bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Control of the Cholesteric Pitch by Some Azo Photochemical Chiral Switches
Authors: Pieraccini Silvia , Gottarelli Giovanni , Labruto Riccardo , Masiero Stefano , Pandoli Omar , Spada Gian Piero 
Published: October 2004

AbstractA few chiral azo compounds, which undergo reversible photochemical switching, are presented. Of these, the most interesting contain the binaphthyl moiety and belong to the C2 (derivatives 1 and 2) or C1 symmetry group (derivatives 3 and 4). These binaphthyl compounds display intense CD and high β values. Photochemical switching has profound effects on both the CD and β values of these compounds; in the case of compound 3, the sign of β changes upon isomerisation. Compound 2 has, to our knowledge, the highest β of the switches reported in the literature and also seems the most interesting owing to its fast response to photochemical stimuli. Nematic phases can be transformed into cholesteric phases with reflection bands in the visible region by doping with reasonable amounts of 1 and 2. The reflection colours can be changed reversibly by photoisomerisation of the switches. Thermal reversion of the colourless UV photostationary state to the green isomeric EE state or to intermediate coloured states is temperature dependent. This can allow the thermal history of a sample to be traced.
2,5‐Diphenyl‐3,4‐bis(2‐pyridyl)cyclopenta‐2,4‐dien‐1‐one as a Redox‐Active Chelating Ligand
Authors: Siemeling Ulrich , Scheppelmann Imke , Heinze Jürgen , Neumann Beate , Stammler Anja , Stammler Hans‐Georg 
Published: October 2004

Abstract2,5‐Diphenyl‐3,4‐bis(2‐pyridyl)cyclopenta‐2,4‐dien‐1‐one (1), a close relative of tetraphenylcyclopentadienone, is a new ligand platform for use in redox switches and sensors. Compound 1 acts as a molecular electrochemical sensor towards a range of divalent metal ions and exhibits favourable two‐wave behaviour. It forms chelates of the type [(1)MX2], whose stability is enhanced by five orders of magnitude upon one‐electron reduction. The bite angle of 1 is close to 90° in these complexes. The attachment of the 14‐valence‐electron Cp*Co fragment to the cyclopentadienone π system reduces the bite angle and thus modulates the binding characteristics of 1.
From Allylic Alcohols to Aldols by Using Iron Carbonyls as Catalysts: Computational Study on a Novel Tandem Isomerization–Aldolization Reaction
Authors: Branchadell Vicenç , Crévisy Christophe , Grée René 
Published: October 2004

AbstractThe tandem isomerization–aldolization reaction between allyl alcohol and formaldehyde mediated by [Fe(CO)3] was studied with the density functional B3LYP method. Starting from the key [(enol)Fe(CO)3] complex, several reaction paths for the reaction with formaldehyde were explored. The results show that the most favorable reaction path involves first an enol/allyl alcohol ligand‐exchange process followed by direct condensation of formaldehyde with the free enol. During this process, formation of the new CC bond takes place simultaneously with a proton transfer between the enol and the aldehyde. Therefore, the role of [Fe(CO)3] is to catalyze the allyl alcohol to enol isomerization affording the free enol, which adds to the aldehyde in a carbonyl‐ene type reaction. Similar results were obtained for the reaction between allyl alcohol and acetaldehyde.
Room‐Temperature Surface‐Erosion Route to ZnO Nanorod Arrays and Urchin‐like Assemblies
Authors: Li Zhengquan , Ding Yue , Xiong Yujie , Yang Qing , Xie Yi 
Published: October 2004

AbstractA solution surface‐erosion route was successfully employed to produce one‐dimensional (1D) ZnO nanostructures. ZnO nanorod arrays and three‐dimensional urchin‐like assemblies could be selectively obtained with different manipulations. In this process, zinc foil was introduced to an organic solution system and acted both as a reactant and substrate to support the 1D nanostructures obtained. This method, without any template, apparatus, surfactants, or additional heterogenous substrates, has greatly simplified the preparation of oriented 1D ZnO nanostructures. In particular, this simple route could be carried out at room temperature over a period as short as several minutes, thus it could be conveniently transferred to industrial applications. The possible formation mechanism, erosion process, and influence factors were also investigated.
New Uses for the Burgess Reagent in Chemical Synthesis: Methods for the Facile and Stereoselective Formation of Sulfamidates, Glycosylamines, and Sulfamides
Authors: Nicolaou K. C. , Snyder Scott A. , Longbottom Deborah A. , Nalbandian Annie Z. , Huang Xianhai 
Published: October 2004

