bluuebunny/crossref_metadata_2025_split huggingface dataset:
Die Renaissance des H/D‐Austausches
Authors: Atzrodt Jens , Derdau Volker , Fey Thorsten , Zimmermann Jochen 
Published: September 2007

AbstractDie steigende Nachfrage nach stabil isotopenmarkierten Verbindungen führt zu einem verstärkten Interesse an H/D‐Austauschreaktionen an Kohlenstoffatomen. Heutzutage werden Deuterium‐markierte Verbindungen als interne Standards in der Massenspektrometrie eingesetzt oder helfen dabei, mechanistische Theorien zu untermauern. Der Zugang zu diesen deuterierten Verbindungen erfolgt über einen Austausch von Wasserstoff gegen Deuterium im Zielmolekül deutlich effizienter und preiswerter als über die klassische Synthese. Schwerpunkt dieses Aufsatzes sind präparative Anwendungen der H/D‐Austauschreaktion zur Herstellung Deuterium‐markierter Substanzen. Die Fortschritte der letzten zehn Jahre werden zusammengefasst und kritisch bewertet.
Electroluminescence and photovoltaic properties of poly(p‐phenylene vinylene) derivatives with dendritic pendants
Authors: Tan Zhan'ao , Tang Rupei , Zhou Erjun , He Youjun , Yang Chunhe , Xi Fu , Li Yongfang 
Published: September 2007

AbstractA copolymer of dendronized poly(p‐phenylene vinylene) (PPV), poly{2‐[3′,5′‐bis (2′‐ethylhexyloxy) bnenzyloxy]‐1,4‐phenylene vinylene}‐co‐poly[2‐methoxy‐5‐(2′‐ethylhexyloxy)‐1,4‐phenylene vinylene] (BE‐co‐MEH–PPV), was synthesized with the Gilch route to improve the electroluminescence and photovoltaic properties of the dendronized PPV homopolymer. The polymer was characterized by ultraviolet–visible absorption spectroscopy, photoluminescence spectroscopy, and electrochemical cyclic voltammetry and compared with the homopolymers poly{2‐[3′, 5′‐bis(2‐ethylhexyloxy) benzyloxy‐1,4‐phenylene vinylene} (BE–PPV) and poly[2‐methoxy‐5‐(2′‐ethylhexyloxy)‐1,4‐phenylenevinylene] (MEH–PPV). Polymer light‐emitting diodes based on the polymers with the configuration of indium tin oxide (ITO)/poly(3,4‐ethylene dioxythiophene) : poly(styrene sulfonate) (PEDOT : PSS)/polymer/Ca/Al were fabricated. The electroluminescence efficiency of BE‐co‐MEH–PPV reached 1.64 cd/A, which was much higher than that of BE–PPV (0.68 cd/A) and a little higher than that of MEH–PPV (1.59 cd/A). Photovoltaic properties of the polymer were studied with the device configuration of ITO/PEDOT : PSS/polymer : [6,6J‐phenyl‐C61‐butyric acid methyl ester] (PCBM)/Mg/Al. The power conversion efficiency of the device based on the blend of BE‐co‐MEH–PPV and PCBM with a weight ratio of 1 : 3 reached 1.41% under the illumination of air mass 1.5 (AM1.5) (80 mW/cm2), and this was an improvement in comparison with 0.24% for BE–PPV and 1.32% for MEH–PPV under the same experimental conditions. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Making sense of credibility on the Web: Models for evaluating online information and recommendations for future research
Authors: Metzger Miriam J. 
Published: September 2007

AbstractThis article summarizes much of what is known from the communication and information literacy fields about the skills that Internet users need to assess the credibility of online information. The article reviews current recommendations for credibility assessment, empirical research on how users determine the credibility of Internet information, and describes several cognitive models of online information evaluation. Based on the literature review and critique of existing models of credibility assessment, recommendations for future online credibility education and practice are provided to assist users in locating reliable information online. The article concludes by offering ideas for research and theory development on this topic in an effort to advance knowledge in the area of credibility assessment of Internet‐based information.
The impact of youth's use of the internet on their use of the public library
Authors: D'Elia George , Abbas June , Bishop Kay , Jacobs Donald , Rodger Eleanor Jo 
Published: September 2007

