bluuebunny/crossref_metadata_2025_split huggingface dataset:
Cerium(III) Triflate versus Cerium(III) Chloride: Anion Dependence of Lewis Acid Behavior in the Deprotection of PMB Ethers
Authors: Bartoli Giuseppe , Dalpozzo Renato , Nino Antonio De , Maiuolo Loredana , Nardi Monica , Procopio Antonio , Tagarelli Antonio 
Published: April 2004

AbstractCerium(III) triflate deprotects p‐methoxybenzyl ethers of simple alcohols better than the cerium(III) chloride/sodium iodide system. It can be used in 1% M instead of equimolecular amounts, giving better yields. Aromatic alcohols rearrange, but the addition of a scavenger overcomes this drawback. Unfortunately, unsaturated alcohols are deprotected with decomposition, probably due to side electrophilic additions to double bonds. A comparison between the mechanisms of cerium triflate and cerium chloride is reported. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)
Characterization and enantiomeric distribution of some terpenes in the essential oil of a Uruguayan biotype of Salvia sclarea L.
Authors: Lorenzo Daniel , Paz Daniel , Davies Philip , Villamil José , Vila Roser , Cañigueral Salvador , Dellacassa Eduardo 
Published: April 2004

AbstractA biotype of clary sage (Salvia sclarea L.) growing in Uruguay was evaluated for its suitability to be cultivated in Uruguay. Essential oils from the inﬂorescences and leaves of plant harvested at full ﬂowering and early seed ripeness stages were obtained by steam distillation and characterized by GC and GC–MS (quadrupole). Twenty‐seven components (91–98% of the total composition) were identiﬁed. The oil was characterized by a high content of linalool (8–22%), linalyl acetate (39–48%) and sesquiterpenes, with germacrene D (8–20%) and (E)‐β‐caryophyllene (3–5%) as the main components. The enantiomeric distribution of α‐pinene, sabinene, β‐pinene, limonene, linalool, linalyl acetate and germacrene D was studied by multidimensional HRGC–HRGC. The development stage did not inﬂuence the oil composition or the enantiomeric distribution of the studied components of the clary sage biotype over the period of evaluation. It is concluded that clary sage can be grown as an economically viable crop in the south of Uruguay. Copyright © 2004 John Wiley & Sons, Ltd.
Essential oils of Varthemia iphionoides from Jordan
Authors: Avato P. , Raffo F. , Aldouri N. A. , Vartanian S. T. 
Published: April 2004

AbstractThe essential oil obtained from plants of Varthemia iphionoides growing wild in Jordan has been analysed by GC and GC–MS. The major consituents are represented by borneol (49.3%) and its acetyl and formyl esters. Copyright © 2004 John Wiley & Sons, Ltd.
Terpenoids of the volatile oil of Bursera graveolens
Authors: Yukawa Chiyoki , Iwabuchi Hisakatsu , Kamikawa Tadao , Komemushi Sadao , Sawabe Akiyoshi 
Published: April 2004

AbstractIn the course of studies on the constituents of the woody material of Bursera graveolens, the aroma components that provide its characteristic spicy, sweet and balsamic odor were investigated using GC/MS. Five compounds, 1–5, were isolated from the volatile oil obtained by diethyl ether extraction of B. graveolens wood chips, and their structures were elucidated by means of NMR studies. Their structures were determined as (−)‐dihydro‐α‐agarofuran (1), (−)‐5,11‐epoxy‐4α,5β,10α‐eudesm‐1‐ene (2), (−)‐4α‐hydroxydihydroagarofuran (3), (−)‐3β,4β‐oxidoagarofuran (4) and (−)‐10‐epi‐γ‐eudesmol (5). Of these, (−)‐5,11‐epoxy‐4α,5β,10α‐eudesm‐1‐ene (2) is a new sesquiterpenoid that has not previously been reported in literature, and the presence of (−)‐dihydro‐α‐agarofuran (1), (−)‐4α‐hydroxydihydroagarofuran (3), (−)‐3β,4β‐oxidoagarofuran (4) and (−)‐10‐epi‐γ‐eudesmol (5) in B. graveolens is reported for the ﬁrst time. Copyright © 2004 John Wiley & Sons, Ltd.
Enzyme‐mediated synthesis of new 1,3‐dioxane odorants related to Floropal®
Authors: Abate Agnese , Brenna Elisabetta , Fuganti Claudio , Serra Stefano 
Published: April 2004

