bluuebunny/crossref_metadata_2025_split huggingface dataset:
Iron‐reducing bacteria can enhance the activation and turnover of the Fe(III)‐fixed phosphorus for mycorrhizal plants
Authors: Zhang Shirong , Wang Rongping , Zhang Lin , Li Shuyi , Feng Gu , Ding Xiaodong 
Published: November 2013

AbstractIn a greenhouse experiment, Medicago sativa was grown in iron‐rich soil colonized with iron‐reducing bacteria (IRB) and/or Glomus mosseae (GM) under different inorganic phosphorus levels, which was to understand the effects of IRB and GM on the activation and turnover of the Fe(III)‐fixed phosphorus. The results showed that at the both P rates, dual‐inoculation treatment stimulated the hyphal growth and increased the shoot P content. IRB could accelerate mycorrhizal colonization, and showed a positive effect on plant biomass and P uptake at both P levels. Compared to sole‐IRB or GM treatment, the dual inoculation treatment increased the soil available P content at both P rates (p < 0.05), which was in the following order: the dual IRB+GM > the sole IRB > the sole GM > control for soil SMP content at low P rate, whilst the dual IRB+GM > the sole IRB ≈ the sole GM > control treatment at high P rate. Compared with the IRB treatment, the GM treatment significantly decreased the soil available P content and the MBP content at low P rate, but made no difference at high P rates. The soil MBC in dual‐inoculation treatment was greatest under the high P level, while the highest soil MBC was the sole‐GM treatment under the low P level. The sole GM treatment showed significantly (p < 0.05) higher soil MBC than that of sole IRB at low P rate (p < 0.05), while there was no significant differences between sole IRB and sole GM at high P rate. Our results suggested that the interaction between GM and IRB had synergetic effect on the mobilization of Fe(III)‐fixed P and their relationship could be regulated by the turnover of MBP. The fact that plants acquired more P via mycorrhizal pathway in the GM‐IRB system suggested that the three symbiont of plant‐GM‐IRB had great ecological and functional significance for P activity in tropical and subtropical soil.
Effects of pretreatment and solution chemistry on solubility of rice‐straw phytoliths
Authors: Ngoc Nguyen Minh , Dultz Stefan , Guggenberger Georg 
Published: November 2013

AbstractRice is a Si‐accumulator plant, whereby Si has physio‐chemical functions for plant growth. Its straw contains high shares of plant silica bodies, so‐called phytoliths, and can, when returned to the soil, be an important Si fertilizer. Release of Si from phytoliths into soil solution depends on many factors. In order to improve prognosis of availability and management of Si located in phytoliths, in this study we analyzed the effect of pretreatment of rice straw by dry and wet ashing and the soil‐solution composition on Si release. Dry ashing of rice straw was performed at 400°C, 600°C, and 800°C and wet ashing of the original straw and the sample from 400°C treatment with H2O2. To identify the impact of soil‐solution chemistry, Si release was measured on separated phytoliths in batch experiments at pH 2–10 and in presence of different cations (Na+, K+, Mg2+, Ca2+, Al3+) and anions (Cl–, NO$ _3^- $, SO$ _4^{2-} $, acetate, oxalate, citrate) in the concentration range from 0.1 to 10 mmolc L–1. After burning rice straw at 400°C, phytoliths and biochar were major compounds in the ash. At an electrolyte background of 0.01 molc L–1, Si released at pH 6.5 was one order of magnitude higher than at pH 3, where the zeta potential (ζ) was close to zero. Higher ionic strength tended to suppress Si release. The presence of cations increased ζ, indicating the neutralization of deprotonated Si‐O– sites. Monovalent cations suppressed Si release more strongly than bivalent ones. Neutralization of deprotonated Si‐O– sites by cations might accelerate polymerization, leading to smaller Si release in comparison with absences of electrolytes. Addition of Al3+ resulted in charge reversal, indicating a very strong adsorption of Al3+, and it is likely that Si‐O‐Al‐O‐Si bonds are formed which decrease Si release. The negative effect of anions on Si release in comparison with deionized H2O might be due to an increase in ionic strength. The effect was more pronounced for organic anions than for inorganic ones. Burning of rice straw at low temperatures (e.g., 400°C) appears suitable to provide silicon for rice in short term for the next growing season. High inputs of electrolytes with irrigation water and low pH with concomitant increase of Al3+ in soil solution should be avoided in order to keep dissolution rate of phytoliths at an appropriate level.
A Late Younger Dryas–Early Holocene tephrostratigraphy for Fosen, Central Norway
Authors: LIND EWA M. , WASTEGÅRD STEFAN , LARSEN JEPPE J. 
Published: November 2013

