bluuebunny/crossref_metadata_2025_split huggingface dataset:
Data Collection in a Flat World: The Strengths and Weaknesses of Mechanical Turk Samples
Authors: Goodman Joseph K. , Cryder Cynthia E. , Cheema Amar 
Published: April 2012

ABSTRACTMechanical Turk (MTurk), an online labor system run by Amazon.com, provides quick, easy, and inexpensive access to online research participants. As use of MTurk has grown, so have questions from behavioral researchers about its participants, reliability, and low compensation. In this article, we review recent research about MTurk and compare MTurk participants with community and student samples on a set of personality dimensions and classic decision‐making biases. Across two studies, we find many similarities between MTurk participants and traditional samples, but we also find important differences. For instance, MTurk participants are less likely to pay attention to experimental materials, reducing statistical power. They are more likely to use the Internet to find answers, even with no incentive for correct responses. MTurk participants have attitudes about money that are different from a community sample's attitudes but similar to students' attitudes. Finally, MTurk participants are less extraverted and have lower self‐esteem than other participants, presenting challenges for some research domains. Despite these differences, MTurk participants produce reliable results consistent with standard decision‐making biases: they are present biased, risk‐averse for gains, risk‐seeking for losses, show delay/expedite asymmetries, and show the certainty effect—with almost no significant differences in effect sizes from other samples. We conclude that MTurk offers a highly valuable opportunity for data collection and recommend that researchers using MTurk (1) include screening questions that gauge attention and language comprehension; (2) avoid questions with factual answers; and (3) consider how individual differences in financial and social domains may influence results. Copyright © 2012 John Wiley & Sons, Ltd.
Strategy Selection in Risky Choice: The Impact of Numeracy, Affect, and Cross‐Cultural Differences
Authors: Pachur Thorsten , Galesic Mirta 
Published: April 2012

ABSTRACTReal‐world decisions often involve options with outcomes that are uncertain and trigger strong affect (e.g., side effects of a drug). Previous work suggests that when choosing among affect‐rich risky prospects, people are rather insensitive to probability information, potentially compromising decision quality. We modeled the strategies of less and more numerate participants in the United States and in Germany when choosing between affect‐rich prospects and between monetarily equivalent affect‐poor prospects. Using large probabilistic national samples (n = 1047 from the United States and Germany), Study 1 showed that compared with more numerate participants, less numerate participants chose the normatively better option (i.e., the one with the higher expected value) less often, guessed more often, and relied more on a simple risk‐minimizing strategy. U.S. participants—although less numerate—selected the normatively better option more frequently and were more consistent across affect‐rich and affect‐poor problems than the German participants. Using a targeted quota sample (n = 118 from Germany), Study 2 indicated that although both more and less numerate participants paid less attention to probability information in affect‐rich than in affect‐poor problems, the two numeracy groups relied on different outcome‐based heuristics: More numerate participants often followed the minimax heuristic, and less numerate participants the affect heuristic. The observed strategy differences suggest that attempts to improve decision‐making need to take into account individual differences in numeracy as well as cultural‐specific experiences in making trade‐offs. Copyright © 2012 John Wiley & Sons, Ltd.
Zinc in the central nervous system: From molecules to behavior
Authors: Gower‐Winter Shannon D. , Levenson Cathy W. 
Published: April 2012

AbstractThe trace metal zinc is a biofactor that plays essential roles in the central nervous system across the lifespan from early neonatal brain development through the maintenance of brain function in adults. At the molecular level, zinc regulates gene expression through transcription factor activity and is responsible for the activity of dozens of key enzymes in neuronal metabolism. At the cellular level, zinc is a modulator of synaptic activity and neuronal plasticity in both development and adulthood. Given these key roles, it is not surprising that alterations in brain zinc status have been implicated in a wide array of neurological disorders including impaired brain development, neurodegenerative disorders such as Alzheimer's disease, and mood disorders including depression. Zinc has also been implicated in neuronal damage associated with traumatic brain injury, stroke, and seizure. Understanding the mechanisms that control brain zinc homeostasis is thus critical to the development of preventive and treatment strategies for these and other neurological disorders.
Physiological effects of free fatty acid production in genetically engineered Synechococcus elongatus PCC 7942
Authors: Ruffing Anne M. , Jones Howland D.T. 
Published: April 2012