AbstractThe enzyme‐mediated synthesis of enantiomerically enriched 1,3‐dioxane odorants analogous to Floropal® is here described. The complete olfactory evaluation of each sample is also reported. The addition of a single methyl group at C5 of the dioxane ring of Floropal® modiﬁes the elicited odour sensation, still preserving a pleasant character. The substitution of the methyl group at C6 with just an ethyl moiety completely changes the odour proﬁle of the molecule. Even subtler are the odour differences generated by conﬁgurational variations. Copyright © 2004 John Wiley & Sons, Ltd.
Development of hydroxyapatite bone scaffold for controlled drug release via poly(ϵ‐caprolactone) and hydroxyapatite hybrid coatings
Authors: Kim Hae‐Won , Knowles Jonathan C. , Kim Hyoun‐Ee 
Published: April 2004

AbstractA scaffold‐coating design, the hydroxyapatite (HA) porous bone scaffold coated with poly(ϵ‐)caprolactone (PCL) and HA powder hybrids, was developed for use as tissue‐regeneration and controlled‐release system. An antibiotic drug, tetracycline hydrochloride (TCH), was encapsulated within the hybrid coating layer through a dip‐coating and solvent‐casting method. Coating cycle and drug loading amount differed to control the level of drug‐release rate. The HA scaffold framework, obtained by a polymeric foam reticulate method, exhibited a highly porous structure, with porosity and pore size of approximately 87% and 180 μm, respectively. The hybrid layer, consisting of PCL sheet and HA fine powders, was uniformly coated on the scaffold surface. The coating layer exhibited only PCL and HA phases and structures, revealing no chemical interaction among the coating components, as observed by X‐ray diffraction (XRD) and Fourier‐transform infrared (FTIR) analyses. The coated‐HA scaffolds showed an effective stress distribution behavior in response to an applied load, as confirmed by the compressive stress–strain curve. The mechanical properties of the coated scaffolds were improved highly with coatings; the compressive strength and elastic modulus of the cyclic coated scaffolds were ∼3–4 times, and the energy absorption were ∼8 times, higher than those without coating. These improvements were attributed mainly to the shielding of framework flaws by a flexible coating layer and partially to the thicker stems (porosity reduction). The dissolution of the coated scaffolds in a phosphate‐buffered saline (PBS) solution increased with incubation time. The drug was released sharply within the initial several hours (∼2 h), but the rate decreased further, showing a sustained release. The release amount was well controlled via coating‐cycle and initial drug loading amount, suggesting the effectiveness of the coating‐scaffold design as a drug‐delivery system. © 2004 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 70B: 240–249, 2004
Leveled Steric Effect in Alkoxyamines of SG1‐Type
Authors: Acerbis Sébastien , Beaudoin Emmanuel , Bertin Denis , Gigmes Didier , Marque Sylvain , Tordo Paul 
Published: April 2004

