bluuebunny/crossref_metadata_2025_split huggingface dataset:
Synthesis of optically active γ‐lactones via lipase‐catalyzed resolution
Authors: Shimotori Yasutaka , Nakahachi Yukihiko , Inoue Keita , Miyakoshi Tetsuo 
Published: June 2007

AbstractBoth enantiomers of the six major kinds of γ‐lactones were synthesized to >98% e.e. in four steps, starting from succinic anhydride. The key features were the syntheses of the various rac‐N‐methyl‐4‐hydroxyalkanamides via Grignard reaction and the enantioselective acetylation and hydrolysis promoted by Novozym 435. Copyright © 2007 John Wiley & Sons, Ltd.
Structure‐Based Design and Synthesis of the First Weak Non‐Phosphate Inhibitors for IspF, an Enzyme in the Non‐Mevalonate Pathway of Isoprenoid Biosynthesis
Authors: Baumgartner Corinne , Eberle Christian , Diederich François , Lauw Susan , Rohdich Felix , Eisenreich Wolfgang , Bacher Adelbert 
Published: June 2007

AbstractIn this paper, we describe the structure‐based design, synthesis, and biological evaluation of cytosine derivatives and analogues that inhibit IspF, an enzyme in the non‐mevalonate pathway of isoprenoid biosynthesis. This pathway is responsible for the biosynthesis of the C5 precursors to isoprenoids, isopentenyl diphosphate (IPP, 1) and dimethylallyl diphosphate (DMAPP, 2; Scheme 1). The non‐mevalonate pathway is the sole source for 1 and 2 in the protozoan Plasmodium parasites. Since mammals exclusively utilize the alternative mevalonate pathway, the enzymes of the non‐mevalonate pathway have been identified as attractive new drug targets in the fight against malaria. Based on computer modeling (cf. Figs. 2 and 3), new cytosine derivatives and analogues (Fig. 1) were selected as potential drug‐like inhibitors of IspF protein, and synthesized (Schemes 2–5). Determination of the enzyme activity by 13C‐NMR spectroscopy in the presence of the new ligands showed inhibitory activities for some of the prepared cytosine and pyridine‐2,5‐diamine derivatives in the upper micromolar range (IC50 values; Table). The data suggest that it is possible to inhibit IspF protein without binding to the polar diphosphate binding site and the side chain of Asp56′, which interacts with the ribose moiety of the substrate and substrate analogues. Furthermore, a new spacious sub‐pocket was discovered which accommodates aromatic spacers between cytosine derivatives or analogues (binding to ‘Pocket III’) and rings that occupy the flexible hydrophobic region of ‘Pocket II’. The proposed binding mode remains to be further validated by X‐ray crystallography.
Reaction Mechanism of Selenate(IV) Ions with Several Thiols in Aqueous Media
Authors: Forastiere Daniel O. , Borghi Elena B. , Morando Pedro J. 
Published: June 2007

AbstractIn several enzymatic systems, selenium (an essential element commonly incorporated as sodium selenite to the human diet) is bonded through a mercapto group of a cysteine residue. The reaction of SeIV (as selenite) with different thiols in aqueous media was studied to increase the information about the mechanism of the enzyme reaction. The influence of the reagents' concentration on the reaction rate and temporal spectral changes was analyzed. A complex with a UV maximum between 270 and 290 nm was formed, which quickly decayed when the thiol concentration was increased. The proposed reaction mechanism includes a fast SeIV–thiol association step followed by two parallel steps (one is first‐order in the complex and the other one is globally second‐order). Kinetics and equilibrium constants were obtained, and the rate dependence of the thiol oxidation on the SeIV concentration was modelled for all thiols tested. Very good agreement between the experimental and calculated curves was observed.
Habaenines A and B, Two New Norditerpenoid Alkaloids from Aconitum habaense
Authors: Yang Shu , Yang Xiao‐Dong , Zhao Jing‐Feng , Zhang Hong‐Bin , Li Liang 
Published: June 2007

