bluuebunny/crossref_metadata_2025_split huggingface dataset:
Temperature Dependence of Interactions between Stable Piperidine‐1‐yloxyl Derivatives and an Ionic Liquid
Authors: Strehmel Veronika , Rexhausen Hans , Strauch Peter , Görnitz Eckhard , Strehmel Bernd 
Published: May 2008

Abstract2,2,6,6‐Tetramethylpiperidine‐1‐yloxyl derivatives substituted with either hydrogen bonding [‐OH, ‐OSO3H] or ionic [‐OSO3−Na+, ‐OSO3−K+, N+(CH3)3I−, N+(CH3)3 N−(SO2‐CF3)2] substituents are investigated in 1‐butyl‐3‐methylimidazolium tetrafluoroborate over a wide temperature range covering both glassy and viscous states. The Vogel–Fulcher–Tammann equation describes the temperature dependence of the ionic liquid viscosity. Quantum chemical calculations of the spin probes at the UB3LYP/6‐311(2d,p++) level are done to describe the dependence of the spin density on nitrogen on the substitution pattern of the 4‐position of the probe. The results of these calculations are also used to understand the experimental results obtained by applying the Spernol–Gierer–Wirtz theory to analyze the viscosity dependence of the rotational correlation time of the spin probes. Significant differences are found between 2,2,6,6‐tetramethylpiperidine‐1‐yloxyl and its derivatives containing substituents that are able to form hydrogen bonds with the ionic liquid. Moreover, derivatives substituted with ionic groups at the 4‐position have a large effect on temperature‐induced solvent viscosity, as this is particularly dependent on the nature of the substituent at the 4‐position. These dependencies include the temperature region that can be used to describe interactions between the spin probes and the ionic liquid, diffusion into the free volume during non‐activated (neutral spin probes) and activated (charged spin probes) processes. Additional parameters are the radii of the ionic liquid and the spin probes, which are calculated and measured approximately. In addition, the temperature dependence of the isotropic hyperfine coupling constants of the spin probes results in information about the micropolarity of the ionic liquid. At room temperature, this is comparable to that of the solvent dimethylsulfoxide.
Interactions of Aromatic Heterocycles with Water: The Driving Force from Free‐Jet Rotational Spectroscopy and Model Electrostatic Calculations
Authors: Maris Assimo , Melandri Sonia , Miazzi Marta , Zerbetto Francesco 
Published: May 2008

AbstractThe interaction of isolated aromatic nitrogen atoms with water is explored within free jets by using rotational spectroscopy. To the existing data on diazines, we add the case of the 1:1 complex of 1,3,5‐triazine and water (where water donates a proton to one of the nitrogen heterocyclic atoms to form a planar adduct). An electrostatic model based on distributed multipoles accurately reproduces the structures of the four azine–water complexes and allows us to understand the forces that stabilize these structures. The applied intermolecular potential allows us to estimate the changes in the thermodynamic functions of the complexes—compared to the separated constituents—and evaluate the temperature at which the complexes are stable under standard conditions.
Stereoselective Synthesis of Quaternary Proline Analogues
Authors: Calaza M. Isabel , Cativiela Carlos 
Published: May 2008

AbstractThis review describes available methods for the diastereoselective and asymmetric synthesis of quaternary prolines. The focus is on the preparation of α‐functionalized prolines in which the pyrrolidine moiety is not embedded in a polycyclic frame. The diverse synthetic approaches are classified according to the bond that is formed to complete the quaternary skeleton.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)
Short‐term forecasts of euro area real GDP growth: an assessment of real‐time performance based on vintage data
Authors: Diron Marie 
Published: May 2008

AbstractForecasters commonly predict real gross domestic product growth from monthly indicators such as industrial production, retail sales and surveys, and therefore require an assessment of the reliability of such tools. While forecast errors related to model specification and unavailability of data in real time have been assessed, the impact of data revisions on forecast accuracy has seldom been evaluated, especially for the euro area. This paper proposes to evaluate the contributions of these three sources of forecast error using a set of data vintages for the euro area. The results show that gains in accuracy of forecasts achieved by using monthly data on actual activity rather than surveys or financial indicators are offset by the fact that the former set of monthly data is harder to forecast and less timely than the latter set. These results provide a benchmark which future research may build on as more vintage datasets become available. Copyright © 2008 John Wiley & Sons, Ltd.
Combining forecasts using optimal combination weight and generalized autoregression
Authors: Kurz‐Kim Jeong‐Ryeol 
Published: May 2008