AbstractSummary: During nitroxide mediated polymerization (NMP) the polymerization time decreases with the increasing rate constant of the cleavage of the NOC bond of the dormant alkoxyamines. Hence, the knowledge of the factors influencing this cleavage is of considerable interest. Recently, we demonstrated that the influence of the nitroxyl moieties of 24 alkoxyamines on the values of the rate constant for the homolysis of the CON bond of the alkoxyamine (kd) was accounted for by a biparametric equation log kd = −3.07 × σU − 0.88 × Es − 5.88, with σU for the universal electrical effect and Es for the steric demand of the substituents bound to the nitroxyl function. During the course of the work, it was assumed for a number of molecules that the steric effect was leveled. We present herein three new SG1‐based alkoxyamines with sufficiently different steric strains to confirm the leveled steric effect.The fit of the rate constant for the homolysis of the CON bond of the alkoxyamines (kds) with the equation log kd = −0.37 × σU − 0.88 × Es when a leveled steric effect is assumed.imageThe fit of the rate constant for the homolysis of the CON bond of the alkoxyamines (kds) with the equation log kd = −0.37 × σU − 0.88 × Es when a leveled steric effect is assumed.
Copolymerization of Ethylene Carbonate and 1,2‐Propylene Carbonate with Tetramethylene Urea and Characterization of the Polyurethanes
Authors: Ubaghs Luc , Novi Christina , Keul Helmut , Höcker Hartwig 
Published: April 2004

AbstractSummary: Tetramethylene urea (TeU, 1) is successfully copolymerized with 1,2‐propylene carbonate (PC, 2) leading to a polyurethane ($\overline M _{\rm n}$ = 12 200; $\overline M _{\rm w}$ 18 400; $\overline M _{\rm w} /\overline M _{\rm n}$ = 1.50) with a Tm of 145.7 °C and a Tg of 53.7 °C. Mechanistic studies with a blocked isocyanate model compound revealed that, at no stage of the reaction is the TeU ring opened to form an isocyanate. Hence, a well‐underlined mechanism for the copolymerization is proposed. Furthermore, TeU is successfully copolymerized with mixtures of PC and ethylene carbonate (EC, 3). From NMR spectroscopic data of the polyurethanes obtained, it is concluded that PC is less reactive than EC. However, it is possible to increase the PC content in poly(TeU‐EC‐stat‐TeU‐PC) by increasing the PC/EC ratio in the feed. 13C NMR spectroscopy reveals that a random copolymer is obtained. This conclusion is supported by differential scanning calorimetry (DSC) data, which show a continuous decrease in Tm with increasing PC content.Tm was found to decrease with increasing PC content.imageTm was found to decrease with increasing PC content.
Synthesis of Poly(ethylene oxide)s with 1,2,4‐Triazol‐4‐yl End Groups – Macroligands for Bistable Metal‐Polymer Complexes
Authors: Saf Robert , Schwarzenbacher Gerald , Mirtl Christian , Hayn Gertraud , Hobisch Josefine , Gatterer Karl 
Published: April 2004

AbstractSummary: Poly(ethylene oxide) methyl ether 4H‐1,2,4‐triazol‐4‐yl (1) has been synthesized as a novel macroligand. ESI‐MS (electrospray ionisation mass spectrometry), MALDI‐TOF (matrix‐assisted laser desorption ionisation time‐of‐flight) MS as well as NMR spectroscopy were used for the accurate determination of number‐average molecular weights ($\overline M _{\rm n}$), the crucial parameter for subsequent synthesis of metal‐polymer complexes of four different samples 1a–d. Reaction of polymer 1a with [Fe(H2O)6](nps)2 (nps = 3‐nitrophenylsulfonate) gave [Fe(1a)3](nps)2, a bistable metal‐polymer complex that exhibited low‐spin (LS) to high‐spin (HS) transitions around T1/2 = 257 K, accompanied by a change in colour from violet (LS) to slightly yellow (HS).The structure of [Fe(1a)3](nps)2 and its magnetic properties.imageThe structure of [Fe(1a)3](nps)2 and its magnetic properties.
Heterogeneity Features of Bulk Atom Transfer Radical Polymerization of Methyl Methacrylate in an Ampoule Reactor
Authors: Wang Aileen R. , Zhu Shiping 
Published: April 2004

