bluuebunny/crossref_metadata_2025_split huggingface dataset:
Growth Mechanism and Chemical Bonding in Scandium‐Doped Copper Clusters: Experimental and Theoretical Study in Concert
Authors: Höltzl Tibor , Veldeman Nele , De Haeck Jorg , Veszprémi Tamás , Lievens Peter , Nguyen Minh Tho 
Published: March 2009

AbstractSize matters! The electronic structure and size‐dependent stability of neutral and cationic scandium‐doped copper clusters have been investigated by mass spectrometric studies (for the cations) and also quantum chemical computations. The proposed reaction paths ultimately lead to the most stable Frank–Kasper‐shaped Cu16Sc+ cluster (shown here), which could be the germ of a new crystallization process.magnified imageElectronic structure and size‐dependent stability of scandium‐doped copper cluster cations, CunSc+, were investigated by using a dual‐target dual‐laser vaporization production scheme followed by mass spectrometric studies and also quantum chemical computations in the density functional theory framework. The neutral species also were studied by using computational methods. Enhanced abundances and dissociation energies were measured in the case of CunSc+ for n=4, 6, 8, 10 and 16, the last of these identified as being extraordinary stable. Neutral clusters are stable with n=5, 7, 9 and 15, which are isoelectronic with respect to the number of the valence s electrons with the stable cationic clusters; hence a simple electron count determines cluster properties to a great extent. The Cu17Sc cluster was found to be a superatomic molecule, containing Cu16Sc+ and Cu− units; however, the charge separation is not as pronounced as in the case of CuLi. Cu15Sc was found to be a stable cluster with a large dissociation energy and a closed electronic structure; hence this can be regarded as a superatom, analogous to the noble gases. The main factors determining the growth patterns of these clusters are the central position of the scandium atom and the successive filling of the shell orbitals. For smaller clusters, the reaction paths appear to diverge yielding various products; however all paths ultimately lead to the most stable Frank–Kasper shaped Cu16Sc cluster, which in turn can be the germ of the crystallization process.
Strong Adsorbability of Mercury Ions on Aniline/Sulfoanisidine Copolymer Nanosorbents
Authors: Li Xin‐Gui , Feng Hao , Huang Mei‐Rong 
Published: March 2009

AbstractThe highest Hg‐ion adsorbance so far, namely up to 2063 mg g−1, has been achieved by poly(aniline‐co‐5‐sulfo‐2‐anisidine) nanosorbents. Sorption of Hg ions occurs mainly by redox and chelation mechanisms (see scheme), but also by ion exchange and physisorption.magnified imagePoly(aniline (AN)‐co‐5‐sulfo‐2‐anisidine (SA)) nanoparticles were synthesized by chemical oxidative copolymerization of AN and SA monomers, and their extremely strong adsorption of mercury ions in aqueous solution was demonstrated. The reactivity ratios of AN and SA comonomers were found to be 2.05 and 0.02, respectively. While AN monomer tends to homopolymerize, SA monomer tends to copolymerize with AN monomer because of the great steric hindrance and electron‐attracting effect of the sulfo groups, despite the effect of conjugation of the methoxyl group with the benzene ring. The effects of initial mercury(II) concentration, sorption time, sorption temperature, ultrasonic treatment, and sorbent dosage on mercury‐ion sorption onto AN/SA (50/50) copolymer nanoparticles with a number‐average diameter of around 120 nm were significantly optimized. The results show that the maximum Hg‐ion sorption capacity on the particulate nanosorbents can even reach 2063 mg of Hg per gram of sorbent, which would be the highest Hg‐ion adsorbance so far. The sorption data fit to the Langmuir isotherm, and the process obeys pseudo‐second‐order kinetics. The IR and UV/Vis spectral data of the Hg‐loaded copolymer particles suggest that some mercury(II) was directly reduced by the copolymer to mercury(I) and even mercury(0). A mechanism of sorption between the particles and Hg ions in aqueous solution is proposed, and a physical/ion exchange/chelation/redox sorption ratio of around 2/3/45/50 was found. Copolymer nanoparticles may be one of the most powerful and cost‐effective sorbents of mercury ions, with a wide range of potential applications for the efficient removal and even recovery of the mercury ions from aqueous solution.
Macrocyclic Hexaureas: Synthesis, Conformation, and Anion Binding
Authors: Meshcheryakov Denys , Böhmer Volker , Bolte Michael , Hubscher‐Bruder Véronique , Arnaud‐Neu Françoise 
Published: March 2009