AbstractA survey of 4,032 youth in grades 5 through 12 was conducted to determine the impact youth's use of the Internet was having on their use of the public library. Results indicated that 100% of the youth had access to the Internet from one or more locations, and that although one quarter of the youth accessed the Internet at the public library, the public library was the least frequently used source of Internet access. For youth without Internet access at home, the public library was also the least used alternate source of access. Approximately 69% of the youth reported that they had visited a public library during the school year. Having Internet access at home did not affect whether or not youth visited the library however, Internet access at home appears to have affected the frequency with which youth visit the library. Youth without Internet access at home visited the library more frequently, whereas youth with Internet access at home visited the library less frequently. Use of the Internet also appeared to have diminished youth's need to use the public library as a source of personal information however, use of the Internet appeared not to have affected their use of the public library for school work or for recreation. Among youth, use of both the Internet and the public library appear to be complementary activities.
Four‐Dimensional Space Groups for Pedestrians: Composite Structures
Authors: Sun Junliang , Lee Stephen , Lin Jianhua 
Published: September 2007

AbstractHigher‐dimensional crystals have been studied for the last thirty years. However, most practicing chemists, materials scientists, and crystallographers continue to eschew the use of higher‐dimensional crystallography in their work. Yet it has become increasingly clear in recent years that the number of higher‐dimensional systems continues to grow from hundreds to as many as a thousand different compounds. Part of the problem has to do with the somewhat opaque language that has developed over the past decades to describe higher‐dimensional systems. This language, while well‐suited to the specialist, is too sophisticated for the neophyte wishing to enter the field, and as such can be an impediment. This Focus Review hopes to address this issue. The goal of this article is to show the regular chemist or materials scientist that knowledge of regular 3D crystallography is all that is really necessary to understand 4D crystal systems. To this end, we have couched higher‐dimensional composite structures in the language of ordinary 3D crystals. In particular, we developed the principle of complementarity, which allows one to identify correctly 4D space groups solely from examination of the two 3D components that make up a typical 4D composite structure.
Simultaneous quantification of three alkaloids of Coptidis Rhizoma in rat urine by high‐performance liquid chromatography: application to pharmacokinetic study
Authors: Tan Bo , Ma Yueming , Shi Rong , Wang Tianming 
Published: September 2007

AbstractA high‐performance liquid chromatographic method with ultraviolet detection was established and validated for quantification of three alkaloids (coptisine, palmatine and berberine) in rat urine. Following a single‐step liquid–liquid extraction, the analytes were separated on a reversed‐phase C18 column with water–formic acid–triethylamine–methanol as the mobile phase at a flow rate of 1 ml/min. The linear ranges of the calibration curves were 1.6–160 ng/ml for all three alkaloids. The lower limit of quantification was 1.6 ng/ml for all three alkaloids. The within‐batch accuracy was 90.4–108.3% for coptisine, 88.6–107.8% for berberine and 88.4–110.1% for palmatine. The between‐batch accuracy was 99.3–100.3% for coptisine, 94.3–100.6% for berberine and 93.7–100.0% for palmatine. The within‐batch and between‐batch precisions were ⩽10.1% and ⩽11.1%, respectively. This method is suitable to determine the three alkaloids of Coptidis Rhizoma in urine simultaneously and thus to investigate the pharmacokinetics of the alkaloids from Xiexin Decoction in rats. Copyright © 2007 John Wiley & Sons, Ltd.
Pharmacokinetics of tramadol and its three main metabolites in healthy male and female volunteers
Authors: Ardakani Yalda H. , Rouini Mohammad‐Reza 
Published: September 2007

AbstractBy using a high‐performance liquid chromatography method, the pharmacokinetics of the tramadol (T) and its three main metabolites, O‐desmethyltramadol (M1), N‐desmethyltramadol (M2) and O,N‐didesmethyltramadol (M5) was studied in healthy male and female Iranian volunteers after oral administration of two 50 mg tramadol hydrochloride tablets. The related pharmacokinetic parameters such as Cmax, Tmax, AUC(0–t), AUC(0–∞), T1/2 and Cl/F were calculated and compared between the two genders. No significant differences were found in the systemic exposure and pharmacokinetic of tramadol, M1 and M2 while there were significant differences in AUCs of M5 in the two genders. It was concluded that to get a more accurate result, the gender dependency of T and its metabolites might be studied in specific phenotypes. Copyright © 2007 John Wiley & Sons, Ltd.
A simplified approach for computer‐aided education of network reconfiguration in radial distribution systems
Authors: Prasad K. , Sahoo N. C. 
Published: September 2007

