bluuebunny/crossref_metadata_2025 huggingface dataset:
Catalytic Asymmetric Reactions of 4‐Substituted Indoles with Nitroethene: A Direct Entry to Ergot Alkaloid Structures
Authors: Romanini Simone , Galletti Emilio , Caruana Lorenzo , Mazzanti Andrea , Himo Fahmi , Santoro Stefano , Fochi Mariafrancesca , Bernardi Luca
Published: October 2015

A domino Friedel–Crafts/nitro‐Michael reaction between 4‐substituted indoles and nitroethene is presented. The reaction is catalyzed by BINOL‐derived phosphoric acid catalysts, and delivers the corresponding 3,4‐ring‐fused indoles with very good results in terms of yields and diastereo‐ and enantioselectivities. The tricyclic benzo[cd]indole products bear a nitro group at the right position to serve as precursors of ergot alkaloids, as demonstrated by the formal synthesis of 6,7‐secoagroclavine from one of the adducts. DFT calculations suggest that the outcome of the reaction stems from the preferential evolution of a key nitronic acid intermediate through a nucleophilic addition pathway, rather than to the expected “quenching” through protonation.
A Convenient Palladium‐Catalyzed Carbonylative Suzuki Coupling of Aryl Halides with Formic Acid as the Carbon Monoxide Source
Authors: Qi Xinxin , Jiang Li‐Bing , Li Hao‐Peng , Wu Xiao‐Feng
Published: October 2015

A practical palladium‐catalyzed carbonylative Suzuki coupling of aryl halides under carbon monoxide gas‐free conditions has been developed. Here, formic acid was utilized as the carbon monoxide source for the first time with acetic anhydride as the additive. A variety of diarylketones were produced in moderate to excellent yields from the corresponding aryl halides and arylboronic acids.
Formation of Highly Strained N‐Heterocycles via Decomposition of Iron N‐Heterocyclic Carbene Complexes: The Value of Labile FeC Bonds
Authors: Haslinger Stefan , Kück Jens W. , Anneser Markus R. , Cokoja Mirza , Pöthig Alexander , Kühn Fritz E.
Published: October 2015

An unusual, highly‐strained annulated 2,2′‐biimdazole was isolated as decomposition product of the outer‐sphere one‐electron oxidation of an iron(II) N‐heterocyclic carbene (NHC) complex bearing a tetradentate bis(NHC)‐bis‐ (pyridine) ligand (NCCN). Reductive elimination leading to the 2,2′‐biimdazole is a consequence of the lability of the FeC bonds in the transient species and also extends to complexes with modified ligands but the same coordination geometry. Closely related by a two‐electron redox step to a family of less‐strained tetraazafulvalenes, the obtained 2,2′‐biimidazolium salts were studied electrochemically. Introduction of methyl substituents at the methylene tether significantly increased the reversibility of the electrochemical reduction. Furthermore, the reactivity of the 2,2′‐biimidazolium salt was examined by oxidative addition of [Ni(cod)2] to the central CC bond, providing a previously unknown way for the formation of NHC transition metal complexes.
Lewis Acid Catalyzed Asymmetric Three‐Component Coupling Reaction: Facile Synthesis of α‐Fluoromethylated Tertiary Alcohols
Authors: Aikawa Kohsuke , Kondo Daisuke , Honda Kazuya , Mikami Koichi
Published: October 2015

A chiral dicationic palladium complex is found to be an efficient Lewis acid catalyst for the synthesis of α‐fluoromethyl‐substituted tertiary alcohols using a three‐component coupling reaction. The reaction transforms three simple and readily available components (terminal alkyne, arene, and fluoromethylpyruvate) to valuable chiral organofluorine compounds. This strategy is completely atom‐economical and results in perfect regioselectivities and high enantioselectivities of the corresponding tertiary allylic alcohols in good to excellent yields.
Emerging innovative therapeutic approaches targeting PCSK9 to lower lipids
Authors: Shantha GPS , Robinson JG
Published: October 2015

Statins are established therapies for cardiovascular disease prevention and ezetimibe has recently been shown to modestly reduce cardiovascular events when added to background statin therapy. Yet here remains a clear unmet need for additional therapies aimed at lowering low density lipoprotein cholesterol (LDL‐C) to further reduce cardiovascular risk. Multiple strategies targeting proprotein convertase subtilisin/kexin type 9 (PCSK9) inhibition have emerged as effective modalities for LDL‐C lowering. PCSK9 monoclonal antibodies are the farthest along in clinical development and alirocumab and evolocumab were approved for clinical use by regulatory agencies in 2015. In addition to robust LDL‐C lowering (nearly 50–65% from baseline), they improve other lipid parameters as well. Adverse events associated with these medications are minimal. Importantly, they improve clinical cardiovascular disease outcomes, although long‐term study results are awaited. Cost may be an important limiting factor in their use and we propose two possible solutions which can potentially curtail cost.
Intramolecularly Stabilized Heavier Tetrylenes: From Monodentate to Bidentate ­Ligands
Authors: Cabeza Javier A. , García‐Álvarez Pablo , Polo Diego
Published: October 2015