AbstractVaried flexibility: Cyclic oligoureas are formed by using anions as templates. Linking of six xanthene and/or diphenyl ether fragments by urea groups leads to the formation of five macrocyclic compounds with a 48‐membered ring with variable flexibility (see picture). Their interaction with anions shows a strong influence of acetate and chloride ions on the cyclization from four precursor molecules.magnified imageFive macrocylic compounds XXXXXX, XXDXXD, XDXDXD, XDDXDD, and DDDDDD with 48‐membered rings, in which six xanthene and/or diphenyl ether fragments are linked through six urea (‐NH‐C(O)‐NH‐) groups, have been synthesized. In the cyclization step, a linear diamine was allowed to react with the appropriate diisocyanate by using a [5+1] (i.e., “XDXDX+D” for XDXDXD), [4+2] (DDDDDD), or [3+3] (XDDXDD) procedure. Compounds XXXXXX and XXDXXD were prepared from two molecules of the dimeric amine XX and two molecules of the respective monomeric diisocyanate (X or D) in a [2+1+2+1] (or 2×[2+1]) reaction. The (nonoptimized) yields in the cyclization step ranged from 45 to 80 %. The linear precursor diamines or diisocyanates were obtained by analogous condensation reactions by using partial protection with a tert‐butoxycarbonyl group. All the macrocyclic compounds and synthetic intermediates were characterized by 1H NMR and mass spectra. Three different crystal structures were obtained for XDDXDD, which show the molecule in a more or less strongly folded conformation determined by intramolecular hydrogen bonding. The interaction of the hexaureas with selected anions was studied by 1H NMR spectroscopy and UV absorption spectrophotometry.
3D electron microscopic reconstruction of segments of rat cerebellar purkinje cell dendrites receiving ascending and parallel fiber granule cell synaptic inputs
Authors: Lu Huo , Esquivel Angelica V. , Bower James M. 
Published: March 2009

AbstractGrowing physiological evidence suggests that there are functional differences between synapses made by the ascending and parallel fiber segments of the granule axon on cerebellar Purkinje cells. Supporting this view, our previous electron microscopic studies suggested that these synapses also contacted different regions of the Purkinje cell dendrite, and in particular that ascending segment synapses are made exclusively on the smallest diameter Purkinje cell dendrites. In the current study we used serial electron microscopic techniques to reconstruct Purkinje cell dendritic segments up to almost 10 μm in length. Using a combination of anatomical and immunological labeling techniques we identified the ascending or parallel fiber origins of the excitatory synaptic inputs onto dendritic spines, as well as the location of inhibitory synapses made directly on the dendritic shaft. The results confirmed that there are regions of the Purkinje cell dendrite receiving exclusively ascending or parallel fiber synapses and that ascending segment synapses are only found on small‐diameter dendrites. In addition, we describe for the first time small‐diameter dendritic regions contacted by both types of excitatory synapses. While our data suggest that the majority of inhibitory inputs to the Purkinje cell tree are associated with parallel fiber synaptic inputs, we also found inhibitory inputs on dendritic regions with mixed ascending and parallel fiber inputs, or exclusively parallel fiber inputs. The finding that ascending and parallel fiber inputs can be segregated on the Purkinje cell dendritic tree provides further evidence that these excitatory granule cell synaptic inputs may be functionally distinct. J. Comp. Neurol. 514:583–594, 2009. © 2009 Wiley‐Liss, Inc.
Self‐Association of [PtII(1,10‐Phenanthroline)(N‐pyrrolidyl‐N‐(2,2‐dimethylpropanoyl)thiourea)]+ and Non‐Covalent Outer‐Sphere Complex Formation with Fluoranthene through π–Cation Interactions: A High‐Resolution 1H and DOSY NMR Study
Authors: Kotzé Izak A. , Gerber Wilhelmus J. , Mckenzie Jean M. , Koch Klaus R. 
Published: March 2009