ABSTRACTA number of rapid climate oscillations occur during the Lateglacial–Early Holocene, 15–8 ka BP period and a well‐developed tephrostratigraphy in association with these oscillations increases the possibilities to correlate climate archives around the North Atlantic. This paper presents a tephrostratigraphy for Fosen peninsula, Central Norway. Both the Vedde Ash ca.12.1 ka BP and the Saksunarvatn Ash ∼10.3 ka BP are important isochrones for correlations of Late Quaternary palaeoenvironmental records in the North Atlantic region and have been assigned ages in GICC05. Beside these tephras we have also identified a new tephra, the Fosen Tephra, with a Borrobol‐type geochemistry that occurs above both the Vedde Ash and the Saksunarvatn Ash with an age ∼10.2 ka BP. Several tephras with Borrobol‐type geochemistry have been identified around the North Atlantic. One group is the Borrobol/Penifiler tephras dated to Greenland Interstadial‐1 and another group is dated to the Early Holocene. We suggest that some of the Early Holocene Borrobol‐type tephras and the Fosen Tephra may actually be the same layer. If so, the Fosen Tephra is spread over a large area of the North Atlantic and has the potential to become an important marker for short‐term climate variability in Scandinavia and in the northern hemisphere.
In vivo optical signatures of neuronal death in a mouse model of Alzheimer's disease
Authors: Lin Alexander J. , Castello Nicholas A. , Lee Grace , Green Kim N. , Durkin Anthony J. , Choi Bernard , LaFerla Frank , Tromberg Bruce J. 
Published: November 2013

BackgroundThere currently is a need for cost‐effective, quantitative techniques to evaluate the gradual progression of Alzheimer's disease (AD). Measurement techniques based on diffuse optical spectroscopy can detect blood perfusion and brain cellular composition changes, through measuring the absorption (µa) and reduced scattering (µs′) coefficients, respectively, using non‐ionizing near‐infrared light. Previous work has shown that brain perfusion deficits in an AD mouse model can be detected. The objective of this study was to determine if µs′ is sensitive to the inflammation and neuron death found in AD.MethodsWe used spatial frequency domain imaging (SFDI) to form quantitative maps of µa and µs′ in 3‐month old male CaM/Tet‐DTA mice harboring transgenes for the doxycyline‐regulated neuronal expression of diphtheria toxin. When doxycycline is removed from the diet, CaM/Tet‐DTA mice develop progressive neuronal loss in forebrain neurons. Mice (n = 5) were imaged longitudinally immediately prior to and after 23 days of lesion induction, and µa and µs′ (30 wavelengths, 650–970 nm) were compared to properties obtained from Tet‐DTA controls (n = 5). Neuron death and infiltration of inflammatory cells in brain cortical slices was confirmed with immunohistochemistry.ResultsNo significant difference in baseline scattering and absorption were measured between CaM/Tet‐DTA mice and controls. After 23 days of lesion induction, brain cortical µs′ was 11–16% higher in the CaM/Tet‐DTA mice than in controls (P < 0.03). Longitudinal imaging showed no significant difference in µs′ between the first and 23rd day of imaging in controls. Removing doxycycline from the diet was associated with a significant decrease in total hemoglobin concentrations (119 ± 9 µM vs. 91 ± 8 µM) (P < 0.05) in controls, but not in CaM/Tet‐DTA mice.ConclusionsNeuronal death and brain inflammation are associated with increased tissue scattering (µs′) and this optical biomarker may be useful in pre‐clinical AD therapy evaluation or monitoring of disease progression in AD patients.Lasers Surg. Med. 46:27–33, 2014. © 2013 The Authors. Lasers in Surgery and Medicine Published by Wiley Periodicals, Inc.
On‐Line Monitoring of Molecular Weight Using NIR Spectroscopy in Reactive Extrusion Process
Authors: Bergmann Björn , Becker Wolfgang , Diemert Jan , Elsner Peter 
Published: November 2013