Intramolecularly stabilized heavier tetrylenes (HTs) are group 14 metalylenes featuring at least one intramolecular D→E interaction between a two‐electron‐donor group (D) and the group 14 atom (E = Si, Ge, Sn or Pb). With regard to their coordination chemistry, they normally bind to transition metals as monodentate ligands through the lone electron pair of their E atom; however, the donor group D initially involved in their internal stabilization can sometimes migrate from the E atom to the transition metal. This ring‐expansion process transforms the original monodentate (κ1E) ligand into a bidentate one (κ2E,D) and enhances the stability of the resulting complex. This review collects and discusses the hitherto known reactions involving this ligand transformation, also shedding light on the factors that make it possible.
Substitution and Catalytic Chemistry of Gyroscope‐Like Complexes Derived from Cl–Rh–CO Rotators and Triply trans Spanning Di(trialkylphosphine) Ligands
Authors: Estrada Alexander L. , Jia Tiezheng , Bhuvanesh Nattamai , Blümel Janet , Gladysz John A.
Published: October 2015

Reactions of trans‐[Rh(CO)(Cl){P{(CH2)14}3P2(Rh–P2)}] (1) with ZnPh2, MeLi, or NaBH4 give the chloride‐substitution products trans‐[Rh(CO)(Ph){P{(CH2)14}3P2(Rh–P2)}] (3, 89 %), trans‐[Rh(CO)(Me){P{(CH2)14}3P2(Rh–P2)}] (94 %, 92 % purity), and trans‐[Rh(CO)(H2BH2){P{(CH2)14}3P2(Rh–P2)}] (5, 99 %). The crystal structures of 3, 5, and the corresponding (fortuitously obtained) bromide complex are determined, and the ability of the X–Rh–CO moieties to rotate is interpreted in terms of their effective radii and the void space within the dibridgehead diphosphine cage. Reaction of 1 and excess PMe3 gives the diphosphine substitution product trans‐[Rh(CO)(Cl)(PMe3)2] (89 %) and the dibridgehead diphosphine P[(CH2)14]3P (58 %). Complex 5 serves as a catalyst precursor for the hydroformylation of 1‐octene (neat or THF, 60 °C, 75 psig 1:1 CO/H2). The locus of catalysis with respect to the diphosphine cage is discussed.
PEGylated DOTA‐AHA‐Based GdIII Chelates: A Relaxometric Study
Authors: Fontes André , Karimi Shima , Helm Lothar , Ferreira Paula M. , André João P.
Published: October 2015

Invited for the cover of this issue are Dr. João Paulo André, Dr. Paula Margarida Ferreira, and Dr. André Fontes at the University of Minho, Braga, Portugal, and Prof. Lothar Helm at the EPFL, Lausanne, Switzerland. The cover image shows the general structure of PEGylated DOTA‐based GdIII chelates developed as potential contrast agents for magnetic resonance imaging. The rotating arrow illustrates the importance of the tumbling behavior of the chelates for their relaxivity.
Conjugation of Bioactive Molecules to a Fluorescent Dithiomaleimide by Photoin­duced and BEt3‐Initiated Thio‐Click Reactions
Authors: Lázár László , Nagy Miklós , Borbás Anikó , Herczegh Pál , Zsuga Miklós , Kéki Sándor
Published: October 2015

Two versions of the free‐radical thiol–ene addition, a photoinduced reaction in the presence of 2,2‐dimethoxy‐2‐phenylacetophenone, and a UV‐light‐free hydrothiolation using triethylborane as the initiator, were studied for the conjugation of fluorescent dithiomaleimide to biologically active compounds. A dithiomaleimide derivative bearing a vinyl ether functionality was prepared as the alkene partner. This was coupled with a range of thiols, including thiosugars, captopril, N‐acetyl‐L‐cysteine, and sodium 2‐sulfonatoethanethiol. The Et3B‐initiated method was superior to the photoinduced reaction, as it minimized decomposition of the sensitive maleimide group. The vinyl ether derivative and the addition products showed green light emission in tetrahydrofuran. The compounds all showed almost identical absorption and emission spectra, proving that the structure of the thiols has no influence on the fluorescence properties of the maleimide part of the molecules. The hydrothiolation products showed relatively high quantum yields.
Banking carbon: a review of organic carbon storage and physical factors influencing retention in floodplains and riparian ecosystems
Authors: Sutfin Nicholas A. , Wohl Ellen E. , Dwire Kathleen A.
Published: October 2015

Rivers are dynamic components of the terrestrial carbon cycle and provide important functions in ecosystem processes. Although rivers act as conveyers of carbon to the oceans, rivers also retain carbon within riparian ecosystems along floodplains, with potential for long‐term (> 102 years) storage. Research in ecosystem processing emphasizes the importance of organic carbon (OC) in river systems, and estimates of OC fluxes in terrestrial freshwater systems indicate that a significant portion of terrestrial carbon is stored within river networks. Studies have examined soil OC on floodplains, but research that examines the potential mechanistic controls on OC storage in riparian ecosystems and floodplains is more limited. We emphasize three primary OC reservoirs within fluvial systems: (1) standing riparian biomass; (2) dead biomass as large wood (LW) in the stream and on the floodplain; (3) OC on and beneath the floodplain surface, including litter, humus, and soil organic carbon (SOC). This review focuses on studies that have framed research questions and results in the context of OC retention, accumulation and storage within the three primary pools along riparian ecosystems. In this paper, we (i) discuss the various reservoirs for OC storage in riparian ecosystems, (ii) discuss physical conditions that facilitate carbon retention and storage in riparian ecosystems, (iii) provide a synthesis of published OC storage in riparian ecosystems, (iv) present a conceptual model of the conditions that favor OC storage in riparian ecosystems, (v) briefly discuss human impacts on OC storage in riparian ecosystems, and (vi) highlight current knowledge gaps. Copyright © 2015 John Wiley & Sons, Ltd.
Do Jumps Matter for Volatility Forecasting? Evidence from Energy Markets
Authors: Prokopczuk Marcel , Symeonidis Lazaros , Wese Simen Chardin
Published: October 2015

