bluuebunny/crossref_metadata_2025_split huggingface dataset:
Preparation de la D‐Methionine (14C‐3) et de la Methionine (14C‐3)
Authors: Pichat L. , Beaucourt J. P. 
Published: October 2006

AbstractLa carbonatation avec 14CO2 du Mméthylthiométhyllithium a fourni l'acide méthylthio‐2 acétique(14C‐1) avec un rendement de 83%, dont la réduction par LiA1H4 a conduit au méthylthio‐2 éthanol‐1 (14C‐1) qui a été transformé en chlorure correspondant par action de la tri‐n‐octylphosphine et CCl4. Le chlorure condensé sur le sodio acétamicomalonate d'éthyle a fourni le (méthylthio‐2 éthyl) acétamidomalonate d'éthyle (14C03) qui a été saponifié en monoester dont la décarboxylation a produit le DL‐méthylthio‐4 acétamido‐2 butyrate d'éthyle (14C‐3). L'hydrolyse par l'α‐chymotrypsine donne la N‐acétyl‐L‐méthionine (14C‐3) que l'on sépare du méthylthio‐4 acétamido‐2‐D‐butyrate d'éthyle (14C‐3). Par hydrolyse chlorhydrique on aboutit respectivement à la L‐méthionine (14C‐3) et à la D‐méthionine (14C‐3) dactivité spécifique: 54 mCi/mM avec des rendements respectifs globaux de 14 et 11% par rapport a 14CO3Ba.
The synthesis of tritium labelled dialkenyl sulphides structurally related to sulphur crosslinks in vulcanized natural rubber
Authors: Ayrey G. , Barnard D. , Houseman T. H. 
Published: October 2006

AbstractDi‐(1,3‐dimethylbut‐2‐enyl‐[4‐3H1]mono‐, di‐and trisulphides have been synthesised via the common intermediate S‐(1,3‐dimethylbut‐2‐enyl‐[4‐3H1] thiouronium bromide (I). Protonation of a mixture of 2‐methylpenta‐1,3‐and ‐2,4‐dienes during formation of (I) was shown to be accompanied by a large kinetic isotope effect such that protonation was 8–10 times more probable than tritonation.
Production of 1‐11C‐acetoacetic acid
Authors: Straatman Maria G. , Hortmann Alfred G. , Welch Michael J. 
Published: October 2006

AbstractInterest in labeled compounds which can be studied as brain metabolites and can be detected in vivo has led to production of carbon‐11 labeled acetoacetic acid (1‐11C‐acetoacetic acid). This synthesis, which was designed specifically for use with short‐lived isotopes, utilizes a solution of the stable enolate anion of acetone, generated by the reaction of CH3Li and isopropenyl acetate, to which the 11CO2 is added to produce the labeled acetoacetic acid in ∼55% yield with a synthesis time of only 40 minutes from the end of bombardment.
Syntheses with stable isotopes: Pyridine‐15N
Authors: Whaley Thomas W. , Ott Donald G. 
Published: October 2006

AbstractThe acid‐catalyzed condensation of either 2‐ethoxy‐3,4‐dihydro‐2H‐pyran or pentanedial (glutaraldehyde) with ammonium‐15N chloride in the presence of methylene blue is a convenient one‐step synthesis of pyridine‐15N.
Markierte verbindungen XIX(1) 3,4,5‐trichlor‐1,2‐dithioliumchloride‐(36CL)
Authors: Boberg Friedrich , Wiedermann Rolf , Kresse Josef 
Published: October 2006

Abstract3.4.5.‐Trichlor‐1.2.‐dithioliumchlorid‐(3.5.‐36Cl) und‐(3.4.5‐36Cl) (1a und 1b) werden aus 3.4.5‐Trichlor‐1.2‐dithioliumchlorid und AlCl3‐(36Cl) oder SbCl3 ‐(36Cl) dargestellt. Folgende Reaktionen beweisen die Markierungsorte: 1a → 4.5‐Dichlor‐1.2‐dithiacyclopentenon‐(3)‐(5‐36Cl) →4‐Chlor‐5‐(N‐methylanilino)‐1.2‐dithiacyclopentenon‐(3); 1b → 4.5‐Dichlor‐1.2‐dithiacyclopentenon‐(3)‐(4.5‐36Cl) → 4‐Chlor‐5‐(N‐methylanilino)‐1.2‐dithiacyclopentenon‐(3)‐(36Cl). ‐ Chloraustausch zwischen 1, Hexachlorpropen und S2Cl2 wird mit 36Cl‐markierten Verbindungen nachgewiessen.
Application D'Une Methode Non Specifique de Tritiation de Molecules Organiques
Authors: Buchman O. , Pri‐Bar I. , Shimoni M. , Smoskowitz L. 
Published: October 2006

