bluuebunny/crossref_metadata_2025_split huggingface dataset:
2‐[(Imidazolylthio)methyl]pyrrolidine as a Trifunctional Organocatalyst for the Highly Asymmetric Michael Addition of Ketones to Nitroolefins
Authors: Xu Dan‐Qian , Wang Li‐Ping , Luo Shu‐Ping , Wang Yi‐Feng , Zhang Shuai , Xu Zhen‐Yuan 
Published: December 2007

AbstractThe direct asymmetric Michael addition of ketones to nitroolefins catalyzed by 2‐[(imidazol‐2‐ylthio)methyl]pyrrolidine, constructed from natural L‐proline and imidazolylthio platforms, with salicylic acid as a co‐catalyst has been developed to give the products in high yields (up to 95 %) and with excellent enantioselectivities (up to 99 % ee). The highly efficient catalytic performance may be attributed to the dual activation of the Michael substrates by the trifunctional organocatalysts and the co‐catalyst salicylic acid, leading to the formation of a stable transition state complex through the synergic effect of hydrogen‐bonding and electrostatic interactions. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)
Determination of Trace Amount of Lead(II) in Sweet Fruit‐Flavored Powder Drinks by Differential Pulse Adsorptive Stripping Voltammetry at Carbon Paste Electrode
Authors: Gholivand M. B. , Malekian M. 
Published: December 2007

AbstractA new method is described for the determination of lead based on the cathodic adsorptive stripping of the lead–nuclear fast red (NFR) at a carbon paste electrode (CPE). The differential pulse voltammograms of the adsorbed complex of lead–NFR are recorded from −0.10 to −0.60 V (versus Ag/AgCl electrode). Optimal conditions were found to be an electrode containing 25% paraffin oil and 75% high purity graphite powder, 4.0×10−5 mol L−1 NFR; buffer solution (pH of 3.0), accumulation potential and time, −0.20 V, 60 and 120 s (for high and low concentration of lead), respectively. The results show that the complex can be adsorbed on the surface of the CPE, yielding one peak at −0.34 V, corresponding to reduction of NFR in the complex at the electrode. The detection limit was found to be 0.2 ng mL−1 with a 120s accumulation time. The linear ranges are from 0.5 to 50 (tacc=120 s) and 50 to 200 ng mL−1 (tacc=60 s). Application of the procedure to the determination of lead in lake water, bottled mineral water, synthetic samples and sweet fruit‐flavored powder drinks samples gave good results.
Slide roof system for dynamic response reduction
Authors: Tian Zhichang , Qian Jiaru , Zhang Liming 
Published: December 2007

AbstractA slide roof system (SRS) is proposed to reduce the dynamic response of buildings to earthquake excitations. A SRS consists of a roof structure, springs and friction materials, providing mass, stiffness and damping, respectively. The method of optimization of stiffness and friction coefficient for the SRS is introduced. A numerical analysis of an eight‐story frame structure subjected to ground motions and shaking table tests of a five‐story frame was carried out to study the effectiveness of the SRS. The results show that the SRS can reduce the maximum dynamic response as much as 60–70% in the first resonate band and 35–50% in the second resonate band. Copyright © 2007 John Wiley & Sons, Ltd.
Value at risk and conditional extreme value theory via markov regime switching models
Authors: Samuel Yau Man Ze‐to 
Published: December 2007

AbstractThis study develops a new conditional extreme value theory‐based (EVT) model that incorporates the Markov regime switching process to forecast extreme risks in the stock markets. The study combines the Markov switching ARCH (SWARCH) model (which uses different sets of parameters for various states to cope with the structural changes for measuring the time‐varying volatility of the return distribution) with the EVT to model the tail distribution of the SWARCH processed residuals. The model is compared with unconditional EVT and conditional EVT‐GARCH models to estimate the extreme losses in three leading stock indices: S&P 500 Index, Hang Seng Index and Hang Seng China Enterprise Index. The study found that the EVT‐SWARCH model outperformed both the GARCH and SWARCH models in capturing the non‐normality and in providing accurate value‐at‐risk forecasts in the in‐sample and out‐sample tests. The EVTSWARCH model, which exhibits the features of measuring the volatility of a heteroscedastic financial return series and coping with the non‐normality owing to structural changes, can be an alternative measure of the tail risk. © 2008 Wiley Periodicals, Inc. Jrl Fut Mark 28:155–181, 2008
The compatibility of one‐factor market models in caps and swaptions markets: Evidence from their dynamic hedging performance
Authors: An Yunbi , Suo Wulin 
Published: December 2007

