bluuebunny/crossref_metadata_2025_split huggingface dataset:
Physiological changes and defense mechanisms induced by cadmium stress in maize
Authors: Pál Magda , Horváth Eszter , Janda Tibor , Páldi Emil , Szalai Gabriella 
Published: March 2006

AbstractHeavy metals such as cadmium (Cd) enter the ecosystem chiefly as the result of human activities. Nowadays the heavy‐metal pollution of the soil is causing ever greater problems, exacerbated by the fact that the heavy metals accumulated in plants may, either directly or indirectly, find their way into animals and human beings. Maize is one of the world's most important crops, ranking third after wheat and rice, so the changes induced by one of the most toxic heavy metals, Cd, in maize plants is a cause of some concern. This review discusses not only the toxic symptoms caused by Cd stress, but also the tolerance mechanisms activated in the plants. Cadmium induces a number of physiological changes, such as growth inhibition, changes in the water and ion metabolism, the inhibition of photosynthesis, changes in enzyme activities, and the formation of free radicals. The synthesis and compartmentalization of phytochelatins is induced shortly after the initiation of Cd stress, while other defense mechanisms also play an important role.
Near‐infrared spectroscopy can predict the composition of organic matter in soil and litter
Authors: Terhoeven‐Urselmans Thomas , Michel Kerstin , Helfrich Mirjam , Flessa Heiner , Ludwig Bernard 
Published: March 2006

AbstractThe usefulness and limitations of near‐infrared reflectance spectroscopy (NIRS) for the assessment of several soil characteristics are still not sufficiently explored. The objective of this study was to evaluate the ability of visible and near‐infrared reflectance (VIS‐NIR) spectroscopy to predict the composition of organic matter in soils and litter. Reflectance spectra of the VIS‐NIR region (400–2500 nm) were recorded for 56 soil and litter samples from agricultural and forest sites. Spectra were used to predict general and biological characteristics of the samples as well as the C composition which was measured by 13C‐CPMAS‐NMR spectroscopy. A modified partial least‐square method and cross‐validation were used to develop equations for the different constituents over the whole spectrum (1st to 3rd derivation). Near‐infrared spectroscopy predicted well the C : N ratios, the percentages of O‐alkyl C and alkyl C, the ratio of alkyl C to O‐alkyl C, and the sum of phenolic oxidation products: the ratios of standard deviation of the laboratory results to standard error of cross‐validation (RSC) were greater than 2, the regression coefficients (a) of a linear regression (measured against predicted values) ranged from 0.9 to 1.1, and the correlation coefficients (r) were greater than 0.9. Satisfactorily (0.8 ≤ a ≤ 1.2, r ≥ 0.8, and 1.4 ≤ RSC ≤ 2.0) assessed were the contents of C, N, and production of DOC, the percentages of carbonyl C and aromatic C and the ratio of alkyl C to aromatic C. However, the N‐mineralization rate and the microbial biomass were predicted unsatisfactorily (RSC < 1.4). The good and satisfactory predictions reported above indicate a marked usefulness of NIRS in the assessment of biological and chemical characteristics of soils and litter.
Kinetics of nonexchangeable‐potassium release and plant response in some calcareous soils
Authors: Jalali M. , Zarabi M. 
Published: March 2006

AbstractNonexchangeable K+ constitutes a slowly available reserve that may significantly influence K+ fertility of soils. Laboratory and greenhouse experiments were conducted to characterize the K+ supply and nonexchangeable K+–release kinetics in 10 calcareous soils using 0.01 M CaCl2 and 0.01 M oxalic acid extractions. Total K+ uptake by wheat (Triticum aestivum L.) grown in the greenhouse was used to measure plant‐available K+. The release of K+ was characterized by an initial fast rate followed by a slower rate. The nonlinear relationship in the early stages of the K+ release may be attributed to the edge sites, and release of K+ from interlayer exchange sites may be responsible for the second part of the K+ release. Kinetics of K+ release was described best with power function, which showed the best fit of the four models tested. Parameters of kinetics models in 0.01 M CaCl2 were significantly related to K+ uptake by wheat. Potassium release was also correlated to initial NH4OAc‐extratable K+ and to HNO3‐extractable K+.
Soil organic matter beyond molecular structure Part I: Macromolecular and supramolecular characteristics
Authors: Schaumann Gabriele E. 
Published: March 2006