AbstractSummary: This work demonstrated the severity of heterogeneity issues with ampoule reactors in bulk atom transfer radical polymerization of methyl methacrylate. The kinetic data of CuII concentration, monomer conversion, and polymer molecular weight varied from location to location along the ampoule. However, the polymer molecular weight versus conversion data from different locations fell into a single theoretical line. All locations except for the bottom part of the ampoule produced polymers having narrow molecular weight distribution.Conversion versus time at different locations for the ATRP of MMA at 70 °C.imageConversion versus time at different locations for the ATRP of MMA at 70 °C.
Molecular weight determination of coordination and organometallic oligomers by T1 and NOE constant measurements: concepts and challenges
Authors: Harvey Pierre D. 
Published: April 2004

AbstractThis paper describes how to determine molecular weights of coordination and organometallic polymers (or rather oligomers) in solution using spin‐lattice relaxation time (T1) and Nuclear Overhauser Enhancement constant (ηNOE) measurements. The methodology is explained using simple organometallic‐complexes such as M(CN‐t‐Bu)4+ complexes (M = Cu, Ag). Very good results are obtained for oligomers that exhibit a rigid structure. Conversely, very poor results are extracted when the materials show flexible chains in the backbone. The typical examples for rigid and flexible oligomers are the {Ag(dmb)2+}n (dmb = 1,8‐diisocyano‐p‐menthane), and {Pd2(dmb)2(diphos)2+}n (diphos = dppa, dppb, dpppent, and dpph) as well as {Pd2(diphos)2(dmb)2+}n (diphos = dppe, dppr, and dpppR; R = O(CH2)2O‐naphthyl), respectively.
Synthesis and lithographic applications of highly metallized cluster‐based polyferrocenylsilanes
Authors: Chan Wing Yan , Cheng Alison Y. , Clendenning Scott B. , Manners Ian 
Published: April 2004

AbstractWe report the use of a cobalt‐clusterized polyferrocenylsilane (Co‐PFS) as a precursor to patterned ferromagnetic ceramics. Co‐PFS was synthesized. Functioning as a negative resist, Co‐PFS lines with widths of 10‐300 μm were patterned using UV‐photolithography, while features as small as 500 nm were afforded by electron‐beam lithography. Subsequent pyrolytic treatment of the lithographically patterned Co‐PFS yielded ferromagnetic ceramics containing Fe/Co nanoparticles. Due to its high metal‐loading, Co‐PFS is a good etch resist for oxygen and hydrogen plasma reactive ion etching. Reactive ion etching of a thin film of Co‐PFS in a secondary magnetic field allowed direct access to ferromagnetic ceramic films, providing a viable alternative to pyrolysis.
Induction Melting of NiTi Shape Memory Alloys – The Influence of the Commercial Crucible Graphite on Alloy Quality
Authors: Frenzel J. , Neuking K. , Eggeler G. 
Published: April 2004

AbstractThe present work studies the performance of three different kinds of commercial crucible graphite materials used during inductive melting of NiTi‐shape memory alloys (SMAs).One low‐density extruded graphite and two isostatically pressed graphite‐materials with different porosity and purity were used for melting NiTi‐SMAs from pure Ni and Ti raw materials. The use of a low grade, lower density graphite crucible led to a high carbon contamination of the alloy. Much better results were obtained using graphite crucibles with higher density and higher purity. But in all cases, the first use of a graphite crucible leads to a higher carbon pickup than the second time of utilization. This can be explained by the formation of a protective TiC rich layer on the surface of the crucible during its first contact with the NiTi melt which acts as a diffusion‐barrier later on. Furthermore, attention has to be paid to the thermal conductivity of the graphite. Using a material with a low thermal conductivity may lead to the formation of cracks at the pouring‐lip of the crucible during casting. This may lead to spalling off of crucible material and can enhance the risk of non‐metallic inclusions in the alloy.
Influence of compression aging on phase transition temperatures in single crystalline Ni‐rich NiTi shape memory alloys
Authors: Michutta J. , Yawny A. , Carroll M. C. , Somsen Ch. , Eggeler G. 
Published: April 2004

