Multiline Approach Research Articles

Revisiting the BE99 method for the study of outflowing gas in protostellar jets

An established method for measuring the hydrogen ionisation fraction in shock-excited gas is the BE99 method, which utilises six bright forbidden emission lines: S\,II N\,II 6583, and O\,I 6363. The main assumptions of this technique are that the gas is in a low-excitation state ($x_ e < 0.3$) and that the equilibrium of the underlying ionisation network is reached. Our aim is to extend the BE99 method by including more emission lines in the blue and near-infrared part of the spectrum ($ and by considering higher hydrogen ionisation fractions ($x_ e > 0.3$). In addition, we investigate how a non-equilibrium state of the gas and the presence of extinction influence the BE99 technique. We numerically solved a network of ionisation reactions in the time domain, which lead to the BE99 equilibrium. We applied the BE99 method on synthetic spectra also in the non-equilibrium state. We extented the BE99 technique to higher ionisation fractions by considering additional reactions, which involve higher ionisation states of oxygen, nitrogen, and sulphur. We tested our concepts on the low-excitation outflow of Par Lup 3-4 and the high-excitation 244-440 Proplyd in Orion. Many additional emission line ratios can in principle be exploited as extended curves (or stripes) in the ($x_ e T_ e $) diagram. If the BE99 equilibrium is reached and extinction is corrected for, all stripes overlap in one location in the ($x_ e T_ e $) diagram indicating the existing gas parameters. We find that the BE99 equilibrium is reached faster than the hydrogen recombination time. The application to the Par Lup 3-4 outflow shows that the classical BE99 lines together with the N\,I lines do not meet in one location in the ($x_ e T_ e $) diagram. This indicates that the gas parameters derived from the classical BE99 method are not fully consistent with other observed line ratios. A multi-line approach is necessary to determine the gas parameters. From our analysis we derive $n_e cm cm $, $T_e = 7\,600\ K K $, and $x_e 0.027-0.036$ for the Par Lup 3-4 outflow. For the 244-440 Proplyd we were able to use the line ratios of S\,II O\,I and OII 7330 in the BE99 diagram to estimate the ionisation fraction at knot E3 ($x_e = 0.58 The BE99 method can be extended by utilising more emission line ratios in the ($x_ e T_ e $) diagram and considering higher ionisation states. Exploiting new line ratios reveals more insights on the state of the gas. Our analysis indicates, however, that a multi-line approach is more robust in deriving gas parameters, especially for high-density gas.

Ultraviolet spectropolarimetry: investigating stellar magnetic field diagnostics

Magnetic fields are important for stellar photospheres and magnetospheres, influencing photospheric physics and sculpting stellar winds. Observations of stellar magnetic fields are typically made in the visible, although infrared observations are becoming common. Here we consider the possibility of directly detecting magnetic fields at ultraviolet (UV) wavelengths using high resolution spectropolarimetry, specifically considering the capabilities of the proposed Polstar mission. UV observations are particularly advantageous for studying wind resonance lines not available in the visible, but they can also provide many photospheric lines in hot stars. Detecting photospheric magnetic fields using the Zeeman effect and Least Squares Deconvolution is potentially more effective in the UV due to the much higher density of strong lines. We investigate detecting magnetic fields in the magnetosphere of a star using the Zeeman effect in wind lines, and find that this could be detectable at high S/N in an O or B star with a strong magnetic field. We consider detecting magnetic fields using the Hanle effect in linear polarization, which is complementary to the Zeeman effect, and could be more sensitive in photospheric lines of rapid rotators. The Hanle effect can also be used to infer circumstellar magnetism in winds. Detecting the Hanle effect requires UV observations, and a multi-line approach is key for inferring magnetic field properties. This demonstrates that high resolution spectropolarimetry in the UV, and the proposed Polstar mission, has the potential to greatly expand our ability to detect and characterize magnetic fields in and around hot stars.

Multi-line enhanced beam model for the analysis of laminated composite structures

A novel approach to the analysis of composite structure is introduced in this paper. One-dimensional (1D) refined finite elements are formulated by making use of the Carrera Unified Formulation (CUF). CUF is a higher-order 1D formulation which was recently introduced by the first author. By exploiting the hierarchical characteristics of CUF, a multi-line approach is developed straightforwardly and used for the analysis of multilayered structures. In the multi-line approach, each layer is modeled by one beam-line discretization. Refined beam elements with different orders of expansion over the cross-sectional plane are then employed along different beam-lines. The compatibility of displacements at the boundary interfaces between beam-lines is ensured by using Lagrange multipliers. The accuracy of the proposed method is verified both through published literature and through finite element solutions using the commercial code MSC/Nastran.

