bluuebunny/crossref_metadata_2025_split huggingface dataset:
Organic Compounds from Insoluble Organic Matter Isolated from the Murchison Carbonaceous Chondrite by Heating Experiments
Authors: Komiya Masatoshi , Shimoyama Akira 
Published: June 2006

Abstract
Insoluble organic matter isolated by an HF/HCl treatment of the Murchison carbonaceous chondrite was heated from room temperature to 800 °C at a rate of 10 °C min−1 under a helium atmosphere. Over 130 organic compounds were identified in its pyrolyzates, which mainly comprised the following two groups: (1) benzene and naphthalene, and their alkyl derivatives; and (2) sulfur-containing heterocycles and their alkyl derivatives. The relative amounts of compounds released with increasing temperature during the heating process were monitored by a mass spectrometer. Those hydrocarbons were observed mainly over a temperature range of 300—600 °C. These results are generally similar to those of Yamato-791198, an Antarctic carbonaceous chondrite which we had previously analyzed. The results indicate that aliphatic and aromatic hydrocarbons, as well as S-containing heterocycles, are the major constituents of the insoluble organic matter of Murchison. Furthermore, the results suggest that the thermal history of Murchison on its parent body was similar to that of Yamato-791198.
Solvent Extraction of Several Anions with Tetrabutylammonium Ion into 1,2-Dichloroethane and Hydration of Anions in the Organic Phase
Authors: Kusakabe Satoshi , Arai Miwa 
Published: June 2006

Abstract
The partition equilibrium of tetrabutylammonium salts Bu4NX, where X− is N3−, NO3−, SCN−, ClO4−, and picrate ion, has been measured between water and 1,2-dichloroethane at 298 K. The distribution ratio of these salts can be explained in terms of the extraction of an ion pair (the extraction constant is defined as Kex = [Bu4N+X−]org/[Bu4N+]aq[X−]aqf±2) and the dissociation and dimerization of the ion pairs in the organic phase. The hydration number of the salt in the organic phase, nh, seems similar among dissociated, ion-paired, and dimerized species. The free energy of phase transfer corrected for the hydration effect in the organic phase, −RT(ln Kex−nh), may be correlated with the Gibbs free energy of hydration of the anions in the aqueous phase.
Structural Effect of Phosphoric Esters Having Bulky Substituents on the Extraction of Rare Earth Elements
Authors: Yoshizuka Kazuharu , Kosaka Hiroshi , Shinohara Takaaki , Ohto Keisuke , Inoue Katsutoshi 
Published: June 2006

Abstract
Phosphoric esters having bis(4-ethylcyclohexyl) (D4ECHPA) and bis(4-cyclohexylcyclohexyl) (D4DCHPA) groups as the alkyl substituents were synthesized in order to investigate their selectivity in the extraction of rare earth elements from acidic nitrate media, together with the apparent molecular weights of the extractants in toluene, the acid dissociation constants and the aqueous distribution coefficients of the extractants. These extractants were found to exist as dimeric species in toluene. The acid dissociation constants of the extractants are nearly the same as that of bis(2-ethylhexyl) hydrogenphosphate (D2EHPA), which is a typical commercial acidic phosphorus extractant. The aqueous distribution coefficients of the extractants become greater in the order D4ECHPA &gt; D2EHPA &gt; D4DCHPA. From the concentration dependencies of the hydrogen ion and extractant on the distribution ratio of rare earth elements, it was concluded that the rare earth elements (M3+) were extracted with D4ECHPA and D4DCHPA (HR) as M(HR2)3 in the organic phase; also, the extraction equilibrium constants (Kex) were evaluated. The extraction equilibrium constants of rare earth elements become greater in the order D4DCHPA &gt; D4ECHPA &gt; D2EHPA. It was very noticeable that the separation factor between HoIII and GdIII, β(Ho/Gd), and β(Yb/Y) with D4ECHPA, and β(Ce/La), β(Pr/La), and β(Ho/Gd) with D4DCHPA are significantly greater than those with D2EHPA. The structural effects of the extractant on the selectivity of rare earth elements are discussed in terms of the molecular modelling. Furthermore, we found that the loading capacity of NdIII with these extractants is excellent compared with that of D2EHPA, due to preventing gelation of the organic phase.
Photochemistry of Cobalt(III) Complexes Containing a Sulfinate-S Ligand. Linkage and Geometrical Isomerization
Authors: Akhter Farooque MD , Hirotsu Masakazu , Sugimoto Isamu , Kojima Masaaki , Kashino Setsuo , Yoshikawa Yuzo 
Published: June 2006

