Omega Centauri: weak MgH-band in red giants directly trace the helium content

High spectral resolution and high signal-to-noise ratio optical spectra of red giants in the globular cluster Omega Centauri are analysed for stellar parameters and chemical abundances of 15 elements including helium by either line equivalent widths or synthetic spectrum analyses. The simultaneous abundance analysis of MgH and Mg lines adopting theoretical photospheres and a combination of He/H$-$ratios proved to be the only powerful probe to evaluate helium abundances of red giants cooler than 4400 K, wherein otherwise helium line transitions (He {\scs I} 10830 and 5876 \AA) present for a direct spectral line analysis. The impact of helium-enhanced model photospheres on the resulting abundance ratios are smaller than 0.15 dex, in agreement with past studies. The first indirect spectroscopic helium abundances measured in this paper for the most metal-rich cluster members reveal the discovery of seven He-enhanced giants ($\Delta$$Y=+$0.15$\pm$0.04), the largest such sample found spectroscopically to date. The average metallicity of $-$0.79$\pm$0.06 dex and abundances for O, Na, Al, Si, Ca, Ti, Ni, Ba, and La are consistent with values found for the red giant branch (RGB-a) and subgiant branch (SGB-a) populations of Omega Centauri, suggesting an evolutionary connection among samples. The He-enhancement in giants is associated with larger $s$-process elemental abundances, which correlate with Al and anticorrelate with O. These results support the formation of He-enhanced, metal-rich population of Omega Centauri out of the interstellar medium enriched with the ejecta of fast rotating massive stars, binaries exploding as supernovae and asymptotic giant branch (AGB) stars.Comment: 20 pages, 13 figures, 6 tables, accepted for publication in MNRA

Survey on Improved Scheduling in Hadoop MapReduce in Cloud Environments

Cloud Computing is emerging as a new computational paradigm shift. Hadoop-MapReduce has become a powerful Computation Model for processing large data on distributed commodity hardware clusters such as Clouds. In all Hadoop implementations, the default FIFO scheduler is available where jobs are scheduled in FIFO order with support for other priority based schedulers also. In this paper we study various scheduler improvements possible with Hadoop and also provided some guidelines on how to improve the scheduling in Hadoop in Cloud Environments.Comment: 5 Pages, 2 figures; International Journal of Computer Applications, November 201

Comparing N-Node Set Importance Representative results with Node Importance Representative results for Categorical Clustering: An exploratory study

The proportionate increase in the size of the data with increase in space implies that clustering a very large data set becomes difficult and is a time consuming process.Sampling is one important technique to scale down the size of dataset and to improve the efficiency of clustering. After sampling allocating unlabeled objects into proper clusters is impossible in the categorical domain.To address the problem, Chen employed a method called MAximal Representative Data Labeling to allocate each unlabeled data point to the appropriate cluster based on Node Importance Representative and N-Node Importance Representative algorithms. This paper took off from Chen s investigation and analyzed and compared the results of NIR and NNIR leading to the conclusion that the two processes contradict each other when it comes to finding the resemblance between an unlabeled data point and a cluster.A new and better way of solving the problem was arrived at that finds resemblance between unlabeled data point within all clusters, while also providing maximal resemblance for allocation of data in the required cluster.Comment: 16 pages, 4 figures, 3 equation

The Reason for the Efficiency of the Pian-Sumihara Basis

A logical explanation as to why the choice of the Pian-Sumihara basis (as a linear basis to approximate stress) leads to greater efficiency in enhanced strain problems, is presented. An Airy stress function and the consequent selective simplification resulting from the differentiation of an implied, single, parent approximating polynomial, are the essence of this argument.Comment: 6 pages, in review (2nd tier journal

Solar twins and the Barium puzzle

Several abundance analyses of Galactic open clusters (OCs) have shown a tendency for Ba but not for other heavy elements (La$-$Sm) to increase sharply with decreasing age such that Ba was claimed to reach [Ba/Fe] $\simeq +0.6$ in the youngest clusters (ages $<$ 100 Myr) rising from [Ba/Fe]$=0.00$ dex in solar-age clusters. Within the formulation of the $s$-process, the difficulty to replicate higher Ba abundance and normal La$-$Sm abundances in young clusters is known as {\it the barium puzzle}. Here, we investigate the barium puzzle using extremely high-resolution and high signal-to-noise spectra of 24 solar twins and measured the heavy elements Ba, La, Ce, Nd and Sm with a precision of 0.03 dex. We demonstrate that the enhanced Ba {\scs II} relative to La$-$Sm seen among solar twins, stellar associations and OCs at young ages ($<$100 Myr) is unrelated to aspects of stellar nucleosynthesis but has resulted from overestimation of Ba by standard methods of LTE abundance analysis in which the microturbulence derived from the Fe lines formed deep in the photosphere is insufficient to represent the true line broadening imposed on Ba {\scs II} lines by the upper photospheric layers from where the Ba {\scs II} lines emerge. As the young stars have relatively active photospheres, Ba overabundances most likely result from the adoption of too low a value of microturbulence in the spectum synthesis of the strong Ba {\scs II} lines but the change of microturbulence in the upper photosphere has only a minor affect on La$-$Sm abundances measured from the weak lines.Comment: 14 pages,14 figures and 5 tables; accepted for publication in Ap