AbstractIn this paper, we consider a combined forecast using an optimal combination weight in a generalized autoregression framework. The generalized autoregression provides not only a combined forecast but also an optimal combination weight for combining forecasts. By simulation, we find that short‐ and medium‐horizon (as well as partly long‐horizon) forecasts from the generalized autoregression using the optimal combination weight are more efficient than those from the usual autoregression in terms of the mean‐squared forecast error. An empirical application with US gross domestic product confirms the simulation result. Copyright © 2008 John Wiley & Sons, Ltd.
Excellent outcome following down-staging of hepatocellular carcinoma prior to liver transplantation: An intention-to-treat analysis
Authors: Yao Francis Y. , Kerlan Robert K. , Hirose Ryutaro , Davern Timothy J. , Bass Nathan M. , Feng Sandy , Peters Marion , Terrault Norah , Freise Chris E. , Ascher Nancy L. , Roberts John P. 
Published: May 2008

Abstract

We previously reported encouraging results of down-staging of hepatocellular carcinoma (HCC) to meet conventional T2 criteria (one lesion 2–5 cm or two to three lesions <3 cm) for orthotopic liver transplantation (OLT) in 30 patients as a test of concept. In this ongoing prospective study, we analyzed longer-term outcome data on HCC down-staging in a larger cohort of 61 patients with tumor stage exceeding T2 criteria who were enrolled between June 2002 and January 2007. Eligibility criteria for down-staging included: (1) one lesion >5 cm and up to 8 cm; (2) two to three lesions with at least one lesion >3 cm and not exceeding 5 cm, with total tumor diameter up to 8 cm; or (3) four to five lesions with none >3 cm, with total tumor diameter up to 8 cm. A minimum observation period of 3 months after down-staging was required before OLT. Tumor down-staging was successful in 43 patients (70.5%). Thirty-five patients (57.4%) had received OLT, including two who had undergone live-donor liver transplantation. Treatment failure was observed in 18 patients (29.5%), primarily due to tumor progression. In the explant of 35 patients who underwent OLT, 13 had complete tumor necrosis, 17 met T2 criteria, and five exceeded T2 criteria. The Kaplan-Meier intention-to-treat survival at 1 and 4 years after down-staging were 87.5% and 69.3%, respectively. The 1-year and 4-year posttransplantation survival rates were 96.2% and 92.1%, respectively. No patient had HCC recurrence after a median posttransplantation follow-up of 25 months. The only factor predicting treatment failure was pretreatment alpha-fetoprotein >1,000 ng/mL.

Conclusion:

Successful down-staging of HCC can be achieved in the majority of carefully selected patients and is associated with excellent posttransplantation outcome. (Hepatology 2008.)
Changing patterns of Hodgkin lymphoma incidence in Singapore
Authors: Hjalgrim Henrik , Seow Adeline , Rostgaard Klaus , Friborg Jeppe 
Published: May 2008

AbstractA bimodal age‐specific incidence pattern with a relatively high proportion of cases occurring in adolescents and young adults is a hallmark of Hodgkin lymphoma (HL) epidemiology in Western industrialized countries. The young adult incidence peak is believed to reflect the association between HL risk in young adults and an affluent childhood socioeconomic environment. However, the dynamic development of the young adult incidence peak following socioeconomic development implied by this interpretation has scarcely been demonstrated in a single population over time. We, therefore, analyzed incidence patterns of HL in Singapore between 1968 and 2004, during which time period a socioeconomic transition towards Western World lifestyles took place. As hypothesized a HL incidence peak emerged among adolescents and young adults in Singapore. Thus, in the age groups 15–19 and 20–24 years incidence rates increased annually by 7.0% (95% confidence interval 3.4%–10.7%) and 3.4% (0.1%–6.8%), respectively, in men and by 13.7% (9.1%–18.6%) and 12.2% (7.8–16.8%), respectively, in women between 1968 and 2004. However, the incidence peak remained considerably lower than what can be observed in young adults in the Western World. It remains to be determined to what extent the current lower incidence of HL in young Asian adults should be attributed to birth cohort phenomena, as would be suggested by continued increase in incidence, and to ethnic variation in HL susceptibility between Asian and non‐Asian populations, respectively. © 2008 Wiley‐Liss, Inc.
Growth inhibition of colon cancer cells by polyisoprenylated benzophenones is associated with induction of the endoplasmic reticulum response
Authors: Protiva Petr , Hopkins Michael E. , Baggett Scott , Yang Hui , Lipkin Martin , Holt Peter R. , Kennelly Edward J. , Bernard Weinstein I. 
Published: May 2008