AbstractAlthough the Burgess reagent (methoxycarbonylsulfamoyltriethylammonium hydroxide, inner salt) has found significant use in chemical synthesis as a dehydrating agent, almost no work has been directed towards its potential in other synthetic applications. As this article will detail, we have found that the Burgess reagent is remarkably effective at accomplishing a number of non‐dehydrative synthetic tasks when applied to appropriate substrates, such as the formation of sulfamidates from 1,2‐diols or epoxyalcohols, α‐ and β‐glycosylamines from carbohydrates, and cyclic sulfamides from 1,2‐aminoalcohols. Beyond delineating the power of these new reaction manifolds, we also describe the construction of a group of alternative Burgess‐type reagents that extends the scope of these new reactions even further.
Readily Prepared Metallo‐Supramolecular Triple Helicates Designed to Exhibit Spin‐Crossover Behaviour
Authors: Tuna Floriana , Lees Martin R. , Clarkson Guy J. , Hannon Michael J. 
Published: October 2004

AbstractNew dinuclear supramolecular cylinders have been designed to exhibit spin‐crossover behaviour, a form of molecular bistability. This has been achieved within the framework of our imine‐based approach to supramolecular architecture by switching from pyridylimine systems to imidazolimines. Spin‐crossover behaviour is achieved while retaining the simplicity and ease‐of‐synthesis of our molecular design. The imidazole groups used also introduce additional NH groups that engage in hydrogen‐bonding to anions and solvents. In the case of the iron(II) tetrafluoroborate complex this hydrogen bonding links supramolecular cylinders into an extended two‐dimensional array. Consistent with this, a sharper spin‐crossover transition is observed for this compound than for the corresponding hexafluorophosphate salt. More subtle anion effects are indicated in the perchlorate salt which gives a two‐step spin conversion, thereby displaying tristability.
Noncovalent Anchoring of Asymmetric Hydrogenation Catalysts on a New Mesoporous Aluminosilicate: Application and Solvent Effects
Authors: Simons Chrétien , Hanefeld Ulf , Arends Isabel W. C. E. , Sheldon Roger A. , Maschmeyer Thomas 
Published: October 2004

AbstractA new Brønsted acidic aluminosilicate, AlTUD‐1, with ideal characteristics for catalyst immobilisation (mesoporous structure, high surface area, and high Altetrahedral/Si ratio), was used successfully for the noncovalent anchoring of two well‐established asymmetric hydrogenation catalysts: [RhI(cod){(R,R)‐MeDuPHOS}]BF4 (1) and [RhI(cod){(S,S)‐DiPAMP}]BF4 (2). The new heterogeneous catalysts, 1‐AlTUD‐1 and 2‐AlTUD‐1, prepared by a straightforward ion‐exchange procedure, were highly active and selective in the asymmetric reduction of dimethyl itaconate (3) and methyl 2‐acetamidoacrylate (4), giving enantiomeric excesses of up to >98 %. The catalysts showed similar behaviour to their homogeneous counterparts. Catalyst 2‐AlTUD‐1 could be re‐used multiple times without loss of enantioselectivity or activity. Leaching of Rh showed a significant dependence on the polarity of the solvent in which the catalysis was performed. By applying tert‐butylmethyl ether (MTBE) as solvent, the loss of Rh could be reduced to <0.1 %. The solvent also had a noteworthy effect on the enantioselectivity in the hydrogenation of 4 (an effect not seen with 3 as substrate), that is, in MeOH the ee was 92 %, in MTBE it dropped to 26 % when using 2‐AlTUD‐1 as catalyst.
Multifunctionalization of Synthetic Polymer Systems through Self‐Assembly
Authors: Gerhardt Warren , Črne Matija , Weck Marcus 
Published: October 2004

AbstractA straightforward methodology towards the replacement of covalent strategies for the synthesis of multifunctional synthetic materials with a self‐assembling strategy that employs multiple noncovalent recognition units to attach multiple functional molecules to a polymeric scaffold is outlined. Design requirements, advantages, and potential applications, as well as the possibility of rapid optimization of materials during the manufacturing process as a result of the parallel character of self‐assembly, are presented. While still in its infancy, this novel methodology may overcome several shortcomings of current covalent multifunctionalization strategies and may yield highly complex materials that are extremely difficult or impossible to fabricate with current methods.
Chemoenzymatic Preparation of Optically Active trans‐Cyclohexane‐1,2‐diamine Derivatives: An Efficient Synthesis of the Analgesic U‐(−)‐50,488
Authors: González‐Sabín Javier , Gotor Vicente , Rebolledo Francisca 
Published: October 2004