AbstractCompeting outer‐sphere self‐association of [PtII(1,10‐phenanthroline)(N‐pyrrolidyl‐N‐(2,2‐dimethylpropanoyl)thiourea)]+Cl– (M) and the hetero‐association of M with fluoranthene (F) have been investigated by means of the significant concentration dependence of 1H NMR chemical shifts as well as by diffusion coefficients obtained from DOSY NMR spectroscopy. The NMR spectroscopic data is only consistent with the formation of a “dimer” M···M aggregate according to 2M [rlhar2] M2 in acetonitrile at several temperatures, with a calculated KD of ca. 46 ± 7 M–1 at 273.5 K. In the presence of the aromatic molecule fluoranthene, relatively strong, presumably π–cation‐type interactions between M and F according to M + F [rlhar2] MF (KB ≈ 67 ± 7 M–1 at 273.5 K) occur in acetonitrile. The calculated ΔrH° and ΔrS° for M···M (–25129 ± 3112 and –61 ± 11 J mol–1) and M···F (–13560 ± 3180 and –17 ± 11 J mol–1, respectively) is indicative of π–cation interactions. Interestingly any potential F···F aggregation interactions are negligible for the fluoranthene concentration range up to 0.1 M, indicating that non‐covalent π–π interactions between fluoranthene molecules 2F [rlhar2] F2 are, in contrast to π–cation interactions, negligible under these conditions in solution. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)
Fluoride‐Free Hiyama and Copper‐ and Amine‐Free Sonogashira Coupling in Air in a Mixed Aqueous Medium by a Series of PEPPSI‐Themed Precatalysts
Authors: Dash Chandrakanta , Shaikh Mobin M. , Ghosh Prasenjit 
Published: March 2009

AbstractA new series of robust, user‐friendly, and highly active PEPPSI‐themed (pyridine‐enhanced precatalyst preparation, stabilization and initiation) (NHC)PdX2(pyridine)‐type (X = Cl, Br) precatalysts of C4–C5 saturated imidazole‐ (1–4) and triazole‐based (5 and 6) N‐heterocyclic carbenes for the Hiyama and Sonogashira couplings under amenable conditions are reported. Specifically 1–6 efficiently catalyze the fluoride‐free Hiyama coupling of aryl halides with PhSi(OMe)3 and CH2=CHSi(OMe)3 in air in the presence of NaOH as a base in a mixed aqueous medium (dioxane/H2O, 2:1 v/v). Along the same lines, these 1–6 precatalysts also promote the Cu‐free and amine‐free Sonogashira coupling of aryl bromides and iodides with phenylacetylene in air and in a mixed aqueous medium (DMF/H2O, 3/1 v/v). The complexes 1–6 were synthesized by the direct reaction of the respective imidazolinium and triazolium halide salts with PdCl2 in pyridine in the presence of K2CO3 as a base. DFT studies on the catalytically relevant palladium(0) (NHC)Pd(pyridine) precursors 1a–6a reveal significant donation from the N‐heterocyclic carbene lone pair onto the unfilled σ* orbital of the trans Pd–pyridine bond. This weakens the Pd‐bound “throwaway” pyridine ligand, and its dissociation marks the initiation of the catalytic cycle.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)
Mechanism for the Oxidation of Sulfides and Sulfoxides with Periodates: Reactivity of the Oxidizing Species
Authors: Ruff Ferenc , Fábián Attila , Farkas Ödön , Kucsman Árpád 
Published: March 2009

AbstractDFT computations have been performed at different levels of theory to identify the mechanism for the oxidation of sulfides and sulfoxides with periodates. The periodate ion (IO4–), periodic acid (HIO4) and their hydrated derivatives all oxidize sulfides to sulfoxides in one‐step oxygen‐transfer reactions and the relative reactivities are HIO4 >> H5IO6 > IO4– > H4IO6– >> H3IO62–. The hydration and dissociation equilibria of the periodates are shifted towards IO4– in neutral and moderately acidic solutions, and sulfides are oxidized mainly with IO4– under normal experimental conditions. The oxygen atoms of the periodates attack the sulfides perpendicularly to the plane of the C–S–C atoms and the S···O···I atoms are in a linear arrangement in the very early transition state (TS). The sulfides are the electron donors and periodates are the electron acceptors in the reactions; the geometries of the TSs are determined by the overlap of the HOMO and the LUMO of the reactants. Other mechanisms can be ruled out because the attack of the sulfur atom of the substrate on the iodine atom of the reactants increases the energy of the system continuously very steeply as the S···I distance decreases. Experimentally derived ΔG‡ values are in good agreement with the ΔG‡ data computed for the oxygen‐transfer mechanism. Sulfoxides are also oxidized to sulfones with IO4– in a one‐step oxygen‐transfer reaction, and the structures of the TSs and the ΔG‡ data are similar to those obtained for the reactions of sulfides. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)
Amphiceramide A and B, Novel Glycosphingolipids from the Marine Sponge Amphimedon compressa
Authors: Costantino Valeria , Fattorusso Ernesto , Imperatore Concetta , Mangoni Alfonso , Teta Roberta 
Published: March 2009

