bluuebunny/crossref_metadata_2025_split huggingface dataset:
Multistep Synthesis Using Modular Flow Reactors: Bestmann–Ohira Reagent for the Formation of Alkynes and Triazoles
Authors: Baxendale Ian R. , Ley Steven V. , Mansfield Andrew C. , Smith Christopher D. 
Published: April 2009

AbstractMultistep in flow: The Seyferth–Gilbert reagent 1 has been applied in a flow system to rapidly synthesize terminal alkynes. The system has been further applied to synthesize triazole 3 from alcohol 2 in a three‐step oxidation/homologation/copper(I)‐catalyzed azide–alkyne cycloaddition sequence without isolation of intermediates (see scheme).magnified image
Content‐based and algorithmic classifications of journals: Perspectives on the dynamics of scientific communication and indexer effects
Authors: Rafols Ismael , Leydesdorff Loet 
Published: April 2009

AbstractThe aggregated journal‐journal citation matrix—based on the Journal Citation Reports (JCR) of the Science Citation Index—can be decomposed by indexers or algorithmically. In this study, we test the results of two recently available algorithms for the decomposition of large matrices against two content‐based classifications of journals: the ISI Subject Categories and the field/subfield classification of Glänzel and Schubert (2003). The content‐based schemes allow for the attribution of more than a single category to a journal, whereas the algorithms maximize the ratio of within‐category citations over between‐category citations in the aggregated category‐category citation matrix. By adding categories, indexers generate between‐category citations, which may enrich the database, for example, in the case of inter‐disciplinary developments. Algorithmic decompositions, on the other hand, are more heavily skewed towards a relatively small number of categories, while this is deliberately counter‐acted upon in the case of content‐based classifications. Because of the indexer effects, science policy studies and the sociology of science should be careful when using content‐based classifications, which are made for bibliographic disclosure, and not for the purpose of analyzing latent structures in scientific communications. Despite the large differences among them, the four classification schemes enable us to generate surprisingly similar maps of science at the global level. Erroneous classifications are cancelled as noise at the aggregate level, but may disturb the evaluation locally.
NERA: Named Entity Recognition for Arabic
Authors: Shaalan Khaled , Raza Hafsa 
Published: April 2009

AbstractName identification has been worked on quite intensively for the past few years, and has been incorporated into several products revolving around natural language processing tasks. Many researchers have attacked the name identification problem in a variety of languages, but only a few limited research efforts have focused on named entity recognition for Arabic script. This is due to the lack of resources for Arabic named entities and the limited amount of progress made in Arabic natural language processing in general. In this article, we present the results of our attempt at the recognition and extraction of the 10 most important categories of named entities in Arabic script: the person name, location, company, date, time, price, measurement, phone number, ISBN, and file name. We developed the system Named Entity Recognition for Arabic (NERA) using a rule‐based approach. The resources created are: a Whitelist representing a dictionary of names, and a grammar, in the form of regular expressions, which are responsible for recognizing the named entities. A filtration mechanism is used that serves two different purposes: (a) revision of the results from a named entity extractor by using metadata, in terms of a Blacklist or rejecter, about ill‐formed named entities and (b) disambiguation of identical or overlapping textual matches returned by different name entity extractors to get the correct choice. In NERA, we addressed major challenges posed by NER in the Arabic language arising due to the complexity of the language, peculiarities in the Arabic orthographic system, nonstandardization of the written text, ambiguity, and lack of resources. NERA has been effectively evaluated using our own tagged corpus; it achieved satisfactory results in terms of precision, recall, and F‐measure.
Selective recognition of thymidine homopolymer (poly T) oligonucleotide with cobalt(II)–4‐[(5‐chloro‐2‐pyridyl)azo]‐1,3‐diaminobenzene complex
Authors: Guo Feng Ling , Li Yuan Fang , Huang Cheng Zhi 
Published: April 2009

