bluuebunny/crossref_metadata_2025_split huggingface dataset:
Organic carbon in soils of Germany: Status quo and the need for new data to evaluate potentials and trends of soil carbon sequestration
Authors: Prechtel Annette , von Lützow Margit , Uwe Schneider Bernd , Bens Oliver , Bannick Claus G. , Kögel‐Knabner Ingrid , Hüttl Reinhard F. 
Published: September 2009

AbstractUncertainties in estimates of soil carbon (C) stocks and sequestration result from major gaps in knowledge of C storage in soils, land‐use history, the variability of field measurements, and different analytical approaches applied. In addition, there is a lack of long‐term datasets from relevant land‐use systems. As in many European countries, a national database on soil organic carbon (SOC) including all relevant information for the determination of soil C stocks is likewise missing in Germany. In this paper, we summarize and evaluate the present state of knowledge on organic‐C contents/pools in soils of Germany and discuss the need for the acquisition and access to new data on soil organic carbon.Despite the number of agricultural sites under permanent soil monitoring, regional surveys on SOC, comprehensive ecosystem studies, and long‐term field experiments, there is a striking lack of data in Germany particularly with regard to agricultural soils. Apart from a missing standardization of methods and homogeneous baseline values, the implementation of a periodic, nation‐wide soil inventory on agricultural soils is required in order to simultaneously record information on land use, land‐use change, and agricultural practice. In contrast, the existing national inventory of forest soils provides information on C‐stock changes in forest soils, although there is some concern with regard to the representativeness of the sampling design to adequately address the problem of spatial heterogeneity and temporal variability.It is concluded that the lack of comprehensiveness, completeness, actuality, data harmonization, and standardized sampling procedures will further prevent the establishment of a SOC database in Germany with regard to the monitoring of trends in soil C pools and fluxes and the assessment of long‐term C‐sequestration potentials of soils under different land use. A future soil inventory should represent the heterogeneity of organic matter through functionally different SOC pools, topsoil characteristics as well as content, pool, and flux data for the deeper mineral‐soil compartments.
Fiber‐optic SERS sensor with optimized geometry: testing and optimization
Authors: Pesapane Andrea , Lucotti Andrea , Zerbi Giuseppe 
Published: September 2009

AbstractA unique, geometry‐optimized, surface‐enhanced Raman scattering (SERS) fiber‐optic sensor has been recently developed and built. Though this class of sensors can be very useful in many applications, their use is greatly hindered by the fact that their reusability can hardly be achieved because of the irreversible adsorption of the analyte molecules on the SERS‐active substrate. Different substrates have been tested on our sensor with the purpose of increasing its reusability by means of cleaning procedures or good reproducibility in manufacturing the sensor, keeping, however, the same enhancement. We show that a partial reusability of the sensor is possible using SERS‐active substrates prepared by a standard process of immobilization of silver nanoparticles with 3‐aminopropyltrimethoxysilane. We also show that a fairly good reproducibility can be achieved with a low‐cost substrate realized in a short time by depositing a layer of polyvinyl alcohol (PVA) containing silver nanoparticles on the etched fiber tip. We prove as well that measurements are possible even with nanoparticles dispersed in the analyte solution instead of using a substrate directly made on the sensor tip. Finally, we have successfully tested our sensor with some molecules cited in EFSA (European Food Safety Authority) and FDA (Food and Drug Administration) reports as molecules for which new detection methods are necessary. Copyright © 2009 John Wiley & Sons, Ltd.
Capillary electrophoresis with dual laser detection in separation of amplified fragment length polymorphism fragments
Authors: Stefanowicz‐Hajduk Justyna , Filipowicz Natalia , Kosinski Igor , Ochocka J. Renata 
Published: September 2009