AbstractStereoespecific syntheses of (±)‐trans‐N,N‐cyclohexane‐1,2‐diamines ((±)‐4 a–g) were carried out from the corresponding (±)‐trans‐N,N‐dialkylaminocyclohexanols by successive treatment with mesyl chloride and aqueous ammonia. The stereochemical outcome indicates the formation of a meso‐aziridinium ion intermediate. Kinetic resolutions of diamines (±)‐4 were efficiently accomplished in aminolysis reactions catalyzed by lipase B from Candida antarctica with ethyl acetate as the solvent and acyl donor. Acetamides and the remaining diamines, isolated as the benzyloxycarbonyl derivatives, were obtained with very high ee values (92–99 %). One of the carbamates was used as a precursor of the analgesic U‐(−)‐50,488.
Rhodium‐Catalyzed Intramolecular Hydroacylation of 5‐ and 6‐Alkynals: Convenient Synthesis of α‐Alkylidenecycloalkanones and Cycloalkenones
Authors: Takeishi Kenzo , Sugishima Koudai , Sasaki Kaori , Tanaka Ken 
Published: October 2004

AbstractA novel intramolecular hydroacylation of 5‐ and 6‐alkynals leading to α‐alkylidenecycloalkanones was accomplished by using cationic a rhodium(I)/BINAP complex. For all cyclizations described, a single (E)‐olefin isomer was obtained. At elevated temperature, hydroacylation and double bond migration of 5‐ and 6‐alkynals proceeded in a one‐pot reaction to give cycloalkenones. An intramolecular hydroacylation of a 7‐alkynal was unsuccessful. This method represents an attractive new route to highly functionalized α‐alkylidenecycloalkanones and cycloalkenones.
Optimal shape of a grain or a fibre cross‐section in a two‐phase composite
Authors: Shenfeld Vladislav , Givoli Dan , Vigdergauz Shmuel 
Published: October 2004

AbstractThe shape of grains or of cross‐sections of fibres in a two‐phase elastic material has an important influence on the overall mechanical behaviour of the composite. In this paper a numerical scheme is devised for determining the optimal shape of a two‐dimensional grain or of a fibre's cross‐section. The optimization problem is first posed mathematically, using a global objective function, and then solved numerically by the finite element method and a specially designed global optimization scheme. Excellent agreement is obtained with analytical results available for extreme cases. In addition, optimal shapes are obtained under more general conditions. Copyright © 2004 John Wiley & Sons, Ltd.
Apoptosis of circulating tumor cells in prostate cancer patients
Authors: Larson Christopher J. , Moreno Jose G. , Pienta Kenneth J. , Gross Steve , Repollet Madeline , O'Hara S. Mark , Russell Thomas , Terstappen Leon W. M. M. 
Published: October 2004

AbstractBackgroundThe prescence of circulating tumor cells (CTCs) in the peripheral blood of cancer patients and their frequency has been correlated with disease status.MethodsIn this study, CTCs were characterized by flow cytometry and fluorescence microscopy after immunomagnetic enrichment from 7.5‐ml blood samples collected from patients with prostate cancer in evacuated blood‐draw tubes that contained an anticoagulant and a preservative. Events were classified as tumor cell candidates if they expressed cytokeratin, lacked CD45, and stained with the nucleic acid dye 4,6‐diamidino‐2‐phenylindole.ResultsIn the blood of prostate cancer patients, only few of these events were intact cells. Other CTC events appeared as damaged cells or cell fragments by microscopy. By flow cytometry, these events stained variably with 4,6‐diamidino‐2‐phenylindole and frequently expressed the apoptosis‐induced, caspase‐cleaved cytokeratin 18. Similar patterns of cell disintegration were observed when cells of the prostate line LNCaP were exposed to paclitaxel before spiking the cells into normal blood samples.ConclusionsThe different observed stages of tumor cell degradation or apoptosis varied greatly between patients and were not found in blood of normal donors. Enumeration of CTCs and identification of CTCs undergoing apoptosis may provide relevant information to evaluate the response to therapy in cancer patients. © 2004 Wiley‐Liss, Inc.
Influence of calcium ions in the flow cytometric analysis of human CD8‐positive cells
Authors: Giroux Martin , Denis François 
Published: October 2004