AbstractIn the present electrical engineering curriculum, power distribution engineering is one of the core courses offered to the students with power systems specialization. Since the distribution systems are mostly radial, the topics related to radial distribution system (RDS) are emphasized in this course. In RDS, network reconfiguration is frequently performed for optimizing system performance. Before the reconfiguration operation is physically performed, it is necessary to have computer‐aided performance assessment of the reconfigured RDS from load flow analysis. For students' education, it is necessary that the students should familiarize themselves with computer simulation of RDS reconfiguration followed by load flow analysis. The purpose of this paper is to clearly and illustratively explain the various underlying sub‐processes involved in the simulation experiment of RDS reconfiguration. The pseudo‐codes in the form of flowcharts and complete C‐language program codes for RDS reconfiguration are also included. © 2007 Wiley Periodicals, Inc. Comput Appl Eng Educ 14: 260–276, 2007; Published online in Wiley InterScience (www.interscience.wiley.com); DOI 10.1002/cae.20103
Using MATLAB to advance the robotics laboratory
Authors: Hamilton Carter 
Published: September 2007

AbstractThe RV‐M1 Movemaster from Mitsubishi Electric is an excellent educational robot for students as they learn to program automated tasks and simulate manufacturing processes. Because it was publicly introduced in 1991, the RV‐M1 utilizes the DOS‐based QBASIC computer code as the primary interface language with the robotic drive unit. Today's students, however, often face great frustration when they work with the unfamiliar QBASIC language and the even more unfamiliar DOS operating system. To address these shortcomings, the Mechanical and Manufacturing Engineering Department at Miami University introduced MATLAB as an alternative Window‐based interface language to better reflect the current educational experience of students and to increase the functionality of the RV‐M1 robotic arms. MATLAB successfully overcomes the limitations of the QBASIC/DOS environment and augments the capability of the RV‐M1. Examples of the extended capability include the use of graphical user interfaces to facilitate student interaction with the robotic arm and the ability to move the robot along contoured paths. With MATLAB, instructors can develop projects that enhance the student experience with the RV‐M1 and give them greater insight into robotic applications. © 2007 Wiley Periodicals, Inc. Comput Appl Eng Educ 14: 205–213, 2007; Published online in Wiley InterScience (www.interscience.wiley.com); DOI 10.1002/cae.20143
Design, navigation, and structure of a hypermedia application for the teaching–learning of pneumatic engineering design drawing
Authors: Ramos Barbero B. , Pelaez Vara J. , García Maté E. , Ruiz Calvo J. 
Published: September 2007

AbstractThis article presents a hypermedia application used to study pneumatics that serves to support the lecturer in the lecture hall and as a self‐study tool for the student. The reason behind the creation of this application is as follows: currently, there is no application in the market, which is equipped with a navigational system to guide the student through this subject matter, which has a system for self‐assessment, and a system to identify those concepts that are of greatest interest or difficulty for the student. The proposed system monitors the time each user spends studying each section, as well as the dates on which each one was studied. Moreover, students are able to monitor their progress in learning the subject matter and identify those areas in which they have to improve. They are also able to simulate any pneumatic circuit in order to check its feasibility or detect any errors. The application has an open, modular structure, which enables changes to be made without its structure being affected. Use of the hypermedia application has supported the tutorial work of lecturers and reduced time spent elaborating on subject matter in the lecture hall, at the same time as facilitating its study. © 2007 Wiley Periodicals, Inc. Comput Appl Eng Educ 14: 248–259, 2007; Published online in Wiley InterScience (www.interscience.wiley.com); DOI 10.1002/cae.20157
Peptide Nucleic Acids and the Origin of Life
Authors: Nielsen Peter E. 
Published: September 2007

AbstractThe possibilities of pseudo‐peptide‐DNA mimics like PNA (peptide nucleic acid) having a role for the prebiotic origin of life prior to an RNA world is discussed on the basis of literature data showing that this type of molecules might have formed on the primitive earth (or other places in the universe), as well as data indicating the possibilities of template‐directed PNA chemical replication and ligation. In particular, the merits of an achiral prebiotic genetic material is discussed.
Physico‐Chemical and Evolutionary Constraints for the Formation and Selection of First Biopolymers: Towards the Consensus Paradigm of the Abiogenic Origin of Life
Authors: Mulkidjanian Armen Y. , Galperin Michael Y. 
Published: September 2007

