Cr Lines Research Articles

Influence of annealing temperature on ζ-CrZn13 formation in electrodeposited Zn–Cr coatings

ABSTRACTElectrоdeposited Zn–Cr alloy coatings, containing 3.6, 5.4 and 9.4 mass % Cr were analysed by DSC and XRD. X-ray diffraction patterns of the samples show that when they are annealed to selected temperatures before and after the heat flow peaks of the DSC curve, there is an irreversible transition in all three alloys from η-(Zn, Cr) to ζ-CrZn13 phase. With increasing Cr content, the start of the transition is shifted to higher temperatures (from 180 to 250°С). The η-(Zn) phase is predominant in the annealed alloy with the lowest content of Cr. In the case of the alloy with the highest Cr content, typical XRD lines of Cr appear along with those of the ζ-CrZn13 phase. The Zn–Cr coating containing 5.4 mass % Cr transforms almost completely into ζ-CrZn13 phase with insignificant traces of residual initial η-(Zn, Cr) phase.

Abstract 419: Single cell-driven secreted proteins as a surrogate biomarker for Cetuximab therapy in colorectal cancer

Abstract Epidermal growth factor receptor (EGFR) blockade is efficacious in KRAS wild-type of colorectal cancer, but acquired resistance is inevitably generated. Here, we established the 5 acquired resistant single cell models (CR cell lines) to cetuximab and investigated the mechanism of acquired resistance using single cell-based whole-exome sequencing and transcriptional profiling. Of these, 4 cell lines have KRAS Q61L mutation and the other has BRAF V600E mutation. From gene enrichment analysis (GSEA), we found that epithelial to mesenchymal transition (EMT) occurs and CXCL chemokine family, which are known as secreted proteins, are overexpressed in the CR cell lines compared with parental cells. Interestingly, we found that CXCL chemokines were strongly secreted/expressed in KRAS/BRAF mutant cell lines and plasma/serum samples from colorectal cancer patients who acquired KRAS/BRAF mutation during cetuximab therapy. CXCL chemokines are regulated coordinately by Slug and NF-B transcription factors and trans-activate EGFR through CXCR2/MMP1/sHB-EGF axis. This process activates MAPK pathway via autocrine. To overcome the resistance to cetuximab, combination treatment of cetuximab and MEK/BRAF inhibitor had a larger antitumor effect compared to the single agents, decreasing the expression of MAPK pathway and secretion of CXCL chemokines. This finding highlights that CXCL chemokines, as a secreted proteins circulating in the bloodstream, show correlation with KRAS/BRAF mutation and could be clinical biomarkers for predicting resistance to anti-EGFR therapy in CRC. Citation Format: Ye-Lim Park, Hwang-Phill Kim, Jun Kyu Kang, Yoo Joo Lim, Sang-Hyun Song, Sae-Won Han, Tae-You Kim. Single cell-driven secreted proteins as a surrogate biomarker for Cetuximab therapy in colorectal cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 419.

Analysis of Soil by Magnetic Field Assisted Calibration-Free Laser Induced Breakdown Spectroscopy (CF-LIBS) and Laser Ablation – Time-of-Flight Mass Spectrometry (LA-TOF-MS)

The qualitative and quantitative analysis of soil samples collected from Sialkot, Pakistan (which contains leather industrial plants), has been performed using laser-induced breakdown spectroscopy (LIBS) and laser ablation time of flight mass spectrometry (LA-TOF-MS). The focused beam of a Q-switched Nd: YAG laser (532 nm) was used to ablate the soil samples in air at atmospheric pressure. The optical emission spectra demonstrate the presence of the spectral lines of Si, Fe, Al, Ca, Ti, K, Cr, Mg, Na, Ba, and Li in all of the samples. The emission lines intensities, electron number densities, and excitation temperatures were significantly enhanced in the presence of an external 0.3 T magnetic field applied perpendicular to the plasma plume. A maximum enhancement factor of approximately 8 was observed in the emission intensity. The emergence of several additional lines has also been detected using the magnetic field-assisted LIBS approach. The elemental composition determined using calibration-free laser-induced breakdown spectroscopy (CF-LIBS), with and without magnetic field, reveals that the external magnetic field only adjusts the laser-generated plasma dynamics without affecting the quantitative analysis of the samples. Importantly, the toxic and heavy elements such as chromium and barium were detected and quantified in all of the soil samples by both of these techniques. The variations in the compositional analysis using CF-LIBS with and without the applied magnetic field and LA-TOF-MS were less than 10%.