AbstractThe direct conversion of carbon dioxide into biofuels by photosynthetic microorganisms is a promising alternative energy solution. In this study, a model cyanobacterium, Synechococcus elongatus PCC 7942, is engineered to produce free fatty acids (FFA), potential biodiesel precursors, via gene knockout of the FFA‐recycling acyl‐ACP synthetase and expression of a thioesterase for release of the FFA. Similar to previous efforts, the engineered strains produce and excrete FFA, but the yields are too low for large‐scale production. While other efforts have applied additional metabolic engineering strategies in an attempt to boost FFA production, we focus on characterizing the engineered strains to identify the physiological effects that limit cell growth and FFA synthesis. The strains engineered for FFA‐production show reduced photosynthetic yields, chlorophyll‐a degradation, and changes in the cellular localization of the light‐harvesting pigments, phycocyanin and allophycocyanin. Possible causes of these physiological effects are also identified. The addition of exogenous linolenic acid, a polyunsaturated FFA, to cultures of S. elongatus 7942 yielded a physiological response similar to that observed in the FFA‐producing strains with only one notable difference. In addition, the lipid constituents of the cell and thylakoid membranes in the FFA‐producing strains show changes in both the relative amounts of lipid components and the degree of saturation of the fatty acid side chains. These changes in lipid composition may affect membrane integrity and structure, the binding and diffusion of phycobilisomes, and the activity of membrane‐bound enzymes including those involved in photosynthesis. Thus, the toxicity of unsaturated FFA and changes in membrane composition may be responsible for the physiological effects observed in FFA‐producing S. elongatus 7942. These issues must be addressed to enable the high yields of FFA synthesis necessary for large‐scale biofuel production. Biotechnol. Bioeng. 2012;109: 2190–2199. © 2012 Wiley Periodicals, Inc.
Measurement of solar spectra relating to photosynthesis and solar cells: An inquiry lab for secondary science
Authors: Ruggirello Rachel M. , Balcerzak Phyllis , May Victoria L. , Blankenship Robert E. 
Published: April 2012

AbstractThe process of photosynthesis is central to science curriculum at all levels. This article describes an inquiry‐based laboratory investigation developed to explore the impact of light quality on photosynthesis and to connect this process to current research on harvesting solar energy, including bioenergy, artificial photosynthesis, and solar cells. This laboratory was used with high‐school science teachers who then took this experience back to their classrooms. During this exercise, teachers used an economical spectroradiometer to measure the solar spectrum and relate this to photosynthetic light absorption by determining the quality of light beneath trees. Following this investigation, teachers learned about the plant‐inspired dye‐sensitized solar cells and constructed one. To connect their light quality investigation to the efficiency of photosynthesis and solar cells, teachers then collected data at locations with varying quality and intensity of light. In sum, this investigation provides a crucial connection between photosynthesis and cutting edge research on solar energy technologies. Our learning experience provides a new instructional model for understanding a little investigated aspect of photosynthesis and connects to authentic scientific research.
Interactive educational tool for compensators design in MATLAB® using frequency response analysis
Authors: Ramirez‐Cortes Juan Manuel , Alarcon‐Aquino Vicente , Gomez‐Gil Pilar , Diaz‐Mendez Alejandro , Ibarra‐Bonilla Mariana , García‐Enriquez Irma 
Published: April 2012

ABSTRACTThis article presents an educational platform developed to support the teaching of compensators design in a basic control theory course. The application consists of a graphical user interface in MATLAB®, and further connection to the plant under study through the data acquisition toolbox, and a data acquisition card. The developed system allows the students to experiment with parameter changes in the controllers under study, such as gain, overshoot, settling time, and peak time, and visualize results obtained from simulated or real signals. The methodology is based on the frequency response analysis. Typical Bode, root locus, and unit step response plots are easily obtained for a system before and after compensation, in a dynamical way. A modular design allows the students to easily upgrade the application in order to include further methodologies. Results derived from its use in undergraduate and graduate courses are presented. MATLAB is a registered trademark of The MathWorks, Inc.© 2012 Wiley Periodicals, Inc. Comput Appl Eng Educ 22:699–707, 2014; View this article online at wileyonlinelibrary.com/journal/cae; DOI 10.1002/cae.21562
A New Application Area for Ag‐NHCs: CO2 Fixation Catalyst
Authors: Taşcı Zeynep , Kunduracıoğlu Ahmet , Kani İbrahim , Çetinkaya Bekir 
Published: April 2012