AbstractGlycolipid analysis of the Caribbean sponge Amphimedon compressa has shown it to contain two novel glycosphingolipids, amphiceramide A (1a) and B (2a), which possess an unusual Δ6‐phytosphingosine. The saccharide chain of amphiceramide A is composed of a β‐glucose residue glycosylated at the 6‐position by an N‐acetyl‐β‐glucosamine and has never been found before in a natural product. The saccharide chain of amphiceramide B consists of an allolactose [Gal(1β→6)Glc] residue β‐linked to the ceramide and is found here for the first time in a natural glycosphingolipid. In addition, the sponge contains a new molecular species, acetamidoglucosyl ceramide (3a), and the known glucosyl ceramide 4a (halicerebroside A) and melibiosyl ceramide 5a (amphimelibioside C). (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)
Efficient Release of Base‐Sensitive Oligonucleotides from Solid Supports using Fluoride Ions
Authors: Lavergne Thomas , Parey Nora , Vasseur Jean‐Jacques , Debart Françoise 
Published: March 2009

AbstractWith the aim to prepare biolabile oligoribonucleotides that are partially or fully base‐sensitive 2′‐O‐pivaloyloxymethyl functionalized, we investigated the cleavage of a silyl‐type linker and a Q‐linker anchored to a solid support under several fluoride ion conditions. Thus, an original fluoride ion treatment was perfected to release oligonucleotides bearing base‐sensitive modifications from solid supports without affecting them and with high efficiency. Chimeric oligouridylates containing both 2′‐OH and 2′‐O‐PivOM groups were obtained in high yield and purity. Moreover, the conditions used to cleave the linker were extended to the release of a base‐sensitive DNA‐oligonucleotide with 4‐N‐acetylcytosine residues; the acetyl groups were maintained.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)
Analysis of PM10 air pollution in Brno based on generalized linear model with strongly rank‐deficient design matrix
Authors: Veselý Vítězslav , Tonner Jaromír , Hrdlivčková Zuzana , Michálek Jaroslav , Kolář Miroslav 
Published: March 2009

AbstractAn analysis of air pollution by suspended particulate matter (PM10) in Brno, the second largest urban agglomeration of the Czech Republic, based on generalized linear model (GLM) is presented. Average daily concentrations coming from PM10 monitoring for the period 1998–2005 have been processed. The measured meteorological factors: air temperature and humidity, direction and wind speed were considered as covariates along with some additional seasonal factors.Three standard and six GLMs with strongly rank‐deficient design matrix have been applied. The rank deficiency is due to overparameterization which allows one more precise modeling involving, among others, identification of significant air pollution sources (PSs).From each of them the parameter estimates were obtained using both standard estimation procedure and a new sparse parameter estimation technique based on a four‐step modification of the basis pursuit algorithm originally suggested for time‐scale analysis of digital signals.As the standard estimation algorithms often fail due to numerical instability caused by strong overparameterization, we have applied this new computationally intensive approach allowing us to reliably identify nearly zero parameters in the model and thus to find numerically stable sparse solutions.The goal of the analysis was to identify the model and algorithm yielding most precise 1‐day forecasts of the level of pollution by PM10 with regard to the meteorological and seasonal covariates. Copyright © 2009 John Wiley & Sons, Ltd.
Tryptic digest analysis by comprehensive reversed phase×two reversed phase liquid chromatography (RP‐LC×2RP‐LC) at different pH's
Authors: François Isabelle , Cabooter Deirdre , Sandra Koen , Lynen Frédéric , Desmet Gert , Sandra Pat 
Published: March 2009

AbstractAs an alternative to the classical approach of combining strong cation exchange SCX‐LC and RP‐LC for the separation of complex proteomic samples, this essay describes the online comprehensive RP‐LC×RP‐LC separation of BSA and human blood serum. High orthogonality and peak capacity are achieved through the application of a significantly different pH in the two dimensions. The coupling of fused‐core columns in series ensures high efficiency in the first dimension, while a previously designed interface with parallel second dimension columns further enhances the separation capability of the comprehensive system.
Characterization of high molecular weight multimeric states of human haptoglobin and hemoglobin‐based oxygen carriers by high‐mass MALDI MS
Authors: Pimenova Tatiana , Pereira Claudia P. , Schaer Dominik J. , Zenobi Renato 
Published: March 2009