AbstractThis contribution reviews and discusses structural aspects of soil organic matter (SOM) and humic substances (HS) with special respect to the macromolecular and the supramolecular view. It can be concluded that (1) dissolved humic acids behave as supramolecular associations of relatively small molecules with an enormous flexibility of reaction of environmental conditions, (2) multivalent cations may increase the apparent molecular weight by the formation of coordinative crosslinks in dissolved and undissolved natural organic matter (NOM), (3) sorption nonlinearity in solid humic acids and SOM may be due to polymer properties of NOM, (4) sorbates affect sorbent characteristics of SOM, and (5) hysteresis and conditioning effects in SOM can up to now best be explained with the polymer analogy. A distinct polydispersivity of SOM over a wide range of molecular masses is to be assumed.The supramolecular and the macromolecular models were derived from humic acids with different composition and on the basis of different sample states. Although the supramolecular model has not explicitely been shown for unfractionated DOM, the combination of all discussed studies suggests supramolecular as well as macromolecular characteristics of NOM. Neither macromolecules nor small molecules can be fully excluded in solid and dissolved SOM. Microregions with different properties provide different types of sorption sites. SOM is suggested to be regarded as amorphous material. This point of view is not restricted to high molecular masses and may supplement our understanding of SOM by the model of physical aging.
Soil organic matter beyond molecular structure Part II: Amorphous nature and physical aging
Authors: Schaumann Gabriele E. 
Published: March 2006

AbstractGlassy, rubbery, and crystalline phases are representatives of supramolecular structures which strongly differ in order, density, and other characteristics. In this contribution, the amorphous nature of soil organic matter (SOM) is reviewed with respect to the glassy/rubbery model, glass transition mechanisms, interactions of SOM with water, and physical aging. Glass‐transition behavior and physical aging are inherent properties of amorphous solids, and numerous spectroscopic investigations give insights into different domain mobilities of humic substances (HS). The correlation between sorption nonlinearity and glassiness of polymers and HS supports a relation between sorption and amorphicity in Aldrich humic acid. Further evidence is still required for the transfer to soil HS and SOM. Sorption and differential scanning calorimetry (DSC) data suggest a correlation between aromaticity and glassiness in HS, and the available data do currently not allow to decide unambiguously between specific sorption and hole filling as explanation. This needs to be verified in future research. Although parts of the investigations have up to now only been conducted with humic substances, the collectivity of available data give strong support for the glassy/rubbery conception of SOM. They clearly indicate that amorphous characteristics cannot be excluded in SOM.This is further supported by the observation of different types of glass‐transition behavior in samples of whole humous soil. In addition to classical glass transitions in water‐free soil samples, water surprisingly acts in an antagonistic way as short‐term plasticizer and long‐term antiplasticizer in a second, nonclassical transition type. Latter is closely connected with physico‐chemical interactions with water and suggests water bridges between structural elements of SOM (HBCL‐model). The gradual increase of Tg* in SOM indicates physico‐chemical aging processes, which are not restricted to polymers. They may be responsible for contaminant aging, changes in surface properties and increased soil compaction in agricultural soils.
Estimating soil stress distribution by using depth‐dependent soil bulk‐density data
Authors: Bachmann Jörg , Hartge Karl Heinrich 
Published: March 2006

AbstractDepth‐dependent soil bulk density (BDS) is usually affected by soil‐specific factors like texture, structure, clay mineralogy, soil organic‐matter content, soil moisture content, and composition of soil solution and is also affected by external factors like overburden‐stress history or hydrological fluxes. Generally, the depth‐dependent BDS cannot be predicted or extrapolated precisely from a limited number of sampling depths. In the present paper, an easy method is proposed to estimate the state of soil mechanical stress by analyzing the packing characteristics of the profile using soil bulk‐density data. Results for homogeneous loess profiles exposed to the site‐specific climatic conditions show that the depth‐dependent relation of void ratio vs. weight of overburden soil can be described systematically so that deviations from the noncompacted reference state can be detected. We observed that precompaction increased from forest soils (reference) to agricultural soils with decreasing depth.
Structure properties and pore dynamics in aggregate beds due to wetting–drying cycles
Authors: Seguel Oscar , Horn Rainer 
Published: March 2006