This paper characterizes the dynamics of jumps and analyzes their importance for volatility forecasting. Using high‐frequency data on four prominent energy markets, we perform a model‐free decomposition of realized variance into its continuous and discontinuous components. We find strong evidence of jumps in energy markets between 2007 and 2012. We then investigate the importance of jumps for volatility forecasting. To this end, we estimate and analyze the predictive ability of several Heterogenous Autoregressive (HAR) models that explicitly capture the dynamics of jumps. Conducting extensive in‐sample and out‐of‐sample analyses, we establish that explicitly modeling jumps does not significantly improve forecast accuracy. Our results are broadly consistent across our four energy markets, forecasting horizons, and loss functions. © 2015 Wiley Periodicals, Inc. Jrl Fut Mark 36:758–792, 2016
Coastal Occupations in Tierra del Fuego, Southernmost South America: A Late Holocene Hunter‐Gatherer Context at Marazzi 2
Authors: Ozán Ivana L. , French Charles , Repetto Flavia Morello , Vásquez Carlos A. , Luppo Tomás
Published: October 2015

This paper focuses on the late Holocene occupation of hunter‐gatherers at the Marazzi 2 site located on the northwestern steppe of Tierra del Fuego, Chile. Our aim is to understand stratigraphy, formation processes, and pedogenesis with respect to human occupation over the last 3000 years. Based on archaeological excavations on a fluvial terrace of the Torcido River, we integrate soil micromorphology, mineralogy, geochemistry, magnetic susceptibility, and geomorphology, as well as the micro‐ and macrofrequency distributions of archaeological material. A micro‐taphonomical perspective is also applied to anthropogenic components recorded in sedimentary thin sections. We discuss various events in the interplay between soil development and human occupation through time. Marazzi 2 was witness to aggradation and pedogenesis with an episode of surface stability coincident with a phase of more intense human occupation at about 860 BC. Taphonomic analysis suggests that there are multiple occupation events mixed together, probably by biomechanical processes, resulting in a palimpsest with poor temporal resolution.
The geology of the 2nd century A.D. Amphitheater Area of Catania, Italy: Historical Eruptions Affecting the Urban District
Authors: Branca Stefano , Branciforti Maria Grazia , Chiavetta Antonio Fernando , Corsaro Rosa Anna
Published: October 2015

The amphitheater of Catania is one of the main architectural structures built during Roman domination of the town. It was constructed in two successive phases between the 1st and 2nd centuries A.D. and fell into disuse from the second half of the 4th century. Detailed geological and petrographic investigations allow better geomorphological reconstruction of the area where the monument was built. In particular, the western and eastern portions of the amphitheater are built on prehistoric lava flows, named Barriera del Bosco and Larmisi, respectively. We infer that the choice of site to build the monument was highly influenced by the morphological setting of the area. In fact, the location at the contact between two lava flow fields facilitated excavation and removal of rocks due to the incoherence of the scoriaceous lateral border of the lava flows. Integrating both archaeological and geological data has revealed that a large number of Neolithic, Greek, and Roman sites are located in the lava fields of Barriera del Bosco and Larmisi within the present urban district of Catania, indicating that during its long history the city was directly impacted by only one lava flow, namely in A.D. 1669.
Identifying the causes, prevention and management of crises in dementia. An online survey of stakeholders
Authors: Ledgerd Ritchard , Hoe Juanita , Hoare Zoë , Devine Mike , Toot Sandeep , Challis David , Orrell Martin
Published: October 2015

Background

Crisis situations in dementia can lead to hospital admission or institutionalisation. Offering immediate interventions may help avoid admission, whilst stabilising measures can help prevent future crises.

Objective

Our objective was to identify the main causes of crisis and interventions to treat or prevent crisis in persons with dementia based on different stakeholder perspectives.

Methods

An online questionnaire was developed to identify the causes of crisis and appropriate interventions in a crisis. Participants included people with dementia, family carers and staff working in health and social care, including emergency and voluntary sectors, and academia.

Results

The results ranked the main causes of crisis, interventions that can prevent a crisis and interventions that can be useful in a crisis. Wandering, falls and infection were highly rated as risk factors for crises across all stakeholder groups. Consumers rated aggression as less important but severity of memory impairment as much more important than the other groups did. Education and support for family carers and home care staff were highly valued for preventing crises. Well‐trained home care staff, communication equipment, emergency contacts and access to respite were highly valued for managing crises.

