bluuebunny/crossref_metadata_2025 huggingface dataset:
Efficient utilization of plastic waste through product design and process adaptation: A case study on stiffness enhancement of beams produced from plastic lumber
Authors: Pio Cristian , Greco Antonio , Maffezzoli Alfonso , Marseglia Alessandro
Published: April 2009

The aim of the present work is the development of a method for structural reinforcement of beams obtained by in‐mold extrusion of plastics from solid urban waste. The beams obtained by in‐mold extrusion are commonly used for outdoor furniture and structures. The material used for such applications is mainly composed of low‐density polyethylene derived from bags and films, with small amounts of high density polyethylene and polypropylene, as well as traces of polyethylene terephthalate. This material is usually referred to as “plastic lumber.” Plastic lumber products have a low stiffness, which results in high deflections under flexural loads, particularly under creep loading. In this study, reinforcing rods of high aspect ratio were incorporated into plastic lumber beams in specific positions with respect to the cross section of the beam. The reinforcement of the plastic lumber beams with fine rods is introduced in the typical intrusion process used for the production of unreinforced beams. Glass fiber reinforced pultruded rods were chosen for this purpose from a preliminary evaluation of different materials. Different diameter glass fiber reinforced pultruded rods, including surface‐abraded systems to increase the roughness, were used for the reinforcement of plastic lumber beams. The reinforced beams were tested in terms of flexural stiffness, creep resistance, and pullout resistance of the embedded rods. The results obtained from the mechanical tests showed a significant enhancement of flexural stiffness and creep resistance behavior. The performance at higher stress levels was shown to be significantly dependent on the interfacial adhesion between rods and polymer matrix. © 2009 Wiley Periodicals, Inc. Adv Polym Techn 27:133–142, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/adv.20131
Variable mold temperature to improve surface quality of microcellular injection molded parts using induction heating technology
Authors: Chen Shia‐Chung , Lin Yu‐Wan , Chien Rean‐Der , Li Hai‐Mei
Published: April 2009

Microcellular foam injection molding provides many advantages over conventional foams and their unfoamed counterparts, but its applications are limited by visible surface quality problems such as silver streaks and swirl marks. In this study, we propose a variable mold temperature method to improve the surface quality of molded parts. Electromagnetic induction heating is used in combination with water cooling to achieve rapid mold surface temperature control during the microcellular foam injection molding process. The effect of processing parameters, such as mold temperature, melt temperature, and injection velocity on the part surface quality, was investigated using surface roughness measurements and visual inspection of the molded parts. The results show that using induction heating to increase the mold surface temperature from 100°C to 160°C can decrease surface roughness of polycarbonate moldings from 25 µm to 6.5 µm. It was also found that the flow marks formed by gas bubbles on the part surface can be removed completely at a mold temperature of 160°C. Further increases in the mold temperature show slight improvements in the surface roughness up to 180°C, at which point the surface roughness starts to level off at 5 µm. This surface roughness value reflects an 80% improvement without a significant increase in cycle time over parts molded at a mold temperature of 60°C using water heating. Higher melt temperature and faster injection speed will also improve the surface quality of microcellular injection molded parts but not as significantly. The usefulness of a variable mold temperature in improving part surface quality during microcellular foam injection molding has been successfully demonstrated. © 2009 Wiley Periodicals, Inc. Adv Polym Techn 27:224–232, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/adv.20133
Overview of polymer micro/nanomanufacturing for biomedical applications
Authors: Yi Allen Y. , Lu Wu , Farson Dave F. , Lee L. James
Published: April 2009

Micro/nanotechnology is initiated from the electronics industry. In recent years, it has been extended to micro/nanoelectromechanic system for producing miniature devices based on silicon and semiconductor materials. However, the use of these hard materials alone is inappropriate for many biomedical devices. Soft polymeric materials possess many attractive properties such as high toughness and recyclability. Some possess excellent biocompatibility, are biodegradable, and can provide various biofunctionalities. Proper combinations of micro/nanoelectronics, polymers, and biomolecules can lead to new and affordable medical devices. In this paper, we briefly review several cleanroom and noncleanroom techniques related to micro/nanomanufacturing of polymeric materials. © 2009 Wiley Periodicals, Inc. Adv Polym Techn 27:188–198, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/adv.20134
Injection molding control: From single cycle to batch control
Authors: Yang Yi , Yao Ke , Gao Furong
Published: April 2009

Closed‐loop control of key process variables in injection molding has become an essential part of the quality assurance system. Advanced control algorithms such as adaptive control and model predictive control have been adopted to deal with the inherent process nonlinearity and time‐varying characteristics. These control algorithms are all focused on single‐cycle control performance. Recently, a multicycle, two‐dimensional model predictive learning control has been developed for batch process control. This method has been applied to injection molding. In this paper, the basic principles of these control algorithms are introduced, with the control performance demonstrated by injection velocity control. © 2009 Wiley Periodicals, Inc. Adv Polym Techn 27:217–223, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/adv.20135
Rapid thermal cycling of injection molds: An overview on technical approaches and applications
Authors: Yao Donggang , Chen Shia‐Chung , Kim Byung H.
Published: April 2009

A heated mold with temperature above the polymer‐softening temperature is highly desired in precision injection molding. The elevated mold temperature reduces unwanted freezing during the injection stage, thus improving moldability and enhancing part quality. The resulting advantages include, but are not limited to, longer flow path, improved feature replication and surface transcription, reduced molecular orientations and residual stresses, smoother surfaces of composites, better control of crystallization, stronger weld lines, etc. However, the heated mold needs to be rapidly cooled during the cooling stage to maintain a short cycle time. Despite the large body of available literature, mold rapid heating and cooling does not represent a well‐developed area of practice. Development of capable techniques for rapidly heating and cooling a mold with a relatively large mass is technically challenging because of the constraints set by the heat transfer process and the endurance limits set by the material properties. This article attempts to offer a constructive overview on the state of the art in mold rapid heating and cooling, with the goal of explaining the working mechanisms and providing unbiased accounts of the pros and cons of existing processes and techniques. Successful applications of existing processes are highlighted and potential improvements of these processes are suggested. The article further intends to provide a fundamental understanding of the constituent elements and corresponding building blocks needed in a workable mold with a rapid heating and cooling capability. An increased understanding of these elements will facilitate the development of more capable new processes. © 2009 Wiley Periodicals, Inc. Adv Polym Techn 27:233–255, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/adv.20136
Study of oriented polyvinyl chloride pipes by inner‐pressing expansion
Authors: Dong W. Y. , Ren D. Y. , Wu D. M. , You S. B. , Zhang B.
Published: April 2009