AbstractBackgroundThe CD8 co‐receptor is an important marker used to identify various lymphocyte subsets. A significant decrease in CD8α staining intensity was observed in the presence of divalent cation chelators.MethodsPeripheral blood mononuclear cells (PBMC) obtained from healthy volunteers were treated with calcium chelators, stained with different anti‐human CD8 mAbs, and analyzed by flow cytometry.ResultsCalcium chelators caused a dose‐dependent decrease in fluorescence intensity, using specific anti‐human CD8α mAbs. This phenomenon was not due to CD8 internalization and could be reversed by the addition of calcium ions. In contrast, calcium depletion increased staining intensity with one anti‐CD8β mAb.ConclusionsDivalent cation chelators are used as cell anti‐clumping agents in MACS or FACS applications. Researchers should be aware that such treatment could lead to the almost complete loss of fluorescence with selected anti‐human CD8α mAbs. Since CD8 staining is used in conjunction with tetramer staining to identify antigen‐specific cytotoxic human T cells, the effect of calcium depletion should be taken into account in experimental design. © 2004 Wiley‐Liss, Inc.
Congestion control scheme for reliable multicast improving intrasession fairness with network support
Authors: Yamaguchi Makoto , Yamamoto Miki 
Published: October 2004

AbstractIn reliable multicast, the same information is transmitted to specified receiving nodes while maintaining reliability, with the information rate aligned to the receiving node with the lowest throughput by end‐to‐end control. However, the consideration of the receiving node with the lowest throughput produces the problem that other receiving nodes belonging to the same multicast group are limited to a considerably lower throughput than their own reception limits. This is a problem inherent to multicast communications, where the receiving nodes generally differ in congestion status. This fairness problem for receiving nodes is called intrasession fairness. In reliable multicast, it is impossible to realize intrasession fairness by using only end‐to‐end control. The purpose of this paper is to realize intrasession fairness by a scheme in which servers independently apply congestion control to the downlink by placing servers in the network and providing network support. The proposed scheme is evaluated by simulation. © 2004 Wiley Periodicals, Inc. Electron Comm Jpn Pt 1, 88(2): 61–70, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecja.10125
Development of performance evaluation system for network systems by client observation
Authors: Saito Hiroki , Chusho Takeshi 
Published: October 2004

AbstractAs Internet technology comes into increasingly wide‐spread use, there is a need for quality control of network service performance to ensure user convenience, such as server access time and response time. Conventional performance evaluations aim at the control of devices at the network layer, but do not consider quality at the application layer. In this paper, the authors propose a method of performance evaluation in end‐point applications to evaluate the quality of service from the viewpoint of user convenience. This method makes possible performance measurement by introducing an observation layer that monitors the behavior of client applications, and by focusing on the request‐response communications between the client and server. A performance evaluation system that uses the principle of the observation layer has been implemented, and it is shown that the performance of an actual running system can be accurately measured, confirming the effectiveness of the performance evaluation system. © 2004 Wiley Periodicals, Inc. Electron Comm Jpn Pt 1, 88(2): 71–80, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecja.20083
Consideration of time sharing output pulse pattern using instantaneous space voltage vector moderation for three‐phase voltage source soft‐switching inverter
Authors: Yoshida Masanobu , Hiraki Eiji , Nakaoka Mutsuo 
Published: October 2004

AbstractIn this paper, we propose a single inductor type resonant AC link snubber as a technique for introducing soft‐switching PWM technology into three‐phase voltage source inverters and explain its circuit operation. We then explain the suitability of instantaneous space voltage vector sinewave modulation compared to sinewave‐triangle wave relative modulation as the sinewave modulation technique of the soft‐switching inverter introducing this resonant AC link snubber, and propose a time sharing pulse pattern based on the operating principle of this resonant AC link snubber. Furthermore, we discuss the limits on the widths of the pulses that can be output when the time sharing pulse output method is used and the soft‐switching inverter performs sinewave modulation, and the need to correct narrow output pulse widths; describe in detail the relationship between the generation principle of the correction pulse pattern and the waveform distortion; and illustrate the simulation results when the minimum pulse width is corrected. Finally, we propose a new time sharing pulse pattern that does not need the minimum pulse width correction by using the time sharing pulse pattern feature for the resonant AC link inverter and demonstrate its effectiveness from the simulation results for this output pulse pattern. © 2004 Wiley Periodicals, Inc. Electron Comm Jpn Pt 1, 88(2): 34–40, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecja.20144
Multiple bitrate output transcoder based on requantizer and reencoder sharing
Authors: Nagayoshi Isao , Kasai Hiroyuki , Hanamura Tsuyoshi , Tominaga Hideyoshi 
Published: October 2004

