bluuebunny/crossref_metadata_2025_split huggingface dataset:
Observable Structures of Small Neutral and Anionic Gold Clusters
Authors: Lee Han Myoung , Kim Kwang S. 
Published: August 2012

AbstractSince gold clusters have mostly been studied theoretically by using DFT calculations, more accurate studies are of importance. Thus, small neutral and anionic gold clusters (Aun and Aun−, n=4–7) were investigated by means of coupled cluster with singles, doubles, and perturbative triple excitations [CCSD(T)] calculations with large basis sets, and some differences between DFT and CCSD(T) results are discussed. Interesting isomeric structures that have dangling atoms were obtained. Structures having dangling atoms appear to be stable up to n=4 for neutral gold clusters and up to n=7 for anionic clusters. The relative stabilities and electronic properties of some isomers and major structures are discussed on the basis of the CCSD(T) calculations. This accurate structure prediction of small gold clusters corresponding to experimental photoelectron spectral peaks is valuable in the field of atom‐scale materials science including nanocatalysts.
Donor‐Induced Helical Inversion of 1,1′‐Binaphthyl Connecting with Two Molybdenum Complexes
Authors: Ma Li , Jin Rizhe , Bian Zheng , Kang Chuanqing , Chen Yu , Xu Jingwei , Gao Lianxun 
Published: August 2012

AbstractAn atropisomeric biaryl molecule with a given absolute configuration could present two opposite helical conformations through the rotation around CC single bond. To the best of our knowledge, the biaryl system is the simplest helical inversion model apart from stereomutation between two enantiomers. Herein, we first report such true helical inversion phenomena of biaryl compounds. Two [MoVIO2(L)]‐type complexes, in which L is a tridentate dioxoanionic pyridine O,N,O‐ligand, are coalesced on the 2,2′,3,3′‐positions of an (R)‐1,1′‐binaphthyl unit and an intramolecular dioxo bridge is formed by two MoO⋅⋅⋅Mo interactions. Exterior strong donors can coordinate to molybdenum to interrupt this dioxo bridge and inversions from negative to positive chirality are explicitly observed by circular dichroism spectroscopy, consistent with single‐crystal X‐ray diffraction analyses.
Fluorescence Study of Energy Transfer in PMMA Polymers with Pendant Oligo‐Phenylene‐Ethynylenes
Authors: Schäfer Johann , Breul Alexander , Birckner Eckard , Hager Martin D. , Schubert Ulrich S. , Popp Jürgen , Dietzek Benjamin 
Published: August 2012

AbstractA spectroscopic characterization of polymers containing rigid π‐conjugated oligo(phenyleneethynylene) chromophores as well as oligo(phenyleneethynylene) and methyl methacrylate is presented. The polymers exhibit molar masses of up to 15 000 g mol−1 and a degree of polymerization between 22 and 80. Emission measurements of the monomeric and polymeric species show that radiative as well as nonradiative rates are influenced by the degree of polymerization due to intramolecular interactions of chromophores pendant to the polymer backbone. Time‐resolved emission anisotropy measurements suggest that energy migrates within the polymers. Steady‐state emission anisotropy measurements also point to energy migration. Additionally, two oligo(phenyleneethynylene)s with different sizes of the conjugated system are copolymerized in order to enable energy trapping due to energy transfer. The shortened energy‐donor fluorescence lifetime within the donor–acceptor copolymers suggest energy transfer. Depending on the degree of polymerization, dispersion of the donor fluorescence lifetime is observed.
An efficient designed prototype technique for OFDM PAPR reduction using FPGA
Authors: Saad W. , El‐Fishawy N. , El‐Rabaie S. , Shokair M. 
Published: August 2012