AbstractThe present paper considers the phase transition behavior of a single crystal Ni‐rich NiTi alloy which was compression aged to produce one single family of Ni4Ti3 precipitates.The single crystal material was produced in a two stage process.Polycrystalline material was first melted under an inert atmosphere and remelted when single crystals were produced. Compression aging treatments in <111>‐orientation were carried out in order to suppress all but one family of Ni4Ti3‐precipitates which nucleate and grow on {111}‐planes of the B2 matrix. The objective of this study is to investigate the influence of Ni4Ti3‐precipitates on the martensitic transformation behavior. It was previously shown that grain boundaries provide heterogeneous nucleation sites for the formation of Ni4Ti3; this results in heterogeneous microstructures which undergo multiple step martensitic transformations. Single crystals avoid grain boundaries and the present study aims at clarifying how homogeneously precipitated particles affect martensitic transformations.
PM‐Composites with Nickel‐Titanium Shape Memory Alloys
Authors: Theisen W. , Schuermann A. 
Published: April 2004

AbstractStarting from NiTi‐powders, composites of nickel‐titanium shape memory alloys (NiTi‐SMA) and different stainless steels as well as of different NiTi‐SMAs were produced by using the process of hot isostatic pressing (HIP). Metallographic investigations focussed on the interface between NiTi‐SMA and stainless steel with special emphasis placed on the characterization of the typical structure of the diffusion zones in both components.
Proximal nerve elongation vs. nerve grafting in repairing segmental nerve defects in rabbits
Authors: Baoguo Jiang , Shibata Minoru , Matsuzaki Hironori , Takahashi Hideaki E. 
Published: April 2004

AbstractIf segmental nerve defects could be repaired by elongating the proximal or distal segments, nerve grafting might be unnecessary. We elongated a 40‐mm proximal segment of an injured median nerve, in the rabbit right forelimb, at a rate of 1 mm/day for 10 days in 10 rabbits and for 15 days in another 10. On the left forelimb of the same rabbits, a 10‐ for 15‐mm segment of the median nerve was removed, and a 10‐ for 15‐mm segment, respectively, of the tibial nerve was grafted in its place. Four months after the initial surgery, nerve conduction velocity (NCV), contractile strength of the flexor digitorum superficialis (FDS), axon count, and axon diameter did not differ significantly between the 10‐mm groups but were better in the 15‐mm grafted group. Elongating the proximal nerve segment may be an alternative to grafting in repairing segmental defects of less than 10 mm. © 2004 Wiley‐Liss, Inc.
A human murine mammary tumour virus‐like agent is an unconvincing aetiological agent for human breast cancer
Authors: Mant Christine , Cason John 
Published: April 2004

AbstractThere has recently been renewed interest in both the scientific literature, and in the media, that a human relative (HMLV) of murine mammary tumour virus (MMTV) may be implicated in the aetiology of up to 42% of sporadic cases of human breast cancer. Such reports are potentially of considerable clinical significance, as aside from the small percentage of genetically acquired breast cancers, the cause of sporadic cases of breast cancer is completely unknown. Indeed, convincing proof of an infectious cause for human breast malignancies would permit the development of new preventative measures, treatment modalities and raise the possibility of prophylactic and therapeutic vaccines. Here we review the historical background for a retroviral cause of human breast cancers and give an up‐to‐date critique of the most recent research findings. We conclude that the available evidence for an infectious aetiology of human breast cancers is unconvincing. Amongst the many cognate arguments against an infective hypothesis for sporadic cases of human breast cancer are the facts that: (i) human tissues lack the appropriate cell‐surface receptor for entry of MMTVs/HMLVs; (ii) unlike all other virally caused human malignancies, immunodeficiency does not predispose to an increased incidence, or prevalence, of human breast cancers; and, (iii) reports of PCR amplification of MMTV/HMLV sequences from breast cancers have been robustly disputed by four independent laboratories. Indeed positive PCR results may be readily explained by the mis‐amplification of host genomic DNA. Hence, the burden of proof currently lies with those who champion a viral cause for sporadic cases of breast cancer. Copyright © 2004 John Wiley & Sons, Ltd.
Continuous and discontinuous phase transitions in hypergraph processes
Authors: Darling R. W. R. , Levin David A. , Norris James R. 
Published: April 2004

