bluuebunny/crossref_metadata_2025_split huggingface dataset:
Electrophilic aromatic substitution and single‐electron transfer (SET) by the phenylium ion in the gas phase: characterization of a long‐lived SET intermediate
Authors: Yao Shengjun , Zhang Xiang , Zhou Jing , Qian Rong , Xu Zhe , Fang Fang , Wei Yuanlong , Wang Cuihong , Yuan Shuai , Guo Yinlong 
Published: August 2008

AbstractGas‐phase mass spectrometric studies and calculations were performed for the reaction of naked phenylium ion with several benzene halides. From these reactions, the molecular ion for biphenyl as the predominant product was obtained only from the reaction of phenylium ions with iodobenzene and bromobenzene. Furthermore, through the collision‐induced dissociation (CID) of the ion at m/z 281, the only dissociation observed is the loss of a phenyl radical, which indicates that a single‐electron transfer (SET) mechanism might have occurred within the reaction. Additionally, according to the comparison between the CID experiments of those isomeric compounds of the σ‐complexes and the CID experiment of the ion at m/z 281 captured in the ion trap, we have also defined the captured ion at m/z 281 as an SET‐intimate ion pair rather than those of σ‐complexes or the diphenyliodonium. Copyright © 2008 John Wiley & Sons, Ltd.
Theoretical and experimental studies of cationized uracil complexes in the gas phase
Authors: Zins Emilie‐Laure , Rochut Sophie , Pepe Claude 
Published: August 2008

AbstractCationized uracil clusters were generated in the gas phase by electrospray ionization (ESI). Mass spectrometry experiments showed that with particular experimental conditions, decameric uracil clusters are magic number clusters. MS/MS experiments demonstrated that the structure of these decameric uracil clusters depends substantially on the size and the charge of the cation. On the basis of the ab initio and density functional theory (DFT) quantum chemistry calculations, structures for these decameric clusters were proposed. These structures are in agreement with the experimental mass spectra of modified nucleobases. Theoretical calculations showed that complexes experimentally observed using ESI‐MS techniques, are not naturally the most stable in the gas phase. Copyright © 2008 John Wiley & Sons, Ltd.
Ultrafast spectroscopy of ZnO/ZnMgO quantum wells
Authors: Davis J.A. , Jagadish C. 
Published: August 2008

AbstractWe review recent work studying the dynamics in zinc oxide quantum wells (QWs) using ultrafast optical spectroscopy. These materials present exciting possibilities for optoelectronic device applications. In order to develop these applications, it is important to understand the mechanisms of the electronic processes occurring in ZnO/ZnMgO QWs. In this review, we discuss the excitonic lifetime and the impact of the internal electric field, the potential profile, phonons, and defects. We also discuss coherence dynamics and the observation of biexcitons at room temperature.
Novel Polyolefins Containing Crystallizable Isotactic Polystyrene Side Chains
Authors: Gall Barbara T. , McCahill Jennifer , Stephan Douglas W. , Mülhaupt Rolf 
Published: August 2008

AbstractVinyl‐terminated isotactic polystyrene macromonomers were copolymerized with ethylene and 1‐octene to new polyolefin graft copolymers with crystallizable polystyrene side chains. The iPS content was varied from 4 to 78 wt.‐% using different metallocene and halfsandwich catalysts. No solubility problems of the stereoregular macromonomer occured, because iPS does not crystallize during polymerization. In addition the polymers show nanophase separation of the polyolefin backbone and the iPS side chains. The crystallization of iPS, having a melting point of about 200 °C, can be achieved by annealing. This synthesis strategy allows the fabrication of a new class of thermoplastic elastomers with improved heat distortion temperatures.magnified image
Carboxylic acid‐containing benzoxazines as efficient catalysts in the thermal polymerization of benzoxazines
Authors: Andreu R. , Reina J. A. , Ronda J. C. 
Published: August 2008