AbstractThis study examines the dynamic hedging performance of the one‐factor LIBOR and swap market models in both caps and swaptions markets, using a procedure similar to the way that these models are used in practice. The effects of different calibration methods on model performance are investigated as well. The LIBOR market models and the swap market models are calibrated to the cross‐sectional Black implied volatilities for caps and swaptions respectively; the test is based on their effectiveness in hedging floors and swaptions that are not used in the calibration. We find that the LIBOR market models outperform the swap market models in hedging floors and perform as well as the swap market models in hedging swaptions. Our results also show that incorporating a humped volatility structure into these models does not significantly improve their hedging performance. © 2008 Wiley Periodicals, Inc. Jrl Fut Mark 28:109–130, 2008
Developmental loss of NT‐3 in vivo results in reduced levels of myelin‐specific proteins, a reduced extent of myelination and increased apoptosis of Schwann cells
Authors: Woolley Adele G. , Tait Karen J. , Hurren Bradley J. , Fisher Lorryn , Sheard Philip W. , Duxson Marilyn J. 
Published: December 2007

AbstractThis work investigates the role of NT‐3 in peripheral myelination. Recent articles, based in vitro, propose that NT‐3 acting through its high‐affinity receptor TrkC may act to inhibit myelin formation by enhancing Schwann cell motility and/or migration. Here, we investigate this hypothesis in vivo by examining myelination formation in NT‐3 mutant mice. On the day of birth, soon after the onset of myelination, axons showed normal ensheathment by Schwann cells, no change in the proportion of axons which had begun to myelinate, and no change in either myelin thickness or number of myelin lamellae. However in postnatal day 21 mice, when myelination is substantially complete, we observed an unexpected reduction in mRNA and protein levels for MAG and P0, and in myelin thickness. This is the opposite result to that predicted from previous in vitro studies, where removal of an inhibitory NT‐3 signal would have been expected to enhance myelination. These results suggest that, in vivo, the importance of NT‐3 as a major support factor for Schwann cells (Meier et al., (1999) J Neurosci 19:3847‐3859) over‐rides its potential role as an myelin inhibitor, with the net effect that loss of NT‐3 results in degradation of Schwann cell functions, including myelination. In support of this idea, Schwann cells of NT‐3 null mutants showed increased expression of activated caspase‐3. Finally, we observed significant reduction in width of the Schwann cell periaxonal collar in NT‐3 mutant animals suggesting that loss of NT‐3 and resulting reduction in MAG levels may alter signaling at the axon‐glial interface. © 2007 Wiley‐Liss, Inc.
Controlled Release of Volatile Aldehydes and Ketones from Dynamic Mixtures Generated by Reversible Hydrazone Formation
Authors: Levrand Barbara , Fieber Wolfgang , Lehn Jean‐Marie , Herrmann Andreas 
Published: December 2007

AbstractDelivery systems generated by reversible hydrazone formation from hydrazine derivatives (see Fig. 1) and carbonyl compounds in H2O efficiently increase the long‐lastingness of volatile aldehydes and ketones (R1R2CO) in various perfumery applications. The hydrazones are usually obtained in an (E) configuration at the imine double bond (NHNC) and, in the case of aliphatic acylhydrazones R′CONHNCR1R2 (R′=alkyl), as syn and anti conformers with respect to the amide bond (CONHN). An average free‐energy barrier of ca. 78 kJ/mol was determined for the amide‐bond rotation by variable‐temperature 1H‐NMR measurements (Fig. 2). In the presence of H2O, the hydrazone formation is entirely reversible, reaching an equilibrium composed of the hydrazine derivative, the carbonyl compound, and the corresponding hydrazone. Kinetic measurements carried out by UV/VIS spectroscopy showed that the same equilibrium was reached for the formation and hydrolysis of the hydrazone. Rate constants are strongly pH‐dependent and increase with decreasing pH (Table 1). The influence of the hydrazine structure on the rate constants is less pronounced than the pH effect, and the presence of surfactants reduces the rate of equilibration (Tables 1 and 3). The full reversibility of the hydrazone formation allows to prepare dynamic mixtures by simple addition of a hydrazine derivative to several carbonyl compounds. Dynamic headspace analysis on dry cotton showed that the presence of a hydrazine derivative significantly increased the headspace concentrations of the different carbonyl compounds as compared to the reference sample without hydrazine (Table 4). The release of the volatiles was found to be efficient for fragrances with high vapor pressures and low H2O solubility. Furthermore, a special long‐lasting effect was obtained for the release of ketones. The simplicity of generating dynamic mixtures combined with the high efficiency for the release of volatiles makes these systems particularly interesting for practical applications and will certainly influence the development of delivery systems in other areas such as the pharmaceutical or agrochemical industry.
Bioactive Saponins and Glycosides. Part 29
Authors: Morikawa Toshio , Matsuda Hisashi , Li Ning , Li Xian , Yoshikawa Masayuki 
Published: December 2007