Conclusions

We identified triggers and interventions that different stakeholders see as important for crisis in dementia. Recognition of these may be critical to planning effective and accepted support and care for people with dementia. Copyright © 2015 John Wiley & Sons, Ltd.
Cost‐effectiveness of exercise as a therapy for behavioural and psychological symptoms of dementia within the EVIDEM‐E randomised controlled trial
Authors: D'Amico Francesco , Rehill Amritpal , Knapp Martin , Lowery David , Cerga‐Pashoja Arlinda , Griffin Mark , Iliffe Steve , Warner James
Published: October 2015

Objective

Although available evidence is modest, exercise could be beneficial in reducing behavioural and psychological symptoms of dementia. We aim to evaluate the cost‐effectiveness of a dyadic exercise regimen for individuals with dementia and their main carer as therapy for behavioural and psychological symptoms of dementia.

Methods

Cost‐effectiveness analysis within a two‐arm, pragmatic, randomised, controlled, single‐blind, parallel‐group trial of a dyadic exercise regimen (individually tailored, for 20–30 min at least five times per week). The study randomised 131 community‐dwelling individuals with dementia and clinically significant behavioural and psychological symptoms with a carer willing and able to participate in the exercise regimen; 52 dyads provided sufficient cost data for analyses.

Results

Mean intervention cost was £284 per dyad. For the subsample of 52 dyads, the intervention group had significantly higher mean cost from a societal perspective (mean difference £2728.60, p = 0.05), but costs were not significantly different from a health and social care perspective. The exercise intervention was more cost‐effective than treatment as usual from both societal and health and social care perspectives for the measure of behavioural and psychological symptoms (Neuropsychiatric Inventory). It does not appear cost‐effective in terms of cost per quality‐adjusted life year gain.

Conclusions

The exercise intervention has the potential to be seen as cost‐effective when considering behavioural and psychological symptoms but did not appear cost‐effective when considering quality‐adjusted life year gains. Copyright © 2011 John Wiley & Sons, Ltd.
MicroRNA expression profiling in bladder cancer: the challenge of next‐generation sequencing in tissues and biofluids
Authors: Matullo Giuseppe , Naccarati Alessio , Pardini Barbara
Published: October 2015

Bladder cancer (BC) is a heterogeneous disease characterized by a high recurrence rate that necessitates continuous cystoscopic surveillance. MicroRNAs (miRNAs) are detectable in tissues and biofluids such as plasma/serum and urine. They represent promising biomarkers with potential not only for detecting BC but also informing on prognosis and monitoring treatment response. In this review, the many aspects of the application of next‐generation sequencing (NGS) to evaluate miRNA expression in BC is discussed, including technical issues as well as a comparison with results obtained by qRT‐PCR. The available studies investigating miRNA profiling in BC by NGS are described, with particular attention to the potential applicability on biofluids. Altered miRNA levels have been observed in BC tissues by NGS, but these results so far only partially overlapped among studies and with previous data obtained by qRT‐PCR. The discrepancies can be ascribed to the small groups of BC patients sequenced. The few available studies on biofluids are mainly focused on implementing RNA isolation and sequencing workflow. Using NGS to analyze miRNAs in biofluids can potentially provide results comparable to tissues with no invasive procedures for the patients. In particular, the analyses performed on exosomes/microvesicles appear to be more informative. Thanks to the improvement of both wet‐lab procedures and pipelines/tools for data analyses, NGS studies on biofluids will be performed on a larger scale. MiRNAs detected in urine and serum/plasma will demonstrate their potentiality to describe the variegated scenario of BC and to become relevant clinical markers.
A new extension of the polarizable continuum model: Toward a quantum chemical description of chemical reactions at extreme high pressure
Authors: Cammi Roberto
Published: October 2015

A quantum chemical method for studying potential energy surfaces of reactive molecular systems at extreme high pressures is presented. The method is an extension of the standard Polarizable Continuum Model that is usually used for Quantum Chemical study of chemical reactions at a standard condition of pressure. The physical basis of the method and the corresponding computational protocol are described in necessary detail, and an application of the method to the dimerization of cyclopentadiene (up to 20 GPa) is reported. © 2015 Wiley Periodicals, Inc.
Bioethanol production from biomass: carbohydrate vs syngas fermentation
Authors: Kennes David , Abubackar Haris Nalakath , Diaz Marío , Veiga María C , Kennes Christian
Published: October 2015

Environmental problems associated with the use of fossil fuels as well as their expected scarcity in the near future requires a search for new alternative fuels produced from renewable sources. Bioethanol is a biofuel that can be obtained from biomass and waste as feedstocks through fermentation. Two major routes allow conversion of the feedstocks to fermentable substrates, i.e. the hydrolytic route and the thermochemical route. In the hydrolytic route, the feedstock undergoes a pretreatment stage first, aimed at facilitating the subsequent hydrolytic treatment. Chemical, physical or biological pretreatments can be applied. Lignocellulosic feedstocks are mainly composed of cellulose, hemicellulose and lignin. The pretreatment attacks the lignin and hemicellulose polymers and makes cellulose more accessible in the next, hydrolytic, stage. The hydrolytic treatment uses enzymes to convert the cellulose polymer to simple, fermentable, sugars, mainly glucose. Simple sugars obtained from hemicellulose and cellulose are then fermented by yeasts to bioethanol. In the thermochemical alternative, the feedstock is gasified, yielding syngas – a mixture largely composed of CO, CO2 and H2 – which can be fermented anaerobically, usually by clostridia, to ethanol or other products. In both cases, downstream processes are then applied to recover and purify the biofuel. The different stages involved in both alternatives are described, and both processes are compared in terms of their main characteristics and development stage. © 2015 Society of Chemical Industry
Subsoil rhizosphere modification by chickpea under a dry topsoil: implications for phosphorus acquisition
Authors: Kabir Md. Enamul , Johansen Chris , Bell Richard W.
Published: October 2015