Based on a new expansion technology for oriented polyvinyl chloride (PVC‐O) pipes, the stress distribution in pipe wall during expansion and the efficiency of the heating process are analyzed theoretically. According to the results of theoretical calculation, the optimal parameter and strength variation for different expansion ratios are studied experimentally. Theoretical calculation results show that the hoop stress and radial stress in pipe wall are near‐linearly distributed, and they are approximately equal. The heating efficiency is gotten by heat transfer calculations for different oil bath temperatures and heating times. After expansion, the intensity and Young's modulus are increased but elongation at break is reduced. All the variations in properties enlarge along with the raise of expansion ratio. Fine appearance and high‐strength PVC‐O pipe can be achieved by optimizing the expansion parameter. © 2009 Wiley Periodicals, Inc. Adv Polym Techn 27:172–181, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/adv.20137
Process optimization and effects of material properties on numerical prediction of warpage for injection molding
Authors: Gao Yuehua , Turng Lih‐Sheng , Wang Xicheng
Published: April 2009

This study aims to illustrate the importance of accurate material property data in the numerical simulation of injection molding by elucidating the effects of variation in material properties on warpage prediction. In addition, it presents an adaptive optimization method based on the Kriging surrogate model that has been developed to intelligently determine the optimal processing parameters for minimizing warpage in a box‐shape part with different and stepwise wall thicknesses. The Kriging surrogate model is a statistics‐based interpolation technique that provides the approximate functional relationship between the performance variables of interest, like warpage, and the factors affecting them, such as the processing parameters. Based on optimal processing parameters, the sensitivity of warpage prediction to two of the most important material properties—shear viscosity and the pvT (pressure–specific volume–temperature) relationship—were analyzed. It is well known that the material property model constants used for numerical simulation can sometimes vary significantly due to inherent experimental measurement errors, the resolution of the testing device, and/or the way the curve fitting is performed to determine the model constants. The results showed that hypothetical and yet reasonable variations in the shear viscosity model constants and in the pvT relationship could significantly affect the magnitude of warpage prediction. © 2009 Wiley Periodicals, Inc. Adv Polym Techn 27:199–216, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/adv.20138
Thermoregulatory sympathetic nervous system activity and diet‐induced waist‐circumference reduction in obese Japanese women
Authors: Fujibayashi Mami , Hamada Taku , Matsumoto Tamaki , Kiyohara Natsuki , Tanaka Seitaro , Kotani Kazuhiko , Egawa Kahori , Kitagawa Yoshinori , Kiso Yoshinobu , Sakane Naoki , Moritani Toshio
Published: April 2009

The present study is designed to investigate how and to what extent sympathovagal behavior in a balanced low‐calorie diet relates to favorable changes of body mass, waist circumference, and/or metabolic risk factors. The study involved 28 mildly obese women without clinical complications, who underwent an 8‐week calorie restriction program using a 1,200‐kcal daily diet with an adequate nutrient content; including two regular meals, and one formula meal replacement. All subjects were examined before and after the dietary intervention. We measured anthropometric parameters, blood pressure, and biochemical blood profiles for lipid metabolism. Autonomic nervous system activity was evaluated by heart rate variability power spectral analysis. The dietary intervention induced moderate, but significant reduction of waist circumference (−5.3% ± 0.8%), body fat percentage (−5.8% ± 0.8%), and body mass (−6.6% ± 0.5%). Linear regression analysis showed that Δvery low frequency (VLF) power reflecting energy metabolic‐ and thermoregulatory sympathetic function significantly correlated to Δwaist circumference (r = −0.53, P < 0.01), Δbody fat percentage (r = −0.39, P < 0.05), Δbody mass (r = −0.43, P < 0.05), ΔHDL‐cholesterol/total cholesterol ratio (HDL‐C/TC) (r = 0.62, P < 0.001), and Δnonesterified fatty acids (NEFA) (r = 0.56, P < 0.01). A stepwise multiple regression analysis additionally revealed that Δwaist circumference (P = 0.024), ΔHDL‐C/TC (P = 0.013), and ΔNEFA (P = 0.016) were significant and independent factors, which contributing to the variance in ΔVLF power (r2 = 0.61). Although causes and consequences of obesity continue to elude researchers, the present study indicates that thermoregulatory sympathetic activity relates to moderate waist‐circumference reduction together with favorable changes of blood lipid profiles after short‐term dietary modification in mildly obese women. Am. J. Hum. Biol. 2009. © 2009 Wiley‐Liss, Inc.
Breastfeeding structure as a test of parental investment theory in Papua New Guinea
Authors: Tracer David P.
Published: April 2009