Ionization age of iron ejecta in the Galactic Type Ia supernova remnant G306.3−0.9

Abstract We present a 190 ks observation of the Galactic supernova remnant (SNR) G306.3−0.9 with Suzaku. To study ejecta properties of this possible Type Ia SNR, the absolute energy-scale at the Fe-K band was calibrated to a level of uncertainty less than 10 eV by a cross-calibration with the Hitomi microcalorimeter using the Perseus cluster spectra. This enabled us for the first time to determine the ionization state of the Fe Kα line of this SNR accurately. The ionization time-scale (τ) of the Fe ejecta was measured to be log10τ (cm−3 s) $= 10.24\, \pm \, 0.03$, significantly smaller than previous measurements. Marginally detected Kα lines of Cr and Mn have ionization time-scales consistent with that of Fe. The global spectrum was well-fitted with shocked interstellar matter (ISM) and at least two ejecta components with different ionization time-scales for Fe and intermediate mass elements (IME) such as S and Ar. One plausible interpretation of the one-order-of-magnitude shorter time-scale of Fe than that of IME ($\log _{10} \tau = 11.17\, \pm \, 0.07$) is a chemically stratified structure of ejecta. By comparing the X-ray absorption column to the H i distribution decomposed along the line of sight, we refined the distance to ∼20 kpc. The large ISM-to-ejecta shocked mass ratio of ∼100 and dynamical time-scale of ∼6 kyr place the SNR in the late Sedov phase. These properties are consistent with a stratified ejecta structure that has survived the mixing processes expected in an evolved SNR.

X-ray spectra of Sagittarius A East and diffuse X-ray background near the Galactic center

AbstractThis paper reports the analysis procedure and results of simultaneous spectral fits of the Suzaku archive data for Sagittarius (Sgr) A East and the nearby Galactic center X-ray emission (GCXE). The results are that the mixed-morphology supernova remnant Sgr A East has a recombining plasma (RP) with Cr and Mn Heα lines, and a power-law component (PL) with an Fe i Kα line. The nearby GCXE has a ∼1.5-times larger surface brightness than the mean GCXE far from Sgr A East, although the spectral shape is almost identical. Based on these results, we interpret that the origins of the RP and the PL with the Fe i Kα line are past big flares of Sgr A⋆.

Effect of organic foliar spray with pulse sprout extract on seed yield and quality of rice (Oryza sativa)

Organic seed is the basic for organic agriculture, since it is a crucial link in the chain from research, breeding, seed production, to organic production. With organic seeds the grower can complete the chain of organic input. To develop an organic foliar spray technique and for organic seed production, experiments were carried out to study the effect of organic foliar spray with pulse sprout extract on rice. In this study, horse gram and cowpea, the unexploited legumes of the tropics with high nutritional quality and comparatively low cost were used for preparing the pulse sprout extracts, an organic foliar spraying material. Higher accumulation of bioactive substances in sprouted seeds offers immense scope to develop an inexpensive and effective organic foliar spray technology so as to achieve better crop growth and higher seed yield of rice, the major staple food of the world. The biochemical analysis was done in both extracts to estimate the total antioxidants activity, soluble protein content, total soluble sugars, ascorbic acid content and minerals like nitrogen, phosphorus, potassium, calcium, iron and zinc. Subsequently, the effect of pulse sprout extract spray in improving crop growth, tillering, productivity, and resultant seed quality of was studied by spraying on the parental lines of rice hybrid CORH3 (A, B and R lines) and rice variety CR 1009. The experiment consisted of four trials. In the first trial, four concentrations of pulse extract (1, 2, 3, and 4%) were evaluated in the R line (medium duration variety) of CORH3 (medium duration). In the subsequent trials, the best concentrations (2 and 3% for horse gram and 1 and 2% for cowpea), determined from the first trial, were evaluated again in two medium duration lines of B line multiplication (AXB) and hybrid seed production (AxR). The fourth trial was done with a long duration variety namely CR 1009. Spraying of pulse sprout extract significantly improved majority of the growth and yield attributes culminating in significantly higher seed yield, in all the four trials. The study firmly revealed foliar sprays with either 3% horse gram sprout extracts or 2% cow pea sprout extract during active tillering and seed filling stages of rice crop, can significantly increase the growth and yield attributes, eventually resulting in higher seed yield, irrespective of the cultivars. It could be concluded that foliar spraying of 3% horse gram sprout extract or 2% cow pea sprout extract at active tillering stage and seed filling enhances seed yield attributes and yield in rice.

