bluuebunny/crossref_metadata_2025 huggingface dataset:
Surface characteristics at Dome A, Antarctica: first measurements and a guide to future ice-coring sites
Authors: Cunde Xiao , Yuansheng Li , Allison Ian , Shugui Hou , Dreyfus Gabrielle , Barnola Jean-Marc , Jiawen Ren , Lingen Bian , Shenkai Zhang , Kameda Takao
Published: June 2008

An assessment of the glaciological and meteorological characteristics of Dome A, the summit of the East Antarctic ice sheet, is made based on field investigations during the austral summer of 2004/05. Knowledge of these characteristics is critical for future international studies such as deep ice-core drilling. The assessment shows that: (1) Dome A is characterized by a very low 10m depth firn temperature, –58.3˚C (nearly 3˚C lower than at EPICA Dome C and 1˚C lower than at Vostok). (2) Automatic weather station (AWS) measurements of snow surface height and reference layers in a snow pit indicate the present-day snow accumulation rate at Dome A is within the range 1–3cmw.e. a–1. Densification models suggest a range of 1–2cmw.e. a–1. This is lower than at other sites along the ice divide of East Antarctica (IDEA). Annual layers at Dome A are thus potentially thinner than at other sites, so that a longer record is preserved in a given ice thickness. (3) The average wind speed observed at Dome A (<4ms–1) is lower than at other sites along IDEA. Together, these parameters, combined with radio-echo sounding data and information on the subglacial drainage distribution beneath Dome A, suggest Dome A as a candidate site for obtaining the oldest ice core.
Spatial and temporal variability in the snowpack of a High Arctic ice cap: implications for mass-change measurements
Authors: Bell Christina , Mair Douglas , Burgess David , Sharp Martin , Demuth Michael , Cawkwell Fiona , Bingham Robert , Wadham Jemma
Published: June 2008

Interpretation of ice mass elevation changes observed by satellite altimetry demands quantification of the proportion of elevation change which is attributable to variations in firn densification. Detailed stratigraphic logging of snowpack structure and density was carried out at ~1km intervals along a 47 km transect on Devon Ice Cap, Canada, in spring (pre-melt) and autumn (during/ after melt) 2004 and 2006 to characterize seasonal snowpack variability across the full range of snow facies. Simultaneous meteorological measurements were gathered. Spring (pre-melt) snowpacks show low variability over large spatial scales, with low-magnitude changes in density. The end-of-summer/ autumn density profiles show high variability in both 2004 and 2006, with vastly different melt regimes generating dissimilar patterns of ice-layer formation over the two melt seasons. Dye-tracing experiments from spring to autumn 2006 reveal that vertical and horizontal distribution of meltwater flow within and below the annual snowpack is strongly affected by the pre-existing, often subtle stratigraphic interfaces in the snowpack, rather than its bulk properties. Strong interannual variability suggests that using a simple relationship between air temperature, elevation and snowpack densification to derive mass change from measurements of elevation change across High Arctic ice caps may be misguided. Melt timing and duration are important extrinsic factors governing snowpack densification and ice-layer formation in summer, rather than averaged air temperatures.
Snow depth in eastern Europe in relation to circulation patterns
Authors: Bednorz Ewa , Wibig Joanna
Published: June 2008

Rotated principal components of the 500 hPa geopotential heights in the Euro-Atlantic sector are used as indicators of circulation pattern intensity. Daily snow-cover depth data for the years 1951–95 from 71 eastern European stations are examined. Maps of linear correlation coefficient between monthly change in snow depth and rotated principal components are presented. The positive and negative extremes of each circulation pattern are analyzed, and positive and negative snow-depth signals indicated. A daily analysis of relationships between snow depth and circulation pattern is performed for three locations. The strongest impact of the atmospheric circulation on changes in snow depth is observed in the south and west of the study area, where the eastern European (EE) and central European circulation patterns are found to have the greatest impact. The North Atlantic Oscillation (NAO) impact on the snow depth in eastern Europe is limited to the beginning and the end of winter. Snow cover has low variability in northeastern Europe (where the Scandinavian (SC) pattern is of greatest importance) and low sensitivity to change in the atmospheric circulation. The decrease in snow-cover depth observed in spring is related to the NAO, SC and EE patterns, the latter being important for snow-cover depth fluctuations over northeastern Europe in April.
Phylogenetic analyses of two mitochondrial metabolic genes sampled in parallel from angiosperms find fundamental interlocus incongruence
Authors: Duvall Melvin R. , Robinson Jace W. , Mattson Jeremy G. , Moore Anni
Published: June 2008

Plant molecular phylogeneticists have supported an analytical approach of combining loci from different genomes, but the combination of mitochondrial sequences with chloroplast and nuclear sequences is potentially problematic. Low substitution rates in mitochondrial genes should decrease saturation, which is especially useful for the study of deep divergences. However, individual mitochondrial loci are insufficiently informative, so that combining congruent loci is necessary. For this study atp1 and cox1 were selected, which are of similar lengths, encode components of the respiratory pathway, and generally lack introns. Thus, these genes might be expected to have similar functional constraints, selection pressures, and evolutionary histories. Strictly parallel sampling of 52 species was achieved as well as six additional composite terminals with representatives from the major angiosperm clades. However, analyses of the separate loci produced strongly incongruent topologies. The source of the incongruence was investigated by validating sequences with questionable affinities, excluding RNA‐edited nucleotides, deleting taxa with unexpected phylogenetic associations, and comparing different phylogenetic methods. However, even after potential artifacts were addressed and sites and taxa putatively associated with conflict were excluded, the resulting gene trees for the two mitochondrial loci were still substantially incongruent by all measures examined. Therefore, combining these loci in phylogenetic analysis may be counterproductive to the goal of fully resolving the angiosperm phylogeny.
Multiple hybridization in the Aristolochia kaempferi group (Aristolochiaceae): evidence from reproductive isolation and molecular phylogeny
Authors: Watanabe Kana , Ohi‐Toma Tetsuo , Murata Jin
Published: June 2008