AbstractThe interactions of cobalt(II)–4‐[(5‐chloro‐2‐pyridyl)azo]‐1,3‐diaminobenzene (5‐Cl‐PADAB) complex with different kinds of homopolymer oligonucleotides in basic medium were investigated based on the measurements of resonance light scattering, UV–vis, circular dichroism spectra and dark field light‐scattering imaging. Experiments showed that only thymidine homopolymer (poly T) oligonucleotides with the length in the range of poly T6 to poly T18 could interact with the Co(II)–5‐Cl‐PADAB complex in alkaline conditions and cause evident color and spectral change. Thus, the binary complex of Co(II)–5‐Cl‐PADAB could be employed as a visual probe for selectively recognizing the poly T oligonucleotides. Copyright © 2009 John Wiley & Sons, Ltd.
Rhodium(I)‐Catalysed Intramolecular [2+2+2] Cyclotrimerisations of 15‐, 20‐ and 25‐Membered Azamacrocycles: Experimental and Theoretical Mechanistic Studies
Authors: Dachs Anna , Torrent Anna , Roglans Anna , Parella Teodor , Osuna Sílvia , Solà Miquel 
Published: April 2009

AbstractNumber of members makes a difference: The [2+2+2] intramolecular cyclotrimerisation of a new series of 20‐ and 25‐membered azamacrocycles catalysed by the Wilkinson's catalyst are reported (see scheme). The 20‐ and 25‐membered azamacrocycles show different reactivity. Why? Theoretical calculations give insight into the reactivity differences observed for the 20‐ and 25‐membered macrocycles.magnified imageA new series of 20‐ and 25‐membered polyacetylenic azamacrocycles have been satisfactorily prepared and completely characterised by spectroscopic methods. Various [2+2+2] cyclotrimerisation processes catalysed by the Wilkinson’s catalyst, [RhCl(PPh3)3], were tested in the above‐mentioned macrocycles. The 25‐membered azamacrocycle (like the previously synthesised 15‐membered azamacrocyle) led to the expected cyclotrimerised compound in contrast to the 20‐membered macrocycle, which is characterised by its lack of reactivity. The difference in reactivity of the 15‐, 20‐ and 25‐membered macrocycles has been rationalised through density functional theory calculations.
The Synthesis, Full Characterisation and Utilisation of Template‐Free Silica Sodalite, a Novel Polymorph of Silica
Authors: King R. S. P. , Dann S. E. , Elsegood M. R. J. , Kelly P. F. , Mortimer R. J. 
Published: April 2009

AbstractEmpty glass: Subjecting ethylene glycol silica sodalite to heat (680 °C) under a nitrogen atmosphere (i) successfully removes the templating agent to give cubic silica sodalite, which, upon consequent heating under an oxygen atmosphere (ii), transforms into a rhombohedral form of the empty sodalite, in effect a novel polymorph of silica.magnified image
Dihydrogen Bonding: Donor–Acceptor Bonding (AH⋅⋅⋅HX) versus the H2 Molecule (AH2X)
Authors: Hugas David , Simon Sílvia , Duran Miquel , Fonseca Guerra Célia , Bickelhaupt F. Matthias 
Published: April 2009

AbstractDihydrogen bond or H2 molecule? The central HH bond in linear H4 can exist in two qualitatively different bonding modes corresponding to two different electronic states, namely a donor–acceptor dihydrogen bond (DHB) and a central H2 molecule with an electron‐pair bond (see figure). This insight evolves from Kohn–Sham density functional analysis and it is further applied here to understand the bonding in more realistic model systems.magnified imageDihydrogen bonds (DHBs) play a role in, among others, crystal packing, organometallic reaction mechanisms, and potential hydrogen‐storage materials. In this work we have analyzed the central HH bond in linear H4, LiH⋅⋅⋅HX, BH4−⋅⋅⋅HX, and AlH4−⋅⋅⋅HX complexes with various X by using the quantitative molecular orbital model contained in Kohn–Sham density functional theory at the BP86/TZ2P level of theory. First, we address the questions of if and how one can distinguish, in principle, between a H⋅⋅⋅H donor–acceptor DHB and the formation of an H2 molecule by using the simple H4 model system. The results of these analyses have been used to gain an understanding of the bonding in more realistic model systems (some of which have been studied experimentally), and how this differs from the bonding in H4.
DNA‐Assisted Self‐Assembly of Pyrene Foldamers
Authors: Häner Robert , Samain Florent , Malinovskii Vladimir L. 
Published: April 2009