Identifying and assessing matrix effect severity in inductively coupled plasma optical emission spectrometry using non-analyte signals and unsupervised learning

An unsupervised data-driven methodology is used to quantify matrix effects caused by carbon and easily ionizable elements (EIEs) in inductively coupled plasma optical emission spectrometry (ICP OES). Background signals from nine plasma naturally-occurring species of Ar, H and O are used with principal component analysis (PCA) and affinity propagation (AP) clustering to evaluate the effects of complex matrices on ionic emission lines of Cd, Co, Cr and Pb. Matrix effect severity is then quantified based on Euclidean distance in principal component space from an average calibration curve point. The method has been applied to spiked solutions of Mediterranean Sea and Dead Sea water samples, and a significant correlation (- 0.997) was found between Euclidean distance and analyte recoveries. For sea water analysis, accurate results are found using external standard calibration (EC) when Euclidean distance < 1 for a given sample, and/or when that sample point groups with the calibration curve after affinity propagation clustering. Thus, by applying the PCA-AP strategy, one needs to perform no addition/recovery experiment to evaluate EC applicability. In addition, it can be carried out on the fly, as the background species used to monitor plasma changes are simultaneously recorded with the analytical signals, and a specific algorithm can be added to the instrument control software to flag instances in which EC may be ineffective. This is a proof-of-concept study, and additional work is required to evaluate the method's applicability to a larger number of analytes and sample matrices. However, the PCA-AP method described here for ICP OES can be used to quantify matrix effects, allowing for informed decisions regarding calibration. It requires no additional sample preparation and can be easily implemented in routine analyses of such complex-matrix samples as sea water.

Evaluation of saltol introgressed back cross inbred lines for salinity tolerance in rice (Oryza sativa L.)

Fifty one backcross inbred lines (BC3F3 population) of ADT 37 introgressed with saltol loci from FL478 controlling salinity tolerance in rice and 17 lines of CR 1009 Sub1 introgressed with saltol loci from FL478 were evaluated for their salinity tolerance along with respective recurrent parents. All 68 backcross inbred lines (BIL) were subjected to genotyping using RM3412 which led to the identification of 20 lines in the genetic background of ADT 37 and 12 lines in the genetic background of CR 1009 harboring saltol loci from FL478. Seedlings of all 32 positive progenies were subjected to phenotypic evaluation under hydroponic conditions (EC levels of 6 dSm−1 and EC 12 dSm−1) by following IRRI's standard protocol (1–9 scale scoring). Out of 32 selected BILs, 14 lines were found to be tolerant and remaining 18 lines were identified to be moderately tolerant. Tolerant lines exhibited very less reduction in their root growth with increased salinity level. Among the tolerant lines, minimum root and shoot length reduction was observed in BIL 1102, BIL 1079 and BIL 1091 at EC 6 dSm−1 level. At EC 12 dSm−1, minimum root and shoot length reduction was observed in BIL 33, BIL 44, BIL 772, BIL 1079, BIL 1091, BIL 1096, BIL 1101 and BIL 1102. Saline tolerant lines viz., BIL 33, BIL 1094, BIL 1096 and BIL 1101 have recorded maximum uptake of K+ in both root and shoot which resulted in low Na+/K+ ratio. The salt tolerant lines identified in this study will be further evaluated in saline soil under different locations to develop salt tolerant varieties.