AbstractTwo new norditerpenoid alkaloids, habaenine A and B (1 and 2), together with two known compounds, were isolated from Aconitum habaense. The structures of the new compounds were elucidated on the basis of spectral analyses as (1α,6α,16β)‐8‐(acetyloxy)‐20‐ethyl‐13‐hydroxy‐1,6,16‐trimethoxy‐4‐(methoxymethyl)‐19‐oxoaconitan‐14‐yl 4‐methoxybenzoate (1) and (1α,6α,16β)‐8‐(acetyloxy)‐13‐hydroxy‐1,6,16‐trimethoxy‐4‐(methoxymethyl)‐aconitan‐14‐yl 4‐methoxybenzoate (2).
Superacid‐Catalyzed Cyclization of Methyl (6Z)‐Geranylfarnesoates
Authors: Grinco Marina , Kulciţki Veaceslav , Ungur Nicon , Jankowski Wieslaw , Chojnacki Tadeusz , Vlad Pavel F. 
Published: June 2007

AbstractMethyl (2Z,6Z,10E,14E)‐ (3) and methyl (2E,6Z,10E,14E)‐geranylfarnesoate (4) were prepared, and then individually cyclized in the presence of the superacid FSO3H. In the case of substrate 3, the scalaranic ester 9 (26%) and the cheilanthanic ester 10 (39%) were isolated. Under the same conditions, substrate 4 afforded a mixture of the corresponding stereoisomers 11 (25%) and 12 (63%). The observed product selectivity supports that the internal, (6Z)‐configured CC bond in these and other biologically relevant substrates plays an essential role in the cyclization process.
New Labdane‐Type Diterpenoids from Amentotaxus argotaenia
Authors: Yang Qin , Ye Guan , Feng Jia‐Quan , Zhao Wei‐Min 
Published: June 2007

AbstractA new labdane diterpene, amentotaxin A (1), and an unprecedented dinorlabdane diterpene, amentotaxin B (2), were isolated from the stems of Amentotaxus argotaenia (Hance) Pilger, together with seven known compounds. Their structures were identified by in‐depth spectroscopic and mass‐spectrometric analyses.
Two New Triterpene Lactones from the Stems of Kadsura polysperma
Authors: Jia Zhengwei , Lu Yan , Liao Zhixin , Chen Daofeng 
Published: June 2007

AbstractTwo new triterpene lactones, polysperlactones A (2) and B (3), were isolated from the stems of Kadsura polysperma, together with the known compounds heteroclitalactone D (1) and schisanlactone E (4). Their structures were elucidated by spectroscopic methods, including 2D‐NMR and HR‐MS techniques. The configuration of 1 was confirmed by X‐ray analysis. Compounds 2 and 3 are members of a rare class of 3,4‐secolanostane metabolites with ring‐expanded or cyclized structures, respectively.
Young mothers' play with their toddlers: individual variability as a function of psychosocial factors
Authors: Driscoll Joan Riley , Easterbrooks M. Ann 
Published: June 2007

AbstractThere is no one style of parenting which characterizes young mothers as a group. In addition, life circumstances play an important role in shaping maternal behaviour. The aim of this study was to identify patterns of maternal play behaviour and contextual (social and personal) factors associated with these different patterns. In this study, 107 young mothers were observed at home during play with their toddlers; maternal behaviour was coded for joint attention (shared focus of mother and toddler attention) and emotional availability (e.g. sensitivity, intrusiveness, hostility). Mothers reported on aspects of their childhood history and current personal functioning and social support. A person‐centred analytic approach, using cluster analysis, revealed three distinct groups of maternal play behaviour: (1) ‘sensitive‐engaged’ (2) ‘inconsistent‐directive,’ and (3) ‘intrusive‐prohibitive’. Multivariate analyses revealed that contextual factors in mothers' lives (e.g. childhood abuse, depressive symptomatology, partner violence, social support, and parenting self‐confidence) were differentially associated with parenting clusters. Copyright © 2007 John Wiley & Sons, Ltd.
Enhanced wear resistance of orthopaedic bearing due to the cross‐linking of poly(MPC) graft chains induced by gamma‐ray irradiation
Authors: Kyomoto Masayuki , Moro Toru , Miyaji Fumiaki , Konno Tomohiro , Hashimoto Masami , Kawaguchi Hiroshi , Takatori Yoshio , Nakamura Kozo , Ishihara Kazuhiko 
Published: June 2007