AbstractLet V denote a set of N vertices. To construct a hypergraph process, create a new hyperedge at each event time of a Poisson process; the cardinality K of this hyperedge is random, with generating function ρ(x) =def∑ ρkxk, where P(K = k) = ρk; given K = k, the k vertices appearing in the new hyperedge are selected uniformly at random from V. Assume ρ1 + ρ2 > 0. Hyperedges of cardinality 1 are called patches, and serve as a way of selecting root vertices. Identifiable vertices are those which are reachable from these root vertices, in a strong sense which generalizes the notion of graph component. Hyperedges are called identifiable if all of their vertices are identifiable. We use “fluid limit” scaling: Hyperedges arrive at rate N, and we study structures of size O(1) and O(N). After division by N, numbers of identifiable vertices and hyperedges exhibit phase transitions, which may be continuous or discontinuous depending on the shape of the structure function − log(1 − x)/ρ′(x), x ∈ (0, 1). Both the case ρ1 > 0, and the case ρ1 = 0 < ρ2 are considered; for the latter, a single extraneous patch is added to mark the root vertex. Published 2004 Wiley Periodicals, Inc. Random Struct. Alg., 2004
Comparison between some common influence coefficient algorithms
Authors: Willis J. P. , Lachance G. R. 
Published: April 2004

AbstractThe quality of the results obtainable from a number of different algorithms available in modern manufacturers' software has been compared using data for a single sample of Ni–Fe–Cr, for considerations of space. The conclusions reached are based on similar comparisons using many samples of different compositions. The aim was to demonstrate that, when all criteria (variable theoretical influence coefficients; total concentration of all elements equals 100%; homogeneous, flat and infinitely thick samples) relating to emission theory are met, a number of valid mathematical expressions are available to the user. The mathematical expressions (algorithms) examined are Lucas‐Tooth and Price, Rasberry–Heinrich and Lachance–Traill, all using empirical influence coefficients; Claisse–Quintin and COLA using linear and hyperbolic variable theoretical influence coefficients, respectively; and Broll–Tertian, Rousseau, Lachance–Claisse and de Jongh, using variable theoretical influence coefficients based on fundamental parameters. The last four algorithms give exactly the same results, despite the fact that the ‘structures’ of the algorithms are all very different and that the magnitudes of the influence coefficients are also very different (except that the magnitudes and signs of influence coefficients are the same for the Broll–Tertian and Rousseau algorithms). If any of the four algorithms is used correctly, each will give acceptable results. Copyright © 2004 John Wiley & Sons, Ltd.
A new approach to correcting theoretical emitted intensities for absorption and enhancement effects
Authors: Willis J. P. , Lachance G. R. 
Published: April 2004

AbstractThis paper introduces the possibility of replacing the usual additive corrections for absorption and enhancement by multiplicative factors. The possibility of deriving simple multiplicative factors to correct for inter‐element matrix effects, namely $a_{s}'$ and $a_{s}''$, to correct for absorption of primary and secondary radiation, respectively, and enhancement ($e_{\rm s}^{*}$), is demonstrated. The use of the new coefficients, $a_{s}'$, $a_{s}''$ and $e_{\rm s}^{*}$, derived directly from mass attenuation coefficients, simplifies the understanding of, and allows the stepwise evaluation of, the excitation of theoretical emitted intensities in XRF spectrometry. The approach is especially useful in providing a more consistent definition of theoretical intensity emitted from an infinitely thick sample, as compared with the classical formalism involving the use of mass attenuation coefficients. The approach has proved particularly useful in the classroom. Copyright © 2004 John Wiley & Sons, Ltd.