AbstractThe first example of the silver‐NHC catalyzed cycloaddition of CO2 to terminal epoxides is reported. The choice of NHC substituents, halides and the nature of additives were determined to be important. Ionic [(Cnmim)2Ag]2[Ag2Br4] (Cnmim=1‐(CnH2n+1)‐3‐methylimidazol‐2‐ylidene; n=4–18) catalysts exhibited a high yield of styrene carbonate (77–92 %) in the presence of 4‐dimethylaminopyridine (DMAP) as a cocatalyst without needing any solvent. The catalytic activity improved as the length of the alkyl groups (n) increased, although substituents longer than C14 did not produce any further beneficial effect. For the protocol performed at 1.5 MPa pressure and 100 °C the TOF was calculated to be 440 h−1. A prolonged reaction time and increased pressure of CO2 increased the yield. Used without any additive, compound C14 was able to fix CO2 with PO (propylene oxide) quantitatively at 120 °C, 2.0 MPa and could be used at least seven times without loss of activity and selectivity. The nucleophilic nature of the anion is decisive for the formation of the product.
On the Stability of Pulse‐Jet Regenerated‐Bag Filter Operation
Authors: Saleem M. , Krammer G. 
Published: April 2012

AbstractProblems with the pulse‐jet bag filter operation have a direct influence on process plant operation and may result in loss of production time. Therefore, long‐term stable operation of the plant is desirable for both the manufacturers and operators. The effects of operating parameters are studied experimentally on filter operation with regeneration between the upper and lower pressure drop limits. Many combinations were identified when the filter operation derailed from stable to unstable operation on changing one of the operating parameters. Filtration velocity, pulse pressure, and the upper limit of pressure drop had the potential of creating instability. A threshold detachment overpressure existed below which the operation led to unstable conditions at a certain filtration velocity and which increased with increasing velocity.
Gold(I) Styrylbenzene, Distyrylbenzene, and Distyrylnaphthalene Complexes: High Emission Quantum Yields at Room Temperature
Authors: Gao Lei , Niedzwiecki Daniel S. , Deligonul Nihal , Zeller Matthias , Hunter Allen D. , Gray Thomas G. 
Published: April 2012

AbstractOne gold(I)‐substituted styrylbenzene, six digold(I) distyrylbenzenes, one tetragold distyrylbenzene, and four digold distyrylnaphthalene complexes were synthesized using base‐promoted auration, alkynylation, triazolate formation, and Horner–Wadsworth–Emmons reactions. The gold(I) fragments are either σ‐bonded to the aromatic system, or they are attached through an alkynyl or triazolate spacer. Product formation was monitored using 31P{1H} NMR spectroscopy. Systems in which gold(I) binds to the central benzene ring or the terminal phenyl rings were designed. All of these complexes have strong ultraviolet absorptions and emit blue light. The position of the gold(I) attachment influences the luminescence efficiency. Complexes with two gold(I) fragments attached to the ends of the conjugated system have fluorescence quantum yields up to 0.94, when using 7‐diethylamino‐4‐methylcoumarin as the emission standard. Density‐functional theory calculations on three high‐yielding emitters suggest that luminescence originates from the distyrylbenzene or ‐naphthalene bridge.
4‐(N,N‐Dimethylamino)pyridine‐Embedded Nanoporous Conjugated Polymer as a Highly Active Heterogeneous Organocatalyst
Authors: Zhang Yuan , Zhang Yong , Sun Ya Lei , Du Xin , Shi Jiao Yi , Wang Wei David , Wang Wei 
Published: April 2012

AbstractWe report herein for the first time the incorporation of a versatile organocatalyst, 4‐(N,N‐dimethylamino)pyridine (DMAP), into the network of a nanoporous conjugated polymer (NCP) by the “bottom‐up” approach. The resulting DMAP‐NCP material possesses highly concentrated and homogeneously distributed DMAP catalytic sites (2.02 mmol g−1). DMAP‐NCP also exhibits enhanced stability and permanent porosity due to the strong covalent linkage and the rigidity of the “bottom‐up” monomers. As a result, DMAP‐NCP shows excellent catalytic activity in the acylation of alcohols with yields of 92–99 %. The DMAP‐NCP catalyst could be easily recovered from the reaction mixture and reused in at least 14 consecutive cycles without measurable loss of activity. Moreover, the catalytic acylation reaction could be performed under neat and continuous‐flow conditions for at least 536 h of continuous work with the same catalyst activity.
The Reaction of Sulfenic Acids with Peroxyl Radicals: Insights into the Radical‐Trapping Antioxidant Activity of Plant‐Derived Thiosulfinates
Authors: Amorati Riccardo , Lynett Philip T. , Valgimigli Luca , Pratt Derek A. 
Published: April 2012