AbstractWe assumed that the extra energy supplied by gamma‐ray irradiation produced cross‐links in 2‐methacryloyloxyethyl phosphorylcholine (MPC) polymer grafted cross‐linked polyethylene (CLPE‐g‐MPC) and investigated its effects on the tribological properties of CLPE‐g‐MPC. In this study, we found that the gamma‐ray irradiation produced cross‐links in three kinds of regions of CLPE‐g‐MPC: poly(MPC) layer, CLPE‐MPC interface, and CLPE substrate. The dynamic coefficient of friction of CLPE‐g‐MPC slightly increased with increasing irradiation doses. After the simulator test, both the nonsterilized and gamma‐ray sterilized CLPE‐g‐MPC cups exhibited lower wear than the untreated CLPE ones. In particular, the gamma‐ray sterilized CLPE‐g‐MPC cups showed extremely low and stable wear. As for the nonsterilized CLPE‐g‐MPC cups, the weight change varied with each cup. When the CLPE surface is modified by poly(MPC) grafting, the MPC graft polymer leads to a significant reduction in the sliding friction between the surfaces that are grafted because water thin films formed can behave as extremely efficient lubricants. Such a cross‐link of poly(MPC) slightly increases the friction of CLPE by gamma‐ray irradiation but provides a stable wear resistant layer on the friction surface. The cross‐links formed by gamma‐ray irradiation would give further longevity to the CLPE‐g‐MPC cups. © 2007 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 2008
Validation of a swallowing disturbance questionnaire for detecting dysphagia in patients with Parkinson's disease
Authors: Manor Yael , Giladi Nir , Cohen Alma , Fliss Dan M. , Cohen Jacob T. 
Published: June 2007

AbstractUnderreporting of swallowing disturbances by Parkinson's disease (PD) patients may lead to delay in diagnosis and treatment, alerting the physician to an existing dysphagia only after the first episode of aspiration pneumonia. We developed and validated a swallowing disturbance questionnaire (SDQ) for PD patients and compared its findings to an objective assessment. Fifty‐seven PD patients (mean age 69 ± 10 years) participated in this study. Each patient was queried about experiencing swallowing disturbances and asked to complete a self‐reported 15‐item “yes/no” questionnaire on swallowing disturbances (24 replied “no”). All study patients underwent a physical/clinical swallowing evaluation by a speech pathologist and an otolaryngologist. The 33 patients who complained of swallowing disturbances also underwent fiberoptic endoscopyic evaluation of swallowing (FEES). According to the ROC test, the “optimal” score (where the sensitivity and specificity curves cross) is 11 (sensitivity 80.5%, specificity 81.3%). Using the SDQ questionnaire substantially reduced Type I errors (specifically, an existing swallowing problem missed by the selected cutoff point). On the basis of the SDQ assessment alone, 12 of the 24 (50%) noncomplaining patients would have been referred to further evaluation that they otherwise would not have undergone. The SDQ emerged as a validated tool to detect early dysphagia in PD patients. © 2007 Movement Disorder Society
A progressive, fatal dystonia‐Parkinsonism syndrome in a patient with primary immunodeficiency receiving chronic IVIG therapy
Authors: Papapetropoulos Spiridon , Friedman Jennifer , Blackstone Craig , Kleiner Gary I. , Bowen Brian C. , Singer Carlos 
Published: June 2007

