bluuebunny/crossref_metadata_2025_split huggingface dataset:
Solution Conformation and Dynamics of the Ion Pairs Originating from the Reaction of B(C6F5)3 with Bisindenyl Dimethyl Zirconium Complexes
Authors: Beringhelli Tiziana , D'Alfonso Giuseppe , Maggioni Daniela , Mercandelli Pierluigi , Sironi Angelo 
Published: November 2004

AbstractThe two ion pairs [(4,7‐Me2indenyl)2ZrMe]+[MeB(C6F5)3]− (1 b) and [(indenyl)2ZrMe]+ [MeB(C6F5)3]− (2 b) have been generated in situ by reaction of stoichiometric B(C6F5)3 with the corresponding dimethyl zirconocenes. It has been shown that molecular mechanics computations, guided by experimental 1H/1H NOE correlations, can provide information on the conformers present in solution. The dynamics of the ion pairs has also been investigated, showing the occurrence of both the processes previously characterized for this class of compounds, namely the B(C6F5)3 migration between the two methyl groups and dissociation–recombination of the whole [MeB(C6F5)3]− anion, the latter process being much faster than the first one (about three order of magnitude). Moreover, it has been shown that in certain conditions intermolecular processes can occur, which mimic the above‐mentioned dissociative exchanges. In particular, the presence of species containing loosely bound [MeB(C6F5)3]− anion fastens the exchange of this anion, while the presence of free B(C6F5)3 accelerates its exchange between the two methyl sites.
An Asymmetric Formal Synthesis of Fasicularin
Authors: Fenster Michaël D. B. , Dake Gregory R. 
Published: November 2004

AbstractAn asymmetric formal synthesis of fasicularin (1) is described. This natural product, isolated from the extracts of the marine invertebrate Nephteis fasicularis, has shown modest cytotoxicity towards Vero cells. Fasicularin is among only two members of the cylindricine family of natural products, along with lepadiformine (2), to possess a trans A–B ring junction. Key steps of this approach to 1 involve a siloxy‐epoxide semipinacol rearrangement of 5 to 6, a B‐alkyl Suzuki–Miyaura coupling reaction by using enol trifluoromethanesulfonate 19 and a substrate‐directed hydrogenation reaction of 24. This formal synthesis also highlights the difficulty in the incorporation of the thiocyanate functionality present in 1.
7‐Azaindolyl‐ and 2,2′‐Dipyridylamino‐Functionalized Molecular Stars with Sixfold Symmetry: Self‐Assembly, Luminescence, and Coordination Compounds
Authors: Jia Wen‐Li , Wang Rui‐Yao , Song Datong , Ball Steven J. , McLean Alastair B. , Wang Suning 
Published: November 2004

AbstractTwo novel star molecules functionalized with 7‐azaindolyl and 2,2′‐dipyridylamino groups have been synthesized. Both molecules possess a sixfold rotation symmetry. Molecule L 1 is based on the hexaphenylbenzene core with the formula of hexa[p‐(7‐azaindolyl)phenyl]benzene, while molecule L 2 is based on the hexakis(biphenyl)benzene core with the formula of hexa[p‐(2,2′‐dipyridylamino)biphenyl]benzene. Both compounds have been characterized by single‐crystal X‐ray diffraction analyses. Molecule L 1 forms extended two‐dimensional layered structure, while L 2 forms interpenetrating columnar stacks in the solid state, as revealed by X‐ray diffraction analyses. Nanowire structures based on columnar stacks through self‐assembly of L 2 on a graphite surface were revealed by an STM study. Molecules L 1 and L 2 are capable of binding to metal ions, resulting in unusual structural motifs. Two AgI complexes with the formulae of [(AgNO3)2(L 1)] (1) and [(AgNO3)3(L 1)] (2) were isolated from the reactions of AgNO3 with L 1. Compound 1 displays extended intermolecular π–π stacking interactions that are responsible for its extended two‐dimensional structure in the crystal lattice. Complex 2 has a “bowl” shape and forms polar stacks in the crystal lattice. A CuII complex with the formula of [{Cu(NO3)2}6(L 2)] (3) was isolated from the reaction of Cu(NO3)2 with compound L 2. The six CuII ions in 3 are chelated by the 2,2′‐dipyridylamino groups of the star ligand L 2. Intermolecular CuO (nitrate) bonds lead to the formation of an extended two‐dimensional coordination network of 3. Both L 1 and L 2 are blue luminescent. Their interactions with AgI or CuII cause drastic quenching of emission. In addition, the luminescence of L 1 and L 2 is sensitive to the presence of protons, which cause a reduction of emission intensity and a red shift of the emission energy.
Shape‐Controlled Synthesis of Metal Nanostructures: The Case of Silver
Authors: Wiley Benjamin , Sun Yugang , Mayers Brian , Xia Younan 
Published: November 2004