Analysis of reinforced and thin-walled structures by multi-line refined 1D/beam models

This paper focuses the attention on the use of appropriate combinations of refined one-dimensional (1D) beam theories to analyze thin-walled, reinforced structures. The cross-section of a slender body is seen as the sum of different sub-domains. Each sub-domain is subsequently used as the cross-section of a beam discretization. Displacement variables are then expanded around the beam axis of each sub-domain by using refined 1D models which are based on the Carrera Unified Formulation. The order of the beam elements can vary in different sub-domains. This subdivision has been called “multi-line” as opposed to the “one-line” approach of classical beam theories. 1D compatibility conditions of the displacements at selected points of the sub-domain interface boundaries are imposed by using Lagrange multipliers. Various problems have been analyzed to highlight the advantages and disadvantages of the present multi-line approach. It is concluded that the multi-line approach appears very effective in the case of thin-walled sections made by locally connected walls as well as in the case of reinforced structures.

Multiline Zeeman signatures through line addition

In order to get a significant Zeeman signature in the polarised spectra of a magnetic star, we usually 'add' the contributions of numerous spectral lines; the ultimate goal is to recover the spectropolarimetric prints of the magnetic field in these line additions. Here we want to clarify the meaning of these techniques of line addition; in particular, we try to interpret the meaning of the 'pseudo-line' formed during this process and to find out why and how its Zeeman signature is still meaningful. We create a synthetic case of line addition and apply well tested standard solar methods routinely used in the research on magnetism in our nearest star. The results are convincing and the Zeeman signatures well detected; Solar methods are found to be quite efficient also for stellar observations. We statistically compare line addition with least-squares deconvolution and demonstrate that they both give very similar results as a consequence of the special statistical properties of the weights. The Zeeman signatures are unequivocally detected in this multiline approach. We may anticipate the outcome that magnetic field detection is reliable well beyond the weak-field approximation. Linear polarisation in the spectra of solar type stars can be detected when the spectral resolution is sufficiently high.

Overlayer thickness determination by XPS using the multiline approach

AbstractAn important analytical application of x‐ray photoelectron spectroscopy is the possibility of determining the overlayer thickness in the nanometer range. The relevant procedure should be based on a realistic theoretical model relating the photoelectron signal intensities, measured for the overlayer and for the substrate, to the overlayer thickness. In the most frequently used procedure, we derive the thickness from the ratio of intensity measured for the overlayer and intensity measured for the substrate. We may expect that the resulting thickness depends on the pair of intensities selected for analysis. This is due to the fact that each calculated intensity has a certain systematic error associated with accuracy of parameters used in calculations.We consider here a possibility of using more than two intensities, for a given element, in the procedure of thickness determination. In this way, we expect that the analysis is more accurate due to the fact that the systematic errors are averaged. In the past, similar approach has been successfully applied to the procedure of surface composition determination. To test the proposed multiline approach, the Au 4f, Ni 2p, and Ni 3p intensities were measured for a series of Ni overlayers deposited on the Au substrate. It has been found that the proposed approach well performs at relatively large overlayer thicknesses. It provides values that are averages of values obtained from other methods. At small overlayer thicknesses, we observe a scatter of thicknesses obtained from different methods which can be due to the discontinuity of the overlayer. Copyright © 2008 John Wiley & Sons, Ltd.

Investigations of Au Segregation in AuNi Alloys by the Line Shape Analysis of Photoelectron Spectra

The surface segregation of Au in Au5Ni95 polycrystalline alloy is studied applying the line shape analysis, known as the fuzzy k-nearest neighbour rule, to the selected X-ray photoelectron and X-ray induced Auger spectra. Each line, characterised by the kinetic electron energy exhibited in the particular transition, samples the depth described by the mean escape depth depending on the inelastic mean free path of electron in the investigated material and the geometry of the measurement. The following electron transitions in the electron kinetic energy range 216.6–1486.6 eV are analysed: Au N5N67V , Ni 2p, Ni L2M23M45–Ni L3M45M45, Au 4d, Au 4f and the valence band transitions (overlapping Au 5d6s and Ni 3d4s transitions). The results of the quantitative analysis using the fuzzy k-nearest neighbour rule are compared to the results of quantitative analysis by the multiline approach which applies the Au 4f and Ni 2p photoelectron transitions. Both methods demonstrate Au surface segregation starting at the temperature above 200◦C. The line shape analysis was shown to be applicable for quantification of the surface region with possibility of investigating the in-depth non-uniform concentration profiles.