A personalized medicine approach to identifying dysregulated epigenetic enzymes in the development of castrate-resistant prostate cancer.

237 Background: Recent advances in proteomic and chromatin immunoprecipitation tools have been crucial in studying cancer epigenetics but the ability to measure directly the enzyme activities of dysregulated histone-modifiers is lacking. We utilize a novel approach to identify altered histone-modifying enzymes in the progression from hormone sensitive (HS) to castrate-resistant prostate cancer (CRPC) progression. Methods: We developed, validated and utilized a high-throughput peptide microarray assay to identify altered histone lysine (de)acetylation activity in tumor lysates. Functional assays, novel HS and CRPC human tumor arrays and xenografts were utilized to confirm these findings. Results: This microarray-based activity assay revealed up-regulated histone acetyltransferase (HAT) activity against specific histone H3 sites in a castrate-resistant CR cell line compared to its hormone-sensitive (HS) isogenic counterpart. NAD+-dependent deacetylation assays revealed down-regulated Sirtuin activity in validated CR lines. Levels of acetyltransferases GCN5, PCAF, CBP and p300 were unchanged between matched HS and CR cell lines. However, auto-acetylation of p300 at K1499, a modification known to enhance HAT activity and a target of deacetylation by SIRT2, was highly elevated in CR cells. Among all 7 Sirtuins, only SIRT2 and SIRT3 protein levels were reduced in CR lines. Interrogation of HS and matched CR xenograft lines reveals that H3K18 hyperacetylation, increased p300 activity, and decreased SIRT2 expression are associated with progression to CR in 8/12 (66%). Tissue microarray analysis revealed that hyperacetylation of H3K18 is a feature of CRPC. Inhibition of p300 results in lower H3K18ac levels and increased expression of androgen receptor. Conclusions: This novel microarray approach provides a method to identify commonly dysregulated chromatin enzymes during progression providing a personalized therapeutic strategy to direct available drugs to target enzymes. Reduced SIRT2 expression and increased p300 activity lead to a concerted mechanism of hyperacetylation at specific histone lysine sites (H3K9, H3K14, and H3K18)

Determination of residual stress distributions in polycrystalline alumina using fluorescence microscopy

Maps of residual stress distributions arising from anisotropic thermal expansion effects in a polycrystalline alumina are generated using fluorescence microscopy. The shifts of both the R1 and R2 ruby fluorescence lines of Cr in alumina are used to create maps with sub-μm resolution of either the local mean and shear stresses or local crystallographic a- and c-stresses in the material, with approximately ±1MPa stress resolution. The use of single crystal control materials and explicit correction for temperature and composition effects on line shifts enabled determination of the absolute values and distributions of values of stresses. Temperature correction is shown to be critical in absolute stress determination. Experimental determinations of average stress parameters in the mapped structure are consistent with assumed equilibrium conditions and with integrated large-area measurements. Average crystallographic stresses of order hundreds of MPa are determined with characteristic distribution widths of tens of MPa. The stress distributions reflect contributions from individual clusters of stress in the structure; the cluster size is somewhat larger than the grain size. An example application of the use of stress maps is shown in the calculation of stress-intensity factors for fracture in the residual stress field.

Thermodynamic properties of the 2D frustrated Heisenberg model for the entire [formula omitted] circle

Using the spherically symmetric self-consistent Green's function method, we consider thermodynamic properties of the S=1/2J1–J2 Heisenberg model on the 2D square lattice. We calculate the temperature dependence of the spin–spin correlation functions cr=〈S0zSrz〉, the gaps in the spin excitation spectrum, the energy E and the heat capacity CV for the whole J1–J2-circle, i.e. for arbitrary φ, J1=cos(φ), J2=sin(φ). Due to low dimension there is no long-range order at T≠0, but the short-range holds the memory of the parent zero-temperature ordered phase (antiferromagnetic, stripe or ferromagnetic). E(φ) and CV(φ) demonstrate extrema “above” the long-range ordered phases and in the regions of rapid short-range rearranging. Tracts of cr(φ) lines have several nodes leading to nonmonotonic cr(T) dependence. For any fixed φ the heat capacity CV(T) always has maximum, tending to zero at T→0, in the narrow vicinity of φ=155° it exhibits an additional frustration-induced low-temperature maximum. We have also found the nonmonotonic behaviour of the spin gaps at φ=270°±0 and exponentially small antiferromagnetic gap up to (T≲0.5) for φ≳270°.