SUMMARYIn this paper, a proposed designed technique to reduce OFDM peak‐to‐average power ratio (PAPR) value is performed. This designed technique contains a new block, which is inserted in the OFDM system. This proposed block is applied to the WiMAX system as an example of the OFDM technology. Afterwards, several MATLAB programs are executed to discuss the behavior and the characteristics of this proposed block. In addition, the effect of its insertion on the original system is studied. Because of this insertion, 0‐dB OFDM PAPR value can be achieved. Furthermore, it can be synthesized practically. This proposed system is implemented over a field‐programmable gate array (FPGA). The designed circuit is characterized by both its low complexity and its high speed. Moreover, it is a portable circuit. This means that it can be implemented over any FPGA kit regardless of its technology. Copyright © 2012 John Wiley & Sons, Ltd.
Climate‐change refugia in the sheltered bays of Palau: analogs of future reefs
Authors: van Woesik Robert , Houk Peter , Isechal Adelle L. , Idechong Jacques W. , Victor Steven , Golbuu Yimnang 
Published: August 2012

AbstractCoral bleaching and mortality are predicted to increase as climate change‐induced thermal‐stress events become more frequent. Although many studies document coral bleaching and mortality patterns, few studies have examined deviations from the expected positive relationships among thermal stress, coral bleaching, and coral mortality. This study examined the response of >30,000 coral colonies at 80 sites in Palau, during a regional thermal‐stress event in 2010. We sought to determine the spatial and taxonomic nature of bleaching and examine whether any habitats were comparatively resistant to thermal stress. Bleaching was most severe in the northwestern lagoon, in accordance with satellite‐derived maximum temperatures and anomalous temperatures above the long‐term averages. Pocillopora populations suffered the most extensive bleaching and the highest mortality. However, in the bays where temperatures were higher than elsewhere, bleaching and mortality were low. The coral‐community composition, constant exposure to high temperatures, and high vertical attenuation of light caused by naturally high suspended particulate matter buffered the corals in bays from the 2010 regional thermal‐stress event. Yet, nearshore reefs are also most vulnerable to land‐use change. Therefore, nearshore reefs should be given high conservation status because they provide refugia for coral populations as the oceans continue to warm.
Gene expression divergence and nucleotide differentiation between males of different color morphs and mating strategies in the ruff
Authors: Ekblom Robert , Farrell Lindsay L. , Lank David B. , Burke Terry 
Published: August 2012

AbstractBy next generation transcriptome sequencing, it is possible to obtain data on both nucleotide sequence variation and gene expression. We have used this approach (RNA‐Seq) to investigate the genetic basis for differences in plumage coloration and mating strategies in a non‐model bird species, the ruff (Philomachus pugnax). Ruff males show enormous variation in the coloration of ornamental feathers, used for individual recognition. This polymorphism is linked to reproductive strategies, with dark males (Independents) defending territories on leks against other Independents, whereas white morphs (Satellites) co‐occupy Independent's courts without agonistic interactions. Previous work found a strong genetic component for mating strategy, but the genes involved were not identified. We present feather transcriptome data of more than 6,000 de‐novo sequenced ruff genes (although with limited coverage for many of them). None of the identified genes showed significant expression divergence between males, but many genetic markers showed nucleotide differentiation between different color morphs and mating strategies. These include several feather keratin genes, splicing factors, and the Xg blood‐group gene. Many of the genes with significant genetic structure between mating strategies have not yet been annotated and their functions remain to be elucidated. We also conducted in‐depth investigations of 28 pre‐identified coloration candidate genes. Two of these (EDNRB and TYR) were specifically expressed in black‐ and rust‐colored males, respectively. We have demonstrated the utility of next generation transcriptome sequencing for identifying and genotyping large number of genetic markers in a non‐model species without previous genomic resources, and highlight the potential of this approach for addressing the genetic basis of ecologically important variation.
Genetic consequences of fragmentation in “arbor vitae,” eastern white cedar (Thuja occidentalis L.), toward the northern limit of its distribution range
Authors: Xu Huaitong , Tremblay Francine , Bergeron Yves , Paul Véronique , Chen Cungen 
Published: August 2012