AbstractUne méthode de marquage de molécules organiques par l'entremise du tritium gazeux a été appliquée à la tritiation non spécifique d'une trentaine de dérivés de structure complexe. Les résultats expérimentaux, comprenant les activités spécifiques obtenues, sont données. L'efficacité de la tritiation catalysée par le noir de platine, formé in situ par le tritium, a été comparée aux faibles rendements d'échange obtenus lorsque le catalyseur est activé, au préalable, par l'hydrogène. Une élévation de la température de réaction augmente l'activité spécifique du substrat tritié.
Syntheses with stable isotopes: Acetylene‐13C2 and lithium acetylide‐13C2 ethylenediamine complex
Authors: Whaley Thomas W. , Ott Donald G. 
Published: October 2006

AbstractAcetylene‐13C2 has been prepared from carbon‐13C dioxide and molten lithium following hydrolisis of the resulting lithium carbide‐13C2. The stable ethylenediamine complex of lithium acetylide‐13C2 has been obtained from the reaction of acetylene‐13C2 with N‐lithioethylenediamine.
Synthesis of carbon‐14 labeled polychlorinated biphenyls
Authors: Hoizumi Kiyoshi , Moriya Takashi 
Published: October 2006

AbstractStarting with benzene‐U‐14C, biphenyl‐U‐14C was synthesized in two steps in approximately 65% yield. Then two kinds of polychlorinated biphenyls‐U‐14C. The yield was more than 35% based on benzene‐U‐14C consumed.
Synthesis of 14C‐labelled 3‐(1‐hydroxy‐2‐piperidinoethyl)‐5‐phenylisoxazole citrate (31252‐S)
Authors: Minato H. , Nagasaki T. , Yokoshima T. , Suga K. , Yamaguchi M. 
Published: October 2006

Abstract3‐(1‐Hydroxy‐2‐piperidinoethyl)‐5‐phenylisoxazole citrate, 31252‐S (I) has been labelled with carbon‐14. The carbon‐14 label was incorporated into the C‐2 position of the side‐chain to give (II) and into the C‐4 position of the isoxazole ring of the molecule to give (III).The carbon‐14 labelled products (II) and (III) were obtained in 27% and 6.4% ratiochemical yield based on methyl iodide‐14C, respectively.
Markierte verbindungen XX (1) N,N′‐diarylharnstoffe aus N‐aroyl‐O‐phenylcarbamoyl‐hydroxylaminen
Authors: Zörkendörfer E. 
Published: October 2006

AbstractDecomposition of N‐aroyl‐O‐arylcarbamoyl‐hydroxylamines VII—N‐(1‐14C) benzoyl‐O‐phenylcarbamoyl‐hydroxylamine (1y). N‐(p‐toluyl)‐O‐phenylcarbamoyl‐hydroxylamine (4) and N‐Benzoyl‐O‐(p‐tolyl) carbamoyl‐hydroxylamine (5) — in various systems yields arylhydroxamic acids X and N, N′‐diarylurea‐mixtures VI/XII/XIII, what is explained by two reaction paths. The reaction of 1y with aniline or p‐toluidine to unlabelled N,N′‐diphenylurea or N‐phenyl‐N′‐(p‐tolyl) urea is showing that the diarylurea is formed from the amine and the phenylcarbamoyl group of 1y.
Synthesis of 3,3‐(14C)‐dimethyl‐1‐phenyltriazene from 14C‐dimethylamine hydrochloride and benzene‐diazonium fluoroborate
Authors: Kolar G. F. , Schweickhardt Ch. 
Published: October 2006

Abstract3,3‐(14C)‐Dimethyl‐1‐phenyltriazene was prepared from recrystallized benzenediazonium fluoroborate which was coupled with 14C‐dimethylamine in excess aqueous sodium carbonate at 0°. The crude product was extracted with ether and purified by distillation. Redistilled 14C‐labelled triazene was obtained in good yield (70.4 and 73.5%) and in high radiochemical purity (better than 99.9% by scan of thin‐layer chromatograms). The specific activities of two preparations, determined by liquid scintillation counting and corrected for quenching, were 244 and 296 μCi/mmole. The determined activities were in close agreement with values computed from the specific activity of 14C‐dimethylamine hydrochloride used in the synthesis.
The synthesis of 14C and 3H‐labeled N‐(2‐p‐azidophenylethyl)‐norlevorphanol
Authors: Degraw J. I. , Engstrom J. S. 
Published: October 2006