Abstract
Photolysis of trans(t-N,S)-[Co{S(O)2CH2COO-S,O}(tren)]+ (1, t–N = tertiary amine nitrogen; tren = tris(2–aminoethyl)amine) with visible light yielded two complexes, orange and red. The molecular structure of the orange complex perchlorate was determined by the X-ray method to be cis(t-N,O(S))-[Co{OS(O)CH2COO-O,O}(tren)]ClO4·H2O (2, O(S) = oxygen of sulfinate group); geometrical isomerization as well as linkage isomerization took place upon photolysis. A mechanism for the geometrical isomerization was proposed. The red complex, which was assigned as trans(t-N,O(S))-[Co{OS(O)CH2COO-O,O}(tren)]+ (3), is thermally unstable and reverts to the starting complex. This observation is in accord with molecular mechanics calculations, which estimate the starting complex to be more stable. The kinetic studies were performed using the HPLC method in the temperature range 28—70 °C, giving ΔH‡ = 100 kJ mol−1 and ΔS‡ = −23 J K−1 mol−1. Photolysis of a cobalt(III) complex containing the l-cysteinesulfinate-S,N ligand, cis(t-N,S)-lsqb;Co{S(O)2CH2CH(COOH)NH2-S,N}(tren)]2+ (4) with visible light provided two types of linkage isomers, cis(t-N,O(C))-[Co{NH2CH(CH2SO2−)COO-N,O}(tren)]+ (4b, O(C) = oxygen of carboxylate group) with an uncoordinated sulfinate group, and a pair of diastereomers of cis(t-N,O(S))-[Co{OS(O)CH2CH(COOH)NH2-O,N}(tren)]2+ (4a). The molecular structures of the perchlorate of 4b and the bromide of 4a with the (S)-sulfur atom have been determined by X-ray diffraction. Isomerization (epimerization) from 4a-R to 4a-S was studied in the temperature range 55—75 °C, giving ΔH‡ = 105 kJ mol−1 and ΔS‡ = −20 J K−1 mol−1. Photolysis of trans(t-N,S)-[Co{S(O)2CH2CH(COOH)NH2-S,N}(tren)]2+ (5) yielded six products. Three of them were the same as those obtained by the photolysis of 4, indicating that geometrical isomerization took place.
Coordination Chemistry of Some Low Coordinate Organophosphorus Compounds of Coordination Number 2
Authors: Yoshifuji Masaaki 
Published: June 2006

Abstract
The structures of transition metal complexes with low coordinate organophosphorus compounds are described; these compounds involve diphosphenes, phosphaethenes, phosphaallenes, phosphabutatrienes, and so on of coordination number 2. They are discussed in terms of X-ray crystallographic analysis and 31P NMR analysis.
Fluorescence Emission and Cycloaddition Reaction Induced by Ionizing Radiation in 2,5-Distyrylpyrazine Molecular Crystal : A Comparison to the Photo-Illuminated Systems
Authors: Ishida Wataru , Takenaka Yasuyuki , Miyatake Yoko , Hase Hirotomo , Ogasawara Masaaki 
Published: June 2006

Abstract
Fluorescence emission and cycloaddition reaction induced in 2,5-distyrylpyrazine crystal by ionizing radiation were studied by means of pulse radiolysis and 60Co γ-ray radiolysis. Lifetimes of the fluorescence in the photo-illuminated crystal were also studied for comparison by using pico-second laser photolysis techniques. The fluorescence spectrum obtained by pulse radiolysis was similar to that obtained by laser-photolysis, which led us to conclude that excimers were formed by electron beam-irradiation as well. The occurrence of [2+2] cycloaddition reaction of DSP by γ-irradiation was monitored by observing the concentration change of the olefinic double bond. The high G-value, 4—5, for the decrease of the olefinic double bond suggested efficient activation of DSP in the irradiated crystal.
Electronic Structures of the Hückel Ring and the Möbius Ring
Authors: Ohmae Takayuki , Aono Shigeyuki 
Published: June 2006

Abstract
The electronic structures of the Hückel- and Möbius type species are investigated in the Hückel approximation. The Green’s function approach is employed to evaluate the total energy, the charge density and the bond order of various series. The results are successfully expressed in analytical forms, which displays the Hückel 4m + 2 and the Möbius 4m rules very clearly.
Rotator Phase in Dodecylammonium Chloride Studied by 1H and 2H Solid NMR and Thermal Measurements
Authors: Tanaka Susumu , Onoda-Yamamuro Noriko , Ishimaru Shin’ichi , Ikeda Ryuichi 
Published: June 2006