AbstractX‐linked agammaglobulinemia (XLA) is a primary immunodeficiency disorder caused by a mutation in the Bruton agammaglobulinemia tyrosine kinase gene that results in severe B‐cell deficiency. So far, neurological complications of XLA have been primarily related to acute and/or chronic central nervous system enteroviral infections. In the last few years a progressive neurodegenerative syndrome of unknown etiology has been described in XLA patients. We describe and present a video of an XLA patient who developed a fatal dementing, dystonia‐Parkinsonism syndrome 14 years into his immune disorder. Physician awareness of this rare syndrome may lead to its better characterization and management. © 2007 Movement Disorder Society
Magnetic resonance imaging and T2 relaxometry of human median nerve at 7 Tesla
Authors: Gambarota G. , Veltien A. , Klomp D. , Van Alfen N. , Mulkern R.V. , Heerschap A. 
Published: June 2007

AbstractMeasurements of T2 relaxation times in tissues have provided a unique, noninvasive method to investigate the microenvironment of water molecules in vivo. As more clinical imaging is performed at higher field strengths, tissue relaxation times need to be reassessed in order to optimize tissue contrast. The purpose of this study was to investigate the water proton T2 relaxation time in human median nerve at 7 T. High‐resolution images of the wrist were obtained using a home‐built dedicated microstrip coil. Gradient echo images provided a good anatomical delineation of the wrist structure, with a clear definition of the median nerve, tendons, bone, and connective tissue within the wrist in an acquisition time of 2 min. Measurements of the T2 relaxation time were performed with a spin echo imaging sequence. The T2 relaxation time of the median nerve was 18.3 ± 1.9 ms, which is significantly shorter than the T2 measured in previous studies performed at 1.5 T and 3 T. Further, the T2 relaxation time of the median nerve is shorter than the T2 relaxation time of other tissues, such as brain tissue, at the same field strength. Since the T2 relaxation time of water protons is sensitive to the water microenvironment, relaxation measurements and, in general, a more quantitative magnetic resonance imaging approach might help in detecting and investigating diseases of peripheral nervous system, such as compressive and inflammatory neuropathies, in humans. Muscle Nerve, 2007
An anisotropic strength criterion for jointed rock masses and its application in wellbore stability analyses
Authors: Chen X. , Yang Q. , Qiu K. B. , Feng J. L. 
Published: June 2007

AbstractIn this paper, an anisotropic strength criterion is established for jointed rock masses. An orientation distribution function (ODF) of joint connectivity, is introduced to characterize the anisotropic strength of jointed rock masses related to directional distributed joint sets. Coulomb failure condition is formulated for each plane of jointed rock masses by joint connectivity, where the friction coefficient and cohesion of the jointed rock mass are related to those of the intact rock and joint and become orientation dependent. When approximating joint connectivity by its second‐order fabric tensor, an anisotropic strength criterion is derived through an approximate analytical solution to the critical plane problem. To demonstrate the effects of joint distribution on the anisotropic strength of jointed rock masses, the failure envelopes are worked out for different relative orientations of material anisotropy and principal stress axes. The anisotropic strength criterion is also applied to wellbore stability analyses. It is shown that a borehole drilled in the direction of the maximum principal in situ stress is not always the safest due to the anisotropic strength of the jointed rock mass. Copyright © 2007 John Wiley & Sons, Ltd.
Kronecker product approximations for dense block Toeplitz‐plus‐Hankel matrices
Authors: Kilmer M. E. , Nagy J. G. 
Published: June 2007