AbstractAggregate hierarchy and porosity changes in aggregate beds as a consequence of wetting–drying cycles were studied in two Andisols and one Mollisol from Chile, collected at two depths. Bulk density and indirect tensile strength were measured in aggregates of different sizes. Aggregate beds were prepared in cylinders with two size classes. Six wetting–drying cycles between 0 and –60 hPa were applied. Bulk density (Db) of soil matrix was controlled after each cycle, and the macroporosity was calculated. A repellency index was measured in one of the Andisols. In addition, also the air permeability was measured after the sixth cycle.It could be proofed, that the aggregate strength is an appropriate parameter to evaluate the aggregate hierarchy, and this parameter is also more sensitive than aggregate Db to discriminate between the effects of land‐use intensity. Aggregate strength is furthermore well correlated with changes in pore water pressure and can be applied to relate strength values with aggregate development level. Only if the predrying exceeds pF > 3.0, aggregate strength correlates with Db. The more pronounced is the land‐use, the higher is the increase of Db values for aggregate beds. The decrease of coarse porosity during wetting–drying cycles can be explained by mass differences between saturated and equilibrated water conditions that considers the water around aggregates and within the contact area. Nevertheless, the relation of relative macroporosity change, calculated by Pexped where Dagg is the Db measured by clod method, and the relative Db change, is useful to explain possible presence of coarse pores inside the aggregates. The newly formed porosity prevents the water repellency, but after six cycles of drying, the repellency index increased in the topsoil while we could detect a decrease in the subsoil samples (under defined conditions in the laboratory) which we assume to be caused by microbial activity. The approaching of aggregates by drying cycles generates in Andisols a reduced area to air fluxes, with low values of air permeability.
Elastomeric Poly(propylene) from “Dual‐side” Metallocenes: Reversible Chain Transfer and its Influence on Polymer Microstructure
Authors: Hild Sabine , Cobzaru Cecilia , Troll Carsten , Rieger Bernhard 
Published: March 2006

AbstractSummary: The influence of the cocatalyst nature on the distribution of the stereoerrors along the polymer chain has been studied using either MAO or [(C6H5)3C+] [(C6F5)4B−] to activate a C1‐symmetric (Flu‐Ind) complex in propene polymerization experiments. The in situ activation with borate indicated the chain back‐skip as the decisive mechanism responsible for stereoerror formation. When MAO is used for activation, additionally the reversible chain transfer to aluminum occurs, which can be called into account as a second mechanism for stereoerror formation. By the combination of 13C NMR, DSC, WAXS and SFM, it was shown that the differences in polymerization mechanisms result in variations of stereoerror formation. Due to this, the isotactic block length niso as well as their distribution along the chain changes. Using MAO activation, polypropenes with crystallizable blocks consisting of 23–32 monomers in isotactic sequences were generated, which co‐crystallized in α‐ and γ‐phase lamellae. When the reversible chain transfer was occluded (in situ borate activation) the bimodal distribution of crystalline lamellae strongly referred to a homogeneous random distribution of stereoerrors. In this case, two crystalline populations were present. The prevailing one, which crystallized in the orthorhombic γ‐modification, contained 23 consecutive isotactic blocks. Additionally, small amounts of α‐phase lamellae were present consisting of longer isotactic blocks (niso > 35). The different crystalline modifications resulted in different polymer morphologies. These changes caused in turn variations in the mechanical properties, such as elasticity and mechanical strength. This clearly shows that, by using different cocatalysts for activating C1‐symmetric complexes, the properties of poly(propylenes) with statistically distributed stereoerrors can be tailored.
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Macromolecule‐Metal Nanoparticle Complexes for Novel Development of Information Technology and Energy Conversion
Authors: Toshima Naoki 
Published: March 2006

AbstractSummary: Macromolecule‐metal nanoparticle complexes have achieved a great deal of attention from the researchers since the nanotechnology boom, because nanoparticles can be easily prepared by chemical reactions, often stabilized by complex formation with macromolecules, and can play important roles in the construction of nanostructured materials for novel technologies. Here I would like to introduce three typical examples which are going to be developed in our group and will be potentially applied to novel information and energy‐conversion technology, i.e., super‐high‐density magnetic recording media, fast‐responsive liquid‐crystal display, and processable thermoelectric materials.
Metal Complexes of Phthalocyanines in Polymers as Suitable Materials for Optical Limiting
Authors: Slodek A. , Wöhrle D. , Doyle J. J. , Blau W. 
Published: March 2006