AbstractHigh‐mass MALDI‐TOF mass spectrometry (MS) is a novel analytical approach to study large biomolecules and their interactions. It is a powerful alternative method to gel electrophoresis (GE) and size exclusion chromatography (SEC) for obtaining information on the molecular weights of macromolecules and for determining protein complexes. The precision of mass measurements (mass accuracy), high sensitivity, speed of the analysis, and tolerance toward sample heterogeneity are the major features of this MS‐based approach. Remarkably, MS provides direct stoichiometric information of macromolecular protein complexes, when noncovalent interactions are stabilized during desorption/ionization by use of chemical cross‐linking reagents. In this study, high‐mass MALDI‐TOF MS was applied to characterize the multimeric state of the human plasma protein haptoglobin (Hp), which is in the mass range of 150–300 kDa. Also, higher order structures of hemoglobin‐based oxygen carriers (HBOCs) and their interactions with human haptoglobin were analyzed. These investigations are of clinical importance and contribute to the overall understanding of specific toxicity and clearance of HBOCs.
Role of ubiquitin–proteasome proteolysis in muscle fiber destruction in experimental chloroquine‐induced myopathy
Authors: Kimura Noriyuki , Kumamoto Toshihide , Oniki Takahiro , Nomura Miwa , Nakamura Kenichiro , Abe Yoshitake , Hazama Yusuke , Ueyama Hidetsugu 
Published: March 2009

AbstractPrevious studies have documented the presence of rimmed vacuoles, atrophic fibers, and increased lysosomal cathepsin activity in skeletal muscle from animal models of chloroquine‐induced myopathy, suggesting that muscle fibers in this type of myopathy may be degraded via the lysosomal‐proteolysis pathway. Given recent evidence of abnormal ubiquitin accumulation in rimmed vacuoles, in this study we chose to examine the significance of the ubiquitin–proteasome proteolytic system in the process of muscle fiber destruction in experimental chloroquine myopathy. Expression of ubiquitin, 26S proteasome proteins, and ubiquitin ligases, such as muscle‐specific RING finger‐1 (MuRF‐1) and atrogin‐1/muscle atrophy F‐box protein (MAFbx), was analyzed in innervated and denervated rat soleus muscles after treatment with either saline or chloroquine. Abnormal accumulation of rimmed vacuoles was observed only in chloroquine‐treated denervated muscles. Ubiquitin and proteasome immunostaining, and ubiquitin, MuRF‐1, and atrogin‐1/MAFbx mRNAs were significantly increased in denervated soleus muscles from saline‐ and chloroquine‐treated rats when compared with contralateral innervated muscles. Further, ubiquitin and ubiquitin ligase mRNA levels were higher in denervated muscles from chloroquine‐treated rats when compared with saline‐treated rats. These data demonstrate increased proteasomes and ubiquitin in denervated muscles from chloroquine‐treated rats and suggest that the ubiquitin–proteasome proteolysis pathway as well as the lysosomal‐proteolysis pathway mediate muscle fiber destruction in experimental chloroquine myopathy. Muscle Nerve 39: 521–528, 2009
Synthesis, characterization, and polymerization of brominated benzoxazine monomers and thermal stability/flame retardance of the polymers generated
Authors: Li Shengfang , Huang Weidong , Liu Xianli , Yu Xin , Xiao Wensheng 
Published: March 2009

AbstractNovel monofunctional brominated benzoxazine 3‐(2,4,6‐tribromophenyl)‐3,4‐dihydro‐2H‐1,3‐benzoxazine (P‐bra) and bifunctional brominated benzoxazine 6,6′‐bis(3‐(2,4,6‐tribromophenyl)‐3,4‐dihydro‐2H‐1,3‐benzoxazinyl) isopropane (B‐bra) were prepared and highly thermally stable polybenzoxazines were obtained by the thermal cure of the corresponding benzoxazines monomers. The chemical structures of these novel monomers were confirmed by FITR, 1H‐NMR and elemental analysis. FTIR spectra and differential scanning calorimetry (DSC) suggested that the polymerization was thermally initiated and occurred via ring‐opening of the monomer in each case. Thermogravimetric analysis (TGA) indicated that brominatation could have a profound effect on increasing char yield and on thermal degradation temperatures. The results of UL‐94 burn test showed that the polybenzoxazines prepared from P‐bra and B‐bra had good flame retardance. Copyright © 2009 John Wiley & Sons, Ltd.
Moving through deprived neighbourhoods
Authors: Clark Andrew 
Published: March 2009

AbstractThe paper explores representations and experiences of residential mobility into and out of deprived urban neighbourhoods. It identifies a particular representation of mobility that suggests that moving in should be avoided and moving out expected. This paper considers this view by exploring experiences of mobility in two deprived urban neighbourhoods. In considering the migration biographies of two neighbouring households, the paper reveals how such biographies provide a way of understanding migration decision‐making in the context of a life‐story. It also reveals ways in which mobility can impact upon how representations of place and individual identities are interpreted and presented. In conclusion, the paper cautions against the uncritical adoption of the term ‘culture of migration’. Copyright © 2009 John Wiley & Sons, Ltd.