AbstractThis paper proposes a video transcoder that realizes efficiently the function of multirate conversion to multiple bitrates. The multirate conversion function is realized as follows. The decoder and the inverse quantizer are shared as a single processor. The requantizer and the reencoder with the same requantization step are shared among outputs. With these provisions, an architecture is proposed whereby the processing complexity in multirate conversion can be reduced. The number of requantization processing operations per macro‐block is examined theoretically, and it is shown that the conversion processing complexity can be formulated as a function of the output bitrate. Lastly, the theoretical evaluation and the evaluation experiment based on these investigations show that the sharing of the requantizer/reencoder is the scheme that reduces the increase of the processing complexity as a function of the number of outputs, and can cope with any number of outputs with two to four times the processing complexity of the single‐rate output scheme. © 2004 Wiley Periodicals, Inc. Electron Comm Jpn Pt 1, 88(2): 21–33, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecja.20146
A study on double resonance H‐type slot antenna
Authors: Itakura Akira , Okano Yoshinobu , Abe Minoru 
Published: October 2004

AbstractMobile communication terminals such as mobile computers will enhance their usefulness by using wireless LAN (2.4 and 5.2 GHz) and Bluetooth (2.4 GHz). However, if both bands are used, separate antennas are needed because the frequencies are different. It is not advantageous to install separate antennas. In this paper, an H‐type slot antenna is proposed as a dual‐frequency antenna that can be integrated with a mobile computer without any extrusion from the computer body. By changing the parameters of the H‐type slot antenna, each resonant frequency can be varied independently so that a design can be straightforward. In a model packaged with an A4 Notebook PC, it is found that the bandwidth for VSWR ≤ 2 is about 22% in the 2.4‐GHz band and about 16% in the 5.2‐GHz band. Regarding the radiation characteristics, it is demonstrated that the average gain is about −4 dBi for conceivable antenna use angle that is practically sufficient. © 2004 Wiley Periodicals, Inc. Electron Comm Jpn Pt 1, 88(2): 11–20, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecja.20148
Optical measurement of sound fields estimated from multiple interference images using Mach‐Zehnder interferometer
Authors: Ezure Tomohiro , Mizutani Koichi , Masuyama Hiroyuki 
Published: October 2004

AbstractIn this paper we discuss the acquisition of sound field information from optical interference patterns detected by a CCD camera. Although noncontact measurements of wide‐beamwidth sound fields based on diffraction techniques such as the Schlieren method yield projected images with high SN ratios, the problem is that sound field information is not projected correctly. In this work, the measurements were made using a Mach‐Zehnder interferometer. Because interference measurements measure light that has passed through a real focus generated by the sound fields, these measurements have a clear advantage over methods like the Schlieren method, in that they create no points at which there is a mismatch between the received light and the diffraction spots. By using CCDs as two‐dimensional time averaging detectors, wide‐range sound fields can be acquired at high speeds. In these experiments, we estimated the optical phase excursion caused by the sound field over an interval along the sound axis from 0 to 25 mm using an ultrasonic wave transducer 8.0 mm in diameter, operating at 1.4 MHz, with a beamwidth of 7 mm. Because there were bands along the sound axis within which our computational algorithm was unable to provide estimated values for the phase deviation, we augmented our primary data set with three other data sets obtained by shifting the phase of the reference light used to generate the interference pattern in the primary measurement by +0.20π, +0.48π, +0.94π (rad), and combining the resulting data sets to interpolate through the gaps in the primary data set, thereby realizing a continuous estimate along the whole sound axis. In this continuous estimate, the data we used to interpolate the primary data set came mostly from the interference pattern whose phase relative to the first measured pattern was in the neighborhood of π/2 rad. By averaging the four estimate results together, we were able to decrease the percentage of no‐data sectors over the entire range 2%. The estimated phase deviation was a gradually decreasing function with distance, starting with a value of about 0.7π rad. © 2004 Wiley Periodicals, Inc. Electron Comm Jpn Pt 2, 87(11): 20–27, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecjb.20067