Evolutionary parental investment theory predicts that parents invest preferentially in offspring best able to translate investments into fitness payoffs. It has also been proposed that where the reproductive prospects of offspring are directly correlated with parental investment and variance in fertility is higher for males than females, parents in better condition should bias investment toward males while those in poorer condition should bias investment toward females. Lactation is arguably among the costliest forms of investment expended by mothers and is thus expected to be allocated in ways consistent with fitness payoffs. Quantitative data collected among 110 Papua New Guinean mother‐infant pairs during 470 h of focal follows on nursing frequency and duration and responses to infant demands by maternal and offspring characteristics are presented to provide empirically‐based descriptions of infant care and tests of evolutionary parental investment theory. Results indicate that mothers show very high levels of investment in offspring. However, although breastfeeding in developing countries is often characterized as on‐demand, fussing and crying by infants were only attended to with breastfeeding about 30% of the time. Contrary to expectations of parental investment theory that parents should invest less in poorer quality offspring, mothers increased investment in offspring in poorer condition. The expectation that mothers in better condition would bias investment toward male offspring was also not supported; better nourished mothers biased investment toward female offspring. This study illustrates how infant feeding data may be used for testing larger evolutionary questions such as those derived from parental investment theory. Am. J. Hum. Biol. 2009. © 2009 Wiley‐Liss, Inc.
Integration of proximate and evolutionary explanation of reproductive strategy: The case of callitrichid primates and implications for human biology
Authors: Tardif Suzette D. , Ross Corinna N.
Published: April 2009

We offer examples of how proximate and evolutionary forms of argument may inform each other in better understanding reproductive strategy in callitrichid primates, the smallest of the anthropoid primates. In addition, we illustrate how comparative approaches, when applied judiciously, can aid in the formulation of hypotheses regarding even seemingly unique traits within a taxonomic group. In the first example, examination of the nature of genetics in cytokine systems that leads to altered ovulation number in sheep suggests some relatively simple changes could explain both the adaptation of increased ovulation number in marmosets and the subsequent decrease in ovulation number in the closely related species, callimico. In the second example, the role of body size and phylogeny in explaining the role of maternal energy constraints upon gestation and lactation is explored, leading to additional hypotheses regarding these relations in a species that is both small but also in a phylogenetic line selected for slow reproduction. Finally, the role of comparative data in the study of proximate and evolutionary explanations of “unique” human reproductive strategies is discussed. Am. J. Hum. Biol., 2009. © 2009 Wiley‐Liss, Inc.
Epidemic of plurality and contributions of assisted reproductive technology therein
Authors: Kapoor Monica , Pal Lubna
Published: April 2009

A commentary on contributions of ART to the pandemic of multiple gestations is presented and mechanistic aspects therein are explored. © 2009 Wiley‐Liss, Inc.
Not really identical: Epigenetic differences in monozygotic twins and implications for twin studies in psychiatry
Authors: Haque F. Nipa , Gottesman Irving I. , Wong Albert H.C.
Published: April 2009

Classical twin studies in the field of psychiatry generally fall into one of two categories: (1) those designed to identify environmental risk factors causing discordance in monozygotic (MZ) twins and (2) those geared towards identifying genetic risk factors. However, neither environment nor differences in DNA sequence can fully account for phenotypic discordance among MZ twins. The field of epigenetics – DNA modifications that can affect gene expression – offers new models to understand discordance in MZ twins. In the past, MZ twins were regarded as genetically‐identical controls for differing environmental conditions. In contrast, the evolving current concept is that epigenetic differences between MZ twins may modulate differences in diverse phenotype, from disease to personality. In this article, we review some twin studies, and discuss the dynamic interactions between stochastic, environmental, and epigenetic variables that influence neurobiological phenotypes. © 2009 Wiley‐Liss, Inc.
Twinning on the brain: The effect on neurodevelopmental outcomes
Authors: Luu Thuy Mai , Vohr Betty
Published: April 2009

Twinning is currently considered a complex multifactorial trait. Few studies have explored how the unique genetic and environmental influences that create twinning affect phenotypes and outcomes. Previous data has shown that twins account for a significant proportion of preterm and low‐birth‐weight infants, who are at risk for long‐term neurodevelopmental disabilities such as cerebral palsy and cognitive impairment. More recently, it has been postulated that even without these co‐morbidities, twinning in and of itself may incur a neurodevelopmental disadvantage even among term newborns. The purpose of this review is to report primarily on neuromotor outcomes of twins compared to singletons. In addition, we describe specific environmental risk factors among twins which are associated with poorer outcomes. Several putative neurodevelopmental modulators are explored, including death of a co‐twin, chorionicity, birth weight discordance, and twin‐twin transfusion. By teasing out environmental influences that potentially influence neurocognitive outcomes, families can receive more specific counseling and developmental services can be provided to those twins at especially high risk. © 2009 Wiley‐Liss, Inc.
MFM/geneticist view on prenatal management of twins
Authors: O'Brien Barbara M.
Published: April 2009

Twin pregnancies are associated with an increase in both fetal and maternal morbidity and mortality. Health care supervision is complex, increasingly requiring care from maternal‐fetal medicine specialists. This review discusses optimal twin prenatal management, which includes recognizing increased twin pregnancy risks specific to twin‐types; counseling families regarding fetal complications, ranging from prematurity to cerebral palsy; screening for aneuploidy and open neural tube defects; specific twin guidelines for diagnostic testing, including chorionic villus sampling and amniocentesis; and monitoring for maternal complications. © 2009 Wiley‐Liss, Inc.
Clinical significance of chimerism
Authors: Abuelo Dianne
Published: April 2009

Twins have been previously classified as either monozygotic or dizygotic. In recent years, fascinating, non‐traditional mechanisms of twinning have been uncovered. We define chimerism versus mosaicism, touch on chimerism in the animal world, and explain timing of chimerism in humans. In addition, we discuss when to suspect chimerism in patients, and how to proceed with diagnostic evaluation and confirmation. © 2009 Wiley‐Liss, Inc.
Simvastatin therapy prevents brain trauma‐induced increases in β‐amyloid peptide levels
Authors: Abrahamson Eric E. , Ikonomovic Milos D. , Dixon C. Edward , DeKosky Steven T.
Published: April 2009