AbstractWe are presenting the application of CE technique with dual‐channel LIF detection for the simultaneous separation of DNA fragments labeled with two different fluorescence dyes. The optimal conditions of the analysis were determined for the separation of amplified fragment length polymorphism (AFLP) fragments labeled with 5′‐6‐carboxyfluorescein (6‐FAM) and the DNA size standard labeled with sulfoindocyanine succinimidyl ester (Cy‐5). CE equipped with both argon ion and diode lasers is a good alternative for sequencers and might be applied in analyses of PCR products generated by various fingerprinting methods.
Self‐Assembly of a Modified Amyloid Peptide Fragment: pH‐Responsiveness and Nematic Phase Formation
Authors: Hamley Ian W. , Castelletto Valeria , Moulton Claire , Myatt Daniel , Siligardi Giuliano , Oliveira Cristiano L. P. , Pedersen Jan Skov , Abutbul Inbal , Danino Dganit 
Published: September 2009

AbstractThe self‐assembly of peptide YYKLVFFC based on a fragment of the amyloid beta (Aβ) peptide, Aβ16–20, KLVFF has been studied in aqueous solution. The peptide is designed with multiple functional residues to examine the interplay between aromatic interactions and charge on the self‐assembly, as well as specific transformations such as the pH‐induced phenol–phenolate transition of the tyrosine residue. Circular dichroism (CD) and Fourier‐transform infrared (FTIR) spectroscopies are used to investigate the conditions for β‐sheet self‐assembly and the role of aromatic interactions in the CD spectrum as a function of pH and concentration. The formation of well‐defined fibrils at pH 4.7 is confirmed by cryo‐TEM (transmission electron microscope) and negative stain TEM. The morphology changes at higher pH, and aggregates of short twisted fibrils are observed at pH 11. Polarized optical microscopy shows birefringence at a low concentration (1 wt.‐%) of YYKLVFFC in aqueous solution, and small‐angle X‐ray scattering was used to probe nematic phase formation in more detail. A pH‐induced transition from nematic to isotropic phases is observed on increasing pH that appears to be correlated to a reduction in aggregate anisotropy upon increasing pH.magnified image
Full‐Color Processible Electrochromic Polymers Based on 4,4‐Dioctyl‐Cyclopentadithiophene
Authors: Wu Chun‐Guey , Lu Ming‐I , Tsai Pei‐Fang 
Published: September 2009

AbstractThree soluble electrochromic copolymers based on 4,4‐di‐octyl‐cyclopentadithiophene (DOCPDT): PDOCPDT‐OT, PDOCPDT‐PT, and PDOCPDT‐Cz were synthesized and the electrochromic properties were investigated. Colorimetric analysis revealed that red‐colored PDOCPDT‐OT, green‐colored PDOCPDT‐PT and their blue mother polymer PDOCTDT are cathodic coloration polymers. PDOCPDT‐Cz is yellow in its neutral state and shows an anodic electrochromism. The structural flexibility, color diversity, processibility and good electrochromic performance make octyl‐cyclopentadithiophene‐containing polymers prominent candidates for electrochromic applications.magnified image
The Preparation of Copolymers Derived from Thiol‐ene/Cationic Systems by Using a Coupling Agent
Authors: Ortiz Ricardo Acosta , Valdez Aida E. Garcia , Duarte M. Lydia Berlanga , Flores Rodolfo Ovando , Soucek Mark D. 
Published: September 2009

AbstractA bifunctional monomer with methacrylate and epoxycyclohexyl groups linked by a tetramethyldisiloxane moiety was used as a coupling agent for dual photo and thermally polymerizable Thiol‐Ene/cationic systems. The thiol‐ene system included a tetrafunctional thiol, a trifunctional acrylate and a radical photoinitiator while the cationic system comprised a difunctional epoxycyclohexyl monomer and a cationic photoinitiator. It was found that in a first stage the methacrylate group of the coupling agent reacted with the components of the thiol‐ene system rendering a polysulfide with pendant epoxycyclohexyl groups. In a second stage these pendant groups copolymerized with the epoxy monomer by means of a thermal treatment at 120 °C. When the obtained polymers were analyzed by DMA, an increase in the storage modulus was noticed in comparison with the polymers where no coupling agent was added.
Plasma Copolymerization of Ethylene Glycol and Allylamine
Authors: Gomez Lidia M. , Morales Pilar , Cruz Guillermo J. , Olayo Ma. Guadalupe , Palacios Cuauhtemoc , Morales Juan , Olayo Roberto 
Published: September 2009