AbstractDuring the last two decades, the common school of thought has split into two, so that the problem of the origin of life is tackled in the framework of either the ‘replication first’ paradigm or the ‘metabolism first’ scenario. The first paradigm suggests that the life started from the spontaneous emergence of the first, supposedly RNA‐based ‘replicators’ and considers in much detail their further evolution in the so‐called ‘RNA world’. The alternative hypothesis of ‘metabolism first’ derives the life from increasingly complex autocatalytic chemical cycles. In this work, we emphasize the role of selection during the pre‐biological stages of evolution and focus on the constraints that are imposed by physical, chemical, and biological laws. We try to demonstrate that the ‘replication first’ and ‘metabolism first’ hypotheses complement, rather than contradict, each other. We suggest that life on Earth has started from a ‘metabolism‐driven replication’; the suggested scenario might serve as a consensus scheme in the framework of which the molecular details of origin of life can be further elaborated. The key feature of the scenario is the participation of the UV irradiation both as driving and selecting forces during the earlier stages of evolution.
Enzyme‐Catalyzed Formation of β‐Peptides: β‐Peptidyl Aminopeptidases BapA and DmpA Acting as β‐Peptide‐Synthesizing Enzymes
Authors: Heck Tobias , Kohler Hans‐Peter E. , Limbach Michael , Flögel Oliver , Seebach Dieter , Geueke Birgit 
Published: September 2007

AbstractIn recent studies, we discovered that the three β‐peptidyl aminopeptidases, BapA from Sphingosinicella xenopeptidilytica 3‐2W4, BapA from S. microcystinivorans Y2, and DmpA from Ochrobactrum anthropi LMG7991, possess the unique feature of cleaving N‐terminal β‐amino acid residues from β‐ and α/β‐peptides. Herein, we investigated the use of the same three enzymes for the reverse reaction catalyzing the oligomerization of β‐amino acids and the synthesis of mixed peptides with N‐terminal β‐amino acid residues. As substrates, we employed the β‐homoamino acid derivatives H‐βhGly‐pNA, H‐β3hAla‐pNA, H‐(R)‐β3hAla‐pNA, H‐β3hPhe‐pNA, H‐(R)‐β3hPhe‐pNA, and H‐β3hLeu‐pNA. All three enzymes were capable of coupling the six β‐amino acids to oligomers with chain lengths of up to eight amino acid residues. With the enzyme DmpA as the catalyst, we observed very high conversion rates, which correspond to dimer yields of up to 76%. The β‐dipeptide H‐β3hAla‐β3hLeu‐OH and the β/α‐dipeptide H‐βhGly‐His‐OH (carnosine) were formed with almost 50% conversion, when a five‐fold excess of β3‐homoleucine or histidine was incubated with H‐β3hAla‐pNA and H‐βhGly‐pNA, respectively, in the presence of the enzyme BapA from S. microcystinivorans Y2. BapA from S. xenopeptidilytica 3‐2W4 turned out to be a versatile catalyst capable of coupling various β‐amino acid residues to the free N‐termini of β‐ and α‐amino acids and even to an α‐tripeptide. Thus, these aminopeptidases might be useful to introduce a β‐amino acid residue as an N‐terminal protecting group into a ‘natural’ α‐peptide, thereby stabilizing the peptide against degradation by other proteolytic enzymes.
The Biochemistry of Drug Metabolism – An Introduction
Authors: Testa Bernard , Krämer Stefanie D. 
Published: September 2007

AbstractThis review continues a general presentation of the metabolism of drugs and other xenobiotics begun in two recent issues ofChemistry & Biodiversity. ThisPartpresents some of the numerous hydrolases involved, their nomenclature, relevant biochemical properties, catalytic mechanisms, and the many reactions of hydrolysis they catalyze. A number of medicinally, environmentally, and toxicologically relevant examples are presented and discussed. The reactions examined include the hydrolysis of carboxylic esters, amides and peptides, lactones, and other labile rings, and esters of inorganic acids. The hydration of epoxides and its enzymology are treated separately.
Synthesis and Characterization of Hydroxy‐Functionalized Models for the Active Site in Fe‐Only‐Hydrogenases
Authors: Apfel Ulf‐Peter , Halpin Yvonne , Görls Helmar , Vos Johannes G. , Schweizer Bernd , Linti Gerald , Weigand Wolfgang 
Published: September 2007

AbstractThe reactions of dl‐1,4‐disulfanylbutane‐2,3‐diol and 1,3‐disulfanylpropan‐2‐ol with dodecacarbonyltriiron have been investigated. As main products, the iron complexes 1 and 2 were isolated and characterized by spectroscopic methods, as well as single crystal X‐ray analysis. Additionally, the unusually large bond angles in the dithiolato bridge was investigated via density‐functional theory (DFT) calculations. Moreover, the electrochemical features have been studied by cyclic voltammetry.
Phenolic Derivatives with Free‐Radical‐Scavenging Activities from Ixeridium gracile (DC.) Shih
Authors: Ma Xue‐Mei , Liu Yong , Shi Yan‐Ping 
Published: September 2007