Elevations in β‐amyloid peptide (Aβ) levels after traumatic brain injury (TBI) may confer risk for developing Alzheimer's disease in head trauma patients. We investigated the effects of simvastatin, a 3‐hydroxy‐3‐methylglutaryl‐CoA reductase inhibitor, on hippocampal Aβ burden in a clinically relevant head injury/intervention model using mice expressing human Aβ. Simvastatin therapy blunted TBI‐induced increases in Aβ, reduced hippocampal tissue damage and microglial activation, and improved behavioral outcome. The ability of statins to reduce post‐injury Aβ load and ameliorate pathological sequelae of brain injury makes them potentially effective in reducing the risk of developing Alzheimer's disease in TBI patients. Ann Neurol 2009;66:407–414
Synthesis of Supramolecular Nanocapsules Based on Threading of Multiple Cyclodextrins over Polymers on Gold Nanoparticles
Authors: Wu Yun‐Long , Li Jun
Published: April 2009

Feststeckende CDs: Auf Goldnanopartikeln (AuNPs) verankerte Polyethylenglycol‐Ketten werden durch mehrere α‐Cyclodextrin(α‐CD)‐Ringe gefädelt, was eine supramolekulare äußere Schicht aus zur Nanopartikeloberfläche senkrechten Pseudopolyrotaxansäulen ergibt. Stopper an den Polymerenden halten α‐CD an der AuNP‐Oberfläche fest, Vernetzen der α‐CD‐Ringe und Entfernen der AuNP‐Kerne liefert supramolekulare Nanokapseln.

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Coherent Activation of DNA Tweezers: A “SET–RESET” Logic System
Authors: Elbaz Johann , Moshe Michal , Willner Itamar
Published: April 2009

Sesam, öffne dich! Aptamer‐Substrat‐Komplexe aktivieren die kohärente Funktion zweier Pinzettenstrukturen, die als “SET‐RESET”‐Logiksystem wirken. Bei Einwirkung von Adenosinmonophosphat (AMP) und Adenosin‐Desaminase (AD) wechseln die Pinzettenstrukturen jeweils zwischen einem fluoreszierenden offenen und einem gelöschten geschlossenen Zustand (Q=Löscheinheit, F=Fluorophor).

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One‐Step Synthesis and Characterization of Gold–Hollow PbSx Hybrid Nanoparticles
Authors: Yang Jian , Peng JunJun , Zhang Qingbo , Peng Feng , Wang Hongjuan , Yu Hao
Published: April 2009

Bleiernes Gold: Hohle PbSx‐Au‐Hybridnanostrukturen von etwa 10 nm Durchmesser wurden unter milden experimentellen Bedingungen mithilfe einer einstufigen Reaktion synthetisiert. Die Redoxreaktion von Goldvorstufen mit PbS‐Nanokristallen in Gegenwart von Dodecylamin liefert die hohlen Hybridnanostrukturen (siehe Bild).

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Cation–Cation Interactions, Magnetic Communication, and Reactivity of the Pentavalent Uranium Ion [U(NtBu)2]+
Authors: Spencer Liam P. , Schelter Eric J. , Yang Ping , Gdula Robyn L. , Scott Brian L. , Thompson Joe D. , Kiplinger Jaqueline L. , Batista Enrique R. , Boncella James M.
Published: April 2009

Die Kommunikation stimmt: Der dimere Bis(imido)uran‐Komplex [{U(NtBu)2(I)(tBu2bpy)}2] (siehe Bild; U grün, N blau, I rot) weist Kation‐Kation‐Wechselwirkungen zwischen [U(NR)2]+‐Ionen auf. Es ist ein f 1‐f 1‐System, das außerdem eine f‐Orbital‐Kommunikation zwischen den Uran(V)‐Zentren bei niedrigen Temperaturen zeigt. Durch Oxidation können Bis(imido)uran(VI)‐Komplexe erhalten werden.

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A Stereoselective Synthesis of the Bromopyrrole Natural Product (−)‐Agelastatin A
Authors: Wehn Paul M. , Du Bois J.
Published: April 2009

Elf Stufen müssen′s sein: Eine neue stereoselektive Synthese von (−)‐Agelastatin A benötigt elf Stufen ausgehend von kommerziell erhältlichem Ausgangsmaterial. Eine Rh‐katalysierte intramolekulare Olefinaziridinierung und die nachfolgende Umsetzung des entstehenden tricyclischen Zwischenprodukts sind die Schlüsselschritte der Synthese (siehe Schema).

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Metabolic Labeling of Sialic Acids in Living Animals with Alkynyl Sugars
Authors: Chang Pamela V. , Chen Xing , Smyrniotis Chris , Xenakis Alexander , Hu Tianshun , Bertozzi Carolyn R. , Wu Peng
Published: April 2009

Süße Hilfe: Sialinsäuren spielen bei vielen Wirt‐Pathogen‐Erkennungsereignissen eine Rolle und markieren embryonale und bösartige Gewebe, was zu einem großen Interesse an Verfahren zur Anreicherung und Identifizierung sialylierter Glycoproteine in komplexen Geweben führt. Nun kann N‐(4‐Pentinoyl)mannosamin zur metabolischen Markierung sialylierter Glycoproteine in lebenden Tieren genutzt werden.

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Ionic Circuits Based on Polyelectrolyte Diodes on a Microchip
Authors: Han Ji‐Hyung , Kim Kwang Bok , Kim Hee Chan , Chung Taek Dong
Published: April 2009

Bei Grün gehen: Eine Polyelektrolytdiode auf einem Mikrochip zeigt ein eindeutiges nichtlineares Gleichrichterverhalten. Mit diesem System lässt sich in Echtzeit die dynamische Verteilung von Ionen in einer geladenen Polymerphase im elektrischen Feld mithilfe von Fluoreszenzbildern visualisieren. Mehrere Polyelektrolytdioden wurden auf einem Mikrochip integriert, um vielfältige Logikgatter auf Basis ionischer Schaltkreise herzustellen (siehe Bild).