AbstractThis work presents the plasma copolymerization of Ethylenglycol and Allylamine with the purpose to obtain thin films of biocompatible random polymers with NH and OH chemical groups. The synthesis used electrical glow discharges with mixtures of the monomers at 13.56 MHz, 10−1 mbar and power between 40 and 120 W. The results were thin films of copolymers with NH, CH, OH, and CC groups of the monomers. The main thermal degradation of the plasma copolymers was found between 100 and 500 °C in one step, suggesting that the material behaves as only one chemical species and not as a mixture. The copolymers absorb an average of 6% of water. The contact angles between the polymers and drops of solutions with concentrations of salts similar to those in the human body vary from 20° to 52° increasing with the power of synthesis. The surfaces varied from smooth to rough as the power of synthesis increases. This physical effect appears as the main variable in increasing the contact angles in the plasma copolymers. The electrical conductivity was in the interval of 10−8 and 10−13 S/m and was considerably influenced by the water content in the polymers. All these data suggests that the plasma copolymers are partially hydrophilic and biocompatible.
Surfactant Concentration Effects on the Aqueous Phase Polymerization of Vinyl Acetate
Authors: Martínez‐Gutiérrez Hugo , Ovando‐Medina Víctor M. , Peralta René D. 
Published: September 2009

AbstractVinyl acetate (VAc) in concentrations below the water saturation value was polymerized by batch processes at 60 °C using low surfactant concentrations of sodium dodecyl sulfate (SDS) and potassium persulfate (KPS) as initiator. The effects of surfactant concentration on the reaction kinetics, particle formation and molecular weight were studied. It was found that the average particle diameters decrease between 277 and 18.7 nm as the surfactant concentration is increased from 0 to 11 mmol/L, whereas the weight average molecular weight (Mw) decreases also, with values between 8.7 × 105 ≤ Mw ≤ 1 × 105 Da. It was observed that particle size distributions are strongly affected by the addition of small amounts of surfactant. For the low monomer concentrations used in the polymerizations (0.0137 g/cm3 of water), particles were very stable and no coagulation was observed. High reaction rates were found in all polymerizations. When no SDS was added to the system, lower polymerization rates were obtained at the onset of the reaction due to the low rate of particle formation. The behavior of polymerization rate was inversely proportional to the surfactant concentration, which was ascribed to the increase in the average number of radicals per particle.
Synthesis of Random Copolymers Poly (methylmethacrylate‐co‐azo monomer) by ATRP‐AGET
Authors: Nájera M.A. , Elizalde L.E. , Vázquez Y. , Santos G. de los 
Published: September 2009

AbstractThe synthesis of the azo molecule 1‐(2‐(4‐nitrophenyl) diazenyl) naphtalen‐2‐ol which has been functionalized with a methacryloxyl fraction is now reported. This azo monomer was copolymerized with methyl methacrylate (MMA) by ATRP where the active species is prepared “in situ” after the reduction reaction of the metal complex Cu (II) ‐ HMTETA by tin 2‐ethylhexanoate in 2‐butanone as solvent. Experimental conditions for the controlled homopolymerization of MMA were established. By adjusting the amount of reducing agent, a good correlation between theoretical and experimental molecular weight was obtained. Such conditions were also employed for the random copolymerization of MMA with the synthesized azo monomer.
Syndiospecific Styrene Polymerization in Aliphatic Solvents Catalyzed by FluTi(OiPr)3/MAO: Study of Polymerization Conditions
Authors: Lugo Luis E. , Charles Rogelio , Pérez Odilia , Cadenas Gregorio , Revilla Javier 
Published: September 2009