Hybridization via distributional changes should be an important factor for plant speciation. Previous cpDNA analyses of the Aristolochia kaempferi group, comprising six taxa in East Asia, showed a distinct phylogeographic structure resulting from distributional changes brought about by paleoclimatic oscillations. However, the cpDNA phylogeny was incongruent with morphologically defined taxa. To explore the evolutionary processes responsible for the inconsistency between cpDNA and morphology, we made artificial crosses and performed phylogenetic analyses using multiple nuclear markers. All crosses among different taxa or cpDNA clades set fruit, if crossing direction is not considered. The five nuclear phylogenies mostly did not support either the taxa or the cpDNA clades. A combined analysis of cpDNA and the PI exon revealed the two major lineages in the group, lacking a prezygotic isolating barrier between them. However, an asymmetric prezygotic isolating barrier occurs between populations of the Japanese main islands and of other areas that belong to different cpDNA subclades. It seems reasonable to conclude that the development of a prezygotic isolating mechanism is not necessarily proportional to the degree of genetic divergence. These results suggested that species boundaries within the group are blurred due to speciational processes associated with multiple hybridization and introgression resulting from repeated contacts among differentiated populations.
Patterns of introduction and diversification of Vanilla planifolia (Orchidaceae) in Reunion Island (Indian Ocean)
Authors: Bory Severine , Lubinsky Pesach , Risterucci Ange‐Marie , Noyer Jean‐Louis , Grisoni Michel , Duval Marie‐France , Besse Pascale
Published: June 2008

The cultivated species Vanilla planifolia is a typical example of a crop introduced from its area of origin (America) to new regions where natural pollinators are absent. Although the Vanilla cultivars are exclusively vegetatively propagated, a high degree of phenotypic variation is observed among the cultivars in their introduction areas such as Reunion Island. To test several hypotheses explaining this variation—different introduction events, somatic mutations and sexual reproduction (through manual pollination)—we used AFLP markers to elucidate the patterns of introduction of V. planifolia. Most of the accessions cultivated in the world were derived from a single accession, possibly the Mexican cultivar Mansa. The patterns of diversification of this cultivated species were also studied and compared with other cultivated (V. tahitensis) and wild (V. pompona and V. bahiana) species. Except for one particular phenotype (‘Aiguille’), which may come from sexual reproduction, cultivated accessions exhibit very low levels of genetic diversity. They have evolved by the accumulation of point mutations through vegetative multiplication. The genetic diversity revealed could not explain the phenotypic diversity, which may be related to epigenetics or polyploidy. This new understanding of the basis of genetic diversity of vanilla may assist to improve management of genetic resources.
To grow or to seed: ecotypic variation in reproductive allocation and cone production by young female Aleppo pine (Pinus halepensis, Pinaceae)
Authors: Climent José , Prada Mª. Aránzazu , Calama Rafael , Chambel Mª. Regina , de Ron David Sánchez , Alía Ricardo
Published: June 2008

Age and size at the first reproduction and the reproductive allocation of plants are linked to different life history strategies. Aleppo pine only reproduces through seed, and, as such, early female reproduction confers high fitness in its infertile highly fire‐prone habitats along the Mediterranean coast because life expectancy is short. We investigated the extent of ecotypic differentiation in female reproductive allocation and examined the relation between early female reproduction and vegetative growth. In a common‐garden experiment, the threshold age and size at first female reproduction and female reproductive allocation at age seven differed significantly among Aleppo pine provenances of ecologically distinct origin. Significant correlations among reproductive features of the provenances and the ecological traits of origin were found using different analytical tools. In nonlinear models of cone counts vs. stem volume, medium‐sized trees (not the largest trees) produced the highest cone yield, confirming that, at the individual level, early female reproduction is incompatible with fast vegetative growth. The contribution of founder effects and adaptation to contrasting fire regimes may be confounding factors. But considering all traits analyzed, the geographical patterns of resource allocation by Aleppo pine suggest ecotypic specialization for either resource‐poor (favoring early reproduction) or resource‐rich (favoring vegetative growth) habitats.
Self‐Sterilized EVOH‐TiO2 Nanocomposites: Interface Effects on Biocidal Properties
Authors: Cerrada Maria L. , Serrano Cristina , Sánchez‐Chaves Manuel , Fernández‐García Marta , Fernández‐Martín Fernando , de Andrés Alicia , Riobóo Rafael J. Jiménez , Kubacka Anna , Ferrer Manuel , Fernández‐García Marcos
Published: June 2008

Nanocomposite materials obtained by TiO2 incorporation into ethylene–vinyl alcohol copolymers, extensively used in food packaging, are prepared via a straightforward melting process. The structural characteristics of the nanocomposites are examined using wide and small angle X‐ray scattering (WAXS/SAXS), and vibrational infrared and Raman spectroscopies. A microscopy (SEM/TEM) study shows that the materials obtained are highly homogeneous at the nanometric scale, exhibiting an intimate contact between both the organic and inorganic components. TiO2 incorporation into this polymer matrix renders self‐sterilized nanocomposite materials upon light excitation, which are tested against nine micro‐organisms (gram‐positive and gram‐negative bacteria, cocci, and yeasts) typically involved in food contamination and/or degradation. Overall, the nanocomposites display an impressive performance in the killing of all micro‐organisms with a maximum for an oxide content between 2–5 wt %. The measurement of the physico‐chemical properties together with the structural characterization of the materials provide conclusive evidence that the nanocomposites biocidal capability born of the nanometric organo‐inorganic interface and rationalize the existence of a maximum as a function of the TiO2 content.
Fullerene Resist Materials for the 32 nm Node and Beyond
Authors: Gibbons Francis P. , Robinson Alex P. G. , Palmer Richard E. , Diegoli Sara , Manickam Mayandithevar , Preece Jon A.
Published: June 2008