Chickpea (Cicer arietinum L.) roots exude carboxylates. While chickpea commonly grows where the topsoil dries out during crop growth, the importance of carboxylate exudation by the roots and mobilization of soil P from below the dry topsoil has not been examined. The study investigates the response of carboxylate exudation and soil P mobilization by this crop to subsoil P fertilizer rate. In constructed soil columns in the glasshouse, the P levels (high, low, and nil P) were varied in the well‐watered subsoil (10–30 cm), while a low level of P in the dry topsoil (0–10 cm) was maintained. At flowering, rhizosphere carboxylates and rhizosphere soil from topsoil and subsoil roots were collected separately and analyzed. The concentration of total carboxylates per unit rhizosphere mass in the subsoil was nearly double that of the topsoil. Plants depleted sparingly soluble inorganic P (Pi), NaOH‐Pi, and HCl‐Pi, along with the labile Pi (water soluble and NaHCO3‐Pi). The P depletion by plants was greater from the subsoil than the topsoil. The study concluded that depletion of sparingly soluble P from the chickpea rhizosphere in the subsoil was linked with the greater levels of carboxylates in the rhizosphere. These findings indicate that chickpea, with its deep rooting pattern, can increase its access to subsoil P when the topsoil dries out during crop growth by subsoil rhizosphere modification.
Phosphate fertilizer form and application strategy affect phosphorus mobility and transformation in a drip‐irrigated calcareous soil
Authors: Wang Jing , Chu Guixin
Published: October 2015

The objective was to increase understanding about how P fertilizer form and application strategy affect P mobility and use efficiency in a drip‐irrigated calcareous soil. The study used two P forms (granular or liquid P) and two application methods (single or repeated application). Phosphorus uptake by roots was simulated by using diffusive gradients in thin films (DGT). Six fractions of inorganic P were obtained using the Jiang‐Gu sequential fractionation scheme. Mobility of P was greater when the fertilizer was applied in liquid rather than granular form. Depending on the fertilizer application rate, Olsen P concentrations 13.5–43 mm from the application point were larger by 22–96% in the liquid P treatment than in the granular P treatment. Liquid P increased DGT‐absorbed P by 29% and Ca2‐P by 17% compared with granular P averagely. The P uptake and PUE were averagely larger by 32 and 121%, respectively, in the liquid P treatment than in the granular P treatment. In conclusion, liquid P fertilization reduces P fixation and increases P diffusion, availability, and bioavailability in calcareous soil. Phosphorus mobility is greater when the fertilizer is applied in a single rather than repeated application.
Increased utilization of postmastectomy radiotherapy in the United States from 2003 to 2011 in patients with one to three tumor positive nodes
Authors: Yao Katharine , Liederbach Erik , Lutfi Waseem , Wang Chi‐Hsiung , Hou Ningqi , Karrison Theodore , Huo Dezheng
Published: October 2015

Background and Objectives

There have been few recent studies that have examined the use of postmastectomy radiotherapy (PMRT) for patients with 1–3 positive nodes.

Methods

We utilized the National Cancer Data Base to examine trends in PMRT for 346,218 patients with Stage I–III breast cancer from 2003 to 2011. Neoadjuvant therapy cases were excluded. Log linear models examined trends in PMRT and logistic regressions were used to examine factors related to PMRT.

Results

The proportion of pT1‐2N1 patients receiving PMRT increased from 23.9% in 2003 to 36.4% in 2011 with an annual percent change (APC) of 6.2% (P < 0.001). There were significant increases in the use of PMRT amongst patients with one (APC = 7.7%), two (APC = 6.7%), and three (APC = 4.2%) positive nodes. In 2011, 27.8%, 43.8%, and 57.8% of patients with one, two or three positive nodes underwent PMRT, respectively. The number of positive nodes and tumor size were the strongest independent predictors of PMRT in the 1–3 node group; lymphovascular invasion, invasive lobular histology, and triple negative phenotypes were also associated with PMRT use.

Conclusion

PMRT for patients with pT1‐2N1 disease has increased with the greatest increase seen in those with one tumor positive node. Tumor factors remain strong independent predictors of PMRT. J. Surg. Oncol. 2015;112:809–814. © 2015 Wiley Periodicals, Inc.
The Camphorquinone/Amine and Camphorquinone/Amine/Phosphine Oxide Derivative Photoinitiating Systems: Overview, Mechanistic Approach, and Role of the Excitation Light Source
Authors: Morlet‐Savary Fabrice , Klee Joachim E. , Pfefferkorn Frank , Fouassier Jean Pierre , Lalevée Jacques
Published: October 2015

The camphorquinone (CQ)/amine and CQ/diphenyl (2,4,6‐trimethylbenzoyl)‐phosphine oxide (TPO)/amine photoinitiating systems (PISs) are largely used in the area of dental resins, but the role of the light source in connection with the excited state processes has not been deeply investigated so far. Here, a state‐of‐the‐art analysis on the photochemistry of these PISs is provided. Novel experiments using electron spin resonance spin trapping, cyclic voltammetry, photolysis as well as the recording of film polymerization profiles (by real time Fourier transform infrared (FTIR) measurements) of a trifunctional low molecular weight acrylate and a more viscous bisphenol A‐glycidyl methacrylate/triethyleneglycol dimethacrylate blend under well‐defined irradiation conditions (dental light‐emitting diode (LED) and monochromatic laser diode; this has not been done before) are carried out. Although a noticeable improvement under a polychromatic Xe lamp is clearly obtained in the literature when using CQ/TPO/amine compared to CQ/amine, the polymerization profiles of the representative (meth)acrylate monomers are only slightly better under a dental blue LED irradiation (band spectrum centred at 477 nm) and not affected under a laser diode at 473 nm. This work allows a complete and final description of the overall initiation mechanisms in these PISs.

