conclusions
- 2015
-
Ingår i: American Journal of Bioethics. - : Informa UK Limited. - 1526-5161 .- 1536-0075. ; 15:9, s. 34-42
-
Tidskriftsartikel (refereegranskat)abstract
- Different types of consent are used to obtain human biospecimens for future research. This variation has resulted in confusion regarding what research is permitted, inadvertent constraints on future research, and research proceeding without consent. The National Institutes of Health (NIH) Clinical Center's Department of Bioethics held a workshop to consider the ethical acceptability of addressing these concerns by using broad consent for future research on stored biospecimens. Multiple bioethics scholars, who have written on these issues, discussed the reasons for consent, the range of consent strategies, and gaps in our understanding, and concluded with a proposal for broad initial consent coupled with oversight and, when feasible, ongoing provision of information to donors. This article describes areas of agreement and areas that need more research and dialogue. Given recent proposed changes to the Common Rule, and new guidance regarding storing and sharing data and samples, this is an important and timely topic.
|
|