Abstract
1H NMR spin-lattice relaxation times, T1 and T1ρ, the second moment M2 of 1H NMR linewidth, 2H NMR spectra, powder X-ray diffraction, electrical conductivity, and thermal measurements have been performed on C12H25NH3Cl and C12H25ND3Cl in the range between room temperature and the melting point. From these measurements, the presence of the rotator phase was revealed above ca. 345 K, where a highly disordered structure characterized by the rapid 2-D self-diffusion as well as the axial rotation of the cations taking place in the lamellar-type double layer structure is formed. These molecular motions, the crystal structure and the thermal nature found in this phase indicate that the rotator phase is close to the plastic crystal and can be described as “a low-dimensional plastic phase”. The determined dynamic parameters of molecular motions in this phase were compared with those in the values reported in the rotator phases of short alkyl chain analogues.
A Study on the Adsorption Characteristics of Acetone and Benzene in Supercritical Carbon Dioxide Measured by Chromatography and IR Spectroscopy
Authors: Jin Do Won , Nitta Tomoshige , Park Dong-Won 
Published: June 2006

Abstract
Chromatographic and FTIR techniques were applied to a study of the absorption characteristics of acetone and benzene on a silica gel (SG800) in supercritical CO2 at 313.2 and 333.2 K. The chromatographic isotherms for acetone and benzene have a maximum at a pressure lower than the critical pressure of CO2, and then decrease with increasing pressure. When the temperature increases, the adsorption isotherms decrease in the low-pressure region, and increase in the high-pressure region, providing a crossover at a relatively high pressure. The elution curves of acetone showed tailing, even at high pressures, while those of benzene showed quasi-Gaussian curves at high pressures. The tailing curves for acetone indicate the existence of heterogeneous sites; evidence of hydrogen-bonding formation with surface silanol groups has been provided by IR spectroscopy.
Intercalation of Anticancer Agent Cytarabine and Its Related Compounds into
γ
-Titanium Phosphate
Authors: Danjo Mayumi , Mizuguchi Yukari , Yagita Yukari , Kakiguchi Kazuyo , Yanagida Tomomi , Tsuhako Mitsutomo 
Published: June 2006

Abstract
The intercalation of nucleic acid-related compounds which have the pyrimidine structure into the layered titanium phosphate, Ti(H2PO4)(PO4)·2H2O (γ-TiP), was examined. The intercalation of cytosine derivatives such as anticancer agent cytarabine was successful. In addition, cytarabine release tests from the obtained cytarabine intercalation compound of γ-TiP were performed in various kinds of solutions containing sodium ions. The release of cytarabine became slower by intercalation into the layered phosphate. Cytarabine release was strongly influenced by the pH value and the concentration of sodium ions in the test solution. In the reaction in aqueous solutions with higher concentrations of sodium ion and/or higher pH values, the ion-exchange of Na+ and protonated cytarabine in the intercalation compound and the disintegration of the layered structure of γ-TiP occurred. On the other hand, in the solutions with the lower sodium ion concentration and the lower pH value, the layered structure of γ-TiP was disintegrated and cytarabine in the interlayer region rearranged.
The Reaction of Polyhalides with Allylsilanes Catalyzed by Copper(I) Chloride
Authors: Mitani Michiharu , Hujita Shigenori 
Published: June 2006

Abstract
Allyltrimethylsilane reacted with polyhalogen compounds in the presence of copper species, such as copper(I) chloride, copper(II) chloride or metallic copper, to form polyhalo compounds containing an allyl group. Other allylsilane derivatives than allyltrimethylsilane were also subjected to a reaction with carbon tetrachloride. 3-Chloro- or 3-bromo-3-trimethylsilyl-1-propene gave 4,4,4-trichloro-1-trimethylsilyl-1-butene. Ethyl 1-trimethylsilylallyl carbonate afforded ethyl 4,4,4-trichloro-1-butenyl carbonate along with a hydrotrichloromethylation product. 2-Methyl-3-trimethylsilyl-1-propene yielded a product based on the addition of a trichloromethyl group followed by hydrogen-elimination from a 2-methyl group.
Direct Oxidation of Methyl Ethers to Carbonyl Compounds with a Combination of Nitrogen Dioxide and Water in the Presence or Absence of Ozone
Authors: Suzuki Hitomi , Takeuchi Toyomi , Mori Tadashi 
Published: June 2006