AbstractSynthetic procedures for N‐(2‐p–azidophenylethyl)‐norlevorphanol (9) labeled with 14C and 3H at the 1‐position of the 2‐phenylethyl moiety are presented. A process for synthesis of p‐nitrophenylacetic‐1‐14C acid from p‐chloro‐nitrobenzene and methyl cyano‐14C‐acetate is described. The nitro acid was converted to 9 in a six step procedure, proceeding through 2‐(p‐aminophenyl)ethanol (6) as a key intermediate. The alcohol (6) was also prepared with 3H label via reduction of methyl p‐aminophenylacetate with sodium borotritide‐aluminium chloride.
Synthesis of hexalabeled thymine and thymidine
Authors: Lawson John A. , Degraw Joseph I. , Anbar Miohael 
Published: October 2006

AbstractThe synthesis of hexalabeled thymine and thymidine are described and field ionization mass spectra are recorded for these materials. Field ionization mass spectrometry is preferred in the utilization of multilabeled compounds as tracers in biomedical applications.
Encapsulation of ZnS:Mn2+ nanocrystals with diblock copolymers
Authors: Kim Sangcheol , Diana Frédéric S. , Petroff Pierre M. , Kramer Edward J. , Ootsu Takeshi , Murase Tomohide 
Published: October 2006

AbstractThe encapsulation of the nanocrystalline manganese‐doped zinc sulfide (ZnS:Mn) in poly(styrene‐b‐2vinylpyridine) (PS‐PVP) diblock copolymers is reported. Below the critical micelle concentration in the absence of nanocrystals (NCs), inverse micelles of PS‐PVP were induced by adding ZnS:Mn NCs, the presence of which was confirmed by scanning force microscope and dynamic light scattering. In toluene, a PS‐selective solvent, the less‐soluble PVP blocks preferentially surround the ligand‐coated ZnS:Mn NCs. For PS‐PVP encapsulated ZnS:Mn NCs, the ratio of blue emission to orange emission of ZnS:Mn NCs is dependent on both the concentration of PS‐PVP and the solvent quality. The pyridine of PVP blocks form complexes with the Zn atoms via the nitrogen lone pair and thus the sulfur vacancies are passivated. As a result, the defect‐related blue emission is selectively quenched even when the micelles are not formed. As the concentration of PS‐PVP encapsulating the ZnS:Mn NCs increases, the intensity of blue emission decreases. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 3227–3233, 2006
A Method for Determining the Theoretical Carcinogenicity of Polycyclic Aromatic Hydrocarbons
Authors: Rachin Emil , Ralev Nicolai 
Published: October 2006

AbstractThe method permits the calculation of the carcinogenicity index of polycyclic aromatic hydrocarbons as a function of a) the number of aromatic rings present in the molecules studied; b) the Dewar reactivity index of the two most reactive centers according to the BAY‐region and DI‐region theories; and c) the distance between these centers given as the number of carbon‐carbon bonds. An excellent correlation is found between the experimentally obtained and the theoretically calculated carcinogenic activities (correlation coefficient 0.948).
Structure – Molar Refraction Relationships of Alkylsilanes Using Molecular Connectivity
Authors: Kupchik Eugene J. 
Published: October 2006

AbstractCorrelation of molar refraction with the first order molecular connectivity index was found to be excellent for alkylsilanes of molecular formula SiCnH2n+4, which include tetraalkylsilanes, trialkylsilanes, dialkylsilanes, and monoalkylsilanes. The separate correlation of molar refraction with the first order molecular connectivity index for each of these four classes of alkylsilanes was also found to be excellent. Excellent correlations were also obtained using an empirically determined first order valence molecular connectivity index. It is shown that the first order molecular connectivity index gives more satisfactory predictions of molar refraction than does the empirically determined first order valence molecular connectivity index.
Upper bounds for the Zagreb indices and the spectral radius of series‐parallel graphs
Authors: Zhou Bo 
Published: October 2006

AbstractThe first Zagreb index M1 is equal to the sum of the squares of the degrees of the vertices, and the second Zagreb index M2 is equal to the sum of the products of the degrees of pairs of adjacent vertices of the respective graph. The spectral radius of a graph is the largest eigenvalue of its adjacency matrix. The Zagreb indices and the spectral radius are all useful molecular structure descriptors. We provide upper bounds for the Zagreb indices M1 and M2 and the spectral radius of series‐parallel graphs, in terms of the number of vertices and the number of edges, and determine the graphs for which the bounds are attained. © 2006 Wiley Periodicals, Inc. Int J Quantum Chem, 2007
Facilitating identity formation, group membership, and learning in science classrooms: What can be learned from out‐of‐field teaching in an urban school?
Authors: Olitsky Stacy 
Published: October 2006

