| 1. |
- Dietrich, M., et al.
(författare)
-
Monitoring of active galactic nuclei. IV. The Seyfert 1 galaxy NGC 4593
- 1994
-
Ingår i: Astronomy and Astrophysics. - 0004-6361 .- 1432-0746. ; 284:1, s. 33-4343
-
Tidskriftsartikel (refereegranskat)abstract
- Results of a five-month campaign of optical monitoring the Seyfert 1 galaxy NGC 4593 are presented. High resolution Halpha and Hbeta spectra and direct images in the Johnson U, B, V, R and I bands were obtained between January and June 1990. The emission lines and the continuum showed strong variations on time scales of weeks to days. The Halpha line varied by more than 30% within only 5 days. Cross-correlating the light curves of the Balmer lines with that of the optical continuum gives a lag of around 4 days. Therefore, this low luminosity Seyfert galaxy may have one of the smallest broad line regions known so far
|
|
| 2. |
- Wanders, I., et al.
(författare)
-
Spectroscopic monitoring of active galactic nuclei. II. The Seyfert-1 galaxy NGC 3516
- 1993
-
Ingår i: Astronomy and Astrophysics. - 0004-6361 .- 1432-0746. ; 269:1-2, s. 39-5353
-
Tidskriftsartikel (refereegranskat)abstract
- The authors present the results of a five month spectroscopic monitoring campaign of the Seyfert-1 galaxy NGC 3516. Using a new calibration method and applying a correction for seeing differences during the various observations they can scale the spectra to each other with a much higher accuracy than hitherto achieved. NGC 3516 shows large amplitude variations on a time scale of several weeks. Asymmetric profile variations occur on the same time scale as the continuum variations. The authors show the presence of a varying dip on the blue wing of the Hbeta profile, which is not present on the Halpha profile, and which corresponds to the absorption features previously seen in the UV emission lines of NGC 3516. From cross-correlation analysis they find a time lag of 14plusmn2 days for the Halpha and 7plusmn3 days for the Hbeta emission-line response to continuum variations
|
|
| 3. |
|
|
| 4. |
- Nilsson, J, et al.
(författare)
-
Competitive elution of protein A fusion proteins allows specific recovery under mild conditions.
- 1994
-
Ingår i: European Journal of Biochemistry. - : Wiley. - 0014-2956 .- 1432-1033. ; 224:1, s. 103-8
-
Tidskriftsartikel (refereegranskat)abstract
- A novel system is described for mild elution of fusion proteins by competitive elution. The approach is based on displacement of immobilized fusions containing a monovalent IgG-binding staphylococcal protein A fragment (Z) from an IgG-affinity matrix by a divalent fragment fused to a serum-albumin-binding region derived from streptococcal protein G. Using real-time interaction analysis, the binding (K(aff)) to polyclonal human IgG was found to be 3.3 (+/- 0.4) x 10(8) M-1 for divalent ZZ and 2.0 (+/- 0.1) x 10(7) M-1 for monovalent Z. This more than tenfold difference in binding strength ensures a high efficiency in the elution step. The competitor protein can specifically be removed and recovered from the elution mixture by subsequent passage through a human serum albumin(HSA)-affinity column, leaving only the target fusion protein in the flow-through fraction. Here, we show that a recombinant Klenow fragment of DNA polymerase I expressed in Escherichia coli can be recovered with high yield, and retained activity, from a crude bacterial lysate by IgG-affinity chromatography using mild conditions during both binding and elution.
|
|
| 5. |
- SVENSSON, BG, et al.
(författare)
-
SIMS AND DEPTH PROFILING OF SEMICONDUCTOR STRUCTURES
- 1994
-
Ingår i: Nuclear Instruments and Methods in Physics Research Section B. - 0168-583X .- 1872-9584. ; 85, s. 363-369
-
Tidskriftsartikel (refereegranskat)abstract
- This paper reviews recent secondary ion mass spectrometry (SIMS) work on (i) isotope shifts in ion implantation profiles, (ii) dopant profiles in silicon and beam-induced oxidation and (iii) surface roughness and profile broadening of Al(x)Ga1-(x)As/GaAs superlattice structures. Comparison is made with other techniques, and, in particular, the issues of depth resolution and conversion between sputtering time and sample depth are emphasized.
|
|