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Synthesis and Crystal Structure of a Silyl‐Stabilized Allyl Cation Formed by Disruption of an Arene by a Protonation–Hydrosilylation Sequence
Authors: Duttwyler Simon , Zhang Yun , Linden Anthony , Reed Christopher A. , Baldridge Kim K. , Siegel Jay S.
Published: April 2009

Die Protonierung eines Mesitylenrings durch das stark saure Areniumcarboran [CH3C6H6][CHB11Me5Br6] löst eine Reaktionskaskade aus, die zu einem stabilen β‐Silylallylkation führt (siehe Bild, H gelb, C blau, Silylallylgruppe rot). Dass die Triebkraft der Reaktion ausreicht, um einen stabilen aromatischen Ring zugunsten einer kationischen reaktiven Zwischenstufe zu zerstören, ist bemerkenswert.

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Computer‐Aided Design of a Sulfate‐Encapsulating Receptor
Authors: Custelcean Radu , Bosano Jerome , Bonnesen Peter V. , Kertesz Vilmos , Hay Benjamin P.
Published: April 2009

Maßanfertigung: Eine neue computergestützte Methode wird vorgestellt, um effizientere selbstorganisierte Käfigrezeptoren zu erhalten. Der resultierende tetraedrische M4L6‐Käfig mit exakt positionierten H‐Brücken‐bildenden Harnstoffgruppen (siehe Struktur; gelb: Vorhersage, blau: experimentell ermittelt, Kalottenmodell: SO42−) erwies sich in Wasser als bemerkenswert starker Sulfatrezeptor.

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Selective Homologation Routes to 2,2,3‐Trimethylbutane on Solid Acids
Authors: Ahn John H. , Temel Burcin , Iglesia Enrique
Published: April 2009

Sieben als magische Kohlenstoffzahl: 2,2,3‐Trimethylbutan (Triptan) entsteht an sauren Zeolithen bei niedrigen Temperaturen selektiv aus Dimethylether. Die Methylierung an weniger substituierten Kohlenstoffatomen, das Verhältnis der Geschwindigkeiten von Methylierung und Wasserstofftransfer bei unterschiedlichen Kettenlängen, eine langsame Gerüstisomerisierung und eine β‐Spaltung von Triptylketten und ihren Vorstufen sind intrinsische Eigenschaften der Carbeniumionen, die zu den bemerkenswerten Triptanselektivitäten in den C7‐Fraktionen führen.

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Synthesis of the DFGH ring system of Type B Physalins: Highly Oxygenated, Cage‐Shaped Molecules
Authors: Ohkubo Megumi , Hirai Go , Sodeoka Mikiko
Published: April 2009

Wie Dominosteine: Um zum komplexen DFGH‐Ringsystem der Titelverbindungen zu gelangen, wird das Schlüsselintermediat einfach mit einer Brønsted‐Base behandelt, wobei sich die tetracyclische käfigförmige Zielstruktur in einer vierstufigen Eintopf‐Dominoreaktion bildet (siehe Schema; Mc=Monochlormesylat, MOM=Methoxymethyl).

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An Aqueous Route to Multicolor Photoluminescent Carbon Dots Using Silica Spheres as Carriers
Authors: Liu Ruili , Wu Dongqing , Liu Shuhua , Koynov Kaloian , Knoll Wolfgang , Li Qin
Published: April 2009

Kohlenstoff leuchtet auf: Ein einfacher chemischer Weg zu mehrfarbig photolumineszierenden Kohlenstoffpunkten, die sich von Polymer/Silica‐Nanokompositen ableiten, nutzt tensidmodifizierte Silicakugeln als Träger und Resole (Phenol/Formaldehydharze) als Kohlenstoffvorstufe (siehe Bild). Die oberflächenpassivierten, biokompatiblen Kohlenstoffpunkte sind potenzielle Bildgebungsreagentien mit Auflösung im Nanometerbereich.

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A Facile System for Encoding Unnatural Amino Acids in Mammalian Cells
Authors: Chen Peng R. , Groff Dan , Guo Jiantao , Ou Weijia , Cellitti Susan , Geierstanger Bernhard H. , Schultz Peter G.
Published: April 2009

Ein Shuttle‐System zur Verwendung von in E. coli selektierten Aminoacyl‐tRNA‐Synthetasen (aaRSs) für den Einbau von nichtnatürlichen Aminosäuren in Säugerzellen wurde entwickelt. Eine in E. coli selektierte Mutante der Pyrrolysyl‐tRNA‐Synthetase (PylRS) aminoacyliert selektiv eine Nonsense‐Suppressor‐tRNA mit einem photoaktivierbaren Lysinderivat. Durch Übertragung dieses orthogonalen tRNA‐aaRS‐Paares in Säugerzellen gelang es, diese nichtnatürliche Aminosäure selektiv in Proteine einzubauen.

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[{Fe(tim)}2]: ein Fe‐Fe‐Dimer mit einer unverbrückten Metall‐Metall‐Bindung und redoxaktiven N4‐makrocyclischen Liganden
Authors: Hess Corinna R. , Weyhermüller Thomas , Bill Eckhard , Wieghardt Karl
Published: April 2009

Gemischtes Doppel: Der dimere Eisenkomplex [{Fe(tim)}2] (siehe Struktur; tim=2,3,9,10‐Tetramethyl‐1,4,8,11‐tetraazacyclotetradeca‐1,3,8,10‐tetraen) ist der erste Komplex mit unverbrückter Fe‐Fe‐Bindung. Die Kristallstruktur belegt, dass der tim‐Ligand reduziert vorliegt und somit redoxaktive Eigenschaften hat. Weitere Messungen und Rechnungen bestätigen, dass [{Fe(tim)}2] eine gemischtvalente Spezies in Bezug auf die Fe‐Ionen wie auch die Liganden ist.