AbstractThis paper explores both the obstacles and the possibilities for students developing identities associated with science by engaging in solidarity‐building classroom interactions. Data come from ethnographic research conducted in a diverse eighth‐grade urban magnet school classroom in which the teacher taught out of field for part of the year. Contrary to expectations, more students participated and reported enjoying science when the teacher was out of field. Analysis of classroom interactions indicated that while in field, the teacher primarily engaged in “front stage” performances that hid her struggles with the material and accentuated students' views of science as an elite status group. The types of solidarity that developed among students often did not involve science language and sometimes involved students rejecting peers' claims to membership. However, when out of field, the teacher allowed students into her “backstage,” where her struggles and learning processes were more explicit. These practices lessened the social distance between teacher and students, and reduced the risks of using science language, thereby encouraging solidarity and group membership. This study provides insights into some of the ways that teachers, particularly those in urban settings characterized by diversity, might be more successful at facilitating identity formation and learning in science. © 2006 Wiley Periodicals, Inc. Sci Ed 91:201–221, 2007
Changing attitudes toward energy conservation: The effect of self‐generated thoughts on the salience of a two‐sided persuasive communication
Authors: Koballa Thomas R. 
Published: October 2006

AbstractThe most logical place to start addressing a new energy ethic and its implications for daily life is the elementary school. While young children tend not to be big energy users, they can be taught to view energy in a different way from the way their parents view it. This can be accomplished by elementary teachers in much the same way that they try to teach good health habits or the practice of looking both ways before crossing the street. Perhaps the elementary school is also the place to begin introducing the idea that energy conservation does not necessarily mean doing with less, but using energy more wisely.Teachers serve as a vital link between what society thinks is important and what is taught to elementary age children. This is especially true when considering that the attitudes that teachers possess can be easily passed on to their students (Hone & Carswell, 1969) and thus reflected in their future behavior (Ajzen & Fishbein, 1980). It is desirable, therefore, that an ethical procedure be identified that enhances the probability of teachers including energy conservation topics in the elementary school curriculum. The persuasive communication model of attitude change has been demonstrated to function as such an ethical procedure within the context of science education (Grabowski, Shrigley, & Welliver, 1980; Koballa & Shrigley, 1983).
Studying conceptual change in learning physics
Authors: Dykstra Dewey I. , Boyle C. Franklin , Monarch Ira A. 
Published: October 2006

AbstractThere is often a severe problem of lack of communication between teacher and pupils. When two people communicate, what passes between them are the words and gestures they use to attempt to convey meaning, not the meaning itself. So a teacher has some ideas which he or she hopes to convey by putting them into words, diagrams or symbols. The child may take note of the words, and so on, but from these has to build up a meaning for them. There is clearly a strong possibility that this meaning created by the child is not the meaning intended by the teacher. This possibility is very high if the type of language used by the teacher, or workcard, or textbook writer, is not familiar to the child. Then various things may happen, as Barnes (1986) has so clearly pointed out: a) The child may ignore what the teacher is saying. b) The teacher may ignore what the pupil is saying (the teacher “controls” knowledge by using unfamiliar language, consequently children'S ideas are devalued and are only heard when they talk among themselves). c) The teacher may insist that the pupils use the “correct” words and so, sound scientific. (We, like Barnes, have seen children praised for “thinking like a scientist” when it is clear that the children are simply “making noises which sound scientific”).
Bridging the gap: An analysis of the needs of second‐year science teachers
Authors: Loughran John 
Published: October 2006

AbstractThis article reports on the themes and issues which impact on the pedagogical development of 14 beginning science teachers at the end of their second year of full‐time teaching. The research data was derived from semistructured interviews with the teachers and endeavors to portray the teachers' perspective of their development. This article demonstrates some of the difficulties associated with learning to teach science when teachers come from a preservice education program that encourages them to consider their understanding of learning and how it relates to their approach to teaching. The teachers in this study recognize how the factors of time, confidence and support each individually influence their teaching. However, when these three factors are considered together and are juxtaposed with the experiences and ideals of their preservice education program, the factors combined become a dilemma as they attempt to bridge the gap between what they hope to do as science teachers and what they can do in the real world of schools. © 1994 John Wiley & Sons, Inc.
Multiculturalism, universalism, and science education
Authors: Stanley William B. , Brickhouse Nancy W. 
Published: October 2006