AbstractThree new acylated oleanane‐type triterpene saponins, theasaponins A6 (1), A7 (2), and B5 (3), were isolated from the saponin fraction of the seeds of the Japanese tea plant Camellia sinensis together with the known constituent foliatheasaponin III (4). The structures of the glycosides 1–3 were elucidated on the basis of spectroscopic, chemical, and physico‐chemical evidence.
An Investigation into Domino‐Heck Reactions of N‐Acylamino‐Substituted Tricyclic Imides: Synthesis of New Prospective Pharmaceuticals
Authors: Bagdatli Emine , Öcal Nüket , Kaufmann Dieter E. 
Published: December 2007

AbstractHeck and domino‐Heck reactions of unsaturated N‐acylamino‐substituted tricyclic imides with aryl(heteroaryl) iodides and phenyl‐ or (trimethylsilyl)acetylene were either carried out in the presence of formate or phenyl‐ and (trimethylsilyl)acetylene, respectively. The CC coupling reactions appeared to be completely diastereoselective, giving the corresponding N‐acylamino‐5‐exo‐aryl (heteroaryl)‐ (5a–c, 6a,b), N‐(benzoylamino)‐5‐exo‐phenyl‐6‐exo‐[(trimethylsilyl)ethynyl]‐ (5d), or 5‐exo‐(4‐chlorophenyl)‐N‐(2,2‐dimethylpropanoylamino)‐6‐exo‐(phenylethynyl)bicyclo[2.2.1]heptane‐2‐endo,3‐endo‐dicarboximide (6c) (Schemes 3 and 4).
Phenolic and Triterpenoid Glycosides from Pyrola calliantha
Authors: Chen Yi‐Lei , Tan Chang‐Heng , Tan Jun‐Jie , Qu Shi‐Jin , Wang Heng‐Bin , Zhang Qiang , Jiang Shan‐Hao , Zhu Da‐Yuan 
Published: December 2007

AbstractPyrocallianthasides A (1) and B (2), a new dimer and a new mono‐deglucosyl trimer of homoarbutin (=4‐hydroxy‐3‐methylphenyl β‐glucopyranoside), and callianthaside A (3), a new ursane‐type triterpene glycoside, together with three known phenolic glycosides and three known ursane‐type triterpenoids, were isolated from the whole plants of Pyrola calliantha. The structures of 1–3 were elucidated by chemical and spectroscopic methods.
Three New Alkaloids from the Traditional Chinese Medicine ChanSu
Authors: Liu Run‐Hui , Luo Heng , Li Yong‐Li , Yang Ming , Li Hui‐Liang , Shen Yun‐Heng , Zhang Chuan , Su Juan , Zhang Wei‐Dong 
Published: December 2007

AbstractThree new alkaloids, named bufoserotonins A–C (1–3), were isolated from the traditional Chinese medicine ChanSu. Their structures were elucidated on the basis of spectroscopic analysis, especially of 2D‐NMR data.
Nanomechanical characterization of polyaniline coated tobacco mosaic virus nanotubes
Authors: Wang Xinnan , Niu Zhongwei , Li Siqi , Wang Qian , Li Xiaodong 
Published: December 2007

