619 research outputs found
Fully ab initio atomization energy of benzene via W2 theory
The total atomization energy at absolute zero, (TAE) of benzene,
CH, was computed fully {\em ab initio} by means of W2h theory as 1306.6
kcal/mol, to be compared with the experimentally derived value 1305.7+/-0.7
kcal/mol. The computed result includes contributions from inner-shell
correlation (7.1 kcal/mol), scalar relativistic effects (-1.0 kcal/mol), atomic
spin-orbit splitting (-0.5 kcal/mol), and the anharmonic zero-point vibrational
energy (62.1 kcal/mol). The largest-scale calculations involved are
CCSD/cc-pV5Z and CCSD(T)/cc-pVQZ; basis set extrapolations account for 6.3
kcal/mol of the final result. Performance of more approximate methods has been
analyzed. Our results suggest that, even for systems the size of benzene,
chemically accurate molecular atomization energies can be obtained from fully
first-principles calculations, without resorting to corrections or parameters
derived from experiment.Comment: J. Chem. Phys., accepted. RevTeX, 12 page
Assessment of W1 and W2 theories for the computation of electron affinities, ionization potentials, heats of formation, and proton affinities
The performance of two recent {\em ab initio} computational thermochemistry
schemes, W1 and W2 theory [J.M.L. Martin and G. de Oliveira, J. Chem. Phys.
111, 1843 (1999}], is assessed for an enlarged sample of thermochemical data
consisting of the ionization potentials and electron affinities in the G2-1 and
G2-2 sets, as well as the heats of formation in the G2-1 and a subset of the
G2-2 set. We find W1 theory to be several times more accurate for ionization
potentials and electron affinities than commonly used (and less expensive)
computational thermochemistry schemes such as G2, G3, and CBS-QB3: W2 theory
represents a slight improvement for electron affinities but no significant one
for ionization potentials. The use of a two-point rather than a
three-point extrapolation for the SCF component greatly enhances the
numerical stability of the W1 method for systems with slow basis set
convergence. Inclusion of first-order spin-orbit coupling is essential for
accurate ionization potentials and electron affinities involving degenerate
electronic states: inner-shell correlation is somewhat more important for
ionization potentials than for electron affinities, while scalar relativistic
effects are required for the highest accuracy. The mean deviation from
experiment for the G2-1 heats of formation is within the average experimental
uncertainty. W1 theory appears to be a valuable tool for obtaining benchmark
quality proton affinities.Comment: Journal of Chemical Physics, in press (303115JCP). 2 RevTeX files,
first is text and tables, second is E-PAPS tables S-1 through S-5. Additional
supplementary material (total energies, basis function exponents) available
at http://theochem.weizmann.ac.il/web/papers/w1w2.htm
2,4-Bis(4-bromophenyl)-3-azabicyclo[3.3.1]nonan-9-one
The title compound, C20H19Br2NO, shows a chair–chair conformation for the azabicycle with an equatorial disposition of the 4-bromophenyl groups [dihedral angle between the aromatic rings = 16.48 (3)°]. In the crystal, a short Br⋯Br contact [3.520 (4) Å] occurs and the structure is further stabilized by N—H⋯O hydrogen bonds and C—H⋯O interactions
2,4-Bis(4-chlorophenyl)-3-azabicyclo[3.3.1]nonan-9-one
In the molecular structure of the title compound, C20H19Cl2NO, the molecule exists in a twin-chair conformation with equatorial dispositions of the 4-chlorophenyl groups on both sides of the secondary amino group; the dihedral angle between the aromatic ring planes is 31.33 (3)°. The crystal structure is stabilized by N—H⋯O interactions, leading to chains of molecules
A Comparative Study of Latin Square Design Under Fuzzy Environments Using Trapezoidal Fuzzy Numbers
This paper deals with the problem of Latin Square Design (LSD) test using Trapezoidal Fuzzy Numbers (Tfns.). The proposed test is analysed under various types of trapezoidal fuzzy models such as Alpha Cut Interval, Membership Function, Ranking Function, Total Integral Value and Graded Mean Integration Representation. Finally a comparative view of the conclusions obtained from various test is given. Moreover, two numerical examples having different conclusions have been given for a concrete comparative study. Keywords: LSD, Trapezoidal Fuzzy Numbers, Alpha Cut, Membership Function, Ranking Function, Total Integral Value, Graded Mean Integration Representation. AMS Mathematics Subject Classification (2010): 62A86, 62F03, 97K8
One-Factor ANOVA Model Using Trapezoidal Fuzzy Numbers Through Alpha Cut Interval Method