AbstractSyndiotactic polymerization of styrene in aliphatic solvents (hexane and cyclohexane) and aliphatic solvent/toluene mixtures was evaluated using a previously reported catalytic system formed by FluTi(OiPr)3/MAO in order to evaluate polymerization reaction conditions and their effect on polymer tacticity. Highly syndiotactic polystyrene was produced indistinctly using pure aliphatic solvent or mixtures with toluene. On the other hand, the effect of polymerization conditions such as temperature, catalyst precursor and styrene concentrations, Al/Ti ratio and aliphatic solvent/toluene ratio over catalytic activity were analyzed.
Catalysts for UHMWPE
Authors: Jones R.L. , Armoush M. 
Published: September 2009

AbstractPolyolefin coordination catalysts useful for producing UHMWPE are surveyed, including classic Ziegler‐Natta (ZN), current commercial generation ZN, metallocene single site, and non‐metallocene. Catalysts were prepared and compared for productivity and selected polymer properties under a variety of conditions. Classic catalysts used were long lived TiCl3 crystalline metal clusters made by reducing TiCl4 by co‐crystallizing with aluminum alkyls. Data presented from the synthesis and polymerization with these catalysts shows temperature and molecular weight response that were expected for these systems. Commercially available titanium on silica/ magnesium chloride was activated with aluminum alkyls and had higher activity than those of the previous generation. Conditions for polymerizing supported metallocenes for producing polymers in the UHMWPE range were described. Long range “non‐metallocenes” of the phenoxy‐imine class were activated with MAO was tested and reported.
Heterogeneous Polymerization of Ethylene and 1‐Hexene with Me3SiCp2ZrH3AlH2/SiO2 Activated with MAO
Authors: González Rebeca , Morales Elsa , García Maricela , Revilla Javier , Charles Rogelio , Collins Scott , Cadenas Gregorio , Lugo Luis , Pérez Odilia 
Published: September 2009

AbstractThe aluminohydride of zirconocene Me3SiCp2ZrH3AlH2 was supported on pre‐treated SiO2, and its catalytic activity for ethylene polymerization and ethylene‐1‐hexene copolymerization was evaluated in order to compare with the corresponding activity of the complex in solution. As expected for systems based on metallocenes, the aluminohydride of zirconocene complex showed higher activity in solution than in suspension, however its thermal and kinetic stability was significantly increased. The effect of the co‐catalyst concentration (MAO) on the activity and the molecular weight of the polymers are also reported in this study, finding that in heterogeneous phase low concentrations of MAO were used to activate the pre‐catalyst. The MW of the polymers and copolymers synthesized with the supported Me3SiCp2ZrH3AlH2/SiO2 could be controlled by adding molecular hydrogen (H2) as chain transfer agent in the polymerization and copolymerization reactions.
Evaluation of the Performance of a Kinetic Model for Free‐Radical Copolymerization of Vinyl/Divinyl Monomers in Supercritical Carbon Dioxide
Authors: Quintero‐Ortega Iraís A. , García‐Moran Pedro R. , Jaramillo‐Soto Gabriel , Vivaldo‐Lima Eduardo , Luna‐Bárcenas Gabriel 
Published: September 2009

AbstractThe performance of a mathematical model for free radical copolymerization kinetics with crosslinking of vinyl/divinyl monomers in supercritical carbon dioxide previously developed in our group is evaluated using experimental data of conversion versus time and gel fraction versus conversion for copolymerization of styrene and divinylbenzene. The effects of process conditions, type of stabilizer and initial divinyl monomer composition were also assessed. Reasonable agreement between model predictions and experimental data was obtained.
Progress in Controlled Grafting‐From by Nitroxide Chemistry
Authors: Saldívar‐Guerra Enrique , Bonilla‐Cruz José , Hernández‐Mireles Brenda , Ramírez‐Manzanares Grisel 
Published: September 2009