Current resist materials cannot simultaneously meet the sensitivity, resolution and line width roughness (LWR) requirements set out by the International Technology Roadmap for Semiconductors (ITRS) for the 32nm node and beyond. Here we present a fullerene‐based, chemically amplified resist system, which demonstrates the potential to fulfill these requirements for next generation lithography. A chemically amplified fullerene resist was prepared, consisting of the derivative MF07‐01, an epoxide crosslinker, and a photoacid generator, such as triarylsulfonium hexafluoroantimonate. The sensitivity of this resist was shown to be between 5 and 10 µC cm−2 at 20 keV for various combinations of post‐application bake and post‐exposure bake conditions. Using 30 keV electron beam exposure, sparse patterns with 15 nm resolution were demonstrated, whilst for dense patterns a half‐pitch of 25 nm could be achieved. The LWR for the densely patterned features is ∼4 nm. The etch durability of the fullerene CA system was shown to be comparable to that of SAL601, a common novolac‐based commercial resist, at almost four times that of silicon.
Tough Lessons From Bone: Extreme Mechanical Anisotropy at the Mesoscale
Authors: Seto Jong , Gupta Himadri S. , Zaslansky Paul , Wagner H. Daniel , Fratzl Peter
Published: June 2008

Bone is mechanically and structurally anisotropic with oriented collagen fibrils and nanometer‐sized mineral particles aggregating into lamellar or woven bone.[1] Direct measurements of anisotropic mechanical properties of sublamellar tissue constituents are complicated by the existence of an intrinsic hierarchical architecture. Methods such as nanoindentation provide insight into effective modulus values; however, bulk material properties cannot sufficiently be characterized since such measurements represent properties of near‐surface volumes and are partially averaged over fibril orientations.[2–5] In this study, we focus on the material properties of bone at one single level of hierarchy. By measuring properties of individual parallel‐fibered units of fibrollamellar bone under tension under controlled humidity conditions, an unusually high anisotropy is found. Here, we clearly demonstrate ratios as large as 1:20 in elastic modulus and 1:15 in tensile strength between orientations perpendicular and parallel to the main collagen fiber orientation in native wet bone; these ratios reduce to 1:8 and 1:7, respectively, under dry conditions. This extreme anisotropy appears to be caused by the existence of periodic, weak interfaces at the mesoscopic length scale. These interfaces are thought to be relevant to the proper mechanical and physiological performance of bone.
Iodobenzene Diacetate/Tetrabutylammonium Iodide‐Induced Aziridination of N‐Tosylimines with Activated Methylene Compounds under Mild Conditions
Authors: Fan Renhua , Ye Yang
Published: June 2008

Aziridination of N‐tosylimines with activated methylene compounds induced by iodobenzene diacetate [PhI(OAc)2] and tetrabutylammonium bromide [Bu4NBr] afforded the corresponding 2,2‐difunctionalized aziridines in good yields with the aid of a catalytic amount of base. The reaction is hypothesized to proceed via a tandem nucleophilic addition‐oxidative cyclization pathway.
Expanding the Scope of Biocatalysis: Oxidative Biotransformations on Solid‐Supported Substrates
Authors: Brooks Sarah J. , Coulombel Lydie , Ahuja Disha , Clark Douglas S. , Dordick Jonathan S.
Published: June 2008

Oxidative biocatalytic reactions were performed on solid‐supported substrates, thus expanding the repertoire of biotransformations that can be carried out on the solid phase. Various phenylacetic and benzoic acid analogues were attached to controlled pore glass beads via an enzyme‐cleavable linker. Reactions catalyzed by peroxidases (soybean and chloro), tyrosinase, and alcohol oxidase/dehydrogenase gave a range of products, including oligophenols, halogenated aromatics, catechols, and aryl aldehydes. The resulting products were recovered following cleavage from the beads using α‐chymotrypsin to selectively hydrolyze a chemically non‐labile amide linkage. Controlled pore glass (CPG) modified with a polyethylene glycol (PEG) linker afforded substantially higher product yields than non‐PEGylated CPG or non‐swellable polymeric resins. This work represents the first attempt to combine solid‐phase oxidative biotransformations with subsequent protease‐catalyzed cleavage, and serves to further expand the use of biocatalysis in synthetic and medicinal chemistry.
Proline‐Mediated Enantioselective Construction of Tetrahydropyridines via a Cascade Mannich‐Type/Intramolecular Cyclization Reaction
Authors: Han Rong‐Gang , Wang Yao , Li Yu‐Ye , Xu Peng‐Fei
Published: June 2008

A highly diastereo‐ and enantioselective synthesis of 2,3‐disubstituted tetrahydropyridines was accomplished via a proline‐mediated cascade Mannich‐type/intramolecular cyclization reaction from preformed N‐PMP (p‐methoxyphenyl) aldimines and inexpensive aqueous tetrahydro‐2H‐pyran‐2,6‐diol.
Chemical Design of Nanoparticle Probes for High‐Performance Magnetic Resonance Imaging
Authors: Jun Young‐wook , Lee Jae‐Hyun , Cheon Jinwoo
Published: June 2008

Synthetic magnetic nanoparticles (MNPs) are emerging as versatile probes in biomedical applications, especially in the area of magnetic resonance imaging (MRI). Their size, which is comparable to biological functional units, and their unique magnetic properties allow their utilization as molecular imaging probes. Herein, we present an overview of recent breakthroughs in the development of new synthetic MNP probes with which the sensitive and target‐specific observation of biological events at the molecular and cellular levels is possible.
Thorpe–Ingold Effect on the Helicity of Chiral Alternating Silylene‐Divinylarene Copolymers
Authors: Yeh Mei‐Yu , Luh Tien‐Yau
Published: June 2008

The concept of the Thorpe–Ingold effect has been used to rationalize the helicity of the silylene‐spaced divinylarene copolymers having chiral substituents. Diisopropylsilylene‐spaced divinylbenzene copolymers having chiral 2‐methylbutoxy substituents have been shown to exhibit a helical conformation. The presence of the bulky isopropyl substituents on silicon would render each of the monomeric units in these copolymers to favor a syn–syn conformation. The copolymer would thus be more folded to form helical morphology as revealed by the notable enhancement of the circular dichroic intensity. The reversible temperature‐dependent circular dichroism (CD) profiles further support the stable helical conformation for the copolymers 4 b and 5 b.
Central bisectionectomy for centrally located hepatocellular carcinoma
Authors: Lee J G , Choi S B , Kim K S , Choi J S , Lee W J , Kim B R
Published: June 2008

Background

Central bisectionectomy, which involves the removal of the central hepatic segments (IVA, IVB, V, VIII) for hepatocellular carcinoma (HCC), is performed to reduce the volume of resected liver and to overcome the problem of insufficient future residual volume.