AbstractPolyisoprenylated benzophenones derived from Garcinia xanthochymus have cytotoxic activity in vitro and antitumor activity in rodent models, but the mechanism is unknown. The purpose of our study was to examine in parallel molecular pathways that are targeted by 3 Garcinia‐derived benzophenones‐xanthochymol (X), guttiferone E (GE) and guttiferone H (GH), in 3 human colon cancer cell lines, HCT116, HT29 and SW480. The IC50 concentrations were determined and the cells were then treated with X, GE or GH at their respective IC50 or IC50x2 concentrations. Effects on the cell cycle, mitochondrial membrane potential and apoptosis were assessed by flow cytometry and caspase activation. Changes in gene expression were assessed with Illumina 24 K gene arrays. We found that X, GE and GH induced loss of mitochondrial membrane potential and G1 arrest at their IC50 concentrations and induced caspase activation at IC50 × 2 concentrations. An analysis of the changes in gene expression revealed that with all 3 compounds and all 3 cell lines there was a marked increase in expression of several genes, including XBP1, ATF4 and DDIT3/CHOP, which are components of the endoplasmic reticulum stress response. The DDIT4/REDD1 gene, an inhibitor of the mTOR survival pathway, was also up‐regulated. Therefore, X, GE and GH appear to inhibit the growth of human colon cancer cells, at least in part, by activating the endoplasmic reticulum stress response and inhibiting the mTOR cell survival pathway. These combined effects may contribute to the anticancer activity of these novel compounds. © 2008 Wiley‐Liss, Inc.
IFN‐γ withdrawal after immunotherapy potentiates B16 melanoma invasion and metastasis by intensifying tumor integrin αvβ3 signaling
Authors: Gong Wei , Zhang Gui‐Mei , Liu Yi , Lei Zhang , Li Dong , Yuan Ye , Huang Bo , Feng Zuo‐Hua 
Published: May 2008

AbstractImmunotherapy can effectively suppress tumor, yet complete tumor eradication occurs infrequently. The metastatic potential of remnant tumor cells after immunotherapy and the underlying mechanisms have not been fully elucidated. Here, we report that the termination of immunotherapy strikingly increases the metastatic potential of remnant melanoma. This is mainly due to the withdrawal of IFN‐γ after immunotherapy. The relief of IFN‐γ stress led to the increase of αvβ3 integrin expression in B16 cells, which increased the adhesion of B16 cells to fibrinogen, fibronectin and laminin. Through αvβ3 signaling, the activation of FAK, upregulation of cdc2, production of active MMP‐2 and MMP‐9 and actin polymerization were intensified in B16 cells stimulated with ECM molecules 24 h after the withdrawal of IFN‐γ. The i.v. injection of such tumor cells into mice resulted in more metastatic tumor nodes in lung and shortened the survival of mice. The pitfall of immunotherapy termination can be remedied by the administration of recombinant CBD‐HepII polypeptide of fibronectin, which effectively inhibits αvβ3 signaling. These findings suggest that the risk of tumor metastasis can be increased after the termination of immunotherapy, due to the withdrawal of IFN‐γ and that targeting αvβ3 signaling pathway can improve the therapeutic effect of immunotherapeutic approaches by reducing such metastatic risk. © 2008 Wiley‐Liss, Inc.
The roles of surface chemistry and topography in the strength and rate of osseointegration of titanium implants in bone
Authors: Sul Young‐Taeg , Kang Byung‐Soo , Johansson Carina , Um Heung‐Sik , Park Chan‐Jin , Albrektsson Tomas 
Published: May 2008