AbstractA number of substrates (polymers and silica) have been functionalized with nitroxide moieties in order to obtain alkoxyamine groups along the substrate. The functionalized substrates have been further heated in the presence of monomers in order to grow controlled grafts by the grafting – from technique. Tested substrates include polybutadiene (PB), polyisoprene (PI), styrene – isoprene (SIS) and styrene – butadiene (SBS) tri‐block copolymers, EPDM, poly (dimethyl‐siloxane) (PDMS), poly(ethylene glycol) and silica. Two chemical paths involving nitroxide chemistry have been used for the functionalization step and are discussed in this work. In the first path, the substrate is heated in the presence of a nitroxide radical (N) and a radical initiator (I) or using only nitroxide. In the second path, useful for substrates containing hydroxyl groups, the functionalization of the substrate is obtained using an N‐oxoammonium TEMPO bromide salt in the presence of triethyl amine, which forms a peroxide group linked on one end to the substrate and on the other end to the TEMPO moiety. The mechanisms, structures and the resulting polymers (functionalized and grafted) have been studied by GPC, spectroscopic techniques and transmission electron microscopy.
Silicon‐Based and Fluorinated Polymeric Surfactants for Nitroxide Mediated Dispersion Polymerization in Supercritical Carbon Dioxide
Authors: Ramírez‐Wong Diana Guadalupe , Posada‐Vélez Carlos Andrés , Saldívar‐Guerra Enrique , Luna‐Bárcenas J. Gabriel , Ott Christina , Schubert Ulrich S. 
Published: September 2009

AbstractBlock copolymers based on siloxanes and fluorinated block copolymers were synthesized and tested as surfactants for nitroxide mediated polymerizations (NMP) in supercritical carbon dioxide. Styrene was polymerized in the presence of TEMPO at 130 °C using various surfactants. Siloxane‐based surfactants were synthesized by a new route based on NMP; the perfluorinated surfactants were also synthesized by NMP. The dispersion polymerizations of styrene in scCO2 reveal conversions of up to 35% in 4 hours at 19.1 MPa. The resulting polydispersity indices lie in the range 1.2–1.4. The best results are obtained using a perfluorinated surfactant. Preliminary copolymerization experiments of the polystyrene macroinitiator in scCO2 have shown successful chain‐extension with butyl acrylate (BuA) resulting in the formation of a poly (St‐b‐BuA) block copolymer.
Temperature‐Sensitive Hydrogels: A Gentle Way of Concentrating Cellulase Enzymes
Authors: Hernandez Elena , Orozco‐Avila Ignacio 
Published: September 2009

AbstractThe swelling behaviour of a poly(N‐isopropylacrylamide) temperature sensitive hydrogel in fermentation broth was determined as a function of the temperature and compared with that in water. The feasibility of the gel as a device for concentration of cellulase enzymes, produced by the fermentation of the fungus Trichoderma reesei RUT C‐30, was also studied. For the same particle size, gels with different composition showed differences in the swelling time and in the extent of swelling. The time required for collapsing was independent of both the monomer concentration and the degree of crosslinking. During swelling, the gels absorb water and low molecular weight solutes (<100 g/mol), excluding macromolecules such as proteins (>10 kD). The enzymes were concentrated in the solution non‐ absorbed by the gels. Mass balances for fermented broth, total soluble protein and enzyme activity showed a good recovery.
Using Chitosan as a Nucleation Agent in Thermoplastic Foams for Heavy Metal Adsorption
Authors: Vázquez Milton O. , Ramírez‐Arreola Daniel E. , Bernache Javier , Gómez Cesar , Robledo‐Ortiz Jorge R. , Rodrigue Denis , González‐Núñez Rubén 
Published: September 2009