Methods

Twenty-seven patients with HCC underwent central bisectionectomy from January 1998 to April 2007 in one hospital. The surgical techniques, clinicopathological characteristics and outcomes were reviewed.

Results

The median operating time was 330 min. Twelve patients developed postoperative complications and two died. The most common complication, occurring in five patients, was bile duct injury leading to biloma or bile leakage. Median follow-up was 19·1 (range 1·4–102·2) months and eight patients developed a recurrence. Twenty-four patients were alive at the time of writing.

Conclusion

Although biliary complications occur somewhat frequently, central bisectionectomy in centrally located HCC can be performed safely to preserve liver volume.
Gold‐Catalyzed Synthesis of Chroman, Dihydrobenzofuran, Dihydroindole, and Tetrahydroquinoline Derivatives
Authors: Hashmi A. Stephen K. , Rudolph Matthias , Bats Jan W. , Frey Wolfgang , Rominger Frank , Oeser Thomas
Published: June 2008

Different furans containing an ynamide or alkynyl ether moiety in the side chain were prepared. The gold‐catalyzed transformation of these compounds delivered dihydroindole, dihydrobenzofuran, chroman, and tetrahydroquinoline derivatives at room temperature through very fast reactions. Furthermore, the stabilizing effect of the heteroatom directly attached to the intermediate arene oxides led to highly selective reactions, even in the case of only mono‐substituted furans, which is quite different from previous results obtained with non‐heteroatom‐substituted alkynes.
New Insights on the Mechanism of the Transition‐Metal Stereoselective Olefin Cyclopropanation
Authors: Soriano Elena , Marco‐Contelles José
Published: June 2008

We have carried out a theoretical analysis of the intermolecular cyclopropanation of propargylic esters with alkenes. DFT calculations allow us to propose a reaction mechanism, and provide explanations for the reasons behind the difference between the inter‐ and intramolecular versions of this process. The results strongly suggest that the entropic effects could modulate the operative mechanism and account for the mechanistic discrepancy. The calculated model also justifies the experimental stereoselectivity on the basis of intra‐ and intermolecular interactions. In addition, we have taken into account other transformations of propargylic carboxylates catalyzed by late transition metals, and the results rationalize the accumulated experimental observations.
Preparation of 2,4‐Disubstituted Cyclopentenones by Enantioselective Iridium‐Catalyzed Allylic Alkylation: Synthesis of 2′‐Methylcarbovir and TEI‐9826
Authors: Dübon Pierre , Schelwies Mathias , Helmchen Günter
Published: June 2008

A broadly applicable synthesis of chiral 2‐ or 2,4‐substituted cyclopent‐2‐enones has been developed by combining asymmetric iridium‐catalyzed allylic alkylation reactions and ruthenium‐catalyzed ring‐closing metathesis. Enantiomeric excesses (ee values) in the range of 95–99 % ee have been achieved. This method offers a straightforward access to biologically active prostaglandins of the PGA type. As an example, an enantioselective synthesis of the prostaglandin‐analogue 13,14‐dihydro‐15‐deoxy‐Δ7‐prostaglandin‐A1‐methyl ester (TEI‐9826) has been carried out. Furthermore, the carbonucleoside 2′‐methylcarbovir has been prepared from O‐protected 4‐hydroxymethyl‐2‐methyl‐cyclopent‐2‐enone by Pd‐catalyzed allylic amination.
Fluorescent Hydrophobic Zippers inside Duplex DNA: Interstrand Stacking of Perylene‐3,4:9,10‐tetracarboxylic Acid Bisimides as Artificial DNA Base Dyes
Authors: Baumstark Daniela , Wagenknecht Hans‐Achim
Published: June 2008

Perylene‐3,4:9,10‐tetracarboxylic acid bisimides (PBs) were incorporated synthetically into oligonucleotides by using automated DNA building‐block chemistry. The 2′‐deoxyribofuranoside of the natural nucleosides was replaced by (S)‐aminopropan‐2,3‐diol as an acyclic linker between the phosphodiester bridges that is tethered to one of the imide nitrogen atoms of the PB dye. The S configuration of this linker was chosen to mimic the stereochemical situation at the 3′‐position of the natural 2′‐deoxyribofuranosides. By using this strategy, up to six PB dyes were incorporated in the middle of 18‐mer DNA duplexes by using interstrand alternating sequences of PBs with thymines or an abasic site analogue. Both PB dimers and PB hexamers as artificial base substitutions inside the duplexes yield characteristic excimer‐type fluorescence. The stacking properties of the PB chromophores are modulated by the presence or absence of thymines opposite the PB modification site in the counterstrand. The interstrand PB dimers can be regarded as hydrophobically interacting base pairs, which display a characteristic fluorescence readout signal. Hence, for the PB hexamers, we proposed a zipperlike recognition motif that is formed inside duplex DNA. The PB zipper shows characteristic excimer‐type emission as a fluorescence readout signal for the pairing interaction.
Reactivity of Ammonia Ligands of the Antitumor Agent Cisplatin: A Unique Dodecanuclear Pt4,Pd4,Ag4 Platform for Four Cytosine Model Nucleobases
Authors: Kampf Gunnar , Sanz Miguel Pablo J. , Morell Cerdà Marta , Willermann Michael , Schneider Alexandra , Lippert Bernhard
Published: June 2008