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Eine asymmetrische organokatalytische Domino‐Michael‐Aldol‐ Reaktion: enantioselektiver Zugang zu chiralen Cycloheptanonen, Tetrahydrochromenonen und polyfunktionalisierten Bicyclo[3.2.1]octanen
Authors: Rueping Magnus , Kuenkel Alexander , Tato Francisco , Bats Jan W.
Published: April 2009

1,2‐Dione im Blick: Eine neue diastereo‐ und enantioselektive Lewis‐Base‐katalysierte Domino‐Michael‐Aldol‐Reaktion setzt α,β‐ungesättigte Aldehyde mit 1,2‐Dionen zu chiralen Bicyclo[3.2.1]octan‐6‐carbaldehyden um. Die Produkte entstehen in guten Ausbeuten und exzellenten Enantioselektivitäten (90–98 % ee) und können weiter in bicyclische Diole und Triole überführt werden. Eine ebenfalls neuartige Retro‐Aldol‐Cyclisierung bietet einen einfachen Zugang zu präparativ wertvollen Tetrahydrochromenonen (siehe Schema).

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Selbstorganisation amphiphiler Nanokristalle
Authors: Carbone Luigi , Manna Liberato , Sönnichsen Carsten
Published: April 2009

Amphiphile Hybridmaterialien bestehen aus polymerbeschichteten Halbleiternanopartikeln, die ein stark tensidähnliches Verhalten aufweisen (siehe Bild). Die Stärke und Dichte der Oberflächenbeschichtung sind die treibenden Organisationskräfte hinter dem Übergang von isolierten Partikeln zu zylindrischen oder vesikulären Überstrukturen.

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Die neue Photokristallographie
Authors: Coppens Philip
Published: April 2009

Kleine Ursache, große Wirkung: In einer jüngsten photokristallographischen Studie wurde ein starker Anstieg der magnetischen Suszeptibilität eines Kristalls beim Bestrahlen mit UV‐Licht beobachtet. Der Suszeptibilitätsanstieg ging mit einer beträchtlichen Verkürzung der Bindungslängen der Nd‐NC‐Fe‐Einheit einher (siehe Bild; Bindungslängen in Å im Grundzustand (schwarz) und im photoinduzierten Zustand (rot)).

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Synthesis of a Chiral Quaternary Carbon Center Bearing a Fluorine Atom: Enantio‐ and Diastereoselective Guanidine‐Catalyzed Addition of Fluorocarbon Nucleophiles
Authors: Jiang Zhiyong , Pan Yuanhang , Zhao Yujun , Ma Ting , Lee Richmond , Yang Yuanyong , Huang Kuo‐Wei , Wong Ming Wah , Tan Choon‐Hong
Published: April 2009

Die perfekte Kombination: Die Titelreaktion ergibt Addukte mit quartären, F‐substituierten Kohlenstoffzentren mit hoher Enantio‐ und Diastereoselektivität (siehe Schema). Mechanismus und Ursprung der Stereoselektivität wurden in DFT‐Rechnungen aufgeklärt, und aus den Übergangszuständen geht ein difunktioneller Charakter der Guanidinkatalyse hervor.

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Synthesis of Supramolecular Nanocapsules Based on Threading of Multiple Cyclodextrins over Polymers on Gold Nanoparticles
Authors: Wu Yun‐Long , Li Jun
Published: April 2009

The CD's stuck: Poly(ethylene glycol) chains anchored onto gold nanoparticles (AuNPs) are threaded by multiple α‐cyclodextrin (α‐CD) rings to form a supramolecular outer layer composed of pseudopolyrotaxane columns perpendicular to the nanoparticle surface. Capping the polymer ends confines α‐CD on the nanoparticle surface, cross‐linking the α‐CD rings and then removing the AuNP cores produces supramolecular nanocapsules.

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Coherent Activation of DNA Tweezers: A “SET–RESET” Logic System
Authors: Elbaz Johann , Moshe Michal , Willner Itamar
Published: April 2009

Open sesame: Aptamer–substrate complexes activate the coherent operation of two tweezers that act as a “SET–RESET” logic system. Each tweezer cycles between a fluorescent open state and a closed quenched state (Q=quencher, F=fluorophore) when triggered by adenosine monophosphate (AMP) and adenosine deaminase (AD).

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One‐Step Synthesis and Characterization of Gold–Hollow PbSx Hybrid Nanoparticles
Authors: Yang Jian , Peng JunJun , Zhang Qingbo , Peng Feng , Wang Hongjuan , Yu Hao
Published: April 2009

Turing lead into gold: Hollow hybrid PbSx–Au nanostructures of about 10 nm in diameter were synthesized using a one‐step reaction under mild experimental conditions. The redox reaction of gold precursors with PbS nanocrystals in the presence of dodecylamine leads to the hollow feature of hybrid nanostructures (see picture).

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Cation–Cation Interactions, Magnetic Communication, and Reactivity of the Pentavalent Uranium Ion [U(NtBu)2]+
Authors: Spencer Liam P. , Schelter Eric J. , Yang Ping , Gdula Robyn L. , Scott Brian L. , Thompson Joe D. , Kiplinger Jaqueline L. , Batista Enrique R. , Boncella James M.
Published: April 2009

Communication is important: The dimeric bis(imido) uranium complex [{U(NtBu)2(I)(tBu2bpy)}2] (see picture; U green, N blue, I red) has cation–cation interactions between [U(NR)2]+ ions. This f1–f1 system also displays f orbital communication between uranium(V) centers at low temperatures, and can be oxidized to generate uranium(VI) bis(imido) complexes.

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A Stereoselective Synthesis of the Bromopyrrole Natural Product (−)‐Agelastatin A
Authors: Wehn Paul M. , Du Bois J.
Published: April 2009

Weaving an intricate web: A stereoselective synthesis of (−)‐agelastatin A has been developed, which requires 11 steps from commercially available starting material. The application of a Rh‐catalyzed intramolecular olefin aziridination reaction and the subsequent manipulation of the resulting tricyclic intermediate (see scheme) punctuate this study.

