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Mode Spectra (mode + spectrum)

Distribution by Scientific Domains

Physics and Astronomy	80%

Distribution within Physics and Astronomy

Astronomy & Astrophysics	50%

Selected Abstracts

Oligosaccharide sequences in Quillaja saponins by electrospray ionization ion trap multiple-stage mass spectrometry

JOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 6 2004
Susanna Broberg
Abstract Ten different samples with 13 previously identified saponin structures from Quillaja saponaria Molina were investigated by electrospray ionization ion trap multiple-stage mass spectrometry (ESI-ITMSn) in positive and negative ion modes. Both positive and negative ion mode MS1,MS4 spectra were analyzed, showing that structural information on the two oligosaccharide parts in the saponin can be obtained from positive ion mode spectra whereas negative ion mode spectra mainly gave information on one of the oligosaccharide parts. Analysis of MS1,MS4 spectra identified useful key fragment ions important for the structural elucidation of Quillaja saponins. A flowchart involving a stepwise procedure based on key fragments from MS1,MS3 spectra was constructed for the identification of structural elements in the saponin. Peak intensity ratios in MS3 spectra were found to be correlated with structural features of the investigated saponins and are therefore of value for the identification of terminal monosaccharide residues. Copyright © 2004 John Wiley & Sons, Ltd. [source]

Anomalous variations in low-degree helioseismic mode frequencies

MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 2 2006
R. Howe
ABSTRACT We compare changes in the frequencies of solar acoustic modes with degree between 0 and 2, as derived from Global Oscillation Network Group (GONG), Birmingham Solar Oscillations Network (BiSON) and Michelson Doppler Imager (MDI) spectra obtained between 1995 and 2003. We find that, after the solar-activity dependence has been removed from the frequencies, there remain variations that appear to be significant, and are often well correlated between the different data sets. We consider possible explanations for these fluctuations, and conclude that they are likely to be related to the stochastic excitation of the modes. The existence of such fluctuations has possible relevance to the analysis of other low-degree acoustic mode spectra such as those from solar-type stars. [source]

Crack free monolithic nitride vertical-cavity surface-emitting laser structures and pillar microcavities

PHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 7 2006
Henning Lohmeyer
Abstract We report on the successful fabrication and optical investigation of monolithicly grown GaN based vertical-cavity surface-emitting laser structures featuring quality factors of 250. Short-period AlN/InGaN superlattices are used for the low-index layers of the distributed Bragg reflectors. Pillar microcavities are realized by focused-ion-beam etching. Micro-photoluminescence measurements reveal the longitudinal and transversal mode spectra of the cavities in good agreement with theoretical calculations based on a vectorial transfer matrix method. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Wavelength dependence of the modal refractive index in 1.3 ,m InGaAsP, AlGaInAs and GaInNAs lasers using high pressure

PHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 2 2003
S. R. Jin
Abstract We report the variation of the modal refractive index at threshold with lasing wavelength in 1.3,,m InGaAsP, AlGaInAs and GaInNAs multiple quantum well lasers by measuring mode spectra under pressure up to 15,kbar. It is shown that the decrease of index with lasing wavelength is about 4% on average in the pressure range studied. We also find that the modal refractive index reduces with increasing injection current and is very sensitive to the injection current around laser threshold. [source]

Polarized diffuse emission at 2.3 GHz in a high Galactic latitude area

MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY: LETTERS (ELECTRONIC), Issue 1 2005
E. Carretti
ABSTRACT Polarized diffuse emission observations at 2.3 GHz in a high Galactic latitude area are presented. The 2°× 2° field, centred at (,= 5h, ,=,49°), is located in the region observed by the BOOMERanG experiment. Our observations were carried out with the Parkes radio telescope, and represent the highest frequency detection to date in a low-emission area. Because of the weaker Faraday rotation effect, the high frequency allows an estimate of the Galactic synchrotron contamination of the cosmic microwave background polarization (CMBP) which is more reliable than that achieved at 1.4 GHz. We find that the angular power spectra of the E - and B -modes have slopes of ,E=,1.46 ± 0.14 and ,B=,1.87 ± 0.22, indicating a flattening with respect to 1.4 GHz. Extrapolated up to 32 GHz, the E -mode spectrum is about three orders of magnitude lower than that of the CMBP, allowing a clean detection even at this frequency. The best improvement concerns the B -mode, for which our single-dish observations provide the first estimate of the contamination on angular scales close to the CMBP peak (about 2°). We find that the CMBP B -mode should be stronger than the synchrotron contamination at 90 GHz for models with tensor-to-scalar perturbation ratio T/S > 0.01. This low level could move down to 60,70 GHz the optimal window for CMBP measurements. [source]