AbstractPhytochemical investigation of the Tibetan medicinal plant Ixeridium gracile resulted in the isolation and identification of twelve flavonoids and two coumarins, compounds 1–14, the dimeric ‘2α,3α‐epoxy‐5,7,3′,4′‐tetrahydroxyflavan‐(4β→8)‐epicatechin’ (1) being a new constituent. The free‐radical‐scavenging potentials of different extract fractions as well as of the pure compounds towards the DPPH (1,1‐diphenyl‐2‐picrylhydrazyl) radical were evaluated, and are discussed in terms of structure–activity relationship (SAR). The flavonoids were found to be the major constituents contributing to the free‐radical‐scavenging activity of I. gracile, but the high concentration of coumarins additionally contributed to the observed activity.
Synthesis and DNA‐Cleavage Properties of Metal Complexes of 1,4,7,10‐Tetraazacyclododecane (Cyclen) Functionalized with a Pendant Benzocrown Ether
Authors: Tan Xin‐Yu , Zhang Ji , Huang Yu , Zhang Yu , Zhou Li‐Hong , Jiang Ning , Lin Hong‐Hui , Wang Na , Xia Chuan‐Qin , Yu Xiao‐Qi 
Published: September 2007

AbstractThe synthesis and DNA‐cleavage properties of a series of novel mononuclear ZnII, CuII, and CoII complexes 2 of a crown‐ether‐functionalized cyclen ligand is described. The Cu complex 2b displayed the highest catalytic activity towards pUC 19 DNA. The effects of reaction time, complex concentration, and pH were investigated, showing that 2b readily and efficiently converts supercoiled (type I ) plasmid DNA to nicked (type II) DNA under physiological conditions (37°, pH 7.4).
Copper(II) Complexes of Salicylaldehyde Hydrazones: Synthesis, Structure, and DNA Interaction
Authors: Wu La‐Mei , Teng Han‐Bing , Ke Xian‐Bing , Xu Wen‐Jin , Su Jiang‐Tao , Liang Shu‐Cai , Hu Xian‐Ming 
Published: September 2007

AbstractThree hydrazone ligands, H2L1–H2L3, made from salicylaldehyde and ibuprofen‐ or naproxen‐derived hydrazides, were prepared and transformed into the corresponding copper(II) complexes [CuIIL1]⋅H2O, [CuIIL2], and [(CuII)2(L3)2]⋅H2O⋅DMF (Scheme). The X‐ray crystal structure of the last‐mentioned complex was solved (Fig. 1), showing a square‐planar complexation geometry, and the single units were found to form a one‐dimensional chain structure (Fig. 2). The interactions of these complexes with CT‐DNA were studied by different techniques, indicating that they all bind to DNA by classical and/or non‐classical intercalation modes.
Chemical and Genetic Diversity of Ligularia latihastata and Ligularia villosa in Yunnan Province of China
Authors: Kuroda Chiaki , Kiuchi Kota , Torihata Atsushi , Takeshita Koichiro , Gong Xun , Shen Yuemao , Hirota Hiroshi , Onuki Hiroyuki , Hanai Ryo 
Published: September 2007

AbstractThe chemical constituents of the root extracts and the nucleotide sequences of the atpB‐rbcL intergenic region of Ligularia latihastata and L. villosa, collected in northwestern Yunnan Province, were studied. In the twelve collected samples of L. latihastata, two major benzofurans, 5,6‐dimethoxy‐2‐(1‐methylethenyl)‐1‐benzofuran (1) and euparin (2) were detected as major components. The minor compound (2R*,3S*)‐5‐acetyl‐2,3‐dihydro‐6‐hydroxy‐2‐(1‐methylethenyl)‐1‐benzofuran‐3‐yl (2Z)‐2‐[(acetoxy)methyl]but‐2‐enoate (4) was found to be susceptible to artifact formation upon extraction with EtOH. The intra‐specific diversity in chemical composition of the samples was small, but the diversity in the atpB‐rbcL sequence was fairly large. Compounds 1 and 2 were also found in the three collected samples of L. villosa, indicating that the two species are chemically close to each other, in agreement with morphological taxonomy.
Ecdysteroid Glycosides from Sida rhombifolia L.
Authors: Jadhav Atul N. , Pawar Rahul S. , Avula Bharathi , Khan Ikhlas A. 
Published: September 2007

AbstractSeven ecdysteroids, including the three new compounds 1–3, were isolated from Sida rhombifolia L. Their structures and configurations were determined by extensive spectroscopic techniques in combination with chemical derivatization. The four known compounds – ecdysone (4), 20‐hydroxyecdysone (5), 2‐deoxy‐20‐hydroxyecdysone‐3‐O‐β‐D‐glucopyranoside (6), and 20‐hydroxyecdysone‐3‐O‐β‐D‐glucopyranoside (7) – are reported for the first time from this plant.