The nature of the late B-type stars HD 67044 and HD 42035

While monitoring a sample of apparently slowly rotating superficially normal bright late B and early A stars in the northern hemisphere, we have discovered that HD 67044 and HD 42035, hitherto classified as normal late B-type stars, are actually respectively a new chemically peculiar star and a new spectroscopic binary containing a very slow rotator HD 42035 S with ultra-sharp lines (vsini = 3.7 km/s) and a fast rotator HD 42035 B with broad lines. The lines of Ti, Cr, Mn, Sr, Y, Zr and Ba are conspicuous features in the high resolution SOPHIE spectrum of HD 67044. The HgII line at 3983.93 A is also present as a weak feature. The composite spectrum of HD 42035 is characterised by very sharp lines formed in HD 42035 S superimposed onto the shallow and broad lines of HD 42035 B. These very sharp lines are mostly due to light elements from C to Ni, the only heavy species definitely present are Sr and Ba. Selected lines of 21 chemical elements from He up to Hg have been synthesized using model atmospheres computed with ATLAS9 and the spectrum synthesis code SYNSPEC48 including hyperfine structure of various isotopes when relevant. Abundances of these key elements have been derived HD 67044 and HD 42035 S. HD 67044 is found to have distinct enhancements of Ti, Cr, Mn, Sr, Y, Zr, Ba and Hg and underabundances in He, C, O, Ca and Sc which shows that this star is not a superficially normal late B-type star, but actually is a new CP star most likely of the HgMn type. HD 42035 S has provisional underabundances of the light elements from C to Ti and overabundances of heavier elements up to barium. More accurate fundamental parameters and abundances for HD 42035 S and HD 42035 B will be derived if we manage to disentangle their spectra. They will help clarify the status of the two components in this interesting new spectroscopic binary.

Chemical spots on the surface of the strongly magnetic Herbig Ae star HD 101412

AbstractDue to the knowledge of the rotation period and the presence of a rather strong surface magnetic field, the sharp‐lined young Herbig Ae star HD 101412 with a rotation period of 42 d has become one of the most well‐studied targets among the Herbig Ae stars. High‐resolution HARPS polarimetric spectra of HD 101412 were recently obtained on seven different epochs. Our study of the spectral variability over the part of the rotation cycle covered by HARPS observations reveals that the line profiles of the elements Mg, Si, Ca, Ti, Cr, Mn, Fe, and Sr are clearly variable while He exhibits variability that is opposite to the behaviour of the other elements studied. Since classical Ap stars usually show a relationship between the magnetic field geometry and the distribution of element spots, we used in our magnetic field measurements different line samples belonging to the three elements with the most numerous spectral lines, Ti, Cr, and Fe. Over the time interval covered by the available spectra, the longitudinal magnetic field changes sign from negative to positive polarity. The distribution of field values obtained using Ti, Cr, and Fe lines is, however, completely different compared to the magnetic field values determined in previous low‐resolution FORS 2 measurements, where hydrogen Balmer lines are the main contributors to the magnetic field measurements, indicating the presence of concentration of the studied iron‐peak elements in the region of the magnetic equator. Further, we discuss the potential role of contamination by the surrounding warm circumstellar matter in the appearance of Zeeman features obtained using Ti lines. (© 2016 WILEY‐VCH Verlag GmbH &amp; Co. KGaA, Weinheim)