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Molecular and Thermal Characterization of a Nearly Perfect Isotactic Poly(propylene)
Authors: Tranchida Davide , Mileva Daniela , Resconi Luigi , Rieger Bernhard , Schöbel Alexander
Published: October 2015

The structure formation upon cooling of the quiescent melt of a nearly defect‐free isotactic poly(propylene) (iPP) homopolymer is investigated in this study. This iPP, having a molecular weight of 1 × 106 g mol−1 and a narrow molecular weight distribution, has been produced with a C2 symmetric hafnocene complex. Information about the crystallization kinetics is collected in a broad range of cooling rates. Standard differential scanning calorimetry is used for cooling rates in the range 3–100 °C min−1 and FSC is employed to analyze the solidification process at cooling rates larger than 100 °C s−1. The near absence of regio‐ and stereo‐defects allows this iPP to crystallize at significantly high temperatures and to form crystals at cooling rates higher than commonly observed for standard Ziegler–Natta iPP. The data reveal that the iPP homopolymer with close‐to‐perfect stereo‐regularity form crystals at high cooling rates as, e.g., α‐nucleated iPP. The defect‐free polymer chain allows the formation of relatively thick lamellar crystals which resulted in a relatively high tensile modulus of 2088 ± 8 MPa.

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The Virtual Element Method for large scale Discrete Fracture Network simulations: fracture‐independent mesh generation
Authors: Berrone Stefano , Benedetto Matìas Fernando , Borio Andrea , Pieraccini Sandra , Scialò Stefano
Published: October 2015

We consider the problem of underground flow simulations in fractured media. This is a large scale, heterogeneous multi‐scale phenomenon involving very complex geological configurations. Within the Discrete Fracture Network (DFN) model, we focus on the resolution of the steady‐state flow in large fracture networks. Exploiting the peculiarity of the Virtual Element Method (VEM), which allows the use of rather general polygonal mesh elements, we propose an approach for building a suitable mesh for representing the solution on DFNs. (© 2015 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Investigation of optimal bipedal walking gaits subject to different energy‐based objective functions
Authors: Römer Ulrich , Fidlin Alexander , Seemann Wolfgang
Published: October 2015

Optimal bipedal walking gaits subject to different energy‐based objective functions are investigated using a simple planar rigid body model of a bipedal robot with upper body, thighs and shanks. The robot's segments are connected by revolute joints actuated by electric motors. The actuators' torques are generated by a trajectory tracking controller to produce periodic walking gaits. A numerical optimization routine is used to find optimal reference trajectories for average speeds in the range of 0.3 – 2.3 m/s to investigate the influence of different objective functions. (© 2015 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Theoretical and numerical aspects in the multiphasic modelling of human brain tissue
Authors: Wagner Arndt , Ehlers Wolfgang
Published: October 2015

A surgical intervention is often required if the functionality of the sensitive human brain tissue is seriously compromised, e. g., due to the occurrence of malignant brain tumours. A promising method for an effective tumour‐treatment procedure is given by the so‐called convection‐enhanced drug delivery (CED), cf. [1]. In this regard, the aim of this contribution is to simulate the expected effects as well as coupled impacts of a (scheduled) CED‐procedure with the help of numerical computations, which base on a sophisticated multiphasic and multi‐physical modelling strategy applied to human brain tissue. In particular, a quaternary porous‐media model, cf. [3–5], is used for the discussion of selected numerical examples and demonstrates the applicability of the model. In detail, the optimal catheter placement and the application of multiple infusion catheters are studied in terms of the occurring anisotropic therapeutic spreading of the infused drug. (© 2015 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Phase‐Field Modeling of Hydraulic Fracture
Authors: Mauthe Steffen , Miehe Christian
Published: October 2015

Hydraulically driven fracture has gained more and more research activity in the last few years, especially due to the growing interest of the petroleum industry. Key challenge for a powerful simulation of this scenario is an effective modeling and numerical implementation of the behavior of the solid skeleton and the fluid phase, the mechanical coupling between the two phases as well as the incorporation of the fracture process. Existing models for hydraulic fracturing can be found for example in [1], where the crack path is predetermined, or in [2] who use a phase field fracture model in an elastic framework, however without incorporating the fluid flow. In this work we propose a new compact model structure for the Biot‐type fluid transport in porous media at finite strains based on only two constitutive functions, that is the free energy function ψ and a dissipation potential ϕ that includes the incorporation of an additional Poiseuille‐type fluid flow in cracks. This formulation is coupled to a phase field approach for fracture and is fully variational in nature, as shown in [3]. In contrast to formulations with a sharp‐crack discontinuity, the proposed regularized approach has the main advantage of a straight‐forward modeling of complex crack patterns including branching. (© 2015 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Investigation of elastoplastic effects of cables under large spatial deformation
Authors: Dörlich Vanessa , Diebels Stefan , Linn Joachim
Published: October 2015

