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Search Results: 1 - 10 of 344859 matches for " D. G. Ladha "
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Theoretical Study of Chloro-N-(4-methoxybenzylidene)aniline Derivatives as Corrosion Inhibitors for Zinc in Hydrochloric Acid
S. Kumar,D. G. Ladha,P. C. Jha,N. K. Shah
International Journal of Corrosion , 2013, DOI: 10.1155/2013/819643
Abstract: The density functional theory (DFT) was used to investigate the corrosion inhibition of three inhibitors on zinc. Quantum chemical parameters such as the energy of highest occupied molecular orbital ( ), the energy of lowest unoccupied molecular orbital ( ), energy gap , hardness , softness , electrophilicity index , the fraction of electrons transferred from inhibitor molecule to the metal surface, energy change when both processes occur, namely, charge transfer to the molecule and backdonation from the molecule ( ), natural charge , and Fukui functions have been calculated by using B3LYP/6-31+G(d) basis set. The relation between the inhibition efficiency and quantum chemical parameters has been discussed in order to elucidate the inhibition mechanism of the chloro-N-(4-methoxybenzylidene)aniline derivatives. 1. Introduction Quantitative structure activity relationship (QSAR) has been a subject of intense interest in many disciplines of chemistry. In addition, the results of quantum chemical calculations are obtained without laboratory measurements, thus saving time and equipment and alleviating safety and disposal concerns [1, 2]. Density functional theory (DFT) has a potential application towards the design and development of organic corrosion inhibitors in corrosion field [3]. These facts have made quantum calculations to be very powerful tool for studying corrosion inhibition mechanism. Zinc is one of the most vital nonferrous metals having extensive use in metallic coating [4]. The use of zinc sheets as roofing materials and in galvanization of steel makes the study of its corrosion an important theme [5]. Zinc is often attacked by aggressive media, such as acids, bases, and salt solutions [6–8]. In acidic solutions, zinc has high solubility and dissolves with the formation of Zn2+ ions. Since the solubility of zinc decreases with increasing pH in acidic solutions, precipitation of Zn(OH)2 occurs when a certain pH value is reached. In alkaline solutions, with , the solubility of zinc increases with increasing pH, and in the high pH range, zinc oxide and hydroxides tend to dissolve with the formation of zincate ions. Zinc oxide is a common corrosion product in diluted solutions of salts such as NaCl or Na2SO4 with zinc hydroxide present in various amounts as a minor component. For scale removal and cleaning of zinc surface with acid solutions, the use of organic inhibitors is one of the most practical methods for protection against corrosion, especially in acidic media [9–13]. The aim of this work is to study the effect of quantum chemical
The lipid organisation of the cell membrane
Ladha, S.
Grasas y Aceites , 2000,
Abstract: Lipids and proteins in biological membranes are arranged in a mosaic of domains in the membrane. These domains represent small-scale heterogeneities in composition, shape and fluidity within the plane of the membrane, over the range of hundreds of nanometers to a few micrometers. They arise from the complex interactions of the heterogeneous mixtures of phospholipids, sterols, and proteins that make up all biological membranes. Los lípidos y las proteínas en las membranas biológicas están dispuestos en un mosaico de campos en la membrana. Estos campos representan heterogeneidades a peque a escala en la composición, forma y fluidez dentro del plano de la membrana, en un rango que va de los cientos de nanómetros a los pocos micrómetros. Estos campos se originan de las complejas interacciones de las mezclas heterogéneas de fosfolípidos, esteroles y proteínas de las que están hechas todas y cada una de las membranas biológicas.
New Approaches to Principal Component Analysis for Trees
Burcu Ayd?n,Gábor Pataki,Haonan Wang,Alim Ladha,Elizabeth Bullitt,J. S. Marron
Statistics , 2012,
Abstract: Object Oriented Data Analysis is a new area in statistics that studies populations of general data objects. In this article we consider populations of tree-structured objects as our focus of interest. We develop improved analysis tools for data lying in a binary tree space analogous to classical Principal Component Analysis methods in Euclidean space. Our extensions of PCA are analogs of one dimensional subspaces that best fit the data. Previous work was based on the notion of tree-lines. In this paper, a generalization of the previous tree-line notion is proposed: k-tree-lines. Previously proposed tree-lines are k-tree-lines where k=1. New sub-cases of k-tree-lines studied in this work are the 2-tree-lines and tree-curves, which explain much more variation per principal component than tree-lines. The optimal principal component tree-lines were computable in linear time. Because 2-tree-lines and tree-curves are more complex, they are computationally more expensive, but yield improved data analysis results. We provide a comparative study of all these methods on a motivating data set consisting of brain vessel structures of 98 subjects.