AbstractSulfenic acids play a prominent role in biology as key participants in cellular signaling relating to redox homeostasis, in the formation of protein‐disulfide linkages, and as the central players in the fascinating organosulfur chemistry of the Allium species (e.g., garlic). Despite their relevance, direct measurements of their reaction kinetics have proven difficult owing to their high reactivity. Herein, we describe the results of hydrocarbon autoxidations inhibited by the persistent 9‐triptycenesulfenic acid, which yields a second order rate constant of 3.0×106 M−1 s−1 for its reaction with peroxyl radicals in PhCl at 30 °C. This rate constant drops 19‐fold in CH3CN, and is subject to a significant primary deuterium kinetic isotope effect, kH/kD=6.1, supporting a formal H‐atom transfer (HAT) mechanism. Analogous autoxidations inhibited by the Allium‐derived (S)‐benzyl phenylmethanethiosulfinate and a corresponding deuterium‐labeled derivative unequivocally demonstrate the role of sulfenic acids in the radical‐trapping antioxidant activity of thiosulfinates, through the rate‐determining Cope elimination of phenylmethanesulfenic acid (kH/kD≈4.5) and its subsequent formal HAT reaction with peroxyl radicals (kH/kD≈3.5). The rate constant that we derived from these experiments for the reaction of phenylmethanesulfenic acid with peroxyl radicals was 2.8×107 M−1 s−1; a value 10‐fold larger than that we measured for the reaction of 9‐triptycenesulfenic acid with peroxyl radicals. We propose that whereas phenylmethanesulfenic acid can adopt the optimal syn geometry for a 5‐centre proton‐coupled electron‐transfer reaction with a peroxyl radical, the 9‐triptycenesulfenic is too sterically hindered, and undergoes the reaction instead through the less‐energetically favorable anti geometry, which is reminiscent of a conventional HAT.
Synthesis of Planar Chiral Iridacycles by Cationic Metal π‐Coordination: Facial Selectivity, and Conformational and Stereochemical Consequences
Authors: Djukic Jean‐Pierre , Iali Wissam , Pfeffer Michel , Le Goff Xavier‐Frédéric 
Published: April 2012

AbstractFacial selectivity during the π‐coordination of pseudo‐tetrahedral iridacycles by neutral (Cr(CO)3), monocationic (Cp*Ru+), and biscationic (Cp*Ir2+) metal centers was directly influenced by the coulombic imbalance in the coordination sphere of the chelated Ir center. We also showed by using theoretical calculations that the feasibility of the related metallacycles that displayed metallocenic planar chirality was dependent to the presence of an electron‐donating group, such as NMe2, which contributed to the overall stability of the complexes. When the π‐bonded moiety was the strongly electron‐withdrawing Cp*Ir2+ group, the electron donation from NMe2 resulted in major conformational changes, with a barrier to rotation of about 17 kcal mol−1 for this group that became spectroscopically diastereotopic (high‐field 1H NMR spectroscopy). This peculiar property is proposed as a means to introduce a new type of constitutional chirality at the nitrogen center: planar chirality at tertiary aromatic amines.
Nickel‐Mediated Inter‐ and Intramolecular Reductive Cross‐Coupling of Unactivated Alkyl Bromides and Aryl Iodides at Room Temperature
Authors: Yan Chang‐Song , Peng Yu , Xu Xiao‐Bo , Wang Ya‐Wen 
Published: April 2012

AbstractA nickel‐mediated intermolecular reductive cross‐coupling reaction of unactivated alkyl bromides and aryl iodides at room temperature has been developed and successfully extended to less explored intramolecular versions and tandem cyclization‐intermolecular cross‐coupling. Highly stereoselective (or stereospecific) synthesis of linear‐fused perhydrofuro[2,3‐b]furan (pyran) and spiroketal skeletons allows rapid access to these useful building blocks, which would be potentially valuable in the synthesis of relevant natural products. A rational explanation for the formation of contiguous stereogenic centers is given.
Nickel(II) and Copper(II) Complexes of β‐Unsubstituted 5,15‐Diazaporphyrins and Pyridazine‐Fused Diazacorrinoids: Metal–Template Syntheses and Peripheral Functionalizations
Authors: Matano Yoshihiro , Shibano Tarou , Nakano Haruyuki , Imahori Hiroshi 
Published: April 2012