Revival of Mathura's ailing Yamuna river

The quality restoration of any river, especially of the Yamuna at Mathura, a religious center in India, is a very complex and interdisciplinary endeavor. River pollution cannot be minimized merely by diverting the routes of drains carrying wastewaters and/or establishing sewage treatment plants. The required strategy for pollution control should not only be a multi-line approach but also be fool proof. The various sources of pollution in the Yamuna river and possible strategies to restore this ailing river to its pristine status are presented in this paper.

X‐ray photoelectron spectroscopy and the pattern recognition method—their application to surface studies in CoPd alloys

AbstractIn the present work, polycrystalline CoPd alloys in varying range of bulk atomic percent composition (Co30Pd70, Co50Pd50 and Co70Pd30) are investigated by means of X‐ray photoelectron spectroscopy (XPS). The results of conventional XPS quantitative multiline (ML) approach are compared to the results obtained on the basis of XPS lines shape analysis, where the selected XPS or X‐ray induced Auger electron (XAES) transitions, are processed using the pattern recognition method known as the fuzzy k‐nearest neighbour (fkNN) rule. The fkNN rule is applied to the following spectra line shapes: Pd MNV, Co 2p, Co LMM, Pd 3d and valence band, analysing electrons in a varying range of selected kinetic energies.Both methods showed the surface segregation of Pd in Co30Pd70 and Co50Pd50 alloys. The results of the ML, the binding energy shift (ΔBE) analysis and the fkNN rule remained in agreement. Discrepancies in quantitative results obtained using different approaches are discussed within the accuracy of the applied methods, differences due to mean escape depth (MED) of electrons in considered transitions, their depth distribution function, the sensitivity of electron transition line shape on the environmental change (weaker effect for the inner shell transitions, and stronger effect for the outer shell transitions and Auger electron spectroscopy (AES) electrons transitions) and the non‐uniform depth profile concentrations. Copyright © 2005 John Wiley & Sons, Ltd.

Quantitative analysis of AuPd alloys from the shape of XPS spectra by the fuzzy rule

AbstractThe quantitative analysis of solid surfaces by XPS requires the determination of spectra intensities, related to atomic concentrations, recorded for constituents of investigated systems. The most reliable method of quantitative analysis is the multiline approach. The estimation of intensities requires satellites and background subtraction. The quantitative and qualitative information from intensity or binding energy shifts may be disturbed by overlapping spectra. To avoid these problems analyses based on the spectra lineshape were developed. These analyses use methods of statistical pattern recognition possible after selecting the set of standard spectra (reference set) consisting of a set of spectra recorded for different chemical states or atomic compositions (classes). The classification quality is characterized by the misclassification rate (error rate) estimated from the reference set. Fuzzy identification referring to the fuzzy membership results in quantitative estimation of chemical states and/or atomic compositions of constituents. The application of such algorithms to different lineshapes recorded at various kinetic energies results in quantification at various information depths. In the present work the fuzzy rule for analysing lineshapes of valence band, Au 4f, Pd 3d and Pd MNN Auger spectra recorded for AuPd alloys, Au and Pd, was found to be efficient and applicable for quantitative analysis of complex systems. Copyright © 2004 John Wiley & Sons, Ltd.

Phase distinction in semi-insulating polycrystalline silicon by pattern recognition of X-ray photoelectron spectroscopy/X-ray-induced Auger electron spectroscopy data

X-ray photoelectron spectroscopy (XPS) and X-ray-induced Auger electron spectroscopy (XAES) supported with the lineshape analysis by the pattern recognition (PR) method and the fuzzy k-nearest neighbor rule (kNN FR) were applied to study semiinsulating polycrystalline silicon layers (SIPOS). The aim of the present work was to obtain the qualitative and quantitative information about the surface region of as-received SIPOS layers. For the purpose of qualitative analysis the binding energies (BE), binding energy shifts (ΔBE), the half widths (FWHM) and the lineshapes of the Si 2p, O 1s and O KLL lines were analysed. The quantitative analysis was performed on the basis of the XPS using sensitivity factor method, multiline (ML) approach and the kNN FR. The performance of the kNN rule is possible after selecting the proper set of reference standard materials to which the rule refers during identification of an ambiguous chemical state. By selecting the reference samples supplying the information about the chemical state of Si, SiOx and SiO2, the kNN rule allowed to distinguish qualitatively these three different phases in SIPOS samples. The particular application of the kNN FR makes possible the quantitative analysis by referring the fuzzy probability of classification for the given chemical state to the concentration of particular constituents in the investigated SIPOS. All the methods applied are consistent in revealing the quantitative results and show that SIPOS is a deeply non-homogeneous material, consisting of two phases: silicon and silicon oxide.