AbstractSummary: Germanium and tin phthalocyanines containing peripheral and axial different substituents were synthesized. Thin multi‐layer films of PMMA and PVC containing monomolecular phthalocyanines were obtained by spin‐coating on glass substrates. The phthalocyanines were characterized by their absorption spectra. Optical limiting properties of the phthalocyanines in solution and in polymer films were investigated.
Membrane Preparation of Polysulfonic Acid Complexes by Layer‐by‐Layer Adsorption
Authors: Tago Takahiro , Shibata Hirokazu , Nishide Hiroyuki 
Published: March 2006

AbstractSummary: The water‐insoluble, thermostable and homogeneous polymer complex membrane formation of polysulfonic acids was examined by modifying the preparation conditions of the layer‐by‐layer adsorption method of the acid and base polymers. The complexation of poly(4‐styrenesulfonic acid) in the 0.15 unit mM solution with poly(allylamine) gave a polymer complex membrane on a gold substrate in which one polymer layer was formed with a thickness of 1 nm. Properties including the proton conductivity of the membrane suggested possible applications of the polymer complex membrane.
Synthesis of A New Terpyridine Ligand Combined with Ruthenium(II) Complex and its Usage in the Stepwise Fabrication of Complex Polymer Wires on Gold
Authors: Ohba Yoshiki , Kanaizuka Katsuhiko , Murata Masaki , Nishihara Hiroshi 
Published: March 2006

AbstractSummary: A ruthenium complex‐combined terpyridine ligand, tpyRu(dpp)‐(epe)‐ tpyPF6, was synthesized. Stepwise coordination reactions at the gold surface using this ligand gave Co‐Ru hetero‐metal complex wires, [1Co1Ru], which underwent reversible redox reactions of both redox complex units.
Preparation of Metal Oxide Nanotubes Using Gelators as Structure‐Directing Agents
Authors: Hanabusa Kenji , Numazawa Tomohiko , Kobayashi Satoshi , Suzuki Masahiro , Shirai Hirofusa 
Published: March 2006

AbstractSummary: Cationic gelators, capable of gelling alcohols, were developed as structure‐directing agents for preparing metal oxides. The sol‐gel polymerization of metal alkoxides using the gelators as templates afforded metal oxide nanotubes. The unique structure of metal oxides was created by transferring the shape of fibrous aggregates of gelator. The electrostatic interaction between cationic gelator and anionic metal oxide precursor plays an important role for acting as templates.
Zero‐Birefringence Optical Polymer by Birefringent Crystal and Analysis of the Compensation Mechanism
Authors: Koike Yasuhiro , Yamazaki Keita , Ohkita Hisanori , Tagaya Akihiro 
Published: March 2006

AbstractSummary: We reported a method for compensating the birefringence of optical polymers by doping them with inorganic birefringent crystals. In this method, an inorganic birefringent material is chosen that has the opposite birefringence to the polymer and needle‐like shape crystals which are oriented when the polymer chains are oriented. The birefringence of the polymer is thus compensated by the opposing birefringence of the crystal. Orientation behavior of the needle‐like crystals and polymers was investigated. The orientation function of the needle‐like crystal was increased with an increase in the aspect ratio of the needle‐like crystal.
Behavior of Linear and Cross‐Linked Polyelectrolytes in Metal Salt Solutions
Authors: Bekturov Esen , Suleimenov Ibragim 
Published: March 2006

AbstractSummary: Comparison of swelling properties of linear and cross‐linked polyelectrolytes on the basis of diffusion theory is carried out. It is shown that viscosity of both positively and negatively charged macromolecules in solutions containing low‐molecualr ions may be predicted with the help of generalized Fuoss's law.
Design of Enzyme‐like Complexing Polymer Sorbents and Metal‐Polymer Complex Catalysts with Memory to Substrates
Authors: Efendiev Ayaz 
Published: March 2006