AbstractThermoplastics/chitosan‐powder composite foams were prepared by extrusion using azodicarbonamide (ACA) as chemical blowing agent. The effect of chitosan content on morphology (cell size, nucleation density and foam density) of the foams was studied. Chitosan particles are located on the bubbles periphery. Morphological quantification showed that foam cell size decreased and cell population increased with addition of chitosan into polymeric matrix from 1 to 10%. Further, optimum chitosan content was obtained for each polymer. Polymers foamed with chitosan were tested as a chelating resin to adsorb chromium (Cr VI) from different concentration solutions.
Acrylic Bone Cements Modified With Bioactive Filler
Authors: Jasso‐Gastinel Carlos Federico , Enriquez Salvador García , Flores Jorge , Reyes‐González Ignacio , Mijares Eduardo Mendizábal 
Published: September 2009

AbstractBioactive cuttlebone Sepia officinalis particles that contain collagen were used to fill poly (methyl methacrylate‐co‐styrene) bone cements, varying size and concentration of filler particles. Cuttlebone was characterized by X‐ray diffraction and plasma atomic emission spectrophotometer. Maximum reaction temperature and cement setting time were determined for composites and reference (copolymer without filler), along with NMR determination of residual monomer concentration. Mechanical properties characterization included stress‐strain, bending, compression, fracture toughness and storage modulus tests. Mechanical results for composites filled with 10 and 30% weight of cuttlebone, complied with norm requirements which opens the possibility for using cuttlebone particles as bioactive filler.
In Situ Production of Polymer‐Capped Silver Nanoparticles for Optical Biosensing
Authors: Giorgetti E. , Giusti A. , Arias E. , Moggio I. , Ledezma A. , Romero J. , Saba M. , Quochi F. , Marceddu M. , Gocalinska A. , Mura A. , Bongiovanni G. 
Published: September 2009

AbstractSummary: We report on the preparation and spectroscopic characterization of a novel nanocomposite consisting of silver nanoparticles and a fluorescent polymer obtained by in situ ps laser ablation of a silver target. While the polymer is able to detect the fungus Paecilomyces variotii by fluorescence quenching, the composite with silver nanoparticles permits an interaction with both cell walls of spores and mycelia without any appreciable reduction of the overall fluorescence quantum yield.
Mammalian Cell Culture on a Novel Chitosan‐Based Biomaterial Crosslinked with Gluteraldehyde
Authors: Fabela‐Sánchez O. , Zarate‐Triviño D. G. , Elizalde‐Peña E. A. , García‐Carvajal Z. , Sánchez I. C. , Parra‐Cid C. , Gómez‐García R. , Ibarra C. , García‐Gaitán B. , Zavala R. , Guevara‐Olvera L. , Villaseñor‐Ortega F. , Muñoz‐Sanchez C. I. , Perez‐Perez C. , Herrera‐Perez S. , Velasquillo C. , Luna‐Barcenas G. 
Published: September 2009

AbstractA novel (Chitosan‐g‐Glycidyl Methacrylate)‐Xanthan, (CTS‐g‐GMA)‐X, hydrogel was successfully synthesized at Cinvestav Queretaro. In the present work, we attempt to study the in vitro biocompatibility of (CTS‐g‐GMA)‐X hydrogels as scaffolds for neural cells obtained from cerebral cortex of mice; skin cells from skin of mice; and chondrocytes from human cartilage. The results obtained in the live/dead assay show that the materials maintain the morphology and viability of the cells. However the high friability of the materials prevented an extended test time in this assay. Therefore, glutaraldehyde (GL) was added to the structure as crosslinking agent to enhance friability. All results point out that [(CTS‐g‐GMA)‐X]‐GL hydrogel is viable as a scaffold for chondrocytes and skin cells; and (CTS‐g‐GMA)‐X for neural cell due to their physicochemical properties and biocompatibility with the cells for both materials.