Showing papers by "Benjamin L. Schulz published in 2005"

Discovery of 10 μm silicate emission in quasars : Evidence of the agn unification scheme

Abstract: According to the unified scheme, AGN are surrounded by a dust-torus, and the observed diversity of AGN properties results from the different orientations relative to our line of sight. The strong resonance of silicate dust at 10 μ m is therefore, as expected, seen in absorption towards many type-2 AGN. In type-1 AGN, it should be seen in emission because the hot inner surface of the dust torus becomes visible. However, this has not been observed so far, thus challenging the unification scheme or leading to exotic modifications of the dust-torus model. Here we report the discovery of the 10 μ m silicate feature in emission in two luminous quasars with the Infrared Spectrograph of the Spitzer Space Telescope.

Spitzer IRS spectroscopy of 3CR radio galaxies and quasars: testing the unified schemes

Abstract: With the Spitzer Space Telescope Infrared Spectrograph (IRS) we have observed seven powerful FR 2 radio galaxies and seven quasars. Both samples, the galaxies and the quasars, are comparable in isotropic 178 MHz luminosity (10$^{\rm 26.5}$ W/Hz $\la$ $ P_{\rm 178\,MHz} \la10^{\rm 29.5}$ W/Hz) and in redshift range (0.05 $\la$ z $\la$ 1.5). We find for both samples similar distributions in the luminosity ratios of high- to low-excitation lines ([NeV] 14.3~ \mu m / [NeII] 12.8~ \mu m ) and of high-excitation line to radio power ([NeV] 24.3~ \mu m / P 178\,MHz ). This solves the long debate about the apparent difference of quasars and radio galaxies in favor of the orientation-dependent unified schemes. Furthermore, the luminosity ratio [OIII] 500.7~ nm / [OIV] 25.9~ \mu m of most galaxies is by a factor of ten lower than that of the quasars. This suggests that the optical emission from the central NLR is essentially absorbed ( A V $\ga$ 3) in the powerful FR 2 galaxies and that the [OIII] 500.7~ nm luminosity does not serve as isotropic tracer for testing the unified schemes.

MUC5B glycosylation in human saliva reflects blood group and secretor status

Abstract: This study aimed to characterize human salivary glycoforms and the natural glycosylation variation of the major ABO blood group bearing high molecular weight glycoprotein fraction MG1, which mainly consists of MUC5B mucin. Reduced and alkylated mucins from individuals of blood group A, B, and O were purified by sodium dodecyl sulfate-agarose/polyacrylamide composite gel electrophoresis (SDS-AgPAGE), blotted to polyvinylidene fluoride (PVDF) membranes, and visualized with alcian blue. O-linked oligosaccharides were released from MUC5B glycoform bands by reductive beta-elimination and analyzed by liquid chromatography (LC) electrospray ion trap mass spectrometry (MS). Slow electrophoretically migrating MUC5B components (sm) were found to be dominated by neutral oligosaccharides, and fast-migrating (fm) components were dominated by sulfated oligosaccharides. ABO blood group-specific sequences were found on all glycoforms, and novel oligosaccharides containing blood group A and B type sequences were sequenced. This is the first molecular description of the influence of the blood group ABO system on salivary MUC5B oligosaccharides. Expanding these results from the three A, B, and O individuals into larger population (29 individuals), we found oligosaccharide sequences corresponding to the blood group of the donor on MUC5B from 23 individuals. The remaining six individuals were characterized by a high degree of sialylation. These individuals were assigned as nonsecretors, whereas blood group-expressing individuals were assigned as secretors. Western blot assays with antibodies confirmed increased expression of Sialyl Lewis a (Si-Le(a)) in the nonsecretors. Our results highlight that salivary MUC5B consists of glycoforms with distinct glycosylation that vary extensively between individuals and that some of this variation is owing to blood group and secretor status.

Mucin glycosylation changes in cystic fibrosis lung disease are not manifest in submucosal gland secretions

Abstract: SMG (submucosal gland) secretions are a major component of the airway surface liquid, are associated with innate immunity in the lung, and have been reported to be altered in lung disease. Changes in lung mucosal glycosylation have been reported in CF (cystic fibrosis), which may be responsible for differential bacterial binding to glycosylated components in the lung mucosa and hence increased pre-disposition to pulmonary infection. Glycoproteomic analysis was performed on SMG secretions collected from explanted bronchial tissue of subjects with severe lung disease, with and without CF, and controls without lung disease. Mucins MUC5B and MUC5AC were shown to be the dominant high-molecular-mass glycoprotein components, with a minor non-mucin glycoprotein component, gp-340, also present. Oligosaccharides containing blood-group determinants corresponding to subjects' blood type were abundant on MUC5B/MUC5AC, as were Lewis-type epitopes and their sialylated analogues, which are ligands for pathogens and leucocytes. No significant differences were found in the glycosylation of MUC5B/MUC5AC or gp-340 between CF and non-CF subjects with severe lung disease, implying that CF does not influence SMG secretion mucin glycosylation in end-stage lung disease. There were also no significant differences found in the glycosylation of these components in severe lung disease compared with non-diseased lungs. This suggests that previously reported changes in the glycosylation of respiratory glycoconjugates in CF, and other pulmonary conditions, are not due to the glycosylation of components in SMG secretions, but may involve other secretions, responses or extracellular factors.