X-ray fluorescent lines from the Compton-thick AGN in M51

Abstract The cold disc/torus gas surrounding active galactic nuclei (AGN) emits fluorescent lines when irradiated by hard X-ray photons. The fluorescent lines of elements other than Fe and Ni are rarely detected due to their relative faintness. We report the detection of Kα lines of neutral Si, S, Ar, Ca, Cr, and Mn, along with the prominent Fe Kα, Fe Kβ, and Ni Kα lines, from the deep Chandra observation of the low-luminosity Compton-thick AGN in M51. The Si Kα line at 1.74 keV is detected at ∼3σ, the other fluorescent lines have a significance between 2 and 2.5 σ, while the Cr line has a significance of ∼1.5σ. These faint fluorescent lines are made observable due to the heavy obscuration of the intrinsic spectrum of M51, which is revealed by NuSTAR observation above 10 keV. The hard X-ray continuum of M51 from Chandra and NuSTAR can be fitted with a power-law spectrum with an index of 1.8, reprocessed by a torus with an equatorial column density of NH ∼ 7 × 1024 cm−2 and an inclination angle of 74°. This confirms the Compton-thick nature of the nucleus of M51. The relative element abundances inferred from the fluxes of the fluorescent lines are similar to their solar values, except for Mn, which is about 10 times overabundant. It indicates that Mn is likely enhanced by the nuclear spallation of Fe.

Laser plasma interaction during visible and IR laser ablation of chromite mineral target

In this work, we present optical emission studies of the laser induced Chromite mineral plasma produced by the fundamental (1064 nm) and second (532 nm) harmonics of a Q-switched pulsed Nd:YAG laser. The spectra predominantly reveal the spectral lines of neutral Cr as well as dominant spectral lines of constituent elements. The experimentally observed line profiles of neutral chromium have been used to extract the electron temperature (Te) using Boltzmann plot method. Whereas, the electron number density (Ne) has been determined from the Stark broadened line profiles. We have also studied the variation of electron temperature and electron number density as a function of laser irradiance at atmospheric pressure. We have also studied the variation of these plasma parameters (Te and Ne) as a function of the laser irradiance as well as distance along the direction of plasma plume. The validity of the assumption of local thermodynamic equilibrium (LTE) is also discussed in the light of the experimental data and analysis.

KIC 4768731: a bright long-period roAp star in theKeplerfield

We report the identification of 61.45 d−1 (711.2 μHz) oscillations, with amplitudes of 62.6 μmag, in KIC 4768731 (HD 225914) using Kepler photometry. This relatively bright (V = 9.17) chemically peculiar star with spectral type A5 Vp SrCr(Eu) has previously been found to exhibit rotational modulation with a period of 5.21 d. Fourier analysis reveals a simple dipole pulsator with an amplitude that has remained stable over a 4-yr time span, but with a frequency that is variable. Analysis of high-resolution spectra yields stellar parameters of Teff = 8100 ± 200 K, log g = 4.0 ± 0.2, [Fe/H] = +0.31 ± 0.24 and v sin i = 14.8 ± 1.6 km s−1. Line profile variations caused by rotation are also evident. Lines of Sr, Cr, Eu, Mg and Si are strongest when the star is brightest, while Y and Ba vary in antiphase with the other elements. The abundances of rare earth elements are only modestly enhanced compared to other roAp stars of similar Teff and log g. Radial velocities in the literature suggest a significant change over the past 30 yr, but the radial velocities presented here show no significant change over a period of 4 yr.

Structures, morphologies, and chemical states of sputter-deposited CrZrN thin films with various Zr contents

Chromium zirconium nitride (CrZrN) thin films were prepared on Si wafers and glasses at various Zr contents by reactive DC magnetron co-sputtering of Cr and Zr metals in Ar and N2 mixture without voltage biasing and external heating. Influences of the Zr contents on crystal structure, cross-section morphology, surface morphology, and chemical composition and chemical state were investigated by X-ray diffraction, field emission scanning electron microscopy, atomic force microscopy, and X-ray photoelectron spectroscopy, respectively. The results showed that N content in the films was increased when Zr content increased. Film microstructure changed from coarse columnar to finer-grain morphology and film surface became smooth caused by grain refinement. Zr–metal and Zr–N bonding fractions were increased with the increasing Zr content, whereas Cr–N was decreased due to being substituted by Zr of Cr atoms in the fcc B1 type crystal structure of (Cr, Zr)N. In addition to an increase in lattice parameter, the substitution of Zr could lead to an increase in interatomic distances which affected bonding length between metals and nitrogen atoms. According to the charge potential model, the increase in bonding distances between atoms resulted in negative shifts in binding energy of electrons of all elements that led to observation of lowering in the separation between photoelectron lines of Cr, Zr, and N elements. The lower separation with the increase of Zr content suggested that bonding between metals and nitrogen became stronger due to the dominance of the covalent character as evidenced by the enhanced hardness of the CrZrN materials.