The reaction of a potential mono(nucleobase) model adduct of cisplatin, cis‐[Pt(NH3)2(1‐MeC‐N3)(H2O)]2+ (6; 1‐MeC: 1‐methylcytosine), with the electrophile [Pd(en)(H2O)2]2+ (en: ethylenediamine) at pH≈6 yields a kinetic product X which is likely to be a dinuclear Pt,Pd complex containing 1‐MeC−‐N3,N4 and OH bridges, namely cis‐[Pt(NH3)2(1‐MeC−‐N3,N4)(OH)Pd(en)]2+. Upon addition of excess Ag+ ions, conversion takes place to form a thermodynamic product, which, according to 1H NMR spectroscopy and X‐ray crystallography, is dominated by a μ‐NH2 bridge between the PtII and PdII centers. X‐ray crystallography reveals that the compound crystallizes out of solution as a dodecanuclear complex containing four PtII, four PdII, and four Ag+ entities: [{Pt2(1‐MeC−‐N3,N4)2(NH3)2(NH2)2(OH)Pd2(en)2Ag}2{Ag(H2O)}2](NO3)10⋅ 6 H2O (10) is composed of a roughly planar array of the 12 metal ions, in which the metal ions are interconnected by μ‐NH2 groups (between Pt and Pd centers), μ‐OH groups (between pairs of Pt atoms), and metal–metal donor bonds (Pt→Ag, Pd→Ag). The four 1‐methylcytosinato ligands, which are stacked pairwise, as well as the four NH3 ligands and parts of the en rings, are approximately perpendicular to the metal plane. Two of the four Ag ions (Ag2, Ag2′) of 10 are labile in solution and show the expected behavior of Ag+ ions in water, that is, they are readily precipitated as AgCl by Cl− ions. The resulting pentanuclear complex [Pt2Pd2Ag(1‐MeC−)2(NH2)2(OH)(NH3)2(en)2](NO3)4⋅7 H2O (11) largely maintains the structural features of one half of 10. The other two Ag+ ions (Ag1, Ag1′) of 10 are remarkably unreactive toward excess NaCl. In fact, the pentanuclear complex [Pt2Pd2AgCl(1‐MeC−)2(NH2)2(OH)(NH3)2(en)2](NO3)3⋅4.5 H2O (12), obtained from 10 with excess NaCl, displays a Cl− anion bound to the Ag center (2.459(3) Å) and is thus a rare case of a crystallized “AgCl molecule”.
Theoretically Rational Designs of Transport Organic Semiconductors Based on Heteroacenes
Authors: HE Yuan‐Hang , HUI Ren‐Jie , YI Yuan‐Ping , SHUAI Zhi‐Gang
Published: June 2008

A Marcus electron transfer theory coupled with an incoherent polaron hopping and charge diffusion model in combining with first‐principle quantum chemistry calculation was applied to investigating the effects of heteroatom on the intermolecular charge transfer rate for a series of heteroacene molecules. The influences of intermolecular packing and charge reorganization energy were discussed. It was found that the sulphur and nitrogen substituted heteroacenes were intrinsically hole‐transporting materials due to the reduced hole reorganization energy and the enhanced overlap between HOMOs. For the oxygen‐substituted heteroacene, it was found that both the electronic couplings and the reorganization energies for holes and electrons were comparative, indicating the application potential of ambipolar devices. Most interestingly, for the boron‐substituted heteroacenes, theoretical calculations predicted a promising electron‐transport material, which is rare for organic materials. These findings provide insights into rationally designing organic semiconductors with specific properties.
Binary Assembly of Au Nanoparticles with Controllable Two‐dimensional Architecture Directed by Phosphate Backbone Modified Oligonucleotide
Authors: MA Yu‐Dan , GUO Yi , LI Jun , YANG Wen‐Sheng
Published: June 2008

A three complementary strand oligonucleotide system was employed to assemble two different‐sized, 15 and 25 nm, Au nanoparticles into binary two‐dimensional (2D) structures. First, two non‐complementary strands of phosphate backbone modified oligonucleotides (PM oligo‐DNA) were loaded on the surface of the 15 and 25 nm Au nanoparticles, respectively. Upon the addition of the third linker DNA, which was half complementary to each of the modified DNA, the Au nanoparticles would be assembled to binary 2D aggregates. The number of the 15 nm Au nanoparticles around a 25 nm Au naoparticle can be readily controlled by the length of the DNA helix used.
A Thermogravimetric Study of Cotton Fabric Flame‐Retardancy by Means of Impregnation with Red Phosphorus
Authors: MOSTASHARI S. M. , FAYYAZ F.
Published: June 2008

The effect of red phosphorus was found to be effective for flame‐retardancy of a pure cotton fabric. The laundered bone‐dried weighed samples were impregnated with red phosphorus at suitable concentrations. Vertical flame spread test was accomplished. The optimum add‐on value to impart flame‐retardancy onto cotton fabric was determined around 3.95 g of red phosphorus per 100 g of fabric. TG/DTG curves of treated samples showed a well‐timed weight loss occurred with regard to untreated specimens. This illustrates the sufficiency of impregnation and support its catalytic action on flame‐retardancy, which is compliance with data obtained via flammability test. The results are in favor of "Chemical Action Theory", "Gas Theory" and "Condensed Phase Retardation".
Extraction and Detection of mRNA from a Single K562 Cell Based on the Functionalized Superparamagnetic Nanoparticles
Authors: ZHU Long‐Zhang , YU Ping‐Guo , SHEN He‐Bai , JIA Neng‐Qin , LONG De‐Hong , ZHOU Hai‐Qing
Published: June 2008

A novel and promising method was developed to extract mRNA from a single cell based on the functionalized superparamagnetic nanoparticles. The oligo(dT)‐coupled magnetite nanobeads were synthesized by the reaction of oligo(dT) and thiol‐modified γ‐Fe2O3 nanoparticles. The single cell was isolated from the massive cultivation according to a semi‐quantum approaching technique and then lysed before mRNA separation. The oligo(dT)‐coupled magnetite nanobeads were added to the crude lysates and then magnetic separation was preformed to get mRNA. The mRNA amplification through a two‐step RT‐PCR method was achieved. The agarose gel electrophoresis of PCR products after amplification shows that mRNA could be extracted from a single cell successfully.
Selective Voltammetric Determination of Uric Acid in the Presence of Ascorbic Acid at Ordered Mesoporous Carbon Modified Electrodes
Authors: WEN Yan‐Li , JIA Neng‐Qin , WANG Zhi‐Yong , SHEN He‐Bai
Published: June 2008