AbstractThe concept of shape‐controlled synthesis is discussed by investigating the growth mechanisms for silver nanocubes, nanowires, and nanospheres produced through a polymer‐mediated polyol process. Experimental parameters, such as the concentration of AgNO3 (the precursor to silver), the molar ratio between poly(vinylpyrrolidone) (PVP, the capping agent) and AgNO3, and the strength of chemical interaction between PVP and various crystallographic planes of silver, were found to determine the crystallinity of seeds (e.g., single crystal versus decahedral multiply twinned particles). In turn, the crystallinity of a seed and the extent of the PVP coverage on the seed were both instrumental in controlling the morphology of final product. The ability to generate silver nanostructures with well‐defined morphologies provides a great opportunity to experimentally and systematically study the relationship between their properties and geometric shapes.
Linear Unsaturated Polyamides: Nylons 6 u18 and 18 u18
Authors: Bennett Carl , Mathias Lon J. 
Published: November 2004

AbstractSummary: Linear unsaturated nylons 6 u18 and 18 u18 have been made containing a double bond in the center of the diacid segment with potential for additional functionalization. Solution state NMR showed the presence of a small portion of cis amide units. Solid state NMR verified the presence of the double bond in the bulk, and that the polyamides were present in the α‐crystalline form. Thermal stability was comparable to linear saturated nylons, and the melting and crystallization temperatures of the unsaturated nylons were lower compared to the saturated analogs.DSC heating and cooling thermograms for nylons 6 u18 and 18 u18.magnified imageDSC heating and cooling thermograms for nylons 6 u18 and 18 u18.
ATRP of Allyl Methacrylate with Alkyl Methacrylates – Crosslinking of Poly(methacrylate)s with Allyl Ester Side Groups
Authors: Mennicken Martina , Nagelsdiek René , Keul Helmut , Höcker Hartwig 
Published: November 2004

AbstractSummary: Random copolymers of methyl methacrylate (MMA), butyl methacrylate (BMA) and allyl methacrylate (AMA) were prepared via atom transfer radical polymerization (ATRP). AMA is a bifunctional monomer with two double bonds of different reactivity: a highly reactive methacrylate double bond and an allyl ester double bond of lower reactivity. In order to obtain linear polymers with pendant allyl ester groups, the copolymerization conditions have to be optimized with respect to the concentration of AMA, the catalyst system applied – especially the ligand – and the temperature. By means of kinetic studies the reaction parameters for a controlled polymerization were determined. The results obtained show that the higher the temperature and the amount of AMA is the higher is the probability of irregular chain growth and side reactions induced by the pendant allyl ester groups such as hydrogen abstraction from the allyl position or radical addition to the allyl ester double bond. The random copolymers were photochemically crosslinked by using 2,2‐dimethoxy‐2‐phenylacetophenone as photoinitiator. The thermal properties of linear and crosslinked polymers were determined. The glass transition temperatures of both show no significant difference at low AMA content and thus low crosslinking densities.GPC eluograms of MMA/BMA (70:30) copolymers with 5 mol‐% AMA at different conversions.magnified imageGPC eluograms of MMA/BMA (70:30) copolymers with 5 mol‐% AMA at different conversions.
Effective fractal dimensions
Authors: Lutz Jack H. 
Published: November 2004

AbstractClassical fractal dimensions (Hausdorff dimension and packing dimension) have recently been effectivized by (i) characterizing them in terms of real‐valued functions called gales, and (ii) imposing computability and complexity constraints on these gales. This paper surveys these developments and their applications in algorithmic information theory and computational complexity theory. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Countable sums and products of metrizable spaces in ZF
Authors: Keremedis Kyriakos , Tachtsis Eleftherios 
Published: November 2004