AbstractThe autocatalytic thermal polymerization behavior of three benzoxazine monomers containing carboxylic acid functionalities is reported. Several mixtures of these carboxylic monomers and 3‐phenyl‐3,4‐dihydro‐2H‐1,3‐benzoxazine were prepared and their thermal polymerization behavior was analyzed by differential scanning calorimetry. The acid character of these reactive monomers increases the concentration of oxonium species, thus catalyzing the benzoxazine ring opening reaction. In this way the polymerization temperature decreased by as much as 100 °C in some cases. The existence of decarboxylation processes at high temperatures has been established by FTIR‐ATR and related to the increase in thermal stability observed by TGA in some cases. A relationship between the presence of carboxylic groups in the resulting materials and their flame retardancy behavior has also been established. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 6091–6101, 2008
Asymmetric, regio‐ and stereo‐selective alternating copolymerization of CO2 and propylene oxide catalyzed by chiral chromium Salan complexes
Authors: Li Bo , Wu Guang‐Peng , Ren Wei‐Min , Wang Yi‐Ming , Rao Dun‐Yan , Lu Xiao‐Bing 
Published: August 2008

AbstractChiral chromium complexes of tetradentate N,N′‐disubstituted bis(aminophenoxide) (designated as Salan, a saturated version of Schiff‐base Salen ligand) in conjunction with an ionic quaternary ammonium salt can efficiently catalyze the copolymerization of CO2 with racemic propylene oxide (rac‐PO) at mild conditions to selectively afford completely alternating poly(propylene carbonate) (PPC) with ∼ 95% head‐to‐tail linkages and moderate enantioselectivity. These new catalyst systems predominantly exceed the previously much‐studied SalenCr(III) systems in catalytic activity, polymer enantioselectivity, and stereochemistry control. The chiral diamine backbone, sterically hindered substitute groups on the aromatic rings, and the presence of sp3‐hydridized amino donors and its N,N′‐disubstituted groups in chiral SalanCr(III) complexes all play significant roles in controlling polymer stereochemistry and enantioselectivity. Furthermore, a relationship between polycarbonate enantioselectivity and its head‐to‐tail linkages in relation to regioselective ring‐opening of the epoxide was also discussed on the basis of stereochemical studies of PPCs derived from the copolymerization of CO2 with chiral PO at various conditions. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 6102–6113, 2008
Studies into Laser Ignition of Confined Pyrotechnics
Authors: Ahmad S. Rafi , Russell D. Anthony 
Published: August 2008

AbstractIgnition tests were carried out on three different pyrotechnics using laser energy from the multimode output from an Ar‐Ion laser (av) at 500 nm and a near‐IR diode laser pigtailed to a fibre optic cable and operating at 808 nm. The pyrotechnics investigated were: G20 black powder, SR44 and SR371C. The confined ignition tests were conducted in a specially designed ignition chamber. Pyrotechnics were ignited by a free space beam entering the chamber through an industrial sapphire window in the case of the Ar‐ion laser. For the NIR diode laser, fibre was ducted through a block into direct contact with the pyrotechnic. The Ar‐Ion laser was chosen as this was found to ignite all three pyrotechnics in the unconfined condition. It also allowed for a direct comparison of confined/unconfined results to be made. The threshold laser flux densities to initiate reproducible ignitions at this wavelength were found to be between ∼12.7 and ∼0.16 kW cm−2. Plotted on the ignition maps are the laser flux densities versus the start of ignition times for the three confined pyrotechnics. It was found from these maps that the times for confined ignition were substantially lower than those obtained for unconfined ignition under similar experimental conditions. For the NIR diode laser flux densities varied between ∼6.8 and ∼0.2 kW cm−2. The minimum ignition times for the NIR diode laser for SR371C (∼11.2 ms) and G20 (∼17.1 ms) were faster than those achieved by the use of the Ar‐ion laser. However, the minimum ignition time was shorter (∼11.7 ms) with the Ar‐ion laser for SR44.
Dickkopf‐1 expression increases early in prostate cancer development and decreases during progression from primary tumor to metastasis
Authors: Hall Christopher L. , Daignault Stephanie D. , Shah Rajal B. , Pienta Kenneth J. , Keller Evan T. 
Published: August 2008