A novel chemically modified electrode was fabricated by immobilizing ordered mesoporous carbon (OMC) onto a glassy carbon (GC) electrode. The electrocatalytic behavior of the OMC modified electrode towards the oxidation of uric acid (UA) and ascorbic acid (AA) was studied. Compared to a glassy carbon electrode, the OMC modified electrode showed a faster electron transfer rate and reduced the overpotentials greatly. Furthermore, the OMC modified electrode resolved the overlapping voltammetric responses of UA and AA into two well‐defined voltammetric peaks with peak separation of ca. 0.38 V. All results show that the OMC modified electrode has a good electrocatalytic ability to UA and AA, and has an excellent response towards UA even in the presence of high concentration AA.
Molecular Weight and Proposed Structure of the Angelica sinensis Polysaccharide‐iron Complex
Authors: WANG Kai‐Ping , CHEN Zhi‐Xiang , ZHANG Yu , WANG Pei‐Pei , WANG Ji‐Hong , DAI Li‐Quan
Published: June 2008

The molecular weight and the proposed structure of the Angelica sinensis polysaccharide‐iron complex (APIC) were studied. Fourier transform infrared spectroscopy, X‐ray powder diffraction, differential scanning calorimetry, transmission electron microscopy, electron paramagnetic resonance, thermogravimetric analysis, atomic force microscopy, and gel filtration chromatography were used to characterize APIC, which is a macromolecule complex composed of Angelica sinensis polysaccharide (ASP) and iron. The structure of APIC was proposed to be a polynuclear ferrihydrite core chelated firmly by an encircling framework of ASP chains, forming a core molecule, which is surrounded by a removable outer protective sheath of colloidal ASP. And the molecular formula of APIC was proposed to be {[(Fe2O3·2.2H2O)1043(ASP)32](ASP)12}, with MW=270000 Da.
Purification of Biliary Protein and Its Effect on Calcium Carbonate Mineralization
Authors: YAO Cheng‐Li
Published: June 2008

The biliary protein (BP) was isolated from pig bile by gel
filtration. The interaction between Ca2+ and protein was measured by
fluorescence spectra. The result showed that there was a strong coordination between biliary
protein and Ca2+. The CaCO3 crystals obtained in systems
with and without BP were characterized by scanning electron microscopy, Fourier transform
infrared spectrography and powder X‐ray diffractometry. The possible formation mechanism of
CaCO3 in biliary protein solution was discussed.
Synthesis, Structure and Characterization of Schiff Base Metal Complexes and Their Electrochemical Properties of Thionyl Chloride Reduction
Authors: CHE Tu‐Lin , GAO Quan‐Chang , ZHAO Jian‐She , ZHANG Gai
Published: June 2008

A symmetric tetradentate Schiff base ligand bis(3‐methoxysalicylidene)‐o‐phenylenediamine (H2L) was prepared. A series of transition metal complexes with this Schiff base ligand have been synthesized and structurally characterized by IR and elemental analysis. The catalysis for reduction of thionyl chloride was studied by means of constant resistance discharge. The result shows that [Mn(III)LCl(H2O)]CH3OH and [Co(II)HLCl(H2O)] have a good catalytic activity for the reduction of thionyl chloride, which improves the cell voltage, the rate of discharge, and the lifetime of Li/SOCl2 batteries.
Formation of Eu2O3 Nanorods through Solvothermal Routes by Surfactant Assistance
Authors: LI Tai‐Shan , LIU Shao‐Pu , CUI Zhi‐Min , LIU Zhong‐Fang
Published: June 2008

Eu2O3nanorods were synthesized and characterized. The crystallites of Eu2O(CO3)2·H2O nanorods and Eu2O3 nanorods were obtained by means of surfactant assistance, with aqueous butanol solution as the solvent and hexamethylene tetramine as the base. The characteristics of the nanorods were analyzed by transmission electron microscopy, high‐resolution transmission electron microscopy, scanning electron microscopy and X‐ray diffraction. The Eu2O3 nanorod is about 80–300 nm in diameter and 1–5 µm in length. The formation mechanism of the 1D products was also proposed.
Synthesis of α‐(Fluorophenyl)pyridine by Palladium‐Catalyzed Cross‐Coupling Reaction
Authors: XU Mao‐Liang , AN Zhong‐Wei , WANG Ge‐Yang , ZHOU Rui , DU Wei‐Song
Published: June 2008

A series of α‐(fluoro‐substituted phenyl)pyridines have been synthesized by means of a palladium‐catalyzed cross‐coupling reaction between fluoro‐substituted phenylboronic acid and 2‐bromopyridine or its derivatives. The reactivities of the phenylboronic acids containing di‐ and tri‐fluoro substituents with α‐pyridyl bromide were investigated in different catalyst systems. Unsuccessful results were observed in the Pd/C and PPh3 catalyst system due to phenylboronic acid containing electron‐withdrawing F atom(s). For the catalyst system of Pd(OAc)2/PPh3, the reactions gave moderate yields of 55% –80%, meanwhile, affording 10% –20% of dimerisation (self‐coupling) by‐products, but trace products were obtained in coupling with 2,4‐difluorophenylboronic acids because of steric hinderance. Pd(PPh3)4 was more reactive for boronic acids with sterically hindering F atom(s), and the coupling reactions gave good yields of 90% and 91% without any self‐coupling by‐product.
Asymmetric Total Synthesis of (−)‐Cladospolide B
Authors: WANG Wen‐Kuan , ZHANG Ji‐Yong , HE Jin‐Mei , TANG Shi‐Bing , WANG Xiao‐Lei , SHE Xue‐Gong , PAN Xin‐Fu
Published: June 2008