Local associations and the barium puzzle

We have observed high-dispersion echelle spectra of main-sequence stars in five nearby young associations -- Argus, Carina-Near, Hercules-Lyra, Orion and Subgroup B4 -- and derived abundances for elements ranging from Na to Eu. These are the first chemical abundance measurements for two of the five associations, while the remaining three associations are analysed more extensively in our study. Our results support the presence of chemical homogeneity among association members with a typical star-to-star abundance scatter of about 0.06 dex or less over many elements. The five associations show log$\epsilon$(Li) consistent with their age and share a solar chemical composition for all elements with the exception of Ba. We find that all the heavy elements (Y, Zr, La, Ce, Nd, Sm and Eu) exhibit solar ratios, i.e., [X/Fe] $\simeq$ 0, while Ba is overabundant by about 0.2-0.3 dex. The origin of the overabundance of Ba is a puzzle. Within the formulation of the s-process, it is difficult to create a higher Ba abundance without a similar increase in the s-process contributions to other heavy elements (La-Sm). Given that Ba is represented by strong lines of Ba II and La-Sm are represented by rather weak ionized lines, the suggestion, as previously made by other studies, is that the Ba abundance may be systematically overestimated by standard methods of abundance analysis perhaps because the upper reaches of the stellar atmospheres are poorly represented by standard model atmospheres. A novel attempt to analyse the Ba I line at 5535 \AA\ gives a solar Ba abundance for stars with effective temperatures hotter than about 5800 K but increasingly subsolar Ba abundances for cooler stars with apparent Ba deficiencies of 0.5 dex at 5100 K. This trend with temperature may signal a serious non-LTE effect on the Ba I line.Comment: (18 pages, 8 figures, 11 tables. This paper has been accepted for publication in Monthly Notices of the Royal Astronomical Society Main Journal.

Eigenvalues and Wiener index of the Zero Divisor graph Γ[Zn]\Gamma[\mathbb {Z}_n]

The Zero divisor Graph of a commutative ring $R$, denoted by $\Gamma[R]$, is a graph whose vertices are non-zero zero divisors of $R$ and two vertices are adjacent if their product is zero. In this paper, we consider the zero divisor graph $\Gamma[\mathbb{Z}_n]$ for $n=p^3$ and $n=p^2q$ with $p$ and $q$ primes. We discuss the adjacency matrix and eigenvalues of the zero divisor graph $\Gamma[\mathbb{Z}_n]$. We also calculate the energy of the graph $\Gamma[\mathbb{Z}_n]$.Comment: 11 page

PERFORMANCE AND EMISSION ANALYSIS OF BIO- DIESEL FUEL WITH TITANIUM- OXIDE COATED PISTON ON 4-STROKE D.I DIESEL ENGINE

Diesel engines are being used extensively for fuel economy but due to gradual depletion of Petroleum resources and increase in exhaust emissions, there is an urgent need for suitable alternative fuels for the diesel engines. As our country is an agricultural country, if the alternate fuels are produced by our farmers it will be beneficial for the country and the farmers also. In recent studies, researchers studied various vegetable oils like canola oil, aloveera oil, soya been oil, flaxseed oil and hone oil etc. Out of all flaxseed oil play an important role as an alternative fuel. But the properties of flaxseed oil are not suitable for the usage in the existing diesel engines without blending with diesel fuel. The performance of the engine depends on the combustion phenomenon and it further depends on the amount of heat retained in the combustion chamber. Hence the present work is planned accordingly to develop an insulated engine by coating the piston with TIO2 material. So that more amount of heat will be retained in the combustion chamber which aids the combustion. Further the performance of flaxseed biodiesel blend namely B10, B20, B30 and B40 are tested and the results are mentioned accordingly

Comprehensive abundance analysis of red giants in the open clusters NGC 2527, 2682, 2482, 2539, 2335, 2251 and 2266

We have analyzed high-resolution echelle spectra of red giant members for seven open clusters in the Galactic anticentre direction to explore their chemical positions. Cluster membership has been confirmed by radial velocity. The spread in temperatures and gravities being very small among the red giants, nearly the same stellar lines were employed for all stars thereby reducing the abundance errors: the errors of the average abundance for a cluster were generally in the 0.02 to 0.05 dex range. Our present sample covers Galactocentric distances of 8.3 to 11.3 kpc and an age range of 0.2 to 4.3 Gyr. A careful comparison of our results for the cluster NGC 2682 (M 67) to other high-resolution abundance studies in the literature shows general good agreement for almost all elements in common.Comment: 15 pages, 4 figures and 13 tables. Table 13 is available in the online version of the pape

Gray-box Adversarial Training

Adversarial samples are perturbed inputs crafted to mislead the machine learning systems. A training mechanism, called adversarial training, which presents adversarial samples along with clean samples has been introduced to learn robust models. In order to scale adversarial training for large datasets, these perturbations can only be crafted using fast and simple methods (e.g., gradient ascent). However, it is shown that adversarial training converges to a degenerate minimum, where the model appears to be robust by generating weaker adversaries. As a result, the models are vulnerable to simple black-box attacks. In this paper we, (i) demonstrate the shortcomings of existing evaluation policy, (ii) introduce novel variants of white-box and black-box attacks, dubbed gray-box adversarial attacks" based on which we propose novel evaluation method to assess the robustness of the learned models, and (iii) propose a novel variant of adversarial training, named Graybox Adversarial Training" that uses intermediate versions of the models to seed the adversaries. Experimental evaluation demonstrates that the models trained using our method exhibit better robustness compared to both undefended and adversarially trained modelComment: Accepted to ECCV 201