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Ionic Circuits Based on Polyelectrolyte Diodes on a Microchip
Authors: Han Ji‐Hyung , Kim Kwang Bok , Kim Hee Chan , Chung Taek Dong
Published: April 2009

Green means go: A polyelectrolyte diode on a microchip exhibits well‐defined nonlinear rectifying behavior. This system visualizes the dynamic distribution of ions in a charged polymer phase under an electric field on a real‐time basis using fluorescence images (see picture). Multiple polyelectrolyte diodes are integrated on a microchip to produce a variety of logic gates based on ionic circuits.

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Synthesis and Crystal Structure of a Silyl‐Stabilized Allyl Cation Formed by Disruption of an Arene by a Protonation–Hydrosilylation Sequence
Authors: Duttwyler Simon , Zhang Yun , Linden Anthony , Reed Christopher A. , Baldridge Kim K. , Siegel Jay S.
Published: April 2009

Sly silyl caught in the act: Protonation of a mesitylene ring by the strongly acidic arenium carborane [CH3C6H6]‐ [CHB11Me5Br6] initiates a cascade reaction that results in a stable β‐silyl allyl cation (see picture, H yellow, C blue, silyl allyl group red). Remarkably, the driving force in the reaction suffices to disrupt a stable aromatic ring in favor of a cationic reactive intermediate.

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Computer‐Aided Design of a Sulfate‐Encapsulating Receptor
Authors: Custelcean Radu , Bosano Jerome , Bonnesen Peter V. , Kertesz Vilmos , Hay Benjamin P.
Published: April 2009

Custom built: A promising new approach towards more efficient self‐assembled cage receptors through computer‐aided design is demonstrated. The resulting M4L6 tetrahedral cage, internally functionalized with accurately positioned urea hydrogen‐bonding groups (see structure; yellow: predicted, blue: experimental, space‐filling: SO42−), proved to be a remarkably strong sulfate receptor in water.

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Selective Homologation Routes to 2,2,3‐Trimethylbutane on Solid Acids
Authors: Ahn John H. , Temel Burcin , Iglesia Enrique
Published: April 2009

Sailing the seven ‘C's: 2,2,3‐Trimethylbutane (triptane) selectively forms from dimethyl ether at low temperatures on acid zeolites. Selective methylation at less‐substituted carbons, relative rates of methylation to hydrogen transfer as a function of chain size, slow skeletal isomerization, and β‐scission cracking of triptyl chains and their precursors are intrinsic properties of carbenium ions and account for the remarkable triptane selectivities within C7 .

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Synthesis of the DFGH ring system of Type B Physalins: Highly Oxygenated, Cage‐Shaped Molecules
Authors: Ohkubo Megumi , Hirai Go , Sodeoka Mikiko
Published: April 2009

Let the dominos fall: Synthesis of the complex DFGH ring system of the title compounds has been accomplished. The approach features simple treatment of the key intermediate with a Brønsted base to afford the tetracyclic cage‐shaped target in one pot through a four‐step domino transformation (see scheme; Mc= monochloromesylate, MOM=methoxymethyl).

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A Facile System for Encoding Unnatural Amino Acids in Mammalian Cells
Authors: Chen Peng R. , Groff Dan , Guo Jiantao , Ou Weijia , Cellitti Susan , Geierstanger Bernhard H. , Schultz Peter G.
Published: April 2009

A shuttle system has been developed to genetically encode unnatural amino acids in mammalian cells using aminoacyl‐tRNA synthetases (aaRSs) evolved in E. coli. A pyrrolysyl‐tRNA synthetase (PylRS) mutant was evolved in E. coli that selectively aminoacylates a cognate nonsense suppressor tRNA with a photocaged lysine derivative. Transfer of this orthogonal tRNA–aaRS pair into mammalian cells made possible the selective incorporation of this unnatural amino acid into proteins.

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[{Fe(tim)}2]: An FeFe Dimer Containing an Unsupported Metal–Metal Bond and Redox‐Active N4 Macrocyclic Ligands
Authors: Hess Corinna R. , Weyhermüller Thomas , Bill Eckhard , Wieghardt Karl
Published: April 2009

Mixed doubles: The dimeric complex [{Fe(tim)}2] (see structure, tim=2,3,9,10‐tetramethyl‐1,4,8,11‐tetraazacyclotetradeca‐1,3,8,10‐tetraene) represents an unprecedented complex containing an unsupported FeFe bond. The crystal structure confirms the presence of reduced tim units, thus indicating ligand redox activity. Spectroscopic and computational studies establish a triplet ground state for [{Fe(tim)}2] and suggest a mixed‐valence compound with respect to both the Fe ions and the ligands.

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Asymmetric Organocatalytic Domino Michael/Aldol Reactions: Enantioselective Synthesis of Chiral Cycloheptanones, Tetrahydrochromenones, and Polyfunctionalized Bicyclo[3.2.1]octanes
Authors: Rueping Magnus , Kuenkel Alexander , Tato Francisco , Bats Jan W.
Published: April 2009

C′mon 1,2‐dione: A new diastereo‐ and enantioselective Lewis base catalyzed domino Michael/aldol reaction converts α,β‐unsaturated aldehydes and 1,2‐diones into chiral bicyclo[3.2.1]octane‐6‐carbaldehydes. The products are produced in good to excellent enantioselectivities (90–98 % ee) and can be transformed into bicyclic diols and triols. Additionally, a retro‐aldol cyclization provides access to valuable tetrahydrochromenones (see scheme).

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Self‐Assembly of Amphiphilic Nanocrystals
Authors: Carbone Luigi , Manna Liberato , Sönnichsen Carsten
Published: April 2009

Amphiphilic hybrid materials are formed from polymer‐coated semiconductor nanoparticles that simulate a surfactant‐like response (see picture). The strength and density of the surface coating are the key assembling forces driving a transition from single particles to cylindrical or vesicular superstructures.