AbstractWe study the role that the axiom of choice plays in Tychonoff's product theorem restricted to countable families of compact, as well as, Lindelöf metric spaces, and in disjoint topological unions of countably many such spaces. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Integration of PV systems on health emergency vehicles. The FIVE project
Authors: Almonacid G. , Muñoz F. J. , de la Casa J. , Aguilar J. D. 
Published: November 2004

AbstractThe main purpose of this paper is to present the FIVE Project (Fotovoltaico Integrado en Vehículos de Emergencias) which involves the integration of a photovoltaic system in a health emergency vehicle. Here, the use of photovoltaic technology is extended to improving the performance of these kinds of vehicles. The fact is that their batteries usually deteriorate prematurely, owing to the high electrical consumption of the medical equipment they have to support, together with the short periods of time that their engines remain running. A consequence of such problems is high maintenance costs due to the frequent changes of batteries, and what is more important, occasional difficulties in starting the vehicle at critical moments. Furthermore, the service battery of the health emergency vehicle has to be charged every day by a battery charger connected to the grid, providing this kind of vehicle a poor autonomy level. In order to solve these problems, the main purpose of this project was to design, implement and evaluate the performance and utility of a health emergency vehicle prototype with an integrated PV generator. The data collected from the prototype evaluation tests have shown that the incorporation of the PV generator solves the problems mentioned above. Besides, the relative cost of the PV generator compared with the high cost of health emergency vehicles can be considered negligible. Copyright © 2004 John Wiley & Sons, Ltd.
Effects of heat treatment on nanocrystalline formations in Fe40Ni40(Si + B)19Mo1–2 amorphous ribbon
Authors: Saiseng S. , Winotai P. , Limsuwan P. 
Published: November 2004

AbstractEffects of heat treatment on Fe40Ni40(Si+ B)19Mo1–2 were monitored by Mössbauer spectroscopy (MR), X‐ray diffraction (XRD) and differential scanning calorimetry (DSC). Mössbauer spectra were fitted by using the PC‐MOS II program to obtain such parameters as hyperfine field, isomer shift and quadrupole splitting of samples annealed for two hours in argon at different temperatures. The change in direction of local magnetization and the transformation of amorphous to crystalline phase were observed. Heat treatments near the crystallization temperature between 450–500 °C resulted in nanograins of α‐Fe, α‐Fe(Si) and t‐Fe2B embedded in the remaining uncrystallized amorphous matrix. DSC data showed that the ribbon exhibited two‐step crystallizations at 454 °C and 525 °C, respectively. The first crystalliza‐ tion corresponded mainly to soft ferromagnetic α‐Fe, α‐Fe(Si) and some minor t‐Fe2B phase forma‐ tions, while the second, corresponded to t‐Fe3B phase. Further heat treatment at 600 °C led to complete crystallizations at which the ferromagnetic phases α‐Fe and α‐Fe(Si) transformed to a paramagnetic phase fcc‐FeNi, and ferromagnetic phases of c‐FeNi3, t‐Fe2B, t‐Fe3B, and Ni2Si, respectively. Due to the high mag‐netic anisotropy of t‐Fe2B and other phases as well as to keep the crystallites in the nano region, the Fe40Ni40(Si‐B)19Mo1–2 ribbon should not be heated above 500 °C for the superior magnetic properties. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Surface structural analysis of monolayer films composed of light elements by x‐ray photoelectron diffraction
Authors: Nakamura H. , Fujihara N. , Nojima M. , Tamura K. , Ishii H. , Owari M. , Oshima C. , Nihei Y. 
Published: November 2004

AbstractFor surface structural analysis on monolayer films composed of light elements, we investigated theoretical x‐ray photoelectron diffraction (XPED) patterns from single‐molecule adsorbing surfaces by using both Cr Lα (572.8 eV) and Al Kα (1486.6 eV) excitations. Forward‐scattering peaks and Kikuchi‐like bands were clearly observed in the pattern excited by Al Kα. In contrast, the features of the XPED patterns excited by Cr Lα were more diffuse. However, the circular patterns excited by Cr Lα are clearer than those excited by Al Kα. This result suggests that the use of a lower energy x‐ray source improves XPED structural analysis on ultrathin films composed of light elements. Copyright © 2004 John Wiley & Sons, Ltd.
Interval estimation of the proportion ratio under multiple matching
Authors: Lui Kung‐Jong 
Published: November 2004