AbstractIn this paper, we consider the approximation of dense block Toeplitz‐plus‐Hankel matrices by sums of Kronecker products of Toeplitz‐plus‐Hankel matrices. We present an algorithm for efficiently computing the matrix approximation that requires the factorization of matrices of much smaller dimension than that of the original. The main results are described for block Toeplitz matrices with Toeplitz‐plus‐Hankel blocks, but the algorithms can be readily adjusted for other related structures that arise in image processing applications, such as block Toeplitz with Toeplitz blocks and block Toeplitz‐plus‐Hankel with Toeplitz‐plus‐Hankel blocks. Our work extends the techniques in Kamm and Nagy (SIAM J. Matrix Anal. Appl. 2000; 22:155–172) and Nagy et al. (SIAM J. Matrix Anal. Appl. 2004; 25:829–841), which consider similar matrices, but with the added restriction that the matrices have a banded/block‐banded structure. We illustrate the effectiveness of our
algorithm by using the output of the algorithm to construct preconditioners for systems from two different applications: diffuse optical tomography and atmospheric image deblurring. Copyright © 2007 John Wiley & Sons, Ltd.
Chain extension as a strategy for the development of improved reverse thermo‐responsive polymers
Authors: Cohn Daniel , Sosnik Alejandro , Malal Ram , Zarka Revital , Garty Shai , Levy Avi 
Published: June 2007

AbstractThe hypothesis that chain extension can be harnessed to the generation of improved reverse thermo‐responsive polymers was tested by following two basic synthetic pathways: (1) the polymerization of poly(ethylene oxide)‐poly(propylene oxide)‐poly(ethylene oxide) (PEO‐PPO‐PEO) triblocks using hexamethylene diisocyanate (HDI) as chain extender and (2) the covalent binding of poly(ethylene glycol) and poly(propylene glycol) chains, using phosgene as the connecting molecule. While in the former, the basic amphiphilic repeating unit is known for its own RTG behavior, the latter polymers consist of segments incapable of exhibiting a reverse thermal gelation (RTG) of their own. Dynamic light scattering (DLS) measurements revealed that the nanostructures formed by the chain extended polymers were markedly larger than those generated by PEO‐PPO‐PEO triblocks. While the size of Pluronic F127 micelles ranged from 15 to 20 nm, the higher molecular weight amphiphiles generated much larger nanostructures (20–400 nm). The chain extended polymers achieved much higher viscosities and their gels displayed enhanced long‐term stability at 37°C. Copyright © 2007 John Wiley & Sons, Ltd.
Lethal drug probe in China: the case of Xinfu clindamycin
Authors: Jing Yonghua , Kelton Christina ML , Li Xing , Guo Jeff Jianfei 
Published: June 2007

AbstractIn China, antibiotics are prescribed frequently, not only for bacterial infections but also for viruses, including the common cold, as well as other illnesses.1, 2 Chinese people tend to believe that antibiotics are a cure for many diseases from skin infections to life‐threatening lung ailments; and antibiotics are their first choice when they think about buying medication.3 Antibiotic abuse is particularly severe in small‐ and medium‐sized towns and rural areas where doctors are not as well educated as in the large cities. Statistics from the World Health Organization reveal that the use of antibiotics in Chinese hospitals can be as high as 80 percent of overall cases, compared with the international average of 30 percent.3 Besides being one source of the specific public health disaster described in the remainder of this article, overprescribing generally leads to building up of resistance to antibiotics, making it more difficult to treat bacterial infections in the future. Copyright © 2007 John Wiley & Sons, Ltd.
Ring‐opening polymerization of lactones using zirconocene catalytic systems: Block copolymerization with methyl methacrylate
Authors: Kostakis Konstantinos , Mourmouris Stylianos , Karanikolopoulos Giorgos , Pitsikalis Marinos , Hadjichristidis Nikos 
Published: June 2007