AbstractSummary: A new principle of design of enzyme‐like complexing polymer sorbents and metal polymer complex catalysts has been developed. The principle is based on the use of memory of polymer composition and consists in conformational prearrangement of macromolecules of noncrosslinked complexing polymer favorable for sorbing metal ions and/or catalyzing substrate position followed by intermolecular crosslinking. It has been shown that prearranged polymer sorbents and catalysts demonstrate significantly improved sorption and catalytic properties.
Metal‐Containing Poly(Organophosphazenes)
Authors: Pertici Paolo , Vitulli Giovanni , Gleria Mario , Facchin Giacomo , Milani Roberto , Bertani Roberta 
Published: March 2006

AbstractSummary: In this paper we highlighted the general situation of metal containing poly(organophosphazenes) and we presented the status of the art in this area in terms of interactions between phosphazene materials and different types of metals. Possible practical utilization of the polymers obtained is also envisaged.
Studies of the Interaction of Platinum Drugs with DNA Using Oligonucleotide Microarrays
Authors: Guiseppi‐Elie Anthony , Taylor Scott , Lingerfelt Louise , Nixon Chris , Georgiana Ryan , Kim Joy , Smith Stephanie , Mangrum Brad , Farell Nicholas 
Published: March 2006

AbstractSummary: A novel method for the study of the interaction of the platinum drug cis‐diamminedichloroplatinum(II) (cis‐DDP or cisplatin) with 50‐mer oligonucleotides that were printed in high throughput microarray format is introduced. Our aim has been to identify sequence level differences in the interaction of various drug candidates that may serve to enable rational targeting of drugs to specific genes. A microarray of 26 control genes commonly used in oligonucleotide, Affymetrix and c‐DNA microarray platforms were microcontact spotted as amine‐terminated 50‐mer oligonucleotides onto glycidoxypropyltimethoxy silane (GPMS)‐modified glass slides. The generalized study format involved hybridization of probes with 10 fluorescently labeled complements as target followed by confocal imaging to reveal original spot intensities. Microarrays were then incubated at 37 °C with hydrolysed cisplatin while in hybridization cassettes, washed in buffer and then scanned again to reveal secondary intensities. We have investigated the influence of cisplatin to stabilize the relative fluorescence intensity via intrastrand crosslinking by studying the impact of varying drug:probe‐DNA mole ratio (0:1 (blank), 1:1, 25:1 and 50:1) and annealing temperatures (36, 46, or 56 °C) on retained intensity. ANOVA revealed that 4 of the 10 genes demonstrated (p < 0.0001) the expected result of increased signal retention with decreased temperature and increased drug concentration.
Modification and Electrochemical Properties of Poly(phenylazomethine) Derivatives
Authors: Higuchi Masayoshi , Hayashi Akari , Yamamoto Kimihisa 
Published: March 2006

AbstractSummary: Oligo(phenylazomethine)s (OPAs) and aniline‐capped OPAs (OPA's) are used as model compounds of polyphenylazomethine (PPA), and their fundamental properties and their modification methods are investigated. Cyclic voltammograms of bis(diphenylmethyleneamino)benzene (OPA2′) showed irreversible redox response in the presence of trifluoroacetic acid. A selective synthesis of oligophenanthridine was achieved through the photocyclization of OPA2′ in concentrated sulfuric acid. Stepwise complexation behavior in dendritic poly(phenylazomethine)s (DPAs) was supported by the shell‐selective reduction of the imines. Using the shell‐selective reduction method and the terminal‐modification method of the DPAs, the core and terminals of DPAs were functionalized by ferrocene units, respectively.
Catalytic Activity of Copper(II) Enzyme‐like Catalysts, Prepared by Molecular Imprinting Technique in Oxidation of Phenols
Authors: Jakubiak Anna , Kolarz Bożena N. , Jezierska Julia 
Published: March 2006

AbstractSummary: Molecularly imprinted polymer copper(II) catalysts were prepared by suspension polymerization of 4‐vinylpyridine, trimethylolpropane trimethacrylate (series A) and additional monomer – acrylonitrile (series B) in the presence of Cu(II) ions and template: 4‐metoxybenzyl alcohol; two samples were also prepared by surface molecular imprinting technique utilizing W/O emulsion. The catalytic activity was tested in model oxidation reactions of hydroquinone and 2,5‐di‐tert‐butylhydroquinone using hydrogen peroxide. The imprinted catalysts were more effective in both reactions than non‐imprinted but their activity strongly depended on Cu(II) loading. Surface imprinted samples showed the highest activity (LH up to 100%).