Abstract
A combination of nitrogen dioxide and water has been found to provide a new agent for the transformation of various alkyl methyl ethers 1 (R = Me) to carbonyl compounds 2 under mild conditions. The oxidation can be achieved successfully in dichloromethane, but hexafluoro-2-propanol was found to be most satisfactory as the solvent. The reaction was generally clean, and simple evaporation gave the expected oxidation product 2 in moderate to good yield. In the presence of ozone, but without water, the similar oxidation was observed only after prolonged reaction time, suggesting that some initial minor reaction with a strong oxidant, possible nitrogen trioxide, afforded an acidic promoter, which then worked as a catalyst similar to that involved in the reaction with a nitrogen dioxide and water system.
Some aspects of modern population mathematics
Authors: Brillinger David R. 
Published: June 2006

AbstractThe purpose of this paper is to survey a number of the technical tools and models that have found use in the study of human and other populations, and to indicate some problems of current interest. These tools and models are varied: integral equations, nonlinear oscillations, differential geometry, dynamical systems, nonlinear operations, bifurcation theory, semigroup theory, martingale theory, Markov processes, diffusion processes, branching processes, ergodic theory, prediction theory and state‐space models. A fairly extensive bibliography is provided. Also an Appendix has been added describing the analysis of a classical entomological data set.
Dropping observations without affecting posterior and predictive distributions
Authors: Draper Norman R. , Guttman Irwin 
Published: June 2006

AbstractSuppose in a distribution problem, the sample informationWis split into two piecesW1andW2, and the parameters involved are split into two sets, π containing the parameters of interest, and θ containing nuisance parameters. It is shown that, under certain conditions, the posterior distribution of π does not depend on the dataW2, which can thus be ignored. This also has consequences for the predictive distribution of future (or missing) observations. In fact, under similar conditions, the predictive distributions usingWor justW1are identical.
Statistics, images, and pattern recognition
Authors: Ripley Brian D. 
Published: June 2006

AbstractData are increasingly being collected in the form of images, especially in fields using remote sensing and microscopy. Statisticians are becoming interested in developing techniques to handle the highly structured data of images. Statistical work in this area is surveyed, and two problems discussed in more detail. The first is a form of image segmentation, classifying the pixels of a satellite picture by land use. The second is the summarization of electron micrographs.
Refining binomial confidence intervals
Authors: Casella George 
Published: June 2006

AbstractA method for refining an equivariant binomial confidence procedure is presented which, when applied to an existing procedure, produces a new set of equivariant intervals that are uniformly superior. The family of procedures generated from this method constitute a complete class within the class of all equivariant procedures. In certain cases it is shown that this class is also minimal complete. Also, an optimally property, monotone minimaxity, is investigated, and monotone minimax procedures are constructed.
Relations between statistics for testing exponentiality and uniformity
Authors: Currie Iain D. , Stephens Michael A. 
Published: June 2006

AbstractIt is shown that Greenwood's statistic for uniformity and the Hahn‐Shapiro and Stephens statistics for exponentiality with known origin are equivalent. It is also shown that the distribution of the Shapiro‐Wilk statistic for testing the hypothesis of exponentiality with unknown origin is obtainable from the distribution of Greenwood's statistic.
On the asymptotic distribution of a class of aligned rank order test statistics in randomized block designs
Authors: Tardif Serge 
Published: June 2006

AbstractIn the present investigation, the unconditional asymptotic distribution of a class of aligned rank order test statistics for randomized block designs is derived under the null hypothesis and for nearby alternatives, as the number of blocks tends to infinity. The proofs of these results are based on the asymptotic equivalence in quadratic mean between aligned observations and their ranks and thus are quite similar to the Hájek and SKidák (1967) approach.
On aliasing and generalized defining relationships of factorial arrangements
Authors: Raktoe B. L. , Pesotan H. , Federer W. T. 
Published: June 2006

AbstractThe concepts of defining contrast (DC), generalized defining relationship (GDR) and aliasing structure (AS) are now well established in the terminology of regression analysis and factorial design theory. There is no complete agreement in the literature about the meaning of regular and irregular fractional factorial designs. This paper provides a workable definition of a regular fraction from a symmetrial prime‐powered factorial. It characterizes the uniqueness of the GDR for fractions from the most general factorial. Results are also présentés on the uniqueness of the GDR for regular designs, on orthogonality aspects of regular and irregular designs, and on group‐theoretic generation of the complete aliasing structure. Examples are provided to illustrate the developments.
Maximum likelihood estimation for mixtures
Authors: Hill David L. , Saunders Roy , Laud Purushottam W. 
Published: June 2006