Quantitative analysis by XPS using the multiline approach

AbstractAn efficient method for quantitative XPS analysis is the so‐called multiline approach. This method does not require standards, it takes into account the instrumental and matrix effects and it derives quantitative information from statistical analysis of all photoelectron intensities visible in the spectra. One can expect the reliability of this approach to be better than the reliability of methods involving uncorrected relative sensitivity factors. This paper summarizes recent improvements in the multiline approach. In particular, a new expression for the universal energy dependence of the inelastic mean free path is currently used. Furthermore, the statistical analysis has been modified in order to account properly for the error in the countrates. Finally, a database with physical constants has been added (photoionization cross‐sections, asymmetry parameters, binding energies, etc.) to avoid errors of polynomial approximations. The modified algorithm of the multiline approach was applied to photoelectron intensities measured for AuCu alloys in four laboratories. Surfaces of these alloys were sputtered with 2 keV Ar+ ions, because at this energy the selective sputtering effects are expected to be negliible. Very consistent results were obtained. The average deviation from the bulk surface composition was found to be equal to ±3.2 at.%. Extensive software implementing the described version of the multiline approach is presently being developed.

Quantitative surface analysis by X-ray photoelectron spectroscopy and X-ray excited auger electron spectroscopy

It is shown that X-ray excited KLL Auger electron spectra allow it to describe measured signal strengths similarly to X-ray photoelectron signals, thus offering valuable information on the quantitative surface composition of a solid sample. The principal equation and corresponding fundamental parameters are discussed. As a result Auger spectra of C, N, O, F, and Na can be easily used in a multiline approach for quantitative analysis. LMM and MNN spectra give rise to more problems, due to their more complicated structure, uncertainties with regard to the background and the influence of Coster-Kronig transitions. These problems are overcome by the use of empirical ratios of the strongest lines of 2p/LMM or 3d/MNN. Since these ratios are independent of sample composition, they allow it to transform the Auger signal into the corresponding photoelectron signal, provided that a standard sample has been measured. Thus a true additional information is obtained and moreover difficulties in cases of photoelectron spectra with overlapping lines from other chemical elements can be overcome.

Genotype ✕ Environment Interactions in Peanut Multiline Populations1

The stabilities of four peanut (Arachis hypogaea L.) multiline populations plus their component lines were determined over a 4‐year period, 1980‐1983, at two locations in Florida. The study was undertaken to provide information concerning the stability of both yield and market quality factors of multiline cultivars vs. the component lines which form them. Each multiline was obtained from a different cross, and was formed by compositing in equal proportions the seed from four early generation, phenotypically similar sib‐lines. The interactions of genotype (population) with environments was highly significant (P = < 0.01) for pod yield and five quality factors (percentage fancy pod, shelling percentage, weight per 100 seeds, percentage of extra large kernels and sound mature kernel yield) studied. Large differences in yield and market quality traits were not found between sib‐lines. However, differences were found in stability estimated from regression coefficients and deviation from regression of multilines compared to their component lines, possibly due to the buffering action resulting from greater genetic variability. Multilines did not have greater stability in all cases, but the difference between the multiline and its least stable component line was generally greater than the difference between the multiline and its most stable component line. This research indicates that the chance of improving the yield stability and market acceptibility of peanut cultivars is increased when the multiline approach is used.

Screening of local and exotic maize lines for stem-borer resistance with special reference to Chilo partellus

After field screening local germplasm for stem-borer ( Chilo partellus , Swin.) resistance for four seasons in two years we identified two sources of resistance, Katumani and Kitale. A cross between them performed better than either of the parents. When exotic lines from CIMMYT, Mexico, reported to be resistant to South and Central American stem-borers were screened at Mbita Point Field Station, to test and confirm their resistance to East African stem-borers, a number of them were found to be resistant to Chilo . It was also noted that the level of their resistance was higher and more broadly based than the local source. This shows that the source of origin is always full of genetic variability. This finding now suggests that a cross between the local and exotic sources should offer a wide scope in the multiple resistance or the multiline approach towards pest management.