Fully reflective deep ultraviolet to near infrared spectrometer and entrance optics for resonance Raman spectroscopy

Abstract: We present the design and performance of a new triple-grating deep ultraviolet to near-infrared spectrometer. The system is fully achromatic due to the use of reflective optics. The minimization of image aberrations by using on- and off- axis parabolic mirrors as well as elliptical mirrors yields a strong stray light rejection with high resolution over a wavelength range between 165 and 1000nm. The Raman signal is collected with a reflective entrance objective with a numerical aperture of 0.5, featuring a Cassegrain-type design. Resonance Raman studies on semiconductors and on correlated compounds, such as LaMnO3, highlight the performance of this instrument, and show diverse resonance effects between 1.96 and 5.4eV.

First detections of the cataclysmic variable AE Aquarii in the near to far infrared with ISO and IRAS: Investigating the various possible thermal and non-thermal contributions

Abstract: We have used ISO to observe the Magnetic Cataclysmic Variable AE Aquarii in the previously unexplored range from 4.8 µ mu p to 170µm in the framework of a coordinated multi-wavelength campaign from the radio to optical wave- lengths. We have obtained for the first time a spectrum between 4.8 and 7.3 µm with ISOCAM and ISOPHOT-P: the major contribution comes from the secondary star spectrum, with some thermal emission from the accretion stream, and possibly some additional cyclotron radiation from the post-shock accretion material close to the magnetised white dwarf. Having re- processed ISOPHOT-C data, we confirm AE Aqr detection at 90 µm and we have re-estimated its upper limit at 170 µm. In addition, having re-processed IRAS data, we have detected AE Aqr at 60 µm and we have estimated its upper limits at 12, 25, and 100 µm. The literature shows that the time-averaged spectrum of AE Aqr increases roughly with frequency from the radio wavelengths up to ∼761 µm; our results indicate that it seems to be approximately flat between ∼761 and ∼90 µm, at the same level as the 3σ upper limit at 170 µm; and it then decreases from ∼90 µ mt o∼7 µm. Thermal emission from dust grains or from a circum-binary disc seems to be very unlikely in AE Aqr, unless such a disc has properties substantially different from those predicted recently. Since various measurements and the usual assumptions on the source size suggest a brightness temperature below 10 9 Ka tλ ≤ 3.4 mm, we have reconsidered also the possible mechanisms explaining the emission already known from the submillimetre to the radio. The complex average spectrum measured from ∼7 µm to the radio must be explained by emission from a plasma composed of more than one "pure" non-thermal electron energy distribution (usually assumed to be a power- law): either a very large volume (diameter ≥ 80 times the binary separation) could be the source of thermal bremsstrahlung which would dominate from ∼10 µ mt o the∼millimetre, with, inside, a non-thermal source of synchrotron which dominates in radio; or, more probably, an initially small infrared source composed of several distributions (possibly both thermal, and non- thermal, mildly relativistic electrons) radiates gyro-synchrotron and expands moderately: it requires to be re-energised in order to lead to the observed, larger, radio source of highly relativistic electrons (in the form of several non-thermal distributions) which produce synchrotron.

Resonant Raman scattering spectroscopy of Ga P 1 − x N x and Ga As 1 − x N x in the ultraviolet range

Abstract: We report resonant Raman scattering studies of $\mathrm{Ga}{\mathrm{P}}_{1\ensuremath{-}x}{\mathrm{N}}_{x}$ and $\mathrm{Ga}{\mathrm{As}}_{1\ensuremath{-}x}{\mathrm{N}}_{x}$ in the ultraviolet (UV) spectral range. For both materials, strong intensity resonances and their rapid degradation near the respective ${E}_{1}$ transition energies exhibited for the zone-center longitudinal optical phonons provide direct evidence that the $L$-point conduction-band edges of $\mathrm{Ga}{\mathrm{P}}_{1\ensuremath{-}x}{\mathrm{N}}_{x}$ and $\mathrm{Ga}{\mathrm{As}}_{1\ensuremath{-}x}{\mathrm{N}}_{x}$ are strongly perturbed by nitrogen impurities. We also show that UV resonant Raman scattering is a powerful means to study higher lying conduction-band electronic states of semiconductor alloys.

Gaplike excitations in the superconducting state of Bi2Sr2CaCu2O8 studied by resonant Raman scattering.

Abstract: We report on the response of the electronic continuum from inelastic light-scattering experiments over an extended energy range between 1.970 and 4.504 eV in the superconducting state of Bi2Sr2CaCu2O8. The formation of a substantial Raman feature at shifts below twice the superconducting gap as well as the additional weight above this energy are found to be strongly dependent on the incident photon energy. For excitation wavelengths observed in ultraviolet, we find an enhancement of the integrated spectral weight below T(c). The resulting composite feature shows three distinct resonances at 2.5, 3.3, and 3.8 eV. We strongly suggest that the superconductivity-induced changes are the result of both the opening of a superconducting gap and the appearance of a collective mode.