Cables are complex components consisting of a multi‐layer structure and various materials. The structural setup includes for example conducting wires, isolating shields and protecting sheaths. This leads to several inelastic effects under large deformations like pull‐out of wires, delamination of layers or friction between the constituents. The materials used in cables belong to different material classes and consequently show different behavior under load. Elastoplastic behavior has to be expected for metallic wires, whereas polymer layers behave viscoelastically. The combination of these inelastic effects caused by the structure and constituents of cables motivates the inclusion of inelasticity in the material model on a phenomenological level. Since cables are flexible, slender structures, they can be described physically correctly by the theory of Cosserat rods. In this context, the constitutive equations are formulated in terms of the sectional quantities. The related model parameters have to be determined in suitable experiments. As cables undergo large multiaxial deformations in applications, uniaxial experiments are not sufficient for their characterization. (© 2015 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Application of fibre BRAGG grating sensors for residual stress analysis
Authors: Hannusch Susann , Stockmann Martin , Ihlemann Jörn
Published: October 2015

Residual stresses are important by the manufacturing of the most components. The analysis of residual stresses using the hole‐drilling method is complicated and is based at the moment solely on strain measurement on the surface. Now, an approach is described where the residual stresses can be calculated on the basis of strain measured in several plains. (© 2015 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A physically motivated model for filled elastomers including strain rate and amplitude dependency in finite viscoelasticity
Authors: Juhre Daniel , Raghunath Rathan , Klüppel Manfred
Published: October 2015

A microstructure‐based model of rubber reinforcement, the so‐called dynamic flocculation model (DFM), is presented describing filler‐induced stress softening and hysteresis by the breakdown and reaggregation of strained filler clusters [1]. An extension of this model allows to consider incomplete deformation cycles that occur in the simulation of arbitrary deformation histories [2]. Good agreement between measurement and the model is obtained for CB‐filled elastomers like NR, SBR or EPDM, loaded along various deformation histories. One very important aspect is that the model parameters can be directly referred to the physical properties.

This benefit is used to extend the model to further essential effects like time‐ and rate‐dependent material behavior. In the limit range above the glass transition temperature these viscoelastic effects originate mainly from the filler‐filler interactions. In the material model these interactions are characterized by two material parameters sv and sd, respectively. The parameter sv defines the strength of the virgin filler cluster, whereas sd represents the strength according to the broken or damaged filler clusters. Both parameters can be defined as functions of time sv,d = ŝv,d(t), which can be motivated by physical meaning [3]. Due to this extension it is possible to capture the very complex strain rate and amplitude dependency during loading and relaxation. (© 2015 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
On the generation of soft magneto‐electric effects through Maxwell interactions
Authors: Keip Marc‐André , Rambausek Matthias
Published: October 2015

This contribution presents a finite‐strain computational homogenization framework for soft magneto‐electro‐elastic solids. We use it in order to determine effective magneto‐electric coupling coefficients of soft composites, which are driven by the interconnection of electrical and magnetical Maxwell stresses. (© 2015 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Efficient time integration in multiplicative inelasticity
Authors: Landgraf Ralf , Shutov Alexey V. , Ihlemann Jörn
Published: October 2015

In Shutov et al. (Comput Methods Appl Mech Eng 265:213–225, 2013), the numerical time integration of a famous large strain model of Maxwell fluid type has been considered. The underlying model is based on the multiplicative decomposition of the deformation gradient and includes a Neo‐Hookean hyperelasticity relation as well as an incompressible viscous flow rule. Shutov et al. presented a time stepping algorithm for implicit time integration of the inelastic flow rule, which is based on Euler backward time discretisation, prevents error accumulation and is iteration free. In this contribution, the basic idea of the this approach is applied to more general models of multiplicative viscoelasticity. Here, extended hyperelastic relations including general functions of the first principal invariant of deformation tensors are regarded. An efficient time stepping algorithm is derived, where only one scalar equation for one scalar unknown has to be solved within every time step. The approach is applied to a specific viscoelastic model. (© 2015 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A Hardening Description based on a Finite‐Deformation Gradient Crystal Plasticity Model: Formulation and Numerical Implementation
Authors: Pouriayevali Habib , Xu Baixiang
Published: October 2015

In this study, a well‐defined finite‐deformation gradient crystal plasticity is employed to study size‐dependence strengthening behavior of a single crystal under simple shear loading. The constitutive model is implemented in the FEM software ABAQUS via a user‐defined element subroutine (UEL). Effect of gradient strengthening, latent hardening and scale‐variation in mechanically plastic response of a single crystal subjected to isothermal quasi‐static loading is studied and discussed. (© 2015 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Parameter Identification by Inverse Modelling of Biaxial Tensile Tests for Discontinous Fiber Reinforced Polymers
Authors: Schemmann Malte , Brylka Barthel , Gajek Sebastian , Böhlke Thomas
Published: October 2015