AbstractWe tested the hypothesis that marginal fragmented populations of eastern white cedar (EWC) are genetically isolated due to reduced pollen and gene flow. In accordance with the central‐marginal model, we predicted a decrease in population genetic diversity and an increase in differentiation along the latitudinal gradient from the boreal mixed‐wood to northern coniferous forest. A total of 24 eastern white cedar populations were sampled along the north‐south latitudinal gradient for microsatellite genotyping analysis. Positive Fis values and heterozygote deficiency were observed in populations from the marginal (Fis = 0.244; PHW = 0.0042) and discontinuous zones (Fis = 0.166; PHW = 0.0042). However, populations from the continuous zone were in HW equilibrium (Fis = −0.007; PHW = 0.3625). There were no significant latitudinal effects on gene diversity (Hs), allelic richness (AR), or population differentiation (Fst). Bayesian and NJT (neighbor‐joining tree) analyses demonstrated the presence of a population structure that was partly consistent with the geographic origins of the populations. The impact of population fragmentation on the genetic structure of EWC is to create a positive inbreeding coefficient, which was two to three times higher on average than that of a population from the continuous zone. This result indicated a higher occurrence of selfing within fragmented EWC populations coupled with a higher degree of gene exchange among near‐neighbor relatives, thereby leading to significant inbreeding. Increased population isolation was apparently not correlated with a detectable effect on genetic diversity. Overall, the fragmented populations of EWC appear well‐buffered against effects of inbreeding on genetic erosion.
Comparing rainfall interception in plantation trials of six tropical hardwood trees and wild sugar cane Saccharum spontaneum L.
Authors: Friesen Patrick , Park Andrew , Sarmiento‐Serrud Aneth Aracelly 
Published: August 2012

ABSTRACTNative hardwood trees are frequently planted to restore forest cover to abandoned agricultural lands in the Neotropics. Few studies compare rainfall interception in such plantations and the vegetation the trees are planted to replace. We compared throughfall (TF) and stemflow (SF) in a mature stand of wild sugar cane Saccharum spontaneum L. and six tropical hardwoods growing in a restoration trial in the Republic of Panama. Interception in trees was dominated by TF, with SF accounting for less than 3% of gross rainfall (Pg). By contrast, SF was a dominant means by which rainfall reached the ground in S. spontaneum, and this dominance became greater at higher Pg. Slopes of Pg/SF regressions were considerably steeper in S. spontaneum than among tree plots. We tentatively concluded that trees intercept more rainfall than S. spontaneum. However, median total I was negative in S. spontaneum when SF was estimated using the median and the median plus maximum absolute deviation of stem densities as a multiplier. Sources of potential bias in S. spontaneum measurements include overestimation of stem density, high inter‐event variability of water volumes in individual SF collectors, and contact between stems diverting SFs. To our knowledge, ours is the first study to compare I in restoration plantings of tropical hardwoods and in S. spontaneum. It is also only the second study to quantify TF and SF in a sugar cane, likely due to the methodological difficulties involved in retrieving reliable estimates of these variables in very dense grass stands. Copyright © 2012 John Wiley & Sons, Ltd.
Alkene Hydrogenation Catalyzed by Nickel Hydride Complexes of an Aliphatic PNP Pincer Ligand
Authors: Vasudevan Kalyan V. , Scott Brian L. , Hanson Susan K. 
Published: August 2012

AbstractTo investigate metal–ligand cooperativity as a strategy for promoting nickel‐catalyzed alkene hydrogenation, cationic and neutral nickel(II) hydride complexes of the aliphatic pincer ligand PNHPCy {PNHPCy = HN[CH2CH2P(Cy)2]2} have been synthesized and characterized. Cationic hydride complex [(PNHPCy)Ni(H)]BPh4 (2) catalyzed the hydrogenation of styrene and 1‐octene under mild conditions. Only low conversion was observed in the hydrogenation of 3,5‐dimethoxybenzaldehyde using 2. The neutral hydride complex (PNPCy)Ni(H) (3) was also found to be an alkene hydrogenation catalyst. Mechanistic experiments suggest that for catalyst 2, the hydrogenation reaction proceeds through a pathway involving initial insertion of the alkene into the Ni–H bond. Contrary to the initial hypothesis, reactivity comparisons with the methyl‐substituted hydride complex [(PNMePCy)Ni(H)]BPh4 {PNMePCy = (CH3)N[CH2CH2P(Cy)2]2} suggest that metal–ligand cooperativity is not involved in these rare examples of mild and homogeneous nickel hydrogenation catalysis.
Evaluation of a model system for the selective study of the lipid peroxidation process
Authors: Mihaljević Branka , Tartaro Ivana , Filipović Vinceković Nada 
Published: August 2012

