| 1. |
|
|
| 2. |
- Betoule, M., et al.
(författare)
-
Improved cosmological constraints from a joint analysis of the SDSS-II and SNLS supernova samples
- 2014
-
Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 568, s. A22-
-
Tidskriftsartikel (refereegranskat)abstract
- Aims. We present cosmological constraints from a joint analysis of type la supernova (SN Ia) observations obtained by the SDSS-II and SNLS collaborations. The dataset includes several low-redshift samples (z < 0.1), all three seasons from the SDSS-11 (0.05 < z < 0.4), and three years from SNLS (0.2 < z < 1), and it totals 740 spectroscopically confirmed type la supernovae with high quality light curves. Methods. We followed the methods and assumptions of the SNLS three-year data analysis except for the following important improvements: I) the addition of the full SDSS-II spectroscopically-confirmed SN la sample in both the training of the SALT2 light-curve model and in the Hubble diagram analysis (374 SNe); 2) intercalibration of the SNLS and SDSS surveys and reduced systematic uncertainties in the photometric calibration, performed blindly with respect to the cosmology analysis; and 3) a thorough investigation of systematic errors associated with the SALT2 modeling of SN la light curves. Results. We produce recalibrated SN la light curves and associated distances for the SDSS-II and SNLS samples. The large SOSS-II sample provides an effective, independent, low -z anchor for the Hubble diagram and reduces the systematic error from calibration systematics in the low -z SN sample. For a flat ACDM cosmology, we find Omega(m), = 0.295 0.034 (stat+sys), a value consistent with the most recent cosmic microwave background (CMB) measurement from the Planck and WMAP experiments. Our result is 1.8 sigma (stat+sys) different than the previously published result of SNLS three-year data. The change is due primarily to improvements in the SNLS photometric calibration. When combined with CMB constraints, we measure a constant dark energy equation of state parameter omega = -1.018 +/- 0,057 (sral+sys) for a fiat universe. Adding baryon acoustic oscillation distance measurements gives similar constraints: omega = 59 -1.027 0.055. Our supernova measurements provide the most stringent constraints to date on the nature of dark energy.
|
|
| 3. |
- Fu, Yifeng, 1984, et al.
(författare)
-
Templated Growth of Covalently Bonded Three-Dimensional Carbon Nanotube Networks Originated from Graphene
- 2012
-
Ingår i: Advanced Materials. - : Wiley. - 0935-9648 .- 1521-4095. ; 24:12, s. 1576-1581
-
Tidskriftsartikel (refereegranskat)abstract
- A template-assisted method that enables the growth of covalently bonded three-dimensional carbon nanotubes (CNTs) originating from graphene at a large scale is demonstrated. Atomic force microscopy-based mechanical tests show that the covalently bonded CNT structure can effectively distribute external loading throughout the network to improve the mechanical strength of the material.
|
|
| 4. |
- Wang, Xiaofeng, et al.
(författare)
-
Evidence for type ia supernova diversity from ultraviolet observations with the hubble space telescope
- 2012
-
Ingår i: Astrophysical Journal. - 0004-637X .- 1538-4357. ; 749:2, s. 126-
-
Tidskriftsartikel (refereegranskat)abstract
- We present ultraviolet (UV) spectroscopy and photometry of four Type Ia supernovae (SNe 2004dt, 2004ef, 2005M, and 2005cf) obtained with the UV prism of the Advanced Camera for Surveys on the Hubble Space Telescope. This data set provides unique spectral time series down to 2000 angstrom. Significant diversity is seen in the near-maximum-light spectra (similar to 2000-3500 angstrom) for this small sample. The corresponding photometric data, together with archival data from Swift Ultraviolet/Optical Telescope observations, provide further evidence of increased dispersion in the UV emission with respect to the optical. The peak luminositiesmeasured in the uvw1/F250W filter are found to correlate with the B-band light-curve shape parameter Delta m(15)(B), but with much larger scatter relative to the correlation in the broadband B band (e.g., similar to 0.4 mag versus similar to 0.2 mag for those with 0.8 mag < Delta m(15)(B) < 1.7 mag). SN 2004dt is found as an outlier of this correlation (at > 3 sigma), being brighter than normal SNe Ia such as SN 2005cf by similar to 0.9 mag and similar to 2.0 mag in the uvw1/F250W and uvm2/F220W filters, respectively. We show that different progenitor metallicity or line-expansion velocities alone cannot explain such a large discrepancy. Viewing-angle effects, such as due to an asymmetric explosion, may have a significant influence on the flux emitted in the UV region. Detailed modeling is needed to disentangle and quantify the above effects.
|
|
| 5. |
- Carlberg, Björn, 1983, et al.
(författare)
-
Polymer-metal nanofibrous composite for thermal management of microsystems
- 2012
-
Ingår i: Materials Letters. - : Elsevier BV. - 1873-4979 .- 0167-577X. ; 75, s. 229-232
-
Tidskriftsartikel (refereegranskat)abstract
- In this letter, a composite structure based on a porous electrospun polyimide structure infiltrated with indium aimed at thermal interface material applications is presented. A porous nanofibrous structure was prepared by electrospinning of polyimide. An interfacial nanocomposite layer of silver nanoparticles partially or fully embedded in the polyimide matrix was synthesized on the fiber surfaces, followed by autocatalytic deposition of a uniform silver coating (using the interfacial layer as an anchored seed layer) serving as a reactive wetting layer for the infiltrating melt. The thermal performance of the composite was evaluated and the thermal conductivity was determined to be 27 W/mK, accompanied by low contact resistance of the metallurgical bond (
|
|
| 6. |
- Carlberg, Björn, 1983, et al.
(författare)
-
Surface-Confined Synthesis of Silver Nanoparticle Composite Coating on Electrospun Polyimide Nanofibers
- 2011
-
Ingår i: Small. - : Wiley. - 1613-6810 .- 1613-6829. ; 7:21, s. 3057-3066
-
Tidskriftsartikel (refereegranskat)abstract
- A methodology for fabricating hierarchical nanostructures by surface-confined synthesis of silver nanoparticles on electrospun polyimide nanofibers is reported. Through surface-confined imide cleavage at the dianhydride domain via immersion in an aqueous KOH solution, potassium polyamate coatings of accurately defined thickness are formed (at a rate of 25 nm h(-1)). By utilizing the ion-exchange capability of the polyamate resin, silver ions are introduced through immersion in an aqueous AgNO(3) solution. Subsequent reduction of the metal ion species leads to the formation of nanoparticles at the fiber surface. Two modes of reduction, chemical and thermal, are investigated in the report, each leading to distinct morphologies of the nanoparticle coatings. Via thermal reduction, a composite surface layer consisting of monodisperse silver nanoparticles (average diameter 5.2 nm) embedded in a re-imidized polyimide matrix is achieved. In the case of chemical reduction, the reduction process occurs preferentially at the surface of the fiber, leading to the formation of silver nanoparticles anchored at the surface, though not embedded, in a polyamic acid matrix. By regulating the modification depth, control of the particle density on the fiber surface is established. In both reduction approaches, the polyimide nanofiber core exhibits maintained integrity.
|
|
| 7. |
|
|