AbstractBACKGROUNDProstate cancer (PCa) frequently metastasizes to the bone and induces osteoblastic lesions. We previously demonstrated through over‐expression of the Wnt inhibitor dickkopf‐1 (DKK‐1) that Wnts contribute to the osteoblastic component of PCa osseous lesions in vivo.METHODSTo test the clinical significance of DKK‐1 expression during PCa progression, tissue microarrays were stained for DKK‐1 protein by immunohistochemistry.RESULTSDKK‐1 expression index (EI) was found to increase in PIN and primary lesions compared to non‐neoplastic tissue (106 ± 10 vs. 19 ± 6, respectively, where the EI is the product of the percent expression and staining intensity). DKK‐1 expression was also found to be higher in all PCa metastatic lesions (56 ± 21 EI) compared to non‐neoplastic tissues but was significantly decreased versus primary PCa lesions (P < 0.008). The decline in DKK‐1 correlated with a shift of β‐catenin staining from the nucleus to the cytoplasm suggesting possible mechanism for the observed decrease in DKK‐1 levels during PCa progression. Within metastatic lesions, DKK‐1 expression was least abundant in PCa bone metastases relative to all soft tissue PCa metastatic lesions except lymph node metastases. High DKK‐1 expression within PCa metastases was further associated with shorter over‐all patient survival.CONCLUSIONSTaken together, these data demonstrate that elevated DKK‐1 expression is an early event in PCa and that as PCa progresses DKK‐1 expression declines, particularly in advanced bone metastases. The decline of DKK‐1 in bone metastases can unmask Wnts' osteoblastic activity. These data support a model in which DKK‐1 is a molecular switch that transitions the phenotype of PCa osseous lesions from osteolytic to osteoblastic. Prostate 68: 1396–1404, 2008. © 2008 Wiley‐Liss, Inc.
Temperature characteristics of a magnetic micro strain gauge
Authors: Hansen Stefan , Rissing Lutz , Gatzen Hans H. 
Published: August 2008

AbstractMagnetoelastic strain gauges applied in weighing machines enable a high resolution excursion measurement. Micro transformers with one part of the flux guide made out of a magnetoelastic material allow the fabrication of magnetic micro systems with high k ‐factors. The sensors were fabricated with Micro Electro‐mechanical Systems (MEMS) technology on silicon substrates. A thinning process before integration into components is required. The thinned sensor chips were integrated into an articulated suspension. For these susceptible sensor elements, special requirements to the assembly process exist. Since the temperature dependence of such systems is of great interest, an evaluation of the temperature characteristics was subject of investigations. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A concept for magnetic data recording on genetically intelligent (“gentelligent”) components
Authors: Wu K.‐H. , Traisigkhachol O. , Gatzen H. H. 
Published: August 2008

AbstractA new approach of data recording during manufacturing is to store information directly on machine components. This way, the components may serve as their own information carrier throughout the whole manufacturing process, and later in the working cycle. Such a concept is called “gentelligent” (for genetically intelligent) and aims at allowing to inherit fabrication and application data to the product's next generation. This requires a new kind of machine parts, which are capable for collecting, preprocessing, and storing information (e.g. temperature and forces during use of the component) on their surface. For storing the required information, proven principles of the peripheral magnetic data recording including inductive writing and a magneto‐optical readout are applied. The storage medium used is a material developed recently: “magnetic magnesium”, i.e. magnesium filled with hard magnetic particles. To allow a magneto‐optical readout based on the Magneto‐optical Kerr Effect (MOKE), bulk material is covered with a soft magnetic layer, called a keeper layer. The keeper layer is supplied to generate a homogeneous magnetic and reflective surface which is not provided by pure “magnetic magnesium”. This paper describes the development of the recording system. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Honey modulates oxidative burst of professional phagocytes
Authors: Mesaik M. Ahmed , Azim M. Kamran , Mohiuddin S. 
Published: August 2008

AbstractThe effects of natural honey and its major sugar constituents (i.e. D‐fructose, D‐glucose, maltose and sucrose) on phagocytic respiratory burst have been studied. Pre‐incubated whole blood and isolated leukocytes with honey samples and sugars were induced for phagocytosis and the level of reactive oxygen species (ROS) was monitored by using chemiluminescence assays. Honey samples were found to decrease the luminol‐enhanced chemiluminescence in opsonized zymosan‐stimulated whole blood and isolated leukocytes with statistically significant differences; indicating inhibition of ROS production including hydrogen peroxide, hydroxyl free radical and hypochlorous acid. Thus honey appears to modify the oxidative burst process by inhibiting phagocytic myeloperoxidase activity. Chemiluminescence assays further showed that among the major sugar constituents of honey, D‐fructose in high concentration exerted an inhibitory effect on exocytosis‐associated myeloperoxidase catalyzed ROS formation. These results pointed out an immuno‐modulatory potential of honey in the course of phagocytosis. Copyright © 2008 John Wiley & Sons, Ltd.
Estimation of the local diffusion tensor and normalization for heterogeneous correlation modelling using a diffusion equation
Authors: Pannekoucke O. , Massart S. 
Published: August 2008