AbstractThe present study investigated the effects of surface chemistry and topography on the strength and rate of osseointegration of titanium implants in bone. Three groups of implants were compared: (1) machine‐turned implants (turned implants), (2) machine‐turned and aluminum oxide‐blasted implants (blasted implants), and (3) implants that were machine‐turned, aluminum oxide‐blasted, and processed with the micro‐arc oxidation method (Mg implants). Three and six weeks after implant insertion in rabbit tibiae, the implant osseointegration strength and rate were evaluated. Surface chemistry revealed characteristic differences of nine at.% Mg for Mg implants and 11 at.% Al for blasted implants. In terms of surface roughness, there was no difference between Mg implants and blasted implants in developed surface ratio (Sdr; p = 0.69) or summit density (Sds; p = 0.96), but Mg implants had a significantly lower arithmetic average height deviation (Sa) value than blasted implants (p = 0.007). At both 3 and 6 weeks, Mg implants demonstrated significantly higher osseointegration strength compared with turned (p = 0.0001, p = 0.0001) and blasted (p = 0.0001, p = 0.035) implants, whereas blasted implants showed significantly higher osseointegration than turned implants at 6 weeks (p = 0.02) but not at 3 weeks (p = 0.199). The present results not only support the hypothesis that biochemical bonding facilitates rapid and strong integration of implants in bone, but also provide evidence for biochemical bonding theory previously proposed by Sul. © 2008 Wiley Periodicals, Inc. J Biomed Mater Res, 2009
Maya blue–green pigments found in Calakmul, Mexico: a study by Raman and UV‐visible spectroscopy
Authors: Garcia Moreno Renata , Strivay David , Gilbert Bernard 
Published: May 2008

AbstractAfter more than two decades of fieldwork in the Maya archaeological site of Calakmul, Mexico, numerous remnants of blue and green pigments have been reported on wall paintings, as well as on funerary paraphernalia, such as masks, miniatures and vases. The importance of these pigments is linked to the sacred values that Maya people associate with blue and green colours since pre‐Columbian times. These hues symbolise water, and are therefore associated with fertility and regeneration. This paper aims to perform a survey of the blue and green pigments used in the Early Classic and Late Classic periods in Calakmul (300–850 A.D.), in order to have a better understanding of their chemical composition and origin. Analyses were performed on microsamples using Raman and UV‐visible spectroscopies to evaluate the possibilities that these techniques can offer in future in situ researches on Mesoamerican archaeological materials and objects. With these analyses, we have documented a large blue–green chromatic palette, which includes the earliest Blue Maya and Green Maya known to date, as well as malachite, pseudomalachite and an unknown‐up‐to‐now blue‐green mineral pigment, veszelyite, used specifically for ritual objects. The results indicate a careful selection of imported products and the mastering of a complex ancient Maya pictorial tradition. Copyright © 2008 John Wiley & Sons, Ltd.
15N1H and 15N–13C couplings in 15N‐enriched dihydroxamic acids
Authors: Schraml Jan , Cigler Petr 
Published: May 2008

Abstract15N‐enriched dihydroxamic acids (HONHCO(CH2)nCONHOH, n = 0, 1, and 2) were prepared and their spectra NMR (1H, 13C, 15N) recorded in dimethyl sulfoxide (DMSO) solutions with the aim of determining 15N coupling constants (15N1H and 15N13C). The results supplement chemical shifts published earlier and yield additional support to the structural conclusions derived from other NMR parameters. Notably, no trace of hydroximic structures could be found in the 15N NMR spectra of these acids. The values of 15N13C coupling constants backed by theoretical calculations support the assignments made earlier for all of the major conformers and for the minor conformer of succinohydroxamic acid. The enrichment revealed that the minor component of malonodihydroxamic acid solution previously considered to be the ZE conformer is in fact the monohydroxamic acid (HOOCCH2CONHOH). Copyright © 2008 John Wiley & Sons, Ltd.
Molecular modeling simulation and experimental measurements to characterize chitosan and poly(vinyl pyrrolidone) blend interactions
Authors: Suknuntha Krit , Tantishaiyakul Vimon , Vao‐Soongnern Visit , Espidel Youssef , Cosgrove Terrence 
Published: May 2008