Most of our traditional tools in descriptive and inferential statistics is based on crispness (preciseness) of data, measurements, random variable, hypotheses, and so on. By crisp we mean dichotomous that is, yes-or-no type rather than more-or-less type. But there are many situations in which the above assumptions are rather non-realistic such that we need some new tools to characterize and analyze the problem. By introducing fuzzy set theory, different branches of mathematics are recently studied. But probability and statistics attracted more attention in this regard because of their random nature. Mathematical statistics does not have methods to analyze the problems in which random variables are vague (fuzzy). In this regard, a simple and new technique for testing the hypotheses under the fuzzy environments is proposed. Here, the employed data are in terms of trapezoidal fuzzy numbers (TFN) which have been transformed into interval data using interval method and on the grounds of the transformed fuzzy data, the one-factor ANOVA test is executed and decisions are concluded. This concept has been illustrated by giving two numerical examples. Keywords: Fuzzy set, , Trapezoidal fuzzy number (TFN), Test of hypotheses, One-factor ANOVA model, Upper level data, Lower level data
A Comparative Study of Chi-Square Goodness-of-Fit Under Fuzzy Environments
Testing goodness-of-fit plays a vital role in data analysis. This problem seems to be much more complicated in the presence of vague data. In this paper, the chi-square goodness-of-fit under trapezoidal fuzzy numbers (tfns.) is proposed using alpha cut interval method. And the ranking grades of tfns. are also used to compute the chi-square test statistic. The proposed technique is illustrated with two different numerical examples along with different methods of ranking grades for a concrete comparative study. Keywords: Chi-square Test, Fuzzy Sets, Trapezoidal Fuzzy Numbers, Alpha Cut, Ranking Function, Graded Mean Integration Representation
Synthesis of Nanocrystalline MgO Particles by Combustion Followed by Annealing Method Using Hexamine as a Fuel
In this work, nanocrystalline MgO particles were prepared through combustion method using magnesium nitrate as oxidizer and hexamine as a fuel. The materials obtained by combustion method were subsequently annealed at 800°C for 3 h to improve the crystallinity and phase purity. The obtained MgO nanomaterials were characterized by powder X-ray diffraction analysis (XRD), infrared (IR) spectroscopy, photoluminescence (PL), near-infrared (NIR) spectroscopy, and scanning electron microscopy (SEM). The cubic crystal structure with lattice parameter, a = 0.4210(4) nm with average crystalline size of 22 nm, is obtained for the nano-MgO particles. The PL emission spectrum of nanocrystalline MgO materials exhibits three emission peaks at 432, 465, and 495 nm which are due to various structural defects. The SEM results expose the fact that the MgO nanomaterials are seemingly porous and highly agglomerated with fine particles. Owing to the higher reflectance of prepared nanocrystalline MgO, it can be used as NIR reflective pigments. The present results prove that the combustion technique using hexamine can produce the materials with high crystallinity. To the best of our knowledge, this is the first report on the synthesis of nanocrystalline MgO materials by combustion method using hexamine as a fuel
PHARMACOGNOSTICAL AND PRELIMINARY PHYTOCHEMICAL SCREENING OF AAVAARAI VIDHAI CHOORANAM
  Objective: To study the organoleptic characters, physio chemical properties and preliminary phytochemicals screening of Siddha formulations Aavaarai Vidhai Chooranam (AVC).Methods: The study drug, AVC was prepared as per procedure given in the text Neerizhivu maruthuvam. Organoleptic characteristics were assessed by appearance, colour, taste and odour. The physiochemical property of trial drug was screened for moisture content, total ash value, acid insoluble ash, water soluble extractive value, alcohol soluble extractive value, pH, reducing sugar, total sugar, total solid content and fat content. Preliminary Phytochemical evaluation of AVC was carried out by the standard procedure. The drug was screened for alkaloids, amino acids & proteins, anthraxquinone, carbohydrate, flavonoids, glycosides, phenols quinones, resins, saponins, steroids tanins, terpenoids and sugar. For which the aqueous extraction of the trial drug was taken by dissolving the 5 g of sample with 50 ml of distilled water and heated over water bath at 60°C. Then extract was filtered and used the filtrates for testing.Results: The trial drug, AVC shown organoleptic characters as per literature evidence, physiochemical properties as moisture content, total ash value, acid insoluble ash, water soluble extractive value, alcohol soluble extractive value, pH, reducing sugar, total sugar, total solid content and fat content were found within normal limits, preliminary phytochemical test showed the presence of flavonoids, tannins, steroids, terpenoids, alkaloids, carbohydrate, proteins, phenols and sugar.Conclusion: Organoleptic characters, physio chemical properties and preliminary photochemica shows that the drug has the quality and potency to treat against diabetes mellitus. To confirm this activity, further research should be done to assess the safety and efficacy of the drug AVC
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