bluuebunny/crossref_metadata_2025_split huggingface dataset:
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

AbstractCurrent 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

AbstractBone 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

AbstractAziridination 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

AbstractOxidative 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

AbstractA 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

AbstractSynthetic 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

AbstractThe 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

AbstractBackgroundCentral 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.MethodsTwenty-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.ResultsThe 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.ConclusionAlthough 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

AbstractDifferent 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

AbstractWe 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

AbstractA 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

AbstractPerylene‐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

AbstractThe 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

AbstractA 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

AbstractA 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

AbstractThe 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

AbstractA 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

AbstractA 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

AbstractThe 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

AbstractThe 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

AbstractA 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

Abstract 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

AbstractA 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.