Time resolved spectroscopy of the cool Ap star HD 213637*

We present an analysis of high time resolution spectra of the chemically peculiar Ap star HD 213637. The star shows rapid radial velocity variations with a period close to the photometric pulsation period. Radial velocity pulsation amplitudes vary significantly for different rare earth elements. The highest pulsation amplitudes belong to lines of TbIII ~360 m/s, PrII ~250 m/s and PrIII ~230 m/s . We did not detect any pulsations from spectral lines of EuII and in Halpha, in contrast to many other roAp stars. We also did not find radial velocity pulsations using spectral lines of other chemical elements, including Mg, Si, Ca, Sc, Cr, Fe, Ni, Y and Ba. There are phase shifts between the maxima of pulsation amplitudes of different rare earth elements and ions, which is evidence of an outwardly running magneto-acoustic wave propagating through the upper stellar atmosphere.

Temperature measurement of laser-induced plasmas from the intensity ratio of two lines emitted from different elements with the same ionization degree.

A new laser induced plasma temperature measuring method with two lines emitted from different elements with the same ionization degree is proposed, assuming local thermodynamic equilibrium condition of the plasma. The influence of measurement error on deduced temperature accuracy was simulated in theory. A solution containing Cu, K, and Cr elements was used as the sample. Plasma was generated at the surface of the solution, and time-resolved spectra were recorded. Two atomic lines, Cu I 324 nm and K I 766 nm, were used to determine the plasma temperature with the proposed method. Four atomic lines and two ionic lines of Cr were selected to deduce plasma temperature with the Saha-Boltzmann plot method for comparison. The temperatures deduced from the two different methods showed similar behavior as a function of time. The results suggested that this method can be useful in cases where only very few lines from a single element are available in the spectrum and Boltzmann or Saha-Boltzmann plots cannot be built.

Stokes IQUV magnetic Doppler imaging of Ap stars – III. Next generation chemical abundance mapping of α2 CVn★

In a previous paper, we presented an updated magnetic field map for the chemically peculiar star α2 CVn using ESPaDOnS and Narval time-resolved high-resolution Stokes IQUV spectra. In this paper, we focus on mapping various chemical element distributions on the surface of α2 CVn. With the new magnetic field map and new chemical abundance distributions, we can investigate the interplay between the chemical abundance structures and the magnetic field topology on the surface of α2 CVn. Previous attempts at chemical abundance mapping of α2 CVn relied on lower resolution data. With our high-resolution (R = 65 000) data set, we present nine chemical abundance maps for the elements O, Si, Cl, Ti, Cr, Fe, Pr, Nd and Eu. We also derive an updated magnetic field map from Fe and Cr lines in Stokes IQUV and O and Cl in Stokes IV. These new maps are inferred from line profiles in Stokes IV using the magnetic Doppler imaging code invers10. We examine these new chemical maps and investigate correlations with the magnetic topology of α2 CVn. We show that chemical abundance distributions vary between elements, with two distinct groups of elements; one accumulates close to the negative part of the radial field, whilst the other group shows higher abundances located where the radial magnetic field is of the order of 2 kG regardless of the polarity of the radial field component. We compare our results with previous works which have mapped chemical abundance structures of Ap stars. With the exception of Cr and Fe, we find no clear trend between what we reconstruct and other mapping results. We also find a lack of agreement with theoretical predictions. This suggests that there is a gap in our theoretical understanding of the formation of horizontal chemical abundance structures and the connection to the magnetic field in Ap stars.