AbstractFolding in the tides: Upon hybridization, pyrene molecules assemble through interstrand stacking interactions to form double‐stranded, helical structures. Structural organization of the pyrene molecules is an intrinsic property of the oligoaryl part and takes place independently of the sequence of the attached DNA. Pyrene helicity is most pronounced in a bi‐segmental chimera, in which a DNA stem is present only at one end of the pyrene section.magnified imageThe self‐organization of oligopyrene foldamers is described. Bi‐ and tri‐segmental oligomers composed of nucleotides and non‐nucleosidic, achiral pyrene monomers form double‐stranded helical structures, as shown by absorbance, fluorescence, and CD spectroscopy. The mixed nature of alternating aromatic and phosphate groups ensures water solubility which, in turn, favors folding of the aromatic units. Pyrene molecules also assemble though interstrand stacking interactions. Structural organization of the pyrene units is an intrinsic property of the oligoaryl part and takes place independently from the sequence of the attached DNA. Chirality transfer from DNA to the pyrene segment leads to formation of a double helix, in which neighboring pyrene units are, in the present case, twisted in a right‐handed manner. Pyrene helicity is most pronounced in a bi‐segmental chimera, in which a DNA stem is present only at one end of the pyrene section.
Three‐Component Synthesis of Highly Functionalized 5‐Acetyloxazoles
Authors: Lechel Tilman , Lentz Dieter , Reissig Hans‐Ulrich 
Published: April 2009

AbstractBy a flexible three‐component synthesis, alkoxy‐substituted enamides are easily available from lithiated alkoxyallenes, nitriles and carboxylic acids (see scheme). The treatment of these versatile intermediates with trifluoroacetic acid provided 5‐acetyloxazoles in moderate to good yields. Different substituents are possible at C‐2 and C‐5 and the 5‐acetyl group is a suitable handle for further synthetic transformations.magnified image
Thermodynamic Controlled Hierarchical Assembly of Ternary Supramolecular Networks at the Liquid–Solid Interface
Authors: Li Yibao , Ma Zhun , Deng Ke , Lei Shengbin , Zeng Qingdao , Fan Xiaolin , De Feyter Steven , Huang Wei , Wang Chen 
Published: April 2009

AbstractBuilding and networking: Ternary supramolecular networks have been formed by coadsorption of dissimilar ternary building units at the liquid–solid interface. The structural characteristics of the networks undergo distinctive transformations as the building units change from binary to ternary components (see graphic).magnified image
Gold‐Catalyzed Reactions of 1,5‐ and 1,6‐Enynes with Carbonyl Compounds: Cycloaddition vs. Metathesis
Authors: Escribano‐Cuesta Ana , López‐Carrillo Verónica , Janssen Dominic , Echavarren Antonio M. 
Published: April 2009

AbstractGold and rings: The gold(I)‐catalyzed addition of aldehydes to 1,6‐enynes gives 1,3‐dienes, by a cycloaddition/fragmentation process. 1,5‐Enynes react with aldehydes and ketones by the 5‐endo‐dig pathway to give the corresponding cycloadducts.magnified image
Pharmacokinetics of nateglinide enantiomers and their metabolites in Goto‐Kakizaki rats, a model for type 2 diabetes mellitus
Authors: Tamura Masafumi , Shiba Sachiko , Kudo Naomi , Kawashima Yoichi 
Published: April 2009

AbstractThe pharmacokinetics of (−)‐N‐(trans‐4‐isopropylcyclohexanecarbonyl)‐D‐phenylalanine (nateglinide) and its enantiomer (L‐enantiomer) was studied in Goto‐Kakizaki (GK) rats after intravenous administration of nateglinide or L‐enantiomer at a dose of 40 μmol/kg body weight. Nateglinide, its L‐enantiomer and their metabolites in serum, bile and urine were determined. The total clearance (CLtot) and the volume of distribution (Vd) was slightly higher for nateglinide than those for L‐enantiomer in control rats, although the differences were not statistically significant. The cumulative excretions of L‐M1 (major metabolite of L‐enantiomer) and L‐M2 (major metabolite of L‐enantiomer) into bile were almost the same as that of M1 (major metabolite of nateglinide)and M2 (major metabolite of nateglinide). In GK rats, CLtot and Vd were higher for nateglinide than those for L‐enantiomer. The cumulative excretion of L‐M1 and L‐M2 were not different from those of M1 and M2, respectively, into bile or urine. CLtot and Vd for nateglinide or L‐enantiomer in GK rats were not different from those in control rats. The total excretion of M1, M2, L‐M1, and L‐M2 into bile or urine in GK rats was not substantially different from that of control rats. These results suggest that the L‐enantiomer of nateglinide shows higher CLtot and Vd compared with nateglinide, especially in the diabetic state. Chirality, 2010. © 2009 Wiley‐Liss, Inc.
Synthesis and chiroptical properties of chiral azoaromatic dendrimers with a C3‐symmetrical core
Authors: Angiolini Luigi , Benelli Tiziana , Giorgini Loris 
Published: April 2009