AbstractMechanical properties of polyaniline (PANI) coated self‐assembled tobacco mosaic virus (TMV) nanotubes were measured by nanoindentation with an atomic force microscope (AFM) probe. The elastic modulus of PANI/TMV core–shell biocomposite tubes (outer diameter: 19 nm, inner diameter: 4 nm, PANI coating thickness: 0.5 nm) was measured from the AFM force‐displacement curves. Structural characteristics of the PANI coating, TMV tube, and their interface were studied by comparing the mechanical properties of individual constituent materials. Results showed that coating with a thin layer of PANI can change the physical and chemical properties of TMV nanotubes. The deformation behavior of such core–shell biocomposite tubes is discussed in conjunction with the obtained AFM force‐displacement curves, van der Waals interaction between PANI and TMV, and mechanical properties of individual constituent materials. © 2007 Wiley Periodicals, Inc. J Biomed Mater Res 87A: 8–14, 2008
Histologic and histomorphometric evaluation of early and immediately loaded implants in the dog mandible
Authors: Moon Seong‐Yong , Kim Su‐Gwan , Lim Sung‐Chul , Ong Joo L. 
Published: December 2007

AbstractNew bone formation around US III OSSTEM implants after early and immediate loading was evaluated in this study. Three premolars and the first and second molars were first removed from the left mandible of five dogs. At 3 weeks after extraction of the teeth in the left mandible, the corresponding teeth in the right mandibles were removed. After 12 weeks of bone healing, five implants were placed in the left mandible. At 3 weeks after placement of implants in the left mandible, another five were placed in the right mandible. At the time of placing implants in the right mandible, four implants on each side were restored using a fixed provisional restoration. The anterior‐most implant was not loaded and was used as controls. Periotest measurements performed immediately after implantation and after 16 weeks loading indicated implant stability for all groups tested. At 16 weeks after loading, the rate of peri‐implant bone formation for the early loaded, immediately loaded (IL), and control implants were observed to be 75.00, 73.37, and 62.04%, respectively. It was thus concluded that early stability was achieved in early and IL implants using fixed provisional restoration, thereby resulting in the high rate of peri‐implant bone formation. © 2007 Wiley Periodicals, Inc. J Biomed Mater Res, 2008
Real‐time cellular uptake of serotonin using fluorescence lifetime imaging with two‐photon excitation
Authors: Botchway Stanley Walter , Parker Anthony William , Bisby Roger Hugh , Crisostomo Ana Goncalves 
Published: December 2007

AbstractThe real‐time uptake of serotonin, a neurotransmitter, by rat leukemia mast cell line RBL‐2H3 and 5‐hydroxytryptophan by Chinese hamster V79 cells has been studied by fluorescence lifetime imaging microscopy (FLIM), monitoring ultraviolet (340 nm) fluorescence induced by two‐photon subpicosecond 630 nm excitation. Comparison with two‐photon excitation with 590 nm photons or by three‐photon excitation at 740 nm shows that the use of 630 nm excitation provides optimal signal intensity and lowered background from auto‐fluorescence of other cellular components. In intact cells, we observe using FLIM three distinct fluorescence lifetimes of serotonin and 5‐hydroxytryptophan according to location. The normal fluorescence lifetimes of both serotonin (3.8 ns) and 5‐hydroxytryptophan (3.5 ns) in solution are reduced to ∼2.5 ns immediately on uptake into the cell cytosol. The lifetime of internalized serotonin in RBL‐2H3 cells is further reduced to ∼2.0 ns when stored within secretory vesicles. Microsc. Res. Tech., 2008. © 2007 Wiley‐Liss, Inc.
Patterns of correlation and covariation of anthropoid distal forelimb segments correspond to Hoxd expression territories
Authors: Reno Philip L. , McCollum Melanie A. , Cohn Martin J. , Meindl Richard S. , Hamrick Mark , Lovejoy C. Owen 
Published: December 2007

AbstractAnthropoids in general and hominoids in particular exhibit differential adaptations in forearm and digital skeletal proportions to a diverse array of locomotor modes. Hox genes act as selector genes with spatially regulated expression patterns during development. Their expression in the forelimb appears to define modules that specify differential skeletal growth. Here we explore forelimb skeletal proportions in a large sample of anthropoids from a background provided by Hoxd expression patterns in late‐stage murine embryonic forelimbs. Interspecific correlation and principal components analyses of primate forelimb data indicate that morphological variation in anthropoids reflects well‐defined developmental modules downstream of Hoxd expression. The phalanges of digit one appear to represent a single growth module, whereas the metacarpals and manual phalanges of the posterior digits correspond to a second, independent, expression territory that extends proximally into the distal zeugopod. In particular, hominoids show very high correlations among the posterior digits and the independence of digit one. In addition, the distal radius is generally highly correlated with the posterior digits and not digit one. Relying on established functional differences among Hox paralogs, we present a model that parsimoniously explains hominoid forearm and digital proportions as a consequence of downstream effects of Hox. We, therefore, suggest that Hox‐defined developmental modules have served as evolutionary modules during manual evolution in anthropoids. J. Exp. Zool. (Mol. Dev. Evol.) 310B:240–258, 2008. © 2007 Wiley‐Liss, Inc.
Co‐expression of MGMTP140K and α‐L‐iduronidase in primary hepatocytes from mucopolysaccharidosis type I mice enables efficient selection with metabolic correction
Authors: Wang Daren , Worsham D. Nicole , Pan Dao 
Published: December 2007