AbstractBlends of chitosan and poly(vinyl pyrrolidone) (PVP) have a high potential for use in various biomedical applications and in advanced drug‐delivery systems. Recently, the physical and chemical properties of these blends have been extensively characterized. However, the molecular interaction between these two polymers is not fully understood. In this study, the intermolecular interaction between chitosan and PVP was experimentally investigated using 13C cross‐polarization magic angle‐spinning nuclear magnetic resonance (13C CP/MAS NMR) and diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS). According to these experimental results, the interaction between the polymers takes place through the carbonyl group of PVP and either the OHC6, OHC3, or NHC2 of chitosan. In an attempt to identify the interacting groups of these polymers, molecular modeling simulation was performed. Molecular simulation was able to clarify that the hydrogen atom of OHC6 of chitosan was the most favorable site to form hydrogen bonding with the oxygen atom of CO of PVP, followed by that of OHC3, whereas that of NHC2 was the weakest proton donor group. The nitrogen atom of PVP was not involved in the intermolecular interaction between these polymers. Furthermore, the interactions between these polymers are higher when PVP concentrations are lower, and interactions decrease with increasing amounts of PVP. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 1258–1264, 2008
Morphology evolution of nanocomposites based on poly(phenylene sulfide)/poly(butylene terephthalate) blend
Authors: Wu Defeng , Wu Lanfeng , Zhang Ming , Zhou Weidong , Zhang Yisheng 
Published: May 2008

AbstractPoly(phenylene sulfide) (PPS)/poly(butylene terephthalate) (PBT) (60/40 w/w) blend nanocomposites (PPS/PBTs) were prepared by direct melt compounding of PPS, PBT, and organoclay. The morphology and rheology of PPS/PBTs were investigated using scanning electron microscope and transmission electron microscope as well as parallel plate rheometer. The intercalated clay tactoids are selectively located in the continuous PBT phase due to their nice affinity. A novel morphology evolution of the immiscible blend matrices is observed with increase of clay loadings. Small addition of clay increases the discrete PPS spherulite domain size. With increasing loading levels, the PPS phase transform to the fibrous structure and finally, to the partial laminar structure at the high loading levels, in which shows a characteristic of large‐scaled phase separation. The presence of clay, however, does not impede the coalescence of the PPS phase because the phase size increases with increasing clay loadings. The elasticity and blend ratio of two matrices are proposed as the important roles on the morphological evolution. Moreover, the laminar structure of PPS phase is very sensitive to the steady shear flow and is easy to be broken down to spherulite droplet at the low shear rate. However, high shear level is likely to facilitate the coalescence of those PPS phase and finally to phase inversion, both contributing to increases of the dynamic modulus after steady shear flow. In conclusion, the morphology of the immiscible polymer blend nanocomposites depends strongly on both the clay loadings and shear history. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 1265–1279, 2008
Self‐organized micropatterns of high aspect ratio polymer nanofibers by wetting of nanopores
Authors: Kong Jie , Yung Kai‐Leung , Xu Yan , He Lan , Lau K. H. , Chan C. Y. 
Published: May 2008

AbstractThe self‐organized micropatterns of high aspect ratio polymer nanofibers were prepared via a facile nanoporous wetting strategy. Various micropatterns with labyrinth‐like or honeycomb‐like topography can be formed in a controllable manner by adjusting the nanoporous template's nanochannel characteristic (deep‐hole or through‐hole), the size of nanopores, and the wetting time. The honeycomb‐like micropattern shows a little higher hydrophobicity than labyrinth‐like micropattern when the diameters of their nanofibers are similar. The formation of various self‐organized micropatterns is mainly dependant on the dilation stress and interaction between nanofibers during the template's removal and solvent evaporation process. The confining or free conditions of unreleased nanofibers' tips in nanopores determine the topography of the resultant self‐organized micropattern, i.e., labyrinth‐like or honeycomb‐like. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 1280–1289, 2008
Advanced electrodes with nanostructured surfaces for electrochemical microsensors
Authors: Klosová K. , Hubálek J. 
Published: May 2008

AbstractNanostructures have recently attracted great interest because of their unique properties and potential use in a broad range of technological applications. In the case of electrochemical microsensors, an array of nanostructures can be used to enlarge the surface area of sensing electrodes and it also has a positive impact on the redox reactions on their surfaces. It is assumed that these microsensors will then have higher sensitivity due to the surface modification. One of the easiest ways to modify an electrode surface by nanostructures is to deposit a metal into a thin nanoporous Al2O3 template which is placed on a gold electrode. Metal ions are attracted to the cathode (the gold electrode) during electrodeposition and fill the nanopores in the template. After completing the electrodeposition process, the template is dissolved and the metal nanostructures are obtained. Both nanorods and nanotubes of various wall‐thicknesses can be created by this method. It has been found that the type of the nanostructure depends on specific electroplating conditions (e.g. pH and concentration) and used template (i.e. diameters of the nanopores). Therefore, it is possible to control the type of the nanostructure by adjusting these electroplating parameters and to create either nanorods or nanotubes on purpose. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)