AbstractAs the background‐error covariance matrix is a key component of any assimilation system, its modelling is an important step. Usually, this matrix is decomposed into correlations and standard deviations matrices. An interesting method for modelling the correlation matrix of the background error for complex geometry, like an ocean grid, consists in computing correlation functions using a diffusion operator. The background‐error correlation functions can be estimated for example from an ensemble of perturbed forecasts. The diffusion operator is able to represent heterogeneous correlation functions at a reasonable numerical cost. But a first challenge resides in the determination of the local diffusion tensor corresponding to the local correlation function. Then the second challenge resides in the determination of the normalization to make sure that the matrix modelled through the diffusion operator is a correlation matrix. In this article, we propose to build a background‐error correlation matrix using a diffusion operator based on a local diffusion tensor. The estimation of this local tensor is performed using an ensemble of perturbed forecasts. A validation within a randomization method illustrates the feasibility and the accuracy of the proposed method. In particular, it is shown that the local geographical variations of diagnosed correlation functions (through an ensemble of perturbed forecast) are well represented.This is first illustrated in an analytical one‐dimensional framework. In that context, the diffusion field and the normalization field are deduced from a given correlation length‐scale field. The resulting length‐scales are shown to correspond to the initial length‐scale when the given length‐scale field spectrum is red. The approximate normalization, computed from the local length‐scale, is close to the true normalization under the same condition of a red spectrum.Then, the method is illustrated in a real context using an ensemble of perturbed forecasts from the MOCAGE–PALM assimilation system. In that case, length‐scale and anisotropy diagnosis reveal the complexity of the correlation of stratospheric ozone forecast errors. The local diffusion tensor deduced from these diagnoses is shown be able to represent such an existing heterogeneity and anisotropy. As in the one‐dimensional case, the approximate normalization, based on the local diffusion tensor, appears to be a really good approximation of the true normalization. Copyright © 2008 Royal Meteorological Society
EBIC and luminescence studies of defects in solar cells
Authors: Breitenstein O. , Bauer J. , Kittler M. , Arguirov T. , Seifert W. 
Published: August 2008

AbstractElectron beam‐induced current (EBIC) can be used to detect electronic irregularities in solar cells, such as shunts and precipitates, and to perform physical characterization of defects by, e.g. measuring the temperature dependence of their recombination activity. Recently also luminescence methods such as electroluminescence (EL) and photoluminescence (PL) have been shown to provide useful information on crystal defects in solar cells. In this contribution it will be shown that the combined application of EBIC, EL and PL may deliver useful information on the presence and on the physical properties of crystal defects in silicon solar cells. Also pre‐breakdown sites in multicrystalline cells can be investigated by reverse‐bias EL and by microplasma‐type EBIC, in comparison with lock‐in thermography investigations. SCANNING 30: 331–338, 2008. © 2008 Wiley Periodicals, Inc.
Dose‐dependent changes in the synaptic strength on dopamine neurons and locomotor activity after cocaine exposure
Authors: Wanat M.J. , Bonci A. 
Published: August 2008

AbstractChanges in synaptic strength on ventral tegmental area (VTA) dopamine neurons are thought to play a critical role in the development of addiction‐related behaviors. However, it is unknown how a single injection of cocaine at different doses affects locomotor activity, behavioral sensitization, and glutamatergic synaptic strength on VTA dopamine neurons in mice. We observed that behavioral sensitization to a challenge cocaine injection scaled with the dose of cocaine received 1 day prior. Interestingly, the locomotor activity after the initial exposure to different doses of cocaine corresponded to the changes in glutamatergic strength on VTA dopamine neurons. These results in mice suggest that a single exposure to cocaine dose‐dependently affects excitatory synapses on VTA dopamine neurons, and that this acute synaptic alteration is directly associated with the locomotor responses to cocaine and not to behavioral sensitization. Synapse 62:790–795, 2008. © 2008 Wiley‐Liss, Inc.
Occupancy of dopamine D2/3 receptors in rat brain by endogenous dopamine measured with the agonist positron emission tomography radioligand [11C]MNPA
Authors: Seneca Nicholas , Zoghbi Sami S. , Skinbjerg Mette , Liow Jeih‐San , Hong Jinsoo , Sibley David R. , Pike Victor W. , Halldin Christer , Innis Robert B. 
Published: August 2008

