The interaction of young massive stars with their environment: A millimeter and submillimeter line study of NGC6334 FIR II

Using the 15-m Swedish ESO Sub-millimeter Telescope (SEST), CO, HCN, and HCO+ observations of the galactic star-forming region NGC6334 FIR II are presented, complemented by [C I] 3^P_1--3^P_0 and 3^P_2--3^P_1 data from the Atacama Pathfinder Experiment (APEX 12-m telescope). Embedded in the extended molecular cloud and associated with the H II region NGC6334--D, there is a molecular "void". [C I] correlates well with 13^CO and other molecular lines and shows no rim brightening relative to molecular cloud regions farther off the void. While an interpretation in terms of a highly clumped cloud morphology is possible, with photon dominated regions (PDRs) reaching deep into the cloud, the data do not provide any direct evidence for a close association of [C I] with PDRs. Kinetic temperatures are ~40--50K in the molecular cloud and >=200K toward the void. CO and [C I] excitation temperatures are similar. A comparison of molecular and atomic fine structure line emission with the far infrared and radio continuum as well as the distribution of 2.2um H_2 emission indicates that the well-evolved H II region expands into a medium that is homogeneous on pc-scales. If the H_2 emission is predominantly shock excited, both the expanding ionization front (classified as subsonic, "D-type") and the associated shock front farther out (traced by H_2) can be identified, observationally confirming for the first time a classical scenario that is predicted by evolutionary models of H II regions. Integrated line intensity ratios of the observed molecules are determined, implying a mean C18^O/C17^O abundance ratio of 4.13+-0.13 that reflects the 18^O/17^O isotope ratio. This ratio is consistent with values determined in nearby clouds. Right at the edge of the void, however, the oxygen isotope ratio might be smaller.Comment: 18 pages, 13 figures, 3 tables, A&A in pres

Estimation of ultrasonic point echoes

One important parameter for an ultrasonic transducer is the echo it yields from a pointlike reflector. It can be measured directly but there are however certain problems connected with this. We propose an alternative method to calculate the echo from a pointlike reflector by measuring the echoes from sliding halfplanes. Using a tomographic way of reasoning, we can calculate the point echoes from these measurements. Two methods to numerically perform this inversion are dealt with. The first one is a regularization technique used in conjunction with the analytical inversion formula. The other approach was to find basis functions that are suitable for the inversion of the measurements. These basis functions depend on which norm and weight function you choose. Numerical solutions are given for chosen weight functions and the inversion is shown for both methods.Godkänd; 1993; 20080221 (ysko

Experimental Determination of the Ultrasonic Echo from a Pointlike Reflector Using a Tomographic Approach

One important parameter for an ultrasonic transducer is the echo it yields from a pointlike reflector. It can be measured directly but there are however certain problems connected with this. This reflector must have such a size that it can be considered a point, which results in a very weak echo and consequently a low SNR. We propose an alternative method to calculate the echo from a pointlike reflector by measuring the echoes from sliding halfplanes. Using a tomographic way of reasoning, we can calculate the single point echo from these measurements. Our approach was to find basis functions that are suitable for the inversion of the measurements. These basis functions depend on which norm and weight function you choose. Numerical solutions are given for chosen weight functions and the inversion is shown for the measurements

Spatial decomposition of the ultrasonic echo using a tomographic approach : Part A: The regularization method

One of the most common methods for making images with ultrasound is to use the pulse-echo method. Under the assumption of a homogeneous medium, the Time-of-flight (TOF), i.e.\ the time elapsed between transmission and reception of an ultrasonic pulse, is proportional to the distance. Methods for estimating the TOF assumes that the echoes only differ in arrival time. If the shape of the echo is dependent on where on the surface it is reflected, this method can yield an inaccurate image. One parameter of the ultrasonic transducer that could be used to improve this method is the {\em single point echo} (SPE), i.e. the echo from a point reflector. The direct measurement of this echo is however not possible due to practical problems and diffraction effects. In this report, we propose a method to experimentally determine the SPE. We use a tomographic approach where we can determine the SPE from a series of measured echoes from sliding halfplanes.Godkänd; 1994; 20080220 (ysko

Estimation of the spatial impulse response of an ultrasonic transducer using a tomographic approach

The impulse response method is often used to study the ultrasonic field radiated by planar or gently curved transducers. These investigations can be extended to include the reflected echoes from point reflectors, which can be used in syntesizing echoes from reflectors of known shapes. The single point echo can be measured directly but there are however certain problems associated with this. This paper proposes an alternative method to estimate the echo from a point-like reflector by measuring the echoes from sliding halfplanes. Using a tomographic approach, the single point echo is estimated from these measurements. To perform the tomographic inversion, a truncated weighted Singular Value Decomposition (SVD) is used in order to catch essential features of the ultrasonic echoes, where the weight functions are chosen specially to suit our application. Numerical solutions are given for the chosen weight functions and an error analysis is carried out.Godkänd; 1995; 20060929 (ysko)</p

The Mn 2p core-level photoelectron spectrum of Pd-Mn bimetallic systems on Pd(100)

It is shown that the Mn 2p spectra of Mn atoms in Pd-Mn bimetallic surface systems formed on Pd(1 0 0) exhibit a satellite, separated 1 eV from the main line, in addition to the 5 eV satellite previously observed for Mn-containing compounds and surface alloys. The main line and the low-energy satellite are both assigned to 2p(5)3d(6) final states whereas the 5 eV satellite is associated with 2p(5)3d(5) final states. The identification of the two low-binding energy peaks is based on ail energy comparison with the Mn 2p --> 3d X-ray absorption spectrum. The relative intensities of the two low-binding energy peaks furthermore vary depending on the Mn atomic environment, reflecting the changes in the properties of the Mn 3d band rather than the geometric position of the Mn atoms. For Mn coverages less than or equal to1 monolayer, the highest degree of Mn 3d localization was found for structures in which the Mn atoms are spread uniformly over the surface. The observed changes in the Mn 2p spectra are discussed in terms of varying Mn-Pd interaction, exchange splitting and magnetic ordering (C) 2003 Elsevier B.V. All rights reserved

Experimental Determination of the Single Point Echo of an Ultrasonic Transducer Using a Tomographic Approach

The impulse response method is often used to study the ultrasonic field radiated by planar or gently curved transducers. This, however, requires one transmitting and one receiving transducer which has to be placed with great accuracy in the ultrasonic field. Here we propose a measuring method with only one transducer which acts both as transmitter and receiver. Echoes from sliding halfplanes are registered and by using tomographic methods, the echo from a single point in the same plane as the halfplanes can then be calculated. Beside the ultrasonic field, these calculations will yield us the transducer&apos;s characteristics. These can be used to extract further information from an echo of an arbitrary surface, such as the gradient of the surface

Estimation of Subsample Time Delay Differences in Narrowband Ultrasonic Echoes Using the Hilbert Transform Correlation

In many areas the time delay of arrival (TDOA) is desired. In the case of narrowband signals we propose a fast and simple method to estimate small time delays. This method is shown to have the same or better accuracy as the cross correlation methods for small delays in the order of fractions of the sample interval. It is based on using the Hilbert transform in correlation between two signals and consists of only one scalar product, which makes it fast. It may also be used in applications with narrowband signals where the measurements are repeatable, such as ultrasonic imaging and nondestructive testing. In ultrasonic applications, due to fluctuations in the insonified media, a small random time shift may be present causing the signals to be misaligned in time