AbstractNew chiral azoaromatic dendrimeric systems have been synthesized starting from 1,3,5‐benzenetricarbonyl trichloride as the core molecule. The simultaneous presence of the (S)‐3‐hydroxy pyrrolidinyl ring as the optically active moiety and the azobenzene donor‐acceptor conjugated system as the photochromic group with permanent dipole moment, makes these systems potentially interesting as materials for advanced applications in nanotechnologies. All the compounds obtained have been characterized with particular attention to the effects induced by changing the electron‐withdrawing group in the chromophoric moiety and to their optical activity. A strong nonlinear enhancement of chiroptical properties related to the number of chiral units linked to the symmetrical core is observed in these derivatives, which indicates the presence of conformationally chiral substructures. Chirality, 2010. © 2009 Wiley‐Liss, Inc.
Enantioselective cyanoformylation of aldehydes catalyzed with solid base mediated chiral V(V) salen complexes
Authors: Khan Noor‐Ul H. , Agrawal Santosh , Kureshy Rukhsana I. , Abdi Sayed H. R. , Pathak Kavita , Bajaj Hari C. 
Published: April 2009

AbstractPolymeric and monomeric V(V) chiral salen complexes‐catalyzed enantioselective ethyl cyanoformylation of aldehydes using ethyl cyanoformate as a source of cyanide was accomplished in the presence of several basic cocatalysts viz., NaOH, KOH, basic Al2O3 and hydrotalcite. Excellent yield (>95%) of chiral ethyl cyanohydrincarbonate with high enantioselectivity up to 94% was achieved in 24–36 h when hydrotalcite was used as an additive. The polymeric catalyst 1 is more reactive than the monomeric catalyst 2 to produce chiral ethyl cyanohydrincarbonate in high optical purity. The chiral polymeric catalyst 1 and cocatalysts hydrotalcite and basic alumina used in this study were recoverable and recyclable several times with retention of its performance. Chirality, 2010. © 2009 Wiley‐Liss, Inc.
A Simplified Numerical Approach to Feedback Controller Design
Authors: Bechtel Tom B. 
Published: April 2009

AbstractA generalized parameter optimization method for computing feedback controller parameters is proposed. The method utilizes the downhill simplex method (DSM), a pattern search algorithm, to determine the optimal parameters that minimize an objective function or performance index. The system model, expressed in terms of state‐space equations is integrated with respect to time at each DSM iteration in order to determine the states. A fourth‐order Runge‐Kutta scheme is used for integrating the state equations. A penalty function approach is used for problems with inequality constraints on the state variables or controls. Though relatively inefficient in terms of the number of function evaluations, DSM requires only that the user provide the model equations, and not their derivatives. Additionally, the DSM code is very compact. Thus, a small and straightforward program allows for controller parameter determination for a variety of state‐space and classical PID feedback control design problems.
Flocculation: a key process in the sediment flux of a large, glacier‐fed lake
Authors: Hodder Kyle R. 
Published: April 2009

AbstractThis study investigates the consequences of flocculation for sediment flux in glacier‐fed Lillooet Lake, British Columbia based on density, fractal dimension, in situ profiles of sediment concentration and size distribution, and settling velocity equations presented in the literature. Sediment flux attributed to macroflocs during the late spring and summer accounts for a significant portion of sediment flux in the lake, equivalent to at least one‐quarter of the average annual sediment flux. Fine sediment is reaching the lake floor faster in flocs than occurs if settling as individual grains. This flux varies both spatially and temporally over the observation period, suggesting a link between deposition via flocculation and the properties of bottom sediments. Macrofloc flux increased through June, reached a peak during July, and then declined into August. Macrofloc flux was greatest in the distal end of the first basin, approximately 10 km from the point of inflow. Relatively high excess densities (∼0·1 g cm–3 at 500 µm) for flocs in situ are consistent with a composition dominated by inorganic primary particles. Microlaminations within Lillooet Lake varves have been linked by earlier workers to discharge events, and the action of turbidity currents, emanating from the Lillooet River. While turbidity currents undoubtedly occur in Lillooet Lake, these results demonstrate flocculation as an adjunct process linking discharge, lake level, macrofloc flux, bulk density and microlaminations. In situ measurements of sediment settling velocity in glacier‐fed lakes are required to better constrain flux rates, and permit comparison between flocculation in lacustrine environments with existing studies of estuarine, marine and fluvial flocculation. Copyright © 2009 John Wiley & Sons, Ltd.
Pumped rainfall simulators: the impact of rain pulses on sediment concentration and size
Authors: Armstrong A. , Quinton J. N. 
Published: April 2009