AbstractThis paper studies maximum likelihood estimation of mixing probabilities ρk, k ≥ l, when the data have a density of the form g = Σpkfkfor known densitiesfk. An application to the shock model of Esary, Marshall and Proschan (1973) is considered in some detail. A simulation study which compares the maximum likelihood estimator to other available estimators for the case of finite mixtures is summarized.
Loss functions and admissibility of normal variance estimators
Authors: Wild C. J. 
Published: June 2006

AbstractLoss functions and admissible estimators of the variance are considered with reference to a continuous family of loss functions in which both squared error in σ2 and squared error in the logarithm of σ2 are embedded. The optimality of estimates with respect to expected loss is found to be very loss‐function dependent and the cost of misspecifying the loss function is found to be high.
Small sample estimation of regression parameters in the three‐variable linear model, with incomplete observations
Authors: Dagenais Marcel G. 
Published: June 2006

AbstractThis paper describes a new method for estimating the parameters, in linear regression models containing one dependent and two independent variables, when some observations are incomplete. The proposed technique is a markedly improved version of an approach described in previous papers [2, 3]. Results of Monte Carlo experiments suggest that the adopted modifications enhance considerably the small sample performance of the estimators.
On the existence and non‐existence of quintic designs
Authors: Duthie Audrey I. 
Published: June 2006

AbstractQuintic designs, a class of PBIB designs having five associate classes, are defined. Properties of NN', where N is the incidence matrix, are examined to present necessary conditions for the existence of quintic designs. The variances of elementary treatment comparisons are found. The block structure of two types of quintic design is studied.
The variability of rainfall acidity
Authors: Eynon Barrett P. , Switzer Paul 
Published: June 2006

AbstractTwo years of rainfall acidity data for the eastern United States were analyzed. The data consist of rainfall‐event pH measurements from a nine station monitoring network. A spatio‐temporal stochastic model, including deterministic components for seasonal variation and rainfall washout, and stochastic components for spatial, temporal, and measurement variation, was fitted to the data. The fitted autocorrelation structure from this model was used, in the process known as Kriging, to obtain BLUE contour maps of seasonal and rainfall adjusted yearly average pH over the monitoring region.
Dose‐response models for time‐to‐response toxicity data
Authors: Kalbfleisch John D. , Krewski Daniel R. , Van Ryzin Ohn 
Published: June 2006

AbstractThis paper concerns the modelling and analysis of toxicity data in which the time to some toxic response is recorded and of importance. The paper begins with a review of a variety of dose‐response models, including log‐linear, proportional hazards, multievent, and compartmental models, that have been suggested and used in this context. Models for competing risks are also reviewed and several possible approaches are considered and discussed in the context of dose response experiments. The formulation of a model for competing risks that utilizes cause‐specific hazards gives a natural basis for the modelling and analysis of certain experimental situations in which only partial information is available on the time to response. Such situations arise, for example, when the presence of tumour is not clinically detectable in carcinogenicity trials. Likelihood construction is discussed, and appropriate likelihood contributions are derived. The paper concludes with a discussion of measures of risk which take account of the time dependence of the toxic response under study.
A review of optimal designs in survey sampling
Authors: Bellhouse David R. 
Published: June 2006

AbstractResults in five areas of survey sampling dealing with the choice of the sampling design are reviewed. In Section 2, the results and discussions surrounding the purposive selection methods suggested by linear regression superpopulation models are reviewed. In Section 3, similar models to those in the previous section are considered; however, random sampling designs are considered and attention is focused on the optimal choice of πj. Then in Section 4, systematic sampling methods obtained under autocorrelated superpopulation models are reviewed. The next section examines minimax sampling designs. The work in the final section is based solely on the randomization. In Section 6 methods of sample selection which yield inclusion probabilities πj=n/Nand πij=n(n‐ 1)/N(N‐ 1), but for which there are fewer thanNCnpossible samples, are mentioned briefly.
On estimating the difference of location parameters of two negative exponential distributions
Authors: Mukhopadhyay Nitis , Hamdy Hosny I. 
Published: June 2006

AbstractFixed‐width confidence intervals for the difference of location parameters of two negative‐exponential distributions have been constructed through two‐stage and purely sequential schemes. The two cases when the scale parameters are equal but unknown, and unequal but unknown, have been dealt with separately. Our two‐stage procedures guarantee the exact confidence coefficient to be at least the nominal prescribed level. Various second‐order expansions are also considered when sequential procedures are proposed. It is noted that no new tables are needed to implement these procedures in practice.