SummaryNear infrared spectroscopy (NIR) is a versatile tool for process control, scientific research and quality management. Consequently it is our aim to utilize NIR technique for the understanding and following of reactive extrusion processes. As preliminary results it was shown the molecular weight of degraded, non‐purified polyester can be measured and forecasted using purely NIR spectra analysis. In this paper we describe the close correlation of the received molecular weight values of partly glycolised Polyethylene terephthalate (PET) samples using reactive extrusion, measured using size exclusion chromatography (SEC) techniques and chemometric models basing on NIR measurements.
Mass Transfer in Miniemulsion Polymerisation
Authors: Jansen T.G.T. , Lovell P.A. , Meuldijk J. , van Herk A.M. 
Published: November 2013

SummaryThe use of very hydrophobic monomers in heterogeneous polymerisations is restricted because of insufficient mass transfer as a result of limited aqueous phase diffusion. Experimental evidence for a mass transfer mechanism in miniemulsion polymerisation that is based on the direct interaction between droplets as well as between droplets and particles (‘collisions’) rather than monomer diffusion is presented. Mass transfer that results in the formation of a copolymer in the miniemulsion polymerisation of a mixture of lauryl methacrylate and 4‐tert‐butyl styrene, is almost non‐existing when physical contact between individual droplets is prevented by a membrane. However, monomer transport by diffusion is observed in reference experiments with more hydrophilic monomers.
Numerical Simulation of Reactive Extrusion for Polycondensation of Poly(p‐phenylene terephthalamide) (PPTA)
Authors: Tang Hao , Zong Yuan , Xi Zhenhao , Zhao Ling 
Published: November 2013

SummaryPoly(p‐phenylene terephthalamide) (PPTA), as a typical high performance fiber with excellent strength and modulus property, is usually synthesized by low temperature solution polycondensation with p‐phenylenediamine(PPD) and terephthaloyl chloride(TPC) in twin screw extruders. Since the polycondensation during the process is a multicomponent reaction with high reactivity and wide viscosity range, the molecular weight and its distribution of PPTA are strongly influenced by mixing behavior of the extruder. In this paper, the polycondensation process in fully‐filled conveying elements of twin screw extruder were analyzed by three‐dimensional numerical simulation using the finite element method. The effects of conveying element geometry, rotating speed on mixing state were studied. In order to understand the mechanism behind the reactive extrusion process of PPTA, reaction extent and instantaneous efficiency of stretch in extruder were calculated simultaneously. The results indicate that the reaction process and mixing behavior of the PPTA flow are strongly interrelated. The increase of rotating speed promotes the reaction extent by enhancing the stretch effect, while larger screw pitch accelerates the reaction by rearranges the proportion of energy for stretch.
Models in the Polymer Industry: What Present? What Future?
Authors: Vale H. , Daiss A. , Naeem O. , Šeda L. , Becker K. , Hungenberg K.‐D. 
Published: November 2013

SummaryAn industrial perspective on the present and future role of kinetic and process models in the polymer industry is presented. A number of selected examples illustrate the current value of model‐based approaches in supporting and accelerating tasks like process optimization, product development and design of polymerization reactors. In addition, future trends for the application of models in the polymer industry are discussed and areas where further improvement is thought to be needed are carefully underlined.
Metallocene Catalyzed Ethylene Polymerization with Specially Designed Catalyst Supports and Reaction Systems
Authors: Lee Sangyool , Kim Sung‐Kyoung , Lee Sangbok , Choi Kyu Yong 
Published: November 2013

SummaryIn heterogeneously catalyzed polymerization of α‐olefins, the characteristics of a solid support material impact the catalyst activity, polymer particle morphology, and resulting polymer properties. Silica is the most widely used support for metallocene catalysts in α‐olefin polymerization processes because of its large surface area and favorable surface properties for catalyst anchoring. Understanding the kinetics of heterogeneous olefin polymerization over a solid‐supported catalyst is often quite complicated because of mass transfer effects and catalyst particle fragmentation during the polymerization. Incomplete or premature fragmentation of support material results in a large fraction of catalyst sites left unavailable for the polymerization, causing some inconsistencies in the performance of the catalyst. Silica‐supported metallocene catalysts for α‐olefin polymerization are known to follow the layer‐by‐layer fragmentation mechanism where the fracture of the silica/polymer layer begins from the surface region of a silica particle and it gradually continues into the center of the particle as fragmentation is complete. In this paper, we present new experimental results on ethylene polymerization with rac‐Et(indenyl)2ZrCl2/MAO catalyst using different types of silica supports to quantitatively assess the effects of support geometry on intrinsic catalytic activity. Flat surface silica, nano‐sized spherical silica, straight cylindrical pore silica, and conventional silica are used as supports. The presence or absence of intraparticle monomer diffusion resistance and particle fragmentation has been shown to have significant effects on the catalytic activity.
Micro‐Cellular Polystyrene Foam Preparation Using High Pressure CO2: The Influence of Solvent Residua
Authors: Nistor Andra , Rygl Adam , Bobak Marek , Sajfrtova Marie , Kosek Juraj 
Published: November 2013