Exploring mod2 n-queens games
Tricia Muldoon Brown,Abrahim Ladha
Mathematics , 2015,
Abstract: We introduce a two player game on an n x n chessboard where queens are placed by alternating turns on a chessboard square whose availability is determined by the number of queens already on the board which can attack that square modulo two. The game is explored along with some variations and its complexity.
International Journal on Computer Science and Engineering , 2011,
Abstract: Feature selection is an important topic in data mining, especially for high dimensional datasets. Feature selection (also known as subset selection) is a process commonly used in machine learning, wherein subsets of the features available from the data are selected for application of a learning algorithm. The best subset contains the least number of dimensions that most contribute to accuracy; wediscard the remaining, unimportant dimensions. This is an important stage of preprocessing and is one of two ways of avoiding the curse of dimensionality (the other is feature extraction). There are twoapproaches in Feature selection known as Forward selection and backward selection. Feature selection has been an active research area in pattern recognition, statistics, and data mining communities.The main idea of feature selection is to choose a subset of input variables by eliminating features with little or no predictive information. Feature selection methods can be decomposed into three broad classes. One is Filter methods and another one is Wrapper method and the third one is Embedded method. This paper presents an empirical comparison of feature selection methods and its algorithms. In view of the substantial number of existing feature selection algorithms, the need arises to count on criteria that enable to adequately decide which algorithm to use in certain situations. This work reviews several fundamental algorithms found in the literature and assesses their performance in a controlled scenario.
Influence of Integrated Weed Management Practices on Dynamics and Weed Control Efficiency in Dry Direct Seeded Rice
KP Bhurer,DN Yadav,JK Ladha,RB Thapa,KR Pandey
Nepal Journal of Science and Technology , 2013, DOI: 10.3126/njst.v14i2.10413
Abstract: Field experiment under dry direct seeded rice(O ryza sativa L.) was conducted during rainy season of 2010 and 2011 at Regional Agriculture Research Station (RARS), Parwanipur, Bara to develop appropriate weed management practices for dry direct- seeded rice. The trial was laid-out in randomized complete block design (RCBD) and replicated thrice. Observations were taken on weed, plant growth and yield attributing, yield, and socio-economic parameters. The weed density, dry weed weight and weed control efficiency resulted significantly different as influenced by integrated weed management practices. Low weed population density, low weed index and highest weed control efficiency resulted by pendimethalin followed by 2, 4- D followed by one hand weeding were at par with weed free check. Highest yield resulted from weed free plot followed by pendimethalin followed by two hand weeding and pendimethalin followed by 2, 4- D followed by one hand weeding. However, the net return per unit investment resulted highest in pendimethalin followed by 2, 4- D followed by one hand weeding. This proved that amid increasing wage rate and labour scarcity integrated weed management through pendimethalin 30 EC (Stomp) @1 kg a. i. /ha as pre- emergence herbicide application followed by 2, 4- D sodium salt 80 WP @ 0.5 kg a. i. /ha followed by one hand weeding or stale seed bed followed by pendimethalin 30 EC (Stomp) @1 kg a. i. /ha followed by bispyribac (Nominee gold) @25 g a. i. /ha 10% @200 ml/ha at 20 days of seeding resulted best alternative for manual hand weeding practices giving higher net return per unit investment. DOI: http://dx.doi.org/10.3126/njst.v14i2.10413 ? Nepal Journal of Science and Technology Vol. 14, No. 2 (2013) 33-42
Effect of integrated weed management practices on performance of dry direct seeded rice (Oryza sativa L.)