AbstractMulticulturalists have recently raised a number of important challenges to the school curriculum, including whose knowledge are we teaching? and who benefits and loses by existing approaches to the curriculum? In this article we examine a number of issues in this debate that are of primary importance to science educators. These issues include: (1) problems with the universalist account of the nature of science that has been the most powerful defense against multiculturalism; (2) an examination of some historical cases that illuminate the consequences of maintaining a universalist perspective on science; and (3) an argument for a multicultural perspective on scientific knowledge. These issues are examined in the context of a national science education reform in which there is considerable consensus that the science curriculum should include teaching about the nature of science. We argue that the nature of science taught in school should reflect a multicultural perspective on scientific knowledge. © 1994 John Wiley & Sons, Inc.
Development and validation of a curriculum theory‐based classroom environment instrument: The technical and emancipatory classroom environment instrument (TECEI)
Authors: Bowen Craig W. 
Published: October 2006

AbstractThe purpose of this article is to delineate various conceptions of curriculum, and use one of these conceptions as a basis for the development of a classroom learning environment instrument titled the Technical and Emancipatory Classroom Environment Instrument (TECEI). The first portion of the article explains how curriculum can be conceived as a technocratic process in which curriculum professionals develop materials and instructional procedures that are implemented by teachers. As an alternative, an overview is given describing how curriculum can be conceived as a social construction that arises through interaction of participants (e.g., students, teachers, administrators, professional societies, and other segments of society). In the second portion of the article this social‐construction conception of curriculum is used as a foundation for a classroom learning environment instrument. The procedures used to develop the TECEI, as well as relevant validation information, is also reported. The study ends by explaining how the instrument might be used by teachers and researchers to enhance science learning and teaching. © 1994 John Wiley & Sons, Inc.
The nature of fourth graders' understandings of electric circuits
Authors: Shepardson Daniel P. , Moje Elizabeth B. 
Published: October 2006

AbstractThe purpose of this study was to interpret the nature of fourth graders' understandings of electric circuits. The qualitative study was guided by constructivist theory and utilized two small groups of four children each. Each child was interviewed prior to and after, as well as observed throughout, the instructional unit on simple electric circuits. The interviews centered around three different electric circuit tasks: predictions and explanations of eight electric circuit problems: the completion and explanation of three electric circuit drawings; and the identification of an electric current diagram, which was based on Osborne's (1983) work. The findings for these children suggested that: (1) the nature of children's understandings of electric circuits is dependent upon the interplay between their understandings of circuit connections and understandings of electric current; (2) prior to instruction children's understandings of electric circuits were scientifically inaccurate and tended to emphasize understandings of circuit connections; (3) children held multiple understandings of electric current prior to instruction, whereas following instruction most children held a single understanding of electric current, albeit scientifically inaccurate; and (4) after instruction children demonstrated a more accurate technical understanding of electric circuits, but only one child demonstrated a scientific understanding of electric current. Based on these findings, conclusions about knowledge restructuring are presented, as well as implications for teaching, assessment, and research. © 1994 John Wiley & Sons, Inc.
Progressive transitions from algorithmic to conceptual understanding in student ability to solve chemistry problems: A lakatosian interpretation
Authors: Niaz Mansoor 
Published: October 2006

AbstractThe main objective of this study is to construct models based on strategies students use to solve chemistry problems and to show that these models form sequences of progressive transitions similar to what the history of science refers to as progressive “problemshifts” that increase the explanatory/heuristic power of the models. Results obtained show the considerable difference in student performance on chemistry problems (mol, gases, solutions, and photoelectric effect) that require algorithmic or conceptual understanding. The difference between student performance on algorithmic and conceptual problems can be interpreted as a process of progressive transitions (models) that facilitate different degrees of explanatory power to student conceptual understanding. A parallel is drawn between the methodology of idealization (simplifying assumptions) used by scientists and the construction of strategies (models) used by students to facilitate conceptual understanding. A major educational implication of this study is that the relationship between algorithmic and conceptual problems is not dichotomous, but rather characterized by a continuum that consists of sequences of models that facilitate greater conceptual understanding. This reconstruction of student strategies to solve problems (progressive transitions) can provide the teacher a framework to anticipate as to how student understanding could develop from being entirely algorithmic to conceptual. © 1995 John Wiley & Sons, Inc.