SummaryPolystyrene (PS) foams are commonly used as heat insulators. Their heat insulation properties can be greatly improved by decreasing the cell size into the range of micrometres, resulting in the so‐called micro‐cellular foams. We prepared micro‐cellular PS foams and studied the influence of toluene residua on the foam structure. First, PS films were prepared by the dip‐coating method using toluene as the solvent. Then, the PS films were foamed by the pressure induced foaming method using high pressure CO2. The foam structures were examined by Scanning Electron Microscopy and X‐ray micro‐tomography. For the industrial PS sample containing nucleation agents, the influence of temperature and depressurization rate on cell size was observed in a way consistent with the literature. However, the obtained cell sizes were much larger. Therefore, the effect of toluene residua on the foaming process was systematically studied. A PS sample without nucleation agents was used to exclude their effect on the foaming process. Toluene acts as a co‐solvent and enhances the CO2 solubility in PS, which should lead to a large amount of small cells. However, at toluene concentrations below 8 %wt, the plasticizing effect of toluene dominates, resulting in enhanced coalescence and cell growth. Foam heat insulation properties improve with increasing porosity. The toluene residua increased the porosity by increasing the cell sizes and lowering the thickness of the compact skin at the film surface. We conclude that toluene residua greatly influence the foam structure and this finding can be potentially used to control the foaming process.
Polymerization of N‐Vinyl Formamide in Homogeneous and Heterogeneous Media and Surfactant Free Emulsion Polymerization of MMA Using Polyvinylamine as Stabilizer
Authors: Zataray J. , Aguirre A. , de la Cal J.C. , Leiza J.R. 
Published: November 2013

SummaryThis work considers the homogeneous aqueous phase polymerization of n‐vinyl formamide(NVF). Thus, the effect of temperature, initiator and monomer concentration in the kinetics and molar mass distribution (MMD) of the polyNVF produced was experimentally assessed. SEC‐MALS analysis was misleading because anomalous elution was found due to interaction of the polyNVF chains with the column. This was solved by analyzing the polyNVF by asymmetric‐flow field flow fractionation chromatography coupled with multi‐angle light scattering and differential refractive index, AF4/MALS/RI. The second part of this work considered the synthesis of nanoparticles based on polyNVF. Two routes were explored. In the first one the inverse microemulsion photopolymerization of NVF was attempted and polyNVF dispersions in isopar M with solids content of 18 wt% and particle sizes in the range 50–70 nm with average molar masses of several millions were obtained. In the second route PolyNVF produced in homogeneous aqueous phase was hydrolyzed to yield polyvinyl amine, PVAm. The resulting water soluble polymers were used to produce polymethyl methacrylate, PMMA, nanoparticles by surfactant free emulsion polymerization initiated by tert‐butyl hydroperoxide TBHP. Stable pH responsive PMMA cationic nanoparticles with amino functionalities in the surface were easily produced.
Experimental Investigation of the Morphology Formation of Polymer Particles in an Acoustic Levitator
Authors: Sedelmayer Robert , Griesing Matthias , Halfar Annelie Heide , Pauer Werner , Moritz Hans‐Ulrich 
Published: November 2013

SummaryDroplet polymerization of N‐vinyl‐2‐pyrrolidone (NVP) and sodium acrylate (NaAA) was carried out in an acoustic levitator for different ambient temperatures and relative humidities. The resulting particle morphologies were compared to particles of two crystalline systems (mannitol and ammonium sulfate) and two disperse systems (silica and styrene ‐ butyl acrylate dispersion), all obtained under similar drying conditions. NVP was found to form a higher amount of crystals with lower temperature and relative humidity, contrary to the behaviour observed for mannitol and ammonium sulfate. The processes of both, polymerization and drying of NaAA lead to similar morphologies at low temperatures and humidities, probably caused by the precipitation of NaAA during polymerization.
Detailed Investigations into Radical Polymerization Kinetics by Highly Time‐Resolved SP–PLP–EPR
Authors: Kattner Hendrik , Buback Michael 
Published: November 2013