An enantioselective total synthesis of (−)‐cladospolide B was described. The key steps in this synthesis include(a) a Sharpless asymmetric dihydroxylation to elaborate syn diol at C‐4 and C‐5 positions; (b) a Mitsunobu esterification to reverse the configuration at C‐11 from (S) to (R); and (c) a ring‐closing metathesis to access the 12‐membered macrocyclic ring.
Highly Efficient Biomimetic Oxidation of Sulfide to Sulfone by Hydrogen Peroxide in the Presence of Manganese meso‐Tetraphenylporphyrin
Authors: ZHOU Xian‐Tai , JI Hong‐Bing , YUAN Qiu‐Lan , XU Jian‐Chang , PEI Li‐Xia , WANG Le‐Fu
Published: June 2008

Low amount of manganese meso‐tetraphenyl porphyrin [Mn(TPP)] was used for highly efficient selective oxidation of sulfide to sulfone by hydrogen peroxide at room temperature. Sulfones were produced directly with yields generally around 90% while the catalyst concentration was only 4×10−5 mol·L−1. In a large‐scale experiment of thioanisole oxidation, the isolated yield of sulfone (87%) was obtained and the turnover number (TON) reached up to 8×106, which is the highest TON for the oxidation systems of sulfide to sulfone catalyzed by metalloporphyrins.
Selective and Efficient Oxidation of Aldehydes to Their Corresponding Carboxylic Acids Using H2O2/HCl in the Presence of Hydroxylamine Hydrochloride
Authors: BAHRAMI Kiumars , KHODAEI Mohammad Mehdi , KAMALI Shahab
Published: June 2008

A wide variety of aldehydes were efficiently converted to their corresponding carboxylic acids in high yields using H2O2/HCl in the presence of hydroxylamine hydrochloride. In addition, selective oxidation of aldehydes in the presence of other functional groups such as hydroxyl group, carbon‐carbon double bond and other heteroatoms can be considered a noteworthy advantage of this method.
Crystal Structure and Properties of the Carboxylic Acid Derivatives of Schizonpeta mulifida (L.) Briq.
Authors: LIU Ju‐Tao , YU Ji‐Cheng , JIANG Hui‐Ming , ZHANG Li‐Ying , ZHAO Xiao‐Jing , FAN Sheng‐Di
Published: June 2008

The chemical constituents of the carboxylic acid derivatives from the ear of Schizonepeta were investigated. 1H and 13C NMR chemical shifts of the carboxylic acid derivatives were accurately assigned. Two carboxylic acid derivative constituents were separated by a silica gel column. The structures were elucidated by the physical and chemical properties, IR, 1H NMR, 13C NMR, MALDI‐TDF‐MS and X‐ray single crystal diffractometry. They were identified as 3‐imino‐N‐(α‐imidoethylamino)butyrolactam and neononane tetracid, respectively. The antitumoral activity on liver tumor cells SMMC‐7721 was determined in vitro. The experimental results showed that the former was better than the latter, and with increasing the concentration of the former the inhibitory activity was increased.
Synthesis and Biological Activities of Alkyl Substituted Triazolethione Schiff Base
Authors: SUN Xiao‐Hong , TAO Yan , LIU Yuan‐Fa , CHEN Bang , JIA Ying‐Qi , YANG Jian‐Wu
Published: June 2008

Eight Schiff bases have been synthesized using 3‐alkyl‐4‐amino‐1,2,4‐triazole‐5‐thione and substituted benzaldehyde as starting materials. The structures of the compounds have been confirmed by 1H NMR, IR and elemental analysis and their biological activities to five vegetable pathogens have been tested. The results showed that they exhibited good fungicidal activities.
Synthesis and Demulsibility of the Terpolymer Demulsifier of Acryl Resin
Authors: KANG Wan‐Li , MENG Ling‐Wei , ZHANG Hong‐Yan , LIU Shu‐Ren
Published: June 2008

Terpolymer demulsifier of acryl resin has been synthesized through solution polymerization with water as a dissolvent, potassium persulfate as an initiator and the monomers of methyl methacrylate, butyl acrylate and acrylic acid as starting materials. The effects of the reaction temperature, dripping time, the amount of monomers and initiator on the dehydration rate of the demulsifier were investigated by an orthogonal experiment. It shows that the stronger influence on the dehydration rate among six factors is reaction temperature, dripping time, and amount of catalyst, while monomer has weak influence. The performance of the demulsifier was evaluated under different demulsification time, temperatures and concentrations of the screened demulsifiers. The result shows that the dehydration rate of the demulsifier can reach over 67%, which is better than that by the emulsion polymerization way.
2‐(1H‐Benzotriazole‐1‐yl)‐1,1,3,3‐Tetramethyluronium Tetrafluoro Borate (TBTU) as an Efficient Coupling Reagent for the Esterification of Carboxylic acids with Alcohols and Phenols at Room Temperature
Authors: BALALAIE Saeed , MAHDIDOUST Maryam , ESHAGHI‐NAJAFABADI Rasoul
Published: June 2008

Esterification of carboxylic acids with alcohols and phenols by using 2‐(1H‐benzotriazole‐1‐yl)‐1,1,3,3‐tetramethyluronium tetrafluoroborate (TBTU) in the presence of triethylamine as a base proceeded smoothly under mild conditions to afford the corresponding esters in good to high yields in acetonitrile at room temperature.
Synthesis and Luminescent Properties of Two New Triphenylamine‐based Compounds with Hetero‐cyclic Ring as Conjugation Bridge
Authors: LI Qian‐Qian , DI Chong‐An , YU Gui , LIU Yun‐Qi , LI Zhen , QIN Jin‐Gui
Published: June 2008

Two new "D‐π‐D" type triphenylamine‐based compounds with a heterocyclic ring, furan or thiophene, as a conjugation bridge were synthesized through a normal Wittig reaction which exhibited good thermal stability and strong luminescence. The preliminary light‐emitting diode results indicate that they are promising candidates for the practical application.
A New Fluorescent Chemosensor for Cu2+ Based on 1,2,3,4,5,6,7,8,9,10‐Decahydroacridine‐1,8‐dione Fluorophore
Authors: LI Lin‐Bo , JI Shun‐Jun , LIU Yu
Published: June 2008