KP Bhurer, DN Yadav, JK Ladha, RB Thapa, K Pandey
Agronomy Journal of Nepal , 2013, DOI: 10.3126/ajn.v3i0.9006
Abstract: Weeds are serious problem in dry direct seeded rice (DDSR). A field experiment was conducted during rainy seasons of 2010 and 2011 at research farm of the Regional Agricultural Research Station (RARS) Parwanipur, to study the effect of integrated weed management practices on the performance of dry direct seeded rice. Ten treatment combinations viz; weedy, weed free (weekly), Pendimethalin fb (followed by) Bispyribac, Pendimethalin fb two hand weeding, Stale seedbed fb Bispyribac, Stale seedbed fb Pendimethalin fb Bispyribac, Mulch 4 t/ha fb Bispyribac fb one hand weeding, Stale seedbed fb mulch 4 t/ha fb Bispyribac, Pendimethalin and Sesbania co-culture fb 2,4-D Na salt fb one hand weeding and Pendimethalin fb 2,4-D fb one hand weeding were tested in a randomized complete block design and replicated thrice. Observations were taken on weed, plant growth and yield attributes, yield, and socio-economic parameters. All weed control treatments significantly reduced the weed density and dry weight of weed resulting significant increase in yield of DSR over weedy check in both years. Weed free treatment resulted the highest yield, however, it was not economical due to high cost of cultivation. The use of Pendimethalin fb 2,4-D fb one hand weeding produced yield (5161 in 2010 and 6160 kg/ha in 2011) which were statistically at par with yield (5305 in 2010 and 6319 kg/ha in 2011) obtained under the weed free treatment. Further, the highest benefit cost ratio (CBR) 1.77 and 2.22 and net return Rs 47700 and 75084/ha during 2010 and 2011, respectively, were obtained under this treatment indicating its superiority over other treatments. The grain yield, yield attributing characters viz. panicles per m2, panicle weight, filled grain per panicle, thousand grain weight as influenced by different weed management practices revealed that higher yield resulted from weed free plot followed by Pendimethalin followed by two hand weeding and Pendimethalin followed by 2,4-D followed by one hand weeding. However, the net return per unit investment resulted highest in Pendimethalin followed by 2,4-D followed by one hand weeding. This proved that amid increasing wage rate and labor scarcity integrated weed management through Pendimethalin 30 EC (stomp) @ 1 kg a. i./ha as pre- emergence herbicide application followed by 2,4-D sodium salt 80 WP @ 0.5 kg a.i./ha followed by one hand weeding or stale seed bed followed by Pendimethalin 30 EC (stomp) @ 1 kg a. i./ha followed by Bispyribac (nominee gold) @ 25 g a. i./ha 10 % @ 200 ml/ha at 20 days of seeding resulted best alternative for
VIX and VIX Futures Pricing Algorithms: Cultivating Understanding  [PDF]
Hancock G. D’Anne
Modern Economy (ME) , 2012, DOI: 10.4236/me.2012.33038
Abstract: This article reviews the development of the S&P 500 volatility index and uses market information to develop algorithms which aid in clarifying some of the salient points in the determination of an index value. Understanding the pertinent points provides insight into the interpretation and limitations of the usefulness of the VIX and other VIX-type contracts.
A Working Classification of Retraction for the Whole Tympanic Membrane  [PDF]
G. D. Barr
International Journal of Otolaryngology and Head & Neck Surgery (IJOHNS) , 2013, DOI: 10.4236/ijohns.2013.24031

Objective: To formulate a reliable classification of tympanic membrane retraction which is easy to use but capable of detecting small differences in retraction. Study Design: Prospective study. Methods: The classification was developed from observations dividing the drum into 3 areas: the pars tensa anterior to the malleus, type I, posterior to the malleus (subdivided into upper and lower) type II, and attic type III. The subclassification on paper is more complicated but using a database it is easy to use. The classification is automatically calculated by the database which can also be converted to numerical form. The classification also allows documentation of active disease in retractions. Photographs of seven retracted ear drums were incorporated into the database and ten otolaryngologists asked to classify them. Five were asked to reclassify the retractions in the same way after 3 months. Results: Intra class correlation was significantly high (>0.9) for pars tensa, attic, and for bony erosion. Cronbach’s alpha values were also high (>0.9) in all groups. Retest values were evaluated with Wilcoxon’s signed rank sum test establishing that there was no significant difference in results. Conclusion: The classification shows reliabiliy and validity allowing detection of small changes in tympanic membrane retraction especially affecting the pars tensa but allows classification of the whole tympanic membrane.

Behind the Rejection of Alternative Measures of Implied Equity Volatility: A Note  [PDF]
G. D. Hancock
Journal of Financial Risk Management (JFRM) , 2013, DOI: 10.4236/jfrm.2013.21002

This note evaluates the risk-adjusted performance of the implied volatility of the NASDAQ index (VXN), Russell 2000 (RVX) and Dow Jones Industrial Averages (VXD). The results are compared to the performance of the implied volatility of the S & P 500 (VIX) in order to identify the unique contribution of each volatility index. Futures and option contracts have been offered on the VXD, VXN and RVX with results so dismal that the contracts were eventually delisted. In May 2012 futures were once again offered on the VXN but there is little market interest as indicated by the low trading volume. This note finds that the equity index implied volatility measures on VXN, RVX and VXD do not offer sufficient benefits beyond what investors can achieve with VIX which may explain, in part, the rejection of derivatives written on those measures of tradable implied index volatility.

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