AbstractThe present paper reports the first comprehensive study on the synthesis, structures, optical and electrochemical properties, and peripheral functionalizations of nickel(II) and copper(II) complexes of β‐unsubstituted 5,15‐diazaporphyrins (M‐DAP; M=Ni, Cu) and pyridazine‐fused diazacorrinoids (Ni‐DACX; X=N, O). These two classes of compounds were constructed starting from mesityldipyrromethane by a metal–template method. Ni‐DAP and Cu‐DAP were prepared in high yields by the reaction of the respective metal–bis(dibromodipyrrin) complexes with NaN3–CuX (X=I, Br), whereas Ni‐DACN and Ni‐DACO were formed as predominant products by the reaction with NaN3. In both cases, the metal centers change their geometry from tetrahedral to square planar during the aza‐annulation; X‐ray crystallographic analyses of M‐DAPs showed highly planar diazaporphyrin π planes. The Q band of Ni‐DAP was redshifted and intensified compared with that of a nickel–porphyrin reference, due to the involvement of electronegative nitrogen atoms at the meso positions. It was found that the peripheral bromination of Ni‐DAP and Ni‐DACO occurred regioselectively to afford Ni‐DAP‐Br4 and Ni‐DACO‐Br, respectively. These brominated derivatives underwent Stille reactions with tributyl(phenyl)stannane to give the corresponding phenylated derivatives, Ni‐DAP‐Ph4 and Ni‐DACO‐Ph. On the basis of the absorption spectra and X‐ray analysis, it has been concluded that the attached phenyl groups efficiently conjugate with the diazaporphyrin π system. The present results unambiguously corroborate that the β‐unsubstituted DAPs and DACXs are promising platforms for the development of a new class of π‐conjugated azaporphyrin‐based materials.
Water‐soluble/dispersible carbazole‐containing random and block copolymers by nitroxide‐mediated radical polymerisation
Authors: Lessard Benoît H. , Marić Milan 
Published: April 2012

AbstractA series of carbazole‐containing water‐dispersible poly(acrylic acid)‐b‐(9‐(4‐vinylbenzyl)‐9H‐carbazole) block copolymers (poly(AA)‐b‐poly(VBK)) and water‐soluble poly(methacrylic acid‐ran‐(9‐(4‐vinylbenzyl)‐9H‐carbazole)) (poly(MAA‐ran‐VBK)) random copolymers were synthesised in a controlled manner (i.e. low polydispersities $(\overline {M_{{\rm w}} } /\overline {M_{n} } < 1.3)$ by nitroxide‐mediated polymerisation (NMP) using an SG1‐based alkoxyamine initiator, BlocBuilder. Poly(AA)‐b‐poly(VBK) block copolymers were most easily accessed by using poly(AA) in its protected form as the macroinitiator for the 9‐(4‐vinylbenzyl)‐9H‐carbazole (VBK) block. Controlled polymerisation of MAA was accomplished using an excess of 10 mol.% SG1 relative to BlocBuilder with VBK as controlling co‐monomer (initial molar feed content fVBK,0 = 0.03–0.20) in dimethylformamide at 80°C. Poly(MAA‐ran‐VBK) copolymers with a final VBK molar composition of FVBK < 0.30 resulted in water‐soluble copolymers. In addition, as macroinitiators, poly(MAA‐ran‐VBK)s were sufficiently pseudo‐living to reinitiate a second batch of monomer (90 mol.% methyl methacrylate with styrene) in organic solvent and by ab initio, surfactant‐free emulsion polymerisation. In both cases, low polydispersity, amphiphilic block copolymers resulted $(\overline {M_{{\rm w}} } /\overline {M_{{\rm n}} } < 1.3)$. © 2012 Canadian Society for Chemical Engineering
Testing uniformity for the case of a planar unknown support
Authors: Berrendero José R. , Cuevas Antonio , Pateiro‐López Beatriz 
Published: April 2012

AbstractA new test is proposed for the hypothesis of uniformity on bi‐dimensional supports. The procedure is an adaptation of the “distance to boundary test” (DB test) proposed in Berrendero, Cuevas, & Vázquez‐Grande (2006). This new version of the DB test, called DBU test, allows us (as a novel, interesting feature) to deal with the case where the support S of the underlying distribution is unknown. This means that S is not specified in the null hypothesis so that, in fact, we test the null hypothesis that the underlying distribution is uniform on some support S belonging to a given class ${\cal C}$. We pay special attention to the case that ${\cal C}$ is either the class of compact convex supports or the (broader) class of compact λ‐convex supports (also called r‐convex or α‐convex in the literature). The basic idea is to apply the DB test in a sort of plug‐in version, where the support S is approximated by using methods of set estimation. The DBU method is analysed from both the theoretical and practical point of view, via some asymptotic results and a simulation study, respectively. The Canadian Journal of Statistics 40: 378–395; 2012 © 2012 Statistical Society of Canada