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The New Photocrystallography
Authors: Coppens Philip
Published: April 2009

Shine your light: Recent work in photocrystallography demonstrates a large photoinduced increase in the magnetic susceptibility of a solid, which is accompanied by significant changes in the bond lengths of the NdNCFe moiety (see picture; black are ground‐state bond lengths in Å, red are photoinduced bond lengths).

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Synthesis of a Chiral Quaternary Carbon Center Bearing a Fluorine Atom: Enantio‐ and Diastereoselective Guanidine‐Catalyzed Addition of Fluorocarbon Nucleophiles
Authors: Jiang Zhiyong , Pan Yuanhang , Zhao Yujun , Ma Ting , Lee Richmond , Yang Yuanyong , Huang Kuo‐Wei , Wong Ming Wah , Tan Choon‐Hong
Published: April 2009

The perfect combination: The title reaction provides adducts having quaternary carbon centers bearing a fluorine atom with high ee and d.r. values (see scheme). The mechanism and origin of stereoselectivity were elucidated by DFT calculations. The bifunctional mode of the guanidine catalysis was demonstrated in the transition states resulting from the DFT results.

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Particle swarm optimization algorithm for constrained problems
Authors: Zhang Jian‐Ming , Xie Lei
Published: April 2009

A novel particle swarm optimization (PSO) algorithm with the evaluation of infeasibility degree (IFD) of constraints is presented for nonlinear programming (NLP) problems with equality and inequality constraints. The IFD of constraints is defined as the sum of the squared values of the constraint violations. The proposed novel PSO updates the local best position and global best position according to the objective value and the value of IFD simultaneously. The results of several numerical tests and one real engineering optimization problem show that the proposed approach is efficient. Copyright © 2009 Curtin University of Technology and John Wiley & Sons, Ltd.
Structure‐sensitivity of CH3 dissociation on Ni(100)from first‐principles calculations
Authors: Zhu Yi‐An , Zhou Xing‐Gui , Chen De , Yuan Wei‐Kang
Published: April 2009

First‐principles calculations are performed to explore the CH3 dissociation on Ni(100). The CH2 species bind most strongly to the hollow site with two CH bonds pointing toward the neighboring surface Ni atoms. Through the calculations of local density of states (LDOSs) and partial charge density, the CHNi three‐center bond is regarded as the key factor determining the CH3 adsorption. The CH3 dissociation on Ni(100) is investigated along two different reaction pathways. After zero‐point energy (ZPE) correction considered, the energy barriers for the CH3 dehydrogenation are calculated to be 0.46 and 0.54 eV. Because these barriers are much lower than that for the CH3 dissociation on Ni(111), the CH3 dehydrogenation is found to be structure‐sensitive. Copyright © 2009 Curtin University of Technology and John Wiley & Sons, Ltd.
Removal of organic dyes in the hybrid photocatalysis/nanofiltration system
Authors: Grzechulska‐Damszel Joanna , Morawski Antoni W.
Published: April 2009

The removal of azo dyes acid red 18 (AR18), direct green 99 (DG99) and acid yellow 36 (AY36) in hybrid photocatalysis/nanofiltration (NF) system was investigated. The photocatalytic reactions were conducted in the flow reactor with immobilized photocatalyst bed. A commercially available titanium dioxide (Aeroxide® P25, Degussa, Germany) was used as a photocatalyst. The solution after the photocatalytic reaction was applied as feed for NF process. The changes of various parameters, including concentration of dyes, pH and conductivity of the solution, total organic carbon (TOC) and total dissolved solids (TDS) content were analyzed during the process.

It was found that azo dyes AR18, DG99 and AY36 solutions could be successfully decolorized in the quartz labyrinth flow reactor with immobilized photocatalyst bed. The rate of color removal can range as follows: AR18 > DG99 > AY36. Copyright © 2009 Curtin University of Technology and John Wiley & Sons, Ltd.
Gas permeation properties of Seragel membrane
Authors: Saeidi M. , Tavakol Moghadam M. , Mahdyarfar M. , Mohammadi T.
Published: April 2009

Gas permeation behavior through a specific type of polymeric membrane was investigated in this work. The main objective of our study was to determine gas permeation properties of a specific polymeric membrane over a range of operating pressures. The diffusive layer of this membrane consists of Butadiene–Sulfone block copolymer and demonstrates high chemical stability in corrosive media. Permeances were determined at the temperature of 35 °C and pressures of 760, 1520, and 3040 cmHg for methane, carbon dioxide, and nitrogen. Gas permeances were also determined for actual binary mixtures of H2S/CH4. Average permeances of 23.17 and 3.75 GPU for H2S and CO2 were achieved respectively, at the pressure range of 380–1140 cmHg. Calculated permeances by a model developed for this membrane in previous literatures have been compared with experimental data in this study and the agreement of the model with H2S/CH4 mixture was also investigated. The results show that the agreement between the pure gas experimental permeances and the data from the model is more in comparison with the experimental gas mixture results. Copyright © 2009 Curtin University of Technology and John Wiley & Sons, Ltd.
Extended NRTL model for PEG + salt based aqueous two‐phase system
Authors: Perumalsamy Muthiah , Murugesan Thanapalan
Published: April 2009

Liquid–liquid equilibrium (LLE) data of aqueous poly(ethylene glycol) (PEG) 2000–sodium citrate systems were determined experimentally at 25°, 35° and 45 °C. Experimental techniques and analytical methods were described in the previous article (T. Murugesan, M. Perumalsamy. J. Chem. Eng. Data. 2005; 50, 1392–1395 [22]). The NRTL (nonrandom, two‐liquid) model, expressed in mass fraction, was used to correlate the LLE of aqueous two‐phase systems (ATPS). The interaction energy parameters of the NRTL model were adjusted using these experimental LLE data. The model described experimental equilibrium data with a good agreement. Copyright © 2009 Curtin University of Technology and John Wiley & Sons, Ltd.