AbstractThe discussions on interval estimation of the proportion ratio (PR) of responses or the relative risk (RR) of a disease for multiple matching have been generally focused on the odds ratio (OR) based on the assumption that the latter can approximate the former well. When the underlying proportion of outcomes is not rare, however, the results for the OR would be inadequate for use if the PR or RR was the parameter of our interest. In this paper, we develop five asymptotic interval estimators of the common PR (or RR) for multiple matching. To evaluate and compare the finite sample performance of these estimators, we apply Monte Carlo simulation to calculate the coverage probability and the average length of the resulting confidence intervals in a variety of situations. We note that when we have a constant number of matching, the interval estimator using the logarithmic transformation of the Mantel–Haenszel estimator, the interval estimator derived from the quadratic inequality given in this paper, and the interval estimator using the logarithmic transformation of the ratio estimator can consistently perform well. When the number of matching varies between matched sets, we find that the interval estimator using the logarithmic transformation of the ratio estimator is probably the best among the five interval estimators considered here in the case of a small number (=20) of matched sets. To illustrate the use of these interval estimators, we employ the data studying the supplemental ascorbate in the supportive treatment of terminal cancer patients. Copyright © 2004 John Wiley & Sons, Ltd.
When using knowledge can hurt performance: the value of organizational capabilities in a management consulting company
Authors: Haas Martine R. , Hansen Morten T. 
Published: November 2004

AbstractThis paper explores the possibility that utilizing the firm's knowledge resources to complete important tasks can backfire and undermine competitive performance. Drawing on organizational capabilities and knowledge‐sharing research, we develop a situated performance view that holds that the value of obtaining and using knowledge within a firm depends on the task situation. Using a data set of 182 sales proposals for client work in a management consulting company, we show that sales teams that had varying needs to learn and differentiate themselves from competitors derived different levels of value from obtaining and using electronic documents and advice from colleagues. Highly experienced teams were more likely than inexperienced teams to lose the sales bids if they utilized such knowledge. Teams that had a high need to differentiate themselves from competitors also had a lower chance of winning if they utilized electronic documents. There were situations, however, where teams performed better if they utilized the firm's knowledge resources. These results suggest that competitive performance depends not on how much firms know but on how they use what they know. Copyright © 2004 John Wiley & Sons, Ltd.
Revisiting the Miles and Snow strategic framework: uncovering interrelationships between strategic types, capabilities, environmental uncertainty, and firm performance
Authors: DeSarbo Wayne S. , Anthony Di Benedetto C. , Michael Song  , Sinha Indrajit 
Published: November 2004

AbstractThe Miles and Snow strategic type framework is re‐examined with respect to interrelationships with several theoretically relevant batteries of variables, including SBU strategic capabilities, environmental uncertainty, and performance. A newly developed constrained, multi‐objective, classification methodology is modified to empirically derive an alternative quantitative typology using survey data obtained from 709 firms in three countries (China, Japan, United States). We compare the Miles and Snow typology to the classification empirically derived utilizing this combinatorial optimization clustering procedure. With respect to both variable battery associations and objective statistical criteria, we show that the empirically derived solution clearly dominates the traditional P‐A‐D‐R typology of Miles and Snow. Implications and directions for future research are provided. Copyright © 2004 John Wiley & Sons, Ltd.
Achieving proportional delay differentiation in wireless LANviacross‐layer scheduling
Authors: Xue Yuan , Chen Kai , Nahrstedt Klara 
Published: November 2004