In the present article we discuss the characterization of the mechanical properties of long fiber reinforced thermoplastics (LFT) and sheet molding compounds (SMC) with biaxial tensile tests and the inverse parameter identification. The full 3D strain field is measured via digital image correlation (DIC). The anisotropic viscoelastic material properties are identified through inverse modelling by comparison of the heterogeneous experimental and simulated strain fields. A Gauss‐Newton type algorithm is used to identify the optimal parameter set [1]. (© 2015 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Harvesting energy with an out‐of‐plane dielectric elastomer generator
Authors: Bortot Eliana , Gei Massimiliano
Published: October 2015

This note concerns the numerical analysis of the performance of an annular membrane dielectric elastomer generator deforming non‐homogeneously out‐of‐plane. The prestretch of the membrane is crucial for an improved behaviour of this device. We evaluate its positive effects on the performance by employing a hyperelastic formulation. Moreover, fixing the external radius, we compare the behaviour of two generators characterized by different values of the radius ratio Re/Ri, namely 2 and 4. Numerical results show that the generator with the smaller ratio has a better performance. (© 2015 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Spreading of Linear Disturbances in Boundary Layers at Mach Number Five and the Effect of Wall Cooling
Authors: Jocksch A. , Kleiser L.
Published: October 2015

We determine inviscid eigensolutions in zero pressure gradient flat plate boundary layers at Mach number five and evaluate the eigensolutions with the method of steepest descent. The resulting wave packets show that with wall cooling the tail of the packets becomes slower. Although the boundary layers investigated are all convectively unstable we interpret the slow tail of the wave packets as a trend towards an absolute instability. From a comparison of the wave packets with turbulent spot transition, we conclude that for wall cooling the general transition properties are close to those of an absolutely unstable flow. (© 2015 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Unified description of bifurcation processes associated with laminar boundary‐layer separation
Authors: Kluwick Alfred , Braun Stefan
Published: October 2015

The presentation will concentrate on flows where no steady state exists if an appropriately defined controlling parameter exceeds a critical value while non‐uniqueness is observed for sub‐critical values of this parameter. Special attention is placed on flow phenomena which are associated with the passage through criticality. Based on a triple deck analysis it found that they can be described as solutions of differential equations of Fisher type which are better known from evolution studies of gene populations. Special examples which will be discussed include 2D marginally separated flows, weakly 3D transonic flows in slender channels and fully 3D subsonic flow past expansion ramps. (© 2015 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Robust Design using classical optimization
Authors: Erschen Stefan , Duddeck Fabian , Zimmermann Markus
Published: October 2015

The complexity of technical products increases significantly, due to an increasing number of interacting design variables of many components and subsystems. At the same time, the need for separated development processes is increasing due to specialization and outsourcing. Solution space methods are designed to solve this conflict. The requirements from an upper level, e.g. performance measures of the whole system, can be cascaded down to requirements on a lower level, e.g. performance measures of the subsystems or components, as it is done in the V‐model approach. The method does not only take the numerous interactions into account but also guarantees the resulting intervals of different parameters to be independent of each other. Unfortunately, the computational cost of the state‐of‐the‐art stochastic approach is high. The approach in this paper shows that the computational effort can be reduced considerably using a gradient based optimization approach for constraint problems. We demonstrate that the approach reduces the required number of function evaluations for a chassis design problem by a factor of 30, but more important, the CPU time for solving the problem by a factor of 20. (© 2015 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Methods with Successive and Parallel Approximations of Inverse Operator for the Nonlinear Least Squares Problem
Authors: Iakymchuk Roman , Shakhno Stepan
Published: October 2015

For solving the nonlinear least‐square problem, we propose iterative methods that use successive and parallel approximations of the inverse operator instead of solving a linear system of equations. The convergence order as well as the convergence radius of the proposed methods are studied. Finally, we carry out numerical experiments on a set of test problems. (© 2015 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
On curvature control in node–based shape optimization
Authors: Schmitt Oliver , Steinmann Paul
Published: October 2015

We present and compare three approaches to control of the curvature of the domain boundary in two–dimensional shape optimization. Since the coordinates of the FE–nodes are used as design variables, objective and constraint functions have to be formulated in terms of the nodal coordinates. Therefore we investigate various formulations for the curvature of the domain boundary in terms of the coordinates of the boundary nodes. In addition, the sensitivities of these expressions with respect to the design nodes are required for the application of gradient–based optimization algorithms. (© 2015 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A kinematic approach based on an equivalent track for a skid‐steering vehicle
Authors: Galati R. , Giannoccaro N.I. , Messina A. , Reina G.
Published: October 2015

The skid‐steering principle is based on controlling the relative velocities of both the tracks as differential drive wheeled vehicles. However, control of tracked locomotion poses a more complex problem because variation of the relative velocity of the two tracks results often in slippage of the vehicle [1]. It is possible to define a kinematic approach able to describe and to improve the motion control and dead‐reckoning of a skid‐steering robot by considering the effects of the slippage but without introducing the complexity of dynamics computation. The equivalent track approach has been applied to a skid‐steering robot characterized by an high maximum payload (75 kg) and by a high power than makes it able to move in very difficult conditions (snow, iced terrains, mud) where the slippage effects become predominant. (© 2015 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Approximation in variation for Mellin integral operators
Authors: Angeloni Laura , Vinti Gianluca
Published: October 2015

We study approximation results for a family of Mellin integral operators in the space of functions of bounded variation in the multidimensional setting, by means of a new concept of variation for multivariate functions. (© 2015 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)