A new chemosensor for Cu2+ was synthesized based on 1,2,3,4,5,6,7,8,9,10‐decahydroacridine‐1,8‐dione dyes, which exhibited an obvious fluorescent selectivity to the sensing of Cu2+ ions over other cations, such as Na+, K+, Ca2+, Cd2+, Co2+, Hg2+, Mg2+, Mn2+, Ni2+, Zn2+, Ag+ and Pb2+. Moreover, it presented a fluorescent switch function when EDTA was added to the compound‐Cu2+ complex in examined systems.
Structures, Vibrational Spectra, and Relative Energetics of CH3COIO3 Isomers
Authors: GE Mao‐Fa , MA Chun‐Ping
Published: June 2008

The structures, vibrational spectra, relative energetics, and enthalpies of formation of CH3COIO3 isomers have been investigated with B3LYP, B3P86 and B3PW91 methods in conjugation with the 6‐31+G(d), 6‐311+G(d,p) and 6‐311++G(3df,3pd) basis sets. The CH3COOIO2 structure was found to be the most stable form among the isomers with an estimated enthalpy of formation of −314.6 kJ·mol−1. The enthalpies of formation for CH3COOOOI, CH3COOOIO and CH3COIO3 are −180.7, −184.9 and −50.6 kJ·mol−1, respectively. The implication of the formation of CH3COIO3 isomers from the atmospheric cross‐reactions of the acetylperoxy (CH3COO2) and iodine monoxide (IO) radicals was examined and the possible dissociation products of the most likely CH3COIO3 isomers were determined.
Theoretical and Experimental Study of Complex Ions from Reactions of Al+ (Cu+) with Amine Molecules
Authors: HU Zheng‐Fa , LUO Li , HU Yi‐Hua
Published: June 2008

The gas phase reactions of metal ions (Al+, Cu+) with amine molecules [CH3NH2=MA, (CH3)2NH=DMA] were investigated using a laser ablation‐molecular beam method. The directly associated product complex ions,Al+‐MA and Al+‐DMA, and the dehydrogenation product ions, Cu+(CH2NH) and Cu+(C2H5N), as well as hydrated ion Cu+(NC2H5·H2O), have been obtained and recorded from the reactions of the metal ions and organic amine molecules, and density functional theory (B3LYP) calculations have been performed to reveal the optimized geometry, energetics, and reaction mechanism of the title reactions with basis set 6‐311+G(d,p) adopted.
Ab initio and DFT Study of the Structural Properties and Thermochemistry of CH3S(O)2OONO2 Atmospheric Molecule and CH3S(O)2OO· Radical
Authors: GE Mao‐Fa , DU Lin , MA Yan‐Ping , HE Sheng‐Gui
Published: June 2008

The conformational properties of methanesulfonyl peroxynitrate, CH3S(O)2OONO2 (MSPN), and its radical decomposition products CH3S(O)2OO· and CH3S(O)2O· were studied by ab initio and density functional methods. The dihedral angle around the S–O and the O–O single bond are calculated to be −70.5° and −97.8° (B3LYP/6‐311++G(3df,3pd)), respectively. The principal unimolecular dissociation pathways for MSPN were studied using complete basis set (CBS) methods. The reaction enthalpies for the channels CH3S(O)2OONO2→ CH3S(O)2OO·+NO2 and CH3S(O)2OONO2→CH3S(O)2O·+NO3 were computed to be 111.0 and 140.9 kJ/mol, respectively. The enthalpies of formation at 298 K for MSPN and CH3S(O)2OO radical were predicted to be −358.2 and −281.3 kJ/mol, respectively.
Facile Biocatalytic Access to 9‐Fluorenylmethyl Polyglycosides: Evaluation of Antiviral Activity on Immunocompetent Cells
Authors: Tramice Annabella , Arena Adriana , De Gregorio Ambra , Ottanà Rosaria , Maccari Rosanna , Pavone Bernadette , Arena Nicoletta , Iannello Daniela , Vigorita Maria Gabriella , Trincone Antonio
Published: June 2008

The biological activities of a series of mono‐ and oligosaccharides (β‐xylosides and α‐glucosides) of 9‐fluorenylmethanol were investigated together with mono‐β‐galactoside and β‐glucoside of this aglycone, produced by biocatalytic routes. By using marine glycoside hydrolases and inexpensive donors such as maltose or xylan, access to mono‐α‐glucoside or mono‐β‐xyloside of 9‐fluorenylmethanol was obtained. Additionally, interesting polyglycoside derivatives were isolated. Biological testing indicated that in vitro treatment with these carbohydrate derivatives may influence the balance of cytokines in the environment of human peripheral blood mononuclear cells (PBMC), restricting the harmful effect of herpes simplex type 2 replication. In fact, these carbohydrate derivatives tested in WISH cells did not show any significant antiviral activity.
Ambipolar Transport in the Smectic E Phase of 2‐Propyl‐5′′‐Hexynylterthiophene Derivative over a Wide Temperature Range
Authors: Funahashi Masahiro , Zhang Fapei , Tamaoki Nobuyuki , Hanna Jun‐ichi
Published: June 2008

5‐Hexyl‐5′′‐hexynyl‐2,2′:5′,2′′‐terthiophene exhibits the smectic E phase below 200 °C and does not crystallize when it is cooled to −100 °C. Between 200 and −100 °C, non‐dispersive transport is observed for holes and electrons with time‐of‐flight spectroscopy. Over the entire temperature range, the electron mobility is approximately twice as high as that of the hole. The hole and electron transport characteristics in the smectic phase below 0 °C are explained by the Gaussian disorder model, which was proposed for amorphous organic semiconductors. The disorder parameters, σ and Σ, are almost the same for holes and electrons. However, the pre‐exponential parameter μ0 for the electron is twice as large as that for the hole, which can be attributed to the difference in the extension of the LUMO of the molecules. The energetic disorder σ is primarily determined by the disorder in the orientation of the permanent dipoles of liquid crystal molecules.