AbstractThe ring‐opening polymerization of ε‐caprolactone (ε‐CL) and δ‐valerolactone (δ‐VL) using nine catalytic systems consisting of a combination of three C2v zirconocene complexes and three borate cocatalysts is discussed. The polymerizations proceed in a well‐controlled manner, producing polymers with relatively high molecular weights and narrow molecular weight distributions. Kinetic experiments of the polymerization of ε‐CL with the catalytic system Cp2ZrMe2/B(C6F5)3 (1) showed a linear dependence between polymerization yield and molecular weight with time, as well as between the molecular weight with the molar ratio of the monomer over the catalyst [ε‐CL]/[Zr], indicating sufficient control of the polymerization reaction. The catalytic system (1) was utilized for the synthesis of well‐defined block copolymers of MMA with ε‐CL and δ‐VL. All samples were characterized by size exclusion chromatography, nuclear magnetic resonance, and differential scanning calorimetry. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 3524–3537, 2007
Laryngeal sensitivity in the neonatal period: From bench to bedside
Authors: Reix Philippe , St‐Hilaire Marie , Praud Jean‐Paul 
Published: June 2007

AbstractLaryngeal sensitivity in the newborn has been a subject of great interest for both researchers and clinicians for a number of years. From a clinical standpoint, laryngeal sensitivity is essential for both preventing foreign substances from entering into the lower airway and for finely tuning upper airway resistance. However, heightened reflexes originating from the laryngeal receptors in newborns and infants, due to neural immaturity, can lead to potentially dangerous cardiorespiratory events. The latter have been linked to apneas of prematurity, apparent life‐threatening events, and sudden infant death syndrome (SIDS). From a physiological standpoint, many mechanisms pertaining to reflexes originating from laryngeal receptors are yet to be fully understood. This short review is an attempt to summarize current knowledge on laryngeal sensitivity and its potential consequences upon control of breathing abnormalities encountered within the first weeks of life. Pediatr Pulmonol. 2007; 42:674–682. © 2007 Wiley‐Liss, Inc.
Accounting for uncertainty in pedotransfer functions in vulnerability assessments of pesticide leaching to groundwater
Authors: Stenemo Fredrik , Jarvis Nicholas 
Published: June 2007

AbstractA simulation tool for site‐specific vulnerability assessments of pesticide leaching to groundwater was developed, based on the pesticide fate and transport model MACRO, parameterized using pedotransfer functions and reasonable worst‐case parameter values. The effects of uncertainty in the pedotransfer functions on simulation results were examined for 48 combinations of soils, pesticides and application timings, by sampling pedotransfer function regression errors and propagating them through the simulation model in a Monte Carlo analysis. An uncertainty factor, fu, was derived, defined as the ratio between the concentration simulated with no errors, csim, and the 80th percentile concentration for the scenario. The pedotransfer function errors caused a large variation in simulation results, with fu ranging from 1.14 to 1440, with a median of 2.8. A non‐linear relationship was found between fu and csim, which can be used to account for parameter uncertainty by correcting the simulated concentration, csim, to an estimated 80th percentile value. For fine‐textured soils, the predictions were most sensitive to errors in the pedotransfer functions for two parameters regulating macropore flow (the saturated matrix hydraulic conductivity, Kb, and the effective diffusion pathlength, d) and two water retention function parameters (van Genuchten's N and α parameters). For coarse‐textured soils, the model was also sensitive to errors in the exponent in the degradation water response function and the dispersivity, in addition to Kb, but showed little sensitivity to d. To reduce uncertainty in model predictions, improved pedotransfer functions for Kb, d, N and α would therefore be most useful. Copyright © 2007 Society of Chemical Industry
Current mechanism in SbSeI crystals based on phonon‐assisted tunnelling emission
Authors: Audzijonis A. , Sereika R. , Lapeika V. , Žaltauskas R. 
Published: June 2007

AbstractSingle crystals of SbSeI were grown by the vapour phase technique. Reverse current–voltage (I –V) characteristics of Ag/SbSeI/Ag system have been measured in the temperature range from 273 to 363 K. Analyses of experimental results are explained on the basis of phonon‐assisted electron tunnelling from the local levels in the metal–crystal interface to the conduction band. Calculated values: electron–phonon interaction, depth of the trap and effective mass of the polaron enabled us to estimate the electron tunnelling probability. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)