AbstractThe effect of molecular environment on the peroxidation of linoleic acid (LA), a polyunsaturated fatty acid (PUFA), initiated by ferrous ions was investigated in acidic and neutral pH conditions. Mixed nonionic surfactants TWEEN®‐20/LA micelles were established as a model system to obtain a surfactant‐in‐lipid aqueous system at high acidity level. The peroxidation of LA was induced by ferrous ions and the kinetics of the produced conjugated dienes was followed by UV measurements and the ferric thiocynate method. Ferrous ions were oxidized only by the preformed LA hydroperoxides, which under established conditions produced lipid alkoxyl and peroxyl radicals as the sole initiators of propagation. The results revealed the LA peroxidation process remained mainly unaffected within the 2.5<pH<5.5 range, while highly pH sensitive around pH 7. The propagation process prevailed at optimal concentrations of 500 µM of LA and 280 µM TWEEN®‐20, and at the ferrous ion concentration up to 75 µM, irrespective of the buffer used.Practical applications: A simple model system in water, suitable for the selective study of the lipid peroxidation propagation phase induced by ferrous ion is presented here. Fatty acids serve as model compounds susceptible to processes associated with oxidative radical initiated‐modifications of lipids. The obtained results contribute to a better understanding of the oxidative behavior of lipids, particularly those soluble in nonionic surfactant micelles in acidic medium. The oxidative stability of the PUFA in model systems containing TWEEN®‐20 and ferrous ion at low pH could be predicted and controlled by measuring the lipid hydroperoxide formation. The experimental conditions presented may also provide a suitable system for the study of the termination phase of lipid peroxidation.
On the Reactivity and Selectivity of Galacturonic Acid Lactones
Authors: Christina Alphert E. , Muns Joey A. , Olivier Jeremy Q. A. , Visser Lotte , Hagen Bas , van den Bos Leendert J. , Overkleeft Herman S. , Codée Jeroen D. C. , van der Marel Gijs A. 
Published: August 2012

AbstractThe reactivity and stereoselectivity of a galacturonic acid 3,6‐lactone thioglycosyl donor, previously described as a highly reactive glycosylating agent, has been investigated by using a series of competition experiments and condensation reactions with different thiophilic activator systems. It is revealed that the relative reactivity of the thioglycosides depends on the activator system used and that p‐nitrophenylsulfenyl triflate shows overall attenuated reactivity differences with respect to the commonly used N‐iodosuccinimide/triflic acid promoter system. With respect to the stereoselectivity of the studied galacturonic acid 3,6‐lactone thioglycosyl donor, it is revealed that a preactivation‐based glycosylation system gives rise to α‐selective glycosylation, whereas an in situ activation protocol leads to the formation of the β‐product with good selectivity. It is hypothesized that these opposingstereoselectivities are the result of different product‐forming intermediates. Where preactivation of the donor leads to the formation of an intermediate β‐triflate, which is substituted in a concerted fashion to provide the α‐product, a 3H4 oxocarbenium ion like species is substituted in the in situ activation experiment to provide the β‐linked product.
Real time hybrid simulation: from dynamic system, motion control to experimental error
Authors: Gao Xiuyu , Castaneda Nestor , Dyke Shirley J. 
Published: August 2012