AbstractEstimates of dopamine D2/3 receptor occupancy by endogenous dopamine using positron emission tomography (PET) in animals have varied almost threefold. This variability may have been caused by incomplete depletion of dopamine or by the use of antagonist radioligands, which appear less sensitive than agonist radioligands to changes in endogenous dopamine. PET scans were performed in rats with the agonist PET radioligand [11C]MNPA ([O‐methyl‐11C]2‐methoxy‐N‐propylnorapomorphine). [11C]MNPA was injected as a bolus plus constant infusion to achieve steady‐state concentration in the body and equilibrium receptor binding in the brain. Radioligand binding was compared at baseline and after treatment with reserpine plus α‐methyl‐para‐tyrosine, which cause ∼95% depletion of endogenous dopamine. Depletion of dopamine increased radioligand binding in striatum but had little effect in cerebellum. Striatal [11C]MNPA binding potential was 0.93 ± 0.12 at baseline and increased to 1.99 ± 0.25 after dopamine depletion. Occupancy of D2/3 receptors by endogenous dopamine at baseline was calculated to be ∼53%. Striatal binding was displaceable with raclopride, but not with BP 897 (a selective D3 compound), thus confirming the D2 receptor specificity of [11C]MNPA binding. Radioactivity extracted from rat brain contained only 8–10% radiometabolites and was insignificantly altered by administration of reserpine plus α‐methyl‐para‐tyrosine. Hence, dopamine depletion did not increase the PET measurements via an effect on radiotracer metabolism. Our in vivo estimate of dopamine's occupancy of D2/3 receptors at baseline is higher than that previously reported using antagonist radioligands and PET, but is similar to that reported using agonist radioligands and ex vivo measurements. Synapse 62:756–763, 2008. Published 2008 Wiley‐Liss, Inc.
Alterations in amphetamine‐stimulated dopamine overflow due to the Nurr1‐null heterozygous genotype and postweaning isolation
Authors: Moore Talisha M. , Brown Timothy , Cade Mirae , Eells Jeffrey B. 
Published: August 2008

AbstractThe nuclear receptor Nurr1 functions to regulate dopamine neurotransmission, as Nurr1‐null heterozygous (+/−) mice have alterations in dopamine function and, when raised in isolation immediately after weaning, have disruptions in sensorimotor gaiting, a behavior altered in schizophrenia and modulated by dopamine neurotransmission. The goal of this study was to determine nigrostriatal and mesoaccumbens dopamine neurotransmission using microdialysis in +/− and wild‐type (+/+) mice raised in groups or isolation. In the striatum, isolation significantly reduced amphetamine‐stimulated dopamine overflow and levels of the dopamine metabolite 3,4‐dihydroxyphenylacetic acid (DOPAC). The +/− genotype alone caused a small, nonsignificant reduction in basal dopamine levels but a significant reduction in basal DOPAC levels. In the nucleus accumbens shell, the +/− genotype elevated basal dopamine levels. Isolation had genotype specific effects, causing an elevation in amphetamine‐stimulated dopamine overflow in +/− mice but a reduction in +/+ mice, resulting in a large difference in stimulated dopamine overflow when comparing the +/+ and +/− isolated mice. These data indicate that a deletion of a single allele of Nurr1, which produces only subtle changes alone, when coupled with a developmental stressor, can dramatically alter mesoaccumbens dopamine neurotransmission. These observations demonstrate how the combination of genetic predisposition and an environmental insult during development can cause dysfunction of dopamine neurotransmission and could contribute to diseases such as schizophrenia or attention deficit hyperactivity disorder. Synapse 62:764–774, 2008. © 2008 Wiley‐Liss, Inc.