AbstractMany pumped rainfall simulators used in soil erosion studies use pulsed rain to control the rainfall intensity. We examined the effect of the rain pulsing on sediment concentration and size using three different pulse cycles with the same rainfall intensity. There was considerable variation in sediment concentration through the pulse cycle: the highest concentration was up to four times that of the lowest concentration. Furthermore, the particle size distribution also varied: the peak median particle size was double the lowest median particle size. The magnitude of differences in sediment concentration and particle size were greater the longer the pulse cycle and these dynamics will vary between rainfall simulators and studies. We suggest the impact of the pulsing on sediment is significant and should be investigated prior to experimentation so that sampling periods are designed to avoid bias introduced by fine temporal scale sediment dynamics. Copyright © 2009 John Wiley & Sons, Ltd.
The Lower Paleolithic of the Indian subcontinent
Authors: Chauhan Parth R. 
Published: April 2009

AbstractThis broad overview highlights the Indian subcontinent as an important and exciting source of new discoveries regarding Lower Paleolithic hominins and their biological and behavioral evolution. Broadly situated in the center of the Old World, the region arbitrarily encompasses Pakistan, India, Nepal, Sri Lanka, Bangladesh, and Bhutan; it represents the richest easternmost domain of classic Acheulean bifaces in the Old World.1 The region comprises diverse ecological zones with complex geological and climatic histories, including a bi‐annual monsoon prevalent since the Miocene, all of which had major impacts on faunal and floral distributions and associated hominin adaptations.
Prevalence and longitudinal stability of negative symptoms in healthy participants
Authors: Emmerson Lindsay C. , Ben‐Zeev Dror , Granholm Eric , Tiffany Megan , Golshan Shah , Jeste Dilip V. 
Published: April 2009

AbstractObjectiveAlthough negative symptoms are prominent in older patients with schizophrenia, it is unknown whether this pattern is prevalent in healthy participants. The objective of this study was to evaluate whether negative symptoms are present in healthy populations and to determine whether they are linked to illness‐related processes or normal aging.MethodsA systemic review of 26 studies that have administered negative symptom assessments to healthy participants was conducted. In addition, 213 (age > 40 years old) healthy participants completed PANSS and SANS ratings at both baseline and 1‐year follow‐up. One‐hundred participants also completed ratings after 3 years.ResultsAcross all reviewed studies, negative symptoms were absent in the majority of participants. Comparable results were found in the current study's large longitudinal evaluation with middle‐aged to older adults.ConclusionsTaken together, the data suggest that healthy volunteers do not suffer from prominent negative symptoms. This finding is consistent with the hypothesis that the greater prevalence and severity of negative symptoms in older patients is not related to normal aging but to illness‐related processes. Copyright © 2009 John Wiley & Sons, Ltd.
No gender differences in brain activation during the N‐back task: An fMRI study in healthy individuals
Authors: Schmidt Heike , Jogia Jigar , Fast Kristina , Christodoulou Tessa , Haldane Morgan , Kumari Veena , Frangou Sophia 
Published: April 2009

AbstractGender differences have been well established in verbal and spatial abilities but few studies have examined if these differences also extend into the domain of working memory in terms of behavioural differences and brain activation. The conclusions that can be drawn from these studies are not clear cut but suggest that even though gender differences might not be apparent from behavioural measures, the underlying neural substrate associated with working memory might be different in men and women. Previous research suggests activation in a network of frontal and parietal regions during working memory tasks. This study aimed to investigate gender differences in patterns of brain activation during a verbal version of the N‐back working memory task, which incorporates the effects of increased demands on working memory. A total of 50 healthy subjects, aged 18 to 58 years, that were equally split by gender were recruited matched for age, levels of education and ethnicity. All subjects underwent functional magnetic resonance imaging. We found that men and women performed equally well in terms of accuracy and response times, while using similar brain regions to the same degree. Our observations indicate that verbal working memory is not affected by gender at the behavioural or neural level, and support the findings of a recent meta‐analysis by Hyde ([ 2005]: Sex Roles 53:717–725) that gender differences are generally smaller than intra‐gender differences in many cognitive domains. Hum Brain Mapp, 2009. © 2009 Wiley‐Liss, Inc.