SummaryInstantaneous initiation of radical polymerization by applying an intense laser pulse on a monomer‐photoinitiator solution in conjunction with time‐resolved detection of radical concentration provides access to a detailed picture of polymerization kinetics. Examples are given of measurement of chain‐length‐dependent termination, of intramolecular chain transfer as well as of reversible‐deactivation radical polymerization, namely of RAFT and ATRP. The enormous potential of the method relates to the fact that the kinetics of the major acting species, i.e., of the radicals, may be directly monitored with high time resolution.
Condensed Mode Cooling in Ethylene Polymerisation: Droplet Evaporation
Authors: Alizadeh Arash , McKenna Timothy F.L. 
Published: November 2013

SummaryA simplified model is used to explore the mechanisms for droplet vaporisation in fluidised bed reactors used for the production of polyethylene in the gas phase. Both homogeneous and heterogeneous vaporisation models are considered. It is shown that for a reasonable range of droplet sizes (less than 1 mm in diameter), droplet vaporisation will be essentially complete at bed heights on the order of 1 m.
Mass moment vector applications to the multi body dynamics with coupled rotations about no intersecting axes
Authors: (Stevanović) Hedrih Katica R. , Stamenković Marija B. 
Published: November 2013

AbstractMulti body system contains finite number of rigid bodies that are placed on each axis, which do not intersect each other. Derivatives of the linear momentum and angular momentum with respect to time by use mass moment vectors and vector rotators for pole and axis, are determined. A number of theorems are defined. (© 2013 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Asynchronous variational Lie group integration for geometrically exact beam dynamics
Authors: Demoures Francois , Gay‐Balmaz Francois , Leitz Thomas , Leyendecker Sigrid , Ober‐Blöbaum Sina , Ratiu Tudor S. 
Published: November 2013

AbstractFor the elastodynamic simulation of a spatially discretized beam, asynchronous variational integrators (AVI) offer the possibility to use different time steps for every element [1]. They are symplectic and conserve discrete momentum maps and since the presented integrator for geometrically exact beam dynamics [2] is derived in the Lie group setting (SO(3) for the representation of rotational degrees of freedom), it intrinsically preserves the group structure without the need for constraints [3]. A decrease of computational cost is to be expected in situations, where the time steps have to be very low in certain parts of the beam but not everywhere, e.g. if some regions of the beam are moving faster than others. The implementation allows synchronous as well as asynchronous time stepping and shows very good energy behaviour, i.e. there is no drift of the total energy for conservative systems. (© 2013 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Numerical Simulation of Anisotropy Directions in Soft Tissues and in Particular in Skin
Authors: Li Xuhui , Raith Stefan , Itskov Mikhail 
Published: November 2013

AbstractOrientation of collagen fibers and their spatial distribution predefine macroscopic mechanical properties of the soft tissue and in particular its anisotropy directions. In this contribution, we apply two different procedures to automatically generate these directions for a 3D FE‐model. The first procedure is based on an analogy with a heat conduction problem. Accordingly, a thermal flux under certain temperature boundary conditions is calculated by the same FE model and is further utilized for the definition of the anisotropy directions. The numerical result shows good agreement with Langer's lines data in human skin. Within the second procedure, the fiber vector field is calculated by the Laplacian smoothing method based on the user defined fiber direction sketches. (© 2013 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Selective proper orthogonal decomposition model reduction for forming simulations
Authors: Radermacher Annika , Reese Stefanie , Hadoush Ashraf Moh'd Hasan 
Published: November 2013

AbstractRobot‐based incremental sheet metal forming is a cost‐effective and flexible method for prototype and low batch size production. The simulation of such processes is very challenging and elaborate from the computational point of view. To reduce the computational effort model reduction techniques such as proper orthogonal decomposition (POD) can be applied. But the reduction of highly non‐linear models in solid mechanics for example forming simulation still leads to problems of efficiency and accuracy. Therefore, the aim of this paper is to present an alternative way to use POD for forming processes. The presented selective POD (SPOD) method is used to split the model into two domains depending on the degree of plastic strain. Only the domain with approximately linear elastic behavior will be reduced by using POD. Utilizing the SPOD method for the example of forming a horizontal flute reduces the computational time up to around 30 per cent. High accuracy with approximation errors smaller than one per mill is achieved. (© 2013 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)