AbstractBackgroundSystemic in vivo gene therapy has resulted in widespread correction in animal models when treated at birth. However, limited improvement was observed in postnatally treated animals with mainly targeting to the liver and bone marrow. It has been shown that an O6‐methylguanine‐DNA‐methyltransferase variant (MGMTP140K) mediated in vivo selection of transduced hematopoietic stem cells (HSC) in animals.MethodsWe investigated the feasibility of MGMTP140K‐mediated selection in primary hepatocytes from a mouse model of mucopolysaccharidosis type I (MPS I) in vitro using lentiviral vectors.ResultsWe found that multiple cycles of O6‐benzylguanine (BG)/1,3‐bis(2‐chloroethyl)‐1‐nitrosourea (BCNU) treatment at a dosage effective for ex vivo HSC selection led to a two‐fold increase of MGMT‐expressing primary hepatocytes under culture conditions with minimum cell expansion. This enrichment level was comparable to that obtained after selection at a hepatic maximal tolerated dose of BCNU. Similar levels of increase were observed regardless of initial transduction frequency, or the position of MGMT (upstream or downstream of internal ribosome entry site) in the vector constructs. In addition, we found that elongation factor 1α promoter was superior to the long‐terminal repeat promoter from spleen focus‐forming virus with regard to transgene expression in primary hepatocytes. Moreover, the levels of therapeutic transgene expression in transduced, enzyme‐deficient hepatocytes directly correlated with the doses of BCNU, leading to metabolic correction in transduced hepatocytes and metabolic cross‐correction in neighbouring non‐transduced MPS I cells.ConclusionsThese results demonstrate that MGMTP140K expression confers successful protection/selection in primary hepatocytes, and provide ‘proof of concept’ to the prospect of MGMTP140K‐mediated co‐selection for hepatocytes and HSC using BG/BCNU treatment. Copyright © 2007 John Wiley & Sons, Ltd.
Reconstituting retroviral (ReCon) vectors facilitating delivery of cytotoxic genes in cancer gene therapy approaches
Authors: Brandtner Eva Maria , Kodajova Petra , Hlavaty Juraj , Jandl Gerrit , Tabotta Walter , Salmons Brian , Günzburg Walter H. , Hohenadl Christine 
Published: December 2007

AbstractBackgroundWe have previously described the generation of reconstituting retroviral (ReCon) vectors designed for cancer gene therapy using cytotoxic gene products. The unique vector structure with a promoter physically separated from the transgene allows generation of stable virus producer cells irrespective of the toxic gene. The mechanism of synthesis of DNA from retroviral RNA dictates that infection leads to the reconstitution of functional expression cassettes in the target cell.MethodsTo improve vector titres, a cytomegalovirus enhancer was inserted upstream of the 5′‐long‐terminal repeat (LTR); the Woodchuck hepatitis virus post‐transcriptional regulatory element and an elongated attachment site upstream of the 3′‐LTR were included. In addition, a bacterial origin of replication was deleted and a functional internal polyadenylation signal mutated. Transcriptional targeting was attempted by introducing mammary tissue‐specific promoters such as the U3 region of mouse mammary tumour virus or the promoter of the whey acidic protein encoding gene. All modifications were analysed in detail with respect to virus production and infectivity. Finally, the vector was armed with the λ‐holin encoding gene and transduced cells were analysed for cytotoxic effects.ResultsDistinct modifications of the vector resulted in a titre improvement of more than 560‐fold. Compatibility of the optimized vector with targeted cellular promoters was demonstrated. When equipped with the cytotoxic gene, stable producer cells could be successfully established and high titre virus infection resulted in rigorous target cell killing.ConclusionsThe ReCon vector in its optimized form is an attractive tool for cancer gene therapy approaches. Copyright © 2007 John Wiley & Sons, Ltd.