SUMMARYReal‐time hybrid simulation (RTHS) has increasingly been recognized as a powerful methodology to evaluate structural components and systems under realistic operating conditions. It is a cost effective approach compared with large scale shake table testing. Furthermore, it can maximally preserve rate dependency and nonlinear characteristics of physically tested (non)structural components. Although conceptually very attractive, challenges do exist that require comprehensive validation before RTHS should be employed to assess complicated physical phenomena. One of the most important issues that governs the stability and accuracy of an RTHS is the ability to achieve synchronization of boundary conditions between the computational and physical substructures. The objective of this study is to propose and validate an H∞ loop shaping design for actuator motion control in RTHS. Controller performance is evaluated in the laboratory using a worst‐case substructure proportioning scheme. A modular, one‐bay, one‐story steel moment resisting frame specimen is tested experimentally. Its deformation is kept within the linear range for ready comparison with the reference closed‐form solution. Both system analysis and experimental results show that the proposed H∞ strategy can significantly improve both the stability limit and test accuracy compared with several existing strategies. Another key feature of the proposed strategy is its robust performance in terms of unmodeled dynamics and uncertainties, which inevitably exist in any physical system. This feature is essential to enhance test quality for specimens with nonlinear dynamic behavior, thus ensuring the validity of the proposed approach for more complex RTHS implementations. Copyright © 2012 John Wiley & Sons, Ltd.
A combined local damage index for seismic assessment of existing RC structures
Authors: Mergos P. E. , Kappos A. J. 
Published: August 2012

SUMMARYA new local damage index for existing RC structures is introduced, wherein deterioration caused by all deformation mechanisms (flexure, shear, anchorage slip) is treated separately for each mechanism. Moreover, the additive character of damage arising from the three response mechanisms, and the increase in degradation rate caused by their interaction, are fully taken into consideration. The proposed local damage index is then applied, in conjunction with a finite element model developed previously by the authors, to assess seismic damage response of several RC column and frame test specimens with substandard detailing. It is concluded that in all cases and independently from the prevailing mode of failure, the new local damage index describes well the damage pattern of the analysed specimens. Copyright © 2012 John Wiley & Sons, Ltd.
Structural behaviour and design criteria of under‐deck cable‐stayed bridges subjected to seismic action
Authors: Camara Alfredo , Ruiz‐Teran Ana M. , Stafford Peter J. 
Published: August 2012

SUMMARYUnder‐deck cable‐stayed bridges are very effective structural systems for which the strong contribution of the stay cables under live loading allows for the design of very slender decks for persistent and transient loading scenarios. Their behaviour when subjected to seismic excitation is investigated herein and a set of design criteria are presented that relate to the type and arrangement of bearings, the number and configuration of struts, and the transverse distribution of stay cables. The nonlinear behaviour of these bridges when subject to both near‐field and far‐field accelerograms has been thoroughly investigated through the use of incremental dynamic analyses. An intensity measure that reflects the pertinent contributions to response when several vibration modes are activated was proposed and is shown to be effective for the analysis of this structural type. The under‐deck cable‐stay system contributes in a very positive manner to reducing the response when the bridges are subject to very strong seismic excitation. For such scenarios, the reduction in the stiffness of the deck because of crack formation, when prestressed concrete decks are used, mobilises the cable system and enhances the overall performance of the system. Sets of natural accelerograms that are compliant with the prescriptions of Eurocode 8 were also applied to propose a set of design criteria for this bridge type in areas prone to earthquakes. Particular attention is given to outlining the optimal strategies for the deployment of bearings. Copyright © 2012 John Wiley & Sons, Ltd.
PCDD/F release during benthic trawler-induced sediment resuspension
Authors: Allan Ian J. , Nilsson Hans C. , Tjensvoll Ingrid , Bradshaw Clare , Næs Kristoffer 
Published: August 2012

Abstract
Benthic trawling can cause the resuspension of large amounts of sediments. Such regular practice in the Grenland fjord system in the south of Norway has the potential to affect the fate, movement, and bioavailability of sediment-associated polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs). A novel mode of exposing passive sampling devices consisting of towing semipermeable membrane devices attached to the trawl net was used to gauge in situ changes in the freely dissolved concentration of PCDD/Fs on benthic trawler–induced sediment resuspension. Significant accumulation of a number of PCDD/F congeners was observed despite the short (5 h) sampler exposure times. On average, a one order of magnitude increase in freely dissolved PCCD/F concentrations was seen within minutes of the sediment being resuspended. This observation was supported by similar changes in filtered PCDD/F concentrations measured by high-volume sampling prior to resuspension and in the sediment plume. Environ. Toxicol. Chem. 2012; 31: 2780–2787. © 2012 SETAC