AbstractProviding service differentiation in wireless networks has attracted much attention in recent research. Existing studies so far have focused on the design of differentiated media access algorithms. Some quality of service (QoS) metrics, such as queueing delay cannot be completely addressed by these approaches. Moreover, without a formalized service differentiation goal that quantifies the outcome of differentiation, the performance of most of the approaches fluctuates, especially in short time‐scales.This paper addresses above problems by introducing the concept of proportional service differentiation, to the domain of wireless network and focuses on providing proportional delay differentiation in wireless LANs. Due to the unique characteristic of distributed medium sharing, the scheduling algorithm employed in wireline networks can not be applied directly to the context of wireless LANs. We argue that delay differentiation in wireless LAN can only be achieved through a joint packet scheduling at the network layer and distributed coordination at the media access control (MAC) layer. Therefore, we present a cross‐layer waiting time priority (CWTP) scheduling algorithm. CWTP consists of two tiers: an intra‐node waiting time priority (WTP) scheduler at the network layer and an inter‐node distributed coordination function at the MAC layer. These two tiers coordinateviaa mapping function, which maps the normalized waiting time at the network layer to the backoff time at the MAC layer. Two mapping schemes, namely linear mapping and piecewise linear mapping, are presented and evaluated in this paper. Extensive simulation results show that the CWTP algorithm can effectively achieve proportional delay differentiation in wireless LANs. Copyright © 2004 John Wiley & Sons, Ltd.
Performance analysis of IEEE 802.11 MAC protocols in wireless LANs
Authors: Zhai Hongqiang , Kwon Younggoo , Fang Yuguang 
Published: November 2004

AbstractIEEE 802.11 MAC protocol is the de facto standard for wireless local area networks (LANs), and has also been implemented in many network simulation packages for wireless multi‐hop ad hoc networks. However, it is well known that, as the number of active stations increases, the performance of IEEE 802.11 MAC in terms of delay and throughput degrades dramatically, especially when each station's load approaches its saturation state. To explore the inherent problems in this protocol, it is important to characterize the probability distribution of the packet service time at the MAC layer. In this paper, by modeling the exponential backoff process as a Markov chain, we can use the signal transfer function of the generalized state transition diagram to derive an approximate probability distribution of the MAC layer service time. We then present the discrete probability distribution for MAC layer packet service time, which is shown to accurately match the simulation data from network simulations. Based on the probability model for the MAC layer service time, we can analyze a few performance metrics of the wireless LAN and give better explanation to the performance degradation in delay and throughput at various traffic loads. Furthermore, we demonstrate that the exponential distribution is a good approximation model for the MAC layer service time for the queueing analysis, and the presented queueing models can accurately match the simulation data obtained from ns‐2 when the arrival process at MAC layer is Poissonian. Copyright © 2004 John Wiley & Sons, Ltd.
On the squeeze effect of lubricants with additives between rough porous rectangular plates
Authors: Naduvinamani N.B. , Fathima S.T. , Hiremath P.S. 
Published: November 2004

AbstractThis paper describes a theoretical analysis of the combined effects of unidirectional surface roughness and the lubricant additives on the performance characteristics of a porous squeeze film lubrication between two rectangular plates of finite dimensions. The lubricant with microstructure additives is modeled as a Stokes couplestress fluid. The stochastic Reynolds type equation is derived to account for the effects due to surface roughness and lubricant additives. The problem is solved analytically using the stochastic method developed by Christensen. It is found that, there exists a critical value of the aspect ratio above which the roughness effects are pronounced due to the size effects of the lubricant additives. Further, this critical value is dependent on the microstructure size of additives. The coarser the microstructure, higher is the critical value of the aspect ratio.
THE MORPHOLOGY AND INTEGRATION OF VALVES AND BANDS IN NAVICULA MUTICA VAR. MUTICA (BACILLARIOPHYCEAE)1
Authors: Phipps Donald W. , Rosowski James R. 
Published: November 2004

ABSTRACT Navicula mutica (Kütz.) var. mutica was isolated from the air, cloned on agar, cultured in soil‐water bottle, and studied with transmission and scanning electron micros‐ropy. The frustules were lanceolate to ovoid with rounded apices, with the apical axis 8.5 ± 3.2 μ and the trans‐apical and the transapical axis 3.6 ± 0.6 μm. Striae were composed of two or three puncta, and the mantle bore a single row of puncta aligned with the striae. The ends of the raphe turned away from an isolated punctual in the central area of the valve. The mantle puncta and one or two of the valve‐face puncta in each stria opened into a series of transapical grooves in the interior of the valve, the grooves contributing to the appearance of striae in the light microscope. The interior of the mantle also possessed a pair of longitudinal grooves, discontinuous at the apices of the valves. An undulate advalvar margin of the valvocopula likely articulates along the interior longitudinal groove of the mantle. The projections of the undulate margin are perhaps positioned between the transapical grooves and along the longitudinal groove between the dentiform structures formed by the intersection of the double‐grooved system. The girdle bands each had two (occasionally three) rows of pores. The pleurae margins were straight and not undulate.